| abstract |
PURPOSE: To obtain the title resin which is light and lowly dispersive, excels in transparency, impact resistance, weathering resistance and processability and is suitable for spectacle lenses, camera lenses, etc., by reacting a specified polythiol with an aliphatic or alicyclic polyisocyanate. n CONSTITUTION: A polythiol (A) of the formula (wherein R is Cl, Br, CH 3 or C 2 H 5 , X is O or S, m is 0W1, n is 0W2, p is 2W4 and q is 0W4), e.g., 1,3-bis(mercaptomethyleneoxy)benzene, is mixed with an aliphatic or alicyclic polyisocyanate (B) (e.g., hexamethylene diisocyanate) in an amount to provide an NCO to SH molar ratio of 0.5W3.0 and, optionally, pentaerythritol tetrakis(mercaptopropionate), etc., (C) as a crosslinking agent (in this case, the amount of component B is increased so as to give an NCO to SH+OH molar ratio of 0.5W3.0), and the obtained mixture is poured into a family mold treated with a mold release and cured by heating. n COPYRIGHT: (C)1988,JPO&Japio |