A novel mild and efficient method to prepare ε-Caprolactam precursor of Nylon 6

Summary of the technology

ε-Caprolactam, the main precursor of the synthetic fibber Nylon 6, is prepared from cyclohexanone oxime by treatment with a new salt as promoter. This procedure requires mild reaction conditions and affords excellent levels of conversion and selectivity to obtain pure ε-caprolactam. No reaction by-products are formed. The new promoter salt is cheap, no corrosive, and easy to prepare. All these characteristics makes the procedure suitable for undustrial purposes.

University of Vigo

New and innovative aspects

The production of ε-caprolactam in industry generally requires high reaction temperatures and strongly acidic media, which cause serious corrosion problems and large amount of by-products. This procedure requires mild reaction conditions (60 ºC or 90 ºC) and avoids the use of corrosive acids or catalyzers. A new salt is used as promoter. No reaction by-products are formed.

Main advantages of its use

This procedure avoids the use of high temperatures or corrosive acids or catalizers. The promoter new salt is cheap, no corrosive and easy to prepare. No reaction by-products are formed. The reaction solvent is water, no toxic organic solvents are needed.


Synthesis of ε-caprolactam: a solution of cyclohexanone and the new salt in water is heated at 90 ºC for 45 min or at 60 ªC for 3 h. The solvent is eliminated and dichloromethane added. The mixture is kept at -18 ºC to precipate the salt that is filtered. The solvent is then removed to give ε-caprolactam impurified with some remaining salt. Later purification can be carried out by sublimation or by liquid-liquid extraction of a solution in water with dichloromethane. This procedure can also be developed with another very similar salt that can be recover and reused, but in this case the reaction time is 6 days at 90 ºC.


Because ε-caprolactam is the main precursor used for the synthesis Nylon 6, its global market have reached around 5 million metric tones per year. Synthetic polyamide Nylon 6 is of the highest importance for the textile industry and development of polymers and material science. Well-known commercial products from nylon 6 are brush bristles, textile stiffeners, film coatings, synthetic leather, plastics, plasticizers, automotive paints, and cross-linking for polyurethanes.

Intellectual property status

Spanish an d PCT patent applications

Current development status

Proof of concept or laboratory prototype

Desired business relationship

License agreement

Technical cooperation - adaptation to specific needs

Related Keywords

  • Coatings
  • Colours and varnish
  • Plastics, Polymers
  • Advanced Textile Materials
  • Clean Industrial Technologies
  • Man made fibres
  • Special chemicals, intermediates
  • Textile fibres
  • Plastic fabricators
  • Fibre-reinforced (plastic) composites
  • Other speciality materials
  • Industrial chemicals
  • Polymer (plastics) materials
  • Other speciality chemicals
  • Other chemicals and materials (not elsewhere classified)
  • textile industry
  • ε-caprolactam
  • nylon
  • nylon 6

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