4,4′-Methylenebis(2-chloroaniline), commonly known as MOCA, is an aromatic amine with the formula C₁₃H₁₂Cl₂N₂. It is primarily used as a curing agent in the manufacture of castable polyurethane products. MOCA facilitates chemical reactions that bond molecules into stable structures, producing tough, abrasion-resistant polymers.
Pure MOCA is a colourless crystalline solid, but in practice it is manufactured and used as yellow, tan, or brown pellets. It is odourless and tasteless but may decompose if heated above 205°C.
What is MOCA used for?
MOCA is a key component in polyurethane products found in many everyday applications, including:
Appliances and electronics: gear systems in office and home devices, computers, and cameras.
Automotive: mouldings and body parts, as well as specialised components in military equipment.
Consumer goods: footwear, sporting goods, and adhesives.
Industrial: coatings, glues, and elastomer compounds where it acts as a curing agent.
Its main function is to create stable, abrasion-resistant structures in polyurethane and elastomer systems.
MOCA is an essential curing agent used in the production of polyurethane products. These materials are commonly found in consumer goods such as footwear, sporting equipment, and adhesives.
In the Environment
Enters the environment through waste disposal from manufacturing plants.
Poorly soluble in water and strongly adheres to soil particles.
Unlikely to evaporate or migrate into groundwater.
Breaks down by sunlight in air and by microorganisms in soil and water.
Can accumulate in the roots of vegetables grown in contaminated soil.
Sources of Emission & Routes of Exposure
Sources of Emission
Industrial: release from factories making polyurethane products (appliances, cameras, computers, and motor vehicles).
Diffuse: low-level emissions in air or dust near polyurethane plants.
Natural: does not occur naturally.
Consumer products: present in stable forms in polyurethane goods such as footwear, sporting gear, computers, and car parts.
Routes of Exposure
Skin and eye contact: the main route of occupational exposure.
Inhalation: dust particles containing MOCA can be inhaled.
Health Effects
Acute Effects
Workers accidentally exposed have reported gastrointestinal distress, kidney damage, and burning of the face and eyes.
Animal studies (rats, mice, guinea pigs) show moderate to high oral toxicity.
Chronic Effects
Limited human data.
Animal studies indicate long-term oral exposure may damage the liver, kidney, and lungs.
The US EPA has set a provisional Reference Dose (RfD) of 0.0007 mg/kg/day based on liver and kidney damage in dogs.
Reproductive/Developmental Effects
No evidence of reproductive or developmental effects in humans or animals.
Cancer Risk
An epidemiological study of 200 exposed workers found 3 cases of bladder cancer, though the study lacked controls and exposure data.
Animal studies show tumour development in the liver, lung, urinary bladder, and mammary glands.
Because of its similarity to benzidine (a known human bladder carcinogen), the EPA classifies MOCA as a Group B2 probable human carcinogen.
Safety
First Aid Measures
Eye contact: Remove contact lenses if present. Rinse eyes with plenty of water for at least 15 minutes and seek medical attention.
Skin contact: Wash thoroughly with water and remove contaminated clothing and shoes. Apply an emollient or antibacterial cream if irritation occurs. Seek medical advice.
Inhalation: Move the affected person to fresh air. If not breathing, provide artificial respiration; if breathing is difficult, give oxygen. Seek medical attention immediately.
Ingestion: Do not induce vomiting unless directed by medical personnel. Loosen tight clothing and call a physician immediately if large quantities are swallowed. Never give anything by mouth to an unconscious person.
Fire and Explosion Hazards
MOCA may be combustible at high temperatures.
Slightly flammable in the presence of heat; not flammable under shock.
Fine dust dispersed in air can present a dust explosion hazard in the presence of an ignition source.
Extinguishing measures:
Small fires: use dry chemical powder.
Large fires: use water spray, fog, or foam (not water jets).
Exposure Controls and Personal Protection
Engineering Controls
Use process enclosures, local exhaust ventilation, or other engineering controls to keep airborne concentrations below recommended limits.
Where dust, fumes, or mist are generated, ensure adequate ventilation.
Personal Protective Equipment
For normal handling: splash goggles, gloves, lab coat, and a certified dust respirator.
For large spills or high-risk exposure: full protective suit, boots, gloves, splash goggles, dust respirator, and a self-contained breathing apparatus (SCBA).
Always consult a safety specialist before handling large quantities.
Regulation
United States
EPA: Environmental Protection Agency has classified MOCA as a hazardous waste that must meet specific disposal requirements. The EPA requires that spills or accidental releases of MOCA into the environment of 10 pounds or more must be reported to EPA.
ACGIH: The American Conference of Governmental Industrial Hygienists (ACGIH) set a maximum level of 0.11 milligrammes of MBOCA per cubic metre (0.11 mg/m³) of workplace air for an 8-hour workday, 40-hour workweek.
NIOSH: The National Institute for Occupational Safety and Health (NIOSH) recommends an exposure limit of 3 micrograms of MOCA per cubic metre of air (3 mg/m³) over a 10-hour day.
These agencies advise avoiding eye and skin contact because this may be a route of significant exposure.
Australia
Safe Work Australia: Safe Work Australia has established a time weighted average concentration for MOCA of 0.02 ppm and 0.22 mg/m³ for an 8-hour workday and 40-hour workweek.
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