KR102245709B1 - Water-soluble base coat composition - Google Patents

Abstract

The present invention relates to a water-soluble base coat composition comprising an acrylic resin, a polyurethane dispersion resin, an acrylic urethane dispersion resin, a urethane resin, a melamine-based curing agent, and an oxazoline-based curing agent.

Description

Water-soluble base coat composition {WATER-SOLUBLE BASE COAT COMPOSITION}

The present invention relates to a water-soluble base coat composition.

In general, the exterior plate of a vehicle body should not cause deterioration and rust of the coating film, and should have durability to maintain the gloss or color of the coating film. Therefore, in the painting process of a vehicle, the vehicle body that has been subjected to the pretreatment process is usually electrodeposited and painted, followed by intermediate painting to improve adhesion and smoothness, and base painting on the intermediately painted vehicle body for the aesthetic appearance of the vehicle body. Thereafter, it is common to coat a clear coat to protect the color of the base coat, improve its appearance, and protect the base coat from the outside.

In the base coat coating and clear coat coating, it is common to apply the clear coat composition after the base coat composition is applied and dried, and cure the clear coat and the base coat together when the clear coat is cured (130 to 150°C). For this reason, conventional base coat compositions are designed based on high temperature curing conditions. However, in order to reduce the cost of the painting process, there is a trend of shortening the process and increasing the demand for a composition that can be cured at a low temperature.

In this regard, Korean Patent Registration No. 158,534 (Patent Document 1) includes a main mixture containing an acrylic polyol, an ester-based solvent, a leveling agent, an additive composed of a slip agent and a wax, and an alcohol-based solvent; And a curing agent mixture containing a polyisocyanate and an ester-based solvent; and a two-component acrylic urethane composition is disclosed. However, as in Patent Document 1, the base coat composition that can be used in conventional low-temperature baking conditions, in particular, heat curing conditions of 120° C. or lower, includes coating paints for automobile repair and compositions for painting parts, but the mechanical properties of the produced coating film are not sufficient. As a result, there is a limit to applying it as a paint for a vehicle body.

Therefore, it is possible to cure at a low temperature of 120° C. or less, and the mechanical properties of the coating film produced therefrom are excellent, and thus research and development of a base coat composition suitable for application for vehicle body painting is required.

Korean Patent Registration No. 158,534 (published on May 28, 1997)

Accordingly, the present invention is to provide a base coat composition capable of producing a coating film having excellent mechanical properties while being curable at a low temperature of 120° C. or less.

The present invention provides a water-soluble base coat composition comprising an acrylic resin, a polyurethane dispersion resin, an acrylic urethane dispersion resin, a urethane resin, a melamine-based curing agent, and an oxazoline-based curing agent.

The base coat composition according to the present invention can be carried out at a low temperature of 120° C. or less, which is a lower temperature than the conventional heat curing temperature in the painting process, and thus it is economical to reduce costs required during the painting process. In addition, the coating film prepared from the composition has excellent mechanical properties, particularly properties such as gloss, impact resistance, water resistance, and cold chipping resistance, so that it can be usefully used for car body painting.

Hereinafter, the present invention will be described in detail.

The water-soluble base coat composition according to the present invention includes an acrylic resin, a polyurethane dispersion resin, an acrylic urethane dispersion resin, a urethane resin, a melamine-based curing agent, and an oxazoline-based curing agent.

Acrylic resin

The acrylic resin serves to improve the rheology and hardness of the coating film prepared from the base coat composition containing the same.

The acrylic resin may be directly synthesized according to a known method, or a commercially available product may be used. For example, the acrylic resin is from the group consisting of allyl methacrylate (AMA), methyl methacrylate (MMA), ethyl acrylate (EA), hydroxy ethyl acrylate (HEA) and methacrylic acid (MAA). It may contain at least one selected monomer-derived unit. For example, the acrylic resin includes allyl methacrylate (AMA), methyl methacrylate (MMA), ethyl acrylate (EA), hydroxy ethyl acrylate (HEA) and methacrylic acid (MAA) as monomers. It can be prepared from a mixture.

In addition, the mixture may further include a divalent acrylic monomer. The divalent acrylic monomer is, for example, 1,4-butanediol diacrylate (1,4-Butanediol diacrylate), 1,4-butanediol dimethacrylate (1,4-Butanediol dimethacrylate), 1,5-penta Diol dimethacrylate (1,5-Pentanediol dimethacrylate), 1,6-hexanediol diacrylate (1,6-Hexanediol diacrylate), 1,6-hexanediol dimethacrylate (1,6-Hexanediol dimethacrylate) , 1,9-Nonanediol dimethacrylate, 1,10-decanediol dimethacrylate, ethylene glycol diacrylate, And ethylene glycol dimethacrylate.

Further, the acrylic resin has a hydroxyl value (OHv) of 5 to 50 mgKOH/g, an acid value (Av) of 5 to 50 mgKOH/g, a glass transition temperature (Tg) of -30 to 30°C, and viscosity at 25°C. May be 20 to 600 cps. In another example, the acrylic resin has a hydroxyl value (OHv) of 5 to 30 mgKOH/g, an acid value (Av) of 5 to 30 mgKOH/g, a glass transition temperature (Tg) of more than 0° C. and 30° C. or less, and at 25° C. The viscosity of may be 20 to 400 cps. When the hydroxyl value of the acrylic resin is within the above range, impact resistance, water resistance, adhesion and cold chipping resistance are secured by improving the curability of the composition, and when the acid value is within the above range, storage stability and coating film hardness are secured, and glass When the transition temperature is within the above range, storage stability is good and appropriate coating properties can be secured. When the viscosity at 25°C is within the above range, there is an effect of easy workability.

In addition, the acrylic resin may be in the form of an emulsion dispersed in deionized water. For example, the acrylic resin is in the form of an emulsion dispersed in a solvent, and may have an average diameter of 50 to 300 nm, or 70 to 170 nm. When the acrylic resin is in the form of an emulsion dispersed in deionized water, there is an effect of lowering the content of volatile organic compounds (VOC) in the paint, and when the average diameter is within the above range, the appearance of the coating film prepared therefrom And particle stability of the composition is good.

In addition, the emulsion-type acrylic resin may have a solid content (NV) of 15 to 50% by weight based on the total weight of the resin. As another example, the emulsion-type acrylic resin may have a solid content of 30 to 50% by weight based on the total weight of the resin. When the solid content of the emulsion-type acrylic resin is within the above range, the workability of the composition including the same is good.

Further, the acrylic resin may be included in the composition in an amount of 20 to 30 parts by weight based on 5 to 10 parts by weight of the polyurethane dispersion resin. As another example, the acrylic resin may be included in the composition in an amount of 22 to 27 parts by weight based on 5 to 10 parts by weight of the polyurethane dispersion resin. When the content of the acrylic resin is within the above range, appropriate rheology can be secured, and the appearance, water resistance, impact resistance, and cold chipping resistance are excellent.

Polyurethane dispersion resin

The polyurethane dispersion resin serves to improve the drying properties of the base coat composition containing the same, and to improve the flexibility of the coating film prepared from the composition.

The polyurethane dispersion resin may be a polyurethane dispersion resin derived from polyester-polycarbonate. For example, the polyurethane dispersion resin may be a polyurethane dispersion resin derived from a polyester-polycarbonate diol.

In addition, the polyurethane dispersion resin may be in the form of a dispersion dispersed in deionized water. For example, the polyurethane dispersion resin may be in the form of a dispersion dispersed in deionized water, and may have an average diameter of 200 nm or less, or 50 to 200 nm.

In addition, the polyurethane dispersion resin may have a viscosity of 10 to 50 cps at 25°C, and a solid content (NV) of 20 to 50 wt% based on the total weight of the dispersion resin. As another example, the polyurethane dispersion resin may have a viscosity of 20 to 40 cps at 25°C, and a solid content (NV) of 25 to 45% by weight based on the total weight of the dispersion resin. When the viscosity of the polyurethane dispersion resin at 25°C is within the above range, the appearance of the prepared coating film and the workability of the composition including the same are excellent, and the solid content is within the above range based on the total weight of the dispersion resin. , It is possible to improve the workability of the composition comprising the same.

Further, the polyurethane dispersion resin may be included in the composition in an amount of 5 to 10 parts by weight based on 20 to 30 parts by weight of the acrylic resin. As another example, the polyurethane dispersion resin may be included in the composition in an amount of 6 to 9 parts by weight based on 20 to 30 parts by weight of the acrylic resin. When the content of the polyurethane dispersion resin is within the above range, there are excellent effects in drying properties, cold chipping resistance, and impact resistance.

Acrylic urethane dispersion resin

The acrylic urethane dispersion resin serves to impart dryness to a base coat composition containing the same, and to improve wettability and surface gloss of a coating film prepared from the composition.

The acrylic urethane dispersion resin may be directly synthesized according to a known method, or a commercially available product may be used. For example, the acrylic urethane dispersion resin may be prepared by reacting a polyol, an acid, an isocyanate, and an acrylate.

At this time, the polyol is polytetramethylene glycol (PTMG), 1,6-hexanediol, ethylene glycol, propylene glycol, diethylene glycol, butylene glycol, neopentyl glycol, trimethylol propane, butanediol, 1,4-hexanediol And it may be one or more selected from the group consisting of 3-methylpentanediol, the acid may be dimethylol propionic acid (DMPA), acrylic acid, adipic acid, phthalic acid, isophthalic acid, terephthalic acid, tetrahydrophthalic acid, hexahydr It may be one or more selected from the group consisting of loftalic acid, adipic acid, fumaric acid, maleic acid, trimellitic acid, malic acid, and aconitic acid. In addition, the isocyanate is isophorone diisocyanate (IPDI), trimethylene diisocyanate, tetramethylene diisocyanate, pentamethylene diisocyanate, hexamethylene diisocyanate, propylene diisocyanate, ethylene diisocyanate, 2,3-dimethylethylene diisocyanate, 1-methyl trimethylene diisocyanate, 1,3-cyclopentene diisocyanate, 1,4-cyclopentene diisocyanate, 1,2-cyclopentene diisocyanate, 1,3-phenylene diisocyanate, 1,4-phenylene diisocyanate , 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, oligomeric isocyanate, isophorone diisocyanate, 4,4-diphenylpropane diisocyanate, xylene diisocyanate, and 1,1,6,6-tetramethyl It may be one or more selected from the group consisting of hexamethylene diisocyanate, and the acrylate is allyl methacrylate (AMA), methyl methacrylate (MMA), ethyl acrylate (EA), hydroxy ethyl acrylate (HEA) And it may include one or more selected from the group consisting of methacrylic acid (MAA).

Further, the acrylic urethane dispersion resin may have a viscosity of 10 to 90 cps at 25°C, a glass transition temperature (Tg) of -30 to 30°C, and an acid value (Av) of 1 to 25 mgKOH/g. As another example, the acrylic urethane dispersion resin may have a viscosity of 20 to 80 cps at 25°C, a glass transition temperature of -20 to 20°C, and an acid value of 5 to 20 mgKOH/g. When the viscosity of the acrylic urethane dispersion resin at 25°C is within the above range, the appearance of the manufactured coating film and the workability of the composition are excellent, and when the glass transition temperature is within the above range, the durability and hardness of the manufactured coating film And physical properties such as chemical resistance can be maintained, and when the acid value is within the above range, there is an effect of improving the hardness of the manufactured coating film.

In addition, the acrylic urethane dispersion resin is in the form of a dispersion in which an acrylic urethane resin is dispersed in a solvent, for example, the acrylic urethane dispersion resin may be in the form of a dispersion in deionized water. In addition, the acrylic urethane dispersion resin may have a solid content (NV) of 20 to 50% by weight and a pH of 6 to 10 based on the total weight. As another example, the acrylic urethane dispersion resin may have a solid content of 30 to 50% by weight and a pH of 7 to 9, or 7.5 to 8.5 based on the total weight. When the solid content of the acrylic urethane dispersion resin is within the above range, the composition has excellent workability, and when the pH is within the above range, the workability of the composition and the appearance of the prepared coating film are excellent.

In addition, the acrylic urethane dispersion resin may be included in the composition in an amount of 1 to 10 parts by weight based on 20 to 30 parts by weight of the acrylic resin. As another example, the acrylic urethane dispersion resin may be included in the composition in an amount of 2 to 9 parts by weight, or 3 to 8 parts by weight based on 20 to 30 parts by weight of the acrylic resin. When the content of the acrylic urethane dispersion is within the above range, there are excellent effects in flowability, cold chipping resistance, impact resistance, and appearance of the paint.

Urethane resin

The urethane resin serves to improve the workability of the base coat composition containing the same, and to improve the appearance characteristics of the coating film prepared from the composition.

The urethane resin may be a urethane diol-based compound. For example, the urethane resin may be a primary amino alcohol such as amino ethanol or amino isopropanol; Or a primary diamine such as ethylene diamine, propylene diamine, 2-methyl-pentane diamine-(1,5) or hexane diamine-(1,6); and a urethane diol obtained by reaction of an alkylene carbonate such as ethylene or propylene carbonate Can be

As another example, the urethane resin may be a urethane diol-based compound, a viscosity of 2,000 to 4,000 cps at 25°C, and a hydroxyl value of 200 to 500 mgKOH/g. As another example, the urethane resin is a urethane diol-based compound, has a viscosity of 2,500 to 3,500 cps at 25°C, a hydroxyl value of 250 to 400 mgKOH/g, and a solid content (NV) of 80 to It may be in a liquid form of 95% by weight, or 84 to 92% by weight. When the viscosity at 25° C. of the urethane resin is within the above range, the composition has an effect of easy workability, and when the hydroxyl value is within the above range, the gloss and appearance characteristics of the prepared coating film are good. In addition, when the urethane resin is used in a liquid form containing a solid content within the above content range, there is an effect of improving the workability of the composition.

In addition, the urethane resin may be included in the composition in an amount of 0.1 to 5 parts by weight based on 20 to 30 parts by weight of the acrylic resin. As another example, the urethane resin may be included in the composition in an amount of 0.1 to 3 parts by weight, or 0.5 to 2 parts by weight based on 20 to 30 parts by weight of the acrylic resin. When the content of the urethane resin is within the above range, there is an effect of improving the flexibility and appearance of the prepared coating film.

Melamine hardener

The melamine-based curing agent serves to cure by crosslinking reaction with each component of the base coat composition, and serves to improve the appearance characteristics and gloss of the coating film prepared from the base coat composition comprising the same.

The melamine-based curing agent may include a hydrophilic melamine resin containing an imino group. For example, the melamine-based curing agent may be in a liquid form containing a hydrophilic melamine resin containing an imino group. As another example, the melamine-based curing agent may be in a liquid form containing a hydrophilic melamine resin containing an imino group, and a solid content (NV) of 85 to 95% by weight based on the total weight of the melamine-based curing agent.

Further, commercially available products of the melamine-based curing agent include Cytec's Cymel 325, Cymel 327 and Cymel 385, INEOS's Resimene HM-2608, Resimene 718 and Resimene 717, and BASF's Luwipal 052 and 072.

Further, the melamine-based curing agent may be included in the composition in an amount of 1 to 5 parts by weight based on 20 to 30 parts by weight of the acrylic resin. As another example, the melamine-based curing agent may be included in the composition in an amount of 1 to 4 parts by weight, or 1.5 to 3.5 parts by weight based on 20 to 30 parts by weight of the acrylic resin. When the content of the melamine-based curing agent is within the above range, appropriate coating properties of the composition containing the melamine-based curing agent can be secured.

Oxazoline hardener

The oxazoline-based curing agent serves to cure by crosslinking reaction with each component of the base coat composition, and serves to improve the appearance characteristics of the coating film prepared from the base coat composition including the same.

The oxazoline-based curing agent may be an oxazoline group-containing polymer. For example, the oxazoline-based curing agent may be in the form of an emulsion of an oxazoline group-containing polymer. When the oxazoline-based curing agent is used in the form of an emulsion of an oxazoline group-containing polymer, the content of VOC (Volatile Organic Compounds) of the paint may be lowered.

In addition, the oxazoline-based curing agent may have a glass transition temperature (Tg) of -70 to 10°C, and a solid content (NV) of 20 to 60% by weight based on the total weight of the oxazoline-based curing agent. As another example, the oxazoline-based curing agent may have a glass transition temperature of -60 to 0° C., and a solid content (NV) may be 30 to 50% by weight based on the total weight of the oxazoline-based curing agent. When the glass transition temperature of the oxazoline-based curing agent is within the above range, it is possible to improve the curing speed and crosslinking density to improve mechanical properties, and when the solid content is within the above range, it is possible to improve workability and reduce the VOC content. .

Further, the oxazoline-based curing agent may be included in the composition in an amount of 1 to 5 parts by weight based on 20 to 30 parts by weight of the acrylic resin. For example, the oxazoline-based curing agent may be included in the composition in an amount of 2 to 5 parts by weight, or 2.5 to 4.5 parts by weight based on 20 to 30 parts by weight of the acrylic resin. When the content of the oxazoline-based curing agent is within the above range, there is an effect of improving the hardness by increasing the crosslinking density.

solvent

The base coat composition may further include a solvent. At this time, the solvent controls the viscosity of the composition and serves to reduce the generation of volatile organic compounds (VOC). For example, the solvent may include one or more types of water selected from the group consisting of deionized water and distilled water. Furthermore, the solvent may further contain an organic solvent in addition to water.

The solvent may be included in the composition in an amount of 5 to 50 parts by weight based on 20 to 30 parts by weight of the acrylic resin. For example, the solvent may be included in the composition in an amount of 10 to 40 parts by weight based on 20 to 30 parts by weight of the acrylic resin. When the solvent content in the composition is within the above range, the water dispersibility of the resins in the composition is lowered, the environmental friendliness that is an advantage of the water-based paint is lowered, and the evaporation of water is not sufficient, resulting in coating defects such as pinholes in the final coating film. It can prevent problems such as spotting.

Pigment

The base coat composition may further include a pigment. The pigment serves to impart color to the prepared coating film. For example, the base coat composition may be an effect pigment for imparting a metallic effect to a coating film, a colored pigment for imparting color and hiding effect in combination with a coating film-forming material, or a combination thereof.

At this time, examples of the effect pigment may include aqueous-treated aluminum flakes, mica pigments, or mixtures thereof. Examples of the colored pigment include oxide-based inorganic pigments, azo, and polycyclic organic pigments containing Vat pigments, anthraquinone-based organic pigments, or mixtures thereof.

The pigment may be included in the composition in an amount of 1 to 20 parts by weight based on 20 to 30 parts by weight of the acrylic resin. For example, the pigment may be included in the composition in an amount of 5 to 15 parts by weight based on 20 to 30 parts by weight of the acrylic resin. When the pigment content in the base coat composition is within the above range, problems such as insufficient hiding power of the prepared film and a decrease in stability of the composition and a decrease in dispersibility of the pigment can be prevented.

additive

The base coat composition may further include at least one additive selected from the group consisting of a co-solvent, a neutralizing agent, a catalyst, an ultraviolet absorber leveling agent, an antifoaming agent, a wetting agent, and a wax.

The additive may be included in the composition in an amount of 10 to 50 parts by weight based on 20 to 30 parts by weight of the acrylic resin. As another example, the additive may be included in the composition in an amount of 20 to 40 parts by weight based on 20 to 30 parts by weight of the acrylic resin.

The co-solvent affects the smoothness of the coating film to be produced, imparts storage stability of the base coat composition, lowers the minimum coating film formation temperature, and controls the volatility of the solvent during painting. In addition, the co-solvent is, for example, ethylene glycol monobutyl ether, diethylene glycol monobutyl ether, propylene glycol, N-methyl-2-pyrrolidone, n-propyl alcohol, i-propyl alcohol, n-butanol, propylene Glycol monomethyl ether, butyl glycol, hexyl glycol, 2-ethylhexyl alcohol, butyl carbitol, butyl cellosolve, dipropylene glycol methyl ether, n-propanol, and the like, but are not limited thereto.

The neutralizing agent serves to improve the storage stability of the base coat composition and adjust the pH (to a pH of 7.5 to 9.0). Further, the neutralizing agent is, for example, trialkylamines such as trimethylamine, triethylamine and tributylamine, N,N-dimethylethanol amine, N,N-dimethylpropanol amine, N,N-dipropylethanol amine And tertiary amines such as N,N-dialkylalkanolamines such as 1-dimethylamino-2-methyl-2-propanol, N-alkyl-N,N-dialkanolamines, and trialkanolamines such as triethanolamine compound; ammonia; Trimethylammonium hydroxide; Sodium hydroxide; Potassium hydroxide; And lithium hydroxide.

The catalyst serves to improve the mechanical properties of the coating film prepared therefrom by preventing incomplete curing of the base coat composition. In addition, the catalyst may include, for example, a phosphate-based compound or a sulfonic acid-based compound.

The UV absorber serves to improve the weather resistance of the final coating film by blocking UV rays reaching the prepared coating film. Furthermore, the ultraviolet absorber may be a benzotriazole-based ultraviolet absorber. For example, the benzotriazole-based ultraviolet absorber is α-[3-[3-(2H-benzotriazol-2-yl)-5-(1,1-dimethylethyl)-4-hydroxyphenyl]-1 -Oxapropyl]-ω-hydroxypoly(oxy-1,2-ethandiyl)(α-[3-[3-(2H-Benzotriazol-2-yl)-5-(1,1-dimethylethyl)-4 -hydroxyphenyl]-1-oxopropyl]-ω-hydroxypoly(oxy-1,2-ethanediyl)), α-[3-[3-(2H-benzotrirazol-2-yl)-5-(1,1- Dimethylethyl)-4-hydroxyphenyl]-1-oxapropyl]-ω-[3-[3-(2H-benzotriazol-2-yl)-5-(1,1-dimethylethyl)-4- Hydroxyphenyl]-1-oxapropoxy]poly(oxy-1,2-ethandiyl)(α-[3-[3-(2H-Benzotriazol-2-yl)-5-(1,1-dimethylethyl) -4-hydroxyphenyl]-1-oxopropyl]-ω-[3-[3-(2H-benzotriazol-2-yl)-5-(1,1-dimethylethyl)-4-hydroxyphenyl]-1-oxopropoxy]poly( oxy-1,2-ethanediyl)), 3-(2H-benzotriazol-2-yl)-5-(1,1-dimethylethyl)-4-hydroxy-methyl ester (3-(2H-benzotriazol-) 2-yl)-5-(1,1-dimethylethyl)-4-hydroxy-methyl ester) and the like.

The leveling agent serves to impart leveling properties and wettability of the produced coating film. In addition, the leveling agent may be a cationic, anionic, or nonionic surfactant, and may include, for example, a nonionic surfactant.

The antifoaming agent serves to suppress the generation of air bubbles generated during the manufacture of the coating material and suppress or remove phenomena such as pinholes or popping caused when the coating film is formed. In addition, the antifoaming agent may be used without particular limitation as long as it is a conventional one that can be used in the coating composition. For example, commercially available products of the antifoaming agent include BYK's BYK-011, BYK-015, BYK-072, Air Product's DF-21, Munzing's agitan 281, and Sannovco's Foamster-324.

The humectant serves to improve the leveling property and wettability of a coating film prepared from a composition comprising the same, and is not particularly limited as long as it is commonly used in a coating composition. For example, the wetting agent may be a polyether-modified polysiloxane-based wetting agent or an acetylene alcohol-type wetting agent.

The wax serves to prevent problems such as sagging due to a slow drying speed of a coating film prepared from a composition containing the wax, and is not particularly limited as long as it is commonly used in a coating composition. For example, the wax may include an ethylene-vinyl-acetate-based wax.

The base coat composition may have a pod cup viscosity of 30 to 100 seconds at 25° C. based on Pod Cup No. 4, and may include 15 to 50% by weight of solids based on the total weight of the composition. As another example, the base coat composition may have a pod cup viscosity of 50 to 70 seconds at 25° C. based on Pod Cup No. 4, and may include 20 to 30% by weight of solids based on the total weight of the composition.

The base coat composition according to the present invention as described above can be performed at a low temperature of 120° C. or less, which is a lower temperature than the conventional heat curing temperature in the painting process, and thus it is economical to reduce the cost required during the painting process. In addition, the coating film prepared from the composition has excellent mechanical properties, particularly properties such as gloss, impact resistance, water resistance, and cold chipping resistance, so that it can be usefully used for car body painting.

Hereinafter, the present invention will be described in more detail through examples. However, these examples are only intended to aid understanding of the present invention, and the scope of the present invention is not limited to these examples in any sense.

In the present invention, functional groups such as the "acid value" and "hydroxyl value" of the resin may be measured by a method well known in the art, and, for example, may represent a value measured by a titration method.

In addition, the'glass transition temperature' of the resin may be measured by a method well known in the art, for example, it may represent a value measured by a method of differential scanning calorimetry (DSC).

[Example]

Examples 1 and 10 Comparative Examples 1 to 5. Preparation of base coat composition

The base coat composition was prepared so that the viscosity was 55 seconds based on Pod Cup No. 4 at 25° C. while stirring and mixing the components in the composition as shown in Tables 1 and 2 below.

Ingredients (parts by weight) Example 1 Example 2 Example 3 Example 4 Example 5 Example 6 Example 7 Example 8 Acrylic resin 25.7 29 24.6 25.7 26.7 25.7 25.7 35.2 Polyurethane dispersion resin 8.4 6.4 9.4 8.4 8 8.4 8.4 6.5 Acrylic urethane dispersion resin 5.7 5.1 5.7 9 6 5.7 5.7 5.7 Urethane resin 1.1 1.1 1.2 1.1 1.2 1.1 1.1 1.9 Melamine hardener 2.6 2.6 2.6 2.6 3.2 2.6 3.5 3.2 Oxazoline hardener 4 4 4 4 4.8 7 0.5 4 Co-solvent 1 One One One One One One One One Cho Yongje 2 8.5 8.5 8.5 8.5 8.5 8.5 8.5 8.5 Co-solvent 3 2.1 2.1 2.1 2.1 2.1 2.1 2.1 2.1 Cho Yongje 4 4.8 4.8 4.8 4.8 4.8 4.8 4.8 4.8 corrector 1.8 1.8 1.8 1.8 1.8 1.8 1.8 1.8 Wax 1.7 1.7 1.7 1.7 1.7 1.7 1.7 1.7 catalyst 0.7 0.7 0.7 0.7 0.7 0.7 0.7 0.7 UV absorber 0.3 0.3 0.3 0.3 0.3 0.3 0.3 0.3 Pigment 8.7 8.7 8.7 8.7 8.7 8.7 8.7 8.7 Antifoam 1.2 1.2 1.2 1.2 1.2 1.2 1.2 1.2 Humectant 2.3 2.3 2.3 2.3 2.3 2.3 2.3 2.3 Distilled water 19.4 18.7 19.4 16.1 17 16.4 22 10.4 Sum 100 100 100 100 100 100 100 100

Ingredients (parts by weight) Example 9 Example 10 Comparative Example 1 Comparative Example 2 Comparative Example 3 Comparative Example 4 Comparative Example 5 Acrylic resin 25.7 23.4 29 29.7 - 29 26.9 Polyurethane dispersion resin 13 6.3 8.4 8.4 10 - 8 Acrylic urethane dispersion resin 5.7 12 5.7 5.7 9 8 - Urethane resin 1.1 1.1 1.1 1.1 1.1 1.5 1.1 Melamine hardener 2.6 2.6 - 5 5 4.2 3.4 Oxazoline hardener 4 4 5 - 4 4 4 Co-solvent 1 One One One One One One One Cho Yongje 2 8.5 8.5 8.5 8.5 8.5 8.5 8.5 Co-solvent 3 2.1 2.1 2.1 2.1 2.1 2.1 2.1 Cho Yongje 4 4.8 4.8 4.8 4.8 4.8 4.8 4.8 corrector 1.8 1.8 1.8 1.8 1.8 1.8 1.8 Wax 1.7 1.7 1.7 1.7 1.7 1.7 1.7 catalyst 0.7 0.7 0.7 0.7 0.7 0.7 0.7 UV absorber 0.3 0.3 0.3 0.3 0.3 0.3 0.3 Pigment 8.7 8.7 8.7 8.7 8.7 8.7 8.7 Antifoam 1.2 1.2 1.2 1.2 1.2 1.2 1.2 Humectant 2.3 2.3 2.3 2.3 2.3 2.3 2.3 Distilled water 14.8 17.5 17.7 17 37.8 20.2 23.5 Sum 100 100 100 100 100 100 100

Hereinafter, manufacturers and product names of each component used in Examples and Comparative Examples are shown in Table 3 below.

division Remark Acrylic resin Hydroxyl value 12mgKOH/g, acid value 11mgKOH/g, glass transition temperature 21℃,
Viscosity at 25°C 60 cps, solid content 35% by weight Polyurethane dispersion resin Viscosity at 25℃ 35cps, solid content 30% by weight
(Daotan TW1236, Allnex) Acrylic urethane
Dispersion resin Viscosity at 25°C 45cps, Tg -8°C, acid value 13.7 mgKOH/g,
Solid content 40% by weight, Ph 8.5 Urethane resin Viscosity at 25°C 3,000 cps, hydroxyl value 325 mgKOH/g,
88% by weight of solid content Melamine hardener Melamine resin containing imino groups (Cymel 325, Cytec) Oxazoline hardener K-2010E, EPOCROS Cho Yongje 1 Butyl Cellosolve Cho Yongje 2 N-methyl-2-pyrrolidone Cho Yongje 3 Butyl carbitol Cho Yongje 4 n-propanol corrector N,N-dimethylethanol amine Wax EVA (Ethylene-Vinyl-Acetate) wax, BYK catalyst Dodecylbenzene sulphonic acid type acid catalyst (XP-221, King Industries) UV absorber Absorbent with benzotriazole-based structure (Tinuvin 384, Ciba) Pigment Aluminum paste (EMR D5620, TOYO) Antifoam Inorganic antifoaming agent containing oil (agitan281, Munzing) Humectant Acetylene alcohol type wetting agent (Surfynol 104BC, Air Product)

Test Example: Evaluation of the properties of the manufactured coating

After applying and drying an intermediate coating material (manufacturer: KCC, product name: FU2290) on the specimen to form an intermediate coating film, the base coat compositions of Examples 1 to 10 and Comparative Examples 1 to 5 were belled at a thickness of 15 μm on a flat surface. Painted. After that, air was blown at 80° C. for 3 minutes to evaporate the water remaining in the paint (drying). A low-temperature curing type clear paint (manufacturer: KCC) was applied on the base coat to a thickness of 40 μm, and cured in an oven at 100° C. for 25 minutes to form a final coating film. The appearance characteristics and physical properties of the final coating film were measured by the following method, and the results are shown in Table 4.

(1) Painting workability

When the base coat composition was coated with the bell, the coating workability was evaluated by the spray state of the composition, and the spray state was judged and compared according to the atomization state.

(2) Appearance of the coating film

For the final coating film, the CF value was measured using a Wave Scan DOI (BYK Gardner), which is an automobile exterior measuring instrument, and it was determined that the higher the CF value, the better the appearance characteristics of the coating film. Specifically, if the CF value was 65 or more, it was evaluated as excellent (◎), if it was 60 or more and less than 65, good (○), if it was 55 or more and less than 60, it was evaluated as normal (△), and if it was less than 55, it was evaluated as bad (×).

(3) gloss

The 20° gloss of the final coating film was measured, and when the measured gloss value is 90 or more, it is excellent (◎), when it is 88 or more and less than 90, it is good (○), when it is 86 or more and less than 88, it is normal (△), and when it is less than 86, it is poor (×). It was evaluated as.

(4) repainting adhesion

After peeling off the base coat and the clear coat among the final coats, the base coat compositions and clear coats of Examples 1 to 10 and Comparative Examples 1 to 5 were recoated and cured in the same manner as described above to prepare a recoat. Thereafter, 100 squares (2 mm wide x 2 mm long) were drawn on the recoating film with a knife blade, and peeled off using a tape to measure adhesion.

At this time, if 100 squares are 100% completely attached, it is excellent (◎), if the remaining squares are 70% or more and less than 100%, good (○), if 50% or more and less than 70%, normal (△), 30% or more and less than 50% The case was evaluated as defective (×).

(5) Impact resistance

When a weight of 500 g was dropped on the final coating film from a height of 30 cm, the surface of the final coating film was observed to evaluate the impact resistance. Specifically, if there is no crack or impact trace on the surface (◎), if there is a trace, it is evaluated as good (○), and if the final coating film is cracked or open, it is evaluated as defective (×).

(6) water resistance

After the final coating film was immersed in a 40°C thermostat for 10 days, the adhesion was measured in the same manner as in item (4), and the same evaluation criteria were applied to evaluate the water resistance of the coating film.

(7) Fill flow

The sample on which the intermediate coating was formed was vertically hung, the base coat compositions of Examples 1 to 10 and Comparative Examples 1 to 5 were coated in the same manner as described above, dried and cured, and then the surface of the prepared coating film was observed, and the coating flow of the composition. Sex was evaluated.

As described above, intermediate and clear coating was applied to the steel plate with holes of 5 mm in diameter previously coated, and then it was observed that the coating formed on the lower end of the hole. The final coating film thickness at the starting point at which flow generation was observed was recorded as the flow limit film thickness. At this time, it was determined that the lower the measured flow limit film thickness value, the poorer the fill flow property.

Specifically, when the flow limit film thickness is 40 µm or more, it is excellent (◎), when it is 35 µm or more and less than 40 µm, it is good (○), when it is 30 µm or more and less than 35 µm, it is normal (△), and when it is less than 30 µm, it is poor (×). It was evaluated as.

(8) Cold chipping resistance

After the final coating was left at -20°C for 3 hours, 50 g of a chipping stone was pushed out with a pressure of 4 bar to hit the surface of the final coating layer. At this time, if the damaged part of the final coating film was less than 1mm, it was evaluated as excellent (◎), if it was more than 1mm and less than 2mm, it was good (○), if it was more than 2mm and less than 3mm, it was evaluated as normal (△), and if it was more than 3mm, it was evaluated as bad (×).

Evaluation item Painting workability Coating appearance Polish Repainting
Adherence Impact resistance Water resistance Fill flow Cold chipping resistance Example 1 ◎ ◎ ◎ ◎ ◎ ◎ ◎ ◎ Example 2 ◎ ◎ ◎ ◎ ○ ○ ◎ ◎ Example 3 ◎ ◎ ◎ ◎ ○ ◎ ◎ ○ Example 4 ◎ ○ ◎ ◎ ◎ ◎ ◎ ○ Example 5 ◎ ◎ ◎ ◎ ○ ○ ◎ ◎ Example 6 ◎ ◎ ◎ ◎ ○ ○ ○ ○ Example 7 ◎ ○ ◎ ◎ ○ ○ ◎ ○ Example 8 ◎ ○ ○ ◎ ○ ○ ◎ △ Example 9 ◎ ○ △ ◎ ○ ◎ ◎ ○ Example 10 ◎ △ ◎ ◎ ○ ◎ ◎ △ Comparative Example 1 ○ x △ ○ x x ○ x Comparative Example 2 ○ △ ○ △ x x △ △ Comparative Example 3 △ x ○ ○ x x △ △ Comparative Example 4 ○ △ x △ x ○ ○ x Comparative Example 5 x x x ○ x △ ○ x

As shown in Table 4, the base coat compositions of Examples 1 to 10 have excellent coating workability and coating flowability, and the coating film prepared therefrom has appearance characteristics, gloss, repainting adhesion, impact resistance, water resistance, and It was found that the mechanical properties of cold chipping resistance were also excellent.

On the other hand, the compositions of Comparative Examples 1 and 2 containing only one type of melamine-based curing agent or oxazoline-based curing agent were poor in workability due to reduced curability, and the coating film prepared therefrom also lacked appearance characteristics, impact resistance and water resistance. In addition, it was found that the composition of Comparative Example 3 that did not contain an acrylic resin had disadvantageous overall physical properties. Further, it was found that the coating film prepared from the composition of Comparative Example 4 not containing the polyurethane dispersion resin lacked gloss, impact resistance, cold chipping resistance, etc., and thus overall physical properties were disadvantageous. In addition, the composition of Comparative Example 5 that does not contain an acrylic urethane dispersion resin lacks coating workability, and the coating film prepared therefrom lacks appearance characteristics, gloss, impact resistance, and cold chipping resistance.

Claims (6)

20 to 30 parts by weight of acrylic resin, 5 to 10 parts by weight of polyurethane dispersion resin, 1 to 10 parts by weight of acrylic urethane dispersion resin, 0.1 to 5 parts by weight of urethane resin, 1 to 5 parts by weight of melamine-based curing agent and 1 to 5 It contains an oxazoline-based curing agent in parts by weight,
The polyurethane dispersion resin has a viscosity of 10 to 50 cps at 25°C,
The urethane resin has a viscosity of 2,000 to 4,000 cps at 25° C., a water-soluble base coat composition. The method according to claim 1,
The acrylic resin has a hydroxyl value (OHv) of 5 to 50 mgKOH/g, an acid value (Av) of 5 to 50 mgKOH/g, a glass transition temperature (Tg) of -30 to 30°C, and a viscosity of 20 at 25°C. To 600 cps, a water-soluble base coat composition. The method according to claim 1,
The polyurethane dispersion resin has a solid content (NV) of 20 to 50% by weight based on the total weight of the polyurethane dispersion resin, a water-soluble base coat composition. The method according to claim 1,
The acrylic urethane dispersion resin has a viscosity of 10 to 90 cps at 25°C, a glass transition temperature (Tg) of -30 to 30°C, an acid value (Av) of 1 to 25 mgKOH/g, and the total weight of the acrylic urethane dispersion resin. Based on the solid content (NV) of 20 to 50% by weight, a water-soluble base coat composition. The method according to claim 1,
The urethane resin is a urethane diol-based compound, a hydroxyl value of 200 to 500 mgKOH/g, and a solid content (NV) of 80 to 95% by weight based on the total weight of the urethane resin, a water-soluble base coat composition. delete