Flame retardant for hydrocarbon diene rubbers

Fire retarded compositions comprise elastomers derived from conjugated, hydrocarbon dienes in combination with a synergistic, three-component flame retardant system comprising (1) a chlorine- and/or bromine-containing fire-retardant additive, (2) alumina trihydrate and (3) an iron oxide.

It is well known to produce fire retarded elastomeric compositions by the 
addition of compounds which reduce flame propagation or substantial 
combustion of the elastomer. These compounds include halogen-containing 
organic compounds, esters of phosphoric acid, metal salts and oxides, 
alumina hydrates, metal borates, etc; see for example U.S. Pat. No. 
3,997,493 which teaches the use of these compounds with styrene-butadiene 
elastomers. Ferric oxide in combination with certain hydrated salts, e.g. 
magnesium carbonate, is taught as a fire retardant composition for 
polyvinyl chloride and its copolymers; see U.S. Pat. No. 3,993,607. 
Similarly the use of combinations of iron compounds and halogen compounds 
in flame-retarding nitrile rubbers is taught in U.S. Pat. Nos. 4,033,916 
and 4,043,958. However, as disclosed in the latter patent these systems 
are relatively ineffective when used in styrene-butadiene rubber (SBR) 
compositions. U.S. Pat. No. 3,697,456 and Canadian Patent No. 1,014,690 
teach the use of iron oxide and other oxides as partial replacements for 
antimony trioxide in flame retarding various polymers containing halogen 
substituents or halogen compounds, e.g. halogen containing polyurethane 
foams. 
Combinations of a halogen compound with antimony oxide have been found most 
effective in flame-retarding SBR and other rubbers (Rubber Chemistry and 
Technology 46 (4), 1114-25 (1973). Additionally, combinations of antimony 
oxide, chlorinated paraffins and hydrated alumina have been studied in SBR 
foams (Rubber Age, April 1973, pp. 25-32). However, the high cost of 
antimony oxide in rubber compositions is a substantial disadvantage. It is 
therefore evident that there is still a need for an effective low cost 
fire retardant system for SBR and other diene elastomers. 
SUMMARY OF THE INVENTION 
Diene elastomer compositions are rendered flame retarded by the addition of 
a synergistic combination of (1) a halogenated organic compound, (2) 
alumina trihydrate and (3) an iron oxide. The compositions may be cellular 
or dense rubbers. This flame-retarding system is especially effective in 
SBR rubber including foams. 
The iron oxide can be either a hydrated or anhydrous form of ferric oxide 
or of ferrosoferric oxide or a mixture thereof. The halogen compound may 
be polymeric or non-polymeric. Where the diene elastomer has incorporated 
therein a halogenated monomer the requirement for halogenated compound may 
be reduced or eliminated depending on the level of halogenated monomer in 
the polymer and the intended use of the finished elastomeric composition. 
DETAILED DESCRIPTION 
This invention relates to a flame retarded composition of diene rubber. As 
used in the specification and claims the term "diene elastomer" means 
natural rubber as well as elastomers prepared from hydrocarbon conjugated 
dienes alone or from a major portion of such dienes in combination with 
one or more ethylenically unsaturated comonomers e.g. styrene, vinyl 
chloride, vinylidene chloride etc. More particularly it relates to a 
method of rendering such diene elastomers flame retarded by the addition 
of a synergist combination of a halogen containing organic compound, 
alumina trihydrate and an iron oxide wherein the oxide is ferric oxide, 
ferrosoferric oxide or mixtures thereof. The term "halogen containing 
organic compound" as used in the specification and claims means a chlorine 
and/or bromine containing compound. 
The diene elastomers which may be rendered flame retarded by the 
compositions of this invention are homopolymers of hydrocarbon conjugated 
dienes as well as copolymers of such hydrocarbon dienes with ethylenically 
unsaturated comonomers, such copolymers containing a major portion of such 
dienes, and mixtures of such diene elastomers and mixtures of such 
homopolymers and copolymers. Illustrative examples of the hydrocarbon 
conjugated dienes of this invention are butadiene and isoprene. The 
comonomers which may be copolymerized with such dienes are C.sub.2 
-C.sub.12 hydrocarbons such as ethylene, propylene, isobutylene, 
methylstyrene, styrene; C.sub.3 -C.sub.8 carboxylic acids such as acrylic, 
methacrylic, ethacrylic, maleic, fumaric, itaconic, or crotonic acid; 
esters of such acids with C.sub.1 to C.sub.8 alcohols; or C.sub.2 to 
C.sub.8 chlorine and/or bromine substituted unsaturated monomers e.g., 
vinyl chloride, vinylidene chloride, 2-chloropropene, chlorostyrene, etc. 
The specific arrangement of comonomer units within the elastomer molecule, 
e.g., random or as blocks or grafts, is not critical. Illustrative 
examples of the copolymers useful in the practice of this invention are 
styrene-butadiene rubber (SBR), carboxylated SBR, chlorostyrene-butadiene 
rubber, isoprene-methylmethacrylate, butadiene-dimethylmaleate, 
isoprene-diethylfumarate, butadiene-acrylic acid copolymers, etc. Mixtures 
of such elastomers may also constitute the elastomer component. The 
elastomer component may also consist of blends of said elastomer with 
minor portions of other halogen-free polymers (e.g. elastomers or resins), 
provided such additives do not destroy the flame retardancy advantage 
inherent in the practice of this invention. 
The halogen containing organic compound may be a polymeric or non-polymeric 
halogen containing compound. As used in the specification and claims the 
term "halogenated compound" means a chlorine and/or bromine substituted 
compound. 
The organic, non-polymeric, halogen containing fire-retardant additives 
which can be utilized in the practice of this invention are well known, 
being of the class of widely recognized fire-retardant additives for 
polymers and including chlorine and/or bromine containing compounds of 
aliphatic, aromatic or alicyclic types having a halogen content of about 
35-85% by weight. Substituents other than halogen, such as hydroxyl, 
anhydride, ether, carboxyl, ester or phosphate ester can also be present 
provided that such substituents do not interfere with the fire-retardant 
activity of the compound in the finished composition or otherwise destroy 
the advantageous properties of the composition. The halogen compounds 
selected should be substantially non-volatile, stable and non-reactive 
toward the polymer and any auxiliary ingredients, e.g. rubber curatives, 
at polymer processing temperatures. 
Illustrative examples of non-polymeric cholorine and bromine compounds 
useful in the practice of this invention include cholorinated paraffins, 
marketed under a variety of trademarks such as "Chlorowax", Unichlor" and 
"Cereclor", tetrabromoethane, hexabromobutene-2, tribromoneopentyl 
alcohol, dibromoneopentyl glycol, dibromobutenediol and its diacetate, 
methyl pentachlorostearate, and tris (mono- and di-haloalkyl) phosphates, 
halogenated aromatics such as hexa-, octa-, and decabromobiphenyls, 
decabromodiphenyl oxide, hexabromobenzene, tribromophenol, 
tetrabromosalicylanilide, tetra(pentabromophenoxy) silane, dibromopropyl 
chlorobenzoate, dibromopropyl maleate, tetrachloro- and tetrabromophthalic 
anhydrides, tetrachloro- and tetrabromobisphenol A and their 
bishydroxypropyl derivatives, halogenated cycloaliphatics, such as 
hexabromocyclododecane, pentabromochlorocyclohexane, bis (cyclohexenyl) 
ethylene hexabromide, hexachlorocyclopentadiene (HCCPD) and its 
derivatives (typically Diels-Alder adducts with normal or cyclic dienes or 
olefins and including, for example, chlorendic acid, chlorendic anhydride, 
dimethyl chlorendate, diallyl chlorendate, perchloropentacyclodecane, and 
HCCPD adducts with furan, benzoquinone, vinylnorbornene, cyclooctadiene, 
pentadiene and the like). 
Optionally, the halogen compound may be a polymeric compound. The polymeric 
halogen containing compounds which may be used in the practice of this 
invention are polychloroprene, chlorinated polyethylene, chlorinated 
polyvinyl chloride, polyvinylidene chloride, chlorosulfonated 
polyethylene, and epichlorohydrin polymers or copolymers. It will be 
evident that the selection of specific polymeric or non-polymeric halogen 
compounds and the method for incorporating them in the composition, which 
methods can vary widely within the well-known art, should be consistent 
with the target physical properties of the finished composition. Mixtures 
of halogen containing compounds may also be employed. 
The amount of halogen compound to be employed in the practice of this 
invention will be determined by the degree of flame retardancy desired and 
the tolerable limits of the other properties of the finished compounded 
elastomer. Generally, about 5 to about 100 parts of halogen compound per 
100 parts of elastomer component by weight is used; preferably about 10 to 
about 85 parts; most preferably about 15 to about 70 parts of halogen 
compound per 100 parts of elastomer component. 
When the diene elastomer comprises a copolymer derived from at least one 
halogenated monomer the amount of halogen compound required can be 
reduced. Where the halogenated monomer comprises at least 5 weight percent 
of the elastomer component the addition of a halogen compound may be 
omitted without departing from the spirit of this invention. In any event 
a total of at least 5 parts by weight either of halogenated organic 
compound or halogenated organic compound plus halogenated monomer per 100 
parts of elastomer component is required. As used in the specification and 
claims the term "halogenated organic compound" includes the halogenated 
monomer incorporated into the elastomer. 
The amount of alumina trihydrate to be employed in the practice of this 
invention can vary within wide limits depending on the product 
requirements. Generally, about 10 to about 700 parts of alumina trihydrate 
per 100 parts of elastomer component by weight can be used. Preferably 
about 10 to about 250 parts of hydrate per 100 parts of elastomer 
component is used; more preferably about 40 to about 200 parts of alumina 
trihydrate is incorporated into the composition. 
The iron oxides which can be used in the practice of this invention include 
both the anhydrous and hydrated forms of ferric oxide and ferrosoferric 
oxide and mixtures thereof. The term "iron oxide" as used in the 
specification and claims means any of the aforegoing forms of iron oxide. 
In general, about 0.5 parts to 100 parts of iron oxide per 100 parts of 
elastomer component by weight is required; preferably about 2 to about 20 
parts, more preferably about 4 to about 10 parts of iron oxide is used. 
The compositions of this invention are readily prepared by conventional dry 
rubber or latex compounding techniques and the scope of the invention is 
not intended to be limited by the manner of preparation of the 
composition. The compositions of this invention include the flame 
retardants previously described as well as auxiliary ingredients known to 
the art for use in elastomer compounding. Illustrative of such auxiliary 
ingredients are curatives, accelerators, activators, plasticizers, 
extenders, fillers, lubricants, antioxidants, antiozonants, stabilizers, 
processing aids, blowing agents, colorants, smoke retardants, auxiliary 
flame retardants etc. and in the case of latex compounds soaps, 
emulsifiers, dispersing aids, preservatives, gelling agents, sensitizers, 
thickeners, etc. While curatives are typically required to provide 
products of suitable properties, they may be omitted in certain compounds 
such as carpet-backing latices and thermoplastic elastomer compositions. 
The compositions of this invention are suitable for a wide variety of 
applications. They may be used, for example, to produce fire retarded, 
dense or cellular articles of commerce, such as conveyor belts, hose 
covers, carpet backing, gasketing, foam seat cushions, foam underlay for 
carpets, etc.

This invention may be more readily appreciated by reference to the 
following examples. 
EXAMPLE 1 
This Example illustrates the novel synergism exhibited by compositions of 
this invention, thereby providing an unexpectedly high degree of 
flame-resistance. In carrying out the comparative studies of this example 
the following base composition was used. 
______________________________________ 
Component Parts by Weight 
______________________________________ 
SBR1500.sup.(1) 100 
Zinc Oxide 5 
Stearic Acid 1 
MBT.sup.(2) 0.5 
Monex.sup.(3) 1.5 
Sulfur 1.5 
______________________________________ 
.sup.(1) SBR 1500 is a coldpolymerized, nonpigmented, rosinacid 
emulsified, saltacid coagulated, staining styrenebutadiene rubber of 23.5 
target bound styrene. 
.sup.(2) mercaptobenzothiazole 
.sup.(3) accelerator containing tetramethylthiuram monosulfide 
The effect of additives on the flame-resistance of the composition is shown 
in the table below. "Chlorowax 70", a chlorinated paraffin, is a 
commercial product containing about 70% by weight chlorine and having a 
specific gravity of about 1.66. Alumina trihydrate (ATH) is a commercial 
product supplied by Reynolds Metals Co. and designated "RH31F". 
The rubber compositions were compounded in a conventional manner on a 
cooled rubber mill. Slab samples were compression molded for 30 minutes at 
330.degree. F. Moldings were cooled prior to removal from the press, and 
specimens were cut to size for testing. Oxygen Index (ASTM D 2863) was 
employed as the test method, since the numerical rating scale of this 
method facilitates precise comparison. ".DELTA.OI" in the table designates 
the increase in Oxygen Index (flame-resistance) over that of the base 
composition provided by the additives and additive combinations shown. 
______________________________________ 
Parts by Weight of Additive 
Alumina 
Chlorowax Tri- Ferric 
Oxygen 
Additives: 
70 hydrate Oxide Index .DELTA.OI 
______________________________________ 
(a) 0 0 0 18.9 -- 
(b) 0 50 0 21.5 +2.6 
(c) 0 0 5 18.8 .about.0 
(d) 0 50 5 20.8 +1.9 
(e) 0 0 8.4 19.1 +0.2 
(f) 0 50 8.4 20.8 +1.9 
(g) 25 0 0 20.3 +1.4 
(h) 25 0 5 21.6 +2.7 
(i) 25 50 0 23.6 +4.7 
(j) 25 50 5 25.9 +7.0 
(k) 64 0 0 24.6 +5.7 
(l) 64 0 8.4 26.6 +7.7 
(m) 64 50 0 30.1 +11.2 
(n) 64 50 8.4 32.4 +13.5 
______________________________________ 
The .DELTA.OI values for compositions (b), (c), (e), and (g) show the 
negligible to small effects of the alumina trihydrate, iron oxide and 
halogen compound, when used individually, on the flame resistance of the 
elastomer composition, while (h), and (i), illustrate the weak to moderate 
effectiveness of the iron oxide/halogen compound and ATH/halogen compound 
combinations. Stocks (d) and (f) illustrate that in the absence of the 
halogen compound, ferric oxide does not abet the activity of ATH. 
The .DELTA.OI comparison (j)&gt;(h) or (i) shows that in the presence of the 
halogen compound the combined metallics (iron oxide and alumina 
trihydrate) are more effective than either individual metallic. This 
relationship persists over a broad range of halogen compound loadings as 
illustrated by the additional comparison (n)&gt;(l) or (m). More strikingly, 
the comparisons (j)&gt;(b)+(h), (j)&gt;(c)+(i), (n)&gt;(b)+(l) and (n)&gt;(c)+(m) 
illustrate that over a broad range of halogen compound levels, the 
addition of the second metallic exerts a fire-retardant effect greater 
than that expected from the component effects. Finally the comparisons 
(j)-(i)&gt;(h)-(g) and (j)-(h)&gt;(i)-(g) show that in the presence of the 
halogen compound the effectiveness of each metallic is abetted by the 
presence of the other metallic. 
EXAMPLE 2 
This Example illustrates the effectiveness of the combinations of this 
invention in providing flame-retarded SBR compositions, as compared to 
known combinations of high performance, including substantially costlier 
systems containing antimony trioxide. Significant comparisons are made at 
equal levels of chloroparaffin. The zinc borate shown is a commercial 
fire-retardant supplied by Humphrey Chemical Corporation and designated 
"ZB-112R". Other additives, base compositions, preparations and tests are 
as described in Example 1. 
______________________________________ 
Parts by Weight 
Additives (o) (p) (q) (r) (s) 
______________________________________ 
Chlorowax 70 
25 25 64 64 64 
Alumina -- 50 -- 50 50 
Trihydrate 
Ferric Oxide 
-- 5 -- -- 8.4 
Antimony 5 -- 20 -- -- 
Trioxide 
Zinc Borate 
5 -- -- 5 -- 
Oxygen Index 
21.8 25.9 31.4 29.8 32.4 
.DELTA.OI +2.9 +7.0 +12.5 +10.9 +13.5 
______________________________________ 
The .DELTA.OI data show that the fire-retardant effectiveness of the new 
combinations is higher than that of typical high-performance systems 
comprising combinations of chloroparaffin with antimony trioxide, antimony 
trioxide/zinc borate and alumina trihydrate/zinc borate. Further 
perspective is provided by the relatively low effectiveness of alternative 
fire-retardant agents and combinations, as illustrated by the examples in 
the table below: 
______________________________________ 
Parts by Weight 
Additives (t) (u) (v) (w) (x) 
______________________________________ 
Tricresyl Phosphate 
20 -- -- -- -- 
Isodecyldiphenyl Phosphate 
-- 20 20 20 -- 
Tetrachlorophthalic Anhydride 
-- -- 22.6 22.6 -- 
Hexabromobiphenyl 
-- -- -- -- 14.7 
Antimony Trioxide 
-- -- -- -- 7 
Ferric Oxide -- -- -- 4.2 -- 
Oxygen Index 19.3 19.0 18.7 19.7 21.0 
.DELTA.OI +0.4 0 0 +0.8 +2.1 
______________________________________ 
EXAMPLE 3 
As shown in this Example, utilization of the novel flame retardant system 
of this invention in combination with additional fire-retardant additives, 
such as antimony trioxide and zinc borate, provides a degree of fire 
retardancy superior to that obtained with costlier conventional 
combinations. The additives, base composition and preparations were as 
described in Examples 1 and 2. 
______________________________________ 
Parts by Weight 
Additives (y) (z) (aa) (bb) (cc) 
______________________________________ 
Chlorowax 70 64 64 64 64 64 
Alumina Trihydrate 
-- -- 50 50 50 
Ferric Oxide -- -- -- -- 8.4 
Antimony Trioxide 
20 40 20 15 10 
Zinc Borate -- -- -- 5 5 
Oxygen Index 31.4 35.8 38.9 40.2 40.7 
UL-94V-1/16"* V-2 V-0 V-1 fails V-0 
______________________________________ 
*Underwriters' Laboratories Vertical Burning Test for Classifying 
Materials 94 V0, 94 V1 or 94 V2. Specimens were 1/16" in thickness, teste 
in "as prepared" condition. Performance ratings in order of descending 
merit are V0 V1 V2 fails. 
The comparative data show that composition (cc), containing the economical 
chloroparaffin/alumina trihydrate/ferric oxide combination and the lowest 
level of costly antimony trioxide, provides the highest levels of 
performance in the flammability tests. 
EXAMPLE 4 
Utilization of the flame retardant system of this invention, with or 
without additional fire-retardant additives, likewise provides a high 
degree of fire retardancy in filler-reinforced SBR compositions, as 
illustrated by the following examples involving SBR/carbon black 
masterbatch. The base composition in all cases is: 
______________________________________ 
Component Parts by Weight 
______________________________________ 
SBR 1606 162 
Zinc Oxide 5 
Stearic Acid 1 
MBTS 0.8 
Monex 1.5 
Sulfur 3.1 
______________________________________ 
SBR 1606 is a cold-polymerized, staining, black SBR masterbatch containing 
52 phr N330 carbon black and 10 phr highly aromatic oil, and having a 
specific gravity of 1.12 and a compound Mooney viscosity (ML-4@212.degree. 
F.) of typically 52. "MBTS" denotes benzothiazyl disulfide. The other 
additives were as defined in Examples 1 to 3. Test materials were prepared 
as in Example 1 except for the compression molding temperature, which was 
300.degree. F. 
______________________________________ 
Parts by Weight 
Additives (dd) (ee) (ff) (gg) (hh) 
______________________________________ 
Chlorowax 70 25 25 25 64 64 
Alumina Trihydrate 
-- 50 55 50 80 
Ferric Oxide -- 4.2 6.5 8.4 8.4 
Antimony Trioxide 
5 -- -- -- -- 
Zinc Borate 5 5 -- 5 5 
Oxygen Index 28.9 29.8 31.7 35.8 37.3 
UL-94V-1/8"* V-0 V-0 V-0 V-0 V-0 
UL-(94-1/16"* V-1 V-1 V-1 V-0 V-0 
______________________________________ 
*Specimens of the thickness indicated were tested as defined in Example 3 
 
The test data show that compositions (ee) through (hh) containing the new 
combinations of the invention are highly flame-resistant. At equal 
chloroparaffin levels, the combinations are higher in overall 
effectiveness than the conventional antimony trioxide system (dd). 
EXAMPLE 5 
This Example illustrates the utility of this invention in providing 
flame-retarded natural rubber compositions. In the table below, the first 
four ingredients were combined in a "B" Banbury internal mixer in a 
conventional manner. The remaining ingredients were incorporated on a 
rubber mill with rolls at 160.degree. F. Slab samples were compression 
molded for 30 minutes at 293.degree. F. After cooling, the specimens were 
removed from the press and cut to size for testing. 
______________________________________ 
Parts by Weight 
Formulation (ii) (jj) 
______________________________________ 
Pale Crepe #1 100 100 
Stearic Acid 3 3 
Zinc Oxide 5 5 
N-330 carbon black 
50 50 
Chlorowax 70 25 25 
Alumina Trihydrate 
50 50 
Ferric Oxide -- 5 
MBTS 0.6 0.6 
Sulfur 2.5 2.5 
Oxygen Index 24.1 28.3 
______________________________________ 
The Oxygen Index data show that composition (jj), containing the fire 
retardants of this invention is more highly flame-retarded than a 
comparable composition containing a conventional combination (ii). 
EXAMPLE 6 
This Example illustrates the utilization of ferrosoferric oxide and of 
other chlorine- or bromine-containing organic fire-retardant additives in 
the combinations of this invention to yield highly flame-retarded 
elastomer compositions. The base composition and the preparative procedure 
were as described in Example 4. Dechlorane Plus 25 is a chlorinated 
organic fire-retardant additive, containing 65% chlorine, marketed by 
Hooker Chemical Corporation. 
______________________________________ 
Parts by Weight 
Additives (kk) (ll) (mm) (nn) (oo) (pp) 
______________________________________ 
Chlorowax 70 25 25 -- -- -- -- 
Dechlorane Plus 25 
-- -- 27 27 -- -- 
Decabromodiphenyl 
-- -- -- -- 21 21 
Oxide 
Alumina Trihydrate 
50 50 50 50 50 50 
Ferrosoferric Oxide 
-- 7 -- -- -- -- 
Ferric Oxide -- -- -- 5 -- 5 
Oxygen Index 26.6 28.0 25.0 28.7 26.9 28.6 
______________________________________ 
The Oxygen Index data show that compositions (ll), (nn), and (pp) 
containing the new combinations are more highly flame-resistant than 
corresponding compositions with conventional combinations containing the 
same halogen compound. 
EXAMPLE 7 
This Example illustrates the utility of this invention in providing highly 
flame-retarded elastomer foams in contrast to conventionally 
flame-retarded analogues. 
The foams prepared in this Example are of the no-gel latex SBR type. No-gel 
latex foams are prepared by whipping or frothing a rubber latex and 
thereafter dehydrating and curing the rubber foam produced thereby. 
Methods of preparing no-gel latex foam are well known in the art. A number 
of such formulations and methods for using those processes for making 
solid foam products are disclosed in U.S. Pat. Nos. Re. 27,366 and 
3,961,001, incorporated herein by reference. A typical SBR composition 
disclosed in the latter is illustrated in the table below. All parts shown 
are by dry weight. 
______________________________________ 
Ingredients Parts 
______________________________________ 
Styrene-butadiene copolymer (LPF-3757, Goodyear) 
100.00 
Alkylated phenol non-staining antioxidant 
(Naugawhite, Uniroyal Chemical) 
1.00 
Sodium hexametaphosphate ("Calgon", Calgon Corp.) 
0.50 
N-octadecyl disodium sulfosuccinate 
(Aerosol 18, American Cyanamide Corp.) 
2.50 
Sodium salt of sulfate monoester of a mixture of 
various fatty alcohols, chiefly lauryl alcohol 
(Aquarex WAQ, duPont) 1.14 
Dry, ground nepheline syenite (Minex 3, American 
Syenite Corp.) 70.0 
Alumina Trihydrate (Hydral 710, Alcoa) 
70.0 
KOH 0.25 
Zinc salt of 2-mercaptobenzothiazole 
(OXAF, Uniroyal Chemical) 1.25 
Sulfur 1.65 
Zinc Oxide 1.25 
Carbon black-channel type 1.10 
Zinc diethyldithiocarbamate 0.75 
(Ethazate, Uniroyal Chemical) 
Sodium polyacrylate (Modicol VD, Nopco Chemical) 
0.11 
______________________________________ 
A no-gel latex SBR foam formulation was prepared with conventional 
fire-retardant additives comprising 140 parts of alumina trihydrate (70 
parts of Hydral 710 and 70 parts of Alcoa C-30-BF), no Minex 3, 20 parts 
of chlorinated paraffin (added as 30.8 parts of Delvet 65, a 65% solids 
dispersion of Chlorowax 70 in water, Diamond Shamrock Chemical Co.) and 5 
parts of antimony trioxide. A 6".times.18".times.15/16" specimen of this 
foam having a density of 5 lb./ft..sup.3 was tested by the proposed 
"Standard Method for Surface Flammability of Flexible Cellular Materials 
Using a Radiant Energy Heat Source" (ASTM Committee D11.17, 01-77 Draft 
Proposal). The specimen showed a flame spread index (Is) of 106. 
In a second preparation, 5 parts of ferric oxide was added to the same 
formulation. A 6".times.18".times.15/16" specimen of this foam, having a 
density of 5 lb./ft..sup.3, showed as Is of 4. 
Thus the foam specimen containing the new combination shows far greater 
flame resistance than the specimen containing the conventional combination 
of fire-retardant ingredients.