JPH0261309B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention is directed to polybutylene terephthalate (hereinafter referred to as polybutylene terephthalate).
This relates to a coating method for resin (referred to as PBT). [Prior Art] PBT resin molded products have recently come to be widely used for automobile parts due to their characteristics such as toughness and heat resistance. When applying a topcoat to a PBT resin molded product for cosmetic purposes, a primer is usually applied to improve the adhesion of the topcoat and hide material defects. Conventionally, methods for painting PBT resin molded products include general degreasing such as steam cleaning with organic solvents such as 1,1,1-trichloroethane or trichloroethylene, alkaline degreasing, and organic solvent wiping. After treatment, a primer for PBT resin is applied by air atomization, baked and dried, and then electrodeposition is applied, an intermediate coat (primer) is applied, and the steel plate is baked and dried.Integration of the steel plate into the automobile body, and the same process is applied to the parts and the car body at the same time. The process of applying the top coat using air atomization and then baking and drying has been used. Conventional primers for PBT resins include, for example, dedicated polyurethane resin paints specially prepared for that purpose. On the other hand, conventional intermediate coatings for car body steel plates include fatty acid-modified polyester resin, oil-free polyester resin,
Epoxy modified polyester resin, epoxy resin,
Melamine resin is used. (For example, JP-A-57-98575). [Problems to be solved by the invention] As described above, conventionally, in order to impart adhesion to PBT resin for the top coat, it was necessary to use a primer specifically designed for PBT resin, which had a composition completely different from that of the intermediate coating for car bodies. Therefore, PBT resin molded products must be coated with a primer on a separate painting line from the car body painting line, and two lines must be installed: a PBT resin molded product painting line and a car body painting line. There were problems in that the line was complicated and painting costs were high. Furthermore, since the base composition of the top coat is different between the PBT resin molded product and the steel plate of the vehicle body, there is a problem in that the finished appearance after the top coat is formed differs. [Means for Solving Problems] The present invention is intended to solve the above problems, and uses the same oil-free polyester resin, epoxy resin, and melamine resin as a primer for PBT resin molded products and as an intermediate coating for steel materials. By using a primer containing PBT resin molded products, it is possible to apply the primer of the PBT resin molded product, the intermediate coating of the steel material, and the top coating of both in one line.
This paper proposes a PBT resin coating method that simplifies the coating process, reduces coating costs, and allows the finished appearance of the PBT resin molded product to be the same as that of the steel plate. In the present invention, a polybutylene terephthalate resin molded product is washed with an organic solvent, and then assembled onto a steel material coated with an electrodeposition coating.Then, in 100 parts by weight of the solid matter of the resin mixture composition, which is a coating film forming component, oil-free polyester 35 to 70 parts by weight of resin, 10 to 40 parts by weight of melamine resin, and 15 to 15 parts by weight of epoxy resin.
This method of coating polybutylene terephthalate resin is characterized in that the molded article and steel material are coated with a primer containing 50 parts by weight, baked and dried, and then a top coat is applied and baked and dried. In the present invention, the PBT resin molded product to be painted is a molded product made of PBT resin, and is applicable to automobile parts and the like. Steel materials that can be assembled and painted with this PBT resin molded product include automobile bodies. One of the components of the resin mixture composition, which is a coating forming component of the primer used for coating PBT resin, is an oil-free polyester resin. This polyester resin is a condensation product of polyols such as glycerin, pentaerythritol, dipropylene glycol, and neopentyl glycol and polybasic acids such as phthalic anhydride, isophthalic acid, adipic acid, and sebacic acid. It does not contain oils such as castor oil, soybean oil, or fatty acids such as coconut oil fatty acids, soybean oil fatty acids, and tall oil fatty acids. This oil-free polyester resin is the main resin of the coating film forming component of the primer, and at the same time contributes to the adhesion with the PBT resin due to the hydrogen bonding force of the hydroxyl groups of this resin. Polyester resins modified with oil or fatty acids have traditionally been used as intermediate coatings for car body steel plates, but due to their strong lipophilic properties,
The hydrogen bond strength is low and the adhesion with PBT resin is poor.
Cannot be used as a primer. The amount of oil-free polyester resin is determined based on 100 parts by weight of the solid matter of the resin mixture composition, which is a film-forming component of the primer.
The amount is 35 to 70 parts by weight, particularly preferably 40 to 60 parts by weight. If it is less than 35 parts by weight, the appearance of the coating film will be poor, and if it exceeds 70 parts by weight, the interlayer adhesion with the PBT resin will be insufficient. Another component of the resin mixture composition that is a film-forming component of the primer is a melamine resin. The melamine resin undergoes a thermosetting reaction with the oil-free polyester resin, imparts solvent resistance to the coating film, and prevents the intermediate coating (primer) coating from swelling during topcoating, resulting in poor finished appearance. Preferred examples of the melamine resin include butylated melamine formaldehyde resins and isobutylated melamine formaldehyde resins. The amount of this melamine resin is 10 to 40 parts by weight based on 100 parts by weight of the solid matter of the resin mixture composition that is a coating film forming component of the primer, but especially
15 to 30 parts by weight are preferred. If it is less than 10 parts by weight, the coating film will have insufficient curability and poor solvent resistance, and if it exceeds 40 parts by weight, the coating film will have insufficient flexibility and poor impact resistance. Another component of the resin mixture composition that is a film-forming component of the primer is an epoxy resin. The epoxy resin functions to give the primer adhesion to the PBT resin through the hydrogen bonding force of the hydroxyl groups within the molecule. As the epoxy resin, a bisphenol type epoxy resin obtained by the reaction of bisphenol A and epichlorohydrin is preferred. The bisphenol type epoxy resin preferably has an epoxy equivalent in the range of 200 to 7,000, particularly preferably in the range of 400 to 3,000. If the epoxy equivalent is less than 200, the hardness of the primer will not be sufficient, and if it exceeds 7000, the compatibility with other resins will be poor. The amount of epoxy resin is based on 100 parts by weight of the solid matter of the resin mixture composition, which is a coating film forming component of the primer.
The amount is 15 to 50 parts by weight, particularly preferably 20 to 40 parts by weight. If it is less than 15 parts by weight, the adhesion to the PBT resin will be insufficient, and if it exceeds 50 parts by weight, the coating film will have insufficient flexibility and poor impact resistance. The primer used in the present invention includes pigments such as titanium dioxide, barium sulfate, calcium carbonate, talc, kaolin, carbon black, and conductive carbon in addition to the above-mentioned resin mixture composition in 100 parts by weight of the solid resin mixture composition. It is preferable to contain 70 to 130 parts by weight. Further, the primer may further contain additives such as a solvent such as xylene, toluene, butyl acetate, and methyl ethyl ketone, a surface conditioner such as an acrylic polymer, and a flow prevention agent such as an amide wax, if necessary. The primer used in the present invention can be produced by a method similar to that used for conventional intermediate coating paints for automobile body steel plates. That is, a primer can be obtained by mixing a pigment and a resin varnish (resin solution), dispersing with a ball mill or roll mill, and then adding the resin varnish or solvent as appropriate and stirring uniformly. There are no particular restrictions on the top coat used in the present invention, but examples of top coats for automobiles include (1) aminoalkyd resin-based 1-coat 1-bake solid color;
(2) Amino acrylic resin 2 coats 1 bake type solid color, (3) Amino acrylic resin 1 coat 1
There are baked metallic colors, and (4) aminoacrylic resin-based two-coat one-baked metallic colors. These top coats can be used as PBT resin top coats in the same way as conventional car body paints, allowing for integrated painting. The painting method first involves cleaning the PBT resin molded product with an organic solvent. On the other hand, after applying electrodeposition coating to the steel material, the above PBT molded product is assembled, then the PBT molded product and the steel material are painted with the primer, baked and dried, and then the top coat is applied on top of that, and the above-mentioned top coat is applied and baked. Perform drying. To explain the case of assembling and painting automobile parts made of PBT resin molded products onto automobile body steel plates, first, the parts made of PBT resin molded products are
After performing a steam cleaning treatment with an organic solvent such as 1,1,1-trichloroethane, the steel plate for an automobile body coated with electrodeposition is assembled. This automobile body steel sheet has been previously subjected to alkaline degreasing, chemical conversion treatment, electrodeposition coating, and baking drying. Next, the primer is applied to PBT resin parts and automobile body steel plates using an air atomization coating machine, an electrostatic air atomization coating machine, etc., and baked at 130 to 150°C for 15 to 40 minutes to harden. Next, the top coat is applied using an air atomizer or electrostatic air atomizer, and
Bake for a minute to harden. When applying the top coat using an electrostatic air atomizer or rotary electrostatic atomizer, the PBT resin molded product is not conductive, so by incorporating conductive carbon into the primer, the top coat can be applied. Efficiency can be improved. The coating film formed by the primer is PBT.
It satisfies both the film quality as a primer for resins and the film quality as an intermediate coat for steel materials, and has excellent adhesion with electrodeposition coatings and top coats on PBT resin materials and steel materials. By applying a top coat on top, the finish is the same between PBT resin and steel, resulting in a top coat with an excellent appearance. In the above description, the PBT molded product may be other than automobile parts, and the steel material may be other than automobile body steel plates. Other molded products and steel materials can also be coated in the same manner as described above, thereby making it possible to obtain a coating film with an excellent appearance. [Effects of the Invention] As described above, according to the present invention, the same primer is used as the primer for PBT resin and the intermediate coating for steel, so that the primer for PBT resin molded products, the intermediate coating for steel, and the intermediate coating for both It is now possible to apply the top coat all in one line, which simplifies the painting process and reduces painting costs.It also provides the same finish and provides a coating film with an excellent appearance. [Example] Next, examples of the present invention and comparative examples are given,
The present invention will be explained in further detail. In the examples, parts indicate parts by weight, and % indicates weight %. Examples 1 to 6, Comparative Examples 1 to 4 (Manufacture of Primer) 100 g of each of the blended compositions of Examples 1 to 6 and Comparative Examples 1 to 4 shown in Table 1 were thoroughly kneaded with Deisorel, and then mixed with a paint shaker. The mixture was kneaded for 1 hour. A mixed solvent of equal weights of aromatic solvent Solbetsuso #100 (manufactured by Exxon, trade name) and butyl acetate was added to the resulting composition, and the spray clay was sprayed in a #4 food cup for 23 seconds (20°C). Then, a primer was manufactured. Details of each component in Table 1 are as follows. Oil-free polyester resin varnish: 230 parts of glycerone 4.3 parts, neopentyl glycol 20.2 parts, adipic acid 14.3 parts and isophthalic acid 24.4 parts
The esterification reaction was carried out at ℃ for 6 hours, and after cooling, a mixed solvent of xylene and methyl isobutyl ketone (1:1) was added.
Polyester resin varnish with the addition of 30.8 parts to make the solid content 60%. Fatty acid modified polyester resin varnish: 23.2 parts of trimethylolpropane, 8.9 parts of adipic acid, 14.8 parts of isophthalic acid and 19.1 parts of soybean oil fatty acid at 230℃
After cooling for 6 hours, about 34 parts of a mixed solvent of xylene and methyl isobutyl ketone (1:1) was added to make a fatty acid-modified polyester resin varnish with a solid content of 60%. Butylated melamine resin varnish: Super Betsukamine J-820-60 (manufactured by Nippon Reichhold Co., Ltd., trade name). Isobutylated melamine resin varnish: Super Betsukamine L-116-70 (manufactured by Nippon Reichhold Co., Ltd.)
Product name) 70% solution. Epoxy resin varnish: Araldite GY−
6071 (manufactured by Ciba Geigy, trade name) 60% solution. Epoxy resin varnish: Epicote 1007 (manufactured by Yuka Ciel Epoxy Co., Ltd., trade name) 60% solution. Titanium dioxide: JR-602 (manufactured by Teikoku Kako Co., Ltd., trade name). Barium sulfate: Precipitated burr SS-50 (manufactured by Sakai Chemical Co., Ltd., trade name). Carbon black: Raven 420 (manufactured by Columbia Carbon, trade name).

【table】

[Table] (Painting test) A cold-rolled steel plate of 0.8 mm x 70 mm x 150 mm was treated with zinc lyphosphate using Bonderite #3004 (trade name, manufactured by Nippon Parkerizing Co., Ltd.) and treated with Aqua No., a cationic electrodeposition paint. 4100 (manufactured by Nippon Oil & Fats Co., Ltd., product name)
was painted and baked at 175℃ for 20 minutes to dry. The dry film thickness of the electrodeposition coating obtained was 15 μm. On the other hand, 3 mm x 80 mm x 80 mm PBT resin (Toray Industries, Inc.)
After washing the plate (manufactured by M.D.) with 1,1,1-trichloroethane vapor (74°C) for 60 seconds, it was assembled to the steel plate coated with the above-mentioned electrodeposition coating, and then the above-mentioned primer was applied by air atomization, 140
Bake dry at ℃ for 30 minutes. The dry coating thickness of the obtained primer was 30 to 35 μm. Next, as a topcoat, Melami No. 1 Red (NOF Co., Ltd.
Co., Ltd. (trade name) was air atomized and baked at 140°C for 30 minutes to dry. The dry film thickness of the resulting top coat was 40 μm. (Coating Film Test) The PBT resin and steel plate test plates obtained in the above steps were subjected to an adhesion test under the test conditions shown below and a visual evaluation of the coating film appearance.
The results are shown in Table 2. For the goban adhesion test, use a cutter knife.
Draw 11 lines vertically and horizontally at mm intervals, and the result is
Cellophane tape was attached to 100 squares and when it was removed all at once, the number of squares that remained because the coating layer could not be peeled off was evaluated. Evaluation criteria is 100/100
(Excellent) to 0/100 (Poor). The visual appearance of the paint film is a visual evaluation of the smoothness of the top coat film. The evaluation criteria is ○
(Excellent), △ (Acceptable), × (Poor).

【table】

[Table] As is clear from the above results, the coating film performance of the examples was more satisfactory than that of the comparative examples for both PBT resin molded products and automobile body steel plates. It can be seen that it is possible to integrally paint parts and reduce costs by reducing the number of painting processes.

Claims (1)

[Scope of Claims] 1. After washing a polybutylene terephthalate resin molded product with an organic solvent, it is assembled onto a steel material coated with an electrodeposition coating, and then the solid matter of the resin mixture composition, which is a coating film forming component, is mixed in 100 parts by weight of the solid matter. , 35 to 70 parts by weight of oil-free polyester resin, melamine resin
The molded product and steel material are coated with a primer containing 10 to 40 parts by weight and 15 to 50 parts by weight of an epoxy resin, baked and dried, and then a top coat is applied and baked to dry. How to paint butylene terephthalate resin. 2. The polybutylene terephthalate resin coating method according to claim 1, wherein the polybutylene terephthalate resin molded product is an automobile part and the steel material is an automobile body steel plate. 3. The method for coating polybutylene terephthalate resin according to claim 1 or 2, wherein the oil-free polyester is a polycondensation product of a polyol and a polybasic acid. 4. The method for coating polybutylene terephthalate resin according to any one of claims 1 to 3, wherein the melamine resin is a butylated melamine formaldehyde resin or an isobutylated melamine formaldehyde resin. 5. The method for coating polybutylene terephthalate resin according to any one of claims 1 to 4, wherein the epoxy resin is a bisphenol type epoxy resin.