METHOD FOR MAKING TRANSPARENT POLYTHIOURETHANE SUBSTRATES IN PARTICULAR OPTICAL SUBSTRATES

A method of fast curing polythiourethane transparent casted substrate, usable for making optical articles such as ophthalmic lenses, which comprises the steps of: 1) Providing a first componentA comprising a polythiourethane prepolymer having isocyanate or isothiocyanate end groups and a viscosity at 25 ~C ranging from 0.02 to 0.4 Pa.s; 2) Providing a second component B comprising a polythiourethane prepolymer having thiol (SH) end groups and a viscosity at 25 ~C ranging from 0.2 to 2.0 Pa.s; 3) Mixing together first and second components A and B and filling a moulding cavity of a casting mould assembly with the resulting mixture ; 4) Curing said mixture to obtain a transparent solid substrate, said curing step comprising: a) a first step for polymerizing said mixture to obtain a gel within 1 to 10 minutes; and b) a second step of post-curing the gel to obtain the transparent solid substrate; and 5) Recovering the transparent solid substrate from the mould.