JP2002194273A - Powder primer for aluminum wheel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a powder coating material which can form a powder primer coating film excellent in corrosion resistance. SOLUTION: This powder primer contains (A) an epoxy-group-containing acrylic base resin, (B) a polycarboxylic acid compound, and (C) an acidic phosphoric acid compound in an amount of 0.01-8 pts.wt. based on 100 pts.wt. (in terms of solid content) sum of ingredients A and B.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a powder primer for aluminum wheels which is suitable for aluminum wheels for automobiles and has excellent adhesion and corrosion resistance.

[0002]

2. Description of the Related Art Steel wheels, aluminum wheels, and the like are used as automobile wheels as attachment members for tubes and tires. Of these, weight reduction,
Aluminum wheels (hereinafter, abbreviated as "aluminum wheels") having excellent anticorrosion properties and design properties are often used. For protection and aesthetics, aluminum wheels are usually used. A thermosetting acrylic resin-based powder coating is applied as a primer coating, and then thermosetting, and then a thermosetting acrylic resin-based organic solvent coating is applied as a top coating.

[0003] However, the coating film coated as described above does not have sufficient adhesion to a substrate and is inferior in corrosion resistance (generation of thread rust) and the like.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned deficiencies, and to improve the adhesion to the substrate and the corrosion resistance (the occurrence of rust).
The present invention relates to an improved aluminum wheel primer. That is, in the present invention, the acidic phosphoric acid compound (C) is contained in an amount of 0.01 to 8 parts by weight based on 100 parts by weight (solid content) of the epoxy group-containing acrylic base resin (A) and the polycarboxylic acid compound (B). The present invention relates to a powder primer for an aluminum wheel, which is contained in a range of parts by weight.

Hereinafter, the powder primer for aluminum wheels of the present invention will be described in detail.

The aluminum wheel (substrate) coated by the primer of the present invention is an automobile wheel which is a mounting member for automobile tubes such as passenger cars, motorcycles, trucks and wagons, and tires. And made of an alloy containing aluminum as a main component or further containing magnesium, silicon, or the like, and may be formed into an arbitrary shape for the purpose of weight reduction and design. An aluminum wheel in which a shot-blasted uneven casting surface or a cut smooth surface is mixed is also included. The surface of the aluminum wheel is preferably subjected to a chemical conversion treatment with a chromate or a phosphate before coating the primer.

Acrylic base resin containing epoxy group (A)
Component: A polymer mainly composed of an acrylic ester and / or a methacrylic ester, wherein the component (A) has a crosslinkable functional group such as glycidyl in the molecule.

The acrylate and methacrylate include glycidyl acrylate, glycidyl methacrylate, glycidyl allyl ether, 3,4-epoxycyclohexylmethyl (meth) acrylate, β
An epoxy group-containing acrylate such as -methylglycidyl (meth) acrylate is used as an essential monomer component, and examples thereof include a copolymer of methyl acrylate, methyl methacrylate, ethyl acrylate, and ethyl methacrylate. The epoxy group-containing acrylate is usually 10 to 80 as a monomer component constituting the resin.
% By weight, especially in the range from 20 to 70% by weight.

Other monomers that can be copolymerized with such acrylates and methacrylates include:
Unsaturated compounds having one or more polymerizable double bonds in one molecule, for example, propyl acrylate, propyl methacrylate, butyl acrylate, butyl methacrylate, hexyl acrylate, hexyl methacrylate, lauryl acrylate, Monoesters of acrylic acid or methacrylic acid such as lauryl methacrylate with a monohydric alcohol having 3 to 20 carbon atoms, acrylonitrile, methacrylonitrile, hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl Acrylate, hydroxypropyl methacrylate, caprolactone hydroxyethyl acrylate, caprolactone hydroxyethyl methacrylate, dimethylaminoethyl acrylate, dimethylaminoethyl methacrylate, styrene, vinyl acetate, Vini Methyl ether, vinyl chloride,
Examples include vinylidene chloride, ethylene, and propylene.

The epoxy group-containing acrylic base resin (A) has a weight average molecular weight of 1,000 to 80,000, preferably 2000 to 60,000, and a glass transition temperature of 20 to 80 ° C., preferably 30 to 70 ° C. It is.

Polycarboxylic acid (B) component: The component (B) is a compound having two or more carboxyl groups in one molecule, and is preferably dodecane diacid, adipic acid, azelaic acid, sebacic acid. And aliphatic acids such as succinic acid, glutaric acid, pimelic acid, brassic acid, itaconic acid, maleic acid, citraconic acid, eicosantioic acid and anhydrides thereof. One or more of these can be used.

The component (B) has a carboxyl group in the component (B) of 0.1 per glycidyl group in the resin (A).
It is blended in an amount in the range of 5 to 2, preferably 0.7 to 1.5. If the compounding ratio is out of the above range, the curability is lowered.

An acidic phosphoric acid compound (C) component; the component (C) is a compound represented by the general formula R _3-n P (O) (OH) _n , wherein R is an alkyl group having 1 to 24 carbon atoms, or Represents a phenyl group,
n represents an integer of 1 or 2). Examples of the alkyl group having 1 to 24 carbon atoms include methyl, ethyl, propyl, butyl, pentyl, hexyl,
Groups such as octyl and stearyl. These groups may be either linear or branched. When there are two R's, they may be the same or different. As the component (C), for example, dibutyl phosphoric acid, di (2-ethylhexyl) phosphoric acid, mono-2-ethylhexyl phosphoric acid, diphenyl phosphoric acid,
Preferred examples include phenylphosphonic acid.

The compounding ratio of the component (C) is in the range of 0.01 to 8 parts by weight, particularly 0.1 to 5 parts by weight, per 100 parts by weight of the total amount of the resins (A) and (B). If the compounding ratio is less than 0.01 parts by weight, the corrosion resistance is reduced, while 8
Exceeding the weight parts is not preferred because the water resistance of the coating film is reduced.

In the present invention, it is preferable to use the following epoxy resin (D) in addition to the above components. The resin (D) is a resin other than the acrylic epoxy resin having two or more epoxy groups in one molecule,
Known per se can be used. Specifically, glycidyl ethers of epihalohydrin such as epichlorohydrin and an aliphatic polyhydroxy compound (for example, glycol or glycerin): epihalohydrin such as epichlorohydrin and an alicyclic polyhydroxy compound (for example, hydrogenated bisphenol A) Glycidyl ethers with epihalohydrin such as epichlorohydrin and aromatic polyhydroxy compounds (for example, bisphenol A, F, novolak phenol, cresol phenol, etc.) with glycidyl ethers such as epichlorohydrin Glycidyl ethers of epihalohydrin and an aromatic polycarboxylic acid compound (such as phthalic acid): epoxy group-containing acrylic resin: epoxidized oil: alicyclic epoxy resin: and the like. Of these, glycidyl ethers of an epihalohydrin such as epichlorohydrin and an aromatic polyhydroxy compound are particularly preferred. For example, Epon 1001, Epon 1002, Epon 100
4, Epon 1007 (product name, manufactured by Shell Chemical Co., Ltd.).

The component (D) has a number average molecular weight of 30.
The range of 0 to 2000 and the epoxy equivalent of 150 to 1100 are preferable. The use of the component (D) improves the corrosion resistance and adhesion of the coating film. The mixing ratio of the component (D) is 100 total amount of the resins (A) and (B).
The range is preferably 20 parts by weight or less, particularly preferably 10 parts by weight or less per part by weight.

In the present invention, in addition to the above components (A) to (D), if necessary, organic coloring pigments, inorganic coloring pigments, fillers, curing catalysts, ultraviolet stabilizers, ultraviolet absorbers, flow modifiers, cissing An inhibitor and the like can be blended.

The powder coating material of the present invention is prepared, for example, by a conventional method, for example, after blending the components (A) to (D) and dry-blending with a mixer, heat-melting and kneading, cooling, coarse pulverization, It can be manufactured by pulverization and filtration.

The powder coating composition of the present invention is obtained by applying a powder coating to an object to be coated and forming a cured coating film by baking (for example, at a temperature of about 160 ° C. for about 30 minutes and at a temperature of about 200 ° C. for about 15 minutes). Can be.

The electrostatic powder coating is preferably performed by a method known per se, for example, electrostatic powder coating, triboelectric powder coating or the like. The coating thickness is not particularly limited, but is about 20 μm.
Suitable ranges are from m to 200 μm, especially from about 30 μm to 150 μm.

An organic solvent-based topcoat such as a colored paint or a clear paint can be applied to the powder coating surface of the primer of the present invention.

As these colored paints or clear paints, thermosetting acrylic resin-based paints are suitable. In particular,
A thermosetting paint obtained by dissolving or dispersing an acrylic resin, a crosslinking agent and a pigment (optional component) in an organic solvent is preferred.

As the acrylic resin, an acrylic resin having one or more functional groups selected from a hydroxyl group, an epoxy group, a carboxyl group, etc., which forms a coating film having excellent weather resistance, smoothness and chemical resistance. And modified resins thereof. As the cross-linking agent, compounds having a functional group capable of undergoing a cross-linking reaction with these functional groups can be used. For example, methylolated and / or alkyl etherified melamine resin, polyisocyanate compound, blocked polyisocyanate And at least one selected from the group consisting of a compound and a carboxyl group-containing compound. As pigments for coloring, coloring pigments and metallic pigments for ordinary paints can be used, for example, titanium white,
Examples thereof include carbon black, phthalocyanine bull, shinkasia red, aluminum powder, mica powder, surface-coated mica powder, and mica-like iron oxide, but are not limited thereto.

It is preferable that such a top coat is applied to the powder-coated surface by an airless spray, an air spray, an electrostatic method or the like. The viscosity at the time of coating is preferably 10 to 30 seconds / ford cup # 4/20 ° C., and the coating thickness is about 15 to 35 μm, especially 2
0 to 30 μm is preferred. If necessary, it is left at room temperature or dried at 100 ° C. or lower, and then heated to 100 to 180 ° C. to crosslink and cure the coating film.

[0025]

1) The primer coating film of the present invention has excellent adhesion to an aluminum surface. 2) The aluminum wheel coated with the primer has excellent corrosion resistance. 3) Since the primer does not contain any pollutants such as chromic acid-based rust preventive pigments, the safety is improved.

[0026]

Next, examples and comparative examples according to the present invention will be described. All parts and percentages are in principle by weight.

Acrylic base resin containing epoxy group (A)
Production Example of Components 70 parts of toluene was put into a normal acrylic resin reaction tank equipped with a stirrer, thermometer, reflux condenser, etc., and heated and stirred.
When the toluene starts to reflux, 35 parts of glycidyl methacrylate, 16 parts of n-butyl methacrylate, 34 parts of methyl methacrylate, 15 parts of styrene and 4 parts of t-butyl peroxy-2-ethylhexanoate as a polymerization initiator are required for about 2 hours. And dropped. After the completion of the dropwise addition, the reflux was continued for another 3 hours, then the reflux was stopped and toluene was allowed to flow out of the reaction vessel. When the temperature of the contents in the reaction tank reached 150 ° C., the remaining toluene was removed by distillation under reduced pressure, and the mixture was cooled to obtain Copolymer 1. The weight average molecular weight of the obtained copolymer 1 was 8,000, and the glass transition temperature was 55 ° C.

Example 1 80 parts of the above copolymer 1, 20 parts of dodecane diacid as component (B), and dibutyl phosphoric acid as component (C) (Note 1)
0.5 parts of Epon 1002 (trade name, manufactured by Shell Chemical Co., Ltd.) as a component (D) was dry-blended using a Henschel mixer at room temperature using a Henschel mixer, and melt-kneaded with an extruder. After cooling this and pulverizing with a pin disk mill,
The mixture was filtered through a 150-mesh sieve to obtain a powder coating.

Examples 2 to 5 The powder coating materials of Examples 2 to 5 were obtained with the components and amounts shown in Table 1.

Comparative Examples 1 and 2 The powder coatings of Comparative Examples 1 and 2 were obtained with the components and amounts shown in Table 1. The blending amounts shown in Table 1 are the amounts blended in parts.

Coating conditions of coating film A powder primer was electrostatically coated on an AC4C plate which had been subjected to a chemical conversion treatment with chromate chromate (AL-1000: manufactured by Nippon Parkerizing Co., Ltd.) so that the film thickness became 100 μm. The composition was cured by heating at 160 ° C. for 30 minutes. Various tests were performed on each of the obtained baked coated plates.
The test results are shown in Table 1. Table 1

[0032]

[Table 1]

In Table 1, (Note) is as follows. (Note 1) Dibutyl phosphoric acid (Note 2) Di (2-ethylhexyl) phosphoric acid (Note 3) Mono-2-ethylhexyl phosphoric acid (Note 4) Diphenyl phosphoric acid (Note 5) Phenylphosphonic acid Test method Coating appearance: Finish of coating The appearance was evaluated based on the following criteria based on glossiness and smoothness. : Good, Δ: slightly poor, ×: poor Adhesion: cross-cut the coating film with a cutter knife so as to reach the substrate, and cut a 1 mm x 1 mm squared gobang.
Make 0 pieces, stick the adhesive cellophane tape on the surface,
After the tape was sharply peeled at 0 ° C., the number of the remaining coated films was examined.は indicates 100 remaining coating films, Δ indicates 99-70 remaining coating films, and x indicates 69 or less remaining coating films.

Water resistance: immersed in water of 40 ° C. for 240 hours,
The coated surface immediately after the pulling was visually evaluated, then dried for 1 hour at room temperature, and the adhesion was examined in the same manner as in the above adhesion test. In the visual evaluation, ○ indicates that there was no abnormality, Δ indicates that there was a slight amount of microblister, and X indicates that there was much blister. The adhesion was evaluated in the same manner as described above. Corrosion resistance: The coating film was cross-cut so as to reach the substrate, and was subjected to salt spraying (JIS K5400-9.1) to 1000.
After testing for a time and then washing and drying, an adhesive cellophane tape is applied to the cross cut portion, and the tape is rapidly peeled at 20 ° C., and then the peeling width of the coating film from the cut portion (one side) or I checked the blister width. ◎ is within 0.5mm,
○ indicates 1 mm or less, Δ indicates 3 mm or more, and X indicates 10 mm or more.

Top coat adhesion: An organic solvent type paint of Magiclon ALC2-1 Clear (Kansai Paint Co., Ltd., trade name) is spray-coated on the powder coating applied on the aluminum wheel, and baked at 140 ° C. for 30 minutes. A topcoat was formed. The adhesion of this coating film was evaluated in the same manner as described above.

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Claims (2)

[Claims] 1. An epoxy group-containing acrylic base resin (A)
And the acidic phosphoric acid compound (C) in an amount of 100 parts by weight (solid content) of the polycarboxylic acid compound (B) and 0.0 parts by weight.
A powder primer for an aluminum wheel, which is contained in an amount of 1 to 8 parts by weight. 2. An acidic phosphoric acid compound (C) having the general formula R
_3-n P (O) (OH) _n (wherein, R represents an alkyl group having 1 to 24 carbon atoms or a phenyl group, and n represents an integer of 1 or 2). The powder primer for an aluminum wheel according to claim 1.