Caprolactam

Description

Caprolactam, CH2CH2CH2CH2CH2NHCO, is a solid material composed of white flakes. Caprolactam is soluble in water and has a specific gravity (in a 70% solution)of 1.05, which is heavier than water. It may also be encountered as a molten material. Caprolactam is toxic by inhalation, with a TLV of (vapor) 5 ppm in air and (dust) 1 mg/m3 of air. The primary uses are in the manufacture of synthetic fibers, plastics, film, coatings, and polyurethanes.

Description

ε-Caprolactam is a crystalline cyclic amide with a melting point of 70 °C. It is soluble in water, most oxygenated and chlorinated solvents, and some hydrocarbons.
Because ε-caprolactam is the only common caprolactam isomer, the ε is usually dropped. It derives its name from ε-aminocaproic acid, or 6-aminohexanoic acid; in principle, the lactam is formed when the terminal carboxylic acid and amino groups react to form the amide.
The amide formation reaction succeeds only when run in dilute solution; otherwise, aminocaproic acid polymerizes (which is a good thing; see below). The commercial synthesis consists of the acid-catalyzed Beckmann rearrangement of cyclohexanone oxime, which was discovered by Prussian chemist and Nobel Prize winner Otto Wallach way back in 1900. Numerous articles and patents have been devoted to improving this method ever since.
Wallach didn’t live to see it, but caprolactam turned out to be extremely valuable. In 1938, Paul Schlack at IG Farben found that heating caprolactam neat to 260 °C causes the ring to open and the terminal functional groups to react to form a long-chain polyamide.
This polymer later became known as “nylon 6”*. It can be formed into high-strength fibers, resins, and films that have dozens of end-use applications ranging from clothing to violin strings to automotive mechanical parts.
*Nylon 6 is similar to—but should not be confused with—nylon 6,6, which is prepared from hexamethylenediamine and adipic acid.

Chemical properties

Caprolactum is a white crystalline combustible solid with an unpleasant odor. The Odor Threshold is 0.3 milligram per cubic meter.

Physical properties

Yellowish solid or white crystals or flakes; amine, spicy aroma. It is soluble in water, chlorinated solvents, petroleum hydrocarbons, cyclohexene, benzene, methanol, ethanol and ether.

The Uses of Caprolactam

Monomer for manufacture of polycaprolactam (Nylon 6) used in carpets, textiles, clothing, and tires

The Uses of Caprolactam

manufacture of synthetic fibers of the polyamide type (Perlon); solvent for high mol wt polymers; precursor of nylon-6, q.v.

The Uses of Caprolactam

ε-Caprolactam is used as a monomer in the preparation of synthetic fibers of the polyamide as well as a solvent for high molecular weight polymers. It is also used in coatings and plasticizers. Further, it is used as a cross linking agent for polyurethanes. In addition to this, it is used to prepare nylon-6, which finds application in fibers and plastics.

What are the applications of Application

ε-Caprolactam is a synthetic precursor of Nylon-6 and other synthetic polymers.

Definition

ChEBI: A member of the class of caprolactams that is azepane substituted by an oxo group at position 2.

Definition

A white crystalline substance used in the manufacture of NYLON.

Preparation

About 90% of the caprolactam is produced by the conventional cyclohexanone process. Cyclohexanone is obtained by catalytic oxidation of cyclohexane with air? or by hydrogenation of phenol and dehydrogenation of the cyclohexanol byproduct. The conversion of cyclohexanone to cyclohexanone oxime followed by Beckmann rearrangement gives caprolactam. About 10% of caprolactam is produced by photonitrosation of cyclohexane or by nitrosation of cyclohexanecarboxylic acid in the presence of sulfuric acid.

Aroma threshold values

High strength odor; spicy type; recommend smelling in a 0.01% solution or less

Synthesis Reference(s)

Journal of the American Chemical Society, 108, p. 7846, 1986 DOI: 10.1021/ja00284a066
The Journal of Organic Chemistry, 60, p. 6662, 1995 DOI: 10.1021/jo00126a006

General Description

Clear to milky white-colored solution with a mild, disagreeable odor. Contact may cause slight irritation to skin, eyes, and mucous membranes. May be mildly toxic by ingestion. The primary hazard is the threat to the environment. Immediate steps should be taken to limit its spread to the environment. As a liquid 2-Oxohexamethylenimine can easily penetrate the soil and contaminate groundwater and nearby streams. Used to make other chemicals.

Air & Water Reactions

Water soluble.

Reactivity Profile

2-Oxohexamethylenimine is hygroscopic. 2-Oxohexamethylenimine can react with strong oxidizing agents and strong bases. 2-Oxohexamethylenimine can also react with chlorinated hydrocarbons and nitro compounds. A potentially explosive reaction occurs with acetic acid + dinitrogen trioxide.

Hazard

Toxic by inhalation. Upper respiratory tract irritant.

Health Hazard

Inhalation causes coughing or mild irritation. Contact with hot liquid will burn eyes and skin.

Fire Hazard

Special Hazards of Combustion Products: Toxic oxides of nitrogen

Flammability and Explosibility

Not classified

Safety Profile

Moderately toxic by ingestion, skin contact, intraperitoneal, and subcutaneous routes. Human systemic effects by inhalation: nose and throat irritation, cough. Experimental reproductive effects. A skin and eye irritant. Potentially explosive reaction with acetic acid + dinitrogen trioxide. When heated to decomposition it emits toxic fumes of NOx

Potential Exposure

Caprolactam is used in the manufacture of nylon, plastics, bristles, film, coatings, synthetic leather, plasticizers, and paint vehicles; as a crossslinking agent for curing polyurethanes; and in the synthesis of lysine

First aid

If this chemical gets into the eyes, remove anycontact lenses at once and irrigate immediately for at least15 min, occasionally lifting upper and lower lids. Seek medical attention immediately. If this chemical contacts theskin, remove contaminated clothing and wash immediatelywith soap and water. Seek medical attention immediately. Ifthis chemical has been inhaled, remove from exposure,begin rescue breathing (using universal precautions, including resuscitation mask) if breathing has stopped and CPR ifheart action has stopped. Transfer promptly to a medicalfacility. When this chemical has been swallowed, get medical attention. Give large quantities of water and inducevomiting. Do not make an unconscious person vomit.

Carcinogenicity

Caprolactam was not mutagenic in bacterial assays or in in vivo rodent assays; it did induce chromosomal aberrations and aneuploidy in human lymphocytes in vitro.

storage

Color Code—Green: General storage may be used.Prior to working with caprolactam you should be trained onits proper handling and storage. Before entering confinedspace where this chemical may be present, check to makesure that an explosive concentration does not exist. Store intightly closed containers in a cool, well-ventilated areaaway from oxidizers and heat. Metal containers involvingthe transfer of this chemical should be grounded andbonded. Drums must be equipped with self-closing valves,pressure vacuum bungs, and flame arresters. Use only nonsparking tools and equipment, especially when opening andclosing containers of this chemical. Sources of ignition,such as smoking and open flames, are prohibited where thischemical is used, handled, or stored in a manner that couldcreate a potential fire or explosion hazard.

Shipping

UN2811 Toxic solids, organic, n.o.s., Hazard Class: 6.1; Labels: 6.1-Poisonous materials, Technical Name Required

Purification Methods

The lactam is distilled under reduced pressure, recrystallised from acetone or pet ether and redistilled. It can be pur

Incompatibilities

Caprolactum decomposes on heating, and on burning producing toxic fumes including nitrogen oxides, ammonia. Reacts violently with strong oxidizers, producing toxic fumes. Toxic decomposition above 400C

Waste Disposal

Controlled incineration (oxides of nitrogen are removed from the effluent gas by scrubbers and/or thermal devices). Also, Caprolactam may be recovered from Caprolactam still bottoms or nylon waste