PAPI 94 POLYMERIC MDI - DOW

Harmful if inhaled. Causes skin irritation. Causes serious eye irritation. May cause allergy or asthma symptoms or breathing difficulties if inhaled. May cause an allergic skin reaction. (See handling precautions). Occupational Exposure Limits (OELs) have been set for Isocyanates in most countries. The atmospheric levels should be maintained below the exposure guidelines.

Avoid contact with eyes, skin, or clothing. Workers should wear appropriate eye protection. Safety glasses are considered a minimum requirement. If there is the possibility of exposure to the eyes, chemical workers’ goggles must be worn. Avoid breathing vapor or mist. Wear protective clothing impervious to Isocyanates, overalls, boots, apron and gloves. If handled indoors, provide mechanical exhaust ventilation. General or local exhaust ventilation should be provided to control airborne levels below the exposure guidelines. During spray operations, airline masks or positive pressure hose masks should be worn because of the high concentration of isocyanate mist in the atmosphere. The vapor pressure of all MDI is low at room temperature (see SDS for values). However, at temperatures over 40°C (104°F), the vapor pressure increases enough that low functionality MDI products begin to constitute a toxic hazard. Aerosol mists can also be problem.

Shipping and storage temperatures for isocyanates are critical. Recommended temperatures should be strictly followed: Isocyanates are products with limited shelf life. Depending upon the isomer and oligomer composition, specific storage temperature and shelf life must be applied. If shipping or storage temperature should fall below recommended temperature, some crystallization could result. Polymeric and modified pure MDI products that have been frozen will exhibit the same dimerization characteristics as pure MDI. Unless proper action is taken to heat or melt the product, dimerization will proceed rapidly and deteriorate the clarity, shelf life and assay of the product. Crystallized isocyanate can be melted, but dimer cannot be removed by heating. Keep container closed as moisture contamination will induce an exothermic reaction with evolution of carbon dioxide (CO2 ) which may cause dangerous pressure generation. Isocyanates should be stored separately from chemicals that may react with them (i.e. amines, polyols, etc.) Bulk Storage: Construction material for tanks, lines, pumps, etc. can be mild steel for storage at temperatures up to 35°C. Series 300 stainless steel or stainless cladding is recommended for storage at temperatures above 35°C. Only low temperature heating media should be used in tank jackets or coils unless adequate circulation or agitation of the isocyanate is maintained. A slight positive pressure using dry inert -40°C (-40°F) dew point nitrogen must be maintained in bulk storage tanks of isocyanate to prevent solids formation from occurring in the presence of atmospheric moisture. If nitrogen is unavailable, a pad of -40°C (-40°F) dew point air may be used. For low viscosity isocyanates, such as pure MDI and TDI, transfer pumps should contain a stainless steel shaft with mechanical seals. Packed glands can leak sufficiently to cause reaction with moisture and subsequent scoring of the pump shaft by the formed ureas. Drum Storage Isocyanates will react when exposed to atmospheric moisture. Where drums are to be partially emptied, it is recommended that a calcium chloride-filled dryer tube be used in the air bleed opening. Should the isocyanate be exposed to moisture, a skin will develop on its surface similar to that found on paint. Normally, however, the remaining liquid under the skin may be used without formulation changes. Filtration should be considered to avoid issues during processing such as restricted filter and injection nozzles. At temperatures below the recommended low storage temperature limit, crystallization of the isocyanate can occur. Unless proper action is taken to heat or melt the product, dimerization will proceed rapidly and deteriorate both the clarity and assay of the product. Crystallized isocyanate can be melted, but dimer cannot be removed by heating.