JP2000044865A - Matte electrodeposition coating and its electrodeposition coating application - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a matte electrodeposition coating capable of forming uniform matte coating films having excellent mechanical characteristics, solvent resistance, weather resistance and workability by using an aqueous resin dispersion containing a specific acrylic resin, an amino resin and a basic substance. SOLUTION: This matte electrodeposition coating comprises an aqueous resin dispersion containing (A) an acrylic resin (preferably having a weight- average mol.wt. of 10,000-100,000) prepared by copolymerizing (i) an α,β-ethylenic unsaturated carboxylic acid monomer such as acrylic acid, (ii) a (meth)acrylic acid ester containing an alicyclic epoxy group, and (iii) one or more other α,β-ethylenic unsaturated monomers, (B) an amino resin such as a melamine resin, and (C) a basic substance such as monomethylamine. The component A is preferably an acrylic resin copolymerized with 0.1-10 wt.% of the component ii and having an acid value of 30-150, and the aqueous resin dispersion is preferably used for electrodeposition coating applications.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a matte electrodeposition paint and a matte electrodeposition coating method. Specifically, (A)
(A) α, β-ethylenically unsaturated carboxylic acid monomer,
(B) an acrylic resin obtained by copolymerizing (meth) acrylic ester containing an alicyclic epoxy group and (c) other α, β-ethylenically unsaturated monomers as essential components; and (B) A matte electrodeposition coating comprising an aqueous microgel, comprising an amino resin, and a matte electrode obtained by using the electrodeposition coating to obtain a coating film by an electrodeposition coating method using an object to be coated as an anode. Related to the coating method.

[0002]

2. Description of the Related Art Heretofore, as a matte paint which does not obscure the hue and fine pattern of the object to be coated itself, one in which micro silica is dispersed in the paint has been generally used.
However, microsilica is inferior in chemical resistance, especially in alkali resistance, and a coating film having good transparency cannot be obtained. There are drawbacks such as a difference in gloss, particularly on the upper and lower surfaces, depending on the part to be coated.

On the other hand, there is known a method of dispersing organic fine particles having a small specific gravity in a coating material. However, this method, for example, a method in which organic fine particles are dispersed in a paint as described in JP-B-51-8975 has practical utility as a general solvent type spray paint or a dip type paint. However, it was unsuitable as an electrodeposition paint. The reason for this is that since the electrophoretic properties of the organic fine particles are not considered at all, the organic fine particles do not have the characteristic of electrophoresis at a constant rate when energized, and sometimes fall off by washing with water.

In the electrodeposition paints and coatings, the viscosity of the electrodeposition bath is set to be substantially the same as the viscosity of water from the viewpoint of diffusion of generated Joule heat and washing properties. The body has such a low viscosity (usually a water content of 80-9
5%) electrolyte has poor uniform dispersibility in a bath, and other than the solvent used for the purpose of adjusting gloss, improving washability, lowering the coating resistance value, etc. in an electrodeposition paint, and other than essential components of the paint. However, there has been a drawback that no consideration has been given to the elimination of contaminating electrolytes.

[0005]

On the other hand, there is known a method of forming an insoluble intra-particle microgel in a resin for electrodeposition paint to achieve low gloss. Various methods for forming microgels have been proposed, one of which is to introduce an alkoxysilyl group into the base resin and form a insoluble intraparticle microgel in the copolymer resin by a condensation reaction with the alkoxysilyl group. Has been proposed. For example, JP-A-59-67396, JP-A-64-14281, and JP-A-05-263296 correspond to this technique, but the gloss value varies depending on the coating conditions, and the cleaning process after electrodeposition. In particular, there are constraints on the electrodeposition coating workability, such as being susceptible to the effects of

[0006]

The inventors of the present invention have conducted intensive studies to solve the problems of matte electrodeposition paints which depend on the condensation reaction of the alkoxysilyl groups, and found that α,
β-ethylenically unsaturated carboxylic acid monomers, (meth) acrylic acid esters containing an alicyclic epoxy group represented by the following general formula, and other α, β-ethylenically unsaturated monomers By using a copolymerized acrylic resin, an electrodeposition paint having an excellent matte appearance and an excellent coating workability and an electrodeposition coating method thereof have been found.

[0007]

Embedded image

That is, the present invention relates to (A) (a) α, β
An ethylenically unsaturated carboxylic acid monomer, (b) an alicyclic epoxy group-containing (meth) acrylic acid ester, and (c) other α, β-ethylenically unsaturated monomers.
A matte electrodeposition paint comprising an aqueous resin dispersion containing an acrylic resin copolymerized as essential components, (B) an amino resin, and (C) a basic substance, and an electrodeposition coating method.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The acrylic resin (A) used in the present invention comprises (a)
α, β-ethylenically unsaturated carboxylic acid monomer, (b) an alicyclic epoxy group-containing (meth) acrylate ester, and (c) other α, β-ethylenically unsaturated monomer. It can be obtained by copolymerization.

The component (a) is water-dispersible in an acrylic resin,
It is used to impart electrophoresis and to form a microgel by reacting with the alicyclic epoxy group of the component (b). For example, acrylic acid, methacrylic acid, crotonic acid, vinyl acetic acid, itaconic acid, Maleic acid, maleic anhydride, fumaric acid, citraconic acid and the like can be mentioned. These may be used alone or in combination of two or more.

The amount of component (a) used is preferably such that the acid value of the acrylic resin is 30 to 150, more preferably 40 to 1
It is used in the range where it becomes 00. If the acid value of the acrylic resin is less than 30, sufficient water dispersion stability cannot be obtained, and the reaction with the alicyclic epoxy group of the component (b) is insufficient.
It is difficult to obtain a sufficient matting effect. On the other hand, if it exceeds 150, the electrophoretic properties are inferior, and the water resistance and weather resistance are reduced.

The component (b) is used to form a microgel by reacting with the carboxyl group of the component (a) as described above. For example, Cyclomer A200, Cyclomer M100, manufactured by Daicel Chemical Industries, Ltd. M101 and the like. In the (meth) acrylate ester containing an alicyclic epoxy group, the reaction between the alicyclic epoxy group and the carboxyl group hardly occurs during the polymerization reaction of the acrylic resin. After the polymerization reaction, after neutralization with a base to disperse in water, a microgel is first produced when the reaction is carried out. On the other hand, in the case of a normal glycidyl group, a reaction between the glycidyl group and the carboxyl group occurs during the polymerization reaction, and the molecular weight becomes higher than necessary, and in extreme cases, gelation occurs during the polymerization reaction, which is not preferable. The amount of component (b) used is preferably from 0.1 to 10% by weight, particularly preferably from 1 to 10% by weight, in the acrylic resin.

As the component (c), an α, β-ethylenically unsaturated monomer having a hydroxyl group that imparts curability by reacting with the (B) amino resin upon baking of a coating film is preferably used. preferable. Illustratively, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxyethyl methacrylate,
Hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, 4-hydroxybutyl methacrylate, and the like, and lactone-modified products thereof, may be used alone or in combination of two or more.

Further, as the other component (c), an alkyl ester of acrylic acid or methacrylic acid, or another vinyl monomer can be used. Specific compounds include, for example, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-propyl acrylate, n-propyl methacrylate, isopropyl acrylate, isopropyl methacrylate, n-butyl acrylate, n-butyl methacrylate, isobutyl acrylate, isobutyl Methacrylate, t-butyl acrylate, t-butyl methacrylate, cyclohexyl acrylate, cyclohexyl methacrylate, lauryl acrylate, lauryl methacrylate, stearyl acrylate, stearyl methacrylate, 2-ethylhexyl acrylate, 2
-Acrylic acid such as ethylhexyl methacrylate, heptyl acrylate, heptyl methacrylate, diethylene glycol monoacrylate, diethylene glycol monomethacrylate, etc., esters of methacrylic acid, styrene, α-methylstyrene, vinyl toluene, vinyl acetate, vinyl acetate, acrylonitrile, methacrylonitrile, etc. And amide monomers such as acrylamide, methacrylamide, methylolacrylamide, methylolmethacrylamide, methoxymethylacrylamide, n-butoxymethylacrylamide, diacetoneacrylamide, and diacetonemethacrylamide. These can be used alone or in combination of two or more.

The component (c) has a hydroxyl value in the copolymer resin of preferably from 40 to 160, more preferably from 50 to 160.
It is used in the range where it becomes 40. If the hydroxyl value is less than 40, the curability is insufficient, and if it exceeds 160, the coating film becomes brittle, the water resistance is reduced, and sufficient performance cannot be obtained.

The preferred weight average molecular weight of the acrylic resin (A) thus copolymerized is 10,000 to 100.
000. When the weight average molecular weight is less than 10,000, the coating film durability cannot be sufficiently obtained, and when it exceeds 100,000, the water dispersibility decreases and the handling property of the paint becomes poor. In particular, the weight average molecular weight is preferably from 20,000 to 70,000 from the viewpoint of matting properties and paint stability. The molecular weight is measured using a GPC measuring device and a polystyrene standard sample. Further, the glass transition temperature of the acrylic resin is preferably from -10 to 60C, and particularly preferably from 10 to 60C.
-40 ° C is preferred in terms of matting and flexibility.

The acrylic resin (A) described above can be prepared by subjecting each of the monomers (a), (b) and (c) to solution polymerization, non-aqueous dispersion polymerization, bulk polymerization, emulsion polymerization, suspension polymerization or the like. Although it can be obtained by polymerization by a known method, solution polymerization is particularly preferred, and the reaction temperature is usually 40 to 1
70 ° C. is chosen.

As the reaction solvent, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol,
Isobutyl alcohol, sec-butyl alcohol, t
-It is preferable to use a hydrophilic solvent such as butyl alcohol, methyl cellosolve, ethyl cellosolve, propyl cellosolve, butyl cellosolve, propylene glycol monomethyl ether, propylene glycol monoethyl ether, and propylene glycol monobutyl ether. As the polymerization initiator, known compounds such as organic peroxides, azo compounds, ammonium persulfate, and potassium persulfate can be used.

As the amino resin (B) used in the present invention, conventionally known melamine resins, benzoguanamine resins, urea resins and the like are exemplified. Among them, preferred are those in which at least a part of the methylol group is lower. Alkyl etherified methylol melamine melamine resin alkoxylated with alcohol, as a lower alcohol,
One or more of methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol and the like can be used. There is no problem even if one kind of melamine resin is used or two or more kinds of melamine resins are combined.

An example of the alkyl etherified methylol melamine resin is Cymel 26 manufactured by Mitsui Cytec.
6, 232, 235, 238, 236, My Court 50
6, 508, Sumimar M-66B manufactured by Sumitomo Chemical Co., Ltd., Nikalac MX-40, MX-45 manufactured by Sanwa Chemical Co., Ltd., but are not limited thereto.

The preferred range of the amount of the (B) amino resin used in the present invention is 40 to 120, more preferably 50 to 110, by weight, based on 100 of the (A) acrylic resin.
If it is less than this range, gloss reduction is insufficient,
Insufficient cross-linking of the coating deteriorates mechanical properties, solvent resistance, chemical resistance, etc. Conversely, if it is too much, the affinity with the acrylic resin becomes insufficient, poor stability of the aqueous dispersion, dispersion Problems such as non-uniformity of the particle size, poor water washability after electrodeposition, water repellency, unevenness of the gloss of the coating film, and milkiness are caused.

The basic substance (C) used in the present invention neutralizes at least a part of the carboxyl groups in the resin (A) in order to disperse the acrylic resin in water. Such basic substances include alkylamines such as monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monoisopropylamine, diisopropylamine, triisopropylamine, monobutylamine, dibutylamine and tributylamine, and diethanolamine. Alkanolamines such as diisopropanolamine, triethanolamine, dimethylethanolamine, diethylethanolamine, ethylenediamine, propylenediamine, diethylenetriamine, triethylene Alkylene polyamines such as Toramin, ammonia, ethylene imine, pyrrolidine, piperidine, piperazine, morpholine, sodium hydroxide and potassium hydroxide. The neutralization ratio with such a basic substance is suitably 30 to 100%.
In particular, when the content is 50 to 90%, water dispersibility is good and gloss unevenness does not occur.

Further, the microgel formation reaction in the present invention is exemplified by (A) mixing an acrylic resin and (B) an amino resin, (C) neutralizing with a basic substance, and dispersing in water to obtain an aqueous resin dispersion. And then the aqueous resin dispersion is treated with 3
A method in which a heating reaction is performed at 0 to 120 ° C, preferably 40 to 100 ° C, may be mentioned. When the temperature is low, the microgelation reaction does not easily proceed, and a short maturing reaction cannot provide a sufficient matting effect. On the other hand, when the temperature is higher than 120 ° C., the microgelation reaction proceeds too much, the fluidity of the coating material is reduced, and a large number of pinholes are formed in the coating film to lower the chemical resistance. Further, the surface roughness of the coating film is remarkable, which is not preferable.

Depending on the required performance, workability, cost and the like, if necessary, for example, xylene resin, epoxy resin, polyester resin, urethane resin, etc. can be used in combination.

The electrodeposition paint obtained according to the present invention is diluted with deionized water or deionized water partially containing a hydrophilic solvent, if necessary, and then subjected to electrodeposition coating. When performing the matte electrodeposition coating in the present invention, the solid concentration of the coating bath is suitably 4 to 20% by weight. If it is lower than 4% by weight, it takes a long time to obtain a required coating film thickness, and 2
If it exceeds 0% by weight, the state of the bath liquid becomes unstable, and the amount of paint taken out of the coating system is also a problem.

With respect to the coating method, the electrodeposition coating is performed using the object to be coated as an anode. The coating voltage is 30 to 350 V, preferably 50 to 300 V, and the energizing time is 0.5 to 7 V.
Minutes, preferably 1 to 5 minutes. The higher the voltage, the shorter the energization time, and conversely, the lower the voltage, the longer the energization time. The coating voltage may be applied by applying the set voltage at the same time as energization or by gradually increasing the set voltage to the set voltage. The coated object is washed with water if necessary, and then heated at 150 to 200 ° C. for 15 to 60 minutes to obtain a final coating film. The coating thickness is preferably from 5 to 30 μm.

The object to which the electrodeposition coating method of the present invention is applied is not particularly limited as long as it has conductivity, but when aluminum or an aluminum alloy is used, it is excellent in performance such as smoothness. In addition, a uniform matte coating is obtained, and mechanical properties, solvent resistance, chemical resistance, weather resistance,
A coating film excellent in workability and the like can be obtained.

[0028]

The present invention will be described below with reference to examples. Parts are parts by weight unless otherwise indicated.

(A) Production of Acrylic Resin (Synthesis of Resin Liquid A1) A reactor having a stirring device, a thermometer, a monomer dropping device, and a reflux cooling device is prepared. (1) Ethylene glycol monobutyl ether 10.2 parts (2) Isopropyl alcohol 40.8 parts (3) 2-ethylhexyl methacrylate 5.0 parts (4) n-butyl acrylate 22.1 parts (5) Methyl methacrylate 33.6 Part (6) Styrene 10.0 parts (7) 2-Hydroxyethyl acrylate 18.6 parts (8) Acrylic acid 7.7 parts (9) Cyclomer M100 3.0 parts (10) Azobisisobutyronitrile 1 1.0 part (11) Azobisisobutyronitrile 1.0 part (1) and (2) are charged into a reactor, and the mixture is heated to reflux temperature with stirring, and (3) to (10) are uniformly mixed in advance. After that, the mixture was dropped over 3 hours. The temperature was maintained at 90 ° C.
1.5 hours after the completion of dropping, (11) was added, and 9
The reaction was continued at 0 ° C. for 1.5 hours and then cooled. A transparent and viscous resin liquid A1 having a resin solid content of 65% and an acid value of 60 mg KOH / g resin solid was obtained.

(Synthesis of Resin Liquid A2) Stirrer, thermometer,
A reactor having a monomer dropping device and a reflux cooling device is prepared. (1) Ethylene glycol monobutyl ether 10.2 parts (2) Isopropyl alcohol 40.8 parts (3) 2-ethylhexyl methacrylate 5.0 parts (4) n-butyl acrylate 20.9 parts (5) Methyl methacrylate 31.8 Part (6) Styrene 10.0 parts (7) 2-Hydroxyethyl acrylate 18.6 parts (8) Acrylic acid 7.7 parts (9) Cyclomer M100 6.0 parts (10) Azobisisobutyronitrile 1 1.0 part (11) Azobisisobutyronitrile 1.0 part (1) and (2) are charged into a reactor, and the mixture is heated to reflux temperature with stirring, and (3) to (10) are uniformly mixed in advance. After that, the mixture was dropped over 3 hours. The temperature was maintained at 90 ° C.
1.5 hours after the completion of dropping, (11) was added, and 9
The reaction was continued at 0 ° C. for 1.5 hours and then cooled. A transparent and viscous resin liquid A2 having a resin solid content of 65% and an acid value of 60 mg KOH / g resin solid was obtained.

(Synthesis of Resin Liquid A3) Stirrer, thermometer,
A reactor having a monomer dropping device and a reflux cooling device is prepared. (1) Ethylene glycol monobutyl ether 10.2 parts (2) Isopropyl alcohol 40.8 parts (3) 2-ethylhexyl methacrylate 5.0 parts (4) n-butyl acrylate 19.7 parts (5) Methyl methacrylate 30.0 Part (6) Styrene 10.0 parts (7) 2-Hydroxyethyl acrylate 18.6 parts (8) Acrylic acid 7.7 parts (9) Cyclomer M100 9.0 parts (10) Azobisisobutyronitrile 1 1.0 part (11) Azobisisobutyronitrile 1.0 part (1) and (2) are charged into a reactor, and the mixture is heated to reflux temperature with stirring, and (3) to (10) are uniformly mixed in advance. After that, the mixture was dropped over 3 hours. The temperature was maintained at 90 ° C.
1.5 hours after the completion of dropping, (11) was added, and 9
The reaction was continued at 0 ° C. for 1.5 hours and then cooled. A clear and viscous resin liquid A3 having a resin solid content of 65% and an acid value of 60 mg KOH / g resin solid was obtained.

[0032]

[Table 1]

A reactor having a stirrer, a thermometer, and a reflux cooling device was prepared.
(1) to (5) were charged according to the blending amount of, and stirred and mixed at 60 ° C for 1 hour. After adding (6), (7) was gradually added to obtain a resin dispersion. Apply this resin dispersion to 8
Incubate at 0 ° C for 6 hours to complete the microgelation reaction,
(8) was added to obtain resin dispersions 1 to 4 having a solid content of 30%.

(Preparation of paint and electrodeposition coating) Examples 1, 2, 3, 4 Comparative Example 1 Using the resin dispersions 1 to 4 obtained in Production Examples 1 to 4,
An electrodeposition bath solution was obtained with the composition shown in Table 2. This electrodeposition bath solution was placed in a PVC tank, and the cathode was made of SUS304 steel plate.
Anodized aluminum alloy plate (alumite film thickness = 9)
μm), and further electrolytically colored black, followed by electrodeposition coating using an aluminum material washed by a conventional method as an anode (object to be coated).

[0035]

[Table 2]

(Evaluation of coating film performance) The specific conditions of electrodeposition coating were as follows: bath temperature 22 ° C., distance between electrodes 12 cm, pole ratio (+/−) 2/1.
In a conventional manner, a current was applied at 130 V to 10 μm, and after the electrodeposition was completed, the film was washed and subsequently baked at 185 ° C. for 30 minutes, and the coating film performance was evaluated. Table 3 shows the results.

[0037]

[Table 3]

Comparative Example 1 A reactor having a stirring device, a thermometer, a monomer dropping device, and a reflux cooling device is prepared. (1) Ethylene glycol monobutyl ether 10.2 parts (2) Isopropyl alcohol 40.8 parts (3) 2-ethylhexyl methacrylate 5.0 parts (4) n-butyl acrylate 20.9 parts (5) Methyl methacrylate 31.8 Part (6) Styrene 10.0 parts (7) 2-hydroxyethyl acrylate 18.6 parts (8) Acrylic acid 7.7 parts (9) Glycidyl methacrylate 6.0 parts (10) Azobisisobutyronitrile 1. 0 parts (11) Azobisisobutyronitrile 1.0 part (1) and (2) were charged into a reactor, heated to reflux temperature with stirring, and (3) to (10) were uniformly mixed in advance. Thereafter, the solution was dropped over 3 hours. The temperature was maintained at 90 ° C.
The reaction product gelled 1.5 hours after the completion of the dropwise addition.

[0039]

(A) (a) α, β-ethylenically unsaturated carboxylic acid monomer, (b) (meth) acrylic acid ester containing an alicyclic epoxy group, (c) other α, β-
By using a resin composition containing an aqueous microgel comprising an acrylic resin copolymerized with an ethylenically unsaturated monomer and (B) an amino resin, an electrodeposition paint having excellent matting properties can be obtained. .

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C09D 161/20 C09D 161/20 163/00 163/00 C25D 13/06 C25D 13/06 B F-term (reference 4D075 AB09 AE03 CB02 DA06 DB02 EA06 EB22 EB45 EB55 EB56 4J038 CG021 CG031 CH171 CJ031 CJ101 CJ131 CJ141 DA162 DA172 DG332 GA06 GA07 HA176 JB03 JB04 JB05 JB32 JB33 KA03 MA08 NA01 NA03 NA03 NA08

Claims (3)

[Claims] (A) (a) an α, β-ethylenically unsaturated carboxylic acid monomer, (b) a (meth) acrylate ester containing an alicyclic epoxy group, and (c) other α Matte electrodeposition paint and electrodeposition coating thereof, comprising an aqueous resin dispersion containing an acrylic resin copolymerized with a β-ethylenically unsaturated monomer, (B) an amino resin, and (C) a basic substance Method. 2. An acrylic resin in which component (A) is (b) an alicyclic epoxy group-containing (meth) acrylate ester copolymerized at 0.1 to 10% by weight and has an acid value of 30 to 150. The matte electrodeposition paint according to claim 1, and an electrodeposition coating method thereof. 3. Component (A) is (b) an alicyclic epoxy group-containing (meth) acrylate ester in an amount of 1 to 10% by weight.
The matte electrodeposition paint according to claim 1, which is an acrylic resin copolymerized and having an acid value of 30 to 150, and the electrodeposition coating method.