The mixed integer linear programming model has been developed for the production scheduling of liquid state polymer process such as a Polybutene(PB). The example process is composed of one reactor, twelve storage tanks and two package types. The reactor produces 9 liquid state products. The products are reserved in tanks and then, packaged into drum or isocontainer. The drum products are stored in a warehouse before they are shipped out to customers but the isocontainer products are shipped directly out to customers. Two major products use multiple tanks. Most tanks are dedicated to a certain product but basically any tank can be shared by any product. The reactor is operated on block mode. The unique characteristic of this scheduling problem exists on the fact that the product in a tank should be locked for 3-15 days in order to check the quality specifications after run-down from the reactor. The primary objective of scheduling is reducing the number of quality checking processes because it causes great loss in production time and tank utilization. The model is composed of about 1,500-2000 integer variables. The branching priorities are adjusted according to the importance of variables based on current manual scheduling practice and it greatly enhanced the convergence of the mixed integer model.