# US 7,612,222 B2 · Method for the redistribution of polyorganosiloxanes

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- Number: US 7,612,222 B2
- Document ID: US7612222B2
- Status: Granted
- Kind: B2
- Application number: 11/885,298
- Filed: 2006-03-15
- Published: 2008-06-19
- Granted: 2009-11-03
- Earliest claimed: 2005-05-16
- Assignees: Dow Corning Corporation
- Inventors: Larry Herbert Wood
- Web page: https://patentgrep.com/patent/US7612222B2

## CPC

- C08G 77/10: Equilibration processes
- C07F 7/0874: {Reactions involving a bond of the Si-O-Si linkage}
- C08G 77/045: {containing less than 25 silicon atoms}
- C08G 77/24: halogen-containing groups
- C08G: MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C07F: ACYCLIC, CARBOCYCLIC OR HETEROCYCLIC COMPOUNDS CONTAINING ELEMENTS OTHER THAN CARBON, HYDROGEN, HALOGEN, OXYGEN, NITROGEN, SULFUR, SELENIUM OR TELLURIUM (metal-containing porphyrins C07D487/22)

## Abstract

Linear hydroxy endblocked linear polyorganosiloxanes, linear chloro-endblocked polyorganosiloxanes, and mixtures thereof, are redistributed in a process by contacting the linear polyorganosiloxanes, with a diorganodichlorosilane having the formula R′2SiCl2, wherein R′ is an alkyl group containing 1-8 carbon atoms; in the presence of an aqueous hydrochloric acid catalyst; to form a redistributed mixture containing cyclic polyorganosiloxanes and chloro-endblocked polyorganosiloxanes. The process generates less amounts of undesired branched siloxane species than processes which utilize an alumina catalyst.

## Claims

### Claim 1

A process for the redistribution of linear hydroxy endblocked polyorganosiloxanes, linear chloro-endblocked polyorganosiloxanes, and mixtures thereof, comprising:
contacting (i) a linear hydroxy endblocked polyorganosiloxane having Formula I:
(ii) a chloro-endblocked polyorganosiloxane having Formula II:
or (iii) a mixture of (i) and (ii)
with (iv) a diorganodichlorosilane having the formula R′2SiCl2 in the presence of a catalyst to form a redistributed mixture comprising cyclic polyorganosiloxanes and chloro-endblocked polyorganosiloxanes having Formula II;
wherein x and y represent integers having a value of 1-5,000 and R′, R1, and R2 represent alkyl groups containing 1-8 carbon atoms;
and wherein the catalyst comprises aqueous hydrochloric acid and it is present in an amount of 0.1-70 percent by weight based on the weight of the linear hydroxy endblocked polyorganosiloxanes, the linear chloro-endblocked polyorganosiloxanes, and the diorganodichlorosilanes; and the aqueous HCl catalyst contains saturated concentrations of HCl at the temperature and pressure conditions at which the redistribution is conducted.

### Claim 2 (depends on 1)

The process according to claim 1 wherein the diorganodichlorosilane is selected from the group consisting of dimethyldichlorosilane, ethylmethyldichlorosilane, diethyldichlorosilane, di-n-propyldichlorosilane, di-i-propyldichlorosilane, hexylmethyldichlorosilane, di-n-butyldichlorosilane, di-i-butyldichlorosilane, di-t-butyldichlorosilane, and n-butylmethyldichlorosilane.

### Claim 3 (depends on 2)

The process according to claim 2 wherein the diorganodichlorosilane is dimethyldichlorosilane.

### Claim 4 (depends on 1)

The process according to claim 1 wherein the cyclic polyorganosiloxane in the redistributed mixture are selected from the group consisting of hexamethylcyclotrisiloxane, octamethylcyclotetrasiloxane, decamethylcyclopentasiloxane, dodecamethylcyclohexasiloxane, tetradecamethylcycloheptasiloxane, and hexadecamethylcyclooctasiloxane.

### Claim 5 (depends on 1)

The process according to claim 1 wherein the linear chloro-endblocked polyorganosiloxanes in the redistributed mixture comprise predominantly polymers wherein the degree of polymerization is 2-8.

### Claim 6 (depends on 1)

The process according to claim 1 wherein the process is carried out at a temperature of 20-25° C.

### Claim 7 (depends on 1)

The process according to claim 1 wherein the contact time for the linear hydroxy endblocked polyorganosiloxanes, linear chloro-endblocked polyorganosiloxanes, or mixtures thereof, and diorganodichlorosilanes with the catalyst to effect redistribution is less than 3 hours.

### Claim 8 (depends on 7)

The process according to claim 7 wherein the contact time is less than 30 minutes.