Process for making a solution of copolymers of maleic anhydride and alkyl vinyl ether in isopropyl acetate of high specific viscosity and at a high solids level

摘要

A process for making a solution of a copolymer of maleic anhydride (MA) and methyl vinyl ether (MVE) monomers the specific viscosity (SV) of the product being about 2.5-6, preferably 3-5, indicating a weight average molecular weight of substantially above one million, preferably above 1.5 million and a solids content of about 20-45%, preferably 30-40, in isopropyl acetate (IPAc), solvent includes the steps of (a) precharging part of MVE in IPAc into a reactor heated to about 50-90° C., and then (b) feeding (i) a solution of MA in IPAc, (ii) the rest of MVE, at a mole ratio of MA:MVE of 1:≧1.5 to 1:3, preferably 1:2.4, and (iii) a free radical initiator dissolved in IPAc, in an amount of 0.02-0.3%, preferably 0.05-0.2%, based on total monomers, into the reactor over time. Powders of such MA/MVE copolymers are made by removing the solvent from the solution.