Abstract: A process for producing a polyurethane plastics having photochromic properties, characterized in that the process comprises in a first step incorporating a reversible cleavage photochromic compound into at least one di-isocyanate compound or at least one polyol or a mixture of a di-isocyanate and one or more polyols or into any other component of a mixture which, when polymerized, will yield a polyurethane; combining the mixture from the first step with any other necessary components to enable polymerization to occur; and polymerizing the resultant mixture to form a polyurethane incorporating the said photochromic compound. The photochromic polyurethane plastics of the invention are useful as intermediate layers in glass or plastics laminates for architectural applications or for use in vehicle windows or roof-lights.

Abstract: A direct casting process for manufacturing a shaped synthetic plastic article, such as an ophthalmic lens, which has photochromic properties, the process comprising incorporating a photochromic spiro-oxazine compound into a mixture comprising a highly reactive polyfunctional monomer and a low amount of a polymerization catalyst, and curing the composition in a mould to form the shaped synthetic plastic article.

Abstract: A method is disclosed for manufacturing transparent plastic articles, primarily plano or opthalmic photoreactive lenses, which comprises incorporating fulgides or fulgimides containing an adamantylidene group in plastics casting or moulding compositions or preformed plastics articles and converting the fulgide or fulgimide in situ into a form in which it confers on the article the property of darkening in the presence of sunlight and fading in its absence.