Incorporating silica filler into polysiloxane rubber

Claim 2

A process for incorporating silica filler into gum consisting essentially of the steps of: (a) mixing components consisting essentially of: curable polysiloxane gum, said gum being substantially non-condensable with heating below about 210° C.; from about 10 to about 400 parts by weight silica filler having Si-bonded hydroxy or alkoxy functional groups for each 100 parts by weight gum and from about 5 to about 50 parts by weight condensable diorganopolysiloxane for each 100 parts by weight filler, said condensable diorganopolysiloxane consisting of the hydrolyzate of diorganodihalogensilanes of the formulas R 1 RSiX 2 , and R 2 2 SiX 2 , wherein R 1 is 3,3,3-trifluoropropyl, R is methyl or ethyl, R 2 is methyl or ethyl, and X is a halogen, said hydrolyzate comprising a mixture of fluoroalkyl-functional cyclic diorganopolysiloxanes having 3 to 10 siloxy units and silanol end-stopped low molecular weight linear diorganopolysiloxanes having hydroxy functionality that is readily reactive with the surface of said silica filler at temperatures less than about 210° C.; and (b) heating said mixture to a temperature of at most about 210° C. for a sufficient time to complete the condensation reaction between said silica filler and said condensable diorganopolysiloxane.

Claim 3

The process of claim 1 wherein said heating step is followed by the step of curing said polysiloxane gum.

Claim 4

The process of claim 1 wherein said heating step is followed by the step of adding a polysiloxane gum cure catalyst.

Claim 5

The process of claim 1 wherein said mixing and heating steps are performed simultaneously.

Claim 6

The process of claim 1 wherein said temperature of heating ranges from about 110° C. to about 210° C.

Claim 7

The process of claim 5 wherein said temperature of heating ranges from about 130° C. to about 180° C.

Claim 8

The process of claim 6 wherein said temperature of heating ranges from about 140° C. to about 160° C.

Claim 9

The process of claim 1 wherein said polysiloxane gum has a viscosity of from about 500,000 to about 300,000,000 centipoise at 23° C.

Claim 10

The process of claim 1 wherein said polysiloxane gum has the general formula R.sub.a SiO.sub.4-a/2 where R is selected from alkyl radicals of 1 to 8 carbon atoms, vinyl radicals, phenyl radicals, haloalkyl radicals of 3 to 10 carbon atoms, halophenyl radicals, hydroxy radicals, alkoxy radicals, aryloxy radicals, cyanoalkyl radicals, and mixtures thereof and a varies from about 1.98 to about 2.01.

Claim 11

The process of claim 1 wherein said polysiloxane gum has the general formula ##STR3## where R 1 may be vinyl, methyl, hydroxy, or alkoxy; R 2 may be vinyl, phenyl, alkyl of 1 to 8 carbon atoms, fluoroalkyl of 3 to 10 carbon atoms, or mixtures thereof; and Y varies from 2,500 to 11,000.

Claim 12

The process of claim 10 wherein said polysiloxane gum is M-stopped.

Claim 13

The process of claim 10 wherein said polysiloxane gum contains vinyl functional groups.

Claim 14

The process of claim 10 wherein said polysiloxane gum contains hydroxy functional groups.

Claim 15

The process of claim 10 wherein said polysiloxane gum contains alkoxy functional groups.

Claim 16

The process of claim 1 wherein said heating step is followed by the step of adding a crosslinking agent.

Claim 17

A mixture consisting essentially of: (a) curable polysiloxane gum, said gum being substantially non-condensable with heating below about 210° C.; (b) from about 10 to about 400 parts by weight silica filler having Si-bonded hydroxy or alkoxy functional groups for each 100 parts by weight gum; and (c) from about 5 to about 50 parts by weight condensable diorganopolysiloxane for each 100 parts by weight filler, said condensable diorganopolysiloxane consisting of the hydrolyzate of diorganodihalogensilanes of the formulas R 1 RSiX 2 , and R 2 2 SiX 2 , wherein R 1 is 3,3,3-trifluoropropyl, R is methyl or ethyl, R 2 is methyl or ethyl, and X is a halogen, said hydrolyzate comprising a mixture of fluoroalkyl-functional cyclic diorganopolysiloxanes having 3 to 10 siloxy units and silanol end-stopped low molecular weight linear diorganopolysiloxanes having hydroxy functionality is readily reactive with the surface of said silica filler at temperatures less than about 210° C.

Claim 18

A mixture consisting essentially of: (a) curable polysiloxane gum, said gum being substantially non-condensable with heating below about 210° C.; (b) from about 10 to about 400 parts by weight silica filler having Si-bonded hydroxy or alkoxy functional groups for each 100 parts by weight gum; and (c) from about 5 to about 50 parts by weight condensable diorganopolysiloxane for each 100 parts by weight filler, said condensable diorganopolysiloxane consisting of the hydrolyzate of diorganodihalogensilanes of the formulas R 1 RSiX 2 , and R 2 2 SiX 2 , wherein R 1 is 3,3,3-trifluoropropyl, R is methyl or ethyl, R 2 is methyl or ethyl, and X is a halogen, said hydrolyzate comprising a mixture of fluoroalkyl-functional cyclic diorganopolysiloxanes having 3 to 10 siloxy units and silanol end-stopped low molecular weight linear diorganopolysiloxanes having hydroxy functionality is readily reactive with the surface of said silica filler at temperatures less than about 210° C.

Claim 19

The mixture of claim 16 wherein said polysiloxane gum has the general formula R.sub.a SiO.sub.4-a/2 where R is selected from alkyl radicals of 1 to 8 carbon atoms, vinyl radicals, phenyl radicals, haloalkyl radicals of 3 to 10 carbon atoms, halophenyl radicals, hydroxy radicals, alkoxy radicals, aryloxy radicals, cyanoalkyl radicals, and mixtures thereof and a varies from about 1.98 to 2.01.

Claim 20

A process for incorporating silica filler into gum consisting essentially of: (a) mixing components consisting essentially of: curable polysiloxane gum, said gum being substantially non-condensable with heating below about 210° C.; from about 10 to about 400 parts by weight silica filler having Si-bonded hydroxy or alkoxy functional groups for each 100 parts by weight gum; an effective amount of crosslinking agent; and from about 5 to about 50 parts by weight condensable diorganopolysiloxane for each 100 parts by weight filler, said condensable diorganopolysiloxane consisting of the hydrolyzate of diorganodihalogensilanes of the formulas R 1 RSiX 2 , and R 2 2 SiX 2 , wherein R 1 is 3,3,3-trifluoropropyl, R is methyl or ethyl, R 2 is methyl or ethyl, and X is a halogen, said hydrolyzate comprising a mixture of fluoroalkyl-functional cyclic diorganopolysiloxanes having 3 to 10 siloxy units and silanol end-stopped low molecular weight linear diorganopolysiloxanes having hydroxy functionality that is readily reactive with the surface of said silica filler at temperatures less than about 210° C.; and (b) heating said mixture to a temperature of at most about 210° C. for a sufficient time to complete the condensation reaction between said silica filler and said condensable diorganopolysiloxane.

Claim 21

A process for incorporating silica filler into gum consisting essentially of: (a) mixing components consisting essentially of: curable polysiloxane gum, said gum being substantially non-condensable with heating below about 210° C.; from about 10 to about 400 parts by weight silica filler having Si-bonded hydroxy or alkoxy functional groups for each 100 parts by weight gum; an effective amount of crosslinking agent; and from about 5 to about 50 parts by weight condensable diorganopolysiloxane for each 100 parts by weight filler, said condensable diorganopolysiloxane consisting of the hydrolyzate of diorganodihalogensilanes of the formulas R 1 RSiX 2 , and R 2 2 SiX 2 , wherein R 1 is 3,3,3-trifluoropropyl, R is methyl or ethyl, R 2 is methyl or ethyl, and X is a halogen, said hydrolyzate comprising a mixture of fluoroalkyl-functional cyclic diorganopolysiloxanes having 3 to 10 siloxy units and silanol end-stopped low molecular weight linear diorganopolysiloxanes having hydroxy functionality that is readily reactive with the surface of said silica filler at temperatures less than about 210° C.; and (b) heating said mixture to a temperature of at most about 210° C. for a sufficient time to complete the condensation reaction between said silica filler and said condensable diorganopolysiloxane.

Claim 22

A mixture consisting essentially of: (a) curable polysiloxane gum, said gum being substantially non-condensable with heating below about 210°0 C.; (b) from about 10 to about 400 parts by weight silica filler having Si-bonded hydroxy or alkoxy functional groups for each 100 parts by weight gum; and (c) from about 5 to about 50 parts by weight condensable diorganopolysiloxane for each 100 parts by weight filler, said condensable diorganopolysiloxane consisting of the hydrolyzate of diorganodihalogensilanes of the formulas R 1 RSiX 2 , and R 2 2 SiX 2 , wherein R 1 is 3,3,3-trifluoropropyl, R is methyl or ethyl, R 2 is methyl or ethyl, and X is a halogen, said hydrolyzate comprising a mixture of fluoroalkyl-functional cyclic diorganopolysiloxanes having 3 to 10 siloxy units and silanol end-stopped low molecular weight linear diorganopolysiloxanes having hydroxy functionality that is readily reactive with the surface of said silica filler at temperatures less than about 210° C., and (d) an effective amount of crosslinking agent.

Claim 23

A mixture consisting essentially of: (a) curable polysiloxane gum, said gum being substantially non-condensable with heating below about 210°0 C.; (b) from about 10 to about 400 parts by weight silica filler having Si-bonded hydroxy or alkoxy functional groups for each 100 parts by weight gum; and (c) from about 5 to about 50 parts by weight condensable diorganopolysiloxane for each 100 parts by weight filler, said condensable diorganopolysiloxane consisting of the hydrolyzate of diorganodihalogensilanes of the formulas R 1 RSiX 2 , and R 2 2 SiX 2 , wherein R 1 is 3,3,3-trifluoropropyl, R is methyl or ethyl, R 2 is methyl or ethyl, and X is a halogen, said hydrolyzate comprising a mixture of fluoroalkyl-functional cyclic diorganopolysiloxanes having 3 to 10 siloxy units and silanol end-stopped low molecular weight linear diorganopolysiloxanes having hydroxy functionality that is readily reactive with the surface of said silica filler at temperatures less than about 210° C., and (d) an effective amount of crosslinking agent.