JP2009203576A - Method for producing stereo complex polylactic acid fiber - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a stereo complex polylactic acid fiber, in which both process conditions and physical properties are good in an FOY process including two steps of a spinning process for obtaining an undrawn fiber and a drawing and thermally treating process. <P>SOLUTION: Provided is the method for producing the stereo complex polylactic acid fiber having a melting point of 200 to 230°C and substantially not having an observed melting point at 150 to 190°C, characterized by including (a) a process for melt-spinning a polylactic acid composition comprising poly L-lactic acid (component A) containing L-lactic acid as a main component and having a mass-average mol.wt. of 50,000 to 300,000 and poly D-lactic acid (component B) containing D-lactic acid as a main component and having a mass-average mol.wt. of 50,000 to 300,000, at a spinning speed of 100 to 2,000 m/min, to obtain the undrawn fiber, (b) a process for drawing the undrawn fiber at one step or at two or more steps so that the drawing at the one step is performed to give a drawing ratio of 0.55 to 2.0 times the CDR of the undrawn fiber in a liquid bath of 20 to 150°C, and give a total drawing ratio of 0.55 to 3.0 times the CDR of the undrawn fiber, and (c) a process for applying a constant length thermal treatment at 130 to 200°C or a relation thermal treatment at 130 to 165°C after the drawing process, [wherein, CDR represents a cold draw ratio for visually finishing a necking phenomenon, when the undrawn fiber is pulled in 25°C water]. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a process (spinning / stretching method, separate stretching method) for obtaining FOY (Fully Oriented Yarn) in which a low-oriented unstretched yarn is collected and then stretched by a stretching machine in a separate step. Further, the present invention relates to a method for producing stereocomplex polylactic acid fibers having high productivity by suppressing fluctuations in fineness and physical properties.

  In recent years, with the growing awareness of protecting the global environment, research and development of aliphatic polyesters as biomass plastics has been actively conducted. Among them, poly-L-lactic acid has a melting point as high as about 170 ° C. among aliphatic polyesters, has excellent mechanical properties, and has made great progress in mass production technology of lactic acid or lactide, which is a raw material for polylactic acid. As a result, it has been put to practical use in applications such as films for agriculture and household goods, resin products such as electrical product casings, clothing fabrics, and medical instruments. However, since poly L-lactic acid has a low melting point compared to polyester (mainly polyethylene terephthalate) and aliphatic polyamide (mainly nylon 6, nylon 6,6), which are general-purpose synthetic fibers for clothing and industrial materials, the melting point of poly L-lactic acid. There is a problem in practical heat resistance that ironing, tumbler drying, hot-fired spun yarn, heat setting of woven fabric, thermoforming as a vehicle interior material, etc. cannot be performed. Therefore, it becomes a big obstacle to replace petroleum-derived plastic with biomass plastic.

  Among them, poly-L-lactic acid containing L-lactic acid as a main component (hereinafter abbreviated as PLLA) and poly-D-lactic acid containing D-lactic acid as a main component (hereinafter abbreviated as PDLA) in a solution state or molten state. By kneading at the molecular level, a stereocomplex polylactic acid crystal in which PLLA molecular chains and PDLA molecular chains are alternately packed in the crystal is formed, and the melting point is 220 to 230 ° C., similar to polybutylene terephthalate or nylon 6. (For example, refer nonpatent literature 1), and examination which makes this stereocomplex polylactic acid into a fiber is made | formed. (For example, refer to Patent Documents 1 to 3 and Non-Patent Document 2.)

  For example, a stereocomplex polylactic acid fiber obtained by melt spinning a composition containing equimolar amounts of poly-L-lactic acid and poly-D-lactic acid is disclosed, but the strength of the obtained fiber is about 0.5 cN / dtex and practical. The strength was not sufficient to provide (see, for example, Patent Document 1).

  Moreover, it is described that the stereocomplex polylactic acid fiber was obtained by melt spinning (for example, refer nonpatent literature 2). 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.

  As described above, the conventional stereocomplex formation method involves stretching and heat-treating an amorphous undrawn yarn obtained by spinning a blend of poly-L-lactic acid and poly-D-lactic acid. In order to sufficiently grow the polylactic acid crystal, a method of performing heat treatment at a temperature equal to or higher than the melting point of the poly L-lactic acid single crystal or the poly D-lactic acid single crystal is the mainstream. Certainly, this high-temperature heat treatment is effective for the formation of stereocomplex polylactic acid crystals, but there is a problem that partial melting of the yarn occurs, and the yarn is coarsely cured or reduced in strength.

  In order to solve this problem, a method has been proposed in which a stereo complex is formed at a stretch on a spinning line from a molten mixture of poly L-lactic acid and poly D-lactic acid (see, for example, Patent Document 2). For example, spinning is performed at a spinning speed of 4000 m / min, and a crystallized unstretched yarn having a stereoization rate of 10 to 35% by wide-angle X-ray diffraction measurement is stretched 1.4 to 2.3 times. It has been proposed to improve partial fusion. However, in order to carry out this method, a spinning speed of about 3000 m / min is insufficient, and a special spinning facility for spinning at a spinning speed of 5000 m / min or more is required. There are also problems that must be overcome. The evaluation of heat resistance in this proposal shows a drastic change such as breaking the knitted fabric and rough hardening by applying a 170 ° C iron to the tube of the fiber, and no consideration has been given to the shrinkage of the clothing in the clothing fiber. However, the study on heat resistance is insufficient. Thus, the present condition is that the technique which manufactures the fiber which has a high stereoization rate and was excellent in the intensity | strength and heat-resistant shrinkage from the undrawn yarn whose stereoization rate is 0% is not completed. In addition, based on the knowledge of polyethylene terephthalate, drawn yarn obtained by drawing and heat setting undrawn yarn (POY: Partially Oriented Yarn) obtained by high-speed spinning as described above has a spinning speed of 2000 m / min or less. Compared to FOY (Fully Oriented Yarn) obtained by normal spinning / drawing method in which the obtained undrawn yarn (UDY: Un Drawn Yarn) is drawn and heat set in a separate process, crystals of relatively large size are formed by orientation crystallization. At the same time, since the orientation of the amorphous part is low, in order to obtain a higher-strength stereocomplex polylactic acid fiber, it is necessary to pursue establishment of a technique by a spinning / stretching method for stretching ordinary UDY.

  In Patent Document 3, undrawn yarn melt-spun at a spinning draft ≧ 50 and take-up speed ≧ 300 m / min is wound once and then stretched, or stretched 2.8 times without winding, and 120 to A fiber having heat resistance of 200 ° C. having two peaks of a polylactic acid homocrystal and a stereocomplex polylactic acid crystal of 190 ° C. or higher by heat treatment at 180 ° C. has been proposed (for example, see Patent Document 3). However, when such a fiber is subjected to processing such as ironing at 180 to 200 ° C., tumbler drying, thermoforming, etc., it causes heat shrinkage and wrinkles accompanying melting of polylactic acid homocrystal, and has practical heat resistance. I could not say. Further, according to the study by the present inventors, the amorphous undrawn yarn of stereocomplex polylactic acid tends to be firm and brittle, and it is difficult to cause neck deformation in the air or in a dry heat atmosphere. For this reason, stretching under dry heat by a contact heater or heating roller used in the separate drawing process of long fibers is very poor in stretchability, and the take-up roller and the yarn guide due to breakage of the stretched single yarn may cause wrinkling. There was a problem that bobbins could not be wound up to the yarn length (the complete winding rate was poor). In order to cover the stretchability, there is a method in which the stretch ratio is divided into a plurality of stages up to a predetermined stretch ratio and stretched little by little. However, there is a drawback that the tension of the neck deformation tends to vary, and the single yarn's strength and diameter are not uniform. It was.

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

  The present invention has been made against the background of the above-described prior art, and the purpose of the present invention is to provide a stereo with excellent process tone and physical properties in the FOY process, which is a two-step process of spinning to obtain an undrawn yarn and a drawing / heat treatment process. It is providing the method of manufacturing a complex polylactic acid fiber.

  As a result of intensive studies to solve the above-mentioned problems, the present inventor, after stretching the first stage stretching in the stretching step in a liquid bath at 20 to 150 ° C., in a dry heat atmosphere or a dry heat heating body It is possible to stabilize both the process tone and quality of the stereocomplex polylactic acid fiber by adopting another drawing method characterized by performing constant length heat treatment at 130 to 200 ° C. or relaxation heat treatment at 130 to 165 ° C. The headline, the present invention has been reached.

That is, the present invention relates to (a) a poly L-lactic acid (component A) having a weight average molecular weight of 50,000 to 300,000 having L lactic acid as a main component and a poly L having a weight average molecular weight of 50,000 to 300,000 having D lactic acid as a main component. A step of obtaining an unstretched yarn by melt-spinning a polylactic acid composition of D-lactic acid (component B) at a spinning speed of 100 to 2000 m / min, (a) the unstretched yarn is stretched in one stage or in multiple stages of two or more stages In stretching, the first stage of stretching is performed in a liquid bath at 20 to 150 ° C. so as to be 0.55 to 2.0 times the CDR of the undrawn yarn, and the total draw ratio is the undrawn yarn. A step of stretching so as to be 0.55 to 3.0 times the CDR of (c), and (c) including a step of performing a constant-length heat treatment at 130 to 200 ° C. or a relaxation heat treatment at 130 to 165 ° C. after the step of stretching. The characteristic melting point is in the range of 200-230 ° C and substantially in the range of 150-190 ° C. A method for producing a stereocomplex polylactic acid fiber that point is not observed, it is possible to solve the above problems by the invention.
[However, CDR represents the draw ratio at which the visual necking phenomenon ends when the undrawn yarn is pulled in water at 25 ° C.] ]

  The production method of the stereocomplex polylactic acid fiber of the present invention increases the plasticity of the undrawn yarn by drawing in a liquid bath and improves the drawability. It is possible to suppress the occurrence of spots, strong elongation spots, etc., and to minimize fluctuations in both quality and process condition as compared with conventional examination techniques. Therefore, not only long fibers of another drawing method, but basically high speed spinning exceeding a spinning speed of 2000 m / min can not be adopted, and it can be applied to the process of short fibers that have secured productivity improvement by another drawing method, This enables mass production of stereocomplex short fibers.

Hereinafter, embodiments of the present invention will be described in detail.
(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%, and still more preferably 98 to 100 mol% of L-lactic acid units. Other repeating units include D-lactic acid units and copolymer units other than lactic acid. The D-lactic acid unit and the copolymer unit other than lactic acid are preferably 0 to 10 mol%, more preferably 0 to 5 mol%, still more preferably 0 to 2 mol%.

  Copolymerized units include ε-caprolactone, δ-valerolactone, γ-valerolactone, β-valerolactone, γ-butyrolactone, β-butyrolactone, β-propiolactone, glycolic acid and other hydroxycarboxylic acids (cyclic esters). Aliphatic glycols having 2 to 30 carbon atoms such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, and succinic acid One or more monomers selected from aliphatic dicarboxylic acids having 2 to 30 carbon atoms such as maleic acid and adipic acid, aromatic diols such as terephthalic acid, isophthalic acid, hydroxybenzoic acid and hydroquinone, and aromatic dicarboxylic acids Unit.

  The poly L-lactic acid preferably has crystallinity. The melting point is preferably 150 to 190 ° C, more preferably 160 to 190 ° C. Furthermore, the poly L-lactic acid has a weight average molecular weight of preferably 50,000 to 300,000, more preferably 140,000 to 250,000. This is because, if these conditions are satisfied, a stereocomplex polylactic acid crystal having a high melting point can be formed and the crystallinity can be increased.

(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%, still more preferably 98 to 100 mol% of D-lactic acid units. Other repeating units include L-lactic acid units and copolymerized units other than lactic acid. The L-lactic acid unit and the copolymer unit other than lactic acid are preferably 0 to 10 mol%, more preferably 0 to 5 mol%, and still more preferably 0 to 2 mol%.

  Copolymerized units include ε-caprolactone, δ-valerolactone, γ-valerolactone, β-valerolactone, γ-butyrolactone, β-butyrolactone, β-propiolactone, glycolic acid and other hydroxycarboxylic acids (cyclic esters). Aliphatic glycols having 2 to 30 carbon atoms such as ethylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, and succinic acid One or more monomers selected from aliphatic dicarboxylic acids having 2 to 30 carbon atoms such as maleic acid and adipic acid, aromatic diols such as terephthalic acid, isophthalic acid, hydroxybenzoic acid and hydroquinone, and aromatic dicarboxylic acids Unit.

  The poly D-lactic acid preferably has crystallinity. The melting point is preferably 150 to 190 ° C, more preferably 160 to 190 ° C. Furthermore, the poly D-lactic acid has a weight average molecular weight of preferably 50,000 to 300,000, more preferably 140,000 to 250,000. This is because, if these conditions are satisfied, a stereocomplex polylactic acid crystal having a high melting point can be formed and the crystallinity can be increased.

(Method for producing poly L-lactic acid or poly D-lactic acid)
Poly-L-lactic acid or poly-D-lactic acid is produced by directly dehydrating condensation of L-lactic acid or D-lactic acid, or once L-lactic acid or D-lactic acid is dehydrated and cyclized with L-lactide or D-lactide. And then ring-opening polymerization. Catalysts used in these methods include divalent tin compounds such as tin octylate, tin chloride or tin dialkoxide, tetravalent tin compounds such as tin oxide, dibutyltin oxide or diethyltin oxide, metal tin, zinc compounds, aluminum A compound, a calcium compound, a lanthanide compound, etc. can be illustrated.

  For poly L-lactic acid and / or poly D-lactic acid, it is preferable that the polymerization catalyst used in the polymerization is removed by washing 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 with a metal polymerization catalyst, a phosphorus oxoacid, a phosphorus oxoacid ester, and an organic phosphorus oxo represented by the following general formula (2) The at least 1 sort (s) selected from an acid compound group is mentioned. 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 (2)
[Wherein, 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 a methyl group, an ethyl group, a propyl group, a butyl group, a hexyl group, and a phenyl group. Examples of the substituent include a halogen atom group, a hydroxy group, an amino group, a carboxyl group, a carboxyl metal base, a sulfonic acid group, and a sulfonic acid metal base.

More specific examples of such deactivators include, for example, organic ligands consisting of a group of chelate ligands having an imino group and capable of coordinating to a polymerized metal catalyst, dihydridooxoline (I) acid, dihydride Tetraoxodiphosphoric acid (II, II), hydridotrioxophosphoric acid (III), dihydridopentaoxodiphosphoric acid (III), hydridopentaoxodiphosphoric acid (II, IV), dodecaoxo hexaphosphorus (III) III, hydride Octaoxotriphosphoric acid (III, IV, IV), octaoxotriphosphoric acid (IV, III, IV), hydridohexaoxodiphosphoric acid (III, V), hexaoxodiphosphoric acid (IV), decaoxotetraphosphoric acid (IV ) Low oxidation number phosphoric acid having an acid number of 5 or less, such as acid, hendecaoxotetralinic (IV) acid, eneoxotriphosphoric acid (V, IV, IV) acid, formula x Is represented by _{2 O · yP 2 O 5,} x / y = 3 of orthophosphoric acid, 2> a x / y> 1, diphosphate than the degree of condensation, triphosphate, tetraphosphate, and the like phosphorus pentachloride acid Polyphosphoric acid and mixtures thereof, metaphosphoric acid represented by x / y = 1, especially trimetaphosphoric acid, tetrametaphosphoric acid, 1> x / y> 0, and part of the phosphorus pentoxide structure Ultraphosphoric acid having such a network structure (sometimes collectively referred to as metaphosphoric acid compounds), acid salts of these acids, monovalent and polyhydric alcohols, or polyalkylene glycols. Examples include partial esters, fully ethers, phosphono-substituted lower aliphatic carboxylic acid derivatives, and the like.

From the viewpoint of catalyst deactivation ability, it is represented by the formula xH ₂ O · yP ₂ O ₅ , x / y = 3 orthophosphoric acid, 2> x / y> 1, and diphosphoric acid and triphosphoric acid from the degree of condensation , Tetraphosphoric acid, polyphosphoric acid called pentaphosphoric acid and mixtures thereof, metaphosphoric acid represented by x / y = 1, especially trimetaphosphoric acid, tetrametaphosphoric acid, 1> x / y> 0 , Ultraphosphoric acid having a network structure in which part of the phosphorus pentoxide structure is left (sometimes collectively referred to as a metaphosphoric acid compound), and acid salts of these acids, monovalent, polyvalent Alcohols, partial esters of polyalkylene glycols, phosphorus oxoacids or acidic esters thereof, phosphono-substituted lower aliphatic carboxylic acid derivatives and the above-mentioned metaphosphoric acid compounds are preferably used.

  The metaphosphoric acid compound used in the present invention is a cyclic metaphosphoric acid in which about 3 to 200 phosphoric acid units are condensed, an ultra-regional metaphosphoric acid having a three-dimensional network structure, or their (alkal metal salt, alkaline earth metal salt, Onium salts).

  Of these, cyclic sodium metaphosphate, ultra-region sodium metaphosphate, phosphono-substituted lower aliphatic carboxylic acid derivative dihexylphosphonoethyl acetate (hereinafter sometimes abbreviated as DHPA) and the like are preferably used.

  The metal ion content in poly L-lactic acid and / or 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)
When poly L-lactic acid and poly D-lactic acid are mixed and crystallized in a solution or in a molten state, only stereocomplex polylactic acid crystals are formed. However, if a sufficient mixed state at the molecular level cannot be achieved, Precursors that can form single crystals of L-lactic acid or single crystals of poly-D-lactic acid may remain. Due to the difference in melt viscosity from the stereocomplex polylactic acid crystal precursor, fineness spots and ejection during melt spinning May cause defects. Accordingly, in order to further stabilize the formation of the stereocomplex, it is more preferable to add a phosphate metal salt (component C) represented by the structural formula of the following general formula (1). The phosphoric acid ester metal salt may be used alone or in combination.

In the general formula (1), R ₁ 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 R ₁ include methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, iso-butyl group, sec-butyl group, and tert-butyl. Examples are groups.

R ₂ and R ₃ 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, iso-butyl group, sec-butyl group, tert-butyl group, and n-amyl. Group, iso-amyl group, sec-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, sec -Nonyl group, decyl group, iso-decyl group, tert-decyl group, undecyl group, dodecyl group, tert-dodecyl group, etc. are mentioned.

M ₁ represents an alkali metal atom such as Li, Na, K, or Rb, an alkaline earth metal atom such as Mg, Ca, or Sr, a zinc atom, or an aluminum atom. p represents 1 or 2. When M ₁ is an alkali metal atom, an alkaline earth metal atom or a zinc atom, q represents 0, and when M ₁ is an aluminum atom, q represents 1 or 2.

Preferable examples of the phosphoric acid ester metal salt represented by the general formula (1) include compounds in which R ₁ is a hydrogen atom, and R ₂ and R ₃ are both tert-butyl groups. As such a phosphoric acid ester metal salt, trade names manufactured by Asahi Denka Co., Ltd., ADK STAB NA-10, NA-11, NA-21, NA-30, NA-35 and the like can be mentioned. The phosphoric acid ester metal salt can be synthesized by a known method.

  The average particle size of the phosphoric acid ester metal salt is preferably 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.

(Polylactic acid composition comprising poly-L-lactic acid and poly-D-lactic acid)
The ratio of poly L-lactic acid (A component) and poly D-lactic acid (B component) constituting the polylactic acid composition in the present invention is A component / B component (mass), preferably 40 / 60-60 / 40, more preferably 45/55 to 55/45, still more preferably 50/50. If it deviates from this range, a poly L-lactic acid single crystal or a poly D-lactic acid single crystal is likely to be generated in addition to the stereocomplex polylactic acid crystal, resulting in a decrease in heat resistance.

  The polylactic acid composition may further contain a phosphate metal salt (component C). The preferable content of the phosphoric acid ester metal salt (component C) is 0.05 to 5 per 100 parts by mass (polylactic acid composition) of poly L-lactic acid (component A) and poly D-lactic acid (component B). 0.0 parts by mass, preferably 0.05-4.0 parts by mass, more preferably 0.1-3.0 parts by mass. If the amount is less than 0.05 parts by mass, crystals of poly L-lactic acid alone or crystals of poly D-lactic acid alone may exist depending on the kneading state of poly L-lactic acid and poly D-lactic acid. Stability may deteriorate. On the other hand, if it is used in an amount larger than 5.0 parts by mass, it may cause thermal decomposition or fiber breakage during fiber formation, which is not preferable.

  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 uniaxial or biaxial melt extruder, or the like. Moreover, in order to supply the agent which consists only of C component, and the pellet containing C component to a fixed quantity, well-known supply apparatuses, such as a screw feeder, a coil feeder, and a vibration type feeder, can be used.

  The polylactic acid composition thus obtained (which may contain a C component as required) can be melt-mixed and transferred to the spinning device as it is or via a metering pump or the like. Further, it may be once pelletized and then supplied to the spinning device. The pellet length in that case 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 polylactic acid composition can also 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 polylactic acid 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 polylactic acid composition preferably has a decrease in mass 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 polylactic acid 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, and not only spinning becomes difficult, but physical properties of the obtained yarn are lowered, which is not preferable. . Further, the amount of residual lactide in the polylactic acid composition is 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.

  In addition to the catalyst, various additives such as matting agents, heat stabilizers, light stabilizers, light stabilizers, neutralizers, nucleating agents, lubricants, thinning agents, as necessary, may be added to the polylactic acid composition described above. Antibacterial agents, flame retardants, antistatic agents, plasticizers, antifoaming agents, color adjusting agents, antioxidants, ultraviolet absorbers, fluorescent whitening agents, dyes and pigments may be added. Poly L-lactic acid and poly D-lactic acid are susceptible to hydrolysis under high temperature and high humidity and in the presence of acid, alkali, etc., so a known hydrolysis inhibitor is added for polyesters such as carbodiimide compounds. Also good.

(Process to obtain undrawn yarn by melt spinning (A))
The polylactic acid composition is melted by an extruder type or pressure melter type melt extruder, then measured by a gear pump, and discharged as a monofilament, a multifilament, or the like from a nozzle provided in the base. The polylactic acid composition may be obtained by melting pellets obtained by previously melt-kneading poly-L-lactic acid, poly-D-lactic acid and, if necessary, a phosphate metal salt with a melt extruder, Supply poly D-lactic acid pellets and phosphate metal salt powder as required, melt, or master chips containing phosphate metal salt in resin in dry blend to melt extruder And may be melted. However, the melting temperature and spinning temperature (transport temperature, spinneret temperature) must be limited to 220 to 260 ° C, preferably 225 to 255 ° C. This is because when it exceeds 260 ° C., poly L-lactic acid and poly D-lactic acid are hydrolyzed and thermally decomposed to generate low molecular weight substances such as lactide. This is because lactic acid crystals begin to form, solidify in the nozzle and the discharged polymer, and the spun single yarn breaks. The shape of the nozzle and the number of nozzles used for spinning are not particularly limited, and any of circular, irregular, solid, hollow and the like can be adopted.

  Thereafter, at a position of 5 to 200 mm below the spinneret, the spinning yarn is blown with air at 10 to 40 ° C. to be cooled and solidified, and then a spinning oil agent is applied for the purpose of reducing friction and converging, and spinning speed. The undrawn yarn is taken up at a speed of 100 to 3000 m / min and wound on a bobbin using a winder, or the undrawn yarn obtained in a container such as a can in a state of a tow of several hundred to several tens of thousands dtex. The spinning speed is not particularly limited, but if it exceeds 3000 m / min, crystals due to orientation crystallization are generated in the undrawn yarn, and the strength after drawing tends to decrease. This is a preferred mode in many cases, and is selected in the range of 100 to 3000 m / min depending on the equipment, the desired fineness, and the high elongation properties. In particular, mass production machines for short fibers often take the process of bundling undrawn yarn tows of tens to thousands of filaments into hundreds to tens of thousands dtex and receiving them in containers such as buckets and cans. In order to store in the container so as not to be entangled, it is preferable to set the spinning speed to 2000 m / min or less with less impact caused by collision with the can or the stored tow.

(Stretching process (b) that performs one-stage stretching or multi-stage stretching of two or more stages)
The unstretched yarn (UDY) is once wound around a bobbin or stored in a container such as a can, and then supplied to a known separate stretcher.
The stretching may be one-stage stretching or multi-stage stretching of two or more stages. However, in the production method of the present invention, the first-stage stretching is carried out in a liquid bath at 20 to 150 ° C. Different from multi-stage drawing at room temperature or dry heat by setting the draw ratio to a relatively high magnification such as double, the draw tension is lowered and the drawing point is fixed at a fixed position, thereby breaking the single yarn in drawing. It is characterized by suppressing stretch spots, fine spots, and strong stretch spots caused by heat, slip, and heat generation.

  Here, CDR is an abbreviation for cold draw ratio, but here, particularly when the undrawn yarn is pulled by hand in water at 25 ° C., when the visual necking phenomenon ends. Represents the draw ratio based on the length of the undrawn yarn. The stereocomplex polylactic acid undrawn yarn obtained at a spinning speed of 100 to 2000 m / min has high yield stress and tends to be brittle, so it breaks in cold drawing performed in normal room temperature air, but it is immersed in water. When cold drawing is performed, a necking phenomenon similar to that of ordinary polyester or the like is confirmed by the plasticizing effect that is presumed to be the permeation and diffusion of water molecules into the undrawn yarn. The first stage of stretching is preferably set to a draw ratio of 0.55 to 2.0 times that of CDR in a liquid bath, but it is important to set the draw ratio so that the drawing roller or drawing pin does not have a drawing point. is there. This is because when the drawing point is applied to the drawing roller or the drawing pin, the undrawn yarn itself is heated by the heat generated by the adiabatic deformation and an undrawn state due to fusion or drawing point variation occurs. As a result, the total draw ratio may be set to 0.55 to 3.0 times the CDR, and may be set according to the targeted high elongation property and heat shrink property. However, even when the first-stage drawing and the total draw ratio are 0.55 to 1.0 times the CDR, the substantial draw ratio, that is, the length of the drawn yarn relative to the length of the undrawn yarn is 1. Excludes less than 0 times. The purpose is to exclude the case where the undrawn yarn is not substantially drawn after passing through the step. It is preferable to carry out the second and subsequent stretching in a liquid bath. If the first stage draw ratio is 2.0 times the CDR or the total draw ratio exceeds 3.0 times the CDR, the polylactic acid composition exceeds the possible draw ratio, and single yarn breakage occurs during drawing. On the other hand, if the draw ratio of the first stage or the total draw ratio is less than 0.55 times the CDR, the stretching points will vary, resulting in partial unstretched parts, strong elongation, heat shrinkage, and fineness. Non-uniformity occurs, or single yarn breakage occurs during stretching, causing problems such as wrinkling on a roller and fusion of a yarn end. Preferably, the first-stage stretching is set to 0.6 to 2.0 times the CDR, and the total stretching ratio is set to 0.6 to 3.0 times the CDR.

  The stretching is preferably performed in a liquid bath at 20 to 150 ° C. Unstretched yarn with stereocomplex polylactic acid crystal forming ability, which is considered to have a dense packing state of amorphous part molecular chains due to poor heat exchange efficiency when stretched in air or in a dry heat atmosphere. It is not possible to make the temperature short enough to deform the neck. If the stretching temperature is less than 20 ° C., the mobility of amorphous molecules is poor and the target stretchability of the present invention cannot be obtained. Further, when the temperature exceeds 150 ° C., poly L-lactic acid single crystals and poly D-lactic acid single crystals partially generated by stretching (each melting point is about 170 ° C.) exist. Can be seen. Preferably it is the range of 40-130 degreeC.

  The medium used for the liquid bath is water, silicone oil, organic solvents such as ethylene glycol and acetone, inorganic salt solutions such as potassium chloride aqueous solution, supercritical carbon dioxide, etc. In view of safety, etc., water is most preferable. For the water bath drawing, a hot water bath or the like known as mass production equipment for polyester short fibers can be used. The stretching temperature in the case of a water bath is preferably 20 to 100 ° C.

(Process to perform constant length heat treatment or relaxation heat treatment (c))
The drawn yarn (DY) is subjected to tension heat treatment or relaxation heat shrinkage to transfer the drawn poly L-lactic acid single crystal precursor or poly D-lactic acid single crystal precursor to a stereocomplex polylactic acid crystal, and an amorphous part It is possible to reduce the thermal shrinkage by promoting the crystallization of the material or removing the distortion of the amorphous part. The tension heat treatment is preferably performed at 130 to 200 ° C, preferably 140 to 190 ° C. When the tension heat treatment temperature is less than 130 ° C., the transition from the poly L-lactic acid or poly D-lactic acid single crystal produced during stretching to the stereocomplex polylactic acid crystal does not proceed. When the tension heat treatment temperature exceeds 200 ° C., melting of the stereocomplex polylactic acid crystal starts, and heat shrinkage and fiber hardening start. On the other hand, the relaxation heat treatment is preferably performed at 130 to 165 ° C, preferably 140 to 160 ° C. When the relaxation heat treatment temperature is less than 130 ° C., the transition from the poly L-lactic acid or poly D-lactic acid single crystal produced during stretching to the stereocomplex polylactic acid crystal does not proceed. When the relaxation heat treatment temperature exceeds 165 ° C., melting of the poly L-lactic acid single crystal or poly D-lactic acid single crystal generated by stretching starts, and heat shrinkage and fiber hardening start.

  The heat treatment may be either a constant-length heat treatment performed in a tensioned state or a relaxation heat treatment performed in a state where no tension is applied, but it is important that the heat treatment be performed in a dry heat state rather than a moist heat state moistened with moisture or an organic solvent. When heat treatment is carried out in a wet heat state, the amorphous part of poly-L-lactic acid or poly-D-lactic acid becomes susceptible to hydrolysis (or solvolysis, etc.) by water molecules or hydroxyl group-containing compounds and alkalis, resulting in high elongation properties It is because toughness falls.

  The constant-length heat treatment can be performed by contacting the heated yarn with a heated medium or an electric heater with a constant tension applied to the drawn yarn, contact with a roller or contact heater, and superheated high-temperature steam ( There is a non-contact heating method using radiant heat such as a steam or hot air circulation chamber or an infrared heater. In the constant length heat treatment, the draft is basically 1.0 times. However, the draft of 0.85 to 1.15 times can be taken in accordance with the shrinkage and elongation change of the fiber accompanying the heat treatment. In addition, in order to remove the water after the liquid bath stretching, it is preferable that a process such as constriction by a roller, low temperature drying by a dry heat roller, blowing warm air or dehumidified air, high pressure air, etc. is additionally provided before the heat treatment.

On the other hand, the relaxation heat treatment includes a method in which the drawn yarn is passed through a hot air circulation chamber, a suction drum through which hot air passes, a heating roller or a contact heater in an overfeed state without tension.
As described above, the heating method for the drawn yarn in the constant length heat treatment or the relaxation heat treatment is preferably performed in a dry heat atmosphere or by contact with a dry heat heater.

  A combination of both constant length heat treatment and relaxation heat treatment is more preferable because a fiber having high strength and low heat shrinkage can be obtained. In that case, since the stereocomplex polylactic acid crystal in the state in which the constant length heat treatment is oriented in the fiber axis direction can be obtained, the constant length heat treatment is set to 130 to 200 ° C., and the relaxation heat treatment is between 40 to 160 ° C. It is preferable to set by. When the relaxation heat treatment temperature is lowered, fibers having higher strength and higher crimpability can be obtained, but heat shrinkage is somewhat high, so that the relaxation heat treatment is preferably performed at 40 ° C. or higher. If it is intended to obtain a fiber having a relatively low strength and a high degree of elongation and a low heat shrinkage rate, the relaxation heat treatment temperature is preferably 160 ° C., but can be increased to 200 ° C.

In the stereocomplex polylactic acid fiber of the present invention, by performing such spinning, stretching, and heat treatment, poly L-lactic acid simple crystals, poly D-lactic acid simple crystals to polycomplexes having progressed from stereocomplex polylactic acid crystals. Lactic acid fibers can be obtained. And the melting | fusing point can be 200-230 degreeC. As explained in the background art section, in poly L-lactic acid, the melting point is 150 to 190 ° C., more strictly, about 170 ° C.,
In the stereocomplex polylactic acid fiber obtained by the method for producing stereocomplex polylactic acid fiber of the present invention, substantially no melting point is observed in the temperature range of 150 to 190 ° C. “Substantially not observed” means that 10 mg of a sample is heated from room temperature to 260 ° C. at a heating rate of 10 ° C./min in a nitrogen atmosphere using a differential scanning calorimeter (DSC) as described later. Represents that no endothermic peak based on crystal melting is observed.

  Therefore, the stereocomplex polylactic acid fiber obtained by the production method of the present invention cannot be ironed at a temperature of 180 ° C. or higher, as was the case with fabrics woven using conventional polylactic acid fiber. No practical problems such as this will occur.

  The fiber production method of the present invention can also be applied to FOY long fibers in which undrawn yarn is drawn in a separate process from spinning, but most mass production machines have separate processes for melt spinning and stretching / heat treatment, and 3000 m / It is particularly suitable for a method for producing short fibers in which high-speed spinning for more than 5 minutes is difficult. When producing short fibers, in addition to the method of drawing with long fibers, a step of cutting with a rotary cutter or the like into a predetermined fiber length according to the application, and if further crimping is required, constant length heat treatment and A step of imparting crimp with an indentation crimper or the like is added during the relaxation heat treatment. In that case, in order to improve crimp imparting property, it can be preheated before the crimper with steam, an electric heater or the like.

Hereinafter, the present invention will be described more specifically by way of examples. However, the present invention is not limited to the examples.
In addition, each item in an Example was measured with the following method.

(1) Reduced viscosity:
0.12 g of a polymer sample was dissolved in 10 mL of tetrachloroethane / phenol (volume ratio 1/1), and the reduced viscosity (mL / g) at 35 ° C. was measured.

(2) Mass average molecular weight (Mw):
The mass average molecular weight of the polymer was determined by GPC (column temperature 40 ° C., chloroform) in comparison with a polystyrene standard sample.

(3) Stereo ratio (Sc ratio)
An X-ray diffraction pattern was recorded on an imaging plate under the following conditions by a 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, and here, each diffraction peak derived from the stereocomplex polylactic acid crystal appearing in the vicinity of 2θ = 12.0 °, 20.7 °, and 24.0 °. From the integrated intensity total ΣI _SCi and the integrated intensity I _{HM of} diffraction peaks derived from homopolylactic acid crystals appearing in the vicinity of 2θ = 16.5 °, the stereoization rate (Sc conversion rate) was determined according to 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. In the present invention, it was evaluated that a stereocomplex polylactic acid fiber was obtained when the Sc conversion rate of the drawn yarn (DY) obtained after drawing was 92% or more.
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 the integrated intensity of each diffraction peak around 2θ = 12.0 °, 20.7 °, and 24.0 °, respectively.
I _HM represents the integrated intensity of the diffraction peak around 2θ = 16.5 °, respectively.

(4) Melting point, crystallization point A TA-2920 differential scanning calorimeter DSC manufactured by TA Instruments was used.
In the measurement, 10 mg of a sample was heated from room temperature to 260 ° C. at a heating rate of 10 ° C./min in a nitrogen atmosphere, and the peak temperatures of the crystal melting endothermic peak and the crystallization exothermic peak were defined as the melting point and the crystallization point, respectively.

(5) Single yarn fineness Measured by the method described in JIS L 1015: 2005 8.5.1 Method A.

(6) Dry strength and dry elongation Measured by the method described in JIS L 1015: 2005 8.7.1 method.

(7) Fiber length Measured by the method described in JIS L 1015: 2005 8.4.1 Method C.

(8) Number of crimps Measured by the method described in JIS L 1015: 2005 8.12.

(9) Oil agent adhesion rate In the JIS L 1015: 2005 8.22 c) method, the sample amount is 9 g, the extraction solvent is methanol (25 ° C.), and the oil extraction is performed by leaving it at 25 ° C. for 30 minutes. The measurement was performed in the same manner except that.

(10) 150 degreeC dry heat shrinkage rate It measured at 150 degreeC by the method as described in JISL1015: 2005 8.15 b) method.

(11) CDR
The undrawn yarn was immersed in water at 25 ° C., the undrawn yarn was chucked at an interval of 10 cm, pulled on both sides, the chuck interval (Lcm) at the point where necking was completed was measured, and the following formula was calculated.
CDR = (L−10) / 10

(12) Single yarn wrinkle on a drawing roller When the drawing was performed for 10 minutes by another drawing method drawing machine for producing short fibers, the number of times of winding around the roller from drawing to tension heat treatment was recorded. When the single yarn wrinkle was visually confirmed, the single yarn wound around the roller was removed with a brass wire brush while the drawing machine was operated, so that the wrinkle could be confirmed again.

(13) Phosphate metal salt content The content of the phosphoric acid ester metal salt was obtained by heating and melting a polylactic acid chip or a polylactic acid fiber sample on a steel plate, and then preparing a test molded body having a flat surface with a compression press. Using this test molded body, phosphorus element and metal element contents were determined using a fluorescent X-ray apparatus (type 3270E manufactured by Rigaku Corporation).
Separately, a polylactic acid chip or a polylactic acid fiber sample was dissolved in a soluble solvent and reprecipitated with methanol. The phosphate ester metal salt component was extracted from the components other than the obtained polylactic acid. The obtained extract component was dissolved in a deuterated trifluoroacetic acid / deuterated chloroform = 1/1 mixed solvent, and then subjected to nuclear magnetic resonance spectrum using JEOL A-600 superconducting FT-NMR manufactured by JEOL Ltd. ( < ¹ > H-NMR) was measured. The chemical structure of the phosphate metal salt contained was identified from the spectral pattern. These results were comprehensively evaluated to calculate the phosphate metal salt content.

(Production Example 1: Production of poly L-lactic acid A1)
After adding 100% by mass of L-lactide having an optical purity of 99.8% (Musashino Chemical Laboratory Co., Ltd.) to the polymerization vessel and replacing the inside of the polymerization vessel with nitrogen, 0.2% by mass of stearyl alcohol and 0% tin octylate as a catalyst 0.05% by mass was 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, and poly L-lactic acid A1 was obtained. The resulting poly L-lactic acid A1 had a reduced viscosity of 2.92 (mL / g) and a weight average molecular weight of 130,000. The melting point (Tm) was 168 ° C. The crystallization point (Tc) was 122 ° C.

(Production Example 2: Production of poly-D-lactic acid B1)
After adding 100% by mass of D-lactide having an optical purity of 99.8% (Musashino Chemical Laboratory Co., Ltd.) to the polymerization vessel and replacing the inside of the polymerization vessel with nitrogen, 0.2% by mass of stearyl alcohol and 0% tin octylate as a catalyst 0.05% by mass was 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, and poly D-lactic acid B1 was obtained. The resulting poly-D-lactic acid B1 had a reduced viscosity of 2.65 (mL / g) and a weight average molecular weight of 130,000. The melting point (Tm) was 176 ° C. The crystallization point (Tc) was 139 ° C.

[Example 1]
After making chips of poly L-lactic acid A1 and poly D-lactic acid B1, and chip blending using a V-type blender at a ratio of poly L-lactic acid A1 / poly D-lactic acid B1 = 50/50 (mass ratio) Drying was performed for 5 hours by circulating dehumidified air at 110 ° C. To 100% by mass of this chip, 0.5% by mass of 2,2′-methylenebis (4,6-di-tert-butylphenyl) sodium phosphate (average particle size 5 μm) was added, and a twin-screw rudder melt spinning machine was used. It was melted at 230 ° C., and was discharged at 430 g / min from a spinneret having 1008 holes with 0.45Φ discharge holes.
Thereafter, the undrawn yarn was wound up at a speed of 1000 m / min while being cooled and solidified by blowing air at 25 ° C. at a position 35 mm below the spinneret. This undrawn yarn had a Sc conversion rate of 0% and had a single crystal melting peak derived from the stereocomplex at 217 ° C. using a differential scanning calorimeter (DSC). The CDR was 2.4 times.

The unstretched yarn is bundled to form a 480,000 dtex tow, stretched 3.07 times in hot water at 60 ° C. (1.28 times the CDR), and then stretched 1.02 times in hot water at 90 ° C., The total draw ratio was 3.13 times (CDR 1.30 times). Thereafter, six metal rollers heated with 0.6 MPa water vapor were passed, and constant length heat treatment (1.0 times) was performed at a tow temperature of 155 ° C. after passing. After that, an oil agent consisting of stearyl phosphate potassium salt was applied, tow heated to 65 ° C. with water vapor was supplied to the indentation type crimper, 18 crimps / 25 mm crimp was applied, and then in the circulating hot air at 45 ° C. Passing for 50 minutes, relaxation heat treatment was performed. Then, it cut with the rotary cutter and obtained the short fiber of 1.47 dtex and 38 mm. The obtained fiber showed a single melting peak of a stereocomplex polylactic acid crystal composed of poly L-lactic acid and poly D-lactic acid in a differential scanning calorimeter (DSC) measurement, and the melting point was 218 ° C. Further, the Sc conversion rate was 100% in wide-angle X-ray diffraction measurement, the fiber strength was 3.3 cN / dtex, the elongation was 33%, and the 150 ° C. heat shrinkage rate was 7.0%.
At this time, the single yarn wrinkle on the drawing roller was 0 times / 10 minutes. The results are shown in Table 1.

[Example 2]
The same procedure as in Example 1 was performed except that the tension heat treatment temperature was 140 ° C. The results are shown in Table 1.

[Comparative Example 1]
The same procedure as in Example 1 was performed except that the tension heat treatment temperature was 120 ° C. The results are shown in Table 1.

[Example 3]
The same procedure as in Example 1 was performed except that the tension heat treatment temperature was 200 ° C. and the relaxation heat treatment temperature was 120 ° C. The results are shown in Table 1.

[Comparative Example 2]
The same procedure as in Example 3 was performed except that the tension heat treatment temperature was 210 ° C. The results are shown in Table 1.

[Example 4]
The same procedure as in Example 1 was performed except that the relaxation heat treatment temperature was 20 ° C. (normal temperature air drying conditions). The results are shown in Table 1.

[Example 5]
This was carried out in the same manner as in Example 1 except that the tension heat treatment was not carried out (bypassed) and the relaxation heat temperature was changed to 155 ° C. The results are shown in Table 2.

[Comparative Example 3]
The same procedure as in Example 5 was performed except that the relaxation heat treatment temperature was 120 ° C. The results are shown in Table 2.

[Comparative Example 4]
The same procedure as in Example 5 was performed except that the relaxation heat treatment temperature was 180 ° C. The results are shown in Table 2.

[Example 6]
The same procedure as in Example 1 was performed except that the total draw ratio was 1.7 times (0.71 times the CDR) compared to the single-stage drawing. The results are shown in Table 2.

[Comparative Example 5]
The same procedure as in Example 1 was performed except that the total stretching ratio was 1.2 times (0.50 times as compared with the CDR). The results are shown in Table 2.

[Example 7]
The spinning speed is 500 m / min (CDR is 3.6 times), the first stage stretching is performed 6.0 times in hot water at 90 ° C. (1.67 times the CDR), and the second stage stretching is 63 times. Implemented except that it was 1.8 times in warm water at 0 ° C, the total draw ratio was 10.8 times (3.00 times that of CDR), the heat treatment temperature was 185 ° C and the relaxation heat treatment temperature was 20 ° C. Performed as in Example 1. The results are shown in Table 2.

[Examples 8 to 10, Comparative Example 6]
The same procedure as in Example 1 was performed except that the type and amount of component C (phosphate metal salt) were changed. The results are shown in Table 3. The drawn yarn obtained in Comparative Example 6 has a Sc conversion rate (DY-Sc conversion rate) of 80% and a melting point peak at 168 ° C in addition to 218 ° C. It was not a stereocomplex polylactic acid fiber that had undergone a transition of.

[Comparative Examples 7-8]
The same procedure as in Example 1 was performed, except that all the drawing media were heated by radiant heat so that the yarn temperature before drawing was 80 ° C. using a non-contact electric heater. The results are shown in Table 3. Comparative Example 7 was subjected to two-stage stretching, and Comparative Example 8 was subjected to four-stage stretching.

  The production method of the stereocomplex polylactic acid fiber of the present invention includes stretching in a liquid bath to increase the plasticity of the unstretched yarn and improve the stretchability. It is possible to suppress the occurrence of spots, strong elongation spots, etc., and to minimize fluctuations in both quality and process condition as compared with conventional examination techniques. Therefore, it is not only possible to adopt high-speed spinning exceeding 2000 m / min, but also to the short fiber process that ensures productivity improvement by the separate-rolling method, as well as long-rolled long-fiber. This enables mass production of stereocomplex short fibers. Furthermore, it can be used as a general-purpose synthetic fiber for clothing and industrial materials, and is very useful.

It is an example of the diffraction intensity profile of the equator direction used for calculation of the stereoification rate (Sc conversion rate) of the fiber obtained in the Example etc.

Claims (4)

(A) Poly L-lactic acid (component A) having a weight average molecular weight of 50,000 to 300,000 having L lactic acid as a main component and poly D-lactic acid having a weight average molecular weight of 50,000 to 300,000 having a main component of D lactic acid (B) (B) In the step of obtaining an unstretched yarn by melt spinning the polylactic acid composition of component) at a spinning speed of 100 to 2000 m / min, (a) In performing the one-stage stretching or the multi-stage stretching of two or more stages of the unstretched yarn, The first stage of drawing is performed in a liquid bath at 20 to 150 ° C. so that the CDR of the undrawn yarn is 0.55 to 2.0 times, and the total draw ratio is 0. 0 of the CDR of the undrawn yarn. A melting point characterized by including a step of performing a constant-length heat treatment at 130 to 200 ° C. or a heat treatment for relaxation at 130 to 165 ° C. after the step of stretching to 55 to 3.0 times, and (c) the step of stretching. 200 to 230 ° C., and substantially no melting point is observed at 150 to 190 ° C. Method for producing a stereo polylactic acid fiber.
[However, CDR represents a draw ratio at which the visual necking phenomenon ends when an undrawn yarn is pulled in water at 25 ° C.] ]   The method for producing a stereocomplex polylactic acid fiber according to claim 1, wherein the first-stage stretching is performed in water at 20 to 100 ° C.   The method for producing a stereocomplex polylactic acid fiber according to any one of claims 1 to 2, wherein a relaxation heat treatment is performed at 40 to 160 ° C after a constant length heat treatment at 130 to 200 ° C. The phosphoric acid ester metal salt (C component) represented by the formula (1) is added in an amount of 0.05 to 5.0 parts by mass per 100 parts by mass of the total of the A component and the B component. The manufacturing method of the stereocomplex polylactic acid fiber of any one of claim | item 1-3.

[Wherein R ₁ represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms, R ₂ and R ₃ each independently represents a hydrogen atom or an alkyl group having 1 to 12 carbon atoms, and M ₁ represents an alkali metal. An atom, an alkaline earth metal atom, a zinc atom or an aluminum atom, p represents 1 or 2, q represents 0 when M ₁ is an alkali metal atom, an alkaline earth metal atom or a zinc atom, and M ₁ represents In the case of an aluminum atom, q represents 1 or 2. ]

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