PREPARATION METHOD OF POLYDIMETHYL SILOXANE CONTAINING BOTH TERMINAL HYDROXYL GROUPS USING OCTAMETHYL CYCLOSILOXANE, POTASSIUM SILOXANE OLEATE AND LOW MOLECULAR WEIGHT SILOXANE HAVING HYDROXYL GROUP

摘要

PURPOSE: A method for preparing polydimethyl siloxane containing both terminal hydroxyl groups which is excellent in storage stability, is free from offensive odor, has a uniform molecular weight and is used as the base polymer of a silicone sealant. CONSTITUTION: The method comprises the steps of polymerizing a cyclic siloxane monomer in the presence of a basic catalyst and a polymerization controller at a temperature of 100-200 deg.C under anhydrous condition; and adding a neutralizer to the polymerization reaction solution to neutralize it under reduced pressure, wherein the basic catalyst is potassium siloxane oleate represented by the formula I, the polymerization controller is a low molecular weight siloxane containing a hydroxyl group represented by the formula II, and the cyclic siloxane monomer is octamethyl cyclosiloxane. In the formula I, n is 1,000-5,000; and in the formula II, n is 5-2,000.