Patent ID: 6864324

Claim:
A liquid phase process for preparing an anhydrous and pure hydroxyl containing polymer in solution and which comprises the steps of: (A) polymerizing a monomer or monomers selected from the group consisting of substituted styrenes, alkyl acrylates, ethylenically unsaturated co-polymerizable monomer or monomers and mixtures thereof in a first solvent in the presence of an initiator for a sufficient period of time of at least oiie minute and at a temperature of from about 30 C to about 100 C to form a polymer and first solvent mixture; (B) purifying the polymer and first solvent mixture by fractionation wherein additional first solvent is added to said mixture, said mixture is heated up to the boiling point of said first solvent and/or stirred for at least one minute, the mixture is allowed to settle, the first solvent is decanted, and further first solvent is added, and repeating this fractionation at least once more, and whereby the polydispersity of said polymer remaining is 2.0 or below; (C) transesterifying said purified mixture of stcp (B) wherein said mixture is refluxed at the boiling point of said first solvent in the presence of a catalyst for a period of time of at least one minute and at a temperature of from about 50 C to about 200 C to form a reaction mixture containing a hydroxyl containing polymer and first solvent; (D) purifying said reaction mixture from step (C) wherein a second solvent is mixed with said reaction mixture in which said second solvent is immiscible, allowing the layers to separate, and removing said second solvent and any dissolved by-products and low weight average molecular weight polymers dissolved therein; (E) passing said purified reaction mixture of step (D) through an ion exchange material in order to remove any catalyst therefrom and thus provide a substantially catalyst-free hydroxyl containing polymer solution; (F) adding a third solvent, which is photoresist compatible, to said hydroxyl containing polymer solution from step (E) and then distilling off the first solvent at a temperature of at least the boiling point of said first solvent for a sufficient period of time in order to remove substantially all of said first solvent to provide a substantially pure hydroxyl containing polymer in solution in said third solvent.