JPH01281175A - Formation of protective film - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to coatings for automobiles, etc., and particularly to a method for forming a protective layer for a decoratively finished layer.

Problems to be Solved by the Invention The present invention provides a coating method that prevents roughening of the protective layer, ensures adhesion, and minimizes problems in painting workability when forming a protective layer on an aesthetic paint film. It's about doing.

Conventional technology Painting for automobiles, etc. is formed from a base coat, intermediate coat, and top coat by electrodeposition. Conventionally, polyester/melamine resin paint, acrylic/melamine resin paint, etc. have been used for the top coat, but they are not always effective in terms of weather resistance. In order to maintain its beauty for a long time, waxing has been done carefully, but it has not been satisfactory.

In order to solve this problem, Japanese Patent Application Laid-Open No. 59-19670. JP-A-59-222267 proposes using a fluorine-containing copolymer as the basic resin component and applying a paint containing a colored pigment. However, the method of painting the color requires a paint tank and piping for each color, and is virtually impossible to implement in a mixed line with general paint due to the cost of installation space and equipment.

For this reason, a method has been proposed (Japanese Patent Application Laid-Open No. 197074/1983) in which a fluorine-containing resin clear is applied on top of the conventional paint film.

Generally, when applying further paint on top of the aesthetic paint film that has already been formed, it is necessary to wipe it with white kerosene to remove dust, dirt, and other substances on the paint film. However, there are problems in that the uneven distribution of static electricity remaining in the cosmetic coating film may cause skin roughness, and the adhesion may also be reduced.

Means for Solving the Problems The method for forming a paint film according to the present invention is to apply a clear paint (I) having excellent adhesion to the finished top coat film.
and a clear paint (If) containing a fluorine-containing copolymer resin having hydroxyl groups in a wet-on-wet manner to form a clear paint film, especially a method for forming a protective film on an automobile's aesthetic paint film. , which is described next (a)
It includes preferred embodiments such as ~(c).

(a) A copolymer resin having a relatively low total number of acid value and OH value and a relatively high number average molecular weight compared to clear coating fl (I), and a relatively high acid value and OH value compared to clear coating fl (II). A method of using a resin containing a fluorine-containing copolymer resin having a number average molecular weight that is relatively low in terms of the total number of .

(b) A method in which the resin constituting the clear paint (II) is a copolymer mixture containing a fluorine-containing resin copolymer having a hydroxyl group as a main component and consisting of an acrylic resin.

(c) Clear paint (I) and clear paint (II)
A composition in which the curing agent comprises an alkyl etherified amino resin and/or an isocyanate compound.

Underneath the protective layer of the present invention is an aesthetic paint film consisting of a solid or metallic top coat, which is usually the final paint film in conventionally known automobiles. Aesthetic coating films are composed of pigments, vehicles, solvents, etc., and the vehicles are mainly polyester/melamine resins.

This polyester resin is composed of a product obtained by reacting a polyhydric alcohol and a polybasic acid by a conventional method, or a product modified by adding about 30% of oil or fat or fatty acid to this product. Melamine resins include n-butylated melamine resins, isobutylated melamine resins, and other melamine resins in which aldehydes such as melamine formaldehyde and paraformaldehyde are added or addition condensation products are etherified with monohydric alcohols having 1 to 4 carbon atoms. is used.

Coloring pigments such as titanium dioxide, carposi black, organic pigments, and extender pigments such as calcium carbonate and barium sulfate are added to this vehicle in an amount of 5 to 60% in the paint formulation.

As mentioned above, this coating film had problems with weather resistance and maintenance of aesthetic appearance.

Acrylic'ft as a vehicle for metallic paints
41J? f and a curing agent are used, and the acrylic resin contains a functional group that can react with an alkyl ester of acrylic acid or methacrylic acid, optionally with other ethylenically unsaturated monomers that can be copolymerized therewith, and with a crosslinking agent. It can be obtained by copolymerizing a monomer having the following by a conventional method.

The coloring agent in this case is mainly made of light-reflecting aluminum or mica foil, and a transparent colored pigment is used in combination with this.

The blending amount of these is about 3 to 30ffi: 1% in the paint.

For these solid and metallic paints, the usual baking method is to use solvents for mold paints, such as aromatic and aliphatic hydrocarbon mixed solvents, alcohols, esters, and ketone solvents with medium to high boiling points. Mix and use as appropriate. Clear paints (■, ■) that protect aesthetic paint films are composed of the following ingredients.

The most preferred clear coating resin for the present invention is a fluorine-containing resin copolymer having hydroxyl groups mixed with a specific acrylic resin and coated on top of a conventional general-purpose top coat to improve the weather resistance of the top coat. In addition to significantly improving solvent resistance and staining resistance, it is also possible to improve, for example, the adhesion of substrates and spear coats without impairing the properties of fluorine-containing copolymers. It is possible to reduce costs without impairing the properties of fluororesin, and the economic effect is also large.

The fluororesin is preferably 40 to 60 mol% of fluoroolefin and 45% of cyclohexyl vinyl ether.
-5 mol%, alkyl vinyl ether 15-5 mol%, and other comonomers 0-30 mol%. As disclosed in the above-mentioned Japanese Patent Publication No. 60-21686, in the fluorine-containing copolymer, if the fluoroolefin content is too low, it is not preferable from the viewpoint of weather resistance, and if it is too high, it is F! There tends to be a problem with the A surface.

Also, a coating film with too low a cyclohexyl vinyl ether content tends to reduce the hardness of the coating film, and a coating film with too low alkyl vinyl ether content tends to reduce the plasticity, so these are undesirable.

Furthermore, it is particularly important to contain hydroxyalkyl vinyl ether in a proportion within the above range from the viewpoint of improving curability without impairing various useful properties as a paint base. In other words, if the hydroxyalkyl vinyl ether content is too high, not only the solubility of the copolymer in organic solvents will decrease, but also the plasticity of the coating film will decrease, and conversely, if the content is too low, the durability and adhesion of the coating film will decrease. Examples of fluoroolefins include perhalon olefins, especially chlorotrifluoroethylene,
Alternatively, tetrafluoroethylene is preferred. As the alkyl vinyl ether, those containing a linear or branched alkyl group having 2 to 8 carbon atoms, and particularly those containing an alkyl group having 2 to 4 carbon atoms, are suitable.

It may contain the fluorine-containing copolymer or comonomers other than the four essential components in an amount not exceeding 30 mol %. Such comonomers include ethylene, propylene, isobutylene, vinyl chloride, vinylidene chloride, methyl methacrylate, butyl acetate, and the like.

The fluorine-containing copolymer is prepared by adding a polymerization medium (for example, an aromatic hydrocarbon such as xylene or toluene, and an ester or ether organic solvent) to a monomer mixture in a predetermined proportion according to a conventional method.
It can be produced by carrying out a copolymerization reaction by allowing a polymerization initiator (for example, a peroxide compound such as benzoyl peroxide and an azo compound such as azobisisobutyronitrile) to act in the coexistence of . The copolymerization reaction temperature is not particularly limited, but it is necessary to maintain a general temperature sufficient to cleave the polymerization initiator.

As the resin used in combination with the fluorine-containing resin copolymer having hydroxyl groups in the clear paint (1), an acrylic resin is preferable.

The acid value of the base resin made of the fluorine-containing resin copolymer and acrylic resin of the clear paint (2) is 10 to 30. Preferably they are 12-25, OH number 45-110, preferably 60-100, Mn 3000-10000, preferably Mn 7500-9000.

When using an amino resin such as a butyl etherified melamine resin as a crosslinking agent for a fluorine-containing copolymer resin, use the former at a solid weight ratio of 80:20 to 60:40, and add a solvent as necessary according to a conventional method. A clear paint (■) containing additives is used.

The acrylic resin is used as a vehicle for clear coatings, and as a combination resin for clear tilI, and can be copolymerized with the ethylene monomer described below according to a conventional method.

” - If used as a rear paint, acid value 10-2
5. Preferably 12-20° OH value 25-60. Preferably it is 30-50, Mn 10,000-25,000, preferably Mn 15,000-22,000.

For example, styrene, α-methylstyrene, 0-methylstyrene, ■-methylstyrene, p-methylstyrene, p-
Aromatic and nyl monomers such as tert-butylstyrene, benzyl acrylate, benzyl methacrylate, acrylic acid or methacrylate esters (methyl acrylate, ethyl acrylate, isopropyl acrylate, n-propyl acrylate, n-butyl acrylate, Isobutyl acrylate, methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, 1ln-propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate,
2-ethylhexyl acrylate, n-octyl acrylate, dodecyl acrylate, lauryl acrylate, 2-ethylhexyl methacrylate, n-octyl methacrylate, dodecyl methacrylate, lauryl methacrylate, sudearyl methacrylate, tridecyl methacrylate, fat and oil fatty acids and an acrylic acid or methacrylic acid ester monomer having an oxirane structure (e.g. an addition reaction product of nistearic acid and glycidyl methacrylate), an addition reaction between an oxirane compound containing an alkyl group of 08 or more and acrylic acid or methacrylic acid Itaconic acid esters (dimethyl itaconate, etc.), maleic acid esters (dimethyl maleate, etc.), fumaric acid esters (
dimethyl fumarate, etc.), acrylonitrile, methacrylatetrile, vinyl acetate, and other ethylenic monomers. In addition, examples of ethylenic monomers having active hydrogen include acrylic acid, droxyethyl,
Droxypropyl acrylate, Droxybutyl acrylate, Droxymethyl methacrylate, Hydroxyethyl methacrylate, Droxypropyl methacrylate,
Ethylene monomers with hydroxyl groups such as droxybutyl methacrylate, N-methylolacrylamide, allyl alcohol, acrylic acid, methacrylic acid, crotonic acid, ethacrylic acid, propyl acrylic acid, isopropylacrylic acid, itaconic acid, maleic anhydride, fumar Examples include ethylenic monomers having carboxyl groups such as acids. The acrylic copolymer resin can be prepared using a general method, for example, by blending the various monomers mentioned above in predetermined proportions.
Obtained by polymerization using conventional methods. For example, a monomer formulation is mixed with a known polymerization catalyst (e.g., azobisisobutyronitrile, benzoyl peroxide, etc.) and a solvent (e.g., xylene, It can be obtained by dropping it into a reaction vessel containing (toluene, mineral spirit, etc.) and aging it.

Amino resin (e.g., butyl etherified melamine resin) is used as a crosslinking agent at a ratio of 80% (solid content weight ratio) to acrylic resin.
: Clear paint I, which is used in a ratio of 20 to 60:40 and is prepared by adding a solvent and, if necessary, additives according to a conventional method.
shall be.

When the resin of clear paint H is thermally cured and an alkyl etherified amino resin is used as a curing agent, the ratio of the copolymer mixture to the alkyl etherified amino resin is preferably 55 to 9515 to 45 on a :ll basis, and Preferably it is 60-80/20-40.

In addition, when using an isocyanate compound as a curing agent, the ratio of the copolymer resin mixture to the isocyanate compound is preferably 0.3 to 1.5, more preferably 0 in molar ratio of isocyanate group/hydroxyl group. .5-1.0
It is.

If the amount of the alkyl etherified amino resin used is too much than the above range, reactions between the alkyl etherified amino resins tend to occur, resulting in a decrease in the plasticity of the coating film, and conversely, if the amount is too small, satisfactory curability may not be obtained. Since the crosslinking density is low, weather resistance, solvent resistance, and stain resistance tend to decrease, which is not preferable.

Examples of the alkyl etherified amine resin include alkyl etherified melamine resins such as methyl etherified, butyl etherified, isobutyl etherified, and methylbutyl mixed etherified melamine resins, urea resins, and benzoguanamine resins.

Note that an acid catalyst (for example, p-
An organic sulfonic acid catalyst such as toluenesulfonic acid) can be added.

On the other hand, if the amount of the isocyanate-based compound is too much than the above range, a large amount of isocyanate will remain inside the resulting coating film, and will react with moisture in the air, reducing weather resistance, adhesion, etc. On the other hand, if it is too small, the mechanical properties, chemical resistance, etc. of the coating film tend to deteriorate, which is not preferable. Examples of the isocyanate compounds include polyisocyanate compounds, and examples of the polyisocyanate compounds include ethylene diisocyanate, propylene diisocyanate, tetramethylene diisocyanate, heisamethylene diisocyanate, phenylene diisocyanate, and isophorone diisocyanate.
In addition, as blocked polyisocyanate compounds,
The polyisocyanate compound as described above is blocked with a blocking agent, and examples of the blocking agent include phenol-based, alcohol-based, mercaptan-based, oxime-based, and imine-based compounds.

In addition to the above-mentioned essential components, the clear paint I and (2) used in the present invention can contain any components commonly incorporated in conventional paint compositions, as long as they do not have the above-mentioned desired properties. Such components include medium to high boiling point aliphatic, alicyclic, aromatic hydrocarbons, esters, ethers, ketones, organic solvents such as alcohols (usually 1 to 90% by weight), and the like. In addition, other conventional additives may be added.

The method of forming a protective layer on an aesthetic paint film in the present invention is to wet a clear paint II and a clear paint ■ consisting of a fluorine-containing copolymer resin having a hydroxyl group and an acrylic copolymer resin on the aesthetic paint film. The method is to apply wet coating one after another, and then simultaneously cure the two coating layers, which is achieved by the following procedure.

Clear paint (2) is applied uniformly according to a conventional method to a dry film thickness of 5 to 15 μm, and after setting for about 2 to 4 minutes, clear paint (2) is applied.

This clear paint (2) is uniformly applied to the undried coated surface of the clear paint (2) according to a conventional method so that the dry film has a thickness of 25 to 40 μm, and after setting for about 10 minutes, it is baked to dry. Standard conditions for baking drying may be 140° C. for 30 minutes.

In the coating film obtained in this way, clear paint I
The coating film shown is the one with clear paint ■.

Below are the coatings of Examples 1 to 3 and the coatings of Metallic Base Comparative Example 1! EII Dandan ------- Coating film composition of Comparative Example 4 Rear coating n-i 蕩-coating! Solid color As a result, good adhesion is ensured between the clear paint and the clear paint (2), and at the same time weather resistance is improved, and maintenance durability associated with waxing etc. is eliminated.

A Acrylic melamine resin metallic base Nippon Paint Co., Ltd. SP-M-80 Silver B Acrylic melamine resin metallic clear Nippon Paint Co. 5P-
0-80 Clear C polyester melamine resin solid color Nippon Bain I- Co., Ltd. Olga-65-White 1-1 Acrylic resin metallic clear Nippon Paint Co., Ltd. SP-M-80 Clear I-2 Fluorine-containing base clear (melamine curing) ) Nippon Paint Co., Ltd. Etalac M-1,0 Clear I-3 Fluorine-containing base clear (urethane hardening)・■-
1 Fluorine-containing top clear (melamine cured) Nippon Paint Co., Ltd. F-Lac 0-10 Clear 11-2 Fluorine-containing top clear (urethane cured)
Examples Table 1-1 Ne10 = No wipe marks Δ = Wipe marks left After wiping the top coat on the - side with white kerosene, the second layer of clear was painted and baked.

Ne2 The baking conditions for each example and comparative example are paint A for decorative coatings.
, B, C, protective layer paint ■-1, ll-1, ll-2
Both were treated at 140°C for 20 minutes.

Table 1-2 Comparative examples of the following margins Table 2 Effects of the invention The present invention provides an aesthetic coating film by forming a protective layer consisting of a clear layer that improves adhesion and a clear layer containing a fluororesin on the aesthetic coating film. This ensures the adhesion of the clear layer containing fluororesin, prevents roughening of the protective layer, and eliminates problems in painting work.

Claims (1)

[Claims] Clear paint I Comprised of a fluorine-containing copolymer resin having hydroxyl groups and an acrylic copolymer resin
1. A method for forming a coating film, which comprises sequentially coating I and I in a wet-on-wet manner, and then simultaneously curing the two coating layers.