Cross-linkable polyurethane rubbers containing polyoxyperfluoroalkylene blocks

Claim 2

Fluorinated polyurethanes having a glass transition temperature lower than -80° C. and comprising perfluoropolyethereal-structure blocks exhibiting an average molecular weight ranging from about 1,000 to 10,000 and rubber-like properties, alternated with structural units of the stiff type, the units of the stiff type being at least, in part, provided with a double bond of the olefinic type, which is suited to give rise to cross-linking of the polymeric chains with a cross-linking system of the radicalic type, the polyurethanes being prepared using diisocyanates of the aliphatic, cycloaliphatic, or aromatic type, or perfluoropolyether diisocyanates.

Claim 3

Fluorinated polyurethanes according to claim 1, wherein they are susceptible of being processed according to conventional methods adopted for vulcanizable rubbers.

Claim 4

Fluorinated polyurethanes according to claim 1 wherein the polyurethane is vulcanized using vulcanizing agents selected from peroxides and sulphur or using treatment with U.V. rays or with an electron beam, characterized by: Tg less than -80° C.; hardness ranging from 50 Shore A to 75 Shore D; tensile strength greater than 30 kg/cm 2 ; limited variation of the modulus of elasticity in the temperature range from -100° C. to +150° C.

Claim 5

Fluorinated polyurethanes according to claim 1 wherein the perfluoropolyethereal structure blocks consist of random distribution sequences of fluorooxyalkylene units selected from: I) (CF 2 CF 2 O) and CF 2 O); II) ##STR4## CF 2 CF 2 O), (CFXO) where X is F or CF 3 ; III)(CH 2 CF 2 CF 2 O) in structures represented by the following formula: --(OCF 2 CF 2 CH 2 )pO R' f O (CH 2 CF 2 CF 2 O)p where R' is a fluoroalyphatic group containing from 1 to 21 carbon atoms, which can contain in the chain one or more heteroatoms, p and q are integers, p+q being greater than 2, R f , p and q being such that the molecular weight is in the above limits; IV) ##STR5## the units being bound to each other in the perfluoropolyethereal chain as follows: ##STR6## wherein R f is a fluoroalyphatic group containing from 1 to 21 carbon atoms, which can contain in the chain one or more heteroatoms, x is 0 or 1, a and b are integers, a+b is greater than 2, R f , x, a and b being such that the molecular weight is within the above range; V) --CF 2 CF 2 )-- or --CF 2 CF 2 CF 2 )-- or --CF(CF 3 )CF 2 )-- units deriving from perfluoropolyethers prepared using a scission process according to U.S. Pat. No. 4,720,527.

Claim 6

Fluorinated polyurethanes according to claim 1, wherein the stiff-type units are derived from a short-chain unsaturated diol and optionally also from a saturated diol or a short-chain diamine.

Claim 7

Fluorinated polyurethanes according to claim 1, wherein the stiff-type units containing a double bond are derived from the use of an unsaturated diol selected from: 2-butene-1,4-diol, trimethylolpropane monoallylether, glycerinmonoallylether.