MOCA / MBOCA CAS 101-14-4

What is MOCA / MBOCA?

MOCA is a chlorinated aromatic diamine with one job, and it does that job better than anything else found in sixty years of looking. Mixed into an isocyanate-terminated prepolymer, it produces cast polyurethane elastomers with a combination of load-bearing capacity, tear strength, abrasion resistance and hydrolytic stability that competing curatives approach but do not match. The mining screens, the paper-mill rolls, the forklift tyres, the pipeline pigs and the sheave liners that outlast everything around them are, more often than not, MOCA-cured.

The chemistry behind that performance is specific. The two chlorine atoms sit ortho to the amine groups, where they pull electron density away from the nitrogen and slow its reaction with isocyanate dramatically. That deactivation is the whole point: it buys the caster a working pot life of several minutes at 100–120 °C, long enough to degas, pour into a complex mould and let the material flow out, before the cure proceeds to completion in an oven. An unsubstituted aromatic diamine would gel in the mixing head. MOCA is slow enough to process and reactive enough to finish.

The same chlorine substitution also builds a hard segment that packs well. The cured urea linkages aggregate into ordered domains that act as physical crosslinks, giving the elastomer its high modulus at temperature and its resistance to compression set. This is why a MOCA-cured part holds its shape under sustained load in a way that a diol-cured part does not, and why the material survives in wet, hot, abrasive service where polyester polyurethanes would normally hydrolyse.

None of that technical merit changes the regulatory position, and we will not pretend otherwise. MOCA is classified as a carcinogen and in the European Union it appears on the REACH authorisation list, which means a specific authorisation is required for use rather than a general assumption of availability. Other jurisdictions impose their own exposure limits, biological monitoring requirements and notification rules. Chelora supplies MOCA to users who have that position settled — we ask for the end-use declaration up front, not as an afterthought, and we would rather have a frank conversation about your authorisation status before an order than discover a problem at the port.

Why cast elastomer producers still specify MOCA

• Pot life you can actually work with Several minutes of flow at casting temperature, enough for degassing and complex moulds, where unsubstituted aromatic diamines gel before the pour is finished.
• Load-bearing performance High modulus and low compression set at elevated temperature, the properties that define a load-wheel, a press pad or a mining screen panel.
• Hydrolytic stability Urea hard segments resist water far better than the ester linkages they often sit alongside, extending life in wet service.
• Abrasion and tear resistance The combination the mining, paper and materials-handling industries buy cast polyurethane for in the first place.
• Sixty years of process data Every casting house has MOCA formulations, cure schedules and part histories. Substitution means requalifying all of it.
• Documented supply Batch amine value, moisture and colour on every COA, with the regulatory paperwork handled as part of the order rather than left to you.

How MOCA is Manufactured

MOCA is made by condensing o-chloroaniline with formaldehyde under acid catalysis — the same reaction type that gives MDA from aniline, with the chlorinated aniline substituted in. The commercial challenge is isomer and oligomer control rather than the condensation itself.

• Condensation o-Chloroaniline reacts with formaldehyde in the presence of hydrochloric acid. The methylene bridge forms para to the amine group on each ring, giving the 4,4′-linked diamine as the dominant product.
• Neutralisation and separation The acidic reaction mass is neutralised and the organic phase separated from the aqueous salt solution, which carries away the catalyst.
• Stripping Unreacted o-chloroaniline is stripped under vacuum and recycled. Residual free chloroaniline is the critical impurity, and the efficiency of this step largely sets the final specification.
• Purification and forming The crude diamine is purified to remove higher oligomers and colour bodies, then pastillated, flaked or held molten depending on how the customer charges it.

Typical Commercial Specification

Typical elastomer-grade specification. Verify against your current COA before relying on these figures in a formulation or a purchase specification.

Physical & Chemical Properties

Reactivity in practice

MOCA's behaviour is dominated by the electron-withdrawing chlorine atoms next to each amine group, which is what makes it processable, and by the aromatic amine chemistry it shares with every other member of that class.

• Reacts with isocyanates to form ureas The hard-segment chemistry behind the elastomer's modulus. Deliberately slower than an unsubstituted aromatic diamine, giving usable pot life at casting temperature.
• Moisture-sensitive in use Water competes for isocyanate and generates carbon dioxide, giving voids and soft spots. Keep the material dry and degas the mix.
• Oxidises and darkens on heating Prolonged holding in the molten state, particularly with air present, darkens the material. Use nitrogen blanketing and avoid holding longer than the casting schedule needs.
• Attacks copper and its alloys Use stainless, lined or coated surfaces for melt tanks, lines and metering equipment.
• Thermally stable within the casting window Stable at normal melt and cure temperatures; overheating promotes colour and side reactions without benefit.
• Absorbed through intact skin This is a handling property, not just a toxicological footnote: exposure control has to assume skin contact matters as much as inhalation.

MOCA Compared With Related Aromatic Amines

These three aromatic amines are grouped together here for a reason that has nothing to do with their chemistry: all carry a carcinogen classification, and for all three the regulatory position rather than the technical specification usually decides whether a given use is possible in a given market. Understanding where each one stands is a prerequisite to buying it.

Stated plainly: the technical question of which curative or feedstock performs best is often settled long before the regulatory one, and it is the regulatory answer that determines whether you can proceed. For MDA and TDA, a very large majority of global volume is consumed as an isolated intermediate within integrated isocyanate plants, where different obligations apply from those on a free-standing industrial use. For MOCA, the position in Europe is specific and restrictive. Establish where your use sits before anything else.

Industries We Supply MOCA To

MOCA has an unusually narrow industrial footprint. Essentially all of it goes into cast polyurethane elastomers, and the industries listed below are the ones that consume those elastomers in service.

Where MOCA is Used

One application dominates, and the technical detail that matters sits inside it rather than across a list of markets.

Hot-cast elastomer processing

The standard route is to heat MOCA to around 110–120 °C, meter it into a prepolymer at a similar temperature, mix, degas and pour. Stoichiometry is calculated from measured amine value against prepolymer NCO, usually at 90–95% of theory — running slightly amine-deficient leaves a small excess of isocyanate that improves properties and tolerates trace moisture. Parts are demoulded warm and post-cured, typically sixteen hours at 100–110 °C, to drive the urea hard segments to full order. The cure schedule is as much a part of the formulation as the ratio.

Why substitution is a project, not a purchase

Alternative curatives exist and are in commercial use — other chlorinated aromatic diamines, diol-amine blends, and proprietary systems. None reproduce MOCA's property profile exactly, and each changes pot life, demould time, hardness and shrinkage. For a casting house with hundreds of part numbers and customer approvals attached to them, switching means requalifying parts, not reordering a drum. We are happy to discuss alternatives honestly, including where they fall short, but the realistic position is that substitution is a programme measured in quarters.

Handling in a casting shop

The practical goal is to eliminate open handling. Pre-weighed sachets charged unopened into the melt tank, closed transfer from melt tank to mixing head, local exhaust at the pour, and enclosed or heavily ventilated demould and trimming areas. Where biological monitoring applies, it is the measure that tells you whether the controls are actually working — air sampling alone understates exposure for a substance absorbed through skin. Treat the packaging decision and the exposure-control design as one conversation; that is how we approach it when quoting.

Quality Control & Testing

Every lot is released against a batch-specific Certificate of Analysis. The methods behind the numbers are standard across the industry, and we are happy to share them or to work to your own in-house test protocol.

• Assay by HPLC Confirms purity and quantifies oligomeric by-products.
• Amine value by titration The figure your mix ratio is calculated from. Reported as measured on every batch.
• Free o-chloroaniline by GC Both a toxicological and a performance control — monofunctional amine caps chain ends and depresses mechanical properties.
• Moisture by Karl Fischer Water causes voids and soft spots in cast parts; controlled at the point of fill.
• Melting range Confirms identity and the absence of significant oligomer or isomer drift.
• Colour on the melt Reported because darkening indicates oxidative history in storage or transit.
• Ash and insolubles Guards against particulates that show as inclusions in clear or thin-section castings.
• Retained samples Held against every batch so a casting problem months later can be traced to the material or ruled out.

Common Process Problems & Likely Causes

Cast elastomer problems traced back to the curative are usually ratio, moisture or thermal history rather than the material itself. The table below is the sequence we work through with customers.

Packaging, Storage & Shipping

• 25 kg lined bags and boxes Pastilles or flake in moisture-barrier liners, the standard format for batch casting.
• Pre-weighed sachets Charged into the melt tank unopened, eliminating open handling and weighing. The preferred option wherever the casting process allows it.
• 250 kg drums For larger users melting a full drum into a holding tank.
• Heated isotanks Molten bulk for continuous casting lines with closed transfer to the mixing head.
• Storage Cool, dry, closed, away from moisture and oxidising agents. Keep original packaging sealed until the point of charge.
• Molten holding Nitrogen blanket, modest temperature, minimum residence. Every hour held hot costs colour and a little performance.

Hazards & Safe Handling

MOCA is classified as a carcinogen and is absorbed through intact skin. The controls below are not precautionary good practice; they are the basis on which the substance is used at all. Always work from the current Safety Data Sheet and your own national occupational exposure and health-surveillance requirements.

• Carcinogen classification. This substance carries a carcinogen classification in major regulatory systems. That is the governing fact in any risk assessment and it should shape plant design, exposure control, worker selection and health surveillance — not sit as a line on a label. Exposure should be reduced to as low as reasonably practicable rather than merely kept below a limit value.
• Closed handling. Open handling of a carcinogen-classified powder is difficult to justify where a closed or enclosed alternative exists. Bulk bags with enclosed discharge, pre-weighed sachets that go into the reactor unopened, and melt-and-pump systems are the normal approaches.
• Health surveillance and biological monitoring. Most jurisdictions require health surveillance for workers exposed to carcinogen-classified aromatic amines. For some, biological monitoring of the substance or its metabolites in urine is established practice and gives a far better picture of real uptake than air sampling alone.
• Skin absorption. Aromatic amines are commonly absorbed through intact skin, which means air monitoring can look acceptable while uptake continues. Glove selection with a verified breakthrough time, and procedures that treat any skin contact as a reportable event, matter more than ventilation alone.
• PPE. Chemical-resistant gloves of a verified material, eye protection, protective clothing that is removed and laundered on site, and respiratory protection appropriate to a carcinogen-classified dust or vapour.
• Hot and molten material. Melting raises vapour and mist exposure substantially and adds thermal burn risk. Treat heated handling as a distinct operation with its own assessment and controls.
• Environment. Harmful or toxic to aquatic life. Do not allow to enter drains, surface water or groundwater. Dispose through a licensed chemical waste contractor, and treat contaminated PPE and packaging as hazardous waste.
• First aid. Remove from exposure, remove contaminated clothing, wash skin thoroughly with soap and water, flush eyes for at least 15 minutes, and seek medical attention with the SDS to hand. Record any exposure incident — it may be relevant to long-term health surveillance.

Regulatory & Compliance Notes

MOCA's regulatory position is more restrictive than its technical merit alone would suggest, and it varies substantially between markets. The notes below are an orientation, not a compliance opinion.

• REACH authorisation list (EU) MOCA is identified as a substance of very high concern and appears on Annex XIV, meaning use in the EU requires a specific authorisation. Unlike MDA, there is no broad isolated-intermediate route for MOCA's principal use, because curing an elastomer is an end use rather than an intermediate step.
• Occupational exposure and monitoring Many jurisdictions set an exposure limit and require biological monitoring — urinary metabolite measurement — because skin absorption makes air sampling an incomplete measure. Check what applies at your site before material arrives.
• Health surveillance Carcinogen classification commonly triggers a statutory health-surveillance programme and exposure-record retention for extended periods. This is an employer obligation and sits outside what a supplier can discharge for you.
• Transport classification UN 2811, Toxic solid, organic, n.o.s., Class 6.1, Packing Group III. Molten shipments are additionally subject to elevated-temperature provisions.
• End-use declaration We ask for a written statement of intended use and the applicable authorisation or exemption position before despatch. This is a condition of supply, not a formality.
• Import and notification regimes Several countries impose notification, licensing or import-permit requirements on carcinogen-classified aromatic amines. Confirm the position for your destination early, because it can affect lead time more than production does.

We Supply MOCA Worldwide

Chelora Chemicals is a supplier and export partner, not a single-plant trader. We ship MOCA / MBOCA from India to customers across Asia, Europe, the Middle East, Africa, and North and South America, handling the export documentation, dangerous-goods 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 Indian ports arranged where it suits the routing.
• Documentation. Commercial invoice, packing list, certificate of origin, COA, SDS and dangerous-goods declaration issued as a complete set.
• Flexible volumes. A single drum for laboratory qualification, through LCL consolidations, up to repeat full loads 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 MOCA from Chelora

Buying MOCA involves two conversations running in parallel: the technical one about your prepolymer system and part requirements, and the regulatory one about authorisation and exposure control. We run both.

• Tell us the prepolymer and the part NCO content, part geometry, target hardness and cure schedule let us advise on grade, amine value band and packing rather than just quoting a tonne rate.
• Settle the paperwork early End-use declaration, authorisation or exemption position, destination requirements. We would rather resolve this at enquiry than at the port.
• Choose the packing deliberately Sachets, bags, drums or molten bulk. This decision does more for worker exposure than any downstream control, so we treat it as part of the technical specification.
• Batch-specific documentation COA with amine value, free chloroaniline and moisture, current SDS and TDS with every consignment.
• Samples for qualification Available where the regulatory position permits, so you can confirm processing behaviour before committing to volume.
• Continuity of supply Scheduled call-offs against a contract, so a casting programme is not exposed to spot market availability for a substance with few alternatives.

How ordering works

• Send the enquiry. Product, grade or specification, 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 and a sample COA, normally within one working day.
• Sample and qualify. For first orders or critical applications, we send a trial quantity so your lab can sign off before you commit.
• Confirm the order. Proforma invoice issued; payment terms agreed against the volume and the relationship.
• Production and QC. Material allocated and released against a batch-specific COA, with a pre-shipment sample where the application calls for it.
• Ship and document. Packed, labelled and loaded with the full export and dangerous-goods document set, and tracked through to arrival.

Related Amines & Intermediates

Related aromatic amines and the aliphatic and cycloaliphatic amines we supply alongside them for polyurethane and epoxy systems.