JP2020196804A - Curing catalyst for electro-deposition coating, electro-deposition coating, and activation method of curing catalyst - Google Patents

Abstract

To provide a technology of a fatty acid bismuth-containing curing catalyst suitable for an aqueous electro-deposition coating.SOLUTION: Catalytic activity of fatty acid bismuth which is a material of a curing catalyst is heightened, to an aqueous electro-deposition coating. For that reason, ethylene diamine is mixed with fatty acid bismuth, and both compounds are allowed to exist in the associated form in the aqueous electro-deposition coating. The curing catalyst which is a mixture of fatty acid bismuth and ethylene diamine shows required curing catalytic function with a comparatively small amount of catalyst, since occurrence of hydrolysis by water is suppressed.SELECTED DRAWING: None

Description

The present invention relates to a technique relating to a curing catalyst useful for water-based electrodeposition coating materials, and relates to a technique relating to an increase in the catalytic activity of a specific bismuth compound to avoid the use of an organic tin compound.

In general, electrodeposition coating, in which coating is performed electrochemically, is excellent in corrosion resistance and circumstance, and is widely used for coating automobile bodies, parts, and the like. The coating process usually spans 2-3 steps (eg, undercoat-intermediate coat-topcoat). In the first-stage undercoating step, the adhesion or adhesion between the paint and the surface to be coated is improved, and effective rust prevention is provided. Then, an aesthetically pleasing painted surface is obtained by the next step of intermediate coating and top coating. For the general background of electrodeposition coating, refer to Non-Patent Document 1.

The paint used for electrodeposition coating (that is, electrodeposition paint) usually contains at least a curing agent for cross-linking the base resin in addition to the base resin, and also contains coloring pigments and additives, and is relatively relatively. It contains a lot of water and is water-based as a whole.

In electrodeposition coating using such an electrodeposition coating material, the coating film is required to have appropriate hardness and corrosion resistance or corrosion resistance. Therefore, a curing catalyst that promotes cross-linking of the curing agent is added to the water-based electrodeposition coating material. Since lead compounds having excellent anticorrosion properties are harmful, the inventors have previously proposed as Patent Document 1 a technique for developing a specific firing composition as an alternative material and blending it in an electrodeposition coating material. did.

Japanese Patent No. 4204049

Automotive Electroplated Coating Technology, Iron and Steel, No. 7, 1980, pp. 185-195

The developed firing composition exhibits not only rust prevention but also a curing catalyst function, and is useful as a material for electrodeposition coatings. Further, by additionally using a known curing catalyst such as dioctyl tin oxide (DOTO), the corrosion resistance of the coating film is further improved, or the baking temperature of the coating film after electrodeposition coating is reduced. Get benefits such as being able to.

However, since the sintered composition requires a firing treatment at a high temperature of, for example, 300 to 1000 ° C., the cost is higher than that of other materials. In addition, organic tin compounds represented by DOTO are strictly regulated from the viewpoint of environmental protection. Therefore, it is desired to avoid using such a problematic curing catalyst as much as possible.

On the other hand, products having a coating film by electrodeposition coating (for example, automobiles) are used in various environments. For example, there are different usage environments, such as in a harsh environment such as a part of Europe where the temperature is as low as below zero, and in a region including Japan where there is no such harshness. The coating film in the latter environment does not require properties such as high anticorrosion properties required in the former environment. Too high corrosion resistance is unnecessary for the coating film in the latter environment. Considering the cost of the product, a coating film having properties suitable for the environment, which can reduce the cost, is required.

From the above viewpoints, as an electrodeposition coating technique used in a general environment including Japan, the inventors have adopted an organotin compound which is problematic in terms of firing treatment at a high temperature as in a firing composition and environmental protection. We focused on technologies that are not used as much as possible.

Therefore, the idea focused on is to effectively use the fatty acid bismuth as a curing catalyst for water-based electrodeposition paints. In water-based electrodeposition paints, fatty acid bismuth is hydrolyzed by the presence of water, so it has been found that there is a problem that an excessive amount must be added.

Therefore, an object of the present invention is to provide a technique capable of enhancing the catalytic activity of fatty acid bismuth as a curing catalyst for water-based electrodeposition coating materials. Other objects of the present invention will become clear from future description.

The electrodeposition technique of the present invention targets a water-based electrodeposition coating material to which water is added, and more specifically, a water-based cationic electrodeposition coating material. The most important point of the present invention is a method for increasing the catalytic activity of the fatty acid bismuth, which is a material for a curing catalyst, with respect to an aqueous electrodeposition coating material. The method is to mix ethylenediamine with bismuth fatty acid and allow both compounds to exist in an aqueous electrodeposition paint in the form of association. Since the curing catalyst, which is a mixture of fatty acid bismuth and ethylenediamine, is suppressed from being hydrolyzed by water, it exhibits the required curing catalyst function with a relatively small amount of catalyst.

Therefore, the present invention can be viewed from a plurality of viewpoints. One viewpoint is to use a mixture of fatty acid bismuth and ethylenediamine as a curing catalyst for water-based electrodeposition paints. Another viewpoint is that it is a water-based electrodeposition coating material containing a mixture of fatty acid bismuth and ethylenediamine as a curing catalyst. Furthermore, it is a view as a method for producing a curing catalyst for water-based electrodeposition coating materials, and is a method for obtaining an aqueous composition by mixing and associating fatty acid bismuth and ethylenediamine.

As the fatty acid bismuth, C _4-15 fatty acid bismuth is preferable, and bismuth trioctylate is particularly preferable. Ethylenediamine includes N- (2-aminoethyl) ethanolamine, N-di (2-aminoethyl) ethanolamine, N, N, N', N'-tetrax (2-hydroxyethyl) ethylenediamine, N, N. , N', N'-tetrakis (2-hydroxypropyl) ethylenediamine, is used by selection. Specifically, it has the following form.
(1) A mixture of tris (2-ethylhexanoate) bismuth and N, N, N', N'-tetrakis (2-hydroxyethyl) ethylenediamine.
(2) A mixture of tris (2-ethylhexanoate) bismuth and N, N, N', N'-tetrakis (2-hydroxypropyl) ethylenediamine.
(3) A mixture of trineodecanoate bismuth and N, N, N', N'-tetrakis (2-hydroxyethyl) ethylenediamine.
(4) A mixture of trineodecanoate bismuth and N, N, N', N'-tetrakis (2-hydroxypropyl) ethylenediamine.

Such a mixture becomes an associative form by mixing. The association is that the same molecule of fatty acid bismuth and ethylenediamine forms a relatively regular aggregate through relatively weak bonds such as hydrogen bonds, charge transfer bonds, and hydrophobic bonds. Therefore, it is considered that the fatty acid bismuth mixed with ethylenediamine is less susceptible to hydrolysis by water as compared with the case of the fatty acid bismuth alone, and as a result, the curing catalyst function is more effectively exhibited. The amount of the curing catalyst used is 0.1 to 10%, preferably 0.5 to 2%, with respect to the solid content of the substrate resin.

Such a mixture of fatty acid bismuth and ethylenediamine can be usefully used as a curing catalyst for electrodeposition coating materials, specifically, cationic electrodeposition coating materials. Furthermore, it can be provided as an electrodeposition coating material containing the same. When these mixtures are used as the composition for electrodeposition coating material, there are no particular restrictions on handling, and the same can be performed in the same manner as in the usual pigment dispersion method. For example, a dispersion paste can be prepared by previously dispersing the mixture in a dispersion resin, and the mixture can be blended. Examples of the pigment dispersion resin include an epoxy-based quaternary ammonium salt-type resin and an acrylic-based quaternary ammonium salt-type resin, which are usually used for cationic electrodeposition paints.

As the base resin, one derived from a bisphenol type epoxy resin having a number average molecular weight of 100 to 10,000, preferably 1000 to 3000 can be used, and the base resin has a base equivalent of 40 to 150 (milli equivalent / 100 g). Preferably, it is 60 to 100 (milli equivalent / 100 g).

A blocked polyisocyanate compound is used as the cross-linking agent. The blocked isocyanate cross-linking agent can be obtained by an addition reaction between an isocyanate blocking agent and a polyfunctional isocyanate. It is desirable that the isocyanate blocking agent dissociates the block and regenerates free isocyanate groups when heated to 100 to 200 ° C. For example, caprolactam, phenol, ethanol, 2-ethylhexyl alcohol, butyl cellosolve, methyl ethyl ketokisum and the like. Further, as the polyfunctional isocyanate compound, a fatty acid, an alicyclic or aromatic polyisocyanate is used. For example, tolylene diisocyanate, xylylene diisocyanate, 4,4'-diphenylmethane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate and its isocyanates.

When neutralizing or water-solubilizing the composition of the electrodeposition coating, the substrate resin and the blocked isocyanate cross-linking agent are dispersed in an aqueous medium using an organic acid such as formic acid, acetic acid, propionic acid, lactic acid, and sulfamic acid as a neutralizing agent. Do it by.

Further, as a paint additive, pigments such as titanium white, carbon black, talc, clay, and silica can be dispersed in the composition of the electrodeposition paint with a pigment dispersion resin and added as a pigment paste. Further, if necessary, other rust preventive pigments such as aluminum phosphate, aluminum phosphomolybate, barium borate and the like, and paint additives such as a surface conditioner and an organic solvent can be blended.

The composition of the electrodeposition coating material of the present invention, which comprises a mixture of fatty acid bismuth and ethylenediamine, is applied to the surface of the substrate by ordinary cationic electrodeposition coating. The cationic electrodeposition coating composition is an electrodeposition bath comprising an electrodeposition coating composition having a solid content concentration of 15 to 25% by weight adjusted with deionized water and a pH adjusted to a range of 5.5 to 7.0. The temperature is kept at 20 to 30 ° C., and the voltage is 100 to 400 V. In this case, the mixture of fatty acid bismuth and ethylenediamine does not exhibit excessive acidity or basicity, and the pH of the electrodeposition bath can be easily adjusted.

The film thickness of the coating film by electrodeposition is, for example, 10 to 50 μm, and the baking temperature of the coating film is, for example, 140 ° C. to 170 ° C., preferably 150 ° C. to 170 ° C. With such a general baking temperature, not only corrosion resistance but also good smoothness of the painted surface can be obtained.
Hereinafter, the present invention will be described in more detail with reference to Production Examples and Examples.

[Adjustment or manufacture of curing catalyst]

Manufacturing example 1
To a 1000 ml eggplant flask, 100 g of BiCAT8210 [manufactured by Shepherd (bismuth trioctylate 28 wt% Bi)] and 50 g of butyl cellosolve were added under a nitrogen gas atmosphere. Next, after stirring at an outside temperature of 40 ° C. for 30 minutes, 130 g of N, N, N', N'-tetrakis (2-hydroxyethyl) ethylenediamine was gradually added. Fever was observed in the reaction system, and the color changed from yellow to reddish brown. The reaction was carried out at an outside temperature of 50 ° C. for 1 hour to obtain 280 g of the title aqueous composition. The bismuth concentration was a quantitative yield of 10 wt%.

Manufacturing example 2
72 g of BiCAT 8210 [manufactured by Shepherd (bismuth trioctylate 28% Bi)] and 68 g of butyl cellosolve were added to a 500 ml eggplant flask in a nitrogen gas atmosphere. Next, 60 g of N, N, N', N'-tetrakis (2-hydroxypropyl) ethylenediamine was gradually added at an outside temperature of 40 ° C.
Fever was observed in the reaction system, and the color changed from yellow to reddish brown. The reaction was carried out at an outside temperature of 50 ° C. for 1 hour to obtain 200 g of the title aqueous composition. The bismuth concentration was a quantitative yield of 10 wt%.

Manufacturing example 3
To a 500 ml eggplant flask, 50 g of BiCAT 8106 [manufactured by Shepherd (bismuth neodecanoate 20 wt% Bi)] was added under a nitrogen gas atmosphere. Next, after stirring at an outside temperature of 40 ° C. for 30 minutes, 50 g of N, N, N', N'-tetrakis (2-hydroxyethyl) ethylenediamine was gradually added. Fever was observed in the reaction system, and the color changed from yellow to reddish brown. The reaction was carried out at an outside temperature of 50 ° C. for 1 hour to obtain 100 g of the title aqueous composition. The bismuth concentration was a quantitative yield of 10 wt%.

Manufacturing example 4
To a 500 ml eggplant flask, 50 g of BiCAT 8106 [manufactured by Shepherd (bismuth neodecanoate 20 wt% Bi)] and 20 g of butyl cellosolve were added under a nitrogen gas atmosphere. Next, 30 g of N, N, N', N'-tetrakis (2-hydroxypropyl) ethylenediamine was gradually added at an outside temperature of 40 ° C. Fever was observed in the reaction system, and the color changed from yellow to reddish brown. The reaction was carried out at an outside temperature of 50 ° C. for 1 hour to obtain 130 g of the title aqueous composition. The bismuth concentration was a quantitative yield of 10 wt%.

Production example 5
To a 500 ml eggplant flask, 50 g of BiCAT8210 [manufactured by Shepherd (bismuth trioctylate 28% Bi)] and 25 g of butyl cellosolve were added under a nitrogen gas atmosphere. Next, 65 g of 2- [2- (dimethylamino) ethyl] methylaminoethanol was gradually added at an outside temperature of 40 ° C. Fever was observed in the reaction system, and the color changed from yellow to reddish brown. The reaction was carried out at an outside temperature of 50 ° C. for 1 hour to obtain 140 g of the title aqueous composition. The bismuth concentration was a quantitative yield of 10 wt%.
[Preparation of 10% solution of bismuth trioctylate]

Add 270 g of butyl acetate to 30 g of bismuth trioctylate (BiCAT, 8210 Shepherd) and disperse with a paint shaker for 5 hours to obtain 300 g of a 10% solution.

[Manufacturing of clear emulsion]

Epon 1004 (epoxy resin manufactured by Yuka Shell Co., Ltd., trade name): 475 g is dissolved in butyl cellosolve: 253 g, and 31 g of diethylamine is added dropwise at 90 to 100 ° C and held at 120 ° C for 3 hours to have an amine value of 47. An amine adduct was obtained. Next, 250 g of a polyamide resin having an amine value of 100 was dissolved in 107 g of methyl isobutyl ketone, reflux dehydrated at 140 to 150 ° C., and the terminal amino groups of the polyamide resin were ketiminated. Hold at 150 ° C for 4 hours, confirm that no water is distilled off, cool to a liquid temperature of 50 ° C, add to the epoxyamine adduct, hold at 80 ° C for 1 hour, solid content 70%, amine value 66. Epoxy-amino-polyamide-added resin varnish was obtained. The above epoxy-amino-polyamide-added resin varnish (34 g) and 15% acetic acid (4 g) are mixed with 9.4 g of butyl cellosolve block product of xylylene diisocyanate, and 50 g of deionized water is added dropwise to obtain a cation electrodeposition clear emulsion having a solid content of 33%. It was.
[Manufacturing of pigment-dispersed resin]

Epototo YD-128 (epoxy equivalent 187, epoxy resin manufactured by Toto Kasei Co., Ltd., trade name) 275 g, Eport YD-011 (epoxy equivalent 475, epoxy resin manufactured by Toto Kasei Co., Ltd., trade name) 349 g, propylene glycol monomethyl ether 342 g The mixture was charged, heated to 100 ° C, stirred for 1 hour, and cooled to 80 ° C. Next, 95 g of diethylaminopropylamine and 77 g of diethanolamine were charged, held at 100 ° C. for 2 hours, and cooled to 70 ° C. The solid content of the obtained dispersed resin was 70%. This resin was neutralized with acetic acid so as to have a pH of 6.5 when the pigment was dispersed, and then dispersed.
[Adjustment of pigment paste]

By using a clear emulsion and a pigment dispersion resin prepared in advance, the mixture was dispersed according to the composition shown in Table 1, pulverized and adjusted with a sand mill to obtain a pigment paste and a cationic electrodeposition coating material.

ここで、実施例１〜５および比較例２のビスマス量は電着塗料固形分の0.7％に調整、それに対し、比較例３のビスマス量は電着塗料固形分の1.4％に調整した。すなわち、比較例３では、ビスマス量を実施例１〜５および比較例２に比べて多く用いた。

実施例１;
トリス（2−エチルヘキサノアート）ビスマスとN,N,N',N'-テトラキス（2−ヒドロキシエチル）
エチレンジアミンとの組成物

実施例２;
トリス（2−エチルヘキサノアート）ビスマスとN,N,N',N'-テトラキス（2−ヒドロキシプロピル）
エチレンジアミンとの組成物

実施例3；
トリネオデカノアートビスマスとN,N,N',N'-テトラキス（2−ヒドロキシエチル）
エチレンジアミンとの組成物

実施例4；
トリネオデカノアートビスマスとN,N,N',N'-テトラキス（2−ヒドロキシプロピル）
エチレンジアミンとの組成物

実施例5；
トリス（2−エチルヘキサノアート）ビスマスと2-〔2-(ジメチルアミノ）エチル)メチルアミノ〕
エタノールとの組成物

Here, the bismuth amount of Examples 1 to 5 and Comparative Example 2 was adjusted to 0.7% of the electrodeposition paint solid content, whereas the bismuth amount of Comparative Example 3 was adjusted to 1.4% of the electrodeposition paint solid content. That is, in Comparative Example 3, the amount of bismuth was used more than in Examples 1 to 5 and Comparative Example 2.

Example 1;
Tris (2-ethylhexanoate) bismuth and N, N, N', N'-tetrakis (2-hydroxyethyl)
Composition with ethylenediamine

Example 2;
Tris (2-ethylhexanoate) bismuth and N, N, N', N'-tetrakis (2-hydroxypropyl)
Composition with ethylenediamine

Example 3;
Trineodecanoart bismuth and N, N, N', N'-tetrakis (2-hydroxyethyl)
Composition with ethylenediamine

Example 4;
Trineodecanoart bismuth and N, N, N', N'-tetrakis (2-hydroxypropyl)
Composition with ethylenediamine

Example 5;
Tris (2-ethylhexanoate) bismuth and 2- [2- (dimethylamino) ethyl) methylamino]
Composition with ethanol

Using the pigment pastes of Examples 1 to 5 and Comparative Examples 1 to 3 as reference examples, a coating film by electrodeposition coating was prepared, and the performance test of the coating film was performed. In the test, a cold-rolled dull steel sheet of 0.8 × 150 × 70 mm treated with zinc phosphate was dipped in the electrodeposition paints obtained in Examples 1 to 5 and Comparative Examples 1 to 3 to serve as a cathode, and electrodeposition coating was performed. It was. The electrodeposition conditions were a voltage of 280 V, a film thickness of about 20 μm was applied, washed with water, and then baked. Baking was performed in a gear oven for 20 minutes at each temperature. Table 2 shows the performance test results of the obtained baked coating film.

この表２の中において、ゲル分率および耐食性については、比較例１を１００として指数で表示している。
他の例（比較例２，３および実施例１〜５）は、比較例１での指数による評価である。この評価において、ゲル分率は100以上の数字で硬化性が向上していることを示し、また、耐食性については、100以下の数で向上を示す評価になる。個々の評価について比較例１を100にした指数で行っているので、当業者には、比較例１〜３、および実施例１〜５の相対的な評価を容易に行うことができるであろう。なお、各試験について説明すると、ゲル分率は日本工業規格のJISK679、また、MIBKラビングは米国試験材料協会のASTMD4752（ここでは、溶剤としてMIBK、つまりメチルイソブチルケトンを用い、それを浸けたガーゼで塗面を１０回こすり、〇：わずかに溶ける、△：表層のみ溶解、×：全体に溶け、溶け度合いに応じて×の数が増えるという評価）、鉛筆硬度は日本工業規格JISK5600、そして、耐食性は塗装面にクロスカットを入れた試験片を塩水に浸し、錆の広がり具合を測定、に準じる。

In Table 2, the gel fraction and corrosion resistance are expressed as indexes with Comparative Example 1 as 100.
Another example (Comparative Examples 2 and 3 and Examples 1 to 5) is the evaluation by the index in Comparative Example 1. In this evaluation, a gel fraction of 100 or more indicates that the curability is improved, and a corrosion resistance of 100 or less indicates an improvement. Since each evaluation is performed using an index with Comparative Example 1 set to 100, those skilled in the art will be able to easily perform relative evaluations of Comparative Examples 1 to 3 and Examples 1 to 5. .. Explaining each test, the gel fraction is JIS K679 of the Japanese Industrial Standards, and MIBK rubbing is ASTM D4752 of the American Test Materials Association (here, MIBK, that is, methyl isobutyl ketone is used as a solvent, and gauze soaked in it is used. Rubbing the coated surface 10 times, 〇: slightly melts, △: melts only the surface layer, ×: dissolves in the whole, evaluation that the number of × increases according to the degree of melting), pencil hardness is Japanese Industrial Standard JIS K5600, and corrosion resistance Soak a test piece with a crosscut on the painted surface in salt water and measure the spread of rust.

Table 2 shows the results of the gel fraction, the MIBK rubbing test, the pencil hardness test, and the corrosion resistance test at four stages of curing temperatures of 170 ° C., 160 ° C., 150 ° C., and 140 ° C. Comparative Example 2 is a case where bismuth octylate is added as a curing catalyst in an amount of 0.7% with respect to the solid content of the electrodeposition coating material, and the case where the curing catalyst is organic tin (DOTO) is not added in Comparative Example 1. In comparison, each performance is an excellent result. Further, Examples 1 to 5 are more excellent evaluation results than Comparative Example 2. Comparative Example 2 and Examples 1 to 5 have the same amount of bismuth as a curing catalyst, but the curing performance of BiCAT 8210 of Comparative Example 2 is inferior to that of Examples 1 to 5. It is considered that this is because the water-insoluble bismuth octylate was hydrolyzed when it was dispersed in the pigment solid content and changed to octylic acid and bismuth hydroxide. In that respect, even when the result of Comparative Example 3 in which bismuth octylate as a curing catalyst was added to the electrodeposition coating solid content at 1.4%, which is twice that of Comparative Example 2, the effect of hydrolysis was observed. It seems to be big. That is, in Comparative Example 2 in which the amount of catalyst was increased, a slight improvement in performance was observed as compared with Comparative Example 1 in which the amount of catalyst was small, but there was a large difference in the degree of performance improvement as compared with Examples 1 to 5. There is. From these, the idea of the present invention, that is, the water-soluble bismuth octylate salt associated with the association of bismuth octylate, which is a fatty acid bismuth, with ethylenediamine produces an effect of reducing or suppressing the hydrolysis reaction and stabilizing the hydrolysis reaction. ..

As described above, according to Examples 1 to 5 of the present invention, it can be seen that the curing catalyst function is effectively improved as compared with the case where the amount of bismuth of the curing catalyst is the same. Therefore, the amount of fatty acid bismuth used as a material for the curing catalyst can be suppressed to an appropriate amount, and a curing catalyst and an electrodeposition coating material containing the same can be provided at a reasonable price.

Claims (6)

A curing catalyst for water-based electrodeposition coating materials, which comprises at least a substrate resin and a curing agent for cross-linking the substrate resin, and is composed of a mixture of fatty acid bismuth and ethylenediamine. The curing catalyst according to claim 1, wherein the mixture of fatty acid bismuth and ethylenediamine is an association of fatty acid bismuth and ethylenediamine.
An aqueous electrodeposition coating material containing at least a base resin and a curing agent for cross-linking the base resin, further comprising a mixture of fatty acid bismuth and ethylenediamine as a curing catalyst. The electrodeposition coating material according to claim 3, wherein the mixture of fatty acid bismuth and ethylenediamine is an association of fatty acid bismuth and ethylenediamine.
A method for producing a curing catalyst for water-based electrodeposition coating materials, which comprises at least a substrate resin and a curing agent for cross-linking the substrate resin. By mixing and associating fatty acids bismuth and ethylenediamine. A method for producing a curing catalyst, which comprises obtaining an aqueous composition.
In a method for increasing the catalytic activity of a curing catalyst containing a bismuth compound, which is intended for use in an aqueous electrodeposition coating material containing at least a base resin and a curing agent for cross-linking the base resin, the fatty acid bismuth is used. A method for activating a curing catalyst, which comprises mixing and associating with ethylenediamine.