Business Community, November 15th In the 30s of the 20th century, lead white was first successfully used in the processing of PVC plastic products, and its thermal degradation problem was initially solved. Subsequently, metal soaps, organotin compounds and other heat stabilizers have been reported one after another. In the 60s and 70s of the 20th century, a variety of new heat stabilizers were developed, such as the successful development of food-grade octyltin heat stabilizer and the commercialization of methyl tin. After the 80s of the 20th century, the technical progress of heat stabilizers was relatively slow, but the research on environmental protection was quite active, such as the OBS organic stabilizer completed by Compton Company in United States in 2000, mainly used in hard products such as pipes.
At present, organotin stabilizers are the main ones in North America, while European countries are mainly calcium-zinc composite stabilizers, and the tin content in plastic products is strictly limited (the allowable content is 0.002mg/kg). However, due to the fact that organotin is a high-efficiency stabilizer, it is a transparent, non-toxic liquid, and the addition amount in PVC pipes is only 0.25%-1.0%, so 20% of the stabilizer share in Europe is still organotin stabilizer.
In the mid-50s of the 20th century, with the localization of PVC production technology, China began to produce heat stabilizers, and the varieties at that time were only alkaline lead salts and stearic acid soaps. In the early 60s of the 20th century, the production of heat stabilizers has been developed, the production technology of general varieties has improved, and product quality testing and standardization have also begun to be emphasized. After decades of development, research, production and application, heat stabilizers have developed into the second largest category of plastic additives, which can be divided into lead stabilizers, calcium and zinc stabilizers, organotin stabilizers, auxiliary stabilizers and so on according to their chemical composition and role.
Lead salt stabilizer is the heat stabilizer with the longest application history and good effect, and is widely used in PVC profiles, pipes, and insulated cable materials. Basic lead salts are currently the most widely used lead stabilizers. Lead stabilizers have good heat resistance, especially long-term thermal stability; Excellent electrical insulation; It has the performance of white pigment, large covering power and good weather resistance; It can be used as an active agent for foaming agent and is inexpensive. The disadvantages of lead stabilizers are: the resulting product is not transparent; Highly toxic; There is initial colorability; Poor compatibility and dispersibility, easy to produce vulcanization pollution.
Calcium-zinc stabilizer is a non-toxic and environmentally friendly heat stabilizer with good lubricity, but its thermal stability is not high, and it has been mostly used in PVC soft products with low thermal stability requirements for a long time or occasionally as an auxiliary heat stabilizer. In recent years, with the development of organic auxiliary additives such as β-dione, polyols, epoxy compounds, etc., calcium-zinc composite heat stabilizers have also been greatly developed. At present, a variety of calcium-zinc composite heat stabilizers with excellent performance have been developed at home and abroad, and are used in profiles, plates and pipes.
Organotin compounds are highly effective heat stabilizers, especially for hard products that require a high degree of transparency and high heat resistance. They often play the functions of photochemical, mechanical and biochemical stabilizers, plasticizers, etc., and are widely used and replace other heat stabilizers, but their prices are high, which limits their application to a certain extent, and people try to replace other heat stabilizers with low-cost tin to meet the needs of price and performance.
Organic auxiliary heat stabilizers are also one of the current research directions. As early as 1940, derivatives of urea such as diphenylthiourea and monophenylindole were recommended for stabilizing PVC. However, due to various willingness, it has not been widely used. In recent years, due to the serious toxicity and pollution problems of metal stabilizers such as lead and cadmium, organic stabilizers have attracted people's attention again, and people hope to develop new varieties with high efficiency and non-toxicity. Organic co-stabilizers do not have a thermal stabilizing effect on their own, but they can improve the performance of thermally stabilized systems. Belonging to this category are: organophosphites, epoxy compounds, antioxidants, polyols, etc.
In the past ten years, the consumption of heat stabilizers in China has increased significantly with the rapid development of the PVC industry. According to incomplete statistics, in 2008, the product structure of heat stabilizers in China was 40.0% lead salts, 17.14% stearates, 27.43% composite types (partially lead), 6.86% organotins, and 8.57% rare earth and others, as detailed in the following table:
In recent years, the output of heat stabilizers in China has been 10,000 tons
Note: In less than 20 years from '95 to 2000, production increased six-fold, which was about 700% of '95.
There are hundreds of PVC stabilizer production plants in China, most of which are located in Zhejiang, Shandong, Hebei, Jiangsu and Guangdong provinces. The top 15 stabilizer manufacturers account for more than 50% of the market share, and 80% of them are compound lead stabilizer manufacturers, and some of the major suppliers are listed in the chart below: