Patent ID: 7312281

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 (1) substituted styrenes and (2) substituted styrenes and (3) an alkyl acrylates, and/or (4) ethylenically unsaturated co-polymerizable monomer or monomers, and (5) mixtures thereof in a first solvent in the presence of an initiator for a sufficient period of time of at least one 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 no higher than 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 step (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 wherein the polymer is insoluble in said second solvent and the impurities are soluble in said second solvent, and allowing the layers of polymer and mixed solvents to separate, and removing a portion of said solvent mixture and any dissolved impurities and low weight average molecular weight polymers dissolved therein, and then adding additional first solvent to resolubilize said polymer 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 or photosensitive coating 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.