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  Curable perfluoropolyether compositions and rubber or gel articles comprising the sameRelated Patent Categories: Synthetic Resins Or Natural Rubbers -- Part Of The Class 520 Series, Involving Inert Gas, Steam, Nitrogen Gas, Or Carbon Dioxide, Processes Of Preparing A Desired Or Intentional Composition Of At Least One Nonreactant Material And At Least One Solid Polymer Or Specified Intermediate Condensation Product, Or Product Thereof, Adding A Nrm To A Preformed Solid Polymer Or Preformed Specified Intermediate Condensation Product, Composition Thereof; Or Process Of Treating Or Composition Thereof, From Silicon-containing ReactantCurable perfluoropolyether compositions and rubber or gel articles comprising the same description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20050277731, Curable perfluoropolyether compositions and rubber or gel articles comprising the same. Brief Patent Description - Full Patent Description - Patent Application Claims
CROSS-REFERENCE TO RELATED APPLICATION [0001] This non-provisional application claims priority under 35 U.S.C. .sctn.119(a) on Patent Application No. 2004-174777 filed in Japan on Jun. 11, 2004, the entire contents of which are hereby incorporated by reference. FIELD OF THE INVENTION [0002] This invention relates to perfluoropolyether compositions which cure into rubber or gel products having heat resistance, oil resistance, chemical resistance, solvent resistance, low-temperature properties, moisture resistance, and low gas permeability and especially, improved acid resistance. The invention also relates to rubber or gel articles obtained by curing the compositions. BACKGROUND ART [0003] Japanese Patent No. 2,990,646 (JP-A 8-199070) discloses a curable composition comprising a linear perfluoropolyether compound containing at least two alkenyl groups per molecule and having a perfluoropolyether structure in its backbone, an organosilicon compound having at least two H--SiOSiO structures per molecule, and a hydrosilylation catalyst, which cures into a product having a good profile of heat resistance, chemical resistance, solvent resistance, water repellency, oil repellency and weatherability. [0004] These perfluoropolyether rubber compositions perform well in most applications. However, their acid resistance is short in those applications requiring chemical resistance such as sealants in semiconductor manufacturing units, sealants and potting materials for use with engine oil, and sealants and potting materials for use in engine exhaust parts. There is a need for perfluoropolyether rubber or gel compositions which are improved in oil resistance and chemical resistance, and especially acid resistance. [0005] JP-A 2000-248166 discloses a curable fluoropolyether base rubber composition comprising a linear fluoropolyether compound having at least two alkenyl groups, an organosilicon compound having at least two SiH groups, a hydrosilylation catalyst, and surface-hydrophobicized microparticulate silica having a specific surface area of at least 50 m.sup.2/g and a nitrogen atom content of 500-5,000 ppm. SUMMARY OF THE INVENTION [0006] An object of the invention is to provide curable perfluoropolyether compositions which are cured into rubber or gel having exhibit good heat resistance, solvent resistance, chemical resistance, weatherability, water repellency and oil repellency and especially acid resistance. Another object is to provide rubber or gel articles comprising the same. [0007] It has been found that perfluoropolyether compositions which cure into rubber or gel products having improved acid resistance are obtainable using a linear perfluoropolyether compound having a weight average molecular weight of 10,000 to 100,000. [0008] In one aspect, the present invention provides a curable perfluoropolyether composition comprising (A) a linear perfluoropolyether compound containing at least two alkenyl groups per molecule, having a perfluoropolyether structure comprising recurring units --C.sub.aF.sub.2aO-- wherein a is an integer of 1 to 6 in its backbone, and having a weight average molecular weight of 10,000 to 100,000; (B) an organosilicon compound containing at least two silicon atom-bonded hydrogen atoms per molecule, selected from the class consisting of (B-1) a cyclic organohydrogenpolysiloxane containing at least one perfluoroalkyl group or perfluoropolyether substituent group per molecule, and (B-2) an organosilicon compound containing at least one perfluoroalkyl group or perfluoropolyether substituent group per molecule wherein all silicon atom-bonded hydrogen atoms form H--Si(CH.sub.2).sub.gSi-- structures wherein g is an integer of 1 to 3; (C) a reinforcing filler; and (D) a hydrosilylation catalyst, the composition being cured into a rubber. [0009] In another aspect, the present invention provides a curable perfluoropolyether composition comprising (A) a linear perfluoropolyether compound as defined above; (B) an organosilicon compound as defined above; (D) a hydrosilylation catalyst; and (E) a polyfluoromonoalkenyl compound containing one alkenyl group per molecule and having a perfluoropolyether structure in its backbone, the composition being cured into a gel. [0010] In this specification, a rubber-like cured product or rubber means a cured product which is able to measure hardness according to JIS K 6253 or ISO 1619 and especially has a hardness of 10 to 80 according to JIS A-type hardness tester or Type A Durometer. On the other hand, gel-like cured product or gel means that a cured product which is unable to measure hardness according to JIS A-type hardness tester or Type A Durometer and has a penetration of 1 to 200, especially 10 to 150 according to JIS K 2220 or ASTM D-1403. [0011] The perfluoropolyether compositions of the invention, when cured, impart rubber or gel products having good heat resistance, oil resistance, chemical resistance, solvent resistance, low-temperature properties, moisture resistance and low gas permeability, and especially improved acid resistance. BRIEF DESCRIPTION OF THE DRAWINGS [0012] FIGS. 1 and 2 are transverse cross-sectional views of electronic packages under test in Example 5. DESCRIPTION OF THE PREFERRED EMBODIMENT [0013] Component (A) of the curable perfluoropolyether compositions according to the invention is a linear perfluoropolyether compound containing at least two alkenyl groups per molecule, having a perfluoropolyether structure, preferably divalent perfluoroalkylether structure, in its backbone, and having a weight average molecular weight (Mw) of 10,000 to 100,000, as determined by gel permeation chromatography (GPC) relative to polystyrene standards. [0014] The perfluoroalkyl ether structures include structures comprising a plurality of recurring units --C.sub.aF.sub.2aO-- wherein a is at each occurrence an integer of 1 to 6, for example, structures represented by the general formula (7): (C.sub.aF.sub.2aO).sub.q (7) [0015] wherein q is an integer of 50 to 600, preferably 50 to 400, more preferably 50 to 200. [0016] Examples of the recurring units --C.sub.aF.sub.2aO-- are: --CF.sub.2O--, --CF.sub.2CF.sub.2O--, --CF.sub.2CF.sub.2CF.sub.2O--, Continue reading about Curable perfluoropolyether compositions and rubber or gel articles comprising the same... Full patent description for Curable perfluoropolyether compositions and rubber or gel articles comprising the same Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Curable perfluoropolyether compositions and rubber or gel articles comprising the same patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. 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