JPH0519591B2 - - Google Patents

Description

[Detailed description of the invention]

[Object of the Invention] (Field of Application of the Invention) The present invention relates to a coating composition for cans for producing coated plates for cans by a wet-on-wet coating method. (Prior art) Conventionally, cans for cans have been coated with thermosetting paint such as epoxy-phenol type paint or epoxy-amino type paint as a protective coating on the inner surface to prevent metal elution and corrosion of the can. There is. Cans for cans are obtained by applying these paints to a metal plate (tin plate, stain-free steel plate, aluminum plate) by roll coating, and processing this coated plate. Therefore, the method of applying these paints to a metal plate is one coat and one bake. However, when this one-coat, one-bake coating is subjected to severe processing such as bending or stretching during the can manufacturing process, the coating often cracks or peels off. It is difficult to balance the performance required for can coatings, such as flavor, retort resistance, and sulfur resistance (blackening of the underlying metal surface due to sulfides contained in the contents). Therefore, we decided to use punched cans and DR, which have particularly severe processing conditions.
(Draw and Redraw) Epoxy for cans
A two-coat, two-bake system is used in which a phenol type paint or epoxy-amino type paint is applied and baked, and then a vinyl type paint, which has excellent bending and stretching properties, is applied. However, manufacturing a coated board using two coats and two bakes requires more time and energy than one coat and one bake. So 2
A wet-on-wet painting method was devised in which one coat of bake is applied, that is, after applying the epoxy-phenol type paint or the epoxy-amino type paint, a vinyl type paint is applied immediately without baking, thereby omitting one baking step. However, the following problems were found. In other words, when wet-on-wet painting is performed using a normal epoxy-phenol paint or epoxy-amino paint that contains a relatively large amount of ester/ether solvents, flow (streak-like irregularities occur on the paint film parallel to the painting direction). ), crawling (the occurrence of crater-like and zigzag-like irregularities on the paint film due to the influence of hot air during baking), etc., occur severely, resulting in an uneven and uneven paint film, which impairs the aesthetic appearance and prevents sufficient coating. It was not possible to obtain membrane performance. Therefore, there has been a strong desire to develop a coating material with excellent coating suitability for wet-on-wet coating methods. (Problems to be Solved by the Invention) The present invention has been made in view of the above-mentioned current situation, and its purpose is to apply an epoxy-phenol type paint or an epoxy-amino type paint as a base coat on a metal plate, and then immediately apply it to the metal plate. To provide a base coat paint that has excellent flow and crawling properties when a vinyl type paint is applied as a top coat. [Structure of the Invention] (Means for Solving the Problems) As a result of intensive research in order to solve the above problems, the present inventors have discovered that aromatic and ketone solvents can be used in large amounts as solvents for base coat paints. Contains
It has been found that the above problems can be completely solved by keeping the amount of ester and ether solvents as small as possible. That is, the present invention provides an epoxy-phenol type paint or an epoxy-phenol type paint on a metal plate.
A paint used in the manufacture of coated plates for cans, in which an amino-type paint and then a vinyl-type paint are applied wet-on-wet and cured by heating.
A wet-on-wet paint composition for cans, characterized in that the solvent composition of the phenol type paint or epoxy-amino type paint satisfies the following formulas (i) to (iv). (i) 70≦AR＋KE≦85 (ii) 20≦ES＋KE (iii) 1≦AL≦20 (iv) 0≦ES≦13 (AR is aromatic solvent, KE is ketone solvent, ES is ester (The ether solvent, AL represents an aliphatic alcohol, and the numbers are weight %.) The following solvents are used in the present invention. Examples of aromatic solvents include aromatic compounds substituted or unsubstituted with alkyl groups, such as toluene, xylene, benzene, ethylbenzene, solvent naphtha No. 1 to 3, Solbetsuso 100 with an aromatic content of 95% to 99.5%, Solbetsuso 150 (all product names,
Examples include aromatic petroleum naphthas such as Etsuso Standard Oil Co., Ltd.). Examples of ketone solvents include solvents having at least one carbonyl group in one molecule, such as acetone, methyl ethyl ketone, diethyl ketone, methyl normal propyl ketone, methyl isobutyl ketone,
Diisopropyl ketone, mesityl oxide methyl butyl ketone, dipropyl ketone, ethyl butyl ketone, methyl isoamyl ketone, methyl amyl ketone, cyclohexanone, ethyl amyl ketone, methoxymethyl pentanone, diisobutyl ketone, methoxymethyl pentanol, diacetone alcohol, Examples include acetophenone and isophorone. Examples of aliphatic alcohols include methyl alcohol, ethyl alcohol, isopropyl alcohol, tert-butyl alcohol, normal propyl alcohol, sec-butyl alcohol, isobutyl alcohol, normal butyl alcohol, pentyl alcohol,
activated amyl alcohol, isoamyl alcohol,
Positive amyl alcohol, positive hexyl alcohol, 2
-Ethylbutyl alcohol, methylamyl alcohol, 2-ethylhexyl alcohol, normal octyl alcohol, etc. Examples of ester/ether solvents include ester bonds, ether bonds, or both bonds in one molecule, such as methyl acetate, ethyl acetate, isopropyl acetate, orthopropyl acetate, ethyl propionate, sec-butyl acetate, and lactate. Orthoethyl acetate, isobutyl acetate, orthobutyl acetate, ethylene glycol monoethyl acetate, propylene glycol monomethyl ether, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, 3-methoxybutanol, ethylene glycol monobutyl ether, Examples include diethylene glycol monobutyl ether. The important point in the present invention is to contain a large amount of aromatic and ketone solvents in the base coat paint and to keep the ester/ether solvents at 13% by weight or less of the total solvent. - The parent solvents in phenolic and epoxy-amino paints are esters, ethers, and ketones, so if these solvents are reduced in the base coat paint, the solubility of epoxy resins, phenolic resins, or amino resins will decrease. In particular, when using a high molecular weight epoxy resin (weight average molecular weight of 1300 or more), the resin becomes suspended and a uniform coating film cannot be obtained. Therefore, as for the solvent composition of the base coat, the total of ester/ether and ketone solvents accounts for the total solvent composition.
It is preferably 20% by weight or more. Furthermore, if the content of the ester/ether solvent exceeds 13% by weight, flow and crawling will deteriorate, the surface of the coating film will become more uneven, and the coating film performance will not be fully exhibited. Furthermore, if the aliphatic alcohol solvent exceeds 26% by weight, or if the total amount of aromatic and ketone solvents exceeds 85% by weight, flow and crawling will similarly deteriorate and the coating surface will become uneven. becomes intense and the coating film performance is not fully demonstrated. The epoxy resin in the epoxy-phenol paint and epoxy-amino paint in the present invention is produced by condensing epihalohydrin and bisphenol A to a high molecular weight in the presence of an alkali catalyst, or by condensing epihalohydrin and bisphenol A to a high molecular weight in the presence of an alkali catalyst. It is produced by condensing a low molecular weight epoxy resin and subjecting this low molecular weight epoxy resin to a polyaddition reaction with bisphenol A. The phenol resin in the epoxy-phenol paint in the present invention is a resin obtained by condensing any phenol component and formaldehyde in the presence of a basic catalyst, and the phenol component includes:
o-cresol, p-cresol, p-tert-butylphenol, p-ethylphenol, 2,3
-xylenol, 2,5-xylenol, p-
Bifunctional phenols such as tert-aminophenol, p-nonylphenol, p-phenylphenol, p-cyclohexylphenol, carbolic acid, m-cresol, m-ethylphenol,
Trifunctional phenols such as 3,5-xylenol and m-methoxyphenol, monofunctional phenols such as 2,4-xylenol and 2,6-xylenol, bisphenol A, bisphenol B, bisphenol F, etc. Tetrafunctional phenols and the like may be used alone or in combination of two or more. The amino resin in the epoxy-amino paint in the present invention is a condensation product of one or more of urea, melamine, benzoguanamine, etc. and formaldehyde, or a part of the methylol group of the condensation product is etherified with alcohol. As the alcohol to be etherified, methyl alcohol, normal butyl alcohol, isobutyl alcohol, etc. are used. The epoxy/phenol type paint or epoxy/amino type paint in the present invention can be obtained by dissolving the resin component in the above-mentioned organic solvent so that the resin solid content is 20 to 50% by weight. The vinyl type paint in the present invention refers to vinyl chloride-vinyl acetate copolymer, vinyl chloride-vinyl acetate-maleic acid copolymer, and vinyl chloride-vinyl acetate-vinyl alcohol copolymer, etc. alone or in combination of two or more. The resin was dissolved in a mixed solvent of a ketone solvent and an aromatic solvent, or a mixed solvent containing an ester/ether solvent or an aliphatic alcohol, to a resin solid content of 20 to 50% by weight. It is something. Furthermore, in order to improve the adhesion with the undercoat paint, an epoxy resin, phenol resin, amino resin, or the like may be blended with the resin component. Hereinafter, the present invention will be specifically explained with reference to Examples. In the examples, "parts" and "%" indicate parts by weight and % by weight. (Example) [Production of epoxy resin solution A] Epicoat 1009 manufactured by Yuka Ciel Epoxy Co., Ltd. was mixed with xylene/cyclohexanone/isophorone 1/1/1.
A 50% epoxy resin solution A was obtained by dissolving it in a mixed solvent. [Manufacture of epoxy resin solution B] Epicote 1007 manufactured by Yuka Ciel Epoxy Co., Ltd. was mixed with Solbetsuso 100/MIBK/Cyclohexanone 1/1/
50% epoxy resin solution B dissolved in mixed solvent of 1
I got it. [Manufacture of phenolic resin solution C] 228 parts of bisphenol A, 40 parts of formaldehyde
After reacting 225 parts of % normal butyl alcohol solution and 17 parts of 25% ammonia aqueous solution at 100°C for 5 hours,
The mixture was diluted by adding 177 parts of xylene, 100 parts of normal butyl alcohol, and 177 parts of cyclohexanone, and further dehydrated to obtain a 36% phenol formaldehyde resin solution C. [Manufacture of phenolic resin solution D] 108 parts of p-cresol, 40 parts of formaldehyde
After reacting 75 parts of % normal butyl alcohol solution and 0.56 parts of magnesium hydroxide at 100°C for 1.5 hours,
Neutralize with phosphoric acid, add 77 parts of xylene, 58 parts of normal butyl alcohol, 77 parts of cyclohexanone, and 200 parts of water, leave to stand for 5 hours, separate and remove the aqueous layer containing the formed salt, and further azeotropically dehydrate. A 36% phenol formaldehyde resin solution D was obtained. [Manufacture of amino resin solution E] Betsukamine P-138 manufactured by Dainippon Ink and Chemicals Co., Ltd.
(butylated urea resin positive-butyl alcohol solution,
(non-volatile content: 60%) was used. [Manufacture of base coat paint] The above resin solutions A to E were mixed as shown in Table 1,
Furthermore, various solvents are added to increase the solvent composition in the paint.
Sixteen types of paints (nonvolatile content: 30%) of Examples 1 to 10 and Comparative Examples 1 to 6 were manufactured as shown in the table.

【table】

[Manufacture of top coat paint]

Vinylite in a mixed solvent of 45 parts of xylene, 25 parts of methyl ethyl ketone, and 30 parts of cyclohexanone.
A top coat paint with a solid content of 25% was produced by dissolving 33 parts of VMCH (manufactured by Union Carbide). [Manufacture of top coat paint] 20 parts of xylene, 15 parts of Solbetsuso 100 (manufactured by Etsuso)
parts, 20 parts of cyclohexanone, 25 parts of methyl isobutyl ketone, 10 parts of isophorone, 10 parts of ethyl cellosolve
Dissolve 26.4 parts of Vinyrite VYHH (manufactured by Union Carbide Co., Ltd.) and 6.6 parts of Vinyrite VAGH (manufactured by Union Carbide Co., Ltd.) in a mixed solvent of
manufactured top coat paints. The obtained paint was first baked on a 0.24 mm thick stain-free steel plate, and the paint film thickness after baking was determined.
Roll coat the paint to a thickness of 6μ, then immediately apply a wet-on-wet top coat paint so that the film thickness after baking is 10μ.
A painted board was obtained by baking at ℃ for 10 minutes. Table 3 below shows the evaluation of the surface condition of each coated board.

〔Effect of the invention〕

The paint composition for cans of the present invention can be used as a base coat for a vinyl type paint that is a top coat.
It is possible to adopt the bake painting method,
Moreover, the obtained baked coating film has the same performance and appearance as the coating film obtained by two coats and two bakes.
Therefore, the thermal energy required for baking the base coat can be saved, and the coating process can also be simplified, which is extremely useful from the viewpoint of energy saving and cost reduction.

Claims (1)

[Scope of Claims] 1. A paint used in the production of painted plates for cans, in which an epoxy-phenol type paint or an epoxy-amino type paint and then a vinyl type paint are applied wet-on-wet on a metal plate and cured by heating. hand,
As the solvent composition of the above epoxy-phenol type paint or epoxy-amino type paint, the following formula (i) ~
A wet-on-wet can coating composition that satisfies (iv). (i) 70≦AR＋KE≦85 (ii) 20≦ES＋KE (iii) 1≦AL≦20 (iv) 0≦ES≦13 (AR is aromatic solvent, KE is ketone solvent, ES is ester Ether solvents, AL stands for aliphatic alcohol, numbers are in weight%.)