Talking about the development status of PVC heat stabilizer

(1) The main function of the lead salt type lead salt stabilizer is to combine the HCL which is desorbed during the degradation of PVC to form a stable lead chloride, which is suitable for the manufacture of opaque products. Lead salt stabilizers are widely used because of their high thermal stability, good electrical insulation, low water absorption and low cost. The main varieties of lead salt heat stabilizers are "three salts" and "two salts". "Three salts" have high heat stability, good electrical insulation performance and large hiding rate; the disadvantage is that they are non-lubricating and have poor dispersibility, and the lubricant should be added in the formulation. "Di-salt" has outstanding weather resistance, strong anti-oxidation and ultraviolet shielding ability, and is an essential stabilizer in outdoor PVC products; the disadvantage is that heat resistance is not as good as "three-salt", when it exceeds 200 °C, "Second salt" is easy to decompose, so it is not suitable for applications where the processing temperature is too high.

(2) Metal soap metal soap can react with HCI and replace unstable chlorine atoms in PVC molecular chain, and is a kind of heat stabilizer with both lubrication effects. Metal soaps have sufficient heat resistance, most of which are non-toxic or low-toxic, and only a few are affected by sulfides, most of which can be used for translucent products. The main metal soap heat stabilizers are lead stearate, barium stearate, cadmium stearate, etc. Among them, lead stearate has good thermal stability, good lubricity and good light resistance, but it It is easily contaminated by sulfides and should not be used in transparent products. The dosage should not be too much, generally about 1 part.

(3) The organotin organotin heat stabilizer has a good stabilizing effect, and it can be used alone or in combination with other soaps, and has good transparency, and extremely low precipitation does not cause scaling, so organotin Stabilizers are one of the main stabilizers for PVC. Organotin stabilizers have excellent light and heat stability, resistance to initial coloration, high transparency and non-toxicity or low toxicity. They are ideal for PVC foods, pharmaceutical packaging, blow molding bottles and drinking water pipes that are widely used in the world. Heat stabilizers. However, the price of organotin-based heat stabilizers is high, and some products have unpleasant odors, which limits their application.

(4) Composite stabilizers The composite stabilizers currently used more are made of metal soaps and salts such as barium, cadmium, calcium and zinc, and are prepared with phosphite. The thermal stability of the crucible is good. When it is used to stabilize PVC, the zinc soap is first consumed by replacing with allyl chloride, and the resulting zinc chloride transfers chlorine to the barium soap, accepts the carboxylic acid and regenerates the zinc soap. The composite stabilizer can impart good aging resistance and thermal stability to the profile products, and has no sulfide pollution, and is suitable for use in outdoor building materials. However, due to the toxicity of cadmium salts, their use is reduced, and even some countries have banned their use.

As far as the current situation is concerned, experts have done a lot of research work on PVC stabilizers. The most mature ones are lead salt system stabilizers and expensive organotin stabilizers that have been used at home and abroad. However, the toxicity of lead salts and the high and odor of organotin are fatal defects of these stabilizers. Therefore, experts have been discussing and researching for many years, hoping to find a non-toxic and moderately effective high-efficiency stabilizer.