A modified high-strength biological film and preparation method thereof

Abstract

The present invention provides a modified high-strength biofilm, which includes the following components by mass: #imgabs0# wherein the modified silica is a hydroxylated silica, which is grafted with acrylic acid and then polymerized with alkyl acrylate to form a network polymer. The modified silica is introduced into the composition of the present invention, which is essentially a network polymer, and the silica particles are "embedded" in the network polymer in the form of covalent bonds and added to the biofilm as a compatibilizer. The prepared biofilm has the characteristic of being able to maintain high strength under extreme environments.

Description

Technical Field

[0001] The invention belongs to the field of packaging material processing, and specifically relates to a modified high-strength biological film and a preparation method thereof. Background Art

[0002] my country is currently a major producer and user of plastics. Plastic products are widely used in various fields of industry and civil use. While bringing convenience to people, they have also caused very profound environmental problems. Plastics based on traditional materials such as polypropylene, polyethylene, and polyvinyl chloride are difficult to degrade due to their high CC bond energy, which adds huge pressure to the subsequent treatment of plastic waste. Therefore, the world now advocates the use of degradable materials to replace traditional plastics. Degradable materials such as polylactic acid are widely used in packaging materials such as garbage bags, express bags, and shopping bags, providing people with new solutions.

[0003] Polylactic acid is of biological origin and has excellent mechanical strength, light transmittance and processability. It is recognized as the most promising green and environmentally friendly material. However, in the field of packaging materials, pure polylactic acid is not enough to be directly processed into finished packaging materials. It needs to be blended with various additives or other substrates to form a film to increase its various performances. At present, in the existing technologies based on polylactic acid, CN101328308A, CN109354844A, CN114672174A, etc., all provide relevant compositions and preparation methods to realize the preparation of polylactic acid material films and their application in packaging materials.

[0004] However, polylactic acid films usually contain fillers such as inorganic particles, which have poor compatibility with polylactic acid or other organic polymers. Especially after long-term storage in extreme environments, various properties will show a significant decline. This is due to the physical blending state in the composition, which accelerates the uneven distribution in extreme environments.

[0005] In summary, it is necessary to develop a new technical solution to solve the problems existing in the prior art. Summary of the invention

[0006] In order to solve the deficiencies in the prior art, the present invention provides a modified high-strength biofilm and a preparation method thereof. The composition of the present invention introduces modified silica, which is essentially a network polymer. The silica particles are "embedded" in the network polymer in the form of covalent bonds and added to the biofilm as a compatibilizer. The prepared biofilm has the characteristic of being able to maintain high strength under extreme environments.

[0007] One object of the present invention is to provide a biofilm, wherein the modified high-strength biofilm comprises the following components in parts by weight:

[0008]

[0009]

[0010] in,

[0011] The modified silicon dioxide is a network polymer formed by grafting hydroxylated silicon dioxide with acrylic acid and then polymerizing with alkyl acrylate.

[0012] Furthermore, the compatibilizer is selected from one or more of polyethylene glycol, maleic anhydride, and tributyl citrate.

[0013] Furthermore, the auxiliary agent is selected from one or more of an antioxidant, talc, a lubricant, and a plasticizer.

[0014] Furthermore, the weight average molecular weight of the polylactic acid is 10000-100000 g / mol.

[0015] Another object of the present invention is to provide a method for preparing the above-mentioned biofilm, the method for preparing the biofilm comprising the following steps:

[0016] S1, hydroxylating silicon dioxide to obtain hydroxylated silicon dioxide;

[0017] S2, immersing the hydroxylated silica in acrylic acid, and ultrasonically heating the silica to obtain acrylic acid-grafted silica;

[0018] S3, in an inert environment, mixing the acrylic acid-grafted silica with an initiator, an alkyl acrylate, and a solvent, heating for polymerization reaction, and removing the solvent to obtain a product;

[0019] S4, blending the product with other ingredients, and feeding it into a screw extruder, plasticizing and extruding it, and then blowing it into a film.

[0020] Furthermore, in step S2, the temperature of the ultrasound is 80-90°C and the time is 2-3h.

[0021] Furthermore, in step S3, the number of carbon atoms of the alkyl group in the alkyl acrylate is 12-18.

[0022] Furthermore, in step S2, the molar ratio of the acrylic acid-grafted silica to the alkyl acrylate is 1:20-40.

[0023] Furthermore, in step S4, the plasticizing temperature is 170-190°C.

[0024] Furthermore, in step S3, the solvent is toluene.

[0025] The present invention has the following beneficial effects:

[0026] Filler silica is added to the biofilm of the present invention, so that the film has a higher hardness. However, generally, solid particle fillers have poor compatibility with polymers such as polylactic acid and PBAT, which will cause uneven dispersion problems, and then cause undesirable situations such as film strength distribution after film formation or uneven degradation rate. This is mainly due to the agglomeration of solid particles in the phase state of the composition. The modified silica added in the present invention is essentially a network material formed by chemically modifying and grafting acrylic acid groups and then free radical copolymerization. The silica solid particles are "embedded" in the network three-dimensional structure in the form of chemical bonds, thereby achieving a stable dispersion effect; and then after blending with silica and other components in the composition, the silica particles in the network structure can produce an adsorption effect with each other due to the effects of surface hydroxyl groups, etc.; and the polymer part in the network structure also has entanglement and compatibility with polylactic acid, PBAT, etc., so that the modified silica forms a compatibilizer in the composition, which greatly improves the stable coexistence of each component in the composition. Therefore, the film product showed excellent results in subsequent mechanical properties tests. DETAILED DESCRIPTION

[0027] The present invention is further described below with reference to specific examples, but the examples do not limit the present invention in any form. Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0028] Unless otherwise specified, the reagents and materials used in the following examples are commercially available.

[0029] The polylactic acid in the embodiment of the present invention is purchased from Dongguan Yingde Plastic Raw Materials Co., Ltd. with a brand number of 4032D.

[0030] The PBAT in the embodiments of the present invention is purchased from BASF.

[0031] In the embodiment of the present invention, the compatibilizer is tributyl citrate and the plasticizer is PEG200, both of which are conventional commercially available materials.

[0032] The modified silicon dioxide in the embodiment of the present invention is prepared by the following steps:

[0033] Nano-silicon dioxide particles (particle size of 60nm) are immersed in a sufficient mixed solution of 25% ammonia water and 25% hydrogen peroxide by mass (silicon dioxide: ammonia water: hydrogen peroxide = 1:10:10, n / n / n), heated to boiling and stirred for 1h, then washed with water, filtered and vacuum dried for 2h to obtain hydroxylated silicon dioxide; then the hydroxylated silicon dioxide is immersed in a sufficient amount of acrylic acid, ultrasonically heated to 80°C for 2h, and then the product is washed with ethanol to obtain acrylic acid-grafted silicon dioxide; finally, in a nitrogen environment, the acrylic acid-grafted silicon dioxide and dodecyl acrylate are blended (1:20, n / n), an appropriate amount of initiator BPO and a sufficient amount of toluene solvent are added, heated to 100°C, reacted for 2h, and the solvent is removed after the reaction is stopped to obtain a modified silicon dioxide product.

[0034] Example 1

[0035] A modified high-strength biofilm comprises the following components in parts by weight:

[0036]

[0037] The modified high-strength biofilm comprises the following steps:

[0038] According to the above mass fractions, various ingredients were blended and added to the screw extruder. They were blended at a high temperature of 170°C to melt the polymer. After extrusion, the film bubble was blown by a fan. After the size of the film bubble was stable, the blowing ratio was adjusted to 3.0, so that the film width reached 1m. The film thickness was adjusted to 15μm by adjusting the main machine speed and traction rate. The obtained film was bidirectionally split and rolled up.

[0039] Example 2

[0040] A modified high-strength biofilm comprises the following components in parts by weight:

[0041]

[0042] The modified high-strength biofilm comprises the following steps:

[0043] According to the above mass fractions, various ingredients were blended and added to the screw extruder. They were blended at a high temperature of 180°C to melt the polymer. After extrusion, the film bubble was blown by a fan. After the size of the film bubble stabilized, the blowing ratio was adjusted to 3.0, so that the film width reached 1m. The film thickness was adjusted to 15μm by adjusting the main machine speed and traction rate. The obtained film was bidirectionally split and rolled up.

[0044] Example 3

[0045] A modified high-strength biofilm comprises the following components in parts by weight:

[0046]

[0047] The modified high-strength biofilm comprises the following steps:

[0048] According to the above mass fractions, various ingredients were blended and added to the screw extruder. They were blended at a high temperature of 175°C to melt the polymer. After extrusion, the film bubble was blown by a fan. After the size of the film bubble stabilized, the blowing ratio was adjusted to 3.0, so that the film width reached 1m. The film thickness was adjusted to 15μm by adjusting the main machine speed and traction rate. The obtained film was bidirectionally split and rolled up.

[0049] Comparative Example 1

[0050] A biofilm, the components, component ratio and preparation method are the same as those in Example 1, the only difference being that no modified silicon dioxide is added to the biofilm.

[0051] Comparative Example 2

[0052] A biofilm, the ingredients, ingredient ratios and preparation methods are the same as those in Example 1, the only difference being that the modified silica is replaced by a physical blend of silica and polylauryl polyacrylate (silicon dioxide:lauryl polyacrylate=1:20, n / n) in equal amounts.

[0053] Test Case

[0054] The performance of the films obtained in Examples 1-3 and Comparative Examples 1-2 was tested.

[0055] Mechanical properties test: The films obtained in Examples 1-3 and Comparative Examples 1-2 were tested according to ASTM D638 plastic tensile properties test standard, divided into two groups: the first group was freshly made films, and the second group was films exposed to a stable high temperature environment (40° C.) in a test box for 45 days, then taken out and tested. There were 5 parallel samples, and the test average was taken.

[0056] The test results are shown in Table 1.

[0057] Table 1 Mechanical properties test results

[0058]

[0059] According to Table 1, the tensile strength (transverse) data of the biofilm samples of Examples 1-3 of the present invention, i.e., fresh products, and the products placed in extreme environments for 45 days are compared. It can be seen that the tensile strength of the samples prepared in the examples does not decrease significantly after being placed at high temperatures for a long time. This is mainly due to the excellent compatibility of the film, which reduces the probability of uneven distribution of mechanical properties or significant attenuation caused by agglomeration of the same components in the film system; while the mechanical properties of the film in the comparative example show obvious attenuation in extreme environments, which indicates that the extreme environment accelerates the destruction of the stable coexistence of the various components in the film system.

[0060] In summary, the present invention overcomes the defects in the prior art and has good application prospects.

[0061] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. A modified high-strength biofilm, characterized in that: The modified high-strength biofilm comprises the following components in parts by mass: Polylactic acid 50-70 parts Modified silica 3-6 parts 3-6 parts of silicon dioxide PBAT 20-25 copies 1-2 parts of compatibilizer Additives; in, The modified silica is a network polymer formed by grafting hydroxylated silica with acrylic acid and then polymerizing with dodecyl acrylate; The method for preparing the modified high-strength biofilm comprises the following steps: S1, hydroxylating silicon dioxide to obtain hydroxylated silicon dioxide; S2, immersing the hydroxylated silica in acrylic acid, and ultrasonically heating the silica to obtain acrylic acid-grafted silica; S3, under an inert environment, mixing the acrylic acid-grafted silica with an initiator, dodecyl acrylate, and a solvent, heating for polymerization reaction, and removing the solvent to obtain a product; S4, blending the product with other ingredients, and putting it into a screw extruder, plasticizing and extruding it, and then blowing it into a film; Acrylic acid grafted silica and dodecyl acrylate are blended in a molar ratio of 1:

20.

2. The modified high-strength biofilm according to claim 1, characterized in that: The compatibilizer is selected from one or more of polyethylene glycol, maleic anhydride and tributyl citrate.

3. The modified high-strength biofilm according to claim 1, characterized in that: The auxiliary agent is selected from one or more of an antioxidant, talc, a lubricant, and a plasticizer.

4. The modified high-strength biofilm according to claim 1, characterized in that: The weight average molecular weight of the polylactic acid is 10000-100000 g / mol.

5. The modified high-strength biofilm according to claim 1, characterized in that: In step S2, the temperature of the ultrasound is 80-90°C and the time is 2-3 h.

6. The modified high-strength biofilm according to claim 1, characterized in that: In step S4, the plasticizing temperature is 170-190°C.

7. The modified high-strength biofilm according to claim 1, characterized in that: In step S3, the solvent is toluene.

Images