Hot-emulsion SBR (styrene–butadiene rubber) production: typical reactor conditions are approximately which temperature and gauge pressure?

Introduction / Context:
SBR is commonly manufactured via free-radical emulsion polymerisation. “Hot SBR” denotes operation around 50 °C (versus “cold SBR” near 5 °C). Recognising typical operating windows helps avoid confusing SBR processes with high-temperature bulk polymerisations.

Given Data / Assumptions:

• Hot SBR temperature is near 50 °C.
• Pressure must maintain monomer in emulsion and control volatility; moderate gauge pressures are typical.

Concept / Approach:
Emulsion polymerisation uses water, surfactant, initiator, monomers (butadiene and styrene), and shortstops. Temperatures around 50 °C accelerate kinetics relative to cold SBR. Pressures of a few kgf/cm2 are sufficient for butadiene containment and reactor operation in stirred vessels.

Step-by-Step Solution:
Select options consistent with emulsion conditions (not bulk high-T).50 °C aligns with “hot SBR”.3–4 kgf/cm2 matches typical moderate pressures.

Verification / Alternative check:
Process descriptions in polymer reaction engineering texts list ~50 °C and a few bar for hot SBR reactors.

Why Other Options Are Wrong:
250 °C: far above emulsion SBR temperatures, risking degradation.1 kgf/cm2 may be too low to manage butadiene vapor pressure and throughput.

Common Pitfalls:
Confusing SBR with high-pressure polyethylene processes which do run at much higher T and P.

Final Answer:
50 °C and 3–4 kgf/cm2