JP2009167539A - Polylactic acid staple fiber and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide high grade polylactic acid staple fibers excellent in hydrolysis resistance and dyeability. <P>SOLUTION: Provided are the polylactic acid staple fibers in which the carboxyl groups of polylactic acid chain ends are sealed with a tri- or more-functional epoxy compound; the surfaces of the fibers are covered with a fatty acid bisamide and/or an alkyl substituted fatty acid monoamide; and the existence rate of devitrified fibers is 10% or less; and a method for producing the same. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a short polylactic acid fiber excellent in high-grade hydrolysis resistance.

  In recent years, polylactic acid having biodegradability has been attracting attention as environmental awareness on a global scale is increasing. Polylactic acid is a polymer made from lactic acid obtained by fermenting starch extracted from a plant, and as a biodegradable polymer using biomass, the balance of mechanical properties, heat resistance, and cost is most excellent. Development of resin products, fibers, films, sheets, and the like using this has been performed at a rapid pitch.

  The development of polylactic acid fibers is preceded by agricultural and civil engineering materials that utilize biodegradability, but applications for clothing, interiors, vehicle interiors, and industrial materials are expected as the next large-scale applications. ing. However, since polylactic acid fibers are biodegradable, their product life is short and their application development is limited.

  In order to solve this problem, Patent Document 1 describes a polylactic acid resin / film having a hydrolysis resistance improved by adding a polycarbodiimide compound. However, since the polycarbodiimide compound has low dispersibility in polylactic acid and high reactivity, a gel having a high molecular weight due to excessive reaction is likely to be generated. Therefore, not only the hydrolysis resistance is insufficient, but also the yarn-making property is unstable and it is difficult to apply to industrial fiber production. Patent Document 2 proposes a method of blocking the terminal carboxyl group of polylactic acid with a terminal blocking agent such as a carbodiimide compound. In this case, the hydrolysis resistance of polylactic acid is improved, but the resulting polylactic acid is colored yellow due to the influence of the end-capping agent, and there are significant restrictions on the development of dyeing applications centering on clothing. It was the current situation. In addition, when these polycarbodiimides and carbodiimide compounds are added, isocyanate gases that are harmful to the human body are generated during spinning, and the impact on the work environment is significant. Separation between production machines and work spaces, reinforcement of gas disposal facilities, etc. Capital investment is essential to ensure the safety of workers.

  In addition, long fibers are used in clothing, interior use, and vehicle interior use, but short fibers are very often used in a form that is processed into a nonwoven fabric or spun yarn. However, in the development of polylactic acid fibers, the development of long fibers is ahead, and various techniques for having a desired function have been proposed. However, short fibers that have the same function as long fibers have not necessarily been obtained.

For example, several attempts have been made to increase the strength of long fibers. Patent Document 3 discloses a technique related to a method for producing a high-quality multifilament by multistage drawing, which is designed based on a technique for producing a long fiber drawn in a multifilament shape having a small total fineness, For example, it is impossible to obtain high-quality polylactic acid short fibers even if the same technique is applied in the production of short fibers that are drawn in a tow shape having a total fineness of 10 to 100 ktex. Patent Document 4 discloses a method for producing a high-quality and high-strength polylactic acid fiber by increasing the drawing temperature, which is also designed based on the production technology for long fibers that are drawn in filament form. It has only been done. In the production of short fibers, heating with a roller is very uneven in heat, so liquid bath stretching is generally employed. Therefore, in order to obtain the stretching temperature proposed in Patent Document 4, it is necessary to employ an organic solvent, which is problematic in various aspects such as safety, environment, and cost. As described above, the present situation is that no practical technique has been found for stably obtaining high-quality polylactic acid fibers in a general short fiber production facility.
Japanese Patent Laid-Open No. 11-80522 JP 2002-180328 A JP 2000-248426 A JP 2000-136435 A

  An object of the present invention is to overcome the above-described problems and provide a polylactic acid short fiber excellent in high-grade hydrolysis resistance.

  Accordingly, the present inventors have intensively studied to solve the above problems, and as a result, have reached the present invention. That is, the polylactic acid short fiber of the present invention has the following configuration. That is, the carboxyl group at the end of the polylactic acid molecular chain is blocked with a trifunctional or higher functional epoxy compound, and the fiber surface is coated with a fatty acid bisamide and / or an alkyl-substituted fatty acid monoamide. A polylactic acid short fiber characterized by the following.

  Moreover, in order to solve said subject, the manufacturing method of the polylactic acid short fiber of this invention has the following structure. That is, a polylactic acid composition containing a tri- or higher functional epoxy compound and a fatty acid bisamide and / or an alkyl-substituted fatty acid monoamide is melt-spun, and the obtained tow is converged so that the total fineness becomes 10 to 100 ktex, This is a method for producing a polylactic acid short fiber which is stretched in a liquid bath at ˜95 ° C. and then mechanically crimped and cut to a predetermined fiber length.

  According to the present invention, it is possible to obtain high-quality polylactic acid short fibers that are excellent in hydrolysis resistance and excellent in dyeability. Such a polylactic acid short fiber can be developed for many uses, and can greatly expand the development width.

  Moreover, the polylactic acid short fiber manufacturing method of the present invention can stably produce the polylactic acid short fiber as described above with good reproducibility.

  The polylactic acid referred to in the present invention refers to a polymerized lactic acid monomer or oligomer such as lactic acid or lactide, and the optical purity of L-form or D-form is preferably 90% or higher, which is preferable because of high melting point. The optical purity of the L-form or D-form is more preferably 97% or more. Further, the above-mentioned monomer and oligomer components may be copolymerized within a range not impairing the properties of polylactic acid. The components to be copolymerized include polyethers such as polyethylene glycol, aliphatic polyesters such as polybutylene succinate and polyglycolic acid, aromatic polyesters such as polyethylene isophthalate, and hydroxycarboxylic acids, lactones, dicarboxylic acids and diols. Examples thereof include an ester bond-forming monomer.

  The method for producing polylactic acid used in the present invention is not particularly limited. Specifically, there is a manufacturing method disclosed in JP-A-6-65360. That is, it is a direct dehydration condensation method in which lactic acid is subjected to dehydration polymerization as it is in the presence of an organic solvent and a catalyst. Further, there is a method in which at least two kinds of homopolymers disclosed in JP-A-7-173266 are copolymerized and transesterified in the presence of a polymerization catalyst. Furthermore, there is a method disclosed in US Pat. No. 2,703,316. That is, an indirect polymerization method in which lactic acid is once dehydrated to form a cyclic dimer and then subjected to ring-opening polymerization.

  In general, the polylactic acid fiber is manufactured by pelletizing the polylactic acid produced by the above-described method, drying it, and then drawing it through melt spinning. However, in polylactic acid fibers, structural breakage may proceed due to excessive stress or insufficient heat during drawing, and abnormally drawn yarn may be generated. With this abnormally stretched yarn, the transparency of the fiber is lost due to unevenness of the fiber surface due to structural breakage and the generation of voids and cracks inside the fiber. For this reason, this abnormally stretched yarn is called “devitrified yarn”. This devitrified yarn has low strength and low elongation compared to normal yarn, and because of the difference in dyeing ability with normal yarn, when dyed, the density of the polylactic acid short fiber is significantly impaired, such as uneven density. .

  In addition, techniques for adding terminal reactive substances such as polycarbodiimide to improve hydrolysis resistance have been disclosed, but many of these terminal reactive substances increase the frequency of devitrification by the addition thereof. That was found by the inventors' investigation. Although the details of this cause are unknown, it is thought that uneven reaction occurs locally due to the low dispersibility of the terminal reactant in polylactic acid and the high reactivity. This causes a local molecular weight difference in the polylactic acid, and also changes the intrinsic viscosity (hereinafter abbreviated as IV). It is considered that stress concentrates in the low IV region during stretching and devitrification occurs.

  In order to alleviate this local IV fluctuation, it is important to select a trifunctional or higher functional epoxy compound as a terminal reactant. Furthermore, it is very important from the viewpoint of improving hydrolysis resistance to react a trifunctional or higher functional epoxy compound with at least a part of polylactic acid, preferably with at least a part of the terminal of polylactic acid. The trifunctional or higher functional epoxy compound is a compound having three or more epoxy groups in one molecule.

  The reason for using an epoxy compound as the substance to be added to polylactic acid is that the epoxy compound has a slower reaction rate than other terminal reactive substances such as carbodiimide, and suppresses excessive reaction during melt-kneading with polylactic acid. It is possible to suppress local IV fluctuation by sufficient dispersion and gradual reaction.

  In addition, it is important to select a trifunctional or higher functional epoxy compound. When an epoxy compound having 2 or less epoxy groups per molecule is selected as the terminal reactive substance, the reactivity of melt kneading is poor, and an excessive amount of epoxy compound is required in order to retain the expected hydrolysis resistance. Therefore, the reactivity cannot be controlled and a large IV fluctuation is caused.

  The trifunctional or higher functional epoxy compound used in the present invention preferably has an isocyanuric acid skeleton as a basic skeleton, and at least one of the three or more epoxy groups constitutes a glycidyl group. preferable. Specifically, the epoxy compound represented by the following general formula (1) is more preferably used as the trifunctional or higher functional epoxy compound from the viewpoints of reactivity, heat resistance, and dispersibility.

(Here, R _{1 to} R ₃ are functional groups including an epoxy group, and at least one of them is a glycidyl group)
Examples of the functional group containing an epoxy group include an epoxy group, a glycidyl group, a glycidyl ether group, a glycidyl ester group, and a glycidylamine group.

  The epoxy compound represented by the general formula (1) is not particularly limited, but triglycidyl isocyanurate, trimethyl glycidyl isocyanurate, triethyl glycidyl isocyanurate, tripropyl glycidyl isocyanurate, diethyl glycidyl methyl glycidyl isocyanurate, Examples include ethyl glycidyl dimethyl glycidyl isocyanurate, diepoxycyclopentylmethyl glycidyl isocyanurate, epoxycyclopentylmethyl diglycidyl isocyanurate, diepoxycyclobutylmethyl glycidyl isocyanurate, and epoxycyclobutylmethyldiglycidyl isocyanurate. In addition, the trifunctional or higher functional epoxy compound used as the end-capping substance may be used alone or in combination.

  Furthermore, in order to obtain a high-quality polylactic acid fiber without devitrification yarn, several measures for improving the long fiber have been proposed. These are related to a method for producing a long fiber drawn in a filament form. In the production of short fibers that are drawn in a tow shape having a large total fineness, sufficient effects cannot be obtained even if the same technique is applied. As a result of investigations by the inventors, it has been found that since short fibers are drawn in a tow shape, local stress concentration occurs due to entanglement / friction of the fibers, thereby causing devitrification.

  In order to alleviate local stress concentration, the polylactic acid fiber of the present invention contains fatty acid bisamide and / or alkyl-substituted fatty acid monoamide (hereinafter abbreviated as “fatty acid amide” generically), and the fiber surface is bleed-out. It was determined that it was important to form a film. The bleed-out refers to a phenomenon in which the fatty acid amide is precipitated on the fiber surface when polylactic acid and the fatty acid amide are simultaneously melted and discharged.

  The fatty acid bisamide referred to in the present invention refers to a compound having two amide bonds in one molecule, such as saturated fatty acid bisamide, unsaturated fatty acid bisamide, aromatic ginseng bisamide, etc., for example, methylene biscaprylic amide, methylene biscaprin. Acid amide, methylene bis lauric acid amide, methylene bis myristic acid amide, methylene bis palmitic acid amide, methylene bis stearic acid amide, methylene bis isostearic acid amide, methylene bis behenic acid amide, methylene bis oleic acid amide, methylene bis eruka Acid amide, ethylene biscaprylic acid amide, ethylene biscapric acid amide, ethylene bislauric acid amide, ethylene bismyristic acid amide, ethylene bispalmitic acid amide, ethylene bisstearic acid amide, ethylene Isostearic acid amide, ethylene bis behenic acid amide, ethylene bis oleic acid amide, ethylene bis erucic acid amide, butylene bis stearic acid amide, butylene bis behenic acid amide, butylene bis oleic acid amide, butylene bis erucic acid amide, Hexamethylene bis stearic acid amide, hexamethylene bis behenic acid amide, hexamethylene bis oleic acid amide, hexamethylene bis erucic acid amide, m-xylylene bis stearic acid amide, m-xylylene bis-12-hydroxy stearic acid amide, p-xylylene bis-stearic acid amide, p-phenylene bis-stearic acid amide, N, N′-distearyl adipic acid amide, N, N′-distearyl sebacic acid amide, N, N′-dioleyl adipic acid amide, , N'- distearyl terephthalic acid amide, methylene bis-hydroxystearic acid amide, ethylenebis-hydroxystearic acid amide, butylene-bis-hydroxystearic acid amide, hexamethylene bis hydroxystearic acid amide.

  The alkyl-substituted fatty acid monoamide referred to in the present invention refers to a compound having a structure in which an amide hydrogen such as a saturated fatty acid monoamide or an unsaturated fatty acid monoamide is replaced with an alkyl group, such as N-lauryl lauric acid amide, N- Palmityl palmitic acid amide, N-stearyl stearic acid amide, N-hebenyl hebenic acid amide, N-oleyl oleic acid amide, N-stearyl oleic acid amide, N-oleyl stearic acid amide, N-stearyl erucic acid amide, N-oleyl And palmitic acid amide. In the alkyl group, a substituent such as a hydroxyl group may be introduced into the structure. For example, methylose stearamide, N-stearyl-12-hydroxystearic amide, N-oleyl-12-hydroxystearin Acid amides and the like are also included in the alkyl-substituted fatty acid amides.

  In the present invention, fatty acid bisamides and alkyl-substituted fatty acid monoamides are used, but these compounds have lower amide reactivity than ordinary fatty acid monoamides, and are less likely to react with polylactic acid during melt molding. In addition, since many of them have a high molecular weight, they generally have good heat resistance and are difficult to sublimate. In particular, fatty acid bisamides can be more preferably used because they are less reactive with polylactic acid due to the lower reactivity of amides, and are high in heat resistance and difficult to sublime due to their high molecular weight. For example, ethylene bis stearic acid amide, ethylene bis isostearic acid amide, ethylene bis behenic acid amide, butylene bis stearic acid amide, butylene bis behenic acid amide, hexamethylene bis behenic acid amide, m-xylylene bis Stearic acid amide is preferred. These fatty acid bisamides and alkyl-substituted fatty acid monoamides may be a single component, or a plurality of components may be mixed.

  The content of the epoxy compound having 3 or more functional groups and the fatty acid amide in the entire short fiber in the present invention is not particularly limited, but the abundance of devitrified yarn is 10% or less and the carboxyl end group content of the polylactic acid molecular chain is 10 equivalents. / Ton or less is preferable. If the abundance of the devitrified yarn exceeds 10%, the stable operability is poor due to the occurrence of yarn breakage and fluffing in high-order processing, and uneven dyeing occurs due to a difference in dyeing ability from the normal yarn. Moreover, when the carboxyl end group amount exceeds 10 equivalents / ton, sufficient hydrolysis resistance cannot be maintained.

  Below, the manufacturing method of the polylactic acid short fiber in this invention is demonstrated.

  The method of incorporating the trifunctional or higher functional epoxy compound and the fatty acid amide into the polylactic acid is not particularly limited. For example, the polylactic acid chip and the epoxy compound and the fatty acid amide are individually dried and then kneaded. A master method in which a master chip is prepared in advance, and a master chip and a polylactic acid chip are chip-blended and melt-spun, and an addition method in which the epoxy compound and the fatty acid amide are directly added at the time of melt-spinning. Moreover, in order to suppress oxidative decomposition of polylactic acid during kneading and melt spinning, it is preferable to seal the inside of the apparatus with nitrogen. Further, when the yarn discharged from the base is applied and converged with an oil agent, and once stored and stretched, the stored yarn is bundled and used as a tow shape.

  The total fineness of the tow subjected to stretching is 10 to 100 ktex, preferably 20 to 80 ktex. If it is less than 10 ktex, the production efficiency is poor, and if it exceeds 100 ktex, the fiber interaction becomes strong and the devitrification yarn improvement effect is not sufficient.

  The temperature of the liquid bath during stretching is 80 to 95 ° C, preferably 85 to 90 ° C. If the temperature is less than 80 ° C., the stress applied during stretching is large, and thus the entire fiber is devitrified. If the temperature exceeds 95 ° C., the temperature is difficult to control because it is close to the boiling point when water is used for the bath liquid, Bubbles due to boiling are generated in the liquid bath, and uniform stretching is hindered.

  After stretching, using a stuffer box or the like, give a mechanical crimp of, for example, about 6 to 15 crests / 25 mm, and cut using a EC cutter or the like so as to obtain a predetermined fiber length of, for example, 10 to 76 mm. By doing so, a polylactic acid short fiber is obtained.

  The polylactic acid short fiber of the present invention is preferably used for sanitary materials, civil engineering materials, agricultural materials, daily life materials, industrial materials, filling cotton applications, clothing applications, and interior applications.

The present invention will be described more specifically with reference to the following examples. However, the present invention is not limited to these specific examples. The method for measuring the characteristics used in this example is as follows.
[Fineness]
The fineness (dtex) was measured by the method shown in JIS L-1015 (revised in 1999).
[Strength]
The strength (cN / dtex) was measured by the method shown in JIS L-1015 (revised in 1999).
[Crimped number]
The number of crimps (crests / 25 mm) was measured by the method shown in JIS L-1015 (revised in 1999).
[Crimp rate]
Crimp rate (%) was measured by the method shown in JIS L-1015 (revised in 1999).
[Terminal amount of carboxyl group]
As described in JP-A-2001-261797, a weighed sample was dissolved in o-cresol adjusted to 5% water content, and an appropriate amount of dichloromethane was added, followed by titration with a 0.02 normal potassium hydroxide methanol solution. Asked.
[Presence of devitrified yarn]
The polylactic acid short fibers are placed on a sample stand so as not to overlap in the same direction, and observed using a stereomicroscope (Nikon stereomicroscope HFX type). For each short fiber, 10 points are observed at random, and it is observed whether there is a devitrified (whitened) region. If there is a devitrified part even at one point, the devitrified yarn is used. As for the level, the short fibers produced are randomly collected from 5 points, and 20 short fibers at each point are confirmed (5 points × 20 pieces = 100 level).

Presence of devitrified yarn (%) = (number of devitrified yarn) / (number of measured short fibers: 100) × 100
[Fiber strength reduction rate]
The polylactic acid short fiber was treated for 300 hours in a thermostat adjusted to a temperature of 70 ° C. and a humidity of 90%, and calculated from the fiber strength before and after the treatment. The strength was measured by the method shown in JIS L-1015 (revised in 1999).

Reduction rate of fiber strength (%) = (fiber strength after treatment) / (fiber strength before treatment) × 100
[Dyeability]
After opening the polylactic acid short fibers, dyeing was performed, and the dyeability was visually confirmed. As an evaluation method, 10 people who arbitrarily selected a dyed sample observed and checked for the presence or absence of uneven dyeing.

○: Nine or more people judged that there was no dyeing unevenness Δ: Five to eight people judged that there was no dyeing unevenness ×: 0-4 people judged that there was no dyeing unevenness Note that the dyeing process was Kayalon Polyrubine BL-S200 [Nippon Kayaku Co., Ltd.] The dyeing solution was adjusted to a dye concentration of 2% by weight and pH 4.5, and the dyeing temperature was 100 ° C. and the dyeing time was 60 minutes.
Example 1
Polylactic acid chips with a melting point of 170 ° C. [Nature Works; 6201D], fatty acid bisamides, ethylene bis-stearic acid amide (EBA) [NOF Corporation; Alfro H-50S], and triglycidyl isocyanurate (TGIC) [Nissan Chemical Company; TEPIC-S] were individually dried, mixed at a weight ratio of 85: 5: 10, melt-kneaded at 220 ° C., and formed into chips to prepare master chips. The same polylactic acid chip as described above and the prepared master chip were mixed at a weight ratio of 90:10 (containing 0.5% EBA and 1.0% TGIC), and melted at a spinning temperature of 230 ° C. with an extruder-type spinning machine. After spinning, the spun yarn was cooled, and the oil agent was applied and converged, and then taken up at 1000 m / min to obtain an undrawn yarn. The obtained undrawn yarn was further converged to form a 25 ktex tow, which was drawn 2.00 times in a 85 ° C. hot water bath and then drawn 1.75 times in a 90 ° C. hot water bath. After that, mechanical crimping was applied with a stuffer box, and after relaxation heat treatment at 145 ° C. for 10 minutes, an alkyl ester oil component was applied by spraying so as to be 0.5% by weight with respect to the fiber, and the fiber length was 38 mm. To obtain polylactic acid short fibers. The properties of the obtained short fibers are shown in Table 1.
(Example 2)
The same polylactic acid chip, EBA and TGIC as those used in Example 1 were individually dried and then mixed at a weight ratio of 82: 8: 10, and melt kneaded and chipped at 220 ° C. A master chip was produced. The same polylactic acid chip as described above and the prepared master chip were mixed at a weight ratio of 90:10 (containing EBA 0.8% and TGIC 1.0%) and melted at an extruder type spinning machine at a spinning temperature of 230 ° C. After spinning, the spun yarn was cooled, and the oil agent was applied and converged. Then, the spun yarn was taken out at 1600 m / min to obtain an undrawn yarn. The obtained unstretched yarn was further converged to form a 100 ktex tow and stretched 2.40 times in a 90 ° C. warm water bath, and then stretched once again in a 90 ° C. warm water bath to 1.20 times. After that, mechanical crimping was applied with a stuffer box, and after relaxation heat treatment at 145 ° C. for 10 minutes, an alkyl ester oil component was applied by spraying so as to be 0.5% by weight with respect to the fiber, and the fiber length was 38 mm. To obtain polylactic acid short fibers. The properties of the obtained short fibers are shown in Table 1.
(Example 3)
EBA was changed to N-stearyl stearamide (SS) [Nippon Kasei Co., Ltd .; Nikka Amide S], the mixing ratio of the production of the master chip was changed to the one shown in Table 2, and the stretching conditions were heated to 80 ° C. A polylactic acid short fiber was produced in the same manner as in Example 1 except that it was changed to 2.00 times, and further 1.75 times in a warm water bath at 80 ° C. The properties of the obtained short fibers are shown in Table 1.
Example 4
The EBA was changed to SS, the mixing ratio of the production of the master chip was changed to that shown in Table 2, and the stretching conditions were 2.00 times in a 95 ° C. hot water bath, and further in a 95 ° C. hot water bath. Polylactic acid short fibers were produced in the same manner as in Example 1 except that the ratio was changed to 75 times. The properties of the obtained short fibers are shown in Table 1.
(Comparative Example 1)
The same polylactic acid chip as used in Example 1 was dried, and then melt-spun at an extruder type spinning machine at a spinning temperature of 230 ° C. After cooling the spun yarn, the oil agent was applied and converged, It was taken up at 1000 m / min, made tow of 80 ktex, stretched 2.00 times in a 85 ° C. warm water bath, and then stretched 1.75 times in a 90 ° C. warm water bath. After that, mechanical crimping was applied with a stuffer box, and after relaxation heat treatment at 145 ° C. for 10 minutes, an alkyl ester oil component was applied by spraying so as to be 0.5% by weight with respect to the fiber, and the fiber length was 38 mm. To obtain polylactic acid short fibers. The properties of the obtained short fibers are shown in Table 1.
(Comparative Examples 2, 3, 4)
Polylactic acid short fibers were produced in the same manner as in Example 1 except that the master chip was changed to one having the mixing ratio shown in Table 2. The properties of the obtained short fibers are shown in Table 1. The terminal reactant used in Comparative Example 4 is a polycarbodiimide compound (PCI) [Nisshinbo Co., Ltd .; Carbodilite LA-1].
(Comparative Example 5)
Polylactic acid short fibers were produced in the same manner as in Example 3 except that the converging tow was drawn at 150 ktex. The properties of the obtained short fibers are shown in Table 1.
(Comparative Example 6)
Polylactic acid short fibers were produced in the same manner as in Example 1 except that the stretching conditions were changed to 2.00 times in a 75 ° C. warm water bath and further 1.50 times in a 75 ° C. warm water bath. . The properties of the obtained short fibers are shown in Table 1.
(Comparative Example 7)
Polylactic acid short fibers were produced in the same manner as in Example 1 except that the stretching conditions were changed to 2.00 times in a 98 ° C hot water bath and further 1.50 times in a 98 ° C hot water bath. . The properties of the obtained short fibers are shown in Table 1.

Claims (4)

The carboxyl group at the end of the polylactic acid molecular chain is blocked with a trifunctional or higher functional epoxy compound, and the fiber surface is coated with a fatty acid bisamide and / or an alkyl-substituted fatty acid monoamide. Polylactic acid short fiber characterized by being. The polylactic acid short fiber according to claim 1, wherein the epoxy compound is represented by the following general formula (1).

(Here, R _{1 to} R ₃ are functional groups including an epoxy group, and at least one of them is a glycidyl group) The polylactic acid short fiber according to claim 1 or 2, wherein the carboxyl end group amount is 10 equivalent / ton or less. A polylactic acid composition containing a trifunctional or higher functional epoxy compound and a fatty acid bisamide and / or an alkyl-substituted fatty acid monoamide is melt-spun, and the obtained tow is converged so that the total fineness becomes 10 to 100 ktex, and 80 to 95 A method for producing a polylactic acid short fiber, which is drawn in a liquid bath at 0 ° C. and then cut into a predetermined fiber length by applying mechanical crimping.