The present invention is described in the German priority application No. 10 2005 013 957.4, filed 26.03.2005, which is hereby incorporated by reference as is fully disclosed herein.

The invention relates to phosphorus-containing thermally stabilized flame retardant agglomerates having high thermal stability with respect to discoloration which comprise aggregates and/or primary particles composed of phosphinic salts and/or of diphosphinic salts, and/or of their polymers, and which cohere with the aid of an auxiliary. The invention also relates to a process for preparation of these phosphorus-containing flame retardant agglomerates and to the use of the same as flame retardants in polymers.

According to the prior art (DE-A-103 47 012), phosphorus-containing flame retardants can be prepared via spray agglomeration. That process uses binders which are intended to stabilize the agglomerate mechanically.

The agglomerates described in the prior art are disadvantageous because they discolor on heating. Since heating of this type takes place during the correct processing of the agglomerates to give flame-retardant molding compositions or to give flame-retardant moldings, disadvantageous discoloration also occurs in these products.

It is an object of the present invention to provide phosphorus-containing thermally stabilized flame retardant agglomerates which have substantially more thermal stability with respect to discoloration.

This object is achieved via an agglomerate of a phosphorus-containing flame retardant, which comprises a suitable auxiliary.

Flame Retardant Agglomerates

Surprisingly, it has been found that selection of a suitable auxiliary can substantially prevent the discoloration of the phosphorus-containing flame retardant agglomerates during heating.

The invention therefore provides phosphorus-containing thermally stabilized flame retardant agglomerates comprising as component A from 6 to 99.99% by weight of aggregates and/or primary particles composed of a phosphinic salt of the formula (I) and/or of a diphosphinic salt of the formula (II), and/or of their polymers, [Image Omitted]
where

R¹and R²are identical or different and are C1-C6-alkyl, linear or branched, and/or aryl;
R³is C₁-C₁₀-alkylene, linear or branched, C₆-C₁₀-arylene, -alkylarylene, or -arylalkylene;
M is Mg, Ca, Al, Sb, Sn, Ge, Zn, Ti, Fe, Zr, Ce, Bi, Sr, Mn, Li, Na, K, and/or a
protonated nitrogen base;
m is from 1 to 4; n is from 1 to 4; and x is from 1 to 4;
as component B from 0 to 90% by weight of a synergist which comprises a nitrogen compound or which comprises a phosphorus compound, or which comprises a phosphorus-nitrogen compound;
as component C from 0 to 20% by weight of compounds of the elements of the second main and/or transition group; and
as component D from 0.01 to 20% by weight of auxiliary.