9. Environmental Considerations

The following recommendations should be interpreted in light of existing and future legislation. The disposal of liquid MDI wastes and used containers may be regulated by local, state, provincial, and federal agencies.

Disposal of Waste MDI Products

MDI products are classified as non-hazardous materials for disposal per US Environmental Protection Agency (EPA) Resource Conservation and Recovery Act (RCRA) and Canadian Provincial regulations. There are three basic methods for disposing of liquid MDI wastes. The choice of method will depend in part on the amount of waste to be treated and the availability of decontaminants. It is important to note that some states have greater restrictions than federal regulations and may consider MDI to be a hazardous waste. Be sure, therefore, to check with the appropriate state and regulatory agencies before disposing of waste MDI or MDI-based
polyurethane foams.

Method 1: Incineration

Incineration under approved, controlled conditions is the preferred method for all but small amounts of MDI product. It should, however, only be done in properly monitored equipment specifically designed for the disposal of noxious
chemical wastes and properly permitted by the local, state, provincial, and federal agencies. In the United States, only federally approved incinerators may be used.

Method 2: Reaction with Liquid Decontaminants

The waste MDI product should be added slowly and stirred into the liquid decontaminant (see Section 8 for preparation of decontaminating solution) in an open-top container. Be sure this process is conducted in a well-ventilated area. It is recommended that one part of MDI be added to ten parts of decontaminating solution. Adding the decontaminating solution to the MDI may produce excessive heat. The amount of MDI product treated should not exceed 10% of the amount of decontaminating solution used. Leave the treated drum for 48 hours in a properly ventilated area to allow evolved carbon dioxide to escape. Decant the liquid and dispose of both the liquid and solid material according to all federal, state, and local regulations.

Method 3: Reaction with Waste Polyol

React MDI waste with activated waste polyol to make low quality polyurethane foam which can be sold or used as
a manufactured product. If the foam produced is to be disposed, applicable regulations must be followed. In the
United States, all foam produced in this manner for disposal is classified as "Non-Hazardous Waste," regulated
under RCRA. This method should only be used when a correct stoichiometric mixing can be guaranteed. Improper mixing will leave a product containing unreacted MDI or polyol. In general, if intended for disposal, this is a less
desirable method for use due to the large volume of foam produced. Caution: The MDI/polyol reaction is exothermic, which may cause spontaneous combustion.

Decontamination and Disposal of Used Containers

MDI products may be delivered in drums. These drums are designed to be one-way packages and cannot be returned to the suppliers.

Residual MDI product will remain in the drum until it has been completely emptied. Local and federal regulations vary concerning the disposal of empty containers. Empty MDI drums are potentially hazardous and should therefore only be handled by trained personnel. Personnel should be trained to empty MDI drums completely. Residual MDI product may remain in the drum after proper draining (this residual must be 0.1-2.0 kilograms, or less than one inch depending on product and drum type, to be considered “empty” by RCRA standards). All MDI drums, after being well drained, should be decontaminated with a prepared decontaminating solution using the following procedure:

1. Spray or pour 5 - 30 liters (2 to 8 gallons) of decontaminating solution into the drum, making sure the walls are well rinsed. This can be achieved by use of a spray head or by rolling the drum for several minutes. The use of high-pressure spray equipment can significantly improve the speed and effectiveness of drum cleaning.
2. Leave drum standing unsealed for at least 48 hours to allow complete reaction. Sealing of the drum must be avoided to prevent pressure buildup by evolved CO2.
3. Pour out liquid decontaminant into a storage vessel. The decontaminating solution can be used several times. There are, however, disadvantages to using this method. The resulting crust can conceal unreacted diisocyanate, especially in the case of drums not having been adequately drained. It is also difficult to remove the crust from the walls of the drum.

This procedure is required to assist reconditioning firms and is often mandatory for the acceptance of the waste
drums for reconditioning. Only after proper cleaning can drums be recycled or scrapped without any hazard. In most countries, organizations of drum scrappers have been formed. They should be consulted for details concerning the collection and reprocessing of both cleaned and uncleaned MDI drums.

If decontaminated drums are to be disposed of, they should be punctured to prevent reuse. Independent of the method used, cleaned MDI drums must not be used for the storage of food or animal fodder.

All local and federal regulations must be complied with when cleaning and disposing of empty MDI drums.

Some nations allow well-drained drums to be sent to a permitted re-conditioner without being decontaminated. If this is allowed, the empty drums must be labeled analogous to the filled drums and all closures must be tight to prevent water contamination. Water contamination can cause CO2 gas to be evolved, which could pressurize the drum and create a serious hazard.

Under no circumstances should empty MDI drums be burned or cut open with a gas or electric torch, as toxic decomposition products may be liberated.

Ecological Effects

Ecotoxicology investigations to date have shown that MDI products are not appreciably toxic to fish, bacteria, and invertebrates (LC50>100 mg/L) or to worms and plants (LC/EC50≥1,000 mg/L).

The reaction products of MDI and water are not biodegradable but are chemically inert. See References: MDI Transportation Guidelines, CPI (2002)