Low-surface-energy anti-permeation barrier coating for food packaging and preparation method of low-surface-energy anti-permeation barrier coating

Abstract

The invention belongs to the technical field of coatings, and particularly relates to a low-surface-energy anti-permeation barrier coating for food packaging and a preparation method of the low-surface-energy anti-permeation barrier coating. The low-surface-energy anti-permeation barrier coating for food packaging comprises the following components in parts by mass: a core-layer emulsion: 15-35 parts of a core-layer monomer, 0.5-1.5 parts of an emulsifier and 20-40 parts of water; a shell emulsion: 40-70 parts of a shell monomer, 5-10 parts of modified abietic acid, 1-3 parts of an emulsifier and 40-70 parts of water; an initiator aqueous solution: 1.5-2 parts of an initiator and 40-50 parts of water; 30 to 50 parts of silicon-containing cardanol modified nano silicon dioxide dispersion liquid; 30 to 50 parts of water; after the low-surface-energy anti-permeation barrier coating for food packaging provided by the invention is used for paper pulp tableware, the oil-proof grade of the paper pulp tableware reaches 12 grade, and the paper pulp tableware can resist water at 100 DEG C and oil at 120 DEG C and has good adhesion resistance.

Description

Technical Field

[0001] This invention belongs to the field of coating technology, specifically relating to a low surface energy impermeable barrier coating for food packaging and its preparation method. Background Technology

[0002] Pulp molding is a type of packaging product made from biomass-converted pulp. Due to its advantages such as wide availability of raw materials, low cost, biodegradability, and recyclability, it is considered to be the most promising green and sustainable packaging material. It is widely used in the food packaging industry, covering disposable tableware, fresh food trays, cup lids, cup holders, etc.

[0003] However, due to the porous structure and hydrophilic properties of the pulp fibers, it cannot meet the requirements for resisting oil and water penetration and must be treated with barrier methods to meet the functional requirements of food packaging.

[0004] Common barrier treatment methods include (1) Petroleum-based plastic coating: Petroleum-based polymer particles are directly laminated onto the surface of ordinary pulp molding after being melted at high temperature. However, when food (especially food with high oil content, high temperature or long contact time) comes into long-term contact with these plastic-containing coatings, there is a risk that plastic components will migrate into the food, and they cannot be degraded under natural conditions; (2) Surface coating barrier coating: A layer of coating is applied to the surface of ordinary pulp molding to form a barrier layer to achieve the purpose of waterproofing and oil prevention. This method can give pulp molding waterproof and oil prevention properties without affecting its recycling, and has good application prospects. However, traditional coatings are usually fluorinated coatings, which have excellent waterproof and oil prevention effects, but have safety hazards and do not meet environmental protection requirements.

[0005] Existing fluorine-free coatings used in food packaging exhibit good waterproof and oil-repellent properties; however, their high-temperature resistance needs improvement. For example, Chinese patent CN 121161649 A discloses a biomass-based biodegradable waterproof and oil-repellent coating, its preparation method, and its application. This biomass-based biodegradable waterproof and oil-repellent coating consists of a waterproof coating and an oil-repellent coating. The waterproof coating comprises stearic acid emulsion, nanocellulose, a waterproofing agent, inorganic fillers, dispersants, defoamers, film-forming aids, pH adjusters, and water. The oil-repellent coating comprises natural resin, plant-based fatty acid esters, chitosan, nanocellulose, a waterproofing agent, an oil-repellent agent, inorganic fillers, dispersants, defoamers, preservatives, pH adjusters, and water. This technical solution can only withstand 95°C hot water for 30 minutes and 95°C hot oil for 30 minutes.

[0006] Chinese patent CN 121135980 A discloses a plastic-free, low-shrinkage, waterproof, and oil-resistant modified acrylate emulsion and its preparation method. By mass, it comprises the following raw materials: 3-12 parts of nano-dispersion, 13-42 parts of hard monomer, 30-55 parts of soft monomer, 3-10 parts of silicon-containing monomer, 4-12 parts of multifunctional monomer, 0.1-3 parts of initiator, and 2-13 parts of reactive emulsifier. The modified acrylate emulsion is formed by soap-free emulsion polymerization of the nano-dispersion, hard monomer, soft monomer, silicon-containing monomer, multifunctional monomer, initiator, and reactive emulsifier. This technical solution can only withstand hot oil for 30 minutes. Summary of the Invention

[0007] The purpose of this invention is to provide a low surface energy anti-permeability barrier coating for food packaging and its preparation method. The low surface energy anti-permeability barrier coating for food packaging provided by this invention uses a specific shell monomer, modified rosin acid and silicon-containing cashew phenol modified nano-silica dispersion to work together. When applied to pulp tableware, it can make the pulp tableware achieve an oil resistance level of 12, and can withstand 100°C water for 12 hours without seepage or penetration, and withstand 120°C oil for 2 hours without seepage or penetration, and also has good anti-stick properties.

[0008] To achieve the above objectives, the present invention provides the following technical solution: The first aspect of this invention provides a low surface energy impermeability barrier coating for food packaging, comprising the following components in parts by weight: Core layer emulsion: 15-35 parts core layer monomer, 0.5-1.5 parts emulsifier and 20-40 parts water; Shell emulsion: 40-70 parts shell monomer, 5-10 parts modified rosin acid, 1-3 parts emulsifier and 40-70 parts water; Initiator aqueous solution: 1.5-2 parts initiator and 40-50 parts water; Silicon-containing cashew phenol modified nano-silica dispersion: 30-50 parts; Water: 30-50 parts; The modifiers for the modified rosin acid include modifier A and modifier B; modifier A is a monomer containing double bonds and epoxy groups; and modifier B is a silane containing epoxy groups.

[0009] In some preferred embodiments, the core layer monomer is a mixture of butyl acrylate and methyl methacrylate in a mass ratio of 1-2:1-2.

[0010] In some preferred embodiments, the shell monomer is a mixture of tert-carboglyceride methacrylate and butyl acrylate in a mass ratio of 1-2:1-2.

[0011] In some preferred embodiments, the emulsifier is selected from one or more of alkylphenol polyoxyethylene ether, sodium dodecyl sulfonate, and Tween.

[0012] In some preferred embodiments, the initiator is selected from one or more of ammonium persulfate, sodium persulfate, and potassium persulfate.

[0013] In some preferred embodiments, the modifier A is selected from one or more of glycidyl acrylate and allyl glycidyl ether.

[0014] In some preferred embodiments, the modifier B is selected from one or more of 3-glycidyl etheroxypropyltrimethoxysilane, 3-glycidyl etheroxypropyltriethoxysilane, and 3-(2,3-epoxypropoxypropyl)methyldiethoxysilane.

[0015] In some preferred embodiments, the modified rosin acid is prepared by adding rosin acid, modifier A, 40-50% by mass of triethylamine, hydroquinone and acetone into a reaction vessel equipped with a condenser and mixing them. The mixture is then heated to react. After the heating reaction is completed, the remaining triethylamine and modifier B are added, and the heating reaction continues. After the second heating reaction is completed, the acetone is removed to obtain the final product.

[0016] In some preferred embodiments, the molar ratio of rosin acid, modifier A and modifier B is 1:0.55-0.6:0.55-0.6.

[0017] In some preferred embodiments, the amount of triethylamine added is 0.5-1.5% of the total mass of rosin acid, modifier A, and modifier B.

[0018] In some preferred embodiments, the amount of hydroquinone added is 0.1-1% of the total mass of rosin acid and modifier A.

[0019] In some preferred embodiments, the amount of acetone added is 45-55% of the total mass of rosin acid and modifier A.

[0020] In some preferred embodiments, the modified rosin acid is prepared by: adding rosin acid, modifier A, 40-50% by mass of triethylamine, hydroquinone, and acetone into a reaction vessel equipped with a condenser and mixing them; first heating the mixture at 70-75°C for 2-3 hours; after the heating reaction is completed, adding the remaining triethylamine and modifier B; continuing to heat the mixture at 70-75°C for 2-3 hours; and finally removing the acetone after the heating reaction is completed to obtain the modified rosin acid.

[0021] In some preferred embodiments, the preparation method of the silicon-containing cashew phenol modified nano silica dispersion is as follows: cashew phenol glycidyl ether and aminosilane coupling agent are mixed, and the mixture is heated and reacted under nitrogen protection to obtain silicon-containing cashew phenol. Nano-silica, silicon-containing cashew phenol, and ethanol were mixed and stirred to obtain a silicon-containing cashew phenol-modified nano-silica dispersion.

[0022] In some preferred embodiments, the aminosilane coupling agent is selected from one or more of 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropylmethyldiethoxysilane, N-aminoethyl-3-aminopropyltrimethoxysilane, N-aminoethyl-3-aminopropyltriethoxysilane, and N-aminoethyl-3-aminopropylmethyldiethoxysilane.

[0023] In some preferred embodiments, the molar ratio of cashew phenol glycidyl ether to aminosilane coupling agent is 1:1.1-1.2.

[0024] In some preferred embodiments, the nano-silica comprises nano-silica with a particle size of 30-100 nm and nano-silica with a particle size of 300-600 nm in a mass ratio of 6-7:3-4.

[0025] In some preferred embodiments, the ratio of the nano-silica, silicon-containing cashew phenol, and ethanol is 2-5g:1mL:20-50mL.

[0026] In some preferred embodiments, the preparation method of the silicon-containing cashew phenol modified nano silica dispersion is as follows: cashew phenol glycidyl ether and aminosilane coupling agent are mixed, and the mixture is heated to 70-80℃ and reacted for 1-2 hours under nitrogen protection to obtain silicon-containing cashew phenol. Nano-silica, silicon-containing cashew phenol, and ethanol are mixed and stirred at 20-30℃ for 5-8 hours to obtain a silicon-containing cashew phenol modified nano-silica dispersion.

[0027] A second aspect of this invention provides a method for preparing a low surface energy impermeability barrier coating for food packaging, comprising the following steps: S1. Mix the core layer monomer, emulsifier, and water, and homogenize and emulsify to obtain a core layer emulsion; mix the shell layer monomer, modified rosin acid, emulsifier, and water, and homogenize and emulsify to obtain a shell layer monomer; mix the initiator and water to obtain an initiator solution; S2. Mix 1 / 3 of the mass of the core emulsion, 1 / 4 of the mass of the initiator solution, and 80-90% of the mass of water, heat and react. After the reaction is complete, add the remaining core emulsion and initiator solution dropwise. After the addition is complete, add the shell emulsion dropwise. After the addition is complete, heat and react to obtain a core-shell emulsion. S3. Mix the core-shell emulsion, the silicon-containing cashew phenol modified nano-silica dispersion, and the remaining water, and stir evenly to obtain a low surface energy impermeability barrier coating for food packaging.

[0028] In some preferred embodiments, step S2 specifically involves: mixing 1 / 3 of the mass of the core emulsion, 1 / 4 of the mass of the initiator solution, and 80-90% of the mass of water, heating the mixture at 70-90°C for 20-40 minutes, adding the remaining core emulsion and initiator solution dropwise over a period of 1.5-2 hours, and adding 1 / 8 of the mass of the initiator solution every 0.5 hours during the dropwise addition. After the dropwise addition is complete, adding the shell emulsion and the remaining initiator solution dropwise over a period of 1.5-2 hours, and heating the mixture at 70-90°C for 1-3 hours to obtain a core-shell emulsion.

[0029] Compared with the prior art, the advantages and beneficial effects of the present invention are as follows: In existing technologies, silanes containing double bonds are typically used to introduce the hydrophobic long chains of silanes into acrylate emulsions, or long-chain alkyl methacrylate monomers are used to improve the hydrophobic and oleophobic properties of barrier coatings. However, the inventors found during the experiment that the effects of both methods were unsatisfactory. This invention creatively prepares a dispersion of modified rosin acid and silicon-containing cashew phenol modified nano-silica. This dispersion, together with the shell monomers (tert-carbon glycerol methacrylate and butyl acrylate), enables the prepared pulp tableware to achieve an oil resistance rating of 12, which can withstand water at 100°C and oil at 120°C, and also has good anti-stick properties.

[0030] Among them, modified rosin acid is obtained by ring-opening reaction of the carboxyl group of rosin acid with the monomer containing double bond and epoxy group and the epoxy group of silane containing epoxy group. Double bond and siloxane are introduced into the rosin acid molecule. Rosin acid has a hydrophobic hydrogenated phenanthrene ring structure. Its combined effect with the hydrophobicity of siloxane makes the barrier coating have excellent hydrophobicity. The silicon-containing cashew phenol-modified nano-silica dispersion is obtained by first performing a ring-opening reaction between the epoxy group of cashew phenol glycidyl ether and the amino group of an aminosilane coupling agent to obtain silicon-containing cashew phenol, and then modifying the nano-silica. The silicon-containing cashew phenol-modified nano-silica fills the shell pores. On the one hand, the long carbon side chain of cashew phenol and the hydrophobicity of siloxane further reduce the surface energy of the coating and block the penetration of hot water or hot oil. On the other hand, the use of nano-silica with different particle sizes improves the rough structure of the coating, further blocking the penetration of hot water and hot oil. Attached Figure Description

[0031] Figure 1 The images show the physical results of the high-temperature oil resistance of Examples 3, 1, 2, 3 and 6. Detailed Implementation

[0032] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] Unless otherwise specified, the raw materials, reagents or apparatus used in the following examples and comparative examples are available from conventional commercial sources or can be obtained by existing known methods.

[0034] The preparation method of modified rosin acid A in Example 1 is as follows: Rosin acid (CAS: 514-10-3), modifier A, 50% by mass of triethylamine, hydroquinone, and acetone were added to a reaction vessel equipped with a condenser and mixed. The mixture was first heated at 75°C for 2 hours. After the heating reaction was completed, the remaining triethylamine and modifier B were added, and the mixture was heated at 75°C for another 3 hours. After the heating reaction was completed, the acetone was removed to obtain the final product.

[0035] Modifier A is allyl glycidyl ether (CAS: 106-92-3); Modifier B is 3-glycidyl etheroxypropyltrimethoxysilane (CAS: 2530-83-8).

[0036] The molar ratio of rosin acid, modifier A, and modifier B is 1:0.55:0.55.

[0037] The amount of triethylamine added is 1% of the total mass of rosin acid, modifier A, and modifier B.

[0038] The amount of hydroquinone added is 0.2% of the total mass of rosin acid and modifier A.

[0039] The amount of acetone added is 50% of the total mass of rosin acid and modifier A.

[0040] The preparation method of modified rosin acid B in Example 2 is as follows: Rosin acid, modifier A, 50% by mass of triethylamine, hydroquinone, and acetone are added to a reaction vessel equipped with a condenser and mixed. The mixture is heated at 75°C for 2 hours. After the reaction is completed, the acetone is removed to obtain the final product.

[0041] Modifier A is allyl glycidyl ether.

[0042] The molar ratio of rosin acid to modifier A is 1:1.1.

[0043] The amount of triethylamine added is 0.5% of the total mass of rosin acid and modifier A.

[0044] The amount of hydroquinone added is 0.2% of the total mass of rosin acid and modifier A.

[0045] The amount of acetone added is 50% of the total mass of rosin acid and modifier A.

[0046] The preparation method of silicon-containing cashew phenol modified nano silica dispersion A in Example 3 is as follows: Cashew phenol glycidyl ether (CAS: 171263-25-5) and aminosilane coupling agent were mixed and reacted at 75°C for 2 hours under nitrogen protection to obtain silicon-containing cashew phenol. Nano-silica, silicon-containing cashew phenol, and ethanol were mixed and stirred at 25°C for 6 hours to obtain a silicon-containing cashew phenol-modified nano-silica dispersion.

[0047] The aminosilane coupling agent is 3-aminopropyltrimethoxysilane (CAS: 13822-56-5); the molar ratio of cashew phenol glycidyl ether to the aminosilane coupling agent is 1:1.1.

[0048] The nano-silica comprises nano-silica with a particle size of 50 nm and nano-silica with a particle size of 500 nm in a mass ratio of 7:3.

[0049] The ratio of nano-silica, silicon-containing cashew phenol, and ethanol is 3g:1mL:30mL.

[0050] The preparation method of silicon-containing cashew nut shell phenol modified nano-silica dispersion B in Example 4 is as follows: Cashew phenol glycidyl ether and aminosilane coupling agent were mixed and reacted at 75°C for 2 hours under nitrogen protection to obtain silicon-containing cashew phenol. Nano-silica, silicon-containing cashew phenol, and ethanol were mixed and stirred at 25°C for 6 hours to obtain a silicon-containing cashew phenol-modified nano-silica dispersion.

[0051] The aminosilane coupling agent is 3-aminopropyltrimethoxysilane; the molar ratio of cashew phenol glycidyl ether to the aminosilane coupling agent is 1:1.1.

[0052] The nano-silica is nano-silica with a particle size of 50 nm.

[0053] The ratio of nano-silica, silicon-containing cashew phenol, and ethanol is 3g:1mL:30mL.

[0054] The preparation method of the silane coupling agent modified nano-silica dispersion in Example 5 is as follows: A mixture of nano-silica, aminosilane coupling agent and ethanol was stirred at 25°C for 6 hours to obtain a dispersion of silicon-containing cashew phenol-modified nano-silica.

[0055] The aminosilane coupling agent is 3-aminopropyltrimethoxysilane; The nano-silica comprises nano-silica with a particle size of 50 nm and nano-silica with a particle size of 500 nm in a mass ratio of 7:3.

[0056] The ratio of nano-silica, aminosilane coupling agent and ethanol is 3g:1mL:30mL.

[0057] Example 1: A low surface energy impermeability barrier coating for food packaging, comprising the following components in parts by weight: Core emulsion: 15 parts core monomer, 0.5 parts emulsifier and 20 parts water; Shell emulsion: 40 parts shell monomer, 5 parts modified rosin acid A, 1.6 parts emulsifier and 45 parts water; Initiator aqueous solution: 2 parts initiator and 40 parts water; Silicon-containing cashew phenol modified nano-silica dispersion A: 30 parts; Water: 30 portions.

[0058] The core layer monomer is a mixture of butyl acrylate and methyl methacrylate in a mass ratio of 1.5:1.

[0059] The shell monomer is a mixture of tertiary glycerol methacrylate (sourced from Foshan Jinjia New Material Technology Co., Ltd.) and butyl acrylate in a mass ratio of 1:1.5.

[0060] The emulsifier is sodium dodecyl sulfonate.

[0061] The initiator is ammonium persulfate.

[0062] The preparation method of the above-mentioned low surface energy impermeability barrier coating for food packaging includes the following steps: S1. Mix the core layer monomer, emulsifier, and water, and homogenize and emulsify to obtain a core layer emulsion; mix the shell layer monomer, modified rosin acid, emulsifier, and water, and homogenize and emulsify to obtain a shell layer monomer; mix the initiator and water to obtain an initiator solution; S2. Mix 1 / 3 of the mass of the core emulsion, 1 / 4 of the mass of the initiator solution, and 90% of the mass of water, and heat at 80°C for 30 min. After the reaction is complete, add the remaining core emulsion and initiator solution dropwise over a period of 2 h. During the dropwise addition process, add 1 / 8 of the initiator solution every 0.5 h. After the dropwise addition is complete, add the shell emulsion and the remaining initiator solution dropwise over a period of 2 h. After the dropwise addition is complete, heat at 80°C for 2 h to obtain a core-shell emulsion. S3. Mix the core-shell emulsion, the silicon-containing cashew phenol modified nano-silica dispersion, and the remaining water, and stir evenly to obtain a low surface energy impermeability barrier coating for food packaging.

[0063] Example 2 The only difference between Example 2 and Example 1 is that the low surface energy impermeability barrier coating for food packaging comprises the following components in parts by weight: Core emulsion: 25 parts core monomer, 0.8 parts emulsifier, and 30 parts water; Shell emulsion: 55 parts shell monomer, 8 parts modified rosin acid A, 2 parts emulsifier and 60 parts water; Initiator aqueous solution: 2 parts initiator and 40 parts water; Silicon-containing cashew phenol modified nano-silica dispersion A: 40 parts; Water: 40 parts; all other contents are the same as in Example 1.

[0064] Example 3 The only difference between Example 3 and Example 1 is that the low surface energy impermeability barrier coating for food packaging comprises the following components in parts by weight: Core emulsion: 35 parts core monomer, 1.2 parts emulsifier and 40 parts water; Shell emulsion: 65 parts shell monomer, 10 parts modified rosin acid A, 2.5 parts emulsifier and 70 parts water; Initiator aqueous solution: 2 parts initiator and 40 parts water; Silicon-containing cashew phenol modified nano-silica dispersion A: 50 parts; Water: 50 parts; all other contents are the same as in Example 1.

[0065] Comparative Example 1 The only difference between Comparative Example 1 and Example 1 is that modified rosin acid A is replaced with an equal amount of modified rosin acid B; all other contents are the same as in Example 1.

[0066] Comparative Example 2 The only difference between Comparative Example 2 and Example 1 is that modified rosin acid A is replaced with an equal mass fraction of γ-methacryloyloxypropyltrimethoxysilane; all other contents are the same as in Example 1.

[0067] Comparative Example 3 The only difference between Comparative Example 3 and Example 1 is that the silicon-containing cashew phenol modified nano silica dispersion A is not added; all other contents are the same as Example 1.

[0068] Comparative Example 4 The only difference between Comparative Example 4 and Example 1 is that the silicon-containing cashew phenol modified nano silica dispersion A is replaced with an equal mass fraction of silicon-containing cashew phenol modified nano silica dispersion B; all other contents are the same as in Example 1.

[0069] Comparative Example 5 The only difference between Comparative Example 5 and Example 1 is that the silicon-containing cashew phenol modified nano silica dispersion A is replaced with an equal mass fraction of silane coupling agent modified nano silica dispersion; all other contents are the same as in Example 1.

[0070] Comparative Example 6 The only difference between Comparative Example 6 and Example 1 is that the shell monomer is a mixture of octadecyl methacrylate and butyl acrylate in a mass ratio of 1:1.5; all other contents are the same as in Example 1.

[0071] Performance testing: The low surface energy impermeability barrier coatings for food packaging described in Examples 1-3 and Comparative Examples 1-6 were applied to the inner surface of pulp tableware at a coating weight of 5 g / m². 2 The wet film thickness was 10 μm, and after curing at 120℃ for 10 min, the following performance tests were performed: 1. Oil resistance rating: Tested using the Kit method.

[0072] 2. High-temperature water resistance: Add 100℃ hot water to each, let stand at room temperature for 24 hours, and observe whether seepage points or penetrations appear on the back of the tableware.

[0073] 3. High-temperature oil resistance: Add hot oil at 120℃ and let stand at room temperature for 2 hours to observe whether seepage points or penetrations appear on the back of the tableware.

[0074] 4. Anti-sticking property: Stack 50 layers of pulp tableware, press them down with a 5KG weight, put them in a 60℃ oven for 48 hours and then cool them down. Observe whether they stick together.

[0075] The results are shown in Table 1 below. Physical images of the high-temperature oil resistance results for Examples 3, 1, 2, 3, and 6 are shown below. Figure 1 As shown.

[0076] Table 1 Testing items Kit oil resistance rating High temperature water resistant High temperature oil resistance Anti-sticking Example 1 12 No seepage points, no osmosis No seepage points, no osmosis No adhesion Example 2 12 No seepage points, no osmosis No seepage points, no osmosis No adhesion Example 3 12 No seepage points, no osmosis No seepage points, no osmosis No adhesion Comparative Example 1 9 There is a seepage point, but no osmosis. There is a seepage point, but no osmosis. Adhesion Comparative Example 2 8 There is a seepage point, but no osmosis. Penetration Adhesion Comparative Example 3 6 Penetration Penetration No adhesion Comparative Example 4 10 There is a seepage point, but no osmosis. Penetration No adhesion Comparative Example 5 8 There is a seepage point, but no osmosis. Penetration No adhesion Comparative Example 6 10 There is a seepage point, but no osmosis. Penetration Adhesion As can be seen from Table 1, the pulp tableware prepared using the low surface energy anti-permeability barrier coatings for food packaging in Examples 1-3 has an oil resistance level of 12. It can withstand water at 100°C for 12 hours without seepage or penetration, and can withstand oil at 120°C for 2 hours without seepage or penetration. It also has good anti-stick properties. The modified rosin acid in Comparative Example 1 was modified only with modifier A, resulting in a decrease in oil resistance, a penetration point in water at 100°C for 12 hours, and penetration into oil at 120°C for 2 hours, as well as adhesion. Comparative Example 2: When modified rosin acid was replaced with γ-methacryloyloxypropyltrimethoxysilane, the oil resistance level decreased, water penetration occurred at 100°C for 12 hours, oil penetration occurred at 120°C for 2 hours, and adhesion occurred. In Comparative Example 3, without the addition of silicon-containing cashew phenol modified nano-silica dispersion, the oil resistance level decreased, and water at 100℃ penetrated after 12 hours, while oil at 120℃ penetrated after 2 hours. In Comparative Example 4, the silicon-containing cashew phenol modified nano-silica dispersion contained only nano-silica of a single particle size, resulting in a decrease in oil resistance. It showed a penetration point in water at 100°C for 12 hours and penetration in oil at 120°C for 2 hours. Comparative Example 5: When the silicon-containing cashew phenol modified nano silica dispersion was replaced with a silane coupling agent modified nano silica dispersion, the oil resistance level decreased, and water at 100°C showed a penetration point after 12 hours, while oil at 120°C showed penetration after 2 hours. In Comparative Example 6, replacing tert-carbon glycerol methacrylate with octadecyl methacrylate in the shell monomer resulted in a decrease in oil resistance; water penetration occurred at 100°C for 12 hours, and oil penetration occurred at 120°C for 2 hours, leading to adhesion.

[0077] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A low surface energy impermeability barrier coating for food packaging, characterized in that, The components include the following parts by mass: Core layer emulsion: 15-35 parts core layer monomer, 0.5-1.5 parts emulsifier and 20-40 parts water; Shell emulsion: 40-70 parts shell monomer, 5-10 parts modified rosin acid, 1-3 parts emulsifier and 40-70 parts water; Initiator aqueous solution: 1.5-2 parts initiator and 40-50 parts water; Silicon-containing cashew phenol modified nano-silica dispersion: 30-50 parts; Water: 30-50 parts; The modifiers for the modified rosin acid include modifier A and modifier B; modifier A is a monomer containing double bonds and epoxy groups; and modifier B is a silane containing epoxy groups.

2. The low surface energy impermeability barrier coating for food packaging according to claim 1, characterized in that, The shell monomer is a mixture of tertiary glycerol methacrylate and butyl acrylate in a mass ratio of 1-2:1-2.

3. The low surface energy impermeability barrier coating for food packaging according to claim 2, characterized in that, Modifier A is selected from one or more of glycidyl acrylate and allyl glycidyl ether; modifier B is selected from one or more of 3-glycidyl etheroxypropyltrimethoxysilane, 3-glycidyl etheroxypropyltriethoxysilane and 3-(2,3-epoxypropoxypropyl)methyldiethoxysilane.

4. The low surface energy impermeability barrier coating for food packaging according to any one of claims 1-3, characterized in that, The modified rosin acid is prepared by adding rosin acid, modifier A, 40-50% by mass of triethylamine, hydroquinone and acetone into a reaction vessel equipped with a condenser and mixing them. The mixture is heated to react. After the heating reaction is completed, the remaining triethylamine and modifier B are added and the heating reaction is continued. After the heating reaction is completed, the acetone is removed to obtain the final product.

5. The low surface energy impermeability barrier coating for food packaging according to claim 4, characterized in that, The molar ratio of rosin acid, modifier A and modifier B is 1:0.55-0.6:0.55-0.

6.

6. The low surface energy impermeability barrier coating for food packaging according to claim 5, characterized in that, The preparation method of the silicon-containing cashew phenol modified nano silica dispersion is as follows: cashew phenol glycidyl ether and aminosilane coupling agent are mixed and reacted under nitrogen protection to obtain silicon-containing cashew phenol. Nano-silica, silicon-containing cashew phenol, and ethanol were mixed and stirred to obtain a silicon-containing cashew phenol-modified nano-silica dispersion.

7. The low surface energy impermeability barrier coating for food packaging according to claim 6, characterized in that, The aminosilane coupling agent is selected from one or more of 3-aminopropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropylmethyldiethoxysilane, N-aminoethyl-3-aminopropyltrimethoxysilane, N-aminoethyl-3-aminopropyltriethoxysilane, and N-aminoethyl-3-aminopropylmethyldiethoxysilane.

8. The low surface energy impermeability barrier coating for food packaging according to claim 7, characterized in that, The molar ratio of cashew phenol glycidyl ether to aminosilane coupling agent is 1:1.1-1.

2.

9. The low surface energy impermeability barrier coating for food packaging according to claim 8, characterized in that, The nano-silica comprises nano-silica with a particle size of 30-100nm and nano-silica with a particle size of 300-600nm, in a mass ratio of 6-7:3-4.

10. A method for preparing a low surface energy impermeability barrier coating for food packaging according to any one of claims 1-9, characterized in that, Includes the following steps: S1. Mix the core layer monomer, emulsifier, and water, and homogenize and emulsify to obtain a core layer emulsion; mix the shell layer monomer, modified rosin acid, emulsifier, and water, and homogenize and emulsify to obtain a shell layer monomer; mix the initiator and water to obtain an initiator solution; S2. Mix 1 / 3 of the mass of the core emulsion, 1 / 4 of the mass of the initiator solution, and 80-90% of the mass of water, heat and react. After the reaction is complete, add the remaining core emulsion and initiator solution dropwise. After the addition is complete, add the shell emulsion dropwise. After the addition is complete, heat and react to obtain a core-shell emulsion. S3. Mix the core-shell emulsion, the silicon-containing cashew phenol modified nano-silica dispersion, and the remaining water, and stir evenly to obtain a low surface energy impermeability barrier coating for food packaging.

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