A coating composition free of bisphenol A and its preparation method and application

Abstract

The present invention belongs to the technical field of coatings, and specifically relates to a coating composition free of bisphenol A, a preparation method thereof and an application thereof. The raw materials of the coating composition include: saturated polyester resin, rosin-modified unsaturated polyester resin, silicone-modified polyester resin, amino resin, phenolic resin, titanium dioxide, graphene oxide, lubricant, leveling agent, defoamer and solvent. The coating composition of the present invention has excellent stability, each component cooperates with each other, and the formula amount is reasonable. The obtained coating composition product is not only stable and uniform in nature, but also has high adhesion ability, and has excellent friction resistance, boiling resistance and acid resistance.

Description

Technical Field

[0001] The invention belongs to the technical field of coatings, and in particular relates to a coating composition free of bisphenol A and a preparation method and application thereof. Background Art

[0002] Metal cans are made of metal sheets through crimping, bonding, and resistance welding. They can be divided into three-piece cans and two-piece cans according to their structure and processing technology. Such metal cans are often used as filling containers for dry powder foods, beverage foods, chemical products, and spray products. Coating metal cans can not only protect metal materials, but also ensure that the contents do not come into direct contact with the metal during the internal coating, thereby causing the product to deteriorate or change in nature.

[0003] Metal food cans often use epoxy resin (also useful organosol resin) as an inner coating to prevent heavy metals in the can from migrating to the food and the contents from corroding the can. Among them, epoxy resin is generally synthesized from substances such as bisphenol A (BPA) and bisphenol F (BPF). Bisphenol A diglycidyl ether (BADGE) and bisphenol F diglycidyl ether (BFDGE) are used as stabilizers to neutralize the hydrochloric acid produced during the material production process to avoid decomposition of the coating.

[0004] The chemical structure of bisphenol A is similar to that of the synthetic estrogen diethylstilbestrol, which gives it estrogenic activity. When it binds to estrogen receptors in the body's cells, it produces estrogenic or anti-estrogen effects, thereby causing endocrine disorders, interfering with the reproductive system, and inducing adverse effects such as precocious puberty in children. Studies have shown that bisphenol A can significantly increase the incidence of cancers such as ovarian cancer, prostate cancer, and leukemia in animals. In daily life, people can come into contact with bisphenol A through breathing, digestion, and skin contact, but the most harmful route of intake is when bisphenol A migrates from food contact materials to food. Especially when heated or in contact with acidic and alkaline substances, bisphenol A molecules will accelerate hydrolysis and are more likely to migrate from food contact materials or containers to food.

[0005] Chinese invention patent application CN103122201A discloses an inner iron-printing coating for food packaging, comprising: (a) bisphenol A, epichlorohydrin and a catalyst; (b) an amino resin crosslinker; (c) a phenolic resin; (d) a solvent; and (e) wax powder; wherein the catalyst is a catalyst for preparing bisphenol A epoxy resin from bisphenol A and epichlorohydrin; the mass ratio of bisphenol A to epichlorohydrin is (0.8-2):1, and the amount of catalyst added is 0.9-4.3w%. The curing time of the inner iron-printing coating described in the invention only takes 25-120s, and continuous printing can be performed; and it also has good corrosion resistance, boiling resistance and flexibility. Although studies have shown that the bisphenol A level exposed to the current coating is safe, coatings that do not contain bisphenol A or any other endocrine disruptors are what people have been pursuing.

[0006] Chinese invention patent application CN109071989A discloses a bisphenol A-free ethylene / (meth)acrylic acid copolymer composition for metal can coatings, the coating composition is prepared by mixing ethylene / (meth)acrylic acid copolymer and phenolic crosslinking agent, does not contain surfactant; the dispersion is stable and does not require a stabilizer to maintain dispersion. However, it has extremely high requirements on the molecular weight of the raw polymer and the content of acrylic acid, and the friction resistance, high temperature cooking resistance, hardness and other properties of the coating prepared by the coating still need to be improved. Summary of the invention

[0007] In view of the problems existing in the prior art, the present invention provides a coating composition free of bisphenol A and a preparation method and application thereof.

[0008] In order to achieve the purpose of the present invention, the following technical solutions are adopted:

[0009] A coating composition free of bisphenol A. The raw materials of the coating composition include: saturated polyester resin, rosin-modified unsaturated polyester resin, silicone-modified polyester resin, high-iminomethyl etherified amino resin, titanium dioxide, graphene oxide, lubricant, leveling agent, defoamer and solvent.

[0010] Preferably, the raw materials of the coating composition include, by weight: 25-35 parts of saturated polyester resin, 15-20 parts of rosin-modified unsaturated polyester resin, 10-15 parts of silicone-modified polyester resin, 10-25 parts of high-iminomethyl etherified amino resin, 1-2 parts of titanium dioxide, 4-5 parts of graphene oxide, 1-5 parts of lubricant, 1-2 parts of leveling agent, 1-3 parts of defoamer and 50-60 parts of solvent.

[0011] Preferably, the defoaming agent is tributyl phosphate.

[0012] Preferably, the lubricant is a mixture of polyethylene wax and polypropylene wax, and the mass ratio of the polyethylene wax to the polypropylene wax is 0.5-1:1.

[0013] Preferably, the solvent is a mixture of methyl acetate, isobutyl alcohol and cyclohexanone, and the mass ratio of methyl acetate, isobutyl alcohol and cyclohexanone is 1:0.8-1.2:0.5-1.

[0014] Preferably, the leveling agent is one or both of an organic silicon leveling agent and a polyacrylate leveling agent.

[0015] The present invention also relates to a method for preparing the coating composition, comprising the following steps:

[0016] (1) mixing a saturated polyester resin, a rosin-modified unsaturated polyester resin, a silicone-modified polyester resin, a high-iminomethyl etherified amino resin and a solvent to obtain a mixture 1;

[0017] (2) adding titanium dioxide and graphene oxide to mixture 1 and stirring to obtain mixture 2;

[0018] (3) Add lubricant, leveling agent and defoamer into mixture 2 and stir to obtain the coating mixture.

[0019] Preferably, the mixing temperature in step (1) is 50-60° C., the mixing speed is 1500-2000 rpm, and the mixing time is 1-2 h.

[0020] Preferably, the stirring speed in step (2) is 1200-1500 rpm, and the stirring time is 30-50 min; the stirring speed in step (3) is 1000-1200 rpm, and the stirring time is 3-5 h.

[0021] The invention also relates to the application of the coating composition in preparing coatings for food packaging or inner walls of beverage cans.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) The present invention uses saturated polyester resin, rosin-modified unsaturated polyester resin, silicone-modified polyester resin and high-imino methyl etherified amino resin, wherein the rosin-modified unsaturated polyester resin, silicone-modified polyester resin and high-imino methyl etherified amino resin produce a synergistic effect, thereby improving the friction resistance, boiling resistance and acid resistance of the coating;

[0024] (2) The coating composition of the present invention has excellent stability, the components are coordinated with each other, the formula amount is reasonable, and the coating composition product prepared is not only stable and uniform in nature, but also has high adhesion ability;

[0025] (3) The coating of the present invention has extremely strong anti-corrosion and anti-rust properties, and the preparation method of the coating of the present invention is simple, fast and has high production efficiency. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with its embodiments. It should be understood that the specific implementation methods described herein are only used to explain the present invention and do not limit the protection scope of the present invention.

[0027] Saturated polyester resin, model: YTDB-102; high iminomethyl etherified amino resin, model: YP5625A; polyethylene wax, model: 9615A; polypropylene wax, model: PP6252; all purchased from Shanghai Kaiyin Chemical Co., Ltd.

[0028] Silicone-modified polyester resin, product name: AD-1681, purchased from Dongguan Aide Synthetic Materials Co., Ltd.;

[0029] Rosin modified unsaturated polyester resin, product name: AS-UV01DP, purchased from Guangzhou Yabiao Technology Co., Ltd.;

[0030] Organic silicon leveling agent, model: HY-5057, was purchased from Beijing Maier Chemical Technology Co., Ltd.

[0031] The technical solution of the present invention is further specifically described below through examples. If there is no characteristic description, the raw materials can be obtained from the market.

[0032] Example 1

[0033] A coating composition free of bisphenol A, wherein the raw materials of the coating composition are, by weight:

[0034] 30 parts of saturated polyester resin, 16 parts of rosin modified unsaturated polyester resin, 14 parts of silicone modified polyester resin, 15 parts of high iminomethyl etherified amino resin, 1.5 parts of titanium dioxide, 4.5 parts of graphene oxide, 3 parts of lubricant (polyethylene wax and polypropylene wax in a mass ratio of 0.8:1), 1.5 parts of silicone leveling agent, 2 parts of tributyl phosphate and 45 parts of solvent (methyl acetate, isobutyl alcohol and cyclohexanone in a mass ratio of 1:1:0.8).

[0035] A method for preparing a coating composition free of bisphenol A, comprising the following steps:

[0036] (1) mixing a saturated polyester resin, a rosin-modified unsaturated polyester resin, a silicone-modified polyester resin, a high-iminomethyl etherified amino resin, a phenolic resin and a solvent at 55° C. and 1800 rpm for 1.5 h to obtain a mixture 1;

[0037] (2) adding titanium dioxide and graphene oxide to mixture 1, stirring at 1300 rpm for 40 min, to obtain mixture 2;

[0038] (3) Add polyethylene wax, polypropylene wax, silicone leveling agent and tributyl phosphate into mixture 2, and stir at 1100 rpm for 4 hours to obtain the coating mixture.

[0039] Example 2

[0040] A coating composition free of bisphenol A, wherein the raw materials of the coating composition are, by weight:

[0041] 25 parts of saturated polyester resin, 15 parts of rosin modified unsaturated polyester resin, 10 parts of silicone modified polyester resin, 10 parts of high iminomethyl etherified amino resin, 1 part of titanium dioxide, 4 parts of graphene oxide, 1 part of lubricant (polyethylene wax and polypropylene wax in a mass ratio of 0.5:1), 1 part of silicone leveling agent, 1 part of tributyl phosphate and 50 parts of solvent (methyl acetate, isobutyl alcohol and cyclohexanone in a mass ratio of 1:0.8:0.5).

[0042] A method for preparing a coating composition free of bisphenol A, comprising the following steps:

[0043] (1) mixing a saturated polyester resin, a rosin-modified unsaturated polyester resin, a silicone-modified polyester resin, a high-iminomethyl etherified amino resin, a phenolic resin and a solvent at 50° C. and 1500 rpm for 2 h to obtain a mixture 1;

[0044] (2) adding titanium dioxide and graphene oxide to mixture 1, stirring at 1200 rpm for 50 min, to obtain mixture 2;

[0045] (3) Add polyethylene wax, polypropylene wax, silicone leveling agent and tributyl phosphate into mixture 2, and stir at 1000 rpm for 5 hours to obtain the coating mixture.

[0046] Example 3

[0047] A coating composition free of bisphenol A, wherein the raw materials of the coating composition are, by weight:

[0048] 35 parts of saturated polyester resin, 20 parts of rosin modified unsaturated polyester resin, 15 parts of silicone modified polyester resin, 25 parts of high iminomethyl etherified amino resin, 2 parts of titanium dioxide, 5 parts of graphene oxide, 5 parts of lubricant (polyethylene wax and polypropylene wax in a mass ratio of 1:1), 2 parts of silicone leveling agent, 3 parts of tributyl phosphate and 60 parts of solvent (methyl acetate, isobutyl alcohol and cyclohexanone in a mass ratio of 1:1.2:1).

[0049] A method for preparing a coating composition free of bisphenol A, comprising the following steps:

[0050] (1) mixing a saturated polyester resin, a rosin-modified unsaturated polyester resin, a silicone-modified polyester resin, a high-iminomethyl etherified amino resin, a phenolic resin and a solvent at 60° C. and 2000 rpm for 1 h to obtain a mixture 1;

[0051] (2) adding titanium dioxide and graphene oxide to mixture 1, stirring at 1500 rpm for 30 min, to obtain mixture 2;

[0052] (3) Add polyethylene wax, polypropylene wax, silicone leveling agent and tributyl phosphate into mixture 2, and stir at 1200 rpm for 3 hours to obtain the coating mixture.

[0053] Comparative Example 1

[0054] A coating composition free of bisphenol A, wherein the raw materials of the coating composition differ from those of Example 1 only in that: 45 parts of rosin-modified unsaturated polyester resin, 0 parts of silicone-modified polyester resin, and 0 parts of high-iminomethyl etherified amino resin, and the rest are consistent with Example 1.

[0055] Comparative Example 2

[0056] A coating composition free of bisphenol A, wherein the raw materials of the coating composition differ from those of Example 1 only in that: 0 parts of rosin-modified unsaturated polyester resin, 21.7 parts of silicone-modified polyester resin, and 23.3 parts of high-iminomethyl etherified amino resin, and the rest are consistent with Example 1.

[0057] Comparative Example 3

[0058] A coating composition free of bisphenol A, wherein the raw materials of the coating composition differ from those of Example 1 only in that: 16 parts of rosin-modified unsaturated polyester resin, 29 parts of silicone-modified polyester resin, 0 parts of high-iminomethyl etherified amino resin, and the rest are consistent with Example 1.

[0059] Comparative Example 4

[0060] A coating composition free of bisphenol A, wherein the raw materials of the coating composition differ from those of Example 1 only in that: 16 parts of rosin-modified unsaturated polyester resin, 0 parts of silicone-modified polyester resin, 29 parts of high-iminomethyl etherified amino resin, and the rest are consistent with Example 1.

[0061] Comparative Example 5

[0062] A coating composition free of bisphenol A, wherein the raw materials of the coating composition differ from those of Example 1 only in that the solvent is isobutyl alcohol and cyclohexanone in a mass ratio of 2.2:1, and the rest is consistent with Example 1.

[0063] Comparative Example 6

[0064] A coating composition free of bisphenol A, wherein the raw materials of the coating composition differ from those of Example 1 only in that the solvent is methyl acetate and cyclohexanone in a mass ratio of 2.2:1, and the rest is consistent with Example 1.

[0065] Comparative Example 7

[0066] A coating composition free of bisphenol A, which differs from Example 1 only in that the preparation method is different. In this comparative example, all components are mixed at the same time and stirred evenly at 1200 rpm.

[0067] Effect test

[0068] Inspect the appearance, butanone wiping resistance, pencil hardness, boiling resistance, acid resistance and sulfur resistance of the samples. The test methods are as follows:

[0069] The coating compositions prepared in Examples 1-3 and Comparative Examples 1-7 were coated on an aluminum substrate by roller coating and baked at 200° C. for 15 minutes to form a film with a thickness of 10 μm.

[0070] Paint coating gloss test: According to GB / T8807-1988 method, use 60° angle for measurement.

[0071] Butanone resistant wiping: refer to the method of standard GB / T17748;

[0072] Pencil hardness: The scratch resistance of the sprayed coating composition was tested according to GB / T6739-2006, with the scratch of the coating film as the test standard. The substrate was tinplate and the pencil was a Chinese pencil.

[0073] Boiling resistance: According to GB / T1733, after the coating is prepared, it is boiled in a high-pressure vertical sterilizer at 127℃-65min in water phase and steam phase;

[0074] Acid resistance: The sample was sterilized in a 5wt% acetic acid aqueous solution at 120℃ and high temperature and pressure for 30min;

[0075] Sulfur resistance: The sample was sterilized in a 1wt% sodium sulfide aqueous solution at 121℃ and high temperature and pressure for 30min;

[0076] Adhesion test method: The adhesion test was conducted according to ASTM D3359 Test Method B and evaluated on a scale of 0-5, where a score of "0" indicates no adhesion failure and a score of "5" indicates that the film completely leaves the substrate. The specific test results are shown in Table 1.

[0077] Table 1 Test results

[0078]

[0079] The above detailed description is a specific description of one feasible embodiment of the present invention. The embodiment is not intended to limit the patent scope of the present invention. Any equivalent implementation or modification that does not deviate from the present invention should be included in the scope of the technical solution of the present invention.

Claims

1. A coating composition free of bisphenol A, characterized in that: The raw materials of the coating composition include, by weight: 25-35 parts of saturated polyester resin, 15-20 parts of rosin-modified unsaturated polyester resin, 10-15 parts of silicone-modified polyester resin, 10-25 parts of high-iminomethyl etherified amino resin, 1-2 parts of titanium dioxide, 4-5 parts of graphene oxide, 1-5 parts of lubricant, 1-2 parts of leveling agent, 1-3 parts of defoamer and 50-60 parts of solvent; The solvent is a mixture of methyl acetate, isobutyl alcohol and cyclohexanone, and the mass ratio of methyl acetate, isobutyl alcohol and cyclohexanone is 1:0.8-1.2:0.5-1; The method for preparing the coating composition comprises the following steps: (1) mixing a saturated polyester resin, a rosin-modified unsaturated polyester resin, a silicone-modified polyester resin, a high-iminomethyl etherified amino resin and a solvent to obtain a mixture 1; (2) adding titanium dioxide and graphene oxide to mixture 1 and stirring to obtain mixture 2; (3) Add the lubricant, leveling agent and defoamer into mixture 2 and stir to obtain the coating mixture.

2. The coating composition according to claim 1, characterized in that The defoaming agent is tributyl phosphate.

3. The coating composition according to claim 1, characterized in that The lubricant is a mixture of polyethylene wax and polypropylene wax, and the mass ratio of the polyethylene wax to the polypropylene wax is 0.5-1:

1.

4. The coating composition according to claim 1, characterized in that The leveling agent is one or both of an organic silicon leveling agent and a polyacrylate leveling agent.

5. A method for preparing the coating composition according to any one of claims 1 to 4, characterized in that: The following steps are involved: (1) mixing a saturated polyester resin, a rosin-modified unsaturated polyester resin, a silicone-modified polyester resin, a high-iminomethyl etherified amino resin and a solvent to obtain a mixture 1; (2) adding titanium dioxide and graphene oxide to mixture 1 and stirring to obtain mixture 2; (3) Add the lubricant, leveling agent and defoamer into mixture 2 and stir to obtain the coating mixture.

6. The preparation method according to claim 5, characterized in that: The mixing temperature in step (1) is 50-60° C., the mixing speed is 1500-2000 rpm, and the mixing time is 1-2 h.

7. The preparation method according to claim 5, characterized in that: The stirring speed in step (2) is 1200-1500 rpm, and the stirring time is 30-50 min; the stirring speed in step (3) is 1000-1200 rpm, and the stirring time is 3-5 h.

8. Use of the coating composition according to any one of claims 1 to 4 in preparing a coating for the inner wall of a food or beverage container.

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