CARBON-POWDER-CONTAINING FIBER AND FIBROUS STRUCTURE

Abstract

 The invention relates to a carbon-powder-containing fiber that contains a plant-derived carbon powder in the fiber, the carbon powder having a specific surface area of 250 m²/g or larger and smaller than 500 m²/g, and a content of the carbon powder relative to the mass of the carbon-powder-containing fiber being 0.2 to 7% by mass.

Description

TECHNICAL FIELD

[0001] The present invention relates to a carbon-powder-containing fiber and a fibrous structure.

BACKGROUND ART

[0002] Black dope dyed yarn has been used for clothing such as black formal clothing and working clothes, and for materials such as gloves and brushes, for which carbon black has been widely used as a component for constituting the yarn. Carbon black has been widely produced by atomizing a petroleum-derived oil as a raw material in a mist form, followed by burning, since such production method is easy to control the particle size.

[0003] For example, Patent Documents 1 and 2 disclose black dope dyed polyester fibers that contain carbon black whose particle size, specific surface area and so forth fall in predetermined ranges. Patent Document 3 also discloses a fiber that contains a carbon powder such as wood charcoal and/or bamboo charcoal, in addition to, or in place of carbon black. Patent Document 4 still also discloses a fiber that contains activated carbon.

PRIOR ART DOCUMENTS

PATENT DOCUMENTS

[0004] 

Patent Document 1: JP-A-2006-241640

Patent Document 2: JP-A-H09-250026

Patent Document 3: JP-A-2002-249922

Patent Document 4: JP-A-2003-38626

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0005] The black dope dyed fibers described in Patent Documents 1 and 2 are fibers that contain carbon black, but are not deodorant. In addition, since the carbon black is a petroleum-derived material, there is a persistent need for the black dope dyed fiber that uses a non-petroleum derived material, from the viewpoint of environmental consideration. The fiber described in Patent Document 3 may contain wood charcoal and/or bamboo charcoal as the carbon powder. Use of the wood charcoal or bamboo charcoal, however, needs large consumption of carbon powder in order to exhibit a sufficient level of deodorization. In some cases, use of a large amount of wood charcoal and bamboo charcoal has, however, degraded the spinnability in a process of fiberization, particularly in a range of fine-denier, leading to lowered productivity. There has also been a case where drop-off of the carbon powder has degraded the workability. Although the fiber that contains activated carbon described in Patent Document 4 could be deodorant, such fiber needs to be produced in a special environment due to high scatterability of the activated carbon during the production, proving the productivity not always satisfiable. Also in some cases, the black dope dyed fiber would be colored only with poor uniformity, due to poor dispersibility of activated carbon in the fiber.

[0006] It is therefore an object of the present invention to provide a black dope dyed fiber which is highly deodorant and uniformly colored, and is producible with high fiber productivity.

SOLUTIONS TO THE PROBLEMS

[0007] The present inventors have achieved the present invention, after intensive studies aimed to solve the aforementioned problems. That is, the present invention encompasses the following preferred embodiments.

[1] A carbon-powder-containing fiber that contains a plant-derived carbon powder in the fiber, the carbon powder having a specific surface area of 250 m²/g or larger and smaller than 500 m²/g, and a content of the carbon powder relative to the mass of the carbon-powder-containing fiber being 0.2 to 7% by mass.

[2] The carbon-powder-containing fiber according to [1], wherein the carbon powder is a carbon powder derived from coconut shell.

[3] The carbon-powder-containing fiber according to [1] or [2], wherein the fiber is a synthetic fiber or a semi-synthetic fiber.

[4] The carbon-powder-containing fiber according to [3], wherein the fiber is a polyester-based fiber or a polyamide-based fiber.

[5] The carbon-powder-containing fiber according to any one of [1] to [4], wherein the carbon powder has an average particle size D₅₀ of 1.5 µm or smaller.

[6] The carbon-powder-containing fiber according to any one of [1] to [5], wherein the carbon powder has a D₉₀ value in a particle size distribution of 4.0 µm or smaller.

[7] The carbon-powder-containing fiber according to any one of [1] to [6], wherein a single yarn fineness is 0.01 to 10 dtex.

[8] A fibrous structure that includes the carbon-powder-containing fiber according to any one of [1] to [7].

EFFECTS OF THE INVENTION

[0008] According to the present invention, it is possible to provide a black dope dyed fiber which is highly deodorant and uniformly colored, and is producible with high fiber productivity. Moreover, the carbon-powder-containing fiber of the present invention is carbon-neutral, thus making it possible to provide an environment-friendly black dope dyed fiber.

DETAILED DESCRIPTION

[0009] Embodiments of the present invention will be described in details below. The scope of the present invention is not limited to the embodiments described herein, instead allowing various modifications without departing from the spirit of the present invention.

[0010] The carbon-powder-containing fiber of the present invention contains a plant-derived carbon powder in the fiber, wherein the carbon powder has a specific surface area of 250 m²/g or larger and smaller than 500 m²/g, and a content of the carbon powder relative to the mass of the carbon-powder-containing fiber is 0.2 to 7% by mass.

[Carbon Powder]

[0011] The carbon powder contained in the carbon-powder-containing fiber of the present invention is a plant-derived carbon powder. The plant-derived carbon powder is obtainable by using plant as a main raw material. The plant-derived carbon powder is considered to have a very intricate structure derived from a plant-specific tissue structure or the like, as compared with a carbon powder, for example, derived from a non-plant material, such as petroleum-derived carbon powder represented by carbon black. In the present invention, addition of a relatively small amount of carbon powder can achieve high deodorizing property, since the carbon powder is a plant-derived powder having a predetermined specific surface area. In addition, the plant-derived carbon powder is carbon-neutral as compared with carbon powders derived from mineral, petroleum and synthetic materials, and is therefore advantageous also from the viewpoint, for example, of environmental protection and commercialization.

[0012] In the present invention, the plant that can be used as a raw material of the plant-derived carbon powder is not particularly limited as long as the carbon powder with the predetermined specific surface area is obtainable, and is exemplified by coconut shell, coffee bean, tea leaf, sugar cane, fruit (orange or banana), straw, and rice shell. Only one kind of these plants may be used, or two or more kinds thereof may be used in a combined manner. From the viewpoint of easy attainability of higher deodorizing property and productivity of the black dope dyed yarn, the plant-derived carbon powder is preferably a carbon powder derived from at least one plant selected from the group consisting of coconut shell, coffee bean, tea leaf, sugar cane, fruit, straw, and rice shell; and is more preferably a carbon powder derived from coconut shell. Use of coconut shell as a starting plant is commercially advantageous, since it is available in large quantities.

[0013] As described previously, the carbon powders of wood charcoal or bamboo charcoal, for example, are difficult to sufficiently enlarge the specific surface area, which is usually not 250 m²/g or larger, and this often makes it difficult to achieve a sufficient level of deodorizing property with a small amount of addition. Meanwhile, activated carbon will have too small specific gravity of carbon powder, and is likely to scatter during manufacture of the carbon-powder-containing fiber, thus limiting the manufacturing conditions. Not only that, the excessively large specific surface area occasionally degrades the productivity or coloring uniformity, due to agglomeration. Meanwhile, carbon black is not plant-derived, and the morphology thereof, with cavities found inside the particle but scarce on the surface, is not considered to achieve a sufficient level of deodorizing property. Hence, the carbon powder in the carbon-powder-containing fiber of the present invention is preferably a carbon powder excluding bamboo charcoal, wood charcoal, activated carbon, and carbon black. In this aspect, the carbon-powder-containing fiber of the present invention, as long as it contains the carbon powder other than bamboo charcoal, wood charcoal, activated carbon, and carbon black, may contain additional carbon powder, besides such carbon powder, selected from the group consisting of bamboo charcoal, wood charcoal, activated carbon, and carbon black, to the extent that the effect of the present invention is not impaired.

[0014] The coconut that serves as the raw material of the coconut shell is not particularly limited, which is exemplified by palm (oil palm), coconut palm, salak, and double coconut. Only one kind of the coconut shells obtained from these coconuts may be used, or two or more kinds thereof may be used in a combined manner. Among them, coconut shells derived from coconut palm or palm, which are biomass waste generated in large quantities after used as food, raw materials for detergent, raw materials for biodiesel oil, and the like, are particularly preferable due to their mass availability and low price.

[0015] The carbon powder contained in the carbon-powder-containing fiber of the present invention has a specific surface area of the carbon powder of 250 m²/g or larger, and smaller than 500 m²/g. When the specific surface area of the carbon powder is less than 250 m²/g, the pores formed on the surface of the carbon powder will be too scarce, and therefore, the obtainable fiber will have only an insufficient level of deodorizing property. This also needs a large amount of carbon powder to be mixed in order to enhance the deodorizing property, thus making the productivity during fiber manufacture tend to degrade, or the carbon powder tend to drop off during fiber manufacture and use. The specific surface area of the carbon powder is preferably 300 m²/g or larger, more preferably 330 m²/g or larger, even more preferably 360 m²/g or larger, yet more preferably 380 m²/g or larger, and particularly preferably 400 m²/g or larger, from the viewpoint of easily enhancing the deodorizing property and the productivity of the carbon-powder-containing fiber.

[0016] Meanwhile, when the specific surface area of the carbon powder is 500 m²/g or larger, the carbon powder will have too small specific gravity, thus making it more likely to scatter during manufacture of the carbon-powder-containing fiber, thus limiting the manufacturing conditions. Not only that, the excessively large specific surface area occasionally degrades the productivity or coloring uniformity, due to agglomeration. The agglomeration will be more likely to occur, presumably because increase in the specific surface area increases the surface energy, making the primary particles more likely to destabilize, increasing the number of functional group exposed on the particle surface, and thus intensifying electrostatic attraction. Similarly, the carbon powder will be more likely to exist in the agglomerated state, when mixed with a component constituting the fiber. This makes it difficult to uniformly disperse the carbon powder when mixed with a component constituting the fiber, such as resin, making the black dope dyed fiber more likely to cause uneven black color, thus degrading the coloring uniformity of the obtainable carbon-powder-containing fiber. Moreover, longer time for mixing, before spun, of the carbon powder with a component constituting the fiber will be necessary in order to obtain uniformly colored black dope dyed fiber. Also yarn breakage due to agglomerate, during spinning of the fiber, will be more likely to occur when spinning a fiber having a small single yarn fineness. Both will degrade the productivity. The specific surface area of the carbon powder is preferably 480 m²/g or smaller, more preferably 470 m²/g or smaller, even more preferably 460 m²/g or smaller, and yet more preferably 450 m²/g or smaller, from the viewpoint of easily enhancing the coloring uniformity and the productivity of the carbon- powder-containing fiber. The specific surface area of the carbon powder is given by BET specific surface area that can be estimated by the nitrogen adsorption method, and can be estimated, for example, by the method described in Examples. The specific surface area of the carbon powder may be measured while using, as a measurement sample, a carbon powder to be used as a material for manufacturing the carbon-powder-containing fiber, or may be measured by using a carbon powder, as a measurement sample, obtained after removing, by dissolution, the resin and the like constituting the fiber from the carbon- powder-containing fiber.

[0017] Method for manufacturing the carbon powder, whose specific surface area falls in the aforementioned range, is exemplified by calcining of the plants enumerated above. The method for manufacturing the carbon powder by calcining the plant is not particularly limited, allowing use of any of known methods in the art. For example, the carbon powder is manufacturable by calcining (carbonizing) a plant as a raw material, typically at a temperature of approximately 300°C or higher and 900°C or lower, for approximately 1 to 20 hours in an inert gas atmosphere. The carbon powder thus obtained by the aforementioned calcining process may be ground and/or classified, in order to adjust the specific surface area to a desired range. In particular, use of plant with relatively high hardness, such as coconut shell, tends to leave coarse powder during the grinding. Hence, the coarse powder is preferably removed by the grinding and/or classification process, from the viewpoint of easily enhancing the productivity of the carbon-powder-containing fiber.

[0018] The inert gas is not particularly limited as long as it is non-reactive with the carbon powder at the calcination temperature, and is exemplified by nitrogen, helium, argon, krypton, or a mixed gas thereof. Nitrogen is preferred. The lower the concentration of the impurity gas, particularly oxygen, contained in the inert gas, the more preferred. A preferred oxygen concentration normally acceptable is 0 to 2000 ppm, which is more preferably 0 to 1000 ppm.

[0019] A mill used for the grinding is not particularly limited, and is exemplified by a bead mill, a jet mill, a ball mill, a hammer mill, and a rod mill, which may be used independently, or in a combined manner. A jet mill functionalized as a classifier is preferable from the viewpoint of easily obtaining a powder having a desired specific surface area, and the like. On the other hand, when using a ball mill, a hammer mill, a rod mill or the like, the specific surface area is adjustable to a desired value by grinding, followed by classification.

[0020] The grinding followed by classification enables more precise adjustment of the specific surface area or the like. The classification is exemplified by sieving classification, wet classification, and dry classification. A wet classifier is exemplified by those making use of principles such as gravity classification, inertial classification, hydraulic classification, or centrifugal classification. A dry classifier is exemplified by those making use of principles such as sedimentary classification, mechanical classification, or centrifugal classification.

[0021] In the grinding process, a single apparatus may be used both for grinding and classification. For example, a jet mill also functionalized as a dry classifier may be used for grinding and classification. Alternatively, an apparatus having independent mill and classifier may be used. In this case, the grinding and the classification may take place continuously, or discontinuously.

[0022] The carbon powder, obtained by calcining the plant under the aforementioned temperature conditions, is also an intermediate product, for example, in the process of manufacturing activated carbon. In the manufacture of activated carbon, the carbon powder obtained as described above is further subjected to activation treatment. The activation treatment is the treatment for forming pores on the surface of the carbon powder to convert it to a porous carbonaceous substance. An activated carbon having a large specific surface area and a large pore volume may thus be manufactured. The activation treatment employed is exemplified by gas activation treatment, and chemical activation treatment. The carbon powder contained in the carbon-powder-containing fiber of the present invention has a specific surface area in the aforementioned above range. The carbon powder having such specific surface area is a non-activated carbon powder, but not an activated carbon which is an activated substance. The activated carbon has a specific surface area exceeding 500 m²/g, proving that, also from this viewpoint, it is not the carbon powder contained in the carbon-powder-containing fiber of the present invention. Also in the process of manufacturing the activated carbon, the aforementioned activation treatment would occasionally be preceded by removal of a fine fraction of the carbon powder which is an intermediate product, for the purpose of improving performances of battery material or purification material manufactured with use of the activated carbon. Although the removed fine powder has usually been discarded or recycled as a fuel, the present invention now enables upcycling of the waste fine powder as a functional material.

[0023] Whether the carbon powder has been activation-treated or not may be confirmed by observing the structure of the carbon powder, for example, under an apparatus such as transmission electron microscope (TEM) or scanning electron microscope (SEM). Hence, the carbon powder contained in the carbon-powder-containing fiber of the present invention is preferably a carbon powder for which a structure having usually been formed by the activation treatment is not observable in TEM or SEM image, and having the specific surface area within the aforementioned range.

[0024] The carbon powder contained in the carbon-powder-containing fiber of the present invention preferably has an average particle size D₅₀, in a particle size distribution, of 1.5 µm or smaller, more preferably 1.3 µm or smaller, even more preferably 1.2 µm or smaller, yet more preferably 1.0 µm or smaller, particularly preferably 0.8 µm or smaller, and particularly more preferably 0.7 µm or smaller from the viewpoint of easily enhancing the spinnability and easily adjusting the specific surface area to the aforementioned range. The average particle size D₅₀ is preferably 0.03 µm or larger, more preferably 0.05 µm or larger, and even more preferably 0.1 µm or larger, from the viewpoint that too small particle size would be more likely to cause secondary agglomeration.

[0025] The carbon powder contained in the carbon-powder-containing fiber of the present invention preferably has D₉₀, in a particle size distribution, of 4.0 µm or smaller, more preferably 3.5 µm or smaller, even more preferably 3.0 µm or smaller, and yet more preferably 2.5 µm or smaller from the viewpoint of easily enhancing the spinnability as a result of removal of coarse powder. From the viewpoint that too small particle size would be more likely to cause secondary agglomeration, D₉₀ is preferably 0.1 µm or larger, more preferably 0.2 µm or larger, and even more preferably 0.5 µm or larger. D₅₀ and D₉₀ in the particle size distribution of the carbon powder may be measured by using, for example, a centrifugal automatic particle size distribution analyzer.

[Fiber]

[0026] The carbon-powder-containing fiber of the present invention is a fiber that contains the aforementioned carbon powder in the fiber. Now, the carbon powder contained in the fiber means that the carbon powder is contained inside the fiber. A part of the carbon powder may, however, be present on the fiber surface. The fiber is not particularly limited as long as it can contain the carbon powder inside thereof, and may be processed into fibrous form, and is exemplified by synthetic fiber and semi-synthetic fiber. The fiber is preferably a synthetic fiber or a semi-synthetic fiber, from the viewpoint of easy inclusion of the carbon powder inside the fiber, and high spinnability.

[0027] The synthetic fibers are exemplified by polyester-based fiber, polyamide-based fiber, polyurethane-based fiber, polyolefin-based fiber, acrylic fiber, vinyl-based fiber, polyarylate-based fiber, and polystyrene-based fiber. The semi-synthetic fiber is exemplified by regenerated cellulose fiber, cellulose derivative fiber, and regenerated protein fiber.

[0028] The polyester-based fiber is a fiber that contains a polyester-based resin as a main component. The polyester-based resin is a resin having a fiber forming ability, which contains aromatic dicarboxylic acid as a main acid component, and is exemplified by polyethylene terephthalate, polybutylene terephthalate, polytrimethylene terephthalate, polytetramethylene terephthalate, polycyclohexanedimethylene terephthalate, and polyethylene -2,6-naphthalenedicarboxylate. The polyester may also be a copolymer having copolymerized therewith a third component such as alcohol component represented by butanediol, or carboxylic acid represented by isophthalic acid; and even may be a mixture of these various polyesters. Among them, polyethylene terephthalate-based polymer is preferred from the viewpoint of handleability and cost.

[0029] The polyamide-based fiber is a fiber that contains polyamide-based resin as a main component. The polyamide-based resin is a polymer having a repeating structural unit linked by an amide bond. Polyamide-based fiber is also referred to as nylon. Also, aramid fiber that contains aromatic polyamide polymer is encompassed by the polyamide-based fiber. The polyamide-based resin is exemplified by aliphatic polyamide and copolymer thereof, such as polyamide 6, polyamide 66, polyamide 610, polyamide 10, polyamide 12, polyamide 6-12; and semi-aromatic polyamide synthesized from aromatic dicarboxylic acid and aliphatic diamine.

[0030] The polyurethane-based fiber is a fiber that contains polyurethane-based resin as a main component, and is exemplified by spandex fiber. The polyolefin-based fiber is a fiber that contains polyolefin-based resin as a main component, and is exemplified by polyethylene fiber, polypropylene fiber, and polymethylpentene fiber. The acrylic fiber is a fiber that contains acrylic resin as a main component, and is exemplified by acrylic fiber and modacrylic fiber. The vinyl-based fiber is a fiber that contains vinyl-based resin as a main component, and is exemplified by polyvinyl alcohol fiber, ethylene-vinyl alcohol copolymer fiber, and vinyl chloride fiber.

[0031] The regenerated cellulose fiber and cellulose derivative fiber are fibers mainly constituted by cellulose and/or derivative thereof, and are exemplified by rayon, cupra, and lyocell. The regenerated protein fiber is a fiber constituted by protein extracted from protein-containing material, and is exemplified by soybean protein fiber, and milk casein fiber.

[0032] In a preferred mode of the carbon-powder-containing fiber of the present invention, the fiber is preferably the polyester-based fiber or the polyamide-based fiber, from the viewpoint of kneadability with the powder, and versatility of the fiber.

[Carbon-Powder-Containing Fiber]

[0033] The carbon-powder-containing fiber of the present invention is a fiber that contains the plant-derived carbon powder in the fiber. The content of the carbon powder in the carbon-powder-containing fiber is 0.2 to 7% by mass, relative to the mass of the carbon-powder-containing fiber. When the content of the carbon powder is less than 0.2% by mass, a sufficient level of deodorizing property is not obtainable, due to insufficient content of the carbon powder. The content of the carbon powder is, from the viewpoint of enhancing the deodorizing property, preferably 0.25% by mass or more, more preferably 0.3% by mass or more, even more preferably 0.4% by mass or more, and yet more preferably 0.5% by mass or more relative to the mass of the carbon-powder-containing fiber. For applications in need of still higher deodorizing property, the content of the carbon powder, relative to the mass of the carbon-powder-containing fiber, is preferably 1% by mass or more, and more preferably 3% by mass or more. Meanwhile, when the content of the carbon powder in the carbon-powder-containing fiber exceeds 7% by mass, yarn breakage cannot be fully suppressed during spinning of the fiber, thus degrading the productivity of the carbon-powder-containing fiber. The content of the carbon powder is, from the viewpoint of easily enhancing the productivity of the carbon-powder-containing fiber, preferably 6.5% by mass or less, more preferably 6% by mass or less, even more preferably 5.5% by mass or less, and yet more preferably 5% by mass or less.

[0034] The single yarn fineness of the carbon-powder-containing fiber is preferably 0.01 to 10 dtex from the viewpoint of spinnability and texture. When the single yarn fineness is at the aforementioned lower limit value or above, the occurrence of yarn breakage during spinning of the fiber tends to be sufficiently suppressed. The single yarn fineness is more preferably 0.05 dtex or larger, and even more preferably 0.1 dtex or larger, from the viewpoint of improving the spinnability. Meanwhile, when the single yarn fineness is at the aforementioned upper limit value or less, knitted or woven fabric manufactured with use of such fiber will be more likely to have a soft finish and a good texture. From the viewpoint of manufacturing a product with the good finish, the single yarn fineness is more preferably 7 dtex or smaller, and even more preferably 4 dtex or smaller.

[0035] The total fineness of the carbon powder-containing fiber is not particularly limited, and may be appropriately set according to applications for which the carbon-powder-containing fiber is used. From the viewpoint of spinnability and versatility, the fineness is preferably 15 to 300 dtex, and more preferably 20 to 200 dtex, meanwhile the number of filaments is preferably 2 to 200 filaments, and more preferably 3 to 100 filaments.

[0036] The strength of the carbon-powder-containing fiber is not particularly limited, and may be appropriately set according to the applications for which the carbon-powder-containing fiber is used. The strength is preferably 1 cN/dtex or larger, more preferably 1.5 cN/dtex or larger, and even more preferably 2 cN/dtex or larger, from the viewpoint of preventing the yarn breakage or fluffing that possibly occurs due to a worn guide, or the like, during knitting or weaving. The strength, attainable by a common melt spinning method, is approximately 5.0 cN/dtex or smaller, whose upper limit value being, however, not specifically limited.

[0037] The elongation of the carbon-powder-containing fiber is not particularly limited, and may be appropriately set according to applications for which the carbon-powder-containing fiber is used. The elongation is, from the viewpoint of yarn workability, preferably 10% or larger, more preferably 20% or larger, and even more preferably 30% or larger. The upper limit value of elongation, although not particularly limited, is preferably 150% or smaller, and more preferably 100% or smaller, from the viewpoint of handleability in a product form.

[0038] The carbon-powder-containing fiber may have various cross-sectional shapes, which is not only circular cross section, but may also be oblate cross section, multi-lobe cross section, or hollow cross section. The carbon-powder-containing fiber may also have a core-sheath structure.

[0039] The carbon-powder-containing fiber of the present invention may optionally contain a freely-selectable additive, as long as the effects of the present invention will not be impaired. Examples of such additives include an antioxidant, a plasticizer, a heat stabilizer, an ultraviolet absorber, an antistatic agent, a lubricant, a filler, and other polymer compound. Only one kind of them may be used, or two or more kinds thereof may be used in a combined manner.

[Method for Manufacturing Carbon-Powder-Containing Fiber]

[0040] The carbon-powder-containing fiber of the present invention may be manufactured with use of the component that constitutes the fiber, the carbon powder, other components as appropriate, an additive, and the like, by using a publicly-known conventional spinning apparatus. For example, the spinning may rely upon melt spinning. More specifically, the fiber may be formed by any manufacturing method including a method in which melt-spinning at low or medium speed is followed by drawing; direct spinning and drawing at high speed; and a method in which spinning is followed by drawing and draw texturing, which are conducted concomitantly or sequentially.

[0041] In one exemplary method of manufacturing, the fiber of the present invention may be manufactured by melting a composition that contains a component constituting the fiber, the carbon powder, and any optional component in a melt extruder, guiding a molten polymer flow to a spinning head, weighing the polymer with a gear pump, ejecting the polymer through a spinning nozzle having a desired shape, optionally followed by drawing, and taking-up. Mixing of the component constituting the fiber with the carbon powder may rely upon direct mixing of these components; or may rely upon preliminary mixing of a partial component and the carbon powder to obtain a master batch, and mixing the master batch with the component constituting the fiber. The melting temperature during the spinning is appropriately adjusted depending on the melting point of the component constituting the fiber, which is usually preferred to be approximately 150 to 300°C. The yarn ejected from the spinning nozzle is taken up as it is at high speed, or drawn as necessary. The drawing is usually conducted at a temperature equal to or higher than the glass transition point of a component that constitutes the fiber, and at a drawing ratio 0.55 to 0.9 times the rupture elongation (HDmax). With the drawing ratio adjusted smaller than 0.55 times the rupture elongation, the fiber having a sufficient strength is less likely to be stably obtainable, meanwhile with the value exceeding 0.9 times the rupture elongation, the fiber becomes more likely to break.

[0042] The drawing may take place after the fiber was ejected from the spinning nozzle, and once taken up on a roll, or may take place subsequent to the drawing, either being acceptable for the present invention. The stretching usually relies upon hot drawing, while using any of hot air, hot plate, hot roller, water bath, and so forth. The take-up speed usually falls in the range approximately from 500 to 6000 m/min, although variable among the cases where the fiber is once taken up and then drawn; where the fiber is spun and drawn in a single process of direct spinning and drawing, followed by taking up; and where the fiber is taken up at high speed without being drawn. The speed of slower than 500 m/min would degrade the productivity, meanwhile the speed exceeding 6000 m/min would make the fiber more likely to break. The cross-sectional shape of the fiber of the present invention is not particularly limited, and may be formed into true circular, hollow, or modified cross section, according to the nozzle shape, with use of a usual technique of melt spinning. The fiber may also have a core-sheath structure having a core part or a sheath part composed of a composition that contains a fiber-forming component and the carbon powder; and a sheath part or a core part composed of a component that contains the fiber. The shape is preferably true circle, from the viewpoint of process passability in fiberization and weaving.

[Fibrous Structure]

[0043] The carbon-powder-containing fiber of the present invention is applicable to various types of fibrous structure (fiber assembly), so that the present invention also provides a fibrous structure that contains the carbon-powder-containing fiber of the present invention. Now, the "fibrous structure" may be multifilament yarn, spun yarn, woven/knitted fabric, nonwoven fabric, paper, artificial leather, or stuffing material composed only of the carbon-powder-containing fiber of the present invention; or may be woven/knitted fabric, or a nonwoven fabric partially with use of the carbon- powder-containing fiber of the present invention, which are exemplified by mixed/union fabric with use of other fiber such as natural fiber, chemical fiber, synthetic fiber or semi-synthetic fiber; woven/knitted fabric with use of textured yarn in the form of blended yarn, commingled yarn, twisted yarn, interlaced yarn, or crimped yarn; cotton-blended nonwoven fabric; and fiber laminate.

[0044] The carbon-powder-containing fiber of the present invention, and the fibrous structure that contains the carbon-powder-containing fiber of the present invention have excellent deodorizing properties and excellent uniformity of black coloring. Hence, the carbon-powder-containing fiber and the fibrous structure of the present invention are applicable, for example, to clothing products such as a shirt, pants, a coat, a uniform, working clothes, an underwear, pantyhose, socks, sportswear, and black formal clothing; interior fabric such as a curtain and a carpet; and material products such as gloves, a brush, a filter, and a sheet.

EXAMPLES

[0045] Hereinafter, the present invention will be described with reference to Examples, but the present invention is not limited to these Examples. Note that the notation "%" in the Examples is used in terms of mass, unless otherwise specifically noted. First, method for measuring the individual physical values will be described.

<Method for Analyzing Particle Size Distribution>

[0046] D₅₀ and D₉₀ of the carbon powder were obtained from particle size analysis with use of an automatic centrifugal particle size distribution analyzer CAPA-500, manufactured by Horiba, Ltd.

<Specific Surface Area>

[0047] The specific surface area of the carbon powder was measured with use of an accurate surface area/pore distribution analyzer ("BELSORP 28SA" manufactured by MicrotracBEL Corp.). A measurement sample was degassed in vacuo at 300°C for 5 hours, and a nitrogen adsorption isotherm at 77K was then measured. The adsorption isotherm thus obtained was used for multipoint analysis based on the BET equation, in which the specific surface area was estimated from a linear section of the obtained curve within a range of relative pressure P/P₀ =from 0.01 to 0.1.

<Production Example 1: Manufacture of Coconut Shell Carbon Powder 1>

[0048] Coconut shell chip was calcined (carbonized) at 500°C in a nitrogen gas atmosphere, washed and dried, dry-ground, and then classified to collect a fine powder. The particle sizes at that time were found to be D₅₀ = 1.5 µm and D₉₀ = 3.8 µm. The fine powder was further dry-ground again to obtain a coconut shell carbon powder 1. The coconut shell carbon powder 1 was found to have a particle size D₅₀ of 0.7 µm, a particle size D₉₀ of 2.2 µm, and a specific surface area of 440 m²/g.

<Production Example 2: Manufacture of Coconut Shell Carbon Powder 2>

[0049] Coconut shell chip was calcined (carbonized) at 500°C in a nitrogen gas atmosphere, washed and dried, dry-ground, classified, and a fine powder was collected to obtain a coconut shell carbon powder 2. The coconut shell carbon powder 2 was found to have a particle size D₅₀ of 1.3 µm, a particle size D₉₀ of 3.8 µm, and a specific surface area of 420 m²/g.

<Production Example 3: Manufacture of Coconut Shell Carbon Powder 3>

[0050] Coconut shell chip was calcined (carbonized) at 450°C in a nitrogen gas atmosphere, washed and dried, dry-ground, and then classified to collect a fine powder. The particle sizes at that time were found to be D₅₀ = 1.5 µm and D₉₀ = 3.8 µm. The fine powder was further dry-ground again to obtain a coconut shell carbon powder 3. The coconut shell carbon powder 3 was found to have a particle size D₅₀ of 0.8 µm, a particle size D₉₀ of 2.2 µm, and a specific surface area of 270 m²/g.

<Production Example 4: Manufacture of Coconut Shell Carbon Powder 4>

[0051] Coconut shell chip was calcined (carbonized) at 400°C in a nitrogen gas atmosphere, washed and dried, dry-ground, and then classified to collect a fine powder. The particle sizes at that time were found to be D₅₀ = 1.5 µm and D₉₀ = 3.8 µm. The fine powder was further dry-ground again to obtain a coconut shell carbon powder 4. The coconut shell carbon powder 4 was found to have a particle size D₅₀ of 0.8 µm, a particle size D₉₀ of 2.4 µm, and a specific surface area of 190 m²/g.

<Production Example 5: Production of Wood Charcoal Fine Powder>

[0052] Wood of ubame oak (Quercus phillyraeoides) was calcined at 1200°C and then rapidly cooled to 350°C to obtain a white coal (Binchoutan charcoal), followed by dry-grinding, to obtain wood charcoal fine powder. The wood charcoal fine powder was found to have a particle size D₅₀ of 0.5 µm, a particle size D₉₀ of 1.9 µm, and a specific surface area of 240 m²/g.

<Example 1>

[0053] The coconut shell carbon powder 1 obtained in Production Example 1 was kneaded with polyamide 6 (nylon 6 1011 FK, manufactured by Ube Industries, Ltd.) in a twin-screw extruder at 280 to 300°C, while controlling the ratio of content of the carbon powder 1 relative to the mass of the finally obtainable carbon- powder-containing fiber as summarized in Table 1, to obtain a resin composition. The resin composition thus obtained was spun through a 24-hole spinneret with a round cross section, at a spinning temperature of 250°C and a discharge rate of 29.4 g/min, the spun yarn was blown with cooling air at a temperature of 25°C, and a humidity of 60%, at a wind speed of 1.0 m/sec. The spun yarn was then introduced into a tube heater (internal temperature: 160°C) having a length of 1.0 m, an inlet guide diameter of 8 mm, an outlet guide diameter of 10 mm, and an inner diameter of 30 mm, located at a position 1.2 m below the spinneret, and then drawn within the tube heater. The yarn output from the tube heater was then oiled with use of an oiling nozzle, and taken up via two godet rollers at a speed of 3500 m/min, to obtain a carbon-powder-containing fiber 1 of 84 dtex/24 filaments.

<Examples 2 and 3>

[0054] Carbon-powder-containing fibers 2 and 3 were obtained in the same manner as in Example 1, except that the contents of the coconut shell carbon powder 1 were changed to the amounts summarized in Table 1.

<Example 4>

[0055] A carbon-powder-containing fiber 4 was obtained in the same manner as in Example 2, except that a spinneret having a cruciform cross section was used.

<Example 5>

[0056] A carbon-powder-containing fiber 5 was obtained in the same manner as in Example 1, except that a resin composition, which was obtained by kneading the coconut shell carbon powder 1 with polyamide 6 (nylon 6 1011 FK, manufactured by Ube Industries, Ltd.), while controlling the ratio of content of the carbon powder 1 relative to the mass of the finally obtainable carbon-powder-containing fiber as summarized in Table 1, was used as a sheath component; that polyamide 6 (nylon 6 1015 B, manufactured by Ube Industries, Ltd.) was used as a core component; and that a spinneret having a core-sheath type cross section was used.

<Example 6>

[0057] A carbon-powder-containing fiber 6 was obtained in the same manner as in Example 2, except that the coconut shell carbon powder 2 obtained in Production Example 2 was used in place of the coconut shell carbon powder 1.

<Example 7>

[0058] A carbon-powder-containing fiber 7 was obtained in the same manner as in Example 2, except that the coconut shell carbon powder 3 obtained in Production Example 3 was used in place of the coconut shell carbon powder 1.

<Example 8>

[0059] A carbon-powder-containing fiber 8 was obtained in the same manner as in Example 1, except that the fiber was spun through a 96-hole spinneret with a round cross section, at a spinning temperature of 250°C and a discharge rate of 29.4 g/min, to change the fineness to 84 dtex/96 filaments.

<Comparative Examples 1 and 2>

[0060] Carbon-powder-containing fibers 9 and 10 were obtained in the same manner as in Example 1, except that the contents of the coconut shell carbon powder 1 were changed to the amounts as summarized in Table 1.

<Comparative Example 3>

[0061] A carbon-powder-containing fiber 11 was obtained in the same manner as in Example 2, except that the coconut shell carbon powder 4 obtained in Production Example 4 was used in place of the coconut shell carbon powder 1.

<Comparative Example 4>

[0062] A wood charcoal fine powder-containing fiber 1 was obtained in the same manner as in Example 2, except that the wood charcoal fine powder obtained in Production Example 5 was used in place of the coconut shell carbon powder 1.

<Comparative Example 5>

[0063] A carbon-black-containing fiber was obtained in the same manner as in Example 1, except that a carbon black ("Vulcan XC-72", manufactured by Cabot Corporation, specific surface area: 214 m²/g) whose amount is summarized in Table 1 was used in place of the coconut shell carbon powder 1.

<Comparative Example 6>

[0064] An activated carbon-containing fiber was obtained in the same manner as in Example 1, except that an activated carbon ("KurarayCoal PW-D", from Kuraray Co., Ltd., specific surface area: 1500 m²/g) was used in place of the coconut shell carbon powder 1.

<Comparative Example 7>

[0065] A wood charcoal fine powder-containing fiber 2 was obtained in the same manner as in Comparative Example 4, except that the content of the wood charcoal fine powder was changed as summarized in Table 1.

[0066] The fibers of Examples and Comparative Examples thus obtained were evaluated with respect to yarn color unevenness, spinnability, and deodorizing property, as described below. The obtained results are summarized in Table 1.

<Evaluation of Yarn Color Unevenness>

[0067] Each of the fibers of Examples and Comparative Examples was knitted with use of a tubular knitting machine into a tubular knitted fabric, and the tubular knitted fabric was then subjected to L* measurement with use of a spectrophotometer "CM-3700A" manufactured by Konica Minolta, Inc., under the conditions of specular component mode: SCE, measurement diameter: LAV (25.4 mm), UV condition: 100% full, viewing angle: 2°, and main light source: C illuminant. The measurement was repeated five times, a difference between the maximum value and the minimum value of the obtained measurement results was found, and the yarn color unevenness was evaluated according to the criteria below. The smaller the difference between the maximum value and the minimum value, the smaller the variation of the hue.

○: Difference between maximum value and minimum value of L^∗ value, less than 2.

×: Difference between maximum value and minimum value of L^∗ value, 2 or larger.

[0068] The fiber obtained in Example 1 demonstrated the L* value minimized at 19.2 and maximized at the 19.8, with a difference of 0.6. The fiber obtained in Example 6 demonstrated the L* value minimized at 17.8 and maximized at the 18.3, with a difference of 0.5. In contrast, the fiber obtained in Comparative Example 6 demonstrated the L* value minimized at 17.0 and maximized at the 19.2, with a difference of 2.2.

<Evaluation of Spinnability>

[0069] The fibers were spun for 12 hours in a row under conditions of the aforementioned Examples and Comparative Examples, during which the number of times of yarn breakage was counted, and evaluated according to the criteria below.

⊙: Count of yarn breakage over 12 hours, once or less.

○: Count of yarn breakage over 12 hours, 2 or more, and 10 or less.

×: Count of yarn breakage over 12 hours, 11 or more.

<Evaluation of Deodorizing Performance>

[0070] In accordance with a deodorizing property test method conforming to The Certification Standards of SEK Mark Textile Products, specified by Kaken Test Center, general incorporated foundation, the fibers were tested by a detector tube method with use of ammonia, with which residual concentration of ammonia after 2 hours was measured. The deodorizing property was evaluated according to the criteria below.

⊙: Residual concentration of ammonia after 2 hours, 20% or less.

○: Residual concentration of ammonia after 2 hours, more than 20%, and 50% or less.

×: Residual concentration of ammonia after 2 hours, more than 50%.

[0071] The carbon-powder-containing fibers of Examples 1 to 8 were found to have the carbon powder contents of 0.2 to 7% by mass, relative to the mass of the carbon-powder-containing fiber, and the specific surface area of the carbon powder of 250 m²/g or larger and smaller than 500 m²/g, proving to have good spinnability and deodorizing property, as well as less yarn color unevenness. In contrast, Comparative Example 1, with the carbon powder content set as low as 0.1% by mass, failed to achieve a sufficient level of deodorizing property. Meanwhile, Comparative Example 2, with the carbon powder content set higher than 7% by mass, was found to cause yarn breakage during manufacture of the fiber, proving insufficient spinnability. It was also found that in Comparative Example 3 that contains the carbon powder having a specific surface area of 190 m²/g, in Comparative Example 4 that uses the wood charcoal fine powder, and in Comparative Example 5 that uses carbon black, all failed to achieve sufficient levels of deodorizing property. Comparative Example 6 that uses activated carbon failed to achieve uniform colorability. Comparative Example 7 that uses a large amount of wood charcoal fine powder was found to achieve good deodorizing property, but with poor spinnability.

Claims

1. A carbon-powder-containing fiber that contains a plant-derived carbon powder in the fiber, the carbon powder having a specific surface area of 250 m²/g or larger and smaller than 500 m²/g, and a content of the carbon powder relative to the mass of the carbon-powder-containing fiber being 0.2 to 7% by mass.

2. The carbon-powder-containing fiber according to claim 1, wherein the carbon powder is a carbon powder derived from coconut shell.

3. The carbon-powder-containing fiber according to claim 1 or 2, wherein the fiber is a synthetic fiber or a semi-synthetic fiber.

4. The carbon-powder-containing fiber according to claim 3, wherein the fiber is a polyester-based fiber or a polyamide-based fiber.

5. The carbon-powder-containing fiber according to any one of claims 1 to 4, wherein the carbon powder has an average particle size D₅₀ of 1.5 µm or smaller.

6. The carbon-powder-containing fiber according to any one of claims 1 to 5, wherein the carbon powder has a D₉₀ value in a particle size distribution of 4.0 µm or smaller.

7. The carbon-powder-containing fiber according to any one of claims 1 to 6, wherein a single yarn fineness is 0.01 to 10 dtex.

8. A fibrous structure comprising the carbon-powder-containing fiber according to any one of claims 1 to 7.