JP3292903B2 - Method for coating polyolefin resin molded body - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

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

[0002]

2. Description of the Related Art Polyolefin resin moldings are inexpensive, have excellent mechanical properties and are recyclable, so they are widely used for automobile outer panels such as bumpers. The molded body is usually coated with a primer and a top coating for aesthetics, prevention of scratches, improvement of weather resistance, and the like. However, this polyolefin-based resin molded article has a poor crystalline structure and has no crystalline group, and has high crystallinity. It was necessary to improve the adhesion by steam cleaning with an organic halogen-based solvent such as 1-trichloroethane and degreased, and etching the surface thereof.

However, organic halogenated solvents such as trichloroethane are cited as one of the causes of ozone depletion in the atmosphere, and it is necessary to pay close attention to their use. It is.

[0004] The above-mentioned primer is mainly composed of polypropylene, and the amount of the organic solvent at the time of coating is large. Activated carbon adsorption method, direct flame combustion method, catalytic combustion (oxidation) method, etc. are used as methods to prevent the volatilization of organic solvent gas in the atmosphere. In the coating field, water-soluble organic solvents such as alcohols are used. A method of trapping the solvent vapor generated in the coating and drying and curing steps in water is often used. However, when the above-mentioned water-soluble organic solvent is applied to the above-mentioned primer containing polypropylene as a main component, the solubility or dispersibility of the resin is inferior and phase separation or the like is caused, which is not preferable.

[0005]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in order to solve the above-mentioned problems of the prior art, and as a result, in a method of sequentially applying a primer and an overcoat composition to a polyolefin resin molded article, particularly, By using a primer having a specific composition, the molded article does not need to be washed with an organic halogen-based solvent such as trichloroethane, and is generated in the primer coating and drying and curing steps without causing phase separation of the primer. The inventors have found that solvent vapor can be captured in water, and have finally completed the present invention.

That is, the present invention provides a coating method which comprises sequentially coating the surface of a polyolefin resin molded article with a primer (A) and a top coat (B) without washing with an organic halogen solvent. As a primer (A),
Maleic acid-modified chlorinated polypropylene (A-1) and urethane-modified polyester resin (A-2) having an acid value of 20 to 60 mgKOH / g, a chlorine content of 18 to 28% by weight, and a weight average molecular weight of 30,000 to 170,000. A water-soluble organic solvent (A-4) having a solubility in water (20 ° C.) of 0.5% by weight or more and a vapor pressure (20 ° C.) of 90 mmHg or less as a resin component and a solvent component (A-3) at the time of coating; )
As a main component, and 8 of the water-soluble organic solvent (A-4).
The present invention relates to a method for coating a polyolefin-based resin molded article, wherein a primer in which 0% by weight or more is a ketone-based water-soluble organic solvent is used.

In the present invention, the molded article of the polyolefin resin to be coated is formed of ethylene, propylene, butylene,
A resin obtained by polymerizing one or more kinds of olefins having 2 to 10 carbon atoms, such as hexene, formed into an arbitrary shape. Such as, but not limited to, bumpers, spoilers, and grills.

In the present invention, when the primer (A) is applied to the polyolefin resin molded article, it is used from the viewpoint of environmental protection such as harmful organic halogen solvents such as trichloroethane and aromatic hydrocarbon solvents. A coating method is employed without using a cleaning agent containing a component of concern.

That is, it is possible to apply the primer (A) on the surface of the molded body without any pretreatment as it is manufactured (molded), but if necessary, it is possible to use a non-polluting aqueous system. It is preferable to remove dust and degrease by wiping and washing with a cleaning agent, steam, an alcohol solvent or the like.

The primer (A) used in the present invention is a paint which is applied directly to a polyolefin resin molded article prior to the application of a top coat, and has an acid value of 20 to 60 mg KOH / g.
A chlorine content of 18 to 28% by weight and a weight average molecular weight of 3
Maleic acid-modified chlorinated polypropylene (A-1) and urethane-modified polyester resin (A-2) having a solubility of 20,000 to 170,000 are used as the resin components, and the solvent component (A-3) at the time of coating has a solubility in water of (20). ℃)
A water-soluble organic solvent (A-4) having a vapor pressure (20 ° C.) of 90 mmHg or less as a main component at 0.5% by weight or more, and 80% by weight or more of the water-soluble organic solvent (A-4) is a ketone type It is a primer composed of a water-soluble organic solvent.

First, the primer (A) used in the present invention
Will be described.

[0012] Maleic acid-modified chlorinated polypropylene (A
The base polypropylene of -1) is a homopolymer of propylene or a copolymer of propylene and one or more olefins selected from ethylene, pentene, hexene, octene, decene, and the like. And so on. The content of propylene in the copolymer is 40% by weight.
More preferably, it is at least 60% by weight.

The above component (A-1) is usually obtained by graft-modifying maleic acid (including maleic anhydride, the same applies hereinafter) to polypropylene as a base, followed by chlorination. The order of chlorination can be reversed or simultaneous. The graft modification may be performed by a method known per se, for example, by reacting maleic acid in an organic solvent solution of polypropylene in the presence of a radical generator. The amount of maleic acid modified, that is, the degree of maleation, is such that the acid value of the resulting maleic acid-modified chlorinated polypropylene (A-1) is 20 to 60 mg.
KOH / g, particularly preferably in the range of 30 to 40 mg KOH / g. When the acid value is less than 20 mgKOH / g, the adhesion to the top coat decreases, and the acid value is 60 mgKOH / g.
If it is larger than g, the water resistance of the primer coating film becomes insufficient, which is not preferable.

The chlorination of maleic acid-modified (graft-modified) polypropylene is carried out by introducing chlorine gas into an organic solution of the graft-modified polypropylene, and the reaction temperature is preferably 50 to 120 ° C. For chlorination, the chlorine content in maleic acid-modified chlorinated polypropylene was 1
The content is preferably in the range of 8 to 28% by weight, particularly 20 to 25% by weight. When the content is less than 18% by weight, the solubility in an organic solvent is reduced, and the storage stability and coating workability of the primer are deteriorated. If the chlorine content is more than 28% by weight, the adhesion to a polyolefin-based resin molded product, the resistance to organic solvents, and the like are undesirably reduced.

The maleic acid-modified chlorinated polypropylene (A-1) has a weight average molecular weight of 30,000 to 170.
000, especially 50,000 to 130,000 are suitable.

Urethane-modified polyester resin (A-2)
Is a reaction product of a polyester polyol and a polyisocyanate compound. The polyester polyol is obtained by polycondensing a polybasic acid and a polyol. Polybasic acid is a compound having two or more carboxyl groups in one molecule, for example, adipic acid, succinic acid, sebacic acid, glutaric acid, maleic acid, fumaric acid,
And aliphatic, aromatic and alicyclic polybasic acids such as phthalic acid, terephthalic acid, hexahydrophthalic acid, tetrahydrophthalic acid, and anhydrides thereof. The polyol is a compound having two or more hydroxyl groups in one molecule, such as ethylene glycol, propylene glycol, diethylene glycol, trimethylene glycol, butanediol, pentanediol, hexanediol, neopentyl glycol, cyclohexanediol, and polylactone polyol. Glycerin, trimethylolpropane and the like. The polybasic acid and the polyol are reacted in such a ratio that the hydroxyl groups become excessive. The polyisocyanate compound is a compound having two or more isocyanate groups in one molecule, for example, aliphatic diisocyanate compounds such as hexamethylene diisocyanate, trimethylene diisocyanate, propylene diisocyanate, dimer diisocyanate, and lysine diisocyanate; isophorone diisocyanate Alicyclic diisocyanate compounds such as methylene bis (cyclohexyl isocyanate), cyclohexane diisocyanate, and cyclopentane diisocyanate; aromatic diisocyanate compounds such as xylylene diisocyanate, metaxylylene diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, and toluidine diisocyanate; Is raised.

The compound (A-2) is obtained by subjecting a hydroxyl group of a polyester polyol to an isocyanate group of a polyisocyanate compound to undergo a urethanization reaction. The ratio of both functional groups can be arbitrarily selected according to the purpose. It is preferable that free isocyanate groups do not remain in the produced urethane-modified polyester resin by reacting isocyanate groups at a ratio of 1 mol or less per unit. In the urethanization reaction, the polyol may be used as a chain extender, if necessary.

In the primer (A) used in the present invention, the above-mentioned maleic acid-modified chlorinated polypropylene (A-1) and urethane-modified polyester resin (A-2) are essential resin components, and their ratio is particularly limited. However, based on the total weight of both components, component (A-1) is 95 to
70% by weight, particularly 90 to 80% by weight, and the component (A-2) is preferably 5 to 30% by weight, particularly preferably 10 to 20% by weight.

Next, the primer (A) used in the present invention
Will be described.

The solvent component (A-3) of the primer (A) used in the present invention has a solubility in water (20 ° C.) of 0.5% by weight or more and a vapor pressure (20 ° C.) of 90% at the time of coating.
mmHg or less water-soluble organic solvent (A-4) as a main component,
In addition, it is necessary that 80% by weight or more of (A-4) is composed of a ketone-based water-soluble organic solvent.

Here, "at the time of coating" defines the solvent component when the primer (A) is coated on the object to be coated, and the solvent component at the time of preparing the primer (A) is used as it is. Means that the above requirement may be satisfied, or that the above requirement may be satisfied as a result of appropriately diluting the solvent component at the time of preparing the primer (A) with a water-soluble organic solvent.

When the solubility (20 ° C.) of water-soluble organic solvent (A-4) in water is 0.5% by weight or more and the vapor pressure (20
C.) is 90 mmHg or less, so that the capturing efficiency in water is improved.

Further, since the water-soluble organic solvent (A-4) is the main component of the solvent component (A-3) of the primer (A), most of the organic solvent generated at the time of coating the primer is dissolved in water. It can be captured, which is effective in preventing pollution. Here, in order to be the main component, more specifically, the content of the water-soluble organic solvent (A-4) in the primer solvent component (A-3) at the time of coating (hereinafter referred to as WS conversion ratio). Is desirably 65% by weight or more.

In addition, the content of the ketone-based water-soluble organic solvent in the water-soluble organic solvent (A-4) (hereinafter, referred to as the ketone conversion ratio of WS) is 80% by weight or more.
The solubility in the maleic acid-modified chlorinated polypropylene (A-1) and urethane-modified polyester resin (A-2) is improved, so that phase separation of the primer (A), pigment sedimentation, and the like can be prevented. If the ketone conversion ratio of WS is less than 80% by weight, phase separation, pigment sedimentation, and the like are likely to occur, which is not preferable.

Examples of the ketone water-soluble organic solvent having such characteristic values include methyl ethyl ketone, methyl isobutyl ketone, methyl butyl ketone, ethyl butyl ketone, cyclohexanone, isophorone and the like.

80% by weight of the water-soluble organic solvent (A-4)
Above, particularly preferably 85% by weight or more of the ketone-based water-soluble organic solvent, and the remaining 20% by weight or less of other water-soluble organic solvents, for example, ethyl acetate, butyl acetate, isobutyl acetate, acetic acid Isopropyl,
Acetate solvents such as secondary butyl acetate, ethylene glycol monomethyl ether acetate, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate; ethanol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, secondary butyl alcohol Alcohol solvents such as tert-butyl alcohol, n-amyl alcohol, n-amyl alcohol, isoamyl alcohol, secondary amyl alcohol, tertiary amyl alcohol, cyclohexanol, ethylene glycol, propylene glycol, and butylene glycol; ethylene glycol monomethyl ether, ethylene glycol monoethyl ether , Ethylene glycol dimethyl ether, ethylene glycol Lumpur diethyl ether, diethylene glycol monomethyl ether, triethylene glycol monoethyl ether and diethylene glycol monobutyl ether;
Ether solvents such as dioxane and dimethyldioxane;
And the like. All of these are water-soluble organic solvents having a solubility in water (20 ° C.) of 0.5% by weight or more and a vapor pressure (20 ° C.) of 90 mmHg or less.

In the solvent (A-4), when the solubility (20 ° C.) is lower than 0.5% by weight or the vapor pressure (20 ° C.) is higher than 90 mmHg, the solubility in water is reduced. The high vapor pressure makes capture in water difficult. On the other hand, if the solubility is 0.5% by weight or more and the vapor pressure is higher than 90 mmHg, the efficiency of trapping the solvent vapor into water decreases because the exhaust air volume of the coating booth is extremely large. When the solubility is less than 0.5% by weight and the vapor pressure is 90 mmHg or less, the solubility in water is low,
The trapping efficiency decreases. Particularly preferred as the solvent (A-4) is a solvent having a solubility (20 ° C.) of 1% by weight or more and a vapor pressure (20 ° C.) of 75 mmHg or less.

Solvent component of primer (A) (A-3)
At the time of coating, the water-soluble organic solvent (A-4)
But a water-insoluble organic solvent other than (A-4), such as toluene, xylene, or other petroleum-based high-boiling aromatic solvent, is used in an amount of 35% by weight or less in (A-3). Can be used together within the range.

The primer (A) contains a resin component and a solvent component as described above, and further contains a coloring pigment, an extender pigment, a metallic pigment, a leveling agent,
An ultraviolet absorber, an antioxidant, a light stabilizer, a chlorine scavenger, a pigment sedimentation inhibitor and the like can be added.

The top coat (B) used in the present invention
Any known resins can be used. For example, a melamine resin, a urea resin, a benzoguanamine resin, a polyisocyanate compound (including a blocked product) may be used for a base resin such as an acrylic resin, a polyester resin, an alkyd resin, and a fluorine resin containing a hydroxyl group. )) Are preferred. The top coating (B) may be a colored coating (solid color), a metallic coating or a clear coating, or may be a combination of these as appropriate and applied a plurality of times.

In the present invention, the coating of the primer (A) on the surface of the polyolefin-based resin molded product is usually suitably performed by a spray coating method such as air spraying. The primer (A) usually has a thickness of 5 to 35 based on the dried and cured coating film.
μm, preferably 10-20 μm, and left at room temperature for several minutes or 5-100 ° C. at 70-100 ° C.
After drying for a minute, the top coat (B) is usually applied at room temperature. The thickness of the overcoat film is usually 20 to 50 μm, preferably 25 to 35 μm based on the cured coating film, and cured by heating at 70 to 160 ° C. for 5 to 60 minutes.

In the coating method of the present invention, in particular, organic solvent vapors and the like generated in the coating step of the primer (A) and the drying and curing step of the coating film can be suitably captured in water.

Most of the scattered or volatilized mist generated in the coating step and the coating film curing step, the solvent vapor, and the volatile products at the time of curing are washed with water and most of them can be captured. As a cleaning method, a normal gas-liquid contact method, for example, a scrubber method, a bubbling method, a shower method, a wet wall method, and the like can be suitably adopted. In particular, a scrubber method, a shower method, and a wet wall method are suitable from the viewpoint of removal efficiency.

The water that has captured paint mist, solvent vapor, etc.
It is sent to a water treatment device and processed. Specifically, an activated sludge method, an air oxidation method, an ozone oxidation method, a coagulation sedimentation method, a pressure flotation method, or the like is used alone or in combination. In particular, a combination is preferred in which the solid content of the paint mist and a part of the water-insoluble solvent in the washing wastewater are treated by a normal pressure flotation method, and the solvent component that has been solubilized is treated by an activated sludge method. The treated water is usually sent back to the washing device for reuse from the viewpoint of water resource reuse.

[0035]

According to the coating method of the present invention, it is necessary to pay close attention to the use of a polyolefin resin molded article to be coated from the viewpoint of environmental protection, or to consider the use of an organic halogenated resin. Even without washing with a system organic solvent, sufficient adhesion of the coating film can be obtained, and in addition, organic solvent vapors and the like generated in the primer coating process and the drying and curing process can be captured in water. This makes it possible to significantly reduce the amount of organic solvent vapor discharged, which is extremely effective in preventing pollution.

[0036]

EXAMPLES Hereinafter, Production Examples, Examples and Comparative Examples will be given,
The present invention will be described more specifically. Parts and% in each example
Are in principle based on weight.

Production Example 1 Preparation of maleic acid-modified chlorinated polypropylene (A-1) A toluene solution of maleic acid-modified chlorinated polypropylene (solid content: 30%) having the characteristic values shown in Table 1 was prepared. a and b are for Examples, and c to g are for Comparative Examples.

[0038]

[Table 1]

Production Example 2 Preparation of urethane-modified polyester resin (A-2) 0.157 mol of isophthalic acid, 0.315 mol of hexahydrophthalic acid, 0.315 mol of adipic acid, 0.14 mol of neopentyl glycol, 1, A polyester resin is synthesized by subjecting 0.51 mol of 6-hexanediol and 0.35 mol of trimethylolpropane to a condensation reaction, and further reacted with 0.05 mol of isophorone diisocyanate to prepare a urethane-modified polyester resin. 7
A 0% xylene solution was obtained.

Production Example 3 Preparation of Pigment Dispersion A titanium white pigment (manufactured by Teikoku Chemicals, JR-602, commercial product) was added to 14.3 parts of a xylene solution having a solid content of 70% of the urethane-modified polyester resin (A-2). Name) 100 parts and methyl ethyl ketone 10 parts were mixed and dispersed by a pebble mill ball mill until the tubing evaluation was 10 μm or less, and 15 parts of methyl ethyl ketone was added to adjust the viscosity to obtain a pigment dispersion Ta. The solid content (resin content and pigment content) content of this dispersion Ta was 79%.

A maleic acid-modified chlorinated polypropylene (A-1) a toluene solution (solid content 30%)
%) Per 100 parts by weight, the above-mentioned titanium white pigment (100 parts) was mixed and dispersed in the same manner as described above, and 30 parts of methyl ethyl ketone was added to adjust the viscosity to obtain a pigment dispersion Tb. The solid content (resin content and pigment content) content of this dispersion Tb was 56%.

Production Example 4 Preparation of Primer A toluene solution of maleic acid-modified chlorinated polypropylene (A-1) (solid content: 30%) and a xylene solution of urethane-modified polyester resin (A-2) (solid content: 7%)
0%) and a pigment dispersion (solid content 79% or 56)
%) In the proportions shown in Table 2 to prepare a primer coating. Here, in the compounding amount of the primer composition in Table 2, the solid content (resin content) of the component (A-1) is the pigment dispersion liquid.
The resin component of (A-1) component in Tb is contained, and (A-2)
The solid content (resin content) of the component is (A-
2) The resin component is included. The compounding amount of the pigment dispersion indicates a pigment content (solid content of the pigment component in the dispersion).

Primer for olefin resin molded article diluted with a water-soluble organic solvent in an amount shown in the solvent column of Table 2 per 100 parts (including solvent) of the obtained coating material to adjust the solvent composition at the time of coating. P1 to P18 were obtained.

[0044]

[Table 2]

The abbreviations of the solvents in the table indicate the following. The numerical values in parentheses indicate the solubility in water at a solubility of 20 ° C. and the vapor pressure at a vapor pressure of 20 ° C., respectively.

MEK: methyl ethyl ketone (solubility: 26.8)
Wt%, vapor pressure 71 mmHg), MIBK: methyl isobutyl ketone (solubility 2.0 wt%, vapor pressure 5 mmHg), CHEX: cyclohexanone (solubility 10.0 wt%, vapor pressure 4 mmH)
g), ETA: ethyl acetate (solubility 2.3% by weight, vapor pressure 7)
IPA: isopropyl alcohol (dissolves in water at any ratio, vapor pressure 32 mmHg), EGME: ethylene glycol monomethyl ether (dissolves in water at any ratio, vapor pressure 6 mmHg).

Among the primers in Table 2, P1, P2, P
8, P9, P11 to P13 and P18 are for the present invention. In addition, P3 to P7 indicate that maleic acid-modified chlorinated polypropylene (A-1) was used for the comparative example.
Are for the comparative example based on the fact that the urethane-modified polyester resin (A-2) is not blended, and that P14 to P16 are based on the fact that the ketone conversion ratio of WS is out of the predetermined range.

Examples 1 to 8 and Comparative Examples 1 to 10 A polypropylene resin injection molded plate for bumpers (manufactured by Mitsubishi Yuka Co., NX-280AK, trade name) was used as an object to be coated, and this was dyed with isopropyl alcohol. After wiping the surface with the gauze soaked in, the primer adjusted to the solvent composition at the time of coating in Production Example 4 was applied by air spray to a thickness of 5 to 15 μm based on the cured coating film, and left at room temperature for 10 minutes. After that, a one-component polyester resin / melamine resin-based topcoat (manufactured by Kansai Paint Co., Ltd., Soflex No. 1200)
White, trade name) painted by air spray
Cured by heating for 0 minutes. The thickness of the top coat cured film is 80 to 120 µm for the adhesion test, and 30 to 40 for the others.
μm.

During the coating of the primer, organic solvent vapors and the like were captured in water by a scrubber method.

Next, the pigment settling property and layer separation property of the primer adjusted to the solvent composition at the time of the above coating, and the adhesion, water resistance and gasoline resistance of the obtained coating film were examined. The test method is as follows.

Pigment sedimentability After the primer was placed in a glass test tube and left at 20 ° C. for 48 hours, the pigment sedimentability was evaluated according to the following criteria.

○ indicates whether there was no pigment sedimentation at the bottom of the test tube,
Or, if the pigment settles up and down 10 times, the pigment can be redispersed by shaking the test tube up and down 10 times. X indicates that the pigment is remarkably settled at the bottom of the test tube, and redispersion is impossible even if the test tube is shaken up and down 10 times.

Layer Separation A primer was placed in a glass test tube and allowed to stand at 20 ° C. for 48 hours, and then the layer separation was evaluated according to the following criteria.

○ indicates that no or no slight layer separation occurred, and even if the test tube was shaken up and down two or three times, the test tube became uniform. X indicates that the layer was not uniform even if it was shaken up and down three times, and x indicates that the layers were clearly separated and separated into two layers and became cloudy.

Adhesion The coating film was slit to a width of 10 mm, and an autograph “AG50
OB type (made by Shimadzu Corp., trade name) at a speed of 50
A 180 ° peel test was performed at a rate of mm / min, and the peel strength was measured. The evaluation of adhesion was based on the following criteria.

○ indicates that the peel strength exceeds 900 g / cm ² and the adhesion is excellent, and △ indicates that the peel strength is 900 to 70.
0 g / cm ² , indicating that the adhesiveness was normal, and x indicates that the peel strength was less than 700 g / cm ² , and that the adhesiveness was poor.
Shown respectively.

After immersing the sample in warm water at 40 ° C. for 10 days, 100 cuts of 2 mm × 2 mm grid were made through the coating with a razor, and a cellophane adhesive tape (JIS-Z152) was formed thereon.
2) was firmly pressed, and the tape on the other side was peeled off at a stretch while keeping the end of the tape at 30 degrees with the coating film surface, and the number of crosses remaining after the peeling was counted. The evaluation of water resistance was based on the following criteria.

○ indicates that the remaining number is 100 and is excellent in water resistance, △ indicates that the remaining number is 90 to 99 and is poor in water resistance, and X indicates that the remaining number is 89 or less and the water resistance is poor. The properties are markedly inferior, respectively.

Gasoline resistance After the sample was immersed in gasoline at a temperature of 20 ° C. for 24 hours, a cross-cut peeling test was performed in the same manner as in the above-mentioned water resistance test. The sex was evaluated.

Table 3 shows the test results.

[0061]

[Table 3]

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masahiko Sakane 33-1, Kanzakicho, Amagasaki-shi, Hyogo Kansai-Paint Co., Ltd. (56) References JP-A-7-18104 (JP, A) JP-A Heisei 6-172565 (JP, A) JP-A-5-239292 (JP, A) JP-A-3-182534 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C08J 7/04 -7/06 C09D 123/26 C08L 1/00-101/16

Claims (1)

(57) [Claims] A primer (A) without washing the surface of a polyolefin resin molded article with an organic halogen solvent.
And a successive coating with a top coat (B), wherein the primer (A) has an acid value of 20-6.
A maleic acid-modified chlorinated polypropylene (A-1) and a urethane-modified polyester resin (A-2) having 0 mgKOH / g, a chlorine content of 18 to 28% by weight, and a weight average molecular weight of 30,000 to 170,000 as resin components; and The solvent component (A-3) at the time of coating has a solubility in water (20 ° C.) of 0.5% by weight or more and a vapor pressure (20 ° C.) of 90%.
mmHg or less water-soluble organic solvent (A-4) as a main component,
A method for coating a molded polyolefin resin, characterized in that a primer in which 80% by weight or more of the water-soluble organic solvent (A-4) is a ketone-based water-soluble organic solvent is used.