Abstract: A platinum catalyst containing (A) a platinum complex having a vinyl-containing organosiloxane ligand and (B) a vinyl-containing organopolysiloxane is prepared by mixing components (A) and (B) such that at least 2 mol of vinyl group in component (B) is available per mol of platinum atom in component (A) and heating the mixture at 40.degree.-100.degree. C. for at least 1 hour. When blended in an addition reaction curing type organosiloxane composition, the platinum catalyst has the advantage that even after long-term storage at elevated temperatures, it remains stable and active enough to cause the organosiloxane composition to cure.

Abstract: According to the method for preparing chitosan of the present invention, chitosan is prepared by inoculating a filamentous fungi belonging to the family Mucoraceae into a culture medium for pre-cultivation containing yeast extract, malt extract, peptone, glucose and magnesium sulfate to perform pre-cultivation and then inoculating the pre-culture into a culture medium for main-cultivation having a composition essentially identical to that of the medium for pre-cultivation to perform the main-cultivation. Particularly preferred filamentous fungi belonging to the family Mucoraceae is Absidia coerulea. According to the method for preparing chitosan through the cultivation of microorganisms, chitosan exhibiting uniform quality can efficiently be produced and the method does not adversely affect the circumferential environment.

Abstract: The polyvinyl alcohol (PVA)-based gel of the invention is reversibly hydrated so that the gel after complete drying can again absorb water to regain the highly elastic gel-like form. Such a reversibly hydrated PVA-base gel can be prepared by impregnating a hydrated gel of PVA with an ethylenically unsaturated, water-soluble ionic monomer together with or without a free-radical polymerization initiator and bringing the thus monomer-impregnated PVA gel under conditions to cause in situ polymerization of the monomer, e.g., by heating or irradiating with actinic rays such as ultraviolet light.

Abstract: A novel isocyanate silane derivative of the following formula ##STR1## in which R represents an unsubstituted or substituted monovalent hydrocarbon group having from 1 to 8 carbon atoms, and n is a value of 0, 1 or 2.

Abstract: The resin compositions for peel-off coatings comprise a certain film-forming polymeric resin, an organopolysiloxane having a polyoxyalkylene group as the side chain, and a solvent. The coating compositions applied to the surfaces of various shaped articles provide protective films thereon, and the films thus formed are tough and can exhibit an excellent peelability even after the lapse of a long period of time or after heating. The coating resin compositions are prepared by a method comprising heating the mixture of the above-named individual components at an elevated temperature, not at room temperature.