Patent GB-622129-A (GB)
Title: Improvements in or relating to the preparation of organosilicic oils
IPC: C08G77/06
Filed: 1946-10-10
Abstract: A two-stage process for the preparation of non-volatile organo-silicic oils comprises as the first stage reacting dimethyldichlorosilicane with concentrated sulphuric acid, i.e. acid of a strength greater than 85 per cent, with the evolution of the combined chlorine in the form of hydrochloric acid gas, and as the second stage diluting the sulphuric acid solution with water or aqueous liquid to bring about separation of an oily product and then separating that product.  Complete removal of hydrogen chloride from the homogeneous solution after the first stage may be effected by the action of a vacuum or a current of gas.  In an example, dimethyl-dichlorosilicane is added gradually to 90 per cent sulphuric acid, followed by more dimethyl dichlorosilicane and then more sulphuric acid.  The solution is divided into five parts which are treated as follows: (a) one part is poured into water keeping the temperature at 25 DEG  C. until the acid is diluted to 25 DEG  C. strength.  After standing two hours the oil is separated, and volatiles removed by heating under vacuum. (b) Another part is added to sufficient water to reduce the strength of the acid to 50 per cent, the mixture stirred at 75 DEG  C. for two hours, and the product then treated as (a).  (c) As in (a), but the acid is reduced only to 75 per cent strength.  The oil may be separated by a volatile solvent.  (d) As in (c), but the mixture with the acid is heated to 50 DEG  C.  (e) As in (c), the oil and sulphuric acid are kept in contact for 20 hours at 25 DEG  C.ALSO:A two-stage process for the preparation of non-volatile organo-silicic oils comprises as the first stage reacting dimethyldichlorosilicane with concentrated sulphuric acid, i.e. acid of a strength greater than 85 per cent, with the evolution of the combined chlorine in the form of hydrochloric acid gas and as the second stage diluting the sulphuric acid solution with water or aqueous liquid to bring about separation of an oily product and then separating that product.  Complete removal of hydrogen chloride from the homogeneous solution after the first stage may be effected by the action of a vacuum or a current of gas.  In an example, dimethyl dichlorosilicane is added gradually to 90 per cent sulphuric acid, followed by more dimethyl dichlorosilicane and then more 91 per cent sulphuric acid.  The solution is divided into five parts which are treated as follows: (a) one part is poured into water, keeping the temperature at 25 DEG  C. until the acid is diluted to 25 per cent strength.  After standing two hours, the oil is separated, and volatiles removed by heating under vacuum; (b) another part is added to sufficient water to reduce the strength of the acid to 50 per cent, the mixture stirred at 75 DEG  C. for two hours, and the product then treated as (a); (c) as in (a) but the acid reduced only to 75 per cent strength.  The oil may be separated by a volatile solvent; (d) as in (c) but the mixture with the acid is heated to 50 DEG  C.; (e) as in (c) but the oil and sulphuric acid are kept in contact for 20 hours at 25 DEG  C.