JP2003221550A - Powder primer for aluminum wheel - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a powder primer which can form powder coating films having excellent machinability. <P>SOLUTION: This powder primer comprising (A) 100 pts.wt. of a carboxy group-containing thermosetting polyester resin, (B) 3 to 150 pts.wt. of a curing agent containing a functional group capable of reacting with the carboxy group and (C) calcium carbonate in an amount of 5 to 80 pts.wt. per 100 pts.wt. of the total amount of the components (A) and (B) is characterized in that a cured coating film formed by curing the powder primer has a coating film physical value including a dynamic modulus (E') of elasticity of 4×10<SP>7</SP>to 2×10<SP>8</SP>dyne/cm<SP>2</SP>at 200°C. <P>COPYRIGHT: (C)2003,JPO

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 an aluminum wheel, which is suitable for an aluminum wheel for an automobile and has excellent machinability.

[0002]

2. Description of the Related Art As a wheel for an automobile, which is a mounting member for a tube, a tire, etc., a steel or aluminum product is used. Of these, aluminum wheels (hereinafter abbreviated as "aluminum wheels"), which are excellent in weight reduction, corrosion resistance, and design, are often used. These aluminum wheels are used for protection and aesthetics. Therefore, for example, a thermosetting powder coating material is usually applied as a primer coating material and then heat-cured, and then a thermosetting acrylic resin organic solvent coating material is applied as a top coating material. In addition, an aluminum wheel with a brilliant cutting design is usually coated with a thermosetting powder coating as a primer coating and thermally cured, and then a thermosetting acrylic resin-based organic solvent type color coating is applied as a top coating. Then, after thermosetting, cutting is performed. Then, the thermosetting acrylic resin-based organic solvent type clear paint is applied again.

However, at the portion cut as described above, the coating film of the powder coating remains in a burr-like state, or the coating film is chipped and the unevenness between the cut surface and the non-cut surface is severe. There was a problem in that a problem such as "becomes" occurs.

As a method of forming a coating film on a casting for cutting, the minimum value of the dynamic elastic modulus (E ') of the cured coating film is 5 × 10 ^8.
There is a method (Patent Publication No. 2871409) of applying a powder coating material having a value of dyne / cm ² or more, and this method solves the problem at the time of cutting. However, in the case of cutting aluminum, and in the case of cutting cast iron castings, for example, aluminum is softer and easier to process, and therefore the impact during cutting is less. Therefore, 5 × 10 ⁸ d
The dynamic elastic modulus (E ′) of yne / cm ² or more is a value which is more than sufficient for a coating film on an aluminum material. Further, such a coating film having a large value of dynamic elastic modulus (E ') has a large unevenness of the coating film and cannot be used as a powder coating primer for aluminum wheels from the viewpoint of smoothness. In addition, such a coating film has a drawback that a thick film is required to ensure smoothness and the amount of the coating material used increases.

[0005]

Means for Solving the Problems As a result of intensive studies to solve the problems of the present invention, as a result, a specific powder primer has a film thickness of 100 μm or less, and the coating film has few irregularities and is smooth. Therefore, they have found that a coating film with improved coating film defects during cutting can be formed, and completed the present invention.

That is, the present invention is 1, the following ingredients (A) Carboxyl group-containing thermosetting polyester resin 100 parts by weight (B) Curing agent containing a functional group that reacts with a carboxyl group                                                       3 to 150 parts by weight (C) Calcium carbonate based on 100 parts by weight of the total amount of (A) + (B),                                                       5-80 parts by weight A powder primer containing
The cured coating formed by baking the liner is heated to 200 ° C.
Dynamic elastic modulus (E ') is 4 × 10⁷dyne / c
m^Two~ 2 x 10⁸dyne / cm ^TwoCoating film physical property values
Powder coating for aluminum wheels characterized by having
Lymer, 2, (B) hardener component is a polyepoxide
Characteristic powder paint primer for aluminum wheels
ー 、 3, (B) hardener component is a monoglycidyl ether compound
And / or monoglycidyl ester compound and phosphoric acid
Have at least one P-OH bond formed by reacting with
Phosphoric acid ester compound (a) and polyglycidyl compound
Phosphoric acid-modified epoxy resin obtained by reacting substance (b)
(B ') or containing this thing
Powder paint primer for aluminum wheels, 4. In the above powder primer, (E)
The total amount of the above-mentioned (A) + (B) is 100 wt.
0.01 to 30 parts by weight with respect to parts
The above-mentioned powder coating for aluminum wheels characterized by
Related to Limer.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The aluminum wheel of the present invention is described below.
A detailed description will be given of the powder primer for solder.

Polyester resin (A) used in the present invention
Is a base resin used in the thermosetting powder coating composition, and the base resin (A) and the curing agent (B) react with each other during baking to form a cured coating film.

The polyester resin (A) has a number average molecular weight of 400 to 20,000, particularly 1,000 to 15,000.
The range of 0 is preferable. When the number average molecular weight is less than 400, the coating film performance is deteriorated, while when it exceeds 20,000, the smoothness of the coating film is deteriorated, which is not preferable. The softening temperature of the resin is 30 to 140 ° C, particularly 35 to 100 ° C.
The range of is preferable. If the softening temperature is lower than 30 ° C., the powder particles may be fused to each other during storage of the powder coating material, which may cause lumps in the coating film.
If the temperature exceeds ℃, the smoothness of the coating film decreases, which is not preferable.

The polyester resin (A) has a resin acid value of 10 to 200 mgKOH / g, particularly 20 to 150 mgK.
The range of OH / g is preferred. Resin acid value is 10mgKOH
If it is less than 100 g / g, the curability is lowered, and the water resistance and corrosion resistance are lowered. On the other hand, if it exceeds 200 mgKOH / g, the hydrophilicity of the coating film is increased, so that the water resistance and the corrosion resistance are lowered.

Examples of the carboxyl group-containing polyester resin (A) include (anhydrous) phthalic acid, isophthalic acid, terephthalic acid, dimethyl isophthalate, dimethyl terephthalate, hexahydro (anhydrous) phthalic acid, and tetrahydro (anhydrous) phthalic acid. Aromatic or alicyclic dicarboxylic acid such as, and (poly) ethylene glycol, (poly) propylene glycol, butylene glycol, butylene glycol, neopentyl glycol, 1,6-hexanediol, dihydric alcohol such as dimethylpropionic acid, etc. are required. Depending on the above, a monocarboxylic acid such as benzoic acid, a trivalent or higher carboxylic acid such as (anhydrous) trimellitic acid, a trivalent or higher alcohol such as trimethylolethane, trimethylolpropane, glycerin or pentaerythritol is used. So that the acid value is within the range By appropriate reaction include resins obtained.

The curing agent (B) has an epoxy group, an amide group or the like which reacts with the carboxyl group of the polyester resin (A) to form a cured coating film. Specifically, for example, polyepoxide, hydroxyalkylamide, triglycidyl isocyanurate, etc. are preferably used.

The polyepoxide has a melting point of about 50 to 1
Those having a range of 40 ° C., an epoxy equivalent of about 200 to 6000, and an average molecular weight of about 900 to 10,000 are preferable.

Specific examples of the polyepoxide include trade names such as Epicote 1002 and ibid 100.
4, same as left 1007 (above, manufactured by Yuka Shell Epoxy Co., Ltd.), Araldite GY-6084, same as left 6097 (made by Ciba-Geigy), DER-662, same as left 664, same as left 667 (manufactured by Dow Chemical Co.). Bisphenol, etc.
Epichlorohydrin type epoxy resin, EPPN-20
1, ibid 202, EOCN-1020, ibid 102S
(Above, Nippon Kayaku Co., Ltd.) novolac type epoxy resin, vinyl polymer (eg, glycidyl (meth))
Radical homopolymers of epoxy group-containing unsaturated monomers such as acrylate and 3,4-epoxycyclohexylmethyl (meth) acrylate, and, if necessary, for example, methyl (meth) acrylate, ethyl ( (Meth) acryl
(Meta) such as methacrylic acid and cyclohexyl (meta) acrylate
Alkyl or cycloalkyl esters of acrylic acid,
Unsaturated hydroxyl group-containing monomers such as hydroxyethyl (meth) acrylate, aromatic compounds such as styrene, radical copolymers with other unsaturated monomers such as nitrile compounds such as (meth) acrylonitrile, etc. ) And the like.

The polyepoxide is preferably a phosphoric acid-modified epoxy resin (B ') below or a mixed resin of the above-mentioned epoxy resin and the phosphoric acid-modified epoxy resin (B').

The phosphoric acid-modified epoxy resin (B ') is a phosphoric ester compound (a) having at least one P-OH bond formed by reacting a monoglycidyl ether compound and / or a monoglycidyl ester compound with phosphoric acid.
And a polyglycidyl compound (b) are reacted to obtain a phosphoric acid-modified epoxy resin.

The monoglycidyl ether compound is a compound represented by the following general formula (I), and the monoglycidyl ester compound is a compound represented by the following general formula (II). Chemical 1

[0018]

[Chemical 1]

In the above general formulas (I) and (II), examples of the alkyl group represented by R and R'include, for example, methyl, ethyl, propyl, butyl, amyl, hexyl, heptyl, octyl, nonyl and decyl. , Straight chain or branched alkyl groups such as undecyl, dodecyl, tridecyl, tetradecyl, pentadecyl, hexadecyl, heptadecyl, octadecyl, nonadecyl, eicosyl, heneicosyl, behenyl, etc., and the alkenyl group includes 1 to 3 in the above alkyl groups. Examples of the aryl group include those having an unsaturated bond.
Examples thereof include a phenyl group and a naphthyl group, and these aryl groups may be substituted with 1 to 3 of the above alkyl groups, and these substituents may be taken together to form a ring.

The monoglycidyl ether compound represented by the above general formula (I) and the monoglycidyl ester compound represented by the above general formula (II) are usually prepared from epichlorohydrin and alcohols, phenols or organic carboxylic acids. It can be easily obtained by the method.

Examples of the monoglycidyl ether compound represented by the above general formula (I) include methyl glycidyl ether, butyl glycidyl ether, 2-ethylhexyl glycidyl ether, sec-butylphenyl glycidyl ether, 2-methyloctyl glycidyl ether, Octadecyl glycidyl ether, phenyl glycidyl ether, tolyl glycidyl ether, octyl phenyl glycidyl ether, etc. are mentioned.

Examples of the monoglycidyl ester compound represented by the above general formula (II) include acetic acid, propionic acid, butyric acid, valeric acid, caproic acid, enanthic acid, caprylic acid, pelargonic acid and 2-ethylhexylic acid. , Neodecanoic acid, capric acid, undecanoic acid, lauric acid, tridecanoic acid, myristic acid, palmitic acid, isostearic acid, stearic acid, 12-hydroxystearic acid, behenic acid, montanic acid, acrylic acid, methacrylic acid, crotonic acid, elaidin Acid, oleic acid, linoleic acid, linoleic acid, benzoic acid, p-tert-butylbenzoic acid, toluic acid, dimethylbenzoic acid, ethylbenzoic acid,
Examples thereof include glycidyl ester compounds of monovalent carboxylic acids such as cuminic acid and n-propylbenzoic acid.

When obtaining the phosphoric acid ester compound as the component (a), the phosphoric acid and the monoglycidyl ether compound represented by the general formula (I) or the monoglycidyl ether compound represented by the general formula (II) are used. What is a glycidyl ester compound?
The epoxy group (epoxy equivalent) of the compound of the general formula (I) or (II) is preferably 0.1 to 0.9 equivalents, and more preferably 0.1 to 1 equivalent of P-OH group of the phosphoric acid. It is used in an amount of 3 to 0.8 equivalent. Here, when the epoxy group is less than 0.1 equivalent, there is a possibility that excess phosphoric acid and a polyglycidyl compound which is the component (b) described below may react to cause gelation. If it exceeds the limit, denaturation becomes difficult, which is not preferable.

Examples of the phosphoric acids include orthophosphoric acid, metaphosphoric acid, pyrophosphoric acid, phosphorous acid, polyphosphoric acid, phosphonic acid, methanephosphonic acid, benzenephosphonic acid, 1-hydroxyethane-1,1-diphosphonic acid, Examples include phosphinic acid.

The polyglycidyl compound (b) used in the phosphoric acid-modified epoxy resin (B ') is a resin other than the above acrylic epoxy resin having two or more epoxy groups in one molecule. Those 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
And the like): epihalohydrin such as epichlorohydrin and an aromatic polyhydroxy compound (eg, bisphenol A, F, novolac phenol)
, Cresol phenol, etc.): glycidyl ethers of an epihalohydrin such as epichlorohydrin and an aromatic polycarboxylic acid compound (for example, phthalic acid): an epoxy group-containing acrylic resin:
Epoxidized oil: alicyclic epoxy resin: and the like.

In the present invention, the amount of the phosphoric acid ester compound which is the component (a) is not particularly limited as long as the epoxy group remains in the adduct, but it is usually the component (b). The amount of the P-OH group of the phosphoric acid ester compound is preferably 0.01 to 0.8 equivalents, and more preferably 0.03 to 0.5 equivalents, relative to 1 equivalent of the epoxy groups of the polyglycidyl compound. When the P-OH group of the phosphoric acid ester compound is less than 0.01 equivalent, the effect of phosphoric acid addition is unlikely to be exhibited, and when it exceeds 0.8 equivalent, the water resistance of the coating film may decrease. There is.

The phosphoric acid-modified epoxy resin (B ') component preferably has a number average molecular weight of 300 to 2000 and an epoxy equivalent of 150 to 2100.

As the hydroxyalkyl amide, β-
Examples of hydroxyethyl adipamide and trade names include XL-552 manufactured by Ems.

The mixing ratio of the curing agent (B) is 3 to 150 parts by weight, particularly 4 to 100 parts by weight of the polyester resin.
A range of 100 parts by weight is preferred. When the amount is less than 3 parts by weight, the curability is deteriorated, so that the coating properties such as water resistance and corrosion resistance are deteriorated. On the other hand, when the amount is more than 150 parts by weight, the uncured curing agent component remains in the coating film, so that the coating film is processed. It is not preferable because the coating properties such as the water resistance, water resistance, and corrosion resistance deteriorate.

As calcium carbonate (C), there are 50 kinds of tantalum, 85 parts of tantalum, 100 parts of tantalum, and NO.
200, Tancal NO. 300 (trade name, manufactured by Takehara Chemical Industry Co., Ltd.) and the like.

The mixing ratio of the calcium carbonate (C) component is
5 per 100 parts by weight of the total amount of resins (A) and (B)
To 80 parts by weight, particularly preferably 5 to 60 parts by weight. If the blending ratio is less than 5 parts by weight, burrs of the coating film will occur during cutting, while if it exceeds 80 parts by weight, the smoothness of the coating film will be reduced, such being undesirable.

In the present invention, in addition to the above, a carboxylic acid compound (D) other than the above polyester resin (A) may be blended if necessary. In particular,
Examples thereof include dodecane diacid, adipic acid, azelaic acid, sebacic acid, and aliphatic acids such as their anhydrides. These may be used alone or in combination of two or more.

The mixing ratio of the carboxylic acid compound (D) is
Based on 100 parts by weight of the total amount of the resins (A) and (B),
It is in the range of 0.01 to 20 parts by weight, particularly 0.1 to 15 parts by weight. If the blending ratio is less than 0.01 parts by weight, the corrosion resistance will be lowered, while if it exceeds 20 parts by weight, the curability of the coating film will be lowered and the discoloration tends to occur after the water resistance test, which is not preferable.

In the primer of the present invention, the above (A)
In addition to the component (D), an organic coloring pigment, an inorganic coloring pigment, a filler, a curing catalyst, an ultraviolet stabilizer, an ultraviolet absorber, a fluidity adjusting agent, an anti-cissing agent and the like can be added if necessary.

The powder coating composition of the present invention can be prepared, for example, by a conventional method, for example, by blending the above-mentioned components (A) to (D) and dry blending them with a mixer, followed by heating, melt-kneading, cooling and roughing. It can be produced by pulverization, fine pulverization and filtration.

The primer of the present invention has an average particle size of 10 to 10.
150 μm, especially 15 to 120 μm from the viewpoint of smoothness of coated surface
Is preferred.

The powder coating composition of the present invention has a standard deviation of particle size distribution of 5 to 40 μm, particularly 10 to 10 from the viewpoint of coating workability.
The range of 30 μm is preferred.

The primer of the present invention has a minimum melt viscosity of 0.1 to 200 Pa · s, especially 5 from the viewpoint of smoothness of the coated surface.
The range of -100 Pa · s is preferable.

The average particle size and standard deviation can be determined by a particle size distribution meter. For the measurement of particle size distribution,
Laser scattering diffraction, electric resistance method, light transmission method, sedimentation method, image analysis method and the like can be mentioned.

The electrostatic powder coating is preferably carried out by a method known per se, such as electrostatic powder coating or triboelectric powder coating. The coating film thickness is not particularly limited, but is approximately 20μ
A range of m to 200 μm, particularly about 30 to 150 μm is suitable.

The primer of the present invention can form a cured coating film by powder coating on an object to be coated and baking (for example, at a temperature of about 160 ° C. for about 30 minutes and at about 180 ° C. for about 15 minutes). it can.

The surface of the cured coating film formed by the primer of the present invention may be further coated with an overcoat paint such as a colored paint or a clear paint.

The primer of the present invention can be applied to an aluminum wheel (object to be coated). Specifically, for example, it is an automobile wheel that is a mounting member for automobiles such as passenger cars, automobiles, trucks and wagons, and tires, and contains aluminum as a main component, or magnesium or It is made of an alloy containing silicon and the like, and it can be formed into any shape for the purpose of weight reduction and design. It also includes an aluminum wheel in which a shot-blasted uneven casting surface and a cut smooth surface are mixed. It is preferable that the surface of the aluminum wheel is subjected to a chemical conversion treatment with a chromate or a phosphate before coating the primer.

[0044]

EFFECTS OF THE INVENTION Since the present invention uses the powder primer having the above constitution, the following effects are exhibited. 1) A primer film having excellent machinability is formed. 2) The brilliant cutting design of the coated object coated with the primer is excellent.

[0045]

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

Example 1 Carboxylic acid group-containing polyester resin (Findick M8860 (manufactured by Dainippon Ink and Chemicals, Inc., trade name, softening temperature 113 ° C., acid value 35 mgKOH / g)) 7
0 parts, polyepoxide curing agent (Epicoat 1002 (produced by Yuka Shell Epoxy Co., Ltd., trade name, bisphenol A type epoxy resin)) 30 parts, calcium carbonate (Tancal NO.200 (produced by Takehara Chemical Industry Co., Ltd., trade name)) ) 40 parts and JR603 (manufactured by TAYCA CORPORATION, titanium oxide) 40 parts are mixed, melt-kneaded by an extruder, cooled, and then finely pulverized by an atomizer to obtain 150.
The polyester resin powder coating material of Example 1 was manufactured by filtering through a mesh.

Example 2 Carboxylic acid group-containing polyester resin (Findick M8962 (manufactured by Dainippon Ink and Chemicals, Inc., trade name, softening temperature 112 ° C., acid value 35 mgKOH / g)) 7
7 parts, epoxy group-containing acrylic resin (Findick A-229-30 (manufactured by Dainippon Ink and Chemicals, Inc., trade name, softening temperature 109 ° C., epoxy equivalent 525 g
/ Eq)) 23 parts, calcium carbonate (Tancal NO. 2)
00 (Takehara Chemical Industry Co., Ltd., trade name) 40 parts,
40 parts of JR603 (manufactured by TAYCA CORPORATION, titanium oxide) are mixed, melt-kneaded by an extruder, and after cooling,
The polyester resin powder coating material of Example 2 was manufactured by finely pulverizing with an atomizer and filtering with 150 mesh.

Comparative Example 1 A polyester resin powder coating material of Comparative Example 1 was produced in the same manner as in Example 1 except that the calcium carbonate component was not used.

Comparative Example 2 A polyester resin powder coating material of Comparative Example 2 was produced in the same manner as in Example 2 except that the calcium carbonate component was not used.

Comparative Example 3 In Example 1, the tantalum NO. A polyester resin powder coating material of Comparative Example 3 was produced in the same manner as in Example 1 except that 100 parts of 200 was used.

Comparative Example 4 In Example 1, the tantalum NO. A polyester resin powder coating material of Comparative Example 4 was produced in the same manner as in Example 1 except that 2 parts of 200 was used.

Conditions for coating film formation Chromate chromate (AL-1000: manufactured by Nihon Parkerizing Co., Ltd.) Electrochemical coating of a powder primer was carried out on an aluminum wheel which had been subjected to chemical conversion treatment so that the film thickness was 100 μm. It was heat-cured at 160 ° C. for 30 minutes. An organic solvent type paint of Magicron ALC-2 color base (manufactured by Kansai Paint Co., Ltd.) is spray-coated on the coated powder coating film so that the film thickness is 20 μm, and it is 2 at 140 ° C.
It was baked for 0 minutes to form a color base coating film. The aluminum wheel coated in this way is cut and subjected to chromate chromate (AL-1000) conversion treatment again, and then Magiclon ALC2-1 clear (manufactured by Kansai Paint Co., Ltd.,
The organic solvent type coating material (commercial name) was spray-coated so that the film thickness was 20 μm, and baked at 140 ° C. for 30 minutes to form an overcoat coating film.

Various evaluations were performed on each of the obtained aluminum wheels. The results are shown in Table 1.

Table 1 shows the evaluation results of the examples and comparative examples.

[0055]

[Table 1] Table 1

Test Method Machinability: The state of coating film defects in the cut portion was evaluated according to the following criteria. ◯: Good, Δ: Slightly bad, ×: Poor coating film appearance: The finish appearance of the coating film was evaluated according to the following criteria from glossiness and smoothness. ◯: Good, Δ: Slightly bad, ×: Bad.

Claims (4)

[Claims] 1. The following ingredients (A) Carboxyl group-containing thermosetting polyester resin 100 parts by weight (B) Curing agent containing a functional group that reacts with a carboxyl group                                                       3 to 150 parts by weight (C) Calcium carbonate based on 100 parts by weight of the total amount of (A) + (B),                                                       5-80 parts by weight A powder primer containing And a cured coating film formed by baking the powder primer
However, the dynamic elastic modulus (E ′) at 200 ° C. is 4 × 10
⁷dyne / cm^Two~ 2 x 10⁸dyne / cm ^TwoDemon
Aluminum wheel characterized by having coating film physical properties
Powder paint primer 2. The powder coating primer for aluminum wheels according to claim 1, wherein the curing agent component (B) is polyepoxide. 3. A phosphoric acid ester compound (a), wherein the curing agent component (B) has at least one P—OH bond formed by reacting a monoglycidyl ether compound and / or a monoglycidyl ester compound with phosphoric acid. The powder coating primer for an aluminum wheel according to claim 1 or 2, further comprising a phosphoric acid-modified epoxy resin (B ') obtained by reacting with the polyglycidyl compound (b), or a resin thereof. 4. The powder primer according to claim 1, further comprising:
The carboxylic acid compound (E) is contained in an amount of 0.01 to 30 parts by weight with respect to 100 parts by weight of the total amount of the (A) + (B). Powder paint primer for aluminum wheels described in.