Abstract: A process for preparing an urethane compound for medical instruments, characterized by reacting a hydroxyl compound (A) with an isocyanate compound (B) in the absence of a catalyst or in the presence of a reaction catalyst other than an organic tin compound to give an urethane compound (I). According to the process, the urethane compound showing high safety can be easily prepared, in particular, while molecular weight of the compound is controlled.

Abstract: A process for preparing an ultraviolet-ray-absorbable and low water-containing soft contact lens, characterized by immersing a low water-containing soft contact lens in a solution (I) prepared by dissolving an ultraviolet-ray absorbing agent in a swelling solution, permeating the ultraviolet-ray absorbing agent to the inside of a swollen low water-containing soft contact lens, and then removing the swelling solution used for swelling of the low water-containing soft contact lens. According to the process, the ultraviolet-ray absorbing agent can be physically captured to the inside of the contact lens to impart ultraviolet-ray absorbability to the contact lens without elution of ultraviolet-ray absorbing agent and the ultraviolet-ray-absorbable and low water-containing soft contact lens can be prepared without inhibition of polymerization.

Abstract: An ocular lens material comprising a polymer prepared by polymerizing a polymerizable component for an ocular lens, containing (A) 20 to 50% by weight of a silicon-containing alkyl acrylate, (B) 20 to 50% by weight of a polysiloxane macromonomer in which a polymerizable group bonds to a siloxane main chain through at least one urethane bond, (C) 10 to 50% by weight of at least one of hydroxyalkyl acrylates and at least one of hydroxyalkyl methacrylates, and (D) 0.01 to 10% by weight of a crosslinkable compound having at least two polymerizable groups, and a process for producing the same. The ocular lens material shows excellent stain resistance and excellent flexibility at the same time in addition to excellent transparency, and can be easily produced by the process.

Abstract: A process is described for treating nitrogen-oxide containing gases at temperature in the range of 300-560.degree. C. in the presence of a cerium containing zeolite catalyst and an excess of an NH-containing compound such as ammonia or an aqueous urea solution as a reducing agent. Excess reducing agent is converted to nitrogen gas during the process. Selective catalytic reduction using ammonia water or an aqueous urea solution as a reducing agent is also described for converting nitrogen oxides in diesel exhaust gas and preventing oxidation of sulfur dioxide.

Abstract: A process for producing an ocular lens characterized by mixing a polymerizable component for an ocular lens with an organic solvent (I) capable of dissolving the polymerizable component, injecting the obtained mixture into a mold having the desired shape for an ocular lens and then, preparing a polymer by the polymerization reaction, immersing the polymer taken off from the mold in an aqueous organic solvent (II) having compatibility with the organic solvent (I), and then, hydrating the polymer, and an ocular lens produced by the process, which is, in particular, remarkably excellent in transparency.

Abstract: An ocular lens material made of a copolymer consisting essentially of (A) a polysiloxane macromonomer having polymerizable groups bonded by one or more urethane bonds to the siloxane main chain and (B) an alkyl (meth)acrylamide, wherein the weight ratio of the polysiloxane macromonomer to the alkyl (meth)acrylamide ranges from 10:90 to 90:10.

Abstract: A soft ocular lens material obtained by copolymerizing polymerizable components comprising (A) a fluorine-containing (meth)acrylate having a hydroxyl group of the formula (I): ##STR1## wherein R.sup.1 is a hydrogen atom or a methyl group, R.sup.2 is a C.sub.5-15 perfluoroalkyl group, and n is 0 or 1, (B) a hydrophilic monomer, and (C) at least one monomer selected from the group consisting of silicon-containing (meth)acrylates and siloxane-containing styrene derivatives, wherein the ratio of the amount of the fluorine-containing (meth)acrylate (A) to the amount of the hydrophilic monomer (B) is from 20/80 to 70/30 by weight ratio, and the ratio of the total amount of the fluorine-containing (meth)acrylate (A) and the hydrophilic monomer (B) to the amount of the monomer (C) is from 30/70 to 90/10 by weight ratio.

Abstract: An ocular lens material made of a copolymer comprising, as main copolymerizable components, (A) a polysiloxane macromonomer having polymerizable groups bonded via one or more urethane bonds to the siloxane main chain and (B) an alkyl (meth)acrylamide, wherein the weight ratio of the polysiloxane macromonomer to the alkyl (meth)acrylamide is from 5/95 to 90/10.