4,4'-Diphenylmethane diisocyanate
[CAS# 101-68-8]

Identification

• Classification: Organic raw materials >> Carboxylic compounds and derivatives >> Carboxylic esters and their derivatives
• Name: 4,4'-Diphenylmethane diisocyanate
• Synonyms: 4,4'-Methylenebis(phenyl isocyanate); 1,1'-Methylenebis(4-isocyanatobenzene); MDI
• Molecular Formula: C₁₅H₁₀N₂O₂
• Molecular Weight: 250.25
• CAS Registry Number: 101-68-8
• EC Number: 202-966-0
• SMILES: C1=CC(=CC=C1CC2=CC=C(C=C2)N=C=O)N=C=O

Properties

• Density: 1.19
• Melting point: 38-44 °C
• Boiling point: 392 °C
• Flash point: 196 °C
• Water solubility: decomposes

Safety Data

• Hazard Symbols: GHS07;GHS08 Danger
• Risk Statements: H315-H317-H319-H332-H334-H335-H351-H371-H373
• Safety Statements: P203-P233-P260-P261-P264-P264+P265-P270-P271-P272-P280-P284-P302+P352-P304+P340-P305+P351+P338-P308+P316-P317-P318-P319-P321-P332+P317-P333+P317-P337+P317-P342+P316-P362+P364-P403-P403+P233-P405-P501

Hazard Classification

Hazard	Class	Category Code	Hazard Statement
Respiratory sensitization	Resp. Sens.	1	H334
Eye irritation	Eye Irrit.	2	H319
Carcinogenicity	Carc.	2	H351
Skin sensitization	Skin Sens.	1	H317
Skin irritation	Skin Irrit.	2	H315
Acute toxicity	Acute Tox.	4	H332
Specific target organ toxicity - repeated exposure	STOT RE	2	H373
Specific target organ toxicity - single exposure	STOT SE	3	H335
Acute toxicity	Acute Tox.	3	H331
Specific target organ toxicity - single exposure	STOT SE	2	H371
Specific target organ toxicity - single exposure	STOT SE	3	H370
Skin irritation	Skin Irrit.	2	H314
Acute toxicity	Acute Tox.	2	H330
Germ cell mutagenicity	Muta.	2	H341
Specific target organ toxicity - repeated exposure	STOT RE	1	H372

• Transport Information: UN 2811

Discovery and Applications

4,4'-Diphenylmethane diisocyanate (MDI) is an organic compound with the molecular formula C15H10N2O2. It was first synthesized during the development of isocyanate chemistry in the mid-20th century and played an important role in the rise of the polyurethane industry. MDI is one of the most important aromatic diisocyanates and is widely used in the production of polyurethane foams, elastomers, and coatings.

MDI is solid at room temperature and usually appears as white to pale yellow crystals. It has a melting point of about 39°C and a boiling point of 200°C (5 mmHg). MDI is very reactive with compounds containing active hydrogen atoms, such as alcohols and amines, forming strong urethane and urea bonds.

MDI is mainly used in the production of polyurethane foams, which are divided into two types: Flexible foams are used in cushioning applications such as furniture, mattresses, and car seats. The flexibility of these foams makes them ideal for comfort and support. Rigid foams: These foams are used for insulation in buildings, refrigerators, and freezers. Their excellent thermal insulation properties help improve energy efficiency and reduce energy costs.

MDI is also used in the production of polyurethane elastomers, which have a wide range of applications due to their durability and flexibility:Polyurethane elastomers are used to make automotive parts such as tires, gaskets and seals. Their wear resistance makes them suitable for harsh environments. These elastomers are used in machinery and equipment that require wear resistance, such as rollers, belts and hoses.

MDI is an important component of the coatings, adhesives, sealants and elastomers (CASE) CASE sector, where it helps produce high-performance materials:Polyurethane coatings derived from MDI provide excellent protection to surfaces, enhancing durability and resistance to chemicals, abrasion and weathering. They are used in automotive painting, industrial coatings and flooring. MDI-based adhesives and sealants have strong adhesive properties and are used in construction, packaging and woodworking. Their versatility and strength make them suitable for a wide range of applications.

MDI is used as a binder in the production of composite wood products such as oriented strand board (OSB) and medium density fiberboard (MDF):These engineered wood products are used in building flooring, roofing and wall coverings. Using MDI as a binder improves the strength and moisture resistance of the products.

Although MDI is very useful, it is also a hazardous chemical. It can cause respiratory and skin irritation, and long-term exposure may cause allergies or asthma. Proper handling, protective equipment, and ventilation are essential when using MDI. In addition, the polyurethane industry is working to develop more sustainable practices, including recycling and using bio-based materials, to reduce environmental impact.

References

2003. Changes in low molecular weight DNA fragmentation in white blood cells after diisocyanate exposure of workers. Archives of Toxicology, 77(8).
DOI: 10.1007/s00204-003-0462-y

2016. Comparison of biological effects with albumin adducts of 4,4′-methylenediphenyl diisocyanate in workers. Archives of Toxicology, 91(4).
DOI: 10.1007/s00204-016-1846-0

2017. Sensitization to diphenylmethane-diisocyanate isomers by a single accidental exposure. Contact Dermatitis, 78(2).
DOI: 10.1111/cod.12853