Two major methods to produce polycaprolactone have been described in the literature: the polycondensation of a hydroxycarboxylic acid (6-hydroxyhexanoic acid) and the ring-opening polymerisation (ROP) of a lactone: ε-caprolactone (ε-CL) read as Epsilon- Caprolactone.

I prefer (ROP) since no small molecule is eliminated or no side product is formed.

This reduces the number of reactors to be used in industrial application. The monomer must be dried & the most widely used catalyst for industrial-scale (ROP) is tin octoate (or stannous octanoate).The temperature required is up to 175 oC. Stirring is applied continuously during polymerization & a stream of inert gas is flushed constantly. The time of reaction is set by the researcher, e.g. 2,3,4 ...hours. The product will come in a molten state. It can be extruded or pelletized afterwards in the manner you desire.