摘要
以氯化镧、对甲基苯甲酸、氢氧化钠为原料合成了对甲基苯甲酸镧。通过元素分析、红外光谱分析、热分析等方法对合成产物进行了表征;通过刚果红试纸法和高温老化箱实验研究了对甲基苯甲酸镧对聚氯乙烯热稳定性能的影响;同时,将对甲基苯甲酸镧与硬脂酸锌、硬脂酸钙、硬脂酸镧和季戊四醇等进行比较,并将对甲基苯甲酸镧与上述一种或者一种以上稳定剂进行复配。结果表明,当对甲基苯甲酸镧单独作为聚氯乙烯(PVC)稳定剂时,稳定性效果不理想,长期稳定性一般,抗变色能力也不好;当对甲基苯甲酸镧/钙锌复合体系/季戊四醇=2∶1∶2时,PVC的稳定时间达到48 min;对甲基苯甲酸镧可以吸收PVC分解释放的HCl生成LaCl_3,减少了HCl对PVC降解的催化作用,从而抑制PVC的降解。
Lanthanum p-methyl benzoate(LPB) was synthesized by using lanthanum chloride, p-Toluic acid and sodium hydroxide as raw materials, and the resultant product was characterized by means of elemental analysis and FTIR. The effect of LPB on the thermal stability and discoloration of polyvinyl chloride(PVC) were investigated by Congo red experiment and high-temperature hot aging tests. Moreover, a comparative study was carried out for LPB with other stabilizers such as zinc stearate, calcium stearete, lanthanum stearate and pentaerythrotol, and LPB was also mixed with other stabilizers to form a complex stabilizer. The results indicated that the thermal stabilizing effect on PVC is not good enough when LPB was used alone, which also resulted in poor long-term stability and anti-discoloration performance. When the mass ratio of LPB/calcium zinc composite/pentaerythrotol mixture was set to 2/1/2 and its total dosage was determined as 4 wt % of PVC, the stability time of PVC reached 48 min. The stable mechanism of LPB could be ascribed to the absorption of the HCl released by the decomposition of PVC. Such absorption could result in the production of LaCl_3 and therefore reduced the catalytic effect of HCl on the degradation of PVC and inhibited the degradation of PVC accordingly.
引文
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