JP4173753B2 - Coating method for aluminum automobile body, chemical conversion liquid, primer surfacer, and multilayer coating used for coating method - Google Patents

Description

【００６０】
（プライマーサーフェーサーの調整）
プライマーサーフェーサー（表中では、「プラサフ」と表記）を表２及び表３に示す種類および割合で配合した。次いで、有機溶剤（トルエン／キシレン／酢酸エチル／酢酸ブチルの質量比＝７０／１５／１０／５）とともに攪拌機により塗装適正粘度になるように攪拌混合し、プライマーサーフェーサー１〜１５を調製した。なおプライマーサーフェーサー１２は、エピ−ビス型エポキシ樹脂を含有しないため、プライマーサーフェーサー１３は、ポリエステル樹脂とメラミン樹脂の含有量が外れるため、プライマーサーフェーサー１４は、扁平状顔料を含有しないため比較例として用いた。
【００６１】
【表２】

【００６２】
【表３】

【００６３】
（複層塗膜の形成）
表８、表９に示す化成処理を施したアルミ素材に、上記プライマーサーフェーサーを乾燥膜厚が５０μｍになるように表８、表９に示す組み合わせで塗装し、室温で１０分間セッティング後、１４０℃の温度で３０分間焼き付けた。次いで、表８、表９に示す上塗り塗料を用いて、上塗り塗膜を形成し、テストピースを得た。上塗り塗膜１は、ソリッド塗料により乾燥膜厚が３５μｍとなるようにソリッド塗膜形成後、３分間セッティングし、１４０℃の温度で３０分間焼き付けた。上塗り塗膜２および３は、メタリック塗料により乾燥膜厚が１５μｍとなるようにメタリック塗膜形成後、３分間セッティングし、トップクリヤー塗料を乾燥膜厚が３５μｍになるようにトップクリヤー塗膜形成後、室温で１０分間セッティングし、１４０℃の温度で３０分間焼き付け
【００６４】
（評価方法と評価基準）
得られたテストピースについて塗装外観（下地隠蔽性、塗膜平滑性）、耐食性（耐塩温水性、耐糸錆性）、アルミ合金素材との密着性（耐水密着性）を以下の評価方法で評価し、結果を表８、表９に示した。
【００６５】
耐塩温水性：テストピースをクロスカット後、５％ＮａＣｌ水溶液に、５５℃で２４０時間浸漬後、塗膜の膨れ、剥がれを目視で評価した。
【００６６】
【表４】

【００６７】
耐糸錆性：テストピースをクロスカット後、塩水噴霧試験（５％ＮａＣｌ水溶液、３５℃連続スプレー）を２４時間、次いで耐湿試験（４０℃で７０％）を２４時間、次いで室温放置を２４時間、これを１サイクルとして４サイクル後に、カット部からの膨れを目視で評価した。
【００６８】
【表５】

【００６９】
耐水密着性：テストピースを４０℃温水に２４０時間浸漬後、室温に冷却後、碁盤目密着テストを実施し、剥がれ具合を評価した。
【００７０】
【表６】

【００７１】
塗装外観：テストピースの水平面について携帯用鮮明度光沢系(ＰＧＤ ＩＶ 型、日本色彩研究所製)を用いＰＧＤ値で評価した。
【００７２】
【表７】

【００７３】
【表８】

【００７４】
【表９】

【００７５】
表１、表２、表３、表８、表９の結果から明らかのように、本実施例は、本発明のアルミ自動車車体の塗膜形成方法、化成液、プライマーサーフェーサーにより複層塗膜を形成したもので、塗装外観（下地隠蔽性、塗膜平滑性）、耐食性（耐塩温水性、耐糸錆性）、アルミ合金素材との密着性（耐水密着性）が良好な複層塗膜が得られた。
一方、比較例では、上記実施例で得られたような複層塗膜は得られなかった。
【００７６】
【発明の効果】
本発明の方法で形成されたアルミ自動車車体の塗膜は、塗装外観（下地隠蔽性、塗膜平滑性）、耐食性（耐塩温水性、耐糸錆性）、アルミ合金素材との密着性（耐水密着性）が良好で、電着塗装工程の省略に伴う塗装工程の簡略化、塗装コスト低減、塗装作業の容易化を行うことができる。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a coating film forming method for an aluminum automobile body, a chemical conversion liquid, a primer surfacer and a multilayer coating film used in the coating film forming method.
[0002]
[Prior art]
The body of an automobile is formed by press-molding a steel plate material or an aluminum alloy plate material to form inner members of the vehicle body such as floor panels and inner panels, and the obtained molded members are joined by welding or the like to form a chassis that is a vehicle body skeleton. To manufacture. Also, car body materials such as doors, roofs, fenders, bonnets, trunk lids, etc. are formed by press-molding steel plate materials and aluminum alloy plate materials, and the exterior members are joined to the chassis and painted to produce the car body.
[0003]
The above-mentioned coating processes include degreasing and cleaning processes, pre-coating processes such as chemical conversion after degreasing, and undercoating processes for the purpose of rust prevention by electrodeposition coating, etc., in order to improve the final appearance of the final topcoat The intermediate coating process is applied, and the top coating process is performed for the purpose of imparting aesthetics to the coating surface, weather resistance, chemical resistance, wear resistance and the like.
The above-described conventional car body painting methods that have been generally used in the past require the above-mentioned processes, so the painting process includes the pretreatment process from the degreasing and cleaning process to the final topcoat. Becomes extremely large. Also, since the painting is carried out in a consistent line, the painting line becomes extremely long, and the rust prevention, undercoating, etc. use the electrodeposition coating method, so an immersion coating device is required and the equipment is large. This is disadvantageous in terms of equipment, and is disadvantageous in that the cost is high, such as maintenance of equipment and management man-hours.
[0004]
In order to simplify the painting of automobile bodies, focusing on pre-coated aluminum alloy plates, the painting process is aimed at simplifying the painting process by omitting the electrodeposition painting process, greatly reducing the number of painting steps, and facilitating painting work. JP-A-2001-17915 discloses an automobile such as a bonnet, a trunk lid, a door, and a fender, which is formed by press-molding a pre-coated metal plate in which a coating containing a rust prevention layer and a lubricating component is formed at least on the outer surface of the metal plate. The process of manufacturing the exterior member that constitutes the outside of the vehicle body, and the inside of the vehicle body such as the floor panel and the inner panel by press-molding a pre-coated metal plate having a rust-preventing layer containing a lubricating component on the surface of the metal plate Forming a plurality of inner members to be formed, joining each of the inner members to manufacture a chassis of the automobile, and connecting each of the exterior members to the shutter. Joined to sea, then the intermediate coating on the surface of the exterior member, the vehicle body painting process of an automobile applying top coating successively is described.
[0005]
However, the method described in the above Japanese Patent Application Laid-Open No. 2001-17915 is formed by press-molding a pre-coated metal plate on which at least the outer surface of the metal plate is formed with a coating containing a rust-preventing layer and a lubricating component, and thereby forming a bonnet, trunk lid, door Since an exterior member constituting the outside of the automobile body such as a fender is used, there may be a problem in terms of weldability when each of the exterior members is joined to the chassis.
[0006]
In addition, automobile body made of aluminum material may be applied with extruded material, cast material, etc. made of aluminum material on the outer plate surface. Since the top coating material is applied, the rust prevention property of the application part such as a molding material or a casting material becomes a problem.
[0007]
[Problems to be solved by the invention]
The object of the present invention is good coating appearance (underlying concealment property, coating film smoothness), corrosion resistance (salt warm water resistance, yarn rust resistance), and good adhesion with aluminum alloy material (water resistance adhesion). Simplifying the painting process by omitting the process, drastically reducing the man-hours for painting, facilitating painting work, coating method for aluminum automobile body, chemical conversion liquid used in the coating film forming method, primer surfacer and coating film formation It is to provide a multilayer coating film formed by the method.
[0008]
[Means for Solving the Problems]
As a result of intensive studies in view of the above problems, the present inventors have arrived at the present invention.
1. A coating film forming method for an aluminum automobile body, in which an automobile body made of an aluminum material having a vehicle body exterior member joined to a chassis to which a vehicle body inner member is joined is sequentially subjected to the following steps (1) to (4).
(1) A process of degreasing the painted surface of an automobile body made of an aluminum material;
(2) a chemical conversion treatment step of applying and drying a chemical conversion liquid mainly containing zirconium phosphate not containing phosphoric acid, zinc phosphate not containing nickel, zirconium phosphate or titanium phosphate;
(3) As a vehicle, containing 40 to 80 parts by mass of a polyester resin, 10 to 50 parts by mass of a melamine resin, and 5 to 30 parts by mass of an epi-bis type epoxy resin in terms of solid content in the vehicle, A primer surfacer coating film forming step of applying and drying and curing a primer surfacer containing a flat pigment, a rust preventive pigment, a color pigment excluding these pigments, and a extender pigment in a solid mass ratio of the vehicle to the pigment of 30/70 to 80/20; as well as
(4) A top coat film forming step in which a top coat is applied and dried and cured.
2. The aluminum automobile body described above, wherein the polyester resin has a number average molecular weight of 2000 to 4000, a hydroxyl value of 50 to 150, an acid value of 5 to 20, and the epi-bis type epoxy resin has a number average molecular weight of 3000 to 10,000. Coating film forming method.
3. The method for forming a coating film on an aluminum automobile body, wherein the melamine resin is a methylated melamine resin or a methyl / butyl mixed melamine resin.
4). The above-mentioned flat pigment is an aluminum flake pigment, talc or clay having an average particle diameter of 5 to 25 μm, and the flat pigment is 0.1 to 3.5% by mass in the total pigment. Film forming method.
5. The method for forming a coating film on an aluminum automobile body, wherein the rust preventive pigment is zinc, calcium or aluminum phosphate or phosphite, and the rust preventive pigment is 0.1 to 10% by mass in the total pigment.
6). Furthermore, the coating film of the above-mentioned aluminum automobile body containing organic bentonite in an amount of 0.1 to 1% by mass with respect to the solid content of the paint and 0.3 to 2.5% by mass of the crosslinkable resin particles with respect to the solid content of the paint. Forming method.
7. A chemical conversion liquid used in the above-described method for forming a coating film on an aluminum automobile body, which mainly contains zirconium that does not contain phosphoric acid, zinc phosphate that does not contain nickel, zirconium phosphate, or titanium phosphate.
8). The vehicle contains 40 to 80 parts by mass of a polyester resin, 10 to 50 parts by mass of melamine resin, and 5 to 30 parts by mass of an epi-bis type epoxy resin in terms of solid content in the vehicle, and a flat pigment as a pigment A primer surfacer for use in the above-described method for forming a coating film on an aluminum automobile body, comprising a rust preventive pigment, a color pigment excluding these, and an extender pigment in a solid mass ratio of vehicle / pigment of 30/70 to 80/20.
9. A multilayer coating film formed by the above-described method for forming a coating film for an aluminum automobile body.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the configuration of the present invention will be described in detail.
<Aluminum car body>
In the vehicle body applied to the method of forming a coating film for an aluminum automobile body according to the present invention, the inner member, chassis, and vehicle body exterior member of the vehicle body are made of an aluminum material. However, it shall include those in which aluminum material is partially used.
[0010]
Here, the vehicle body inner member refers to a plurality of inner members such as various inner panels such as a floor panel member, a pillar member, a roof rail member, a side sill member, a bulkhead member, and a cross member member. The chassis refers to a vehicle body skeleton formed by molding an inner member of a vehicle body and joining the obtained molded member by welding, rivet connection, screw connection, or the like. The car body exterior members are fenders arranged on the front and rear sides of the press-molded chassis, the hood that is the hood of the front engine room, the trunk lid or tail gate on the rear, the doors arranged on the front and back of both sides, The roof panel etc. which comprise a ceiling exterior board. The exterior member is joined by a joining method such as rivet joining or screw joining to the chassis. An aluminum alloy is used as the aluminum material. By using an aluminum alloy, it has rust prevention and can eliminate the need for electrodeposition coating. As the chassis constituent member, an aluminum alloy material plate, shape, casting or the like is used.
[0011]
<Degreasing process>
The degreasing step applied to the method for forming a coating film of an aluminum automobile body according to the present invention uses an alkaline degreasing agent having a pH of 10.5 to 12.5, a degreasing temperature of 40 to 50 ° C., a degreasing time of 1 to 5 minutes, and an alkali. It is the process of processing by the spraying method of the aqueous solution or the dip dipping method.
[0012]
(Degreasing agent)
A degreasing agent applied to the degreasing step is subjected to a degreasing cleaning process to remove fats and oils such as mineral oil and animal and vegetable oil adhering to the surface of the object to be treated. As a degreasing detergent used for such a degreasing washing process, a builder mainly comprising an acid or an alkali and a non-ionic or anionic surfactant as a main component are generally used. As the alkali builder, those mainly composed of phosphate or silicate have been used from the viewpoint of detergency, but recently, alkali builder mainly composed of silicate is preferably used. Alkali builders in which carbonates and the like are further blended with such silicates are also used. It contains an alkali silicate, a water-soluble polycarboxylate, and a nonionic surfactant.
[0013]
In order to make the pH value of the degreasing liquid 10.5 or more, a chemical for increasing the pH value is blended in addition to the essential components. Examples of such agents include alkali carbonates such as sodium hydrogen carbonate, sodium carbonate, potassium hydrogen carbonate, and potassium carbonate; caustic alkalis such as potassium hydroxide and sodium hydroxide, which can be used alone. Or two or more types are used together.
[0014]
Examples of the alkali silicate include alkali metal salts of orthosilicate such as orthosilicate sodium and potassium orthosilicate; alkali metal salts of metasilicate such as sodium metasilicate and potassium metasilicate; sesquisilicate such as sodium sesquisilicate and potassium sesquisilicate These may be used alone or in combination of two or more. The water-soluble polycarboxylate is a homopolymer or copolymer of unsaturated carboxylic acids having one polymerizable double bond, and the carboxyl group is neutralized with an alkali metal such as sodium or potassium. Salt is preferred. As said nonionic surfactant, a conventionally well-known thing is mentioned, for example. Among various nonionic surfactants, from the viewpoint of excellent detergency and low fish toxicity, monoalkyl ether of polyethylene oxide is preferable, excellent detergency, low fish toxicity and antifoaming property. From the point of being excellent (low foaming property), a monoalkyl ether of polyethylene oxide polypropylene oxide is preferable. Among these monoalkyl ethers, an alkylene oxide adduct of an aliphatic alcohol, in which 50 mol% or more of the alkylene oxide is ethylene oxide, and less than 50 mol% is propylene oxide and / or butylene oxide, Is preferably a nonionic surfactant having a temperature in the range of 25 to 50 ° C. The pH value of the degreasing liquid needs to be 10.5 or more, and is preferably in the range of 10.5 pH to 12.5.
[0015]
<Chemical conversion treatment process>
The chemical conversion treatment step applied to the method of forming a coating film for an aluminum automobile body of the present invention is carried out by washing with water by spraying or dip dipping for 15 seconds to 5 minutes at room temperature after the degreasing treatment, and if necessary, titanium phosphate-based In this step, the surface is adjusted, and then chemical conversion treatment is performed using a chemical conversion liquid mainly composed of zirconium not containing phosphoric acid, zinc phosphate not containing nickel, zirconium phosphate, or titanium phosphate. In the chemical conversion treatment, the chemical conversion solution is treated at a pH of 2.5 to 4.5, a chemical conversion temperature of 40 to 55 ° C., a chemical conversion time of 15 seconds to 5 minutes, a spraying method or a dip dipping method.
[0016]
(Chemical conversion liquid)
The chemical conversion liquid used in the coating method for coating an aluminum automobile body of the present invention is mainly composed of zirconium that does not contain phosphoric acid, zinc phosphate that does not contain nickel, zirconium phosphate, or titanium phosphate.
[0017]
Chemical conversion liquid mainly composed of zirconium not containing phosphoric acid:
Zr ion: 50 to 200 mg / L, preferably 80 to 120 mg / L,
F ion: 50-1500 mg / L, preferably 100-140 mg / L,
pH: 2.5-4.5, preferably 2.5-3.5
Zr ion source: ammonium zirconate, zircon hydrofluoric acid, zircon nitrate, etc.
F ion source: borofluoride, silicofluoride, etc. as complex fluoride, hydrofluoric acid, potassium fluoride, sodium fluoride, ammonium fluoride, potassium acid fluoride, sodium acid fluoride, acid fluoride as simple fluoride Ammonium etc.
[0018]
Chemical conversion liquid mainly composed of zinc phosphate not containing nickel:
Zn ion: 0.5 to 2 g / L, preferably 0.8 to 1.2 g / L (substantially Ni is not included, and if Ni is included, corrosion resistance and adhesion are insufficient),
PO₄Ion: 5-30 g / L, preferably 15-25 g / L,
Mn ion: 0.6-3 g / L, preferably 1.1-1.5 g / L,
F ion: 0.05 to 1.5 g / L, preferably 0.6 to 1.0 g / L (including complex fluoride and simple fluoride),
NO₂Ion: 0.01 to 0.2 g / L, preferably 0.1 to 0.15 g / L,
NO_ThreeIon: 1-15 g / L, preferably 4-10 g / L,
Zn ion source: zinc oxide, zinc carbonate, zinc nitrate, etc.
PO₄Ion source: phosphoric acid, zinc phosphate, manganese phosphate, etc.
Mn ion source: Manganese carbonate, manganese nitrate, manganese chloride, manganese phosphate, etc.
F ion source: borofluoride, silicofluoride, etc. as complex fluoride, hydrofluoric acid, potassium fluoride, sodium fluoride, ammonium fluoride, potassium acid fluoride, sodium acid fluoride, acid fluoride as simple fluoride Ammonium etc.
NO₂Ion source: sodium nitrite, ammonium nitrite, etc.
NO_ThreeIon source: sodium nitrate, ammonium nitrate, zinc nitrate, manganese nitrate, nickel nitrate, etc.
[0019]
Chemical conversion liquid mainly composed of zirconium phosphate:
Zr ions: 0.02 to 0.25 g / L, preferably 0.02 to 0.1 g / L (when Ti ions are used in combination, the total amount of Zr ions and Ti ions is 0.02 to 0.25 g / L) L, preferably 0.1 to 0.2 g / L),
PO₄Ion: 0.01-1 g / L, preferably 0.03-0.4 g / L,
F ion: 0.01 to 0.5 g / L, preferably 0.1 to 0.3 g / L,
pH: 1.5-4, preferably 2.5-3
Zr ion source: ammonium zirconate, zircon hydrofluoric acid, zircon nitrate, etc.
Ti ion source: titanium hydrofluoric acid, ammonium titanate, etc.
PO₄Ion source: phosphoric acid, zinc phosphate, manganese phosphate, etc.
F ion source: borofluoride, silicofluoride, etc. as complex fluoride, hydrofluoric acid, potassium fluoride, sodium fluoride, ammonium fluoride, potassium acid fluoride, sodium acid fluoride, acid fluoride as simple fluoride Ammonium etc.
[0020]
Chemical conversion liquid mainly composed of titanium phosphate:
Ti ion: 0.02 to 0.25 g / L, preferably 0.02 to 0.1 g / L (when Zr ions are used in combination, the total amount of Ti ions and Zr ions is 0.02 to 0.25 g / L) L, preferably 0.1 to 0.2 g / L),
PO₄Ion: 0.01-1 g / L, preferably 0.1-0.5 g / L,
F ion: 0.01 to 0.5 g / L, preferably 0.1 to 0.3 g / L,
pH: 1.5-4, preferably 2.5-3.5,
Ti ion source: titanium hydrofluoric acid, ammonium titanate, etc.
Zr ion source: ammonium zirconate, zircon hydrofluoric acid, zircon nitrate, etc.
PO₄Ion source: phosphoric acid, zinc phosphate, manganese phosphate, etc.
F ion source: borofluoride, silicofluoride, etc. as complex fluoride, hydrofluoric acid, potassium fluoride, sodium fluoride, ammonium fluoride, potassium acid fluoride, sodium acid fluoride, acid fluoride as simple fluoride Ammonium etc.
[0021]
<Primer surfacer coating film formation process>
The primer surfacer coating film forming step applied to the method for forming a coating film of an aluminum automobile body according to the present invention is performed by spray coating or roll coating of the primer surfacer, and the formed primer surfacer coating film is preferably 120 to 180 ° C., 15 It is a step of baking and drying for ˜60 minutes. As for the dry film thickness of the said primer surfacer coating film, 20-100 micrometers is preferable. If it is less than 20 μm, it is difficult to conceal the base, and if it exceeds 100 μm, there is a risk of poor appearance of the coating.
[0022]
[Primer surfacer]
The primer surfacer used in the method for forming a coating film for an aluminum automobile body according to the present invention is, as a vehicle, 40 to 80 parts by mass of a polyester resin, 10 to 50 parts by mass of a melamine resin, and 5 to 30 parts by mass in terms of solid content in the vehicle. Part of an epi-bis type epoxy resin, a pigment containing a flat pigment, a rust preventive pigment, a colored pigment excluding these pigments, and an extender pigment in a solid content mass ratio of vehicle / pigment of 30 / 70-80 / 20 is there.
[0023]
If the polyester resin is less than 40 parts by mass in terms of solid content in the vehicle, the adhesion with the top coat film and the chipping resistance may be reduced, and if it exceeds 80 parts by mass, the curability is lowered and the aluminum substrate is reduced. There is a possibility that the adhesiveness with the lowering. If it is less than 10 parts by mass in terms of solid content in the vehicle of the melamine resin resin, there is a fear that the curability is lowered and the adhesion to the aluminum substrate is reduced, and if it exceeds 50 parts by mass, the adhesion with the top coat film is reduced. And chipping resistance may be reduced. If it is less than 5 parts by mass in terms of solid content in the vehicle of the epi-bis type epoxy resin, the adhesion to the aluminum substrate may be reduced, and if it exceeds 30 parts by mass, the coating appearance may be reduced.
[0024]
When the above flat pigment, rust preventive pigment, colored pigment excluding these, and extender pigment are in a mass ratio of the solid content of the vehicle and the pigment, preferably less than 30/70, the adhesion to the aluminum substrate is lowered and the coating appearance is lowered. If it exceeds 80/20, the base concealing property may be lowered.
[0025]
Preferably, the primer surfacer comprises, as a vehicle, 50 to 70 parts by mass of a polyester resin, 15 to 45 parts by mass of melamine resin, and 10 to 20 parts by mass of an epi-bis type epoxy resin in terms of solid content in the vehicle. The pigment contains a flat pigment, a rust preventive pigment, a colored pigment excluding these pigments, and an extender pigment in a solid content mass ratio of 40/60 to 70/30 between the vehicle and the pigment.
[0026]
The film-forming resin in the vehicle is a polyester resin and an epi-bis type epoxy resin. The polyester resin preferably has a number average molecular weight of 2000 to 4000, a hydroxyl value of 50 to 150, and an acid value of 5 to 20. is there. A preferred number average molecular weight of the epi-bis type epoxy resin is 3000 to 10,000. The unit of hydroxyl value and acid value is mgKOH / g.
[0027]
If the number average molecular weight of the polyester resin is less than 2,000, the coating film hardness may be lowered, and if it exceeds 4000, the coating appearance may be lowered. If the hydroxyl value is less than 50, the coating film hardness may be lowered and the crosslinking density may be insufficient, and if it exceeds 150, the coating appearance may be deteriorated. If the acid value is less than 5, the coating film hardness may be lowered and the crosslinking density may be insufficient, and if it exceeds 20, the coating appearance may be deteriorated. The number average molecular weight of the polyester resin is more preferably 2500 to 3500, the hydroxyl value is 70 to 120, and the acid value is 8 to 15. The number-average molecular weight of the epi-bis type epoxy resin is more preferably 3500 to 6000. If the number average molecular weight of the epi-bis type epoxy resin is less than 3000, the adhesion to the aluminum substrate may be lowered, and if it exceeds 10,000, the coating appearance may be lowered.
[0028]
As the polyester resin, a resin that is a condensation product of a polyhydric alcohol and a polycarboxylic acid is used. It also includes alkyd resins obtained by adding components that provide fatty acid residues derived from natural or semi-dry oils. These resins contain a proportion of free hydroxyl and / or carboxyl groups that are available for reaction with conventional crosslinking agents.
[0029]
Polyhydric alcohols suitable for the production of the polyester resin include ethylene glycol, propylene glycol, butylene glycol, 1,6-hexylene glycol, neopentyl glycol, glycerol, trimethylol propane, trimethylol ethane, pentaerythritol, dipentaerythritol. Including trit, tripentaerythritol, hexanetriol, and condensation products of trimethylolpropane with ethylene oxide or propylene oxide.
[0030]
Polycarboxylic acids suitable for the production of polyester resins are succinic acid (or its anhydride), adipic acid, azelaic acid, sebacic acid, maleic acid (or its anhydride), fumaric acid, muconic acid, itaconic acid, phthalic acid (Or its anhydride), isophthalic acid, terephthalic acid, trimellitic acid (or its anhydride), and pyromellitic acid (or its anhydride). Fatty acids derived from flaxseed oil, soybean oil, tall oil, dehydrated castor oil, fish oil, and tung oil as derived from natural or semi-drying oils Fatty acids derived from safflower oil, sunflower oil, and cottonseed oil Include. Usually, it is preferable that the oil length of such an alkyd resin does not exceed 50%. A monofunctional saturated carboxylic acid can be further blended for the purpose of imparting plasticity to the polyester. Examples of such acids are C₄~ C₂₀ Of saturated aliphatic acids, benzoic acid, p-tertiary butyl benzoic acid, and abietic acid.
[0031]
As said epi-bis type | mold epoxy resin, what has at least 2 or more epoxy group in 1 molecule is used suitably, Specifically, resin etc. which are obtained by reaction of bisphenol and epichlorohydrin are mentioned. Examples of bisphenol include bisphenol A and F. Examples of the epi-bis type epoxy resin include Epicoat 1007 and Epicoat 1009 (both are trade names, manufactured by Shell Chemical Co., Ltd.), and these are chained using a chain extender such as diol, dicarboxylic acid, or diamine. Extended ones can also be used. For example, an epibisepoxy resin, which is obtained by extending the chain with a diol, dicarboxylic acid, diamine or the like can be used. By using the epi-bis type epoxy resin, the corrosion resistance and the adhesion with the aluminum material can be improved.
[0032]
The melamine resin is more preferably a methylated melamine resin etherified with a methyl group alone, a n-butyl group or i-butyl group, and a methyl / butyl mixed etherified melamine resin etherified with a methyl group. By using a methylated melamine resin or a methyl / butyl mixed etherified melamine resin, it is possible to improve the base concealing property by controlling the coating film shrinkage.
[0033]
As the pigment, flat pigments, rust preventive pigments, colored pigments excluding these, and extender pigments are used.
[0034]
The flat pigment is preferably an aluminum flake pigment, talc or clay having an average particle diameter of 5 to 25 μm. If the average particle diameter is less than 5 μm, there is a fear that the concealment improvement of the base roughness may be insufficient, and it exceeds 25 μm. There is a fear that the coating film appearance is insufficient. The flat pigment is preferably 0.1 to 3.5% by mass in the total pigment. By using a flat pigment, it is possible to improve the hiding of the surface roughness. If the above flat pigment is less than 0.1% by mass in the total pigment, there is a fear that the concealment improvement of the base roughness will be insufficient, and if it exceeds 3.5% by mass, the coating film appearance may be insufficient. .
[0035]
  The anticorrosive pigment is preferably zinc phosphate or calcium phosphate.,Aluminum phosphate, zinc phosphite, calcium phosphite,Alternatively, aluminum phosphite is used, and the rust preventive pigment is preferably 0.1 to 10% by mass in the total pigment. By using a rust preventive pigment, corrosion resistance can be improved. If the rust preventive pigment is less than 0.1% by mass in the total pigment, the corrosion resistance may be insufficiently improved, and if it exceeds 10% by mass, the coating film appearance may be insufficient.
[0036]
Further, as the colored pigment, organic pigments such as azo lake pigments, phthalocyanine pigments, indigo pigments, perylene pigments, quinophthalone pigments, dioxazine pigments, quinacridone pigments, isoindolinone pigments, metal complex pigments, etc. Inorganic pigments such as yellow lead, yellow iron oxide, bengara, titanium dioxide, and carbon black.
[0037]
Further, the extender pigment preferably includes barium sulfate, barium carbonate, calcium carbonate, magnesium carbonate, silica and the like.
[0038]
Further, the organic bentonite is preferably 0.1 to 1% by mass with respect to the solid content of the paint, and if the organic bentonite content is less than 0.1% by mass, the base concealing property may be lowered. The paint appearance and gloss may be reduced. More preferably, it is 0.3-0.7 mass%. By using the organic bentonite, the underlying concealment can be improved by controlling the viscoelasticity of the coating film.
[0039]
Furthermore, the crosslinkable resin particles are preferably contained in an amount of 0.3 to 2.5% by mass based on the solid content of the paint. If the crosslinkable resin particles are less than 0.3% by mass, the base concealing property may be lowered, and if it exceeds 2.5% by mass, the effect commensurate with the addition may be insufficient. As the crosslinkable resin particles, for example, emulsification of alkyd resin or polyester resin synthesized by using a monomer having a zwitterionic group in the molecule described in JP-A-58-129066 as one of polyhydric alcohol components. Those obtained by emulsion polymerization of an ethylenically unsaturated monomer in an aqueous medium in the presence of a resin having a function and a polymerization initiator are preferred. As the monomer having the zwitterionic group in the molecule, -N (+)-R-COO (-) or -N (+)-R-SO₃Shown as (-) (R may be substituted C₁~ C₆And those having two or more hydroxyl groups in one molecule can be preferably used. As such a monomer, a hydroxyl group-containing aminosulfonic acid type zwitterionic compound is preferable in terms of resin synthesis.
[0040]
The resin having a zwitterionic group having emulsifying ability synthesized in the above monomer in the molecule has an acid value of 30 to 150 mg KOH / g, preferably 40 to 150 mg, KOH / g, number average molecular weight. It is good to use the polyester resin of 500-5000, Preferably it is 700-3000. If the upper limit is exceeded, the resin handling properties will be reduced, and if the lower limit is not reached, the resin having emulsifying ability will be detached or the solvent resistance will be reduced if a coating film is formed. Moreover, the ethylenically unsaturated monomer that is emulsion-polymerized in the synthesis of the crosslinkable resin particles is a monomer having two or more radically polymerizable ethylenically unsaturated groups in the molecule. Such a monomer having two or more radically polymerizable ethylenically unsaturated groups in the molecule is preferably contained in the range of 0.1 to 10% by weight in the total monomers. This amount is selected to the extent that sufficient crosslinking is provided so that the particulate polymer does not dissolve in the solvent.
[0041]
The crosslinkable resin particles generally do not contain a low molecular emulsifier or protective colloid contained in an emulsion resin, and copolymerize monomers having two or more radically polymerizable ethylenically unsaturated groups in the molecule. Therefore, cross-linkable resin particles having water resistance, solvent resistance, gloss and the like that are insoluble in organic solvents and having an average particle size of 0.02 to 0.5 μm are preferable. By using the crosslinkable resin particles, the underlying concealment can be improved by controlling the viscoelasticity of the coating film.
[0042]
The primer surfacer can have an effect of suppressing the occurrence of repelling by adding a curing catalyst as necessary. Examples of the curing catalyst include metaphosphoric acid, orthophosphoric acid, pyrophosphoric acid, tripolyphosphoric acid, phosphoric acid, trimetaphosphoric acid, triphosphoric acid, tetrametaphosphoric acid, phosphorous acid, monobutyl phosphoric acid, monoethylhexyl phosphoric acid, monolauryl phosphoric acid, phenyl acid phosphate, methane Examples thereof include at least one selected from sulfonic acid, ethanesulfonic acid, benzenesulfonic acid, dodecylbenzenesulfonic acid, naphthalenesulfonic acid, toluenesulfonic acid, nonylnaphthalenesulfonic acid, and dinonylnaphthalenedisulfonic acid. More preferred is monolauryl phosphoric acid, dodecylbenzenesulfonic acid, toluenesulfonic acid, dinonylnaphthalene disulfonic acid, or dinonylnaphthalenesulfonic acid.
[0043]
In addition to the above components as additives, the primer surfacer includes an anti-settling agent and an ultraviolet absorber that are a polyamide wax which is a lubricating dispersion of an aliphatic amide and a polyethylene wax which is a colloidal dispersion mainly composed of polyethylene oxide. Antioxidants, leveling agents, surface conditioners such as silicone and organic polymers, sagging inhibitors, thickeners, antifoaming agents, lubricants and the like can be added as appropriate. These additives can improve the performance of paints and coating films by blending them at a ratio of 15 parts by mass or less with respect to 100 parts by mass of the total solid content of the resin and the crosslinking agent. .
[0044]
The above-mentioned primer surfacer is usually provided with the above-described components dissolved or dispersed in a solvent. Any solvent can be used as long as it dissolves or disperses the vehicle, and an organic solvent and / or water can be used. Examples of the organic solvent include those usually used in the paint field. Examples thereof include hydrocarbons such as toluene and xylene, ketones such as acetone and methyl ethyl ketone, esters such as ethyl acetate, cellosolve acetate and butyl cellosolve, alcohols and the like. Water is preferably used when the use of organic solvents is restricted from an environmental point of view. In this case, an appropriate amount of a hydrophilic organic solvent may be contained.
[0045]
<Top coat formation process>
The top coat film forming step applied to the coating film forming method for an aluminum automobile body of the present invention includes a top coat solid paint containing a color pigment as a top coat, or a top coat base paint containing a glitter pigment and / or a color pigment. This is a step of forming a top coat film using a transparent top coat top clear paint to be formed on the top coat base film formed by this top coat base paint.
[0046]
Formation of the above-mentioned top coat solid coat or top coat base coat is performed by spray coating or roll coating, but when the top coat film formed is baked and dried, it is preferably 120 to 180 ° C., 20 to 30 minutes, Bake and dry.
[0047]
As for the dry film thickness of the said top coat solid coating film, 20-100 micrometers is preferable. As for the dry film thickness of the said top coat base coating film, 10-100 micrometers is preferable. The dry film thickness of the top-coated top clear coating film is preferably 20 to 100 μm. When the preferable lower limit is less than 10 or 20 μm, it is difficult to conceal the base, and when it exceeds 100 μm, there is a possibility that poor appearance of the coating may occur. A top coat film is formed on the outer surface of the exterior member of the vehicle body, coating of the vehicle body is completed, and then the process proceeds to the outfitting process.
[0048]
(Top coat)
The above topcoat paint is composed of at least one thermosetting resin selected from an acrylic resin, a polyester resin, a fluororesin, an epoxy resin, a polyurethane resin, a polyether resin, and a modified resin thereof, and various crosslinks. Various pigments, solvents, and additives such as modifiers, ultraviolet absorbers, leveling agents, dispersants, antifoaming agents, and the like can be blended with the mixture of the agent. Various additives can be used. However, the top-coated top clear paint contains no pigment, or even if it contains a pigment in an amount that does not impair the transparency. In these resins, the resin system may be any of organic solvent type, aqueous type and powder type.
[0049]
As the top coat, a top coat solid paint containing a color pigment, or a top coat base paint containing a glitter pigment and / or a color pigment, and a top coat top clear having transparency formed on a coating film formed by the top coat base paint Use paint.
[0050]
In addition, as a top-coated top clear coating, a coating containing a carboxyl group-containing polymer and an epoxy group-containing polymer described in JP-B-8-19315 is a top-coated base coating film containing a pigment in a measure against acid rain and wet on wet. It is preferably used from the viewpoint of not disturbing the orientation of the glittering pigment when coated on the surface.
[0051]
[Multi-layer coating film]
The multilayer coating film of the present invention is formed by the above-described method for forming a coating film for an aluminum automobile body.
[0052]
【Example】
EXAMPLES Next, although an Example and a comparative example are given and this invention is demonstrated more concretely, this invention is not limited only to these Examples.
[0053]
Examples 1-17, Comparative Examples 1-4
(Chemical conversion treatment)
As Examples 1-9, 11-13, 16, 17, and Comparative Examples 1-3, the chemical conversion treatment demonstrated below was performed.
[0054]
Degreased "Surf Cleaner SD280A" (made by Nippon Paint Co., Ltd.) using aluminum material cut out of aluminum alloy (JIS A 6022 alloy equivalent) with car body exterior member joined to chassis with car body inner member joined ) And “Surf Cleaner SD280B” (manufactured by Nippon Paint Co., Ltd.) (water concentration A is adjusted to 1.5 mass%, B is adjusted to 0.75 mass%, pH is about 11) at 42 ° C. for 2 minutes. Degreased and then washed with water for 15 seconds at room temperature using tap water.
[0055]
Next, chemical conversion treatment was performed using any one of chemical conversion liquids 1 and 3 to 5 whose compositions and treatment methods are shown in Table 1. After chemical conversion treatment, after standing at 25 ° C. for 30 seconds, use tap water, rinse with spray water at 25 ° C. for 15 seconds, further use ion-exchanged water, wash with spray water at 25 ° C. for 15 seconds, and then heat with hot air at 80 ° C. for 10 seconds. Dried for minutes.
[0056]
On the other hand, as Examples 10, 14, 15 and Comparative Example 4, the chemical conversion treatment described below was performed.
[0057]
Degreased "Surf Cleaner SD280A" (made by Nippon Paint Co., Ltd.) using aluminum material cut out of aluminum alloy (JIS A 6022 alloy equivalent) with car body exterior member joined to chassis with car body inner member joined ) And “Surf Cleaner SD280B” (manufactured by Nippon Paint Co., Ltd.) (water concentration A is adjusted to 1.5 mass%, B is adjusted to 0.75 mass%, pH is about 11) at 42 ° C. for 2 minutes. Degreased and then washed with water for 15 seconds at room temperature using tap water.
[0058]
Next, the surface was adjusted by immersing in a surface conditioner “Surffine 5N-10” (manufactured by Nippon Paint Co., Ltd., concentration: 0.1% by mass) at 25 ° C. for 30 seconds. Next, chemical conversion treatment was performed using chemical conversion liquid 2 or 6 whose composition and treatment method are shown in Table 1. After chemical conversion treatment, after standing at 25 ° C. for 30 seconds, use tap water, rinse with spray water at 25 ° C. for 15 seconds, further use ion-exchanged water, wash with spray water at 25 ° C. for 15 seconds, and then heat with hot air at 80 ° C. for 10 seconds. Dried for minutes. In addition, since the chemical conversion liquid 6 is a chemical conversion liquid containing nickel, it was used as a comparative example.
[0059]
[Table 1]

[0060]
(Adjustment of primer surfacer)
Primer surfacers (indicated in the table as “Plasaf”) were blended in the types and proportions shown in Tables 2 and 3. Subsequently, together with an organic solvent (mass ratio of toluene / xylene / ethyl acetate / butyl acetate = 70/15/10/5), the mixture was stirred and mixed with a stirrer so as to obtain an appropriate coating viscosity, thereby preparing primer surfacers 1 to 15. In addition, since the primer surfacer 12 does not contain an epi-bis type epoxy resin, the primer surfacer 13 does not contain the polyester resin and the melamine resin, so the primer surfacer 14 does not contain a flat pigment and is used as a comparative example. It was.
[0061]
[Table 2]

[0062]
[Table 3]

[0063]
(Formation of multilayer coating)
The primer surfacer was applied to the aluminum materials subjected to the chemical conversion treatment shown in Tables 8 and 9 in the combinations shown in Tables 8 and 9 so that the dry film thickness was 50 μm. After setting at room temperature for 10 minutes, 140 ° C. And baked at the temperature of 30 minutes. Subsequently, the top coat film was formed using the top coat shown in Table 8 and Table 9, and the test piece was obtained. The top coating film 1 was set for 3 minutes after the solid coating film was formed with a solid paint so that the dry film thickness was 35 μm, and baked at a temperature of 140 ° C. for 30 minutes. Top coating films 2 and 3 were formed with a metallic paint so that the dry film thickness was 15 μm, then set for 3 minutes, and the top clear paint was formed after the top clear film was formed so that the dry film thickness was 35 μm. Set at room temperature for 10 minutes and bake at 140 ° C for 30 minutes
[0064]
(Evaluation method and evaluation criteria)
Evaluation of coating appearance (undercoating concealment, smoothness of coating film), corrosion resistance (salt warm water resistance, yarn rust resistance), and adhesion to aluminum alloy material (water resistance adhesion) using the following evaluation methods. The results are shown in Tables 8 and 9.
[0065]
Salt hot water resistance: The test piece was cross-cut, immersed in a 5% NaCl aqueous solution at 55 ° C. for 240 hours, and the swelling and peeling of the coating film were visually evaluated.
[0066]
[Table 4]

[0067]
Yarn rust resistance: After cross-cutting a test piece, a salt spray test (5% NaCl aqueous solution, 35 ° C. continuous spray) is performed for 24 hours, then a moisture resistance test (70% at 40 ° C.) is performed for 24 hours, and then left at room temperature for 24 hours. This was regarded as one cycle, and the swelling from the cut portion was visually evaluated after 4 cycles.
[0068]
[Table 5]

[0069]
Water-resistant adhesion: The test piece was immersed in warm water at 40 ° C. for 240 hours, cooled to room temperature, then subjected to a cross-cut adhesion test, and the degree of peeling was evaluated.
[0070]
[Table 6]

[0071]
Appearance of coating: The horizontal surface of the test piece was evaluated by the PGD value using a portable vivid gloss system (PGD IV type, manufactured by Nippon Color Research Laboratory).
[0072]
[Table 7]

[0073]
[Table 8]

[0074]
[Table 9]

[0075]
As is apparent from the results of Table 1, Table 2, Table 3, Table 8, and Table 9, this example shows that the multilayer coating film is formed by the coating method of the aluminum automobile body of the present invention, the chemical conversion liquid, and the primer surfacer. It is a multi-layer coating film that has good appearance (coating concealment, smooth coating), corrosion resistance (salt warm water resistance, yarn rust resistance), and adhesion to aluminum alloy materials (water adhesion). Obtained.
On the other hand, in the comparative example, the multilayer coating film as obtained in the above example was not obtained.
[0076]
【The invention's effect】
The coating film of the aluminum automobile body formed by the method of the present invention has a coating appearance (underlying concealment property, coating film smoothness), corrosion resistance (salt warm water resistance, yarn rust resistance), and adhesion to an aluminum alloy material (water resistance) Adhesion) is good, and the coating process can be simplified, the coating cost can be reduced, and the painting work can be simplified due to the omission of the electrodeposition coating process.

Claims (5)

A method of forming a coating film on an aluminum automobile body made of an aluminum material in which a vehicle body exterior member is bonded to a chassis in which a vehicle body inner member is bonded, which is sequentially subjected to the following steps (1) to (4):
(1) A process of degreasing the painted surface of an automobile body made of an aluminum material;
(2) Zirconium conversion liquid containing 50 to 200 mg / L of Zr ions and no phosphoric acid,
A zinc phosphate conversion solution containing 0.5 to 2 g / L of Zn ions and 5 to 30 g / L of PO ₄ ions and not containing nickel,
Zirconium phosphate chemical containing 0.02 to 0.25 g / L of Zr ions and 0.01 to 1 g / L of PO ₄ ions ,
It contains 0.02 to 0.1 g / L of Zr ions, the combined amount of Zr ions and Ti ions is 0.02 to 0.25 g / L in combination with Ti ions, and 0.01 to ₄ PO ₄ ions. Zirconium phosphate conversion solution containing ˜1 g / L,
A titanium phosphate chemical containing 0.02 to 0.25 g / L of Ti ions and 0.01 to 1 g / L of PO ₄ ions , or
It contains 0.02 to 0.1 g / L of Ti ions, the combined amount of Zr ions and Ti ions is 0.02 to 0.25 g / L in combination with Zr ions, and 0.01 to ₄ PO ₄ ions. A titanium phosphate chemical containing ˜1 g / L,
A chemical conversion treatment step of coating and drying any of the chemical conversion liquids of
(3) As a vehicle, containing 40 to 80 parts by mass of a polyester resin, 10 to 50 parts by mass of a melamine resin, and 5 to 30 parts by mass of an epi-bis type epoxy resin in terms of solid content in the vehicle, A flat pigment, a rust preventive pigment, a colored pigment excluding these, and an extender pigment are contained in a solid content mass ratio of vehicle / pigment of 30/70 to 80/20, and organic bentonite is 0.1 to the solid content of the paint. A primer surfacer coating film forming step in which a primer surfacer is applied and dried and cured, and containing (4) a top coating material. Top coat film forming process for coating and drying and curing:
Because
The aluminum automobile body, wherein the rust preventive pigment contained in the primer surfacer is zinc, calcium or aluminum phosphate or phosphite, and the rust preventive pigment is 0.1 to 10% by mass in the total pigment. Coating film forming method.   The number average molecular weight of the polyester resin is 2000 to 4000, the hydroxyl value is 50 to 150, the acid value is 5 to 20, and the number average molecular weight of the epi-bis type epoxy resin is 3000 to 10,000. Coating method for aluminum automobile body.   The method for forming a coating film on an aluminum automobile body according to claim 1 or 2, wherein the melamine resin is a methylated melamine resin or a methyl / butyl mixed melamine resin.   The flat pigment is an aluminum flake pigment, talc or clay having an average particle diameter of 5 to 25 µm, and the flat pigment is 0.1 to 3.5% by mass in the total pigment. A coating film forming method for an aluminum automobile body according to item 1.   The multilayer coating film formed by the coating-film formation method of the aluminum vehicle body of any one of Claim 1 to 4.