Process for preparing a flexible polyurethane foam
View Patent ↗Process for preparing flexible polyurethane foam by reacting an MDI-based polyisocyanate and a polyether polyol with a high oxyethylene content in a mold.
1. A process for preparing a flexible polyurethane foam having an apparent overall density of 15–150 kg/m 3 comprising reacting in a mould a polyisocyanate and an isocyanate-reactive composition in the presence of water, wherein the reaction is conducted at an isocyanate index of 40 to 120, the polyisocyanate comprising:
a) 80–100% by weight of a diphenylmethane diisocyanate comprising at least 40% 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 5% by weight, and
b) 20–0% by weight of another polyisocyanate, and the isocyanate-reactive composition comprising:
a) 70–100% by weight of a polyether polyol having an average nominal functionality of 2–8, an average equivalent weight of 750–5000, an average molecular weight of 2000–12000, an oxyethylene content of 60–90% by weight and a primary hydroxyl content of 70–100% calculated on the number of primary and secondary hydroxyl groups in the polyol, and
b) 30–0% by weight of one or more other isocyanate-reactive compounds not being water.
2. The process of claim 1 , wherein the density of the flexible polyurethane foam is 25–50 kg/m 3 .
3. The process of claim 1 , wherein the amount of water is 0.8–5% by weight calculated on all other ingredients used.
4. The process of claim 2 , wherein the amount of water is 0.8–5% by weight calculated on all other ingredients used.
5. The process of claim 1 , wherein the reaction is conducted at an isocyanate index of 70–110.
6. The process of claim 2 , wherein the reaction is conducted at an isocyanate index of 70–110.
7. The process of claim 3 , wherein the reaction is conducted at an isocyanate index of 70–110.
8. The process of claim 4 , wherein the reaction is conducted at an isocyanate index of 70–110.
9. The process of claim 1 , wherein the oxyethylene content is 65–85% by weight, the average nominal functionality is 2–6, the average equivalent weight is 1000–4000 and the average molecular weight is 2000–10000 and the diphenylmethane diisocyanate comprises at least 85% by weight of 4,4′-diphenylmethane diisocyanate and/or a variant thereof.
10. The process of claim 1 , wherein the resilience of the foam is 40–80%.
11. The process of claim 1 , wherein 1 the resilience of the foam is 50–80%.
12. The process of claim 1 , wherein the variant has an NCO value of at least 20% by weight.
13. The process of claim 1 , wherein the process is conducted with restricted foam rise.
14. The process of claim 1 , wherein 1 the foam is allowed to rise in a closed mould.
15. The process of claim 1 , wherein an external mould release agent is applied onto at least those surfaces of the mould which will be in contact with the ingredients used for preparing the foam and/or the finished foam.
16. The process of claim 1 , wherein the process is conducted in a metal or epoxy resin mould.
17. A moulded flexible polyurethane foam having an apparent overall density of 25–50 kg/m 3 , an oxyethylene content of 35–60% by weight based on the weight of the foam, and a resilience of 50–80% and comprising oxyethylene and oxypropylene groups in a ratio of 1.5:1–9:1 w/w.
18. The moulded flexible polyurethane foam of claim 17 , wherein the foam has a load bearing capacity (CLD 40) of 1–15 kPa.
19. The moulded flexible polyurethane foam of claim 17 , wherein the foam has been prepared in a closed mould.