New Catalysts for Low VOC in Flexible Slabstock Foam

Abstract

Until recently it was only the automotive industry that demanded a serious reduction of the amount of volatile organic compounds (VOC) from the (usually molded) polyurethane foam which is being used in their products. Now the end-users of bedding, furniture and carpet backing foam have joined them, and this time the pressure is on the manufacturers of flexible slabstock foam. It is for this reason that Nitroil Performance Chemicals have investigated if the solutions developed by this company for the molding area can also be applied to conventional slabstock. The main sources of VOC were additives like silicone surfactants and amine catalysts. For HR molding Nitroil evaluated a series of reactive amines in comparison to industrial standard amine catalysts such as triethylenediamine and bisdimethylaminoethylether. It appeared that by using only reactive amines the mine emission could be eliminated, and the total VOC could be reduced by 50% for TDI-based formulations and by 80% for MDI-based ones. Laboratory evaluation of reactive amines in a commercially used conventional slabstock formulation showed results of a similar nature. By replacing the standard non-reactive amines by reactive ones, reaction profiles could be obtained that were very similar to that of the reference formulation. The physical foam properties were only slightly affected. It could be demonstrated that a relation exists between the reactivity of the reactive amines and their effect on those properties that have a connection to cell-opening. Furthermore, it could be shown that some of the reactive amines (in particular PC CAT ^® BDP) had a beneficial effect on the initial foam “feel” (indentation), an important comfort operty. As for VOC: The amine contribution was eliminated. The main part of the remaining VOC consisted of ethylhexanoic acid, originating from the stannous octoate. As this was also reduced when reactive amines were used the total reduction of VOC was considerably larger than that caused by the amine elimination only. It varied from 30 to 75%. This might still be improved by improvements in the tin catalyst area and (to a much lesser extent) of the silicone surfactant.