Abstract: In an optical waveguide tube comprising a tubular cladding filled with a solid core having a higher refractive index than the cladding, a light transmissive window member is disposed in close contact with at least the end face of the core on a light incident side for protecting the core end face from thermal influence and contamination. Means disposed around the cladding and the window member for securing the window member to the cladding may be a tape wrapped around them or a heat shrinkable sleeve or a ferrule. Alternatively, a ferrule surrounding the outer periphery of the cladding at each end is fastened for securing the cladding to the core at each end for preventing the core from projecting out of the cladding. The ferrule may have a collar disposed in abutment with the core end face.

Abstract: A molded article of rigid polyurethane foam is manufactured by using a mold of separable upper and lower mold sections mated to define a cavity therebetween. A film of polypropylene which is previously vacuum formed in conformity to the mold cavity is closely set within the cavity and secured to the lower mold section outside the cavity. A rigid polyurethane foam-forming raw material is introduced into the cavity and on the film and caused to foam and expand in place to mold an article of rigid polyurethane foam. Thereafter, the molded article is lifted together with the film from the mold cavity by a pneumatic pressure or ejector pin. The molded article is stripped from the film to remove only the molded article from the mold without taking the entire film out of the mold. The once lifted film is returned to the original shape by vacuum suction for replacing the film in the cavity.

Abstract: Disclosed herein is a method of manufacturing a rigid polyurethane foam molding for energy absorption, including the steps of introducing a rigid polyurethane foam raw material composed primarily of a polyhydroxy compound and a polyisocyanate compound into a cavity in a mold, and blowing and reacting the rigid polyurethane foam raw material in the cavity, wherein a pack ratio of a core portion of the molding ranges from 0.5 to less than 1.2. Accordingly, the rigid polyurethane foam molding can obtain a plateau value comparable to that of a rigid polyurethane foam slab stock foam suitable for an energy absorbent pad.

Abstract: A method for recovering polyol from a polyurethane comprises dissolving the polyurethane in a specific aliphatic diol and heating the dissolved polyurethane in the presence of a halogenated ester of phosphoric acid to recover the polyisocyanate used for the production of the polyurethane as a solid form and the polyol used for the production of the polyurethane together with the polyol having urethane bond formed by reaction with the aliphatic diol as a liquid.

Abstract: A process for obtaining a polyol-containing homogeneous liquid composition, which can be directly reused as a polyol component for the production of rigid polyurethane foam, from a rigid polyurethane foam, which comprises treating said foam at a temperature of from 150.degree. to 220.degree. C in the presence of a mixture of (a) an aliphatic diol having 4-7 carbon atoms and having a boiling point higher than 160.degree. C and (b) a monoalkanolamine having 2 to 8 carbon atoms, the amount of said monoalkanolamine (b) present in said mixture being within the range of from 1 to 20 percent by weight.