A composition comprising a curable, ethylenically unsaturated compound containing ester linkages and an effective fire retardant amount of N,N'-ethylene bis(salicylidene iminato) FE II, its oxidation product, or a mixture thereof, is disclosed. Also disclosed is a process for rendering fire retardant a curable ethylenically unsaturated composition containing ester linkages comprising adding to said composition an effective fire retardant amount of N,N'-ethylene bis(salicylidene iminato) FE II, its oxidation product, or a mixture thereof.

BACKGROUND OF THE INVENTION 
This invention relates to fire retardant, curable, ethylenically 
unsaturated compositions containing ester linkages. This invention also 
relates to a process for rendering fire retardant a curable, ethylenically 
unsaturated composition containing ester linkages. 
Fire retardant, curable, ethylenically unsaturated compositions are known 
from, inter alia, U.S. Pat. No. 4,013,815. The compositions contain 
unsaturated polyester resin which is cured by copolymerization of an 
unsaturated polyester and an ethylenically unsaturated monomer. Most iron 
compounds mentioned in the U.S. patent, such as ferric acetate, ferric 
formate, and ferrous tartrate, when added in an amount of 0.55 to about 50 
percent, by weight, based on unsaturated polyester, are found to be fire 
retardant only to such a degree that at least 4.4 percent, by weight, of 
halogen, based on the amount of cured polyester resin must still be 
present in order for the compositions to be effectively fire retardant. 
In view of the increasingly stringent demands made on industrial products, 
especially with respect to their effect on the environment, there is a 
very great need for unsaturated polyester resin compositions which have 
been made fire retardant without the inclusion of halogen compounds. 
In view of the foregoing, an object of this invention is to provide 
curable, ethylenically unsaturated compositions containing ester linkages 
which have been made sufficiently fire retardant without the necessity for 
including a halogen compound. 
SUMMARY OF THE INVENTION 
There has now been discovered a composition comprising a curable, 
ethylenically unsaturated compound containing ester linkages and an 
effective fire retardant amount of N,N'-ethylene bis(salicylidene iminato) 
FE II, its oxidation product, or a mixture thereof. 
There has also been discovered a process for rendering fire retardant a 
composition containing a curable, ethylenically unsaturated compound 
containing ester linkages. The process comprises adding to said 
composition an effective fire retardant amount of N,N'-ethylene 
bis(salicylidene iminato) FE II, its oxidation product, or a mixture 
thereof. 
DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The compound N,N'-ethylene bis(salicylidene iminato) FE II, which has also 
been referred to in literature as bis(salicylidene) ethylene diimino iron 
(II), will, for the sake of brevity, be referred to hereinafter as Fe 
(salen). The oxidation product derived from Fe (salen) may be expressed by 
the formula [Fe (salen)].sub.2 O. The structure of the latter compound is 
described in Coordination Chemistry Reviews, 9 (1972-1973) 311-337, 
Elsevier Scientific Publishing Company, Amsterdam. 
Fe (salen) and [Fe (salen)].sub.2 O are both soluble in ethylenically 
unsaturated compositions which are based on an ester group-containing 
compound and can be readily incorporated into it directly. The preparation 
of the compound may be performed as indicated in Chemical Abstracts 49, 
5186 i(1955) for the corresponding cobalt compound, utilizing iron 
chloride, salicylaldehyde, and ethylenediamine. 
It is extremely surprising that the iron compounds which are utilized in 
the practice of the present invention impart greatly enhanced fire 
retardancy to the present products upon the curing thereof, but have very 
little detrimental effect on the curing of the compounds. From the results 
of comparative experiments it has been determined that, for instance, the 
ferrous and ferric acetyl acetonates mentioned in U.S. Pat. No. 4,013,815, 
which are also known by the terms 2,4-pentanedione-Fe II and 
2,4-pentanedione-Fe III, do display a strongly fire retardant effect in 
polyester resin compositions which contain very little, if any halogen, 
but are not suitable for the present purpose because of too rapid curing 
(see Table IV hereinbelow). Although the foregoing drawback may be 
minimized by taking special precautions, such an encapsulation, it will 
become evident that some solutions will encounter a large number of 
practical and economic drawbacks. 
Of the curable, ethylenically unsaturated compositions based on an ester 
group-containing compound which may be used in accordance with the present 
invention for the preparation of fire retardant material, particularly 
suitable are those which are derived from a polycarboxylic compound and a 
polyhydric alcohol. Within the scope of the present invention 
polycarboxylic compounds include, for example, polycarboxylic acids, 
polycarboxylic anhydrides, polycarboxylic halides, and polycarboxylic 
esters. The unsaturation may be provided in the polycarboxylic compound or 
in the alcohol or in both. Typically the unsaturation is provided in one 
or more ethylenically unsaturated polycarboxylic compounds such as maleic 
acid, fumaric acid, ethylmaleic acid, itaconic acid, citraconic acid, 
mesaconic acid, and aconitic acid, or the acid chlorides, esters, or 
anhydrides derived therefrom. 
Examples of typical ethylenically unsaturated alcohols include 
2-butene-1,4-diol, 2-pentene-1,5-diol, and the unsaturated hydroxy ethers 
such as glycerol monoallyl ether and pentaerythritol diallyl ether. 
The saturated polycarboxylic compounds which are suitable for use of the 
preparation of the present polyester resins may be derived from an 
aliphatic, cycloaliphatic, aromatic, or heterocyclic group. Examples of 
the foregoing include phthalic acid, isophthalic acid, terephthalic acid, 
adipic acid and/or succinic acid and the acid halides, acid anhydrides, 
and esters derived therefrom. 
Examples of suitable saturated polyvalent alcohols include ethylene glycol, 
diethylene glycol, propylene glycol, dipropylene glycol, 1,4-butanediol, 
1,5-pentanediol, 1,6-hexanediol, 2,2,4-trimethylpentane-1,3 diol, 1,4 
cyclohexane dimethanol, glycerol, mannitol, sorbitol, substituted 
bisphenols, 2,2-bis(4-hydroxycyclohexyl) propane, and mixtures of the 
foregoing compounds. 
Although the presence of halogen in the unsaturated compositions according 
to the present invention is not necessary in order to obtain fire 
retardant properties, the presence, in itself of halogen--for instance to 
obtain certain physical and/or chemical properties--is not excluded from 
the scope of the present invention. 
Halogenated acids which may be used in the preparation of unsaturated 
polyester resins include tetrachlorophthalic acid and diclorosuccinic 
acid. Examples of halogenated alcohols include 2,3-difluorobutane-1,4-diol 
and 2,2-dichloromethyl propane-1,3-diol. 
Moreover, the properties of unsaturated polyesters may still be modified by 
the incorporation therein of suitable monofunctional carboxylic acids 
and/or alcohols. Examples of suitable alcohols include 2,2-dichloroethanol 
and 1,1,1-trifluoropropane-2-ol. Examples of monofunctional acids include 
lauric acid and oleic acid. 
Furthermore, the properties of unsaturated polyesters can be endlessly 
varied by the use of various types of acids and alcohols such as an 
unsaturated acid, a saturated acid, and a saturated alcohol. 
In the preparation of unsaturated polyesters the starting materials 
generally used are maleic acid, maleic anhydride, or fumaric acid and 
ethylene glycol, 1,2-propylene glycol, or 1,3-butane diol. In addition to 
using bifunctional alcohols and acids in the formation of unsaturated 
polyesters, compounds having a combined hydroxyl and carboxyl function may 
be employed. In this respect, use may be made of hydroxy-pivalic acid. 
If, in addition to bifunctional alcohols or acids, a small proportion of 
tri- or polyfunctional compounds is allowed to participate in the 
condensation, some degree of branching may be obtained. Examples of such 
compounds include 2,3,5-hexane tricarboxylic acid, trimellitic acid, 
glycerol, trimethylol propane, pentaerythritol, and 
tris-.beta.-hydroxyethyl isocyanurate. In addition, the unsaturated 
polyesters may still contain groups other than ester groups, such as 
amide, imide, and urethane groups. Thus, the molecular weight of 
polyesters can be considerably increased by reacting the terminal groups 
with diisocyanates. 
The preparation of unsaturated polyesters may take place in the melt or by 
azeotropic condensation. When use is made of acid anhydrides and epoxides, 
the preparation in the melt is effected by polyaddition. The typical 
procedure starts from approximately equivalent amounts of acids and 
alcohols, which are esterified to the desired molecular weight at 
170.degree. to 230.degree. C. Use may be made of catalysts such as 
para-toluene sulphonic acid, benzene sulphonic acid and .beta.-naphthalene 
sulphonic acid. 
The curing of unsaturated polyesters typically takes place in the presence 
of an ethylenically unsaturated copolymerizable monomer, such as styrene, 
or less often, diallyl phthalate or triallyl cyanurate. Other monomers 
which may be used in curing are .alpha.-methyl styrene, vinyl toluene, 
2-chlorostyrene, 2,5-diclorostyrene, para-divinyl benzene, methacrylic 
methyl ester, acrylic methyl ester, acrylic-tertiary-butyl ester, 
acrylonitrile, acrylamide, triacryl formal, vinyl acetate, N-vinyl 
pyrrolidone, 2-vinyl pyridine, N-vinyl carbazole, and mixtures of the 
foregoing compounds. 
In place of the aforementioned diallyl phthalates, suitable monomers 
include, for example, one or more of the following compounds: diallyl 
fumarate, allyldiglycol carbonate, allyllidene diacetate, dimethallyl 
terephthalate, butane diol diallyl ether, glycerol diallyl ether adipate, 
and the tetraallyl ether of tetramethylol acetylene diurea. 
In addition to the aforementioned typically monomers there may also be 
present other copolymerizable compounds such as maleimide and esters and 
half esters of maleic acid and fumaric acid. Several salts derived from 
the aforementioned half esters and polyvalent metals such as, aluminium, 
dissolve in polyester resins. The dissolution is often accompanied by a 
considerable increase in viscosity, which may be of importance with 
respect to moulding materials. The amount of ethylenically unsaturated 
monomer in the mixture is also chosen so that after polymerization, a 
thermosetting polymer is obtained. Depending upon the desired properties, 
the weight percentage of unsaturated polyester in the polyester resin may 
vary from about 10 to about 90 percent, without the use of any further 
additives. 
The polymerization reaction is generally commenced by a free-radical 
initiating catalyst, resulting in a cross-linked and cured polyester 
resin. The temperature at which the reaction is initiated is dependent 
upon the catalyst system which is utilized. When use is made of cobalt 
naphthenate and methylethyl ketone peroxide curing may be effected at room 
temperature. The unsaturated polyester and the ethylenically unsaturated 
monomer are preferably mixed at elevated temperature in order to bring 
about better dissolution and homogenization. To prevent premature 
polymerization it is preferable that, prior to the mixing operation, a 
polymerization inhibitor be included in the unsaturated polyester. 
Subsequently, a catalyst and, if need be, also an accelerator are added. 
The percentage by weight of polymerization inhibitor is generally in the 
range of from about 0.001 to about 1 percent, by weight, of the mixture to 
be polymerized. 
Examples of polymerization inhibitors which may be successfully applied 
include hydroquinone, benzoquinone, para tertiary butylcatechol, 
para-phenylene diamine, trinitrobenzene, and picric acid. Examples of 
suitable catalysts include benzoyl peroxide, acetyl peroxide, lauryl 
peroxide, methylethyl ketone peroxide and cumene hydroperoxide. The amount 
to be used is dependent on the activity and the presence of inhibitors and 
generally varies from about 0.01 to about 10 percent, by weight, based on 
the amont of resin. 
The polymerization reaction may also be promoted by the use of accelerators 
such as metals or metal salts, such as cobalt octoate, cobalt maleate and 
cobalt naphthenate, or amines such as dimethylamine, dibutylamine, or 
mercaptans such as dodecyl mercaptan. The accelerators are generally 
employed in the same amount as, or in a smaller amount than, the catalyst. 
It has been found that not only typical unsaturated polyesters, but also 
compositions based on an ethylenically unsaturated ester having the 
following formula: 
##STR1## 
wherein R.sub.1 and R.sub.2 are independently selected from the group 
consisting of hydrogen and methyl, and m and n are integers from about 1.0 
to about 3.0, are suitable for the preparation of fire retardant 
compositions according to the present invention. It is preferred, however, 
that as the ethylenically unsaturated ester, 
2,2-bis-[para-(.beta.-hydroxyethoxy)phenyl] propane dimethacrylate should 
be used. 
Curing may be effected in a manner corresponding to the aforementioned 
process for use with unsaturated polyesters, utilizing a free-radical 
initiator such as a peroxidic compound, an azo compound, or a compound 
such as hexaphenyl ethane or 
1,2-diphenyl-1,2-dicyanoethane-1,2-dicarboxylic dimethyl ester. Preferably 
one should utilize radical initiators which are useful at temperatures in 
the range from about 60.degree. to about 175.degree. C., preferably in the 
range from about 120.degree. to about 160.degree. C. As indicated above 
for the unsaturated polyesters, curing may also take place at lower 
temperatures in the presence of the aforementioned initiators in 
combination with polymerization accelerators such as cobalt octoate or 
amines such as dimethyl aniline. Curing may also be effected by means of 
UV radiation in the presence of UV-initiators, or by irradiation with 
accelerated electrons, typically known as electron-beam curing. 
The organic iron compound Fe (salen), [Fe (salen)].sub.2 O, and mixtures 
thereof, may be incorporated into one or more of the reaction components 
at any time prior to curing. 
It has been found that along with the other desired properties, sufficient 
fire retardancy typically may be obtained if the iron compound is used in 
an amount from about 0.1 to about 10 percent, by weight, calculated on the 
mixture of fire retardant additive and components participating in the 
curing process. It is also possible, however, to use concentrations in the 
order of, for example, 15 or 20 percent. 
The concentration at which the best fire retardancy is obtained is 
dependent upon the composition of the cured compositions. It will not be 
difficult for one skilled in the art to establish the optimum range within 
which maximum protection against fire is obtained. It has been found that 
such a range may be dependent upon whether a filler has been included. 
Suitable fillers include various metal oxides, glass fibers, asbestos 
fibers, mica, colemanite, powdered chalk, powdered quartz, powdered 
aluminium mica, aluminium oxide, aluminium hydroxide, aluminium sulphate, 
wollastonite, ground and precipitated chalk, magnesium carbonate, kaolin, 
titanium dioxide, and talc. 
It has also been found that the presence of antimony trioxide, which is 
often utilized as a synergist in fire retardant additives for polymers, 
produces an opposite effect in the compositions of the present invention. 
The concentration of fillers to be incorporated into the present curable 
compositions is dependent upon many factors, including both physical and 
economic considerations. The best fire retardant properties are typically 
obtained when the filler is utilized in an amount from about 2 to about 60 
percent, by weight, based on the mixture of filler and components 
participating in the curing process in the presence of an iron compound 
which is itself utilized in an amount from about 0.1 to about 5 percent, 
by weight, based on the mixture of fire retardant additives and components 
participating in the curing process. 
It has been found that a distinctly synergistic effect may result from the 
use of the foregoing combination of substances. For a number of 
applications, the goal will be a cured composition having optimum fire 
retardant properties obtained at a minimum filler concentration, to 
achieve the foregoing goal, the present invention provides a curable 
composition containing a filler in an amount of from about 5 to about 20 
percent, based on the mixture of filler and components participating in 
the curing process, in the presence of an amount of iron compound of 0.1 
to 3.5 percent, by weight, based on the mixture of iron compound and 
components participating in the curing process.

The present invention is further illustrated by the following non-limiting 
examples: 
The fire retardant properties obtained in the following examples were 
determined by measuring the Oxygen Index (OI) in conformity with ASTM D 
2863-70, unless otherwise indicated. The higher the OI obtained, the more 
fire retardant is the cured composition. The resins utilized in the 
examples were composed as follows: 
Resin 1 
An unsaturated polyester was prepared from 15.2 parts by weight of phthalic 
anhydride; 23.5 parts by weight of maleic anhydride and 27.3 parts by 
weight of propylene glycol. The resulting product was mixed with 34 parts 
by weight of styrene, 2 parts by weight of a 50% by weight solution in 
water of methyl ethyl ketone peroxide and 0.5 parts by weight of a 1% by 
weight solution in water of cobalt octoate. Curing for 24 hours at 
20.degree. C. was followed by after-curing for 2 hours at 120.degree. C. 
Resin 2 
The unsaturated polyester for this resin was prepared from 22.1 parts by 
weight of phthalic anhydride; 14.6 parts by weight of maleic anhydride; 
21.6 parts by weight of propylene glycol and 4.8 parts by weight of 
diethylene glycol. The unsaturated polyester obtained with these 
components was mixed with 36.9 parts by weight of styrene; 2 parts by 
weight of a 50% by weight solution in water of methyl ethyl ketone 
peroxide and 0.5 parts by weight of a 1% by weight solution in water of 
cobalt octoate. Curing was effected in the manner indicated under Resin 1. 
Resin 3 
The unsaturated polyester was prepared from 19.7 parts by weight of 
isophthalic acid; 11.6 parts by weight of maleic anhydride and 24.7 parts 
by weight of neopentyl glycol. The unsaturated polyester thus obtained was 
mixed with 44 parts by weight of styrene, 2 parts by weight of a 50% by 
weight solution in water of methyl ethyl ketone peroxide and 0.5 parts by 
weight of a 1% by weight solution in water of cobalt octoate. Curing was 
effected as indicated for Resin 1. 
Resin 4 
The resin was prepared by radical polymerization of 100 parts of 
2,2-bis-(p-(.beta.-hydroxy-ethoxy)-phenyl) propane dimethacrylate in the 
presence of 2 parts of a 40% by weight solution in water of dibenzoyl 
peroxide. Curing took place at a temperature of 70.degree. C. and lasted 
24 hours, followed by after-curing for 2 hours at 120.degree. C. 
Resin 5 
The unsaturated polyester for this resin was prepared from 9.8 parts by 
weight of maleic anhydride; 14.8 parts by weight of phthalic anhydride; 
6.8 parts by weight of ethylene glycol and 8.7 parts by weight of 
1,2-propanediol. Of the unsaturated polyester thus obtained 65 parts by 
weight were mixed with 35 parts by weight of styrene, 2 parts by weight of 
a 50% by weight solution in water of methyl ethyl ketone peroxide and 0.5 
parts by weight of a 1% by weight solution in water of cobalt octoate. 
Curing was carried out as indicated under Resin 1. 
The resin compositions described in the following examples were invariably 
obtained by thoroughly mixing the fire retardant additives along with 
fillers, when utilized, into a mixture of the unsaturated compositions. It 
was then determined that the Fe (salen) and its oxidation product, [Fe 
(salen)].sub.2 O, completely dissolves in the mixture. After the required 
cross-linking agents had been added, the resin compositions were cured in 
glass vessels having the dimensions standardized for OI (Oxygen Index) 
bars in accordance with ASTM D2863-70. The results are summarized in the 
tables. The concentrations of additives in the form of fire retardant 
compound and filler are expressed in grams of additive per 100 grams of 
resin (thus, the components participating in the curing process, plus 
additives). 
EXAMPLE I 
Of the above-mentioned 5 resins the Oxygen Index as a function of the Fe 
(salen) concentration was determined. 
The results are listed in the following Table I. 
TABLE I 
______________________________________ 
Amount of Fe 
(salen) in g per 
Oxygen Index (OI) 
Resin No. 
100 g mixture 
Resin Resin + Fe (salen) 
.DELTA.OI 
______________________________________ 
0.32 18.7 22.9 4.2 
1.61 18.7 22.0 3.3 
3.22 18.7 22.6 3.9 
6.44 18.7 22.1 3.4 
9.67 18.7 20.9 2.2 
2 0.32 19.0 20.1 1.1 
1.61 19.0 24.2 5.2 
3.22 19.0 26.8 7.8 
6.44 19.0 24.1 5.1 
9.67 19.0 22.7 3.7 
3 0.32 19.4 21.0 1.6 
1.61 19.4 23.0 3.6 
3.22 19.4 22.5 3.1 
6.44 19.4 22.5 3.1 
9.67 19.4 22.4 3.0 
4 0.32 17.7 24.3 6.6 
1.61 17.7 24.5 6.8 
3.22 17.7 23.5 5.8 
6.44 17.7 23.0 5.3 
9.67 17.7 20.3 2.6 
5 0.32 18.5 20.0 1.5 
1.61 18.5 22.0 3.5 
3.22 18.5 24.9 6.4 
6.44 18.5 23.9 5.4 
9.67 18.5 22.7 4.2 
______________________________________ 
EXAMPLE II 
The following table gives the results of experiments with 1.61 g Fe (salen) 
per 100 g resin No. 3 plus Fe (salen), to which also 10 g filler per 100 g 
mixture had been added. 
TABLE II 
______________________________________ 
Oxygen Index 
Resin Resin + Fe Resin + 
Resin + Fe 
Filler No. 3 (salen) filler (salen) + filler 
______________________________________ 
Talc 19.4 23.0 19.4 27.3 
Wollastonite 
(CaSiO.sub.3).sub.3 
19.4 23.0 19.4 27.4 
CaCO.sub.3 
19.4 23.0 20.3 25.0 
Mica 19.4 23.0 20.4 25.4 
TiO.sub.2 
19.4 23.0 20.8 25.3 
______________________________________ 
The above tables clearly demonstrates the considerable synergistic effect 
produced on the one hand as a result of the indicated amounts of Fe 
(salen) and on the other hand as a result of the various fillers. 
EXAMPLE III 
In this example the results are given of a number of OI-measurements on the 
Resins 2 and 3, use having been made of varying amounts of Fe (salen) and 
filler. 
The results are listed in the following table. 
TABLE III 
__________________________________________________________________________ 
Amount of Fe 
(salen) in g 
Amount of 
per 100 g talc in g 
Oxygen Index 
mixture of 
per 100 g Resin + Fe 
Resin 
Fe(salen) + 
resin + Resin + 
Resin + 
(salen) + 
No. resin talc Resin 
Fe(salen) 
talc talc 
__________________________________________________________________________ 
2 2.0 10.0 19.0 
25.6 19.0 26.4 
2.0 40.0 19.0 
25.6 21.0 23.4 
5.0 10.0 19.0 
24.0 19.0 25.0 
5.0 40.0 19.0 
24.0 21.0 22.5 
10.0 10.0 19.0 
22.0 19.0 23.2 
10.0 40.0 19.0 
22.0 21.0 24.6 
3 2.0 10.0 19.4 
25.4 19.4 28.3 
2.0 40.0 19.4 
25.4 20.8 26.5 
5.0 10.0 19.4 
23.0 19.4 25.0 
5.0 40.0 19.4 
23.0 20.8 25.8 
10.0 10.0 19.4 
21.6 19.4 23.6 
10.0 40.0 19.4 
21.6 20.8 24.0 
__________________________________________________________________________ 
EXAMPLE IV (COMATIVE EXAMPLE) 
In this example the results are given of experiments on the one hand with 
Fe (salen) and on the other hand with other bis(salicyclidene) ethylene 
diimino metal compounds. Moreover, the results are included obtained with 
other known iron compounds. 
The various data are listed in the following table. 
The compounds mentioned therein are referred to by their trivial names, and 
term Co (salen) referring to the cobalt compound, the term Ni (salen) to 
the nickel compound, and the term Mn (salen) to the manganese compound. 
In all cases the concentration of the fire retardant additive was 2 grams 
per 100 grams of resin plus additive. 
The filler was talc. Its concentration was 10 g per 100 g of resin plus 
filler. 
TABLE IV 
__________________________________________________________________________ 
Oxygen Index 
Resin + talc 
Resin + fire 
+ fire re- 
Resin 
retardant 
tardant 
Resin 
Fire retardant compound 
Resin 
+ talc 
additive 
additive 
Notes 
__________________________________________________________________________ 
2 Fe(salen) 19.0 
19.0 
25.6 26.4 according to 
invention 
Mn(salen) 19.0 
19.0 
19.2 -- 
Ni(salen) 19.0 
19.0 
19.2 -- 
Co(salen) 19.0 
19.0 
18.9 -- 
3 Fe(salen) 19.4 
19.4 
25.4 28.3 according to 
invention 
Mn(salen) 19.4 
19.4 
20.0 22.3 
Ni(salen) 19.4 
19.4 
20.4 20.8 
Co(salen) 19.4 
19.4 
19.4 21.0 
2 Fe.sub.2 O.sub.3 
19.0 
19.0 
20.7 -- 
Ferrooxalate 2 H.sub.2 O 
19.0 
19.0 
19.2 -- 
Ferric phosphate 
19.0 
19.0 
18.7 -- 
EDTA-Fe(III) Na 
19.0 
19.0 
19.7 -- 
2,4-pentane dione Fe(III) 
19.0 
19.0 
23.6 -- unsuitable for 
2,4-pentane dione Fe(II) 
19.0 
19.0 
20.0 -- use because of 
too rapid curing 
Ferric citrate 
19.0 
19.0 
19.0 -- 
Ferrocene 19.0 
19.0 
-- -- unsuitable be- 
cause of inhib- 
iting effect on 
curing reaction 
Basic ferric acetate 
19.0 
19.0 
21.3 -- 
3 Fe.sub.2 O.sub.3 
19.4 
19.4 
21.0 22.0 
Ferrooxalate 2H.sub.2 O 
19.4 
19.4 
19.5 20.6 
Ferric phosphate 
19.4 
19.4 
19.0 20.2 
EDTA-Fe(III) Na 
19.4 
19.4 
21.2 23.5 
2,4-pentane-dione-Fe(II) 
19.4 
19.4 
24.0 24.6 Unsuitable be- 
cause of too 
rapid curing 
3 2,4-pentane-dione-Fe(III) 
19.4 
19.4 
25.5 26.8 unsuitable be- 
cause of too 
rapid curing 
Ferric citrate 
19.4 
19.4 
20.0 20.4 
Ferrocene 19.4 
19.4 
24.4 25.3 unsuitable be- 
cause of inhib- 
iting effect on 
curing reaction 
Basic ferric acetate 
19.4 
19.4 
20.6 21.9 
__________________________________________________________________________ 
The results mentioned in the above table clearly show that the use of Fe 
(salen) as fire retardant additive in curable ethylenically unsaturated 
compositions based on a compound containing ester groups unexpectedly 
leads to far better results than obtained with other known iron compounds.