1. Introduction
Because of its poor thermal stability, PVC will degrade when the temperature is higher than 110 ℃, the color will turn yellow, and the mechanical properties will decrease. Therefore, it is necessary to add heat stabilizers during its processing. The traditional non-toxic composite stabilizers are mainly Compound stabilizer of calcium stearate and zinc stearate. However, its stabilizing effect is low, and it is still not ideal when it is compounded with various auxiliary stabilizers such as polyols, β-diketones, and epoxy compounds. When the self-developed new organic zinc salt with a long-chain structure is used as a heat stabilizer, it can provide PVC with excellent stability and color retention.
PVC heat stabilizer is a national key project in the Eleventh Five-Year Plan period and has won 2 national invention patents.
2. Process route, technical characteristics, etc.
Among the several types of stabilization reactions by heat stabilizers, only the reaction to replace the unstable chlorine atoms in PVC and the anti-oxidation reaction are to fundamentally prevent the degradation and cross-linking of PVC. Others such as absorption of hydrogen chloride and destruction Both the positive carbanion and the double bond addition reaction are the remedies when the polyvinyl chloride has been degraded (after the HCl has been removed and some double bonds have been formed). Therefore, the basis for improving the initial coloring of PVC is the substitution of stabilizers. The ability to destabilize chlorine atoms. The self-developed new type of organic zinc soap, due to its structural relationship, can easily form coordination bonds with the carbon atoms corresponding to the unstable chlorine atoms in PVC under the action of heat and light, and finally replace the unstable chlorine atoms in PVC. Fundamentally prevent the degradation reaction of PVC from removing HCl. Therefore, this new type of zinc soap has extremely excellent thermal stability, and can keep the product white for a long time, and the new type of zinc salt is simple to prepare, can be prepared by one-step method, the process is simple, and it can be mass-produced. The structure also makes it have good compatibility with PVC.
Table 1. When the new zinc salt is used as PVC heat stabilizer, the color of the product changes with the degradation time

3. Application and economic benefits
　　 Polyvinyl chloride (PVC) is the third largest synthetic resin after polyethylene (PE) and polypropylene (PP). PVC products have the characteristics of light weight, softness, high mechanical strength, corrosion resistance, insulation, transparency, etc., and are widely used in industry, agriculture, construction, packaging and other fields. Statistics show that in 2005, the national PVC production capacity reached 9.72 million tons, and in 2006 it increased sharply to 12.84 million tons, an increase of 32%. In 2007, the national PVC production capacity will continue to grow and is estimated to reach 15.02 million tons. Therefore, PVC must be processed in the process. The heat stabilizer used has a huge market. At present, the commonly used heat stabilizers on the market include lead salt stabilizers, organotins, composite stabilizers, and auxiliary stabilizers. Lead salt stabilizers have excellent thermal stability and are currently the largest variety of thermal stabilizers in my country, but they are highly toxic and endanger human health, and their use has been gradually banned or restricted at home and abroad. The Ministry of Construction has also issued a decree banning lead salt stabilizers in water supply pipes. Non-toxic, non-polluting, and high-efficiency composite heat stabilizers have become a research hotspot. Therefore, our high-efficiency non-toxic organic zinc salt and calcium soap compound used as a composite stabilizer has huge potential economic benefits.