JPH07331133A - Matte electrodeposition coating composition containing fluororesin and method of coating therewith - Google Patents

Abstract

PURPOSE:To provide a matte electrodeposition coating composition which does not hide the hue and fine pattern of a substrate itself and a method of matte electrodeposition coating. CONSTITUTION:This composition contains a hydroxylated and carboxylated fluororesin, an acetoacetylated compound, an amine and water, an aldehyde, an alkoxylated methylolmelamine having a capability of being diluted with water of at most 4.0cc and an acidic compound having a pka of at most 1.9.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a fluororesin-containing matte electrodeposition coating composition and a coating method thereof.

[0002]

2. Description of the Related Art Conventionally, the use of fine acrylic resin particles in a matte electrodeposition coating has been devised in Japanese Patent Application Laid-Open No. 61-141771. Here, the acrylic resin fine particles are characterized by being mixed with acrylic resin in an amount of 2 to 20%. There was a problem in practical use because the sedimentation of the body in the electrodeposition paint bath was remarkable and the difference in gloss value was large depending on the part of the object to be coated.

[0003]

As a fluororesin-containing matte electrodeposition coating method for solving the above problems, a method of using a microgel by utilizing an alkoxysilane group for a matting technique is disclosed in JP-A-2-166173. Japanese Patent Laid-Open No. 2-2
Although it has been devised in Japanese Patent No. 18769 and Japanese Patent Laid-Open No. 3-140379, there are constraints on the workability of electrodeposition coating, such as the gloss value fluctuating depending on the coating conditions and being easily affected by the cleaning process after electrodeposition. is there.

[0004]

The present invention provides a fine gel particle which can be electrodeposited in water by adding an aldehyde after neutralizing and diluting an acetoacetylated fluororesin with amines and water. And an alkoxylated methylol melamine resin having a water dilutability of 4.0 cc or less as a curing agent, and an acidic compound having a pka of 1.9 or less as a catalyst for lowering the curing temperature. It has been found that the above problems can be solved. The present invention provides a matte electrodeposition coating composition containing (A) a hydroxyl group- and carboxyl group-containing fluororesin, (B) an acetoacetyl group-containing compound (C) amines, and water (D) aldehydes. ,
Further, (E) a matte electrodeposition coating composition containing an alkoxylated methylol melamine resin having a water dilutability of 4.0 cc or less,
Further, the present invention proposes a fluororesin matte electrodeposition coating composition characterized by containing an acidic compound having (F) pka of 1.9 or less, and a matte electrodeposition coating method using the same.

The matte electrodeposition coating composition of the present invention and its coating method will be described in detail below. As the fluorine resin having a hydroxyl group and a carboxyl group of (A),
As devised in JP-A-1-289874, those in which a carboxyl group is introduced by using acrylic acid, vinyl acetic acid or allyloxyacetic acid as a carboxyl group-containing monomer, or JP-A-58-136605. As devised in JP-A-6-41223, etc., those obtained by reacting a fluorine-containing fluororesin with a dibasic acid anhydride to introduce a carboxyl group can be used. The acid value of the fluororesin having a hydroxyl group and a carboxyl group is suitably 10 to 200 (mgKOH / g resin solid content). Acid value is 10 (mgK
If less than OH / g resin solid content), after neutralization with amines,
200 (mgKOH /
g resin solid content), the electrophoretic property is poor and the performance such as alkali resistance is also degraded. Regarding the hydroxyl value, it is appropriate that the hydroxyl value after the hydroxyl value is consumed by acetoacetylation by the compound (B) having an acetoacetyl group described later is 30 to 230 (mgKOH / g resin solid content). . Hydroxyl value is 30 (mgK
If it is less than (OH / g resin solid content), a sufficient crosslinked coating film cannot be obtained, and if it exceeds 230, the water resistance is poor and sufficient coating film performance cannot be obtained. The hydroxyl value consumed by the acetoacetylation needs to be considered in addition to 30 to 230 (mg KOH / g resin solid content) in advance. Furthermore, it is useful to add a solvent in order to maintain good water dispersibility of the fluororesin. As such a solvent, an inert solvent should be selected in consideration of (B) acetoacetylation with a compound having an acetoacetyl group, and specifically, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, diethylene glycol dimethyl ether, Glycol ethers such as diethylene glycol diethyl ether are suitable. After completion of the acetoacetylation, a hydroxyl group-containing solvent such as ethylene glycol monoethyl ether may be used if necessary. Next, the compound containing an acetoacetyl group of (B) is (A)
It is a compound for acetoacetylating a hydroxyl group of a fluororesin with diketene or acetoacetyl ester. Examples of such compounds include methyl acetate represented by Chemical formula 1 and

[0006]

[Chemical 1]

Ethyl acetoacetate represented by Chemical formula 2,

[0008]

[Chemical 2]

Examples include t-butyl acetoacetate represented by Chemical Formula 3 and the like.

[0010]

[Chemical 3]

The acetoacetyl group (B) introduced by the compound having an acetoacetyl group is suitably 5 to 100 mmol in 100 g of the resin solid content of the (A) fluororesin. If it is less than 5 mmol, the fine gel particles necessary for matting are insufficient, and if it exceeds 100 mmol, the smoothness of the coating film is insufficient.

The acetoacetylated fluororesin thus obtained was mixed with, for example, an acrylic resin, an amino resin, a xylene resin, an epoxy resin, a polyester resin, etc., if necessary depending on the required performance, workability, cost and the like. After that, it may be subjected to the next dilution with neutralized water. In addition, it is also possible to utilize the mixture of these miscible resins as necessary after neutralization to water dilution.

The amines shown in (C) are for water-dispersing or water-solubilizing an acetoacetylated fluororesin by neutralization, and alkyl such as monoethylamine, diethylamine, triethylamine, diethanolamine, diisopropanolamine and the like. Alternatively, there are alkanolamines and the like. Other examples include cyclic amines such as pyridine and ammonia. Also, depending on the case, KOH, Na
An inorganic alkali such as OH can also be used. A useful degree of neutralization is 0.3 to 1.5 equivalents with respect to the carboxylic acid.
If it is less than 0.3 equivalent, it is difficult to disperse in water, and if it exceeds 1.5 equivalent, the electrophoretic property is poor, which is not preferable. The water used here is preferably deionized water. Further, it is also a useful method to pre-mix a predetermined amount of the above-mentioned amine in deionized water before use. Further, a method of adding a resin solution to amine water, a method of adding a neutralized resin to water, and the like can be appropriately used. The higher the degree of neutralization with amines in (C) and the higher the degree of dilution with deionized water, the finer the particle size of the gel particles obtained. In addition, various anionic and nonionic surfactants control the particle size and
It is added if necessary for stable dispersion.

Next, (D) aldehydes will be described.
Resin particles dispersed in water with (A) a fluororesin, (B) a compound having an acetoacetyl group, (C) amines and water are crosslinked and condensed with the aldehydes of (D) to form a fine gel. Generate particles. (D) Formalin and a formalin condensate such as paraform are useful as the aldehydes. Besides, aliphatic aldehydes such as acetaldehyde, propyl aldehyde, butyraldehyde, aromatic aldehydes such as benzaldehyde, and aldehyde condensates such as glyoxal can also be used. It is preferable to add 0.1 to 10 mol, preferably 0.2 to 2 mol, relative to 1 mol of the acetoacetyl group.

Next, (E) an alkoxylated methylol melamine resin having a water dilutability of 4.0 cc or less will be described in detail. The water dilutability is determined by the following method. Weigh 5 g of the sample and 5 g of isopropanol in a 100 ml beaker with a fine balance and after mixing, add water from the burette while keeping the temperature at 25 ° C and stir, read the number of milliliters of water required for cloudiness, and dilute with water. The cc number of sex. The end point of the dropping is the place where the printed letters (type 4) placed under the beaker become unreadable. The alkoxylated methylol melamine resin having a low water-dilutability is manufactured by a conventional method, but can be obtained by higher alkoxylation or increasing the degree of condensation. That is, industrially, a melamine resin prepared by mixing methanol and butanol is useful for electrodeposition, but it is obtained by increasing the butanol ratio, and at the same time, it is also obtained by increasing the degree of polymerization by condensation of the melamine resin itself. . The (E) melamine resin causes a crosslinking reaction with the hydroxyl group of the (A) fluororesin by baking. In some cases, the combined use with a water dilutability of more than 4 cc is carried out as necessary. It is appropriate to use 10 to 100 parts by weight of the (E) melamine resin with respect to 100 parts by weight of the (A) fluororesin. If it is less than 10 parts by weight, a sufficient crosslinked coating film cannot be obtained, and if it exceeds 100 parts by weight, the melamine resin becomes excessive, and similarly a sufficient crosslinked coating film cannot be obtained. The subsequent washability will be reduced.

(E) The action of the alkoxylated methylol melamine resin having a water dilutability of 4.0 cc or less is considered as follows. In the process of electrodeposition-cleaning-baking, when the cleaning water is unevenly deposited on the electrodeposition coating film after cleaning, the temperature rising speed of the object to be coated in the baking furnace is delayed, and In this case, since the etching effect due to the adhered moisture is different from that of the non-adhered portion, the gloss and appearance of the finished coating film after baking will be defective. Particularly, industrially, a filtrate such as a UF membrane or an RO membrane is generally used as the washing water, and since it contains a water-soluble solvent, an amine, etc.,
This problem is industrially likely to occur. Here, a melamine resin having a water-dilutability of 4.0 cc or less does not dissolve in water and exhibits water repellency, and thus is necessary to eliminate such a problem. With a melamine resin having a water dilutability of more than 4 cc, such an effect cannot be expected.

Next, the acidic compound having (F) pka of 1.9 or less will be described. The acidic compound having (F) pka of 1.9 or less includes (E) melamine resin, (A) hydroxyl group, and
It is not always necessary to carry out the crosslinking with the fluororesin containing a carboxyl group at a generally industrial baking temperature, that is, at 180 ° C. However, due to the recent need for energy saving, the baking temperature in the low temperature range, for example, 1
It is required to obtain good coating performance at 50 ° C.
In that case, an acidic compound having a pka of 1.9 or less is essential. At the baking temperature in this low temperature range, pka is 1.
If the acidic compound exceeds 9, good coating performance cannot be exhibited. The suitable addition amount is 0.1 to 2 parts by weight with respect to 100 parts by weight of the (A) fluororesin. Such an acidic compound is
It is not effective for those that evaporate during baking, and sulfonic acid catalysts are most useful. A typical example is an aromatic sulfonic acid such as p-toluenesulfonic acid. Specifically, p-
Examples thereof include monosulfonic acids such as dodecylbenzenesulfonic acid and disulfonic acids such as dihexylnaphthalenedisulfonic acid. Neutralize these acidic compounds with amines and use them as salts. Furthermore, use them after so-called masking so as to effectively act during baking, such as by esterifying with low molecular weight epoxy resin, lower alcohol, etc. Doing is also significant.

In the present invention, in order to obtain a fine gel from such a composition, it is necessary to age it under the following conditions.
Such conditions should be appropriately selected, but under ordinary stirring, the temperature is 5 to 100 ° C, the time is 5 minutes to 48 hours, preferably 20 to 100 ° C, and 30 minutes to 3 hours are industrially advantageous. The matte electrodeposition coating composition of the present invention containing the components (A) to (D) and (E) and (F) is diluted with deionized water and a solvent containing water as a main component, if necessary. The electrodeposited coating film can be obtained by applying a predetermined voltage with the object to be coated as an anode, and if necessary, after washing by a conventional method, a matte coating film can be obtained through a baking step.

[0019]

EXAMPLES The present invention will be described below with reference to examples. (A) Production Example of Fluororesin Having Hydroxyl Group and Carboxyl Group The following fluororesin was produced according to JP-A-6-41223. Hydroxyl group consisting of chlorotrifluoroethylene, cyclohexyl vinyl ether, ethyl vinyl ether and hydroxybutyl vinyl ether 145 (m
A fluororesin-containing polymer having a gKOH / g resin solid content) was obtained. Next, it was reacted with hexahydrophthalic anhydride in a xylene solution to obtain a fluororesin having a hydroxyl group and a carboxyl group. The solvent of the obtained fluororesin was changed from xylene to diethylene glycol dimethyl ether, and the resin solid content was adjusted to 55.0%. The obtained resin was a viscous resin liquid having an acid value of 50 (mgKOH / g resin solid content) and a hydroxyl value of 96 (mgKOH / g resin solid content).

(B) Production Example of Fluorocarbon Resin Acetoacetylated 181.8 parts by weight of the fluorocarbon resin of (A) was charged into a reaction apparatus having a stirrer, a thermometer, and a reflux cooling device, and 135 ° C.
The temperature was raised to 1.8 parts by weight, and 1.8 parts by weight of t-butyl acetoacetate was added, and the mixture was kept at 135 ± 3 ° C. for 2 hours, after distilling off t-butanol, it was cooled. Resin solid content = 55.2%,
A transparent and viscous resin liquid having an acid value of 50 (mg KOH / g resin solid content) was obtained.

Example 1 Production Example of Fluororesin Matte Electrodeposition Coating Bath (1) 183.6 parts by weight of acetoacetylated fluororesin solution of (B) (2) Triethylamine 7.2 parts by weight (3) Deionized water 152.6 parts by weight (4) Alkoxylated methylol melamine resin 30.0 parts by weight (Niwak MX-40, manufactured by Sanwa Chemical Co., Ltd.) (5) Formalin (35% formaldehyde aqueous solution) 0.4 parts by weight ( 6) Deionized water 300.0 parts by weight (7) Deionized water 951.2 parts by weight At 30 ° C. (1) under stirring (2), (3), (4)
Was added, and the mixture was stirred for 1 hour until it became uniform, then (5) was added, the temperature was raised to 80 ° C., and the mixture was further stirred for 2 hours and cooled. After that, (6) and (7) were added to obtain an electrodeposition coating solution. The temperature is 22 ° C., resin solid content = 8%, PH = 9.
1. A cloudy electrodeposition coating solution having a liquid resistivity = 1850 Ω · cm was obtained.

(Example of electrodeposition coating and confirmation of fine gel particles)
The obtained electrodeposition coating solution was placed in a 3-liter vinyl chloride tank. The cathode is SUS-304, and the anode (object to be coated) is
The 6063S aluminum alloy plate was anodized (alumite film thickness = 9 μm), electrolytically colored black, and washed with hot water by a conventional method. With a bath temperature of 22 ° C., a distance between the electrodes of 12 cm, and a pole ratio (+/−) of 2/1, electricity was applied and washed at 170 V to 10 μm by a conventional method.
It was baked and dried at 80 ° C. for 30 minutes. The results are shown in Table 1.

(Examples 2 to 3) With the composition shown in Table 1, an electrodeposition coating solution having a solid content of 8% was prepared in the same manner as in Example 1, and electrodeposition and baking were performed. The results are shown in Table 1.

(Comparative Examples 1 to 3) With the composition shown in Table 1, an electrodeposition coating solution having a solid content of 8% was prepared in the same manner as in Example 1, and electrodeposition and baking were performed. The results are shown in Table 1.

[0025]

[Table 1]

* 1 Sumimar M-8B (Sumitomo Chemical Co., Ltd.) Water dilution = 2.6cc * 2 Catalyst 600 (Mitsui Cytec Co., Ltd.) Aliphatic sulfonic acid with a pka of less than 1.0 * 3 Sample 1 after deionized water addition in Example 1 (6)
100 g of acetone is added to 0 g, and the change in turbidity is visually observed. * 4 LPA-3000 / 3100 manufactured by Otsuka Electronics Co., Ltd.
by. * 5 Appearance of coating film after 98 ° C x 5 hours.

[0027]

The composition of the present invention has transparency.
Gel fine particles for forming fine irregularities that do not impair the metallic feeling of the base can be obtained in water that is indispensable for normal electrodeposition, regardless of forced or mechanical micronization methods such as sand mill dispersion and ball mill dispersion. In addition, when the electrodeposition coating bath obtained by the composition of the present invention is used for electrodeposition coating, the fine particles themselves have a good electrophoretic property, and the uniform dispersibility in the bath is excellent. Therefore, a uniform matte electrodeposition coating film having a good design property was obtained.

Claims (4)

[Claims] 1. A fluorine resin containing (A) a hydroxyl group- and carboxyl group-containing fluororesin (B) an acetoacetyl group-containing compound (C) amines and water (D) aldehydes Matte electrodeposition coating composition. 2. A fluorine resin having (A) a hydroxyl group and a carboxyl group, (B) an amine having a compound having an acetoacetyl group (C), water (D) an aldehyde, and (E) a water dilutability of 4.0 cc or less. 1. A matte electrodeposition coating composition containing a fluororesin, which contains the alkoxylated methylol melamine resin as described in 1. 3. A fluorine resin having (A) a hydroxyl group and a carboxyl group, (B) an amine having a compound having an acetoacetyl group (C), water (D) an aldehyde, and (E) a water dilutability of 4.0 cc or less. 1. A matte electrodeposition coating composition containing a fluororesin, which comprises the alkoxylated methylol melamine resin, and an acidic compound having a (F) pka of 1.9 or less. 4. A matte electrodeposition containing a fluororesin, characterized in that a coating film is obtained by an electrodeposition coating method using the electrodeposition coating composition according to claim 1, claim 2 or claim 3. How to paint.