JPH01123099A - Electrodeposition coating method - Google Patents

Abstract

PURPOSE:To stably obtain an electrodeposited coating film having fine appearance and superior performance by partially neutralizing carboxyl groups in a fluorine-contg. polymer as a film forming component, emulsifying the polymer in water, carrying out further neutralization and using the resulting aq. suspension contg. fine particles. CONSTITUTION:An electrically conductive article is immersed in an aq. suspension contg. a fluorine-contg polymer as a film forming component and DC is supplied between the article as the anode and a counter electrode to coat the article with the polymer by electrodeposition. In this coating method, carboxyl groups in the fluorine-contg. polymer having >=5, preferably about 5-100 acid value and a certain hydroxyl value are neutralized to 0.02-0.3 equiv. ratio with a basic compd. and the polymer is emulsified in water in the form of particles of a particle size A. A basic substance is further added to carry out neutralization to 0.5-1.2 equiv. ratio and the particle size is regulated to <=1/5 of the particle size A. The coating liq. contg. the fluorine-contg. polymer undergoes no change with the lapse of time and an electrodeposited paint film having fine appearance and superior performance is stably obtd. by using the coating liq.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an electrodeposition coating method. More specifically, the present invention relates to a method of electrodepositing a fluorine-containing polymer having an acid value of 5 or more and a hydroxyl value onto a conductive article.

(Prior art) As electrodeposition coating methods, anionic electrodeposition coating and cationic electrodeposition coating are known. In anionic electrodeposition coating, the carboxyl group of polycarboxylic acid resin is At least a portion of the compound is neutralized to make it water-dispersible, and in an aqueous solution or dispersion diluted with water, a conductive article is used as an anode and a counter electrode is provided, and a DC voltage is applied between the two. As a result, electrodeposition coating is performed.

On the other hand, in recent years, attempts have been made to electrodeposit fluorine-containing polymers, for example, in JP-A-62-59676;
It is disclosed in Japanese Patent No. 2-127362.

However, even if fluorine-containing polymers are water-solubilized and electrodeposition coating liquids are prepared in the same way as ordinary polycarboxylic acid resins, they have poor stability over time and may form precipitates, and when they are electrodeposited, the coating film may deteriorate. However, there are problems such as the formation of craters and a varnished appearance, and the current situation is that stable products cannot be obtained and have not yet been put into practical use.

(Problems to be Solved by the Present Invention) An object of the present invention is to stably obtain an electrodeposition coating film that does not change over time and exhibits a beautiful coating appearance and excellent coating performance. An object of the present invention is to provide a method for electrocoating a fluoropolymer.

(Means for Solving the Problems) To summarize the present invention, a conductive article is immersed as an anode in an aqueous solution containing a fluorine-containing polymer as a coating film forming component, and a direct current is applied between it and a counter electrode. In a method of electrodepositing a fluoropolymer on a conductive article, (1) the carboxyl group of the fluoropolymer having an acid value of 5 or more and a hydroxyl value is (
2) Neutralize with a basic compound to give an equivalent ratio of 0.02 to 0.3, (3) emulsify this in water to form particles with a particle diameter of A, (4) then add a basic compound to this. In order to obtain particles of particle size B by adding the equivalent ratio to 0.5 to 1.2, an aqueous liquid containing a fluorine-containing polymer whose particle size is adjusted to B/A = 115 or less as a coating film forming component is used. The present invention relates to an electrodeposition coating method characterized by the following.

According to research conducted by the present inventors, fluorine-containing polymers exhibit unique properties during the water solubilization stage compared to acrylic polymers commonly used in electrodeposition coatings, and they can be easily applied using conventional methods. We found that dilution with water results in an unstable aqueous solution with poor stability over time.

Based on this knowledge, the present invention makes it possible to water-solubilize a fluoropolymer in two stages, and to use an aqueous liquid having a specific particle size, it is possible to form a stable and beautiful electrodeposited coating with excellent stability over time. This is what we found and completed.

To explain the present invention in more detail, the fluoropolymer used in the present invention has an acid value and a hydroxyl value, and the acid value is at least 5 or more, preferably 5 to 100 in order to be applied to electrodeposition coating. Use a range. Considering paintability, coating film performance, etc., an acid value in the range of 7 to 70 is particularly preferred.

To make the fluoropolymer solubilized in water, first, a part of the carboxyl group is neutralized with a basic compound of 0.02 to 0.3 equivalents to the carboxyl group, and this is added to the fluoropolymer.
．． Emulsify by mixing in 8 to 2.0 times the amount of deionized water. Next, (2) a basic compound is further added, and the water solubilization is completed at a concentration of 0.5 to 1.2 equivalent m per carboxyl group. The end point of this water solubilization is the stage at which the resin particle diameter in the second stage is at least 115 or less compared to the resin particle diameter in the first stage.

This adjustment of the resin particle size is a factor that affects the stability over time of the aqueous resin liquid of the fluoropolymer, and if the resin particle size cannot be adjusted to 115 or less in the second step, the stability over time will be poor. Undesirable.

The basic compound may be one commonly used, such as ammonia, monomethylamine, dimethylamine, trimethylamine, monoethylamine,
Primary to tertiary alkylamines such as diethylamine, triethylamine, monoisopropylamine, diisopropylamine, triisopropylamine, monobutylamines, dibutylamines, and tributylamines, monoethanolamine, jetanolamine, triethanol amines, monoisopropanolamine, diisopropanolamine, triisopropanolamine, flukanolamines such as dimethylaminoethanol and diethylaminoethanol etc., alkylene polyamines such as ethylenediamine, propylenediamine, diethylenetriamine and triethylenetetramine etc. ,
These include alkyleneimines such as ethyleneimine and propyleneimine, piperazine, morpholine, pyrazine and pyridine.

The electrodeposition coating liquid used in the present invention contains the fluoropolymer and aminoplast as coating film-forming components, and the blending ratio is 50 to 97 parts by weight of the fluoropolymer and 50 to 50 parts by weight of the aminoplast. A range of 3 parts by weight is preferred.

If the amount of the fluoropolymer used is less than 50 parts by weight, the excellent performance of the fluoropolymer cannot be imparted to the coating film;
If it exceeds 97 parts by weight, the coating film will not be sufficiently crosslinked and the coating performance will deteriorate, which is not preferable.

Electrodeposition coating liquid whose main component is fluorine-containing polymer is
For example, it can be manufactured by the following method.

First, a resin composition is formed as follows.

Into a reaction vessel equipped with a stirrer and a thermometer, add (a) a fluorine-containing polymer containing carboxyl groups and hydroxyl groups, which is the raw material for component (b) aminoplast, and an organic solvent, and then stir thoroughly. Mix.

Examples of organic solvents include those that are water-soluble and have an affinity for the resin, such as methanol, ethanol, n-propanol, isopropanol, n-7 tanol, isobutanol, secondary butanol, tertiary butanol, and pentanol. Alcohols such as, cellosolves such as methyl cellosolve, ethyl cellosolve, isopropyl cellosolve, butyl cellosolve, secondary butyl cellosolve, etc. are used.

The amount of organic solvent in the electrodeposition coating liquid is based on the coating film forming components.
It is used in a range of 25 to 150% by weight. Next, as described above, a basic compound is added in two steps to make it water-solubilized, and deionized water is added to dilute this to an appropriate resin solid content concentration to prepare an electrodeposition coating solution. use.

In preparing the electrodeposition coating liquid, there is no problem even if the fluorine-containing polymer is neutralized in advance as described above and mixed with 7-minoplast.

In the present invention, the electrodeposition coating liquid has a resin solid content concentration of 3 to 50.
It is used after adjusting the amount within the range of about % by weight.

At this time, commonly used colorants, paint additives, etc. can be mixed and used.

The conductive article is used as an anode in the electrodeposition coating solution prepared in this way, and after applying a DC voltage between it and the counter electrode, the conductive article is pulled up and heated and baked after washing or without washing. A fluorine-containing polymer electrodeposition coating film that is uniform and has excellent gloss is formed on the surface of the conductive article.

In the electrodeposition coating method of the present invention, the coating film is baked at 130°
C-250'C1 Preferably 15 at 140-230'C
Achieved under the conditions of ~60 minutes.

If it is necessary to adjust the gloss of the electrodeposition coating, a commonly used inorganic or organic gloss remover may be added to the electrodeposition coating solution.

The electrically conductive article to which the present invention is directed may be any material that has electrical conductivity, and is not limited in shape, size, material, etc., such as iron, copper, aluminum, magnesium, titanium, etc. Examples include alloys thereof, and furthermore, plastics having a metal plating layer or other conductive layer formed on the surface. These conductive articles are usually subjected to chemical conversion treatment before electrocoating, but the types of chemical conversion treatment are as follows:
For example, various phosphate treatments, chromate treatments, boehmite treatments, anodic oxidation treatments, etc. are suitable.

(Examples) Examples will be shown below to more specifically explain the present invention. In addition, unless otherwise specified, the number of parts indicates parts by weight.

Example 1 [Preparation of electrodeposition coating liquid A] A container with an acid value of 20 mFl-KOH/g and a hydroxyl value of 60 m
g・KOH/tj fluorine-containing polymer (manufactured by Asahi Glass Co., Ltd.) 2
20g of melamine resin (trade name: Cymel HM-6 manufactured by Mitsui Cyanamid Co., Ltd.)>20g were charged and stirred with a disper to mix uniformly.Next, 25g of butyl cellosolve was added.
1. A mixture of 1.15 g of triethylamine was added and mixed roughly. Deionized water 2007 was gradually added to this to obtain an emulsion with a particle size of 10 μm.

Next, 150 g of deionized water, 2.9 g of triethylamine
The mixture was gradually added to obtain a finely divided aqueous solution having a particle size of 5 Qnm. Furthermore, 650 g of deionized water was added to this to prepare an electrodeposition coating liquid A having a resin solid content of 11.0% by weight.

[Preparation of electrodeposition coating liquid B-F] In preparing electrodeposition coating liquid A, the same method was used except that the type of fluoropolymer and the blended amounts of triethylamine and deionized water were changed as shown in Table 1. Electrodeposition coating liquids B and C of fluoropolymer were prepared.

[Preparation of electrodeposition coating liquid F] Container D, acid value 20 mg -KOH/'j, hydroxyl value 6
0η・KOH/g fluorine-containing polymer (Asahi Glass Co., Ltd. 220
g and melamine resin (trade name: Cymel HM-6 manufactured by Mitsui Cyanamid Co., Ltd. > 203) were charged and mixed uniformly by stirring with a disper.Next, a mixture of 25 g of butyl cellosolve and 4.04 g of triethylamine was added and further mixed. 1,000 g of deionized water at 30°C was gradually added to the solution to prepare electrodeposition coating liquid F of a fluorine-containing polymer with a particle size of 5 Qnm.
was prepared.

[Preparation FA of electrodeposition coating liquid G] Electrodeposition coating liquid G was prepared by carrying out all the same methods except for changing the type of fluorine-containing polymer and changing the amount of triethylamine in preparing electrodeposition coating liquid F. did.

Example 1 A 10 cm x 10 cm aluminum test plate (JIS △-1100> was anodized using a conventional method to form an anodized film with a thickness of 10 μm. After that, it was immersed in electrodeposited resin solution A as an anode, and a stainless steel plate was used as a counter electrode. The wires were connected and a direct current was applied between the two electrodes at a voltage of 160 to 180 volts for 3 minutes.However, the electrodeposition coating was carried out so that the WA thickness was constant by passing an amount of electricity of about 20 coulombs.

After the electrodeposition coating was completed, the test board was removed from the solution, washed with water, and then
The coating film was baked by heating and drying at 180'C for 30 minutes.

Examples 2 to 3 and Comparative Examples 1 to 4 Electrodeposition coating was performed in the same manner as in Example 1 except that the electrodeposition resin liquid A shown in Table 1 was used instead.

As described above, the electrodeposition coating film performance of the fluorine-containing polymers obtained in Examples 1 to 3 and Comparative Examples 1 to 4 was as shown in Table 1.

The coating film performance was evaluated by the following method.

1. Weather resistance: Gloss retention after 30,000 hours of exposure using a Sunshine Weather-Ometer.

2. Alkali resistance...JIS H-8602 method was implemented and evaluation was made using rating No.

3. Acid resistance: Evaluated by rating No. according to JIS H-8602 method.

4. Boiling water resistance: Evaluation was performed using the method of JIS H-8602 and rating No.

5. Throwing property: The coating film thickness was measured at 20 points on the surface of the test board and evaluated based on the difference in film thickness.

◎・・Less than 0.5μ7n ○・・Less than 0.5 to 2μm △・・Less than 2 to 3μm The coating stability was as shown in Table 2.

The following margin Examples 4 to 6 In the method of Example 1, the objects to be coated were changed to aluminum test plates, iron plates subjected to chemical conversion treatment (phosphate), iron plates subjected to nickel plating (thickness 10 μm), copper plates Electrodeposition coating was performed using a polyester filament shear fabric that had been plated (thickness: 2 μm).

The electrodeposition coating conditions were as shown below.

As a result, a coating film with a uniform and beautiful surface appearance was formed in each case.

In general, when electrodeposition coating solution A was stored in an atmosphere at 30°C for 60 days and electrodeposition was applied to each object in the same manner as above, an eroded electrodeposition film was formed without any change. It was done.

<Effects of the Invention> The electrodeposition coating method of the present invention has the effect of stably obtaining an electrodeposition coating film of a fluorine-containing polymer that exhibits a beautiful and excellent coating appearance and excellent coating film performance even over time. .

Applicant: Honey Kasei Co., Ltd.

Claims (1)

[Scope of Claims] 1. A conductive article is immersed as an anode in an aqueous solution containing a fluorine-containing polymer as a coating film-forming component, and a direct current is applied between the conductive article and a counter electrode to form a coating film on the conductive article. In the method of electrodeposition coating a fluoropolymer, (1) carboxyl groups of a fluoropolymer having an acid value of 5 or more and a hydroxyl value are replaced with (2) a basic compound such that the equivalent ratio is 0.02 to 0.3. Neutralize, (3) emulsify this in water to form particles of particle size A, (4) then add a basic compound to this to make the equivalent ratio 0.5 to 1.2, and form particles of particle size B. An electrodeposition coating method characterized by using an aqueous liquid containing a fluorine-containing polymer whose particle size is adjusted to B/A=1/5 or less as a coating film-forming component.