PLA modified material as well as preparation method and application thereof

Abstract

The invention discloses a PLA modified material as well as a preparation method and application thereof, and belongs to the field of biodegradation. Aiming at the problems of short shelf life and insufficient performance of the existing PLA material product, the invention provides a PLA modified material which comprises the following components in parts by weight: 50-70 parts of PLA; 20 to 50 parts of an inorganic material; 3-5 parts of a plasticizer; 0.01 to 1 part of a compatilizer; 0.1 to 1 part of a lubricant; 0.1 to 1 part of an antioxidant; the invention relates to a PBST polymer, a preparation method of the PBST polymer is improved, raw materials for forming the PBST polymer are added in sequence, and one of the raw materials is recycled. According to the invention, the PBST polymer and the PLA are blended, and the complementarity of the PBST polymer and the PLA is fully utilized to obtain the composite material with high strength and good toughness; the PBST polymer is used for toughening the PLA, so that the use performance of the PLA material during freezing or cold storage is improved, the crystallization property and heat resistance of the PLA material are promoted, the overall performance of the PLA material is improved, and the shelf life of a PLA product can be remarkably prolonged.

Description

Technical Field

[0001] The invention belongs to the technical field of biodegradation, and more specifically, relates to a PLA modified material, a preparation method and an application thereof. Background Art

[0002] Polylactic acid (PLA), as a widely used biodegradable aliphatic polyester, can be sustainably produced by fermentation of starchy plant microorganisms. It has received widespread attention in the past 20 years and is believed to be able to replace petroleum-based plastics in food packaging, biomedicine, and smart textiles. PLA has good processing properties and excellent mechanical strength, Young's modulus, optical transparency, and biodegradability, but it also has some disadvantages (high brittleness, slow crystallization rate, and low heat deformation temperature), which limits the development and application of PLA.

[0003] In order to improve the insufficient performance of PLA, a simple and economical blending modification method is often used. In PLA straws, PBS, PBAT, etc. are mainly used for blending modification to improve the performance of PLA straws, but they still cannot meet the use requirements. PLA is hard and brittle, with a slow crystallization rate, which leads to a short shelf life of PLA straw products and is difficult to meet the actual environment. If the storage time or transportation time is too long, the straws are prone to brittleness, resulting in unusability, which has always been a common headache in the industry. PBS is used for modification. PBS has the advantages of convenient processing, good heat resistance, and a heat deformation temperature of more than 100°C. However, PBS has the disadvantages of low molecular weight, poor fluidity, low body strength, and insufficient toughness. As a result, although PLA straws meet the requirements for high-temperature use, the toughness does not meet the requirements, which makes it easier to cause the straws to become brittle and have a short shelf life. At the same time, most PLA straw customers require that PBAT ingredients should not be contained, mainly because PBAT is prone to precipitate small molecules at low temperatures.

[0004] Corresponding improvements have also been made to the above problems, such as China Patent Publication No. CN118240346A, published on June 25, 2024, which discloses a PBS / PLA fully biodegradable material for hot drink straws and its preparation method and application. The present invention uses grafted PDLA-g-PBS as a compatibilizer to prepare a PBS / PLA / PDLA-g-PBS blended alloy. During melt blending, the grafted PDLA-g-PBS improves the interfacial force between PBS and PLA, thereby improving the mechanical properties of the PBS / PLA fully biodegradable material. With the grafted PDLA-g-PBS as a compatibilizer, the PLA segment can be in-situ compounded with the PDLA segment to form SC crystals. The tiny SC crystals can be used as crystal nuclei to improve the crystallization ability of the blended alloy, thereby significantly improving the heat resistance of the alloy. The shortcomings of this patent are that although the heat resistance is greatly improved, the overall cost is increased and when the grafted material is used as a compatibilizer, the active groups in its molecules may react with other components in the blending system, resulting in unexpected chemical reactions or degradation, thereby affecting the performance of the final product.

[0005] Another example is Chinese patent application number CN202210224645.8, published on May 6, 2022. The patent discloses a biodegradable, high-temperature resistant polylactic acid straw, including the following components by weight: 1-50 parts of PLLA, 50-95 parts of PBS, 0.01-10 parts of compatibilizer, 0.01-5 parts of dispersant, 0.01-5 parts of plasticizer, 0.01-5 parts of coupling agent, 0.01-5 parts of chain extender and 1-50 parts of filler. Among them, the compatibilizer promotes the compatibility between the raw materials; during the extrusion molding process, PLLA will generate quasi-orthorhombic crystals and orthorhombic crystals during crystallization; PBS in the raw material can be used as a PLLA nucleating agent to increase the crystallization rate, and further crystallization without annealing, simplifying the preparation process; at the same time, it can also optimize the crystal structure of the straw, thereby improving the heat resistance of the straw. The shortcoming of this patent is that: the compatibility of the blend alloy is improved to a certain extent, but the heat resistance of the blend alloy still does not reach the ideal level. Summary of the invention

[0006] 1. Problems to be solved In view of the problem that the products of existing PLA materials have a short shelf life and insufficient performance, the present invention provides a PLA modified material, a preparation method and an application. The present invention blends PBST polymer with PLA to fully utilize the complementarity of the two to obtain a composite material with both high strength and good toughness; PLA is toughened by PBST polymer to improve the performance of PLA materials when frozen or refrigerated, promote the crystallization performance and heat resistance of PLA materials, improve the overall performance of PLA materials, and significantly extend the shelf life of PLA products.

[0007] 2. Technical solution To solve the above problems, the present invention adopts the following technical solutions.

[0008] A PLA modified material comprises the following components by weight: PLA: 50~70 parts; Inorganic materials: 20~50 parts; Plasticizer: 3~5 parts; Compatibilizer: 0.01~1 part; Lubricant: 0.1~1 part; 0.1~1 part of antioxidant; PBST polymer: 0-30 parts; wherein the preparation method of PBST polymer is as follows: Esterification reaction: mixing and heating three raw materials, namely, a catalyst, one or more C2-C10 aliphatic diols or alicyclic diols, and C4-C20 aliphatic dibasic acids or their ester derivatives to obtain a mixed reactant; Polycondensation reaction: Aromatic dibasic acid or its ester derivative is added to the mixed reactants and heated, and polycondensation reaction is carried out under vacuum conditions to obtain PBST polymer.

[0009] Furthermore, the catalyst is rare earth-tetrabutyl titanate; one or more of the C2-C10 aliphatic diols or alicyclic diols are 1,4-butanediol; the C4-C20 aliphatic dibasic acid or its ester derivative is succinic acid; and the aromatic dibasic acid or its ester derivative is terephthalic acid.

[0010] Furthermore, the molar ratio of 1,4-butanediol:succinic acid:terephthalic acid is: (0~2):(0~2):(1~3).

[0011] Furthermore, in the preparation method of the PBST polymer, during the polycondensation reaction, the 1,4-butanediol volatilized during the reaction is recovered and condensed and then re-enters the polycondensation reaction, and the non-volatile 1,4-butanediol is extracted before the vacuum operation.

[0012] Furthermore, the inorganic material is activated talc.

[0013] Furthermore, the plasticizer is a mixture of one or more of TBC, ATBC, and polyethylene glycol; and the lubricant is a mixture of one or more of oleamide, erucamide, and EBS.

[0014] Furthermore, the compatibilizer is any one of PP-G-MAH, PLA-G-MAH, cyanate ester, and 3510P.

[0015] Furthermore, the antioxidant is one of antioxidant 215, antioxidant 264, antioxidant 1010, antioxidant 168 and antioxidant 164, or a combination of two or more thereof.

[0016] A method for preparing a PLA modified material as described in any one of the above, comprising the following steps: S1: PLA, PBST polymer, compatibilizer and plasticizer are mixed to obtain a premix; S2: adding the inorganic material, the lubricant and the antioxidant to the premix and mixing them to obtain a final mixture; S3: The final mixture is discharged, extruded and pelletized to obtain a PLA modified material.

[0017] An application of the PLA modified material as described in any one of the above items, wherein the PLA modified material is used for straws.

[0018] 3. Beneficial effects Compared with the prior art, the present invention has the following beneficial effects: The invention solves the problem of insufficient toughness and easy aging of PBS by blending and modifying PLA and PBST polymer, thereby extending the shelf life of PLA modified materials; the PBST polymer belongs to a fat-aromatic polymer and can meet the food safety contact requirements; the preparation method of the PBST polymer is innovated to make it not only biodegradable but also have excellent thermodynamic properties and processability, so that the complementarity between PLA and PBST polymer is enhanced, and the complementarity between the two is fully utilized to obtain a composite material with both high strength and good toughness; at the same time, PLA is toughened by the PBST polymer, the use performance of the PLA material during freezing or refrigeration is improved, and the crystallization performance and heat resistance of the PLA material are promoted, thereby improving the overall performance of the PLA material; and the shelf life of the PLA product can be significantly extended by the mutual cooperation between various raw materials. DETAILED DESCRIPTION

[0019] The present invention is further described below in conjunction with specific embodiments.

[0020] A PLA modified material comprises the following components by weight: PLA: 50-70 parts; PLA (polylactic acid) is a widely used biodegradable aliphatic polyester that can be sustainably produced through fermentation of starch plant microorganisms. It has attracted widespread attention in recent years and is believed to be able to replace petroleum-based plastics in areas such as food packaging, biomedicine and smart textiles; Inorganic materials: 20-50 parts; Inorganic materials are dispersed in the PLA matrix and become nucleation sites, increasing the nucleation density and thus promoting the crystallization process of PLA; the crystallization rate of PLA is increased and the crystallinity is increased accordingly, which helps to improve the heat resistance, mechanical properties and dimensional stability of PLA; Plasticizer: 3~5 parts; Plasticizer can slightly reduce the intermolecular forces in most of the system. When the polymer is deformed, the molecular chains can slide and rotate with each other, thereby reducing the internal friction between polymer molecules and increasing fluidity; Compatibilizer: 0.01~1 part; the compatibilizer can not only improve the compatibility of PLA and PBST polymer, but also increase the molecular weight of PLA and PBST polymer in the system, and further consume the terminal carboxyl and terminal hydroxyl content in the system; Lubricant: 0.1~1 part; Lubricant can not only reduce the friction between polymer molecules, but also reduce the friction between polymer and the surface of processing equipment, thereby reducing the flow resistance of the melt, reducing the melt viscosity, improving the fluidity of the melt, avoiding the adhesion of the melt to the equipment, and improving the surface finish of the product; 0.1~1 part of antioxidant; the antioxidant protects the polymer in the system, and can protect PLA, preventing the thermal oxidation degradation of PLA and PBST; PBST polymer: 0-30 parts; wherein the preparation method of PBST polymer is as follows: Esterification reaction: mixing and heating three raw materials, namely, a catalyst, one or more C2-C10 aliphatic diols or alicyclic diols, and C4-C20 aliphatic dibasic acids or their ester derivatives to obtain a mixed reactant; Polycondensation reaction: Aromatic dibasic acid or its ester derivative is added to the mixed reactant and heated, and polycondensation reaction is carried out under vacuum conditions to obtain PBST polymer. The PBST polymer prepared by this preparation method not only has excellent thermodynamic properties, but also has biodegradability, can toughen PLA, improve the performance of PLA materials when frozen or refrigerated, and can promote the crystallization performance and heat resistance of PLA materials.

[0021] The invention solves the problem of insufficient toughness and easy aging of PBS by blending and modifying PLA and PBST polymer, thereby extending the shelf life of PLA modified materials; the PBST polymer belongs to a fat-aromatic polymer and can meet the food safety contact requirements; the preparation method of the PBST polymer is innovated to make it not only biodegradable but also have excellent thermodynamic properties and processability, so that the complementarity between PLA and PBST polymer is enhanced, and the complementarity between the two is fully utilized to obtain a composite material with both high strength and good toughness; at the same time, PLA is toughened by the PBST polymer, the use performance of the PLA material during freezing or refrigeration is improved, and the crystallization performance and heat resistance of the PLA material are promoted, thereby improving the overall performance of the PLA material; and the shelf life of the PLA product can be significantly extended by the mutual cooperation between various raw materials.

[0022] In one embodiment, the catalyst is rare earth-tetrabutyl titanate; one or more of the C2-C10 aliphatic diols or alicyclic diols is 1,4-butanediol; the C4-C20 aliphatic dibasic acid or its ester derivative is succinic acid; the aromatic dibasic acid or its ester derivative is terephthalic acid. It is explained here that rare earth-tetrabutyl titanate is specifically used as a catalyst in this embodiment. Because the synthesis and preparation of PBST polymer adopts a high-temperature and high-vacuum polycondensation process, thermal degradation side reactions are prone to occur during the high-temperature polycondensation process, resulting in low quality and poor hue of the obtained product. The solution to this problem is to use a high-efficiency catalyst to reduce side reactions. However, when the titanium-based catalyst is used alone, it is unstable and the product is prone to yellowing. Therefore, a composite system of rare earth-tetrabutyl titanate is used, which not only has a higher catalytic activity, but also improves product quality.

[0023] In one embodiment, the molar ratio of 1,4-butanediol:succinic acid:terephthalic acid is: (0-2): (0-2): (1-3). In the preparation process of PBST polymer, butanediol and succinic acid are the main chain segment components of PBST polymer, and the change of their ratio will directly affect the molecular structure and performance of the polymer; and the introduction of terephthalic acid can increase the rigidity of the polymer chain segment, improve the melting point, thermal stability and mechanical strength of the polymer; therefore, ensuring that the three substances are within a reasonable molar ratio range can control the progress of the polymerization reaction and the performance of the product, so that both effect and efficiency are taken into account.

[0024] In one embodiment, in the preparation method of PBST polymer, during the polycondensation reaction, 1,4-butanediol volatilized during the reaction is recovered and condensed and then re-enters the polycondensation reaction. Since 1,4-butanediol is an important monomer for synthesizing BS system and BT system and is toxic, it is recovered and condensed. First, a certain amount of excess 1,4-butanediol is conducive to the positive reaction and ensures sufficient reaction; second, its own characteristics are considered to ensure the safety of the entire process; and the non-volatile 1,4-butanediol is extracted before the vacuum operation. Before the vacuum operation, the remaining 1,4-butanediol is extracted because the polycondensation reaction is essentially a copolymerization reaction of the BA system and the BT system. 1,4-butanediol will produce a side reaction tetrahydrofuran THF at this temperature, resulting in an increase in the viscosity of the system, which is not conducive to the polycondensation reaction, so it is extracted. At the same time, preferably, 1,4-butanediol needs to be extracted before the polycondensation reaction, and the extraction method is: gradually heating to 260°C and then extracting, mainly considering that BT esterification is not complete, heating is conducive to accelerating esterification, ensuring that TPA is fully consumed, and considering that the polycondensation is carried out at 260°C, at this temperature, the polycondensation reaction can maintain a faster rate, while avoiding excessively high temperatures that cause product decomposition or side reactions, thereby ensuring product quality.

[0025] In one embodiment, the inorganic material is activated talc; the activated talc itself has high thermal stability and fire resistance, and can maintain stable physical properties under high temperature environment; the activated talc acts as a nucleating agent for PLA, and promotes the crystallization process of PLA by providing a large number of nucleation sites; this helps to accelerate the crystallization rate and increase the crystallinity, thereby improving the heat resistance and mechanical properties of PLA; and a strong interaction is formed between the activated talc and the PLA matrix, which can significantly improve the rigidity and strength of PLA.

[0026] In one embodiment, the plasticizer is a mixture of one or more of TBC, ATBC, and polyethylene glycol; the lubricant is a mixture of one or more of oleamide, erucamide, and EBS. The compatibilizer is any one of PP-G-MAH, PLA-G-MAH, cyanate ester, and 3510P. The antioxidant is one or a combination of two or more of antioxidant 215, antioxidant 264, antioxidant 1010, antioxidant 168, and antioxidant 164.

[0027] A method for preparing a PLA modified material as described in any one of the above, comprising the following steps: S1: PLA, PBST polymer, compatibilizer and plasticizer are fully mixed in a high-speed mixer at 1200 r / min for 120s-180s to obtain a premix; S2: adding the inorganic material, the lubricant and the antioxidant to the premix and mixing them to obtain a final mixture; S3: The final mixture is fed into a twin-screw extruder for extrusion and pelletization to obtain a PLA modified material.

[0028] The preparation method of the invention is simple to operate and has a short process. The PBST polymer and PLA are blended and modified, and a compatibilizer, a plasticizer, an inorganic material, a lubricant and an antioxidant are added to assist the mixing of the PBST polymer and the PLA, so that the finally prepared PLA modified material has excellent mechanical properties and stable performance.

[0029] An application of the PLA modified material as described in any one of the above items, wherein the PLA modified material is used for straws. The PLA modified material is used in the field of straws, so that the shelf life of the straws is greatly improved.

[0030] Example 1 A PLA modified material comprises the following components by weight: 68 parts of PLA, 15 parts of PBST polymer, 25 parts of activated talc, 0.5 parts of erucamide, 0.3 parts of antioxidant 168, 0.3 parts of antioxidant 1010, 0.4 parts of ATBC, and 0.2 parts of chain extender 3510P. The melt index of PLA at 190°C / 2.16kg is 4-5g / 10min. The preparation method of the PBST polymer is as follows: Esterification reaction: add 0.5 mol succinic acid (SA), 1.5 mol 1,4-butanediol (BDO) and 0.1% catalyst rare earth-titanate tetrabutyl ester into a 500 mL four-necked flask, slowly raise the temperature to 150°C and stir to react for 2-3 hours to ensure sufficient reaction to obtain a mixed reactant; Condensation reaction: 0.5 mol of terephthalic acid (TPA) is added to the mixed reactants, and then the temperature is slowly raised to 220°C. During the reaction, the volatilized 1,4-butanediol (BDO) is condensed through a hot water reflux tube and flows back into the reaction system, i.e., the four-necked flask. After 3.5 hours of reaction, all the water generated by the esterification reaction is evaporated, and then the temperature is gradually raised to 260°C, the remaining BDO is extracted, and the vacuum is gradually evacuated to about 60Pa. The polycondensation reaction is carried out under vacuum conditions for 5-8 hours to obtain PBST polymer.

[0031] Example 2 A PLA modified material comprises the following components by weight: 63 parts of PLA, 15 parts of PBST polymer, 25 parts of activated talc, 0.5 parts of erucic acid amide, 0.3 parts of antioxidant 168, 0.3 parts of antioxidant 1010, 0.4 parts of ATBC, and 0.2 parts of chain extender 3510P. The melt index of PLA at 190°C / 2.16kg is 4-5g / 10min. The preparation method of the PBST polymer is as follows: Esterification reaction: add 0.5 mol succinic acid (SA), 1.5 mol 1,4-butanediol (BDO) and 0.1% catalyst rare earth-titanate tetrabutyl ester into a 500 mL four-necked flask, slowly raise the temperature to 150°C and stir to react for 2-3 hours to ensure sufficient reaction to obtain a mixed reactant; Polycondensation reaction: 0.75 mol of terephthalic acid (TPA) is added to the mixed reactants, and then the temperature is slowly raised to 220°C. During the reaction, the volatilized 1,4-butanediol (BDO) is condensed through a hot water reflux tube and flows back into the reaction system, i.e., the four-necked flask. After 3.5 hours of reaction, all the water generated by the esterification reaction is evaporated, and then the temperature is gradually raised to 260°C, the remaining BDO is extracted, and the temperature is gradually evacuated to about 60Pa. The polycondensation reaction is carried out under vacuum conditions for 5-8 hours to obtain a PBST polymer.

[0032] Example 3 A PLA modified material comprises the following components by weight: 58 parts of PLA, 15 parts of PBST polymer, 25 parts of activated talc, 0.5 parts of erucamide, 0.3 parts of antioxidant 168, 0.3 parts of antioxidant 1010, 0.4 parts of ATBC, and 0.2 parts of chain extender 3510P. The melt index of PLA at 190°C / 2.16kg is 4-5g / 10min. The preparation method of the PBST polymer is as follows: Esterification reaction: add 0.75 mol succinic acid (SA), 1.5 mol 1,4-butanediol (BDO) and 0.1% catalyst rare earth-titanate tetrabutyl ester into a 500 mL four-necked flask, slowly raise the temperature to 150°C and stir to react for 2-3 hours to ensure sufficient reaction to obtain a mixed reactant; Condensation reaction: 0.5 mol of terephthalic acid (TPA) is added to the mixed reactants, and then the temperature is slowly raised to 220°C. During the reaction, the volatilized 1,4-butanediol (BDO) is condensed through a hot water reflux tube and flows back into the reaction system, i.e., the four-necked flask. After 3.5 hours of reaction, all the water generated by the esterification reaction is evaporated, and then the temperature is gradually raised to 260°C, the remaining BDO is extracted, and the vacuum is gradually evacuated to about 60Pa. The polycondensation reaction is carried out under vacuum conditions for 5-8 hours to obtain PBST polymer.

[0033] Example 4 A PLA modified material comprises the following components by weight: 58 parts of PLA, 15 parts of PBST polymer, 25 parts of activated talc, 0.5 parts of erucamide, 0.3 parts of antioxidant 168, 0.3 parts of antioxidant 1010, 0.4 parts of ATBC, and 0.2 parts of chain extender 3510P. The melt index of PLA at 190°C / 2.16kg is 4-5g / 10min. The preparation method of the PBST polymer is as follows: Esterification reaction: add 0.75 mol succinic acid (SA), 1.5 mol 1,4-butanediol (BDO) and 0.1% catalyst rare earth-titanate tetrabutyl ester into a 500 mL four-necked flask, slowly raise the temperature to 150°C and stir to react for 2-3 hours to ensure sufficient reaction to obtain a mixed reactant; Polycondensation reaction: 0.75 mol of terephthalic acid (TPA) is added to the mixed reactants, and then the temperature is slowly raised to 220°C. During the reaction, the volatilized 1,4-butanediol (BDO) is condensed through a hot water reflux tube and flows back into the reaction system, i.e., the four-necked flask. After 3.5 hours of reaction, all the water generated by the esterification reaction is evaporated, and then the temperature is gradually raised to 260°C, the remaining BDO is extracted, and the temperature is gradually evacuated to about 60Pa. The polycondensation reaction is carried out under vacuum conditions for 5-8 hours to obtain a PBST polymer.

[0034] Comparative Example 1 A PLA modified material includes the following components by weight: 58 parts of PLA, 15 parts of PBS, 25 parts of activated talc, 0.5 parts of erucic acid amide, 0.3 parts of antioxidant 168, 0.3 parts of antioxidant 1010, 0.4 parts of ATBC, and 0.2 parts of chain extender 3510P. The melt index of PLA at 190°C / 2.16kg is 4-5g / 10min, and the melt index of PBS at 190°C / 2.16kg is 3-5g / 10min.

[0035] Comparative Example 2 A PLA modified material includes the following components by weight: 58 parts of PLA, 15 parts of PBAT, 25 parts of activated talc, 0.5 parts of erucic acid amide, 0.3 parts of antioxidant 168, 0.3 parts of antioxidant 1010, 0.4 parts of ATBC, and 0.2 parts of chain extender 3510P. The melt index of PLA at 190°C / 2.16kg is 4-5g / 10min, and the melt index of PBAT at 190°C / 2.16kg is 3-8g / 10min.

[0036] The PLA modified materials in Examples 1-4 and Comparative Examples 1-2 were used to prepare straws, and their performance was tested. The test items included Vicat softening point, tensile strength, elongation at break, Izod notched impact strength, and aging performance. The tests were performed according to the test standards. The test results are shown in Table 1 below:

[0037] As can be seen from Table 1, when PBST synthesized with different molar ratios of SA and TPA is used to modify PLA, the melt index is basically 2~3g / 10min, which is conducive to the extrusion of the straw extruder. Compared with Comparative Examples 1 and 2, the tensile strength is at the same level, and the elongation at break is increased, which increases the toughness of the PLA material to a certain extent and improves the brittle defects of PLA. Under the conditions of temperature 85°C and humidity 85%, the aging time is at least 22H, which is higher than 8H in Comparative Example 1 and 17H in Comparative Example 2. Considering that PLA straws have a certain shelf life and transportation period in actual use, the market requires PLA aging time of at least 24 hours. Considering the export distance, storage method and other factors, the aging time of 30H is the most guaranteed, so Example 2 can be the most preferred.

[0038] The examples described in the present invention are merely descriptions of the preferred implementation modes of the present invention, and are not intended to limit the concept and scope of the present invention. Without departing from the design concept of the present invention, various modifications and improvements made to the technical solutions of the present invention by engineers and technicians in this field should all fall within the protection scope of the present invention.

Claims

1. A PLA modified material, characterized in that: The following components are included by weight: PLA: 50~70 parts; Inorganic materials: 20~50 parts; Plasticizer: 3~5 parts; Compatibilizer: 0.01~1 part; Lubricant: 0.1~1 part; 0.1~1 part of antioxidant; PBST polymer: 0-30 parts; wherein the preparation method of PBST polymer is as follows: Esterification reaction: mixing and heating three raw materials, namely, a catalyst, one or more C2-C10 aliphatic diols or alicyclic diols, and C4-C20 aliphatic dibasic acids or their ester derivatives to obtain a mixed reactant; Polycondensation reaction: adding an aromatic dibasic acid or its ester derivative to the mixed reactant and heating it, and performing a polycondensation reaction under vacuum conditions to obtain a PBST polymer; The catalyst is rare earth-tetrabutyl titanate; one or more of the C2-C10 aliphatic diols or alicyclic diols are 1,4-butanediol; the C4-C20 aliphatic dibasic acid or its ester derivative is succinic acid; the aromatic dibasic acid or its ester derivative is terephthalic acid; The molar ratio of succinic acid: terephthalic acid is: (0~2): (0~2): (1~3).

2. A PLA modified material according to claim 1, characterized in that: In the preparation method of the PBST polymer, during the polycondensation reaction, the 1,4-butanediol volatilized during the reaction is recovered and condensed and then re-enters the polycondensation reaction, and the non-volatile 1,4-butanediol is extracted before the vacuum operation.

3. A PLA modified material according to claim 1, characterized in that: The inorganic material is activated talc.

4. A PLA modified material according to claim 1, characterized in that: The plasticizer is one of TBC, ATBC, and polyethylene glycol, or a mixture of multiple thereof; the lubricant is one of oleamide, erucamide, and EBS, or a mixture of multiple thereof.

5. A PLA modified material according to claim 1, characterized in that: The compatibilizer is any one of PP-G-MAH, PLA-G-MAH, cyanate ester, and 3510P.

6. A PLA modified material according to claim 1, characterized in that: The antioxidant is one of antioxidant 215, antioxidant 264, antioxidant 1010, antioxidant 168 and antioxidant 164, or a combination of two or more thereof.

7. A method for preparing a PLA modified material according to any one of claims 1 to 6, characterized in that: The steps include: S1: PLA, PBST polymer, compatibilizer and plasticizer are mixed to obtain a premix; S2: adding the inorganic material, the lubricant and the antioxidant to the premix and mixing them to obtain a final mixture; S3: The final mixture is discharged, extruded and pelletized to obtain a PLA modified material.

8. An application of the PLA modified material according to any one of claims 1 to 7, characterized in that: The PLA modified material is used for straws.

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