JP2001000913A - Flat electrodeposition coating and electrodeposition coating method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a stable coating film quality by a simple control of bath liquid with good water dispersibility and hardly causing change with time in the composition of the bath liquid. SOLUTION: This electrodeposition coating contains acrylic resin produced by copolymerization of α,β-ethylenically unsaturated carboxylic acid monomers, hydroxy group-containing α,β-ethylenically unsaturated monomers, cross-linking group-containing α,β-ethylenically unsaturated monomers, and other α, β- ethylenically unsaturated monomers, and also a melamine resin-containing proply ether group.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a matte electrodeposition paint and a matte electrodeposition coating method. Specifically, (A)
The present invention relates to an anionic matte electrodeposition paint containing a specific acrylic resin and (B) a melamine resin having a propyl ether group, and particularly suitable for coating an aluminum material, and a method for electrodeposition coating the same.

[0002]

2. Description of the Related Art Conventionally, anodized aluminum materials have been widely used for building materials such as window frames, doors, exteriors and the like of buildings and houses because of their light weight, high strength, and excellent corrosion resistance. For the coating of aluminum material, an anionic electrodeposition paint having a one-coat and good finish is generally used. A typical example of the anionic electrodeposition paint is a melamine-curable electrodeposition paint obtained by mixing a water-based acrylic resin containing a carboxyl group and a hydroxyl group with a melamine resin crosslinking agent and dispersing in water. Is the mainstream.

As the melamine resin, an alkyl etherified melamine resin obtained by converting an amino group to methylol using formaldehyde and further etherifying a methylol group with an alcohol is generally used. Industrial alcohols include methanol, n-butanol and isobutanol.

[0004]

However, each alcohol has the following disadvantages. That is, since the methyl etherified melamine resin has too good compatibility with the acrylic resin, phase separation of the melamine resin hardly occurs at the time of baking, and thus there is a problem that the smoothness and the solid feeling of the coating film are poor. In addition, since methyl etherified melamine resin is water-soluble,
Over time, some of the melamine resin dissolves into the water from the water-dispersed particles and stays in the bath solution without depositing on the object to be coated. There is a problem that it is difficult to obtain quality.

[0005] On the other hand, butyl etherified melamine resin is oil-soluble and therefore does not dissolve in the bath solution, but has insufficient compatibility with hydrophilic acrylic resin containing a carboxyl group and a hydroxyl group and is stable. It is difficult to obtain a proper aqueous dispersion. Further, when the hydrophilicity of the acrylic resin is reduced in order to improve the compatibility with the melamine resin, there is a problem that the water dispersion stability of the acrylic resin itself is impaired.
Further, even when a paint having good dispersion stability is obtained, there is a problem that the milkyness and opacity of the coating film due to phase separation of the melamine resin are increased, so-called white blurring is increased and the commercial value is reduced. .

For this reason, melamine resins generally used at present are so-called mixed ether type melamine resins sharing a methyl ether group and a butyl ether group. In the mixed ether type melamine resin, water solubility and oil solubility are balanced, and the above problems are improved to some extent.However, the ratio of methyl etherification to butyl etherification is not constant in each molecule. The above-mentioned problems are not completely solved because those having many groups and those having many butyl ether groups (there are also those having a methyl ether group or a butyl ether group alone). Therefore, in order to obtain stable coating quality, strict bath liquid management is required.

[0007] From the above, a new matte electrodeposition coating material having good water dispersibility, little change in composition of the bath solution with time, and stable coating film quality obtained by simple bath solution management can be obtained. It has been demanded.

[0008]

In order to solve the above-mentioned problems, the present inventors have focused on a new type of melamine resin. That is, the present invention comprises (A) (a) an α, β-ethylenically unsaturated carboxylic acid monomer, (b) a hydroxy group-containing α, β-ethylenically unsaturated monomer, and (c) a cross-linking functional group. Α, β-ethylenically unsaturated monomer, (d) an acrylic resin copolymerized with another α, β-ethylenically unsaturated monomer, and (B) a melamine resin having a propyl ether group Anionic matte electrodeposition paint and its electrodeposition coating method.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.

The component (a) of the acrylic resin (A) of the present invention
Is for imparting water dispersibility and electrophoresis to an acrylic resin. Examples include acrylic acid, methacrylic acid, crotonic acid, vinyl acetic acid, itaconic 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 in the acrylic resin is 10 to 150, more preferably 20 to 1
It is used in the range where it becomes 00. If the acid value of the acrylic resin is less than 10, it is difficult to obtain sufficient water dispersion stability, and if it exceeds 150, the electrophoretic properties and deposition properties are reduced, and the water resistance and alkali resistance of the coating film are reduced.

The component (b) reacts with the melamine resin at the time of baking of a coating film to impart curability. For example, 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. Can be used.

The component (b) has a hydroxyl value in the acrylic resin of preferably 20 to 200, more preferably 4 to 200.
It is used in the range of 0 to 160. If the hydroxyl value is less than 20, it is difficult to secure the flow property during baking. On the other hand, if it exceeds 200, the coating film becomes brittle, the water resistance is reduced, and it is difficult to obtain sufficient performance. In addition, the stability of the coating decreases, and the water washability of the coating film after electrodeposition also decreases.

The component (c) stably forms an insoluble microgel in the acrylic resin and imparts matting performance. For example, acetoacetoxyethyl acrylate, acetoacetoxyethyl methacrylate,
γ-acryloxypropyltrimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-acryloxypropyltriethoxysilane, γ-methacryloxypropyltriethoxysilane, β-methyl substituted glycidyl acrylate, β-methyl substitution Glycidyl methacrylate and the like are mentioned. After water dispersion is performed in the following manner, a microgel is generated in the dispersed particles to reduce the gloss.

Further, as the component (d) which is a component forming the skeleton of the acrylic resin, an alkyl ester of acrylic acid or methacrylic acid or other vinyl monomers 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-ethylhexyl methacrylate, heptyl acrylate, heptyl methacrylate, diethylene glycol monoacrylate Over DOO, acrylic acid and diethylene glycol monomethacrylate, esters of methacrylic acid, styrene, alpha-methyl styrene,
Vinyl monomers such as vinyltoluene, vinyl acetate, acrylonitrile, methacrylonitrile, acrylamide, methacrylamide, methylolacrylamide, methylolmethacrylamide, methoxymethylacrylamide,
Amide monomers such as n-butoxymethylacrylamide, diacetone acrylamide, diacetone methacrylamide and the like can be mentioned. These can be used alone or in combination of two or more.

The preferred weight average molecular weight of the acrylic resin (A) 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, in terms of matting properties and paint stability, the weight average molecular weight is 20,000 to 70.
000 is preferred.

The acrylic resin (A) as described above is obtained by subjecting each of the monomers (a), (b), (c) and (d) to solution polymerization, non-aqueous dispersion polymerization, bulk polymerization, emulsion polymerization,
It can be obtained by polymerization by a known method such as suspension polymerization, but particularly preferred is solution polymerization, and the reaction temperature is usually 40 to 170 ° C.

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. Known polymerization initiators such as organic peroxides, azo compounds, ammonium persulfate, and potassium persulfate can be used as the polymerization initiator.

In order to disperse the obtained acrylic resin in water, at least a part of the carboxyl groups in the resin is neutralized with a basic substance such as an organic amine or an inorganic base.
Such basic substances include monomethylamine, dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, monoisopropylamine, diisopropylamine, triisopropylamine,
Monobutylamine, dibutylamine, alkylamines such as tributylamine, diethanolamine, diisopropanolamine, triethanolamine, dimethylethanolamine, alkanolamines such as diethylethanolamine, ethylenediamine, propylenediamine,
Examples include alkylenepolyamines such as diethylenetriamine and triethylenetetramine, ammonia, ethyleneimine, pyrrolidine, piperidine, piperazine, morpholine, sodium hydroxide, potassium hydroxide and the like. The neutralization ratio with such a basic substance is suitably from 30 to 120%, and particularly preferably from 50 to 100%, since water dispersibility is good and gloss unevenness does not occur.

The raw materials used in the synthesis of the propyl etherified melamine resin (propylated melamine resin) (B) used in the present invention are 1 to 10 mol of formaldehyde, 0.0 mol of propyl alcohol per 1 mol of melamine.
A ratio of 5 to 30 mol is preferred. 1 formaldehyde
When the amount is less than the mole, the methylolation and the alkyl etherification are insufficient, and the curability at the time of baking and the solubility in the acrylic resin are poor. On the other hand, if it exceeds 10 moles, it becomes substantially excessive in the reaction with melamine and must be removed in a subsequent step, which is economically disadvantageous. When the amount of propyl alcohol is less than 0.05 mol, the solubility of the obtained resin is inferior, and when it exceeds 30 mol, the excess must be removed at the time of production, which is not practical.

As a specific production method, predetermined amounts of melamine, formaldehyde, and propyl alcohol are charged and heated to methylolate, and then an acid catalyst is added to carry out an alkyl etherification reaction with propyl alcohol. Thereafter, the reaction system may be neutralized, and if necessary, dealcoholized to a predetermined concentration under normal pressure or reduced pressure.

The propyletherified melamine (B) of the present invention may be any one of the functional groups as long as the substituted alkyl chain is a propoxy group. The functional groups other than the propylether group present in the melamine resin include an imino group, It is also used in a mixture of other substituents such as an iminomethylol group and a methylol group.

When the propylated melamine resin of the present invention is used, it has good water dispersibility, little change in the composition of the bath solution over time, excellent coating workability, especially excellent water washability, and also has a smoothness in coating film quality. It is possible to produce a matte electrodeposition coating material having excellent feeling of holding meat, dice mark hiding property, and non-milky property. The amount of the propylated melamine resin of the present invention to be used is preferably 40 to 120, more preferably 60 to 100, by weight based on 100 of the acrylic resin. When the amount is less than this range, there is almost no melamine resin separated on the surface of the coating film during the baking process, sufficient flowability is not secured, and a coating film having a rough, smooth, and solid feeling is obtained. It is hard to be. In addition, dice marks and pre-processing unevenness concealment properties are also reduced. On the other hand, if the amount is large, the affinity with the acrylic resin becomes insufficient, and the melamine resin is partially separated from the acrylic resin in the aqueous dispersion, resulting in poor stability of the aqueous dispersion, non-uniform dispersion particle size, and electrodeposition. Problems such as poor water washability, water repellency, unevenness in gloss of the coating film, and milkiness are likely to occur.

In the present invention, for example, xylene resin, polyester resin, urethane resin and the like can be used in combination, if necessary, depending on the required performance, workability, cost and the like. In this case, it is used in the same manner as the melamine resin. Further, it can be applied to a coloring type electrodeposition paint in combination with a pigment.

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 the matte electrodeposition coating composition of the present invention is applied, the solid content concentration of the coating bath is suitably from 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 electrodeposition coating method, the electrodeposition coating is performed using the object to be coated as an anode.
Preferably, the voltage is 50 to 300 V, and the energization time is 0.5 to 300 V.
7 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. 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.

[0028]

The present invention will be described below with reference to examples. Parts are parts by weight unless otherwise indicated. 1. Synthesis of Acrylic Resin Synthesis Examples 1 to 4 (Synthesis of Resin Liquids A1 to A4) A reactor having a stirrer, a thermometer, a monomer dropping device, and a reflux cooling device is prepared.

According to the composition of Synthesis Example 1 shown in Table 1,
(1) and (2) were charged into a reactor, the temperature was raised to the reflux temperature under stirring, (3) to (12) were uniformly mixed in advance, and then added dropwise over 3 hours. The temperature was maintained at 90 ° C.
1.5 hours after the completion of the dropping, (13) was added, and 9
The reaction was continued at 0 ° C. for 1.5 hours to obtain a transparent and viscous resin liquid A1 having a resin solid content of 65%. Table 1 shows the characteristic values of the obtained resin liquid A1.

[0030]

[Table 1]

An acrylic resin was synthesized based on the composition shown in Table 2 under the same conditions as in Synthesis Example 1 to obtain transparent viscous resin liquids A2 to A4 having a resin solid content of 65%. The obtained resin liquid A2
Table 2 shows the characteristic values of No. 4.

[0032]

[Table 2]

2. Synthesis of propyl etherified melamine resin Synthesis Example 5 In a reactor equipped with a stirrer, a thermometer, a reflux cooling device, and a nitrogen inlet tube according to the formulation in Table 3, (1), (2),
(3) was charged and heated to the reflux temperature. 1 at reflux temperature
After performing the methylolation reaction for an hour, (4) was added, and the alkyl etherification reaction was performed for 3 hours under reflux. Thereafter, the mixture was neutralized with a 1 / 10N aqueous sodium hydroxide solution, and isopropyl alcohol was distilled off under reduced pressure to obtain an isopropyl etherified amino resin (M1). The obtained resin had a solid content of 80%.

[0034]

[Table 3]

Synthesis Example 6 An n-propyl etherified amino resin (M2) was obtained in the same manner as in Production Example except that n-propyl alcohol was used in place of isopropyl alcohol of Synthesis Example 5.

3. Preparation of Water-Dispersed Resin Liquid A reactor having a stirrer, a thermometer, and a reflux cooling device is prepared, and (1) to (8) are charged into the reactor according to the blending amounts of Production Examples 1 to 7 at 60 ° C. Stir and mix for 1 hour. This was prepared in advance (9)
And (10) were gradually added to obtain a water-dispersed resin solution. In the case of Production Examples 2 and 6, a predetermined amount of (11) formalin was added to this water-dispersed resin solution, and the other components were left as they were.
The microgelation reaction was carried out by keeping the temperature under the conditions shown in (1), and finally (12) was added to adjust the solid content to 30% to obtain Dispersed Resin Liquids 1 to 6.

[0037]

[Table 4]

4. Production of electrodeposition paint and electrodeposition coating Examples 1-4 Comparative Examples 1-3 Using the water-dispersed resin liquids obtained in Production Examples 1-7, Table 5
The electrodeposition bath liquid was obtained with the composition shown in Table 1. This electrodeposition bath solution was placed in a PVC bath, the cathode was made of SUS304 steel plate, and the alumite treatment was applied to the 6063S aluminum alloy plate (alumite film thickness = 9 μm).
m), and further subjected to electrolytic coloring to black, followed by electrodeposition coating using an aluminum material washed by a conventional method as an anode (object to be coated).

[0039]

[Table 5]

5. Evaluation of coating film performance The specific conditions of electrodeposition coating are bath temperature 22 ° C, distance between electrodes 12c.
m, the pole ratio (+/-) 2/1, and 130
V was applied so that the coating thickness became 10 μm, and after the electrodeposition was completed, the coating was washed and subsequently baked at 185 ° C. for 30 minutes, and the coating performance was evaluated. Table 6 shows the results.

[0041]

[Table 6]

(Note) Evaluation method (1) Gloss value: 60 ° gloss was measured with a gloss meter. (2) Pencil hardness: JIS-K-5400 tear determination. (3) After making 100 grids on the coating film with a cutter knife and sticking Cellotape (registered trademark) on it,
Observe the close contact state when the cellophane tape is quickly peeled off. 100/100: No peeling 0/100: All peeling (4) Alkali resistance: After immersion in 1% NaOH at 20 ° C. for 48 hours, the state of the coated surface was observed. (5) Acid resistance: After immersion in 5% sulfuric acid at 20 ° C. for 48 hours, the state of the coated surface was observed. (6) Appearance of coating film Dice mark ○: Dice mark is not conspicuous ×: Dice mark is conspicuous Smoothness ○: Good smoothness ×: Rough skin Non-milky ○: Less milky feeling, good ×: Milky feeling (white blur) (7) Rinseability: After electrodeposition, immerse in a 2% isopropyl alcohol aqueous solution for 3 minutes, pull up and leave for 3 minutes to observe the appearance. Furthermore, baking is performed and the appearance of the coating film is observed. ：: No water repellent phenomenon was observed during standing after immersion, and no streak-like gloss unevenness was observed in the coating film. ×: Water repellency is observed during standing after immersion. Alternatively, streak-like gloss unevenness or the like occurs in the coating film.

[0043]

EFFECT OF THE INVENTION (A) (a) an α, β-ethylenically unsaturated carboxylic acid monomer, (b) a hydroxy group-containing α, β-ethylenically unsaturated monomer, and (c) a crosslinking functional group Has α,
Water dispersion obtained from β-ethylenically unsaturated monomer, (d) acrylic resin copolymerized with other α, β-ethylenically unsaturated monomer, and (B) melamine resin having propyl ether group Using resin liquid, bath liquid stability, coating workability, smoothness of coating film, dice mark hiding property,
A matte electrodeposition paint having excellent non-milky properties was obtained.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int. Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) C09D 5/44 C09D 5/44 B 133/00 133/00 161/28 161/28

Claims (5)

[Claims] 1. A method comprising: (A) (a) an α, β-ethylenically unsaturated carboxylic acid monomer, (b) a hydroxy group-containing α, β-ethylenically unsaturated monomer, and (c) a crosslinking functional group. Has α,
Anionic type containing a β-ethylenically unsaturated monomer, (d) an acrylic resin copolymerized with another α, β-ethylenically unsaturated monomer, and (B) a melamine resin having a propyl ether group Matte electrodeposition paint and its electrodeposition coating method. 2. An acrylic resin (A) having an acid value of 10 to 150.
The anionic matte electrodeposition paint according to claim 1, which has a hydroxyl value of 20 to 200 and a method of electrodeposition coating. 3. The anion according to claim 1, wherein the α, β-ethylenically unsaturated monomer (c) having a crosslinking functional group is a monomer having a β-methyl-substituted glycidyl group in a side chain. -Type matte electrodeposition paint and its electrodeposition coating method. 4. The anionic matte according to claim 1, wherein the α, β-ethylenically unsaturated monomer (c) having a crosslinking functional group is a monomer having an acetoacetyl group in a side chain. Electrodeposition paint and electrodeposition coating method. 5. The anionic matte according to claim 1, wherein the α, β-ethylenically unsaturated monomer (c) having a crosslinking functional group is a monomer having an alkoxysilyl group in a side chain. Electrodeposition paint and electrodeposition coating method.