Толилен-2,4-диизоцианат

Описание

Toluene diisocyanate (TDI), (OCN)2C6H3CH3, is a water-white to pale-yellow liquid with a sharp, pungent odor. It reacts with water to release carbon dioxide. The specific gravity is 1.22, which is heavier than water. TDI is toxic by inhalation and ingestion, and is a strong irritant to skin and other tissue, particularly the eyes. The TLV is 0.005 ppm in air, and the IDLH is 10 ppm. The target organs are the respiratory system and the skin. The four-digit UN identification number is 2078. The NFPA 704 designation is health 3, flammability 1, and reactivity 3. The white section at the bottom of the diamond has a W with a slash through it, indicating water reactivity. The primary uses of TDI are in the manufacture of polyurethane foams, elastomers, and coatings.

Химические свойства

colourless to light yellow liquid

Физические свойства

Clear, colorless to light yellow liquid with a pungent, fruity odor. Odor threshold concentration in air is 2.14 ppm_v (Leonardos et al., 1969).

Использование

Occupational asthma is the principal cause of work-related respiratory disease in the industrial world. Toluene-2,4-diisocyanate (TDI) is one of the most common respiratory sensitizers leading to occupational asthma.

Определение

ChEBI: A toluene meta-diisocyanate in which the isocyanato groups are at positions 2 and 4 relative to the methyl group on the benzene ring.

Общее описание

2,4-TDI is an environmental contaminant belonging to the class of diisocyanates. It is commercially used as a starting material for varnishes, paints, elastomers, polyurethane foams, wire enamels, etc.

Реакции воздуха и воды

Reacts with water with the evolution of carbon dioxide and formation of insoluble polyureas that are relatively nontoxic and inert [Merck 11th ed. 1989)].

Профиль реактивности

Tolylene-2,4-diisocyanate is explosive in the form of vapor when exposed to heat, flame or sparks. Undergoes potentially violent polymerization reaction with strong bases or acyl chlorides. Reacts with water to liberate carbon dioxide. Potential explosion if stored in polyethylene containers due to absorption of water through the plastic. Emits very toxic fumes of oxides of nitrogen when heated to decomposition [Lewis, 3rd ed., 1993, p. 1251].

Опасность

Toxic by ingestion and inhalation; strong irritant to skin and tissue, especially to eyes. Respiratory sensitization.

Угроза здоровью

Can cause death. Contact with skin may cause allergic eczema. Substance is very corrosive to eyes. Chronic exposure may cause chronic lung disease. As a vapor TDI is a powerful irritant to the respiratory tract. Chronic loss of respiratory function may occur. Acute asthmatic bronchitis or frank asthma may occur. A splash in the eyes of workmen has caused keratitis and conjunctivitis. Tolylene-2,4-diisocyanate causes inflammation of the skin, also chemical pneumonitis and pulmonary edema.

Пожароопасность

When heated to decomposition Tolylene-2,4-diisocyanate emits very toxic fumes of cyanide and nitrogen oxides. Reacts violently with amines, alcohol, bases and warm water causing fire and explosion hazards. Avoid strong oxidizers, water, acids, bases, amines, etc., cause foam and splatter. Avoid heating. Hazardous polymerization may occur. Concentrated alkaline compound such as sodium hydroxide or tertiary amines may cause run-away polymerization. Slow, not hazardous polymerization may occur above 235F.

Воспламеняемость и взрывоопасность

TDI is a combustible liquid (NFPA rating = 1). Explosive limits in air are 0.9 to 9.5% by volume. Carbon dioxide or dry chemical extinguishers should be used for TDI fires.

Химическая реактивность

Reactivity with Water: A non violent reaction occurs forming carbon dioxide gas and an organic base; Reactivity with Common Materials: No reactions; Stability During Transport: Stable; Neutralizing Agents for Acids and Caustics: Not pertinent; Polymerization: Slow polymerization occurs at temperatures above 113°F. The reaction is not hazardous; Inhibitor of Polymerization: Not pertinent.

Профиль безопасности

Confirmed carcinogen. Poison by ingestion, inhalation, and intravenous routes. Human systemic effects by inhalation: unspecified changes to the eyes and sense of smell, respiratory obstruction, cough, sputum, and other pulmonary and gastrointestinal changes. Mutation data reported. A severe skin and eye irritant. Capable of producing severe dermatitis and bronchial spasm. A common air contaminant. Combustible when exposed to heat or flame. Explosive in the form of vapor when exposed to heat or flame. To fight fire, use dry chemical, CO2. Potentially violent polymerization reaction with bases or acyl chlorides. Reaction with water releases carbon dioxide. Storage in polyethylene containers is hazardous due to absorption of water through the plastic. When heated to decomposition it emits highly toxic fumes of NOx. See also ISOCYANATES.

Канцерогенность

Acute toxicity. Industrial experience has demonstrated that acute exposure to TDI vapors can produce severe irritant effects on mucous membranes, the respiratory tract, and the eyes. An acute attack of an asthma-like syndrome may occur. Exposure to high concentrations may lead to chemical bronchitis with severe bronchospasm, chemical pneumonitis, pulmonary edema, headache, and insomnia.With sufficient exposure, all persons would appear to experience these effects even on their first exposure.
Chronic and subchronic toxicity. Repeated exposures at lower concentrations of TDI may produce a chronic-like syndrome in many people. Symptoms may include coughing, wheezing, tightness or congestion in the chest, and shortness of breath and appear to be related to hypersensitization. Interstitial pulmonary fibrosis does not occur from moderately elevated exposures to TDI (mean 0.07, peak 0.2 ppm).
Exposure to TDI may lead to immunological sensitization. Some individuals become sensitized on first exposure; others may develop symptoms after exposure over days, months, or years. Other workers have experienced only minimal or no respiratory symptoms for several months of low level exposure, then suddenly develop acute asthmatic reactions to the same level. The nature of the sensitization process is unknown, and many authors have referred to it as an “allergy;” the respiratory response in sensitized people is referred to as true asthma, comparable to asthma excited by pollens and other exoallergens. Some TDI-sensitized people, however, have no history of prior allergic disease.

Экологическая судьба

Chemical/Physical. Slowly reacts with water forming carbon dioxide and polyureas (NIOSH, 1997; Windholz et al., 1983).

хранилище

work with TDI should be conducted in a fume hood to prevent exposure by inhalation, and splash goggles and impermeable gloves should be worn at all times to prevent eye and skin contact.

Методы очистки

It is purified by fractionation in a vacuum and should be stored in a dry atmosphere. It is soluble in organic solvents but reacts with H2O, alcohols (slowly) and amines, all of which could cause explosive polymerisation. It darkens on exposure to light. It has a sharp pungent odour, is TOXIC and is IRRITATING TO THE EYES. [Siefken Justus Liebigs Ann Chem 562 75, 96, 127 1949, Bayer Angew Chem 59 257 1947.] It is a reagent for covalent crosslinking of proteins [Wold Methods Enzymol 25 623 1972.] [Beilstein 13 IV 243.]

Несовместимости

Contact with strong oxidizers may cause fires and explosions. Contact with water, acids, bases, and amines can lead to reactions that liberate heat and CO2 and cause violent foaming and spattering. TDI will attack some forms of plastic, rubber, and coatings.

Утилизация отходов

Excess TDI and waste material containing this substance should be placed in an appropriate container, clearly labeled, and handled according to your institution's waste disposal guidelines.

Меры предосторожности

Occupational workers should be careful during use and waste disposal of toluene diisocyanate. Use and storage of toluene diisocyanate requires precautions. It polymerizes under the infl uence of bases, tertiary amines, and acyl chlorides with fi re or explosion hazard. On combustion, it forms toxic vapors and gases, including nitrogen oxides and isocyanates. Toluene diisocyanate reacts readily with water, acids, and alcohols, and causes explosion hazard. The development of any unusual signs or symptoms, such as headache, increased pain or a discharge from the eyes, increased redness or pain or a pus-like discharge in the area of a skin burn within 24 h after exposure to toluene diisocyanate, requires immediate medical support to the exposed worker.