JPS59191769A - Thermosetting coating - Google Patents

Abstract

PURPOSE:To provide thermosetting coatings for two-coat and one-bake, by incorporating cellulose acetate butyrate resins (CAB), melamine resins, CAB/melamine resin co-condensates, and acrylic resins having reactivity with melamine resins, as vehicles. CONSTITUTION:CAB and melamine resins are caused to react in a solvent (e.g., methyl isobutyl ketone) to form a soln. of CAB and melamine resins contg. CAB/melamine resin co-condensates as a part. Then, an acrylic resin (or polyester resin) having functional groups capable of crosslinking with the melamine resin is mixed with said resin soln. to yield thermosetting coatings contg. resin compsns. comprising 30-87pts. crosslinkable said acrylic resins (A), 3-40pts. CAB(B), and 10-40pts. melamine resin (C) (wherein 3pts. or more components B and C each present in a form of co-condensate).

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a thermosetting paint containing as a vehicle a resin composition containing a main resin such as an acrylic resin or a polyester resin, and a melamine resin and a cellulose acetate butyrate resin (hereinafter abbreviated as CAB). Regarding.

The so-called two-coat, one-bake coating, which is applied using a wet-on-wet method, is widely used for painting automobiles and the like, especially for metallic coatings. In this case, when applying wet-on-wet clear paint over base paint,
The blending of the base paint and clear paint causes poor finishes such as color unevenness in the appearance of the finished paint film and decreased image clarity. Therefore, as a method to eliminate this compatibility, the compatibility of the main resins of the base paint and clear paint is made worse by, for example, making the clear resin non-polar and the base resin polar, but as a result, melamine In the hardening type, the compatibility between the base resin and melamine resin deteriorates, and the degree of crosslinking of the base resin decreases.
This causes a decrease in the water resistance of the base coating film and delamination between the base coating film and the clear coating film.

Japanese Patent Publication No. 49-38005 proposes mixing CAB into the base paint. However, although this may solve the problem of compatibility, the main resin of the base paint and CA
Main resins that can be used are limited due to compatibility with B. In particular, it has poor compatibility with styrene-containing acrylic resins.

Therefore, JP-A-55-13347] proposed graft polymerization of CAB Niacrylic monomer, and
Although we are trying to solve the problem of compatibility with the main resin,
The problem of compatibility with melamine resins still remains.

The present invention utilizes the fact that CAB and melamine resin are co-condensed in an organic solvent in the presence of an acid catalyst, and the main resin and CAB
In a system consisting of a resin and a melamine resin, the above-mentioned problems have been successfully solved by allowing at least a portion of the CAB resin and the melamine resin to exist as a co-condensate of both.

According to the present invention, in terms of solid content ratio, (a) acrylic resin or polyester resin having a functional group capable of crosslinking with melamine resin 3 to 87 parts (+)) cellulose acetate butyrate) resin 3
(c) 10 to 40 parts of melamine resin in such proportions that the total amount is 100 parts, of which (b) at least 3 parts of cellulose acetate butyrate;
(C) at least 3 parts of the melamine resin are present in the form of a co-condensate with cellulose acetate butyrate; A thermosetting paint is provided.

The thermosetting paint of the present invention can be used in combination with a suitable rear paint.
When used as a base paint that is applied in one coat and bake, the compatibility with the clear paint is eliminated, and the compatibility of CAB with the melamine resin and main resin within the base paint is improved. and sharpness), and the water resistance of the coating film is also improved. The paint of the present invention can also be used as a top coat, in which case dripping of the paint can be prevented.

CAB is commercially available in various grades depending on its viscosity and degree of substitution, but generally those with good solubility and low viscosity, such as EAB-551-0, 2, EAB-3,
81-0, 1 etc. are preferred.

There are no particular restrictions on the melamine resin as long as it is one that is normally used for thermosetting paints.

Co-condensation of CAB and melamine resin is carried out by dissolving CAB in a solvent such as methyl isobutyl ketone (MIBK), adding an acid catalyst such as phthalic anhydride if necessary, adding melamine resin to it, heating it, and carrying out the reaction. You can get it.

The ratio of CAB and melamine resin is selected in the range of 9=1 to 1:9 by weight. If the proportions of both are appropriately balanced, all of the CAB and melamine resin in the resin composition may be of the co-condensed type; otherwise, the missing components may be of the non-co-condensed type. It may be added to the resin composition. However, if the proportion of these non-cocondensed table-type components in the resin composition becomes excessive, the compatibility will be impaired, so the proportion of co-condensation type CAB and melamine resin in 100 parts by weight of the resin composition is 3 to 40 parts by weight, respectively. It must be a department. The weight ratio of total CAB and total melamine resin in the resin composition is determined to be 100% of the composition, respectively, in view of the degree of conformity elimination by CAB and the required degree of crosslinking of the main resin with melamine resin.
It should be 3 to 40 parts by weight and 10 to 40 parts by weight.

Acrylic resins and polyester resins can be used as the main resin. These main resins must have functional groups such as hydroxyl groups and carboxyl groups that can crosslink with the melamine resin. Methods for producing these acrylic resins and polyester resins are known and will be explained below.

General method for producing acrylic resins a) Add ethylenic monomers with hydroxyl groups in an amount such that the hydroxyl value of the resin solid content is 40 to 15o b) Add ethylenic monomers with carboxyl groups to an acid value of 5 to 5o in the resin solid content and C) above a.
) and another ethylenic monomer that can be copolymerized with b) in a proportion of 100 parts by weight per unit.

Specifically, the ethylenic monomer a) includes hydroxyethyl acrylate, hydroxypropyl acrylate, hydroxybutyl acrylate, hydroxymethyl methacrylate, hydroxyethyl methacrylate, and hydroxypropyl methacrylate. , hydroxybutyl methacrylate, N-methylolacrylamide, allyl alcohol, and the like.

Specifically, the ethylenic compound having a carboxyl group (7-1)) includes acrylic acid, methacrylic acid, crotonic acid, ethacrylic acid, propyl acrylic acid, isopropylacrylic acid, itaconic acid, maleic anhydride, and fumaric acid. etc.

Other ethylenic monomers C) include acrylic I alkyl esters (methyl acrylate,
ethyl acrylate, isopropyl acrylate, n-propyl acrylate, n-butyl acrylate, isobutyl acrylate, monobutyl acrylate, 2-ethylhexyl acrylate, octyl acrylate, dotesyl acrylate, etc.), methacrylic acid Alkyl esters (methyl methacrylate, ethyl methacrylate, isopropyl methacrylate, mn-propyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, monobutyl methacrylate, 2-ethylhexyl methacrylate, n-methacrylate
-octyl, tostyl methacrylate, stearyl methacrylate, etc.), addition reaction products of fat and oil fatty acids and acrylic acid or methacrylic acid ester monomers having an oxirane structure (e.g. addition reaction products of stearic acid and glycidyl methacrylate), alkyl groups of C8 or more An addition reaction product of an oxirane compound containing acrylic acid or methacrylic acid 7- (eg, Japanese Patent No. 583185).

No. 609322), styrene, O! -Methylstyrene, 0-methylstyrene, m-methylstyrene, p-methylstyrene + pi-butylstyrene, benzyl acrylate, benzyl methacrylate.

Itaconate esters (such as dimethyl itaconate).

Maleic acid ester (dimethyl nato maleate).

Fumaric acid ester (dimethyl fumarate etc.), Aku IJ
Examples thereof include O nitrile, methacrylonitrile, ff) [4i nitrile, and the like.

The purpose acrylic multi-component copolymer is the above-mentioned three types of monomers (a
) to (c) at a predetermined ratio (
100 parts in total) and polymerize using a conventional method. For example, it can be obtained by mixing a seven-mer mixture with a known polymerization catalyst, dropping the mixture into a reaction vessel containing a solvent heated to a polymerizable temperature, and aging the mixture.

General methods for producing polyesters, such as coconut oil, soybean oil, castor oil, dehydrated castor oil, linseed oil, tung oil, safflower oil, tall oil, or with or without these fatty acids,
Ethylene glycol, diethylene glycol, trimethylolethane, trimethylolpropane, glycerin,
Polyhydric alcohols such as 1,6-hexanediol and pentaerythritol, and phthalic acid, isophthalic acid, adipic acid, and succinic acid.

Polybasic acids such as curtaric acid, cepatic acid, and tetrahydrophthalic acid or their anhydrides, and monobasic acids as necessary,
It can be obtained by condensation at a temperature of 180 to 240°C.

Next, a two-coat, one-bake base paint, which is a typical application of the paint of the present invention, and a method of applying the same will be explained.

2-coat, 1-bake painting method For clear paint, in addition to the appropriate thermosetting main resin composition, various solvents, surface preparation agents, ultraviolet absorbers,
It may contain light stabilizers and the like.

In addition to the resin composition containing the CAB/melamine resin co-condensate and the main resin, the base paint contains various solvents,
It may contain metal powder such as aluminum powder, coloring agents such as pigments and dyes, fillers, surface preparation agents, and the like.

Conventional techniques may be employed to form a coating film in two coats and one bake using a base paint and a clear paint having the above formulations. For example, each paint is diluted to a specified viscosity with a diluting solvent, the base paint is spray applied to a film thickness of approximately 20 μm, and after setting for approximately 3 minutes, the clear paint is spray applied to a film thickness of approximately 30 μm. After setting for about 5 minutes, it may be baked at a predetermined temperature for a predetermined time.

The present invention will be specifically explained below with reference to Production Examples and Examples. In these examples, "parts" and "%" are by weight.

Production Example 1 MIBK was placed in a reaction vessel equipped with a stirring bar, a cooling tube, and a thermometer.
176 parts, 96 parts of EAB-551-0,2 (CAB manufactured by Eastman Kodak Company) were added, and the mixture was heated and stirred at 100°C. When CAB was dissolved, 0.4 parts of phthalic anhydride was added.
Kneepan 205E-60 (manufactured by Mitsui Toatsu Co., Ltd., butanol-modified melamine formaldehyde resin, solid content 60%)
Add 400 parts and carry out the reaction at 100'C for 2 hours,
Resin solid content 50%, Gardner bubble viscosity 2-2. A resin solution A was obtained.

Production Example 2 @ EAB-551-0,22 by the same method as Production Example 1
5 copies, MIBK 100 copies, knee pants 205E-6037
5 parts, 0.2 parts of phthalic anhydride, resin solid content 50%,
Resin solution B of Gardner foam viscosity was obtained.

Production Example 3 In the same manner as Production Example 1, EAB-551-0,21
80 copies, MIBK 454 copies, knee pants 205E-603
3.4 parts, 0.3 parts of phthalic anhydride, resin solid content 30
%, and a Gardner bubble viscosity of Z1-Z2 was obtained.

Production Example 4 EAB-381-0,1 (
Resin solid content 50% from Eastman Kodak Company CAB) 96 parts, 11-tBK 176 parts, Kneepan 205E-60 400 parts, phthalic anhydride 0.4 parts.

A resin solution having a Gardner bubble viscosity of Z6 was obtained.

Production Example 5 Reaction volume F equipped with a stirring bar, cooling tube, thermometer, and dropping funnel
In F1J, 40 parts of doluol and 10 parts of n-butanol were charged, and the temperature was raised to 105°C. While maintaining the temperature, 535 parts of methyl methacrylate and 3 parts of butyl acrylate were added.
A mixed solution of 0 parts, 2-hydroxyethyl methacrylate, 15 parts, 1.5 parts of acrylic acid, and 1 part of t-butylperoxy-2-ethylhexanate was added dropwise at a uniform rate over 3 hours, and held for 2 hours after the completion of the dropwise addition. Then, the reaction was completed and a resin solution E was obtained.

Resin solid content 50%, good compatibility with Kneepan 205E-60.

Production Example 6 ゛In the same manner as Production Example 5, 5 parts of styrene, 28.5 parts of methyl methacrylate, 50 parts of ethyl acrylate, 15 parts of 2-hydroxyethyl methacrylate, and 1.5 parts of acrylic acid were added.
A resin solution F was obtained from the sample. Resin 12 - 50% solids, no compatibility with Kneepan 205E-60.

Production Example 7 In Production Example 6, dolol was changed to 52 parts, and EAB5
Resin solution G was obtained in the same manner except that 12 parts of 51-0.2 were added. Solid content 50%, knee bread 205E-60
There is no compatibility with

Production Example 8 77.4 parts of hexahydrophthalic anhydride, 66.5 parts of isophthalic acid, 146 parts of adipine e, and 25.5 parts of trimethylolpropane were placed in a reaction vessel equipped with a stirring bar, a cooling tube, and a thermometer.
6 g, 52.7 parts of neopentyl glycol, and 554 parts of 1,6-hexanediol were charged and heated. When the raw materials are melted and stirring becomes possible, stirring is started, the temperature is raised to 230'C, and a dehydration condensation reaction is carried out. When the resin acid value reached 8, the reaction was terminated, and after cooling, 106 parts of pheasant was added to obtain a resin solution H with a resin solid content of 70%.

Production Example 9 70 parts of pheasant roll and 10 parts of n-butanol were charged into a reaction vessel equipped with a stirring bar, a thermometer, a cooling tube, and a dropping funnel, and after raising the temperature to 120°C, 30 parts of styrene and 2-methacrylic acid were added. 20 parts of ethylhexyl, 1 part of methyl methacrylate
0 parts, n-butyl methacrylate 10.1 parts, n-butyl acrylate 14.5 parts, 2-hydroxyethyl methacrylate 13.9 parts, methacrylic acid 1.5 parts and azobisisobutyronitrile 2 parts. The mixed solution was let down through a dropping funnel for 3 hours, and after aging for 30 minutes, 20 parts of quijirole and 0 parts of benzoyl peroxide were added.
．． 5 parts of the mixed solution was poured down, and then aged for 2 hours to complete the reaction, to obtain a resin solution (2) with a resin solid content of 50%.

Production Example 10 Resin Solution I and Kneepan 205 E-60 were mixed so that the resin solid content ratio was 70/30 by weight, and diluted with a Kijiroll in a flat 4 Ford cup for 25 seconds (20°C). Then, it was made into a clear paint.

Example A mixture as shown in Table 1 below was dispersed and mixed if necessary, and mixed with a mixed solvent consisting of 60 parts of toluene, 20 parts of isobutanol, and 20 parts of 2-ethoxyethyl acetate in a flat 4 Ford cup. The mixture was diluted to 20°C (20°C) and used as a base paint.

(Left below) The base paint prepared in Examples 1 to 7 and Comparative Examples 1 to 5 and then the clear paint prepared in Production Example 1o were applied to an intermediate coated steel plate so that the dry film thickness of the former was 2071% and the latter was 30μ. , in a washing booth with a temperature of 23℃ and a humidity of 85%.
The former was spray applied in two stages with an interval of 2 minutes, then the latter was spray applied wet-on in one stage with an interval of 3 minutes, and then the coated board was baked in a dryer at 140 ° C for 30 minutes. A test plate was prepared. The intermediate coated steel plate used was a polished mild steel plate that had been degreased and chemically treated and coated with automotive electrodeposition paint and intermediate coat paint on a line.

The finished appearance of each of the above test plates was evaluated for gloss and color unevenness. Regarding gloss, those with extremely good gloss were rated ○, and those with slightly poor quality were rated ×2. Regarding color unevenness, those with no color unevenness were rated ○, and those with visible color unevenness were rated ×.

In addition, each of the above test plates was tested using a Sunshine Weather Meter (
(manufactured by Suga Test Instruments) (irradiated for 1,000 hours), and then tested and evaluated using a humidity tester (50°C, 998% relative humidity, 96 hours). The evaluation was rated ○ if no significant loss of gloss was observed, and rated × if significant loss of gloss was observed. The results are shown in Table 2.

Table 2 428

Claims (2)

[Claims] (1) Solid content weight ratio: (a) 30 to 87 parts of an acrylic resin or polyester resin having a functional group capable of crosslinking with a melamine resin; (b) 3 to 4 parts of a cellulose acetate butyrate resin;
0 parts (c) The total of 10 to 40 parts of melamine resin is 1
00 parts, of which (b) at least 3 parts of the cellulose acetate butyrate is present in the form of a co-condensate with the melamine resin, and (C) at least 3 parts of the melamine resin is the cellulose acetate butyrate. A thermosetting paint characterized in that it contains as a vehicle a resin composition existing in the form of a co-condensate with. (2) The thermosetting paint according to claim 1, which is a two-coat, one-bake base paint.