Abstract: Polyolefin foam bead having a high-density crust and a method for manufacturing the same are disclosed. The novel polyolefin foam bead having an surface layer (crust) which is higher in density than its inner structure can be manufactured by the method comprised of impregnating a polyolefin resin with a forming agent by stirring the mixture of the polyolefin resin particles, water and the foaming agent in a pressure vessel under heat, followed by diffusing out the foaming agent from the surface layer of the resin particle to decrease the concentration of the foaming agent in the surface layer. Thereafter, the polyolefin resin is foamed by discharging the resin particles to low pressure environment.

Abstract: A method for manufacturing polyolefin foam beads by a continuous process is disclosed by which the polyolefin foam beads can be produced with increased efficiency and productivity. The method comprises a step of impregnating foaming agent into polyolefin resin by mixing polyolefin resin particles, water and the foaming agent in a impregnation chamber under heat and pressure, followed by a step of storing the polyolefin resin containing the foaming agent in a storing chamber under heat and pressure. Thereafter, the resin particles are subjected to a foaming step by continuously or intermittently discharging the resin particles from the storing chamber to a low pressure expansion chamber by utilizing a discharging device, in the same time period when a next batch of polyolefin resin is added and mixed in the impregnation chamber after being supplied with the resin particles from a resin supply chamber.

Abstract: A method for manufacturing polyolefin foam beads by a continuous process is disclosed by which the polyolefin foam beads can be produced with increased efficiency and productivity.

Abstract: A side-chain type second-order nonlinear optical polymer compound having a repeating unit as represented in general structure (I), --(--MO--).sub.m --(--ITCN--NLO--).sub.n --, wherein the sum of m and n is from 5 to 10000 and m and n satisfy m/(m+n)=from 0.05 to 0.95; ITCN--NLO is ##STR1## X is not present, or represents alkylene having from 1 to 6 carbon atoms or aromatic hydrocarbon having from 6 to 12 carbon atoms; Y is a bonding group selected from the group consisting from ether, ester, amide, alkylamino having from 1 to 5 carbon atoms, carbamate and sulfone; NLO is a general second-order nonlinear optical chemical group in which a conjugated aromatic ring can be unsubstituted or substituted by an electron-donor and/or electron-acceptor; and MO is any polymerizable monomer copolymerizable with ITCN--NLO, and a nonlinear optical material prepared with the same arc disclosed.