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
MDI is a white to light-yellow, odorless
flakes. A liquid above 37C.
Chemical Properties
white to light yellow flakes or crystals
Uses
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.
Uses
Diphenylmethane-4,4-diisocyanate (MDI)is widely used in the production ofrigid urethane foam products, coatings, andelastomers..
Uses
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.
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.
Definition
ChEBI: A diisocyanate consisting of diphenylmethane with two isocyanate groups at the 4- and 4'-positions.
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
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/m
3, 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.
Health Hazard
Breathlessness, chest discomfort, and reduced pulmonary function.
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).
