Synthesis And Application Of Plasticized And Thermally Stabilized Bifunctional PVC Additives

The structure of PVC determines its instability during processing,therefore,it is necessary to add a plasticizer and a heat stabilizer.Plasticizers and heat stabilizers are widely used today,but most of them are small molecules with a single function.On the other hand,synthetic raw materials of commercially available phthalate plasticizers,particularly phthalic acid(anhydride),are derived from crude oil,are difficult to regenerate,and they all have some toxicity.Many factors lead phthalate urgent need to develop alternatives.In addition,the current domestic melamine market overcapacity,bio-based non-toxic degradable succinic acid production market is growing,the development of these two chemicals downstream products is of great significance.Firstly,melamine is reacted with succinic anhydride and tetrahydrophthalic anhydride at 40? for 48 hours to form two melamine diamic acid.The melamine is first reacted with succinic anhydride at 25? for 48 hours,and then reacted with tetrahydrophthalic anhydride at 40? for 48 hours to obtain the third melamine diamic acid.The test results show that the three synthesized melamine diamide acids have a poor thermal stability effect alone.After combined with the commercially available complex calcium-zinc heat stabilizer,it is found that the residual heat stability time of Congo red is 9.5,20.5,16.5 minutes when 1 phr(parts per hundred of resin)of compound calcium-zinc heat stabilizer is combined with 1 phr of melamine diamic acid.The residual heat stability time of 2 phr and 3 phr of composite calcium-zinc heat stabilizer is 10.2 and 16.0 minutes,respectively.This shows that the three melamine diamic acids have excellent auxiliary heat stabilizing effects.Torque Rheometer test results show that the dynamic thermal stability time of 2 phr of melamine diamide acid with 2 phr of calcium-zinc composite thermal stabilizer compound used is significantly higher than 4 phr composite calcium-zinc heat stabilizer,and melamine diamic acid can significantly improve the long-term thermal stability of PVC.Secondly,all of melamine diamic acid are converted into the corresponding melamine diamide acid calcium and the melamine diamide acid zinc salt by a neutralization reaction and a metathesis reaction.Through the process exploration,it is found that H2O is used as a reaction solvent and reacted with CaCl2 and ZnCl2 by raising the temperature to 75? and prolonging the reaction time from 3 to 24 hours,the melamine diamide acid calcium salt and the melamine diamide acid zinc salt were easily obtained.The melamine diamide calcium salt and the zinc salt are compounded in a 1:1 mass ratio.The test results showed that the dynamic thermal stability time of 4 phr of the three melamine diamide calcium and zinc salts is 16.3,17.2,16.7 minutes,respectively.The dynamic thermal stability time of 4 phr composite calcium-zinc heat stabilizers is only 14.3 minutes.When the additive addition amount is increased to 6 phr,the dynamic heat stability time is further increased;if the additive addition amount is increased to 8 parts,the dynamic heat stability time is not increased.Therefore,a small amount of melamine diamide calcium salt and melamine diamide zinc salt have excellent heat stability and can be used as a main heat stabilizer for PVC.Further,when the mass ratio of the calcium salt to the zinc salt is about 3:1,the heat stabilization effect is the best.Finally,the plasticizing effect of melamine diamide acid calcium salt and zinc salt is not obvious,but do not significantly reduce the performance of PVC.The synthesis of melamine diamic acid and its calcium zinc salt provides a preliminary reference for the application of melamine in PVC.