| 摘要 |
<p>The process comprises the stages of (a) forming a quasi prepolymer rich in isocyanate gps. by reacting all the diisocyanate with part of the polyol; and (b) reacting the quasi prepolymer with the remainder of the polyol and all the chain extending agent. Stage (b) is carried out by reacting sufficient of the quasi prepolymer with the remaining polyol and all the chain extending agent to form a prepolymer rich in hydroxyl gps., and reacting this prepolymer in the liq. phase with the remainder of the quasi prepolymer to form the polyurethane. Process allows the prodn. of urethane casting compsns. with adequate pot life and good rate of cure compared with prior are systems. The compsns. are esp. useful for the prodn. of cast polyurethane rubber articles with excellent dynamic resilience, e.g. for making solid tyres. Specific constituents of the compsn. are 4,41-diphenylmethane diisocyanate; polyester polyols, polyether polyolols or polylactones; and chain extending agents such as ethane diol, butane 1,4-diol, diethylene glycol and 1,4-bis-(2-hydroxyethoxy)benzene.</p> |
