JPH0346188B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for forming a high-thickness chipping coating film for a two-coat one-paste coating method suitable for vehicles, chemical plants, and building materials. [Prior Art] Conventionally, as a high film thickness type paint made of a resin and a pigment, a paint in which the type, amount, particle size, etc. of the pigment is specified has been disclosed (Japanese Patent Laid-Open No. 57855/1983). In addition, as a high film thickness type paint, the baking process is
There is a method of baking in two stages: 5 to 30 minutes at a temperature of 130°C and a further 10 to 50 minutes at a temperature of 120 to 180°C (Japanese Patent Application Laid-open No. 58564/1983). There is also a disclosure of a paint with a high film thickness in which benzoin is added to the paint (Japanese Unexamined Patent Publication No. 167766/1983). Sagging and flaking (foaming) caused by applying high film thickness paint using the above methods.
We are trying to improve sexual performance. Traditionally, this type of paint was designed for two coats and two bakes, and when baked after applying an intermediate coat on top of a high film thickness paint without pre-curing (pre-baking) as in the two-coat, one-bake method, the painted surface Fine irregularities occur on the surface, damaging the appearance of the painted surface. In addition, the two-coat, one-bake method for obtaining a good painted surface appearance requires a setting time of at least 30 minutes after the paint is applied, which reduces productivity because it removes wrinkles and scatters the solvent after applying the high-film thickness paint. There's a problem. In addition, in order to reduce the amount of foxing that gets caught up during painting and to prevent the solvent from scattering, the distance from the object to be coated must be kept low during painting.
Spray painting must be done from a distance of at least 50 cm. There is also a method of increasing the heating residue, but this increases the viscosity of the paint and causes other paint film defects such as underarms, blistering, etc.
Dustiness appears, which is undesirable. [Problems to be Solved by the Invention] When the above-mentioned high film thickness paint and intermediate coating paint are applied using the two-coat, one-bake method, it is possible to prevent appearance defects such as unevenness on the surface of the paint film and improve the quality of the paint film. The purpose is to create a coating film with improved leveling properties. [Means for Solving the Problems] The method for forming a high-thickness chipping coating film of the present invention contains a methylated melamine resin or a mixture of a methylated melamine resin and a butylated melamine resin as a hardening agent, and the pigment concentration (hereinafter abbreviated as PWC)
A first step of forming a first wet coating film by applying a high film thickness paint containing a non-polar medium boiling point solvent that is 60% by weight or more and less than 70% by weight, and on the first wet coating film. a second step of applying an intermediate coating containing a butylated melamine resin as a hardening agent to form a second wet coating film, and integrally baking and curing the first wet coating film and the second wet coating film. and a third step of causing. The method for forming this high-thickness chippig coating consists of a first step of applying a high-thickness paint, a second step of applying an intermediate coat, wet-on-wet, and a third step of baking. to form a cured coating film. For this reason, the curing agent for high film thickness paints is mainly methylated melamine resin, which has a faster curing reaction rate than the commonly used butylated melamine resin. In other words, in order to prevent traces of bubbles, solvents, and reactive gases in the chip material of high film thickness paint from remaining on the intermediate coat surface that is applied wet-on-wet to the upper surface of the paint film, the curing reaction speed is increased. By blending a methylated melamine resin with a fast rate of oxidation, it is possible to cure a high-thickness coating film before the intermediate coating film has not yet cured. This allows a smooth chipping-resistant coating to be formed. If the pigment concentration (PWC) is less than 60% by weight, wrinkles and sagging properties will deteriorate, and if PWC exceeds 70% by weight, chipping resistance and painted surface will deteriorate, which is not preferable. Non-polar medium-boiling point solvents include trimethylbenzene, dimethylethylbenzene, tetramethylbenzene, etc. alone or in combination, with a boiling point of 160 to 190℃.
can be used. The coating film using high film thickness type paint has a film thickness of 100~
It is 300μ. The intermediate coating applied in the second step is an alkyd-based coating in which the curing agent is a butylated melamine resin, which has a slower reactivity than the methylated melamine resin used in high-film thickness coatings. This alkyd paint is a general automotive interior paint and can be used in any color as long as the curing agent is the above-mentioned butylated melamine resin. The coating film formed by this intermediate coating is formed to a thickness of 20 to 50 μm. The main components of high film thickness type paints are resins, pigments, and solvents, and if necessary, necessary antifoaming agents, antisettling agents, leveling agents, etc. may be added to the above components. As the resin component, any well-known coating resin can be used without any particular limitation, but polyester resins, oryl free-alkyd resins, urethane resins, acrylic resins, etc. are preferred. As the pigment, necessary extender pigments and coloring pigments are selected and used, and specifically, calcium carbonate, silica, iron oxide, barium sulfate, aluminum silicate, titanium oxide, zinc oxide, etc. can be used. [Effects of the Invention] In the method for forming a high-thickness chipping coating of the present invention, the curing agent is a methylated melamine resin or a mixture of a methylated melamine resin and a butylated melamine resin, and the PWC is 60 to 60. Applying a paint containing less than 70% by weight of a non-polar medium-boiling solvent;
A paint whose curing agent is a butylated melamine resin is applied as an intermediate paint by a two-coat, one-bake method.
The curing properties of high-thickness paints are very fast as the intermediate coat is applied wet-on-wet on the top surface, so it can compensate for defects such as unevenness on the surface of high-thickness paints, and eliminate wrinkles, sagging, dust, etc. A painted surface with excellent gloss and image clarity is formed. Furthermore, the setting time for the painted object is about 2 minutes, which improves productivity, and the coating distance is only 30 cm, which has the advantage of being able to be used with existing equipment. [Example] The present invention will be explained below with reference to Examples. Example 1 85 parts by weight of polyester resin (Betsucolite M-6205, manufactured by Dainippon Ink Co., Ltd.) and methylated melamine resin (Cymel 301, manufactured by Mitsui Toatsu Chemical Co., Ltd.) as a curing agent.
20 parts by weight, pigment silica (Toyane silica, Marueju Co., Ltd.)
) 100 parts by weight, pigment titanium oxide (Tipaque,
R-680, manufactured by Ishihara Sangyo Co., Ltd.) 10 parts by weight, pigment calcium carbonate (MC-S, manufactured by Maruo Calcium Co., Ltd.)
7 parts by weight, additive BYK-052 (manufactured by Bikkumarinckrodt), 1 part by weight each of Nakyur #3525 (manufactured by King), solvent volume ratio of trimethylbenzene: dimethylbenzene: tetramethylbenzene = 1:2:7 45 parts by weight of the product (manufactured by Maruzen Sekiyu Co., Ltd.) in a disper.
The mixture was mixed and stirred for 15 minutes, dispersed for 20 minutes using a sand grinder, and after adjusting the viscosity, defoamed for 10 minutes under reduced pressure of about 70 mmHg to produce a high film thickness type paint. The PWC of this paint is 65
It was in weight%. The intermediate paint used was an oil-free alkyd resin paint (manufactured by Kansai Paint Co., Ltd.) containing butylated melamine resin as a hardening agent. Painting method: Airless apply the high film thickness paint above on a vertical iron plate to a film thickness of approximately 100 to 350 μm. After setting for 2 minutes, apply wet-on-wet intermediate coating to create a film of approximately 40 μm. After forming a thick intermediate coat and setting for 10 minutes, apply at a temperature of 140℃.
I baked it for 30 minutes. Evaluation of paint film Flank film thickness: Maximum film thickness without flakes (including blistering) on the painted surface after baking (unit: μ) Sagging film thickness: Maximum film thickness without sagging on the painted surface after baking (unit: μ) Dust property: The conspicuousness of the dust when it is scattered.Glossiness: Reflective gloss at 60 degrees using a gloss meter (unit: %).Visibility: PGD value using a sharpness tester.Results of evaluating the above five items. are shown in Table 2. Both the armpit film thickness and the sagging film thickness were 350μ, dust was inconspicuous, the gloss was 96%, and the image clarity was 0.5, resulting in a high film thickness coating. Examples 2 to 5 High film thickness type paints were prepared in the same manner as in Example 1, with the proportions shown in Table 1.

【table】

【table】
Unit: parts by weight

[Table] *○...Dust is not noticeable ×...Dust is noticeable However, in Example 3, the curing agent was methylated butylated melamine resin (Cymel 1116, manufactured by Mitsui Toatsu Co., Ltd.).
In Example 4, the composition ratio of the solvent was trimethylbenzene:dimethylbenzene:tetramethylbenzene=
The same material as in Example 1 was used except that the ratio was 1:6:3. The results of coating and evaluation in the same manner as in Example 1 are shown in Table 2. The coating surface was almost the same as in Example 1. Comparative Example A paint was prepared in the same manner as in Example 1, and the paint was applied.
The coating film was evaluated. The blending ratios are shown in Table 1, and the evaluation results are shown in Table 2. Comparative Example 1 uses a conventional butylated melamine resin as a hardening agent for a high film thickness type paint.
The procedure was the same as in the example except that the material (manufactured by Co., Ltd.) was used. Compared to Example 1, Comparative Example 1 has a lower gloss level of 85%. Comparative Example 2 has the same composition as Example 1 except that the solvent was replaced with DBE (manufactured by DuPont Chemical Co., Ltd.) whose main component is a polar solvent succinate ester. In Comparative Example 2, the glossiness is even worse than in Comparative Example 1. In Comparative Example 3, the compounded substances were the same as in Example 1, but the pigment concentration PWC was 55, which was a smaller value than that of the present invention.
% by weight, the coating film, armpit film thickness, and sagging film thickness are small, that is, armpit and sagging easily occur. Comparative Example 4, on the other hand, has a PWC value larger than that of the present invention, and has good wrinkles and sagging, but poor dust properties, low gloss, and low image clarity. Therefore, by using a methylated melamine resin curing agent and a non-polar medium boiling point (160 to 190°C) solvent for high film thickness chipping paints, we have developed a high film thickness with a PWC of 60 to 70% by weight. It has been shown that a good chipping coating with a high film thickness can be obtained by a two-coat, one-bake coating method using an alkyd resin coating containing a mold coating and a butylated melamine resin curing agent as an intermediate coating.

Claims (1)

[Claims] 1 Contains a methylated melamine resin or a mixture of a methylated melamine resin and a butylated melamine resin as a curing agent, and has a pigment concentration (hereinafter abbreviated as PWC).
A first step of forming a first wet coating film by applying a high film thickness paint containing a non-polar medium boiling point solvent that is 60% by weight or more and less than 70% by weight, and on the first wet coating film. a second step of applying an intermediate coating containing a butylated melamine resin as a hardening agent to form a second wet coating; and baking and curing the first wet coating and the second wet coating integrally. A method for forming a high thickness chipping coating film, comprising a third step. 2. The method for forming a high thickness chipping coating according to claim 1, wherein the non-polar solvent has a boiling point of 160 to 190°C.