JPS60202158A - Improved aqueous coat composition for forming protective film - Google Patents

Abstract

PURPOSE:The titled compsn. with excellent coating workability and protective characteristics capable of being easily removed with an alkali soln. even after prolonged outdoor exposure, prepd. by incorporating aq. dispersion of a specified vinyl copolymer. CONSTITUTION:5-30pts.wt. alpha,beta-monoethylenically unsaturated acid such as maleic acid and 100pts.wt. polymerizable vinyl monomer comprising 1-15pts.wt. hydrophilic monomer such as 2-hydroxyethyl (meth)acrylate having one polymerizable unsaturated bond in the molecule, a polyoxyethylene chain of average M.W. of 1,500-15,000 and the terminal group consisting of H or 1-4C alkyl and 1-100pts.wt. other copolymerizable monomer such as methyl (meth)acrylate, are copolymerized in the presence of a radical polymn. initiator in a water-soluble org. solvent to obtain a vinyl-base copolymer. Then the copolymer is dispersed in water.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved aqueous coating composition for forming a voice protection film, and more particularly, the present invention relates to an improved aqueous coating composition for forming a voice protection film, and more particularly, the present invention relates to an improved aqueous coating composition for forming a voice protection film, and more particularly, the composition comprises a specific amount of an α,β-monoethylenically unsaturated acid and a specific hydrophilic monomer. It has excellent coating workability and protective properties, and contains as an essential component an aqueous vinyl copolymer dispersion (hereinafter also referred to as acrylic resin dispersion) obtained from a polymerizable cinyl monomer. Furthermore, the present invention relates to a coating composition that can be removed very easily with an alkaline aqueous solution even after long-term outdoor exposure, and the composition of the present invention can coat metals, glass, glass, pre-painted objects, plated objects, etc.
Suitable for protecting objects to be coated that do not undergo any alteration due to alkali treatment, especially for protecting large objects such as automobiles, vehicles, aircraft, or mechanical parts, and for primary rust prevention of metals such as steel. Very useful, especially Stritz J? Suitable as pull paint.

By the way, before cars and other vehicles are delivered to consumers, their surfaces may become contaminated with dust, soot, salts, iron powder, in rare cases bird excrement, direct sunlight, wind and rain, etc. , stains, discoloration, rust and cracks may occur. Further, among metal articles, steel is an extremely important material in industry, but it is easily oxidized and rusts due to the action of moisture and oxygen in the air.

These are factors that significantly reduce product value.
Since this often occurs and their removal requires a great deal of effort and expense, it is necessary to protect the surface of such products in advance.

Many protection methods and compositions have been proposed for this purpose.

For example, there is a method of applying a protective composition and then mechanically peeling it off each time, but since most of these protective compositions are solvent-based, they pose a fire hazard and are toxic to the human body. The disadvantage is that such peeling requires a correspondingly large amount of effort, especially in the case of large objects.

Another method is to remove the protective composition with a solvent, but since it is a wax-based protective composition, it is difficult to remove it from direct sunlight if it has been stored for a long time. In the case of receiving fcD, the altered quality of 9 is also present, so removal work can be said to be extremely difficult and difficult.
This method also poses serious problems in terms of the danger of fire and toxicity to the human body since a large amount of solvent is used in the removal process, as well as the treatment of wastewater and wastewater.

Furthermore, as primary rust preventive agents for steel materials, oil, grease, wax, or small amounts of organic amines, zinc naphthenate, petroleum oxidation products, funnel oil, alkali metal salts, or alkaline earth metal salts are added to these. Although anti-rust oils and the like are known, steel materials coated with such secondary anti-rust agents exhibit good anti-corrosive properties as long as the period of transportation or storage is short, and secondary anti-corrosive oils and the like are known. Although it can be easily removed by alkaline treatment after roe, this rust-preventing effect is almost impossible in recent years, when it is often left piled outdoors or stored under water droplets. It will no longer be possible to demonstrate your full potential.

In addition, since these anti-corrosion coatings are liquid coatings, they have poor mechanical strength and are easily damaged, and the anti-corrosion coatings can easily fall off from the surface of the steel due to contact with nearby objects. It also has the disadvantage that it is easily damaged and therefore rusts in such areas.

°In recent years, water-based resins have been developed as a method that is suitable for protecting large objects, has fewer problems with fire, toxicity, and wastewater treatment, is easy to remove, and provides good protection. A method of using an alkaline aqueous solution in the removal process with a protective composition is also disclosed in JP-A-49-97835.50-1.
9835.50-89427 and 56-22368, but none of them are yet fully satisfactory in terms of paint workability, removability, or film properties such as water resistance of the film. It has not become something useful.

However, in view of these circumstances, the inventors of the present invention have conducted intensive research to improve the coating workability, releasability, and physical properties of the coating film of an aqueous coating composition for forming a protective film. We have discovered an aqueous coating composition for forming a protective film, a so-called strippable paint, which has the following characteristics and can be removed extremely easily with an alkaline aqueous solution even after long-term outdoor exposure.
The present invention has now been completed.

That is, the present invention comprises 5 to 30 parts by weight of one or more α,β-monoethylenically unsaturated acids, one polymerizable unsaturated bond in the molecule, and an average molecular weight of 1. ．．
100 of a polymerizable vinyl monomer having a polyoxyethylene chain of 500 to 15,000 and containing a hydrophilic monomer whose end group is a hydrogen atom or a C4 to C4 alkyl group in a proportion of 1 to 15 parts by weight. Part by weight of a vinyl copolymer is copolymerized in a water-soluble organic solvent, and the resulting vinyl copolymer is then dispersed in water.

Particularly for coatings containing dispersion as an essential component.
The present invention provides an aqueous coating composition for forming a protective film that has significantly improved workability, protective properties, and coating performance after long-term outdoor exposure.

Here, the acrylic resin dispersion used to obtain the composition of the present invention is obtained by combining a polymer obtained by solution polymerization with a water-soluble organic solvent without using an emulsifier or a protective cotetraide as is commonly used. It is an aqueous dispersion that is stably dispersed in water due to the action of hydrophilic groups, and because of this, it does not have the drawbacks of acrylic resins or problems such as ``6 sag'' during painting, and emulsion polymerization. Acrylic obtained by
It does not have problems such as foaming after coating, which is a disadvantage of emulsions, and is extremely advantageous in practical terms.

The acrylic resin dispersion is prepared, for example, by the method described below.

First, one or two α,β-monoethylenically unsaturated acids
having one α,β-monoethylenically unsaturated bond (polymerizable vinyl group) in one molecule, and having a hydrogen atom or a C1-C4 alkyl group as a terminal group, and an average molecular weight of 1 , 500 to 15,000 hydrophilic monomers and a hydrophilic monomer having a polyoxyethylene chain of 500 to 15,000, respectively, in a specific proportion, are copolymerized in a hydrophilic organic solvent, and then dispersed in water. can get.

In particular, typical examples of the α,β-monoethylenically unsaturated acids mentioned above include maleic acid, fumaric acid, itaconic acid, crotonic acid, and (meth)(acrylic acid), but especially acrylic acid, Methacrylic acid is preferred.

The appropriate amount of the unsaturated acid used is 5 to 30 parts by weight, preferably 8 to 20 parts by weight, per 100 parts by weight of the total polymerizable vinyl monomer.

If the amount used is less than 5 parts by weight, the peelability of the protective film due to alkali is likely to be poor;
If more than 0 parts by weight is used, no further improvement in strippability due to alkali can be expected, and on the contrary, the content of free calginic acid will increase, which is uneconomical. Both of these are undesirable because they have an adverse effect on the painted surface.

On the other hand, polyoxyethylene chains having one unsaturated bond and an average molecular weight of 1,500 to 15,000 in the above-mentioned molecule, the terminal group of which is a hydrogen atom or a C4 to C4
Typical examples of hydrophilic monomers having an alkyl group in 4 include 2-hydroxyethyl (meth)acrylate, 2-human tetraxyglovir (meth)acrylate, or (,#')7acrylic acid. -4-hydroxy-n-
A compound obtained by adding ethylene oxide to a vinyl monomer containing a hydroxytetraxyl group such as butyl, or a compound with an average molecular weight of 1,500-15,000, in which one of the terminal groups is a hydrogen atom or a C1 to C4 alkyl group. polyoxyethylene glycol derivatives, in which the other is a hydroxyl group, and vinyl group-containing carnic acid monomers such as (meth)acrylic acid, cinnamic acid or itaconic acid (α,β-monoethylenically unsaturated acids) ), as well as methyl (meth)acrylate, ethyl (meth)acrylate, (
n-propyl meth)acrylate, n-butyl (meth)acrylate or tert-(meth)acrylate
Examples include compounds obtained by transesterifying a vinyl group-containing ester monomer such as butyl with a polyoxyethylene glycol derivative as described above.

The average molecular weight of the polyoxyethylene chain portion in the hydrophilic monomer must be within the range of 1,500 to 15,000.

If the molecular weight of this chain portion is less than 1,500, a sufficient effect cannot be expected in water dispersion of the resulting copolymer solution, and conversely, if it exceeds 15,000,
Since the number of copolymerizable vinyl groups (α, β-monoethylenically unsaturated bonds) per unit molecular weight of the hydrophilic polymer is extremely small, the water dispersion effect of the copolymer solution is also remarkable. Both are undesirable because of the decrease in

The average molecular weight of the polyoxyethylene chain portion of the monomer is preferably 2,000 to 10,000°, more preferably 3,000 to 8,000.

The amount of the monomer used is 100% of the total polymerizable vinyl monomer. It is 1 to 15 parts by weight, preferably 2 to 10 parts by weight.

If the amount of the monomer used is less than 1 part by weight, the water dispersion effect of the resulting copolymer solution may not be sufficient, and therefore it becomes difficult to obtain a stable aqueous dispersion.
On the other hand, if the amount exceeds 15 parts by weight, the water dispersion effect of the resulting copolymer solution will not be as visible as expected, and it may become uneconomical, or such a copolymer may become uneconomical. Both are unfavorable, since the water resistance of the combination will be reduced.

Furthermore, other polymerizable vinyl monomers that can be copolymerized with the α,β-monoethylenically unsaturated acids and hydrophilic monomers listed above include methyl (meth)acrylate, ethyl (meth)acrylate, (meth)acrylic acid-
n-Butyl, 2-ethylated hexyl (meth)acrylate, lauryl (meth)acrylate, (meth)acrylic acid
(meth)acrylic acid esters such as 2-hydroxyethyl, 2-hydroxypropyl (meth)acrylate, 2-hydroxy-3-chloropropyl (meth)acrylate, and (β-methyl)glycidyl (meth)acrylate; Class;
α, β-monoethylenically unsaturated amides such as (meth)acrylamide, N-methyl (meth)acrylamide, N-methylol (meth)acrylamide; α,β-monoethylenically unsaturated nitriles such as (meth)acrylonitrile Typical examples include vinyl chloride, vinyl halides such as vinylidene chloride, styrene, α - Methylstyrene, kakistyrene derivatives of vinyltoluene, vinyl acetate, vinyl gropionate, "Beova" (Product from Shell, Netherlands)
Vinyl esters such as ethylene, α-olefins such as globylene, conjugated dienes such as butadiene, or persimmon maleate esters of dimethyl maleate and dibutyl maleate, etc. can also be used, and these may be used alone. It may be used or a combination of two or more types may be used.

The acrylic resin dispersion, which is an essential component of the composition of the present invention, is prepared by mixing the various polymerizable vinyl monomers listed above in a water-soluble organic solvent as exemplified below. 1so-proanol, n-
propoxyglopanol, diacetone alcohol, ls
o -Fta/-A/, alcohols such as n-butanol, or propylene glycol monomethyl ether, methyl cellosolve, ethyl cellosolve, ethylene glycol mono-1SO-globyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, dioxane These include -11-noether alcohols and ethers, and these may be used alone or in combination of two or more.

The amount of the solvent used is not particularly limited, but is usually 9 parts by weight per 100 parts by weight of the above-mentioned total amount of polymerizable vinyl monomers.
A suitable range is 10 to 100 parts by weight.

In preparing the acrylic resin dispersion, benzoyl peroxide, lauroyl peroxide, di-tert-butyl monooxide, tert-butyl peroctate,
Known and commonly used radical polymerization initiators such as organic peroxides such as tert-butylno-Q-benzoate or acetyl peroxide, or nido-lyl systems such as azobisisobutyronitrile or azobisisovaleronitrile are used. Good.

The method for preparing the vinyl copolymer solution to obtain the acrylic resin dispersion is not particularly limited, and the above-mentioned water-soluble organic solvent solution containing the hydrophilic monomer is heated and stirred. Alternatively, a method may be used in which a polymerizable monomer containing an α,β-monoethylenically unsaturated acid mentioned above and a radical polymerization initiator are dropped, or a water-soluble organic solvent, a radical polymerization initiator, a hydrophilic monomer, and a
, a polymerizable vinyl monomer containing β-monoethylenically unsaturated acid may be added dropwise in parallel, or α, β, and β-monoethylenically unsaturated acids may be added dropwise in parallel.
- Copolymerizing a polymerizable vinyl monomer containing a monoethylenically unsaturated acid with a radical polymerization initiator, adding the remaining hydrophilic monomer in the latter half of the copolymerization reaction,
It is also possible to use a method of making the mixture quench.

In order to prepare the desired acrylic resin dispersion using the vinyl copolymer solution obtained in this way, it is sufficient to add water to the vinyl copolymer solution, and by doing this, the desired dispersion can be easily prepared. is obtained.

The dispersion of the vinyl copolymer solution with water may be carried out by gradually adding and dispersing the copolymer solution while stirring the water, or conversely, by gradually adding water to the copolymer solution. Alternatively, a method may be used in which the emulsification is effected by adding the liquid to the liquid and emulsifying it by phase inversion.

Generally, the vinyl copolymer solution is heated to about 50 to 100°C.
It is more preferable to use a method of heating the mixture and gradually adding water dropwise while stirring well to effect phase inversion emulsification, since this makes it easier to obtain a stable acrylic resin dispersion having a fine particle size.

When the film obtained using the thus obtained acrylic resin dispersion or aqueous dispersion of divinyl copolymer is required to have more protection when exposed outdoors for a long period of time, In the composition of the present invention containing the vinyl copolymer aqueous dispersion as an essential component, phenyl salicylate, 4-tart to butylphenyl salicylate, 2,4-dihydroxybenzophenone, 2-oxy-4-methoxybenzophenone, 2 - One or more UV absorbers such as various salicylic acid derivatives such as hydroxy-4-methoxybenzophenone, benzophenone derivatives, or benzotriazole derivatives, based on the weight of the vinyl copolymer aqueous dispersion. It can also be added within a range of 0.2 to 5%.

In addition, acid components (free carboxyl groups, etc.) present in the aqueous copolymer dispersion can be neutralized with a volatile alkali such as ammonia or ralpholine, if necessary. Of course, it may be added in the form of a pre-dissolution in the water added during the preparation of the aqueous dispersion, or it may be added directly to the separated liquid after the preparation of the aqueous dispersion. .

On the other hand, neutralizing the aqueous dispersion with sodium hydroxide, potassium hydroxide, or triethanolamine, which has a low volatilization rate, is not preferable because the water resistance of the formed film will be significantly reduced.

In order to protect the surface of the object to be coated using the aqueous coating composition of the present invention, known and commonly used methods such as coating with a four-circle coater, curtain flow coater, brush type 9, flow coating, spraying, or dipping may be used. After coating the object to be coated, it may be dried at room temperature or forced drying.

The thickness of the dry film of the chicken sashimi is suitably within the range of 5 to 70 .mu.m, preferably 10 to 30 .mu.m.

In order to remove the protective film of the composition of the present invention thus formed, an alkaline aqueous solution (alkaline agent) as exemplified below may be used, and it can be easily removed by the action of such an alkaline agent.

That is, a 0.2 to 5% by weight aqueous solution of various basic compounds such as ammonia, sodium hydroxide, potassium hydride, calcium hydroxide, metasilicon, sodium acid, and sodium orthosilicate heated to 10 to 80°C. 1 to the painted object
It can be easily and completely removed by spraying for about 0 seconds to 10 minutes, preferably 15 seconds to 5 minutes, or by immersing the coated object in the basic aqueous solution for the above period of time.

The aqueous coating composition of the present invention can be applied to any substrate as long as it does not change in quality due to treatment with an alkaline agent (alkali treatment), such as steel, cast iron, stainless steel, etc. - Suitable for protecting steel, plated or chromated materials, glass, various plastics, or ceramics.
In particular, it is extremely effective as a so-called strippable paint for protecting large objects such as automobiles, vehicles, aircraft, or mechanical parts, and for primary rust prevention of metals such as steel.

Next, the present invention will be specifically explained with reference to Examples and Comparative Examples. In the following, all parts and parts are based on weight unless otherwise specified.

Example 1 In a 2-ton flask equipped with a stirrer/thermometer, dropping funnel, reflux condenser, and inert gas inlet, 300 parts of ethylcerone as a solvent and a methyl group as the terminal group were added.
and the average molecular weight of the polyoxyethylene chain portion is 6.000
35 parts of methyl methacrylate derivatives were charged and exposed to 130°C in a nitrogen stream. Separately, 434 parts of methyl methacrylate, 210 parts of n-butyl acrylate and methacrylic acid were added as polymerizable vinyl monomers. 56 parts of t
Art-butylhuman 0 peroxide was injected from a separate dropping funnel, and dropwise copolymerization was carried out over a period of 3 hours.

After the dropwise addition was completed, the same temperature was maintained for 6 hours to complete the polymerization reaction.

Next, the vinyl copolymer solution obtained in this way was heated to 80%
℃, 615 parts of water was added dropwise at the same temperature over about 2 hours, and then the temperature was lowered to 25℃ and the mixture was made alkaline with 5% ammonia water. A uniform aqueous dispersion with a tinge of color was obtained.

The vinyl copolymer aqueous dispersion obtained here has a non-volatile content (NV) of 45.2% and a Pruck Field viscosity (hereinafter simply referred to as viscosity) at 25°C of 1.40.
0 cps, pH 8.2, and average particle size 0
．． The coating composition was diluted with deionized water until the aqueous dispersion t-v was 20 μm or less.
SG-3310) and 150°C.
A primary anti-rust film with a thickness of 12 μm was formed by forced drying for 0 minutes. No sagging or foaming on the painted surface was observed during the painting process, and the various performances of the resulting protective film were investigated. However, the pencil hardness is H to 2H, and the adhesion to the base is 100/10'0 (1
+mnmncellophane tea), has excellent water whitening resistance,
and salt spray test (JIS Z-2371-1955
It was found that the method (method) was extremely good, with no total thermal rusting observed even after 48 hours.

It was also confirmed that when this protective film was immersed in a 3% sodium orthosilicate aqueous solution for 3 minutes and then washed with water, the protective film was completely removed during the immersion.

Example 2 In a reactor similar to Example 1, 3007 parts of n-butylcellosorg and 21 parts of hydrogen atoms at the terminals, an average molecular weight of the polyoxyethylene chain portion of s, ooo, and CH2=CH-OCO were added. (Charge the acrylate represented by the structural formula -CH2CH2O+nH, and while heating it to 130°C in a nitrogen stream, 6 parts of azobisisobutyronitrile, 330 parts of styrene, 300 parts of n-butyl acrylate, A mixture consisting of 70 parts of methacrylic acid was added dropwise from another dropping port over a period of about 3 hours.

After completing the dropwise addition, the same temperature was maintained for 10 hours to complete the copolymerization reaction, the resulting copolymer solution was cooled to 80°C, and 580 parts of water was added dropwise at the same temperature over about 2 hours. Then, after cooling to 25°C, the pH was made alkaline with 5% ammonia water, resulting in a uniform, slightly bluish color.
W is 44.8%, viscosity is 1.140 ape, - is 8
．． An aqueous dispersion of a copolymer having an average particle size of 0.2 μm or less was obtained.

Thereafter, the coating composition thus obtained had an iNV of 20
The aqueous coating composition was diluted with deionized water until the dry film thickness was 5 μm on a 100 x 150 x O, 4wn stainless steel plate (SUS 24BA).
The film was coated to give a primary protective film of m and dried for 2 days at room temperature.

There was no "sagging" during painting, and when we investigated the performance of the protective film, the anchor chain hardness was 100/10 in the 2H1 base test.
0, has excellent water whitening resistance, and has a rating of 48 in the salt spray test.
It was found that an extremely good aqueous coating composition for forming a protective film was obtained, in which no rusting was observed after a period of time had elapsed. It was also confirmed that the protective film was completely dissolved and removed simply by soaking and then washing with water.

Example 3 300 parts of n-butyl cellosolve were charged in a reactor similar to that of the actual flow side 1, heated to 130° C. under a nitrogen atmosphere, and then 6 parts of tart-butyl peroxy-2-ethylhexanoate were charged. and 160 parts of styrene, 240 parts of methyl methacrylate, and 2 parts of 2-ethylhexyl acrylate.
A mixture consisting of 65 parts of acrylic acid and 35 parts of acrylic acid was added dropwise from another dropping port over a period of 3 hours. 70 parts of methacrylate 000 was divided into three parts, and the divided additions were also made in parallel every hour. After completion of the dropwise addition, the same temperature was maintained for 8 hours to complete the copolymerization reaction.

Next, the temperature of the obtained copolymer solution was lowered to 60°C, and 640 parts of water was added dropwise over about 2 hours. After the dropwise addition was completed, the copolymer solution was cooled to 2-5°C, and it became uniform and had a bluish tinge. Ta,
■ is 45.2%, viscosity is 3.060cpg, p)l
An aqueous copolymer dispersion was obtained in which the particle diameter was 3.2 and the average particle diameter was 0.2 μm or less.

The aqueous coating composition was then diluted with deionized water to a NV of 20 x 20
The coating was applied to an ABS board made of 0x2 using an airless sprayer so that the dry film thickness was 20 μm.

°The painted surface had a lot of "sagging", and a good painted surface was obtained by hot air drying at 60℃ for 30 minutes, but the pencil hardness was H, the base grain test was 100/100, and it was immersed in water for 48 hours. It was confirmed that an extremely good protective film was formed without causing any whitening.

It was also confirmed that the protective film was completely eluted and removed when the protective film was immersed in an aqueous solution of dibasic sodium hydroxide at 50° C. for 2 minutes and then washed with water.

Example 4 The amounts of methyl methacrylate, 2-ethylhexyl acrylate and acrylic acid used were 160 parts and 240 parts, respectively.
An aqueous dispersion of the copolymer was obtained in the same manner as in Example 3, except that the amounts were changed to 140 parts and 140 parts.Then, this dispersion was used as an aqueous coating composition for coating.

The painted surface obtained in this way has no 6" sag and is 3" at 60℃.
Although a good protective film was obtained with hot air drying for 0 minutes,
This film has a lead wire hardness of H and a base grain test of 100/10.
It was confirmed that an extremely good protective film was formed without any whitening even after being immersed in water for 48 hours.

It was also confirmed that the protective film was completely eluted and removed when the protective film was immersed in an aqueous solution of IJ (hydroxide) at 150° C. for 2 minutes and then washed with water.

Comparative Example 1 In order to compare the performance with Emulsilon, an acrylic copolymer obtained by emulsion polymerization, Emulsilon was prepared with the following composition according to a conventional emulsion polymerization method.

Methyl methacrylate 441 parts n-butyl acrylate 210 Methacrylic acid 49 Lauryl mercaptan 0.1 Sodium dodecylbenzenesulfonate 28 Ammonium persulfate 2.1 Ion exchange water 1,094.8 // Obtained here The emulsilon had a W content of 40.4%, a viscosity of 190 cps, and -3.4. After diluting this emulsilon with deionization to 20% W, 120 x 200 x 2 m+ Naru ABS
When we sprayed the board with an airless sprayer to a dry film thickness of 20 μm, there were countless air bubbles in the painted surface, giving it the appearance of artificially finely foamed surfaces. Furthermore, when the water resistance of the coating film was investigated, the entire surface turned white after 24 hours of immersion, and blisters were also observed, indicating that it could not be of any practical use as a protective coating.

Comparative Example 2 To compare the performance of water-soluble acrylic resin, a control resin solution was obtained by copolymerizing the following composition in a solvent using a conventional method, and then neutralizing and diluting with water. However, the property values of this product are NY: 40.5%, viscosity: 2.3
00 cps methyl methacrylate 350 parts n-butyl acrylate 280 methacrylic acid 70 n-butylcetetrasol 490 tert-butyl-oxybenzoate 7 triethanolamine 84 1.771// and - It was 9.24.

Next, the Nv of this water-soluble acrylic resin solution was 20
When the solution was diluted with deionized water until it was completely dry and then applied to a polished mild steel plate (described above) without spraying, significant sagging occurred and a uniform coating could not be obtained.

Thereafter, forced drying was performed at 150° C. for 10 minutes to obtain a coating film. As for the performance of the coating film obtained here, the pencil hardness was H and the base grain test was 97/100, but the water resistance was such that significant blistering occurred after 48 hours, making it difficult to use as a protective coating film. , it was not a substitute that could be put to practical use.

Representative Patent Attorney Katsutoshi Takahashi

Claims (1)

[Claims] 5 to 30 parts by weight of one or more α,β-monoethylenically unsaturated acids, and one polymerizable unsaturated bond in the molecule, and an average molecular weight of 1,500 to 15, 00
100 parts by weight of a polymerizable vinyl monomer containing 1 to 15 parts by weight of a hydrophilic monomer which also has a polyoxyethylene chain of 0 and whose terminal group is a hydrogen atom or a C5 to C4 alkyl group. An alkali-removable paint comprising as an essential component an aqueous dispersion of a vinyl copolymer obtained by copolymerizing in a water-soluble organic solvent and then dispersing the resulting vinyl copolymer in water. An improved protective film-forming aqueous coating composition capable of forming a film.