Emanation Free Catalysis for the Production of Polyether Polyurethane Foam

摘要

Growing concerns about emanations from polyurethane foam were the reasons for many changes over the last few years, both in the raw materials and in the formulations. The compounds being responsible for the overall emissions from foam were identified and on the basis of newly developed analytical methods and standards, research work has been carried out in order to meet the new criteria. For example, alternative ways of manufacturing and stabilizing polyols became the new standard several years ago. Besides the changes in the quality of the bulk materials, the suppliers of the additives - the surfactants, amines and tin catalysts - also developed low emission solutions. Surfactants with low amount of fugitive compounds and amines of the reactive type have previously been the subject of several presentations. However, one of the identified compounds from the overall emissions from polyurethane foam - the 2-ethylhexanoic acid (2-EHA) -has been the subject of only a small number of papers. The 2-EHA is the decomposition product of the stannous octoate, the KOSMOS~(~R) 29, which is well known as the gelling catalyst in polyurethane foaming. According to the Daimler-Chrysler VOC analysis [1], a dynamic headspace analysis, 2-EHA accounts for the biggest portion of the identified volatile compounds in hot cured foams, usually followed by the amine related emissions. The limits that were set by Daimler-Chrysler as the latest target were very low: 100 ppm in the VOC analysis is the current figure. But in today's conventional foams, results as high as 500 ppm VOC are typical. The target figure of only 100 ppm is roughly equivalent to 50% of the current 2-EHA contribution and similar in size to the amine portion in the overall emission. These values are obtained from the analysis of foam, produced using a standard formulation for a 25 kg/m3 density flexible polyether foam. Many approaches to reduce the emission of volatiles were based on the application of reactive amines. Suitable alternative amine catalysts have now been identified, which no longer contribute to the emanations, However, regarding the overall emission rate, a big portion has still remained almost unchanged throughout the years -the 2-EHA.