KR102327893B1 - Powder Coating Composition - Google Patents

Abstract

The present invention relates to a powder coating composition capable of securing excellent weather resistance and mechanical properties while realizing a matte appearance.

Description

Powder Coating Composition

The present invention relates to a powder coating composition capable of securing excellent weather resistance and mechanical properties while realizing a matte appearance.

Recently, the use of powder coating compositions having matte or low gloss properties is increasing in order to improve the appearance and marketability of automobiles. is increasing to

The powder coating composition includes various kinds of curing agents in order to secure physical properties such as flexibility and heat resistance of the coating film and to control the smooth curing reaction and speed of the coating composition. For example, triglycidyl isocyanurate has been widely used as a curing agent in the field of matte powder coating compositions because of its excellent weather resistance and mechanical properties and easy low-temperature curing. However, triglycidyl isocyanurate is classified as a toxic substance with strong genetic variability, and thus the scope of its use is gradually limited.

Research to replace the triglycidyl isocyanurate curing agent is continuing. For example, in Korean Patent Laid-Open No. 10-2007-0092586, in order to realize low gloss and secure mechanical properties such as impact resistance and adhesion, polyethylene wax, mer Disclosed is a powder coating composition comprising captobenzothiazole, an acrylate monomer and a styrene monomer. However, the paint lacks weather resistance and does not satisfy the matte properties required in the recent automobile parts field.

The present invention provides a powder coating composition that can secure excellent weather resistance and mechanical properties while realizing a matte appearance.

The present invention provides a first composition comprising a first polyester resin, a curing agent, and an ultraviolet absorber; and a second composition comprising a second polyester resin, a curing agent, and a UV absorber, wherein the powder coating composition includes a benzotriazole-based compound and a triazine-based compound as a UV absorber. .

The present invention provides a powder coating composition capable of securing excellent weather resistance and mechanical properties while realizing a matte appearance. The powder coating composition according to the present invention is environmentally friendly by applying a non-toxic curing agent, and can implement excellent weather resistance and matte appearance, so it is suitable for application to automotive exterior parts (eg, wipers).

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated. However, it is not limited only by the following content, and each component may be variously modified or selectively mixed as needed. Accordingly, it should be understood to include all modifications, equivalents and substitutes included in the spirit and scope of the present invention.

The powder coating composition according to the present invention comprises: a first composition comprising a first polyester resin, a curing agent, and an ultraviolet absorber; and a second composition including a second polyester resin, a curing agent, and a UV absorber, wherein the powder coating composition includes a benzotriazole-based compound and a triazine-based compound as the UV absorber. The powder coating composition of the present invention may further include pigments and additives commonly used in the powder coating field, if necessary. Hereinafter, the composition of the powder coating composition of the present invention will be described.

polyester resin

The powder coating composition according to the present invention includes a polyester resin as a main resin. The polyester resin reacts with the curing agent to form a coating film, and serves to secure the basic properties of the coating film, high corrosion resistance, workability, chemical resistance, hardness, and adhesion.

The polyester resin may be a carboxyl polyester resin having a carboxyl (-COOH) group at the polymer terminal. The carboxyl polyester resin has a crosslinked structure introduced therein, and is prepared by polymerizing at least one of monomers and polymers having a hydroxyl group as a terminal functional group and at least one of monomers and polymers having a carboxyl group as a terminal functional group under a catalyst. it could be

The monomer having the hydroxyl group as a terminal functional group may include a polyfunctional alcohol, and the polyfunctional alcohol may be a difunctional or more, for example, 2 to tetrafunctional alcohol. The type of the polyfunctional alcohol is not particularly limited, and for example, ethylene glycol, diethylene glycol, triethylene glycol, propylene glycol, and trimethylolpropane. ), methyl propanediol, pentaethylene glycol, tripropylene glycol, cyclohexanedimethanol, 1,2-butylene glycol, One selected from the group consisting of neopentyl glycol, 1,6-hexanediol, and glycerol or a mixture thereof may be used.

The polymer having the hydroxyl group as a terminal functional group may be prepared by polymerizing a monomer having the hydroxyl group as a terminal functional group. The type of the polymer having the hydroxyl group as a terminal functional group is not particularly limited, and for example, one selected from the group consisting of polyethylene glycol and poly propylene glycol or a mixture thereof may be used. have. The polymer having the hydroxyl group as a terminal functional group may contain 1 to 20 parts by weight, for example, 1 to 10 parts by weight, of the polyfunctional alcohol based on 100 parts by weight of the total polymerization unit.

The monomer having the carboxyl group as a terminal functional group may include a polyfunctional acid, and the polyfunctional acid may be a difunctional or more, for example, 2 to tetrafunctional acid. The type of the polyfunctional acid is not particularly limited, for example, terephthalic acid, isophthalic acid, 1,4-cyclohexanedicarboxylic acid (1,4-Cyclohexane dicarboxylic acid), adipic acid (Adipic acid), sebacic acid, phthalic anhydride, trimellitic anhydride, benzoic acid, one selected from the group consisting of tetrahydrophthalic anhydride, or Mixtures thereof may be used. For example, the polyfunctional acid may be isophthalic acid. When the polyfunctional acid of the polyester resin includes isophthalic acid, excellent weather resistance and matte appearance may be secured.

The polymer having the carboxyl group as a terminal functional group may be prepared by polymerizing a monomer having the carboxyl group as a terminal functional group.

In the present invention, two or more types of polyester resins having different acid values and viscosities may be mixed as the polyester resin. By mixing polyester resins having different acid values and viscosities, excellent workability, corrosion resistance, adhesion, weather resistance and appearance can be secured.

The polyester resin has an acid value of 10 to 30 mgKOH/g, for example, 15 to 25 mgKOH/g of a first polyester resin and an acid value of 40 to 70 mgKOH/g, for example, 50 to 62 mgKOH/g. 2 It may include a polyester resin. If the acid values of the first polyester resin and the second polyester resin exceed the above range, the implementation of matte gloss may be limited or the pinhole phenomenon may be severe due to moisture generation according to the condensation reaction. Physical properties may be deteriorated, and there may be problems in that weather resistance and corrosion resistance are deteriorated.

As an example, the viscosity of the first polyester resin (200 ℃, ICI viscometer) may be 30 to 70 poise, for example, 40 to 60 poise, and the viscosity of the second polyester resin (200 ℃, ICI viscometer) is 10 to 50 poise, for example 20 to 40 poise. When the viscosity of the first polyester resin and the second polyester resin satisfies the above ranges, flowability and dispersibility are excellent, and workability of the coating composition can be secured.

The content of the first polyester resin may be 60 to 90% by weight, for example, 65 to 85% by weight, based on the total weight of the first composition including the first polyester resin. The content of the second polyester resin may be 60 to 90% by weight, for example, 65 to 85% by weight, based on the total weight of the second composition including the second polyester resin. When the content of the first polyester resin and the second polyester resin falls within the above-described ranges, the basic physical properties of the coating film are good, excellent corrosion resistance, chemical resistance and appearance characteristics are expressed, and adhesion with other substrate layers can be improved

The content of the polyester resin may be 60 to 90% by weight, for example, 65 to 85% by weight, based on the total weight of the powder coating composition. When the content of the polyester resin falls within the above-described range, the basic physical properties of the coating film are good, excellent corrosion resistance, chemical resistance and appearance characteristics can be expressed, and adhesion with other substrate layers can be improved.

hardener

The powder coating composition according to the present invention includes a curing agent. The curing agent causes a curing reaction with the polyester resin to prevent deformation due to heat, and serves to increase the adhesion strength of the coating film.

For example, the curing agent may include a hydroxy alkyl amide resin. The hydroxyalkyl amide resin may improve mechanical properties and scratch resistance by improving the flexibility and crosslinking density of the coating film through condensation or addition reaction with the polyester resin.

In the powder coating composition according to the present invention, the curing rate of the first composition including the first polyester resin and the curing rate of the second composition including the second polyester resin may be different. For example, the curing reaction of the first composition may proceed at a slow rate, for example, 140 seconds or more, and the curing reaction of the second composition may proceed at a high rate, for example, within 50 seconds.

The content of the curing agent included in the first composition may be 0.1 to 10% by weight, for example, 1 to 5% by weight, based on the total weight of the first composition, and the content of the curing agent included in the second composition is the second It may be 0.1 to 20% by weight, for example 5 to 15% by weight, based on the total weight of the composition. When the content of the curing agent in the first composition is less than the above range, the adhesion of the coating film may decrease due to a decrease in the crosslinking density, and when the content of the curing agent in the second composition exceeds the above range, pinholes may occur and deterioration of external physical properties may occur.

The content of the curing agent may be 1 to 15% by weight, for example, 2 to 10% by weight, based on the total weight of the powder coating composition. When the content of the curing agent is less than 1% by weight, the degree of curing, corrosion resistance, chemical resistance, etc. of the coating film may be reduced, and if it exceeds 15% by weight, processability of the coating film may be deteriorated.

UV absorber

The powder coating composition according to the present invention includes two types of ultraviolet absorbers. The type of the ultraviolet absorber is not particularly limited, and for example, a mixture of benzotriazole-based and triazine-based compounds may be used.

The benzotriazole-based UV absorber is not particularly limited as long as it is a compound derived from benzotriazole, for example, 2(2'-hydroxy-5'-methyl-phenyl)benzotriazole, (2'-hydroxy-5 '-phenyl)benzotriazole, 2-(2'-hydroxy-4-(2-ethylhexyl)phenoxy)benzotriazole or compounds derived from the above compounds may be used.

Examples of the triazine-based ultraviolet absorber include 6-[bis(2,4-dimethylphenyl)-1,3,5-triazine, 6-[bis(2,4-dimethylphenyl)-1,3, 5-triazine, compounds derived from hydroxyphenyl-s-triazine, such as tris[2,4,6-[2-{4-(octyl-2-methylethanoate)oxy-2hydroxyphenyl} ]-1,3,5-triazine compound and the like may be used, but is not limited thereto.

The molecular weight of the ultraviolet absorber is not particularly limited, but for example, the molecular weight of the benzotriazole-based ultraviolet absorber may be 300 g/mol or more, for example, 310 to 600 g/mol, and the molecular weight of the triazine-based compound is 450 g /mol or more, for example 550 to 700 g/mol. When the molecular weight of the ultraviolet absorber satisfies the above-mentioned range, durability and weather resistance of the coating film may be improved.

The range of the wavelength that the ultraviolet absorber absorbs is not particularly limited, but, for example, among ultraviolet absorbers that absorb wavelengths in the UVA (320 to 400 nm) region, and ultraviolet absorbers that absorb wavelengths in the UVB (280 to 320 nm) region. One or more types may be used. For example, an ultraviolet absorber that absorbs a wavelength of a UVA (320 to 400 nm) region and a UV absorber that absorbs a wavelength of a UVB (280 to 320 nm) region may be mixed and used.

The content of the ultraviolet absorber included in the first composition may be 1 to 10% by weight, for example, 1 to 5% by weight, based on the total weight of the first composition, and the content of the ultraviolet absorber included in the second composition is Based on the total weight of the second composition, 1 to 10% by weight, for example, 5 to 10% by weight. When the content of the ultraviolet absorber of the first composition and the content of the ultraviolet absorber of the second composition are out of the above ranges, deterioration of weather resistance may occur.

The content of the ultraviolet absorber may be 1 to 10% by weight, for example, 1 to 5% by weight, based on the total weight of the powder coating composition. When the content of the ultraviolet absorber satisfies the above-mentioned range, the weather resistance and accelerated weather resistance (WOM) of the powder coating composition may be improved.

pigment

The powder coating composition of the present invention may include conventional pigments known in the art, such as extender pigments, colored pigments, or mixtures thereof.

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

As the extender pigment, those commonly used in powder coating compositions may be used without limitation, and non-limiting examples include calcium carbonate, clay, talc, magnesium silicate, kaolin, mica, silica, aluminum silicate, aluminum hydroxide, sulfuric acid. barium, etc. The above-mentioned components may be used alone or two or more may be used in combination.

Colored pigments can be used to express a desired color (colored) in powder coatings or to increase the strength or gloss of a coating film. As these pigments, organic pigments, inorganic pigments, metallic pigments, aluminum-paste, pearls, etc. commonly used in powder coatings may be used without limitation, and these may be used alone or in combination of two or more. can Non-limiting examples of usable pigments include azo-based, phthalocyanine-based, iron oxide-based, cobalt-based, carbonate-based, sulfate-based, silicate-based, chromate-based pigments and the like, for example, titanium dioxide, zinc oxide, bismuth vanadate. , cyanine green, carbon black, iron oxide, iron sulfur oxide, navy blue, cyanine blue, and mixtures of two or more thereof.

The pigment may be included in an amount of 1 to 40% by weight, for example, 5 to 25% by weight, based on the total weight of the powder coating composition. When the content of the pigment is within the aforementioned range, the color expression of the coating film may be excellent, and mechanical properties, impact resistance, adhesion, and the like of the coating film may be improved.

additive

The powder coating composition of the present invention may optionally further include additives commonly used in the powder coating field within a range that does not impair the intrinsic properties of the composition.

Non-limiting examples of additives usable in the present invention include leveling agents, pinhole inhibitors, waxes, stress reducing agents, dispersing agents, flow improving agents, cratering inhibitors, coupling agents, gloss control agents, adhesion improving agents, flame retardants, matting agents, etc. There are, these may be used alone or two or more of them may be used in combination.

The leveling agent is to improve the appearance characteristics of the coating film while enhancing adhesion in the composition by leveling the coating composition so that it is coated evenly and smoothly. For example, there are acrylic, silicone, polyester, amine-based leveling agents, and the like, but is not particularly limited thereto.

The pinhole inhibitor may cause volatile substances to be released from the coating film during the curing process, thereby preventing pinholes in the coating film and improving the appearance characteristics. Non-limiting examples of pinhole inhibitors include amide-based, polypropylene-based, and stearic acid-based pinhole-blocking agents. For example, the pinhole inhibitor may be benzoin or a mixture of benzoin and an amide-based pinhole inhibitor.

Other additives that can be used include light stabilizers (such as HALS), antioxidants (such as phenolic antioxidants), heat stabilizers (such as phenolic heat stabilizers), wetting agents (such as polyether-modified polydimethylsiloxane), lubricants, surface conditioners, surfactants, defoamers (eg, dimethylpolysiloxane), slip agents, stain inhibitors, softeners, thickeners, polymers, waxes, and the like. These may be used alone or two or more of them may be used in combination. These additive components enhance the workability of the paint and the smoothness of the paint film.

The additive may be appropriately added within a content range known in the art, for example, may be included in an amount of 0.1 to 10% by weight based on the total weight of the powder coating composition. When the content of the additive is within the above-described range, the appearance and hardness of the coating film may be improved.

The powder coating composition according to the present invention comprises: a first composition comprising a first polyester resin, a curing agent, and an ultraviolet absorber; and a second composition including a second polyester resin, a curing agent, and an ultraviolet absorber, wherein the powder coating composition includes a benzotriazole-based compound and a triazine-based compound as an ultraviolet absorber. The mixing ratio of the first composition and the second composition is not particularly limited, but may be 40: 60 to 60: 40, for example, 45: 55 to 55: 45 by weight. When the mixing ratio of the first composition and the second composition satisfies the above-mentioned range, a matte surface can be effectively implemented.

The powder coating composition according to the present invention may be prepared by a method known in the art, and for example, may be prepared through processes such as raw material basis weight, dry pre-mixing, dispersion and coarse pulverization, pulverization and classification.

For example, a raw material mixture containing a polyester resin, a curing agent, an ultraviolet absorber, and optionally a pigment, an additive, etc. is put into a container mixer and uniformly mixed, and the mixed composition is melt-mixed and then pulverized. have. For example, the raw material mixture is melt-dispersed at 70 to 130° C. by a melt-kneading device such as a kneader or an extruder to produce chips with a predetermined thickness (eg, 1 to 5 mm). Thereafter, the prepared chips are pulverized to a range of 40 to 80 μm using a grinding device such as a high-speed mixer, and then classified to prepare a powder coating composition.

The classification process is not particularly limited, and, for example, may be filtered with 80 to 120 mesh. Accordingly, it is possible to obtain a powder coating having an average particle size in the range of 25 to 55 μm. The average particle diameter of the powder is not particularly limited, but when it satisfies the above-described range, coating workability and appearance characteristics of the coating film may be improved.

In order to improve the fluidity of the powder coating, the surface of the powder coating particles according to the present invention may be coated with a fine powder such as silica. As a method of performing such a treatment, a pulverizing mixing method in which fine powder is added while mixing, or a dry mixing method using a Henschel mixer or the like can be used.

Hereinafter, the present invention will be described in more detail through examples. However, the following examples are provided to help the understanding of the present invention, and the scope of the present invention is not limited to the examples in any sense.

[Example 1-5]

According to the composition shown in Table 1 below, each component was put into a mixing tank and premixed, and then melt-dispersed at 100° C. in a disperser to prepare chips. The prepared chips were pulverized with a high-speed mixer to prepare a first composition and a second composition having an average particle size of 25 to 55 μm, and then the first composition and the second composition were mixed in a weight ratio of 50:50 to obtain the results of Examples 1-5. A powder coating composition was prepared. In Table 1 below, the usage unit of each composition is weight %.

[Example 6-10]

According to the composition shown in Table 2 below, each component was put into a mixing tank and premixed, and then melt-dispersed in a disperser at 100° C. to prepare chips. The prepared chips were pulverized with a high-speed mixer to prepare a first composition and a second composition having an average particle size of 25 to 55 μm, and then the first composition and the second composition were mixed in a weight ratio of 45:55 to obtain the results of Examples 6-10. A powder coating composition was prepared. In Table 2 below, the usage unit of each composition is % by weight.

[Example 11-13]

According to the composition shown in Table 3 below, each component was put into a mixing tank and premixed, and then melt-dispersed at 100 °C in a disperser to prepare chips. The prepared chips were pulverized with a high-speed mixer to prepare a first composition and a second composition having an average particle size of 25 to 55 μm, and then the first composition and the second composition were mixed in a weight ratio of 60:40 to obtain the results of Examples 11-13. A powder coating composition was prepared. In Table 3 below, the usage unit of each composition is % by weight.

[Comparative Example 1-6]

A powder coating composition of Comparative Example 1-6 was prepared in the same manner as in Examples 1-5, except that it was prepared according to the compositions shown in Tables 4 and 5 below.

Polyester resin 1: carboxyl-terminated polyester resin (acid value 20 mgKOH/g, viscosity (200°C, ICI viscometer) 53 poise)

Polyester resin 2: carboxyl-terminated polyester resin (acid value 15 mgKOH/g, viscosity (200°C, ICI viscometer) 40 poise)

Polyester resin 3: carboxyl-terminated polyester resin (acid value 25 mgKOH/g, viscosity (200°C, ICI viscometer) 60 poise)

Polyester resin 4: carboxyl-terminated polyester resin (acid value 50 mgKOH/g, viscosity (200°C, ICI viscometer) 24 poise)

Polyester resin 5: carboxyl-terminated polyester resin (acid value 62 mgKOH/g, viscosity (200°C, ICI viscometer) 16 poise)

Polyester resin 6: carboxyl-terminated polyester resin (acid value 55 mgKOH/g, viscosity (200°C, ICI viscometer) 33 poise)

Polyester resin 7: carboxyl-terminated polyester resin (acid value 5 mgKOH/g, viscosity (200°C, ICI viscometer) 60 poise)

Polyester resin 8: carboxyl-terminated polyester resin (acid value 75 mgKOH/g, viscosity (200°C, ICI viscometer) 20 poise)

Curing Agent: Hydroxyalkyl Amide Curing Agent (Hydrogen Equivalents (HEW): 84)

UV absorber 1: benzotriazole (molecular weight: 316 g/mol)

UV absorber 2: benzotriazole (molecular weight: 560 g/mol)

UV absorber 3: benzotriazole (molecular weight: 442 g/mol)

UV absorber 4: hydroxyphenyl-s-triazine (molecular weight: 630 g/mol)

UV absorber 5: hydroxyphenyl-s-triazine (molecular weight: 678 g/mol)

UV absorber 6: hydroxyphenyl-s-triazine (molecular weight: 584 g/mol)

Extender pigment: Heavylite (Sibelco)

Colored pigment: carbon black (orion engineered carbon)

Additive 1: Leveling agent (Estron)

Additive 2: Benzoin (Miwon Specialty Chemicals)

Additive 3: Antioxidant (Double bond chemical)

Additive 4: HALS (BASF)

Additive 5: Matting wax (Sibelco)

[Experimental Example - Evaluation of Physical Properties]

The physical properties of the powder coating compositions prepared in Examples 1-13 and Comparative Examples 1-6, respectively, were measured as follows, and the results are shown in Tables 6 to 10 below.

Specimen preparation

75 mm (horizontal) Х150 mm (length) Х0.4 mm (thickness) of aluminum was prepared and treated with chromate to prepare a specimen. On the prepared specimens, the powder coating compositions according to Examples 1-13 and Comparative Examples 1-6 were respectively electrostatically spray coated to form a coating film having a thickness of 60 to 80 μm.

gel time

0.1 g of the powder coating composition according to Example 1-13 and Comparative Example 1-6 was heated with a hot plate at 205° C., and the time (sec) it took to become a liquid and then harden was measured.

Polish

The gloss of the coating film formed on each specimen was measured using a BYK Glossmeter.

(Less than 25%: Excellent, 25% or more and less than 30%: Good, 30% or more: Poor)

adherence

According to ISO 2409, 10 cells were made at intervals of 1 mm in each specimen, and the degree of peeling was observed after the adhesive test of the tape.

(No peeling: Pass, Peeling: Fail)

pinhole

Using the powder coating compositions according to Examples 1-13 and Comparative Examples 1-6, the thickness of the coating film in which the pinhole was generated was measured.

(130 μm or more: good, 120 μm or more and less than 130 μm: normal, less than 120 μm: poor)

Accelerated Weathering (QUV-B)

1) According to ASTM G154, each specimen was irradiated for 700 hours in a UVB 313 lamp area, and then gloss was measured. Gloss retention was calculated by comparing the gloss of the specimen coating film before and after the test.

(65% or more: Excellent, 55% or more and less than 65%: Good, 50% or more and less than 55%: Normal, 50% or less: Poor)

2) According to ASTM G154, each specimen was irradiated for 500 hours in the UVB 313 lamp area, and then gloss was measured. Gloss retention was calculated by comparing the gloss of the specimen coating film before and after the test.

(80% or more: Excellent, 70% or more and less than 80%: Good, 50% or more and less than 70%: Normal, 50% or less: Poor)

Accelerated Weatherability (WOM)

According to SAE J2527, each specimen was subjected to a 3,000 KJ test, and then gloss was measured. Gloss retention was calculated by comparing the gloss of the specimen coating film before and after the test.

(80% or more: Excellent, 70% or more and less than 80%: Good, 50% or more and less than 70%: Normal, 50% or less: Poor)

As shown in Tables 6 to 10, the coating film formed of the powder coating composition of Examples 1-13 according to the present invention was generally superior in physical properties to the coating film formed of the powder coating composition of Comparative Examples 1-6. In particular, it was confirmed that the coating film formed of the powder coating composition of Examples 1-13 secured matt properties and had excellent weather resistance.

Claims (4)

A first composition comprising a first polyester resin, a curing agent and a UV absorber and a second composition comprising a second polyester resin, a curing agent and a UV absorber,
The first polyester resin has an acid value of 15 to 25 mgKOH/g, and the second polyester resin has an acid value of 50 to 62 mgKOH/g,
The powder coating composition comprises a benzotriazole-based compound and a triazine-based compound as ultraviolet absorbers. The powder coating composition according to claim 1, wherein the viscosity (200 °C, ICI viscometer) of the first polyester resin is 30 to 70 poise, and the viscosity (200 °C, ICI viscometer) of the second polyester resin is 10 to 50 poise. . According to claim 1, wherein the first composition comprises 60 to 90% by weight of the first polyester resin, 0.1 to 10% by weight of the curing agent, and 1 to 10% by weight of the ultraviolet absorber,
The second composition is a powder coating composition comprising 60 to 90% by weight of a second polyester resin, 0.1 to 20% by weight of a curing agent, and 1 to 10% by weight of a UV absorber. The powder coating composition according to claim 1, wherein the mixing ratio of the first composition and the second composition is 40:60 to 60:40 by weight.