Resin compositions, e.g., epoxy resin compositions, comprising flame retardant materials obtained by heating phosphonic acid salts at temperatures above 200 C., have excellent properties and exhibit manageable curing behavior. Laminates, composites, molded articles and the like, which have excellent flame retardant properties and physical characteristics, are readily prepared from the resin compositions of the invention.

Resin compositions comprising flame retardant materials obtained by heating phosphonic acid salts at temperatures above 200 C., have excellent properties and exhibit manageable curing behavior. Laminates, composites, molded articles and the like, which have excellent flame retardant properties and physical characteristics, are readily prepared from the resin compositions of the invention.

Resin compositions comprising flame retardant materials obtained by heating phosphonic acid salts at temperatures above 200 C., have excellent properties and exhibit manageable curing behavior. Laminates, composites, molded articles and the like, which have excellent flame retardant properties and physical characteristics, are readily prepared from the resin compositions of the invention.

Resin compositions comprising flame retardant materials obtained by heating phosphonic acid salts at temperatures above 200 C., have excellent properties and exhibit manageable curing behavior. Laminates, composites, molded articles and the like, which have excellent flame retardant properties and physical characteristics, are readily prepared from the resin compositions of the invention.

Resin compositions comprising flame retardant materials obtained by heating phosphonic acid salts at temperatures above 200 C., have excellent properties and exhibit manageable curing behavior. Laminates, composites, molded articles and the like, which have excellent flame retardant properties and physical characteristics, are readily prepared from the resin compositions of the invention.

There is provided herein a method of making hydroxymethylphosphonate comprising reacting paraformaldehyde, at least one dialkyl phosphite and at least one trialkyl phosphite, in the presence of at least one amine catalyst.

There is provided herein a method of making hydroxymethylphosphonate comprising reacting paraformaldehyde, at least one dialkyl phosphite and at least one trialkyl phosphite, in the presence of at least one amine catalyst.

The present invention provides a thermosetting resin composition comprising (A) a metal salt of disubstituted phosphinic acid, (B) a maleimide compound having a N-substituted maleimide group in a molecule, (C) a 6-substituted guanamine compound or dicyandiamide and (D) an epoxy resin having at least two epoxy groups in a molecule and a prepreg and a laminated plate which are prepared by using the same. The prepregs obtained by impregnating or coating a base material with the thermosetting resin compositions of the present invention and the laminated plates produced by laminating and molding the above prepregs are balanced in all of a copper foil adhesive property, a glass transition temperature, a solder heat resistance, a moisture absorption, a flame resistance, a relative dielectric constant and a dielectric loss tangent, and they are useful as a printed wiring board for electronic instruments.

The present invention provides a thermosetting resin composition comprising (A) a metal salt of disubstituted phosphinic acid, (B) a maleimide compound having a N-substituted maleimide group in a molecule, (C) a 6-substituted guanamine compound or dicyandiamide and (D) an epoxy resin having at least two epoxy groups in a molecule and a prepreg and a laminated plate which are prepared by using the same. The prepregs obtained by impregnating or coating a base material with the thermosetting resin compositions of the present invention and the laminated plates produced by laminating and molding the above prepregs are balanced in all of a copper foil adhesive property, a glass transition temperature, a solder heat resistance, a moisture absorption, a flame resistance, a relative dielectric constant and a dielectric loss tangent, and they are useful as a printed wiring board for electronic instruments.

What are described are flame retardant mixtures comprising a) salt of a phosphinic acid of the formula (I)

##STR00001## in which R.sub.1 and R.sub.2 are independently alkyl, cycloalkyl, aryl or aralkyl that are optionally substituted, M is an m-valent cation, and m is 1 to 4, b) salt of a phosphinic acid of the formula (II) that differs from component a)

##STR00002## in which R.sub.3 is optionally substituted alkyl, cycloalkyl, cycloalkylalkyl, aryl or aralkyl, preferably with alkyl radicals as substituents, R.sub.4 is alkyl with an even number of carbon atoms, with the proviso that, if R.sub.1 and/or R.sub.2 are alkyl, R.sub.4 has twice, three times or four times the number of carbon atoms of R.sub.1 or R.sub.2, M is an n-valent cation, and n is 1 to 4, c) organylphosphonate, d) phosphite, e) silicate, alumosilicate and/or silicon dioxide which is solid at 25 C., f) a representative selected from the group of triazine complex, polyphosphate, hypophosphite, nitrogen-containing diphosphate, organophosphate, phosphazene and/or polyphosphonate, g) optionally a representative selected from the group of metal hydroxide, metal carbonate, metal borate, zinc stannate and/or intumescent additive, and h) optionally pigment.

The mixtures can be used for production of flame-retardant polymer compositions comprising thermoplastic and elastomeric polymers that are of excellent suitability for production of cable sheaths or cable insulations.