Recently, Taiwan’s “plasticizers” (phthalate esters) have become more and more fierce, and the number of products and enterprises found has been increasing. To ensure food safety and people’s health, prevent phthalate esters. Food Pollution, Ministry of Industry and Information Technology issued the "Emergency Notice on Prevention of Pollution of Phthalates" on June 30, 2011. The author believes that it is one of the effective ways to prevent the pollution of toxic plastics and accelerate the development of trimellitic anhydride industry. Trimellitic anhydride separates meta-trimethylbenzene from reforming C9 aromatics and uses it to produce fine chemical products. The trimellitic anhydride downstream products are widely used in plasticizers, powder coatings, insulating materials, etc., and have the advantages of non-toxicity, heat resistance, low volatility, oil resistance, processability, etc. in household appliances, building materials, automobiles, aviation, and aerospace. In other fields, it has broad development prospects. * Relevant departments should increase policy support to promote the healthy and sustainable development of the trimellitic anhydride industry.
I. Development status of trimellitic anhydride industry in China
1. Overview of trimellitic anhydride products
Trimellitic anhydride (TMA), the molecular formula is C9H4O5, chemical name 1,2,4-benzenetricarboxylic anhydride, referred to as meta-anhydride.
It is obtained by oxidation and dehydration of meta-trimethylbenzene, its appearance is white crystal, melting point ≥ 163 ° C, soluble in water, ethanol, acetone, dimethylformamide, ethyl acetate, slightly soluble in toluene, carbon tetrachloride And petroleum ether. Because the molecular structure of trimellitic anhydride contains carboxylic acid and anhydride functional groups, it has the chemical properties of benzoic acid and phthalic anhydride, has high reactivity, can produce a series of valuable fine chemicals, and is an important chemical raw material for modern new materials. .
The main use of trimellitic anhydride:
(1) Different types of plasticizers can be obtained by reacting trimellitic anhydride with different alcohols, among which trioctyl trimellitate (TOTM) formed by esterification with octanol has excellent heat resistance, low volatility and oil resistance. And processability, widely used as a plasticizer for PVC heat-resistant plasticizers, anti-solvent cross-linked vinyl chloride resin, primary plasticizer for 90 ° C and 105 ° C heat-resistant cable formulations, and used as a 6000V, 10000V high-voltage cable The required matching plasticizer.
(2) The powder coating prepared by using trimellitic anhydride as raw material to produce polyester resin and then mixing with epoxy resin in a ratio of 1:1 has the advantages of non-volatile, non-toxic, solvent-free pollution, convenient coating and rapid curing. Widely used in air conditioners, washing machines, refrigerators, electric fans, water heaters, microwave ovens, electric ovens, rice cookers, computers, televisions, mobile phones and other home appliances industries; also used in automobiles, motorcycles, bicycles, instrumentation machinery and equipment, steel Door steel windows, aluminum alloy doors and windows, safes, aerospace equipment, chemical anti-corrosion, hardware tools, pipeline anti-corrosion and other fields.
(3) Polyamidoimide can be obtained by reacting trimellitic anhydride with aromatic diamine, and reacting with hydroquinone and 4,4-diamine diol ether to obtain polyester imide, which have good heat resistance. It has good electrical insulation performance and mechanical properties. It also has good wear resistance at high temperatures. It is mainly used for insulation materials of F and H grade motors, such as enameled wire lacquer, impregnating varnish, silicon steel lacquer and film. It can be used in 230~ Long-term use at 250 °C.
(4) Trimellitic anhydride can also be used as an epoxy resin curing agent, a rapid curing agent for printing inks, and the like.
2. Production of trimellitic anhydride in China
At present, most enterprises at home and abroad adopt batch oxidation process, the production process is backward, the product quality is unstable, and the repeated temperature rise and fall causes the service life of production equipment to be greatly reduced, the equipment is seriously corroded, the safety performance is poor, and the environmental protection pressure is large. High consumption, energy is not effectively recycled and comprehensive utilization. Zhenjiang Zhengdan Chemical Industry Co., Ltd. and other enterprises currently use continuous oxidation process, which has the world's advanced level. Among them, Zhenjiang Zhengdan Chemical Industry Co., Ltd. patent - "Continuous oxidation process for the production of trimellitic anhydride" (patent number ZL02143030.6), in November 2010 by the * Intellectual Property Office as the China Patent * Award, related equipment It has also obtained a number of invention patents and utility model patents, which have shown strong market advantages, cost advantages, quality advantages and scale effects in terms of production cost and product quality.
3. Market demand for trimellitic anhydride in China
According to incomplete statistics, the total consumption of trimellitic anhydride in the world in 2010 was about 230,000 tons, of which US consumption accounted for about 31% of total consumption, Western Europe accounted for about 28%, China accounted for about 25%, and Japan accounted for about 11.5%. %, about 4.5% in other regions. In 2010, the consumption of trimellitic anhydride in China was about 58,000 tons, of which about 50% was used to produce trimellitate plasticizers, 40% was used to make mixed polyester resin powder coatings, and 10% was used to manufacture *insulating materials. , high temperature curing agent, etc.
4. Successful experience of China's trimellitic anhydride enterprises in operating conditions and advantages of demonstration enterprises
Due to the large differences in the production technologies of domestic trimellitic anhydride companies, the quality of products is also very different. The PA content of most companies produces products that far exceed EU standards and are subject to certain restrictions in global market sales. Zhenjiang Zhengdan Chemical Industry Co., Ltd. and other enterprises with its advanced production technology, the production of PA content ≤ 300PPM, has been widely recognized by users in the domestic and foreign markets.
Second, the main factors restricting the development of trimellitic anhydride industry in China
1. Supply of raw materials is tight
In the trimellitic anhydride industrial chain, the production of trimellitic anhydride, the raw material of trimethylbenzene, plays an important role. The meta-trimethylbenzene is mainly derived from the heavy aromatics of the xylene bottoms in the reforming unit of the refinery. Its composition is complex, and it is rich in C9 and C10 aromatic hydrocarbons such as meta-xylene, methyl ethylbenzene, mesitylene, trimethylbenzene and tetramethylbenzene. Separation of meta-trimethylbenzene from it by rectification. In the 1950s, foreign countries began to separate meta-xylene from reforming C9 aromatics, and used it to produce fine chemical products. After decades of development, its application fields have been broadened and a relatively complete system has been formed. The use of C9 aromatics in China started relatively late. In the early 1980s, the purity of hexamethylene was ≥95%, and its corresponding downstream products were gradually developed. Domestically reformed C9 aromatic hydrocarbons contain about 30% of meta-xylene, and high-tech fine separation can obtain trimethylbenzene with a purity of ≥98.5%. However, because these heavy aromatic hydrocarbons have relatively close boiling points, separation is difficult, and the heavy octane has a higher octane number, so most of the C9 aromatic hydrocarbons are used as gasoline blending components.
2. Industrial policy lags behind
On May 18, 2011, an environmental protection organization published a survey report that an environmental hormone, phthalate, which may cause cancer or cause genital developmental changes in male babies, was detected in many types of plastic infants. Supplies and children's toys. As a general term for organic compounds, phthalate (PA) is mainly used as a plasticizer for plastics. It is widely used in children's plastic toys, medical equipment, cosmetics, pesticides, artificial leather and food packaging materials. However, phthalate is also an environmental hormone with similar estrogen effects (also known as environmental hormones or endocrine disruptors), which refers to a class of exogenous chemicals that interfere with normal human hormone function, which may affect humans. The reproductive function, immune system and nervous system of various organisms have been published as endocrine disruptors by the World Health Organization as early as 1995, and are a kind of environmental pollutants that cause harm to the reproductive system of animals.
In November 1999, the European Commission had begun to impose restrictions on some phthalates by decree. An EU directive passed by the European Union in 2005 stipulates that the comprehensive percentage of the concentration of three harmful phthalates such as DEHP (domestic called DOP), DBP and BBP in all toys and child-rearing products produced and imported shall not exceed 0.1. %. In February 2011, the EU again produced a killer and listed the above three phthalates directly into the chemical “elimination list”. The move means that these three phthalates will disappear in the EU market after three to five years without special authorization. The United States, Japan, South Korea, Australia, Argentina and other countries have also made similar restrictions on the content of phthalates in toys and other plastic products related to human body and health food.
Since the promulgation of the European Union standard, plasticizers containing phthalates have been largely eliminated from plastic products exported to the EU. However, since there is no clear limit on the content of phthalates in toys and other plastic products related to human body and health foods, for the sake of cost, domestic products are still using phthalates in large quantities. At present, phthalate plasticizers still account for more than 80% of the total domestic plasticizer consumption. Trioctyl trimellitate (TOTM) produced from trimellitic anhydride is a non-toxic and environmentally friendly plasticizer with similar plasticizing properties to phthalates. It is a phthalate plasticizer. An ideal substitute for the agent. However, due to the lag of relevant domestic industrial policies and the lack of standards, the rapid development of TOTM and trimellitic anhydride industries has been severely restricted.
Third, to promote the healthy development of trimellitic anhydride industry
1. Prospects for the development of trimellitic anhydride industry
The application of trimellitic anhydride in the plasticizer industry, TOTM is a non-toxic and environmentally friendly plasticizer with high temperature resistance, anti-aging, corrosion resistance, migration resistance and excellent insulation properties. It has been fully affirmed in the plasticizer industry. Development, especially the EU ROHS Directive and REACH regulations have raised the requirements for environmental protection standards, affirming that TOTM will gradually replace the currently used dioctyl phthalate (DOP) in the plasticizer industry. Due to the tendency of DOP plasticizer to precipitate benzene, it will cause certain harm to the human body. EU regulations have clearly restricted the use of phthalate plasticizers in PVC products. According to relevant reports, environmentally-friendly plasticizers in Europe and the United States account for 80%, while the Chinese market uses less than 20% of environmentally friendly plasticizers. According to relevant statistics, in 2010 China's DOP production capacity was 2 million tons/year, and it has an annual growth rate of around 3%. In 2010, the TOTM domestic market demand was around 80,000 tons, and the consumption of trimellitic anhydride was about 28,000 tons. With the continuous improvement of people's environmental protection and safety awareness, the demand of TOTM in China's market will increase dramatically in recent years. The proportion of TOTM in plasticizers will increase rapidly, so it will bring new products to trimellitic anhydride. Development opportunities, the demand for trimellitic anhydride in the plasticizer industry is expected to reach 90,000 tons by 2015. The application of trimellitic anhydride in the powder coating industry, with the rapid development of China's light industrial appliances, automobiles, building materials and other industries in recent years, the demand for environmentally friendly and excellent powder coatings is increasing. According to statistics from the Powder Coatings Association, domestic The annual production capacity of powder coatings has increased from 20,000 tons in the early 1990s to 910,000 tons in 2010, and is expected to reach 1.05 million tons in 2011. The rapid growth of powder coating capacity has also driven the rapid growth of the market demand for trimellitic anhydride. It is estimated that by 2015, China's powder coatings will reach 1.7 million tons, of which 850,000 tons of mixed polyester resin powder coatings will consume about 42,000 tons of trimellitic anhydride.
In addition, polyamide-imide and polyesterimide can be used not only as insulating materials, but also in the manufacture of molded plastic parts such as electrical components, valve parts, bearings, and jet engine parts. Further development can provide new markets and new impetus for the development of trimellitic anhydride industry. It is estimated that by 2015, about 18,000 tons of trimellitic anhydride will be consumed. In summary, it is expected that by 2015, the demand for trimellitic anhydride in the domestic market will reach nearly 150,000 tons, and the development prospects are good.
2. Policy support and industrial orientation to accelerate the development of trimellitic anhydride industry
(1) Vigorously develop continuous oxidation production technology, eliminate backward production capacity, strengthen joint and technical exchanges between enterprises in the same industry, further improve energy conservation and environmental protection, promote technology upgrading and healthy development of trimellitic anhydride industry in China, and improve China. The competitive advantage of trimellitic anhydride products in the international market further expands the international market share.
(2) Encourage the domestic and international heavy aromatics resources through multiple channels, encourage the comprehensive utilization of C9 aromatics, expand the production scale of meta-xylene, increase the supply of meta-xylene, and alleviate the contradiction between supply and demand in the market. At the same time, we will increase our technical investment and strive to make breakthroughs in the technology of preparing meta-trimethylbenzene from the alkylation of toluene and xylene, and completely solve the problem of single source of meta-xylene raw materials.
(3) Introduce relevant policies as soon as possible to limit the use of phthalate plasticizers and keep in line with international standards.