Study On The Preparation And Mechanism Of Rare-earth Cyclic Organic Acid Stabilizer

Lanthanum p-methyl benzoate?LPB?and Lanthanum aminobenzoate?LAB?were synthesized from P-toluylic acid,P-aminobenzoic acid,and Lanthanum nitrate.The molecular formulas of two rare earth stabilizers were determined by IR,thermal analysis and elemental analysis.At the same time,two kinds of rare earth stabilizers were added into PVC samples as PVC stabilizers,and the thermal stability of rare earth stabilizers was studied by Congo red experiment and High temperature hot aging test.The experimental results showed that when LPB was used as PVC stabilizer,the thermal stability time was12 min.When LAB was used as PVC stabilizer,the thermal stability was the best,and the thermal stability time was up to 23 min.And the anti-discoloration performance of PVC samples was also good.The thermal stability of the rare earth stabilizer was studied by mixing with Zinc stearate,Calcium stearate and Pentaerythritol?PE?.It was found that LAB could effectively inhibit the phenomenon of"zinc-sintering",but the inhibition of LPB on"zinc-sintering"was not obvious enough.Therefore,Cerium aminobenzoate?CAB?and Lanthanum&Cerium aminobenzoate?LCAB?were synthesized with P-aminobenzoic acid,Lanthanum nitrate or Cerium nitrate as raw materials to study the influence of different rare earth elements on the stability of rare earth stabilizer.The thermal stability of CAB,LCAB and LAB were studied.The results of Congo red experiment and High temperature hot aging test showed that when three rare earth stabilizers acted independently,the advantages and disadvantages of thermal stability are as follows:LAB>CAB>LCAB.However,in compound experiments,the thermal stability of composite stabilizers compounded by CAB or LCAB with Zinc stearate,Calcium stearate or PE was slightly better than that of composite stabilizers compounded by LAB.Among of them,when the compounding scheme was LCAB:Zinc stearate:PE=1:1:3,the thermal stability time reached 60 min;CAB:Zinc stearate:PE=1:1:3,the thermal stability time reached 50 min,compared with the rare earth stabilizer alone,the composite thermal stabilizer gave PVC samples better anti-discoloration performance and longer thermal stability time.La³⁺or Ce³⁺in the rare earth stabilizer can absorb the HCl gas released in the process of PVC degradation,thus reducing the content of HCl gas and achieving the stability effect on PVC samples.The IR spectra showed that lanthanum or cerium ions in rare earth stabilizer can combine with Cl^-in PVC samples to form LaCl₃ or CeCl₃.The rare earth stabilizer was added to the PVC samples and the torque rheometer was used to carry out the simulation experiment of PVC processing.The experimental results showed that the rare earth stabilizer could promote the plasticization of PVC and greatly shorten the plasticizing time of PVC samples in the processing process.