Curable fluorosilicone rubber composition

• US 5,236,997 A
• Filed: 02/18/1992
• Issued: 08/17/1993
• Est. Priority Date: 02/18/1991
• Status: Expired due to Fees

• Current Assignee: Shin-Etsu Chemical Company Limited
• Original Assignee: Shin-Etsu Chemical Company Limited
• Inventors: Fujiki, Hironao
• Primary Examiner(s): Bleutge, John C.
• Assistant Examiner(s): MOORE, MARGARET G
• Application Number:
  US07/836,589
• Time in Patent Office: 546 Days
• Field of Search: 524/863, 524/864, 524/731, 528/42, 528/34, 528/17, 528/18, 525/477
• US Class Current: 524/731
• CPC Class Codes: C08L 2666/28 Non-macromolecular organic substances
• CPC Class Codes: C08L 83/08 containing silicon bound to organic groups containing atoms other than carbon, hydrogen and oxygen
• CPC Class Codes: C08L 83/14 in which at least two but not all the silicon atoms are connected by linkages other than oxygen atoms C08L83/10 takes precedence

Abstract

A room temperature-curable fluorosilicone rubber composition is disclosed, which is capable of giving a cured silicone rubber having excellent resistance against organic solvents and petroleums withhigh curability despite the high fluorine content which may cause steric hindfrance against the curing reaction due to the bulkiness of the fluorine-containing substituent groups. Different from conventional fluorine-containing diorganopolysiloxanes, in which the fluorine-containing substituent groups are bonded to the silicon atoms at random positions throughout the molecule, several silicon atoms from each of the molecular chain ends of the diorganopolysiloxane as the principal ingredient of the inventive composition are free from fluorine-containing substituent groups so that the crosslinking reaction with the silanolic hydroxy groups bonded to the terminal silicon atoms is not disturbed by the fluorine-containing groups in the vicinity of the terminal silanol groups.

Claims

1. A curable fluorosilicone rubber composition which is a uniform blend comprising:

(a) 100 parts by weight of a fluorine-substituted organopolysiloxane represented by the general formula

space="preserve" listing-type="equation">X--[--(--SiR.sub.f R--O--).sub.m --(--SiR.sub.2 --O--).sub.n-1 --SiR.sup.1 R--]--X,

in which R is a monovalent hydrocarbon group having 1 to 8 carbon atoms, R_f is a fluorine-substituted alkyl group or a fluorine-substituted alkyl group having one or more of etheric oxygen atoms --O-- or amide linkages --CONH-- between carbon atoms, R¹ is R or R_f, X is a group represented by the general formula

space="preserve" listing-type="equation">--Q--(--SiMe.sub.2 --O--).sub.a-1 --SiR.sup.2.sub.2 --OH

Me being a methyl group, Q being a divalent group of the formula --O--Si(CH₃)₂ --O-- or a divalent hydrocarbon group having 2 to 10 carbon atoms, R² being an atom or group selected from the class consisting of a hydrogen atom, a hydroxy group, a methyl group and a vinyl group and the subscript a being an integer of 1 to 20, and the subscripts m and n are each a positive integer with the proviso that m+n is in the range from 10 to 3000;

(b) from 0.5 to 20 parts by weight of an organosilicon compound having, in a molecule, at least three hydrolyzable groups bonded to the silicon atom or atoms;

(c) up to 500 parts by weight of an inorganic filler; and

(d) a curing catalyst in an amount sufficient to cure the composition into an elastomeric form.

2. The curable fluorosilicone rubber composition as claimed in claim 1, wherein the subscript a is a positive integer of 2 to 20.

3. The curable fluorosilicone rubber composition as claimed in claim 1, wherein the group denoted by R_f is a 3,3,3-trifluoropropyl group or a 2-(perfluorobutyl)ethyl group.

4. The curable fluorosilicone rubber composition as claimed in claim 1, wherein the group denoted by R is a methyl group.

5. The curable fluorosilicone rubber composition as claimed in claim 1, wherein the group denoted by R¹ is R.