JP5068462B2 - Base coat coating composition - Google Patents

Description

  The present invention relates to a coating composition for a base coat that is suitably used for a base coat when multilayer coating is applied to, for example, an automobile exterior material.

For example, the surface of an automobile exterior material is often painted for the purpose of imparting, improving, and protecting design properties. Also, different types of paints may be applied in multiple layers for the purpose of imparting higher designability.
As one of such multilayer coatings, there is a method in which a metallic coating film is formed by applying a base coat coating composition containing metal powder (undercoating), and a transparent top coat is applied thereon. . For example, ABS resin is used for radiator grills, wheel caps, etc., which are exterior parts of automobiles, and polypropylene is used for side protector moldings, bumper protection moldings, mat guards, etc. Paint is applied.
The coating film formed in this way is required to have excellent resistance to gasoline and gasohol (gasoline to which alcohol is added), which is expected to expand its use as a fuel, in addition to a good metallic tone.

For example, Patent Document 1 discloses a two-component curable type composition containing a metal powder and a thermosetting resin as a resin component as a base coat coating composition capable of forming a coating film having excellent chemical resistance. Has been. Patent Document 2 discloses a coating composition for a base coat that can form a coating film excellent in gasoline resistance and the like, which contains a metal powder and contains a hydroxyl group-containing resin and a cellulose derivative as resin components. Yes.
JP-A-61-93870 JP-A-9-323062

However, since the coating composition for base coat described in Patent Document 1 is a two-component curable type, after preparing the coating composition, it is necessary to paint it on the object in a short time, and the pot life There was a problem of short. If the pot life is short, workability and handleability deteriorate, which is not preferable. In addition, a certain temperature and time are required for sufficient curing.
On the other hand, since the coating composition for base coat described in Patent Document 2 is a one-component drying type, it does not have the above-mentioned problems caused by a two-component curable coating and has excellent gasoline resistance of the coating film. It is said that there is. However, gasohol resistance evaluated in a test more severe than gasoline resistance is not described, and gasohol resistance may be insufficient.

  The present invention has been made in view of the above circumstances, and is a base coat coating composition that can be used as a one-component dry-type coating composition and can form a coating film excellent in resistance to gasohol and the like. The issue is to provide.

Base coat composition of the present invention, (meth) viewed contains a resin component containing at least 1% by weight of copolymer of acrylic resin and cellulose acetate resin, the copolymer, the cellulose acetate resin The (meth) acrylic resin is a graft polymer in which a (meth) acrylic resin is grafted, and the (meth) acrylic resin is a monomer component comprising methyl methacrylate, n-butyl acrylate, 2-hydroxyethyl acrylate, and methacrylic acid. It is characterized by being obtained by polymerizing .
The copolymer is preferably composed of 0.1 to 50% by mass of the cellulose acetate- based resin and 99.9 to 50% by mass of the (meth) acrylic resin .

  ADVANTAGE OF THE INVENTION According to this invention, the coating composition for basecoats which can be used as a one-component dry-type coating composition and can form the coating film excellent in tolerance, such as gasohol resistance, can be provided.

The present invention will be described in detail below.
The base coat coating composition of the present invention (hereinafter referred to as a coating composition) is used for forming a base coat formed as an undercoat of a top coat in multilayer coating, and comprises a resin component. contains.
And this resin component contains 1 mass% or more of the copolymer of (meth) acrylic-type resin and fiber-type resin.

  Examples of the fiber resin include cellulose acetate resin, nitrified cotton, carboxymethyl cellulose resin, hydroxyethyl cellulose resin, and cationized cellulose resin. As the fiber-based resin, these may be used alone or in combination of two or more. In particular, cellulose acetate resin, cellulose acetate butyrate resin, cellulose acetate propionate resin, etc. Cellulose acetate-based resins are preferred because of their good heat resistance and compatibility with (meth) acrylic resins.

  The (meth) acrylic resin is produced from a monomer component containing a (meth) acrylic monomer. Examples of the (meth) acrylic monomer include (meth) acrylic acid, 2 -Aliphatic (meth) acrylic such as hydroxyethyl (meth) acrylate, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, 2-ethylhexyl (meth) acrylate System monomers and the like.

  Such a (meth) acrylic monomer is preferably contained in an amount of 50% by mass or more, and 80% by mass or more in the monomer component used for producing the (meth) acrylic resin. Is more preferable. Furthermore, it is preferable that 100 mass% is contained. Within such a range, the coating film formed from the obtained coating composition has excellent resistance such as weather resistance. Examples of other monomers that can be used in addition to the (meth) acrylic monomer include vinyl monomers such as vinyl acetate, styrene, and maleic anhydride.

  Although the (meth) acrylic monomer may be used alone or in combination of two or more, it is particularly preferable to use only an aliphatic (meth) acrylic monomer. Furthermore, it is preferable to use at least an aliphatic (meth) acrylic monomer containing a hydroxyl group and / or a carboxyl group among the aliphatic (meth) acrylic monomers. When such a thing is used, the tolerance of the coating film formed from the obtained coating composition improves more, and high gasohol resistance is expressed. More preferable monomer components are methyl methacrylate 50 to 80% by mass, n-butyl acrylate 10 to 40% by mass, 2-hydroxyethyl acrylate 0.1 to 10% by mass, and methacrylic acid 0.1 to 5% by mass. %.

Furthermore, the hydroxyl value of the (meth) acrylic resin obtained by polymerizing the monomer component is preferably 20 to 60, and the glass transition temperature (Tg) is preferably 20 to 60 ° C. For example, when a monomer component in which methyl methacrylate, n-butyl acrylate, 2-hydroxyethyl acrylate, and methacrylic acid are used in the above ratio is polymerized, such a hydroxyl value and a glass transition temperature (meth) An acrylic resin can be obtained.
In addition, the preferred weight average molecular weight and number average molecular weight of the (meth) acrylic resin are respectively It is the range of 5000-100000 and 3000-50000.

  The copolymer of the (meth) acrylic resin and the fibrous resin may be a copolymer obtained by randomly copolymerizing these resins, but the (meth) acrylic resin is grafted on the fibrous resin. A graft polymer is particularly preferable, and when this is used, a coating composition capable of forming a coating film particularly having high resistance such as gasohol resistance can be provided. Here, when a mere (meth) acrylic resin is used as a resin component, the gasohol resistance of the coating film becomes insufficient, and the coating film bleeds when a top coat is provided on the formed coating film. This problem is also likely to occur. In addition, when a simple fiber-based resin is used as a resin component, the above-described bleeding problem is hardly generated, but the coating film has insufficient gasohol resistance.

As a method for producing a graft polymer in which a (meth) acrylic resin is grafted on a fibrous resin, for example, a (meth) acrylic monomer is used in the presence of the fibrous resin and an organic peroxide is used. There is a way to polymerize. According to this method, hydrogen is extracted from the fibrous resin to generate radicals, from which the (meth) acrylic monomer is graft-polymerized.
In this case, the ratio of the fiber-based resin to the (meth) acrylic resin in the copolymer, preferably the graft polymer, is 0.1 to 50% by mass for the fiber-based resin and 99 for the (meth) acrylic resin. When it is .9 to 50% by mass (the total amount is 100% by mass), the resistance of the coating film formed from the obtained coating composition is further improved, and high gasohol resistance tends to be exhibited. More preferably, the fibrous resin is 0.5 to 30% by mass, the (meth) acrylic resin is 99.5 to 70% by mass, and more preferably, the fibrous resin is 0.5 to 10% by mass, ( The meth) acrylic resin is 99.5 to 90% by mass.

When such a copolymer is contained at least 1% by mass in the resin component, it can impart high gasohol resistance to the formed coating film, and other resistance such as gasoline resistance and water resistance is sufficient. Become. Therefore, the content of the copolymer in the resin component can be appropriately set in the range of 1 to 100% by mass according to other purposes required for the coating film.
For example, when a coating composition is applied to an object made of ABS resin, an acrylic polyol is used in combination with such a copolymer as a resin component to form a coating film to be formed and the object made of ABS resin. The adhesion may be improved. In addition, when a coating composition is applied to an object composed of an olefin resin such as polypropylene, a (meth) acrylic resin grafted chlorinated polyolefin resin (acrylic modified chlorinated polyolefin resin) is used together with such a copolymer as a resin component. It is preferable to use a polyolefin resin modified with a (meth) acrylic resin, etc. in view of the stability of the coating composition and the adhesion to the object. Furthermore, when it is desired to further increase the drying rate of the coating film, a fiber-based resin having good solvent separation may be used in combination with the copolymer as the resin component.

  Other resins that can be used together with the copolymer as the resin component include (meth) acrylic resins such as acrylic polyols described above, polyolefin resins modified with (meth) acrylic resins, etc., fiber-based resins, and polyester-based resins. Examples thereof include resins, polycarbonate resins, polyurethane resins and the like. These other resins may be used alone or in combination of two or more as required.

  Furthermore, the solvent for dissolving or disperse | distributing the resin component mentioned above can be used suitably for a coating composition. Examples of the solvent include hydrocarbon solvents such as toluene, xylene, solvent naphtha, methylcyclohexane, and ethylcyclohexane; ester solvents such as ethyl acetate, butyl acetate, ethylene glycol monomethyl ether, acetone, methyl ethyl ketone, methyl isobutyl ketone, Examples include ketone solvents such as diisobutyl ketone, and these may be used alone or in combination of two or more.

In addition, the coating composition may include, as an optional component, a pigment for coloring or a metal powder for imparting metallic design, as appropriate, and various additives may be included. Also good.
Examples of pigments include inorganic pigments such as carbon black, titanium oxide, iron oxide, lead chromate, organic pigments such as phthalocyanine blue, phthalocyanine green, and quinacridone red, and extender pigments such as kaolin, barium sulfate, and calcium carbonate. May be used alone or in combination of two or more.
As the metal powder, a powder made of a metal such as aluminum, iron oxide, or stainless steel can be used. Moreover, as a metal powder, a flaky thing can be used and the paste-like thing kneaded with various solvents previously may be used.
As the additive, additives commonly used in paints such as an ultraviolet absorber, an antioxidant, a surface conditioner, a plasticizer, and a pigment settling inhibitor can be appropriately used.

Although there is no restriction | limiting in particular in the ratio of the resin component in a coating composition, For example, when it is a spray coating use, 10-60 mass% is preferable as solid content in a coating composition, More preferably, it is 20-50 mass%. It is. If it is less than 10% by mass, the thickness of the coating film to be formed becomes thin, and there may be cases where sufficient designability and protective effect cannot be imparted to the object to be coated. And the appearance may deteriorate.
Further, the ratio of the solid content in the optional coating composition is not particularly limited, but when used, the pigment is usually used in a range of 50% by mass or less in the coating composition, and the metal powder is usually used. It is used in the range of 20% by mass or less. Moreover, when these are used together, it is preferable that these total usage-amounts are the range of 40 mass% or less.

The coating composition can be prepared by mixing a resin component containing 1% by mass or more of the above-described copolymer and an optional component used as necessary with a roll mill or the like. The coating composition thus prepared is of a one-component drying type, and is applied to various objects so that the dry coating thickness is usually 5 to 50 μm. For example, the base coat is applied by drying at room temperature. Can be formed.
There is no restriction | limiting in the material of a target object, Resin, a metal, etc. are mentioned, For example, olefin resin, such as ABS resin and a polypropylene, is mentioned as resin.
Examples of the coating method include a spray coating method, a brush coating method, a roller coating method, a curtain coating method, a flow coating method, and a dip coating method. Although there is no particular limitation, the spray coating method is preferable from the viewpoint of workability and the like. It is.

On top of the base coat formed in this way, a top coat paint is applied, which is usually thick. A top coat of about 10 to 50 μm is formed.
There are no particular restrictions on the topcoat paint, but two-component curable thermosetting paints, active energy ray curable paints, and the like can be used. The basecoat comprising the paint composition of the present invention is a topcoat comprising these. Adheres well to the coat.
Examples of the thermosetting paint include the Fujikura Kasei Recrak series and the Fujisoft series.

There is no restriction | limiting in particular as an active energy ray hardening-type coating material, The UV coating material etc. which harden | cure by an ultraviolet-ray etc. can be used. The UV paint is usually constituted by combining a monomer, an oligomer, a polymer, a photopolymerization initiator, and a solvent. Examples of the monomer include a monofunctional monomer and a bifunctional or higher polyfunctional monomer. The monofunctional monomer is mainly used as a reactive diluent, and the polyfunctional monomer is used as a crosslinking component. The oligomer is the main component of the paint and governs physical properties such as adhesion. The polymer is used for the purpose of relaxing the shrinkage stress during curing and improving adhesion. The solvent enhances the paintability of the paint thickened by the addition of the oligomer or polymer, and also enhances the adhesion by the anchor effect or diffusion effect on the object. A photopolymerization initiator absorbs ultraviolet rays and cleaves to generate radicals to initiate polymerization of monomers and oligomers.
Further, the active energy ray-curable coating material may be a solventless type that does not contain a solvent from the viewpoint of the environment.
As a suitable active energy ray-curable coating material, Fujikura Kasei Fujihard series and the like can be mentioned.

Thus, according to the coating composition containing a copolymer of a (meth) acrylic resin and a fibrous resin as a resin component, the coating film has sufficient gasohol resistance as well as water resistance and gasoline resistance. It is suitable for painting on automobile exterior materials.
In addition, since such a coating composition can be used as a one-component dry type, there is no problem that the pot life is short, and the workability and handleability are excellent.

Hereinafter, the present invention will be specifically described with reference to examples.
[Example 1]
As a graft polymer (1) obtained by grafting a (meth) acrylic resin to a cellulose acetate butyrate resin (CAB), Harima Chemical Co., Ltd. Hariacron AP-3690 (trade name) was used (solid content 50 mass). %). This is obtained by polymerizing a (meth) acrylic monomer using an organic peroxide in the presence of CAB, and the (meth) acrylic resin (1) in this graft polymer is methacrylic. It is manufactured from a monomer component consisting of 1.5% by mass of acid, 8.3% by mass of 2-hydroxyethyl acrylate, 23.4% by mass of n-butyl acrylate, 66.8% by mass of methyl methacrylate, The hydroxyl value of the resin was 40 and the glass transition temperature was 40 ° C. The mass ratio of the cellulose acetate butyrate resin and the (meth) acrylic resin in the graft polymer (1) was 1.8 / 98.2.
This graft polymer (1), an aluminum paste containing aluminum powder (trade name: FM7680K, manufactured by Toyo Aluminum Industry Co., Ltd.) and butyl acetate as a solvent are mixed, and 40% by mass of the graft polymer (1) ( A one-component dry coating composition containing 4 mass% of aluminum powder was prepared.
The coating composition was spray-coated on a three ABS base material (object) with a spray gun so that the dry coating thickness was 15 μm, and left at room temperature for about 5 minutes to form a base coat.
Next, on the formed base coat, three kinds of paints made by Fujikura Kasei Co., Ltd. (Recrack 3000 Clear, Recrack 3300 Clear, and Recrack 4800 Clear (both are trade names)) have a dry coating thickness of 20 μm. Then, the coating was dried and cured to obtain three types of base materials on which three types of top coats were respectively formed. The drying and curing conditions are 60 ° C. × 30 minutes for those using RECRUCK 3000 clear, 80 ° C. × 30 minutes for those using RECRUCK 3300 clear, and 80 ° C. × for those using RECRUCK 4800 clear. The condition was 90 minutes.
Thus, as shown below, water resistance, gasoline resistance, and gasohol resistance were evaluated for the three types of base materials on which the base coat and the top coat were formed. The composition and evaluation results of the coating composition (1) are shown in the table.

[water resistant]
After immersing the base material on which the coating film is formed in warm water of 40 ° C. for 240 hours, the coating film is cut into a 10 × 10 grid pattern with a width of 1 mm and a tape is attached to the grid pattern part. The peeling operation was performed. The case where no coating film is attached to the tape is shown in the table as ◯, and even when one grid is attached and peeled off, it is shown as x. Cellophane tape was used as the tape.
[Gasoline resistance]
After immersing the base material on which the coating film is formed in gasoline at room temperature for 1 hour, the coating film is cut into a 10 mm square grid with a width of 1 mm and a tape is attached to the grid pattern. The peeling operation was performed. The case where no coating film is attached to the tape is shown in the table as ◯, and even when one grid is attached and peeled off, it is shown as x. Cellophane tape was used as the tape.
[Gaso-hole resistance]
After immersing the substrate on which the coating film was formed at room temperature for 1 hour (using gasoline containing 10% by mass of ethanol), the state of the coating film was visually evaluated. A case where there is no change from before immersion is shown in the table as ◯, and a case where a change such as floating on the coating film and wrinkles is observed is indicated as x.

[Examples 2-6, Comparative Examples 1-6]
A one-component drying type coating composition was prepared in the same manner as in Example 1 except that the composition shown in the table was used, and a base coat was formed on each of the three ABS base materials using the coating composition. Subsequently, three types of coating materials similar to those of Example 1 were applied onto the formed base coat and dried, respectively, to obtain three types of base materials on which different top coats were formed. And about these, evaluation similar to Example 1 was performed. The composition and evaluation results of each coating composition are shown in the table.

[Example 7]
Instead of the graft polymer (1), the graft polymer (2) was used. This graft polymer (2) is different from the graft polymer (1) in that the mass ratio of cellulose / acetate / butyrate resin to (meth) acrylic resin is 10/90. Then, a one-component dry coating composition was prepared in the same manner as in Example 1 except that the composition shown in the table was used, and a base coat was formed on each of the three ABS base materials using the coating composition. Three types of coating materials similar to those of Example 1 were applied on the base coat and dried to obtain three types of base materials on which different top coats were formed. And about these, evaluation similar to Example 1 was performed. The composition and evaluation results of each coating composition are shown in the table.

[Examples 8 to 9, Comparative Example 7]
A one-component dry coating composition was prepared in the same manner as in Example 1 except that the composition shown in the table was used, and a base coat was formed on a polypropylene substrate using this. Next, a coating made by Fujikura Kasei Co., Ltd. (Recrack 3000 Clear (trade name)) was applied on the formed base coat so that the dry coating thickness was 20 μm, then dried and cured, and the top coat was applied. The base material in which was formed was obtained. The drying and curing conditions were 60 ° C. × 30 minutes. And about this, evaluation similar to Example 1 was performed. The composition and evaluation results of each coating composition are shown in the table.

The contents of each component in the table are as follows.
(1) Acrylic polyol A: manufactured by Hitachi Chemical Co., Ltd., Hitaroid 3001 (trade name), hydroxyl value 30, glass transition temperature 30 ° C., solid content 50 mass%
(2) Acrylic polyol B: manufactured by Toray Fine Chemical Co., Ltd., Cotax LH649 (trade name), hydroxyl value 30, glass transition temperature 50 ° C., solid content 55 mass%
(3) CAB-A: manufactured by Eastman Chemical Co., CAB551-0.2 (trade name), cellulose acetate butyrate resin, solid content 100 mass%
(4) CAB-B: manufactured by Eastman Chemical Co., CAB551-0.01 (trade name), cellulose acetate butyrate resin, solid content 100 mass%
(5) Acrylic styrene polyol: manufactured by Dainippon Ink & Chemicals, Inc. Acrydec A-801P (trade name), hydroxyl value 50, glass transition temperature 50 ° C., solid content 50 mass%
(6) Chlorinated polyolefin: manufactured by Nippon Paper Industries Co., Ltd., Supercron 892L (trade name), solid content 20% by mass, chlorine content 22%, glass transition temperature 80-90 ° C
(7) Acrylic-modified chlorinated polyolefin: manufactured by Fujikura Kasei Co., Ltd. (13% by mass of chlorinated polypropylene having a chlorine content of 21% and 87% by mass of acrylic resin)

As is apparent from the table, the coating composition of each example using at least a graft polymer obtained by grafting a (meth) acrylic resin to a cellulose / acetate / butyrate resin as a resin component is a group composed of ABS or PP. It was shown that a coating film having excellent gasohol resistance and high resistance to the material can be formed. In Examples 2 to 9, acrylic polyol, cellulose acetate butyrate resin, chlorinated polyolefin, and acrylic-modified chlorinated polyolefin are used in combination as a resin component, and the proportion of the graft polymer in the resin component is low. However, high tolerance was still developed.
On the other hand, in each comparative example, a coating film having only water resistance or water resistance and gasoline resistance could be formed, but the gasohol resistance was poor.

Claims (2)

Including a resin component containing 1% by mass or more of a copolymer of a (meth) acrylic resin and a cellulose acetate resin ;
The copolymer is a graft polymer obtained by grafting the (meth) acrylic resin onto the cellulose acetate resin.
The (meth) acrylic resin is obtained by polymerizing monomer components consisting of methyl methacrylate, n-butyl acrylate, 2-hydroxyethyl acrylate, and methacrylic acid, and a base coat coating composition characterized in that . 2. The base coat according to claim 1, wherein the copolymer is composed of 0.1 to 50% by mass of the cellulose acetate- based resin and 99.9 to 50% by mass of the (meth) acrylic resin. Paint composition.