JPH0616998A - Composition for coating - Google Patents

Abstract

PURPOSE:To provide a coating composition capable of forming coating films excellent in characteristics such as solvent resistance and lifting resistance on the surfaces of plastic molded products. CONSTITUTION:The composition for coatings contains (A) a main agent component containing (a) an acrylic resin having tertiary amino groups and carboxyl groups in the molecule and (b) an acrylic resin having hydroxyl groups in the molecule and (B) a curing component containing an epoxy group-containing compound and an isocyanate compound.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composition for coating a plastic molded product, and particularly a coating for forming a coating film having excellent properties such as solvent resistance and lifting resistance on the surface of the plastic molded product. The present invention relates to a composition for use.

[0002]

2. Description of the Related Art Acrylo-butadiene-styrene copolymer (A
Plastics such as BS resin), polystyrene-based copolymers, polycarbonate-based copolymers, and polyphenylene oxide have excellent moldability, mechanical strength, and low price, so they are used in a wide range of fields including automobile parts manufacturing. There is. And, these plastic molded products are generally painted for surface protection and cosmetics. Conventionally, acrylic lacquer, acrylic urethane resin paint or acrylic epoxy resin paint having good adhesion to the plastic molded products. And the like, and is applied in a system such as 1 coat 1 bake, 2 coat 1 bake or 3 coat 2 bake. In this coating process, if dust adheres to the surface of the coated molded product or if defective parts due to sagging or cracking of the coating film occur, the quality of the coating film is maintained in order to maintain the quality of the coating film. , The defective part must be sanded until the material of the plastic molded product is exposed, or it must be repaired with a light sanding and then repainted.

However, when the coating film of a plastic molded product is dried, it must be baked and cured at a low temperature of about 100 ° C. or lower in order to prevent the molded product itself from being deformed by heat. The coating film formed on the surface of the plastic molded product by using the coating material generally has poor solvent resistance and insufficient material adhesion. Therefore, if the coating film is repainted, it will be used for repainting. There was a problem that the solvent of the coating composition penetrated into the coating film already formed, and the phenomenon of "lifting" in which the coating film swelled from the surface of the material occurred. Therefore, the conventional coating material which is liable to cause the lifting is not practical in the industrial production line for coating the plastic molded product. On the other hand, if a cross-linking accelerator or cross-linking catalyst is added to such a coating, the initial reaction rate will increase even in low-temperature baking.
The solvent resistance is improved, and lifting of the coating film is less likely to occur during repainting, but on the other hand, after mixing the curing agent with the paint, the viscosity of the paint increases in an extremely short time due to the effect of the crosslinking accelerator, etc. However, there is a problem that the pot life is shortened and clear coloring occurs.

[0004]

DISCLOSURE OF THE INVENTION The present invention solves the above problems and provides a coating composition capable of forming a coating film having excellent properties such as solvent resistance and lifting resistance on the surface of a plastic molded article. The purpose is to provide things. That is, according to the present invention, one-coat / one-bake, two-coat / one-bake or three-coat / two-bake system laminated coating is applied on a plastic molded article such as ABS resin, and dried at low temperature to form a coating film, and immediately after the formation. It is intended to provide a coating composition in which lifting is unlikely to occur even when paint is repeatedly applied to the coating composition and the pot life is long.

[0005]

Means for Solving the Problems As a result of research for solving the above-mentioned problems, the present inventors have found that a main agent containing a copolymer having a carboxyl group and a tertiary amino group, and a copolymer having a hydroxyl group. When a curing agent component containing both a compound having an epoxy group and an isocyanate compound is added to the component, in addition to the reaction between the tertiary amino group of the main component and the epoxy group in the curing agent component, Carboxyl groups and hydroxyl groups in the main component react with the isocyanate in the curing agent component, a film with strong adhesiveness is formed by both reactions, immediately after applying the coating material to the plastic molded article, re-application. We also obtained the finding that lifting does not occur. Therefore, the present invention provides a main ingredient component containing (a) a copolymer having a tertiary amino group and a carboxyl group in the molecule, and a copolymer (b) having a hydroxyl group in the molecule.
It is intended to provide a coating composition containing (A) and a curing agent component (B) containing a compound having an epoxy group and an isocyanate compound. Hereinafter, the present invention will be described in detail.

The copolymer (a) constituting the main component (A) used in the present invention is a copolymer having a tertiary amino group and a carboxyl group in the molecule and has a base number of 4
Acrylic resins with an acid value of -30 to 30 mg KOH / g, an acid value of 2 to 40 mg KOH / g and a number average molecular weight of 5,000 to 20,000 are suitable. This copolymer (a) contains a polymerizable monomer having a carboxyl group and a polymerizable monomer having a tertiary amino group as essential components, and further, if necessary, is copolymerized with these monomers. It can be produced by copolymerizing other possible polymerizable monomers. The polymerizable monomer having a carboxyl group is a polymerizable monomer having at least one carboxyl group and at least one polymerizable unsaturated bond in the molecule, and as a specific example, (Meth) acrylic acid,
Examples thereof include monocarboxylic acids such as crotonic acid, dicarboxylic acids such as itaconic acid, fumaric acid and maleic acid, and monoester compounds of these dicarboxylic acids.

The polymerizable monomer having a tertiary amino group is a polymerizable monomer having at least one tertiary amino group and at least one polymerizable unsaturated bond in the molecule. Then, as specific examples, N, N-dimethylaminoethyl (meth) acrylate, N, N-dimethylamino (meth) acrylate, 2-vinylpyridine, 4-vinylpyridine, N, N-dialkylallylamine, and the like are used. Can be mentioned. In addition, examples of other polymerizable monomers that can be copolymerized with the monomer include, for example,
Methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth)
(Meth) acrylic acid esters such as acrylate, stearyl (meth) acrylate and cyclohexyl (meth) acrylate; vinyl aromatic compounds such as styrene, α-styrene and vinyltoluene; vinyl acetate, vinyl propionate, (meth) acrylonitrile, (Meth) acrylamide, N, N-dimethyl (meth) acrylamide, N-methylpyrrolidone, vinyl chloride, propylene,
Examples include α-olefins. The copolymer (a) of the present invention is
These monomers are combined in an appropriate amount and the base number is 4 to 30 mg K
OH / g, acid value 2-40 mg KOH / g, and number average molecular weight
It is preferably produced by polymerizing so as to be 5,000 to 20,000.

The base number of this copolymer (a) is 4 to 30 mg.
KOH / g, especially 5 to 20 mg KOH / g is preferred. If the base number due to the tertiary amino group is higher than the above range, the water resistance and solvent resistance are deteriorated, and conversely, if the base value is low, the reactivity with the compound having an epoxy group tends to be lowered. Copolymer
The acid value of (a) is 2-40 mg KOH / g, especially 3-30 mg KOH.
/ g is preferred. When the acid value is higher than the above range, the molecular weight of the copolymer is lowered and the physical properties are lowered. On the contrary, when the acid value is too low, the reactivity with the isocyanate compound tends to be lowered. The number average molecular weight of the copolymer (a) is 5,000 to 20,000,
Particularly, it is preferable to set it to 8,000 to 17,000. If the number average molecular weight is higher than the above range, the appearance of the coating film will be poor after finishing, and if it is too low, the water resistance and weather resistance of the coating film will tend to be poor. As the copolymer (b) constituting the main component (A) used in the present invention, an acrylic resin having a hydroxyl value of 2 to 60 mg KOH / g and a number average molecular weight of 5,000 to 20,000 is suitable. This copolymer (b) is produced by copolymerizing a polymerizable monomer having a hydroxyl group and another polymerizable monomer copolymerizable with the monomer.

The polymerizable monomer having a hydroxyl group is a polymerizable monomer having at least one hydroxyl group and at least one polymerizable unsaturated bond in the molecule. Examples thereof include ethyl (meth) acrylate, hydroxypropyl (meth) acrylate, and hydroxybutyl (meth) acrylate. Other polymerizable monomers that can be copolymerized with the above-mentioned monomer include, for example, methyl (meth) acrylate, ethyl (meth) acrylate, propyl (meth) acrylate, butyl (meth). (Meth) acrylic acid esters such as acrylate, stearyl (meth) acrylate and cyclohexyl (meth) acrylate; vinyl aromatic compounds such as styrene, α-styrene and vinyltoluene; vinyl acetate, vinyl propionate, (meth) acrylonitrile, (Meth) acrylamide, N, N-dimethyl (meth) acrylamide, N-methylpyrrolidone, vinyl chloride, propylene, α-olefin and the like, which can be used alone or in combination of two or more kinds. As the other polymerizable monomer copolymerizable with the above-mentioned monomer, a polymerizable monomer having a carboxyl group and / or a polymerizable monomer having a tertiary amino group can be used in combination. The copolymer (b) having a hydroxyl group is prepared by combining these monomers in an appropriate amount and having a hydroxyl value of 2 to 60 mg KO.
It is preferably produced by polymerizing by a usual method so that H / g and the number average molecular weight become 5,000 to 20,000.

The hydroxyl value of the copolymer (b) is 2 to 60 mg KO.
H / g, especially 5 to 50 mg KOH / g is preferred. If the hydroxyl value is higher than the above range, the viscosity of the coating composition is increased and the workability is deteriorated. On the contrary, if it is too low, the reactivity with the isocyanate compound tends to be lowered. Also a copolymer
The number average molecular weight of (b) is 5,000 to 20,000, especially 8,000 to
It is preferably 17,000. If the number average molecular weight is higher than the above range, the appearance of the coating film after finishing tends to be poor, and if it is too low, the water resistance and weather resistance of the coating film tend to be poor. Furthermore, when preparing the main ingredient (A), the copolymer
It is preferable to add 25 to 400 parts by weight, and particularly 40 to 250 parts by weight of the copolymer (b) to 100 parts by weight of (a). If the mixing ratio is outside the above range, the reactivity with the curing agent component tends to decrease.

The compound having an epoxy group which constitutes the curing agent component (B) of the present invention is preferably a compound having two or more epoxy groups in the molecule, of which glycidyl ether of a polyhydric alcohol is particularly preferable. Specific examples of the compound having an epoxy group include ethylene glycol diglycidyl ether, hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, glycerin diglycidyl ether, diglycerin polyglycidyl ether, and sorbitol polyglycidyl ether. Especially, sorbitol polyglycidyl ether is particularly preferable because it has almost no skin irritation, high coating hardness, and excellent water resistance. As the isocyanate compound constituting the curing agent component (B) of the present invention, diisocyanates and polyisocyanates having at least two isocyanate groups in the molecule are preferable, and specific examples thereof include hexamethylene diamine. Isocyanate, tetramethylene diisocyanate, aliphatic such as xylene diisocyanate and isophorone diisocyanate, tolylene diisocyanate, diphenylmethane diisocyanate, phenylene diisocyanate,
Aromatic diisocyanates such as naphthalene diisocyanate and dimethyl diisocyanate, alicyclic diisocyanates, their dimers, trimers, mixtures thereof, and these isocyanate compounds in excess. It is a reaction product obtained by reacting with a polyhydroxy compound such as ethylene glycol, diethylene glycol, neopentyl glycol, trimethylolpropane, hexanetriol, and glycerol.

The curing agent component (B) of the present invention preferably contains 5 to 300 parts by weight, particularly 50 to 150 parts by weight, of the above isocyanate compound with respect to 100 parts by weight of the compound having an epoxy group. If the content of the isocyanate compound is more than the above range, the physical properties are unbalanced and the coating performance becomes insufficient, the water resistance further decreases, and conversely if it is too small, the solvent resistance decreases and lifting occurs. Tends to be easier. In the present invention, the isocyanate group equivalent of the isocyanate compound in the curing agent component (B), and the main component
The equivalence ratio [NCO / (OH + COOH)] of the hydroxyl group and the carboxyl group in the copolymer (A) is 0.8 / 1.0 to 1.2
/1.0, especially within the range of 0.9 / 1.0 to 1.1 / 1.0 is preferable because the original coating film performance is exhibited. Also,
Base value equivalent in the copolymer of the main component (A) and the curing agent component
Equivalent ratio to the epoxy group equivalent of the compound having an epoxy group in (B) is 0.6 / 1.0 ~ 6.0 / 1.0, 0.8 / 1.0 ~ 3.0
It is preferable to set the ratio within the range of / 1.0 because the original coating film performance is exhibited.

Considering the relationship of each component as described above, the preferred embodiment of the present invention is (a) having a base number of 4 to 30 mg KO.
H / g, acid value 2-40 mg KOH / g, and number average molecular weight
5,000 to 20,000, an acrylic resin having a tertiary amino group and a carboxyl group in the molecule, and (b) a hydroxyl value of 2 to 60 mg KOH / g and a number average molecular weight of 5,000 to
A coating composition comprising a main component (A) containing an acrylic resin having a hydroxyl group in the molecule and a curing agent component (B) containing a compound having an epoxy group and an isocyanate compound, which is 20,000. Equivalent ratio [NCO / (OH + COOH)] of isocyanate group equivalent of nato compound and total equivalent of hydroxyl group and carboxyl group in acrylic resin
The coating composition has a ratio of 0.8 / 1.0 to 1.2 / 1.0, and an equivalent ratio of the base number equivalent in the acrylic resin to the epoxy group equivalent of the compound having an epoxy group is 0.6 / 1.0 to 6.0 / 1.0.

As described above, the present invention is based on a copolymer having a tertiary amino group and a carboxyl group, a main agent component comprising a copolymer having a hydroxyl group, and a curing agent component comprising a compound having an epoxy group and an isocyanate compound. In addition to the reaction between the tertiary amino group in the main agent component and the epoxy group in the curing agent component, the carboxyl group and hydroxyl group in the main agent component also react with the isocyanate in the curing agent component. As a combination of an epoxy group-containing compound and an isocyanate compound,
It forms a coating film that adheres to various plastic molding materials such as polystyrene-based polymers in one coat, and that does not cause lifting even when repainted immediately. In the coating composition of the present invention, if necessary, various inorganic pigments including sintered pigments, extender pigments, metal pigments, etc., organic pigments, dyes, and defoamers, dispersants, antisettling agents, flow control agents. Various additives such as agents, thixotropic agents, ultraviolet absorbers, conductivity imparting agents, antistatic agents, and surfactants can be added.

Examples of the solvent used for preparing a paint from the coating composition of the present invention include usual paint solvents such as xylene, toluene, methyl ethyl ketone, ethyl acetate, methyl cellosolve and diethylene glycol monoethyl ether acetate. it can. Incidentally, 100 parts by weight of the coating composition of the present invention, these solvents 50 ~ 200
It is preferred to use parts by weight. The coating composition of the present invention can be applied not only to plastics but also to substrates such as metal, glass, ceramics, wood, etc. Further, the coating composition of the present invention can be used in a 2 coat 1 bake or 3 coat 2 bake system. It is also useful as a primer, a base coat and a clear coat in the laminated coating of.

[0016]

INDUSTRIAL APPLICABILITY The present invention can be finished as a coating film by coating a plastic molded article such as ABS resin and drying at a temperature of from room temperature to about 120 ° C., and has excellent adhesion, weather resistance and water resistance. Provided is a coating composition capable of forming a coating film having various properties such as properties and solvent resistance. Furthermore, the coating composition of the present invention is an unprecedented epoch-making coating composition capable of obtaining a coating film that does not cause lifting even when repainted.

[0017]

EXAMPLES The present invention will now be described in more detail by way of examples. The "parts" and "%" in the examples are based on weight. [Examples 1 to 4 and Comparative Examples 1 to 5] Metallic base coat paints were prepared by mixing and dispersing the respective raw materials at the compounding ratios (unit: parts) shown in Tables 1 to 4, and the paints were prepared.
Spray coating is applied to the ABS resin molded product so that the thickness of the cured film is 15 μm, and after leaving it for 3 minutes, the clear coat prepared with the compounding ratios shown in Tables 1 to 4 has a cured film thickness of 25 μm. So painted. Apply undried overcoat at room temperature to 10
After left for a minute, it was baked at 75 ° C. for 20 minutes and a performance test was conducted.
Further, these test pieces were each ground with # 400 sandpaper to expose the ABS resin material, and then the same top coat (clear coat) was applied onto each test piece again. Furthermore, after the test piece was baked at 75 ° C. for 20 minutes, the presence or absence of lifting was confirmed. The pencil hardness, flexibility, solvent resistance, adhesiveness, pot life and lifting were evaluated as follows.

Pencil hardness: The pencil scratch value is displayed based on JIS K 5400. Flexibility: The coating film of the test piece was directed outward, and the occurrence of bending, cracking, peeling, etc. was visually determined using a core rod having a diameter of 20 cm. ○: Almost no change ×: Crack or peeling occurred on the coating film Solvent resistance: After immersing xylol in gauze and wiping the coating film 30 times, the swelling, whitening, and scratch resistance of the coating film were visually observed. It was judged. ◯: Almost no change ×: Coating swells, scratches are conspicuous, and tends to be whitened Adhesion: After 500 hours of accelerated test with a sunshine weatherometer, the size of the coating according to JIS K5400 is 1 mm.
100 pieces of 1 mm squares were made, and an adhesive cellophane tape was adhered to the surface thereof, and the number of coatings remaining after sharply peeling off was measured. ◯: 95/100 to 100/100 x: 94/100 or less Pot life: Each paint was allowed to stand for 12 hours and then air spray coating was performed to judge whether or not repainting was possible. ◯: Repaintable ×: Not repaintable Lifting property: Even if repainted, it was visually judged whether or not the undercoating film was raised or the sanding boundary surface did not appear. ◯: No abnormalities ×: Abnormality occurrences such as lifting are shown in Table 5 below.

<Preparation Method of Molded Article Used in Coating Test> AB
S material "Nougatuck MVFI" (trade name by Sumitomo Dow)
Was wiped with isopropyl alcohol and the surface was washed to obtain the molded product.

[0020]

[Table 1]Table 1 ──────────────────────────────────── Main agent A-1 A-2 A-3 A-4 A-5 A-6 A-7 A-8 ──────────────────────────────────── Hydroxyl group Containing acrylic resin varnish Note 1) 60 70 35 Amino acrylic resin varnish containing hydroxyl group Note 2) 30 20 35 50 Amino acrylic resin varnish containing carboxyl group (a) Note 3) 30 40 Carboxyl group containing amino acrylic resin varnish (b) Note 4) 70 20 Carboxyl group-containing amino Acrylic resin varnish (c) Note 5) 35 35 Aluminum paste Note 6) 10 10 10 Butyl acetate 10 10 10 10 10 10 10 10 10 Xylol 20 20 20 20 20 20 20 20 20

[0021]

[Table 2] Table 2 ──────────────────────────────────── Hardener B-1 B- 2 B-3 B-4 ──────────────────────────────────── Sorbitol-type glycidyl epoxy Note 7) 50 25 10 Hexamethylene diisocyanate adduct Note 8) 50 25 40 Butyl acetate 20 20 20 20 Cyclohexanone 20 20 20 20 Methyl ethyl ketone 10 10 10 10

Note 1) "Acridic A-801" (trade name, manufactured by Dainippon Ink and Chemicals, Inc.) Resin hydroxyl value 50 mg KOH / g, number average molecular weight 12,000, solvent: mixture of xylol and butyl acetate, solid content 50 % Note 2) "Cotax LK-714" (trade name, manufactured by Toray Industries, Inc.) Resin base number 19 mg KOH / g, Resin hydroxyl value 8.6 mg KOH /
g, number average molecular weight 10,000, solvent: mixture of toluene and isobutanol, solid content 50% Note 3) "Cotax LK-724" (trade name of Toray Industries, Inc.) Resin base number 19 mg KOH / g, resin acid number 3.3 mg KOH / g, number average molecular weight 14,200 Solvent: Mixture of toluene and isopropyl alcohol, solid content 50% Note 4) "Acridic A-914" (trade name of Dainippon Ink and Chemicals, Inc.) Resin base number 5-9 mg KOH / g, resin acid value 12-16 mg KOH
/ g, number average molecular weight 11,000, solvent: mixture of toluene and n-butanol, solid content 50% Note 5) "Acridic KZ-646" (trade name, manufactured by Dainippon Ink and Chemicals, Inc.) Resin base number 14.2 mg KOH / g, Resin acid value 12-16 mg KOH
/ g, number average molecular weight 8,000, solvent: mixture of xylene and n-butanol, solid content 65% Note 6) "Alpaste 1109M" (trade name of Toray Aluminum Co., Ltd.) Note 7) "Denacol 612" (Nagase Kasei Kogyo) Company name) Epoxy equivalent 170 g / eg, solid content 100% Note 8) "Sumijour N-75" (Sumitomo Bayer Urethane Co., Ltd. product name) Solid content 75%, isocyanate content 16.5%

[0023]

[Table 3] Table 3 ────────────────────────────────── Actual Example Process 1 2 3 4 ─ ───────────────────────────────── Metallic base A-2 A-2 A-2 A-3 Base curing agent B-3 B-3 B-3 B-4 Coat base / curing agent 100 100 100 100/20/20/20/20 ────────────────────── ───────────── Clear base agent A-6 A-7 A-8 A-6 coat hardener B-3 B-3 B-3 B-4 base agent / hardener 100 100 100 100 / 20/20/20/20

[0024]

[Table 4] Table 4 ────────────────────────────────── Comparative Comparison Process 1 2 3 4 5 ────────────────────────────────── Metallic base A-1 A-2 A-2 A-2 A- 2 Base curing agent B-3 B-1 B-2 B-2 B-2 Coat main agent / curing agent 100 100 100 100 100 100/20/20/20/20/20/20 ──────────── ─────────────────────── Clear base agent A-4 A-6 A-5 A-6 A-8 Coat curing agent B-3 B-1 B -2 B-2 B-2 main agent / curing agent 100 100 100 100 100/20/20/20/20/20

[0025]

[Table 5] Table 5 ────────────────────────────────── Actual Example Ratio Comparative Example Test Content 1 2 3 4 1 2 3 3 4 5 ─────────────────────────────────── Pencil hardness BBBB3B3B3B 3B 3B or less or less or less or less or less Flexibility ○ ○ ○ ○ ○ ○ ○ ○ ○ Solvent resistance ○ ○ ○ ○ × × × × × Adhesion ○ ○ ○ ○ ○ × ○ ○ ○ Pot life ○ ○ ○ ○ × ○ ○ ○ ○ Lifting ○ ○ ○ ○ × × × × ×

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Office reference number FI technical display location C09D 201/02 PDN 7415-4J

Claims (3)

[Claims] 1. A main agent component (A) containing (a) a copolymer having a tertiary amino group and a carboxyl group in the molecule, and (b) a copolymer having a hydroxyl group in the molecule, and an epoxy group. And a curing agent component (B) containing an isocyanate compound and an isocyanate compound. 2. The copolymer (a) has a base number of 4 to 30 mg KOH.
/ g, acid value 2-40 mgKOH / g, and number average molecular weight 5,000-
The copolymer (b) has a hydroxyl value of 2 to 60 mg KOH / g and a number average molecular weight of 5,000 to 20,00.
The coating composition according to claim 1, which is a copolymer of 0. 3. The equivalent ratio [NCO / (OH + COOH)] of the isocyanate group equivalent of the isocyanate compound and the total equivalent of hydroxyl groups and carboxyl groups in the copolymers (a) and (b) is
0.8 / 1.0 to 1.2 / 1.0, and the copolymer (a) and
The coating composition according to claim 1 or 2, wherein the equivalent ratio of the base number equivalent in (b) and the epoxy group equivalent of the compound having an epoxy group is 0.6 / 1.0 to 6.0 / 1.0.