JPH0286674A - Synthetic resin molding and its production - Google Patents

Abstract

PURPOSE:To make it possible to form a synthetic resin molding improved in adhesion to a coating film obtained from, especially, a water-based coating material by applying a specified water-based primer to a synthetic polyolefin resin substrate and applying a topcoating material to the surface of the primer. CONSTITUTION:This synthetic resin molding is at least constituted of (I) a synthetic polyolefin resin substrate, (II) a layer (water-based primer layer) of a composition based on a copolymer of a polyisocyanate compound having at least two isocyanate groups in the molecule with a hydroxylic monomer and/or an alpha,beta-unsaturated carboxylic acid monomer and other monomers and having an isocyanate group content of 0.5-4wt.% based on the total solid matter, and (III) a coating material.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a synthetic resin molded article in which the adhesion of a coating film to a substrate is significantly improved, and a method for producing the same. In particular, the present invention relates to polyolefin-based synthetic resin molded articles with improved adhesion to substrates of coating films obtained from water-based coating materials such as water-based adhesives, water-based inks, and water-based paints, and methods for producing the same.

(Prior art) Conventional polyolefin synthetic resin molded articles such as polyolefin films and sheets are inexpensive, have excellent mechanical and chemical properties, and have excellent water resistance and chemical resistance. However, polyolefins generally have the disadvantage of poor adhesion to various polymers due to their low polarity. It is said that there is a problem in the adhesion of the applied adhesive or paint ink to the base material.In particular, water-based adhesives such as latex adhesives, water-based paints that use latex polymer as a vehicle, etc. Water-based coating materials such as water-based inks inherently have problems with water resistance, especially water-resistant adhesion, and when coated on polyolefin films and sheets that have poor adhesion, they can be exposed to high humidity or come into contact with water. Adhesion to the substrate under these conditions has been pointed out as a major practical problem.

Various types of undercoating agents have been proposed to solve this problem. By the way, in recent years, water-based adhesives, water-based paints, water-based inks, and other water-based paints have become widely used for the purpose of saving resources, improving the working environment, and eliminating the risk of fire. A water-based primer should be used, and many such water-based primers have been proposed. For example, JP-A-59-196381, JP-A-59-204678, JP-A-60-44.
Publication No. 573 discloses a method of using a titanium compound or a zirconium compound alone or as a composition added to an acrylic latex as a water-based undercoat for polyolefin sheets.

Also, JP-A-60-76587 and JP-A-62-10
No. 181 gives an example of using a specific self-crosslinking acrylic latex or acrylamine compound as a water-based undercoat.

(Problems to be Solved by the Invention) However, in these conventionally known methods, when applying water-based coating materials such as water-based adhesives, water-based paints, and water-based inks to polyolefin synthetic resin base materials, is not necessarily sufficient. It has a serious drawback of poor adhesion to substrates, particularly under conditions of high humidity or contact with water.

(Means for solving problems) The present invention solves the above problems.

That is, the present invention comprises: 1-(i) a polyolefin-based synthetic resin base material, (1) a polyfunctional isocyanate compound containing two or more isocyanate groups in the compound, and a hydroxyl group-containing monomer and/or α,β unsaturated A composition material whose main component is a copolymer of a carboxylic acid monomer and other monomers and whose isocyanate group content is 0.5 to 4% by weight based on the total solid content, and (11) at least one of the coating materials. The surface of the synthetic resin molded article consisting of three layers, and 2. the polyolefin synthetic resin base material, is subjected to an oxidation treatment sufficient to increase the critical surface tension by 5 dynes/crIL or more than that before treatment, and then (4) isocyanate is applied. A self-emulsifying polyfunctional isocyanate solution prepared by mixing a polyfunctional isocyanate compound containing two or more groups in the compound, a poorly water-soluble organic solvent that has no substantial reactivity with the isocyanate group, and a surfactant; B) Hydroxyl group-containing monomer and/or α.

An aqueous dispersion containing particles of a copolymer obtained by polymerizing a β-unsaturated carboxylic acid monomer and other monomers has an isocyanate group content of 0 based on the total solid content of the solid liquid and (B) liquid. The present invention relates to a method for producing a synthetic resin molded article, characterized in that a mixture of .5 to 4% by weight is applied, dried, and then a coating material is applied thereon.

Hereinafter, a method for manufacturing a synthetic resin molded article of the present invention will be described.

The polyolefin synthetic resin base material used in this invention is made of polyolefin resin such as polyethylene or polypropylene, which is formed into a film or sheet with a thickness of 20μ to 500μ by stretching or non-stretching.
There are extrusion molded products such as micro-sized films and sheets, and other molded products obtained by various molding methods such as injection molding.

These polyolefin synthetic resin base materials are subjected to corona discharge treatment, fire treatment, chemical oxidation using an oxidizing agent, etc. to improve the critical surface tension of the polyolefin synthetic resin base material before treatment according to JIS K6768 K. The surface oxidation treatment is applied to the surface of the polyolefin synthetic resin base material so that the critical surface tension is 5 dynes/CML or more thicker. This reaction creates a functional group that can react with the isocyanate groups in the primer formulation, and this reaction improves the adhesion between the primer formulation and the polyolefin synthetic resin base material, and ultimately improves the adhesion between the primer formulation and the polyolefin synthetic resin base material and the top coat material and the polyolefin synthetic resin base. This is essential in order to improve the adhesion to the material.If this surface preparation is not performed or the treatment effect is below 5 dynes/cm, water-based adhesiveness will not be achieved even if the formulation specified in the present invention is used. The effect of improving the adhesion between a water-based coating material such as a water-based paint, a water-based ink, and a polyolefin synthetic resin base material cannot be achieved sufficiently.

The water-based undercoat used in this invention includes a polyfunctional isocyanate compound containing two or more isocyanate groups, a poorly water-soluble organic solvent that has no substantial reactivity with the isocyanate groups, and a surfactant. A self-emulsifying polyfunctional isocyanate solution (hereinafter referred to as
solid-liquid), hydroxyl group-containing monomer and/or α.

From β-unsaturated carboxylic acid monomers, and other monomers such as (meth)acrylic acid alkyl ester monomers, vinyl aromatic monomers, aliphatic diene monomers, ethylene, and other vinyl monomers. An aqueous dispersion type mixture is used, which is prepared by mixing an aqueous dispersion (hereinafter referred to as Bj liquid) containing a copolymer of selected monomers as particles.

In the self-emulsifying polyfunctional isocyanate solution which is liquid (A) of this water-dispersed formulation, the polyfunctional isocyanate compound containing two or more isocyanate groups in the compound includes aliphatic isocyanates such as hexamethylene diisocyanate, m - and p-phenylene diisocyanate, tolylene, 2,4- and 2,6-diisocyanate, diphenylmethane-4,4'-siquanate,
naphthylene-1,5-cyisocyanate), chlorphenylene-2,4-diisocyanate, diphenylene-4,
Aromatic isocyanates such as 4'-1 diisocyanate, 4,4'-diisocyanate-3,3'-diphenyl, 3-methyl-diphenylmethane-4,4'-diisocyanate, polymethylene polyphenylisocyanate and diphenyl ether diisocyanate. , and cycloaliphatic isocyanates such as cyclohexane-2,4- and -2,3-diisocyanate, isophorone diisocyanate. Further, polyfunctional isocyanate adducts obtained by polymerizing such polyfunctional isocyanates with three components such as water, oxygen-containing compounds, and water can also be used. Among these polyfunctional isocyanate compounds, aliphatic and alicyclic isocyanates or their adducts, which have a relatively slow reaction rate with water, are particularly preferably used.

The poorly water-soluble organic solvent used in liquid (3) of the water-dispersed formulation is one that does not substantially have reactivity with isocyanate groups, and is preferably 20 parts by weight based on 100 parts by weight of the polyfunctional isocyanate compound. The above is added. The slightly water-soluble organic solvent is preferably one that can completely dissolve the polyfunctional isocyanate compound. Typical examples of these slightly water-soluble organic solvents include aromatic and alicyclic hydrocarbons such as toluene, xylene, benzene, ethylbenzene, and cyclohexane. When the amount of the poorly water-soluble organic solvent added is 20 parts by weight or less, the purpose of adding the organic solvent is to delay the reaction between water as a dispersion medium and the polyfunctional isocyanate, thereby extending the pot life of the water-dispersed formulation. However, the effectiveness of this method is insufficient, and only formulations with short pot lives can be obtained.

As the surfactant in the base solution of the formulation, various surfactants containing polyethylene glycol groups as hydrophilic groups, whose hydrophilic groups do not lose their function upon reaction with isocyanate groups, are suitably used. Preferred surfactants include furkylphenyl ether of polyethylene glycol and sorbitan ester of polyethylene glycol.The amount of this surfactant added is the combined amount of the polyfunctional isocyanate compound and the poorly water-soluble organic solvent.
It is preferable to add 3% to 15% by weight based on 00 parts by weight. These surfactants can be added in advance to a mixture of a polyfunctional isocyanate compound and a poorly water-soluble organic solvent, but depending on the type of surfactant, its surface activity may decrease during storage due to reaction with isocyanate groups. If it causes a significant decrease in performance, it can be added to the mixture of these polyfunctional isocyanate compounds and poorly water-soluble organic solvents immediately before mixing with liquid CB).

In the liquid (B) of the water-dispersed formulation, the total amount of the hydroxyl group-containing monomer and/or α, β unsaturated carboxylic acid monomer is 0.5 to 15ii%, and the remaining 85 to 15ii%. 99.5% by weight of monomers include monomers selected from (meth)acrylic acid alkyl ester monomers, vinyl aromatic monomers, aliphatic diene monomers, ethylene, and other vinyl monomers. An aqueous dispersion containing particles of a polymer obtained by copolymerizing polymers is used. Here, as the hydroxyl group-containing monomer, a radical monomer having one or more hydroxyl groups in the molecule is used, examples of which include 2-hydroxyethyl acrylate, 2-hydroxyethyl methacrylate, and acrylic acid. Examples include 2-hydroxypropyl, 2-hydroxypropyl methacrylate, 4-hydroxybutyl acrylate, and 4-hydroxybutyl methacrylate. Further, as the α,β unsaturated carboxylic acid monomer, for example, acrylic acid, methacrylic acid, itaconic acid, fumaric acid, etc. are used. Other (meth)acrylic acid alkyl ester monomers used include methyl methacrylate, butyl methacrylate, methyl acrylate, ethyl acrylate, methyl acrylate, and 2-ethylhexyl acrylate. , cycloexyl acrylate, etc. Examples of vinyl aromatic monomers include styrene and vinyltoluene. Examples of aliphatic diene monomers include butadiene, isoprene, and the like. Other vinyl monomers include vinyl esters such as vinyl acetate, vinyl propionate, vinyl versatate, vinyl cyanides such as butyl methacrylate, vinyl chloride, vinylidene chloride, etc. There are types.

In the monomer composition of such a copolymer, the hydroxyl group-containing monomer and/or α, l unsaturated carboxylic acid monomer are present in a total amount of 0.5 to 15% by weight. Preferably, it is polymerized.

The total amount of copolymerization of these two types of monomers is 0.5% by weight.
If this is taken as the standard, a formulation using it will be inferior in the desired effect of improving adhesion to a substrate. On the other hand, if the amount exceeds 15% by weight, the effect of improving adhesion to the substrate under conditions of high humidity or contact with water will not be sufficient in combination with the amount of polyfunctional isocyanate compound specified in the present invention.

A polymer aqueous dispersion obtained by copolymerizing these monomers is used as a (Bl solution) and is used as an undercoat in combination with a self-emulsifying polyfunctional isocyanate solution (liquid (2)) immediately before coating. , the blending ratio is set such that the isocyanate group content in the solid content of the blend falls within the range of 0.5% by weight to 4% by weight. Isocyanate group content refers to the amount of molecules fik42 in the solid content that ultimately forms a solid film after excluding volatile components such as water and poorly water-soluble organic solvents in a water-dispersed formulation.
It refers to the weight percent occupied by isocyanate groups. If the isocyanate group content in the formulation is less than 0.5% by weight, the effect of improving adhesion to the substrate will not be sufficient (on the contrary, if it exceeds 4it%, the formulation will foam in a short time after mixing the two parts. This may cause practical problems such as .

When a polyolefin synthetic resin base material is subjected to a certain degree of surface oxidation treatment and coated with the specific formulation specified in this application, it is possible to apply a water-based coating agent such as a water-based adhesive, water-based paint, or water-based ink. Although it is not clear why polyolefin-based synthetic resin molded articles can be obtained that have excellent adhesion to substrates, especially under conditions of high humidity or contact with water,
Functional groups such as carboxyl groups and hydroxyl groups generated on the surface of the polyolefin synthetic resin base material by oxidation treatment and hydroxyl group-containing monomers and α, β monomers copolymerized with the polymer in the blend (B) solution. A so-called co-crosslinking reaction occurs between the hydroxyl groups and carboxyl groups based on saturated carboxylic acids and the polyfunctional isocyanate compound in the compound (base solution), resulting in a crosslinking reaction between the base polyolefin sheets and the coating film of the compound. The first reason is thought to be that the adhesion was significantly improved.

Furthermore, the water-based coating agent coated on top of this has strong adhesion to the coating film of the compound, which is a highly polar and non-crystalline polymer, including mutual diffusion of molecules, resulting in such good properties. It is presumed that adhesion to the base material was developed.

As an example of a specific method for carrying out the present invention, a solid content of 5.
A water-dispersed formulation according to the present invention, adjusted to 35% by weight, is applied to a dry coating thickness of 0.5μ to 2μ and dried to form a polyolefin with excellent adhesion to a substrate. Film sheets are obtained. A water-based coating material such as a water-based adhesive, water-based paint, or water-based ink is further applied onto this polyolefin film or sheet, but this can be done immediately after the above compound is applied and dried, or for a certain period of time depending on the purpose. It is also possible to apply the coating after the process.

However, in order for the composition defined by the present invention to exhibit its performance, curing for about one week is required at a temperature of 20°C.

Note that the top coating material applied to the polyolefin synthetic resin base material is not limited to water-based coating materials, but also various organic solvent-based coating materials, such as solvent-based adhesives, solvent-based paints, and solvent-based inks. It is.

Furthermore, any known coating method can be used to apply the composition as an undercoat to the polyolefin synthetic resin base material. Examples include various roll coating methods, gravure coating methods, spray coating methods, and the like.

Various known additives may be added to the water-dispersed formulation used in the present invention, as long as they do not impair its properties.

Examples include antifoaming agents, wetting agents for improving wetting to polyolefin synthetic resin substrates, and viscosity modifiers for improving coating properties.

The polyolefin synthetic resin molded article with improved substrate adhesion obtained by the present invention can be used in a wide range of applications, but a typical application is a polyolefin adhesive sheet coated with a water-based adhesive. Can be mentioned. Also, polyolefin film products printed with water-based ink,
Typical examples include polyolefin synthetic resin molded articles coated with water-based paints. There are also polyolefin adhesive sheets that combine these and have excellent ink adhesion, which are made by coating a compound on both sides of a polyolefin film that has been subjected to corona discharge treatment on both sides, and coating one side with an adhesive and the other side with a water-based ink. .

EXAMPLES The present invention will be specifically explained below with reference to Examples, but it goes without saying that the present invention is not limited to these Examples.

In addition, all parts in the text mean parts by weight.

Note that the adhesion to the base material was determined by the following method.

The adhesion of the polyolefin sheet to the base material using an adhesive as the top coating material was determined by 5US304, which was removed as an adherend.
Using a stainless steel plate, the polyolefin adhesive sheet to be tested was pressed using a rubber roller with a weight of 2 kg specified in JIS ZO237, and after being left for 3 days at 20°C and 65% RH, the peeling rate was 3 o o mv'+
A 180° peel test was conducted.

After pressing the adhesive sheet, the adhesive sample was immersed in water at 20'C for 3 days, and immediately after being taken out, it was heated at 18°C.

A peel test was conducted under the same conditions as above. Adhesion to the substrate was determined by K in this 180° peel test to determine whether adhesive failure occurred at the polyolefin sheet interface.

Adhesion to the base material when a water-based paint or the like, which does not inherently have adhesiveness, was used as the top coating material was determined by the following method. That is, a top coat is applied to a polyolefin substrate with or without a primer coat, and after drying,
The polyester-based adhesive tape was strongly crimped using the 2 kg roller mentioned above to avoid air bubbles.
It was left in a dry state under 65% RIII conditions and in water at 20°C for 3 days, and immediately after being taken out, it was rapidly peeled off at a 90° angle, and the top coat film was removed from the polyolefin molded product (to determine whether it would separate or not). Observed.

Reference Example 1 300 parts of n-butyl acrylate, 175 parts of methyl methacrylate, 20 parts of 2-hydroxyethyl methacrylate, 5 parts of methacrylic acid, 2 parts of sodium lauryl sulfate,
3 parts of polyoxyethylene alkylphenyl ether sodium sulfate surfactant, 2 parts of ammonium persulfate, and 300 parts of ion-exchanged water were charged into a flotation tank, and stirred and emulsified using a homogenizer to obtain a homogeneous emulsion. Subsequently, 200 parts of ion-exchanged water and 1 part of ammonium persulfate were charged in advance into a reactor equipped with a stirrer, a condenser, and a temperature control device, and the temperature was raised to 80°C. The emulsion was poured into the reaction tank for 4 hours while maintaining the reaction tank temperature at 80"GK under sufficient stirring.
It dripped over time. After completion of the dropwise addition, stirring was continued for 1 hour while keeping the internal temperature at 80°C to complete the reaction and obtain a stable latex.

Reference Example 2 In an autoclave equipped with a stirrer and a temperature control device, 350 parts of ion-exchanged water, 1.0 part of sodium dodecylbenzenesulfonate, and carboxy-modified polystyrene latex (average particle size 0.035μ, solid content concentration) were added as seed particles. 32% by weight) was added, and the internal temperature was set at 60°C. This autoclave was preconditioned (Il
A mixture of 100 parts of ion-exchanged water, 1 part of sodium hydroxide, 0.5 parts of sodium dodecylbenzenesulfonate, 2.5 parts of Nucol 506 (manufactured by Nippon Nyukazai) and 10 parts of sodium persulfate, and (II) ion. Exchange water 1
00 parts of sodium hydroxide, 0.5 parts of sodium dodecylbenzenesulfonate, 2.5 parts of Ninicor 506 (manufactured by 8 bottles emulsifier), and 10 parts of sodium sulfite; 200 copies, /(
A mixture of 7200 parts of chile, 25 parts of methyl methacrylate, 20 parts of 2-hydroxyethyl methacrylate, and 5 parts of methacrylic acid was mixed with (■) solution (Irl solution in 3.5 hours, (to) The liquid was fed at a uniform addition rate over 3 hours.The reaction was carried out under nitrogen pressure, and the internal temperature was kept at 60℃ during feeding.
℃ and stirred at a stirring speed of 300 rpm. After the addition of liquid (II) and liquid (Irl), the reaction temperature was maintained as it was and polymerization was continued for an additional hour to obtain a stable latex. The polymerization rate of the obtained latex was 98%.

Example 1 Hexamethylene diisocyanate adduct (Duraney) 24A-10 as a polyfunctional isocyanate compound
0 (manufactured by Asahi Kasei), 5 parts of toluene as a poorly water-soluble organic solvent, and 1 part of Nucor 85 (manufactured by Nippon Nyukazai), a tesorbitan surfactant as a surfactant, were mixed to form a water-dispersed formulation. A self-emulsifying polyfunctional isocyanate solution, which is a solid-liquid product, was obtained. Next, 8 parts of this liquid (4), 100 parts of the acrylic latex obtained in Reference Example 1 as a Bl liquid, and 100 parts of ion-exchanged water were stirred and mixed to obtain a water-dispersed mixture. The content of isocyanate groups in the solid content of the blend was 1.6 wt.

Using this formulation, a biaxially oriented PP film subjected to corona discharge treatment under the condition that the critical surface tension is 7 dynes/- higher than that before treatment, the dry coating thickness 4 was approximately 1.0μ. After coating, it was heated and dried at 90° C. for 1 minute. Polytron 59059 (manufactured by Asahi Kasei), a repeelable acrylic latex adhesive, was applied to the biaxially stretched PP film coated with this compound until the dry coating film was 1.
It was coated to give a thickness of 0μ and dried at 105°C for 5 minutes. After curing this pressure-sensitive adhesive sheet test piece for 7 days at 20° C. and 65% RH, the adhesion to the substrate was measured. The obtained measured values of substrate adhesion were as shown in Table 1.

Example 2, Comparative Example 1 In Example 1, by changing the mixing ratio of the solid liquid of the formulation and the (Bl liquid), formulations having the isocyanate group content in the solid content of the formulation shown in Table 2 were obtained. A pressure-sensitive adhesive sheet test piece was obtained using this formulation and all other conditions were the same as in Example 1.The adhesion of this pressure-sensitive sheet sample to the substrate was 2.
It was as shown in the table.

Example 3 The styrene-butadiene latex obtained in Reference Example 2 was
B) A water-dispersed formulation was obtained in the same manner as in the example except that liquid B) was used. The isocyanate group content in the solid content of this formulation is approximately 1.8! It was i-%.

Using this formulation, a pressure-sensitive adhesive sheet test piece was obtained in the same manner as in Example 1 except for the above. When we measured the substrate adhesion of this pressure-sensitive adhesive sheet test specimen, no interfacial destruction was observed at the biaxially stretched PP film interface in both the dry substrate adhesion test and the wet substrate adhesion test. , it was found that it showed good adhesion to the substrate.

Example 4, Comparative Example 2 Using the polymerization method and conditions described in Reference Example 1, and changing only the monomer composition, a copolymer latex having the composition shown in Table 1 was obtained. These copolymer latexes were prepared using the same fAl liquid as in Example 1, and the ratio of the solid liquid to the (Bl liquid, and therefore the isocyanate group content in the solid content of the formulation) was the same as in Example 1. A mixture was obtained.Using this, a pressure-sensitive adhesive sheet test piece was obtained in the same manner and under the same conditions as in the example.The substrate adhesion of this pressure-sensitive adhesive sheet test piece was 1-1.
It was as shown in the table.

Example 5 In Example 1, the polyfunctional isocyanate compound (Duraney) 24A-Zoo was replaced with Coronate, which is a tolylene diisocyanate adduct (manufactured by Nippon Polyurethane, isocyanate group content: 13% by weight), or Millionate MR, which is polymethylene polyphenylisocyanate. (manufactured by Nippon Polyurethane, isocyanate group-containing f
Adhesive sheet test specimens were obtained in the same manner except that 31% by weight) was used. The adhesion of these adhesive sheet test specimens to the substrate was as shown in Table 3.

Example 6 Tibeke R930, a titanium white pigment (manufactured by Hemuri Sangyo)
750 parts, sodium tripolyphosphate 1 part, Boyz 53
020 parts, 10 parts of Adekanol Un-420, and 2 parts of water
250 parts of mill base prepared by thoroughly mixing and dispersing 19 parts using a ball mill, 500 parts of Polytron F830, which is an acrylic latex, and 30 parts of butyl cellosolve.
1 part and 220 parts of water were mixed with stirring to obtain a white water-based ink. This white water-based ink was coated on a biaxially stretched PP film coated with the formulation obtained in the same manner as in Example 1, so that the dry coating thickness was 10 μm, and the coating was applied under the conditions of 20°C and 65% RH. After leaving for 7 days, it was subjected to a test. In a substrate adhesion test of this aqueous ink-coated sheet, no peeling of the ink from the PP film interface was observed either during drying or after immersion in water.

Example 7, Comparative Example 3 The degree of corona discharge treatment of the biaxially stretched PP film was varied to obtain a surface oxidized film exhibiting an increase in critical surface tension as shown in Table 4. Using this film, a pressure-sensitive adhesive sheet test piece was obtained in the same manner as in Example 1. The substrate adhesion of this pressure-sensitive adhesive sheet test piece was as shown in Table 174.

Example 8 Example 1 was deposited on an injection molded polypropylene plate whose critical surface tension was increased by 8 dynes/Fu from before treatment by corona discharge treatment.
The formulation was applied in the same manner as above. On this coated polypropylene plate, the same white water-based paint used in Example 6 was applied to a dry thickness of 10 μm, and after curing for 7 days at 20°C and 65% RH, a substrate adhesion test was performed. went. As a result of this test, no separation of the coating film from the polypropylene plate was observed either during drying or after immersion in water.

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Claims (1)

[Claims] 1. (i) polyolefin-based synthetic resin base (ii) a polyfunctional isocyanate compound containing two or more isocyanate groups in the compound, and a hydroxyl group-containing monomer and/or α,β unsaturated A composition layer containing a copolymer of a carboxylic acid monomer and another monomer as a main component and having an isocyanate group content of 0.5 to 4% by weight based on the total solid content, and (iii) a coating material. A synthetic resin molded article consisting of at least three layers. 2. The surface of the polyolefin synthetic resin base material is subjected to an oxidation treatment sufficient to increase the critical surface tension by 5 dynes/cm or more compared to that before treatment, and then (A) a polyolefin containing two or more isocyanate groups in the compound is treated. A self-emulsifying polyfunctional isocyanate solution prepared by mixing a functional isocyanate compound, a poorly water-soluble organic solvent that has no substantial reactivity with the isocyanate group, and a surfactant, and (B) a hydroxyl group-containing monomer and/or or α, β
An aqueous dispersion containing particles of a copolymer obtained by polymerizing an unsaturated carboxylic acid monomer and other monomers is prepared such that the isocyanate group content relative to the total solid content of liquids (A) and (B) is A method for manufacturing a synthetic resin molded article, comprising applying a mixture of 0.5% to 4% by weight, drying the mixture, and then applying a coating material thereon.