Anti Cold Flow Additivefor PUR Flexible Slabstock Foams

摘要

Since the development of High Resilient (HR) foams, the slab stock foam producers are facing the problem of the socalled Cold Flow effect. In the past DBTL was in use to give the slab stock the necessary additional stability, since DBTL isbanned, Stannous-2-ethylhexoate is more and more in use. But the hardness increase with Stannous-2-ethylhexoate is notstrong enough to reach a sufficient mechanical stability. The Cold Flow effect results in a trapezium shape of the slab stockblock and is caused by the use of ingredients with higher reactivity like polyols with a high content of primary hydroxylgroups,special foam stabilizers and cross-linkers. This higher reactivity leads to the faster forming of the urethane bonds.This and the use of different kind of Silicones as foam stabilizer prevent the forming of crystallized urea agglomerates in themacro phase. But these hard urea segments are important to stabilise the foam block mechanically and chemically.The use of filled polyols like polymer polyols (SAN), PHD- or PIPA-Polyols in HR foams helps to overcome thisproblem, but can not totally solve it. Additives with retarded cross linking properties can help but lead to a furtheracceleration of the cross linking reaction. Therefore they have a negative influence on the processing properties of the foam.There is now a new not accelerating but retardant cross linking additive for improving the shape of slab stock blocksavailable. This new material not only improves the slab stock foam shape, it also increases the hardness and broadens theprocessing latitude.With this paper we want to show how this new additive acts and which advantages it can offer to the polyurethane slabstock foam industry.