Abstract: The pressure of air to be fed into each of air cells (51-54) of an air mattress body (50) is selected by an air pressure selector (12) based on body information entered through an entry control panel (20), thereby adjusting the mattress hardness. Meanwhile, an operating mode selector switch (17) selects one of a rest mode and a pressure switch mode as an operating mode of the air mattress body (50).

Abstract: There is provided a filament of improved light transmission having a sheath-core composite structure formed of a methyl methacrylate polymer core material and a fluorine-containing polymer sheath material. The light transmitting filament is characterized in that the methyl methacrylate polymer core material is prepared by the specific procedure of continuous bulk polymerization and subsequent removal of volatile contents, wherein the polymerization is performed in a continuously and thoroughly stirred reaction vessel at a low catalyst concentration and a relatively high temperature and with improved conversion. The light transmitting filament possesses an absorption coefficient (k) of no greater than 6 .times. 10.sup.-.sup.3 cm.sup.-.sup.1.

Abstract: A method and an apparatus for removing the heat of polymerization evolved during a polymerization procedure carried out while the liquid polymerization mixture is stirred in a reactor are provided. A condensable vapor present in the space above the liquid level of the polymerization mixture inside the reactor is condensed by a cooling means provided in said space while the inner pressure of the reactor is maintained at a level such that the polymerization mixture does not boil. Preferably, the vapor phase is stirred.

Abstract: A process of producing methyl methacrylate polymers is provided wherein the monomer are polymerized by a bulk polymerization procedure at 150.degree. to 180.degree.C with a conversion of 50 to 80% and the volatiles predominantly comprised of the unreacted monomer, separated from the polymer product, are cyclically reused as a part of the monomer feed for polymerization. In such a monomer feed cycle system, oligomers are substantially removed from the volatiles and then the volatiles are blended with a virgin monomer feed for polymerization, the content in the volatiles of impurities having boiling points of lower than 200.degree.C at normal pressure is maintained within the range of 5 to 20% by weight.