One component epoxy curing agents comprising hydroxyalkylamino cycloalkanes
View Patent ↗Liquid epoxy curing agents that have improved latency over conventional liquid curing agents while retaining the physical properties of the cured material are disclosed. These liquid curing agents can be used for curing epoxy resins, or in combination with dicyandiamide (DICY) based curing agents in order to accelerate DICY curing.
1. A latent heat curable composition comprising: i) dicyandiamide, ii) at least one liquid tertiary amine salt, and iii) at least one epoxy resin, and wherein the liquid tertiary amine salt comprises a salt of at least one carboxylic acid and at least one tertiary amine represented by the formula:
wherein A is oxygen, R is an alkylene chain of 1-6 carbon atoms and the hydroxyl group may be attached to any of the carbon atoms; R 1 , R 2 are independently H, alkyl (1-20 carbon atoms), haloalkyl (1-20 carbon atoms), aryl, or hydroxyl; X— is a carboxylate anion of 1-40 carbon atoms; and n is 1;
and wherein the composition has a viscosity of about 6,000 to about 20,000cp at a temperature of about 25C and is at least 85% cured when exposed to a temperature of 80C for 2 hours.
2. The composition of claim 1 wherein the carboxylic acid comprises at least one member of selected from the group of acetic acid and TOFA.
3. The composition of claim 1 wherein the tertiary amine salt comprises N-hydroxyethylmorpholine.
4. The composition of claim 1 wherein the carboxylic acid comprises at least one member selected from the group consisting of acetic acid, propanoic acid, hexanoic acid, 2-ethyihexanoic acid, decanoic acid, tall oil fatty acid (TOFA), dimer acid and mixtures thereof.
5. The composition of claim 4 wherein the carboxylic acid comprises tall oil fatty acid.
6. The composition of claim 4 wherein the carboxylic acid comprises at least one member selected from the group of acetic acid and TOFA.
7. The composition of 4 wherein the carboxylic acid comprises hexanoic acid.
8. The composition of claim 6 wherein the tertiary amine comprises N-hydroxyethylmorpholine.
9. The composition of claim 1 wherein the tertiary amine comprises N-hydroxyethylmorpholine and the acid comprises TOFA.
10. The composition of claim 1 wherein the composition comprises about 90 to about 95 wt. % epoxy resins, about 2 to about 20 wt. % tertiary amine salts and about 3 to about 8 wt. % dicyandiamide.
11. The composition of claim 1 wherein the amount of tertiary amine salt ranges from about 2 to about 20 wt. % of the composition.
12. The composition of claim 1 wherein the epoxy resin comprises at least one multifunctional epoxy resin and at least one monofunctional epoxide.
13. The composition of claim 1 wherein the molar ratio of tertiary amine to carboxylic acid ranges from about 1.0 to about 1.1.
14. The composition of claim 1 wherein the composition has a delta H from about 120 to about 400 J/g.
15. A cured epoxy resin obtained from the composition of claim 1 .
16. The cured epoxy resin of claim of claim 15 wherein the cured epoxy resin is cured within a pipe.
17. A latent curing and heat activated composition comprising: i) curing agent comprising dicyandiamide and at least one liquid tertiary amine salt curing agent accelerator having a viscosity of about 150 to about 200 cP, and ii) at least one epoxy resin; wherein the liquid tertiary amine salt comprises at least one salt of at least one carboxylic acid and N-hydroxyethylmorpholine and the carboxylic acid comprises at least one of hexanoic acid and tall oil fatty acid, and wherein the composition is at least 85% cured when exposed to a temperature of 80 C for 2 hours.