A low smoke generating, high char forming, substantially nondripping flame resistant thermoplastic multi-block copolyester wherein the weight ratio of high melting point blocks to low melting point blocks is from about 8:1 to 1:4, and said copolyester has a melting point below about 175.degree. C., said copolyester composition containing a bromine containing flame retardant; antimony trioxide; a drip suppressant for the multi-block copolyester, 25-65 parts per 100 parts multi-block copolyester of 50-88% alumina trihydrate and 12-50% of a magnesium compound selected from the group consisting of magnesium carbonate, magnesium oxide, and particulate magnesium hydroxide and, optionally, containing calcium carbonate and, preferably, containing a coupling agent having a hydrolyzable moiety containing titanium or silicon and an organophilic group.

BACKGROUND OF THE INVENTION 
This application is a continuation-in-part of Application Ser. No. 57,564 
filed June 15, 1987 which is a continuation-part of Application Ser. No. 
890,712, filed July 30, 1986 all now abandoned. 
Thermoplastic multi-block copolyester elastomers have gained acceptance in 
many fields because of their outstanding physical properties which are 
unique in relation to other thermoplastic polymers. However, copolyester 
elastomers are flammable and this limits their usefulness for preparing 
electrical parts, wire coverings for telecommunications, optical fiber 
outer jacketing and other applications where fire retardant materials are 
needed. 
Numerous halogenated organic compounds either alone or in combination with 
antimony trioxide have been tested and recommended for use in polyester 
homopolymers or random copolyesters, as have various inorganic additives. 
Because of the relatively high flammability of multi-block copolyesters, 
the ease with which such copolyesters undergo degradation during melt 
processing, and the difficulty of retaining a useful amount of flexibility 
in the multi-block copolyesters in the presence of significant amounts of 
added materials, there still is a need for fully acceptable fire resistant 
multi-block copolyester compositions that are substantially nondripping 
when burned and, most importantly, the copolyester compositions should 
generate a minimum amount of smoke and form a large amount of char when 
burned. Also, the thermoplastic compositions must be extrudable and retain 
a good combination of physical properties. The present invention provides 
flame resistant multi-block copolyester compositions which do not exhibit 
enhanced degradation. The compositions of this invention are low smoke 
generating and high char forming; do not drip when burned; and have V-O 
ratings for flammability according to the UL-94 Vertical Burn Test. 
Recently, substantially nondripping flame resistant multi-block copolyester 
compositions have been developed by incorporating in the copolyester a 
combination of a flame retardant to resist burning and a drip suppressant 
such as fumed colloidal silica or an organophilic clay. Such flame 
resistant copolyester compositions that are substantially nondripping are 
described in U.S. Pat. No. 4,521,557 to McKenna dated June 4, 1985 and 
U.S. Pat. No. 4,582,866 to Shain dated April 16, 1986, both patents 
assigned to E. I. du Pont de Nemours and Company. These flame resistant 
copolyester compositions referred to above are quite useful especially for 
coverings on optical fibers and wire since they are substantially 
nondripping when burned. However, these flame resistant nondripping 
multi-block copolyester compositions when burned generate considerable 
amounts of smoke and, unfortunately, only small amounts of char. For many 
uses, for example plenum cable covering, the compositions should not only 
be flame resistant but the compositions should be as smokeless as 
possible. Smoke, of course, presents a serious hazard during a fire and 
causes secondary damage over a large area involved in the fire. Also, it 
is important that the compositions form a high percentage of char when 
burned. High char formation is beneficial because char has enough 
integrity to remain in place, for example, on a bundle of wires, while the 
polymer is burning and the char functions during the fire as an insulator. 
The char keeps some of the heat of the external fire away from the wire 
bundle, minimizing its contribution to the flame and maximizing the length 
of time during which the wires perform their normal function. Many 
compositions have been rejected by manufacturers because of the large 
amounts of smoke they generate and the small amount of char formation made 
by the polymers when burned. 
The present invention that is directed to a novel copolyester composition 
is especially useful for covering bundles of insulated telecommunication 
wires, e.g., optical fibers, metal wires, etc., with a flame-protective 
jacketing material. The copolyester compositions of the present invention 
are not only flame resistant and substantially nondripping but, in 
addition, most importantly, these compositions burn without generating 
much smoke and they form large amounts of char. The copolyester 
compositions of this invention can be characterized as low smoke 
generating and high char forming, primarily due to the addition of 
relatively small amounts of char-forming additives, and can do so without 
intumescing into a ceramic barrier. The copolyesters used in the flame 
retardant compositions have a melt flow rate of at least 0.4 g/10 minutes, 
usually 0.9 g/10 minutes, at 190.degree. C. which makes the compositions 
readily processible. Also, to substantially improve the physical 
properties of the composition of this invention coupling agents, when 
added, have unexpectedly substantially increased the tensile strength of 
the compositions. 
SUMMARY OF THE INVENTION 
The present invention provides a low smoke generating, high char forming, 
substantially nondripping, flame resistant thermoplastic copolyester 
composition which comprises 
(a) a multi-block copolyester, or blends thereof, of film forming molecular 
weight consisting essentially of (A) repeating high melting point blocks 
comprising repeating short chain ester units having the formula 
##STR1## 
wherein D is a divalent radical remaining after the removal of hydroxyl 
groups from a low moleclar weight diol having a molecular weight not 
greater than 250 and R is a divalent radical remaining after the removal 
of carboxyl groups from a dicarboxylic acid having a molecular weight not 
greater than 300, D and R being selected so that a polymer consisting 
essentially of short chain ester units having a number average molecular 
weight of at least 5000 has a melting point of at least 150.degree. C., 
(B) repeating low melting point blocks which are derived from compounds 
containing hydroxyl groups or carboxyl groups or mixtures thereof having a 
number average molecular weight of 400-4000 and a melting point not 
greater than about 100.degree. C., and (C) an amount of difunctional 
radicals sufficient to join repeating blocks (A) and (B) to form a 
multi-block copolyester, the weight ratio of (A) to (B) being from about 
8:1 to 1:4, preferably from about 5:1 to 1:2, said multi-block copolyester 
having a melting point below about 175 .degree. C., preferably 
130.degree.-170 .degree. C., 
(b) about 5-45 parts per 100 parts of said multi-block copolyester of a 
bromine containing organic flame retardant containing at least 50% by 
weight bromine, 
(c) about 0.20-1.5 parts per part of said bromine containing organic flame 
retardant of antimony trioxide, 
(d) a drip suppressant for the multi-block copolyester, and 
(e) from about 25-65 parts per hundred parts multi-block copolyesters of 
inorganic compounds comprising 50-88 percent alumina trihydrate and 12-50 
percent of a magnesium compound selected from the group consisting of (1) 
magnesium carbonate, (2) magnesium oxide, and (3) particulate magnesium 
hydroxide with 90% of the particles of magnesium hydroxide having a 
maximum dimension no more than 1 micrometer and the particles of magnesium 
hydroxide being surface treated to prevent agglomeration. 
The low smoke generating, high char forming compositions preferably contain 
a coupling agent which, quite surprisingly, substantially increases the 
tensile strength and improves the elongation at break of the copolyester 
compositions. The coupling agents that are used in the copolyester 
composition are compounds having a hydrolyzable moiety containing titanium 
or silicon and also an organophilic group. The hydrolyzable moieties are 
usually aliphatic orthosilicate or orthotitanate groups. 
The compositions of the present invention are readily processible by 
conventional rubber extrusion techniques. The compositions are especially 
useful for plenum cable jacketing for telecommunication wires and optical 
fibers due principally to the low amount of smoke generated and the high 
amount of char formed when the compositions are burned, the high melt flow 
indices and the high tensile strength of the thermoplastic compositions. 
DETAILED DESCRIPTION OF THE INVENTION 
The novel low smoke generating, high char forming, flame resistant 
thermoplastic multi-block copolyester compositions have incorporated 
therein effective amounts of a bromine containing organic flame retardant; 
antimony trioxide; a drip suppressant for the multi-block copolyester, 
e.g., an organophilic clay, fumed colloidal silica, or 
polytetrafluoroethylene, usually having particle sizes less than about 200 
micrometers; about 25-65 parts, preferably 30-60 parts, per hundred parts 
multi-block copolyester of inorganic compounds comprising 50-88 percent, 
preferably 60-75 percent, alumina trihydrate and 12-50 percent, preferably 
25-40 percent of a magnesium compound selected from the group consisting 
of (1) magnesium carbonate (2) magnesium oxide, and (3) particulate 
magnesium hydroxide with 90 percent of the particles of magnesium 
hydroxide having a maximum dimension no more than 1 micrometer and the 
particles of magnesium hydroxide are surface treated to prevent 
agglomeration. The incorporation of the magnesium compound and alumina 
trihydrate in the flame resistant, substantially nondripping multi-block 
copolyester composition does not substantially interfere with the other 
properties of the composition and, surprisingly, results in a composition 
that when burned, has a V-O rating under the UL-94 Vertical Burn Test, 
generates a very low percentage of smoke and a very high percentage of 
char when compared to similar compositions without the magnesium compounds 
described herein. 
It has been found that a superior copolyester composition can be made if 
the composition contains inorganic compounds such as alumina trihydrate 
and a magnesium compound selected from magnesium carbonate, magnesium 
hydroxide and magnesium oxide, plus a coupling agent. The addition of a 
coupling agent has the beneficial effect of substantially increasing the 
tensile strength and improving the elongation at break of the copolyester 
composition without detracting from the other valuable properties of low 
smoke generation and high char formation of the polymer composition. The 
coupling agents used in the present invention contain a hydrolyzable 
moiety containing titanium or silicon and also an organophilic group. 
Usually, the hydrolyzable moiety is one or more aliphatic silicate 
orthoester groups or aliphatic titanate orthoester groups, and can be a 
chelate group. Representative organophilic groups in the coupling agent 
include: phosphate esters, pyrophosphate esters, phosphite esters, 
carboxylic esters, aromatic orthoesters, sulfonyl esters, alkyl or 
substituted alkyl esters, vinyl esters and epoxy esters. Representative 
coupling agents, such as described above, have the following chemical 
structures. Organotitanate coupling agents of the formula (RO).sub.m 
-Ti(OXR.sup.2 Y).sub.n where (RO) is a monoalkoxy group or two (RO) groups 
are a chelate group, usually the alkoxy group contains 1-5 carbon atoms, X 
is sulfonyl, phosphato, pyrophosphato or phosphito; R.sup.2 is an 
alkylidene group, usually containing 3-20 carbon atoms or an arylene 
group, usually containing 6-12 carbon atoms; Y is hydrogen, an alkyl 
group, usually containing 1-6 carbon atoms, a vinyl group, an amino group 
or a mercapto group; m is 1-3 and n is 1-3. Silane coupling agents of the 
formula YRSiX.sub.3 where Y is a functional organic group, especially an 
amino, a methacryloxy or epoxy group; R is an alkylidene group, usually 
containing 2-4 carbon atoms, and X is a hydrolyzable group, especially 
alkoxy, usually containing 1-2 carbon atoms. 
Representative coupling agents having a hydrolyzable moiety containing 
titanium or silicon and an organophilic group include titanium IV, bis 
(dioctyl) pyrophosphato-O, oxyethylanediolato, (adduct), dioctyl hydrogen 
phosphite; tetraisopropyl, di[dioctylphosphito]titanate; 
di[dioctylpyrophosphito]ethylene titanate; methacrylic functional amine 
salt of di[dioctylpyrophosphato]ethylene titanate; isopropyl, 
tri(dioctylphosphato) titanate; isopropyl tri (dioctylpyrophosphato) 
titanate; titanium di (dioctylphosphate oxyacetate; isopropyl 
triisostearoyl titanate; titanium dimethacrylate, oxyacetate; isopropyl 
diisostearyl-methacryl titanate; isopropy1,4-aminobenzenesulfonyl titanium 
isostearate, methacrylate oxyacetate; isopropyl, tri-cumylphenyl titanate; 
isopropyl,tri(dioctylpyrophosphato) titanate. Representative silane 
coupling agents include compounds having the formula (RO).sub.3 
Si--R.sub.1 --SO.sub.2 N.sub.3 where R is an alkyl group,usually having 
1-2 carbon atoms, and R.sub.1 is an alkylidene group,usually having 1-4 
carbon atoms. Other representative silane coupling agents include 
3-aminopropyltriethoxysilane, vinyl triethoxysilane, 
3-methacryloxypropyl,trimethoxysilane, beta-cyclohexylethyltrimethoxy 
silane, 3-chloroisobutyltriethoxysilane, vinyl-tris (beta-methoxyethoxy) 
silane; gamma amino propyltriethoxy silane; 
gamma-mercaptopropyltrimethoxysilane and gamma 
chloropropyltrimethoxysilane. 
The coupling agents used in the present invention are well known in the art 
and they are also described in Modern Plastics Encyclopedia 1984-1985, 
pages 121, 123 to 125; Ken-React References Manual, Bulletin No. KR-0278-7 
Rev. and U.S. Pat. Nos. 4,083,820, 4,096,110, 4,094,853, and 4,163,004, 
the disclosures of which are incorporated herein by reference. 
The amount of coupling agent added to the copolyester elastomer can be from 
about 0.1-5 parts per 100 parts copolyester, usually 0.5-3 parts. The 
coupling agents can be added to the copolyester composition either in 
solid form or mixed with a carrier such as mineral oil. 
The coupling agents can be added to the composition either before or after 
the inorganic material, e.g., alumina trihydrate and magnesium compound, 
has been added. Preferably, they are added to the non-polymeric 
ingredients, with vigorous agitation, before the melt blending step. The 
reaction between the coupling agent and the inorganic material and 
copolyester elastomer occurs when the composition is at elevated 
temperatures of the order of about 150.degree.-200.degree. C. 
It is believed that the inorganic portion of the coupling agent reacts with 
the hydroxy groups on the surface of the particles of the inorganic 
compound and the organic portion of the coupling agent readily blends with 
the copolyester elastomer. The most important effect is that the 
copolyester composition shows a significant and unexpectedly high increase 
in tensile strength without detrimentally affecting the other properties 
of the flame retardant composition. 
The thermoplastic multi-block copolyesters useful in this invention consist 
essentially of repeating blocks of repeating short chain ester units, as 
described above, which have high melting points (at least 150.degree. C.) 
and repeating low melting point blocks (not greater than 100.degree. C.) 
which have a number average molecular weight of about 400-4000. The low 
melting point and high melting point blocks are joined together by 
difunctional radicals which, for example, can be derived by reaction of 
the high or low melting point blocks with diols, dicarboxylic acids, 
diepoxides or diisocyanates. The high melting blocks crystallize at useful 
service temperatures to provide physical crosslinks in the multi-block 
elastomer while the low melting blocks provide elastomeric 
characteristics. At processing temperatures, generally of the order of 
150.degree.-200.degree. C., the high melting point blocks melt and the 
molten polymer may be processed as a thermoplastic. The melt processing 
temperature must be below the decomposition temperature of alumina 
trihydrate; otherwise the copolyester will be hydrolyzed, decreasing its 
molecular weight and therefore its physical properties. Preferably each 
copolyester should have a melting point, as measured by differential 
scanning calorimetry, ASTM D-3418 within the range of from about 
130.degree.-175.degree. C. A copolyester having a melting point below 
about 175.degree. C. can be obtained by procedures well known in the art, 
for example, by regulating the number of short-chain ester units in the 
copolyester or blend of copolyesters. The fewer the short-chain ester 
units, which are the hard segments, the lower the melting point, or a 
copolyester can be prepared using a mixture of dicarboxylic acids, e.g., 
isophthalic acid and terephthalic acid to lower the melting point of the 
copolyester elastomer. 
The ratio of high melting point blocks to low melting point blocks can be 
between 8:1 and 1:4, preferably between 5:1 and 1:2. When a mixture of 
two or more different copolyesters is used, the weight average of their 
high melting point block:low melting point block ratios is within one of 
the above ranges. It is important that the ratio of high melting point 
blocks to low melting point blocks in the copolyester is within the range 
described to obtain the properties needed for the uses contemplated. For 
example, if the amount of high melting point blocks exceeds the ratio, the 
resulting composition will not have sufficient flexibility to bend without 
cracking. 
The high melting point blocks which comprise repeating short chain ester 
units of the formula 
##STR2## 
are derived from one or more low molecular weight diols, HODOH, having a 
molecular weight not greater than 250 and one or more dicarboxylic acids, 
HOOCRCOOH, having a molecular weight of not greater than 300. 
The term "low molecular weight diols" as used herein should be construed to 
include equivalent ester-forming derivatives, provided, however, that the 
molecular weight requirement pertains to the diol only and not to its 
derivatives. 
Aliphatic or cycloaliphatic diols with 2-15 carbon atoms are preferred, 
such as ethylene, propylene, tetramethylene, pentamethylene, 
2,2-dimethyltrimethylene, hexamethylene, and decamethylene glycols, 
dihydroxy cyclohexane and cyclohexane dimethanol. Unsaturated diols such 
as butene-2-diol-1,4 can also be used, particularly in minor amounts in 
admixture with butanediol-1,4. 
The term "dicarboxylic acids" as used herein, includes equivalents of 
dicarboxylic acids having two functional carboxyl groups which perform 
substantially like dicarboxylic acids in reaction with glycols and diols 
in forming copolyester polymers. These equivalents include esters and 
ester-forming derivatives, such as acid anhydrides. The molecular weight 
requirement pertains to the acid and not to its equivalent ester or 
ester-forming derivative. 
Both aliphatic dicarboxylic acids, such as cyclohexane dicarboxylic acid, 
and aromatic dicarboxylic acids can be used, preferably aromatic 
dicarboxylic acids are employed. Among the aromatic dicarboxylic acids for 
preparing the copolyester polymers, those with 8-16 carbon atoms are 
preferred, particularly the phenylene dicarboxylic acids, i.e., phthalic, 
terephthalic and isophthalic acids and their dimethyl esters and mixtures 
thereof. 
The diol and dicarboxylic acid must be chosen to provide a melting point of 
at least 150.degree. C. for a polymer having a number average molecular 
weight of at least 5000 and being derived exclusively from short chain 
ester units. Preferred high melting point blocks are derived from ethylene 
glycol or 1,4-butanediol by reaction with terephthalic acid alone or in 
admixture with up to about 30% by weight isophthalic acid or phthalic acid 
or mixtures thereof. Polymers based on 1,4-butanediol are especially 
preferred. 
The low melting point blocks in said multi-block copolyesters can be 
provided by a variety of compounds having number average molecular weights 
of 400-4000 which contain hydroxyl groups or carboxyl groups or mixtures 
thereof. Suitable compounds for forming low melting blocks include 
poly(alkylene oxide) glycols, polyoxyalkylene diimide diacids, low melting 
polyester glycols and hydrocarbon glycols or diacids. 
Representative poly(alkylene oxide) glycols that can be used to make the 
multi-block copolyester have a carbon-to-oxygen atomic ratio of about 
2.0-4.3 and have a number average molecular weight of about 400-4000 and 
include poly(ethylene oxide) glycol, poly(1,2- and 1,3-propylene oxide) 
glycol, poly(tetramethylene oxide) glycol, random or block copolymers of 
ethylene oxide and 1,2-propylene oxide, and random or block copolymers of 
tetrahydrofuran with minor amounts of a second monomer such as ethylene 
oxide. Preferred poly(alkylene oxide) glycols include poly(tetramethylene 
oxide) glycol having a number average molecular weight of 600-1600, 
especially 800-1200, and ethylene oxide-capped poly(propylene oxide) 
glycol having a number average molecular weight of 1500-2800 and an 
ethylene oxide content of 15-35% by weight. 
Polyoxyalkylene diimide diacids suitable for use herein are high molecular 
weight diimide diacids wherein the average molecular weight is greater 
than about 700, most preferably greater than about 900. They may be 
prepared by the imidization reaction of one or more tricarboxylic acid 
compounds containing two vicinal carboxyl groups or an anhydride group and 
an additional carboxyl group which must be esterifiable and preferably is 
nonimidizable with a high molecular weight polyoxylalkylene diamine. 
In general, the polyoxyalkylene diimide diacids useful herein may be 
characterized by the following formula: 
##STR3## 
wherein each R is independently a trivalent organic radical, preferably a 
C.sub.2 to C.sub.20 aliphatic, aromatic or cycloaliphatic trivalent 
organic radical; each R, is independently hydrogen or a monovalent organic 
radical preferably selected from the group consisting of C.sub.1 to 
C.sub.6 aliphatic and cycloaliphatic radicals and C.sub.6 to C.sub.12 
aromatic radicals, e.g. benzyl, most preferably hydrogen; and G is the 
radical remaining after the removal of the terminal (or as nearly terminal 
as possible) hydroxy groups of a long chain ether glycol having an average 
molecular weight of from about 600 to about 12000, preferably from about 
900 to about 4000, and a carbon-to-oxygen atomic ratio of from about 1.8 
to about 4.3. The polyetherimide esters which can be derived from these 
polyoxyalkylene diimide diacids are described in U.S. Pat. Nos. 4,556,705 
and 4,556,688. 
The required low melting (i.e., below about 100.degree. C.) polyester 
glycols are either polylactones or the reaction products of low molecular 
weight diols (i.e., less than about 250) and an aliphatic dicarboxylic 
acid. Representative low melting polyester glycols are obtained by 
reaction of diols such as ethylene glycol, 1,4-butanediol, pentanediol, 
hexanediol, 2,2-dimethyl-1,3-propanediol and mixtures of ethylene glycol 
and propylene glycol with diacids such as adipic acid, glutaric acid, 
pimelic acid, suberic acid and isosebacic acid. Polylactone glycols 
derived from unsubstituted and substituted caprolactone or butyrolactone 
are also useful as low melting polyester glycols. Preferred polyester 
glycols include polycaprolactone glycol and poly(tetramethylene adipate) 
glycol having number average molecular weights of 800-2500. 
Representative hydrocarbon glycols or diacid derivatives which can be used 
to provide low melting point blocks include polybutadiene or polyisoprene 
glycols and saturated hydrogenation products of these materials. 
Dicarboxylic acids formed by oxidation of polyisobutylene/diene copolymers 
are also useful materials. Dimer acid, particularly the more highly 
refined grades, is a useful hydrocarbon diacid which can be used alone or 
in combination with other low melting point compounds such as the 
poly(alkylene oxide) glycols and polyoxyalkylene diimide diacids to 
provide low melting point blocks. 
The multi-block copolyester described herein of film forming molecular 
weight can be made by procedures known in the art. Copolyesters in which 
the low melting point blocks are provided by poly(alkylene oxide) glycols 
or hydrocarbon glycols or diacids are readily made by ester interchange 
reactions followed by polycondensation. Different procedures are required 
when the low melting point block is provided by a polyester glycol because 
ester exchange can take place with the high melting point ester blocks 
which ultimately destroys the blockiness of the polymer. 
A typical procedure for preparing multi-block copolyesters by ester 
interchange involves heating a dicarboxylic acid or its methyl ester with 
a poly(alkylene oxide) glycol or hydrocarbon glycol (or diacid or mixtures 
thereof) and a molar excess of low molecular weight diol in the presence 
of a catalyst at about 150.degree.-260.degree. C. and a pressure of 0.05 
to 0.5 MPa, usually ambient pressure, while distilling off water formed by 
esterification and/or methanol formed by ester interchange. The glycol or 
the diacid that provide the low melting point blocks are incorporated into 
the polymer through difunctional radicals provided by the dicarboxylic 
acid in the case of the glycols, or by the low molecular weight diols in 
the case of the diacids. The particular amount of difunctional radicals 
incorporated into the polymer will vary and depends on the molecular 
weights and the ratio of the high and low melting point blocks and the 
functional groups on the blocks. However, in all cases the difunctional 
radicals constitute a minor amount of the total weight of the polymer. 
Depending on temperature, catalyst, glycol excess and equipment, this 
reaction can be completed within a few minutes, e.g., about two minutes, 
to a few hours, e.g., about two hours. This procedure results in the 
preparation of a low molecular weight prepolymer which can be carried to a 
high molecular weight multi-block copolyester by distillation of the 
excess of short-chain diol. The second process stage is known as 
"polycondensation". 
Additional ester interchange occurs during this polycondensation which 
serves to increase the molecular weight of the polymer. Best results are 
usually obtained if this final distillation or polycondensation is run at 
less than about 670 Pa, preferably less than about 250 Pa, and about 
200.degree.-280.degree. C., preferably about 220.degree.-260.degree. C., 
for less than about two hours, e.g., about 0.5 to 1.5 hours. It is 
customary to employ a catalyst while carrying out ester interchange 
reactions. While a wide variety of catalysts can be employed, organic 
titanates such as tetrabutyl titanate used alone or in combination with 
magnesium or calcium acetates are preferred. The catalyst should be 
present in an amount of about 0.005 to 2.0 percent by weight based on 
total reactants. 
Batch or continuous methods can be used for any stage of polymer 
preparation. Polycondensation of prepolymer can also be accomplished in 
the solid phase by heating divided solid prepolymer in a vacuum or in a 
stream of inert gas to remove liberated low molecular weight diol. 
Several procedures have been used to prepare multi-block copolyesters 
wherein the low melting point blocks are polyesters as well as the high 
melting point blocks. One procedure involves carrying out a limited ester 
interchange reaction in the presence of an exchange catalyst between two 
high molecular weight polymers such as poly(butylene terephthalate) and 
poly(butylene adipate). Ester exchange at first causes the introduction of 
blocks of one polyester in the other polyester chain and vice versa. When 
the desired multi-block polymer structure is formed the catalyst is 
deactivated to prevent further interchange which ultimately would lead to 
a random copolyester without any blockiness. This procedure is described 
in detail in U.S. Pat. No. 4,031,165 to Saiki et al. Other useful 
procedures involve coupling of preformed blocks of high and low melting 
point polyester glycols. Coupling can be accomplished by reaction of a 
mixture of the blocks with a diisocyanate as described in European Patent 
No. 0013461 to Huntjens et al. Coupling can also be accomplished by 
heating the mixed blocks in the presence of terephthaloyl or isophthaloyl 
bis-caprolactam addition compounds. The caprolactam addition compounds 
react readily with the terminal hydroxyl groups of the polyester blocks, 
splitting out caprolactam and joining the blocks through ester linkages. 
This coupling method is described in Japanese Patent No. 700740 (Japanese 
Patent Publication No. 73/4115). Another procedure of use when the low 
melting blocks are to be provided by polycaprolactone involves reacting a 
preformed high melting point block terminated with hydroxyl groups with 
epsilon-caprolactone in the presence of a catalyst such as dibutyl tin 
dilaurate. The caprolactone polymerizes on the hydroxyl groups of the high 
melting point ester block which groups serve as initiators. The resulting 
product is a segmented polymer having high melting point blocks with low 
melting point polycaprolactone blocks. The segmented polymer is hydroxyl 
terminated and may be chain extended to give high molecular weight 
products by reaction with a diepoxide such as diethylene glycol diglycidyl 
ether, see Japanese Patent Publication No. 83/162654. 
The flame resistance of the multi-block compositions of this invention is 
partly due to the combination of a bromine containing organic flame 
retardant and antimony trioxide. The organic flame retardant is 
incorporated in the copolyester in amounts of about 5-45 parts per hundred 
parts of multi-block copolyester, preferably 24-30 parts per hundred parts 
of multi-block copolyester. Any bromine containing organic flame retardant 
which has a bromine content of at least 50% by weight and that, 
preferably, exhibits a weight loss not greater than 5% at 200.degree. C. 
as determined by thermogravimetric analysis in air at a heating rate of 
10.degree. C./minute can be used. These parameters insure that the flame 
retardant will be effective in the amounts specified and that the flame 
retardant will not volatilize or degrade during processing. Preferably, 
the organic flame retardant added to the copolyester composition is free 
of functional groups that form ester linkages. Representative 
bromine-containing organic flame retardants include decabromodiphenyl 
ether, octabromodiphenyl ether, tetrabromophthalic anhydride, 
bis(tribromophenoxy)ethane, bis(pentabromophenoxy)ethane, 
hexabromocyclododecane and N,N'-ethylenebis(tetrabromophthalimide). Of 
these N,N'-ethylenebis(tetrabromophthalimide) is especially preferred 
because of its high melting point, good stability and resistance to 
blooming. The flame retardant, N,N'-ethylenebis(tetrabromophthalimide), 
can be prepared by reacting 2 moles of tetrabromophthalic anhydride with 1 
mole of ethylene diamine in a suitable solvent such as 
N-methyl-2-pyrrolidone at about 200.degree. C., as described in U.S. Pat. 
No. 4,374,220. Preferably, the diimide should be in finely divided form, 
usually having particles of less than about 100 mesh or 100 micrometers, 
when added to the copolyester composition. 
The antimony trioxide, optionally containing small amounts of antimony 
pentoxide, is incorporated in the multi-block copolyester in an amount of 
about 0.20-1.5 parts, preferably about 0.3-0.6 parts, per part of bromine 
containing organic flame retardant. Any of the commercially available 
sources of antimony trioxide can be used in the copolyester composition. 
It is convenient to use a small particle size, for example, 0.2-0.25 
micrometers. 
In order to minimize or eliminate dripping when exposed to a flame, the 
multi-block copolyester compositions contain a drip suppressant. Various 
drip suppressants can be used in this composition and the magnesium 
compound incorporated in the multi-block copolyester also aids in 
preventing the copolyester from dripping when burned. Preferably, the drip 
suppressant is an organophilic clay, fumed colloidal silica or 
polytetrafluoroethylene. In all cases it is convenient to use a drip 
suppressant having a small particle size, for example, less than about 500 
micrometers. 
When organophilic clay is used as the drip suppressant, it is present in 
the copolyester compositions in an amount of at least about 1, preferably 
about 2-10 parts, most preferably 3-7 parts, per 100 parts of the 
multi-block copolyester. The organophilic clay used is the reaction 
product of at least one quaternary ammonium salt with a smectite-type clay 
having an ion exchange capacity of at least 75 meq/100 g of clay, said 
quaternary ammonium salts having the formula 
##STR4## 
wherein M.sup.- is selected from the group consisting of chloride, 
bromide, iodide, nitrite, hydroxide, acetate, methyl sulfate and mixtures 
thereof, wherein R.sub.1 is an alkyl group having 12 to 22 carbon atoms 
and wherein R.sub.2, R.sub.3 and R.sub.4 are selected from the group 
consisting of hydrogen, alkyl groups containing 1 to 22 carbon atoms, aryl 
groups and aralkyl groups containing 1-22 carbon atoms in the alkyl chain. 
Smectite-type clays which are useful in preparing the required organophilic 
clays include bentonite, montmorillonite, hectorite and saponite clays 
with bentonite and hectorite clays being preferred. The clays should have 
an ion exchange capacity of at least 75 meq/100 g of clay and preferably 
at least 95 meq/100 g of clay. Useful quaternary ammonium salts for 
modifying the clay by ion exchange must contain a cation having at least 
one long chain alkyl substituent having 12 to 22 carbon atoms. For reasons 
of economy most commercially available useful quaternary ammonium salts 
have one or more alkyl groups derived from hydrogenated tallow which is 
principally an octadecyl group. The preferred anion is the chloride ion. 
Representative quaternary ammonium salts which are useful in preparing the 
organophilic clays that can be used in the present invention include 
methyl benzyl di(hydrogenated tallow) ammonium chloride, 
dimethyl benzyl (hydrogenated tallow) ammonium chloride, 
dimethyl di(hydrogenated tallow) ammonium chloride, 
methyl tri(hydrogenated tallow) ammonium chloride, and 
benzyl tri(hydrogenated tallow) ammonium chloride. 
An especially preferred clay is bentonite treated with a mixture of 10-90% 
by weight dimethyl benzyl (hydrogenated tallow) ammonium chloride and 
dimethyl di(hydrogenated tallow) ammonium chloride. 
The multi-block copolyester composition can contain at least about 2 parts, 
preferably about 3-20 parts, most preferably 3-8 parts, per 100 parts of 
copolyester, of the drip suppressant fumed colloidal silica. Usually, the 
drip suppressant has a mean particle diameter of less than 500, most 
preferably less than 100, millimicrons. 
The multi-block copolyester composition can contain at least about 0.2 
parts, preferably 0.2-2 parts, most preferably 0.2-1 parts, per 100 parts 
multi-block copolyester of polytetrafluoroethylene as an effective drip 
suppressant. The polytetrafluoroethylene is usually in the form of a 
powder. 
To substantially reduce smoke generation when the multi-block copolyester 
thermoplastic composition is burning and to promote the formation of char, 
it is necessary to add to the multi-block copolyester the inorganic 
compounds alumina trihydrate and certain magnesium compounds in specific 
amounts. It has been discovered that, quite surprisingly, when the 
multi-block copolyester composition containing a brominated organic flame 
retardant contains 25-65 parts by weight, preferably 30-60 part by weight, 
per 100 parts of the multi-block copolyester of inorganic compounds of 
50-88 percent alumina trihydrate, preferably 60-75 percent, and 12-50 
percent, preferably 25-40 percent of a magnesium compound comprising 
magnesium carbonate or magnesium oxide or particulate magnesium hydroxide 
with 90 percent of the particulate magnesium hydroxide having a maximum 
dimension of no more than 1 micrometer and the particles of magnesium 
hydroxide are surface treated to prevent agglomeration, the resultant 
multi-block copolyester composition when burned shows a substantial 
reduction in the amount of smoke generated and the burned copolyester 
forms an unexpectedly high amount of char. It is believed that the low 
amount of smoke generated and high char formation, both values determined 
by the Arapahoe Smoke Chamber and Char Test, described below, are due 
primarily to the presence in the multi-block copolyester of the magnesium 
compound and alumina trihydrate. 
The surface of the particulate magnesium hydroxide that is incorporated 
into the composition is treated to prevent, among other things, excessive 
agglomeration of particles. Excessive agglomeration causes the melt index 
value to decrease and processing becomes impractical. Any conventional 
material that can be coated on the surface of the magnesium hydroxide 
particles to prevent agglomeration is satisfactory. A composition that is 
both hydrophobic and hydrophilic, such as soaps, fatty acids, and salts of 
fatty acids, are especially effective. The hydrophilic portion of, for 
example, a fatty acid is attracted to the magnesium hydroxide and the 
hydrophobic portion is directed to the outer surface of the treated 
particle. Usually and conveniently, the particles of magnesium hydroxide 
are coated with a fatty acid or an inorganic salt of a fatty acid, usually 
having 10-20 carbon atoms, especially calcium stearate or calcium oleate. 
The particles of magnesium hydroxide can have various shapes. It has been 
found that hexagonal shaped particles are preferred because these 
particles show less of a tendency to agglomerate than, for example, 
spherical particles. 
The particles of magnesium oxide are preferably coated with calcium 
stearate to improve the melt flow index of the thermoplastic composition 
and, accordingly, its processibility. 
The alumina trihydrate that is used in the present invention in the amounts 
disclosed has a small particle size, generally the average particle 
diameter is no greater than about 30 micrometers, usually not greater than 
about 2 micrometers. 
Calcium carbonate can be used to replace up to about 50% of the alumina 
trihydrate when magnesium hydroxide is used. In other words, the 
thermoplastic composition can contain 30-60 parts per hundred parts 
copolyester of inorganic compounds comprising 12-50 percent magnesium 
hydroxide and the balance alumina hydrate and calcium carbonate with the 
proviso that the amount of calcium carbonate is not greater than the 
amount of alumina trihydrate. The thermoplastic composition preferably 
contains about 25-44 percent calcium carbonate based on 30-60 parts per 
hundred parts multi-block copolyester of total inorganic compounds having 
a valence of 2 or 3, i.e. magnesium hydroxide and alumina trihydrate, and 
the amount of calcium carbonate is not greater than the amount of alumina 
trihydrate, e.g. 25-44 percent, present in the composition. The addition 
of calcium carbonate together with the magnesium hydroxide is beneficial 
because it aids in high temperature smoke reduction and char formation. 
Not only do compositions of the present invention give V-O flammability 
ratings in the UL-94 Vertical Burn Test of Underwriters Laboratories Inc., 
and show reduced smoke and increased char in the Arapahoe Smoke Chamber 
and Char Test, but in Steiner Tunnel Tests (UL-910), reported in examples, 
cables jacketed with the magnesium hydroxide containing thermoplastic 
composition passed all phases of the test. 
Any method which provides uniform mixing of the additives with the 
multi-block copolyester can be used to prepare the compositions of this 
invention. A preferred procedure involves dry blending all of the 
ingredients together followed by melt blending of the dry blend in single 
or twin screw extruder-mixers or internal mixers such as the Farrell 
Continuous Mixer (FCM) at a temperature above the melting point of the 
copolyester. The compositions can also be made by adding the flame 
retardant, antimony trioxide, drip-suppressant, e.g., organophilic clay, 
alumina trihydrate, magnesium compound, e.g., particulate magesium 
hydroxide, and optionally calcium carbonate, and a coupling agent, to the 
molten copolyester in a batch mixer or vessel provided with agitation 
means. The solid ingredients can be added separately in any order or may 
be dry blended prior to addition to the molten copolyester if desired. 
Another convenient procedure for preparing the compositions of this 
invention makes use of a concentrated masterbatch of flame retardant, 
antimony trioxide, drip suppressant, alumina trihydrate, magnesium 
compound and coupling agent bound together by a minor amount of 
multi-block copolyester. Usually the concentrated masterbatch contains 15 
to 35 percent by weight of copolyester which serves to bind the additive 
ingredients into pellets. The pellets of concentrated additive ingredients 
can be dry blended with pellets of unaltered copolyester and the pellet 
blend can in turn be fed directly to an injection molding machine or 
extruder to form flame resistant, low smoke generating, high char forming 
finished articles directly. The required concentrates can be prepared by 
mixing procedures such as those described hereinbefore. 
It is usually desirable to stabilize the multi-block copolyester 
compositions of this invention against heat and/or light. Antioxidants, 
such as hindered phenols or aryl amines, are known to be effective for 
this purpose. Mixtures of these antioxidants with esters of 
thiodipropionic acid, mercaptides, phosphite esters and the like are 
useful. Stabilization against light can be obtained by compounding the 
copolyester with UV-absorbers and/or hindered amine photostabilizers. The 
use of these various agents in copolyesters is known to those skilled in 
the art. In addition to these additives, one can add minor amounts of 
fillers and colorants as desired and processing aids, such as stearic 
acid. 
The compositions of this invention can be readily processed by a variety of 
techniques such as injection molding, compression molding and extrusion. 
Extrusion techniques are used for making cable jackets and optical fibers.

EXAMPLES 
In the following examples, which further illustrate the present invention, 
parts and percentages are by weight unless otherwise indicated. 
Copolyester A is prepared according to the following procedure: To a flask 
fitted with a distillation column and a stainless steel stirrer with a 
paddle cut to conform with the internal radius of the flask and positioned 
about 3 mm from the bottom of the flask, the following starting materials 
are charged: 
______________________________________ 
dimethyl terephthalate 40.27 parts 
dimethyl isophthalate 11.7 parts 
poly(tetramethylene oxide) 
44.7 parts 
glycol (number average 
molecular weight 1000) 
1,4-butanediol 30 parts 
N,N'--hexamethylenebis(3,5- 
0.15 parts 
di-tert-butyl-4-hydroxy- 
hydrocinnamamide) 
N,N'--trimethylenebis(3,5- 
0.15 parts 
di-tert-butyl-4-hydroxy- 
hydrocinnamamide) 
tetrabutyl titanate 0.3 parts 
______________________________________ 
The flask is placed in an oil bath at 160.degree. C., agitated for five 
minutes and then 0.3 parts of tetrabutyl titanate/1,4-butanediol solution 
is added. Methanol distills from the reaction mixture as the temperature s 
slowly raised to 250.degree. C. over a period of one hour. When the 
temperature reaches 250.degree. C., the pressure is gradually reduced to 
about 270 Pa within 20 minutes. The polymerization mass is agitated at 
250.degree. C. for 55-90 minutes. The condensation polymerization is 
discontinued by releasing the vacuum under nitrogen and the resulting 
viscous molten product is scraped from the flask in a nitrogen (water and 
oxygen free) atmosphere and allowed to cool. The resulting polymer has a 
melt flow rate of 5 g/10 min, measured at 190.degree. C. by ASTM method 
D1238 condition E and a Shore D hardness value of 40 as measured by ASTM 
method D2240. The weight ratio of high melting point blocks to low melting 
point blocks is 1:1.06. The polymer had a melting point of 143.degree. C. 
After shredding, the polymer is extruded at 200.degree. C. to a 3-4 mm 
strand and cut into pellets 4-5 mm long. 
Copolyester B was prepared by substantially the same procedure described 
above for the preparation of Copolyester A except that the following 
ingredients in the amounts given below were used. 
______________________________________ 
Dimethyl terephthalate 52.5 parts 
Dimethyl isophthalate 22.5 parts 
poly(tetramethylene oxide) 
15.9 parts 
glycol (number average 
molecular weight 1000) 
1,4 butanediol 55 parts 
N,N'--hexamethylenebis 0.15 parts 
(3,5-di-tert-butyl-4- 
hydroxy-hydrocinnamamide) 
N,N'--trimethylenebis (3,5- 
0.15 parts 
di-tert-butyl-4-hydroxy- 
hydrocinnamamide) 
tetrabutyl titanate 0.3 parts 
______________________________________ 
The resulting polymer has a melt flow rate of about 4.5 g/10 min measured 
at 190.degree. C. by ASTM method D 1238 condition E and a Shore D hardness 
of 60 as measured by ASTM method D 2240. The weight ratio of high melting 
point blocks to low melting point blocks in this polymer is 1:0.22. The 
polymer has a melting point of 168.degree. C. After shredding, the polymer 
is extruded at 200.degree. C. to a 3-4 mm strand and cut into pellets 4-5 
mm long. 
Arapahoe Smoke Chamber and Char Test 
Measurement of Smoke and Char Generation by use of the Arapahoe Smoke 
Chamber, Model 705, Arapahoe Chemicals, Boulder, Colo. is as follows: 
11/2".times.1/2".times.1/8" [38.1.times.12.7.times.3.175 mm] molded sample 
of the thermoplastic multi-block copolyester composition is burned for 30 
seconds in an airflow of 4.5 cfm (0.13 m.sup.3/ min), using a calibrated 
propane burner. The smoke is collected on filter paper and weighed. The 
remaining char on the sample is removed and weighed. The percent smoke and 
percent char are calculated as follows. 
##EQU1## 
The following ASTM methods are employed in determining the properties of 
the polymer compositions prepared in the examples which follow. 
______________________________________ 
Tensile strength and D-412 
elongation at break, 
Melt flow rate D1238 
(method E) 
Torsional Modulus (Clash-Berg) 
D1043 
Shore D hardness D2240 
______________________________________ 
The flammability characteristics are determined according to the vertical 
burning test of the Underwriters Laboratories, Inc., Standard UL 94, 1980. 
The V-O classification indicates a higher degree of flame retardance than 
does a V-2 classification. 
Organophilic clay is the reaction product of bentonite with a mixture of 
83% by weight of dimethyl di(hydrogenated tallow) ammonium chloride and 
17% by weight methyl benzyl di(hydrogenated tallow) ammonium chloride. The 
organophilic clay contains 60% by weight of non-volatiles at about 
700.degree. C. by thermogravimetric analysis. 
Magnesium hydroxide has a hexagonal platelet particle shape where the 
maximum dimension of the particles is 0.8 micrometers and the particles 
are coated with a calcium salt of a fatty acid. 
EXAMPLES 1-2 
Flame resistant compositions having a low percent of smoke generation and a 
high percent of char formation are prepared by dry blending the 
ingredients listed below in the amounts given in the following table in a 
mixer. The resultant dry blend is then compounded in a Haake Rheocord 
sigma blade mixer heated to about 200.degree. C. to obtain a uniform 
mixture. 
______________________________________ 
Parts By Weight 
Comparative 
Ingredient 1 2 Example 
______________________________________ 
Copolyester A 100 100 100 
N,N'--ethylenebis(tetrabromo- 
25 25 25 
phthalimide) 
Antimony trioxide (Laurel 
12.5 12.5 12.5 
Fireshield Ultrafine II) 
Magnesium hydroxide 
20 30 0 
Organophilic clay 
5 5 5 
(Average Particle Diameter, 
44 micrometers) 
Alumina trihydrate 
40 30 20 
(Average Particle Diameter, 
1.1 micrometers) 
Stearic Acid 1 1 1 
Calcium Carbonate 
-- -- 40 
______________________________________ 
The resulting composition is granulated and compression molded at 
200.degree. C. Test specimens of the thermoplastic composition having the 
following dimensions, 127 mm.times.12.7 mm.times.3.2 mm 
(5".times.1/2".times.1/8"), are prepared by compression molding. Test 
results at specimen thickness of 3.2 mm for UL-94 Vertical Burn Test 
indicate the compositions have a V-O rating and are drip resistant during 
burning after either ignition. The compositions have high tensile 
strengths, and the melt flow rates show they are readily processible. 
Additionally, the specimens show unexpectedly low smoke generation and 
unexpectedly high char formation relative to unmodified comparative flame 
retardant Copolyester A that is the same as the composition of Example 1 
except that it does not contain magnesium hydroxide. 
______________________________________ 
Properties 
Composition of 
Stress/Strain Example Comparative 
at 23` C. 1 2 Example 
______________________________________ 
Tensile Strength, kPa 
9377 9894 -- 
Melt Flow Rate, 2.64 2.5 0.44** 
g/10 min. at 190` C. 
Arapahoe smoke 
Chamber and Char Test 
% Smoke 0.98 1.03 6.7 
% Char 60.1 58.0 25.3 
UL-94 Vertical Burn Test 
V-O V-O -- 
3.2 mm thickness 
______________________________________ 
*at 230` C. 
EXAMPLES 3-8 
The procedure described above in Examples 1 and 2 was repeated using the 
ingredients indentified below in the amounts given. 
______________________________________ 
Parts By Weight 
Ingredients 3 4 5 6 7 8 
______________________________________ 
Copolyester A 100 100 100 100 100 100 
N,N'--ethylenebis 
25 25 25 25 -- -- 
(tetrabromo- 
phthalimide) 
Decabromodiphenyl 
-- -- -- -- 25 -- 
oxide 
Tetradecabromodi- 
-- -- -- -- -- 25 
phenoxy benzene 
Antimony trioxide 
12.5 12.5 12.5 12.5 12.5 12.5 
Organophilic clay 
5 5 5 5 5 5 
Magnesium hydroxide 
10 10 10 15 10 10 
Alumina trihydrate 
25 40 30 25 30 30 
Calcium carbonate 
25 10 20 20 20 20 
Stearic acid 1 1 1 1 1 1 
______________________________________ 
Test specimens were prepared as in Example 1 at 200.degree. C. and the 
results are given below. 
______________________________________ 
Properties 
Stress-Strain at 23` C. 
3 4 5 6 7 8 
______________________________________ 
Tensile Strength, 
10508 9191 9929 8991 7585 7929 
kPa 
Melt Flow Rate, 
3.3 3.4 3.1 3.5 3.8 4.5 
g/10 min. at 190` C. 
Arapahoe Smoke 
Chamber and Char Test 
% Smoke 2.1 2.0 2.2 1.7 2.6 2.7 
% Char 54.4 49.6 49.3 52 44.4 48.6 
UL-94 Vertical Burn 
V-O V-O V-O V-O V-O V-O 
Test 3.2 mm thickness 
______________________________________ 
The compositions have a V-O rating and did not drip when burned after 
either ignition. The compositions have a high tensile strength, and the 
melt flow rates indicate they are readily processible. The specimens show 
unexpectedly low smoke generation and unexpectedly high char formation. 
EXAMPLE 9 
A bundle of 25 pairs of 24 gauge copper wires each insulated with 0.14-0.15 
mm of tetrafluoroethylene-hexafluoropropylene copolymer [Du Pont 
Teflon/FEP] was extrusion jacketed with 0.38 mm of the composition of 
Example 1 and in another test with 0.5 mm of the same composition. The 
jacketed cables were tested in accordance with Underwriters' Laboratory 
UL-910 "Test Method for Fire and Smoke Characteristics of Electrical and 
Optical Fiber Cables used in Air-Handling Spaces", using the UL Steiner 
Tunnel. The results are given below. 
______________________________________ 
Maximum Flame Propagation 
Distance Optical Density 
Sample Feet Meters Peak Average 
______________________________________ 
Cable with 0.38 mm 
3.0 -- 0.17 0.08 
jacket 
Cable with 0.5 mm 
3.5 -- 0.20 0.08 
jacket 
Maximum Values 
5.0 1.524 0.50 0.15 
For Passing Test 
______________________________________ 
The experimental cable sample with the composition of the present invention 
passed the Steiner Tunnel test in all respects and the UL tests for 
abrasion, cold bend, and the joist pull. 
EXAMPLE 10 
______________________________________ 
Ingredient Parts By Weight 
______________________________________ 
Copolyester A 100 
N,N'ethylenebis(tetrabromo- 
25 
phthalimide) 
Antimony trioxide 12.5 
Organophilic Clay 5 
Stearic Acid 1 
Calcium Stearate 4 
Magnesium Oxide 20 
(Maglite Y) 
Alumina trihydrate 
40 
(Average Particle 
Diameter 1.1 Micrometers) 
______________________________________ 
Test specimens were prepared as described in Example 1 at 200.degree. C. 
and the results are given below. 
______________________________________ 
Properties 
Stress/Strain at 23` C. 
Example 10 
______________________________________ 
Tensile Strength, kPa 
10.340 
Melt Flow Rate, 4.1 
g/10 min. at 190` C. 
Arapahoe Smoke Chamber 
and Char Test 
% Smoke 2.6 
% Char 43 
UL-94 Vertical Burn Test 
V-O 
3.2 mm thickness 
______________________________________ 
The composition had a V-O rating and was low smoke generating and showed 
high char formation. 
EXAMPLES 11-13 
______________________________________ 
Parts By Weight 
Ingredient 11 12 13 
______________________________________ 
Copolyester A 100 100 100 
N,N'ethylenebis(tetrabromo- 
25 25 25 
phthalimide) 
Antimony trioxide 12.5 12.5 17.5 
Organophilic Clay 5 5 5 
Stearic Acid 1 1 1 
Calcium Stearate 4 -- -- 
Magnesium Stearate 
-- 10 -- 
Basic magnesium carbonate 
20 10 -- 
Magnesium hydroxide 
-- -- 20 
Alumina trihydrate 
40 40 40 
(Average Particle 
Diameter 1.1 micrometers) 
______________________________________ 
Test specimens were prepared as described in Example 1 and the results are 
given below. 
______________________________________ 
Properties 
Example Example Example 
Stress/Strain at 23` C. 
11 12 13 
______________________________________ 
Tensile Strength, kPa 
8964 10,136 10,618 
Melt Flow Rate 1.0 6.8 1.6 
g/10 min. at 190` C. 
Arapahoe Smoke 
Chamber and Char Test 
% Smoke 2.2 2.6 1.8 
% Char 42 37 47.5 
UL-94 Vertical Burn 
V-O V-O V-O 
Test, 3.2 mm thickness 
______________________________________ 
The composition had V-O ratings, they generated small percentages of smoke 
but high percentage of char when burned. 
EXAMPLE 14 
Flame resistant compositions having a low percent of smoke generation and a 
high percent of char formation and high tensile strength are prepared by 
dry blending the ingredients listed below in a mixer in the amounts given 
in the following table. The organotitanate coupling agent, (OC(O)CH.sub.2 
O)Ti[OP(O)(OH) OP(O)(OC.sub.8 H.sub.17).sub.2 ]HP(O)(OC.sub.8 
H.sub.17).sub.2 and mineral oil were added dropwise to the nonpolymeric 
ingredients while they were vigorously agitated in a high intensity mixer. 
The treated ingredients were than dry blended with the copolyester in a 
Haake Rheocord sigma blade mixer heated to about 190.degree. C. to obtain 
a uniform mixture. The resultant composition was extruded as an 0.46 mm 
coating over a cable bundle, as described in Example 9. The Arapahoe Smoke 
Chamber and Char Test resulted in 1.6% smoke and the char was 51%. The 
product had a V-O rating in the UL-94 test. The cable jacket was removed 
and tensile tests run at 5.08 cm per minute. The tensile strength was 
21,720 kPa and the elongation at break was 590%. 
EXAMPLE 15 
The procedure described above in Example 14 was substantially repeated 
except that all ingredients with the exception of Copolyester A were first 
dry blended in a glass container and 1 part of the silane sulfonyl azide 
(CH.sub.3 CH.sub.20).sub.3 Si--R--SO.sub.2 N.sub.3, available as Az-Cup N 
liquid manufactured by Hercules, Inc., was added to the mix while 
stirring. The mixture was then melt blended, as described in Example 14, 
with Copolyester A and 0.51 mm thick slabs were compression molded. 
Tensile testing of the die-cut samples gave a tensile strength value of 
11,240 kPa at break. 
EXAMPLE 16 
The procedure described above in Example 14 was substantially repeated 
except that 0.5 parts of liquid 3-aminopropyltriethoxysilane was added in 
place of the organotitanate coupling agent. The tensile strength at break 
was found to be 11,350 kPa and the melt flow was 3.3 g/10 minutes. 
______________________________________ 
Ingredient 14 15 16 
______________________________________ 
Copolyester A 100 100 100 
N,N'--ethylenebis (tetrabromo 
25 25 25 
phthalimide) 
Antimony oxide 12.5 12.5 12.5 
Magnesium hydroxide 
20 20 20 
Organophilic clay 5 5 5 
Alumina trihydrate 
40 40 40 
Stearic acid 1 1 1 
Coupling agent Organoti- 
Azido- Silane 
tanate silane 
Quantity of coupling Agent 
1.0 1.0 0.5 
Tensile strength, kPa 
21,720 11,240 11,350 
______________________________________ 
The compositions not only were low smoke generating and showed high char 
formation but had unusually high tensile strength values. 
EXAMPLES 17-18 
Flame and smoke retarded compositions having low smoke high char formation 
with low flaming time were prepared by blending the ingredients listed 
below in a mixer heated to about 170.degree. C. to obtain a uniform 
mixture. 
______________________________________ 
Ingredient 17 18 
______________________________________ 
Copolyester A 50 0 
Copolyester B 50 100 
N,N'--ethylenebis(tetrabromo 
30 30 
phthalimide) 
Antimony trioxide 10 10 
Magnesium hydroxide 18 18 
Alumina trihydrate 36 36 
Organophilic clay 5 5 
Stearic acid 1 1 
Mineral oil 2 2 
Coupling agent (titanium 
1 1 
di (dioctylpyrophosphate) 
oxyacetate 
Melt flow rate, ASTM D1238 
.5 .5 
method E, g/10 min 
Tensile strength, kPa 
17,269 21,328 
Elongation to break, % 
415 305 
Arapahoe Smoke Chamber 
and Char test 
% Smoke 4.9 7.0 
% Char 13.3 21.0 
% burned (amount burned/ 
3.18 2.83 
initial wt) 
UL-94 Vertical Burn Test 
V-O V-O 
1.6 mm thickness 
______________________________________ 
The Arapahoe Smoke Chamber and Char Test results for Examples 17 and 18 
should not be compared directly with the results in the previous Examples. 
Because part or all of Copolyester A was replaced with Copolyester B, the 
% smoke data are with resulting higher aromatic content and lower ether 
content, the % smoke data are higher and the % char data are lower. On the 
other hand, a much smaller portion of the sample was burned in the 
Arapahoe test, and this is desirable performance. Also, the tensile 
strength was high in Examples 17 and 18. 
EXAMPLE 19 
A coaxial cable with a single 22 gage (0.635 mm) copper conductor insulated 
with foamed Teflon /(tetrafluoroethylene/hexafluoropropylene copolymer 
with 16 weight % HFP) 1.52 mm thick and shielded with bare copper (11.5 
ohms/kilometer) braid, 95% shield coverage was extrusion jacketed with 
0.51 mm of the composition of Example 17. The jacketed cable was tested as 
in Example 9 and the results were: 
Maximum flame propagation distance=3 feet=0.91 meters 
Peak optical density=0.28 
Average optical density=0.06