Influence On The Preparation And PVC Thermal Stability Of Azabenzene Ring Rare Earth Stabilizer

Using 2,3-pyrazinedicarboxylic acid（2,3-PDA）,2-aminonicotinic acid（2-ANA）and lanthanum nitrate（La（NO₃）₃）as raw materials,two rare earth heat stabilizers,lanthanum2,3-pyrazinedicarboxylic acid（2,3-LPDA）and lanthanum 2-aminonicotinic acid（2-LANA）,were synthesized respectively.It was characterized by infrared spectroscopy,thermal analysis,elemental analysis and ICP analysis,and the molecular formulas of the two rare earth heat stabilizers were determined.The static thermal stability time of 2,3-LPDA was30 min and that of 2-LANA was 27 min,and the anti-discoloration performance of2,3-LPDA was better than that of 2-LANA.The dynamic thermal stability time of2,3-LPDA was 34.66min and the apparent activation energy（Ea）was 102.94Nm/s;The dynamic thermal stability time of 2-LANA is 27.45min,and the Ea is 105.54nm/s.2-LANA has stronger ability to inhibit PVC degradation than 2,3-LPDA.After compounding the two rare earth heat stabilizers with other stabilizers respectively,The thermal stability time was 66 min when 2-LANA:Zn St₂:PE=2:1:2;The best anti-tarnish property was obtained when 2-LANA:Ca/Zn stabilizer:PE=1:1:3.In addition,the dynamic thermal stability of 2-lana and its compound stabilizer is better than that of2,3-LPDA and its compound stabilizer,and the Ea value of 2-LANA and its compound stabilizer is higher than that of 2,3-LPDA and its compound stabilizer,indicating that2-LANA and its compound stabilizer can more effectively inhibit the HCl released by PVC degradation and weaken the degradation ability of PVC.2-LANA has better rheological and mechanical properties than 2,3-LPDA.When 2-LANA:Ca/Zn stabilizer:PE=1:1:3,its rheological and mechanical properties are the best.Then,cerium 2-aminonicotinate acid（2-CANA）and lanthanum cerium2-aminonicotinate acid（2-LCANA）were synthesized from 2-ANA,cerium nitrate,lanthanum nitrate and sodium hydroxide.The effects of different rare earth heat stabilizers on the thermal stability of PVC were studied.The order of static and dynamic thermal stability of single rare earth heat stabilizer is 2-LANA>2-LCANA>2-CANA.The best static and dynamic thermal stability of rare earth heat stabilizer is 2-LANA:Zn St₂:PE=2:1:2,the static and dynamic thermal stability times are 66min and 64.91min respectively,and the Ea is 118.54k J/mol;2-LANA:Zn St₂:PE=2:1:2,the static and dynamic thermal stability time are 38min and 38.78min respectively,and the Ea is93.51k J/mol.The rheological and mechanical properties of 2-LANA and its compound stabilizer are the best.Therefore,2-LANA is the best rare earth heat stabilizer,and the synergistic effect is remarkable after compounding with other stabilizers.However,considering the rare earth separation cost,lanthanum cerium stabilizer can be preferentially selected to reduce the rare earth separation cost and improve the resource utilization.Rare earth heat stabilizer can effectively absorb HCl released by PVC in the process of thermal degradation and generate La Cl₃ and Ce Cl₃,which can delay the thermal degradation of PVC to a certain extent,reduce the formation of conjugated double bonds,improve the anti discoloration ability of PVC and achieve the purpose of PVC thermal stability.However,2,3-LPDA will release NO₂ in the processing process,resulting in air pollution.Therefore,it is more appropriate to select non-toxic and environmental friendly2-LANA,2-CANA and 2-LCANA as heat stabilizers.