Trimethyl-1,6-hexamethylene diisocyanate

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Abbreviation:TMHDI, TMDI, TMHMDI

Chemical Name: Mixture of 2,2,4- and 2,4,4-trimethyl-1,6-hexamethylene diisocyanate

Industrial products are generally a mixture of two isomers, 2,2,4-TMHDI and 2,4,4-TMHDI, in a mass ratio of approximately 1:1.

Molecular Formula: C₁₁H₁₈N₂O₂

Molecular Weight: 210.28

The CAS number for the 50/50 (mass ratio) mixture of the two isomers is 34992-02-4; the CAS number for the 40/60 mixture is 28679-16-5. The CAS numbers for 2,2,4-TMHDI are 16938-22-0, 83259-64-7, and 132878-86-5, and the EINECS number is 241-001-8; the CAS number for 2,4,4-TMHDI is 15646-96-5, and the EINECS number is 239-714-4.

Structural Formula

Physical and Chemical Properties

Colorless or light yellow liquid with a pungent odor. Typical physical properties of TMHDI products are shown in Table 1-23.

Characteristics and Uses

Due to its aliphatic characteristics, TMHDI is used in the production of light-resistant and weather-resistant polyurethanes. Compared with cycloaliphatic diisocyanates, polyurethanes or polyurethane-modified resins based on TMHDI have good flexibility and compatibility, and low-viscosity prepolymers can be obtained. TMHDI is used in the production of prepolymers for coatings, and its application areas include: thermosetting systems, waterborne polyurethanes, and radiation-curable polyurethane-acrylates.

The reactivity of TMHDI is lower than that of aromatic isocyanates, but higher than that of cycloaliphatic isocyanates. It can be catalyzed by 0.001% to 0.01% dibutyltin dilaurate.

Acute Toxicity:

Oral LD₅₀ in rats = 4810 mg/kg, inhalation LC₅₀ in rats = 0.70 mg/(L·4h), dermal LD₅₀ in rats > 7000 mg/kg.