JP2001293431A - Method for coating polyolefin molding - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating method by which a highly adhesive double- layered coating film is formed on a polyolefin molding. SOLUTION: A first primer containing >=70 wt.% chlorinated polyolefin, in a solid component ratio, and a second primer containing <70 wt.% chlorinated polyolefin, in a solid component ratio, are applied on the polyolefin molding, then an overcoat coating is applied, and the molding is coated by this method.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coating method for forming a multi-layer coating film having excellent adhesion on a polyolefin molded article.

[0002]

2. Description of the Related Art Lightweight and highly moldable polyolefin is used in place of metal for bumpers, fenders, radiator grills, etc. on the outer panel of an automobile body. Top coats are applied to improve aesthetics and durability. Since the surface of the polyolefin is generally non-polar and has insufficient adhesion to the coating film, a primer containing a chlorinated polyolefin is preliminarily applied before the top coat. However, in such a primer, when the content of the chlorinated polyolefin is increased in order to improve the adhesion with the polyolefin, the adhesion with the top coat decreases. On the contrary, when the content is reduced, the adhesion with the polyolefin is reduced. Has a defect of decreasing.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to improve the above-mentioned deficiencies and to provide a novel primer coating which has excellent adhesion to both polyolefins (substrates) and topcoats. Regarding the method of coating a polyolefin molded body,
As a result of diligent research, they have found that the object can be achieved by using two types of primers, a first primer containing a large amount of chlorinated polyolefin and a second primer containing a small amount of chlorinated polyolefin, to complete the present invention. Reached.

That is, according to the present invention, a first primer containing a chlorinated polyolefin at a solid content ratio of 70% by weight or more and a second primer containing a chlorinated polyolefin at a solid content ratio of less than 70% by weight are contained in a polyolefin molded article. A method for applying a polyolefin molded article is provided, which comprises sequentially applying a primer and then applying a top coat.

Hereinafter, the method of the present invention will be described in detail. The polyolefin molded article is an object to be coated with the first primer, the second primer, and the like. Specifically, a (co) polymer comprising an olefin-based monomer such as ethylene, propylene, or butene, or a copolymer of these with other polymerizable monomers, is formed into a desired shape by molding an automobile body. Bumpers, fenders, radiator grills, etc. on the outer panel. It is preferable that the surfaces of these molded bodies are appropriately subjected to washing, surface treatment, and the like by a method known per se before coating the first primer.

The first primer is an organic solvent-based liquid composition containing a chlorinated polyolefin in a solid content ratio of 70% by weight or more, and is a paint applied to the surface of a polyolefin molded product prior to the second primer.

[0007] The first primer is a composition comprising chlorinated polyolefin and an organic solvent as essential components, and optionally further blending other paint resins, crosslinking agents, pigments, paint additives and the like as needed. .

The chlorinated polyolefin is a chlorinated polyolefin having a chlorination rate of 5 to 40%, particularly 1
5-30% is suitable. As the polyolefin to be chlorinated, one or two or more polymers selected from ethylene, propylene, butene, methylbutene, and the like, and those olefins and vinyl acetate, butadiene, acrylate, methacrylate, and the like. And copolymers. Among them, chlorinated polyethylene, chlorinated polypropylene, chlorinated ethylene-propylene copolymer, chlorinated ethylene-vinyl acetate copolymer and the like are particularly preferable. The chlorinated polyolefin may have a functional group such as a hydroxyl group or a carboxyl group in the molecule, and may have a number average molecular weight of 1,000 to 10,000.
0, especially in the range of 3000 to 30000 is suitable.

As the organic solvent, a known organic solvent capable of dissolving or dispersing a chlorinated polyolefin can be used.
Hydrocarbons such as toluene, xylene, hexane, heptane, butanol, hexanole, cyclohexano-
Alcohols such as benzyl and benzyl alcohol, ketones such as methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone and isophorone, ethers such as dioxane, ethylene glycol monomethyl ether, diethylene glycol monomethyl ether, and ethyl acetate. And ester systems such as ethylene glycol monoethyl ether acetate and diethylene glycol monoethyl ether acetate.

Other coating resins and cross-linking agents which can be appropriately compounded in the first primer include, for example, acrylic resins, polyester resins, urethane resins, cellulose acetate butyrate, melamine resins, (block) polyisocyanate compounds and the like. Can be peeled off. Also,
These paint resins may be graft-polymerized to the above-mentioned chlorinated polyolefin, but the other graft-polymerized paint resins are distinguished from the above-mentioned chlorinated polyolefins. These other coating resins may have a crosslinkable functional group such as a hydroxyl group in the molecule, and have a hydroxyl value of 0 to 150 mgKOH, particularly 20.
~ 100mgKOH, and the number average molecular weight is 1000 ~
A range of 10,000 is suitable. In addition, as the pigment component, a coloring pigment for an ordinary paint, an extender pigment, and the like can be used.

The first primer is a composition comprising a chlorinated polyolefin and an organic solvent as essential components, and optionally further blending other paint resins, crosslinking agents, pigments, paint additives, and the like. In particular, the content of the chlorinated polyolefin is 70 to 100% by weight, particularly 90 to 1% by weight, based on the total solid content contained in the first primer at the time of coating.
A range of 00% by weight is suitable. If the content of the chlorinated polyolefin is less than 70% by weight, adhesion to a polyolefin molded article (substrate) is undesirably reduced.

The solid content of the first primer at the time of coating is preferably 1 to 10% by weight, particularly preferably 3 to 5% by weight.

In the present invention, the first primer may be coated on the entire surface of the polyolefin molded product,
In particular, for example, the surface of a polyolefin molded product located near an inlet (generally referred to as a “gate portion”) for injecting a polyolefin melted during injection molding into a mold is compared with other portions. It is preferable that the adhesion to the coating film is not sufficient and at least the first primer is applied to such hardly adhered portions.

The application of the first primer to the polyolefin molded product can be performed by, for example, air spray coating, airless spray coating, dip coating, brush coating, or the like. In addition, painting can be performed by gently rubbing the surface of the object to be coated with a waste or gauze impregnated with the first primer. The coating thickness is 0.01 to 2μ.
m, especially in the range of 0.05 to 0.5 μm is suitable,
Even if the second primer is applied thereon, it is preferable because a step does not easily occur at the boundary with the portion where the first primer is not applied.

In the present invention, a first primer is applied to the entire surface or a part of a polyolefin molded product, and the coating film is left at room temperature as appropriate, or dried at room temperature to 140 ° C. for 1 to 40 minutes to dry or dry. After curing, apply the second primer. The second primer is to be applied to a polyolefin molded product on which the first primer is partially or entirely applied, and is an organic solvent-based liquid composition containing a chlorinated polyolefin in a solid content ratio of less than 70% by weight.

The second primer contains a chlorinated polyolefin, another paint resin (including a cross-linking agent) and / or a pigment component, and an organic solvent. A liquid paint prepared by blending can be used. The chlorinated polyolefin used in the second primer, other paint resins, a cross-linking agent, a pigment component, an organic solvent, and the like can be preferably used as those exemplified in the first primer, Description is omitted.

The second primer is prepared so that the content of the chlorinated polyolefin is lower than that of the first primer. Based on this point, the two primers can be clearly distinguished. That is, the content of the chlorinated polyolefin in the second primer is preferably less than 70% by weight, and particularly preferably in the range of 30 to 60% by weight, based on the total solid content contained in the second primer at the time of coating. When the content of the chlorinated polyolefin is 70% by weight or more, the adhesion to the overcoat film decreases, which is not preferable.

The solid content of the second primer during coating is preferably 10 to 40% by weight, particularly preferably 20 to 30% by weight. The second primer is preferably applied to the entire surface of the polyolefin molded product on which the first primer is applied partially or entirely, and may be applied by, for example, air spray coating, airless spray coating, dip coating, brush coating, or the like. The coating thickness is 5-30 μm, especially 10
A range of from 15 to 15 μm is suitable.

After applying the second primer, the coated film is left at room temperature as appropriate, or is dried or cured by heating at room temperature to 140 ° C. for 1 to 40 minutes, and then overcoated on the coated surface of the second primer. Apply paint.

As the overcoat paint, known solid color paints, metallic paints and clear paints can be used, and these can be applied as appropriate. A solid color paint is a thermosetting paint or a thermoplastic paint containing a resin composition, a solid color pigment and an organic solvent, and a metallic paint contains a resin composition, a metallic pigment (including a light interference pigment) and an organic solvent. The clear paint is a thermosetting paint or a thermoplastic paint that forms a colorless transparent or colored transparent coating containing a resin composition and an organic solvent, and these are all known. Paint can be used.

As a method of forming a top coat by using these top coats, for example, a single-layer coat by one coat finish with a solid color paint, a solid color paint or a metallic paint, and then a clear paint are applied. There is a method of finishing with a multi-layer coating film by two-coat finishing which is appropriately applied.

[0022]

Advantages of the Invention After sequentially applying the above-mentioned first primer and second primer having different chlorinated polyolefin contents to the polyolefin molded article, and then applying the top coat, the adhesion between the polyolefin molded article and the top coat is obtained. Could be improved. First
After coating the primer on the surface of the polyolefin molded product located at the `` gate portion '' which is referred to as the hardly adhered portion, and then applying the second primer, the hardly adhered portion has a polyolefin molded body and a topcoat film. Adhesion could be improved.

[0023]

EXAMPLES Examples and comparative examples according to the present invention will be described below. Parts and percentages are based on weight, and the thickness of the coating is for the cured coating. 1. Sample 1) Coating object a: A polypropylene plate having a gate portion (manufactured by Mitsubishi Yuka Co., Ltd., trade name “YK-1”, size 7.5 × 15.
0 × 0.3 cm) was degreased with pure water and isopropyl alcohol. 2) First primer a: "Supercron 892L" (manufactured by Nippon Paper Industries, Ltd.)
Product name, chlorinated polypropylene resin with a chlorination rate of 20%,
An organic solvent solution obtained by mixing and dissolving 15 parts (solids content: 3 parts) in 70 parts of toluene and 15 parts of xylene, having a number average molecular weight of 25,000 and a solid content of 20%.
The content of chlorinated polypropylene resin in the solid content is 100
%. 3) Second primer a: 73 parts of "Supercron 892L" (solid content 14.
6 parts), "Beccosol EZ-3530-80" (manufactured by Dainippon Ink and Chemicals, Inc., trade name, alkyd resin,
27 parts (solid content: 21.6 parts)
An organic solvent solution obtained by mixing and dissolving in an equal weight mixed solvent of toluene and xylene, having a viscosity of 14 seconds / ford cup # 4
At / 20 ° C., the content of chlorinated polypropylene resin in the solid content is 40%. 4) Primer for single layer a: 73 parts of "Supercron 892L" (solid content 14.
6 parts) and 27 parts (21.6 parts of solid content) of "Beccosol EZ-3530-80" are mixed and dissolved in an equal weight mixed solvent of toluene and xylene.
At 4 seconds / ford cup # 4/20 ° C., the content of chlorinated polypropylene resin in the solid content is 40% (for comparison). b: "Supercron 892L" (manufactured by Nippon Paper Industries,
Product name, chlorinated polypropylene resin with a chlorination rate of 20%,
An organic solvent solution obtained by mixing and dissolving 15 parts (solids content: 3 parts) in 70 parts of toluene and 15 parts of xylene, having a number average molecular weight of 25,000 and a solid content of 20%.
The content of chlorinated polypropylene resin in the solid content is 100
% (For comparison).

2. EXAMPLES AND COMPARATIVE EXAMPLES Example 1 A first primer (a) was coated on a half surface of a substrate including a gate portion with a brush so as to have a thickness of 0.3 μm, and allowed to stand at room temperature for 5 minutes. Second primer (a) on the entire surface of the product
Was applied to a film thickness of 13 μm by air spray, left at room temperature for 10 minutes, and then heated at 70 ° C. for 15 minutes to dry both coating films. Then, a top coat for plastic (“SOFLEX 200”, manufactured by Kansai Paint Co., Ltd., trade name) was applied on the entire surface to be coated by air spray so as to have a film thickness of 30 μm, and left at room temperature for 10 minutes. 70
C. for 30 minutes to dry the top coat. The performance test results of the multilayer coating film thus formed show that both the adhesion and the water resistance of the top coating film at the gate and other portions are ○, and the coating boundary of the first primer (a) was No step was observed visually.

Comparative Example 1 A single-layer primer (a) was applied to the entire surface of an object to be coated by air spray so as to have a thickness of 13 μm, left at room temperature for 10 minutes, and then heated at 70 ° C. for 15 minutes. The film was dried, and then a plastic top coat (“SOFLEX 200”) was applied by air spray to a thickness of 30 μm on the entire surface to be coated, left at room temperature for 10 minutes, and then heated at 70 ° C. The coating was heated for 30 minutes to dry the top coat. As a result of the performance test of the multilayer coating film thus formed, the adhesion between the coating material and the primer coating film at the gate portion and the water resistance of the multilayer coating film were x. Comparative Example 2 A single-layer primer (b) was applied to the entire surface of the object by air spray so as to have a film thickness of 13 μm, left at room temperature for 10 minutes, and then heated at 70 ° C. for 15 minutes to dry the coating film. Then, apply a plastic top coat ("Soflex 200") to the entire surface to be coated by air spray so as to have a thickness of 30 μm, leave at room temperature for 10 minutes, and then heat at 70 ° C. for 30 minutes. Then, the top coat was dried. The performance test results of the multi-layer coating film thus formed show that the adhesion and water resistance between the top coating film and the primer are ×
Met.

The performance test method is as follows. Interlayer adhesion: Cut the multi-layer coating film to reach the substrate with a cutter, and make 100 pieces of 2 mm x 2 mm gobang,
This is a result of examining the number of remaining gobang-like coatings on the surface of which a sticky cellophane tape was stuck and the tape was rapidly peeled off at 20 ° C. ○: 100 remaining, △: 99-9
X indicates that 89 or less are left.

Water resistance: The results were obtained by immersing the test plate in hot water at 40 ° C. for 240 hours, drying it, and then performing an adhesion test in the same manner as the above-mentioned interlayer adhesion. O indicates that 100 pieces remain, Δ indicates that 99 to 90 pieces remain, and X indicates that 89 or less remain.

Continued on the front page F term (reference) 4D075 AE03 CA13 DA23 DB36 DC13 EA07 EA41 EB07 EB13 EB22 EB32 EB35 EB38 EB56 4J038 BA041 BA042 CB021 CB022 CB031 CB032 CB051 CB052 CB121 GA CB101 CB101 CB101 CB101 CB101 CB101 MA14 NA12 PC08

Claims (2)

[Claims] 1. A polyolefin molded article comprising a first primer containing at least 70% by weight of chlorinated polyolefin at a solid content ratio and 70% by weight of chlorinated polyolefin at a solid content ratio.
A method for coating a polyolefin molded article, comprising sequentially applying a second primer containing less than 10%, and then applying a top coat. 2. The coating method according to claim 1, wherein the solid content of the first primer at the time of coating is 1 to 10% by weight.