PVC heat stabilizers catalysis

PVC heat stabilizers catalyst. Such stabilizers include lead salts , organic acids, metal soaps , organic tin compounds , epoxy compounds , phenol salts and metal thiolate salt. They can react with HCL , inhibition PVC de HCL response.
2 ) replacement of PVC molecules suppress  Metallic stearate unstable allylic chlorine atoms off the PVC. Such as organic tin stabilizer of PVC unstable molecule ligand binding chlorine atoms in the ligand , a chlorine atom with an unstable organotin substitution . 3 ) the addition reaction of a polyene structure , a large conjugated system damage formation and reduce coloration . A salt of an unsaturated acid or ester containing double bonds , and the PVC molecules conjugated diene double bond addition reaction , thereby destroying the conjugated structure, and color.
4 ) to capture free radicals and prevent the oxidation reaction . Such as adding phenolic heat stabilizers can block off the HCL, is due to give phenol H atom radical degradation of PVC macromolecules with radical coupling reaction with O2 to form a substance can not be , and has a thermal stability. Such thermal stabilizers may have one or several functions of both .
Ideal PVC heat stabilizer should be a multi-functional substance , or a mixture of some materials , they can achieve the following functions: First, replacement lively, unstable substituent ; second is to absorb and neutralize the release of PVC during processing HCL, eliminating the autocatalytic degradation of the HCL ; third neutralization or passivation of the catalytic metal ions from the degradation and other harmful impurities ; Fourth, through the chemical reaction forms an unsaturated bond can block the  PVC processing aid continued growth inhibition degradation coloring ; five is the best protection against ultraviolet radiation shielding effect . Typically heat stabilizers according to their performance with the use of special , rare cases used alone , and most varieties are powdery , some are highly toxic chemicals. For ease of use , to prevent dust poisoning, reduce toxic substances or replaced by non-toxic substances, at home and abroad in recent years developed many kinds of composite stabilizer , for example , the world famous German brand composite stabilizer Bear series , the United States , Germany, Japan, Netherlands and other countries or organotin compound organotin stabilizers have considerable market share in China . Therefore , efforts to promote the application developed in China with high efficiency , low cost , no dust pollution and non-toxic or low toxicity of new composite stabilizer , is the urgent need for the development of the plastics industry .
Ideal thermal stabilizer should also absorb HCL, remove the active site , the addition of a conjugated polyene chain , destruction carbenium salts and prevent auto-oxidation , etc. , which does not produce a product of catalytic degradation of PVC . The actual heat stabilizers with different functions due to exhibit different thermal stability characteristics ,
1 ) cadmium , zinc soap is typical of aluminium stearate  early -type heat stabilizers , can quickly absorb HCL, and Cd, Zn in the catalyst to effectively replace PVC chain carboxylate unstable chlorine atom , thereby effectively suppressing the initial degradation and coloring , but because of consumption of fast transformation products CdC12, ZnC12, but also off the HCL PVC efficient catalysts , which will lead to degradation of the material PVC vicious suddenly darkened , so long-term thermal stability .
2 ) barium, calcium soap is a typical long-term thermal stabilizers, only the function of absorbing HCL , PVC can not effectively suppress coloration , but the transformation products BaC12, CaC12 non- catalytic activity , does not cause a sudden black PVC , long-term heat stability better.