KR100692932B1 - Color steel sheet for self-cleaning appliances and its manufacturing method - Google Patents

Abstract

The present invention is steel plate (1); Zinc or zinc alloy plating layer (2); Chromate or non-chromate pretreatment layer 3; High polymer polyester undercoat film layer 4; High molecular oil free polyester resin A with a number average molecular weight of 17,000-20,000, glass transition temperature (Tg) of 30 ° C-50 ° C, and OH value of 10-20, number average molecular weight of 22,000-28,000, glass transition temperature (Tg ) 3 ℃ ~ 8 ℃, OH value is 3 ~ 8 high polymer oil free polyester resin B, number average molecular weight is 15,000 ~ 19,000, glass transition temperature (Tg) is 8 ℃ ~ 15 ℃, and OH value is 8 ~ Self-cleaning top coat comprising melamine or polyisocyanate, a curing accelerator, a surface modifier, a storage stabilizer and a self-cleaning accelerator as a main resin and a crosslinking agent mixed with at least two resins from the group consisting of 15 high-polymer oil-free polyester resin C It relates to a self-cleaning color steel sheet for home appliances, in particular an air conditioner, comprising a coating layer (5).

The color steel sheet of the present invention is intended to be used as an exterior material of home appliances, especially air conditioners, and has excellent self-cleaning force and shows the same effect as before in the basic properties of steel sheet, such as workability, corrosion resistance and weather resistance, and at the same time, a different gloss (60 °). Criteria) showed rapid self-cleaning function without deterioration.

Self-cleaning, color steel, self-cleaning accelerator

Description

Self-cleaning Color Coated Steel Plate for Use in Home Appliance And Manufacturing Method Thereof}

1 is an enlarged cross-sectional view schematically showing the configuration of a color steel sheet of the present invention.

The present invention relates to a color steel sheet for home appliances, and has excellent self-cleaning properties suitable for home appliances, in particular, outdoor air conditioners (hereinafter, referred to as "air conditioners"), while having excellent basic properties such as workability, corrosion resistance, and weather resistance, and having a different gloss. The present invention relates to a color steel sheet formed with a functional coating film capable of rapidly expressing self-cleaning function without deterioration.

The exterior of the building, which is always exposed to the outside environment, is easily polluted due to contamination factors such as dust, dust, rain or snow, so regular management is required to maintain cleanliness, thereby increasing the management cost. In order to reduce the situation, continuous research in related industries is being conducted.

It is currently applied to paint the surface of the building with the self-cleaning paint, or apply the roofing material and the sandwich panel manufactured by using the color steel sheet for building materials with the self-cleaning (Patent No. 317084) to the outside of the building. Some are being solved.

Contrary to the construction materials exposed to the outside, home appliances color steel plates, which are mostly used indoors, are fundamentally blocked from pollutants and lack the relevant research because they do not feel the necessity of product cleanliness management. In the case of the air conditioner, which is exposed to the polluted environment, the exterior becomes easily soiled, the R & D is continuously conducted to combine the self-cleaning, which is applied to the building materials, with the color steel sheet for the air conditioner as a way to improve the pollution in related industries. Has come.

However, in the case of self-cleaning color steel sheets for air conditioners, in addition to the high processability, corrosion resistance, and weather resistance, which are the basic properties of color steel sheets for home appliances and building materials, self-cleaning properties applied to building materials have to be provided, but it was difficult to show these properties together. .

Resin for PCM (Pre-Coated Metal) paint (Regular Polyester), which is generally used for building materials, has functional groups such as hydroxyl group and carboxyl group in the backbone of the resin. It has a lot of branches) and it is easy to crosslink with melamine (for example, Hexa-Methoxymethyl melamine) resin used as a crosslinking resin (hardener) of the coating film and a hydrophilic material that has a network structure and gives self-cleaning property when crosslinking. As a result, the fouling resistance and self-cleaning property of the coating film were good, but the elongation of the coating film was extremely limited after the film formation.

In the case of home paints, polyester resins for flexible polyester paints have a linear structure of resin and linear polymers with low OH values. In addition to being weak in self-cleaning due to its low degree, the linear polymer having a high molecular weight has a strong hydrophobic effect, which is inherently vulnerable to corrosion and fouling resistance.

In order to improve such a disadvantage, the present inventors have a steel plate (1) for self-cleaning home appliances; Zinc or zinc alloy plating layer (2); Chromate or non-chromate pretreatment layer 3; High polymer polyester undercoat film layer 4; High molecular oil free polyester resin A with a number average molecular weight of 17,000-20,000, glass transition temperature (Tg) of 30 ° C-50 ° C, and OH value of 10-20, number average molecular weight of 22,000-28,000, glass transition temperature (Tg ) 3 ℃ ~ 8 ℃, OH value is 3 ~ 8 high polymer oil free polyester resin B, number average molecular weight is 15,000 ~ 19,000, glass transition temperature (Tg) is 8 ℃ ~ 15 ℃, and OH value is 8 ~ A self-cleaning top coat comprising melamine or polyisocyanate, a curing accelerator, a surface modifier, a storage stabilizer and a storage stabilizer as a main resin and a crosslinking agent mixed with at least two resins from the group consisting of 15 high polymer oil-free polyester resins C. There has been previously filed a self-cleaning color steel sheet for household appliances, in particular an air conditioner comprising a layer 5 (Patent Application No. 10-2005-0007920). However, in this case, it was found that the surface modifier used to impart hydrophilicity did not sufficiently express self-cleaning in a short time.

Accordingly, the present invention is to solve the above problems, the object of the present invention is not only excellent in the basic physical properties such as self-cleaning, processability, corrosion resistance and weather resistance, but also the rapid self-cleaning function can be rapidly expressed without any deterioration of gloss. It is intended to manufacture color steel sheets for air conditioners, especially air conditioners.

The object of the present invention described above

Steel plate shape (1); Zinc or zinc alloy plating layer (2); Chromate or non-chromate pretreatment layer 3; High polymer polyester undercoat film layer 4; High molecular oil free polyester resin A with a number average molecular weight of 17,000-20,000, glass transition temperature (Tg) of 30 ° C-50 ° C, and OH value of 10-20, number average molecular weight of 22,000-28,000, glass transition temperature (Tg ) Is 3 ~ 8 ℃, OH value is 3 ~ 8 high polymer oil-free polyester resin B, number average molecular weight is 15,000 ~ 19,000, glass transition temperature (Tg) is 8 ℃ ~ 15 ℃, and OH value is 8 ~ A self-cleaning top coat comprising melamine or polyisocyanate, a curing accelerator, a surface modifier, a storage stabilizer and a self-cleaning accelerator as a main resin and a crosslinking agent mixed with at least two resins from the group consisting of 15 high polymer oil-free polyester resins C. It is achieved by a self-cleaning colored steel sheet, particularly for home appliances, comprising a coating layer (5).

At this time, the coating material for forming the undercoat layer 4 has a high average molecular weight of 15,000-20,000, a glass transition temperature (Tg) of 10 to 20 ° C, and an OH value of 5 to 13 Melamine or polyisocyanate resin, antirust pigment, additive as a mixed resin and crosslinking agent of a high polymer oil-free polyester resin E having an average molecular weight of 20,000-26,000, a glass transition temperature (Tg) of 3 to 10 ° C., and an OH value of 3 to 8 , Curing accelerators and solvents.

When the crosslinking agent is a melamine, a paratoluene sulfonic acid type, dinonyl naphthalene sulfonic acid type, dinonyl naphthalene disulfonic acid type, dodecylbenzene sulfonic acid, and the like are used as the crosslinking agent when the crosslinking agent is polyisocyanate. Amine, metal salt, naphthenic acid and the like are used.

The surface modifier applied to the above-mentioned degree of coating uses polyalkyl silicate, the molecular weight is 4,000 to 10,000, and the degree of polymerization is preferably 5 to 80.

The storage stabilizer applied to the above-mentioned top coat is preferably an alkoxy compound having a mass average molecular weight of 100 to 1000.

In addition to the above self-cleaning agent, an organic or inorganic pigment may be added.

It is preferable that the said color steel sheets are 3 ~ 13 microns (micrometer) of undercoat films, respectively, and 10-25 microns of a self-cleaning top coat film layer, respectively.

In addition, if a metallic and / or pearl-based color is applied to the top coat layer 5 according to demand, a clear coat layer 6 may be added as a final finish coating.

At this time, the self-cleaning applied to the top coat is applied to the uppermost clear coating layer.

As the plated base steel sheet (1) used in the present invention, most of the known ones such as zinc-aluminum-silica alloy plated steel sheets and plated steel sheets subjected to electrolytic and hot dip galvanizing can be applied. Etc. can also be used.

The pretreatment layer 3 is for improving the corrosion resistance of the steel sheet, adhesion of primer (undercoat) paint, etc., and an eco-friendly non-chromate layer is preferable, but the corrosion resistance is slightly lower than that of the existing chromate coating. Chromate or chromium trivalent pretreatments are commonly used.

Hereinafter, the self-cleaning topcoat, which is a feature of the present invention, will be described in detail.

The binder constituting the paint for self-cleaning air conditioner may be a high polymer oil-free polyester resin or a modified high polymer oil-free polyester resin as a basic resin in the composition of the paint, and a high polymer oil-free polyester resin in terms of physical properties such as processability. Is recommended. The high polymer oil-free polyester resin has a number average molecular weight of 17,000 to 20,000, a glass transition temperature (Tg) of 30 ° C to 50 ° C, and an OH value of 10 for stable bonding with a raw material having self-cleaning properties and to provide excellent basic properties. High polymer oil free polyester resin A of -20, number average molecular weight of 22,000-28,000, glass transition temperature (Tg) of 3 ° C. to 8 ° C., and OH value of 3 to 8 high polymer oil free polyester resin B and number A resin having a mean molecular weight of 15,000 to 19,000, a glass transition temperature (Tg) of 8 ° C. to 15 ° C., and an OH value of 8 to 15 high polymer oil-free polyester resin C mixed with at least two or more resins. use. The glass transition temperature (Tg) was measured by differential thermal analysis (DTA) and the number average molecular weight was measured by gel permeation chromatography (GPC).

In the self-cleaning air conditioner color steel sheet, it is necessary to have the processability as a basic property and to be self-cleaning. Therefore, the linear polymer should be used for the paint. Because of their weak self-cleaning. Therefore, in the present invention, by using the three kinds of high-polymer oil-free polyester resins as shown in Table 1 below to the top coating, the bond with the self-cleaning raw material was designed to enable a high processability.

High Polymer Oil Free Polyester Type Molecular Weight Tg OH value A 17,000-20,000 30-50 10-20 B 22,000-28,000 3-8 3-8 C 15,000-19,000 8-15 8-15

In the present invention, it is preferable to use the high polymer oil-free polyester resin in 10 to 30% by weight of the total coating composition, if the content is less than 10% by weight greatly reduces the flexibility and processability of the coating film, 30% by weight If exceeded, the fouling resistance and hardness of a coating film fall rapidly.

In the present invention, a melamine type or a polyisocyanate type may be used as the crosslinking resin, and the melamine crosslinking resin has a high alkylated group type, a high imino group type, and a partially alkylated layer. Partially Alkylated type and the like can be used, and polyisocyanate crosslinking agents that can be used include hexamethylene diisocyanate (HMDI), isophorone diisocyanate (IPDI: Isophorone Diisocyanate) and xylene diisocyanate (XDI). , 2, 4, 6-triisocyanatetoluene and similar properties can be applied. For the purpose of PCM, products using masking isocyanate groups and dissociating by heat are mainly used.

In the present invention, the melamine or polyisocyanate crosslinking agent is preferably used in an amount of 2 to 10% by weight based on the total coating composition. If the crosslinking agent content is less than 2% by weight, the solvent resistance and hardness of the coating film are drastically reduced, and the content is 10 Exceeding the weight% lowers the flexibility and impact resistance of the coating film. In the present invention, it is preferable to use a hexamethoxymethylmelamine type and a partially alkylated type crosslinking agent among the highly alkylated type, and when the urethane crosslinking agent is used, the physical properties are good. Because of this high price, it is not competitive.

As a curing accelerator used to promote the crosslinking of the main resin high polymer oil-free polyester resin and the crosslinking resin melamine to increase the density of the coating film, paratoluene sulfonic acid type, dinonyl naphthalene sulfonic acid type, dinonyl naphthalene disulfone Acid-based, dodecylbenzenesulfonic acid, and the like, and the content is preferably used in the range of 0.2 ~ 1.5%. If the curing accelerator is less than 0.2%, curing of the coating film is insufficient depending on the working conditions. If the curing accelerator exceeds 1.5%, the coating film hardens too rapidly, resulting in popping or deterioration of workability during coating. It causes coating film shrinkage.

In addition, amine (Amine) -based, metal salt-based, naphthenic acid-based, etc. are used as a curing accelerator used to increase the density of the coating film by promoting crosslinking between a saturated high-polymer polyester resin and a polyisocyanate which is a crosslinking resin. It is preferable to use 0.02-1.00% of silver.

As the amine catalyst, triethyl amine, N, N-diethylcyclohexylamine, 2,6-diethylmorphorine, triethyl diamine, dimethylamino ethyl adipate Dimethylamino ethyladipate), diethylethanolamine, N, N-dimethyl benzyl amine, etc., and metal salt catalysts include potassium oleate and tetra-2-ethyl. -Hexyl titanate (Tetra-2-ethyl-hexyl titanate), tin chloride (SnCl ₄ ), iron chloride (FeCl ₃ ), dibutyl tin dilaurate (DBTDL), etc. Examples include zinc-naphthenate, lead-naphthenate, cobalt-naphthenate, calcium-naphthenate, and the like.

If the amount is less than 0.02%, curing of the coating film is insufficient depending on the working conditions, and if it exceeds 1.00%, curing of the coating film occurs too rapidly, resulting in popping or shrinkage in the coating film during painting. .

In the present invention, polyalkyl silicate is used as a surface modifier of the coating film, which imparts a hydrophilic group to the surface of the coating film, thereby lowering the water contact angle, and when contaminants are adsorbed on the surface of the coating film, rainwater spreads widely on the surface of the coating film. It will float in the water and have a self cleaning effect that can be washed away with water. The polyalkyl silicate used as the surface modifier of the present invention is not only excellent in chemical resistance and storage stability, but is also converted into a hydrophilic material having a hydroxyl group (OH) which lowers the water contact angle by moisture or rainwater in the air after coating. The ability is also excellent. The molecular weight of the silicate is used in the 4,000 ~ 10,000, and when the 4,000 or less, the mixed with the resin is high, the surface injury effect and workability of the methoxysilyl group is lowered. Is lowered.

The polyalkyl silicate preferably has a degree of polymerization of 5 to 80 as a substance in which an alkyl group is substituted in the main chain and the side chain. If the degree of polymerization is less than 5, the surface modification effect is greatly reduced, and if the degree of polymerization exceeds 80, the storage stability of the paint And poor workability. As the alkyl group introduced into the main chain and the side chain of the polyalkyl silicate, a methyl group or an ethyl group may be substituted. Examples of commercially available polyalkyl silicates that can be used in the present invention include methyl silicate 51 (Colcote), ethyl silicate 40 (Huls), methyl silicate 51, methyl silicate 56, methyl silicate 56S, methyl silicate 57 (Mitsubishi Chemical Corporation). ), And it is preferable to use a methyl silicate system in the present invention.

In the present invention, the surface modifier is contained 2 to 10% by weight, preferably 4 to 7% by weight of the total coating composition. When the content of the polyalkyl silicate is less than 2% by weight, the self-cleaning effect of the coating film is remarkably lowered. When the content of the polyalkyl silicate is more than 10% by weight, the raw material cost of the paint increases and the stability of the paint decreases, which is not preferable.

The reaction rate between methoxy silyl groups (SiOMe) is stable when relatively no moisture, but there is a characteristic that a rapid reaction occurs in the presence of moisture or in the presence of a hydroxyl group (-OH) of the resin. Therefore, the hydroxyl group of the resin in the paint should be shielded or the moisture content should be minimized. In the present invention, it is necessary to shield the hydroxyl group (-OH) contained in the hydroxyl group (-OH) and other composition components of the main resin, and for this purpose, an alkoxy compound is used as the storage stabilizer. When the alkoxy compound contains a mass average molecular weight of 100 to 1000, when the mass average molecular weight is less than 100, the storage stability is deteriorated. When the alkoxy compound exceeds 1000, an excess is added to cure the coating film. Inferior defects will occur. Examples of alkoxy compounds that can be used in the present invention include KBM 13, manufactured by Shin Nitsu, Japan, trimethyl ortho formate, Hutris, USA, triethyl ortho formate, trimethyl ortho acetate, and additives from BAYER, Germany. ADDITIVE TI.

In the present invention, the storage stabilizer is contained in 1 to 5% by weight of the total coating composition, when the content is less than 1% by weight, the storage stability effect is insignificant, and when used in excess of 5% by weight, a dense coating film causes a price increase and hardening inhibition There is a disadvantage that can not form.

In the present invention, as a self-cleaning promoter for imparting hydrophilicity, the fumed silica is contained in the total coating composition in an amount of 0.1 to 0.5% by weight. When the content is less than 0.1% by weight, the self-cleaning expression is insignificant. It is not preferable because the thixotrophy rises sharply, resulting in poor painting workability and antifoaming, and film smoothness. Examples of fumed silica that can be used in the present invention include Aerosil # 200, 300, 380 series of Degussa, Germany, and HDK-N20 manufactured by Walker, Germany.

It is preferable that the top coat of this invention has the following composition ratios.

(Content based on 100% (wt) of resin solids)

division ingredient Content (weight ratio)% Main resin 2 or more types of mixed resins from the group of high polymer oil-free polyester resins A, B and C 10-30 Crosslinking agent Melamine or polyisocyanate 2-10 Curing accelerator Paratoluene sulfonic acid series etc. (crosslinking agent-melamine) 0.2-1.5 Amine series, etc. (crosslinking agent-polyisoisonate) 0.02-1.00 Surface modifier Polyalkylsilicates 2-10 Storage stabilizer Alkoxy compounds 1-5 Self-cleaning accelerator Fumed silica 0.1-0.5

On the other hand, the self-cleaning paint can be used without limitation organic or inorganic pigments. As the pigment, it is preferable to use a pigment capable of imparting heat resistance and chemical resistance suitable for the paint for PCM. In addition, the basic particles of the pigment should also be considered sufficiently, such pigments include cyanine blue, titanium oxide white, iron oxide red, carbon black, chrome yellow and the like. In addition, sieving pigment, minusil, talc, cray, silica compounds and the like can be used.

In addition, if a metallic and / or pearl-based color is applied to the top coat layer 5 according to demand, a clear coat layer 6 may be added as a final finish coating.

The composition of the clear paint is composed of constituent components other than the pigment as the base paint, and at this time, the self-cleaning imparted to the top coat is applied to the uppermost clear coat layer.

Hereinafter will be described with respect to the road.

In addition to the corrosion resistance, which is the basic property of the self-cleaning air conditioner, the undercoat, in addition to the interlayer adhesion to the base and the top coat, enhances low temperature workability to provide sufficient buffering action at the interface between the base and the top coating layer during the winter forming work. By doing so, the crack of the material generated during processing is designed to be absorbed in the lower layer without developing to the upper layer.

Important factors for imparting such physical properties include high-polymer oil-free polyester resins, which are main resins and auxiliary resins, and melamine or polyisocyanate, cross-linking resins, curing accelerators, additives, rust preventive pigments, and solvents.

The resin of the undercoat has a high average molecular weight of 15,000-20,000, a glass transition temperature (Tg) of 10-20 ° C., an OH value of 5-13, and a high polymer oil-free polyester resin D having a number average molecular weight of 20,000-26,000. Transition temperature (Tg) 3-10 degreeC and the OH value use the mixed resin of the high polymer oil-free polyester resin E which is 3-8.

The crosslinking resin and the curing accelerator are used by adjusting the same raw material as the topcoat to the characteristics of the undercoat.

As a solvent to be used, a high boiling point hydrocarbon-based and ester-based and a ketone-based for viscosity control are selected and used in consideration of the popping property and painting workability.

 The pigments used in the undercoat use conventional chromium and lead-based rust preventive pigments for corrosion resistance. However, in response to the trend of the global environmental regulations, non-toxic rust preventive pigments without lead or chromium may be used according to demand. have.

Existing rust preventive pigments include Red Leed, Zinc Potassium Chromate, Zinc Tetraoxy Chromate, and Strontium Chromate containing lead and chromium. Representative Borate-based barium metaborate, Molybdate-based zinc molybdate (Zinc Molybdate), calcium zinc molybdate (Calcium Zinc Molybdate), Phosphate-based zinc phosphate (Zinc Phosphate), aluminum triphosphate ( Aluminum Triphosphate and silicate include Calcium Borosilicate, Phosphosilicate, Calcium Ion-exchanged Silicate, Magnesium Ion-exchanged Silicate, etc. . The use of chromium and lead-based rust preventive pigments is usually 4-10% in the case of general home appliances or building materials, but in the case of air conditioners, it is preferable to use 15-20% in order to give high corrosion resistance.

If the amount of use is less than 15%, the rust resistance is drastically lowered, and if the amount is more than 20%, the oil absorption of the resin is increased, which is disadvantageous in workability deterioration, painting workability and cost increase.

Non-toxic anti-rust pigment is preferably 7-12%. If the amount is less than 7%, the rust resistance is drastically lowered. If the amount is more than 12%, the oil absorption of the resin is increased, which is not only disadvantageous in processability, painting workability and price competitiveness, but also no difference in rust resistance.

It is preferable that the undercoat of this invention has the following composition ratios.

(Content based on 100% (wt) of resin solids)

division ingredient Content (weight ratio)%  Suzy Hamipolymer Oil Free Polyester Resin D 10-20 Hamipolymer Oil Free Polyester Resin E 5-10 Melamine resin or polyisocyanate resin 3-8  Antirust Pigment (Optional) Chrome 15-20 Non chrome system 7-12 additive Deforming Agent 0.1-1.0 Dispersant 0.3-0.5  Curing accelerator Paratoluene sulfonic acid series etc. (crosslinking agent-melamine) 0.2-1.5 Amine series, etc. (crosslinking agent-polyisoisonate) 0.02-1.00   solvent Hydrocarbon system 20-30 Ester 3-10 Ether system 10-20 Acetate 1-10 Ketone 5-15

In addition, an object of the present invention, the zinc or zinc alloy plating layer (2), the electroplating or hot-dip galvanizing treatment on the base steel sheet 1, chromate or non-chromium at a line speed of 50 ~ 120 mpm The acid salt was applied to the surface with a thin film on a roll coating method and dried at a temperature of 60 to 140 ° C. to pretreat the chromate layer of 20 to 80 mg / m ² or the non-chromate layer of 30 to 150 mg / m ² . Forming a layer (3); Coating a high polymer polyester undercoat on the pretreatment layer (3), and heating and drying at PMT 190 to 240 ° C. to form a undercoat layer (4); And a number average molecular weight of 17,000 to 20,000, a glass transition temperature (Tg) of 30 ° C. to 50 ° C., and an OH value of 10 to 20 high polymer oil-free polyester resin A, a number average molecular weight of 22,000 to 28,000, and a glass transition temperature ( Tg) is 3 ~ 8 ℃, OH value is 3-8, high polymer oil-free polyester resin B, number average molecular weight is 15,000 ~ 19,000, glass transition temperature (Tg) is 8 ℃ ~ 15 ℃, and OH value is 8 A self-cleaning agent comprising melamine or polyisocyanate, a curing accelerator, a surface modifier, a storage stabilizer and a self-cleaning accelerator as a main resin and a crosslinking agent mixed with at least two resins from the group consisting of the high polymer oil-free polyester resin C of ˜15. It is achieved by providing a self-cleaning color steel sheet for household appliances, in particular an air conditioner, comprising coating a top coat and heating and drying it to PMT 190-240 ° C. to form a top coat layer 5.

In addition, when a metallic and / or pearl-based color is applied to the top coat layer 5, a step of forming a clear coat layer 6 as a final finish coating may be added.

The dry film thickness (DFT) of each layer constituting the above-described cross-sectional film is 3 to 13 microns (µm) in the bottom coat layer, 10 to 25 microns in the self-cleaning top coat layer, and 8 to 15 microns in the clear coat layer. desirable.

When the thickness of the top coat is less than 10 μm, the self-cleaning property is inferior, and at 25 μm or more, it is disadvantageous in terms of economy.

The coating method of the present invention includes a conventional floor coating method in addition to the roll coating method.

The present invention will be described in detail with reference to Examples and Comparative Examples, but the present invention is not limited to Examples.

Specimen specifications, coating conditions, and relative comparative paints used in the examples are as follows.

<Test conditions>

A) Specimen size and painting condition

-Test material: Thickness 0.8mm GI (hot dip galvanized steel sheet)

-Dry film thickness: 4 ~ 6 ㎛ undercoat, 15 ~ 17 ㎛ with top coat

-Surface gloss: 80% or more

B) Drying condition:

-PMT: Top coat 232 ℃, Bottom coat 224 ℃

-Drying time (RT): 45sec

< Example  1 and Example  2>

The undercoat layer was coated with 10 microns and then coated with a self-cleaning material prepared at the compounding ratio of Table 4 below with reference to Table 1 constituting the top coat main resin thereon.

division Example 1 (parts by weight) Example 2 (parts by weight) Main resin (high polymer oil free polyester resin) A 5.5 5.5 B 9.5 9.5 C 3.5 3.5 Melamine 4.5 4.5 Pigment (TiO ₂ ) 23 23 Paratoluenesulfonic acid 0.5 0.5 Polyalkylsilicates 5 5 Alkoxy compounds 1.5 1.5 Fumed silica 0.3 0.6 Other additives One One Solvents 46 46

The final blended viscosity is appropriately adjusted as a solvent based on 110 seconds (FORD CUP # 4, 25 ° C).

< Comparative Example 1 , Comparative Example 2 and Comparative Example 3 >

Comparative Example 1 Color steel sheet for conventional air conditioner (for LG electron supply) of Allied Steel Co., Ltd. Comparative Example 2 Color steel sheet for self-cleaning air conditioner of Yonhap Steel Co., Ltd. (Patent Application No. 10-2005-0007920) Comparative Example 3 Self-cleaning colored steel sheet for building materials of Yonhap Steel Co., Ltd. (Patent No. 317084)

Experimental Example

The physical properties of Examples 1, 2, Comparative Example 1, Comparative Example 2 and Comparative Example 3 were compared to Table 6 below.

division Example 1 Example 2 Comparative Example 1 Comparative Example 2 Comparative Example 3 1. Pencil hardness HB HB HB HB HB 2.C.E.T 100/100 100/100 100/100 100/100 100/100 3. Shock test Good Good Good Good Good 4.Gloss (60 degrees) 84 82 83 85 56 5.Water resistance Good Good Good Good Good 6.20 ℃ Machinability 0T 0T 0T 0T 4T 7. Cold resistance (0 ℃) 3T 3T 3T 3T 8T 8 solvent resistance 100 times ↑ 100 times ↑ 100 times ↑ 100 times ↑ 100 times ↑ 9.corrosion resistance Good Good Good Good Good 10. Water contact angle 40-45 40-45 70-75 60-65 45-50 11.Carbon contamination (△ E) 0.65 0.61 17.05 0.68 0.54

-Pencil hardness of 1: Using the "Uni Pencil" manufactured by Mitsubishi Corporation, Japan.

-C.E.T of 2: Cross cut after 6mm extrusion to make 100 scale at 1mm interval

-Impact test of 3: 1 / 2f x 0.5kg x 50cm

-Gloss of 4: Initial value of 60 degree gloss measurement result with Gloss Meter

-Boiling water resistance of 5: Evaluation of coating state after immersion in boiling water (more than 98 ℃) for 1 hour

-Processability at 20 ℃ of 6: Evaluation of cracking on the processed part after machining with vise at 20 ℃ (1T per sheet thickness)

-Cold-resistance of 7: Remove the specimen by keeping it at -10 ℃ for 1 hour, and leave it at room temperature for 1 hour, then process it with vise

-Solvent resistance of 8: MEK Rubbing

-Corrosion resistance of 9: Salt Spray Test 35 ℃, 5% NaCl, 24 hours

Water contact angle of 10: Drop 1 drop of water onto the dried coating with a dropper, and after 30 minutes, measure the contact angle between the coating and the water using the FTA2000 (First Ten Angstroms, USA).

-Carbon pollution of 11: Soak in 10% weight carbon black aqueous solution (60 ℃) for 24 hours and wash it with flowing gauze or sponge to measure color difference

As shown in Table 6, as a result of using fumed silica as a self-cleaning accelerator in the range of 0.1 to 0.5% by weight based on the total coating composition, in Examples 1 and 2, the hardness and gloss of the basic physical properties of the steel sheet were not significantly reduced. In comparison with the products of the comparative example, the processability, corrosion resistance, solvent resistance, etc. showed the same or superior effect, and the water contact angle was 30 minutes earlier than the existing 1-3 hours, and the result of the measurement was also superior. there was. Good water contact angle at such a fast time means that the self-cleaning effect can be sufficiently expressed even with low precipitation.

Carbon contamination, which is a measure of the degree of contamination resistance, also showed a good effect.

The color steel sheet of the present invention is intended to be used as an exterior material of an air conditioner, especially for home appliances, and has excellent self-cleaning power and has the same or more effects as before, in the basic properties of steel sheet, such as workability, corrosion resistance, and weather resistance, and particularly, a loss of gloss. The effect of rapidly expressing self-cleaning in a short time was remarkably improved.

Claims (6)

Steel plate shape (1); Zinc or zinc alloy plating layer (2); Chromate or non-chromate pretreatment layer 3; A high polymer oil-free polyester resin D having a number average molecular weight of 15,000-20,000, a glass transition temperature (Tg) of 10 to 20 ° C., and an OH value of 5 to 13, and a number average molecular weight of 20,000-26,000, and a glass transition temperature (Tg). ) High polymer polyester containing melamine or polyisocyanate, rust preventive pigment, additive, curing accelerator and solvent as main resin and crosslinking agent mixed with high polymer oil-free polyester resin E with 3 ~ 10 ℃ and OH value of 3 ~ 8 A coat layer 4; High molecular oil free polyester resin A with a number average molecular weight of 17,000-20,000, glass transition temperature (Tg) of 30 ° C-50 ° C, and OH value of 10-20, number average molecular weight of 22,000-28,000, glass transition temperature (Tg ) 3 ℃ ~ 8 ℃, OH value is 3 ~ 8 high polymer oil free polyester resin B, number average molecular weight is 15,000 ~ 19,000, glass transition temperature (Tg) is 8 ℃ ~ 15 ℃, and OH value is 8 ~ 0.1 to 0.5% by weight of melamine or polyisocyanate, curing accelerator, surface modifier, storage stabilizer and total coating composition as main resin, crosslinking agent mixed with at least two resins from the group consisting of 15 high polymer oil-free polyester resin C Self-cleaning color steel sheet comprising a self-cleaning top coat layer (5) containing a self-cleaning accelerator made of fumed silica satisfying the range. The self-cleaning color steel sheet according to claim 1, further comprising a clear coating layer (6) on the top coat layer. delete Surface plating of chromate or non-chromate by roll coating method on zinc or zinc alloy plated layer (2), electroplated or hot-dipped galvanized on the steel sheet (1) at a line speed of 50-120 mpm In a thin film and dried at a temperature of 60-140 ° C. to form the pretreatment layer 3 with a chromate layer of 20-80 mg / m ² or a non-chromate layer of 30-150 mg / m ² . step; Coating a high polymer polyester undercoat on the pretreatment layer (3), and heating and drying at PMT 190 to 240 ° C. to form a undercoat layer (4); And a number average molecular weight of 17,000 to 20,000, a glass transition temperature (Tg) of 30 ° C. to 50 ° C., and an OH value of 10 to 20 high polymer oil-free polyester resin A, a number average molecular weight of 22,000 to 28,000, and a glass transition temperature ( Tg) is 3 ~ 8 ℃, OH value is 3-8, high polymer oil-free polyester resin B, number average molecular weight is 15,000 ~ 19,000, glass transition temperature (Tg) is 8 ℃ ~ 15 ℃, and OH value is 8 0.1 to 0.5% by weight of melamine or polyisocyanate, curing accelerator, surface modifier, storage stabilizer and total coating composition as main resin, crosslinking agent mixed with at least two resins from the group consisting of high polymer oil-free polyester resin C of -15 Self-cleaning comprising coating a self-cleaning topcoat comprising a self-cleaning promoter consisting of fumed silica that satisfies the% range and heating and drying to 190-240 ° C. to form a top coat layer 5. Manufacturing Method of Color Steel Sheet The method of manufacturing a self-cleaning color steel sheet according to claim 4, further comprising the step of forming a clear coating layer (6) on the top coat layer. delete

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