Unsaturated polyester resin compositions

1. An unsaturated polyester resin composition comprising an unsaturated polyester resin, a manganese compound, a 1,3-dioxo compound, and a base, wherein the manganese compound is a manganese 2+ or manganese 3+ salt or complex, the manganese compound is present in an amount of at least 0.01 mmol manganese per kg of primary resin system, and wherein the base is an organic base with pK a ≧10 or the base is an alkali metal or earth alkaline metal compound, wherein the alkali earth or alkali metal compound is an oxide, hydroxide, carboxylate, carbonate or hydrocarbonate, and wherein the molar ratio between the 1,3-dioxo compound and a basic functionality of the base is from 170:1 to 1:30, and wherein the resin composition has a cobalt concentration of lower than 0.01 mmol Co per kg primary resin system, and the resin composition is curable with a peroxide, and wherein the 1,3-dioxo compound is a compound having the following formula:

wherein,

X and Y are individually H, C 1 -C 20 alkyl, C 6 -C 20 aryl, alkylaryl, arylalkyl, part of a polymer chain, OR 3 , or NR 3 R 4 ;

R 1 , R 2 , R 3 , and R 4 each individually represents hydrogen (H), or a C 1 -C 20 alkyl, aryl, alkylaryl or arylalkyl group, and each optionally may contain one or more hetero-atoms selected from the group consisting of oxygen atoms, phosphor atoms, nitrogen atoms, sulphur atoms and substituents thereof;

a ring optionally may present between R 1 and R 2 , R 1 and R 3 , R 2 and R 4 , or combinations thereof; and

at least one of R 3 and R 4 may optionally be part of a polymer chain, attached to a polymer chain or contain a polymerizable group.

2. The resin composition according to claim 1 , wherein the manganese compound is a manganese carboxylate or a manganese acetoacetate.

3. The resin composition according to claim 1 , wherein at least one of X and Y is C 1 -C 20 alkyl, C 6 -C 20 aryl or combinations thereof.

4. The resin composition according to claim 1 , wherein at least one of X and Y is a methyl group.

5. The resin composition according to claim 4 , wherein the 1,3-dioxo compound is acetylacetone.

6. The resin composition according to claim 1 , wherein the amount of the 1,3-dioxo compound is from 0.05 to 5% by weight, calculated on the total weight of the primary resin system of the resin composition.

7. The resin composition according to claim 1 , wherein the organic base is a nitrogen containing compound.

8. The resin composition according to claim 7 , wherein the nitrogen containing compound is an amine.

9. The resin composition according to claim 1 , wherein the base is an alkaline metal or earth alkaline metal compound.

10. The resin composition according to claim 9 , wherein the potassium compound is a potassium carboxylate.

11. The resin composition according to claim 1 , wherein the base is present in an amount of from 0.001 to 2000 mmol/kg of primary resin system.

12. The resin composition according to claim 1 , wherein a molar ratio between the manganese and the basic functionality of the base is from 3:1 to 1:1500.

13. The resin composition according to claim 1 , wherein a molar ratio between the manganese and the dioxo compound is from 2:1 to 1:5000.

14. The resin composition according to claim 1 , wherein the resin composition further comprises a radical inhibitor.

15. Cured objects and structural parts obtained from the resin composition according to claim 1 , obtained by curing the resin composition with a peroxide.

16. A process for radically curing the resin composition according to claim 1 , comprising adding a peroxide to the resin composition and curing the resin composition in the absence of cobalt.

17. The process according to claim 16 , wherein the peroxide is at least one selected from the group consisting of hydroperoxides, perethers and perketones.

18. The process according to claim 17 , wherein the peroxide is methylethylketone peroxide.

19. The resin composition according to claim 8 , wherein the amine is a tertiary amine.

20. The resin composition according to claim 9 , wherein the base is a potassium compound.

21. The resin composition according to claim 14 , wherein the inhibitor is at least one selected from the group consisting of phenolic compounds, stable radicals, catechols and phenothiazines.