JP4003017B2 - Coating method of polyolefin moldings - Google Patents

Description

【００５０】
【発明の効果】
（１）ポリオレフィン成型体に、２Ｃ１Ｂ方式でパール仕上げ塗装することが可能になった。
【００５１】
（２）従来の４Ｃ２Ｂ方式や３Ｃ１Ｂ方式に比べ、塗膜性能は同等又はそれ以上であり、しかも塗装ラインの占有面積が小さくてすみ、生産効率が向上し、コストダウンとなるので好ましい。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a novel coating method capable of applying a pearl finish to a polyolefin molded body by a 2-coat 1-bake (hereinafter referred to as “2C1B”) method.
[0002]
[Prior art]
The pearl finish of a polyolefin molding, for example, a white pearl finish, is conventionally applied by a primer containing a chlorinated polyolefin resin, a hydroxyl group-containing polyester resin, a white base paint containing a hydroxyl group-containing acrylic resin and a melamine resin, or a hydroxyl group-containing polyester. It is common to paint a pearl base paint containing a resin or a hydroxyl group-containing acrylic resin and a melamine resin and a clear paint containing a hydroxyl group-containing acrylic resin and a melamine resin in a 4-coat 2-bake (hereinafter referred to as “4C2B”) method. Is. It has also been proposed to apply a white primer containing a chlorinated polyolefin resin, the pearl base paint, and the clear paint in a three-coat one-bake (hereinafter referred to as “3C1B”) method. However, these methods are not preferable because each of them has a process of 3 coats or more, which occupies a large area of the coating line, lowers the production efficiency, and increases the cost.
[0003]
[Problems to be solved by the invention]
An object of the present invention is to provide a method capable of performing pearl finish coating of a polyolefin molded body by a 2C1B system in place of the conventional 4C2B system or 3C1B system.
[0004]
[Means for Solving the Problems]
The present inventor has eagerly studied to develop a new coating method that enables the pearl finish coating of a polyolefin molded body, particularly white pearl finish, to be replaced with the conventional 4C2B method or 3C1B method by the 2C1B method. As a result, using a colored primer with a specific composition that combines the performance of both a primer and a white base paint, and using a pearl-based clear paint that combines the performance of both a pearl base paint and a clear paint, the 2C1B system By painting, a coating method having performance equivalent to or better than the multilayer coating film obtained by the above 4C2B method or 3C1B method and having a simplified process can be established, and the present invention is completed. It was.
[0005]
That is, the present invention comprises (A) a hydroxyl group-containing polyester resin, (B) a hydroxyl group-containing acrylic-modified chlorinated polyolefin resin, and (C) an aminoaldehyde resin, and these blending ratios are those three components. Based on the total solid content of (A) component 10 to 70% by weight, (B) component 10 to 70% by weight, (C) component 10 to 40% by weight of a colored primer containing a resin component, The present invention relates to a method for coating a polyolefin molded article, characterized in that a pearl clear coating is applied to an uncured coating surface, and then both the coating films are heated and cured simultaneously.
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Below, the coating method of this invention is demonstrated more concretely.
[0007]
The polyolefin molded body, which is the object to be coated in the present invention, is an arbitrary shape of a resin obtained by polymerizing one or more selected from olefins having 2 to 10 carbon atoms such as ethylene, propylene, butylene and hexene. , Formed into a size, such as a bumper, spoiler, front apron, fender, and the like.
[0008]
In the coating method of the present invention, the colored primer (I) is first applied to such an object to be coated.
[0009]
The colored primer (I) is a colored primer mainly composed of a resin component comprising (A) a hydroxyl group-containing polyester resin, (B) a hydroxyl group-containing acrylic-modified chlorinated polyolefin resin, and (C) an aminoaldehyde resin.
[0010]
The hydroxyl group-containing polyester resin (A) is obtained by subjecting a polybasic acid and a polyhydric alcohol to an esterification reaction or a transesterification reaction by a conventional method. A polybasic acid is a compound having two or more carboxyl groups in one molecule. For example, phthalic acid, isophthalic acid, terephthalic acid, succinic acid, adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, dimethyl isophthalate Dimethyl terephthalate, tetrahydrophthalic acid, hexahydrophthalic acid, hexahydroisophthalic acid, hexahydroterephthalic acid, het acid, maleic acid, fumaric acid, itaconic acid, pyromellitic acid, trimellitic acid, and their anhydrides Can be mentioned. Polyhydric alcohol is a compound having two or more hydroxyl groups in one molecule. For example, ethylene glycol, propylene glycol, butylene glycol, hexanediol, diethylene glycol, triethylene glycol, dipropylene glycol, neopentyl glycol, Examples include ethylene glycol, glycerin, trimethylol ethane, trimethylol propane, pentaerythritol and the like.
[0011]
The polyester resin (A) has a hydroxyl value of 20 to 200 mgKOH / g, particularly 35 to 150 mgKOH / g, an acid value of 0 to 50 mgKOH / g, particularly 1 to 30 mgKOH / g, and a number average molecular weight of 1,000 to 30, 000, in particular within the range of 2,000 to 20,000.
[0012]
The hydroxyl group-containing acrylic-modified chlorinated polyolefin resin (B) is, for example, a monomer component containing a hydroxyl group-containing acrylic monomer and a chlorinated polyolefin chlorinated within a range of 5 to 50% by weight of chlorine content. And obtained by graft copolymerization.
[0013]
The monomer component copolymerized with the chlorinated polyolefin contains at least a hydroxyl group-containing acrylic monomer and other acrylic monomers. Among these, examples of the hydroxyl group-containing acrylic monomer include C2-C8 hydroxyalkyl esters of acrylic acid or methacrylic acid such as hydroxyethyl acrylate, hydroxyethyl methacrylate, hydroxypropyl acrylate, and hydroxypropyl methacrylate. The hydroxyl group-containing acrylic monomer introduces a functional group (hydroxyl group) into the component (B) for chemically reacting with the aminoaldehyde resin (C) as a crosslinking agent to form a cured coating film. It is preferably contained in the monomer component in an amount of 5 to 30% by weight, and usually used so that the hydroxyl value of the component (B) is in the range of 20 to 150 mgKOH / g, particularly 30 to 130 mgKOH / g. Is suitable.
[0014]
Other acrylic monomers that can be used in combination with the hydroxyl group-containing acrylic monomer include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth) acrylate, and hexyl (meth) acrylate. C1-20 alkyl esters of acrylic acid or methacrylic acid such as lauryl (meth) acrylate. Furthermore, monomers other than these, such as styrene, vinyl toluene, (meth) acrylic acid, glycidyl (meth) acrylate, and acrylonitrile can also be used in combination.
[0015]
The chlorinated polyolefin to be graft-copolymerized with the monomer component is a component for improving the adhesion between the polyolefin molded body to be coated and the colored primer (I) coating film, and the chlorine content is the monomer content. It is preferable to be within the range of 5 to 50% by weight, particularly 10 to 40% by weight, based on the chlorinated polyolefin before copolymerization with the components.
[0016]
Examples of the chlorinated polyolefin include polypropylene, polybutene-1, polypentene-1, 4-methylpentene, low density polyethylene, high density polyethylene, ethylene-propylene copolymer, and ethylene-propylene-diene copolymer. It is done.
[0017]
Graft copolymerization of the monomer component and chlorinated polyolefin is performed by solution polymerization. The organic solvent to be used is preferably an aromatic hydrocarbon solvent such as toluene or xylene. In addition, an ester solvent, a ketone solvent, an alcohol solvent, a chlorine solvent, an aliphatic hydrocarbon solvent, or a cyclic aliphatic hydrocarbon solvent. An organic solvent such as a solvent can be used in combination. In the copolymerization, a polymerization initiator such as a peroxide initiator such as benzoyl peroxide or an azo initiator such as azobisisobutyronitrile can be used. Quinones such as hydroquinone may be used as a polymerization terminator. In this copolymerization method, it is preferable that the chlorinated polyolefin is appropriately dissolved and diluted with an organic solvent, added with an initiator and then heated, and then reacted while gradually adding monomer components.
[0018]
The composition ratio between the monomer component and the chlorinated polyolefin in the graft copolymerization reaction can be arbitrarily selected according to the desired performance of the coating film. For example, the monomer is based on the total amount of both components. The components are suitably in the range of 30 to 90% by weight, in particular 40 to 80% by weight, and the chlorinated polyolefin in the range of 70 to 10% by weight, in particular 60 to 20% by weight.
[0019]
The aminoaldehyde resin (C) is a cross-linking agent of the above components (A) and (B), for example, one or more amino acids selected from melamine, urea, benzoguanamine, acetoguanamine, steroguanamine, spiroguanamine and the like. A component obtained by reacting formaldehyde with a methylol product and further etherified by reacting one or more alcohols selected from monoalcohols having 1 to 10 carbon atoms can be mentioned. In (C), an imino group may remain, and a methylol group and an ether group may be mixed in the same molecule. The molecular weight of (C) is suitably in the range of 200 to 3,000.
[0020]
The resin component in the colored primer (I) used in the coating method of the present invention is composed of (A) a hydroxyl group-containing polyester resin, (B) a hydroxyl group-containing acrylic-modified chlorinated polyolefin resin, and (C) an aminoaldehyde resin. The mixing ratio of these components is a solid content ratio based on the total amount of these three components, and the component (A) is 10 to 70% by weight, preferably 20 to 60% by weight, and the component (B). Is 10 to 70% by weight, preferably 20 to 60% by weight, and component (C) is 10 to 40% by weight, preferably 15 to 35% by weight.
[0021]
The colored primer (I) is a resin component composed of (A) a hydroxyl group-containing polyester resin, (B) a hydroxyl group-containing acrylic-modified chlorinated polyolefin resin and (C) an aminoaldehyde resin, and a colorant mixed in an organic solvent. It can be prepared by dissolving or dispersing.
[0022]
Examples of the colorant include inorganic pigments such as titanium oxide, zinc white, carbon black, cadmium red, molybdenum red, chromium yellow, chromium oxide, Prussian blue, and cobalt blue; azo pigments, phthalocyanine pigments, quinacridone pigments, isoindoline pigments, Color pigments for paints such as organic pigments such as selenium pigments and perylene pigments can be used. Among these, by using a white pigment such as titanium oxide or zinc white to make a white-colored primer (I), when a pearl clear paint is applied to the coated surface, a white pearl finish coating film is obtained.
[0023]
The blending amount of the colorant is suitably 0.5 to 160 parts by weight, particularly 60 to 100 parts by weight, per 100 parts by weight of the resin component composed of the components (A), (B) and (C).
[0024]
Examples of the organic solvent include hydrocarbon solvents such as hexane, heptane, xylene, toluene, and cyclohexane; ester solvents such as methyl acetate, ethyl acetate, ethylene glycol monomethyl ether, and diethylene glycol monomethyl ether; isopropyl ether, ethylene glycol Ether solvents such as monomethyl ether and diethylene glycol monobutyl ether; alcohol solvents such as ethyl alcohol, butyl alcohol and hexyl alcohol; ketone solvents such as methyl isobutyl ketone, methyl ethyl ketone, isophorone and acetophenone;
[0025]
If necessary, the colored primer (I) can be blended with a surface conditioner, a curing accelerating catalyst, a repellency inhibitor, an ultraviolet absorber, an antioxidant, a quencher, and the like.
[0026]
The pearl clear paint (II) is a paint to be applied to the surface of the uncured colored primer (I). Specifically, the vehicle component and the pearl pigment are mixed in an organic solvent and dissolved or dispersed. Can be prepared.
[0027]
The vehicle component in the pearl-based clear paint (II) is composed of a base resin and a crosslinking agent. Examples of the base resin include an acrylic resin having a functional group such as a hydroxyl group, a carboxyl group, and an epoxy group, an alkyd resin, a polyester resin, and a fluororesin. Moreover, as a crosslinking agent, the melamine resin which can react with these functional groups of base resin, an epoxy group containing compound or resin, a carboxyl group containing compound or resin, a polyisocyanate compound, a block polyisocyanate compound etc. are mention | raise | lifted. The ratio of these base resin and cross-linking agent is, for example, based on the total amount of both components, 50-90 wt. 20% by weight is suitable.
[0028]
The pearl pigment is a flake pigment that exhibits a pearl tone color due to light interference, and examples thereof include mica and mica whose surface is coated with a metal oxide such as titanium oxide or iron oxide. These pigments have a longitudinal dimension of about 1 to 30 μm, particularly 5 to 25 μm, and a thickness of about 0.05 to 5 μm, particularly 0.1 to 3 μm. The blending amount of the pearl pigment is preferably 1 to 50 parts by weight, particularly 5 to 20 parts by weight, per 100 parts by weight (solid content) of the vehicle component.
[0029]
Examples of the organic solvent include hydrocarbon solvents such as hexane, heptane, xylene, toluene, and cyclohexane; ester solvents such as methyl acetate, ethyl acetate, ethylene glycol monomethyl ether, and diethylene glycol monomethyl ether; isopropyl ether, ethylene glycol Ether solvents such as monomethyl ether and diethylene glycol monobutyl ether; alcohol solvents such as ethyl alcohol, butyl alcohol and hexyl alcohol; ketone solvents such as methyl isobutyl ketone, methyl ethyl ketone, isophorone and acetophenone;
[0030]
In the coating method of the present invention, for example, the coating viscosity of the colored primer (I) is adjusted to 15 to 20 seconds with a Ford Cup # 4 (20 ° C.) on a polyolefin molded body (object), and the dry film thickness is 15 to After coating with air spray, airless spray, electrostatic coating, etc. so as to be 25 μm, and then let stand at room temperature for about 1 to 20 minutes, the pearl clear paint (II) is applied to the uncured coating surface. Adjust the coating viscosity of clear paint (II) to 15-20 seconds with Ford Cup # 4 (20 ° C) and apply with air spray, airless spray, electrostatic coating, etc. so that the dry film thickness is 20-60μm. Then, after leaving at room temperature for about 1 to 20 minutes, heating at 80 to 200 ° C., preferably 100 to 140 ° C. for about 10 to 40 minutes, and coloring primer (I) and clear paint (II) Simultaneous coating of both coatings In response, the 2C1B method in which a cured coating film is formed is carried out.
[0031]
【Example】
Hereinafter, the present invention will be described more specifically with reference to production examples, examples and comparative examples. Unless otherwise specified, “parts” and “%” mean “parts by weight” and “% by weight”, respectively.
[0032]
Production Example 1 Preparation of article to be coated A polypropylene resin molded board for bumper (size: 15 x 10 x 1 cm) was used, and the surface was wiped clean with gauze soaked with isopropyl alcohol to make the article to be coated. .
[0033]
Production Example 2 Preparation of colored primer (I-1)
(1) A phthalic anhydride, hexahydrophthalic anhydride, adipic acid, neopentyl glycol, 1,6-hexanediol and trimethylolpropane are used to conduct an esterification reaction by a usual method, and a solid content is 60%. A xylene solution of a hydroxyl group-containing polyester resin was obtained. The resin has a hydroxyl value of 103 mgKOH / g, an acid value of 5 mgKOH / g, and a number average molecular weight of 3,000.
[0034]
(2) To 40 parts of chlorinated polypropylene (chlorination rate 29%), 60 parts of a monomer component consisting of hydroxyethyl methacrylate, methyl methacrylate and n-butyl methacrylate were grafted together in toluene in the presence of benzoyl peroxide. Polymerization was performed to obtain a hydroxyl group-containing acrylic-modified chlorinated polyolefin resin having a solid content of 40%. The hydroxyl value of this resin is 56 mgKOH / g.
[0035]
(3) 50 parts of the 60% hydroxyl group-containing polyester resin solution (solid content 30 parts), 125 parts of the 40% hydroxyl group-containing acrylic-modified chlorinated polyolefin resin (solid content 50 parts), 60% aminoaldehyde resin ("Uban 20SE") (Mitsui Toatsu Co., Ltd., trade name, butyl etherified melamine resin, molecular weight 1,500)) 33 parts (solid content 20 parts) and titanium white pigment 100 parts are mixed and dispersed in a solvent (xylene), and the viscosity is 17 seconds ( Ford cup # 4/20 ° C.) to obtain a colored primer (I-1) for the present invention.
[0036]
Production Example 3 Preparation of Colored Primer (I-2) 67 parts of 60% hydroxyl group-containing polyester resin solution obtained in Production Example 2 (1) (solid content 40 parts), 40% hydroxyl group obtained in Production Example 2 (2) 100 parts of acrylic-modified chlorinated polyolefin resin (40 parts solids), 33 parts of 60% aminoaldehyde resin (“Uban 20SE”) (20 parts solids) and 100 parts of titanium white pigment are mixed and dispersed in a solvent (xylene). The viscosity was adjusted to 17 seconds (Ford Cup # 4/20 ° C.) to obtain a colored primer (I-2) for the present invention.
[0037]
Production Example 4 Preparation of Colored Primer (I-3) 33 parts of 60% hydroxyl group-containing polyester resin solution obtained in Production Example 2 (1) (20 parts solids), 40% hydroxyl group obtained in Production Example 2 (2) 150 parts of acrylic-modified chlorinated polyolefin resin (solid content 60 parts), 33 parts of 60% aminoaldehyde resin (“Uban 20SE”) (solid content 20 parts) and 100 parts of titanium white pigment are mixed and dispersed in a solvent (xylene). The viscosity was adjusted to 17 seconds (Ford Cup # 4/20 ° C.) to obtain a colored primer (I-3) for the present invention.
[0038]
Production Example 5 Preparation of colored primer (I-4)
(1) Graft-copolymerize 70 parts of monomer component consisting of hydroxyethyl methacrylate, ethyl methacrylate and methyl methacrylate in 30 parts of chlorinated polypropylene (chlorination rate 25%) in toluene in the presence of benzoyl peroxide. Thus, a hydroxyl group-containing acrylic-modified chlorinated polyolefin resin having a solid content of 40% was obtained. The hydroxyl value of this resin is 47 mgKOH / g.
[0039]
(2) 33 parts of the 60% hydroxyl group-containing polyester resin solution obtained in Production Example 2 (1) (solid content 20 parts), 150 parts of the 40% hydroxyl group-containing acrylic modified chlorinated polyolefin resin (solid content 60 parts), 60% Aminoaldehyde resin (“Uban 20SE”) 33 parts (solid content 20 parts) and titanium white pigment 100 parts were mixed and dispersed in a solvent (xylene), adjusted to a viscosity of 17 seconds (Ford Cup # 4/20 ° C.), A colored primer (I-4) for the present invention was obtained.
[0040]
Production Example 6 Preparation of Colored Primer (I-5) 133 parts of 60% hydroxyl group-containing polyester resin solution obtained in Production Example 2 (1) (solid content 80 parts), 33 parts of 60% aminoaldehyde resin (“Uban 20SE”) (Solid content 20 parts) and titanium white pigment 100 parts are mixed and dispersed in a solvent (xylene), adjusted to a viscosity of 17 seconds (Ford Cup # 4/20 ° C.), and a colored primer (I-5) for comparison is prepared. Obtained.
[0041]
Production Example 7 Preparation of Pearl Clear Paint (II-1) “Soflex No. 1611” (Kansai Paint Co., Ltd., trade name, hydroxyl value 100 mg KOH / g, hydroxyl group-containing acrylic resin 70 having a number average molecular weight of 17,000 Per 100 parts (solid content) of plastic and clear paint for plastics containing 30 parts of butylated melamine resin (solid content), surface coating with titanium oxide, "Exterior Mearlin Fine Pearl", trade name, manufactured by Marl Corporation 1 part of mica, longitudinal dimension 5-25 μm, thickness 0.1-1 μm is mixed and dispersed, adjusted to a viscosity of 20 seconds (Ford Cup # 4/20 ° C.), and pearl clear paint (II- 1) was obtained.
[0042]
Examples 1 to 4 and Comparative Example 1
The colored primer obtained in any one of Production Examples 2 to 6 was applied to the object obtained in Production Example 1 by air spray so that the dry film thickness was 20 μm, and allowed to stand at room temperature for 10 minutes. On the coated surface, the pearl clear paint obtained in Production Example 7 was applied by air spray so that the dry film thickness was 30 μm, allowed to stand at room temperature for 10 minutes, and then heated at 120 ° C. for 30 minutes. The film was cured simultaneously. The performance of the obtained coating film was examined by the following test method.
[0043]
Test method Initial adhesion: Within 24 hours after forming the coating film, using a cutter, cut 11 pieces perpendicular to the coating surface at intervals of 2 mm so as to reach the substrate, and the size of 2 mm × 2 mm 100 pieces were made, adhesive cellophane tape was attached to the coated surface, and the coated surface was observed after abrupt peeling. ○ indicates that no galvanic coating film is peeled off, △ indicates that 1-10 galvanic coating films are peeled off, and x indicates that 11 or more galvanic coating films are peeled off. Each of them is shown.
[0044]
Water resistance: The coated surface after the test piece was immersed in warm water at 40 ° C. for 240 hours was observed. ○ indicates that no glossiness, blistering, adhesion deterioration, etc. are observed, △ indicates that glossiness, blistering, adhesion deterioration, etc. are slightly observed, × indicates that there are many glossiness, swelling, adhesion deterioration, etc. It shows that each.
[0045]
Acid resistance: 0.2 cc of sulfuric acid aqueous solution having a concentration of 3% was spot-dropped on the coated surface of the test piece, left at 20 ° C. and a humidity of 75% RH for 4 hours, washed, and then the coated surface was observed. ○ indicates that no lustre, bulge, etc. are observed, △ indicates that some lustre, bulges, etc. are observed, and x indicates that many lustre, bulges, etc. are observed.
[0046]
Alkali resistance: 0.2 cc of caustic soda aqueous solution having a concentration of 1% was spot-dropped on the coated surface of the test piece, left at 20 ° C. and a humidity of 75% RH for 4 hours, washed with water, and the coated surface was observed. ○ indicates that no lustre, bulge, etc. are observed, △ indicates that some lustre, bulges, etc. are observed, and x indicates that many lustre, bulges, etc. are observed.
[0047]
Weather resistance: Using a material specified in “Sunshine Weather Omometer, JIS B 7753” (Sunshine carbon arc type weather resistance tester), the coating surface and adhesion were observed after 1,200 hours. In the observation of the coated surface, ○ indicates that no gloss, bulge, etc. are observed, △ indicates that some gloss, bulges, etc. are observed, and X indicates that many gloss, bulges, etc. are observed. . Adhesion was performed in the same manner as the above initial adhesion.
[0048]
Table 1 shows the test results of the paint used and the coating film performance.
[0049]
[Table 1]

[0050]
【The invention's effect】
(1) A pearl finish coating can be applied to a polyolefin molded body by the 2C1B method.
[0051]
(2) Compared to the conventional 4C2B method and 3C1B method, the coating film performance is equal to or higher than that, and the area occupied by the coating line is small, so that the production efficiency is improved and the cost is reduced.

Claims (1)

The polyolefin molded body is composed of (A) a hydroxyl group-containing polyester resin, (B) a hydroxyl group-containing acrylic-modified chlorinated polyolefin resin, and (C) an aminoaldehyde resin, and the blending ratio thereof is based on the total solid content of these three components. (A) Component 10 to 70% by weight, (B) Component 10 to 70% by weight, (C) Component 100 to 100 % by weight, and white pigment 0.5 to 160 parts by weight A coating method of a polyolefin molded body, characterized in that a white-colored colored primer is applied, a pearl clear paint is applied to the uncured coating surface, and then both the coating films are heated and cured simultaneously.