US3989733A
Expired / Lapsed
US
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Process for the preparation of cyclic polydiorganosiloxanes
Assignee: Shin-Etsu Chemical Co Ltd
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Filing: 1973-12-28
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Granted: 1976-11-02
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Expires: 1993-12-28
Abstract
Abstract Cyclic polydiorganosiloxanes, in particular, cyclic trisiloxanes are continuously prepared from mixed polydiorganosiloxane, the starting material, by subjecting them to thermal cracking and rectification in a reactor composed of a column, vertically held, comprising a catalyst zone at the lower part in which the thermal cracking takes place to produce cyclic polydiorganosiloxanes and a rectification zone at the upper part in which the cyclic polydiorganosiloxanes are rectified into several fractions and a still positioned below the column. The cyclic polydiorganosiloxanes have structures different from the starting polydiorganosiloxanes.
Inventors
- 👤 Haruo Okamoto
- 👤 Isao Yanagisawa
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 11:07
CPC Classifications
C; C07; C07F; C07F7/00; C07F7/02; C07F7/08; C07F7/0834; C07F7/0838; C07F7/0872; C07F7/0874; C07F7/21
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
115 words
In a process for the thermal cracking of polydiorganosiloxanes in the presence of an alkaline catalyst to produce cyclic polydiorganosiloxanes, the improvement which comprises carrying out the reaction using the following steps: a. introducing the starting polydiorganosiloxane into the upper portion of the catalytic zone of a vertical reaction column; b. thermally cracking the starting polydiorganosiloxane within the catalytic zone to produce vapors of a cyclic polydiorganosiloxane; c. discharging any unreacted material to a still in communication with the bottom of the reaction column; d. rectifying the vapors in a rectification zone in communication with the top of the catalytic zone; and e. removing the rectified cyclic polydiorganosiloxane from the top of the rectification zone.
Claim 2
Dependent Claim
115 words
In a process for the thermal cracking of polydiorganosiloxanes in the presence of an alkaline catalyst to produce cyclic polydiorganosiloxanes, the improvement which comprises carrying out the reaction using the following steps: a. introducing the starting polydiorganosiloxane into the upper portion of the catalytic zone of a vertical reaction column; b. thermally cracking the starting polydiorganosiloxane within the catalytic zone to produce vapors of a cyclic polydiorganosiloxane; c. discharging any unreacted material to a still in communication with the bottom of the reaction column; d. rectifying the vapors in a rectification zone in communication with the top of the catalytic zone; and e. removing the rectified cyclic polydiorganosiloxane from the top of the rectification zone.
Claim 3
Dependent Claim
39 words
The process as claimed in claim 1 wherein said catalytic zone is packed with a granular hydroxide of an alkali metal or a packing material having a fused layer of hydroxide of an alkali metal adhered to its surface.
Claim 4
Dependent Claim
39 words
The process as claimed in claim 1 wherein said catalytic zone is packed with a granular carbonate of an alkali metal or a packing material having a fused layer of carbonate of an alkali metal adhered to its surface.
Claim 5
Dependent Claim
30 words
The process as claimed in claim 1 wherein said catalytic zone is packed with alternate layers of a granular hydroxide or carbonate of an alkali metal and a packing material.
Claim 6
Dependent Claim
26 words
The process as claimed in claim 4 wherein said packing material is covered with a fused layer of a hydroxide or carbonate of an alkali metal.
Claim 7
Dependent Claim
29 words
The process as claimed in claim 1 wherein said rectification zone is packed with a material selected from the group consisting of McMahon packing, Raschig rings and Stedman packing.
Claim 8
Dependent Claim
24 words
The process as claimed in claim 1 wherein said catalytic zone is heated to a temperature in the range from 100° to 300° C.
Claim 9
Dependent Claim
22 words
The process as claimed in claim 1 wherein lithium hydroxide or a carbonate of an alkali metal is placed in said still.
Claim 10
Dependent Claim
30 words
The process as claimed in claim 1 wherein said raw material polydiorganosiloxane is selected from the group consisting of the hydrolyzates of halogen substituted or unsubstituted diorganodichlorosilanes and mixtures thereof.
Claim 11
Dependent Claim
28 words
The process as claimed in claim 1 wherein said raw material polydiorganosiloxane is diluted with a solvent having a boiling point higher than that of said cyclic polydiorganosiloxane.
Claim 12
Dependent Claim
44 words
The process of claim 1 which comprises thermally cracking raw material polysiloxane selected from the group consisting of linear polydiorganosiloxanes and cyclic polydiorganosiloxanes having a degree of polymerization higher than 3, to produce hexaorganocyclotrisiloxane and subjecting said hexaorganocyclotrisiloxane to rectification in the rectification zone.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1979-11-02 | 1980-05-03 | 1980-11-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-11-02 | 1984-05-03 | 1984-11-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-11-02 | 1988-05-03 | 1988-11-02 | $7700.00 | Window Closed / Lapsed |