JPH07157711A - Water-based coating composition - Google Patents

Abstract

PURPOSE:To obtain a water-based coating composition composed of a specific amount of a specific water-soluble resin, a waterbased thermosetting resin and a curing agent and having excellent storage stability, water resistance and corrosion resistance. CONSTITUTION:This coating composition is composed of (A) a water-soluble resin produced by copolymerizing preferably 50-90 pts.wt. of a phosphate- modified epoxy resin (preferably a compound having an acid value of <=5 mgKOH/g and a phosphorus content of 1-8% and obtained by the reaction of an epoxy resin mixture consisting of preferably 70-95wt.% of bisphenol-type epoxy resin and 5-30wt.% of novolak epoxy resin with a phosphoric acid ester composed mainly of a monohydroxyphosphoric acid diester) and preferably 10-50 pts.wt. of an ethylenic unsaturated monomer containing carboxyl group and making the copolymer to be soluble in water by neutralizing the carboxyl group with a basic compound, (B) an aqueous thermosetting resin (e.g. water-soluble or water-dispersible alkyd resin) and (C) a curing agent. The amount of the component A is 2-20 pts.wt. based on 100 pts.wt. of the coating composition.

Description

Detailed Description of the Invention

[0001]

The present invention contains a water-soluble resin obtained by solubilizing a copolymer of a phosphoric acid ester-modified epoxy resin and a carboxyl group-containing ethylenically unsaturated monomer in water with a basic substance as an essential component. The present invention relates to a water-based coating composition for producing a coating film having excellent water resistance and corrosion resistance.

[0002]

2. Description of the Related Art In recent years, restrictions on the concentration of organic solvents in paints are being tightened. The resin forms currently used for water-based paints include emulsion type and water-soluble type.
Since the emulsion type uses a large amount of hydrophilic emulsifiers, these remain in the coating film after the coating film is formed, and there is a drawback that the physical properties such as water resistance are deteriorated. Further, the water-soluble type generally needs to have a high acid value in order to be water-soluble, but a high acid value has a drawback of poor water resistance, and a low acid value causes a problem of poor stability. Phosphoric acid-modified epoxy resin is known as a method for improving these drawbacks. Although the water resistance is improved by this, there is a drawback that the stability of the coating is remarkably inferior.

[0003]

DISCLOSURE OF THE INVENTION The present invention solves the above problems and provides a water-based coating composition having good coating stability and excellent coating film water resistance.

[0004]

The gist of the present invention is a water-soluble resin obtained by copolymerizing a phosphoric acid ester-modified epoxy resin and a carboxyl group-containing ethylenically unsaturated monomer,
A coating composition comprising an aqueous thermosetting resin and a curing agent, wherein the water-soluble resin is contained in an amount of 2 to 20 parts by weight per 100 parts by weight of the aqueous coating composition. Is. That is, in the present invention, the acid value is 5 mgKOH / g or less and the oxirane oxygen content is 0.2% in order to improve the adhesiveness by modifying the epoxy resin with a phosphoric acid ester and further improve the stability of the coating material. Reduced to below and copolymerized with a carboxyl group-containing ethylenically unsaturated monomer, and by neutralizing the copolymer with a basic substance, good stability, and excellent water resistance and corrosion resistance It is possible to obtain a water-based coating composition that gives coating film physical properties such as. Hereinafter, the present invention will be described in detail.

The epoxy resin used in the present invention is preferably a mixed epoxy resin of bisphenol type and novolac type. The bisphenol type epoxy resin is preferably a bisphenol A type or a bisphenol F type diglycidyl ether type. The epoxy resin can be used in a molecular weight range of about 312 to 10,000, but if the molecular weight is large, the phosphorus content of the phosphate ester-modified compound is lowered and the effect of the present invention is diminished.
Preferably, the molecular weight range is from 312 to 2,000.
It is a degree. As the novolac type epoxy resin, phenol novolac, orthocresol novolac, alkylphenol novolac, etc. can be used, but the phenol novolac type is preferred. The mixing ratio of bisphenol type epoxy resin and novolac type epoxy resin is
It is preferably in the range of 70:30 to 95: 5% by weight. This is because when the novolac type epoxy resin is 5% by weight or less, the water resistance and corrosion resistance are not sufficiently improved, and when it is 30% by weight or more, gelation occurs during the phosphoric ester reaction.

The preferred phosphoric acid ester used in the present invention is a monohydrooxyphosphoric acid diester, but a mixture with a dihydrooxyphosphoric acid monoester can also be used. Examples of the phosphoric acid ester include dibutyl phosphate, dioctyl phosphate, monoisodecyl phosphate, di (2-ethylhexyl) phosphate, ethyl acid phosphate, butyl acid phosphate, isopropyl acid phosphate,
Isodecyl acid phosphate, tridecanol acid phosphate, butoxyethyl acid phosphate, 2-ethylhexyl acid phosphate, β-chloroethyl acid phosphate, heptyl acid phosphate, (2-hydroxyethyl methacrylate)
Examples thereof include acid phosphates, but are not limited to these.

The reaction of adding the phosphoric acid ester to the epoxy resin of the present invention is preferably carried out with the acid equivalent of the phosphoric acid ester being within the range of 0.2 to 0.9 per 1 equivalent of the epoxy group. This is because when the content is 0.2 or less, the phosphorus content decreases, and when the content is 0.9 or more, unreacted phosphate ester remains and the acid value increases. The reaction temperature is 50 to 150.
C., preferably 80 to 120.degree. C., the phosphoric acid ester is gradually added to the heated epoxy resin in 30 minutes to 2 hours to further increase the acid value to 10 mgKOH / g or less.
Allow to react for 10 hours. The phosphorus content of the adduct is preferably 1 to 8%, and if it is 1% or less, the corrosion resistance is poor, and if it is more than 8%, it is not so good. Further, when the acid value is 10 mgKOH / g or more, the storage stability as a composition for water-based coating is poor, so the acid value is 10 mgKOH.
/ G or less, preferably 5 mgKOH / g or less. The reaction is preferably carried out without a solvent, but a solvent may be used. In particular, when copolymerizing a phosphoric acid ester-modified epoxy resin and a carboxyl group-containing ethylenically unsaturated monomer as described later, if a hydrophilic solvent is used as a solvent, it is necessary to change the solvent in the next step. It is preferable because it does not exist. If a large amount of epoxy groups remain after the reaction, ester-type grafts with poor hydrolysis resistance will occur when copolymerizing with a carboxyl group-containing ethylenically unsaturated monomer, so that the oxirane oxygen content after the reaction is 0.2 % Or less is preferable. As a means for reducing the oxirane oxygen content, a phosphoric acid ester-modified epoxy resin is copolymerized with a carboxyl group-containing ethylenically unsaturated monomer, and then the copolymer is reacted with a tertiary fatty acid. preferable. This reaction can be made 0.2% or less by adding 0.5 to 1.0 mol of a tertiary fatty acid to the remaining epoxy group and reacting at 100 to 180 ° C. for 1 to 10 hours. .

The copolymerization of the phosphoric acid ester-modified epoxy resin of the present invention with the carboxyl group-containing ethylenically unsaturated monomer means that the phosphoric acid ester-modified epoxy resin is mixed with the carboxyl group-containing ethylenically unsaturated monomer by a conventional method. Addition polymerization of a monomer, specifically, addition polymerization of a phosphoric acid ester-modified epoxy resin with a carboxyl group-containing ethylenically unsaturated monomer in the presence of a free radical generator in an organic solvent solution Is. The carboxyl group-containing ethylenically unsaturated monomer used in the present invention contains a monoethylenically unsaturated carboxylic acid containing a carboxyl group such as acrylic acid, methacrylic acid or fumaric acid as an essential component, and other It may contain a carboxyl group-containing ethylenically unsaturated monomer and forms a water-dispersible salt by copolymerization with an epoxy resin.
It should be noted that acrylic acid and / or methacrylic acid must be contained at least 3% or more in the total ethylenically unsaturated monomer in order to be water-soluble. As the unsaturated monomer other than acrylic acid or methacrylic acid, methyl acrylate, ethyl acrylate, isopropyl acrylate, butyl acrylate,
Acrylic acid esters such as isoamyl acrylate, 2-ethylhexyl acrylate and decyl acrylate, and corresponding methacrylic acid alkyl esters,
Styrene, vinyltoluene, 2-methylstyrene, t-
Styrene monomers such as butyl styrene, hydroxyethyl acrylate, hydroxyethyl methacrylate, polyethylene glycol monomethacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate, and other hydroxyl group-containing monomers, methylol groups such as N-methylol acrylamide, dimethylol acrylamide, etc. The monomer can be selected from one or more of a content monomer, an alkoxymethyl group-containing monomer such as N-butoxymethylacrylamide, an epoxy group-containing monomer such as glycidyl acrylate and glycidyl methacrylate, and acrylonitrile.

Examples of the free radical generator used in the present invention include benzoyl peroxide, perbutyl octate, t-butyl hydroperoxide, azobisisobutyronitrile and the like. Particularly preferred is benzoyl peroxide. It is an oxide. These are used as at least 1.5% by weight or more in the total ethylenic monomer. Hydrophilic organic solvents that can be used in the copolymerization of the present invention include alkyl alcohols such as methanol, ethanol, propanol, butanol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, ethylene glycol isopropyl ether, ethylene glycol monobutyl ether, diethylene glycol. Examples thereof include ether alcohols such as monomethyl ether and diethylene glycol monoethyl ether, and ether esters such as ethylene glycol monomethyl ether acetate and ethylene glycol monoethyl ether acetate. Further, an inert organic solvent which is immiscible with water can also be used, and examples thereof include aromatic hydrocarbons such as toluene and xylene, esters such as ethyl acetate and butyl acetate, and ketones such as acetone and methyl ethyl ketone. It is preferable that these organic solvents can be removed by distillation under normal pressure or reduced pressure.

In the copolymerization of the present invention, it is preferable to use 50 to 90% by weight of a phosphoric acid ester-modified epoxy resin and 10 to 50% by weight of a carboxyl group-containing ethylenically unsaturated monomer. When the amount of the modified epoxy resin is less than 50% by weight, the corrosion resistance targeted by the present invention is insufficient, and when it is more than 90% by weight, a good dispersion cannot be obtained. The temperature of the copolymerization reaction is 40 to 200 ° C., preferably 60 to 150.
React at 3 ° C for 3 to 10 hours. The acid value of the obtained copolymer product is usually 10 to 300, especially 30 to 100 mgK.
It is preferably in the range of OH / g.

To solubilize the copolymerization product obtained in the present invention in water, a basic compound such as amine or ammonia may be added to neutralize the carboxyl group partially or entirely. Examples of the compound include ammonia or triethylamine, triethanolamine, monomethylamine, monoethylamine, monomethanolamine, dimethanolamine, trimethanolamine, dimethylethanolamine, etc., but those having a boiling point of 120 ° C. or higher have corrosion resistance of the coating film. Since the improvement effect is not sufficient, those having a boiling point of 120 ° C. or less are preferable, and triethylamine is particularly preferable.

Examples of the water-based thermosetting resin used in the present invention include water-soluble or water-dispersible alkyd resins, oil-free alkyd resins, polyester resins and acrylic resins, but are not limited thereto. is not. The curing agent used in the present invention is amino resin, resole resin or the like. Further, various additives such as a color pigment, a rust preventive pigment, an anti-sagging agent, and a surface conditioner can be blended if necessary. The water-based coating composition of the present invention thus obtained is particularly heat-cured with an aqueous amino resin, and the water-based thermosetting resin is an alkyd resin obtained by using a drying oil or its fatty acid. In addition, a metal dryer can be added for use as an always dry type paint. The resin composition for an aqueous coating composition of the present invention thus obtained can provide a coating film having excellent storage stability and water resistance and corrosion resistance.

[0013]

EXAMPLES AND COMPARATIVE EXAMPLES The present invention will be specifically described below with reference to examples, but the present invention is not limited to these examples. The "parts" are parts by weight unless otherwise specified.

Production Example 1 YD-128 (bisphenol A type liquid epoxy resin manufactured by Tohto Kasei Co., epoxy equivalent = 187 g / eq) was placed in a reaction vessel equipped with a stirrer, a thermometer, a reflux condenser and a dropping funnel.
00 parts and YDPN-638 (Tono Kasei Co., Ltd. phenol novolac type epoxy resin, epoxy equivalent = 178 g / e
q) After adding 200 parts and heating to 100 ° C., dibutyl phosphate (acid value = 264 mgKOH / g) 804.5
Parts were added dropwise over 1 hour and reacted for an additional 6 hours. Furthermore, neo acid (manufactured by Exxon Chemical Co., acid value = 321 mgKOH /
g) 95.6 parts and 0.1 part of triphenylphosphine as a catalyst were charged and reacted at 150 ° C. for 8 hours to give an acid value of 3.9 mgKOH / g and an oxirane oxygen content of 0.03.
%, A phosphoric acid ester-modified epoxy resin having a number average molecular weight of 2,500 was obtained. 320 parts of the above phosphoric acid ester-modified epoxy resin was added to ethylene glycol monobutyl ether 7
0.6 part was added and dissolved by heating to 115 ° C., and a mixture of 23.0 parts of methacrylic acid, 57 parts of methyl methacrylate and 6.5 parts of 75% benzoyl peroxide was added at a temperature of 1 in the reaction vessel.
After adding dropwise for 2 hours so as to maintain the temperature of 15 to 120 ° C., the mixture was reacted for another 2 hours at the same temperature to obtain a copolymer having an acid value of 42 mgKOH / g. Next, 41 parts of ethylene glycol monobutyl ether was added and heated to 80 ° C., 33.3 parts of triethylamine was added dropwise over 1 hour, and then 202.3 parts of ion-exchanged water was added over 2 hours, and the viscosity was 950 cp.
A water-soluble resin having a pH of 6.7 at s / 25 ° C. was obtained.

Production Example 2 240 parts of a modified resin having an acid value of 3.9 mgKOH / g, an oxirane oxygen content of 0.03% and a number average molecular weight of 2,500 and 37.5 parts of n-butyl alcohol described in Production Example 1.
112.5 parts of ethylene glycol monobutyl ether was placed in a reaction vessel and dissolved at 115 ° C., followed by 17.3 parts of methacrylic acid, 9.1 parts of styrene monomer, 0.3 part of ethyl acrylate, and 75% benzoyl peroxide. 2.4 parts of the mixture was added dropwise over 2 hours, and further reacted at the same temperature for 2 hours to obtain a copolymer having an acid value of 60 mgKOH / g. Next, the mixture was cooled to 85 ° C., 27.7 parts of triethylamine and 5 parts of deionized water.
Add 60 parts and mix, viscosity = 870 cps / 25 ° C.,
A water-soluble resin having a pH of 7.4 was obtained.

Production Example 3 YD-128, 186 parts and ethylene glycol monobutyl ether, 70 parts, were placed in the same reaction vessel as in Production Example 1 and heated to 100 ° C., and then butyl acid phosphate (acid value = 437 mgKOH / G) 93 parts in 30 minutes and then reacted at 100 ° C. for 2 hours to give an acid value of 99.4 mgK.
A modified resin having OH / g, oxirane oxygen content = 0.4% and number average molecular weight = about 1200 was obtained. Next, after cooling to 80 ° C., 48.5 g of dimethylethanolamine and 264 g of ion-exchanged water were added dropwise, pH = 8.2, viscosity = 64 cp.
s / 25 ° C., resin content = 50%, solvent content = 10%, water content =
40% colorless and transparent water-soluble resin was obtained.

Example 1 Aqueous acrylic resin as a water-based thermosetting resin (33.3 as a solid content of Almatex W911 manufactured by Mitsui Toatsu Co., Ltd.)
Part, titanium oxide as a pigment (Taipaque R manufactured by Ishihara Sangyo Co., Ltd.
830), 54 parts, 13 parts of an amino resin (CYMEL 303 manufactured by Mitsui Cyanamid Co., Ltd.) as a curing agent, and Production Example 1
10 parts of the water-soluble resin obtained in 1. above was added to the solid content, and 0.3 parts of p-toluenesulfonic acid amine salt (4040 manufactured by Mitsui Cyanamid Co., Ltd.) as a catalyst was added thereto to obtain an aqueous paint.

Example 2 A coating material of Example 2 was obtained by using the same procedure as in Example 1 except that the water-soluble resin obtained in Production Example 2 was used.

Comparative Example 1 A coating material of Comparative Example 1 was obtained in the same manner as in Example 1 except that the water-soluble epoxy resin was not added.

Comparative Example 2 A coating material of Comparative Example 2 was obtained by using the same procedure as in Example 1 except that the water-soluble resin obtained in Production Example 3 was used.

Comparative Example 3 A coating material of Comparative Example 3 was obtained in the same manner as in Example 1 except that the water-soluble resin obtained in Production Example 4 was used.

Table 1 shows the results of evaluation of stability and coating film physical properties of the coating materials prepared in Examples and Comparative Examples. The test method is as follows. -Stability test of paint After the paint was stored at a temperature of 40 ° C for 1 month, the presence or absence of separation was examined. Coating film physical property test A zinc phosphate-treated steel plate, 50 × 150 × 0.3 mm test piece was coated with a bar coater so that the dry film thickness was 25 to 30 μm, and baked for 20 minutes in a dryer set at 160 ° C. . Pencil hardness test The pencil hardness test was conducted according to JIS K5400 pencil scratch test. -Adhesion test A cross-cut tape peeling test was conducted, and the results are shown in Table 1 as ◯: no peeling, Δ: slightly peeling, and x: whole surface peeling. -Water resistance test A coated plate was immersed in water and subjected to hot water treatment at 100 ° C for 2 hours, and then a cross-cut tape peeling test was performed as an observation of the state of the coating film and an adhesion test. -Corrosion resistance test After cross-cutting with a cutter knife so as to reach the base material of the coating film, spray 5% salt water at 35 ° C for 240 hours,
The state of the cross cut portion was observed. When there was no abnormality in the coating film, it was evaluated as ○, when blister was generated, it was evaluated as △, and when blister generation was large, it was evaluated as ×. Also, measure the rust width from the cross-cut part, ○: rust width 1 mm or less, △; rust width 1-2 m
It is shown in Table 1 as m, x; 3 to 4 mm.

[0023]

[Table 1]

[0024]

As is apparent from Table 1, the water-based coating composition of the present invention can provide a coating film having excellent storage stability, water resistance and corrosion resistance.

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[Procedure amendment]

[Submission date] January 5, 1994

[Procedure Amendment 1]

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Table 1 shows the results of evaluating the stability and coating film physical properties of the coating materials prepared in Examples and Comparative Examples. The test method is as follows. -Stability test of paint After the paint was stored at a temperature of 40 ° C for 1 month, the presence or absence of separation was examined. Coating film physical property test A zinc phosphate-treated steel plate, 50 × 150 × 0.3 mm test piece was coated with a bar coater so that the dry film thickness was 25 to 30 μm, and baked for 20 minutes in a dryer set at 160 ° C. . Pencil hardness test The pencil hardness test was conducted according to JIS K5400 pencil scratch test. -Adhesion test A cross-cut tape peeling test was conducted, and the results are shown in Table 1 as ◯: no peeling, Δ: slightly peeling, and x: whole surface peeling. -Water resistance test A coated plate was immersed in water and subjected to hot water treatment at 100 ° C for 2 hours, and then a cross-cut tape peeling test was performed as an observation of the state of the coating film and an adhesion test. -Corrosion resistance test After cross-cutting with a cutter knife so as to reach the base material of the coating film, spray 5% salt water at 35 ° C for 240 hours,
The state of the cross cut portion was observed. When there was no abnormality in the coating film, it was evaluated as ○, when blister was generated, it was evaluated as △, and when blister generation was large, it was evaluated as ×. Also, measure the rust width from the cross-cut part, ○: rust width 1 mm or less, △; rust width 1-2 m
It is shown in Table 1 as m, x; 3 to 4 mm.

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[0022]

[Table 1]

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[0023]

As is apparent from Table 1, the water-based coating composition of the present invention can provide a coating film having excellent storage stability, water resistance and corrosion resistance.

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Claims (5)

[Claims] 1. A coating composition comprising a water-soluble resin obtained by copolymerizing a phosphoric acid ester-modified epoxy resin and a carboxyl group-containing ethylenically unsaturated monomer, an aqueous thermosetting resin, and a curing agent. A water-based coating composition containing the water-soluble resin in an amount of 2 to 20 parts by weight per 100 parts by weight of the water-based coating composition. 2. The phosphoric acid ester-modified epoxy resin is 7
It is a reaction product of an epoxy resin having 0 to 95% by weight of bisphenol type and 5 to 30% by weight of novolac type, and a phosphoric acid ester containing monohydroxyphosphoric acid diester as a main component, and an acid value of 5 mgKOH / g or less. The phosphorus content is 1 to 8%, and the aqueous coating composition according to claim 1. 3. The water-based coating composition according to claim 1, wherein the phosphoric acid ester-modified epoxy resin has an oxirane oxygen content of 0.2% or less. 4. The water-soluble resin is obtained by copolymerizing 50 to 90 parts by weight of the modified epoxy resin with 10 to 50 parts by weight of a carboxyl group-containing ethylenically unsaturated monomer, and then converting the carboxyl group into a base. The water-based coating composition according to claim 1, which is a water-soluble resin neutralized with a hydrophilic compound. 5. The acid value of a copolymer obtained by copolymerizing a modified epoxy resin and a carboxyl group-containing ethylenically unsaturated monomer is in the range of 30 to 80 mgKOH / g, and is neutralized. The water-based coating composition according to claim 4, wherein the basic compound to be used is an amine having a boiling point of 120 ° C. or less or ammonia.