Styrene → Styrene-butadiene-styrene

Participants

Reaction Steps

In a 200 L pressure-resistant vessel filled with dry nitrogen, 75 kg of cyclohexane as a solvent and 45 g of sec-butyllithium as a polymerization initiator were added and, subsequently, 6.4 kg of styrene was added. After polymerization at 50° C., 0.21 kg of tetrahydrofuran as a Lewis base was added and, subsequently, 29.6 kg of butadiene and 6.4 kg of styrene were added in this order. When polymerization was carried out, a triblock copolymer of styrene-butadiene-styrene type was obtained. The block copolymer had a branching degree (α) of 0.154. The block copolymer obtained was subjected to hydrogenation at a hydrogen pressure of 2 MPa and a reaction temperature of 100° C. in cyclohexane using Pd/C as a catalyst. The reaction was carried out while sampling the reaction system at certain time intervals and the reaction was stopped in a stage where the ratio of hydrogenation of the hydrogenated block copolymer has become 90 mol %, yielding a styrene-hydrogenated butadiene-styrene block copolymer (SEBS). The resulting block copolymer had a weight average molecular weight of 100400 and a styrene content of 30% by weight.

Provenance & Evidence