JPH10273620A - One-part type thermosetting color base / primer coating and method for finish coating reactive injection molded articles using the same - Google Patents

Abstract

(57) [Summary] [PROBLEMS] A baking step can be omitted once, energy costs can be reduced, a high sealing property, a glossy coating appearance can be provided, and the coating can be used for two-tone finish coating. Another object of the present invention is to provide a one-pack type thermosetting color base / primer coating which can ensure high coating film adhesion. SOLUTION: The one-component type thermosetting color base / primer coating is a primer coating containing a resin component essentially containing a polyester-modified urethane polyol and a melamine resin, a curing catalyst, a pigment and a solvent. The acid-based catalyst is essential, and the ratio to the total amount of the polyester-modified urethane polyol and melamine resin is 0.5 to 2% by weight based on the solid content, and the solvent is a high-boiling aromatic compound having a boiling point of 150 ° C or more. A group hydrocarbon is essential and a high boiling point solvent having a boiling point of 150 ° C. or higher is contained in an amount of 20 to 40% by weight of the whole solvent. The amount is adjusted so as to be 50 to 60% by weight.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved one-part thermosetting color base / primer coating and a method for finishing a reactive injection molded article using the same.

[0002]

2. Description of the Related Art Conventionally, RIM (Reaction Injection Moldi
ng), R-RIM (Reinforced Reaction Injection Mo)
lding) To paint a reactive injection molded product such as a urethane bumper and finish it with 3 coats of mica color, first,
After applying a primer paint for a color base and baking and drying, a mica base paint and a clear paint are applied again on a wet-on-wet basis, and baking and drying are performed.
In this coating method, baking needs to be performed twice, so that the baking step causes an increase in cost as viewed from the equipment and the coating step, and simplification of the baking step has been desired.

[0003]

Therefore, in order to simplify the baking process, the reactive injection-molded article is coated with a primer paint for a color base, and then a mica base paint and a clear paint are applied on a wet-on-wet basis. It has been proposed to apply by a three-coat one-bake method in which stacking and baking are performed only once.

However, in the coating method according to the above proposal,
Drilled holes (pinholes) scattered on the surface of reactive injection molded products
And the surface gloss of the coating film were not satisfactory. Further, there is also a problem in interlayer adhesion when a cured coating film of a different color is formed to obtain a two-tone finish coating film. Therefore, the problem to be solved by the present invention is that the baking step can be omitted once, the energy cost can be reduced, the sealability is high, the glossy coating appearance can be provided, and the two-tone finish can be obtained. An object of the present invention is to provide a one-pack type thermosetting color base / primer coating which can ensure high coating film adhesion even when used for coating.

Another problem to be solved by the present invention is that the baking step can be omitted once, a high sealing property, a glossy coating appearance can be provided, and a high coating adhesion in the case of two-tone finish coating. It is an object of the present invention to provide a finish coating method for a reactive injection molded article, which can ensure the finish.

[0006]

Means for Solving the Problems In order to solve the above-mentioned problems, the present inventors have proposed a curing catalyst containing paratoluenesulfonic acid or phosphoric acid, containing a urethane polyol, a melamine resin, a pigment, an additive and a solvent. Conventionally known one-pack type thermosetting color base / primer paint
A coating system for coating by the bake method was studied. As a result, the amount of non-volatile components in the wet coating when coated using the color base / primer coating is greatly related to both the sealing performance and the glossiness. The primer coating is easy to enter the hole (pinhole) and the sealing performance is improved. However, if the amount of the non-volatile component is too small, the primer coat is easily mixed with the mica base coat and the clear coat, and a glossy coating film is formed. Difficult to obtain,
On the other hand, if the amount of the non-volatile component in the wet coating film is increased, mixing of the coating film is less likely to occur, and a sufficient glossiness can be obtained on the coating film surface. As a result, it was found that blisters and pinholes were easily formed on the surface of the coating film, and in this case also, a good appearance could not be obtained on the coating film surface. Thus, it was found that strict adjustment of the amount of the non-volatile component was necessary to simultaneously satisfy the filling performance and the gloss of the coating film surface. The present inventors have further researched, and the amount of the curing catalyst in the one-pack type thermosetting color base / primer coating is also related to the sealing performance.If the curing catalyst is too small, it is difficult to cure, and the coating film strength is low. It was found that the sealing performance deteriorated for the reason.

The first one-pack type thermosetting color base / primer coating material according to the present invention and the three-coat one-bake finish coating method using the same are thus completed. Next, the inventors of the present invention applied a three-coat, one-bake method using a color base / primer paint adjusted to an amount of a nonvolatile component and an amount of a catalyst satisfying both the sealing property and the glossiness, and obtained. This one-part type thermosetting film was prepared by applying a base paint of another color partially over the surface of the cured coating film of the basic color, and then applying a clear paint over it and then baking it to obtain a two-tone finish coating. Even when a color base primer coat was used, it was found that delamination occurred between the first color clear coat and the second color base coat. To solve this point, further research was conducted, and two-tone finish coating was used. Finding that the amount of curing catalyst must not be too large to obtain interlayer adhesion, and that the type of curing catalyst and solvent should be optimized. Obtained, thereby completing the two-tone finishes how to use this and according the second one-pack type thermosetting color base combined primer coating of the present invention. That is, the cause of peeling between the first color clear coat and the second color base coat is that the curing catalyst contained in the color base / primer coating is baked through wet-on-wet coating to the first color clear coat. It was found that bleeding (migration) accelerates the curing of the clear coat. As a result, it is possible to reduce the amount of bleeding of the catalyst if the amount of the curing catalyst is appropriately suppressed. The present inventors have found that bleeding of the curing catalyst can be prevented by this affinity if the composition is optimized to have the property, and the present invention has been completed.

Accordingly, the first one-pack type thermosetting color base / primer paint according to the present invention is a primer paint containing a resin component containing a polyester-modified urethane polyol and a melamine resin, a curing catalyst, a pigment and a solvent. The curing catalyst essentially requires a sulfonic acid-based catalyst, and the ratio to the total amount of the polyester-modified urethane polyol and the melamine resin is 0.5 to 2% by weight on a solid content basis. A high-boiling aromatic hydrocarbon having a boiling point of 150 ° C. or higher is essential, and a high-boiling solvent having a boiling point of 150 ° C. or higher is contained in an amount of 20 to 40% by weight of the entire solvent. It is adjusted so that the amount after one minute from the application to the surface is 50 to 60% by weight. .

The second one-pack type thermosetting color base / primer coating according to the present invention is a primer coating containing a resin component essentially containing a polyester-modified urethane polyol and a melamine resin, a curing catalyst, a pigment and a solvent. The curing catalyst essentially comprises dinonylnaphthalenedisulfonic acid, and the proportion of the total amount of the polyester-modified urethane polyol and the melamine resin is 0.5 to 1.5% by weight on a solid basis, and the solvent is A high-boiling aromatic hydrocarbon having a boiling point of 150 ° C. or more, and a high-boiling solvent having a boiling point of 150 ° C. or more containing 20 to 40% by weight of the entire solvent. It is adjusted so that the amount after one minute from the application to the material surface is 50 to 60% by weight. To.

A three-coat, one-bake finish coating method for a reactive injection molded article according to the present invention comprises applying the first one-pack type thermosetting color base / primer paint according to the present invention to the surface of the reactive injection molded article. A primer paint film is formed, a base paint film is applied on the primer paint film to form a base paint film, and a clear paint film is applied on the base paint film to form a clear paint film. A baking step of simultaneously baking the primer coating film, the base coating film and the clear coating film to form a cured coating film on the surface of the reactive injection molded article.

The two-tone finish coating method for a reactive injection molded article according to the present invention comprises applying the second one-part type thermosetting color base / primer paint according to the present invention to the surface of the reactive injection molded article. Forming a film, applying a base paint on the primer paint film to form a base paint film, and applying a clear paint film on the base paint film to form a clear paint film; A first baking step of simultaneously baking the primer coating film, the base coating film, and the clear coating film to form a cured coating film of a basic color on the surface of the reactive injection molded article; (1) A base paint of another color is partially applied to the surface of the cured coating film of the basic color obtained in the baking step to form a coating film of another color, and a clear paint is applied over the coating film of another color. 2nd chestnut A second paint film forming step of forming a paint film, and simultaneously baking the different color paint film and the second clear paint film to form a partially different cured paint film on the surface of the basic color cured film film; A second baking step of forming a film.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION As the polyester-modified urethane polyol in the color base / primer paint according to the present invention, OHV (hydroxyl value) = 10 to 50 KOHm
g / g, Mw = 30,000 to 80,000, and a urethane conversion ratio of 5 to 20% are preferable. The melamine resin in the color base / primer paint according to the present invention is an alkyl etherified melamine, and examples thereof include methyl etherified melamine, butyl etherified melamine, and isobutyl etherified melamine.

The mixing ratio of the polyester-modified urethane polyol (U) and the melamine resin (M) can be appropriately selected in a weight ratio U / M = 70/30 to 90/10. As the type of the curing catalyst in the color base / primer coating according to the present invention, when used for three coats and one bake coating, those which require a sulfonic acid-based catalyst such as paratoluenesulfonic acid and dinonylnaphthalenedisulfonic acid are preferable. Among them, those in which dinonylnaphthalenedisulfonic acid is essential are more preferable. In the case of two-tone finish coating, the curing catalyst is preferably one in which dinonylnaphthalenedisulfonic acid is essential. When a phosphoric acid-based catalyst is used in an amount described below (0.5 to 2% by weight), it cannot be used as a curing catalyst because the reactivity is low and the sealing property tends to decrease.

Regarding the addition amount of the curing catalyst, 3 coats 1
The amount added in the case of baking is 0.5 to 2% by weight based on the solid content based on the total amount of the polyester-modified urethane polyol and the melamine resin, and the amount added in the case of two-tone finishing is based on the solid content. 0.5-1.5% by weight
It is necessary to If the addition amount is less than 0.5% by weight, it is difficult to cure, the coating film strength becomes low, and the sealing property becomes insufficient. On the other hand, when the addition amount exceeds 1.5% by weight, delamination occurs at the time of two-tone finish coating.
If the addition amount is more than 2% by weight, curing of the clear coat is promoted at the time of 3 coats and 1 bake coating, and shrinkage occurs, and the appearance is deteriorated.

Other components in the color base / primer paint used in the present invention include coloring pigments such as titanium oxide, carbon black and iron oxide; extenders such as talc, precipitated barium and silica; and ultraviolet rays such as benzotriazole. An absorbent; a surface conditioner and the like can be used as needed. In the color base / primer paint according to the present invention, it is necessary to use at least an aromatic hydrocarbon as a high-boiling solvent having a temperature of 150 ° C. or higher as a diluting solvent used for coating. The high-boiling aromatic hydrocarbon solvent is not particularly limited, but may be Solvesso 100
(Boiling point: 152-164 ° C, manufactured by Exxon Chemical Co., Ltd.)
Solvesso 150 (boiling point: 190-200 ° C., manufactured by Exxon Chemical Co., Ltd.), Swazol 1000 (boiling point: 159-
166 ° C., manufactured by Maruzen Oil Co., Ltd.). In this case, when the ketone-based solvent is used as a main component, the property of dissolving the reactive injection molded article is strong, and the sealing property is enhanced because it promotes the generation of bubbles from the elementary holes in the surface of the reactive injection molded article. It tends to decrease, causing blisters and pinholes. When an alcohol-based, ester-based, or ether-based solvent is used as a main component, delamination occurs during multicolor finish coating such as two-tone finish. This is because alcohol-based, ester-based, and ether-based solvents do not have a function of stopping the curing catalyst.

The amount of the non-volatile component in the primer paint for color base according to the present invention is adjusted so that the amount after one minute from the application of the primer paint to the substrate surface is 50 to 60% by weight. is required. If it is less than 50%, a high appearance cannot be obtained because the primer coat is mixed with the base coat and the clear, and if it exceeds 60%, the sealing performance deteriorates and appearance defects such as blisters and pinholes occur.

In the primer coating for color base according to the present invention, the diluting solvent at the time of coating contains a high boiling solvent having a boiling point of 150 ° C. or higher in an amount of 20 to 40% by weight in order to adjust the amount of the non-volatile components as described above. is necessary. Examples of the base paint and clear paint used in the finish coating method of the present invention include commonly used one-pack melamine cured paints and one-pack blocked isocyanate cured paints. That is, the base paint is a one-pack melamine-curable paint, and is a resin such as an acrylic resin, an alkyd resin, a polyester resin, or a melamine resin; a bright pigment such as aluminum or mica; a coloring such as titanium oxide, carbon black, or iron oxide. Pigments; extender pigments such as talc, precipitated barium and silica; organic solvents such as toluene, xylene, ethyl acetate, butyl acetate, methyl ethyl ketone and methyl isobutyl ketone; melamine resin curing catalysts such as paratoluenesulfonic acid and dodecylbenzenesulfonic acid; UV absorbers such as benzotriazole; anti-settling agents such as organic amide compounds;
It contains a surface conditioner and the like, and the mixing ratio of each is not particularly limited and can be appropriately selected. As a commercial product,
For example, R-331 manufactured by Nippon Bee Chemical Co., Ltd. may be mentioned. Clear paint is a one-part melamine or blocked isocyanate curable paint, acrylic resin,
Resins such as alkyd resin, polyester resin, melamine resin, and blocked isocyanate resin; organic solvents such as toluene, xylene, ethyl acetate, butyl acetate, methyl ethyl ketone, and methyl isobutyl ketone; melamine resin curing such as paratoluenesulfonic acid and dodecylbenzenesulfonic acid It contains a catalyst; a blocked isocyanate dissociation catalyst such as bis (dibutyltin) maleate; an ultraviolet absorber such as benzotriazole; a surface conditioner, and the like, and the mixing ratio of each is not particularly limited and can be appropriately selected. Examples of commercially available products include R-343 manufactured by Nippon Bee Chemical Co., Ltd. for the melamine-curable type, and R-362 manufactured by Nippon Bee Chemical Co., Ltd. for the blocked isocyanate-curable type.

There are no particular restrictions on the coating conditions when the finish coating according to the present invention is carried out using the above-mentioned paints. The coating thickness is, for example, 10 to 50 μm for the primer coat, 10 to 20 μm for the base coat, and 20 to 30 μm for the clear coat. The baking temperature and time are, for example, 110 to 130 ° C. and 20 to 60 minutes.
The coating is performed by, for example, an air spray method.

Examples of the reactive injection molding used include polyols such as polyether polyols and MDI.
It is obtained by curing a polyisocyanate such as a systemic isocyanate with a curing catalyst such as triethylenediamine, and suitably includes a reinforcing agent such as glass flake, a coloring agent, an antioxidant, and the like.

[0020]

【Example】

(Example 1) 1) Preparation of color base / primer coating polyester modified urethane polyol (OHV = 20K)
OHmg / g, Mw = 40000, urethane conversion rate = 10
%), 20 parts of melamine resin (Melan 8000, manufactured by Hitachi Chemical Co., Ltd.), 100 parts of titanium oxide, and 1 part of dinonylnaphthalenedisulfonic acid as a catalyst, and then Solvesso 100 (Exxon Chemical Co., Ltd.) Made) 30
Parts, 30 parts of toluene, 10 parts of isopropyl alcohol,
N with a thinner consisting of 20 parts of methyl isobutyl ketone
o. The mixture was diluted with a 4 Ford cup so as to have a viscosity of 14 seconds at 20 ° C. to prepare a color base / primer paint.

2) Coating The diluted color base / primer coating is R-RIM.
The urethane is applied with an air spray to a dry film thickness of 40 μm, and after an interval of 3 minutes, a base coat (Nippon Bee Chemical Co., Ltd., R-331) is applied to the dry film thickness of 15 μm and further 3 minutes. After an interval, clear (R-36, manufactured by Nippon Bee Chemical Co., Ltd.)
2) is applied to a dry film thickness of 30 μm,
It was baked and dried at 20 ° C for 20 minutes to obtain a three-coat finish film. This coating film was evaluated for gloss and fillability according to the following evaluation methods.

3) The baking of the above 2) is performed at 130 ° C. for 60 hours.
Then, another base coat and clear were applied in the same manner, and baked and dried at 120 ° C. for 20 minutes to obtain a two-tone finish coating film. This coating film was evaluated for gloss, fillability and adhesion according to the following evaluation methods. -Evaluation Method- 20 ° gloss was measured with a digital variable-angle gloss meter manufactured by Gloss Suga Test Machine Co., Ltd. A measured value of 80 or more was evaluated as ○, and a measured value of less than 80 was evaluated as ×. Swelling in the eye tightness visually examine the presence or absence of a pin hole, both recognized not as a ○, either slightly, is recognized as the △, one was evaluated as × that observed significantly. Adhesion A cross-cut cellophane tape peel test was performed in accordance with JIS K5400. 100 cross-cuts of 2 mm square were prepared and subjected to a cellophane tape peeling test. When the number of cross-cuts not peeled was 100, it was evaluated as ○, and when the number of cross-cuts not peeled was 99 or less, it was evaluated as x. (Example 2) The urethane polyol used in Example 1 was
OHV = 15KOHmg / g, Mw = 40000, urethane conversion = 15% A two-tone finish coating film was obtained in the same manner. (Examples 3 and 4) In Example 1, the addition amount of the catalyst (dinonylnaphthalenedisulfonic acid) was changed as shown in Table 1, and a two-tone finish coating film was similarly obtained. (Examples 5 and 6) In Example 1, the amount of Solvesso 100 was changed as shown in Table 1, and a two-tone finish coating film was similarly obtained. (Example 7) In Example 1, the addition amount of the catalyst was changed as shown in Table 2, and a two-tone finish coating film was similarly obtained. (Example 8) In Example 1, the catalyst and the amount of addition thereof were changed as shown in Table 2, and a two-tone finish coating film was obtained in the same manner. (Comparative Example 1) In Example 1, the amount of the catalyst added was changed as shown in Table 2, and a two-tone finish coating film was similarly obtained. (Comparative Examples 2-3) In Example 1, the catalyst and the amount added were changed as shown in Table 2, and a two-tone finish coating film was obtained in the same manner. (Comparative Examples 4 to 9) In Example 1, as shown in Tables 2 and 3, the type and amount of the high boiling point solvent were changed, and a two-tone finish coating film was similarly obtained. (Comparative Example 10) In Example 1, the type of the catalyst and the type of the high boiling point solvent were changed as shown in Table 3 and the primer paint for color base was applied, and then baked and dried at 120 ° C for 5 minutes. The clear was painted (3 coats 2 bake). Furthermore, 3) of Example 1 was performed to obtain a two-tone finish coating film.

[0023]

[Table 1]

[0024]

[Table 2]

[0025]

[Table 3]

[0026]

According to the present invention, the one-pack type thermosetting color base / primer coating composition of the present invention can eliminate the baking step once, reduce energy costs, have a high sealing property, and provide a glossy coating film. Appearance can be imparted, and high coating film adhesion can be ensured even when used for two-tone finish painting.
In particular, when this paint is used for coating reactive injection molded products such as RIM and R-RIM urethane, a three-coat finish film can be obtained by a single baking and drying process. This makes it possible to efficiently manufacture bumpers and the like for automobiles.

The finish coating method of the reactive injection molded article of the present invention can eliminate the baking step once, provide a high sealing property, give a glossy coating appearance, and provide a high coating quality in the case of two-tone finish coating. Adhesion can be secured.

──────────────────────────────────────────────────続 き Continuing on the front page (51) Int.Cl. ⁶ Identification symbol FI C09D 175/04 C09D 175/04 (72) Inventor Toshiki Takagi 2-4-1-1, Shodai Otani, Hirakata-shi, Osaka Japan B.C. Inside the corporation

Claims (4)

[Claims] 1. A primer paint containing a resin component, a curing catalyst, a pigment and a solvent, which essentially contain a polyester-modified urethane polyol and a melamine resin, wherein the curing catalyst essentially contains a sulfonic acid-based catalyst. The ratio to the total amount of the polyester-modified urethane polyol and the melamine resin is 0.5% based on the solid content.
The solvent essentially contains a high-boiling aromatic hydrocarbon having a boiling point of 150 ° C. or higher and contains a high-boiling solvent having a boiling point of 150 ° C. or higher in an amount of 20 to 40% by weight of the whole solvent. The amount of non-volatile components is determined by applying a primer paint to the surface of the substrate.
A one-pack type thermosetting color-base / primer coating, characterized in that the amount after a lapse of minutes has been adjusted to be 50 to 60% by weight. 2. A primer coating material containing a resin component, a curing catalyst, a pigment and a solvent, which essentially contain a polyester-modified urethane polyol and a melamine resin, wherein the curing catalyst contains dinonylnaphthalenedisulfonic acid, The ratio to the total amount of the polyester-modified urethane polyol and the melamine resin is 0.5 to 1.5% by weight on a solid basis, and the solvent essentially includes a high-boiling aromatic hydrocarbon having a boiling point of 150 ° C or higher. It also contains a high boiling point solvent having a boiling point of 150 ° C. or higher in an amount of 20 to 40% by weight of the entire solvent.
A one-pack type thermosetting color-base / primer coating, characterized in that the amount after a lapse of minutes has been adjusted to be 50 to 60% by weight. 3. A primer coating film is formed by applying the one-component type thermosetting color base / primer coating material according to claim 1 on the surface of the reactive injection molded article, and a base coating material is applied on the primer coating film. Forming a base paint film by stacking and applying a clear paint on the base paint film to form a clear paint film; and a primer paint film, a base paint film and a clear paint film. A baking step of simultaneously baking the film to form a cured coating film on the surface of the reactive injection molded product, a three-coat finish coating method for the reactive injection molded product. 4. A primer coating film is formed by applying the one-component type thermosetting color base / primer coating material according to claim 2 on the surface of the reactive injection molded article, and a base coating material is applied on the primer coating film. A first paint film forming step of forming a clear paint film by applying a clear paint over the base paint film to form a base paint film; A first baking step of simultaneously baking the paint film to form a cured film of the basic color on the surface of the reactive injection molded article; and partially covering the surface of the cured film of the basic color obtained in the first baking process. A second coating film forming step of forming a second coating film by forming a second coating film by applying another base coating material in a different color to form a second coating film, and applying a clear coating film on the other coating film; The different color paint film and A second baking step of simultaneously baking the second clear paint film to form a cured film of a different color partially on the surface of the cured film of the basic color. .