Process for the production of spray polyurethane elastomers and the elastomers produced by this process
View Patent ↗Polyurethane elastomers having solids contents greater than 40% by weight are produced from a sprayable polyurethane-forming system composed of an isocyanate component and an isocyanate-reactive component. The isocyanate component has a solids content of from 40 to 80 wt. %, based on total weight of isocyanate component and is made up of at least one aromatic polyisocyanate having an NCO content of from 24 to 33%, a functionality of from 2 to 3 and at least one solid filler. The isocyanate-reactive component has a solids content of from 40 to 80 wt. %, based on total weight of the isocyanate-reactive component and is composed of at least one polyether polyol having a hydroxyl number of from 25 to 40 and a functionality of from 2 to 4, and at least one solid filler.
1. A polyurethane-forming composition suitable for the production of a polyurethane elastomer by spraying comprising:
a) an isocyanate component having a solids content of from 40 to 80 wt. %, based on total weight of isocyanate component and a viscosity at 25° C of less than 4,000 mPa.s comprising:
(i) at least one aromatic polyisocyanate having an NCO content of from 24 to 33%, a functionality of from 2 to 3 and
(ii) at least one solid filler present in an amount sufficient to obtain the solids content of a)
and
b) an isocyanate-reactive component having a solids content of from 40 to 80 wt. %, based on total weight of the isocyanate-reactive component and a viscosity at 25° C of less than 4,000 mPa.s comprising:
(i) at least one polyether polyol having a hydroxyl number of from 25 to 40 and a functionality of from 2 to 4, and
(ii) at least one solid filler present in an amount sufficient to obtain the solids content of b)
wherein the total solids contents of a) plus b) is from 40 to 80 wt. %, based on total weight of the polyurethane-forming system.
2. The composition of claim 1 in which the polyisocyanate is a polymeric MDI, a modified MDI or a mixture thereof.
3. The composition of claim 1 in which the solid filler for each of components a) and h) is selected from barium sulfate and calciuria carbonate.
4. The composition of claim 1 in which the same filler is used in each of components a) and b).
5. The composition of claim 4 in which the filler is barium sulfate.
6. The composition of claim 1 in which the solid filler is present in the isocyanate component in an amount of from 50 to 70% by weight.
7. The composition of claim 1 in which the solid filler is present in the isocyanate reactive component in an amount of from 50 to 70% by weight.
8. The composition of claim 1 in which the total solids content is from 50 to 70% by weight.
9. The composition of claim 1 in which the viscosity of each of the isocyanate component and the isocyanate-reactive component is less than 3000 mPa.s.
10. The composition of claim 1 in which the isocyanate and the isocyanate-reactive components are reacted in an NCO/OH ratio of from 60 to 160.
11. The composition of claim 1 in which component b) further includes an amine-based polyether polyol having a hydroxyl number of from 600 to 660 mg KOH/g.
12. The composition of claim 1 in which component b) further includes a propylene oxide-based triol having a hydroxyl number of from 220 to 260 mg KOH/g.
13. The composition of claim 12 in which component b) further includes an amine-based polyether polyol having a hydroxyl number of from 600 to 660 mg KOH/g.
14. An elastomer produced by spraying the polyurethane-forming composition of claim 1 .
15. An elastomer produced by spraying the polyurethane-forming composition of claim 5 .
16. A process for the production of a polyurethane elastomer comprising spraying the composition of claim 1 .