KR101521357B1 - Composition for manufacturing primer free layer of color steel sheet - Google Patents

Abstract

The present invention relates to a composition for manufacturing a primer free layer of a color steel sheet. When manufacturing a primer free layer of a color steel sheet using a composition according to the present invention, it is environment friendly since a pretreatment process using chromium is omitted. Additionally, coating thickness of a primer free layer manufactured by the composition of the present invention is less than 1 micrometer, therefore production costs of steel manufactures may be reduced, and power consumption may be reduced since PMT temperature of the primer layer is 80°C or lower.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a composition for producing a primer-free layer of a colored steel sheet,

The present invention relates to a composition for producing a primer-free layer of a colored steel sheet.

Colored steel sheets are widely used for household appliances and construction materials because of their excellent strength and easy processing. However, the steel sheet has a weak point that it is easily corroded. In order to compensate it, the surface of the steel sheet is coated with zinc or aluminum and treated with chromate to improve the corrosion resistance. In this way, the corrosion resistance of the steel sheet is improved by coating the steel plate subjected to the plating and the chromate treatment, and the decorative effect is increased by using various colors of the paint.

Conventional surface-treated steel sheets containing hexavalent chromium, called chromate films, are characterized by their excellent corrosion resistance and have been used for a long time in AV (audio and video) apparatuses, apparatus parts, copiers, printers, and steel plates for washing machines. However, when chromate is used, the chromate forms a hydrogen bond with the Fe oxide layer of the substrate layer to obtain excellent film properties such as adhesion and punching property, and exhibits good film characteristics even after SRA (Stress Relief Annealing). However, the composition of the conventional coating liquid is required to contain chromium oxide, which may cause adverse effects on the human body and environmental problems. Due to these problems, the use of heavy metals, including hexavalent chromium, has been limited due to the fact that environmental regulations such as RoHS (Restriction of the use of Hazardous Substances) It is inevitable.

In the conventional PCM steel sheet, the pretreatment layer, the primer layer and the upper layer are formed stepwise on the base steel sheet in the constitution. In the case of the primer layer of the conventional steel sheet, the coating thickness is 5 micrometers or more, and the PMT temperature according to the thickness is formed to be high in the small bushing, thereby increasing the power consumption rate.

Accordingly, there is a need for a method for manufacturing a color steel sheet which is economical, has high corrosion resistance and processability, and is environmentally friendly at the same time by minimizing the process steps.

An object of the present invention is to provide a composition for producing a primer-free layer of a colored steel sheet.

In order to achieve the above object,

The present invention relates to a composition for producing a primer-free layer of a colored steel sheet, which comprises ethylene acroleic acid, polycarbonate diol, methyl methacrylate, titanium dioxide, a lithium compound and a phosphate compound, a silane coupling agent, a hardener and a solvent .

When preparing a primer-free layer of a color steel sheet with the composition according to the present invention, it is eco-friendly since it does not undergo a pretreatment process using conventional chromium. In addition, since the coating thickness of the primer-free layer constituting the color steel sheet is less than 1 micrometer, the load of the steel maker can be reduced, and the power consumption of the primer-free layer can be reduced as the PMT of the primer- In addition, unlike existing products, it is possible to reduce the manufacturing cost of color coated steel sheet, which requires two coatings and two baking processes.

Fig. 1 shows a comparison between a conventional color steel plate (left) and a color steel plate (right) according to the present invention.
2 compares the performance evaluation results of the color coated steel plate primer-free layer according to Example 2 of the present invention with respect to thickness. (SAMPLE A: primer-free layer A; sample B: primer-free layer B; # 3: primer-free layer A) Primer Free Layer Thickness 1 占 퐉 6 # Primer Free Layer Thickness 2 占 퐉 # 9 Primer Free Layer Thickness 3 占 퐉)
3 is a result of comparing the T-Bending performance evaluation results of the color steel sheet (PMT 80 ° C of the primer-free layer) of the present invention and the comparative example (primer layer PMT 232 ° C) according to Example 3 of the present invention (left: T-Bending result of the present invention; Right: T-Bending result of Comparative Example; from top to bottom are 0T, 1T, 2T respectively).

Hereinafter, the present invention will be described in detail.

The present invention relates to a composition for producing a primer-free layer of a colored steel sheet, which comprises ethylene acroleic acid, polycarbonate diol, methyl methacrylate, titanium dioxide, a lithium compound and a phosphate compound, a silane coupling agent, a hardener and a solvent .

The present invention also relates to a process for the preparation of a composition comprising 10 to 20% by weight of ethylene acylic acid, 1 to 10% by weight of polycarbonate diol, 1 to 50% by weight of methyl methacrylate, 1 to 5% by weight of titanium dioxide, 1 to 5% Free layer of a colored steel sheet, which comprises 0.1 to 1% by weight of a silane coupling agent, 0.1 to 3% by weight of a silane coupling agent, 0.1 to 8% by weight of a curing agent, and 30 to 70% by weight of a solvent.

As used herein, the term "base steel sheet" means steel materials such as cold-rolled steel sheet and coated steel sheet, and known non-ferrous metals. The base steel sheet may include non-ferrous metals such as aluminum, stainless steel, and copper, but is not limited thereto. The coated steel sheet may be a galvanized steel sheet, a galvanized steel sheet, a galvanized steel sheet, a hot-dip galvanized steel sheet, a Zn-Al alloy coated steel sheet, a Zn-Al-Si alloy coated steel sheet or an Al-coated steel sheet; Electroplated steel sheets such as two-layer zinc-alloyed steel sheet, zinc-coated steel sheet, Zn-based alloy coated steel sheet and two-layered zinc-base alloy coated steel sheet; Vapor-phase coated steel sheets such as weather galvanized steel sheets; And organic coated steel sheets such as colored zinc plated steel sheets, thin film organic coated steel sheets, and organic composite coated steel sheets. However, the present invention is not limited thereto.

As used herein, the term "primer-free layer" is a layer in which a pretreatment layer and a primer layer, which constitute a conventional color steel sheet, are integrated into one. The pretreatment layer is formed by treating a known chemical conversion coating such as a phosphoric acid coating, a chromate, a thin film adhesion coating, or the like to enhance adhesion and corrosion resistance in the process of manufacturing a color steel sheet. The " primer layer " usually means a lower coating layer for imparting corrosion resistance to a colored steel sheet and adhesion to a top coat layer. The undercoating layer may include a polyester-based, epoxy-based, acrylic-based primer, or a modified primer-based primer, and is generally formed to a thickness of 5 탆.

In the present invention, a primer-free layer combining the functions of a conventional pretreatment layer and a primer layer is used without duplicating the conventional pretreatment layer and the primer layer described above, that is, without separately forming a primer layer.

As used herein, the term " top layer " is formed on the primer-free layer of the present invention to have a thickness of about 15 to 20 탆 and serves to impart corrosion resistance, workability, and color to the color steel sheet.

Forming a primer-free layer on the base steel sheet and curing the base steel sheet; And forming a top layer on the primer-free layer and curing the primer layer by a two-coat, two-bake method.

In the composition for forming the primer-free layer of the present invention, the silane coupling agent is a basic compound that imparts barrier property and corrosion resistance to the steel sheet, and includes aminosilane, mercapto silane, vinyl methoxy silane, vinyl trimethoxy silane, vinyl epoxysilane , Vinyltriethoxysilane, 3-aminopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-methacryloxypropyltrimethoxysilane, and gamma -glycidoxypropyltriethoxysilane and their It is preferable to use at least one substance selected from the mixture. And more preferably 3-glycidoxypropyltrimethoxysilane.

The curing agent may be selected from urea, ethylenethiourea, iminourea, carboimide, block isocyanate melamine, melamine curing agent, isocyanate curing agent, aziridine, epoxy curing agent and mixtures thereof, It is preferred to use ethylene thiourea and iminourea.

The lithium compound is preferably a lithium polysilicate, but not limited thereto.

The phosphoric acid compound is preferably a zinc phosphate compound or aluminum phosphate but is not limited thereto.

The solvent serves to uniformly mix the compositions. Examples of the solvent having the above properties include general solvents such as aromatic hydrocarbons, aliphatic hydrocarbons, ketones, esters, ethers and alcohols, and non-toxic organic solvents such as odorless mineral spirits and distilled water Solvents, and mixtures thereof. However, the present invention is not limited thereto, and it is particularly preferable to use a distilled water as a water-soluble type.

Conventional colored steel sheets are generally manufactured by a 3-coating, 3-bake process including a chromium-type pretreatment coating layer, a primer coating layer (lower layer) and a top layer. However, the color steel sheet of the present invention can be manufactured by a 2-coating process and a 2-bake process, in which the pretreatment coating layer and the primer coating layer are integrated into a primer-free layer. In addition, the process of pretreatment of environmentally regulated substances such as chromium used in the pretreatment step of existing color steel sheets is omitted, and thus, environmentally friendly color steel sheets can be produced.

The composition may further comprise 10 to 20% by weight of ethylene acroleic acid, 1 to 10% by weight of polycarbonate diol, 1 to 50% by weight of methyl methacrylate, 1 to 5% by weight of titanium dioxide, 1 to 5% But is not limited to, 0.1 to 1 wt%, a silane coupling agent 0.1 to 3 wt%, a curing agent 0.1 to 8 wt%, and a solvent 30 to 70 wt%.

Ethylene acrylic acid is a factor affecting corrosion resistance and when applied in an amount of 10 to 20% by weight, corrosion resistance may be improved. However, if it is outside the above range, corrosion resistance and processability may be deteriorated. PCDL based on water-dispersible polyurethane resin (PUD) is a factor affecting processability. When elongation is less than 400, it may cause deterioration of processability. If it exceeds 600, it may deteriorate solvent resistance. Methyl methacrylate may be applied in an amount of 1 to 50% by weight, and if it is out of the range, solvent resistance and corrosion resistance may be deteriorated. Titanium dioxide is used as an additive to improve dispersibility and corrosion resistance as a chelate structure and may contain 1 to 5% by weight, but if it is out of the range, the workability may be deteriorated. The coupling agent comprising 3-glycidoxypropyltrimethoxysilane, which is a silane coupling agent, can give a solid coupling to the material and coating film, and when applied in the range of about 0.1 to 3% by weight, , Solvent resistance and processability, but deviating from the above range may cause deterioration of storage stability. The curing agent serves to increase the degree of crosslinking of the coating film, and if it is applied in an amount of 0.1 to 5% by weight, it may help improve the solvent resistance and corrosion resistance, but if it is out of the above range, it may cause deterioration of workability. When the structure including lithium polysilicate is applied in an amount of 1 to 5% by weight or less, corrosion resistance may be improved. However, if the amount is within the above range, the structure may deteriorate storage stability. When the structure containing phosphoric acid is applied in an amount of 0.1 to less than 1% by weight, the adhesion to the material can be improved, and if it is out of the above range, the adhesion to the material may be deteriorated. When the content of the solvent is less than 30% by weight, the composition is not uniformly mixed. When the content of the solvent is more than 70% by weight, the drying time of the primer-free layer is increased and the efficiency of the manufacturing process may be lowered.

The thickness of the primer-free layer made of the composition may be 0.5 to 2 탆, but is not limited thereto, and may preferably be 1 탆. Conventional colored steel sheets include a pretreatment and a primer undercoat layer formation step, in which case the thickness of the undercoat layer is formed to be 5 占 퐉 or more. However, when the preprocessing and the formation of the primer undercoat layer are carried out, the manufacturing cost is increased and the price competitiveness is degraded. Alternatively, the thickness of the primer-free layer of the color steel sheet manufactured using the composition of the present invention may be as thin as 1 占 퐉 or less, thereby reducing the manufacturing cost of the steelmaker.

In addition, the step of forming the primer-free layer with the composition of the present invention may be performed at a temperature of 70 ° C to 140 ° C, but is not limited thereto. Preferably, the PMT temperature is 80 ° C or lower .

In the case of the undercoating layer of the conventional color steel sheet, the PMT is controlled to about 200 to 250 ° C due to the characteristics of the resin composition for imparting the curing temperature and workability of the curing agent. However, since the curing of each coating layer can not be performed within a predetermined time at a low temperature, particularly at a PMT of less than 200 ° C, the drying efficiency is lowered and sufficient drying is impossible. However, when the primer-free layer of the present invention is used, it is possible to control the PMT to 80 DEG C or less. The use of the low-temperature curing type primer-free layer enables sufficient drying even at a low temperature, thereby reducing the process cost and reducing the emission amount of carbon dioxide.

The upper layer formed on the primer-free layer may contain 10 to 55 parts by weight of a pigment, 5 to 50 parts by weight of a solvent, 10 to 30 parts by weight of a light aromatic solvent naphtha, and 10 to 30 parts by weight of an aromatic solvent naphtha in 100 parts by weight of a polyester resin But it is not limited thereto and can be produced by a method for producing a general top coat layer known in the art. The upper layer can be formed by curing the PMT at 180 to 250 ° C, and the upper layer can be formed to have a thickness of 13 to 18 μm.

Hereinafter, the present invention will be described in more detail with reference to Examples. It is to be understood by one of ordinary skill in the art that these embodiments are only for illustrating the present invention and that the scope of the present invention is not construed as being limited by these embodiments.

< Example  1> Collar  Produce

A method of manufacturing a color coated steel sheet according to an embodiment of the present invention will now be described.

First, a primer-free layer was formed on the hot-dip galvanized steel sheet (GI). The primer-free layer contained 15 wt% of ethylene acrylic acid, 10 wt% of PCDL, 25 wt% of methyl methacrylate, 2 wt% of 3-glycidoxypropyltrimethoxysilane coupling agent Non-cr type water-soluble solution containing 3% by weight of a curing agent, 3% by weight of a thiourea curing agent, 3% by weight of lithium polysilicate, 0.5% by weight of triammonium phosphate and 41.5% by weight of distilled water Lt; / RTI &gt; The solution was hot-air heated to a PMT of 80 DEG C on a hot-dip galvanized steel sheet (GI) and coated with a thickness of 1 mu m to form a primer-free layer. Thereafter, an upper layer was formed on the primer-free layer. The upper layer was made of a general resin composition containing 35 parts by weight of pigment, 30 parts by weight of solvent, 20 parts by weight of light aromatic solvent naphtha and 15 parts by weight of aromatic solvent naphtha based on 100 parts by weight of polyester resin. The thickness of the upper layer was 15 탆 and the PMT was hardened at 232 캜 to obtain a color steel sheet of the present invention.

< Example  2> Color steel plate  Performance evaluation by thickness

<2-1> primer Free layer  Comparison of solution properties

The solution of primer-free layer for performance evaluation by thickness was prepared as follows.

The primer-free A solution is the same as the method of producing the primer-free layer of the colored steel sheet of Example 1 above. The primer-free B solution was prepared by adding 3% by weight of a urea curing agent to the composition of the solvent used in the preparation of the primer-free layer of the colored steel sheet of Example 1, adjusting the amount of distilled water to 100% %.

The primer-free layer was hot-air dried and cured at 80 DEG C to prepare three primer pores A and B each having a thickness of 1, 2, and 3 mu m, respectively.

First, the properties of the primer-free A and B solutions were compared (Table 1).

Comparison of primer-free A and B solution properties sample primer free  A primer free  B method of inspection ingredient Organic-inorganic hybrid type Organic-inorganic hybrid type
(3% addition of hardener) - Exterior White opaque liquid White opaque liquid Visual inspection Viscosity (25 ° C, cPs) 7.5 7.5 Brookfield Viscometer pH 8.8 8.8 pH meter Solid content (%) 15.0 15.0 110 ° C, 1 hour drying Storage stability 2 months at room temperature 2 months at room temperature Store at room temperature (5 ~ 30 ℃)

As a result, the primer-free A and B solutions were white opaque liquid, viscosity 7.5 cPs, pH 8.8, solids content 15.0% and storage stability for 2 months.

<2-2> Collar  Performance evaluation

The performance of the steel sheet was evaluated using a color steel sheet using the primer-free A and B solutions of the present invention and a color steel sheet having a conventional chromium pretreatment layer as comparative examples. As a comparative example, a color steel plate having a conventional chromium pretreatment process was used. The color steel sheet of the comparative example includes a pretreatment layer including a chromium type solution, a primer layer having a thickness of 5 탆 and a top layer having a thickness of 15 탆, and a color steel sheet (See color steel plate structure on the left in Fig. 1).

The performance evaluation of the color steel sheet was evaluated in terms of adhesion amount, top gloss, abrasion resistance, pencil hardness, impact resistance, CCT & Erichsen, T-BEND and corrosion resistance.

The color coated steel plate adhesion amount was measured by a wet measurement method in the case of the primer-free layer, and the adhesion amount of the upper layer was measured by a QN-7500-FN dry film measuring instrument of AUTOMATION Corporation.

The gloss of the top layer was measured using a gloss meter of BYK. The glossiness was judged from the measured value at an incident angle of 60 °. When the glossiness is 27 or less, it meets the quality standard.

The abrasion resistance items were evaluated using MEK (methylethylketone) steel agent. After rubbing the steel plate for 80 ~ 100 times at a load of 1 ~ 2kg / f, the peeling of the coating film was confirmed. If it is rubbed more than 80 times and there is no abnormality in appearance, it meets the quality standard.

Pencil hardness items were measured using a Mitsubishi Pencil which is standardized by hardness. F or more.

The impact resistance items were evaluated using an impact resistance tester manufactured by DuPont. Cracks and peeling of the coating film after dropping 500 g of the weight at a height of 500 mm were confirmed. The cellophane tape was adhered to the test section, and then peeled off and peeled off. If the coating film crack does not occur when the tape is detached and attached under the above conditions, the quality standard is satisfied.

CCT & Erichsen items were evaluated by using a cross cut machine on a color steel plate. 100 checkerboard patterns were made on the steel sheet at intervals of 1 mm, and pressed to an area of 6 to 7 mm with an Erichsen tester. Then, a cellophane tape was adhered to the test section, and then peeled off and peeled off. If the coating film crack does not occur when the tape is detached and attached under the above conditions, the quality standard is satisfied.

The processability (T-BEND) item was evaluated by 2T-bending, followed by sticking a cellophane tape to the test section, peeling it, and confirming the presence or absence of peeling. If the coating film crack does not occur when the tape is detached and attached under the above conditions, the quality standard is satisfied.

The corrosion resistance items were evaluated as plate corrosion resistance, X-cut corrosion resistance and edge-cut corrosion resistance. The X-cut and Edge-cut corrosion resistance was evaluated after 500 hours after cutting on the surface of the steel sheet. QN-7500-FN of Q-FOG was used for the salt water dispensing machine. If there is no rust after 500 hours, it meets the quality standard of plate corrosion resistance. When the occurrence of blisters is less than 3 mm after 500 hours, the quality standard of X-cut is satisfied. When BLISTER occurs less than 18mm after 500 hours, it meets the corrosion-resistance quality standard of edge-cut.

The performance evaluation results of the thickness of the color steel plate are as follows (Table 2).

<Results of color steel sheet performance evaluation according to primer-free layer thickness>

As a result of evaluation, there was no difference in performance according to the thickness of the primer-free layer. The top gloss was 24.5 when a primer-free layer having a thickness of 1 탆 was used, and there was no difference in performance compared with 24.4 of a color steel sheet using the underlayer 5 탆 of the comparative example. The abrasion resistance showed an equivalent performance result of 100 times in both the color steel sheet of the present invention and the comparative example. The pencil hardness also showed equivalent performance to H in both the color steel sheet of the present invention and the comparative example. Impact Resistance, Workability CCT-Erichsen evaluation also showed no cracks in both the color steel sheet of the present invention and the comparative example (FIG. 2). In the corrosion resistance evaluation, neither the color steel sheet of the present invention nor the comparative example showed flaking, and the blister also showed no difference in performance below the reference value.

This is a result indicating that the color steel sheet having the primer-free layer having thicknesses of 1, 2, and 3 占 퐉 according to the present invention is equal to or more than the comparative example having the 5 占 퐉 thick primer layer having the pre-treatment step.

< Example  3> Color steel plate primer Free layer PMT Star performance evaluation

<3-1> primer Free layer PMT Star Solution Characteristics

The color steel sheet for performance evaluation according to temperature was a color steel sheet having a primer free layer thickness of 1 占 퐉 using the method of manufacturing the primer-free layer of Example 1 described above.

In order to confirm the performance evaluation for each PMT in the composition for producing the primer-free layer of the colored steel sheet, the PMT curing temperature (PMT, ° C) of the primer-free layer was 80/100/120/130 / 140 ° C were set for each color steel sheet. In particular, although the minimum curing temperature of the primer-free layer of the present invention was set at 80 캜, it was found that sufficient drying was possible even at a low temperature of 80 캜 or below when PMT dropped below 80 캜 during drying.

First, the solution properties of the primer-free layer of this example were compared (Table 3).

Comparison of solution properties of primer-free layer sample Primer-free method of inspection ingredient Combination Type - Exterior White opaque liquid Visual inspection Viscosity (25 ° C, cPs) 7.5 Brookfield Viscometer pH 8.8 pH meter Solid content (%) 15.0 110 ° C, 1 hour drying Storage stability 2 months at room temperature Store at room temperature (5 ~ 30 ℃)

As a result of the test, the primer-free solution of the present invention was a white opaque liquid having a viscosity of 7.5 cPs, a pH of 8.8, a solid content of 15.0% and storage stability of 2 months.

<3-2> Collar  Performance evaluation

Five colored steel plates having the primer-free PMT condition of 80/100/120/130/140 ° C. of Example <3-1> of the present invention and a color steel plate having a conventional chromium pretreatment layer (comparative example) . As a comparative example, a color steel plate having a conventional chrome pretreatment process was used (refer to the color steel plate structure on the left side of FIG. 1). The color steel sheet of the comparative example was a general color steel sheet product comprising a pretreatment layer containing a chromium type solution, a primer layer having a thickness of 5 탆 and a top coat layer having a thickness of 15 탆 and being produced by a 3-coating and 3-bake process Left steel plate structure). The PMT of the primer layer of the color steel sheet of the comparative example has a high curing temperature of 232 캜.

The performance evaluation of the color steel sheet was evaluated by dividing into the items of adhesion amount, top gloss, abrasion resistance, pencil hardness, impact resistance, workability (T-BEND) and corrosion resistance.

The color coated steel sheet was measured by a wet measurement method in the case of the primer-free layer, and the adhesion amount of the upper layer was measured by a QN-7500-FN dry film measuring instrument of AUTOMATION Corporation.

The gloss of the top layer was measured using a BYK gloss meter. The glossiness was judged from the measured value at an incident angle of 60 °. When the glossiness is 27 or less, it meets the quality standard.

The abrasion resistance items were evaluated using MEK (methylethylketone) steel agent. The steel sheet was rubbed 80 ~ 100 times with a load of 1 ~ 2kg / f. If it is rubbed more than 80 times and there is no abnormality in appearance, it meets the quality standard.

Pencil hardness items were measured using a Mitsubishi Pencil which is standardized by hardness. F or more.

The impact resistance items were evaluated using an impact resistance tester manufactured by DuPont. Cracks and peeling of the coating film after dropping 500 g of the weight at a height of 500 mm were confirmed. The cellophane tape was adhered to the test section, and then peeled off and peeled off. If the coating film crack does not occur when the tape is detached and attached under the above conditions, the quality standard is satisfied.

The processability (T-BEND) item was evaluated by 2T-bending, followed by sticking a cellophane tape to the test section, peeling it, and confirming the presence or absence of peeling. In this section, 0T and 1T banding were further tested. If the coating film crack does not occur when the tape is detached and attached under the above conditions, the quality standard is satisfied.

The corrosion resistance items were evaluated as plate corrosion resistance, X-cut corrosion resistance and edge-cut corrosion resistance. The X-cut and Edge-cut corrosion resistance was evaluated after 500 hours after cutting on the surface of the steel sheet. QN-7500-FN of Q-FOG was used for the salt water dispensing machine. If there is no rust after 500 hours, it meets the quality standard of plate corrosion resistance. When the occurrence of blisters is less than 3 mm after 500 hours, the quality standard of X-cut is satisfied. When BLISTER occurs less than 18mm after 500 hours, it meets the corrosion-resistance quality standard of edge-cut.

The performance evaluation results of PMT of the primer-free layer of the color steel sheet of the present invention are as follows (Table 4)

&Lt; Evaluation result of color steel sheet for each PMT of primer-free layer >

As a result of the evaluation, it was found that there was no difference in the performance of the color steel sheet according to the PMT curing temperature of the primer-free layer. When the primer-free layer having a PMT hardening temperature of 80/100/120/130/140 ° C was used, the top gloss was 27, and there was no difference in performance compared to the color steel sheet using the underlayer 5 μm of the comparative example. The abrasion resistance showed an equivalent performance result of 100 times in both the color steel sheet of the present invention and the comparative example. Also, the pencil hardness showed the same performance as H in both the color steel sheet for each PMT of the present invention and the comparative example. Impact Resistance and Workability CCT-Erichsen evaluation also showed no cracks in both the PMT-specific color steel sheets and the comparative examples of the present invention. In the corrosion resistance evaluation, neither the color steel sheet of the present invention nor the comparative example produced no flaking, and the blister also showed no difference in performance below the reference value.

It can be seen that the color steel sheet prepared by setting the curing temperature of the primer-free layer of the present invention at 70 to 140 ° C is equal to or more than the conventional color steel sheet of the comparative example having a PMT temperature of 200 ° C or more .

In particular, the curing temperature of the primer-free layer of the present invention is set at 80 캜, but when the temperature is lowered to 80 캜 or lower during drying, sufficient drying can be performed even at a low temperature of 80 캜 or below, thereby reducing the process cost and the emission amount of carbon dioxide It can be seen that there is an effect.

Claims (6)

10 to 20% by weight of ethylene acylic acid, 1 to 10% by weight of polycarbonate diol, 1 to 50% by weight of methyl methacrylate, 1 to 5% by weight of titanium dioxide, 1 to 5% by weight of lithium compound and 0.1 to 1% , 0.1 to 3 wt% of a silane coupling agent, 0.1 to 8 wt% of a curing agent, and 30 to 70 wt% of a solvent, to form a primer-free layer of a colored steel sheet.
The method according to claim 1,
The silane coupling agent is selected from the group consisting of amino silane, mercapto silane, vinyl methoxy silane, vinyl trimethoxy silane, vinyl epoxysilane, vinyl triepoxy silane, 3-aminopropyl triethoxy silane, 3- glycidoxypropyl trimethoxy Silane, 3-methacryloxypropyltrimethoxysilane,? -Glycidoxypropyltriethoxysilane, and mixtures thereof. The composition of claim 1,
The method according to claim 1,
Wherein the curing agent is selected from the group consisting of urea, ethylenethiourea, iminourea, carboimide, block isocyanate melamine, melamine curing agent, isocyanate curing agent, aziridine, epoxy curing agent and mixtures thereof. Free layer of the composition.
The method according to claim 1,
Wherein the lithium compound is a lithium polysilicate (Lithium Poly silicate).
The method according to claim 1,
Wherein the phosphoric acid compound is a zinc phosphate compound or aluminum phosphate.
The method according to claim 1,
Wherein the solvent is selected from the group consisting of distilled water, aromatic hydrocarbons, aliphatic hydrocarbons, ketones, esters, ethers, alcohols, odorless mineral spirits, and mixtures thereof.

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