Method for making transparent polythiourethane substrates in...

Plastic and nonmetallic article shaping or treating: processes – Optical article shaping or treating

Reexamination Certificate

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Details

C264S001320, C264S240000, C106S169400, C525S457000, C525S458000, C528S067000

Reexamination Certificate

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06887401

ABSTRACT:
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 component A 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; andb) a second step of post-curing the gel to obtain the transparent solid substrate; and5) Recovering the transparent solid substrate from the mould.

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