Study On Maleic Anhydride Derivatives For Thermal Stabilizer Of Poly(Vinyl Chloride)

The production of Poly(vinyl chloride)is the second largest general purpose synthetic resin only to Polyethylene(PE).PVC is widely used in most areas because of its good overall performance.However,PVC is easy to degrade in the process of processing.Therefore,it is necessary to add a certain amount of heat stabilizer to inhibit the occurrence of thermal degradation.At present,most of the heat stabilizers sold on the market are toxic,expensive or harmful to the environment,which makes the safe non-toxic,green and efficient heat stabilizer become an important research object.In this paper,the effects of maleic anhydride derivatives on the thermal stability of PVC were studied.The main works are as follows:(1)One-step synthesis of ZnMA-I was synthesized by maleic acid with excess zinc oxide,and ZnMA-II was prepared by mixing zinc maleate and Zinc Oxide in a certain proportion.The thermal stability of ZnMA-I and ZnMA-II on PVC was compared by Congo red test,dynamic test,UV-vis,thermogravimetric analysis(TGA)and infrared(FTIR).The results show that the thermal stability of ZnMA-I is better than that of ZnMA-II,which is mainly due to the diverse complexes in ZnMA-I.Further studies show that these complexes can replace unstable chlorine atoms,absorb hydrogen chloride and occur Diels-Alder reaction with the degraded PVC chains to achieve the purpose of improving the thermal stability.(2)In order to solve the problem of "zinc burning",sodium monoethyl maleate was prepared by utilizing maleic anhydride as template.The thermal stability mechanism of sodium monoethyl maleate to PVC was studied by Congo red test,UV-vis and TGA.The results show that the thermal stability mechanism of sodium monoethyl maleate on PVC is mainly due to the absorption of hydrogen chloride during the degradation of PVC and the formation of Diels-Alder reaction with the conjugated double bonds produced by degradation of PVC,which has achieved the purpose of prolonging the thermal stability time,but following with poor initial color stability.(3)In order to further prolong the thermal stability time,in this paper,maleic acid diethylene glycol ester is prepared through the reaction of maleic acid and ethylene glycol,then it react with epichlorohydrin to synthesize epoxy terminated maleic acid double ethylene glycol diglycidyl ether ester(MADGE).The thermal stability and its mechanism of MADGE under different contents were studied by Congo red test,dynamic test,UV-vis,TGA and FTIR.The results demonstrate that MADGE has good thermal stability to PVC and can achieve the purpose of prolonging the heat settling time because of its strong ability to absorb hydrogen chloride and the occurrence of Diels-Alder reaction with the degraded PVC chain.(4)In order to realize the ideal industrial application of high efficiency and environment-friendly stabilizer,we mixed CaSt2 and ZnSt2 at a molar ratio of 1:1,followed the mixture was mixed with maleic acid diethylene glycol glycidyl ether ester for small test.It was found that the composite stabilizer added with maleic acid diethylene glycol glycidyl ether ester had better thermal stability effect on PVC and exhibited some plasticizing effect.Based on this,we have developed a thermal stabilizer for injection products and have cooperated with enterprise in the pilot.The product not only reached the ROSH standard,but also got the higher evaluation of customer after using it.