CA1102469A - Flame retardant compositions comprising block copolyesters of polybutylene terephthalate - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE

Novel flame retardant thermoplastic compositions comprising block copolyesters useful as molding resins are prepared by mixing a flame retardant compound with a product resulting from the transesterification of (a) straight or branched chain poly(1,4-butylene terephthalates) and (b) a copolyester of a linear aliphatic dicarboxylic acid and, optionally, an aromatic dibasic acid such as terephthalic or isophthalic acid with one or more straight or branched chain dihydric aliphatic glycols.

Description

8C~-2368 6~

This invention relates to flame retardant composition~ comprising a thermoplastic copolyester prepared by the trans~sterification of (a) straight or branched chain pol~(l,4-butylene terephthalates) and (b) a copolyester o~ a linear aliphatic dicarboxylic acid and, optionally, aromatic dibasic acids such as isophthalate or terephthalic acid with one or more straight or branched chain dihydric aliphatic glycols, and a flame retardant agent. The compositions are useful as molding resin components.
Poly(1,4~butylen~ terephthalate) is a widely used molding resin because of its rapid crystallization and also because of its rigidity~ good dimensional stability, low water absorption and good electrical properties.
The resin also has high heat resistance, inherent lubricity and excellent chemical resistance.
One restriction on the use of this valuable resin, however, is the ~act that the impact strengths of moldings tend to be somewhat inadequate for applications where the molded part is likely to be subjected to severe ser-vice conditions. This has led to work to upgrade .
.

` 8CH-2368 : this property of poly~l,4-butylene ter~phthalate) because, both in straight and branched chain modifications, it is so superior to m~ny other molding materials, ~specially with respect to its surface gloss when molded.
It has beell discovered that if a poly(l,4-butylene terephthalate) resin i9 chemically modified by bei.ng segmented in a copolyester in which the major portion o~ the repeating units are poly(l,4-butylene tere-phthalate~ blocks and the minor portion o -the repeating units are blocks of a copolyester of a linear aliphatic dicarboxylic acid with one or more straight or branched chain dihydric aliphatic glycols, and optionally~ an aromatic dibasic acid, such as isophthalic or tere-phthalic acid, then the r~sulting block copoly-esters will have enhanced impact resistance, comparea to the resin itself. The improvement in impact resistance i9 achieved with minimal loss of other physical properties and is ac-companied with a measurable increase in tough-ness. It is believed that the presence of the internal blocks of other polyesters modifies the rate at which poly(l,4-butylene terephthalate) crystalli2es from the melt in a very desira~le ``' ` `11 :
~ 8C~-2368 l ¦ manner. -~ I . :.
3 ¦ In particular, if certain aliphatic, or partially 4 ¦ aliphatic/aromatic, polyesters, are added to the reactor ¦ during the preparation of poly(l,4 butylene terephthalate) 6 ¦ after ester interchange be~ween dialkyl terephthalate and 1,4-7 ¦ butanedlol, there is caused a most desirable rnodification in 8 ¦ the properties o the resulting polyester molding resins.
9 I .
¦ By way of illus~ration, poly(neopentyl-adipate), 11 ¦ poly(l,4-hexylene-neopenty1-adipate-isophthalate), poly(l,6-12 ¦ hexylene-(0.7)adipate-(0.3)isophthalate); poly(l,4-hexylene-13 ¦ (0.5~adipate~-(0.5~isophthala~e) and poly(l,6-hexylene-(0.7)- .
14 ¦ aæelate-(0.3)isophthalate), each having a hydroxyl number in the ¦ range of 32 to 3~, corresponding to a number average molecular 16 ¦ weight of 3000 to 3500, are used as the so~rce of blocks. These 17 ¦ polyesters are added, respectively, to a reastor after the es~er 18 ¦ interchange be~ween l,~l-butanediol and dimethyl ~ereph~halate is 19 ¦ complete and any excess of bu~anediol has been removed by dis-20 ¦ tillation under a mild vacuum........................................ .:

2~ 1 . ..
22 ¦ After completion of the reaction and molding the 23 ¦ block copolyesters, the moldings are improved in ~oughness and 24 ¦ reduced in notch sensitivity as compared to bars molded ~rom 25 ¦ unmodified poly(l,4-butylene terephthalate). There is insub- :
26 ¦ stantial loss in flex modulus and strength. F.ven at only 10%
27 ¦ of the aliphatic/aromatic polyester content, the increase in 28 ¦ i~pact strength is so marked that some of the samples cannot .
29 ¦ e~en be broken. .

_ I _ ___ ._ . _ ._ _ _ _. _ ... . __ ._ . . ........ _ .. ... ~

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The effect on crystallization behavior is also noteworthy. The copolyester block components significantly reduce the crystallization rate of the molding resin. This is desirable, since it allows longer time Eor the polymer melt to flow through thin walled sections of amold beore the cool-ing product solidifies.
In addition to their use in injection molding applications, the polyester coreactants have also been found to be beneficial in improving ~he properties of poly(l,4-buty-lene terephthalate) resins used in other applications, such as profile extrusion, extrusion-and injection blow molding, thermo-forming, foam molding; in these cases small amounts of ester-forming branching agents may be added to enhance the melt elas~i-city properties of the products for easier processing.
The block copolyester products have also been convert-- ed to valuable modifications by adding reinforcing fillers, such as glass fibers, talc, and the like. Surprisingly, the increased toughness of the new block copolyesters compensates for the - greater brittleness usually induced by the incorporation of such non-soluble additives and fillers.
It has now been discovered that the block copoly-esters can be converted to a particularly valuable family of flame retardant compositions by adding a flame retardant agent, such as monomolecular and polymeric halogenated aromatic compounds, with or without flame retardant synergists, 5uch as antimony compounds, or phosphorus compounds, or the like.

` ~ ` 1~24~

1 Sumoto, Imanaka and Shirai, Japanese Patent 2 Publication ~9-99150, da~ed September 19, 1974, disclose

3 flame retardant compositions comprisi.ng block copolyesters

4 which, however~ are differerlt Erom those used herein. The methods of preparation in Sumoto et al will give high randomiæa-6 tion of the blocks because all ingredients, dimethyl ester of aromatic dicarboxylic acid, diol and the polymer or producing 8 "soft polymer ~egment" are mixed together and heated with a 9 transesterifications catalyst. In contrast, applicants' ..
copolyesters are no~ highly randomlzed because the coreactant 11 is not added until the ester interchange has been completed 12 and the excess butanediol has been removed. This reaction is 13 a transesterification between a poly(l,4-butylene terephthalate?, 14 prepolymer or polymer, and the coreactant es~er. The other methods in Sumoto e~ al give segmented copolyesters joined ;
16 through linking compounds such as diisocyanates, lactone mono-17 mers, and the like, i.e., ~here ls no connection by linkages .:
18 consisting essentially of ester linkages.
:` 19 . ':
2Q Description of the Invention.- According to ~his 21 invention, there are provided flame retardant compositio~s 22 comprising a thermoplastic copolyester which consists 23 eæsentially-of blocks derived from:
24 ~a~ a tenninally-reactive poly(l,4-butylene terephthalate); and 2~ (b) (i~ a terminally-reactive aromatic/
27 alipha~ic copolyester of a dicarboxylic acid selected from the 28 group consisting of terephthalic acid, i.soph~halic aci.d, 29 naphthalene dicarbo~ylic acids, phenyl indane dicarboxylic acid and compounds of the formula:

_ . _ _ ., . _ _ _ . . . .. . _ _ .. _. _._ . , ............ . _",~, ~

. - ' ' - '^ ' ' . . ~ . ~ .

~ 8CH-2368 ;` ~1(~2~9 H0 C ~ - X - ~ - - C - - O~

in which X may be alkylene or alkylidene of from 1 to 4 carbon atoms, carbonyl, sulfonyl, oxygen or a bond between the benzene xings and an aliphatic dicarboxylic acid having from 6 to 12 carbon atoms in the chain, with one or more straight or branched : chain dihydric aliphatic glycols havin~ from 4 to 10 carbon atoms in the chain, said copolyester having at least 10~ and preferably 35~ of aliphatic units being derived rom a dicarboxylic acid; or (ii) an aliphatic polyester of a straight chain aliphatic dicarboxylic acid having from 4 to 12 carbon atoms in the chain and a straight or branched chain dihydric aliphatic glycol, said blocks being connected by interterminal linkages consisting essentially of ester linkages It is essential that the copolyester component be prepared by the reaction of terminally-reactive poly(butylene terephthalate), pre~erably lo~ molecular weight, and a terminally-reactive copolyester or polyester as defined in paragraph (b), in the presence of a catalyst for transesterification, such as zinc acetate, manganese acetate, titanium esters, and the like.
The terminal groups can comprise hydroxyl, carboxyl, carbo-alkoxy, and the like, including reactive derivatives thereof.

-ll ll 3 ;Z9~ 9 8CH- 2 36 8 ~ ¦ The result of reaction between two terminally reactive groups, 2 of course, mus~. be an ester linkage. After initi~l mixing, 3 polymerization is carried out under standard conditions, e.g., 4 220 to 28QC., in a high vacuum, e.g., 0.1 to 2 mm Hg, to form the block copolymer of minimum randomization in terms of distribution of chain segments.
~ , :' 8 The copolyester or poLyester designated component 9 (b) (i) is preferably prepared from terephthalic acid or isop~-10 thalic acid or a reactive derivative thereof and a glycol, 11 which may be a s~raight or branched chain aliphatic glycol.
12 Illustratively, the glycol will be 1,4-bu~anediol; 1,5-pentane-13 diol; 1,6-hexanediol; l,9-nonanediol; l,10-decanediol; neopentyl 14 glycol; 1,4-cyclohexanediol, 1,4-cyclohexane dimethanol, a mixture of any of the foregoing, or the like. Illustrative 1~ of suitable aliphatic dicarboxylic acids for the mixed aromatic/
17 aliphatic embodiments are suberic, sebacic, azelaic, adipic 18 acids, and the like.
1~ .
2Q The copolyesters of the polyester designated 21 component (b) may be prepared by ester interchange in 22 accordance with standard procedures. The polyesters design~ted 23 (b3 (i) are most preferably derived from an aliphatic glycol 24 and a mixture of aromatic and aliphatic dibasic acids in which the mole ratlo concentration of aromatic to aliphatic acids is 26 from between 1 to 9 znd ~ to 1, with an especially preferred 27 range being from about 3 to 7 to about 7 to 3.

~9 :' . ' .11 E3OEI~2368 i ~ ~ 2~ 6 ~

1 The aliphatic polyesters aesignated component (b) 2 (ii) will contain substantially ~toichiometric amounts of the 3 aliphatic diol and the aliphatic dicarboxylic acid, although 4 hydroxy-ccntaining terminal groups are preerred.
S ':
6 In additi.on to their ease of formation by well-7 known procedures, both ~he arornatic/aliphatic copolyesters (b) 8 (i) and the aliphatic polyesters (b) (ii) are commercially ~ available. One source or such materials is the Ruco Division/
~ l Hooker Chemical Company, Hicksville, New York, U.S.A. which 11 ~ designates its compounds as "Rucoflex".

13 The block copolyesters of this invention preferably 14 comprise from 95 to 50 parts by wei.ght of the segments of poly(l, 4-butylene terephthalate). The poly(l,4-butylene terephthalate) 16 blocks, before incorporation in the block copolyesters, will 17 preferably have an intrinslc viscosity of above 0.1 dl./g. and 18 preferably, between 0.1 and 0.5 dl./g., as measured in a 60:40 19 mixture of phenolttetrachloroethane at 30C~ The balance, 5 to 20 50 parts by weight of the copolyester will comprise blocks of 21 component ~b).
2~
23 As will be lmd~rstood by those skilled in ~his 24 art, the poly(l,4-butylene terephthalate) block (a) can be straight chain or branched, e.g., by use of a branchlng 26 component, e.g., 0.05 to 3 mole %, based on terephthalate 27 units, of a branching component which contains a~ least three 28 ester-forming groups. This can be a polyol, e.g., penta-29 erythritol, trimethylolpropane, and the like, or a polybasic acid compound, e.g., trimethyl trimesate, and the like.

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24~9 8CH--2 36 8 ~ wide variety of flam~ retardant agents can be u~ed - in intimate admixture with the block copolyesters, with or without reinforcing agents, to produce the flame retardant compositions of this invention. Illustrative flame retardant agents are disclosed in U~S. 3,833,685, dated Sapt~mher 3, 1974, U.S. 3,334,154, dated August 1, 1967, u~S. 3,915,926, dated October 28, 1975 and U~S~ 3,671,~87, dated June 20~ 1972. Other 1ame retardant agents are disclosed in U4S ~ 3,681,281, dated August 1, 1972 and U.S. 3,557,053, dated January 19, 1971, U.S.
3,830,~71, dated August 20, 1974 and U.K. 1,358,080.
In g~neral, the flame retardant agent~ useful in this invention comprise a family o~ chemical compounds well known to those skilled in the art. Generally speaking, the more im~ortant of these compounds contain chemical elements employed for their ability to impart flame resistance, e.g., bromine, chlorine, antimony, pho~phorus and nitrogen. It is preferred that the flame retardant addltive comprises a halogenated organic compo~md (brominated or chlorinated~; a halogen-con-taining organic compound in admixture with antimony oxide;
elemental phosphorus or a phosphorus compound; a halogen-containing compound in admixture with a phosphorus compound or compounds containing phosphorus-nitrogen bonds or a mixture of two or more of thP foregoing.
The amount of flame retaxdant agent used is not critical to the invention, so long as it is present in a minor proportion based on said composition -- major proportions ~ill detract from physical properties -- but at laast sufficient to render the block polyester resin (and any other flammable resin component) ~on--burning or self-extinguishing, Those ~ 8C~-7368 skilled in the ar~ are well aware that the amount will vary with th~ nature of the resin and with the ef~iciency of the additive. In general, however, the amount of additive will be from 0.5 to 50 parts by weight per 100 parts of resin~
A preferred range will be from about 3 to 40 parts and an especially preferred range will be from about 8 to 40 paxts of additiva per 100 parts o~ resin. Smaller amounts of com~
pounds highly concentrated in the elements responsible for flame retardance will be suPficient, e.g., elemental red phos-phorus will be pre~erred at 0.5 to 2~0 parts by weight per 100 parts of resin, while phosphorus in the form of triphenyl phos-. .
~` phate will ~e used at 25 parts of phosphate per 100 parts of resin, and so forth. Halogenated aromatics will be used at 8 to 40 parts and synergists, e.g., antimony o~ide will be use~
at about 2 to 10 parts by weight per 100 parts of resin.
Among the useful halogen-containing compounds are those of the formula:

~,'', :
.. .. .

( T ~ Ar 1~

wherein R is a~kylene or substituted alkylene, alkylidene or cyc~
loaliphatic linkage, e.g., me~hylene, ethylene, propylene, isopropylene, isopropylidene, butylene, isobutylene, amylene, , ., ~9 8C~-2368 1 cyclohexylene, cyclopentylidene, and the like; a linkage 2 select~d from the group conslsting of ether; carbonyl; amine;
3 a sulfur-containing linkage, e.g., sulfide, sulfoxide, sulone; ,;
a phosphorus-containing linkage; and the like. R can also consist of two or more alkylene or alkylidene linkages connected 6 by such groups as aromatic, amino, ether, carbonyl, sulfide, 7 `sulfoxide, sulfone, a phosphorus-contain:ing linkage, and the 8 like. Other groups which are represented by R will occur to 9 those skilled in the art.
11 Ar and Ar' are mono- or polycarbocyclic aromatic 12 groups such as phenylene, biphenylene, terphenylene, naphthylene, 1~ and the like. Ar and Ar' may be the same or different.

Y is a substituent selected from the gxoup consisting 16 of organic~ inorganic, or organometallic radicals. The sub-17 stituents represented by Y include (1) halogen, e.g., chlorine, 18 bromine, iodine, or fluorine or (2) ether groups of the general 19 formula OE, wherein E is 2 monovalent hydrocarbon radical ~O similar to X or (3) monovalent hydrocarbon groups of the type 21 represented by R or (4) other substituents, e.g., nitro, cyano, 22 etc., said substituents being essentially inert provided there 23 be at least one and preferably two halogen atoms per aryl, e.g., 24 phenyl nucleus.
26 X is a monovalent hydrocarbon group exemplified by 27 the following: alkyl, such as me~hyl, ethyl, propyl, isopropyl, 28 butyl, decyl, and the like; aryl groups, such as phenyl, naph-29 thyl, biphenyl, xylyl, tolyl, and the like; aralkyl groups, such as benzyl, ethylphenyl, and the like; cycloaliphatic groups ~ ~ 469 ~CH-2368 ` ' `:
l such as cyclopentyl, cyclohexyl, and the like; as well as 2 monovalent hydrocarbon growps containing inert substituents 3 therein. It will bP understood that where more than one X is 4 used, they may be alike or different.
. ~ . ' '.' 6 The letter d represents a whole number ranging from 7 1 to a maximum equivalent ~o the number of replaceable hydrogens 8 substituted on the aromatic rings comprising Ar or Ar'. The 9 le~ter e represents a whQle number ranging from O to a maximum controlled by the number of repIaceable hydrogens on R. The 11 letters a, b and c represent whol~ numb~rs including O. When 12 b is not O, neither a nor c may be 0. Otherwise either a or c, 13 but not both, may be 0. Where b is 0, the aromatic groups are ;
14 joined by a carbon-carbon bond.
16 The hydroxyl and Y substituents on the aromatic 17 groups, Ar and Ar' can be varied in the ortho, meta or para 18 positions on ~he aromatic rings and the groups can be in any l9 possible geometric relationship with respect to one another.
.
~1 Included within the scope of the above formula 22 are biphenyls of which the following are representative:
23 2,2-bis-(3,5 ~ichlorophenyl)propane 24 bis-(2-chlorophenyl)methane bis-(2,6-dibromophenyl)methane 26 l,l-bis-4(4-iodophenyl)ethane 27 1,2-bis-~2,4-dichlorophenyl)e~hane 28 1,1-bis-(2-chloro-4-iodophenyl)ethane 29 1,1 bis-(2-chloro 4-me~hylpllenyl)ethane 1,1-bis-(3,5-dichlorophenyl)ethane .

llOZ469 ac~-236~ ~

l 2,2-bis-(3-phenyl-4 bromophenyl)ethane 2,6~bis-~4,6-dichloronaph~hyl)propane 3 2,2-bis-t2,6-dichlorophenyl~pentane 4 ~,2-bis-(315-dichlorophenyl~hexane ...
bis-(4-chlorophenyl)phenylmethane 6 bis-(3,5-dichlorophenyl)cyclohexylmethane bis-(3-nitro-4-bromophenyl)methane 8 bis-(4 hydroxy-2,6-dichloro-3-methoxyphenyl)methane 2,2-bis~(3,5-dichloro-4-hydroxyphenyl)propane 2,2-bis-~3-bromo-4-hydroxyphenyl)propane .
ll 2,2-bis-(3,5-dibromo-4-hydroxyphenyl)propane.

13 The preparation of ~hese and other applicable 14 biphenyls are known in the arti In place of the divalent aliphatic group in the above examples may be substituted sulfide, 16 sulfoxy, and the like. .
17 .
18 Included within the above structural formula are :.
substi~uted benzenes ex~mplified by l,3-dichlorobenzene, l,4-dibromobenzene, l,3-dichloro-4-hydroxybenzene, hexachlorobenzene, 21 hexabromobenzene, and biphenyls such as 2,2'-dichlorobiphenyl, 22 2,4'-dibromobiphenyl, and 2,4'~dichlorbiphenyl. .

24 Preferred flame retardant additives consist of aromatic carbonate homopolymers having repeating units of the 2B formula l .

_ .... _ ~ ~

8CH~2368 ~, ~
,~
~1, 4 ~ ) q 8 .
9 '.:
wherein Rl and R2 are hydrogen, (lower)alkyl or phenyl, xl 11 and X~ are bromo or chloro and m and r are from 1 to 4. These 12 materials may be prepared by techniques well known to those 13 skilled in the art. Also preferred are aromatic carbonate 14 copolymers in which from 25 ~o 75 weight percent of the repeating units compris`e chloro- or bromo-substituted dihydric phenol, -16 glycol or dicarboxylic acid units. See, e.g., A.D. Wambach, 17 U.S. 3,915,926, above-mentioned.

l9 In addition, preferred are aromatic halogen compounds such as chlorinated benzene, bromina~ed benzene, 21 chlorinated biphenyl, chlorinated terphenyl, brominated biphenyl, 22 brominated terphenyl, or a compound comprising two phenyl 23 radicals separated by a divalent alkylene or oxygen group and 24 having at least two chlorine or bromine atoms per phenyl nucleus, and mixtures of at least t~o of the foregoing.

27 In general, ~he preferred phosphorus compounds are 28 selected from elemental phosphorus or organic phosphonic acids, 29 phosphonates, phosphinates, phosphonites, phosphinites, phos-phene oxides, phosphenes, phosphites or phospha~es. Illustra~ive ll 6~ 8C~ 368 '' . . ., 1 are triphenyl phosphine oxide. This can be used alone or ~.
miY.ed with hexabromobenzene or a chlorinated biphenyl and, 3 optionally, an~imony oxide.

Typical of the preferred phosphorus compounds to 6 be employed in this invention would be those having the general 7 for~ula:

9 X"n ll 11 Y'_ P--Y" .
12 y,l, 14 in which X' - S or 0, and n = 0 or l, Y', Y" and Y"' are the same or different and represent alkyl, cycloalkyl, aryl, alkyl 16 substituted aryl, halogen substituted aryl, aryl substituted 17 alkyl, alkyloxy, cycloalkyloxy, halogen substituted alkyloxy, 18 aryloxy, halogen substitu~ed aryloxy, or halogen. Two of the 19 Y's may be combined into a cyclic structure, or one or two of the Y's may be difunctional in which case the compounds consists 21 of short or long chain compounds containing a plurality of P
22 atoms per molecule. Typical examples of suitable phosphorus 23 compounds include: triphenyl phosphate, diphenyl phenyl 24 phosphonate, phenyl diphen~l phosphinate, triphenyl phosphine, triphenyl phosphine oxide, tris~p-bromophenyl) phosphate, 26 neopentyl phenyl phosphonate, tris(dibromopropyl~ phosphate, 27 dibenzyl phenyl phosphonate, poly~l,4 cyclo hexylene dimethylene) 28 phenyl phosphonat~, penta~rythritol bis(~-bromophenyl) phospho-29 nate, and the like. A preferred flame r~tardant is tris~tri-~0 bromophenyl) phosphate.

,,ll ~ Z4~ 8CH~2 36 8 ' .: . ' l Also suitable as flame retardant additives or this 2 invention ar~ compounds con~aining phosphorus-nitrogen bonds, 3 such as phosphonitrilic chloride, phosphorus es~er amides, 4 phosphoric acid amides, phosphonic acid amines, phosphinic acid S amides, (tris(aziridinyl) phosphine~oxide. These flame 6 retardant addltives are commercially available.
7 ' 8 The block copolyesters may be employed as s~ch in 9 the fabrication of molded articles or they may be blended with other polymers, especially preferably poly(l,4-butylene tere-11 phthalate) straight chain or branched (as described), and with 12 stabilizers, reinforcing agents and/or flame retardant additives.

14 In one feature of the invention, the flame retardant compositions may be combined with a normally flammable high 16 molecular weight poly(l,4-butylene terephthalate), i.e., 17 having an intrinsic viscosity of at least 0.7 dl.tg., as measured 1~ in a 60:40 mixture of phenol/tetrachloroethane at 30C. These l9 composi~ions can vary broadly, but, preferably, will contain from 5 to 95 parts by weight of the block copolyester and from 21 95 to 5 parts by weight of the high molecular weigh~ poly(l,4-2~ butylene terephthalate), s~raight chain or branched. Of course 23 a sufficien~ amount of flame retardant additive will be present 24 to insure that the entire combination is flame retardant.

26 The present invention contempla~es reinforced 27 flame retardant compositions, too. Suitable reinforcing agents 28 are well known but, illustratively, they may b~ selected from 29 the group consisting of metals, such as aluminum, iron or nickel particles and the like, and non-me~als, such as carbon fil~nents, _ _ . . _. ... __. ..... .. .,--._._ . . . .. . _-- _ .... _ _ _i, ~_ 1 ~2~

,, 1 silicates, such as acieular calcium silicate, asbestos, 2 titanium dioxide, potassium titanate and titanate whiskers, 3 wollastonite, glass flakes and fibers~ It is also to be 4 understood that unless the filler adds to the strength and stiffness of the composition, it is only a filler ~nd not a 6 reinforcing filler as contemplated herein.

8Although it is only necessary to have at least a g reinforcing amount of the reinforcement present~ in general the - 10 reinforced compositions will comprise from 1 to 80% by weight 11 o the total composition of the reinforcing agent.

13In particular, the preferred reinforcing fillers 14 are of glass, and it is usually preferred to employ fibrous glass filaments comprised of lime-aluminum borosilicate glasis 16 that is relatively soda free. This is known as "E" glass.
17 ~owever, other glasses are useful where electrical properties 18 are not important, e.g., the low soda glass ~lown as "C'1 glass.
19 The filaments are made by standard processes, e.g., by siteam or air blowing, flame blowing and mech~nical pulling. The 21filament diameters range from abou~ 0.00012 to 0.00075 inch, 22 but this is not cri~ical to the present invention. Glass fibers 23 may be surface coated in accordance with standard procedureis to 24 improve their reinforcing performances. In general, bes~
properties will be obtained from reinforced compositions that 26 contain from 20 to 3~ percent by weight of the glass reinforced 27 composition.

.. , . :1. . ., ~ llOZ469 8CII-2368 ~ ~

1 The length of glass filam~nts and whether or not 2 they are b~mdled into fibers and the fibers bundled in turn to 3 yarns, ropes or rovings, or woven into mats, and the like, are 4 also not critical to the practice of the invention. In preparing the present co~positions, it is convenient to use the filamentous 6 glass in the form of chopped strands of from about 1/8 inch to 7 about 1 inch long, preferably, less than 1/4 inch long. In 8 articles that are molded from the compositions of the invention, 9 even shorter lengths wi.ll be enco~mtered because, during com-pounding, considerable fragmentation will occur. This is 11 desirable, however, because the best properties are exhibited 12 by thermoplastic injection molded articles in which the filament 13 lengths lie between about 0.000005 inch and 0.12 ~1/8 inch).

Compositions of this invention can be prepared 16 by a number of procedures. In one way, the reinforcement, 17 e.g., fillers or fibers, pigments, stabilizers, etc., are put .:
18 into an extrusion compounder with the resinous components to 19 produce molding pellets. The additives are dispersed in a matrix of the resin in the process. In another procedure, the 21 additive(s) and resin are dry blended then either Eluxed on 22 a mill and com~inuted, or they are extruded and chopped. The 23 additives can also be mixed wlth the resin(s) and directly 24 ~olded, e.g., by injection or transfer molding techniques.
26 It is always importan~ to thoroughly free all of the 27 ingredients: resin, reinforcement, and other addi~ives from 28 as much water as possible _ . _ _ . . _ .. . .. . . .

1 In addition, compounding should be carried out to insure that the residence time in the machine is short;
3 ~he temperature is carefully controlled; the friction hea~
4 is utilized; and an intimate blend between the resin and the

5 reinforcem~nt and/or other addi~ives is obtained. ;.

7 Although it is not essential, best results are 8 obtained if the ingredients are pre-compounded, pelletized and then molded. Pre-compounding can be carried out in con-ventional equipment. For example, after carefully pre-drying 11 the copolyester, and polyester resins and the additives, e.g., 12 reinforcing agent, e.g., under vacuum at 100C. Eor 12 hours, 13 a single screw extruder is fed with a dry blPnd of the ingre 14 dients, the screw employed having a long transition section to insure proper melting. On the other hand, a twin screw 16 extrusion machine, e.g., a 28 mm Werner Pleiderer machine 17 can be fed with ~esin and additives at the feed port and lg reinforcement downs~ream. In either ca~se, a generally suitable 19 machine temperature will be about 450 to 460F.
~0 . , 21 The pre-compounded composition can be extruded 22 and cut up into moldin~ compounds such as conventional granules, .
23 pellets, etc., by standard techniques.

The composition can be molded in any equipment 27 conventionally used for thermoplastic compositions.

`~
j llQ~469 ~c~-236~ ~

l ~he following procedures illustrate the preparation 2 o certain copolyes~ers which are used to prepare co~positions 3 within the scope of this invention. They are not ~o be 4 construed to limit the scope of the invention.

6 PROCEDURE A

7 In~o a 500 ml., 3-neck ~lask is weighed llO grams

8 (0~5 moles) of a poly(l,4-butylene terephthalate) prepolymer, containing residue of tetraoctyl ~itana~e transes~erification catalyst,having an intrinsic viscosity of about O.l dl./g., ll as measured in a 60:40 mixture of phenol/~etrachloroethane 12 at 30C. After evacuating the flask and purging with ni~rogen, 13 the flask is submerged in an oil bath heated to 235C. The 14 agitator is turned on and stirrin~ maintained at low speed while the prepolymer melts. Upon completion of the mel~ing, 54 grams 16 of poly(neopentyl-adipate~ (number average molecular weight 17 3000) is added to the stirred melt while maintaining a nitrogen 18 bleed. Since the addition of the poly(neopentyl-adipate) 19 causes some solidification o~ the mass, a few minu~es are spent 20 re-melting the mixture. Aspirator vacuum is applied and the ,1-21 temperature is raised to 252 to 255C. A vacuum of 12 to 13 mm 22 is attalned and a slow, steady distillation commenced. After 23 about ~0 minutes full vacuum is applled via plLmp and maintained 24 at 0.3 to 0.4 mm of mercury throughou~ the polycondensation.
¦ Ap~poximately one hour later, the vacuum is shu~ off and the 2S ¦ system brought to equilibrium. The material is soft and elastic 27 ¦ and adheres to aluminum foil tenaciously. The block copolymer 28 1 consists of 34% poly(neope~.tyl-adipate) and 66% polybutylene 29 ¦ terephthalate, and has an intrinsic viscosity of 0.66 dl./g., I as measured in a 60:40 mix~ure of phenol/tetrachloroethane at 31 1 30C.

-~I ~C~-2368 l ~

Into a 500 ml., 3-neck flask is weighed 110 grams 3 ~0.5 moles~ of the poly(l,4-butylene terephthala~e) prepolymer 4 employed in Example l. After successive evacuations and nitro-S gen purges, the flask is immersed in an oil ba~h at 235C. Ater 6 melting, 10.3 grams (0.48 moles) of poly(neopentyl-adipate) ? is added. Aspirator vacuum of about 10 mm of mercury is 8 commenced and the tempera~ure was raised to 255C. over a

9 six-hour period. Fifteen minutes later, pump vacuum is applied to raise the vacuum to about 0.2 mm of mercury. The 11 reaction ls continued for one hour after removal of vacuu~, the 12 polymer is removed according to the method of Procedure A.

A reactor is charged with 35.3 lbs. of dimethyl 16 terephthalate, a stoichiometric excess of 1,4-butanediol and 17 8.0 grams of tetraisopropyl titanate. The temperature i5 13 raised in stages to 202C. and the vacuum is increased to 1/3"
19 Hg. After one hour and 25 minutes, the vacuum is removed and 4 lbs. of poly(neopentyl-adipate) (molecular weight 3Q0Q) is 21 added. The low molecular weight poly(l,4-butylene terephthalate) 22 is transferred to another reactor and polymerization is carried 23 out at about 250C. and at a pressure of about 0.2 mm of mercury.
24 After two hours, the ~acuum is released and the poLymer is obtained in band form by hand and is chopped after it is cooled 26 to room temperature. The block copolyes~2r has the following 27 properties:
2~

:

.. ,.. __ .__,.__. ..... ,..... ........ , ,.. ,, .. ,.. _..... . ___ ,, . . . `,, ,: ' i'. . .' '.'' "': '''. '','. ,; ,; ,: 1, i ;

~2~69 IV = 0 81 as measured in a 60:40 mix~ure of phenol/tetrachloroethane at 30G.

3 Melting range 175 to 197C.
4 Composition - 9% poly~neopentyl-adipa~e~
Notched Izod ft.lbs./in. 1.21 6 Tensile strength, psi at yield5,632 7 Elongation, % 350 Flexural strength, psi 7,900 9 Flexural modulus 226,000 . .:

12 A low molecular weight poly(l,4-butylene terephtha-13 late) (110 grams) having an intrinsic viscosity of about 0.1 dl./
14 g., as measured in a 6Q:40 mixture of phenol/tetrachloroethane is placed in a 3-neck, 300 ml. flask; the flask is purged three 16 times with nitrogen and dipped into a 250C. oil bath. Upon melting, 33.17 g~ams of poly(l J 6-hexylene-(0.5) adipate-(0.5) 18 isophthalate~, with an approximate number average molecular 19 weight of 1600, is added and the aspirator is started and is run for 23 minutes before the-pump is star~ed. The reaction 21 ls run under full pump vacuum for 135 minutes at an average 22 pressure of Q.2 ~m and temperature of 250C. A sof~, mllky 23 white product (105.3 grams) is obtained having the following 24 ¦ analysis:
25 I IV = 0.71 dl./g., as measured in a 60:40 mix~ure 26 ¦ of phenol/tetrachloroethane at 30C.
27 I Mel~ing range 133 to 164~C.
28 ! Flexural strength, psi 1,700 29 I Flexural modulus, psi 38, 270 30 I Tensile strength, psi at yield-2,930 31 ~ Elongation, % 386 '' ' ' ', ..`1 ~ 8CH-23~8 PROCEDURE E, The general procedure of Procedure D is followed 3 in preparing a block copolyester of poly(l,4rbu~ylene tere-4 phthalate) (110.4 grams) and poly(l,6-hexylene-(0.5) adipate-(0.5) isophthalate) (33.3 grams) (number average molecular 6 weigh~ 3000). There s ob~ained 110.75 grams of a soft, creamy 7 white product that has the following physical properties:
8 Polyesterdiol content 23%
IV = 0.91 dl./g., as measured in a 60:40 mixture of phenol/tetrachloroethane at 30C.
11 Melting range 124 to 162C.
$2 Flexurzl strength~ psi 1,430 13 Flexural modulus, psi 30,520 14 Tensile strength, psi at yield 2,630 15 ¦ Elongation, % 436 17 ¦ PROCEDURE F
18 ¦ Into a 3-neck, 300 ml. flask is placed 110 grams 19 ¦ of the poly(l,4-butylene terephthalate) employed in Procedure E.
¦ This is melted at 235C. (after nitrogen purging) and 33.2 grams 21 ¦ of poly(l,4-butylene-adipate) (number average molecular weight 22 ¦ 1600) is added. After complete melting, the aspirator vacuum 23 is applied for about 20 minutes. Then full vacuum vla pump is 24 started, the temperature is raised to 250C. and the reaction continued. A vacuum o:f 0.3 mm is attained for a short period 26 but rises to 5 mm because of a leak. Ater finding the leak, 27 0.3 mm is restored and vacuum is main~ained for about three 28 hours. An off white mzterial is collected which has the 29 following physical properties:
3~

i ~lOZ469 ~C~-2368 l ~ Polyesterdiol content 23%
2 IV = 0.90 dl./g., as measured in a 60:40 mixture 3 of phenol/tetrachloroethane at 30C.

4 Melting r~nge 165 to 188C.
Flexural strength, psi 2,440 6 Flexural modulus, psi 56,080 7 Tensile strength, psi at yield3,S30 8 Elongation, % 348 PROCEDURE G
11 Into a 3-neck flask is weighed 110 gr~ms of 12 poly(l,4-butylene terephthalate) (IV = 0.1 dl./g., as measured 13 in a 60:40 mix~ure of phenol/tetrachloroethane at 30OC.j. Aiter 14 purging with nitrogen, and melting the polymer at 235C., 34 grams of poly(ethylene-co~1,4-butylene-adipate) (n~mber average 16 molecular weight 3000) is added; and vacuum is applied as the 17 temperature is raised to 250C. After two hours, a flesh-18 colored polymer is recovered that has the following properties:
1~ Po].yesterdiol content 23.6%
IV = 0.92 dl./g., as measured in a 60:40 mixture 21 of phenol/tetrachloroethane at 30C.
22 Melting range 138 to 171C.
23 Flexural stren~th, psi 1,980 24 Flexural modulus, psi 43,540 Tensile strength, psi at yield2,900 26 psi at break3,400 227 Elongation, % 410 , .... ..... ......... ......... . .... . .... ............ . .

~¦ 8CH-2368 ~2~
.. .

2 Into a 3-neck flask is weighed 110 grams o~
3 poly(l,4-butylene terephthalate) (IV of about 0.1 dl./g., as 4 measured in a 60:40 mixture of phenol/tetrachloroe~hane at ~0C.). After purging with vacuum and N2 and melting at 235C.
6 with stirring, 32.9 grams of a copolyester o~ adipic acid, 7 ethylene glycol and 1,4-butanediol is added. Stirring is 8 continued until melting is complete. Then the vacuum aspirator 9 is applied and the temperature is raised to 25~C. over a 50~
minute period. Twenty minutes later, the vacuum pump is turned 11 on and full vacuum (0.3 mm Hg) is maintained ~or one hour and 12 ¦ 25 minutes. The polymer has an off white color having the 13 ¦ following properties:
14 Polyesterdiol content 23%
IV = 0.81 dl./g., as measured in a 60:40 mi.xture 16 of phenolj~etrachloroethane at 30C.
17 Melting range 145 to 174C.
18 Flexural strength, psi 2,085 19 Flexural moaulus, psi 47,475 Tensile strength, p9i at yield3,170 21 Elongation, % 30 24 A block copolyester of poly(l,4 butylene terephtha-late) IV = 0.1 dl./g., as measured in 60:40 mixture of phenol/
26 tetrachloroethane at 30C.) and poly(neopentyl-adlpate) 27 (number average molecular weight 2700) is prepared according to 28 thc ~eneral procedurc of l~roccdure ~l. Thc block copolycster has 29 ~he following properties:

~ 110~:4~9 ~CE~-2368 l IV = 0~g4 dl./g., as measured in a 60:40 mixture 2 of phenol/~etrachloroethane at 30C.
Melting range 105 to 152C.
4 Flexural strength, psi 1,100 Flexural modulus, psi 24,130 6 Tensile strength, psi at yield 2,100 7 psi at break 2,045 8 Elongation, % 250 PROCEDURE J
ll A 20-gallon re~ctor is charged with 35.3 lbs. of 12 dimethylterephthalate, 32.6 lbs. of 1,4-butanediol (stoichio~
13 metric excess) and 8.0 grams of tetraisopropyl titanate.
14 Because the theoretical charge of methanol is not recovered, an additional 7.7 lbs. of 1,4-butanediol is added. The methanol 16 finally distills and it is assumed that a pluggage has held 17 it up. The poly(l,4-butylene tereph~halate) is found to ~ave an 18 IV ~f 0.2 dl./g., as measured in a 60:40 mix~ure of phenol/
19 tetrachloroe~hane at 30C. At this point, 9. 5 lbs . of a poly-(neopentyl-adipate) ~number average molecular weight 3500) is 21 added and the polycondensa~ion is run for two hours and 50 22 minutes. A ribbon of the block copolymer having the following 23 physical properties is collected by hand for future dicing:
24 Polyesterdiol content 19%
IV = 0.68 dl./g , as measured in a 60:40 mixture of phenol/tetrachloroe~hane at 30C.

27 Melting range 154 to 176C.
2& Specific gravity = 1.263 (before drying) 29 Specific gra~ity = 1.271 (after drying).

___ . , . ... _ .__.. ~

2~

PROCEDU~E K
A 10~gallon polyesteriEication reactor is charged with 30 lhs. of dimethyl terephthalate, 24 lbs. o~ 1,4-butanediol and 11 grams of tetra~2-ethylhexyl)titanate. The mixture is gradually heated with stirring to 220 to 225C. while methanol distills off (approximately 1 1/2 hours). Subsequently, a vacuum is applied to the vessel and the excess bukanediol is distilled (approximately 1 hour requlred~. Then 1.54 lbs. of poly(neopentyl-adipate), MW 3200-3500, is added. The tempera-ture is raised to 250 to 255C. and the vacuum increased to 0.2 to 0.4 mm Hg until the product reaches a melt viscosity of 6100 poises*. The vacuum is released with nitrogen and the product cast onto a chilled roll through a slide valve in ~he bottom of the reactor. The resulting band is granulated in a dicer into approximately 1/8" cubes. The cubes are extxuded, chopped and molded into test bars that have the following physical properties:
Gardner Impact in./lbs. 300 Notched Izod, ftOlbs./inO 1.0 Tensile strength, 10 psi 7.3 20 Tensile elongation, ~ 304 Flexural strength, 103 pis 12.1 Flexural modulus, 103 psi 329 Deflection Temp., F r 264 pis 127 25 Crystallization rates, 200F.
time to initial crystallization, Ti 2.0 time to 50~ crystallization 0.6 DSC Data Tm ~ Hf Tc ~ Hc C. cal/g. C. cal/g.
21~ 7.0 163 10~8 * M~- = melt viscosity in poises at 250C. using melt index pro-cedure with 21,600 g~ weight and .042 x .615" orifice~

~ 6~

2 Using the same procedure as Procedure K, the 3 following block copolyesters are prepared with poly(l,4-butylene terephthalate) blocks and blocks comprising the listed aliphatic/
copolyesters and usin~ 11 grams of tetra(2-ethylhexyl~ titanate 6 as a transesterification catalyst:
7 xample ~e~ Wei~ht (lbs.
8 L di~ethyl terephthalate 27 9 1,4-butanediol 25 poly(l,6-hexylene (0.7) a~elate-11 ~0.3) isophthalate) 3 12 M dimethyl terephthalate 27 13 1,4~butanediol 25 14 polyneopentyl-adipate 3 N dimethyl terephthalate 27 16 1,4 butanediol 25 17 poly(l,4-hexylene-(0.5) adipate- -18 (0.5) isophthalate) 3 19 O dimethyl terephthalate~ 27 1,4-butanediol - 25 21 poly(l,6-hexylene-~0.7) adipate-22 (0,3) isophthalate) 3 23 P dimethyl terephthalate 27 24 1,4-butanediol 25 .
poly(l,6-hexylene-co-neopentyl-26 adipate-co-i=ophthalate) 3 ~29 3~ 1 . - 2~ -~ _ . ~

" ,:,`1 8CH-23~8 ~l~Zg~
. .' 1Description o:E the Preferred Embodiments.- The 2 following examples illustrate the present invention. They 3 are not to be construed as limiting the claims in any manner 4 whatsoever.

6EXAMPLES 1 - 2 ' A polybutylene terephthalate homopolym~r and two 8block copolymers with (1,6-hexylene-(0.7) azelate-(0.3) iso 9 phthalate (PHAI) are use~ to prepare flame retarded polymer blends. The blends are prepared by extrusion and the physical 11 data are determined on molded test specimen~:
12 Example (parts by wei~ht)A'~' 1 2 13 PHAI content of the polymer 0 8.5 12 14 Block copolymer conten~ 69 69 69 Copolycarbonate of BPA
and tetrabromo BPA
16 (27% bromine)'~';* 26 26 26 17 Antimony oxide 5 5 5 18 Properties 19 Flammability tUL-g4) V-0 V-O V-O
Notched Izod, ft.lbs./in. .74 1.4 1.2 21 Tensile strength, psi9,100 7,900 6,700 22 Tensile elongation, %31 138 206 23 Flexural strength, psi 15,800 14,000 11,700 24 Flexural modulus, psi409,000366,000 307,000 26 *Comparative Example 27 ~'rJ~ Procedure A, U.S. 3,936,400, modified 2a Q2~69 ~iCH-2368 F,XAMPLES 3 - 4 2 Similar blends a.s in Examples 1 - 2 are made up, 3 which contain, in addition, glass fiber reinforcem~n~:
4 ~ ~* 3 ._ _ 5 PHAI content of the yolymer 0 8.5 12 6 Block copolymer content52 52 52 7 Copolycarbonate of BPA**
and tetrabromo BPA
~ ` (27% bromine) 13 13 13 9 Antimony oxide 5 5 5

10 Glass fibers30 30 30 ll Properties l2 Flammability (UL-94) V-0 V-0 V-0 13 Notched Izod, ft.lbs./in.1.4 1.7 1.8 14 Tensile strength, psi 18.5 16.7 15.4 15 Flexural strength, psi28,300 26,200 24,400 16 Flexural modulus, psi1,219,000 1,146,000 1,011,000 17 Deflection Temp., F., 264 psi 399 347 336 .

*Comparative Exam~le J~;Procedure A, U.S. 3,936,400 23 Compositions according to this inventlon will be 24 obtained if the teachings of the examples are followed, and the following substitutions are made:
26 for the block copolyesters of poly(l,4-butylene 27 terephthalate) with poly(l,4-hexylene-(0.7) azelate-(0.3) 28 isophthalate), subs~ituted block copolyesters prepared by 29 Procedures A-K and M-P, respectlvely, or one in which the poly (1,l-4 butylene terephthalate) has been made in the presence of a ~ ___ ., . _. _ __ . . . . _ . . .

~ Z~9 8C11-236~

l small amount of pentaeryt11~ito.l ~r trimethylolpropane as a 2 branching agent;
3 for the copolycarborlate or tetrabromobisphenol-A
and bisphenol-A, substitute, respectively, 2,2-his-(3,5-dibromo~
4-hydroxyphenyl)propane, decabromodiphenyl ether, hexabromoben-6 zene, triphenyl phosphine oxide, or tris~tribromophenyl)phosphate 7 as flame retardant additives; and for glass as a reinfo:rcing 8 agent, substitute talc, mica or kaolin as a reinforcing agent.
: 9 .
Obviously~ other modiications and ~ariations ll of the present invention are possible in the light of the above 12 teachings. It is, therefore, to be understood that changes may 13 be made in the particular embodiments of the invention described 14 which are within the full intended scope of the invention as lL defined the app~nded c1ai~s, ~9 _ _ _ _ _ _ _, _ _ , _ _ . ... .. . A.. _ _ . ... ' ' ' ' ' . ' . ' ~ ' ' ~. ' ' ' ' ' ' , ' ' ' '; ' ' . 1 . ' . . ' ' ` ` ', , , ',, ',, '

Claims (28)

The embodiments of the invention in which an exclu-sive property or privilege is claimed are defined as follows:

1. A flame retardant composition comprising (A) a thermoplastic copolyester which consists essentially of blocks derived from:
(a) a terminally-reactive straight chain or branched chain poly(1,4-butylene terephthalate) whereof at least 50% of said blocks are derived; and (b)(i) a terminally-reactive aromatic/aliphatic copolyester of a dicarboxylic acid selected from the group consisting of terephthalic acid, isophthalic acid, naphthalene dicarboxylic acids, phenyl indane dicarboxylic acid and compounds of the formula:

in which X may be alkylene or alkylidene of from 1 to 4 carbon atoms, carbonyl, sulfonyl, oxygen or a bond between the benzene rings and an aliphatic dicarboxylic acid having from 6 to 12 carbon atoms in the chain, with one or more straight or branched chain dihydric aliphatic glycols having from 4 to 10 carbon atoms in the chain, said copolyester having at least 10% of aliphatic units being derived from a dicarboxylic acid; or (ii) a terminally-reactive aliphatic polyester of a straight chain aliphatic dicarboxylic acid having from 4 to 12 carbon atoms in the chain and a straight or branched chain aliphatic glycol, said blocks being connected by inter-terminal linkages consisting essentially of ester linkages and (B) a flame retardant amount of a flame retardant agent.

2. A composition as defined in claim 1 wherein said flame retardant agent comprises a halogenated organic compound, a halogen-containing organic compound in admixture with antimony oxide; elemental phosphorus or a phosphorus compound; a halogen containing compound in admixture with a phosphorus compound, a compound containing phosphorus-nitrogen bonds or a mixture of two or more of the foregoing.

3. A composition as defined in claim 2 wherein the amount of flame retardant agent comprises from 0.5 to 50 parts by weight per 100 parts of flammable resinous components, in-cluding said block copolyester, in said composition.

4. A flame retardant composition as defined in claim 1 wherein block (a) is branched.

5. A flame retardant composition as defined in claim 4 wherein block (a) includes from 0.05 to 3 mole %, based on the terephthalate units, of a branching component which contains at least three ester-forming groups.

6. A flame retardant composition as defined in claim 5 wherein the branching component is a polyol.

7. A flame retardant composition as defined in claim 6 wherein the branching component is pentaerythritol.

8. A flame retardant composition as defined in claim 6 wherein the branching component is trimethylolpropane.

9. A flame retardant composition as defined in claim 1 wherein block (b) is a copolyester of isophthalic acid and a straight chain aliphatic dicarboxylic acid having from 6 to 12 carbon atoms in the chain, with one or more straight or branched chain dihydric aliphatic glycols having from 4 to 10 carbon atoms in the chain.

10. A flame retardant composition as defined in claim 1 wherein block (b) is a polyester of a straight chain aliphatic dicarboxylic acid having from 6 to 12 carbon atoms and a branched chain dihydric aliphatic glycol.

11. A flame retardant composition as defined in claim 9 wherein component (b) is poly(1,6-hexylene-azelate-co-isophthalate).

12. A flame retardant composition as defined in claim 11 wherein component (b) is poly(1,6-hexylene-(0.7)-azelate-co-(0.3)isophthalate).

13. A flame retardant composition as defined in claim 9 wherein component (b) is poly(1,6-hexylene-adipate-co-isophthalate).

14. A flame retardant composition as defined in claim 9 wherein component (b) is poly(1,6-hexylene-(0.5)-adipate-co-(0.5)isophthalate).

15. A flame retardant composition as defined in claim 9 wherein component (b) is poly(1,6-hexylene-(0.7)-adipate-co-(0.3)-isophthalate).

16. A flame retardant composition as defined in claim 9 wherein component (b) is poly(1,6-hexylene-co-neopentyl-adipate-co-isophthalate).

17. A flame retardant composition as defined in claim 10 wherein component (b) is poly(neopentyl-adipate).

18. A flame retardant composition as defined in claim 10 wherein component (b) is poly(1,4-butylene-adipate).

19. A flame retardant composition as defined in claim 1 wherein component (b) is poly(ethylene-co-1,4-butylene-adipate).

20. A flame retardant composition as defined in claim 1 which also includes (C) a thermoplastic poly(1,4-butylene terephthalate)resin.

21. A flame retardant composition as defined in claim 20 wherein said resin component is branched

22. A flame retardant molding composition as defined in claim 21 wherein said branched resin component includes from 0.05 to 3 mole %, based on terephthalate units, of a branching component which contains at least three ester-forming groups.

23. A flame retardant composition as defined in claim 20 wherein said resin component comprises from 95 to 50 parts by weight of said composition of a poly(1,4-butylene terephthalate) having an intrinsic viscosity of at least about 0.7 dl./g., as measured in a 60:40 mixture of phenol/tetrachloro-ethane at 30°C.

24. A flame retardant composition comprising a copolyester as defined in claim 1 and a reinforcing amount of a reinforcing filler.

25. A flame retardant composition as defined in claim 20 which also includes a reinforcing amount of a reinforcing filler.

26. A flame retardant composition as defined in claim 24 wherein said reinforcing agent comprises filamentous glass.

27. A flame retardant composition as defined in claim 25 wherein said reinforcing agent comprises filamentious glass.

28. A flame retardant composition as defined in claim 2 which also includes from 1 to 80% by weight of the total composition of a filamentous glass reinforcing agent.