Calcium and zinc stabilizers are generally classified into solid calcium zinc stabilizers and liquid calcium zinc stabilizers.
The calcium-zinc stabilizer is synthesized by a special compounding process mainly composed of a calcium salt, a zinc salt, a lubricant, an antioxidant, and the like. It can not only replace toxic stabilizers such as lead and cadmium salts and organotins, but also has good thermal stability, light stability and transparency and tinting strength. Practice has proved that in PVC resin products, the processing performance is good, the heat stability is equivalent to the lead salt stabilizer, and it is a good non-toxic stabilizer.
The appearance of the calcium-zinc stabilizer is mainly white powder, flake, and paste. Powdered calcium-zinc stabilizer is used as the most widely used non-toxic PVC stabilizer, and is commonly used in food packaging, medical equipment, wire and cable materials, etc. At present, PVC calcium-zinc stabilizers for rigid pipes have appeared in China.
The thermal stability of powdered calcium-zinc stabilizer is not as good as that of lead salt. It has certain lubricity, poor transparency and easy to spray. In order to improve its stability and transparency, antioxidants such as hindered phenols, polyols, phosphites, and β-diketones are often added to improve.
The two major systems of calcium-zinc stabilizers are mainly divided into hydrotalcite systems and zeolite systems.
The price of powdered calcium-zinc stabilizers is uneven and is not regulated by a standard national standard.
The liquid calcium-zinc stabilizer is mainly in the form of a pale yellow oily liquid. The difference between the stability of the powder and the liquid is not large. The liquid calcium-zinc stabilizer generally has a large solubility, and has good dispersibility in the PVC resin powder, and the effect on transparency is far less than that of the powder stabilizer. However, liquid stabilizers are more likely to precipitate. Need to choose the right solvent.
Liquid stabilizers are commonly used in PVC products with a total plasticizer content of greater than 10 to 20 phr.
Metal soaps and auxiliaries have greater solubility in solvents; low volatility, high flash point, low viscosity, colorless or light color, no odor, no toxicity or low toxicity. For example, mineral oil such as liquid paraffin, white oil, diesel oil, and spindle oil is used as a solvent. It is worth noting that some solvents contain polycyclic aromatic hydrocarbons. According to the relevant provisions of Section 30 of the German Food and Commodity Law (LMBG), the maximum allowable limit of total PAH is 10 mg (10 PPM), BaP benzo (a) 芘The maximum allowable limit is 1mg (1PPM), and some countries in the European Union are also preparing to adopt this standard. The auxiliary stabilizer itself does not have thermal stability, but it can improve the stability efficiency because there is no single-component cadmium assist, and the main phosphites, epoxy compounds and phenolic antioxidants, β-diketones and other auxiliary substances It is especially important.
It has good dispersibility, compatibility, processing fluidity, wide adaptability, excellent surface finish, good thermal stability, small initial hue, no precipitation, and no heavy metals and other toxic components. , no vulcanization phenomenon; Congo red test time is long, has excellent electrical insulation, no impurities, high efficiency and weather resistance; wide application range, strong practicability, less dosage, versatility; white products, whiteness Better than its competitors.
Variety specifications and uses
According to different uses, there are different varieties of calcium-zinc composite stabilizers: CZ-1, CZ-2, CZ-3, etc., which are used for plastic products such as pipes, profiles, pipe fittings, plates, injection molding, blown film, cable materials, etc. .
Problems that calcium and zinc stabilizers must replace in order to replace lead salts
The liquid calcium zinc stabilizer is a composite 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 easy to be precipitated, is used in a small amount, and is convenient to use. The main disadvantage is that the lubricity is poor, the softening point of the product is lowered, and the long-term storage will deteriorate.
The solid composite calcium-zinc soap stabilizer is mainly composed of stearic acid soap, followed by lauric acid soap and oleic acid soap. The product is characterized by good lubricity, does not reduce the softening point of PVC hard products, and is suitable for the processing of rigid PVC pipes and profiles.
The products obtained by the micro-emulsification technology overcome the above disadvantages. People pay attention to improving from two aspects: in order to improve the initial coloration, a sufficient amount of zinc soap is used, and a chelating agent is used to detoxify zinc chloride. As a high-zinc blend: reduce the amount of zinc soap to suppress zinc burning, and change the initial coloring with an additive, which is a low-zinc blend. Not only is it widely used in soft products, its thermal stability effect and transparency are recognized, but it has also been successfully applied to hard product processing. In order to keep the calcium/zinc system to maintain a small initial coloration, it can also inhibit zinc burning.
Generally, the lead salt is only attached to the surface of the PVC particles, and its action is equivalent to hindering the fusion between the PVC particles, which will significantly delay the plasticization, reduce the friction between the PVC particles, reduce the shearing effect in the PVC, and the processing equipment bears a low load. The amount of lead salt is more, and the finer the particles of lead salt, the more obvious the secondary effect.
Traditional environmentally friendly products, such as calcium-zinc stabilizers, have a certain affinity in the plasticization process due to the high electronegativity, and the polar groups have a certain affinity with the acute nodes of the PVC resin, forming a strong bond of the bond energy, thereby weakening or The attraction of the ionic bonds of each layer of PVC is eliminated, and the segments in which the PVC is intertwined are easily diffused, and the boundary between the molecular groups is easy to be small, thereby promoting the plasticization of the PVC resin. This causes the melt pressure to increase rapidly after the resin is partially plasticized, the melt viscosity decreases, the temperature rises, and the plasticizing temperature decreases. Resin transition plasticization.
Moreover, since the conventional PVC processing equipment is used for the processing of the lead salt stabilizer, even if a sufficient amount of the lubricant is added, the resin cannot be further plasticized in a sufficient time, and the original lubrication balance is destroyed. The use of late PVC melt consumes a large amount of heat stabilizer in the homogenization section, and at the same time does not achieve the desired viscosity and elasticity to meet the needs of rigid PVC production. This is a problem that calcium and zinc stabilizers must solve in replacing lead salts.
CH400, CH401, CH402 calcium-zinc composite heat stabilizer is an environmentally-friendly and efficient multi-functional liquid calcium-zinc composite heat stabilizer. It has excellent thermal stability and transparency, and it does not cause surface precipitation and migration when used in PVC products. It has better effect with heat resistant oil, methyl epoxide and epoxidized soybean oil. It is suitable for PVC slurry processing and is widely used in PVC processing such as plastic molding, plastic coating and dip coating.
The product not only has good compatibility and viscosity control, but also provides excellent initial coloration and color retention. This product has proven to be an excellent heat stabilizer. It has good compatibility, low volatility, low mobility and good light resistance. It is suitable for PVC products such as soft pipe, granulation, calendered film, toys, conveyor belt, advertising cloth and wallpaper.
(1) It can replace organotin stabilizer and lead salt stabilizer to meet the environmental and sanitary requirements of non-toxic wire and cable; (2) It has excellent initial whiteness and thermal stability, and is resistant to sulfide pollution; (3) It has good lubrication. Sexual and unique coupling, giving the filler a good dispersibility, enhancing the wrapping with the resin, improving the performance of the product, reducing mechanical wear and prolonging the service life of the equipment; (4) both toughening and promoting melting, plasticizing flow Good (5) can give the PVC mixture a good uniform plasticization and high-speed melt flow, so that the surface of the product is smooth.
Recommended dosage: 2-5PHR of total mixture