JP2021195383A - Powder coating composition - Google Patents

Abstract

To provide a powder coating composition which enables formation of a coated film excellent in appearance and weather resistance.SOLUTION: A powder coating composition contains, with respect to 100 pts.mass of the total amount of a polyester resin having an acid value of 30-60 mg/KOH and a curing agent, 1.0-15.0 pts.mass of a curing agent, 0.1-5.0 pts.mass of an ultraviolet absorber, 0.1-5.0 pts.mass of a hindered amine-based photostabilizer, and 0.5-5.0 pts.mass of a leveling agent.SELECTED DRAWING: None

Description

The present invention relates to a powder coating composition capable of forming a coating film having excellent appearance and weather resistance.

In general, powder paints are inferior in appearance to solvent-based paints, and therefore have been mainly used in applications where aesthetics are not so required, such as gas cylinders and exteriors of building materials. In recent years, in the paint industry, as an alternative to conventional solvent-based paints, there has been a demand for environment-friendly paints that do not contain volatile organic compounds (VOCs) at all, do not require exhaust treatment or wastewater treatment, and can be recovered and reused. Therefore, there is an increasing need for the development of powder paints with excellent appearance.

Thermosetting resins such as polyester resin, acrylic resin, fluororesin, and epoxy resin are used as the main resin constituting the powder coating. Of these, powder paints containing polyester resin or fluororesin as the main resin have an excellent balance of various performances such as weather resistance and mechanical properties, but have not yet achieved the appearance required by the latest market. On the other hand, powder coating materials mainly composed of epoxy resin have excellent appearance but have difficulty in weather resistance, so that they cannot fully meet the demands of the market. As described above, powder paints having excellent weather resistance or powder paints having excellent appearance are known, but powder paints having both of them highly compatible are not yet known. Is the current situation.

Patent Documents 1 and 2 describe powder coating materials containing a fluororesin and a polyester resin and having excellent weather resistance, but they are not satisfactory in terms of appearance.

Japanese Unexamined Patent Publication No. 2017-179091 Japanese Unexamined Patent Publication No. 2011-11117

An object of the present invention is to provide a powder coating composition capable of forming a coating film having excellent appearance and weather resistance.

As a result of diligent studies, the present inventors have found that a powder coating composition containing a polyester resin having a predetermined acid value, a curing agent, an ultraviolet absorber, and a hindered amine-based light stabilizer has an excellent appearance and is generally used. It was found that it has better weather resistance than the polyester resin-containing powder paint. Furthermore, in a preferred embodiment, they have found that they have good adhesion, impact resistance, coating film hardness, and recoatability, and have completed the present invention.

That is, the present invention [1] contains 1.0 to 15.0 parts by mass of the following component (B) and the following component (C) with respect to 100 parts by mass of the total amount of the following component (A) and the following component (B). A powder coating composition containing 0.1 to 5.0 parts by mass, the following component (D) by 0.1 to 5.0 parts by mass, and the following component (E) by 0.5 to 5.0 parts by mass.
Component (A): Polyester resin having an acid value of 30 to 60 mg / KOH Component (B): Hardener Component (C): UV absorber Component (D): Hindered amine-based light stabilizer Component (E): Leveling agent [2 The powder coating composition according to [1], wherein the polyester resin has a glass transition temperature (Tg) of 50 to 70 ° C.
[3] The powder coating composition according to [1] or [2], wherein the polyester resin has a number average molecular weight (Mn) of 1000 to 10000.
[4] The powder coating composition according to any one of [1] to [3], wherein the curing agent is β-hydroxyalkylamide.
[5] The powder coating composition according to any one of [1] to [4], wherein the ultraviolet absorber is a benzotriazole-based ultraviolet absorber and / or a hydroxyphenyltriazine-based ultraviolet absorber.
[6] The powder coating composition according to any one of [1] to [5], which does not contain an epoxy resin.

According to the present invention, it is possible to provide a powder coating composition capable of forming a coating film having excellent appearance and weather resistance.

<Powder coating composition>
The powder coating composition according to the present embodiment contains a polyester resin having an acid value of 30 to 60 mg / KOH, a curing agent, an ultraviolet absorber, a hindered amine-based light stabilizer, and a leveling agent as essential components. In the present specification, the polyester resin having an acid value of 30 to 60 mg / KOH is "component (A)"; the curing agent is "component (B)"; the ultraviolet absorber is "component (C)"; the hindered amine system. The light stabilizer may be referred to as "component (D)"; the leveling agent may be referred to as "component (E)".

In the present specification, when a numerical range is indicated by using "~", the numerical values at both ends thereof are included.

[Component (A): Polyester resin having an acid value of 30 to 60 mg / KOH]
The powder coating composition according to the present embodiment is characterized by containing a polyester resin having an acid value of 30 to 60 mg / KOH from the viewpoint of forming a coating film having both appearance and weather resistance.

The polyester resin according to the present embodiment can be produced, for example, by an esterification reaction or a transesterification reaction with a polybasic acid component and a polyhydric alcohol component.

As the polybasic acid component, for example, alicyclic polybasic acid, aliphatic polybasic acid, aromatic polybasic acid and the like can be used, and aromatic polybasic acid is preferable. The polybasic acid component may be an acid anhydride, an ester, or the like, which is equivalent to the polybasic acid in the reaction system. That is, the polyester resin typically contains a structural unit derived from a polybasic acid and a structural unit derived from a polyhydric alcohol.

The alicyclic polybasic acid is generally a compound having one or more alicyclic structures (mainly 4- to 6-membered rings) and two or more carboxyl groups in one molecule, and is, for example, 1,2-cyclohexanedicarboxylic. Acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 4-cyclohexene-1,2-dicarboxylic acid, 3-methyl-1,2-cyclohexanedicarboxylic acid, 4-methyl-1,2-cyclohexane Examples thereof include dicarboxylic acid, 1,2,4-cyclohexanetricarboxylic acid, 1,3,5-cyclohexanetricarboxylic acid, 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid. , And 4-cyclohexene-1,2-dicarboxylic acid is preferred, and 1,2-cyclohexanedicarboxylic acid is more preferred. These can be used alone or in combination of two or more.

The aliphatic polybasic acid is generally an aliphatic compound having two or more carboxyl groups in one molecule, and a dicarboxylic acid having an alkylene chain having 4 to 18 carbon atoms is preferable. Specific examples of the aliphatic polybasic acid component include succinic acid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brushic acid, octadecanedioic acid, and the like. Examples include citric acid. These can be used alone or in combination of two or more.

The aromatic polybasic acid is generally an aromatic compound having two or more carboxyl groups in one molecule, and is, for example, phthalic acid, isophthalic acid, terephthalic acid, naphthalenedicarboxylic acid, 4,4'-biphenyldicarboxylic acid. Examples thereof include acids, trimellitic acids and pyromellitic acids, with terephthalic acid, isophthalic acid, trimellitic acid and anhydrous phthalic acid being preferred. These can be used alone or in combination of two or more.

As the polyhydric alcohol component, a polyhydric alcohol having two or more hydroxyl groups in one molecule can be preferably used. Examples of the polyhydric alcohol include alicyclic diols, aliphatic diols, aromatic diols, and trihydric or higher polyhydric alcohols.

The alicyclic diol is generally a compound having one or more alicyclic structures (mainly 4- to 6-membered rings) and two hydroxyl groups in one molecule, and is, for example, 1,4-cyclohexanedimethanol, tri. Dihydric alcohols such as cyclodecanedimethanol, hydrogenated bisphenol A, and hydrogenated bisphenol F; polylactone diols obtained by adding a lactone compound such as ε-caprolactone to these dihydric alcohols can be mentioned. These can be used alone or in combination of two or more.

The aliphatic diol is generally an aliphatic compound having two hydroxyl groups in the molecule, and is, for example, ethylene glycol, propylene glycol, diethylene glycol, trimethylene glycol, tetraethylene glycol, triethylene glycol, dipropylene glycol, 1, 4-butanediol, 1,3-butanediol, 2,3-butanediol, 1,2-butanediol, 3-methyl-1,2-butanediol, 2-butyl-2-ethyl-1,3-propane Diol, 1,2-pentanediol, 1,5-pentanediol, 1,4-pentanediol, 2,4-pentanediol, 2,3-dimethyltrimethylethylene glycol, tetramethylene glycol, 3-methyl-1,5 -Pentanediol, 2,2,4-trimethyl-1,3-pentanediol, 1,6-hexanediol, 1,5-hexanediol, 1,4-hexanediol, 2,5-hexanediol, 1,9 -Nonandiol, 1,10-decanediol, 1,12-dodecanediol, neopentyl glycol; polyether diol compounds such as polyethylene glycol, polypropylene glycol, polybutylene glycol and the like can be mentioned, with ethylene glycol and neopentyl glycol being preferred. .. These can be used alone or in combination of two or more.

Aromatic diols are generally aromatic compounds having two hydroxyl groups in one molecule. Examples of the aromatic diol include an ester diol compound such as bis (hydroxyethyl) terephthalate; and an alkylene oxide adduct of bisphenol A. These can be used alone or in combination of two or more.

Examples of the trihydric or higher polyhydric alcohol include glycerin, trimethylolethane, trimethylolpropane, diglycerin, triglycerin, 1,2,6-hexanetriol, pentaerythritol, dipentaerythritol, sorbitol, and mannit. Trivalent or higher alcohols; polylactone polyol compounds obtained by adding a lactone compound such as ε-caprolactone to these trihydric or higher alcohols; tris (2-hydroxyethyl) isocyanurate, tris (2-hydroxypropyl) isocyanurate, Examples thereof include tris (hydroxyalkyl) isocyanurate such as tris (2-hydroxybutyl) isocyanurate. Of these, trimethylolpropane is particularly preferable.

The method for producing the polyester resin according to the present embodiment is not particularly limited, but for example, the polybasic acid component and the polyhydric alcohol component are reacted in a nitrogen stream at 150 to 250 ° C. for 5 to 10 hours for esterification. It can be produced by carrying out a reaction or a transesterification reaction. During the esterification or transesterification reaction, a catalyst may be used to accelerate the reaction. As the catalyst, known catalysts such as dibutyltin oxide, antimony trioxide, zinc acetate, manganese acetate, cobalt acetate, calcium acetate, lead acetate, tetrabutyl titanate, and tetraisopropyl titanate can be used.

The polyester resin according to the present embodiment can be modified with fatty acids, fats and oils, monoepoxy compounds, monoalcohol compounds, polyisocyanate compounds and the like during the preparation of the resin, or after the esterification reaction or the transesterification reaction.

Examples of fatty acids include palm oil fatty acid, cottonseed oil fatty acid, hemp oil fatty acid, rice bran oil fatty acid, fish oil fatty acid, tall oil fatty acid, soybean oil fatty acid, flaxseed oil fatty acid, tung oil fatty acid, rapeseed oil fatty acid, castor oil fatty acid, and dehydrated castor oil. Fatty acids such as fatty acids and safflower oil fatty acids; lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid and the like can be mentioned.

Examples of fats and oils include palm oil, cottonseed oil, hemp oil, rice bran oil, fish oil, tall oil, soybean oil, flaxseed oil, tung oil, rapeseed oil, castor oil, dehydrated castor oil, safflower oil and the like.

Examples of the polyisocyanate compound used for the above modification include aliphatic diisocyanate compounds such as lysine diisocyanate, hexamethylene diisocyanate, and trimethylhexane diisocyanate; hydrogenated xylylene diisocyanate, isophorone diisocyanate, methylcyclohexane-2,4-diisocyanate, and methylcyclohexane. Alicyclic diisocyanate compounds such as -2,6-diisocyanate, 4,4'-methylenebis (cyclohexylisocyanate), 1,3- (isocyanatomethyl) cyclohexane; aromatics such as tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, etc. Diisocyanate compound; organic polyisocyanate such as trivalent or higher polyisocyanate such as lysine triisocyanate itself, or an adduct of each of these organic polyisocyanates with polyhydric alcohol, low molecular weight polyester resin, water, etc., or each of the above. Examples thereof include cyclized polymers of organic diisocyanates (for example, isocyanurate), billet-type adducts, and the like. These can be used alone or in combination of two or more.

The polyester resin according to this embodiment preferably has an acid group such as a carboxyl group from the viewpoint of having a predetermined acid value. Further, it may have a hydroxyl group, a thiol group, a carboxyl group, an amino group, an amide group, an epoxy group, an isocyanate group, an allyl group and the like. These functional groups can also be adjusted to the selection of the curing agent described later.

The acid value of the polyester resin according to this embodiment is 30 to 60 mgKOH / g, preferably 33 to 60 mgKOH / g. By setting the acid value of the polyester resin in the above range, the appearance and weather resistance can be improved in a well-balanced manner. In the present embodiment, the acid value is based on the alkali neutralization titration using phenolphthalein as an indicator, based on the number of mg of potassium hydroxide required to neutralize the acidic free functional group contained in 1 g of the resin. It is obtained by a conventional method and can be measured by a potential difference titration method (JIS K 0070: 1992).

The number average molecular weight (Mn) of the polyester resin according to the present embodiment is preferably 1000 or more, and more preferably 1500 or more, from the viewpoint of preventing the coating film from becoming hard and brittle and reducing the impact resistance. The number average molecular weight (Mn) of the polyester resin is preferably 10,000 or less, more preferably 7,000 or less, still more preferably 4000 or less, from the viewpoint of preventing the coating film from becoming soft and the surface hardness from decreasing. In the present specification, the number average molecular weight (Mn) can be measured as a standard polystyrene-equivalent value by a gel permeation chromatography (GPC) method.

The glass transition temperature (Tg) of the polyester resin according to the present embodiment is preferably 50 ° C. or higher, more preferably 55 ° C. or higher, from the viewpoint of mechanical properties. The glass transition temperature (Tg) of the polyester resin is preferably 70 ° C. or lower, more preferably 65 ° C. or lower, from the viewpoint of excellent appearance. In the present specification, the glass transition temperature (Tg) is measured by a differential scanning calorimeter (DSC).

The polyester resin can be produced by a known method. Further, those commercially available from DIC Corporation, Daicel Ornex Co., Ltd., Japan U-Pica Co., Ltd., DSM Corporation and the like can also be used. The polyester resins listed above may be used alone or in combination of two or more.

[Component (B): Curing agent]
The powder coating composition according to the present embodiment contains a curing agent together with the polyester resin described above. The polyester resin can form a crosslinked bond by the reaction of the hydroxyl group or carboxyl group of the resin with the curing agent.

Examples of the curing agent that can be used in the present embodiment include β-hydroxyalkylamide, blocked isocyanate, triglycidyl isocyanurate and the like. Blocked isocyanate blocking agents are known to be toxic. In addition, triglycidyl isocyanurate is known to have skin irritation. Considering the safety of the paint and the environmental load, it is preferable to use β-hydroxyalkylamide as a curing agent. When importance is attached to coating film hardness and hydrolysis resistance, it is preferable to use blocked isocyanate as a curing agent. The curing agent may be used alone or in combination of two or more.

The β-hydroxyalkylamide is not particularly limited as long as it is a compound in which a hydroxy group is substituted on the β-position carbon of the amide group. For example, the hydroxy group is substituted on the β-position carbon of the amide group in one molecule. A compound containing one or more (preferably 2 to 6) structures having a structure can be used.

Specific examples of β-hydroxyalkylamide include, for example, N, N-di (β-hydroxyethyl) adipamide, bis (β-hydroxyethyl) adipamide, bis (β-hydroxypropyl) adipamide, and bis [N, N-. Examples thereof include di (β-hydroxyethyl)] adipamide and bis [N, N- (β-hydroxypropyl)] adipamide. Examples of commercially available β-hydroxyalkylamides include Primid XL-552, QM-1260, SF-4510 manufactured by EMS-CHEMIE, PROSID H, S, 411, H30A, H50A manufactured by SIR, and Hungzhou Right Chemical Co., Ltd. HAA Hardner KC522 manufactured by MEGARA RESINS, Magamide XL manufactured by MEGARA RESINS, and the like can be mentioned.

The blocked isocyanate is produced, for example, by reacting a polyisocyanate obtained by reacting an aliphatic, aromatic or aromatic aliphatic diisocyanate with a small molecule compound having active hydrogen with a blocking agent and masking it. Can be done. Examples of the diisocyanate include tolylene diisocyanate, 4,4'-diphenylmethane isocyanate, xylylene diisocyanate, hexamethylene diisocyanate, 4,4'-methylene bis (cyclohexyl isocyanate), methylcyclohexanediisocyanate, bis (isocyanatemethyl) cyclohexane, and isophorone. Examples thereof include diisocyanate, diisocyanate dimerate, and lysine diisocyanate. The low molecular weight compound having active hydrogen contains, for example, water, ethylene glycol, propylene glycol, trimethylolpropane, glycerin, sorbitol, ethylenediamine, ethanolamine, diethanolamine, hexamethylenediamine, isocyanurate, uretidione, and a hydroxyl group. Examples thereof include low molecular weight polyester and polycaprolactone. Examples of the blocking agent include alcohols such as methanol, ethanol and benzyl alcohol; phenols such as phenol and crezone; lactams such as caprolactam and butyrolactam; oximes such as cyclohexanone, oxime and methylethylketooxime. .. Specific examples of the blocked isocyanate include isophorone diisocyanate blocked with ε-caprolactam (Vestagon B1530 manufactured by Evonik, Cleran UI manufactured by Bayer) and the like.

Specific examples of triglycidyl isocyanurate include Araldite manufactured by Huntsman.

The content of the component (B) in 100 parts by mass of the total amount of the component (A) and the component (B) is 1.0 part by mass or more from the viewpoint of weather resistance, adhesiveness, and impact resistance. Yes, 3.0 parts by mass or more is preferable, and 5.0 parts by mass or more is more preferable. On the other hand, from the viewpoint of improving the appearance, it is 15.0 parts by mass or less, preferably 12.0 parts by mass or less, and more preferably 10.0 parts by mass or less.

When the component (B) is β-hydroxyalkylamide, the number of hydroxyl groups (-OH) of β-hydroxyalkylamide relative to the number of carboxyl groups (-COOH) of the polyester resin ((-OH) / (-COOH)). )) Is preferably 0.5 or more, more preferably 0.7 or more, further preferably 0.8 or more, and particularly preferably 0.9 or more. When (-OH) / (-COOH) is less than 0.5, the weather resistance and mechanical properties tend to decrease. Further, (-OH) / (-COOH) is preferably 1.5 or less, more preferably 1.4 or less, further preferably 1.3 or less, and particularly preferably 1.2 or less. When (-OH) / (-COOH) exceeds 1.5, weather resistance and water resistance tend to decrease.

[Component (C): UV absorber]
The powder coating composition according to the present embodiment contains an ultraviolet absorber from the viewpoint of weather resistance. It is known that the ultraviolet absorber absorbs ultraviolet rays of 290 to 380 nm, which are harmful to the coating film, converts them into harmless heat energy, and exhibits an effect semi-permanently as long as it exists in the coating film. Effective for retention and discoloration and fading of pigments.

Examples of the ultraviolet absorber include benzotriazole-based, hydroxyphenyltriazine-based, benzophenone-based, hydroxyphenylbenzotriazole-based, cyanoacrylate-based, malonic acid ester-based, and salicylate ester-based ultraviolet absorbers, and benzotriazole-based ultraviolet rays. Absorbents and / or hydroxyphenyltriazine-based UV absorbers are preferred, and benzotriazole-based UV absorbers are more preferred. Specific examples of the benzotriazole-based ultraviolet absorber include, for example, Tinuvin PS, 99-2, 326, 328, 384-2, 900, 928, 1130 manufactured by BASF, Chisorb 5571 manufactured by Double Bond Chemical Co., Ltd., and Taki. Light Ace UV-710, 730, 750 manufactured by Chemical Co., Ltd., DAINSORB T series manufactured by Daiwa Chemical Industry Co., Ltd., Praxel UVA-103 manufactured by Daicel Co., Ltd., JF-77 manufactured by Johoku Chemical Industry Co., Ltd. , 7980, 83, Seasove 700 series manufactured by Cipro Chemical Co., Ltd., RPA-0010, 0016 manufactured by Sannan Synthetic Chemical Co., Ltd., Hostabin 3310, 3315 manufactured by Clariant Co., Ltd. and the like. Specific examples of the hydroxyphenyltriazine-based ultraviolet absorber include, for example, Tinuvin 400, 405, 460, 477, 479 manufactured by BASF, and Seesove 100, 101, 102, 103, 015, 106, 107 manufactured by Sipro Kasei Co., Ltd. , 151, ADEKA Tab LA-32, LA-36, etc. manufactured by ADEKA Corporation. The above-mentioned ultraviolet absorber may be used alone or in combination of two or more.

From the viewpoint of weather resistance, the content of the ultraviolet absorber with respect to 100 parts by mass of the total amount of the component (A) and the component (B) is 0.1 part by mass or more, preferably 0.3 part by mass or more. 0.5 parts by mass or more is more preferable, 0.7 parts by mass or more is further preferable, and 0.9 parts by mass or more is particularly preferable. Further, from the viewpoint of peaking out the effect and cost, it is 5.0 parts by mass or less, preferably 4.0 parts by mass or less, more preferably 3.0 parts by mass or less, still more preferably 2.0 parts by mass or less, 1 5.5 parts by mass or less is particularly preferable.

[Component (D): Hindered amine-based light stabilizer]
In the powder coating composition according to the present embodiment, a Hindered Amine Light Stabilizer (HALS) is preferably used together with an ultraviolet absorber from the viewpoint of weather resistance. It is known that HALS does not absorb light of 290 nm or more and captures radicals generated by deterioration of the main resin by ultraviolet rays or heat.

Specific examples of HALS include Tinuvin111FDL manufactured by BASF, 144, 292, 5100, and ADEKA STAB LA-63P, LA-72, LA-77Y, LA-81 manufactured by ADEKA Corporation. The above-mentioned HALS may be used alone or in combination of two or more.

From the viewpoint of weather resistance, the content of HALS with respect to 100 parts by mass of the total amount of the component (A) and the component (B) is 0.1 part by mass or more, preferably 0.2 part by mass or more, and 0. 3 parts by mass or more is more preferable, 0.4 parts by mass or more is further preferable, and 0.5 parts by mass or more is particularly preferable. Further, from the viewpoint of peaking out the effect and cost, it is 5.0 parts by mass or less, preferably 3.0 parts by mass or less, more preferably 2.0 parts by mass or less, further preferably 1.2 parts by mass or less, and 0. 9.9 parts by mass or less is particularly preferable.

[Ingredient (E): Leveling agent]
The powder coating composition according to the present embodiment contains a leveling agent from the viewpoint of further improving the appearance.

Examples of the leveling agent include an olefin polymer (weight average molecular weight [hereinafter referred to as Mw] 500 to 5,000, for example, low molecular weight polyethylene and low molecular weight polypropylene); an olefin polymer [Mw 500 to 20,000, for example. Ethylene- (meth) acrylic copolymer]; (meth) acrylic copolymer [Mw 1,000 to 20,000]; polyvinylpyrrolidone (Mw 1,000 to 20,000); silicone-based leveling agent [Mw 1,000 to 20,000] 000, for example, polydimethylsiloxane, polyphenylsiloxane, carboxyl, ether, polydimethylsiloxane modified with epoxy, etc., fluorinated silicone] and the like. The leveling agent may be used alone or in combination of two or more.

The content of the leveling agent with respect to 100 parts by mass of the total amount of the component (A) and the component (B) is 0.5 parts by mass or more, preferably 0.6 parts by mass or more, and 0. 7.7 parts by mass or more is more preferable. Further, from the viewpoint of peaking out the effect and cost, it is 5.0 parts by mass or less, preferably 3.0 parts by mass or less, and more preferably 2.0 parts by mass or less.

(Other additives)
In the powder coating composition according to the present embodiment, in addition to the above-mentioned components, resin components other than the polyester resin, pigments, surface conditioners, flow conditioners, silicones, waxes, defoamers, pigment dispersants, etc. Antioxidants, magnetic powders, armpit inhibitors such as benzoin, plasticizers, charge control agents, antibacterial agents, antifungal agents, insect repellents, algae repellents, water repellents, coupling agents and the like may be blended.

The content of the fluororesin with respect to 100 parts by mass of the total amount of the component (A) and the component (B) is, for example, less than 5.0 parts by mass, less than 2.0 parts by mass, less than 1.0 part by mass, 0. It may be less than 5 parts by mass, less than 0.1 parts by mass, less than 0.01 parts by mass, and may be a powder coating composition containing no fluororesin.

The content of the epoxy resin with respect to 100 parts by mass of the total amount of the component (A) and the component (B) is, for example, less than 2.0 parts by mass, less than 1.0 part by mass, less than 0.5 parts by mass, 0. It may be less than 1 part by mass and less than 0.01 part by mass, and may be a powder coating composition containing no epoxy resin.

The powder coating composition according to this embodiment may contain a pigment for coloring. The pigment may be used alone or in combination of two or more. Examples of pigments include inorganic pigments such as titanium oxide, bismuth, iron oxide, aluminum powder, glass, metal powder, carbon black, pearl mica, transparent pearl mica, colored mica, and interfering mica; quinacridone and diketopyrrolopyrrole. System, Naphthol AS system, Kinoxalin system, Isoindolinone system, Isoindrin system, Indanslon system, Perylene system, Perinone system, Anthraquinone system, Dioxazine system, Benzoimidazolone system, Kinoftalone system, Anthrapyrimidine system, Phthalocyanine system, Examples thereof include organic pigments such as halogenated phthalocyanine-based pigments, azo pigments (azomethine metal complex, condensed azo, etc.), copper phthalocyanine, ultramarine blue, and condensed polycyclic pigments. From the viewpoint of heat resistance and weather resistance, inorganic pigments such as titanium oxide, bismuth, iron oxide, aluminum powder, glass, metal powder, carbon black, pearl mica, transparent pearl mica, colored mica, and interference mica; quinacridone-based, Diketopyrrolopyrrole, Naphthol AS, Kinoxalin, Isoindoline, Isoindoline, Indanslon, Perylene, Perinone, Anthraquinone, Dioxazine, Benzoimidazolone, Kinophathalone, Anthrapyrimidine , Phthalocyanine-based, halogenated phthalocyanine-based, azomethine metal complex, copper phthalocyanine and other organic pigments are preferable. It is preferable not to contain rust preventive pigments such as metal phosphates and extender pigments such as barium sulfate because they tend to reduce weather resistance and luster.

Examples of the pigment dispersant include polymer-type dispersants containing a polar group having an adsorptive property to the pigment, and examples thereof include those exemplified in JP-A-11-80647. In addition, commercially available products can also be used. The molecular weight of the dispersant is usually 10 to 1,000,000. Polar groups having adsorptivity to pigments include acidic groups such as phosphoric acid group, carboxylic acid group, sulfonic acid group and sulfamic acid group and their neutralizing bases, amino groups and amino group neutralizing bases, quaternary. Examples thereof include an ammonium group, an amide group and an imide group. Examples of the main skeleton of the polymer-type dispersant include (co) polymers of vinyl-based monomers such as acrylic acid esters, styrene, and vinyl acetate, polyesters, and polyamide polyamines. The pigment dispersant may be used alone or in combination of two or more.

When the pigment dispersant is contained, the content of the component (A) and the component (B) with respect to 100 parts by mass is preferably 0.1 to 10.0 parts by mass, preferably 0.3 to 5.0 parts by mass. Parts are more preferable, and 0.5 to 3.0 parts by mass are even more preferable.

Examples of the antioxidant include a phenol-based antioxidant, a phosphorus-based antioxidant, a sulfur-based antioxidant, an aromatic amine-based antioxidant, and the like. The above-mentioned antioxidant may be used alone or in combination of two or more.

When the antioxidant is contained, the content of the component (A) and the component (B) with respect to 100 parts by mass is preferably 0.1 to 10.0 parts by mass, preferably 0.3 to 5.0 parts by mass. Parts are more preferable, and 0.5 to 3.0 parts by mass are even more preferable.

When benzoin is contained as an armpit inhibitor, the content of the component (A) and the component (B) with respect to 100 parts by mass is preferably 0.1 to 10.0 parts by mass, and 0.3 to 5. 0 parts by mass is more preferable, and 0.5 to 3.0 parts by mass is further preferable.

When the flow adjusting agent is contained, the content of the component (A) and the component (B) with respect to 100 parts by mass is preferably 0.1 to 1.0 parts by mass, preferably 0.2 to 0.5 parts by mass. The unit is more preferable.

<Manufacturing method of powder coating composition>
The powder coating composition according to the present embodiment is obtained by dry-blending a mixture of the above components (A), (B), (C), (D), (E) and other additives with a Henshell mixer or the like. It can be produced by melt-kneading at, for example, 100 to 160 ° C. using a kneader, cooling the obtained kneaded product, finely pulverizing the obtained kneaded product with a hammer type impact crusher, and classifying with a flue.

<Painting method of powder coating composition>
The obtained powder coating composition is coated and baked on the object to be coated by a known electrostatic coating method, fluid dipping coating method, etc., and the dry film thickness after baking is 30 to 150 μm, preferably 50 to 80 μmm. Can be painted like. The baking can be performed, for example, at 170 to 230 ° C. for 10 to 30 minutes. The base material on which the powder coating composition can be applied is not particularly limited, and for example, zinc, iron, aluminum, magnesium, steel and alloys thereof, metal base materials such as zinc-plated steel plates, and chemical treatment coatings on these metal surfaces. Examples thereof include those in which the metal surface is anodized, those in which the metal surfaces are anodized, and those in which a primer coating or electrodeposition coating is applied to these metal substrates as needed. Examples of the chemical conversion treatment liquid used for forming the chemical conversion treatment coating include a phosphate treatment liquid, a zirconium treatment liquid, and a chromate treatment liquid.

The powder coating composition according to the present embodiment is suitably used for applications that require appearance and weather resistance, such as construction machinery, agricultural machinery, and stock houses.

Although the present invention will be described based on examples, the present invention is not limited to the examples.

Hereinafter, various materials used in Examples and Comparative Examples are collectively shown.
Polyester resin 1-5, 7, 8: Polyester resin produced in Production Example 1 described later Polyester resin 6: CRYLCOAT 2630-2 (acid value: 33 mg / KOH, Tg: 62 ° C., Mn) manufactured by Dycel Ornex Co., Ltd. : 2500)
Epoxy resin: EPICLON 4050 manufactured by DIC Corporation
Curing agent: Primid XL-552 (β-hydroxyalkylamide) manufactured by EMS-CHEMIE AG.
UV absorber 1: BASF's Tinuvin 326 (benzotriazole UV absorber)
UV absorber 2: Tinuvin400 (hydroxyphenyltriazine UV absorber) manufactured by BASF.
HALS: Tinuvin 292 manufactured by BASF
Leveling agent: BYK 360P (polyacrylate adsorbed on silicon dioxide) manufactured by Big Chemie Japan Co., Ltd.
Anti-corrosion pigment: K-WHITE # 105 manufactured by TAYCA CORPORATION
Pigment dispersant: BYK 3951P manufactured by Big Chemie Japan Co., Ltd.
Antioxidant: BASF's Irganox 245

Production Example 1: Synthesis of polyester resins 1 to 5, 7 and 8 20 mol (3320 g) of terephthalic acid, 80 mol (13280 g) of isophthalic acid, 100 mol (11556 g) of neopentyl glycol mixed with 10% by mass of water, and 20 mol (1240 g) of ethylene glycol were added. It was charged in a reaction vessel, pressure was applied, and an esterification reaction was carried out at a temperature of 260 ° C. for 4 hours. After transferring the obtained esterified product to a polycondensation reaction tank, dibutyltin oxide was added as a polycondensation catalyst, the pressure was reduced, and the polycondensation reaction was carried out at 280 ° C. for 4 hours to obtain a resin having an extreme viscosity. Next, 8.5 mol (l (1411 g)) of isophthalic acid was added to the obtained resin, and a depolymerization reaction was carried out at 250 ° C. for 2 hours under normal pressure to obtain a polyester resin 1 and the polyester resin 1. The charged composition was changed in the same manner to obtain polyester resins 2 to 5, 7, and 8. Oxidation (mg / KOH), glass transition temperature (Tg), and number average molecular weight (Mn) of each obtained polyester resin. ) Is shown in the table below.

(Examples and comparative examples)
According to the formulation shown in Table 2, each compound was dry-blended with a Henschel mixer and then melt-kneaded at about 100 ° C. using a kneader. After cooling the obtained kneaded material, it was finely pulverized with a hammer type impact crusher and classified with a 200 mesh wire mesh to prepare powder coating compositions of Examples 1 to 9 and Comparative Examples 1 to 9. In addition, (-OH) / (-COOH) in Table 2 shows the number of hydroxyl groups (-OH) which β-hydroxyalkylamide has with respect to the number of carboxyl groups (-COOH) which polyester resin has.

<Preparation of test plate>
A zinc phosphate-based chemical conversion treatment was applied to a cold-rolled steel sheet (70 mm × 150 mm × 0.8 mm) to form a chemical conversion treatment film. Next, each powder coating composition is electrostatically powder coated on the chemical conversion coating film using an electrostatic coating machine PG-1 (manufactured by Asahi Sanac Co., Ltd.) so that the dry film thickness is 70 μm. did. Next, each test plate was obtained by heating and drying under the condition that the surface temperature of the object to be coated was 160 ° C. and the holding time was 20 minutes.

<Evaluation of appearance>
A long wave (Lw value) of the Wave Scan value of the surface on which the coating film was formed was measured using a microwave scan manufactured by BYK-Gardner. The Lw value is an index indicating the amount of unevenness, and the smaller the Lw value, the smoother the coating film surface. The Lw value shall be 50 or less as the performance target value.

<Evaluation of weather resistance>
Using a xenon arc lamp type weathering tester (XWOM), an accelerated exposure test was performed for 720 hours at ^{an irradiation intensity of 180 W / m 2 in accordance with JIS K 5600-7-7: 2008.} The gloss retention rate and the color difference ΔE * were measured based on the test plate before exposure. A color difference meter (CM-3500d manufactured by Konica Minolta Co., Ltd.) was used for measuring the color difference. A microtrigloss gloss meter manufactured by BYK-Gardner was used for measuring the gloss. The gloss value was evaluated as 20 degree gloss. The performance target values are 70% or more for the gloss retention rate and 2.5 or less for the color difference ΔE *.

<Evaluation of adhesion>
According to the grid tape method described in JIS K 5600-5-6: 1999, use a knife to reach the substrate on the coated surface of the coated plate, and use a knife at intervals of 2 mm to make 11 pieces vertically and horizontally in parallel. A cut was made to form a goban grain, a cellophane adhesive tape was attached to the surface thereof, and the goban grain coated surface after the tape was rapidly peeled off was evaluated. Of the 100 Goban eyes, the Goban eyes in which 50% or more of the coating film remained in the Goban eyes were counted. The performance target value is 100/100.

<Evaluation of impact resistance (weight drop resistance)>
In order to evaluate the resistance of the coating film to a drop height of 50 cm in accordance with JIS K 5600-5-3 (DuPont type), cracking and peeling of the coating film were observed using a punch Φ1 / 2 inch and a weight of 500 g. .. Those having no cracks and peeling in the coating film were indicated by "+", and those having cracks and / or peeling in the coating film were indicated by "-".

<Evaluation of coating film hardness (pencil hardness)>
The hardness of the coating film of the test plate was evaluated by a pencil scratch test specified in JIS K 5600-5-4: 1999 due to tearing of the coating film. The performance target value is that the pencil hardness at which the coating film is torn is H or more.

<Evaluation of recoatability>
A solvent-based repair paint (Ureol 600 manufactured by Kawakami Paint Co., Ltd.) was applied over the test plate. The above-mentioned adhesion test was performed on the obtained test plate, and the Goban-grained coated surface after the tape was rapidly peeled off was evaluated.

From the results in Table 2, it can be seen that the powder coating composition of the present invention has a good appearance and weather resistance. Further, in a preferred embodiment, it can be seen that it has good adhesion, impact resistance, coating film hardness, and recoatability. In Comparative Example 5, the Lw value could not be measured because the surface of the coating film was too inferior in smoothness.

Since the powder coating composition of the present invention has a good appearance and weather resistance, it is particularly useful as a coating material used for construction machinery, agricultural machinery, stock houses and the like.

Claims (6)

The following component (B) is 1.0 to 15.0 parts by mass and the following component (C) is 0.1 to 5.0 parts by mass with respect to 100 parts by mass of the total amount of the following component (A) and the following component (B). A powder coating composition containing 0.1 to 5.0 parts by mass of the following component (D) and 0.5 to 5.0 parts by mass of the following component (E).
Component (A): Polyester resin having an acid value of 30 to 60 mg / KOH Component (B): Curing agent Component (C): Ultraviolet absorber Component (D): Hindered amine-based light stabilizer Component (E): Leveling agent The powder coating composition according to claim 1, wherein the polyester resin has a glass transition temperature (Tg) of 50 to 70 ° C. The powder coating composition according to claim 1 or 2, wherein the polyester resin has a number average molecular weight (Mn) of 1000 to 10000. The powder coating composition according to any one of claims 1 to 3, wherein the curing agent is β-hydroxyalkylamide. The powder coating composition according to any one of claims 1 to 4, wherein the ultraviolet absorber is a benzotriazole-based ultraviolet absorber and / or a hydroxyphenyltriazine-based ultraviolet absorber. The powder coating composition according to any one of claims 1 to 5, which does not contain an epoxy resin.