Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – At least one aryl ring which is part of a fused or bridged...
Reexamination Certificate
2001-07-02
2004-03-16
Wu, David W. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
At least one aryl ring which is part of a fused or bridged...
C526S249000, C526S254000, C526S255000, C428S407000, C428S463000
Reexamination Certificate
active
06706794
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a thermosetting fluorine-containing resin powder coating composition which gives a coating film having further improved weather resistance. The powder coating composition is suitable for coating on an exterior member for building.
BACKGROUND ART
Compositions described in JP-B-6-104792, etc. are known as a thermosetting fluorine-containing resin powder coating composition.
The thermosetting powder coating composition is prepared by dry-blending a resin for coating in the form of powder, pellet, granule or tablet, a curing agent, a pigment and other additives for coating, melt-kneading the mixture at a temperature of not less than a melting temperature of the resin to give a uniform composition and then pulverizing. Further after an average particle size, particle size distribution, etc. are adjusted by means of classification, or the like, electric charge is given to the composition by means of electrostatic coating, fluidized bed coating, or the like and then the composition is coated on a substrate and cured by heating to form a coating film. In the preparation process, a heating temperature at melt-kneading of the composition is usually from 50° to 140° C., and a heating temperature at forming the coating film is usually from 150° to 220° C.
However in case where the powder coating composition was prepared from the thermosetting fluorine-containing resin by the above-mentioned preparation process, it was difficult to regulate color development. Though the reason for that is not clear, it is presumed that impurities, etc. in the fluorine-containing resin react with a pigment, thereby inhibiting color development. Also the fluorine-containing resin has a problem that when titanium oxide and other pigment are used together, floating of the pigment occurs remarkably at melt-kneading and weather resistance is inferior as compared with a solvent-based coating composition comprising similar components. It is presumed that the reason for that is such that dispersibility of the pigment in the fluorine-containing resin at a melt-kneading step is not good and thus the pigment is not dispersed uniformly in a coating film at forming the coating film.
Also a weather resistance test by exposing in Florida for 10 years is described in AAMA2605 which is a standard for aluminum building materials of AAMA (American Architectural Manufacturers Association), and a coating composition which is prepared from a thermoplastic solvent type or thermosetting solvent type fluorine-containing resin by using titanium oxide and other pigment together and satisfies such a weather resistance standard was identified. However a coating film obtained from a thermosetting powder coating composition and satisfying that standard has not yet been known.
An object of the present invention is to provide a thermosetting fluorine-containing resin powder coating composition which has enhanced weather resistance particularly and also improved pigment dispersibility by a combination use of titanium oxide and other specific pigment.
DISCLOSURE OF INVENTION
The present invention relates to a powder coating composition which comprises (A) a fluorine-containing copolymer having a crosslinkable reactive group and (B) a curing agent being capable of forming crosslinkage by reacting with the crosslinkable reactive group of the fluorine-containing copolymer in a weight ratio (A)/(B) of 40/60 to 98/2, and also contains rutile titanium oxide and other pigment.
A preferable fluorine-containing copolymer (A) is a thermosetting fluorine-containing copolymer having a crosslinkable reactive group, which comprises a fluoroolefin unit and has a fluorine content of not less than 10% by weight, a MFR (melt flow rate) of from 0.1 to 100 g/10 min measured at 100° to 180° C. and a glass transition temperature of from 30° to 120° C. Also the copolymer (A) may comprise a resin containing no fluorine as a resin for powder coating composition.
Examples of the preferable other pigment are inorganic pigments such as a baked pigment, organic pigments and carbon powder.
It is preferable that a particle size ratio of the above-mentioned titanium oxide to the other pigment is from 1/0.01 to 1/20.
The powder coating composition of the present invention can give a coating film meeting the AAMA2604 standard and further stricter AAMA2605 standard.
The powder coating composition of the present invention is suitable for coating on exterior members for building, for example, aluminum sash which are excellent particularly in weather resistance.
BEST MODE FOR CARRYING OUT THE INVENTION
Various fluorine-containing polymers can be used as the thermosetting fluorine-containing copolymer (A) having a crosslinkable reactive group which is used in the present invention. For example, there are a copolymer having a fluoroolefin unit, an acrylic copolymer having a fluoroalkyl group in its side chain, a partly fluorinated polyester, and the like. Particularly preferred is a thermosetting fluorine-containing copolymer having a crosslinkable reactive group which comprises a fluoroolefin unit and also has a fluorine content of not less than 10% by weight, a MFR (melt flow rate) of from 0.1 to 100 g/10 min measured at 100° to 180° C. and a glass transition temperature of from 30° to 120° C.
Examples of the fluoroolefin are tetrafluoroethylene, chlorotrifluoroethylene, trifluoroethylene, vinylidene fluoride, hexafluoropropylene, pentafluoropropylene, and the like. The fluoroolefin may be selected optionally depending on characteristics required for a coating film, components of the copolymer and combination with the curing agent. Those fluoroolefins can be used solely or in combination of two or more thereof. Examples of the crosslinkable reactive group of the thermosetting fluorine-containing copolymer to be used in the present invention are hydroxyl group, carboxyl group, amido group, amino group, mercapto group and glycidyl group and in addition, activated halogen such as bromine and iodine, isocyanate group, and the like.
Examples of a method for introducing such a crosslinkable reactive group into the copolymer are a method of copolymerizing monomer having a crosslinkable reactive group, a method of decomposing a part of the copolymer, a method of reacting a reactive group of the copolymer with a compound giving a crosslinkable reactive group thereto, and the like.
Examples of the comonomer which can introduce a suitable crosslinkable reactive group by copolymerization are, for instance, monomers having hydroxyl group or a group which can be converted to hydroxyl group and having a double bond copolymerizable with fluoroolefin. Examples thereof are one or a mixture of two or more of hydroxyalkyl vinyl ethers such as hydroxyethyl vinyl ether, hydroxypropyl vinyl ether, hydroxybutyl vinyl ether, hydroxyisobutyl vinyl ether and hydroxycyclohexyl vinyl ether; esters of hydroxyalkylcarboxylic acid and vinyl alcohol such as vinyl hydroxyacetate, vinyl hydroxypropionate, vinyl hydroxybutyrate, vinyl hydroxyvalerate, vinyl hydroxyisobutyrate and vinyl hydroxycyclohexanecarboxylate; hydroxyalkyl allyl ethers such as hydroxyethyl allyl ether, hydroxypropyl allyl ether, hydroxybutyl allyl ether, hydroxyisobutyl allyl ether and hydroxycyclohexyl allyl ether; hydroxyalkyl allyl esters such as hydroxyethyl allyl ester, hydroxypropyl allyl ester, hydroxybutyl allyl ester, hydroxyisobutyl allyl ester and hydroxycyclohexyl allyl ester; hydroxyalkyl esters of acrylic acid or methacrylic acid such as 2-hydroxyethyl acrylate, hydroxypropyl acrylate, 2-hydroxyethyl methacrylate and hydroxypropyl methacrylate; partly fluorine-substituted compounds thereof; and the like. One or two or more thereof may be selected and used as a comonomer for introducing hydroxyl group.
Examples of the comonomer having carboxyl group are, for instance, &agr;,&bgr;-unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, succinic acid, succinic anhydride, fumaric acid, fumaric anhydride, crotonic acid, maleic acid and maleic anhydride and
Fukagawa Ryoichi
Iwakiri Miyuki
Iwakiri Ryuji
Tanizawa Daisuke
Tano Keisuke
Daikin Industries Ltd.
Hu Henry S.
Iwakiri Miyuki
Sughrue & Mion, PLLC
Wu David W.
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