A high-temperature resistant, water-soluble polyvinyl alcohol packaging film, its preparation method and application

Abstract

This application relates to the field of packaging materials, and more specifically mentions a high-temperature resistant water-soluble polyvinyl alcohol (PVA) packaging film, its preparation method, and its applications. The high-temperature resistant water-soluble PVA packaging film uses the following raw materials: polyvinyl alcohol, modified polyvinyl alcohol, a compound composition, modified nanoparticles, surfactants, and deionized water. The film material ultimately obtained by this application not only possesses excellent mechanical properties but also maintains good water solubility and barrier properties while exhibiting excellent high-temperature resistance. This solves the contradiction in existing PVA films where high-temperature resistance is achieved by sacrificing other properties, and avoids the complex process of multi-layer co-extrusion film formation, further saving equipment costs. It meets the comprehensive performance requirements of the current packaging field for PVA films and has excellent application prospects.

Description

Technical Field

[0001] This application relates to the field of packaging materials, and more specifically mentions a high-temperature resistant water-soluble polyvinyl alcohol packaging film, its preparation method, and its application. Background Technology

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

[0003] However, traditional PVA films have insufficient high-temperature resistance and mechanical properties. They are prone to softening, sticking, or partial decomposition in high-temperature environments (>80℃). Furthermore, they cannot effectively maintain their shape in aqueous and high-humidity environments, resulting in softening and hydrolysis. These problems severely limit their application in demanding scenarios (such as high-temperature retort packaging, industrial high-temperature packaging, and hot melt adhesive carrier tapes).

[0004] To address these issues, existing engineers have proposed three main improvement directions. For example, chemical crosslinking improvement involves adding crosslinking agents to enhance the crosslinking effect within the system, thereby constructing a stable internal system and improving mechanical and thermal stability. However, this method often sacrifices the film's water solubility, leading to a significant decrease in its water dissolution rate. Secondly, methods include adding inorganic fillers such as nano-calcium carbonate and mesoporous silica to improve the film's heat resistance and mechanical strength. However, this method has a significant negative impact on the film's aging resistance and water solubility, failing to guarantee the film's basic application performance. Finally, there is the method of combining an outer heat-resistant coating (such as polylactic acid) with an inner PVA layer. However, the multi-layer structure increases processing costs, and the coating material is usually non-water-soluble, contradicting the original intention of fully degradable design. Summary of the Invention

[0005] Therefore, in order to effectively solve the performance balance contradiction and process complexity problem of existing water-soluble polyvinyl alcohol packaging films, this application provides a high-temperature resistant water-soluble polyvinyl alcohol packaging film and its preparation method. The final film material not only has good mechanical properties, but also maintains good water solubility and barrier properties while having excellent high-temperature resistance. This solves the contradiction of existing PVA films sacrificing other properties for high-temperature resistance, and avoids the use of complex multi-layer co-extrusion film formation process, further saving equipment costs. It meets the comprehensive performance requirements of the current packaging field for PVA films and has excellent application prospects.

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

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

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

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

[0010] In 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] In a preferred embodiment, the degree of polymerization of the polyvinyl alcohol is 1500~2500.

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

[0013] In a preferred embodiment, the degree of alcoholysis 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, vinylpyrrolidone and sodium styrene sulfonate are mixed in proportion and added to methanol solution, heated to 65~70℃, and azobisisobutyronitrile is added and reacted at the temperature for 6~8h to obtain a preproduct; S2: Sodium hydroxide is added to the preproduct, heated to 45~55℃ and reacted at the temperature for 4~5h until the reaction reaches the required degree of alcoholysis, and the product is filtered and washed after completion to obtain the final product.

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

[0016] In a preferred embodiment, the mass ratio of the preproduct to sodium hydroxide is (90~100):(20~30).

[0017] In a preferred embodiment, the required degree of alcoholysis 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 between the added multi-group monomers and its own molecular chains. This significantly increases the mutual "adhesion" between systems, reduces the gaps between molecules and molecular chains, and connects the migration channels of internal fine branches, greatly increasing the diffusion paths of gas and water molecules within the system. Furthermore, the introduced cross-linking structure further reduces crystallinity, achieving excellent barrier properties while maintaining good water solubility. On the other hand, by combining the multi-active groups on the surface of the modified nanoparticles added in this application, the interaction forces between the resin and solid particles, and between particles themselves, can be achieved, promoting the degree of internal cross-linking, enhancing the interaction forces between molecular chain segments, and significantly improving the system's resistance to molecular chain slippage. This results in excellent mechanical properties, and under high-temperature and other active environments, it can inhibit molecular chain movement and the migration efficiency of active molecules, thus maintaining good high-temperature resistance.

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

[0020] In 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] In 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 in the packaging film resin system and inhibits water molecule penetration, but also, through its overall synergistic effect, effectively reduces the amount of modified polyvinyl alcohol used. Furthermore, by utilizing the carbon, oxygen, and hydrogen elements in the polyvinyl alcohol backbone, it retains good degradation and water solubility, maintains suitable crystallinity, and ensures degradation and water solubility efficiency. On the other hand, the added hyperbranched structure forms a non-covalent hydrogen bond network with PVA through terminal hydroxyl groups, assisting in stress dispersion and inhibiting crack propagation. The retained aromatic rings or ester groups, through free radical capture and char layer formation, delay thermal degradation and help improve high-temperature resistance. Finally, the polyglycerol's multi-hydroxyl structure competes with PVA for water molecule binding through hydrogen bonds, reducing free hydroxyl exposure, and forms a dynamic cross-linked network with the hyperbranched polyester-assisted system, restricting internal movement paths, thereby comprehensively improving the overall performance of the packaging film.

[0023] In 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 an N,N-dimethylformamide solution, adding succinic anhydride and N-β-aminoethyl-γ-aminopropyltrimethoxysilane, and reacting 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 the final product.

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

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

[0027] In a preferred embodiment, the titanium dioxide has an average particle size of 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 combine with the modified resin system, thereby increasing the number of stress transmission points and inhibiting further crack propagation under external forces. Furthermore, its excellent interfacial bonding with the polyvinyl alcohol resin system significantly reduces the micropore size and crack length in the film system, thus maintaining suitable hydrophilicity and water-permeability at low temperatures and ensuring good water solubility.

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

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

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

[0032] In a preferred embodiment, the reinforcing agent is at least one selected from gelatin, agar, sodium carboxymethyl cellulose, chitosan, and polyacrylamide.

[0033] In a preferred embodiment, the reinforcing agent is a combination of sodium carboxymethyl cellulose and chitosan.

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

[0035] In a preferred embodiment, the defoamer is at least one of silicone defoamers.

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

[0037] In a preferred embodiment, the crosslinking agent is at least one of boric acid, citric acid, epichlorohydrin, and sodium tripolyphosphate.

[0038] In a preferred embodiment, the crosslinking agent is boric acid.

[0039] In a preferred embodiment, the film-forming agent is at least one selected from polyvinylpyrrolidone, hydroxypropyl methylcellulose, polyethylene oxide, polyethylene glycol, and polyacrylic acid.

[0040] In a preferred embodiment, the film-forming agent is a combination of polyvinylpyrrolidone and polyethylene glycol.

[0041] In a preferred embodiment, the mass ratio of polyvinylpyrrolidone to polyethylene glycol is (4~4.5):(1.4~1.6).

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

[0043] In 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: Polyvinyl alcohol, modified polyvinyl alcohol, compound composition and modified nanoparticles are added to deionized water and stirred at 90°C for 3-4 hours to dissolve; S2: The remaining raw materials are added sequentially, and each addition is stirred at 80°C at a constant temperature of 200-250 rpm for 0.6-1 hours to obtain a mixture; S3: The mixture is cast onto a preheated substrate at a temperature of 70-80°C. After casting, it is thermoformed at 85-90°C in a blower oven for 0.5-0.8 hours. After cooling, the film is peeled off, and then the obtained film is equilibrated at a temperature of 25-30°C and a relative humidity of 45-50% for 20-24 hours.

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

[0046] The beneficial effects of this application are:

[0047] 1. The high-temperature resistant water-soluble polyvinyl alcohol packaging film provided in this application not only has good mechanical properties, but also maintains good water solubility and barrier properties while having excellent high-temperature resistance. It solves the contradiction of existing PVA films sacrificing other properties for high-temperature resistance, and avoids the use of complex multi-layer co-extrusion film forming process, further saving equipment costs. It meets the comprehensive performance requirements of the current packaging field for PVA films and has excellent application prospects.

[0048] 2. The high-temperature resistant water-soluble polyvinyl alcohol packaging film provided in this application, by adding modified polyvinyl alcohol resin, can form a dense internal hydrogen bond network through the interaction between the added multi-group monomers and its own molecular chains, thereby greatly increasing the mutual "adhesion" between the systems, reducing the gaps between molecules and molecular chains, and connecting the migration channels of the internal fine branches, greatly increasing the diffusion path of gas and water molecules in the system, and further reducing the crystallinity through the introduced cross-linking structure, thereby obtaining excellent barrier properties while maintaining good water solubility.

[0049] 3. The high-temperature resistant water-soluble polyvinyl alcohol packaging film provided in this application can also achieve interaction between the modified polyvinyl alcohol resin and the resin and solid particles, and between particles, by cooperating with the multi-active groups on the surface of the modified nanoparticles added in this application. This promotes the degree of internal cross-linking, enhances the interaction between molecular chain segments, and greatly improves the system's resistance to molecular chain slippage, thereby obtaining excellent mechanical properties. Moreover, it can inhibit the movement of molecular chains and the migration efficiency of active molecules in high-temperature and other active environments, thus maintaining good high-temperature resistance. Detailed Implementation

[0050] The detailed embodiments will use specific examples to more intuitively demonstrate and illustrate the content of the invention described in this application. Furthermore, 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.

[0051] Example 1

[0052] The high-temperature resistant water-soluble polyvinyl alcohol packaging film, by weight, consists of the following raw materials: 61.5 parts polyvinyl alcohol, 42.3 parts modified polyvinyl alcohol, 14.6 parts compound composition, 5.2 parts modified nanoparticles, 2.1 parts surfactant, 4.4 parts reinforcing agent, 0.6 parts defoamer, 2.8 parts crosslinking agent, 1.4 parts film-forming agent, 1.1 parts leveling agent, and 110 parts deionized water.

[0053] The polyvinyl alcohol has a degree of polymerization of 1700 and a degree of alcoholysis of 99%, and was purchased as PVA-1799 from Sinopec Sichuan Chemical Company.

[0054] The preparation method of modified polyvinyl alcohol, by mass, specifically includes the following steps: S1: 78 parts of vinyl acetate, 8.2 parts of hydroxyethyl acrylate, 3.4 parts of vinylpyrrolidone and 1.2 parts of sodium styrene sulfonate are mixed in proportion and then added to 120 parts of methanol solution. The mixture is heated to 65°C, and 1.1 parts of azobisisobutyronitrile are added and the reaction is maintained at this temperature for 6.5 h to obtain the preproduct; S2: 25 parts of sodium hydroxide are added to 100 parts of the preproduct, and the mixture is heated to 50°C and the reaction is maintained at this temperature for 4.5 h until the desired degree of alcoholysis reaches 88%. After the reaction is completed, the product is filtered and washed to obtain the final product.

[0055] The compound composition is a combination of hyperbranched polyester, polyglycerol and formamide in a mass ratio of 6:1.1:1.9.

[0056] The hyperbranched polyester was purchased from China Lankeluo Company as L-6126 product; the polyglycerol was purchased from Shandong Binzhou Jinsheng Chemical Company as JP-20 dipolyglycerol product.

[0057] The modified nanoparticles are modified titanium dioxide. The preparation method, by weight, includes the following steps: S1: 10 parts of titanium dioxide are added to 150 parts of N,N-dimethylformamide solution, along with 1.8 parts of succinic anhydride and 0.7 parts of N-β-aminoethyl-γ-aminopropyltrimethoxysilane. The mixture is reacted at 70°C for 2.5 hours to obtain pretreated titanium dioxide; S2: 10 parts of pretreated titanium dioxide are added to 100 parts of ethanol solution and stirred at 220 rpm for 45 minutes. Then, 1.4 parts of polyethyleneimine are added, and the mixture is stirred at 65°C for 3 hours. After completion, the mixture is centrifuged and filtered, and then vacuum dried at 80°C to obtain the final product.

[0058] Polyethyleneimine was purchased from Wuhan Lanabai Pharmaceutical Chemical Co., Ltd. in China as a 10,000 molecular weight product.

[0059] The average particle size of titanium dioxide is 35 nm.

[0060] The surfactant is a composition of sodium dodecyl sulfate, tributyl phosphate and PEG-40 hydrogenated castor oil in a mass ratio of 4.3:1.4:2.3.

[0061] A composition of sodium carboxymethyl cellulose and chitosan in a mass ratio of 3.8:1.2.

[0062] The defoamer is organosilicon defoamer BYK-022; the crosslinking agent is boric acid.

[0063] The film-forming agent is a composition of polyvinylpyrrolidone K30 and polyethylene glycol 800 in a mass ratio of 4.4:1.6.

[0064] The leveling agent is a combination of BYK-333 and perfluoroalkyl ethyl acrylate in a mass ratio of 2.8:0.7.

[0065] The preparation method of high-temperature resistant water-soluble polyvinyl alcohol packaging film includes the following steps: S1: Polyvinyl alcohol, modified polyvinyl alcohol, compound composition and modified nanoparticles are added to deionized water and stirred at 90°C for 3 hours to dissolve; S2: The remaining raw materials are added sequentially, and each addition is stirred at 80°C and 220 rpm for 0.8 hours to obtain a mixture; S3: The mixture is cast onto a preheated substrate at 75°C. After casting, it is thermoformed at 85°C in a blower oven for 0.6 hours. After cooling, the film is peeled off, and then the resulting film is equilibrated at 25°C and 45% relative humidity for 24 hours.

[0066] Example 2

[0067] The only difference between this embodiment and Example 1 is as follows: The high-temperature resistant water-soluble polyvinyl alcohol packaging film, by weight, consists of the following raw materials: 55 parts polyvinyl alcohol, 45 parts modified polyvinyl alcohol, 12.5 parts compound composition, 4.1 parts modified nanoparticles, 2.1 parts surfactant, 4.2 parts reinforcing agent, 0.7 parts defoamer, 2.6 parts crosslinking agent, 1.2 parts film-forming agent, 1 part leveling agent, and 115 parts deionized water.

[0068] The compound composition is a combination of hyperbranched polyester, polyglycerol and formamide in a mass ratio of 6.5:1:1.8.

[0069] The surfactant is a composition of sodium dodecyl sulfate, tributyl phosphate and PEG-40 hydrogenated castor oil in a mass ratio of 5:1:2.

[0070] The film-forming agent is a composition of polyvinylpyrrolidone K30 and polyethylene glycol 800 in a mass ratio of 4:1.5.

[0071] The leveling agent is a combination of BYK-333 and perfluoroalkyl ethyl acrylate in a mass ratio of 2.5:0.8.

[0072] Example 3

[0073] The only difference between this embodiment and Example 1 is as follows: The high-temperature resistant water-soluble polyvinyl alcohol packaging film, by weight, consists of the following raw materials: 65 parts polyvinyl alcohol, 38 parts modified polyvinyl alcohol, 17.5 parts compound composition, 5.4 parts modified nanoparticles, 2.1 parts surfactant, 4.8 parts reinforcing agent, 0.6 parts defoamer, 2.6 parts crosslinking agent, 1.2 parts film-forming agent, 1 part leveling agent, and 125 parts deionized water.

[0074] The compound composition is a combination of hyperbranched polyester, polyglycerol and formamide in a mass ratio of 5.5:1.5:2.2.

[0075] The surfactant is a composition of sodium dodecyl sulfate, tributyl phosphate and PEG-40 hydrogenated castor oil in a mass ratio of 4:2:2.5.

[0076] The film-forming agent is a composition of polyvinylpyrrolidone K30 and polyethylene glycol 800 in a mass ratio of 4.5:1.4.

[0077] The leveling agent is a combination of BYK-333 and perfluoroalkyl ethyl acrylate in a mass ratio of 3:0.6.

[0078] Comparative Example 1

[0079] The only difference between this comparative example and Example 1 is as follows: the high-temperature resistant water-soluble polyvinyl alcohol packaging film, by weight, consists of the following raw materials: 85 parts polyvinyl alcohol, 15 parts modified polyvinyl alcohol, 14.6 parts compound composition, 5.2 parts modified nanoparticles, 2.1 parts surfactant, 4.4 parts reinforcing agent, 0.6 parts defoamer, 2.8 parts crosslinking agent, 1.4 parts film-forming agent, 1.1 parts leveling agent, and 110 parts deionized water.

[0080] Comparative Example 2

[0081] The only difference between this comparative example and Example 1 is as follows: the high-temperature resistant water-soluble polyvinyl alcohol packaging film, by weight, contains the following raw materials: 61.5 parts polyvinyl alcohol, 42.3 parts modified polyvinyl alcohol, 5.5 parts compound composition, 2.2 parts modified nanoparticles, 2.1 parts surfactant, 4.4 parts reinforcing agent, 0.6 parts defoamer, 2.8 parts crosslinking agent, 1.4 parts film-forming agent, 1.1 parts leveling agent, and 110 parts deionized water.

[0082] Comparative Example 3

[0083] The only difference between this comparative example and Example 1 is as follows: The preparation method of modified polyvinyl alcohol, by mass, specifically includes the following steps: S1: 90 parts of vinyl acetate, 5.5 parts of hydroxyethyl acrylate, 0.8 parts of vinylpyrrolidone and 0.5 parts of sodium styrene sulfonate are mixed in proportion and then added to 140 parts of methanol solution. The mixture is heated to 65°C, and 1.1 parts of azobisisobutyronitrile are added and the reaction is maintained at this temperature for 6.5 hours to obtain the preproduct; S2: 25 parts of sodium hydroxide are added to 100 parts of the preproduct, and the mixture is heated to 50°C and the reaction is maintained at this temperature for 4.5 hours until the desired degree of alcoholysis reaches 88%. After the reaction is completed, the product is filtered and washed to obtain the final product.

[0084] Comparative Example 4

[0085] The only difference between this comparative example and Example 1 is that the compound composition is a combination of hyperbranched polyester, polyglycerol and formamide in a mass ratio of 9:0.5:0.2.

[0086] Comparative Example 5

[0087] The only difference between this comparative example and Example 1 is that the compound composition is a combination of hyperbranched polyester, polyglycerol and formamide in a mass ratio of 1:2.5:2.

[0088] Comparative Example 6

[0089] The only difference between this comparative example and Example 1 is as follows: the modified nanoparticles are modified titanium dioxide, and the preparation method, by mass, specifically includes the following steps: 10 parts are added to 100 parts of ethanol solution, stirred at 220 rpm for 45 min, then 1.4 parts of polyethyleneimine are added, stirred at 65°C for 3 h, centrifuged and filtered after completion, and then vacuum dried at 80°C to obtain the final product.

[0090] Comparative Example 7

[0091] The only difference between this comparative example and Example 1 is as follows: the modified nanoparticles are modified titanium dioxide, and the preparation method, by mass, specifically includes the following steps: S1: 10 parts of titanium dioxide are added to 150 parts of N,N-dimethylformamide solution, 3.2 parts of succinic anhydride and 0.2 parts of N-β-aminoethyl-γ-aminopropyltrimethoxysilane are added, and the mixture is kept at 70°C for 2.5 h to obtain pretreated titanium dioxide; S2: 10 parts of pretreated titanium dioxide are added to 100 parts of ethanol solution, stirred at 220 rpm for 45 min, then 4.5 parts of polyethyleneimine are added, and the mixture is stirred at 65°C for 3 h. After completion, the mixture is centrifuged and filtered, and then vacuum dried at 80°C to obtain the final product.

[0092] Performance Evaluation

[0093] 1. The packaging films prepared in the examples and comparative examples were subjected to mechanical tests of tensile strength, referring to ASTM D638. The average value of 10 tests was recorded in Table 1.

[0094] 2. The packaging films prepared in the examples and comparative examples were subjected to barrier tests. The oxygen and water vapor transmission rates were tested according to ASTM D3985 and ASTM E96, respectively. The average value of 10 tests was recorded in Table 1.

[0095] 3. The packaging films prepared in the examples and comparative examples were subjected to water solubility tests. Referring to the standard ASTM D5523, the sample size of the packaging film was 25 mm × 25 mm × 20 μm. The samples were immersed in distilled water at 25°C. The time was recorded after the start of immersion. After 300 seconds, the transparency of the solution and the residue were observed. If the solution was clear and turbid and there were no visible residues (solubility ≥ 99.5%), it was considered qualified. Otherwise, it was considered unqualified. 100 samples were tested in each group, and the pass rate was recorded in Table 1.

[0096] 4. The packaging films prepared in the examples and comparative examples were subjected to high-temperature resistance tests. Referring to ASTM D1204, the test conditions were: 100℃ for 1 hour. The percentage change in film size after the test was recorded, and the average value of 10 tests was recorded in Table 1.

[0097] Table 1 Performance Test Results

[0098]

[0099] Based on the final performance test results of the examples and comparative examples, comparative examples 1-7 achieved worse performance results compared to the examples. The examples, on the other hand, used a modified resin with superior performance and a more reasonable compounding agent scheme, which enabled the formation of a dense internal hydrogen bond network. This significantly increased the mutual "stickiness" between the systems, reduced the gaps between molecules and molecular chains, and connected the migration channels of the internal fine branches. This greatly increased the diffusion paths of gas and water molecules within the system. Furthermore, the introduced cross-linking structure further reduced the crystallinity, achieving excellent barrier properties while maintaining good water solubility.

Claims

1. A high-temperature resistant, water-soluble polyvinyl alcohol packaging film, characterized in that: The raw materials, by weight, are: 50-70 parts polyvinyl alcohol, 30-50 parts modified polyvinyl alcohol, 10-20 parts compound composition, 3-8 parts modified nanoparticles, 1.5-2.5 parts surfactant, 3-7 parts reinforcing agent, 0.5-1 part defoamer, 2-3 parts crosslinking agent, 1-1.5 parts film-forming agent, 0.8-1.4 parts leveling agent, and 100-150 parts deionized water; The degree of polymerization of the polyvinyl alcohol is 1500~2500; the degree of alcoholysis of the polyvinyl alcohol is 90~99%. The preparation method of the modified polyvinyl alcohol specifically includes the following steps: S1: Vinyl acetate, hydroxyethyl acrylate, vinylpyrrolidone and sodium styrene sulfonate are mixed in proportion and added to methanol solution, heated to 65~70℃, and azobisisobutyronitrile is added and reacted at the temperature for 6~8h to obtain the preproduct; S2: Sodium hydroxide is added to the preproduct, heated to 45~55℃ and reacted at the temperature for 4~5h until the reaction reaches the required degree of alcoholysis, and after completion, the product is filtered and washed to obtain the final product; The mass ratio of vinyl acetate, hydroxyethyl acrylate, vinylpyrrolidone, and sodium styrene sulfonate is (70~80):(8~9):(3~4):(1~1.5). The compound composition is a combination of hyperbranched polyester, polyglycerol and formamide, in a mass ratio of (5.5~6.5):(1~1.5):(1.8~2.4). The modified nanoparticles are modified titanium dioxide; the preparation method of the modified titanium dioxide specifically includes the following steps: S1: Add titanium dioxide to N,N-dimethylformamide solution, add succinic anhydride and N-β-aminoethyl-γ-aminopropyltrimethoxysilane, and react at 60~70℃ for 2~3h to obtain pretreated titanium dioxide; S2: Add the pretreated titanium dioxide to ethanol solution, stir at 200~300rpm for 40~50min, then add polyethyleneimine, stir at 60~70℃ for 2~4h, centrifuge and filter, and then vacuum dry at 75~80℃ to obtain the product; The mass ratio of the 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). The average particle size of the titanium dioxide is 30~50nm; The surfactant is a composition of sodium dodecyl sulfate, tributyl phosphate and PEG-40 hydrogenated castor oil in a mass ratio of (4~5):(1~2):(2~2.5).

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 compound 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 modified polyvinyl alcohol has a mass ratio of modified nanoparticles to reinforcing agent of (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 preproduct to sodium hydroxide is (90~100):(20~30); the required degree of alcoholysis in the preparation method S2 of the modified polyvinyl alcohol is 80~90%.

5. A method for preparing a high-temperature resistant, water-soluble polyvinyl alcohol packaging film according to any one of claims 1 to 4, characterized in that: Specifically, the following steps are included: S1: Add polyvinyl alcohol, modified polyvinyl alcohol, the compound composition, and modified nanoparticles to deionized water and stir at 90°C for 3-4 hours to dissolve. S2: Add the remaining raw materials sequentially, stirring at 80°C and 200-250 rpm for 0.6-1 hours each time to obtain a mixture. S3: Cast the mixture onto a preheated substrate at 70-80°C. After casting, thermoform the film at 85-90°C in a blower oven for 0.5-0.8 hours. After cooling, peel off the film and equilibrate it at 25-30°C and 45-50% relative humidity for 20-24 hours.

6. The application of a high-temperature resistant, water-soluble polyvinyl alcohol packaging film according to any one of claims 1 to 4 in the fields of food packaging, electronic packaging, textile packaging, and agricultural seed film.

Images