共聚甲醛非均相碱液端基稳定化方法的研究

Study on Terminal Stabilization of Polyoxymethylene Copolymer by Aqueous Alkali in Heterogeneous Phase

采用非均相碱液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种类、用量、液比（碱性处理液体积与共聚甲醛质量之比）、处理温度及处理时间对端基稳定化效果的影响。通过比较共聚甲醛稳定化前后熔体质量流动速率（MFR）的变化，判断共聚甲醛分子链在稳定化处理中是否发生降解断链。测定稳定化前后共聚甲醛在222℃真空下60min内的热失重率评价稳定化的效果及共聚甲醛的稳定性。实验结果表明，碱性催化剂的碱性过强会使共聚甲醛在处理过程中发生碱解，导致树脂MFR升高。利用三乙胺作为碱性催化剂时，共聚甲醛经过稳定化处理后，MFR保持较好，当处理液pH值控制在12～13之间、处理液中三乙胺的质量分数为1％、液比在（3～5）：1之间、处理温度为140℃、处理时间为60min时，端基稳定化的处理效果最好。

Polyoxymethylene copolymer （Co-POM） was stabilized by the aqueous alkali in heterogeneous phase to eliminate the unstable hemiformal terminal groups. The effects of processing conditions, such as the variety and content of alkali, liquor ratio, the temperature and time of stabilization, on the terminal stabilization were stud- ied. The melt flow index （MFI） and the weight loss rate at 222 ℃ of the Co-POM in vacuum were detected to evaluate the stability of the Co-POM after terminal stabilizatio;3. The results showed stronger alkali would induce the increase of MFI of Co-POM. It＇s indicated the stronger alkali would result in the chain scission of Co-POM during the terminal stabilization. The triethylamine was moderate alkali. And after stabilized by aqueous triethylamine, the MFI of Co-POM kept in about 9.0 g/10 rain. The optimum conditions of terminal stabilization were that Co-POM was stabilized in aqueous solution containing 1% triethylamine （ pH： 12- 13 ） at 140 ℃ for 60min and liquor ratio was controlled in （3- 5）： 1.