JPS6024192B2 - Electrodeposition coating method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a coating method in which a cationic powder military paint is applied to an object to be coated by dipping, and after forming a coating consistency, the unpainted portions are again electrodeposited.

A coating film obtained by applying a cationic powder electrodeposition coating composition prepared by dispersing a heat-fusible resin powder in a water-diluted cationic resin solution described in Published Patent Application No. 48-43731 is powder coating. Although it is possible to obtain coating film performance that is as excellent as that of a coating film made using a paint film, the throwing power is inferior to that of ordinary anionic electrodeposition paints or cationic electrodeposition paints, so the bag-like structure of the coated object There were practical problems as the interior and parts with complex shapes could hardly be painted.

As a measure to prevent such coating film defects, a coating method that combines two electrodeposition coatings has been implemented. According to this coating method, the normal cationic powder electrodeposition coating film of the first Since the electrical resistance of the area is high, the second coating is not applied even if it is a thin film of the first cationic powder electrodeposition coating, and the coating is selectively applied only to the unpainted areas. Since a film is formed, the second coating has the advantage of being concentrated on areas that were not coated with the first cationic powder electrodeposition coating.

However, even in this case, because the volume specific electrical resistance value of the first military coat coating is high, the coating film is not formed sufficiently at the boundary between the first and second military coat coatings, and furthermore, once In the case of the regular Kame-adhesive paint film formed on the boundary area, the military-adhesive paint film is re-dissolved by the Kame-adhesive washing water containing the Kame-adhesive paint and the physically attached flea paint. As a result, there is a part that is not coated at all at the boundary between the first cationic powder electrodeposition coating and the second fin coating, and the coating performance, especially corrosion resistance, in this area is affected. There was a big problem of being inferior. The present inventors conducted various studies in order to improve the coating performance by ensuring sufficient coating film formation at the boundary between the first cationic powder electrodeposition coating and the second electrodeposition coating. As a result, we have completed the present invention. That is, the present invention contains conductive powder and has a temperature of 20°C.
Apply the first haze coating to the object using a cationic powder electrodeposition paint that can form a coating film with a volume specific electrical resistance value in the range of 1 x 107 to 1 x 1 and 301 cm at 0V. ,
Apply 30 qo of the coated plate immediately after electrodeposition to the unpainted area of the electrodeposition paint.
A second haze coating is applied using a lightning coating that has a remelting rate of 15% (wt%, the same shall apply hereinafter) or less of the haze coating when left in a dew bath for 1 minute. The gist is a tortoise coating method that is characterized by the following:
A cationic powder electrodeposition paint capable of forming a coating film having the specific volume electric resistance value described above was used for the first dew coating, and an anionic electrocoating powder having the remelting rate described above was used for the second deposition coating. In this embodiment, a paint or a cationic electrodeposition paint is used.

The volume specific electrical resistance value referred to in this specification is based on ASTM
- This is a value measured at 2000, 20V according to D-257-61.

Further, the remelting rate of the stuck coating film is measured by the following method.

First, using a test plate whose weight has been measured in advance, the adhesive paint is bathed in a glass or plastic electrocoating bath, and the magnetic coating is applied at a distance of 15 nodes, an electrode area ratio of 1:1, and an ordinary temperature of 30 oo. Electrodeposition is performed for about 3 minutes at a voltage that provides a standard film thickness while stirring with a stirrer. Also, record the amount of electricity at that time. Immediately thereafter, the test plate coated with the paint was washed with water and placed next to it under standard competition conditions. The weight of the coating after baking on this test board was measured and designated as A (evening). Also,
The redissolution test plate was electrocoated under the above-mentioned conditions so that the amount of electricity was equal, and then the test plate was immersed for 10 minutes at 30oC in an electrocoat with stirring stopped, and then washed with water in the same manner. It is obtained by baking under standard baking conditions.

If the weight of this adjacent coating film is B (Y), then the redissolution rate (%
) is represented by {(A-B)÷A}×100. In the present invention, as the cationic powder electrodeposition paint to be applied for the first time, any commonly used cationic powder electrodeposition paint can be used, but the coating strength formed from such military paint is It usually has a high specific volume electric resistance value of 1 and 40 m or more at 20°C and 20V, and is unsuitable if the paint is mixed as is.

In other words, even if a second lightning coating is applied after forming an electrodeposited coating film with such a high specific volume electric resistance value, the characteristics of the first cationic powder electrodeposition coating film This is because, due to the high electrical resistance, a coating film sufficient to exhibit the desired performance is not formed at the boundary between the first and second electrodeposited coatings. Therefore, in the present invention, it is essential to blend a conductive substance powder into the electrodeposition paint so that the volume specific electrical resistance value of the coating film formed therefrom is within a specific range.

As the conductive powder, conductive carbon is preferred, and graphite, acetylene black, oil furnace type carbon, etc. are used, but other types of conductive carbon may be used. Regarding the particle size of the conductive carbon, it is sufficient that it falls within the particle size range used for ordinary decorative paints, and it is also possible to use a surfactant to improve the dispersibility of conductive carbon in the electrodeposition paint. .

In the present invention, the above-mentioned conductive powder is blended into a cationic powder electrodeposition paint, and the volume specific electrical resistance value of the box coating film formed from this is 107 to 1 and 3 at 20q0120V.
If the cationic powder electrodeposition paint is applied as the first coat and then the second military coat is applied, the first electrodeposition paint is regulated to 0. The second coating film is sufficiently formed in the uncoated and thin areas of the coating, and as a result, it is possible to obtain excellent coating performance even in the boundary area between the first and second coating films. Become. The volume specific electrical resistance value of the first cationic powder electrodeposition coating is 10.
When using a haze paint that does not reach 701 arc, not only does it have the disadvantage that it is difficult to form a sufficient haze paint film, but also in the subsequent second electrodeposition coating.
This is not preferable because unnecessary or excessive electrodeposition paint is also deposited on the surface of the second dew-deposited coating.

The amount of conductive carbon to be blended in order to obtain the specific volume electric resistance value in the above range can be expressed as follows: Taking acetylene black, graphite, and carbon black as examples, 100 parts of solid content in the tortoise paint (parts by weight, the same applies hereinafter) is suitably 4 to 4 parts.

This amount is much larger than the amount added to adhesive paints for coloring purposes. In other words, carbon black and graphite are usually added in small amounts, no more than 1 to 2 parts per 10 solids in electronic paint.
The addition of conductive powder in the present invention is essentially different from the addition of pigment in its purpose and amount. The second coating used in the present invention is an anionic or cationic type that is commonly used, but the coating film formed from such a coating immediately after coating is so-called In terms of suitability and suitability for collecting washing water, the redissolution rate is usually about 25 to 50%, at least about 20%.

In the case of paints with such a high redissolution rate,
The second exposed coating formed at the boundary between the first cationic powder electrodeposited coating and the second exposed coating will not only cause re-dissolution in the coating bath, but also Even after being removed from the dew, re-dissolution continues due to the paint that has physically adhered to it. In addition, during the washing process with military washing water containing ultrafiltration furnace fluid and turtle coating,
The gutter coating tends to re-dissolve, and as a result of this re-dissolution phenomenon, there are areas in the boundary areas that are not covered at all by the first cationic powder electrodeposition paint or the second electrodeposition coating. , a defect occurs in that the coating film performance, especially the corrosion resistance, is not good in this area. Therefore, in the present invention, the remelting rate of the second military uniform coating is determined by the type and amount of neutralizing agent in the exposed paint (neutralization equivalent), the resin acid value or the resin base value,
It is essential to reduce the amount to 15% or less, preferably 10% or less, by changing the molecular weight of the resin, the type of solvent and its blending amount, etc. Among these, three particularly effective means are selection of the type and amount of the neutralizing agent. In the case of anionic electrodeposition paints, the types of neutralizing agents are monoethanolamine,
Alkylamine compounds such as triethylamine, diethyl-3 amine, triethylamine, and potassium hydroxide give better results than alkanolamine compounds such as diethanolamine and triethanolamine. Further, the amount of the neutralizing agent to be blended has a particularly large contribution to the redissolution rate, and the smaller the amount to be blended, the more effective it is in reducing the redissolution rate. In ordinary anionic electrodeposition paints, the neutralization equivalent in the formulation of a neutralizing agent is relatively high due to the flea adhesion properties and workability of box deposition. Although it is practically used in the range of 0.8 to 1.2 equivalents,
In the present invention, it is preferable that the anionic electrodeposition paint used for the second coating be lower than this, and about 0.4 to 0.
6 equivalents is suitable. In the case of cationic electrodeposition paints, organic acids such as acetic acid, hydroxyl acetic acid, propionic acid, acetic acid, and succinic acid, as well as inorganic acids such as sulfuric acid, hydrochloric acid, and phosphoric acid, can be used as neutralizing agents. Among them, hydroxyl acetic acid, acetic acid, etc. give good results.

The blending amount of the neutralizing agent has a large influence on the redissolution rate, and in order to reduce the redissolution rate, it is better to have a smaller blending amount. In ordinary cationic electrodeposition paints, the neutralization equivalent in the formulation of a neutralizing agent is relatively high due to electrodeposition characteristics, workability for dew coating, etc., and for dew paint resins with a resin base number of approximately 50 to 150, the neutralization equivalent is approximately 0. 8
A range of 1.2 to 1.2 equivalents is said to be appropriate, but for the cationic electrodeposition paint used in the second coating in the present invention, lower amounts are preferred, and approximately 0.1 to 0.5 equivalents are appropriate. be.

For any type of military paint that is applied in the second coat, if the re-dissolution rate of the turtle coat is approximately 15% or more, the corrosion resistance will be lost at the interface with the first cationic powder electrodeposition coat. This tends to cause a decrease in the temperature, which does not meet the purpose of the present invention.

As described above, in the case of coating using the fin coating method according to the present invention, the second coating is not applied to the normal cationic powder electrodeposited film part of the first coating, and the fin coating of the first coating is The second electrodeposition paint is efficiently applied only to the uncoated areas and thin film areas of the powder electrodeposition paint, and the re-dissolution rate is small, so the first cationic powder electrodeposition paint is applied in the normal water washing process, etc. At the boundary with the electrodeposition coating, the second coating was not redissolved, and as a result, the boundary between the first cationic powder electrodeposition coating and the second haze coating Sufficient coating hardness is formed in the area, making it possible to significantly improve coating film performance, especially corrosion resistance.

After painting by the method of the present invention, it is of course possible to apply a finishing coat if necessary. For example, in the case of finishing an automobile body, it is sufficient to apply the usual automobile top coat paint after the second military uniform coating. Next, the present invention will be explained in more detail with reference to Examples and Comparative Examples.

All parts in Examples and Comparative Examples are parts by weight. Example 1 Cationic powder electrodeposition paint A in which conductive carbon (Graphite, manufactured by Chuetsu Graphite Co., Ltd.) was added to the surface treatment solution according to steps 1 and 2 in Table 1 for the first cationic powder electrodeposition coating. -1, A-2, and A-3 (3 types) were coated and baked under the conditions of Step 3 in Table 1, and then anionic electrodeposition paint A-4 was applied as a second electrodeposition coating. used, first
Three types of test specimens were prepared by painting under the conditions of surface step 4.

For comparison, after the first cationic powder electrodeposition coating, aniosoelectrodeposition paint A with a redissolution rate of 20%, which will be described later, was used.
-5 (Comparative Example 1) under the conditions of Step 4 in Table 1, three types of test pieces were also added.

Table 2 shows the test results for these test pieces and the volume specific electrical resistance values of the cationic powder electrodeposition coating strength (first time).

In addition, three types of cationic powder electrodeposition paints A-1 and A-2
, A-3 was prepared by adding permanent acetic acid and deionized water to the paint of Example 1 of JP-A-48-43731 (an aminoepoxy resin obtained by reacting Epicoat 1001 manufactured by Shell Chemical Co., Ltd. and jetanolamine) to obtain a diluted solution with water. Ta.

Next, the water diluted solution was added with Epicort 1004 manufactured by Shell Chemical Co., Ltd.
Butvar D510 manufactured by Monsanto, an average particle size of 4 containing rutile titanium oxide and dicyandiamide
Solids content 12% pH 4.0ml mixed with epoxy powder.
Conductive carbon paste P-1 shown below was added to the cationic powder electrodeposition paints (4 to 4.5). Conductive carbon paste P-1> Aminoepoxy resin binder 143 parts (7 parts of aminoepoxy resin made by reacting 4 parts of Epicoat 1001 manufactured by Shell Chemical Co., Ltd. and 105 parts of jetanolamine)
0% inpropyl alcohol solution) flaky graphite
10 Ikariko (Graphite manufactured by Chuetsu Graphite Company) Glacial acetic acid 6
．． 2 Parts Ethylene Glycol 20 Counts A fin-guiding carbon paste P-1 was prepared by dispersing the above-mentioned formulation in a vepule mill for 4 times.

<Charteon type all-electrodeposited crucian carp> (Note) While applying cationic powder electrodeposition paint with a disper,
Gradually add a predetermined amount of conductive carbon paste P-1,
After mixing and dispersing, it is diluted with deionized water to a solids content of 12%.

The anionic electrodeposition paint A-4 contained 10 parts of polyptadiene resin varnish (resin acid value 100, neutralization equivalent with triethylamine 0.5), 35 parts of titanium white, and 5 parts of talc.
1 part and 0.5 part of strontium chromate were blended and dispersed in a bevel mill for 2 hours. The redissolution rate of the flea coating film obtained from this paint was 90%. Comparative Example 1 In the formulation of the cationic powder electrodeposition paint of Example 1, no military conducting carbon was added to the cationic powder electrodeposition paint of Example 1 (bath solid content 12% pH 4.4 to 4.5) was used.

In addition, in the formulation of the anionic electrodeposition paint A-4 of Example 1, a polybutadiene varnish having a neutralization equivalent of 0.80 with triethylamine was used to prepare an anionic electrodeposition paint A-5 for the second time. The redissolution rate of the tortoise coating film obtained from this paint was 20%. Using each of the above-mentioned paints, coating was performed according to the coating process shown in Table 1, and test pieces were prepared.

For comparison, the above cationic powder electrodeposition paint (without conductive carbon added) was applied under the conditions of Step 3 in Table 1, and then the anionic electrodeposition paint A-4 of Example 1 was applied under the conditions of Step 3 in Table 1. A test piece coated under condition 4 was also added.

The test results for these test pieces are shown in Table 2.

Table 1 Note). It has the same structure as the device described in the drawing of Tokukonuma No. 50-8467, the inner diameter of the tube is thin, the dimensions of the test strip are 15 x 0.6 inches, the dimensions of the test panel are 4 x 12 inches, and the bottom The gap between the tube and the end of the tube is 1 inch, and a stirrer for isoban is attached.

The same equipment was used for the table below. Table 2 Note) Salt water spray resistance is based on JIS Z2371K.

The same applies to the table below. Example 2 A cationic powder electrodeposition paint in which conductive carbon (Laben 1500, manufactured by Columbia Carbon Co., USA) was added as the first coating to the surface treated board according to steps 1 and 2 in Table 3. Four types of test pieces were prepared by coating B-1, B-2, B-3, and B-4 (4 types) under the conditions shown in Table 3.

For comparison, after the first cationic powder electrodeposition coating, cationic electrodeposition paint B- with a redissolution rate of 37%, which will be described later, was used.
6 (Comparative Example 2) under the conditions of Step 4 in Table 1, three types of test pieces were also added. Table 4 shows the test results for these test pieces and the volume specific electrical resistance values of the cationic powder electrodeposited coating (first time). In addition, four types of cationic powder electrodeposition paints B-1, B-2, B-3, B-4
is the cationic powder electrodeposition paint of Example 1 (bath solid content 12%)
, PH4.4 to 4.5), conductive carbon paste P-2 shown below was added.

<Conductive carbon paste P-2> Aminoepoxy resin binder 143 parts (same aminoepoxy resin binder used in the conductive carbon paste of Example 1) Raven 1500 1
0 Hanabe Columbian Carbon Co.) Glacial acetic acid
6.2 parts ethylene glycol
20 parts of the above mixture in a bevel mill
■A conductive carbon paste was created over time.

<Cationic powder electrodeposition paint> Note) While applying the cationic powder electrodeposition paint to 100 parts of the solid content of the cationic powder electrodeposition paint using a disper, apply a predetermined amount of conductive force - Bonbaset P-2. After gradual addition and mixing and dispersion, it is diluted with deionized water to a solids content of 12%.

In addition, cationic electrodeposition paint B-5 was formulated with 10 parts of epoxy polyamino resin varnish (resin base value 8u, neutralization equivalent with hydroxyl acetic acid 0.3), 2 parts of titanium white, and 5 parts of purified clay. It was made by dispersing it in a vebble mill for 20 hours.

The redissolution rate of the exposed coating film obtained from this paint was 4%. Cationic powder electrodeposition paint B-1, B-2 of Example 3
, B-3, and B-4, two types of first-time cationic electrodeposition paints were prepared using 1 part and 5 parts of conductive carbon.

The volume specific electrical resistance values of the mist coatings obtained from these paints are 1.0 x 1 and 4 (with 1 part added) and 21 x 1.
(added 50 parts) was Q. In addition, in the formulation of the cationic military paint B-5 of Example 2, an epoxy polyamino resin varnish with a neutralization equivalent of 0.80 by hydroxyl acetic acid was used, and a second cationic electrodeposition paint B-3 was used. made.

The redissolution rate of the tortoise coating film obtained from this paint was 37%. According to the painting process and method in Table 3, the above two types 1
After applying the cationic electrodeposition paint for the first time,
A test piece was prepared by applying cationic electrodeposition paint B-6 for the second time.

For comparison, the above-mentioned first-time cationic powder coating (two types) was applied under the conditions of Step 3 in Table 3, and then the cationic electrodeposition coating B-5 (Example 2) was applied.
Two types of test pieces each coated with a re-dissolution rate of 4%) under the conditions of Step 4 in Table 3 were also added.

The test results for these test pieces are shown in Table 4.

Table 3 Table 4

Claims (1)

[Claims] 1. Contains conductive powder and has a power of 1×10^ at 20°C and 20V.
Apply the first electrodeposition coating to the object using a cationic powder electrodeposition paint that can form a coating film with a volume specific electrical resistance value in the range of 7 to 1 x 10^1^3 Ωcm. , Apply an electrodeposition paint to the uncoated area of the electrodeposition paint, which has a redissolution rate of 15% by weight or less when the coated plate immediately after electrodeposition is immersed in an electrodeposition bath at 30°C for 10 minutes. An electrodeposition coating method characterized in that a second electrodeposition paint is applied using the electrodeposition paint. 2. The electrodeposition coating method according to claim 1, wherein the paint used for the second electrodeposition coating is an anionic electrodeposition paint. 3. The electrodeposition coating method according to claim 1, wherein the paint used for the second electrodeposition coating is a cationic electrodeposition paint.