JP2000033330A - Flatted electrodeposition coating method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flatted electrodeposition coating material and a flatted electrodeposition coating method simple in the operation condition of electrodeposition, high in the productivity of a line and capable of stable operation, free from causing the degradation of performance and cost up and capable of optionally adjusting luster. SOLUTION: This electrodeposition coating material composed of a water based resin dispersion containing (A) an acrylic resin obtained by copolymerizing (a) α,β-ethylenically unsaturated carboxylic acid monomer, (b) β-methyl group- substituted glycidyl (meth)acylate and (c) the other α,β-ethylenically unsaturated carboxylic acid monomer, (B) an amino resin and (C) a basic material is used and the glossiness is adjusted by changing a coating voltage.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a matte electrodeposition coating method. Specifically, using an electrodeposition paint containing (A) a specific acrylic resin, (B) an amino resin, and (C) a basic substance, performing electrodeposition using an object to be coated as an anode, and changing the coating voltage, The present invention relates to a matte electrodeposition coating method capable of arbitrarily adjusting the gloss of a film.

[0002]

2. Description of the Related Art Aluminum building materials are currently mainly black materials (colored black after alumite treatment).
A matte type paint is preferably used. The gloss standard is generally around 10 to 25, but needs have been diversified in recent years, and it is required to slightly change the gloss depending on the material.

There are several methods for adjusting the gloss of the electrodeposited coating film. One method is to adjust the gloss by dividing the energization into two stages and changing the coating voltage and the energization time, respectively ( See JP-A-2-285094 and JP-A-6-108291. Another method is to adjust the gloss by mixing a predetermined amount of a low gloss electrodeposition paint and a high gloss electrodeposition paint (JP-A-7-278889).
Reference). A method of changing gloss by changing the film thickness has also been proposed (Japanese Patent Publication No. Sho 62-24).
No. 519). However, any of the methods has the following problems, and a solution is required.

[0004]

In the two-stage energizing method, since the coating voltage and the energizing time are different, the setting conditions must be changed during the electrodeposition, and the operation is complicated. In the method of using two kinds of electrodeposition paints having different glosses, it is necessary to adjust the mixing ratio of the two paints each time the required gloss value changes, especially in a line for coating many kinds of materials. There are problems that productivity is reduced and stable operation is difficult. In the method of changing the thickness of the coating film, if the thickness of the coating film is reduced, problems such as weather resistance and chemical resistance occur. Conversely, if the thickness of the coating film is increased, the cost of the coating increases.

The present invention solves the above-mentioned problems in the prior art, does not require complicated operation conditions for electrodeposition, enables high line productivity, enables stable operation, and leads to performance degradation and cost increase. It is intended to provide a matte electrodeposition paint and a matte electrodeposition coating method which can adjust the gloss arbitrarily.

The present inventors have studied the relationship between the paint composition, the coating conditions, and the like, and the gloss, and have found that in an electrodeposition paint using a specific acrylic resin, the operation simply by changing the coating voltage can reduce the performance and increase the cost. It has been found that the gloss can be adjusted arbitrarily without connection.

[0007]

That is, the present invention provides (A)
(A) α, β-ethylenically unsaturated carboxylic acid monomer,
(B) β-methyl group-substituted glycidyl (meth) acrylate, and (c) an acrylic resin copolymerized with another α, β-ethylenically unsaturated monomer, (B) an amino resin, and (C) a basic resin. This is a matte electrodeposition coating method that uses an electrodeposition coating made of an aqueous resin dispersion containing a substance and adjusts the gloss by changing the coating voltage. However, the component (b) β-methyl group-substituted glycidyl (meth) acrylate can be represented by the following general formula.

[0008]

Embedded image

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with respect to paints and coating methods. The acrylic resin (A) used in the present invention comprises (a) an α, β-ethylenically unsaturated carboxylic acid monomer, (b) β-methyl-substituted glycidyl (meth) acrylate, and (c) other α , Β-
It can be produced by copolymerizing an ethylenically unsaturated monomer.

The component (a) is water-dispersible in an acrylic resin,
It is used for imparting electrophoresis and for forming a microgel by reacting with the β-methyl group-substituted glycidyl group of the component (b). For example, acrylic acid, methacrylic acid, crotonic acid, vinyl acetic acid, itacone Acid, maleic acid, maleic anhydride, fumaric acid, citraconic acid and the like. 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 β-methyl-substituted glycidyl group of the component (b) is insufficient, so that a sufficient matting effect can be obtained. Hateful. Also one
If it exceeds 50, the electrophoretic properties will be poor, and the water resistance and weather resistance will decrease.

The component (b) is used for forming a microgel by reacting with the carboxyl group of the component (a) as described above. β-methyl group-substituted glycidyl (meth) acrylate hardly reacts with β-methyl group-substituted glycidyl group and carboxyl group during the polymerization reaction of the acrylic resin as compared with glycidyl group having no β-methyl group. . After the polymerization reaction, after neutralization with a basic substance to disperse in water and then carry out a heating reaction, a microgel is formed for the first time. On the other hand, in the case of a glycidyl group having no β-methyl group, a reaction between the glycidyl group and a 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. This difference is
When an acrylic resin copolymerized with methyl group-substituted glycidyl (meth) acrylate is used, it is considered to be a factor that can adjust the gloss by changing the coating voltage. The amount of the component (b) used is preferably 0.1 to 10% by weight in the acrylic resin (A).
0% by weight is particularly preferred.

The component (c) is preferably an α, β-ethylenically unsaturated monomer having a hydroxyl group which imparts curability by reacting with the amino resin (B) during baking of a coating film. . Examples thereof include 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, 4-hydroxybutyl methacrylate, and the like, and lactone-modified products thereof. Species or a mixture of two or more species can be used.

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) preferably has a hydroxyl value in the copolymer resin of from 40 to 160, particularly preferably from 50 to 160.
It is used in the range of ~ 140. Hydroxyl value of 4
If it is less than 0, 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, more preferably from 10 to 4C.
0 ° C. is preferred in terms of matting and flexibility.

The acrylic resin (A) described above can be prepared by subjecting each of the monomer components (a), (b) and (c) to solution polymerization, non-aqueous dispersion polymerization, bulk polymerization, emulsion polymerization, suspension polymerization, etc. Can be obtained by a known method, but particularly preferred is solution polymerization, and the reaction temperature is usually 4
0-170 ° 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 amino resin (B) used in the present invention is 40 to 120, more preferably 50 to 110, and still more preferably 65 to 100, by weight, based on 100 of the (A) acrylic resin. By changing the coating voltage, a desired gloss adjustment can be made. In addition, the rough skin of the coating film is suppressed, and the smoothness, the feeling of holding the body, the dice mark hiding property,
A coating film having excellent pretreatment unevenness concealing properties is obtained. When the amount is less than this range, the gloss is insufficiently reduced, and the mechanical properties, solvent resistance, chemical resistance, etc. are reduced due to insufficient crosslinking of the coating film. And the problems such as poor stability of the aqueous dispersion, non-uniform dispersion particle size, poor washability after electrodeposition, water repellency, uneven gloss of the coating film, and opalescence.

The (C) basic substance used in the present invention includes:
(A) In order to disperse the acrylic resin in water, it neutralizes at least a part of the carboxyl groups in the resin, and is, for example, an organic amine or an inorganic base. Examples of such a basic substance include alkylamines such as monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monoisopropylamine, diisopropylamine, triisopropylamine, monobutylamine, dibutylamine, and tributylamine, diethanolamine, diisopropanol. Amines, triethanolamine, dimethylethanolamine, alkanolamines such as diethylethanolamine, ethylenediamine, propylenediamine, diethylenetriamine, alkylenepolyamines such as triethylenetetramine, ammonia, ethyleneimine, pyrrolidine, piperidine, piperazine, morpholine, sodium hydroxide, Potassium hydroxide is exemplified. 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.

In order to obtain a stable matting effect in the present invention, (A) an acrylic resin and (B) an amino resin are mixed, and (C) neutralized with a basic substance to effect water dispersion. Thereafter, it is preferable to carry out a microgelation reaction. The reaction temperature is preferably from 30 to 120 ° C, more preferably from 40 to 120 ° C.
100 ° C.

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. In this case, it is used in the same manner as the melamine resin.

When the matte electrodeposition paint of the present invention is applied, the solid concentration of the paint bath is suitably from 4 to 20% by weight. When the amount is lower than 4% by weight, it takes a long time to obtain a required coating film thickness. When the amount exceeds 20% by weight, the state of the bath becomes unstable, and the amount of the paint taken out of the coating system is also large. It is.

The reason why the gloss of the electrodeposition paint used in the present invention changes depending on the coating voltage is not clear, but one of the reasons is that in electrodeposition coating, Joule heat is generated in accordance with the amount of electricity supplied when the paint is deposited. Although it occurs, it is considered that the amount of Joule heat generated differs depending on the coating voltage, which affects the heat flow property of the deposited coating film, and that the glossiness changes due to the difference in smoothness of the coating film. On the other hand, moisture is released from the deposited coating film into the coating bath due to the electroosmosis phenomenon, but the degree varies depending on the coating voltage. It is possible that the gloss of the film changes. Therefore, in the present invention, by specifying the coating composition, particularly the acrylic resin composition as described above, it is possible to arbitrarily adjust the gloss by utilizing the flow property due to Joule heat specific to electrodeposition coating and the electroosmosis phenomenon. It is considered possible.

Regarding the coating conditions, the range of the coating voltage is preferably 50 to 300 V, and the energizing time is 0.4 to 8
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. In the present invention, when the coating voltage is around 130 V or lower, a coating film having a film thickness of 10 μm and a gloss of about 10 can be obtained. On the other hand, when the coating is performed by applying a coating voltage of 200 V or more, a coating film having a film thickness of 10 μm and a gloss of about 25 is obtained. By changing the coating voltage in this manner, a gloss value of 10 to 25 required in the market can be arbitrarily adjusted.

The coated object is washed with water if necessary,
Then, it is baked at 150 to 200 ° C. for 15 to 60 minutes to obtain a final coating film. The thickness of the coating film is preferably about 10 μm, but is not limited thereto, and may be 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. However, 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. For electrodeposition coating, an object to be coated is used as an anode, an electrodeposited deposition film is obtained by applying a predetermined voltage, and if necessary, washed by a conventional method, and then, through a baking process, low gloss, mechanical properties,
A coating film excellent in solvent resistance, chemical resistance, weather resistance, workability and the like can be obtained.

[0030]

The present invention will be described below with reference to examples. Parts are parts by weight unless otherwise indicated. (A) Production of Acrylic Resin Production Example 1 (Synthesis of Resin Liquid A1) A reactor having a stirrer, 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) M-GMA (Note) 3.0 parts (10) Azobisisobuty Ronitrile 1.0 part (11) Azobisisobutyronitrile 1.0 part (Note) M-GMA: β-methyl-substituted glycidyl methacrylate (1) and (2) are charged into a reactor and refluxed with stirring. The temperature was raised to (3) to (10), and the mixture was dropped uniformly 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.

Production Examples 2 and 3 (Synthesis of Resin Solutions A2 and A3) Resin Solution A2 Resin Solution A3 (1) Ethylene glycol monobutyl ether 10.2 parts 10.2 parts (2) Isopropyl alcohol 40.8 parts 40.8 Parts (3) 2-ethylhexyl methacrylate 0 parts 4.1 parts (4) n-butyl acrylate 22.9 parts 22.3 parts (5) methyl methacrylate 34.7 parts 31.1 parts (6) styrene 10.0 parts 11.3 parts (7) 2-hydroxyethyl acrylate 21.7 parts 18.6 parts (8) Acrylic acid 7.7 parts 9.6 parts (9) M-GMA 3.0 parts 3.0 parts (10) Azobisisobutyronitrile 1.0 part 1.0 part (11) Azobisisobutyronitrile 1.0 part 1.0 part With the above composition, a reaction was carried out in the same manner as the resin liquid A1 to obtain a resin solid content. 65 %, Acid value A2: 60 mg KOH / g resin solid content, A3: 75 mg KOH / g resin solid content) to obtain a transparent and viscous resin liquid.

Production of water-dispersed resin liquid

[0033]

[Table 1]

A reactor having a stirrer, a thermometer, and a reflux cooling device was prepared, and (1) to (6) were charged into the reactor according to the amounts of Production Examples 4, 5, and 6 shown in Table 1. The mixture was stirred and mixed at 60 ° C. for 1 hour. After adding (7) to this, (8) was gradually added to obtain a dispersion resin liquid.
This dispersion resin solution was kept at 80 ° C. for 6 hours to carry out a microgelation reaction, and (9) was added to adjust the solid content to 30%.
Dispersion resin liquids 1, 2, and 3 were obtained.

Preparation of paint and electrodeposition coating Examples 1, 2, and 3 Using the dispersion resin liquids obtained in Production Examples 4, 5, and 6, electrodeposition bath liquids were obtained in the formulations shown in Table 2. This electrodeposition bath solution was placed in a PVC tank, the cathode was made of SUS304 steel plate, and the 6063S
Alumite treatment on aluminum alloy plate (alumite film thickness = 9μ)
m), and after electrolytic coloring to black, electrodeposition coating was performed using an aluminum material washed by a conventional method as an anode (object to be coated).

[0036]

[Table 2]

Evaluation of coating film performance The specific conditions of electrodeposition coating were as follows: bath temperature 22 ° C., distance between electrodes 12c.
m, pole ratio (+/-) 2/1, coating voltage 100,
The film thickness is 10 at 130, 160, 190 and 220V.
The electrode was energized so as to have a thickness of μm, washed after completion of the electrodeposition, and subsequently baked at 185 ° C. for 30 minutes to evaluate the gloss. Table 3 shows the results.

[0038]

[Table 3]

[0039]

EFFECT OF THE INVENTION (a) α, β-ethylenically unsaturated carboxylic acid monomer, (b) β-methyl group-substituted glycidyl (meth) acrylate, and (c) other α, β-ethylenically unsaturated (A) an acrylic resin obtained by copolymerizing a monomer,
When using an electrodeposition paint composed of an aqueous resin dispersion containing (B) an amino resin and (C) a basic substance, a coating thickness of 10 μm can be arbitrarily adjusted in a range of 10 to 25 by changing a coating voltage. Can be adjusted.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) C09D 161/20 C09D 161/20 (72) Inventor Toshinobu Yamashita 6-10-73 Minamitsukaguchi-cho, Amagasaki-shi, Hyogo Prefecture No. Shinto Paint Co., Ltd. F term (reference) 4D075 AB53 BB89Y BB91Y CB02 DB07 DC01 EA06 EA10 EB22 EB24 EB32 EB52 EB56 4J038 CG141 CJ101 CJ271 DA142 DA162 DA172 DB371 GA06 MA08 MA10 NA01 PA04

Claims (3)

[Claims] (A) (a) an α, β-ethylenically unsaturated carboxylic acid monomer, (b) β-methyl-substituted glycidyl (meth) acrylate, and (c) other α, β-
Acrylic resin copolymerized with ethylenically unsaturated monomer,
A matte electrodeposition coating method in which a coating voltage is changed to adjust gloss using an electrodeposition coating material comprising an aqueous resin dispersion containing (B) an amino resin and (C) a basic substance. 2. The acid value of the component (A) is from 30 to 150,
The matte electrodeposition coating method according to claim 1, wherein (b) an electrodeposition coating containing an acrylic resin obtained by copolymerizing 0.1 to 10% by weight of glycidyl (meth) acrylate substituted with β-methyl group. 3. The acid value of the component (A) is from 30 to 150,
The matte electrodeposition coating method according to claim 1, wherein (b) an electrodeposition coating material containing an acrylic resin obtained by copolymerizing 1 to 10% by weight of β-methyl group-substituted glycidyl (meth) acrylate.