Solid composite calcium zinc stabilizers are mainly composed of stearic acid soap, followed by lauric acid soap and oleic acid soap. The product is characterized by good lubricity and does not lower the softening point of PVC hard products, making it suitable for processing hard PVC pipes and profiles.
The products processed using microemulsification technology overcome the aforementioned drawbacks People focus on two aspects for improvement: to improve initial coloring, a sufficient amount of zinc soap is added, and chelating agents are used to render zinc chloride harmless. This is known as high zinc coordination: reducing the amount of zinc soap added to suppress zinc burning, and using additives to change initial coloring. This method is known as low zinc coordination., Not only widely used in soft products, its thermal stability effect and transparency have been recognized, but also successfully applied in hard product processing. In order to maintain minimal initial coloring and suppress zinc burning in the calcium/zinc system
Generally, lead salts only adhere to the surface of PVC particles, which acts as a hindrance to the fusion between PVC particles, significantly delaying plasticization, reducing friction between PVC particles, and minimizing shear within PVC. Processing equipment can withstand lower loads. The more lead salt is used, the finer the particles of lead salt, and the more obvious the effect.
Traditional environmentally friendly products such as calcium zinc stabilizers, due to their high electronegativity, have a certain affinity between polar groups and acute nodes of PVC resin during the plasticization process, forming strong bond energy complexes, thereby weakening or eliminating the attraction of ion bonds in various layers of PVC. This makes the chain segments of PVC that are entangled with each other easy to diffuse, and the boundaries between molecular groups are easy to narrow, promoting the plasticization of PVC resin. This triggers a rapid increase in melt pressure, a decrease in melt viscosity, an increase in temperature, and a decrease in plasticizing temperature after the resin is partially plasticized in the feeding section. Resin transition plasticization has occurred again.
Due to the fact that traditional PVC processing equipment is designed for processing with lead salt stabilizers, even adding sufficient amounts of lubricant cannot prevent further plasticization of the resin in sufficient time, and also disrupts the original lubrication balance. The use of PVC melt in the homogenization stage consumes a large amount of heat stabilizer, but cannot achieve ideal viscosity and elasticity to meet the production needs of hard PVC. This is a problem that calcium zinc stabilizers must solve in replacing lead salts
Post time: Nov-20-2024
