A degradable biofilm and its preparation method

Abstract

The present invention provides a degradable biofilm and a preparation method thereof, which are made of the following raw materials in parts by weight: 60-70 parts of PBAT, 30-40 parts of PLA, 5-10 parts of microcrystalline cellulose composite modified particles, 0.5-2 parts of chain extender, 1-2 parts of coupling agent, 0.5-1 part of anti-hydrolysis agent, and 0.5-1 part of antioxidant; the degradable biofilm is obtained through processes such as mixing, extrusion granulation, casting cooling, and biaxial stretching. Among them, the microcrystalline cellulose is modified to prepare composite modified particles through procedures such as carboxylation, crosslinking, and monohydroxy capping grafting to a specific degree, so that the degradable biofilm of the present invention has both good mechanical properties and waterproof and breathable functions at the same time.

Description

Technical Field:

[0001] The present invention relates to the field of degradable plastics, and more specifically to a degradable biofilm and a preparation method thereof. Background Art:

[0002] With the progress of modern technology and the continuous expansion of the application fields of plastic products, "white pollution" has become a global problem to be solved. Against this background, degradable polymer materials have become a research hotspot at home and abroad.

[0003] Poly(butylene adipate-co-terephthalate) (PBAT), a copolyester synthesized from aliphatic dibasic acids, aromatic dibasic acids and butanediol, as a new type of biodegradable material, has broad application prospects. However, the current production process of PBAT is not yet mature, and the market price is 2-3 times that of ordinary plastics. In addition, the mechanical property defects of PBAT (such as low tensile strength) also limit its commercial use. Blending modification is the most commonly used method in plastic modification. Therefore, PBAT can be blended with substances with low price and high strength to improve its comprehensive performance and reduce costs.

[0004] In the blending research of PBAT, the commonly selected blending materials themselves have some defects. Cellulose has unique properties, such as low density, high toughness and strength, and degradability, etc.; however, cellulose also has certain defects. Mainly because it is a polyhydroxy compound with certain water absorption. If directly blended with hydrophobic polyester, incompatibility will occur. In addition, in the fields of daily agricultural films, ground films, disposable medical protective clothing, sanitary drug packaging, food packaging, etc., both degradability and

[0005] Patent CN114456359A discloses a tear-resistant and puncture-resistant PBAT copolyester material. Adipic acid, 1,4-butanediol, terephthalic acid, glycerol, and tetrabutyl titanate are blended and undergo two-step esterification and polycondensation in three stages to obtain PBAT-GL-0.6 copolyester; then, citric acid and microcrystalline cellulose are continuously added for the third-step esterification to obtain a tear-resistant and puncture-resistant PBAT copolyester material. However, this scheme requires the preparation of a specific PBAT copolyester, with a high cost.

[0006] CN113527847A discloses a degradable breathable film. Anisotropic inorganic fillers are added to PLA / PBAT. At the same time, during the process of blowing a polymer masterbatch containing rod-shaped or sheet-shaped nano-fillers into a film, by controlling the traction speed and blow-up ratio of the film blowing machine, micropores and three-dimensional pore networks are generated in the film under the appropriate stretching in the transverse and longitudinal directions, thereby improving the gas permeability of the film. However, this scheme is only applicable to methods such as blowing.

[0007] Therefore, the preparation of a degradable biofilm with excellent mechanical properties, breathability and waterproofness has broad application prospects in the fields of packaging and the like. Summary of the Invention:

[0008] The present invention intends to provide a degradable biofilm and a preparation method thereof. This material has excellent mechanical properties and controllable biodegradability.

[0009] The present invention obtains modified microcrystalline cellulose through modification steps such as carboxylation, crosslinking and grafting of microcrystalline cellulose, and thus prepares a degradable biofilm of PBAT / PLA / modified microcrystalline cellulose. This film has both excellent mechanical properties and breathability and waterproof functions.

[0010] To achieve the technical purpose of the present invention, the present invention provides a degradable biofilm, which is made from the following raw materials in parts by weight: 60-70 parts of PBAT, 30-40 parts of PLA, 5-10 parts of microcrystalline cellulose composite modified particles, 0.5-2 parts of chain extender, 1-2 parts of coupling agent, 0.5-1 part of anti-hydrolysis agent, and 0.5-1 part of antioxidant.

[0011] Further, the chain extender is a copolymer of styrene-methyl methacrylate-glycidyl methacrylate.

[0012] Further, the coupling agent is one or more of silane coupling agents, aluminate coupling agents, and aluminum-titanium composite coupling agents.

[0013] Further, the anti-hydrolysis agent is a carbodiimide anti-hydrolysis agent.

[0014] Further, the antioxidant is one or more of antioxidant 1010, antioxidant 168, antioxidant 1076 or antioxidant 1790.

[0015] Further, the preparation method of the microcrystalline cellulose composite modified particles is as follows: disperse microcrystalline cellulose in a citric acid solution, use hydrochloric acid as a catalyst, and carry out a hydrolysis reaction at 50-90 °C for 2-6 h; repeatedly wash the obtained reaction suspension with distilled water until it is neutral; treat the suspension in an ultrasonic cell disruptor for 0.5-1 h to obtain an aqueous solution of carboxylated microcrystalline cellulose, and successively add aluminum hydroxide and monohydroxy-terminated silicone oil for modification to form a gel. After aging at room temperature for 12-24 h, dry it to constant weight at 80-100 °C and grind it to obtain microcrystalline cellulose composite modified particles.

[0016] The material-liquid ratio of the microcrystalline cellulose to the citric acid solution is between 1:20 and 1:40; the concentration of the citric acid solution is between 2-4 mol / L; the concentration of the hydrochloric acid solution is between 5-6 mol / L; the dosage of the hydrochloric acid solution accounts for 1-5% of the citric acid solution.

[0017] The dosage of aluminum hydroxide accounts for 1-3% of the mass of microcrystalline cellulose, the dosage of mono-hydroxy terminated silicone oil accounts for 0.5-2% of the mass of microcrystalline cellulose, and the average molecular weight is 1000-2000 g / mol.

[0018] The preparation method of the degradable biofilm includes the following steps:

[0019] (1) Mix 60-70 parts of PBAT, 30-40 parts of PLA, 5-10 parts of microcrystalline cellulose composite modified particles, 0.5-2 parts of chain extender, 1-2 parts of coupling agent, 0.5-1 part of hydrolysis inhibitor, and 0.5-1 part of antioxidant in a mixer and stir evenly, then add them into a twin-screw extruder for extrusion, air cooling, and pelletizing to obtain the masterbatch of PBAT / PLA / modified microcrystalline cellulose;

[0020] (2) Cast the masterbatch prepared in step (1) using a casting machine and obtain a sheet after cooling;

[0021] (3) Biaxially stretch the sheet obtained in step (2), and then perform heat setting to obtain the PBAT / PLA / modified microcrystalline cellulose film.

[0022] Further, the temperature of the mixer in step (1) is 80-110 °C, and the rotation speed is 800-1200 r / min.

[0023] Further, the extrusion temperatures of the first to sixth zones of the twin-screw extruder in step (1) are 110, 120, 130, 130, 120, and 120 °C respectively, and the head temperature is 120 °C.

[0024] Further, the casting temperature in step (2) is 180-200 °C, and the cooling temperature is 20-30 °C.

[0025] Further, the biaxial stretching in step (3) includes: first performing longitudinal stretching, and then performing transverse stretching, where the longitudinal stretching temperature is 95-105 °C, the stretching ratio is 3-4, the transverse stretching temperature is 100-110 °C, the stretching ratio is 3-5, and the heat setting temperature is 110-115 °C.

[0026] In the present invention, the microcrystalline cellulose is carboxylated and modified, and at the same time, the generated carboxyl groups are crosslinked with aluminum hydroxide to form composite particles with a certain crosslinking network. At the same time, mono-hydroxy terminated silicone oil is added to endow the composite particles with better hydrophobicity, which can ensure that the modified microcrystalline cellulose can be better dispersed in the polymer. At the same time, the introduction of mono-hydroxy terminated silicone oil, while further enhancing the hydrophobicity and dispersibility, will cause the presence of long chains with a certain degree of freedom in the system, which can improve the moisture permeability of the overall material.

[0027] For carboxylation modification, the carboxyl content in microcrystalline cellulose should not be too high. When the carboxyl content is too high, the internal cross-linking network of microcrystalline cellulose will be too dense, which will instead make the dispersion effect of the modified microcrystalline cellulose in the PBAT / PLA polymer system worse, increase the tendency of phase separation, and ultimately lead to a decrease in mechanical properties.

[0028] The modified microcrystalline cellulose in the present invention can be used as a nucleating agent in the system. At the same time, during biaxial stretching, when the film is subjected to a stretching force, interfacial micropores are formed, further enhancing the gas permeability of the film in the present invention.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] (1) The present invention modifies microcrystalline cellulose by carboxylation, cross-linking and grafting, improving the dispersibility of microcrystalline cellulose in the PBAT / PLA polymer system; at the same time, the water contact angle of the film of the present invention is above 90°, and the moisture permeability is above 130 g / m 2 / 24 h, indicating that it has the dual functions of waterproof and breathable at the same time.

[0031] (2) The present invention controls the degree of carboxylation of microcrystalline cellulose to ensure that the internal cross-linking network of microcrystalline cellulose maintains an appropriate density, thereby maintaining the dispersibility of the modified microcrystalline cellulose in the PBAT / PLA polymer system, and thus ensuring the mechanical properties of the degradable biofilm.

[0032] (3) The present invention utilizes the nucleating agent effect of the modified microcrystalline cellulose, and through biaxial stretching, further increases the gas permeability of the film. Specific embodiments:

[0033] To make the purpose, technical solutions and advantages of the implementation of the present invention clearer, the technical solutions of the present invention will be further described below through specific embodiments. Those skilled in the art should know that the embodiments are only for helping to understand the technical content and technical effects of the present invention, and should not be regarded as a limitation of the present invention.

[0034] PBAT and PLA in the examples and comparative examples of the present invention are all purchased from Guangdong Kingfa Sci. & Tech. Co., Ltd., microcrystalline cellulose is purchased from Qufu Tianli Pharmaceutical Excipients Co., Ltd., and the chain extender is a styrene-methyl methacrylate-glycidyl methacrylate copolymer of model KL-E4370B, and other auxiliaries are all common commercially available products.

[0035] The present invention conducts a total of 4 examples and 3 comparative examples.

[0036] Example 1:

[0037] Preparation of microcrystalline cellulose modified composite particles:

[0038] Disperse 3 parts by mass of microcrystalline cellulose in a citric acid (3 mol / L) solution with a material-liquid ratio of 1:20. At the same time, add hydrochloric acid (6 mol / L) accounting for 5% of the volume of the citric acid solution as a catalyst, and carry out stirring reaction hydrolysis at 80 °C for 3 h; repeatedly wash the obtained reaction suspension with distilled water until it is neutral; treat the suspension in an ultrasonic cell disruptor for 0.5 h to obtain an aqueous solution of carboxylated microcrystalline cellulose. Then, add 0.06 part by mass of aluminum hydroxide and 0.03 part by mass of monohydroxy-terminated silicone oil in sequence for modification to form a gel, age it at room temperature for 24 h, dry it to constant weight at 80 °C, and grind it to obtain microcrystalline cellulose composite modified particles.

[0039] Preparation method of degradable biofilm:

[0040] (1) Mix 70 parts of PBAT, 30 parts of PLA, 5 parts of microcrystalline cellulose composite modified particles, 2 parts of chain extender KL-E4370B, 1 part of silane coupling agent KH-550, 1 part of hydrolysis-resistant agent Bio-SW100, and 0.5 part of antioxidant 1010 in a mixer at 90 °C and a rotation speed of 1000 r / min. After mixing and stirring evenly, add them into a twin-screw extruder for extrusion, air cooling, and pelletizing. The extrusion temperatures of the first to sixth zones of the twin-screw extruder are 110, 120, 130, 130, 120, and 120 °C respectively, and the head temperature is 120 °C to obtain a masterbatch of PBAT / PLA / modified microcrystalline cellulose.

[0041] (2) Add the masterbatch prepared in step (1) to a casting machine and cast at 180 °C, and then cool at 20 °C to obtain a sheet.

[0042] (3) First, longitudinally stretch the sheet obtained in step (2), and then transversely stretch it. The longitudinal stretching temperature is 95 °C and the stretching ratio is 3, and the transverse stretching temperature is 105 °C and the stretching ratio is 4. Then, heat-set it at 110 °C to obtain a PBAT / PLA / modified microcrystalline cellulose film.

[0043] Example 2:

[0044] Preparation of microcrystalline cellulose modified composite particles:

[0045] Disperse 3 parts by mass of microcrystalline cellulose in a citric acid (3 mol / L) solution with a material-liquid ratio of 1:30. At the same time, add hydrochloric acid (6 mol / L) accounting for 5% of the volume of the citric acid solution as a catalyst, and carry out stirring reaction hydrolysis at 90 °C for 2.5 h; repeatedly wash the obtained reaction suspension with distilled water until it is neutral; treat the suspension in an ultrasonic cell disruptor for 0.5 h to obtain an aqueous solution of carboxylated microcrystalline cellulose. Then add 0.06 parts by mass of aluminum hydroxide and 0.05 parts by mass of monohydroxy-terminated silicone oil for modification to form a gel, age at room temperature for 24 h, dry to constant weight at 90 °C, and grind to obtain microcrystalline cellulose composite modified particles.

[0046] Preparation method of degradable biofilm:

[0047] (1) Mix 70 parts of PBAT, 35 parts of PLA, 8 parts of microcrystalline cellulose composite modified particles, 1 part of chain extender KL-E4370B, 1.5 parts of aluminate coupling agent DL4111, 1 part of hydrolysis inhibitor Bio-SW500, and 0.5 part of antioxidant 168 in a mixer at 90 °C with a rotation speed of 1000 r / min, stir evenly, then add them into a twin-screw extruder for extrusion, air cooling, and pelletizing. The extrusion temperatures of the first to sixth zones of the twin-screw extruder are 110, 120, 130, 130, 120, and 120 °C respectively, and the head temperature is 120 °C to obtain a masterbatch of PBAT / PLA / modified microcrystalline cellulose.

[0048] (2) Add the masterbatch prepared in step (1) to a casting machine and cast at 180 °C, and then cool at 20 °C to obtain a sheet.

[0049] (3) First longitudinally stretch the sheet obtained in step (2), and then transversely stretch it. The longitudinal stretching temperature is 100 °C and the stretching ratio is 4, and the transverse stretching temperature is 100 °C and the stretching ratio is 5. Then heat set at 110 °C to obtain a PBAT / PLA / modified microcrystalline cellulose film.

[0050] Example 3:

[0051] Example 3 uses the microcrystalline cellulose composite modified particles prepared in Example 1.

[0052] Preparation of degradable biofilm:

[0053] (1) Mix 60 parts of PBAT, 30 parts of PLA, 8 parts of microcrystalline cellulose composite modified particles, 2 parts of chain extender KL-E4370B, 1.5 parts of aluminate coupling agent DL4111, 1 part of hydrolysis inhibitor Bio-SW100, and 0.5 part of antioxidant 1010 in a mixer at 90 °C with a rotation speed of 1000 r / min. After mixing and stirring evenly, add them into a twin-screw extruder for extrusion, air cooling, and pelletizing. The extrusion temperatures of the first to sixth zones of the twin-screw extruder are 110, 120, 130, 130, 120, and 120 °C respectively, and the head temperature is 120 °C to obtain the masterbatch of PBAT / PLA / modified microcrystalline cellulose;

[0054] (2) Add the masterbatch prepared in step (1) to a casting machine and cast at 180 °C, and then cool at 20 °C to obtain a sheet;

[0055] (3) First longitudinally stretch the sheet obtained in step (2), and then transversely stretch it. The longitudinal stretching temperature is 90 °C and the stretching ratio is 3. The transverse stretching temperature is 100 °C and the stretching ratio is 4. Then heat set at 110 °C to obtain the PBAT / PLA / modified microcrystalline cellulose film.

[0056] Comparative Example 1:

[0057] The difference from Example 1 is that the material ratio of microcrystalline cellulose to citric acid is 1:50.

[0058] Comparative Example 2:

[0059] The difference from Example 1 is that mono-hydroxy terminated silicone oil is not added.

[0060] Comparative Example 3:

[0061] The difference from Example 3 is that the dosage of microcrystalline cellulose composite modified particles is 2 parts by mass.

[0062] The following standard methods are used to test the various properties of the above standard specimens:

[0063] Mechanical property test: Test the tensile strength and elongation at break of the PBAT nanocomposite film sample in the manufacturing example according to the standard of GB / T1040.3 - 2006. Cut the film into samples with a specification of (10 mm × 160 mm), the clamp spacing is 40 mm, the tensile speed is 200 mm / min, repeat the test 5 times, and take the average value to obtain the tensile strength and elongation at break.

[0064] Waterproof property (water contact angle) test: Use a contact angle measuring instrument for testing. Horizontally place the sample on the platform of the contact angle measuring instrument, inject distilled water onto the sample surface through a microinjector, observe the change in the contact angle size, and the test range is 0 - 180°.

[0065] Moisture permeability test: The test was carried out using a moisture permeability tester. Before the test, according to the provisions in GB / T26253-2010, the sample was placed in an environment with a temperature of 25°C and a relative humidity of 50% for 4 hours. Test conditions: temperature 25°C, relative humidity 90%, atmospheric pressure, test time 4 hours.

[0066] The test results of mechanical properties, moisture permeability and waterproof properties are shown in Table 1.

[0067]

[0068] From the results of Examples 1-3 and Comparative Examples 1-3, the microcrystalline cellulose of the present invention was modified by carboxylation, crosslinking and monohydroxy capping grafting. At the same time, the degree of carboxylation of the microcrystalline cellulose was controlled and the biaxial stretching operation was carried out, so that the obtained degradable biofilm had good mechanical properties and waterproof and breathable functions at the same time.

[0069] From the comparison between the examples and Comparative Example 1, when the degree of carboxylation of the microcrystalline cellulose is too high, it will lead to an overly dense internal crosslinking network of the microcrystalline cellulose, which will instead deteriorate the dispersion effect of the modified microcrystalline cellulose in the PBAT / PLA polymer system, and will affect the mechanical properties and breathable function of the final product.

[0070] From the comparison between the examples and Comparative Example 2, when the monohydroxy-capped silicone oil is not added, although it will not affect the mechanical properties, due to the lack of hydrophobic groups with degrees of freedom, the waterproof and breathable properties of the film will be affected.

[0071] From the comparison between the examples and Comparative Example 3, when the amount of the modified microcrystalline cellulose is reduced, it will seriously affect the number of interfacial micropores formed under the action of stretching, and ultimately have an adverse impact on the breathable performance.

[0072] It should be noted that this application is not limited to the above embodiments. The above embodiments are only examples, and embodiments with the same structure and the same function and effect as the technical idea within the technical solution scope of this application are all included in the technical scope of this application. In addition, within the scope of not departing from the gist of this application, various deformations that can be thought of by those skilled in the art on the embodiments, and other methods constructed by combining some constituent elements in the embodiments are also included in the scope of this application.

Claims

1. A degradable biofilm, characterized in that, It is made from the following raw materials in parts by weight: 60 - 70 parts of PBAT, 30 - 40 parts of PLA, 5 - 10 parts of microcrystalline cellulose composite modified particles, 0.5 - 2 parts of chain extender, 1 - 2 parts of coupling agent, 0.5 - 1 part of hydrolysis inhibitor, 0.5 - 1 part of antioxidant; The preparation method of the microcrystalline cellulose composite modified particles is as follows: Disperse microcrystalline cellulose in a citric acid solution, use hydrochloric acid as a catalyst, and carry out a hydrolysis reaction at 50 - 90 °C for 2 - 6 h; repeatedly wash the obtained reaction suspension with distilled water until neutral; treat the suspension in an ultrasonic cell disruptor for 0.5 - 1 h to obtain an aqueous solution of carboxylated microcrystalline cellulose, and successively add aluminum hydroxide and monohydroxy-terminated silicone oil for modification to form a gel. After aging at room temperature for 12 - 24 h, dry it to constant weight at 80 - 100 °C and grind to obtain microcrystalline cellulose composite modified particles; The material-liquid ratio of microcrystalline cellulose to the citric acid solution is between 1:20 and 1:40; the concentration of the citric acid solution is between 2 - 4 mol / L; the concentration of the hydrochloric acid solution is between 5 - 6 mol / L; the amount of the hydrochloric acid solution accounts for 1 - 5% of the citric acid solution.

2. The degradable biofilm according to claim 1, characterized in that, The hydrolysis inhibitor is a carbodiimide hydrolysis inhibitor; the chain extender is a styrene-methyl methacrylate-glycidyl methacrylate copolymer; the coupling agent is one or more of a silane coupling agent, an aluminate coupling agent, and an aluminum-titanium composite coupling agent; the antioxidant is one or more of antioxidant 1010, antioxidant 168, antioxidant 1076, or antioxidant 1790.

3. The biodegradable biofilm according to claim 1, characterized in that, During the preparation of the microcrystalline cellulose composite modified particles, the amount of the aluminum hydroxide used accounts for 1 - 3% of the mass of the microcrystalline cellulose; the amount of the monohydroxy-terminated silicone oil used accounts for 0.5 - 2% of the mass of the microcrystalline cellulose, and the average molecular weight is between 1000 - 2000 g / mol.

4. The preparation method of the degradable biofilm according to any one of claims 1 to 3, characterized in that: It includes the following steps: (1) Mix 60 - 70 parts of PBAT, 30 - 40 parts of PLA, 5 - 10 parts of microcrystalline cellulose composite modified particles, 0.5 - 2 parts of chain extender, 1 - 2 parts of coupling agent, 0.5 - 1 part of hydrolysis inhibitor, and 0.5 - 1 part of antioxidant in a mixer and stir evenly, then add them into a twin-screw extruder for extrusion, air cooling, and pelletizing to obtain a masterbatch of PBAT / PLA / modified microcrystalline cellulose; (2) Add the masterbatch prepared in step (1) into a casting machine for casting, and obtain a sheet after cooling; (3) Carry out biaxial stretching on the sheet obtained in step (2), and then heat set to obtain a PBAT / PLA / modified microcrystalline cellulose film.

5. The method according to claim 4, wherein The temperature of the mixer in step (1) is 80 - 110 °C, and the rotation speed is 800 - 1200 r / min.

6. The method according to claim 4, characterized in that The extrusion temperatures of the first to sixth zones of the twin-screw extruder in step (1) are 110, 120, 130, 130, 120, and 120 °C respectively, and the head temperature is 120 °C.

7. The method according to claim 4, characterized in that, The temperature of casting in step (2) is 180 - 200 °C, and the cooling temperature is 20 - 30 °C.

8. The method according to claim 4, characterized in that, The biaxial stretching in step (3) includes: first performing longitudinal stretching and then transverse stretching. The temperature of the longitudinal stretching is 95 - 105 °C, the stretching ratio is 3 - 4, the temperature of the transverse stretching is 100 - 110 °C, the stretching ratio is 3 - 5, and the temperature of the heat setting is 110 - 115 °C.

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