Abstract: According to the present invention, heterocyclic copolymers comprising recurring units [A] and [B] having specific structures are obtained by hydrolyzing reaction products of diisocyanate compounds having specific structures with tolidine diisocyanate and hydrogen cyanide.The heterocyclic copolymers thus obtained are excellent in mechanical strength, heat resistance and solvent resistance.

Abstract: In the present invention, a petroleum fraction containing arsenic is brought into contact with an adsorbent comprising a substrate such as an active carbon, bituminous coal or organic polymeric compound having introduced therein a sulfur element, particularly represented by mercapto moiety, and therefore arsenic in the petroleum fraction can be removed at a high percent removal by means of simple equipment, and, even if highly reactive olefins are contained in the petroleum fraction, these olefins do not polymerize, thus troubles do not occur.

Abstract: This invention relates to a polyolefin composition with an improved weather resistance, which comprises a polyolefin blended with (1) a benzotriazole compound, (2) a heterocyclic hindered amine compound and (3) a phenyl benzoate compound or nickel complex compound.