In nylon-6 production from caprolactam, the typical conversion level achieved in the polymerisation step is approximately what percentage?

Introduction / Context:
Conversion in nylon-6 polymerisation impacts molecular weight, residual monomer content, and downstream devolatilisation requirements. High conversion is desired to minimise extractables and improve mechanical properties.

Given Data / Assumptions:

• Nylon-6 melt polymerisation is typically driven to high conversion before finishing/stripping.
• Residual caprolactam is later reduced via extraction or vacuum devolatilisation.

Concept / Approach:
Industrial practice aims for high monomer-to-polymer conversion, often around 90% or above in the main reactor stage, followed by finishing steps to remove unreacted lactam and cyclic oligomers and to tune molecular weight by controlled solid-state or melt treatment.

Step-by-Step Solution:
Select a high, realistic conversion target.90% aligns with common operations prior to finishing.

Verification / Alternative check:
Process descriptions indicate high conversion with subsequent extraction to meet low residual monomer specs for fibres and films.

Why Other Options Are Wrong:
25–70% are too low for efficient industrial practice and would leave excessive lactam.

Common Pitfalls:
Assuming 100% conversion in practice; polymer processes usually approach but do not reach complete conversion before finishing.

Final Answer:
90