Patent ID: 6121412
Filing Date: 2000-09-19
Classification: G03F

Abstract:
A method for producing a film forming novolak resin, which comprises, in the following order:a) condensing formaldehyde, para-formaldehyde or formalin with one or more phenolic compounds, in the presence of an acid catalyst and thereby producing a novolak resin;b) adding a photoresist solvent, and optionally a water-soluble organic polar solvent, to the novolak resin reaction mixture from step a), at a ratio of photoresist solvent to water soluble organic polar solvent of from 10/90 to 100/0;c) feeding the mixture from step b) into a liquid/liquid centrifuge at a feed rate of from 0.04 to 400 liters per minute and at a temperature of from 0.degree. C. up to a maximum temperature that is less than the boiling point of the lower boiling solvent in the mixture from step b), and then feeding a substantially pure C.sub.5 -C.sub.8 alkane, water or aromatic hydrocarbon solvent into the liquid/liquid centrifuge at a feed rate of from 0.04 to 400 liters/min., at a ratio of optional water-soluble organic polar solvent and photoresist solvent from step b) to C.sub.5 -C.sub.8 alkane, water or aromatic solvent, of from 5:1 to 0.5:1;d) rotating the liquid/liquid centrifuge containing the mixture from step c) at a speed of at least 500 rpm and thereby separating the mixture from step c) into two phases, and then collecting the two phases, each from 2 separate outlet ports, into two separate containers, wherein the heavier phase (H) contains the novolak resin fraction, in the optional water-soluble organic polar solvent and the photoresist solvent with a minor amount of the C.sub.5 -C.sub.8 alkane, water or aromatic hydrocarbon solvent, and the lighter phase (L) contains: 1) the novolak resin oligomer and unreacted phenols fraction, 2) C.sub.5 -C.sub.8 alkane, water or aromatic hydrocarbon solvent, 3) optional water-soluble organic polar solvent, and 4) photoresist solvent;e) as the lighter phase (L) of the two-phase system of step d) is collected, optionally separating the lighter phase (L) into two second separate phases, the lighter of these two second phases containing the C.sub.5 -C.sub.8 alkane, water or the aromatic hydrocarbon solvent and a minor amount of the water-soluble organic polar solvent and the photoresist solvent, the heavier of these two second phases containing low molecular weight novolak oligomers and unreacted phenolic compounds, dissolved in the optional water-soluble organic polar solvent and the photoresist solvent, with the C.sub.5 -C.sub.8 alkane, water or aromatic hydrocarbon;f) removing residual C.sub.5 -C.sub.8 alkane water or aromatic hydrocarbon solvent from the heavier phase (H) from step d) and leaving the novolak resin dissolved in the photoresist solvent.