New polyol improves foam production

Pranaya Pradhan, PO-D Technical Support Manager at Shell’s Bangalore Technology Centre

The introduction of a new additive polyol, which enhances the polymer stability and hardness of low density polyurethane foam, has been designed to help foam producers improve the safety of workers, raise foam quality and reduce their overall formulation costs.

The majority of low density foam is produced in developing markets where the emphasis is on low cost production and more affordable foam products. These foams are typically used in less demanding foam applications including packaging, bedding and disposable mattresses.

While cheaper to make, low density foams are harder to process as the foam is less stable during production, which can lead to a high rate of waste or sub-standard foam. Many manufacturers have resorted to formulation ‘quick fixes’, by using very high levels of TDI (toluene diisocyanate) in the formulation in order to improve foam stability.

The reaction between the polyol and TDI is at the heart of the foaming process. Increasing the TDI content promotes faster polymerisation, which can help to reduce the amount of flawed foam being produced. This approach has significant drawbacks, however, as it not only increases costs for these ‘foamers’ but also raises safety issues as a result of the increased TDI vapour levels in the production environment.

Emissions from normal concentrations of TDI can be managed by adequate venting and personal protective equipment, but higher concentrations become much harder to deal with and can be a serious threat to the health of workers.

Alternative approaches

Recognising this as a major issue for a key group of customers, the Propylene Oxide-Derivatives (PO-D) technical services team at Shell’s Bangalore Technology Centre in India looked into alternative approaches. They explored different formulation options, resulting in the development of CARADOL MD250-10, an additive polyol that enhances the polymerisation rate and hence stability during the foaming process.

“By using the additive polymer, customers can achieve the required foam hardness at normal levels of TDI concentration,” explains Pranaya Pradhan, Manager of PO-D Technical Support. “This enables them to improve the safety of workers while achieving higher foam quality and production reliability.

“Stabilising the foam with an additive polyol rather than increasing the level of TDI may also help to reduce overall formulation costs because they can avoid wasting excess TDI, which simply evaporates during the foaming process.”

This feature was added to the Innovations section in October 2010