Anti-degradation enhanced PLA filament and preparation method thereof

Abstract

The invention discloses an anti-degradation enhanced PLA filament and a preparation method thereof, and belongs to the technical field of fiber manufacturing. The anti-degradation enhanced PLA filament is prepared from the following raw materials in parts by weight: 80 to 90 parts of PLA and 10 to 20 parts of NCO-terminated prepolymer containing a carbodiimide structure. A terminal NCO prepolymer containing a carbodiimide structure is used for carrying out chain extension on PLA, the carbodiimide structure can be connected to a macromolecular chain while the molecular weight of the PLA filament is increased, terminal carboxyl groups generated by hydrolysis of PLA can be rapidly captured and reacted by the carbodiimide structure, so that the terminal carboxyl groups are prevented from catalyzing rapid degradation of PLA, and the service life of the PLA filament is prolonged. The overall molecular weight of the PLA filament is not reduced, so that the hydrolytic stability of the PLA filament is improved. The PLA filament has excellent elongation, dyeing performance and hydrolysis resistance, can be used for garment materials, and prolongs the service time of the PLA garment materials.

Description

Technical Field

[0001] The invention relates to the technical field of fiber manufacturing, and in particular to a degradation-resistant enhanced PLA filament and a preparation method thereof. Background Art

[0002] Polylactic acid (PLA) fiber not only has excellent processing performance, can adapt to traditional processes such as solution spinning and melt spinning, as well as new spinning processes such as electrospinning and supercritical fluid method, but also has excellent performance in use. Specifically, PLA is weakly acidic, similar to the acidity and alkalinity of the skin, and has biocompatibility; the lactic acid substances released during the degradation process of PLA help to eliminate keratin, promote metabolism, and help the growth of skin collagen, so PLA has skin beauty and skin care properties; PLA can also effectively adsorb acetic acid, ammonia, isovaleric acid, nonenal and other substances, and has the characteristics of deodorization and mildew prevention; the moisture regain of PLA fiber is 0.4-0.6, and it has a special profile cross-section with a wicking effect, so it has the characteristics of moisture conduction and quick drying; comprehensive comparison of various fabrics, PLA fabric has good dimensional stability, the comfort of cotton, the drape of viscose, and the strength of polyester. The above properties of PLA make it have broad application prospects in the field of clothing.

[0003] However, due to the characteristics of high crystallinity and high rigidity, PLA fibers have the disadvantages of poor toughness, poor skin affinity, low water washing color fastness, and insufficient drape of the prepared textile fabrics. More importantly, there are a large number of ester bonds in the PLA molecule, which is very easy to hydrolyze. This first leads to a significant reduction in the molecular weight of the PLA fiber during the processing, and secondly, the fabrics prepared from the PLA fiber lose a lot of mechanical properties after washing, have poor durability, and have a short service life. According to relevant data, PLA fibers will lose more than 20% of their mechanical properties after being soaked in hot water at 50°C for 1 hour. At present, many PLA fiber clothing projects have been stopped due to their extremely easy degradation and unstable mechanical properties. PLA fabrics have not been fully promoted in the market, and consumers have not been able to enjoy the excellent performance of PLA fabrics. How to effectively improve the water washing stability of PLA fibers is the primary problem to be solved by technicians in this field. Summary of the invention

[0004] The purpose of the present invention is to provide a degradation-resistant enhanced PLA filament and a preparation method thereof to solve the problems existing in the above-mentioned prior art. The PLA filament of the present invention has excellent elongation, dyeing performance and hydrolysis resistance, improves the drape and skin-friendliness of PLA fabrics, can be used for clothing fabrics, and prolongs the service life of PLA clothing fabrics.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] One of the technical solutions of the present invention is a degradation-resistant enhanced PLA filament, wherein the raw materials include 80-90 parts of PLA and 10-20 parts of a terminal NCO prepolymer containing a carbodiimide structure, and the terminal NCO prepolymer containing a carbodiimide structure is used as a chain extender of PLA.

[0007] The carbodiimide structure is -N=C=N-.

[0008] The use of a terminal NCO prepolymer containing a carbodiimide structure to extend the PLA chain can increase the molecular weight of the PLA filament while connecting the carbodiimide structure to the macromolecular chain. The terminal carboxyl groups generated by the hydrolysis of PLA will be quickly captured and reacted by the carbodiimide structure, which not only prevents the terminal carboxyl groups from catalyzing the rapid degradation of PLA, but also does not reduce the overall molecular weight of the PLA filament, thereby improving the hydrolysis stability of the PLA filament.

[0009] Furthermore, the structure of the PLA contains one or more of a terminal hydroxyl group, a terminal amino group and a terminal carboxyl group; and the weight average molecular weight of the PLA is greater than 30,000.

[0010] Furthermore, the weight average molecular weight of the PLA is preferably 35,000-113,000.

[0011] Furthermore, the PLA is a PLA slice.

[0012] Furthermore, the water content of the PLA is less than 0.03%.

[0013] Furthermore, the terminal NCO prepolymer containing a carbodiimide structure is a macromolecular polyol-modified terminal NCO prepolymer containing a carbodiimide structure or a macromolecular polyamine-modified terminal NCO prepolymer containing a carbodiimide structure.

[0014] Furthermore, the preparation step of the macromolecular polyol-modified NCO-terminated prepolymer containing a carbodiimide structure comprises: mixing a macromolecular polyol and a polyisocyanate mixture containing carbodiimide-modified MDI at 70 to 80° C., stirring and reacting for 20 to 40 minutes, vacuuming for 2 to 4 hours, and then cooling to 40 to 50° C. and aging for 44 to 52 hours to obtain the macromolecular polyol-modified NCO-terminated prepolymer containing a carbodiimide structure;

[0015] Alternatively, the preparation step of the macromolecular polyamine-modified end NCO prepolymer containing a carbodiimide structure includes: mixing a macromolecular polyamine and a polyisocyanate mixture containing carbodiimide-modified MDI at 40 to 50° C., stirring for reaction for 20 to 40 minutes, vacuuming for 2 to 4 hours, and then cooling to 30 to 40° C. and aging for 44 to 52 hours to obtain the macromolecular polyamine-modified end NCO prepolymer containing a carbodiimide structure.

[0016] Furthermore, the number average molecular weight of the macromolecular polyol is 800-4000, or the number average molecular weight of the macromolecular polyamine is 800-4000.

[0017] Furthermore, the macromolecular polyol includes one or more of polyether polyol, polycaprolactone polyol, polylactic acid polyol, polyacrylic acid polyol and polyester polyol.

[0018] Further, the polyether polyol includes one or more of polyethylene glycol, poly-1,2-propylene glycol, poly-1,3-propylene glycol, polybutylene glycol, ethylene glycol / propylene glycol copolymer and ethylene glycol / butylene glycol copolymer.

[0019] Furthermore, the polyester polyol includes one or more polyester polyols prepared from one or more of adipic acid, sebacic acid, terephthalic acid, succinic acid and one or more of ethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, and 1,6-hexanediol as raw materials.

[0020] Furthermore, the macromolecular polyamine includes one or more polyetheramines obtained by ammoniation of polyethylene glycol, poly 1,2-propylene glycol, poly 1,3-propylene glycol, polybutylene glycol, ethylene glycol / propylene glycol copolymer or ethylene glycol / butylene glycol copolymer under high temperature and high pressure.

[0021] Furthermore, the NCO content of the polyisocyanate mixture containing carbodiimide-modified MDI is 25-35%.

[0022] Furthermore, the molar number of NCO contained in the polyisocyanate mixture containing carbodiimide-modified MDI is 160 to 200% of the molar number of hydroxyl groups contained in the macromolecular polyol;

[0023] Alternatively, the molar number of NCO contained in the polyisocyanate mixture containing carbodiimide-modified MDI is 160 to 200% of the molar number of amine groups contained in the macromolecular polyamine.

[0024] Furthermore, the NCO content of the macromolecular polyol-modified NCO-terminated prepolymer containing a carbodiimide structure is 2 to 6 wt %, or the NCO content of the macromolecular polyamine-modified NCO-terminated prepolymer containing a carbodiimide structure is 2 to 6 wt %.

[0025] Technical solution 2 of the present invention: The method for preparing the above-mentioned degradation-resistant enhanced PLA filament comprises the following steps:

[0026] PLA is melted and plasticized to obtain a PLA melt; the PLA melt is pressurized and filtered to obtain a refined melt; a terminal NCO prepolymer containing a carbodiimide structure is preheated to 80-100° C. and then mixed with the refined melt to obtain a mixed melt; the mixed melt is spun and aged to obtain the degradation-resistant enhanced PLA filament.

[0027] Furthermore, the melt plasticization is carried out in a single screw extruder, and the single screw extruder has 7 stages of temperature control.

[0028] Furthermore, the temperature of the melt plasticization is 170-230° C. (specifically referring to the operating temperature range of a single-screw extruder).

[0029] Furthermore, the aging conditions include: temperature of 30° C., humidity of 60%, and time of 7 days.

[0030] Furthermore, the process further comprises a filtering step after preheating the NCO-terminated prepolymer containing a carbodiimide structure to 80-100° C. and mixing it with the refined melt.

[0031] Furthermore, the specific operation steps of spinning and aging include: spraying the mixed melt into filament melt through a spinneret, and sequentially undergoing cooling, twisting, oiling, pulling, wire guiding, and winding processes to obtain a PLA yarn tube; aging the PLA yarn tube at a temperature of 30° C. and a humidity of 60% for 7 days to obtain a degradation-resistant enhanced PLA filament finished product.

[0032] The third technical solution of the present invention: application of the above-mentioned degradation-resistant enhanced PLA filaments in the preparation of clothing fabrics.

[0033] The present invention discloses the following technical effects:

[0034] (1) The present invention uses a terminal NCO prepolymer containing a carbodiimide structure to extend the chain of PLA. Compared with the use of other common isocyanates such as HDI (hexamethylene diisocyanate), MDI (diphenylmethane diisocyanate), IPDI (isophorone diisocyanate), HMDI (dicyclohexylmethane diisocyanate) and the like for chain extension, the carbodiimide structure can be connected to the macromolecular chain while increasing the molecular weight of the PLA filaments. The terminal carboxyl groups generated by the hydrolysis of PLA will be quickly captured and reacted by the carbodiimide structure, which not only prevents the terminal carboxyl groups from catalyzing the rapid degradation of PLA, but also does not reduce the overall molecular weight of the PLA filaments, thereby improving the hydrolysis stability of the PLA filaments, and further increasing the service life of the fabrics prepared from the PLA filaments.

[0035] (2) The present invention introduces a terminal NCO prepolymer containing a carbodiimide structure having a flexible chain segment (a macromolecular polyol-modified terminal NCO prepolymer containing a carbodiimide structure or a macromolecular polyamine-modified terminal NCO prepolymer containing a carbodiimide structure, wherein the macromolecular polyol or macromolecular polyamine is modified to introduce a flexible chain segment) into the PLA macromolecular chain. The physical compatibility between the modified chain segment and the PLA macromolecular chain can be ignored, and the toughness of PLA can be intrinsically improved. The elongation at break of the PLA filament prepared by the present invention is increased to more than 100%, and the clothing fabric prepared from such PLA filament will have better drape and skin-friendliness.

[0036] (3) The introduction of the terminal NCO prepolymer chain segment containing carbodiimide structure destroys the crystallization of PLA macromolecules and can create larger pores between PLA filament molecules, which facilitates the entry of disperse dyes into the PLA filaments. After dyeing and cooling, the pores are surrounded by lactic acid segments, thereby improving the dyeing rate of PLA filaments.

[0037] (4) The molecular weight of PLA was increased by reacting the terminal NCO prepolymer containing carbodiimide structure with small molecular weight PLA chips. Thus, PLA filaments with excellent performance were successfully prepared using small molecular weight PLA chips, which reduced the difficulty of preparing PLA chips, the raw material of PLA filaments, and was conducive to large-scale promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0039] Figure 1 This is a physical picture of the finished PLA filament prepared in Example 3. DETAILED DESCRIPTION

[0040] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as limiting the present invention, but should be understood as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0041] It should be understood that the terms described in the present invention are only for describing a particular embodiment and are not intended to limit the present invention. In addition, for the numerical range in the present invention, it should be understood that each intermediate value between the upper and lower limits of the scope is also specifically disclosed. The intermediate value in any stated value or stated range, and each smaller range between any other stated value or intermediate value in the described range is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded in the scope.

[0042] Unless otherwise indicated, all technical and scientific terms used herein have the same meanings as those generally understood by those skilled in the art. Although the present invention describes only preferred methods and materials, any methods and materials similar or equivalent to those described herein may also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of a conflict with any incorporated document, the content of this specification shall prevail.

[0043] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments of the present invention description without departing from the scope or spirit of the present invention. Other embodiments derived from the present invention description will be apparent to the skilled artisan. The present invention description and examples are exemplary only.

[0044] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0045] As a first aspect of the present invention, the present invention provides a degradation-resistant enhanced PLA filament, wherein the raw materials include, by weight, 80 to 90 parts of PLA and 10 to 20 parts of a terminal NCO prepolymer containing a carbodiimide structure.

[0046] The carbodiimide structure is -N=C=N-.

[0047] As a preferred embodiment of the present invention, the PLA contains one or more of terminal hydroxyl groups, terminal amino groups and terminal carboxyl groups in its structure; the weight average molecular weight of the PLA is greater than 30,000, preferably 35,000-113,000.

[0048] As a preferred embodiment of the present invention, the PLA is a PLA slice.

[0049] As a preferred embodiment of the present invention, the water content of the PLA is less than 0.03%. The PLA with a water content of less than 0.03% is obtained by drying PLA slices with dry nitrogen until the water content is less than 0.03%. That is, the initial raw material is PLA slices, and the PLA slices need to be dried to a water content of less than 0.03% before processing and preparing the anti-degradation enhanced PLA filaments.

[0050] As a preferred embodiment of the present invention, the PLA can be obtained by condensation polymerization of lactic acid, by ring-opening polymerization of lactide, or by polymerization of lactic acid or lactide (one of the two) and other monomers, wherein the proportion of the other monomers in all monomers is less than 20wt%; the specific preparation process is not limited, and conventional preparation methods in the art can be selected.

[0051] As a preferred embodiment of the present invention, the other monomers include ε-caprolactone, 1,2-ethylene glycol, 1,2-propylene glycol, 1,3-propylene glycol, 1,4-butylene glycol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, hexamethylene diisocyanate (HDI), diphenylmethane diisocyanate (MDI), polyethylene glycol (PEG), polyacetic acid alcohol (PGA) and polytrimethyl carbonate (PTMC) One or more.

[0052] As a preferred embodiment of the present invention, the terminal NCO prepolymer containing a carbodiimide structure is a macromolecular polyol-modified terminal NCO prepolymer containing a carbodiimide structure or a macromolecular polyamine-modified terminal NCO prepolymer containing a carbodiimide structure.

[0053] As a preferred embodiment of the present invention, the preparation step of the macromolecular polyol-modified NCO prepolymer containing a carbodiimide structure comprises: mixing a macromolecular polyol and a polyisocyanate mixture containing carbodiimide-modified MDI at 70 to 80° C., stirring and reacting for 20 to 40 minutes, vacuuming for 2 to 4 hours, and then cooling to 40 to 50° C. and aging for 44 to 52 hours to obtain the macromolecular polyol-modified NCO prepolymer containing a carbodiimide structure;

[0054] Alternatively, the preparation step of the macromolecular polyamine-modified end NCO prepolymer containing a carbodiimide structure includes: mixing a macromolecular polyamine and a polyisocyanate mixture containing carbodiimide-modified MDI at 40 to 50° C., stirring for reaction for 20 to 40 minutes, vacuuming for 2 to 4 hours, and then cooling to 30 to 40° C. and aging for 44 to 52 hours to obtain the macromolecular polyamine-modified end NCO prepolymer containing a carbodiimide structure.

[0055] As a preferred embodiment of the present invention, the number average molecular weight of the macromolecular polyol is 800-4000, or the number average molecular weight of the macromolecular polyamine is 800-4000.

[0056] As a preferred embodiment of the present invention, the macromolecular polyol includes one or more of polyether polyol, polycaprolactone polyol, polylactic acid polyol, polyacrylic acid polyol and polyester polyol.

[0057] As a preferred embodiment of the present invention, the polyether polyol includes one or more of polyethylene glycol, poly-1,2-propylene glycol, poly-1,3-propylene glycol, polybutylene glycol, ethylene glycol / propylene glycol copolymer and ethylene glycol / butylene glycol copolymer.

[0058] As a preferred embodiment of the present invention, the polyester polyol includes one or more polyester polyols prepared from one or more of adipic acid, sebacic acid, terephthalic acid, succinic acid and one or more of ethylene glycol, 1,3-propylene glycol, 1,2-propylene glycol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, neopentyl glycol, and 1,6-hexanediol as raw materials.

[0059] As a preferred embodiment of the present invention, the macromolecular polyamine includes one or more polyetheramines obtained by ammoniation of polyethylene glycol, poly 1,2-propylene glycol, poly 1,3-propylene glycol, polybutylene glycol, ethylene glycol / propylene glycol copolymer or ethylene glycol / butylene glycol copolymer under high temperature and pressure.

[0060] As a preferred embodiment of the present invention, the NCO content in the polyisocyanate mixture containing carbodiimide-modified MDI is 25-35%.

[0061] The polyisocyanate mixture containing carbodiimide-modified MDI is actually a liquefied MDI, which is obtained by introducing carbodiimide groups into MDI to make it liquid at room temperature. In the preparation process of carbodiimide-modified MDI, first, under the action of a catalyst, part of the MDI monomer is first converted into a polyisocyanate containing a carbodiimide structure, and this polyisocyanate containing a carbodiimide structure can be further cyclized with isocyanate to generate a polyisocyanate containing a uretonimine group. The obtained liquefied MDI is a polyisocyanate mixture containing part of the carbodiimide groups and uretonimine groups, that is, a polyisocyanate mixture containing carbodiimide-modified MDI.

[0062] Common liquefied MDI on the market include BASF 103C, Covestro CD-C, Wanhua 100LL, Tosoh MX, Mitsui LL, Dow 143LP and Huntsman 2020. The polyisocyanate mixture containing carbodiimide-modified MDI in the specific embodiment of the present invention is selected from any one of them.

[0063] As a preferred embodiment of the present invention, the molar number of NCO groups contained in the polyisocyanate mixture containing carbodiimide-modified MDI is 160 to 200% of the molar number of hydroxyl groups contained in the macromolecular polyol;

[0064] Or, the molar number of NCO contained in the polyisocyanate mixture containing carbodiimide modified MDI is 160-200% of the molar number of amine groups contained in the macromolecular polyamine. The molar number of hydroxyl groups contained in the macromolecular polyol is obtained by converting the weight of the macromolecular polyol and the hydroxyl value of the macromolecular polyol; the molar number of amine groups contained in the macromolecular polyamine is obtained by converting the weight of the macromolecular polyamine and the amine value of the macromolecular polyamine; the molar number of NCO groups contained in the polyisocyanate mixture containing carbodiimide modified MDI is obtained by converting the weight of the polyisocyanate mixture containing carbodiimide modified MDI and the NCO content therein.

[0065] The NCO content of the macromolecular polyol-modified NCO prepolymer containing a carbodiimide structure or the macromolecular polyamine-modified NCO prepolymer containing a carbodiimide structure is affected by the molecular weight of the macromolecular polyol, or the molecular weight of the macromolecular polyamine, and the NCO content of the polyisocyanate mixture containing carbodiimide-modified MDI. As a preferred embodiment of the present invention, the NCO content of the macromolecular polyol-modified NCO prepolymer containing a carbodiimide structure is 2 to 6 wt%, or the NCO content of the macromolecular polyamine-modified NCO prepolymer containing a carbodiimide structure is 2 to 6 wt%.

[0066] As a preferred embodiment of the present invention, the raw materials of the anti-degradation PLA filaments may further include 0-5 parts of auxiliary agents.

[0067] As a preferred embodiment of the present invention, the auxiliary agent includes one or more of a lubricant, an antioxidant, a toner and a pigment.

[0068] As a second aspect of the present invention, the present invention provides a method for preparing the above-mentioned degradation-resistant enhanced PLA filament (melt spinning preparation method), comprising the following steps:

[0069] PLA is melted and plasticized to obtain a PLA melt; the PLA melt is pressurized and filtered to obtain a refined melt; a terminal NCO prepolymer containing a carbodiimide structure is preheated to 80-100° C. and then mixed with the refined melt to obtain a mixed melt; the mixed melt is spun and aged to obtain the degradation-resistant enhanced PLA filament.

[0070] As a preferred embodiment of the present invention, the melt plasticization is carried out in a single-screw extruder, and the single-screw extruder has 7 stages of temperature control.

[0071] As a preferred embodiment of the present invention, the temperature of the melt plasticization is 170-230° C. (specifically referring to the operating temperature range of a single-screw extruder).

[0072] As a preferred embodiment of the present invention, after preheating the NCO-terminated prepolymer containing a carbodiimide structure to 80-100° C. and mixing it with the refined melt, the process further includes a filtering step.

[0073] As a preferred embodiment of the present invention, the specific operation steps of spinning and aging include: spraying the mixed melt into a filament melt through a spinneret, and sequentially undergoing cooling, twisting, oiling, pulling, wire guiding, and winding steps to obtain a PLA yarn tube; aging the PLA yarn tube at a temperature of 30° C. and a humidity of 60% for 7 days to obtain a degradation-resistant enhanced PLA filament finished product.

[0074] As a preferred embodiment of the present invention, the preparation method more specifically comprises the following steps:

[0075] The PLA slices were dried with dry nitrogen until the moisture content was less than 0.03%;

[0076] The dried PLA slices are metered by a weight-loss pump at 80 to 90 parts by mass per hour and injected into a single screw extruder for melting and plasticization to obtain a uniform melt;

[0077] The melt is pressurized by a melt pump and then filtered through a filter screen to obtain a refined melt;

[0078] Preheating the NCO-terminated prepolymer containing a carbodiimide structure to 80-100° C., pumping it into a static mixer at a rate of 10-20 parts by mass per hour together with the refined melt through a metering pump to mix evenly, and then filtering through a filter to remove gel impurities to obtain a mixed melt;

[0079] The mixed melt is ejected into filament melt through a spinneret, and then goes through the processes of air blowing cooling, twisting, oiling, pulling, wire guiding, and winding to obtain a PLA filament tube;

[0080] The PLA filament bobbins were aged for 7 days at a temperature of 30° C. and a humidity of 60% to obtain a degradation-resistant enhanced PLA filament product.

[0081] As a third aspect of the present invention, the present invention provides the use of the above-mentioned degradation-resistant enhanced PLA filaments in the preparation of clothing fabrics.

[0082] The degradation-resistant enhanced PLA filament and the preparation method thereof of the present invention are further described below in conjunction with specific embodiments.

[0083] Three types of PLA slices are used in the following examples and comparative examples, wherein PLA slice 1 is a PLA slice having a weight average molecular weight of 35,000 g / mol and a hydroxyl value of 1.6 mgKOH / g obtained by direct polycondensation of lactic acid; PLA slice 2 is a PLA slice having a weight average molecular weight of 81,000 g / mol and a hydroxyl value of 0.7 mgKOH / g obtained by ring-opening polymerization of lactide; PLA slice 3 is a PLA slice having a weight average molecular weight of 113,000 g / mol and a hydroxyl value of 0.5 mgKOH / g obtained by ring-opening polymerization of lactide; all three PLA slices are provided by Yangzhou Huitong New Materials Co., Ltd.

[0084] The NCO content of BASF 103C used in the following examples and comparative examples is 28.5 wt %.

[0085] The “parts” referred to in the following embodiments and comparative examples are all “parts by mass”.

[0086] Example 1

[0087] A degradation-resistant enhanced PLA filament, the preparation steps are as follows:

[0088] The PLA slice 1 was dried with dry nitrogen until the moisture content was less than 0.03%;

[0089] The dried PLA slice 1 was metered by a weight-loss pump at 90 parts by mass per hour and injected into a single screw extruder for melting and plasticization to obtain a uniform melt. The temperatures of the single screw extruder sections 1-7 were 180° C., 190° C., 200° C., 210° C., 220° C., 210° C. and 200° C., respectively.

[0090] The melt is pressurized by a melt pump and then filtered through a filter screen to obtain a refined melt;

[0091] The macromolecular polyol-modified NCO prepolymer containing a carbodiimide structure is preheated to 80° C., and is metered by a metering pump at 10 parts by mass per hour together with the refined melt into a static mixer (PLA slices are injected into a single-screw extruder for melting and plasticization, pressurization, filtration, and injection into a static mixer is a continuous process, so the rate at which the refined melt is injected into the static mixer is the same as the rate at which the PLA slices are injected into the single-screw extruder) and mixed evenly, and then the gel impurities are removed through a filter to obtain a mixed melt;

[0092] The mixed melt is ejected into filament melt through a spinneret, and then goes through the steps of air cooling, twisting, oiling, pulling, wire guiding and winding to obtain a 75D / 36F PLA filament bobbin (75D represents the thickness of the PLA filament, and 36F represents that the PLA filament is composed of 36 small filaments of uniform thickness). The PLA filament bobbin is aged at a temperature of 30°C and a humidity of 60% for 7 days to obtain the final anti-degradation enhanced PLA filament finished product.

[0093] The preparation method of the macromolecular polyol-modified NCO-terminated prepolymer containing a carbodiimide structure is as follows: at 80° C., 80.0 parts by mass of a macromolecular polyol (polyethylene sebacate polyol having a number average molecular weight of 800 and a hydroxyl value of 140 mg KOH / g, referred to as PES-800) is added to 53.1 parts by mass of BASF 103C, wherein the molar number of NCO groups contained in BASF 103C is 180% of the molar number of hydroxyl groups contained in the macromolecular polyol, stirring the reaction for 20 minutes, then vacuumizing for 2 hours, then cooling to 50° C. and aging for 48 hours, and after aging, a macromolecular polyol-modified NCO-terminated prepolymer containing a carbodiimide structure having an NCO content of 5.0 wt% (referred to as P-PES1) is obtained.

[0094] Example 2

[0095] A degradation-resistant enhanced PLA filament, the preparation steps are as follows:

[0096] The PLA slice 2 was dried with dry nitrogen until the moisture content was less than 0.03%;

[0097] The dried PLA slice 2 was metered by a weight-loss pump at 88 parts by mass per hour and injected into a single screw extruder for melting and plasticization to obtain a uniform melt. The temperatures of the single screw extruder sections 1-7 were 180°C, 190°C, 200°C, 210°C, 220°C, 210°C and 200°C, respectively.

[0098] The melt is pressurized by a melt pump and then filtered through a filter screen to obtain a refined melt;

[0099] The macromolecular polyamine-modified NCO prepolymer containing a carbodiimide structure is preheated to 90° C., and 12 parts by mass per hour is metered into a static mixer together with the refined melt to be mixed evenly, and then the gel impurities are removed through a filter to obtain a mixed melt;

[0100] The mixed melt is ejected into filament melt through a spinneret, and then goes through the steps of air blowing cooling, twisting, oiling, pulling, wire guiding and winding to obtain a 75D / 36F PLA filament bobbin. The PLA filament bobbin is aged at a temperature of 30°C and a humidity of 60% for 7 days to obtain the final anti-degradation enhanced PLA filament product.

[0101] The preparation method of the macromolecular polyamine-modified NCO-terminated prepolymer containing a carbodiimide structure is as follows: at 50° C., 100.0 parts by mass of a macromolecular polyamine (polyethylene glycol amine having a number average molecular weight of 1000 and an amine value of 112.2 mg KOH / g, referred to as PEINE-1000) is added to 56.0 parts by mass of BASF 103C, wherein the molar number of NCO groups contained in BASF 103C is 190% of the molar number of amine groups contained in the macromolecular polyamine, the mixture is stirred for reaction for 20 minutes, vacuumized for 2 hours, and then cooled to 40° C. and aged for 48 hours. After the aging, a macromolecular polyamine-modified NCO-terminated prepolymer containing a carbodiimide structure having an NCO content of 4.8 wt% (referred to as P-PEINE2) is obtained.

[0102] Example 3

[0103] A degradation-resistant enhanced PLA filament, the preparation steps are as follows:

[0104] The PLA slice 3 was dried with dry nitrogen until the moisture content was less than 0.03%;

[0105] The dried PLA slice 3 was metered by a weight loss pump at 86 parts by mass per hour and injected into a single screw extruder for melting and plasticization to obtain a uniform melt. The temperatures of the single screw extruder sections 1-7 were 180°C, 190°C, 200°C, 210°C, 220°C, 210°C and 200°C, respectively.

[0106] The melt is pressurized by a melt pump and then filtered through a filter screen to obtain a refined melt;

[0107] The NCO-terminated prepolymer modified with a macromolecular polyol containing a carbodiimide structure is preheated to 90° C., and is pumped into a static mixer together with a refined melt at a rate of 14 parts by mass per hour by a metering pump to be mixed evenly, and then the gel impurities are removed by a filter to obtain a mixed melt;

[0108] The mixed melt is ejected into filament melt through the spinneret, and then goes through the processes of air cooling, twisting, oiling, pulling, wire guiding and winding to obtain 75D / 36F PLA filament bobbins. The PLA filament bobbins are aged for 7 days at a temperature of 30°C and a humidity of 60% to obtain the final anti-degradation enhanced PLA filament product (the actual picture of the finished product is as shown in the figure). Figure 1 shown).

[0109] The preparation method of the macromolecular polyol-modified NCO-terminated prepolymer containing a carbodiimide structure is as follows: at 80° C., 150.0 parts by mass of a macromolecular polyol (polyethylene glycol having a number average molecular weight of 1500 and a hydroxyl value of 74.8 mg KOH / g, referred to as PEG-1500) is added to 56.0 parts by mass of BASF 103C, wherein the molar number of NCO groups contained in BASF 103C is 190% of the molar number of hydroxyl groups contained in the macromolecular polyol, the mixture is stirred for reaction for 30 minutes, vacuumized for 3 hours, and then cooled to 50° C. for aging for 48 hours. After aging, a macromolecular polyol-modified NCO-terminated prepolymer containing a carbodiimide structure having an NCO content of 3.6 wt% (referred to as P-PEG3) is obtained.

[0110] Example 4

[0111] A degradation-resistant enhanced PLA filament, the preparation steps are as follows:

[0112] The PLA slice 2 was dried with dry nitrogen until the moisture content was less than 0.03%;

[0113] The dried PLA slice 2 was metered by a weight loss pump at 84 parts by mass per hour and injected into a single screw extruder for melting and plasticization to obtain a uniform melt. The temperatures of the single screw extruder sections 1-7 were 180°C, 190°C, 200°C, 210°C, 220°C, 210°C and 200°C, respectively.

[0114] The melt is pressurized by a melt pump and then filtered through a filter screen to obtain a refined melt;

[0115] The macromolecular polyamine-modified NCO prepolymer containing a carbodiimide structure is preheated to 90° C., and 16 parts by mass per hour is metered into a static mixer together with the refined melt by a metering pump to mix evenly, and then the gel impurities are removed by a filter to obtain a mixed melt;

[0116] The mixed melt is ejected into filament melt through a spinneret, and then goes through the steps of air blowing cooling, twisting, oiling, pulling, wire guiding and winding to obtain a 75D / 36F PLA filament bobbin. The PLA filament bobbin is aged at a temperature of 30°C and a humidity of 60% for 7 days to obtain the final anti-degradation enhanced PLA filament product.

[0117] The preparation method of the macromolecular polyamine modified end NCO prepolymer containing a carbodiimide structure is as follows: at 50° C., 200.0 parts by mass of a macromolecular polyamine (polytetramethylene glycol amine having a number average molecular weight of 2000 and an amine value of 56.1 mg KOH / g, referred to as PTINE-2000) is added to 57.5 parts by mass of BASF 103C, wherein the molar number of NCO groups contained in BASF 103C is 195% of the molar number of amine groups contained in the macromolecular polyamine, the reaction is stirred for 40 minutes, and then vacuumed for 4 hours, and then cooled to 40° C. and aged for 48 hours to obtain a macromolecular polyamine modified end NCO prepolymer containing a carbodiimide structure having an NCO content of 3.1wt% (referred to as P-PTINE4).

[0118] Example 5

[0119] A degradation-resistant enhanced PLA filament, the preparation steps are as follows:

[0120] The PLA slice 2 was dried with dry nitrogen until the moisture content was less than 0.03%;

[0121] The dried PLA slice 2 was metered by a weight loss pump at 82 parts by mass per hour and injected into a single screw extruder for melting and plasticization to obtain a uniform melt. The temperatures of the single screw extruder sections 1-7 were 180°C, 190°C, 200°C, 210°C, 220°C, 210°C and 200°C, respectively.

[0122] The melt is pressurized by a melt pump and then filtered through a filter screen to obtain a refined melt;

[0123] The NCO-terminated prepolymer containing a carbodiimide structure and modified by a macromolecular polyol is preheated to 100° C., and 18 parts by mass per hour is metered into a static mixer together with the refined melt to be mixed evenly, and then the gel impurities are removed through a filter to obtain a mixed melt;

[0124] The mixed melt is ejected into filament melt through a spinneret, and then goes through the steps of air cooling, twisting, oiling, pulling, wire guiding and winding to obtain a 75D / 36F PLA filament bobbin. The PLA filament bobbin is aged at a temperature of 30°C and a humidity of 60% for 7 days to obtain a final anti-degradation PLA filament product.

[0125] Among them, the preparation method of the macromolecular polyol modified terminal NCO prepolymer containing a carbodiimide structure is: at 80° C., 300.0 parts by mass of a macromolecular polyol (polycaprolactone polyol with a number average molecular weight of 3000 and a hydroxyl value of 37.4 mg KOH / g, referred to as PCL-3000) is added to 58.9 parts by mass of BASF 103C, wherein the molar number of NCO groups contained in BASF 103C is 200% of the molar number of hydroxyl groups contained in the macromolecular polyol, stirring the reaction for 40 minutes, then vacuuming for 4 hours, and then cooling to 50° C. and ripening for 48 hours to obtain a macromolecular polyol modified terminal NCO prepolymer containing a carbodiimide structure with an NCO content of 2.3wt% (referred to as P-PCL5).

[0126] Comparative Example 1

[0127] A PLA filament, the preparation steps are as follows:

[0128] The PLA slice 2 was dried with dry nitrogen until the moisture content was less than 0.03%;

[0129] The dried PLA slice 2 was metered by a weight-loss pump at 88 parts by mass per hour and injected into a single screw extruder for melting and plasticization to obtain a uniform melt. The temperatures of the single screw extruder sections 1-7 were 180°C, 190°C, 200°C, 210°C, 220°C, 210°C and 200°C, respectively.

[0130] The melt is pressurized by a melt pump and then filtered through a filter screen to obtain a refined melt;

[0131] BASF 103C was preheated to 90°C, and 12 parts by mass per hour were metered by a metering pump and pumped into a static mixer together with the refined melt for uniform mixing, and then the gel impurities were removed through a filter to obtain a mixed melt;

[0132] The mixed melt is ejected into filament melt through a spinneret, and then goes through the steps of air cooling, twisting, oiling, pulling, wire guiding, winding, and hot plate stretching to obtain a 75D / 36F PLA filament bobbin. The PLA filament bobbin is aged at a temperature of 30°C and a humidity of 60% for 7 days to obtain a final PLA filament product.

[0133] Comparative Example 2

[0134] A PLA filament, the preparation steps are as follows:

[0135] The PLA slice 2 was dried with dry nitrogen until the moisture content was less than 0.03%;

[0136] The dried PLA slice 2 was metered by a weight-loss pump at 88 parts by mass per hour and injected into a single screw extruder for melting and plasticization to obtain a uniform melt. The temperatures of the single screw extruder sections 1-7 were 180°C, 190°C, 200°C, 210°C, 220°C, 210°C and 200°C, respectively.

[0137] The melt is pressurized by a melt pump and then filtered through a filter screen to obtain a refined melt;

[0138] The macromolecular polyol-modified NCO-terminated prepolymer without carbodiimide structure is preheated to 90° C., and 12 parts by mass per hour is metered into a static mixer together with the refined melt by a metering pump to mix evenly, and then the gel impurities are removed by a filter to obtain a mixed melt;

[0139] The mixed melt is ejected into filament melt through a spinneret, and then goes through the steps of air cooling, twisting, oiling, pulling, wire guiding and winding to obtain a 75D / 36F PLA filament bobbin. The PLA filament bobbin is aged for 7 days at a temperature of 30°C and a humidity of 60% to obtain a final PLA filament product.

[0140] Among them, the preparation method of the macromolecular polyol modified terminal NCO prepolymer without carbodiimide structure is: at 80°C, 150.0 mass parts of macromolecular polyol (polyethylene glycol with a number average molecular weight of 1500 and a hydroxyl value of 74.8 mg KOH / g, referred to as PEG-1500) are added to 47.5 mass parts of MDI (diphenylmethane diisocyanate), wherein the molar number of NCO groups contained in MDI is 190% of the molar number of hydroxyl groups contained in the macromolecular polyol, stirring the reaction for 30 minutes, then vacuuming for 3 hours, and then cooling to 50°C for aging for 48 hours. After the aging, a macromolecular polyol modified terminal NCO prepolymer without carbodiimide structure with an NCO content of 3.8wt% (referred to as P-PEG6) is obtained.

[0141] Comparative Example 3

[0142] A PLA filament, the preparation steps are as follows:

[0143] The PLA slice 2 was dried with dry nitrogen until the moisture content was less than 0.03%;

[0144] The dried PLA slice 2 was metered by a weight loss pump at 88 parts by mass per hour and injected into a single screw extruder for melting and plasticization to obtain a uniform melt. The temperatures of the single screw extruder sections 1-7 were 180°C, 190°C, 200°C, 210°C, 220°C, 210°C and 200°C, respectively.

[0145] The melt is pressurized by a melt pump and then filtered through a filter screen to obtain a refined melt;

[0146] The NCO-terminated prepolymer modified with a macromolecular polyol containing a carbodiimide structure is preheated to 90° C., and is pumped into a static mixer together with a refined melt at a rate of 12 parts by mass per hour by a metering pump to be mixed evenly, and then a mixed melt is obtained after removing gel impurities through a filter screen;

[0147] The mixed melt is ejected into filament melt through a spinneret, and then goes through the steps of air cooling, twisting, oiling, pulling, wire guiding and winding to obtain a 75D / 36F PLA filament bobbin. The PLA filament bobbin is aged for 7 days at a temperature of 30°C and a humidity of 60% to obtain a final PLA filament product.

[0148] The preparation method of the macromolecular polyol-modified NCO-terminated prepolymer containing a carbodiimide structure is as follows: at 80° C., 40.0 parts by mass of a macromolecular polyol (polyethylene glycol having a number average molecular weight of 400 and a hydroxyl value of 281 mg KOH / g, referred to as PEG-400) is added to 56.0 parts by mass of BASF 103C, wherein the molar number of NCO groups contained in BASF 103C is 190% of the molar number of hydroxyl groups contained in the macromolecular polyol, the mixture is stirred for reaction for 30 minutes, vacuumized for 3 hours, and then cooled to 50° C. for aging for 48 hours. After aging, a macromolecular polyol-modified NCO-terminated prepolymer containing a carbodiimide structure having an NCO content of 7.8 wt% (referred to as P-PEG7) is obtained.

[0149] Comparative Example 4

[0150] A PLA filament, the preparation steps are as follows:

[0151] The PLA slice 2 was dried with dry nitrogen until the moisture content was less than 0.03%;

[0152] The dried PLA slice 2 was metered by a weight-loss pump at 88 parts by mass per hour and injected into a single screw extruder for melting and plasticization to obtain a uniform melt. The temperatures of the single screw extruder sections 1-7 were 180°C, 190°C, 200°C, 210°C, 220°C, 210°C and 200°C, respectively.

[0153] The melt is pressurized by a melt pump and then filtered through a filter screen to obtain a refined melt;

[0154] The NCO-terminated prepolymer modified with a macromolecular polyol containing a carbodiimide structure is preheated to 90° C., and is pumped into a static mixer together with a refined melt at a rate of 12 parts by mass per hour by a metering pump to be mixed evenly, and then a mixed melt is obtained after removing gel impurities through a filter screen;

[0155] The mixed melt is ejected into filament melt through a spinneret, and then goes through the steps of air cooling, twisting, oiling, pulling, wire guiding and winding to obtain a 75D / 36F PLA filament bobbin. The PLA filament bobbin is aged for 7 days at a temperature of 30°C and a humidity of 60% to obtain a final PLA filament product.

[0156] The preparation method of the macromolecular polyol-modified NCO-terminated prepolymer containing a carbodiimide structure is as follows: at 80° C., 500.0 parts by mass of a macromolecular polyol (polyethylene glycol having a number average molecular weight of 5000 and a hydroxyl value of 22.5 mg KOH / g, referred to as PEG-5000) is added to 56.0 parts by mass of BASF 103C, wherein the molar number of NCO groups contained in BASF 103C is 190% of the molar number of hydroxyl groups contained in the macromolecular polyol, stirring the reaction for 30 minutes, then vacuumizing for 3 hours, then cooling to 50° C. and aging for 48 hours. After aging, a macromolecular polyol-modified NCO-terminated prepolymer containing a carbodiimide structure having an NCO content of 1.3 wt% (referred to as P-PEG8) is obtained.

[0157] Comparative Example 5

[0158] A PLA filament, the preparation steps are as follows:

[0159] PLA slice 3 was dried with dry nitrogen until the moisture content was less than 0.03%;

[0160] The dried PLA slice 3 is injected into a single screw extruder for melting and plasticization to obtain a uniform melt, and the temperatures of sections 1-7 of the single screw extruder are 180° C., 190° C., 200° C., 210° C., 220° C., 210° C. and 200° C. respectively;

[0161] The melt is pressurized by a melt pump and then filtered through a filter screen to obtain a refined melt;

[0162] The refined melt is ejected into filament melt through a spinneret, and then goes through the steps of air cooling, twisting, oiling, pulling, wire guiding and winding to obtain a 75D / 36F PLA filament bobbin. The PLA filament bobbin is aged for 7 days at a temperature of 30°C and a humidity of 60% to obtain a final PLA filament product.

[0163] Test Example 1

[0164] The finished PLA filaments of Examples 1-5 and Comparative Examples 1-5 after aging were subjected to molecular weight test, hydrolysis resistance test and dyeing performance test.

[0165] (1) Molecular weight test: The finished PLA filaments were dissolved in HPLC grade chloroform and then tested for their weight average molecular weight by GPC (gel permeation chromatography).

[0166] (2) Anti-degradation test: The mechanical properties of the finished PLA filaments were tested with reference to FZ / T 54098-2017 "Polylactic acid drawn yarns", as well as the mechanical properties of the finished PLA filaments after being immersed in tap water at 50°C for 1 h and 24 h, respectively, and then dried in a constant temperature room at 23°C and 50% humidity for 48 h.

[0167] (3) Dyeing performance test: Set the bath ratio to 1:20, dyeing pH = 4.5, dye concentration 2% (owf), use disperse blue dye to dye the matured PLA filament product at 90°C for 30 min, dye at 40°C, and heat up at a rate of 1°C / min. Use an ultraviolet spectrophotometer to test the maximum absorbance of the dye solution before and after dyeing, and calculate the dye uptake rate:

[0168] Dyeing rate = (absorbance before dyeing - absorbance after dyeing) / absorbance before dyeing × 100%.

[0169] The raw material composition statistics of the PLA filaments of Examples 1-5 and Comparative Examples 1-5 are shown in Table 1, the molecular weight and anti-degradation performance test results are shown in Table 2, and the dyeing performance test results are shown in Table 2. The spinnability of the PLA filaments of Examples 1-5 and Comparative Examples 1-5 during the melt spinning preparation process is also statistically analyzed, as shown in Table 2.

[0170] Table 1

[0171] PLA slices Chain Extender Example 1 90 PLA ​​slices 1 10 parts P-PES1, NCO content 5.0% Example 2 88 PLA slices 2 12 parts P-PEINE2, NCO content is 4.8% Example 3 86 PLA slices 3 14 parts P-PEG3, NCO content is 3.6% Example 4 84 PLA slices 2 16 parts P-PTINE4, NCO content is 3.1% Example 5 82 PLA slices 2 18 parts P-PCL5, NCO content is 2.3% Comparative Example 1 88 PLA slices 2 12 parts BASF 103C Comparative Example 2 88 PLA slices 2 12 parts P-PEG6, NCO content is 3.8% Comparative Example 3 88 PLA slices 2 12 parts P-PEG7, NCO content is 7.8% Comparative Example 4 88 PLA slices 2 12 parts P-PEG8, NCO content is 1.3% Comparative Example 5 100 PLA ​​slices 3 0 copies

[0172] Table 2

[0173]

[0174] -Indicates loss of mechanical properties and cannot be tested.

[0175] As shown in Table 2, after introducing the end NCO prepolymer containing carbodiimide structure modified by macromolecular polyol or macromolecular polyamine, the molecular weight of PLA filaments in Examples 1 to 5 was increased to more than 180,000, the dye uptake rate was more than 95%, the dry strength of PLA filaments was greater than 3cN / dtex, the dry elongation was more than 100%, and after being soaked in hot water for 1h and 24h, they still maintained high mechanical properties. Comparative Example 1 directly used BASF 103C, which had poor compatibility with PLA and could not effectively destroy the crystallization of PLA molecules, resulting in unstable spinning and low dye uptake. Comparative Example 2 used a macromolecular polyol-modified end NCO prepolymer containing no carbodiimide structure, which also increased the molecular weight of PLA filaments, but after 24h hydrolysis, the strength basically dropped to 0, and the problem of PLA filaments not being resistant to hydrolysis was still not solved. Comparative Example 3 increased the molecular weight of PLA filaments and solved the hydrolysis resistance problem of PLA filaments, but still had the problem of low elongation. The NCO content of the prepolymer used in Comparative Example 4 is too low, the reactive groups are too few, and the molecular weight of the PLA filament is improved too little. At the same time, the compatibility of the prepolymer and PLA is also poor, the spinning is unstable, and the carbodiimide group is introduced less, resulting in poor hydrolysis resistance. After immersion in 50°C hot water for 1h, the strength of the PLA filament in Comparative Example 5 is 2.14cN / detx, and the retention rate is 75.9%. After immersion in 50°C hot water for 24h, the PLA filament directly loses its mechanical strength and cannot be tested for performance. Therefore, it can be seen that the introduction of the carbodiimide structure can effectively improve the hydrolysis resistance of the PLA filament, so that the PLA does not lose its molecular weight during the spinning process, and maintains good mechanical strength during the later hot water immersion process. The introduction of the terminal NCO prepolymer containing the carbodiimide structure modified by macromolecular polyols and macromolecular polyamines can improve the hydrolysis resistance of the PLA filament, while improving the elongation at break, and improving the drapability and skin-friendliness of the PLA filament. Therefore, the technical solution of the present invention can effectively improve the washing stability of PLA filaments, and can be applied to clothing fabrics to solve the problem of poor durability of PLA clothing fabrics.

[0176] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A degradation-resistant enhanced PLA filament, characterized in that: The raw materials include, by weight, 80-90 parts of PLA and 10-20 parts of a terminal NCO prepolymer containing a carbodiimide structure.

2. The degradation-resistant enhanced PLA filament according to claim 1, characterized in that: The PLA structure contains one or more of terminal hydroxyl groups, terminal amino groups and terminal carboxyl groups; the weight average molecular weight of the PLA is greater than 30,000.

3. The degradation-resistant enhanced PLA filament according to claim 1, characterized in that: The terminal NCO prepolymer containing a carbodiimide structure is a macromolecular polyol-modified terminal NCO prepolymer containing a carbodiimide structure or a macromolecular polyamine-modified terminal NCO prepolymer containing a carbodiimide structure.

4. The degradation-resistant enhanced PLA filament according to claim 3, characterized in that: The preparation step of the macromolecular polyol-modified NCO prepolymer containing a carbodiimide structure comprises: mixing a macromolecular polyol and a polyisocyanate mixture containing carbodiimide-modified MDI at 70-80° C., stirring and reacting for 20-40 minutes, vacuuming for 2-4 hours, and then cooling to 40-50° C. and aging for 44-52 hours to obtain the macromolecular polyol-modified NCO prepolymer containing a carbodiimide structure; Alternatively, the preparation step of the macromolecular polyamine-modified end NCO prepolymer containing a carbodiimide structure includes: mixing a macromolecular polyamine and a polyisocyanate mixture containing carbodiimide-modified MDI at 40 to 50° C., stirring for reaction for 20 to 40 minutes, vacuuming for 2 to 4 hours, and then cooling to 30 to 40° C. and aging for 44 to 52 hours to obtain the macromolecular polyamine-modified end NCO prepolymer containing a carbodiimide structure.

5. The degradation-resistant enhanced PLA filament according to claim 4, characterized in that: The number average molecular weight of the macromolecular polyol is 800-4000, or the number average molecular weight of the macromolecular polyamine is 800-4000.

6. The degradation-resistant enhanced PLA filament according to claim 4, characterized in that: The NCO content of the polyisocyanate mixture containing carbodiimide-modified MDI is 25-35 wt %.

7. The degradation-resistant enhanced PLA filament according to claim 4, characterized in that: The molar number of NCO contained in the polyisocyanate mixture containing carbodiimide-modified MDI is 160 to 200% of the molar number of hydroxyl groups contained in the macromolecular polyol; Alternatively, the molar number of NCO contained in the polyisocyanate mixture containing carbodiimide-modified MDI is 160 to 200% of the molar number of amine groups contained in the macromolecular polyamine.

8. The degradation-resistant enhanced PLA filament according to claim 3, characterized in that: The NCO content of the macromolecular polyol-modified NCO-terminated prepolymer containing a carbodiimide structure is 2-6 wt %, or the NCO content of the macromolecular polyamine-modified NCO-terminated prepolymer containing a carbodiimide structure is 2-6 wt %.

9. The method for preparing the degradation-resistant enhanced PLA filament according to any one of claims 1 to 8, characterized in that: The following steps are involved: PLA is melted and plasticized to obtain a PLA melt; the PLA melt is pressurized and filtered to obtain a refined melt; a terminal NCO prepolymer containing a carbodiimide structure is preheated to 80-100° C. and then mixed with the refined melt to obtain a mixed melt; the mixed melt is spun and aged to obtain the degradation-resistant enhanced PLA filament.

10. Use of the degradation-resistant enhanced PLA filament according to any one of claims 1 to 8 in the preparation of clothing fabrics.

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