| 摘要 |
Process for the preparation of watery emulsion of two or more polyvinylic alcohols (PVa) for the production of polyvinylchloride (PVC-S) in watery suspension in which at least a first polyvinylacetate (PVAc) with molecular weight measured in K value comprised between 30 and 110, preferably 50 is utilized and, with technique of alcoholysis acid or basic, to carry out the transesterification of the PVAc up to values of saponification number (NS) comprised between 598 and 135 preferably between 598 and 312, optimally 511; loading from 0.1 to 5 times preferably 0.7 times in weight respect to the first PVAc, of at least a second PVAc in solution of ethylic alcohol or methylic alcohol having molecular weight measured in K value comprised between 10 and 110, preferably 10 and 50, optimally 27; stopping the alcoholysis in order that, in the final alcoholic solution, the respective PVAc result is perfectly mixed in order to obtain: a) at least a first PVA, with saponification number, comprised between 230 and 95, preferably 230 soluble in water; b) at least a second PVA, with NS comprised between 598 and 312, preferably 480, insoluble in water; distilling during the stop of the alcoholysis or to termination, the residual solvents, adjoining water after the stopping of the alcoholysis with the scope of obtaining the coagulation in water of the second PVA in form of microparticles with granulometric distribution comprised between 0.01 micron and 10 microns. |
