JPH07122049B2 - Paint composition - Google Patents

Description

The present invention relates to a coating composition, and more specifically, to a scattering substance (fumes) generated from an alkyl etherified guanamine resin generated during baking and curing of the coating composition. ) And a coating film having excellent water resistance, hardness and processability.

(Prior Art) The outer surface of a beverage can containing soft drinks or the like and a food can for packaging food can prevent corrosion of the can material, enhance aesthetic commercial value, and withstand the heat treatment process during food sterilization. It is formed by coating. Conventionally, as these coating materials, thermosetting coating materials in which an alkyl etherified melamine resin or an alkyl etherified benzogamine resin and a resin selected from polyester resin, acrylic resin, epoxy resin and the like are used are used. However, in these coatings, low-molecular-weight substances from alkyl etherified melamine resins and alkyl etherified benzoguanamine resins are scattered during baking, and adhere to the oven furnace and solidify, causing product defects due to falling onto the coated object and the furnace. There are problems such as frequent internal cleaning.

Alkyl etherified melamine resin used conventionally,
Alkyl etherified benzoguanamine resin is a mixture of molecules containing one to several tens of triazine rings with bound formaldehyde and its methyl or butyl ether groups, and the proportion of triazine ring in one resin is more than 10% by weight. is there. In particular, water-based paints contain a large amount of methyl ether groups in order to make them easily compatible with water, and the proportion of triazine rings in one molecule is 30% by weight or more.

The molecules with one triazine ring had a small molecular weight and did not react during baking, causing fumes.

(Problems to be Solved by the Invention) The present invention has been made in view of the above circumstances, and an object thereof is to obtain an alkyl etherified melamine resin or an alkyl etherified benzoguanamine resin generated during baking of a paint. The present invention provides a coating composition with reduced fumes. The present invention further provides a coating composition useful as a can outer surface coating which is excellent in water resistance, hardness, workability and the like of the coating film.

[Structure of Invention]

(Means for Solving the Problems) That is, the present invention provides (A) guanamine obtained by addition reaction of a guanamine compound represented by the following general formula with formaldehyde and etherification with a monohydric alcohol having 1 to 4 carbon atoms. Resin 10-40
% By weight (B) Polyether polyol having a molecular weight of at least 300 5 to 30% by weight (C) Polyester resin or acrylic resin having a hydroxyl value of 20 to 300, and at least one resin selected from bisphenol type epoxy resin 30 to 85% by weight % Coating composition.

(However, X is Is. ) The guanamine resin (A) in the present invention is a compound having the above structural formula, addition reaction with formaldehyde, and
It is a guanamine resin obtained by an etherification reaction with a monohydric alcohol such as methyl alcohol, ethyl ercol, n-butyl alcohol, iso-butyl alcohol.

The polyether polyol in the present invention has a molecular weight of at least 300, and is preferably a polyether polyol represented by the following general formula in which 1 to 20 mol of ethylene oxide or 1,2-propylene oxide is added to both ends.

(However, R ₁ and R ₃ have a hydrogen atom or a methyl group, and R ₂
Represents a bond composed of ether bonds, and m and n are 1 to 20.
Represents the integer. ) More specifically explaining the structural unit of R _{2 in} the above general formula,
Consisted of ethylene oxide or 1,2-propylene oxide and a polyhydric alcohol, for example, glycerin, trimethylolpropane, hexanetriol, pentaerythritol, bisphenol A, sorbitol, sucrose, or other repeating units, or the polyhydric alcohol alone. To be done.

Preferred polyether polyols include the above general formula
There is a polyalkylene oxide adduct of bisphenol A having a molecular weight of 300 to 1600 in which R ₂ is bisphenol A.

The resin (C), which is the third resin component of the coating composition in the present invention, is a polyester resin or an acrylic resin having a hydroxyl value of 20 to 300, or a bisphenol type epoxy resin.

As the polyester resin, for example, an oil-free polyester resin obtained by dehydration-condensing a polyhydric alcohol and a polycarboxylic acid or an anhydride thereof with a hydroxyl group / carboxyl group of 1.0 or more, preferably an acid value of 5 or less and a hydroxyl value of 20 to 300 There is an alkyd resin obtained by water-stop condensation of a polyhydric alcohol and a higher fatty acid (including a polycarboxylic acid if necessary). In particular, as the water-based paint, the above oil-free polyester resin or alkyd resin is further reacted with a polyvalent carboxylic acid or an anhydride thereof to give an acid value of 10 or more, and dissolved or dispersed in an aqueous medium in the presence of a volatile base. Possible aqueous polyester resins are used.

Examples of the polyhydric alcohol include ethylene glycol, propylene glycol, 1,3-butylene glycol, 1,6-hexanediol, diethylene glycol, dipropylene glycol, neopentyl glycol, triethylene glycol and other dihydric alcohols, trimethylolethane,
There are dihydric or higher alcohols such as trimethylolpropane, trishydroxymethylaminomethane, pentaerythritol, dipentaerythritol, and diglycerin. Examples of the polycarboxylic acid or acid anhydride include (anhydrous)
Phthalic acid, isophthalic acid, terephthalic acid, (anhydrous) succinic acid, adipic acid, azelaic acid, sebacic acid, tetrahydro (anhydrous) phthalic acid, hexahydro (anhydrous) phthalic acid, (anhydrous) hymic acid, (anhydrous) maleic acid, There are fumaric acid, itaconic acid, (anhydrous) trimellitic acid, methylenecyclohexene tricarboxylic acid (anhydride), (anhydrous) pyromellitic acid and the like.

The acrylic resin in the present invention comprises, for example, a hydroxyl group-containing vinyl monomer, a (meth) acrylic acid alkyl ester copolymerizable therewith, an N-alkoxyalkyl-substituted amide-containing vinyl monomer, an aromatic vinyl monomer, and an ethylenically unsaturated carboxylic acid. An acrylic resin having a hydroxyl value of 20 to 300, which is obtained by the addition polymerization of the selected monomers appropriately, is preferable. As the aqueous paint, an aqueous acrylic resin that can be dissolved or dispersed in an aqueous medium in the presence of a volatile base containing an ethylenically unsaturated carboxylic acid as a component and having an acid value of 10 or more is used.

Examples of the hydroxyl group-containing vinyl monomer include hydroxymethyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyamyl acrylate, hydroxyhexyl acrylate and corresponding methacrylates.

Vinyl monomers copolymerizable with hydroxyl group-containing vinyl monomers include ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, stearyl methacrylate, methacrylic acid. (Meth) acrylic acid alkyl ester such as cyclohexyl acid, N- (methoxymethyl) acrylamide, N- (isobutoxymethyl) acrylamide, N-alkoxyalkyl-substituted amide group-containing vinyl monomer such as N- (butoxymethyl) acrylamide, styrene Aromatic vinyl compounds such as vinyltoluene and α-methylstyrene, ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, crotonic acid, maleic acid, fumaric acid and itaconic acid,
There are vinyl acetate, vinyl ethyl ether, etc., which can be appropriately selected.

Examples of the bisphenol type epoxy resin include bisphenol A diglycidyl ether and bisphenol A.
There are diglycidyl ether type epoxy resins such as di-β-methyl-diclycidyl ether, tetrahydroxyphenylmethane tetraglycidyl ether, novolac glycidyl ether and diglycidyl ether of bisphenol A alkylene oxide adduct. As the water-based paint, a water-based epoxy resin is used which is capable of being dissolved or dispersed in an aqueous medium in the presence of a volatile base having an acid value of 10 or more by adding a polycarboxylic acid or an anhydride thereof to an epoxy group.

Examples of the volatile base used for making the film-forming resin having a carboxyl group aqueous in the water-based paint include ammonia, monoethanolamine, dimethylamine, diethylamine, triethylamine, diethanolamine, triethanolamine, dimethylaminoethanol, Organic amines such as diethylaminoethanol, dimethylaminomethanol, diethylaminoethanol and morpholine are available.

At least one resin selected from guanamine resin (A), polyether polyol (B), polyester resin or acrylic resin having a hydroxyl value of 20 to 300, and bisphenol type epoxy resin of the coating composition of the present invention (C (A) is 10 to 40% by weight, (B) is 5 to 30% by weight, and (C) is 30 to 30% by weight as a resin solid content.
It is 85% by weight. When the content of the guanamine resin (A) is 10% by weight or less, the coating film hardness tends to decrease, and when it is 40% by weight or more, the processability is poor. Further, if the content of the polyether polyol (B) is 5% by weight or less, the workability of the coating film becomes poor, and if it is 30% by weight or more, the coating film hardness decreases.

In the coating composition of the present invention, if necessary, an acid catalyst or an amine-blocked one thereof as a curing aid, such as p-toluenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenedisulfonic acid, etc., is added to the resin solid content of 10%.
0.1 to 1 part can be added to 0 part.

Further, conventionally known leveling agents, defoaming agents, lubricants, pigments and the like can be added to the coating composition of the present invention.

As a method for coating the coating composition of the present invention, known means such as roll coating, spraying and brush coating can be used.

The coating composition of the present invention can be selected from a wide range of baking conditions from baking at 150 to 200 ° C. for about 10 minutes to high temperature short time baking at about 250 ° C. for 10 seconds.

(Examples) Hereinafter, the present invention will be described with reference to Examples. In the examples, "part" means "part by weight" and "%" means "% by weight".

Production Example 1 (guanamine resin solution (a1)) A four-necked flask equipped with a thermometer, a stirrer, a reflux condenser, and a nitrogen gas injection tube was charged with a spiroguanamine compound having the following structure.
27.4 parts, formaldehyde-containing 40% n-butanol solution (Formit NB; Koei Chemical Co., Ltd.) 43.2 parts, n-butanol 2
7.4% was charged and heated at 100 ° C for 30 minutes. Phthalic anhydride 0.0
After 4 parts were charged, the mixture was heated and refluxed for dehydration to react at 130 ° C. for 6 hours, then cooled and filtered with a filter paper (holding particle size 5 μ). The solid content was adjusted to 65% with n-butanol.

Production Example 2 (Guanamin resin solution (a2)) Using the same apparatus as in Example 1, 40.5 parts of spiroguanamine used in Example 1 and formaldehyde-containing methanol 40
% Solution (Hormite MH; manufactured by Koei Chemical Co., Ltd.) was charged, and the pH was adjusted to 8.0 with sodium methylate, and the temperature was adjusted to 60 ° C.
Heated for 60 minutes. 0.06 parts of phthalic anhydride was charged, and after heating and reacting at 60 ° C. for 8 hours, methanol and water were removed under reduced pressure, 25 parts of isopropyl alcohol was further added, and the mixture was filtered out in the same manner as in Production Example 1. The solid content was adjusted to 65% with isopropyl alcohol.

Production Example 3 (Guanamin Resin Solution (a3)) Using the same apparatus as in Example 1, 23.2 parts of phthaloguanamine having the following structure, 40% solution of formaldehyde-containing methanol (Hormite MB; Koei Chemical Co., Ltd.) 47.0 parts, n-butanol 2
9.8 parts were charged and heated at 100 ° C for 30 minutes.

Phthalic anhydride (0.05 parts) was charged, the mixture was heated and refluxed for dehydration to react at 130 ° C. for 6 hours, then cooled, and filtered out in the same manner as in Production Example 1. The solid content was adjusted to 65% with n-butanol.

Production Example 4 (Polyester resin solution (c1)) In a four-necked flask equipped with a thermometer, a stirrer, a reflux condenser, a dropping tank, and a nitrogen gas blowing tube, 12.0 parts of phthalic anhydride, 47.5 parts of adipic acid, ethylene glycol 15.1 parts and neopentyl glycol 25.4 parts were charged and heated to 210 ° C. When the acid value became 5 or less, cooling was started, and 93 parts of ethylene glycol monobutyl ether was added at 170 ° C. After cooling, a transparent viscous polyester resin solution (c1) having a solid content of 50% and a hydroxyl value of 45 was added. Obtained.

Production Example 5 (acrylic resin solution (c2)) Using the same apparatus as in Production Example 1, 100 parts of n-butanol was charged, and the temperature was adjusted to 10 with stirring while introducing nitrogen gas.
Keep at 5 ℃, and add hydroxyethyl acrylate 1 from the dropping tank.
5 parts, butyl acrylate 30 parts, ethyl acrylate 20
Parts, styrene 35 parts, benzoyl peroxide 3 parts 4 parts of a mixture
Dropped over time. Keep the temperature at 105 ° C even after dropping 1
After a lapse of time, 0.3 part of benzoyl peroxide was added, and after 1 hour, the reaction was terminated, and after cooling, a transparent viscous acrylic resin solution (c2) having a solid content of 50% and a hydroxyl value of 97 was obtained.

Production Example 6 (Aqueous acrylic resin solution (c3)) Using the same apparatus as in Production Example 1, 100 parts of n-butanol was charged and the temperature was adjusted to 10 while stirring while introducing nitrogen gas.
Keep at 5 ℃, and add hydroxyethyl acrylate 1 from the dropping tank.
A mixture of 5 parts, 40 parts of butyl acrylate, 33 parts of styrene, 12 parts of acrylic acid and 3 parts of benzoyl peroxide was added dropwise over 4 hours. After the dropping was completed, the temperature was kept at 105 ° C., 1 hour later, 0.3 part of benzoyl peroxide was added, and the reaction was terminated 1 hour later. Cool and dimethylaminoethanol below 80 ℃
14.8 parts was added, and then 100 parts of water was added, and the pressure was reduced to 80
Solvent is removed at -100 ° C, solid content 50% hydroxyl value 73, solvent content 20%, transparent viscous aqueous acrylic resin solution (c3)
Got

Example 1 23.1 parts of guanamine resin solution (a1), polyether polyol (b1) (propylene oxide 8 of bisphenol A 8)
5 parts by mole, polyester resin solution (c1) 60 parts,
Paratoluene sulfonic acid 0.1 parts, silicone leveling agent 0.1 part, xylene 6.9 parts, methyl isobutyl ketone 5
Parts, and the resin solid content is 30 parts of guanamine resin (a1),
A paint containing 10 parts of polyether polyol (b1) and 60 parts of polyester resin (c1) was prepared.

Examples 2 to 8 According to the same method as in Example 1, the guanamine resin solution (a
1) to (a3) and polyether polyol (b
1), (b2) (polyether polyol (b2) is a 20 mol ethylene oxide adduct of bisphenol A), and polyester resin solution (c1), acrylic resin solution (c2), or bisphenol A type epoxy resin (Epon # 007 A coating composition having a resin solid content of 40% was prepared by adjusting the resin solid content ratio as shown in Table 1 by Shell Chemical Co., Ltd.

Example 9 18.5 parts of guanamine resin solution (a2), 4 parts of polyether polyol (b2), 48 parts of aqueous acrylic resin solution (c3), 0.1 part of amine-blocked paratoluenesulfonic acid, 0.1 part of silicone-based leveling agent, water 29.5 Parts were mixed to prepare a paint having a resin solid content of 30 parts of guanamine resin (a2), 10 parts of polyether polyol (b2), and 60 parts of aqueous acrylic resin (c3).

Example 10 According to the same method as in Example 9, guanamine resin (a2),
A coating material having a resin solid content of 40% was prepared by using the polyether polyol (b2) and the aqueous acrylic resin (c3) in a resin solid content ratio as shown in Table 1.

Comparative Example 1 According to the same method as in Example 1, a melamine resin having 50% or more of hexamethoxymelamine having one triazine ring in the molecule (manufactured by Mitsui Toatsu Chemicals, Inc., Cymel 303: the following examples are the same). 15 parts, 70 parts polyester resin solution (c1),
Paratoluene sulfonic acid 0.1 part, silicone leveling agent 0.1 part, xylene 7 parts, methyl isobutyl ketone 8
Parts were mixed to prepare a paint having a resin solid content of 30 parts of Cymel 303 and 70 parts of polyester resin (c1).

Comparative Example 2 According to the same method as in Example 5, a coating material was prepared so that Cymel 303 and the aqueous acrylic resin (c3) had the resin solid content ratio shown in Table 1.

Comparative Example 3 18.5 parts of guanamine resin (a2), water-based acrylic resin (c3)
56 parts, amine-blocked paratoluenesulfonic acid 0.1
Part, silicone leveling agent 0.1 part, and water 25.5 parts were mixed to prepare a paint having a paint solid content of 30 parts of guanamine resin (a2) and 70 parts of aqueous acrylic resin (c3).

The paints obtained in Examples 1 to 10 and Comparative Examples 1 to 3 were subjected to a paint stability test, a heat loss test and a coating film physical property test according to the following methods, and the results are shown in Table 1.

Each test method is as follows.

○ Paint stability test After each paint was stored at room temperature for two months, the state of gelation and separation of the resin was observed.

○ Heat loss test A 0.23 mm thick electroplated tin roll coat is applied to the dried film so that the film thickness is 7 μm, dried at 100 ° C. for 30 minutes, cooled, and the weight of the film is measured. After that, baking was performed at 200 ° C. for 2 minutes and 180 ° C. for 10 minutes respectively, and after cooling, the weight was measured again.

The same test was performed 5 times for the weight loss by heating, and the average value was obtained. The heating loss was calculated according to the following formula.

However, X = (100 ° C-30 minutes) coating weight during baking Y = coating weight after each baking condition ○ Coating film physical property test Roll coating with a film thickness of 7μ in the same manner as in the heating weight loss test Then, it was baked in a gas oven at an ambient temperature of 180 ° C for 10 minutes to prepare a painted panel.

-Solvent resistance test A rubbing test was conducted with methyl ethyl ketone to check the number of reciprocations until the coating film peeled.

-Water resistance test The coated panel was immersed in water and heat-treated at 100 ° C for 30 minutes, and then the whitening state of the coating film was evaluated.

-Pencil brush hardness test The pencil hardness test was based on the JIS standard.

-Adhesion test An edge peel test was performed.

-Workability test An Erichsen test was performed.

-Impact resistance test DuPont type, 1/2 inch, 500g load was performed.

[Effects of the Invention] The coating composition of the present invention is particularly excellent in that it has less fumes due to guanamine resin generated during baking and curing of the coating, and also has coating stability, water resistance, coating hardness, and coating processing. It has excellent properties and has basic performance as a coating material for coating beverage cans, food cans, etc.

Claims (2)

[Claims] (A) Guanamine resin represented by the following general formula, which is formed by addition reaction with formaldehyde and etherified with monohydric alcohol having 1 to 4 carbon atoms: 10 to 40% by weight (B) Molecular weight Contains at least 300 polyether polyol 5 to 30% by weight (C) hydroxylated 20 to 300 polyester resin or acrylic resin, and at least 30 to 85% by weight of at least one resin selected from bisphenol type epoxy resins. Coating composition. (However, X is Is. ) 2. The polyether polyol (B) has a molecular weight of 30.
The coating composition according to claim 1, which is a polyalkylene oxide adduct of bisphenol A having a value of 0 to 1600.