Method for making transparent polythiourethane substrates in...

C - Chemistry – Metallurgy – 08 – G

Patent

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C08G 18/10 (2006.01) C08G 18/38 (2006.01) G02B 1/04 (2006.01)

Patent

CA 2465796

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.

La présente invention concerne un procédé de durcissement rapide d'un substrat coulé en poly(thio)uréthane transparent pouvant être utilisé dans la fabrication d'articles optiques tels que des lentilles ophtalmiques. Le procédé de l'invention comprend les étapes suivantes : (1) on fabrique un premier composant A comprenant un prépolymère de poly(thio)uréthane possédant des groupes terminaux isocyanate ou isothiocyanate et une viscosité à 25 ·C comprise entre 0,02 et 0,4 Pa.s ; (2) on fabrique un second composant B comprenant un prépolymère de poly(thio)uréthane possédant des groupes terminaux thiol (SH) et une viscosité à 25 ·C comprise entre 0,2 et 2,0 Pa.s ; (3) on mélange le premier composant A et le second composant B et on remplit la cavité de moule d'un ensemble de moule de coulage avec le mélange obtenu ; (4) on fait durcir ledit mélange afin d'obtenir un substrat solide transparent, l'étape de durcissement comprenant : a) une première étape de polymérisation dudit mélange afin d'obtenir un gel dans un délai de 1 à 10 minutes ; et b) une seconde étape de post-durcissement du gel afin d'obtenir le substrat solide transparent précité ; et (5) on retire le substrat solide transparent du moule.

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