4,4'-Diphenylmethane diisocyanate

Description

4,4'-Diphenylmethane-diisocyanate (MDI) is used in the manufacture of various polyurethane products - elastic and rigid foams, paints, lacquers, adhesives, binding agents, synthetics rubbers, and elastomeric fibers.

Chemical properties

white to light yellow flakes or crystals

Chemical properties

MDI is a white to light-yellow, odorless flakes. A liquid above 37C.

The Uses of 4,4'-Diphenylmethane diisocyanate

Diphenyl methane diisocyanate (MDI) is widely used in polyurethane coatings, this product is made of polyurethane foam used as a warm (cold), building materials, vehicle, ship parts; masterwork can made car Block, buffer, synthetic leather, non plastic polyurethane, polyurethane elastic fiber, no plastic elastic fibers, films, adhesives.

The Uses of 4,4'-Diphenylmethane diisocyanate

Diphenylmethane-4,4-diisocyanate (MDI)is widely used in the production ofrigid urethane foam products, coatings, andelastomers..

The Uses of 4,4'-Diphenylmethane diisocyanate

Diphenylmethane-4,4-diisocyanate is used in the preparation of polyurethane resin and Spandex fibers; bonding of rubber to rayon; diisoeyanate in the production of polyurethane lacquers, foam plastics, rubber, and glues.

Definition

ChEBI: A diisocyanate consisting of diphenylmethane with two isocyanate groups at the 4- and 4'-positions.

Preparation

Phosgene (800 g, 8 mol) (for a safe source) was dissolved in o-dichlorobenzene (2000 mL), and the resulting solution was cooled in an ice-salt bath. To the stirred solution, a hot solution of 4,4'-diaminodiphenylmethane (200 g, 1.01 mol) in o-dichlorobenzene (1000 mL) was slowly added through a heated dropping funnel. The rate of addition was regulated so that the temperature of the phosgene solution did not rise substantially above 0°C. The fine suspension that resulted was slowly heated and additional phosgene (700 g, 7.1 mol) was added at 130 °C until a clear solution appeared. After purging with carbon dioxide, the solvent was removed in vacuo and the product was purified by vacuum distillation. At 156–158 °C (0.1 mmHg), 215 g (0.85 mol, 84%) of 4,4’-diphenylmethane diisocyanate was obtained. Several procedures for the preparation of isocyanates with phosgene have been described. Nevertheless, many of them require the delivery of gaseous phosgene from an external source, such as a pressurized cylinder.

General Description

Diphenylmethane-4,4-diisocyanate is a light yellow colored solid. 4,4'-Diphenylmethane diisocyanate is not soluble in water. 4,4'-Diphenylmethane diisocyanate may be toxic by ingestion, inhalation, or skin absorption. If in a solution 4,4'-Diphenylmethane diisocyanate may or may not burn depending on the nature of the material and/or the solvent. It's used to make plastics.

Air & Water Reactions

4,4'-Diphenylmethane diisocyanate is not soluble in water.

Reactivity Profile

Isocyanates and thioisocyanates, such as 4,4'-Diphenylmethane diisocyanate, are incompatible with many classes of compounds, reacting exothermically to release toxic gases. Reactions with amines, aldehydes, alcohols, alkali metals, ketones, mercaptans, strong oxidizers, hydrides, phenols, and peroxides can cause vigorous releases of heat. Acids and bases initiate polymerization reactions in these materials. Some isocyanates react with water to form amines and liberate carbon dioxide. Base-catalysed reactions of isocyanates with alcohols should be carried out in inert solvents. Such reactions in the absence of solvents often occur with explosive violence, [Wischmeyer(1969)].

Health Hazard

Breathlessness, chest discomfort, and reduced pulmonary function.

Health Hazard

MDI can present a moderate to severe healthhazard, because of respiration of its vapors and particulates. It can contaminate the environment during foam application; concentrations in air were measured as high as5 mg/m³, mostly as particulates (ACGIH1986).
The toxic route is primarily inhalation.The vapor pressure of this compound atambient temperature is very low, 0.00014torr at 25°C. However, when heated to about75°C, the acute health hazard is greatlyenhanced (Hadengue and Philbert 1983). Theacute toxic symptoms were found to besimilar to those of toluene-2,4-diisocyanateand other aromatic isocyanates. Inhalation ofits vapors or particulates can cause bronchitis, coughing, fever, and an asthma-likesyndrome. Other symptoms were nausea,shortness of breath, chest pain, insomnia,and irritation of the eyes, nose, and throat.The immunologic response, however, variedamong humans. Exposure to 0.1–0.2 ppmfor 30 minutes is likely to manifest the acutetoxic effects in humans.
MDI is an eye and skin irritant. Contactwith skin can produce eczema. The acuteoral toxicity of this compound is very low,considerably lower than that of toluene-2,4-diisocyanate. The lethal dose for rats was31.7 g/kg.
MDI showed positive in mutagenic testingon Salmonella typhimurium. There is noreport that indicates its carcinogenicity.

Fire Hazard

Noncombustible; flash point (open cup) 202°C (395°F). MDI reactions with strong oxidizers, acids, and bases can be vigorous.

Flammability and Explosibility

Non flammable

Contact allergens

MDI is used in the manufacture of various polyurethane products: elastic and rigid foams, paints, lacquers, adhesives, binding agents, synthetic rubbers, and elastomeric fibers.

Safety Profile

Poison by inhalation. Mildly toxic by ingestion. Human systemic effects by inhalation: increased immune response and body temperature. A skin and eye irritant. An allergic sensitizer. Questionable carcinogen. Mutation data reported. A flammable liquid. When heated to decomposition it emits toxic fumes of NOx and SOx.

Potential Exposure

MDI is used in the production of polyurethane foams and plastics; polyurethane coatings; elastomers, and thermoplastic resins.

First aid

If this chemical gets into the eyes, remove anycontact lenses at once and irrigate immediately for at least15 min, occasionally lifting upper and lower lids. Seek med-ical attention immediately. If this chemical contacts theskin, remove contaminated clothing and wash immediatelywith soap and water. Seek medical attention immediately. Ifthis chemical has been inhaled, remove from exposure,begin rescue breathing (using universal precautions, includ-ing resuscitation mask) if breathing has stopped and CPR ifheart action has stopped. Transfer promptly to a medicalfacility. When this chemical has been swallowed, get medi-cal attention. Give large quantities of water and inducevomiting. Do not make an unconscious person vomit.Medical observation is recommended for 24- -48 h afterbreathing overexposure, as pulmonary edema may bedelayed. As first aid for pulmonary edema, a doctor orauthorized paramedic may consider administering a corticosteroid spray.

Environmental Fate

Due to its low vapor pressure (0.000 62 Pa at 20 ℃), MDI partitioning to the atmosphere is limited; and vapors are rapidly eliminated by reaction with hydroxyl radicals (22 h half-life). Degradation by either direct photolysis or hydrolysis by water vapor to methylenedianiline (MDA) does not play a significant role in the atmospheric fate of MDI. In water, the isocyanate group of MDI can be rapidly hydrolyzed to an amine (<1 min half-life) that in turn reacts at a much faster rate with another isocyanate group to yield urea. Because MDI has two isocyanate groups, these reactions lead to cross-linked polyureas, which are inert, insoluble solids. Unless MDI is well dispersed in water, these processes result in the formation of a solid polyurea crust that encases the unreacted material, restricts both water ingress and amine egress, and leads to higher yields of polyurea. Under stirred aqueous conditions, the fraction of 4,4'-MDI converted to 4,4'-MDA is less than 1%; unstirred, the fraction is 0.005%. MDI released to soil will not exhibit significant transport to other environmental media due to the favored reaction with water to form inert polyureas and binding to the soil biomass. As expected, pMDI and the waterinsoluble oligo- and polyureas that form when pMDI enters an aqueous environment showed no biodegradation over 28 days in a guideline study.

storage

Color Code—Blue: Health Hazard/Poison: Storein a secure poison location. Prior to working with thischemical you should be trained on its proper handling andstorage. Store at temperatures indicated on labels, separatelyfrom acids, bases, amines, alcohols and ammonia, and withventilation along the floor. Since MDI will react with moisture in the air, the storage area should be a dry place, awayfrom all sources of fire or ignition.

Shipping

UN2811 Toxic solids, organic, n.o.s., Hazard Class: 6.1; Labels: 6.1-Poisonous materials, Technical Name Required

Toxicity evaluation

The primary health concern with exposure to MDI is dermal and respiratory sensitization. Both are initiated by conjugation of MDI isocyanate groups with macromolecules at the point of contact, which forms a hapten that subsequently activates immunologic processes resulting in sensitization. Data in animals indicate dermal contact with MDI can lead to respiratory sensitization. However, the human relevance of these observations is unclear since there are no validated animal models that accurately reflect the respiratory sensitization process and responses seen in humans. The low incidence of pulmonary tumors observed in chronic inhalation studies at maximum tolerated concentrations of pMDI is most likely the result of nongenotoxic cell proliferation associated with chronic inflammation and/or hyperplasia rather than a direct effect on DNA.

Incompatibilities

May form explosive mixture with air. Isocyanates are highly flammable and reactive with many compounds, even with themselves. Incompatible with oxidizers (chlorates, nitrates, peroxides, permanganates, perchlorates, chlorine, bromine, fluorine, etc.); contact may cause fires or explosions. Reaction with moist air, water or alcohols may form amines and insoluble polyureas and react exothermically, releasing toxic, corrosive or flammable gases, including carbon dioxide; and, at the same time, may generate a violent release of heat increasing the concentration of fumes in the air. Incompatible with amines, aldehydes, alkali metals, ammonia, carboxylic acids, caprolactum, alkaline materials, glycols, ketones, mercaptans, hydrides, organotin catalysts, phenols, strong acids, strong bases, strong reducing agents such as hydrides, urethanes, ureas. Elevated temperatures or contact with acids, bases, tertiary amines, and acylchlorides may cause explosive polymerization. Attacks some plastics, rubber and coatings. May accumulate static electrical charges, and may cause ignition of its vapors. Unstable above 100F/38C. Polymerizes at temperatures above 204C. Contact with metals may evolve flammable hydrogen gas.

Waste Disposal

Controlled incineration (oxides of nitrogen are removed from the effluent gas by scrubbers and/or thermal devices).