Honeycomb sandwich panels and the use of a two component polyurethane adhesive in the manufacture thereof

1. A process of manufacturing a honeycomb sandwich panel comprising:

mixing a component C 1 and a component C 2 of a two component polyurethane adhesive composition to obtain a mixed two component polyurethane adhesive;

joining a panel substrate S 1 to a honeycomb core with the mixed two component polyurethane adhesive;

joining a panel substrate S 2 to the honeycomb core with the mixed two component polyurethane adhesive; and

pressing and heating, at a temperature of 50 to 100° C., a joint of the honeycomb sandwich panel by means of a heated press,

wherein:

the component C 1 comprises at least one polyol P 1 having a bisphenol-A or bisphenol-F moiety, at least one polyester polyol or polyether polyol P 2 , and at least one heat-activated polyurethane catalyst CA; and

the component C 2 comprises at least one polyisocyanate PI.

2. The process according to claim 1 , wherein the adhesive has a Shore D hardness of 70 to 90 after heating at a temperature of 65 to 70° C. for 5 minutes.

3. The process according to claim 1 , wherein at least one of the panel substrate S 1 and the panel substrate S 2 is made of a metal.

4. The process according to claim 1 , wherein the honeycomb core is made of a metal.

5. The process according to claim 1 , wherein the joint is heated at a temperature of 60 to 80° C.

6. The process according to claim 1 , wherein the polyol P 1 has a molecular weight Mw between 200 and 600 g/mol.

7. The process according to claim 1 , wherein the heat-activated polyurethane catalyst CA is based on a tertiary amine.

8. The process according to claim 1 , wherein the polyisocyanate PI is a diisocyanate.

9. The process according to claim 1 , wherein at least one of the component C 1 and component C 2 further comprises a thixotropic agent.

10. The process according to claim 1 , wherein the Brookfield viscosity, when measured directly after mixing of the components C 1 and C 2 with a rotor nr. 5 and a rotor speed of 10 rotations per minute at a temperature of 23° C. (Brookfield DV 11 ), is in the range of 3,000 to 15,000 mPas.

11. The process according to claim 1 , wherein the adhesive has an open time of 10 to 60 minutes at a temperature of 23° C. and a relative humidity of 50%.

12. The process according to claim 1 , wherein the adhesive has a curing time of 5 to 10 minutes at a temperature of 60° C. to 80° C.

13. The process according to claim 1 , wherein the two component polyurethane adhesive composition comprises the polyisocyanate PI in such an amount that a ratio of the isocyanate groups in component C 2 to the groups reactive to isocyanate groups in component C 1 is 0.8 to 1.2.

14. A process of manufacturing an article comprising:

performing the process of manufacturing a honeycomb sandwich panel according to claim 1 , and

providing the honeycomb sandwich panel to the article under manufacture.

15. A process of manufacturing a transport vessel comprising:

performing the process of manufacturing a honeycomb sandwich panel according to claim 1 , and

providing the honeycomb sandwich panel to the transport vessel under manufacture.

16. A process of constructing a building comprising:

performing the process of manufacturing a honeycomb sandwich panel according to claim 1 , and

providing the honeycomb sandwich panel to the building under construction.

17. The process according to claim 1 , wherein the polyol P 1 has a molecular weight Mw between 300 and 500 g/mol.

18. The process according to claim 1 , wherein the heat-activated polyurethane catalyst CA is based on a cyclic tertiary amine.

19. The process according to claim 1 , wherein the polyisocyanate PI is methylene diphenyl 4,4′-diisocyanate, methylene diphenyl 2,4′-diisocyanate, methylene diphenyl 2,2′-diisocyanate (MDI) or polymeric MDI (PMDI).

20. The process according to claim 1 , wherein the adhesive has an open time of 30 to 45 minutes at a temperature of 23° C. and a relative humidity of 50%.