Water-proof and oil-proof coating for heat-sealable paper-based food packaging and preparation method of water-proof and oil-proof coating

Abstract

The invention discloses a waterproof and oilproof coating for heat-sealable paper-based food packaging and a preparation method thereof, the waterproof and oilproof coating is characterized by comprising a polymer A and a polymer B. The polymer A is used for pre-coating a coating, the polymer A and the polymer B are compounded into a mixture through mechanical stirring, and the mixture is used for surface coating of the coating; the polymer A is prepared by polymerizing and modifying any one or more monomers of vinyl acetate, vinyl pyrrolidone, docosyl vinyl ether and (methyl) allyl glycidyl ether; the polymer B comprises a core layer and a shell layer, and each of the core layer and the shell layer comprises a hydrophilic monomer and an acrylate monomer. The pre-coating polymer A prepared by hydrolyzing vinyl acetate as a main material has very strong film-forming property and can achieve better closed film-forming and leveling effects on a paper-based material, a waterproof and oil-proof layer coated on the upper surface and the rear surface can be better retained on the surface, and the combination of the two layers can achieve very good water vapor resistance, oil resistance, water resistance and the like.

Description

Technical Field

[0001] The present invention relates to a waterproof and oil-proof coating, specifically a waterproof and oil-proof coating for heat-sealable paper-based food packaging and a preparation method thereof. Background Art

[0002] Although the most common polyethylene (PE) coated paper in the market has mature market applications, since a layer of PE coating is used to block leakage, the recyclability of the entire paper is greatly reduced. The paper coated with PE film cannot be degraded either. Most of the papers can only be incinerated or landfilled after being discarded, which has an impact on the environment and causes waste of resources. Therefore, a waterproof and oil-proof coating for heat-sealable paper-based food packaging and a preparation method thereof are proposed. Summary of the Invention

[0003] The purpose of the present invention is to propose a waterproof and oil-proof coating for heat-sealable paper-based food packaging and a preparation method thereof to solve the above problems.

[0004] To achieve the above object, the present invention provides the following technical solution: A waterproof and oil-proof coating for heat-sealable paper-based food packaging, which is characterized by comprising polymer A and polymer B. Polymer A is used for pre-coating the coating, and polymer A and polymer B are compounded into a mixture by mechanical stirring, and the mixture is used for top-coating the coating surface; the polymer A is prepared by polymerization modification of any one or more monomers of vinyl acetate, vinyl pyrrolidone, docosyl vinyl ether, (meth) allyl glycidyl ether; the polymer B comprises a core layer and a shell layer, and both the core layer and the shell layer comprise hydrophilic monomers and acrylate monomers.

[0005] Further preferably, the mass ratio of vinyl acetate, vinyl pyrrolidone, docosyl vinyl ether, (meth) allyl glycidyl ether in the polymer A is 100:5-10:10-20:0.5-5.

[0006] Further preferably, the molecular weight of the polymer A is controlled at 50,000-100,000, and the alcoholysis degree is controlled above 99%.

[0007] Further preferably, the hydrophilic monomer in the core layer and the shell layer of the polymer B is one of sodium acrylamidodimethylsulfonate, sodium vinylsulfonate, sodium methacrylamidoisopropylsulfonate, and is used in combination with allyl polyether sulfate.

[0008] More preferably, the acrylate monomers in the polymer B core layer are multiple ones such as methyl (meth)acrylate, isooctyl acrylate, dicyclopentenyl oxyethyl acrylate, 3,3,5-trimethylcyclohexyl acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, etc., and the glass transition temperature of the core layer is controlled at 30-50°C; the acrylate monomers in the shell layer are multiple ones such as methyl methacrylate, isooctyl acrylate, octadecyl acrylate, docosyl acrylate, methyl acrylate, ethyl acrylate, butyl acrylate, and the glass transition temperature of the shell layer is controlled at -20-0°C.

[0009] More preferably, the mass ratio of the hydrophilic monomer to the acrylate monomer in the polymer B core-shell structure is 1-5:100.

[0010] More preferably, the coating amount of the polymer A pre-coating is 4-8 g / m2.

[0011] More preferably, the mass ratio of the polymer A to the polymer B in the polymer A and polymer B compound mixture is 1:1, and the coating amount of the top coating is 6-10 g / m2.

[0012] More preferably, the coating is applied by a doctor blade coating method, and during drying, it is dried by a combination of hot air and hot roll methods, and the drying temperature range is 105-150°C.

[0013] A preparation method of a waterproof and oil-proof coating for heat-sealable paper-based food packaging, characterized in that the preparation method is as follows: When preparing the polymer A: Polymerize vinyl acetate, vinyl pyrrolidone, docosyl vinyl ether, (meth)allyl glycidyl ether at 70-80°C in ethanol for 2-6 h. After polymerization, keep warm for 2-4 h, add liquid alkali at 40-50°C, carry out alcoholysis reaction for 4-8 h, then distill out ethanol and by-products, add water to dissolve the polymer to obtain a hydrophobic cross-linked polyvinyl alcohol finished product; the concentration of the finished product is 30-40%; When preparing the polymer B: The polymer B is prepared by a soap-free emulsion polymerization and core-shell emulsion process. Under aqueous conditions, first dropwise add the core layer mixed monomers at 70-90°C for 2-4 h, then dropwise add the shell layer mixed monomers for 4-8 h, initiate the polymerization with persulfate, and keep warm for 2-4 h after dropping to obtain the polymer, and the concentration of the polymer is controlled at 40-50%.

[0014] The beneficial effects of the present invention: (1) The pre-coated polymer A prepared with vinyl acetate hydrolysis as the main raw material has extremely strong film-forming properties, can achieve a better closed film formation and leveling effect on paper-based materials, and the waterproof and oil-proof layer of the top coating can be better retained on the surface after coating. The combination of the two layers can achieve excellent water vapor resistance, oil resistance, water resistance and other properties; (2) The surface coating is compounded with Polymer A and Polymer B. The soft-shell and hard-core structure of Polymer B enables heat sealing at a relatively low heat-sealing temperature, achieving better heat-sealing efficiency. After being compounded with Polymer A, the adhesion problem of the soft-shell and hard-core structure is solved; (3) The soap-free process is adopted to optimize the product formula and process flow, ensuring that the coating meets the safety standards of food contact materials at home and abroad and enhancing the safety of the coating in the food contact environment. Specific implementation manners

[0015] Next, we will further illustrate a waterproof and oil-proof coating for heat-sealable paper-based food packaging and its preparation method according to the present invention. Example 1

[0016] Polymer A is polymerized in ethanol at 70°C for 4 hours by using 100 g of vinyl acetate, 10 g of vinyl pyrrolidone, 10 g of docosyl vinyl ether, and 0.5 g of (meth)allyl glycidyl ether. After polymerization, it is kept warm for 4 hours. At a temperature of 50°C, liquid alkali is added for alcoholysis reaction for 6 hours. Then, ethanol and by-products are distilled off, and water is added to dissolve the polymer to obtain a hydrophobic cross-linked polyvinyl alcohol product, which has excellent film-forming properties and oil-proof performance, as well as certain hydrophobicity. When used for pre-coating, it can achieve good film-forming performance and does not affect the surface coating operation. The concentration of the finished product is 40%, the alcoholysis degree is controlled at 99.5%, and the molecular weight is 60,000; Polymer B is prepared by the core-shell emulsion process. The core layer contains hydrophilic monomers and acrylate monomers. Among them, the hydrophilic monomers sodium acrylamidodimethylsulfonate and allyl polyether sulfate total 2 g. The acrylate monomers in the core layer are methyl methacrylate, isooctyl acrylate, and 3,3,5-trimethylcyclohexyl acrylate, with a total of 100 g, and the glass transition temperature is designed at 35°C. The shell layer contains hydrophilic monomers and acrylate monomer raw materials. Among them, the hydrophilic monomers sodium acrylamidodimethylsulfonate and allyl polyether sulfate total 0.8 g. The acrylate monomers in the shell layer are methyl methacrylate, isooctyl acrylate, stearyl acrylate, behenyl acrylate, and ethyl acrylate, with a total of 80 g, and the glass transition temperature is designed at -5°C. Under aqueous conditions, the core layer mixed monomers are added dropwise at 90°C for 2 hours, and then the shell layer mixed monomers are added dropwise for 4 hours. Polymerization is initiated by persulfate. After the addition is completed, the reaction is kept warm for 4 hours to obtain the polymer, and the polymer concentration is controlled at 50%. Example 2

[0017] Polymer A is prepared by polymerizing 100 g of vinyl acetate, 7.5 g of vinyl pyrrolidone, 20 g of docosyl vinyl ether, 2.5 g of (meth)allyl glycidyl ether in ethanol at 75 °C for 2 h. After polymerization, it is kept warm for 3 h. At 40 °C, liquid alkali is added and alcoholysis reaction is carried out for 8 h. Then ethanol and by-products are distilled off, and water is added to dissolve the polymer. The concentration of the finished product is 30%, the degree of alcoholysis is controlled at 99.6%, and the molecular weight is 50,000; Polymer B is prepared by core-shell emulsion process. The core layer contains hydrophilic monomers and acrylate monomers. Among them, the hydrophilic monomers sodium vinyl sulfonate and allyl polyether sulfate total 3 g. The acrylate monomers in the core layer are isooctyl acrylate, dicyclopentenyl oxyethyl acrylate, 3,3,5-trimethylcyclohexyl acrylate, and ethyl methacrylate, totaling 100 g. The glass transition temperature is designed to be 43 °C. The shell layer contains hydrophilic monomers and acrylate monomer raw materials. Among them, the hydrophilic monomers sodium vinyl sulfonate and allyl polyether sulfate total 2.1 g. The acrylate monomers in the shell layer are octadecyl acrylate, docosyl acrylate, and ethyl methacrylate, totaling 70 g. The glass transition temperature is designed to be -9 °C. Under aqueous conditions, at 70 °C, the core layer mixed monomers are first added dropwise for 4 h, and then the shell layer mixed monomers are added dropwise for 6 h. Polymerization is initiated by persulfate. After dropping, the reaction is kept warm for 3 h to obtain the polymer, and the polymer concentration is controlled at 40%. Example 3

[0018] Polymer A is prepared by polymerizing 100 g of vinyl acetate, 5 g of vinyl pyrrolidone, 15 g of docosyl vinyl ether, 5 g of (meth)allyl glycidyl ether in ethanol at 80 °C for 6 h. After polymerization, it is kept warm for 2 h. At 45 °C, liquid alkali is added and alcoholysis reaction is carried out for 4 h. Then ethanol and by-products are distilled off, and water is added to dissolve the polymer. The concentration of the finished product is 35%, the degree of alcoholysis is controlled at 99.2%, and the molecular weight is 80,000; Polymer B is prepared by core-shell emulsion process. The core layer contains hydrophilic monomers and acrylate monomers. Among them, the hydrophilic monomers sodium salt of methacrylamidopropyl sulfonate and allyl polyether sulfate total 5 g. The acrylate monomers in the core layer are isooctyl acrylate, dicyclopentenyl oxyethyl acrylate, 3,3,5-trimethylcyclohexyl acrylate, and ethyl acrylate, totaling 100 g. The glass transition temperature is designed to be 48 °C. The shell layer contains hydrophilic monomers and acrylate monomer raw materials. Among them, the hydrophilic monomers sodium salt of methacrylamidopropyl sulfonate and allyl polyether sulfate total 3 g. The acrylate monomers in the shell layer are methyl methacrylate, octadecyl acrylate, docosyl acrylate, and butyl acrylate, totaling 60 g. The glass transition temperature is designed to be -16 °C. Under aqueous conditions, at 80 °C, the core layer mixed monomers are first added dropwise for 3 h, and then the shell layer mixed monomers are added dropwise for 8 h. Polymerization is initiated by persulfate. After dropping, the reaction is kept warm for 2 h to obtain the polymer, and the polymer concentration is controlled at 45%; Application Cases

[0019] In this application, the doctor blade coating method is adopted during coating, and drying is carried out by combining hot air and hot roller methods, and the drying temperature range is 105-150°C.

[0020] The protection scope of the present invention is not limited to the above embodiments and their transformations. Routine modifications and substitutions made by those skilled in the art based on the content of this embodiment all fall within the protection scope of the present invention.

Claims

1. A waterproof and oil-proof coating for heat-sealable paper-based food packaging, characterized in that The invention comprises polymer A and polymer B, wherein polymer A is used for coating pre-coating, polymer A and polymer B are compounded by mechanical stirring, and the mixture is used for coating surface coating; the polymer A is prepared by polymerization modification of any one or more monomers selected from vinyl acetate, vinyl pyrrolidone, docosyl vinyl ether, and (methyl) allyl glycidyl ether; the polymer B comprises a core layer and a shell layer, and the core layer and the shell layer both comprise a hydrophilic monomer and an acrylate monomer.

2. The water-proof and oil-proof coating for heat-sealable paper-based food packaging according to claim 1, characterized in that: The mass ratio of vinyl acetate, vinyl pyrrolidone, behenyl vinyl ether and (methyl) allyl glycidyl ether in the polymer A is 100:5-10:10-20:0.5-5.

3. The water-proof and oil-proof coating for heat-sealable paper-based food packaging according to claim 2, characterized in that: The molecular weight of the polymer A is controlled at 50,000-100,000, and the alcoholysis degree is controlled at more than 99%.

4. The water-proof and oil-proof coating for heat-sealable paper-based food packaging according to claim 1, characterized in that: The hydrophilic monomer in the core layer and the shell layer of polymer B is one of sodium acrylamidodimethylsulfonate, sodium vinylsulfonate, and sodium methacrylamide isopropylsulfonate, which is used in combination with allyl polyether sulfate.

5. The water-proof and oil-proof coating for heat-sealable paper-based food packaging according to claim 4, characterized in that: The acrylate monomers in the core layer of polymer B are various types of methyl (meth)acrylate, isooctyl acrylate, dicyclopentenyloxyethyl acrylate, 3,3,5-trimethylcyclohexyl acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, etc., and the glass transition temperature of the core layer is controlled at 30-50°C; the acrylate monomers in the shell layer are various types of methyl methacrylate, isooctyl acrylate, octadecyl acrylate, behenyl acrylate, methyl acrylate, ethyl acrylate, butyl acrylate, and the glass transition temperature of the shell layer is controlled at -20-0°C.

6. The water-proof and oil-proof coating for heat-sealable paper-based food packaging according to claim 4, characterized in that: The mass ratio of the hydrophilic monomer to the acrylate monomer in the core-shell structure of the polymer B is 1-5:

100.

7. The water-proof and oil-proof coating for heat-sealable paper-based food packaging according to claim 1, characterized in that: The coating amount of the polymer A pre-coat is 4-8 g / m2.

8. The water-proof and oil-proof coating for heat-sealable paper-based food packaging according to claim 1, characterized in that: The mass ratio of polymer A to polymer B in the composite mixture of polymer A and polymer B is 1:1, and the coating amount of the top coating is 6-10g / m2.

9. The water-proof and oil-proof coating for heat-sealable paper-based food packaging according to claim 1, characterized in that: The coating is applied by blade coating and dried by a combination of hot air and hot rollers at a drying temperature of 105-150°C.

10. The method for preparing a water-proof and oil-proof coating for heat-sealable paper-based food packaging according to any one of claims 1 to 9, characterized in that: The preparation method is as follows: When preparing polymer A: vinyl acetate, vinyl pyrrolidone, docosyl vinyl ether, (methyl) allyl glycidyl ether, polymerize in ethanol at 70-80°C for 2-6 hours, keep warm for 2-4 hours after polymerization, add liquid alkali at 40-50°C, carry out alcoholysis for 4-8 hours, then evaporate ethanol and by-products, add water to dissolve the polymer, and obtain a hydrophobic cross-linked polyvinyl alcohol product; the concentration of the finished product is 30-40%; Preparation of polymer B: polymer B is prepared by soap-free emulsion polymerization and core-shell emulsion process. Under aqueous conditions, the core layer mixed monomer is first added dropwise at 70-90°C for 2-4 hours, and then the shell layer mixed monomer is added dropwise for 4-8 hours. Persulfate is used to initiate the polymerization. After the addition is completed, the reaction is kept warm for 2-4 hours to obtain a polymer, and the polymer concentration is controlled at 40-50%.

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