Nof Corporation

Asahi Glass Company, Limited

Nippon Oil Fats Co., Ltd.

Chiaki Sagawa

Nobuyuki Miyazaki

Masao Unoki

Motoi Kamba

Kenzou Maeda

Haruki Ito

Toru Kurashina

Manabu Katagiri

Eiji Shimada

Shingo Okamoto

A thermosetting powdery coating composition which comprises, in admixture: (A) from 40 to 98 parts by weight of a fluorine-containing copolymer, which is a copolymer of a fluoroolefin and a comonomer having a crosslinkable reactive group, e.g., hydroxy, carboxyl, amino and glycidyl groups, containing at least 10% by weight of fluorine and having an intrinsic viscosity of 0.05-2 dl/g (30.degree. C., tetrahydrofuran), a glass transition temperature of 30.degree.-120.degree. C. and a weight loss by heating which does not exceed 2% and (B) from 60 to 2 parts by weight of a curing agent capable of forming crosslinks by reacting with the crosslinkable reactive groups in (A), except for the composition wherein (A) is a hydroxyl group and a weight loss by heating which does not exceed 2% and (B) is a blocked isocyanate compound. The powdery coating composition is excellent in the dispersibility of pigments and efficiency in the coating works therewith and capable of giving a coating film having improved adhesion to a substrate surface, surface luster, impact resistance and insusceptibility to staining.

Thermosetting powdery coating composition

A thermosetting powder coating composition which contains a resin composition containing (a) 60 to 97 weight % of a fluororesin having reactive group for crosslinking in the molecule which contains 10 weight % or more of fluorine and has glass transition temperature in the range from 35.degree. to 120.degree. C., (b) 3 to 40 weight % of a hardener which can form crosslinking by reaction with the reactive group for crosslinking in the fluororesin (a), (c) 0.01 to 10 weight parts of a synthetic wax or a natural wax based on 100 weight parts of the resin composition and (d) 0.001 to 1.0 weight parts of a material as a coupling agent based on 100 weight parts of the resin composition, forms a coating layer which has the same degree of water repellency and slipping property as those formed from polytetrafluoroethylene powder while the excellent weatherability, acid resistance and adhesion to substrates are retained. A coating layer having excellent adhesive property and impact resistance can be formed therewith on a stainless steel substrate without chemical pretreatment or coating with a primer.

Thermosetting powder coating material

A powder coating composition comprises 100 weight parts of the total of a polyester resin having a hydroxyl value in the range from 20 to 100 KOH mg/g and a blocked polyisocyanate compound, 0.01 to 3 weight parts of an organotin compound and 0.01 to 10 weight parts of a carboxylic acid compound having an acid value of 1000 KOH mg/g or less which can form a complex compound by reaction with the organotin compound. The amount of the polyester resin is in the range from 95 to 50 weight % and the amount of the blocked polyisocyanate compound is in the range from 5 to 50 weight % respectively based on the total of the polyester resin and the blocked polyisocyanate compound. A precoat steel plate is prepared by coating the powder coating composition described above on a steel plate by a electrostatic powder coating method to form a coating layer having a thickness in the range from 20 to 120 .mu.m and curing the coating composition by baking at a temperature in the range from 190.degree. to 300.degree. C. for a time in the range from 20 seconds to 10 minutes. The powder coating composition can be cured without formation of blisters and pin holes under a desired condition by controlling the rate of the curing reaction.

Powder coating material and a recoat steel plate

A thermosetting powder coating composition comprises (a) a fluororesin having reactive group for crosslinking in the molecule which contains 10 weight % or more of fluorine and has glass transition temperature in the range from 35.degree. to 120.degree. C., (b) a hardener which can form crosslinking by reaction with the reactive group for crosslinking in the fluororesin (a) and (c) a synthetic wax or a natural wax. The amount of the fluororesin is in the range from 60 to 97 weight % and the amount of the hardener is in the range from 3 to 40 weight % based on the total of the fluororesin and the hardener. The amount of the synthetic wax or the natural wax is in the range from 0.01 to 10 weight parts based on 100 weight parts of the total of the fluororesin and the hardener. The coating layer formed from the thermosetting fluororesin powder coating composition has the same degree of water repellency and slipping property to those of the coating layer formed from polytetrafluoro-ethylene powder while the excellent weatherability, acid resistance and adhesion to substrates are retained.

The thermosetting powdery coating composition of the invention comprises (A) from 40 to 98 parts by weight of a fluorinecontaining copolymer, which is a copolymer of a fluoroolefin and a comonomer having a crosslinkable reactive group, e.g., hydroxy, carbonyl, amino and glycidyl groups, containing at least 10% by weight of fluorine and having an intrinsic viscosity of 0.05-2 dl/g (30.degree. C., tetrahydrofuran) and a glass transition temperature of 30.degree.-120.degree. C. and (B) from 60 to 2 parts by weight of a curing agent capable of forming crosslinks by reacting with the crosslinkable reactive groups in (A). The powdery coating composition of the invention is excellent in the dispersibility of pigments and efficiency in the coating works therewith and capable of giving a coating film having improved adhesion to the substrate surface, surface luster, impact resistance and insusceptibility to stain.

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Tokyo, Japan

Chiaki Sagawa