Preparation method of ultraviolet curing coating used in metal packaging field

Abstract

The invention discloses a preparation method of an ultraviolet curing coating used in the field of metal packaging. The ultraviolet curing coating is prepared from the following components in parts by weight: 10 to 30 parts of special modified acrylate, 20 to 50 parts of urethane acrylate, 10 to 40 parts of functional active monomer, 2 to 5 parts of photoinitiator and 0.5 to 3 parts of surface additive. According to the present invention, the excellent characteristics of thin coating, high gloss, high leveling property and fullness can be ultimately achieved, the scratch resistance exceeds 2000 g can be obtained under the condition that the thickness is less than 5 [mu] m, the 3 cm deep drawing canning coating does not crack, and the coating can be widely used in the fields of metal can packaging and the like with various deep drawing and stretching requirements.

Description

Technical Field

[0001] The invention belongs to the technical field of ultraviolet curing coating preparation, and in particular relates to a method for preparing ultraviolet curing coating used in the field of metal packaging. Background Art

[0002] There are all kinds of metal packaging in our lives, which are widely used in food, medicine, daily necessities, industrial products, instruments and meters, etc. The coating used for metal packaging is very important. It must not only have good adhesion and surface effects, but also have strict requirements in terms of rust resistance, scratch resistance, wear resistance and metal processing and forming. Especially for the food packaging category with the largest consumption, the final coating after curing must meet the food packaging standards, etc. The amount of coating used for metal packaging is very large, but the market is still using traditional solvent-type coatings, which require a large oven with a temperature of more than 150°C and baking for about 15 minutes to fully cure the coating. The large amount of VOC emitted during the process affects human health and environmental protection.

[0003] Therefore, it is of great significance to develop new pollution-free and low-energy metal coatings, and UV-curing coatings are a very important direction, which have the advantages of solvent-free, environmentally friendly, fast curing and high production efficiency.

[0004] Chinese patent CN201710307621.8 proposes a method for preparing UV iron printing coating, the main component of which is a mixture of thermoplastic acrylate and epoxy acrylate, which cannot meet the deep drawing requirements of two-piece cans, and the energy required for coating curing must reach 400mj / cm 2 The above is also not applicable to food packaging. Although the cationic curing technology disclosed in Chinese patent CN202110498122.8 can meet the needs of food packaging, the current market price of cationic raw materials is expensive, there are few choices, the curing speed is slow, and there is high brittleness, which cannot meet the needs of high-deep punching. Summary of the invention

[0005] In order to solve the VOC emission and high energy consumption problems of traditional solvent-baked coatings, and further improve the performance of UV-curable coatings in the field of metal cans such as tinplate printing, and accelerate the replacement of traditional solvent-based coatings with thermal baking technology by UV-curing technology in the field of metal packaging, the present invention provides a method for preparing UV-curable coatings for metal packaging. The present invention proposes a synthesis of modified acrylate and polyurethane acrylate, which can be used in metal packaging such as tinplate printing and cans with active monomers, additives, photoinitiators and other ingredients, and has achieved new breakthroughs in curing, deep drawing performance, scratch resistance, surface effects, safety performance and other aspects.

[0006] The technical solution adopted by the present invention is:

[0007] A method for preparing a UV-curable coating for metal packaging, characterized in that the UV-curable coating is composed of the following components in parts by weight:

[0008] Special modified acrylate: 10-30 parts

[0009] Polyurethane acrylate: 20-50 parts

[0010] Functional active monomer: 10-40 parts

[0011] Photoinitiator: 2-5 parts

[0012] Surface additive: 0.5-3 parts;

[0013] The synthesis steps of the special modified acrylate are as follows: a mixture of 2-acrylic acid-2-hydroxy-3-phenoxypropyl ester, 4-hydroxybutyl acrylate and styrene is controlled at a reaction temperature of 75-80°C under nitrogen protection conditions, slowly added dropwise for reaction for 4-4.5 hours, then the temperature is controlled at 55-60°C, 2,6-di-tert-butyl-p-cresol is added, isocyanate ethyl acrylate is slowly added dropwise, and reacted for 4-4.5 hours, washed with ethyl acetate and rotary evaporated, then polyether modified siloxane is added at 50-55°C, fully reacted for 1-2 hours, and then modified nano-SiO2 and polytetrafluoroethylene powder are added respectively, and reacted for 4-5 hours to obtain the final product.

[0014] Furthermore, the 2-hydroxy-3-phenoxypropyl 2-acrylic acid, 4-hydroxybutyl acrylate, styrene, ethyl isocyanate acrylate, modified nano-SiO2, polytetrafluoroethylene powder, polyether-modified siloxane, azobisisobutyronitrile, and 2,6-di-tert-butyl-p-cresol are respectively calculated in parts by mass: 40-60 parts of 2-hydroxy-3-phenoxypropyl 2-acrylic acid, 20-30 parts of 4-hydroxybutyl acrylate, 30-40 parts of styrene, 28-42 parts of ethyl isocyanate acrylate, 3-6 parts of modified nano-SiO2, 3-5 parts of polytetrafluoroethylene powder, 1-3 parts of polyether-modified siloxane, 0.5-1.5 parts of azobisisobutyronitrile, and 0.2-1.0 parts of 2,6-di-tert-butyl-p-cresol.

[0015] Furthermore, the polyurethane acrylate is composed of the following components in parts by weight:

[0016] Polyester polyol: 40-50 parts

[0017] 4,4′-dicyclohexylmethane diisocyanate: 10-14 parts

[0018] N-(3-aminopropyl) acrylamide: 5-7 parts

[0019] 4-tert-Butylcyclohexyl acrylate: 5-20 parts

[0020] Catalyst: 0.05-0.20 parts

[0021] Inhibitor: 0.1-0.5 parts;

[0022] 4-tert-butylcyclohexyl acrylate and a polymerization inhibitor are added to 4,4′-dicyclohexylmethane diisocyanate under nitrogen protection, the temperature is controlled at 35-40° C., N-(3-aminopropyl) acrylamide is slowly added dropwise, and then the temperature is raised to 60-65° C., and the reaction is carried out for 3-3.5 hours. Then, polyester polyol is added, a catalyst is added, and the reaction is carried out at 68-73° C. for 2 hours, and then the temperature is raised to 75-80° C. and the reaction is carried out for 2 hours to obtain the polyurethane acrylate.

[0023] Furthermore, the synthesis steps of the modified nano-SiO2 are: nano-SiO2 is dispersed in a butyl acetate solvent of γ-methacryloxypropyltrimethoxysilane, reacted at 78-82°C for 3-3.5h, washed and rotary evaporated, and dried at 60-65°C for 12h to obtain the modified nano-SiO2; wherein the modified nano-SiO2, γ-methacryloxypropyltrimethoxysilane and butyl acetate are 10-30 parts, 15-30 parts and 40-100 parts by mass, respectively.

[0024] Furthermore, the polyester polyol has a number average molecular weight of 2000 g / mol and is a copolymer containing a carbonate structure;

[0025] The inhibitor is p-hydroxyanisole;

[0026] The catalyst is one or more of bis(dimethylaminoethyl)ether, dibutyltin dilaurate, organic tin, organic bismuth and pentamethyldiethylenetriamine.

[0027] Furthermore, the functionally active monomer is one or more of ethoxylated trimethylolpropane triacrylate, 3,3,5-trimethylcyclohexyl acrylate, cyclohexyl methacrylate, cyclotrimethylolpropane formal acrylate, 2-phenoxyethyl acrylate, 1,6-hexanediol diacrylate, and tricyclodecane dimethanol diacrylate.

[0028] Furthermore, the photoinitiator is one or more of polymerized [2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]propanone, bimolecular 2-hydroxy-2-methylpropiophenone, bimolecular hydroxycyclohexylphenyl ketone, bimolecular methyl o-benzoylbenzoate, and polymerized methyl benzoate.

[0029] Furthermore, the UV-curing coating in the field of metal packaging has a viscosity range of 200-800 mPa.s / 25°C as required, which is suitable for thin-coating roller coating construction technology.

[0030] Furthermore, the polytetrafluoroethylene powder is a powder with a particle size less than 5 um.

[0031] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0032] 1. The present invention is applicable to UV-curable coatings in the field of metal packaging, and is suitable for thin-film roller coating construction technology. Under the coating condition of less than 5um film thickness, its curing energy is less than 300mj / cm 2 , can be cured instantly. Compared with the existing light curing technology, the scratch resistance can reach 2000g, which can meet the requirements of deep drawing of two-piece cans with a coating of 3cm without cracking. It has good surface effect, low toxicity and low migration, and is suitable for a variety of metal packaging needs.

[0033] 2. The polyurethane acrylate of the present invention is specially designed to have the characteristics of strong anti-oxidation and polymerization inhibition, fast curing speed for thin coatings, and excellent toughness, which makes an important contribution to the high deep drawing performance of UV-curing coatings.

[0034] 3. The present invention is widely applicable to various fields such as metal can packaging requiring deep drawing and stretching. DETAILED DESCRIPTION

[0035] The specific implementation of the embodiment of the present invention is described in detail below. It should be understood that the specific implementation described here is only used to illustrate and explain the embodiment of the present invention, and is not used to limit the embodiment of the present invention.

[0036] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0037] The present invention will be described in detail below with reference to exemplary embodiments.

[0038] The preparations used in the present invention are all commercially available conventional products as long as they are qualified industrial products regardless of the manufacturer.

[0039] In the present invention, the following terms have the specified meanings:

[0040]

[0041]

[0042] Example 1 Preparation of modified nano-SiO2

[0043] Prepare according to the following formula composition

[0044]

[0045] First add component No. 3 to the flask, then add the above-mentioned components 1 and 2, react at 80°C for 3 hours, wash with ethyl acetate several times and rotary evaporate, and dry at 60°C for 12 hours to obtain 29.5g and 23g of the desired products respectively.

[0046] Example 2 Preparation of special modified acrylate

[0047] The resin is synthesized according to the following formula:

[0048]

[0049] The above components No. 1, 2, 3, and 10 were added to a flask. Under nitrogen protection, the reaction temperature was controlled at 75-80°C, and group 9 was slowly added and reacted for 4 hours. The temperature was then controlled at 55-60°C, and group 8 was slowly added and reacted for 4 hours. The isocyanate was tested to be less than 0.1%. After washing with ethyl acetate and rotary evaporation, group 7 was added at 50°C and fully reacted for 1 hour. Then groups 4, 5, and 6 were added respectively. After reacting for 5 hours, the final products were 119g and 117g respectively. 、 150g, 135g.

[0050] Example 3 Preparation of polyurethane acrylate

[0051] The resin is synthesized according to the following formula:

[0052]

[0053] Add the above 4 and 6 components to the flask, add 2 components under nitrogen protection, control the temperature at 35-40℃, slowly drop 1 component, then heat to 60-65℃ and react for 3h, then add 3 and 5 components respectively and react at 70℃ for 2h, then heat to 75-80℃ and react for 2h to obtain 70g of product. 、 72.5 g, tested isocyanate less than 0.1%.

[0054] Example 4 Preparation of UV-curable coating

[0055]

[0056]

[0057] Example 5 Test methods and results

[0058] Substrate: Tinplate coated with white tin;

[0059] Curing light source: medium pressure mercury lamp;

[0060] Curing energy: 300mj / cm 2 , the poorly cured formulations were cured several more times so that their performance could be tested.

[0061] Construction method: roller coating, coating film thickness is 3-5um;

[0062] Impact resistance: 1kg, 50cm;

[0063] Deep drawing: 3cm forming by punching machine.

[0064]

[0065]

[0066] From the above data, we can see that compared with market samples, the self-synthesized special modified acrylates and polyurethane acrylates have outstanding excellent properties, greatly improving the scratch resistance, curing effect and deep drawing performance. Through formula debugging, we finally successfully developed a low-energy, fast-curing UV-curing coating with low migration, which meets food packaging standards and can be applied to a variety of metal packaging requirements.

[0067] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for preparing a UV-curable coating for metal packaging, characterized in that: The UV curing coating is composed of the following components in parts by weight: Special modified acrylate: 10-30 parts Polyurethane acrylate: 20-50 parts Functional active monomer: 10-40 parts Photoinitiator: 2-5 parts Surface additive: 0.5-3 parts; The synthesis steps of the special modified acrylate are as follows: a mixture of 2-acrylic acid-2-hydroxy-3-phenoxypropyl ester, 4-hydroxybutyl acrylate and styrene is controlled at a reaction temperature of 75-80°C under nitrogen protection conditions, azobisisobutyronitrile is slowly added dropwise for reaction for 4-4.5 hours, the temperature is then controlled at 55-60°C, 2,6-di-tert-butyl-p-cresol is added, isocyanate ethyl acrylate is slowly added dropwise for reaction for 4-4.5 hours, washing with ethyl acetate and rotary evaporation are performed, polyether modified siloxane is added at 45-55°C, the reaction is fully performed for 1-2 hours, and modified nano-SiO2 and polytetrafluoroethylene powder are respectively added for reaction for 4-5 hours to obtain the final product.

2. The method for preparing a UV-curable coating for metal packaging according to claim 1, characterized in that: The 2-hydroxy-3-phenoxypropyl 2-acrylic acid, 4-hydroxybutyl acrylate, styrene, ethyl isocyanate acrylate, modified nano-SiO2, polytetrafluoroethylene powder, polyether-modified siloxane, azobisisobutyronitrile and 2,6-di-tert-butyl-p-cresol are respectively calculated in parts by mass: 40-60 parts of 2-hydroxy-3-phenoxypropyl 2-acrylic acid, 20-30 parts of 4-hydroxybutyl acrylate, 30-40 parts of styrene, 28-42 parts of ethyl isocyanate acrylate, 3-6 parts of modified nano-SiO2, 3-5 parts of polytetrafluoroethylene powder, 1-3 parts of polyether-modified siloxane, 0.5-1.5 parts of azobisisobutyronitrile and 0.2-1.0 parts of 2,6-di-tert-butyl-p-cresol.

3. The method for preparing a UV-curable coating for metal packaging according to claim 1, characterized in that: The polyurethane acrylate is composed of the following components in parts by weight: composition: Polyester polyol: 40-50 parts 4,4′-dicyclohexylmethane diisocyanate: 10-14 parts N-(3-aminopropyl) acrylamide: 5-7 parts 4-tert-Butylcyclohexyl acrylate: 5-20 parts Catalyst: 0.05-0.20 parts Inhibitor: 0.1-0.5 parts; 4-tert-butylcyclohexyl acrylate and a polymerization inhibitor are added to 4,4′-dicyclohexylmethane diisocyanate under nitrogen protection, the temperature is controlled at 35-40° C., N-(3-aminopropyl) acrylamide is slowly added dropwise, and then the temperature is raised to 60-65° C., and the reaction is carried out for 3-3.5 hours. Then, polyester polyol is added, a catalyst is added, and the reaction is carried out at 68-73° C. for 2 hours, and then the temperature is raised to 75-80° C. and the reaction is carried out for 2 hours to obtain the polyurethane acrylate.

4. The method for preparing a UV-curable coating for metal packaging according to claim 1, characterized in that: The synthesis steps of the modified nano-SiO2 are as follows: the nano-SiO2 is dispersed in a butyl acetate solvent of γ-methacryloxypropyltrimethoxysilane, reacted at 78-82°C for 3-3.5h, washed and rotary evaporated, and dried at 60-65°C for 12h to obtain the modified nano-SiO2; wherein the modified nano-SiO2, γ-methacryloxypropyltrimethoxysilane and butyl acetate are 10-30 parts, 15-30 parts and 40-100 parts by mass, respectively.

5. The method for preparing a UV-curable coating for metal packaging according to claim 1, characterized in that: The polyester polyol has a number average molecular weight of 2000 g / mol and is a copolymer containing a carbonate structure; The inhibitor is p-hydroxyanisole; The catalyst is one or more of bis(dimethylaminoethyl)ether, dibutyltin dilaurate, organic tin, organic bismuth and pentamethyldiethylenetriamine.

6. The method for preparing a UV-curable coating for metal packaging according to claim 1, characterized in that: The functionally active monomer is one or more of ethoxylated trimethylolpropane triacrylate, 3,3,5-trimethylcyclohexyl acrylate, cyclohexyl methacrylate, cyclotrimethylolpropane formal acrylate, 2-phenoxyethyl acrylate, 1,6-hexanediol diacrylate, and tricyclodecane dimethanol diacrylate.

7. The method for preparing a UV-curable coating for metal packaging according to claim 1, characterized in that: The photoinitiator is one or more of polymerized [2-hydroxy-2-methyl-1-[4-(1-methylvinyl)phenyl]acetone, bimolecular 2-hydroxy-2-methylphenylacetone, bimolecular hydroxycyclohexylphenylketone, bimolecular methyl o-benzoylbenzoate, and polymerized methyl benzoate.

8. A method for preparing a UV-curable coating for metal packaging according to any one of claims 1 to 7, characterized in that: The UV-curing coating used in the metal packaging field has a viscosity range of 200-800 mpa.s / 25°C configured as required, and is suitable for a thin-coating roller coating construction process.

9. The method for preparing a UV-curable coating for metal packaging according to claim 1, characterized in that: The polytetrafluoroethylene powder is a powder with a particle size of less than 5 μm.

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