Patent US4197251A successfully refreshed from Google Patents.
US4197251A
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Process for producing octamethylcyclotetrasiloxane
Assignee: Asahi Kasei Corp
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Filing: 1979-03-05
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Granted: 1980-04-08
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Expires: 1999-03-05
Abstract
Abstract Octamethylcyclotetrasiloxane can be produced from dimethylsiloxane effectively by suppressing the by-production of undesirable other siloxanes by reacting dimethylsiloxane in the presence of an alkaline catalyst, an inert solvent and recycled by-produced cyclic dimethylsiloxanes containing at least hexamethylcyclotrisiloxane in a reactor, while distilling volatile cyclic dimethylsiloxanes produced, said recycled by-produced cyclic dimethylsiloxanes containing at least hexamethylcyclotrisiloxane having been separated from the volatile cyclic dimethylsiloxanes by recovering octamethylcyclotetrasiloxane and recycled to the reactor.
Inventors
- 👤 Keizo Hirakawa
- 👤 Makoto Honda
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 15:23
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: 15
Claim 1
Independent Claim
61 words
In a process for producing octamethylcyclotetrasiloxane comprising reacting dimethylsiloxane in a reactor containing an inert solvent and an alkaline catalyst, distilling volatile cyclic dimethylsiloxanes during the reaction, and separating by-produced cyclic dimethylsiloxanes containing at least hexamethylcyclotrisiloxane from the volatile cyclic dimethylsiloxanes to yield octamethylcyclotetrasiloxane, the improvement which comprises recycling the separated by-produced cyclic dimethysiloxanes containing at least hexamethylcyclotrisiloxane to the reactor.
Claim 2
Dependent Claim
61 words
In a process for producing octamethylcyclotetrasiloxane comprising reacting dimethylsiloxane in a reactor containing an inert solvent and an alkaline catalyst, distilling volatile cyclic dimethylsiloxanes during the reaction, and separating by-produced cyclic dimethylsiloxanes containing at least hexamethylcyclotrisiloxane from the volatile cyclic dimethylsiloxanes to yield octamethylcyclotetrasiloxane, the improvement which comprises recycling the separated by-produced cyclic dimethysiloxanes containing at least hexamethylcyclotrisiloxane to the reactor.
Claim 3
Dependent Claim
31 words
A process according to claim 1, wherein the reactor has an opening for evaporation and a fractional distillation column the bottom of which is directly connected to the opening for evaporation.
Claim 4
Dependent Claim
59 words
A process according to claim 1, wherein the reaction is carried out under a pressure in the range of 0.03P.sub.4 ≦P.sub.r -P.sub.s ≦0.14P.sub.4 wherein P r is the reaction pressure; P 4 is the vapor pressure of pure octamethylcyclotetrasiloxane at the reaction temperature; and P s is the vapor pressure of the pure inert solvent at the reaction temperature.
Claim 5
Dependent Claim
72 words
A process according to claim 1, wherein the reaction is carried out in a total siloxane concentration in the reaction solution ranging from the upper limit of 60% by weight to the lower limit of ##EQU4## wherein P r is the reaction pressure; P 4 is the vapor pressure of pure octamethylcyclotetrasiloxane at the reaction temperature; and P s is the vapor pressure of the pure inert solvent at the reaction temperature.
Claim 6
Dependent Claim
24 words
A process according to claim 1, wherein the by-produced cyclic dimethylsiloxanes are separated from the volatile cyclic dimethylsiloxanes distilled form the reactor by distillation.
Claim 7
Dependent Claim
109 words
A process according to claim 1, wherein the insert solvent is an aryl hydrocarbon having 10 or more carbon atoms, a dialkyl ether having 10 or more carbon atoms, an aryl alkyl ether having 10 or more carbon atoms, a partially hydrogenerated aryl hydrocarbon having 10 or more carbon atoms, an alkyl hydrocarbon having 11 or more carbon atoms, an aryl alkyl hydrocarbon having 11 or more carbon atoms, or a diaryl ether having 11 or more carbon atoms, or a mixture of two or more of them, said inert solvent having a boiling point of 185° C. or more and a melting point of 100° C. or less.
Claim 8
Dependent Claim
17 words
A process according to claim 1 or 6, wherein the inert solvent is diphenyl ether and/or biphenyl.
Claim 9
Dependent Claim
16 words
A process according to claim 1, wherein the alkaline catalyst is an alkaline compound of potassium.
Claim 10
Dependent Claim
18 words
A process according to claim 8, wherein the alkaline compound of potassium is potassium hydroxide and/or potassium dimethylsilanolate.
Claim 11
Dependent Claim
21 words
A process according to claim 1, wherein the reaction is carried out at a temperature of 120° C. to 200° C.
Claim 12
Dependent Claim
16 words
A process according to claim 1, wherein the starting dimethylsiloxane is a hydrolyzate of industrial dimethyldichlorosilane.
Claim 13
Dependent Claim
41 words
A process according to claim 1, wherein the starting dimethylsiloxane is a low molecular weight polydimethylsiloxane recovered from a production process of high molecular weight polydimethylsiloxanes, or a mixture of the low molecular weight polydimethylsiloxane and a hydrolyzate of industrial dimethyldichlorosilane.
Claim 14
Dependent Claim
53 words
A process according to claim 1, wherein the starting dimethylsiloxane is fed to the reactor continuously and the by-produced cyclic dimethylsiloxanes are recycled to the reactor continuously, the ratio of a recycling rate of the by-produced cyclic dimethylsiloxanes to a feeding rate of the starting dimethylsiloxane being 0.02/1 to 1.2/1 on weight basis.
Claim 15
Dependent Claim
36 words
A process according to claim 1 or 5, wherein a ratio of a recycling rate of the by-produced cyclic dimethylsiloxanes to a distilling rate of the by-produced cyclic dimethylsiloxanes is 0.2/1 to 3.0/1 on weight basis.
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) | 1983-04-08 | 1983-10-08 | 1984-04-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1987-04-08 | 1987-10-08 | 1988-04-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1991-04-08 | 1991-10-08 | 1992-04-08 | $7700.00 | Window Closed / Lapsed |