A high-barrier water-based coating liquid resistant to high-temperature cooking and its preparation method

Abstract

This application discloses a high-temperature retort-resistant, high-barrier water-based coating liquid and its preparation method, belonging to the field of water-based coating liquid technology. The key technical point is that it is a high-temperature retort-resistant, high-barrier water-based coating liquid. By mass percentage, the raw materials used include the following components: 10-25% modified PVA / sulfonated modified EVOH blend resin, 3-8% crosslinking agent, 2-6% nano-barrier filler, 1-3% adhesion promoter, 0.3-1.0% wetting and dispersing agent, 0.1-0.5% defoamer, and the balance being deionized water. The coating liquid of this application can be widely used in packaging scenarios requiring high-temperature retort sterilization, such as food and pharmaceutical products. The resulting coating has high adhesion to the base film, enabling the BOPA film to simultaneously possess excellent high-temperature retort resistance and gas barrier properties. It is also environmentally friendly, low-cost, and represents a replacement for imported high-end products of the same type.

Description

Technical Field

[0001] This application relates to the field of water-based coating liquid technology, and in particular to a high-barrier water-based coating liquid for coating biaxially oriented nylon films that is resistant to high-temperature cooking and a method for preparing the same. Background Technology

[0002] With the continuous development of the food and pharmaceutical industries, the requirements for packaging safety and shelf life are constantly increasing, leading to the widespread application of high-temperature retort packaging. Biaxially oriented nylon (BOPA) film, with its excellent mechanical strength and puncture resistance, has become one of the core substrates for high-temperature retort packaging. However, the gas barrier properties of ordinary BOPA film, such as its ability to block oxygen and water vapor, are insufficient. This necessitates the use of functional coating solutions to enhance its barrier properties and meet actual packaging needs. This highlights the increasing importance of coating solutions in the packaging materials field, and the development of related technologies is crucial for ensuring product quality and extending shelf life.

[0003] In existing technologies, to improve the gas barrier properties of BOPA films, ordinary PVA-based coating solutions are often used, which simply aim for high barrier properties. However, these coating solutions have poor water resistance and retort resistance. After coating, BOPA films are easily subjected to high-temperature retort at 121°C for more than 30 minutes, resulting in coating peeling, blistering, swelling, and other phenomena. This leads to a sharp decline in barrier performance, which cannot meet the packaging requirements for long-term high-temperature retort sterilization. On the other hand, coating solutions that focus on retort resistance are difficult to achieve the ideal barrier effect and cannot simultaneously meet the core requirements of "high barrier + resistance to 121°C retort".

[0004] While solvent-based coating solutions can improve retort resistance to some extent, their high VOC emissions fail to meet environmental protection requirements. Imported water-based high-barrier retort-resistant coating solutions, while offering superior performance, are expensive, leading to high costs for downstream packaging products. Furthermore, most coating solutions still suffer from insufficient adhesion between the coating and the BOPA base film, making the coating prone to peeling during subsequent processing (such as printing and lamination), affecting the integrity and safety of the packaging. Summary of the Invention

[0005] To address the aforementioned technical issues, this application provides a high-temperature resistant, retortable, high-barrier water-based coating liquid and its preparation method. This coating liquid can be widely used in packaging applications such as food and pharmaceuticals that require high-temperature retorting sterilization. The coating formed after coating has high adhesion to the base film, enabling the BOPA film to simultaneously possess excellent high-temperature retort resistance and gas barrier properties. Furthermore, it is environmentally friendly, low-cost, and achieves a replacement for imported high-end products of the same type.

[0006] In a first aspect, the present invention provides a high-barrier aqueous coating liquid resistant to high-temperature cooking, which adopts the following technical solution:

[0007] A high-barrier water-based coating liquid resistant to high-temperature cooking, comprising the following components by mass percentage:

[0008] 10-25% modified PVA / sulfonated modified EVOH blend resin;

[0009] Crosslinking agent 3-8%;

[0010] Nano barrier fillers 2-6%;

[0011] Adhesion promoter 1-3%;

[0012] Wetting and dispersing agent 0.3-1.0%;

[0013] Defoamer 0.1-0.5%;

[0014] Deionized water balance.

[0015] By adopting the above technical solution, this application uses modified PVA / sulfonated modified EVOH blend resin as the core barrier component. With the combined action of crosslinking agent, nano barrier filler, adhesion promoter, wetting and dispersing agent, defoamer, and other components, the coating liquid possesses high barrier performance, effectively blocking oxygen and water vapor penetration and extending the shelf life of the packaged product. After being coated onto a BPA base film, and subjected to high-temperature boiling at 121℃ for 30-60 minutes, the coating exhibits high peel strength and strong adhesion to the BPA base film, meeting the requirements of subsequent printing, lamination, and other processing techniques, and is less prone to coating peeling. Furthermore, the coating liquid of this application is an aqueous system with low VOC content, meeting national environmental protection requirements. The raw materials used in the formula are all domestically sourced and readily available, and the production cost is only 60-70% of that of imported similar products. It is environmentally friendly and cost-controllable, and can directly replace imported products, promoting the localization and upgrading of the packaging industry.

[0016] Specifically, the modified PVA resin of this application enhances water resistance, while the sulfonated modified EVOH resin strengthens gas barrier properties. Their combined use achieves a synergistic improvement in both barrier properties and retort resistance. Furthermore, the sulfonated modification of the EVOH resin introduces sulfonate groups, giving it strong hydrophilicity and ionization properties, allowing it to dissolve and disperse evenly with the modified PVA resin under heating and stirring conditions. The crosslinking agent increases the crosslinking density of the coating, reducing the likelihood of swelling and peeling during retort preparation. The layered structure of the nano-barrier filler forms a dense barrier network, reducing gas permeation channels and thus working in conjunction with the sulfonated modified EVOH resin to enhance the barrier performance of the coating solution. The adhesion promoter of this application enhances the interfacial bonding between the coating and the BOPA base film, thereby reducing the possibility of coating peeling. The wetting and dispersing agent improves the wettability of the coating solution on the BOPA base film surface, preventing pinholes. The defoamer eliminates bubbles generated during preparation and coating, ensuring coating smoothness. The deionized solvent acts as a solvent carrier, adjusting the viscosity of the coating solution.

[0017] The preparation route of the sulfonated modified EVOH resin in this application is as follows: EVOH resin powder → swelling with 1,2-dichloroethane → addition of chlorosulfonic acid / sodium bisulfite → reaction at 60-80℃ → neutralization → washing with water → drying → dissolution of EVOH-SO3Na in hot water to obtain the sulfonated modified EVOH resin. The EVOH resin powder is a crystalline polymer material formed by copolymerization of ethylene and vinyl alcohol, with an ethylene content of 29-32 mol%, preferably 30-32 mol%. If the ethylene content is below 29 mol%, although the barrier properties are extremely high, it is difficult to modify by water solubility, easily becomes hygroscopic and embrittled, and is prone to delamination / whitening when cooked at 121℃. If the ethylene content is above 35 mol%, although the processing is good, the barrier properties are significantly reduced, failing to meet the barrier requirements for retort packaging. Therefore, this application controls the ethylene content in the EVOH resin powder to 29-32 mol%, achieving the best balance between barrier properties, retort resistance, and the difficulty of water-soluble modification, which is suitable for the coating liquid formulation of this application.

[0018] In a preferred embodiment, the coating liquid comprises the following components by weight percentage:

[0019] 15-20% modified PVA / sulfonated modified EVOH blend resin;

[0020] Crosslinking agent 4-6%;

[0021] 3-5% nano-barrier filler;

[0022] Adhesion promoter 1.5-2.5%;

[0023] Wetting and dispersing agent 0.5-0.8%;

[0024] Defoamer 0.2-0.3%;

[0025] Deionized water balance.

[0026] By adopting the above technical solution, this application further optimizes the dosage ratio of each raw material component in the coating liquid, thereby further improving the barrier properties and boiling resistance of the coating liquid.

[0027] In a preferred embodiment, the mass ratio of modified PVA resin to sulfonated modified EVOH resin in the modified PVA / sulfonated modified EVOH blend resin is 1:(0.8-1.2).

[0028] By adopting the above technical solution, this application optimizes the ratio between modified PVA resin and sulfonated modified EVOH resin, which can achieve the best balance between coating liquid barrier performance and boiling resistance performance, and avoid the performance shortcomings caused by a single resin.

[0029] In a preferred embodiment, the crosslinking agent includes aliphatic aldehydes, blocked isocyanates, and deionized water.

[0030] By adopting the above technical solution, this application uses a mixture of fatty aldehyde, blocked isocyanate, and deionized water as a crosslinking agent. The fatty aldehyde enables rapid initial crosslinking, while the blocked isocyanate is unblocked during high-temperature drying, completing deep crosslinking and forming a dense crosslinked network. The crosslinking agent in this application exhibits high stability in aqueous systems and does not easily swell after crosslinking, significantly improving the coating solution's resistance to boiling. It is also perfectly compatible with modified PVA / sulfonated modified EVOH blend resins, exhibiting high crosslinking efficiency without affecting the stability of the coating solution. Furthermore, all raw materials are domestically available and conventional, resulting in low cost. If only fatty aldehyde is used, the temperature resistance is insufficient; if only blocked isocyanate is used, problems such as slow crosslinking speed and poor adhesion arise.

[0031] In a preferred embodiment, the mass ratio of the fatty aldehyde, the blocked isocyanate and the deionized water is (2-3):1:(5-8).

[0032] In a preferred embodiment, the mass ratio of the fatty aldehyde, the blocked isocyanate, and the deionized water is 2.5:1:6.

[0033] By adopting the above technical solution, this application optimizes the dosage ratio of fatty aldehyde, blocked isocyanate, and deionized water, which promotes the formation of a dense network structure by the crosslinking agent, thereby improving the coating liquid's performance in various aspects, such as resistance to boiling. Experimental data shows that when the mass ratio of fatty aldehyde, blocked isocyanate, and deionized water is 2.5:1:6, the resulting crosslinking agent has a better effect on improving the performance of the coating liquid.

[0034] In a preferred embodiment, the crosslinking agent is prepared by the following method:

[0035] At a speed of 500-800 r / min, the blocked isocyanate and deionized water are mixed and stirred for 10-15 min. Then, while stirring, the fatty aldehyde is added. The temperature is then raised to 40-50℃, and the mixture is stirred at this temperature for 20-30 min. After cooling to room temperature, the mixture is filtered to obtain the crosslinking agent.

[0036] The fatty aldehyde is added slowly, with a dropping rate of 5-8 mL / min.

[0037] In a preferred embodiment, the nanobarrier filler is a nanobarrier filler that has undergone surface modification treatment with a silane coupling agent.

[0038] In a preferred embodiment, the surface modification treatment of the silane coupling agent is carried out at a temperature of 60-80°C for 2-3 hours.

[0039] By adopting the above technical solution, this application uses silane coupling agent to modify the surface of nano barrier filler, which can further improve the compatibility between nano barrier filler and other components, so that nano barrier filler can be fully and uniformly dispersed in the system, reducing the possibility that its agglomeration will affect the barrier effect.

[0040] Secondly, this application provides a method for preparing a high-barrier, high-barrier water-based coating liquid resistant to high-temperature cooking, which adopts the following technical solution:

[0041] A method for preparing a high-barrier water-based coating liquid resistant to high-temperature cooking includes the following steps:

[0042] S1. Mix the modified PVA / sulfonated modified EVOH blend resin with deionized water, heat to 80-90℃, stir until completely dissolved, and then cool to 40-50℃ to obtain the resin mother liquor.

[0043] S2. Add crosslinking agent, adhesion promoter, wetting and dispersing agent and defoamer to the resin mother liquor, and stir at 800-1000 r / min for 20-30 min.

[0044] S3. Add the nano barrier filler to the product obtained in step S2 and continue stirring for 30-40 minutes while maintaining the rotation speed. Then, homogenize the mixture 1-2 times under a pressure of 20-30 MPa.

[0045] S4. Adjust the viscosity of the system to 20-50 mPa·s (25℃), and then filter it through a 200-300 mesh filter to obtain a high-barrier water-based coating liquid that can withstand high-temperature cooking.

[0046] By adopting the above technical solution, the preparation method of this application is simple, easy to operate, requires no special equipment, can be adapted to existing coating liquid production lines, and is easy to scale up for mass production.

[0047] In summary, the present invention has the following beneficial effects:

[0048] 1. After the coating liquid of this application is applied to the BOPA base film, the coating does not peel off, bubble, or swell after being boiled at 121°C for 30-60 minutes. The coating has good structural integrity and the barrier performance decay rate after boiling is ≤10%, which is far superior to the existing coating liquid.

[0049] 2. After the coating liquid of this application is applied to the BOPA base film, it significantly improves the peel strength of the BOPA film, meets the requirements of subsequent printing, lamination and other processing processes, is not prone to coating peeling, and does not delaminate or precipitate after being stored at 25°C for 6 months, showing excellent stability.

[0050] 3. The coating liquid of this application is an all-water system with a VOC content of ≤5g / L, which meets the national environmental protection standards. Moreover, all the raw materials used are domestically produced and easy to purchase. The production cost is only 60-70% of that of imported similar products, which has a significant cost-performance advantage.

[0051] 4. The preparation method of this application is simple and easy to operate, requires no special equipment, can be adapted to existing coating liquid production lines, and is easy to scale up for mass production. Detailed Implementation

[0052] The present application will be further described in detail below with reference to the embodiments. All reagents, unless otherwise specified, are commercially available conventional reagent products.

[0053] The modified PVA resin used in this application is PVA1799 type, with a degree of alcoholysis of 99% (mol / mol).

[0054] The EVOH resin powder of this application is a crystalline polymer material formed by copolymerization of ethylene and vinyl alcohol, with an ethylene content of 29-32 mol%, which is more preferably 30-32 mol%. In the specific embodiments of this application, the EVOH resin powder of this application is illustrated using Mitsubishi Chemical's DT2903 (ethylene content 29 mol%, MFI 3.0) or Nippon Synthetic Chemical's ST230(2) (ethylene content 29 mol%, extremely low oxygen permeability) as examples.

[0055] In the specific embodiments of this application, pentylene glycol is used as a representative of aliphatic aldehydes.

[0056] The blocked isocyanate in this application is Covestro BL 3175.

[0057] The nano-barrier filler in this application is nano-montmorillonite or nano-silica. In the specific embodiments of this application, nano-montmorillonite is used as an example for explanation.

[0058] In the specific embodiments of this application, the silane coupling agent is described using silane coupling agent KH-560 as an example.

[0059] The adhesion promoter in this application is an aminosilane coupling agent. In the specific embodiments of this application, KH-550 is used as an example for illustration.

[0060] The wetting and dispersing agent in this application is a nonionic surfactant. In the specific embodiments of this application, polyoxyethylene octylphenol ether is used as an example for illustration.

[0061] The defoamer used in this application is an organosilicone defoamer. In the specific embodiments of this application, Evonik TEGO is used. ® The Foamex 810 will be used as an example for explanation.

[0062] <Example 1>

[0063] A high-barrier water-based coating liquid resistant to high-temperature boiling is provided, the raw materials of which include the following components: 10 kg of modified PVA / sulfonated modified EVOH blend resin, 8 kg of crosslinking agent, 2 kg of nano-montmorillonite, 3 kg of aminosilane coupling agent (KH-550), 0.3 kg of polyoxyethylene octylphenol ether, 0.5 kg of silicone defoamer, and 76.2 kg of deionized water;

[0064] The mass ratio of modified PVA resin to sulfonated modified EVOH resin is 1:0.8.

[0065] Preparation method of sulfonated modified EVOH resin: EVOH resin powder → swelling with 1,2-dichloroethane → addition of chlorosulfonic acid / sodium bisulfite → reaction at 70℃ → neutralization → washing with water → drying → dissolving EVOH-SO3Na in hot water to obtain sulfonated modified EVOH resin.

[0066] The crosslinking agent includes glutaraldehyde, blocked isocyanate, and deionized water in a mass ratio of 2:1:8;

[0067] The preparation method of this crosslinking agent includes the following steps:

[0068] At a speed of 500 r / min, the blocked isocyanate and deionized water were mixed and stirred for 15 min. Then, glutaraldehyde was added dropwise while stirring at a rate of 5 mL / min. The temperature was then raised to 40 °C and stirred for 30 min. After cooling to room temperature, the mixture was filtered to obtain the crosslinking agent.

[0069] The preparation method of this high-temperature resistant, retortable, high-barrier water-based coating liquid includes the following steps:

[0070] S1. Mix modified PVA resin, sulfonated modified EVOH resin and some deionized water, heat to 80°C, stir until completely dissolved, and then cool to 40°C to obtain resin mother liquor.

[0071] S2. Add crosslinking agent, aminosilane coupling agent (KH-550), polyoxyethylene octylphenol ether, and organosilicon defoamer to the resin mother liquor, and stir at 800 r / min for 30 min.

[0072] S3. Add nano-montmorillonite to the product obtained in step S2 and continue stirring for 30 minutes while maintaining the stirring speed. Then, homogenize twice under a pressure of 20 MPa.

[0073] S4. Detect the viscosity of the system. Adjust the viscosity of the system to 20 mPa·s (25℃) by adding deionized water or concentrating the solution. Then filter the solution through a 200-mesh filter to obtain a high-barrier water-based coating liquid that can withstand high-temperature cooking.

[0074] <Example 2>

[0075] A high-barrier water-based coating liquid resistant to high-temperature boiling is provided, the raw materials of which include the following components: 25 kg of modified PVA / sulfonated modified EVOH blend resin, 3 kg of crosslinking agent, 6 kg of nano montmorillonite, 1 kg of aminosilane coupling agent (KH-550), 1 kg of polyoxyethylene octylphenol ether, 0.1 kg of organosilicon defoamer, and 63.9 kg of deionized water;

[0076] The mass ratio of modified PVA resin to sulfonated modified EVOH resin is 1:1.2.

[0077] Preparation method of sulfonated modified EVOH resin: EVOH resin powder → swelling with 1,2-dichloroethane → addition of chlorosulfonic acid / sodium bisulfite → reaction at 70℃ → neutralization → washing with water → drying → dissolving EVOH-SO3Na in hot water to obtain sulfonated modified EVOH resin.

[0078] The crosslinking agents include glutaraldehyde, blocked isocyanate, and deionized water in a mass ratio of 3:1:5;

[0079] The preparation method of this crosslinking agent includes the following steps:

[0080] At a speed of 800 r / min, the blocked isocyanate and deionized water were mixed and stirred for 10 min. Then, glutaraldehyde was added dropwise while stirring at a rate of 8 mL / min. The temperature was then raised to 50 °C and stirred for 20 min. After cooling to room temperature, the mixture was filtered to obtain the crosslinking agent.

[0081] The preparation method of this high-temperature resistant, retortable, high-barrier water-based coating liquid includes the following steps:

[0082] S1. Mix modified PVA resin, sulfonated modified EVOH resin and some deionized water, heat to 90°C, stir until completely dissolved, and then cool to 50°C to obtain resin mother liquor.

[0083] S2. Add crosslinking agent, aminosilane coupling agent (KH-550), polyoxyethylene octylphenol ether, and organosilicon defoamer to the resin mother liquor, and stir at 1000 r / min for 20 min.

[0084] S3. Add nano-montmorillonite to the product obtained in step S2 and continue stirring for 40 minutes while maintaining the stirring speed. Then, homogenize once under a pressure of 30 MPa.

[0085] S4. Detect the viscosity of the system. Adjust the viscosity of the system to 50 mPa·s (25℃) by adding deionized water or concentrating the solution. Then filter the solution through a 300-mesh filter to obtain a high-barrier water-based coating liquid that can withstand high-temperature cooking.

[0086] <Example 3>

[0087] A high-barrier water-based coating liquid resistant to high-temperature boiling is provided, the raw materials of which include the following components: 15 kg of modified PVA / sulfonated modified EVOH blend resin, 4 kg of crosslinking agent, 3 kg of nano-montmorillonite, 1.5 kg of aminosilane coupling agent (KH-550), 0.5 kg of polyoxyethylene octylphenol ether, 0.2 kg of silicone defoamer, and 75.8 kg of deionized water;

[0088] The mass ratio of modified PVA resin to sulfonated modified EVOH resin is 1:1.

[0089] Preparation method of sulfonated modified EVOH resin: EVOH resin powder → swelling with 1,2-dichloroethane → addition of chlorosulfonic acid / sodium bisulfite → reaction at 70℃ → neutralization → washing with water → drying → dissolving EVOH-SO3Na in hot water to obtain sulfonated modified EVOH resin.

[0090] The crosslinking agents include glutaraldehyde, blocked isocyanate, and deionized water in a mass ratio of 2:1:5;

[0091] The preparation method of this crosslinking agent includes the following steps:

[0092] At a speed of 600 r / min, the blocked isocyanate and deionized water were mixed and stirred for 12 min. Then, glutaraldehyde was added dropwise while stirring at a rate of 6 mL / min. The temperature was then raised to 45 °C and stirred for 25 min. The mixture was then cooled to room temperature and filtered to obtain the crosslinking agent.

[0093] The preparation method of this high-temperature resistant, retortable, high-barrier water-based coating liquid includes the following steps:

[0094] S1. Mix modified PVA resin, sulfonated modified EVOH resin and some deionized water, heat to 85°C, stir until completely dissolved, and then cool to 45°C to obtain resin mother liquor.

[0095] S2. Add crosslinking agent, aminosilane coupling agent (KH-550), polyoxyethylene octylphenol ether, and organosilicon defoamer to the resin mother liquor, and stir at 900 r / min for 25 min.

[0096] S3. Add nano-montmorillonite to the product obtained in step S2 and continue stirring for 35 minutes while maintaining the stirring speed. Then, homogenize once under a pressure of 25 MPa.

[0097] S4. Detect the viscosity of the system. Adjust the viscosity of the system to 35 mPa·s (25℃) by adding deionized water or concentrating the solution. Then filter the solution through a 250-mesh filter to obtain a high-barrier water-based coating liquid that can withstand high-temperature cooking.

[0098] <Example 4>

[0099] A high-barrier water-based coating liquid resistant to high-temperature boiling, the raw materials used include the following components: 20 kg of modified PVA / sulfonated modified EVOH blend resin, 6 kg of crosslinking agent, 5 kg of nano montmorillonite, 2.5 kg of aminosilane coupling agent (KH-550), 0.8 kg of polyoxyethylene octylphenol ether, 0.3 kg of organosilicon defoamer, and 65.4 kg of deionized water;

[0100] The mass ratio of modified PVA resin to sulfonated modified EVOH resin is 1:1.

[0101] Preparation method of sulfonated modified EVOH resin: EVOH resin powder → swelling with 1,2-dichloroethane → addition of chlorosulfonic acid / sodium bisulfite → reaction at 70℃ → neutralization → washing with water → drying → dissolving EVOH-SO3Na in hot water to obtain sulfonated modified EVOH resin.

[0102] The crosslinking agent includes glutaraldehyde, blocked isocyanate, and deionized water in a mass ratio of 3:1:8;

[0103] The preparation method of this crosslinking agent includes the following steps:

[0104] At a speed of 600 r / min, the blocked isocyanate and deionized water were mixed and stirred for 12 min. Then, glutaraldehyde was added dropwise while stirring at a rate of 6 mL / min. The temperature was then raised to 45 °C and stirred for 25 min. The mixture was then cooled to room temperature and filtered to obtain the crosslinking agent.

[0105] The preparation method of this high-temperature resistant, retortable, high-barrier water-based coating liquid includes the following steps:

[0106] S1. Mix modified PVA resin, sulfonated modified EVOH resin and some deionized water, heat to 85°C, stir until completely dissolved, and then cool to 45°C to obtain resin mother liquor.

[0107] S2. Add crosslinking agent, aminosilane coupling agent (KH-550), polyoxyethylene octylphenol ether, and organosilicon defoamer to the resin mother liquor, and stir at 900 r / min for 25 min.

[0108] S3. Add nano-montmorillonite to the product obtained in step S2 and continue stirring for 35 minutes while maintaining the stirring speed. Then, homogenize once under a pressure of 25 MPa.

[0109] S4. Detect the viscosity of the system. Adjust the viscosity of the system to 35 mPa·s (25℃) by adding deionized water or concentrating the solution. Then filter the solution through a 250-mesh filter to obtain a high-barrier water-based coating liquid that can withstand high-temperature cooking.

[0110] <Example 5>

[0111] A high-barrier water-based coating liquid resistant to high-temperature boiling, the raw materials used include the following components: 20 kg of modified PVA / sulfonated modified EVOH blend resin, 6 kg of crosslinking agent, 5 kg of nano montmorillonite, 2.5 kg of aminosilane coupling agent (KH-550), 0.8 kg of polyoxyethylene octylphenol ether, 0.3 kg of organosilicon defoamer, and 65.4 kg of deionized water;

[0112] The mass ratio of modified PVA resin to sulfonated modified EVOH resin is 1:1.

[0113] Preparation method of sulfonated modified EVOH resin: EVOH resin powder → swelling with 1,2-dichloroethane → addition of chlorosulfonic acid / sodium bisulfite → reaction at 70℃ → neutralization → washing with water → drying → dissolving EVOH-SO3Na in hot water to obtain sulfonated modified EVOH resin.

[0114] The crosslinking agent includes glutaraldehyde, blocked isocyanate, and deionized water in a mass ratio of 2.5:1:6;

[0115] The preparation method of this crosslinking agent includes the following steps:

[0116] At a speed of 600 r / min, the blocked isocyanate and deionized water were mixed and stirred for 12 min. Then, glutaraldehyde was added dropwise while stirring at a rate of 6 mL / min. The temperature was then raised to 45 °C and stirred for 25 min. The mixture was then cooled to room temperature and filtered to obtain the crosslinking agent.

[0117] The preparation method of this high-temperature resistant, retortable, high-barrier water-based coating liquid includes the following steps:

[0118] S1. Mix modified PVA resin, EVOH resin and some deionized water, heat to 85°C, stir until completely dissolved, then cool to 45°C to obtain resin mother liquor.

[0119] S2. Add crosslinking agent, aminosilane coupling agent (KH-550), polyoxyethylene octylphenol ether, and organosilicon defoamer to the resin mother liquor, and stir at 900 r / min for 25 min.

[0120] S3. Add nano-montmorillonite to the product obtained in step S2 and continue stirring for 35 minutes while maintaining the stirring speed. Then, homogenize once under a pressure of 25 MPa.

[0121] S4. Detect the viscosity of the system. Adjust the viscosity of the system to 35 mPa·s (25℃) by adding deionized water or concentrating the solution. Then filter the solution through a 250-mesh filter to obtain a high-barrier water-based coating liquid that can withstand high-temperature cooking.

[0122] <Example 6>

[0123] A high-barrier water-based coating liquid resistant to high-temperature boiling is provided, comprising the following components: 20 kg of modified PVA / sulfonated modified EVOH blend resin, 6 kg of crosslinking agent, 5 kg of modified nano-montmorillonite, 2.5 kg of aminosilane coupling agent (KH-550), 0.8 kg of polyoxyethylene octylphenol ether, 0.3 kg of silicone defoamer, and 65.4 kg of deionized water.

[0124] The mass ratio of modified PVA resin to sulfonated modified EVOH resin is 1:1.

[0125] Preparation method of sulfonated modified EVOH resin: EVOH resin powder → swelling with 1,2-dichloroethane → addition of chlorosulfonic acid / sodium bisulfite → reaction at 70℃ → neutralization → washing with water → drying → dissolving EVOH-SO3Na in hot water to obtain sulfonated modified EVOH resin.

[0126] The crosslinking agent includes glutaraldehyde, blocked isocyanate, and deionized water in a mass ratio of 2.5:1:6;

[0127] The preparation method of this crosslinking agent includes the following steps:

[0128] At a speed of 600 r / min, the blocked isocyanate and deionized water were mixed and stirred for 12 min. Then, glutaraldehyde was added dropwise while stirring at a rate of 6 mL / min. The temperature was then raised to 45 °C and stirred for 25 min. The mixture was then cooled to room temperature and filtered to obtain the crosslinking agent.

[0129] The preparation method of this high-temperature resistant, retortable, high-barrier water-based coating liquid includes the following steps:

[0130] S0. Mix nano-montmorillonite with some deionized water and disperse at 1800 r / min for 35 min. Then add silane coupling agent KH-560, heat to 70℃, and stir for 2.5 h to obtain modified nano-montmorillonite dispersion.

[0131] S1. Mix modified PVA resin, sulfonated modified EVOH resin and some deionized water, heat to 85°C, stir until completely dissolved, and then cool to 45°C to obtain resin mother liquor.

[0132] S2. Add crosslinking agent, aminosilane coupling agent (KH-550), polyoxyethylene octylphenol ether, and organosilicon defoamer to the resin mother liquor, and stir at 900 r / min for 25 min.

[0133] S3. Add the modified nano-montmorillonite dispersion to the product obtained in step S2, and continue stirring at the same speed for 35 min. Then, homogenize it once under a pressure of 25 MPa.

[0134] S4. Detect the viscosity of the system. Adjust the viscosity of the system to 35 mPa·s (25℃) by adding deionized water or concentrating the solution. Then filter the solution through a 250-mesh filter to obtain a high-barrier water-based coating liquid that can withstand high-temperature cooking.

[0135] <Comparative Example 1>

[0136] The difference from Example 3 is that no sulfonated modified EVOH resin is added, only modified PVA resin is used, and the rest is the same as Example 3.

[0137] <Comparative Example 2>

[0138] The difference from Example 3 is that no modified PVA resin is added, only sulfonated modified EVOH resin is used, and the rest is the same as Example 3.

[0139] <Comparative Example 3>

[0140] The difference from Example 3 is that the mass ratio of modified PVA resin to sulfonated modified EVOH resin is 1:0.5, and the rest is the same as in Example 3.

[0141] <Comparative Example 4>

[0142] The difference from Example 3 is that the mass ratio of modified PVA resin to sulfonated modified EVOH resin is 1:2, while the rest is the same as in Example 3.

[0143] <Comparative Example 5>

[0144] The difference from Example 3 is that the crosslinking agent is only a single glutaraldehyde crosslinking agent, while the rest is the same as in Example 3.

[0145] <Comparative Example 6>

[0146] The difference from Example 3 is that the crosslinking agent is only a single blocked isocyanate crosslinking agent, while the rest is the same as in Example 3.

[0147] <Comparative Example 7>

[0148] The difference from Example 3 is that the mass ratio of glutaraldehyde to blocked isocyanate is 1:1, while the rest is the same as in Example 3.

[0149] <Comparative Example 8>

[0150] The difference from Example 3 is that the mass ratio of glutaraldehyde to blocked isocyanate is 5:1, while the rest is the same as in Example 3.

[0151] <Performance Detection>

[0152] The coating solutions prepared in the above examples and comparative examples were coated onto the surface of a BOPA base film made from ordinary polyamide 6 using a microgravure coating method. After pre-baking at 85°C for 40 seconds and heat curing at 130°C for 2 minutes, the resulting dry film thickness was 1.2 μm. Following further curing at 23°C / 50% humidity for 24 hours, a BOPA film was obtained. To emphasize the performance degradation after boiling, this application requires the BOPA film to be fabricated into a typical structure before relevant performance tests. The typical structure is a BOPA / / BOPA / / RCPP structure, with an adhesive application amount of 3.5 g / m³. 2 The above refers to RCPP, which is a cast polypropylene film with a thickness of 70 μm.

[0153] The relevant performance tests mainly included retort resistance, barrier properties, adhesion, and stability. Retort resistance was measured by the time it took for the coating to remain intact and blister-free after being boiled at 121℃. Barrier properties included oxygen and moisture barrier properties; oxygen barrier was tested according to the method described in GB / T 19789-2021, and moisture barrier was tested according to the method described in GB / T 26253-2010. Adhesion was tested according to the method described in GB / T 8808-1988, with a sample width of 15mm, a length of 200mm, and a stretching speed of 200mm / min. Stability was measured by the absence of stratification and precipitation after storage at 25℃ for 6 months, indicating excellent stability. The test results are shown in Table 1.

[0154] Table 1 Performance Test Results

[0155]

[0156] As shown in Table 1, after the coating solutions prepared in Examples 1-6 of this application were coated onto the BOPA base film to form typical structures for testing, the coatings showed no peeling, bubbling, or swelling after being boiled at 121°C for 30-60 minutes, exhibiting good structural integrity; the oxygen permeability before boiling was 0.4-0.8 cm⁻¹. 3 / m 2 After 24 hours at 0.1 MPa, the oxygen permeability remained at 0.8 cm³. 3 / m 2 • 24h • within 0.1Mpa; water vapor permeability after cooking ≤ 3g / m 2 • After 24 hours of cooking, the peel strength is above 3.8 N / 15 mm. After storage at 25°C for 6 months, there is no delamination or sedimentation, demonstrating excellent stability. Experimental data shows that the coating liquid of this application possesses both high resistance to cooking and barrier properties, effectively preventing oxygen and moisture penetration, extending the shelf life of the packaged product, and is less prone to coating peeling, meeting the requirements of subsequent printing, lamination, and other processing techniques.

[0157] A comparison of the data from Comparative Examples 1-4 with that of Example 3 shows that the performance test results of Comparative Examples 1-4 are worse than those of Example 3. This indicates that by using modified PVA resin and sulfonated modified EVOH resin in combination and optimizing the ratio of their amounts, this application can fully leverage their synergistic effect and achieve the best balance between barrier properties and boil resistance.

[0158] A comparison of the data from Comparative Examples 5-8 and Example 3 shows that the performance test results of Comparative Examples 5-8 are worse than those of Example 3. This indicates that by using glutaraldehyde and blocked isocyanate in combination and optimizing their dosage ratio, this application can fully leverage their synergistic effect, thereby improving the water resistance and high temperature resistance of the coating.

[0159] The embodiments described herein are merely illustrative of preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape, and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A high-barrier water-based coating liquid resistant to high-temperature cooking, characterized in that, The raw materials used, by weight percentage, include the following components: 10-25% modified PVA / sulfonated modified EVOH blend resin; Crosslinking agent 3-8%; Nano barrier fillers 2-6%; Adhesion promoter 1-3%; Wetting and dispersing agent 0.3-1.0%; Defoamer 0.1-0.5%; Deionized water balance.

2. The high-barrier water-based coating liquid resistant to high-temperature cooking as described in claim 1, characterized in that, The coating liquid comprises the following components by mass percentage: 15-20% modified PVA / sulfonated modified EVOH blend resin; Crosslinking agent 4-6%; 3-5% nano-barrier filler; Adhesion promoter 1.5-2.5%; Wetting and dispersing agent 0.5-0.8%; Defoamer 0.2-0.3%; Deionized water balance.

3. The high-barrier water-based coating liquid resistant to high-temperature boiling as described in claim 1 or 2, characterized in that, The mass ratio of modified PVA resin to sulfonated modified EVOH resin in the modified PVA / sulfonated modified EVOH blend resin is 1:(0.8-1.2).

4. A high-barrier water-based coating liquid resistant to high-temperature boiling as described in claim 1 or 2, characterized in that, The crosslinking agent includes fatty aldehydes, blocked isocyanates, and deionized water.

5. The high-barrier water-based coating liquid resistant to high-temperature boiling as described in claim 4, characterized in that, The mass ratio of the fatty aldehyde, the blocked isocyanate and the deionized water is (2-3):1:(5-8).

6. The high-barrier water-based coating liquid resistant to high-temperature boiling as described in claim 5, characterized in that, The mass ratio of the fatty aldehyde, the blocked isocyanate, and the deionized water is 2.5:1:

6.

7. The high-barrier water-based coating liquid resistant to high-temperature boiling as described in claim 4, characterized in that, The crosslinking agent is prepared by the following method: At a speed of 500-800 r / min, the blocked isocyanate and deionized water are mixed and stirred for 10-15 min. Then, while stirring, the fatty aldehyde is added. The temperature is then raised to 40-50℃, and the mixture is stirred at this temperature for 20-30 min. After cooling to room temperature, the mixture is filtered to obtain the crosslinking agent.

8. A high-barrier water-based coating liquid resistant to high-temperature boiling as described in claim 1 or 2, characterized in that, The nano barrier filler is a nano barrier filler that has undergone surface modification treatment with a silane coupling agent.

9. The high-barrier water-based coating liquid resistant to high-temperature boiling as described in claim 8, characterized in that, The surface modification treatment of the silane coupling agent is carried out at a temperature of 60-80℃ for 2-3 hours.

10. A method for preparing the high-barrier water-based coating liquid with high temperature resistance and retort properties as described in claim 1, characterized in that, Includes the following steps: S1. Mix the modified PVA / sulfonated modified EVOH blend resin with deionized water, heat to 80-90℃, stir until completely dissolved, and then cool to 40-50℃ to obtain the resin mother liquor. S2. Add crosslinking agent, adhesion promoter, wetting and dispersing agent and defoamer to the resin mother liquor, and stir at 800-1000 r / min for 20-30 min. S3. Add the nano barrier filler to the product obtained in step S2 and continue stirring for 30-40 minutes while maintaining the rotation speed. Then, homogenize the mixture 1-2 times under a pressure of 20-30 MPa. S4. Adjust the viscosity of the system to 20-50 mPa·s (25℃), and then filter it through a 200-300 mesh filter to obtain a high-barrier water-based coating liquid that can withstand high-temperature cooking.

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