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