KR20200065675A - Powder coating composition - Google Patents

Abstract

The present invention relates to a powder paint composition for automobiles, having water resistance, acid resistance and high hardness. The powder paint composition comprises: a resin component including an acrylic copolymer resin, and a polyester resin; and a curing agent.

Description

Powder coating composition {POWDER COATING COMPOSITION}

The present invention relates to a powder coating composition having water resistance, acid resistance, and high hardness, in particular, a powder coating composition for automobiles.

Powder coating technology has been developed since the 1970s, and recently, powder coating has emerged as an eco-friendly coating instead of general coating. This powder coating is used in Korea due to its eco-friendly properties and the development of resins, additives and equipment technology. It is a rapidly growing situation worldwide.

The powder coating is applied to a coating method of coating the surface of an object to be coated by an electrostatic method and melting and homogenizing powder particles through heat drying such as thermal curing to improve the coating film. This paint is required in various fields because it has a low risk of poisoning due to the volatilization of a solvent and a low risk of fire compared to a liquid paint, and has an advantage of easy regeneration of the paint as it is easy to paint. In recent years, high functionality is required in relation to global warming and strengthening of UV exposure, while water resistance, acid resistance, and hardness to withstand external environments are required to be applied to automobiles.

As the powder coating, acrylic resins have been generally used, but this has the disadvantages that water resistance and acid resistance are insufficient to be applied to automobile paints and hardness is also poor. Accordingly, there is a need to develop a powder coating material having improved water resistance, acid resistance, and hardness to withstand an external environment that can be used as a powder coating material for automobiles.

JP 4094049 B2

In the present invention, the disadvantages of the acrylic resin can be improved by applying a polyester coating to the acrylic resin for application to automotive paints. In addition, the acrylic resin was mainly used only for transparent applications, but in the present invention, it has been improved to increase compatibility with pigments, so that it can be applied to various uses as automotive paints.

The present invention is to provide a coating composition that can be used as a powder coating for automobiles having improved water resistance, acid resistance and hardness to withstand external environments.

In order to solve the above problems, the present invention is a resin component comprising an acrylic copolymer resin obtained by polymerizing an acrylic monomer and an unsaturated polyalkylene glycol monomer, and a polyester resin; And it provides a powder coating composition comprising a curing agent.

According to the present invention, by applying an unsaturated polyalkylene glycol monomer to the acrylic resin to impart compatibility with the polyester resin, while having the advantages of hardness and acid resistance, which is the advantage of the polyester resin, the dispersibility with the pigment can also be improved, Various applications are possible for automotive paints.

Figure 1 shows the constituent components of the powder coating resin according to an embodiment of the present invention.

The present invention is an acrylic copolymer resin obtained by polymerizing an acrylic monomer and an unsaturated polyalkylene glycol monomer, and a resin component comprising a polyester resin; And it relates to a powder coating composition comprising a curing agent.

The acrylic monomer may have the structure of Formula 1 below.

[Formula 1]

In the above formula, R ₁ is a hydroxy group or an alkyl group having 1 to 10 carbon atoms, and R ₂ is hydrogen or methyl.

The acrylic monomer may be selected from the group consisting of alkyl acrylate monomers or alkyl methacrylate monomers.

As the acrylic monomer having the alkyl group, methyl methacrylate, ethyl methacrylate, isobutyl methacrylate, normal butyl methacrylate, tertiary butyl methacrylate, normal hexyl methacrylate, 2-ethylhexyl methacrylate, Isobornyl methacrylate, cyclohexyl methacrylate, methyl acrylate, ethyl acrylate, propyl acrylate, isobutyl acrylate, normal butyl acrylate, tertiary butyl acrylate, 2-ethylhexyl acrylate, normal octyl acrylic Late, isobornyl acrylate, cyclohexyl acrylate, and the like can be used.

The unsaturated polyalkylene glycol monomer may have the structure of Formula 2 below.

[Formula 2]

In the above formula,

R ¹ , R ² and R ³ are each independently hydrogen, an alkyl group having 1 to 10 carbon atoms, a sulfone group, a carboxy group, or a combination thereof,

X is absent, -CH ₂ -, -(CH ₂ ) ₂ -, -(CH ₂ ) ₃ -,

R ^a is an alkylene group having 2 to 10 carbon atoms,

R ⁴ is hydrogen,

n is an integer from 2 to 50.

The unsaturated polyalkylene glycol monomer may have an average added mole number of 2 to 50 oxyalkylene groups.

The acrylic copolymer resin contained in the powder coating composition according to the present invention can be obtained by polymerizing the acrylic monomer and the unsaturated polyalkylene glycol monomer at a temperature condition at which a half-life of the initiator is expressed using a radical polymerization initiator.

The unsaturated polyalkylene glycol monomer may be included in an amount of 15 to 80% by weight, particularly 20 to 60% by weight, based on the weight of the acrylic copolymer resin. When the unsaturated polyalkylene glycol monomer is less than 15% by weight, compatibility with a polyester resin and pigment dispersibility may be deteriorated, and when it is more than 80% by weight, weather resistance, which is an advantage of acrylic resin, may be deteriorated.

The polyester resin may be a carboxylated polyester containing a carboxyl group. In addition, the polyester resin may have a molecular weight (Mw) of 3,000 to 20,000.

The carboxylated polyester resin may have the structure of Formula 3 below.

[Formula 3]

In the above formula, n may be an integer from 10 to 80.

When the molecular weight of the carboxylated polyester is less than 3000, adhesion, impact resistance, and the like may be deteriorated, and when it exceeds 20000, viscosity may increase and workability may be deteriorated, making it difficult to apply to a continuous process.

The resin component may include an acrylic copolymer resin: polyester resin in a weight ratio of 1:0.3 to 2.

When the weight ratio of the acrylic copolymer resin: polyester resin is less than 1:0.3, compatibility with the polyester resin and pigment dispersibility may be deteriorated, and when it is greater than 1:2, weather resistance, which is an advantage of the acrylic resin, may be deteriorated.

The curing agent may be one having an amide group. The curing agent having an amide group may be hydroxyalkylamine.

The composition according to the present invention may include 2 to 10 parts by weight, or 2 to 7 parts by weight of the curing agent, based on 100 parts by weight of the resin component composed of the acrylic copolymer resin and the polyester resin in a ratio of 1:0.3 to 2% by weight. . When the content of the curing agent is less than 2 parts by weight, the degree of crosslinking is low, and thus hardness, tensile strength, etc. may be lowered, and when it is more than 10 parts by weight, crosslinking degree may increase and cracks may occur.

The composition according to the present invention may further include at least one selected from catalysts, flow control additives and pigments.

As the pigment, calcium carbonate, silica, aluminum oxide, carbon black, TiO ₂ and the like can be used, and in particular, TiO ₂ can be used.

The composition according to the present invention may contain 0.5 to 3 parts by weight of a flow control additive with respect to 100 parts by weight of the total amount of the acrylic copolymer resin, the polyester resin and the curing agent. When the content of the additive is less than 0.5 part by weight, the flowability of the resin may be deteriorated, and when it is more than 3 parts by weight, the storage property of the resin may be deteriorated.

The composition according to the present invention may contain 0.05 to 1.5 parts by weight of the catalyst with respect to 100 parts by weight of the total amount of the polyester resin, the acid-modified polypropylene resin, and the curing agent. When the content of the catalyst is less than 0.05 parts by weight, the reactivity may decrease, and when it exceeds 1.5 parts by weight, the viscosity of the resin may be excessively increased by overreaction.

The composition according to the present invention may contain 50 to 95 parts by weight of a pigment with respect to 100 parts by weight of the total amount of the polyester resin, the acid-modified polypropylene resin and the curing agent. When the content of the pigment is less than 50 parts by weight, coating film hardness and scratch performance may be deteriorated, and when it exceeds 95 parts by weight, flexibility and leveling property of the coating film may be deteriorated.

The powder coating composition according to the present invention can be used as automobile paint. In particular, the powder coating composition according to the present invention was applied to an acrylic resin with an unsaturated polyalkylene glycol monomer to impart compatibility with a polyester resin. Accordingly, it has the advantages of hardness and acid corrosion resistance, which are the advantages of the polyester resin, and improves dispersibility with the pigment, thereby enabling various uses for automotive coatings.

Hereinafter, the operation and effect of the invention will be described in more detail through specific examples of the invention. However, this is provided as an example of the invention, and the scope of the invention is not limited in any way.

Example

<Production Example> Preparation of acrylic copolymer resin

In a 2-liter reactor equipped with a stirrer, a 4-neck flask, and a condenser, 100 g of methacrylate, 50 g of vinyl polyalkylene glycol (molecular weight 300), 5 g of benzoic peroxide and 3 g of 3-MPA (3-mercaptopropionic acid) were charged, and the reactor Was heated to 120° C. under normal pressure and reacted over 4 hours. After completion of the reaction, an acrylic copolymer resin was prepared by standing for 2 hours and aging.

Example 1

Acrylic copolymer resin obtained in Preparation Example 1 360g, Crylcoat 7630 (Cytec Co.) 240g, VESTAGON HA 320 (Evonik Co., hydroxyalkylamide crosslinking agent) 30g, Benzoin (Catalyst, Estron chemical Co.) 2g, 8 g of MODAFLOW® POWDER III (flow control additive, manufactured by Cytec), and 540 g of Ti-pure R-706 (TiO2, manufactured by Dupont) were added to a 3 liter can, and then premixed with a high-speed stirrer. Melt and mix uniformly in an extruder in the range of 100-130° C., and cool the mixture on a cooling roller. Subsequently, a powder coating composition having an average particle size of 20 to 60 micrometers was prepared by grinding through a hammer mill or a fritz mill, and then passing through a sieve. The powder coating composition was applied to a pre-treated 0.9mm rolled steel sheet, and thermally cured to prepare a coated film specimen having a thickness of about 90 micrometers to measure each property.

Example 2

A powder coating composition was prepared in the same manner as in Example 1, except that 300 g of the acrylic copolymer resin obtained in Preparation Example 1 and 300 g of Crylcoat 7630 (manufactured by Cytec) were used as the resin. Thereafter, the physical properties of the powder coating composition were measured in the same manner as in Example 1.

Example 3

A powder coating composition was prepared in the same manner as in Example 1, except that 240 g of the acrylic copolymer resin obtained in Preparation Example 1 and 360 g of Crylcoat 7630 (manufactured by Cytec) were used as the resin. Thereafter, the physical properties of the powder coating composition were measured in the same manner as in Example 1.

Comparative Example 1

A powder coating composition was prepared in the same manner as in Example 1, except that 600 g of Crylcoat 7630 (manufactured by Cytec) was used as the resin. Thereafter, the physical properties of the powder coating composition were measured in the same manner as in Example 1.

Comparative Example 2

A powder coating composition was prepared as in Example 1, except that 300 g of Almatex PD-4418 (manufactured by Anderson Development) was used as the resin and 35 g of DDDA was used as a curing agent. Thereafter, the physical properties of the powder coating composition were measured in the same manner as in Example 1.

Table 1 below shows the composition of each component used in Examples and Comparative Examples.

<Experimental Example>

For the powder coating compositions prepared in Examples and Comparative Examples, the appearance, adhesion, hardness, acid resistance and accelerated weather resistance are measured by the following experimental methods. The measurement results are shown in Table 2 below.

Appearance: The smoothness and defects of the coating film were visually determined.

Adhesion: After making 3 cross cuts of 1*1mm and peeling off 3 times with Nichiban tape (manufactured by Nichiban, product name CT-24, standard 24mm*35m), a square grid that remains without detachment among 100 squares Numbers were expressed as numbers.

Hardness: The hardness of the coating film was evaluated using a pencil hardness tester according to the method according to ASTM D3363.

Acid resistance: After coating a 5% hydrochloric acid solution on the coating film, the surface is covered with a cover glass, and after standing at room temperature for 4 hours, the state of the coating film is evaluated.

The evaluation score was set to a high value for which there was no change in the appearance of the coating and a low value for peeling, that is, a case where there was no change in the appearance of the coating was set to 5, and a case where staining of the coating appearance was caused by acid was set to 3.

Accelerated weather resistance: Using Weather-0-Meter (manufactured by Xenon-Arc), the specimen is taken out after 500 hours of exposure to a wavelength of 340 nm UV, washed with a neutral detergent, and compared to the initial gloss of the coated film compared to the gloss after processing the specimen to maintain the gloss. And the color difference value (ΔE).

As can be seen from Table 2, according to the present invention, by using an acrylic copolymer resin prepared by polymerizing an acrylic monomer and an unsaturated polyalkylene glycol monomer, to obtain a powder coating composition having water resistance, acid resistance and excellent hardness Can be. In addition, the conventionally used acrylic resin was mainly used only for transparent applications, but in the present invention, the dispersibility with pigments can also be improved, so that various applications can be developed for automotive paints.

Claims (5)

A resin component comprising an acrylic copolymer resin obtained by polymerizing an acrylic monomer and an unsaturated polyalkylene glycol monomer, and a polyester resin; And
A powder coating composition comprising a curing agent. The powder coating composition of claim 1, wherein the acrylic copolymer resin and the polyester resin contain 2 to 10 parts by weight of a curing agent with respect to 100 parts by weight of the resin component composed of a 1:0.3 to 2 weight ratio. The powder coating composition according to claim 1 or 2, further comprising at least one selected from catalysts, flow control additives, and pigments. The powder coating composition according to claim 1 or 2, wherein the unsaturated polyalkylene glycol monomer is included in an amount of 15 to 80% by weight based on the weight of the acrylic copolymer resin. The powder coating composition according to claim 1 or 2, wherein the unsaturated polyalkylene glycol monomer has an average added molar number of oxyalkylene groups of 2 to 50.

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