KR101920688B1 - Pre-Coated Metal Composition of Magnesium Alloy Steel Sheet for Outdoor Air-Conditioner and PCM Sheet Using the Same - Google Patents

Abstract

The present invention relates to a PCM coating composition for an air conditioner outdoor unit using a magnesium alloy steel sheet as a base material, and a PCM coated steel sheet produced by the method, and to provide a PCM coating composition for an outdoor air conditioner excellent in corrosion resistance and moldability It has its purpose.
To this end, the present invention relates to a PCM (Pre-Coated Metal) coating composition for an air conditioner outdoor unit containing a resin as a main component, a dispersed pigment and a solvent, wherein the polyester resin for the undercoat has a Tg of from 10 ° C to 30 ° C , A molecular weight (Mn) of 10,000 to 20,000, and an OH value of 5 to 10, which is contained in an amount of 20 to 30% by weight based on the whole composition, and the polyester resin for phase has a Tg of 30 to 50 (M n) of 20,000 to 35,000 and an OH value of 10 to 30,000, a molecular weight (Mn) of 15,000 to 30,000, an OH value of 20 to 25, To 15% by weight of a high molecular polyester resin B is mixed in a ratio of A: B = 30:70, and is contained in an amount of 20 to 30% by weight based on the total composition.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a PCM coating composition for an air conditioner outdoor unit using a magnesium alloy steel sheet, and a PCM coated steel sheet produced thereby.

The present invention relates to a PCM (Pre-Coated Metal) coating composition for an air conditioner outdoor unit using a magnesium alloy steel sheet as a base material, and to a PCM coated steel sheet produced by the method. More particularly, And a PCM coated steel sheet produced by the method. The present invention relates to a PCM coating composition for an air conditioner outdoor unit, which comprises a magnesium alloy steel sheet which can satisfy both molding processability, weather resistance and durability of a coating film.

Examples of the method of coating the steel sheet include a post coating method in which a steel sheet is formed and processed and then painted, and a precoating method in which a steel sheet is coated before molding.

The post coating method has a disadvantage in that it is difficult to produce a uniform product and to mass-produce, although the equipment cost is low and it is advantageous in producing a small amount.

The precoating method has an advantage that a uniform product can be produced and a large amount of paint can be produced in a short time with less loss of paint.

The steel sheet coated with the above-described pre-coating method is referred to as a pre-coated steel sheet, and the paint used in such a precoating method is called a PCM coating.

The above-mentioned PCM steel sheet can be directly manufactured as soon as it is formed and processed, and a galvanized steel sheet is mainly used as a steel sheet material.

The above-mentioned PCM steel sheet has an advantage that quality can be ensured, production can be increased by continuous production, and cost can be reduced.

Generally, the coating process of the PCM steel sheet is performed continuously. The pre-treatment layer is formed by applying the zinc or chromate or the organic coating while uncoating the cold-rolled coiled steel sheet, and then drying it through an oven.

Subsequently, the undercoat layer is formed by applying the undercoat layer by a transfer of the coating roll, and then the undercoat layer is formed by passing through the oven. The topcoat layer is formed by applying the overcoat layer and then dried while passing through the oven.

The PCM steel sheet produced by the above-described method is widely used for various construction interior / exterior materials, household electric appliances and the like.

On the other hand, the steel sheet used in an air conditioner outdoor unit must have high corrosion resistance because it is exposed to a harsh environment.

In order to satisfy the above conditions, a magnesium alloy steel plate with high corrosion resistance is used for an air conditioner outdoor unit.

However, the above magnesium alloy steel sheet is excellent in corrosion resistance, but has a problem in that the molding processability is inferior to that of the existing Galvanized Iron (GI) or Electrolytic Galvanized Iron (EGI).

On the other hand, the evaluation method of the corrosion resistance (Salt Spray Test) X part (480 hours) is used as the property evaluation method of the coated steel sheet used in the air conditioner outdoor unit.

However, the accelerated corrosion resistance evaluation method described above excludes the evaluation of the edge portion of the steel sheet, and it is pointed out that the edge corrosion resistance of the outdoor PCM steel sheet to which the GI material is applied is weak.

It is an object of the present invention to provide a PCM coating composition for an air conditioner outdoor unit, which is made of a magnesium alloy steel sheet having high corrosion resistance characteristics and excellent moldability.

Another object of the present invention is to improve the corrosion resistance of the magnesium alloy steel plate edge portion.

It is still another object of the present invention to provide a PCM coated steel sheet for an air conditioner outdoor unit made of a magnesium alloy steel sheet improved in molding workability of a magnesium alloy steel sheet having high corrosion resistance.

In order to achieve the above object, the present invention provides a PCM (Pre-Coated Metal) coating composition for an air conditioner outdoor unit made of a magnesium alloy steel sheet containing a main resin, a dispersed pigment and a solvent, Polyester resin is a high molecular polyester resin having a Tg of 10 to 30 占 폚, a molecular weight (Mn) of 10,000 to 20,000 and an OH value of 5 to 10 and being contained in an amount of 20 to 30% The staining resin has a Tg of 30 ° C to 50 ° C, a molecular weight (Mn) of 15,000 to 30,000 and an OH value of 20 to 25, and a polyester resin A having a Tg of 10 ° C to 30 ° C and a molecular weight (Mn) Of 20,000 to 35,000 and an OH value of 10 to 15 are mixed in a ratio of A: B = 30: 70 and contained in an amount of 20 to 30% by weight based on the total composition.

Also, the undercoat forming the undercoating layer is characterized by containing 3 to 8% by weight of a curing agent composed of a hexamethoxymethylmelamine type melamine resin having NV of 98% or more.

Also, the top coat forming the top coating layer contains 5 to 10% by weight of a curing agent composed of a hexamethoxymethylmelamine melamine resin having NV of 98% or more.

Further, the undercoat forming the undercoating layer is characterized by containing 3 to 5% by weight of TiO2 and 5 to 15% by weight of the anticorrosive pigment.

Further, it is characterized by containing TiO2, carbon black and colored pigment in an amount of 15 to 25% by weight in the top coating forming the top coat layer.

Further, the undercoat forming the undercoating layer is characterized by containing 50 to 65 wt% of an organic solvent in which an aliphatic hydrocarbon-based, ketone-based, and ester-based solvent are mixed.

Further, the top coat forming the top coat layer is characterized by containing 40 to 60% by weight of an organic solvent containing an aliphatic hydrocarbon-based, ketone-based, and ester-based solvent.

According to the present invention, it is possible to provide a PCM coating composition for an air-conditioner outdoor unit made of a magnesium alloy steel sheet excellent in molding workability while maintaining high corrosion resistance characteristics.

Further, the corrosion resistance of the edge portion of the magnesium alloy steel sheet used in the air conditioner outdoor unit is improved.

And also has an effect of improving the molding processability which is a disadvantage of the magnesium alloy steel sheet having high corrosion resistance.

1 is a sectional view of a PCM coated steel sheet produced according to the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail.

The PCM coating composition according to the present invention is a PCM (Pre-Coated Metal) coating composition for an air conditioner outdoor unit made of a magnesium alloy steel sheet containing a resin as a main component, a dispersed pigment and a solvent, wherein the undercoat layer 30 A polyester resin for a base to be formed has a Tg of 10 to 30 占 폚, a molecular weight (Mn) of 10,000 to 20,000, and an OH value of 5 to 10, 30% by weight.

The polyester resin for phase development forming the top coat layer 40 is a polyester resin A having a Tg of 30 to 50 占 폚, a molecular weight (Mn) of 15,000 to 30,000 and an OH value of 20 to 25, Polymeric polyester resin B having a Tg of 10 to 30 占 폚, a molecular weight (Mn) of 20,000 to 35,000 and an OH value of 10 to 15 was mixed in a ratio of A: B = 30: 70, 20 to 30% by weight.

Also, 3 to 8% by weight of a curing agent composed of a hexamethoxymethylmelamine melamine resin having NV of not less than 98% is contained in the undercoat forming the undercoat layer 30.

The top coat forming the top coat layer 40 also contains 5 to 10% by weight of a curing agent consisting of a hexamethoxymethylmelamine melamine resin having NV of 98% or more.

Also, TiO2 is contained in an amount of 3 to 5% by weight and the anticorrosive pigment is contained in an amount of 5 to 15% by weight in the undercoat forming the undercoat layer 30.

Further, TiO2, carbon black and colored pigment are contained in an amount of 15 to 25% by weight in the top coat forming the top coat layer 40. [

Further, the undercoat forming the undercoat layer 30 contains 50 to 65 wt% of an organic solvent in which an aliphatic hydrocarbon-based, ketone-based, and ester-based solvent are mixed.

The top coat forming the top coat layer 40 contains 40 to 60 wt% of an organic solvent containing an aliphatic hydrocarbon-based, ketone-based, and ester-based solvent.

The highly corrosion-resistant magnesium alloy steel sheet used for the air conditioner outdoor unit promotes the formation of Simonkolleite (Zn5 (OH) 8Cl2 H2O), which is a dense corrosion product in a very stable state, in the plating layer.

The corrosion product is formed on the surface of the plating layer like a film to prevent corrosion of the base steel sheet.

Further, when the cutting surface is generated, the upper coating layer is melted to cover the cross-section, thereby promoting the growth of stable corrosion products.

However, the above-mentioned magnesium alloy steel sheet of high corrosion resistance has a disadvantage in that the corrosion resistance is excellent as compared with the general GI material but the molding processability is poor.

In order to solve such a problem, in the present invention, a highly porous resin paint is applied to a coated steel sheet for an air conditioner outdoor unit.

That is, to improve the workability of the coated steel sheet, a coating film composed of a polymeric polyester as a main resin and a curing agent as melamine is formed.

Accordingly, it is possible to manufacture a coated steel sheet suitable for an air conditioner outdoor unit by having excellent molding workability together with high corrosion resistance.

Each component of the coating composition according to the present invention will be described below.

≪ Polyester Resin >

The polyester resin for use in the present invention is a polyester resin having a Tg of 10 to 30 占 폚, a molecular weight (Mn) of 10,000 to 20,000 and an OH value of 5 to 10, 20 to 30% by weight.

The polyester resin for phase inversion used in the present invention has a Tg of 30 to 50 캜, a molecular weight (Mn) of 15,000 to 30,000 and an OH value of 20 to 25, and a polyester resin A having a Tg of 10 캜 Polymeric polyester resin B having a molecular weight (Mn) of 20,000 to 35,000 and an OH value of 10 to 15 is mixed at a ratio of A: B = 30: 70 to 20 to 30% by weight .

That is, the present invention employs a high molecular weight polyester resin having a high molecular weight in order to compensate the processing performance, which is a weak point of the magnesium alloy steel sheet.

When a polyester resin having a low molecular weight is applied, there is a problem that a coating film breakage occurs at a bending portion of the work.

In addition, when a polyester resin having a low Tg is applied, the hardness of the coating film is lowered and the coating film tends to be retreated.

Table 1 below shows the average physical properties of the resin applied to the present invention.

division
Resin Properties Remarks
Underwater Award Solid (%) 30 to 50% 30 to 50% 20 to 40% OH Value 5 to 10 20-25 10 to 15 Molecular weight (Mn) 10,000 to 20,000 15,000 ~ 30,000 20,000 ~ 35,000 Tg (占 폚) 10 to 30 30 to 50 10 to 30

< Curing agent>

In the present invention, a hexamethoxymethylmelamine resin is contained in an amount of 3 to 8% by weight and an upper limit of 5 to 10% by weight based on the total coating composition, in order to cure the polyester resin.

If the content of the curing agent is less than 3 or 5% by weight based on the total coating composition, there may be a problem of deterioration of coating film hardness. If the content of the curing agent exceeds 8 or 10% by weight, there is a problem of lowering the bendability of the coating film.

Therefore, the content of the curing agent is preferably within the above range.

<Pigment>

It is preferable that the pigment contains 3 to 8% by weight of TiO2 with respect to the total composition and 5 to 15% by weight with respect to the total composition of pigments having a corrosive power of the calcium ion substitution reaction.

If the content of the anticorrosive pigment is less than 5 wt%, the detergency is deteriorated. If the content exceeds 15 wt%, the bendability of the coating film is deteriorated.

Further, TiO2 and carbon black (black pigment) are contained in the top coating in an amount of 15 to 25% by weight based on the total composition.

When the content of the pigment is less than 15% by weight, the color is not easily realized. When the content of the pigment is more than 25% by weight, the bending property of the coating film is lowered.

Therefore, the content of the pigment is preferably within the above range.

<Solvent>

The coating composition according to the present invention contains an appropriate amount of an organic solvent in consideration of handling, characteristics during coating and the like.

As the organic solvent, it is preferable to use an aliphatic hydrocarbon-based solvent, a ketone-based solvent, and an ester-based solvent in combination.

The content of the solvent in the primer is in the range of 50 to 65 wt% with respect to the total coating composition, and the content of the solvent in the primer is in the range of 40 to 60 wt% with respect to the entire coating composition.

Table 2 below shows the product design conditions of the present invention.

The product design conditions of the present invention division
Product design (% by weight) Remarks Lower normal course Polyester 20 ~ 30 20 ~ 30
(A / B = 30/70) Hardener
(Hexamethoxymethylmelamine) 3 to 5 5 to 10 Pigment
Pigment 3 to 5 15-25 Anticorrosive pigment 5 to 15 - solvent 50 to 70 40 to 60 additive 1-2 1-2

Hereinafter, the product design test result of the product according to the present invention will be described.

<Product design test result>

The test specimens were prepared by applying pretreated POSMAC 0.8T DQ material to a dry film thickness of 5 μm and an upper film thickness of 15 μm (total film thickness of 20 μm).

The test specimens baked under the conditions of drying at 232 ° C were subjected to the physical properties test, and the results are shown in the following [Table 3].

Results of physical property test No. Test Items standard result One Coat state Limit Sample Good 2 Film thickness Top 18 ~ 24㎛ 20 탆 3 color Limit Sample Good 4 Polish More than 75% 40% 5 Pencil hardness F or more F 6 Cross Skirt Test 100/100 100/100 7 Erichsen test No crack or peeling of coating film at over 6.0mm Good 8 Impact test No visual crack Good 9 Flexibility test 180˚ / 0 ℃ -3T There should be no crack after bending
180˚ / 20 ℃ -0T No crack after bending
Judged with a 10x magnifying glass 20 ° C 0T
0 ℃ 4T
NO Crack 10 Corrosion resistance test
(Salt spray test) After 480 hr, the maximum peeling width of the cross-cut and the cut part should be 3 mm or less.
There should be no flat surface after 780 hrs. 3 mm or less. 11 Alkali resistance test No swelling after immersion in 5% NaOH, 5% CH3COOH solution for 24 hours Good 12 Endurance test After standing for 240 hr in a solution of 5% synthetic detergent (LG super tie) at 50 ° C and washing with water, the appearance should be judged visually. Good 13 Number of test After leaving for 1 hour at 100 ° C, take out the film for 2 hours, and there should be no change in film (swelling, etc.) Good 14 Weatherability test Dew Cycle Weather Meter △ E2.5 or less after 270 hr test, 75% or more gloss retention rate, Good 15 Solvent resistance test After 24hr immersion in alkaline conditions of toluene and benzene, there should be no film swelling Good 16 Stain resistance test Wet red, blue, and black lines with Monami Magic and leave at RT 30 ℃ for 24 hr. After washing with xylene, there will be no marks on the film. Good 17 Ultraviolet ray test After Toshiba 20W, 20Cm, 24hr irradiation, ΔE should be less than 1.5 Good 18 Drawing test A 100/100 Good 19 Cold workability -10 ± 2 ° C for 1 hour, and no impact cracking, peeling, whitening will occur when the impact test is carried out. Good 20 Rubbing test The test piece shall be rubbed 100 times under 1Kg load by putting the ethanol into the melted Jelly Jung and the film shall not be buried. 21 Re-construction There will be no peeling after the reinspection coin test.
Crochet 100X100 Good

As can be seen from the above experimental results, the PCM coated steel sheet made of the magnesium alloy steel sheet according to the present invention exhibits good moldability while maintaining the characteristics of high corrosion resistance.

Therefore, according to the present invention, it is possible to manufacture a PCM coated steel sheet suitable for an air conditioner outdoor unit exposed to a harsh environment.

10: Substrate steel
20: Pre-treatment layer
30: Lower coating layer
40: top coat layer
50: backside layer

Claims (8)

1. A PCM (Pre-Coated Metal) coating composition for an air conditioner outdoor unit containing a resin as a main component and a dispersed pigment and a solvent,
The lower polyester resin is a high molecular polyester resin having a Tg of 10 to 30 占 폚, a molecular weight (Mn) of 10,000 to 20,000 and an OH value of 5 to 10, %,
The polyester resin for phase is a polyester resin A having a Tg of 30 ° C to 50 ° C, a molecular weight (Mn) of 15,000 to 30,000 and an OH value of 20 to 25 and a polyester resin A having a Tg of 10 ° C to 30 ° C, (Mn) of 20,000 to 35,000 and an OH value of 10 to 15 are mixed in a ratio of A: B = 30: 70 to 20 to 30% by weight based on the total composition,
To the undercoat forming the undercoat layer 30,
3 to 8% by weight of a curing agent composed of a hexamethoxymethylmelamine melamine resin having an NV of 98% or more,
3 to 5% by weight of TiO2, 5 to 15% by weight of a rust preventive pigment,
50 to 65% by weight of an organic solvent containing an aliphatic hydrocarbon-based solvent, a ketone-based solvent, and an ester-based solvent is contained,
In the top coat forming the top coat layer 40,
5 to 10% by weight of a curing agent composed of a hexamethoxymethylmelamine type melamine resin having an NV of 98% or more,
TiO2, carbon black (Carbon Black) and 15 to 25% by weight of a colored pigment,
Wherein an organic solvent containing an aliphatic hydrocarbon, an aliphatic hydrocarbon-based, a ketone-based, and an ester-based solvent is contained in an amount of 40 to 60% by weight. delete delete delete delete delete delete A PCM coated steel sheet for an air conditioner outdoor unit made of a magnesium alloy steel sheet, which is produced by using the PCM coating composition according to claim 1.

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