JPS6241610B2 - - Google Patents

Description

[Detailed description of the invention]

(Industrial Application Field) This invention relates to a coating method for applying a topcoat of urethane resin paint to plastics through an undercoat of a primer.The purpose of this invention is to facilitate the preparation and application of the primer and to perform the baking process in one time. The goal is to bond each coating layer as strongly as one piece of baked paint. (Prior Art and its Problems) Conventionally, if paint is baked directly onto plastics, the paint will not adhere at all, so there is a method of applying baking paint using a chlorine group-containing resin as an undercoat primer. However, the chlorine content of chlorine-containing resins used for painting is not specified, and for undercoating, considering that it dissolves in the solvent of topcoat paint,
It is common knowledge in the industry to use a material with an average molecular weight of 100,000 or more, but there are the following problems. That is, when preparing a primer, it has poor solubility in solvents and compatibility with other resins, and may cause gelation in some cases. When applying the primer by spray or brush, stringing phenomenon and brush lines occurred. There was a correlation between the primer's adhesion to plastics and paint, where one was good and the other was bad, and in some cases peeling occurred easily between layers with weak adhesion. In addition, in the past, if a top coat was applied after the undercoat was normally dried, there was a risk that the undercoat would peel off or shrink due to the solvent in the topcoat, so it was usually necessary to bake the primer, then apply a topcoat and bake again. It was troublesome and it was difficult for the topcoat to adhere to the undercoat once it was baked. (Means for Solving the Problem) The present invention is a coating method in which plastics are undercoated with a primer, dried, and then topcoated with polyurethane paint and baked. A mixed resin obtained by mixing a solvent-dried resin containing a chlorinated polyolefin resin with a mold resin via a solvent is added with an OH group having an OH value of 5 to 20 and internal curing of the oxidative polymerization resin. In addition, the chlorine content of the chlorinated polyolefin resin is 25 to 50% by weight, and the average molecular weight is 5000.
~70,000, all of the above problems are solved by providing a urethane coating method for plastics, which is characterized in that it is configured so that both the primer and top coat can achieve the same performance as an integrated baking coating in one baking operation. solve. (Structure of the Invention) In the present invention, plastics are coated with a primer coat, dried, and then top coated with a polyurethane paint and baked. Plastics include polyethylene, polypropylene, polyethylene terephthalate, unsaturated polyester, polyamide, and other plastics, and these can be suitably coated. The primer is a mixed resin obtained by mixing an oxidatively polymerized resin with a solvent-dried resin containing a chlorinated polyolefin resin via a solvent, and an OH group with an OH value of 5 to 20 for the mixed resin and the oxidatively polymerized resin. A mold resin mixed with an internal curing agent is used. As the oxidation-polymerizable resin, alkyd resins, unsaturated polyester resins, and other resins are preferably used. Toluene and other solvents are preferably used as the solvent. As the chlorinated polyolefin resin, chlorinated polyethylene resin, chlorinated polypropylene resin, chlorosulfonated polyethylene resin, chlorosulfonated polypropylene resin, and others are preferably used. Chlorinated polyolefin resin has a chlorine content of 25
~50% by weight and an average molecular weight of 5,000 to 70,000 is used. As the solvent drying resin, acrylic resin, vinyl chloride resin, vinyl acetate resin, vinyl chloride/vinyl acetate copolymer resin, and others are preferably used. Solvent-dried resins are formulated to eliminate the drawbacks of slow-drying oxidation-polymerized resins, and for that purpose, 50 to 200 parts by weight of solvent-dried resins are added to 100 parts by weight of oxidative-polymerized resins. It is desirable to blend. Zirconium naphthenate is used as an internal hardening agent.
Lead naphthenate, cobalt naphthenate, etc. are preferably used. In the case of including an OH group, for example, the following chemical formula such as ethylene glycol monomethacrylate is added to the oxidative polymerization type resin or the solvent drying type resin including the chlorinated polyolefin resin. However, R ₁ is hydrogen or methyl group R ₂ is an alkyl group An OH group-containing compound is graft-polymerized in the presence of a peroxide catalyst such as benzoyl peroxide or dicumyl peroxide, or polyacrylic polyol, Epoxy resin polyol, polyether polyol, polyester polyol, etc.
OH groups can be removed by blending an OH group-containing low polymer, or by adjusting the manufacturing conditions so that OH groups remain during the production of an oxidation polymerization resin. You should include it. The OH group is blended in order to cause the urethane reaction to occur in just the right amount between the primer and the isocyanate group of the topcoat polyurethane resin.
For such purposes, OH groups are
Blend so that the OH value is 5 to 20. If the OH value exceeds 20, OH groups that do not participate in the reaction with the isocyanate groups of general top-coating polyurethane resins remain, resulting in poor water resistance. The reason why the primer is formulated as described above in this invention is as follows. Primer preparation work involves mixing solvent-dried resins, including chlorinated polyolefin resins, with oxidatively polymerized resins through a solvent.
Among chlorinated polyolefin resins, if the chlorine content is less than 25% by weight, it will have poor solubility in solvents, and if it exceeds 50% by weight, it will gel at room temperature. hard. On the other hand, when a chlorine content of 25 to 50% by weight and an average molecular weight of 5,000 to 70,000 is used, the solubility in solvents is good and gelation does not occur, allowing smooth preparation. Primer application is performed by spraying or brushing the above-mentioned primer on the plastic and then drying it. However, if a primer with a chlorine content exceeding 50% by weight or an average molecular weight exceeding 70,000 is used, Stringing phenomenon sometimes occurs, and brush lines occur when applying with a brush, making it impossible to perform smooth application work. On the other hand, when using chlorinated polyolefin resins with a chlorine content of 25 to 50% by weight and an average molecular weight of 5,000 to 70,000, stringiness occurs.
Smooth application work is possible without creating brush lines. When the primer dries, a primer film is formed, but the chlorine content of the chlorinated polyolefin resin is 50% by weight as a primer component.
If the average molecular weight is less than 5,000, it will hardly adhere to plastics, and if the average molecular weight is less than 5,000, it will not form a film, and both cannot be put to practical use. Furthermore, if a solvent-drying resin is not included in the primer component, it will take time to dry, resulting in stagnation of work. Furthermore, if an internal hardening agent is not blended into the primer component, the internal hardening will not occur even for a long time due to the drying effect alone, and a film will need to be formed by baking, which will require the baking of the subsequent top coat. 2
Requires multiple burn-ins. On the other hand, if a chlorinated polyolefin resin with a chlorine content of 25 to 50% by weight and an average molecular weight of 5,000 to 70,000 is used as the primer component, and an internal curing agent is used, such defects will not occur. In a short period of time, a durable film is formed that firmly adheres to the plastic. When polyurethane paint is applied and baked on the primer film, a polyurethane paint film is formed on the surface of the primer film, but if an internal hardener is not used as a primer component, it is necessary to form the primer film by baking as described above. Therefore, the polyurethane paint becomes incompatible with the surface of the primer coating. Furthermore, if a chlorinated polyolefin resin with an average molecular weight of 70,000 or more is used as a primer component, the polyurethane paint will similarly become incompatible with the surface of the primer coating due to poor compatibility with other resins. Furthermore, if an OH group is not separately applied as a primer component, there is almost no room for urethane bonds to form between the primer film and the polyurethane paint film, resulting in two-layer separation. Furthermore, if a chlorinated polyolefin resin with a chlorine content of less than 25% by weight is used as a primer component, the paint will not adhere. In this way, if an internal curing agent is not used as a primer component, a chlorinated polyolefin resin with an average molecular weight of 70,000 or more and a chlorine content of less than 25% by weight is used, and OH groups are not separately blended, the primer The film and the polyurethane paint film are merely surface-to-surface adhesion with no integrity at the boundary between the layers, and sufficient adhesive strength cannot be obtained. On the other hand, an internal curing agent is used as a primer component, and the chlorine content of the chlorinated polyolefin resin is 25 to 50% by weight and the average molecular weight is 5000.
~70000 is used and OH is applied to the mixed resin.
If an OH group with a value of 5 to 20 is added separately,
Without such defects, the surface of the uncured primer coating and the polyurethane paint coating have good compatibility and are integrated between the layers to form a urethane bond, thereby achieving sufficient adhesive strength. Furthermore, if the OH value is less than 20, there is no problem with water resistance. (Effects of the Invention) The present invention is a coating method in which plastics are undercoated with a primer, dried, and then topcoated with polyurethane paint and baked. A mixed resin obtained by mixing a solvent-dried resin containing a chlorinated polyolefin resin with an OH group having an OH value of 5 to 20 and an internal curing agent for the oxidative polymerization resin are added to the mixed resin. Moreover, the chlorine content of the chlorinated polyolefin resin is
25-50% by weight and average molecular weight of 5000-5000
This urethane coating method for plastics is characterized in that it is configured so that both the primer and the topcoat can achieve the same performance as an integrated baking coating in one baking operation by using 70,000 yen.It has the following effects. When preparing primers, solvent-dried resins containing chlorinated polyolefin resins and other solvents are mixed into oxidative polymerization resins using a solvent.
Since a compound containing ~50% by weight and an average molecular weight of 5,000 to 70,000 is used, it has good solubility in solvents and does not gel at room temperature, allowing smooth preparation. In the primer application process, the primer is applied to the plastic by spraying or brushing, but the primer component is a chlorinated polyolefin resin with a chlorine content of 25 to 50% by weight and an average molecular weight.
5,000 to 70,000 is used, so there is no stringing phenomenon during spraying, and there is no risk of brush streaks occurring when brushing, allowing for smooth application work. Drying of the primer is done by applying the primer to the plastic and letting it dry.
Since a chlorinated polyolefin resin having a chlorine content of 25 to 50% by weight and an average molecular weight of 5,000 to 70,000 is used as the primer component, it has good adhesion to plastics and can form a film. The polyurethane paint film is formed by overcoating the primer film with polyurethane paint and baking it, but an internal curing agent is used as the primer component, and the chlorine content of the chlorinated polyolefin resin is 25%.
~50% by weight with an average molecular weight of 5,000 to 70,000 is used, and an OH group with an OH value of 5 to 20 is separately added to the mixed resin, so the surface of the uncured primer coating and the polyurethane coating are different. With good compatibility, the layers melt together and form a urethane bond, providing sufficient adhesive strength. In addition, in one baking operation, both the primer and topcoat can achieve the same performance as an integrated baking operation. Next, by listing examples and test examples of this invention, the above-mentioned effects will be made clearer. (Example) Example 1 (Primer formulation) Acrylated alkyd resin 30 parts by weight [Manufactured by Harima Kasei Co., Ltd., trade name Harifthal KV905 Solid content 50% by weight] Chlorinated polyethylene resin 30 parts by weight [Osaka Soda Co., Ltd. ), product name Emullux A Chlorine content 25% by weight Average molecular weight 5000 Solid content 20% by weight Acrylic resin 10 parts by weight [Mitsubishi Rayon Co., Ltd., product name Dianal BR77 Average molecular weight 80000 Solid content 50 Weight%] Polyacrylic polyol 30 parts by weight (OH value 20) [Mitsui Toatsu Co., Ltd., product name Olester Q161 Viscosity Z1 to Z2 (solid content 56% by weight)] Zirconium naphthenate 1 part by weight Toluene (solvent) ) 10 parts by weight The OH value is for a mixed resin made by mixing the previous three. After coating the polyethylene molded product with a primer obtained by mixing the above mixture and drying it,
A commercially available polyurethane resin paint was applied and baked. Example 2 (Primer formulation) Alkyd resin 40 parts by weight [manufactured by Nippon Reichhold Co., Ltd., product name Betsukosol 1334 solid content 50% by weight] Chlorinated polypropylene resin 25 parts by weight [manufactured by Toyo Kasei Co., Ltd., product Name: Hardren Chlorine content: 50% by weight Average molecular weight: 70000 Solid content: 20% by weight] Vinyl chloride/vinyl acetate copolymer resin 10 parts by weight [Product name: Denka Vinyl 100C, manufactured by Denki Kagaku Co., Ltd. Solid content: 50% by weight] Epoxy resin polyol 25 parts by weight (OH value 5) [Manufactured by Ciel Co., Ltd., product name Ehikoat Viscosity Z1 to Z2 (solid content 56% by weight)] Lead naphthenate 1 part by weight Toluene (solvent) 10 parts by weight The OH value is The former three are for mixed resins. A polypropylene molded product was undercoated with a primer obtained by mixing the above-mentioned composition, dried, and then topcoated with a commercially available polyurethane resin paint and baked. (Example) The procedure was the same as in Example 1 except that the primer formulation in Example 1 was partially changed as described below. Comparative Example 1...The chlorine content of the chlorinated polyethylene resin was 20% by weight. Comparative Example 2: The chlorine content of the chlorinated polyethylene resin was 55% by weight. Comparative Example 3: The average molecular weight of the chlorinated polyethylene resin was 4,500. Comparative Example 4: The average molecular weight of the chlorinated polyethylene resin was 75,000. Comparative Example 5: Polyacrylic polyol was excluded. Comparative Example 6: Zirconium naphthenate was excluded. Primer preparation work, primer application work, primer drying,
The state of urethane resin paint application and baking was observed. Primer preparation work Examples 1, 2 and Comparative Examples 3, 5, and 6 were easily dissolved in toluene, but Comparative Example 1 was difficult to dissolve, and Comparative Example 2 may gel at room temperature. However, the material of Comparative Example 4 did not dissolve uniformly. Primer application work Examples 1 and 2 and Comparative Examples 1, 3, 5, and 6 had no stringing during spraying and no brush streaks when applying with a brush, but those of Comparative Examples 2 and 4 had no stringing or brush lines when applying with a brush. A streak appeared. Primer drying When the adhesion of the primer film to plastics was measured using JISK5400's cellophane tape test method, it was 100/100 for Examples 1 and 2 and Comparative Examples 4 and 5, but Comparative Example 2
The one in Comparative Example 3 was 50/100, the one in Comparative Example 6 was 0/100 because no film was formed, and the one in Comparative Example 6 was 80/100.
It was hot. Urethane resin paint application and baking When the adhesion of the urethane resin paint film to the primer film was measured using the same test method as above, it was 100/100 in Examples 1 and 2, but in Comparative Example 1. 30/100 in Comparative Example 2, 60/100 in Comparative Example 2 and 5/100 in Comparative Example 3, and 5/100 in Comparative Example 4.
80/100 for those of Comparative Example 5, 50/100 for those of Comparative Example 5.
100, and that of Comparative Example 6 was 70/100. It will be shown below that Examples 1 and 2 are also excellent in properties other than those mentioned above.

[Table] The method for measuring the characteristics in the above examples is as follows. Alkali resistance: Determined by immersing in a 5% caustic soda aqueous solution for one day and observing changes in appearance before and after immersion. Acid resistance: Judged by immersing in a 5% sulfuric acid aqueous solution for 1 day and observing changes in appearance before and after immersion. Gasoline resistance: Judged by soaking in gasoline for one day and observing changes in appearance before and after soaking. Weather resistance: Sunshine Carbon 1000 of JISK5400
Measured in hours. Impact resistance: JISK5400B Dupont tester 300g/20
Judged in cm. Boiling water resistance: Judged by immersing in boiling water for 2 hours and observing changes in appearance before and after immersion. Humidity resistance: Leave in an atmosphere at 50°C and 95% humidity for 10 days, and observe changes in appearance before and after leaving to judge. From the above results, it can be seen that Example 1 was comprehensively superior in primer preparation work, coating work, and adhesion between the plastic and each coating, and was also excellent in other properties.

Claims (1)

[Claims] 1. A coating method in which plastics is undercoated with a primer, dried, and then topcoated with polyurethane paint and baked, and the primer is a chlorinated polyolefin-based resin that is coated with an oxidative polymerization type resin via a solvent. A mixed resin obtained by mixing a solvent-drying resin containing a resin with an OH group having an OH value of 5 to 20 and an internal curing agent for the oxidation polymerization type resin, and in addition, the chlorine Reduce the chlorine content of polyolefin resin from 25 to 50.
Weight% and average molecular weight 5000-70000
A urethane coating method for plastics, characterized in that the primer and top coat are made to exhibit the same performance as an integrated baking coating in one baking operation.