Long-Chain Dicarboxylic Acids Are in Short Supply  
By Song Chao     

Long-chain dicarboxylic acids refer to aliphatic dicarboxylic acids with carbon chains containing more than 10 carbon atoms. They are mainly used for the synthesis of perfumes, engineering plastics, nylon fibers, hot melt adhesives, lubricants, plasticizers and liquid crystal.

1. Production in China

The chemical synthesis of long-chain dicarboxylic acids has several decades of history. But due to the limitations of the complex production processes, the output of long-chain dicarboxylic acids by chemical synthesis is always very low. Another production route, the fermentation process, can produce a series of long-chain dicarboxylic acids with 11 to 18 carbon atoms. It has mild process conditions and is clean and environment-friendly and can realize large-scale industrial production. So the fermentation process has developed rapidly in recent years. Due to the rapid development of nylon and hot melt adhesives, the demand for long-chain dicarboxylic acids is growing rapidly. Long-chain dicarboxylic acids are now in short supply.
    At present, among major chemical companies in the world, only DuPont and Germany's Hoechst use the chemical synthesis method to produce long-chain dicarboxylic acids. Since Japan's NIHA successfully developed and industrially produced tridecanedioic acid (1,11-undecanedicarboxylic acid) with the fermentation process, the fermentation process has begun to be widely used.
   Since the 1980s, Chinese companies have used the fermentation process to produce long-chain dicarboxylic acids on a small scale. Since the 1990s, they have mainly produced tridecanedioic acid. Now, China has a total tridecanedioic acid capacity of 300 t/a, of which Shanghai INDA Electromechanics Co. Ltd. has 200 t/a, and Fushun Petrochemical Research Institute, 100 t/a. After the Institute of Microbiology, Chinese Academy of Sciences developed a fermentation technology to produce long-chain dicarboxylic acids using wax oil as substrate and successfully realized the industrial production of long-chain dicarboxylic acids with this technology in 2005, China has become the world's only country which has achieved the large-scale industrial production of several long-chain dicarboxylic acids with microbiological technology. The fermentation method is to produce dicarboxylic acids in the particles of cells. Compared with the chemical synthesis method, the fermentation method has a simple process, mild production conditions, high yield, low costs and no pollution, and its entire production process is carried out under normal temperature and pressure.
   The successful promotion of the fermentation technology for the production of long-chain dicarboxylic acids in China has made China the world leader in the technological level and production scale of long-chain dicarboxylic acids, and also promotes the rapid development of China's hot melt adhesives and engineering plastics industries. Up to now, China's long-chain dicarboxylic acid capacity is approximately 80 000 t/a.

China's major long-chain dicarboxylic acid producers
   (thousand t/a)
Company                              Capacity    Location
Zibo Guangtong Chemical Co., Ltd.    1.5     Zibo, Shandong province
Shanghai Cathay Holdings Limited    25.0    Jining, Shandong province
Qingjiang Petrochemical Co., Ltd.     1.0    Huai'an, Jiangsu province
Shandong Hilead Biotechnology Co., Ltd.    30.0    Laiyang, Shandong province
Longhetong Biochemical Technology Co., Ltd.    15.0    Haiyang, Shandong province
Source: CNCIC


2. The use of long-chain dicarboxylic acids in downstream industries

Long-chain dicarboxylic acids are mainly used for the production of engineering plastics, hot melt adhesives, lubricants, perfumes and pharmaceuticals. Undecane diacid is used to produce polyamide engineering plastics and is the major raw material of synthetic nylon (PA) 1010 and nylon 611. Dodecanedioic acid (DDDA) is mainly used for the production of high-grade polyamide engineering plastics and is the major raw material of synthetic nylon 1212 and nylon 612. It can also be used for the synthesis of high-grade lubricants, anti-rust agents, powder coatings, high-grade hot melt adhesives and other polymers. Tridecanedioic acid is used for the synthesis of perfumes. Tetradecane diacid has unique uses in powder coatings and perfumes industries. Pentadecane diacid is mainly used in the perfumes and pharmaceutical industries. It can be used for the synthesis of cyclopentadecanone and cyclopentadecanolide and musk ketone (3-methylcyclopentadecanone) and can replace natural musk to prepare a variety of precious traditional Chinese medicines. Hexadecane diacid has all the functions of DDDA and can also be used in the powder coatings and perfumes industries.
   Synthesis of high-grade nylon engineering plastics (PF nylon) - Engineering plastics synthesized from long-chain dicarboxylic acids such as DDDA and tridecanedioic acid have excellent tensile resistance and abrasion resistance and thus can improve the performance of various tires and increase the use life of tires by 5 - 10 times. Due to its excellent heat resistance and molding processability, PF nylon can be molded with precision injection molding technology. It can replace non-ferrous metals and be widely used in machinery, automobiles and other industries. Due to its excellent corrosion resistance, insulation and pliability, PF nylon can be made into fiber-optic sheathings, oil pipelines and surface-to-air missiles and parachute ropes.
   Synthesis of high-grade hot melt adhesives - Long-chain dicarboxylic acids can be used to synthesize hot melt adhesives which can be used to glue color picture tubes and deflection coils. At 100 degrees centigrade, such adhesives can be used for a long time. High-grade hot melt adhesives for clothes have excellent durability in laundering and dry-cleaning, and good shape-keeping ability. DDDA and other long-chain dicarboxylic acids containing even-numbered carbon atoms are important raw materials for the synthesis of high-grade hot-melt adhesives. With the export of shoes increasing annually, China's shoes manufacturers have a vigorous demand for high-quality and environmentally friendly hot melt adhesives. Hot melt adhesives do not use organic solvents and are in line with environmental requirements. They are the future development direction of adhesives. The rapid market development of hot melt adhesives will accelerate the growth in the manufacture of long-chain dicarboxylic acids.
   Synthesis of nylon powder coatings - nylon powders mainly include PA1010 powder, PA1010/6 powder, PA1010/66/6 powder, as well as PA11, PA12 and epoxy resin-modified nylon composite powder. Among them, as a type of high-carbon raw materials, PA11 and PA1010 powders have excellent weathering resistance and abrasion resistance, widely used in the production of powder coatings, fillers, adhesives, pharmaceuticals and cosmetics and gradually used more and more in decoration, silencers and shock absorption. High-grade nylon powder coatings synthesized from long-chain dicarboxylic acids have light density, low water absorption, good cold resistance, high surface hardness, good flexibility, good abrasion resistance, good pollution removal and are very safe to use. With the rebound of the