Preparation of organic pieces of optical quality and especially organic lenses

A method of preparing photochromic or non-photochromic organic articles of optical quality by radical polymerisation of a mixture of radically polymerisable monomers, wherein said method comprises:

• a) adjusting, by pre-polymerisation, the viscosity of said mixture to a value between 0.4 and 2 Pa.s;
• b) pouring said pre-polymerised mixture into a mould;
• c) photogelifying, in said mould, said pre-polymerised mixture until its gel point;
• d) completing the polymerisation of said pre-polymerised and gelified mixture in said mould by heat treatment;
• wherein the method further comprises adding an effective amount of at least one thermal catalyst and of at least one photoinitiator in said mixture of monomers for the implementation of said pre-polymerisation, photogelification, and polymerisation;
• wherein said photoinitiator(s) are present in an amount less than or equal to 0.009 parts by weight per 100 parts by weight of said mixture of monomers;
• and wherein said mixture of monomers comprises one or more difunctional monomers having formula (A) or formula (A′) and one or more difunctional monomers having formula (B), (B′), or (B″), wherein formula (A) is
• in which:
• R1, R′1, R, and R′, identical or different, are independently a hydrogen or a methyl group;
• m and n are, independently, integers between 0 and 4, inclusive;
• X and X′, identical or different, are a halogen;
• and
• p and g are, independently, integers between 0 and 4, inclusive;
• wherein formula (A′) is
• in which:
• R1, and R′1, identical or different, are independently a hydrogen or a methyl group;
• and
• R is a straight or branched alkyl radical having 2 to 8 carbon atoms, a cycloalkyl radical having 3 to 6 carbon atoms, or an ether radical of formula (R′—O—R″) in which R′ and R″, identical or different, are independently a straight or branched alkyl radical having 2 to 4 carbon atoms;
• wherein formula (B) is
• in which:
• R1, R′1, R2, and R′2, identical or different, are independently hydrogen or a straight or branched alkyl radical;
• R3 and R4, different, are independently one hydrogen and the other an alkenyl radical having 2 to 6 carbon atoms;
• R′3 and R′4, different, are independently one hydrogen and the other an alkenyl radical having 2 to 6 carbon atoms;
• Z represents a carbamate function (—NH—CO—O—), a thiocarbamate function (—NH—CO—S—), or a urea function (—NH—CO—NH—);
• Z′, independent from Z, represents a carbamate function (—O—CO—NH—), a thiocarbamate function (—S—CO—NH—), or a urea function (—NH—CO—NH—);
• R′ represents a straight or branched alkyl radical having 2 to 4 carbon atoms;
• R, identical or different when n≧2, is a straight or branched alkyl radical having 2 to 4 carbon atoms;
• Y, identical or different when n≧2, is oxygen or sulphur;
• and
• n is an integer defined such that the total number of carbon atoms contained in the long chain situated between the two moieties Z and Z′ is at least equal to 18;
• wherein formula (B′) is
• in which:
• R1, R2, R3, R4, R′1, R′2, R′3, R′4, R, and Y are as defined above with reference to formula (B);
• and
• n is an integer defined such that the total number of carbon atoms contained in the long chain of moiety (R—Y)n is at least equal to 22;
• and
• wherein formula (B″) is
• in which:
• R1, R2, R3, R4, R′1, R′2, R′3, R′4, R, R′, and Y are as defined above with reference to formula (B);
• Z′ is a carbamate function (—O—CO—NH—), or Z′ is a thiocarbamate function (—S—CO—NH—);
• and
• n is an integer defined such that the total number of carbon atoms contained in the long chain of moiety (R—Y)nR′ is at least equal to 22.