JP2002239455A - Method of coating aluminum wheel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a rust-preventing primer coating having excellent edge covering properties on an aluminum wheel having a cut surface and/or casting surface. SOLUTION: The rust preventing primer coating material is prepared by blending 5-20 pts.wt. epoxide resin (B) having epoxy equivalent of 210-1,000 with 100 pts.wt. acrylic resin (A) having a weight average molecular weight of 30,000-150,000, -30 to 20 deg.C glass transition point, a hydroxyl value of 10 to 80 and an acid value 2 to 40, and further blending 0.5 to 20 pts.wt. blocked polyisocyanate (C) having a blocking agent having 120 to 150 deg.C reaction starting temperature to 100 pts.wt. of the acrylic resin (A) to obtain a primer resin, to which 3 to 20 pts.wt. organic bentonite (D) per 100 pts.wt. solid portion of the primer resin and 5 to 30 pts.wt. amide based wet dispersing agent (E) expressed in terms of the solid portion per 100 pts.wt. organic bentonite (D) are blended.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating method for forming a rust-preventive primer coating film on an aluminum wheel having a cut surface and / or a casting surface, and further forming a top clear coating film. .

[0002]

2. Description of the Related Art Aluminum wheels are generally cast,
Or after being formed into a wheel shape by forging, etc.
A cutting process is performed. A paint such as a clear paint is applied on the aluminum wheel after the cutting for the purpose of imparting aesthetics and weather resistance.

[0003] However, it is known that a sharp edge portion exists in the cut portion, and thread-like rust is generated from such an edge portion. For the purpose of preventing the generation of such rust, conventionally, the aluminum wheel surface is rust-proofed with chromic acid before painting, or painted with a paint containing a rust-preventive pigment such as zinc chromate. are doing.

[0004] However, heavy metals such as chromium are harmful substances, and their use is not preferable from the viewpoint of environmental health. Therefore, a rust-preventive primer coating containing no heavy metal such as chromium is desired. JP-A-1-194797 and JP-A-6-57178 propose a rust-free clear coating composition containing no chromium.
In the method of forming a coating film disclosed in the publication, after applying these rust-preventive primer coating materials, a thick top clear coating material is further applied thereon.

[0005]

However, even when the rust-preventive primer coating disclosed in the above publication is used, it may not be possible to obtain a sufficiently good edge cover property, and the desired protection against aluminum wheels may not be obtained. In some cases, the rust effect could not be provided. Further, not only the edges of the cut surface but also the casting surface have irregularities on the surface, and therefore, a rust-preventive primer coating having excellent edge coverage on the casting surface is also required.

It is an object of the present invention to provide a method for coating an aluminum wheel which can form a rust-preventive primer coating film having excellent edge cover properties.

[0007]

According to the present invention, there is provided a method for coating an aluminum wheel, comprising applying a rust-preventive primer coating to an aluminum wheel having a cut surface and / or a casting surface to form a rust-preventive primer coating film. And a top clear coating formed by applying a top clear coating thereon, wherein the rust-preventive primer coating comprises:
Weight average molecular weight 30,000-150,000, glass transition point -30 ° C-20 ° C, hydroxyl value 10-80 (mg KOH
/ G) and 100 parts by weight of an acrylic resin having an acid value of 2 to 40 (mg KOH / g), and (B) an epoxy equivalent of 21.
5 to 20 parts by weight of epoxy resin of 0 to 1000 are blended,
Further, for 100 parts by weight of (C) acrylic resin (A),
(D) 3 to 20 parts by weight based on 100 parts by weight of the above-mentioned primer resin solid content, to a primer resin obtained by mixing 0.5 to 20 parts by weight of a blocked polyisocyanate having a blocking agent having a reaction initiation temperature of 120 to 150 ° C. Part of the organic bentonite and (E) the organic bentonite (D) 100
It is characterized by being a paint containing an amide-based wetting and dispersing agent having a solid content of 5 to 30 parts by weight with respect to parts by weight.

According to the coating method of the present invention, by using the above-mentioned rust-preventive primer paint, a rust-preventive primer coating film having excellent edge coverage can be formed, and a good rust-preventive effect can be imparted to an aluminum wheel. can do.

In the coating method of the present invention, the rust-preventive primer coating further comprises (F) a urea-based rheology in which the solid content of the primer resin is 0.05 to 5.0 parts by weight based on 100 parts by weight of the solid content of the primer resin. An imparting agent may be blended.

Such a urea-based rheology-imparting agent (F)
The adhesion of the rust-preventive primer coating film can be further improved by blending. The rust-preventive primer coating used in the present invention is an organic bentonite (D)
And a amide-based wetting and dispersing agent (E) are added to a solvent, mixed and dispersed, and a pregel is preferably mixed with a primer resin solution.

When a urea-based rheology-imparting agent (F) is further added to the rust-preventive primer coating, it is preferably added after the pregel and the primer resin solution are mixed.

In the present invention, a color base coating film may be provided between the antirust primer coating film and the top clear coating film. That is, a color base paint may be applied on the rust-preventive primer coating to form a color base paint, and then a top clear paint may be applied on the color base paint to form a top clear paint.

[0013] The aluminum wheel of the present invention is characterized by being coated by the coating method of the present invention.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION The rust-preventive primer coating used in the coating method of the present invention comprises an acrylic resin (A), an epoxy resin (B) and a blocked polyisocyanate (C).
Is obtained by blending

The acrylic resin (A) can be obtained by polymerizing a compound having two or more radically polymerizable ethylenically unsaturated groups in a molecule by an ordinary method. The compounds having an ethylenically unsaturated group include the following.

(A): having a hydroxyl group such as hydroxylmethyl (meth) acrylate, hydroxylethyl (meth) acrylate, hydroxylpropyl (meth) acrylate, hydroxylbutyl (meth) acrylate, N-methylolacrylamine, etc. Ethylene monomer (b): Ethylene monomer having a carboxyl group such as (meth) acrylic acid, crotonic acid, itaconic acid, fumaric acid, maleic acid, etc. (c): Methyl (meth) acrylate, ethyl (meth) acrylate (Meth) such as propyl (meth) acrylate, butyl acrylate, n-propyl acrylate, n-butyl acrylate, isobutyl acrylate, 2-ethylhexyl acrylate, n-octyl acrylate, and n-dodecyl acrylate Monomers such as alkyl acrylate d): the weight-average molecular weight of the (a) and (b) and copolymerizable ethylenic monomer, and (e) :( meth) acrylonitrile, styrene and acrylic resin (A) 30000-1
50,000, preferably 40,000 to 10,000
0. If the weight-average molecular weight is too small, the rust-preventing effect is reduced, and if the weight-average molecular weight is too large, the coating workability is reduced.

The glass transition point is -30 ° C to 20 ° C,
Preferably it is -20 to 0 ° C. If the glass transition temperature is too low, the rust-preventive effect is reduced, and if the glass transition point is too high, the chipping resistance at low temperatures is reduced.

The hydroxyl value is from 10 to 80, preferably from 15 to 25. If the hydroxyl value is too low, the adhesion will decrease, and if it is too high, the rust-preventive effect will decrease. The acid value is from 2 to 40, preferably from 10 to 30. If the acid value is too low or too high, the chipping resistance decreases.

The epoxy resin (B) is a general-purpose epoxy resin comprising a compound having two or more epoxy groups in one molecule. Specifically, for example, bisphenol A, bisphenol F, Glycidyl ether epoxy resin of polyphenol compounds such as 1,2,2-tetrakis (4'-hydroxyphenyl) ethane; glycidyl ether epoxy resin of polyhydric phenols such as catechol, resorcin, hydroquinone, and phloroglucin; ethylene glycol; Butanediol,
Glycidyl ether epoxy resins of polyhydric alcohols such as glycerol, erythritol and polyoxyalkylene glycol; novolak epoxy resins; cycloaliphatic epoxy resins such as vinylcyclohexene dioxide, limonene dioxide, dicyclopentadiene dioxide; Polyglycidyl ester-based epoxy resins of ester condensates of acids and polycarboxylic acids such as cyclohexane-1,2-dicarboxylic acid; and polyglycidylamine-based epoxy resins. Here, a glycidyl ether epoxy resin or a cycloaliphatic epoxy resin having an epoxy equivalent of 210 to 1000 is preferably used.

When the epoxy equivalent falls below the above range,
The chipping resistance decreases, and conversely, the higher the epoxy equivalent, the lower the water resistance. The epoxy resin (B) is blended in an amount of 5 to 20 parts by weight, preferably 8 to 15 parts by weight, based on 100 parts by weight of the acrylic resin (A). When the amount of the epoxy resin (B) decreases, the water-resistant adhesion decreases, and when the amount of the epoxy resin (B) increases, the chipping resistance at low temperatures decreases.

The blocked polyisocyanate (C) is a polyisocyanate blocked by a blocking agent having a reaction initiation temperature of 120 to 150 ° C., and includes hexamethylene diisocyanate, ethylene diisocyanate, propylene diisocyanate, tetramethylene diisocyanate,
Decamethylene diisocyanate, metaphenylene diisocyanate, triphenylmethane triisocyanate,
Various diisocyanates such as cyclohexyl isocyanate, phenylene diisocyanate, tolylene diisocyanate (TDI), xylylene diisocyanate (XDI), isophorone diisocyanate (IPDI), and adducts, hydrates and condensates of these with polyols are blocked by heat. Phenol-based, lactam-based, active methylene-based, alcohol-based, amine-based, oxime-based, urea-based, and imine-based blocking agents from which is released.

The term "reaction initiation temperature" as used herein means a temperature at which the elastic modulus changes from a decrease (thermoplastic) to an increase (thermosetting) when a constant temperature rise is given in the process of curing the paint as a coating film. . If the reaction initiation temperature is too low, yellowing occurs, and the chipping resistance at low temperatures decreases. Also,
If the reaction start temperature is too high, the water resistance will decrease.

The blocked polyisocyanate (C) is used in an amount of 0.5 to 100 parts by weight of the acrylic resin (A).
20 parts by weight, preferably 1 to 5 parts by weight are blended. If the amount of the blocked polyisocyanate (C) is too small, the water resistance will be poor, and if it is too large, the adhesion to the overcoat film will be poor.

The rust-preventive primer coating used in the present invention comprises a primer resin comprising the above-mentioned acrylic resin (A), the above-mentioned epoxy resin (B) and the above-mentioned block polyisocyanate (C), and an organic bentonite (D).
And an amide-based wetting and dispersing agent (E).

The organic bentonite (D) is obtained by intercalating an organic ammonium salt between layers of bentonite. Examples thereof include “Benton 34” (dimethyl dioctadecyl ammonium bentonite / quaternary ammonia-18 bentonite, National Red Co., Ltd.), trade name "Benton 38" (magnesium montmorillonite / quaternary ammonia-18 hectorite, manufactured by National Red Co., Ltd.), trade name "Organite A" (complex of montmorillonite and trialkylbenzylammonium salt, Nippon Organic Clay Co., Ltd.) and trade name “New D Orben” (dimethyl C ₁₈ H ₃₇ N ^{+ of} bentonite, manufactured by Shiraishi Industry Co., Ltd.).

The compounding amount of the organic bentonite (D) is 3 to 20 parts by weight, preferably 6 to 12 parts by weight, based on 100 parts by weight of the solid content of the primer resin. If the amount of the organic bentonite (D) is too small, the sagging property and the edge covering property deteriorate. If the amount of the organic bentonite (D) is too large, the adhesion will be poor.

The amide wetting and dispersing agent (E) is a wetting and dispersing agent containing a salt of polyaminoamide and a low molecular weight acid polymer or a polar acid ester. Specifically, trade name “Anti-Terra-U” (a solution of a salt of an unsaturated polyaminoamide and a low molecular weight acid polymer, BYK Ch
emie) and trade name "Disperbyk-1"
01 "(a solution of a salt of a long-chain polyaminoamide and a polar acid ester, manufactured by BYK Chemie) or the like.

The amount of the amide wetting and dispersing agent (E) is
5 to 100 parts by weight of the organic bentonite (D)
The amount is such that the solid content is 30 parts by weight, preferably 10 to 25 parts by weight. If the amount of the amide-based wetting and dispersing agent (E) is too small, the sagging property and the edge covering property deteriorate.
If the amount of the amide-based wetting and dispersing agent (E) is too large, the paint tends to aggregate.

The rust-preventive primer coating used in the present invention may further contain a urea-based rheology-imparting agent (F). By blending the urea rheology imparting agent (F), the adhesion of the rust-preventive primer coating film can be further improved.

As the urea-based rheology imparting agent (F),
Any rheology-imparting agent for a compound having a urea skeleton may be used. Specifically, trade name “BYK-411” (modified urea solution, manufactured by BYK Chemie) or the like can be used.

The amount of the urea-based rheology-imparting agent (F) is 0.05 to 5.0 parts by weight, preferably 0.1 to 2.0 parts by weight, based on 100 parts by weight of the above-mentioned primer resin solids. This is the amount that will be used. If the amount of the urea-based rheology-imparting agent is too small, the adhesion will be poor. If the amount of the urea-based rheology-imparting agent (F) is too large, the water resistance is deteriorated.

Although the method of preparing the rust-preventive primer coating is not particularly limited, it is preferable that the rust-preventive primer coating be prepared by blending in the following order as described above. First, an organic bentonite and an amide-based wetting and dispersing agent are mixed in the presence of a solvent to prepare a pregel. Next, this pregel is added and dispersed in a primer resin previously dissolved in a solvent. When using a urea rheology-imparting agent, a urea-based rheology-imparting agent is added to this dispersion and mixed.

The rust preventive primer paint of the present invention is used as a paint after being diluted with a general organic solvent such as toluene or ethyl acetate, and has a solid content of 7%.
It is preferably prepared to be 調製 40% by weight, preferably 10-25% by weight.

After the rust-preventive primer coating is applied, it is dried and baked to form a rust-preventive primer coating. The baking conditions are not particularly limited as long as the coating film can be dried or cured at a temperature and time. For example, baking is performed at a temperature of room temperature to 160 ° C. for 1 to 30 minutes.

If necessary, a top clear coating may be applied on the rust-preventive primer coating without baking the coating by so-called wet-on-wet. The top clear coating applied on the rust-preventive primer coating is not particularly limited, and those containing a film-forming thermosetting resin, a curing agent and the like can be used. Examples of the form of the clear coating include a solvent type, an aqueous type and a powder type.

Preferred examples of the solvent-type clear coating include a combination of an acrylic resin and / or a polyester resin and an amino resin, and a combination of an acrylic resin and / or a polyester resin and an isocyanate, in terms of transparency or acid etching resistance. Acrylic resin having a carboxylic acid / epoxy curing system in combination with an agent and / or
Or a combination of polyester resins, and the like.

Examples of the water-based clear paint include a resin obtained by neutralizing a film-forming resin contained in the above-mentioned solvent-based clear paint with a base to form an aqueous solution. Things can be mentioned. This neutralization can be carried out before or after the polymerization by adding a tertiary amine such as dimethylethanolamine and triethylamine.

On the other hand, as the powder type clear coating material, an ordinary powder coating material such as a thermoplastic and thermosetting powder coating material can be used. Because a coating film with good physical properties can be obtained,
Thermosetting powder coatings are preferred. Specific examples of the thermosetting powder coating include epoxy-based, acrylic-based, and polyester-based powder clear coatings, and an acrylic-based powder clear coating having good weather resistance is particularly preferable.

As the powder type clear coating material, an epoxy-containing acrylic resin / polycarboxylic acid type powder coating material is particularly preferable because it has no volatile matter at the time of curing, has a good appearance, and has little yellowing. preferable.

Further, the clear paint may contain a curing catalyst, a surface conditioner, and the like, if necessary. The baking conditions for the top clear coating film are appropriately set according to the top clear coating used.

In the present invention, the thickness of the rust preventive primer coating is not particularly limited, but is generally about 10 to 15 μm. The thickness of the top clear coating film is not particularly limited, but is generally about 25 to 150 μm.

The coating method of the present invention may be applied to an aluminum wheel having a cut surface after the cutting step or, as described above, to an aluminum wheel having a casting surface.

Before applying the rust-preventive primer coating, the aluminum wheel may be subjected to a pretreatment. Examples of the pretreatment include a chromium treatment or a non-chromium treatment, and a non-chromium treatment is preferable.

In the case where the aluminum wheel is colored by painting, a colored base paint may be applied to the aluminum wheel before cutting, followed by cutting.

FIGS. 3 and 4 are cross-sectional views showing a state where a laminated coating film is formed on an aluminum wheel having a cut surface and a casting surface by the coating method of the present invention. On the surface of the aluminum wheel 11, a casting surface 11a and a cutting surface 11b formed by a cutting process are formed. In FIG. 3, the casting surface 11a and the cutting surface 11
b, a rust-preventive primer coating film 12 is formed thereon, and a top clear coating film 13 is formed on the rust-preventive primer coating film 12. In FIG. 4, a rust-preventive primer coating film 12 is formed on the casting surface 11a and the cutting surface 11b, a color base coating film 14 is formed on the rust-preventive primer coating film 12, and In addition, a top clear coating film 13 is formed.

FIGS. 5 and 6 are cross-sectional views showing a state in which a laminated coating film is formed in accordance with the coating method of the present invention on an aluminum wheel having only a casting surface, on which no cut surface is formed by the cutting process. is there. In FIG. 5, a rust-preventive primer coating film 12 is formed on a casting surface 11 a of an aluminum wheel 11, and a top clear coating film 13 is formed on the rust-preventive primer coating film 12. 6, a rust-preventive primer coating 12 is formed on the casting surface 11a of the aluminum wheel 11, a color base coating 14 is formed on the rust-preventive primer coating 12, and Has a top clear coating film 13 formed thereon.

[0047]

EXAMPLES Hereinafter, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to the following examples, and can be carried out by appropriately changing the scope of the invention without changing its gist. It is something.

[Preparation of Primer Resin] Acrylic Resin 1
9 parts by weight of an epoxy resin and 2 parts by weight of block isocyanate were blended with 00 parts by weight to prepare a primer resin. As the solvent, 103 parts by weight of toluene and 100 parts by weight of ethyl acetate were used. In addition, some of these solvents were used when preparing a pregel of an organic bentonite and an amide-based wetting and dispersing agent as described later. Therefore, the amount of the solvent obtained by subtracting the amount of the solvent used for the preparation of the pregel is used in the preparation of the primer resin.

As the acrylic resin, a weight average molecular weight of 80
000-90000, glass transition point -7 ° C, hydroxyl value 1
6. Those having an acid value of 25 were used. The epoxy resin used had an epoxy equivalent of 450 to 500. As the blocked isocyanate, an aliphatic polyisocyanate (trade name “Desmodur BL3175”,
Sumitomo Bayer Urethane Co., Ltd.) was used.

[Preparation Examples 1 to 9]
An organic bentonite, an amide-based wetting and dispersing agent, and if necessary, a urea-based rheology-imparting agent were added to the primer resin to prepare a rust-preventive primer coating. The order of compounding was as follows. An organic bentonite and an amide-based wet swelling agent were previously added and dispersed in a solvent to prepare a pregel, and the pregel was added to and dispersed in a primer resin solution. In addition,
When a urea-based rheology-imparting agent was blended, it was added and blended thereafter.

The mixing ratios shown in Table 1 are based on the primer resin,
The amount of solid content is shown for each of the organic bentonite, the wetting and dispersing agent, and the rheology-imparting agent. In addition, as for the wetting and dispersing agent, the mixing ratio is shown based on 100 parts by weight of the organic bentonite.

The following were used as the organic bentonite, amide-based wetting and dispersing agent, and urea-based rheology-imparting agent.・ Organic bentonite: trade name “Benton 38” manufactured by National Red Co., Ltd. ・ Amide wetting and dispersing agent: trade name “Anti-Terr”
aU ", manufactured by BYK Chemie, solid content 50% by weight ・ Urea-based rheology-imparting agent: trade name" BYK-41 "
1 ", BYK Chemie, modified urea solution, solid content 25% by weight

[0053]

[Table 1]

[Examples 1 to 8 and Comparative Example 1] An aluminum plate (AC4C) as an object to be coated was coated with the rust-preventive primer coating material of the preparation example shown in Table 2 and then applied to Table 2
And baked under the conditions shown in Table 2 to form a coating film.

The following paints were used for the top clear coating.・ O-150: Trade name “Super Rack O-150 Clear” (acryl melamine curing type clear paint, manufactured by Nippon Paint Co., Ltd.) ・ nax Superior: brand name “nax Superior Rio”
(Acrylic isocyanate-curable clear paint, manufactured by Nippon Paint Co., Ltd.) PD-A400: trade name "Powax A-400 Clear" (acid epoxy-curable powder clear paint, manufactured by Nippon Paint Co., Ltd.) The coating was performed so that the thickness became 12 μm. The top clear paint is PD-A4 so that the dry film thickness of O-150 is 25 μm, and the dry film thickness of nax Superior is 30 μm.
About 00, it painted so that dry film thickness might be set to 100 micrometers.

The obtained coating film was evaluated for adhesion and rust prevention as follows. -Adhesion: 100 cut lines are formed by forming 11 cuts in the coating film with a cutter knife in the longitudinal direction and the horizontal direction so as to have a width of 2 mm each, and an adhesive tape is stuck thereon. After peeling, the number of grids where the coating film was peeled off was measured. When the number of peeled grids is 0,
That is, 0/100 is ○, 1-3 / 100 is △, 4-10 / 100 is 〜１０,
Those that exceeded × were evaluated as ×.

Rust prevention: After forming a cross cut on the coating film with a cutter knife, put it in a salt water spray tester according to JIS Z2371 for 24 hours, wash the coating film surface with water, and then heat at 40 ° C. and humidity. A cycle in which the sample was put in an 80-90% constant temperature and humidity box for 120 hours, and then left at room temperature for 24 hours was defined as one cycle, and after repeating this cycle for 12 cycles, the maximum length of the thread rust generated in the cut portion was measured. Was evaluated.

Those having a rust length of 2 mm or less were evaluated as ◎, those having a rust length of 4 mm or less were evaluated as ○, and those having a rust length exceeding 4 mm were evaluated as x. Further, the rust-preventive primer paints of Preparation Examples 1 to 9 were evaluated for edge cover properties as follows.

FIG. 1 is a front view showing a test apparatus for evaluating the edge cover property, and FIG. 2 is a side view. The blade 2 of the cutter knife is provided on the side surface 1b of the support base 1 with a blade edge 2a.
Is mounted vertically upright. The reason that the side surface of the blade 2 of the cutter knife is attached so as to be in contact with the side surface 1b of the support 1 is that the contact area between the blade 2 of the cutter knife and the support 1 is increased, and the blade 2 of the cutter knife and the support 1 By improving the heat transfer between
This is to make the temperature of the blade 2 of the cutter knife close to the temperature of the support base 1. Further, by making the material of the support base 1 the same as the material of the object to which the paint is actually applied, a temperature change close to the temperature change of the object at the time of baking the coating film can be obtained.
Can be applied to the blade 2 of the cutter knife. Support table 1
Under the base plate 4 having a larger area than the support 1
Is provided.

The coating gun 3 is arranged on the blade 2 of the cutter knife, and the paint to be measured is sprayed from the coating gun 3 and adhered onto the cutting edge 2a. At this time,
Coating is performed by adjusting the discharge amount or the number of coatings so that the thickness of the coating film changes stepwise. Here, the thickness of the coating film is 8 to
Overcoating was performed while changing the coating area so as to change stepwise within a range of 15 μm.

The thickness of the coating film adhered on the cutting edge 2a can be measured by measuring the thickness of the coating film applied on the upper surface 1a of the support 1. When the support 1 has irregularities on the surface, such as an aluminum casting, it may be difficult to measure the thickness of the coating film on the upper surface 1a of the support 1. In such a case, the thickness of the coating film applied on the cutting edge 2a can be obtained by measuring the thickness of the coating film applied on the upper surface 4a of the base plate 4 under the support base 1.

The primer coating applied on the cutting edge 2a is as follows:
In the same manner as in the above Examples and Comparative Examples, baking was performed at 140 ° C. for 20 minutes. As the blade 2 of the cutter knife, a trade name "replaceable blade for NT cutter BA-150" (A blade, blade thickness 0.38 mm, material SK2, manufactured by Nippon Transfer Paper Co., Ltd.) was used.

One terminal of the tester was brought into contact with the conductive portion of the blade 2 and the other terminal was brought into contact with a portion having a thickness of 12 μm, and the edge coverage was evaluated based on the presence or absence of electrical conduction. Specifically, when there was no electrical conduction even when the other terminal was moved along the cutting edge at a portion having a predetermined film thickness, it was judged as “no line conduction” and was evaluated as “○”. Also, when the other terminal is moved, electrical continuity is recognized in certain parts in some places,
It was judged that there was “point conduction”, and was evaluated as △. When electrical continuity was observed in all portions having a predetermined film thickness, it was judged as "conducted" and rated as "x".

Table 2 shows the evaluations of the edge cover properties, adhesion properties, and rust prevention properties obtained as described above.

[0065]

[Table 2]

As is clear from the results shown in Table 2, in Examples 1 to 8 using the rust-preventive primer coatings of Preparation Examples 2 to 9 according to the present invention, good edge coverage was obtained. In Examples 4 to 8 using the rust-preventive primer coating materials of Preparation Examples 5 to 9 in which a urea-based rheology-imparting agent was blended, good adhesion of the coating film was obtained.

The same rust-preventive primer coating and top clear coating as in Examples 1 to 8 were applied to the aluminum wheel after the cutting step, and the rust-preventing effect was evaluated. Was. In particular, a good rust prevention effect was obtained at the edge of the cut surface where a good rust prevention effect could not be obtained by the conventional coating method.

[0068]

According to the present invention, a rust-preventive primer coating film having excellent edge cover properties can be formed, and a good rust-preventive effect can be imparted to an aluminum wheel.

[Brief description of the drawings]

FIG. 1 is a front view showing an edge cover property evaluation test apparatus used in an example of the present invention.

FIG. 2 is a side view showing an edge cover property evaluation test apparatus used in an example of the present invention.

FIG. 3 is a cross-sectional view showing a state where a rust-preventive primer coating and a top clear coating are formed on an aluminum wheel having a cut surface and a casting surface.

FIG. 4 is a cross-sectional view showing a state in which a rust-preventive primer coating, a color base coating, and a top clear coating are formed on an aluminum wheel having a cut surface and a casting surface.

FIG. 5 is a sectional view showing a state in which a rust-preventive primer coating film and a top clear coating film are formed on an aluminum wheel having a casting surface.

FIG. 6 is a cross-sectional view showing a state when a rust-preventive primer coating film, a color base coating film, and a top clear coating film are formed on an aluminum wheel having a casting surface.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Support stand 1a ... Upper surface of a support stand 1b ... Side surface of a support stand 2 ... Blade of a cutter knife 2a ... Blade edge of a cutter knife 3 ... Painting gun 4 ... Base plate 4a ... Upper surface of a base plate 11 ... Aluminum wheel 11a ... Aluminum wheel Cast surface 11b: Cutting surface of aluminum wheel 12: Anti-rust primer coating 13: Top clear coating 14: Color base coating

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) C09D 133/00 C09D 133/00 163/00 163/00 175/04 175/04 175/04 (72) Inventor Yasutaka Horiuchi 19-17 Ikedanakacho, Neyagawa-shi, Osaka, Japan Nippon Paint Co., Ltd. (72) Inventor Masakazu Oi 5-9, Yonbancho, Chiyoda-ku, Tokyo Topy Industries Co., Ltd. 5-9, Yonbancho-ku, Tokyo Topy Industries Co., Ltd. (72) Inventor Takusho Saito 5-9, Yonbancho, Chiyoda-ku, Tokyo Tokyo, Japan (72) Inventor Tatsuya Oguri 4 Chiyoda-ku, Tokyo Bancho 5-9, Topy Industries Co., Ltd. (72) Inventor Takayuki Sato 5-9, Yobancho, Chiyoda-ku, Tokyo Topy Industries Co., Ltd. F term (reference) 4D075 AE03 CA33 DB07 DC13 EA41 EA4 EA4 3 EB22 EB33 EB38 EB52 EB53 EB55 EB56 4J038 CG031 CG071 CG141 CH031 CH061 CH121 CJ011 CJ031 CJ131 DB062 DB072 DB112 DB262 DG302 HA506 JB14 JB24 KA10 MA14 NA03 PC02

Claims (6)

[Claims] An rust-preventive primer coating is applied to an aluminum wheel having a cut surface and / or a casting surface to form a rust-preventive primer coating, and then a top clear coating is applied thereon. In the method for coating an aluminum wheel for forming a clear coating film, the rust-preventive primer coating material comprises: (A) a weight average molecular weight of 30,000 to 150,000, a glass transition point of -30 ° C to 20 ° C, a hydroxyl value of 10 to 80, and an acid value of 2 (B) Epoxy resin 5 having an epoxy equivalent of 210 to 1000 with respect to 100 parts by weight of acrylic resin
To 20 parts by weight, and 0.5 to 20 parts by weight of a blocked polyisocyanate having a blocking agent having a reaction initiation temperature of 120 to 150 ° C. based on (C) 100 parts by weight of the acrylic resin (A). (D) 3 to 20 parts by weight of organic bentonite based on 100 parts by weight of the solid content of the primer resin; and (E) 5 to 30 parts by weight of organic bentonite based on 100 parts by weight of the organic bentonite (D). A method for coating an aluminum wheel, comprising a paint containing an amide-based wetting and dispersing agent having a solid content. 2. The rust preventive primer coating composition further comprises (F) a urea-based rheology-imparting agent having a solid content of 0.05 to 5.0 parts by weight based on 100 parts by weight of the primer resin solids. 2. The method according to claim 1, wherein
A method for painting an aluminum wheel according to the above. 3. The rust prevention by mixing a pregel prepared by adding an organic bentonite (D) and an amide wetting and dispersing agent (E) to a solvent and mixing and dispersing the mixture, and a solution of the primer resin. The method for coating an aluminum wheel according to claim 1 or 2, wherein a primer coating is prepared. 4. The rust-preventive primer paint according to claim 3, wherein a urea-based rheology-imparting agent (F) is further added to a mixture of the pregel and the primer resin solution. How to paint aluminum wheels. 5. The method according to claim 1, wherein a color base coating is applied on the rust-preventive primer coating to form a color base coating, and then a top clear coating is applied thereon. 2. The method for coating an aluminum wheel according to claim 1. 6. An aluminum wheel coated by the method according to claim 1. Description: