Cold SBR (styrene–butadiene rubber) emulsion polymerisation: typical operating temperature and gage pressure are approximately what?

Introduction / Context:
SBR is produced by emulsion polymerisation of styrene and butadiene. Two major variants exist: hot SBR (~50°C) and cold SBR (~5°C). Operating conditions affect molecular weight distribution, branching, and final properties like abrasion resistance and tensile strength.

Given Data / Assumptions:

• “Cold” SBR is polymerised at low temperature near 5°C.
• Gage pressures are modest for emulsion reactors; 1 kgf/cm2 is close to atmospheric with small overpressure.
• Negative temperatures like -20°C are atypical for standard cold SBR production.

Concept / Approach:
Lower temperature in emulsion polymerisation reduces chain transfer and branching, giving improved mechanical properties versus hot SBR. Reactor pressure mainly maintains phase equilibrium and containment; high pressure is unnecessary in standard aqueous emulsions for SBR.

Step-by-Step Solution:
Identify cold SBR temperature setpoint ≈ 5°C.Confirm modest pressure near 1 kgf/cm2.Eliminate options with extreme sub-zero temperature or higher pressure not typical for cold SBR.

Verification / Alternative check:
Industrial references differentiate hot (≈50°C) and cold (≈5°C) SBR recipes, with cold SBR yielding better abrasion resistance for tyre treads.

Why Other Options Are Wrong:
-20°C: not standard; increases cost/complexity with limited benefit.0°C and 1 or 3 kgf/cm2: less characteristic than 5°C at near-atmospheric pressure.

Common Pitfalls:
Confusing bulk solution polymerisation conditions with emulsion conditions; SBR mainstream production is emulsion-based.

Final Answer:
5°C and 1 kgf/cm2