VIBRATION INSULATING MATERIAL

PURPOSE:To provide a vibration insulating material composed of a low-expansion polyurethane elastomer having excellent adhesivity, by reacting an organic polyisocyanate with a polyether polyol having specific average number of functional groups and number-average molecular weight, and a chain extender in the presence of a foaming agent (water). CONSTITUTION:An organic polyisocyanate (e.g. 4,4'-diphenlmethane diisocyanate) is made to react with a polyether polyol (e.g. glycerin) having an average number of functional groups of 2.5-3.5 (preferably 2.8-3.3) and a number-average molecular weight of 4,500-8,500(preferably 4,500-6,500) and a chain extender (a low molecular difunctional compound such as ethylene glycol) at ratios to give an NCO index of 90-110, in the presence of a foaming agent (e.g. water), a catalyst for urethane formation, a foam stabilizer, etc. to obtain a low-expansion polyurethane elastomer having a bulk density of 0.4-0.8g/cm and a spring constant per unit are of 3-10kg/cm . USE:For the base plate of a metal punching press, the pad of a compressor, and the cushioning material of railway.