Technology Study Of Shortening PVC Suspension Polymerization Production Period

In order to insuring quality of resin, increasing efficiency of production, decreasing costs of production, the effects on suspension polymerization production period and product quality were studied systematically by selecting compound kinds of initiators and dispersants, design of formulas, orders of charge and discharge quantity, oil-water ratio, the progresses of pumping water and stirring rate in this work. Based on the experiments in 14m3and 33m3 reactors, the capability and behavior characteristics of binary composite high efficiency initiator mixture were also studied by polymerization time and the acceleration characters of the polymerization reaction, heat transfer and actual amount of the residual initiator in detail. The suitable initiator mixture, dispersing agent formulas and the corresponding conditions on production, which were suitable to industrial production were found, too. The polymerization reaction time was shortened remarkably, the standards of resin product were also kept. The facts of practical run tests were that the achievement had stood a severe proof, the results of study took on high production efficiency, strong flexibility and product stabilization . Moreover ,it obtained better economic benefits. The expectant study objects of cut suspension polymerization production period were achieved. The main results were obtained as follows:1 Compared with old initiator system, the initiator mixture were taken on the special characteristicsrhighly initiator efficiency, stable capabilities, and convenience of mixed and used. Under keeping equipments existed, it cut the time of suspension polymerization in 2.5h, and shorting degree was 33%. The formula was that ACSP:TBCP(ratio of quality) equals 3.322-3.903:7.322-7.492; Concentration was 1.54mol/t,VCM;2 With the help of computer control system, Applying ealing charge quantity technology, the assistant operation time was cut greatly. It were30min(pumpingwater),0min(vacuuming),50min(rising temperature),30min(monomer recovery) in turn. And degree of shorting time was cut in 35.5% comparatively; 3 On the basis of using ACSP-TBCP as high effective initiator and applying two-step stirring project with low oil-water ratio, Technology, which was the method of adding new type of composite dispersant, water, monomer and initiator mixture in reaction vessel, was carried out. Not only were the homogeneity of monomer and initiator in VCM improved, but also the ratio of conversion were increased. At the same time, heat transfer, porosity and plasticizing rate of resin were advanced and, the amounts of "rapid particular " and the degree of adhesion were also reduced . The results showed that particle form of PVC resin was improved remarkably. The average time of clearing the vessel was shortened in 30min; 4 Using monomer pump, the rate of charge of quantity was improved greatly.accordingly, the time were cut in 12min 20min in turn, and low molecular weightpolymer was reduced, too.5 Using reciprocating discharge pump of reactant, the rate of discharge wasimproved greatly .The time was cut in 20 min.6 Putting stress on the influence to the configuration structure, PVC resin model SG3 were also examined with pumping water in the reaction midway. The plasticizeing rate of resin and conversion of monomer were increased;7 Choosing technique of large flow circle cooling, the polymerizationtemperature was locked up at 53±0.1°C.So viscosity number was stabilitatedgreatly,Andassistant polyerization time was cut, too;8 Concert with two-step stirring project, new type composite dispersant was added by stages and, its dosage was reduced to 0.03%. The constitute of first group was:KH-17/60SH-50/LL-02/Span =0.3:1.8:0.4:0.2, its used amount equals 70%of gross; The constitute of second group dispersant was: KH-17/60SH-50/LL02/ calcium- zinc complex salts = 0.5:1.0:0.5:0.2, its used amount equals 30%of gross; It was proved that the composite dispersant had good functional stabilization and compatibility with the initiator mixture and capable of improving the particulate configuration of resin remarkably;9 Applicating two-step stirring project, the rater of stirring was 250r/min atthe prophase of polymerization , and normal rate was lOOr/min. this methodinsured good heat transfer, and better dispersed function .10 With low oil-water ratio, porosity of resin was advanced. The results showedthat particle form of PVC resin was improved remarkably. The oil- water ratioequals 1:1.5-1:1.55.