THREE-DIMENSIONAL KNIT FABRIC, INTERLINING MATERIAL AND COMPLEX FABRIC

Abstract

 A three-dimensional knit fabric comprising a yarn constituting front and back knit layers and a connecting yarn composed of a monofilament, which connects the front and back knit layers, wherein the three-dimensional front and back knit layers are preferably composed only of a monofilament and at least one of the knit layers has a largest void with an area of 0.1 to 6 mm². By forming a laminate using the three-dimensional knit fabric as an interlining material, the three-dimensional knit fabric and the laminate do not settle even if they are used for a long time because their repeated compressive residual strain is low. Moreover, by using a laminate composed of a thick three-dimensional knit layer as an interlining material, lamination with a nonwoven fabric by a needle punch and entangling by spunlacing become possible, and therefore the laminate can be suitably used for a felt for papermaking, air filters, water squeezing materials and filter materials.

Description

Technical Field

[0001] The present invention relates to a three-dimensional knit fabric comprising a yarn constituting front and back knit layers and a connecting yarn composed of a monofilament, which connects the front and back knit layers, which knit fabric is suitable as a filter material, in particular, a filter for liquid or gas in the form of a laminate, and relates to an interlining material using the three-dimensional knit fabric and a multilayered laminate comprising the three-dimensional knit fabric and another material.

Background Art

[0002] Conventionally, for uses of filter materials such as air filters and liquid filters, a nonwoven fabric alone, a laminate of nonwoven fabrics, a mesh woven fabric alone or a woven fabric with different fabric densities is used as it is, or a woven fabric integrated with a nonwoven fabric of short or continuous fiber such as synthetic fiber by a needle punch is generally used. For example, in the press part which is a type of a liquid filter in a papermaking process, water is squeezed out of wet paper with a needle felt and a pair of press rolls to produce paper. Various laminates are widely used as filter materials for water squeezing. For the structure of such laminates, a single felt material composed of a nonwoven fabric or a laminate of felt materials is used as a liquid filter or an air filter, or a laminate using a reinforcing structure as an interlining material therewith is used. For example, a needle felt used for water squeezing is generally composed of upper and lower felt materials of a nonwoven fabric and a mesh woven fabric which is an interlining material. It is required that the upper and lower felt materials are hardly clogged even after long time use. In addition, it is required that use of an interlining material as a reinforcing material make the felt material difficult to be extended due to settling. When used as a long material such as a felt for papermaking, elongation of felt probably affects the duration of use. A mesh woven fabric, woven or knitted fabric made of ordinary high strength fiber or a structure in which strands are aligned and partly bonded is practically used as an interlining material, i.e., a reinforcing material.

[0003] Interlining materials must first have high strength, small elongation, and be easily entangled or integrated with nonwoven fabric or felt laminated on the upper and lower sides, and difficult to be separated therefrom. In particular, for air filters and liquid filters, excellent filterability, maintaining the initial filterability when repeatedly used and good dimensional stability with little elongation are required. For example, when a filter material without an interlining material is used for a press roll for water squeezing, the thickness of felt is significantly reduced by repeated compression, and the water squeezing properties and the durability are not sufficient.

[0004] Patent Document 1 discloses a method in which an opening is formed in an anti-rewetting layer in order to improve the water squeezing properties of a felt used as a felt for papermaking. However, the water squeezing properties are not sufficient even in the method, and neither was the durability.

[0005] Patent Document 2 discloses that a felt for papermaking excellent in durability can be obtained by using a polyketone fiber for the pad layer. However, the durability is insufficient when the felt for papermaking is merely composed of such a specific material. Thus, interlining materials and laminates which can be entangled well when laminated and integrated so as to form an air filter or a liquid filter, do not settle and can maintain sufficient effects such as water squeezing properties are in demand.

[0006] [Patent Document 1] JP-A-2003-89990
[Patent Document 1] JP-A-2003-119687

[Disclosure of the Invention]

[Problems to be Solved by the Invention]

[0007] An object of the present invention is to provide a novel three-dimensional knit fabric having excellent filterability, in particular, filterability for fine particles, excellent water squeezing properties and excellent durability when used for various filters as a laminate, an interlining material and a laminate using the same.

[Means for Solving the Problems]

[0008] The present inventors have conducted intensive studies to solve the aforementioned problems and focused on the high void retaining ability of a three-dimensional knit fabric, and found that the filterability and the durability of a filter material are significantly improved by using the three-dimensional knit fabric as an interlining material and laminating and integrating a nonwoven fabric on the upper and lower sides, and completed the present invention.

[0009] Accordingly, the present invention provides:

(1) A three-dimensional knit fabric comprising a yarn constituting front and back knit layers and a monofilament connecting yarn for connecting the front and back knit layers, wherein at least one of the three-dimensional front and back knit layers has a largest void with an area of 0.1 to 6 mm²;

(2) The three-dimensional knit fabric according to (1), wherein the connecting yarn of the three-dimensional knit fabric is a monofilament of 15 to 1000 dtex;

(3) The three-dimensional knit fabric according to (1) or (2), wherein the knit fabric has a repeated compressive residual strain of 20% or less;

(4) The three-dimensional knit fabric according to any one of (1) to (3), wherein the knit fabric is used for a felt for papermaking;

(5) An interlining material comprising the three-dimensional knit fabric according to any one of (1) to (4), wherein both the front and back knit layers of the three-dimensional knit fabric comprise a monofilament of 10 to 300 dtex;

(6) An interlining material comprising the three-dimensional knit fabric according to any one of (1) to (5), wherein the interlining material is used for laminating another material on one side of both the front and back knit layers;

(7) An interlining material comprising the three-dimensional knit fabric according to any one of (1) to (5), wherein the interlining material has a permeation rate of water of 1 to 10 ml/cm²·second;

(8) An interlining material comprising the three-dimensional knit fabric according to any one of (1) to (6), wherein the interlining material is used for a felt for papermaking which is laminated on at least one side thereof;

(9) A laminate comprising a nonwoven fabric laminated on at least one side of the interlining material according to (1) to (7);

(10) The laminate according to (9), comprising a nonwoven fabric made of at least one member of a synthetic fiber, a regenerated fiber and a natural fiber having a single yarn size of 0.01 to 25 dtex;

(11) The laminate according to (9) or (10), wherein the nonwoven fabric and the interlining material are integrated by needlepunching;

(12) The laminate according to (9) or (10), wherein the nonwoven fabric and the interlining material are integrated by spunlacing;

(13) The laminate according to any one of (9) to (12), wherein the laminate has a permeation rate of water of 0.4 to 2.0 ml/cm²·second;

(14) The laminate according to any one of (9) to (12), wherein the laminate has an air pressure loss of 300 Pa or less; and

(15) The laminate according to any one of (9) to (14), wherein the laminate has a particle collection efficiency of 80% or more for particles of 0.1 to 5.0 µm.

[Advantages of the Invention]

[0010] When the three-dimensional knit fabric and the interlining material and the laminate comprising the three-dimensional knit fabric of the present invention are used as an air filter, a liquid filter, in particular, a felt for papermaking, there is an advantage that water squeezing properties of the felt for papermaking can be significantly improved and the compression recovery and the compressive residual strain are small, and the practical durability is excellent.

[Best Mode for Carrying out the Invention]

[0011] The present invention is described in detail below.

[0012] The three-dimensional knit fabric of the present invention can be knitted by a double raschel knitting machine or a double circular knitting machine with two needle rows. Knit layers having a plurality of openings such as mesh knit layers or marquisette knit layers may be used for the front and back knit layers. In particular, denbigh structure and queens cord structure are preferred because the irregularities on the surface are small. The front and back knit layers may have the same or different knit structure.

[0013] The three-dimensional knit fabric comprises a yarn constituting front and back knit layers and a connecting yarn composed of a monofilament, which connects the front and back knit layers. A synthetic fiber monofilament having a single yarn size of 15 dtex to 1000 dtex is preferably used as the connecting yarn. The size is more preferably 50 dtex to 400 dtex, most preferably 100 dtex to 300 dtex.

[0014] The type of the monofilament to be used is not particularly limited, but monofilaments composed of a melt spinnable synthetic resin such as polyester, polyamide, polypropylene or polyethylene may be used. The cross-sectional shape of the yarn may be circular or polygonal including a triangular shape, an L-shape, a T-shape, a Y-shape, a W-shape, a four-leaf shape, an eight-leaf shape, a flat shape or a dog bone shape, a multi-leaf shape, a hollow shape or an indefinite shape. A circular cross-section is preferred because the tensile strength is high.
Monofilaments made of synthetic fiber make it possible to diminish decrease in the thickness due to repeated compression and significantly prevent deterioration of water squeezing properties when used as, for example, a felt for paper making in the form of a laminate. When a monofilament having a single yarn size of less than 15 dtex is used as the connecting yarn or a multifilament is directly used, the three-dimensional knit fabric has poor thickness retaining properties for repeated compression. Use of a monofilament having a single yarn size of 1000 dtex or more as the connecting yarn is not preferred because the flexural rigidity of the monofilament is too high and knitting of the three-dimensional knit fabric is extremely difficult.

[0015] Such monofilaments may be produced by a method of producing a monofilament using air cooling or water cooling with known melt spinning.

[0016] An ordinary melt spinnable fiber made of synthetic resin, regenerated fiber and natural fiber may be used as the fiber constituting front and back knit layers of the three-dimensional knit fabric. The type of the constituent fiber is not particularly limited, but synthetic fibers composed of polyester, polyamide, polyacrylonitrile, polypropylene, polyethylene, aramid, polyketone, polyphenylenesulfide or polyetheretherketone resin, which can be formed by melt spinning, dry spinning or wet spinning, may be used. The cross-sectional shape of the fiber may be circular or polygonal including a triangular shape, an L-shape, a T-shape, a Y-shape, a W-shape, a four-leaf shape, an eight-leaf shape, a flat shape or a dog bone shape, a multi-leaf shape, a hollow shape or an indefinite shape. The fiber constituting the front and back knit layers has a size of preferably 0.1 dtex to 300 dtex for the three-dimensional knit fabric. The single yarn size is more preferably 10 to 300 dtex. The fiber is more preferably a monofilament of 20 dtex or more. A three-dimensional knit fabric comprising front and back knit layers and a connecting yarn composed only of a monofilament is most preferred. Use of a multifilament of 0.1 dtex or less for front and back knit layers is not preferred because yarns constituting the front and back knit layers of the three-dimensional knit fabric are broken by a needle when short fiber is integrated with the three-dimensional knit layers which is an interlining material by a needle punch, and the broken part of the yarns is depressed in a concave shape, and the laminate has poor durability.

[0017]  When a monofilament having a single yarn size of 300 dtex or more is used as the fiber constituting the front and back knit layers, the flexural rigidity of the monofilament is too high and therefore knitting of the three-dimensional knit fabric is extremely difficult.

[0018] When the three-dimensional knit fabric of the present invention is used as, in particular, a laminate in which layers are laminated on the upper and lower sides, use of a monofilament having a size of 10 dtex or more as the fiber constituting the front and back knit layers of the three-dimensional knit fabric is preferred because it makes it possible to prevent breakage of fiber in the step of entangling and integration by needlepunching and there is no decrease in the strength of the three-dimensional knit fabric.

[0019] In the three-dimensional knit fabric comprising a yarn constituting front and back knit layers and a connecting yarn composed of a monofilament, which connects the front and back knit layers, one of the many voids formed on at least one side of the front and back knit layers must have a maximum area of 0.1 mm² to 6.0 mm². When a void in at least one side of the front and back knit layers has a maximum area of less than 0.1 mm², the laminate has poor permeability of air or liquid, and consequently the filterability is reduced. A maximum area of more than 6.0 mm² is not preferred because entanglement with nonwoven fabric laminated on upper and lower sides is poor, and the shape of the void remains on the surface of the laminate even after lamination, and therefore when the three-dimensional knit fabric is used as a laminate for papermaking, the pattern of the knit fabric is transferred to wet paper after dehydration, sometimes causing wrinkles or breakage of wet paper.

[0020]  The three-dimensional knit fabric may be used as an interlining material used for laminating with another material. Nonwoven fabrics, cotton materials or paper materials may be used as another material to be laminated. Another material is made of at least one member of a synthetic fiber, a regenerated fiber, a natural fiber and pulp, and a nonwoven fabric material (hereinafter felt) composed of short fiber having a single yarn size of 0.01 to 25 dtex can be used. When the fiber material constituting the felt has a size of less than 0.01 dtex, the felt has poor compression recovery, and so when the laminate is used as a filter, decrease in the thickness is large, the pressure loss is increased and the filtration efficiency is reduced. Also, when the fiber material has a size of 25 dtex or more, increasing the density of nonwoven fabric is difficult and consequently sufficient efficiency of the filter material cannot be obtained. The cross-sectional shape of the constituent fiber may be circular or polygonal including a triangular shape, an L-shape, a T-shape, a Y-shape, a W-shape, a four-leaf shape, an eight-leaf shape, a flat shape or a dog bone shape, a multi-leaf shape, a hollow shape or an indefinite shape.

[0021] The felt has a weight of preferably 10 to 2000 g/m², more preferably 15 g/m² or more. Which felt is to be used can be accordingly determined depending on the purpose of use.

[0022] The interlining material composed of the three-dimensional knit fabric and the felt laminated on the upper and lower sides thereof can be entangled by a known needle punch method or a columnar stream.

[0023] The needle punch method is a method for mechanical entangling by a needle. The felt and the interlining material composed of the three-dimensional knit fabric can be laminated and entangled and integrated by a needle punch machine. The needle density which is an index of entanglement is preferably 5 to 50 times/cm², which may be changed depending on the fiber material to be used.

[0024] Entangling by a columnar stream is a method using a known spun lace machine, in which water is ejected at high pressure in a columnar stream through pores, thereby entangling upper and lower layers by hydraulic power. The felt and the three-dimensional knit fabric may be entangled so that they are not separated.

[0025] Entangling with a needle punch machine is effective for a felt having a relatively large single yarn size of, for example, 1 to 25 dtex, and is useful for liquid filters. On the other hand, entangling with a columnar stream is effective for a felt having a small single yarn size of 0.01 to 1 dtex and is useful for air filters.

[0026] Preferably, the three-dimensional knit fabric used as an interlining material of a liquid filter has a permeation rate of liquid, for example, water of 1 to 10 ml/cm²·second. When the permeation rate of water is 1 ml/cm²·second or less, filtration efficiency and water squeezing properties are poor. Also, tufting is difficult in the step of integrating the felt and the three-dimensional knit fabric by a needle punch. A permeation rate of water of 10 ml/cm²·second or more is not preferred because filtration efficiency is reduced when the laminate is used as a filter.

[0027] Preferably, the three-dimensional knit fabric used as an interlining material of an air filter has an air pressure loss of 300 Pa or less. An air pressure loss of 300 Pa or more is not preferred because energy required for passing fluid to be filtered is high and a fan with high energy is needed. Also, there is a defect that the life of the filter is shortened due to clogging.

[0028]  The laminate may also be used as an air filter substrate, a liquid filter material, in particular, a substrate for a felt for papermaking.

[0029] The thickness of the three-dimensional knit fabric used for a felt for papermaking in the form a laminate is not particularly limited, but the thickness is preferably about 1.5 mm to 6 mm in view of the water squeezing properties and the durability. The water squeezing properties herein described mean dehydration of wet paper materials by applying pressure from the upper and the lower sides using the laminate.

[0030] Preferably, the three-dimensional knit fabric and the laminate using the three-dimensional knit fabric as an interlining material herein used have a permeation rate of water of 0.4 to 2.0 ml/cm²·second. A permeation rate of water of 0.4 ml/cm²·second or less is not preferred because water squeezing properties are poor. A permeation rate of water of more than 2.0 ml/cm²·second is not preferred because filtration efficiency is reduced when the knit fabric or the laminate is used as a filter and the pattern of the interlining material to be used is transferred.
Also, the laminate may be used as an air filter.
When used as an air filter, filtration of fine particles in the air and maintaining filtration efficiency and pressure loss are important. A fiber having a single yarn size of 0.01 to 25 dtex prepared by a method of producing nonwoven fabric, for example, a melt blow method, a spunbond method or a dry method may be used.
The single yarn size is preferably 0.02 to 1 dtex. A known spun lace machine is used for lamination and entangling with the three-dimensional knit fabric. A felt having a weight of about 20 to 200 g/m² is preferred. The same or different felt may be used on the upper and lower sides of the three-dimensional knit fabric. Preferably, the laminate has a pressure loss of 300 Pa or less. Preferably, the laminate has collection efficiency for particles of 0.1 to 5.0 µm of 80% or more.
The pressure loss and the collection efficiency for particles can be measured by a known method (e.g., JP-A-07-100315).

[Examples]

[0031] The present invention is described in detail below, but the present invention is not limited to Examples.

[0032] Methods of producing the three-dimensional knit fabric and methods of evaluating the same are described below.

1. Method of producing three-dimensional knit fabric

[0033] Three-dimensional knit fabric A: Using a double raschel knitting machine of 18 gauge equipped with 5 guide bars and having a bed gap of 4.6 mm, 200 dtex nylon 6 monofilament yarns were fed from guide bars (L2, L3) located at the center to the guide in a 1-in 1-out arrangement as the connecting yarn, 167 dtex/48f polyethylene terephthalate multifilament yarns were fed from a guide bar (L1) located in front of the knitting machine to the guide in an all-in arrangement as yarns for the front knit layer, and 167 dtex/48f polyethylene terephthalate multifilament yarns were fed from two guide bars (L4, L5) located at the back of the knitting machine to the guide in a 1-in 1-out arrangement as yarns for the back knit layer at a knitting density of 20.4 courses/2.54 cm to give a three-dimensional knit fabric having mesh front and back layers with the following knit structure. The three-dimensional knit fabric was scoured at 75°C and heat set (180°C) while stretching. The resulting three-dimensional knit fabric has dimensions of a thickness of 2.5 mm, 27.2 courses/2.54 cm and 13.2 wales/2.54 cm. The maximum void has an area of 1.1 mm² on the L1 side and 11.4 mm² on the L5, L6 side.

(knit structure)

[0034] 

L1:2422/2022/2422/2022/2422/2022/
2422/2022/2422/2022/2422/2022

L2:4668/8664/4668/8620/0268/8664/
4642/4246/4642/42810/81042/4246

L3:4642/4246/4642/42810/81042/4246/
4668/8664/4668/8620/0268/8664

L4:4446/4442/4446/4442/4446/4442/
2220/2224/2220/2224/2220/2224

L5:2220/2224/2220/2224/2220/2224/
4446/4442/4446/4442/4446/4442

[0035] Three-dimensional knit fabric B: Knitting was performed under the same conditions as in the three-dimensional knit fabric A except that 235 dtex/34f nylon 6 multifilament yarns were used as the connecting yarn of the three-dimensional knit fabric A, and the three-dimensional knit fabric thus obtained was scoured and heat set while stretching. The resulting three-dimensional knit fabric has dimensions of a thickness of 1.3 mm, 27.2 courses/2.54 cm and 13.2 wales/2.54 cm. The maximum void has an area of 1.2 mm² on the L1 side and 12.0 mm² on the L5, L6 side.

[0036] Three-dimensional knit fabric C: Using a double raschel knitting machine of 18 gauge equipped with 5 guide bars and having a bed gap of 4.3 mm, 200 dtex nylon 6 monofilament yarns were fed from guide bars (L2, L3) located at the center to the guide in a 1-in 1-out arrangement as the connecting yarn, 133 dtex nylon 6 monofilament yarns were fed from a guide bar (L1) located in front of the knitting machine to the guide in an all-in arrangement as yarns for the front knit layer, and 133 dtex nylon 6 monofilament yarns were fed from two guide bars (L4, L5) located at the back of the knitting machine to the guide in an all-in arrangement as yarns for the back knit layer at a knitting density of 20.7 courses/2.54 cm to give a three-dimensional knit fabric with the following knit structure. The three-dimensional knit fabric was scoured at 75°C and heat set (180°C) while stretching. The resulting three-dimensional knit fabric has dimensions of a thickness of 3.2 mm, 24.0 courses/2.54 cm and 21.0 wales/2.54 cm. The maximum void has an area of 0.2 mm² on the L1 side and 0.4 mm² on the L5, L6 side.

(knit structure)

[0037] 

L1:0222/10888/

L2:4620/2046/

L3:0264/6402/

L4:2220/2224/

L5:8800/0088/

Three-dimensional knit fabric D: Knitting was performed under the same conditions as in the three-dimensional knit fabric C except that 156 dtex/48f nylon 6 multifilament yarns were used in L1, L4 and L5 of the three-dimensional knit fabric C, and the three-dimensional knit fabric thus obtained was scoured and heat set while stretching. The resulting three-dimensional knit fabric has dimensions of a thickness of 3.4 mm, 24.0 courses/2.54 cm and 21.0 wales/2.54 cm. The maximum void has an area of 0.3 mm² on the L1 side and 0.6 mm² on the L5, L6 side.

[0038] Three-dimensional knit fabric E: Using a double raschel knitting machine of 18 gauge equipped with 6 guide bars and having a bed gap of 5.6 mm, 200 dtex nylon 6 monofilament yarns were fed from guide bars (L3, L4) located at the center as the connecting yarn, 167 dtex/48f polyethylene terephthalate multifilament yarns were fed from two guide bars (L1, L2) located in front of the knitting machine as yarns for the front knit layer, and 167 dtex/48f polyethylene terephthalate multifilament yarns were fed from two guide bars (L5, L6) located at the back of the knitting machine as yarns for the back knit layer in a 1-in 1-out arrangement to L1, L4, L5 guides and in a 1-in 1-out arrangement to L2, L3 and L6 guides. The knitting density was set to 20.4 courses/2.54 cm and a three-dimensional knit fabric having mesh front and back layers with the following knit structure was obtained.

[0039] The three-dimensional knit fabric thus obtained was scoured at 70°C and heat set (180°C) while stretching. The resulting three-dimensional knit fabric has dimensions of a thickness of 4.0 mm, 27.2 courses/2.54 cm and 13.2 wales/2.54 cm.

(knit structure)

[0040] 

L1 :4644/4244/4644/4244/4644/4222/
2022/2422/2022/2422/2022/2444/

L2:2022/2422/2022/2422/2022/2444/
4644/4244/4644/4244/4644/4222/

L3:6868/6464/6868/2020/6868/6464/
4242/4646/4242/810810/4242/4646/

L4:4242/4646/4242/810810/4242/4646/
6868/6464/6868/2020/6868/6464/

L5:4446/4442/4446/4442/4446/4442/
2220/2224/2220/2224/2220/2224/

L6:2220/2224/2220/2224/2220/2224/
4446/4442/4446/4442/4446/4442/

2. Method of measuring repeated compressive residual strain

[0041] The repeated compressive residual strain was measured in accordance with "repeated compressive residual strain" measurement method A in JIS K6400. Servopulser made by Shimadzu Corporation was used as the tester and a compression terminal with a diameter of 10 cm was used. Test pieces of 15 cm square were stacked so that the total thickness was 20 to 25 mm and the four corners were fastened by tying with a sewing yarn so that the pieces do not move during measurement, and the repeated compressive residual strain was measured with setting the compression terminal at the center of the sample.

3. Method of measuring maximum surface void

[0042] Areas of voids in the three-dimensional knit fabric were measured at 5 sites where voids were relatively large using an image processing apparatus "VH-7000" made by KEYENCE CORPORATION and the maximum value of the areas was employed.

4. Method of measuring compression recovery

[0043] The test was performed under the same conditions as in the "method of measuring repeated compressive residual strain" except that a laminated felt in which a synthetic fiber assembly 22 was planted on a three-dimensional knit fabric 10 and/or a synthetic fiber monofilament woven fabric 21 by a needle punch so that the total weight per unit area of each sample was the same was used and the compression load was 1t. The compression recovery of a felt for papermaking was calculated from the following formula. The value in this test is expressed by an index based on the typical laminated felt used in Comparative Example 1 as 1.0.

[0044] 

(A):

thickness (mm) before test

(B):

thickness (mm) after completion of test

5. Method of measuring permeation of water

[0045] A required number of each of evaluation samples of the three-dimensional knit fabric and a commercially available craft felt having a weight of about 250 g/m² (100% polyester, about 2 mm thick, available from MOTOHIRO & CO., LTD.) are cut into 250 mm x 250 mm. The pieces are sufficiently immersed in water and then polyethylene sheet is put on the evaluation samples of the three-dimensional knit fabric and the craft stacked as shown in Figure 5, and a plastic cylinder with a diameter of about 95 mm and a height of about 110 mm is placed thereon and 500 ml of water is poured from the top. At this stage, a load (about 10 to 15 kg) under which water does not leak through the plastic cylinder and the polyethylene sheet is applied thereto. In this state, with holding the end of the polyethylene sheet, the sheet is removed from the plastic cylinder and each sample quietly and quickly so that water does not leak. At the same time, the time for water in the plastic cylinder to disappear from the surface of each sample is measured by a stopwatch.

[Example 1]

[0046] First, the repeated compressive residual strain of the three-dimensional knit fabric A knitted by the above-described method was measured. As a result, the repeated compressive residual strain was 15%. A felt for papermaking as shown in Figure 2 was prepared using the three-dimensional knit fabric A. Herein, the L1 side of the three-dimensional knit fabric A was placed on a side which did not come into contact with a synthetic fiber monofilament woven fabric. As a result of evaluation of the compression recovery, the compression recovery of the felt was higher than that of a conventional felt for papermaking in which the three-dimensional knit fabric was not used.

[0047] The evaluation data of each sample is summarized in Table 1.

[Example 2]

[0048] The repeated compressive residual strain of the three-dimensional knit fabric C knitted by the above-described method was measured. As a result, the repeated compressive residual strain was 8%. A felt for papermaking as shown in Figure 2 was prepared using the three-dimensional knit fabric C and the compression recovery was evaluated. As a result, the compression recovery of the felt was higher than that of a conventional felt for papermaking in which the three-dimensional knit fabric was not used.

[0049] The evaluation data of each sample is summarized in Table 1.

[Example 3]

[0050] The repeated compressive residual strain of the three-dimensional knit fabric D knitted by the above-described method was measured. As a result, the repeated compressive residual strain was 10%. A felt for papermaking as shown in Figure 2 was prepared using the three-dimensional knit fabric D and the compression recovery was evaluated. As a result, the compression recovery of the felt was higher than that of a conventional felt for papermaking in which the three-dimensional knit fabric was not used.

[0051] The evaluation data of each sample is summarized in Table 1.

[Comparative Example 1]

[0052] A conventional felt for papermaking as shown in Figure 4 in which the three-dimensional knit fabric was not used was prepared and the compression recovery was evaluated. As a result, the compression recovery of the felt was lower than that of the felts of Examples 1, 2 and 3.

[0053] The evaluation data of each sample is summarized in Table 1.

[Comparative Example 2]

[0054] The repeated compressive residual strain of the three-dimensional knit fabric B knitted by the above-described method was measured to be 30%. A felt for papermaking as shown in Figure 2 was prepared using the three-dimensional knit fabric B and the compression recovery was evaluated. As a result, although some effect on the compression recovery was found compared to a conventional felt for papermaking in which the three-dimensional knit fabric was not used, the effect was not as high as those in Examples 1, 2 and 3.
The evaluation data of each sample is summarized in Table 1.

[Comparative Example 3]

[0055] The repeated compressive residual strain of the three-dimensional knit fabric E knitted by the above-described method was measured to be 15%. A felt for papermaking as shown in Figure 2 was prepared using the three-dimensional knit fabric E. As a result of evaluating the compression recovery, although the compression recovery of the felt was higher than that of a conventional felt for papermaking in which the three-dimensional knit fabric was not used, wrinkles were found in wet paper and impact on the wet paper was so great that the felt could not be practically used.

[0056] The evaluation data of each sample is summarized in Table 1.

[0057] 

[Table 1]

		Ex. 1	Ex. 2	Ex. 3	Comp. Ex. 1	Comp. Ex. 2	Comp. Ex. 3
Residual strain (%) of three-dimensional knit fabric		15	8	10	―	30	15
Maximum area (mm2) of void on three-dimensional knit fabric surface	L1 side	1.1	1.2	0.2	―	1.2	11.4
	L4, L5 sides	11.4	12.0	0.4		12.0	11.4
Compression recovery of papermaking felt (index)		1.2	1.3	1.3	1.0	1.05	1.2

[Example 4]

[0058] Two nonwoven fabrics having a weight of 30 g/m² composed of polyethylene terephthalate having an average single yarn diameter of 0.05 dtex prepared by a melt blow method were laminated on the upper and lower sides of the three-dimensional knit fabric C, and they were entangled and integrated by a columnar stream. In this case, the laminate has a particle collection efficiency for particles of 0.1 to 5.0 µm of 85% and a pressure loss of 250 Pa, and is useful as a filter.

[Example 5]

[0059] A piece of craft felt was each laminated on the upper and lower sides of the three-dimensional knit fabric A (permeation rate of water of the fabric: 6 ml/cm²·second) previously cut into a pre-determined size, and the permeation rate of water thereof was measured. As a result, the permeation rate of water was as high as 0.52 ml/cm²·second.

[0060] The evaluation data is summarized in Table 2.

[Example 6]

[0061] Two pieces of craft felt were each laminated on the upper and lower sides of the three-dimensional knit fabric A, and the permeation rate of water thereof was measured. As a result, the permeation rate of water was as high as 0.60 ml/cm²·second.

[0062] The evaluation data is summarized in Table 2.

[Example 7]

[0063] A piece of craft felt was each laminated on the upper and lower sides of the three-dimensional knit fabric C (permeation rate of water of the fabric: 8 ml/cm²·second), and the permeation rate of water thereof was measured. As a result, the permeation rate of water was as high as 1.64 ml/cm²·second.

[0064] The evaluation data is summarized in Table 2.

[Example 8]

[0065] Two pieces of craft felt were each laminated on the upper and lower sides of the three-dimensional knit fabric C, and the permeation rate of water thereof was measured. As a result, the permeation rate of water was as high as 1.01 ml/cm²·second.

[0066] The evaluation data is summarized in Table 2.

[Comparative Example 5]

[0067] The permeation rate of water of a piece of craft felt alone was measured without using the three-dimensional knit fabric, and as a result, the permeation rate of water was 0.10 ml/cm²·second, which was extremely low.

[Comparative Example 6]

[0068] The permeation rate of water was measured after stacking two pieces of craft felt, and as a result, the permeation rate of water was 0.17 ml/cm²·second, which was extremely low.

[0069] The evaluation data is summarized in Table 2.

[Comparative Example 7]

[0070] The permeation rate of water was measured after stacking three pieces of craft felt, and as a result, the permeation rate of water was 0.24 ml/cm²·second, which was extremely low.

[0071] The evaluation data is summarized in Table 2.

[Comparative Example 8]

[0072] The permeation rate of water was measured after stacking four pieces of craft felt, and as a result, the permeation rate of water was 0.31 ml/cm²·second, which was extremely low.

[0073] The evaluation data is summarized in Table 2.

[Comparative Example 9]

[0074] The permeation rate of water was measured after stacking five pieces of craft felt, and as a result, the permeation rate of water was 0.33 ml/cm²·second, which was extremely low.

[0075] The evaluation data is summarized in Table 2.

[Comparative Example 10]

[0076] The permeation rate of water was measured after stacking six pieces of craft felt, and as a result, the permeation rate of water was 0.17 ml/cm²·second, which was extremely low.

[0077] The evaluation data is summarized in Table 2.

[0078] 

[Industrial Applicability]

[0079] The three-dimensional knit fabric of the present invention comprises a knit fabric constituting front and back sides and a connecting yarn composed of a monofilament. Since at least one of the three-dimensional front and back knit fabrics has voids, the three-dimensional knit fabric is useful as an interlining material of a laminate with various other materials, and has a characteristic that the repeated compressive residual strain is small. Moreover, by using a thick three-dimensional knit layer as an interlining material, lamination with a nonwoven fabric by a needle punch and entangling by spunlacing become possible, and the laminate can be suitably used for a felt for papermaking, air filters, water squeezing materials and filter materials.

[Brief Description of Drawings]

[0080] 

Figure 1 is a schematic front perspective cross-sectional view of a laminate using the three-dimensional knit fabric of the present invention as an interlining material;

Figure 2 is a schematic cross-sectional view of a laminate using a piece of the three-dimensional knit fabric of the present invention and a piece of synthetic fiber monofilament woven fabric as an interlining material;

Figure 3 is a schematic cross-sectional view of a laminate using a piece of the three-dimensional knit fabric of the present invention and two pieces of synthetic fiber monofilament woven fabric as interlining materials;

Figure 4 is a schematic cross-sectional view of a conventional laminate in which the three-dimensional knit fabric is not used; and

Figure 5 is a schematic cross-sectional view of an apparatus for measuring permeation of water.

[Description of Symbols]

[0081] 

10

interlining material comprising three-dimensional knit fabric of present invention

11

front knit layer of three-dimensional knit fabric

12

back knit layer of three-dimensional knit fabric

13

connecting yarn of three-dimensional knit fabric

20

laminate using three-dimensional knit fabric of present invention

21

synthetic fiber monofilament woven fabric

22

synthetic fiber assembly

30

laminate using three-dimensional knit fabric of present invention

40

conventional laminate in which three-dimensional knit fabric is not used

50

apparatus for measuring permeation of water

51

plastic cylinder

52

polyethylene sheet

53

three-dimensional knit fabric

54

sample receptacle

55

water receiver

Claims

1. A three-dimensional knit fabric comprising a yarn constituting front and back knit layers and a monofilament connecting yarn for connecting the front and back knit layers, characterized in that at least one of the three-dimensional front and back knit layers has a largest void with an area of 0.1 to 6 mm².

2. The three-dimensional knit fabric according to claim 1, characterized in that the connecting yarn of the three-dimensional knit fabric is a monofilament of 15 to 1000 dtex.

3. The three-dimensional knit fabric according to claim 1 or 2, characterized in that the knit fabric has a repeated compressive residual strain of 20% or less.

4. The three-dimensional knit fabric according to any one of claims 1 to 3, characterized in that the knit fabric is used for a felt for papermaking.

5. An interlining material comprising the three-dimensional knit fabric according to any one of claims 1 to 4, characterized in that both the front and back knit layers of the three-dimensional knit fabric comprise a monofilament of 10 to 300 dtex.

6. An interlining material comprising the three-dimensional knit fabric according to any one of claims 1 to 5, characterized in that the interlining material is used for laminating another material on one side of both the front and back knit layers.

7. An interlining material comprising the three-dimensional knit fabric according to any one of claims 1 to 6, characterized in that the interlining material has a permeation rate of water of 1 to 10 ml/cm²·second.

8. An interlining material comprising the three-dimensional knit fabric according to any one of claims 1 to 7, characterized in that the interlining material is used for a felt for papermaking which is laminated on at least one side thereof.

9. A laminate comprising a nonwoven fabric laminated on at least one side of the interlining material according to claims 1 to 8.

10. The laminate according to claim 9, comprising a nonwoven fabric made of at least one member of a synthetic fiber, a regenerated fiber and a natural fiber having a single yarn size of 0.01 to 25 dtex.

11. The laminate according to claim 9 or 10, characterized in that the nonwoven fabric and the interlining material are integrated by needlepunching.

12. The laminate according to claim 9 or 10, characterized in that the nonwoven fabric and the interlining material are integrated by spunlacing.

13. The laminate according to any one of claims 9 to 12, characterized in that the laminate has a permeation rate of water of 0.4 to 2.0 ml/cm²·second.

14. The laminate according to any one of claims 9 to 12, characterized in that the laminate has an air pressure loss of 300 Pa or less.

15. The laminate according to any one of claims 9 to 14, characterized in that the laminate has a particle collection efficiency of 80% or more for particles of 0.1 to 5.0 µm.

Drawing