JPH11302590A - Removable aqueous coating composition and temporary protection of automobile shell plate coating by using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composition capable of forming a protecting membrane excellent in peeling property, peeling stability and adoptability to an environment, and useful for a temporary protection of an automobile shell plate coating. SOLUTION: This removable aqueous coating composition contains a copolymer emulsion obtained by an emulsion polymerization of polymerizable unsaturated monomers in multiple stages so as to contain >=2 kinds of copolymers having different glass transition temperatures in a same particle [e.g.; the copolymer containing (B) an acrylic having (-)50-10 deg.C glass transition temperature and obtained by performing an emulsion polymerization in the presence of an acrylic copolymer having 0-100 deg.C glass transition temperature and obtained by performing an emulsion polymerization of a monomer mixture (M) containing a (meth)acrylic acid ester as an essential component and as necessary other polymerizable unsaturated monomers except for acrylonitrile, by adding the monomer (M) therein, and has >=10 deg.C difference in the glass transition temperatures of the copolymers (A) and (B)].

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a peelable aqueous coating composition useful for temporarily protecting the surface of a coating film of an automobile outer panel and other painted articles, and an automobile outer panel using the composition. It relates to a method for temporarily protecting a coating film.

[0002]

2. Description of the Related Art Temporarily protecting the coating film of products whose surfaces are painted such as metal products such as automobiles, vehicles, machine parts and household goods, woodwork products, glass products, plastic products and rubber products. Is commonly done.

[0003] For example, from the completion of these coated products to the end to the end of the customer, during storage in outdoor stock yards, transportation by self, rail, trailer, ship, etc.,
Scratch of the paint film due to contact with other objects, dust and dust in the air, iron powder, salt, soot, bird droppings, body fluids and dead bodies of insects, sun rays, wind and rain (especially acid rain), etc.
Discoloration, contamination, etc. occur, and the product value decreases,
In order to prevent this, temporary protection is required during the period from the completion of the painted product to the end of the customer. Conventionally, various methods have been performed as described below to temporarily protect such a coated product, but none of these methods has been sufficient.

[0004] A dispersion of an aliphatic hydrocarbon-based solvent of waxes is applied. In this method, an emulsion in which a detergent is dispersed in a hydrocarbon solvent or water is used to remove the applied temporary film.For example, when this is applied to an automobile, the emulsion is applied to the inside of a door or a hinge portion. The rust preventive and the rust preventive wax are removed at the same time, and the coating film swells with these solvents, and also has environmental problems such as fire danger and wastewater treatment.

[0005] A wax-solid powder organic solvent type dispersion is applied by mixing a solid powder with the wax to reduce the strength of the wax coating and easily remove the protective coating by hand wiping. It has poor temporary protection, easily falls off when touched by hand, and is easily contaminated by acid rain.

[0006] An emulsion containing an alkali-soluble acrylic resin as a main component is used as an aqueous temporary protective agent (for example, US Pat. No. 5,428,095). Since it contains a large amount of carboxyl group-containing monomers such as acrylic acid and methacrylic acid, it is difficult to peel off and it is removed with an aqueous alkali solution, which requires a great deal of man-hours, and also requires wastewater treatment. There are also challenges.

Further, as an aqueous temporary protective agent, (meth)
It is known to use an acrylic resin emulsion containing acrylonitrile (for example, see JP-A-60-161).
No. 465, JP-A-3-259966), which is excellent in film strength and peelability, but it is difficult to dispose of the peeled film because it contains (meth) acrylonitrile. That is, if the coating is buried in the ground, there is a possibility of water pollution, and if incinerated, hydrogen cyanide gas is generated and the air may be polluted.

It is also known to use a paint containing vinyl acetate emulsion as a main component as an aqueous protective agent (eg, US Pat. No. 5,143,949), but the acid resistance and water resistance are not sufficient.

As a method for forming a protective film by applying these temporary protective agents to the coating surface of a vehicle, see, for example, JP-A-7-8
0397, JP-A-7-80398, JP-A-7-80
No. 399 or the like can be employed. According to these methods, the coating surface of the vehicle is washed with water, the washing water is drained, a temporary protective agent is applied and dried to form a protective film,
Alternatively, a protective film is formed by applying a temporary protective agent to the coating surface of the body and drying after coating the body in the manufacturing process of the automobile and before assembling. However, when the temporary protective agent exemplified above is used in these methods, sagging occurs in the step of applying the temporary protective agent, or a crack-like coating surface abnormality occurs in the protective film during drying, or the obtained protective film However, there were problems such as that the strength and elongation had large temperature dependence.

As described above, when a temporary protective agent is used, it is important to use a composition having the following characteristics a) to g).

A) It has an appropriate adhesiveness to the coating film to be protected, and the adhesiveness does not change significantly with the coating temperature or aging. It can be easily peeled off as one continuous sheet.

B) Spray coating, roller coating, and brush coating can be performed.

C) It has excellent protection functions such as prevention of stains and contamination by acid rain, iron powder, etc., and prevention of contact with objects and damage due to chipping.

D) The coating has appropriate elasticity, strength, elongation and durability, and its properties such as strength and elongation are hardly affected by the coating temperature. In other words, when peeling outdoors, there are problems such as that the film is too stretched in the high temperature period in summer and cannot be peeled off, and in the low temperature period in winter, the film is broken and the film is broken and cannot be peeled in a sheet form. Hateful. E) It has water resistance, weather resistance, and heat stability necessary for outdoor storage.

F) No additives such as solvents, plasticizers and dispersants which swell the coating film to be protected or cause coating surface abnormalities such as deformation, discoloration, spots and blurs.

G) Since the peeled film is to be discarded, it does not contain any components which are harmful to the human body and the environment even when buried or incinerated.

[0017]

Means for Solving the Problems The present inventors have made the above-mentioned-
As a result of intensive studies to solve the problems of the above and develop a releasable aqueous temporary protective coating composition having the above-mentioned properties a) to g), at least a copolymer having a different glass transition temperature in the same particle is obtained. When a releasable aqueous coating composition containing a copolymer emulsion containing two or more kinds is used, the resulting protective coating has an adhesive force that is not greatly changed by the coating temperature and is easy even after a long period of time. The present invention was found to be able to provide temporary protection without any environmental problems even in landfilling or incineration after the separation, and thus completed the present invention.

That is, according to the present invention, emulsion polymerization is carried out in multiple stages using a polymerizable unsaturated monomer so that at least two or more copolymers having different glass transition temperatures are contained in the same particle. Copolymer emulsion (I)
And a method for temporarily protecting a coating film on an automobile outer panel, which is applied to a surface of a cured top coating film coated on an automobile outer panel.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The composition and method of the present invention will be described below.

The composition of the present invention is obtained by performing emulsion polymerization in multiple stages using a polymerizable unsaturated monomer as a film-forming component, so that at least two or more copolymers having different glass transition temperatures within the same particle are obtained. It contains the copolymer emulsion (I) to be included. Glass transition temperature difference (ΔTg) between at least two kinds of copolymers contained here
Is preferably at least 10 ° C. or higher, preferably 20 ° C. or higher, more preferably 30 ° C. or higher.

The glass transition temperature (Tg) of the copolymer referred to in the present invention is a value determined by differential scanning calorimetry (DSC) according to JIS K7121.

The copolymer emulsion (I) is usually prepared by subjecting a mixture of polymerizable unsaturated monomers to a first stage emulsion polymerization using a polymerization initiator in the presence of an emulsifier to obtain a copolymer emulsion. After the above, in the copolymer emulsion, a mixture of the following polymerizable unsaturated monomers is obtained by performing the emulsion polymerization of the second and subsequent steps sequentially and similarly using an emulsifier and a polymerization initiator. is there.

In the present invention, as the copolymer emulsion (I), a monomer containing a polymerizable unsaturated monomer other than (meth) acrylonitrile and, if necessary, especially a (meth) acrylic ester is essential. After obtaining an acrylic copolymer (A) emulsion having a glass transition temperature of 0 to 100 ° C., preferably 20 to 70 ° C. obtained by emulsion polymerization of the mixture, a (meth) acrylic acid ester is essential in the emulsion. If necessary, a monomer mixture containing a polymerizable unsaturated monomer other than (meth) acrylonitrile is added, and the glass transition temperature obtained by emulsion polymerization is -5.
After the copolymer emulsion containing the acrylic copolymer (B) at 0 to 10 ° C, preferably -30 to 5 ° C, or the acrylic copolymer (B) obtained by the first-stage emulsion polymerization, 2 A copolymer emulsion containing the acrylic copolymer (A) obtained by the second-stage emulsion polymerization can be suitably used. In any case, the difference (ΔTg) between the glass transition temperatures of (A) and (B) is at least 10 ° C. or more, preferably 20 ° C. or more, and more preferably 30 ° C. or more. If the ΔTg is less than 10 ° C., the releasability in the outdoors largely depends on the environmental temperature. In the high temperature period in summer, the adhesiveness is high and the film is too long to be peeled off. It is not preferable because the film is lowered and the film cannot be peeled off in the form of a cracked sheet.

The (meth) acrylate used in the production of the acrylic copolymers (A) and (B) includes, for example, methyl (meth) acrylate, ethyl (meth) acrylate and propyl (meth) acrylate. ) Acrylates, butyl (meth) acrylates, 2-ethylhexyl (meth) acrylates, cyclohexyl (meth) acrylates
G, octyl (meth) acrylate, lauryl (meth)
Alkyl or cycloalkyl esters of (meth) acrylic acid having 1 to 24 carbon atoms, such as acrylate and isobornyl (meth) acrylate; 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) Examples thereof include hydroxyalkyl esters of (meth) acrylic acid having 2 to 8 carbon atoms, such as acrylate.

Other polymerizable unsaturated monomers other than the above (meth) acrylates and (meth) acrylonitriles include, for example, styrene, vinyltoluene, methylstyrene, chlorostyrene, N-vinylpyrrolidone, ethylene Butadiene, chloroprene, vinyl propionate, vinyl acetate, vinyl chloride, vinyl isobutyl ether, methyl vinyl ether, 2-ethylhexyl vinyl ether; (meth) acrylic acid, maleic acid, crotonic acid, β-carboxyethylacrylic acid A carboxyl group-containing monomer such as a late, 2-acrylamido-2-methylpropanesulfonic acid, allylsulfonic acid,
(Meth) acrylamide, sulfonic acid group-containing monomers such as styrenesulfonic acid sodium salt, sulfoethyl methacrylate and its sodium salt and ammonium salt;
Amide group-containing monomer such as dimethylaminopropyl (meth) acrylamide, dimethylaminoethyl (meth)
Acrylate, adduct of glycidyl (meth) acrylate with amines, etc .; (meth) acrylate having a polyoxyethylene chain; ethylene glycol di (meth)
Polymerization of polyvalent alcohols such as acrylate, 1,4-butanediol di (meth) acrylate, 1,6-hexanediol di (meth) acrylate, and trimethylolpropane tri (meth) acrylate Unsaturated monocarboxylic acid esters; polymerizable unsaturated alcohol esters of polybasic acids such as 1,1,1-trishydroxymethylethanedi (meth) acrylate; divinylbenzene, allyl (meth) acrylate These are appropriately used depending on the desired performance.

In the production of the acrylic copolymers (A) and (B), the mixing ratio of the (meth) acrylic acid ester and the other polymerizable unsaturated monomer is adjusted so as to fall within the respective glass transition temperature ranges. The amount of the (meth) acrylic acid ester is 1 to 100% by weight, preferably 50 to 9%, based on the total amount of the two components in each step, except for the above.
Suitably, it is 9.8% by weight and the other polymerizable unsaturated monomer is 99 to 0% by weight, preferably 50 to 0.2% by weight. Water-soluble monomers as other polymerizable unsaturated monomers
In the case where is used, it is preferable to suppress the use amount to 10% by weight or less from the viewpoint of the water resistance of the obtained film, and particularly, a carboxyl group-containing monomer and an amide group-containing monomer are used.
In the case of (1), when the amount is large, the adhesion to the coating film to be protected is high, and peeling of the coating film becomes difficult.

In the present invention, a copolymer emulsion in which the acrylic copolymers (A) and (B) are non-crosslinked can be used as the copolymer emulsion (I). Either one or both of the unions (A) and (B) contain, as a monomer component, a monomer containing 0.1 to 30% by weight of a carbonyl group-containing α, β-ethylenically unsaturated monomer in the monomer mixture. An acrylic copolymer that can be crosslinked with a hydrazide compound or the like obtained by copolymerizing the mixture may be used. By using this, it is possible to impart a characteristic that the obtained film has high strength, moderate elongation, and low temperature dependence of strength and elongation.

Examples of the carbonyl group-containing α, β-ethylenically unsaturated monomer include acrolein, diacetone acrylamide, diacetone methacrylamide,
Examples include acetoacetoxyethyl methacrylate, formyl styrene, and vinyl alkyl ketones having 4 to 7 carbon atoms (eg, vinyl methyl ketone, vinyl ethyl ketone, vinyl butyl ketone). Of these, diacetone acrylamide and diacetone methacrylamide are particularly preferred.

As the above copolymer emulsion (I),
In the case of an emulsion containing a crosslinkable acrylic copolymer having a carbonyl group, a carbonyl group-containing α, β-ethylenically unsaturated monomer may be used as one of the other polymerizable unsaturated monomers. The mixing ratio of each monomer in each step at this time is not particularly limited except that it falls within the corresponding glass transition temperature range. For example, the mixing ratio of the carbonyl group-containing α, β-ethylenically unsaturated monomer is 0.1%. ~
30% by weight, preferably 0.5 to 10% by weight, (meth)
The acrylate is preferably 99.9 to 70% by weight, preferably 99.5 to 90% by weight, and the other polymerizable unsaturated monomer is suitably 0 to 20% by weight, preferably 0 to 5% by weight. It is.

As described above, the copolymer emulsion (I)
Is a crosslinkable type having a carbonyl group introduced therein, the emulsion may contain a hydrazide compound as a crosslinking agent. The hydrazide compound has at least two hydrazide groups in one molecule. Examples thereof include 2 to 18 such as oxalic acid dihydrazide, malonic acid dihydrazide, succinic dihydrazide, glutaric acid dihydrazide, adipic acid dihydrazide, and sebacic acid dihydrazide. Aliphatic carboxylic acid dihydrazide having two carbon atoms; dihydrazide of monoolefinically unsaturated dicarboxylic acid such as maleic acid dihydrazide, fumaric acid dihydrazide, itaconic acid dihydrazide; carbonic acid dihydrazide, bissemicarbazide, polyisocyanate compound and polyoxyethylene Aqueous semicarbazide compound obtained by reacting a hydrazine derivative with a reaction product with an active hydrogen compound having a hydrophilic group such as a chain (JP-A-8-1513)
No. 58); phthalic acid, terephthalic acid or isophthalic acid dihydrazide, and dihydrazide of pyromellitic acid, trihydrazide or tetrahydrazide; nitrilotriacetic acid trihydrazide, citric acid trihydrazide, 1,
2,4-benzenetrihydrazide; ethylenediaminetetraacetic acid tetrahydrazide, 1,4,5,8-naphthoic acid tetrahydrazide; hydrazine or hydrazine hydrate (hydrazine hydroxide) is used as a low polymer having a lower alkyl ester group of carboxylic acid. And carbohydrazide, 1,3-bis (hydrazinocarboethyl) -5-isopropylhydantoin, etc. (see Japanese Patent Publication No. 52-22878). If the hydrazide compound is too strong in hydrophobicity, it is difficult to disperse in water and a uniform crosslinked coating film cannot be obtained, so a relatively low molecular weight (about 300 or less) compound having moderate hydrophilicity should be used. In the above examples, dihydrazide of a dicarboxylic acid such as adipic dihydrazide and sebacic dihydrazide is preferable.

The hydrazide compound is added in an amount of 0.02 to 3.0 equivalents, preferably 0.02 to 3.0 equivalents, per equivalent of the carbonyl group in the carbonyl group-containing copolymer emulsion (I). A suitable amount is from 0.1 to 2.0 equivalents.

As described above, the copolymer emulsion (I)
In the above, those containing at least two kinds of acrylic copolymers (A) and (B) can be used, and (A) and (B) each have one or both of a non-crosslinked type and a crosslinked type. Alternatively, both (A) and (B) may include a non-crosslinked type and a crosslinked type that fall within the respective glass transition temperature ranges. The acrylic copolymers (A) and (B) are (A) / (B) = 95/5 in terms of solid content weight ratio.
It is suitable that the content is 5/95, preferably 95/5 to 50/50.

In the composition of the present invention, the above-mentioned copolymer emulsion (I) is used as a film-forming component. However, if necessary, another copolymer emulsion (II) may be used in combination. In that case, the copolymer emulsion (I)
And the other copolymer emulsion (II) are preferably mixed at a solid content weight ratio of (I) / (II) = 95/5 to 5/95.

The copolymer emulsion (II) includes:
It has the same or different glass transition temperature as the vinyl acetate emulsion or ethylene-vinyl acetate emulsion conventionally used in the field of paints, or the acrylic copolymer (A) or (B) in the copolymer emulsion (I). An emulsion obtained by emulsion-polymerizing a monomer mixture containing an emulsion of an acrylic copolymer, for example, a (meth) acrylic acid ester and optionally containing other polymerizable unsaturated monomers except for (meth) acrylonitrile. Copolymer emulsions and the like can be used.

Further, the copolymer emulsion (II) is subjected to emulsion polymerization in multiple stages using a polymerizable unsaturated monomer so that at least two or more copolymers having different glass transition temperatures are contained in the same particle. The copolymer emulsion may be different from the copolymer emulsion (I).

The composition of the present invention further comprises a release aid (C)
Can be blended. When the peeling aid (C) is used in combination, the resulting film has an appropriate adhesion to the surface of the coating film to be protected and has a remarkably long function in peeling without damaging the coating film. The period (3 to 5 times) can be maintained.

As such a release aid, at least one compound selected from a wax type, a silicone type, a fluorine type and the like can be suitably used. These are dissolved in water,
Alternatively, any of dispersed or powdered materials can be used. Specific examples of the wax system include plant systems; animal systems such as candeli wax, carnauba wax, rice wax, wood wax, and jojoba oil;
Minerals such as beeswax, lanolin, and whale wax; minerals; petroleum, such as montan wax, ozokerite, and ceresin; synthetic hydrocarbons such as paraffin wax, microcrystalline wax, and petrolatum; Fisher-Tropsch wax, polyethylene oxide wax, polyethylene wax, Acrylic-ethylene copolymer wax, etc.
Modified waxes; montan wax derivatives, paraffin wax derivatives, microcrystalline wax derivatives, etc .; hydrogenated waxes; hydrogenated castor oil, hydrogenated castor oil derivatives, etc .; and others; 12-hydroxystearic acid, stearamide, phthalic anhydride, bisamide, amide , glycerin ester, sorbitan ester, higher alcohol - Le (C ₁₂ or more, preferably more than C _18), higher fatty acids (C ₁₂ or more, preferably more than C _18), and the like.

These wax systems have a melting point of about 15-25.
Those having a range of 0 ° C, preferably about 20-180 ° C, are desirable. If the melting point is outside the above range, the water resistance and acid resistance of the coating may be reduced.

As the silicone compound, silicone oil having a siloxane bond as a main skeleton, silicone powder, silicone emulsion, silicone water-soluble resin and the like can be used. Specifically, dimethyl polysiroquine,
Methylphenyl polysiloxane, cyclic dimethylpolysiloxane, fluoropolysiloxane, modified (amino, epoxy, polyether, alcohol, fluorine, mercapto,
Carboxyl, alkyl higher fatty acids), for example, SH203, BY16- under trade names (manufactured by Toray Silicone).
828, SF8411, SF8418, BY16-83
8, SF8422, BY16-848, SH3771,
Silicone oils such as SH3746, SF8419, FS1265; R900, R901, R902, F10
0, F101, F200, F201, F202, F20
3, F400, F300, F301, F250, E50
0, E501, E600, E601, E602, E60
3, silicon powder such as E850; SH204, SH
490, SH7024, SH7028, SH7036,
Silicone emulsion such as SH7060; SH37
And silicone-soluble resins such as SH3749 and SH3771. The above-mentioned silicone powder is usually about 0.1 to 100 μm, preferably about 5 to 50 μm.
m.

Above all, it is hardly soluble in water, and can be easily made into a water dispersion by a small amount of a surfactant, and is well oriented in the lower layer of the coating to form an interface with the coating to be protected. Excellent in the function of alleviating the increase in adhesion due to aging that occurs in the molecular weight of 1,000 to 1,000 represented by the following general formula
20,000 polyether modified silicone oil is optimal.

[0041]

Embedded image

(Where m and n are positive integers and P
OA represents a polyether moiety modified by ethylene oxide or propylene oxide. As the fluorine-based compound, those having a molecular weight of 1,000 to 20,000 containing a fluoroalkyl group in the molecule are preferable. Specific examples include perfluoroalkylcarboxylates, perfluoroalkylphosphates, perfluoroalkyltrimethylammonium salts, perfluoroalkylpentanones, and perfluoroalkylEO adducts. Also, as trade names (manufactured by Asahi Glass Co., Ltd.), Surflon S-111, Same Left S-112, Same Left S-113, Same Left S
-121, Same left S-131, Same left S-132, Same left S-
142, left S-145, left S-131S, left S-
145S and the like.

Use of a wax compound or a silicone compound among these release aids has the advantage that a coating excellent in water resistance and acid resistance can be easily obtained.

The amount of the peeling aid (C) used is usually about 0.5 to 10 parts by weight, preferably about 1 to 5 parts by weight in the case of wax, based on 100 parts by weight of the resin solids in the composition. Parts, about 0.01 to 10 parts by weight, preferably about 0.1 to 5 parts by weight for silicone compounds, and about 0.01 to 5 parts by weight, preferably about 0 to 5 parts for fluorine compounds. .01
~ 3 parts by weight are preferred.

The composition of the present invention may further contain, if necessary, a weathering aid (D) comprising an ultraviolet absorber and / or a light stabilizer and a pigment (E), particularly titanium white.

The purpose of using the weathering aid (D) comprising the ultraviolet absorber and / or the light stabilizer is that when left outdoors for more than a few months, the film elongation is reduced by light deterioration, The coating adheres to the outer coating film of the automobile and the peeling property is reduced, and therefore, when peeling, the peeling is likely to occur and a large number of man-hours may be required. It is to obtain good peelability afterwards. The ultraviolet absorber and the light stabilizer can be used alone or in combination.

Conventionally known UV absorbers can be used. Specific examples thereof include phenyl salicylate, p-octylphenyl salicylate, 4-t
salicylic acid derivatives such as tert-butylphenyl salicylate; 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone, 2,2'-dihydroxy-4-methoxybenzophenone, 2-hydroxy-4-methoxy-2 '-Carboxybenzophenone, 2-hydroxy-4-methoxy-5-sulfobenzophenone trihydrate, 2,2'-dihydroxy-
4,4'-dimethoxybenzophenone, 2-hydroxy-4-octoxybenzophenone, 2-hydroxy-4
Octadecyloxybenzophenone, sodium 2,2
'-Dihydroxy-4,4'-dimethoxy-5-sulfobenzophenone, 2,2', 4,4'-tetrahydroxybenzophenone, 4-dodecyloxy-2-hydroxybenzophenone, 5-chloro-2-hydroxybenzophenone, resorcino- Rumonobenzoate, 2,4-dibenzoylresorcinol, 4,6-dibenzoylresorcinol, hydroxydodecylbenzophenone, 2,
2'-dihydroxy-4 (3-methacryloxy-2-
Benzophenones such as (hydroxypropoxy) benzophenone; benzotriazoles such as 2- (2'-hydroxy-5'-methylphenyl) benzotriazole; and other compounds (such as anilide oxalate and cyanoacrylate). .

Conventionally known light stabilizers can be used. Primarily a hindered amine derivative,
Specifically, bis- (2,2 ', 6,6'-tetramethyl-4-piperidinyl) sebate, 4-benzoyloxy-2,2', 6,6'-tetramethylpiperidine and the like are preferable. is there.

The amount of the weathering aid (D) can be arbitrarily selected according to the purpose. The ultraviolet absorber is used in an amount of 0.1 to 10 parts by weight, based on 100 parts by weight of the resin solids in the composition. Preferably 0.5 to 5 parts by weight, 0.1 to 5 parts by weight of the light stabilizer, preferably 0.3 to 3 parts by weight.

The purpose of use of the pigment (E) is to obtain a whitened film by mixing a pigment, particularly titanium white, in an aqueous dispersion and then blending it with the composition of the present invention. , Enhances the barrier effect against UV, heat, etc.,
The purpose is to improve the releasability over time. In addition, by adding the titanium white, the shrinkage stress generated in the coating can be reduced, which means that a large stress is generated in the coating when exposed to a low temperature in a state where the coating is absorbed by rain or snow, especially in winter. This is effective because it prevents floating or peeling off at the end face of the applied film, and prevents the film from spontaneously peeling off due to a strong wind or the like.

Examples of the pigment (E) include coloring pigments such as titanium white, carbon black, phthalocyanine blue and phthalocyanine line, and extender pigments such as talc, calcium carbonate, silica, barium sulfate, clay and mica. These can be used alone or in combination of two or more. Of these, titanium white is particularly preferred.

The amount of the pigment (E) is from 3 to 50 parts by weight, preferably from 10 to 30 parts by weight, based on 100 parts by weight of the resin solids in the composition. If less than 3 parts by weight, ultraviolet light,
The barrier effect against heat and the like is small, and the stress relaxation ability is extremely small. Further, when the amount is more than 50 parts by weight, the elongation of the film is reduced, and the film is easily peeled when peeled off, and the water absorption of the film is increased. .

The composition of the present invention is prepared, for example, by adding a release aid (C), a weatherability aid (D), a pigment (E) and the like to an aqueous emulsion in advance in the copolymer emulsion (I), if necessary. Mix in. The aqueous emulsion of the components (C) to (E) can be formed by a method such as mechanical dispersion or dispersion with an emulsifier. The composition of the present invention may further contain known coating surface adjusters, defoamers, thickeners, and the like, if necessary.

The present invention also provides a method for temporarily protecting the cured coating film by applying the releasable aqueous coating composition obtained as described above to the surface of a cured top coating film applied to an automobile outer panel. .

In the present invention, the top-coat cured coating to which the above-mentioned releasable aqueous coating composition is applied can be obtained by applying a conventionally known curable coating composition to the outer panel of an automobile and baking it at an appropriate temperature and time. Preferably, the cured coating film has a glass transition temperature adjusted to a range of 50 to 130 ° C. Examples of the curable paint include a clear paint, a metallic pigment (aluminum powder, mica-like powder, mica-like powder coated with titanium oxide, etc.) and, if necessary, a metallic paint containing a color pigment, and a solid color containing a color pigment. -Paints and the like can be used. The type of the curable coating may be any type such as an aqueous type, an organic solvent type, and a powder type. Examples of the curable resin composition constituting the curable paint include acrylic resins, polyester resins, alkyd resins, fluorine resins, and silicone resins.
Composed of a base resin such as an epoxy resin or an epoxy resin and a crosslinking agent such as an amino resin, a polyisocyanate compound, a polycarboxylic acid compound or a polyepoxy compound; and a self-curing monomer (for example, N-butoxymethylacrylamide). And the like, and particularly preferred are acrylic resin-based, aminoalkyd resin-based, and urethane resin-based coating films. An extender, various additives, and the like can be arbitrarily compounded in the curable coating. The above-mentioned cured coating film is applied, for example, by applying the above-mentioned cured coating material directly to a material (for example, metal, plastic, and inorganic material) or to the surface of a coating film obtained by applying a primer, an intermediate coat, or a base coat. Those cured so that the glass transition temperature falls within the above range can be used.

In the present invention, if the glass transition temperature of the cured coating film is lower than 50 ° C., the peelable coating film will not easily peel off due to long-term outdoor exposure, and the cured coating film after peeling will have peeling marks, stains, glossiness, etc. If the glass transition temperature is higher than 130 ° C., on the other hand, the adhesive strength of the peelable film becomes too small and the film may be spontaneously peeled off during storage. Here, the glass transition temperature of the cured coating film is
The free coating film (width 5 mm, length 20 mm, thickness 30 μm) was measured using a Dynamic Visco Elastometer Model Vibron (DPV-II-EA type, manufactured by Toyo Baldwin).

In the method of the present invention, the above-mentioned releasable aqueous coating composition is desirably provided with a solid content of 30 to 80% by weight.
Preferably 40 to 70% by weight, viscosity 0.3 to 5.0 Pa
S, preferably 0.7 to 3.0 Pa · s, and a surface tension of 40 mN / m or less, preferably 35 mN / m or less. If the solid content is less than 30% by weight, crack-like coating surface abnormalities tend to occur, while if it exceeds 80% by weight, the liquid viscosity increases and the mechanical stability decreases, which is not preferable from the viewpoint of coating.

When the viscosity is less than 0.3 Pa · s, the applied coating liquid tends to drips, while when the viscosity exceeds 5.0 Pa · s,
The resulting coating surface is poor in smoothness and has severe irregularities. In addition, in the case of roller or brush coating, problems such as poor rotation are caused and coating workability is extremely reduced, which is not preferable. Adjustment to such a viscosity range is performed by using polyacrylic acid
D, acrylic acid alkyl ester / methacrylic acid copolymer, polyacrylic sulfonate, polyether type such as polyoxyalkylene alkylphenyl ether, urethane-modified polyether type, ethylenebisaliphatic carboxylic acid amide, It can be easily carried out by adding a viscoelasticity modifier such as hydroxyethyl cellulose.

If the surface tension exceeds 40 mN / m, it is not preferable because good wettability cannot be obtained with respect to the coating film of an automobile outer panel, and it becomes difficult to form a continuous coating film due to poor wetting such as repelling. The surface tension can be adjusted by a polyether-modified silicone oil such as dimethylpolysiloxane modified with ethylene oxide or propylene oxide, a perfluoroalkyl carboxylate, a perfluoroalkyl phosphate, a perfluoroalkylamine. This can be achieved by adding a water-soluble wetting improver such as a fluorine-based surfactant such as an oxide. In the present invention, as a method of applying the above composition on an automobile outer panel coating film, brush coating, roller coating, or the like may be used.
Coating, spray-coating, and other conventional coating methods can be employed. The coated film is heated for 1 hour or 2 hours at room temperature, and when heated, for example, at 50 ° C. for 20 minutes, or 70 ° C. By heating for 10 minutes, it is possible to obtain a dry state that does not melt away even when exposed to rain immediately after drying. In addition, the mid-infrared or far-infrared
After the irradiation for one second or one minute, the drying time can be shortened by heating at an ambient temperature of 50 ° C. to 70 ° C. for 2 to 3 minutes. The thickness of the coating is suitably from 20 to 200 μm, preferably from 50 to 100 μm, as a dry thickness.

The formation of the temporary protective film on the coating film of the automobile outer panel as described above is carried out between the painting step and the assembling step in the automobile manufacturing process or on the completed vehicle after the assembling step.

In the former method, after the coating process of the automobile outer panel in the automobile manufacturing process, and before the assembling process, the surface of the cured top coat applied to the automobile outer panel in the coating process is coated with the above-mentioned releasable aqueous coating composition. After applying the material and forming a peelable film,
This method comprises a step of drying the peelable film in a hot-air drying furnace or preliminary drying in an infrared drying furnace and then drying in a hot-air drying furnace.

In the latter method, the surface of the cured top coat coated on the outer panel of the completed car is washed with water and drained, and then the above-mentioned releasable aqueous coating composition is applied to the surface of the cured top coat to release. This is a method of forming a releasable film, irradiating the releasable film with infrared rays and drying, and then drying the releasable aqueous film with hot air.

Regardless of which method is used, it is preferable to adjust the solid content concentration and the viscosity of the releasable aqueous coating composition within the above ranges. If the solid content concentration or the viscosity is out of the range, a crack-like coating surface abnormality may occur during drying, which is not desirable.

[0064]

The present invention will be described more specifically with reference to the following examples. Note that “parts” and “%” in Examples and Comparative Examples are used.
Is based on weight.

Production Example 1 of Copolymer Emulsion Production Example 1 312 parts of deionized water was placed in a two-liter four-necked flask equipped with a reflux condenser, a stirrer, a thermometer, and a dropping funnel.
Newcol 707SF (trade name, manufactured by Nippon Emulsifier Co., Ltd.)
0.9 part of an anionic emulsifier (solid content: 30%) was added, and the mixture was maintained at 80 ° C. after nitrogen replacement. 0.4 parts of ammonium persulfate was added thereto, and 15 minutes after the addition, a pre-emulsion obtained by emulsifying the following composition (A) was added dropwise over 140 minutes.

Deionized water 245 parts Methyl methacrylate 358.4 parts n-butyl acrylate 196 parts Acrylic acid 5.6 parts 30% Newcol 707SF 37.3 parts Ammonium persulfate 0.56 parts Then, a pre-emulsion obtained by emulsifying the following composition (B) was dropped over 60 minutes.

Deionized water 105 parts Methyl methacrylate 81.6 parts n-butyl acrylate 156 parts Acrylic acid 1.2 parts Acrylamide 1.2 parts 30% Newcol 707SF 16 parts Ammonium persulfate 0.24 parts After dropping, After 30 minutes, add ammonium persulfate 0.8
A solution prepared by dissolving the solution in 7 parts of deionized water was added dropwise over 30 minutes, and the temperature was maintained at 80 ° C. for 2 hours. Then 40-60
℃, adjust the pH to 7-8 with aqueous ammonia,
Copolymer emulsion having a nonvolatile content of 53.6% (I-1)
I got

Production Examples 2 to 8 The same procedures as in Production Example 1 were carried out except that the monomer compositions (A) and (B) and the dropping time were set to the mixing ratios shown in Table 1 and the amount of deionized water was adjusted. By the method, copolymer emulsions (I-2) to (I-8) having different solid contents were obtained.
Table 1 also shows the property values of each emulsion. Adipic dihydrazide as a cross-linking agent was added to the emulsion after adding aqueous ammonia.

The glass transition temperature of each of the copolymers was determined by JI
Differential scanning calorimetry (DS) according to S K 7121
C). Specifically, the acrylic copolymer emulsion was placed in a container (aluminum sample pan having a diameter of 5 mm) so that the weight after drying was about 10 mg,
The whole container was dried at 105 ° C for 1 hour to prepare a sample.
C / 5200 "(Seiko Instruments
A DSC curve was drawn using a thermal analysis system (manufactured by Seiko Instruments Inc.), and the glass transition temperature was determined from the detected peak.

[0070]

[Table 1]

Preparation of Release Aid (C) To 30 parts of modified silicone oil TSF4445 (manufactured by Toshiba Silicone, polyether modified silicone oil), 2 parts of polyoxyethylene sorbitan monooleate and 68 parts of water were added. After stirring well, an emulsion of silicone oil having a solid content of 30% was obtained.

Preparation of Weathering Aid (D) Tinuvin 1130 (benzotriazole derivative, liquid, manufactured by Ciba Geigy Co., Ltd.) was added to 30 parts of this polyoxyethylene sorbitan monooleate (5 parts) and water (65 parts). Was added and stirred well to obtain an ultraviolet absorber emulsion having a solid content of 30%.

As an aqueous dispersion of an ultraviolet absorber, commercially available Sand PT-21D (a benzotriazole-based aqueous dispersion, manufactured by Sando Corporation) was directly blended. The light stabilizer SANOL LS-292 (a hindered amine derivative, liquid, manufactured by Sankyo Co., Ltd.) is prepared by adding 5 parts of polyoxyethylene sorbitan monooleate and 45 parts of water to 50 parts of the mixture, and stirring the mixture thoroughly. A 50% light stabilizer emulsion was obtained.

Preparation of Pigment (E) 12 parts of a 40% aqueous solution of sodium polycarboxylate and 160 parts of water were added to 560 parts of titanium white R-700 (rutile titanium white, manufactured by DuPont), and the mixture was stirred well. It was dispersed to a particle size of 10 microns or less by a disperser to obtain an aqueous dispersion of titanium white.

Examples 1 to 11 and Comparative Example 1 Copolymer emulsions (I-1) to
(I-8) was mixed in the blending amount (solid content) and combination shown in Table 2, respectively, and the release aid, ultraviolet absorber, light stabilizer and pigment were adjusted as described above with respect to 100 parts of the resin solid content. Are added in the types and amounts (solid content) shown in Table 2, respectively.
By stirring and mixing, each peelable aqueous coating composition was obtained.

To these compositions, if necessary, a polyoxyalkylenealkylphenyl ether and a perfluoroalkylamine oxide are added to adjust the viscosity and the surface tension as shown in Table 2. 3050 (trade name, zinc phosphate surface treating agent,
Mild steel sheet (thickness 0.7)
mm) to aminoalkyd resin paint (Kansai Paint Co., Ltd.)
Amylac (trade name) is spray-coated on a coated plate (cured glass transition temperature of about 82 ° C.) at 140 ° C. for 30 minutes, and dried at 70 ° C. for 10 minutes to give a dry film thickness of 60 to 70 μm. A functional film was formed. Table 2 summarizes the results of these performance tests.

(* 1) Viscosity: The viscosity of the coating solution was measured using a B-type viscometer manufactured by Tokyo Keiki Co., Ltd. The measurement conditions were a coating liquid temperature of 20 ° C. and a rotor rotation speed of 60 rpm.

(* 2) Surface tension: The surface tension of the coating solution was measured using a Kyowa CBVP surface tensiometer manufactured by Kyowa Chemical Co., Ltd.

(* 3) Film forming property: dry film thickness of 60 to 70 μm
m and immediately left for 1 hour under the conditions of an ambient temperature of 20 ° C. and a wind speed of 0.5 to 0.7 m / s, and the state of the coated surface was observed.

○: No abnormality. A continuous film is formed. Δ: Crack-shaped abnormality is observed in 30% or less of the coated surface. X: Crack-shaped abnormality is observed in 30% or more of the coated surface. (* 4) Peelability (initial) : After forming the film, leave it at 20 ° C. for 1 day, and then peel off the peelable coating composition film applied to the test plate from the end at a speed of 1 m / 30 seconds by hand. Were tested at 0 ° C., 20 ° C., and 40 ° C., respectively, and evaluated according to the following criteria.

◎: Very easy peeling ○: Easy peeling ：: Slightly heavy △: Heavy but peelable △ ^* : Coating is brittle and difficult to peel in sheet form ×: Not peelable (* 5) Peelability (heat resistance): After leaving the test plate at 80 ° C. for 300 hours, the peelability was tested by the same method as (* 4) at a coating temperature of 20 ° C.

(* 6) Peelability (accelerated weathering resistance): A QUV accelerated backlash test using an accelerated weathering resistance tester manufactured by Q Panel Co., Ltd. 480 hours (20 cycles) as one cycle, and the peelability was determined by the same method as (* 4).
The test was performed at 0 ° C.

(* 7, * 8) Strength and Elongation of Coating: Measured at 0 ° C. and 20 ° C. using an Instron type tensile tester (Autograph, manufactured by Shimadzu Corporation). At that time, the tensile speed was 50 mm / min, and the weight was 5 kg.

Strength of coating ◎: 120 kgf / cm ² or more: 70 to 120 kgf / cm ² ：: 40 to 70 kgf / cm ² ×: 40 kgf / cm ² or less Elongation of coating ◎: 300 to 800% O: 100 to 300 % Δ-1: 60 to 100% Δ-2: 800% or more ×: 60% or less (* 9) Coating combustion test: Conducted according to JIS K 7217 by the following method to check for the generation of hydrogen cyanide gas.

[0085]

[0086]

[0087]

According to the present invention, since a liquid aqueous coating composition is applied, it is possible to cope with a complicated shape of an automobile, and the peelable film formed according to the present invention has an adhesive property. The force can be easily separated manually or by a high-speed water flow into a single sheet even after a long period of time, without a great change in the force due to the coating temperature. Further, the coating after peeling has no environmental problem even in landfilling or incineration.

[0088]

[Table 2]

Claims (13)

[Claims] 1. A copolymer in which at least two or more copolymers having different glass transition temperatures are contained in the same particle by performing emulsion polymerization in multiple stages using a polymerizable unsaturated monomer. An exfoliable aqueous coating composition comprising the emulsion (I). 2. The copolymer emulsion (I) emulsifies a monomer mixture containing (meth) acrylic acid ester as essential and optionally other polymerizable unsaturated monomer except (meth) acrylonitrile. In the presence of an acrylic copolymer (A) having a glass transition temperature of 0 to 100 ° C. obtained by polymerization, (meth) acrylic acid ester is essential, and if necessary, other polymerization excluding (meth) acrylonitrile Acrylic copolymer (B) having a glass transition temperature of −50 to 10 ° C. obtained by adding and polymerizing a monomer mixture containing an unsaturated monomer, and (A) and (B) The releasable aqueous coating composition according to claim 1, wherein the difference in the glass transition temperature of the composition is at least 10 ° C or more. 3. The copolymer emulsion (I) emulsifies a monomer mixture containing (meth) acrylic acid ester as required and optionally other polymerizable unsaturated monomer except (meth) acrylonitrile. Acrylic copolymer (B) having a glass transition temperature of −50 to 10 ° C. obtained by polymerization
A glass transition obtained by emulsion polymerization by adding a monomer mixture containing (meth) acrylic acid ester as required and optionally other polymerizable unsaturated monomer except for (meth) acrylonitrile in the presence of The releasable aqueous coating according to claim 1, which comprises an acrylic copolymer (A) having a temperature of 0 to 100C, and wherein the difference between the glass transition temperatures of (A) and (B) is at least 10C or more. Composition. 4. One or both of the acrylic copolymers (A) and (B) may comprise a carbonyl group-containing α, β-ethylenically unsaturated monomer as a monomer component.
The releasable aqueous coating composition according to claim 2 or 3, which is contained in the mixture in an amount of 0.1 to 30% by weight. 5. The releasable aqueous coating composition according to claim 4, wherein the hydrazide compound is contained such that the hydrazide group is present in an amount of 0.02 to 3.0 equivalents relative to 1 equivalent of the carbonyl group in the emulsion particles. 6. The copolymer emulsion (I) comprises the acrylic copolymers (A) and (B) in a solid content ratio by weight of (A)
The releasable aqueous coating composition according to any one of claims 2 to 5, wherein the composition contains (A) / (B) = 95/5 to 5/95. 7. The copolymer emulsion (I) is mixed with another copolymer emulsion (II) in a solid content weight ratio of (I) /
The releasable aqueous coating composition according to any one of claims 1 to 6, wherein (II) is mixed at a ratio of 95/5 to 5/95. 8. Other copolymer emulsion (II)
Copolymer emulsion (I) in which at least two or more copolymers having different glass transition temperatures are contained in the same particle by emulsion polymerization in multiple stages using a polymerizable unsaturated monomer. The releasable aqueous coating composition according to claim 7, which is a copolymer emulsion different from the above. 9. The releasable aqueous solution according to claim 1, wherein the release aid (C) is contained in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of the resin solid content in the composition. Coating composition. 10. The peelable aqueous coating composition according to claim 1, further comprising at least one weathering aid (D) selected from the group consisting of an ultraviolet absorber and a light stabilizer. . 11. The pigment (E) is contained in an amount of 3 to 50 parts by weight based on 100 parts by weight of a resin solid content in the composition.
The releasable aqueous coating composition according to any one of claims 1 to 10. 12. The releasable aqueous coating composition according to claim 11, wherein the pigment (E) is titanium white. 13. A copolymer having different glass transition temperatures within the same particle by subjecting the surface of a top coat cured coating film applied to an outer panel of an automobile to emulsion polymerization in multiple stages using a polymerizable unsaturated monomer. A method for temporarily protecting a paint film for an automobile outer panel, comprising applying a releasable aqueous coating composition containing a copolymer emulsion (I) containing at least two kinds of coalesced coalesce.