JP6022054B2 - Organic resin non-crimped staple fiber and method for producing the same - Google Patents

Description

  The present invention relates to an organic resin non-crimped staple fiber having uniform dispersibility in a medium.

  In recent years, staple fibers (referred to as short fibers) obtained from wholly aromatic polyamides having excellent properties such as mechanical properties, electrical properties, heat resistance, flame retardancy, and dimensional stability, or polyesters having higher cost advantages. In some cases, a wet nonwoven fabric using a part or all of the raw material is used as a wet nonwoven fabric such as an electrical insulating paper or a cleaning web of a copying machine (see, for example, Patent Document 1). In addition, similar wet nonwoven fabrics are widely used in industrial material field applications such as resin material reinforcing materials and daily life field applications. Short fibers made of an organic resin used in these wet nonwoven fabrics are required to have a finer fineness with increasing demands for flexibility and thinning / densification of the nonwoven fabric. At the same time, in order to achieve thinning and densification of the nonwoven fabric, it is necessary to improve the dispersibility of the short fibers in the dispersion medium when forming the wet nonwoven fabric. From this viewpoint, the fiber length of the short fibers should be further shortened. Is required.

  However, as the fiber aspect ratio (the ratio of fiber length to fiber diameter) increases as the fiber becomes finer, the fibers tend to be entangled with each other. Become. In order to avoid this defect, shortening the fiber length and keeping the aspect ratio small reduces the fuzzy ball-shaped defect due to the entanglement of the fibers, but this time it is agglomerated by the short fibers caught due to defective cut ends at the fiber ends. There was a problem that defects were likely to occur in products such as nonwoven fabrics. In particular, in a very fine fiber of 0.6 decitex or less, if a known guillotine cutter is used, it can be cut into almost any fiber length including less than 1 millimeter, that is, the aspect ratio can be reduced. However, because of the mechanism of the cutting equipment, the gripping of the fibers at the time of cutting is not sufficient, and cut end defects are very likely to occur (see, for example, Patent Document 2). In addition, if the cut ends of the short fibers are defective, the short fibers are aggregated due to being caught, resulting in defects in the nonwoven fabric and the reinforcing material, resulting in defects in the final product. In particular, when an organic resin having a high fiber strength is used, the sharpness of the cutter blade may deteriorate in a short time because the friction between the resin and the metal when cutting the fiber is very high. In addition, even short fibers with fineness are prone to have cut ends that have protrusions at the end, or have a cut surface that is not perpendicular to the fiber axis but oblique, and technically have little dispersion failure. As for organic resins in general, uncrimped short fibers are not marketed. On the other hand, an invention relating to a uniform fiber having a small fiber diameter length and a fiber length distribution and a fiber paper using a fiber having a feature in a shape having a protrusion is also known (see Patent Documents 3, 4 and 5). ).

JP 2011-232509 A JP 2009-221611 A JP 2007-092235 A Japanese Patent Laid-Open No. 2000-119989 JP 2001-295191 A

  The present invention has been made based on the above background, and relates to an organic resin non-crimped staple fiber (short fiber) that is uniformly dispersed in a medium without causing an aggregation defect.

As a result of intensive studies to solve the above problems, the present inventor employs the following configuration in order to solve the above problems.
1. The fineness is 0.0001 to 0.6 dtex, the fiber length is 0.01 to 5.0 millimeters, the moisture content is 10 to 200% by weight, the cut end coefficient defined below is 1.00 to 1.40, The present inventors have found that defects can be suppressed by an organic resin non-crimped staple fiber having a fiber length relative variation coefficient (CV%) of 0.0 to 15.0%, and have reached the present invention. The cut end coefficient and the fiber length relative variation coefficient are defined by the following equations.
(1) Cut end coefficient = b / a
(The fiber diameter of a single crimped staple fiber is a, and the maximum cut end diameter is b.)
(2) Relative variation coefficient of fiber length (CV%) = (standard deviation of fiber length) / (average value of fiber length) × 100 (%)
In both (1) and (2), the number of single yarns measured is 50.
Preferably, the present invention adopts the following configuration.
2. 2. The organic resin-free crimped staple fiber according to 1 above, wherein the uncrimped staple fiber is a polyester-free crimped staple fiber, a wholly aromatic polyamide-free crimped staple fiber, or a polyolefin-free crimped staple fiber.
3. Uncrimped staple fiber is polyethylene terephthalate-free crimped staple fiber, polytrimethylene terephthalate-free crimped staple fiber, polytetramethylene terephthalate-free crimped staple fiber, polyethylene naphthalate-free crimped staple fiber, polytrimethylene naphthalate-free Crimped staple fiber, polytetramethylene naphthalate uncrimped staple fiber, meta-type wholly aromatic polyamide uncrimped staple fiber, para-type wholly aromatic polyamide uncrimped staple fiber, polyethylene uncrimped staple fiber or polypropylene The organic resin non-crimped staple fiber according to any one of 1 to 2 above, which is a crimped staple fiber.
4). 4. The organic resin-free crimped staple fiber according to any one of 1 to 3, wherein the uncrimped staple fiber is a composite fiber composed of two or more organic resins.

  According to the present invention, in a non-crimped staple fiber made of an organic resin, when used in a wet nonwoven fabric or a staple fiber reinforced resin, the staple fiber is uniformly dispersed in a dispersion medium and the generation of aggregates is suppressed. Can do. As a result, the nonwoven fabric obtained by using the uncrimped staple fiber as a material is a nonwoven fabric in which the staple fibers are uniformly dispersed. As a result, it is possible to obtain a good non-woven fabric which is free from defects such as uneven dispersion of micro staple fibers, variation in basis weight and thickness, and has uniform air permeability and liquid permeability. Furthermore, there are few defects in the final product obtained by processing the non-woven fabric, etc., and the reliability of the physical properties of the final product (reliability regarding quality assurance) can be improved, and the yield of intermediate products (non-woven fabric, resin moldings, etc.) is improved. be able to. Therefore, the present invention has a great merit from the viewpoint of resource saving and economy.

It is a schematic diagram of the cut end part of the organic resin crimped staple fiber of the present invention.

Drawing reference

a Fiber diameter of single yarn b Maximum width of fiber cut end (maximum diameter if the shape of the cut end is circular or nearly circular)

(Organic resin composition)
(polyester)
Hereinafter, embodiments of the present invention will be described in detail. First, the case where polyester is used as a specific example of the organic resin of the present invention will be described. Examples of the polyester include polyalkylene terephthalate such as polyethylene terephthalate, polytrimethylene terephthalate, or polybutylene terephthalate (polytetramethylene terephthalate), or polyethylene naphthalate, polytrimethylene naphthalate, or polybutylene naphthalate (polytetramethylene). Examples thereof include polyesters of aromatic dicarboxylic acids and aliphatic diols such as polyalkylene naphthalates such as naphthalate). Polyesters obtained from alicyclic dicarboxylic acids such as polyalkylenecyclohexanedicarboxylate and aliphatic diol, polyesters obtained from aromatic dicarboxylic acid such as polycyclohexanedimethylene terephthalate and alicyclic diol, polyethylene succinate, poly Examples thereof include polyesters obtained from aliphatic dicarboxylic acids such as butylene succinate or polyethylene adipate and aliphatic diols, or polyesters obtained from polyhydroxycarboxylic acids such as polylactic acid and polyhydroxybenzoic acid.

  Or the copolymer and blend body by arbitrary ratios of these polyester components are illustrated. Depending on the purpose, as dicarboxylic acid components, isophthalic acid, phthalic acid, alkali metal salt of 5-sulfoisophthalic acid, quaternary ammonium salt of 5-sulfoisophthalic acid, quaternary phosphonium salt of 5-sulfoisophthalic acid, succinic acid , Adipic acid, suberic acid, sebacic acid, cyclohexanedicarboxylic acid, α, β- (4-carboxyphenoxy) ethane, 4,4-dicarboxyphenyl, 2,6-naphthalenedicarboxylic acid, 2,7-naphthalenedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid or 1,4-cyclohexanedicarboxylic acid or a diester compound composed of an organic group having 1 to 10 carbon atoms may be copolymerized in one component or in two or more components. Depending on the purpose, diethylene glycol, 1,2-propanediol, 1,2-butanediol, 1,3-butanediol, 1,6-hexanediol, neopentyl glycol, 1,4-cyclohexanedimethanol can be used as the diol component. , 2,2-bis (p-β-hydroxyethylphenyl) propane, polyethylene glycol, poly (1,2-propylene) glycol, poly (trimethylene) glycol or poly (tetramethylene) glycol, one component or two or more components It may be copolymerized. Furthermore, one or two or more components of hydroxycarboxylic acid such as ω-hydroxyalkylcarboxylic acid, pentaerythritol, trimethylolpropane, trimellitic acid, or trimesic acid, or a compound having three or more carboxylic acid components or hydroxyl groups It may be branched by copolymerization. Also included are mixtures of polyesters having different compositions as exemplified above.

(Totally aromatic polyamide: Meta-type wholly aromatic polyamide)
Next, the case where a wholly aromatic polyamide is used will be described as a specific example of the organic resin constituting the organic resin-free crimped staple fiber of the present invention. Further, as an embodiment of the wholly aromatic polyamide staple fiber, a meta-type wholly aromatic polyamide staple fiber will be described as an example. The meta type wholly aromatic polyamide used as a raw material for the meta type wholly aromatic polyamide staple fiber used in the organic resin crimped staple fiber of the present invention is composed of a meta type aromatic diamine component and a meta type aromatic dicarboxylic acid component. Therefore, other copolymer components such as para type may be copolymerized within a range not impairing the object of the present invention.

  Particularly preferred for use in the present invention is a meta-type wholly aromatic polyamide having a metaphenylene isophthalamide unit as a main component from the viewpoints of mechanical properties and heat resistance. The meta-type wholly aromatic polyamide composed of metaphenylene isophthalamide units preferably contains 90% by mole or more, more preferably 95% by mole or more, particularly preferably 95% by mole or more of all repeating units. Preferably it is 100 mol%.

  Examples of the meta type aromatic diamine component used as a raw material for the meta type wholly aromatic polyamide include metaphenylene diamine, 3,3′-diaminodiphenyl ether, 3,3′-diaminodiphenyl sulfone, 3,4′-diaminodiphenyl ether, or 3 , 4′-diaminodiphenyl sulfone, etc., or one or two aromatic rings of these aromatic diamine compounds have a substituent such as halogen, an alkyl group having 1 to 3 carbon atoms, or an alkoxy group having 1 to 3 carbon atoms. It is a derivative having. Specific examples include 2,4-tolylenediamine, 2,6-tolylenediamine, 2,4-diaminochlorobenzene, 2,6-diaminochlorobenzene, and the like. Especially, it is preferable that it is a metaaromatic diamine component which contains only metaphenylenediamine or metaphenylenediamine 70 mol% or more as a meta type aromatic diamine component.

  Examples of the meta-type aromatic dicarboxylic acid component that is a raw material for the meta-type wholly aromatic polyamide include a meta-type aromatic dicarboxylic acid dihalide. Examples of the meta-type aromatic dicarboxylic acid dihalide include isophthalic acid dihalide such as isophthalic acid dichloride, isophthalic acid bromide or isophthalic acid diiodide, and halogens, alkyl groups having 1 to 3 carbon atoms, and carbon atoms having 1 to 3 carbon atoms in these aromatic rings. Examples thereof include derivatives having a substituent such as an alkoxy group, such as 3-chloroisophthalic acid dichloride, 3-methoxyisophthalic acid dichloride, and the like. Especially, it is preferable that it is the total aromatic dicarboxylic acid dihalide which contains only 70 mol% or more of isophthalic-acid dichloride or isophthalic-acid dichloride.

(Totally aromatic polyamide: a copolymer component of meta-type wholly aromatic polyamide)
Examples of copolymer components that can be used other than the above-mentioned meta-type aromatic diamine component and meta-type aromatic dicarboxylic acid component include, for example, paraphenylene diamine, 2,5-diaminochlorobenzene, 2,5- Benzene derivatives such as diaminobromobenzene and aminoanisidine (2-amino-4-methoxyaniline), 1,5-naphthylenediamine, 1,6-naphthylenediamine, 4,4′-diaminodiphenyl ether, 4,4 ′ -Diaminodiphenyl ketone, 4,4'-diaminodiphenylamine, 4,4'-diaminodiphenylmethane and the like. On the other hand, the aromatic dicarboxylic acid component includes terephthalic acid dichloride, 1,4-naphthalenedicarboxylic acid dichloride, 2,6-naphthalenedicarboxylic acid dichloride, 4,4′-biphenyldicarboxylic acid dichloride, and 4,4′-diphenyl ether dicarboxylic acid. A dichloride etc. are mentioned. If the copolymerization ratio of these copolymer components is too large, the properties of the meta-type wholly aromatic polyamide are likely to be lowered. Therefore, the copolymerization ratio is 20 mol% or less based on the total dicarboxylic acid component of the meta-type wholly aromatic polyamide. It is preferable. In particular, a suitable meta-type wholly aromatic polyamide is a polyamide in which 90 mol% or more of all repeating units are metaphenylene isophthalamide units, and polymetaphenylene isophthalamide is particularly preferable.

(Totally aromatic polyamide: Para-type wholly aromatic polyamide)
Next, the case where para type wholly aromatic polyamide staple fiber is used as an embodiment of the staple fiber made of wholly aromatic polyamide will be described. Para-type wholly aromatic polyamide used as an example of the para-type wholly aromatic polyamide staple fiber used as an example of the organic resin uncrimped staple fiber of the present invention includes polyparaphenylene terephthalamide and polyparaphenylene terephthalamide. , 3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl sulfone, 3,4'-diaminodiphenyl sulfone, or 4,4'-diaminodiphenyl sulfone Examples include para-type wholly aromatic polyamides obtained by copolymerization of p-type, and para-type wholly aromatic polyamides obtained by copolymerizing a small amount of isophthalic acid and metaphenylenediamine. Preferred is copolyparaphenylene-3,4'-oxydiphenylene terephthalamide or polyparaphenylene terephthalamide. More preferably, copolyparaphenylene-3,4'-oxydi, which comprises terephthalic acid as an acid component, a mixed diamine component containing 40 mol% or more of paraphenylenediamine and 40 mol% or more of 3,4'-diaminodiphenyl ether. A wholly aromatic polyamide that is phenylene terephthalamide is preferred.

  Examples of the aromatic diamine component that can be used in the para-type wholly aromatic polyamide include paraphenylene diamine, 4,4′-diaminodiphenyl ether, 4,4′-diaminodiphenyl sulfone, etc., or one of these aromatic diamine compounds or It is a derivative having substituents such as halogen, an alkyl group having 1 to 3 carbon atoms, and an alkoxy group having 1 to 3 carbon atoms on two aromatic rings. Specifically, for example, 2,5-tolylenediamine, 2,5-diaminochlorobenzene, 2,5-diaminobromobenzene and the like can be exemplified. Especially, it is preferable that it is the total aromatic diamine component which contains only paraphenylene diamine as a para type | mold aromatic diamine component, or 70 mol% or more of paraphenylene diamine.

  Examples of the para type aromatic dicarboxylic acid component that is a raw material of the para type wholly aromatic polyamide include para type aromatic dicarboxylic acid dihalide. Examples of the para-type aromatic dicarboxylic acid dihalide include terephthalic acid dihalides such as terephthalic acid dichloride, terephthalic acid bromide or terephthalic acid diiodide, and halogens, alkyl groups having 1 to 3 carbon atoms, and carbon atoms having 1 to 3 carbon atoms in these aromatic rings Examples thereof include derivatives having a substituent such as an alkoxy group such as 3-chloroterephthalic acid dichloride, 3-methoxyterephthalic acid dichloride, and the like. Of these, terephthalic acid dichloride alone or a wholly aromatic dicarboxylic acid dihalide containing 70 mol% or more of terephthalic acid dichloride is preferable.

(Fully aromatic polyamide: copolymerization component of para-type wholly aromatic polyamide)
Examples of copolymer components that can be used in addition to the para-type aromatic diamine component and the para-type aromatic dicarboxylic acid component include, for example, metaphenylene diamine, 2,4-diaminochlorobenzene, and 2,6-diamino as aromatic diamines. Benzene derivatives such as chlorobenzene, 2,4-diaminobromobenzene, 2,6-diaminobromobenzene, 2-amino-4-methoxyaniline, 3-amino-4-methoxyaniline, 1,3-naphthylenediamine, 1, 4-naphthylenediamine, 1,5-naphthylenediamine, 1,6-naphthylenediamine, 3,4′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ketone, 3,4′-diaminodiphenylamine, 3,4 Examples include '-diaminodiphenylmethane. On the other hand, as the aromatic dicarboxylic acid component, isophthalic acid dichloride, 1,3-naphthalenedicarboxylic acid dichloride, 2,7-naphthalenedicarboxylic acid dichloride, 3,4'-biphenyldicarboxylic acid dichloride, 3,4'-diphenyl ether dicarboxylic acid A dichloride etc. are mentioned. When the copolymerization ratio of these copolymerization components is too large, the characteristics of the para- type wholly aromatic polyamide are likely to deteriorate. Therefore, the copolymerization ratio is 20 mol% or less based on the total dicarboxylic acid component of the para- type wholly aromatic polyamide. It is preferable. Furthermore, in the case of the above-mentioned para- type wholly aromatic polyamide uncrimped staple fiber, the notation representing the meta type and the meta type was used as a para type or a para type as appropriate. Even in such a case, it goes without saying that the organic resin-free crimped staple fiber of the present invention belongs to the category of the invention.

(Polyolefin)
Furthermore, the case where polyolefin is used as a specific example of the organic resin constituting the uncrimped staple fiber of the present invention will be described. Polyolefins used as the organic resin of the present invention include isotactic polypropylene, syndiotactic polypropylene, atactic polypropylene, high density polyethylene, medium density polyethylene, linear low density polyethylene, low density polyethylene, ethylene / propylene random Copolymerized polyolefin, or polyethylene or polypropylene obtained by block copolymerization or graft copolymerization of the third component is preferable. The third component in this case is vinyl acetate, vinyl chloride, styrene, methyl acrylate, ethyl acrylate, isopropyl acrylate, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, acrylic acid, methacrylic acid, maleic acid, maleic anhydride, Examples thereof include vinyl chloride, vinylidene chloride, acrylonitrile, and acrylamide. Among these, particularly selected from the group consisting of high density polyethylene, ethylene / propylene random copolymer, polyethylene obtained by block copolymerization or graft copolymerization of maleic anhydride, and polypropylene obtained by block copolymerization of maleic anhydride. Preferably, the at least one polyolefin produced. In addition, a plurality of types of polyolefins may be selected from the above-mentioned polyolefins and used by mixing them.

  As organic resins other than the above, polyamides such as nylon-6, nylon-6, 6 and the like, polyoxymethylene, polyphenylene ether, polyphenylene sulfide, cellulose, polysulfone, polyethersulfone, polycarbonate, polyarylate and the like may be used. it can. The various organic resins mentioned above include known additives such as pigments, dyes, matting agents, antifouling agents, antibacterial agents, deodorants, fluorescent whitening agents, antioxidants, flame retardants. , A polyester composition containing a stabilizer, an ultraviolet absorber, a lubricant, or the like. In the organic resin uncrimped staple fiber of the present invention, from the above viewpoint, the uncrimped staple fiber is any of polyester uncrimped staple fiber, wholly aromatic polyamide uncrimped staple fiber, or polyolefin uncrimped staple fiber. One kind of organic resin-free crimped staple fiber is preferred. In the organic resin uncrimped staple fiber of the present invention, the uncrimped staple fiber is polyethylene terephthalate uncrimped staple fiber, polytrimethylene terephthalate uncrimped staple fiber, polytetramethylene terephthalate uncrimped staple fiber, polyethylene. Naphthalate-free crimped staple fiber, Polytrimethylene naphthalate-free crimped staple fiber, Polytetramethylene naphthalate-free crimped staple fiber, Meta-type wholly aromatic polyamide No-crimped staple fiber, Para-type wholly aromatic polyamide One of the organic resin crimped staple fibers of any one of crimped staple fiber, polyethylene uncrimped staple fiber or polypropylene uncrimped staple fiber Rukoto also preferred.

(Cross sectional shape and configuration of uncrimped staple fiber)
An example of the cross-sectional shape of the organic resin crimped staple fiber in the present invention is a solid fiber or a hollow fiber as long as the outer periphery of the cross-section in the direction perpendicular to the fiber axis direction is a round cross-section. Or a composite fiber. Also, the cross-sectional shape of the fiber is not limited to a round cross section, and may be an elliptical cross section, a multi-leaf cross section such as a 3-8 leaf cross section, or an irregular cross section such as a triangular cross section to an octagonal polygon cross section. Here, the fiber cross section represents a fiber cross section perpendicular to the fiber axis. Further, the structure of the fiber is not limited to a fiber made of a single component organic resin. The uncrimped staple fiber of the present invention may be a composite fiber composed of two or more organic resins. Examples of the composite form of the composite fiber include concentric core-sheath type composite fiber, eccentric core-sheath type composite fiber, side-by-side type composite fiber, sea-island type composite fiber, segment pie type composite fiber, and the like.
By adopting the configuration of these composite fibers, the organic resin uncrimped staple fiber of the present invention is made into a fiber having a fineness of 0.01 dtex or less, for example, or a binder fiber to be bonded to other fibers by heat and pressure can do.

  Specifically, the composite fiber containing polyester includes, as a core component, polyalkylene terephthalate such as polyethylene terephthalate, polytrimethylene terephthalate, or polybutylene terephthalate, poly (ethylene naphthalate), polytrimethylene naphthalate, or polybutylene naphthalate. A core-sheath composite fiber in which an alkylene naphthalate is disposed and a copolymer polyester or polyolefin is disposed as a sheath component can be exemplified. Moreover, the sea-island type | mold composite fiber by which the organic resin of the said core component is arrange | positioned at an island component, and the organic resin of the said sheath component is arrange | positioned at the sea component can be mentioned. Furthermore, the side by side type | mold composite fiber or segment pie type | mold composite fiber by which the organic resin of the said core component is arrange | positioned at one component, and the organic resin of the said sheath component is arrange | positioned at the other component can be mentioned. Examples of the copolymer component of the copolymer polyester include one or more compounds that can be copolymerized with the above-described polyester component, such as isophthalic acid and polyethylene glycol.

  As the composite fiber containing polyolefin, polypropylene (any of the above-mentioned types of polypropylene) is disposed as a core component, and polyethylene (any of the above-mentioned types of polyethylene may be used) as a sheath component. , Ethylene-propylene random copolymer polyolefin, or core-sheath type composite fiber in which polyethylene or polypropylene copolymer polyethylene obtained by block copolymerization or graft copolymerization of a third component is disposed. Moreover, the sea-island type | mold composite fiber by which the organic resin of the said core component is arrange | positioned at an island component, and the organic resin of the said sheath component is arrange | positioned at the sea component can be mentioned. Furthermore, the side by side type | mold composite fiber or segment pie type | mold composite fiber by which the organic resin of the said core component is arrange | positioned at one component, and the organic resin of the said sheath component is arrange | positioned at the other component can be mentioned.

  The uncrimped staple fiber of the present invention may be an undrawn staple fiber or a drawn staple fiber. The unstretched staple fiber is suitably used when used as a binder fiber that is adhered to other fibers by heat and pressure using a calendar roller or the like.

(Fineness, fiber length and crimp of uncrimped staple fiber)
The single fiber fineness of the organic resin-free crimped ultrafine staple fiber of the present invention as described above is 0.0001 to 0.6 dtex, preferably 0.007 to 0.55 dtex, more preferably 0.01 to 0.00. 53 dtex. If the single yarn fineness is less than 0.0001 dtex, the entanglement of the staple fibers of the present invention tends to be poor due to significant entanglement between the staple fibers. In addition, if the single yarn fineness is small, there are many difficult points in terms of yarn production technology. More specifically, not only is it difficult to stably produce fibers of good quality due to the occurrence of yarn breakage and fluff in the yarn making process, but the cost of staple fibers is also unfavorable. In addition, when the single yarn fineness is small, the contact area between the cutter and the fiber is large when cutting the fiber, which increases the discharge resistance due to fiber-metal friction, and is disadvantageous in that the blade breaks and the blade edge wear increases. It may be. However, even in the case of a non-crimped staple fiber having an ultrafine fineness of 0.0002 to 0.006 dtex even if the single yarn fineness is small, it is excellent in moisture permeable waterproofness, odor adsorbability, and the collection efficiency of minute matter. In some cases, the present invention has an effect different from that of the staple fiber having the above fineness, such as being suitable for use in abrasive cloths for magnetic disks, battery separators or capacitor papers. It can be one. On the other hand, when the single yarn fineness exceeds 0.6 dtex, it is difficult to obtain non-woven fabric strength, paper strength, and non-woven fabric density in a low-weight area where the characteristics of ultrafine fibers can be obtained.

Furthermore, the fiber length of the organic resin crimped staple fiber of the present invention is 0.01 to 5.0 millimeters, preferably 0.015 to 4.0 millimeters, more preferably 0.02 to 3.5 millimeters, and still more preferably. Is 1.0 to 3.3 millimeters. On the other hand, when the fiber length is longer than 5.0 mm, defects tend to occur due to the entanglement of the fibers. In addition, when the fiber length is less than 0.01 mm, the aspect ratio represented by the fiber length / width of the fiber cross section or the diameter of the ellipse becomes too small. It is not preferable from the viewpoint of strength. The fiber length is arbitrarily selected according to the purpose of use and processability. If the staple fiber has the above ultrafine fineness and the fiber length is in the range of 0.015 to 0.06 mm, even if the fiber length is short, it has the same effect as the staple fiber having the ultrafine fineness. This can be one of the preferred embodiments.
The staple fiber of the present invention needs to be crimped without actively crimping. If the staple fiber is crimped, it may be difficult to uniformly disperse it when dispersed in a dispersion medium, and when the nonwoven fabric is produced from the staple fiber, the nonwoven fabric is reduced in weight. May also be difficult.

(Cut end factor of uncrimped staple fiber)
The uncrimped staple fiber of organic resin in the present invention needs to have a cut end coefficient defined by the present invention of 1.00 to 1.40 in order to express the degree of cut end failure. Here, in order to explain the cut end coefficient in detail, a schematic diagram of the end of the uncrimped staple fiber of the present invention is shown in FIG. In FIG. 1, the maximum width in the direction perpendicular to the fiber axis of the cut end portion on the side surface of the uncrimped staple fiber magnified with an optical microscope (the maximum diameter when the shape of the cut end portion is circular or substantially circular) ) Is b and the thickness of the single yarn (or the fiber diameter or fiber width of the single yarn) is a, the cut end coefficient is expressed by a numerical value obtained by dividing b by a. The cut end coefficient means how much the shape of the cut end portion of the staple fiber is widened with respect to the normal single yarn thickness, and can be used as an index indicating the quality of the shape of the cut end portion. A staple fiber having an index greater than 1.00 has a shape in which, when cutting the fiber, the fiber is crushed by the pressure applied in a direction perpendicular to the fiber axis, and the end of the staple fiber is greatly expanded. This widened shape is not simply a shape obtained by enlarging the shape of the fiber cross section, but a shape that can be said to be an asymmetrical shape. That is, in many cases, the shape is different from the cross section of the fiber, and when the fiber cross section is a round cross section, the widened shape often does not become a round cross section. In addition, when the fiber cross section is an atypical cross section, the greatly widened shape often does not become the atypical cross section. When the cut end coefficient as the index is 1.00 to 1.40, even if the cut end has a shape different from the fiber cross section itself of the single yarn fiber, it is uniformly dispersed in the dispersion medium, and Generation | occurrence | production of the aggregate can be suppressed and there can exist the effect of this invention. However, when the index exceeds 1.40, the maximum width b of the greatly expanded shape becomes a defective shape. When the staple fiber having such a poor cut end shape is dispersed in the dispersion medium, the projection at the end of the staple fiber is caught with another staple fiber that is about to be dispersed in the dispersion medium. The hooked portion serves as a nucleus, and further staple fibers of other normal cut ends are further wound, and an undispersed mass of staple fibers is easily generated in the dispersion medium. Such an undispersed mass leads to defects in appearance and performance in the product when a product such as a nonwoven fabric is produced using the uncrimped staple fiber of the present invention. Therefore, in order to reduce the occurrence of such defects, it is necessary to suppress fibers including defective cut ends to a certain level or less. As a result of intensive studies, we can suppress the occurrence of defects by setting the cut edge coefficient to 1.00 or more and 1.40 or less, and when it exceeds 1.40, protrusions and catches on the cut edge. As a result, the present invention was completed. Note that the case where the cut end coefficient is 1.00 indicates that the shape of the cut end portion of the staple fiber and the shape of the fiber cross section are the same in all uncrimped staple fibers. This cutting edge coefficient cannot take a numerical value less than 1.0 in a cutting method that can be normally performed. Here, the cut end coefficient is obtained by observing the cut end side surfaces of 50 uncrimped staple fibers collected at random with an optical microscope or a scanning electron microscope, and using a length measuring function provided in those microscopes. Measurement was performed, and the average value was calculated and evaluated. When the cut edge coefficient is 1.00 to 1.40, preferably 1.001 to 1.35, and more preferably 1.01 to 1.30, good medium dispersibility without aggregates is exhibited. Incidentally, 1.00 is the best state as described above.

(Fiber length variation of non-crimped staple fiber)
In the uncrimped staple fiber of the present invention, it is necessary to suppress variation in fiber length. When 50 uncrimped staple fibers are randomly extracted and the fiber length is measured, the fiber length relative fluctuation The coefficient (percentage obtained by dividing the standard deviation by the average value) is 0.0% to 15.0%, preferably 0.01% to 14.0%, more preferably 0.1% to 13.0%. Is desirable. When the variation in fiber length is large, fibers having a large aspect ratio (fiber length / fiber diameter) are generated, and the probability that the fibers come into contact with each other and become entangled when stirred in the dispersion medium increases. In particular, as the fineness (fiber diameter) decreases, this effect becomes more significant. Therefore, it is important to suppress variations in fiber length. Here, the relative variation coefficient of the fiber length is enlarged by an optical microscope or a scanning electron microscope in a state where 50 staple fiber samples are randomly taken out, a cover glass is placed, and the weight of the cover glass is applied. The enlarged image is measured by the length measurement function of the optical microscope or scanning electron microscope, the fiber length is measured, the average value and the standard deviation are calculated, and the fiber length relative variation coefficient is calculated by the standard deviation / average value. Calculated. The uncrimped staple fiber of the present invention is preferably a drawn yarn. By using a drawn yarn, when a wet nonwoven fabric or the like is produced from the uncrimped staple fiber of the present invention, the strength necessary for the nonwoven fabric such as sufficient tensile strength can be achieved.

(Water content of uncrimped staple fiber)
In the uncrimped staple fiber of the present invention, the moisture content needs to be 10 to 200% by weight. When the moisture content is less than 10% by weight, the staple fibers are not easily bundled with each other, and the cut end coefficient and the fiber length variation coefficient tend to be large values, which is not preferable. On the other hand, when the moisture content exceeds 200% by weight, water is largely removed from the fiber tow, and the handleability of the fiber bundle in the cutting step may be deteriorated, which is not preferable. It is preferable that moisture is applied in a process prior to the cutting process in the process of manufacturing staple fibers. If the desired moisture content is within the above range and is small, the oiling roller can be used.If the desired water content is within the above range and too large, the water can be squeezed by immersing in water, holding it with a nip roller, and squeezing. It can be adjusted by giving. When the moisture content is lower, a method of applying water by spraying can also be adopted. When water is applied by spraying, it can be performed in a step after the cutting step. The moisture content is preferably 12 to 150% by weight, more preferably 13 to 120% by weight, and even more preferably 16 to 100% by weight.

(Method for producing organic resin non-crimped staple fiber)
The organic resin uncrimped staple fiber of the present invention described above can be produced, for example, by the following method.

(Manufacturing method of polyester crimped staple fiber)
First, the case of polyester uncrimped staple fibers will be described. First, a polyester polymer is melted, discharged from a die using a known spinning equipment, and taken up at a speed of 100 to 2000 m / min while cooling with cooling air to obtain an undrawn yarn. Subsequently, the undrawn yarn obtained is drawn in warm water at 70 to 100 ° C. or in steam at 100 to 125 ° C. to give an oil agent to obtain a drawn yarn. Further, the drawn yarn is subjected to a drying treatment and, if necessary, a relaxation heat treatment to obtain a fiber bundle, which is then cut into a fiber length of 0.01 to 5.0 mm to obtain a crimped staple fiber. be able to.

  As described above, it is preferable to employ a step of applying water to the fiber bundle before cutting the fiber bundle. The method for applying water to the fiber bundle is not particularly limited, but examples thereof include a method of applying water by a spray method, an oiling roller method, and an immersion method after the relaxation heat treatment and before supplying to the cutter. Especially, an oiling roller system is preferable when providing the moisture content of said range uniformly. Moreover, when applying by a spray method or an oiling roller method, in order to provide water uniformly to a fiber bundle, it is appropriate to apply water from both front and back sides of the fiber bundle.

  Next, the method for cutting the fiber from the fiber bundle into a predetermined length is not particularly limited. However, the so-called guillotine cutter type fiber bundle cutting device, especially when cutting fibers with a small single yarn fineness, causes the fibers to bend or buckle, and the fibers do not come into contact with the cutting blade at right angles. And uneven fiber lengths may occur. This guillotine cutter type fiber bundle cutting device employs a method in which a fixed blade and a moving blade are provided as shear blades, and a fiber bundle is pushed and cut by a predetermined cutting length against these shear blades. It is thought that irregularities occur. Therefore, the cut end coefficient and the fiber length relative variation coefficient (variation in fiber length) in the present invention are increased, and may not be appropriate.

  Therefore, when using the guillotine cutter type fiber bundle cutting device, when cutting, the movement of the fiber bundle is restrained so that the fiber bundle is not bent or buckled by its own weight or the pressing of the cutter blade. It is appropriate to do. As a method of restraining the fiber bundle, a method of including the fiber bundle with a sheet-like material is generally performed. However, there are cases where the movement of the fiber bundle cannot be sufficiently restricted by a method such as inclusion with paper. On the other hand, the fiber bundle is immersed in water, defoamed, and frozen to create an icicle to fix the fiber bundle, and then the fiber bundle is cut together with the icicle with a guillotine cutter type cutting device. A cutting method for removing water) is preferred. This is because, in this method, since there is little deviation between fibers, the relative variation coefficient of fiber length (variation of fiber length) is good, and it becomes difficult to cause cut end defects. In this case, a dry ice column can be used instead of the ice column.

  Further, as another method of cutting the fiber bundle into a predetermined length, there is a method using a rotary cutter such as an Eastman type in which a large number of cutter blades are directed radially outward at equal intervals. This method is a method in which a fiber bundle is wound on a rotary cutter blade and continuously cut to a predetermined length while pressing the fiber wound on the cutter blade against the cutting blade. In this cutting method, there is a limit to the distance between the cutter blades that can discharge the uncrimped staple fiber after cutting. However, at the previous stage of the rotary cutter device, the cut ends that are generated due to misalignment between the single yarns by applying an appropriate tension to the fiber bundles in a state where the single yarns constituting the fiber bundle are uniformly aligned without slack. There is a merit that a defective shape and variation in fiber length hardly occur, which is preferable. However, due to the structure of the apparatus, there may be a problem that the discharge resistance of the fiber after cutting is large and a problem that the cutter blade is broken. In response to these problems, the structure of the device has been expanded so that the space after fiber cutting is reduced to reduce the discharge resistance, and the surface of the cutter blade is diamond-like coated to prevent the cutter blade from breaking. By performing the process to reduce the fiber-metal friction, the target fiber having a fiber length of 5.0 mm or less or a shorter fiber having a fiber length of 3.0 mm or less can be stably obtained.

  Such a rotary cutter device generally includes a cutter blade and a feed roller that supplies a fiber bundle to the cutter blade. At this time, a draft ratio between the rotary cutter and the feed roller [(rotary cutter It is desirable to set the (circumferential speed) / (ratio of the peripheral speed of the feed roller)] to 1.01-1.05. When the draft ratio is smaller than 1.01, variations in the tension state of each single yarn fiber in the fiber bundle occur when the long fiber is cut, and the fiber length of the obtained staple fiber tends to vary. A draft ratio greater than 1.05 is not preferable because the fiber itself may be mechanically stretched to change the physical properties of the fiber. That is, when a rotary cutter device is used, staple fibers with a relative fiber length variation coefficient of 0.0 to 15.0% can be obtained by setting the draft ratio as described above. Moreover, it is desirable that the fiber bundle is cut by pressing against the cutter blade edge of the rotary cutter with a pressure roll installed at regular intervals. By gradually pressing and cutting the fibers with a pressure roll, the resistance when the cut fibers pass between the cutter blades can be reduced, and the cut end shape can be prevented from being deformed. In addition, by pressing the cutter blade edge at regular intervals, the amount of fiber bundles that can be wound on the rotary cutter can be made constant during continuous operation. The fiber bundles wound around the outermost periphery are relaxed in the fiber direction as they go to the center of the rotor, and then cut in contact with the cutter blade. However, if the amount of fiber bundles varies at this time, the degree of relaxation varies. This is because the fiber length varies.

(Method for producing meta-type wholly aromatic polyamide uncrimped staple fiber)
Next, the case of a fully aromatic polyamide uncrimped staple fiber will be described. Hereinafter, the wholly aromatic polyamide staple fiber in the present invention is a meta type wholly aromatic polyamide staple fiber as a specific example, and the production method thereof is a meta type wholly aromatic polyamide production process, a spinning solution adjustment process, a spinning / coagulation process. The description will be divided into a plastic stretching bath stretching process, a washing process, a saturated steam treatment process, a dry heat treatment process, and a cutting process.

[Meta-type wholly aromatic polyamide production process]
The method for producing the meta-type wholly aromatic polyamide is not particularly limited. For example, it is produced by solution polymerization or interfacial polymerization using a meta-type aromatic diamine component and a meta-type aromatic dicarboxylic acid dichloride component as raw materials. be able to. For example, metaphenylenediamine and isophthalic acid dichloride can be used as raw materials. The degree of polymerization of the meta-type wholly aromatic polyamide is suitably in the range of 1.3 to 3.0 dL / g as the intrinsic viscosity (IV) measured using concentrated sulfuric acid at 30 ° C. as a solvent.

[Spinning liquid preparation process]
An example of a general method for producing a meta-type wholly aromatic polyamide uncrimped staple fiber used in the present invention is shown below. First, long fibers are manufactured through the steps described below. Thereafter, the obtained long fiber is subjected to a cutting step to obtain a meta-type wholly aromatic polyamide staple fiber.

  In the spinning solution preparation step, the meta type wholly aromatic polyamide is dissolved in an amide solvent to prepare a spinning solution (meta type wholly aromatic polyamide polymer solution). In preparing the spinning solution, the spinning solution is usually prepared using an amide solvent. Examples of the amide solvent used include N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethylacetamide (DMAc) and the like. Of these, NMP or DMAc is preferably used from the viewpoints of solubility and handling safety. As the concentration of the spinning solution, an appropriate concentration may be appropriately selected from the viewpoint of the coagulation speed in the next spinning and coagulation step and the solubility of the meta-type wholly aromatic polyamide. In the case where the polyamide is polymetaphenylene isophthalamide and the solvent is NMP, it is usually preferably in the range of 10 to 30% by mass.

[Spinning and coagulation process]
In the spinning / coagulation step, the spinning solution (meta-type wholly aromatic polyamide polymer solution) obtained in the above step is spun into a coagulation solution and coagulated to obtain a porous fibrous material. The spinning device is not particularly limited, and a conventionally known wet spinning device can be used. Further, the number of spinning holes, the arrangement state, and the hole shape of the spinneret are not particularly limited as long as they can be stably wet-spun. For example, the number of holes is 500 to 30,000, and the spinning hole diameter is 0. A multi-hole spinneret for staple fibers (for short fibers) of 0.05 to 0.2 mm may be used. The temperature of the spinning solution (meta-type wholly aromatic polyamide polymer solution) when spinning from the spinneret is suitably in the range of 10 to 90 ° C. The coagulation bath is substantially composed of an aqueous solution composed of two components of an amide solvent and water. The amide solvent in this coagulation bath composition is not particularly limited as long as it dissolves the meta-type wholly aromatic polyamide and is miscible with water, but in particular, N-methyl-2-pyrrolidone, Dimethylacetamide, dimethylformamide, dimethylimidazolidinone (1,3-dimethyl-2-imidazolidinone, etc.) and the like can be suitably used. The mixing ratio (weight ratio) of the amide solvent and water is preferably 10/90 to 90/10, more preferably 30/70 to 70/30.
Further, an inorganic sodium salt, potassium salt, magnesium salt, or calcium salt may be dissolved in the coagulation bath in an amount of 0.1 to 8.0% by weight as necessary.

[Plastic stretching bath stretching process]
In the plastic drawing bath drawing step, while the fiber bundle composed of the porous fibrous material (thread body) obtained by coagulation in the coagulation bath is in the plastic state, the fiber bundle is put in the plastic drawing bath. Stretch treatment. The plastic drawing bath for obtaining the fiber used in the present invention comprises an aqueous solution of an amide solvent and is substantially free of salts. The amide solvent is not particularly limited as long as it swells the meta-type wholly aromatic polyamide and is well mixed with water. Examples of such amide solvents include N-methyl-2-pyrrolidone, dimethylacetamide, dimethylformamide, dimethylimidazolidinone and the like.

  The temperature and composition of the plastic stretching bath are closely related to each other, but can be suitably used as long as the mass concentration of the amide solvent is 20 to 70% by mass and the temperature is in the range of 20 to 70 ° C. . From this range, when the mass concentration of the amide solvent is low or the temperature is low, plasticization of the porous fibrous material does not proceed sufficiently, and it becomes difficult to obtain a sufficient draw ratio in plastic drawing. On the other hand, when the mass concentration of the amide solvent is higher than this range or when the temperature is high, the surface of the porous fiber is dissolved and fused, making it difficult to produce a good yarn.

  In obtaining the fiber used in the present invention, the draw ratio in the plastic draw bath is preferably in the range of 1.5 to 10 times, more preferably in the range of draw ratio of 2.0 to 6.0 times. And When the draw ratio is less than 1.5 times, the mechanical properties such as strength and elastic modulus of the resulting fiber are lowered, and when the nonwoven fabric is produced using the fiber of the present invention, the necessary breaking strength is achieved. May be difficult to do. Moreover, it becomes difficult to sufficiently promote the solvent removal from the porous fibrous material, and it becomes difficult to make the amount of residual solvent in the finally obtained fiber 1.0% by mass or less.

[Washing process]
In the washing step, the fiber that has undergone the plastic drawing bath drawing step is sufficiently washed with water. Washing is preferably performed in multiple stages because it affects the quality of the resulting fiber. In particular, the temperature of the cleaning bath in the cleaning step and the concentration of the amide solvent in the cleaning bath liquid affect the state of extraction of the amide solvent from the fibers and the state of penetration of water from the cleaning bath into the fibers. For this reason, it is preferable to control the temperature condition and the concentration condition of the amide solvent by setting the washing process in multiple stages for the purpose of bringing them into an optimum state.

[Saturated steam treatment process]
In the saturated steam treatment process, the fibers washed in the washing process are heat-treated in saturated steam. By performing the saturated steam treatment, the orientation can be enhanced while suppressing the crystallization of the fibers. Heat treatment in a saturated steam atmosphere can be uniformly heat-treated to the inside of the fiber bundle as compared with dry heat treatment, and uniform fibers can be obtained. The draw ratio in the saturated steam treatment process is closely related to the expression of fiber strength. The draw ratio may be arbitrarily selected in consideration of the physical properties required for the product. In the present invention, the range is 0.7 to 5.0 times, preferably 1.1 to 2.0 times. When the draw ratio is less than 0.7, the convergence of the fiber bundle (yarn) in a saturated water vapor atmosphere is lowered, which is not preferable. On the other hand, when the draw ratio exceeds 5.0 times, the single yarn breakage during drawing increases, and fluff and process yarn breakage are not preferable. The time for the saturated steam treatment is preferably in the range of 0.5 to 5.0 seconds. When processing a traveling fiber bundle continuously, the processing time is determined by the traveling distance and traveling speed of the fiber bundle in the steam treatment tank. That's fine.

[Dry heat treatment process]
In the dry heat treatment step, the fiber that has undergone the saturated steam treatment step is dried and heat treated. The dry heat treatment method is not particularly limited, and examples thereof include a method using a hot plate, a heat roller and the like. By passing through the dry heat treatment, it is possible to finally obtain a long fiber of meta-type wholly aromatic polyamide. The heat treatment temperature in the dry heat treatment step is preferably in the range of 250 to 400 ° C, more preferably in the range of 300 to 380 ° C. When the dry heat treatment temperature is less than 250 ° C., the porous fibers cannot be sufficiently densified, so that the obtained fibers have insufficient mechanical properties. On the other hand, if the dry heat treatment temperature is higher than 400 ° C., the fiber surface is thermally deteriorated and the quality is lowered, which is not preferable.

  The draw ratio in the dry heat treatment step is closely related to the expression of the strength of the obtained fiber. The draw ratio can be selected arbitrarily according to the strength required for the fiber. Among them, the draw ratio in the dry heat treatment step is preferably in the range of 0.7 to 4.0 times, and more preferably in the range of 1.5 to 3.0 times. When the draw ratio is less than 0.7 times, the mechanical tension of the fiber is lowered because the process tension is lowered. On the other hand, when the draw ratio is more than 4.0 times, the single yarn breaks during drawing. Increases, and fluff and process breakage occur. In addition, the draw ratio here is represented by ratio of the fiber length after a process with respect to the fiber length before a stretch process similarly to having demonstrated with the said saturated steaming process. For example, a draw ratio of 0.7 times means that the fiber is subjected to a limit shrinkage treatment to 70% of the original length by a dry heat treatment step, and a draw ratio of 1.0 times means a constant length heat treatment. The treatment time in the dry heat treatment step is preferably in the range of 1.0 to 45 seconds. The treatment time can be adjusted by the traveling speed of the fiber bundle and the contact length with a hot plate, a heat roller or the like.

[Cutting process]
In the wholly aromatic polyamide uncrimped staple fiber of the present invention, the meta-type wholly aromatic polyamide continuous fiber subjected to the dry heat treatment is cut into a predetermined length in the cutting step. Here, the method of cutting the fiber into a predetermined length is not particularly limited. However, a so-called guillotine cutter type fiber bundle cutting device that employs a method in which a fixed blade and a moving blade are provided as shear blades and a fiber bundle is extruded by a predetermined cutting length with respect to these shear blades and cut. When a fiber having a small yarn fineness is cut, the fiber is bent or buckled, and the fiber does not come into contact with the cutting blade at a right angle, so that oblique cutting or uneven fiber lengths may easily occur. Therefore, the cut end coefficient and the fiber length relative variation coefficient (variation in fiber length) in the present invention are increased, and may not be appropriate. Hereinafter, in consideration of the same matters as the above-mentioned polyester uncrimped staple fibers, by performing the same cutting operation, staple fibers having predetermined physical properties even in the case of meta-type wholly aromatic polyamide uncrimped fibers are obtained. Can be obtained.

  In the processes from the meta type wholly aromatic polyamide production process to the cutting process as described above, when the notation representing the meta type and the meta type is appropriately replaced with the para type or the para type, the corresponding para Needless to say, this represents a method for producing an organic resin-free crimped staple fiber of the present invention made of a type wholly aromatic polyamide.

(Manufacturing method of polyolefin crimped staple fiber)
A production method in the case of polyolefin will be described. In the method for producing a polyolefin-free crimped staple fiber, first, the organic resin used in the above-described method for producing a polyester-free crimped staple fiber is replaced with a desired type of polyolefin from polyester. Furthermore, by replacing at least a part or all of the conditions normally employed when melt spinning the employed polyolefin with the above-described polyester uncrimped staple fiber production method, the desired polyolefin uncrimped staple is obtained. Fiber can be manufactured.

(Moisture content in cutting process and effect of invention)
As described above, even in non-crimped staple fibers made of polyester, wholly aromatic polyamide, polyolefin, or any other organic resin, the moisture content of the fiber bundle supplied to the rotary cutter is in the range of 10 to 200%. It is desirable. When the moisture content of the fiber bundle is 10% or more, when the fibers are converged and cut, they come in contact with the cutter blade at right angles and uniformly, so that when the fiber is cut, the cutter blade Against the fiber so that the pressure is uniform. As a result, the cut end coefficient and the fiber length relative variation coefficient are improved. As a result, the obtained staple fiber having a good cut end coefficient and relative fiber length relative variation coefficient is unlikely to generate a fiber having a large aspect ratio. As a result, since the catching with other fibers is suppressed, it can be uniformly dispersed in the medium without causing a cohesive defect. On the other hand, when the moisture content exceeds 200%, water drops off from the state of tow and fiber bundles and the handling property in the process deteriorates. Therefore, the moisture content is suitably up to 200%. Moreover, the moisture content of the organic resin non-crimped staple fiber obtained can also be made into the said numerical range by keeping the moisture content of the fiber bundle of the process of cut | disconnecting a fiber in said numerical range. As long as the effect of the present invention is not impaired, the surface of the uncrimped staple fiber made of an organic resin is a surface treatment agent such as a dispersant, a light-proofing agent, a smoothing agent, an adhesive, and an agent obtained by combining them. It may be processed. Among these, in the case of polyester uncrimped staple fibers and polyolefin uncrimped staple fibers, it is preferable to provide a polyester / polyether copolymer having affinity for both the organic resin and the dispersion medium.

  The organic resin non-crimped staple fiber of the present invention can be uniformly dispersed in a dispersion medium when used in wet nonwoven fabrics or staple fiber reinforced resin, and can suppress the generation of aggregates. As a result, the nonwoven fabric obtained by using the uncrimped staple fiber as a material is a nonwoven fabric in which the staple fibers are uniformly dispersed. As a result, it is possible to obtain a good non-woven fabric which is free from defects such as uneven dispersion of micro staple fibers, variation in basis weight and thickness, and has uniform air permeability and liquid permeability. Furthermore, there are few defects in the final product obtained by processing the non-woven fabric, etc., and the reliability of the physical properties of the final product (reliability regarding quality assurance) can be improved, and the yield of intermediate products (non-woven fabric, resin moldings, etc.) is improved. be able to. Therefore, the present invention has a great merit from the viewpoint of resource saving and economy.

Examples Examples and the like are given below in order to make the constitution and effects of the present invention more specific, but the present invention is not limited to these examples. In addition, unless otherwise indicated, it shall represent a weight part, and each physical-property value in an Example and a comparative example was measured in accordance with the following method.

(1) Intrinsic viscosity: [η]
In the case of polyester fibers, 0.12 g of a fiber (polymer) sample was dissolved in 10 mL of a tetrachloroethane / phenol mixed solvent (volume ratio 1/1), and the intrinsic viscosity (dL / g) at 35 ° C. was measured. In the case of a wholly aromatic polyamide fiber, the fiber (polymer) was dissolved in 97% by mass concentrated sulfuric acid and measured at 30 ° C. using an Ostwald viscometer.

(2) Melt flow rate: MFR
The melt flow rate was measured according to Japanese Industrial Standard JIS K 7210 condition 4 (measurement temperature 190 ° C., load 21.18 N). The melt flow rate is a value measured using a polymer pellet immediately before melt spinning as a sample.

(3) Melting point: Tm
TA-2920 differential scanning calorimeter DSC manufactured by TA Instruments was used. In the measurement, 10 mg of a polymer sample was heated from room temperature to 260 ° C. at a temperature rising rate of 10 ° C./min in a nitrogen atmosphere, and the peak top temperature of the crystal melting endothermic peak was defined as the melting point.

(4) Single yarn fineness It measured by the method as described in Japanese Industrial Standard JIS L 1015: 2005 8.5.1 Method A. That is, it measured by the following method. A small amount of the fiber sample is drawn in parallel with a hammer and placed on the Rash paper placed on the cutting table. A gauge plate is pressure-bonded while a straight fiber sample is stretched with an appropriate force, and cut into a length of 30 mm with a blade such as a safety razor. Count 300 fibers as a set, weigh the mass, and determine the apparent fineness. From the apparent fineness and the equilibrium moisture content measured separately, the positive fineness is calculated by the following equation. The average value of the positive fineness is calculated five times.
F = [(100 + R0) / (100 + Rc)] × D
F: Positive fineness D: Apparent fineness R0: Official moisture content (%) (value specified in Japanese Industrial Standard JIS L 0105 4.1)
Rc: equilibrium moisture content (%)

(5) Cut end factor Fifty uncrimped staple fibers are randomly taken out, placed on a cover glass, and enlarged with an optical microscope or a scanning electron microscope in a state where the weight of the cover glass is applied. Using the measuring function of the microscope, the maximum diameter b of the cut end and the fiber diameter a of the single yarn were measured as shown in FIG. 1, and the cut end coefficient was calculated from the following equation.
Cut edge coefficient = b / a
The cut end coefficient was evaluated by the average value of the numerical values obtained for each fiber.

(6) Relative variation coefficient of fiber length 50 uncrimped staple fibers are taken out at random, placed on a cover glass, magnified with an optical microscope or a scanning electron microscope in a state where the weight of the cover glass is applied, and the optical microscope or scanning is performed. The length of the fiber was measured by the length measuring function of the scanning electron microscope, the average value and the standard deviation were calculated, and then the fiber length relative variation coefficient (CV%) was calculated by the following equation.
Fiber length relative variation coefficient (CV%) = (standard deviation of fiber length) / (average value of fiber length) × 100 (%)

(7) Moisture content About 100 g of fibers containing moisture are dried in a hot air circulation dryer at 120 ° C. until they are completely dried. It calculated | required by following Formula from the weight W0 of the data before drying, and the weight W1 of the sample after drying.
Moisture content (%) = [(W0−W1) / W1] × 100

(8) Dispersibility in water In order to determine the presence or absence of fiber cohesive defects due to cut ends and fiber length, the dispersibility of the obtained fibers in water was evaluated. 500 cc of softened water was put into a 1000 cc beaker, and 0.5 g of the fiber cut into a predetermined fiber length was put therein. This is filtered through a wire mesh having a mesh of 0.15 mm square, the number of fiber lumps having a size of 1 square millimeter or more remaining on the wire mesh is counted, and the case where the fiber lumps are 3 or less is marked with ◯, The case where 3-5 pieces are recognized is indicated by Δ, and the case where 5 or more pieces are recognized is indicated by x.

Example 1
A polyethylene terephthalate (PET) chip containing 0.3% by weight of titanium dioxide and having an intrinsic viscosity of 0.64 dL / g is melted at 290 ° C. and discharged from a spinneret having 3000 round holes at a discharge rate of 450 g / min. This was taken up at a speed of 1320 m / min to obtain a polyethylene terephthalate undrawn yarn having a single yarn fineness of 1.14 dtex. The unstretched yarns are aligned and, as a 140,000 dtex tow, stretched in two stages so that the total draw ratio is 2.51 times in warm water, and then the polyester / polyether copolymer is added to the polyester fiber weight. 0.3 wt% was applied. After the polyester / polyether copolymer was applied, drying and heat setting were performed in a relaxed state at 120 ° C. to obtain a stretched polyethylene terephthalate fiber bundle having a single yarn fineness of 0.51 dtex and no crimp. The obtained stretched polyethylene terephthalate fiber bundle is given water with an oiling roller so that the moisture content is 15%, and an Eastman rotary cutter with a blade interval of 3.0 mm so that the fiber length of the staple fiber is 3.0 mm. The fiber was cut using a mold fiber cutting device. In this cutting, the draft ratio between the rotary cutter and the feed roller was set to 1.02, and the fiber was cut while pressing the fiber bundle against the cutter blade with a pressure roll. Table 1 shows the evaluation results of the obtained polyester uncrimped staple fiber such as fineness, moisture content, cut end coefficient, fiber length relative variation coefficient, and dispersibility in water.

Example 2
An uncrimped staple fiber was obtained by performing the same operation as in Example 1 except that the staple fiber was cut so that the fiber length was 1.5 mm. The evaluation results of the obtained polyester uncrimped staple fiber are shown in Table 1.

Example 3
A stretched polyethylene terephthalate fiber bundle without crimps obtained in Example 1 is dipped in water, gripped with a nip roller and squeezed to a moisture content of 30%, and a fiber bundle in which four of them are arranged in parallel is prepared. did. The fiber bundle was frozen in an atmosphere temperature of −12 ° C. for 15 hours while immersed in boiling water filled in a cylindrical container to obtain a fiber bundle encapsulated in ice. The fiber bundle included in ice was cut with a known guillotine cutter type fiber bundle cutting device (Ono Uchi Seisakusho, model: D100) adjusted to a fiber length of 1.5 mm. Table 1 shows the evaluation results of the polyester non-crimped staple fibers obtained after melting the ice. Hereinafter, the cutting method in which the fiber bundles encapsulated with ice performed in Examples 3 to 5 are formed and cut with a guillotine cutter is represented as “ice column + guillotine” in Tables 1 and 3.

Example 4
Ultra-long fiber bundles were produced from sea-island type composite fibers by the following operation. Polyethylene terephthalate having a melt viscosity of 120 Pa · sec at 285 ° C. was selected as the island component, and 4% by weight of polyethylene glycol having a number average molecular weight of 4000 as the sea component and 9 mol% of 5-sodium sulfoisophthalic acid were copolymerized at 285 ° C. A modified copolymerized polyethylene terephthalate having a melt viscosity of 135 Pa · sec was selected. Next, using a composite fiber spinneret with a sea component: island component weight ratio of 30:70 and 400 islands, the melt was spun at a spinning speed of 1500 m / min, and was drawn at a rate of 3.9 times. A body fiber (sea-island type composite fiber) was obtained. After the drawn ultrafine fiber precursor fibers are bundled to obtain a fiber bundle of 500,000 dtex, the obtained fiber bundle is immersed in a 4% by weight sodium hydroxide aqueous solution at 75 ° C. for 15 minutes. The speed was adjusted, soaked and passed. As a result, an ultrafine fiber bundle (single fiber diameter of 750 nanometers, 0.0056 dtex) in which 27.6% by weight was reduced was obtained from the fiber bundle of the ultrafine fiber precursor fiber.

  This ultra-fine long fiber bundle was immersed in water and held and squeezed with a nip roller to make the moisture content 100%, and then a fiber bundle was prepared in which four were arranged in parallel. This fiber bundle was frozen for 15 hours at an atmospheric temperature of −12 ° C. while immersed in boiling water filled in a cylindrical container to obtain a fiber bundle encapsulated in ice. The fiber bundle included in ice was cut using a known guillotine cutter type fiber bundle cutting device (Ono Uchi Seisakusho, model: D100) adjusted to a fiber length of 0.05 mm. Table 1 shows the evaluation results of the polyester non-crimped staple fibers obtained after melting the ice.

Example 5
Example 4 Example 4 except that using a base having 1500 islands, spinning, drawing, and cutting so that the single yarn fineness is 0.0004 dtex (fiber diameter 200 nanometers) and the fiber length is 0.02 millimeters. The same operation as 4 was performed. The evaluation results of the obtained polyester uncrimped staple fiber are shown in Table 1.

Comparative Example 1
Ten stretched polyethylene terephthalate fiber bundles without crimps obtained in Example 1 were bundled to make 1.4 million dtex and then included in paper. Next, the contained fiber bundle was cut with a known guillotine cutter type fiber bundle cutting apparatus (Ono Uchi Seisakusho, model: D100) adjusted to have a fiber length of 3.0 mm, to obtain an uncrimped staple fiber. . Table 2 shows the evaluation results of the obtained polyester uncrimped staple fibers.

Comparative Example 2
An uncrimped staple fiber was obtained by performing the same operation as in Comparative Example 1 except that the fiber length of the staple fiber was cut to 1.5 mm. Table 2 shows the evaluation results of the obtained polyester uncrimped staple fibers.

Comparative Example 3
Except for cutting with the draft ratio between the rotary cutter and the feed roller set to 0.98, the same operation as in Example 1 was performed to obtain a non-crimped staple fiber. Table 2 shows the evaluation results of the obtained polyester uncrimped staple fibers.

Example 6
[Spinning liquid preparation process]
In a reaction vessel equipped with a thermometer, a stirrer, and a raw material inlet, 815 parts of N-methyl-2-pyrrolidone (hereinafter abbreviated as “NMP”) dehydrated with molecular sieves was placed, and metaphenylenediamine was added to this NMP. After dissolving 108 parts, it was cooled to 0 ° C. To this cooled metaphenylenediamine solution, 203 parts of isophthalic acid chloride purified by distillation and pulverized in a nitrogen atmosphere was added and allowed to react. The reaction temperature rose to about 50 ° C., stirring was continued for 60 minutes at this temperature, and the mixture was further heated to 60 ° C. for reaction for 60 minutes.

After completion of the reaction, 70 parts of calcium hydroxide was added to the polymerization solution in the form of fine powder and neutralized and dissolved over 60 minutes (primary neutralization). A slurry liquid in which 4 parts of the remaining calcium hydroxide was dispersed in 83 parts of NMP was prepared, and the prepared slurry liquid (neutralizing agent) was added to the primary neutralized polymerization solution with stirring (secondary medium) sum). Secondary neutralization was carried out by stirring at 40 to 60 ° C. for about 60 minutes to prepare a polymer solution (spinning solution) in which calcium hydroxide was completely dissolved.
The polymer concentration of the polymer solution (spinning solution) (that is, the number of parts by weight of the polymer with respect to 100 parts by weight of the polymer and NMP) is 14, and the intrinsic viscosity (IV) of the resulting polymetaphenylene isophthalamide polymer is It was 2.37 dL / g. Further, the calcium chloride concentration and the water concentration of this polymer solution (spinning solution) were 46.6 parts of calcium chloride and 15.1 parts of water with respect to 100 parts of the polymer.

[Spinning and coagulation process]
The spinning solution prepared in the spinning solution preparation step was spun by discharging from a die having a hole diameter of 0.07 millimeters and a hole number of 500 into a coagulation bath having a bath temperature of 40 ° C. The composition of the coagulation liquid is a liquid having a mass ratio of water, NMP, and calcium chloride of 48: 48: 4, and is passed through the coagulation bath at an immersion length (effective coagulation bath length) of 70 cm at a yarn speed of 5 m / min. It was. The density of the porous fibrous material after the coagulation bath was 0.71 g / cm ³ .

[Plastic stretching bath stretching process]
Subsequently, the film was stretched at a stretch ratio of 3.0 in a plastic stretching bath. The composition of the plastic stretching bath used at this time was a liquid having a mass ratio of water, NMP, and calcium chloride of 44: 54: 2, and the temperature was 40 ° C.

[Washing process]
The plastic-stretched fiber bundle was sufficiently washed with cold water at 30 ° C., and then sufficiently washed with hot water at 60 ° C. It was confirmed that the concentration of the amide solvent in the cold water and warm water after washing was sufficiently lowered.

[Saturated steam treatment process]
Subsequently, heat treatment with saturated steam was performed at a draw ratio of 1.1 times in a container kept at a saturated steam pressure of 0.05 MPa. In the heat treatment, conditions such as the travel distance of the fiber bundle and the travel speed of the fiber bundle were adjusted so that the fiber bundle was treated with saturated steam for about 1.0 second.

[Dry heat treatment process]
Subsequently, after performing a dry heat treatment on a hot plate having a surface temperature of 360 ° C. at a draw ratio of 1.0 (constant length), the obtained polymetaphenylene isophthalamide fiber was wound up.

[Physical properties of long fibers]
The obtained polymetaphenylene isophthalamide drawn fiber is sufficiently densified and has a fineness of 0.8 dtex, a density of 1.33 g / cm ³ , a tensile strength of 3.68 cN / dtex, and an elongation of 42%. It showed mechanical properties, quality did not vary, and no abnormal yarn was found.

[Cutting process]
A fiber bundle was prepared from the polymetaphenylene isophthalamide fiber wound up after the dry heat treatment obtained above. Water was applied to the obtained fiber bundle so that the moisture content was 15%. Next, the draft ratio between the rotary cutter and the feed roller is set to 1.02 using an Eastman rotary cutter type fiber cutting device having a blade interval of 3.0 mm so that the fiber length of the staple fiber is 3.0 mm. The fiber bundle was cut while pressing the fiber bundle against the cutter blade with a pressure roll. Table 3 shows the evaluation results of the obtained meta-type wholly aromatic polyamide uncrimped staple fiber, such as fineness, moisture content, cut end coefficient, relative variation coefficient of fiber length, and dispersibility in water.

Example 7
Four fiber bundles made from polymetaphenylene isophthalamide fibers wound up after the dry heat treatment obtained in Example 6 and provided with water were arranged in parallel to prepare fiber bundles. These four fiber bundles arranged in parallel are immersed in boiling water filled in a cylindrical container and frozen at an ambient temperature of −12 ° C. for 15 hours. Obtained. The fiber bundle included in ice was cut with a known guillotine cutter type fiber bundle cutting device (Onouchi Seisakusho, model: D100) adjusted to a fiber length of 1.0 mm. Table 3 shows the evaluation results of the meta-type wholly aromatic polyamide uncrimped staple fibers obtained after melting the ice.

Example 8
The same operation as in Example 7 was performed except that the staple fiber was cut so that the fiber length was 0.02 mm. Table 3 shows the evaluation results of the meta-type wholly aromatic polyamide non-crimped staple fibers obtained after melting ice.

Comparative Example 4
A known guillotine cutter type obtained by adjusting the fiber bundle obtained from the polymetaphenylene isophthalamide fiber wound after the dry heat treatment obtained in Example 6 and water to 3.0 mm. Using a fiber bundle cutting device (Onouchi Manufacturing Co., Ltd., model: D100), it was cut to obtain crimped staple fibers. The evaluation results of the obtained meta-type wholly aromatic polyamide uncrimped staple fiber are shown in Table 4.

Comparative Example 5
A known guillotine cutter type obtained by adjusting the fiber bundle obtained from the polymetaphenylene isophthalamide fiber wound in the heat treatment after dry heat treatment obtained in Example 6 and having a fiber length of 1.0 mm. Using a fiber bundle cutting device (Onouchi Manufacturing Co., Ltd., model: D100), it was cut to obtain crimped staple fibers. The evaluation results of the obtained meta-type wholly aromatic polyamide uncrimped staple fiber are shown in Table 4.

Comparative Example 6
Except for cutting with the draft ratio between the rotary cutter and the feed roller set to 0.98, the same operation as in Example 6 was performed to obtain an uncrimped staple fiber. The evaluation results of the obtained meta-type wholly aromatic polyamide uncrimped staple fiber are shown in Table 4.

Example 9
High-density polyethylene (HDPE) having an MFR of 20 g / 10 min and a melting point Tm of 131 ° C. is selected as the low melting point thermal adhesive component, and an isotactic polypropylene having an MFR of 39 g / 10 min and Tm of 160 ° C. as the fiber-forming component. (PP) was selected. Each of these polyolefins is melted with a separate extruder, each of which is a molten polymer at 245 ° C., HDPE is the sheath component, PP is the core component, and the composite ratio is sheath: core = 50: 50 (weight ratio). Using a concentric core-sheath type composite spinneret having 1336 discharge holes, they were combined and melted and discharged. At the time of this melt discharge, the die temperature was 260 ° C., and the discharge rate was 190 g / min. Further, the discharged polymer was air-cooled with a cooling air of 27 ° C. at a position 31 mm below the base, and after the polyether / polyester copolymer emulsion was applied to the yarn with an oiling roller, it was wound at 1300 m / min. An undrawn yarn was obtained. This unstretched yarn is bundled, stretched 4.10 times in warm water at 95 ° C., and after imparting a polyether / polyester copolymer as a stretching oil, it is dried at 105 ° C. for 60 minutes to obtain a single yarn fineness. A polyethylene / polypropylene composite fiber bundle having 0.32 dtex and a total fineness of 70,000 denier was obtained. The resulting composite fiber bundle was given water with an oiling roller so that the moisture content was 15%, and Eastman rotary cutter fiber with a blade interval of 3.0 mm so that the fiber length of the staple fiber was 3.0 mm. The fiber was cut with a cutting device. At the time of this cutting, the draft ratio between the rotary cutter and the feed roller was set to 1.02, and the fiber was cut while pressing the fiber bundle against the cutter blade with a pressure roll. Table 3 shows the evaluation results of the resulting polyolefin uncrimped composite staple fiber, such as fineness, moisture content, cut end coefficient, fiber length relative variation coefficient, and dispersibility in water.

Example 10
As an organic resin constituting the staple fiber, isotactic polypropylene (PP) having an MFR of 39 g / 10 min and a melting point Tm of 160 ° C. was selected. Next, this PP was melted with an extruder, and melted and discharged as a molten polymer at 255 ° C. using a spinneret having 3000 circular discharge holes. At this time, the die temperature was 260 ° C. and the discharge rate was 190 g / min. Further, the discharged polymer was air-cooled with a cooling air of 27 ° C. at a position 25 mm below the die, and wound at 1300 m / min to obtain an undrawn yarn. This unstretched yarn was bundled and stretched at 2.70 times in warm water at 95 ° C., and then a polyether / polyester copolymer was applied as a stretching oil. Thereafter, the drawn yarn was dried at 110 ° C. for 60 minutes to obtain a polypropylene fiber bundle having a single yarn fineness of 0.30 dtex and a total fineness of 70,000 denier. The obtained polypropylene fiber bundle is given water with an oiling roller so that the moisture content is 15%, and Eastman rotary cutter type fiber with a blade interval of 3.0 mm so that the fiber length of the staple fiber is 3.0 mm. The fiber was cut with a cutting device. At the time of this cutting, the draft ratio between the rotary cutter and the feed roller was set to 1.02, and the fibers were cut while pressing the fiber bundle against the cutter blade with a pressure roll. The evaluation results of the obtained polypropylene uncrimped staple fibers are shown in Table 5.

Example 11
As an organic resin constituting the staple fiber, high density polyethylene (HDPE) having an MFR of 20 g / 10 min and a melting point Tm of 131 ° C. was selected. Next, this HDPE was melted with an extruder, and melted and discharged as a molten polymer at 210 ° C. using a spinneret having 144 circular discharge holes. At this time, the die temperature was 210 ° C., and the discharge rate was 15 g / min. Furthermore, the discharged polymer was air-cooled with a cooling air of 27 ° C. at a position 25 mm below the die and wound at 1000 m / min to obtain an undrawn yarn. This unstretched yarn was bundled and stretched by 3.60 times in warm water at 95 ° C., and then a polyether / polyester copolymer was applied as a stretching oil. Thereafter, the drawn yarn was dried at 105 ° C. for 60 minutes to obtain a polyethylene fiber bundle having a single yarn fineness of 0.32 dtex and a total fineness of 70,000 denier. The obtained polyethylene fiber bundle is given water with an oiling roller so that the moisture content becomes 15%, and Eastman rotary cutter type fiber with a blade interval of 3.0 mm so that the fiber length of the staple fiber becomes 3.0 mm. The fiber was cut with a cutting device. In this cutting, the draft ratio between the rotary cutter and the feed roller was set to 1.02, and the fiber was cut while pressing the fiber bundle against the cutter blade with a pressure roll. The evaluation results of the obtained polyethylene uncrimped staple fiber are shown in Table 5.

Comparative Example 7
Twenty polypropylene / polyethylene core-sheath type composite fiber bundles without crimping after applying water obtained in Example 9 were bundled to make 1.4 million dtex, and then included in paper. Next, the contained core-sheath type composite fiber bundle is cut with a known guillotine cutter type fiber bundle cutting device (Ono Uchi Seisakusho, model: D100) adjusted to have a fiber length of 3.0 millimeters, and is not crimped staple. I got a fiber. Table 6 shows the evaluation results of the obtained polypropylene / polyethylene core-sheath type composite staple fiber.

Comparative Example 8
Twenty polypropylene fiber bundles after applying water obtained in Example 10 were bundled to make 1.4 million dtex, and then included in paper. Next, the contained polypropylene fiber bundle is cut with a known guillotine cutter type fiber bundle cutting device (Ono Uchi Seisakusho, model: D100) adjusted to have a fiber length of 3.0 mm, thereby obtaining an uncrimped staple fiber. It was. The evaluation results of the obtained polypropylene uncrimped staple fiber are shown in Table 6.

Comparative Example 9
Twenty polyethylene fiber bundles after applying water obtained in Example 11 were bundled to make 1.4 million dtex, and then included in paper. Next, the encapsulated polyethylene fiber bundle is cut with a known guillotine cutter type fiber bundle cutting device (Ono Uchi Seisakusho, model: D100) adjusted to have a fiber length of 3.0 mm, thereby obtaining an uncrimped staple fiber. It was. The evaluation results of the obtained polyethylene uncrimped staple fiber are shown in Table 6.

Comparative Example 10
Except for cutting with the draft ratio between the rotary cutter and the feed roller set to 0.98, the same operation as in Example 9 was performed to obtain an uncrimped staple fiber. The evaluation results of the obtained polyethylene / polypropylene core-sheath type composite crimped staple fiber are shown in Table 7.

Comparative Example 11
Except for cutting with the draft ratio between the rotary cutter and the feed roller set to 0.98, the same operation as in Example 10 was performed to obtain an uncrimped staple fiber. Table 7 shows the evaluation results of the obtained polypropylene uncrimped staple fibers.

Comparative Example 12
After applying water with a spray so as to have a moisture content of 1.0%, the same operation as in Example 1 was performed except that it was supplied to a rotary cutter and cut to obtain a crimped staple fiber. Table 7 shows the evaluation results of the obtained polyester uncrimped staple fibers.

Claims (5)

The fineness is 0.0001 to 0.6 dtex, the fiber length is 1.0 to 5.0 millimeters, the moisture content is 10 to 100% by weight, and the cut end coefficient defined below is 1.00 to 1.07. Organic resin non-crimped staple fiber for wet nonwoven fabrics having a fiber length relative variation coefficient (CV%) of 0.0 to 15.0%.
[Here, the cut end coefficient and the fiber length relative variation coefficient are defined by the following equations.
(1) Cut end coefficient = b / a
(The fiber diameter of a single crimped staple fiber is a, and the maximum cut end diameter is b.)
(2) Relative variation coefficient of fiber length (CV%) = (standard deviation of fiber length) / (average value of fiber length) × 100 (%)
In both (1) and (2), the number of single yarns measured is 50. ]   The organic resin-free crimped staple fiber according to claim 1, wherein the uncrimped staple fiber is a polyester-free crimped staple fiber, a wholly aromatic polyamide-free crimped staple fiber, or a polyolefin-free crimped staple fiber.   Uncrimped staple fiber is polyethylene terephthalate-free crimped staple fiber, polytrimethylene terephthalate-free crimped staple fiber, polytetramethylene terephthalate-free crimped staple fiber, polyethylene naphthalate-free crimped staple fiber, polytrimethylene naphthalate-free Crimped staple fiber, polytetramethylene naphthalate uncrimped staple fiber, meta-type wholly aromatic polyamide uncrimped staple fiber, para-type wholly aromatic polyamide uncrimped staple fiber, polyethylene uncrimped staple fiber or polypropylene The organic resin non-crimped staple fiber according to claim 1, wherein the staple fiber is a crimped staple fiber.   The organic resin non-crimped staple fiber according to claim 1, wherein the non-crimped staple fiber is a composite fiber composed of two or more organic resins. A fiber having a fineness of 0.0001 to 0.6 dtex and a moisture content of 10 to 200% by weight is supplied to a rotary cutter and cut to a fiber length of 1.0 to 5.0 mm. draft ratio organic resin No crimped staple fibers manufacturing method of Ru der 1.01 to 1.05 between the feed rollers.

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