Abstract: A porous article having excellent heat resistance, a finely cellular structure, and a low dielectric constant; and a process for producing the porous article which comprises subjecting a polymer composition having a micro-domain structure comprising a continuous polymer phase and dispersed therein a discontinuous phase having an average diameter smaller than 10 &mgr;m to a treatment for removing the ingredient constituting the discontinuous phase by at least one operation selected from vaporization and decomposition and by an extraction operation to thereby make the polymer porous. The ingredient constituting the discontinuous phase has a weight average molecular weight of, e.g., 10,000 or lower. Liquefied carbon dioxide, supercritical carbon dioxide, or the like can be used as an extraction solvent for the ingredient constituting the discontinuous phase.

Abstract: An acrylic pressure-sensitive adhesive composition which contains a high molecular weight polymer, is excellent in cohesive force and adhesive strength and can be prepared without using an organic solvent. The acrylic pressure-sensitive adhesive composition is produced by a process which comprises radical-polymerizing monomers containing an alkyl (meth)acrylate using carbon dioxide as a diluent to thereby prepare a pressure-sensitive adhesive composition containing an acrylic polymer having a weight average molecular weight of 400,000 or more. The polymerization pressure ranges from, for example, about 5.7 to 40 MPa, AND the polymerization temperature ranges from, for example, about 20 to 100° C.

Abstract: A microporous soundproofing material constituted of an expanded material formed through the step of impregnating a thermoplastic elastomer with an inert gas at a high pressure and then decompressing the impregnated elastomer. The soundproofing material has a high characteristic impedance, is clean and lightweight, and has excellent flexibility. This microporous soundproofing material includes: a microporous soundproofing material which is constituted of an expanded material formed through the step of impregnating an unexpanded molding comprising a thermoplastic elastomer with an inert gas at a high pressure and then decompressing the impregnated molding; and a microporous soundproofing material which is constituted of an expanded material formed by impregnating a molten thermoplastic elastomer with an inert gas at a high pressure and then subjecting the impregnated elastomer to molding simultaneously with decompression.

Abstract: An acrylic pressure-sensitive adhesive which is produced by advantageous continuous polymerization and has a reduced low molecular component content and therefore hardly contaminates an adherend, and a process of producing such an adhesive. The process comprises continuously feeding a monomer mainly comprising at least one alkyl (meth)acrylate, a radical polymerization initiator and carbon dioxide to a continuous reactor through a mixer and performing continuous bulk polymerization at a polymerization temperature of 50 to 180° C. for a residence time of 0.5 to 60 minutes in a continuous reaction zone of said reactor.

Abstract: A heat-resistant polymer foam is disclosed which has excellent heat resistance, a fine cellular structure, and a low apparent density. The heat-resistant polymer foam comprises a heat-resistant polymer having a glass transition point of 120° C. or higher, e.g., a polyimide or polyether imide, and has an average cell diameter of from 0.01 &mgr;m to less than 10 &mgr;m. This heat-resistant polymer foam can be produced by, for example, impregnating a heat-resistant polymer under pressure with an non-reactive gas such as carbon dioxide, which is in, e.g., a supercritical state, reducing the pressure, and then heating the polymer at a temperature exceeding 120° C. to foam the polymer.

Abstract: A method and apparatus for producing a foamed pressure-sensitive adhesive tape or sheet having a fine cell structure with a good production efficiency without through complicated steps are provided. The method comprises subjecting a mixture containing monomers of a polymer constituting a foamed pressure-sensitive adhesive layer to polymerization in an inert fluid in a supercritical state or a liquid state under pressure, and ejecting the polymerized composition obtained on a substrate under a pressure lower than the pressure in the polymerization to form a foamed pressure-sensitive adhesive layer applied on the substrate. The apparatus comprises a pressure vessel for polymerizing monomers of a polymer constituting a foamed pressure-sensitive adhesive layer under pressure, an inert fluid supplying means for supplying an inert fluid in a supercritical state or a liquid state to the pressure vessel, and an ejection means for ejecting the polymerized composition obtained by polymerizing the monomers.

Abstract: A resin tablet for sealing a semiconductor formed by solidifying a molten thermosetting resin composition by cooling, wherein the content of volatile matters in the tablet is 0.05% by weight or less, and the content of gelled particles in the tablet is 0 for the particles of 60 mesh on and is 10 ppm or less for the particles of 100 mesh on.

Abstract: A resin tablet for sealing by transfer molding a semiconductor, which is obtained by cooling and solidifying a molten resin composition, is disclosed. The tablet has a compressibility of not less than 98% and a metallic impurity content of less than 50 ppm, preferably with the amount of fine powders of 250 mesh or smaller adhered thereto being controlled below 0.05% by weight based on the tablet and a water content being controlled below 0.1% by weight.