Isocyanates hazards

The isocyanate and polyol storage units must not share pumps or any fittings. The fitting must be such that there is no way that the wrong material can be added to a tank. All tanks must be clearly labeled with their contents and the appropriate safety signs, for example, isocyanate hazard signs. Most regulatory authorities will require the tanks to be in a suitably sized bunded (diked) area. 

EXPLOSION and FIRE CONCERNS combustible NFPA rating (NA) reacts violently with alcohols and isocyanates hazardous polymerization will occur containers may explode under fire conditions incompatible with amines, alcohols, water, acids, strong alkalies, and heat heating to decomposition emits carbon monoxide, carbon dioxide, hydrogen cyanide, and oxides of nitrogen and sulfur use water spray, dry chemical powder, carbon dioxide, or foam for firefighting purposes. 

Paisley DPG (1969) Isocyanate hazard from wire insulation an old hazard in a new guise. Br J Ind Med 26 79-81... 

Precaution Combustible vapor is flamm. DOT poisonous material explosive and violent reactions possible polymerizes violently when combined with isocyanates Hazardous Decomp. Prods. CO, COj heated to decomp., emits acrid smoke and irritating tomes... 

The most overlooked hazard and contaminant is water (99). Water reacts with isocyanates at room temperature to yield both ureas and large quantities of carbon dioxide. The presence of water or moisture can produce a sufficient amount of CO2 to overpressurize and mpture containers. As Httle as 30 mL of water can result in 40 L of carbon dioxide which could result in pressures of up to 300 kPa (40 psi). For these reasons, the use of dry nitrogen atmospheres is recommended during handling. If a plant air system must be used, purification equipment, such as oil traps and drying beds, should be installed between the source and the isocyanate vessel. 

IntensiHcation This involves using so little hazardous material that it does not matter if it all leaks out. For example, at Bhopal, methyl isocyanate (MIC), the material that leaked and killed over 2000 people, was an intermediate for which it was convenient but not essential to store. Within a few years many companies had reduced their stocks of MIC and other hazardous intermediates. 

Substitution If intensification is not possible, then an alternative is to consider using a safer material in place of a hazardous one. Thus it may be possible to replace flammaole solvents, refrigerants, and heat-transfer media by nonflammable or less flammable (high-boiling) ones, hazardous products by safer ones, and processes which use hazardous raw materials or intermediates by processes which do not. As an example of the latter, the product manufactured at Bhopal (carbatyl) was made from three raw materials. Methyl isocyanate is formed as an intermediate. It is possible to react the same raw materials in a different order so that a different and less hazardous intermediate is formed. 

There is persisting interest in nylon-RIM materials as alternatives to polyurethane-RIM. Advantages of the nylon materials are the better shelf life and lower viscosity of the reaction components, ability to mould thick-walled articles, absence of a need for mould lubrication and the ability to avoid using isocyanates with their associated hazards. The main disadvantages of nylon-RIM are the need to have heated storage tanks and elevated temperature reactions, difficulties in catalyst handling and the high water absorption of the product. Possible markets include exterior car body components and appliance and business machine components. 

Among the hazardous chemical weapons scheduled class 1-3, methyl isocyanate becoming more and more important as a precursor [83]. This is just one among a number of substances which could be made via micro-reactor synthesis. Especially in the case of so-called binary weapons, where two relatively harmless substances are mixed to give a weapon, on-site mixing is demanded this can be accomplished with high performance by micro reactors. Pocket-sized miniature plants can neither be monitored nor detected. 

Another reaction with hazardous potential is the synthesis of methyl isocyanate from mefhylformamide, which was investigated using a micro reactor in industry [74],... 

The reaction rates of diisocyanates are strongly influenced by their molecular structure. The reactivity of isocyanate groups is enhanced by adjacent electron-withdrawing substituents. Aromatic rings are very effective electron withdrawing groups, and it is for this reason that the majority of commercial diisocyanates are aromatic. Many of the diisocyanates used commercially consist of mixtures of isomers. Some of the more important commercial diisocyanates are illustrated in Fig. 25.6. Diisocyanates must be handled carefully to avoid exposing workers to their hazardous vapors. 

Reportable Quantity Adjustment for Lead Metal, Lead Compounds, Lead-containing Hazardous Wastes, and Methyl Isocyanate-Final rule (40 CFR 117, 302, and 355) lead... 

Figure 1-11 The upper reaction is the methyl isocyanate route used at Bhopal. The lower reaction suggests an alternative reaction scheme using a less hazardous intermediate. Adapted from Chemical and Engineering News (Feb. 11, 1985), p. 30.

This handbook provides detailed working procedures for those exposed to isocyanates and other chemicals used in flexible foam manufacture, supplying hazard data for individual chemicals and recommending handling practices. This second edition provides the most up-to date information regarding topics covered in the first edition and also includes a code of practice for the manufacture of polyurethane elastomers using MbOCA. 

Amendments to the EC Directives regulating the reclassification of free isocyanate levels came into effect on January 1. Underthe new regulations, TDI prepolymers must be labelled according to the content of free TDI. In preparation for the new regulations, suppliers have been moving to offer finished products with lower levels of free TDI, if possible, to below the minimum required level for hazard labelling. 

Tyrer FH Hazards of spraying with two-pack paints containing isocyanates. Soc Occup Med 29 22-24, 1979... 

Certain structural features, including whether it contains functional groups such as aldehydes, ketones, nitriles, or isocyanates, often define a class of chemicals. If information on the mechanism of action of a hazardous property of a chemical is not known, or if variances in the chemical s hazard through structural modification cannot be determined, then the assumption that certain chemically reactive functional groups can react similarly with the body or in the environment is often a good starting point in the process of evaluating the safety of solvents. 

Polymethylene Polyphenyl Isocyanate — Fire Hazards Flash Point (deg. F) 425 OC ... 

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