4,4'-Methylenebis(2-chloroaniline)

4,4'-Methylenebis(2-chloroaniline), often abbreviated as MOCA, is an aromatic diamine used primarily as a curing agent for polyurethane elastomers. It is a synthetic organic compound characterized by two 2-chloroaniline moieties linked by a methylene bridge.

Properties and Characteristics

MOCA typically appears as a pale yellow to light amber solid at room temperature. It has a relatively low melting point, typically in the range of 95-100°C (203-212°F), which facilitates its use in liquid polyurethane casting processes. Its solubility in water is low, but it dissolves readily in many organic solvents.

Uses

The primary application of MOCA is in the curing of isocyanate-terminated polyurethane prepolymers. When MOCA is mixed with the prepolymer, it reacts with the isocyanate groups, causing chain extension and crosslinking, which leads to the formation of a solid, durable polyurethane elastomer. This elastomer is used in a variety of applications, including:

• Industrial wheels and tires
• Rollers and casters
• Mining screens
• Seals and gaskets
• Coatings and linings

Safety and Hazards

MOCA is classified as a suspected human carcinogen and is subject to strict regulations in many countries. Exposure can occur through inhalation, skin absorption, or ingestion. Proper handling procedures, including the use of personal protective equipment (PPE) such as respirators, gloves, and protective clothing, are essential to minimize exposure. Due to its potential carcinogenic effects, efforts have been made to develop and use alternative curing agents with lower toxicity.

Regulation

Due to its health hazards, the use of MOCA is regulated by various governmental agencies and organizations, including the Occupational Safety and Health Administration (OSHA) and the European Chemicals Agency (ECHA). These regulations often specify exposure limits and require employers to implement engineering controls and administrative procedures to protect workers. In some jurisdictions, its use is restricted or banned altogether.

Synonyms

MOCA is also known by several other names, including:

• 4,4'-Methylenebis(o-chloroaniline)
• Bisamine
• MBOCA
• 3,3'-Dichloro-4,4'-diaminodiphenylmethane