Preparation

Isophorone diisocyanate (IPDI) is prepared by the phosgenation of isophorone diamine (l-amino-3-aminomethyl-3,5,5-trimethylcydohexane):

Air & Water Reactions

Insoluble in water. Isophorone diisocyanate may be sensitive to moisture.

Reactivity Profile

Isophorone diisocyanate reacts with all substances containing active hydrogen atoms such as water, alcohols, phenols, amines, mercaptans, amides, urethanes and ureas.

Hazard

A severe irritant, toxic by skin absorption.

Health Hazard

Like most other isocyanates, IPDI exhibitsmoderate toxicity via inhalation. The acutetoxic symptoms are somewhat similar tothose of toluene-2,4- diisocyanate and diphenylmethane-4,4'-diisocyanate. Thus thetoxicity of such types is a characteristic ofthe -N=C=O functional group and to agreat extent is independent of the nature ofthe ring.Inhalation of its vapor can cause bronchitis, asthma, tightness of chest, and dyspnea in humans. Recovery from these effectsmay occur in a short period from a lowconcentration exposure.IPDI is an irritant to the skin and eyes.Exposure to Isophorone diisocyanate produces skinsensitization and eczema. Its oral toxicity isvery low.LC50 value, inhalation (rats): 123 mg/m3/4 hrLD50 value, skin (rats): 1060 mg/m3There is no report of its carcinogenic orreproductive effects in animals or humans.

Fire Hazard

When heated to decomposition, Isophorone diisocyanate emits toxic fumes of nitrogen oxides.

Environmental Fate

IPDI is a synthetic organic chemical, which does not occur naturally in the environment. At room temperature, it is a liquid. It is miscible with alcohol, diglycol, monoethyl ether, ether, acetone, carbon tetrachloride, benzene, chlorobenzene, kerosene, and olive oil. IPDI decomposes in water producing CO2, which can produce significant pressure in a closed container. Upon contact with water or moist air, IPDI will react to form stable, insoluble polyurea solids. This reactivity dramatically limits the mobility of these products in the event of a spill (spills are localized and have only transient impact), and the products will tend to remain in, and react within, the environment to which they are released. IPDI is not readily biodegradable. It reacts with water forming solid insoluble polyurea, isophorone diamine (IPDA), and CO2, thus the predominant removal mechanism is expected to be hydrolysis. The rate constant of the OH radical sensitized indirect photodegradation of isophorone diisocyanate corresponds to a half-life of 1.8 days at a 24 h mean OH radical concentration of 500 000 molecules per cm3. A preliminary hydrolysis test resulted in a dissipation half-life of 0.84 h (approximately 50 min) at 23 ℃. Polyurea is more or less inert and – due to its molecular size – not bioavailable. No biodegradation (0% degradation within 28 days) was observed in a manometric respiratory test performed with domestic, nonadapted activated sludge. As no degradation occurred in the test on ready biodegradability, it is not expected that a significant degradation would occur in a simulation test (water and soil). The test substance is considered as nonbiodegradable in surface water, sediment, and soil. However, biodegradation is considered as irrelevant as primary degradation step anyway because immediate hydrolysis takes place. Due to hydrolysis in water, bioaccumulation of IPDI is not expected. The bioaccumulation potential of the hydrolysis product IPDA is considered to be low (log Kow = 0.99). There are no data on terrestrial bioaccumulation available.

Toxicity evaluation

The toxicological properties of isocyanates are attributed to the –N=C=O group. The consequence is that in the hydrolysis of IPDI predominantly polyurea molecules are formed with liberation of CO2. The polyurea molecules are insoluble in water. Beside these insoluble main hydrolysis products, there are minor amounts of other hydrolysis products having a low to moderate molecular weight and these are more or less water soluble (e.g., isophorone diamine). The local toxic effect of the substance IPDI is not related to metabolic mechanisms, because it is a simple destruction of membranes due to corrosivity of the substance.

Waste Disposal

Disposal is by chemical incineration of IPDIsolution in a combustible solvent.

Definition

ChEBI: A diisocyanate in which the two isocyanate groups are linked by an isophorone substituent.

General Description

A clear to light-yellow liquid. Slightly denser than water and insoluble in water. Toxic by inhalation and skin absorption. Very irritating to skin. Used to make polyurethane coatings.