Curable fluoropolyether rubber compositions

#This invention relates to curable fluoropolyether rubber compositions which cure into parts having good water repellency, oil repellency, heat resistance, solvent resistance, chemical resistance, weather resistance and parting property as well as improved acid resistance.

#Japanese Patent No. 2,990,646 (JP-A 8-199070) discloses a composition comprising (A) a straight-chain fluoropolyether compound having at least two alkenyl groups in a molecule and a perfluoroalkyl ether structure in the backbone, (B) an organosilicon compound having at least two H—SiOSi structures in a molecule, and (C) a hydrosilylation catalyst, which cures into parts having a good profile of heat resistance, chemical resistance, solvent resistance, parting property, water repellency, oil repellency and weather resistance.

#Although this fluoropolyether rubber composition performs well in most applications, a need for higher acid resistance exists in special applications associated with semiconductors, engine oils and the like where acid resistance is necessary.

#Examples of the invention are given below by way of illustration and not by way of limitation. The viscosity is a measurement at 25° C. All parts are by weight.

#To 100 parts of a polymer of formula (i) below (viscosity 8,500 cs, average molecular weight 22,000, and vinyl content 0.009 mol/100 g) was added 20 parts of dimethylsiloxy-treated fumed silica having a specific surface area of 200 m2/g. They were mixed, heat treated and milled on a three-roll mill. To the mixture were added 2.64 parts of a fluorinated organosilicon compound of formula (ii) below, 0.2 part of a toluene solution of a catalyst in the form of chloroplatinic acid modified with CH2═CHSiMe2OSiMe2CH═CH2 (platinum concentration 1.0 wt %), and 0.4 part of a 50% toluene solution of ethynyl cyclohexanol. They were mixed to give composition I. It was deaerated in vacuum, placed in a rectangular frame of 2 mm deep, deaerated again, and press cured at 100 kg/cm2 and 150° C. for 10 minutes. From the cured sample, a specimen was cut out and measured for physical properties according to JIS K-6251 and 6253. The results are shown below.

#Hardness (Durometer type A) 40 Elongation 540% Tensile strength 10.7 MPa (i) (ii)