Heat-resistant and hydrolysis-resistant polylactic acid modified master batch, and preparation method and application thereof

Abstract

The application provides a heat-resistant and hydrolysis-resistant polylactic acid modified master batch as well as a preparation method and application thereof. The modified master batch comprises modified master batch A, modified master batch B and cellulose nanocrystals, and the modified master batch A comprises the following components in parts by mass: 70-80 parts of PLLA and 20-30 parts of PDLA; the modified master batch B comprises the following components: 20-30 parts of PLLA and 70-80 parts of PDLA. The modified fiber provided by the application has a long service life and excellent heat resistance and hydrolysis resistance, and has a long functional time, and can meet the use in the fields of daily necessities such as clothes, threads and fishing nets.

Description

Technical Field

[0001] This invention relates to the field of polymer materials technology, specifically to a heat-resistant and hydrolysis-resistant polylactic acid fiber modified masterbatch. Background Technology

[0002] Entering the 21st century, humanity faces an increasingly severe problem of fossil fuel depletion. Excessive energy consumption has also led to excessive emissions of gases such as CO2, causing global warming and various extreme climate changes. Therefore, on the one hand, people are striving to develop new green and renewable energy sources such as hydrogen, solar, and wind power; on the other hand, they are actively seeking new ways to reduce energy consumption.

[0003] Polylactic acid (PLA), a bioplastic synthesized from corn starch or biomass, has advantages such as high mechanical strength, good biocompatibility and biodegradability. As a representative material for the development of the biodegradable materials industry, it has attracted much attention and has been reported to have broad application research in packaging films, textile fibers, medical stents, straws, tableware and other fields.

[0004] In these application areas, polylactic acid (PLA) fibers used in the textile fiber industry are made from PLA through polycondensation and melt spinning. PLA fiber is a synthetic fiber whose raw materials are readily available and easy to cultivate, and whose waste is biodegradable in nature. It decomposes into carbon dioxide and water in soil or seawater through microbial action. When burned, it does not emit toxic gases or cause pollution, making it a sustainable and eco-friendly fiber. Its fabrics have a good hand feel, good drape, and UV resistance, with low flammability and excellent processing properties, making them suitable for various fashion apparel, casual wear, and hygiene products.

[0005] A serious problem exists in the application of polylactic acid (PLA) fibers and their textiles: although they can be used normally at room temperature, once the ambient temperature rises above the glass transition temperature (Tg≈57℃) of PLA, the performance of PLA fibers and their products deteriorates sharply, and they become deformed and sticky, limiting their application range. In addition, PLA fibers are prone to hydrolysis, which leads to an increase in carboxyl groups, and the performance of PLA fibers also deteriorates sharply. Therefore, solving the heat resistance and hydrolysis problems of PLA fibers is the key to realizing the large-scale application of PLA fibers in the clothing industry. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a heat-resistant and hydrolysis-resistant polylactic acid modified masterbatch, its preparation method, and its application.

[0007] In a first aspect, the present invention provides a heat-resistant and hydrolysis-resistant polylactic acid modified masterbatch, said modified masterbatch comprising modified masterbatch A, modified masterbatch B, and cellulose nanocrystals, in parts by mass.

[0008] The modified masterbatch A comprises the following components:

[0009] PLLA 70-80 servings (e.g., 70, 72, 74, 76, 78, 80 servings);

[0010] and

[0011] PDLA 20-30 doses (e.g., 20, 22, 24, 26, 28, or 30 doses).

[0012] The modified masterbatch B comprises the following components:

[0013] PLLA 20-30 servings (e.g., 20 servings, 22 servings, 24 servings, 26 servings, 28 servings, 30 servings);

[0014] and

[0015] PDLA 70-80 copies (e.g., 70, 72, 74, 76, 78, 80 copies).

[0016] According to some embodiments of the modified masterbatch of the present invention, modified masterbatch A and modified masterbatch B further include a lubricant and an antioxidant.

[0017] According to some embodiments of the modified masterbatch of the present invention, the lubricant is 0.5 to 5 parts, for example, 0.5 parts, 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts, or 5 parts.

[0018] According to some embodiments of the modified masterbatch of the present invention, the lubricant is 0.5 to 1.5 parts.

[0019] According to some embodiments of the modified masterbatch of the present invention, the antioxidant is 0.5 to 5 parts, for example, 0.5 parts, 1 part, 1.5 parts, 2 parts, 2.5 parts, 3 parts, 3.5 parts, 4 parts, 4.5 parts, or 5 parts.

[0020] According to some embodiments of the modified masterbatch of the present invention, the antioxidant is 0.5 to 1.5 parts.

[0021] In some embodiments of the modified masterbatch according to the present invention, the lubricant is vinyl bis-stearamide.

[0022] According to some embodiments of the modified masterbatch of the present invention, the antioxidant is BASF 1010.

[0023] According to some embodiments of the modified masterbatch of the present invention, the mass ratio of modified masterbatch A to modified masterbatch B in the modified masterbatch is (1:9) to (9:1), for example, 1:9, 2:8, 3:7, 4:6, 5:5, 6:4, 7:3, 8:2, 9:1.

[0024] According to some embodiments of the modified masterbatch of the present invention, the content of the cellulose nanocrystals in the modified masterbatch is 1.5% to 2.5% by mass, for example, 1.5%, 2%, or 2.5%.

[0025] According to some embodiments of the modified masterbatch of the present invention, the poly-L-lactic acid (PLLA) has an optical purity of 95% to 99.5%, a weight-average molecular weight of 50,000 to 300,000, and a melt flow rate (MFR) of 5 to 15 g / 10 min at 190°C and a pressure of 2.16 kg weight.

[0026] According to some embodiments of the modified masterbatch of the present invention, the polydextral lactic acid (PDLA) has an optical purity of 95% to 99.5%, a weight-average molecular weight of 50,000 to 300,000, and a melt flow rate (MFR) of 5 to 15 g / 10 min at 190°C and a pressure of 2.16 kg weight.

[0027] According to some embodiments of the modified masterbatch of the present invention, the cellulose nanocrystals are prepared by acid hydrolysis, wherein the acid solution used in the preparation is perchloric acid solution, and the average particle size of the obtained cellulose nanocrystals is 30 nm to 70 nm.

[0028] A second aspect of the present invention provides a method for preparing heat-resistant and hydrolysis-resistant polylactic acid modified masterbatch, comprising the following steps:

[0029] (1) Mix modified masterbatch A and modified masterbatch B; then contact with additives and cellulose nanocrystals and knead to obtain component C;

[0030] (2) Component C is granulated and dried to obtain the polylactic acid modified masterbatch.

[0031] According to some embodiments of the preparation method of the present invention, in step (1), the mixing temperature is 155℃~170℃, for example 155℃, 160℃, 165℃, 170℃.

[0032] According to some embodiments of the preparation method of the present invention, the mixing time is 10 to 30 minutes, for example, 10 minutes, 15 minutes, 20 minutes, 25 minutes, or 30 minutes.

[0033] According to some embodiments of the preparation method of the present invention, in step (2), the granulation is carried out by using a single or twin screw extruder.

[0034] According to some embodiments of the preparation method of the present invention, the temperatures of the first, second, third, and fourth zones of the single screw in the single-twin screw extruder are 190–200°C, 190–195°C, 195–200°C, and 190–200°C, respectively.

[0035] According to some embodiments of the preparation method of the present invention, the temperatures of the twin screw zones one, two, three, four, five and six of the twin screw extruder are 160-180℃, 190-195℃, 195-200℃, 190-200℃, 195-200℃ and 190-200℃ respectively.

[0036] According to some embodiments of the preparation method of the present invention, the particle size of the modified masterbatch is 2 to 5 mm, for example 2 mm, 3 mm, 4 mm, 5 mm, and / or the water content of the modified masterbatch is ≤500 ppm.

[0037] According to some embodiments of the preparation method of the present invention, the mass ratio of modified masterbatch A to modified masterbatch B in the modified masterbatch is (1:9) to (9:1) by mass parts.

[0038] According to some embodiments of the preparation method of the present invention, the content of the cellulose nanocrystals in the modified masterbatch is 1.5-2.5% by mass percentage;

[0039] According to some embodiments of the preparation method of the present invention, the modified masterbatch A comprises the following components: 70-80 parts of PLLA and 20-30 parts of PDLA;

[0040] According to some embodiments of the preparation method of the present invention, the modified masterbatch B comprises the following components: 20-30 parts of PLLA and 70-80 parts of PDLA;

[0041] According to some embodiments of the preparation method of the present invention, the additive is selected from any one or more of plasticizers, ultraviolet absorbers, antistatic agents, lubricants, and anti-hydrolysis agents.

[0042] According to some embodiments of the preparation method of the present invention, the content of the auxiliary agent in the modified masterbatch is 2-6% by mass percentage.

[0043] According to some embodiments of the preparation method of the present invention, the mass ratio of the plasticizer, ultraviolet absorber, antistatic agent, lubricant and anti-hydrolysis agent is 1:1:1:0.5:0.5.

[0044] In a third aspect, the present invention provides a polylactic acid modified fiber, which is prepared from the modified masterbatch described in the first aspect of the present invention or the modified masterbatch obtained by the preparation method of the second aspect of the present invention.

[0045] The polylactic acid modified fiber according to the present invention is prepared by means of: feeding the modified masterbatch into a spinning machine for melt spinning to obtain the polylactic acid modified fiber.

[0046] According to the polylactic acid modified fiber of the present invention, the spinning temperature in the melt spinning is 200-230°C, for example, 200°C, 210°C, 220°C, or 230°C.

[0047] According to the polylactic acid modified fiber of the present invention, the temperature for stretching and orientation during melt spinning is 80°C to 90°C, for example, 80°C, 82°C, 85°C, 86°C, 88°C, or 90°C.

[0048] According to the polylactic acid modified fiber of the present invention, in the melt spinning process, the stretching ratio of the stretching orientation is 3.5-4.5 times, for example 3.5 times, 3.8 times, 4 times, 4.2 times, and 4.5 times.

[0049] A fourth aspect of the present invention provides the application of the modified masterbatch described in the first aspect of the present invention or the modified masterbatch obtained by the preparation method of the second aspect of the present invention in daily consumer goods.

[0050] According to some embodiments of the application described in this invention, the daily necessities are clothing, thread, or fishing nets.

[0051] The beneficial effects of the present invention are as follows: The modified masterbatch provided by the present invention improves the orientation degree of polylactic acid modified fiber, thereby improving the crystallinity and elongation at break of polylactic acid modified fiber. At the same time, the polylactic acid modified fiber of the present invention also has significant improvements in heat resistance and hydrolysis resistance, which can meet the performance requirements of daily necessities such as clothing, yarn, and fishing nets. Detailed Implementation

[0052] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. The specific embodiments described herein are for illustrative purposes only and are not intended to limit the invention in any way. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of this disclosure. Such structures and techniques have also been described in many publications.

[0053] Preparation of modified masterbatch A and modified masterbatch B

[0054] In the various embodiments and comparative examples of this invention, the modified masterbatch A uses the following material and mass ratio: PLLA:PDLA:lubricant (vinyl bis-stearamide):antioxidant (BASF 1010) = 75:25:0.5:0.5. The modified masterbatch B uses the following material and mass ratio: PLLA:PDLA:lubricant:antioxidant = 25:75:0.5:0.5. The PLLA has an optical purity of 98%, a weight-average molecular weight of 200,000, and a melt flow rate of 10 g / 10 min at 190°C and 2.16 kg weight pressure. The PDLA also has an optical purity of 98%, a weight-average molecular weight of 200,000, and a melt flow rate of 10 g / 10 min at 190°C and 2.16 kg weight pressure.

[0055] Modified masterbatch A and modified masterbatch B were prepared according to the following method:

[0056] 1) Dry PLLA and PDLA at -0.1MPa and 80℃ for 30 minutes;

[0057] 2) Place the dried PLLA and PDLA into the high-speed mixer, start the high-speed mixer, and then slowly add the lubricant and antioxidant sequentially from the auxiliary material port. After stirring for 2 minutes, pour out the mixed material and record it as component A / or component B.

[0058] 3) Component A or component B is melt-extruded and granulated using a single-screw or twin-screw extruder. The single screw in the extruder is divided into four zones: zones 1-4 have temperatures of 190–200℃, 190–195℃, 195–200℃, and 190–200℃, respectively. The twin screw in the extruder is divided into six zones: zones 1-6 have temperatures of 160–180℃, 190–195℃, 195–200℃, and 190–200℃, respectively. At 00℃, 190~200℃, 195~200℃, and 190~200℃, during the granulation process, component A or component B is first placed in the hopper. Through the operation of the feeder, component A or component B is slowly introduced from the hopper into the single screw. After passing through the single screw, component A or component B becomes molten. Then, it is extruded through the twin screws. After cooling and pelletizing, quasi-modified masterbatch A or quasi-modified masterbatch B is obtained.

[0059] 4) Place the quasi-modified masterbatch A or quasi-modified masterbatch B into a vibrating screen and screen it to obtain 2-5 mm quasi-modified masterbatch A or quasi-modified masterbatch B. Then, put the screened quasi-modified masterbatch A or quasi-modified masterbatch B into an oven for drying. The drying method is vacuum drying with a vacuum degree of -0.09 to -0.1 MPa, a drying temperature of 70 to 90℃, and a drying time of 4 to 6 hours. After drying until the moisture content is less than 500 ppm, modified masterbatch A or modified masterbatch B is obtained.

[0060] Preparation of polylactic acid modified masterbatch

[0061] In the embodiments and comparative examples of this invention, the formulations of modified masterbatch A and modified masterbatch B of polylactic acid modified masterbatch were added according to Table 1. The additives in the polylactic acid fiber modified masterbatch were a mixture of plasticizer, ultraviolet absorber, antistatic agent, lubricant, and anti-hydrolysis agent in a mass ratio of 1:1:1:0.5:0.5. The plasticizer was triethyl citrate, the ultraviolet absorber was UV-328, the antistatic agent was styrene-based resin, the lubricant was polyethylene wax, and the anti-hydrolysis agent was SAG-005. The content of additives in the polylactic acid modified masterbatch was 4%. The preparation method of polylactic acid modified masterbatch is as follows:

[0062] 1) Place the dried modified masterbatch A and modified masterbatch B into a high-speed mixer, start the high-speed mixer, stir for 2 minutes, and then pour out the mixed material, which is recorded as component C;

[0063] 2) Component C, additives and cellulose nanocrystals with a particle size of 50 nm are put into a mixer and mixed at 155℃~170℃ for 20 min to obtain component D; the cellulose nanocrystals used in this application are prepared by acid hydrolysis and the acid used is perchloric acid.

[0064] 3) Component D is added to a single-screw and twin-screw extruder for extrusion granulation. The single screw in the extruder is divided into four zones: zones one, two, three, and four, with temperatures of 190–200℃, 190–195℃, 195–200℃, and 190–200℃ respectively. The twin screw in the extruder is divided into six zones: zones one, two, three, four, five, and six, with temperatures of 160–180℃, 1… At temperatures of 90–195℃, 195–200℃, 190–200℃, 195–200℃, and 190–200℃, during the granulation process, component D is first placed in a hopper. Through the operation of the feeder, component D is slowly introduced from the hopper into a single screw. After passing through the single screw, component D becomes molten. Then, it is extruded through a twin screw. After cooling and pelletizing, quasi-modified masterbatch D is obtained.

[0065] 4) Place the quasi-modified masterbatch D into a vibrating screen and screen it to obtain 2-5 mm quasi-modified masterbatch D. Then, put the screened quasi-modified masterbatch D into an oven for drying. The drying method is vacuum drying with a vacuum degree of -0.09 to -0.1 MPa, a drying temperature of 70 to 90°C, and a drying time of 4 to 6 hours. After drying until the moisture content is less than 500 ppm, polylactic acid fiber modified masterbatch is obtained.

[0066] Preparation of polylactic acid modified fibers

[0067] Example 1

[0068] In this embodiment, modified masterbatch A and modified masterbatch B are added according to Table 1 in the polylactic acid modified masterbatch, and the mass content of cellulose nanocrystals in the modified masterbatch is 2%, and then they are mixed and granulated.

[0069] After the above granulation is completed, the polylactic acid modified masterbatch of this embodiment is obtained. The polylactic acid modified masterbatch of this embodiment is fed into a spinning machine for melt spinning to obtain polylactic acid modified fiber. The spinning temperature is 230°C. Then, stretching and orientation are performed at a temperature of 85°C and a stretching ratio of 4 times.

[0070] Examples 2 to 9

[0071] In Examples 2 to 9, modified masterbatch A and modified masterbatch B in polylactic acid modified masterbatch were added according to Table 1, and the mass content of cellulose nanocrystals in the modified masterbatch was 2%. The subsequent granulation and spinning processes were as described in Example 1.

[0072] Comparative Example 1

[0073] In this comparative example, modified masterbatch A and modified masterbatch B were added according to Table 1 in the polylactic acid modified masterbatch, and the mass content of cellulose nanocrystals in the modified masterbatch was 3%. The subsequent granulation and spinning processes were as described in Example 1.

[0074] Comparative Example 2

[0075] In this comparative example, modified masterbatch A and modified masterbatch B were added according to Table 1 in the polylactic acid modified masterbatch, and the mass content of cellulose nanocrystals in the modified masterbatch was 1%. The subsequent granulation and spinning processes were as described in Example 1.

[0076] Comparative Example 3

[0077] The difference between this comparative example and Example 1 is that the polylactic acid modified masterbatch does not contain modified masterbatch A, and the subsequent preparation method is the same as that in Example 1.

[0078] Comparative Example 4

[0079] The difference between this comparative example and Example 1 is that the polylactic acid modified masterbatch does not contain modified masterbatch B, and the subsequent preparation method is the same as that in Example 1.

[0080] Comparative Example 5

[0081] The difference between this comparative example and Example 1 is that the polylactic acid modified masterbatch does not contain cellulose nanocrystals, and the subsequent preparation method is the same as that in Example 1.

[0082] Comparative Example 6

[0083] The difference between this comparative example and Example 1 is that the stretching and orientation temperature is 75°C during the stretching and orientation process, and the subsequent preparation method is the same as that in Example 1.

[0084] Comparative Example 7

[0085] The difference between this comparative example and Example 1 is that the stretching and orientation temperature is 95°C during the stretching and orientation process, and the subsequent preparation method is the same as that in Example 1.

[0086] Comparative Example 8

[0087] The difference between this comparative example and Example 1 is that the stretching ratio is 3 times during the stretching and orientation process, and the subsequent preparation method is the same as that of Example 1.

[0088] Comparative Example 9

[0089] The difference between this comparative example and Example 1 is that the stretching ratio is 5 times during the stretching and orientation process, and the subsequent preparation method is the same as that of Example 1.

[0090] Comparative Example 10

[0091] The difference between this comparative example and Example 1 is that the acid solution used to prepare cellulose nanocrystals is a sulfuric acid solution, and the subsequent preparation method is the same as that in Example 1.

[0092] Comparative Example 11

[0093] The difference between this comparative example and Example 1 is that the cellulose nanocrystals used in this comparative example have a particle size of 80 nm, and the subsequent preparation method is the same as that in Example 1.

[0094] Comparative Example 12

[0095] The difference between this comparative example and Example 1 is that the cellulose nanocrystals used in this comparative example have a particle size of 20 nm, and the subsequent preparation method is the same as that in Example 1.

[0096] Table 1

[0097]

[0098]

[0099] Note: The types and proportions of additives in the polylactic acid modified masterbatches of the above embodiments and comparative examples are the same. The specific mass ratio is plasticizer: UV absorber: antistatic agent: lubricant: antihydrolysis agent = 1:1:1:0.5:0.5. The plasticizer is triethyl citrate, the UV absorber is UV-328, the antistatic agent is styrene-based resin, the lubricant is polyethylene wax, and the antihydrolysis agent is SAG-005.

[0100] The polylactic acid modified fibers prepared in Examples 1-9 and the polylactic acid modified fibers prepared in Comparative Examples 1-12 were subjected to performance testing. The main performance indicators tested included the heat resistance and hot water hydrolysis resistance of the polylactic acid modified fibers.

[0101] 1) Heat resistance test of polylactic acid modified fiber

[0102] The heat resistance of polylactic acid modified fibers is usually measured by the fiber's heat shrinkage rate. The detection methods for heat shrinkage rate are generally divided into dry heat shrinkage and wet heat shrinkage. This invention uses dry heat shrinkage for testing. The testing standard is GB / T 6505-2017. The heat treatment temperature is 150℃ and 180℃, and the heat treatment time is 10min. The test results are shown in Table 2.

[0103] Table 2

[0104]

[0105] As shown in Table 2, the heat shrinkage rate of each embodiment of the present invention is significantly lower than that of the comparative example. Therefore, the polylactic acid modified fiber of the present invention has good heat resistance.

[0106] 2) Test of the resistance to hot water hydrolysis of polylactic acid modified fibers

[0107] The method for measuring the hot water hydrolysis resistance of polylactic acid modified fibers is as follows: the polylactic acid modified fibers are placed in a constant temperature and humidity chamber and aged for 54 hours at 85℃ and 85%RH (calculated according to the Hallberg Peck model, this is approximately equivalent to three years of use at 23℃ and 50%RH (room temperature)). The tensile properties of the aged fibers are compared with the initial tensile properties to determine the hot water hydrolysis resistance of the fibers. For accuracy, five polylactic acid modified fibers are tested for each example and comparative example, and the average value is taken. The test results are shown in Table 3.

[0108] Table 3

[0109] Example 1 84 Example 2 86 Example 3 91 Example 4 89 Example 5 87 Example 6 85 Example 7 83 Example 8 82 Example 9 80 Comparative Example 1 62 Comparative Example 2 64 Comparative Example 3 44 Comparative Example 4 47 Comparative Example 5 58 Comparative Example 6 52 Comparative Example 7 48 Comparative Example 8 50 Comparative Example 9 67 Comparative Example 10 45 Comparative Example 11 68 Comparative Example 12 72

[0110] As shown in Table 3, the ratio values ​​of Examples 1 to 9 of the present invention are much higher than those of the respective pairs, indicating that the polylactic acid modified fiber of the present invention has good resistance to hot water hydrolysis.

[0111] The test results above show that the modified fiber provided by this invention has a long service life and excellent heat resistance and hydrolysis resistance, and its functionality lasts for a long time, which can meet the requirements for use in daily necessities such as clothing, yarn, and fishing nets.

[0112] The preferred embodiments of the present invention have been described in detail above; however, the present invention is not limited thereto. Within the scope of the inventive concept, various simple modifications can be made to the technical solutions of the present invention, including combinations of various technical features in any other suitable manner. These simple modifications and combinations should also be considered as the content disclosed in the present invention and are all within the protection scope of the present invention.

Claims

1. A heat-resistant and hydrolysis-resistant polylactic acid modified masterbatch, comprising modified masterbatch A, modified masterbatch B, and cellulose nanocrystals, in parts by mass, The modified masterbatch A comprises the following components: PLLA 70-80 servings; and PDLA 20-30 copies The modified masterbatch B comprises the following components: PLLA 20-30 servings; and 70-80 PDLA doses; By mass parts, in the heat-resistant and hydrolysis-resistant polylactic acid modified masterbatch, the mass ratio of modified masterbatch A to modified masterbatch B is (1:9) to (9:1). The cellulose nanocrystals are present in the heat-resistant and hydrolysis-resistant polylactic acid modified masterbatch at a mass percentage of 1.5-2.5%, and the average particle size of the cellulose nanocrystals is 30 nm-70 nm. The cellulose nanocrystals are prepared by acid hydrolysis, and the acid used in the acid hydrolysis is perchloric acid.

2. The heat-resistant and hydrolysis-resistant polylactic acid modified masterbatch according to claim 1, characterized in that, The modified masterbatch A and modified masterbatch B also include lubricants and antioxidants.

3. The heat-resistant and hydrolysis-resistant polylactic acid modified masterbatch according to claim 2, characterized in that, By weight parts The lubricant is 0.5-5 parts; the antioxidant is 0.5-5 parts; And / or, the lubricant is vinyl bis-stearamide; and / or, the antioxidant is BASF 1010.

4. The heat-resistant and hydrolysis-resistant polylactic acid modified masterbatch according to claim 3, characterized in that, By weight parts The lubricant is 0.5 to 1.5 parts; the antioxidant is 0.5 to 1.5 parts.

5. The heat-resistant and hydrolysis-resistant polylactic acid modified masterbatch according to any one of claims 1 to 4, characterized in that, The PLLA has an optical purity of 95%–99.5%, a weight-average molecular weight of 50,000–300,000, and a melt flow rate of 5–15 g / 10 min at 190°C and a pressure of 2.16 kg weight; and / or The PDLA has an optical purity of 95%–99.5%, a weight-average molecular weight of 50,000–300,000, and a melt flow rate of 5–15 g / 10 min at 190°C and a pressure of 2.16 kg weight.

6. A method for preparing the heat-resistant and hydrolysis-resistant polylactic acid modified masterbatch according to any one of claims 1-5, comprising the following steps: (1) Mix modified masterbatch A and modified masterbatch B; then contact with additives and cellulose nanocrystals and knead to obtain component C; (2) Component C is granulated and dried to obtain the heat-resistant and hydrolysis-resistant polylactic acid modified masterbatch; The cellulose nanocrystals are present in the heat-resistant and hydrolysis-resistant polylactic acid modified masterbatch at a mass percentage of 1.5-2.5%, and the average particle size of the cellulose nanocrystals is 30 nm to 70 nm.

7. The preparation method according to claim 6, characterized in that, In step (1), the mixing temperature is 155℃~170℃, and / or The mixing time is 10-30 minutes.

8. The preparation method according to claim 6, characterized in that, In step (2), the granulation is carried out using a single or twin screw extruder.

9. The preparation method according to claim 8, characterized in that, The temperatures of the single screw in the single-twin screw extruder in zones one, two, three, and four are 190–200℃, 190–195℃, 195–200℃, and 190–200℃, respectively.

10. The preparation method according to claim 9, characterized in that, The temperatures of the twin screw extruder in the single and twin screw extruder in zones one, two, three, four, five, and six are 160–180℃, 190–195℃, 195–200℃, 190–200℃, 195–200℃, and 190–200℃, respectively.

11. The preparation method according to claim 6, characterized in that, The heat-resistant and hydrolysis-resistant polylactic acid modified masterbatch has a particle size of 2-5 mm, and / or the moisture content of the heat-resistant and hydrolysis-resistant polylactic acid modified masterbatch is ≤500 ppm.

12. The preparation method according to claim 6, characterized in that, The additives are selected from any one or more of plasticizers, ultraviolet absorbers, antistatic agents, lubricants, and anti-hydrolysis agents.

13. The preparation method according to claim 6, characterized in that, The content of the additive in the heat-resistant and hydrolysis-resistant polylactic acid modified masterbatch is 2-6% by mass percentage.

14. A polylactic acid modified fiber, which is prepared from the heat-resistant and hydrolysis-resistant polylactic acid modified masterbatch according to any one of claims 1-5 or the heat-resistant and hydrolysis-resistant polylactic acid modified masterbatch obtained by any one of claims 6-13.

15. The polylactic acid modified fiber according to claim 14, characterized in that, The method for preparing the polylactic acid modified fiber includes: feeding the heat-resistant and hydrolysis-resistant polylactic acid modified masterbatch into a spinning machine for melt spinning to obtain the polylactic acid modified fiber. In the melt spinning, the spinning temperature is 200~230℃, the stretching and orientation temperature is 80℃~90℃, and the stretching ratio of the stretching and orientation is 3.5~4.5 times.

16. The application of the heat-resistant and hydrolysis-resistant polylactic acid modified masterbatch according to any one of claims 1-5 or the heat-resistant and hydrolysis-resistant polylactic acid modified masterbatch obtained by any one of claims 6-13 in daily consumer goods.

17. The application of the heat-resistant and hydrolysis-resistant polylactic acid modified masterbatch according to claim 16 in daily necessities, characterized in that, The daily necessities mentioned are clothing, thread, or fishing nets.

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