Commixtures for use in rheology modification

1. A composition that is curable at a temperature (T cur ) from 60° C. to 250° C., said composition comprising:

i) a binder; and

ii) a commixture for use as a sag control agent (SCA) in said composition and comprises:

(a) a thixotropy-inducing particulate polyurea product having a melting temperature (T m1 ) at least 10° C. below the curing temperature (T cur ), thereby satisfying the requirement T m1 <(T cur −10° C.); and

(b) a second thixotropy-inducing particulate component having a melting temperature (T m2 ) such that retains its particulate nature at temperatures at least up to said curing temperature (T cur ).

2. A composition according to claim 1 , curable at a temperature (T cur ) greater than 90° C.

3. A composition according to claim 1 , curable at a temperature (T cur ) between 120° C. and 150° C.

4. A composition according to claim 1 , wherein the melting temperature of said first polyurea component (a) is higher than (T cure −60° C.).

5. A composition according to claim 4 , wherein said polyurea reaction product (a) of the commixture is derived from a chiral, mono-amine provided in enantiomeric excess.

6. A composition according to claim 1 , wherein the melting temperatures of the polyurea product (a) and said second particulate component (b) satisfy the requirement T m2 ≧(T m1 +10° C.).

7. A composition according to claim 6 , wherein said polyurea reaction product (a) of the commixture is derived by reaction of an amine with the isocyanurate derivative of hexamethylene-1,6-diisocyanate (HMDI).

8. A composition according to claim 1 , wherein the polyurea reaction product (a) of the commixture is derived by reaction of an amine with a substituted or unsubstituted linear aliphatic polyisocyanate or its isocyanurate.

9. A composition according to claim 8 , wherein said polyurea reaction product (a) of the commixture is derived by reaction of an amine with hexamethylene-1,6-diisocyanate (HMDI).

10. A composition according to claim 1 , wherein said second particulate component (b) of the commixture is selected from the group consisting of silica, polymeric microgels, clays and polyurea based products.

11. A composition according to claim 1 , wherein said second particulate component (b) of the commixture is a polyurea reaction product.

12. A composition according to claim 11 , wherein said second component (b) polyurea reaction product is derived by reaction of a polyisocyanate with an amine and wherein said polyisocyanate is selected from the group consisting of HMDI, trans-1,4-cyclohexylene diisocyanate, m-xylylene diisocyanate, p-xylylene diisocyanate, tetramethylxylylene diisocyanate and toluene diisocyanate.

13. A composition according to claim 12 , wherein said amine used to derive said second component (b) is selected from the group consisting of n-aliphatic amines, cyclohexylamine, benzylamine and 2-phenethylamine.

14. A composition according to claim 1 , wherein said commixture comprises 5-95 weight % of said first polyurea reaction product (a) and, reciprocally, 95-5 weight % of said second particulate product (b).

15. A composition according to claim 1 , further comprising a solvent.

16. A composition according to claim 1 , further comprising a cross-linking agent.

17. A composition according to claim 16 , wherein said cross-linking agent of the coating composition comprises blocked isocyanates.

18. A composition according to claim 16 , wherein said cross-linking agent of the coating composition is of a non-isocyanate type.

19. A composition according to claim 18 , wherein said cross-linking agent of the coating composition is of a melamine formaldehyde type.

20. A composition according to claim 1 , comprising from 0.05 to 10 wt % of the commixture (relative to the total weight of the composition).

21. A method of curing a composition comprising a binder and as a sag control agent (SCA) a commixture of (a) a thixotropy-inducing particulate polyurea product having a melting temperature T m1 and (b) a second thixotropy-inducing particulate component having a melting temperature T m2 where T m2 >(T m1 +10° C.), said method comprising heating said composition to a curing temperature T cur greater than 60° C. to 250° C., said T cur being characterized in that:

i) T m1 <(T cur −10° C.)

ii) said second component is retained in a particulate state thereat.

22. A method according to claim 21 , wherein said curing process occurs on a substrate to which the composition has been applied.

23. A method according to claim 21 , wherein said curing temperature T cur is in the range from 120° C. to 150° C.