ROD SEALING SYSTEM

摘要

This invention provides a rod sealing system comprising a buffering, a rod seal, and a dust seal provided in that order from a fluid pressure side toward an external side between annular gaps between two reciprocating members. The buffering is formed of a thermoplastic polyurethane molded product that has been produced by reacting (A) a high-molecular weight polycarbonate diol having a number average molecular weight Mn of 500 to 6000, (B) an aromatic diisocyanate, and (C) a low-molecular weight diol as a chain elongation agent at an NCO/OH ratio of 0.95 to 1.20 followed by heat treatment under such conditions that the hard phase glass transition point (Tg) as measured by differential scanning calorimetry is 170ºC or above, preferably 170 to 230ºC, and the endothermic peak area (?H) of Tg is not less than 5 J/g. The buffering formed of this thermoplastic polyurethane molded product is excellent, for example, in heat resistance, particularly heat resistance enough to withstand a service environment up to 120ºC, compression permanent deformation resistance, and eccentricity following property.