High-toughness PLA blend and preparation method thereof

Abstract

The invention discloses a high-toughness PLA (polylactic acid) blend and a preparation method thereof, and the high-toughness PLA blend is prepared from the following components: polylactic resin, polyvinylidene fluoride, modified mica powder and a compatilizer. The invention provides a brand new high-toughness PLA blend. Researches show that the high-toughness PLA blend has relatively good toughness; besides, compared with the addition of unmodified mica powder, the modified mica powder prepared by the invention is added into the high-toughness PLA blend, so that the haze of the high-toughness PLA blend can be remarkably reduced. In conclusion, the high-toughness PLA blend disclosed by the invention not only has relatively good toughness, but also has relatively low haze; therefore, the method has important application value when being used for preparing the thin film.

Description

Technical Field

[0001] The invention relates to the technical field of polymer materials, and in particular to a high-toughness PLA blend and a preparation method thereof. Background Art

[0002] In order to cope with the increasingly severe environmental pollution problem, degradable plastics have received more and more attention. Polylactic acid (PLA) is converted from renewable resources such as plant starch. It can be completely degraded into carbon dioxide and water by microbial action in the natural environment. In addition, due to its high mechanical strength, good processing performance and unique biodegradability, it has shown broad application prospects in many fields such as agricultural mulch, food packaging, and medical products.

[0003] Although PLA has many advantages, its inherent brittleness has become the main obstacle to its widespread application. In order to overcome the brittleness of PLA, researchers are constantly exploring toughening and modification strategies. Therefore, providing a high-toughness PLA blend has important application prospects. Summary of the invention

[0004] In order to overcome at least one of the technical problems existing in the prior art, the present invention provides a high-toughness PLA blend and a preparation method thereof.

[0005] The technical solution of the present invention is as follows:

[0006] A high-toughness PLA blend is prepared from the following components: polylactic acid resin, polyvinylidene fluoride, modified mica powder and a compatibilizer.

[0007] Preferably, the high-toughness PLA blend is prepared from the following components in parts by weight: 100-200 parts of polylactic acid resin; 50-100 parts of polyvinylidene fluoride; 30-50 parts of modified mica powder; and 3-6 parts of compatibilizer.

[0008] Preferably, the high-toughness PLA blend is prepared from the following components in parts by weight: 140-180 parts of polylactic acid resin; 50-80 parts of polyvinylidene fluoride; 30-40 parts of modified mica powder; and 3-5 parts of compatibilizer.

[0009] Preferably, the high-toughness PLA blend is prepared from the following components in parts by weight: 150 parts of polylactic acid resin; 60 parts of polyvinylidene fluoride; 40 parts of modified mica powder; and 5 parts of compatibilizer.

[0010] The preparation method of the high-toughness PLA blend comprises the following steps:

[0011] The pretreatment method of modified mica powder is as follows:

[0012] (1) preparing an acid solution;

[0013] (2) adding mica powder to an acid solution and stirring for 1 to 3 hours, separating the mica powder, and washing it to neutrality;

[0014] (3) adding the mica powder treated in step (2) into water, and then adding a modifier to perform pulping for 2 to 5 hours; after the pulping is completed, the pulp is dried to obtain modified mica powder;

[0015] Preparation of high-toughness PLA blends:

[0016] Polylactic acid resin, polyvinylidene fluoride, modified mica powder and a compatibilizer are mixed evenly and then melt-extruded through a twin-screw extruder to obtain a high-toughness PLA blend.

[0017] In the method for preparing the high-toughness PLA blend, the specific preparation method of the acid solution in step (1) is: adding hydrochloric acid to water to prepare a hydrochloric acid aqueous solution with a mass fraction of 10-20%.

[0018] In the method for preparing the high-toughness PLA blend, the ratio of mica powder to acid solution in step (2) is 1 kg: 3 to 6 L.

[0019] In the preparation method of the high-toughness PLA blend, the usage ratio of mica powder to acid solution is 1kg:5L.

[0020] In the above-mentioned method for preparing the high-toughness PLA blend, the usage ratio of mica powder, modifier and water in step (3) is 1kg:0.2-0.3kg:2-4L.

[0021] In the method for preparing the high-toughness PLA blend, the modifier is selected from sodium stearate and / or sodium hexametaphosphate.

[0022] The beneficial effects of the present invention are:

[0023] The present invention provides a new high-toughness PLA blend; studies have shown that the high-toughness PLA blend has good toughness; in addition, adding the modified mica powder prepared in the present application to the high-toughness PLA blend can significantly reduce the haze of the high-toughness PLA blend compared to adding unmodified mica powder. In summary, the high-toughness PLA blend of the present invention not only has good toughness, but also has low haze; therefore, it has important application value to be used in preparing thin films. DETAILED DESCRIPTION

[0024] The present invention is further explained below in conjunction with specific examples, but the examples do not limit the present invention in any form.

[0025] The polylactic acid resin in the following embodiments is polylactic acid resin with a brand number of 2002D produced by NatureWorks, USA; the polyvinylidene fluoride is polyvinylidene fluoride resin with a brand number of 6008 produced by Solvay, USA;

[0026] The compatibilizer is maleic anhydride grafted polylactic acid; the maleic anhydride grafted polylactic acid is prepared according to the following document: "Yu Rentong, et al. Preparation of maleic anhydride grafted polylactic acid by reactive extrusion [J], Polymer Materials Science and Engineering, 2009, 25 (3): 85-88."

[0027] The remaining raw materials are all common raw materials that can be purchased by those skilled in the art.

[0028] Example 1 Preparation of high-toughness PLA blend

[0029] Take 150 parts of polylactic acid resin, 60 parts of polyvinylidene fluoride, 40 parts of ordinary mica powder and 5 parts of compatibilizer, mix them evenly, and then melt-extrude them through a twin-screw extruder to obtain the high-toughness PLA blend.

[0030] Example 2 Preparation of high-toughness PLA blend

[0031] Take 150 parts of polylactic acid resin, 60 parts of polyvinylidene fluoride, 40 parts of modified mica powder and 5 parts of compatibilizer, mix them evenly, and then melt extrude them through a twin-screw extruder to obtain the high-toughness PLA blend;

[0032] The pretreatment method of the modified mica powder is as follows:

[0033] (1) Add hydrochloric acid to water to prepare a 15% hydrochloric acid aqueous solution.

[0034] (2) adding mica powder to a hydrochloric acid aqueous solution and stirring for 2 h, separating the mica powder, and washing until neutral; wherein the ratio of mica powder to hydrochloric acid aqueous solution is 1 kg:5 L;

[0035] (3) adding the mica powder treated in step (2) into water, and then adding a modifier to perform pulping for 3 hours; after the pulping is completed, the slurry is dried to obtain the modified mica powder;

[0036] In step (3), the dosage ratio of mica powder to modifier and water is 1kg:0.25kg:3L; the modifier is sodium stearate.

[0037] Example 3 Preparation of high-toughness PLA blend

[0038] Take 150 parts of polylactic acid resin, 60 parts of polyvinylidene fluoride, 40 parts of modified mica powder and 5 parts of compatibilizer, mix them evenly, and then melt extrude them through a twin-screw extruder to obtain the high-toughness PLA blend;

[0039] The pretreatment method of the modified mica powder is as follows:

[0040] (1) Add hydrochloric acid to water to prepare a 15% hydrochloric acid aqueous solution.

[0041] (2) adding mica powder to a hydrochloric acid aqueous solution and stirring for 2 h, separating the mica powder, and washing until neutral; wherein the ratio of mica powder to hydrochloric acid aqueous solution is 1 kg:5 L;

[0042] (3) adding the mica powder treated in step (2) into water, and then adding a modifier to perform pulping for 3 hours; after the pulping is completed, the slurry is dried to obtain the modified mica powder;

[0043] In step (3), the dosage ratio of mica powder to modifier and water is 1kg:0.25kg:3L; the modifier is sodium hexametaphosphate.

[0044] Example 4 Preparation of high-toughness PLA blend

[0045] Take 150 parts of polylactic acid resin, 60 parts of polyvinylidene fluoride, 40 parts of modified mica powder and 5 parts of compatibilizer, mix them evenly, and then melt extrude them through a twin-screw extruder to obtain the high-toughness PLA blend;

[0046] The pretreatment method of the modified mica powder is as follows:

[0047] (1) Add hydrochloric acid to water to prepare a 15% hydrochloric acid aqueous solution.

[0048] (2) adding mica powder to a hydrochloric acid aqueous solution and stirring for 2 h, separating the mica powder, and washing until neutral; wherein the ratio of mica powder to hydrochloric acid aqueous solution is 1 kg:5 L;

[0049] (3) adding the mica powder treated in step (2) into water, and then adding a modifier to perform pulping for 3 hours; after the pulping is completed, the slurry is dried to obtain the modified mica powder;

[0050] In step (3), the dosage ratio of mica powder to modifier and water is 1kg:0.25kg:3L; the modifier is composed of sodium stearate and sodium hexametaphosphate in a mass ratio of 1:1.

[0051] The elongation at break of the high-toughness PLA blends prepared in Examples 1 to 4 was tested with reference to the method in GB / T 1040.1-2018; the haze of the high-toughness PLA blends prepared in Examples 1 to 4 was tested with reference to the method in GB / T 2410-2008; the test results are shown in Table 1.

[0052] Table 1. Performance test results of the high-toughness PLA blend of the present invention

[0053] Elongation at break Haze High-toughness PLA blend prepared in Example 1 165.6％ 8.3％ High-toughness PLA blend prepared in Example 2 179.2％ 5.1％ Example 3 High-toughness PLA blend prepared 175.1％ 5.5％ Example 4 High-toughness PLA blend prepared 178.3％ 2.4％

[0054] It can be seen from the experimental results in Table 1 that the elongation at break of the high-toughness PLA blends prepared in Examples 1 to 4 is between 165.6% and 178.3%. The modified mica powder of the present application is used in the system, and its elongation at break is effectively improved, and the prepared high-toughness PLA blend has good toughness.

[0055] It can be seen from the experimental results in Table 1 that the high-toughness PLA blends prepared in Examples 2 and 3 have significantly lower haze than that in Example 1; and the high-toughness PLA blend prepared in Example 4 has the lowest haze, which is further significantly lower than that in Examples 2 and 3. The inventors found in their research that adding modified mica powder modified by sodium stearate and sodium hexametaphosphate to the high-toughness PLA blend can further significantly reduce the haze of the high-toughness PLA blend, compared with the modified mica powder modified by adding sodium stearate or sodium hexametaphosphate alone.

Claims

1. A high-toughness PLA blend, characterized in that: The invention is prepared from the following components: polylactic acid resin, polyvinylidene fluoride, modified mica powder and compatibilizer.

2. The high-toughness PLA blend according to claim 1, characterized in that The invention is prepared from the following components in parts by weight: 100-200 parts of polylactic acid resin; 50-100 parts of polyvinylidene fluoride; 30-50 parts of modified mica powder; and 3-6 parts of compatibilizer.

3. The high-toughness PLA blend according to claim 1, characterized in that: The invention is prepared from the following components in parts by weight: 140-180 parts of polylactic acid resin; 50-80 parts of polyvinylidene fluoride; 30-40 parts of modified mica powder; and 3-5 parts of compatibilizer.

4. The high-toughness PLA blend according to claim 1, characterized in that The invention is prepared from the following components in parts by weight: 150 parts of polylactic acid resin; 60 parts of polyvinylidene fluoride; 40 parts of modified mica powder; and 5 parts of a compatibilizer.

5. The method for preparing the high-toughness PLA blend according to any one of claims 1 to 4, characterized in that: The following steps are included: The pretreatment method of modified mica powder is as follows: (1) preparing an acid solution; (2) adding mica powder to an acid solution and stirring for 1 to 3 hours, separating the mica powder, and washing it to neutrality; (3) adding the mica powder treated in step (2) into water, and then adding a modifier to perform pulping for 2 to 5 hours; after the pulping is completed, the pulp is dried to obtain modified mica powder; Preparation of high-toughness PLA blends: Polylactic acid resin, polyvinylidene fluoride, modified mica powder and a compatibilizer are mixed evenly and then melt-extruded through a twin-screw extruder to obtain a high-toughness PLA blend.

6. The method for preparing the high-toughness PLA blend according to claim 5, characterized in that: The specific preparation method of the acid solution in step (1) is: adding hydrochloric acid into water to prepare a hydrochloric acid aqueous solution with a mass fraction of 10-20%.

7. The method for preparing the high-toughness PLA blend according to claim 5, characterized in that: In step (2), the dosage ratio of mica powder to acid solution is 1kg:3-6L.

8. The method for preparing the high-toughness PLA blend according to claim 7, characterized in that: The dosage ratio of mica powder to acid solution is 1kg:5L.

9. The method for preparing the high-toughness PLA blend according to claim 5, characterized in that: The dosage ratio of mica powder, modifier and water in step (3) is 1kg:0.2-0.3kg:2-4L.

10. The method for preparing a high-toughness PLA blend according to claim 5, characterized in that: The modifier is selected from sodium stearate and / or sodium hexametaphosphate.