JPH03179067A - Coating composition - Google Patents

Abstract

PURPOSE:To improve the adhesiveness of a top coating film by compounding a vinylic copolymer contg. specific epoxidized acrylic monomer units into a coating compsn. CONSTITUTION:An acrylic monomer having no functional group other than a double bond, a carboxylated acrylic monomer, a hydroxylated acrylic monomer, an epoxidized acrylic monomer, and other vinylic monomers are copolymerized in the presence of a radical polymn. initiator in an org. solvent at 130-150 deg.C for 2-3hr to give a vinylic copolymer having an average mol.wt. of 1000-50000 and contg. 30-60wt.% epoxidized acrylic monomer units. The copolymer is compounded in an amt. of 40-80wt.% (based on the coating film- forming component) into a coating compsn.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention is a two-tone paint coating for automobiles (painting specification in which two types of top coats are used to create two colors). The present invention relates to a coating composition that can be used for MfJL films and the like.

<Conventional technology> In recent years, in the field of automobile painting, there has been a demand for high definition and the development of new designs that include color.In the conventional top coating process for automobile painting, most of the coatings are monotone specifications consisting of a single color. However, from a design perspective, there is a gradual increase in two-tone specifications that use two types of top coats.

The method for creating this two-tone paint film is to first apply and bake a top coat that is applied only to vertical surfaces (becomes the lower layer paint film), then mask off the part that will become the lower layer paint film, and then The entire horizontal area from the top of the surface is painted and baked with a different type of top coat to form the upper layer), and the masking is finally removed. The problem with this two-tone specification is that the lower coating film and the upper coating film have poor adhesion between the eyebrows, and peeling occurs around the inside of the door or at the steps. Currently, the top coats for automobiles include IC/IB type solid (generally a polyester/melamine baked-on type), 2C/IB type metallic solid pearl (generally an acrylic/melamine baked-on type base coat and clear). -painted with w) and 3C/2
It is classified as type B pearl (generally, an acrylic/melamine baking type pearl base and clear are applied W-O-W on a polyester/melamine baking type color base coating and then baked). The combination of two types of topcoat for two-tone specifications is selected from among these, but in terms of adhesion, it is 2C/IB or 3G/2B type, which uses acrylic/melamine baking type clear as the lower layer coating, and the upper layer coating. is Ic
/IB type solid combinations tend to decrease in particular.

Common techniques for lower layer coatings to improve the adhesion of upper layer coatings include suppressing coating hardness (for example, lowering the acrylic/melamine resin ratio and controlling crosslinking density) and controlling the number of residual functional groups in the coating ( For example, the number of hydroxyl groups or carboxyl groups may be increased to serve as a crosslinking point with the upper coating film. However, the former method tends to result in a decrease in chemical resistance and gasoline resistance, while the latter method results in a decrease in water resistance and weather resistance. Therefore, in the prior art described above, it is difficult to find a balance to improve the adhesion of the two-tone specification formed by the 2C/IB or 3G/2B type lower layer coating and the IC/IB type solid upper layer coating. This is a very difficult problem.

<Problems to be Solved by the Invention> The purpose of the present invention is to improve the upper coating film in two-tone specifications (especially when IC/IB solid is used) without impairing chemical resistance, gasoline resistance, water resistance, and weather resistance. ) providing improved adhesion of the undercoat (especially 2C/IB or 3C/2
The object of the present invention is to provide a coating composition that can form acrylic/melamine-type clear paints (B), etc.

<Means for Solving the Problems> According to the present invention, a vinyl copolymer having an average molecular weight of 1,000 to 50,000 and containing 30 to 60% by weight of an epoxy group-containing acrylic monomer is included in the coating film forming component. 40-80
A coating composition is provided, characterized in that the composition is blended in a weight percent.

The present invention will be explained in more detail below.

The coating composition of the present invention is characterized by containing a specific amount of a specific vinyl copolymer as a resin component.

The vinyl copolymer used in the coating composition of the present invention has an average molecular weight of 1,000 to 50,000 and contains 30 to 60% by weight of an epoxy group-containing acrylic monomer. If the average molecular weight is less than 1,000, the coating film hardness and water resistance are insufficient, and if it exceeds 50,000, the two-tone adhesion is insufficient, and the content of the epoxy group-containing acrylic monomer is 30% by weight. If it is less than 60% by weight, the two-tone adhesion effect will be insufficient, and if it exceeds 60% by weight, water resistance and weather resistance will decrease, so it is necessary to keep the content within the above range. The epoxy group of the epoxy group-containing monomer is ring-opened when the resin component is cured and remains as a secondary hydroxyl group, so when used for two-tone specifications, etc.
Adhesion with the upper coating film can be increased.

Examples of vinyl monomers constituting the vinyl copolymer include unsaturated double monomers such as methyl (meth)acrylate, ethyl acrylate, butyl methacrylate, octyl (meth)acrylate, dodecyl (meth)acrylate, and octadecyl (meth)acrylate. Acrylic monomers that have no functional groups other than bonds; Acrylic monomers that contain carboxyl groups such as acrylic acid and methacrylic acid;
Contains hydroxyl groups such as 2-hydroxyethyl (meth)acrylate, hydroxypropyl (meth)acrylate, the reaction product of 2-hydroxyethyl methacrylate and caprolactone (trade name: "Plaxel FM Nanatsuma" manufactured by Daicel Industries, Ltd.) Acrylic monomers containing epoxy groups such as glycidyl (meth)acrylate; Esters of maleic acid and monohydric alcohol; Others such as styrene, α-methylstyrene, vinyl acetate, vinyl chloride, etc. vinyl monomers can be preferably used.

In order to produce the vinyl copolymer used in the present invention by FA, the above-mentioned vinyl monomer is subjected to solution polymerization in an organic solvent in the presence of a radical polymerization initiator, preferably with
It can be produced by heating at 50°C and carrying out a polymerization reaction for 2 to 3 hours. Examples of the organic solvent include toluene, xylene, and the product name "Turupetz #100".
Aromatic hydrocarbon solvents such as J (manufactured by Exxon Chemical Co., Ltd.); ester solvents such as ethyl acetate, butyl acetate, ethylene glycol monoethyl acetate, propylene glycol monomethyl ether acetate; methyl isobutyl ketone, methyl amyl ketone, etc. ketone solvents; alcohol solvents such as butyl alcohol and amyl alcohol;
Ether alcohol solvents such as ethylene glycol monobutyl ether can be used, and as the polymerization initiator, benzoyl peroxide, lauroyl peroxide, t-butyl peroxybenzoate, azobisisobutyronitrile, etc. can be used.

In the present invention, the blending ratio of the vinyl copolymer is as follows:
The amount is in the range of 40 to 80% by weight in the film-forming components of the coating composition. If the blending ratio is less than 40% by weight, the water resistance, weather resistance, and two-tone adhesion will not be sufficient, and if it exceeds 80% by weight, the weatherability and water resistance will not be sufficient, so it is necessary to keep it within the above range. be. Here, the coating film-forming components are:
These include resins, pigments, additives, etc.

In the coating composition of the present invention, the vinyl copolymer 100
Up to 70 parts by weight, preferably up to 50 parts by weight, based on parts by weight, of crosslinking agent can be added. Crosslinking agent: 70
If the amount exceeds 1 part by weight, the weather resistance, water resistance, and two-tone adhesion of the coating film will deteriorate, which is not preferable. The crosslinking agent can be selected depending on the type of vinyl copolymer used in the present invention.6 For example, when the vinyl copolymer uses an acrylic monomer having a hydroxyl group, as the crosslinking agent, Polyisocyanate compounds, amino resins, etc. are suitable.

Examples of such polyisocyanate compounds include hexamethylene diisocyanate, inphorone diisocyanate, methylcyclohexane-2,4-(or-
2,6-)diisocyanate, 4,4-methylenebis(
diisocyanates such as cyclohexyl isocyanate, or adducts of each of these diisocyanates with polyhydric alcohols such as ethylene glycol and trimethylolpropane, biurettes added with water, or polymers of these diisocyanates, and Examples include blocked isocyanate compounds obtained by blocking each of the above polyisocyanate compounds with a lower-hydric alcohol, ε-caprolactam, or the like. In addition, examples of the amino resin include resins obtained by adding formaldehyde to melamine, benzoguanamine, etc., and then etherifying it with a monohydric alcohol having 1 to 4 carbon atoms. be able to. Furthermore, when using an acrylic monomer having a carboxyl group as the vinyl copolymer, a polyvalent epoxy compound etc. can be used as a crosslinking agent. When using a monomer, a polyhydric carboxylic acid compound or the like can be used as a crosslinking agent.

In the coating composition of the present invention, in addition to the above-mentioned components, a solvent, a pigment, an additive, etc. can be added as necessary. Further, other resins having compatibility such as Agril resin can be added within a range that does not adversely affect the effects obtained by the present invention.

The coating composition of the present invention can be used as a lacquer-type coating without a crosslinking agent as long as it contains the vinyl copolymer.
It can also be used as a clear paint that does not contain pigments.

The objects to be coated when using the coating composition of the present invention include metals,
Examples include various materials such as synthetic resin, wood, glass, and concrete, as well as automobiles and home appliances.

It can be used for a variety of purposes such as building materials and pre-coating metals.

<Effects of the Invention> The coating composition of the present invention exhibits excellent coating film hardness, scratch resistance, and stain resistance without impairing weather resistance and water resistance, and furthermore, has extremely good two-tone adhesion. , can be used for a variety of painting purposes.

<Example> Next, the present invention will be specifically explained using a synthesis example, an example, and a comparative example. Hereinafter, all parts and percentages are based on weight unless otherwise specified.

1 in a flask equipped with a stirrer, a reflux condenser, and a thermometer.
Based on the formulation of Synthesis Example 1 shown in Table 1.

80.0 parts of xylene was charged and the temperature was raised to 140°C. Then, based on the formulation shown in Table 1, the following monomers and polymerization initiator were added dropwise at 140°C over 3 hours.

Glycidyl methacrylate 30.0 parts Styrene 30.0 parts n-butyl methacrylate 10.0 parts Dodecyl methacrylate
10.0 parts Praxel FM-2*)
20.0 parts t-butyl peroxybenzoate 1.8
Part) Daicel Chemical Industries, Ltd. 1a, trade name, 2-hydroxyethyl methacrylate 1 mol and caprolactone 2
Reaction product with moles.

Next, 0.5 part of t-butyl peroxybenzoate was added, and the reaction was further continued at 140°C for 2 hours to obtain a resin solution having a heating residue of 55.4% and a number average molecular weight of 4900 as shown in Table 1.

The same reaction apparatus as in Synthesis Example 1 was used, except that the solvent, monomer, and polymerization initiator shown in Table 1 were used as planned.

The reaction was carried out in the same manner as in Synthesis Example 1. Obtained 1-6
Ratios 1 to 6 With respect to the resin solutions obtained in each of the above synthesis examples, paints were prepared using vR according to a conventional paint-forming method at the blending ratios shown in Table 2. The resulting paint was coated with Bonderite 0311.
A test piece was obtained by coating a steel plate treated with No. 4 to a dry film thickness of about 30 μm and baking it at 140° C. for 30 minutes. Next, performance tests were conducted regarding gloss, water resistance, weather resistance, and two-tone adhesion shown in Table 2. The results are summarized in Table 2. The measurement methods for each performance test are shown below.

According to JIS K 5400, 6, 7 60 degree specular gloss.

120 in a humidity tester with a folding book stand at a temperature of 45℃ and a relative humidity of 100%.
After standing for a period of time, it was judged as follows.

○ No abnormality × If even the slightest blister occurs, the color difference (ΔE) after being exposed to a sunshine weather meter for 1000 hours according to JIS D 0205, 7.6 accelerated weathering test method was determined as follows.

○ ΔE is within 2.0 × ΔE is 2.0 or more Two-tone 1 For each test piece obtained in Examples 1 to 6 and Comparative Examples 1 to 6,
IC/IB solid “Melami 41” manufactured by NOF Corporation
500B505. Product name: Approximately 30μm dry film thickness
After baking at 140° C. and allowing it to stand for 24 hours, a cross cut was made with a knife and a cellophane peel test was performed, and the results were evaluated as follows.

O No abnormality 7-13 Ratio 7-11 Paints were prepared from the resin solutions obtained in each of the synthesis examples described above according to a conventional paint-forming method at the blending ratios shown in Table 3. The resulting paint was bonderite #3114.
Paint the treated steel plate to a dry film thickness of approximately 30 μm,
After standing for 7 days at 20°C and 75% relative humidity, the weather resistance and water resistance tests shown in Table 3 were conducted in the same manner as in Examples 1 to 4, and the pencil hardness test was conducted according to JIS D 0202, 8, 10 pencil scratch test. I followed. As is clear from the results shown in Table 2, Examples 1 to 6 using the coating compositions of the present invention have excellent gloss, water resistance, and weather resistance, and are also excellent in two-tone adhesion. It turns out that there is.

Furthermore, as is clear from the results in Table 3, Examples 7 to 13 using the coating compositions of the present invention were found to exhibit excellent hardness, weather resistance, and water resistance.

Claims (1)

[Scope of Claims] 1) A vinyl copolymer having an average molecular weight of 1,000 to 50,000 and containing 30 to 60% by weight of an epoxy group-containing acrylic monomer is blended in an amount of 40 to 80% by weight in the coating film forming components. A paint composition characterized by: 2) Claim 1 characterized in that it contains 70 parts by weight or less of a crosslinking agent based on 100 parts by weight of the vinyl copolymer.
Paint composition as described.