In actual cooperation, in addition to requiring stabilizers to meet the needs of thermal stability, they are often required to have excellent processability, weather resistance, initial coloring, light stability, and strict requirements for their odor and viscosity. At the same time, polychloride Vinyl products are also ever-changing, including pipes, sheets, blow-molded parts, injection molded parts, foam products, paste resins, etc. Therefore, the choice of heat stabilizers in the processing of PVC is very important, and most of the processing formulas need to be developed by the processing manufacturers.
(1) Excellent transparency The biggest advantage of organotin stabilizers is that they have excellent transparency. The use of organotin stabilizers in PVC formulations can produce crystalline products. Because of this, organotin can be used in bottles, containers, corrugated boards, various types of rigid packaging containers, hoses, profiles, films, etc.
(2) Extraordinary thermal stability There is no other type of thermal stabilizer that can surpass it in terms of thermal stability. Therefore, it is the preferred stabilizer for rigid PVC, and some varieties have better performance in soft products. Applicable to all PVC homopolymers, such as emulsion, suspension, and bulk PVC, as well as vinyl chloride copolymers, graft polymers, and polymer blends.
(3) The product is non-toxic. Most organotin stabilizers are non-toxic. In addition, the migration of organotin stabilizers in rigid PVC is minimal. Therefore, organotin stabilizers are the preferred heat stabilizers for PVC for food contact.
(4) Good compatibility. Organotin stabilizers have good compatibility with PVC, so there is generally no precipitation on the metal surface like a lead salt stabilizers and metal soap stabilizer systems.
(5) Poor lubricity. Sulfur-containing tin stabilizers have poor self-lubricity. Therefore, many commercially available sulfur-containing organotins are equipped with lubricants to prevent the hot melt from adhering to processing equipment during processing.
(6) High cost Compared with other types of stabilizers, the comprehensive performance of organotin stabilizers is closer to the ideal stabilizer. However, all organotin stabilizers, regardless of their structure, have the main disadvantage that their manufacturing cost is much higher than that of lead stabilizers or metal soap compounds. In recent years, by adopting new synthesis technology, or reducing its usage in formula, its formula cost has been reduced. In the 1970s, foreign countries developed low-priced tin products, which reduced the tin content, and also reduced the price to a certain extent.
1.2 Lead salt
(1) l Excellent stability experiments have proved that among the commonly used basic lead salts, the heat resistance of sulfite is better than that of sulfate, and the heat resistance of sulfate is better than that of phosphite. The tribasic lead sulfate, which is widely used in the PVC industry, has a higher effective lead content and shows better thermal stability than other products.
(2) Excellent insulation. Because lead salt is non-ionic and non-conductive, it is inert, which makes lead salt stabilizers widely used in wire and cable industries.
(3) Excellent weather resistance. Many salt compounds can act as white pigments and can show strong covering power, so they have strong weather resistance.
(4) Poor transparency Transparency is a problem related to weather resistance. When used in wires, cables and record materials, there is no need to care about transparency, because most of these products are white or very dark black.
(5) Inexpensive lead salt stabilizers are the lowest price among all stabilizers. Therefore, despite the continuous introduction of new stabilizers, lead salt stabilizers still dominate the stabilizer market after half a century. The composite lead salt introduced to solve the dust and dispersion problem has increased in price, but still maintains a competitive advantage with other types of stabilizers.
(6) The toxicity of the toxic lead salt stabilizer limits its application in many occasions with strict hygiene requirements. For example, many countries have revised the lead content standards in drinking water, and it is impossible to use lead salt in PVC water pipes.
(7) Poor dispersibility The dispersibility of salt lead is poor, but the newly launched one-package product is equipped with a lubricant, which solves the dispersibility problem to a certain extent. Because the lead salt stabilizer has the above characteristics, it is especially suitable for high-temperature processing. It is widely used in various opaque hard and soft products and cable materials, such as various pipes, plates, indoor and outdoor profiles, foam plastics, artificial leather and wires, Cables, records, welding rods, etc. The most important lead salt stabilizers are tribasic lead sulfate, dibasic lead phosphite, dibasic lead stearate and so on.