Chemical apparatus and process disinfecting – deodorizing – preser – Process disinfecting – preserving – deodorizing – or sterilizing – Maintaining environment nondestructive to metal
Reexamination Certificate
2001-07-02
2003-10-21
Warden, Sr., Robert J. (Department: 1744)
Chemical apparatus and process disinfecting, deodorizing, preser
Process disinfecting, preserving, deodorizing, or sterilizing
Maintaining environment nondestructive to metal
C428S407000, C427S385500, C427S388100
Reexamination Certificate
active
06635221
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method of inhibiting rust from arising on a metallic substrate in case of coating the metallic substrate with a thermosetting fluorine-containing resin powder coating composition.
BACKGROUND ART
It is known that a coated article being excellent in weather resistance can be obtained by applying a thermosetting fluorine-containing resin powder coating composition on a metallic substrate (JP-B-6-104792, JP-A-6-345822, JP-A-6-184243, etc.).
Also it is described in JP-A-6-184243 that a fluorine-containing resin copolymer containing no chlorotrifluoroethylene is excellent particularly in yellowing resistance of a coating film at a weather resistance test.
As mentioned above, a priority has been given to characteristics of a coating film, and with respect to a relation between a substrate and a coating film, only adhesion between them has been taken up as a problem to be solved.
However though a substrate coated with a thermosetting fluorine-containing resin powder coating composition exhibits excellent gloss retention and a minimum change of color difference because of excellent weather resistance of the fluorine-containing resin, the composition has a problem with rust on a contact surface of a metallic substrate in outdoor use. Particularly when the fluorine-containing powder coating composition is directly coated on a metallic substrate to form a coating film without using a primer, rusting arises remarkably.
This problem with rusting of a metallic substrate coated with a thermosetting fluorine-containing resin powder coating composition has not yet been solved.
DISCLOSURE OF INVENTION
The present invention relates to the method of inhibiting rust of a metallic substrate by coating the metallic substrate with a thermosetting fluorine-containing resin powder coating composition which does not contain essentially chlorine atom.
BEST MODE FOR CARRYING OUT THE INVENTION
The thermosetting fluorine-containing resin powder coating composition to be used in the method of the present invention basically comprises a thermosetting fluorine-containing resin and a curing agent, the both of which contain no chlorine essentially.
Examples of the thermosetting fluorine-containing resin containing no chlorine are, for instance, copolymers which comprise a fluoroolefin unit containing no chlorine atom as an essential component and have a crosslinkable reactive group.
Examples of the fluoroolefin containing no chlorine atom are, for instance, tetrafluoroethylene, monofluoroethylene, trifluoroethylene, vinylidene fluoride, hexafluoropropylene, pentafluoropropylene, and the like. The fluoroolefin can be optionally selected depending on characteristics required on a coating film and a combination with other copolymer component and curing agent. Those fluoroolefins can be used in combination of two or more thereof. Particularly preferable fluoroolefins are perfluoroolefins such as tetrafluoroethylene and hexafluoropropylene from the viewpoint of copolymerizability with vinyl ether and/or vinyl ester monomers.
Examples of the crosslinkable reactive group of the thermosetting fluorine-containing resin to be used in the present invention are hydroxyl group, carboxyl group, amido group, amino group, mercapto group, glycidyl group, 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 the 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 vinyl alcohol and hydroxyalkylcarboxylic acid 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 in addition, fluorine-substituted monomer such as perfluorobutenoic acid, and the like. Also examples of the comonomer having glycidyl group are, for instance, glycidyl (meth)acrylate, glycidyl vinyl ether, glycidyl allyl ether, and the like. Examples of the comonomer having amino group are, for instance, amino alkyl vinyl ether, amino alkyl allyl ether, and the like. Examples of the comonomer having amido group are, for instance, (meth)acrylamide, methylolacrylamide, and the like. Examples of the comonomer having nitrile group are, for instance, (meth)acryronitrile, and the like. Examples of the comonomer having isocyanate group are, for instance, vinyl isocyanate, isocyanate ethyl acrylate, and the like. It is particularly preferable to use a vinyl or allyl ether or ester compound as a comonomer for introducing a crosslinkable reactive group from the viewpoint of excellent copolymerizability with the fluoroolefin.
Example of the method for partly decomposing the copolymer is a method of copolymerizing a monomer having a hydrolyzable ester group after polymerization and then hydrolyzing the copolymer to generate carboxyl group in the copolymer. Also it is possible to form crosslinkage directly by transesterification in a curing reaction without carrying out ester hydrolysis mentioned above.
As the method for reacting the copolymer with a compound giving a crosslinkable reactive group thereto, for example, a method of introducing carboxyl group by reacting a divalent carboxylic acid anhydride such as succinic anhydride with a fluorine-containing copolymer having hydroxyl group, or the like method can be employed suitably.
In addition to the above-mentioned fluoroolefin unit and the unit having a crosslinkable reactive group, a comonomer copolymerizable with those two components can be copolymerized with the fluorine-containing copolymer to be used in the present invention in order to reduce a melting point or a glass transition temperature of the fluorine-containing copolymer for further enhancing workability at coating and imparting physical properties such as proper hardness, flexibility and gloss to the coating film. Example of such an optional comonomer to be used is one which has an unsaturated group being active so as to be copolymerizable with the fluoroolefin and does not lower weather resistance of the coating film remarkably.
Suitable examples of such an optional comonomer are ethylenically unsaturated compounds, for instance, alkyl vinyl ethers such as ethyl vinyl ether, propyl vinyl ether, butyl vinyl ether, isobutyl vinyl ether and cyclohexyl vinyl ether; esters of vinyl alcohol and alkylcarboxylic acid such as vinyl acetate, vinyl propionate, vinyl butyrate, vinyl isobutyrate,
Fukagawa Ryoichi
Iwakiri Miyuki
Iwakiri Ryuji
Tanizawa Daisuke
Tano Keisuke
Conley Sean E.
Daikin Industries Ltd.
Iwakiri Miyuki
Sughrue & Mion, PLLC
Warden, Sr. Robert J.
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