JPH11172165A - Electrodeposition coating composition having excellent scratch resistance and elecrodeposition coating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject composition generating remarkably decreased scratch defect compared with the single use of an acrylic resin and useful for the coating of aluminum, or the like, by combining an acrylic resin with colloidal silica. SOLUTION: This composition contains (A) an acrylic resin containing alkoxysiliyl group and carboxyl group, (B) an aqueous resin dispersion produced from an organic/inorganic composite resin reacted with colloidal silica by neutralizing the resin with a basic substance (e.g. monomethylamine) and (C) an amino resin. It is preferable e.g. to use a copolymer of an α,β-ethylenic unsaturated carboxylic acid monomer, an alkoxysilyl-containing α,β-ethylenic unsaturated monomer and other, α,β-ethylenic unsaturated monomer as the component A and an alkoxymethylated melamine resin produced by alkoxylating at least a part of methylol group with a lower alcohol as the component C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an anodic deposition type electrodeposition paint for coating metal products such as aluminum and iron, and a method for the electrodeposition coating, which forms a coating film having excellent abrasion resistance. And an electrodeposition coating method for the same.

[0002]

2. Description of the Related Art Conventionally, various coatings have been performed for the purpose of preventing corrosion of metal products such as aluminum and iron, protecting the surface, and imparting aesthetic appearance. Among them, anodic deposition type electrodeposition coating is often performed because it has particularly excellent film thickness uniformity, high coating efficiency, suitability for unmanned coating, low pollution by low organic solvent content, excellent corrosion resistance and weather resistance etc. I have. However, recently, among these painted products, in fields in which the appearance of the surface is regarded as important, such as aluminum sashes and steel furniture, deterioration of the appearance due to abrasion has come to be regarded as a problem.

On the other hand, an organic resin, which is one of the main constituents of a coating film, has an extremely low hardness as compared with an inorganic substance such as metal powder, sand, or an abrasive which can cause abrasion, and thus has a sufficient hardness. This has been the case without improvement in coating strength. Particularly, in a coating film containing no inorganic pigment, the improvement of the scratch resistance is strongly desired.

[0004]

SUMMARY OF THE INVENTION
The present inventors have conducted intensive studies on introducing a high hardness inorganic component into an organic coating film, and found that by combining an acrylic resin and colloidal silica, the abrasion resistance can be significantly reduced as compared with the case of using the acrylic resin alone. Thus, the present invention has been completed.

[0005]

That is, the present invention is obtained by neutralizing, with a basic substance, an organic / inorganic composite resin obtained by reacting an acrylic resin having an alkoxysilyl group and a carboxyl group with colloidal silica. An electrodeposition coating composition containing an aqueous resin dispersion and an amino resin, and an electrodeposition coating method thereof.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail.
The acrylic resin used in the present invention comprises (a) α, β
An ethylenically unsaturated carboxylic acid monomer, (b) an alkoxyl group-containing α, β ethylenically unsaturated monomer, and (c)
It can be obtained by copolymerizing other α, β ethylenically unsaturated monomers. The acid value derived from the monomer (a) is 20 to 150, preferably 30 to 100, and the content of the monomer (b) is preferably 0.1 to 10 parts by weight based on 100 parts by weight of all the monomers. .

The above-mentioned monomer (a) mainly gives the acrylic resin water dispersibility, electrophoresis, catalytic action at the time of baking, and the like. For example, acrylic acid, methacrylic acid, crotonic acid, vinyl acetic acid, Examples include 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 the monomer (a) used is such that the acid value of the resin is 2
It is used in the range of 0 to 150, preferably 30 to 100. If the acid value of the acrylic resin is less than 20, sufficient water dispersion stability cannot be obtained, and if it exceeds 150, the electrophoretic property is inferior when performing electrodeposition coating, and the water resistance and weather resistance are preferably reduced. Absent.

The monomer (b) is a monomer that reacts with —SiOH groups present on the surface of colloidal silica as an inorganic component. Examples thereof include divinyldimethoxysilane, divinyl-β-dimethoxyethoxysilane, Vinyl trimethoxysilane, vinyltriethoxysilane, vinyltris-β-methoxyethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropyltriethoxysilane, and the like. These may be used alone or in combination of two or more.

The amount used is based on 100 parts by weight of all monomers.
0.1 to 10 parts by weight is preferred.If the amount is less than this range, the reaction with the colloidal silica is not sufficient, and if the amount is large, the reaction proceeds excessively, so that the intended aqueous resin dispersion cannot be obtained, or Even if it is obtained, the stability of the electrodeposition paint obtained from the aqueous resin dispersion becomes poor.

In order to efficiently crosslink with the amino resin, it is preferable to copolymerize an OH group-containing monomer as the monomer (c). For example, 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, 2
-Hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, 4-hydroxybutyl methacrylate and the like, and
These lactone modified products include diethylene glycol monoacrylate, diethylene glycol monomethacrylate, triethylene glycol monoacrylate, triethylene glycol monomethacrylate, tetraethylene glycol monoacrylate, tetraethylene glycol monomethacrylate, and the like. These may be used alone or in combination of two or more.

The OH group-containing monomer is preferably used in such a range that the hydroxyl value in the acrylic resin is 40 to 100. When the hydroxyl value is less than 30, the curability is insufficient, and when it exceeds 150, the coating film becomes brittle, and the water resistance is lowered, so that it is not preferable because sufficient performance cannot be obtained.

Further, as the monomer (c), 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,
Acrylic acid such as diethylene glycol monomethacrylate, esters of methacrylic acid, styrene, α-methylstyrene, vinyl toluene, vinyl acetate, acrylonitrile, vinyl monomers such as methacrylonitrile, acrylamide, methacrylamide, methylolacrylamide,
Amide monomers such as methylol methacrylamide, methoxymethyl acrylamide, n-butoxymethyl acrylamide, diacetone acrylamide, diacetone methacrylamide and the like can be mentioned. These can be used alone or in combination of two or more.

The preferred number average molecular weight of such an acrylic resin is 3,000 to 60,000. When the number average molecular weight is 3,000 or less, sufficient coating durability cannot be obtained,
On the other hand, if it is more than 60,000, the water dispersibility decreases, and the handling of the paint becomes poor. The number average molecular weight is preferably from 5,000 to 40,000 from the viewpoint of particularly good appearance of the coating film and coating stability. The glass transition temperature of the acrylic resin is preferably from -10 to 60C, particularly preferably from 10 to 40C.

The above-mentioned acrylic resin is prepared by subjecting each of the monomers (a), (b) and (c) to a known method such as solution polymerization, non-aqueous dispersion polymerization, bulk polymerization, emulsion polymerization and suspension polymerization. , But particularly preferred is solution polymerization, and the reaction temperature is usually 40 to 170 ° C.
Is selected. 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.

On the other hand, colloidal silica which is an inorganic component used in the present invention is a colloid solution in which a component having SiO ₂ as a basic unit is dispersed in water or an organic solvent. The particle size is preferably from 1 to 200 nm, more preferably from 4 to 100 nm. -SiOH groups are present on the surface of the colloidal silica particles and react with the monomer (b) having an alkoxysilyl group to form a chemical bond, and as a result, an organic / inorganic composite is achieved. .

The above-mentioned reaction method is not particularly limited. A method in which the monomers (a), (b) and (c) are copolymerized in advance to obtain an acrylic resin, followed by reaction with colloidal silica, After reacting the product (b) with colloidal silica, copolymerizing with the monomers (a) and (c), copolymerizing the monomers (a), (b) and (c) in the presence of colloidal silica There is a method of polymerization. In any of the reaction methods, the reaction temperature is preferably 20 to 150 ° C, and 40 to 10 ° C.
0 ° C. is more preferred. As the reaction solvent, both an aqueous solvent and an organic solvent can be used, and an aqueous colloidal silica or an organic solvent colloidal silica is used according to each.

The colloidal silica used in the present invention is a product of Nissan Chemical Industry Co., Ltd., a product of Catalyst Chemical Industry Co., Ltd. or a product of Asahi Denka Kogyo Co., Ltd., and is provided in an aqueous or organic solvent system. For example, Snowtex 2
0, 30, 40, N, O, UP, Snowtex MA-
ST-M, IPA-ST, EG-ST, MEK-ST,
Cataloid S-20L, S-30L, SI-30, SI
-40, SI-350, SI-550, SN, Oscar 1132, 1332, 1432, 1632, Adelite AT-20, AT-40, AT-50, AT-30A,
AT-20Q and the like.

In order to disperse the organic / inorganic composite resin of the present invention in water, at least a part of the carboxyl groups in the acrylic resin is neutralized with a basic substance such as an organic amine or an inorganic base. Examples of such basic substances 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,
Examples include morpholine, sodium hydroxide and potassium hydroxide. The neutralization rate with such a basic substance is 30 to 1
00% is suitable, but especially 50 to 80% is preferable because water dispersibility is good and coating unevenness does not occur.

The water used for the water dispersion is desirably deionized water. As a specific method of water dispersing, a method in which a resin solution is poured into water in which a basic substance is previously mixed, a method in which a resin neutralized with a basic substance is poured into water, and the like, may be appropriately used. it can.

Examples of the amino resin used as a cross-linking agent for the organic / inorganic composite resin include conventionally known melamine resins, benzoguanamine resins, and urea resins. Among them, preferred ones are those having a methylol group. An alkoxymethylated melamine resin at least partially alkoxylated with a lower alcohol. As the lower alcohol, one or more of methyl alcohol, ethyl alcohol, propyl alcohol, butyl alcohol and the like can be used. The mixing of the amino resin and the organic / inorganic composite resin is preferably performed before the organic / inorganic composite resin is dispersed in water. However, this method may be used as long as dispersion stability is ensured and there is no hindrance to electrodeposition coating. Not limited.

Further, the electrodeposition paint obtained by the present invention is
If necessary, it is diluted with deionized water or deionized water partially containing a hydrophilic solvent, and then subjected to electrodeposition coating. For electrodeposition coating, an object to be coated is used as an anode, an electrodeposition deposition film is obtained by applying a predetermined voltage, and if necessary, after washing by a conventional method, through a baking process, scratch resistance,
A coating film having excellent abrasion resistance can be obtained.

Depending on the required performance, workability, cost and the like, if necessary, for example, xylene resin, epoxy resin, polyester resin, urethane resin and the like can be used in combination. In this case, it is used in the same manner as the amino resin.

[0024]

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

Production of Acrylic Resin (Production 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 40.7 parts (3) 2-ethylhexyl methacrylate 3.1 parts (4) n-butyl acrylate 26.8 parts (5) methyl methacrylate 29. 4 parts (6) Styrene 13.5 parts (7) 2-hydroxyethyl acrylate 17.6 parts (8) γ-methacryloxypropyltrimethoxysilane 2.5 parts (9) Acrylic acid 7.1 parts (10) Azo Bisisobutyronitrile 1.0 part (11) Azobisisobutyronitrile 0.5 part (1) and (2) are charged into a reactor, and the mixture is heated to the reflux temperature with stirring to obtain (3) to (10). ) Was previously uniformly mixed and then added dropwise over 3 hours. The temperature was maintained at 90 ± 3 ° C. 1.5 hours after the completion of the dropwise addition, (11) was charged, and the reaction was further continued at 90 ± 3 ° C. for 1.5 hours, followed by cooling.
A transparent and viscous resin liquid having a resin solid content of 65% and an acid value of 55 mg KOH / g resin solid was obtained.

(Production Example 2) 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 40.7 parts (3) 2-ethylhexyl methacrylate 9.3 parts (4) n-butyl acrylate 21.5 parts (5) methyl methacrylate 23. 1 part (6) Styrene 16.2 parts (7) 2-hydroxyethyl acrylate 15.6 parts (8) γ-methacryloxypropyltrimethoxysilane 2.5 parts (9) Acrylic acid 11.8 parts (10) Azo Bisisobutyronitrile 1.0 part (11) Azobisisobutyronitrile 0.5 part (1) and (2) are charged into a reactor, and the mixture is heated to the reflux temperature with stirring to obtain (3) to (10). ) Was previously uniformly mixed and then added dropwise over 3 hours. The temperature was maintained at 90 ± 3 ° C. 1.5 hours after the completion of the dropwise addition, (11) was charged, and the reaction was further continued at 90 ± 3 ° C. for 1.5 hours, followed by cooling.
A transparent and viscous resin liquid having a resin solid content of 65% and an acid value of 91 mg KOH / g resin solid was obtained.

Production of Organic / Inorganic Composite Resin (Production Example 3) In a reactor having a stirrer, a thermometer, and a reflux cooling device, 152.4 parts of the resin liquid of Production Example 1, Sumimal M-66B (manufactured by Sumitomo Chemical Co., Ltd.) ) 78.0 parts, colloidal silica A (Snowtex IPA-S manufactured by Nissan Chemical Industries, Ltd.)
T) After mixing 100.0 parts for 1 hour at a temperature of 60 ° C, 4.9 parts of triethylamine and 358.0 parts of deionized water were charged into a similar reactor separately prepared, and the mixture was maintained at 60 ° C. By slowly adding dropwise, a resin aqueous dispersion having a solid content of 30% was obtained. The temperature of the dispersion was raised to 70 ° C. and maintained at the same temperature for 6 hours to obtain a composite resin liquid A.

(Production Example 4) The resin liquid 152.4 of Production Example 2 was added to a reactor having a stirring device, a thermometer, and a reflux cooling device.
, Sumimar M-66B (Sumitomo Chemical Co., Ltd.) 78.0
After mixing 333.0 parts of colloidal silica A (Snowtex IPA-ST manufactured by Nissan Chemical Industries, Ltd.) at a temperature of 60 ° C. for 1 hour, 8.3 parts of triethylamine and 355.0 parts of deionized water were placed in a similar reactor separately prepared. The mixture was slowly added dropwise while maintaining the temperature at 60 ° C. to obtain a resin aqueous dispersion having a solid content of 30%. The temperature of the dispersion was raised to 70 ° C. and maintained at the same temperature for 6 hours to obtain a composite resin liquid B.

(Production Example 5) In a reactor having a stirrer, a thermometer and a reflux cooling device, 4.9 parts of triethylamine was added.
Colloidal silica B (Snowtex-manufactured by Nissan Chemical Co., Ltd.)
30) 102.4 parts of deionized water and 358.0 parts of deionized water were charged and mixed in advance at 60 ° C. for 1 hour, and 152.4 parts of the resin solution of Production Example 1 and 78.0 Nikarac MX-40 (manufactured by Sanwa Chemical Co., Ltd.) Part slowly dripped, solid content 30%
Was obtained. This dispersion was heated to 70 ° C.
The mixture was kept at the same temperature for 6 hours to obtain a composite resin liquid C.

(Production Example 6) A reactor having a stirrer, a thermometer and a reflux cooling device was charged with 8.3 parts of triethylamine.
Colloidal silica B (Snowtex-manufactured by Nissan Chemical Co., Ltd.)
30) 333.0 parts and 355.0 parts of deionized water were charged and mixed in advance at 60 ° C. for 1 hour, and 152.4 parts of the resin solution of Production Example 2 and Nikarac MX-40 (manufactured by Sanwa Chemical Co.) 78.0. Part slowly dripped, solid content 30%
Was obtained. This dispersion was heated to 70 ° C.
The mixture was maintained at the same temperature for 6 hours to obtain a composite resin liquid D.

(Production Example 7) The resin liquid 152.4 of Production Example 1 was added to a reactor having a stirring device, a thermometer, and a reflux cooling device.
After mixing 78.0 parts of Sumimal M-66B (manufactured by Sumitomo Chemical Co., Ltd.) at a temperature of 60 ° C. for 1 hour, 4.9 parts of triethylamine and 358.
0 parts were charged, and the above mixture was slowly added dropwise while maintaining the temperature at 60 ° C. to obtain a resin aqueous dispersion having a solid content of 30%.
The temperature of the dispersion was raised to 70 ° C. and maintained at the same temperature for 6 hours to obtain a composite resin liquid E.

(Production Example 8) The resin liquid 152.4 of Production Example 2 was added to a reactor having a stirrer, a thermometer, and a reflux cooling device.
After mixing 18.0 parts of Sumimal M-66B (manufactured by Sumitomo Chemical Co., Ltd.) at a temperature of 60 ° C. for 1 hour, 8.3 parts of triethylamine and 354.
6 parts were charged, and the above mixed solution was slowly added dropwise while maintaining the temperature at 60 ° C. to obtain a resin aqueous dispersion having a solid content of 30%.
The temperature of the dispersion was raised to 70 ° C. and maintained at the same temperature for 6 hours to obtain a composite resin liquid F.

Preparation of electrodeposition coating and electrodeposition coating Examples 1, 2, 3, 4 Comparative Examples 1, 2 Using the composite resin liquids obtained in Production Examples 3 to 8, Table 1,
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).

The specific conditions of the electrodeposition coating were as follows: a bath temperature of 22 ° C., a distance between the electrodes of 12 cm, and a pole ratio (+/−) of 2/1. After post-washing and subsequent baking at 185 ° C. for 30 minutes, the coating film performance was evaluated. Table 3 shows the results.

[0035]

[Table 1]

[0036]

[Table 2]

[0037]

[Table 3]

(Note) Evaluation method (1) Gloss: 60 ° gloss was measured with a gloss meter. (2) Scratch resistance: A corrugated paper was loaded with a load of 10 g / square cm, and the degree of scratching after visually rubbing the coated plate for 50 reciprocations with a 5 cm stroke was evaluated visually. ○ = Scratch is not visible. Δ = Scratch is visible, but not so white as a sheet. × = The scar looks like a white surface. (3) Pencil hardness: JIS-K-5400 Judgment of tear. (4) Vickers hardness: Fisher scope H100
Using V, measure the hardness at a load of 50 mN. (5) Alkali resistance: Observation of the coated surface after immersion in 48% 1% NaOH for 48 hours. (6) Acid resistance: After immersion in 5% sulfuric acid at 20 ° C for 48H, the state of the coated surface was observed.

[0039]

The electrodeposition coating composition of the present invention is applied to metal parts such as aluminum sashes, steel furniture, home appliances, etc., so that it has excellent scratch resistance and good coating appearance, mechanical properties, A coating film having chemical resistance and solvent resistance can be obtained.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI // C09D 133/14 C09D 133/14 (72) Inventor Eiji Masuda 6-10-73 Minamitsukaguchi-cho, Amagasaki-shi, Hyogo Shinto Paint Co., Ltd.

Claims (1)

[Claims] 1. An aqueous resin dispersion obtained by neutralizing, with a basic substance, an organic / inorganic composite resin obtained by reacting an acrylic resin containing an alkoxysilyl group and a carboxyl group with colloidal silica, and an amino resin. And an electrodeposition coating method for the same.