What Is Caprolactam?
Caprolactam, abbreviated as ε-caprolactam, is a type of lactam, which is a cyclic amide. It is a key intermediate in the manufacture of Nylon 6, a widely used synthetic resin and fiber.
Uses of Caprolactam
The primary use of caprolactam is in the production of Nylon 6 through ring-opening polymerization. About 60% of global Nylon 6 demand is for fiber applications, including clothing, tire cords, and carpets. The remaining 40% is for resin applications in engineering plastics and films. Caprolactam is also utilized in synthesizing copolyamides by copolymerization with other monomers.
Properties of Caprolactam
Caprolactam appears as white, leaf-like crystals. It is hygroscopic, deliquescent, and soluble in water, ether, ethanol, benzene, chloroform, and dimethylformamide. Upon heating or combustion, it decomposes, producing nitrogen oxides and ammonia, and reacts vigorously with strong oxidizers. Caprolactam hydrolyzes to ε-aminocaproic acid and has a melting point of 156°F (69°C), boiling point of 512.6°F (267°C), and flash point of 257°F (125°C).
Structure of Caprolactam
Caprolactam, also known as 6-hexanolactam, lactam ε-aminocaprolactam, lactam 6-aminocaproic acid, and lactam 6-aminohexanoic acid, is a cyclic structure derived from ε-aminocaproic acid. Its molecular formula is C6H11NO, with a molecular weight of 113.16 g/mol and a density of 1.01 g/cm³.
Other Information on Caprolactam
1. Caprolactam Synthesis
Caprolactam is synthesized via various methods, most commonly by the Beckmann rearrangement of cyclohexanone oxime, derived from benzene, phenol, or toluene. The fuming sulfuric acid used in this process produces significant ammonium sulfate as a byproduct.
2. Alternative Methods of Caprolactam Synthesis
Alternative synthesis methods include a gas-phase Beckmann rearrangement using high-silica MFI zeolite catalysts, which does not produce ammonium sulfate byproducts. This method is efficient with zeolites containing low alumina content. Another method involves the cyanuric chloride-catalyzed Beckmann rearrangement, which eliminates the need for toxic nitrosyl chloride and is more efficient than previous methods, producing minimal waste products.