PVA / sio2 organic-inorganic hybrid coating liquid and preparation method thereof, water-boiling-resistant composite packaging film and preparation method thereof

Abstract

The present application relates to the field of packaging materials, in particular to a PVA / SiO2 organic-inorganic hybrid coating liquid and a preparation method thereof, a water-boiling-resistant composite packaging film and a preparation method thereof. The PVA / SiO2 organic-inorganic hybrid coating liquid is prepared by mixing polyvinyl alcohol, tetraethyl orthosilicate, methyl triethoxysilane, amino resin, organic cosolvent, water and acid catalyst in a certain proportion and according to a certain process, which can greatly improve the cohesive strength and structural density of the coating, effectively inhibit the penetration of water molecules, significantly reduce the oxygen transmission rate in a high humidity environment, and endow excellent water resistance and wet stability. On this basis, combined with a specific reactive polyurethane primer and an optimized coating process, the inherent high oxygen resistance and environmental protection advantages of PVA are fully utilized, and through organic-inorganic synergistic crosslinking and strong interfacial chemical anchoring, the synergy and unity of high barrier property, excellent water-boiling resistance and strong interlayer adhesion are realized for the first time.

Description

Technical Field

[0001] This invention relates to the field of packaging materials, and particularly to a PVA / SiO2 organic-inorganic hybrid coating liquid and its preparation method, and a water-resistant composite packaging film and its preparation method. Background Technology

[0002] Polyvinyl alcohol (PVA), a water-soluble polymer, has been widely used in high-barrier flexible packaging materials in the food, pharmaceutical, and electronics industries due to its excellent oxygen barrier properties (oxygen permeability as low as 0.5-2 cm³ / (m²·day·atm) under dry conditions), good film-forming properties, biodegradability, and the advantages of abundant raw material sources and low cost. Especially with increasingly stringent environmental performance requirements, PVA, as a halogen-free, water-coated, and food-safety-compliant green barrier coating, demonstrates significant application value and market prospects.

[0003] However, PVA molecules are rich in hydrophilic hydroxyl groups (-OH), making them highly susceptible to water absorption and swelling under high humidity or high-temperature boiling conditions. This leads to coating structure damage, drastic deterioration of barrier properties, and even delamination from the substrate. This inherent defect severely limits the use of PVA in demanding applications requiring high-temperature boiling (e.g., 90-100℃, 30 min) or long-term high-humidity storage (e.g., 85% RH). For example, patent application CN119286319A discloses a high-barrier composite coating liquid and its preparation method. The coating liquid in this patent is made by blending PVA emulsion and maleic anhydride copolymer. However, this coating and the base film only have hydrogen bonds and electrostatic interactions. After high-temperature boiling, the hydrogen bonds and electrostatic interactions will break, causing the PVA coating to peel off from the substrate, resulting in bag breakage and unusable material. For example, the literature "Preparation and Swelling Adsorption Properties of PVA / TEOS / GA Hybrid Film" discloses the preparation and optimal ratio of PVA / TEOS / GA hybrid film, but the use of glutaraldehyde for crosslinking easily leads to coating embrittlement and does not solve the problem of weak interfacial bonding with substrates such as BOPA / BOPP / PET. After boiling in water, the hydrogen bond failure leads to a sharp drop in peel strength, which is difficult to meet the requirements of water-resistant packaging applications.

[0004] To overcome the above problems, existing technologies attempt to improve the water resistance of PVA through crosslinking modification, blending with hydrophobic polymers, surface coating, or introducing inorganic nanofillers. For example, while using aldehydes, isocyanates, or epoxy crosslinking agents can improve water resistance to some extent, they are often accompanied by coating embrittlement, decreased transparency, or the risk of small molecule migration; while simply adding silica (SiO2) nanoparticles is prone to agglomeration, making it difficult to form a continuous and dense network, thus providing limited barrier improvement.

[0005] In recent years, constructing PVA / SiO2 organic-inorganic hybrid systems based on the sol-gel method has been considered an effective approach. This method utilizes an in-situ generated SiO2 network to form chemical bonds with PVA, significantly improving water resistance while maintaining high barrier properties. However, existing PVA / SiO2 hybrid coatings still face the problem of insufficient interfacial adhesion with plastic substrates (such as BOPA, BOPP, and PET)—especially after boiling in water, water molecules penetrate from the substrate side, causing the interfacial interactions, primarily based on hydrogen bonds, to fail. This leads to a significant decrease in the peel strength of the composite film, making it difficult to meet the practical requirements of boil-resistant packaging. Summary of the Invention

[0006] In view of this, the present invention provides a PVA / SiO2 organic-inorganic hybrid coating solution and its preparation method, as well as a water-resistant composite packaging film and its preparation method. The present invention can effectively improve the barrier properties, water resistance, and strong interfacial properties of products.

[0007] This invention provides a PVA / SiO2 organic-inorganic hybrid coating solution, the raw materials for which are prepared include:

[0008] Polyvinyl alcohol: 5-15 parts by weight;

[0009] Silicon source 1: 1~2 parts by weight;

[0010] Silicon source 2: 0.5~1 parts by weight;

[0011] Amino resin: 0.3~0.4 parts by weight;

[0012] Organic cosolvent: 5 parts by weight;

[0013] Water: 82~100 parts by weight;

[0014] Acid catalysts: several;

[0015] in,

[0016] The silicon source 1 is tetraethyl orthosilicate;

[0017] The silicon source 2 is methyltriethoxysilane.

[0018] Preferably, the amino resin is at least one of melamine-formaldehyde resin and urea-formaldehyde resin;

[0019] The acid catalyst is at least one of an organic acid catalyst and an inorganic acid catalyst; wherein the organic acid catalyst is at least one of formic acid, acetic acid, p-toluenesulfonic acid, and citric acid; and the inorganic acid catalyst is at least one of hydrochloric acid and phosphoric acid.

[0020] The amount of acid catalyst used is such that the pH value of the acid-added system is 4-5 before any other substances are added, after the acid catalyst is added.

[0021] The organic co-solvent is preferably at least one of methanol, ethanol, and isopropanol.

[0022] Preferably, the amino resin is a methyl etherified high-imino melamine-formaldehyde resin.

[0023] Preferably, the amino resin is methyl etherified high-imino melamine-formaldehyde resin CYMEL®327;

[0024] The acid catalyst is citric acid.

[0025] This invention also provides a method for preparing the PVA / SiO2 organic-inorganic hybrid coating solution described in the above technical solution, comprising the following steps:

[0026] S1. Mix and dissolve polyvinyl alcohol with water to obtain a polyvinyl alcohol solution;

[0027] S2. Lower the system temperature to 50-60℃, add silicon source 1 and organic co-solvent, add acid catalyst dropwise to adjust the pH of the system to 4-5, and maintain the reaction at the above temperature while stirring; then, add silicon source 2 dropwise, and maintain the reaction at the above temperature while stirring.

[0028] S3. Add amino resin dropwise to the system and stir to react, to obtain PVA / SiO2 organic-inorganic hybrid coating solution.

[0029] Preferably, step S1 specifically includes: mixing polyvinyl alcohol with water and stirring to dissolve the mixture while maintaining a temperature of 80~90°C to obtain a polyvinyl alcohol solution;

[0030] The acid catalyst is added at a rate of 3-6 mL / min;

[0031] The dropping rate of the silicon source 2 is 3~10 mL / min;

[0032] The amino resin is added at a rate of 9-15 mL / min.

[0033] This invention also provides a method for preparing a water-resistant composite packaging film based on a PVA / SiO2 hybrid coating, comprising the following steps:

[0034] K1. The thin film substrate is subjected to corona treatment to obtain a corona-treated substrate;

[0035] K2. Apply the primer to the surface of the corona-treated substrate obtained in step K1, and dry it to form a primer layer.

[0036] K3. Apply the coating liquid to the surface of the primer layer and dry it to form a PVA organic-inorganic hybrid barrier layer.

[0037] K4. Apply the adhesive to the surface of the PVA organic-inorganic hybrid barrier layer and dry it to form an adhesive layer.

[0038] K5. An organic film is laminated onto the surface of the adhesive layer to form a heat-sealing layer, thereby obtaining a composite packaging film;

[0039] Wherein, the coating liquid in step K3 is the PVA / SiO2 organic-inorganic hybrid coating liquid described in the above technical solution or the PVA / SiO2 organic-inorganic hybrid coating liquid prepared by the preparation method described in the above technical solution.

[0040] Preferably, in step K2, the primer is a mixture of water-based pure polycarbonate structured polyurethane emulsion and isocyanate curing agent;

[0041] The aqueous pure polycarbonate structured polyurethane emulsion is Covestro Bayhydrol® U 2757; the isocyanate curing agent is Covestro Bayhydur® ultra 3100.

[0042] In step K2, the dry coating amount is 0.5~1.5 g / m². 2 The drying temperature is 80~100℃;

[0043] In step K3, the dry coating amount is 0.5~1.0 g / m². 2 The drying temperature is 110~140℃;

[0044] In step K4, the dry coating amount is 3.0~3.5 g / m². 2 The drying temperature is 50~60℃;

[0045] In step K4, the adhesive is preferably a two-component polyurethane adhesive.

[0046] Preferably, in step K1, the goal of the corona treatment is to make the surface wetting tension of the thin film substrate ≥52dyn / cm;

[0047] In step K4, the adhesive is a two-component polyurethane adhesive, Henkel LOCTITE LIOFOL LA 7835 / LA 6256;

[0048] In step K5, the organic film is a CPP film or a PE film.

[0049] The present invention also provides a water-resistant composite packaging film based on a PVA / SiO2 hybrid coating prepared by the preparation method described in the above technical solution.

[0050] The PVA / SiO2 organic-inorganic hybrid coating solution provided by this invention is prepared by mixing polyvinyl alcohol, tetraethyl orthosilicate, methyltriethoxysilane, amino resin, organic co-solvent, water, and acid catalyst in a certain proportion and according to a specific process. This significantly improves the cohesive strength and structural density of the coating, effectively inhibits water molecule penetration, significantly reduces oxygen permeability (OTR) in high humidity environments, and imparts excellent water resistance and wet stability to the coating. Based on this, combined with a specific reactive polyurethane primer and an optimized coating process, it not only fully leverages the inherent high oxygen barrier and environmental advantages of PVA, but also achieves a synergistic unity of high barrier properties, excellent water resistance, and strong interlayer adhesion for the first time through organic-inorganic synergistic crosslinking and strong interfacial chemical anchoring. It is particularly suitable for the field of high-temperature boil-resistant food packaging where safety, functionality, and processability requirements are stringent. This invention solves both the problem of PVA's lack of water resistance and the problem of interlayer adhesion between the PVA coating and the substrate film. Existing coating equipment can be used, making the operation simple, efficient, and cost-effective.

[0051] The test results show that the oxygen permeation rate (OTR) of the composite membrane product of the present invention is below 2.0 cm³ / (m²·day) before and after boiling. The failure mode of the composite membrane before boiling is tearing (i.e. the material body is damaged but the interlayer is not peeled off), which shows high adhesion. After boiling, the peel strength is ≥3.0 N / 15 mm. It achieves excellent comprehensive performance with high barrier properties, resistance to boiling at 100℃ for 30 minutes, and peel strength ≥3.0 N / 15 mm after boiling. Attached Figure Description

[0052] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0053] Figure 1 This is a schematic diagram of the water-resistant composite packaging film with a PVA / SiO2 hybrid coating provided by the present invention. Detailed Implementation

[0054] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0055] In this article, the technical features described in an open-ended manner include both closed technical solutions composed of the listed features and open technical solutions that include the listed features.

[0056] The term “and / or” as used herein includes any and all combinations of one or more of the related listed items.

[0057] In this document, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when a range refers to an integer, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0058] In this article, when referring to units for data ranges, if the unit is only followed by the right endpoint, it means that the units for the left and right endpoints are the same. For example, 80~90℃ means that the units for the left endpoint "80" and the right endpoint "90" are both in degrees Celsius.

[0059] [First Aspect] This invention provides a PVA / SiO2 organic-inorganic hybrid coating solution, the raw materials for which are prepared include:

[0060] Polyvinyl alcohol: 5-15 parts by weight;

[0061] Silicon source 1: 1~2 parts by weight;

[0062] Silicon source 2: 0.5~1 parts by weight;

[0063] Amino resin: 0.3~0.4 parts by weight;

[0064] Organic cosolvent: 5 parts by weight;

[0065] Water: 82~100 parts by weight;

[0066] Acid catalysts: several;

[0067] in,

[0068] The silicon source 1 is tetraethyl orthosilicate;

[0069] The silicon source 2 is methyltriethoxysilane.

[0070] In this invention, the source of the polyvinyl alcohol (PVA) is not particularly limited; it can be a commercially available product or prepared according to methods known in the art. In this invention, the amount of polyvinyl alcohol used is 5-15 parts by weight, specifically 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 parts, etc.

[0071] In this invention, the source of the silicon source 1, namely tetraethyl orthosilicate (TEOS), is not particularly limited; it can be a commercially available product or prepared according to methods known in the art. In this invention, the amount of tetraethyl orthosilicate used is 1-2 parts by weight, specifically 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.8, 1.9, or 2.0 parts.

[0072] In this invention, the silicon source 2, namely methyltriethoxysilane (MTES), can be a commercially available product or prepared according to methods known in the art. In this invention, the amount of methyltriethoxysilane used is 0.5 to 1 part by weight, specifically 0.5 parts, 0.6 parts, 0.7 parts, 0.75 parts, 0.8 parts, 0.9 parts, or 1.0 parts.

[0073] In this invention, the amino resin is an aqueous amino resin, preferably at least one of melamine-formaldehyde resin and urea-formaldehyde resin, more preferably melamine-formaldehyde resin, further preferably methyl etherified high-imino melamine-formaldehyde resin, and most preferably CYMEL®327 (from Allnex, USA). In this invention, the amount of the amino resin used is 0.3~0.4 parts by weight, specifically 0.3 parts, 0.35 parts, or 0.4 parts.

[0074] In this invention, the organic co-solvent is preferably at least one of methanol, ethanol, and isopropanol, more preferably ethanol. The organic co-solvent is preferably an anhydrous solvent, such as anhydrous ethanol. In this invention, the amount of the organic co-solvent is 5 parts by mass. The above parts by mass represent the relationship between the amounts of the organic co-solvent and other components. For example, if PVA is 5-15 parts, the organic co-solvent is 5 parts, i.e., the mass ratio of PVA to organic co-solvent is (5-15):5; for example, if PVA is 30 parts, the organic co-solvent can be 10 parts.

[0075] In this invention, the water is preferably deionized water. The amount of water used in this invention is 82-100 parts by weight, specifically 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99, 100 parts, etc.

[0076] In this invention, the acid catalyst is at least one of an organic acid catalyst and an inorganic acid catalyst. Preferably, the organic acid catalyst is at least one of formic acid, acetic acid, p-toluenesulfonic acid, and citric acid, more preferably citric acid. Preferably, the inorganic acid catalyst is at least one of hydrochloric acid and phosphoric acid, more preferably phosphoric acid. In this invention, the amount of acid catalyst used is preferably such that the pH value of the acid-added system is 4-5 before the addition of other substances, specifically 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.9, or 5.0.

[0077] [Second Aspect] This invention provides a method for preparing the PVA / SiO2 organic-inorganic hybrid coating solution described in the above technical solution, comprising the following steps:

[0078] S1. Mix and dissolve polyvinyl alcohol with water to obtain a polyvinyl alcohol solution;

[0079] S2. Lower the system temperature to 50-60℃, add silicon source 1 and organic co-solvent, add acid catalyst dropwise to adjust the pH of the system to 4-5, and maintain the reaction at the above temperature while stirring; then, add silicon source 2 dropwise, and maintain the reaction at the above temperature while stirring.

[0080] S3. Add amino resin dropwise to the system and stir to react, to obtain PVA / SiO2 organic-inorganic hybrid coating solution.

[0081] The types and amounts of polyvinyl alcohol, water, silicon source 1, organic co-solvent, acid catalyst, silicon source 2, and amino resin are consistent with those described in the previous technical solution, and will not be repeated here.

[0082] Regarding step S1 :

[0083] S1. Mix and dissolve polyvinyl alcohol with water to obtain a polyvinyl alcohol solution.

[0084] In this invention, preferably, step S1 specifically includes: mixing polyvinyl alcohol with water and stirring to dissolve it while maintaining a temperature of 80-90°C to obtain a polyvinyl alcohol solution. The specific temperatures mentioned above can be 80°C, 81°C, 82°C, 83°C, 84°C, 85°C, 86°C, 87°C, 88°C, 89°C, or 90°C. The stirring rate is preferably 100-1000 rpm, specifically 100 rpm, 200 rpm, 300 rpm, 400 rpm, 500 rpm, 600 rpm, 650 rpm, 700 rpm, 800 rpm, 900 rpm, or 1000 rpm. The stirring and dissolving time is preferably 1-2 hours, specifically 1 hour, 1.5 hours, or 2 hours.

[0085] More preferably, step S1 in this invention includes: adding polyvinyl alcohol to water at 80-90°C, and stirring to dissolve the polyvinyl alcohol solution while maintaining the temperature at 80-90°C. The water temperature can specifically be 80°C, 81°C, 82°C, 83°C, 84°C, 85°C, 86°C, 87°C, 88°C, 89°C, or 90°C. The 80-90°C temperature can specifically be 80°C, 81°C, 82°C, 83°C, 84°C, 85°C, 86°C, 87°C, 88°C, 89°C, or 90°C. The stirring rate is preferably 100-1000 rpm, specifically 100 rpm, 200 rpm, 300 rpm, 400 rpm, 500 rpm, 600 rpm, 700 rpm, 800 rpm, 900 rpm, or 1000 rpm. The stirring and dissolving time is preferably 1-2 hours, specifically 1 hour, 1.5 hours, or 2 hours.

[0086] Regarding step S2 :

[0087] S2. Lower the system temperature to 50~60℃, add silicon source 1 and organic co-solvent, add acid catalyst dropwise to adjust the pH value of the system to 4~5, and maintain the reaction at the above temperature while stirring; then, add silicon source 2 dropwise, and maintain the reaction at the above temperature while stirring.

[0088] In this invention, after step S1, the system is first cooled to 50-60°C, specifically 50°C, 51°C, 52°C, 53°C, 54°C, 55°C, 56°C, 57°C, 58°C, 59°C, 60°C, etc. After cooling to the above temperatures, silicon source 1 and organic co-solvent are added. Preferably, silicon source 1 and organic co-solvent are added as a mixture, i.e., the silicon source 1 and organic co-solvent are pre-mixed to form a mixture before being added to the system.

[0089] In this invention, after adding silicon source 1 and organic co-solvent, an acid catalyst is added dropwise. The preferred dropwise addition rate of the acid catalyst is 3-6 mL / min, specifically 3 mL / min, 4 mL / min, 5 mL / min, 6 mL / min, etc. Controlling the addition rate at this rate ensures the product's effectiveness. If the acid catalyst is added directly in one step, it can easily lead to excessively rapid hydrolysis of TEOS, resulting in excessive local cross-linking. This invention adjusts the pH of the system to 4-5 by adding the acid catalyst, specifically 4.0, 4.1, 4.2, 4.3, 4.4, 4.5, 4.6, 4.7, 4.9, 5.0, etc. After pH adjustment, the reaction is maintained at the aforementioned temperature (i.e., 50-60°C) with stirring. The stirring speed of the stirring reaction is preferably 100~200 rpm, specifically 100 rpm, 110 rpm, 120 rpm, 130 rpm, 140 rpm, 150 rpm, 160 rpm, 170 rpm, 180 rpm, 190 rpm, 200 rpm, etc. The stirring reaction time is preferably 1~1.5 h, specifically 1 h, 1.5 h, etc.

[0090] In this invention, after the above-described stirring reaction, silicon source 2 is added dropwise. The preferred dropping rate is 3-10 mL / min, specifically 3 mL / min, 4 mL / min, 5 mL / min, 6 mL / min, 7 mL / min, 8 mL / min, 9 mL / min, 10 mL / min, etc. Controlling the dropping rate at this speed helps ensure the uniformity of crosslinking and the density of the three-dimensional crosslinked network structure, thereby ensuring the product's barrier properties. After the dropwise addition, the reaction is maintained at the aforementioned temperature (i.e., 50-60°C) with stirring. The preferred stirring speed is 100-200 rpm, specifically 100 rpm, 110 rpm, 120 rpm, 130 rpm, 140 rpm, 150 rpm, 160 rpm, 170 rpm, 180 rpm, 190 rpm, 200 rpm, etc. The preferred reaction time is 3-4 hours, specifically 3 hours, 3.5 hours, 4 hours, etc.

[0091] The reaction process in step S2 of this invention is maintained at 50~60℃ and pH 4~5, which can ensure both the hydrolysis rate of TEOS and MTES and a suitable condensation rate.

[0092] Regarding step S3 :

[0093] S3. Add amino resin dropwise to the system and stir to react, to obtain PVA / SiO2 organic-inorganic hybrid coating solution.

[0094] In this invention, the amino resin is preferably added dropwise at a temperature of 50-60°C, specifically at 50°C, 51°C, 52°C, 53°C, 54°C, 55°C, 56°C, 57°C, 58°C, 59°C, 60°C, etc. The preferred dropping rate of the amino resin is 9-15 mL / min, specifically 9 mL / min, 10 mL / min, 11 mL / min, 12 mL / min, 13 mL / min, 14 mL / min, 15 mL / min, etc. Controlling the dropping rate at this level allows for faster and better uniform dispersion in the solution, thus facilitating the formation of an ideal product structure. The preferred stirring rate for the stirring reaction is 300-400 rpm, specifically 300 rpm, 310 rpm, 320 rpm, 330 rpm, 340 rpm, 350 rpm, 360 rpm, 370 rpm, 380 rpm, 390 rpm, 400 rpm, etc. The preferred stirring time is 25-40 minutes, specifically 25 minutes, 30 minutes, 35 minutes, 40 minutes, etc. After stirring, a PVA / SiO2 organic-inorganic hybrid coating solution is obtained.

[0095] The preparation method provided by this invention introduces alcohol solvents, especially anhydrous ethanol, as co-solvents and reaction media, which can significantly promote the hydrolysis kinetics of TEOS. TEOS hydrolyzes to generate highly reactive silanol groups (Si-OH). These groups form a dense Si-O-Si inorganic three-dimensional network structure through intermolecular dehydration condensation reactions, and can also undergo dehydration condensation with the hydroxyl groups (-OH) on the polyvinyl alcohol (PVA) molecular chain to construct Si-OC covalent bonds in situ. Thus, an interpenetrating inorganic SiO2 network is generated in situ within the PVA organic phase, forming a highly cross-linked organic-inorganic hybrid system. Furthermore, to optimize the mechanical properties and structural integrity of the coating, this invention employs a stepwise silicon source addition strategy: First, silicon source 1 (TEOS) is pre-hydrolyzed and partially condensed under controlled conditions to form a continuous and dense SiO2 primary inorganic framework, providing a foundation for the coating's high barrier properties; subsequently, silicon source 2 (MTES) is introduced, and its hydrolysis products are in-situ grafted onto the surface and pores of the already formed SiO2 network, deriving hydrophobic methyl groups (Methyl groups) on it. Flexible side chains or local crosslinking points of ) are used to construct a hybrid coating with a gradient structure of "rigid inorganic framework - flexible organic modification". This structure effectively alleviates the internal stress concentration caused by drying shrinkage, winding stress or high-temperature cooking while maintaining extremely low OTR, significantly improving the coating's resistance to microcracks and flexibility, and preventing the barrier function from failing due to microcracks. Furthermore, this invention introduces amino resin as a multifunctional polymer crosslinking agent. The amino resin molecule contains abundant hydroxymethyl ( ), amino ( The active groups, such as amino groups (-NH-) and imino groups, can undergo etherification or condensation crosslinking reactions with the hydroxyl groups (-OH) in PVA molecules under acidic conditions, and can also undergo addition reactions with the residual isocyanate groups (-NCO) in the polyurethane primer. This constructs a strong chemical bridge between the PVA / SiO2 hybrid coating and the polyurethane primer layer, significantly improving the adhesion strength of the two-phase interface. Furthermore, the amino resin has a flexible long-chain structure, which, while increasing the crosslinking density, effectively alleviates the coating embrittlement problem caused by excessive crosslinking, giving the PVA / SiO2 hybrid coating good flexibility and crack resistance, ensuring its reliability in complex processing and usage environments. This invention, through the combination of specific raw materials and specific process steps, such as the stepwise introduction of the silicon source and the final introduction of the amino resin, not only significantly improves the cohesive strength and structural density of the coating, but also effectively inhibits water molecule penetration, significantly reduces oxygen permeability (OTR) in high humidity environments, and endows the coating with excellent water resistance and wet stability.

[0096] [Third Aspect] This invention provides a method for preparing a water-resistant composite packaging film based on a PVA / SiO2 hybrid coating, comprising the following steps:

[0097] K1. The thin film substrate is subjected to corona treatment to obtain a corona-treated substrate;

[0098] K2. Apply the primer to the surface of the corona-treated substrate obtained in step K1, and dry it to form a primer layer.

[0099] K3. Apply the coating liquid to the surface of the primer layer and dry it to form a PVA organic-inorganic hybrid barrier layer.

[0100] K4. Apply the adhesive to the surface of the PVA organic-inorganic hybrid barrier layer and dry it to form an adhesive layer.

[0101] K5. An organic film is laminated onto the surface of the adhesive layer to form a heat-sealing layer, thereby obtaining a composite packaging film;

[0102] In step K3, the coating liquid is the PVA / SiO2 organic-inorganic hybrid coating liquid described in the above technical solution or the PVA / SiO2 organic-inorganic hybrid coating liquid prepared by the preparation method described in the above technical solution.

[0103] Regarding step K1 :

[0104] K1. The thin film substrate is subjected to corona treatment to obtain the corona-treated substrate.

[0105] In this invention, the film substrate is preferably a biaxially oriented nylon film (BOPA). The thickness of the film substrate is preferably 15 μm. The corona treatment process is not particularly limited and can be performed according to conventional methods in the art. The goal of the corona treatment is to achieve a surface wetting tension of the film substrate ≥ 52 dyn / cm, preferably 52~56 dyn / cm, specifically 52 dyn / cm, 53 dyn / cm, 54 dyn / cm, 55 dyn / cm, 56 dyn / cm, etc.

[0106] Regarding step K2 :

[0107] K2. Apply the primer to the surface of the corona-treated substrate obtained in step K1, and dry it to form a primer layer.

[0108] In this invention, the primer is preferably a mixture of a waterborne pure polycarbonate structured polyurethane emulsion and an isocyanate curing agent. The waterborne pure polycarbonate structured polyurethane emulsion is preferably Covestro Bayhydrol® U 2757. The isocyanate curing agent is preferably a hydrophilic blocked aliphatic polyisocyanate, more preferably Covestro Bayhydur® ultra3100. In this invention, the mass ratio of the waterborne pure polycarbonate structured polyurethane emulsion to the isocyanate curing agent is preferably 100:20. After uniformly mixing the waterborne pure polycarbonate structured polyurethane emulsion and the isocyanate curing agent to obtain the primer, it should be used as soon as possible.

[0109] In this invention, the preferred method for coating the substrate surface after corona treatment in step K1 is wire rod coating. After coating, drying is performed. The preferred drying temperature is 80-100℃, specifically 80℃, 85℃, 90℃, 95℃, 100℃, etc. The preferred drying time is 30-60s, specifically 30s, 35s, 40s, 45s, 50s, 55s, 60s, etc.; drying until completely dry. After drying, a primer layer is formed. In this invention, the preferred dry coating amount in this step is 0.5-1.5 g / m³. 2 Specifically, it can be 0.5g / m 2 0.6g / m 2 0.7g / m 2 0.8g / m 2 0.9g / m 2 1.0g / m 2 1.1g / m 2 1.2g / m 2 1.3g / m 2 1.4g / m 2 1.5g / m 2 wait.

[0110] This invention employs a water-based pure polycarbonate-type polyurethane emulsion combined with an excess of isocyanate curing agent as the primer layer, unlike traditional PVA coatings which rely solely on weak interfacial interactions with the substrate film via hydrogen bonds. In this system, the unreacted isocyanate groups (-NCO) carried by the polyurethane main chain ends and the added isocyanate curing agent possess high chemical reactivity. During coating, they can undergo in-situ covalent bonding with free functional groups (such as -NH2, -COOH, etc.) present on the substrate film surface, as well as oxide groups generated after corona treatment, forming stable urethane or urea covalent bonds. Simultaneously, the excess -NCO groups can further crosslink with the active groups in the upper PVA / SiO2 organic-inorganic hybrid coating, constructing a chemical bonding network that permeates the primer-barrier layer. Therefore, even under harsh operating conditions such as boiling in water, when water molecules permeate from the substrate side causing hydrogen bonding to fail, the coating and substrate can still maintain high peel strength through stable covalent bonds, thereby ensuring the integrity and functionality of the composite film structure.

[0111] Regarding step K3 :

[0112] K3. Apply the coating liquid to the surface of the primer layer and dry it to form a PVA organic-inorganic hybrid barrier layer.

[0113] In this invention, the coating liquid is the PVA / SiO2 organic-inorganic hybrid coating liquid described in the above technical solution or the PVA / SiO2 organic-inorganic hybrid coating liquid prepared by the preparation method described in the above technical solution.

[0114] In this invention, the coating method is not particularly limited and can be any conventional coating method in the art. After coating, drying is performed. In this invention, the drying temperature is preferably 110~140℃, specifically 110℃, 115℃, 120℃, 125℃, 130℃, 135℃, 140℃, etc. The drying time is preferably 30~60s, specifically 30s, 35s, 40s, 45s, 50s, 55s, 60s, etc.; drying until completely dry. After drying, a PVA organic-inorganic hybrid barrier layer is formed on the surface of the primer layer. In this invention, the dry coating amount in this step is preferably 0.5~1.0g / m³. 2 Specifically, it can be 0.5g / m 2 0.6g / m 2 0.7g / m 2 0.75g / m 2 0.8g / m 2 0.9g / m 2 1.0g / m 2 wait.

[0115] Regarding step K4 :

[0116] K4. Apply the adhesive to the surface of the PVA organic-inorganic hybrid barrier layer and dry it to form an adhesive layer.

[0117] In this invention, the adhesive is preferably a two-component polyurethane adhesive, more preferably Henkel LOCTITELIOFOL LA 7835 / LA 6256.

[0118] In this invention, the coating method is not particularly limited and can be any conventional coating method in the art. After coating, drying is performed. In this invention, the drying temperature is preferably 50~60℃, specifically 50℃, 51℃, 52℃, 53℃, 54℃, 55℃, 56℃, 57℃, 58℃, 59℃, 60℃, etc. The drying time is preferably 30~60s, specifically 30s, 35s, 40s, 45s, 50s, 55s, 60s, etc.; drying until completely dry. After drying, an adhesive layer is formed on the surface of the barrier layer. In this invention, the dry basis coating amount in this step is preferably 3.0~3.5g / m³. 2 Specifically, it can be 3.0g / m 2 and 3.5g / m 2 wait.

[0119] Regarding step K5 :

[0120] K5. The organic film is laminated onto the surface of the adhesive layer to form a heat-sealing layer, thereby obtaining a composite packaging film.

[0121] In this invention, the organic film is preferably a CPP film (cast polypropylene film) or a polyethylene film (PE film). Specifically, the CPP film is preferably a retort-resistant RCPP film with a temperature resistance >120℃. In industrial applications, CPP films are classified into retort-resistant grade (industrial abbreviation RCPP) and non-retort-resistant grade (ordinary grade, industrial abbreviation GCPP or ordinary CPP). This invention uses a retort-resistant RCPP film. The polyethylene film is preferably a high-temperature resistant retort-resistant PE film. The thickness of the organic film is preferably 25~70μm, specifically 25μm, 30μm, 35μm, 40μm, 45μm, 50μm, 55μm, 60μm, or 70μm.

[0122] In this invention, the preferred method of lamination is hot-press lamination. After lamination, a heat-sealing layer is formed.

[0123] In this invention, after the organic film is laminated onto the surface of the adhesive layer, it is preferable to further perform a curing treatment. The curing temperature is preferably 45~55℃, specifically 45℃, 50℃, 55℃, etc., more preferably 50℃. The curing time is preferably 36~48h, specifically 36h, 40h, 44h, 48h, etc., more preferably 48h. After curing, a composite packaging film product is obtained.

[0124] [Fourth aspect] The present invention provides a water-resistant composite packaging film based on a PVA / SiO2 hybrid coating prepared by the preparation method described in the above technical solution.

[0125] The composite packaging film provided by this invention comprises, in sequence, a substrate layer, a base adhesive layer, a PVA organic-inorganic hybrid barrier layer, an adhesive layer, and a heat-sealing layer. See also... Figure 1 , Figure 1 This is a schematic diagram of the water-resistant composite packaging film based on a PVA / SiO2 hybrid coating provided by the present invention. In the diagram, 1 is the heat-sealing layer, 2 is the adhesive layer, 3 is the PVA organic-inorganic hybrid barrier layer, 4 is the primer layer, and 5 is the substrate. The types and preparation methods of each layer are consistent with those described in the previous technical solution and will not be repeated here. The primer is an aqueous polycarbonate-type polyurethane emulsion containing –NCO groups, used to form covalent bonds with the functional groups on the substrate surface; the amino resin in the PVA-based hybrid coating reacts simultaneously with the –OH groups of PVA and the –NCO groups of polyurethane, acting as an interfacial crosslinking bridge.

[0126] This invention constructs an organic-inorganic synergistic network that combines high barrier properties, strong interfacial strength, water resistance, and flexibility by specifically selecting and matching a PVA / SiO2 hybrid system, a polyurethane primer, and an amino resin crosslinking agent. The composite film exhibits excellent performance after boiling, with an OTR < 2.0 cm³ / (m²·day) and a peel strength ≥ 3.0 N / 15mm. While other barrier materials, primers, or crosslinking agents exist, the ternary synergistic system of this invention can simultaneously achieve high barrier properties, resistance to boiling at 100°C for 30 minutes, and a peel strength ≥ 3.0 N / 15mm after boiling, while meeting the requirements of food contact safety, high-speed coating processes, and low-cost manufacturing. The composite packaging film provided by this invention can be used in flexible packaging for food and pharmaceutical products that require high-temperature cooking or storage in high-humidity environments.

[0127] To further understand the present invention, preferred embodiments of the present invention are described below in conjunction with examples. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the present invention, and not for limiting the scope of the claims of the present invention.

[0128] Example 1

[0129] 1. Raw material formulation of PVA / SiO2 organic-inorganic hybrid coating solution:

[0130] PVA: 8 portions;

[0131] Silicon Source 1 (TEOS): 1 copy;

[0132] Silicon source 2 (MTES): 0.5 parts;

[0133] Amino resin (CYMEL®327): 0.3 parts;

[0134] Anhydrous ethanol: 5 parts;

[0135] Deionized water: 82 parts;

[0136] Acid catalyst (citric acid): to make the pH of the acid-added system 4.5 before any other substances are added, after the addition of the acid catalyst.

[0137] 2. Preparation of PVA / SiO2 organic-inorganic hybrid coating solution:

[0138] S1. Slowly add PVA particles to deionized water at 80°C, stir at 500 rpm and keep warm for 1.5 hours until completely dissolved to obtain a PVA solution.

[0139] S2. Cool the system to 50℃, add a mixture of silicon source 1 and anhydrous ethanol, and add citric acid dropwise (3 mL / min) to adjust the pH of the system to 4.5. Stir and maintain the temperature at 150 rpm for 1 h. Then, add silicon source 2 dropwise (3 mL / min) and stir at 50℃ and 150 rpm for 3.5 h.

[0140] S4. At 50°C, add amino resin dropwise to the system (dropping rate 9 mL / min), and stir at 350 rpm for 30 min to obtain PVA / SiO2 organic-inorganic hybrid coating solution.

[0141] 3. Preparation of water-resistant composite packaging film with PVA / SiO2 hybrid coating:

[0142] K1. A 15μm thick BOPA film is selected as the substrate and subjected to corona treatment to make the surface wetting tension of the film substrate reach 52dyn / cm, thus obtaining the corona-treated substrate.

[0143] K2. A waterborne pure polycarbonate structured polyurethane emulsion (Covestro Bayhydrol® U 2757) and a hydrophilic blocked aliphatic polyisocyanate (Covestro Bayhydur® ultra 3100) are mixed evenly at a mass ratio of 100:20 to obtain a primer. The primer is then evenly applied to the corona-treated substrate surface obtained in step K1 using a wire rod, with a dry coating amount of 0.5 g / m². 2 Then dry at 80℃ for 60 seconds until completely dry to form the base adhesive layer.

[0144] K3. The PVA / SiO2 organic-inorganic hybrid coating solution obtained in this embodiment is uniformly coated on the surface of the primer layer, with a dry coating amount of 0.5 g / m². 2 Then, it is dried at 110℃ for 60 seconds until completely dry to form a PVA organic-inorganic hybrid barrier layer.

[0145] K4. A two-component polyurethane adhesive (Henkel LOCTITE LIOFOL LA 7835 / LA 6256) is uniformly coated onto the surface of the PVA organic-inorganic hybrid barrier layer, with a dry coating amount of 3.0 g / m². 2 Then dry at 50℃ for 60 seconds until completely dry to form an adhesive layer.

[0146] K5. A 25μm thick retort-resistant RCPP film is hot-pressed onto the surface of the adhesive layer to form a heat-sealing layer, and then placed in a 50℃ constant temperature oven for 48 hours to obtain a composite packaging film product.

[0147] Example 2

[0148] 1. Raw material formulation of PVA / SiO2 organic-inorganic hybrid coating solution:

[0149] PVA: 10 units;

[0150] Silicon Source 1 (TEOS): 2 copies;

[0151] Silicon Source 2 (MTES): 1 copy;

[0152] Amino resin (CYMEL®327): 0.4 parts;

[0153] Anhydrous ethanol: 5 parts;

[0154] Deionized water: 100 parts;

[0155] Acid catalyst (citric acid): to make the pH of the acid-added system 4.0 before any other substances are added, after the addition of the acid catalyst.

[0156] 2. Preparation of PVA / SiO2 organic-inorganic hybrid coating solution:

[0157] S1. Slowly add PVA particles to deionized water at 90℃, stir at 800rpm and keep warm for 1 hour until completely dissolved to obtain a PVA solution.

[0158] S2. Cool the system to 60℃, add a mixture of silicon source 1 and anhydrous ethanol, and add citric acid dropwise (6 mL / min) to adjust the pH of the system to 4.0. Stir and maintain the temperature at 200 rpm for 1 h. Then, add silicon source 2 dropwise (10 mL / min) and stir at 60℃ and 200 rpm for 4 h.

[0159] S4. At 60°C, add amino resin dropwise to the system (dropping rate 15 mL / min), and stir at 400 rpm for 30 min to obtain PVA / SiO2 organic-inorganic hybrid coating solution.

[0160] 3. Preparation of water-resistant composite packaging film with PVA / SiO2 hybrid coating:

[0161] K1. A 15μm thick BOPA film is selected as the substrate and corona treatment is performed to make the surface wetting tension of the film substrate reach 54dyn / cm, thus obtaining the corona-treated substrate.

[0162] K2. A waterborne pure polycarbonate structured polyurethane emulsion (Covestro Bayhydrol® U 2757) and a hydrophilic blocked aliphatic polyisocyanate (Covestro Bayhydur® ultra 3100) are mixed evenly at a mass ratio of 100:20 to obtain a primer. The primer is then evenly applied to the corona-treated substrate surface obtained in step K1 using a wire rod, with a dry coating amount of 1.5 g / m². 2 Then dry at 100℃ for 30 seconds until completely dry to form the base adhesive layer.

[0163] K3. The PVA / SiO2 organic-inorganic hybrid coating solution obtained in this embodiment is uniformly coated on the surface of the primer layer, with a dry coating amount of 1.0 g / m². 2 Then, it is dried at 130℃ for 20 seconds until completely dry to form a PVA organic-inorganic hybrid barrier layer.

[0164] K4. A two-component polyurethane adhesive (Henkel LOCTITE LIOFOL LA 7835 / LA 6256) is uniformly coated onto the surface of the PVA organic-inorganic hybrid barrier layer, with a dry coating amount of 3.5 g / m². 2 Then dry at 60℃ for 60 seconds until completely dry to form an adhesive layer.

[0165] K5. A 45μm thick retort-resistant RCPP film is hot-pressed onto the surface of the adhesive layer to form a heat-sealing layer, and then placed in a 50℃ constant temperature oven for 48 hours to obtain a composite packaging film product.

[0166] Example 3

[0167] 1. Raw material formulation of PVA / SiO2 organic-inorganic hybrid coating solution:

[0168] PVA: 9 units;

[0169] Silicon Source 1 (TEOS): 1.5 parts;

[0170] Silicon source 2 (MTES): 0.75 parts;

[0171] Amino resin (CYMEL®327): 0.35 parts;

[0172] Anhydrous ethanol: 5 parts;

[0173] Deionized water: 91 parts;

[0174] Acid catalyst (citric acid): to make the pH of the acid-added system 4.2 before any other substances are added, after the addition of the acid catalyst.

[0175] 2. Preparation of PVA / SiO2 organic-inorganic hybrid coating solution:

[0176] S1. Slowly add PVA particles to deionized water at 85℃, stir at 650 rpm and keep warm for 1.5 hours until completely dissolved to obtain a PVA solution.

[0177] S2. Cool the system to 55℃, add a mixture of silicon source 1 and anhydrous ethanol, and add citric acid dropwise (4 mL / min) to adjust the pH of the system to 4.2. Stir and maintain the temperature at 180 rpm for 1 h. Then, add silicon source 2 dropwise (6 mL / min) and maintain the temperature at 55℃ and 180 rpm for 3.5 h.

[0178] S4. At 55°C, add amino resin dropwise to the system (dropping rate 12 mL / min), and stir at 380 rpm for 30 min to obtain PVA / SiO2 organic-inorganic hybrid coating solution.

[0179] 3. Preparation of water-resistant composite packaging film with PVA / SiO2 hybrid coating:

[0180] K1. A 15μm thick BOPA film is selected as the substrate and corona treatment is performed to make the surface wetting tension of the film substrate reach 56dyn / cm, thus obtaining the corona-treated substrate.

[0181] K2. A waterborne pure polycarbonate structured polyurethane emulsion (Covestro Bayhydrol® U 2757) and a hydrophilic blocked aliphatic polyisocyanate (Covestro Bayhydur® ultra 3100) are mixed evenly at a mass ratio of 100:20 to obtain a primer. The primer is then evenly applied to the corona-treated substrate surface obtained in step K1 using a wire rod, with a dry coating weight of 1.0 g / m². 2 Then dry at 90℃ for 45 seconds until completely dry to form the base adhesive layer.

[0182] K3. The PVA / SiO2 organic-inorganic hybrid coating solution obtained in this embodiment is uniformly coated on the surface of the primer layer, with a dry coating amount of 0.75 g / m². 2 Then, it is dried at 120℃ for 40 seconds until completely dry to form a PVA organic-inorganic hybrid barrier layer.

[0183] K4. A two-component polyurethane adhesive (Henkel LOCTITE LIOFOL LA 7835 / LA 6256) is uniformly coated onto the surface of the PVA organic-inorganic hybrid barrier layer, with a dry coating amount of 3.0 g / m². 2 Then dry at 55℃ for 60 seconds until completely dry to form an adhesive layer.

[0184] K5. A 35μm thick retort-resistant RCPP film is hot-pressed onto the surface of the adhesive layer to form a heat-sealing layer, and then placed in a 50℃ constant temperature oven for 48 hours to obtain a composite packaging film product.

[0185] Example 4

[0186] 1. Raw material formulation of PVA / SiO2 organic-inorganic hybrid coating solution: same as in Example 3.

[0187] 2. Preparation of PVA / SiO2 organic-inorganic hybrid coating solution: Same as in Example 3.

[0188] 3. Preparation of water-resistant composite packaging film with PVA / SiO2 hybrid coating:

[0189] The procedure was carried out as described in Example 3, except that the dry base coating amount of the primer layer in step K2 was 1.5 g / m². 2 In step K3, the dry coating amount of the PVA organic-inorganic hybrid barrier layer is 1.0 g / m². 2 In step K5, a 70μm thick retort-resistant PE film is used as the heat-sealing layer.

[0190] Comparative Example 1 (without base coat)

[0191] According to Example 3, the difference is that in the process of preparing the composite packaging film, the step K2 of coating the base layer is not performed. Instead, the PVA / SiO2 organic-inorganic hybrid coating liquid is directly coated on the surface of the substrate obtained after corona treatment in step K1.

[0192] Comparative Example 2 (Base adhesive without curing agent)

[0193] The method was implemented according to Example 3, except that in the process of preparing the composite packaging film, the primer used in step K2 was a water-based pure polycarbonate structure polyurethane emulsion (Covestro Bayhydrol® U 2757), without the addition of isocyanate curing agent.

[0194] Comparative Example 3 (Amino Resin-Free)

[0195] The method was implemented according to Example 3, except that no amino resin was added to the raw material formulation of the PVA / SiO2 organic-inorganic hybrid coating solution.

[0196] Comparative Example 4 (Conventional PVA Coating Solution)

[0197] The method was implemented according to Example 3, except that the PVA / SiO2 organic-inorganic hybrid coating solution was replaced with a conventional PVA coating solution. The conventional PVA coating solution was prepared by the following method: 9 parts by mass of PVA and 91 parts by mass of deionized water were weighed, and the PVA particles were slowly added to deionized water at 85°C. The mixture was stirred at 650 rpm and kept at the temperature for 1.5 hours until completely dissolved. After cooling to room temperature, the conventional PVA coating solution was obtained.

[0198] Comparative Example 5 (two silicon sources added without step-by-step addition)

[0199] The process was carried out according to Example 3, except that during the preparation of the PVA / SiO2 organic-inorganic hybrid coating solution, silicon source 2 was added directly (without dripping, all at once) while adding the mixture of silicon source 1 and anhydrous ethanol. Then, citric acid was added dropwise (6 mL / min) to adjust the pH of the system to 4.0, and the mixture was stirred and kept warm at 200 rpm for 5 h.

[0200] Performance testing :

[0201] The performance of the composite membrane products obtained in each embodiment and comparative example was tested, and the results are shown in Table 1.

[0202] (1) Oxygen permeability test: The test was conducted according to GB / T 1038-2022 "Test method for gas permeability of plastic films and sheets". The test conditions were 23℃ and 0% relative humidity. The oxygen permeability (OTR) before and after boiling was tested. The boiling treatment conditions were: the composite film was placed in a 100℃ water bath and boiled for 30 minutes. After removing it, the surface moisture was wiped dry and the test was conducted immediately.

[0203] (2) Peel strength test: The test was conducted according to GB / T 8808-1988 "Peel Test Method for Flexible Composite Plastic Materials". The composite film was cut into standard specimens 15 mm wide, and the peel strength was tested before boiling and after boiling in a 100℃ water bath for 30 minutes. After boiling, the samples were removed, the surface moisture was wiped off, and the test was conducted immediately. A universal testing machine was used to perform a T-type peel test at a peel speed of 300 mm / min, and the peel strength value (N / 15 mm) was recorded.

[0204] Table 1: Performance Test Results

[0205]

[0206] Test results show that the oxygen permeation rate (OTR) of the composite membrane products in all embodiments of the present invention after boiling is below 2.0 cm³ / (m²·day). Before boiling, the composite membrane exhibits tearing (i.e., the material itself is damaged but the layers are not yet separated), demonstrating high adhesion. After boiling, the peel strength is ≥3.0 N / 15 mm, and no bubbles or detachment of the coating occur. The peel strength of the comparative composite membrane products drops to below 2.5 N / 15 mm after boiling, while the OTR of comparative examples 4-5 even increases to over 50 cm³ / (m²·day). The water resistance of the present invention is significantly superior to that of the comparative examples, achieving excellent performance in terms of high barrier properties, resistance to boiling at 100°C for 30 minutes, and a peel strength ≥3.0 N / 15 mm after boiling.

[0207] This document uses specific examples to illustrate the principles and implementation methods of the present invention. The descriptions of these embodiments are merely to aid in understanding the method and core ideas of the present invention, including the best mode, and to enable any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that those skilled in the art can make various improvements and modifications to the present invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims. The scope of protection of this patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements similar to those expressed in the claims, or if they include equivalent structural elements that are not substantially different from those expressed in the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A PVA / SiO2 organic-inorganic hybrid coating solution, characterized in that, Its raw materials include: Polyvinyl alcohol: 5-15 parts by weight; Silicon source 1: 1~2 parts by weight; Silicon source 2: 0.5~1 parts by weight; Amino resin: 0.3~0.4 parts by weight; Organic cosolvent: 5 parts by weight; Water: 82~100 parts by weight; Acid catalysts: several; in, The silicon source 1 is tetraethyl orthosilicate; The silicon source 2 is methyltriethoxysilane.

2. The coating liquid according to claim 1, characterized in that, The amino resin is at least one of melamine-formaldehyde resin and urea-formaldehyde resin; The acid catalyst is at least one of an organic acid catalyst and an inorganic acid catalyst; wherein the organic acid catalyst is at least one of formic acid, acetic acid, p-toluenesulfonic acid, and citric acid; and the inorganic acid catalyst is at least one of hydrochloric acid and phosphoric acid. The amount of acid catalyst used is such that the pH value of the acid-added system is 4-5 before any other substances are added, after the acid catalyst is added. The organic co-solvent is preferably at least one of methanol, ethanol, and isopropanol.

3. The coating liquid according to claim 1 or 2, characterized in that, The amino resin is a methyl etherified high-imino melamine-formaldehyde resin.

4. The coating liquid according to claim 3, characterized in that, The amino resin is methyl etherified high imino melamine formaldehyde resin CYMEL®327; The acid catalyst is citric acid.

5. A method for preparing a PVA / SiO2 organic-inorganic hybrid coating solution according to any one of claims 1 to 4, characterized in that, Includes the following steps: S1. Mix and dissolve polyvinyl alcohol with water to obtain a polyvinyl alcohol solution; S2. Lower the system temperature to 50-60℃, add silicon source 1 and organic co-solvent, add acid catalyst dropwise to adjust the pH of the system to 4-5, and maintain the reaction at the above temperature while stirring; then, add silicon source 2 dropwise, and maintain the reaction at the above temperature while stirring. S3. Add amino resin dropwise to the system and stir to react, to obtain PVA / SiO2 organic-inorganic hybrid coating solution.

6. The preparation method according to claim 5, characterized in that, Step S1 specifically includes: mixing polyvinyl alcohol with water, stirring and dissolving at 80~90℃ to obtain a polyvinyl alcohol solution; The acid catalyst is added at a rate of 3-6 mL / min; The dropping rate of the silicon source 2 is 3~10 mL / min; The amino resin is added at a rate of 9-15 mL / min.

7. A method for preparing a water-resistant composite packaging film based on a PVA / SiO2 hybrid coating, characterized in that, Includes the following steps: K1. The thin film substrate is subjected to corona treatment to obtain a corona-treated substrate; K2. Apply the primer to the surface of the corona-treated substrate obtained in step K1, and dry it to form a primer layer. K3. Apply the coating liquid to the surface of the primer layer and dry it to form a PVA organic-inorganic hybrid barrier layer. K4. Apply the adhesive to the surface of the PVA organic-inorganic hybrid barrier layer and dry it to form an adhesive layer. K5. An organic film is laminated onto the surface of the adhesive layer to form a heat-sealing layer, thereby obtaining a composite packaging film; Wherein, the coating liquid in step K3 is the PVA / SiO2 organic-inorganic hybrid coating liquid according to any one of claims 1 to 4 or the PVA / SiO2 organic-inorganic hybrid coating liquid prepared by the preparation method according to any one of claims 5 to 6.

8. The preparation method according to claim 7, characterized in that, In step K2, the primer is a mixture of water-based pure polycarbonate structured polyurethane emulsion and isocyanate curing agent; The aqueous pure polycarbonate structured polyurethane emulsion is Covestro Bayhydrol® U 2757; the isocyanate curing agent is Covestro Bayhydur® ultra 3100. In step K2, the dry coating amount is 0.5~1.5 g / m². 2 The drying temperature is 80~100℃; In step K3, the dry coating amount is 0.5~1.0 g / m². 2 The drying temperature is 110~140℃; In step K4, the dry coating amount is 3.0~3.5 g / m². 2 The drying temperature is 50~60℃; In step K4, the adhesive is preferably a two-component polyurethane adhesive.

9. The preparation method according to claim 7, characterized in that, In step K1, the goal of the corona treatment is to make the surface wetting tension of the thin film substrate ≥52 dyn / cm; In step K4, the adhesive is a two-component polyurethane adhesive, Henkel LOCTITE LIOFOL LA 7835 / LA6256; In step K5, the organic film is a CPP film or a PE film.

10. A water-resistant composite packaging film based on a PVA / SiO2 hybrid coating, prepared by any one of claims 7 to 9.

Images