Phosphine oxide hydroxyaryl mixtures with novolac resins for co-curing epoxy resins

1. A flame-retardant curable epoxy composition comprising:

(a) an epoxy resin;

(b) a co-crosslinking polyhydroxy mixture including:

(i) a mixture of phosphine oxides including hydroxyaryl phosphine oxides of the formulae:

(A) a mono(hydroxyaryl)phosphine oxide of the formula:

wherein R 1 is a divalent, substituted or unsubstituted arylene moiety and R 2 is a monovalent, substituted or unsubstituted aryl moiety or is an alkyl moiety or is an aralkyl moiety; and

(B) a bis(hydroxyaryl)phosphine oxide of the formula:

wherein R 1 and R 2 are defined as above; and

(C) a tris(hydroxyaryl)phosphine oxide of the formula:

wherein R 1 is defined as above; and

(D) optionally containing minor amounts of a pentavalent phosphine oxide of the formula:

wherein R 2 is defined as above; and

(ii) a phenolic co-crosslinking composition comprising a phenolic component having a hydroxyfunctionality of two or more.

2. The curable epoxy composition according to claim 1 , wherein the epoxy resin is based on epichlorohydrin and bisphenol A.

3. The curable epoxy composition according to claim 1 , wherein the epoxy resin is based on epichlorohydrin and bisphenol F.

4. The curable epoxy composition according to claim 1 , wherein the epoxy resin is a novolac epoxy resin.

5. The curable epoxy composition according to claim 1 , having a phosphorous content of from about 0.2 wt. percent to about 5 wt. percent.

6. The curable epoxy composition according to claim 5 , having a phosphorous content of from about 1 wt. percent to about 4 wt. percent.

7. The curable epoxy composition according to claim 6 , having a phosphorous content of from about 2 wt. percent to about 3 wt. percent.

8. The curable epoxy composition according to claim 1 , wherein the polyhydroxy mixture has a hydroxy content of from about 50 mole % to about 150 mole % of the stoichiometric amount required to cure the epoxy resin.

9. The curable epoxy composition according to claim 8 , wherein the polyhydroxy mixture has a hydroxy content of from about 75 mole % to about 125 mole % of the stoichiometric amount required to cure the epoxy resin.

10. The curable epoxy composition according to claim 9 , wherein the polyhydroxy mixture has a hydroxy content of from about 85 mole % to about 110 mole % of the stoichiometric amount required to cure the epoxy resin.

11. The curable epoxy composition according to claim 1 , wherein from 1 mole % to about 99 mole % of the hydroxy moieties in the mixture are novolac resin hydroxyl groups.

12. The curable epoxy composition according to claim 1 , wherein from 25 mole % to about 75 mole % of the hydroxy moieties in the mixture are novolac resin hydroxyl groups.

13. The curable epoxy composition according to claim 1 , wherein from about 1 mole % to about 99 mole % of the hydroxy moieties in the mixture are phosphine oxide hydroxyaryl moieties.

14. The curable epoxy composition according to claim 13 , wherein from about 25 mole % to about 75 mole % of the hydroxy moieties in the mixture are phosphine oxide hydroxyaryl moieties.

15. The curable epoxy composition according to claim 1 , wherein said co-crosslinking composition comprises a novolac resin.

16. The curable epoxy composition according to claim 15 , wherein said novolac resin comprises a nitrogen heteroaryl aldehyde copolymer.

17. The curable epoxy composition according to claim 16 , wherein said nitrogen heteroaryl aldehyde copolymer is selected from the group consisting of benzoguanamine phenol formaldehyde resins, acetoguanamine phenol formaldehyde resins, melamine phenol formaldehyde resins, benzoguanamine cresol formaldehyde resins, acetoguanamine cresol formaldehyde resins, melamine cresol formaldehyde resins, and mixtures thereof.

18. The curable polyhydroxy mixture according to claim 15 , wherein said novolac resin is selected from the group consisting of phenol formaldehyde resins, cresol formaldehyde resins and mixtures thereof.