Low-monomer polyurethane foams

摘要

Cross-linkable foamable composition with low content of monomeric isocyanates, containing a pre-polymer of polyester diols and/or polyether dials reacted i) with asymmetric aromatic diisocyanates to form a reaction product with OH and NCO groups, ii) subsequent addition of and reaction with symmetric aromatic diisocyanate in a quantity at least equivalent to the available OH-groups, 0.1 to 30 wt % additives, at least one propellant, wherein the polyols have a molar mass (MN) of less than 5000 g/mol, and the reaction product has a content of less than 0.1 wt % monomeric asymmetric isocyanate and less than 2 wt % monomeric symmetric isocyanate.

主权项

1. A crosslinkable composition with a low content of monomeric isocyanates comprising:
a) a prepolymer produced from polyester polyols and/or polyether polyols reacted i) with an asymmetric aromatic diisocyanate to yield a reaction product containing OH and NCO groups, ii) subsequent reaction with symmetrical aromatic diisocyanates in a quantity at least equivalent to the OH groups present, wherein the prepolymers have a viscosity from 10,000 to 150,000 mPas at 50° C. (measured by Brookfield, EN ISO 2555), b) 0.1 to 30 wt % additives based on weight of the prepolymer and the additives, and c) at least one blowing agent in a quantity capable of foaming the composition; wherein the polyols exhibit a molar mass (MN) of less than 5000 g/mol, and the prepolymer a) has a content of monomeric asymmetric diisocyanates (A) of less than 0.1 wt % and of monomeric symmetric diisocyanates (S) of less than 2 wt % and the NCO(isocyanate S):OH ratio of the OH groups still present to the NCO groups of the symmetrical diisocyanate of ii) is 1:1 to 2.7:1, and 4,4′-MDI is used.