JP3232712B2 - Coating method of polyolefin resin molded product - Google Patents

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 article.

[0002]

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

For this reason, when the above-mentioned polyolefin resin material is coated, the surface of the polyolefin resin material is subjected to a pretreatment such as a flame treatment, a corona discharge treatment, a plasma treatment, and a chromic acid mixed solution treatment. ,
The surface of the polyolefin-based resin material is activated and made highly polar in advance to improve the adhesion of the paint. However, the method of performing these pretreatments is not only complicated in the process and involves a great deal of capital investment and time loss, but also cannot always say that the adhesion of the paint is sufficiently improved. Can be difficult to even apply.

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

[0005] In order to solve these drawbacks, a chlorinated polyolefin resin having a chlorine content of 50% by weight or less and having strong adhesion to the polyolefin resin material has been proposed as a coating composition for a polyolefin resin material. There has been proposed a composition comprising an alkyd resin or an acrylic resin for improving weather resistance and solvent resistance, which are drawbacks of a 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. JP-A-62-18434 discloses that
A resin system in which an isocyanate compound is combined with a copolymer of a chlorinated polyolefin resin, an acrylic monomer, and a chlorinated polydiene.

[0009]

However, the above a
In the resin mixture of (1), the chlorine content must be 35% by weight or less, the resin solution is easily separated into two phases, and when it is used as a paint, the dispersion stability of the pigment, the luster, adhesion, There are drawbacks such as insufficient solvent properties, weather resistance, and physical properties.

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

[0011] Even in the resin system of the above c, the solvent resistance and the weather resistance are insufficient and have not reached a practical stage.

The above a, b, and c are all limited to those that do not require strict weather resistance for coating films, such as home electric appliances and automobile interior parts. It is not suitable for exterior parts that require weather resistance.

To solve the above-mentioned disadvantages, the present inventors have already disclosed in JP-A-4-1322783 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 a terminal as a main component, a coating main agent, and a coating curing agent mainly containing a polyfunctional isocyanate compound. A method for coating a polyolefin-based resin molded article in which a two-part curable coating material obtained by mixing is applied to the surface of the polyolefin-based resin molded article is disclosed.

The present invention largely eliminates the conventional disadvantages and makes it possible to significantly reduce the total cost required for painting.

However, when a solid color, such as white or yellow, which is difficult to obtain a sufficient hiding power, is applied to a black-colored material, a large amount of a coloring pigment needs to be blended. The finished appearance is difficult to obtain.
In addition, since it is a two-part curable paint, the main agent and the curing agent must be mixed before painting, and the time from when the curing agent is added to when the curing reaction proceeds to some extent and the painting becomes difficult In other words, since it has a so-called pot life, it has an aspect of being restricted in work.

The present invention has been made in view of the above circumstances, and is applied directly to the surface of a polyolefin-based resin, and has properties such as adhesion, weather resistance, chemical resistance, solvent resistance, finished appearance and opacity. While providing excellent coating performance,
An object of the present invention is to provide a method for coating a polyolefin-based resin molded product, which can be easily performed without any restrictions on a coating operation.

[0017]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, a polyol resin, a chlorinated polyolefin resin, and a crosslinkable resin capable of reacting with a hydroxyl group have been defined as essential components. By applying an undercoat paint with excellent adhesion and opacity to the surface of the polyolefin resin material and a top coat paint with a reduced amount of the coloring pigment, the adhesion of the polyolefin resin material to the surface Has excellent physical coating properties such as weather resistance, chemical resistance, and solvent resistance, and has found a coating method for a polyolefin-based resin molded article with excellent coating film appearance, and completed the present invention. Was.

That is, in the present invention, the following component (A) and the following component (B) are blended and / or graft-copolymerized with a coloring pigment, and the weight ratio of component (A) / component (B) = 95/5 to 50/50, and 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 paint contained so as to be in a range of 0/50 to a polyolefin resin molded article and forming an undercoat layer on the surface of the resin molded article; ) And the following component (C) as the main components of the binder, and the component (C) was contained such that the weight ratio was in the range of component (A) / component (C) = 90/10 to 50/50. And a step of applying a top coat paint and forming a top coat layer on the surface of the undercoat layer.

The component (A) in the coating composition used in the present invention, that is, the polyol resin, may be an acrylic polyol resin, a polyester polyol resin, a polyether polyol resin, an alkyd polyol resin, or the like. It is preferable to use a resin or a polyester polyol resin.

In the component (A), examples of the hydroxyl group-containing α, β-unsaturated monomer constituting the acrylic polyol resin include, for example, 2-hydroxyethyl acrylate, 2-hydroxyethyl acrylate,
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 and the like, and adducts thereof with ε-caprolactone, Plaxel FM
Monomer or Praxel FA monomer (trade name, manufactured by Daicel Chemical Industries, Ltd.) and the like are blended so that the hydroxyl value is 20 to 150 mgKOH / g in the component (A). When the hydroxyl value is less than 20, in the undercoat paint, the interlayer adhesion with the top coat paint film is reduced, and in the top coat paint, a sufficient crosslinked paint film cannot be formed, and the solvent resistance and the chemical resistance Inferior to etc. On the other hand, when the hydroxyl value exceeds 150, the polarity of the resin is too high in the undercoat paint, the compatibility with the component (B) (chlorinated polyolefin resin) is reduced, and the water resistance in the topcoat paint is low. This is not preferred because the property tends to decrease.

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-modified acrylate, acyl-modified methacrylate and the like can be used.

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

The polybasic acid constituting the polyester polyol resin as the component (A) includes 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, and other commonly used polybases for polyester production Acids and their esters
They can be used alone or in combination of two or more. Examples of polyhydric alcohols include ethylene glycol, propylene glycol, diethylene glycol, tripropylene glycol, butanediol, pentanediol, hexanediol, 2-butyl-2-ethyl-1,3-propanediol, neopentyl glycol, and 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, dihydric alcohols such as polytetramethylene ether glycol, 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 using one or more of the above-mentioned polybasic acids and one or more of the polyhydric alcohols and esterifying them by a known and commonly used method. In the present invention, an acrylic polyol resin and a polyester polyol resin can be used in combination as the component (A).

Further, α, β-unsaturated monomers represented by 2-isocyanateethyl methacrylate having isocyanate groups in an amount of 0.2 to 0.5 equivalent to 1 equivalent of hydroxyl group of the 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 common method such as solution polymerization to obtain the component ( A graft copolymer of A) and component (B) is obtained. In this case, the number average molecular weight of the polyester polyol resin involved in the reaction is from 500 to 3,000, preferably from 700 to 2,000. Number average molecular weight of 50
If it is less than 0, good appearance of the coating film cannot be expected, and if it exceeds 3000, there is a risk of gelation in the course of the polymerization reaction.

Similarly, the component (B) (chlorinated polyolefin resin) includes, for example, chlorinated polymers synthesized from at least one of ethylene, propylene and butadiene, and unsaturated polycarboxylic acids or acid anhydrides thereof. It is a conventionally known chlorinated polyolefin resin such as a modified product. Examples of the unsaturated polycarboxylic acid or acid anhydride used herein include acrylic (meth) cinnamic acid, crotonic acid, maleic acid, maleic anhydride, itaconic acid, and fumaric acid. These chlorinated polyolefin resins have a chlorine content of 10 to 50% by weight, preferably 15% by weight.
４０40% by weight, number average molecular weight of 3,000 to 10,000
0, preferably 5000 to 50,000 can be used.

If the chlorine content is less than 10% by weight, the stability of the solution is poor particularly at low temperatures, the affinity with the component (A) at the time of polymerization is poor, and the appearance of the coating film is poor.
If the content is more than 10% by weight, the adhesion to the surface of the polyolefin resin material and the weather resistance are poor. The number average molecular weight is 3
If it is less than 000, the solvent resistance, hardness and adhesion are inferior, and if it exceeds 100,000, the viscosity of the resin solution is too high, so that more diluting solvent is required, and the solid content of the coating material at the time of coating becomes lower, and the coating film thickness becomes lower. Is difficult to obtain, and the coating workability is deteriorated.

In the undercoat coating composition used in the present invention, the components (A) and (B) are in a weight ratio of component (A) / component (B) = 95/5 to 50/50. Used. When the component (A) is the component (A) / the component (B) =
When it is more than 95/5, the adhesion to the polyolefin resin material is reduced, and the component (A) / component (B) = 50
If the ratio is less than / 50, the solvent resistance and the water resistance decrease. On the other hand, the component (B) does not need to be particularly used in the topcoat paint in order to ensure the adhesion of the undercoat paint to the polyolefin resin material.

A crosslinkable resin capable of reacting with a hydroxyl group, as component (C), aminoplast resins such as melamine resin, urea resin, guanamine resin, and as isocyanate prepolymer, for example, tolylene diisocyanate, diphenylmethane diisocyanate, isophorone diisocyanate ( IPDI), hexamethylene diisocyanate (HDI), trimethylhexane diisocyanate, methylcyclohexane diisocyanate, methylene bis (cyclohexyl isocyanate), (isocyanatomethyl) cyclohexane, and other diisocyanates;
Polypropylene glycol, polyether polyol,
Adducts with polycaprolactone polyol, trimethylolethane, trimethylolpropane, hexanetriol, pentaerythritol, water, and the like, multimers of these diisocyanates, and blocks of these isocyanate prepolymers can be used.

Component (C) is in the range of {Component (A) + Component (B)} / Component (C) = 100/0 to 50/50 by weight 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 top coat paint. When the top coat paint forms a sufficient crosslinked coating film, the undercoat paint composition contains components ( A) and the component (B) in a weight ratio of the 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 increases, and the component (B) (chlorinated polyolefin-based resin) and Is reduced in compatibility.

On the other hand, in the top coat coating composition, the component (C) is expressed by weight ratio of component (A) / component (C) = 90.
/ 10 to 50/50. Component (C)
However, when the ratio of 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, and weather resistance are poor. If the ratio is lower than component (A) / component (C) = 50/50, the crosslinked structure is too dense, the coating film becomes brittle, and the impact resistance decreases,
Furthermore, when aminoplast resin is used as a crosslinking agent,
In addition to the above-mentioned disadvantages, the acid resistance is undesirably lowered.

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

As the extender, kaolin, barium sulfate, calcium carbonate and the like can be used.

As the organic solvent, any organic solvent can be used as long as the solubility of the resin component is allowed. Specifically, for example, hydrocarbon solvents such as toluene, xylene, solvent naphtha, methylcyclohexane, and ethylcyclohexane; ester solvents such as methyl acetate, ethyl acetate, butyl acetate, and ethylene glycol monomethyl ether; acetone, methyl ethyl ketone, and methyl Ketone solvents such as isobutyl ketone and diisobutyl ketone can be used. These solvents can be used alone or in combination of two or more.

As the additives, it is possible to use additives used in ordinary paints, for example, ultraviolet absorbers, light stabilizers, antioxidants, surface conditioners, pigment sedimentation inhibitors and the like.

As a method for producing a paint using the paint composition of the present invention, a method similar to that of a conventional topcoat paint is used. That is, the pigment and a part of the resin solution, and if necessary, a solvent are added and mixed, and dispersed to a required particle size by a dispersing machine such as a sand grind mill, a ball mill, and an attritor. It is obtained by adding the agent and stirring uniformly. In this case, the coating method of the present invention is a two-coat one-bake type formed of an undercoat paint and a topcoat paint. Are preferably similar, and it is particularly preferable that the color difference (ΔE) between the two is adjusted 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 and cleaning treatment, for example, degreasing and cleaning with an organic solvent such as 1,1,1-trichloroethane, or degreasing with an alkali or acid was performed as a base adjustment of the surface of the polyolefin resin material to be coated. Thereafter, the paint 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 formed of an undercoat paint and a top coat paint, the undercoat paint is applied first without drying, and then the top coat is applied thereon. Coating paint can be applied and baked at a time to obtain a finished coating film.

[0039]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings showing embodiments.

Production Examples 1 to 7 (Component (A); Preparation of Acrylic Polyol Resin) Into a flask equipped with a stirrer, a cooling pipe and a thermometer, 994 parts by weight of toluene was charged according to the composition shown in FIG. While heating to 100 ° C to make it uniform. Then, 400 parts by weight of isobornyl acrylate, 26 parts of methyl methacrylate
0 parts by weight, a mixture of 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 were added dropwise over 2 hours. After stirring for an hour, the mixture is cooled to 80 ° C., 1 part by weight of azobisisobutyronitrile is added, and stirring is 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 of the produced acrylic polyol resin solutions (A1) to (A7)
1 and the hydroxyl value of the resin are shown in FIG.

Production Examples 8 to 10 (Component (A); Preparation of Polyester Polyol Resin) In a flask equipped with a stirrer, a rectification tower, a cooling tube, a water separator and a thermometer, 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 charging 1.2 parts by weight and 256.8 parts by weight of neopentyl glycol, the mixture is heated and stirred, and 160 ° C. to 230 ° C. over 4 hours while distilling off the condensed water generated outside the system.
The temperature was raised at a constant rate. After the temperature was raised to 230 ° C., the pressure inside the system was reduced, and the condensation reaction was continued while maintaining the same temperature. When the acid value became 10 or less, the reaction was terminated.
After cooling to 0 ° C, 551.8 parts by weight of toluene was charged and stirred uniformly 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. FIG. 2 shows the solid content weight% of each of the produced polyester polyol resin solutions (A8) to (A10) and the hydroxyl value of the resin.

Production Examples 11 to 13 (Preparation of Graft Copolymer Resin of Component (A) and Component (B)) In a flask equipped with a stirrer, a condenser and a thermometer,
According to the composition shown in FIG. 1, 694 parts by weight of toluene and chlorinated polypropylene (Harden BS manufactured by Toyo Kasei Kogyo Co., Ltd.)
-40; chlorine content 40% by weight, heating residue 50% by weight)
Charge 600 parts by weight, and heat to 100 ° C. while stirring to make it uniform. 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 mixture of 03 parts by weight and 5 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 80 ° C., 1 part by weight of azobisisobutyronitrile was added. Stirring is continued for 5 hours to obtain a graft copolymer resin solution (AB1) of component (A) and component (B).
Hereinafter, 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 of the graft copolymer resin solutions (AB1) to (A1) of the produced component (A) and component (B)
FIG. 1 shows the weight percentage of the solid content of B3) and the hydroxyl value in the component (A) of the resin.

Production Example 14 (Preparation of graft copolymer resin of component (A) and component (B)) A flask equipped with a stirrer, a rectification tower, a cooling tube, a water separator and a thermometer was charged with hexahydroanhydrophthalic anhydride. 520 parts by weight of an acid and 480 parts by weight of neopentyl glycol were charged and heated and stirred, and the resulting condensed water was distilled out of the system, and the temperature was raised from 160 ° C to 230 ° C over 4 hours at a constant rate. Was. After the temperature was raised to 230 ° C., the pressure inside the system was reduced, and the condensation reaction was continued while maintaining the same temperature. The reaction was terminated when the acid value became 5 or less, cooled to 80 ° C., charged with 205 parts by weight of isocyanatoethyl methacrylate, and the addition reaction was continued at 80 ° C. for 1 hour with stirring to form an ethylenic double bond at the terminal. The obtained polyester resin is obtained. The number average molecular weight of the obtained resin was 860, and the hydroxyl value was 65.

Next, 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) were charged into another flask equipped with a stirrer, a condenser, and a thermometer. The mixture is heated to 100 ° C. while stirring to make it uniform. Then, 140 parts by weight of isobornyl acrylate, 80.5 parts by weight of methyl methacrylate, 2-ethylhexyl acrylate 7
3.5 parts by weight, 332.5 parts by weight of butyl acrylate,
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 component (A) and 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) and chlorinated polypropylene (Hard Len 15LLB, manufactured by Toyo Kasei Kogyo Co., Ltd., containing chlorine) Rate: 30% by weight; heating residue: 30% by weight) 71 parts by weight and 100 parts by weight of titanium oxide were mixed, and the mixture was charged into an attritor and dispersed for 4 hours. Then, isocyanate prepolymer, modaflow, xylene and butyl acetate were mixed. The undercoat paint (U1) was prepared.

(Adjustment of Top Coat Paint) According to the composition 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 the mixture was charged into an attritor and dispersed for 4 hours. An isocyanate prepolymer, modaflow, xylene, and butyl acetate were mixed to prepare a topcoat paint (T1).

(Coating on Resin Molded Product) As an object to be coated, a polyolefin resin (trade name: S, manufactured by Mitsui Toatsu Chemicals, Inc.)
The automobile bumper molded in NB-4) is 1,1,1-
The mixture was degreased with trichloroethane vapor (74 ° C.) for 60 seconds and air-dried. The above undercoat paint (U1)
Was adjusted with a thinner of toluene / ethyl acetate = 70/30 (weight ratio) to a viscosity of 13 seconds (Ford cup # 4, 20 ° C.), and then subjected to air spray coating so that the dry coating film pressure became 20 μm. Flash off for 1 minute. Next, the above 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 on a wet-on-wet basis. Coating was performed by air spray coating so that the pressure was 20 μm. Then, after leaving it to stand indoors for 10 minutes, it was dried by heating at 80 ° C. for 30 minutes, and after 24 hours, a coating film performance test was performed. The coating film performance test method is as follows. FIG. 6 shows the result.

"Test Method for Coating Film Performance" (Finish appearance) A coating having good gloss on the coated surface, no remarkable surface roughness, and no coating film defects such as repelling, wrinkles, and color unevenness was accepted.

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

(Adhesion) JIS-K-5400 (19)
90) A scotch tape test of 8.5.2.

(Gasoline resistance) A part of the painted molded product was immersed in regular gasoline (Nippon Oil Co., Ltd., trade name Nisseki Silver Gasoline) at 20 ° C. for 30 minutes.
In the state of being taken out, observation of the coated surface state of the immersion part and an adhesion test are performed. Regarding the state of the painted surface, those having no abnormalities were regarded as acceptable.
100/100 was accepted as the remaining number of items.

(Acid resistance) 0.2 ml of 0.1 N sulfuric acid was dropped on the coated surface, and the solution was dried at 20 ° C. and 75% RH (relative humidity).
After standing for 4 hours, the plate is washed with water and the state of the coated surface is observed. If no abnormality was found, it was accepted.

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

(Moisture resistance) Painted product was treated at 50 ° C. and 98% R
After being left in a constant temperature and humidity chamber of H for 240 hours, the state of the coated surface is observed and the adhesion test is performed in the state of taking out. Regarding the state of the painted surface, those having no abnormalities were regarded as acceptable.
00/100 was accepted.

(Weather resistance) 70 × 150
mm test piece was cut out and JIS-K-5400 (19
90) Perform accelerated weathering test according to 9.8.1. 100
The retention rate (%) of the 60-degree specular gloss after the 0-hour test {(gloss after the test / initial gloss) × 100} was measured, and the adhesion test was performed. A sample having a gloss retention of 80% or more and no discoloration was accepted, and an adhesion test was 100/100 as the remaining number for Goban 100.

Note that notes 1) to 7) in the figure are shown below. Note 1) "Hard Len 15LLB" Toyo Kasei Kogyo Co., Ltd., chlorine content 30% by weight, heating residue 30% by weight, trade name Note 2) "Hard Len BS-40" Toyo Kasei Kogyo Co., Ltd., chlorine content 40% by weight Note 3) "Supercron 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 Industrial Co., Ltd., NCO content 21% by weight, heating residue 100% by weight, trade name Note 5) "Desmodule TPLS2759" Sumitomo Bayer Urethane Co., Ltd., NCO content 8.9% by weight, heating residue 75% by weight, Brand name, Blocking agent: Methyl ethyl ketoxime Note 6) "Uban 122" Mitsui Toatsu Chemicals, Butylated melamine resin, Heating residue 60% by weight, Product Note 7) “Modaflow” Monsanto Co., Ltd., acrylic copolymer, 100% by weight of heating residue, trade name (Examples 2 to 22, Comparative Examples 1 to 10) Same as Example 1 from the composition of FIGS. The undercoat paint (U2) to (U21) and the top coat paint (T2)
To (T8) and the undercoat paints (U2) to (U21) and the top coat paint (T2).
2) to (T8) were applied to a resin molded product under the conditions shown in FIG. 6 and FIG. 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, it is possible to apply directly to the surface of exterior parts for automobiles such as bumpers molded from a polyolefin resin material, Very good coated molded articles can be obtained in various properties required for a top coat such as water resistance, weather resistance, acid resistance, alkali resistance, gasoline resistance, moisture resistance, and finished appearance.

On the other hand, in Comparative Example 1, since the hydroxyl value of the component (A) in the undercoat paint (U16), that is, (A6) was less than 20, the interlayer between the topcoat paint film (T1) and Poor adhesion and poor moisture resistance, whereas Comparative Example 2
Then, the component (A) in 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, glossiness 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) In component (A), component (A) / component (B) = 95
/ 5, the adhesion to the surface of the polyolefin resin material is poor. On the other hand, in Comparative Example 5, the component (A) in the undercoat paint (U20) is component (A) / component (B) = 50 / Gasoline resistance because less than 50,
Poor moisture resistance.

In Comparative Example 6, the undercoat paint (U2
In 1), component (C) is {component (A) + component (B)} /
Since the component (C) is more than 50/50, the polarity of the resin is increased, the compatibility with the component (B) is reduced, and the finished appearance and gloss are inferior.

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.
In this case, the component (A) in the top coat paint (T6), that is, the hydroxyl value of (A7) exceeds 150, so that the moisture resistance is poor.

In Comparative Example 9, the top coat paint (T7)
In the above, the component (C) is calculated as follows: component (A) / component (C) = 90/1
Since it is less than 0, a sufficient crosslinked coating film cannot be formed, resulting in poor gasoline resistance, acid resistance, alkali resistance, moisture resistance, and weather resistance. On the other hand, in Comparative Example 10, the top coat paint (T8)
Medium, 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 is coated on a surface of a conventional special product. It is possible to apply directly without using any treatment, primer coating, or mixing with a curing agent, so the effects of coating efficiency, paint management, cost savings, etc. are remarkable, and adhesion, weather resistance, A coating film excellent in chemical properties, solvent resistance, finished appearance and the like can be formed.

Further, according to the method for coating a polyolefin-based resin molded product of the present invention, the topcoat layer formed of the topcoat paint is formed on the surface of the undercoat layer formed of the undercoat paint. On the other hand, even in the case of coating white, yellow, etc., sufficient concealing properties can be expected without containing a large amount of color pigment.

[Brief description of the drawings]

FIG. 1 is a chart showing a production example 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 a production example of an undercoat paint.

FIG. 4 is a table showing a production example of an undercoat paint.

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

FIG. 6 is a table showing the results of a coating film performance test.

FIG. 7 is a table showing the results of a coating film performance test.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI C09D 151/06 C09D 151/06 161/20 161/20 167/00 167/00 175/00 175/00 // C09D 123/28 123/28 (56) References JP-A-4-185654 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B05D 1/00-7/26 C08J 7/04 CES C09D 133 / 14 C09D 151/06 C09D 161/20 C09D 167/00 C09D 175/00 C09D 123/28

Claims (2)

(57) [Claims] 1. Component (A) and component (B) blended and / or graft-copolymerized with a coloring pigment and having a weight ratio of component (A) / component (B) = 95.
/ 5 to 50/50, and the following component (C) in a weight ratio of {Component (A) + Component (B)} /
A step of applying an undercoat paint containing the component (C) in a range of 100/0 to 50/50 to a polyolefin-based resin molded product, and forming an undercoat layer on the surface of the resin molded product; Colored with a pigment, the following components (A) and (C)
Are the main components of the binder, and the weight ratio of the component (C) to the component (A) / component (C) = 90/10 to 50/50.
A step of applying a top coat paint contained in such a manner as to fall within the range described above, and forming a top coat layer on the surface of the undercoat layer. (A) a polyol resin having a hydroxyl value of 20 to 150 mgKOH / g (B) a chlorinated polyolefin resin having a chlorine content of 50% by weight or less (C) a crosslinkable resin capable of reacting with a hydroxyl group 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.