JPH02212569A - Coating composition - Google Patents

Abstract

PURPOSE:To obtain a coating compsn. which gives a coating film excellent in the corrosion resistance, water resistance and hardness by compounding a specific modified epoxy resin compsn. contg. a phosphoric acid component with an acrylic or polyester resin and an aminoplast resin. CONSTITUTION:A coating compsn. is prepd. from 2-30 pts.wt. modified epoxy resin compsn. obtd. by reacting an arom. epoxy resin (with an epoxy equivalent of 170-4000; pref. a glycidyl ether of bisphnol A), an alcohol or alcoholic hydroxyl group-contg. low-MW resin (with a number-average MW of 3000 or lower, and a hydroxyl value of 150 or higher) in a molar amt. more than that of the epoxy group of the epoxy resin, and a phosphoric acid (pref. orthophosphoric acid) at 60-150 deg.C and stopping the reaction when the epoxy equivalent reaches 10000 or higher; 20-83 pts.wt. acrylic resin (with a number average MW of 4000-30000) or a polyester resin (with a number-average MW of 1000-20000); and 15-50 pts.wt. aminoplast resin (pref. completely etherified hexamethoxymelamine).

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.

The present invention relates to a coating composition that can form a coating film with excellent corrosion resistance, water resistance, and coating hardness.

(Prior Art) A painting process in which a metal base material is coated with a rust-preventing primer and then finished with a top coat has been used for a long time. For example, combinations of alkyd resins, acrylic resins, polyester resins, etc. and amino resins are known as top coatings. However, these days, there are many demands for l-coat finishing to satisfy both aesthetic and anti-corrosion functions. For this reason, a method has been adopted in which the surface of the metal base material is subjected to a phosphate-based or chromate-based chemical conversion treatment and then finished with one coat, but this method is unsatisfactory in terms of corrosion resistance. In particular, it can be used as a coating material that has excellent corrosion resistance to prevent can material corrosion as well as aesthetic appearance on the surface of can material, water resistance that can withstand high-temperature hot water treatment to sterilize the food contents, and coating hardness that prevents damage during transportation. At present, performance is required.

[Structure of the invention]

(!! Means for Solving Problem 1) The present invention has been made in view of the above-mentioned current situation. Phosphoric acid, which is a component with excellent corrosion resistance, is introduced into the resin itself, and it acts as a curing catalyst. Corrosion resistance is achieved by improving water resistance, improving coating film hardness by using aromatic epoxy resin as the basic skeleton resin, and improving crosslinking density by introducing a compound with a high hydroxyl value.

The present invention provides a coating composition with excellent water resistance and coating hardness.

That is, the present invention relates to (a) aromatic epoxy resin.

A modified epoxy resin composition obtained by reacting phosphoric acid and a low molecular alcohol or its derivative, or a low molecular weight resin containing an alcoholic hydroxyl group with a number average molecular weight of 3000 or less and a hydroxyl value of 150 or more, (b) an acrylic resin or a polyester resin, and , (c) A coating composition characterized in that the resin component is an aminoplast resin.

Examples of the aromatic epoxy resin in the present invention include 2.

There are diglycidyl ether type epoxy resins such as bisphenol A diglycidyl ether, bisphenol A di-β-methyl-diglycidyl ether tetrahydroxyphenylmethane tetraglycidyl ether, novolak glycidyl ether, and bisphenol A alkylene oxide adduct diglycidyl ether. Particularly preferred is a bisphenol A diglycidyl ether type epoxy resin.

What is the epoxy equivalent of these aromatic epoxy resins?

170 to 4000 are used. If the epoxy equivalent is less than 170, the coating film hardness will be poor, and if it is more than 4000, the corrosion resistance will be poor.

The alcohol component used in the production of the modified epoxy resin in the present invention is a low molecular weight alcohol.

Examples include alcoholic hydroxyl group-containing polyester resins and acrylic resins.

Examples of low molecular weight alcohols include n-butanol, isobutanol, n-amyl alcohol, activated amyl alcohol, isoamyl alcohol, tertiary amyl alcohol, n-hexyl alcohol, methyl amyl alcohol, 2-ethyl butanol, n- -Hebutasol, 2-Heptatool.

2-ethylhexanol, 3.5.5-trimedelhexanol, n-nonyl alcohol, undecyl alcohol, n-dodecyl alcohol, trimethylnonyl alcohol, n-tetradecyl alcohol.

m alcohols such as heptadecyl alcohol, cyclohexanol, 2-methylcyclohexanol;

Ethylene glycol, propylene glycol, 1゜3-
Butylene glycol, 1,6-hexanediol, diethylene glycol, dipropylene glycol, neopentyl glycol 5 Dihydric alcohols such as triethylene glycol 1 Trimethylolethane Trimethylolpropane, trishydroxymethylaminomethane, pentaerythrithot, dipenta Erythritol Dihydric or higher alcohols such as diglycerin and polyhydric alcohols in which part of the hydroxyl group is converted into alkyl ether 1 For example, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether 1 ethylene glycol mono Butyl ether.

Propylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, diethylene glycol monobutyl ether, diethylene glycol monoethyl ether,
Diethylene glycol monoisopropyl ether, diethylene glycol monobutyl ether, dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether.

Dipropylene glycol monoisopropyl ether.

Examples include dipropylene glycol monobutyl ether.

These low molecular weight alcohols can be used as a solvent during the production of modified epoxy resins.

Alcoholic hydroxyl group-containing polyester resins include polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, neopentyl glycol, triethylene glycol, dipropylene glycol, glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, and dipropylene glycol. Pentaerythritol, 13-butylene glycol, bentanediol, trimethylbentanediol, 1,6-hexanediol, 1,4-dicyclohexane dimetatool, (hydrogenated) bisphenol A, bisphenol dihydroxypropyl ether, etc. Phthalic acid (anhydrous), isophthalic acid (anhydride), isophthalic acid,
Terephthalic acid, (anhydrous) succinic acid, adipic acid.

Azelaic acid, cepatic acid, tetrahydrophthalic acid (anhydride), hexahydrophthalic acid (anhydride), hymic acid (anhydrous), maleic acid (anhydride), fumaric acid.

It is obtained by synthesizing itaconic acid, trimellitic acid (anhydride), methylenecyclohexenetricarboxylic acid (anhydride), pyromellitic acid (anhydride), etc., by controlling the molecular weight while adding hydroxyl equivalents as one or a mixture of two or more. It is something that can be done.

As an acrylic resin containing alcoholic hydroxyl groups.

Hydroxymethyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate.

Hydroxyamyl acrylate Hydroxyl group-containing vinyl monomers such as hydroxyhexyl acrylate and corresponding methacrylates, and vinyl monomers copolymerizable with these, such as ethyl acrylate.

Butyl acrylate, 2-ethylhexyl acrylate.

Cyclohexyl acrylate, methyl methacrylate.

Acrylic acid erkyl esters or methacrylic acid alkyl esters such as ethyl methacrylate, butyl methacrylate, stearyl methacrylate, cyclohexyl methacrylate, N-(methoxymethyl)acrylamide, N-
(isobutoxymethyl)acrylamide, N-alkoxyalkyl substituted amide-containing vinyl monomers such as N-(butoxymethyl)acrylamide, aromatic vinyl monomers such as styrene, vinyltoluene, α-methylstyrene, etc., (meth)acrylic acid, maleic It is obtained by synthesizing a carboxyl group-containing vinyl monomer such as acid or fumaric acid by reducing the reaction solid content, adding a large amount of an initiator, or controlling the molecular weight using a chain transfer agent.

Phosphoric acids in the present invention include acids produced by hydration of niline pentoxide, such as metaphosphoric acid, birophosphoric acid, orthophosphoric acid, trisonic acid, and tetraphosphoric acid; used. Orthophosphoric acid is preferred.

The modified epoxy resin composition (al) of the present invention is prepared by adding a molar excess of low molecular alcohol or alcoholic hydroxyl group-containing low molecular weight resin and phosphoric acid to an aromatic epoxy resin, and It can be obtained by reacting at a temperature of about 150°C and finishing the reaction when the epoxy equivalent is 10,000 or more.

In the present invention, the acrylic resin as the component (b) is 1, for example, 3
Carboxyl group-containing vinyl monomers such as (meth)acrylic acid, maleic acid, and fumaric acid, and vinyl monomers copolymerizable with these, such as hydroxymethyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyamyl acrylate, hydroxyhexyl acrylate, and corresponding Hydroxyl group-containing vinyl monomers such as methacrylate, ethyl acrylate, butyl acrylate.

2-ethylhexyl acrylate, cyclohexyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, stearyl methacrylate.

Acrylic acid alkyl esters such as cyclohexyl methacrylate or methacrylic acid alkyl esters N-alkoxyalkyl 1tA amide-containing vinyl monomers such as N-(methoxymethyl)acrylamide, N-(isobutoxymethyl)acrylamide, N-(butoxymethyl)acrylamide, It is obtained by copolymerizing aromatic vinyl monomers such as styrene, vinyltoluene, and α-methylstyrene. Preferably number average molecular weight 4000-30
There are 000 acrylic resins.

The polyester resin as component ('b) in the present invention is 9, for example, ethylene glycol or propylene glycol.

1.3-butylene glycol, 1.6-hexanediol, diethylene glycol, dipropylene glycol,
neopentyl glycol, triethylene glycol,
(Hydrogenation) Dihydric alcohols such as bisphenol A, trimethylolethane, trimethylolpropane, trishydroxymethylaminomethane.

Pentaerythritol Dipentaerythritol, diglycerin, and other divalent or higher alcohols are used as alcohol components.
(anhydrous) phthalic acid, isophthalic acid, terephthalic acid (anhydrous) succinic acid, adipic acid, azelaic acid.

Cepatic acid, Tetrahydrophthalic acid (Anhydride), Hexahydrophthalic acid (Anhydrous) Himic acid.

Polycarboxylic acids or their anhydrides such as (anhydride) maleic acid, fumaric acid, itaconic acid, (anhydride) trimellitic acid, methylenecyclohexenetricarboxylic acid (anhydride), (anhydride) pyromellitic acid, and as necessary Using monobasic acids such as benzoic acid and [-butylbenzoic acid] as the acid component, 1i! An oil-free polyester resin formed by combining the above-mentioned alcohol component and the above-mentioned acid component with castor oil and dehydrated castor oil.

Tung oil, safflower oil, soybean oil, linseed oil, tall oil.

An alkyd resin obtained by adding an oil component such as coconut oil and one or a mixture of two or more of these fatty acids to the above acid component and alcohol component and reacting the three components, and an unsaturated bond. There is a graft-modified polyester resin in which an acrylic resin is grafted onto a polyester resin having the following properties. The number average molecular weight of the polyester resin is 1000 to 2000.
0 is preferred.

The aminoplast resin (c) in the present invention is an alkyl etherified melamine resin, an alkyl etherified benzoguanamine resin, or an alkyl etherified urea resin.

Alkyl etherified resins of diguanamine in which two triazine rings are bonded to a phenylene nucleus, alkyl etherified glycol resins, and the like are used alone or in combination of two or more. Preferably, fully etherified hexamethoxymelamine is used.

In the coating composition of the present invention, the modified epoxy resin composition (al) is preferably blended in an amount of 2 to 30 parts by weight in the solid content of the coating resin in order to exhibit corrosion resistance, water resistance, and coating hardness in a well-balanced manner.Acrylic The resin or polyester resin (b) is blended in an amount of 20 to 83 parts by weight in the solid content of the paint resin.If it is less than 20 parts by weight, the flexibility will be poor, and if it exceeds 83 parts by weight, the coating film hardness will be poor.

Aminoplast resin (c1) is preferably used in an amount of 15 to 50 parts by weight based on the solid content of the paint resin. If it is less than 15 parts by weight, water resistance and coating film hardness tend to be poor, and if it exceeds 50 parts by weight, flexibility tends to be poor. There is.

The coating composition of the present invention may optionally contain an amine-blocked acid catalyst as a curing aid, such as p-)luenebenzenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenedisulfonic acid, etc., at a resin solid content of 100 parts. 0.1 to 1 part is added to form a paint.

The coating composition of the present invention includes a pigment, a leveling agent, an antifoaming agent,
Lubricants can also be added. It is preferable to mix the pigment after kneading it with an acrylic resin or polyester resin solution to create a pigment paste.

Furthermore, the coating composition of the present invention further includes a butadiene resin.

Epoxy resins, salt-vinyl acetate resins, and the like can also be mixed.

The coating composition of the present invention can be applied to a substrate by known means such as roll coating, spray brushing, etc. Examples of the base material include metal base materials such as electric tin coated steel plate, tin free tail, and aluminum.

In addition, the coating composition of the present invention has a temperature of 150 to 200°C-10
It can be hardened under a wide range of baking conditions, from baking for about a minute to short-time baking at a high temperature of about 250° C. for about 5 seconds.

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

Production Example 1 (Production of modified epoxy resin solution A1) In a four-eye flask equipped with a thermometer, stirrer, reflux condenser, and nitrogen gas blowing tube, 60 parts of diethylene glycol monobutyl ether and Epicote 828 (trade name of Yuka Shell Epoxy Co., Ltd.) were added. ) After heating and melting at 70°C,
Add 10.4 parts of orthophosphoric acid (0.5 mol based on the epoxy group) and stir while introducing nitrogen gas to 130 ml.
The mixture was heated to .degree. C., reacted until the epoxy equivalent reached 11.000, and then cooled to 50.degree. C. or lower to obtain a modified epoxy resin solution A1 with a solid content of 60%.

Production Example 2 (Production of modified epoxy resin solution A2) In a four-eye flask similar to Production Example 1, 35 parts of ethylene glycol monoethyl ether and 100,479.5 parts of Epicoat were charged and dissolved by heating at 90°C, followed by 2.2 parts of orthophosphoric acid. (0.5 mol based on the epoxy group), heated to 130°C while stirring while introducing nitrogen gas, and reacted until the epoxy equivalent weight was 1,000 months. After that, 27.2 parts of ethylene glycol monobutyl ether was added. The modified epoxy resin solution A2 with a solid content of 60% was added and further cooled to below 50°C.
was gotten.

Production Example 3 (Production of Modified Epoxy Resin Solution A3) 50.
0 parts, adipic acid 23.4 parts, terephthal M 26.6
230 minutes while stirring while introducing nitrogen gas.
℃, reacted until the acid value became 5 or less, and then cooled to a hydroxyl value of 185. A polyester resin having a number average molecular weight of z500 was obtained. Next, at 100°C, Epicoat 1001.
After charging 1.02 parts and heating and dissolving, orthophosphoric acid 6.31 parts
(0.3 mol based on the epoxy group) was heated to 130°C, reacted until the epoxy equivalent became 12,000 or more, and then cooled to form ethylene glycol monobutyl ether 1.
Modified epoxy resin solution A with 60% solid content by adding 31 parts
3 was obtained.

Production Example 4 (Production of modified epoxy resin solution A4) 48.4 parts of neopentyl glycol and 51.6 parts of terephthalic acid were placed in a four-eye flask similar to Production Example 3, and heated to 230°C while stirring while introducing nitrogen gas. The mixture was heated, reacted until the acid value became 5 or less, and then cooled.

Hydroxyl value 180. A polyester resin having a number average molecular weight of 1600 was obtained. Next, at 100°C, Epicoat 1.00
1. After charging 98.8 parts and heating and dissolving, orthophosphoric acid 10
．． Prepare 2 parts (0.5 mol based on the epoxy group) 13
The mixture was heated to 0°C, reacted until the epoxy equivalent became 12,000 or more, then cooled, and 132 parts of ethylene glycol monobutyl ether was added to obtain a modified epoxy resin solution A4 with a solid content of 60%.

Production Example 5 (Production of modified epoxy resin solution A5) 145 parts of ethylene glycol monoethyl ether and 5 parts of propyl mercaptan were placed in the same four-eye flask as in Production Example 1, and heated to 115°C while stirring while introducing nitrogen gas. After that, add 20 parts of α-methylstyrene, 5 parts of acrylic acid, and 40 parts of 2-hydroxypropyl acrylate to the drop tank.
parts, 35 parts of ethyl acrylate, 0.0 parts of benzoyl peroxide.
8 parts of the mixture were added dropwise over 3 hours. then 11
Keep at 5℃.

After reacting for 1 hour, 0.1 part of benzoyl peroxide was added and the reaction was further continued for 1 hour, then cooled and ethylene glycol monoethyl ether was distilled off under reduced pressure at 80°C to give a hydroxyl value of 1.
75. An acrylic resin solution with a number average molecular weight of 2100 and a solid content of 85% was obtained. Next is Ebiko 1-1001. 9
After charging 7.4 parts and heating and melting at 90°C.

10.0 parts of orthophosphoric acid (0.5 mol based on the epoxy group) was charged and heated to 130°C until the epoxy equivalent was 12.
000 or more, the mixture was cooled, and 12 parts of ethylene glycol monoethyl ether was added.

A modified epoxy resin solution A5 having a solid content of 60% was obtained.

Production Example 6 (Production of Acrylic Resin Solution B2) 100 parts of n-butanol was charged into a four-eye flask similar to Production Example 1, and 10 parts of acrylic acid was added from the dropping tank while maintaining the temperature at 105°C and introducing nitrogen gas while stirring.

A mixture of 20 parts of 2-hydroxyethyl methacrylate, 40 parts of styrene, 30 parts of butyl acrylate, and 3 parts of benzoyl peroxide was added dropwise over 3 hours. then 1
0.3 part of benzoyl peroxide was added, the reaction was continued for 1 hour, and the mixture was cooled to 60°C or less to obtain an acrylic resin solution B with a solid content of 50% and a number average molecular weight of 10,000.
1 was obtained.

Production Example 7 (Production of Polyester Resin Solution B2) In a four-eye flask similar to Production Example 3, 44.4 parts of neopentyl glycol, 26.0 parts of adipic acid, and 29.9 parts of terephthal were added.
Add 6 parts and stir while introducing nitrogen gas.23
Heated to 0°C, reacted until the acid value became 10 or less, then cooled, added 58.1 parts of ethylene glycol monobutyl ether at 150°C, further cooled to 60°C or less,
A polyester resin solution B2 with a solid content of 60% was obtained.

Example 1 16.7 parts of modified epoxy resin solution A, 33.3 parts of acrylic resin solution Bl, hexamethoxymelamine (Imel 303 manufactured by Mitsui Toatsu Chemical Co., Ltd.; the same applies to the following examples) 10.
5 parts amine-blocked paratoluenesulfonic acid 0.
1 part, xylene 23.9 parts, cyclohexanone 23.9 parts
1 part and 0.1 part of a silicone leveling agent were mixed to form a paint.

Examples 2 to 12 Paints were prepared in the same manner as in Example 1, with the resin compositions changed as shown in Table 1.

Further, Comparative Examples 1 to 3 show coatings that do not contain the modified epoxy resin of the present invention.

The paints obtained in Examples 1 to 12 and Comparative Examples 1 to 3 were subjected to coating tests, physical property tests after baking and curing, and paint stability tests, and the results are shown in Table 1.

○Paint stability test; After storing each paint at room temperature for two months, the resin gels.

The state of separation was observed.

0 Paint film physical property test; Fig 0.23 N electroplated tin plate was coated with a roll coat to a film thickness of 7 μm after drying, and baked for 10 minutes at an ambient temperature of 190°C with a gas open to create a painted panel. .

○Water resistance test: The painted panel was immersed in water and heat treated at 100°C for 30 minutes and at 125°C for 30 minutes, and then the whitening state of the paint film was evaluated.

O processability test; An Erichsen test was performed.

○Impact resistance test; The test was conducted using a DuPont type A inch and a load of 500 g.

O Pencil hardness test: Evaluation was performed using a pencil hardness test method in accordance with JIS standards.

○Adhesion test: A cross-cut peel test was conducted.

○Salt water spray resistance test; After cutting a test piece with the surface other than the painted surface sealed until it reaches the base material, place it in a salt water spray tester (JIS-Z-2371) to check for any blisters or rust from the 5 cross force joints. It shows the time it takes for the fin to reach three fins on one side.

○ Salt water immersion resistance test; After cutting the test piece under seal except for the painted surface until it reached the base material, it was immersed in 5% saline solution at 37°C.

Either the blisters or rust from the cross-cut part is 3 times wide.
The time taken to reach mm is shown.

〔Effect of the invention〕

The coating composition of the present invention has excellent corrosion resistance, water resistance, and coating hardness, so when used as an exterior coating for a can, it prevents corrosion of the can material, and can withstand high-temperature hot water treatment for sterilizing foods. *It is possible to form a coating film on the outer surface of the can that is resistant to scratches.

Claims (1)

[Claims] 1. (a) An aromatic epoxy resin containing phosphoric acid and a low molecular weight alcohol or a derivative thereof or a number average molecular weight of 3
000 or less, a modified epoxy resin composition obtained by reacting a low molecular weight resin containing an alcoholic hydroxyl group with a hydroxyl value of 150 or more, (b) an acrylic resin or a polyester resin, and (c) an aminoplast resin as the resin component. A paint composition characterized by: