Water-based barrier coating and preparation method thereof

Abstract

The present invention provides a water-based barrier coating and a preparation method thereof, and relates to the technical field of polymer chemistry, the water-based barrier coating comprises the following components: 20-40% of a mixed resin dispersion liquid; 60%-80% of a self-crosslinking polyacrylate emulsion; 1%-2% of talcum powder; 1%-2% of a nanocellulose aqueous dispersion; 0.1%-0.5% of a leveling agent; 0.01%-0.05% of a defoaming agent; 0.01%-0.05% of a bactericide; 3.44% to 5.44% of water; by mixing the mixed resin dispersion liquid, the self-crosslinking polyacrylate emulsion with the hard-core and soft-shell structure and a plurality of auxiliaries, under the synergistic effect of all the components, the prepared barrier coating has excellent heat sealing performance and waterproof and oil-proof performance requirements, and meanwhile, the barrier coating has the advantages of being good in barrier property and good in barrier property. And the product can be kept stable in a boiling water environment, does not generate floating foam, and meets the sanitary safety standard of food contact materials.

Description

Technical Field

[0001] This invention relates to the field of polymer chemistry, specifically to an aqueous barrier coating and its preparation method. Background Technology

[0002] With the continued advancement of global "paper-for-plastic" environmental policies, developing environmentally friendly barrier coating materials that can replace traditional polyolefin films (such as polyethylene (PE) and polypropylene (PP) has become an important research direction in the food packaging field. While traditional PE and PP films possess excellent barrier properties and processing adaptability, they are difficult to degrade and recycle, exhibiting significant environmental shortcomings. Furthermore, the core technologies and related patents for high-performance food contact grade polyolefin materials are largely concentrated in a few international chemical companies, resulting in significant reliance on domestic supply and hindering the independent control of the industrial chain.

[0003] Currently, some existing water-based coating materials on the market, when applied to food packaging, especially in the field of water-coated paper cups such as coffee cups, milk tea cups, disposable paper tea cups, as well as instant noodle containers and fast food boxes, often suffer from insufficient boiling water resistance, easy foaming, high residue levels, or inadequate waterproofing, oil resistance, and heat-sealing performance to meet practical application requirements. Therefore, developing a barrier coating that can simultaneously meet high-performance requirements and food contact safety standards is of great significance. Summary of the Invention

[0004] To address the problems of insufficient boiling water resistance, easy foaming, and inadequate waterproofing, oil resistance, and heat-sealing properties in existing barrier coatings, this invention discloses a water-based barrier coating and its preparation method. By mixing a mixed resin dispersion with a self-crosslinking polyacrylate emulsion having a hard core and soft shell structure, along with various additives, the prepared barrier coating, through the synergistic effect of the components, not only possesses excellent heat-sealing and waterproofing / oil resistance properties, but also remains stable in boiling water environments without producing foam, thus meeting the hygiene and safety standards for food contact materials.

[0005] The technical solution adopted by this invention to solve its technical problem is: A water-based barrier coating comprising the following components: Mixed resin dispersion 20%-40%; Self-crosslinking polyacrylate emulsion 60%-80%; Talc 1%-2%; 1%-2% nanocellulose aqueous dispersion; Leveling agent 0.1%-0.5%; Defoamer 0.01%-0.05%; Fungicide 0.01%-0.05%; Water content: 3.44%-5.44%.

[0006] Optionally, the solid content of the mixed resin dispersion is 15-25%.

[0007] Optionally, the self-crosslinking polyacrylate emulsion is an aqueous acrylate emulsion with a core-shell structure.

[0008] Another object of the present invention is to provide a method for preparing the water-based barrier coating as described above, comprising the following preparation steps: S11: According to the formula, after mixing the self-crosslinking polyacrylate emulsion and the mixed resin dispersion evenly, add talc, nanocellulose aqueous dispersion, leveling agent, defoamer, bactericide and water, and stir thoroughly to obtain the composite coating emulsion. S12: The above composite coating emulsion is applied to the substrate, and after drying and curing, a water-based barrier coating is obtained.

[0009] Optionally, the mixed resin dispersion comprises, by weight, the following components: 15-20 parts of EAA resin; 4-5 parts of EMAA resin; pH adjuster 5-10 parts; 70-75 parts water; 0.2-1 part defoamer.

[0010] Optionally, the acid monomer content of both the EAA resin and the EMAA resin is 10%-15%.

[0011] Optionally, the mixed resin dispersion is prepared according to the following method: According to the formula, EAA resin, EMAA resin, pH adjuster and some water are stirred evenly, heated to 95-98℃ under normal pressure, kept at the temperature for 1-2 hours, and then the remaining water is added; then the temperature is lowered to 25-40℃, defoamer is added, and after stirring evenly, a mixed resin dispersion is obtained, which is then filtered and discharged for later use.

[0012] Optionally, the ratio of the amount of water used to the amount of water used is (60-65):(13-15).

[0013] Optionally, the pH adjuster is selected from at least one of N,N-dimethylethanolamine and ammonia.

[0014] Optionally, the defoamer is a polyether siloxane copolymer emulsion containing fumed silica.

[0015] The present invention has the following beneficial effects: The water-based barrier coating and its preparation method provided by this invention involve preparing a mixed resin dispersion by configuring EAA resin and EMAA resin in a certain proportion, and then compounding it with a self-crosslinking polyacrylate emulsion with a hard core and soft shell structure. Using EO-free reactive emulsifiers and functional additives, the prepared water-based barrier coating, under the synergistic effect of multiple components, not only possesses excellent waterproof and oil-proof properties and heat-sealing strength, effectively replacing traditional non-degradable PE and PP films, but also exhibits superior boiling water resistance, remaining stable in boiling water environments without wrinkling or foaming, meeting the requirements for high-temperature food packaging. Furthermore, the preparation process of this invention can be carried out at low temperature and normal pressure, ensuring safety and reliability, and is suitable for large-scale commercial production. The entire process uses a water-based system with no solvent addition, and third-party testing confirms compliance with food contact grade material standards, achieving ultra-low residue. The raw materials and optimized coating and drying processes used are highly compatible with existing papermaking and coating processing equipment, providing a reliable guarantee for large-scale stable production. Detailed Implementation

[0016] The present invention will now be described in further detail. The embodiments described below are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0017] To address the problems of insufficient boiling water resistance, easy foaming, and inadequate waterproofing, oil resistance, and heat-sealing properties in existing barrier coatings, this invention provides a water-based barrier coating comprising the following components: Mixed resin dispersion 20%-40%; Self-crosslinking polyacrylate emulsion 60%-80%; Talc 1%-2%; 1%-2% nanocellulose aqueous dispersion; Leveling agent 0.1%-0.5%; Defoamer 0.01%-0.05%; Fungicide 0.01%-0.05%; Water content: 3.44%-5.44%.

[0018] Specifically, maintaining a high proportion of self-crosslinking polyacrylate emulsion in the composition preserves the emulsion's inherent waterproof, oil-proof, and heat-sealing properties. Adding a certain proportion of mixed resin dispersion further enhances its moisture-barrier properties. Preferably, the mixed resin dispersion has a solid content of 15-25%, more preferably 18-22%. This range precisely balances storage stability and film-forming efficiency, reducing the introduction of moisture while ensuring fluidity, preventing coating defects caused by excessive moisture evaporation during drying, and improving compatibility with the acrylic emulsion. If the solid content is too low (<15%), the system viscosity will be insufficient, leading to easy stratification and high transportation costs; if the solid content is too high (>25%), dispersion will be difficult and gelation will occur.

[0019] Talc powder can also be replaced by kaolin with an aspect ratio > 25. The present invention preferably has a concentration of 5%-8% for the nanocellulose aqueous dispersion. Nanocellulose forms a three-dimensional network through hydrogen bonds, which not only prevents sedimentation but also penetrates into the polymer pores to enhance the toughness and density of the coating.

[0020] The nanocellulose aqueous dispersion is prepared by the following method: take the nanocellulose stock solution, add a certain amount of water and mix directly to prepare a concentration of 5%-8%, and stir at a high speed of 1500-2000 rpm for 20-30 minutes to obtain the solution.

[0021] The defoamer of the present invention is preferably selected from at least one of polyether defoamers, mineral oil defoamers and vegetable oil defoamers; further, the defoamer is preferably a polyether siloxane copolymer emulsion containing fumed silica.

[0022] The preferred leveling agent of this invention is selected from at least one of polyether-modified polydimethylsiloxane leveling agents and non-silicone acrylate leveling agents.

[0023] The bactericide of the present invention is preferably selected from at least one of hydrogen peroxide and chlorine dioxide.

[0024] Another object of the present invention is to provide a method for preparing the water-based barrier coating as described above, comprising the following preparation steps: S11: According to the formula, the self-crosslinking polyacrylate emulsion and the mixed resin dispersion are physically mixed and stirred at a speed of 200-300 rpm. After the mixture is evenly mixed, talc, nanocellulose aqueous dispersion, leveling agent, defoamer, bactericide and water are added. After stirring thoroughly, the composite coating emulsion is obtained. S12: The above composite coating emulsion is applied to the substrate in two coats, with the coating speed controlled at 20-30 cm / s. Then, it is dried and cured at a temperature of 125℃-135℃ to obtain a water-based barrier coating.

[0025] The synergistic effect of core-shell emulsion and mixed resin dispersion ensures a strong bond between the coating and the paper substrate. A two-coating process is used to achieve layered construction: the first coating fills the pores of the substrate, and the second coating forms a complete barrier layer, effectively avoiding cracking or uneven shrinkage problems that may be caused by a single thick coating. At the same time, the optimized medium-temperature drying process (125℃-135℃) ensures slow evaporation of moisture and full cross-linking reaction, while taking into account energy consumption control and film quality. It prevents high-temperature blistering and substrate damage, and makes the entire process system highly compatible with existing papermaking and coating equipment, providing a reliable guarantee for large-scale stable production.

[0026] Furthermore, the present invention preferably comprises the following components in parts by weight: 15-20 parts of EAA resin; 4-5 parts of EMAA resin; pH adjuster 5-10 parts; 70-75 parts water; 0.2-1 part defoamer.

[0027] The preferred method for preparing the mixed resin dispersion is as follows: According to the formula, EAA resin, EMAA resin, pH adjuster and some water are stirred evenly, heated to 95-98℃ under normal pressure, kept at the temperature for 1-2 hours, and then the remaining water is added; then the temperature is lowered to 25-40℃, defoamer is added, and after stirring evenly, a mixed resin dispersion is obtained, which is then filtered and discharged for later use.

[0028] In this invention, the acidic monomer content of both EAA and EMAA resins is preferably 10%-15%. This range of acidic monomer content ensures that the resin has sufficient carboxyl group density: too low an acidic monomer content results in poor water dispersibility; too high a content reduces the water resistance of the coating. The ionic groups formed after neutralization impart stable dispersibility, while unneutralized carboxyl groups can form hydrogen bonds with the functional groups of acrylate, enhancing the cohesive strength of the composite system.

[0029] In this invention, the preferred ratio of water to the remaining water is (60-65):(13-15). By using a high proportion of water in the initial stage, the resin is ensured to fully swell and be completely neutralized. The subsequent addition of low-temperature water can achieve rapid cooling and precise viscosity adjustment, thereby ensuring complete reaction while avoiding resin thermal degradation and improving production efficiency.

[0030] The preferred method for preparing the self-crosslinked polyacrylate emulsion of the present invention includes the following preparation steps: S21: Preparation of core layer preemulsion: Add 200-400 parts water, 2-4 parts emulsifier, 0.2-0.5 parts chain transfer agent, and 0.1-0.5 parts pH adjuster to a reaction vessel, start stirring, and adjust the stirring speed to 200-300 rpm. While stirring, add 30-50 parts hard monomer, 15-30 parts soft monomer, and 5-10 parts functional monomer. After mixing evenly, the core layer preemulsion is obtained. S22: Preparation of shell preemulsion: Add 150-200 parts water, 4-8 parts emulsifier, 0.3-1.5 parts chain transfer agent, and 0.1-0.5 parts pH adjuster to an emulsification tank, start stirring, and adjust the stirring speed to 1000-1200 rpm. While stirring at high speed, add 100-150 parts hard monomer, 35-60 parts soft monomer, 5-40 parts functional monomer, and 10-30 parts oil-resistant monomer. After stirring at high speed for 30-40 minutes, the shell preemulsion is obtained. S23: Preparation of initiator aqueous solution: prepared from 0.8-2 parts initiator and 8-10 parts water; S24: Preparation of self-crosslinking polyacrylate emulsion: S241: Heat the core layer preemulsion in the reactor to 75-80℃, add the initiator aqueous solution, heat to 82-85℃, and hold for 15-20 minutes; S242: At 82-85℃, add shell pre-emulsion dropwise to the above solution for 2-2.5 hours, and continue to keep warm for 2-3 hours; then cool down to 55-60℃, add 0.2-1 parts of oxidant and 0.2-1 parts of reducing agent, keep warm for 0.5-1 hours, then heat up to 70-75℃, keep warm for 1.5-2 hours, and then cool down. S243: While cooling the above solution, vacuum treatment is performed for no less than 0.5 hours. After cooling to room temperature, 8-20 parts of neutralizing agent are added to adjust the pH to 8-9 to obtain a self-crosslinking polyacrylate emulsion.

[0031] The preferred hard monomer of the present invention is selected from at least one of styrene, acrylonitrile, methyl methacrylate, and isobornyl methacrylate.

[0032] The soft monomer of the present invention is preferably selected from at least one of butyl acrylate, n-butyl methacrylate, and isooctyl acrylate.

[0033] The preferred functional monomers of this invention are selected from at least one of acrylic acid, methacrylic acid, itaconic acid, acrylamide, N-hydroxymethylacrylamide, and N-hydroxyethylacrylamide.

[0034] The preferred oil-resistant monomer of the present invention is selected from at least one of lauryl acrylate, lauryl methacrylate, octadecyl acrylate, and N-(methoxymethyl)acrylamide.

[0035] The preferred emulsifier of this invention is a reactive emulsifier containing unsaturated double bonds that can be copolymerized by free radicals and does not contain EO; allyl ether hydroxypropyl sulfonate is preferably selected as the main emulsifier; furthermore, a small amount of co-emulsifier may also be used in this invention, which is selected from at least one of sodium dodecyl sulfate, sodium dodecyl sulfonate, and sodium dodecylbenzene sulfonate; This reactive emulsifier participates in the copolymerization reaction through unsaturated double bonds in its molecule, and is permanently anchored to the polymer backbone in the form of covalent bonds. This fundamentally eliminates the risk of traditional emulsifiers migrating and precipitating in boiling water, causing foaming. At the same time, its EO-free molecular design avoids the environmental and safety hazards of APEO-type substances, making the product fully compliant with strict food contact material safety standards.

[0036] This invention constructs a high-performance barrier coating through multiple synergistic effects. First, a self-crosslinking polyacrylate emulsion is synthesized using a core-shell polymerization process: the hard core provides a rigid framework and heat resistance, the soft shell ensures film-forming flexibility, and the functional monomers introduce crosslinking sites during the reaction, enabling the emulsion to form a three-dimensional network structure during film formation, significantly improving water resistance and mechanical strength. Second, the carboxyl groups in the EAA / EMAA mixed resin dispersion are neutralized by a pH adjuster under alkaline conditions to form an aqueous dispersion. When its polyolefin segments are blended with the acrylate emulsion, physical interpenetration occurs, and the interfacial bonding is enhanced through the polar interaction between the ester / carboxyl groups and the acrylate. Finally, an EO-free reactive emulsifier is selected to participate in the copolymerization of the self-crosslinking polyacrylate emulsion and bonds with the monomers through double bonds, preventing small molecule migration and fundamentally eliminating foaming. In addition, the long alkyl chains of the oil-resistant monomers are oriented on the coating surface, synergistically blocking oil molecule penetration with the sheet-like filler, while nanocellulose enhances the coating density through hydrogen bonds, ultimately achieving a unified effect of boiling water resistance, high barrier properties, and no foaming.

[0037] The preferred chain transfer agent of the present invention is selected from at least one of n-dodecyl mercaptan, isododecyl mercaptan, and dimethylstyrene dimer (AMSD).

[0038] The preferred oxidant in this invention is selected from at least one of tert-butyl hydrogen peroxide and hydrogen peroxide.

[0039] The reducing agent of the present invention is preferably selected from at least one of sodium bisulfite and ferrous sulfate.

[0040] The neutralizing agent of the present invention is preferably selected from at least one of dimethylethanolamine, triethylamine, and ammonia.

[0041] The preferred pH adjuster is selected from at least one of N,N-dimethylethanolamine and ammonia.

[0042] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, specific embodiments of the present invention will be described in detail below.

[0043] Unless otherwise specified, the bactericide used in the embodiments and comparative examples of this invention is hydrogen peroxide; the leveling agent is the non-silicone acrylate leveling agent BYK-381; the pH adjuster is N,N-dimethylethanolamine; the defoamer is TEGO® Foamex 825 (purchased from Evonik); the initiator is ammonium persulfate; the oxidant is tert-butyl hydrogen peroxide; the reducing agent is sodium bisulfite; and the neutralizing agent is dimethylethanolamine. In this invention, the acidic monomer content of EAA resin and EMAA resin is 10%-15%. In the examples below, ESCOR™ 5100 (purchased from ExxonMobil) and Nucrel™ 925 (purchased from DuPont) are used as EAA resin and EMAA resin, respectively.

[0044] Example 1 This embodiment provides a water-based barrier coating, comprising the following components: 20% mixed resin dispersion; Self-crosslinking polyacrylate emulsion 80%; 1% talc; A 5% concentration of nanocellulose aqueous dispersion was 1%; Leveling agent 0.1%; Defoamer 0.01%; 0.01% bactericide; Water 3.44%.

[0045] The preparation method of the above-mentioned water-based barrier coating includes the following preparation steps: S11: According to the formula, the self-crosslinking polyacrylate emulsion and the mixed resin dispersion are physically mixed and stirred at 200 rpm. After the mixture is uniform, talc, nanocellulose aqueous dispersion, leveling agent, defoamer, bactericide and water are added. After stirring thoroughly, the composite coating emulsion is obtained. S12: The above composite coating emulsion is applied to the substrate in two coats at a speed of 20 cm / s, and then dried and cured at 125°C to obtain a water-based barrier coating.

[0046] Specifically, the mixed resin dispersion is prepared according to the following method: According to the formula, 15 parts of EAA resin, 4 parts of EMAA resin, 5 parts of pH adjuster and 60 parts of water are mixed evenly. Under normal pressure, the temperature is raised to 95°C and kept at that temperature for 1 hour. Then, 13 parts of water are added. The temperature is then lowered to 25°C and 0.2 parts of defoamer are added. After stirring evenly, a mixed resin dispersion is obtained and filtered for later use.

[0047] The method for preparing self-crosslinking polyacrylate emulsion includes the following preparation steps: S21: Preparation of core layer preemulsion: According to the formula in Table 1, add water, emulsifier, chain transfer agent and pH adjuster into the reactor, start stirring and adjust the stirring speed to 200 rpm, add hard monomer, soft monomer and functional monomer while stirring, and after mixing evenly, the core layer preemulsion is obtained. S22: Preparation of shell preemulsion: According to the formula in Table 2, add water, emulsifier, chain transfer agent and pH adjuster into the emulsification tank, start stirring and adjust the stirring speed to 1000 rpm. While stirring at high speed, add hard monomer, soft monomer, functional monomer and oil-resistant monomer according to the formula in Table 2. After stirring at high speed for 30 minutes, the shell preemulsion is obtained. S23: Preparation of initiator aqueous solution: prepared from 0.8 parts initiator and 8 parts water; S24: Preparation of self-crosslinking polyacrylate emulsion: S241: Heat the core layer preemulsion in the reactor to 75°C, add an initiator aqueous solution, heat to 82°C and hold for 15 minutes; S242: At 82℃, add shell pre-emulsion dropwise to the above solution for 2 hours, and continue to keep warm for 2 hours; then cool down to 55℃, add oxidant and reducing agent according to the formula in Table 3, keep warm for 0.5 hours, then heat up to 70℃, keep warm for 1.5 hours, and then cool down. S243: While cooling the above solution, vacuum treatment is performed for 1 hour. After cooling to room temperature, neutralizing agent is added according to the formula in Table 3 to adjust the pH to 8, thus obtaining a self-crosslinking polyacrylate emulsion.

[0048] Example 2 This embodiment provides a water-based barrier coating, comprising the following components: 40% mixed resin dispersion; 60% self-crosslinking polyacrylate emulsion; 2% talc; 8% nanocellulose aqueous dispersion 2%; Leveling agent 0.5%; Defoamer 0.05%; 0.05% bactericide; Water 5.44%.

[0049] The preparation method of the above-mentioned water-based barrier coating includes the following preparation steps: S11: According to the formula, the self-crosslinking polyacrylate emulsion and the mixed resin dispersion are physically mixed and stirred at 300 rpm. After the mixture is evenly mixed, talc, nanocellulose aqueous dispersion, leveling agent, defoamer, bactericide and water are added. After stirring thoroughly, the composite coating emulsion is obtained. S12: The above composite coating emulsion is applied to the substrate in two coats at a speed of 30 cm / s, and then dried and cured at 135°C to obtain a water-based barrier coating.

[0050] Specifically, the mixed resin dispersion is prepared according to the following method: According to the formula, 20 parts of EAA resin, 5 parts of EMAA resin, 10 parts of pH adjuster and 65 parts of water are mixed evenly. Under normal pressure, the temperature is raised to 98°C and kept at that temperature for 2 hours. Then, 15 parts of water are added. The temperature is then lowered to 40°C and 1 part of defoamer is added. After stirring evenly, a mixed resin dispersion is obtained and filtered for later use.

[0051] The method for preparing self-crosslinking polyacrylate emulsion includes the following preparation steps: S21: Preparation of core layer preemulsion: According to the formula in Table 1, add water, emulsifier, chain transfer agent and pH adjuster into the reactor, start stirring and adjust the stirring speed to 300 rpm, add 50 parts hard monomer, 30 parts soft monomer and 10 parts functional monomer while stirring, mix evenly and the core layer preemulsion is obtained. S22: Preparation of shell preemulsion: Add water, emulsifier, chain transfer agent and pH adjuster to emulsification tank according to the formula in Table 2, start stirring and adjust the stirring speed to 1200 rpm. While stirring at high speed, add hard monomer, soft monomer, functional monomer and oil-resistant monomer according to the formula in Table 2. After stirring at high speed for 40 min, the shell preemulsion is obtained. S23: Preparation of initiator aqueous solution: prepared from 2 parts initiator and 10 parts water; S24: Preparation of self-crosslinking polyacrylate emulsion: S241: Heat the core layer preemulsion in the reactor to 80°C, add an initiator aqueous solution, heat to 85°C and hold for 20 minutes; S242: At 85℃, add shell pre-emulsion dropwise to the above solution for 2.5 hours, and continue to keep warm for 3 hours; then cool down to 60℃, add oxidant and reducing agent according to the formula in Table 3, keep warm for 1 hour, then heat up to 75℃, keep warm for 2 hours, and then cool down. S243: While cooling the above solution, vacuum treatment is performed for 1.5 hours. After cooling to room temperature, neutralizing agent is added according to the formula in Table 3 to adjust the pH to 9, thus obtaining a self-crosslinking polyacrylate emulsion.

[0052] Example 3 This embodiment provides a water-based barrier coating, comprising the following components: 30% mixed resin dispersion; 70% self-crosslinking polyacrylate emulsion; Kaolinite with a diameter-to-thickness ratio > 25: 1.5%; A 6% concentration nanocellulose aqueous dispersion of 1.5%; Leveling agent 0.3%; Defoamer 0.03%; 0.04% bactericide; Water 4.44%.

[0053] The preparation method of the above-mentioned water-based barrier coating includes the following preparation steps: S11: According to the formula, the self-crosslinking polyacrylate emulsion and the mixed resin dispersion are physically mixed and stirred at 250 rpm. After the mixture is uniform, talc, nanocellulose aqueous dispersion, leveling agent, defoamer, bactericide and water are added. After stirring thoroughly, the composite coating emulsion is obtained. S12: The above composite coating emulsion is applied to the substrate in two coats at a speed of 25 cm / s, and then dried and cured at 130°C to obtain a water-based barrier coating.

[0054] Specifically, the mixed resin dispersion is prepared according to the following method: According to the formula, 18 parts of EAA resin, 4 parts of EMAA resin, 8 parts of pH adjuster and 62 parts of water are mixed evenly. Under normal pressure, the temperature is raised to 97°C and kept at that temperature for 1.5 hours. Then, 14 parts of water are added. The temperature is then lowered to 30°C and 0.5 parts of defoamer are added. After stirring evenly, a mixed resin dispersion is obtained and filtered for later use.

[0055] The method for preparing self-crosslinking polyacrylate emulsion includes the following preparation steps: S21: Preparation of core layer preemulsion: Add water, emulsifier, chain transfer agent and pH adjuster to the reaction vessel according to the formula in Table 1, start stirring and adjust the stirring speed to 250 rpm, add hard monomer, soft monomer and functional monomer to it while stirring, and after mixing evenly, the core layer preemulsion is obtained. S22: Preparation of shell preemulsion: Add water, emulsifier, chain transfer agent and pH adjuster to emulsification tank according to the formula in Table 2, start stirring and adjust the stirring speed to 1100 rpm. While stirring at high speed, add hard monomer, soft monomer, functional monomer and oil-resistant monomer according to the formula in Table 2. After stirring at high speed for 30 minutes, the shell preemulsion is obtained. S23: Preparation of initiator aqueous solution: prepared from 1 part initiator and 9 parts water; S24: Preparation of self-crosslinking polyacrylate emulsion: S241: Heat the core layer pre-emulsion in the reactor to 77°C, add the initiator aqueous solution, heat to 83°C and hold for 15 minutes; S242: At 83℃, add shell pre-emulsion dropwise to the above solution for 2.5 hours, and continue to keep warm for 3 hours; then cool down to 58℃, add oxidant and reducing agent according to the formula in Table 3, keep warm for 1 hour, then heat up to 72℃, keep warm for 1.5 hours, and then cool down. S243: While cooling the above solution, vacuum treatment is performed for 0.6 hours. After cooling to room temperature, neutralizing agent is added according to the formula in Table 3 to adjust the pH to 8, thus obtaining a self-crosslinking polyacrylate emulsion.

[0056] Example 4 This embodiment provides a water-based barrier coating, comprising the following components: 25% mixed resin dispersion; 75% self-crosslinking polyacrylate emulsion; 2% of kaolinite with a diameter-to-thickness ratio > 25; 2% nanocellulose aqueous dispersion with a concentration of 7%; Leveling agent 0.1%; Defoamer 0.05%; 0.03% bactericide; Water 5.44%.

[0057] The preparation method of the above-mentioned water-based barrier coating includes the following preparation steps: S11: According to the formula, the self-crosslinking polyacrylate emulsion and the mixed resin dispersion are physically mixed and stirred at 200 rpm. After the mixture is uniform, talc, nanocellulose aqueous dispersion, leveling agent, defoamer, bactericide and water are added. After stirring thoroughly, the composite coating emulsion is obtained. S12: The above composite coating emulsion is applied to the substrate in two coats at a speed of 30 cm / s, and then dried and cured at 125°C to obtain a water-based barrier coating.

[0058] Specifically, the mixed resin dispersion is prepared according to the following method: According to the formula, 15 parts of EAA resin, 5 parts of EMAA resin, 8 parts of pH adjuster and 60 parts of water are mixed evenly. Under normal pressure, the temperature is raised to 96°C and kept at that temperature for 2 hours. Then, 13 parts of water are added. The temperature is then lowered to 40°C and 1 part of defoamer is added. After stirring evenly, a mixed resin dispersion is obtained and filtered for later use.

[0059] The method for preparing self-crosslinking polyacrylate emulsion includes the following preparation steps: S21: Preparation of core layer preemulsion: Add water, emulsifier, chain transfer agent and pH adjuster to the reaction vessel according to the formula in Table 1, start stirring and adjust the stirring speed to 200 rpm, add hard monomer, soft monomer and functional monomer to it while stirring, and after mixing evenly, the core layer preemulsion is obtained. S22: Preparation of shell preemulsion: Add water, emulsifier, chain transfer agent, and pH adjuster to the emulsification tank according to the formula in Table 2, start stirring, and adjust the stirring speed to 1000 rpm. While stirring at high speed, add hard monomer, soft monomer, functional monomer, and 10-30 parts of oil-resistant monomer according to the formula in Table 2. After stirring at high speed for 40 minutes, the shell preemulsion is obtained. S23: Preparation of initiator aqueous solution: prepared from 2 parts initiator and 8 parts water; S24: Preparation of self-crosslinking polyacrylate emulsion: S241: Heat the core layer preemulsion in the reactor to 75°C, add an initiator aqueous solution, heat to 82°C and hold for 20 minutes; S242: At 82℃, add shell pre-emulsion dropwise to the above solution for 2 hours, and continue to keep warm for 3 hours; then cool down to 60℃, add oxidant and reducing agent according to the formula in Table 3, keep warm for 1 hour, then heat up to 70℃, keep warm for 2 hours, and then cool down. S243: While cooling the above solution, vacuum treatment is performed for 1 hour. After cooling to room temperature, neutralizing agent is added according to the formula in Table 3 to adjust the pH to 9, thus obtaining a self-crosslinking polyacrylate emulsion.

[0060] Example 5 This embodiment provides a water-based barrier coating, comprising the following components: 35% mixed resin dispersion; 65% self-crosslinking polyacrylate emulsion; Talc 1.5%; A 5% concentration of nanocellulose aqueous dispersion was 1%; Leveling agent 0.1%; Defoamer 0.04%; 0.05% bactericide; Water 3.44%.

[0061] The preparation method of the above-mentioned water-based barrier coating includes the following preparation steps: S11: According to the formula, the self-crosslinking polyacrylate emulsion and the mixed resin dispersion are physically mixed and stirred at 200 rpm. After the mixture is uniform, talc, nanocellulose aqueous dispersion, leveling agent, defoamer, bactericide and water are added. After stirring thoroughly, the composite coating emulsion is obtained. S12: The above composite coating emulsion is applied to the substrate in two coats at a speed of 25 cm / s, and then dried and cured at 125°C to obtain a water-based barrier coating.

[0062] Specifically, the mixed resin dispersion is prepared according to the following method: According to the formula, 20 parts of EAA resin, 5 parts of EMAA resin, 5 parts of pH adjuster and 60 parts of water are mixed evenly. Under normal pressure, the mixture is heated to 98°C and kept at that temperature for 1.5 hours. Then, 15 parts of water are added. The mixture is then cooled to 35°C and 0.2 parts of defoamer are added. After stirring evenly, a mixed resin dispersion is obtained and filtered for later use.

[0063] The method for preparing self-crosslinking polyacrylate emulsion includes the following preparation steps: S21: Preparation of core layer preemulsion: Add water, emulsifier, chain transfer agent and pH adjuster to the reaction vessel according to the formula in Table 1, start stirring and adjust the stirring speed to 300 rpm, add hard monomer, soft monomer and functional monomer to it while stirring, and after mixing evenly, the core layer preemulsion is obtained. S22: Preparation of shell preemulsion: Add water, emulsifier, chain transfer agent and pH adjuster to emulsification tank according to the formula in Table 2, start stirring and adjust the stirring speed to 1200 rpm. While stirring at high speed, add hard monomer, soft monomer, functional monomer and oil-resistant monomer according to the formula in Table 2. After stirring at high speed for 40 min, the shell preemulsion is obtained. S23: Preparation of initiator aqueous solution: prepared from 2 parts initiator and 8 parts water; S24: Preparation of self-crosslinking polyacrylate emulsion: S241: Heat the core layer preemulsion in the reactor to 75°C, add an initiator aqueous solution, heat to 85°C and hold for 15 minutes; S242: At 85℃, add shell pre-emulsion dropwise to the above solution for 2 hours, and continue to keep warm for 2 hours; then cool down to 55℃, add oxidant and reducing agent according to the formula in Table 3, keep warm for 1 hour, then heat up to 70℃, keep warm for 1.5 hours, and then cool down. S243: While cooling the above solution, vacuum treatment is performed for 0.8 hours. After cooling to room temperature, neutralizing agent is added according to the formula in Table 3 to adjust the pH to 8, thus obtaining a self-crosslinking polyacrylate emulsion.

[0064] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that no EAA resin was added.

[0065] Comparative Example 2 The difference between Comparative Example 2 and Example 1 is that no EMAA resin was added.

[0066] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that commercially available HPB 4110 polyacrylate emulsion (purchased from BASF) was used instead of the self-crosslinking polyacrylate emulsion.

[0067] Comparative Example 4 The difference between Comparative Example 4 and Example 1 is that the water-based barrier coating comprises the following components: 70% mixed resin dispersion; 30% self-crosslinking polyacrylate emulsion; 2% of kaolinite with a diameter-to-thickness ratio > 25; 2% nanocellulose aqueous dispersion with a concentration of 7%; Leveling agent 0.1%; Defoamer 0.05%; 0.03% bactericide; Water 5.44%; The remaining steps remain the same.

[0068] Comparative Example 5 The difference between Comparative Example 5 and Example 1 is that ESCOR™ 5100 was replaced with 5980I (purchased from SK Chemicals, with an acid monomer content of 20.5%).

[0069] Comparative Example 6 The difference between Comparative Example 6 and Example 1 is that the mixed resin dispersion was prepared according to the following method: According to the formula, 8 parts of EAA resin, 3 parts of EMAA resin, 5 parts of pH adjuster and 60 parts of water are mixed evenly, heated to 97°C and kept at that temperature for 1 hour, then 13 parts of water are added; then the temperature is lowered to 25°C and 0.2 parts of defoamer are added. After mixing evenly, a mixed resin dispersion is obtained, which is then filtered and discharged for later use. The remaining steps remain the same.

[0070] Comparative Example 7 The difference between Comparative Example 7 and Example 1 is that the mixed resin dispersion was prepared according to the following method: According to the formula, 19.5 parts of EAA resin, 6.5 parts of EMAA resin, 5 parts of pH adjuster and 60 parts of water are mixed evenly, heated to 97°C and kept at that temperature for 1 hour, then 13 parts of water are added; then the temperature is lowered to 25°C and 0.2 parts of defoamer are added. After mixing evenly, a mixed resin dispersion is obtained, which is then filtered and discharged for later use. The remaining steps remain the same.

[0071] Comparative Example 8 The difference between Comparative Example 8 and Example 1 is that the emulsifier allyl ether hydroxypropyl sulfonate in the self-crosslinking polyacrylate emulsion was replaced with ER-30 emulsifier containing EO (purchased from ADEKA).

[0072] Performance Evaluation The relevant properties of the water-based barrier coatings obtained in Examples 1-5 and Comparative Examples 1-8 were tested, and the specific test results are shown in Table 4. As can be seen from the data in the table above, the water-based barrier coating and its preparation method provided in the various embodiments of the present invention, by configuring EAA resin and EMAA resin into a mixed resin dispersion in a certain proportion, compounding it with a self-crosslinking polyacrylate emulsion with a hard core and soft shell structure, and selecting reactive emulsifiers and functional additives that do not contain EO, under the synergistic effect of multiple components, the prepared water-based barrier coating not only has excellent waterproof and oil-proof properties and heat-sealing strength, but also has excellent boiling water resistance, and can remain stable in boiling water environment without wrinkling or foaming.

[0073] The difference between Comparative Example 1 and Example 1 is that no EAA resin was added, resulting in a decrease in the boiling water resistance of the prepared water-based barrier coating.

[0074] The difference between Comparative Example 2 and Example 1 is that no EMAA resin was added, resulting in a decrease in the boiling water resistance of the prepared water-based barrier coating.

[0075] The difference between Comparative Example 3 and Example 1 is that commercially available polyacrylate emulsion HPB4110 (purchased from BASF) was used instead of self-crosslinking polyacrylate emulsion. The water-based barrier coating prepared in this way had slightly reduced oil resistance, while the performance of other indicators remained the same, proving that Example 1 had better oil resistance than similar products on the market.

[0076] The difference between Comparative Example 4 and Example 1 is that the ratio of the mixed resin dispersion to the self-crosslinking polyacrylate emulsion was changed, and the heat-sealing, waterproof and oil-proof properties of the prepared water-based barrier coating all decreased.

[0077] The difference between Comparative Example 5 and Example 1 is that ESCOR™ 5100 was replaced with 5980I (purchased from SK Chemicals, with an acid monomer content of 20.5%), and the water-based barrier coating prepared had reduced water and oil resistance.

[0078] The difference between Comparative Example 6 and Example 1 is that the solid content of the mixed resin dispersion is 13%, which is less than 15%. The prepared water-based barrier coating has poor heat-sealing properties, is not resistant to boiling water, and cannot meet the requirement of heat sealing at 200°C. In practical applications, it cannot meet the normal cup-making process requirements.

[0079] The difference between Comparative Example 7 and Example 1 is that the solid content of the mixed resin dispersion is 26%, which is higher than 25%, resulting in a decrease in the oil resistance and boiling water resistance of the prepared water-based barrier coating.

[0080] The difference between Comparative Example 8 and Example 1 is that the emulsifier allyl ether hydroxypropyl sulfonate in the self-crosslinking polyacrylate emulsion was replaced with ER-30 emulsifier containing EO (purchased from ADEKA). The performance indicators of the prepared water-based barrier coating were basically the same, but foam was generated and it contained EO, which posed a certain safety hazard.

[0081] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A water-based barrier coating, characterized in that, It includes the following components: Mixed resin dispersion 20%-40%; Self-crosslinking polyacrylate emulsion 60%-80%; Talc 1%-2%; 1%-2% nanocellulose aqueous dispersion; Leveling agent 0.1%-0.5%; Defoamer 0.01%-0.05%; Fungicide 0.01%-0.05%; Water content: 3.44%-5.44%.

2. The water-based barrier coating as described in claim 1, characterized in that, The solid content of the mixed resin dispersion is 15-25%.

3. The water-based barrier coating as described in claim 1, characterized in that, The self-crosslinking polyacrylate emulsion is an aqueous acrylate emulsion with a core-shell structure.

4. The method for preparing the water-based barrier coating according to any one of claims 1-3, characterized in that, The preparation steps include the following: S11: According to the formula, after mixing the self-crosslinking polyacrylate emulsion and the mixed resin dispersion evenly, add talc, nanocellulose aqueous dispersion, leveling agent, defoamer, bactericide and water, and stir thoroughly to obtain the composite coating emulsion. S12: The above composite coating emulsion is applied to the substrate, and after drying and curing, a water-based barrier coating is obtained.

5. The method for preparing the water-based barrier coating as described in claim 4, characterized in that, The mixed resin dispersion comprises, by weight, the following components: 15-20 parts of EAA resin; 4-5 parts of EMAA resin; pH adjuster 5-10 parts; 70-75 parts water; 0.2-1 part defoamer.

6. The method for preparing the water-based barrier coating as described in claim 5, characterized in that, The acid monomer content of both EAA resin and EMAA resin is 10%-15%.

7. The method for preparing the water-based barrier coating as described in claim 5, characterized in that, The mixed resin dispersion was prepared according to the following method: According to the formula, EAA resin, EMAA resin, pH adjuster and some water are stirred evenly, heated to 95-98℃ under normal pressure, kept at the temperature for 1-2 hours, and then the remaining water is added; then the temperature is lowered to 25-40℃, defoamer is added, and after stirring evenly, a mixed resin dispersion is obtained, which is then filtered and discharged for later use.

8. The method for preparing the water-based barrier coating as described in claim 7, characterized in that, The ratio of the amount of water used to the amount of water remaining is (60-65):(13-15).

9. The method for preparing the water-based barrier coating as described in claim 5, characterized in that, The pH adjuster is selected from at least one of N,N-dimethylethanolamine and ammonia.

10. The method for preparing the water-based barrier coating as described in claim 5, characterized in that, The defoamer is a polyether siloxane copolymer emulsion containing fumed silica.

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