Preparation method of PLA / PBS biodegradable material with chain extension modified PBS as compatibilizer

Abstract

The invention provides a preparation method of a PLA / PBS biodegradable material with chain extension modified PBS as a compatibilizer. The preparation method comprises the following steps: firstly, preparing an NBDI-TMP (norbornane diisocyanate-trimethylolpropane) chain extender by taking norbornane diisocyanate (NBDI) and trimethylolpropane (TMP) as raw materials, and performing melt extrusion on the NBDI-TMP (norbornane diisocyanate-trimethylolpropane) chain extender and PBS to obtain a series of chain extension modified PBS; pBS subjected to chain extension modification is used as a compatibilizer to improve the compatibility of the PLA / PBS composite material, so that the mechanical property of the composite material is improved. The obtained product has excellent strength and toughness, and can be applied to injection molding, hot pressing, plastic uptake, extrusion molding and other processes.

Description

Technical Field

[0001] The invention belongs to the technical field of biodegradable material processing, and in particular relates to a method for preparing a PLA / PBS biodegradable material using chain-extended modified PBS as a compatibilizer. Background Art

[0002] Butylene succinate (PBS) and polylactic acid (PLA) as biodegradable polyesters are widely valued by scientific researchers in various countries because of their degradability and good thermal and mechanical properties. Because the molecular structure of such polyesters contains ester bonds that are easily hydrolyzed and broken, they are currently the research hotspots in the field of environmentally friendly materials. However, although commercialized PBS and PLA can already meet some market application needs, due to the limitations of the material synthesis process and the material molecular structure itself, their comprehensive performance is still difficult to meet the needs of large-scale industrial applications. The disadvantage of large brittleness limits the further application of PLA, and the disadvantage of low strength and difficulty in blown film molding without modification limits the widespread application of PBS. Physically blending PLA and PBS can obtain materials with better comprehensive performance, but the compatibility between PLA and PBS after physical blending is poor. Therefore, generally, the method of adding a compatibilizer is adopted to improve the compatibility of the two through chemical reaction or synergy to obtain a PLA / PBS composite material with better comprehensive performance.

[0003] The Chinese invention patent with application number 202311852817.7 discloses a method for preparing a PLA\PBS heat-resistant biodegradable plastic, including PLA: 50-100 parts of PBS: 50-100 parts of a compatibilizer: 1-5 parts of an initiator: 0.1-2 parts of a compatibilizer. The compatibilizer is mainly formed by the reaction of tris(1-chloro-2-propyl) phosphate and epoxy propionic acid. The epoxy propionic acid has a carboxyl group. Under the catalysis of triethylamine, it can react with the halogenated hydrocarbon on the tris(1-chloro-2-propyl) phosphate, thereby grafting the epoxy group on the tris(1-chloro-2-propyl) phosphate molecular chain. In addition, the tris(1-chloro-2-propyl) phosphate contains three side chains, which increases the amount of epoxy groups and greatly enhances the compatibilization effect of the phosphate bond. The compatibilizer used in this scheme is a small molecule component formed by the reaction of tri(1-chloro-2-propyl) phosphate and epoxy propionic acid. Small molecule components are not easy to disperse in the PLA / PBS mixed material and are prone to large-area agglomeration, thus affecting the final compatibilization effect. In addition, the compatibilizer has three epoxy groups, which are easy to form cross-linking points in the material during the mixing process. If it is finally used in film products, white spot defects will be formed in the film, thereby affecting the performance of the film.

[0004] The Chinese invention patent with application number 202110370521.6 discloses a method for chain extension and modification of biodegradable polyester and its application. The specific method includes the following steps: 1) A first biodegradable polyester melt is pumped out from a prepolymerization kettle by a melt metering gear pump, and a chain extender is injected into the melt pipeline after cooling; 2) The first biodegradable polyester melt and the chain extender enter a melt mixing device together and are mixed evenly, and then enter a melt homogenizer for a chain extension and homogenization reaction, and a prepolymerized chain-extended modified biodegradable polyester melt is obtained after the reaction; 3) A second biodegradable polyester melt is pumped out from a prepolymerization kettle by a melt metering gear pump and enters a condensation kettle for a polymerization reaction, and a prepolymerized thickening polyester melt is obtained after the reaction; 4) The prepolymerized chain-extended modified biodegradable polyester melt and the prepolymerized thickening polyester melt are mixed and then enter a thickening kettle for a thickening reaction, and a chain-extended modified biodegradable polyester melt is obtained after the reaction, and pelletized after cooling to obtain chain-extended modified biodegradable polyester chips. The raw materials for preparing the first biodegradable polyester melt and the second biodegradable polyester melt include at least one of PBAT, PBST, PBS, PBA, PBT, PHB, PVA, PHA, PLA, PCL, and PPC. The chain extender is selected from at least one of epoxy resin, ethylene oxide, toluene diisocyanate, isophorone diisocyanate, diphenylmethane diisocyanate, dicyclohexylmethane diisocyanate, hexamethylene diisocyanate, and lysine diisocyanate. The disadvantage of this scheme is that the preparation of the entire material is based on polyester raw materials, that is, a chain extension modification performed during the polymerization process of polyester. A series of equipment such as a prepolymerization kettle, a melt mixing kettle, a polycondensation kettle, and a viscosity increasing kettle will be used in the whole process. Each reactor has strict requirements on temperature and vacuum, and the process is relatively complicated. Summary of the invention

[0005] The invention aims to provide a method for preparing a PLA / PBS biodegradable material using a chain-extended modified PBS as a compatibilizer, which overcomes the shortcomings of the prior art, adopts two degradable materials, PLA and PBS, adopts synthesized norbornane diisocyanate-trimethylolpropane NBDI-TMP to prepare the chain-extended modified PBS, and uses the chain-extended modified PBS as a compatibilizer to improve the compatibility of the PLA / PBS composite material, thereby obtaining good comprehensive performance.

[0006] To achieve the above object, the present invention is implemented through the following technical solutions:

[0007] A method for preparing a PLA / PBS biodegradable material using chain-extended modified PBS as a compatibilizer comprises the following steps:

[0008] Step 1) preparing a chain extender NBDI-TMP (norbornane diisocyanate-trimethylolpropane);

[0009] Step 2) melt-processing the chain extender, PBS, and dibutyltin laurate to perform chain extension modification on the PBS to obtain a chain extension modified PBS;

[0010] Step 3) melt-processing PLA, PBS, chain-extended modified PBS, and dibutyltin laurate to obtain a PLA / PBS composite material.

[0011] The raw materials of the chain extender NBDI-TMP in step 1) are composed by weight of 2 parts of norbornane diisocyanate (NBDI), 40 parts of butyl acetate, 1 part of trimethylolpropane (TMP), and 2‰ parts of dibutyltin laurate.

[0012] The preparation steps of the chain extender NBDI-TMP in step 1) are as follows:

[0013] Step 1*) Add the formulated amount of norbornane diisocyanate (NBDI) and butyl acetate into a reaction kettle equipped with a mechanical stirring device and a condensation reflux device, and heat to 80° C.;

[0014] Step 2*) heating dried trimethylolpropane (TMP) until it is melted, and slowly adding it dropwise into a four-necked flask;

[0015] Step 3*) After the addition of TMP is completed, dibutyltin laurate is added to ensure sufficient reaction. The whole process is protected by nitrogen to obtain the chain extender NBDI-TMP.

[0016] The raw materials for chain extension and modification of PBS in step 2) are composed by weight: 100 parts of PBS, 0.2-0.8 parts of chain extender NBDI-TMP, and 0.2‰-0.8‰ parts of dibutyltin laurate. The raw materials are preferably composed by weight: 0.6 parts of chain extender NBDI-TMP, 100 parts of PBS, and 0.6‰ parts of dibutyltin laurate.

[0017] The technical parameters of the melt processing in step 2) are: the temperature of the twin-screw extruder is 140-200°C, the rotation speed is 120r / min. The temperature of the twin-screw extruder is preferably 150°C.

[0018] The raw materials in step 3) are composed by weight of: 60-100 parts of PLA, 5-40 parts of PBS, 2-6 parts of chain-extended modified PBS, and 2‰-6‰ parts of dibutyltin laurate. The preferred composition is: 70 parts of PLA, 30 parts of PBS, 5 parts of chain-extended modified PBS, and 5‰ parts of dibutyltin laurate.

[0019] The temperature of the melt processing extrusion granulation in step 3) is 160-200°C, the rotation speed is 120r / min, and the temperature is preferably 180°C.

[0020] The working principle of the technical solution of the present invention is as follows: in the preparation of the chain extender NBDI-TMP, norbornane diisocyanate (NBDI) and trimethylolpropane (TMP) serve as reaction raw materials, the isocyanate groups at both ends of NBDI can react with the terminal hydroxyl groups of TMP, and by controlling the reaction ratio and reaction conditions, the reaction generates NBDI-TMP with two isocyanate groups and one hydroxyl group at the terminal. Butyl acetate serves as an organic solvent, and dibutyltin laurate serves as a reaction catalyst.

[0021] In the preparation of chain-extended modified PBS, PBS acts as a base resin, and the chain extender NBDI-TMP acts as a reactive chain extender. The two isocyanate groups of NBDI-TMP react with the terminal carboxyl / hydroxyl groups of PBS to achieve chain extension of PBS. By controlling the reaction ratio and process conditions, chain-extended modified PBS still with isocyanate terminal groups is generated. Dibutyltin laurate acts as a reaction catalyst.

[0022] In the PLA / PBS composite material, PLA and PBS are both base resins of biodegradable materials, dibutyltin laurate is used as a reaction catalyst, and the chain-extended modified PBS acts as a reactive compatibilizer, which is similarly compatible with the base resin PBS. The isocyanate end group it carries can further react with the terminal hydroxyl / carboxyl group of PLA under the action of the catalyst, thereby playing the role of a compatibilizer in the base resin and improving the compatibility between PLA / PBS.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1) The present invention uses NBDI (norbornane diisocyanate) with an isocyanate group and TMP (trimethylolpropane) to synthesize a chain extender modifier NBDI-TMP with two isocyanate groups and one hydroxyl group. The advantage of two isocyanate groups and one hydroxyl group is that during the compatibilization reaction, by strictly controlling the reaction ratio, the synthesized compatibilizer only has two terminal isocyanate groups, and no cross-linking points will be formed in the system, so that no cross-linking point defects will be formed when preparing a film, and the performance of the product will not be affected;

[0025] 2) Using the synthesized NBDI-TMP as a chain extension modifier to perform chain extension modification on PBS, the generated chain extension modified PBS is used as a compatibilizer. The chain extension modified PBS has a terminal isocyanate group and can further participate in the reaction. Isocyanate itself has the possibility of a compatibilization reaction, but small isocyanate molecules are not easy to disperse in the PLA / PBS mixed material and are prone to large-scale agglomeration, thus affecting the final compatibilization effect. The chain extension modified PBS of this scheme is a polymer with a terminal isocyanate group, which has good compatibility with the PBS in the PLA / PBS mixed material, so it can be well dispersed in the system, and the compatibilization effect will not be poor due to the dispersion problem of the compatibilizer;

[0026] 3.) Using the chain-extended modified PBS as a compatibilizer, the PLA / PBS composite material is modified for compatibilization. The terminal isocyanate groups in the chain-extended modified PBS can further react with the terminal hydroxyl / terminal carboxyl groups of PLA. The generated PLA-(NBDI-TMP)-PBS polymer can be used as a compatibilizer between PLA and PBS, effectively improving the compatibility between PLA and PBS, improving the comprehensive performance of the composite material, and achieving a balance between material strength and toughness;

[0027] 4) The catalyst used in the preparation of chain extender NBDI-TMP, chain extender modified PBS and PLA / PBS composite material is dibutyltin laurate, so there is no need to consider the side reaction caused by the inconsistency of the catalysts before and after, and the process is simple; and the tin ions in dibutyltin laurate have good electron affinity, and the catalytic rate is relatively mild. In the preparation process of chain extender modified PBS, the chain extension reaction can occur after the chain extender is fully dispersed, which can effectively control the dispersion rate and reaction rate of the chain extender and reduce the side reaction;

[0028] 5) The reactive groups used by the chain extender NBDI-TMP and the compatibilizer chain extender modified PBS are both isocyanate groups, which have high reactivity. The activity of isocyanate groups is higher than that of epoxy groups. Therefore, a good compatibilization effect can be achieved at a small usage amount. In addition, the rigid structure of norbornane is introduced into the structure, and mixing it into the composite material can improve the strength and stiffness of the material to a certain extent.

[0029] 6) The material used in the scheme of the present invention is commercially available polyester, which does not involve the polymerization process of polyester. In the whole scheme, the preparation of the chain extender NBDI-TMP involves a reaction kettle, which can be prepared at low temperature and normal pressure; the preparation of the compatibilizer and the blending and compounding of the materials only require a twin-screw extruder, the process is simple, and the reaction and processing conditions are easy to meet. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a synthetic route diagram of the chain extender NBDI-TMP in an embodiment of the present invention;

[0031] Figure 2 It is a synthetic route diagram of the compatibilizer, i.e., the chain-extending modified PBS in the embodiment of the present invention;

[0032] Figure 3 This is the synthesis route of the compatibilizer, i.e., PLA-(NBDI-TMP)-PBS polymer, in the embodiment of the present invention, wherein the product in the box is the product that truly plays the role of the compatibilizer, and the others are possible by-products. DETAILED DESCRIPTION

[0033] The technical solution of the present invention will be clearly and completely described below in conjunction with specific embodiments. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments.

[0034] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the specific embodiments required to be used in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the specific embodiments described below are some implementation methods of the present invention. For ordinary technicians in this field, other specific embodiments can be obtained based on these specific embodiments without paying creative work.

[0035] The components of the embodiments of the present invention generally described and shown in the specific embodiments herein can be arranged and designed in countless different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the specific embodiments is not intended to limit the scope of the invention claimed, but merely represents selected embodiments of the present invention.

[0036] Example 1

[0037] Step 1: Add 2 parts of norbornane diisocyanate (NBDI) and 40 parts of butyl acetate to a reaction kettle equipped with a mechanical stirring device and a condensing reflux device, and heat to 80°C; heat 1 part of dried trimethylolpropane (TMP) until it melts, and slowly drop it evenly within 100 minutes; after the TMP drop is completed, add 2‰ parts of dibutyltin laurate (catalyst), and continue to keep warm for 2 hours. The whole process is protected by nitrogen to obtain the chain extender NBDI-TMP;

[0038] Step 2: 100 parts of PBS, 0.6 parts of chain extender NBDI-TMP and 0.6‰ parts of catalyst dibutyltin laurate are melt-blended in a twin-screw extruder at a temperature of 150° C. and a rotation speed of 120 r / min to obtain a chain-extended modified PBS;

[0039] Step 3: 70 parts of PLA, 30 parts of PBS, 5 parts of chain-extended modified PBS (compatibilizer), and 5‰ parts of dibutyltin laurate (catalyst) were melt-blended in a twin-screw extruder at a temperature of 180° C. and a rotation speed of 120 r / min to obtain a PLA / PBS composite material.

[0040] Example 2

[0041] Step 1: Same as Example 1;

[0042] Step 2: 100 parts of PBS, 0.2 parts of chain extender NBDI-TMP, and 0.3‰ parts of catalyst dibutyltin laurate are melt-blended in a twin-screw extruder at a temperature of 150° C. and a rotation speed of 120 r / min to obtain a chain-extended modified PBS;

[0043] Step 3: 80 parts of PLA, 20 parts of PBS, 3 parts of chain-extended modified PBS (compatibilizer), and 4‰ parts of dibutyltin laurate (catalyst) were melt-blended in a twin-screw extruder at a temperature of 180° C. and a rotation speed of 120 r / min to obtain a PLA / PBS composite material.

[0044] Example 3

[0045] Step 1: Same as Example 1.

[0046] Step 2: 100 parts of PBS, 0.4 parts of chain extender NBDI-TMP, and 0.5‰ parts of catalyst dibutyltin laurate are melt-blended in a twin-screw extruder at a temperature of 150°C and a rotation speed of 120 r / min to obtain a chain-extended modified PBS.

[0047] Step 3: 90 parts of PLA, 10 parts of PBS, 4 parts of chain-extended modified PBS (compatibilizer), and 3.5‰ parts of dibutyltin laurate (catalyst) were melt-blended in a twin-screw extruder at a temperature of 180° C. and a rotation speed of 120 r / min to obtain a PLA / PBS composite material.

[0048] Example 4

[0049] Step 1: Same as Example 1.

[0050] Step 2: 100 parts of PBS, 0.25 parts of chain extender NBDI-TMP, and 0.55‰ parts of catalyst dibutyltin laurate are melt-blended in a twin-screw extruder at a temperature of 150°C and a rotation speed of 120 r / min to obtain a chain-extended modified PBS.

[0051] Step 3: 60 parts of PLA, 40 parts of PBS, 5.5 parts of chain-extended modified PBS (compatibilizer), and 4.5‰ parts of dibutyltin laurate (catalyst) were melt-blended in a twin-screw extruder at a temperature of 180° C. and a rotation speed of 120 r / min to obtain a PLA / PBS composite material.

[0052] Example 5

[0053] Step 1: Same as Example 1.

[0054] Step 2: 100 parts of PBS, 0.35 parts of chain extender NBDI-TMP, and 0.45‰ parts of catalyst dibutyltin laurate are melt-blended in a twin-screw extruder at a temperature of 150°C and a rotation speed of 120 r / min to obtain a chain-extended modified PBS.

[0055] Step 3: 65 parts of PLA, 35 parts of PBS, 4.5 parts of chain-extended modified PBS (compatibilizer), and 5.5‰ parts of dibutyltin laurate (catalyst) were melt-blended in a twin-screw extruder at a temperature of 180°C and a rotation speed of 120 r / min to obtain a PLA / PBS composite material.

[0056] Example 6

[0057] Step 1: Same as Example 1.

[0058] Step 2: 100 parts of PBS, 0.27 parts of chain extender NBDI-TMP, and 0.53‰ parts of dibutyltin laurate are melt-blended in a twin-screw extruder at a temperature of 150°C and a rotation speed of 120 r / min to obtain a chain-extended modified PBS.

[0059] Step 3: 85 parts of PLA, 15 parts of PBS, 4.25 parts of chain-extended modified PBS (compatibilizer), and 2.5‰ parts of dibutyltin laurate (catalyst) were melt-blended in a twin-screw extruder at a temperature of 180° C. and a rotation speed of 120 r / min to obtain a PLA / PBS composite material.

[0060] Example 7

[0061] Step 1: Same as Example 1.

[0062] Step 2: 100 parts of PBS, 0.52 parts of chain extender NBDI-TMP, and 0.28‰ parts of catalyst dibutyltin laurate are melt-blended in a twin-screw extruder at a temperature of 150° C. and a rotation speed of 120 r / min to obtain a chain-extended modified PBS.

[0063] Step 3: 68 parts of PLA, 32 parts of PBS, 3.6 parts of chain-extended modified PBS (compatibilizer), and 4.4‰ parts of dibutyltin laurate (catalyst) were melt-blended in a twin-screw extruder at a temperature of 180° C. and a rotation speed of 120 r / min to obtain a PLA / PBS composite material.

[0064] Example 8

[0065] Step 1: Same as Example 1.

[0066] Step 2: 100 parts of PBS, 0.43 parts of chain extender NBDI-TMP, and 0.37‰ parts of catalyst dibutyltin laurate are melt-blended in a twin-screw extruder at a temperature of 150° C. and a rotation speed of 120 r / min to obtain a chain-extended modified PBS.

[0067] Step 3: 78 parts of PLA, 22 parts of PBS, 3.75 parts of chain-extended modified PBS (compatibilizer), and 2.25‰ parts of dibutyltin laurate (catalyst) were melt-blended in a twin-screw extruder at a temperature of 180° C. and a rotation speed of 120 r / min to obtain a PLA / PBS composite material.

[0068] Example 9

[0069] Step 1: Same as Example 1.

[0070] Step 2: 100 parts of PBS, 0.475 parts of chain extender NBDI-TMP, and 0.475‰ parts of dibutyltin laurate are melt-blended in a twin-screw extruder at a temperature of 150°C and a rotation speed of 120 r / min to obtain a chain-extended modified PBS.

[0071] Step 3: 62 parts of PLA, 38 parts of PBS, 3.25 parts of chain-extended modified PBS (compatibilizer), and 3.25‰ parts of dibutyltin laurate (catalyst) were melt-blended in a twin-screw extruder at a temperature of 180° C. and a rotation speed of 120 r / min to obtain a PLA / PBS composite material.

[0072] Example 10

[0073] Step 1: Same as Example 1.

[0074] Step 2: 100 parts of PBS, 0.55 parts of chain extender NBDI-TMP, and 0.45‰ parts of catalyst dibutyltin laurate are melt-blended in a twin-screw extruder at a temperature of 150° C. and a rotation speed of 120 r / min to obtain a chain-extended modified PBS.

[0075] Step 3: 72 parts of PLA, 28 parts of PBS, 4.35 parts of chain-extended modified PBS (compatibilizer), and 5.65‰ parts of dibutyltin laurate (catalyst) were melt-blended in a twin-screw extruder at a temperature of 180° C. and a rotation speed of 120 r / min to obtain a PLA / PBS composite material.

[0076] Comparative Example 1

[0077] Step 1: Add 2 parts of norbornane diisocyanate (NBDI) and 40 parts of butyl acetate to a reaction kettle equipped with a mechanical stirring device and a condensing reflux device, and heat to 80°C; heat 1 part of dried trimethylolpropane (TMP) until it melts, and slowly drip it within 100 minutes; after the TMP dripping is completed, add 2‰ parts of catalyst dibutyltin laurate, and continue to keep warm for 2 hours. The whole process is protected by nitrogen to obtain the chain extender NBDI-TMP.

[0078] Step 2: 100 parts of PBS, 0.6 parts of prepared NBDI-TMP, and 0.6‰ parts of catalyst dibutyltin laurate are melt-blended in a twin-screw extruder at a temperature of 150° C. and a rotation speed of 120 r / min to obtain a compatibilizer, i.e., a chain-extended modified PBS.

[0079] Step 3: 70 parts of PLA, 30 parts of PBS, and 5 parts of a compatibilizer were melt-blended in a twin-screw extruder at a temperature of 180° C. and a rotation speed of 120 r / min to obtain a PLA / PBS composite material.

[0080] Comparative Example 2

[0081] Step 1: Add 2 parts of norbornane diisocyanate (NBDI) and 40 parts of butyl acetate to a reaction kettle equipped with a mechanical stirring device and a condensing reflux device, and heat to 80°C; heat 1 part of dried trimethylolpropane (TMP) until it melts, and slowly drip it within 100 minutes; after the TMP dripping is completed, add 2‰ parts of catalyst dibutyltin laurate, and continue to keep warm for 2 hours. The whole process is protected by nitrogen to obtain the chain extender NBDI-TMP.

[0082] Step 2: 70 parts of PLA, 30 parts of PBS, 5 parts of chain extender NBDI-TMP, and 6‰ parts of catalyst were melt-blended in a twin-screw extruder at a temperature of 180°C and a rotation speed of 120 r / min to obtain a PLA / PBS composite material.

[0083] Comparative Example 3

[0084] 70 parts of PLA and 30 parts of PBS were melt-blended in a twin-screw extruder at a temperature of 180° C. and a rotation speed of 120 r / min to obtain a PLA / PBS composite material.

[0085] Table 1 Test results of PLA / PBS composite materials of Examples 1 to 12 and Comparative Examples 1 to 3

[0086] Sample Tensile Strength Elongation at break Impact strength Example 1 45.9 448.7 7.94 Example 2 46.4 383.3 6.03 Example 3 49.5 321.7 5.57 Example 4 37.2 500.3 8.49 Example 5 42.1 457.1 8.11 Example 6 48 360.7 5.98 Example 7 43.6 452.9 8.06 Example 8 46.1 391.4 6.45 Example 9 39.3 477.5 8.28 Example 10 46.0 425.8 6.96 Comparative Example 1 39.5 184.5 4.19 Comparative Example 2 43 423.6 6.37 Comparative Example 3 40.8 187.2 4.21

[0087] From the data in Table 1, it can be seen that compared with Comparative Example 3, under the condition that PBS modified by NBDI-TMP chain extension is used as a compatibilizer, the strength and toughness (elongation at break and impact strength) of the PLA / PBS composite material achieve a good balance, which not only improves the disadvantages of PLA's large brittleness, but also improves the disadvantages of PBS's low strength, and can further broaden its application. Among them, Example 1 presents the best balance between strength and toughness, and achieves the best comprehensive performance. And compared with Comparative Example 2, the chain extension modified PBS as a compatibilizer presents a better compatibilization effect than NBDI-TMP directly as a compatibilizer.

[0088] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a PLA / PBS biodegradable material using chain-extended modified PBS as a compatibilizer, characterized in that: The specific steps include: Step 1) preparing a chain extender NBDI-TMP (norbornane diisocyanate-trimethylolpropane); Step 2) melt-processing the chain extender, PBS, and dibutyltin laurate to perform chain extension modification on the PBS to obtain a chain extension modified PBS; Step 3) melt-processing PLA, PBS, chain-extended modified PBS, and dibutyltin laurate to obtain a PLA / PBS composite material.

2. The method for preparing a PLA / PBS biodegradable material using a chain-extended modified PBS as a compatibilizer according to claim 1, characterized in that: The raw materials of the chain extender NBDI-TMP in step 1) are composed by weight of 2 parts of norbornane diisocyanate (NBDI), 40 parts of butyl acetate, 1 part of trimethylolpropane (TMP), and 2‰ parts of dibutyltin laurate.

3. The method for preparing a PLA / PBS biodegradable material using a chain-extended modified PBS as a compatibilizer according to claim 2, characterized in that: The preparation steps of the chain extender NBDI-TMP in step 1) are as follows: Step 1*) Add the formulated amount of norbornane diisocyanate (NBDI) and butyl acetate into a reaction kettle equipped with a mechanical stirring device and a condensation reflux device, and heat to 80° C.; Step 2*) heating dried trimethylolpropane (TMP) until it is melted, and slowly and evenly adding it dropwise into the reaction kettle within 100 minutes; Step 3*) After the addition of TMP is completed, dibutyltin laurate is added and the reaction is continued for 2 hours under nitrogen protection to obtain a chain extender NBDI-TMP.

4. The method for preparing a PLA / PBS biodegradable material using a chain-extended modified PBS as a compatibilizer according to claim 1, characterized in that: The raw materials for preparing the chain-extended modified PBS in step 2) are composed by weight of: 100 parts of PBS, 0.2-0.8 parts of chain extender NBDI-TMP, and 0.2‰-0.8‰ parts of dibutyltin laurate.

5. The method for preparing a PLA / PBS biodegradable material using a chain-extended modified PBS as a compatibilizer according to claim 4, characterized in that: The raw material composition by weight in the step 2) is preferably: 0.6 parts of chain extender NBDI-TMP, 100 parts of PBS, and 0.6‰ parts of dibutyltin laurate.

6. The method for preparing a PLA / PBS biodegradable material using a chain-extended modified PBS as a compatibilizer according to claim 1, characterized in that: The technical parameters of the melt processing in step 2) are: the temperature of the twin-screw extruder is 140-200° C., and the rotation speed is 120 r / min.

7. The method for preparing a PLA / PBS biodegradable material with chain-extended modified PBS as a compatibilizer according to claim 6, characterized in that: The temperature of the twin-screw extruder in step 2) is preferably 150°C.

8. The method for preparing a PLA / PBS biodegradable material with chain-extended modified PBS as a compatibilizer according to claim 1, characterized in that: The raw materials in step 3) are composed by weight of: 60-100 parts of PLA, 5-40 parts of PBS, 2-6 parts of chain-extended modified PBS, and 2‰-6‰ parts of dibutyltin laurate.

9. The method for preparing a PLA / PBS biodegradable material using a chain-extended modified PBS as a compatibilizer according to claim 8, characterized in that: The raw material weight composition in step 3) is preferably: 70 parts of PLA, 30 parts of PBS, 5 parts of chain-extended modified PBS, and 5‰ parts of dibutyltin laurate.

10. The method for preparing a PLA / PBS biodegradable material with chain-extended modified PBS as a compatibilizer according to claim 1, characterized in that: In the step 3), the temperature of the melt processing extrusion granulation is 160-200° C. and the rotation speed is 120 r / min.

11. The method for preparing a PLA / PBS biodegradable material with chain-extended modified PBS as a compatibilizer according to claim 10, characterized in that: The temperature of the melt processing extrusion granulation in step 3) is preferably 180°C.

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