共聚甲醛熔融端基稳定化方法的研究

Study on Terminal Stabilization of Polyoxymethylene Copolymer by Melting Extrusion

采用熔融挤出法对共聚甲醛进行端基稳定化处理。研究了稳定化过程中碱性催化剂、挤出机脱挥能力以及温度对端基稳定化效果的影响。通过测定不稳定端基含量、熔体质量流动速率(MFR)和黄色指数(YI)评价共聚甲醛端基稳定化效果。研究结果表明:碱性催化剂可催化加速不稳定端基的分解,改善端基稳定化效果;但碱性催化剂碱性不宜过强,否则会引起树脂碱解、变色。挤出机脱挥能力越强,越有利于甲醛的快速脱除,端基稳定化效果愈好。处理温度过高会引起分子主链的断裂,过低不利于不稳定端基的快速分解,在205～215℃之间为宜。

Polyoxymethylene copolymer was stabilized by melting extrusion to eliminate its unstable terminals. The effects of processing condition, such as alkaline catalysts, the devolatilization capacity of extruder, and the temperature on terminal stabilization were investigated. The terminal stabilization was evaluated by unstable terminal content, melt flow rate （MFR） and yellow index （YI）. The results showed that the alkaline catalysts could accelerate the decomposition of unstable terminals and promote terminal stabilization. However, the alkaline should not be too strong; otherwise, it would cause the resin alkaline hydrolysis or discoloration. The stronger the devolatilization capacity, the better the stabilization effect was. The appropriate treatment temperature was 205 -215℃, the unstable terminals could decompose quickly and the molecular chains would not break obviously.