KR102217675B1 - 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, a polyester 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 typically electro-deposited 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. Afterwards, 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 painting and clear coat painting, 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 curable 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 a coating material for automobile repair and a composition for painting parts, but the mechanical properties of the produced coating film are not sufficient. There is a limit to applying it as a paint for car 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, a polyester 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, so that the cost required during the painting process can be reduced, so it is economical. 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, and thus can be usefully used for vehicle 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, a polyester 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 selected from the group consisting of allyl methacrylate (AMA), methyl methacrylate (MMA), ethyl acrylate (EA), hydro ethyl acrylate (HEA), and methacrylic acid (MAA). It may contain one or more monomer-derived units. For example, the acrylic resin includes allyl methacrylate (AMA), methyl methacrylate (MMA), ethyl acrylate (EA), hydro ethyl acrylate (HEA) and methacrylic acid (MAA) as monomers. It may 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 dimethrylate (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 (1,9-Nonanediol dimethacrylate), 1,10-decanediol dimethacrylate (1,10-Decanediol dimethacrylate), ethylene glycol diacrylate (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. As 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, and 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 and particle stability are 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, workability 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, it is possible to secure an appropriate rheology, and has excellent appearance, water resistance, impact resistance, and cold chipping resistance.

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% by weight 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, there is an effect of excellent appearance and workability, and when the solid content is within the above range, there is an effect of improving workability.

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 acrylic resin. When the content of the polyurethane dispersion resin is within the above range, excellent drying properties, cold chipping resistance, and impact resistance are effective.

Polyester resin

The polyester resin serves to improve the flexibility and appearance characteristics of the coating film prepared from the base coat composition comprising the same.

The polyester resin may be prepared by reacting a carboxylic acid compound and a diol compound. For example, the polyester resin is adipic acid (AA), isophthalic acid (IPA), trimalic anhydride (TMA), alicyclic acid, phthalic anhydride, isophthalic acid, terephthalic acid, succinic acid, adipic acid, fumaric acid, male At least one carboxylic acid compound selected from the group consisting of using acid anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, and derivatives thereof; And 1,6-hexanediol (1,6-HD), neopentyl glycol (NPG), trimethylol propane (TMP), ethylene glycol, propylene glycol, diethylene glycol, butanediol 1,4-hexanediol and 3-methyl It can be prepared by reacting at least one diol compound selected from the group consisting of pentanediol.

In addition, the polyester resin may be in a liquid form having a solid content (NV) of 50 to 85% by weight based on the total weight of the resin. As another example, the polyester resin may be in a liquid form having a solid content (NV) of 65 to 75% by weight based on the total weight of the resin. When a polyester resin is used in a liquid form, there is an effect of easy workability during manufacture, and when a polyester resin in a liquid form having a solid content within the above range is used, there is an effect of easy workability during manufacture.

Further, the polyester resin has a hydroxyl value (OHv) of 50 to 150 mgKOH/g, an acid value (Av) of 10 to 100 mgKOH/g, a Gardner viscosity P to U, and a weight average molecular weight (Mw) of 500 to 2,000 g May be /mol. In another example, the polyester resin has a hydroxyl value (OHv) of 80 to 120 mgKOH/g, an acid value (Av) of 10 to 80 mgKOH/g, a Gardner viscosity of Q to T, and a weight average molecular weight of 700 to 1,300 g May be /mol. When the hydroxyl value of the polyester resin is within the above range, water dispersibility and coating properties are good, and when the acid value is within the above range, storage stability and crosslinking density are improved, so that cold chipping resistance is good, and Gardner viscosity is When it is within the above range, there is an effect of easy workability, and when the weight average molecular weight is within the above range, there is a good effect of coating properties and appearance.

In addition, the polyester 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 polyester resin may be included in the composition in an amount of 3 to 8.5 parts by weight based on 20 to 30 parts by weight of the acrylic resin. When the content of the polyester resin is within the above range, excellent appearance, impact resistance and cold chipping resistance can be secured.

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 is 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 urethane diol obtained by reaction of an alkylene carbonate such as ethylene or propylene carbonate Can be

As another example, the urethane resin is a urethane diol-based compound, has a viscosity of 2,000 to 4,000 cps at 25°C, and a hydroxyl value (OHv) of 200 to 500 mgKOH/g. In 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, there is an effect of easy workability, and when a liquid form containing solids within the above content range is used, there is an effect of improving workability. In addition, when the hydroxyl value of the urethane resin is within the above range, the gloss and appearance characteristics of the prepared coating film are good.

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

In addition, commercially available products of the melamine-based hardener 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, 072, and the like.

Furthermore, 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 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 can be reduced.

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, the curing speed and crosslinking density can be improved to improve mechanical properties, and when the solid content is within the above range, workability and VOC content can be reduced. .

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, pure water, ultrapure water, and distilled water. Furthermore, the solvent may further contain an organic solvent in addition to water.

The base coat composition may include 20 to 95 parts by weight of a solvent based on 100 parts by weight of the acrylic resin. For example, the base coat composition may include 25 to 90 parts by weight of a solvent based on 100 parts by weight of an acrylic resin. If the solvent content in the composition is within the above range, the problem of deteriorating the water dispersibility of the resins in the composition, the problem of lowering the environmental friendliness, which is an advantage of the aqueous paint, and coating defects such as pinhole generation in the final coating film due to insufficient evaporation of water 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 pigments include oxide-based inorganic pigments, azo, and polycyclic organic pigments containing Vat pigments, anthraquinone-based organic pigments, or mixtures thereof.

The base coat composition may include 10 to 50 parts by weight of a pigment based on 100 parts by weight of an acrylic resin. For example, the base coat composition may include 20 to 40 parts by weight of a pigment based on 100 parts by weight of an acrylic resin. When the pigment content in the base coat composition is within the above range, problems such as a lack of 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 base coat composition may include 50 to 150 parts by weight of an additive based on 100 parts by weight of the acrylic resin. For example, the base coat composition may include 60 to 120 parts by weight of an additive based on 100 parts by weight of an 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, 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-dimethylethanolamine, N,N-dimethylpropanolamine, N,N-dipropylethanolamine And trialkanolamines such as N,N-dialkylalkanolamines such as 1-dimethylamino-2-methyl-2-propanol, N-alkyl-N,N-dialkanolamines, and triethanolamines, etc. Amine compounds; 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 includes, for example, an amine group-containing phosphate 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 paint and to suppress or eliminate 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, commercial 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 system or an acetylene alcohol type wetting agent.

The wax serves to prevent problems such as sagging due to a slow drying rate 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 contain 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 wt% 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, and thus can be usefully used for vehicle 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 values such as'acid value' and'hydroxyl value' of the resin can be measured by a method well known in the art, for example, a value measured by a titration method.

In addition, the'weight average molecular weight' of the resin can be measured by a method well known in the art, for example, it can represent a value measured by the method of GPC (gel permeation chromatograph).

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 to 10 and 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 26.7 29 25.7 24.6 25.7 25.7 35 Polyurethane dispersion resin 8.4 8 6.4 8.4 9.4 8.4 8.4 6.5 Polyester resin 5.7 6 5.1 9 5.7 5.7 5.7 5.7 Urethane resin 1.1 1.2 1.1 1.1 1.2 1.1 1.1 2.1 Melamine hardener 2.6 3.2 2.6 2.6 2.6 2.6 3.5 3.2 Oxazoline hardener 4 4.8 4 4 4 7 0.5 4 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 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 Ultraviolet 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 17 18.7 16.1 19.4 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 Polyester 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 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 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 Ultraviolet 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 Comparative Examples and Examples are shown in Tables 3 and 4 below.

division Remark Acrylic resin Emulsion form 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 Dispersion form Allnex, Daotan TW1236
(Viscosity 35 cps at 25°C, solid content 30% by weight) Polyester resin Liquid Hydroxyl value 110mgKOH/g, acid value 35mgKOH/g, Gardner viscosity Q~T,
Weight average molecular weight 1,050g/mol, solid content 70% by weight Urethane resin Urethane diol King Industries, K-FLEX UD-350W (Viscosity at 25℃ 3,000cps, hydroxyl value 325 mgKOH/g, solid content 88% by weight) Melamine hardener Melamine resin containing imino groups (Cymel 325, Cytec) Oxazoline hardener EPOCROS, K-2010E

ingredient Remark Cho Yongje 1 Butyl Cellosolve Cho Yongje 2 N-Methyl Pyrrolidone Cho Yongje 3 Butyl Carbitol Cho Yongje 4 n-propanol corrector Dimethylethanol amine (BASF) Wax EVA (Ethylene-Vinyl-Acetate) wax, BYK catalyst Dodecylbenzene Sulphonic Acid Type Acid Catalyst (XP-221, King Industries) Ultraviolet absorber Absorbent with benzotriazole-based structure (Tinuvin 384, Ciba) Pigment Aluminum paste (metal pigment 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 film

After applying and drying an intermediate coating (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 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 in the following manner, and the results are shown in Table 5.

(1) Painting workability

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

(2) appearance

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 (×). 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. Afterwards, the adhesiveness was measured on the re-coating film by the Go wood method.

Specifically, in the Badukmok method, 100 squares (2 mm wide x 2 mm long) were drawn on the re-coating film with a blade and removed 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%, it is good (○), if it is 50% or more and less than 70%, it is normal (△), and if it is less than 50%, it is bad ( ×).

(5) Impact resistance

When a weight of 500 g was dropped on the final coating film at a height of 30 cm, the surface of the final coating film was observed to evaluate the impact resistance. Specifically, when there was no evidence of cracking or impact on the surface (◎), when there was a mark, it was evaluated as normal (△), and when the final coating film was cracked or opened, it was evaluated as defective (x).

(6) water resistance

After the final coating was immersed in a 40°C thermostat for 10 days, the adhesion was measured in the same manner as in the Go wood method in item (4), and the water resistance of the coating was evaluated by applying the same evaluation criteria.

(7) Fill flow

The specimen with the intermediate coating film was vertically hung, and 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. Sex was evaluated.

As described above, medium 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.

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 bad (×). Evaluated as.

(8) Cold chipping resistance

After the final coating was left at -20°C for 3 hours, 50g of the chipping stone was pushed out with a pressure of 4bar to hit the surface of the final coating. 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 stamp
Workability Coating
Exterior 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 Comparative Example 2 ○ △ ○ △ x x △ △ Comparative Example 3 △ x ○ ○ x x △ △ Comparative Example 4 ○ △ x ○ x ○ ○ x Comparative Example 5 x ○ x ○ x ○ ○ x

As shown in Table 5, the base coat compositions of Examples 1 to 10 are excellent in coating workability and coating flow, and the coating film prepared therefrom has appearance properties, gloss, repaint 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 curability and thus workability, 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, and the like, and thus overall physical properties were disadvantageous. In addition, the composition of Comparative Example 5 that does not contain a polyester resin lacks coating workability, and a coating film prepared therefrom lacks 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 polyester 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 parts by weight It contains an oxazoline-based curing agent, and the acrylic resin has an acid value of 5 to 30 mgKOH/g,
The urethane resin is a urethane diol-based compound, has a viscosity of 2,000 to 4,000 cps at 25°C, a hydroxyl value of 200 to 500 mgKOH/g, and a solid content of 80 to 95% by weight based on the total weight of the urethane resin Phosphorus, water-soluble base coat composition. The method according to claim 1,
The acrylic resin has a hydroxyl value of 5 to 50 mgKOH/g, a glass transition temperature of -30 to 30°C, and a viscosity of 20 to 600 cps at 25°C, a water-soluble base coat composition. The method according to claim 1,
The polyurethane dispersion resin has a viscosity of 10 to 50 cps at 25° C., and a solid content of 20 to 50% by weight based on the total weight of the dispersion resin, a water-soluble base coat composition. The method according to claim 1,
The polyester resin has a hydroxyl value of 50 to 150 mgKOH/g, an acid value of 10 to 100 mgKOH/g, a Gardner viscosity P to U, and a weight average molecular weight of 500 to 2000 g/mol, a water-soluble base coat composition . delete The method according to claim 1,
The oxazoline-based curing agent has a glass transition temperature (Tg) of -70 to 10°C, a water-soluble base coat composition.