KR101365198B1 - Water-soluble paint composition for plastics and method of manufacturing paint film using the same - Google Patents

Abstract

The aqueous coating composition for plastic parts is 35-65 weight% of non-chlorine olefin resins; 5-40 weight percent polyurethane dispersion; 0.1-3% by weight of a material wetting agent; Antifoam 0.1-2% by weight; 1 to 13 weight percent of a matting agent; Thickener 0.2-2% by weight; 0.1 to 5 wt% of the pigment and 2 to 50 wt% of the solvent. Adhesion, chemical resistance, scratch resistance and the like can be produced in an environmentally friendly water-based paint. High added value of plastic material can be realized.

Description

WATER-SOLUBLE PAINT COMPOSITION FOR PLASTICS AND METHOD OF MANUFACTURING PAINT FILM USING THE SAME}

The present invention relates to an aqueous coating composition for plastic parts and a method of forming a coating film using the same, and more particularly, to an aqueous coating composition for plastic parts, which is excellent in physical properties such as abrasion resistance, adhesiveness, and heat resistance, and which can substitute oil paint. It is related with the formation method of the used coating film.

In recent years, the production of plastics has increased significantly. Plastics have a number of advantages, such as being light and pigmented without corrosion compared to metals, but when used in general products, paintability and other functionality need to be imparted to increase the value of the product.

In addition, plastics are vulnerable to deformation due to chemicals, erosion, ultraviolet rays, heat, and the like. In addition, plastics have surface area defects due to marks, surface defects and color limitations during injection. In order to solve these problems, conventionally, oily acrylic lacquer is coated to compensate for defects of plastic materials.

Such conventional oil-based acrylic lacquer paints have good physical properties such as heat resistance, moisture resistance, and adhesion, but have a poor scratch resistance, so that the texture is not cold and soft when in contact with the coating film and human skin. there was.

In addition, the organic solvents contained in the paints are volatile organic compounds (volatile organic compounds) to cause environmental pollution, odor is bad and harm the health of workers, etc. are being formulated by various environmental laws at home and abroad. . Environmental protection programs in developed countries continue to attempt to reduce organic solvent content.

Accordingly, various aqueous paint compositions for plastic materials using aqueous solvents have been studied instead of oily solvents. However, in order to be applied to plastic parts for automobiles, paint compositions having more excellent properties in addition to the physical properties required for general plastics are required.

Plastics used in automobile interiors are largely composed of dashboards, door trims, center facia panels, center consoles, audio panels, grip handles, etc. Varies.

Plastics used in automobiles are particularly vulnerable to chemicals, erosion, ultraviolet rays, heat deformation, etc., and may have surface defects from appearance marks, surface defects, and color restrictions in appearance. In addition, scratches are easily generated by external forces, and quality problems frequently occur because of the inability to restore them. Accordingly, there is a demand for a coating method that can realize physical properties such as excellent adhesion and scratch resistance.

Therefore, the technical problem of the present invention is not only environmentally friendly and safe to the human body, but also good scratch resistance by realizing the coating properties and elasticity, excellent scratch resistance, and soft texture, such as abrasion resistance, adhesion, and heat resistance, which are advantages of oil paints. It is to provide an aqueous coating composition for plastic materials that can provide a plastic material capable of realizing a high value-added plastic material.

Another object of the present invention is to provide a method for forming a coating film using the above-described aqueous coating composition for plastic materials.

The aqueous coating composition for plastic parts for realizing the object of the present invention described above is 35 to 65% by weight of non-chlorine olefin resin, 5 to 40% by weight of polyurethane dispersion, 0.1 to 3% by weight of material wetting agent, 0.1 to 2% by weight of antifoaming agent. %, 1-13 weight% of matting agents, 0.2-2 weight% of thickeners, 0.1-5 weight% of pigments, and 2-50 weight% of solvents.

In one embodiment, the non-chlorine olefin resin is a grafted maleic acid, the pH is in the range of 6.5 to 7.5 and the particle size is in the range of 80 to 180mm.

In one embodiment, the polyurethane dispersion is synthesized by reacting a polyol and an isocyanate including acrylic polyol, polyester polyol and polycarbonate polyol, pH 6-9, tensile strength 4,000-6,000 psi, weight Average molecular weights range from 8,000 to 15,000.

In one embodiment, the quencher comprises at least one of micronized silica dispersion and talc having an average particle diameter of 1 ~ 30㎛ range.

Method for forming a coating film for achieving another object of the present invention described above is 35 to 65% by weight of non-chlorine olefin resin, 5 to 40% by weight of polyurethane dispersion, 0.1 to 3% by weight of the material wetting agent, 0.1 defoamer 0.1 on the plastic material Applying and drying a coating composition comprising 2 wt% to 2 wt%, 1 to 13 wt% of matting agent, 0.2 to 2 wt% of thickener, 0.1 to 5 wt% of pigment, and 2 to 50 wt% of solvent, and topcoat paint composition Applying and drying.

In one embodiment, the coating composition for the top coat is a water-dilutable polyurethane resin 25 to 55% by weight, water dispersion polyurethane resin 10 to 30% by weight, curing agent 1 to 20% by weight, matting agent 1 to 20% by weight, 0.5 to 5% by weight of light stabilizer, 0.1 to 2% by weight of antifoaming agent, 0.1 to 3% by weight of material wetting agent, 0.1 to 3% by weight of slip agent; 0.01 to 2% by weight of a curing accelerator, 0.1 to 2% by weight of a thickener, and 2 to 40% by weight of a solvent.

In one embodiment, the water-dilutable polyurethane resin is a) 5-30% by weight of isocyanate having an average number of functional groups of 2 or more based on the total amount of the resin b) Hydrophilic polyols 2 ~ 2 having an average of 2 or more functional groups 10% by weight c) 30 to 60% by weight polyol compound comprising polycarbonate polyol and / or polyester polyol, 5 to 25% by weight solvent and 1 to 5% by weight neutralizer.

In one embodiment, the a) isocyanate having an average number of functional groups of 2 or more toluene diisocyanate, 4,4-diphenyl methane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexyl methane diisocyanate and At least one compound selected from the group consisting of polyfunctional isocyanates derived from them.

In one embodiment, b) the hydrophilic polyol having an average number of functional groups of 2 or more dimethyl propionic acid, dimethylbutanoic acid, polyoxyethylene glycol, polycaprolactone diol containing a carboxyl group in the side chain, sulfonic acid group in the side chain At least one compound selected from the group consisting of polyetherdiol having and a polyol having a polyoxyethylene group substituted with an alkoxy group in the side chain.

In one embodiment, the polyol compound comprising c) a polycarbonate polyol and a polyester polyol has a weight average molecular weight of 500 ~ 5,000 range.

In one embodiment, the plastic material is a plastic parts for automobiles and the coating composition is coated on the plastic material to 15 ~ 30㎛ thickness and dried, the topcoat coating composition is coated to 30 ~ 60㎛ thickness Allow to dry.

When the coating process is performed using such an aqueous coating composition for plastic parts, the coating properties such as abrasion resistance, adhesion, heat resistance, and elasticity are excellent, and excellent chemical resistance, scratch resistance, and smooth texture can be realized, but the smell after drying of the coating film And can prevent cracking and erosion of plastic materials. Eventually, it is possible to produce an aqueous plastic coating composition which is environmentally friendly and safe for human body, which can realize high added value.

Hereinafter, the present invention will be described in more detail. While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are further described in the text. It should be understood, however, that the invention is not intended to be limited to the particular forms disclosed, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

In this application, the terms "comprises" or "having" are intended to indicate that there is a feature, ingredient, step, process, composition, or combination thereof described on the specification, one or more other features or ingredients, It is to be understood that it does not preclude the presence or possibility of addition of steps, processes, compositions or combinations thereof.

Also, unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

Hereinafter, the present invention will be described in detail.

According to one embodiment, 35 to 65% by weight of non-chlorine olefin resin, 5 to 40% by weight of polyurethane dispersion, 0.1 to 3% by weight of material wetting agent, 0.1 to 2% by weight of antifoaming agent, 1 to 13% by weight of matting agent, and thickener 0.2 There is provided an aqueous coating composition for plastics containing from 2% by weight to 0.1% by weight of pigment and from 2 to 50% by weight of a solvent.

The polyolefin is obtained by polymerizing an olefin having a double bond at the terminal, and examples thereof include polyethylene, polypropylene and polyisobutylene. Polyolefin-based resins are widely used in automobiles, and in particular, the bumper and the main decoration of the interior are mainly manufactured using polypropylene among polyolefins. When using polypropylene parts in a car, the painting process is essential to match the color of the car.

In general, polypropylene is non-polar in molecular structure and has a high internal crystallinity, and thus has very low coating film adhesion. Therefore, in order to attach the desired paint on the polypropylene material, a chemical or physical process is required. Conventionally, hydrofluoric acid and ozone treatment methods are used for chemical treatment, and plasma and corona discharge methods are used for physical treatment. However, these methods have high processing costs and environmental problems. Therefore, the coating composition of this invention was prepared using non-chlorine olefin resin and acrylic emulsion as a primer and color base paint. This coating composition is applied to a plastic part to form a primer and base coating film.

The formed primer and base coating provides excellent coating properties and improves quality, especially when applied to plastic materials. The topcoat coating composition is applied onto the primer and base coating film. The coating composition for the top coat is not particularly limited and known compositions can be applied without exception.

Especially as a topcoat coating composition, 25-55 weight% of water-dilutable polyurethane resins, 10-30 weight% of water dispersion polyurethane resins, 1-20 weight% of hardening | curing agents, 1-20 weight% of matting agents, light eyes, for example 0.5-5% by weight of tablets, 0.1-2% by weight of antifoaming agent, 0.1-3% by weight of material wetting agent, 0.1-3% by weight of slip agent; 0.01 to 2% by weight of a curing accelerator, 0.1 to 2% by weight of a thickener, and 2 to 40% by weight of a solvent.

The kind and role of each component of the coating composition for forming the primer and base coating film will be described in more detail.

<Non-chlorine olefin resin>

As an eco-friendly resin that does not contain chlorine, it is a polyolefin resin grafted maleic acid using a solution method rather than a conventional melting method. It has few unreacted materials and shows excellent adhesion without chemical treatment and physical surface treatment. Compared to the forced emulsification type and the conventional self-emulsification type, the particle size can be easily controlled, the stability is excellent, and the water resistance, corrosion resistance, adhesion and gloss are excellent.

As a self-emulsifying resin in which a polar group is introduced into a non-chlorine polypropylene resin skeleton and emulsified without using an emulsifier, the pH is preferably in the range of 6.5 to 7.5 and a weight average molecular weight in the range of 100,000 to 150,000.

The amount of non-chlorine olefin resin used in preparing the coating composition is in the range of 35 to 65% by weight based on the total amount of the composition. If the amount thereof is less than 35% by weight, there is a problem that the physical properties of the coating film, such as adhesion and chemical resistance, are deteriorated.If the amount thereof is more than 65% by weight, the physical properties such as sunscreen and PVC plasticizer are lowered and dispersible. There is a problem of deterioration in storage.

<Polyurethane Dispersion>

Polyurethane dispersions can be synthesized by reacting polyols and isocyanates. Polyols used in the polyurethane dispersion include acrylic polyols, polyester polyols, polycarbonate polyols, and the like. The polyurethane dispersion preferably has a pH of 6 to 9, a tensile strength of 4,000 to 6,000 psi, and a weight average molecular weight of 8,000 to 15,000.

The amount of polyurethane dispersion used in preparing the coating composition is in the range of 5 to 40% by weight based on the total amount of the composition. If the amount thereof is less than 5% by weight, there is a problem that the physical properties of the coating film such as adhesion and solvent resistance are lowered. If the amount thereof is more than 40% by weight, the coating film becomes hard to cause elasticity and smell. .

<Material wetting agent>

Material wettability is basically determined by the difference between the surface tension of the paint and the surface tension of the workpiece. The general rule is that the paint surface tension must be at least equal to or less than the surface tension of the subject. If the paint does not spread or adhere well to the painted surface, the surface tension of the paint is higher than the surface tension of the subject. Water-based water-based paints generally have very high surface tensions, which often causes material wettability.

Polyether siloxane copolymer, polydimethyl siloxane, polyether modified polydimethyl siloxane, etc. are preferred in order to strongly reduce the surface tension of the paint to improve the material wettability, to prevent crater phenomena, and to provide slip property on the surface. It may be included in the range of 0.1 to 3% by weight relative to. If the content thereof is less than 0.1% by weight, a problem of poor appearance may occur due to dust on the surface of the coating, and if it exceeds 3% by weight, it may cause a problem of deterioration of adhesion during repainting.

<Defoamer>

Bubbles in the paint are always undesirable. Bubbles are generated during the production process, so it is impossible to hold the optimum amount when packing the paint, and the bigger problem is that bubbles are generated when the paint is applied, creating a surface defect. Of course, bubbles are not only bad looking, but also have a problem in reducing the inherent performance of the paint having a protective function. Defoamers are therefore one of the essential ingredients for almost all formulations.

The use of a non-silicone antifoaming agent is preferred and preferably in the range of 0.1 to 2% by weight relative to the coating composition. If its content is less than 0.1% by weight, the defoaming effect is insufficient, and if it exceeds 2% by weight it may cause a problem of adhesion deterioration during repainting.

<Quenching agent>

As the matting agent that serves to reduce or eliminate the gloss of the material, silica gel, precipitated silica, titanium dioxide, talc and the like can be used. In particular, in the present invention, it is preferable to use micronized silica dispersion and talc having an average particle diameter of about 1 to 30 µm. If the average particle diameter thereof exceeds 30 μm, a problem may occur in that the surface of the coating film becomes rough and the appearance of the coating film is poor and the scratchability thereof may be deteriorated.

The matting agent including micronized silica dispersion and talc having an average particle diameter of about 1 to 30 μm is preferably included in the coating composition in a range of 1 to 13 wt%, and if the content is in the above range, the photosensitive (quenching) surface of the It has the effect of improving the texture. The amount of quencher used is in the range of 1 to 13% by weight based on the total amount of the composition. If its content is less than 1% by weight, it is difficult to obtain a matting effect, and if it exceeds 13% by weight, there is a weak problem in scratching.

Thickeners; Rheology Regulators>

It is preferable to select and use from an acrylic thickener and a urethane thickener, and it is good to contain in 0.2 to 2 weight% with respect to a coating composition. If the content thereof is less than 0.2% by weight, there is a problem that workability is lowered due to the flow of paint during coating, and if it exceeds 2% by weight, storage property may be degraded and the appearance of the coating may be poor.

<Pigment>

The pigment is selected according to the desired color and mixed and used, preferably 0.1 to 5 based on the total amount of the composition by appropriately mixing the selected from titanium dioxide, carbon black, yellow pigment, blue pigment, green pigment, red pigment, etc. It should be in the weight% range. If the content thereof is less than 0.1% by weight, there is a problem in that coloring and concealment is difficult, and when it exceeds 5% by weight, there is a problem in adhesion between the material and the paint.

<Solvent>

The solvent is selected from ethyl acetate, propyl acetate, butyl acetate, ethylene glycol methyl ether, diethylene glycol methyl ether, butylene glycol methyl ether, dibutylene glycol methyl ester, propylene glycol methyl ether, dipropylene glycol methyl ether, and the like, and mixed appropriately. To 2 to 50% by weight, based on the total amount of the composition. When the content thereof is less than 2% by weight, there is a problem that the surface leveling is lowered, and when the content exceeds 50% by weight, there is a problem that may cause an odor.

The aqueous coating composition containing each component as described above can be used for plastic parts as a primer and a color base coating.

The topcoat coating composition coated on top after the coating of the primer and color base coating is not particularly limited and various compositions are applicable. Preferably 25 to 55% by weight of the water-dilutable polyurethane resin, 10 to 30% by weight of the water-dispersible polyurethane resin, 1 to 20% by weight of the curing agent, 1 to 20% by weight of the matting agent, 0.5 to 5% by weight of the light stabilizer, and antifoaming agent 0.1 To 2% by weight, material wetting agent 0.1 to 3% by weight, slip agent 0.1 to 3% by weight, curing accelerator 0.01 to 2% by weight, thickener 0.1 to 2% by weight and solvent 2 to 40% by weight. Types and roles will be described in more detail.

<Water-dilutable polyurethane resin containing a hydroxyl group>

The water-dilutable polyurethane resin comprising a hydroxyl group as a main component comprises a) an isocyanate having an average number of functional groups of 2 or more, b) a hydrophilic polyol having an average number of functional groups of 2 or more, and c) a polycarbonate polyol and / or a polyester polyol. Polyol compounds and the like.

In a general water-dispersed polyurethane reaction, isocyanate is left in the sock end to be solubilized, and polyhydric amine or the like is used as a chain extender to form urea groups in the sock end to prepare a prepolymer, which is then dispersed in water. However, the water-dispersed polyurethane obtained in this way is difficult in reproducibility and molecular weight control at the time of dispersion. In particular, the softening of the coating film after curing due to the lack of functional groups that can cause a curing reaction when applied to the paint adversely affects the coating properties such as weather resistance, abrasion resistance, etc., which is insufficient to be used as a water-soluble coating (clear) for automobiles.

In addition, the general water-dispersed polyurethane is difficult to secure the painting workability due to the large molecular weight, hard properties are strong, lack of excellent elasticity and soft feeling, it is necessary to further improve the properties for use as automotive interior paints.

According to one embodiment of the present invention, the coating composition for application for the top coat is prepared without using a chain extender and in the preparation of the polyurethane prepolymer 10-80 mgKOH by adjusting the equivalent ratio of OH / NCO to 1.4 ~ 2 / g. When the residual hydroxyl group is applied to the paint, it can harden the reaction with the water-dispersed polyisocyanate, thereby bringing a great improvement in the paint properties such as weather resistance and abrasion resistance. In order to facilitate NV control at the time of paint preparation, a water-dilutable polyurethane resin including a hydroxyl group which can be diluted in water without water dispersion was prepared.

The composition ratio of the composition material constituting the water-dilutable polyurethane resin containing a hydroxyl group is, for example, 5 to 30% by weight of isocyanate having 2 or more average functional groups, 2 to 10% by weight of hydrophilic polyol having 2 or more average functional groups, poly 30 to 60 wt% of carbonate polyol and polyester polyol, 5 to 25 wt% of solvent and 1 to 5 wt% of neutralizing agent.

The composition of the water-dilutable polyurethane resin containing the hydroxyl group will be described in more detail below.

First, isocyanates having an average number of functional groups of 2 or more include toluene diisocyanate, 4,4-diphenyl methane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexyl methane diisocyanate and polyfunctional isocyanates derived therefrom. At least one of these may be used. In particular, at least one or more of isophorone diisocyanate and dicyclohexyl methane diisocyanate can be used.

The isocyanate is preferably used in the range of 5 to 30% by weight based on the total weight of the water-dilutable polyurethane resin containing a hydroxyl group. If the amount thereof is less than 5% by weight, mechanical properties and chemical resistance may be deteriorated. If the amount is more than 30% by weight, the viscosity may be high, making it difficult to synthesize.

Hydrophilic polyols having an average number of functional groups of 2 or more act as hydrophilicity to the urethane chain to enable water dispersion, dimethyl propionic acid, dimethylbutanoic acid, polyoxyethylene glycol, containing carboxyl groups in the side chains. At least one of polycaprolactone diol, polyetherdiol having a sulfonic acid group in the side chain, and a polyol having a polyoxyethylene group substituted with an alkoxy group in the side chain can be used. Hydrophilic polyol is preferably used 2 to 10% by weight based on the total weight of the water-dilutable polyurethane resin containing the hydroxyl group. If the amount thereof is less than 2% by weight, it may be difficult to disperse the water due to lack of hydrophilicity. If the amount thereof exceeds 10% by weight, the water resistance may be lowered.

As a polyol compound comprising a polycarbonate polyol and / or a polyester polyol, it is advantageous in terms of chemical resistance and productivity to use a polyol compound having a weight average molecular weight in the range of 500 to 5,000. More preferably, polyol compounds comprising polycarbonate diols and / or polyester diols are used.

A solvent can use a general solvent, Preferably, N-methylpyrrolidone, acetone, methyl ethyl ketone, dimethylformamide, glycol ether ester, hydrogenated furan, etc. are mentioned. It is good to use at least 1 type selected from these. The solvent is preferably used 5 to 25% by weight based on the total weight of the water-dilutable polyurethane resin containing the hydroxyl group, if used outside the above range may be difficult to manufacture or may take a long time to dry when used as a coating agent have.

As the neutralizing agent, N-methyldiethanolamine, triethanolamine and the like can be used. Preferably, triethanolamine is used. The amount of the neutralizing agent is preferably used 1 to 5% by weight based on the total weight of the water-dilutable polyurethane resin, when using less than 1% by weight of the neutralizing agent is insufficient, and when used in excess of 5% by weight odor and Since there may be a problem causing discoloration, it is better to use within the above range.

The polyester polyol used to prepare the polyurethane resin as a main component can be prepared by condensation reaction of an alcohol compound and an acid. Specifically, about 500 to 5,000 in which a condensation reaction of an alcohol compound such as polyester or methyl propanediol with a diethylene glycol and adipic acid as a matrix and a weight average molecular weight of about 500 to 5,000 and an acid such as adipic acid or isophthalic acid is carried out. Polyester polyols having a weight average molecular weight of can be preferably used.

Polycarbonate polyol is prepared by condensation reaction of an alcohol compound and a carbonate compound, specifically, a polyol synthesized by condensation reaction of an alcohol compound such as hexanediol and cyclohexanedimethanol with a carbonate including diethyl carbonate, and having a weight average molecular weight of about 500 The thing of -5,000 can be used preferably.

A water-dilutable polyurethane resin comprising a hydroxyl group using a polyester polyol was prepared as follows.

First, a polyester having a weight average molecular weight of 500 to 5,000 obtained by using N-methylpyrrolidone 94 g, diethylene glycol 78 g and adipic acid as a matrix in a reaction vessel equipped with a reflux cooler, a nitrogen gas inlet tube, a thermometer, and a stirrer. 660 g of polyol and 3 g of dimethylpropionic acid were mixed and sufficiently stirred under a nitrogen stream. A hexamethylene diisocyanate 60g was added to a polyester polyol and dimethylpropionic acid mixture, and heated to about 60 to 100 ° C., followed by stirring for about 6 hours to prepare a polyester polyurethane prepolymer including a hydrophilic group. After cooling to 60 ~ 70 ℃ to neutralize the triethylamine 2g to neutralize the prepolymer neutralization in the range of about 90 ~ 100% to prepare a polyester-based water-dilutable polyurethane resin having a hydroxyl group.

Next, the water-dilutable polyurethane resin containing a hydroxyl group using a polycarbonate polyol was prepared as follows.

First, 100 g of N-methylpyrrolidone and 2.5 g of dimethylpropionic acid were sufficiently mixed and dissolved in a reaction vessel provided with a reflux cooler, a nitrogen gas inlet tube, a thermometer, a stirrer, and the like at 50 to 60 ° C. 60 g of hexamethylene diisocyanate was added to the dissolved dimethyl propionic acid while paying attention to exotherm, and the temperature was raised to about 60 to 100 ° C., followed by stirring for about 0.5 to 1.5 hours to prepare a prepolymer containing a hydrophilic group and leaving the isocyanate group in the sock end. .

Thereafter, 700 g of polycarbonate polyol having a weight average molecular weight of 500 to 5,000 prepared by condensation reaction of 80 g of hexanediol and 100 g of diethyl carbonate was added to the prepolymer, followed by stirring for about 6 hours under a nitrogen stream at a temperature of about 60 to 100 ° C. Polyester polyurethane prepolymers were prepared comprising hydrophilic groups. After cooling to 60 ~ 70 ℃ to neutralize the prepolymer 2g triethylamine neutralization in the range of about 90 ~ 100% to prepare a polycarbonate water dilutable polyurethane resin having a hydroxyl group.

In preparing the coating composition, the amount of the polyurethane resin to be used is in the range of about 25 to 55% by weight based on the total amount of the composition. If the amount thereof is less than about 25% by weight, there is a problem of deterioration of coating properties such as adhesion and scratch resistance, and if the amount thereof exceeds about 55% by weight, storage and elasticity are deteriorated. .

<Water Dispersion Polyurethane Resin>

The water-dispersed polyurethane resin can be synthesized by reacting polyol and isocyanate. As a polyol used for manufacture of the said water-dispersed polyurethane resin, an acrylic polyol, polyester polyol, polycarbonate polyol, etc. are mentioned. In addition, the water-dispersed polyurethane resin preferably has a pH of 6 to 10, a tensile strength of 5 to 35 mPa, and an elongation at break of 600 to 800%.

The amount of the water-dispersed polyurethane resin used in preparing the coating composition is in the range of about 10 to 30% by weight based on the total amount of the coating composition. If the amount thereof is less than about 10% by weight, there is a problem of deterioration of coating properties such as adhesion and solvent resistance, and if the amount thereof is more than about 30% by weight, the coating is hardened to cause texture degradation and odor. There is.

<Curing agent>

The curing agent added for curing the coating composition is preferably isophore diisocyanate and hydrophilic hexamethylene diisocyanate having excellent yellowing resistance and weather resistance, and preferably included in the range of about 1 to 20% by weight based on the coating composition. If the content is less than about 1% by weight, there is a problem that it is difficult to secure the properties of the coating film because hardening of the paint does not occur.If the content exceeds about 20% by weight, the pot life is shortened due to the excessive amount of hardener. This can cause problems.

<Quenching agent>

As the matting agent that serves to reduce or eliminate the gloss of the material, silica gel, precipitated silica, titanium dioxide and the like can be used. In particular, in the present invention, it is preferable to use a micronitized silica dispersion having an average particle diameter of about 1 to 30 µm. If the average particle diameter thereof exceeds about 30 μm, the surface of the coating film may be coarse, resulting in poor appearance and deterioration of scratchability. Therefore, it is preferable to use a dispersion having the above-described particle size range.

The matting agent containing the micronized silica dispersion having an average particle diameter of about 1 to 30 μm is preferably included in the paint composition in a range of about 1 to 20 wt%, and if the content is within the above range, the photosensitive (quenching) surface texture There is an effect to improve. The amount of quencher used is in the range of about 1 to 20% by weight, based on the total amount of the composition. If the content thereof is less than about 1% by weight, it is difficult to obtain a matting effect, and when the content thereof exceeds about 20% by weight, there is a weak problem in scratching.

<Light stabilizer>

The light stabilizer is effective to prevent aging, color change, etc. of the coating film generated by exposure to light for a long time, and performs UV blocking, light energy absorption and conversion, and free radical removal. UV absorbers and UV hindered amine light stabilizers, which are organic amine compounds with steric hindrance, should be mixed and used. As the ultraviolet absorbing light stabilizer, various kinds such as benzophenone series, oxanilide series, benzotriazole series and triazine series can be used. As the organic amine light stabilizer, 4-benzoyloxy-2,2,6,6-tetramethylbiferridine, 2,4-di-tert-butylphenyl-3,5-di-tert-butyl-hydroxybenzoide Etc. can be used. Preferably, the ratio of the ultraviolet absorber to the UV-inhibited amine light stabilizer system is suitably used in a weight ratio of about 2: 1. If the content thereof is less than about 0.5% by weight, there is a problem that the coating film is easily yellowed and gloss is degraded over time, and when the content is more than about 5% by weight, the paint storage stability becomes unstable.

<Defoamer>

Bubbles occur during the various stages of agitation, dispersion and painting. Since this causes surface defects such as cratering and weakening the coating film on the dry coating film, antifoaming agent should be used to suppress the bubble removal and the formation of bubbles. Suitable chemical structures as antifoaming agents are those having low surface tension molecules such as silicones, mineral oils, fatty acids and fluorocarbons. The use of non-silicone and modified polysiloxane antifoaming agents is preferred and preferably in the range of 0.1 to 2% by weight relative to the coating composition. If its content is less than 0.1% by weight, the defoaming effect is insufficient, and if it exceeds 2% by weight it may cause a problem of adhesion deterioration during repainting.

<Material wetting agent>

Material wettability is basically determined by the difference between the surface tension of the paint and the surface tension of the workpiece. The general rule is that the paint surface tension must be at least equal to or less than the surface tension of the subject. If the paint does not spread or adhere well to the painted surface, the surface tension of the paint is higher than the surface tension of the subject. Water-based water-based paints generally have very high surface tensions, which often causes material wettability.

Polyether siloxane copolymer, polydimethyl siloxane, polyether modified polydimethyl siloxane, etc. are preferred in order to strongly reduce the surface tension of the paint to improve the material wettability, to prevent crater phenomena, and to provide slip property on the surface. It may be included in the range of 0.1 to 3% by weight relative to. If the content thereof is less than 0.1% by weight, a problem of poor appearance may occur due to dust on the surface of the coating, and if it exceeds 3% by weight, it may cause a problem of deterioration of adhesion during repainting.

<Sleeping agent>

The silicone additive can improve the slipperiness of the coating film surface. Sometimes it can be thought of in connection with other physical properties of the coating as well as simple slip properties. In the case of good slip resistance, scratch resistance and fouling resistance are improved, easy washing and adhesion resistance are improved. It is preferable to include in the range of 0.1 to 3% by weight relative to the coating composition. If the content thereof is less than 0.1% by weight, physical properties such as wear resistance and scratch resistance are lowered. If the content is more than 3% by weight, it may cause a problem of deterioration of adhesion during repainting.

<Hardening accelerator>

As a hardening accelerator, trimethylenediamine, octosan tin, dibutyltin dilaurate, lead 2-ethylhexate, etc. are preferable, and it is good to contain in 0.01 to 2weight% of a coating composition. If the content is less than 0.01% by weight, the drying time is long, and the physical properties such as chemical resistance, moisture resistance, and abrasion resistance are lowered. When the content is more than 2% by weight, the paint hardens too rapidly, and during painting work. A popping phenomenon occurs in the coating film or shrinkage of the coating film.

Thickeners; Rheology Regulators>

It is preferable to select and use from an acryl-type thickener and a urethane thickener, and it is good to contain in 0.1-2 weight% with respect to a coating composition. If the content thereof is less than 0.1% by weight, there is a problem that workability is reduced due to the flow of paint during coating, and if it exceeds 2% by weight, storage property may be deteriorated and the coating appearance may be poor.

<Solvent>

The solvent is selected from ethyl acetate, propyl acetate, butyl acetate, ethylene glycol methyl ether, diethylene glycol methyl ether, butylene glycol methyl ether, dibutylene glycol methyl ester, propylene glycol methyl ether, dipropylene glycol methyl ether, and the like, and mixed appropriately. It is to be in the range of 2 to 40% by weight based on the total amount of the composition. If the content thereof is less than 2% by weight, there is a problem that the surface leveling is lowered, and if it exceeds 40% by weight, there is a problem that may cause an odor.

In addition to the above components, it has excellent physical properties such as abrasion resistance, adhesion, and heat resistance, but uses water-based paint instead of oil-based paint to prevent odor after coating film drying and to prevent cracks and erosion of plastic materials, and is environmentally friendly and safe for human body. In addition, the coating composition for automobile plastics that can provide good scratch resistance may further contain various additives such as slip agents and anti-settling agents, and the amount of these additives may be appropriately adjusted according to the desired end use and various factors. Can be used.

Hereinafter, the present invention will be described in more detail with reference to examples and comparative examples, but it should be understood that the present invention is not limited only to these examples. Table 1 shows the components for preparing the primer and color base coating composition and their contents, and Table 2 shows the components for preparing the topcoat coating composition and its contents.

TABLE 1

<Table 2>

The following tests were carried out using the primer and color base coating composition and the top coat coating composition samples for plastics prepared according to the above Examples and Comparative Examples.

<Test Example: Evaluation of Coating Film Properties>

Each primer and base prepared in the composition shown in Table 1 on the polypropylene test piece was coated with a thickness of about 15 ~ 30㎛, and left for about 10 minutes at room temperature and then dried at 80 ℃ for 10 minutes. Then, each topcoat coating composition prepared by the composition shown in Table 2 for 10 minutes and then coated with a thickness of about 30 ~ 60㎛ and left for about 15 minutes at room temperature, and then at about 80 ℃ for about 30 minutes Dry to complete the sample. Using the completed sample, various evaluation tests were performed for each of the following items.

Adhesion test at room temperature: After 11-cut cross-cuts at 2mm intervals in the horizontal and vertical directions on the specimen, the surface is cleaned with a soft brush and firmly attached with a prescribed tape of the appropriate width and length. The number of peeled coating scales was counted by pulling strongly at an angle of 90 °. Also referred to as a checker board adhesion test, the number of peelings was measured on a total of 100 checkerboard scales, and the greater the number of peeling scales, the poorer the adhesiveness was.

Heat test: The specimens were left at 110 ° C. for 300 hours, then taken out and left at room temperature for 1 hour, and then immediately subjected to the above adhesion test.

Light test: Under XENON ARC, irradiate the specimen to a total cumulative amount of light of 1050 KJ / m ² under black panel temperature of 89 ± 3 ℃, in-vehicle humidity of 50 ± 5%, and RH illuminance of 340nm. The adhesion test was performed after washing with an aqueous detergent solution, drying with air, and leaving at room temperature for 1 hour.

Scratch test: When the coated specimens according to Example 1 and Comparative Examples 1 to 3 were moved vertically to the coating surface by using a sapphire scratcher under a load of 100 mm and 0.5 kgf in accordance with JIS K 6718, the coating film was evaluated for damage. The result was confirmed. At this time, evaluation of the scratch property was shown to be excellent (5)-poor (1) according to the grade.

Moisture resistance test: After leaving the specimen at the temperature of 50 ± 2 ℃ and relative humidity of 95 ± 2% for 168 hours, remove it and remove the surface moisture by air blow. And immediately after the adhesion test.

Sun Cream Resistance: Lay up two sheets of white cotton cloth of the same size on an acrylic plate (50mm × 50mm) and apply 0.25g sunscreen to the entire surface. Place the sunscreen on the coated specimen and press the acrylic plate to bring it into close contact. It is left to stand in a thermostat at 80 ± 2 ℃ for 1 hour and then taken out to remove the white cloth and acrylic plate. Leave at room temperature for 10-15 minutes, rinse with neutral detergent and dry. The surface state of the coating film was investigated and immediately tested for adhesion.

PVC plasticizer: Laminate the same size PVC pads (equivalent to 60 wt% of plastic material) on an acrylic plate (50mm × 50mm) and place the pads on the coated specimen and apply 0.1kgf load to the acrylic plate (Painting specimens-PVC pad-acrylic plate-load order). After leaving for 1 hour in a thermostatic chamber at 110 ± 2 ℃, take it out and remove the load, acrylic plate and PVC pad. Leave at room temperature for 10-15 minutes, rinse with neutral detergent and dry. The surface state of the coating film was investigated and immediately tested for adhesion.

The coating film properties were averaged after evaluating five specimens for each composition, and the results are shown in Table 3.

<Table 3>

As shown in Table 3, it can be seen that the coating film prepared using the primer and color base coating composition according to Example 1 exhibited excellent physical properties. In particular, when the composition according to Example 1 is used as the primer and color base coating composition, and the composition according to Example 2 which satisfies the preferred component ratio condition is used as the top coat coating composition, room temperature adhesion, heat resistance, and light resistance It can be seen that all physical properties such as scratch resistance, moisture resistance, sun cream resistance, and PVC plasticizer resistance are the best.

As described above, according to the coating composition and the coating method of the plastic part of the present invention, the insufficient scratch resistance of the existing oil-based paint can be remarkably improved, and in addition, the physical properties such as adhesion, chemical resistance, and alkali resistance are improved. It can be protected from ultraviolet rays, heat, chemicals, etc. for a long time, it is possible to improve the design of the coating material, to impart a soft touch and to increase the strength of the painted surface, thereby realizing high added value of plastic material for automobiles.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention as defined in the appended claims. You will understand.

Claims (17)

Formed by grafting maleic acid, having a polar group introduced into the skeleton, having a pH of 6.5 to 7.5 and a weight average molecular weight of 100,000 to 150,000, ranging from 35 to 65% by weight of a non-chlorine olefin resin;
5 to 40 weight percent polyurethane dispersion having a pH of 6 to 9, a tensile strength of 4.000 to 6.000 psi, and a weight average molecular weight of 8,000 to 15,000;
0.1-3% by weight of a material wetting agent;
Antifoam 0.1-2% by weight;
1 to 13 weight percent of a matting agent;
Thickener 0.2-2% by weight;
Pigment 0.1-5% by weight and
The aqueous coating composition for plastics containing 2-50 weight% of solvents. delete delete The coating composition according to claim 1, wherein the polyurethane dispersion is synthesized by reacting a polyol and an isocyanate including an acrylic polyol, a polyester polyol, and a polycarbonate polyol. delete The coating composition of claim 1, wherein the matting agent comprises at least one of a micronized silica dispersion and talc having an average particle diameter in the range of 1 to 30 μm. It is formed by grafting maleic acid on a plastic material, the polar group is introduced into the skeleton, the pH ranges from 6.5 to 7.5 and 35 to 65% by weight of non-chlorine olefin resin having a weight average molecular weight of 100,000 to 150,000; 5 to 40 weight percent polyurethane dispersion having a pH of 6 to 9, a tensile strength of 4,000 to 6,000 psi, and a weight average molecular weight of 8,000 to 15,000; 0.1-3% by weight of a material wetting agent; Antifoam 0.1-2% by weight; 1 to 13 weight percent of a matting agent; Thickener 0.2-2% by weight; Applying and drying the aqueous coating composition for plastics containing 0.1 to 5 wt% of a pigment and 2 to 50 wt% of a solvent; And
A method of forming a coating film comprising applying and drying a topcoat coating composition. According to claim 7, wherein the topcoat coating composition is 25 to 55% by weight of the water-dilutable polyurethane resin; Water dispersion polyurethane resin 10-30% by weight; 1 to 20% by weight of curing agent; 1 to 20 wt% matting agent; 0.5 to 5 wt% light stabilizer; Antifoam 0.1-2% by weight; 0.1-3% by weight of material absorbent; 0.1 to 3% by weight of slip agent; 0.01-2 wt% of a curing accelerator; Thickener 0.1 to 2% by weight; And 2 to 40% by weight of a solvent. The method of claim 8, wherein the water-dilutable polyurethane resin is based on the total amount of the resin a) 5 to 30% by weight isocyanate having an average number of functional groups of 2 or more b) Hydrophilic polyols 2 to 2 having an average number of functional groups of 2 or more 10 wt% c) 30 to 60 wt% of a polyol compound comprising polycarbonate polyol and / or polyester polyol, 5 to 25 wt% of a solvent and 1 to 5 wt% of a neutralizing agent. The method of claim 9, wherein a) the isocyanate having an average number of functional groups of 2 or more is selected from toluene diisocyanate, 4,4-diphenyl methane diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, dicyclohexyl methane diisocyanate and At least one compound selected from the group consisting of polyfunctional isocyanates derived from them. The method of claim 9, wherein b) the hydrophilic polyol having an average number of functional groups of 2 or more is dimethyl propionic acid, dimethylbutanoic acid, polyoxyethylene glycol, polycaprolactone diol containing a carboxyl group in the side chain, sulfonic acid group in the side chain At least one compound selected from the group consisting of polyetherdiol having and a polyol having a polyoxyethylene group substituted with an alkoxy group in the side chain. The method of claim 9, wherein the polyol compound comprising c) a polycarbonate polyol and / or a polyester polyol has a weight average molecular weight in the range of 500 to 5,000. The method according to claim 7, wherein the plastic material is a plastic parts for automobiles, the coating composition is coated on the plastic material in a thickness of 15 to 30㎛ and dried, the topcoat coating composition is coated in a thickness of 30 to 60㎛ Forming method characterized in that the drying after. delete delete The method of claim 7, wherein the polyurethane dispersion is synthesized by reacting a polyol and an isocyanate including an acrylic polyol, a polyester polyol, and a polycarbonate polyol. delete