Claims
- 1. A process for preparing linear triorganosiloxy-terminated organopolysiloxane fluids consisting essentially of
- (1) feeding a mixture of linear polydiorganosiloxanediols and cyclic polyorganosiloxanes said mixture comprising a diorganodichlorosilane hydrolyzate wherein said mixture has a content of cyclic polyorganosiloxanes greater than about 14 weight percent and a silanol content greater than about 1000 ppm by weight to a reaction zone comprising:
- (a) a fixed bed of equilibration, catalyst;
- (a') a fixed bed of equilibration catalyst in the presence of a hexaorganodisiloxane chain stopper; or
- (a") a condensation/disproportionation catalyst in the presence of a hexaorganodisiloxane chain stopper; until a first stage product is obtained and
- (2) thereafter
- (b) feeding the first stage product of step (a) to a reaction zone comprising a condensation/disproportionation catalyst and hexaorganodisiloxane chain stopper;
- (b') feeding the first stage product of step (a') to a reaction zone comprising a condensation/disproportionation catalyst; or
- (b") feeding the first stage product of step (a") to a reaction zone comprising a fixed bed of equilibration catalyst; wherein said condensation/disproportionation catalyst is selected from the group consisting of:
- (i) phosphonitrilic halides;
- (ii) linear oligomeric phosphonitrilic halides;
- (iii) a reaction product between the group consisting of phosphonitrilic halides and linear oligomeric phosphonitrilic halides and the group consisting of water, alcohols, carboxylic acids, an organopolysiloxane that will react with said phosphonitrilic halide and an organosilane that will react with said phosphonitrilic halide; and
- (iv) mixtures thereof; whereby a low molecular weight triorganosiloxy terminated oil mixture having no more than about 14-16% by weight cyclic polyorganosiloxane and a silanol content below about 200 ppm by weight is produced.
- 2. A process as defined in claim 1, wherein the equilibration catalyst comprises an acidic or basic equilibration catalyst selected from the group consisting of an acid treated clay, an ion exchange resin, an acid treated carbon black and mixtures thereof.
- 3. A process as defined in claim 1, wherein the condensation/disproportionation catalyst comprises a linear oligomeric phosphonitrilic halide.
- 4. The process of claim 3 wherein the equilibration catalyst comprises an acidic or basic equilibration catalyst selected from the group consisting of an acid treated clay, an ion exchange resin, an acid treated carbon black and mixtures thereof.
- 5. The process of claim 4 wherein said catalyst is acid treated clay.
Parent Case Info
This is a divisional of application Ser. No. 08/091,898 filed on Jul. 15, 1993, now U.S. Pat. No. 5,408,025.
US Referenced Citations (12)
Foreign Referenced Citations (3)
Number |
Date |
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0324186 |
Jul 1989 |
EPX |
1488369 |
Oct 1977 |
GBX |
1488370 |
Oct 1977 |
GBX |
Divisions (1)
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Number |
Date |
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Parent |
91898 |
Jul 1993 |
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