Caprolactam CAS 105-60-2

What is Caprolactam?

Caprolactam is a cyclic amide, C₆H₁₁NO, a white crystalline solid melting at 69 °C. It is traded both as flake and as molten liquid in heated tanks, and it is hygroscopic enough that moisture control matters in both forms.

Its sole significant use is nylon 6. Ring-opening polymerisation gives polyamide 6 for textile fibre, carpet yarn, tyre cord, engineering resin and film.

Most caprolactam is made from cyclohexanone via the oxime and Beckmann rearrangement, with ammonium sulphate as a large co-product on conventional routes.

Because it ends up in fibre, the specification is unusually demanding on trace impurities that affect polymer colour and dyeability rather than on bulk purity.

Why Caprolactam specifically

• A strained seven-membered ring. Opens under heat and water initiation to polymerise cleanly into a linear polyamide.
• The nylon 6 monomer. A single-step polymerisation, simpler than the salt chemistry nylon 66 requires.
• Fibre-critical purity. Trace impurities show up as colour and dye streaks in finished yarn.
• Fully recyclable. Nylon 6 can be depolymerised back to caprolactam, which supports closed-loop carpet and fishing net recycling.

How Caprolactam is Manufactured

Caprolactam is made from cyclohexanone or cyclohexane, with the route determining how much ammonium sulphate co-product is generated.

• Cyclohexanone production. From cyclohexane oxidation or phenol hydrogenation, the starting point for most routes.
• Oximation. Cyclohexanone reacts with hydroxylamine to cyclohexanone oxime.
• Beckmann rearrangement. The oxime rearranges to caprolactam in fuming sulphuric acid, which is then neutralised with ammonia to give ammonium sulphate.
• Low-sulphate routes. Vapour-phase Beckmann rearrangement and HPO processes reduce or eliminate the ammonium sulphate co-product.
• Purification. Extraction, crystallisation and distillation remove the trace impurities that affect polymer quality.
• Flaking or molten dispatch. The product is flaked for bagged supply or kept molten for heated bulk delivery.

Typical Commercial Specification

Figures below are representative of commercial fibre-grade caprolactam. Engineering resin grades carry slightly wider limits — tell us the application and we will send the matching sheet.

Physical & Chemical Properties

Behaviour in the process

Caprolactam is stable but fussy about moisture, air and temperature:

• Strongly hygroscopic. Flake picks up moisture rapidly from humid air, which affects polymerisation stoichiometry.
• Discolours in air when molten. Oxidation raises APHA colour and permanganate number; nitrogen blanketing is standard.
• Solidifies at 69 °C. Molten handling needs heated, traced systems; a cooled line becomes a solid plug.
• Polymerises with water initiation. Heat plus water opens the ring, which is exactly the polymerisation reaction nylon 6 producers run.

Caprolactam Grades and Nylon Alternatives

Caprolactam is bought by grade, and the grades differ in the trace specifications that matter for fibre rather than in purity.

Stated plainly: nylon 6 and nylon 66 are different polymers with different melting points, dye behaviour and moisture pick-up. The choice between them is a product decision made long before the purchasing conversation.

Industries We Supply Caprolactam To

Caprolactam goes to a small number of large polymerisation plants, with textile and engineering applications downstream.

Where Caprolactam is Used

Nylon 6 fibre and resin account for essentially all caprolactam demand.

In nylon 6 manufacture

Caprolactam is polymerised by hydrolytic ring opening, initiated by a small amount of water at around 250 °C, producing a polymer in equilibrium with about 10% residual monomer and oligomer that must be extracted. The permanganate number and volatile bases specifications matter here because the impurities they detect affect chain termination, molecular weight distribution and the way the fibre takes dye.

Flake versus molten supply

Molten caprolactam avoids the energy and moisture pick-up of remelting flake, and large nylon plants normally take it that way. Flake suits smaller consumers and longer supply chains, but it must be kept dry and sealed because the material is strongly hygroscopic.

Quality Control & Testing

Every lot is released against a batch-specific Certificate of Analysis, with permanganate number and volatile bases reported because they, not purity, define fibre grade.

• Caprolactam purity — by gas chromatography, the bulk grade measure.
• Permanganate number — the sensitive test for oxidisable trace impurities affecting fibre quality.
• Volatile bases — measured because amine impurities affect chain termination and dyeing.
• Colour and UV absorbance — confirming freedom from oxidation and contamination.
• Water content — critical for flake, because the material is strongly hygroscopic.
• Iron and crystallisation point — confirming contamination freedom and identity.

Common Process Problems & Likely Causes

When caprolactam causes trouble, it is usually PM, VB, moisture or oxidation. This table is the shortcut our technical desk works through before anyone opens a complaint file.

Packaging, Storage & Shipping

• Standard packing. 25 kg bags and jumbo bags for flake; heated ISO tank containers and road tankers for molten product.
• Moisture control. Flake is strongly hygroscopic. Keep bags sealed and store in dry, covered warehousing.
• Nitrogen blanketing. Molten caprolactam oxidises and discolours in air; blanket storage and transfer systems.
• Temperature control. Hold molten product above 75 °C. Below 69 °C it solidifies and plugs lines.
• Material compatibility. Stainless steel for molten service; carbon steel contributes iron and colour.
• Segregation. Keep apart from strong oxidisers, acids and bases.
• Shelf life. Typically 12 months for sealed flake in dry storage; molten product should be used promptly.
• Transport classification. Not classified as dangerous goods; molten shipments are declared as elevated temperature cargo.

Hazards & Safe Handling

Caprolactam has moderate toxicity and is not classified as dangerous goods, but it is a skin and respiratory irritant, and molten material presents a thermal burn risk.

• Irritation. Irritating to skin, eyes and respiratory tract. Dust from flake handling is the main exposure route.
• Occupational exposure. Typical limits are around 5 mg/m³ for dust and 20 mg/m³ for vapour; confirm the limits in your jurisdiction.
• Hot liquid. Molten caprolactam above 75 °C causes thermal burns and solidifies on skin, which worsens the injury.
• Dust control. Use enclosed transfer and extraction when handling flake; fines are generated by repeated conveying.
• Low acute toxicity. Harmful if swallowed in quantity but not acutely toxic in normal industrial handling.
• PPE. Gloves, eye protection and dust mask for flake handling; heat-resistant gloves and face shield for molten work.
• Environment. Harmful to aquatic life; contain spills and prevent entry to drains.

Regulatory & Compliance Notes

Caprolactam is unregulated for transport in solid form with application-specific rules for food-contact nylon. The notes below are orientation rather than legal advice.

• GHS classification. Skin, eye and respiratory irritation, with acute toxicity Category 4 by ingestion in some classifications.
• Transport. Not classified as dangerous goods. Molten shipments are declared as elevated temperature substances.
• Food contact. Residual caprolactam monomer limits apply to nylon 6 food contact films and articles in the EU, US and other markets.
• REACH and inventories. Registered under EU REACH and listed on the major chemical inventories.
• Textile standards. Downstream yarn and fabric must meet OEKO-TEX and similar standards, which trace back to monomer and additive purity.
• Quality agreements. Nylon 6 producers commonly expect documented PM, VB and water limits with change control.

We Supply Caprolactam Worldwide

Chelora Chemicals is a supplier and export partner, not a single-plant trader. We ship Caprolactam from India and from partner sources to customers across Asia, Europe, the Middle East, Africa, and North and South America, handling the export documentation, transport paperwork and freight so the material arrives ready to use.

• Incoterms. EXW, FOB, CIF, CFR and DAP quoted to suit your purchasing terms and freight arrangements.
• Ports. Regular shipments through Nhava Sheva (JNPT) and Mundra, with other ports arranged where routing and cargo rules allow.
• Documentation. Commercial invoice, packing list, certificate of origin, COA, SDS and the transport declaration issued as a complete set.
• Flexible volumes. From a pallet of bagged flake up to repeat bulk shipments on a supply contract.
• Supply continuity. Because we are independent of any one producer, a plant turnaround or a shipping disruption at one source does not have to become your stock-out.

Buying Caprolactam from Chelora

We are an independent sourcing and supply partner. For caprolactam that means settling three things at enquiry: whether you take flake or molten product, the permanganate and volatile bases limits your fibre line requires, and the heated logistics or dry storage your receiving setup can support.

• Documentation on every lot. Batch-specific COA (purity, permanganate number, volatile bases, colour), plus SDS and the full transport paperwork.
• Analysis before commitment. Representative analysis shared ahead of a commercial order so your lab can qualify the material.
• Quantities. From a pallet of bagged flake through to full bulk shipments on contract supply.
• Grade matching. Fibre or engineering grade, in flake or molten form, to the PM, VB and water limits your polymerisation requires.
• Inspection. Independent third-party inspection available at loading when the contract requires it.
• Related products. Nylon 6, Adipic Acid, Phenol and other feedstocks alongside Caprolactam from one supplier.

How ordering works

• Send the enquiry. Product, grade or purity, quantity, destination port and the Incoterm you buy on. If you have a spec sheet, attach it — it saves a round trip.
• We quote. Price, lead time, packing format and a sample COA, normally within one working day.
• Qualify the supply. For first orders or critical applications, we share the analysis and handling documentation so your technical and safety teams can sign off before you commit.
• Confirm the order. Proforma invoice issued; payment terms agreed against the volume and the relationship.
• Allocation and QC. Material allocated and released against a batch-specific COA, with an independent inspection where the contract calls for it.
• Ship and document. Filled, labelled and loaded with the full export document set, and tracked through to arrival.

Related Products

Buyers of caprolactam often source related nylon chain products alongside it — nylon 6 chip, adipic acid and ammonia are commonly bought on the same programme.