KR20090019361A - A multi-layered coating, a thermosetting paint composition to form the same, and a plastic molded article having the multi-layered coating - Google Patents

Abstract

A multi-layered coating is provided to show the metallic texture in a plastic molding product through a dry plating process, and to ensure excellent cohesive property, wetproof property, abrasion resistance, heat resistance, light-proof property, and chemical resistance. A multi-layered coating comprises an undercoat layer(2), a dry plating layer(3) and a top layer(4). The undercoat layer is formed from two-part thermosetting undercoat pigment containing acrylpolyol resin, polyester polyol resin, and hardener and solvent. The dry plating layer is formed on the surface of the undercoat layer. The top layer is formed from a thermosetting top coating composition including low molecular weight acrylpolyol resin, high molecular weight acrylpolyol resin, and hardener and solvent, and is formed on the surface of the dry plating layer.

Description

A MULTI-LAYERED COATING, A THERMOSETTING PAINT COMPOSITION TO FORM THE SAME, AND A PLASTIC MOLDED ARTICLE HAVING THE MULTI-LAYERED COATING}

The present invention relates to a multi-layer coating, a thermosetting paint composition for forming the same, and a plastic molded article comprising the multi-layer coating, and more particularly, 1) formed on the surface of the base material, acrylic polyol resin, polyester polyol resin An undercoat layer formed from a two-part thermosetting undercoat composition comprising a curing agent and a solvent; 2) a dry plating layer formed on the surface of the undercoat layer; And 3) a top coat layer formed on the surface of the dry plating layer and formed from a thermosetting top coat composition comprising a low molecular weight acrylic polyol resin, a high molecular weight acrylic polyol resin, a curing agent, and a solvent. The present invention relates to a multilayer coating having improved coating properties such as heat resistance, deposited metal adhesion, moisture resistance, appearance, abrasion resistance, moisture resistance, and light resistance, a thermosetting coating composition for forming the same, and a plastic molded article including the multilayer coating.

In general, plastic molded articles may have various shapes and mechanical properties, and thus, the application range of the plastic molded article is being expanded as a metal substitute. Among these plastic materials, the basic physical properties may be superior to metals.

In order to give the plastic molded article a texture similar to that of metal, a plating process is performed after molding to give the same gloss and appearance as the metal. As such a method of surface plating, electroless plating by activation of plastic surface, wet plating method such as electroplating, or dry plating method of plating by vapor deposition in a vacuum state are mainly used.

The wet plating method is performed by electroless plating of nickel (Ni) or copper (Cu) on a plastic molded product that has undergone an etching process and an activation process, followed by an electroplating process using chromium (Cr). It has been reported that more than 90% of the metal coating products are processed by this method (Korean Patent Publication No. 2000-0000794). Using the wet plating method, the nickel (Ni) layer formed on the entire surface of the plastic molded article, the copper or copper / nickel alloy (Cu / Ni) layer formed on the surface thereof, and the chromium (Cr) plated layer for expressing the texture of the metal material formed on the surface thereof. A multilayer coating consisting of is obtained.

The surface coating through the wet plating method is widely applied to decorative materials such as automobiles, furniture, household appliances, etc. In particular, since the surface of the plastic molded article is activated by chemicals, it has an advantage of obtaining an excellent adhesion film.

However, despite these advantages, the wet plating method is still applicable only to composite resins containing ABS resins or ABS resins, although the plating possible material is somewhat expanded, and many other engineering plastics do not form a plating film. There is a disadvantage that the applicable material is limited. In addition, most of the chemicals used for wet plating contain heavy metals, and the industrial wastewater containing these heavy metals provides a direct cause of environmental pollution, and the excessive amount of indirect capital for wastewater purification. There are problems such as causing expenses.

In order to compensate for the above-mentioned damage of wet plating, Korean Laid-Open Patent Publication No. 2000-0000794 proposes a dry plating method in which adhesion to metal and ceramic thin films is improved by forming fine iron on the surface of plastic in applying dry plating method to plastic molded products. In addition, Korean Patent Laid-Open Publication No. 2003-74590 discloses a method of performing electroless plating after forming a hydrophilic functional group on a polymer material by plasma. In addition, Korean Patent Application No. 1998-50396 discloses a method of performing electroless or electroplating by coating a conductive polymer to activate the surface. However, these techniques are merely for promoting the adhesion of plastic materials of metal deposition films, and there is a problem in that they do not provide coating properties suitable for application for automobile parts.

On the other hand, U.S. Patents 3,068,683 and 5340451, European Patent No. 268821, etc., propose a method of electroless plating by sputtering catalyst metal after plasma treatment, but this also can be applied to automotive interior and exterior parts. It does not provide.

Unlike the wet plating method having various harmful effects due to the use of chemicals as described above, the dry plating method is mainly used to form a metal thin film by vacuum deposition, especially for electromagnetic shielding coating method of a mobile phone.

However, in the case of the dry plating method, it is difficult to control the initial vacuum degree in the vacuum chamber due to various gases such as H ₂ O, CO, NH ₃ generated in the plastic molded article, and these gases deteriorate the properties of the plated film such as adhesion and appearance. There is a problem that can not be applied to plastic molded parts for automotive parts.

In addition, in the case of the composition applied as a coating material for automobile headlamps, the physical properties such as adhesion to the deposited film by dry plating, heat resistance, water resistance, and the appearance of the coating film are good, but the types of molded products (ABS, PC, PC / PBT, etc.) Applicable paint products are limited according to the present invention, and in particular, the physical properties of the paint composition applied to the upper surface after metal plating are insufficient to satisfy the physical property specifications of automobile parts and home appliances.

The present invention is to solve the above problems of the prior art, by reducing the defects of the deposition process due to the mold defect of the molded article and the gas elution blocking, release agent, etc., in the physical and chemical vapor deposition method in the vacuum chamber of the vacuum evaporator It enables metal plating by means of solution to solve the environmental problems of existing wet plating, improve productivity, and reduce the cost due to material defects, and various materials such as ABS, PC, ABS / PC, PC / PBT, heat-resistant ABS, etc. It can be applied to automotive interior parts and decorative materials for home appliances, and has excellent adhesion property with metal deposition film, moisture resistance, heat resistance, abrasion resistance, light resistance, etc., so that it can satisfy the film property specifications required for automotive parts and home decoration materials. The technical problem is to provide a multilayer coating, a thermosetting paint composition for forming the same, and a plastic molded article including the multilayer coating. The.

The present invention to solve the above technical problems, 1) an undercoat layer formed on the surface of the substrate, formed from a two-component thermosetting paint coating composition comprising an acrylic polyol resin, a polyester polyol resin, a curing agent and a solvent; 2) a dry plating layer formed on the surface of the undercoat layer; And 3) a top coat layer formed on the surface of the dry plating layer and formed from a thermosetting top coat composition comprising a low molecular weight acrylic polyol resin, a high molecular weight acrylic polyol resin, a curing agent, and a solvent.

According to another aspect of the present invention, there is provided a two-component thermosetting undercoat composition comprising an acrylic polyol resin, a polyester polyol resin, a curing agent and a solvent.

According to another aspect of the present invention, there is provided a thermosetting top coat composition comprising a low molecular weight acrylic polyol resin, a high molecular weight acrylic polyol resin, a curing agent and a solvent.

According to another aspect of the present invention, there is provided a plastic molded article comprising the multilayer coating of the present invention.

According to the present invention, it is possible to exhibit a metal texture on the plastic molded article through a dry plating process rather than the conventional wet plating method, and a multilayer coating having excellent material adhesion, moisture resistance, abrasion resistance, heat resistance, light resistance, chemical resistance, and the like. It can be applied to various plastic molded materials such as automobile parts and home appliances.

In order to form the multilayer coating of the present invention on the surface of the substrate, first, a two-part thermosetting undercoat composition comprising an acrylic polyol resin, a polyester polyol resin, a curing agent and a solvent is applied on the surface of the substrate to form a undercoat layer. .

The dry coating composition for dry plating should have excellent material adhesion to be applied to various substrates, especially plastic molded articles, and should have a function that the dry plating layer applied after the coating is uniformly deposited. In the present invention, in order to obtain such a coating material composition, an acrylic polyol resin exhibiting adhesion to various materials, a polyester polyol resin having excellent appearance and excellent adhesion with a dry plating layer, and the acrylic polyol resin and a polyester resin are cured. The undercoat composition which consists of a hardening | curing agent and the solvent which can maintain paint stability and compatibility to make two-component type is used.

In addition, the coating composition according to the present invention, in addition to the above-mentioned components, additives such as adhesion enhancers for improving moisture resistance and cold cycle cycleability, leveling agents and antifoaming agents to improve smoothness and spray workability, acrylic polyols and polyesters A curing accelerator for promoting the reaction of the polyol with the curing agent may be further included.

In the paint composition of the present invention, the acrylic polyol resin included as the main resin includes a weight average molecular weight of 10,000 to 40,000, a hydroxyl value of 20 to 100 mg KOH, and a glass transition temperature (Tg) of 20 to 50 ° C based on solid content. Polyol copolymer resins are preferably used, and those capable of room temperature curing are also preferred.

The acryl polyol resin is excellent in coating properties such as smoothness and gloss of the coating film, moisture resistance, metal deposition adhesion, material adhesion, and the like, and is preferably contained in an amount of 20 to 60% by weight in the entire undercoat composition. If the acrylic polyol resin content is less than 20% by weight of the overall coating composition, the material adhesion is easily lowered, the dryness may be poor, and the moisture resistance may be easily lowered, thereby deteriorating the physical properties of the metal deposition film. There is a risk of degrading the efficiency and workability of the process. In addition, when the acrylic polyol resin content is more than 60% by weight, there is a possibility that the adhesion between the metal deposition film and the undercoat may be poor, the spray workability is deteriorated, the smoothness of the coating film is poor, and the curing density of the coating film is low. There is a risk of poor moisture resistance, metal deposition adhesion, impact resistance.

Preferred examples of the acryl polyol resin include ternary copolymer resins of an acrylic compound represented by CH ₂ = CR ¹ COOR ² , a hydroxyl group-containing acrylic compound represented by CH ₂ = CR ³ COO-R ⁴ OH, and a vinyl monomer. Can be. R ¹ and R ³ represent a hydrogen atom or a methyl group, R ² represents a hydrogen atom or a monovalent substituted or unsubstituted aliphatic hydrocarbon group having 1 to 6 carbon atoms, and R ⁴ represents a divalent substituted or unsubstituted carbon atom having 1 to 6 carbon atoms. Aliphatic hydrocarbon group. Examples of the substituted or unsubstituted aliphatic hydrocarbon group having 1 to 6 carbon atoms include an aliphatic hydrocarbon group having 1 to 6 carbon atoms substituted or unsubstituted with an alkyl group or alkoxy group having 1 to 4 carbon atoms, specifically methyl, ethyl, propyl, Butyl, isobutyl, hexyl, ethylhexyl, methoxyethyl group and the like, but is not limited thereto.

Examples of the general formula CH ₂ = CR ¹ COOR ² are acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate, Butyl methacrylate, isobutyl acrylate, isobutyl methacrylate, hexyl acrylate, hexyl methacrylate, and the like. Examples of the general formula CH ₂ = CR ³ COO-R ⁴ OH include 2-hydroxyethyl acrylate. , 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, and the like. In addition, examples of the vinyl monomers include styrene and vinyltoluene.

As the polyester polyol resin included as an auxiliary resin in the paint composition of the present invention, the weight average molecular weight is 2,000 to 8,000, the hydroxyl group is 80 ~ 300 mg KOH, the glass transition temperature (Tg) is -30 to 30 The acid value and the acid value are preferably 1 to 10 mgKOH.

The polyester polyol resin is used to improve the appearance, curing density, deposition plating layer adhesion, moisture resistance, impact resistance, etc. of the coating film, it is preferably contained in 10 to 50% by weight of the total coating material composition. When the polyester polyol resin is contained in the undercoat composition in less than 10% by weight, the appearance of the coating film is significantly lowered, the metal texture of the deposited layer is poor, the deposition adhesion is lowered, and the curing density is lowered. Wet and impact resistance may be impaired. In addition, when the polyester polyol resin content exceeds 50% by weight, the curing density increases, but the impact resistance is poor, the adhesion of the material is lowered, the initial drying speed is slowed, whitening phenomenon, rainbow (rainbow light) phenomenon Due to the occurrence of poor heat resistance, the deposition appearance may be poor after the dry plating, which is a subsequent process.

Preferred examples of the polyester polyol resin include polymers produced by condensation reactions of glycol monomers and monomers having acid groups, and preferred examples of the glycol monomers are neopentyl glycol, trimethylol propane, diethylene glycol, tri Ethylene glycol, 1,6-hexanediol, 1,4-butanediol, 1,4-cyclohexane amethanol, and mixtures thereof. Preferred examples of the acid group-containing monomer include terephthalic acid, maleic anhydride, fumaric acid, Phthalic anhydride, isophthalic acid, tetrahydrophthalic anhydride, adipic acid and mixtures thereof.

As a curing agent for curing the acrylic polyol resin and the polyester polyol resin, polyisocyanates capable of reacting with hydroxyl groups in the resins and being at room temperature or forced curing (75 ° C. ± 5 ° C. × 40-50 minutes) are preferably used. . Specifically, one or more selected from among homopolymers or modified substances of methylene diisocyanate, toluene diisocyanate and xylene diisocyanate which are excellent in curing rate, adhesion, coating hardness, heat resistance and the like and which are inexpensive are used. When isocyanate is generally used, light resistance, which is insufficient, is not required in the undercoat composition, and is excellent in adhesiveness and moisture resistance to various plastic molded articles, coating hardness, etc., and is relatively inexpensive and has advantages in terms of economy.

In the present invention, the polyisocyanate curing agent is preferably used in an amount such that the equivalent ratio of the hydroxyl group and the polyisocyanate group in the acrylic polyol resin and the polyester polyol resin is 1: 0.8 to 1: 1.2. When the amount of the polyisocyanate curing agent used is less than or above the above range, there is a risk that the curing will not be sufficient or the curing will be excessive, resulting in the failure to obtain desired coating properties.

In the present invention, the solvent is used to maintain the thickness of the coating film and to improve the coating workability, and includes non-polar solvents such as n-heptane, toluene, xylene, petroleum compounds and n-hexane; Ethyl acetate, n-butyl acetate, isobutyl acetate, ethylene glycol monoethyl ether acetate, dibasic ester, 3-methoxy butyl acetate, amyl acetate, butyl glycol acetate, methyl ethyl ketone, methyl isobutyl ketone, acetone, diiso Polar solvents, such as butyl ketone, isophorone, and cyclohexanone, and the mixture of the said nonpolar solvent and a polar solvent can be suitably selected and used according to the characteristic and volatilization rate of resin. There is no particular limitation on the amount of solvent used, but when the solvent is used too much, there is a problem of deterioration of adhesion or durability in the overall physical properties, and when used in a small amount, it is difficult to expect an effect due to the use of the solvent. Preferably from 10 to 30% by weight of solvent is used per 100% by weight of the total undercoat composition.

In addition to the above components, the paint coating composition of the present invention improves the adhesion between the paint coating film and the metal deposition layer to improve adhesion of various deposited metals, moisture resistance, chemical resistance, and cold cycle cycle, Additives, such as leveling and antifoaming agents to increase the smoothness to improve the appearance of the coating film and improve spray workability, and a curing accelerator for promoting the reaction of the acrylic polyol and the polyester polyol with the curing agent may be further included.

Preferred examples of adhesion promoters usable in the present invention include 2- (3,4 epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldiethoxysilane, 3 -Glycidoxypropyltriethoxysilane, 3-methacryloxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropylmethyldiethoxysilane, 3-methacryloxypropyltri Ethoxysilane, 3-aminopropyltriethoxysilane, 3-aminopropyltriethoxysilane, N-2 (aminoethyl) -aminopropylmethyldimethoxysilane, N-2 (aminoethyl) 3-aminopropyltri Silane coupling agents, such as a methoxysilane, are mentioned. The adhesion promoter is preferably contained in 0.01 to 2.0% by weight in 100% by weight of the paint coating composition. If the content of the adhesion promoter is less than 0.01% by weight per 100% by weight of the coating composition, there is no adhesion promotion effect. If the content of the adhesion promoter is higher than 2.0% by weight, the paint storage stability, pot life, transparency of the coating film, etc. may be deteriorated.

In the present invention, an additive such as a leveling agent and an antifoaming agent may be used in order to improve the smoothness of the coating and to improve the appearance of the coating, to improve the wettability of the material, and to show the antifoaming effect in the manufacture of the coating. 0.1-5 weight% is used normally per 100 weight% of coating compositions.

In addition, in the present invention, a curing accelerator (or curing catalyst) for accelerating the reaction between the acrylic polyol and the polyester polyol and the curing agent to shorten the coating film drying and curing time can be used. Preferred curing accelerators include those selected from tetramethylbutanediamine, bicyclooctane, dibutyltindilaurate, triethylenediamine and mixtures thereof. There is no restriction | limiting in particular in the usage-amount of a hardening accelerator, A small amount normally about 0.001 to 1.0 weight% is used per 100 weight% of coating compositions.

In forming the multilayer coating of the present invention on the surface of the substrate, the components as described above are mixed to prepare a thermosetting paint coating composition, the viscosity of which is appropriately adjusted and then applied on the surface of the substrate to form the undercoat. After forming, it is dried and a dry plating layer is formed on the surface of the dried undercoat. The method of forming the dry plating layer is not particularly limited, and may be formed by a general dry plating process using a vacuum evaporator, and the type of metal included in the dry plating layer is also not particularly limited. It can select suitably according to a physical property.

When the dry plating layer is formed as described above, a top coat layer is formed on the surface by applying a thermosetting top coat composition comprising a low molecular weight acrylic polyol resin, a high molecular weight acrylic polyol resin, a curing agent, and a solvent.

The topcoat composition applied on the surface after the dry plating process should have excellent adhesion to the deposited film for the protection of the metal deposition film, coating appearance, moisture resistance, cold / heat cycle resistance, sun cream resistance, plasticizer performance, and abrasion resistance. It should have coating properties such as light resistance and heat resistance. In order to obtain such a top coating composition, in the present invention, a low molecular weight acrylic polyol resin, a deposition plating layer, and the like, which have excellent coating properties such as curing rate of the coating film, adhesion to the deposited film, smoothness and gloss, moisture resistance, coating hardness, light resistance, and the like. A top coat comprising a high molecular weight acrylic polyol resin for improving adhesion between the top coat compositions, heat resistance, abrasion resistance, etc., a curing agent for curing the low molecular weight and high molecular weight acrylic polyol resin, and a solvent capable of maintaining paint stability and compatibility. A coating composition is used.

In addition, the topcoat composition according to the present invention, in addition to the above components, additives such as adhesion enhancers for enhancing moisture resistance and cold cycle cycleability, leveling and antifoaming agents to improve smoothness and spray workability, acrylic polyols and curing agents and A curing accelerator for promoting the reaction may be further included.

As the low molecular weight acrylic polyol resin included as a main resin in the top coat composition according to the present invention, the weight average molecular weight is 2,000 to 15,000, the hydroxyl group is 80 ~ 150 mg KOH, the glass transition temperature (Tg) is 0 ~ 30 Copolymerized acrylic polyol resins which are deg. C are preferably used, and those capable of room temperature curing are also preferred. If the weight average molecular weight of the low molecular weight acrylic polyol resin is less than the above-mentioned range, the initial drying property may be delayed and the working time may be long. Faster speed can shorten pot life, excessively high hardening density can easily break the coating, resulting in poor adhesiveness, and if it exceeds the above range, relatively high viscosity can cause problems such as poor film smoothness and glossiness. And, the molecular weight is increased, the curing density is lowered, the wear resistance may be poor, there is a problem that the moisture resistance may be worsened.

The low molecular weight acrylic polyol resin is preferably contained 20 to 60% by weight per 100% by weight of the top coat composition. If the content is less than 20% by weight, the curing rate is lowered, adhesion with the deposited plating layer is poor, moisture resistance is lowered, and the corrosion of the deposition plated layer can be promoted, and the curing density can be lowered to lower the wear resistance. have. On the other hand, if the content exceeds 60% by weight, the coating film is easily broken, adhesion with the deposited plating layer is poor, and the use of a hardener may increase, thereby increasing the paint price.

Preferred examples of the low molecular weight acrylic polyol resin include a weight average molecular weight of 2,000 to 15,000, a hydroxyl group is a copolymerized acrylic polyol resin of 80 ~ 150 mg KOH, the glass transition temperature (Tg) 0 ~ 30 ℃ based on the solid content CH ₂ = CR ¹ COOR may be a terpolymer resin of an acrylic compound and a CH ₂ = CR ³ COOR hydroxyl group-containing acrylic compound and the vinyl monomer represented by ⁴ OH represented by ^2. R ¹ and R ³ represent a hydrogen atom or a methyl group, R ² represents a hydrogen atom or a monovalent substituted or unsubstituted aliphatic hydrocarbon group having 1 to 6 carbon atoms, and R ⁴ represents a divalent substituted or unsubstituted carbon atom having 1 to 6 carbon atoms. Aliphatic hydrocarbon group. Examples of the substituted or unsubstituted aliphatic hydrocarbon group having 1 to 6 carbon atoms include an aliphatic hydrocarbon group having 1 to 6 carbon atoms substituted or unsubstituted with an alkyl group or alkoxy group having 1 to 4 carbon atoms, specifically methyl, ethyl, propyl, Butyl, isobutyl, hexyl, ethylhexyl, methoxyethyl group and the like, but is not limited thereto.

Examples of the general formula CH ₂ = CR ¹ COOR ² are acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate, Butyl methacrylate, isobutyl acrylate, isobutyl methacrylate, hexyl acrylate, hexyl methacrylate, and the like. Examples of the general formula CH ₂ = CR ³ COO-R ⁴ OH include 2-hydroxyethylacryl. The rate, 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, etc. are mentioned. In addition, examples of the vinyl monomers include styrene and vinyltoluene.

The high molecular weight acrylic polyol resin included as an auxiliary resin in the top coat composition according to the present invention includes a weight average molecular weight of 15,000 to 30,000, a hydroxyl value of 20 to 120 mg KOH, and a glass transition temperature (Tg) of 30 to 70. Acrylic polyol resins which are degrees Celsius are preferably used. If the weight average molecular weight of the high molecular weight acrylic polyol resin is less than the above-mentioned range, the curing density of the coating film becomes high, the coating film is easily broken, and the adhesion may be degraded.The amount of isocyanate used as a curing agent increases, so that the paint price increases, and curing There is a problem that the speed is faster and the pot life is short, and when the above range is exceeded, there are problems such as poor smoothness and glossiness of the coating film, and poor wear resistance due to a decrease in curing density.

The high molecular weight acrylic polyol resin is preferably contained 10 to 50% by weight per 100% by weight of the top coat composition. If the content is less than 10% by weight, the adhesion of the coating film is significantly lowered. If the content is more than 50% by weight, the coating appearance may be poor during spraying, and the coating film gloss may be lowered.

Preferred examples of the high molecular weight acrylic polyol resin, 20 ~ 120 mg a weight average molecular weight of 15,000 ~ 30,000, a hydroxyl value of a solid content based on KOH, an acrylic polyol resin with a glass transition temperature (Tg) of 30 ~ 70 ℃ CH ₂ = CR COOR ¹ can be given a terpolymer resin of an acrylic compound and a CH ₂ = CR ³ COOR hydroxyl group-containing acrylic compound and the vinyl monomer represented by ⁴ OH represented by ^2. R ¹ and R ³ represent a hydrogen atom or a methyl group, R ² represents a hydrogen atom or a monovalent substituted or unsubstituted aliphatic hydrocarbon group having 1 to 6 carbon atoms, and R ⁴ represents a divalent substituted or unsubstituted carbon atom having 1 to 6 carbon atoms. Aliphatic hydrocarbon group. Examples of the substituted or unsubstituted aliphatic hydrocarbon group having 1 to 6 carbon atoms include an aliphatic hydrocarbon group having 1 to 6 carbon atoms substituted or unsubstituted with an alkyl group or alkoxy group having 1 to 4 carbon atoms, specifically methyl, ethyl, propyl, Butyl, isobutyl, hexyl, ethylhexyl, methoxyethyl group and the like, but is not limited thereto.

Examples of the general formula CH ₂ = CR ¹ COOR ² are acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, propyl acrylate, propyl methacrylate, butyl acrylate, Butyl methacrylate, isobutyl acrylate, isobutyl methacrylate, hexyl acrylate, hexyl methacrylate, and the like. Examples of the general formula CH ₂ = CR ³ COO-R ⁴ OH include 2-hydroxyethyl acrylate. , 2-hydroxyethyl methacrylate, 2-hydroxypropyl acrylate, 2-hydroxypropyl methacrylate, 3-hydroxypropyl acrylate, 3-hydroxypropyl methacrylate, and the like. In addition, examples of the vinyl monomers include styrene and vinyltoluene.

As a curing agent for curing the acrylic polyol resin, polyisocyanate capable of reacting with hydroxyl groups in the resins and curing at room temperature or forced curing (75 ° C. ± 5 ° C. × 40-50 minutes) is preferably used. Specifically, 1 or more types are selected and used out of homopolymers or modified bodies of hexamethylene diisocyanate and isophorone diisocyanate which are excellent in coating film appearance and light resistance.

In the present invention, the polyisocyanate curing agent is preferably used in an amount such that the equivalent ratio of the hydroxyl group and the polyisocyanate group in the acrylic polyol resin and the polyester polyol resin is 1: 0.8 to 1: 1.2. When the amount of the polyisocyanate curing agent used is less than or above the above range, there is a risk that the curing will not be sufficient or the curing will be excessive, resulting in the failure to obtain desired coating properties.

In the present invention, the solvent is used to maintain the thickness of the coating film and to improve the coating workability, and includes non-polar solvents such as n-heptane, toluene, xylene, petroleum compounds and n-hexane; Ethyl acetate, n-butyl acetate, isobutyl acetate, ethylene glycol monoethyl ether acetate, dibasic ester, 3-methoxy butyl acetate, amyl acetate, butyl glycol acetate, methyl ethyl ketone, methyl isobutyl ketone, acetone, diiso Polar solvents such as butyl ketone, isophorone and cyclohexanone; And the mixture of the nonpolar solvent and the polar solvent can be appropriately selected and used in accordance with the properties and volatilization rate of the resin. Although there is no particular limitation on the amount of solvent used, it is difficult to meet the specified coating thickness in terms of workability when too much solvent is used, and appearance defects may occur due to the flow of the paint, and when used in a small amount, spray workability of the paint, coating film leveling, etc. It is difficult to expect improvement in appearance quality. Preferably 10 to 30% by weight of solvent per 100% by weight of the total topcoat composition is used.

In addition to the above components, the top coating composition of the present invention, synthetic wax for abrasion resistance enhancement, additives such as leveling agent and antifoaming agent to improve coating appearance and improve spray workability, acrylic polyol resin and curing agent, A curing accelerator for promoting the reaction may be further included.

As the topcoat composition of the present invention, additives such as leveling agents and antifoaming agents, curing accelerators, and the like described above in the undercoat composition can be used.

Synthetic wax that can be used in the topcoat composition of the present invention serves to reduce the hardening shrinkage stress of the topcoat film and to promote adhesion with the metal deposition layer, and also exists in the form of fine particles on the surface of the coating film, thereby providing abrasion resistance of the topcoat. Improve. As the synthetic wax, a synthetic wax prepared from polyethylene, polypropylene, polyamide, polytetrafluoroethylene, or a mixture thereof is preferable, and liquid wax dispersed in powder or solvent may be used. As the property, a synthetic wax having an average particle size of 5 to 15 microns, a softening point of 60 ° C. to 150 ° C., and an acid value of 5 mgKOH / g or less is preferable.

The synthetic wax is preferably contained 0.1 to 7.0% by weight per 100% by weight of the top coat composition, if the content is less than 0.1% by weight does not improve the wear resistance and adhesion promoting effect, if the content exceeds 7.0% by weight of the transparency of the coating film It may make it poor and may inhibit coating film smoothness.

Hereinafter, the present invention will be described in more detail with reference to the following examples. However, the scope of protection of the present invention is not limited by these examples.

Example  And Comparative example

One. Undercoat  Preparation of the composition and Subfloor  Formation, and Of dry plating layer  formation

The coating composition was prepared using the components and corresponding amounts of the coating compositions shown in Table 1 below. Main resin, part of auxiliary resin, part of solvent and part of various additives were mixed and stirred for 1 hour. While continuing to stir this mixture, some of the solvent and some of the various additives were mixed and stirred for 1 hour. Thereafter, a TDI Trimer (toluene diisocyanate trimer) curing agent (R6603, manufactured by KCC Co., Ltd.) was added to the mixture to prepare a paint coating composition. The viscosity of the prepared paint composition was adjusted to 13-15 seconds (FORD CUP # 4), coated on a plastic molded product, dried at 75 ° C. for 50 minutes, and subjected to a dry plating process using a vacuum evaporator (Al ( Aluminum) deposition, made by Korea Vacuum.

[Table 1] Combination table of the paint coating composition

2. Topcoat  Preparation of the composition and Topcoat  formation

Using the components described in Table 2 and the amount of each used to prepare a topcoat composition. Main resin, part of auxiliary resin, part of solvent and part of various additives were mixed and stirred for 1 hour. While continuing to stir the mixture, a portion of the solvent and a part of various additives were mixed and stirred for 1 hour, and then the synthetic wax was slowly added and a particle size of 15 µm or less was obtained using a particle size meter. .

The viscosity of the prepared topcoat composition was adjusted to 15 to 16 seconds (FORD CUP ＃ 4), coated on a plastic molded article subjected to the dry plating process, dried at 75 ° C. for 50 minutes, and left to stand at room temperature for 3 days to test the physical properties. It progressed, and the result is shown in Table 3 and Table 4.

[Painting conditions and painting system]

-Dilution: 30-70 weight% of butyl acetate, the xylene, and the methyl isobutyl ketone mixed solvent were used, and the viscosity was adjusted (coating material composition: 13-15 sec, topcoat composition: 15-16 sec).

-Coating system: ABS, heat-resistant ABS, PC, PC / ABS, PC / PBT materials were used as the coating material. The surface was cleaned with isopropyl alcohol and the surface was cleaned by air blowing and then air sprayed.

1) Undercoat thickness: 20 ~ 30㎛

2) After the undercoating process, drying was performed, and after drying, the dry plating process was performed.

3) Top coat: The coating film was coated with a thickness of 25 to 35 μm and cured at 75 ° C. for 50 minutes.

[Table 2] Top coat composition formulation table

[Table 3] Property Evaluation Results-Examples

[Table 4] Property Evaluation Results-Comparative Example

* O.K: good; N.G: Bad

Property measurement method

1 is a view schematically showing the layer structure of a multilayer coating of the present invention formed on a plastic molded article.

2 is a view schematically showing an embodiment of the method of forming a multilayer coating of the present invention on a plastic molded article according to the process flow.

* Explanation of symbols in the drawings

1: plastic molding

2: subfloor

3: Dry plating layer (metal deposition)

4: top layer

Claims (11)

1) an undercoat layer formed on the surface of a substrate and formed from a two-component thermosetting undercoat composition comprising an acrylic polyol resin, a polyester polyol resin, a curing agent, and a solvent; 2) a dry plating layer formed on the surface of the undercoat layer; And 3) a top coat layer formed on the surface of the dry plating layer and formed from a thermosetting top coat composition comprising a low molecular weight acrylic polyol resin, a high molecular weight acrylic polyol resin, a curing agent, and a solvent. A two-component thermosetting undercoat composition comprising an acrylic polyol resin, a polyester polyol resin, a curing agent, and a solvent. The acrylic polyol resin according to claim 2, wherein the acrylic polyol resin is an acrylic polyol copolymer resin having a weight average molecular weight of 10,000 to 40,000, a hydroxyl value of 20 to 100 mg KOH, and a glass transition temperature (Tg) of 20 to 50 ° C based on solid content. Paint compositions. The polyester polyol resin has a weight average molecular weight of 2,000 to 8,000, the hydroxyl value of the solid content of 80 ~ 300 mg KOH, the glass transition temperature (Tg) is -30 ~ 30 ℃, and the acid value is 1 ~ 10mgKOH A paint composition, characterized in that. The undercoat composition according to claim 2, further comprising an adhesion promoter. The undercoat composition according to claim 2, wherein the curing agent is a polyisocyanate curing agent. A thermosetting top coat composition comprising a low molecular weight acrylic polyol resin, a high molecular weight acrylic polyol resin, a curing agent, and a solvent. According to claim 7, wherein the low molecular weight acrylic polyol resin is a weight average molecular weight of 2,000 ~ 15,000, the hydroxyl group is a copolymerized acrylic polyol resin of 80 ~ 150 mg KOH, the glass transition temperature (Tg) 0 ~ 30 ℃ based on the solid content. Top coat composition characterized in that. The top coat composition according to claim 7, wherein the high molecular weight acrylic polyol resin has a weight average molecular weight of 15,000 to 30,000, a hydroxyl value of 20 to 120 mg KOH, and a glass transition temperature (Tg) of 30 to 70 ° C. . 8. The topcoat composition of claim 7, further comprising a synthetic wax. A plastic molded article comprising the multilayer coating of claim 1.

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