SHEET-SHAPED ITEM AND MANUFACTURING METHOD THEREFOR

Abstract

 A sheet-shaped item including ultrafine fiber bundles that are obtained by gathering a plurality of ultrafine fibers comprising a thermoplastic resin, said sheet-shaped item comprising a base material layer and a nap layer, wherein the base material layer is a fiber entanglement comprising ultrafine fiber bundles, the nap layer has a nap consisting of ultrafine fibers on at least one surface of the sheet-shaped item, and the sheet-shaped item satisfies all of the following conditions (1)-(3). (1) The average single-fiber diameter of the ultrafine fibers is 0.1 µm to 10µm. (2) Among the ultrafine fibers, the average fiber length of the ultrafine fibers in the nap layer is 250µm to 500µm. (3) The surface coverage of the ultrafine fibers in the nap layer is 60% to 100%. A sheet-shaped item with a fine surface and superior glossiness is thus provided.

Description

TECHNICAL FIELD

[0001] The present invention relates to a sheet-shaped item and a method for the production thereof.

BACKGROUND ART

[0002] Sheet-shaped items that consist mainly of nonwoven fabrics of ultrafine fibers and elastomeric polymers have good features such as high durability and high uniformity that cannot be matched by natural leathers and have been used in a variety of products including seat materials and facing materials for vehicles, interior materials, shoes, and clothing. In particular, for napped sheet-shaped items, which are produced by polishing etc. of the surface of a sheet-shaped item to raise the ultrafine fibers on the surface, a variety of materials have been proposed to suit different purposes, ranging, for example, from those having uniform, even surfaces to those having irregular surfaces such as the sheet-shaped item disclosed in Patent document 1, which has a touch like the mellow smoothness of nubuck.

[0003] Of these, disclosed items having uniform, even surfaces include, for example, sheet-shaped items suitable for polishing purposes having napped surfaces in which nanofiber-level ultrafine fibers are densely aligned, such as those disclosed in Patent documents 2 and 3.

PRIOR ART DOCUMENTS

PATENT DOCUMENTS

[0004] 

Patent document 1: International Publication WO 2016/051711

Patent document 2: Japanese Unexamined Patent Publication (Kokai) No. 2016-47560

Patent document 3: Japanese Unexamined Patent Publication (Kokai) No. 2015-209594

SUMMARY OF INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0005] By the way, techniques for providing sheet-shaped items having improved gloss to develop an elegant, refined appearance have been called for in order to allow suede-like sheet-shaped items having smooth, uniform surfaces as disclosed in Patent documents 2 and 3, rather than sheet-shaped items having nonuniform, irregular surfaces as disclosed in Patent document 1, to be applied to production of interior materials, shoes, and clothing. However, the conventional sheet-shaped items having smooth, uniform surfaces are suited for polishing purposes and therefore, they are inferior in properties such as light-fastness and gloss required by interior materials, shoes, and clothing and have to be improved in abrasion resistance to prevent breakage during practical use.

[0006] Thus, the main object of the present invention is to provide a sheet-shaped item having an elegant appearance, more specifically a sheet-shaped item having dramatically improved surface features such as densely packed ultrafine fibers, gloss, and abrasion resistance.

MEANS OF SOLVING THE PROBLEMS

[0007] As a result of intensive studies aiming to meet the above object, the inventors found that the conventional sheet-shaped items for polishing purposes fail to have adequate gloss because the average fiber length of ultrafine fibers in the nap layer is so short that rays of light incident on the sheet-shaped items undergo diffuse reflection and also found that the quantities of the elastomeric polymers used as binder are so small that adequate abrasion resistance cannot be achieved. More specifically, they arrived at the present invention after finding that for the development of a suede-like artificial leather having a surface with a dense touch and elegant, excellent gloss, it is important that the surface coverage and fiber length of ultrafine fibers in the nap layer are in specific ranges and also that the quantity of the elastomeric polymer contained is in a specific range to ensure abrasion resistance.

[0008] The main object of the present invention is to solve the aforementioned problem.

[0009] The sheet-shaped item according to the present invention is a sheet-shaped item including ultrafine fiber bundles each containing a plurality of ultrafine fibers of a thermoplastic resin, the sheet-shaped item having a base material layer and a nap layer, the base material layer containing a fiber entanglement of the ultrafine fiber bundles, the nap layer including a nap formed only of the ultrafine fibers and covering at least one surface of the sheet-shaped item, and all of the requirements (1) to (3) given below being satisfied:

(1) the ultrafine fibers have an average single fiber diameter of 0.1 µm or more and 10 µm or less,

(2) of the ultrafine fibers, those ultrafine fibers contained in the nap layer have an average fiber length of 250 µm or more and 500 µm or less, and

(3) in the nap layer, the surface coverage of the ultrafine fibers is 60% or more and 100% or less.

[0010] In a preferred embodiment of the sheet-shaped item according to the present invention, the sheet-shaped item consists mainly of the ultrafine fiber bundles and an elastomeric polymer, and the elastomeric polymer is contained in the interior of the fiber entanglement.

[0011]  In a preferred embodiment of the sheet-shaped item according to the present invention, the ultrafine fiber bundles contain 10 or more and 400 or less ultrafine fibers per bundle.

[0012] In a preferred embodiment of the sheet-shaped item according to the present invention, the ultrafine fibers in the nap layer have a CV (coefficient of variation) in the average fiber length of 30% or less.

[0013] In a preferred embodiment of the sheet-shaped item according to the present invention, the elastomeric polymer added accounts for more than 0 mass% and 60 mass% or less relative to the ultrafine fibers.

[0014] The production method for the sheet-shaped item according to the present invention is a method for producing the aforementioned sheet-shaped item characterized in that a silicone-based lubricant is added to 0.01 mass% or more and 3.0 mass% or less relative to the mass of the sheet-shaped item, followed by buffing treatment of the product surface after drying the sheet-shaped item.

[0015] In a preferred embodiment of the production method for the sheet-shaped item according to the present invention, the grinding rate in buffing the product surface is 20 g/m² or more and 250 g/m² or less.

[0016] In a preferred embodiment of the production method for the sheet-shaped item according to the present invention, the buffing treatment of the product surface is performed at least twice or more in multiple stages using sandpapers of increasingly finer grits or of the same grit number.

[0017] In a preferred embodiment of the production method for the sheet-shaped item according to the present invention, the number of times torn with a Schiefer type abrasion tester is 20 or more per 0.10 mm thickness of the sheet-shaped item as determined by the test specified in ASTM D4158-08 (2016) "Standard Guide for Abrasion Resistance of Textile Fabrics (Uniform Abrasion)" (abrasion resistance evaluation method) using a sand paper of grit number 180 under a load of 2 lbs.

ADVANTAGEOUS EFFECTS OF THE INVENTION

[0018] According to the present invention, by adjusting the surface coverage of the ultrafine fibers and the fiber length of ultrafine fibers in the nap layer to the aforementioned ranges, it is possible to provide a sheet-shaped item that has an elegant appearance, i.e. dramatically improved ultrafine fiber denseness and gloss on the surface of the sheet-shaped item and shows high abrasion resistance during practical use, so that it can be suitably used for such products as interior materials, shoes, and clothing.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] [Fig. 1] Fig. 1 is a conceptual diagram illustrating the method for measuring the average fiber length of ultrafine fibers in the nap layer of the sheet-shaped item according to the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0020] The sheet-shaped item according to the present invention is a sheet-shaped item including ultrafine fiber bundles each containing a plurality of ultrafine fibers of a thermoplastic resin, the sheet-shaped item having a base material layer and a nap layer, the base material layer containing a fiber entanglement of the ultrafine fiber bundles, the nap layer including a nap formed only of the ultrafine fibers and covering at least one surface of the sheet-shaped item, and all of the requirements (1) to (3) given below being satisfied:

(1) the ultrafine fibers have an average single fiber diameter of 0.1 µm or more and 10 µm or less,

(2) of the ultrafine fibers, those ultrafine fibers contained in the nap layer have an average fiber length of 250 µm or more and 500 µm or less, and

(3) in the nap layer, the surface coverage of the ultrafine fibers is 60% or more and 100% or less.

[0021] This structure allows the sheet-shaped item to have a good appearance characterized by high ultrafine fiber denseness and gloss as described above. The constitution of the sheet-shaped item according to the present invention is described in detail below.

(Thermoplastic resin)

[0022] The sheet-shaped item according to the present invention contains ultrafine fibers of a thermoplastic resin to constitute the sheet-shaped item, and examples of the thermoplastic resin include polyesters such as polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, and polylactic acid, polyamides such as polyamide 6, polyamide 66, and polyamide 12, polyolefins such as acrylic, polyethylene, and polypropylene, and melt-spinnable resins such as polyphenylene sulfide (PPS) and thermoplastic cellulose. In particular, polyesters are preferred from the viewpoint of strength, dimensional stability, and light resistance. From the viewpoint of environment protection, fibers produced from recycled materials or plant-derived materials may be used. Many of the condensation polymers such as polyesters and polyamides that are used to produce fibers are preferred because they have high melting points and high heat resistance. Furthermore, ultrafine fibers of different materials may be used in combination.

[0023] In another preferred embodiment, the thermoplastic resins may contain inorganic particles such as titanium oxide particles, lubricants, pigments, thermal stabilizers, UV absorbers, conductive agents, heat storage agents, and antibacterial agents depending on desired physical properties to be imparted to the sheet-shaped item.

(Ultrafine fibers)

[0024] For the present invention, it is important that the ultrafine fibers have an average single fiber diameter of 0.1 µm or more and 10 µm or less. Controlling the average single fiber diameter at 10 µm or less, preferably 8.0 µm or less, and more preferably 7.0 µm or less, serves to obtain a sheet-shaped item having a high-quality surface that is dense and soft to the touch. When forming a nap layer on the surface, furthermore, the number of napped fibers per unit area is increased and this leads to a more even surface.

[0025] On the other hand, controlling the average single fiber diameter of the ultrafine fibers at 0.1 µm or more, preferably 1.0 µm or more, allows the resulting sheet-shaped item to have a high monofilament strength and stiffness, and ensures high post-dyeing color development performance, high fiber dispersibility during raising treatment performed by, for example, grinding with sandpaper etc., and easy untangling.

[0026] Note that the value of the average single fiber diameter of ultrafine fibers to be adopted for the present invention should be measured as described below:

(a) the surface of the sheet-shaped item is photographed by a scanning electron microscope (SEM),

(b) 100 ultrafine fibers are selected randomly and the single yarn diameters of the 100 ultrafine fibers are measured, and

(c) the arithmetic average of the 100 measurements are calculated and rounded off to one decimal place to give the average single fiber diameter.

[0027] If the ultrafine fibers have modified cross sections as described below, however, the diameter and the area of the circumscribed circle about the cross section of each fiber is calculated and the equivalent diameter calculated from the ratio of the actual area of the cross section of the fiber to the area of the circumscribed circle is used to determine the average single fiber diameter of these fibers.

[0028] Examples of the cross-sectional shapes of ultrafine fibers used for the present invention include, in addition to circle, ellipse, flattened shape, polygon such as triangle, sector, cruciform, and other modified shapes, of which appropriate one is selected to allow the sheet-shaped item to have desired properties.

[0029] For the present invention, ultrafine fibers used to constitute a fiber entanglement are in the form of ultrafine fiber bundles each containing a plurality of ultrafine fibers. Such a ultrafine fiber bundle containing a plurality of ultrafine fibers is in the form of a so-called bundle in which a plurality of ultrafine fibers are at least partially in contact with each other. Specifically, they may be joined by, for example, partial fusion or they may be coagulated.

[0030] For the present invention, it is preferable for an ultrafine fiber bundle to contain 10 fibers per bundle or more and 400 fibers per bundle or less, more preferably 15 fibers per bundle or more and 200 fibers per bundle or less. If the number of fibers is less than 10 fibers per bundle, the ultrafine fibers will be low in denseness and, for example, mechanical properties such as abrasion resistance tend to deteriorate. If the number of fibers is more than 400 fibers per bundle, on the other hand, the fiber-opening property during the napping step will deteriorate, and the fiber distribution in the napped surface tends to be low in uniformity.

(Sheet-shaped item)

[0031] The sheet-shaped item according to the present invention consists mainly of a base material layer and a nap layer. The base material layer is in the form of a fiber entanglement of the ultrafine fiber bundles. The nap layer includes a nap formed only of the ultrafine fibers and covers at least one surface of the sheet-shaped item.

[0032] For the present invention, it is important that the average fiber length of ultrafine fibers in the nap layer is 250 µm or more and 500 µm or less. Here, the present inventors examined the average fiber length of ultrafine fibers contained in the nap layer to allow quantitative evaluation of indicators of gloss. Having gloss means having a surface with a high specular reflectance, which indicates that the nap layer has an even surface. Accordingly, the surface tends to increase in gloss with an increasing fiber length of ultrafine fibers. If the average fiber length of ultrafine fibers contained in the nap layer is 500 µm or more, however, the ultrafine fibers are so long that they have a rumpled appearance and therefore, it is not preferred. If it is less than 250 µm, the surface of the nap layer decreases in evenness and light undergoes diffuse reflection on the surface of the nap layer, leading to insufficient gloss. Controlling the average fiber length of ultrafine fibers contained in the nap layer at 250 µm or more and 500 µm or less, preferably 300 µm or more and 400 µm or less, serves to obtain a sheet-shaped item having a high gloss.

[0033] With reference to the conceptual diagram given in Fig. 1, the average fiber length (µm) of the ultrafine fibers in the nap layer is determined according to the procedure described below, and the value thus obtained is adopted.

(a) Brush the napped fibers against the grain using a lint brush to align them to each other.

(b) Photograph a cross section of the sheet-shaped item by SEM at a magnification of 40.

(c) In the SEM image taken above, draw a line L connecting the roots of the ultrafine fibers in the nonwoven fabric or, if fiber bundles are present, connecting the top ends of the fiber bundles.

(d) Draw a line U connecting the top ends of the napped fibers that are located at the front in the observed plane.

(e) Draw a plurality of thickness-directional parallel lines Pn (P1, P2, P3, ..., P15) at intervals of 200 µm.

(f) Measure the length of the L-U segment of each line Pn.

(g) Select nine different lines Pn, measure the length of the segment of each line, and calculate their arithmetic average.

(h) Perform this procedure for 10 positions distributed evenly over the sheet-shaped item.

(i) Calculate the arithmetic average of these arithmetic average values and round it off to one decimal place to represent the average fiber length (µm) of the ultrafine fibers in the nap layer.

[0034] A sufficiently high degree of gloss can be developed by controlling the CV in the average fiber length of ultrafine fibers in the nap layer at 30% or less, more preferably 25% or less. The CV in the average fiber length of ultrafine fibers as referred to herein is determined by measuring the aforementioned average fiber length values, calculating the arithmetic average and standard deviation, and dividing the standard deviation by the average to give a quotient expressed in percentage (%). The uniformity increases as this value decreases.

[0035] For the present invention, it is important that the surface coverage of the ultrafine fibers in the nap layer is 60% or more and 100% or less. If the surface coverage of the ultrafine fibers is adjusted to 60% or more, preferably 65% or more, a dense nap is formed and it is possible to obtain a sheet-shaped item having an elegant surface appearance and a very soft-to-touch surface and undergoing little loss of fibers. Regarding the surface coverage of the ultrafine fibers, the napped surface was enlarged by SEM at an observing magnification of 30 to 70 so that the existence of napped fibers was visible. The ratio of the combined area of the napped fiber portions to the total area of 4 mm² was calculated by image analysis software and it was adopted as the coverage of napped fibers. The ratio of the combined area can be calculated by separating the napped portions and non-napped portions by analyzing the photographed SEM image using ImageJ image analysis software and binarizing the data with a threshold of 100. When calculating the coverage of napped fibers, substances that are not napped fibers may be included as napped fibers in the calculation and may have a large influence on the coverage of napped fibers. In such a case, the image was modified manually and it is re-calculated assuming that such a portion is a non-napped portion.

[0036] The aforementioned ImageJ image analysis software can be cited as a good example of an image analysis system, but the image analysis system to be used here is not limited to the ImageJ image analysis software as long as it contains image processing software having the function of calculating the ratio between areas prescribed pixels. Note that the ImageJ image processing software is a generally used program developed by the National Institutes of Health, USA. The ImageJ image processing software has the function of defining a necessary region in a photographed image and performing pixel analysis.

[0037] It is preferable that the sheet-shaped item according to the present invention has an elastomeric polymer in addition to ultrafine fiber bundles and that the elastomeric polymer is contained in the interior of the aforementioned fiber entanglement.

[0038] Specifically, it is preferable that the elastomeric polymer accounts for more than 0 mass% and 60 mass% or less relative to the mass of the ultrafine fibers in the fiber entanglement. When the elastomeric polymer accounts for more than 0 mass%, preferably 3 mas% or more, relative to the mass of the ultrafine fibers, it is possible to impart a moderate degree of compressive property to the sheet-shaped item. Regarding the mass of the elastomeric polymer necessary to achieve high abrasion resistance, it becomes possible to impart moderate degrees of compressive property and abrasion resistance to the sheet-shaped item when the elastomeric polymer contained therein accounts for more than 20 mass%, preferably 25 mass% or more, relative to the mass of the ultrafine fibers in the fiber entanglement. In the case where the mass of the elastomeric polymer accounts for more than 60 mass%, the fibers may not have good fiber-opening property during the napping step and the flexibility of the sheet-shaped item may decrease.

[0039] In the case where the sheet-shaped item is to be used after being dyed, the amount of the elastomeric polymer may be preferably small because a difference in color tone can occur between the fibers in the fiber entanglement and the elastomeric polymer after dyeing. From the viewpoint of environmental consideration, on the other hand, the inclusion of an excessive amount of an elastomeric polymer is not preferred because the consumption of organic substances in the production process will increase. In the case where fibers produced from recyclable materials or plant-derived materials are adopted, their recycling and disposal become easier to perform as the amount of the elastomeric polymer decreases.

[0040] The elastomeric polymer may contain, if necessary, pigments such as carbon black, dye, fungicide, antioxidant, UV absorber, light-resistant agents such as photostabilizer, flame retardant, penetrant, lubricant, antiblocking agents such as silica and titanium oxide, water repellent agent, viscosity adjusting agent, surface active agents such as antistatic agent, antifoam agent, fillers such as cellulose, coagulation modifier, and inorganic particles of silica, titanium oxide, etc.

[0041] Elastomeric polymers that can be used for the present invention include polyurethane-based elastomers, polyurea, polyacrylic acid, ethylene-vinyl acetate elastomer, acrylonitrile-butadiene elastomer, styrene-butadiene elastomer, polyvinyl alcohol, and polyethylene glycol, of which polyurethane-based elastomers are preferred from the viewpoint of durability and compressive property. The elastomeric polymer may contain a plurality of elastomeric polymers.

[0042] The polyurethane-based elastomers that are used particularly preferably for the present invention include polyurethane and polyurethane-polyurea elastomer.

[0043] For the sheet-shaped item according to the present invention, it is important that the number of times torn with a Schiefer type abrasion tester is 20 or more per 0.10 mm thickness of the sheet-shaped item as determined by the test specified in ASTM D4158-08 (2016) "Standard Guide for Abrasion Resistance of Textile Fabrics (Uniform Abrasion)" (abrasion resistance evaluation method) using a sandpaper of grit number 180 under a load of 2 lbs. A sheet-shaped item having high tear resistance can be obtained when the number of times torn with a Schiefer type abrasion tester per 0.10 mm thickness of the sheet-shaped item is 20 or more, more preferably 25 or more, and still more preferably 35 or more.

[0044] The number of times torn with a Schiefer type abrasion tester (times/0.10 mm) was measured as follows: performing an abrasion test using a Schiefer type abrasion tester in which the abrasion face (diameter 50 mm) of the nap layer of a sheet-shaped item is abraded against a sandpaper of grit number 180 used as abradant under a load of 2 lbs, counting the number of times until the abrasion testing machine stops as a result of tearing of the sheet-shaped item to actuate the limiter, and dividing it by the thickness of the sheet-shaped item to calculate the number of times torn with a Schiefer type abrasion tester per 0.10 mm of the thickness (times/0.10 mm).

(Production method for sheet-shaped item)

[0045] The production method for the sheet-shaped item is described in more detail below.

(a) A step for forming a fiber entanglement of ultrafine fiber-generating fibers

[0046] In the production method for the sheet-shaped item according to the present invention, it is preferable that a fiber entanglement of ultrafine fiber-generating fibers is formed first. Doing so makes it possible to form a fiber entanglement containing entangled ultrafine fiber bundles more easily compared with forming a fiber entanglement directly from ultrafine fibers.

[0047] It is particularly preferable that the aforementioned ultrafine fiber-generating fibers are islands-in-the-sea fibers. There are different types of islands-in-the-sea fibers including islands-in-the-sea composite fibers, which are produced using a spinneret designed for islands-in-the-sea composites in which the two components, i.e. sea component and island component, are disposed side by side as they are spun into a yarn, and mixed yarn fibers, which are produced by spinning a combined batch of the two components, i.e. sea component and island component. Of these islands-in-the-sea fibers, islands-in-the-sea composite fibers are preferred because ultrafine fibers that are controlled with high accuracy can be obtained and also because sufficiently long ultrafine fibers can be obtained to contribute to increased strength of nonwoven fabrics and sheet-shaped items containing nonwoven fabrics.

[0048] Regarding the ratio between the sea component and the island component in the islands-in-the-sea composite fibers, it is preferable that the mass ratio of the island fibers to the islands-in-the-sea composite fibers is preferably 0.2 or more and 0.9 or less, more preferably 0.2 or more and 0.8 or less. If this mass ratio is 0.2 or more, the sea component removal ratio can be decreased to ensure improved productivity. If the mass ratio is 0.9 or less, it is preferable because the fiber-opening property of the island fibers will improve and the confluence of streams of the island component can be prevented.

[0049] Here, for the aforementioned islands-in-the-sea composite fibers, materials of the island component that forms ultrafine fibers in the step described later are as listed above as examples of thermoplastic resin. On the other hand, useful materials of the sea component include polyethylene, polypropylene, polystyrene, polystyrene copolymers, polyester copolymers produced through copolymerization of sodium sulfoisophthalic acid, polyethylene glycol, etc., and polylactic acid. It is preferable to use polystyrene or a polystyrene copolymer as the sea component in order to realize a high degree of shrinkage in the densification-shrinkage treatment step described later.

[0050] For the formation of the aforementioned fiber entanglement of ultrafine fiber-generating fibers, it is preferable to form a nonwoven fabric etc. of ultrafine fiber-generating fibers. Doing so makes it possible to improve the surface quality of the sheet-shaped item by raising it in the subsequent step.

[0051] Examples of the aforementioned nonwoven fabric include nonwoven fabrics produced by a papermaking technique, short fiber nonwoven fabrics produced by forming a laminated web from short fibers using a carding machine, cross wrapper, or the like, followed by needle punching, water jet punching, or the like, and long fiber nonwoven fabrics produced by the spunbond method, melt blowing method, or the like, from which an appropriate one may be selected so that the intended properties will be developed, but short fiber nonwoven fabrics are preferred from the viewpoint of texture and quality.

[0052] In the short fiber nonwoven fabrics, the fiber length of ultrafine fiber-generating fibers is preferably 8 mm or more and 90 mm or less. By adjusting the fiber length to 8 mm or more, it becomes possible to obtain a sheet-shaped item having high abrasion resistance attributed to entanglement. By adjusting the the aforementioned fiber length to 90 mm or less, on the other hand, it becomes possible to obtain a sheet-shaped item having good compressive property and surface quality. The fiber length is more preferably 25 mm or more and 90 mm or less. Fibers having a fiber length of less than 8 mm cannot be entangled easily and such fibers tend to come off easily during the production process of the sheet-shaped item. On the other hand, fibers having a fiber length of more than 90 mm can be entangled easily, but a nap layer formed thereof tends to be low in abrasion resistance and inferior in surface quality.

[0053] It is preferable for the needles used for the needle punching treatment to have 1 to 9 needle barbs. By using a needle having one or more needle barbs, it becomes possible to perform efficient entanglement of the fibers. By using a needle having 9 or less needle barbs, on the other hand, damage to the fibers can be reduced.

[0054] The number of punches is preferably 1,000 punches/cm² or more and 6,000 punches/cm² or less. If the number of punches is 1,000 punches/cm² or more, high denseness will be realized and highly precise finishing can be achieved. On the other hand, if the number of punches is 6,000 punches/cm² or less, it serves to prevent a decline in processability, damage to fibers, and decrease in strength.

[0055] When performing the water jet punching treatment, it is preferable to use water in a columnar form. Specifically, water is preferably squirted under a pressure of 2 MPa to 60 MPa through a nozzle having a diameter of 0.05 mm to 1.0 mm.

[0056] The nonwoven fabric formed of ultrafine fiber-generating fibers treated by needle punching or water jet punching preferably has an apparent density of 0.15 g/cm³ or more and 0.45 g/cm³ or less. An apparent density of 0.15 g/cm³ or more serves to form a nonwoven fabric having high morphological stability and dimensional stability and also serves to prevent nonuniform processing and formation of scratch defects during the polishing step. On the other hand, an apparent density of 0.45 g/cm³ or less serves to maintain adequate spaces among fibers to accommodate an elastomeric polymer.

[0057] From the viewpoint of increasing the denseness, the nonwoven fabric of ultrafine fiber-generating fibers obtained in this way may be shrunken by either or both of dry heat and wet heat to achieve a higher density. In addition, the nonwoven fabric may be compressed in the thickness direction by calendering etc.

(b) A step for integrating a fiber entanglement and a reinforcing layer as a layer stack

[0058] The sheet-shaped item according to the present invention may have a reinforcing layer in the interior or on the surface with the aim of improving the strength etc., and the fiber entanglement formation step may be followed by a step for integrating it with this reinforcing layer as a layer stack. The aforementioned reinforcing layer may be in the form of woven fabric, knitted fabric, nonwoven fabric (including paper), or a film-like material such as plastic film and thin metal sheet.

[0059] In the case where the reinforcing layer is in the form of woven or knitted fabric of fibers, the yarn used in them is preferably a synthetic fiber such as polyester, polyamide, polyethylene, polypropylene, or a copolymer thereof. In particular, it is preferable to adopt synthetic fibers of polyester, polyamide, or a copolymer thereof, which may be used alone or as a composite or a mixture thereof. The yarn used in the woven or knitted fabric may be in the form of filament yarn, spun yarn, mixed yarn of filaments and short fibers, etc. It is preferable for the fibers used in these yarns to have an average monofilament diameter of about 0.1 µm or more and 20 µm or less from the viewpoint of texture of the sheet-shaped item.

[0060] When the needle punching technique is used for the stack integration step, the woven or knitted fabric may be broken by the needles, depending on the type of the yarn used, and this may cause a decrease in the strength of the sheet-shaped item. As a means of suppressing this, it is preferable for the woven or knitted fabric to be formed of a twisted yarn.

[0061] In the case where the yarn used in the woven or knitted fabric is a twisted yarn, the monofilaments constituting the yarn may not be bound sufficiently and may be easily caught and damaged by the needles if its twist count is 500 T/m or less. On the other hand, an excessively large twist count may lead to an excessively stiff yarn, and this is not preferred because the resulting sheet-shaped item will not have a soft texture. Accordingly, the twist count of such a twisted yarn is preferably 500 T/m or more and 4,500 T/m or less, more preferably 1,000 T/m or more and 4,000 T/m or less, still more preferably 1,500 T/m or more and 4,000 T/m or less, and most preferably 2,000 T/m or more and 4,000 T/m or less.

[0062] Regarding the fineness of the yarn constituting the woven or knitted fabric (total fineness in the case of multifilament), the metsuke (weight per unit surface area) of the woven or knitted fabric working as a reinforcing layer and also the metsuke of the sheet-shaped item will increase when the fineness is 200 dtex or more. As a result, the sheet-shaped item becomes so high in rigidity that it will be difficult for the sheet-shaped item to be flexible enough to serve as material for interior finishing, shoes, and clothing. Accordingly, it is preferably 30 dtex or more and 150 dtex or less, more preferably 50 dtex or more and 130 dtex or less. The monofilaments constituting the yarn used in the woven or knitted fabric used for the present invention may have an average monofilament fineness of 1 dtex or more and 10 dtex or less. Also usable are ultrafine fibers having a monofilament fineness of 0.001 dtex or more and 1 dtex or less.

[0063] The woven or knitted fabric used for the present invention may be a woven or knitted fabric containing composite fibers in which two or more polymers are combined in the form of side-by-side type or core-in-sheath type composite fiber (hereinafter occasionally referred to as "composite fiber of side-by-side type etc."). For example, in the case of a composite fiber of side-by-side type etc. containing two or more polymers having different intrinsic viscosities (IV), different inner strains are caused in the two components as the stress is concentrated on the component having a higher viscosity during drawing. Because of this inner strain, the higher-viscosity component will undergo a larger shrinkage due to a difference in the elastic recovery after the drawing step and a difference in heat shrinkage in the heat treatment step, and the strain is caused in monofilaments, thereby leading to the formation of coil-shaped crimps.

[0064] Furthermore, examples of the woven fabric that can be used for the present invention include plain, twill, or satin fabrics, and various other woven fabrics based on the woven structures thereof. On the other hand, examples of the knitted fabric include those produced by warp knitting, weft knitting (such as tricot), or lacemaking, and various other knitted fabrics based on the knitted structures thereof. Of these, woven fabrics are preferred from the viewpoint of workability, and plain weave fabrics are particularly preferred from the viewpoint of cost.

(c) A step for adding a water soluble resin

[0065] In the case of the production of a sheet-shaped item including the aforementioned fiber entanglement that contains an elastomeric polymer in the interior thereof, it is preferable that the elastomeric polymer is substantially absent inside the fiber bundles of ultrafine fibers in a nonwoven fabric (fiber entanglement) formed of entangled fiber bundles of ultrafine fiber so that the surface of the resulting sheet-shaped item has a dense and uniform fiber distribution. If the elastomeric polymer is present inside the fiber bundles, the elastomeric polymer must be adhered to the ultrafine fibers. As a result, surface fibers will be easily torn off during the buffing step and a nap layer will not be formed easily.

[0066] To produce a structure in which the elastomeric polymer is substantially absent inside the fiber bundles of ultrafine fibers, a preferred method, for example, is to perform a step for adding a water soluble resin to a nonwoven fabric of ultrafine fiber-generating type islands-in-the-sea composite fibers prior to the step for adding an elastomeric polymer. By incorporating this step for adding a water soluble resin, the surfaces of the fibers contained in the fiber bundles of ultrafine fibers and those contained in the woven or knitted fabric will be protected by the water soluble resin, and the surface regions where the fibers are in direct contact with the elastomeric polymer will be located discontinuously, instead of continuously, on the surfaces of the fibers contained in the fiber bundles of ultrafine fibers and those contained in the woven or knitted fabric, thus serving to maintain an appropriate adhesion area. The time point of applying the water soluble resin may be either before or after the ultrafine fiber-generating treatment step, which will be described later, as long as it is before adding the elastomeric polymer.

[0067] Examples of the water soluble resin include polyvinyl alcohol, polyethylene glycol, saccharide, and starch. Of these, polyvinyl alcohols having a saponification degree of 80% or more are preferred.

[0068] A preferred method is adding polyvinyl alcohol to protect most of the circumferential surface of each fiber, then dissolving and removing the sea component of the islands-in-the-sea composite fibers using a solvent that cannot dissolve polyvinyl alcohol, subsequently impregnating them with a solution of an elastomeric polymer, coagulating them in water or in an aqueous organic solvent solution, and removing the polyvinyl alcohol.

[0069] Here, the amount of polyvinyl alcohol added preferably accounts for 0.1 mass% or more and 70 mass% or less relative to the mass of the fibers contained in the nonwoven fabric.

(d) A step for generating ultrafine fibers

[0070] In the case where islands-in-the-sea composite fibers are used as ultrafine fiber-generating fibers, the step for generating ultrafine fibers from the ultrafine fiber-generating fibers by, for example, dissolving and removing the sea component from the islands-in-the-sea composite fibers is carried out either before or after the steps for adding an elastomeric polymer and a silicone-based lubricant, which will be described later, and either before or after the buffing step, which will be described later.

[0071] The aforementioned solvent used for dissolving the sea component is an organic solvent such as toluene and trichloroethylene when the sea component is a polyolefin such as polyethylene, polystyrene, etc. An aqueous alkali solution of sodium hydroxide or the like can be used when the sea component is, for instance, polylactic acid or copolymerized polyester.

[0072] This step can be carried out by immersing the fiber entanglement of ultrafine fiber-generating fibers in a solvent as listed above, followed by squeezing the liquid.

[0073] Useful instruments for this step include continuous dyeing machine, vibro washer type sea remover, jet dyeing machine, wins dyeing machine, and jigger dyeing machine.

(e) A step for adding an elastomeric polymer

[0074] In addition, the elastomeric polymer may also be added to the interior of the aforementioned fiber entanglement or to the interior of the fiber entanglement integrated with a reinforcing layer to form a stack.

[0075] The polyurethane-based elastomer used for the present invention is a polyurethane-based elastomer dissolved in a solvent or a water-dispersible polyurethane-based elastomer. Useful examples include organic solvent-type polyurethane resin (Crisvon (registered trademark) MP-812 NB, manufactured by DIC Corporation) and water-dispersible polyurethane resin (Hydran (registered trademark) WLI-602, manufactured by DIC Corporation).

[0076] When the polyurethane-based elastomer used is an organic solvent-type one, it is preferable to apply the wet coagulation technique that is designed to realize coagulation by immersion in water. When the polyurethane-based elastomer used is a water-dispersible polyurethane, it is preferable to apply the steam coagulation technique. When using a water-dispersible polyurethane-based elastomer, it is preferably one having heat-sensitive coagulation property. If the water-dispersible polyurethane-based elastomer used does not have heat-sensitive coagulation property, migration occurs to cause concentration on the surface layer of the fiber entanglement when the solution of the polyurethane-based elastomer is subjected to dry coagulation, and the resulting sheet-shaped item containing the polyurethane-based elastomer tends to harden.

[0077] Here, heat-sensitive coagulation is a property such that as a solution of a polyurethane-based elastomer is heated, the solution of a polyurethane-based elastomer decreases in flowability and starts to coagulate after reaching a certain temperature (heat-sensitive coagulation temperature).

[0078] The heat-sensitive coagulation temperature of a solution of a water-dispersible polyurethane-based elastomer is preferably 40°C or higher and 90°C or lower. If the heat-sensitive coagulation temperature is adjusted to 40°C or higher, the solution of the polyurethane-based elastomer will be highly stable during storage, making it possible to restrict the sticking of the polyurethane-based elastomer to the machine during operation. On the other hand, if the heat-sensitive coagulation temperature is adjusted to 90°C or lower, the migration of the polyurethane-based elastomer in a fiber entanglement can be restrained, allowing it to be localized in the interior.

[0079] In order to adjust the heat-sensitive coagulation temperature as stated above, a heat-sensitive coagulation agent may be added as appropriate. Examples of the heat-sensitive coagulation agent include inorganic salts such as sodium sulfate, magnesium sulfate, calcium sulfate, and calcium chloride; and radical reaction initiators such as sodium persulfate, potassium persulfate, ammonium persulfate, azobisisobutyronitrile, and benzoyl peroxide.

[0080] There are no specific limitations on the wet coagulation temperature when using a solvent-type polyurethane-based elastomer. In the case of a water-dispersible polyurethane-based elastomer, furthermore, it is only required to be higher than the heat-sensitive coagulation temperature of the polyurethane-based elastomer and it is preferably, for example, 40°C or higher and 100°C or lower. By adjusting the temperature of wet coagulation in hot water to 40°C or higher, more preferably 80°C or higher, the time required for the coagulation of the polyurethane-based elastomer can be shortened to further restrain its migration.

[0081] The temperature of steam coagulation is only required to be equal to or higher than the heat-sensitive coagulation temperature of the water-dispersible polyurethane-based elastomer, and it is preferably, for example, 40°C or higher and and 200°C or lower. By adjusting the temperature of steam coagulation to 40°C or higher, more preferably 80°C or higher, the time required for the coagulation of the polyurethane-based elastomer can be shortened to further restrain its migration. On the other hand, by adjusting the temperature of steam coagulation to 200°C or lower, more preferably 160°C or lower, thermal degradation of the polyurethane-based elastomer can be prevented.

[0082] Polyurethane-based elastomers preferred for the present invention include those polyurethane-based elastomers that can be obtained by reaction of a polymer diol, an organic diisocyanate, and a chain extender.

[0083] Examples of the above polymer diol include polycarbonate-based diols, polyester-based diols, polyether-based diols, silcone-based diols, and fluorine-based diols, as well as copolymers of combinations thereof. In particular, the use of a polycarbonate-based diol or a polyether-based diol is preferred from the viewpoint of hydrolysis resistance, and the use of a polycarbonate-based diol is preferred from the viewpoint of abrasion resistance.

[0084] A polycarbonate-based diol as described above can be produced, for example, through ester exchange reaction between alkylene glycol and carbonic ester or through reaction of phosgene or a chloroformic ester with alkylene glycol.

[0085] For example, useful alkylene glycols include linear alkylene glycols such as ethylene glycol, propylene glycol, 1,4-butane diol, 1,5-pentane diol, 1,6-hexane diol, 1,9-nonane diol, and 1,10-decane diol; branched alkylene glycols such as neopentyl glycol, 3-methyl-1,5-pentane diol, 2,4-diethyl-1,5-pentane diol, and 2-methyl-1,8-octane diol; alicyclic diols such as 1,4-cyclohexane diol; aromatic diols such as bisphenol A; and others such as glycerin, trimethylol propane, and pentaerythritol. For the present invention, each of these diols may be either a polycarbonate-based diol that is produced from a single alkylene glycol or a copolymerized polycarbonate-based diol that is produced from two or more types of alkylene glycols.

[0086] Examples of such polyester-based diols include polyester diols produced by condensing one of various low molecular weight polyols and a polybasic acid.

[0087] For example, one or a plurality selected from the following can be used as the low molecular weight polyols described above: ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,3-butane diol, 1,4-butane diol, 2,2-dimethyl-1,3-propane diol, 1,6-hexane diol, 3-methyl-1,5-pentane diol, 1,8-octane diol, diethylene glycol, triethylene glycol, dipropylene glycol, tripropylene glycol, cyclohexane-1,4-diol, and cyclohexane-1,4-dimethanol.

[0088] In addition, an adduct formed by adding one of various alkylene oxides to bisphenol A is also usable.

[0089] Furthermore, for example, one or a plurality selected from the following can be used as the polybasic acid described above: succinic acid, maleic acid, adipic acid, glutaric acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, dodecane dicarboxylic acid, phthalic acid, isophthalic acid, terephthalic acid, and hexahydroisophthalic acid.

[0090] Examples of polyether-based diols that can be used for the present invention include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and copolymerized diols that are formed by combining these substances.

[0091] It is preferable for the polymer diol to have a number average molecular weight in the range of 500 or more and 4,000 or less in the case where the molecular weight of the polyurethane-based elastomer is constant. If the number average molecular weight is preferably adjusted to 500 or more, more preferably 1,500 or more, it serves to prevent the resulting sheet-shaped item from becoming stiff. In addition, a number average molecular weight of 4,000 or less, preferably 3,000 or less, allows the polyurethane-based elastomer to maintain strength.

[0092] Examples of organic diisocyanates that can be used for the present invention include aliphatic diisocyanates such as hexamethylene diisocyanate, dicyclohexylmethane diisocyanate, isophorone diisocyanate, and xylylene diisocyanate; and aromatic diisocyanates such as diphenylmethane diisocyanate and tolylene diisocyanate, which may be used in combination.

[0093] Preferred chain extenders include amine-based chain extenders such as ethylene diamine and methylene bisaniline; and diol-based chain extenders such as ethylene glycol. In addition, a polyamine that is obtained by reacting polyisocyanate and water can also be used as a chain extender.

[0094] The polyurethane used for the present invention may be employed in combination with a crosslinking agent with the aim of improving water resistance, abrasion resistance, hydrolysis resistance, etc. The crosslinking agent may be either an external crosslinking agent to be added to the polyurethane-based elastomer as a third component or an internal crosslinking agent that introduces a reaction point to act as a crosslinking structure in the polyurethane molecular structure in advance. The use of an internal crosslinking agent is preferred because crosslinking points can be formed uniformly in the polyurethane molecular structure, thereby mitigating the decrease in flexibility.

[0095] A compound containing an isocyanate group, an oxazoline group, a carbodiimide group, an epoxy group, a melamine resin, or a silanol group can be used as such a crosslinking agent.

(f) A step for adding a silicone-based lubricant

[0096] In the case of performing "(b) A step for adding a water soluble resin", that is, in the case of producing a sheet-shaped item including the aforementioned fiber entanglement that contains an elastomeric polymer in the interior thereof, it is preferable that a silicone-based lubricant is added to the sheet after coagulating the elastomeric polymer in the fiber entanglement impregnated therewith, so that it account for 0.01 mass% or more and 3.0 mass% or less relative to the mass of the sheet-shaped item. If added to 0.01 mass% or more, the silicone-based lubricant covers the surface of the coagulated elastomeric polymer to ensure easy separation between the elastomeric polymer and ultrafine fibers in the nap layer formation step, which will be described later, thus serving for efficient dispersion of the ultrafine fibers to facilitate the formation of a uniform nap layer. On the other hand, if added to more than 3.0 mass%, the silicone acts for increasing slippage, making the formation of a uniform nap layer difficult. It is more preferable that the silicone-based lubricant accounts for 0.1 mass% or more and 2.0 mass% or less relative to the mass of the sheet-shaped item. For example, SM7036EX, manufactured by Toray Coatex Co., Ltd., can serve as the silicone-based lubricant.

[0097] The available methods for adding a silicone-based lubricant include the method of impregnating the sheet with a silicone oil solution and the method of adding it by spraying, of which the method of impregnating the sheet with a silicone oil solution is preferred to ensure uniform addition.

[0098] It is preferable that the addition of silicone oil is performed immediately after coagulating the elastomeric polymer. In the case where polyurethane is coagulated in water, for example, it is preferable that the addition of silicone oil is performed before the heating for drying moisture.

(g) A step for cutting in half

[0099] In the case where an elastomeric polymer and/or silicone-based lubricant is added to the fiber entanglement after the ultrafine fiber-developing step, the sheet-shaped item may be cut in half, or cut into more than two parts, in the thickness direction after that step. Doing this is preferred because sheet-shaped items can be produced more efficiently.

(h) A step for forming a nap layer

[0100] The sheet-shaped item according to the present invention has a base material layer and a nap layer as described above, and the nap layer includes a nap formed only of the ultrafine fibers and covers at least one surface of the sheet-shaped item.

[0101] Such a nap is generally produced by buffing. The buffing technique referred to herein is preferably performed by, for example, grinding the sheet surface of an ultrafine fiber nonwoven fabric using a sandpaper or a roll sander. In particular, the use of a sandpaper for raising a sheet surface serves to produce a uniform, dense nap.

[0102] As described above, the addition of a silicone-based lubricant to the sheet-shaped item before the raising step serves to ensure easy separation between the elastomeric polymer and the ultrafine fibers and develop a glossy, thick nap. It also serves to protect the ultrafine fiber surface, develop fusion bonding inhibiting effect, and improve the fiber-opening property of the fibers due to its lubricating effect. The addition of an antistatic agent before raising the sheet-shaped item is also preferred because it works to prevent grinding powder generated from the ground sheet-shaped item from depositing on the sandpaper.

[0103] To allow the napped surface to have a uniform, dense nap with a high coverage of napped fibers, the surface of the fiber entanglement, such as nonwoven fabric, or the entity of the fiber entanglement may be treated in a wet state in water or a chemical solution, but it is preferable that the sheet is in a dry state in the raising step. If the sheet is in a wet state, the sandpaper will also become wet and suffer breakage during continuous processing, resulting in a shortened paper life. In addition, drying will be necessary after the raising step in order to remove water, which is not preferred because it will lead to a decrease in production efficiency.

[0104] A smaller grinding load is preferred in order to form a uniform nap over the surface of the sheet. A good method for decreasing the grinding load is to adopt a multi-stage buffing step that includes at least two or more, preferably three or more, buffing stages, and furthermore, a highly uniform nap can be produced by using sandpapers of increasingly finer grits or of the same grit number in the multiple stages. Regarding the grit number of sandpaper, it is preferable that the sandpaper to be used has a grit P in the range of 120 to 600 as specified in JIS R6252 (2006) "Polishing paper".

[0105] To allow the ultrafine fibers in the nap layer of a sheet surface to have a CV in the average fiber length of ultrafine fibers of 30% or less, it is preferable that the grinding rate in the buffing step is 20 g/m² or more and 250 g/m² or less, preferably 30 g/m² or more and 100 g/m² or less. A grinding rate of less than 20 g/m² leads to a large variation in the fiber length of ultrafine fibers in the nap layer and a large proportion of incident light to the napped surface undergoing diffuse reflection, resulting in an insufficient gloss. In addition, there will occur defects such as exposed polyurethane in the surface.

(i) Dyeing step

[0106] The sheet-shaped item may be dyed to suit particular needs. A preferred dyeing method for the sheet-shaped item is the use of a jet dyeing machine because such a machine serves to knead the sheet-shaped item while dyeing it so that the sheet-shaped item is softened. The elastomeric polymer may degrade if the dyeing temperature for the sheet-shaped item is too high, whereas dyeing may not be achieved completely if it is too low, and therefore, it is preferable to use an appropriate temperature to suit the type of the fiber. In general, the dyeing temperature is preferably 80°C or higher and 150°C or lower, more preferably 110°C or higher and 130°C or lower.

[0107] An appropriate dye may be selected to suit the type of the fibers contained in the sheet-shaped item. For example, a dispersed dye may be used for a polyester-based fiber, and an acidic dye or a metal-containing dye may be used for a polyamide-based fiber. Moreover, a combination of these dyes may also be employed.

[0108] It is also preferable that a dyeing auxiliary is used in the step for dyeing the sheet-shaped item. The use of a dyeing auxiliary can serve to improve the uniformity and reproducibility of dyeing. In addition, finishing with a softening agent (such as silicone), an antistatic agent, a water repellent, a flame retardant, a light resistance agent, an antimicrobial agent, etc. may be performed simultaneously with dyeing in the same bath or after the dyeing step.

[0109] Here, it is preferable that the sheet-shaped item according to the present invention is free of partial crimped portions or resin-coated portions in the napped surface. Here, such partial crimped portions include hot embossed portions. Surface irregularities can be formed on the surface of the sheet-shaped item by partial crimping or resin coating, but such treatment can create portions where no nap is present on the surface. In such nap-free portions, it may be impossible to develop denseness and gloss as intended by the present invention. However, when the intended uses merely require partial presence of a good texture, an appropriate treatment as described above may be conducted as necessary.

[0110] The apparent density of the sheet-shaped item according to the present invention is preferably 0.100 g/cm³ or more and 0.900 g/cm³ or less, more preferably 0.200 g/cm³ or more and 0.700 g/cm³ or less. An apparent density of 0.100 g/cm³ or more allows the sheet-shaped item to have good denseness and mechanical property, whereas an apparent density of 0.900 g/cm³ or less prevents its texture from becoming stiff.

[0111] For the present invention, the apparent density of the sheet-shaped item should be measured as described below:

(A) Measure the metsuke (weight per unit surface area) of the sheet-shaped item by the method specified in JIS L 1096 (2010) "Fabric test method for woven fabrics and knitted fabrics" 8.3.2. Specifically, two 20 cm × 20 cm test pieces sampled and separately subjected to mass measurement (g), and their arithmetic average was expressed in mass per m² (g/m²).

(B) Measure the thickness of the sheet-shaped item at five equally-spaced measuring points aligned in the width direction under a 10 kPa load using a thickness gauge (with a disk diameter of 9 mm or more) graduated at intervals of 0.01 mm, followed by calculating the arithmetic average.

(C) Calculate the apparent density by the equation given below from the metsuke and thickness of the sheet-shaped item determined in (A) and (B) and round off the calculation to the three decimal places.

[0112] It is preferable for the sheet-shaped item to have a thickness of 0.1 mm or more and 7 mm or less. A thickness of 0.1 mm or more, preferably 0.3 mm or more, allows the sheet-shaped item to have high morphological stability and dimensional stability. On the other hand, a thickness of 7 mm or less, preferably 5 mm or less, allows the sheet-shaped item to have high moldabililty.

[0113] The sheet-shaped item according to the present invention has an elegant appearance and very even texture to the touch and also has high abrasion resistance, thus serving suitably as material for clothes such as shirts, jackets, uppers and trims of various shoes including casual shoes, sports shoes, men's shoes, and women's shoes, bags, belts, wallets, and accessories of clothes such as buttons and pockets.

Examples

[0114] The sheet-shaped item according to the present invention will be described in more detail later with reference to Examples, although the present invention is not limited to these Examples. First, the evaluation methods and evaluation conditions used in Examples are described below. For the various properties, measurements were taken by the methods described above unless otherwise specified.

<Evaluation methods>

(1) Average single fiber diameter

[0115] A scanning electron microscope (VE-7800, manufactured by Keyence Corporation) was used for measuring the average single fiber diameter.

(2) Intrinsic viscosity (IV) of polymer

[0116] A 0.8 g amount of a specimen polymer was dissolved in 10 mL of o-chlorophenol (hereinafter occasionally abbreviated as OCP) and the relative viscosity ηr at a temperature of 25°C was determined using an Ostwald viscometer and the equation given below, followed by calculating the intrinsic viscosity (IV) by the equation given below:

• ηr = η/η₀ = (t×d) / (t₀×d₀)
• intrinsic viscosity (IV) = 0.0242η_r + 0.2634

(Here, η is the viscosity of the polymer solution; η₀ is the viscosity of the OCP; t is drop time (seconds) of the solution; d is the density (g/cm³) of the solution; t₀ is the drop time (seconds) of the OCP; and do is the density (g/cm³) of the OCP.)

(3) Melt flow rate (MFR) of polymer

[0117] The quantity (g) of resin extruded in 10 minutes was measured according to the MFR measuring method specified in ISO 1133 (2005) "Plastics - determination of the melt mass-flow rate (MFR) and the melt volume-flow rate (MVR) of thermoplastics". The measuring run was performed 3 times repeatedly and the arithmetic average of the measurements was adopted as the MFR (g/10 min).

(4) Average fiber length (µm) of ultrafine fibers in nap layer and CV (%) in average fiber length of ultrafine fibers

[0118] A VE-7800 scanning electron microscope manufactured by Keyence Corporation was used for measuring the average fiber length (µm) of ultrafine fibers and CV (%) in average fiber length of ultrafine fibers.

(5) Surface coverage (%) of ultrafine fibers in nap layer

[0119] AVE-7800 scanning electron microscope manufactured by Keyence Corporation and ImageJ image processing software were used for measuring the surface coverage (%).

(6) Appearance quality

[0120] The quality of a sample was rated according to the three stage (A, B, and C) criterion shown below based on visual inspection and sensory evaluation by a total of 20 raters made up of 10 healthy male adults and 10 healthy female adults. The rating given by the greatest number of raters was taken as the final rating in external appearance quality. A sample judged to be acceptable was given the rating of A.

A: Fibers are dispersed favorably and have high denseness and gloss.

B: Fibers are dispersed favorably, but have slightly inferior denseness and gloss.

C: Fibers are very poorly dispersed overall, and have inferior denseness and gloss.

<Abbreviations of chemical substances>

[0121] 

• PU: polyurethane
• DMF: N,N-dimethyl formamide
• PET: polyethylene terephthalate
• PVA: polyvinyl alcohol

[Example 1]

[0122] Polyethylene terephthalate (PET) having an intrinsic viscosity (IV) of 0.718, used as island component, and polystyrene having an MFR of 18 g/10 minutes, used as sea component, were melt-spun through a spinneret designed for 36-island islands-in-the-sea composite fiber with an island/sea mass ratio of 55/45, followed by drawing, crimping, and subsequent cutting to 51 mm to prepare raw stock of islands-in-the-sea composite fiber having a monofilament fineness of 3.1 dtex.

[0123] This raw stock of islands-in-the-sea composite fiber was processed by carding and cross-wrapping to provide a laminated web, which was then needle-punched at a punch density of 600 punches/cm² and further needle-punched at a punch density of 2,900 punches/cm² to produce a sheet.

[0124] This sheet was shrunk in hot water at 96°C and then impregnated with a 10% aqueous solution of PVA, followed by drying in hot air at a temperature of 110°C for 10 minutes to provide a sheet in which the mass of the PVA accounted for 30 mass% of the mass of the sheet. This sheet was immersed in trichloroethylene to dissolve and remove the sea component to provide a sea-free sheet containing ultrafine fibers entangled in a woven fabric. SEM observation of a cross section of the sea-free sheet showed that it had an average single fiber diameter of 2.1 µm.

[0125] This sea-free sheet containing ultrafine fibers was immersed in a solution of polycarbonate-based polyurethane in DMF with a solid content adjusted to 12%, followed by coagulating the polyurethane in an aqueous solution with a DMF concentration of 30%. Subsequently, the PVA and DMF were removed in hot water and then the sheet was impregnated with a silicone oil emulsion liquid having a concentration adjusted to 1 mass%, followed by adding a silicone-based lubricant in such a manner that it accounted for 0.5 mass% relative to the total of the mass of the fibers and the mass of the polyurethane. Subsequently, drying was performed in hot air at 110°C for 10 minutes to provide a sheet in which the mass of the polyurethane accounted for 30 mass% relative to the mass of the island component of the sheet (total mass of the ultrafine fibers and the above-mentioned woven or knitted fabric).

[0126] Then, the resulting sheet was cut in half in the thickness direction and the cut surface of the half-cut sheet was ground at a rate of 100 g/m² using endless sandpaper belts having sandpaper grit numbers of 180, 180, and 240 to form a napped surface.

[0127] The sheet thus obtained was dyed using a jet dyeing machine under the condition of 110°C and then dried by a drying machine to produce a sheet-shaped item having a thickness of 0.5 mm and an apparent density of 0.360 g/cm³.

[0128] The resulting sheet-shaped item had an average fiber length of ultrafine fibers in the nap layer of 370 µm, CV in the average fiber length of ultrafine fibers of 15%, surface coverage of ultrafine fibers in the nap layer of 80%, number of times torn with a Schiefer type abrasion tester of 65 times/0.10 mm, and appearance quality rating of A.

[Example 2]

[0129] Polyethylene terephthalate (PET) having an intrinsic viscosity (IV) of 0.718, used as island component, and polystyrene having an MFR of 18 g/10 minutes, used as sea component, were melt-spun through a spinneret designed for 36-island islands-in-the-sea composite fiber with an island/sea mass ratio of 55/45, followed by drawing, crimping, and subsequent cutting to 51 mm to prepare raw stock of islands-in-the-sea composite fiber having a monofilament fineness of 3.1 dtex.

[0130] This raw stock of islands-in-the-sea composite fiber was processed by carding and cross-wrapping to provide a laminated web, which was then needle-punched at a punch density of 600 punches/cm² and further needle-punched at a punch density of 2,900 punches/cm² to produce a sheet.

[0131] This sheet was shrunk in hot water at 96°C and then impregnated with a 10% aqueous solution of PVA, followed by drying in hot air at a temperature of 110°C for 10 minutes to provide a sheet in which the mass of the PVA accounted for 25 mass% of the mass of the sheet. This sheet was immersed in trichloroethylene to dissolve and remove the sea component to provide a sea-free sheet containing ultrafine fibers entangled in a woven fabric. SEM observation of a cross section of the sea-free sheet showed that it had an average single fiber diameter of 2.1 µm.

[0132] This sea-free sheet containing ultrafine fibers was immersed in a solution of polycarbonate-based polyurethane in DMF with a solid content adjusted to 10%, followed by coagulating the polyurethane in an aqueous solution with a DMF concentration of 30%. Subsequently, the PVA and DMF were removed in hot water and then the sheet was impregnated with a silicone oil emulsion liquid having a concentration adjusted to 1 mass%, followed by adding a silicone-based lubricant in such a manner that it accounted for 0.2 mass% relative to the total of the mass of the fibers and the mass of the polyurethane. Subsequently, drying was performed in hot air at 110°C for 10 minutes to provide a sheet in which the mass of the polyurethane accounted for 25 mass% relative to the mass of the island component of the sheet (total mass of the ultrafine fibers and the above-mentioned woven or knitted fabric).

[0133] Then, the resulting sheet was cut in half in the thickness direction and the cut surface of the half-cut sheet was ground at a rate of 60 g/m² using endless sandpaper belts having sandpaper grit numbers of 180, 180, and 240 to form a napped surface.

[0134] The sheet thus obtained was dyed using a jet dyeing machine under the condition of 110°C and then dried by a drying machine to produce a sheet-shaped item having a thickness of 0.5 mm and an apparent density of 0.360 g/cm³.

[0135] The resulting sheet-shaped item had an average fiber length of ultrafine fibers in the nap layer of 260 µm, CV in the average fiber length of ultrafine fibers of 20%, surface coverage of ultrafine fibers in the nap layer of 73%, number of times torn with a Schiefer type abrasion tester of 40 times/0.10 mm, and appearance quality rating of A.

[Example 3]

[0136] Polyethylene terephthalate (PET) having an intrinsic viscosity (IV) of 0.718, used as island component, and polystyrene having an MFR of 18 g/10 minutes, used as sea component, were melt-spun through a spinneret designed for 36-island islands-in-the-sea composite fiber with an island/sea mass ratio of 55/45, followed by drawing, crimping, and subsequent cutting to 51 mm to prepare raw stock of islands-in-the-sea composite fiber having a monofilament fineness of 3.1 dtex.

[0137] This raw stock of islands-in-the-sea composite fiber was processed by carding and cross-wrapping to provide a laminated web, which was then needle-punched at a punch density of 600 punches/cm² and further needle-punched at a punch density of 2,900 punches/cm² to produce a sheet.

[0138] This sheet was shrunk in hot water at 96°C and then impregnated with a 15% aqueous solution of PVA, followed by drying in hot air at a temperature of 110°C for 10 minutes to provide a sheet in which the mass of the PVA accounted for 40 mass% of the mass of the sheet. This sheet was immersed in trichloroethylene to dissolve and remove the sea component to provide a sea-free sheet containing ultrafine fibers entangled in a woven fabric. SEM observation of a cross section of the sea-free sheet showed that it had an average single fiber diameter of 2.1 µm.

[0139] This sea-free sheet containing ultrafine fibers was immersed in a solution of polycarbonate and polyester-based polyurethane in DMF with a solid content adjusted to 9.5%, followed by coagulating the polyurethane in an aqueous solution with a DMF concentration of 30%. Subsequently, the PVA and DMF were removed in hot water and then the sheet was impregnated with a silicone oil emulsion liquid having a concentration adjusted to 1 mass%, followed by adding a silicone-based lubricant in such a manner that it accounted for 0.6 mass% relative to the total of the mass of the fibers and the mass of the polyurethane. Subsequently, drying was performed in hot air at 110°C for 10 minutes to provide a sheet in which the mass of the polyurethane accounted for 23 mass% relative to the mass of the island component of the sheet (total mass of the ultrafine fibers and the above-mentioned woven or knitted fabric).

[0140] Then, the resulting sheet was cut in half in the thickness direction and the cut surface of the half-cut sheet was ground at a rate of 70 g/m² using endless sandpaper belts having sandpaper grit numbers of 180, 180, and 240 to form a napped surface.

[0141] The sheet thus obtained was dyed using a jet dyeing machine under the condition of 110°C and then dried by a drying machine to produce a sheet-shaped item having a thickness of 0.5 mm and an apparent density of 0.360 g/cm³.

[0142] The resulting sheet-shaped item had an average fiber length of ultrafine fibers in the nap layer of 400 µm, CV in the average fiber length of ultrafine fibers of 10%, surface coverage of ultrafine fibers in the nap layer of 90%, number of times torn with a Schiefer type abrasion tester of 45 times/0.10 mm, and appearance quality rating of A.

[Example 4]

[0143] Nylon 6 having an MFR of 58.3 g/10 minutes, used as island component, and polystyrene copolymerized with 22 mol% 2-ethylhexyl acrylate (Co-PSt) having an MFR of 300 g/10 minutes, used as sea component, were melt-spun through a spinneret designed for 36-island islands-in-the-sea composite fiber with an island/sea mass ratio of 30/70, followed by drawing, crimping, and subsequent cutting to 51 mm to prepare raw stock of islands-in-the-sea composite fiber having a monofilament fineness of 24 µm.

[0144] This raw stock of islands-in-the-sea composite fiber was processed by carding and cross-wrapping to provide a laminated web, which was then needle-punched at a punch density of 600 punches/cm² and further needle-punched at a punch density of 2,900 punches/cm² to produce a sheet. This sheet was shrunk in hot water at 85°C and then impregnated with a 15% aqueous solution of PVA, followed by drying in hot air at a temperature of 110°C for 10 minutes to provide a sheet in which the mass of the PVA accounted for 50 mass% of the mass of the sheet. This sheet was immersed in trichloroethylene to dissolve and remove the sea component to provide a sea-free sheet containing ultrafine fibers entangled in a woven fabric. SEM observation of a cross section of the sea-free sheet showed that it had an average single fiber diameter of 1.0 µm.

[0145]  This sea-free sheet containing ultrafine fibers was immersed in a solution of polyether and polyester-based polyurethane in DMF with a solid content adjusted to 9%, followed by coagulating the polyurethane in an aqueous solution with a DMF concentration of 30%. Subsequently, the PVA and DMF were removed in hot water and then the sheet was impregnated with a silicone oil emulsion liquid having a concentration adjusted to 0.5 mass%, followed by adding a silicone-based lubricant in such a manner that it accounted for 0.1 mass% relative to the total of the mass of the fibers and the mass of the polyurethane. Subsequently, drying was performed in hot air at 100°C for 10 minutes to provide a sheet in which the mass of the polyurethane accounted for 20 mass% relative to the mass of the island component of the sheet (total mass of the ultrafine fibers and the above-mentioned woven or knitted fabric).

[0146] Then, the resulting sheet was cut in half in the thickness direction and the cut surface of the half-cut sheet was ground at a rate of 30 g/m² using endless sandpaper belts having sandpaper grit numbers of 150, 180, and 180 to form a napped surface.

[0147] The sheet thus obtained was dyed using a jet dyeing machine under the condition of 85°C and then dried by a drying machine to produce a sheet-shaped item having a thickness of 0.5 mm and an apparent density of 0.300 g/cm³.

[0148] The resulting sheet-shaped item had an average fiber length of ultrafine fibers in the nap layer of 280 µm, CV in the average fiber length of ultrafine fibers of 28%, surface coverage of ultrafine fibers in the nap layer of 62%, number of times torn with a Schiefer type abrasion tester of 20 times/0.10 mm, and appearance quality rating of A.

[Example 5]

[0149] Nylon 6 having an MFR of 58.3 g/10 minutes, used as island component, and polystyrene copolymerized with 22 mol% 2-ethylhexyl acrylate (Co-PSt) having an MFR of 300 g/10 minutes, used as sea component, were melt-spun through a spinneret designed for 280-island islands-in-the-sea composite fiber with an island/sea mass ratio of 30/70, followed by drawing, crimping, and subsequent cutting to 51 mm to prepare raw stock of islands-in-the-sea composite fiber having a monofilament fineness of 24 µm.

[0150] This raw stock of islands-in-the-sea composite fiber was processed by carding and cross-wrapping to provide a laminated web, which was then needle-punched at a punch density of 600 punches/cm² and further needle-punched at a punch density of 2,900 punches/cm² to produce a sheet. This sheet was shrunk in hot water at 85°C and then impregnated with a 12% aqueous solution of PVA, followed by drying in hot air at a temperature of 100°C for 10 minutes to provide a sheet in which the mass of the PVA accounted for 40 mass% of the mass of the sheet. This sheet was immersed in trichloroethylene to dissolve and remove the sea component to provide a sea-free sheet containing ultrafine fibers entangled in a woven fabric. SEM observation of a cross section of the sea-free sheet showed that it had an average single fiber diameter of 1.0 µm.

[0151] This sea-free sheet containing ultrafine fibers was immersed in a solution of polyether and polyester-based polyurethane in DMF with a solid content adjusted to 10%, followed by coagulating the polyurethane in an aqueous solution with a DMF concentration of 30%. Subsequently, the PVA and DMF were removed in hot water and then the sheet was impregnated with a silicone oil emulsion liquid having a concentration adjusted to 0.1 mass%, followed by adding a silicone-based lubricant in such a manner that it accounted for 0.01 mass% relative to the total of the mass of the fibers and the mass of the polyurethane. Subsequently, drying was performed in hot air at 110°C for 10 minutes to provide a sheet in which the mass of the polyurethane accounted for 35 mass% relative to the mass of the island component of the sheet (total mass of the ultrafine fibers and the above-mentioned woven or knitted fabric).

[0152] Then, the resulting sheet was cut in half in the thickness direction and the cut surface of the half-cut sheet was ground at a rate of 40 g/m² using endless sandpaper belts having sandpaper grit numbers of 150, 180, and 180 to form a napped surface.

[0153] The sheet thus obtained was dyed using a jet dyeing machine under the condition of 85°C and then dried by a drying machine to produce a sheet-shaped item having a thickness of 0.5 mm and an apparent density of 0.300 g/cm³.

[0154] The resulting sheet-shaped item had an average fiber length of ultrafine fibers in the nap layer of 260 µm, CV in the average fiber length of ultrafine fibers of 10%, surface coverage of ultrafine fibers in the nap layer of 70%, number of times torn with a Schiefer type abrasion tester of 30 times/0.10 mm, and appearance quality rating of A.

[Example 6]

[0155] Polyethylene terephthalate (PET) having an intrinsic viscosity (IV) of 0.718, used as island component, and polystyrene having an MFR of 18 g/10 minutes, used as sea component, were melt-spun through a spinneret designed for 50-island islands-in-the-sea composite fiber with an island/sea mass ratio of 80/20, followed by drawing, crimping, and subsequent cutting to 51 mm to prepare raw stock of islands-in-the-sea composite fiber having a monofilament fineness of 3.1 dtex.

[0156] This raw stock of islands-in-the-sea composite fiber was processed by carding and cross-wrapping to provide a laminated web, which was then needle-punched at a punch density of 600 punches/cm² and further needle-punched at a punch density of 2,900 punches/cm² to produce a sheet. This sheet was shrunk in hot water at 96°C and then impregnated with a 5% aqueous solution of PVA, followed by drying in hot air at a temperature of 110°C for 10 minutes to provide a sheet in which the mass of the PVA accounted for 30 mass% of the mass of the sheet. This sheet was immersed in trichloroethylene to dissolve and remove the sea component to provide a sea-free sheet containing ultrafine fibers entangled in a woven fabric. SEM observation of a cross section of the sea-free sheet showed that it had an average single fiber diameter of 7.0 µm.

[0157] This sea-free sheet containing ultrafine fibers was immersed in a solution of polycarbonate-based polyurethane in DMF with a solid content adjusted to 11%, followed by coagulating the polyurethane in an aqueous solution with a DMF concentration of 30%. Subsequently, the PVA and DMF were removed in hot water and then the sheet was impregnated with a silicone oil emulsion liquid having a concentration adjusted to 5 mass%, followed by adding a silicone-based lubricant in such a manner that it accounted for 2.0 mass% relative to the total of the mass of the fibers and the mass of the polyurethane. Subsequently, drying was performed in hot air at 110°C for 10 minutes to provide a sheet in which the mass of the polyurethane accounted for 40 mass% relative to the mass of the island component of the sheet (total mass of the ultrafine fibers and the above-mentioned woven or knitted fabric).

[0158] Then, the resulting sheet was cut in half in the thickness direction and the cut surface of the half-cut sheet was ground at a rate of 160 g/m² using endless sandpaper belts having sandpaper grit numbers of 120, 150, and 180 to form a napped surface.

[0159] The sheet thus obtained was dyed using a jet dyeing machine under the condition of 110°C and then dried by a drying machine to produce a sheet-shaped item having a thickness of 1.0 mm and an apparent density of 0.400 g/cm³.

[0160] The resulting sheet-shaped item had an average fiber length of ultrafine fibers in the nap layer of 350 µm, CV in the average fiber length of ultrafine fibers of 25%, surface coverage of ultrafine fibers in the nap layer of 65%, number of times torn with a Schiefer type abrasion tester of 80 times/0.10 mm, and appearance quality rating of A.

[Example 7]

[0161] Nylon 6 having an MFR of 58.3 g/10 minutes, used as island component, and polystyrene copolymerized with 22 mol% 2-ethylhexyl acrylate (Co-PSt) having an MFR of 300 g/10 minutes, used as sea component, were melt-spun through a spinneret designed for 100-island islands-in-the-sea composite fiber with an island/sea mass ratio of 30/70, followed by drawing, crimping, and subsequent cutting to 51 mm to prepare raw stock of islands-in-the-sea composite fiber having a monofilament fineness of 24 µm.

[0162] This raw stock of islands-in-the-sea composite fiber was processed by carding and cross-wrapping to provide a laminated web, which was then needle-punched at a punch density of 600 punches/cm² and further needle-punched at a punch density of 2,900 punches/cm² to produce a sheet. This sheet was shrunk in hot water at 85°C and then impregnated with a 20% aqueous solution of PVA, followed by drying in hot air at a temperature of 100°C for 10 minutes to provide a sheet in which the mass of the PVA accounted for 60 mass% of the mass of the sheet. This sheet was immersed in trichloroethylene to dissolve and remove the sea component to provide a sea-free sheet containing ultrafine fibers entangled in a woven fabric. SEM observation of a cross section of the sea-free sheet showed that it had an average single fiber diameter of 1.0 µm.

[0163] This sea-free sheet containing ultrafine fibers was immersed in a solution of polyether and polyester-based polyurethane in DMF with a solid content adjusted to 9%, followed by coagulating the polyurethane in an aqueous solution with a DMF concentration of 30%. Subsequently, the PVA and DMF were removed in hot water and then the sheet was impregnated with a silicone oil emulsion liquid having a concentration adjusted to 3 mass%, followed by adding a silicone-based lubricant in such a manner that it accounted for 1.0 mass% relative to the total of the mass of the fibers and the mass of the polyurethane. Subsequently, drying was performed in hot air at 110°C for 10 minutes to provide a sheet in which the mass of the polyurethane accounted for 5 mass% relative to the mass of the island component of the sheet (total mass of the ultrafine fibers and the above-mentioned woven or knitted fabric).

[0164] Then, the resulting sheet was cut in half in the thickness direction and the cut surface of the half-cut sheet was ground at a rate of 50 g/m² using endless sandpaper belts having sandpaper grit numbers of 150 and 180 to form a napped surface.

[0165] The sheet thus obtained was dyed using a jet dyeing machine under the condition of 85°C and then dried by a drying machine to produce a sheet-shaped item having a thickness of 0.5 mm and an apparent density of 0.300 g/cm³.

[0166] The resulting sheet-shaped item had an average fiber length of ultrafine fibers in the nap layer of 400 µm, CV in the average fiber length of ultrafine fibers of 25%, surface coverage of ultrafine fibers in the nap layer of 99%, number of times torn with a Schiefer type abrasion tester of 10 times/0.10 mm, and appearance quality rating of A.

[Example 8]

[0167] Polyethylene terephthalate (PET) having an intrinsic viscosity (IV) of 0.718, used as island component, and polystyrene having an MFR of 18 g/10 minutes, used as sea component, were melt-spun through a spinneret designed for 36-island islands-in-the-sea composite fiber with an island/sea mass ratio of 55/45, followed by drawing, crimping, and subsequent cutting to 51 mm to prepare raw stock of islands-in-the-sea composite fiber having a monofilament fineness of 3.1 dtex.

[0168] This raw stock of islands-in-the-sea composite fiber was processed by carding and cross-wrapping to provide a laminated web, which was then needle-punched at a punch density of 600 punches/cm² and further needle-punched at a punch density of 2,900 punches/cm² to produce a sheet.

[0169] This sheet was shrunk in hot water at 96°C and then immersed in trichloroethylene to dissolve and remove the sea component to provide a sea-free sheet containing ultrafine fibers entangled in a woven fabric. SEM observation of a cross section of the sea-free sheet showed that it had an average single fiber diameter of 2.1 µm.

[0170] Then, the resulting sheet was cut in half in the thickness direction and the cut surface of the half-cut sheet was ground at a rate of 20 g/m² using endless sandpaper belts having sandpaper grit numbers of 180, 180, and 240 to form a napped surface.

[0171] The sheet thus obtained was dyed using a jet dyeing machine under the condition of 110°C and then dried by a drying machine to produce a sheet-shaped item having a thickness of 0.5 mm and an apparent density of 0.360 g/cm³.

[0172] The resulting sheet-shaped item had an average fiber length of ultrafine fibers in the nap layer of 250 µm, CV in the average fiber length of ultrafine fibers of 29%, surface coverage of ultrafine fibers in the nap layer of 62%, number of times torn with a Schiefer type abrasion tester of 7 times/0.10 mm, and appearance quality rating of A.

[Example 9]

[0173] Polyethylene terephthalate (PET) having an intrinsic viscosity (IV) of 0.718, used as island component, and polystyrene having an MFR of 18 g/10 minutes, used as sea component, were melt-spun through a spinneret designed for 16-island islands-in-the-sea composite fiber with an island/sea mass ratio of 80/20, followed by drawing, crimping, and subsequent cutting to 51 mm to prepare raw stock of islands-in-the-sea composite fiber having a monofilament fineness of 3.1 dtex.

[0174] This raw stock of islands-in-the-sea composite fiber was processed by carding and cross-wrapping to provide a laminated web, which was then needle-punched at a punch density of 600 punches/cm² and further needle-punched at a punch density of 2,900 punches/cm², followed by combining the web with a plain weave fabric (in which a multifilament (84 dtex, 72 filaments) with a twist count of 2,500 T/m formed of a single fiber formed of single component with an intrinsic viscosity (IV) of 0.65 is used as warp and weft with a weaving density of 97 ends/2.54 cm × 76 picks/2.54 cm) to provide a sheet. This sheet was shrunk in hot water at 96°C and then impregnated with a 5% aqueous solution of PVA, followed by drying in hot air at a temperature of 110°C for 10 minutes to provide a sheet in which the mass of the PVA accounted for 20 mass% of the mass of the sheet. This sheet was immersed in trichloroethylene to dissolve and remove the sea component to provide a sea-free sheet containing ultrafine fibers entangled in a woven fabric. SEM observation of a cross section of the sea-free sheet showed that it had an average single fiber diameter of 4.4 µm.

[0175] This sea-free sheet containing ultrafine fibers was immersed in a solution of polycarbonate-based polyurethane in DMF with a solid content adjusted to 11%, followed by coagulating the polyurethane in an aqueous solution with a DMF concentration of 30%. Subsequently, the PVA and DMF were removed in hot water and then the sheet was impregnated with a silicone oil emulsion liquid having a concentration adjusted to 1 mass%, followed by adding a silicone-based lubricant in such a manner that it accounted for 0.2 mass% relative to the total of the mass of the fibers and the mass of the polyurethane. Subsequently, drying was performed in hot air at 110°C for 10 minutes to provide a sheet in which the mass of the polyurethane accounted for 27 mass% relative to the mass of the island component of the sheet (total mass of the ultrafine fibers and the above-mentioned woven or knitted fabric).

[0176] Then, the resulting sheet was cut in half in the thickness direction and the cut surface of the half-cut sheet was ground at a rate of 60 g/m² using endless sandpaper belts having sandpaper grit numbers of 120, 150, and 180 to form a napped surface.

[0177] The sheet thus obtained was dyed using a jet dyeing machine under the condition of 110°C and then dried by a drying machine to produce a sheet-shaped item having a thickness of 1.0 mm and an apparent density of 0.400 g/cm³.

[0178]  The resulting sheet-shaped item had an average fiber length of ultrafine fibers in the nap layer of 450 µm, CV in the average fiber length of ultrafine fibers of 20%, surface coverage of ultrafine fibers in the nap layer of 80%, number of times torn with a Schiefer type abrasion tester of 55 times/0.10 mm and appearance quality rating of A.

[Example 10]

[0179] Polyethylene terephthalate (PET) having an intrinsic viscosity (IV) of 0.718, used as island component, and polystyrene having an MFR of 18 g/10 minutes, used as sea component, were melt-spun through a spinneret designed for 16-island islands-in-the-sea composite fiber with an island/sea mass ratio of 80/20, followed by drawing, crimping, and subsequent cutting to 51 mm to prepare raw stock of islands-in-the-sea composite fiber having a monofilament fineness of 3.1 dtex.

[0180] This raw stock of islands-in-the-sea composite fiber was processed by carding and cross-wrapping to provide a laminated web, which was then needle-punched at a punch density of 600 punches/cm² and further needle-punched at a punch density of 2,900 punches/cm², followed by combining the web with a plain weave fabric (in which a multifilament (84 dtex, 72 filaments) with a twist count of 2,500 T/m formed of a single fiber formed of single component with an intrinsic viscosity (IV) of 0.65 is used as warp and weft with a weaving density of 97 ends/2.54 cm × 76 picks/2.54 cm) to provide a sheet. This sheet was shrunk in hot water at 96°C and then impregnated with a 5% aqueous solution of PVA, followed by drying in hot air at a temperature of 110°C for 10 minutes to provide a sheet in which the mass of the PVA accounted for 20 mass% of the mass of the sheet. This sheet was immersed in trichloroethylene to dissolve and remove the sea component to provide a sea-free sheet containing ultrafine fibers entangled in a woven fabric. SEM observation of a cross section of the sea-free sheet showed that it had an average single fiber diameter of 4.4 µm.

[0181] This sea-free sheet containing ultrafine fibers was immersed in a solution of polycarbonate-based polyurethane in DMF with a solid content adjusted to 11%, followed by coagulating the polyurethane in an aqueous solution with a DMF concentration of 30%. Subsequently, the PVA and DMF were removed in hot water and then the sheet was impregnated with a silicone oil emulsion liquid having a concentration adjusted to 1 mass%, followed by adding a silicone-based lubricant in such a manner that it accounted for 0.05 mass% relative to the total of the mass of the fibers and the mass of the polyurethane. Subsequently, drying was performed in hot air at 110°C for 10 minutes to provide a sheet in which the mass of the polyurethane accounted for 27 mass% relative to the mass of the island component of the sheet (total mass of the ultrafine fibers and the above-mentioned woven or knitted fabric).

[0182]  Then, the resulting sheet was cut in half in the thickness direction and the cut surface of the half-cut sheet was ground at a rate of 80 g/m² using endless sandpaper belts having sandpaper grit numbers of 120, 120, and 150 to form a napped surface.

[0183] The sheet thus obtained was dyed using a jet dyeing machine under the condition of 110°C and then dried by a drying machine to produce a sheet-shaped item having a thickness of 1.0 mm and an apparent density of 0.400 g/cm³.

[0184] The resulting sheet-shaped item had an average fiber length of ultrafine fibers in the nap layer of 300 µm, CV in the average fiber length of ultrafine fibers of 28%, surface coverage of ultrafine fibers in the nap layer of 63%, number of times torn with a Schiefer type abrasion tester of 50 times/0.10 mm, and appearance quality rating of A.

[Comparative example 1]

[0185] Nylon 6 having an MFR of 58.3 g/10 minutes, used as island component, and polystyrene copolymerized with 22 mol% 2-ethylhexyl acrylate (Co-PSt) having an MFR of 300 g/10 minutes, used as sea component, were melt-spun through a spinneret designed for 500-island islands-in-the-sea composite fiber with an island/sea mass ratio of 30/70, followed by drawing, crimping, and subsequent cutting to 51 mm to prepare raw stock of islands-in-the-sea composite fiber having a monofilament fineness of 24 µm.

[0186] This raw stock of islands-in-the-sea composite fiber was processed by carding and cross-wrapping to provide a laminated web, which was then needle-punched at a punch density of 600 punches/cm² and further needle-punched at a punch density of 2,900 punches/cm² to produce a sheet. This sheet was shrunk in hot water at 85°C and then impregnated with a 12% aqueous solution of PVA, followed by drying in hot air at a temperature of 100°C for 10 minutes to provide a sheet in which the mass of the PVA accounted for 45 mass% of the mass of the sheet. This sheet was immersed in trichloroethylene to dissolve and remove the sea component to provide a sea-free sheet containing ultrafine fibers entangled in a woven fabric. SEM observation of a cross section of the sea-free sheet showed that it had an average single fiber diameter of 0.5 µm.

[0187] This sea-free sheet containing ultrafine fibers was immersed in a solution of polyether and polyester-based polyurethane in DMF with a solid content adjusted to 9%, followed by coagulating the polyurethane in an aqueous solution with a DMF concentration of 30%. Subsequently, the PVA and DMF were removed in hot water and then the sheet was impregnated with a silicone oil emulsion liquid having a concentration adjusted to 1.0 mass%, followed by adding a silicone-based lubricant in such a manner that it accounted for 0.2 mass% relative to the total of the mass of the fibers and the mass of the polyurethane. Subsequently, drying was performed in hot air at 110°C for 10 minutes to provide a sheet in which the mass of the polyurethane accounted for 25 mass% relative to the mass of the island component of the sheet (total mass of the ultrafine fibers and the above-mentioned woven or knitted fabric).

[0188] Then, the resulting sheet was cut in half in the thickness direction and the cut surface of the half-cut sheet was ground at a rate of 15 g/m² using endless sandpaper belts having sandpaper grit numbers of 150 and 180 to form a napped surface.

[0189] The sheet thus obtained was dyed using a jet dyeing machine under the condition of 85°C and then dried by a drying machine to produce a sheet-shaped item having a thickness of 0.5 mm and an apparent density of 0.300 g/cm³.

[0190] The resulting sheet-shaped item had an average fiber length of ultrafine fibers in the nap layer of 200 µm, CV in the average fiber length of ultrafine fibers of 35%, surface coverage of ultrafine fibers in the nap layer of 70%, number of times torn with a Schiefer type abrasion tester of 23 times/0.10 mm, and appearance quality rating of B.

[Comparative example 2]

[0191] Nylon 6 having an MFR of 58.3 g/10 minutes, used as island component, and polystyrene copolymerized with 22 mol% 2-ethylhexyl acrylate (Co-PSt) having an MFR of 300 g/10 minutes, used as sea component, were melt-spun through a spinneret designed for 300-island islands-in-the-sea composite fiber with an island/sea mass ratio of 30/70, followed by drawing, crimping, and subsequent cutting to 51 mm to prepare raw stock of islands-in-the-sea composite fiber having a monofilament fineness of 24 µm.

[0192] This raw stock of islands-in-the-sea composite fiber was processed by carding and cross-wrapping to provide a laminated web, which was then needle-punched at a punch density of 600 punches/cm² and further needle-punched at a punch density of 2,900 punches/cm² to produce a sheet. This sheet was shrunk in hot water at 85°C and then impregnated with a 12% aqueous solution of PVA, followed by drying in hot air at a temperature of 100°C for 10 minutes to provide a sheet in which the mass of the PVA accounted for 40 mass% of the mass of the sheet. This sheet was immersed in trichloroethylene to dissolve and remove the sea component to provide a sea-free sheet containing ultrafine fibers entangled in a woven fabric. SEM observation of a cross section of the sea-free sheet showed that it had an average single fiber diameter of 1.0 µm.

[0193]  This sea-free sheet containing ultrafine fibers was immersed in a solution of polyether and polyester-based polyurethane in DMF with a solid content adjusted to 9%, followed by coagulating the polyurethane in an aqueous solution with a DMF concentration of 30%. Subsequently, the PVA and DMF were removed in hot water and then drying was performed in hot air at 110°C for 10 minutes to provide a sheet in which the mass of the polyurethane accounted for 30 mass% of the mass of the island component of the sheet (total mass of the ultrafine fibers and the above-mentioned woven or knitted fabric).

[0194] Then, the resulting sheet was cut in half in the thickness direction and the half-cut sheet was infiltrated with water so that the mass of the sheet containing water reached 200% of its dry mass, followed by squeezing the liquid. Then, the cut surface was ground at a rate of 15 g/m² using endless sandpaper belts having sandpaper grit numbers of 150, 180, and 180 to form a napped surface.

[0195] The sheet thus obtained was dyed using a jet dyeing machine under the condition of 85°C and then dried by a drying machine to produce a sheet-shaped item having a thickness of 0.5 mm and an apparent density of 0.300 g/cm³.

[0196] The resulting sheet-shaped item had an average fiber length of ultrafine fibers in the nap layer of 150 µm, CV in the average fiber length of ultrafine fibers of 40%, surface coverage of ultrafine fibers in the nap layer of 80%, number of times torn with a Schiefer type abrasion tester of 25 times/0.10 mm, and appearance quality rating of C.

[Comparative example 3]

[0197] Polyethylene terephthalate (PET) having an intrinsic viscosity (IV) of 0.718, used as island component, and polystyrene having an MFR of 18 g/10 minutes, used as sea component, were melt-spun through a spinneret designed for 25-island islands-in-the-sea composite fiber with an island/sea mass ratio of 80/20, followed by drawing, crimping, and subsequent cutting to 51 mm to prepare raw stock of islands-in-the-sea composite fiber having a monofilament fineness of 3.1 dtex.

[0198] This raw stock of islands-in-the-sea composite fiber was processed by carding and cross-wrapping to provide a laminated web, which was then needle-punched at a punch density of 600 punches/cm² and further needle-punched at a punch density of 2,900 punches/cm² to produce a sheet. This sheet was shrunk in hot water at 96°C and then impregnated with a 5% aqueous solution of PVA, followed by drying in hot air at a temperature of 110°C for 10 minutes to provide a sheet in which the mass of the PVA accounted for 35 mass% of the mass of the sheet. This sheet was immersed in trichloroethylene to dissolve and remove the sea component to provide a sea-free sheet containing ultrafine fibers entangled in a woven fabric. SEM observation of a cross section of the sea-free sheet showed that it had an average single fiber diameter of 5.0 µm.

[0199] This sea-free sheet containing ultrafine fibers was immersed in a solution of polycarbonate-based polyurethane in DMF with a solid content adjusted to 10%, followed by coagulating the polyurethane in an aqueous solution with a DMF concentration of 30%. Subsequently, the PVA and DMF was removed using hot water. Subsequently, drying was performed in hot air at 110°C for 10 minutes to provide a sheet in which the mass of the polyurethane accounted for 15 mass% relative to the mass of the island component of the sheet (total mass of the ultrafine fibers and the above-mentioned woven or knitted fabric).

[0200] Then, the resulting sheet was cut in half in the thickness direction and the cut surface of the half-cut sheet was ground at a rate of 15 g/m² using an endless sandpaper belt having sandpaper grit number of 120 to form a napped surface.

[0201] The sheet thus obtained was dyed using a jet dyeing machine under the condition of 110°C and then dried by a drying machine to produce a sheet-shaped item having a thickness of 1.0 mm and an apparent density of 0.400 g/cm³. Subsequently, the raised surface of the dyed fiber base material was embossed using an embossing roll with a design simulating a shallow contraction creases along pores in natural leather. The embossing roll had a protruding portion with a width of 220 µm and a pressing depth of 750 µm, and the protruding portion accounted for 13% of the total area. Embossing was performed under the conditions of an embossing roll surface temperature of 140°C, a pressure of 0.3 MPa, and an embossing roll speed of 1.5 m/min to produce a sheet-shaped item.

[0202] The resulting sheet-shaped item had an average fiber length of ultrafine fibers in the nap layer of 300 µm, CV in the average fiber length of ultrafine fibers of 40%, surface coverage of ultrafine fibers in the nap layer of 50%, number of times torn with a Schiefer type abrasion tester of 16 times/0.10 mm, and appearance quality rating of C.

[Comparative example 4]

[0203] Polyethylene terephthalate (PET) having an intrinsic viscosity (IV) of 0.718, used as island component, and polystyrene having an MFR of 18 g/10 minutes, used as sea component, were melt-spun through a spinneret designed for 25-island islands-in-the-sea composite fiber with an island/sea mass ratio of 55/45, followed by drawing, crimping, and subsequent cutting to 51 mm to prepare raw stock of islands-in-the-sea composite fiber having a monofilament fineness of 3.1 dtex.

[0204] This raw stock of islands-in-the-sea composite fiber was processed by carding and cross-wrapping to provide a laminated web, which was then needle-punched at a punch density of 600 punches/cm² and further needle-punched at a punch density of 2,900 punches/cm² to produce a sheet. This sheet was shrunk in hot water at 96°C and then impregnated with a 10% aqueous solution of PVA, followed by drying in hot air at a temperature of 110°C for 10 minutes to provide a sheet in which the mass of the PVA accounted for 30 mass% of the mass of the sheet. This sheet was immersed in trichloroethylene to dissolve and remove the sea component to provide a sea-free sheet containing ultrafine fibers entangled in a woven fabric. SEM observation of a cross section of the sea-free sheet showed that it had an average single fiber diameter of 2.0 µm.

[0205] This sea-free sheet containing ultrafine fibers was immersed in a solution of polycarbonate-based polyurethane in DMF with a solid content adjusted to 10%, followed by coagulating the polyurethane in an aqueous solution with a DMF concentration of 30%. Subsequently, the PVA and DMF were removed in hot water and then the sheet was impregnated with a silicone oil emulsion liquid having a concentration adjusted to 10 mass%, followed by adding a silicone-based lubricant in such a manner that it accounted for 6.0 mass% relative to the total of the mass of the fibers and the mass of the polyurethane. Subsequently, drying was performed in hot air at 110°C for 10 minutes to provide a sheet in which the mass of the polyurethane accounted for 20 mass% relative to the mass of the island component of the sheet (total mass of the ultrafine fibers and the above-mentioned woven or knitted fabric).

[0206] Then, the resulting sheet was cut in half in the thickness direction and the cut surface of the half-cut sheet was ground at a rate of 20 g/m² using endless sandpaper belts having sandpaper grit numbers of 180 and 180 to form a napped surface.

[0207] The sheet thus obtained was dyed using a jet dyeing machine under the condition of 110°C and then dried by a drying machine to produce a sheet-shaped item having a thickness of 0.5 mm and an apparent density of 0.360 g/cm³.

[0208] The resulting sheet-shaped item had an average fiber length of ultrafine fibers in the nap layer of 600 µm, CV in the average fiber length of ultrafine fibers of 40%, surface coverage of ultrafine fibers in the nap layer of 45%, number of times torn with a Schiefer type abrasion tester of 28 times/0.10 mm, and appearance quality rating of C.

[Comparative example 5]

[0209] Polyethylene terephthalate (PET) having an intrinsic viscosity (IV) of 0.718, used as island component, and polystyrene having an MFR of 18 g/10 minutes, used as sea component, were melt-spun through a spinneret designed for 25-island islands-in-the-sea composite fiber with an island/sea mass ratio of 55/45, followed by drawing, crimping, and subsequent cutting to 51 mm to prepare raw stock of islands-in-the-sea composite fiber having a monofilament fineness of 3.1 dtex.

[0210] This raw stock of islands-in-the-sea composite fiber was processed by carding and cross-wrapping to provide a laminated web, which was then needle-punched at a punch density of 600 punches/cm² and further needle-punched at a punch density of 2,900 punches/cm² to produce a sheet. This sheet was shrunk in hot water at 96°C and then impregnated with a 3% aqueous solution of PVA, followed by drying in hot air at a temperature of 110°C for 10 minutes to provide a sheet in which the mass of the PVA accounted for 10 mass% of the mass of the sheet. This sheet was immersed in trichloroethylene to dissolve and remove the sea component to provide a sea-free sheet containing ultrafine fibers entangled in a woven fabric. SEM observation of a cross section of the sea-free sheet showed that it had an average single fiber diameter of 2.0 µm.

[0211] This sea-free sheet containing ultrafine fibers was immersed in a solution of polycarbonate-based polyurethane in DMF with a solid content adjusted to 10%, followed by coagulating the polyurethane in an aqueous solution with a DMF concentration of 30%. Subsequently, the PVA and DMF were removed in hot water and then the sheet was impregnated with a silicone oil emulsion liquid having a concentration adjusted to 5 mass%, followed by adding a silicone-based lubricant in such a manner that it accounted for 2.0 mass% relative to the total of the mass of the fibers and the mass of the polyurethane. Subsequently, drying was performed in hot air at 110°C for 10 minutes to provide a sheet in which the mass of the polyurethane accounted for 65 mass% relative to the mass of the island component of the sheet (total mass of the ultrafine fibers and the above-mentioned woven or knitted fabric).

[0212] Then, the resulting sheet was cut in half in the thickness direction and the cut surface of the half-cut sheet was ground at a rate of 20 g/m² using endless sandpaper belts having sandpaper grit numbers of 150, 180, 240, 320, and 600 to form a napped surface.

[0213] The sheet thus obtained was dyed using a jet dyeing machine under the condition of 110°C and then dried by a drying machine to produce a sheet-shaped item having a thickness of 0.5 mm and an apparent density of 0.360 g/cm³.

[0214] The resulting sheet-shaped item had an average fiber length of ultrafine fibers in the nap layer of 330 µm, CV in the average fiber length of ultrafine fibers of 40%, surface coverage of ultrafine fibers in the nap layer of 45%, number of times torn with a Schiefer type abrasion tester of 100 times/0.10 mm, and appearance quality rating of C.

[Table 1]

	Example 1	Example 2	Example 3	Example 4	Example 5	Example 6	Example 7	Example 8	Example 9	Example 10
Number of ultrafine fiber (per bundle)	36	36	36	36	280	50	100	36	16	16
Average single fiber diameter (µm)	2.1	2.1	2.1	1	1	7	1	2.1	4.4	4.4
Elastomeric polymer diol	poly carbonate-based	poly carbonate-based	polycarbonate/ polyester-based	polyether/ polyester-based	polyether/ polyester-based	poly carbonate-based	Polyether/ polyester-based	-	poly carbonate-based	poly carbonate-based
Elastomeric polymer added (%)	30	25	23	20	35	40	5	0	27	27
Average fiber length in nap laver (um)	370	260	400	280	260	350	400	250	450	300
CV in average fiber length in nap layer (%)	15	20	10	28	10	25	25	29	20	28
Napped surface coverage of ultrafine fibers in nap layer (%)	80	73	90	62	70	65	99	62	80	63
Existence/absence of silicone-based lubricant	existent	existent	existent	existent	existent	existent	existent	absent	existent	existent
Amount of silicone-based lubricant added (%)	0.5	0.2	0.6	0.1	0.01	2.0	1.0	0	0.2	0.05
Product surface ground rate in buffing step (g/m2)	100	60	70	30	40	160	50	20	60	80
Repetitions of buffing	3	3	2	3	3	3	2	3	3	3
Exposed polyurethane in surface	absent	absent	absent	absent	absent	absent	absent	absent	absent	absent
Number of times torn with Schiefer type abrasion tester (per 0.10 mm)	65	40	45	20	30	80	10	7	55	50
Appearance	A	A	A	A	A	A	A	A	A	A

[Table 2]

	Comparative example 1	Comparative example 2	Comparative example 3	Comparative example 4	Comparative example 5
Number of ultrafine fibers (per bundle)	500	300	25	25	25
Average single fiber diameter (µm)	0.5	1	5	2	2
Elastomeric polymer diol	polyether/ polyester-based	polyether/ polyester-based	polycarbonate-based	poly carbonate-based	poly carbonate-based
Elastomeric polymer added (%)	25	30	15	20	65
Average fiber length in nap layer (µm)	200	150	300	600	330
CV in average fiber length in nap layer (%)	35	40	40	40	40
Napped surface coverage of ultrafine fibers in nap layer (%)	70	80	50	45	45
Existence/absence of silicone- based lubricant	existent	absent	absent	existent	existent
Amount of silicone-based lubricant added (%)	0.2	0	0	6.0	2.0
Product surface ground rate in buffing step (g/m2)	15	15	15	20	20
Repetitions of buffing	2	3	1	2	5
Exposed polyurethane in surface	existent	existent	existent	absent	existent
Number of times torn with Schiefer type abrasion tester (per 0.10 mm)	23	25	16	28	100
Appearance	B	C	C	C	C

INDUSTRIAL APPLICABILITY

[0215] The sheet-shaped item according to the present invention has an elegant appearance and very even texture to the touch and also shows high moldability and accordingly, it can be suitably used mainly as interior materials with highly elegant appearance of epidermis materials for furniture, chairs and walls, and also seats, ceilings, interiors, etc. of vehicles including automobiles, trains, and aircraft; shirts, jackets, uppers and trims, etc. of casual shoes, sports shoes, men's shoes, women's shoes, etc., bags, belts, wallets, etc., and clothing materials used as parts thereof; and industrial materials such as wiping cloth, filters, and CD curtains.

Claims

1. A sheet-shaped item comprising ultrafine fiber bundles each containing a plurality of ultrafine fibers of a thermoplastic resin, the sheet-shaped item having a base material layer and a nap layer, the base material layer containing a fiber entanglement of the ultrafine fiber bundles, the nap layer including a nap formed only of the ultrafine fibers and covering at least one surface of the sheet-shaped item, and all of the requirements (1) to (3) given below being satisfied:

(1) the ultrafine fibers have an average single fiber diameter of 0.1 µm or more and 10 µm or less,

(2) of the ultrafine fibers, those ultrafine fibers contained in the nap layer have an average fiber length of 250 µm or more and 500 µm or less, and

(3) in the nap layer, the surface coverage of the ultrafine fibers is 60% or more and 100% or less.

2. The sheet-shaped item claimed in claim 1, further comprising an elastomeric polymer in addition to the ultrafine fiber bundles, wherein the elastomeric polymer is contained in the interior of the fiber entanglement.

3. The sheet-shaped item claimed in either claim 1 or 2, wherein each of the ultrafine fiber bundles contains 10 or more and 400 or less ultrafine fibers per bundle.

4. The sheet-shaped item claimed in any one of claims 1 to 3, wherein the CV in the average fiber length of ultrafine fibers in the nap layer is 30% or less.

5. The sheet-shaped item claimed in any one of claims 2 to 4, wherein the elastomeric polymer added accounts for 0 mass% or more and 60 mass% or less relative to the ultrafine fibers.

6. A production method for the sheet-shaped item claimed in any one of claims 1 to 5 comprising addition of a silicone-based lubricant to 0.01 mass% or more and 3.0 mass% or less relative to the mass of the sheet-shaped item and subsequent buffing of the product surface performed after drying the sheet-shaped item.

7. The production method for the sheet-shaped item claimed in claim 6, wherein the grinding rate in buffing the product surface is 20 g/m² or more and 250 g/m² or less.

8. The production method for the sheet-shaped item claimed in claim 7, wherein the buffing of the product surface is performed at least twice or more in multiple stages using sandpapers of increasingly finer grits or of the same grit number.

9. The sheet-shaped item claimed in any one of claims 2 to 5, wherein the number of times torn with a Schiefer type abrasion tester is 20 or more per 0.10 mm thickness of the sheet-shaped item as determined by the test specified in ASTM D4158-08 (2016) "Standard Guide for Abrasion Resistance of Textile Fabrics (Uniform Abrasion)" (abrasion resistance evaluation method) using a sandpaper of grit number 180 under a load of 2 lbs.

Drawing