KR102072849B1 - Coating Composition - Google Patents

Abstract

The present invention relates to a coating composition for coil coating comprising a phosphate ester group-containing polyester polyol, a curing agent, an acid catalyst, a non-chromium-based rust preventive pigment, and a solvent.

Description

Coating composition

The present invention relates to a coating composition for coil coating (for example, PCM (Pre-coated metal)) excellent in corrosion resistance.

The base material used for PCM is a metal steel plate, and there exist a zinc-based galvanized or alloy steel plate, an aluminum-based galvanized or alloy steel plate, and other metal materials of zinc and aluminum. The surface of such a metal is generally unstable, so that oxygen and moisture in the atmosphere, various ions contained in the moisture and the like to form a compound, thereby causing oxidation and corrosion. As a method for preventing such corrosion, a method of increasing the corrosion resistance by forming a stable film on the metal surface by applying a chromium (Cr) -containing treatment liquid such as chromate chromate or phosphate chromate to a metal is applied. .

However, with the stricter regulations for environmental preservation around the world, restrictions on the use of harmful substances to humans and the environment are being enacted. Accordingly, in Europe, since 2003, the use of steel sheets containing hexavalent chromium in automobile materials has been regulated, and this movement has been occurring in the United States, Japan, and around the world.

In accordance with the above-mentioned trend, the pretreatment of steel sheet is replaced with phosphate from chromic acid, and research on various inorganic and organic coating technologies that can replace chromate treatment in post-treatment of precoated steel plate and pretreatment of coated steel plate have. Examples of the aforementioned surface treatment techniques include molybdate coating, permanganate coating, rare earth metal salt coating, organic-phosphate coating, and silane-based silane) coating, zirconium coating, organic coating, and the like have been proposed.

In order to replace the chromium-based rust preventive pigments included in PCM paints, non-chromic rust preventive pigments such as silica, aluminum polyphosphate, zinc phosphate, magnesium phosphate and calcium phosphate have been developed. However, when the non-chromic rust preventive pigments are used, they do not exhibit the desired level of corrosion resistance, and when the content of the non-chromic rust preventive pigments is increased to compensate for this, there is a decrease in alkali resistance.

Therefore, the situation is required to develop a coating composition for PCM that can continue to exhibit excellent corrosion resistance even without using a chromium-based component.

Republic of Korea Patent No. 0644767 Republic of Korea Patent No.

The present invention provides a coating composition for coil coating that can exhibit excellent corrosion resistance and adhesion without containing chromium.

The present invention provides a coating composition for coil coating comprising a phosphate ester group-containing polyester polyol, a curing agent, an acid catalyst, a non-chromium-based rust preventive pigment, and a solvent.

The present invention also provides a steel sheet for PCM comprising a steel sheet and a coating film formed from the coating composition for coil coating.

By applying the coating composition according to the present invention, the adhesion with the base can be improved and the corrosion resistance can be increased. Accordingly, excellent adhesion, corrosion resistance and alkali resistance can be exhibited without using a chromium-based rust preventive pigment.

The coating composition according to the present invention may satisfy both domestic environmental regulations and stricter overseas environmental regulations for chromium (Cr ⁶⁺ ), which is one of four heavy metals harmful to the environment.

BRIEF DESCRIPTION OF THE DRAWINGS It is a schematic diagram which evaluates the corrosion resistance (SST: salt spray test) of the coating composition of Example 1 and Comparative Examples 1-4.

Hereinafter, the present invention will be described in detail. However, the present invention is not limited only to the following contents, and each component may be variously modified or optionally mixed as necessary. Therefore, it is to be understood that all changes, equivalents, and substitutes included in the spirit and scope of the present invention are included.

Coating Composition

The coating composition according to the present invention comprises a phosphate ester group-containing polyester polyol resin, a curing agent, an acid catalyst, a pigment containing a non-chromium-based rust preventive pigment, and a solvent. If necessary, it may further include conventional additives in the paint field for epoxy resin and coil coating.

Hereinafter, looking at the composition of the coating composition in detail.

Phosphate  Ester polyester  Polyol resin

An object of the present invention is to provide a coating composition for coil coating, such as a primer coating composition for home appliances / architectural interior and exterior materials PCM, which does not contain chromium-based components and can exhibit excellent corrosion resistance and good adhesion.

Coating compositions based on polyester polyol resins polycondensed using conventional alcohols and carboxylic acids exhibit poor physical properties in terms of corrosion resistance and adhesion when they do not contain chromium-based components. In contrast, the coating composition according to the present invention can improve the corrosion resistance and adhesion of the chromium-free coating by applying a phosphoric acid-modified polyester polyol resin as the main resin.

In the coating composition according to the present invention, the phosphate ester group-containing polyester polyol resin is used as the main resin. The main resin reacts with the curing agent to form a coating film, to give gloss, and to secure the basic physical properties of the coating film and excellent corrosion resistance, processability, chemical resistance, hardness, adhesion, and the like.

The phosphate ester group-containing polyester polyol resin has a number average molecular weight (Mn) of 2,000 to 10,000 g / mol, such as 2,000 to 7,000 g / mol, and a weight average molecular weight (Mw) of 3,000 to 15,000 g / mol, such as 3,000 to 13,000 g / mol, a solid value hydroxyl value (OH value) is 10 to 60 mgKOH / g, an acid value is 15 to 40 mgKOH / g, the glass transition temperature (Tg) may be -30 to 30 ℃. If the number average molecular weight is 2,000 g / mol or less, adhesion and workability is inferior, if more than 10,000 g / mol adhesion is good but the viscosity may increase. If the hydroxyl value is 10 mgKOH / g or less, the curability of the coating film, and if it is 60 mgKOH / g or more may be inferior to the adhesion and processability. If the glass transition temperature is less than -30 ℃ chemical resistance is lowered, if the glass transition temperature is more than 30 ℃ processability may be inferior.

The phosphate ester group-containing polyester polyol may contain a phosphate ester group represented by Formula 1 below in a molecule, but is not particularly limited thereto. Thus, when a coating film (for example, a undercoat film) is formed by containing a specific phosphate modified polyester polyol resin, the high corrosion resistance and adhesive effect derived from the phosphate ester group can be improved.

In the above formula, R may be hydrogen or an alkyl group having 1 to 20 carbon atoms.

The phosphate ester group-containing polyester polyol resin according to the present invention is prepared using at least one acid monomer containing a carboxylic acid functional group and at least one polyfunctional alcohol monomer, a metal catalyst, a phosphorus (P) -containing acid, and the like. Can be.

The production method comprises the steps of i) polymerizing at least one acid monomer and at least one polyfunctional alcohol monomer containing a carboxylic acid functional group in the presence of a metal catalyst to prepare a polyester polyol prepolymer; and ii) the polyester. And a second step of preparing the phosphate ester group-containing polyester polyol resin using the polyol prepolymer and phosphorus containing acid. However, the present invention is not limited to the above-described manufacturing method, and the steps of each process may be modified or selectively mixed as necessary.

Hereinafter, the manufacturing method will be described by dividing the process step by step.

i) polyester  Polyol Prepolymer  Manufacturing stage ('first stage')

A polyester polyol prepolymer is prepared by mixing at least one acid monomer containing a carboxylic acid functional group and at least one polyfunctional alcohol monomer to polymerize in the presence of a metal catalyst.

Acid monomer

As the acid-based monomer, conventional carboxylic acids and derivative compounds thereof in the art including carboxylic acid functional groups may be used without limitation. Examples include at least one functional aromatic carboxylic acid, aliphatic carboxylic acid, alicyclic carboxylic acid, fatty acid, dimeric acid, or mixtures thereof.

Non-limiting examples of acidic monomers that can be used include isophthalic acid, terephthalic acid, dimethyl terephthalate, dimethyl isophthalate, trimellitic anhydride, adipic acid, azalic acid, sebacic acid, succinic anhydride, freth Thalic unhydride, hexahydrophthalic unhydride, methyl hexahydrophthalic unhydride, tetrahydrophthalic unhydride, methyl tetrahydrophthalic unhydride, 12-hydroxy stearic acid, stearic acid , Benzoic acid, isononanoic acid, dodecanedioic acid, dimeric fatty acid, hydrogenated dimeric fatty acid, fumaric acid, maleic hydride and the like. The above components may be used alone or in combination of two or more thereof.

The dimer acid may be represented by the following Chemical Formula 2, but is not particularly limited thereto.

In one example, the acid monomers of the present invention include at least one functional aromatic carboxylic acid, aliphatic carboxylic acid and fatty acid and dimer acid. The acid monomer may be a mixture including 30 to 80 equivalent% of at least one aromatic carboxylic acid, 5 to 40 equivalent% of aliphatic carboxylic acid, and 5 to 30 equivalent% of fatty acid and dimer acid, based on 100 equivalent% of the total acid monomer. .

Of the acid monomer raw material, the amount of the aromatic raw material (eg, aromatic carboxylic acid) may be 30 to 80 equivalent% based on 100 equivalent% of the total acid monomer. When the aromatic carboxylic acid is used in less than 30 equivalent%, the glass transition temperature of the coating film may be lowered and alkali resistance may be lowered. When the aromatic carboxylic acid is used in an amount of more than 80 equivalent%, the adhesion to the base or the top may be lowered, resulting in poor corrosion resistance. The viscosity of the sharp rises may cause problems in workability.

Among the acid monomer raw materials, the amount of aliphatic carboxylic acid used may be 5 to 40 equivalent% based on 100 equivalent% of the total acid monomer. If the amount of the aliphatic carboxylic acid is less than 5 equivalent%, the processability of the coating film is lowered, and there is a problem in the application of the product. If the amount exceeds 40 equivalent%, the glass transition temperature of the coating film is lowered and the alkali resistance is lowered.

In the acid monomer raw material, the amount of fatty acid and dimer acid may be 5 to 30 equivalent% based on 100 equivalent% of the total acid monomer. When the amount of the fatty acid and the dimer acid is less than 5 equivalent%, the hydrophobicity of the coating may decrease, so that the barrier effect and corrosion resistance to the base may be lowered. When the amount of the fatty acid and the dimer acid is less than 30 equivalent%, the adhesion to the base may be increased due to the nonpolar increase of the coating. This can fall.

Multifunctional  Alcohol monomer

As the polyfunctional alcohol monomer, an alcohol and a derivative compound thereof in the art including a bifunctional or higher alcohol functional group may be used without limitation. Examples include aliphatic alcohols, alicyclic alcohols, ethoxylated bisphenol A alcohols, or mixtures thereof.

As the polyfunctional alcohol monomer, carbon atoms of 2 to 16 alcohols may be used, and non-limiting examples thereof include ethylene glycol, propylene glycol, dipropylene glycol, tripropylene glycol, 1,3-butylene glycol, 1,4 Butanediol, 1,5-pentanediol, 1,6-hexanediol, 2-butyl-2-ethyl-1,3-propanediol, cyclohexanedimethanol, diethylene glycol, glycerin, 2-methyl-1,3 -Propanediol, neopentyl glycol, pentaerythritol, tris-hydroxyethyl isocyanate, trimethylol ethane, trimethylol propane, ethoxylated bisphenol A, ditrimethylol propane and the like. The above-mentioned components may be used alone or in combination of two or more thereof.

The ethoxylated bisphenol A may be represented by the following Chemical Formula 3, but is not particularly limited thereto.

Here, n is an integer of 1 to 5, for example may be 1 to 3.

In one example, the polyfunctional alcohol monomer of the present invention includes at least bifunctional aliphatic alcohols, alicyclic alcohols, and ethoxylated bisphenol A alcohols. The polyfunctional alcohol monomer may be a mixture of 50 to 90 equivalent% of bifunctional or higher alcohol and 10 to 50 equivalent% of at least one ethoxylated bisphenol A alcohol based on 100 equivalent% of the total alcohol monomer. .

In the polyfunctional alcohol monomer raw material, the amount of trifunctional or higher functional alcohol monomer raw material may be 20 equivalent% or less based on 100 equivalent% of the total polyfunctional alcohol monomer. When the amount of the trifunctional alcohol monomer is more than 20 equivalent%, the workability is lowered and the alkali resistance may be good, but the corrosion resistance may be reduced due to the decrease in adhesion to the base.

The ethoxylated bisphenol A may be used in combination of two kinds, for example, first ethoxylated bisphenol A (BSA-20, n = 1 in Formula 3) and second ethoxylated bisphenol A (BSA- 60, n = 3) in Formula 3 may include 10 to 50 equivalents based on 100 equivalents of total alcohol monomer.

The amount of the ethoxylated bisphenol A may be 10 to 50 equivalent% based on 100 equivalent% of the total polyfunctional alcohol monomer. If the amount of the ethoxylated bisphenol A is less than 10 equivalent%, the corrosion resistance is inferior due to a decrease in adhesion to the body. If the amount of the ethoxylated bisphenol A is less than 10 equivalent%, the corrosion resistance may be improved, but the alkali resistance may be reduced due to the increase in the number of ether bonds. have.

As an example of a method for producing a polyester polyol prepolymer, the reactant and the reaction catalyst are introduced into a reactor equipped with a stirrer, a thermometer, a nitrogen injection tube, and a cooling device, and heated to 240 to 260 ° C while removing condensed water while injecting an inert gas. React. The acid monomer containing the carboxylic acid functional group and the polyfunctional alcohol monomer are controlled so as to have an equivalent ratio of alcohol / carboxylic acid of 1.05 to 1.20. As the reaction catalyst, a conventional metal catalyst used in preparing a polyester polyol resin may be used, and as an example, a tin catalyst may be used. The metal catalyst may be used in the range of 0.01 to 0.1% by weight based on the total weight of solids of the polyester polyol prepolymer.

The polyester polyol prepolymer according to the present invention has a number average molecular weight (Mn) of 1,000 to 6,000 g / mol, a solid based hydroxyl value (OH value) of 30 to 80 mgKOH / g, and an acid value of 0 to 10 mgKOH / g. Can be. When the hydroxyl value of the polyester polyol prepolymer is less than 30 mgKOH / g and the number average molecular weight exceeds 6,000 g / mol, it may be difficult to form a phosphate polyester (PE) group in the second step reaction described later. On the other hand, when the hydroxyl value is more than 80 mgKOH / g and the number average molecular weight is less than 1,000 g / mol, the base material coating or coating coating of the undercoat to which the final resin is applied may be lowered and corrosion resistance may be reduced.

ii) Phosphate  Ester polyester  Step of preparing polyol resin ('second step')

The phosphate ester-modified polyester polyol resin is prepared by reacting the polyester polyol prepolymer, which is the product of the first step, with a phosphorus (P) -containing acid.

Non-limiting examples of phosphorus-containing acids that can be used include phosphoric acid (Phosphoric acid, Formula 4), phosphorous acid (Phosphorous acid, Formula 5), Phosphorus pentoxide (Formula 6), or mixtures thereof.

As an example of a method for preparing a phosphate ester group-containing polyester polyol resin, the polyester polyol prepolymer prepared in the first step is subjected to azeotropic distillation at 160 to 210 ° C while injecting a phosphorus-containing acid into the reactor and injecting an inert gas, React while removing condensed water.

The amount of the phosphorus-containing acid may be 1 to 3 wt% based on the total weight of solids of the polyester polyol prepolymer. When the amount of the phosphorus-containing acid is less than 1% by weight, the corrosion resistance may not be improved by increasing the adhesion of the body, and when it exceeds 3% by weight, the corrosion resistance may be improved, but the reaction may not be smooth. Corrosion of the equipment may proceed.

Phosphoric acid-modified polyol resin according to the present invention not only contains a phosphate ester group in the molecule, but also satisfies specific physical properties, thereby exhibiting excellent corrosion resistance, alkali resistance and processability. The phosphate ester group-containing polyester polyol resin of the present invention has a number average molecular weight (Mn) of 2,000 to 10,000 g / mol, a weight average molecular weight (Mw) of 3,000 to 15,000 g / mol, and a hydroxyl value (OH value) of 10 To 60 mgKOH / g, an acid value of 15 to 40 mgKOH / g, and a glass transition temperature of -30 to 30 ° C.

In the present invention, the content of the phosphate ester group-containing polyester polyol resin may be 30 to 60% by weight, for example 25 to 40% by weight, based on the total weight (100% by weight) of the coating composition. When the content of the phosphate ester group-containing polyester polyol resin is less than 30% by weight, deterioration of corrosion resistance, processability and curability is caused, and when the content of the phosphate ester group-containing polyester polyol is greater than 60% by weight, the hiding power may be weakened.

Epoxy resin

The coating composition according to the present invention may further comprise an epoxy resin as necessary. The epoxy resin is used as an auxiliary resin together with the polyester polyol resin to impart adhesion to the substrate to the coating film.

As the epoxy resin, conventional epoxy resins known in the art can be used without limitation, for example, bisphenol A, bisphenol F, cresol novolac, dicyclopentazene, trisphenylmethane, naphthalene, biphenyl type and these Hydrogenated epoxy resins and the like can be used. The said epoxy resin can be used individually or in mixture of 2 or more types.

In the present invention, the content of the epoxy resin is not particularly limited, and may be, for example, 3 to 10% by weight based on the total weight (100% by weight) of the coating composition. When the content of the epoxy resin falls within the above range, the basic physical properties of the coating film is good, it may exhibit excellent corrosion resistance, chemical resistance, adhesion.

Hardener

In the coating composition according to the present invention, the curing agent serves to cure the polyol resin to form a stable coating film.

What is generally used for resin which has a hydroxyl group can be used as said hardening | curing agent without limitation, For example, a melamine resin etc. can be used. Non-limiting examples of the melamine resin that can be used in the present invention is methoxy melamine resin, methoxy / butoxy mixed melamine resin and the like. For example, hexamethylol melamine, hexamethoxymethyl melamine, hexabutoxymethyl melamine or mixtures thereof and the like can be used. The molecular weight of the melamine resin may range from 300 to 1,000.

In the present invention, the amount of the curing agent may be 3 to 10% by weight based on the total weight (100% by weight) of the coating composition. When the content of the curing agent is less than 3% by weight, the degree of curing, chemical resistance, etc. of the coating film is lowered, and when it exceeds 10% by weight, the flexibility, adhesion of the coating film may be lowered.

Acid catalyst

In the coating composition according to the present invention, the acid catalyst serves as a curing accelerator for improving the density of the coating film by promoting the curing of the phosphate ester group-containing polyester polyol resin and the curing agent (melamine resin).

Acid catalysts that may be used include sulfonic acid compounds, non-limiting examples of which are para-toluene sulfonic acid (p-TSA), dinonylnaphthalene sulfonic acid (DNNSA), which are shielded with amines or epoxy. Dinonylnaphthalene disulfonic acid, dodecylbenzene sulfonic acid (DDBSA). These may be used alone or in combination of two or more thereof.

In the present invention, the content of the acid catalyst may be 0.1 to 3% by weight based on the total weight (100% by weight) of the coating composition. If the content of the acid catalyst is less than 0.1% by weight uncured, there is a disadvantage in that the hardness, chemical resistance is lowered, if it exceeds 3% by weight the unreacted acid catalyst remains in the coating film and adhesion and chemical resistance is lowered.

Pigment

The paint composition according to the present invention includes a pigment as necessary, and may be a conventional rust preventive pigment, extender pigment, colored pigment or two or more thereof.

The rust preventive pigment is a substance to which the corrosion resistance is improved, and the rust preventive pigment according to the present invention includes a non-chromium pigment. Non-limiting examples of the non-chromium pigments include calcium silica, zinc phosphate, organonitro compound zinc salt, calcium silicate, zinc potassium and the like. In one example, a calcium ion exchanged silica (Calcium ion exchanged Silica) type of pigment may be used. The above-mentioned components may be used alone or in combination of two or more thereof. In particular, chromium pigments and non-chromium pigments may be mixed and used as necessary, for example, when applied to harsh corrosive environments.

In the present invention, the content of the rust preventive pigment may be 15% by weight or less, for example, 5 to 15% by weight based on the total weight (100% by weight) of the coating composition. When the blending amount of the rust preventive pigment is less than 5% by weight, the corrosion resistance is not sufficient, and when it exceeds 15% by weight, alkali resistance, adhesion, boiling resistance and processability may be lowered. In the conventional coating composition for coil coating, an excessive amount of chromium-based rust preventive pigment was used to exhibit high corrosion resistance. In this case, the raw material cost of the paint was increased, and the adhesion to the fluorine-based top coat was inferior. On the contrary, in the present invention, although the content of the non-chromium-based rust preventive pigment is limited to 15 wt% or less based on the total weight (100 wt%) of the coating composition, it may exhibit excellent corrosion resistance effect.

The extender pigment fills the pores in the coating film, complements the coating film formation, and plays a role in imparting a salvage or mechanical property to the coating film. Therefore, when the extender pigment is included, a good coating appearance can be obtained and hardness, impact resistance, and rust resistance can be improved.

In the present invention, the extender pigment may be used without limitation conventionally used in the coating composition for coil coating, non-limiting examples include calcium carbonate, clay, talc, magnesium silicate, kaolin, mica, silica, aluminum silicate, aluminum Hydroxides, barium sulfate, barium sulfate and the like. The above-mentioned components may be used alone or in combination of two or more thereof. The particle size of the extender pigment is not particularly limited, and can be appropriately adjusted within the range of the general particle size applied to the coating composition. For example, an average particle diameter of 500 to 1,000 nm can be used.

The content of the extender pigment may be 2 to 6 wt% based on the total weight (100 wt%) of the coating composition. When the content of the extender pigment is less than 2% by weight, the hardness of the coating film may be lowered. If the content of the extender pigment is greater than 6% by weight, the adhesion may be lowered, and the cured coating film may cause micro cracks and adversely affect water resistance.

Colored pigments are included for the purpose of expressing the desired color in the paint. As the colored pigment, organic pigments, inorganic pigments, metallic pigments, aluminum pastes (Al-paste), pearls, etc. which are commonly used in coil coating coating may be used without limitation, and these may be used alone or in combination of two or more thereof. can do.

In the present invention, the content of the colored pigment may be 1 to 10% by weight based on the total weight (100% by weight) of the coating composition. When the content of the colored pigment is less than 1% by weight, the appearance of the color may be deteriorated due to the insignificant color, and when it exceeds 10% by weight, the dispersibility, storage stability, and the basic physical properties of the paint may be reduced.

solvent

In the coating composition according to the present invention, as the solvent, conventional organic solvents known in the art may be used without limitation.

The organic solvents include aromatic hydrocarbons, ester solvents, ether solvents, alcohol solvents, and mixtures thereof. Non-limiting examples of organic solvents that can be used include Cocosol # 100 (Kocosol # 100, K-100, SK Energy), Cocosol # 150 (Kocosol # 150, K-150, SK Energy), and cyclohexa. Paddy, xylene, toluene, cellosolve acetate, methyl ethyl ketone, dibasic ester, propylene glycol methyl ether acetate, n-butyl acetate, propylene glycol monomethyl acetate, 3-methoxy butyl acetate, ethylene glycol butyl ether, diethylene Glycol methyl ether, diethylene glycol ethyl ether, diethylene glycol butyl ether, ethanol, isopropanol, n-butanol, amyl alcohol or a mixed solvent thereof.

In the present invention, the content of the organic solvent may be a residual amount that satisfies the total weight ((100% by weight) of the coating composition, for example, 15 to 40% by weight based on the total weight (100% by weight) of the coating composition. When the content of the solvent falls within the above-described range, workability may be improved and excellent physical properties of the coating film may be exhibited.

additive

The coating composition according to the present invention may further include conventional additives used in the field of coating compositions for coil coating in a range that does not impair the effects of the invention.

Non-limiting examples of additives that can be used include dispersants, leveling agents, adhesion improving agents, curing retardants, surface conditioners, antifoaming agents, surfactants, softeners, thickeners, weathering additives, desiccants, appearance modifiers, hygroscopics, quenchers, coupling agents or Mixtures of two or more thereof. The aforementioned additives may be added to the composition in amounts known in the art, and the content thereof is not particularly limited. For example, it may be 0.1 to 10% by weight based on the total weight (100% by weight) of the paint composition.

The dispersant serves to disperse each material constituting the composition and to prevent re-agglomeration through distance maintenance, so as to express uniform physical properties of the coating film. As the dispersant, conventional ones known in the art may be used. For example, a dispersant of a high molecular weight block copolymer type may be used.

The leveling agent is for leveling the composition so that the composition is coated smoothly and smoothly, thereby improving the appearance properties of the coating film while promoting adhesion in the composition. As the leveling agent, conventional ones known in the art may be used without limitation, and for example, acrylic, silicone, polyester, and amine leveling agents may be used.

An adhesion improving agent is added in order to improve the adhesiveness with the base of a coating film. Examples of the adhesion improving agent that can be used include silane-based adhesion improving agent, polyester-based adhesion improving agent and mixtures thereof.

Antifoaming agent is a mixture of lipophilic and polysiloxane and serves to enhance the appearance of the coating film by suppressing bubbles generated during coating, and conventional antifoaming agents known in the art may be used without limitation. As an example, a polysiloxane type antifoaming agent can be used.

The matting agent is added to the coating composition to scatter light at the surface of the coating film to reduce gloss. Non-limiting examples of usable matting agents include Synthesized Silica matting agents, polypropylene matting agents, polyethylene matting agents, or mixtures thereof. As the particle size of the matting agent is adjusted, the surface area of the undercoat can be increased to improve adhesion to the top coat.

The curing retardant may be used to adjust the curing rate of the surface of the coating film to improve the smoothness of the coating film and to suppress the phenomenon of paping, for example, triethylamine, dimethylethanolamine, and the like.

The coating composition of the present invention may be prepared according to conventional methods known in the art, and for example, to specify a phosphate ester group-containing polyester polyol resin, an epoxy resin, a curing agent, an acid catalyst, a pigment, an additive, and a solvent having the above-described composition. It can be prepared by mixing in proportions.

<PCM steel plate>

This invention provides the PCM steel plate provided with the coating film formed using the coating composition mentioned above.

The PCM steel sheet includes a steel sheet and at least one coating layer formed on the surface of the steel sheet, wherein at least one of the at least one coating layer is formed from a coating composition containing the above-described phosphate ester group-containing polyester polyol resin. It includes. In one example, the one or more coating film layer includes a lower coat layer and a top coat layer formed from the coating composition of the present invention, it may include a clear layer if necessary. The top coat and the clear layer may be formed by applying, without limitation, a conventional top coat or clear coat, respectively, in the art.

The steel sheet can be used without limitation metal plate used in the interior and exterior materials in the field, for example, cold rolled steel (CR), zinc hot dipping steel (GI), electro-zinc steel (EGI), alloy-plate steel ( GA), copper sheet or tin-plate steel, hot-dip galvanized steel sheet, alloyed hot-dip galvanized steel sheet, electro-galvanized steel sheet, hot-dip aluminum-zinc alloy plated steel sheet, aluminum sheet, and the like.

The thickness of the coating layer formed on the metal plate is not particularly limited, and as an example, the dry coating layer may have a thickness of 3 to 25 μm.

PCM steel sheet according to the present invention may be prepared according to a conventional method in the art, it may be composed of a step of coating the above-described coating composition on a metal plate as a substrate (Substrate) and then drying.

Conventional coating methods known in the art may be applied as the coating method of the coating composition, for example curtain coating, roll coating, immersion coating, bar coating and spray coating may be applied. The baking conditions can be appropriately changed according to the atmosphere conditions to be baked according to the width and thickness of the baking sheet, and the line speed, for example, PMT (peak metal temperature) may be carried out for 35 to 40 seconds under the conditions of 190 to 230 ℃. .

PCM steel sheet prepared as described above is pretreated with chromate or the like before coating, or even without using a chromium-based rust preventive pigment, because it exhibits excellent corrosion resistance, processability and substrate adhesion, it can be usefully used for building interior and exterior materials. However, it is not limited only to the said use.

Hereinafter, the present invention will be described in more detail with reference to Examples. However, the following examples are only for the purpose of understanding the present invention, and the scope of the present invention is not limited to the examples in any sense.

Synthesis Example 1 Preparation of phosphate ester group-containing polyester polyol (A)

160g of neopentylglycol, 63g of BSA-20 (Ethoxylated BPA), BSA-60 (Ethoxylated from Hannong Chemical) in a four-necked flask equipped with thermometer, stirring device, filling column, H separator, condenser and heating equipment BPA) 93 g, phthalic unhydride 88 g, terephthalic acid 68 g, adipic acid 50 g, dimeric patty acid 99 g, trimellitic anhydride 24 g, Fascat 4101 (pmc organometallix) 0.03 g and condensed water under an inert gas atmosphere The reaction was carried out by raising the temperature to 250 ° C. while removing the residue. After cooling at acid value 18, 24 g of xylene was added, and azeotropic distillation was performed at 230 ° C. When the acid value became 5 or less, it was cooled and diluted with 81 g of Cocosol 100 (SK chem Co., Ltd.). A prepolymer having 40 mgKOH / g, an acid value of 3.5 mgKOH / g, and a solid content of 85% was obtained.

While maintaining the prepolymer at a temperature of 180 ° C., 14 g of phosphoric acid (H ₃ PO ₄ ) was added dropwise uniformly for 5 hours, and when the dropwise addition was completed, the temperature was raised to 200 ° C. until the acid value of the solid content was 20 mgKOH / g. Proceeded. When the reaction was completed, the mixture was diluted with 75 g of cocosol 100, 82 g of butyl cellosolve, and 65 g of butanol. And a phosphate ester group-containing polyester polyol resin having a hydroxyl value of 30 mgKOH / g and a glass transition temperature of 5 ° C.

Synthesis Example 2 Preparation of Polyester Polyol Resin (B)

Synthetic four-necked flask equipped with thermometer, stirring device, filling column, H separator, condenser and heating equipment, 157g neopentylglycol, BSA-20 (Ethoxylated BPA) 62g, BSA-60 (Ethoxylated BPA) 92 g, phthalic unhydride 97 g, terephthalic acid 83 g, adipic acid 46 g, dimeric patty acid 101 g, trimellitic unhydride 11 g, Fascat 4101 (pmc organometallix) 0.03 g and condensed water under an inert gas atmosphere The reaction was carried out by raising the temperature to 250 ° C. while removing the residue. Cooled at acid value 20, added 24 g of xylene, and subjected to azeotropic distillation at 230 ° C. When the acid value is 5 or less, it is cooled and diluted with 376 g of Cocozol 100 (SK chem). A polyester polyol resin having a molecular weight of 5,400 g / mol, a weight average molecular weight of 14,000 g / mol, an acid value of 3.8 mgKOH / g, a hydroxyl value of 30 mgKOH / g, and a glass transition temperature of 3 ° C was obtained.

Synthesis Example 3 Preparation of Polyester Polyol Resin (C)

Synthetic four-necked flask equipped with thermometer, stirring device, filling column, H separator, condenser and heating equipment, 242 g of neopentyl glycol, 121 g of phthalic anhydride, 103 g of terephthalic acid, 56 g of adipic acid, 125 g of dimeric patty acid, 14 g of trimellitic anhydride and 0.03 g of Fascat 4101 (pmc organometallix) were added thereto, and the reaction was carried out by heating up to 250 ° C. while removing condensed water under an inert gas atmosphere. Cooled at acid value 20, added 24 g of xylene, and subjected to azeotropic distillation at 230 ° C. and cooled when the acid value was 5 or less. A polyester polyol resin having a molecular weight of 4,900 g / mol, a weight average molecular weight of 13,700 g / mol, an acid value of 4.1 mgKOH / g, a hydroxyl value of 30 mgKOH / g, and a glass transition temperature of 0 ° C was obtained.

Synthesis Example 4 Preparation of Polyester Polyol Resin (D)

178g of neopentylglycol, 70g of BSA-20 (Ethoxylated BPA), BSA-60 (Ethoxylated of Hannongsung Co., Ltd.) in a four-necked flask equipped with thermometer, stirring device, filling column, H separator, condenser and heating equipment BPA) 104g, phthalic anhydride 132g, terephthalic acid 99g, adipic acid 58g, 13g of trimellitic anhydride, 0.03g of Fascat 4101 (pmc organometallix Co., Ltd.) to 250 ℃ while removing the condensed water under an inert gas atmosphere The reaction was carried out by raising the temperature. After cooling at acid value 20, 24g of xylene was added, and azeotropic distillation was performed at 230 ° C. When the acid value became 5 or less, it was cooled and diluted with 376g of Cocozol 100 (SK chem Co., Ltd.). A polyester polyol resin having a molecular weight of 5,200 g / mol, a weight average molecular weight of 14,000 g / mol, an acid value of 3.5 mgKOH / g, and a hydroxyl value of 27 mgKOH / g glass transition temperature of 8 ° C was obtained.

[ Example  One]

To the coating composition of Example 1 was prepared according to the composition of Table 1.

[ Comparative example  1-4]

To the coating composition of Comparative Example 1-4 was prepared according to the composition of Table 1 below.

[ Experimental Example . Property evaluation]

After coating the coating composition prepared in Example 1 and Comparative Examples 1-4 to a thickness of 5 ㎛ on GI (Galvanized Iron) material, the specimen was prepared by painting PCM RMP building material top coat (KCC) at 20 ㎛ It was. Then, the physical properties of each specimen were measured by the following method, and the results are shown in Table 2. Each physical property was evaluated in the order of 5 (good), 4, 3, 2, 1, 0 (poor).

(1) Corrosion resistance (SST: Salt spray test)

The specimen is placed in a salt spray test (SST) instrument and sprayed with a 5% NaCl aqueous solution at a temperature of 35 ° C. for a period of time, and then the left and right edges of the specimen, the center cutting (cutting marks), below The depth (mm) of the corrosion site of the edge part was measured and evaluated (see FIG. 1).

(2) Anti-alkali resistance

Specimens were immersed in a 5% NaOH aqueous solution for 24 hours to evaluate the presence of blisters.

(3) T bending

The specimens were bent to evaluate the crack level of the coating film and the peeling-off of the coating film after taping.

As shown in Table 2, the coating composition of Example 1 to which the phosphate ester group-containing polyester polyol resin is applied shows excellent properties in terms of corrosion resistance and alkali resistance compared to the coating compositions of Comparative Examples 1 to 3 not containing the same. gave. In particular, it was confirmed that Example 1 exhibits the same corrosion resistance and alkali resistance as Comparative Example 4 to which a conventional chromium (Cr) -based rust preventive pigment is applied.

From the above results, it was found that the phosphate ester group-containing polyester polyol resin of the present invention increased the adhesion to the base and increased the corrosion resistance. Accordingly, the paint of the present invention in which a phosphate ester group-containing polyester polyol resin and an environmentally friendly non-chromium-based rust preventive pigment is suitably blended is useful as a chromium-free paint having excellent corrosion resistance and alkali resistance. Can be applied.

Claims (9)

A phosphate ester group-containing polyester polyol, a curing agent, an acid catalyst, a non-chromic antirust pigment, and a solvent,
The phosphate ester group-containing polyester polyol comprises a reaction product of a polyester polyol prepolymer and a phosphorus (P) containing acid,
The polyester polyol prepolymer is a polycondensate of a mixture comprising at least one acid monomer containing a carboxylic acid functional group and at least one polyfunctional alcohol monomer,
The acid monomer is a coating composition based on 100 equivalent% of all acid monomers, a mixture comprising 30 to 80 equivalent% of at least one aromatic carboxylic acid, 5 to 40 equivalent% of aliphatic carboxylic acid and 5 to 30 equivalent% of fatty acid and dimer acid. According to claim 1, wherein the phosphate ester group-containing polyester polyol has a number average molecular weight (Mn) of 2,000 to 10,000 g / mol, a solid-based hydroxyl value (OH value) of 10 to 60 mgKOH / g, glass transition temperature Coating composition whose (Tg) is -30-30 degreeC. The coating composition according to claim 1, wherein the polyester polyol prepolymer has a number average molecular weight (Mn) of 1,000 to 6,000 g / mol and a solid content hydroxyl value (OH value) of 30 to 80 mgKOH / g. delete delete According to claim 1, wherein the polyfunctional alcohol monomer is based on 100 equivalent% of the total alcohol monomer,
50 to 90 equivalent% of a bifunctional or higher aliphatic alcohol and
10-50 equivalent% of at least one ethoxylated bisphenol A alcohol
Coating composition which is a mixture consisting of. The coating composition according to claim 1, wherein an equivalent ratio (alcohol / carboxylic acid) of the acid monomer and the polyfunctional alcohol monomer is 1.05 to 1.20. The coating composition according to claim 1, wherein the amount of the phosphorus (P) -containing acid is 1 to 3% by weight based on the total weight of the solids of the polyester polyol prepolymer. According to claim 1, 30 to 60% by weight of the phosphate ester group-containing polyester polyol, 3 to 10% by weight of the curing agent, 0.1 to 3% by weight of the acid catalyst, 5 to 15% by weight of the non-chromic rust-preventive pigments And a residual amount of solvent satisfying 100% by weight of the total composition.

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