JPH0692559B2 - Paint composition - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a coating composition, and more specifically, a coating composition capable of forming a coating film excellent in corrosion resistance, water resistance and coating film hardness. It relates to a composition.

(Prior Art) The coating process of applying a rust-preventive primer to a metal substrate and then finishing with a top coat has been performed for a long time. As the top coating material, for example, a combination of an alkyd resin, an acrylic resin, a polyester resin or the like and an amino resin is known. However, these days, it is often required that one coat finish fulfills both beauty and anticorrosion functions. For this reason, a method of applying a phosphate-based or chromate-based chemical conversion treatment to the surface of a metal substrate and then finishing it with one coat is used.
It was unsatisfactory in terms of corrosion resistance. Especially as an excellent coating material on the surface of the can material, as well as good corrosion resistance to prevent corrosion of the can material, water resistance to withstand high temperature hot water treatment to sterilize the food that is the content, and coating hardness that does not easily scratch during transportation. At present, the performance of is required.

[Structure of Invention]

(Means for Solving the Problems) The present invention has been made in view of the above-mentioned circumstances, and introduces phosphoric acid, which is a component having excellent corrosion resistance, into the resin itself, and at the same time, it functions as a curing catalyst to improve water resistance. A coating composition having improved corrosion resistance, water resistance and coating hardness is provided by improving the coating hardness with an aromatic epoxy resin as a basic skeleton resin and improving the crosslink density by introducing a high hydroxyl value compound. It is a thing.

That is, the present invention is a modified product obtained by reacting (a) an aromatic epoxy resin with phosphoric acid and a low molecular weight alcohol or a derivative thereof or an alcoholic hydroxyl group-containing low molecular weight resin having a number average molecular weight of 3,000 or less and a hydroxyl value of 150 or more. A coating composition comprising an epoxy resin composition, (b) an acrylic resin or polyester resin, and (c) an aminoplast resin as resin components.

The aromatic epoxy resin in the present invention is, for example, bisphenol A diglycidyl ether or bisphenol A.
There are diglycidyl ether type epoxy resins such as di-β-methyl-diglycidyl ether, tetrahydroxyphenylmethane tetraglycidyl ether, novolac glycidyl ether and diglycidyl ether of bisphenol A alkylene oxide adduct. Particularly preferred is a diglycidyl ether type epoxy resin of bisphenol A. The epoxy equivalent of these aromatic epoxy resins is 170 to 4000. When the epoxy equivalent is 170 or less, the coating film hardness does not appear, and when it is 4000 or more, the corrosion resistance is poor.

Examples of the alcohol component used for producing the modified epoxy resin in the present invention include low molecular weight alcohol, alcoholic hydroxyl group-containing polyester resin, acrylic resin and the like.

As low molecular weight alcohols, n-butanol, isobutanol, n-amyl alcohol, active amyl alcohol, isoamyl alcohol, secondary amyl alcohol, tertiary amyl alcohol, n-hexyl alcohol, methylamyl alcohol, 2-ethylbutanol, n -Heptanol, 2-heptanol, 2-ethylhexanol, 3,5,5-trimethylhexanol, n-nonyl alcohol, undecyl alcohol, n-dodecyl alcohol, trimethylnonyl alcohol, n-tetradecyl alcohol, heptadecyl alcohol, cyclo Monohydric alcohols such as hexanol and 2-methylcyclohexanol, 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, and dihydric alcohols such as diglycerin and some of the hydroxyl groups of polyhydric alcohols Alkyl etherified, for example, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol monoisopropyl ether, ethylene glycol monobutyl ether, propylene glycol monobutyl ether, propylene glycol monomethyl ether, propylene glycol monoethyl ether, diethylene glycol monobutyl ether , Diethylene glycol monoethyl ether, diethylene glycol monoisopro Ether, diethylene glycol mono-butyl ether,
Examples include dipropylene glycol monomethyl ether, dipropylene glycol monoethyl ether, dipropylene glycol monoisopropyl ether, and dipropylene glycol monobutyl ether. These low molecular weight alcohols can be used as a solvent in the production of the modified epoxy resin.

Examples of the alcoholic hydroxyl group-containing polyester resin include polyhydric alcohols such as ethylene glycol, diethylene glycol, propylene glycol, neopentyl glycol, triethylene glycol, dipropylene glycol, glycerin, trimethylolethane, trimethylolpropane, pentaerythritol, diether. One or one of pentaerythritol, 1,3-butylene glycol, pentanediol, trimethylpentanediol, 1,6-hexanediol, 1,4-dicyclohexanedimethanol, (hydrogenated) bisphenol A, bisphenol dihydroxypropyl ether, etc. Used as a mixture of two or more kinds, as polyvalent carboxylic acid or its anhydride, (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, fumaric acid, itaconic acid, (anhydrous) It is obtained by synthesizing trimellitic acid, methylenecyclohexene tricarboxylic acid (anhydride), (anhydrous) pyromellitic acid, etc. as a mixture of one kind or two or more kinds while controlling the molecular weight under the equivalent of hydroxyl group.

Examples of the alcoholic hydroxyl group-containing acrylic resin include hydroxyl group-containing vinyl monomers such as hydroxymethyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyamyl acrylate, hydroxyhexyl acrylate, and corresponding methacrylates, and vinyl monomers copolymerizable therewith, for example, , Ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, methyl methacrylate, ethyl methacrylate, butyl methacrylate, stearyl methacrylate, cyclohexyl methacrylate, etc. Acrylic acid alkyl ester or alkyl methacrylate ester , N- (methoxymethyl) acrylamide, N- (isobutoxymethyl) acrylamide, N
Vinyl monomers containing N-alkoxyalkyl-substituted amides such as-(butoxymethyl) acrylamide, styrene,
Aromatic vinyl monomers such as vinyltoluene, α-methylstyrene, etc., vinyl monomers containing carboxyl groups such as (meth) acrylic acid, maleic acid, fumaric acid, etc. to reduce the reaction solid content, or to add a large amount of initiator, Alternatively, it is obtained by controlling the molecular weight using a chain transfer agent and synthesizing it.

Examples of the phosphoric acid in the present invention include acids formed by hydration of diphosphorus pentoxide such as metaphosphoric acid, pyrophosphoric acid, orthophosphoric acid, diphosphoric acid, and tetraphosphoric acid, and are used as one kind or a mixture of two or more kinds. It is preferably orthophosphoric acid.

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

In the present invention, the acrylic resin as the component (b) is, for example,
Carboxyl group-containing vinyl monomers such as (meth) acrylic acid, maleic acid, and fumaric acid, and vinyl monomers copolymerizable therewith, such as hydroxymethyl acrylate, hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxyamyl acrylate, hydroxyhexyl acrylate, and the like. Hydroxyl group-containing vinyl monomer such as methacrylate, ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, cyclohexyl acrylate, methyl methacrylate,
Acrylic alkyl ester or methacrylic acid alkyl ester such as ethyl methacrylate, butyl methacrylate, stearyl methacrylate, cyclohexyl methacrylate, N- (methoxymethyl) acrylamide, N- (isobutoxymethyl) acrylamide, N- (butoxymethyl) N-alkoxyalkyl-substituted amide-containing vinyl monomers such as acrylamide, styrene, vinyltoluene,
Obtained by copolymerizing with an aromatic vinyl monomer such as α-methylstyrene, preferably having a number average molecular weight of 4000 to
There are 30,000 acrylic resins.

The polyester resin as the component (b) in the present invention is, for example, ethylene glycol, propylene glycol, 1,3-
Butylene glycol, 1,6-hexanediol, diethylene glycol, dipropylene glycol, neopentyl glycol, triethylene glycol, dihydric alcohols such as (hydrogenated) bisphenol A, trimethylolethane, trimethylolpropane, trishydroxymethylaminomethane, Pentaerythritol, dipentaeryt, diglycerin, and other divalent alcohols are used as alcohol components, and (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, fumaric acid, itaconic acid, (anhydrous)
Polyvalent carboxylic acids such as trimellitic acid, methylenecyclohexentricarboxylic acid (anhydride), (anhydrous) pyromellitic acid or their anhydrides, and monobasic acids such as benzoic acid and t-butylbenzoic acid which are optionally used in combination. Is an oil-free polyester resin obtained by condensation with an acid component, or in addition to the above alcohol component and the above acid component, castor oil, dehydrated castor oil, tung oil, safflower oil, soybean oil, linseed oil, tall oil, coconut oil, etc. , And an alkyd resin obtained by reacting three components by adding an oil component, which is one or a mixture of two or more of those fatty acids, to the above acid component and alcohol component, and a polyester having an unsaturated bond. There is a graft-modified polyester resin obtained by grafting a resin with an acrylic resin modified by grafting. The number average molecular weight of polyester resin is 1000 to 2
0000 is preferable.

The aminoplast resin (c) in the present invention is an alkyl etherified melamine resin, an alkyl etherified benzoguanamine resin, an alkyl etherified urea resin, an alkyl etherified resin of diguanamine having two triazine rings bonded to a phenylene nucleus, or an alkyl etherified resin. A glycol resin or the like is used alone or in combination of two or more. Preference is given to fully etherified hexamethoxymelamine.

In the coating composition of the present invention, the modified epoxy resin composition (a) is preferably added in an amount of 2 to 30 parts by weight based on the solid content of the coating resin in order to exhibit the corrosion resistance, water resistance and coating film hardness in a well-balanced manner. The acrylic resin or polyester resin (b) is mixed in 20 to 83 parts by weight in the solid content of the coating resin.
If it is less than 20 parts by weight, the flexibility is poor, and if it exceeds 83 parts by weight, the coating film hardness is poor. The aminoplast resin (c) is preferably used in an amount of 15 to 50 parts by weight in the solid content of the coating resin.
If it is less than 15 parts by weight, water resistance and coating film hardness are poor, and if it exceeds 50 parts by weight, flexibility tends to be poor.

In the coating composition of the present invention, if necessary, an amine-blocked acid catalyst such as p-toluenebenzenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenedisulfonic acid or the like is used as a curing aid with respect to 100 parts of the resin solid content. 0.1
Add 1 part to make a paint.

A pigment, a leveling agent, a defoaming agent, and a lubricant can be added to the coating composition of the present invention. The pigment is preferably blended after kneading an acrylic resin or polyester resin solution to prepare a pigment paste. Furthermore, the coating composition of the present invention further comprises a butadiene resin, an epoxy resin,
A vinyl chloride-based resin or the like can also be mixed.

The coating composition of the present invention can be applied to a substrate by a known means such as roll coating, spraying or brush coating. As the base material, there are metal base materials such as electric tin-plated steel plate, tin-free steer, and aluminum.

Further, the coating composition of the present invention can be cured under 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 5 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 (Production of modified epoxy resin solution A1) 60 parts of diethylene glycol monobutyl ether in a four-necked flask equipped with a thermometer, a stirrer, a reflux condenser, and a nitrogen gas blowing tube, Epicoat 828 (trade name of Yuka Shell Epoxy Co., Ltd.) ) 40 parts were charged and dissolved by heating at 70 ° C, 10.4 parts orthophosphoric acid (0.5 mol relative to the epoxy group) was charged and heated to 130 ° C while stirring while introducing nitrogen gas, and reacted until the epoxy equivalent became 11,000. After that, it was cooled to below 50 ° C to obtain a modified epoxy resin solution A1 having a solid content of 60%.

Production Example 2 (Production of Modified Epoxy Resin Solution A2) The same four-necked flask as in Production Example 1 was charged with 35 parts of diethylene glycol monoethyl ether and 79.5 parts of Epicoat 1004 and dissolved by heating at 90 ° C. to obtain orthophosphoric acid 2.2 parts (epoxy group). 0.5 mol) was added to the mixture, and the mixture was heated to 130 ° C with stirring while introducing nitrogen gas, reacted until the epoxy equivalent reached 11,000, added with 27.2 parts of ethylene glycol monobutyl ether, and further cooled to 50 ° C or less, 60% solid content
A modified epoxy resin solution A2 of was obtained.

Production Example 3 (Production of Modified Epoxy Resin Solution A3) Neopentyl glycol 5 was placed in a four-necked flask equipped with a thermometer, a stirrer, a reflux condenser with a separation tank, and a nitrogen gas blowing tube.
0.0 part, adipic acid 23.4 parts, terephthalic acid 26.6 parts were charged and heated to 230 ° C while stirring while introducing nitrogen gas, reacted until the acid value became 5 or less, then cooled and hydroxyl value 18
A polyester resin having a number average molecular weight of 1,500 was obtained. Next, at 100 ° C, 1,100 parts of Epicoat 100 were charged, and after heating and dissolution, 6.31 parts of orthophosphoric acid (0.3 mol based on epoxy group) was charged and heated to 130 ° C, reacted until the epoxy equivalent was 12,000 or more, and then cooled. Modified epoxy resin solution A with a solid content of 60% by adding 131 parts of ethylene glycol monobutyl ether
3 was obtained.

Production Example 4 (Production of Modified Epoxy Resin Solution A4) The same four-necked flask as in Production Example 3 was charged with 48.4 parts of neopentyl glycol and 51.6 parts of terephthalic acid and heated to 230 ° C. while stirring while introducing nitrogen gas, After reacting until the acid value becomes 5 or less, it is cooled and the hydroxyl value is 180 and the number average molecular weight is
1600 polyester resins were obtained. Next, at 100 ° C, 1,98.8 parts of Epicoat 100 was charged, and after heating and melting, orthophosphoric acid 1
Charge 0.2 parts (0.5 mol based on epoxy group), heat to 130 ° C, react until the epoxy equivalent exceeds 12,000 and then cool, add 132 parts ethylene glycol monobutyl ether and add 60% solid modified epoxy. Resin solution A4 was obtained.

Production Example 5 (Production of Modified Epoxy Resin Solution A5) The same four-necked flask as in Production Example 1 was charged with 145 parts of ethylene glycol monoethyl ether and 5 parts of propyl mercaptan and stirred at 115 ° C. while introducing nitrogen gas.
After heating to 20 ° C, 20 parts of α-methylstyrene, 5 parts of acrylic acid, 40 parts of 2-hydroxypropyl acrylate,
A mixture of 35 parts of ethyl acrylate and 0.8 part of benzoyl peroxide was added dropwise over 3 hours. Then keep at 115 ℃,
After reacting for 1 hour, adding 0.1 part of benzoyl peroxide, reacting for another hour, cooling and distilling off ethylene glycol monoethyl ether under reduced pressure at 80 ° C. to obtain a hydroxyl value of 175, a number average molecular weight of 2100 and a solid content of 85%. Acrylic resin solution of was obtained. Next, 100 parts of Epicoat 100, 97.4 parts were charged and dissolved by heating at 90 ° C, and then 10.0 parts of orthophosphoric acid (
Mol) was added and the mixture was heated to 130 ℃ and the epoxy equivalent was 12,000.
After reacting until the above temperature, the mixture was cooled and 121 parts of ethylene glycol monobutyl ether was added to obtain a modified epoxy resin solution A5 having a solid content of 60%.

Production Example 6 (Production of Acrylic Resin Solution B2) n-Butanol 100 was placed in the same four-necked flask as in Production Example 1.
Parts were charged and kept at 105 ° C while introducing nitrogen gas, from the dropping tank, acrylic acid 10 parts, 2-hydroxyethyl methacrylate 20 parts, styrene 40 parts, butyl acrylate.
A mixture of 30 parts and 3 parts of benzoyl peroxide was added dropwise over 3 hours. Then, the mixture was reacted at 105 ° C. for 1 hour, 0.3 part of benzoyl peroxide was added, reacted for 1 hour and cooled to 60 ° C. or lower to obtain an acrylic resin solution B1 having a solid content of 50% and a number average molecular weight of 10,000.

Production Example 7 (Production of Polyester Resin Solution B2) The same four-necked flask as in Production Example 3 was charged with 44.4 parts of neopentyl glycol, 26.0 parts of adipic acid, and 29.6 parts of terephthalate and heated to 230 ° C. while stirring while introducing nitrogen gas. After heating and reacting until the acid value becomes 10 or less, it is cooled, 58.1 parts of ethylene glycol monobutyl ether is added at 150 ° C, and further cooled to 60 ° C or less to obtain a polyester resin solution B2 having a solid content of 60%. Was given.

Example 1 6.7 parts of modified epoxy resin solution A1 and acrylic resin solution B1 3
3.3 parts, hexamethoxymelamine (Mitsui Toatsu Chemicals, Inc.)
Cymel 303 manufactured by the same company; the same applies to the following examples) 10.5 parts, amine-blocked paratoluenesulfonic acid 0.1 part, xylene 23.9
Part, 23.9 parts of cyclohexanone and 0.1 part of a silicone leveling agent were mixed to form a paint.

Examples 2 to 12 By the same method as in Example 1, the resin composition was changed as shown in Table 1 to form coating materials.

Further, Comparative Examples 1 to 3 show coating materials containing no modified epoxy resin of the present invention.

The coating tests of the paints obtained in Examples 1 to 12 and Comparative Examples 1 to 3, the coating film physical properties test after baking and curing, and the paint stability test were conducted and shown in Table 1.

○ 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.

○ Physical property test of coating film: An electroplated tin plate with a plate thickness of 0.23 mm was coated by roll coating to a film thickness of 7 μ after drying, and baked in a gas oven at an ambient temperature of 190 ° C for 10 minutes to prepare a coated panel. .

○ Water resistance test; dip coating pulse in water, 100 ℃ -30 minutes and 125 ℃
After heat treatment for -30 minutes, the whitening state of the coating film was evaluated.

Workability test: An Erichsen test was conducted.

○ Impact resistance test: DuPont type 1/2 inch, 500 g load was tested.

○ Pencil hardness test: It was evaluated by the pencil hardness test method according to JIS standard.

○ Adhesion test: A goose eye peel test was performed.

○ Salt water spray resistance test: After cutting a test piece that has a sealed part other than the coated surface until it reaches the base, put it in a salt water spray tester (JIS-Z-2371).
Either blister or rust from the cross cut part has a width of 3 mm
Indicates the time to reach.

○ Salt water immersion resistance test: Cut the test piece under seal except the coated surface until it reaches the base material, and then dip it in 5% saline solution at 37 ° C to remove any blisters or rust from the cross cut part. The time required to reach a width of 3 mm is shown.

〔The invention's effect〕

Since the coating composition of the present invention is excellent in corrosion resistance, water resistance and coating film hardness, it prevents corrosion of the can material when used as an outer surface coating of a can and withstands high temperature hot water treatment for sterilizing food, It is possible to form a coating film on the outer surface of the can which is not easily scratched during transportation.

Claims (1)

[Claims] 1. A modification obtained by reacting (a) an aromatic epoxy resin with phosphoric acid, a low molecular weight alcohol or a derivative thereof, or an alcoholic hydroxyl group-containing low molecular weight resin having a number average molecular weight of 3,000 or less and a hydroxyl value of 150 or more. A coating composition comprising an epoxy resin composition, (b) an acrylic resin or a polyester resin, and (c) an aminoplast resin as resin components.