Calcium-Zinc Stabilizer Replaces Lead Salts We Need to Solve
Liquid calcium zinc stabilizers are complexes of calcium zinc organic salts , phosphites, polyols , antioxidants and solvents . The liquid calcium zinc stabilizer has good compatibility with the resin and the plasticizer, has good transparency, is not easily precipitated, has less amount, and is easy to use . The main disadvantages are poor lubricity, reduced softening point of the product, and deterioration of long-term storage .
The solid composite calcium-zinc soap stabilizer is mainly stearic acid soap, followed by lauric acid soap and oleic acid soap . The product is characterized by good lubricity and does not reduce the softening point of PVC hard products . It is suitable for the processing of rigid PVC pipe and profile materials.
Products that are processed using microemulsification techniques overcome these shortcomings . People focus on improvement in two areas: to improve the initial coloration, to incorporate a sufficient amount of zinc soap, and to use a chelating agent to harm zinc chloride . As a high-zinc compound: reduce the amount of zinc soap to suppress zinc burn, use additives to change the initial coloring, this approach becomes a low zinc compound. , Not only widely used in soft products, its thermal stability and transparency have been recognized, but also successfully applied to the processing of hard products. In order to make the calcium/zinc system keep both the initial coloration and the zinc burning.
The general lead salt is only attached to the surface of PVC particles, and its role is equivalent to impeding the fusion of PVC particles, which will significantly postpone plasticization, reduce the friction between PVC particles, and reduce the shearing effect in PVC. The processing equipment will bear lower loads. The amount of lead salt is more, the finer the particles of lead salt, the more obvious the secondary effect.
Traditional environmental products such as calcium and zinc stabilizers, in the plasticization process, due to the greater electronegativity, the polar groups have a certain affinity with the acute nodes of the PVC resin to form bonds with stronger bond strength, thus weakening or Elimination of the attraction of the ionic bonds of the various layers of the PVC makes it easy for the PVC segments intertwined with each other to disperse, and the boundary between the molecular groups is easy to be small, thereby promoting the plasticization of the PVC resin. This caused the melt pressure to increase rapidly, the melt viscosity decreased, the temperature increased, and the plasticization temperature decreased after the plasticization of the resin in the feed section . Another resin transition plasticized .
Because traditional PVC processing equipment is used for the processing of lead and salt stabilizers, even adding a sufficient amount of lubricant will not prevent further plasticization of the resin in sufficient time, and it will destroy the original lubrication balance . In the late stage of use, the PVC melt consumes a large amount of heat stabilizers in the homogenization section, and at the same time, it does not reach the ideal viscosity and elasticity to meet the rigid PVC production needs. This is a problem that calcium and zinc stabilizers must solve in order to replace lead salts.
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