Flame retardant epoxy resins comprising phosphorus containing flame retardants

1. A flame retardant epoxy resin composition comprising

a) an epoxy resin,

b) from 1% to 60%, by weight based on the total weight of the flame retardant epoxy resin composition, of a flame retardant material obtained by a process comprising heating at temperatures of about 200° C. or higher from about 0.01 hour to about 20 hours one or more than one compound of formula (I)

 wherein

R is C 1-12 alkyl, C 6-10 aryl, C 7-15 alkylaryl, or C 7-15 arylalkyl, wherein said alkyl, aryl, alkylaryl, or arylalkyl are unsubstituted or are substituted by halogen, hydroxyl, amino, C 1-4 alkylamino, di-C 1-4 alkylamino, C 1-4 alkoxy, carboxy or C 2-5 alkoxycarbonyl;

M is a metal,

y is a number of from 1 to 4 so that M (+)y is a metal cation where (+)y represents the charge formally assigned to the cation, and p is a number of from 1 to 4, and

c) a curing agent.

2. The flame retardant epoxy resin composition according to claim 1 wherein the flame retardant material (b) is obtained by a process comprising:

i) preparing an intermediate salt complex by treating one or more phosphonic acid compound with one or more appropriate metal compound to give an intermediate salt complex corresponding to formula (I) comprising multiple values for R and/or M, and then heating the intermediate salt complex at temperatures of about 200° C. or higher for about 0.01 hour to about 20 hours;

or

ii) preparing an intimate salt mixture by combining two or more individual metal phosphonic acid salts of formula (I) which have differing values for R and/or M, and then heating the intimate salt mixture at temperatures of about 200° C. or higher for about 0.01 hour to about 20 hours;

or

(iii) heating at temperatures of about 200° C. or higher for about 0.01 hour to about 20 hours two or more separate metal phosphonic acid salts of formula (I), which differ by having different values for R and/or M to form individual flame retardant materials that are subsequently mixed together to form a blended flame retardant material.

3. The flame retardant epoxy resin composition according to claim 1 wherein M in formula (I) is Li, K, Na, Mg, Ca, Ba, Zn, Zr, B, Al, Si, Ti, Sn or Sb.

4. The flame retardant epoxy resin composition according to claim 1 wherein M in formula (I) is Al or Ca.

5. The flame retardant epoxy resin composition according to claim 1 wherein in formula (I) R is unsubstituted C 1-6 alkyl, C 6 aryl, C 7-10 alkylaryl, or C 7-12 arylalkyl.

6. The flame retardant epoxy resin composition according to claim 1 further comprising d) one or more compounds selected from the group consisting of additional flame retardants, synergists and flame retardant adjuvants.

7. The flame retardant epoxy resin composition according to claim 1 wherein the curing agent comprises a phenolic cross linker, a diamine, a polyamine, a dicyandiamide or a substituted dicyandiamide.

8. The flame retardant epoxy resin composition according to claim 1 wherein the epoxy resin comprises an epoxy novolac resin and/or a novolac cross linker.

9. The flame retardant epoxy resin composition according to claim 1 further comprising one or more additional resin selected from the group consisting of cyanate resins, bismaleimide resins, polyimide resins, phenolic resins, furan resins, xylene formaldehyde resins, ketone formaldehyde resins, urea resins, melamine resins, aniline resins, alkyd resins, unsaturated polyester resins, diallyl phthalate resins, triallyl cyanate resins, triazine resins, polyurethane resins, polyolefin resins, polyphenylene ether resins, benzocyclobutene resins, benzoxazine resins and silicone resins.

10. A laminate comprising a cured flame retardant epoxy composition according to claim 1 .