Abstract: In the embodiments, an aqueous hydrochloric acid solution instead of hydrogen chloride gas and solid triphosgene instead of phosgene gas may be used in the process of preparing a diisocyanate from a diamine through a diamine hydrochloride. In addition, the embodiments provide processes for preparing a diisocyanate composition and an optical lens of higher quality, in which the reaction temperature of a diamine hydrochloride composition and triphosgene is controlled to a specific range, or a crude diisocyanate composition obtained from the reaction of a diamine hydrochloride composition and triphosgene is distilled at a specific temperature range, or the molar ratio of a diamine hydrochloride and triphosgene is adjusted to a specific range.

Abstract: One embodiment relates to a polymerizable composition and an optical material produced therefrom which has excellent lightfastness and minimized color defects, and more specifically, the polymerizable composition according to one embodiment includes UV absorbers having, as the main absorption wavelength, either a long-wavelength region or a short-Wavelength region Within the UV region, wherein the UV absorbers do not absorb in the Visible light region. Accordingly, the polymerizable composition may be used to provide an optical material having excellent lightfastness and minimized color defects.