Thermal insulating structures

1. In combination with a substrate for use subsea, a thermal insulating structure applied to the substrate and for use subsea, the thermal insulating structure including comprising:

a flexible inner tie coat which is bonded to the substrate, the tie coat consisting of the reaction product of a first material and a second material, the first material consisting of respective amounts of a cold curing phenolic resin and an anti cissing agent, and respective amounts of materials selected from the group consisting of a plasticizer, a silane coupling agent, fumed silica, cenospheres, water, and a dispersion aid, and the second material consisting of a partial phosphate ester and respective amounts of materials selected from the group consisting of a cure accelerator and water; a foam insulating layer which is the reaction product of a first material including a cold cure phenolic syntactic resin and a second material including a partial phosphate ester and which insulating layer includes between 15 and 30% by weight cenospheres and a nitrile butadiene rubber flexibilizer up to a maximum of 20% by weight; and an outer protective layer which is the reaction product of a first material including a cold cure phenolic resin and a second material including a partial phosphate ester, the outer protective layer having a greater thickness than the inner tie coat layer.

2. The combination according to claim 1 , in which the tie coat, insulating layer and/or outer layer each includes between 0.5 and 2.5% by weight of an amino functional silane coupling agent.

3. The combination according to claim 1 , in which in the tie coat the first material includes 50-75% by weight phenolic resin.

4. The combination according to claim 1 , in which the phenolic resin of the tie coat first material is a resol phenolic resin, has a water content of not greater than 16% by weight, and/or includes up to 2% by weight ethanediol as a plasticiser.

5. The combination according to claim 1 , in which the tie coat first material includes between 1 and 4% by weight fumed silica, and includes between 15 and 30% by weight cenospheres.

6. The combination according to claim 1 , in which the cenospheres have a specific gravity of between 0.005 and 0.02.

7. The combination according to claim 1 , in which the tie coat second material includes: between 90 and 98% by weight partial phosphate ester; up to 1% by weight sulphonic acid as a cure accelerator; and/or up to 10% by weight water.

8. The combination according to claim 1 , in which the ratio of first to second materials of the tie coat is between 5:1 and 10:1.

9. The combination according to claim 1 , in which the proportion of first material to second material of the insulating layer is between 4:1 and 10:1.

10. The combination according to claim 1 , in which the ratio of first material to second material of the outer layer is between 10:1 and 20:1.

11. The combination according to claim 1 , in which the insulating layer first material includes between 35 and 75% by weight phenolic resin; in which the phenolic resin of the insulating layer first material is a resol phenolic resin; and/or has a water content not greater than 16% by weight.

12. The combination according to claim 1 , in which the insulating layer first material includes up to 7% by weight di ethyl phosphonate as a plasticizer.

13. The combination according to or claim 1 , in which the insulating layer first material includes: up to 2.5% by weight of the silane coupling agent;

includes up to 5% by weight glass strands between 3 and 12 mm long; and includes up to 5% by weight zirconia fibre.

14. The combination according to claim 1 , in which the insulating layer second material includes up to 3% by weight para toluene sulphonic acid as a curing accelerator, and includes water.

15. The combination according to claim 1 , in which: the outer layer first material includes between 50 and 100% by weight of the phenolic resin; the phenolic resin of the outer layer first material is a resol phenolic resin; the phenolic resin of the outer layer first material has a water content of not greater than 16% by weight; the outer layer first material includes up to 2.5% by weight of a silane coupling agent; the outer layer first material includes up to 1% by weight ethanediol; and/or the outer layer first material includes up to 4% by weight fumed silica.

16. The combination according to claim 1 , in which fibre reinforcement is included in the outer layer, and the fibres are of glass or carbon.

17. The combination according to claim 1 , in which the inner tie coat layer is 0.15 to 1 mm thick.

18. The combination according to claim 1 , in which the outer protective layer is 3 to 5 mm thick.