Stock material or miscellaneous articles – Composite – Of fluorinated addition polymer from unsaturated monomers
Reexamination Certificate
2001-05-10
2004-01-06
Zacharia, Ramsey (Department: 1773)
Stock material or miscellaneous articles
Composite
Of fluorinated addition polymer from unsaturated monomers
C428S422000, C427S195000, C525S055000, C525S165000, C525S121000, C525S377000, C526S242000, C526S250000, C526S254000
Reexamination Certificate
active
06673454
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a thermosetting powder coating composition. Particularly the present invention relates to a thermosetting powder coating composition which is less affected by mixing of other powder coating composition at coating.
BACKGROUND ART
Powder coating compositions containing a fluorine-containing resin are known in various patent publications such as JP -B-6-104792, JP-A-1-103670 and JP-A-8-41131, and can give a coated article being excellent in weather resistance and having a good appearance.
In an actual coating site of a powder coating, from the viewpoint of productivity, coating and baking of plural powder coatings are carried out on one coating line, and operation of the line is changed over for each powder coating.
However only by mixing of a small amount of the powder coating containing a fluorine-containing resin to other resin powder coating, various defects arise on a coating film of the other resin. This is one of the reasons why fluorine-containing resin-based powder coatings are not spread on the market irrespective of excellent physical properties of a coating film thereof.
The present inventors have continued their studies to find out a fluorine-containing resin powder coating composition which is less affected by mixing of other coating composition on a coating line and have found that the above-mentioned defects attributes to miscibility of a fluorine-containing resin with other resin and further that a fluorine-containing copolymer featured by insolubility in tetrahydrofuran (THF) can solve the above-mentioned problem. Thus the present invention was completed.
DISCLOSURE OF INVENTION
Namely the present invention relates to the thermosetting powder coating composition characterized in that the composition comprises (A) a fluorine-containing copolymer having crosslinkable functional group and (B) a curing agent and that the fluorine-containing copolymer (A) has a perfluoroolefin unit, has a fluorine content of not less than 10% by weight and is not dissolved in THF substantially.
It is preferable that the fluorine-containing copolymer (A) having crosslinkable functional group has a melting point of not more than 160° C. and a melt flow rate (MFR) of from 1 to 1,000 g/10 min when measured at 130° C. at a load of 2.1 kg.
Examples of the preferred fluorine-containing copolymer (A) having crosslinkable functional group are those comprising tetrafluoroethylene (TFE), hexafluoropropylene (HFP), ethylene (ET) and monomer unit having crosslinkable functional group and being copolymerizable therewith or those comprising TFE, HFP, isobutylene (IB) and monomer unit having crosslinkable functional group and being copolymerizable therewith.
Example of the preferred crosslinkable functional group is at least one of hydroxyl, carboxyl and epoxy.
Further it is preferable to introduce a vinyl ester compound unit, for example, vinyl benzoate unit and/or vinyl pivalate unit as a unit constituting the copolymer (A).
The present invention also relates to a coated article obtained by coating the above-mentioned thermosetting powder coating composition to a substrate and then baking it.
BEST MODE FOR CARRYING OUT THE INVENTION
First the fluorine-containing copolymer (A) having crosslinkable functional group and used in the present invention is explained below.
The fluorine-containing copolymer (A) having crosslinkable functional group is one which has at least the following characteristics (1) to (4).
(1) Having a Perfluoroolefin Unit
Example of perfluoroolefin is, for instance, at least one of perfluoroolefins such as TFE, HFP and perfluoro(vinyl ether). Particularly TFE and HFP are preferred. When the copolymer has a perfluoroolefin unit, a coating film being excellent in weather resistance, water resistance and stain-proofing property can be obtained. It is preferable that the perfluoroolefin unit is contained in the copolymer in an amount of not less than 5% by mole, especially 10 to 95% by mole.
(2) Having a Fluorine Content of Not Less Than 10% by Weight
The fluorine content derives from the perfluoroolefin unit and/or other fluorine-containing monomer. The fluorine content is not less than 10% by weight, preferably 20 to 75% by weight for the same reason as in (1) above.
Examples of the other fluorine-containing monomer are, for instance, vinylidene fluoride, trifluoroethylene, monofluoroethylene, chlorotrifluoroethylene, and the like. Those other fluorine-containing monomer units are optional units. A content thereof is not more than 30% by mole, usually 0 to 10% by mole.
(3) Being Insoluble in THF Substantially
Being insoluble in THF means being inferior in compatibility with a resin soluble in THF. Namely when after coating of a powder coating of a resin soluble in THF, the powder coating of the present invention is coated on the same coating line, or when carrying out coating in the reverse order, the fluorine-containing copolymer (A) is less affected by other resin, and the influence of mixing of the fluorine -containing copolymer (A) on the other powder coating can be decreased.
Being insoluble substantially encompasses the case of being soluble in THF in a concentration of less than 0.5% by weight. This is because when substantially measuring an intrinsic viscosity [&eegr;] of the resin in THF solution, a reliable intrinsic viscosity [&eegr;] cannot be measured unless the copolymer has a solubility of about 0.5% by weight or more.
Examples of the resin which is soluble in THF and is used for a powder coating are, for instance, an acrylic resin, polyester resin, epoxy resin, fluorine-containing resin described in JP-B-6-104792, and the like.
(4) Having Crosslinkable Functional Group
The crosslinkable functional group has functions of giving a curing site to the fluorine-containing copolymer (A) and giving a highly hard coating film subjected to thermosetting by a reaction with a curing agent, thus increasing a surface hardness while maintaining good flexibility.
In the present invention, examples of the crosslinkable functional group are, for instance, functional groups represented by the formulae (i):
wherein R is an alkyl group having 1 to 3 carbon atoms.
Among the above-mentioned functional groups, preferred are those represented by the formulae (ii):
Examples of the monomer capable of introducing such a functional group are, for instance, perfluorobutenoic acid (PFBA), a fluorine-containing monomer having an ether unit described in JP-A-8-67795 and in addition, non-fluorine-containing monomer having carboxyl such as maleic anhydride (MAL); hydroxyl-containing monomer such as hydroxybutyl vinyl ether (HBVE) and allyl alcohol; epoxy-containing monomer such as glycidyl vinyl ether (GVE); vinylmethoxysilane, vinylethoxysilane, monomer having hydrolyzable silyl group described in JP-A-8-120211, monomer having aminopropoxy group, and the like.
From the viewpoint of reactivity in the baking temperature range in case of combination use with a known curing agent, preferred are PFBA, carboxyl-containing monomer such as maleic anhydride, hydroxyl-containing monomer such as HBVE and glycidyl-containing monomer such as GVE.
The crosslinkable functional group forms a curing site, and its amount varies depending on reactivity of the functional group and kind of a curing agent. It is preferable that based on the whole fluorine-containing resin, an acid value is from 1 to 300 mgKOH/g, a hydroxyl value is from 1 to 200 mgKOH/g or an equivalent of epoxy is from 5 to 15,000 equivalents.
It is further preferable that the copolymer has the following characteristics.
(5) Having a Melting Point of Not More Than 160° C.
When the melting point is in this range, a good flow characteristic is given at baking.
(6) MFR Being From 1 to 1,000 g/10 min when Measured at 130° C. at a Load of 2.1 kg (The Measuring Conditions are Hereinafter the Same)
MFR is an important factor at melt-kneading or baking, particularly at baking. The larger the MFR is, the more the flowing property of molten resin increases. Therefore a smooth and uniform co
Fukagawa Ryoichi
Iwakiri Miyuki
Iwakiri Ryuji
Kitahara Takahiro
Nagai Go
Daikin Industries Ltd.
Iwakiri Miyuki
Zacharia Ramsey
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