Adhesive derived from dimeric fatty acid or dimeric fatty diol

1. A moisture-curable adhesive comprising a reaction product of:

(i) at least one polyisocyanate; and

(ii) at least one polyester formed from:

a) a carboxylic acid component, comprising:

i) 60 to 100% by weight of dimer fatty acids, relative to the weight of the total weight of dicarboxylic acids; and

ii) 0 to 40% by weight of non-dimer fatty acids, relative to the weight of dicarboxylic acids, wherein the non-dimer fatty acids are aliphatic dicarboxylic acids having terminal carboxyl groups and a 2 to 20 carbon chain; and

b) a polyol component;

wherein:

i) the NCO:OH molar ratio of the at least one polyisocyanate and the at least one polyester is 6:1 to 10:1 and the adhesive has an isocyanate content in the range of 10 to 40% NCO;

ii) the molecular weight of the at least one polyester has a number average molecular weight in the range from 750 to 4,000; and

iii) the at least one polyester has a hydroxyl value in the range of between 75 to 200 mgKOH/g and an acid value of less than 0.5 mgKOH/g.

2. The adhesive according to claim 1 wherein the polyisocyanate has a viscosity at 25° C. in the range from 100 to 300 mPa.s.

3. The adhesive according to claim 1 wherein the dimer is formed from C 14 to C 22 alkyl chains.

4. The adhesive according to claim 1 , wherein said dimer fatty acid comprises 10 to 30% by weight, relative to weight of said dimer fatty acid, of trimer fatty acid.

5. The adhesive according to claim 1 , wherein the polyol component, comprises:

i) a low molecular weight polyol component; or

ii) a dimer fatty diol.

6. The adhesive according to claim 5 , wherein the low molecular weight polyol component has a molecular weight in the range from 50 to 650.

7. The adhesive according to claim 5 , wherein the low molecular weight polyol component comprises ethylene glycol and/or propylene glycol.

8. The adhesive according to claim 1 , wherein the molecular weight of the said at least one polyester has a number average molecular weight in the range from 800 to 2,500.

9. The adhesive according to claim 1 , wherein the glass transition temperature (Tg) of the said at least one polyester is in the range from −50 to −20° C.

10. The adhesive according to claim 1 , having a number average molecular weight in the range from 850 to 2,000.

11. The adhesive according to claim 1 , having an isocyanate content in the range from 12 to 30% by weight NCO, relative to the weight of the adhesive.

12. The adhesive according to claim 5 , comprising from 14 to 30% by weight, relative to the weight of the adhesive, of the reaction product of dimer fatty acid and dimer fatty diol.

13. The adhesive according to claim 1 , which has, after curing, a lap shear adhesion value of greater than 6 MPa.

14. The adhesive according to claim 1 , which has, after curing, a creep rupture adhesion value at a stress value of 8 MPa of greater than 1,000,000 seconds in air at 23° C.

15. The adhesive according to claim 1 , which has, after curing, a creep rupture adhesion value at a stress value of 6 MPa of greater than 2,500 seconds in water at 90° C.

16. The adhesive according to claim 1 , which has, after curing, a creep rupture adhesion value at a stress value of 4 MPa of greater than 500,000 seconds in water at 90° C.

17. The adhesive according to claim 1 , wherein the creep rupture adhesion value in water at 90° C. is at least 70% of the value in air at 23° C.

18. The adhesive according to claim 1 , wherein the creep rupture adhesion value in water at 90° C. is at least of the value in air at 23° C.

19. A substrate coated with the moisture-curable adhesive as defined in claim 1 .

20. A method of constructing a wooden article comprising contacting wood with the moisture-curable adhesive as defined in claim 1 .

21. Wooden joists, wooden frames and/or external wooden cladding adhered together using the moisture-curable adhesive as defined in claim 1 .

22. The adhesive according to claim 1 , comprising a total dimer fatty acid reaction product content of not more than 40% by weight, relative to the weight of the adhesive.

23. A moisture-curable adhesive having a viscosity at 23° C. of not more than 40 Pa.s, consisting of a reaction product of:

(i) at least one polyisocyanate; and

(ii) at least one polyester formed from:

a) a carboxylic acid component, comprising:

i) 60 to 100% by weight of dimer fatty acids, relative to the weight of the total weight of dicarboxylic acids; and

ii) 0 to 40% by weight of non-dimer fatty acids, relative to the weight of the total weight of dicarboxylic acids, wherein the non-dimer fatty acids are aliphatic dicarboxylic acids having terminal carboxyl groups and a 2 to 20 carbon chain; and

b) a polyol component;

wherein:

i) said reaction product comprises terminal isocyanate groups;

ii) the NCO:OH molar ratio of the at least one polyisocyanate and the at least one polyester is 6:1 to 10:1;

iii) the adhesive has an isocyanate content in the range of 10 to 40% NCO;

iv) the molecular weight of the at least one polyester has a number average molecular weight in the range from 750 to 4,000; and

v) the at least one polyester has a hydroxyl value in the range of between 75 to 200 mgKOH/g and an acid value of less than 0.5 mgKOH/g.

24. The adhesive according to claim 23 , further comprising unreacted polyisocyanate.

25. The adhesive according to claim 23 , having a viscosity at 23° C. of not more than 30 Pa.s.

26. A moisture-curable adhesive having a viscosity at 23° C. of not more than 30 Pa.s, comprising a reaction product of:

(i) at least one polyisocyanate; and

(ii) at least one polyester formed from:

a) a carboxylic acid component, comprising:

i) 60 to 100% by weight of dimer fatty acids, relative to the weight of the total weight of dicarboxylic acids; and

ii) 0 to 40% by weight of non-dimer fatty acids, relative to the weight of dicarboxylic acids, wherein the non-dimer fatty acids are aliphatic dicarboxylic acids having terminal carboxyl groups and a 2 to 20 carbon chain; and

b) a polyol component;

wherein:

i) the NCO:OH molar ratio of the at least one polyisocyanate and the at least one polyester is 6:1 to 10:1;

ii) the adhesive has an isocyanate content in the range of 10 to 40% NCO;

iii) said reaction product comprises terminal isocyanate groups;

iv) the molecular weight of the at least one polyester has a number average molecular weight in the range from 750 to 4,000; and

v) the at least one polyester has a hydroxyl value in the range of between 75 to 200 mgKOH/g and an acid value of less than 0.5 mgaKOH/g.

27. The adhesive according to claim 26 , comprising a total dimer fatty acid reaction product content of not more than 40% by weight, relative to the weight of the adhesive.

28. The adhesive of claim 1 , wherein the at least one polyester is formed from 100% by weight of dimer fatty acids, relative to the weight of the total weight of dicarboxylic acids.

29. The adhesive of claim 28 , wherein the at least one polyester is formed from ethylene glycol and/or propylene glycol and the molar ratios of said ethylene glycol and/or propylene glycol to dimer fatty acid used to form the at least one polyester is in the range from 1.15 to 2:1.