Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
2001-09-10
2003-12-16
Mulcahy, Peter D. (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C524S500000, C524S545000, C525S195000, C525S196000, C252S511000
Reexamination Certificate
active
06664336
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to an aqueous curing composition of a fluoroelastomer and an article coated with a fluoroelastomer. In particular, the present invention relates to an aqueous curing composition comprising a fluororesin, and an article coated with a coating film formed from such a composition.
BACKGROUND ART
Fluoroelastomer coating compositions are widely used as industrial materials with being coated on or impregnated in fabric, fibers, metals, plastics, rubbers and other various substrates by making use of good heat resistance, weather resistance, oil resistance, solvent resistance and chemical resistance of the fluoroelastomers.
A coating film can be imparted with durability and non-tackiness, when the fluoroelastomer coating compositions contain a fluororesin or a terminal-modified perfluoropolyether (perfluoropolyether having a terminal functional group reactive with the fluoroelastomer such as —NH
2
, —CH
2
OH, etc.)
However, the fluoroelastomer is used as a surface coating of a roll which is used in office automation (OA) equipment (e.g. a copying machine, a printer, etc.), the coating film still has insufficient durability, and thus it is desired to improve the durability of the coating film of the fluoroelastomer.
DISCLOSURE OF THE INVENTION
One object of the present invention is to provide an aqueous curing composition of a fluoroelastomer, which can improve the durability and non-tackiness of a coating film thereof by bleeding up a relatively large amount of a fluororesin or an optional terminal-modified perfluoropolyether to the surface of the coating film, when the coating film is formed from the coating composition containing the fluororesin and optionally the terminal-modified perfluoropolyether.
Another object of the present invention is to provide an article coated with a fluoroelastomer, which can solve the above drawbacks of the articles coated with a film formed from the conventional aqueous curing composition of a fluoroelastomer, in particular, the rolls of the office automation equipment.
The above objects can be achieved by an aqueous curing composition of a fluoroelastomer comprising a fluoroelastomer, a fluororesin, a curing agent, an optional terminal-modified perfluoropolyether, and at least one additive component selected from the group consisting of surfactants which leave 0.3 wt. % or less of a decomposition residue after being heated at 300° C. for 30 minutes and polar solvents having a boiling point of 300° C. or less and a surface tension of at least 30 dyne/cm at room temperature, and an article at least a part of the surface of which is coated with a coating film formed from such an aqueous curing composition of a fluoroelastomer.
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the components contained in the composition of the present invention will be explained.
(A) Fluoroelastomer
The fluoroelastomer is usually supplied in the form of an aqueous dispersion. The aqueous dispersion of the fluoroelastomer is prepared by dispersing a fluorine-containing elastomeric copolymer (fluoroelastomer) in water at a concentration of 10 to 75% by weight in the presence of a surfactant.
The fluorine-containing elastomeric copolymer is a fluorine-containing copolymer containing repeating units represented by —CH
2
— in the backbones. One typical example of such a copolymer is a fluorine-containing elastic copolymer comprising vinylidene fluoride. Examples of such copolymer are copolymers comprising at least one repeating unit selected from the group consisting of —CF
2
—CH
2
—, —CH
2
—CH
2
— and —CH
2
—CH(CH
3
)—, and at least one repeating unit selected from the group consisting of —CF
2
—CF(CF
3
)—, —CF
2
—CF
2
—and —CF
2
—CF(ORf)— in which Rf is a fluoroalkyl group having 1 to 6 carbon atoms.
Specific examples of such copolymers include vinylidene fluoride-hexafluoropropylene copolymers, vinylidene fluoride-tetrafluoroethylene-hexafluoropropylene copolymers, ethylene-hexafluoropropylene copolymers, tetrafluoroethylene-propylene copolymers, etc. Among them, the vinylidene fluoride copolymers are preferable from the viewpoint of their crosslinkability.
Such fluorine-containing elastomeric copolymers are commercially distributed under the trade name of “DAIEL®” (available from Daikin Industries, Ltd.), “VITONE FLOMES®” (available from E. I. dupont), “AFLAS®” (available from ASAHI GLASS Co., Ltd.), etc.
(B) Curing agent and curing accelerator
The curing agent to be contained in the aqueous curing composition of the present invention may be either a conventional diamine curing agent or a conventional polyol curing agent.
Examples of the diamine curing agent include an aminosilane compound of the formula:
wherein R′ is a methyl group or an ethyl group, X is a single bond, —C
2
H
4
NH—, —CONH— or —C
2
H
4
NH—C
2
H
4
NH—NH—, and y is 2 or 3, or its partially or completely hydrolyzed products, and a polyaminosiloxane compound of the formula:
wherein R
1
, R
2
and R
3
represent independently of each other a hydrogen atom, an alkyl group having 1 to 6 carbon atom, an amino group, a polyamino group, or an alkyl group having 1 to 6 carbon group at least one hydrogen atom of which is replaced with an amino group or a polyamino group provided that at least two of R
1
, R
2
and R
3
are or have amino groups or at least one of R
1
, R
2
and R
3
is or has a polyamino group.
The polyol curing agent used in the present invention may be a compounds or a polymer having at least two hydroxyl groups, in particular, phenolic hydroxyl groups in a molecule, and having a curing capability. Specific examples of polyol curing agents include salts of basic compounds with phenol compounds such as
and polyphenols represented by the formula:
wherein Z is —CH
2
— or —CH
2
OCH
2
—, Y is a hydrogen atom, a halogen atom, an alkyl group having 1 to 4 carbon atoms, —CH
2
OR or —OR in which R is an alkyl group having 1 to 4 carbon atoms, and n is an integer of 0 to 100.
Examples of the basic compounds include ammonium salts, tertiary amines (e.g. 1,8-diazabicyclo-(5.4.0)-undecene-7, etc.), phosphonium salts (e.g. benzyltriphenylphosphonium chloride, methyltriphenylphosphoniummethyl methanephosphonate, etc.), alkali metals (e.g. lithium, sodium, potassium, etc.) and alkaline earth metals (beryllium, magnesium, calcium, barium, etc.). Among them, the salts of hydroquinone, bisphenol A, bisphenol AF and the resol type polyphenols are preferable from the viewpoint of the properties of the coating film.
When the polyol curing agent is used, the following compounds may be compounded as the optional curing accelerators:
Quaternary Ammonium Salts
A quaternary ammonium salt of the formula:
N(Ra)
4
A or (Ra)
3
N—Rc—N(Rb)
3
.2A
wherein A is an acid radical or a hydroxyl group; Ra and Rb are the same or different and represent an alkyl group having 1 to 20 carbon atoms, a halogenated alkyl group having 1 to 20 carbon atoms or an aryl group having 6 to 20 carbon atoms, provided that two or more of Ra and Rb may together form a carbocyclic group or a heterocyclic group; Rc is an alkylene group having 2 to 21 carbon atom or a phenylenedialkylene group having 8 to 12 carbon atoms.
Examples of acid radicals include halides, sulfate, sulfite, bisulfite, thiosulfate, sulfide, polysulfide, hydrogen sulfide, thiocyanate, carbonate, bicarbonate, nitrate, carboxylate, borate, phosphate, biphosphate, phosphite, perchlorate, bifluoride, arsenate, ferricyanide, ferrocyanide, molybdate, selenate, selenite, uranate, tungstate, etc.
Specific examples of quaternary ammonium salts include alkyl and aralkyl quaternary ammonium salts (e.g. trimethylbenzylammonium chloride, triethylbenzylammonium chloride, dimethyldecylbenzylammonium chloride, triethylbenzylammonium chloride, myristylbenzyldimethylammonium chloride, dodecyltrimethylammonium chloride, dimethyltetradecylbenzylammonium chloride, trimethyltetradecylammonium chloride, coconuttrimethylammonium chloride, stearyltrimethylammonium chloride, distearyldimethylammonium chloride, tetrabutylammonium hydroxide, 1,4-phen
Nakatani Yasukazu
Ogita Koichiro
Terasaka Kiyotaro
Tomihashi Nobuyuki
Daikin Industries Ltd.
Hu Henry S
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