Introduction of stabilizers

stabilizer

　　Stabilizers, in general, are agents that increase the stability of solutions, colloids, solids, and mixtures. It can slow down the reaction, maintain the chemical balance, reduce the surface tension, and prevent the light, heat decomposition or oxidation decomposition. Narrow sense, mainly refers to maintain polymers, plastics, rubber, synthetic fiber and other stability, to prevent decomposition and aging of reagents. Pure PVC resin is very sensitive to heat, when heating temperature reached 90Y above, there will be a slight thermal decomposition reaction, when the temperature rises to 120C decomposition reaction intensified, in 150C, 10 minutes, PVC from the original white resin will gradually become yellow to red - Brown - black. The decomposition process of PVC resin is a series of chain reactions caused by the reaction of HCL removal, and finally leads to macromolecular chain scission. The mechanism of thermal stability to prevent thermal decomposition of PVC is achieved by the following aspects. By capturing PVC produced by thermal decomposition of HCl, the catalytic degradation of HCl can be prevented.

Lead salts are mainly based on this mechanism. In addition, there are metal soaps, organic tin, phosphite and epoxy.

• displacement of active allyl chloride atoms. Metal soaps, phosphite lipids, and organotin can act according to this mechanism.

• react with free radicals to terminate free radical reactions. Organic tin and phosphite grease act according to this mechanism.

• conjugated with conjugated double bonds to inhibit the growth of conjugate chains.

Organotin and epoxy species act according to this mechanism.

• decompose peroxide and reduce the number of free radicals. Organic tin and phosphite grease act according to this mechanism.

• passivation of metal ions that catalyze the removal of HCl

　　The second main stabilizers, which are inferior to lead salts, have less thermal stability than lead salts, but they are both lubricity. Metal soap is fatty acid (lauric acid, stearic acid, naphthenic acid) metals (lead, barium, cadmium, zinc, calcium salt, etc.) with stearic acid salt is most commonly used in the active order: Zn >Cd >Pb >Ca salt salt salt salt salt >Ba. Metallic soaps are generally not used alone. They are often used in combination with metal soaps or with lead salts and organic tin. In addition to Gd and Pb are non-toxic, in addition to Pb and Ca are transparent, no sulfide pollution, and therefore widely used in soft PVC, such as non-toxic, transparent products.

　　The so-called metal soap is a general term for the metal salts of higher fatty acids. The metal base is generally calcium, barium, cadmium, zinc, magnesium, oleic acid and other unsaturated fatty acids, fatty acid, stearic acid and ricinoleic acid replacement C8-C16 fatty acids, unsaturated fatty acid, in addition to non fatty acid alkyl phenols. According to the function of metal soap can be divided into cadmium, zinc, and barium, calcium, magnesium. The main function of cadmium and zinc soap is to capture HCL and replace allyl chloride. It is Lewis acid, which catalyzes the removal of hydrogen chloride from polyvinyl chloride and accelerates its deterioration. Especially, zinc chloride can produce the so-called "zinc burn". Barium, calcium and magnesium soap can capture hydrochloric acid, but they can not replace allyl chloride. Therefore, the ability to grow polyene chains can not be inhibited when they are used alone, but the chloride produced by them does not promote the removal of hydrochloric acid. These two kinds of metal soaps have different stabilizers, and they can be used in combination. There are synergistic effects between metal soap and many organic stabilizing agents. Calcium barium stabilizers have excellent stability, but because of its toxicity, it has gradually been replaced by other stabilizers, stable combination of low toxicity based on barium zinc and calcium zinc stabilizer, but the zinc burning shortcomings, so to add phosphite in the system of epoxy compound, polyols such as high zinc with the additives in. The beta two ketone compound can be used as a coloring modifier for low zinc coordination agents.