Nanoporous laminates
View Patent ↗A process of making a nanoporous substrate, such as the matrix in an electrical laminate, by grafting onto an organic resin backbone a thermolabile functionality by reacting hydrogen active groups of the organic resin with a compound containing thermolabile groups; then thermally degrading the thermolabile groups grafted on the organic resin to form a nanoporous laminate. Advantageously, the nanoporous electrical laminate has a low dielectric constant (Dk) because of the nanopores present in the laminate matrix.
1. An organic resin matrix composition comprising:
(a) a curable reaction product of: (a1) an organic resin featuring hydrogen active groups and (a2) a compound containing a thermolabile carbonate group, wherein the thermolabile carbonate group is grafted onto the backbone of the organic resin by reaction of said compound with said hydrogen active groups;
(b) a curing agent;
(c) an optional solvent; and
(d) an optional catalyst;
wherein heating of the organic resin matrix composition to a temperature of about 120° C. to about 220° C. results in thermal degradation and volatilization of the thermolabile group such that nano size voids are produced in the resulting cured organic resin matrix.
2. The composition of claim 1 wherein the organic resin is selected from the group consisting of epoxy resins, phenolic resins, polimide resins, polyamide resins, polyester resins, polyether resins, bismaleimide triazine resins, cyanate ester resins, vinyl ester resins, hydrocarbon resins, and mixture of thereof.
3. The composition of claim 1 wherein the organic resin is selected from the group consisting of a brominated epoxy resin, a phosphorus-containing epoxy resin, an epoxy resin with an epoxy equivalent weight higher than 500, and mixture thereof.
4. The composition of claim 1 wherein the thermolabile group is tert-butyl carbonate.
5. The composition of claim 1 wherein the thermolabile group is present in an amount such that the weight percent of thermolabile groups in the resin composition is from about 0.01 weight percent to about 10 weight percent, based on solids.
6. The composition of claim 1 wherein the solvent is a ketone, an acetate of glycol ethers or mixtures thereof.
7. The composition of claim 1 wherein the solvent is present in an amount of from about 10 parts by weight to about 60 parts by weight, based on 100 parts by weight of the composition.
8. A light weight cured product of the composition of claim 1 featuring nano size voids.
9. A varnish comprising the composition of claim 1 and optional desired additives.
10. A fiber reinforced composite article comprising a fiber reinforcement impregnated or coated with the varnish of claim 9 .
11. The fiber reinforced composite article of claim 10 wherein said varnish is dried, cured, or partially cured to from a laminate, a prepreg, or an insulating coating for an electric circuit.
12. A prepreg comprising a woven fabric impregnated with the varnish of claim 9 , wherein said varnish is at least partially cured.
13. A laminate comprising: the prepreg of claim 12 and a layer of metal disposed on at least one surface of said prepreg, wherein said varnish is fully cured.
14. The laminate of claim 13 wherein the woven fabric is a woven glass fabric.
15. A printed wiring board comprising the laminate of claim 14 .
16. A process of producing a coated article comprising: coating said article with the varnish of claim 9 ; and heating the coated article to cure said varnish.
17. The process of claim 16 wherein the article is a metal foil.
18. The process of claim 17 wherein the metal foil is a copper foil or an aluminum foil.