| abstract |
A process for preparing diorganopolysiloxanes containing terminal triorganosiloxy groups which comprises reacting in a 1st step, a cyclic diorganopolysiloxane and/or diorganodichlorosilane hydrolyzate with from 0.05 to 3 percent by weight of triorganochlorosilane, based on the weight of the cyclic diorganopolysiloxane and/or diorganodichlorosilane hydrolyzate employed in the presence of from 1 to 50 ppm by weight of phosphonitrile chloride, based on the total weight of the organosilicon compounds employed, to form a reaction mixture containing alpha -triorganosiloxy- omega -chlorodiorganopolysiloxane, and in a 2nd step, adding to the reaction mixture obtained in the 1st step and containing the alpha -triorganosiloxy- omega -chlorodiorganopolysiloxane, a diorganopolysiloxane having one Si-bonded hydroxyl group in each of the terminal units in an amount of from 1 to 1.2 gram-moles of Si-bonded hydroxyl group in this diorganopolysiloxane per gram-atom of Si-bonded chlorine in the triorganochlorosilane, and in a 3rd step, adding hexaorganodisilazane to the reaction mixture of the 2nd step in order to deactivate the phosphonitrile chloride and remove hydrogen chloride from the diorganopolysiloxanes containing terminal triorganosiloxy groups and thereafter removing the low-boiling components by distillation. |