聚6-羟基己酸碱性条件下的水解反应研究

探究了碱性条件下聚6-羟基己酸水解反应的机理和最优化工艺条件。实验过程中选用碱度较大的氢氧化钠及碱度较小的碳酸氢钠作为反应试剂。研究表明:碱度不同,其反应机理,反应工艺条件亦不同。碱度越大,OH~-浓度越大,亲核基团OH~-]直接进攻聚6-羟基己酸的酯基结构,使酯基键发生断裂反应,生成小分子的6-羟基己酸;反应工艺条件缓和,在100℃的集热式恒温加热磁力搅拌器中既可完全解聚。碱度大的氢氧化钠参与反应的最优化工艺条件:氢氧化钠/聚6-羟基己酸摩尔比为4.4,乙二醇/聚6-羟基己酸摩尔比为6.5,水用量100g,催化剂0.1g,反应时间2h,反应温度100℃条件下,6-羟基己酸产率达到84.07%;碱度小的碳酸氢钠钠参与反应的最优化工艺条件:碱度越小,OH~-浓度越小,在反应初期亲核基团-OCH_2CH_2OH]占主导地位,发生醇解反应的概率大,整个反应体系为醇解反应与水解反应相互促进进行;反应工艺条件苛刻,须在180℃密闭高压釜中完全解聚。碳酸氢钠/聚6-羟基己酸摩尔比为1.1,乙二醇/聚6-羟基己酸摩尔比为3,水用量100g,催化剂0.1g,反应时间1h,反应温度180℃~190℃条件下,6-羟基己酸产率达到90.38%。在整个反应系统中,乙二醇作为溶剂来使用。

Study on the Hydrolysis of Poly(6-hydroxycaproic acid)under Alkalinity Conditions

This article explores hydrolysis reaction mechanism and optimal process conditions of the poly (6-hydroxycaproic acid) under alkalinity conditions.The results show that the greater the alkalinity,the greater the concentration of OH-,and affinity groups OH-] direct attack on poly(6-hydroxy acid) ester group structure,make the ester bond cleavage reaction occurs,generating small molecule 6-hydroxy acid.Reaction process conditions are relatively mild.In the collector constant heating magnetic stirrer can complete depolymerization with the temperature of 100℃.Under the conditions that sodium hydroxide/poly(6-hydroxy acid) molar ratio of 4.4,glycol/poly(6-hydroxy acid) molar ratio of 6.5,water consumption of 100g,catalyst of 0.1g,reaction time of 2h,the reaction temperature of 100℃,6-hydroxycaproic acid yield up to 84.07％.The smaller the alkalinity,the smaller the concentration of OH-,and in the early stage of the reaction,the affinity group -OCH2CH2OH] was dominant,and the probability of occurrence of alcoholysis reaction is great,and alcoholysis reaction and alkaline reaction are mutually promoting in the entire reaction system.Reaction process conditions are relatively harsh,must be fully depolymerization at 180℃ sealed autoclave.Under the conditions that sodium bicarbonate/poly(6-hydroxy acid) molar ratio of 1.1,glycol/poly(6-hydroxy acid) molar ratio of 3,water consumption of 100g,catalyst of 0.1g,reaction time of 1h,the reaction temperature of 180℃ ～ 190℃,6-hydroxycaproic acid yield up to 90.38％.In the whole reaction system,ethylene glycol is used as a solvent.