JPS5825110B2 - Mizukeihifufusseibutsu - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an aqueous coating composition that provides a good coated surface.

In recent years, water-based coating compositions have been replacing conventionally used organic solvent-based coating compositions in the automotive and light electrical coating industries due to air pollution problems, fire dangers in the painting process, and hygiene issues. It is attracting attention.

Conventionally, as this type of water-based thermosetting acrylic coating composition, Japanese Patent Publication No. 37-7641, Japanese Patent Publication No. 44-22749,
Special Publication No. 185805-1970, Special Publication No. 3866-1970, Special Publication No. 1.6090-1977, and Special Publication No. 286-1977
The techniques shown in No. 84 are known, some of which have already been put into practical use, and are superior to conventional coating compositions in several respects such as physical properties and chemical stability. However, since the main solvent is water, the formed coating film is prone to defects such as repellency and dents, which is a drawback.

Conventionally, silicone and fluororesin-based compounds have been known as surfactants to improve these drawbacks, but it is difficult to use such surfactants, and the type of surfactant added to the coating material is difficult. It has been recognized that if the selection or the appropriate amount of addition is made incorrectly, the occurrence of cissing, dents, etc. will be promoted, and the interlayer adhesion between coating films will be adversely affected.

It goes without saying that these silicone and fluororesin compounds are expensive.

On the other hand, homopolymers of alkyl esters of acrylic acid or methacrylic acid as shown in Japanese Patent Publication No. 48-12854 are available as substances that can be used to improve the above-mentioned drawbacks, but these substances are not suitable for water-soluble resins. Even if this resin is used as a modifier for water-soluble coating materials, it is difficult to form a coating film with improved repellency, dents, etc., and the coating surface also tends to have a yuzu skin. have.

Therefore, the present inventors are currently conducting intensive studies to develop an aqueous coating material that does not have the above-mentioned drawbacks. 5 to 25% by weight of monoethylenically unsaturated carboxylic acid Hydroxyalkyl ester of α/β monoethylenically unsaturated carboxylic acid and/or N-alkoxyalkylated product of α/β monoethylenically unsaturated carboxylic amide 5
Adding an acrylic copolymer obtained by copolymerizing ~25% by weight to an aqueous acrylic coating composition improves the fluidity and pigment wettability of the coating material, and also worsens the interlayer adhesion of the coating film. The present inventors have discovered that the occurrence of cissing, dents, etc. can be prevented without having to do so, and have completed the present invention.

That is, the gist of the present invention is (A) ((4) 50 to 90% by weight of an acrylic ester having an alkyl group having 2 to 12 carbon atoms (b) α/β monoethylenically unsaturated carboxylic acid 5 ~25
Weight% (・→ Copolymerization of 5 to 25% by weight of a hydroxyalkyl ester of an α/β monoethylenically unsaturated carboxylic acid and/or an N-alkoxyalkylated product of an αβ monoethylenically unsaturated carboxylic acid amide in a water-soluble organic solvent. 0.01 to 10 parts by weight of an acrylic copolymer obtained by (B) Copolymer salt 9 obtained by partially or completely neutralizing an acrylic copolymer having an acid value of 10 to 100 with a base
An aqueous coating composition containing 0 to 99.99 parts by weight and an aqueous solvent and having a good coated surface condition.

Next, each component used in carrying out the present invention will be explained.

Specific examples of acrylic esters having an alkyl group having 2 to 12 carbon atoms used in the production of the acrylic copolymer used in the present invention include ethyl acrylate, n-propyl acrylate, isopropyl acrylate, and n-butyl acrylate. Acrylate, imbutyl acrylate, tertiary butyl acrylate, amyl acrylate, n-octyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, etc., and these compounds may be used alone or in a combination of two or more. It is necessary to copolymerize it into the acrylic copolymer in a proportion of 50 to 90% by weight.

Specific examples of α/β monoethylenically unsaturated carboxylic acids include acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid, and monoesters of divalent acids and monovalent alcohols among these acids. In the present invention, it is particularly preferable to use acrylic acid and methacrylic acid, and these compounds may be copolymerized into the copolymer in a proportion of 5 to 25% by weight in the form of one type or a combination of two or more types. is necessary.

The copolymerization amount of these acids may be selected as appropriate within the above range, but it should be reduced when using an acrylic ester with a small number of carbon atoms, and increased when using an acrylic ester with a large number of carbon atoms. It is desirable to do so.

Furthermore, when a copolymer with an acid copolymerization amount of 5% by weight or less is used, the effect as a modifier is small, so that the object of the present invention cannot be achieved. On the contrary, copolymerized materials tend to cause cissing, dents, etc., and are therefore not preferred.

Specific examples of hydroxyalkyl esters of α/β monoethylenically unsaturated carboxylic acids include 2-hydroxyethyl (meth)acrylate, 3-hydroxypropyl (meth)acrylate, and 4-hydroxybutyl (meth)acrylate.

Also, N- of α/β monoethylenically unsaturated carboxylic acid amide
Specific examples of alkoxyalkylated products include N-methoxyethyl (meth)acrylamide, N-ethoxymethyl (
Examples include meth)acrylamide, N-butoxymethyl(meth)acrylamide, and the like.

These compounds are used to prevent poor interlayer adhesion of a coating film when an acrylic copolymer useful as a surface-active substance is added to an aqueous acrylic coating composition.

If the amount used is less than 5% by weight, the effect will be small.
If it exceeds % by weight, the resulting acrylic copolymer will have a high viscosity and poor storage stability, which is not preferable.

The acrylic copolymer obtained by copolymerizing the above monomers can be produced by a known solution polymerization method.

For example, preferred polymerization solvents include monovalent saturated aliphatic alcohols having 1 to 5 carbon atoms, particularly isopropyl alcohol, n-butanol, and other ethylene glycol derivatives, particularly methyl cellosolve, ethyl cellosolve, and butyl cellosolve.

Also, water-soluble solvents such as diacetone alcohol and acetone can be used.

Further, as a polymerization initiator, a general radical generating catalyst such as azobisisobutyronitrile, benzoyl peroxide, etc. may be used for polymerization at a polymerization temperature range of 60 to 140°C using -butylperoxyisopropyl carbonate, etc. .

The molecular weight of the acrylic copolymer obtained in this way can vary by adjusting the amount of polymerization initiator and reaction conditions, but the most effective one as a surface active substance has an average molecular weight of 5,000 to 40,000. degree, preferably about 20,000.

The resin obtained by solution polymerization as described above can be used as a modifier as it is, but in order to make it water-soluble, it is preferable to use a resin that has been partially or completely neutralized with a base.

Neutralizing agents that can be used for this purpose include ammonia, primary, secondary
or tertiary aliphatic or alicyclic amines such as isopropylamine, n-butylamine, n-amylamine, diethylamine, diisopropylamine, n-dibutylamine, diisobutylamine, triethylamine, n-tributylamine, monoethanolamine, ethyl Examples include monoethanolamine, beta-dimethylethanolamine, diethylethanolamine, cyclohexylamine, morpholine, and piperidine.

The amount of these bases to be used is preferably selected depending on the amount of carboxyl groups contained in the copolymer.

In the case of the present invention, the appropriate amount of the above-mentioned acrylic copolymer to be used is 0.01 to 10 parts by weight based on the total composition, and if it is less than 0.601 parts by weight, there will be no effect, and if it is more than 10 parts by weight, it will have an adverse effect. No Jiki.

This is not preferable because it increases dents, etc., and a particularly preferable range is 0.1 to 3 parts by weight based on the solid content of the vehicle.

The copolymer salt (B) obtained by partially or completely neutralizing an acrylic copolymer having an acid value of 10 to 100 used in the present invention has acid components such as acrylic acid, methacrylic acid, itaconic acid, and maleic acid. , methyl (meth)acrylate, ethyl ( methacrylate, propyl (meth)acrylate,
Isopropyl (meth)acrylate, Butyl (meth)acrylate, Isobutyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, Lauryl (meth)acrylate
Acrylate, (meth)acrylic acid esters such as stearyl (meth)acrylate, benzyl (meth)acrylate, and cyclohexyl (meth)acrylate, styrene, tertiary isotyl styrene, vinyltoluene, (
meth)acrylonitrile, vinyl acetate, vinyl propionate, vinyl persate ester (meth)acrylamide, monoesters of α/β monoethylenically unsaturated carboxylic acids and polyols such as ethylene glycol, glopylene glycol, and 3-butylene glycol. Class, N-
It is a salt obtained by copolymerization using N-methylolamide group-containing monomers such as methylol(meth)acrylamide, or N-alkoxyalkylamide group-containing monomers such as N-alkoxyalkyl(meth)acrylamide.

When these acrylic copolymers have an acid value of 10 or less, their solubility in the aqueous solvent used in the present invention decreases, so it is difficult to form a coating composition when such resins are used. , or may form a dressing composition,
There is a serious problem in practical use because of its low dissolution or dispersion stability.

When the acid value of the resin is 100 or more, the solubility or dispersibility of the resin in water-soluble organic solvents improves, but the viscosity of the resulting coating material composition increases significantly, making it difficult to form a coating material suitable for coating. is difficult.

Furthermore, the coating film formed is brittle, and it is difficult to form a coating film with excellent chemical resistance and corrosion resistance, which is undesirable.

In order to dissolve or disperse these acrylic copolymers in an aqueous solvent, it is desirable to neutralize the carboxylic acid contained in the copolymers with a base.

If the degree of neutralization is low, the solubility or dispersibility of the acrylic copolymer salt in an aqueous solvent will decrease, and the stability of the coating material composition will decrease, which is not preferred.

Further, if the amount of the base is too large, the water resistance and corrosion resistance of the formed coating film will decrease, which is not preferable.

The base used at this time can be the same as that explained in the section regarding the copolymer carrier.

In the present invention, the appropriate amount of the above-mentioned acrylic copolymer salt to be used is 90 to 9199 parts by weight based on the total composition.

Modifiers such as urea resin, melamine resin, silicone resin, urethane resin, etc. can be added to these acrylic copolymer salts if necessary.

The aqueous solvent used in carrying out the present invention refers to a mixture consisting of water and a water-soluble organic solvent, where the ratio of water and water-soluble organic solvent is in the range of 30/70 to 9515 (weight ratio). is appropriate.

If the water content is less than 30% by weight, explosions and fires occur during paint baking, and hygiene problems are likely to occur.
If it exceeds 5% by weight, it is not preferable because it causes sagging, wrinkles, etc. during coating film formation.

The coating composition of the present invention can be used as a clear solution, but it can also be used as a colored solution.

Metal oxides such as titanium dioxide, zinc oxide, metal flakes, sulfates, carbon black, silica, talc, organic lake pigments or other organic dyes can be used to color the coating compositions of the invention.

The coating composition of the present invention can be applied by conventional spraying, brushing,
It can be applied to the substrate by methods such as roll coating, dip coating, curtain flow coating, and electrostatic coating, and the coating film can be cured by baking at about 100 to 200°C for 10 to 30 minutes.

The water-based coating composition of the present invention can be applied to base materials such as metal, concrete, asbestos, wood, stone, textiles, leather, and paper, but especially metal plates such as iron and aluminum that require a good coating surface condition. When applied as a surface coating material, it exhibits particularly excellent performance.

The present invention will be explained in more detail with reference to Examples below.

All parts used in the examples are parts by weight.

Example 1 (1) Production of acrylic copolymer (I) 30 parts of n-butanol and 45 parts of ethyl cellosolve were charged into a reaction vessel equipped with a stirrer, a reflux condenser, a thermometer and a dropping funnel, and the mixture was heated to 115°C. After raising the temperature to , a mixture consisting of 10 parts of methacrylic acid, 10 parts of 2-hydroxyethyl methacrylate, 16 parts of ethyl acrylate, 64 parts of n-butyl acrylate, and 0.5 parts of t-butylperoxyisopropyl carbonate was added from the dropping funnel for 2 hours. 0.1 part of t-butylperoxyisopropyl carbonate was added 2 hours and 4 hours after the completion of the dropwise addition, and the reaction was completed by further holding at 115°C for 2 hours. The resulting product had the following properties: solid content 57.5%, viscosity (Gardner-Holdt) Z, and acid value 3644.

Furthermore, the average molecular weight of this product was measured and was found to be 23,000.
Met.

(2) Production of an acrylic copolymer with an acid value of 10 to 100 In a reaction vessel equipped with a stirrer, a reflux condenser, and a thermometer, 62 parts of inpropyl alcohol, 12 parts of 2-hydroxyethyl methacrylate, and 40 parts of styrene are placed. parts, N-butoxymethylacrylamide 8 parts, ethyl acrylate 41.4 parts
3.6 parts of itaconic acid, 1 part of 2-mercaptoethanol, and 0.4 part of azobisisobutyronitrile were charged, and the temperature was raised to 80°C over 1 hour.

3rd hour, 4th hour, 5th hour, 6th hour after the start of the reaction,
Add 0 azobisisobutyronitrile at 7th and 8th hours.
．． 1.0.15.0.25.0.3.0.4.0.5 parts at a time, and 133 hours after the start of the reaction, 20 parts of isopropyl is added to terminate the reaction.

The obtained acrylic copolymer had a solid content of 55%, a viscosity of U,
It had a characteristic value of acid value 15.

Next, 4.9 parts of β-dimethylaminoethanol was added to neutralize the mixture.

(3) Preparation of paint The above-mentioned acrylic copolymer (I), acrylic copolymer salt (n) having an acid value of 10 to 100, methylated melamine resin, pigment, and aqueous solvent are mixed and kneaded to form the following composition. A white enamel was prepared.

Acrylic copolymer (I) 4.4 parts Acrylic copolymer salt (I[) having an acid value of 10 to 100 145
Part Nikaratsuk MW-12LF (70%) 29 parts Titanium dioxide (R-820) 100 parts Water
42 parts Butyl cellosolve 42.6 parts The above white enamel was diluted with water/butyl cellosolve-50150 thinner to a viscosity of 30 seconds on a Ford Kag surface 4 and treated with zinc phosphate on a mild steel plate (0.8 parts m thickness size l 00 mm
300111n) was sprayed and set for 10 minutes, then baked at 150℃ for 20 minutes to dry to a dry film thickness of 3.
A white coating film of 5μ was obtained.

This coated surface had extremely good leveling, excellent image clarity, and no abnormal phenomena such as repelling or denting were observed.

In addition, in order to examine the interlayer adhesion of the above-mentioned paint, white enamel was painted on the above-mentioned paint film to a dry film thickness of 35 μm (75 μm in total), baked at 150°C for 20 minutes, and then a cross was applied to the painted surface. A cut was made and a peeling test was performed using cellophane tape, but no abnormality was observed and the interlayer adhesion of the coating film was good.

On the other hand, among the components of the above-mentioned white enamel, acrylic copolymer (
A white enamel prepared without mixing I) was painted and baked using the same method as described above, and there was a fine orange peel on the painted surface, and the occurrence of cissing, dents, etc. was noticeable. .

(Number of repellents and dents: 100 or more) Example 2 (1) Production of acrylic copolymer (6) In the same reaction vessel used in the production of acrylic copolymer (I) in Example 1, - 26 parts of butanol and 40 parts of ethyl cellosolve were heated to 115°C, then 10 parts of methacrylic acid,
20 parts of N-butoxymethylacrylamide, 14 parts of ethyl acrylate, 56 parts of n-butyl acrylate, t-
A mixture consisting of 0.5 parts of butyl peroxyisopropyl carbonate was added dropwise from the dropping funnel over 2 hours, and 0.1 parts of
-Butylperoxyisopropyl carbonate was added and the reaction was further maintained at 115°C for 2 hours to complete the reaction.

β-dimethylaminoethanol after cooling to 20°C 10.4
It was neutralized by adding 1.

The obtained product has a solid content of 57.5%, a viscosity of XY, and an acid value of 35.
．． It had a characteristic value of 1.

Furthermore, when the average molecular weight of this product was measured, it was found that MW=23.
It was 000.

(2) Production of acrylic copolymer salt (5) having an acid value of 10 to 100. Butyl cellosolve was 43 parts, 2-human xyethyl acrylate 15
35 parts of styrene, 7.5 parts of itaconic acid, 20 parts of ethyl acrylate, and 22-5 parts of n-butyl acrylate were reacted to produce an acrylic copolymer.

The obtained product had a solid content of 70.5%, a viscosity of Z6, and an acid value of 4.
It had a characteristic of 0.5.

Next, 10.3 parts of β-dimethylaminoethanol was added to neutralize the product.

(3) Preparation of paint The following white enamel was prepared by mixing and kneading the above-mentioned acrylic copolymer, acrylic copolymer salt having an acid value of 10 to 100, and methylated melamine resin, pigment, and water.

Acrylic copolymer salt ([1112 parts Acrylic copolymer salt having an acid value of 10 to 100) 114 parts Two-color MW-22 (70%) 29 parts Titanium dioxide (R
-820) 100 parts water
118 parts The above white enamel was diluted with water and Ford cup waste 4 to a viscosity of 30 seconds and treated with zinc phosphate on a mild steel plate (0.8 mm thick, size 100 mm
The coating was sprayed onto a 300°C, set for 10 minutes, and then baked at 170°C for 20 minutes to dry to obtain a white coating with a dry thickness of 35μ.

This painted surface had good image clarity, and no abnormal phenomena such as scratches, dents, etc. were observed.

In addition, in order to examine the interlayer adhesion of the above-mentioned paint, white enamel was painted on the above-mentioned paint film to a dry film thickness of 35 μm (70 μm in total), baked at 150°C for 20 minutes, and then a cloth was applied to the painted surface. A cut was made and a peeling test was performed using cellophane tape, but no abnormality was observed and the interlayer adhesion of the coating film was good.

On the other hand, among the components of the above-mentioned white enamel, acrylic copolymer (
The painted surface of the paint film obtained by painting and baking the white enamel prepared without mixing the river using the same method as described above is
Occurrence of dents was observed.

(Number of repellents and dents: 50) Comparative Example 1 26 parts of n-butanol, 40 parts of ethyl cellosolve, n-butyl acrylate) 1 00 parts were reacted to produce a homopolymer of n-butyl acrylate.

The obtained product had a solid content of 60.5%, a viscosity of F, and an acid value of 0.
It had a characteristic value of 3.

A white enamel similar to that in Example 2 was prepared by using this homopolymer of n-butyl acrylate in place of the acrylic copolymer (II1) in Example 2, and a zinc phosphate-treated mild steel plate (0.8 mm thick) was prepared. Size 100mm x 300mm)
The coating was sprayed, set for 10 minutes, and then baked at 170° C. for 20 minutes to dry to obtain a white coating with a dry thickness of 35 μm.

This coating film was found to be sticky, and also had yuzu skin, repellency, and dents.

(More than 100 cracks and dents)

Claims (1)

[Scope of Claims] 1(A) (a) 50 to 90% by weight of an acrylic ester having an alkyl group having 2 to 12 carbon atoms (b) α-
5-25% by weight of β-monoethylenically unsaturated carboxylic acid 5-25% by weight of N-alkoxyalkylated product of a/β-monoethylenically unsaturated carboxylic acid hydroxyalkyl ester and/or αβ-monoethylenically unsaturated carboxylic acid amide Acrylic copolymer o, oi ~ 10 parts by weight (B) obtained by copolymerizing % of acrylic copolymer in a water-soluble organic solvent Partially neutralizing or completely neutralizing an acrylic copolymer having an acid value lO ~ 100 with a base Summed copolymer salt 9
An aqueous coating composition comprising 0 to 99.99 parts by weight and an aqueous solvent.