JPS58147467A - Composition for electrodeposition coating - Google Patents

Abstract

PURPOSE:To prepare the titled compound which has excellent solvent resistance and chemical resistance and high hardness, and can be baked at a low temperature, by mixing and reacting an acrylic resin containing carboxyl group and hydroxyl group with a water-insoluble butylated melamine resin in the presence of an alcohol. CONSTITUTION:An acrylic resin having an acid value of >=20 and containing hydroxyl group is mixed and reacted with a substantially water-insoluble butylated melamine resin (preferably >=90% of the resin is insoluble in water) in the presence of an alcohol (preferably isopropyl alcohol, etc.) to obtain the objective composition. The acrylic resin is preferably the one obtained by the solution polymerization of a monomer containing carboxyl group in the molecule[e.g. (meth)acrylic acid]or a monomer containing hydroxyl group in the molecule (e.g. 2-hydroxyethyl acrylate) with a copolymerizable monomer such as ethyl acrylate.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coating composition suitable for electrodeposition coating, having excellent solvent and chemical resistance, high hardness, and capable of being baked at low temperatures. More specifically, there are anionic and cationic types of electrodeposition coatings, that is, an anodic deposition type and a cathodic deposition type. This invention relates to a type of resin composition that is crosslinked with melamine resin.

As is well known, the 7-ion type acrylic composition for electrodeposition is a water-soluble material obtained by neutralizing a copolymer of a carboxylic acid monomer such as acrylic acid with an amine or other base, and a melamine resin or a benzohanamine resin is used for curing. A common method is to blend the acrylic resin with hydroxyl groups and other functional groups.

As the melamine resin used as a crosslinking agent for the acrylic resin for electrodeposition, so-called methylated melamine or melamine resin such as hexamethoxymelamine was initially used. However, these materials are water-soluble or partially water-soluble and have a high affinity for water, and have the disadvantage that the amount of deposited during electrodeposition is small compared to acrylic resin, which is the main resin during electrodeposition, that is, their co-propagation is low. Painting - When replenishing paint repeatedly, there was a problem in that melamine or melamine resin accumulated.

On the other hand, n-butoxymethylated or isobutoxymethylated, so-called butylated melamine, which is usually used for coatings, contains a hydroxyl group and is often substantially insoluble in water. These have high reactivity with acrylic resin, which is the main resin, and can be baked at a lower temperature than Girime 1-ki/Melami/type.
+i+ When deposited in a bath, the co-advancement with the acrylic resin during electrodeposition is generally good, close to 100φ, but the disadvantage is that it tends to separate and settle, and it deposits on the top surface of the dipped object, causing coating surface abnormalities. There is.

As an alternative method to improve the balance between co-progressivity and sedimentation property, there is also a method in which part of the butoxy in hexamethoxyl is replaced with butoxy, as proposed by Japanese Patent Publication No. 4B-17455. However, even with this method, the balance between coprogression and sedimentation has not been fully resolved.

In order to take advantage of the low-temperature baking properties and other excellent properties of butylated melamine resin, the inventors of the present invention have intensively investigated prevention of sedimentation in a '11L bath. As a result, we discovered a method for producing a 77 IJ electrodeposition composition that has nearly 100% co-propagation with the melamine resin, has excellent solvent and chemical resistance without precipitation of the melamine resin, and can be baked at low temperatures. be.

That is, the present invention uses an acrylic resin containing a hydroxyl group with a resin acid value of 20 or more,
This is an electrodeposition coating composition characterized by reacting a substantially water-insoluble butylated melamine resin in the presence of alcohol.

The acrylic resin used in the present invention can be used as long as it has an acid value of 20 or more and contains a hydroxyl group, but preferably acrylic resin containing a carboxylic acid in its molecule in the presence of an alcohol. A monomer having 1,000 yen of hydroxyl groups and/or a fullyl acrylic ester such as ethyl acrylate and butyl acrylate, and/or a fullyl methacrylate such as methyl methacrylate and butyl methacrylate, and if necessary, acrylic acid esters such as acrylic acid 7mide and methacrylate. 7mid, their derivatives, and/
Alternatively, a resin copolymerized by a conventional method by solution polymerization with a monomer copolymerizable with the above, such as styrene, is used.

Examples of monomers containing carboxylic acid in the molecule include acrylic acid, tutaacrylic acid, ichunic acid, and maleic acid, and examples of monomers containing a hydroxyl group in the molecule include 2-hydroxyethyl 7 acrylate, 2-hydroxyethyl methacrylate, 2-hydroxyethyl 7 acrylate or 2-
There is human hydroxypropyl methacrylate.

The butylated melamine resin used in the present invention is methylyl melamine or n-butyl ether or isobutyl ether of its condensate, and is preferably substantially insoluble in water and preferably partially contains methylol groups. The manufacturing method may be any known method, and is described, for example, in Melamine Resin, published by Nikkan Kogyo Shimbun, pp. 75-76.

Also, even if it is commercially available as melamine resin for paint,
Any butylated (n-butyl or inobutyl) melamine that is substantially insoluble in water can be used. The term "substantially insoluble in water" as used herein refers to 1 which is 1.90% or more insoluble in water.

The presence of furcol is required when acrylic resin and melamine resin undergo a thermal reaction. It is believed that when the acrylic resin containing a hydroxyl group and the above-mentioned melamine resin are heated in the presence of an acid to a temperature of 0°C or higher, preferably 0°C or higher, the melamine resin reacts with the compound having a hydroxyl group and bonds with it. Melamine resin bonds with acrylic resin by reacting with hydroxyl groups contained in acrylic resin, but when alcohol is present, acrylic resin and alcohol react competitively, regulating the reaction between acrylic resin and melamine resin. This is because it can be considered. The alcohol used is
From the viewpoint of toxicity, boiling point, and suitability for electrodeposition, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, monobutoxy glycol, monoethoxy glycol, etc. are preferably used. Other alcohols can also be used, such as tools, but are not limited to these.

The amount used depends on the properties of acrylic resin and melamine resin,
It should be used appropriately depending on the amount used.

The temperature range for the reaction is preferably 50°C or higher and up to the boiling point of the solvent, but as mentioned above, in order to increase the reaction rate,
More preferably, the temperature is 0°C or higher.

A direct effect of the present invention is, as previously mentioned, that it prevents the precipitation of butylated melamine resin when substantially hydraulically insoluble butylated melamine resin is used for electrodeposition.

This invention can be said to have made it possible for the first time to use a butylated melamine resin that is substantially insoluble in water for use in electrodeposition compositions; Provided is an electrodeposition composition which has excellent properties such as chemical resistance and which can be baked at a lower temperature than conventional compositions.

The coating composition of the present invention is finally used for electrodeposition coating after the carboxylic acid contained therein is neutralized with an amine or other base, and the composition is made water-soluble or dispersed in water. Pigments and other additives may be added during or at the end for use in electrodeposition.

Next, the present invention will be explained in detail with reference to Examples.

Example 1 50 parts of isopropyl alcohol and butylcep! Pour in 10 parts of liquid and heat. To this are added 6 parts of acrylic acid, 5 parts of 2-hydroxyethyl methacrylate, 5 parts of styrene, 30 parts of methyl methacrylate, 29 parts of ethyl acrylate, 20 parts of butyl acrylate, 3 parts of dodecylmercaptan, and 1 part of azobisisobutyronitrile. A mixture consisting of 4
Drip in time.

After further stirring for 1 hour, 1 part of azobisisobutyronitrile was added three times every 30 minutes at reflux temperature to react, and the polymerization was completed by stirring for another 1 hour, and the acrylic resin I
I got it. This resin has a resin acid value of 44.5 per solid content.
KOHmp/P, solid content Fi6Z5ch.

44.6 parts of Super Beckamine G-821 (trade name, butylated melamine, manufactured by Dainippon Ink & Chemicals Co., Ltd.) having a solid content of 60% per 10 parts of this acrylic resin is added, and the mixture is heated to 80°C for 5 hours and stirred. Thereafter, 32 parts of triethylamine and 1 part of 35-lutidine are added and stirred, water is gradually added to dissolve, and if necessary, triethylamine is added to adjust the solid content to 10% and the pH to 82. Electrodeposition is applied in a stainless steel beaker at 70V with the beaker as the cathode and a zinc phosphate treated iron plate as the adjacent electrode while stirring, and baked at 150°C for 30 minutes to form a coating film with hardness H and good alkali resistance and solvent resistance. I got it. In the infrared absorption spectrum, the co-progression of acrylic resin and melamine resin is 100.
%. When stirring was stopped and the zinc phosphate treated iron plate was bent into an L shape and suspended, electrodeposition coating was performed in the same manner, but there was no abnormality on the top surface of the L shape. Further, the electrodeposition bath was left for one week with stirring stopped, but no sedimentation was observed.

Comparative Example 1 When Super Beckamin G82'l was added to the acrylic resin l in Example I, and then simply stirred and dissolved in water in the same manner, the result was a zinc phosphate treated board bent into an L shape, a painted board. Deposition of sediment was observed on the upper surface.

Comparative Example 2 In place of Super Beckamin G321 in Actual M Example 1,
Nikaratsuku MY-30, which is water-soluble or has high water affinity (
(Product name: Methylated melamine manufactured by Sanwa Chemical Co., Ltd.)
When the same procedure was carried out using 27 parts, the temperature was 150°C x 30
After baking, the hardness was B, and the coating film was damaged by Furfur.

Example 2 10 parts of methacrylic acid, 2 parts of 2-hydroxyethyl methacrylate, 10 parts of styrene, 15 parts of methyl methacrylate, 51 parts of ethyl acrylate, 10 parts of butyl methacrylate, 2 parts of dodecylmercaptan, and azobisisobutylene (
A mixture consisting of 1 part of J21ril was mixed with 30 parts of inopropyl alcohol and 30 parts of butyl alcohol in the same manner as in Example 1.
The acrylic resin (2) was obtained by adding the mixture dropwise to a heated solvent consisting of 50% of the mixture. The solid content was 621% and the resin acid value was 625. This resin has a solid content of 60% Kneepan 208E (product name, []\
12 parts of butylated melamine (manufactured by γ Kasei Co., Ltd.) was added, and the mixture was heated at reflux temperature for 8 hours.

After cooling, 6 parts of 1-reproduced tylamine were added and stirred, and 30 parts of Kuibake R-920 (trade name: titanium oxide manufactured by Ishihara Sangyo Co., Ltd.) was dispersed with a small amount of inopropyl alcohol using a conventional method. Water is gradually added, and if necessary, triethylamine is added to adjust the pH to 8.8 and the solid content to 15% to prepare an electrodeposition bath.

As in Example I, an iron phosphate treated plate was used, and the voltage was +00V.
When coated with 150°C and baked at 150°C for 30 minutes, a white coated product with a film thickness of 20 μm, good gloss, and hardness of 3H was obtained.

Patent applicant: Higashishi Co., Ltd.

Claims (1)

[Claims] An electrodeposition coating composition comprising a heptacrylic resin having a resin acid value of 20 or more and containing hydroxyl groups, mixed with a substantially water-insoluble butylated melamine resin in the presence of alcohol, and reacted with the mixture.