| abstract |
A process for preparing a polyisocyanurate polyurethane material, which process comprises reacting a polyisocyanate and an isocyanate-reactive composition, wherein the reaction is conducted at an isocyanate index of 150 to 5000 and in the presence of a trimerisation catalyst, wherein the polyisocyanate comprises a) 80-100% by weight of diphenylmethane diisocyanate comprising at least 40%, preferably at least 60% and most preferably at least 85% by weight of 4,4′-diphenylmethane diisocyanate and/or a variant of said diphenylmethane diisocyanate which variant is liquid at 25° C. and has an NCO value of at least 20% by weight (polyisocyanate a), and b) 20-0% by weight of another polyisocyanate (polyisocyanate b), the amount of polyisocyanate a) and polyisocyanate b) being calculated on the total amount of this polyisocyanate a) and polyisocyanate b), and wherein the isocyanate-reactive composition comprises a) 80-100% by weight of a polyether polyol having an average nominal functionality of 2-6, an average equivalent weight of 1100-5000 and an oxyethylene (EO) content of 50-90% by weight and b) 20-0% by weight of one or more other isocyanate-reactive compounds, the amount of polyol a) and isocyanate-reactive compound b) being calculated on the total amount of this polyol a) and compound b) and wherein the hardblock content is at most 49%. |