Continuous devolatilization of silanol-terminated silicone polymer

Claim 2

A process for continuously producing a substantially cyclic polysiloxane-free linear diorganopolysiloxane fluid which is chain-stopped primarily with hydroxy groups, said process comprising the steps of: (i) feeding steam and a linear diorganopolysiloxane fluid chain-stopped primarily with hydroxy groups, said fluid also containing low-boiling cyclic polysiloxanes, into an evacuated, tortuous, confined passageway to form a turbulent mixture of said linear diorganopolysiloxane fluid and steam in the passageway; (ii) passing said mixture of linear diorganopolysiloxane fluid and steam through the tortuous passageway under partial vacuum and at a temperature below that at which said cyclic polysiloxanes would normally vaporize at atmospheric pressure, to form a vaporized mixture comprising steam and cyclic polysiloxanes freed from said linear diorganopolysiloxane fluid; (iii) removing said vaporized mixture comprising steam and cyclic polysiloxanes and said linear diorganopolysiloxane fluid which is substantially free of said cyclic polysiloxanes from the tortuous passageway; and (iv) separating said vaporized mixture of steam and cyclic polysiloxanes from said substantially cyclic polysiloxane-free linear diorganopolysiloxane fluid.

Claim 3

A process as defined in claim 1 wherein said cyclic diorganosiloxanes comprise from about 9 to about 18% by weight of the feed stock, on a steam-free basis, in step (i), and less than 2% by weight of the final product, in step (iv).

Claim 4

A process as defined in claim 1 wherein said linear diorganopolysiloxane fluid is a dimethylpolysiloxane fluid chain-stopped primarily with hydroxy groups, and said cyclic polysiloxanes comprise cyclic methylpolysiloxanes.

Claim 5

A process as defined in claim 1 wherein said diorganopolysiloxane fluid has a viscosity in the range of from about 1,000 to about 1,000,000 cps. at 25° C.

Claim 6

A process as defined in claim 1 wherein the pressure is in the range from about 30 to about 70 mm.

Claim 7

A process as defined in claim 1 wherein the temperature is in the range from about 50° to about 175° C.

Claim 8

A process as defined in claim 1 wherein step (iv) is carried out in a separator, from which said vaporized mixture of steam and cyclic polysiloxanes is continuously removed as a first stream and said substantially cyclic polysiloxane-free linear diorganopolysiloxane fluid is removed as a second stream.

Claim 9

A process for continuously producing a substantially cyclic methylpolysiloxane-free linear dimethylpolysiloxane fluid which is chain-stopped primarily with hydroxy groups, said process comprising the steps of: (i) feeding steam and a linear dimethylpolysiloxane fluid chain-stopped primarily with hydroxy groups, said fluid also containing low-boiling cyclic methylpolysiloxanes, into an evacuated, tortuous, confined passageway to form a turbulent mixture of said linear dimethylpolysiloxane fluid and steam in the passageway; (ii) passing said mixture of linear dimethylpolysiloxane fluid and steam through the tortuous passageway at a pressure of from about 30 to about 70 mm Hg and a temperature of from about 50° to about 175° C., to form a vaporized mixture comprising steam and cyclic methylpolysiloxanes freed from said linear dimethylpolysiloxane fluid; (iii) removing said vaporized mixture comprising steam and cyclic dimethylsiloxanes and said linear dimethylpolysiloxane fluid which is substantially free of said cyclic dimethylsiloxanes from the tortuous passageway; and (iv) separating said vaporized mixture of steam and cyclic dimethylsiloxanes from said substantially cyclic methylpolysiloxane-free linear dimethylpolysiloxane fluid.

Claim 10

A process for continuously producing a substantially cyclic methylpolysiloxane-free linear dimethylpolysiloxane fluid which is chain-stopped primarily with hydroxy groups, said process comprising the steps of: (i) feeding steam and a linear dimethylpolysiloxane fluid chain-stopped primarily with hydroxy groups, said fluid also containing low-boiling cyclic methylpolysiloxanes, into an evacuated, tortuous, confined passageway to form a turbulent mixture of said linear dimethylpolysiloxane fluid and steam in the passageway; (ii) passing said mixture of linear dimethylpolysiloxane fluid and steam through the tortuous passageway at a pressure of from about 30 to about 70 mm Hg and a temperature of from about 50° to about 175° C., to form a vaporized mixture comprising steam and cyclic methylpolysiloxanes freed from said linear dimethylpolysiloxane fluid; (iii) removing said vaporized mixture comprising steam and cyclic dimethylsiloxanes and said linear dimethylpolysiloxane fluid which is substantially free of said cyclic dimethylsiloxanes from the tortuous passageway; and (iv) separating said vaporized mixture of steam and cyclic dimethylsiloxanes from said substantially cyclic methylpolysiloxane-free linear dimethylpolysiloxane fluid.

Claim 11

A process as defined in claim 8 wherein said cyclic methylpolysiloxanes comprise from about 9 to about 18% by weight of the feed stock, on a steam-free basis, in step (i), and less than 2% by weight of the final product, in step (iv).

Claim 12

A process as defined in claim 1 wherein said linear diorganopolysiloxane has the formula: ##STR2## wherein R and R 1 can be the same or different, and are each organic radicals selected from alkyl, aryl, haloalkyl, haloaryl, alkenyl, alkaryl, aralkyl, haloalkenyl, cyanoalkyl, cycloalkyl, cycloalkenyl, and n has a value of at least 10.