Method for epoxy foam production using a liquid anhydride
View Patent ↗An epoxy resin mixture with at least one epoxy resin of between approximately 50 wt % and 100 wt %, an anhydride cure agent of between approximately 0 wt % and approximately 50 wt %, a tert-butoxycarbonyl anhydride foaming agent of between proximately 0.1-20 wt %, a surfactant and an imidazole or similar catalyst of less than approximately 2 wt %, where the resin mixture is formed from at least one epoxy resin with a 1-10 wt % tert-butoxycarbonyl anhydride compound and an imidazole catalyst at a temperature sufficient to keep the resin in a suitable viscosity range, the resin mixture reacting to form a foaming resin which in the presence of an epoxy curative can then be cured at a temperature greater than 50° C. to form an epoxy foam.
1. A method of making an epoxy foam, comprising forming a resin mixture of at least one epoxy resin with a 0.1-20 wt % tert-butoxycarbonyl anhydride compound and an imidazole catalyst at a temperature sufficient to keep said resin mixture reacting to form a foaming resin, thereby making an epoxy foam.
2. The method of claim 1 wherein said imidazole catalyst is 1-methyl imidazole.
3. The method of claim 1 wherein a surfactant is added in forming said resin mixture.
4. The method of claim 1 wherein said imidazole catalyst is added at a concentration of between approximately 0.3 wt % and approximately 2 wt %.
5. The method of claim 1 wherein said at least one epoxy resin is selected from the group consisting of a diglycidyl ether of bisphenol A compound, a phenolic novolac compound, and a phthalic acid derivative based epoxy cure agent.
6. The method of claim 1 wherein said at least one epoxy resin is selected from a resin with a terminal reactive epoxy group.
7. The method of claim 3 wherein said surfactant is added at a concentration less than approximately 2 wt %.
8. The method of claim 3 wherein said surfactant is selected from the group consisting of an anionic surfactant, a cationic surfactant and a non-ionic surfactant.
9. The method of claim 3 wherein said surfactant is selected from an organo polysiloxane compound, an amine alkylbenzene sulfonate compound, an alkyl phenol ethoxylate compound, a silicone-based non-ionic compound, a poly ethyleneoxide block non-ionic compound, and a nonionic alkoxylate-polyethylene glycol mono(nonyl phenyl)ether compound.
10. The method of claim 1 wherein a curing agent is added to said resin mixture.
11. The method of claim 10 wherein said curing agent is added at a concentration less than approximately 100 wt %.
12. The method of claim 10 wherein said curing agent is selected from tetrahydro phthalic anhydride, methyl-tetrahydro phthalic anhydride, hexahydro phthalic anhydride, methyl-hexahydro phthalic anhydride, nadic methyl anhydride, phthalic anhydride, methylphthalic anhydride, benzophenonetetracarboxylic dianhydride, and pyromellitic acid anhydride, or similar anhydrides.
13. The method of claim 1 wherein an inorganic additive is added to said resin mixture to control a property selected from a mechanical property, foam hardness, foam char behavior and foam thermal property.
14. The method of claim 13 wherein said inorganic additive is selected from a clay, wollastonite, and mica.
15. A method of making an epoxy foam, comprising:
forming a resin mixture of at least one epoxy resin with 10-100 pph anhydride epoxy cure agent, 0.1-20 wt % tert-butoxycarbonyl anhydride compound, a surfactant and an imidazole catalyst at a temperature sufficient to keep said resin mixture reacting to form a foaming resin; and
curing said foaming resin at a temperature greater than 50° C. to form an epoxy foam.
16. The method of claim 1 , wherein the temperature is less than 100° C.