JPS6136871B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a vehicle intermediate coating paint suitable for use on a cationic electrodeposited coating as an intermediate coating for a vehicle. Conventionally, intermediate coatings for vehicles are made by mixing resin, melamine resin as a hardening agent, solvent, pigment, and acid catalyst.
It was obtained by uniformly dispersing. This conventional paint has been applied to a vehicle in advance and cured, then applied onto an obtained undercoat film, and then baked to form a paint film.
On the other hand, the undercoat film is usually obtained by electrodeposition using an anionic electrodeposition paint, but compared to that of anionic electrodeposition paint, the undercoat film obtained using a cationic electrodeposition paint is Due to its structure, it inevitably has a high degree of basicity (residual secondary amine, -NH group). If the degree of basicity (residual secondary amine, -NH group) increases, the curing of the melamine-curing paint applied thereon will be inhibited, and in the case of long-term deterioration such as deterioration of water resistance, the cationic electrodeposition coating will form. It has the disadvantage that moisture is present at the interface with the conventional intermediate coating film for vehicles, and the adhesion between the two coating films deteriorates, resulting in a peeling phenomenon of the coating film. Therefore, there is an urgent need in the industry to prevent the above-mentioned peeling. SUMMARY OF THE INVENTION An object of the present invention is to provide a novel intermediate coating for vehicles that eliminates the above-mentioned drawbacks. The purpose of the present invention is to provide a new intermediate coating composition for vehicles, which is different from the conventional intermediate coating composition by containing an adhesion agent consisting of a polyamide resin and a blocked isocyanate-modified polyester resin. This is achieved by creating a chemical bond between the intermediate coating for vehicles and the cationic electrodeposition coating. This invention will be explained in detail below. First, the polyamide resin as used in the present invention refers to a polycondensate of diamine (including derivatives) and dibasic acid (including derivatives), and has a basic amino group. Further, typical examples of the diamine are ethylenediamine,
These include hexamethylene diamine, diethylene triamine, triethylene tetramine, tetraethylene pentamine, pentaethylene, hexamine, propylene diamine, and butylene diamine. Typical examples of the dibasic acids are dicarboxylic acids such as phthalic acid, adipic acid, sebanic acid, malonic acid, succinic acid, fumaric acid, maleic acid, azelaic acid, dodecylsuccinic acid, and dimer fatty acids. be. Furthermore, when using diamines and dibasic acids, it is preferable to select one or more of the above-mentioned diamines and use them depending on the purpose. Blocked isocyanate-modified polyester resin is obtained by reacting isocyanate and polyester resin in advance and blocking this reaction product with a blocking agent. Typical examples of isocyanates used here include m- or p-phenylene diisocyanate, 4,
4′-diphenylmethane diisocyanate, 2,
4′- or 2,6-tolylene diisocyanate,
These are m- or p-xylene diisocyanate, hexamethylene diisocyanate, dimer acid diisocyanate and isophorone diisocyanate. Further, as the polyester resin, one having a number average molecular weight of 500 to 3000 is used. Typical examples of blocking agents include methanol, ethanol, propanol, butanol, hexanol,
These include cyclohexanol, benzyl alcohol, ethylene glycol monoethyl ether, ethylene glycol monobutyl ether, dimethylaminoethanol, diethylaminoethanol, acetoxime, methyl ethyl ketone oxime, acetylacetone, acetoacetate, malonic acid ester, ε-caprolactam, and phenol. and the isocyanate exemplified above,
One or more types of polyester resin and blocking agent are selected and used. In addition, the blending ratio of the adhesion promoter is 0.01 to 0.01 parts by weight of polyamide in 100 parts by weight of the intermediate coating for all vehicles of this invention.
2 parts by weight, blocked isocyanate-modified polyester resin 0.02 to 4 parts by weight, and more preferably,
They are 0.1 to 1 part by weight and 0.2 to 2 parts by weight, respectively. Next, as the resin used in this invention, any well-known paint resin can be used, and although there are no particular restrictions, polyester resins are preferred, particularly urethane-modified polyester resins, oil-free alkyd resins, urethane resins, and phenol-modified resins. and acrylic resin. Typical examples of melamine resins used as curing agents in the present invention include hexamethoxymethylated melamine, butoxybutylated melamine, and mixed etherified melamine. As the acid catalyst, nonylnaphthalenesulfonic acid, dodecylbenzenesulfonic acid, p-toluenesulfonic acid, hydrochloric acid, phosphoric acid, etc. can be used. Next, as the solvent used in this invention, any well-known solvent can be used, but preferably at least two or more solvents selected from the group consisting of a low boiling point solvent of 120°C or less and a high boiling point solvent of 120°C or more are used. It is to be. Next, the term "pigment" as used in this invention is a general term for extender pigments and coloring pigments, and any well-known pigments can be used. Typical examples include calcium carbonate,
Silica, alumina, iron oxide (including red iron oxide),
These include aluminum silicate (clay, kaolin, etc.), asbestos, hydrated magnesium silicate (including talc), barium sulfate, glass beads, zinc white, and titanium oxide. In addition, intermediate coatings for vehicles are required to have a higher film thickness than undercoat and topcoat paints, but in this case, among the above pigments, calcium carbonate, silica, iron oxide, aluminum silicate, and titanium oxide are used. and zinc white are preferred. When used, it is preferable to select and use at least two or more of these pigments and adjust the particle size distribution of the pigments. This particle size distribution shall be 30 parts by weight or less for pigments distributed within the range of 0.01 to 5μ, assuming 100 parts by weight of the total pigment, and 35 parts by weight or more for pigments distributed within the range of 5 to 30μ, and 30 to 30 parts by weight. Favorable results are obtained when the amount of pigment distributed within the 70μ range is 25 parts by weight or less. By using a combination of a pigment with a small particle size and a pigment with a large particle size, a smooth coating film can be obtained. In addition, the blending ratio of the pigment of this invention is 100 to 100 parts by weight of the resin.
The amount is 500 parts by weight, preferably 150 to 400 parts by weight. As mentioned above, the six ingredients essential to this invention are a resin, a melamine resin as a hardening agent, a pigment, an acid catalyst, a solvent, and an adhesion imparting agent. foaming agent,
If a leveling agent, an anti-settling agent, etc. are used in combination, an even more preferable intermediate coating for vehicles can be obtained. Normally, if defoaming is completely achieved, a smooth surface of the coating film can be obtained, so defoaming agents often double as leveling agents. , antifoaming agents such as acrylic copolymers, etc.
Preferably, it is a non-silicone antifoaming agent. Examples of anti-settling agents include fatty acid ester polymers, synthetic waxes, and silica-based anti-settling agents. If these compounding agents are used in too large a quantity, the properties will be impaired, so it is better to limit the amount to 0.01 to 5 parts by weight per 100 parts by weight of the resin. When the novel vehicle intermediate coating obtained by this invention is applied to a cationic electrodeposited coating film and baked to form a film, the block isocyanate-modified polyester resin and the cationic electrodeposited The basic groups (residual secondary amines, -NH groups) of the deposited coating form chemical bonds and form a strong bond, which improves the adhesion between the two coatings by several degrees. The reason why polyamide resin is blended as an adhesion agent is that the free isocyanate groups of the blocked isocyanate-modified polyester resin (isocyanate groups that do not chemically bond with the -NH groups remaining in the cationic electrodeposition coating) and the curing agent melamine. This is to prevent the melamine resin from reacting with the resin, reducing the amount of melamine resin crosslinked with the resin, reducing the crosslinking density, and impairing the flexibility and elasticity of the coating film. Although the cationic electrodeposited vehicle intermediate coating composition of the present invention can be used for any vehicle, it is particularly effective in fields that require severe working conditions and performance, such as automotive intermediate coating compositions. (Example 1) 13.2 parts by weight of polyester (oil-free alkyd) resin with a non-volatile content of 60% (Betsucolite M-6003, manufactured by Dainippon Ink and Chemicals Co., Ltd.) and a non-volatile content of 70%.
% of butoxybutylated melamine resin (Yuban 20SE, manufactured by Mitsui Toatsu Chemical Co., Ltd.) as a hardening agent and 6.1 parts by weight of calcium carbonate with a particle size distribution of 0.01 to 3μ.
6.3 parts by weight, 44.3 parts by weight of silica with a particle size distribution of 1 to 50 parts by weight, 2 parts by weight of titanium oxide, and benzoin.
1.0 parts by weight, 0.6 parts by weight of dodecylbenzenesulfonic acid (catalyst), 0.2 parts by weight of acrylic resin (antifoaming agent), 10.0 parts by weight of cyclohexanone, 13.3 parts by weight of xylol, 2.0 parts by weight of n-butanol, and polyamide resin (Vermicide 125, Henkel Nippon Co., Ltd.) 0.3 parts by weight and blocked isocyanate modified polyester resin (Chemiflex 315×
A, 1.0 part by weight of an adhesion agent consisting of 0.7 parts by weight of Sanyo Chemical Industries, Ltd.) was blended, stirred and mixed with a disper for 15 minutes, passed through a sand mill and dispersed, and then defoamed at a reduced pressure of approximately 70 cmHg. An intermediate paint for vehicles was obtained. (Examples 2 and 3) The blending ratio of the adhesion imparting agent was 0.7 parts by weight of polyamide resin (same as in Example 1) and blocked isocyanate-modified polyester resin (same as in Example 1).
1.4 parts by weight and polyamide resin (same as Example 1)
1 part by weight, blocked isocyanate modified polyester resin (same as Example 1), 2 parts by weight, polyester (oil-alkyd) with a non-volatile content of 60%.
An intermediate coating for a vehicle was obtained under the same compounding conditions and in the same manner as in Example 1, except that the blending ratio of the resin (same as in Example 1) was 12.2 parts by weight and 11.2 parts by weight. These were named Examples 2 and 3 in that order. (Comparative Example 1) Same as Example 1 except that the adhesion imparting agent was not blended and the blending ratio of polyester (oil-free alkyd) resin with a non-volatile content of 60% (same as in Example 1) was 14.2 parts by weight. Comparative Example 1 was obtained by obtaining an intermediate coating for a vehicle using the same compounding conditions and the same method. (Comparative Example 2) An intermediate coating for a vehicle was prepared under the same compounding conditions and in the same manner as in Example 1, except that 1 part by weight of polyamide resin (same as in Example 1) was blended instead of the adhesion imparting agent. This was designated as Comparative Example 2. In order to examine the adhesion performance of the vehicle intermediate paints obtained in Examples 1 to 3 and Comparative Examples 1 to 2, each paint was applied by airless spraying onto an iron plate that had been undercoated by cationic electrodeposition. After coating and leaving at room temperature for 5 minutes, pre-cure at 110℃ for 7 minutes, and after-cure at 140℃ for 30 minutes to create a test piece, according to JISK5400.
A 2 mm cross-cut test was conducted immediately after the test piece was prepared (initial stage) and after being immersed in 40°C hot water for 10 days (after water deterioration). The results are shown in Table 1 below.

[Table] In addition, it was applied with an airless spray onto an iron plate that had been primed by cationic electrodeposition in advance, left for 3 days (left between steps), pre-cured at 110℃ for 7 minutes, and then post-cured at 140℃ for 30 minutes. A test piece was prepared by curing, and a 2mm goblin test was conducted after water deterioration according to JISK5400, and there were no abnormalities in any of the vehicle intermediate paints obtained in the example. , and those obtained in the comparative examples all showed abnormalities. As is clear from the above results, the present invention provides an extremely practical intermediate coating for vehicles that has good adhesion performance to a coating film formed by cationic electrodeposition.

Claims (1)

[Scope of Claims] 1. An intermediate coating for vehicles for cationic electrodeposited coatings, which comprises at least a resin, a melamine resin as a hardening agent, a solvent, a pigment, an acid catalyst, and an adhesion promoter; The intermediate coating for a vehicle for use in a cationic electrodeposition coating is characterized in that the intermediate coating is composed of a polyamide resin and a blocked isocyanate-modified polyester resin. 2. The cationic electrodeposition coating film according to claim 1, wherein the blending ratio of the polyamide resin and the blocked isocyanate-modified polyester resin is 100 to 500 parts by weight of the blocked isocyanate-modified polyester resin to 100 parts by weight of the polyamide resin. Intermediate paint for vehicles. 3. The adhesion imparting agent is blended in a proportion of 0.01 to 1 part by weight of polyamide resin and 0.02 to 2 parts by weight of blocked isocyanate-modified polyester resin in 100 parts by weight of the cationic electrodeposited vehicle intermediate coating. A cationic electrodeposited intermediate coating for vehicles according to claim 1. 4 The amine value of the polyamide resin is 150 to
250, the intermediate coating for a vehicle for a cationic electrodeposition coating according to claim 1, wherein the blocked isocyanate-modified polyester resin has an NCO content of 2 to 10%.