Flame-retardant polymer compositions contain a flame-retardant system consisting of a phosphorus/nitrogen-component, aluminum hydroxide, and a least one synergetically active component selected from the group consisting of organic nitrogen compounds, polyalcohols or derivatives thereof, the phosphorus/nitrogen-component being ammonium polyphosphate, if desired.

This invention relates to flame-retardant polymer compositions, preferably 
duroplastic polymer compositions and more preferably to unsaturated 
polyester resins. 
It is known that flame-retardant properties can be imparted to unsaturated 
polyester resins by admixing these resins either with an inorganic 
flame-retardant agent, such as aluminum hydroxide, or organic 
flame-retardant agent, such as a chloroparaffin or a halogenated biphenyl, 
or by chemically modifying the acid or alcohol component of the 
unsaturated monomer, commonly by halogenation. In the event of the 
unsaturated polyester being one containing halogen, the polyester is 
frequently admixed additionally with antimony trioxide acting as a 
synergist (cf. "Handbook of Plastics Flammability and Combustion 
Toxicology", Noyes Publications, Park Ridge, N.J., U.S.A. (1983)). 
In U.S. Pat. No. 3,810,862, it has been disclosed that flame-retardant 
properties can be imparted to polyolefins using a mixture of ammonium 
polyphosphate, melamine and dipentaerythritol or of melamine pyrophosphate 
and dipentaerythritol. 
Flame-retardant systems based on ammonium polyphosphate, melamine and 
polyamide 6 have been disclosed in U.S. Pat. No. 4,198,493, and further 
systems of this kind based on ammonium polyphosphate, melamine and 
tris-2-hydroxyethylisocyanurate or ammonium polyphosphate, pentaerythritol 
or tripentaerythritol and tris-2-hydroxyethyl-isocyanurate, and also 
ammonium polyphosphate, cyanuric acid and tris-2-hydroxyethyl-isocyanurate 
have been disclosed in U.S. Pat. No. 4,198,493. 
Still further compositions based on ammonium polyphosphate, 
melamine-cyanurate and hydroxyalkyl esters of isocyanuric acid have been 
suggested in EP-PS No. 204 027 for imparting flame-retardant properties to 
polyolefins. 
Although aluminum hydroxide used separately and combinations of ammonium 
polyphosphate with a synergetically active compound were found to have no 
effective flame-retardant activity for unsaturated polyesters, we have now 
unexpectedly discovered that the combination of aluminum hydroxide with 
ammonium polyphosphate and various synergetically active substances is a 
highly effective flame-retardant system for unsaturated polyesters. 
The term unsaturated polyester resin (UP-resins) is used herein to denote 
those products which are obtainable by means of a condensation reaction 
from saturated or unsaturated dicarboxylic acids or their anhydrides and a 
diol. The dicarboxylic acids most useful for this purpose are maleic acid, 
which is commonly used in the form of its anhydride, and fumaric acid. 
Propane diol-1,2 is the representative customarily selected from the diol 
series. Styrene which is miscible with a polyester resin in whatever ratio 
and is easy to copolymerize, is the reactive monomer most frequently used. 
Unsaturated polyester resins normally contain between 30 and 40 weight % 
of styrene (cf. Ullmanns Encyklopadie der technischen Chemie, volume 19, 
pages 79-88, Verlag Chemie, Weinheim, (1980)). 
The present invention relates more particularly to a flame-retardant 
polymer composition which is characterized in that it contains a 
flame-retardant system consisting essentially of a 
phosphorus/nitrogen-component, aluminum hydroxide, and at least one 
synergetically active component selected from the group consisting of 
organic nitrogen compounds, polyalcohols or derivatives thereof. 
Further preferred and separate features typical of the flame-retardant 
polymer compositions of this invention provide: 
(a) for the flame-retardant polymer composition to contain, as the 
phosphorus/nitrogen-component, 5-45 parts by weight of ammonium 
polyphosphate per 100 parts by weight of polymer; 
(b) for the said ammonium polyphosphate to contain 0.5-25 weight % of a 
water-insoluble artificial, preferably cured, resin encapsulating the 
individual ammonium polyphosphate particles; 
(c) for the said ammonium polyphosphate to contain 0.5-25 weight % of a 
reaction product of a polyisocyanate with a carbodiimidization catalyst, 
the polycarbodiimide formed encapsulating the individual ammonium 
polyphosphate particles; 
(d) for the said ammonium polyphosphate to contain 0.5-25 weight % of a 
reaction product of a polyisocyanate and a polyhydroxy compound, the 
polyurethane formed encapsulating the individual ammonium polyphosphate 
particles; 
(e) for the said ammonium polyphosphate to contain 0.5-25 weight % of a 
reaction product of a polyisocyanate with a trimerization catalyst, the 
polyisocyanurate formed encapsulating the individual ammonium 
polyphosphate particles; 
(f) for the said ammonium polyphosphate to contain 0.5-25 weight % of a 
reaction product of a polyisocyanate and water, the polyurea formed 
encapsulating the individual ammonium polyphosphate particles; 
(g) for the said ammonium polyphosphate to contain 0.5-25 weight % of a 
cured melamine/formaldehyde-resin, the melamine/formaldehyde resin 
encapsulating the individual ammonium polyphosphate particles; 
(h) for the said ammonium polyphosphate to contain 0.5-25 weight % of a 
cured epoxide resin, the epoxide resin encapsulating the individual 
ammonium polyphosphate particles; 
(i) for the organic nitrogen compound used to be melamine and/or a melamine 
derivative; 
(j) for the organic nitrogen compound used to be cyanuric acid or 
isocyanuric acid and/or a derivative of these acids; 
(k) for the organic nitrogen compound used to be a condensation product of 
ethylene, urea and formaldehyde; 
(l) for the polyalcohol used to be pentaerythritol and/or a derivative 
thereof; 
(m) for the polyalcohol used to be dipentaerythritol and/or a derivative 
thereof; 
(n) for the flame-retardant polymer composition to contain 1 to 25 parts by 
weight of the synergetically active component per 100 parts by weight of 
polymer; 
(o) for the said flame-retardant polymer composition to contain 50-175 
parts by weight of aluminum hydroxide per 100 parts by weight of polymer; 
(p) for the said flame-retardant polymer composition to contain the said 
ammonium polyphosphate and said synergetically active component in a ratio 
by weight of 1:1 to 10:1; 
(q) for the said flame-retardant composition to contain the said aluminum 
hydroxide and said combination of ammonium polyphosphate and 
synergetically active component in a ratio by weight of 1:1 to 15:1; 
(r) for the said flame-retardant polymer composition to be a duroplastic; 
(s) for the said flame-retardant polymer composition to be an unsaturated 
polyester; 
(t) for the said flame-retardant polymer composition to be reinforced by 
means of glass fibers. 
The aluminum hydroxide should conveniently be used in the form of those 
products which have been disclosed in U.S. Pat. Nos. 4,340,579 and 
4,421,876, respectively. 
The ammonium polyphosphate which should preferably be used is a 
free-flowing, pulverulent, scarcely water-soluble ammonium polyphosphate 
of the formula (NH.sub.4 PO.sub.3).sub.n, where n is a number between 20 
and 1000, especially 500 and 1000; it should preferably be used in the 
form of particles of which more than 99% have a size of less than 45 .mu.m 
.