Process for making rigid urethane-modified polyisocyanurate foams

1. A process for preparing rigid urethane-modified polyisocyanurate foam comprising the step of reacting an organic polyisocyanate with a polyfunctional isocyanate-reactive component comprising at least 30 wt % of polyester polyols in the presence of a blowing agent, selected from the group consisting of, an alkane, an alkene, a cycloalkane, or combinations thereof, wherein the blowing agent consists of carbon and hydrogen atoms, a urethane catalyst, and a metal salt trimerisation catalyst characterized in that the process is carried out in the presence of a carboxylic acid that is functionalised with at least one OH, SH, NH 2 , NHR, NO 2 or halogen functional group and R is an alkyl, cycloalkyl or aryl group, wherein the urethane catalyst is used in an amount ranging from 0.1 to 3.5% by weight based on the isocyanate-reactive component and the metal salt trimerisation catalyst is used in an amount ranging from 0.4 to 4.5% by weight based on the isocyanate-reactive component.

2. The process according to claim 1 wherein the carboxylic acid has a molecular weight below 250.

3. The process according to claim 1 wherein the carboxylic acid has a pKa value in water of between 1 and 5.5.

4. The process according to claim 2 wherein the carboxylic acid has a pKa value in water of between 1 and 5.5.

5. The process according to claim 1 wherein the carboxylic acid is functionalised in α or β position with respect to the carboxyl group.

6. The process according to claim 5 wherein said functionalised carboxylic acid corresponds to the general formula X n —R′—COOH wherein X is OH, SH, NH 2 , NHR, NO 2 or halogen, R′ is an at least divalent hydrocarbon moiety, n is an integer having a value of at least 1 and allows for mono and polyfunctional substitution on the hydrocarbon moiety.

7. The process according to claim 1 wherein said carboxylic acid is used in an amount ranging from 0.05 to 5% by weight based on the isocyanate-reactive component.

8. The process according to claim 2 wherein said carboxylic acid is used in an amount ranging from 0.1 to 2% by weight based on the isocyanate-reactive component.

9. The process according to claim 1 wherein the metal salt trimerisation catalyst is an alkali metal salt of an organic carboxylic acid.

10. The process according to claim 2 wherein the metal salt trimerisation catalyst is an alkali metal salt of an organic carboxylic acid.

11. The process according to claim 10 wherein the metal salt trimerisation catalyst is potassium acetate or potassium 2-ethylhexanoate.

12. The process according to claim 1 wherein the reaction is carried out at an isocyanate index of 150 to 450%.

13. A rigid urethane-modified polyisocyanurate foam obtained by reacting an organic polyisocyanate with a polyfunctional isocyanate-reactive component comprising at least 30 wt % of polyester polyols in the presence of a blowing agent, selected from the group consisting of, an alkane, an alkene, a cycloalkane, or combinations thereof, wherein the blowing agent consists of carbon and hydrogen atoms, a urethane catalyst, and a metal salt trimerisation catalyst characterized in that the process is carried out in the presence of a carboxylic acid functionalised with at least one OH, SH, NH 2 , NHR, NO 2 or halogen functional group, wherein R is an alkyl, cycloalkyl or aryl group, wherein the urethane catalyst is used in an amount ranging from 0.1 to 3.5% by weight based on the isocyanate-reactive component and the metal salt trimerisation catalyst is used in an amount ranging from 0.4 to 4.5% by weight based on the isocyanate-reactive component.

14. A process for preparing rigid urethane-modified polyisocyanurate foam comprising the step of reacting an organic polyisocyanate with a polyfunctional isocyanate-reactive component comprising at least 30 wt % of polyester polyols in the presence of a blowing agent and a metal salt trimerisation catalyst characterized in that the process is carried out in the presence of a functionalised carboxylic acid having at least one OH, SH, NH 2 , NHR, NO 2 , or halogen functional group, wherein R is an alkyl, cycloalkyl or aryl group and the metal salt trimerisation catalyst is used in an amount ranging from 0.5 to 5% by weight based on the isocyanate-reactive component and the functionalised carboxylic acid is used in an amount ranging from 0.1 to 2% by weight based on the isocyanate-reactive component; and wherein the blowing agent is selected from the group consisting of, an alkane, an alkene, a cycloalkane, or combinations thereof, and blowing agent consists of carbon and hydrogen atoms.

15. The process according to claim 13 wherein the carboxylic acid is functionalised in α or β position with respect to the carboxyl group.

16. The process according to claim 13 wherein the carboxylic acid corresponds to the general formula X n —R′—COOH wherein X is OH, SH, NH 2 , NHR, NO 2 or halogen, R′ is an at least divalent hydrocarbon moiety, n is an integer having a value of at least 1 and allows for mono and polyfunctional substitution on the hydrocarbon moiety.

17. The process according to claim 1 , wherein the blowing agent is selected from the group of n-butane, iso-butane, 2,3-dimethylbutane, cyclobutane, n-pentane, iso-pentane, technical grade pentane mixtures, cyclopentane, methylcyclopentane, neopentane, n-hexane, iso-hexane, n-heptane, iso-heptane, cyclohexane, methylcyclohexane, 1-pentene, 2-methylbutene, 3-methylbutene, 1-hexene, and mixtures thereof.

18. The process according to claim 13 , wherein the blowing agent is selected from the group of n-butane, iso-butane, 2,3-dimethylbutane, cyclobutane, n-pentane, iso-pentane, technical grade pentane mixtures, cyclopentane, methylcyclopentane, neopentane, n-hexane, iso-hexane, n-heptane, iso-heptane, cyclohexane, methylcyclohexane, 1-pentene, 2-methylbutene, 3-methylbutene, 1-hexene, and mixtures thereof.

19. The process according to claim 14 , wherein the blowing agent is selected from the group of n-butane, iso-butane, 2,3-dimethylbutane, cyclobutane, n-pentane, iso-pentane, technical grade pentane mixtures, cyclopentane, methylcyclopentane, neopentane, n-hexane, iso-hexane, n-heptane, iso-heptane, cyclohexane, methylcyclohexane, 1-pentene, 2-methylbutene, 3-methylbutene, 1-hexene, and mixtures thereof.