JPH01299875A - Coating composition - Google Patents

Abstract

PURPOSE:To obtain a coating composition which forms a decreased amount of dust when cured by baking and can give a coating film improved in hardness and processability, by mixing a guanamine resin with a polyether polyol and a specified resin. CONSTITUTION:A guanamine compound (i) of formula I (wherein X is a group of formula II or III) and formaldehyde (ii) are subjected to an addition reaction, and the adduct is etherified with a 1-4C monoalcohol (iii) to obtain a guanamine resin (a). 10-40wt.% component (a) is mixed with 5-30wt.% polyether polyol (b) of an MW >=300 (e.g., bisphenol A/polyalkylene oxide adduct of an MW of 300-600), 30-85wt.% at least one resin (c) selected from among a polyester resin, an acryl resin and a bisphenol epoxy resin each of which has a hydroxyl value of 20-300 and, optionally, an acid catalyst as a curing agent, a levelling agent, an antifoamer, a lubricant, a pigment, etc., (d).

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to coating compositions, and more particularly to coating compositions.

Paint baking relates to a paint composition that reduces fumes caused by alkyl etherified guanamine resin generated during curing and has excellent water resistance, hardness, and processability of the paint film.

(Prior art) Beverage cans for storing soft drinks, etc. 1 The outer surface of food cans for packaging food products prevents corrosion of the can material, increases aesthetic commercial value, and can withstand the heat treatment process during food sterilization. It is covered with a coating film. Conventionally, these paints are thermosetting paints in which an alkyl etherified melamine resin or an alkyl etherified penzoguamine resin is combined with a resin selected from polyester resins, acrylic resins, epoxy resins, etc. However, when these paints are baked, low molecular weight substances from alkyl etherified melamine resins and alkyl etherified benzoguanamine resins are scattered.
Problems have arisen, such as adhesion and solidification in the oven, resulting in product defects due to falling onto the object to be coated, and the need to frequently clean the oven.

Conventionally used alkyl etherified melamine resin,
Alkyl etherified benzoguanamine resin.

It is a mixture of molecules containing bound formaldehyde and one to several dozen triazine rings having methyl or butyl ether groups, and the proportion of triazine rings in one molecule of resin is 10% by weight or more. In particular, water-based paints contain a large amount of methyl ether groups to make them more compatible with water, and the proportion of one molecule containing a triazine ring is 30% by weight.
That's all.

Since a single molecule of these triazine rings has a small molecular weight, burning sometimes does not occur and causes fumes.

(Problem to be solved by the invention) The present invention has been made in view of the above-mentioned current situation.

For that purpose, paint baking sometimes occurs.

The present invention provides a coating composition in which fumes caused by alkyl etherified melamine resin and alkyl etherified benzoguanamine resin are reduced. The present invention further provides a coating composition that is useful as a can exterior coating and has excellent coating film water resistance, hardness, processability, and the like.

[Structure of the invention]

(Means for solving problems) In other words, the present invention is as follows.

(A) Guanamine resin obtained by addition reaction of a guanamine compound represented by the following general formula with formaldehyde and etherification with a monoalcohol having 1 to 4 carbon atoms.
10-40% by weight (B) polyether polyol with a molecular weight of at least 300
A coating composition containing 5 to 30% by weight (C) 30 to 85% by weight of at least one resin selected from a polyester resin or acrylic resin having a hydroxyl value of 20 to 300, and a bisphenol type epoxy resin.

(However, X.

It is. ) The guanamine resin (A) in the present invention is obtained by addition reaction of a compound having the above structural formula with formaldehyde.

and guanamine resin obtained by etherification reaction with monoalcohols such as methyl alcohol, ethyl alcohol, n-butyl alcohol, and 1so-butyl alcohol.

The polyether polyol in the present invention has a molecular weight of at least 300, and preferably has 1 to 2 ethylene oxides or 1,2-propylene oxides at both ends.
A polyether polyol represented by the following general formula with 0 mol added is preferred.

RI R3 (However, R,
, R3 represents a hydrogen atom or a methyl group, +R2 represents a bond composed of an ether bond, m and n are 1 to 2
To explain more specifically the structural unit of R2 in the above general formula (representing an integer of 0), ethylene oxide or I, 2
- Propylene oxide and polyhydric alcohols, such as glycerin, trimethylolpropane, hexanetriol.

It is composed of repeating units formed by reactions such as pentaerythritol, bisphenol A, sorbitol, sucrose, etc., or the above-mentioned polyhydric alcohol alone.

Preferred polyether polyols include polyether polyols having a molecular weight of 300 to 1,600 and in which the general formula R2 is bisphenol A.
There is a polyalkylene oxide adduct of bisphenol A.

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

There is a bisphenol type epoxy resin.

As a polyester resin, for example, a polyhydric alcohol and a polyhydric carboxylic acid or its anhydride are dehydrated and condensed with a hydroxyl group/carboxyl group of 1.0 or more, preferably with an acid value of 5 or less and a hydroxyl value of 20 to 300. There are oil-free polyester resins and alkyd resins obtained by anhydrous condensation of polyhydric alcohols and higher fatty acids (including polyhydric carboxylic acids as necessary). especially.

The water-based paint is made by reacting the oil-free polyester resin or alkyd resin with a polyvalent carboxylic acid or its anhydride to give an acid value of 10 or more, which can be dissolved or dispersed in an aqueous medium in the presence of a volatile base. Water-based polyester resin is used.

The polyhydric alcohols include ethylene glycol, propylene glycol, 1,3-butylene glycol, 1
, 6-hexanediol, diethylene glycol, dipropylene glycol, neopentyl glycol, dihydric alcohols such as triethylene glycol, trimethylolethane, trimethylolpropane, trishydroxymethylaminomethane, pentaerythritol, dipentaerythritol, diglycidyl, etc. There are alcohols with a valence of more than 2. The polyhydric carboxylic acid or acid anhydride is as follows:
(anhydrous) phthalic acid, isophthalic acid, terephthalic acid, (
anhydrous) succinic acid, adipic acid, azelaic acid, cepatic acid.

Tetrahydro (anhydrous) phthalic acid, hexahydro (anhydrous)
Phthalic acid, Himic acid (anhydride), Maleic acid (anhydride), Fumaric acid, Itaconic acid, (Anhydride) trimellitic acid, Methylenecyclohexenetricarboxylic acid (anhydride)
, (anhydrous) pyromellitic acid, etc.

The acrylic resin in the present invention is made of 2, for example, a hydroxyl group-containing vinyl monomer, a (meth)acrylic acid alkyl ester copolymerizable therewith, a N-alkoxyalkyl substituted amide-containing vinyl monomer, an aromatic vinyl monomer, and an ethylenically unsaturated carboxylic acid. It is obtained by addition polymerization with appropriately selected monomers. Preferably hydroxyl value 20-30
This is an acrylic resin with a temperature of 0. As a water-based paint, it also contains an ethylenically unsaturated carboxylic acid as a component with an acid value of 1o.
An aqueous acrylic resin that can be dissolved or dispersed in an aqueous medium in the presence of the above volatile base is used.

The hydroxyl group-containing vinyl monomers include hydroxymethyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyamyl acrylate, hydroxyhexyl acrylate, and corresponding methacrylates.

Vinyl monomers that can be copolymerized with the hydroxyl group-containing vinyl monomer include ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, stearyl methacrylate, and methacrylate. (meth)acrylic acid alkyl esters such as cyclohexyl acid, N-(methoxymethyl)acrylamide, N-(
N-alkoxyalkyl-substituted amide group-containing vinyl monomers such as isobutoxymethyl)acrylamide and N-(butoxymethyl)acrylamide, styrene, and vinyltoluene.

Aromatic vinyl compounds such as α-methylstyrene, acrylic acid, methacrylic acid, crotonic acid, maleic acid.

Ethylenically unsaturated carboxylic acids such as fumaric acid and itaconic acid, vinyl acetate, vinyl ethyl ether, etc.

It can be selected as appropriate.

As a bisphenol type epoxy resin, 1 is an example.

Bisphenol A diglycidyl ether, bisphenol A di-β-methyl-diglycidyl ether.

There are diglycidyl ether type epoxy resins such as 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 prepared by adding a polyhydric carboxylic acid or its anhydride to an epoxy group and can be dissolved or dispersed in an aqueous medium in the presence of a volatile base having an acid value of 10 or more.

Volatile bases used to make film-forming resins having carboxyl groups water-based in water-based paints include 2, such as ammonia, monoethanolamine, dimethylamine, diethylamine, triethylamine, jetanolamine, triethanolamine, dimethylamino. There are organic amines such as ethanol, diethylaminoethanol, dimethylaminomethanol, diethylaminoethanol, and morpholine.

Guanamine resin (A) of the coating composition of the present invention.

Polyether polyol (B) and hydroxyl value 20
A preferred blending ratio of at least one resin (C) selected from polyester resins or acrylic resins of 300 to 300, and bisphenol-type epoxy resins is (A) 10 to 40% by weight as resin solid content.

(B) 5 to 30% by weight, and (C) 30 to 85% by weight. If the guanamine resin (A) is less than 10% by weight, the coating hardness tends to decrease, and if it is more than 40% by weight, the processability is poor. Moreover, if the polyether polyol (B) is less than 5% by weight, the processability of the coating film will be poor.

When the amount exceeds 30% by weight, the hardness of the coating film decreases.

The coating composition of the present invention may optionally contain an acid catalyst or an amine-blocked product thereof as a curing aid, such as p-toluenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenedisulfonic acid, etc., at a resin solid content of 10%.
0.1 to 1 part can be added to 0 part.

Furthermore, conventionally known leveling agents, antifoaming agents, lubricants, R additives, etc. can be added to the coating composition of the present invention.

The coating method of the coating composition of the present invention is roll coating.

Known means such as spraying and brushing 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-term baking at 250°C for about 10 seconds.

(Example) The present invention will be explained below with reference to Examples. In the examples, 1 part means part by weight, and 1% means % by weight.

Production Example 1 (Guanamine resin solution (al)) In a Yotsuro flask equipped with a thermometer, stirrer, reflux condenser, and nitrogen gas blowing tube, 27.4 parts of a spiroguanamine compound having the following structure and a 40% solution of formaldehyde-containing n-butanol were added. (formin)NB (manufactured by Koei Chemical Co., Ltd.) 43.2 parts and n-butanol 27.4 parts were added.

It was heated at 100°C for 30 minutes. 0.04 part of phthalic anhydride was charged, and the reaction mixture was heated and dehydrated under reflux for 6 hours until the temperature reached 130°C, after which the mixture was cooled and filtered out using a filter paper (retained particle size: 5 μm). The solid content was adjusted to 65% with n-butanol.

Production Example 2 (Guanamine resin solution (a2)) Spiguanamine 4 used in Example 1 using the same equipment as Example 1
0.5 parts of formaldehyde-containing methanol 40% solution (Formin MH; manufactured by Koei Chemical Co., Ltd.) 59.5 parts, the pH was adjusted to 8.0 with sodium methylate, and the pH was adjusted to 8.0 with sodium methylate.
Heated at 0°C for 60 minutes.

Add 0.06 part of phthalic anhydride and continue heating to 60
After reacting at °C for 8 hours, methanol and water were removed under reduced pressure, 25 parts of isopropyl alcohol was 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 (Guanamine Resin Solution (A3)) Using the same equipment as in Example 1, 23.2 parts of phthaloguanamine having the following structure, 47.0 parts of a 40% formaldehyde-containing methanol solution (Formit NB; manufactured by Koei Kagaku Co., Ltd.), 29.8 parts of n-butanol was charged and heated at 100°C for 30 minutes.

0.05 part of phthalic anhydride was charged, and the reaction mixture was heated and dehydrated under reflux for 6 hours until the temperature reached 130° C., 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 (c 1)) In a four-way flask equipped with a thermometer, a stirrer, a reflux condenser, one dropping tank, and a nitrogen gas blowing tube, 12.0 parts of phthalic anhydride, 47.5 parts of adipic acid, 15.1 parts of ethylene glycol and 25.4 parts of neopentyl glycol were charged and heated to 210°C. Start cooling when the acid value becomes 5 or less.
At 70°C, 93 parts of ethylene glycol monobutyl ether was added, and after cooling, a transparent and viscous polyester resin solution (C1) having a solid content of 50% and a hydroxyl value of 45 was obtained.

Production Example 5 (Acrylic resin solution (C2)) Using the same equipment as in Production Example 1, add 100 parts of n-butanol, and while stirring while introducing nitrogen gas, maintain the temperature at 105°C and add hydroxyethyl from the dropping tank. 15 parts of acrylate, 30 parts of butyl acrylate, 20 parts of ethyl acrylate
A mixture of 1 part, 35 parts of styrene, and 3 parts of benzoyl peroxide was added dropwise over 4 hours. After the dropwise addition was completed, the temperature was maintained at 105°C, and after 1 hour, 0.3 parts of benzoyl peroxide was added. After 1 hour, the reaction was terminated. After cooling, a transparent, active acrylic resin solution with a solid content of 50% and a hydroxyl value of 97 was obtained ( c2) was obtained.

Production Example 6 (Aqueous acrylic resin solution (c3)) Production Example 1
Using the same equipment as above, charge 100 parts of n-butanol and bring the temperature to 105% while stirring while introducing nitrogen gas.
Hydroxyethyl acrylate 1 from the drop tank kept at ℃
A mixture of 5 parts of butyl acrylate, 40 parts of styrene, 12 parts of acrylic acid, and 3 parts of benzoyl peroxide was added dropwise over 4 hours. Keep the temperature at 105℃ even after dropping 1
After an hour, 0.3 part of benzoyl peroxide was added, and the reaction was terminated after 1 hour. After cooling and adding 14.8 parts of dimethylaminoethanol at 80°C or lower and further adding 100 parts of water, the solvent was removed at 80 to 100°C under reduced pressure to give a solid content of 50% and a hydroxyl value of 73. A transparent and active aqueous acrylic resin solution (c3) with a solvent content of 20% was obtained.

Example 1 23.1 parts of guanamine resin solution (al), 5 parts of polyether polyol (BL) (8 mol adduct of bisphenol A with propylene oxide), polyester resin solution &
(c 1 ) 60 parts, para-toluenesulfonic acid 0, 1
part, 0.1 part of silicone leveling agent, 6.0 parts of xylene.
9 parts and 5 parts of methyl isobutyl ketone were mixed.

The resin solid content was 30 parts of guanamine resin (al), 10 parts of polyether polyol (bl), and polyester resin (c).
l) A paint containing 60 parts was prepared.

Examples 2 to 8 According to the same method as in Example 1, guanamine resin solution (a
l) to (a3), and polyether polyol (b
l), (b2) (polyether polyol (b2)
is a 20 mol ethylene oxide adduct of bisphenol A), a polyester resin solution (c1), an acrylic resin solution (c2), or a bisphenol A type epoxy resin (Epon #007, manufactured by Shell Chemical Co., Ltd.).
The resin solid content was adjusted to a resin solid content ratio of 4.
A 0% paint was prepared.

Example 9 18.5 parts of guanamine resin solution (a2), 4 parts of polyether polyol (b2), aqueous acrylic resin solution (c3)
) 48 parts, amine-blocked para-toluenesulfonic acid 0.1 part, silicone leveling agent 0°1 part, water 29
5 parts, and the resin solid content is guanamine resin (a2).
A coating composition containing 30 parts of polyether polyol (b2) and 60 parts of water-based acrylic resin (c3) was prepared.

Example 10 Guanamine resin (a2) according to the same method as Example 9
, polyether polyol (b2), and aqueous acrylic resin (c3) at resin solid content ratios as shown in Table 1 to prepare a paint having a resin solid content of 40%.

Comparative Example 1 15 parts of melamine resin containing 50% or more of hexamethoxymelamine having one triazine ring in two molecules (manufactured by Mitsui Toatsu Chemical ■, Cymel 303: the same applies to the following examples) in the same manner as in Example 1 , polyester resin solution (cl)
70 parts of paratoluenesulfonic acid, 0.1 part of silicone leveling agent, 7 parts of xylene, and 8 parts of methyl isobutyl ketone were mixed.

A paint was prepared in which the resin solid content was 30 parts of Cymel 303 and 70 parts of polyester resin (cl).

Comparative Example 2 According to the same method as in Example 5, a paint was prepared by mixing Cymel 303 and water-based acrylic resin (c3) so that the resin solid content ratio was as shown in Table 1.

Comparative Example 3 18.5 parts of guanamine resin (a2), 5.6 parts of aqueous acrylic resin (c3), 0.1 part of amine-blocked paratoluenesulfonic acid, 0°1 part of silicone leveling agent,
Mix 25.5 parts of water and make sure that the solid content of the paint is guanamine resin (
A paint containing 30 parts of a2) and 70 parts of a water-based acrylic resin (c3) was prepared.

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

Each test method is as follows.

0 Paint Stability Test After each paint was stored at room temperature for 2 months, the state of gelation and separation of the resin was observed.

O Heating loss test Plate thickness o: 23 mm electroplated tin plate was roll coated to a film thickness of 7 μm after drying.

After drying at 100°C for 30 minutes and cooling, the weight of the coating film is measured. Thereafter, baking was performed at 200°C for 2 minutes and at 180°C for 10 minutes, and after cooling, the weight was measured again.

For heating loss, the same test was conducted five times and the average value was determined. Incidentally, the heating loss was determined according to the following formula.

However, X = (100℃ - 30 minutes) Coating film weight at baking time Y = Coating film weight after each coating condition Painted with a coat and heated to 180℃ in a gas oven.
The panel was baked for 10 minutes to create a painted panel.

・Solvent resistance test A rubbing test was conducted using methyl ethyl ketone to determine the number of times the coating was rubbed back and forth until it peeled off.

・Water resistance test The painted panel was immersed in water and heat treated at 100°C for 30 minutes, after which the whitening state of the paint film was evaluated.

・Pencil hardness test method Evaluation was performed using a pencil hardness test method in accordance with IS standards.

・Adhesion test A cross-cut peeling test was conducted.

・Workability test An Erichsen test was performed.

・Impact resistance test The test was conducted using a DuPont method, 1/2 inch, and a load of 500 g.

〔Effect of the invention〕

The coating composition of the present invention is particularly excellent in that there is less fume caused by guanamine resin generated during coating during curing, and is also excellent in coating stability, water resistance, coating hardness, and coating processability. It has basic performance as coating paint for beverage cans, food cans, etc.

Claims (1)

[Claims] 1. (A) Guanamine resin 1 obtained by addition-reacting a guanamine compound represented by the following general formula with formaldehyde and etherifying it with a monohydric alcohol having 1 to 4 carbon atoms.
0 to 40% by weight (B) 5 to 30% by weight of a polyether polyol having a molecular weight of at least 300 (C) At least 30% of a resin selected from polyester resins or acrylic resins having a hydroxyl value of 20 to 300, and bisphenol type epoxy resins A coating composition containing ~85% by weight. ▲There are mathematical formulas, chemical formulas, tables, etc.▼ (However, X is ▲There are mathematical formulas, chemical formulas, tables, etc.▼, or ▲Mathematical formulas,
There are chemical formulas, tables, etc.▼. ) 2. Polyether polyol (B) has a molecular weight of 300 to 1
600, a polyalkylene oxide adduct of bisphenol A.