High-temperature-resistant water-soluble polyvinyl alcohol packaging film as well as preparation method and application thereof

Abstract

The invention relates to the field of packaging materials, in particular to a high-temperature-resistant water-soluble polyvinyl alcohol packaging film as well as a preparation method and application thereof. The high-temperature-resistant water-soluble polyvinyl alcohol packaging film is prepared from the following raw materials: polyvinyl alcohol, modified polyvinyl alcohol, a compound composition, modified nanoparticles, a surfactant, deionized water and the like. The finally prepared film material not only has good mechanical properties, but also can maintain good water solubility, barrier property and other properties while having excellent high temperature resistance, solves the contradictory problem that the high temperature resistance of the existing PVA film is changed by sacrificing other properties, avoids the complex process of multi-layer co-extrusion film formation, and is suitable for large-scale production. And the equipment cost is further saved, the comprehensive performance requirements of the existing packaging field on the PVA film are met, and the method has very excellent application prospects.

Description

Technical Field

[0001] The present application relates to the field of packaging materials, and more specifically to a high-temperature resistant water-soluble polyvinyl alcohol packaging film, a preparation method thereof, and applications thereof. Background Art

[0002] Polyvinyl alcohol (PVA) film, due to its excellent water solubility, biodegradability, and film-forming properties, is considered a key development direction for green packaging materials. With the advancement of environmental protection policies, water-soluble PVA film has great potential for application in food packaging, electronics packaging, textile packaging, and agricultural seed film.

[0003] However, traditional PVA films lack high-temperature resistance and mechanical properties. They are prone to softening, adhesion, or partial decomposition in high-temperature environments (>80°C). In addition, they cannot effectively maintain their shape in aqueous and high-humidity environments, and soften and hydrolyze. These problems severely limit their application in high-requirement scenarios (such as high-temperature cooking packaging, industrial high-temperature packaging, and hot-melt adhesive carriers).

[0004] In order to solve the above problems, existing technicians have proposed three general improvement directions. For example, chemical cross-linking improvement, by adding a cross-linking agent to improve the cross-linking effect in the system, in order to build an internal stable system to improve the mechanical and thermal stability, but this method will often sacrifice the water solubility of the film, resulting in a significant decrease in its water solubility rate. Secondly, there are methods including adding inorganic fillers such as nano-calcium carbonate and mesoporous silica to improve the heat resistance and mechanical strength of the film, but at the same time this method has a large negative impact on the aging resistance and water solubility of the film, and cannot guarantee the basic application effect of the film; finally, there is a method of compounding an outer heat-resistant coating (such as polylactic acid) with an inner layer of PVA, but the multi-layer structure increases the processing cost, and the coating material is usually non-water-soluble, which goes against the original intention of the full degradation design. Summary of the Invention

[0005] Therefore, in order to effectively solve the performance balance contradiction and process complexity problems of existing water-soluble polyvinyl alcohol packaging films, the present application provides a high-temperature resistant water-soluble polyvinyl alcohol packaging film and a preparation method thereof. The film material finally obtained not only has good mechanical properties, but also has excellent high-temperature resistance while maintaining good water solubility and barrier properties. It solves the contradictory problem of existing PVA films in exchange for high-temperature resistance by sacrificing other properties, avoids the use of complex multi-layer co-extrusion film-forming processes, further saves equipment costs, meets the comprehensive performance requirements of PVA films in the existing packaging field, and has very excellent application prospects.

[0006] The high-temperature resistant water-soluble polyvinyl alcohol packaging film comprises the following raw materials, calculated by mass: 50-70 parts of polyvinyl alcohol, 30-50 parts of modified polyvinyl alcohol, 10-20 parts of compound composition, 3-8 parts of modified nanoparticles, 1.5-2.5 parts of surfactant, 3-7 parts of enhancer, 0.5-1 part of defoaming agent, 2-3 parts of cross-linking agent, 1-1.5 parts of film-forming agent, 0.8-1.4 parts of leveling agent, and 100-150 parts of deionized water.

[0007] As a preferred embodiment, the mass ratio of the polyvinyl alcohol, modified polyvinyl alcohol and the compound composition is (55~68): (36~45): (12~18).

[0008] As a preferred embodiment, the mass ratio of the polyvinyl alcohol, modified polyvinyl alcohol and the compound composition is (58~62): (40~43): (14~16).

[0009] As a preferred embodiment, the mass ratio of the modified polyvinyl alcohol, modified nanoparticles and enhancer is (36~45): (4~6): (4~5.5).

[0010] As a preferred embodiment, the mass ratio of the modified polyvinyl alcohol, modified nanoparticles and reinforcing agent is (40-43): (5-5.5): (4.2-4.8).

[0011] As a preferred embodiment, the degree of polymerization of the polyvinyl alcohol is 1500~2500.

[0012] As a preferred embodiment, the degree of polymerization of the polyvinyl alcohol is 1700-2000.

[0013] As a preferred embodiment, the alcoholysis degree of the polyvinyl alcohol is 90-99%.

[0014] As a preferred embodiment, the preparation method of the modified polyvinyl alcohol specifically includes the following steps: S1: vinyl acetate, hydroxyethyl acrylate, vinyl pyrrolidone and sodium styrene sulfonate are mixed in proportion, methanol solution is added, the temperature is raised to 65-70°C, azobisisobutyronitrile is added and the reaction is kept warm for 6-8 hours to obtain a pre-product; S2: sodium hydroxide is added to the pre-product, the temperature is raised to 45-55°C and the reaction is kept warm for 4-5 hours until the reaction reaches the desired degree of alcoholysis. After completion, the product is filtered and washed, and the product is obtained.

[0015] As a preferred embodiment, the mass ratio of vinyl acetate, hydroxyethyl acrylate, vinyl pyrrolidone and sodium styrene sulfonate is (70-80): (8-9): (3-4): (1-1.5).

[0016] As a preferred embodiment, the mass ratio of the pre-product to sodium hydroxide is (90-100): (20-30).

[0017] As a preferred embodiment, the required alcoholysis degree in the preparation method S2 of the modified polyvinyl alcohol is 80-90%.

[0018] The modified polyvinyl alcohol resin can form a dense internal hydrogen bond network through the interaction of the added multi-group monomer and its own molecular chain, thereby greatly increasing the mutual "stickiness" between the systems, reducing the gaps between molecules and molecular chains, and then connecting the migration channels of the internal fine branches, greatly increasing the diffusion paths of gas and water molecules in the system, and further reducing the crystallinity through the introduction of the cross-linked structure, while maintaining good water solubility while obtaining excellent barrier properties. On the other hand, by coordinating the multi-active groups on the surface of the modified nanoparticles added in this application, it is possible to achieve interaction forces between the resin and solid particles, and between particles, promote the degree of internal cross-linking, enhance the force between molecular chain segments, and greatly improve the system's resistance to molecular chain slippage, thereby obtaining excellent mechanical properties, and being able to inhibit the movement of molecular chains and the migration efficiency of active molecules in active environments such as high temperatures, thereby maintaining good high temperature resistance.

[0019] As a preferred embodiment, the compound composition is a composition of hyperbranched polyester, polyglycerol and formamide.

[0020] As a preferred embodiment, the mass ratio of the hyperbranched polyester, polyglycerol and formamide is (5.5-6.5): (1-1.5): (1.8-2.4).

[0021] As a preferred embodiment, the mass ratio of the hyperbranched polyester, polyglycerol and formamide is (5.8~6.2): ​​(1.1~1.2): (1.9~2.1).

[0022] The addition of the aforementioned composite compound not only effectively reduces the number of free hydroxyl groups within the packaging film resin system and inhibits water molecule penetration, but its overall assistive effect also effectively reduces the amount of modified polyvinyl alcohol used. Furthermore, through the carbon, oxygen, and hydrogen elements in the polyvinyl alcohol backbone, it retains good degradation water solubility, maintains appropriate crystallinity, and ensures degradation and water-solubility efficiency. Furthermore, the added hyperbranched structure forms a non-covalent hydrogen bond network with PVA via terminal hydroxyl groups, helping to disperse stress and inhibit crack propagation. The retained aromatic ring or ester structure, through free radical capture and carbon layer formation, delays thermal degradation and helps improve high-temperature resistance. Finally, the polyhydroxy structure of polyglycerol competes with PVA for water molecules through hydrogen bonds, reducing the exposure of free hydroxyl groups. It also forms a dynamic cross-linked network with the hyperbranched polyester assist system, restricting internal migration paths, thereby overall improving the comprehensive performance of the packaging film.

[0023] As a preferred embodiment, the modified nanoparticles are modified titanium dioxide.

[0024] As a preferred embodiment, the preparation method of the modified titanium dioxide specifically includes the following steps: S1: adding titanium dioxide to N,N-dimethylformamide solution, adding succinic anhydride and N-β-aminoethyl-γ-aminopropyltrimethoxysilane, and keeping the reaction at 60~70℃ for 2~3h to obtain pretreated titanium dioxide; S2: adding the pretreated titanium dioxide to an ethanol solution, stirring at 200~300rpm for 40~50min, then adding polyethyleneimine, stirring at 60~70℃ for 2~4h, centrifuging and filtering after completion, and then vacuum drying at 75~80℃ to obtain.

[0025] As a preferred embodiment, the mass ratio of titanium dioxide, succinic anhydride and N-β-aminoethyl-γ-aminopropyltrimethoxysilane is (8-10): (1.5-2): (0.6-0.8).

[0026] As a preferred embodiment, the mass ratio of the pretreated titanium dioxide to polyethyleneimine is (9-10): (1.2-1.6).

[0027] As a preferred embodiment, the average particle size of the titanium dioxide is 30-50 nm.

[0028] The addition of modified titanium dioxide not only forms a dense physical barrier within the film system, extending the diffusion path, but also allows more surface active groups to interact with the modified resin system, thereby increasing the number of stress transfer points and inhibiting further crack expansion when external forces act. Furthermore, its excellent interfacial bonding with the polyvinyl alcohol resin system can significantly reduce the micropore diameter and crack length in the film system, thereby maintaining appropriate hydrophilicity and water permeability in low-temperature environments, ensuring good water solubility.

[0029] As a preferred embodiment, the surfactant is a composition of sodium lauryl sulfate, tributyl phosphate and PEG-40 hydrogenated castor oil.

[0030] As a preferred embodiment, the mass ratio of sodium lauryl sulfate, tributyl phosphate and PEG-40 hydrogenated castor oil is (4-5): (1-2): (2-2.5).

[0031] As a preferred embodiment, the mass ratio of sodium lauryl sulfate, tributyl phosphate and PEG-40 hydrogenated castor oil is (4.2-4.5): (1.2-1.6): (2.1-2.3).

[0032] As a preferred embodiment, the enhancer is at least one of gelatin, agar, sodium carboxymethyl cellulose, chitosan and polyacrylamide.

[0033] As a preferred embodiment, the enhancer is a combination of sodium carboxymethyl cellulose and chitosan.

[0034] As a preferred embodiment, the mass ratio of sodium carboxymethyl cellulose to chitosan is (3-4): (1-1.4).

[0035] As a preferred embodiment, the defoaming agent is at least one of silicone defoaming agents.

[0036] As a preferred embodiment, the defoamer is organosilicon defoamer BYK-022.

[0037] As a preferred embodiment, the cross-linking agent is at least one of boric acid, citric acid, epichlorohydrin and sodium tripolyphosphate.

[0038] As a preferred embodiment, the cross-linking agent is boric acid.

[0039] As a preferred embodiment, the film-forming agent is at least one of polyvinyl pyrrolidone, hydroxypropyl methylcellulose, polyethylene oxide, polyethylene glycol and polyacrylic acid.

[0040] As a preferred embodiment, the film-forming agent is a combination of polyvinyl pyrrolidone and polyethylene glycol.

[0041] As a preferred embodiment, the mass ratio of polyvinyl pyrrolidone to polyethylene glycol is (4-4.5): (1.4-1.6).

[0042] As a preferred embodiment, the leveling agent is a composition of BYK-333 and perfluoroalkyl ethyl acrylate.

[0043] As a preferred embodiment, the mass ratio of BYK-333 to perfluoroalkyl ethyl acrylate is (2.5-3): (0.6-0.8).

[0044] As a preferred embodiment, the preparation method of the high-temperature resistant water-soluble polyvinyl alcohol packaging film specifically includes the following steps: S1: adding polyvinyl alcohol, modified polyvinyl alcohol, compound composition and modified nanoparticles to deionized water, stirring and dissolving at 90°C for 3~4 hours; S2: subsequently adding the remaining raw materials in sequence, stirring at a constant temperature of 80°C and a speed of 200~250rpm for 0.6~1 hour each time to obtain a mixed solution; S3: casting the mixed solution onto a preheated substrate, the substrate temperature is 70~80°C, after the casting is completed, thermoforming at 85~90°C in a blowing oven for 0.5~0.8h, removing the film after cooling, and then equilibrating the obtained film at a temperature of 25~30°C and a relative humidity of 45~50% for 20~24 hours, and the film is obtained after completion.

[0045] The present application further defines the application of the high-temperature resistant water-soluble polyvinyl alcohol packaging film in the fields of food packaging, electronic packaging, textile packaging and agricultural seed film.

[0046] This application has the following beneficial effects: 1. The present application provides a high-temperature resistant water-soluble polyvinyl alcohol packaging film, which not only has good mechanical properties, but also has excellent high-temperature resistance while maintaining good water solubility and barrier properties. It solves the contradictory problem of existing PVA films sacrificing other properties in exchange for high-temperature resistance, avoids the use of complex multi-layer co-extrusion film-forming processes, further saves equipment costs, meets the comprehensive performance requirements of PVA films in the existing packaging field, and has very excellent application prospects.

[0047] 2. A high-temperature resistant water-soluble polyvinyl alcohol packaging film provided in the present application, in which the modified polyvinyl alcohol resin is added, can form a dense internal hydrogen bond network through the interaction between the added multi-group monomer and its own molecular chain, thereby greatly increasing the mutual "stickiness" between the systems, reducing the gaps between molecules and between molecular chains, and then connecting the migration channels of the internal small branches, greatly increasing the diffusion paths of gas and water molecules in the system, and further reducing the crystallinity through the introduction of cross-linked structure, thereby obtaining excellent barrier properties while maintaining good water solubility.

[0048] 3. The present application provides a high-temperature resistant water-soluble polyvinyl alcohol packaging film. The modified polyvinyl alcohol resin added thereto can also cooperate with the multi-active groups on the surface of the modified nanoparticles added thereto to achieve interaction between the resin and solid particles, and between particles, promote the degree of internal cross-linking, enhance the interaction between molecular chain segments, and greatly improve the system's resistance to molecular chain slippage, thereby obtaining excellent mechanical properties. In addition, the film can inhibit the movement of molecular chains and the migration efficiency of active molecules in active environments such as high temperatures, thereby maintaining good high-temperature resistance. DETAILED DESCRIPTION

[0049] The following embodiments are merely practical examples used to illustrate and explain the technical solutions in the specification and should not limit the scope of the claims to be protected by this application.

[0050] Example 1 The high-temperature resistant water-soluble polyvinyl alcohol packaging film, calculated by mass, comprises the following raw materials: 61.5 parts of polyvinyl alcohol, 42.3 parts of modified polyvinyl alcohol, 14.6 parts of compound composition, 5.2 parts of modified nanoparticles, 2.1 parts of surfactant, 4.4 parts of enhancer, 0.6 part of defoaming agent, 2.8 parts of cross-linking agent, 1.4 parts of film-forming agent, 1.1 parts of leveling agent, and 110 parts of deionized water.

[0051] The polyvinyl alcohol has a degree of polymerization of 1700 and a degree of alcoholysis of 99%, and was purchased from the PVA-1799 product sold by Sinopec Sichuan Wei Chemical Company.

[0052] The preparation method of modified polyvinyl alcohol specifically comprises the following steps, calculated by mass: S1: 78 parts of vinyl acetate, 8.2 parts of hydroxyethyl acrylate, 3.4 parts of vinyl pyrrolidone and 1.2 parts of sodium styrene sulfonate are mixed in proportion, 120 parts of methanol solution are added, the temperature is raised to 65°C, 1.1 parts of azobisisobutyronitrile are added, and the mixture is kept warm for 6.5 hours to obtain a pre-product; S2: 25 parts of sodium hydroxide are added to 100 parts of the pre-product, the temperature is raised to 50°C, and the mixture is kept warm for 4.5 hours until the reaction reaches the desired alcoholysis degree of 88%. After completion, the product is filtered and washed, and the product is obtained.

[0053] The composite composition is a composition of hyperbranched polyester, polyglycerol and formamide, with a mass ratio of 6:1.1:1.9.

[0054] Hyperbranched polyester was purchased from the L-6126 product sold by Lankelu Company in China; polyglycerol was purchased from the JP-20 diglycerol product sold by Jinsheng Chemical in Binzhou, Shandong, China.

[0055] The modified nanoparticles are modified titanium dioxide, and the preparation method thereof, calculated by mass, specifically includes the following steps: S1: adding 10 parts of titanium dioxide to 150 parts of N,N-dimethylformamide solution, adding 1.8 parts of succinic anhydride and 0.7 parts of N-β-aminoethyl-γ-aminopropyltrimethoxysilane, and keeping the reaction at 70°C for 2.5 hours to obtain pretreated titanium dioxide; S2: adding 10 parts of pretreated titanium dioxide to 100 parts of ethanol solution, stirring at 220 rpm for 45 minutes, then adding 1.4 parts of polyethyleneimine, stirring at 65°C for 3 hours, centrifuging and filtering after completion, and then vacuum drying at 80°C to obtain the product.

[0056] Polyethyleneimine was purchased from Wuhan Lanabai Pharmaceutical Chemical Co., Ltd., China, with a molecular weight of 10,000.

[0057] The average particle size of titanium dioxide is 35 nm.

[0058] The surfactant is a composition of sodium lauryl sulfate, tributyl phosphate and PEG-40 hydrogenated castor oil, with a mass ratio of 4.3:1.4:2.3.

[0059] The composition of sodium carboxymethyl cellulose and chitosan has a mass ratio of 3.8:1.2.

[0060] The defoaming agent is silicone defoaming agent BYK-022; the cross-linking agent is boric acid.

[0061] The film-forming agent is a composition of polyvinyl pyrrolidone K30 and polyethylene glycol 800, with a mass ratio of 4.4:1.6.

[0062] The leveling agent is a composition of BYK-333 and perfluoroalkyl ethyl acrylate, with a mass ratio of 2.8:0.7.

[0063] The preparation method of high-temperature resistant water-soluble polyvinyl alcohol packaging film specifically includes the following steps: S1: adding polyvinyl alcohol, modified polyvinyl alcohol, a compound composition and modified nanoparticles into deionized water, stirring and dissolving at 90°C for 3 hours; S2: subsequently adding the remaining raw materials in sequence, stirring at a constant temperature of 80°C and a speed of 220 rpm for 0.8 hours each time to obtain a mixed solution; S3: casting the mixed solution onto a preheated substrate at a substrate temperature of 75°C, and after the casting is completed, thermoforming is carried out in a blowing oven at 85°C for 0.6 hours, and the film is removed after cooling. Thereafter, the obtained film is equilibrated in an environment with a temperature of 25°C and a relative humidity of 45% for 24 hours, and the film is obtained after completion.

[0064] Example 2 The only difference between this embodiment and Example 1 is that the raw materials of the high temperature resistant water-soluble polyvinyl alcohol packaging film, in parts by mass, are: 55 parts of polyvinyl alcohol, 45 parts of modified polyvinyl alcohol, 12.5 parts of the compound composition, 4.1 parts of modified nanoparticles, 2.1 parts of a surfactant, 4.2 parts of a reinforcing agent, 0.7 parts of a defoaming agent, 2.6 parts of a cross-linking agent, 1.2 parts of a film-forming agent, 1 part of a leveling agent, and 115 parts of deionized water.

[0065] The composite composition is a composition of hyperbranched polyester, polyglycerol and formamide, with a mass ratio of 6.5:1:1.8.

[0066] The surfactant is a composition of sodium lauryl sulfate, tributyl phosphate and PEG-40 hydrogenated castor oil in a mass ratio of 5:1:2.

[0067] The film-forming agent is a composition of polyvinyl pyrrolidone K30 and polyethylene glycol 800, with a mass ratio of 4:1.5.

[0068] The leveling agent is a composition of BYK-333 and perfluoroalkyl ethyl acrylate, with a mass ratio of 2.5:0.8.

[0069] Example 3 The only difference between this embodiment and Example 1 is that the raw materials of the high temperature resistant water-soluble polyvinyl alcohol packaging film, in parts by mass, are: 65 parts of polyvinyl alcohol, 38 parts of modified polyvinyl alcohol, 17.5 parts of the compound composition, 5.4 parts of modified nanoparticles, 2.1 parts of a surfactant, 4.8 parts of a reinforcing agent, 0.6 parts of a defoaming agent, 2.6 parts of a cross-linking agent, 1.2 parts of a film-forming agent, 1 part of a leveling agent, and 125 parts of deionized water.

[0070] The composite composition is a composition of hyperbranched polyester, polyglycerol and formamide, with a mass ratio of 5.5:1.5:2.2.

[0071] The surfactant is a composition of sodium lauryl sulfate, tributyl phosphate and PEG-40 hydrogenated castor oil in a mass ratio of 4:2:2.5.

[0072] The film-forming agent is a composition of polyvinyl pyrrolidone K30 and polyethylene glycol 800, with a mass ratio of 4.5:1.4.

[0073] The leveling agent is a composition of BYK-333 and perfluoroalkyl ethyl acrylate, with a mass ratio of 3:0.6.

[0074] Comparative Example 1 The only difference between this comparative example and Example 1 is that the high temperature resistant water-soluble polyvinyl alcohol packaging film, in parts by mass, comprises the following raw materials: 85 parts of polyvinyl alcohol, 15 parts of modified polyvinyl alcohol, 14.6 parts of the compound composition, 5.2 parts of modified nanoparticles, 2.1 parts of a surfactant, 4.4 parts of a reinforcing agent, 0.6 parts of a defoaming agent, 2.8 parts of a cross-linking agent, 1.4 parts of a film-forming agent, 1.1 parts of a leveling agent, and 110 parts of deionized water.

[0075] Comparative Example 2 The only difference between this comparative example and Example 1 is that the high temperature resistant water-soluble polyvinyl alcohol packaging film, in parts by mass, comprises the following raw materials: 61.5 parts of polyvinyl alcohol, 42.3 parts of modified polyvinyl alcohol, 5.5 parts of the compound composition, 2.2 parts of modified nanoparticles, 2.1 parts of a surfactant, 4.4 parts of a reinforcing agent, 0.6 parts of a defoaming agent, 2.8 parts of a cross-linking agent, 1.4 parts of a film-forming agent, 1.1 parts of a leveling agent, and 110 parts of deionized water.

[0076] Comparative Example 3 The only difference between this comparative example and Example 1 is that the preparation method of modified polyvinyl alcohol, in parts by mass, specifically comprises the following steps: S1: 90 parts of vinyl acetate, 5.5 parts of hydroxyethyl acrylate, 0.8 parts of vinyl pyrrolidone and 0.5 parts of sodium styrene sulfonate are mixed in proportion, 140 parts of methanol solution are added, the temperature is raised to 65°C, 1.1 parts of azobisisobutyronitrile are added and the mixture is kept warm for 6.5 hours to obtain a pre-product; S2: 25 parts of sodium hydroxide are added to 100 parts of the pre-product, the temperature is raised to 50°C, the mixture is kept warm for 4.5 hours, until the reaction reaches the desired alcoholysis degree of 88%, and the product is filtered and washed after completion.

[0077] Comparative Example 4 The only difference between this comparative example and Example 1 is that the composite composition is a composition of hyperbranched polyester, polyglycerol and formamide, with a mass ratio of 9:0.5:0.2.

[0078] Comparative Example 5 The only difference between this comparative example and Example 1 is that the composite composition is a composition of hyperbranched polyester, polyglycerol and formamide, with a mass ratio of 1:2.5:2.

[0079] Comparative Example 6 The only difference between this comparative example and Example 1 is that the modified nanoparticles are modified titanium dioxide, and the preparation method thereof, in parts by mass, specifically comprises the following steps: adding 10 parts of the modified titanium dioxide to 100 parts of an ethanol solution, stirring at 220 rpm for 45 minutes, then adding 1.4 parts of polyethyleneimine, stirring at 65°C for 3 hours, centrifuging and filtering after completion, and then vacuum drying at 80°C to obtain the product.

[0080] Comparative Example 7 The only difference between this comparative example and Example 1 is that the modified nanoparticles are modified titanium dioxide, and the preparation method thereof, in parts by mass, specifically comprises the following steps: S1: adding 10 parts of titanium dioxide to 150 parts of N,N-dimethylformamide solution, adding 3.2 parts of succinic anhydride and 0.2 parts of N-β-aminoethyl-γ-aminopropyltrimethoxysilane, and keeping the mixture at 70°C for 2.5 hours to obtain pretreated titanium dioxide; S2: adding 10 parts of pretreated titanium dioxide to 100 parts of ethanol solution, stirring at 220 rpm for 45 minutes, then adding 4.5 parts of polyethyleneimine, stirring at 65°C for 3 hours, centrifuging and filtering after completion, and then vacuum drying at 80°C to obtain the product.

[0081] Performance evaluation 1. The packaging films prepared in the examples and comparative examples were subjected to mechanical tests of tensile strength according to ASTM D638. The average values ​​of 10 tests were recorded in Table 1.

[0082] 2. The packaging films prepared in the examples and comparative examples were subjected to barrier property tests, with oxygen and water vapor transmission rates tested according to ASTM D3985 and ASTM E96, respectively. The average values ​​of 10 tests were recorded in Table 1.

[0083] 3. The packaging films prepared in the Examples and Comparative Examples were tested for water solubility according to ASTM D5523. Samples of packaging film had a size of 25 mm × 25 mm × 20 μm. The samples were immersed in 25°C distilled water. The soaking time was recorded after the start of the soaking period. After 300 seconds, the clarity and residue of the dissolved solution were observed. If the solution was clear and free of turbidity and no visible residue was present (dissolution rate ≥ 99.5%), the solution was considered qualified; otherwise, it was considered unqualified. 100 samples were tested in each group, and the pass rate is recorded in Table 1.

[0084] 4. The packaging films prepared in the examples and comparative examples were subjected to a high temperature resistance test according to ASTM D1204. The test temperature was 100°C for 1 hour. The film dimensional change rate after the test was recorded in %. The average value of 10 tests was recorded in Table 1. Table 1 Performance test results

[0085] Judging from the final performance test results of the embodiments and comparative examples, comparative examples 1 to 7 achieved worse performance results than the embodiments. However, the embodiments, due to the use of modified resins with better performance and a more reasonable compounding auxiliary agent scheme, were able to form a dense internal hydrogen bond network, thereby greatly increasing the mutual "stickiness" between the systems, reducing the gaps between molecules and between molecular chains, and thus connecting the migration channels of the internal small branches, greatly increasing the diffusion paths of gas and water molecules in the system, and further reducing the crystallinity by introducing a cross-linked structure, thereby achieving excellent barrier properties while maintaining good water solubility.

Claims

1. A high temperature resistant water-soluble polyvinyl alcohol packaging film, characterized by: The raw materials are as follows, in parts by mass: 50-70 parts of polyvinyl alcohol, 30-50 parts of modified polyvinyl alcohol, 10-20 parts of compound composition, 3-8 parts of modified nanoparticles, 1.5-2.5 parts of surfactant, 3-7 parts of reinforcing agent, 0.5-1 part of defoaming agent, 2-3 parts of cross-linking agent, 1-1.5 parts of film-forming agent, 0.8-1.4 parts of leveling agent, and 100-150 parts of deionized water; The degree of polymerization of the polyvinyl alcohol is 1500-2500; the alcoholysis degree of the polyvinyl alcohol is 90-99%; The preparation method of the modified polyvinyl alcohol specifically comprises the following steps: S1: vinyl acetate, hydroxyethyl acrylate, vinyl pyrrolidone and sodium styrene sulfonate are mixed in proportion, methanol solution is added, the temperature is raised to 65-70° C., azobisisobutyronitrile is added and the mixture is kept warm for 6-8 hours to obtain a pre-product; S2: sodium hydroxide is added to the pre-product, the temperature is raised to 45-55° C. and the mixture is kept warm for 4-5 hours until the reaction reaches the desired alcoholysis degree, and the product is filtered and washed after completion. The mass ratio of vinyl acetate, hydroxyethyl acrylate, vinyl pyrrolidone and sodium styrene sulfonate is (70-80): (8-9): (3-4): (1-1.5).

2. The high temperature resistant water-soluble polyvinyl alcohol packaging film according to claim 1, characterized in that: The mass ratio of the polyvinyl alcohol, modified polyvinyl alcohol and the composite composition is (55-68): (36-45): (12-18).

3. The high temperature resistant water-soluble polyvinyl alcohol packaging film according to claim 2, characterized in that: The mass ratio of the modified polyvinyl alcohol, the modified nanoparticles and the reinforcing agent is (36-45): (4-6): (4-5.5).

4. The high temperature resistant water-soluble polyvinyl alcohol packaging film according to claim 3, characterized in that: The mass ratio of the pre-product to sodium hydroxide is (90-100): (20-30); the required alcoholysis degree in the preparation method S2 of the modified polyvinyl alcohol is 80-90%.

5. The high temperature resistant water-soluble polyvinyl alcohol packaging film according to claim 4, characterized in that: The composite composition is a composition of hyperbranched polyester, polyglycerol and formamide, with a mass ratio of (5.5-6.5): (1-1.5): (1.8-2.4).

6. The high temperature resistant water-soluble polyvinyl alcohol packaging film according to claim 5, characterized in that: The modified nanoparticles are modified titanium dioxide; The preparation method of the modified titanium dioxide is specifically The following steps are involved: S1: adding titanium dioxide to N,N-dimethylformamide solution, adding succinic anhydride and N-β-aminoethyl-γ-aminopropyltrimethoxysilane, and heating at 60-70°C for 2-3 hours to obtain pretreated titanium dioxide; S2: Add the pretreated titanium dioxide to the ethanol solution, stir at 200-300 rpm for 40-50 min, then add polyethyleneimine, stir at 60-70°C for 2-4 h, centrifuge and filter, then vacuum dry at 75-80°C to obtain the product; The mass ratio of titanium dioxide, succinic anhydride and N-β-aminoethyl-γ-aminopropyltrimethoxysilane is (8-10): (1.5-2): (0.6-0.8); The mass ratio of the pretreated titanium dioxide to polyethyleneimine is (9-10): (1.2-1.6).

7. The high temperature resistant water-soluble polyvinyl alcohol packaging film according to claim 6, characterized in that: The average particle size of the titanium dioxide is 30-50 nm.

8. The high temperature resistant water-soluble polyvinyl alcohol packaging film according to claim 7, characterized in that: The surfactant is a composition of sodium lauryl sulfate, tributyl phosphate and PEG-40 hydrogenated castor oil, with a mass ratio of (4-5): (1-2): (2-2.5).

9. A method for preparing the high-temperature resistant water-soluble polyvinyl alcohol packaging film according to any one of claims 1 to 8, characterized in that: The specific steps include: S1: Add polyvinyl alcohol, modified polyvinyl alcohol, compound composition and modified nanoparticles into deionized water, stir and dissolve at 90℃ for 3~4h; S2: Subsequently add the remaining raw materials in sequence, and stir at a constant temperature of 80℃ and a speed of 200~250rpm for 0.6~1h each time to obtain a mixed solution; S3: Cast the mixed solution onto a preheated substrate with a substrate temperature of 70~80℃. After casting, thermoform in a blowing oven at 85~90℃ for 0.5~0.8h, remove the film after cooling, and then equilibrate the obtained film at a temperature of 25~30℃ and a relative humidity of 45~50% for 20~24h.

10. Use of the high-temperature resistant water-soluble polyvinyl alcohol packaging film according to any one of claims 1 to 8 in the fields of food packaging, electronic packaging, textile packaging and agricultural seed film.

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