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
1999-03-25
2001-06-26
Yoon, Tae H. (Department: 1714)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C524S236000, C524S330000, C525S374000, C525S378000
Reexamination Certificate
active
06252006
ABSTRACT:
This application is the national phase under 35 U.S.C. §371 of PCT International Application No. PCT/JP97/02853 which has an International filing date of Aug. 19, 1997 which designated the United States of America.
1. Field of the Invention
The present invention relates to a coating composition of a fluororubber. In particular, the present invention relates to a curable composition of a fluororubber suitable for coating, which comprises a fluorine-containing copolymer, a polyol curing agent, and a specific curing accelerator.
2. Prior Art
When fluororubbers are cured with polyols, curing accelerators (basic compounds) are added to curable compositions. However, when curing accelerators are added to the curable compositions of fluororubbers, for example coating compositions, the pot life of the compositions is shortened, since the compositions are gelled. Thus, two or more pack type compositions are prepared and practically used, but practically usable one-pack type compositions are not known.
It may be contemplated to use a curing accelerator having a low reactivity to formulate a polyl-curable fluororubber coating composition in the form of a one-pack composition. However, such a composition requires a long time and heating at high temperatures to obtain a coated film by drying and calcining the coating compositions.
SUMMARY OF THE INVENTION
One object of the present invention is to formulate a polyol-curable fluororubber composition in the form of a one-pack type composition having a long pot life, and to provide a curable composition of a fluororubber which can provide a cured coating film having a high strength in a short time at a relatively low temperature.
Another object of the present invention is to provide a one-pack type curable composition of a fluorine-containing copolymer, which can be applied by dispenser type coating or screen printing, even when the concentration of the fluorine-containing copolymer is high.
To achieve these objects, the present invention provides a coating composition of a fluororubber comprising a fluorine-containing elastomeric copolymer which comprises repeating units of the formula: —CH
2
— in the backbone, a polyol curing agent, and a complex compound of a quaternary ammonium salt having a pKa of at least 8 and an organic acid as a curing accelerator.
DETAILED DESCRIPTION OF THE INVENTION
Now, each component contained in the composition of the present invention will be explained.
(A) A fluorine-containing elastomeric copolymer contained in the composition of the present invention is a fluorine-containing copolymer comprising repeating units of the formula: —CH
2
— in the backbone. Typical examples of such a copolymer include fluorine-containing copolymers comprising vinylidene fluoride. Specific examples of such copolymers are those copolymers comprising repeating units having the following structures:
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
—CH
2
— and —CF
2
—(ORf)CF— in which Rf is a fluoroalkyl group having 1 to 6 carbon atoms.
Specific examples of such copolymers are a copolymer comprising vinylidene difluoride and hexafluoropropylene, a copolymer comprising vinylidene difluoride, tetrafluoroethylene and hexafluoropropylene, a copolymer of ethylene and hexafluoropropylene, a copolymer of tetrafluoroethylene and propylene, and the like.
Such fluorine-containing elastomeric copolymers are commercially distributed under the trade name of “DAIEL” (trademark) (available from Daikin Industries, Ltd.), “VITONE FLOME” (available from E. I. duPont), “AFLAS” (available from ASAHI GLASS Co., Ltd.), etc.
(B) Polyol Curing Agents
Polyol curing agents used in the present invention are compounds or polymers 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 are phenol compounds such as
wherein Z is —CH
2
— or —CH
2
OCH
2
—, Y is a hydrogen atom, a halogen atom, —R, —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.
Among them, hydroquinone, bisphenol A, bisphenol AF, and resorcinol phenolic resins are preferable.
(C) Curing accelerators
Examples of quaternary ammonium salts which constitute curing accelerators which are used in the present invention include the following compounds:
Quaternary Ammonium Salts
A quaternary ammonium salt of the formula:
NR
4
X or R
3
N—R′—NR
3
.2X
wherein X is an acid radical or a hydroxyl group; R groups 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 7 to 20 carbon atoms, provided that two or more R groups may together form a carbocyclic group or a heterocyclic group; R′ 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, coconut-trimethylammonium chloride, stearyltrimethylammonium chloride, distearyldimethylammonium chloride, tetrabutylammonium hydroxide, 1,4-phenylenedimethylene-bistrimethylammonium dichloride, ethylenebistriethylammonium dibromide, etc.), and quaternary 1,8-diaza-bicyclo[5.4.0]-7-undecenium salts (e.g. 8-methyl-1,8-diaza-bicylo[5.4.0]-7-undecenium chloride, 8-methyl-1,8-diaza-bicylo[5.4.0]-7-undecenium iodide, 8-methyl-1,8-diaza-bicylo[5.4.0]-7-undecenium hydroxide, 8-methyl-1,8-diaza-bicylo[5.4.0]-7-undecenium methylsulfate, 8-methyl-1,8-diaza-bicylo[5.4.0]-7-undecenium bromide, 8-propyl-1,8-diaza-bicylo[5.4.0]-7-undecenium bromide, 8-dodecyl-1,8-diaza-bicylo[5.4.0]-7-undecenium chloride, 8-dodecyl-1,8-diaza-bicylo[5.4.0]-7-undecenium hydroxide, 8-eicosyl-1,8-diaza-bicylo[5.4.0]-7-undecenium chloride, 8-tetracosyl-1,8-diaza-bicylo[5.4.0]-7-undecenium chloride, 8-benzyl-1,8-diaza-bicylo[5.4.0]-7-undecenium chloride, 8-benzyl-1,8-diaza-bicylo[5.4.0]-7-undecenium hydroxide, 8-phenethyl-1,8-diaza-bicylo[5.4.0]-7-undecenium chloride, 8-(3-phenylpropyl)-1,8-diaza-bicylo[5.4.0]-7-undecenium chloride, etc.).
Organic acids having 1 to 9 carbon atoms, preferably 1 to 4 carbon atoms are used as organic acids constituting the curing accelerators of the present invention.
Organic acids having 10 or more carbon atoms are less preferable, since they remain in coated films.
Preferable examples of organic acids are monocarboxylic acids such as fumaric acid, acetic acid, propionic acid, etc.; and dicarboxylic acids such as oxalic acid, malonic acid, succinic acid, etc.
Organic acids are used to suppress the polyol curing of fluorine-containing copolymers in the compositions. The curing of fluorine-containing copolymers is suppressed by organic acids in the compositions, but the organic acids evaporate or decompose when the compositions are applied onto a substrate, dried and calcined. Thus, the above basic compounds accelerate the curing reaction.
The composition of the present invention comprises 0.1 to 10 wt. parts, preferably 1 to 5 wt. parts of a polyol curing agent, and 0.01 to 10 wt. parts, preferably 0.05 to 5 w
Kinoshita Toshiyuki
Terasaka Kiyotaro
Tomihashi Nobuyuki
Birch & Stewart Kolasch & Birch, LLP
Daikin Industries Ltd.
Yoon Tae H.
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