Abstract: The polyvinyl chloride resin composition of the invention is highly heat-resistant as a result of compounding with an organic tin mercaptide compound as a heat stabilizer but is still free from the problem of the unpleasant odor emitted by the mercaptide compound owing to a specific deodorizing agent compounded therewith so that the composition is suitable as a molding resin composition for food containers. The above mentioned deodorizing agent is a diterpenic acid such as abietic acid or a rosin which is a crude mixture of several kinds of diterpenic acids obtained as a natural product.

Abstract: The invention provides a very simple but effective means for preventing surface oxidation of fine metal powders by coating the metal powder with an organic dye. This method of surface-oxidation prevention is particularly useful for the preparation of a so-called plastic magnet which is prepared by uniformly blending a dye-coated fine powder of a magnetic alloy such as a rare earth-cobalt based permanent magnet with a thermoplastic resin such as a nylon or polyphenylene sulfide resin followed by molding the resin-powder blend into a magnet form. In addition to the remarkably improved magnetic properties of the thus prepared plastic magnets as a result of high loading and absence of degradation by oxidation, the danger of spontaneous ignition of the magnet powder in molding can be eliminated almost completely. Surface treatment of the dye-coated magnet powder with a silicone fluid gives further improved results.

Abstract: The plastic magnet composition provided by the invention comprises a thermoplastic resin as a binder and a powder of a metallic or alloy-type magnet which is coated on the particle surface with a phosphorus-containing compound having at least one phosphorus-to-oxygen linkage in a molecule such as phosphoric acid and related compounds. By virtue of the surface coating, the magnet powder is freed from the degradation by air oxidation and the danger of ignition in the molding process so that plastic magnets of high performance can be readily manufactured with safety. The advantages of the coating layer are further increased when the coating layer is formed of a combination of the phosphorus-containing compound and an organic dye compound. An overcoating on the thus coated magnet powder with an organopolysiloxane has an effect of increased lubricity.