JP2002249718A - Coating composition, method for forming film and coated product having film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a coating composition comprising a nonaqueous dispersion resin, having a suppressed value of electrical resistance during coating and further high storage stability. SOLUTION: This coating composition comprises an ammonium salt of an organic carboxylic acid and the nonaqueous dispersion resin and is characterized by having 0.1-0.5 MΩ value of the electrical resistance during coating.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a coating composition having a controlled electric resistance and excellent storage stability, and more particularly to a metallic base coating composition.
The present invention relates to a method for forming a coating film using the coating composition and an object to be coated having a coating film formed by the method for forming a coating film.

[0002]

2. Description of the Related Art Generally, a car body and parts of an automobile are subjected to a chemical conversion treatment with zinc phosphate or the like on the surface of a steel sheet to be coated, and then a base coat, a middle coat and a top coat are applied in this order. It is painted, but a metallic base paint and a clear paint to be painted thereon may be used as a top coat.

[0003] Of these, the metallic base paint is often electrostatically applied as a solvent type paint having a glittering pigment containing a metallic pigment such as aluminum flake. At the time of this electrostatic coating, the glitter pigment particles become continuous in the coating with an increase in the coating amount, thereby causing conductivity in the coating, and there is a risk of sparking and stopping the production line. Therefore, the electric resistance of the paint at the time of painting is adjusted so as to be low. Conventionally, an electric resistance value at the time of coating has been adjusted by adding an alcohol such as methanol or butanol to a paint whose viscosity has been adjusted.

By the way, non-aqueous dispersion resin (N
AD) has been used for painting equipment, automobiles and the like because of its low pollution, resource saving, and excellent coating workability and durability due to its flow characteristics. JP-A-57-1
No. 77068 discloses a non-aqueous dispersible resin coating composition containing dispersed particles obtained by graft-polymerizing a monomer component in the presence of an acrylic copolymer. According to this, a coating film having excellent surface hardness and impact resistance can be obtained by dispersing the dispersed particles in the coating film even after curing to form a non-uniform structure. However, when an alcohol is added to a paint containing a non-aqueous dispersion resin, the electric resistance value is suppressed, but there is a problem that storage stability is reduced.

[0005]

SUMMARY OF THE INVENTION In view of the above problems, the present invention is directed to a coating composition containing a non-aqueous dispersion resin, which has a reduced electric resistance during coating and a high storage stability. It is intended to provide a coating composition having the following.

[0006]

Means for Solving the Problems The present inventor has proposed that by adding an ammonium salt of an organic carboxylic acid to a coating composition containing a non-aqueous dispersion resin, the electric resistance during coating can be suppressed, The present inventors have found that the basicity of the ammonium salt of an organic carboxylic acid suppresses viscosity increase during storage as appropriate and is excellent in storage stability, and completed the present invention.

That is, the present invention provides a coating composition containing an ammonium salt of an organic carboxylic acid and a non-aqueous dispersion resin, wherein the coating composition has an electrical resistance of 0.1 to 0.1.
It is a coating composition characterized by being 0.5 MΩ.
The coating composition may further contain a metallic glitter pigment. The ammonium salt of the organic carboxylic acid is 0.01 to 2 parts by weight based on the solid content of the coating composition.
% By weight. The present invention is also a method for forming a coating film, comprising a step of applying the coating composition to an object to be coated, and a step of further applying a clear coating material on a wet basis. The present invention is further an object to be coated having a coating film formed by a coating film forming method. Hereinafter, the present invention will be described in detail.

[0008] The coating composition of the present invention contains a non-aqueous dispersion resin. The non-aqueous dispersion resin comprises a core portion having a high SP value and a shell portion having a low SP value. Since the core portion has a high SP value, it is insoluble in the solvent in the paint, so that the swelling ratio due to the solvent can be reduced, and high storage stability can be maintained. The core portion, further, when the coating composition of the present invention is uncured intermediate coating, base coating, other coatings such as clear coating and wet-on-wet in the case of laminating with wet-on-wet, Color return caused by delicate mixing with the paint can be prevented. The shell part having a low SP value functions as a dispersion stabilizer. Further, since the non-aqueous dispersion resin is a non-crosslinked particle, the minimum viscosity at the time of baking can be reduced. Further, the particles themselves can be cross-linked by a curing agent contained as necessary in the coating composition, and in this case, they can be a coating film forming component.
It is possible to increase the amount of addition. Therefore, by the non-aqueous dispersion resin, a coating composition having a high solid content is obtained, and it is possible to reduce the amount of an environmentally desirable solvent. It is also possible to obtain a coating film with high sharpness and gloss.

In the present specification, the SP value is called a solubility parameter, and indicates a measure of solubility. SP values are described in SUH, CLARKE, J. Mol. P
oligomer Science, A-1, Volume 5, 16
It can be calculated by the method described on pages 71 to 1681 (1967).

The non-aqueous dispersion resin preferably has an SP value of 11 to 14, and a difference between the SP value of the core portion and the SP value of the shell portion is preferably 0.5 to 3.
If the difference in SP value is less than 0.5, the non-volatile content of the coating material cannot be reduced, and the coating swells or dissolves, and the viscosity control effect of the core portion is reduced, so that storage stability may be reduced. In addition, undercoat concealment is small, furthermore, in the case of laminating with wet-on-wet and other paints such as intermediate paints, base paints, clear paints, familiarity occurs between these paints, There is a possibility that a coating film having an excellent finished appearance cannot be obtained. When the difference in SP value exceeds 3, dispersion may become unstable, separation may occur, or when wet-on-wet coating is performed, the dispersion may be mixed with the above-mentioned other paints to cause inversion or cracking. The difference between the SP values is more preferably 1 to 3. S of the later-described film-forming resin contained in the coating composition of the present invention
The relationship between the P value and the SP value of the non-aqueous dispersion resin is that the SP value of the non-aqueous dispersion resin can be suppressed when the wet-on-wet coating is performed. Higher values are preferred.

The non-aqueous dispersion resin preferably has a hydroxyl value of 100 to 400, more preferably 130.
~ 300. If it is less than 100, the curability of the paint may decrease, and if it exceeds 400, the water resistance may decrease. The non-aqueous dispersion resin preferably has an acid value of 0 to 200 mgKOH / g, more preferably 0 to 50 mgKOH / g. 200mg KOH
/ G, the water resistance of the resulting coating film may decrease. The nonaqueous dispersion resin has an average particle diameter (D ₅₀₎ is preferably 0.05 to 5 [mu] m, more preferably from 0.05 to 1 [mu] m. If it is less than 0.05 μm, the non-volatile content of the paint may decrease, and if it exceeds 5 μm, the viscosity control effect may be poor, storage stability may decrease, or appearance may be poor.

The non-aqueous dispersion resin is prepared as non-crosslinked resin particles insoluble in a mixture of a dispersion-stable resin and an organic solvent by copolymerizing a polymerizable monomer in the mixture. Can be. The dispersion-stable resin constitutes the shell part, and the copolymerized polymerizable monomer constitutes the core part. The Tg of the dispersion stable resin is preferably 30 ° C. or lower. When the temperature exceeds 30 ° C., the appearance of the coating film is poor, and the chipping resistance may decrease.

As the polymerizable monomer, a monomer having a functional group is preferable. By having the above functional group,
The obtained non-aqueous dispersion resin can react with a curing agent optionally contained in the coating composition of the present invention to form a three-dimensionally crosslinked coating film. Representative examples of the polymerizable monomer having the above functional group are as follows. As those having a hydroxyl group, for example,
Hydroxyethyl (meth) acrylate, hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, hydroxymethyl (meth) acrylate, allyl alcohol, adduct of hydroxyethyl (meth) acrylate with ε-caprolactone And the like.

On the other hand, those having an acid group include those having a carboxyl group, a sulfonic acid group and the like, and examples of those having a carboxyl group include (meth) acrylic acid, crotonic acid, ethacrylic acid, propyl Acrylic acid, isopropyl acrylic acid, itaconic acid, maleic anhydride, fumaric acid and the like can be mentioned. Examples of those having a sulfonic acid group include t-butylacrylamide sulfonic acid. When a polymerizable monomer having an acid group is used, a part of the acid group is preferably a carboxyl group. Further, a glycidyl group-containing unsaturated monomer such as glycidyl (meth) acrylate, m-isopropenyl-
Isocyanate group-containing unsaturated monomers such as α, α-dimethylbenzyl isocyanate and isocyanatoethyl acrylate are also included.

As other polymerizable monomers, for example,
Methyl (meth) acrylate, ethyl (meth) acrylate, isopropyl (meth) acrylate, n-propyl (meth) acrylate, n-butyl (meth) acrylate,
T-butyl (meth) acrylate, isobutyl (meth) acrylate, 2-ethylhexyl (meth) acrylate,
Alkyl (meth) acrylates such as n-octyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, and tridecyl methacrylate; acrylic acid or methacrylate monomers having an oil fatty acid and an oxirane structure (E.g., an addition reaction product of stearic acid and glycidyl methacrylate); an addition reaction product of an oxirane compound containing an alkyl group having at least C ₃ and acrylic acid or methacrylic acid; styrene, α-methylstyrene, o- Methyl styrene, m-methyl styrene, p-methyl styrene, pt-butyl styrene; benzyl (meth) acrylate; itaconic acid ester (dimethyl itaconate); maleic acid ester (dimethyl maleate); fumaric acid ester (Dimethyl fumarate, etc.); , Acrylonitrile, methacrylonitrile; methyl isopropenyl ketone; vinyl acetate; veoba monomer (trade name, manufactured by Shell Chemical Company), vinyl propionate, vinyl pivalate, vinyl propionate; ethylene, propylene, butadiene, N, N-dimethylaminoethyl Acrylate, N, N-dimethylaminoethyl methacrylate, acrylamide, vinylpyridine and the like can be mentioned. The polymerizable monomers can be used alone or in combination of two or more of those having a functional group and other monomers.

The above polymerizable monomer is preferably copolymerized in the presence of a radical polymerization initiator. Examples of the radical polymerization initiator include azo initiators such as 2,2'-azobisisobutyronitrile and 2,2'-azobis (2,4-dimethylvaleronitrile); benzoyl peroxide, lauryl peroxide And a peroxide-based initiator such as t-butyl peroctoate. The amount of these initiators used is preferably 0.2 to 10 parts by weight, more preferably 0.5 to 5 parts by weight, per 100 parts by weight of the total of polymerizable monomers. In general, the polymerization reaction in an organic solvent containing a dispersion-stable resin is preferably performed in a temperature range of about 60 to 160 ° C. for about 1 to 15 hours.

The dispersion-stable resin to be present when the above-mentioned polymerizable monomer is copolymerized is not particularly limited as long as it can stably synthesize a non-aqueous dispersion resin in an organic solvent. Specifically, the hydroxyl value is preferably 1
It is 0-250, more preferably 20-180. 10
If the amount is less than the above, the curability, adhesion, stability, etc. decrease,
If it exceeds 50, dispersion becomes unstable. The acid value of the dispersion stable resin is preferably from 0 to 100 mgKOH / g, more preferably from 0 to 50 mgKOH / g. 100m
If it exceeds gKOH / g, the water resistance of the coating film decreases. The number average molecular weight of the dispersion stable resin is 2
000 to 10,000 are preferred. If it is less than 2,000, dispersion becomes unstable, and if it exceeds 10,000, the non-volatile content of the paint decreases.

The method for producing the dispersion-stable resin is not particularly limited, and examples thereof include a method obtained by radical polymerization in the presence of a radical polymerizable initiator, a method obtained by a condensation reaction and an addition reaction, and the like. As the dispersion stable resin, an acrylic resin, a polyester resin, a polyether resin, a polycarbonate resin, a polyurethane resin, or the like can be used. The monomer used to obtain the dispersion-stable resin can be appropriately selected according to the properties of the resin, but has a functional group such as a hydroxyl group or an acid group used in the polymerizable monomer. It is preferable to use a monomer, and if necessary, a monomer having a functional group such as a glycidyl group or an isocyanate group may be used. The monomer having a functional group is capable of forming a three-dimensionally crosslinked coating film by reacting the obtained non-aqueous dispersion resin with a curing agent contained as necessary in the resin composition of the present invention. it can.

The monomer used to obtain the above-mentioned dispersion-stable resin preferably has 10 to 50% by weight of a monomer having a side chain having 10 or more carbon atoms based on the total amount of the monomer. If the content is less than 10% by weight, the coating with other coating materials such as an intermediate coating material, a base coating material, and a clear coating material is caused when wet-on-wet coating is performed. If it exceeds 50% by weight, separation may occur in the base paint,
Inversion and cracking may occur when mixed with the other paints described above.

Further, it is preferable that the above monomer has a hydrophilic group in an amount of 20 to 50% by weight based on the total amount of the polymerizable monomer. If it is less than 20% by weight, curability, adhesion and stability may be poor. If it exceeds 50% by weight, the dispersibility may be unstable. Examples of the hydrophilic group include a hydroxyl group, a carboxyl group, an amide group, and an ether group.

The ratio between the above-mentioned dispersion stabilizer and the above-mentioned polymerizable monomer can be arbitrarily selected according to the purpose. For example, based on the total weight of both components, the dispersion-stabilizing resin is preferably 3%. ８０80% by weight, more preferably 5-60% by weight, and the polymerizable monomer is preferably 97-20% by weight, more preferably 95-40% by weight. Further, the total concentration of the dispersion stabilizer and the polymerizable monomer in the organic solvent is preferably from 30 to 80% by weight, more preferably from 40 to 60% by weight, based on the total weight.

The non-aqueous dispersion resin thus obtained is preferably contained in an amount of 1 to 50% by weight based on the solid content of the coating composition of the present invention.
If it is less than 1% by weight or more than 50% by weight,
The appearance of the resulting coating film may be reduced. More preferably, it is 2 to 45 parts by weight. In the present invention, the resin solid content means a solid content of a film-forming resin containing a base resin and a curing agent contained as needed, as described below, and a total amount of solid content of a non-aqueous dispersion resin. Is what you do.

The coating composition of the present invention further comprises an ammonium salt of an organic carboxylic acid. Conventionally, when an alcohol is added to a coating composition containing the above-described non-aqueous dispersion resin for electric resistance adjustment, a high SP value core of the non-aqueous dispersion resin swells and thickens. However, there was a problem that storage stability was reduced. However, in the present invention, since it contains the ammonium salt of the organic carboxylic acid, even when the liquidity of the coating material is increased by the basic component, it is considered that the viscosity increase during storage is appropriately suppressed, As a result, high storage stability is maintained, and the electric resistance value of the paint at the time of coating can be adjusted to be low. When an amine such as triethylamine is added in place of the ammonium salt of the organic carboxylic acid used in the present invention, the storage stability is improved, but the electric resistance value cannot be reduced.

The ammonium salt of an organic carboxylic acid used in the present invention is not particularly limited, and examples thereof include alkanol ammonium salts of unsaturated acidic carboxylic acid esters and alkyl ammonium salts of aromatic carboxylic acids such as tetrabutyl ammonium salt of salicylic acid. Is mentioned.

As such an ammonium salt of an organic carboxylic acid, for example, a commercially available product can be used. For example, BYK-E manufactured by BYK Chemie as an alkanol ammonium salt of an unsaturated acidic carboxylic acid ester can be used.
S80 (trade name), Dispalon 112 manufactured by Kusumoto Chemicals
(Product name) and the like.

The content of the ammonium salt of the organic carboxylic acid depends on the acidity / basicity and the content of the glittering pigment optionally contained in the coating composition of the present invention. , 0.01 to 2% by weight. If it is less than 0.01% by weight, the storage stability may be poor. If it exceeds 2% by weight, the electric resistance may not be sufficiently reduced. More preferably, 0.
05 to 1.5% by weight.

The coating composition of the present invention has an electrical resistance of 0.1 to 0.5 MΩ when applied. If it is less than 0.1 MΩ, it is difficult to perform electrostatic coating efficiently,
If it exceeds MΩ, the conductivity of the coating formed at the time of coating becomes too high, causing leaks and sparks, and in some cases, shutting down the production line. Preferably, 0.2 to 0.
4 MΩ. In the present specification, the electric resistance value is measured using a Rohmsburg Mega Ohm Tester.

The coating composition of the present invention usually contains a pigment in addition to the above-mentioned ammonium salt of an organic carboxylic acid and a non-aqueous dispersion resin. The pigment is not particularly limited, and includes, for example, pigments used in conventional coating compositions. For example, brilliant pigments, coloring pigments, extenders and the like can be used. INDUSTRIAL APPLICABILITY The coating composition of the present invention is suitably used for a coating containing a metallic glitter pigment in that the electrical resistance value can be reduced.

The metallic glittering pigment is not particularly restricted but includes, for example, aluminum, aluminum oxide, copper,
An uncolored or colored metallic brilliant material such as a metal or alloy such as zinc, iron, nickel and tin, and a mixture thereof can be mentioned. Further, a glittering pigment having conductivity such as graphite is included in the present invention. In addition to the coating composition of the present invention, interference mica powder, colored mica powder,
It may contain white mica powder or colorless colored flat pigment.

The shape of the brilliant pigment is not particularly limited.
Further, it may be colored, but for example, has an average particle size (D ₅₀ ) of 2 to ₅₀ μm and a thickness of 0.1 to 5 μm
Is preferable. Average particle size 10-35μ
Those having a range of m are excellent in glitter and are more preferable. The pigment concentration (PWC) of the glitter pigment in the coating composition is generally 23% by weight or less. If it exceeds 23% by weight, the appearance of the coating film may be reduced, or the reduction of the electric resistance may be insufficient. Preferably, it is 0.01 to 20% by weight,
More preferably, it is 0.01 to 18% by weight.

The coloring pigment is not particularly limited, and examples thereof include azo chelate pigments, insoluble azo pigments, condensed azo pigments, phthalocyanine pigments, indigo pigments, perinone pigments, perylene pigments, dioxane pigments, and quinacridone pigments. Organic color pigments such as pigments, isoindolinone pigments, metal complex pigments; graphite, yellow iron oxide, red iron oxide,
Examples include inorganic color pigments such as carbon black and titanium dioxide. The extender is not particularly limited, and examples thereof include calcium carbonate, barium sulfate, clay, and talc.

As the pigment, one or a combination of two or more of glittering pigments, coloring pigments and extenders can be used. As the pigment, for example,
It can be used as a metallic base paint by adding a glittering pigment, or can be used as a solid base paint by blending a coloring pigment such as red, blue or black and / or an extender pigment without blending a glittering pigment. Can also.

The concentration (PWC) of the entire pigment is preferably 1 to 60% by weight based on the total amount of the pigment and the solid content of the resin. If the content exceeds 60% by weight, the pigment content is too large, so that the appearance of the coating film deteriorates.

The coating composition of the present invention contains a film-forming resin in addition to the above-mentioned non-aqueous dispersion resin. The film-forming resin is not particularly limited, and examples thereof include base resins such as an acrylic resin, a polyester resin, an alkyd resin, an epoxy resin, and a urethane resin. These base resins are amino resins and / or block isocyanate resins. Used in combination with a curing agent such as The film-forming resin is preferably a combination of an acrylic resin, a polyester resin, and a melamine resin from the viewpoint of pigment dispersibility and workability. These can be used alone or in combination of two or more.

The coating film forming resin is preferably used in an amount of 30 to 90 parts by weight or less based on 100 parts by weight of the solid content of the coating composition of the present invention. If the amount is less than 30 parts by weight, sagging may occur or the appearance may be deteriorated. If the amount exceeds 90 parts by weight, the physical properties and appearance of the coating film may be deteriorated.

The coating composition of the present invention may further contain conventionally known additives such as a viscosity controlling agent, an anti-bake agent and a diluting solvent. As the viscosity control agent,
Polyamides such as swelling dispersions of fatty acid amides, amide-based fatty acids, and phosphates of long-chain polyaminoamides; polyethylene-based ones such as colloidal swelling dispersions of polyethylene oxide; organic acids such as smectite clay and montmorillonite Bentonite-based inorganic pigments such as aluminum silicate and barium sulfate; flat pigments which exhibit viscosity depending on the shape of the pigment;

The coating composition of the present invention is preferably a solvent type from the viewpoint of preventing the core portion of the non-aqueous dispersion resin from swelling and lowering the storage stability. The solvent used in the coating composition of the present invention is not particularly limited, but as described above, the non-aqueous dispersion resin having a high SP value core portion and a low SP value shell portion swells to increase the viscosity of the coating material. In order to prevent this, for example, SP such as butyl acetate, n-hexane, xylene, toluene, etc.
Solvents having a relatively low value of 7.5 to 9.0 are preferable, and SP values of 9.5 to 1 such as alcohols are preferable.
When a solvent having a relatively high value of 4 is used, the solvent having the high SP value is preferably suppressed to 0 to 5% by weight based on the total weight of the solvent in the coating composition of the present invention at the time of coating.

In the coating composition of the present invention, the above-mentioned non-aqueous dispersion resin, the ammonium salt of an organic carboxylic acid, a film-forming resin, a pigment, and other components are kneaded and dispersed using a kneader, a roll, or the like. Can be obtained by methods known to those skilled in the art. When the ammonium salt of the organic carboxylic acid is, for example, an alkanol ammonium salt of an unsaturated acidic carboxylic acid ester, resins,
It is preferable to add the pigment and other components after mixing.

The nonvolatile content of the coating composition of the present invention thus obtained is preferably 30 to 70% by weight at the time of coating. If it is less than 30% by weight, the amount of the solvent is too large, so that it is not possible to obtain an environmentally desirable high solid coating composition, and the volume shrinkage before and after curing of the coating film becomes large. May be inferior. If it exceeds 70% by weight, the viscosity is too high, so that the storage stability, the appearance of the coating film and the workability may be poor. More preferably, 40
６０60% by weight. Since the coating composition of the present invention contains the non-aqueous dispersion resin described above, the solid content in the coating composition can be made relatively high.

The coating composition of the present invention is applied to an object to be coated. Examples of the object to be coated include various substrates, for example, metal, glass, plastic, and foam.
In particular, metal products that can be subjected to cationic electrodeposition coating are suitable. Examples of the metal products include iron, copper, aluminum,
Metals such as tin and zinc; alloys and castings containing these metals. Specifically, the vehicle body and parts of automobiles such as passenger cars, trucks, motorcycles, and buses are exemplified.
It is particularly preferable that these metals have been previously subjected to a chemical conversion treatment with a phosphate, a chromate, or the like.

The coating composition of the present invention can be used as an intermediate coating, a base coating, and / or a clear coating, for example, in the coating of an automobile body or parts, but the electrical resistance value is adjusted to be low. Is preferably used as a metallic base paint because it preferably contains a glitter pigment and tends to have high conductivity.

The method for applying the coating composition of the present invention is not particularly limited, and for example, a method known to those skilled in the art can be used. Such a method includes, for example, an air electrostatic spray commonly referred to as a “react gun”; a rotary atomization commonly referred to as a “micro-micro (μμ) bell”, a “micro (μ) bell”, a “metabell” and the like. It can be performed by using a type electrostatic coating machine or the like. Preferably, a method using a rotary atomization type electrostatic coating machine or the like is used.

When the coating composition of the present invention is applied to an automobile body or the like, in order to enhance the design, it is applied by multi-stage coating by air electrostatic spraying, preferably by two-stage coating, or by air. It is preferable to carry out by a coating method combining an electrostatic spray and the above-mentioned rotary atomizing type electrostatic coating machine.

The dry film thickness of the coating film obtained by using the coating composition of the present invention varies depending on the application, but it is 5 to 45 μm as an intermediate coating film, 5 to 35 μm as a base coating film, and 5 to 35 μm as a clear coating film. 10 to 80 μm. Exceeding these upper limits may result in poor image clarity or inconveniences such as unevenness and flow during coating. Below the lower limit, the unevenness of the base may not be concealed and the film may break.

An object to which the coating composition of the present invention is applied is an automobile body or the like, and an intermediate coating film, a base coating film, and a clear coating film are formed in this order on the electrodeposition-coated object. In this case, these coating films can be applied by a wet-on-wet method while each of them is uncured, and then the resulting coating films can be simultaneously baked and cured by a so-called three-coat one-bake method. After baking and curing the intermediate coating film, the base coating material and the clear coating material are applied on a wet-on-wet basis, and the resulting base coating film and clear coating film are baked and cured at the same time. Can be

The baking curing temperature of the above coating film is usually 10
The temperature is 0 to 180 ° C, preferably 120 to 160 ° C. The curing time varies depending on the curing temperature,
10 to 60 minutes is appropriate. The intermediate coating film before baking and curing in the above-described two-coat one-bake method and the base coating film before applying the clear paint, and the intermediate coating film before applying the base paint and the base before applying the clear paint in the three-coat one-bake method The coating film is allowed to stand at room temperature for a certain period of time, or is subjected to a preheating step at, for example, 60 to 100 ° C. to evaporate the solvent and moisture, and the coating film can be dried in advance. A film is obtained.

The total thickness of the intermediate coating film, the base coating film and the clear coating film thus obtained is usually 3
0 to 300 μm. If it exceeds 300 μm, the physical properties of the film such as a thermal cycle decrease, and if it is less than 30 μm, the strength of the film itself decreases. Preferably, 50 to 250 μm
It is.

Since the coating composition of the present invention contains the above-mentioned ammonium salt of an organic carboxylic acid, the electric resistance at the time of coating of the coating can be adjusted to be low, and the storage stability of the coating is prevented from being lowered. be able to. The coating film forming method of the present invention, by the simple method as described above, physical properties,
A coating film excellent in appearance and the like can be obtained. Accordingly, the coating composition of the present invention, the coating film forming method and the object to be coated having the coating film formed by the above-described coating film forming method are suitably used for coating the body and parts of automobiles, and are used for automobile bodies and the like. It is more preferably used in electrostatic coating as a metallic base coating.

[0049]

The present invention will now be described in detail with reference to specific examples.
However, the present invention is limited by the following examples.
Not something. Parts and% mean parts by weight and weight%, respectively.
To taste.Production Example 1 Production of amide group-containing acrylic resin  Nitrogen inlet tube, stirrer, temperature controller, dropping funnel and deca
Into a 1 L reaction vessel equipped with a cooling tube
Charge 80 parts of silene and 20 parts of butyl acetate, and adjust the temperature.
120 ° C. Next, 5 parts of styrene and methyl methacrylate
30 parts, 4-hydroxybutyl acrylate 1
1.5 parts, ethyl acrylate 38.3 parts, ethyl meta
Acrylate 7 parts, methacrylic acid 2.3 parts, acrylamide
5 parts and t-butyl peroxy-2 as a polymerization initiator
-Charge 2.5 parts of ethyl hexanoate into the dropping funnel
A monomer solution was prepared. Keep the inside of the reaction vessel at 120 ° C.
The monomer solution was added dropwise over 3 hours. After dripping
It was kept at 120 ° C. for another hour. Number average molecular weight 140
00, hydroxyl value 45 and acid value 15 mg KOH / g
Thus, an acrylic resin varnish having a hydroxyl group was obtained.

[0050]Production Example 2 Production of polyester resin  Thermometer, stirrer, cooling pipe, nitrogen inlet pipe, water separator and
415 parts of isophthalic acid and adipine
90 parts of acid, 100 parts of trimethylolpropane, neopen
200 parts of tyl glycol, 2,2-dimethyl-3-hydride
Roxypropyl-2,2-dimethyl-3-hydroxyp
195 parts of lopionate and 2 parts of dibutyltin oxide
And heated to 210 ° C. However, 16
From 0 ° C to 210 ° C at a constant heating rate over 3 hours
The temperature was raised. The generated condensed water was distilled out of the system. 21
When the temperature reaches 0 ° C, keep it warm, and after 1 hour, keep it in the reaction tank.
30 parts of xylene as a reflux solvent is gradually added to
The reaction was switched to condensation in the presence and continued. Resin acid value
When 8.5 mg KOH / g (solid content) is reached, 15
After cooling to 0 ° C, 200 parts of ε-caprolactone was added and
After keeping the temperature at 50 ° C for 2 hours, it was cooled to 100 ° C. Change
430 parts of xylene was added to the mixture, and the number average molecular weight was 2700,
Value 7 mgKOH / g (solid content), hydroxyl value 93 mgKO
Non-volatile content 7 containing H / g (solid content) polyester resin
0% varnish was obtained.

[0051]Production Example 3 Production of non-aqueous dispersion resin
Construction  (A) Production of dispersion-stable resin Vinegar is placed in a container equipped with a stirrer, a temperature controller, and a reflux condenser.
90 parts of butyl acrylate are charged and then a solution having the following composition: methyl methacrylate 38.9 parts stearyl methacrylate 38.8 parts 2-hydroxyethyl acrylate 22.3 parts 20 parts of azoisobutyronitrile 5.0 parts And heat with stirring to raise the temperature
I let it. Remaining 85 parts of the above mixed solution at 110 ° C. for 3 hours
And then 0.5 parts of azoisobutyronitrile and vinegar
A solution consisting of 10 parts of butyl acid was added dropwise over 30 minutes. Anti
The reaction solution was stirred and refluxed for another 2 hours to reduce the rate of change to resin.
After raising, the reaction was terminated and the solid content was 50%, number average
An acrylic resin having a molecular weight of 5600 and an SP value of 9.5 was obtained.

(B) Preparation of Nonaqueous Dispersion Resin 35 parts of butyl acetate is charged into a container equipped with a stirrer, a temperature controller and a cooler, and the acrylic resin 60 obtained in the above (a) production of dispersion stable resin is prepared. The department was charged. Next, a solution having the following composition: styrene 7.0 parts methacrylic acid 1.8 parts methyl methacrylate 12.0 parts ethyl acrylate 8.5 parts 2-hydroxyethyl acrylate 40.7 parts azoisobutyronitrile 1.4 parts Was added dropwise at 100 ° C. for 3 hours, and then a solution consisting of 0.1 part of azoisobutyronitrile and 1 part of butyl acetate was added to 30 parts of
In minutes. When the reaction solution was further stirred for 1 hour, an emulsion having a solid content of 60% and a particle size of 0.18 μm was obtained. This emulsion is diluted with butyl acetate,
A butyl acetate dispersion having a viscosity of 300 cps (25 ° C.) and a particle size of 0.18 μm and a nonaqueous dispersion resin content of 40% was obtained. The Tg of this non-aqueous dispersion resin is 23
C., the hydroxyl value was 162, the number average molecular weight was 15,000, and the weight average molecular weight was 300,000. SP value is 1
The difference in SP value between the shell portion and the core portion, which were dispersion stable resins, was 2.3.

[0053]Examples 1-2  <Preparation of coating composition> Obtained in Production Example 1 in a 2 L vessel
50 parts of the obtained amide group-containing acrylic resin,
Aluminum flakes (Alpaste manufactured by Toyo Aluminum)
91-0562) with respect to the solid content weight of the coating composition.
% (PWC), and 5 parts of butyl acetate
And 5 parts of xylene. After that, the desk disperser
For 15 minutes. After the dispersion is completed, the pigment paste
Was. The prepared pigment paste was mixed with the poly obtained in Production Example 2.
10 parts of ester resin, non-aqueous dispersion obtained in Production Example 3
10 parts resin, butylated melamine as curing agent
(Mitsui Cytec U-20N-60) 30 parts
After mixing, as ammonium salt of organic carboxylic acid
Alkanol ammonium of unsaturated acidic carboxylic acid ester
Um salt (BYK-ES80 manufactured by BYK Chemie)
To 1.2% by weight of the solid content of the paint or tetrasalicylic acid
Butyl ammonium salt is 0.1% based on the solid weight of paint
To prepare a metallic base coating composition. this
In the preparation of the coating composition, the blending amount is the solid content weight
by.

<Coating method> After treatment with zinc phosphate, Power Top V-6 (cationic electrodeposition paint manufactured by Nippon Paint Co., Ltd.)
Is electrodeposited to a dry film thickness of 20 μm.
On a coated plate baked at 0 ° C. for 30 minutes, an intermediate coating (OP-2 gray, manufactured by Nippon Paint Co., Ltd.) was previously coated with ethyl acetate /
After diluting for 19 seconds (using a No. 4 Ford cup at 20 ° C.) with a dilution thinner composed of ethylethoxypropanol = 6/4, the dried film thickness was 20 μm.
"metabell" (rotary atomizing type electrostatic coating machine)
Painted. After coating, setting was performed for 5 minutes, and baking was performed at 140 ° C. for 30 minutes using a dryer.

Next, the above metallic base coating composition was previously prepared for 16 seconds (No. 3 Ford) using a diluted thinner consisting of butyl acetate / S-100 (an aromatic organic solvent manufactured by Exxon) = 50/50. Use a cup at 20 ° C
30 cm from the object to be coated using a “metallic bell” so that the dry film thickness becomes 15 μm.
Two stages were painted from a distance. There was a 1.5 minute interval between the two applications. After the second application, setting was performed for 8 minutes.

Next, an acid epoxy curing type solvent clear paint (MAC O-380 clear manufactured by Nippon Paint Co., Ltd.) was used.
One stage coating was performed with a “microbell” so as to have a dry film thickness of 30 μm, and setting was performed for 7 minutes. Next, the obtained coated plate was baked in a dryer at 140 ° C. for 30 minutes.

<Evaluation Method> The following evaluation was performed on the obtained metallic base coating composition, and the results are shown in Table 1. 1. Electric resistance value The electric resistance value at the time of coating was measured using a Rohmsburg Mega Ohm tester. 2. Storage stability The viscosity was 30 seconds (using a No. 4 Ford cup, 20
(Measured in ° C.) was adjusted to 6
Viscosity measured after 16 hours at 0 ° C. (unit: seconds, N
o. 4 Measured at 20 ° C using a Ford cup)
It was represented by the difference (unit: second) from 0 second. 3. Sparks and leaks Whether or not sparks and leaks occurred during painting was examined based on whether or not the spark guard was activated. Moreover, when the obtained laminated | multilayer coating film was evaluated visually, it turned out that it has favorable finished appearance.

[0058]Comparative Example 1  Ammonia of organic carboxylic acid in metallic base coating composition
Except that no sodium salt was added.
The paint was adjusted, painted, and evaluated.Comparative Examples 2-3  Organic carboxylic acids in metallic base coating compositions
Methanol instead of ammonium salt
Except for adding 3% or 5% to the amount,
In the same manner, paint preparation, coating, and evaluation were performed.

[0059]

[Table 1]

From Table 1, it can be seen that Comparative Example 1, in which the metallic base coating composition did not contain either methanol or an ammonium salt of an organic carboxylic acid, had good storage stability but high electrical resistance during coating. Also, Comparative Examples 2 and 3 containing methanol had low electrical resistance values, but storage stability was reduced, whereas Comparative Examples 2 and 3 containing ammonium salts of organic carboxylic acids showed electrical resistance values. Was suppressed and high storage stability was found. Table 1 also shows that, for Comparative Example 1, the spark guard was activated during application of the metallic base paint, causing sparks and leaks. However, for Examples 1-2 and Comparative Examples 2-3, the above-mentioned spark guard was used. Did not work, and no sparks or leaks occurred, so it was found that the coating could be performed well.

[0061]

Since the coating composition of the present invention has the above-mentioned structure, it is possible to adjust the electric resistance at the time of coating to a low value and to prevent a decrease in storage stability. It is preferably used for coating of vehicle bodies and parts, particularly when electrostatic coating is performed as a metallic base paint. The coating film forming method of the present invention and the object to be coated having the coating film obtained by the above-mentioned coating film forming method use the above-mentioned coating composition, and thus are similarly suitably used for coating automotive bodies and the like.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B32B 27/20 B32B 27/20 A C09D 7/12 C09D 7/12 F term (Reference) 4D075 AE10 CB13 DB02 DC12 EC05 EC11 4F100 AH03A AH03H AK01A AK25 AK41 AT00B BA03 BA07 BA10B BA10C CA13A CC00A CC00C EH462 GB32 JG04 JG04A JL00 JN01C JN24A JN24H YY00A 4J038 CB001 CC091 CG031 CG071 CG071 CG071 CG071 CG071 HA066 HA146 HA546 JA66 JB10 JB16 KA08 KA12 KA18 MA07 MA10 MA14 NA21 NA26 PA19 PB07 PC02 PC03 PC08

Claims (5)

[Claims] 1. A coating composition containing an ammonium salt of an organic carboxylic acid and a non-aqueous dispersion resin, wherein the coating composition has an electrical resistance of 0.1 to 0.5 MΩ. Paint composition. 2. The coating composition according to claim 1, wherein the coating composition further contains a metallic glitter pigment. 3. The coating composition according to claim 1, wherein the ammonium salt of the organic carboxylic acid is 0.01 to 2% by weight based on the weight of the solid content of the coating composition. 4. A method for forming a coating film, comprising: a step of applying the coating composition according to claim 1, 2 or 3 to an object to be coated, and a step of further applying a clear coating material wet-on-wet. Method. 5. An object to be coated having a coating film formed by the coating film forming method according to claim 4.