Modified polylactic acid fiber composition and application thereof

Abstract

The invention discloses a modified polylactic acid fiber composition and application thereof, and the modified polylactic acid fiber composition comprises a biodegradable high polymer material and a compound nucleating agent, wherein the biodegradable high polymer material is prepared from poly (L-lactic acid) (PLLA), polyhydroxyalkanoate (PHA) and a PLLA-PHA block copolymer; the compound nucleating agent comprises a PLA (polylactic acid)-based compound component and a norbornene dicarboxylic acid complex TMX-2, and the mass ratio of the norbornene dicarboxylic acid complex TMX-2 to the PLA-based compound component is (0.02-0.6): 1. The PLLA, the PHA, the PLLA-PHA, the PDLA, the sb-PLA and the TMX-2 are compounded and synergistically influenced, so that three continuous phase network structures are formed in the blended fiber, and the fiber has high strength, high heat resistance and high flexibility.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of polylactic acid fibers, and particularly relates to a modified polylactic acid fiber composition and application thereof. BACKGROUND

[0002] Overexploitation of fossil energy such as coal, oil and natural gas not only causes energy depletion, but also causes great pollution to the environment. Therefore, it has become a mainstream trend in today's society that a completely biodegradable material derived from biomass energy gradually replaces traditional materials. Both polylactic acid and polyhydroxyalkanoate have good biodegradability, biocompatibility and renewability, and are popular green and environmentally friendly materials at present.

[0003] Polylactic acid (PLA) is a new material with good biocompatibility and biodegradability. Its production process is to prepare lactic acid from starch extracted from plant resources as raw material, and then to synthesize polylactic acid by chemical method. Polylactic acid can be completely decomposed into carbon dioxide and water through the decomposition of microorganisms in the composting process, and can be prepared into films, sheets, fibers and the like. With the progress of science and technology, the production process of polylactic acid is continuously improved, and the production cost is continuously reduced. In recent years, polylactic acid materials are widely used in medical, packaging, textile and other fields. However, polylactic acid fibers have problems of poor high temperature resistance, poor flexibility and low strength.

[0004] Polyhydroxyalkanoate (PHAs) is a natural high molecular biological material synthesized by microbial fermentation. Most monomers of this kind of biodegradable plastic are 3-hydroxy fatty acids with a chain length of 3-14 carbon atoms, and the side chain R is a highly variable saturated or unsaturated, straight-chain or branched-chain, aliphatic or aromatic group. Due to the diversity of the side chain structure, this kind of material has more than 100 polymer structures. Polyhydroxyalkanoate is a material that can be completely biodegraded in the marine environment, and has good biocompatibility, thermoplastic processability and biodegradability. However, polyhydroxyalkanoate has the disadvantages of easy degradation, slow crystallization speed, poor mechanical strength and low processing efficiency in the process of thermoplastic processing to prepare various shaped bodies, which seriously limits the popularization and application of polyhydroxyalkanoate materials.

[0005] At present, there are more reports on the preparation of PLA / PHAs fibers. CN118272962A discloses a composition for preparing modified bio-based polymer fibers and a modified bio-based polymer fiber and a preparation method thereof. The composition comprises biodegradable plastic and lithium bis-trifluoromethanesulfonimide, wherein the content of the lithium bis-trifluoromethanesulfonimide is 0.1-5 parts by weight relative to 100 parts by weight of the biodegradable plastic. The modified bio-based polymer fiber has good dyeing properties. CN115305600A discloses a modified polylactic acid fiber and a preparation method thereof. The prepared fiber sample comprises A component and B component: the A component comprises polyhydroxyalkanoate, adipic acid butanediol ester and terephthalic acid butanediol ester copolymer and polybutylene succinate; the B component comprises polylactic acid; and a blended fiber with good dyeing performance is obtained by melt spinning. CN105220264A discloses a modified polylactic acid fiber and a preparation method thereof. The mass percentage composition of the fiber is: polylactic acid 70-98%, resin 1-15% and modifier 1-15%. The breaking strength of the fiber prepared according to the mass percentage is greater than or equal to 1.5 cN / dtex. CN102146597B discloses a degradable fiber containing PHBV and a preparation method thereof. The degradable fiber prepared according to the application is a binary mixture of PHBV and polylactic acid, and the mass fraction is 100 parts of degradable fiber containing 1-89 parts of PHBV and 11-89 parts of binary mixture containing polylactic acid. The mechanical strength of the filament fiber provided by the application can reach 2.0 cN / dtex.

[0006] Obviously, people have realized that it is of great practical significance to develop PLA / PHAs fibers. However, although the fiber samples prepared by the prior art realize the co-use of PLA and PHA materials, the fiber performance is still low, and high-performance PLA / PHAs fiber samples with high strength, high heat resistance and high flexibility cannot be obtained, which seriously limits the practical application of PLA / PHAs fiber materials. SUMMARY

[0007] This section is intended to summarize some aspects of the embodiments of the application and briefly introduce some preferred embodiments. Some simplifications or omissions may be made in this section and the abstract and title of the specification to avoid obscuring the purpose of this section, the abstract and the title, and such simplifications or omissions cannot be used to limit the scope of the application.

[0008] In view of the above and / or problems existing in the prior art, the present application is proposed.

[0009] Therefore, the purpose of the present application is to overcome the deficiencies in the prior art and provide a composition of modified polylactic acid fiber.

[0010] To solve the above technical problems, the application provides the following technical scheme: a modified polylactic acid fiber composition, comprising a biodegradable polymer material and a compounded nucleating agent;

[0011] The biodegradable polymer material comprises poly-L-lactic acid (PLLA), polyhydroxyalkanoate (PHA) and PLLA-PHA block copolymer.

[0012] The compounded nucleating agent comprises a PLA-based compounded component and a norbornene dicarboxylic acid complex TMX-2, wherein the mass ratio of the norbornene dicarboxylic acid complex TMX-2 to the PLA-based compounded component is 0.02-0.6:1.

[0013] As a preferred scheme of the composition, the preparation method of the PLLA-PHA block copolymer comprises the following steps:

[0014] The PLLA and the PHA are dried, and the moisture content of the PLLA is controlled to be below 100 ppm and the moisture content of the PHA is controlled to be below 500 ppm.

[0015] The PLLA, the PHA and sodium caprylate are melt plasticized by a double-screw extruder, and the melt temperature is 160-180 DEG C and the rotation speed of the double-screw extruder is 108-180 rpm.

[0016] The sample strip extruded after melt plasticization of the double-screw extruder is pre-crystallized in a water tank at 50 DEG C for 1-3 min.

[0017] The sample strip after pre-crystallization is dried by blowing off the residual moisture on the surface with an air knife.

[0018] The PLLA-PHA block copolymer is obtained by cutting and collecting the sample strip through a cantilever type pelletizer.

[0019] As a preferred scheme of the composition, the PLA-based compounded component comprises a PDLA and sb-PLA compounded system, wherein the weight ratio of the PDLA to the sb-PLA is 5:1.

[0020] As a preferred scheme of the composition, the preparation method of the sb-PLA comprises drying PLLA and poly-D-lactic acid (PDLA) and controlling the moisture content to be below 100 ppm.

[0021] The PLLA, the PDLA and sodium caprylate are melt plasticized by a double-screw extruder, and the melt temperature is 160-180 DEG C and the rotation speed of the double-screw extruder is 108-180 rpm.

[0022] The sample strip extruded after melt plasticization of the double-screw extruder is pre-crystallized in a water tank at 50 DEG C for 1-3 min.

[0023] After pre-crystallization, the sample is dried by air knife, and then cut by a cantilever granulator to obtain sb-PLA.

[0024] As a preferred scheme of the composition, the weight average molecular weight of the PLLA is 800-250 thousand, and the molar content of the L optical isomer in the PLLA is 88-99%.

[0025] The weight average molecular weight of the PDLA is 180 thousand, and the molar content of the D optical isomer in the PDLA is greater than 99%.

[0026] The weight average molecular weight of the PHA is 1.2-8.1 million.

[0027] As a preferred scheme of the composition, the weight average molecular weight of the PLLA is 800-250 thousand, and the molar content of the L optical isomer in the PLLA is 88-99%.

[0028] As a preferred scheme of the composition, the weight average molecular weight of the PLLA is 800-250 thousand, and the molar content of the L optical isomer in the PLLA is 88-99%.

[0029] As a preferred scheme of the composition, the weight average molecular weight of the PLLA is 800-250 thousand, and the molar content of the L optical isomer in the PLLA is 88-99%.

[0030] As a preferred scheme of the composition, the weight average molecular weight of the PLLA is 800-250 thousand, and the molar content of the L optical isomer in the PLLA is 88-99%.

[0031] The chain extender is 0.1-3 parts by weight.

[0032] The plasticizer is 3-25 parts by weight.

[0033] The anti-hydrolysis agent includes at least one of polycarbodiimide, carbodiimide and oxazoline.

[0034] The chain extender includes chain extender ADR4468.

[0035] The plasticizer includes plasticizer ATBC.

[0036] Another object of the present application is to provide an application of the modified polylactic acid fiber composition in preparing high-strength, high-flexibility and heat-resistant polylactic acid fibers.

[0037] The composition is spun through the spinning nozzle of the melt spinning spinneret.

[0038] The temperature of the melt spinning is 175-235 DEG C, and the spinning speed is 300-3000 m / min.

[0039] As a preferred scheme of the application, the application further comprises drying after the blending, and the moisture of the dried raw material is less than 100 ppm.

[0040] The drying temperature is 95-105 DEG C, and the drying time is 5-10 h.

[0041] The application has the following advantages:

[0042] (1) The application uses sodium octoate to catalyze the preparation of PLLA-PHA block copolymer, which greatly improves the compatibility of PLLA, PHA and PLLA-PHA in the system, and helps to form a double-continuous phase structure of PHA crystal and PLLA crystal.

[0043] (2) The application uses sodium octoate to catalyze the preparation of sb-PLA (PLLA-PDLA block copolymer), which greatly reduces the phase separation between PLLA and PDLA in the melt cooling process in the system, and promotes the formation of a double-continuous phase structure of SC-PLA crystal, PLLA crystal or PDLA crystal.

[0044] (3) In the application, TMX-2 promotes the formation of SC-PLA crystals, and promotes the epitaxial crystallization of PLLA crystals on the surface of SC-PLA crystals, forming a crystal structure similar to a kebab, which greatly improves the fiber strength and heat resistance.

[0045] (4) In the application, PDLA, sb-PLA and TMX-2 synergistically promote crystallization to form a network-like crystal structure.

[0046] (5) The application of PLLA, PHA, PLLA-PHA, PDLA, sb-PLA and TMX-2 is compounded, and the synergistic effect is achieved, so that a three-continuous phase network structure is formed in the blended fiber, and the fiber has high strength, high heat resistance and high flexibility. BRIEF DESCRIPTION OF DRAWINGS

[0047] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings needed to be used in the embodiments will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort. Among them:

[0048] Figure 1 The crystallogram of the complex nucleating agent in the embodiment 3 of the present application.

[0049] Figure 2 The DSC curve of the modified polylactic acid fiber prepared in the embodiment 3 and the comparative example 9 of the present application and the pure polylactic acid fiber. DETAILED DESCRIPTION

[0050] In order to make the above-mentioned objects, features and advantages of the present application more apparent and easy to understand, the specific embodiments of the present application will be described in detail below.

[0051] In the following description, many specific details are set forth in order to provide a thorough understanding of the present application. However, the present application can be practiced in other ways not described herein, and the skilled in the art can make similar generalizations without departing from the scope of the present application, so the present application is not limited to the specific embodiments disclosed below.

[0052] Secondly, the "one embodiment" or "embodiment" referred to herein means that the specific features, structures or characteristics can be included in at least one implementation of the present application. The "in one embodiment" appearing in different places in the specification does not mean the same embodiment, nor is it an independent or selective embodiment excluding other embodiments.

[0053] In the present application, unless otherwise stated, "PLLA" means left-handed polylactic acid; "PDLA" means right-handed polylactic acid; "sb-PLA" means sodium octanoate catalyzed preparation of PLLA-PDLA stereoblock copolymer; "PHA" means polyhydroxyalkanoate; "PLLA-PHA" means ester exchange catalyst preparation of PLLA-PHA block copolymer; "TMX-2" means norbornene dicarboxylic acid complex.

[0054] The experimental materials used in the following examples are commercially available from conventional biochemical reagent companies, unless otherwise specified.

[0055] The present application will be described in detail below through examples. In the following examples and comparative examples:

[0056] (1)Mechanical properties (including tensile strength, elongation at break, modulus) were measured by a universal tensile testing machine (referring to GB / T 14344);

[0057] (2)Boiling water shrinkage was measured by boiling the fiber in a thermostatic water bath (referring to GB / T 6505);

[0058] (3)PLLA, PDLA were purchased from TotalEnergies Corbion, PLLA, PHA, sodium caprylate catalyst, TMX-2 and related additives were all commercially available.

[0059] The first aspect of the present application provides a composition for preparing high-strength, high-flexibility and heat-resistant polylactic acid fiber, which comprises biodegradable plastic and a compounded nucleating agent.

[0060] According to the present application, the biodegradable plastic can be a biodegradable high molecular material commonly used in the art, preferably PLLA, PHA, PLLA-PHA.

[0061] More preferably, the content of the PLLA is 60-94 parts by weight, preferably 67-89 parts by weight, and more preferably 73-80 parts by weight, based on 100 parts by weight of the biodegradable plastic.

[0062] More preferably, the content of the PHA is 5-30 parts by weight, preferably 8-25 parts by weight, and more preferably 15-20 parts by weight, based on 100 parts by weight of the biodegradable plastic.

[0063] More preferably, the content of the PLLA-PHA is 1-10 parts by weight, preferably 3-8 parts by weight, and more preferably 5-7 parts by weight, based on 100 parts by weight of the biodegradable plastic.

[0064] More preferably, the content of the compounded nucleating agent is 3-15 parts by weight, preferably 4-12 parts by weight, and more preferably 5-8 parts by weight, based on 100 parts by weight of the biodegradable plastic.

[0065] According to the present application, the compounded nucleating agent comprises a PLA-based compounded component and TMX-2; the PLA-based compounded component is preferably a PDLA and sb-PLA compounded system; the weight ratio of PDLA and sb-PLA in the PLA-based compounded component is fixed at 5:1, and a better nucleation promoting effect can be obtained at this mass ratio.

[0066] According to the preferred embodiment of the present application, the mass ratio of the TMX-2 to the PLA-based complexing component is (0.02-0.6):1, preferably (0.05-0.4):1, i.e. the mass ratio of the TMX-2 to the PLA-based complexing component is between (0.5:10) and (4:10).

[0067] According to the present application, the weight average molecular weight of the PLLA is 800-2500 thousand, and the molar content of the L optical isomer in the PLLA is 88-99%; the weight average molecular weight of the PDLA is 1800 thousand, and the molar content of the D optical isomer in the PDLA is greater than 99%; the higher molecular weight polylactic acid defined in the present application can further improve the melt strength of the blending system and the mechanical properties of the blending fiber during the preparation of the fiber; the PLLA with higher molar content of the L optical isomer and the PDLA with higher molar content of the D optical isomer defined in the present application can further improve the crystallization ability of the system, and further improve the mechanical properties and heat resistance of the blending fiber; more preferably, the weight average molecular weight of the PLLA is 1000-2300 thousand, the molar content of the L optical isomer in the PLLA is 92-98%, the weight average molecular weight of the PDLA is 1800 thousand, and the molar content of the D optical isomer in the PDLA is greater than 99%, which can better improve the aforementioned effects during the preparation of the fiber.

[0068] According to the present application, the weight average molecular weight of the PHA is 12-81 million, and the high weight average molecular weight PHA defined in the present application can further improve the problem of low melt strength of PHA, and further improve the mechanical strength of the blending fiber. More preferably, the weight average molecular weight of the PHA is 38-78 million, which can further improve the aforementioned effects and further improve the crystallization ability.

[0069] In particular, when the weight average molecular weight and other conditions of the PLLA, PDLA and PHA are not within the range described above, the dripping of the spinneret is obvious and the fiber is frequently broken, and it is difficult to obtain continuous long fibers.

[0070] According to the present application, the preparation method of the sb-PLA comprises: blending and extruding the PLLA and the PDLA through a double screw extruder, and adding sodium caprylate for catalysis during the extrusion process to obtain the sb-PLA.

[0071] Further, the preparation method of the sb-PLA comprises:

[0072] Step one: dry the PLLA and the PDLA, and control the moisture content to be less than 100 ppm;

[0073] Step two: melt plasticize PLLA, PDLA and sodium caprylate through a double screw extruder, the melt temperature is 160-180℃, the rotation speed of the double screw extruder is 108-180rpm;

[0074] Step three: pre-crystallize the sample strip extruded after melt plasticizing through the double screw extruder in a water tank at 50℃ for 1-3min; dry the surface residual moisture of the pre-crystallized sample strip with an air knife; then collect the sample strip by cutting through a cantilever granulator to obtain sb-PLA chips;

[0075] According to the present application, the preparation method of the PLLA-PHA includes: blending and extruding the above PLLA and the above PHA through a double screw extruder, adding sodium caprylate for catalysis in the extrusion process to prepare a PLLA-PHA block copolymer.

[0076] Further, the preparation method of the PLLA-PHA block copolymer includes:

[0077] Step one: dry PLLA and PHA, control the moisture content of PLLA below 100ppm and control the moisture content of PHA below 500ppm;

[0078] Step two: melt plasticize PLLA, PHA and sodium caprylate through a double screw extruder, the melt temperature is 160-180℃, the rotation speed of the double screw extruder is 108-180rpm;

[0079] Step three: pre-crystallize the sample strip extruded after melt plasticizing through the double screw extruder in a water tank at 50℃ for 1-3min; dry the surface residual moisture of the pre-crystallized sample strip with an air knife; then collect the sample strip by cutting through a cantilever granulator to obtain PLLA-PHA chips;

[0080] Select the higher molecular weight PLLA and PDLA defined in the present application, in the process of preparing fibers, select low content PDLA to interact with PLLA to form SC-PLA fibrous crystals, which on the one hand act as fibrous nucleation points to promote PLLA α-type crystallization, and on the other hand cooperate with PLLA α-type crystalline crystals to form a network skeleton; promote the strength, heat resistance and flexibility of the blended fibers to be improved;

[0081] Further, select the PLLA-PHA block copolymer defined in the present application to greatly improve the compatibility of PLLA and PHA in the PLLA, PHA and PLLA-PHA system, which helps to form a bicontinuous phase structure, further promoting the improvement of the strength, heat resistance and flexibility of the blended fibers;

[0082] Further, the sb-PLA defined in the application can greatly weaken the phase separation between PLLA and PDLA in the melt cooling process of the PLLA, PDLA and sb-PLA system, promote the formation of SC-PLA crystal continuous phase structure, form high-density fibrous crystal structure, and further improve the strength, heat resistance and flexibility of the blended fiber.

[0083] According to the application, the weight average molecular weight of the PHA is 380-780 thousand, and the use of the PHA with high weight average molecular weight defined in the application can further improve the problem of low melt strength of the PHA, improve the mechanical strength of the blended fiber, impart higher crystallization ability, and further reduce the modulus and improve the fiber softness.

[0084] According to the application, the content of the norbornene dicarboxylic acid complex is 0.1-2.8 parts by weight, preferably 0.2-2 parts by weight, and more preferably 0.5-1.0 parts by weight, relative to 100 parts by weight of the biodegradable plastic. As an organic nucleating agent, the norbornene dicarboxylic acid complex can form nanofibrous crystals in situ during the melting process, promote the formation of SC-PLA crystals, promote the epitaxial crystallization of PLLA crystals on the surface of SC-PLA crystals, form a crystal structure similar to a kebab, further form a network crystal structure, accelerate the crystallization rate, increase the nucleation density, and promote the grain size refinement, thereby greatly improving the fiber strength, heat resistance and flexibility.

[0085] According to the application, the PLLA, PHA, PLLA-PHA, PDLA, sb-PLA and TMX-2 are compounded and synergistically affected, so that three continuous phase network structures are formed in the blended fiber, and the fiber has high strength, high heat resistance and high flexibility.

[0086] According to the application, one or more of the anti-hydrolysis agent, plasticizer and chain extender can be further included in the composition, so as to further improve the mechanical properties and heat resistance of the high-strength, high-flexibility and heat-resistant polylactic acid fiber prepared from the composition.

[0087] According to the present application, the content of the anti-hydrolysis agent is 0.1-2 parts by weight, preferably 0.3-1.5 parts by weight, relative to 100 parts by weight of the biodegradable plastic. The content of the chain extender is 0.1-3 parts by weight, preferably 0.5-2 parts by weight, relative to 100 parts by weight of the biodegradable plastic. The content of the plasticizer is 3-25 parts by weight, preferably 4-20 parts by weight, relative to 100 parts by weight of the biodegradable plastic. Defining the anti-hydrolysis agent, the chain extender and the plasticizer within the aforementioned ranges can further significantly improve the molecular weight, crystallization ability of the blending system, and the mechanical properties, flexibility and heat resistance of the blended fiber. More preferably, the content of the anti-hydrolysis agent is 0.5-0.9 parts by weight, the content of the chain extender is 0.8-1.2 parts by weight, and the content of the plasticizer is 5-15 parts by weight, relative to 100 parts by weight of the biodegradable plastic, according to which preferred embodiment the aforementioned effects can be further improved. The mechanical properties, flexibility and heat resistance of the high-strength, high-flexibility and heat-resistant polylactic acid fiber prepared by using the composition are better.

[0088] According to the present application, the anti-hydrolysis agent is mainly used to solve the problem of moisture absorption and easy degradation of polylactic acid, and to improve the hydrolysis resistance of the polymer fiber. The anti-hydrolysis agent used in the present application can be the anti-hydrolysis agent commonly used in the art for preparing polymer fibers, but preferably the anti-hydrolysis agent is selected from at least one of polycarbodiimide, carbodiimide and oxazoline. More preferably, the anti-hydrolysis agent is selected from at least one of polycarbodiimide and carbodiimide, wherein the carbodiimide also known as carbodiimide contains N=C=N functional groups. In some embodiments of the present application, the preferred anti-hydrolysis agent is polycarbodiimide.

[0089] According to the present application, the chain extender is mainly used to improve the interfacial compatibility of the polymer fiber, thereby ensuring the preparation of a fiber sample with good performance. Since there is a certain difference in the solubility parameter of polyhydroxyalkanoate and polylactic acid, direct blending of the two components can cause phase separation of the prepared composition or fiber sample, resulting in poor performance of the prepared fiber sample, and even continuous production is not possible. Therefore, a chain extender is usually added during fiber preparation. The chain extender is a low molecular weight multi-functional alcohol or amine compound containing hydroxyl or amino groups. In some embodiments of the present application, the preferred chain extender is ADR4468.

[0090] According to the present application, preferably, the composition further comprises a plasticizer, which is mainly used to reduce the processing temperature, broaden the temperature range, and solve the problem of easy decomposition of PHA under high temperature conditions. In some embodiments of the present application, the preferred plasticizer is ATBC.

[0091] The second aspect of the present application provides a method for preparing high-strength, high-flexibility and heat-resistant polylactic acid fiber, which comprises: melt spinning the composition after blending to prepare high-strength, high-flexibility and heat-resistant polylactic acid fiber.

[0092] According to the method of the present application, the melt spinning further comprises: spinning the composition through the spinning hole of the melt spinning spinneret. Preferably, the spinning hole of the melt spinning spinneret is circular in cross section, wherein the diameter of the circular cross section is not particularly limited and can be selected as needed.

[0093] According to the method of the present application, the conditions of the melt spinning comprise: a spinning temperature of 175-235℃ and a spinning speed of 300-3000m / min; preferably, the spinning temperature is 195-220℃ and the spinning speed is 1500-2500m / min.

[0094] According to the method of the present application, the method further comprises drying before the melt spinning after blending, wherein the moisture of the raw material after drying is maintained below 100ppm.

[0095] According to the preferred embodiment of the present application, the conditions of the drying comprise: a temperature of 95-105℃ and a time of 5-10h.

[0096] According to a particularly preferred embodiment of the present application, the method comprises:

[0097] (1) polylactic acid with a weight average molecular weight of 150-200 thousand, and the molar content of L optical isomer in PLLA is 96-98%, and the molar content of D optical isomer in PDLA is greater than 99%; polyhydroxyalkanoate with a weight average molecular weight of 70-76 thousand; PDLA and sb-PLA are formed into a PLA-based complex component with a weight ratio of 5:1; TMX-2 and the PLA-based complex component are formed into a complex nucleating agent with a weight ratio of 0.05-0.4:1; the anti-hydrolysis agent is polycarbodiimide; the chain extender is ADR4468; and the plasticizer is ATBC.

[0098] (2) PLLA is 73-80 parts by weight, PHA is 15-20 parts by weight, and PLLA-PHA is 5-7 parts by weight; based on 100 parts by weight of PLLA, PHA and PLLA-PHA, the components of the complex nucleating agent, the anti-hydrolysis agent, the chain extender and the plasticizer are mechanically mixed in a ratio of 5-8 parts by weight, 0.5-0.9 parts by weight, 0.8-1.2 parts by weight and 5-15 parts by weight, respectively; the blended material is hot air dried, the drying temperature is 98-100℃, and the drying time is 7-9 hours.

[0099] The preparation methods of PLLA-PHA, sb-PLA and PLA-based complex component used in the following examples are as follows:

[0100] (1) The preparation method of PLLA-PHA: PLLA and PHA are dried, and the moisture content of PLLA after drying is 47 ppm, and the moisture content of PHA is 360 ppm;

[0101] 67 parts of PLLA, 33 parts of PHA, and 0.15 parts of sodium octanoate (relative to 100 parts by weight of PLLA and PHA) are melt plasticized by a twin-screw extruder, and the melting temperature is 180°C, and the rotation speed of the twin-screw extruder is 180 rpm;

[0102] The sample strip extruded after melt plasticization of the twin-screw extruder is pre-crystallized in a water tank at 50°C for 2 min; the surface residual moisture of the pre-crystallized sample strip is blown dry by an air knife; and then the sample strip is collected by a cantilever type pelletizer to obtain PLLA-PHA chips;

[0103] (2) The preparation method of sb-PLA: PLLA and PDLA are dried, and the moisture content of PLLA after drying is 44 ppm, and the moisture content of PDLA is 39 ppm;

[0104] 50 parts of PLLA, 50 parts of PDLA, and 0.1 parts of sodium octanoate (relative to 100 parts by weight of PLLA and PDLA) are melt plasticized by a twin-screw extruder, and the melting temperature is 180°C, and the rotation speed of the twin-screw extruder is 180 rpm;

[0105] The sample strip extruded after melt plasticization of the twin-screw extruder is pre-crystallized in a water tank at 50°C for 2 min; the surface residual moisture of the pre-crystallized sample strip is blown dry by an air knife; and then the sample strip is collected by a cantilever type pelletizer to obtain sb-PLA chips;

[0106] (3) The preparation method of the PLA-based complex component: PDLA and sb-PLA prepared in step 2 are blended at a ratio of 5:1 to obtain a PLA-based complex component.

[0107] The third aspect of the present application provides a high-strength, high-flexibility, heat-resistant polylactic acid fiber prepared by the method.

[0108] According to the present application, the high-strength, high-flexibility, heat-resistant polylactic acid fiber prepared by the method of the present application has a tensile strength of 2.3-4.2 cN / dtex, an elongation at break of 16.7%-43.5%, a modulus of 25.8-51.7 cN / dtex, and a boiling water shrinkage of 3.8%-14.2%.

[0109] Example 1

[0110] (1) Take PLLA with a weight average molecular weight of 150,000, and the molar content of L optical isomer in PLLA is 98%;

[0111] PHA with a weight average molecular weight of 760,000; the PLA-based complex component and TMX-2 are mixed at a weight ratio of 0.4:1 to form a complex nucleating agent;

[0112] (2) 80 parts by weight of PLLA, 15 parts by weight of PHA, and 5 parts by weight of PLLA-PHA;

[0113] The components of the complex nucleating agent, the anti-hydrolysis agent, the chain extender, and the plasticizer are mechanically mixed at a ratio of 8 parts by weight, 0.9 parts by weight, 1.2 parts by weight, and 15 parts by weight, respectively, based on 100 parts by weight of PLLA, PHA, and PLLA-PHA (the anti-hydrolysis agent is polycarbodiimide; the chain extender is ADR4468; and the plasticizer is ATBC, which is the same in the following examples), and the blend is hot air dried at a temperature of 100°C for 9 hours;

[0114] (3) The dried blend is extruded and spun through a conventional melt spinning device, the shape of the spinneret hole is circular, the spinning temperature is 220°C, the spinning speed is 2500 m / min, and the blend long fiber is obtained by winding; finally, the blend long fiber is drawn and heat set, the drawing temperature is 110°C, and the drawing multiple is 2, to obtain the modified polylactic acid fiber.

[0115] The properties of the modified polylactic acid fiber are detected, and the detection results are shown in Table 1.

[0116] Example 2

[0117] (1) PLLA with a weight average molecular weight of 200,000, and the molar content of L optical isomer in PLLA is 96%;

[0118] PHA with a weight average molecular weight of 700,000; the PLA-based complex component and TMX-2 are mixed at a weight ratio of 0.05:1 to form a complex nucleating agent;

[0119] (2) 73 parts by weight of PLLA, 20 parts by weight of PHA, and 7 parts by weight of PLLA-PHA;

[0120] The components of the complex nucleating agent, the anti-hydrolysis agent, the chain extender, and the plasticizer are mechanically mixed at a ratio of 5 parts by weight, 0.5 parts by weight, 0.8 parts by weight, and 5 parts by weight, respectively, based on 100 parts by weight of PLLA, PHA, and PLLA-PHA, and the blend is hot air dried at a temperature of 98°C for 7 hours;

[0121] (3) The blended material after drying is extruded by a traditional melt spinning equipment, the shape of the spinneret hole is circular; the spinning temperature is 195°C, the spinning speed is 1500 m / min, and the blended long fiber is obtained by winding; finally, the blended long fiber is drawn and heat set, the drawing temperature is 110°C, the drawing multiple is 2.5 times, and the modified polylactic acid fiber is obtained.

[0122] The performance of the modified polylactic acid fiber is detected, and the detection results are shown in Table 1.

[0123] Example 3

[0124] (1) PLLA with a weight average molecular weight of 170,000 and a molar content of L optical isomer in PLLA of 97%; and PHA with a weight average molecular weight of 730,000;

[0125] (2) Preparation method of PLLA-PHA: PLLA and PHA are dried, the moisture content of PLLA after drying is 47 ppm, and the moisture content of PHA is 360 ppm;

[0126] 67 parts of PLLA, 33 parts of PHA, and 0.15 parts of sodium octanoate (relative to 100 parts by weight of PLLA and PHA) are melt plasticized by a double screw extruder, the melting temperature is 180°C, and the rotation speed of the double screw extruder is 180 rpm;

[0127] The sample strip extruded after melt plasticization by the double screw extruder is pre-crystallized in a water tank at 50°C for 2 minutes; the surface residual moisture of the pre-crystallized sample strip is blown dry by an air knife; and then the sample strip is collected by a cantilever type pelletizer to obtain PLLA-PHA chips;

[0128] (3) Preparation method of sb-PLA: PLLA and PDLA are dried, the moisture content of PLLA after drying is 44 ppm, and the moisture content of PDLA is 39 ppm;

[0129] 50 parts of PLLA, 50 parts of PDLA, and 0.1 parts of sodium octanoate (relative to 100 parts by weight of PLLA and PDLA) are melt plasticized by a double screw extruder, the melting temperature is 180°C, and the rotation speed of the double screw extruder is 180 rpm;

[0130] The sample strip extruded after melt plasticization by the double screw extruder is pre-crystallized in a water tank at 50°C for 2 minutes; the surface residual moisture of the pre-crystallized sample strip is blown dry by an air knife; and then the sample strip is collected by a cantilever type pelletizer to obtain sb-PLA chips.

[0131] (4) Preparation method of PLA-based complex component: PDLA and sb-PLA are blended at a ratio of 5:1 to obtain a PLA-based complex component;

[0132] The PLA-based complex component and TMX-2 are mixed at a weight ratio of 0.2:1 to form a complex nucleating agent;

[0133] The crystallogram of the complex nucleating agent is shown in Figure 1 It can be seen that PDLA, sb-PLA and TMX-2 synergistically promote crystallization, and the formed crystallogram of the lamb skewer structure is shown in

[0134] (5) 76 parts by weight of PLLA, 18 parts by weight of PHA and 6 parts by weight of PLLA-PHA; based on 100 parts by weight of PLLA, PHA and PLLA-PHA, the components of the complex nucleating agent, the anti-hydrolysis agent, the chain extender and the plasticizer are mechanically mixed at a ratio of 7 parts by weight, 0.7 parts by weight, 0.9 parts by weight and 10 parts by weight respectively, the blend is hot air dried, the drying temperature is 99°C, and the drying time is 8 hours;

[0135] (6) The dried blend is extruded and spun through a traditional melt spinning equipment, the shape of the spinneret hole is circular; the spinning temperature is 210°C, the spinning speed is 2000 m / min, and the blend long fiber is obtained by winding; finally, the blend long fiber is drawn and heat set, the drawing temperature is 110°C, the drawing multiple is 2.2 times, and the modified polylactic acid fiber is obtained. The DSC curve of the modified polylactic acid fiber prepared in Example 3 is shown in Figure 2 .

[0136] The properties of the modified polylactic acid fiber are detected, and the detection results are shown in Table 1.

[0137] Example 4

[0138] (1) 23 million of PLLA with a weight average molecular weight and 99% of L optical isomer molar content in PLLA, 78 million of PHA with a weight average molecular weight, and a complex nucleating agent formed by mixing a PLA-based complex component and TMX-2 at a weight ratio of 0.6:1;

[0139] (2) 89 parts by weight of PLLA, 8 parts by weight of PHA and 3 parts by weight of PLLA-PHA; based on 100 parts by weight of PLLA, PHA and PLLA-PHA, the components of the complex nucleating agent, the anti-hydrolysis agent, the chain extender and the plasticizer are mechanically mixed at a ratio of 4 parts by weight, 0.3 parts by weight, 0.5 parts by weight and 4 parts by weight respectively, the blend is hot air dried, the drying temperature is 105°C, and the drying time is 5 hours;

[0140] (3) The dried blend is extruded and spun through a conventional melt spinning device, the shape of the spinneret hole is circular; the spinning temperature is 235℃, the spinning speed is 3000m / min, and the blend long fiber is obtained by winding; finally, the blend long fiber is drawn and heat set, the drawing temperature is 110℃, the drawing multiple is 1.8 times, and the modified polylactic acid fiber is obtained.

[0141] The properties of the modified polylactic acid fiber are detected, and the detection results are shown in Table 1.

[0142] Example 5

[0143] (1) PLLA with a weight average molecular weight of 100,000 and a molar content of L optical isomer in PLLA of 92%; PHA with a weight average molecular weight of 380,000; the PLA-based complex component and TMX-2 are mixed at a weight ratio of 0.02:1 to form a complex nucleating agent;

[0144] (2) PLLA is 67 parts by weight, PHA is 25 parts by weight, and PLLA-PHA is 8 parts by weight; based on 100 parts by weight of PLLA, PHA and PLLA-PHA, the components of complex nucleating agent, anti-hydrolysis agent, chain extender and plasticizer are mechanically mixed at a ratio of 12 parts by weight, 1.5 parts by weight, 2 parts by weight and 20 parts by weight respectively, and the blend is dried by hot air, the drying temperature is 95℃, and the drying time is 10 hours;

[0145] (3) The dried blend is extruded and spun through a conventional melt spinning device, the shape of the spinneret hole is circular; the spinning temperature is 175℃, the spinning speed is 300m / min, and the blend long fiber is obtained by winding; finally, the blend long fiber is drawn and heat set, the drawing temperature is 110℃, the drawing multiple is 5.5 times, and the modified polylactic acid fiber is obtained.

[0146] The properties of the modified polylactic acid fiber are detected, and the detection results are shown in Table 1.

[0147] Example 6

[0148] (1) PLLA with a weight average molecular weight of 100,000 and a molar content of L optical isomer in PLLA of 92%; PHA with a weight average molecular weight of 380,000; the PLA-based complex component and TMX-2 are mixed at a weight ratio of 0.02:1 to form a complex nucleating agent;

[0149] (2) PLLA is 70 parts by weight, PHA is 22.5 parts by weight, and PLLA-PHA is 7.5 parts by weight; based on 100 parts by weight of PLLA, PHA and PLLA-PHA, the components of the compounded nucleating agent, anti-hydrolysis agent, chain extender and plasticizer are mechanically mixed in a ratio of 10 parts by weight, 1.2 parts by weight, 1.5 parts by weight and 18 parts by weight respectively, and the blend is hot air dried, the drying temperature is 103℃, and the drying time is 6 hours;

[0150] (3) The dried blend is extruded and spun through a traditional melt spinning device, the shape of the spinneret hole is circular; the spinning temperature is 210℃, the spinning speed is 2800m / min, and the blended long fiber is obtained by winding; finally, the blended long fiber is drawn and heat set, the drawing temperature is 110℃, the drawing multiple is 1.9 times, and the modified polylactic acid fiber is obtained.

[0151] The performance of the modified polylactic acid fiber is detected, and the detection results are shown in Table 1.

[0152] Example 7

[0153] (1) PLLA with a weight average molecular weight of 220,000 and a molar content of L optical isomer in PLLA of 85%; PHA with a weight average molecular weight of 530,000; the PLA-based compounded component and TMX-2 form a compounded nucleating agent in a weight ratio of 0.03:1;

[0154] (2) PLLA is 85 parts by weight, PHA is 11 parts by weight, and PLLA-PHA is 4 parts by weight; based on 100 parts by weight of PLLA, PHA and PLLA-PHA, the components of the compounded nucleating agent, anti-hydrolysis agent, chain extender and plasticizer are mechanically mixed in a ratio of 4.5 parts by weight, 0.4 parts by weight, 0.6 parts by weight and 4.7 parts by weight respectively, and the blend is hot air dried, the drying temperature is 97℃, and the drying time is 9 hours;

[0155] (3) The dried blend is extruded and spun through a traditional melt spinning device, the shape of the spinneret hole is circular; the spinning temperature is 185℃, the spinning speed is 1000m / min, and the blended long fiber is obtained by winding; finally, the blended long fiber is drawn and heat set, the drawing temperature is 110℃, the drawing multiple is 4.2 times, and the modified polylactic acid fiber is obtained.

[0156] The performance of the modified polylactic acid fiber is detected, and the detection results are shown in Table 1.

[0157] Example 8

[0158] (1) PLLA with a weight average molecular weight of 250,000 and a molar content of L optical isomer in the PLLA of 98%; PHA with a weight average molecular weight of 120,000; the PLA-based complex component and TMX-2 are mixed at a weight ratio of 0.3:1 to form a complex nucleating agent;

[0159] (2) 94 parts by weight of PLLA, 5 parts by weight of PHA, and 1 part by weight of PLLA-PHA; based on 100 parts by weight of PLLA, PHA, and PLLA-PHA, the components of the complex nucleating agent, the anti-hydrolysis agent, the chain extender, and the plasticizer are mechanically mixed at a ratio of 3 parts by weight, 0.1 part by weight, 0.1 part by weight, and 3 parts by weight, respectively; the blended material is hot air dried, the drying temperature is 95°C, and the drying time is 9 hours;

[0160] (3) The dried blended material is extruded and spun through a traditional melt spinning device, the shape of the spinneret hole is circular; the spinning temperature is 210°C, the spinning speed is 2500 m / min, and the blended long fiber is obtained by winding; finally, the blended long fiber is drawn and heat set, the drawing temperature is 110°C, the drawing multiple is 2 times, and the modified polylactic acid fiber is obtained.

[0161] The properties of the modified polylactic acid fiber are detected, and the detection results are shown in Table 1.

[0162] Example 9

[0163] (1) PLLA with a weight average molecular weight of 80,000 and a molar content of L optical isomer in the PLLA of 99%; PHA with a weight average molecular weight of 810,000; the PLA-based complex component and TMX-2 are mixed at a weight ratio of 0.1:1 to form a complex nucleating agent;

[0164] (2) 60 parts by weight of PLLA, 30 parts by weight of PHA, and 10 parts by weight of PLLA-PHA; based on 100 parts by weight of PLLA, PHA, and PLLA-PHA, the components of the complex nucleating agent, the anti-hydrolysis agent, the chain extender, and the plasticizer are mechanically mixed at a ratio of 15 parts by weight, 2 parts by weight, 3 parts by weight, and 25 parts by weight, respectively; the blended material is hot air dried, the drying temperature is 105°C, and the drying time is 7 hours;

[0165] (3) The dried blended material is extruded and spun through a traditional melt spinning device, the shape of the spinneret hole is circular; the spinning temperature is 195°C, the spinning speed is 1000 m / min, and the blended long fiber is obtained by winding; finally, the blended long fiber is drawn and heat set, the drawing temperature is 110°C, the drawing multiple is 4.2 times, and the modified polylactic acid fiber is obtained.

[0166] The properties of the modified polylactic acid fiber are detected, and the detection results are shown in Table 1.

[0167] Example 10

[0168] (1) PLLA with a weight average molecular weight of 240,000 and a molar content of L optical isomers in the PLLA of 89%; PHA with a weight average molecular weight of 250,000; the PLA-based complex component and TMX-2 are mixed at a weight ratio of 0.04:1 to form a complex nucleating agent;

[0169] (2) 64 parts by weight of PLLA, 27 parts by weight of PHA, and 9 parts by weight of PLLA-PHA; based on 100 parts by weight of PLLA, PHA, and PLLA-PHA, the components of the complex nucleating agent, the anti-hydrolysis agent, the chain extender, and the plasticizer are mechanically mixed at a ratio of 14 parts by weight, 1.8 parts by weight, 2.4 parts by weight, and 23 parts by weight, respectively; the blended material is hot air dried, the drying temperature is 95°C, and the drying time is 5 hours;

[0170] (3) The dried blended material is extruded and spun through a traditional melt spinning device, the shape of the spinneret hole is circular; the spinning temperature is 235°C, the spinning speed is 2000 m / min, and the blended long fiber is obtained by winding; finally, the blended long fiber is drawn and heat set, the drawing temperature is 110°C, the drawing multiple is 2.2 times, and the modified polylactic acid fiber is obtained.

[0171] The performance of the modified polylactic acid fiber is detected, and the detection results are shown in Table 1.

[0172] Example 11

[0173] (1) PLLA with a weight average molecular weight of 90,000 and a molar content of L optical isomers in the PLLA of 97%; PHA with a weight average molecular weight of 800,000; the PLA-based complex component and TMX-2 are mixed at a weight ratio of 0.5:1 to form a complex nucleating agent;

[0174] (2) 92 parts by weight of PLLA, 6 parts by weight of PHA, and 2 parts by weight of PLLA-PHA; based on 100 parts by weight of PLLA, PHA, and PLLA-PHA, the components of the complex nucleating agent, the anti-hydrolysis agent, the chain extender, and the plasticizer are mechanically mixed at a ratio of 3.5 parts by weight, 0.2 parts by weight, 0.3 parts by weight, and 3.4 parts by weight, respectively; the blended material is hot air dried, the drying temperature is 97°C, and the drying time is 8 hours;

[0175] (3) The dried blended material is extruded and spun through a traditional melt spinning device, the shape of the spinneret hole is circular; the spinning temperature is 175°C, the spinning speed is 1500 m / min, and the blended long fiber is obtained by winding; finally, the blended long fiber is drawn and heat set, the drawing temperature is 110°C, the drawing multiple is 2.5 times, and the modified polylactic acid fiber is obtained.

[0176] The properties of the modified polylactic acid fiber were detected, and the detection results are shown in Table 1.

[0177] Comparative Example 1

[0178] According to the method of Example 3, except that: the PLLA-PHA block copolymer is not catalytically prepared, and in step (5), “PLLA-PHA is 6 parts by weight” is replaced with “PLLA is 4 parts by weight, and PHA is 2 parts by weight”;

[0179] Other process parameters are the same as those in Example 3.

[0180] The detection results are shown in Table 1.

[0181] Comparative Example 2

[0182] According to the method of Example 3, except that: the sb-PLA is not catalytically prepared;

[0183] Other process parameters are the same as those in Example 3.

[0184] The detection results are shown in Table 1.

[0185] Comparative Example 3

[0186] According to the method of Example 3, except that: the PLA-based complex component and TMX-2 are replaced with a weight ratio of 0.8:1 instead of 0.2:1;

[0187] Other process parameters are the same as those in Example 3.

[0188] The detection results are shown in Table 1.

[0189] Comparative Example 4

[0190] According to the method of Example 3, except that: TMX-2 is not added; other process parameters are the same as those in Example 3.

[0191] The detection results are shown in Table 1.

[0192] Comparative Example 5

[0193] According to the method of Example 3, except that: PDLA is not added in the complex nucleating agent; other process parameters are the same as those in Example 3.

[0194] The detection results are shown in Table 1.

[0195] Comparative Example 6

[0196] According to the method of Example 3, except that: PDLA and sb-PLA are not added in the complex nucleating agent; other process parameters are the same as those in Example 3.

[0197] The test results are shown in Table 1.

[0198] Comparative Example 7

[0199] The method of Example 3 is the same as in Example 3, except that PDLA and TMX-2 are not added to the nucleating agent; all other process parameters are the same as in Example 3.

[0200] The test results are shown in Table 1.

[0201] Comparative Example 8

[0202] The method of Example 3 is the same as that of Example 3, except that sb-PLA and TMX-2 are not added to the compound nucleating agent; all other process parameters are the same as those of Example 3.

[0203] The test results are shown in Table 1.

[0204] Comparative Example 9

[0205] The method of Example 3 is followed, except that no compound nucleating agent is added; all other process parameters are the same as in Example 3; the modified polylactic acid fiber prepared in Comparative Example 9 is described below. Figure 2 ,pass Figure 2 It can be seen that the cold crystallization peak in the curves of Example 3 and Comparative Example 9 shifts significantly towards the low temperature direction, indicating that the crystallization ability is significantly promoted.

[0206] The test results are shown in Table 1.

[0207] Table 1

[0208]

[0209]

[0210] As can be seen from Examples 1 to 11, the composite formulation of PLLA, PHA, PLLA-PHA, PDLA, sb-PLA, and TMX-2 in this invention has a synergistic effect, resulting in the formation of three continuous phase network structures within the blended fibers, which gives the fibers high strength, high heat resistance, and high flexibility.

[0211] As can be seen from Comparative Examples 1 to 9, in this invention, PDLA, sb-PLA, and TMX-2 work together to promote crystallization, forming a network crystal structure, which greatly improves fiber strength and heat resistance.

[0212] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the present invention.

Claims

1. A composition for modified polylactic acid fibers, characterized in that: This includes biodegradable polymer materials and compound nucleating agents; The biodegradable polymeric materials include polylactic acid (PLLA), polyhydroxyalkanoate (PHA), and PLLA-PHA block copolymers. The compound nucleating agent comprises a PLA-based compound component and a norbornene dicarboxylic acid complex TMX-2, wherein the mass ratio of the norbornene dicarboxylic acid complex TMX-2 to the PLA-based compound component is 0.02 to 0.6:

1.

2. The composition according to claim 1, characterized in that: The preparation method of the PLLA-PHA block copolymer includes, Dry PLLA and PHA, controlling the moisture content of PLLA to below 100 ppm and the moisture content of PHA to below 500 ppm; PLLA, PHA, and sodium octanoate are melt-plasticized using a twin-screw extruder at a melting temperature of 160–180°C and a twin-screw extruder speed of 108–180 rpm. The extruded sample after being melted and plasticized by a twin-screw extruder was pre-crystallized in a water bath at 50°C for 1–3 min. After pre-crystallization, the surface moisture of the sample was dried using an air knife; The PLLA-PHA block copolymer is then collected by pelletizing using a cantilever pelletizer.

3. The composition according to claim 1 or 2, characterized in that: The PLA-based compound component includes a PDLA and sb-PLA compound system, wherein the weight ratio of PDLA to sb-PLA is 5:

1.

4. The composition according to claim 3, characterized in that: The preparation method of the sb-PLA includes, PLLA and dextrorotatory polylactic acid PDLA were dried to control the moisture content to below 100 ppm. PLLA, PDLA, and sodium octanoate were melt-plasticized using a twin-screw extruder at a melting temperature of 160–180°C and a twin-screw extruder speed of 108–180 rpm. The extruded sample after being melted and plasticized by a twin-screw extruder was pre-crystallized in a water bath at 50°C for 1–3 min. After pre-crystallization, the surface moisture of the sample was dried by an air knife, and then pelletized and collected by a cantilever pelletizer to obtain sb-PLA.

5. The composition according to claim 4, characterized in that: The weight-average molecular weight of the PLLA is 80,000 to 250,000, and the molar content of the L optical isomer in the PLLA is 88% to 99%. The weight-average molecular weight of the PDLA is 180,000, and the molar content of the D optical isomer in the PDLA is greater than 99%. The weight-average molecular weight of the PHA is 120,000 to 810,000.

6. The composition according to any one of claims 1, 2, 4 or 5, characterized in that: Based on 100 parts by weight of total biodegradable polymer materials, the PLLA comprises 60-94 parts by weight, the PHA comprises 5-30 parts by weight, and the PLLA-PHA comprises 1-10 parts by weight.

7. The composition according to claim 6, characterized in that: Based on 100 parts by weight of total biodegradable polymer materials, the compound nucleating agent is 3 to 15 parts by weight.

8. The composition according to claim 7, characterized in that: The composition further includes an anti-hydrolysis agent, a plasticizer, and a chain extender; Of which, based on 100 parts by weight of total biodegradable polymer materials, the anti-hydrolysis agent is 0.1 to 2 parts by weight; The chain extender is 0.1 to 3 parts by weight; The plasticizer is 3 to 25 parts by weight; The anti-hydrolysis agent includes at least one of polycarbodiimide, carbodiimide, and oxazoline; The chain extender includes chain extender ADR4468; The plasticizer includes plasticizer ATBC.

9. The use of the composition according to any one of claims 1 to 8 in the preparation of high-strength, high-flexibility, heat-resistant polylactic acid fibers, characterized in that: include, The composition is spun through the spinneret holes of a melt spinning spinneret; The temperature of the melt spinning is 175–235°C, and the spinning speed is 300–3000 m / min.

10. The application as described in claim 9, characterized in that: The process, prior to melt spinning after blending, also includes drying, with the moisture content of the dried raw material maintained below 100 ppm; wherein... The drying temperature is 95–105°C, and the time is 5–10 hours.

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