JP5155095B2 - Polylactic acid fiber - Google Patents

Description

  The present invention relates to a fiber made of polylactic acid fiber and having practical strength, heat resistance and low heat shrinkage, and a method for producing the same.

  In recent years, for the purpose of protecting the global environment, biodegradable polymers that are decomposed in a natural environment have attracted attention and are being studied all over the world. As biodegradable polymers, polyhydroxybutyrate, polycaprolactone, aliphatic polyester, and polylactic acid are known. These can be melt-molded and are expected as versatile polymers. Among these, since polylactic acid can be produced from natural products such as lactic acid or lactide, the use of polylactic acid is not just a biodegradable polymer, but is also being considered for use as a general-purpose polymer in consideration of the global environment. is there. Polylactic acid is highly transparent and tough, but it is easily hydrolyzed in the presence of water, and is decomposed without polluting the environment after disposal, so it is expected as a general-purpose polymer with little environmental impact.

  The melting point of polylactic acid is in the range of 150 to 170 ° C., and when used as clothing fibers, the ironable temperature is limited to low temperatures. In addition, when used as an industrial fiber, there is a problem that the manufacturing temperature is not suitable for rubber materials and resin-coated cloths that are exposed to a high temperature of about 150 ° C.

  On the other hand, poly L-lactic acid (hereinafter sometimes abbreviated as PLLA) consisting only of L-lactic acid units and poly D-lactic acid (hereinafter sometimes abbreviated as PDLA) consisting only of D-lactic acid units. It is known that stereocomplex polylactic acid is formed by mixing in a solution or in a molten state (Non-patent Document 1). This stereocomplex polylactic acid is known to have a higher melting point and higher crystallinity than PLLA and PDLA. Various studies have also been made on fibers using stereocomplex polylactic acid.

  For example, Patent Document 1 discloses a stereocomplex polylactic acid fiber obtained by melt spinning a composition containing equimolar amounts of poly L-lactic acid and poly D-lactic acid, but has insufficient heat resistance and is practically used. Not enough to serve.

  Non-Patent Document 2 describes that a stereocomplex polylactic acid fiber is obtained by melt spinning. This document describes that a stereocomplex fiber is obtained by heat-treating an undrawn yarn obtained by melt-spinning a melt blend of poly-L-lactic acid and poly-D-lactic acid. The orientation is relaxed, and the strength of the resulting fiber remains at 2.3 cN / dtex.

  Thus, the conventional method for forming a stereocomplex involves stretching and heat-treating an amorphous undrawn yarn obtained by spinning a blend of poly L-lactic acid and poly D-lactic acid. That is, in the prior art, in order to sufficiently grow the stereocomplex, it is effective to perform the heat treatment at a temperature equal to or higher than the melting point of poly L-lactic acid or poly D-lactic acid single crystal. The mainstream was one carried out at a temperature higher than the melting point of the single crystal. Certainly, this high-temperature heat treatment was effective for stereocomplex formation, but when heat-treated at a high temperature, there was a problem that partial melting of the yarn occurred and the yarn was coarsely cured or reduced in strength.

  In order to solve this problem, Patent Document 2 proposes a method of forming a stereocomplex at once from a melt of polylactic acid on a spinning line. For example, spinning is performed at a spinning speed of 4,000 m / min, and a crystallized undrawn yarn having a stereoization ratio of 10 to 35% as measured by wide angle X-ray diffraction (XRD) is drawn 1.4 to 2.3 times. It has been proposed to improve the partial fusing of the yarn by doing so. However, in order to carry out this method, a spinning speed of about 3,000 m / min is insufficient, and a special spinning facility for spinning at a spinning speed of 5,000 m / min or more is required. There are still some problems that must be overcome in practical implementation. In addition, the evaluation of heat resistance in this proposal shows a drastic change such as breaking of the knitted fabric and rough hardening by applying a 170 ° C iron to the fiber knitting, and although the strength and heat resistance were improved to some extent, the fiber No consideration was given to the heat shrinkage of the fabric, and there was a problem in its use for clothing. Thus, the present condition is that the technique which manufactures the fiber which has a high stereo ratio and was excellent in intensity | strength and heat-resistant shrinkage is not completed.

  Patent Document 3 discloses that an undrawn yarn melt-spun at a spinning draft ≧ 50 and take-up speed ≧ 300 m / min is once wound and then stretched or stretched 2.8 times without being wound. A fiber having heat resistance of 200 ° C. having two peaks of polylactic acid homocrystal and 190 ° C. or higher stereocomplex crystal by heat treatment at ˜180 ° C. has been proposed. On the other hand, Patent Document 4 proposes that a polylactic acid capable of forming a stereocomplex contains a phosphoric ester metal salt as a crystal nucleating agent to improve the heat resistance and impact resistance of a molded product.

  However, neither method has studied heat shrinkage in clothing fibers made of polylactic acid, and development of a polylactic acid fiber that can be produced with high strength, low heat shrinkage rate and good process productivity and a method for producing the same are greatly desired. It was rare.

JP 63-24014 A JP 2003-293220 A Japanese Patent Laid-Open No. 2005-23512 JP 2003-192894 A Macromolecules, 24, 5651 (1991). Seni Gakkai Preprints (1989)

  An object of the present invention is to stably provide a fiber made of polylactic acid and having excellent strength, heat resistance, and low heat shrinkability.

  When the present inventors have melt-spun poly L-lactic acid (component A) and poly D-lactic acid (component B), the presence of a phosphate ester metal salt (component C) is substantially amorphous. It was found that an undrawn yarn comprising a stereocomplex was obtained. Moreover, even when this undrawn yarn was drawn, it was found that a low-temperature melting peak due to poly L-lactic acid and poly D-lactic acid was not observed. Furthermore, the present inventors have found that partial melting of polylactic acid is not observed even when the drawn yarn is heat-treated at high temperature.

That is, according to the present invention,
(a) Poly L-lactic acid (component A) having a weight average molecular weight of 100,000 to 200,000, (b) Weight average molecular weight of 10
10 to 200,000 poly-D-lactic acid (component B) and (c) 100 parts by weight of the total of component A and component B
Or a composition containing 0.01 to 5 parts by weight of a phosphoric acid ester metal salt.
-7.0 cN / dTex, elongation is 20-40%, shrinkage at 180 ° C is 5-30%
A method for producing a polylactic acid fiber, which is obtained at a spinning speed of 300 to 1000 m / min.
The drawn yarn is once wound into a package, and the winding speed in the drawing process is 300 to 1000 m /
After stretching by 3.5 to 6.0 times in min, heat set at 160 to 230 ° C. with a contact heater
A process for producing polylactic acid fibers, characterized in that
Is provided.

  A high-strength, low-heat-shrinkable polylactic acid fiber with less fuzz and yarn breakage and good quality can be stably provided.

  The fiber of the present invention is an undrawn yarn obtained by spinning a composition containing poly L-lactic acid (component A), poly D-lactic acid (component B) and a phosphate ester metal salt (component C) at 300 to 1000 m / min. Can be wound around a package, stretched 3.5 to 6.0 times, and then heat set at 160 to 230 ° C. with a contact heater.

(Poly L-lactic acid: A component)
Poly L-lactic acid mainly consists of L-lactic acid units. The L-lactic acid unit is a repeating unit derived from L-lactic acid. The poly L-lactic acid preferably contains 90 to 100 mol%, more preferably 95 to 100 mol%, still more preferably 98 to 100 mol% of L-lactic acid units. Other repeating units include D-lactic acid units and units other than lactic acid. The D-lactic acid unit and the units other than lactic acid are preferably 0 to 10 mol%, more preferably 0 to 5 mol%, still more preferably 0 to 2 mol%.

  Examples of units other than lactic acid include hydroxycarboxylic acids such as glycolic acid, caprolactone, butyrolactone, propiolactone, ethylene glycol, 1,3-propanediol, 1,2-propanediol, 1,4-propanediol, 1,5 -Propanediol, hexanediol, octanediol, decanediol, dodecanediol, aliphatic diols having 2 to 30 carbon atoms, succinic acid, maleic acid, adipic acid, aliphatic dicarboxylic acids having 2 to 30 carbon atoms, terephthalic acid And units derived from one or more monomers selected from aromatic diols such as isophthalic acid, hydroxybenzoic acid, and hydroquinone, and aromatic dicarboxylic acids.

The poly L-lactic acid preferably has crystallinity. The melting point is preferably 150 to 190 ° C, more preferably 160 to 190 ° C. This is because, if these conditions are satisfied, a stereocomplex crystal having a high melting point can be formed and the crystallinity can be increased.
The poly L-lactic acid has a weight average molecular weight of preferably 50,000 to 300,000, more preferably 100,000 to 250,000.

(Poly D-lactic acid: B component)
Poly D-lactic acid mainly consists of D-lactic acid units. The D-lactic acid unit is a repeating unit derived from D-lactic acid. The poly-D-lactic acid preferably contains 90 to 100 mol%, more preferably 95 to 100 mol%, and still more preferably 98 to 100 mol% of D-lactic acid units. Other repeating units include L-lactic acid units and units other than lactic acid. The L-lactic acid unit and the units other than lactic acid are preferably 0 to 10 mol%, more preferably 0 to 5 mol%, still more preferably 0 to 2 mol%.

  Examples of units other than lactic acid include hydroxycarboxylic acids such as glycolic acid, caprolactone, butyrolactone, propiolactone, ethylene glycol, 1,3-propanediol, 1,2-propanediol, 1,4-propanediol, 1,5 -Propanediol, hexanediol, octanediol, decanediol, dodecanediol, aliphatic diols having 2 to 30 carbon atoms, succinic acid, maleic acid, adipic acid, aliphatic dicarboxylic acids having 2 to 30 carbon atoms, terephthalic acid And units derived from one or more monomers selected from aromatic diols such as isophthalic acid, hydroxybenzoic acid, and hydroquinone, and aromatic dicarboxylic acids.

The poly D-lactic acid preferably has crystallinity. The melting point is preferably 150 to 190 ° C, more preferably 160 to 190 ° C. This is because, if these conditions are satisfied, a stereocomplex crystal having a high melting point can be formed and the crystallinity can be increased.
Poly D-lactic acid has a weight average molecular weight of preferably 100,000 to 200,000, more preferably 110,000 to 170,000.

  Poly-L-lactic acid or poly-D-lactic acid is produced by a method of directly dehydrating condensation of L-lactic acid or D-lactic acid, or L-lactic acid or D-lactic acid is once subjected to dehydration cyclization to form lactide, followed by ring-opening polymerization. It can be manufactured by a method. Catalysts used in these methods include divalent tin compounds such as tin octylate, tin chloride, and tin alkoxides, tetravalent tin compounds such as tin oxide, butyltin oxide, and ethyltin oxide, metal tin, zinc compounds, aluminum compounds, Examples include calcium compounds and lanthanide compounds.

  For poly L-lactic acid and poly D-lactic acid, it is preferable that the polymerization catalyst used in the polymerization is washed away with a solvent or the catalytic activity is deactivated. A catalyst deactivator can be used to inactivate the catalyst activity.

As a catalyst deactivator, an organic ligand consisting of a group of chelate ligands having an imino group and capable of coordinating to a metal polymerization catalyst, a phosphorus oxoacid, a phosphorus oxoacid ester, and an organic phosphorus oxoacid compound represented by the formula (3) There may be mentioned at least one selected from the group. The catalyst deactivator is preferably blended in an amount of 0.3 to 20 equivalents, more preferably 0.4 to 15 equivalents, and even more preferably 0.5 to 10 equivalents per equivalent of the metal element in the catalyst at the end of the polymerization. .
_{X 1 -P (= O) m} (OH) n (OX 2) 2-n (3)
In the formula, m is 0 or 1, n is 1 or 2, and X ₁ and X ₂ each independently represent a hydrocarbon group optionally having a substituent having 1 to 20 carbon atoms. Examples of the hydrocarbon group include alkyl groups having 1 to 20 carbon atoms such as a methyl group, an ethyl group, a propyl group, and a butyl group.

  The metal ion content in poly L-lactic acid and poly D-lactic acid is preferably 20 ppm or less from the viewpoint of heat resistance and hydrolysis resistance of the fiber. The metal ion content is preferably such that the content of each metal selected from alkaline earth metals, rare earths, transition metals of the third period, aluminum, germanium, tin and antimony is 20 ppm or less.

(Phosphate metal salt: C component)
As the phosphoric acid ester metal salt (component C), a compound represented by the following formula (1) or (2) is preferably exemplified. The phosphoric acid ester metal salt may be used alone or in combination.

  In Formula (1), R1 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms. Examples of the alkyl group having 1 to 4 carbon atoms represented by R1 include a methyl group, an ethyl group, an n-propyl group, an iso-propyl group, an n-butyl group, a sec-butyl group, and an iso-butyl group. .

  R2 and R3 each independently represent a hydrogen atom or an alkyl group having 1 to 12 carbon atoms. Examples of the alkyl group having 1 to 12 carbon atoms include methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, sec-butyl group, iso-butyl group, tert-butyl group, amyl group, tert-amyl group, hexyl group, heptyl group, octyl group, iso-octyl group, tert-octyl group, 2-ethylhexyl group, nonyl group, iso-nonyl group, decyl group, iso-decyl group, tert-decyl group, An undecyl group, a dodecyl group, a tert-dodecyl group, etc. are mentioned.

  M1 represents an alkali metal atom such as Na, K or Li or an alkaline earth metal atom such as Mg or Ca. p represents 1 or 2.

Preferable examples of the phosphoric acid ester metal salt represented by the formula (1) include those in which R ₁ is a hydrogen atom and R ₂ and R ₃ are both tert-butyl groups.

In the formula (2), R ₄ , R ₅ and R ₆ each independently represents a hydrogen atom or an alkyl group having 1 to 12 carbon atoms. Examples of the alkyl group having 1 to 12 carbon atoms include methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, sec-butyl group, iso-butyl group, tert-butyl group, amyl group, tert-amyl group, hexyl group, heptyl group, octyl group, iso-octyl group, tert-octyl group, 2-ethylhexyl group, nonyl group, iso-nonyl group, decyl group, iso-decyl group, tert-decyl group, An undecyl group, a dodecyl group, a tert-dodecyl group, etc. are mentioned.

  M2 represents an alkali metal atom such as Na, K or Li or an alkaline earth metal atom such as Mg or Ca. p represents 1 or 2.

  Preferable examples of the phosphoric acid ester metal salt represented by the formula (2) include those in which R4 and R6 are methyl groups and R5 is tert-butyl group. As a phosphoric acid ester metal salt, trade name, NA-11, manufactured by ADEKA Co., Ltd. can be mentioned. The phosphoric acid ester metal salt can be synthesized by a known method.

  As described in JP-A-2003-192884, the compound represented by the formula (1) or (2) is a compound known as a crystal nucleating agent for polylactic acid. However, in the present invention, M1 and M2 in the formulas (1) and (2) are an alkali metal atom or an alkaline earth metal atom. When M1 and M2 in Formula (1) and Formula (2) are other metals such as aluminum, the heat resistance of the compound itself is low, and a sublimation product is generated during spinning, which may make spinning difficult. is there.

  The phosphoric acid ester metal salt (component C) preferably has an average primary particle size of 0.01 to 10 μm, more preferably 0.05 to 7 μm. It is industrially difficult to make the particle size smaller than 0.01 μm, and it is not necessary to make it so small. On the other hand, if it is larger than 10 μm, the frequency of yarn breakage increases during spinning and drawing.

  The content of the phosphoric acid ester metal salt (component C) is 0.01 to 5 parts by weight per 100 parts by weight in total of the poly L-lactic acid (component A) and the poly D-lactic acid (component B), preferably 0.00. 05 to 5 parts by weight, more preferably 0.05 to 4 parts by weight, particularly preferably 0.1 to 3 parts by weight. If the amount is less than 0.01 parts by weight, the desired effect is hardly recognized. On the other hand, if it is used in a larger amount than 5 parts by weight, it is not preferable because thermal decomposition or fiber breakage may occur during fiber formation.

  The ratio of poly L-lactic acid (component A) to poly D-lactic acid (component B) is component A / component B (weight), preferably 40 / 60-60 / 40, more preferably 45 / 55-55. / 45, more preferably 50/50.

  For mixing the A component, the B component, and the C component, various conventionally known methods can be used. For example, the A component, the B component, and the C component can be mixed with a tumbler, a V-type blender, a super mixer, a nauta mixer, a Banbury mixer, a kneading roll, a monoaxial or biaxial extruder, and the like.

The composition thus obtained can be melt-mixed and transferred to the spinning device as it is or via a metering pump. The temperature for melting and mixing is preferably higher than the melting point of the resulting stereocomplex polylactic acid, and preferably higher than 220 ° C. Further, it may be once pelletized and then supplied to the spinning device. The pellet length is preferably 1 to 7 mm, the major axis is 3 to 5 mm, and the minor axis is 1 to 4 mm. The pellet shape is preferably uniform. The pelletized composition can be transferred to a spinning device using a normal melt extruder such as a pressure melter type or a single-screw or twin-screw extruder type. In forming the stereocomplex crystal, it is important to sufficiently mix the A component and the B component, and it is particularly preferable to mix them under shear stress.
The composition may contain a carbodiimide compound. Thermal decomposition and hydrolysis resistance obtained by containing a carbodiimide compound are improved.

  As carbodiimide compounds, dicyclohexylcarbodiimide, diisopropylcarbodiimide, diisobutylcarbodiimide, dioctylcarbodiimide, octyldecylcarbodiimide, di-tert-butylcarbodiimide, dibenzylcarbodiimide, diphenylcarbodiimide, N-octadecyl-N′-phenylcarbodiimide, N-benzyl-N ′ -Phenylcarbodiimide, N-benzyl-N'-tolylcarbodiimide, di-o-toluylcarbodiimide, di-p-toluylcarbodiimide, bis (p-aminophenyl) carbodiimide, bis (p-chlorophenyl) carbodiimide, bis (o-chlorophenyl) ) Carbodiimide, bis (o-ethylphenyl) carbodiimide, bis (p-ethylphenyl) carbodiimi Bis (o-isopropylphenyl) carbodiimide, bis (p-isopropylphenyl) carbodiimide, bis (o-isobutylphenyl) carbodiimide, bis (p-isobutylphenyl) carbodiimide, bis (2,5-dichlorophenyl) carbodiimide, bis (2 , 6-Dimethylphenyl) carbodiimide, bis (2,6-diethylphenyl) carbodiimide, bis (2-ethyl-6-isopropylphenyl) carbodiimide, bis (2-butyl-6-isopropylphenyl) carbodiimide, bis (2,6 -Diisopropylphenyl) carbodiimide, bis (2,6-di-tert-butylphenyl) carbodiimide, bis (2,4,6-trimethylphenyl) carbodiimide, bis (2,4,6-triisopropylphenyl) Carbodiimide, bis (2,4,6-tributylphenyl) carbodiimide, diβ-naphthylcarbodiimide, N-tolyl-N′-cyclohexylcarbodiimide, N-tolyl-N′-phenylcarbodiimide, p-phenylenebis (o-toluylcarbodiimide) , P-phenylenebis (cyclohexylcarbodiimide, p-phenylenebis (p-chlorophenylcarbodiimide), 2,6,2 ′, 6′-tetraisopropyldiphenylcarbodiimide, hexamethylenebis (cyclohexylcarbodiimide), ethylenebis (phenylcarbodiimide), Examples thereof include mono- or polycarbodiimide compounds such as ethylenebis (cyclohexylcarbodiimide).

  Examples of such commercially available polycarbodiimide compounds include Carbodilite LA-1 and HMV-8CA sold under the trade name of Carbodilite sold by Nisshinbo Co., Ltd.

  The composition preferably has a decrease in weight average molecular weight of 20% or less when melted at 260 ° C. When the molecular weight is drastically reduced at high temperatures, spinning is not only difficult, but physical properties of the obtained yarn are lowered, which is not preferable.

  The composition preferably has a moisture content of 100 ppm or less. When the moisture content is high, hydrolysis of the poly L-lactic acid component and the poly D-lactic acid component is promoted, the molecular weight is remarkably lowered, spinning becomes difficult, and physical properties of the obtained yarn are lowered, which is not preferable.

  Further, the amount of residual lactide in the composition is preferably 3,000 ppm or less, more preferably 1,000 ppm or less, and particularly preferably 400 ppm or less. Since lactide in the polylactic acid obtained by the lactide method may vaporize during melt spinning and cause yarn unevenness, it is preferable for the purpose of obtaining a good yarn to suppress the lactide amount to 400 ppm or less.

(Melt spinning)
The composition is melted by an extruder type or pressure melter type melt extruder, weighed by a gear pump, filtered in a pack, and then discharged as monofilaments, multifilaments, etc. from a nozzle provided on the base. And spun. The shape of the base and the number of the bases are not particularly limited, and any of circular, irregular, solid, hollow and the like can be adopted. The discharged yarn is immediately cooled and solidified, then converged, added with oil, and wound. The winding speed at this time is 300 to 1000 m / min, preferably 300 to 800 min. When the winding speed is less than 300 m / min, it is necessary to stretch at a high magnification in order to obtain a sufficient strength. Therefore, an increase in fluff and the occurrence of frequent yarn breaks occur, resulting in stable yarn production. Have difficulty. In the case of a high speed exceeding 1000 m / min, rubbing with a roller or a guide during spinning or a stereo complex is partially formed and single yarn breakage or yarn breakage occurs, which is not preferable.

(Stretching)
Stretching needs to be carried out at 3.5 to 6.0 times. If it is less than 3.5 times, sufficient strength cannot be obtained, and if it exceeds 6.0 times, strength reduction due to whitening due to devitrification, single yarn breakage, and yarn breakage occur. The preheating for stretching can be performed by using a flat plate or pin contact heater, a non-contact hot plate, a heat medium bath, etc. in addition to raising the temperature of the roll. The stretching temperature is preferably 70 to 140 ° C, more preferably 80 to 130 ° C.

(Heat treatment)
The heat treatment step is a step of heat treating the drawn yarn. The heat treatment is performed at 160 to 230 ° C, preferably 170 to 220 ° C, more preferably 180 to 200 ° C. For the heat treatment, it is necessary to use a contact heater such as a hot roller or a plate heater, and the heat treatment may be continuous with or separated from the stretching step. By heat-treating, it is possible to obtain a fiber having a high stereo ratio, excellent heat shrinkage resistance and iron resistance, and a strength of 3.0 cN / dTex or more. Further, if heat treatment is performed at a temperature lower than 150 ° C., a sufficient stereoization ratio cannot be obtained, which may cause problems in heat shrink resistance and iron resistance.

  In the present invention, the spinning and drawing process needs to be separate, and the undrawn yarn obtained at a spinning speed of 300 to 1000 m / min is once wound on a package, drawn 3.5 to 6.0 times, and then contacted. By performing heat setting at 160 to 230 ° C. with a heater, a high-strength stereocomplex polylactic acid fiber excellent in yarn production can be obtained. When directly spinning and drawing without winding, the fiber passing speed in the drawing and heat treatment process is 1000 m / min or more, so the friction with the roller and guide increases, and yarn breakage and fluff are generated. It becomes easy to do. In addition, when the winding speed in stretching exceeds 1000 m / min, the friction increases in the same manner, which is not preferable because the process passability decreases. On the other hand, when it is less than 300 m / min, productivity is lowered, which is not preferable.

  In the present invention, since the drawn yarn does not have a low-temperature crystal melting phase of poly L-lactic acid or poly D-lactic acid, it can be heat-treated at a temperature equal to or higher than the crystal melting point of poly L-lactic acid or poly D-lactic acid. It does not show thermal fusion or breakage of partial melting of a single crystal of poly L-lactic acid or poly D-lactic acid, and can be heat-treated at 170 ° C. or higher, for example, 190 ° C. higher than the melting point of the single crystal. As a result, it is possible to obtain a fiber that exhibits a high stereo ratio and is excellent in strength and heat resistance. Since this fiber is excellent in heat resistance, there are few troubles such as heat fusion during production, and it is excellent in heat shrinkage.

<fiber>
The polylactic acid fiber of this invention consists of a composition containing A component, B component, and C component, and an intensity | strength is 3.0-7.0 cN / dtex. The A component, B component, and C component are as described above.

  The strength of the polylactic acid fiber of the present invention is 3.0 cN / dtex or more, more preferably 3.5 cN / dtex or more. The higher the upper limit, the better. However, the upper limit is actually about 7.0 cN / dtex. When the strength is 7.0 cN / dtex or more, it is necessary to increase the molecular weight of the polymer to be used, which is not preferable because the spinning property is lowered.

  The polylactic acid fiber of the present invention has a heat shrinkage rate at 150 ° C. of preferably 5.0 to 30.0%, more preferably 6.0 to 20.0%, still more preferably 8.0 to 15.0%. It is. If the heat shrinkage rate is large, the textile product shrinks and becomes smaller when it is exposed to high temperatures, such as ironing, and becomes unusable.

  The stereo ratio of the polylactic acid fiber of the present invention is preferably 90 to 100%, more preferably 95 to 100%, and still more preferably 98 to 100%.

  The polylactic acid fiber of the present invention has a substantially single melting peak in differential scanning calorimetry (DSC) measurement, the melting peak temperature is 195 ° C. or higher, and wide-angle X-ray diffraction (XRD) measurement. The stereo ratio due to is 90% or more. The fibers of the present invention have iron resistance at 170 ° C.

<Fiber products>
The polylactic acid fiber of the present invention can also be used as a raw yarn for yarn processing such as false twisting, mechanical crimping, and indentation crimping. Moreover, it can also be set as the spun yarn using a long fiber, a short fiber, and a short fiber. Since the fiber of the present invention has a high stereo ratio and is excellent in strength, heat resistance and low heat shrinkability, it can be made into various garment fiber products such as woven fabrics, knitted fabrics and nonwoven fabrics. That is, the present invention includes a garment fiber product containing the fiber of the present invention.

  Specifically, apparel such as shirts, blousons, pants and coats, apparel materials such as cups and pads, interior uses such as curtains, carpets, mats and furniture, belts, nets, ropes, heavy cloths, bags, felts Further, it can be suitably used for industrial material applications such as filters and vehicle interior applications.

  The fiber of the present invention does not have a single crystal phase of poly L-lactic acid or poly D-lactic acid. Therefore, even if ironing is performed on the fiber product made of the fiber of the present invention, there is no fear that a part of the fiber is softened, melted and contracted. Since the textile product of the present invention does not impair the fabric quality, texture, and dimensions by ironing, it can be expected to be used in industrial applications that are expected to be used at high temperatures.

Hereinafter, the polylactic acid fiber of the present invention will be described by way of examples, but is not limited thereto.
The fiber properties were measured by the following measurement methods.

Strength and elongation:
The measurement was performed using a “Tensilon” tensile tester manufactured by Orientec Co., Ltd. under the conditions of a sample length of 25 cm and a tensile speed of 30 cm / min.

Thermal shrinkage:
Shrinkage at 180 ° C. Measured according to JIS L-1013 8.18.2 a).

Stereo ratio:
An X-ray diffraction pattern was recorded on an imaging plate by the transmission method using a ROTA FLEX RU200B type X-ray diffractometer manufactured by RIKEN. In the obtained X-ray diffraction pattern, a diffraction intensity profile in the equator direction is obtained. Here, the integrated intensity of each diffraction peak derived from the stereocomplex crystal appearing in the vicinity of 2θ = 12.0 °, 20.7 °, and 24.0 °. Was obtained from the total intensity ΣI _SCi and the integrated intensity I _HM of the diffraction peak derived from the homocrystal appearing in the vicinity of 2θ = 16.5 ° in accordance with the following formula. Incidentally, as shown in FIG. 1, ΣI _SCi and I _HM were estimated by subtracting diffuse scattering due to background or amorphous in the diffraction intensity profile in the equator direction.
X-ray source: Cu-Kα ray (confocal mirror)
Output: 45kV x 70mA
Slit: 1mmΦ ~ 0.8mmΦ
Camera length: 120mm
Integration time: 10 minutes Sample: 3cm length, 35mg
Sc conversion rate = ΣI _SCi / (ΣI _SCi + I _HM ) × 100
Here, ΣI _SCi = I _SC1 + I _SC2 + I _SC3
I _SCi (i = 1 to 3) is 2θ = 12.0 °, 20.7 °,
Integrated intensity of each diffraction peak around 24.0 °

Heat-resistant:
A 10 cm square cloth was made from the fibers to be tested and ironed for 30 seconds with an iron adjusted to a surface temperature of 170 ° C., and the heat resistance was judged from changes in the cloth width shape, dimensions, and texture. The determination was made according to the following criteria.
Pass: ○ Keeps the shape, dimensions and texture of the cloth before treatment without fusing single yarn.
FAIL: X Single yarn was fused, heat deformation of the cloth before treatment, or change to a stiff texture.

[Example 1]
Make chips of poly L lactic acid [component A] and poly D milk (component B)
Production Example 1: Production of poly-L-lactic acid 100 parts by weight of L-lactide (manufactured by Musashino Chemical Laboratory Co., Ltd.) having an optical purity of 99.8% was added to the polymerization vessel, and the inside of the system was purged with nitrogen. 2 parts by weight and 0.05 part by weight of tin octylate as a catalyst were added, and polymerization was carried out at 190 ° C. for 2 hours to produce a polymer. This polymer was washed with an acetone solution of 7% 5N hydrochloric acid to remove the catalyst to obtain a polymer A1. The resulting polymer A1 had a reduced viscosity of 2.92 (mL / g) and a weight average molecular weight of 190,000. The melting point (Tm) was 168 ° C. The crystallization point (Tc) was 122 ° C.

Production Example 2: Production of poly-D lactic acid 100 parts by weight of D-lactide (manufactured by Musashino Chemical Laboratory Co., Ltd.) having an optical purity of 99.8% was added to the polymerization vessel, and the inside of the system was purged with nitrogen. 2 parts by weight and 0.05 part by weight of tin octylate as a catalyst were added and polymerized at 190 ° C. for 2 hours to produce a polymer. This polymer was washed with an acetone solution of 7% 5N hydrochloric acid to remove the catalyst to obtain a polymer A2. The obtained polymer A2 had a reduced viscosity of 2.65 (mL / g) and a weight average molecular weight of 200,000. The melting point (Tm) was 176 ° C. The crystallization point (Tc) was 139 ° C.

  Chip blending was performed using the V-type blender at a ratio of the above polymer A / polymer B = 50/50 (weight ratio), and then dried under reduced pressure at 110 ° C. for 5 hours. To 100 parts by weight of this chip, 0.5 parts by weight of 2,2-methylenebis (4,6-di-tert-butylphenol) sodium salt (ADK STAB NA-11) (average particle size 5 μm) is added and a biaxial rudder is attached. The melt was melted at 230 ° C. using a melt spinning machine, and discharged from a die having 48 holes of 0.25Φ at 40 g / min.

After cooling with a spinning cylinder, the fibers were bundled, an oil agent was added, and the undrawn yarn was wound up at the speed shown in Table 1.
This undrawn yarn was preheated at 80 ° C. and heat treated at the draw ratio and temperature shown in Table 1 to obtain 167 dtex / 48 fil fiber.

[Examples 2 to 4, Comparative Examples 1 to 5]
Polylactic acid fibers were produced under the same conditions as in Example 1 except for the conditions shown in Table 1.

  It has low environmental impact, can provide fibers with excellent strength, heat resistance, and low heat shrinkability, and is useful as a fiber for clothing, materials, and vehicles.

Claims (1)

  (a) Poly L-lactic acid (A component) having a weight average molecular weight of 100,000 to 200,000, (b) Poly D-lactic acid (B component) having a weight average molecular weight of 100,000 to 200,000, and (c) A component and B component And a composition containing 0.01 to 5 parts by weight of a phosphoric acid ester metal salt per 100 parts by weight in total, with a strength of 3.0 to 7.0 cN / dTex, an elongation of 20 to 40%, and 180 ° C. In which the unstretched yarn obtained at a spinning speed of 300 to 1000 m / min is once wound around a package, and the winding speed in the stretching step is 300 to 300%. A method for producing a polylactic acid fiber, comprising stretching at a rate of 3.5 to 6.0 times at 1000 m / min and then performing heat setting at 160 to 230 ° C. with a contact heater.