CN111334171A - High-stretch anti-dyeing food packaging can inner coating and preparation method and application thereof - Google Patents

Abstract

The invention discloses a high-stretch anti-dyeing coating in a food packaging can, which comprises the following components in percentage by mass: 5-15% of polyester polyol, 0.1-30% of pigment, 0.1-1% of dispersing agent, 0.1-1% of wax powder, 5-25% of vinyl ether-tetrafluoroethylene copolymer, 30-65% of high-molecular copolyester, 3-12% of blocked isocyanate, 0.1-1% of catalyst, 0.5-2% of adhesion promoter, 0.1-0.8% of auxiliary agent and the balance of organic solvent.

Description

High-stretch anti-dyeing food packaging can inner coating and preparation method and application thereof

Technical Field

The invention relates to the field of food packaging can coatings, in particular to a high-tensile anti-dyeing food packaging can inner coating and a preparation method and application thereof.

Background

At present, the total yield of canned food is nearly 5000 ten thousand tons every year all over the world, and the variety is more than 2500. It is predicted that the global canned food industry will grow at a 3.8% annual compound growth rate, and the market will reach about 7189 billion yuan by 2021. Chinese can occupies an important position in the international market, and China has become the largest export country of cans in the world at present. The product is sold in developed countries such as multiple countries in the world. According to the latest data of the national statistical bureau, in 2018, the accumulated finished yield of the canned food enterprises of 807 families with the scale of China is 1027.99 ten thousand tons, and the export amount is 54.25 hundred million dollars. With the great improvement of production processes and equipment of can enterprises in China, the can industry is rapidly developed, the characteristics of safety, nutrition and convenience of can food are more and more favored by consumers, the domestic demand rises year by year, the can industry in China is better in the international market at present, and the can industry in China has good development prospects under the pull of dual requirements of domestic and foreign markets in the future. By the forecast of 2023, the market scale of the can industry in China is expected to break through 3200 hundred million yuan.

In the field of metal packaging cans, three tinplate cans with large calibers are widely applied to packaging cans of milk powder, coffee powder, tea, seafood, luncheon meat, sardine and the like for sealing and storing food.

In recent years, with the invention and the rise of the technology of the high-tensile two-piece packaging tin, the technology is simple and reasonable, the existing procedures for producing three-piece can products are reduced, the production efficiency is improved, and the environment protection is facilitated. Meanwhile, the body of the packaging can is integrated with the bottom cover, welding seams are not formed, the sealing requirement of food and medicines on the large-diameter packaging can be met, the risk of pollution of the packaging can is avoided, the safety performance of food and medicines is fully guaranteed, and the packaging can is rapidly and widely applied to the market. Because the process needs to stretch the material for multiple times, the material is finally formed into the can product with the length-diameter ratio of 2:1 or even higher. After the finished canned food is provided for a food processing factory, different types of foods are packaged in the can for high-temperature cooking, so that the nutrition, health and safety of the foods are ensured. Foods rich in anthocyanins and natural pigments are gradually sought after by the public for their beauty and health functions due to their excellent radical scavenging and antioxidant abilities. With the expansion of the application of the food can market and the requirement of individual customization of customers, the pursuit of higher tensile property of the coating and the resistance to chemical and dyeing after high tensile property is a constant pursuit of the coating in the two-piece metal packaging can.

The organic protective coatings most commonly used in three tinplate cans, such as PVC organosols and epoxy phenolic resin coating systems, have not been suitable because of the high levels of hard monomer components inherent in the resin molecules, which have not met the high tensile requirements, and the potential health hazards associated with vinyl chloride monomer residues and BPA residues.

Chinese patent CN201310714858 provides a double-coating food packaging material coating which has high sulfur resistance and salt corrosion resistance and does not contain PVC, BPA, BPF and derivatives thereof, and a preparation method and application thereof. The prior art two-layer coating system is completely free of BAP and PVC and is suitable for use in coating food packaging materials. The prior art can replace the traditional PVC organic sol and epoxy phenolic resin coating and has good flexibility, but the reaction of polyester resin, phenolic resin and amino resin is utilized in the prior art, so that a paint film is too brittle and cannot achieve chemical resistance after high stretching.

Chinese patent CN201210570896 provides a single-coating metal beverage and food can internal coating, a preparation method and an application thereof, wherein the coating comprises the following components in percentage by mass: 35-70% of saturated polyester, 1-15% of amino resin, 3-20% of phenolic resin and 1.8-2.5% of auxiliary agent. The single-coating prepared by the prior art is resistant to high-temperature sterilization, acid boiling and the like, has good flexibility, can be used as an inner coating of an easy-open cover, an inner coating of a two-piece deep-drawing food can and an inner wall coating of a three-piece beverage can, and is suitable for storing carbonated beverages, beer, sardine, luncheon meat, tomato sauce and the like; the weight of a single coating film reaches 13g/m2, the double-coating process of epoxy primer and organic sol finish in a sheet coating mode can be replaced, and the double-coating process is free from whitening after cooking, good in adhesive force and free of feather films. In the prior art, the reaction of polyester resin with phenolic resin and amino resin is also utilized, the elongation of a film formed by the film is insufficient due to the poor stretchability of the amino resin and the phenolic resin, the chemical resistance after high stretching cannot be achieved, and the coating does not have the anti-dyeing capability due to the high surface tension of the polyester resin.

Chinese patent CN200610041362 thermosetting fluorocarbon resin for metal coiled materials and coating thereof, provides preparation of thermosetting fluorocarbon resin and coating thereof, the prior art uses chlorotrifluoroethylene-vinyl acetate copolymer and cross-linking agent for curing, and fluorine coating which is suitable for coating metal coiled materials, has good methyl ethyl ketone wiping resistance, good aging resistance and excellent flexibility is obtained. Because the content of the chlorotrifluoroethylene monomer in the copolymer reaches 45-55 percent, the copolymer has higher hardness and cannot be used in a new two-piece can food can making process.

Disclosure of Invention

The invention aims to provide a high-stretching anti-dyeing food packaging can inner coating.

In order to solve the technical problems, the technical scheme of the invention is as follows:

the high-stretch anti-dyeing food packaging can internal coating comprises the following components in percentage by mass: 5-15% of polyester polyol, 0.1-30% of pigment, 0.1-1% of dispersing agent, 0.1-1% of wax powder, 5-25% of vinyl ether-tetrafluoroethylene copolymer, 30-65% of high-molecular copolyester, 3-12% of blocked isocyanate, 0.1-1% of catalyst, 0.5-2% of adhesion promoter, 0.1-0.8% of auxiliary agent and the balance of organic solvent.

Further, the polyester polyol is a micro-branched or branched polyester polyol solution polymerized by polyol and polybasic acid, the molecular weight of the polyester polyol is 10000-3000, and the hydroxyl value content is 1-4%; the acid value is less than 10mg KOH/g.

The macromolecular copolymer resin is a linear chain or slightly branched saturated polyester solution formed by polymerizing polyalcohol and polybasic acid, the glass transition temperature of the macromolecular copolymer resin is 20-70 ℃, the molecular weight is 10000-30000, the hydroxyl value is 3-20 mgKOH/g, and the acid value is less than 10mg KOH/g.

Further, the pigment is an inorganic or organic pigment, including but not limited to rutile titanium dioxide.

Further, the vinyl ether-tetrafluoroethylene copolymer is a polyvinyl ether-tetrafluoroethylene solution obtained by polymerizing tetrafluoroethylene, vinyl ether or vinyl ester; the vinyl ether-tetrafluoroethylene copolymer has fluorine content of more than or equal to 30 percent, glass transition temperature of more than or equal to 30 ℃, molecular weight of 5000-30000, hydroxyl value of 20-100 mgKOH/g and acid value of less than 10mg KOH/g.

Further, the wax powder is PTFE wax or PTFE modified wax.

The invention also provides a preparation method of the coating, which comprises the following steps:

the preparation method of the high-stretch anti-dyeing food packaging can inner coating comprises the following steps:

s1: weighing polyester polyol, pigment, dispersant, wax powder, vinyl ether-tetrafluoroethylene copolymer, high-molecular copolyester, blocked isocyanate, catalyst, adhesion promoter, auxiliary agent and organic solvent according to a specified proportion;

s2: sequentially adding polyester polyol, an organic solvent, pigment, a dispersant and wax powder into a container while stirring, then dispersing at a high speed of 800-;

s3: continuously adding the vinyl ether-tetrafluoroethylene copolymer, the high-molecular copolyester, the blocked isocyanate, the catalyst, the adhesion promoter, the auxiliary agent and the organic solvent into the material A while stirring, and then dispersing at a high speed of 800-1200r/min for 10-15 minutes until the materials are uniformly dispersed to obtain a material B;

s4: and standing and filtering the material B, and controlling the viscosity to be 60-140 s to obtain the finished product coating.

The invention also provides a using method of the coating, which comprises the following steps:

s1: coating the coating on a metal plate with the thickness of 0.19-0.35 mm;

s2: baking at 241 deg.C for 10-20s, and drying to control the film weight of the metal plate coating at 8-20g/m 2;

s3: and (3) high-stretching the metal plate to obtain the finished food can.

The invention has the beneficial effects that:

1. the coating has excellent stretch resistance, and still has good physical and chemical properties after being formed into a can manufacturing process of a finished food can with the length-diameter ratio as high as 2: 1.

2. After can making and forming, natural pigment food containing anthocyanins is steamed and cooked in the can under the sterilization condition of 121 ℃ for 60min without being dyed.

3. The coating has excellent corrosion resistance, and after can making and forming, the inner wall of the can is steamed and boiled under the test condition of mixing 3% of acetic acid and 1% of citric acid at 121 ℃ for 60min and 3% of NaCl, so that the coating does not whiten and lose gloss, and the coating has excellent adhesion.

4. The method is suitable for roll coating of metal coils, and the coating with the film weight of 8-20gsm can be prepared by one-time coating.

5. The color is rich, the variety is various, and the customization demand of customer is particularly suitable.

6. The paint does not contain any toxic monomer, and the paint does not contain toxic substances such as BPA, PVC and the like.

Detailed Description

The following further describes the embodiments of the present invention.

The high-stretch anti-dyeing food packaging can internal coating comprises the following components in percentage by mass: 5-15% of polyester polyol, 0.1-30% of pigment, 0.1-1% of dispersing agent, 0.1-1% of wax powder, 5-25% of vinyl ether-tetrafluoroethylene copolymer, 30-65% of high-molecular copolyester, 3-12% of blocked isocyanate, 0.1-1% of catalyst, 0.5-2% of adhesion promoter, 0.1-0.8% of auxiliary agent and the balance of organic solvent.

The polyester polyol is a polyester polyol solution with a micro-branched chain or a branched chain, which is formed by polymerizing polyol and polybasic acid, the molecular weight of the polyester polyol solution is 10000-3000, and the hydroxyl value content is 1-4%; the acid value is less than 10mg KOH/g, and preferably Desmophen series of Bayer Germany, and more preferably Desmophen T1652T 1665, T1775.T1200, T1150 of Bayer Germany, and K-FLEX188 of King of America.

The macromolecular copolymer resin is a linear chain or slightly branched chain type saturated polyester solution polymerized by polyalcohol and polybasic acid, the glass transition temperature of the macromolecular copolymer resin is 20-70 ℃, the molecular weight is 10000-30000, the hydroxyl value is 3-20 mgKOH/g, the acid value is less than 10mg KOH/g, the macromolecular copolymer resin can be preferably selected from Mitsubishi chemical TP series, Woodford polyester L series, more preferably selected from TP217, TP235, TP236, TP249, TP294, TP220 and TP290, and one or more selected from Woodford L411, L651 and L658.

The pigment is inorganic or organic pigment meeting FDA food requirements, and comprises rutile titanium dioxide, organic pigment solid beauty series of BASF, bright beautiful series, and can be preferably American mu titanium dioxide TS-6200, organic pigment solid beauty transparent DPP @ Red BP, yellow 2RLP, bright beautiful @ bright red BTR, and bright beautiful @ Green GFNP.

The vinyl ether-tetrafluoroethylene copolymer is a polyvinyl ether-tetrafluoroethylene solution polymerized by tetrafluoroethylene, vinyl ether or vinyl ester, the fluorine content is more than or equal to 30 percent, the glass transition temperature is more than or equal to 30 ℃, the molecular weight is 5000-30000, and the hydroxyl value is 20-100 mg KOH/g; the acid value is less than 10mg KOH/g, and preferably one of Japan gold GK series, Japan DIC FLUONATE series, and stannionless Wanbo fluorocarbon chemical WF-JT318, and preferably Japan gold GK570, GK520, stannionless Wanbo fluorocarbon WF-JT318, and Japan DIC K703K 705.

The wax powder is PTFE wax or PTFE modified wax with high melting point, preferably 3000, 2300 of Cernas, Germany, BYK-CERAFLOUR 996, DuPont MP1000, USA.

The dispersant is a polymer dispersant suitable for coils, and one of dispersant series BYK 170, BYK180, BYK2000 and BYK2008 of BYK can be preferably used.

The blocked isocyanate refers to blocked HDI and blocked IPDI isocyanate meeting FDA food grade requirements, and can be preferably one of Coxichu BL 3165, BL 3175, BL3272, 3370, 3470, BL4265, BL340 Asahi-converted into MF-K60X, SBN-70D, MF-B60X, TPA-B80X, TKA-B75S and E402-B80T.

The catalyst is one of the catalysts conforming to the FDA, including but not limited to organic tin, organic bismuth, organic aluminum and organic lithium, and is preferably one of environment-friendly catalysts of Borchi Kat 0243, Borchi Kat024, Borchi Kat0244 and Borchi Kat315 of Bayer in Germany.

The adhesion promoter is epoxy phosphate and polyester phosphate series commonly used for food packaging materials.

The organic solvent is a common high-boiling-point organic solvent combination, such as aromatic hydrocarbon solvent, alcohol solvent, ether solvent, ester solvent or ketone solvent, and preferably one or a mixture of Solvesso100, n-butanol, DBE, ethylene glycol monobutyl ether and cyclohexanone.

The auxiliary agent is an acrylic acid leveling defoaming agent commonly used for food packaging coatings.

The raw materials and the monomers for synthesizing the raw materials do not contain PVC and BPA, meet the requirement of FDA food certification and can be normally purchased and obtained by the market.

The using method of the coating comprises the following steps:

s1: coating the coating on a metal plate with the thickness of 0.19-0.35 mm;

s2: baking at 241 deg.C for 10-20s, and drying to control the film weight of the metal plate coating at 8-20g/m 2;

s3: and (3) high-stretching the metal plate to obtain the finished food can.

The mechanism of the invention is as follows: the fluorocarbon resin vinyl ether-tetrafluoroethylene copolymer has the advantages that the fluorocarbon resin vinyl ether-tetrafluoroethylene copolymer is chemically stable, hydrophobic, oleophobic, low in surface energy and high in corrosion resistance, a high-performance polyester-isocyanate coating system is chemically modified under the assistance of polyester polyol with better flexibility and higher reaction activity, a composite coating which has high polyester stretchability, high-temperature cooking resistance, fluorocarbon pollution resistance and good corrosion resistance is obtained after reaction, meanwhile, due to the introduction of pigment and wax, the fluorocarbon resin vinyl ether-tetrafluoroethylene copolymer has the physical shielding effect, the permeation of micromolecular water, micromolecular acid and ions is isolated, the lotus leaf effect is formed by a micro-nano structure formed by the fluorocarbon coating, and the permeation and residue of natural food pigments such as anthocyanin are prevented.

Compared with the prior art, the invention has the following advantages and effects:

1. the coating has excellent stretch resistance, and still has good physical and chemical properties after being formed into a can manufacturing process of a finished food can with the length-diameter ratio as high as 2: 1.

2. After can making and forming, natural pigment food containing anthocyanins is steamed and cooked in the can under the sterilization condition of 121 ℃ for 60min without being dyed.

3. The coating has excellent corrosion resistance, and after can making and forming, the inner wall of the can is steamed and boiled under the test condition of mixing 3% of acetic acid and 1% of citric acid at 121 ℃ for 60min and 3% of NaCl, so that the coating does not whiten and lose gloss, and the coating has excellent adhesion.

4. The method is suitable for roll coating of metal coils, and can prepare a coating with the film weight of 8-20g/m2 by one-time coating.

5. The color is rich, the variety is various, and the customization demand of customer is particularly suitable.

6. The paint does not contain any toxic monomer, and the paint does not contain toxic substances such as BPA, PVC and the like.

Examples 1-5 are preparation of coatings of different color types:

TABLE 1 preparation of clear base coating compositions (unit: wt%)

TABLE 1

Transparent base coats of examples 1-5 were prepared according to the materials and formulations in table 1, and the specific steps were: according to the formula mass ratio of table 1, according to the sequence, adding polyester polyol, organic solvent, pigment, dispersant and wax powder in turn while stirring for high-speed dispersion at the speed of 800-1200r/min for 15 minutes, grinding the coating by a sand mill until the fineness is less than or equal to 15um to prepare a semi-finished product A material for later use, adding vinyl ether-tetrafluoroethylene copolymer, high-molecular copolyester, blocked isocyanate, catalyst, adhesion promoter, defoaming and leveling agent and organic solvent in turn according to the mass ratio in turn, then dispersing at the speed of 800-1200r/min for 10-15 minutes until the mixture is uniformly dispersed, standing, filtering for later use, and controlling the viscosity at 60-140 s (coating 4 cups at 25 ℃).

Preparation of comparative examples 1-2:

according to the formula shown in Table 1, according to the sequence, adding polyester polyol, high-molecular copolyester, an organic solvent, pigment, wax powder and a dispersing agent in turn while stirring at a high speed of 800-1200r/min for 15 minutes, grinding the coating by using a sand mill until the fineness is less than or equal to 15 microns to prepare a semi-finished product A material for later use, adding vinyl ether-tetrafluoroethylene copolymer, high-molecular copolyester, blocked isocyanate, a catalyst, an adhesion promoter, a defoaming and leveling agent and an organic solvent in turn into the material A while stirring at a mass ratio, dispersing at a high speed of 800-1200r/min for 10-15 minutes until the materials are uniformly dispersed, standing, filtering for later use, and controlling the viscosity at 60-140 s (coating 4 cups at 25 ℃).

Preparation of comparative example 3:

the coating produced by the commercial CN201210570896 patent technology is purchased, dispersed at a high speed of 800-1200r/min for 10-15 minutes until the dispersion is uniform, and kept stand and filtered for later use.

Performance testing of food packaging material coatings:

coating the coating on a metal plate with the thickness of 0.19-0.35mm by using a wire rod, wherein the metal plate can be an alloy aluminum material or a tinplate, baking for 10-20s at the temperature of 241 ℃ of the metal plate, and testing after a target dry film weight is 8-20g/m & lt 2 & gt to prepare a coated plate, and the performance of the test is shown in table III

The method for detecting the main performance of the coating comprises the following steps:

methyl Ethyl Ketone (MEK) resistance test: a1 kg iron hammer is wrapped by cotton cloth, soaked in liquid Methyl Ethyl Ketone (MEK) solvent and moved back and forth to wipe the tested surface, and one time is recorded back and forth until the metal substrate is exposed after the coating is damaged, and the wiping times are recorded as the MEK value.

And (3) testing the adhesive force: before and after cooking, a cross is cut by a hundred-grid knife to form a shape of # and observed after being torn and pulled for 3 times by a 3M adhesive tape, the performance difference is compared, the test result is divided into 1-10 grades, 10 represents the best, and 1 represents the worst.

Contact angle test: the contact angle tester of the Chengding precision instrument is used for testing the contact angle between a water drop and the coating, the contact angle is hydrophilic when less than 90 degrees, and the contact angle is hydrophobic when more than 90 degrees.

Boiling in water to whiten: and (4) observing the whitening degree of the paint film, and grading the test result into 1-10 grades, wherein 10 represents the best, and 1 represents the worst.

Conductivity value: the integrity of the coating was tested with a current tester: the conductive value is more than 1mA, and the paint film is broken.

Stretch resistance: punching the coated plate according to the length-diameter ratio of 2:1 to prepare 350ml canned food, and observing whether the paint film is whitish and cracked. The test results are graded into 1-10 grades, with 10 being the best and 1 being the worst.

Dyeing property: the staining of the coating after cooking in water containing 1% anthocyanins at 121 ℃ for 60min was visually observed.

Corresponding performance tests were performed on examples 1 to 5 and comparative examples 1 to 3, respectively, and the comparison results are shown in table 2.

From the results of table 2, it can be seen that:

the polyurethane coatings, fluorocarbon coatings, and prior art polyester amino coatings prepared separately for comparative examples 1, 2, and 3 all suffer from different drawbacks: the polyurethane coating has good tensile resistance, but has small contact angle and poor corrosion resistance and dyeing resistance; although the fluorocarbon coating has good anti-dyeing capability, the tensile resistance is insufficient, so that the corrosion resistance and the chemical resistance are poor; the prior art has certain flexibility, but under the condition of high stretching, the flexibility, the corrosion resistance and the anti-dyeing capability are poor, and the invention of different embodiments has ideal performances. Thus, it can be seen that: the high-stretching deep-drawing lunch meat inner wall coating obtained by the invention overcomes the defects of high temperature resistance, sterilization and insufficient corrosion resistance existing after the existing food packaging material coating is used for drawing two deep-drawing cans with the length-diameter ratio of up to 2: 1; but also solves the problem that the natural pigment food containing anthocyanin is easy to be dyed in the prior art. Meanwhile, the coating uses the pigment which meets FDA food certification, has rich colors and is particularly suitable for increasingly expanded customization requirements of customers.

Table two: high-tensile metal food packaging can in-can anti-dyeing coil coating performance contrast table

TABLE 2

The embodiments of the present invention have been described in detail, but the present invention is not limited to the described embodiments. It will be apparent to those skilled in the art that various changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, and the scope of protection is still within the scope of the invention.

Claims (8)

1. High tensile anti-dyeing food packaging can inner coating, which is characterized in that: the coating comprises the following components in percentage by mass: 5-15% of polyester polyol, 0.1-30% of pigment, 0.1-1% of dispersing agent, 0.1-1% of wax powder, 5-25% of vinyl ether-tetrafluoroethylene copolymer, 30-65% of high-molecular copolyester, 3-12% of blocked isocyanate, 0.1-1% of catalyst, 0.5-2% of adhesion promoter, 0.1-0.8% of auxiliary agent and the balance of organic solvent.

2. The high stretch anti-stain food package can interior coating of claim 1, wherein: the polyester polyol is a polyester polyol solution with micro-branched chains or branched chains, which is formed by polymerizing polyol and polybasic acid, the molecular weight of the polyester polyol is 10000-3000, and the hydroxyl value content is 1-4%; the acid value is less than 10mg KOH/g.

3. The high stretch anti-stain food package can interior coating of claim 1, wherein: the macromolecular copolymer resin is a linear chain or slightly branched chain type saturated polyester solution polymerized by polyalcohol and polybasic acid, the glass transition temperature of the macromolecular copolymer resin is 20-70 ℃, the molecular weight is 10000-30000, the hydroxyl value is 3-20 mgKOH/g, and the acid value is less than 10mg KOH/g.

4. The high stretch anti-stain food package can interior coating of claim 1, wherein: the pigment is an inorganic or organic pigment, including but not limited to rutile titanium dioxide.

5. The high stretch anti-stain food package can interior coating of claim 1, wherein: the vinyl ether-tetrafluoroethylene copolymer is a polyvinyl ether-tetrafluoroethylene solution formed by polymerizing tetrafluoroethylene, vinyl ether or vinyl ester; the polyvinyl ether-tetrafluoroethylene copolymer has fluorine content of more than or equal to 30 percent, glass transition temperature of more than or equal to 30 ℃, molecular weight of 5000-30000, hydroxyl value of 20-100 mg KOH/g and acid value of less than 10mg KOH/g.

6. The high stretch anti-stain food package can interior coating of claim 1, wherein: the wax powder is PTFE wax or PTFE modified wax.

7. The preparation method of the high-stretch anti-dyeing coating in the food packaging can is characterized by comprising the following steps: the method comprises the following steps:

s1: weighing polyester polyol, pigment, dispersant, wax powder, vinyl ether-tetrafluoroethylene copolymer, high-molecular copolyester, blocked isocyanate, catalyst, adhesion promoter, auxiliary agent and organic solvent according to a specified proportion;

s2: sequentially adding polyester polyol, an organic solvent, pigment, a dispersant and wax powder into a container while stirring, then dispersing at a high speed of 800-;

s3: continuously adding the vinyl ether-tetrafluoroethylene copolymer, the high-molecular copolyester, the blocked isocyanate, the catalyst, the adhesion promoter, the defoaming and leveling agent and the organic solvent into the material A while stirring, and then dispersing at a high speed of 800-1200r/min for 10-15 minutes until the materials are uniformly dispersed to obtain a material B;

s4: and standing and filtering the material B, and controlling the viscosity to be 60-140 s to obtain the finished product coating.

8. The application method of the high-stretch anti-dyeing coating in the food packaging tin is characterized in that: the method comprises the following steps:

s1: coating the coating on a metal plate with the thickness of 0.19-0.35 mm;

s2: baking at 241 deg.C for 10-20s, and drying to control the film weight of the metal plate coating at 8-20g/m 2;

s3: and (3) high-stretching the metal plate to obtain the finished food can.