JPS62253673A - Coating film-protective composition removable with alkali - Google Patents

Abstract

PURPOSE:To provide the titled composition effective for prevention of the deterioration of undercoating due to water, ultraviolet light, etc., outstanding in protective effect against scratching, for use in coating on automobiles, etc., comprising specified proportion of ultraviolet absorber and aqueous dispersion containing an emulsion polymerization product having specific glass transition temperature. CONSTITUTION:(A) An aqueous dispersion containing a polymer with a glass transition temperature -10-40 deg.C prepared by emulsion polymerization of 100pts. wt. of a monomer mixture made up of (i) 70-95pts.wt. of a 1-4C alkyl ester of (meth)acrylic acid, (ii) 5-20pts.wt. of an alpha,beta-monoethylenic unsaturated carboxylic acid, and (iii) 0-25pts.wt. of a copolymerizable alpha,beta-monoethylenic monomer and (B) an ultraviolet absorber are blended in a weight ratio 100:0.1-100:5 (on a solid basis) to obtain the objective composition not impairing undercoating film in the protective coating operation, outstanding in workability, and also removable with an aqueous alkali when unnecessary.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention is directed to an alkyl (meth)acrylic acid ester having an alkyl group of 1 to 4 carbon atoms, 70 to 95 parts by weight, α.

5 to 20 parts by weight of β-monoethylenically unsaturated carboxylic acid,
and other copolymerizable α,β-monoethylenic monomers by emulsion polymerization of a monomer mixture consisting of 0 to 25 parts by weight! [11] It consists of an aqueous dispersion of an emulsion polymer whose glass transition temperature is in the range of 110°C to 40°C and an ultraviolet absorber. The present invention relates to an aqueous paint film protection composition that has a protective effect on paint films and can be easily removed with alkaline water when no longer needed.

[Prior art and its drawbacks]

The beauty of automobiles, various equipment, machinery products, and parts can be improved by painting, but these products need to be protected from scratches during transportation, or when left outdoors due to exposure to water and sunlight (particularly ultraviolet rays). Various protection methods have been devised or implemented in order to prevent deterioration. For example: ■ Packaging with thermoplastic resin sheets such as polyvinyl chloride, polyethylene, polypropylene, etc. or heat-sealing packaging, ■ Application of so-called guard wax whose main component is polyethylene wax or microcrystalline wax, ■ Painted object (base) Applying paint or resin that has poor adhesion to the surface and peeling it off when it is no longer needed - Application of so-called ripper paint,
There are protection methods such as, but ■ is when the shape of the packaged object becomes complex and large.

Each type has its own drawbacks, such as the packaging or its removal being difficult, (1) requiring time and effort to remove wax, and (2) requiring time and effort to peel and remove when the shape of the object to be coated becomes complex.

On the other hand, in order to prevent scratches or rust on metal surfaces such as steel materials and mechanical parts, a method has been implemented in which an alkali-soluble resin is temporarily coated, and when it is no longer needed, it is dissolved and removed with alkaline water.

With this method, various coating methods such as spraying, brushing, and dipping can be used depending on the shape of the object to be coated, and the coating is easy to apply, and if a coating is not required, it can be easily removed with alkaline water. It has the excellent feature of being able to However, if this method is applied to the protection of painted surfaces, it may damage the underlying painted surface due to resin solvents, plasticizers, etc., or the protection effect against deterioration of the underlying painted surface due to ultraviolet rays may not be sufficient. There are drawbacks.

[Problem that the invention seeks to solve]

In view of the drawbacks of the prior art described above, the present inventors have developed an automobile,
For products that emphasize aesthetics by painting various equipment and machinery products or parts, we prevent scratches during transportation of these painted products, or from water and sunlight (especially ultraviolet rays) when left outdoors. We conducted extensive research on protective compositions that can be used to prevent paint film deterioration. As a result, a mixture having a specific mixing ratio of an aqueous dispersion containing an emulsion polymer having a specific glass transition temperature and a UV absorber prepared by emulsion polymerization of a monomer mixture with a specific composition. When applied to a painted surface, it has an excellent scratch prevention effect on the underlying painted surface and an excellent deterioration prevention effect against water and ultraviolet rays, and can be applied easily and without damaging the underlying painted surface during protective coating. The present inventors have discovered that excellent properties can be obtained, such as the ability to easily remove the protective coating film with weakly alkaline water, and have completed the present invention.

[Structure of the invention]

To summarize the present invention, 1. The present invention includes (A) as an essential component.
: 70 to 95 parts by weight of (meth)acrylic acid alkyl ester having an alkyl group of 1 to 4 carbon atoms, α.

5 to 20 parts by weight of β-monoethylenically unsaturated carboxylic acid,
and other copolymerizable α.

It was prepared by emulsion polymerization of 100 parts by weight of a monomer mixture consisting of 0 to 25 parts by weight of a β-monoethylenic monomer. It consists of an aqueous dispersion containing a polymer having a glass transition temperature in the range of 110°C to 40°C, and (B): an ultraviolet absorber, and the mixing ratio of (A):(B) is respectively Solid weight ratio: ioo: o, i~100:
It is an object of the present invention to provide an aqueous alkali-removable paint film protection composition characterized in that the paint film protection composition has an alkali-removal range of 5.

Hereinafter, the configuration of the present invention will be explained in detail.

The aqueous dispersion as component (A) used in the present invention contains a specific amount of (meth)acrylic acid alkyl ester whose alkyl group has 1 to 4 carbon atoms and α,β-monoethylenically unsaturated carboxylic acid. It is prepared by emulsion polymerization.

Examples of the alkyl (meth)acrylate having 1 to 4 carbon atoms in the alkyl group include methyl (meth)acrylate and ethyl (meth)acrylate.

n-propyl (meth)acrylate, 1so-propyl (meth)acrylate, n-butyl (meth)acrylate, (
1so-butyl meth)acrylate, (meth)acrylic F
Examples include tert-butyl, which may be used alone or as a mixture of two or more.

The amount thereof is 70 to 95 parts by weight based on 100 parts by weight of total monomers.

Examples of the α,β-monoethylenically unsaturated carboxylic acids include acrylic acid, methacrylic acid, crotonic acid, itaconic acid, fumaric acid, and maleic acid, which may be used alone or as a mixture of two or more. 5~
20 parts by weight are used.

In the present invention, other copolymerizable monomers can be used during emulsion polymerization. Examples of such copolymerizable monomers include aromatic vinyl compounds such as styrene and vinyltoluene; heterocyclic vinyl compounds such as vinylpyrrolidone; vinyl acetate, vinyl propionate,
Vinyl esters such as vinyl versatate; vinyl chloride.

Vinyl halides such as vinylidene chloride and vinylidene fluoride; α-olefins such as ethylene and propylene; (meth)acrylic acids with alkyl carbon atoms of 5 or more, such as 2-ethylhexyl (meth)acrylate and lauryl (meth)acrylate; Esters; (meth)acrylamide, (meth)acrylonitrile, (meth)acrylic acid β
- and droxyethyl, glycidyl (meth)acrylate,
Examples include monomers having a polar group such as allyl glycidyl ether, and these are used singly or as a mixture of two or more in an amount of 0 to 25 parts by weight based on the total monomers.

In the present invention, the (meth)acrylic acid alkyl ester having an alkyl group having 1 to 4 carbon atoms, which is an essential monomer component, is used to improve the alkali solubility of the polymer obtained by emulsion polymerization.
From the viewpoint of weather resistance and water resistance, 70 out of 100 parts by weight of total monomers
~95 parts by weight are used.

If the amount used exceeds 95 parts by weight, the alkali solubility of the coating obtained from the resulting polymer will be poor, and if it is less than 70 parts by weight, the balance between the alkali solubility, weather resistance, and water resistance of the coating will be poor, which is not preferable.

In addition, the amount of α,β-monoethylenically unsaturated carboxylic acid to be used should be determined based on the balance between the alkali solubility and water resistance of the resulting polymer; More preferably, 7 to 15 parts by weight are used. If the amount exceeds 20 parts by weight, the hydrophilicity of the obtained polymer will become too high, and although the coating has excellent alkali solubility, the water resistance will be poor, which is undesirable.
If the amount used is less than part by weight, the alkali solubility of the coating will be poor, which is also not preferable.

Other copolymerizable monomers should be selected and used based on the balance between hydrophilicity and hydrophobicity of the resulting polymer, and if necessary, 0 to 25 parts by weight based on 100 parts by weight of the total monomers may be used. Ru.

The aqueous dispersion of the emulsion polymer that is component (A) used in the present invention can be prepared by polymerizing the above monomer mixture by a conventional emulsion polymerization method. At that time, it is necessary that the glass transition temperature of the resulting polymer is in the range of 110°C to 40°C, more preferably 0°C to 30°C.
The one is good. If the glass transition temperature exceeds 40°C, it is undesirable because the film forming properties will be poor, and if it is below -10°C, the film will become severely softened at room temperature, the water resistance of the film will be poor, and the undercoat surface will be less likely to be scratched by external impact. Poor prevention effect.

Known and commonly used emulsifiers are used for emulsion polymerization, such as anionic emulsifiers, nonionic emulsifiers, cationic emulsifiers, and other reactive emulsifiers.
These can be used alone or as a mixture of two or more.

Also, known and commonly used protective colloids such as polyvinyl alcohol and hydroxyethyl cellulose may be used in combination.

In the present invention, there are no particular restrictions on the types and amounts used of these emulsifiers and protective colloids, but it is usually preferable to use an anionic emulsifier and a nonionic emulsifier in combination.The amount used depends on the water resistance and dryness of the resulting polymer film. Considering the properties of the emulsifier, it is usually used in an amount of 0.2 to 4 parts by weight per 100 parts by weight of the monomer mixture, but if a nonionic emulsifier with an HLB of 14 or less is used, it may deteriorate the underlying coating film. Therefore, the amount used is preferably 1 part by weight or less.

In addition, there is no particular limit to the molecular weight of the obtained polymer, but
Considering the balance between water resistance, weather resistance, and alkali solubility of the polymer film, a small amount of a known and commonly used chain transfer agent such as lauryl mercaptan, or a known and commonly used crosslinking agent such as vinyl silanes and divinylbenzene may be used as necessary. It's okay.

There is no particular restriction on the particle size of the obtained polymer, but from the viewpoint of improving the film-forming properties, water resistance, and alkali solubility of the coating, the smaller the particle size, the better; however, on the contrary, if the particle size is too small, The weight average particle diameter should be 0.05 to 0.2μ because the viscosity of the emulsion polymer becomes significantly high and workability is poor.
It is preferable that it is in the range of .

In the present invention, a polymerization initiator is normally used when producing component (A), and any catalyst that is generally used in emulsion polymerization can be used. Representative examples include water-soluble inorganic peroxides or persulfates such as hydrogen peroxide and ammonium persulfate; organic peroxides such as cumene hydroperoxide and benzoyl peroxide;
These include azo compounds such as azobisisobutyronitrile, and these may be used alone or as a mixture of two or more. The amount used is about 0.1 to 2% by weight based on the total amount of monomers. Note that a known redox polymerization method using these catalysts in combination with metal ions and a reducing agent may be employed.

In the present invention, the various monomers described above at the time of g* of component (A) may be added all at once, in portions, or continuously by dropwise addition to the polymerization reaction system. Examples of ultraviolet absorbers as component (B) used in the present invention include methyl salicylate, phenyl salicylate, and salicylic acid. Salicylic acid esters such as cresyl and benzyl salicylate; 2-hydroxybenzophenone, 2-hydroxy-4-benzyloxybenzophenone 5
2-hydroxy-4-octoxybenzophenone, 2-
Benzophenones such as hydroxy-5-chlorobenzophenone and 2-aminobenzophenone: 2-(2'-hydroxy-5'-t-butylphenyl)benzotriazole, 2-(2'-hydroxy-5'-t-butylphenyl) )-5-chlorobenzotriazole, 2- (2'-
Benzotriazoles such as hydroxy-55-methoxyphenyl)benzotriazole and 2-(2'-hydroxy-3',5'-di-neopentylphenyl)benzotriazole; ethyl 2-cyano-3,3-diphenylacrylate , 2-ethylhexyl 2-cyano-3゜3-diphenylacrylate, α-cyano-β-methyl-4-
Substituted acrylonitriles such as methyl methoxycinnamate:
Nickel complex salts such as 2,2'-thiobis(4-octylferulate) nickel complex salt, (2,2'-thiobis(4-t-octylphenolate))-n-butylamine nickel complex salt, p-methoxybenzylidene malone UV absorbers such as dimethyl acid, resorcinol monobenzoate, hexamethyl phosphoric triamide, and 2,5-diphenyl-p-benzoquinone can be mentioned. These are 1
As a mixture of 5 types or 2 or more types, the solid content is 0.1 to 5! based on 100 parts by weight of the solid content of the emulsion polymer in the aqueous dispersion, which is the component (A). 11 parts used.

If the amount used is less than 0.1 part by weight, not only will the resulting protective coating not have a sufficient protective effect against deterioration caused by ultraviolet rays on the base coating, but the protective coating itself will deteriorate and denature due to ultraviolet rays, and during alkali removal. , which is undesirable because it becomes difficult to remove. On the other hand, if the amount used exceeds 5 parts by weight, the effect of the ultraviolet absorber will be saturated even if more than this amount is used, which is not appropriate.More preferably, the solid of the emulsion polymer in component (A) The solid content of the ultraviolet absorber is preferably 0.3 to 3 parts by weight per 100 polymerized parts.

The emulsion polymer in component (A) and the ultraviolet absorber in component (B) may be mixed by dissolving the ultraviolet absorber in a small amount of an organic solvent and then adding the solution to the emulsion polymer, or At the time of emulsion polymerization, the ultraviolet absorber may be mixed in advance by dissolving it in the monomer mixture and performing emulsion polymerization.

The aqueous alkali-removable paint film protection composition of the present invention has excellent film forming properties, film physical properties, and storage stability.

To improve painting workability, etc., various compounds 1, such as organic solvents such as film-forming aids, various water-soluble resins, and antifoaming agents.

It is possible to use preservatives, thickeners, freeze stabilizers, etc., but in consideration of the negative effect on the base coating, the total amount of organic solvents used is preferably 10% by weight or less in the composition, more preferably It is preferable to keep it at 4% by weight or less.

〔Example〕

Next, the present invention will be explained in more detail with reference to Examples. All parts and percentages hereinafter are based on weight unless otherwise specified.

Example 1 A stainless steel reaction vessel was charged with 140 parts of deionized water, 1 part of sodium lauryl sulfate, and 1 part of polyoxyethylene nonylphenyl ether of HL B 18.

0.5 part of ammonium persulfate was added while heating to 75 to 80°C and stirring under a nitrogen stream.

Next, a mixture consisting of 48 parts of n-butyl acrylate, 42 parts of methyl methacrylate, 5 parts of acrylic acid, and 5 parts of methacrylic acid was added dropwise over 180 minutes to copolymerize.
The polymerization was further maintained at the same temperature for 60 minutes to complete the polymerization.

Next, cool to 30°C and add 5% ammonia water and water for a total of 10
The pH was adjusted to 6.5 at the same time. Hydroxyphenylbenzotriazole UV absorber Tinuvin 328 (Ciba・
Add a solution of 0.5 parts of Geigy Co. I and 0.5 parts of the hindered bisphenol ultraviolet absorber Tsukulyzer N5-6 (manufactured by Iriuchi Shinko Kagaku Kogyo ■) in 5 parts of toluene, and mix thoroughly until uniform. Stirred. The resulting aqueous dispersion composition had a non-volatile content of 40%, a viscosity of 240 cps, p
H6.5, the polymer glass transition temperature was 15°C (theoretical value), this was the composition! shall be.

Example 2 The composition of the monomer mixture was changed to 1 2-ethylhexyl acrylate.
Example 1 except that 5 parts of ethyl acrylate, 40 parts of ethyl acrylate, 33 parts of methyl methacrylate, and 12 parts of methacrylic acid were used.
The same method was repeated. The resulting aqueous dispersion composition had a nonvolatile content of 40%, a viscosity of 310 cps, and a pH of 6.5.
, the polymer glass transition temperature was 17°C (theoretical value),
This is referred to as composition (2).

Example 3 A stainless steel reaction vessel was charged with 140 parts of deionized water, 1 part of sodium lauryl sulfate, and 1 part of HLBlg polyoxyethylene nonylphenyl ether, and heated under a nitrogen stream for 70 minutes.
Heat to 5-80℃ and remove ammonium persulfate while stirring.
．． I prepared 5 parts.

Next, a mixture consisting of 48 parts of n-butyl acrylate, 42 parts of methyl methacrylate, 5 parts of acrylic acid, and 5 parts of methacrylic acid was added dropwise over 180 minutes.

After copolymerization, the mixture was further maintained at the same temperature for 60 minutes to complete the polymerization.

Next, cool to 30°C and add 5% ammonia water and water for a total of 10
The pH was adjusted to 6.5 at the same time. 1 part of the hindered amine UV absorber Sanol 292 (manufactured by Ciba Geigy) and the hindered bisphenol UV absorber N5-6
A solution of 1 part dissolved in 8 parts of toluene was added and stirred thoroughly until uniform.

The resulting aqueous dispersion composition had a nonvolatile content of 40% and a viscosity of 25%.
0cps, p)! 6.5, polymer glass transition temperature 1
The temperature was 5°C (theoretical value), and this is referred to as composition (2).

Example 4 A stainless steel reaction vessel was charged with 145 parts of deionized water, 1 part of sodium lauryl sulfate, and 1 part of HLBlg polyoxyethylene nonylphenyl ether, and heated under a nitrogen stream for 7 hours.
Heat to 5-80℃ and remove ammonium persulfate while stirring.
．． I prepared 5 parts.

Next, to a mixture consisting of 48 parts of n-butyl acrylate, 42 parts of methyl methacrylate, 5 parts of acrylic acid, and 5 parts of methacrylic acid, 60.5 parts of the hindered bisphenol ultraviolet absorber Tsukulyzer N5 and salicylic acid ester ultraviolet rays were added. Absorbent G-Soap 201 (Shiraishi Calcium■
@) A solution of the O and S parts was added dropwise for 180 minutes to copolymerize, and the polymerization was further maintained at the same temperature for 60 minutes to complete the polymerization.

Then, the PI (PI) was adjusted to 6.5 with a total of 10 parts of 5% aqueous ammonia and water. The resulting aqueous dispersion composition had a nonvolatile content of 40%, a viscosity of 110 cps, a pH of 6.5, and a polymer glass transition temperature of 15°C. (theoretical value), and this is designated as composition (■).

Comparative Example 1 The composition of the monomer mixture was changed to 2-ethylhexyl acrylate 4
5 parts, 10 parts of styrene, 35 parts of methyl methacrylate,
The same procedure as Example 1 was repeated except that 5 parts of acrylic acid and 5 parts of methacrylic acid were used.

The resulting aqueous dispersion composition had a nonvolatile content of 40% and a viscosity of 16.
0 cps, pH 6.5, polymer glass transition temperature 11
℃ (theoretical value), and this is designated as composition I'.

Comparative Example 2 The same procedure as in Example 1 was repeated except that the composition of the monomer mixture was 48 parts of n-butyl acrylate, 48 parts of methyl methacrylate, and 4 parts of acrylic acid. The resulting aqueous dispersion composition had a nonvolatile content of 40%, a viscosity of 200 cps,
pH 6.5, polymer glass transition temperature 14°C (theoretical value)
This will be referred to as composition (■').

Comparative Example 3 The composition of the monomer mixture was 28 parts of acrylic wIn-butyl,
The same procedure as in Example 1 was repeated except that 62 parts of methyl methacrylate, 5 parts of acrylic acid, and 5 parts of methacrylic acid were used. The resulting aqueous dispersion composition had a non-volatile content of 40%.
The composition had a viscosity of 220 eps, a PI (6°5.

Comparative Example 4 The composition of the monomer mixture was 50 parts of n-butyl acrylate, 2z parts of ethyl acrylate, 18 parts of methyl methacrylate,
The same procedure as in Example 1 was repeated except that S part acrylic acid and 5 parts methacrylic acid were used.

The resulting aqueous dispersion composition had a nonvolatile content of 40% and a viscosity of 25%.
0 cps, pH 6.5, polymer glass transition temperature -1
The temperature was 3.degree. C. (theoretical value), and this is designated as composition (■').

Comparative Example 5 The composition of the monomer mixture was 48 parts of n-butyl acrylate, 27 parts of methyl methacrylate, and 25 parts of methacrylic acid, and the emulsifier composition was 1 part of sodium lauryl sulfate, HL B
The same procedure as in Example 1 was repeated except that 3 parts of polyoxyethylene nonylphenyl ether of No. 18 was used. The resulting aqueous dispersion composition had a non-volatile content of 40% and a viscosity of 120c.
ps, pH 6.5, and polymer glass transition temperature 17° C. (theoretical value). This is designated as composition v'.

Comparative Example 6 An emulsion polymer was synthesized by the same method as in Example 1 without the post-addition of an ultraviolet absorber and toluene. The resulting aqueous dispersion composition had a nonvolatile content of 41% and a viscosity of 220%.
eps, pH 6.5, polymer glass transition temperature 15°C (
theoretical value). This is referred to as composition ■'.

Comparative Example 7 Hydroxyphenylbenzotriazole ultraviolet absorber Tinuvin 32 was added to 250 parts of the composition VI' described in Comparative Example 6.
80.03 parts of the hindered bisphenol ultraviolet absorber Tsukulyzer MS-60.03 parts dissolved in 5 parts of toluene were added and sufficiently stirred until uniform. The resulting aqueous dispersion composition had a nonvolatile content of 40% and a viscosity of 2.
40eps, pH 6°5. Polymer glass transition temperature 15
°C (theoretical value). This is referred to as composition (■').

The compositions of Compositions 1 to 1 and Compositions I' to 2' described in Examples 1 to 4 and Comparative Examples 1 to 7, respectively, are summarized in Table 1.

(Space below) Application Example 1 To compare the water resistance, acid resistance, and alkali solubility (alkali removability) of the coatings of Compositions I to ■ and Compositions ■' to ■', three coats of each composition were placed on a glass plate. It was applied with a mill applicator and dried for one day at 25° C. and 60% humidity to form a coating film.

Regarding Composition 1, 5 parts of dibutyl phthalate was post-added to m'ioo part of the composition to form a coating film, since it would not form a film under the drying conditions as it was.

Each glass plate was immersed in tap water at 20° C. for 3 days, and changes in the coating were visually determined.

Further, a similarly prepared coating film was immersed in 20° C. water adjusted to pH 1.0 with nitric acid for one day, and changes in the coating film were visually determined.

Further, a similarly prepared coating film was immersed in 2% ammonia water at 20°C for 20 minutes, or in a sodium hydroxide aqueous solution adjusted to pH 12.5 at 40°C for 1 minute.

The state of the coating was visually determined.

The results are summarized in Table 2.

Application example 2 Steel plate with so-called metallic coating of two-coat one-bake consisting of acrylic resin and melamine resin and oil length 30%
PWC 40% baking paint consisting of alkyd resin and melamine resin and using titanium oxide pigment was painted, so-called solid color coated steel plate, and compositions 1 and n were applied, respectively.
, m, IV, I[[', IV'.

V', VI', and ■' were applied using a pan coater to a dry film thickness of 100 μm, and dried at 25° C. and 60% humidity for one day to form a coating film. As shown in Table 2, compositions 1' and n' had poor alkali removal properties, so the following tests were not conducted. In addition, composition ■' is Application Example 1
As mentioned above, due to poor film-forming properties, the composition m'i'o
5 parts of dibutyl phthalate was added to 0 parts by weight and subjected to the test.

In order to evaluate the protective effect of the protective coating on the scratches on the base coating of the test plate coated with each composition, the test plate with each protective coating and the test plate without the protective coating as a blank were drawn at 20°C. The test was performed using a testing machine (manufactured by Toyo Seiki Seisakusho), and the test plate was then immersed in 2% ammonia water at 20°C for 20 minutes to remove the protective coating, washed with water, and air-dried to remove the metallic coating, which is the base coating. The presence or absence of scratches on the film and solid color coating was visually determined.

Next, in order to evaluate the effect of each composition on the base coating film, a similarly prepared test plate with a protective coating was left at room temperature for one week, and then the test plate was soaked in 2% ammonia water at 20°C for 20 minutes. After soaking for 1 minute, remove the retaining WI coating, wash with water, air dry, and measure the gloss retention rate of each base coating using a gloss meter mode.
Measured using GM26D (6O') (Murakami Color Technology Research Institute layer).

Also, the protective effect and protection of UV rays on the base coating film of the protective coating! ! 1! In order to evaluate the weather resistance of the film itself, a similarly prepared test plate with protective coating and a blank test plate without protective coating were used as Sunshine Weather-0.
A 2000 hour accelerated weathering test was carried out using Meta.

After the test, the test plate was immersed in 2% ammonia water at 20°C for 20 minutes, and the state of the protective coating was visually judged.If the protective coating film was difficult to remove, it was further soaked with absorbent cotton in 2% ammonia water. The gloss retention rate of each base coating film was measured using a gloss meter in the same manner as described above after washing with water and air drying.

Next, in order to evaluate the protective effect of the protective coating on the base coating against acids, test plates with protective coating and blank test plates with no protective coating were prepared in the same way and adjusted to pH 1°0 with nitric acid. After being immersed in water at 20°C for 1 day, it was taken out, and after washing, it was immersed in 2% ammonia water at 20°C for 20 minutes to remove the protective coating, and the gloss retention rate of the base coating after washing with water and air drying was evaluated. It was measured using a gloss meter in the same manner as above.

The above results are summarized in Table 3.

(The following is a blank space) As shown in Tables 2 and 3, the aqueous alkali-removable paint film protection composition of the present invention is as follows.

Its own protective coating has excellent water resistance, acid resistance, and alkali removability, and it also has an excellent protection effect against scratches on the base coat, and has excellent weather resistance and acid resistance against the base coat. be effective.

In particular, what should be noted in relation to the comparative examples is that even in the comparative examples in Table 2, where the alkali removability of the protective coating film itself was considered to be good (comparative examples ■' to ■'), As shown, it has deteriorated after the weathering test.

This indicates that in the composition of the present invention consisting of the emulsion polymer component with a specific monomer composition and the ultraviolet absorber component in a specific ratio, these components act synergistically to maintain good weather resistance. It means.

〔Effect of the invention〕

The aqueous alkali-removable paint film protection composition of the present invention consists of a (meth)acrylic acid ester polymer component having excellent weather resistance and durability and a UV absorber component as essential components. Therefore, when the composition of the present invention is applied onto a paint film, an excellent effect of preventing deterioration of the base paint film due to water and ultraviolet rays can be obtained. It also has an excellent protective effect against scratches caused by impact, and if a protective film becomes unnecessary, it can be easily dissolved and removed with alkaline water.

Furthermore, since the paint film protection composition of the present invention is water-based, there is less risk of damaging the underlying paint film during protective coating, and it has excellent workability.

Claims (1)

[Scope of Claims] (A): 70 to 95 parts by weight of (meth)acrylic acid alkyl ester having an alkyl group having 1 to 4 carbon atoms, 5 to 20 parts by weight of α,β-monoethylenically unsaturated carboxylic acid, and Monomer mixture 1 consisting of 0 to 25 parts by weight of other copolymerizable α,β-monoethylenic monomers
An aqueous dispersion containing a polymer having a glass transition temperature of -10°C to 40°C, prepared by emulsion polymerization of 00 parts by weight. (B): an aqueous alkali consisting of an ultraviolet absorber and characterized in that the mixing ratio of (A):(B) is in the range of 100:0.1 to 100:5 in terms of solid content weight ratio, respectively. Removable paint protection composition.