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, me¶tal soaps, organotin compounds and other heat stabilizers have been reported one after another.♣ In the 60s and 70s of the 20th century, a variety ofα new heat stabilizers were developed, such as the successful develop¥ment of food-grade octyltin heat stabilizer and the commercialization of methyl tin. After the 8₹0s of the 20th century, the technical progress of heat st>abilizers was relatively slow, but the research on environmental protection was quite act≤ive, such as the OBS organic stabilizer completed by Compton Company in Un ited States in 2000, mainly used in hard products suc→h as pipes.
At present, organotin stabilizers are the main ones in North America, while European countries arβe mainly calcium-zinc composite stabilizers, and the tin content in plastic products i>s strictly limited (the allowable content is 0.002mg/kg). However, due to the fact that organoti∞n 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 stil¥l organotin stabilizer.
In the mid-50s of the 20th century, with the localization of PVC± production technology, China began to produce heat sπtabilizers, and the varieties at that time were only alkaline l∏ead salts and stearic acid soaps. In the early 60s of the 20th century, the producδtion of heat stabilizers has been developed, the production technology of general varie$ties has improved, and product quality testing and standardization have also begun to be emphaδsized. 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 rolαe.
Lead salt stabilizer is the heat stabilizer with the longest applica→tion history and good effect, and is widely used in PVC profiles, pipesΩ, and insulated cable materials. Basic lead salts a≥re currently the most widely used lead stabilizers. Lead stabilizers have good heat re<sistance, especially long-term thermal stability; Excellent electrical insulation; It∑ has the performance of white pigment, large covering power a×nd 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 pr↕oduct is not transparent; Highly toxic; There is initial colorability; Poor compatibility and d≠ispersibility, easy to produce vulcanization pollution.
Calcium-zinc stabilizer is a non-toxic and environmentally fri→endly heat stabilizer with good lubricity, but its thermal stability is not high, and it ha♥s been mostly used in PVC soft products with low thermal stability requirements for a lon₽g time or occasionally as an auxiliary heat stabilizer. In recent years, with the develo£pment of organic auxiliary additives such as β-dione, polyols, epo§xy compounds, etc., calcium-zinc composite heat stabilizers have also been÷ greatly developed. At present, a variety of calcium-zinc composite heat stab÷ilizers with excellent performance have been develope×d at home and abroad, and are used in profiles, plates and pipes.
Organotin compounds are highly effective heat stabilizers, especially for har®d products that require a high degree of transpareβncy and high heat resistance. They often play the functions of photochemical, me$chanical and biochemical stabilizers, plasticizers, etc., and are widely useπd and replace other heat stabilizers, but their prices are high, which limits their app₽lication to a certain extent, and people try to replace o ther heat stabilizers with low-cost tin to meet the needs of price and perform₹ance.
Organic auxiliary heat stabilizers are also one of the current research directγions. As early as 1940, derivatives of urea such as diphenylthiourea and monophenylindole× were recommended for stabilizing PVC. However, due t→o 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 attenδtion 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 st≈abilized systems. Belonging to this category are: organophosphites, epoxy compounds, antioxidantΩs, polyols, etc.
In the past ten years, the consumption of heat sta≈bilizers in China has increased significantly with the rapid developmen♦t of the PVC industry. According to incomplete statistics, in 2008, the product str¥ucture 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 Chi★na has been 10,000 tons
Note: In less than 20 years from '95 to 2000, production increased six-fold, w♠hich was about 700% of '95.
There are hundreds of PVC stabilizer production plants in China, mos↓t of which are located in Zhejiang, Shandong, Hebei, Jia<ngsu and Guangdong provinces. The top 15 stabilizer manufactuλrers account for more than 50% of the market share, and 80% of them are compound lead stabilize÷r manufacturers, and some of the major suppliers are lis§ted in the chart below: