Styrene → Styrene-butadiene-styrene

Participants

Reaction Steps

hSBS: 201 kg Cyclohexane and 9.1 kg styrene were charged to an 80 gal stainless steel reactor at about 50° C. 2428 mL of about 12 wt. % s-butyllithium were then charged to the reactor to initiate polymerization. The styrene polymerization was allowed to proceed at about 50° C. until completion and a sample was collected for GPC. The molecular weight at this step was determined to be 4.8 kg/mole. An additional 0.38 kg of styrene was added and allowed to polymerize. GPC analysis of this polymer indicated that the molecular weight was 5.0 kg/mole. Butadiene was added at a rate of about 1 kg/min. Within less than a minute of starting the butadiene program, 198 grams of 1,2-diethoxypropane were added and then the butadiene addition rate was increased to 1.5 kg/min. A total of 36.05 kg of butadiene was added, the temperature was maintained between about 50° C. and 55° C., and the polymerization was allowed to continue until completion. A sample collected at the end of this step had a molecular weight of 26.0 kg/mole, a vinyl content of 73.7% and a polystyrene content of 24.1% by 1H NMR. The S-B diblock polymer was then coupled by the addition of 114 mL of methyl trimethoxysilane, resulting in a polymer in which 94% of the diblock chains are coupled, the majority (82%) being linear, and the remainder being primarily 3-arm radial species. 55 ml of methanol were added to ensure termination. This polymer was then hydrogenated to a residual unsaturation of 0.12 meq olefin/g using a Co/Al catalyst (1.7:1 Al:Co (mole/mole), about 22 PPM Co) at 700 psi hydrogen, 85° C. to form a selectively hydrogenated styrene-butadiene- styrene polymer; about 60 kg of the total 125 kg of polymer solution was added in the initial batch charge and the remainder was added at a rate as required to maintain the reaction temperature in the desired range. The catalyst was oxidized and extracted by contacting the cement with aqueous phosphoric acid while sparging with an N2/O2 gas blend; in addition, about 100 mL of caprylic acid was added. The cement was then neutralized by sparging with ammonia, washed with deionized water and stabilized by the addition of Ethanox 330 (0.2 wt. % polymer basis) and Irgafos 168 (0.3 wt.% polymer basis). The resulting Inventive hSBS polymer had a melt flow rate of 220 g/10 min.

Provenance & Evidence