Hydroxyphenyl phosphine oxide mixtures and their use as flame retardants for epoxy resins

1. An epoxy resin composition comprising the reaction product of an epihalohydrin and a hydroxyphenyl or alkoxyphenyl phosphine oxide composition comprising:

(i) from about 10 to about 50 wt % of a first mixture of mono-(hydroxyphenyl) or (alkoxyphenyl) phosphine oxide isomers each having the formula (I):

(ii) from about 30 to about 60 wt % of a second mixture of bis-(hydroxyphenyl) or (alkoxyphenyl) phosphine oxide isomers each having the formula (II):

(iii) from about 10 to about 50 wt % of a third mixture of tris-(hydroxyphenyl) or (alkoxyphenyl) phosphine oxide isomers each having the formula (III):

iv) 0 to 10 mol % of triphenyl phosphine oxides of the formula IV:

wherein R is hydrogen or an alkyl group containing from 1 to 6 carbon atoms, R 1 and R 2 are the same or different and each is an alkyl group containing from 1 to 6 carbon atoms, each of x and y is an integer from 0 through 4, and each OR group is in the ortho or para position with respect to the bond between the P atom and the associated phenyl group such that, for each mixture (i), (ii) and (iii), the ratio of the number of OR groups in the ortho-position with respect to the bond between the P atom and the associated phenyl group to the number of OR groups in the para-position with respect to the bond between the P atom and the associated phenyl group is from about 20:80 to about 3:97.

2. The epoxy resin composition of claim 1 , wherein each of x and y is zero.

3. The epoxy resin composition of claim 1 , wherein R is hydrogen.

4. The epoxy resin composition of claim 1 comprising about 15 to about 30 wt % of the first mixture (i), about 40 to about 55 wt % of the second mixture (ii) and about 15 to about 30 wt % of the third mixture (iii).

5. The epoxy resin composition of claim 3 comprising from 1 to 10 wt % of triphenyl phosphine oxides of the formula IV:

6. A curable epoxy resin composition comprising (a) an epoxy resin and (b) a cross-linking system comprising a hydroxyphenyl or alkoxyphenyl phosphine oxide composition comprising:

(i) from about 10 to about 50 wt % of a first mixture of mono-(hydroxyphenyl) or (alkoxyphenyl) phosphine oxide isomers each having the formula (I):

(ii) from about 30 to about 60 wt % of a second mixture of bis-(hydroxyphenyl) or (alkoxyphenyl) phosphine oxide isomers each having the formula (II):

(iii) from about 10 to about 50 wt % of a third mixture of tris-(hydroxyphenyl) or (alkoxyphenyl) phosphine oxide isomers each having the formula (III):

iv) 0 to 10 mol % of triphenyl phosphine oxides of the formula IV:

wherein R is hydrogen or an alkyl group containing from 1 to 6 carbon atoms, R 1 and R 2 are the same or different and each is an alkyl group containing from 1 to 6 carbon atoms, each of x and y is an integer from 0 through 4, and each OR group is in the ortho or para position with respect to the bond between the P atom and the associated phenyl group such that, for each mixture (i), (ii) and (iii), the ratio of the number of OR groups in the ortho-position with respect to the bond between the P atom and the associated phenyl group to the number of OR groups in the para-position with respect to the bond between the P atom and the associated phenyl group is from about 20:80 to about 3:97.

7. The curable epoxy resin composition of claim 6 , wherein each of x and y is zero.

8. The curable epoxy resin composition of claim 6 , wherein R is hydrogen.

9. The curable epoxy resin composition of claim 6 comprising about 15 to about 30 wt % of the first mixture (i), about 40 to about 55 wt % of the second mixture (ii) and about 15 to about 30 wt % of the third mixture (iii).

10. The curable epoxy resin composition of claim 8 comprising from 1 to 10 wt % of triphenyl phosphine oxides of the formula IV: