Tolylene-2,4-diisocyanate
[CAS# 584-84-9]

Identification

• Classification: Organic raw materials >> Carboxylic compounds and derivatives >> Carboxylic esters and their derivatives
• Name: Tolylene-2,4-diisocyanate
• Synonyms: 4-Methyl-1,3-phenylene diisocyanate; 2,4-Diisocyanatotoluene; TDI
• Molecular Formula: C₉H₆N₂O₂
• Molecular Weight: 174.16
• CAS Registry Number: 584-84-9
• EC Number: 209-544-5
• SMILES: CC1=C(C=C(C=C1)N=C=O)N=C=O

Properties

• Density: 1.1±0.1 g/cm³ Calc.^*, 1.225 g/mL (Expl.)
• Melting point: 21.1 - 22.2 ºC (Expl.)
• Boiling point: 251.0 ºC 760 mmHg (Calc.)^*, 251.1 ºC (Expl.)
• Flash point: 110.5±30.7 ºC (Calc.)^*, 126.1 - 127.2 ºC (Expl.)
• Solubility: wate:r reacts (Expl.)
• Index of refraction: 1.559 (Calc.)^*, 1.567-1.569 (Expl.)

^* Calculated using Advanced Chemistry Development (ACD/Labs) Software.

Safety Data

• Hazard Symbols: GHS06;GHS08 Danger
• Hazard Statements: H315-H317-H319-H330-H334-H335-H351-H412
• Precautionary Statements: P203-P233-P260-P261-P264-P264+P265-P271-P272-P273-P280-P284-P302+P352-P304+P340-P305+P351+P338-P316-P318-P319-P320-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
Skin irritation	Skin Irrit.	2	H315
Carcinogenicity	Carc.	2	H351
Skin sensitization	Skin Sens.	1	H317
Specific target organ toxicity - single exposure	STOT SE	3	H335
Chronic hazardous to the aquatic environment	Aquatic Chronic	3	H412
Eye irritation	Eye Irrit.	2	H319
Acute toxicity	Acute Tox.	1	H330
Acute toxicity	Acute Tox.	2	H330
Serious eye damage	Eye Dam.	1	H318
Eye irritation	Eye Irrit.	2A	H319
Specific target organ toxicity - repeated exposure	STOT RE	1	H372
Specific target organ toxicity - single exposure	STOT SE	2	H371

• Transport Information: UN 2078

Discovory and Applicatios

Tolylene-2,4-diisocyanate, commonly abbreviated as TDI, is an aromatic diisocyanate with the chemical formula C₉H₆N₂O₂. It consists of a tolyl group (a methyl-substituted benzene ring) with isocyanate functional groups (–N=C=O) positioned at the 2- and 4-positions of the aromatic ring. This structural arrangement gives TDI its high reactivity toward nucleophiles such as alcohols and amines, making it a key building block in polymer chemistry.

The discovery of TDI dates back to the early 20th century during research into isocyanate chemistry, which began after the industrial interest in polyurethane production emerged. Chemists identified the potential of aromatic diisocyanates to react with polyols to form polyurethane materials with superior mechanical properties. TDI was recognized for its balanced reactivity and ability to produce flexible and rigid polyurethane foams, adhesives, coatings, and elastomers.

Tolylene-2,4-diisocyanate is primarily used in the production of polyurethanes. When reacted with polyols, it forms urethane linkages that provide elasticity, durability, and chemical resistance. TDI-based polyurethanes are commonly found in flexible foams used in furniture, automotive seating, bedding, and insulation materials. Its reactivity can be adjusted through the 2,4- and 2,6-isomer ratio, allowing control over polymer rigidity, hardness, and processing characteristics.

In addition to flexible foams, TDI is employed in the manufacture of coatings, adhesives, sealants, and elastomers. The isocyanate groups readily react with alcohols, amines, and water, enabling crosslinking reactions that yield tough, chemically resistant films and adhesives. TDI-derived elastomers are used in wheels, rollers, gaskets, and other applications where mechanical strength and abrasion resistance are important.

Industrial production of TDI involves the nitration of toluene to form dinitrotoluene, which is then reduced to the corresponding diamine. This diamine undergoes phosgenation to introduce the isocyanate groups, yielding TDI. Safety and handling are critical considerations due to the highly reactive and toxic nature of isocyanates; industrial facilities employ rigorous controls to prevent exposure and manage environmental release.

Tolylene-2,4-diisocyanate remains a cornerstone of the polyurethane industry, valued for its reactivity, versatility, and ability to produce materials with tailored mechanical and chemical properties. Its role in flexible foams, elastomers, and coatings highlights its central importance in both industrial applications and everyday consumer products.

References

1998. Immunohistochemical characterization of the cellular infiltrate in airway mucosa of toluene diisocyanate (TDI)-induced asthma: comparison with allergic asthma. Journal of Korean Medical Science.
DOI: 10.3346/jkms.1998.13.1.21

2007. Skin Exposure to Isocyanates: Reasons for Concern. Environmental Health Perspectives.
DOI: 10.1289/ehp.9557

2021. Eco-friendly Route for Thermoplastic Polyurethane Elastomers with Bio-based Hard Segments Composed of Bio-glycol and Mixtures of Aromatic�Aliphatic and Aliphatic�Aliphatic Diisocyanate. Journal of Polymers and the Environment.
DOI: 10.1007/s10924-020-01992-5

2025. Recent Advances in Functionalized Nanocellulose Materials in Nanobiotechnology. Carbohydrate Polymer Nanotechnologies.
DOI: 10.1007/978-981-96-2171-2_1