JPH06142606A - Coating method for polyolefin rein molded good - Google Patents

Abstract

PURPOSE:To enable direct coating and to assure excellent coating efficiency and various kinds of coating film performance, such as durability, by forming an under coat layer consisting of specific components on the surfaces of resin molded goods, then forming a top coat layer consisting of specific components on the surface of this layer. CONSTITUTION:The resin molded goods are subjected to coating by forming the under coat layer on these goods, then forming the top coat layer on the surface thereof. The under coat layer is colored by coloring pigments and is formed by applying a coating material prepd. by incorporating the following two components A, B at 95/5 to 50/50 weight ratios into the coating material, then incorporating the following component C therein at 100/0 to 50/50 weight ratios. On the other hand, the top coat layer is colored by coloring pigments and is formed by applying a coating material prepd. by incorporating the following two components A, C at 90/10 to 50/50 weight ratios as the main components of a binder into the coating material. A: a polyol resin having 20 to 150mgKOH/ g hydroxyl group value. B: a chlorinated polyolefin resin having <=50wt.% chlorine content. C: a cross-linkable resin reacting with a hydroxyl group.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for coating a polyolefin resin molded product.

[0002]

2. Description of the Related Art Generally, polyolefin resin materials, which are excellent in chemical resistance, water resistance, moldability, etc., and are lightweight and inexpensive, are widely used as industrial materials such as household appliances and automobile parts. However, since it has a low polarity and is crystalline, ordinary paint cannot be applied as it is and painting is difficult.

Therefore, when the above-mentioned polyolefin resin material is coated, the surface of the polyolefin resin material is subjected to pretreatment such as flame treatment, corona discharge treatment, plasma treatment, and chromic acid mixture treatment. ,
The surface of the polyolefin resin material is preliminarily activated and highly polarized to improve the adhesion of the coating material. However, these pretreatment methods are complicated in process, enormous capital investment and time loss, and it cannot be said that the improvement of the adhesiveness of the paint is sufficient, and the shape of the object to be coated may not be sufficient. Can even be difficult to apply.

On the other hand, as a method of coating without these special pretreatments, the surface of a polyolefin resin material is currently washed with a solvent such as 1,1,1-trichloroethane and a special primer having good adhesion is coated. After that, a method of applying a paint having excellent coating film performance is used. However, in this method, a lot of time and labor are required to coat the dedicated primer, and the dedicated primer is expensive, so that the total cost is increased.

In order to solve these drawbacks, a chlorinated polyolefin resin having a chlorine content of 50% by weight or less and having a strong adhesion to the polyolefin resin material is used as a coating composition for a polyolefin resin material. A composition comprising an alkyd resin or an acrylic resin has been proposed in order to improve the weather resistance, solvent resistance and the like, which are drawbacks of the chlorinated polyolefin resin alone.

For example: a. JP-A-57-200438 discloses a mixture of a chlorinated polyolefin resin and an acrylic resin.

B. JP-A-59-27968 and JP-A-62-149734 disclose a resin system in which a copolymer of a chlorinated polyolefin resin and an acrylic monomer is combined with an isocyanate compound.

C. Japanese Patent Laid-Open No. 62-18434 discloses
Resin system in which a copolymer of chlorinated polyolefin resin, acrylic monomer and chlorinated polydiene is combined with an isocyanate compound.

[0009]

However, the above-mentioned a
In the resin mixture of 1, the chlorine content must be 35% by weight or less, and the resin solution easily separates into two phases, and when used as a paint, dispersion stability of the pigment, gloss of the coating film, adhesion, It has drawbacks such as insufficient solvent resistance, weather resistance and physical properties.

In the resin system of b above, the stability of the resin solution is better than that of a, but the gloss and weather resistance of the coating film are insufficient.

Even in the resin system of the above c, the solvent resistance and weather resistance are insufficient, and it has not reached the stage of practical use.

All of the above a, b, and c are limited to those that do not require severe weather resistance for coating films such as home electric appliances and automobile interior parts, and are severe for automobile bumpers and the like. It is not suitable for exterior parts that require weather resistance.

In order to solve the above-mentioned drawbacks, the inventors of the present invention have already disclosed in JP-A-4-132783 that a chlorinated polyolefin, an acrylic monomer having a hydroxyl group or an ethylene monomer copolymerizable therewith. A mixture with a monomer, and a polymer resin obtained by polymerizing a polyester prepolymer having an ethylenic double bond at the end as a main component, a coating main agent, and a coating curing agent having a polyfunctional isocyanate compound as a main component. Disclosed is a method for coating a polyolefin resin molded product by coating a mixed two-component curable coating on the surface of the polyolefin resin molded product.

The present invention generally eliminates the conventional drawbacks and makes it possible to significantly reduce the total cost required for coating.

However, when a solid color such as white or yellow which is difficult to obtain a sufficient hiding power is applied to a material colored in black, it is necessary to add a large amount of a coloring pigment, and therefore, a high gloss and dullness is obtained. It is difficult to obtain the finished appearance.
In addition, since it is a two-component curing type paint, it is necessary to mix the main agent and the curing agent before coating, and further, the time from the addition of the curing agent until the curing reaction proceeds to some extent and the coating becomes difficult. Since it has a so-called pot life, it has one aspect of being restricted in work.

The present invention has been made in view of the above circumstances, and is directly applied to the surface of a polyolefin resin to obtain adhesion, weather resistance, chemical resistance, solvent resistance, finished appearance and concealment. While giving excellent coating performance,
It is an object of the present invention to provide a method for coating a polyolefin-based resin molded product, which has no restrictions in coating work and can be easily performed.

[0017]

Means for Solving the Problems As a result of intensive studies to achieve the above object, the present inventors have found that a polyol resin, a chlorinated polyolefin resin, and a crosslinkable resin capable of reacting with a hydroxyl group are essential components. Adhesion to the surface of a polyolefin resin material by applying an undercoat paint that has excellent adhesion and hiding power to the surface of a polyolefin resin material and a topcoat paint that has a low content of color pigments The present invention finds a coating method for a polyolefin resin molded article which has excellent physical coating performance such as excellent weather resistance, chemical resistance, solvent resistance, etc. and has excellent coating appearance and completes the present invention. It was

That is, according to the present invention, the following components (A) and (B) are blended and / or graft-copolymerized with a coloring pigment, and the weight ratio is (A) / (B) = It is contained in the range of 95/5 to 50/50, and further contains the following component (C) in a weight ratio of {component (A) + component (B)} / component (C) = 100/0 to 5
A step of applying an undercoat coating material contained in a range of 0/50 to a polyolefin resin molded article to form an undercoat layer on the surface of the resin molded article, and coloring with a coloring pigment, ) And the following component (C) as the main component of the binder, and the component (C) was contained in a weight ratio of component (A) / component (C) = 90/10 to 50/50. It is a two-coat one-bake solid color coating method in which the steps of applying a top coat coating and forming a top coat layer on the surface of the undercoat layer are sequentially performed.

Examples of the component (A), that is, the polyol resin in the coating composition used in the present invention include acrylic polyol resin, polyester polyol resin, polyether polyol resin, alkyd polyol resin and the like. It is preferable to apply a resin or a polyester polyol resin.

As the hydroxyl group-containing α, β-unsaturated monomer constituting the acrylic polyol resin in the component (A), for example, 2-hydroxyethyl acrylate, 2-
Hydroxypropyl acrylate, 3-hydroxypropyl acrylate, 2-hydroxybutyl acrylate, 3-hydroxybutyl acrylate, 4-hydroxybutyl acrylate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl methacrylate, 3-
Hydroxypropyl methacrylate, 2-hydroxybutyl methacrylate, 3-hydroxybutyl methacrylate, 4-hydroxybutyl methacrylate, etc., and their adducts with ε-caprolactone, Praxel FM
Monomer or Praxel FA monomer (trade name, manufactured by Daicel Chemical Industries, Ltd.) is available, and is mixed so that the hydroxyl value is 20 to 150 mgKOH / g in the component (A). When the hydroxyl value is less than 20, the interlayer adhesion between the undercoat paint and the topcoat coating film decreases, and in the topcoat paint, a sufficient cross-linked coating film cannot be formed and the solvent resistance and chemical resistance are low. Inferior to On the other hand, when the hydroxyl value exceeds 150, the polarity of the resin becomes too high in the undercoat paint, the compatibility with the component (B) (chlorinated polyolefin resin) decreases, and the water resistance of the topcoat paint is reduced. It is not preferable because it tends to decrease the properties.

Other copolymerizable α, β-unsaturated monomers used in combination with these hydroxyl group-containing α, β-unsaturated monomers include methyl acrylate, ethyl acrylate, propyl acrylate and isopropyl acrylate. , N-butyl acrylate, isobutyl acrylate, n-hexyl acrylate, octyl acrylate, 2-ethylhexyl acrylate, lauryl acrylate, cyclohexyl acrylate, methyl methacrylate, ethyl methacrylate, propyl methacrylate, isopropyl methacrylate, n-butyl methacrylate, isobutyl methacrylate, n- Hexyl methacrylate, octyl methacrylate, 2-ethylhexyl methacrylate, lauryl methacrylate, cyclohexyl methacrylate, Glycidyl acrylate, glycidyl methacrylate, methoxyethyl acrylate, methoxybutyl acrylate, ethoxyethyl acrylate, methoxyethyl methacrylate, methoxybutyl methacrylate, ethoxy butyl methacrylate,
Acrylic acid, methacrylic acid, maleic acid, itaconic acid,
Crotonic acid, acrylamide, N-methylolacrylamide, styrene, p-tert-butylstyrene, vinyltoluene, vinyl acetate, acrylonitrile, acyl group-modified acrylate, acyl group-modified methacrylate and the like can be used.

The acrylic polyol resin is the above α, β-
It is obtained by copolymerizing an unsaturated monomer by a known and commonly used method such as solution polymerization. Further, in the presence of the component (B) (chlorinated polyolefin resin), the above α, β-unsaturated monomer is copolymerized by a well-known and conventional method such as solution polymerization to prepare the component (A) and the component (B). The graft copolymer of is obtained. As an example thereof, it can be obtained by carrying out solution polymerization at a polymerization temperature of 60 to 100 ° C. using a polymerization initiator that generates a radical such as benzoyl peroxide and azobisisobutyronitrile. In this case, the normal component (A)
And a component (B), and a graft copolymer obtained by grafting the component (A) on the component (B). In the present invention, one obtained by this grafting reaction alone or a component (A) and / or component (B)
Of the present invention {component (A) + component (B)}
Can be used as

As the polybasic acid constituting the component (A) polyester polyol resin, phthalic anhydride, isophthalic acid, terephthalic acid, tetrahydrophthalic anhydride,
Hexahydrophthalic anhydride, trimellitic anhydride, pyromellitic anhydride, tetrachlorophthalic anhydride, adipic acid, azelaic acid, sebacic acid, succinic acid, 1,4-cyclohexanedicarboxylic acid, etc. Acids and their esters 1
It is possible to use one kind or a mixture of two or more kinds. Examples of the polyhydric alcohol include ethylene glycol, propylene glycol, diethylene glycol, tripropylene glycol, butanediol, pentanediol, hexanediol, 2-butyl-2-ethyl-1,3-propanediol, neopentyl glycol, 2,2. , 4
-Trimethyl-1,3-pentanediol, hexylene glycol, 1,4-cyclohexanedimethanol, bisphenol A, ethylene oxide adduct of bisphenol A, propylene oxide adduct of bisphenol A, hydrogenated bisphenol A, hydrogenated bisphenol A Ethylene oxide adduct, hydrogenated bisphenol A propylene oxide adduct, polytetramethylene ether glycol and other dihydric alcohols, glycerin, trimethylolethane, trimethylolpropane, hexanetriol, pentaerythritol, 1,4-cyclohexyldimethanol Etc. can be used alone or in combination of two or more.

The polyester polyol resin is obtained by esterification by one of the above polybasic acids and one or more of the polyhydric alcohols and one or more of the polyhydric alcohols by a known and conventional method. In the present invention, an acrylic polyol resin and a polyester polyol resin can be used together as the component (A).

Further, α, β-unsaturated monomer represented by 2-isocyanate ethyl methacrylate having 0.2 to 0.5 equivalent of isocyanate group per 1 equivalent of hydroxyl group of polyester polyol resin, or anhydrous. A compound having an ethylenic double bond at the terminal obtained by reacting an acid anhydride having a double bond represented by maleic acid,
In the presence of the component (B) (chlorinated polyolefin resin), the α, β-unsaturated monomer constituting the acrylic polyol resin is copolymerized by a known and commonly used method such as solution polymerization to give the component ( A graft copolymer of A) and component (B) is obtained. In this case, the polyester polyol resin used in the reaction has a number average molecular weight of 500 to 3000, preferably 700 to 2000. Number average molecular weight is 50
If it is less than 0, a good coating appearance cannot be expected, and if it exceeds 3000, there is a risk of gelation in the course of the polymerization reaction.

Similarly, as the component (B) (chlorinated polyolefin resin), for example, a chlorinated product of a polymer synthesized from at least one of ethylene, propylene and butadiene, an unsaturated polycarboxylic acid thereof or an acid anhydride thereof is used. It is a conventionally known chlorinated polyolefin resin such as a modified product. The unsaturated polycarboxylic acid or acid anhydride thereof used here includes acrylic (meth) cinnamic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid, fumaric acid and the like. These chlorinated polyolefin resins have a chlorine content of 10 to 50% by weight, preferably 15
-40% by weight, number average molecular weight of 3,000 to 10,000
0, preferably 5000-50000 can be used.

When the chlorine content is less than 10% by weight, the stability of the solution is poor especially at low temperatures, the affinity with the component (A) when polymerized is poor, and the appearance of the coating film is poor.
If the content exceeds 10% by weight, the adhesion and weather resistance to the surface of the polyolefin resin material are poor. The number average molecular weight is 3
If it is less than 000, solvent resistance, hardness, and adhesion are poor, and if it exceeds 100,000, the viscosity of the resin solution is too high, so more diluting solvent is needed, the solid content of the coating during coating becomes low, and the coating thickness Is difficult to obtain and the coating workability is deteriorated, which is not preferable.

In the undercoat coating composition used in the present invention, component (A) and component (B) are in a weight ratio of component (A) / component (B) = 95/5 to 50/50. Used. Component (A) is component (A) / component (B) =
If it is more than 95/5, the adhesion to the polyolefin resin material is reduced, and the component (A) / component (B) = 50.
When it is less than / 50, solvent resistance and water resistance are lowered. On the other hand, since the undercoat paint ensures the adhesiveness to the polyolefin resin material, it is not necessary to use the component (B) in the topcoat paint.

A crosslinkable resin capable of reacting with a hydroxyl group, the component (C) is an aminoplast resin such as a melamine resin, a urea resin or a guanamine resin, and an isocyanate prepolymer is, for example, tolylene diisocyanate, diphenylmethane diisocyanate or isophorone diisocyanate ( IPDI), hexamethylene diisocyanate (HDI), trimethylhexane diisocyanate, methylcyclohexane diisocyanate, methylenebis (cyclohexylisocyanate), (isocyanatemethyl) cyclohexane and the like, and elene glycol, polyethylene glycol,
Polypropylene glycol, polyether polyol,
Addition products such as polycaprolactone polyol, trimethylolethane, trimethylolpropane, hexanetriol, pentaerythritol, and water, multimers of these diisocyanates, and blocks of these isocyanate prepolymers can be used.

The component (C) is in a weight ratio of {component (A) + component (B)} / component (C) = 100/0 to 50/50 in the undercoat coating composition used in the present invention. Used in. The method for coating a polyolefin resin molded article according to the present invention comprises an undercoat paint and a topcoat paint, and when the topcoat paint forms a sufficient cross-linked coating film, in the undercoat paint composition, a component ( A) and component (B) in a weight ratio, component (A)
/ If the component (B) is used in the range of 95/5 to 50/50, the water resistance and the solvent resistance are not particularly inferior even if the component (C) is not contained. When the component (C) is more than {component (A) + component (B)} / component (C) = 50/50, the polarity of the resin becomes high and the component (B) (chlorinated polyolefin resin) The compatibility of is reduced.

On the other hand, in the topcoat coating composition, the component (C) is in a weight ratio of component (A) / component (C) = 90.
It is used in the range of / 10 to 50/50. Ingredient (C)
However, when component (A) / component (C) is less than 90/10, a sufficient crosslinked coating film cannot be formed, and physical properties such as water resistance, solvent resistance, chemical resistance, weather resistance, etc. are not achieved. When the ratio is more than component (A) / component (C) = 50/50, the crosslinked structure becomes too dense and the coating film becomes brittle, and the impact resistance decreases.
When using aminoplast resin as a crosslinking agent,
In addition to the above-mentioned drawbacks, the acid resistance also decreases, which is not preferable.

In the coating composition used in the present invention,
In addition to the above essential components, color pigments, extender pigments, other resins, solvents, additives and the like can be used.

The coloring pigment is not particularly limited, but inorganic pigments such as titanium oxide, carbon black, iron oxide, lead chromate, and organic pigments such as phthalocyanine blue, phthalocyanine green, and quinacridone red can be used.

Kaolin, barium sulfate, calcium carbonate and the like can be used as the extender pigment.

The organic solvent can be used within a range that allows the solubility of the resin component. Specifically, for example, hydrocarbon solvents such as toluene, xylene, solvent naphtha, methylcyclohexane, ethylcyclohexane; ester solvents such as methyl acetate, ethyl acetate, butyl acetate, ethylene glycol monomethyl ether acetate; acetone, methyl ethyl ketone, methyl Ketone solvents such as isobutyl ketone and diisobutyl ketone can be used. The above solvents can be used alone or in combination of two or more.

As the additives, it is possible to use additives commonly used in paints, such as ultraviolet absorbers, light stabilizers, antioxidants, surface conditioners, pigment settling inhibitors and the like.

As a method for producing a coating composition using the coating composition of the present invention, the same method as the conventional top coating composition is used. That is, a part of the pigment and the resin solution, and if necessary, a solvent is added and mixed, and after being dispersed to a required particle size by a disperser such as a sand grind mill, a ball mill, an attritor, the rest of the resin solution, the solvent and the addition. It is obtained by adding the agent and stirring uniformly. In this case, since the coating method of the present invention is a two-coat one-bake type consisting of an undercoat paint and a topcoat paint, from the viewpoint of color tone stability of the finished paint film, the undercoat paint and the topcoat paint are particularly preferable. Are preferably similar in color tone, and it is particularly preferable to adjust the color difference (ΔE) between the two to be 3 or less.

[0038]

The coating composition used in the present invention can be applied directly to the surface of a polyolefin resin material. The outline of the coating method is shown below. First, a known degreasing cleaning treatment, for example, a degreasing cleaning with an organic solvent such as 1,1,1-trichloroethane or a degreasing treatment with an alkali or an acid is performed as a ground control for the surface of the polyolefin resin material that is the surface to be coated. After that, the above coating material is directly applied to the surface to be coated by air atomization coating, airless coating or the like, and dried to form a coating film. In this case, since the coating method of the present invention is a two-coat one-bake type consisting of an undercoat paint and a topcoat paint, the undercoat paint is first applied, and then the topcoat is applied on top without drying. It is possible to obtain a finished coating film by coating the coating materials and baking them at once.

[0039]

The present invention will be described in detail below with reference to the drawings showing the embodiments.

Production Examples 1 to 7 (Component (A); Preparation of Acrylic Polyol Resin) A flask equipped with a stirrer, a cooling pipe and a thermometer was charged with 994 parts by weight of toluene according to the formulation of FIG. 1 and stirred. While heating to 100 ° C, homogenize. Next, 400 parts by weight of isobornyl acrylate and 26 of methyl methacrylate
A mixed solution of 0 parts by weight, 131 parts by weight of 2-ethylhexyl methacrylate, 106 parts by weight of butyl acrylate, 103 parts by weight of 2-hydroxyethyl acrylate and 5 parts by weight of benzoyl peroxide was added dropwise over 2 hours, and further at the same temperature 1 After continuing stirring for an hour, the mixture was cooled to 80 ° C., 1 part by weight of azobisisobutyronitrile was added, and stirring was continued for 5 hours to obtain an acrylic polyol resin solution (A1).
Hereinafter, acrylic polyol resin solutions (A2) to (A7) are produced from the formulation of FIG. 1 by the same procedure. Each acrylic polyol resin solution (A1) to (A7) produced
The solid content% by weight and the hydroxyl value of the resin are shown in FIG.

Production Examples 8 to 10 (Component (A); Preparation of Polyester Polyol Resin) A flask equipped with a stirrer, a rectification column, a cooling pipe, a water separator and a thermometer was used according to the formulation shown in FIG. Isophthalic acid 33
4.2 parts by weight, hexahydrophthalic anhydride 155.2 parts by weight, adipic acid 294 parts by weight, trimethylolpropane 116.8 parts by weight, 1,6-hexanediol 29
After 1.2 parts by weight and 256.8 parts by weight of neopentyl glycol were charged, the mixture was heated and stirred to distill the generated condensed water out of the system, and the temperature was changed from 160 ° C to 230 ° C over 4 hours.
The temperature was raised at a constant heating rate. After the temperature was raised to 230 ° C., the pressure inside the system was reduced and the temperature was maintained at the same temperature to continue the condensation reaction. When the acid value becomes 10 or less, the reaction is terminated and 100
After cooling to ° C, 551.8 parts by weight of toluene was charged and uniformly stirred to obtain a polyester polyol resin solution (A8). Hereinafter, polyester polyol resin solutions (A9) and (A10) are obtained from the formulation of FIG. 2 by the same procedure. The solid content weight% of each polyester polyol resin solution (A8) to (A10) produced and the hydroxyl value of the resin are shown in FIG.

Production Examples 11 to 13 (Preparation of Graft Copolymer Resin of Component (A) and Component (B)) A flask equipped with a stirrer, a cooling tube and a thermometer,
According to the formulation of FIG. 1, 694 parts by weight of toluene, chlorinated polypropylene (Hardlen BS manufactured by Toyo Kasei Co., Ltd.)
-40: Chlorine content 40% by weight, heating residue 50% by weight)
Charge 600 parts by weight and heat to 100 ° C. with stirring to homogenize. Then, isobornyl acrylate 300
Parts by weight, methyl methacrylate 104 parts by weight, 2-ethylhexyl acrylate 148 parts by weight, butyl acrylate 45 parts by weight, 2-hydroxyethyl acrylate 1
A mixed solution of 03 parts by weight and 5 parts by weight of benzoyl peroxide was added dropwise over 2 hours, and the mixture was further stirred at the same temperature for 1 hour and then cooled to 80 ° C. to obtain 1 part by weight of azobisisobutyronitrile. Addition is continued for 5 hours to obtain a graft copolymer resin solution (AB1) of the component (A) and the component (B).
Hereinafter, the graft copolymer resin solutions (AB2) and (AB3) of the component (A) and the component (B) are obtained from the formulation of FIG. 1 by the same procedure. Each graft copolymer resin solution (AB1) to (A) of the produced component (A) and component (B)
The solid content weight% of B3) and the hydroxyl value in the resin component (A) are shown in FIG.

Production Example 14 (Preparation of Graft Copolymer Resin of Component (A) and Component (B)) Hexahydroanhydrophthalic acid was added to a flask equipped with a stirrer, a rectification column, a condenser, a water separator and a thermometer. Charge 520 parts by weight of acid and 480 parts by weight of neopentyl glycol, heat and stir, and raise the temperature of the mixture from 160 ° C. to 230 ° C. at a constant heating rate over 4 hours while distilling the generated condensed water out of the system. It was After the temperature was raised to 230 ° C., the pressure inside the system was reduced and the temperature was maintained at the same temperature to continue the condensation reaction. The reaction is terminated when the acid value becomes 5 or less, cooled to 80 ° C., charged with 205 parts by weight of isocyanate ethyl methacrylate, and the addition reaction is continued at 80 ° C. for 1 hour with stirring to form an ethylenic double bond at the end. The polyester resin having is obtained. The number average molecular weight of the obtained resin was 860 and the hydroxyl value was 65.

Next, another flask equipped with a stirrer, a condenser and a thermometer was charged with 789 parts by weight of toluene, 100 parts by weight of the obtained polyester resin, and 400 parts by weight of chlorinated polypropylene (Hardlen BS-40). , And heat to 100 ° C with stirring to make it uniform. Next, 140 parts by weight of isobornyl acrylate, 80.5 parts by weight of methyl methacrylate, 2-ethylhexyl acrylate 7
3.5 parts by weight, butyl acrylate 332.5 parts by weight,
A mixture of 73.5 parts by weight of 2-hydroxyethyl acrylate and 10 parts by weight of benzoyl peroxide was added dropwise over 2 hours, and stirring was continued at the same temperature for 1 hour.
After cooling to 0 ° C., 1 part by weight of azobisisobutyronitrile is added and stirring is continued for 5 hours to obtain a graft copolymer resin solution (AB4) of the component (A) and the component (B). As shown in FIG. 1, the solid content of the obtained graft copolymer resin solution (AB4) was 50% by weight, and the hydroxyl value in the resin component (A) was 5%.
It was 0.

(Example 1) (Preparation of undercoat paint) 100 parts by weight of an acrylic polyol resin solution (A1), chlorinated polypropylene (Hardlen 15LLB manufactured by Toyo Kasei Kogyo KK, containing chlorine) according to the formulation shown in FIG. 71% by weight, heating residue 30% by weight), and 100 parts by weight of titanium oxide were mixed, and the mixture was placed in an attritor and dispersed for 4 hours. Isocyanate prepolymer, modaflow, xylene and butyl acetate were mixed, An undercoat paint (U1) was prepared.

(Preparation of Top Coat Paint) According to the formulation shown in FIG. 5, 200 parts by weight of an acrylic polyol resin solution (A4) and 70 parts by weight of titanium oxide were mixed and placed in an attritor and dispersed for 4 hours. An isocyanate prepolymer, modaflow, xylene, and butyl acetate were mixed to prepare a top coat paint (T1).

(Coating on resin molded product) As an object to be coated, a polyolefin resin (manufactured by Mitsui Toatsu Chemicals, Inc., trade name S)
NB-4) bumper for automobiles, 1,1,1-
The mixture was degreased with trichloroethane vapor (74 ° C.) for 60 seconds and naturally dried. Undercoat paint (U1) mentioned above
Was adjusted to a viscosity of 13 seconds (Ford cup # 4, 20 ° C.) with a thinner of toluene / ethyl acetate = 70/30 (weight ratio), and air spray coating was performed so that the dry coating film pressure was 20 μm. Flash off for 1 minute. Then, the top coat paint (T1) was adjusted to a viscosity of 16 seconds (Ford cup # 4, 20 ° C.) with a thinner of xylene / butyl acetate = 60/40 (weight ratio), and then dried by wet on wet coating. The coating was repeated by air spray coating so that the pressure was 20 μm. Then, after leaving it in the room for 10 minutes, it was heated and dried at 80 ° C. for 30 minutes, and after 24 hours, a coating film performance test was carried out. The coating film performance test method is as follows. The result is shown in FIG.

"Coating Performance Test Method" (Finishing Appearance) Those having a good gloss on the coated surface, no remarkable skin roughness, and no coating defects such as cissing, armpits, and color unevenness were passed.

(60 degree specular gloss) JIS-K-540
0 (1990) 7.6 shows the measured value, 90
The above was passed.

(Adhesiveness) JIS-K-5400 (19) is applied to the front, side surfaces, upper surface, and lower surface of the coated molded product.
90) Performed a burdock cellophane tape test of 8.5.2, and judged that no peeling was observed at all.

(Gasoline resistance) After immersing a part of the coated molded article in regular gasoline (manufactured by Nippon Oil Co., Ltd., trade name Nisseki Silver Gasoline) at 20 ° C. for 30 minutes,
In the taken out state, observation of the coated surface state of the dipped portion and adhesion test are performed. Regarding the coating surface condition, those with no abnormalities were accepted and the adhesion test was conducted with 100
The remaining number was about 100/100 was passed.

(Acid resistance) 0.2 ml of 0.1 N sulfuric acid was dropped on the coated surface, and the temperature was adjusted to 2 at 20 ° C. and 75% RH (relative humidity).
After leaving it for 4 hours, it is washed with water and the state of the coated surface is observed. Those with no abnormalities were accepted.

(Alkali resistance) 0.2 ml of 0.1 N sodium hydroxide was dropped on the coated surface, and the temperature was 20 ° C. and 75% R.
After standing at H for 24 hours, it is washed with water and the state of the coated surface is observed.
Those with no abnormalities were accepted.

(Moisture resistance) Painted molded product at 50 ° C., 98% R
After leaving it in the H constant temperature and humidity chamber for 240 hours, the state of the coated surface and the adhesion test are performed in the taken out state. Regarding the coated surface condition, no abnormality was recognized as a pass, and for the adhesion test, the remaining number for the scoring 100 was 1
00/100 was passed.

(Weather resistance) 70 × 150 from the coated molded product
mm test piece was cut out, and JIS-K-5400 (19
90) Carry out accelerated weathering test according to 9.8.1. 100
The retention (%) of the 60-degree specular gloss after the 0-hour test {(gloss after test / initial gloss) × 100} was measured, and an adhesion test was performed. When the gloss retention rate was 80% or more and no discoloration was observed, the result was passed, and the adhesiveness test was 100/100 when the remaining number of the crevices was 100.

Note that the notes 1) to 7) in the figure are shown below. Note 1) "Hardlen 15LLB" Toyo Kasei Co., Ltd., chlorine content 30% by weight, heating residue 30% by weight, trade name Note 2) "Hardlen BS-40" Toyo Kasei Co., Ltd., chlorine content 40% by weight , Heating residue 50% by weight, trade name Note 3) "Super Clone 507" Sanyo Kokusaku Pulp Co., Ltd., chlorine content 66% by weight, heating residue 40% by weight, trade name Note 4) "Duranate THA-100" Asahi Kasei Industry Co., Ltd., NCO content 21% by weight, heating residue 100% by weight, trade name Note 5) "Desmodur TPLS2759" Sumitomo Bayer Urethane Co., Ltd., NCO content 8.9% by weight, heating residue 75% by weight, Product name, blocking agent; methyl ethyl ketoxime Note 6) "Uban 122" Mitsui Toatsu Chemicals, Inc. Butylated melamine resin, heating residue 60% by weight, product Note 7) “Modaflow” Monsanto Co., Ltd., acrylic copolymer, heating residue 100% by weight, trade name (Examples 2 to 22, Comparative Examples 1 to 10) From the formulation of FIGS. 3 to 5 is the same as Example 1. Undercoat paints (U2) to (U21) and topcoat paint (T2)
To (T8), and these undercoat paints (U2) to (U21) and topcoat paint (T8).
2) to (T8) were applied to the resin molded product under the conditions shown in FIGS. 6 and 7, and the same coating film performance test as in Example 1 was performed. The individual results are shown in FIGS. 6 and 7.

As is clear from the results of Examples 1 to 22, by applying the coating method of the present invention, the surface of automobile exterior parts such as bumpers molded from a polyolefin resin material can be directly coated and adhered. In terms of various properties required for the topcoat coating film, such as properties, weather resistance, acid resistance, alkali resistance, gasoline resistance, moisture resistance, and finished appearance, it is possible to obtain an extremely good coated molded article.

On the other hand, in Comparative Example 1, since the hydroxyl value of the component (A) in the undercoat paint (U16), that is, (A6), is less than 20, the interlayer with the topcoat coating film (T1) is Poor adhesion and moisture resistance, while Comparative Example 2
Then, the component (A) of the undercoat paint (U17),
That is, since the hydroxyl value of (A7) exceeds 150,
The compatibility with the component (B) is not sufficient and the finished appearance, gloss and moisture resistance are poor.

In Comparative Example 3, the undercoat paint (U1
Since the chlorine content of the component (B) in 8), that is, the chlorinated polyolefin (B3) exceeds 50% by weight, the adhesion to the surface of the polyolefin resin material and the moisture resistance are poor.

In Comparative Example 4, the undercoat paint (U1
9), component (A) is component (A) / component (B) = 95
/ 5, the adhesion to the surface of the polyolefin resin material is poor, while in Comparative Example 5, the component (A) in the undercoat paint (U20) is component (A) / component (B) = 50 / Since it is less than 50, gasoline resistance,
Poor moisture resistance.

In Comparative Example 6, the undercoat paint (U2
In 1), the component (C) is {component (A) + component (B)} /
Since the component (C) exceeds 50/50, the polarity of the resin becomes high, the compatibility with the component (B) decreases, and the finished appearance and gloss are poor.

In Comparative Example 7, the top coat paint (T5)
Since the hydroxyl value of the component (A), that is, (A6), is less than 20, a sufficient crosslinked coating film cannot be formed, and gasoline resistance, acid resistance, and alkali resistance are poor, while Comparative Example 8
Then, since the hydroxyl value of the component (A) in the top coat paint (T6), that is, (A7), exceeds 150, the moisture resistance is poor.

In Comparative Example 9, the top coat paint (T7)
Inside, component (C) is component (A) / component (C) = 90/1
Since it is less than 0, a sufficient cross-linked coating film cannot be formed, and gasoline resistance, acid resistance, alkali resistance, moisture resistance and weather resistance are poor. On the other hand, in Comparative Example 10, the top coat paint (T8)
Inside, component (C) is component (A) / component (C) = 50/5
Since it exceeds 0, the acid resistance is poor.

[0064]

As described above, according to the method for coating a polyolefin-based resin molded product according to the present invention, the surface of an automobile exterior component such as a bumper molded from a polyolefin-based resin material can be made to have a special appearance. Since it has become possible to directly paint without applying various treatments, primer coating, or mixing with a curing agent, the effects such as coating efficiency, paint management, and cost saving are remarkable, and the adhesion, weather resistance, and resistance A coating film having excellent chemical properties, solvent resistance, and finished appearance can be formed.

Further, according to the method for coating a polyolefin resin molded article according to the present invention, since a topcoat layer made of a topcoat paint is formed on the surface of the undercoat layer made of the undercoat paint, the material colored black. On the other hand, it is possible to expect a sufficient hiding property without containing a large amount of the coloring pigment even when painting in white, yellow or the like.

[Brief description of drawings]

FIG. 1 is a table showing production examples of an acrylic polyol resin solution and a graft copolymer resin solution.

FIG. 2 is a chart showing a production example of a polyester polyol resin solution.

FIG. 3 is a table showing an example of manufacturing an undercoat paint.

FIG. 4 is a chart showing an example of manufacturing an undercoat paint.

FIG. 5 is a table showing a production example of a top coat paint.

FIG. 6 is a chart showing results of coating film performance tests.

FIG. 7 is a chart showing results of coating film performance tests.

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location C09D 151/06 PGX 7142-4J 161/20 PHK 8215-4J 167/00 PKZ 8933-4J 175/00 PHP 8620-4J // C09D 123/28 PFA 7107-4J

Claims (2)

[Claims] 1. A color pigment, a blend and / or a graft copolymerization of the following component (A) and the following component (B), and a weight ratio of component (A) / component (B) = 95.
/ 50 to 50/50, and further contains the following component (C) in a weight ratio of {component (A) + component (B)} /
A step of applying an undercoat paint containing component (C) in the range of 100/0 to 50/50 to a polyolefin resin molded article to form an undercoat layer on the surface of the resin molded article; Colored with a pigment, the following component (A) and the following component (C)
As the main component of the binder, and the component (C) in a weight ratio of component (A) / component (C) = 90/10 to 50/50.
And a step of forming a topcoat layer on the surface of the undercoat layer by applying a topcoat coating material contained so as to fall within the range. (A) Polyol resin having a hydroxyl value of 20 to 150 mgKOH / g (B) Chlorinated polyolefin resin having a chlorine content of 50% by weight or less (C) Crosslinkable resin capable of reacting with hydroxyl groups 2. The method for coating a polyolefin resin molded article according to claim 1, wherein the component (C) is an aminoplast resin, an isocyanate prepolymer, and a block of the isocyanate prepolymer.