Patent ID: 8729175

Claim:
A process to form a fluoroelastomer gel having the following properties: appearance: transparent gelatinous solid; water content between 10 percent and 90 percent by weight; density between 1.1 and 2.1 g/cm 3 ; said gel satisfies the following test: the gel subjected to drying in a stove at 90° C. until a constant weight gives a curable fluoroelastomer, said process comprising the following steps, starting from a fluoroelastomer polymerization latex: Ao. optionally, mixing of the fluoroelastomer latex with a semicrystalline (per)fluoropolymer latex, in an amount from 0 percent to 70 percent by weight, referred to the total of dry weight fluoroelastomer and semicrystalline (per)fluoropolymer; A. optionally, dilution with water of the polymerization latex of the fluoroelastomer, or of the mixture Ao, until obtaining a fluoroelastomer concentration, expressed in g polymer/kg latex, in the range 50-600; B. optionally, mixing of the polymerization latex Ao, or of the diluted latex A, or of the starting latex, with one or more organic compounds soluble in the latex aqueous phase, capable to lower the latex freezing point without causing the latex coagulation, said one or more organic compounds being such and/or in an amount such that the resulting mixture has the freezing point at a temperature lower than or equal to the glass transition temperature Tg (° C.) of the latex fluoroelastomer; C. preparation of an aqueous solution containing an electrolyte, optionally said solution being added with one or more organic compounds as defined in B, soluble in the latex aqueous phase, i.e. capable to lower the freezing point of the solution C, and such and/or in an amount such that the resulting solution C has a freezing point lower than or equal to the freezing point of the mixture prepared in B; D. cooling of the polymerization latex, or of the mixture Ao, or of the diluted latex A, or of the mixture B, until a temperature T1 lower than or equal to the glass transition temperature of the latex fluoroelastomer; E. cooling of the aqueous solution C at a temperature T2 lower than or equal to the glass transition temperature of the latex fluoroelastomer, or T2 being substantially equal to T1; F. formation of a gel by dripping of the mixture D into the solution E; G. optionally, washing with water of the gel obtained in F; H. optionally, gel drying and obtainment of the fluoroelastomer.