9. Environmental Considerations

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

Disposal of Waste TDI

Waste TDI products are hazardous materials and must always be disposed of in accordance with local and federal pollution control regulations. There are three basic methods for disposing of liquid TDI wastes. The choice of method will depend in part on the amount of waste to be treated and the availability of decontaminates. In the United States, TDI treatment and disposal are regulated under the Resource Conservation and Recovery Act (RCRA). Under RCRA, any facility generating more than 1,000 kilograms (2,205 pounds) of hazardous waste per month must obtain a permit from the Environmental Protection Agency (EPA) to treat TDI products for disposal.

Method 1: Incineration

Incineration under approved, controlled conditions is the preferred method for all but small amounts of TDI product. It should, however, only be done in properly supervised 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 federal approved incinerators may be used.

Method 2: Reaction with liquid decontaminants

The waste TDI product should be added slowly and stirred into the liquid decontaminates (See Section 8 for preparation of decontaminate solution) in an open-top container. Be sure this process is conducted in a well ventilated area. TDI should be added to the decontaminate. Adding the decontaminate solution to the TDI may produce excessive heat. The amount of TDI product to be treated should not exceed 10% of the amount of decontaminant used. Leave the treated drum for 48 hours in a properly ventilated area; this will remove the toxic hazard. Decant the liquid and dispose of both the liquid and solid material according to all local, state, provincial and federal regulations. The decontamination products are classified as hazardous wastes in the United States
and generally in Europe.

Method 3: Reaction with waste polyol

React TDI waste with activated waste polyol to make a low-quality polyurethane foam, which can be sold or used as a manufactured product. If the foam produced is to be disposed of, all regulations must be adhered to. In the United States, all foam produced in this manner for disposal is classified as “Hazardous Waste,” regulated under RCRA. In Europe, such foam, if free of unreacted components, can generally be incinerated or disposed of as normal house waste in an authorized waste disposal area. This method should only be used when a correct stoichiometric mixing can be guaranteed. Improper mixing will leave a product containing unreacted TDI 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 TDI/ polyol reaction is exothermic, which may cause spontaneous combustion.

Decontamination and Disposal of Used Containers

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

Residual TDI product will remain in the drum until it has been completely emptied. Local and federal regulations vary concerning the disposal of empty containers. Empty TDI drums are potentially hazardous and should, therefore, only be handled by trained personnel. Personnel should be trained to empty TDI drums completely. Residual MDI product may remain in the drum after proper draining (the 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 TDI drums, after being well drained, should be decontaminated with a prepared decontamination solution using the
following procedure:

1. Spray or pour 5 – 30 liters (2 – 8 gallons) of decontamination solution into the drum, making sure the walls are well rinsed. This can be achieved by using 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 the drum standing unsealed for at least 48 hours to allow complete reaction. Sealing of the drum must be avoided to prevent pressure build-up by evolved CO2.
3. Pour out the liquid decontaminate into a storage vessel. This solution can be used several times. There are two disadvantages to using this simple method. The resulting crust can conceal unreacted diisocyanate, especially in the case of drums not having been adequately drained. Furthermore, it is 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 TDI drums.

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

Comply with all local and federal regulations when cleaning and disposing of empty TDI 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 ones 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 TDI drums be burned or cut open with a gas or electric torch, as toxic decomposed products may be liberated.

Ecological Effects

Environmental toxicity test data is reported as follows:

Daphnia magna, 24hr LC50 - >500 mg / L. Practically nontoxic

Zebra Fish, Static 24hr LC50 - >500 mg / L. Practically nontoxic

Redwing Blackbird, Oral LD50 - 100 mg / L. Not appreciably toxic