Nearly all cyclohexane is consumed in the production of cyclohexanol and cyclohexanone, which are then used mainly to make adipic acid and caprolactam respectively. Adipic acid accounts for 60% of cyclohexane demand and is used to make nylon 6,6. Around 75% of global caprolactam is used in nylon 6 manufacture.
Smaller outlets for cyclohexane include its use as a solvent, a reaction diluent and in chemical synthesis. It is also a starting material for KA Oil (cyclohexanone-cyclohexanol mixture) and can substitute benzene in some applications.
The major use for adipic acid is to produce nylon 6,6 for which the predominant market is fibres. These fibres are used in apparel such as ladies’ hosiery (stockings), sleepwear and underwear, carpets and home furnishings. Other nylon 6,6 fibres applications include tyre cord, fishing line, brush bristles and tough fabrics for parachutes, backpacks, luggage and business cases.
Nylon 6,6 engineering resins are the next largest use of adipic acid. They are employed in automotive parts and items such as bearings, gears and cams. Other applications include industrial machinery and electrical and electronic equipment. Fillers and modifiers can be incorporated to further enhance properties.
Non-nylon uses for adipic acid include unsaturated polyesters and plasticisers for vinyl chloride, nitrocellulose and cellulose acetate polymers.
Polyester polyols are made by reacting adipic acid with ethylene glycol or propylene glycol. Polyurethanes made from these polyester polyols have higher oil and abrasion resistance when compared to polyurethanes made from polyether polyols, the other major polyol.
The other major outlet for cyclohexane is caprolactam which is used to make nylon 6. Nylon 6 fibres and filaments constitute the bulk of the caprolactam market and are employed in carpeting, textiles, hosiery and tyre cords. Nylon 6 engineering resins find applications in automotive components. Small amounts of caprolactam are used in a variety of speciality and fine chemicals.
Nylon growth, which is the main driver in the cyclohexane market, has stagnated in many applications to below GDP levels although there is still some growth in nylon plastics for automotive and other resin applications. Nylon 6 sees stronger growth than nylon 6,6.
World demand for nylon 6 and nylon 6,6 fibres has been sluggish with markets declining in the US and western Europe. The market in China is growing due to its stronger domestic economy and as a global supplier of finished goods. Competition from other fibres such as polyesters and changing consumer preferences are some of the other factors affecting demand. Demand has been better for nylon industrial filaments used in heavy equipment tyres and conveyor belts.
Nylon resins used as engineering thermoplastics have performed better. These materials have tough physical properties such as high tensile strength, excellent abrasion, chemical and heat resistance, which allow them to replace metals. Automotive applications have been growing where there has been a drive to replace metals with plastics to reduce the weight of motor vehicles.
The European cyclohexane market has seen zero to small growth up to 2%/year. Markets are expected to stabilize with flat growth in 2010-2012 and not expected to return to pre-crisis demand levels for at least five years.
Any new investment will be focussed on Asia, particularly China, and the Middle East. Extra cyclohexane will be needed for the proposed caprolactam and nylon 6 plants planned by Saudi Arabia’s PetroRabigh in its second phase expansion project due for completion in 2014.
Updated: October 2010