二元羧酸稀土热稳定剂的合成和应用研究

Synthesis and Application of Rare Earth Dicarboxylates as Thermal Stabilizers for PVC

通过双滴加法制备了一系列二元羧酸稀土盐，采用稀土离子滴定测定产物的产率，用红外光谱检测其结构，并通过刚果红法和热烘法两种热稳定试验方法研究了二元羧酸稀土盐对聚氯乙烯（PVC）的热稳定作用，并与硬脂酸稀土、二聚酸钙等热稳定剂作了比较。结果表明，二元羧酸稀土盐能有效延长PVC的热稳定时间，减缓PVC的变色速度，尤其是二聚酸镧碱式盐（Ⅱ）可使PVC刚果红变色时间长达74min，180℃热烘90min基本不变色；不同稳定剂对PVC热稳定效果的对比发现相同酸根的镧盐热稳定效果比铈盐好，己二酸的稀土盐热稳定效果差于二聚酸的铈盐，二聚酸碱式盐热稳定效果好于二聚酸正盐。

Rare earth dicarboxylates were prepared by adding dicarboxylic acid and liquid sodium hydroxide to liquid rare earth nitrates simultaneously. The yield was determined via complexometric titration of rare earth ions and the structure was identified by FTIR. Effects of this stabilizer on PVC were tested by Congo Red and heating methods and compared with other heat stabilizers, such as rare earth stearates, calcium dimeric carboxylates. Testing showed that this new heat stabilizer for PVC was very effective, especially alkali lanthanum dimeric carboxylates （ Ⅱ ）, which imparted PVC a thermal stability for 74 minutes without color change in 90 minutes at 180 ℃. The heat stability of PVC with lanthanum salts was better than that with cerium salts. It was also found that rare earth dimeric carboxylates had better thermal stabilizing effect on PVC than rare earth adipates, alkali dimeric carboxylates had better thermal stabilizing effect than dimeric carboxylates.