Polyurethanes polymerizable composition and method for producing optical resin of the same

A polymerizable composition comprising an alicyclic isocyanate compound represented by the formula (3)

• (a) at least one compound of a polythiol compound having at least two thiol groups in one molecule and/or a polythiol compound having at least two thiol groups and at least one (poly)sulfide bond other than the thiol group in one molecule which is
• 4-mercaptomethyl-1,8-dimercapto-3,6-dithiaoctane, and
• (b) at least one compound of a polyhydroxy compound having at least two hydroxy groups in one molecule and/or a (poly)hydroxy(poly)mercapto compound having at least one hydroxy group and at least one thiol group in one molecule selected from 2 mercaptoethanol, pyrogallol, glycerine 1,3-bis(3-mercaptopropionate) and bis(3-mercaptopropionate)malate and wherein, if the mole number of hydroxy group and thiol group of the polyhydroxy compound having at least two hydroxy groups in one molecule and/or the (poly)hydroxy(poly)mercapto compound having at least one hydroxy group and at least one thiol group in one molecule, are A and B respectively, and the mole number of the thiol group of the polythiol compound having at least two thiol groups and/or the polythiol compound having at least two thiol groups and at least one (poly)sulfide bond other than the thiol group in one molecule, is C, A/(A+B+C) is from 0.1 to 40% and wherein the polymerizable composition provides a resin that exhibits a greater tensile strength compared to the same resin prepared in the absence of (b).