JP2010031320A - Film forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a coated article with a film excellent in coating film hardness, impact resistance, adhesion property and finish appearance on a stainless steel substrate. <P>SOLUTION: A method for forming a film on the stainless steel substrate includes: dipping the stainless steel substrate in an aqueous solution or an aqueous dispersion of at least one metal salt chosen from the group consisting of an alkali metal salt of silicic acid and an alkali metal salt of metaboric acid and applying electricity so as to form a film; and subsequently conducting electrodeposition of an anionic electrodeposition paint (B) on the film to form the coating film. The anionic electrodeposition paint (B) comprises 50-75 pts.mass of a carboxyl group-containing resin (b1), 5-25 pts.mass of an amino resin (b2) and 0.1-25 pts.mass of an isophorone diisocyanate compound blocked with methyl amyl ketoxime (b3) based on 100 pts.mass total solid content of the carboxyl group-containing resin (b1), the amino resin (b2) and the isophorone diisocyanate compound blocked with methyl amyl ketoxime (b3). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a film forming method capable of forming a coating film excellent in coating film hardness, impact resistance, adhesion, and finish on a stainless steel substrate.

Traditionally, stainless steel uses the fact that chromium (Cr) in the composition combines with oxygen in the air to form a passive film on the surface, making it a highly corrosion-resistant material that can be used outdoors, in humid places, and in chemicals. It has been used in machine tools and kitchen facilities.
In recent years, exterior parts made of stainless steel with an electrodeposition coating have come to be used for electronic equipment parts such as mobile phones because of the demand for weight reduction and high design. However, when the parts are rubbed with clothes, dropped or stepped on, the electrodeposition coating film may be scratched or peeled off, and countermeasures are required.

  Conventionally, anionic electrodeposition coating has been performed on stainless steel, but when the coating film hardness is increased, the scratch resistance is improved, but the impact resistance and adhesion are reduced. On the other hand, when the coating film hardness was lowered, the impact resistance and adhesion were improved, but the scratch resistance was lowered, and a coating film that could be compatible was not found.

  In addition, for aluminum or aluminum alloys, aluminum or aluminum alloys contacted with hot water or water vapor containing or not containing ammonia or amines (so-called boehmite). After applying the treatment to the coated object) in an aqueous solution of one or more oxyacid salts selected from borate, phosphate, chromate, molybdate, vanadate, etc. And the coating method characterized by applying a coating material to this to-be-coated object is disclosed (patent documents 1-3). However, only by applying the contents described in these patent documents, the coating hardness and impact resistance of the stainless steel substrate, particularly the surface of the stainless steel substrate having a mirror-like surface, is a problem for improving adhesion. It was not easy to obtain a coating film excellent in properties and adhesion.

  In addition, inventions relating to the combined use of amino resins and blocked polyisocyanates as crosslinking agents for anionic electrodeposition coatings are disclosed (Patent Documents 4 and 5). However, Patent Document 4 and Patent Document 5 do not show nor suggest a method for obtaining a coating film excellent in coating film hardness, impact resistance, adhesion, and finish.

JP 50-36326 A Japanese Patent Laid-Open No. 50-80223 JP 50-110944 A Japanese Patent Laid-Open No. 5-186720 Japanese Patent Laid-Open No. 5-186720

  The problem to be solved is to obtain a coating film having excellent coating film hardness, impact resistance, adhesion, and finish on a stainless steel substrate.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have made stainless steel into at least one aqueous solution or aqueous dispersion selected from an alkali metal salt of silicic acid and an alkali metal salt of metaboric acid ( After immersing in the bath of A) and conducting the energization treatment, we found that the problem can be solved by electrodeposition coating a specific anionic electrodeposition paint (B) to form a coating film, and the invention was completed It came to do.

That is, the present invention is “1. A film formed by immersing in an aqueous solution or aqueous dispersion (A) of at least one metal salt selected from an alkali metal salt of silicic acid and an alkali metal salt of metaboric acid and conducting an energization treatment. Then, the following anion electrodeposition coating (B) is electrodeposited on the coating to form a coating film on the stainless steel substrate,
Anionic electrodeposition paint (B): carboxyl group-containing resin (b1), amino resin (b2) and methylamylketoxime blocked isophorone diisocyanate compound (b3) with a total solid content of 100 parts by mass ( b1) Anion electrodeposition paint containing 50 to 75 parts by mass, amino resin (b2) 5 to 25 parts by mass, and methylamyl ketoxime blocked isophorone diisocyanate compound (b3) 0.1 to 25 parts by mass. The anionic electrodeposition paint (B) is a coloring pigment and / or with respect to a total solid content of 100 parts by mass of the carboxyl group-containing resin (b1), amino resin (b2) and methylamylketoxime blocked isophorone diisocyanate compound (b3). Or the method for forming a film on a stainless steel substrate according to 1 above, comprising 0.1 to 30 parts by mass of a luster pigment,
3. An electronic device component formed by molding stainless steel, which is covered with a film obtained by the method for forming a film on a stainless steel substrate according to 3.1 or 2.

  The coating film on the stainless steel substrate obtained by the film forming method of the present invention can provide a coating film having excellent coating film hardness, impact resistance, adhesion, and finish. The stainless steel obtained by the film forming method of the present invention is useful as an exterior part of an electronic device (for example, for a digital camera or a mobile phone) that is supposed to be rubbed, dropped or stepped on clothes.

  Hereinafter, the film forming method of the present invention will be described.

Stainless steel:
Stainless steels that can be used in the film forming method of the present invention include conventionally known stainless steels such as ferrite (α), martensite (M), austenite (γ), and austenite / ferrite two-phase (γ + α). Can be used.

  Specifically, for example, austenitic stainless steel such as SUS304, SUS305, SUS310, SUS316 and SUSMX7; philite stainless steel such as SUS430, martensitic stainless steel such as SUS403, SUS410, SUS416 and SUS420; precipitation hardening stainless steel such as SUS631; Stainless steel such as can be used.

An aqueous solution or aqueous dispersion (A) of at least one metal salt selected from an alkali metal salt of silicic acid and an alkali metal salt of metaboric acid:
The film forming method of the present invention comprises an aqueous solution or an aqueous dispersion (A) (hereinafter referred to as silicic acid) of at least one metal salt selected from an alkali metal salt of silicic acid and an alkali metal salt of metaboric acid using the stainless steel as an anode. At least one metal salt selected from an alkali metal salt of metaboric acid and an alkali metal salt of metaboric acid in a bath of “aqueous solution or aqueous dispersion (A)”). Process. Furthermore, the energization process can be repeated as necessary.

Moreover, water solubility or water dispersibility (A) may be used independently, and 2 or more types may be mixed and used for it. In this case, several kinds of aqueous solutions or aqueous dispersions (A) are used as separate baths, and stainless steel is immersed in each of the aqueous solutions or aqueous dispersions (A) and subjected to energization treatment.
Examples of the alkali metal salt of silicic acid include silicates such as sodium silicate, potassium silicate, and lithium silicate.

Examples of the alkali metal salt of metaborate include lithium metaborate (LiBO ₂ .2H ₂ O), sodium metaborate (NaBO ₂ ), and potassium metaborate (KBO ₂ ). Among these, sodium silicate and sodium metaborate are preferable in terms of impact resistance and adhesion.

  The film formation method of the present invention, that is, stainless steel is immersed in an aqueous solution or aqueous dispersion (A) bath and subjected to an energization treatment, for example, stainless steel is immersed in an aqueous solution of “sodium silicate” and energized. When the treatment is performed, a film of “silica gel (also referred to as“ water glass ”)” is formed on the stainless steel substrate according to the following formula (1).

Na ₂ SiO ₃ + 2H ⁺ → 2Na ⁺ + H ₂ SiO ₃ Formula (1)
It is thought that such “silica gel” contributes to the improvement of adhesion to stainless steel. Further, when an alkali metal salt of metaboric acid is used in the aqueous solution or aqueous dispersion (A), a “borate gel” film is formed on the stainless steel substrate, and the “borate gel” is formed on the electrodeposition coating film and the stainless steel. Contributes to improved adhesion and impact resistance with steel.
In addition, as a density | concentration of aqueous solution or aqueous dispersion (A), it is bath stability that this metal salt is 0.1-20 mass%, Preferably it is 1-10 mass%, More preferably, it is 2-8 mass%. From the viewpoint of impact resistance and adhesion formed.

In the energization treatment, stainless steel is immersed in a water-soluble or water-dispersible (A) bath, the liquid temperature is adjusted to 10 to 40 ° C., and stainless steel is used as an anode in accordance with a normal electrodeposition coating method. Do. The current density at this time is 0.1 A / dm ^{2 to} 5 A / cm ² , preferably 0.2 A / dm ^{2 to} 3 A / cm ² , and energized for 10 seconds to 300 seconds, preferably 30 seconds to 200 seconds. Thus, a film can be formed on the stainless steel substrate.

  When stainless steel is immersed in multiple water-soluble or water-dispersible (A) baths and subjected to energization treatment, if it is the same type of water-soluble or water-dispersible (A) bath, it is immersed in water without being washed and energized again. Process. In the case of different types of water-soluble or water-dispersible (A), immediately after washing with water to remove undeposited metal salt adhering to the surface, in a different type of water-soluble or water-dispersible (A) bath The film can be formed by immersing in water and applying an electric current treatment to wash with water.

  After washing with water in the above, drying at normal temperature or drying at 40 to 80 ° C. for 1 minute to 60 minutes can be performed as necessary. The thickness of the film is preferably 0.01 to 3 μm, more preferably 0.1 to 1.0 μm from the viewpoint of impact resistance, adhesion and finish.

[Anion electrodeposition paint (B)]
The anionic electrodeposition paint (B) used in the film forming method of the present invention is characterized by containing a carboxyl group-containing resin (b1), an amino resin (b2), and a methyl amylketoxime blocked polyisophorone diisocyanate (b3). To do. By using the anion electrodeposition coating composition (B) having the above composition, a coating film excellent in coating film hardness, impact resistance, adhesion and finish, and a coated article having the coating film can be obtained.

Carboxyl group-containing resin (b1):
The carboxyl group-containing resin (b1) has at least one carboxyl group in one molecule, and more preferably is a resin having at least one hydroxyl group. Specific examples include resins such as acrylic resins, polyester resins, polyether resins, polycarbonate resins, and urethane resins. Among these, acrylic resins are preferred from the viewpoints of coating film hardness and finish.

  The above acrylic resin is produced by copolymerizing a carboxyl group-containing radical polymerizable unsaturated monomer, if necessary, a hydroxyl group-containing radical polymerizable unsaturated monomer, and other radical polymerizable unsaturated monomers. can do.

Examples of the carboxyl group-containing radical polymerizable unsaturated monomer include acrylic acid,
Examples include monomers such as methacrylic acid, crotonic acid, itaconic acid, maleic acid, and fumaric acid. Examples of the hydroxyl group-containing radical polymerizable unsaturated monomer include 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, 3-hydroxypropyl (meth) acrylate, hydroxybutyl (meth) acrylate, and Other than this, Plaxel FM1 (manufactured by Daicel Chemical Industries, trade name, caprolactone-modified (meth) acrylic acid hydroxy esters), Plaxel FM2 (same as left), Plaxel FM3 (same as left), Plaxel FA1 (same as left), Plaxel FA2 (same as left), Plaxel FA3 (same as left) and the like.

Examples of the other radical polymerizable unsaturated monomer include γ- (meth) acryloyloxypropyltrimethoxysilane, γ- (meth) acryloyloxypropylmethyldimethoxysilane, and γ- (meth) acryloyloxypropyltriethoxy. Alkoxysilyl group-containing unsaturated monomers such as silane and vinyltrimethoxysilane; for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, (meth ) hexyl acrylate, (meth) acrylate, octyl (meth) acrylate, lauryl (meth) alkyl or cycloalkyl esters of C ₁ -C ₁₈ (meth) acrylic acid such as cyclohexyl acrylate, aromatic such as styrene Group vinyl monomers, amino acid (meth) acrylate , N- butoxymethyl (meth) acrylamide, N- methylol - Le (meth) (meth) acrylamide and its derivatives such as acrylamide, (meth) acrylonitrile compounds, and the like.

As the acrylic resin, usually the above carboxyl group-containing radical polymerizable unsaturated monomer,
It is obtained by subjecting a hydroxyl group-containing radically polymerizable unsaturated monomer and other radically polymerizable unsaturated monomer to a radical polymerization reaction with a polymerization initiator in a solvent as required. In this polymerization reaction, the carboxyl group-containing polymerizable unsaturated monomer is 1 to 20% by mass, preferably 4 to 10% by mass, and the hydroxyl group-containing radical polymerizable unsaturated monomer is 0 to 40% by mass, preferably 5%. The range of -30 mass% and the other radical polymerizable unsaturated monomer is 40-99 mass%, preferably 60-91 mass%.

  Examples of the solvent used for the polymerization reaction include alcohols such as propyl alcohol, isopropyl alcohol, n-butyl alcohol, t-butyl alcohol, isobutyl alcohol, diethylene glycol monobutyl ether, methyl carbitol, 2-methoxyethanol, 2-ethoxy. Ethanol, 2-isopropanoxyethanol, 2-butoxyethanol, diethylene glycol, diethylene glycol monoethyl ether, diethylene glycol monobutyl ether, triethylene glycol monomethyl ether, 1-methoxy-2-propanol, 1-ethoxy-2- Ethers such as propanol and dipropylene glycol monomethyl ether can be preferably used.

Other than this, for example, aromatics such as xylene and toluene; acetone,
Ketones such as methyl ethyl ketone, 2-pentanone, 2-hexanone, methyl isobutyl ketone, isophorone, cyclohexanone; methyl acetate, ethyl acetate, pentyl acetate, 3-methoxybutyl acetate, 2-ethylhexyl acetate, benzyl acetate, cyclohexyl acetate, propionic acid Esters such as methyl and ethyl propionate can be used in combination.

  As the radical polymerization initiator used for radical copolymerization, for example, benzoyl peroxide, di-t-butyl hydroperoxide, t-butyl hydroperoxide, cumyl peroxide, cumene hydroperoxide, diisopropyl benzanthane hydroperoxide, Peroxides such as t-butylperoxybenzoate, lauryl peroxide, acetyl peroxide, t-butylperoxy-2-ethylhexanoate, α, α'-azobisisobutylnitrile, azobisdimethylvaleronitrile, azo Examples include azo compounds such as biscyclohexanecarbonitrile. The acrylic resin has a weight average molecular weight of 5,000 to 150,000, preferably 20,000 to 100,000.

  The weight average molecular weight is determined in accordance with JIS K 0124-83, and four separations (TSK gel2000HXL, TSK gel2500HXL, TSK gel3000HXL, TSK gel4000HXL) are used as separation columns at a flow rate of 1.degree. It was determined from a chromatograph obtained with an RI refractometer and a calibration curve of polystyrene, using 0 ml / min, tetrahydrofuran for GPC as an eluent.

Amino resin (b2):
As the amino resin (b2), conventionally known compounds can be used. For example, the amino resin (b2) can be obtained by reacting an amino component such as melamine resin, urea, benzoguanamine, acetoguanamine, steroguanamine, spiroguanamine, dicyandiamide and the aldehyde. Examples include methylolated amino resins and alkyl etherified products of the methylolated amino resins.

  As the methylolated amino resin, a methylolated melamine resin is preferable, and a part or all of the methylol group of the methylolated melamine resin is one kind of methanol, ethanol, propanol, butanol, octyl alcohol, 2-ethylhexyl alcohol, or the like. A melamine resin modified with two or more monohydric alcohols can be used.

  Commercially available products of the above melamine resins include, for example, Uban 20SE-60, Uban 225 (all are trade names manufactured by Mitsui Chemicals), Super Becamine G840, Super Becamine G821 (All are Dainippon Ink. Butyl etherified melamine resin such as Chemical Industry Co., Ltd. (trade name); Sumimar M-100, Sumimar M-40S, Sumimar M-55 (all are trade names made by Sumitomo Chemical Co., Ltd.), Cymel 232, Cymel 303, Cymel 325, Cymel 327, Cymel 350, Cymel 370 (all are made by Nihon Cytec Industries, Inc., trade name), Nicarak MS17, Nicarak MX15, Nicarak MX430, Nicarak MX600 (all are made by Sanwa Chemical Co., Ltd., trade name) ), Regimin 741 (M Methyl etherified melamine resins such as Santo Co., Ltd. (trade name); Cymel 235, Cymel 202, Cymel 238, Cymel 254, Cymel 272, Cymel 1130 (all of which are Mitsui Cytec Co., Ltd., trade name), Summir M66B (Sumitomo) Mixed etherified melamine resin of methylation and isobutylation, etc., manufactured by Kagaku Co., Ltd .; methylation of Cymel XV805 (trade name, manufactured by Mitsui Cytec Co., Ltd.), Nicalac MS95 (trade name, manufactured by Sanwa Chemical Co., Ltd.), etc. And n-butylated mixed etherified melamine resin.

Methyl amylketoxime blocked isophorone diisocyanate compound (b3):
The anionic electrodeposition paint (B) used in the present invention contains a certain amount of methyl amyl ketoxime blocked isophorone diisocyanate compound (b3) as a crosslinking agent.
The methyl amyl ketoxime blocked isophorone diisocyanate compound (b3) (hereinafter sometimes abbreviated as “compound (b3)”) blocked the isocyanate group of isophorone diisocyanate with methyl amyl ketoxime (2-heptanone oxime). A compound.

  Conventional polyisocyanate compounds include, for example, (o-, m-, p-) tolylene diisocyanate, (o-, m-, p-) xylylene diisocyanate, phenylene diisocyanate, diphenylmethane-2,2'-diisocyanate, Diphenylmethane-2,4′-diisocyanate, diphenylmethane-4,4′-diisocyanate, crude MDI [polymethylene polyphenylisocyanate], bis (isocyanatemethyl) cyclohexane, tetramethylene diisocyanate, hexamethylene diisocyanate, methylene diisocyanate, isophorone diisocyanate, etc. An aromatic, aliphatic or alicyclic polyisocyanate compound; a cyclized polymer or biuret of these polyisocyanate compounds; or a combination thereof. It can gel.

  On the other hand, the blocking agent for blocking the polyisocyanate compound includes oxime compounds such as methyl ethyl ketoxime, methyl amyl ketoxime and cyclohexanone oxime; phenol compounds such as phenol, para-t-butylphenol and cresol; n-butanol, 2- Aliphatic alcohols such as ethyl hexanol; Aromatic alkyl alcohols such as phenyl carbinol and methyl phenyl carbinol; Ether alcohol compounds such as ethylene glycol monobutyl ether and diethylene glycol monoethyl ether; ε-caprolactam, γ-butyrolactam, etc. Lactam compounds; and the like.

  In the film forming method of the present invention, the “silica gel” or the “borate gel” film is formed on a stainless steel substrate. Next, a methyl amyl ketoxime block containing an isocyanate group with excellent adhesion to the "silica gel" or "borate gel" film and not destabilizing the "silica gel" or "borate gel" film By repeatedly applying the coating film of the anionic electrodeposition coating composition (B) containing a certain amount of isophorone diisocyanate compound, a coating film that satisfies all of the desired coating film hardness, impact resistance, adhesion, and finishability can be obtained. I found out.

  Here, a coating film obtained by electrodeposition coating of an anionic electrodeposition coating using the methyl amyl ketoxime-blocked isophorone diisocyanate compound (b3) is excellent in low-temperature curability and thus has a coating film hardness. Further, methyl amyl ketoxime (molecular weight 129) used as a blocking agent has a higher molecular weight than methyl ethyl ketoxime (molecular weight 87), which is useful for improving low-temperature curability, and the blocking agent released upon heating and drying is cured by coating film. Initially, it acts as a plasticizer to increase the flowability of the coating film, thereby providing a coated article with excellent smoothness and good finish.

  Moreover, conventionally well-known "other blocked polyisocyanate compound" can be used together with a compound (b3). Examples of the polyisocyanate compound used for other blocked polyisocyanate compounds include the polyisocyanate compounds. On the other hand, examples of the blocking agent include the blocking agent.

  Examples of other commercially available block polyisocyanate compounds include Burnock D-750, Burnock D-800, Burnock DN-950, Burnock DN-970 or Burnock DN-15-455 (Dainippon Ink Chemical, Inc.). Manufactured by Kogyo Co., Ltd., trade name), Death Module L, Death Module N, Death Module HL, Death Module IL or Death Module N3390 (above, manufactured by Bayer Products), Takenate D-102, Takenate D-202, Takenate D- 110N or Takenate D-123N (Takeda Pharmaceutical Co., Ltd., trade name), Coronate L, Coronate HL, Coronate EH or Coronate 203 (Nippon Polyurethane Industry, trade name) or Duranate 24A-90CX (Asahi Kasei Kogyo Co., Ltd., product) ), And the like.

  The mixing ratio of the carboxyl group-containing resin (b1), the amino resin (b2) and the compound (b3) in the anionic electrodeposition paint (B) is the solid content of the resin (b1), amino resin (b2) and compound (b3). Based on a total of 100 parts by weight, carboxyl group-containing resin (b1) 50 to 75 parts by weight, preferably 50 to 65 parts by weight, amino resin (b2) 5 to 25 parts by weight, preferably 10 to 20 parts by weight, The compound (b3) is contained in an amount of 0.1 to 25 parts by mass, preferably 1 to 15 parts by mass from the viewpoints of coating film hardness, impact resistance, adhesion, and finish.

  In addition, in the anion electrodeposition paint (B), when other blocked polyisocyanate compound is used in combination, a carboxyl group-containing resin (b1), an amino resin (b2), a methylamyl ketoxime blocked isophorone diisocyanate compound (b3) And 50 to 75 parts by mass of the carboxyl group-containing resin (b1), preferably 60 to 75 parts by mass, and 5 to 25 parts by mass of the amino resin (b2) with respect to 100 parts by mass of the total solid content of the blocked polyisocyanate compound. , Preferably 10 to 20 parts by mass, 1 to 15 parts by mass of methyl amyl ketoxime blocked isophorone diisocyanate compound (b3), preferably 5 to 15 parts by mass, 0.1 to 10 parts by mass of other blocked polyisocyanate compounds, Preferably 1 to 5 parts by weight of coating film hardness and finish Preferable from.

  The aqueous dispersion of the carboxyl group-containing resin (b1) is carried out by adding the amino resin (b2) and the compound (b3) to the carboxyl group-containing resin (b1) and, if necessary, other blocked polyisocyanate compounds. An aqueous dispersion can be obtained while adding a basic compound and deionized water and stirring with a disper or the like.

  Basic compounds include primary amines such as ethylamine, propylamine, butylamine, benzylamine, monoethanolamine, neopentanolamine, 2-aminopropanol, 3-aminopropanol; diethylamidiethanolamine, di-n- or di- Secondary monoamines such as iso-propanolamine, N-methylethanolamine, N-ethylethanolamine; tertiary monoamines such as dimethylethanolamine, trimethylamine, triethylamine, triisopropylamine, methyldiethanolamine, dimethylaminoethanol; diethylenetriamine And polyamines such as hydroxyethylaminoethylamine, ethylaminoethylamine, and methylaminopropylamine. The blending ratio of the basic compound is preferably in the range of 0.1 to 1.2 equivalents as a neutralization equivalent.

  A color pigment and / or a luster pigment can be added to the anion electrodeposition coating material (B) used in the present invention, if necessary. Examples of the coloring pigment include titanium dioxide, carbon black, zinc white, molybdenum red, Prussian blue, cobalt blue, phthalocyanine pigment, azo pigment, quinacridone pigment, isoindoline pigment, selenium pigment, and perylene pigment. These can be used alone or in combination of two or more.

  Bright pigments include, for example, aluminum pigments, evaporated aluminum pigments with leafing properties, metal oxide-coated alumina flakes, metal oxide-coated silica flakes, graphite pigments, natural mica (mica) and synthetic mica with iron oxide and titanium oxide. Metal oxide coated mica coated with metal oxide such as, titanium flake, stainless steel flake, oxybismuth chloride, plate-like iron oxide pigment, metal plated glass flake, metal oxide coated glass flake, hologram pigment, etc. Can be used alone or in combination of two or more.

  The amount of the colored pigment and / or glitter pigment is such that the carboxyl group-containing resin (b1), amino resin (b2), compound (b3), and other blocked polyisocyanate compounds blended as necessary. The range of 0.1 to 30 parts by mass, preferably 1 to 20 parts by mass with respect to 100 parts by mass of the total solid content is appropriate in terms of impact resistance and finish.

Regarding Film Forming Method In the film forming method of the present invention, stainless steel is immersed in an aqueous solution or aqueous dispersion (A), and the film thickness of the deposited film is 0.01 to 3.0 μm, preferably 0.1 to 0.1 μm. After conducting the energization treatment to 1.0 μm, the anion electrodeposition coating with the anion electrodeposition coating (B) is performed so that the dry film thickness is 30 μm or less, preferably 5 to 20 μm, more preferably 8 to 17 μm. To do.
Subsequently, after washing with water (non-rinse) or with water (rinse), it is obtained by heating and drying. Subsequently, after setting at room temperature, it can carry out by drying by heating. The heating and drying conditions are usually 130 to 200 ° C, preferably 150 to 190 ° C, and 20 to 50 minutes, preferably 25 to 40 minutes.

  Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited thereby. “Parts” and “%” indicate “parts by mass” and “% by mass”.

Production Example 1 Hardener No. 1 (Methyl amyl ketoxime blocked IPDI)
222 parts of isophorone diisocyanate and 256 parts of methyl amyl ketoxime were added to the reaction vessel, and the temperature was raised to 70 ° C. Sampling was performed over time, and it was confirmed by absorption of unreacted isocyanate groups by infrared absorption spectrum measurement. The resin solid content was adjusted with ethylene glycol monobutyl ether. 1 was obtained.

Production Example 2 Curing Agent No. 2 (Methyl ethyl ketoxime blocked IPDI)
222 parts of isophorone diisocyanate and 174 parts of methyl ethyl ketoxime were added to the reaction vessel, and the temperature was raised to 70 ° C. Sampling was performed over time, and it was confirmed by absorption of unreacted isocyanate groups by infrared absorption spectrum measurement. The resin solid content was adjusted with ethylene glycol monobutyl ether. 2 was obtained.

Production Example 3 Hardener No. 3 (cyclohexanone oxime blocked IPDI)
222 parts of isophorone diisocyanate and 226 parts of cyclohexanone oxime were added to the reaction vessel, and the temperature was raised to 70 ° C. Sampling was performed over time, and it was confirmed by absorption of unreacted isocyanate groups by infrared absorption spectrum measurement. The resin solid content was adjusted with ethylene glycol monobutyl ether. 3 was obtained.

Production Example 4 Acrylic resin solution No. Production Example 1 In a reaction vessel, 21 parts of a mixed solvent (Note 1) was charged and maintained at 85 ° C., and the following “mixture (A)” was dropped over 3 hours, and then 3 parts of azobisdimethylvaleronitrile was added. After the addition and reaction at 85 ° C. for 4 hours, the solid content was adjusted with a mixed solvent (see Note 1), and the acrylic resin solution no. 1 was produced.
"Mixture (A)"
Styrene 5 parts Methyl methacrylate 36.0 parts Ethyl acrylate 37.5 parts 2-Ethylhexyl methacrylate 4.0 parts Acrylic acid 5.5 parts 2-Hydroxyethyl methacrylate 12.0 parts Azobisdimethylvaleronitrile 2.1 parts (Note 1) ) Mixed solvent: propylene glycol monomethyl ether / isopropyl alcohol / n-butyl alcohol / ethylene glycol monobutyl ether = 42 parts / 42 parts / 42 parts / 84 parts.

Production Example 5 Emulsion No. Production of 70% acrylic resin solution No. 1 obtained in Production Example 1 above. No. 1 85.7 parts (solid content 60 parts), Cymel 232 (Note 2) 30 parts (solid content 30 parts), 80% curing agent No. 1 1 was added to 12.5 parts (solid content 10 parts), triethylamine 1.9 parts (0.4 neutralization equivalent) and water 119.9 parts, and the solid content was adjusted to 40% emulsion No. . 1 was obtained.

  (Note 2) Cymel 232: product name, methyl / butyl mixed etherified melamine resin, manufactured by Mitsui Cytec.

Production Examples 6 to 10 Emulsion No. 2-No. 6 Production of emulsion No. 6 was carried out in the same manner as in Production Example 5 except that the contents in Table 1 were used. 2-No. 6 was obtained.

Production Example 11 Pigment Dispersion Paste No. Production Example 1 1 60% amine-neutralized acrylic resin pigment dispersion resin (weight average molecular weight 36,000, hydroxyl value 70 mg KOH / g, acid value 56 mg KOH / g) 9.6 parts (solid content 5.8 parts), CR- 97 (Note 3) 10.0 parts of triethylamine and 11.5 parts of deionized water were charged and dispersed in a ball mill for 20 hours to obtain a pigment dispersion paste No. 50 having a solid content of 50%. 1 was obtained.

Production Examples 12 to 16 Pigment dispersion paste No. 2-No. Production Example 6 In the same manner as in Production Example 11 except that the blending contents shown in Table 2 were used, the pigment dispersion paste No. 2-No. 6 was obtained.

(* 3) CR-97: manufactured by Ishihara Sangyo Co., Ltd., trade name, titanium white (* 4) Carbon black MA-100: manufactured by Mitsubishi Chemical Corporation, trade name, carbon black (* 5) Metacene KM1000: manufactured by Toyo Aluminum Co., Ltd. Product name, vapor-deposited aluminum pigment imparted with leafing properties, average particle size of 11.1 μm, particle thickness of 0.025 μm
(Note 6) SF640: manufactured by Toyo Ink Manufacturing Co., Ltd., trade name, quinacridone color pigment, solid content 36%, pigment content 30%
(Note 7) EMF BLUE 2R: manufactured by Toyo Ink Manufacturing Co., Ltd., trade name, phthalocyanine blue color pigment, solid content 40%, pigment content 28%
(Note 8) EMF YELLOW H2RN-2: manufactured by Toyo Ink Manufacturing Co., Ltd., trade name, diazo yellow color pigment, solid content 40%, pigment content 32%.

Production Example 17 Anion electrodeposition paint Production of emulsion No. 1 having a solid content of 40%. No. 1 250 parts (100 parts solids), pigment dispersion paste No. 1 No. 1 was diluted with 31.6 parts (solid content 15.8 parts) and deionized water 956.4 parts to obtain an anionic electrodeposition paint No. 1 having a solid content of 8%. 1 was obtained.

Production Examples 18 to 24 2-No. Production of No. 8 Anionic electrodeposition paint No. 8 was prepared in the same manner as in Production Example 13 except that the contents of Table 3 were used. 2-No. 8 was obtained.

Comparative Production Example 1 Anionic electrodeposition paint No. 1 9-No. 13 except that the content of the preparation in Production Table 4 of No. 13 is used. 9-No. 13 was obtained.

Preparation of test plate (1) SUS304 (150 mm × 70 mm × 0.5 mm, austenitic stainless steel) was degreased by immersing it in a sulfuric acid aqueous solution at 25 ° C. and 100 g / l for 5 minutes, and then 10% by mass of sodium silicate. SUS304 was immersed in an aqueous solution as an anode, energized for 60 seconds at a constant current density of 0.01 A / cm ² , then washed with water to prepare a test plate (1). The film thickness of the test plate (1) was 0.3 μm.

Preparation of test plate (2) SUS430 (150 mm × 70 mm × 0.5 mm, ferritic stainless steel) was degreased by immersing it in 100 g / l sulfuric acid aqueous solution at 25 ° C. for 5 minutes, and then 10% by mass of metaboric acid after the SUS430 in aqueous sodium energized for 40 seconds at a constant current density of 0.01 a / cm ² was immersed as an anode, washed with water and create test plate (2). The film thickness of the test plate (2) was 0.5 μm.

Example 1 Multi-layer coating No. 1
Anionic electrodeposition paint No. 1 bath was subjected to electrodeposition coating at 150 V for 2 minutes so that the test plate (1) became an anode. Subsequently, it heat-dried at 180 degreeC for 20 minute (s), and multilayer film No. 15 with a dry film thickness of 15 micrometers was obtained. 1 was obtained.

Examples 2 to 16 Multi-layer coating No. 2-No. 16
Except for the steps shown in Tables 5 and 6, in the same manner as in Example 1, the multilayer coating No. 2-No. 16 was obtained. In addition, the coating film performance is shown.

Comparative Example 1 17
Anionic electrodeposition paint No. 1 bath was subjected to electrodeposition coating at 150 V for 2 minutes so that the test plate (1) became an anode. Subsequently, the film was baked and dried at 180 ° C. for 20 minutes to obtain a multilayer film No. 1 having a dry film thickness of 15 μm. 17 was obtained.

Comparative Examples 2 to 10 18-No. 32
Except for the steps shown in Tables 7 and 8, in the same manner as in Example 1, the multilayer coating No. 18-No. 32 was obtained. In addition, the coating film performance is shown.

  (Note 6) Pencil hardness: A pencil scratch test specified in JIS K 5600-5-4 (1999) was performed on the coating film of the test plate, and the coating film was evaluated by scratches.

  (Note 7) Impact resistance: DuPont specified in JIS K 5600-5-3 (1999) after placing each coated plate in a constant temperature and humidity chamber at a temperature of 20 ° C. ± 1 and a humidity of 75 ± 2% for 24 hours. Attach a cradle and a striker of the specified size to the impact tester, place the test plate with the coated surface facing upward, and sandwich it between them, and then put a weight of 500g on the striker (1/2 inch) The drop height (cm) at which cracks and peeling occurred on the coating film (front surface) due to impact was measured.

(Note 8) Adhesion: In accordance with JIS K 5600-5-6 (1999) grid pattern-tape method, a knife is used to reach the substrate surface of the paint plate in the vertical direction at intervals of about 1 mm. Eleven incisions were made in parallel to each other to form a goblet, a vinyl adhesive tape was stuck on the surface, and the gobain coated surface after the tape was abruptly peeled was evaluated according to the following criteria.
A: No peeling of the coating film is observed at all. ○: A slight peeling is observed on a part of the coating film in the knife scratch. Δ: 1 to 20 of the 100 gobangs are peeled. There are 21 or more peeled pieces out of each piece.

(Note 9) Finishability: The surface of the coating film was visually observed and evaluated according to the following criteria.
A: No abnormality is observed in the coating film.
O: At least one of round feeling and glossiness is slightly recognized.
Δ indicates at least one of round feeling and glossiness.
X is markedly reduced by at least one of round feeling and glossiness.

(Note 10) Designability: The appearance of the coating film was visually evaluated. The evaluation criteria are as follows.
A has a metallic or pearl-like depth or three-dimensional effect on the coating surface.
B has no metallic or pearly depth or three-dimensional appearance on the coating surface.

  The coating film forming method of the present invention can provide a coated article having excellent coating film hardness, impact resistance, adhesion, and finish on a stainless steel substrate.

Claims (3)

After immersing in a bath of an aqueous solution or aqueous dispersion (A) of at least one metal salt selected from an alkali metal salt of silicic acid and an alkali metal salt of metaboric acid to form a film, then the film A method for forming a film on a stainless steel substrate, characterized in that a coating film is formed by electrodeposition-coating the following anionic electrodeposition paint (B).
Anionic electrodeposition paint (B): carboxyl group-containing resin with respect to a total solid content of 100 parts by mass of carboxyl group-containing resin (b1), amino resin (b2), and methylamylketoxime-blocked isophorone diisocyanate compound (b3) (B1) Anion electrodeposition paint containing 50 to 75 parts by mass, amino resin (b2) 5 to 25 parts by mass, and methylamyl ketoxime blocked isophorone diisocyanate compound (b3) 0.1 to 25 parts by mass The anionic electrodeposition paint (B) is a coloring pigment and / or with respect to a total solid content of 100 parts by mass of the carboxyl group-containing resin (b1), the amino resin (b2), and the methylamyl ketoxime blocked isophorone diisocyanate compound (b3). Alternatively, the method for forming a film on a stainless steel substrate according to claim 1, comprising 0.1 to 30 parts by mass of a luster pigment. An electronic device part formed by molding stainless steel, which is covered with a film obtained by the method for forming a film on a stainless steel substrate according to claim 1 or 2.