CA1153495A - Flame-retarded high impact polystyrene composition - Google Patents

Abstract

ABSTRACT

A flame-retarded polystyrene composition which does not bloom comprising at least about 50 percent (by combined weight of polystyrene, poly [brominated phenylene oxide], and enhancing agent) of high impact polystyrene, from about 9 to 22 percent (by weight) of poly(brominated pheny-lene oxide), and from 1 to about 10 percent (by weight) of enhancing agent is disclosed.

Description

DESCRIPTION OF THE PRIOR ART
Polystyrene is a versatile thermoplastic which may be used in low density insulation foams, molded parts, extruded and formed sheets for containers and appliances, high density foamed parts, formed dinnerware, and the like.
For many applications the polystyrene--containing object must be flame retarded. Many flame-retarded polystyrenes contain a flame retardant which exudes to the surface after the polystyrene has been formed into a molded object. The exudation, which is also known as blooming, has several very adverse effects: it contaminates liquids and other products in contact with the polystyrene, ana it decreases the concentration of the flame retardant in the polystyrene.
Blends of polystyrene and poly(phenylene oxide) are wcll known to the art. These blends, however, are 1ammable. Thus, e.~., U.S. patent 3,663,654 discloses that the "admixture of a polyphellylene ether with a styrene resin destroys flame retardant properties";

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Example 4 of this patent teaches that a blend of 20 parts of poly(2,6-dimethyl-1,4-phenylene ether), 80 parts of high impact polystyrene, and 1 part of red phosphorus ". . . is incapable of passing the Under-writers' Laboratory test . . ." described in Under-writers' Laboratories in its Bulletin No. 94. Thus, e.g., U.S. patent 3,639,506 discloses that ". . . many blends comprising a s-tyrene resin, even in low concen-tration, with a polyphenylene ether have poor flame retardant properties and are unable to meet the require-ments established by various testing laboratories such as the Underwriters' Laboratories"; Example 1 of this patent teaches that a blend containing 55 parts of poly(2,6-dimethyl-1,4-phenylene ether) and 45 parts of high impact polystyrene, after being molded into test bars and tested for flammability, ". . . burned completely and dripped after ignition thereof."
Applicant has discovered that, unexpectedly, a particular three-component blend which contains at least 50 percent (by weight) of high impact polystyrene, at least 9 percent (by weight) of a particular poly-(brominated phenylene oxide), and an enhancing agent is non-blooming, is flame-retarded, and possesses excellent physical properties.
PREFERRED EMBODIMENTS
The flame-retarded composition of this invention contains at least about 50 percent (by combined weight of polystyrene, poly Cbrominated phenylene oxide~ , and enhancing agent) of high impact polystyrene. It is preferred that the flame-retarded composition of this invention contain at leas-t 65 percent (by combined weight) of high impact polystyrene.
Any of the high impact polystyrenes known in the art may be used in the compositions of this invention.
The high impact polystyrene composition used in the flame-retarded composition of this invention con-tains polymer units derived from the compound of the formula RC =CH2 ~Z(P) wherein R is hydrogen, lower alkyl, or halogen; Z is a member selected from the class consisting of vinyl~ ' hydrogen, chlorine, and lower alkyl; and p is a whole number equal to from 0 to 5; said polymer units comprise ......... at least 25 percent (by weight) of the high impact polystyrene composition.
The flame-retarded polystyrene compositions of this invention contain from about 1 to about 10 percent (by combined weight of polystyrene, poly Cbrominated phenylene oxid~ , and enhancing agent) of enhancing agent and from about 9 to 22 percent (by combined weight) of poly(brominated phenylene oxide) condensation product which is derived from brominated phenol; this condensation product has a repeating structural unit of the formula )a ~r~ (H ) b (Q)c ~ ~t.3~S
wherein a is an integer of from about 1 to about 4, b is an inte~er of from about 0 to about 2, c is an integer of from about l to about 5, a plus b plus c equal 5, and Q is a monovalent bond from a carbon atom in the aromatic nucleus of said repeating structural unit to an oxygen atom bonded to an aromatic nucleus~
This monovalent bond may exist any place on the aro-matic nuclei in the composition wherein there was a carbon-bromine bond; it is formed by the displacement of bromine. Thus, for example, it may exist in the posi~ion para to the oxygen-carbon bond. One repeating structural unit which has this para bond may be repre-sented y the f ~mul~ ¦ ~ L

wherein x is 2,3 or 4 (and preferrably is 2 or 3);
this repeating unit forms linear chains. Thus, in other instances where c is 1, the monovalent bond may exist at the ortho position (hereinafter referred to as "II"). The bond may exist at both the ortho and para positions when c is 2 (hereinafter referred to as "III"); and it may exist ortho, ortho, and para to the carbon-oxygen bond when c is 3 (hereinafter referred to as "IV"). The poly(bromophenylene oxide) condensa-tion product contains at least one of the repeating structural units denoted I, II, III, and IV. At least 80 percent (by weight) of this product is comprised of polymer chains containing one or more of these units.

The poly~brorninated phenylene oxide) product has a molecular weight of at leas-t about 750. The molecular weight of this product may be determined by the vapor phase osmometry method described in ASTM test ~2503-67.
It is preferred, however, to determine the molecular weight of this product by the gel permeation chromato-graphy method known to the art; and, unless otherwise specified, references to molecular weight in this specification refer to number-average molecular-weights determined in accordance with the gel permeation method with polystyrene reference standards.
In the gel permeation method used to ascertain the molecular weights of the poly~brominated phenylene oxide) compositions described in this specification, four Waters Assoclates, Inc., stainless steel columns packed with Styragel ~ are connected in series; these columns, each of which measures 48" long x 0.375" in diameter, have pore sizes of 15,000 - 50,000 angstroms, 8,000 angstroms, 250 angstroms, and 250 angstroms, respectively.
The solvent utilized is tetrahydrofuran; 33r 5 milligrams of the poly(brominated phenylene oxide) sample are mixed with 15.0 milliliters of tetrahydrofuran, and the mixture is introduced into the chromatograph. A flow rate of 1 milliliter of tetrahydrofuran per minute is used. The chromatograph is calibrated with commercially availa~le polystyrene standards, and the molecular weight values found are reported in terms of polystyrene.
It is preferred that the number averaye molecular weight of the poly(brominated phenylene oxide) composi-tions of this invention be less than about 100,000. It 34L~S
is more pre~erred that said nurtl~er averaye molecular weight be less than about 10,000. In the most preferred embodiment, said number average molecular weight is less than about 4,500.
One or more polymeric units containing at least four aromatic nuclei comprise at least about 80 percent of the weight of the poly(brominated phenylene oxide) composition described in this specification.
The poly(brominated phenylene oxide) condensation product is derived from a brominated phenol selected from the group consisting of tribromophenol, tetra-bromophenol, and pentabromophenol. It is preferred that the brominated phenol be selected from the group consisting of tribromophenol and tetrabromophenol; and it is most preferred that the brominated phenol be tribromophenol.
The poly(brominated phenylene oxide) condensation product contains from about 17 to about 31 percent (by weight) of carbon, from about 0 to about 1.0 per-cent (by weight) of elemental hydrogen, from about 3 to about 8 percent (by weight) of elemental oxygen, and at least about 60 percent (by weight) of elemental bromine. It is preferred that this product contain from about 62 to about 66 percent (by weight) of ele-mental bromine.
The flame-retarded polystyrene composition of this invention contains from about 1 to about 10 percent (by combined weight) oE enhancing agent. The enhancing agents known in the art may be used in the compositlons of this invention; some of these are, e.g., the oxides ~5~5 and halides of the metals of groups IVA and VA of the Periodic Table such as the oxides and halides of anti-mony, bismuth, arsenic, tin, lead, and germanium; anti-mony oxychloride, antomony chloride, antimony oxide, stannic oxide, stannic chloride, arsenous oxide, arsenous chloride, and the like. Other enhancing agents well known to those skilled in the art may be used.
The flame retardant additive utilized in the poly-styrene composition of this invention contain.s poly-(brominated phenylene oxide) and enhancing agent. Poly-(brominated phenylene oxide) comprises at least about 50 percent (by combined weight of poly [brominated pheny--lene oxide~ and enhancing agent) of the flame xetardant additive. It is preferred that the poly(brominated phenylene oxide) comprise at least 70 percent (by combined weight of poly ~brominated phenylene oxide~
and enhancing agent) of this additive.
- The followiny examples are provided for the purpose of further illustration only and are not intended to be limitative of the invention disclosed. Unless otherwise specified, all parts are by weight, all weights are in grams, all temperatures are in degxees centi-grade, and all volumes are in rnilliliters.

. . _ .
Two thousand milliliters of water, 164 grams of sodium hydroxide, 10.7 grams of "Emulsifier 334" (an aryl polyether emulsifier sold by the Milliken Chemical Corporation), 0.7 grams of dodecyl sodium sulfate, and 1,324 grams of 2,4,G-tribromophenol were charged to a five-liter flask fitted with mechanical stirring, a 3~
thermome-ter, and a reElux condenser. The reaction mixture was flrst heated to 100 degrees centigrade and maintained at that tempera-ture for one minute; then it was cooled to a temperature of 33 degrees centigrade.
To this mixture was charged 133 milliliters of toluene and 20 grams of benzoyl peroxide. An exothermic reac-tion occurred, and the reaction temperature was then maintained at 55 degrees centigrade for 0.5 hours.
Thereafter, 25 grams of sodium hydroxide were added to the reaction mixture. The reaction mixture was then filtered, the filter cake was washed with 15 liters of water, and the filter cake was dried to give 932 grams of product.

-In substantial accordance with the procedure described in Example 1, poly(brominated phenylene oxide) compositions with different softening point ranges and molecular weights were prepared. The mole-cular weights of these products were determined in accordance with two different methods: the vapor phase osmometry method described in test ASTM D2503-67, and the gel permeation chromatography test described in this specification wherein polystyrene was used as a reference. The results obtained in the former test are referred to as "V.P.O. Molecular Weight". Three results were obtained in the latter test and are expres-sed as ''Mw'' (weight average molecular weight), "Mn"
(number average molecular weiyht~, and "H.I." (the "heterogeneity index" which is calculated by dividing the weight average molecular weight by the number ~' averaye molecular weight). The results of -these experiments are summarized in Table I.
TABLE I
_ _ SOFTENING
POINT V.P.O~
EXAMPLE RAN OE , MOLECULAR
NUMBER DEGREES C. WEIGHT Mn Mw H.I.

2 210-2258370 35318~19 2.3b

3 210-230~10,0~0 45428622 1.90

4 188-2003540 2741~549 1.66 225-240> 10,000 7395123~0 1.67 7 160-1751735 24893630 1.46 8 210-~27> 10,000 42879387 2.19 9 205-2203295 32776610 2.02 205-2203735 35107150 2.04 11 205-2204670 38328125 2.12 12 160-1801875 28334028 1.42 13 190-2052480 28375327 1.88 14 190-2103855 33024460 1.35 200-2153200 31895733 1.80 High impac~ polystyrene plastic compositions were - --- prepared by incorporating one of the flame retardants described in Examples 2 through 15 and antimony tri-oxide into "Cosden Polystyrene 825 TVPl", a high impact polystyrene available from the Cosden Oil and Chemical Company. These additives were admixed with the poly-styrene by addition to a Brabender Prep Center Mixer ("Measuring Head", Model R6, C. W. Brabender Instruments, Inc., South Hackensack, N.J.); the mixer was equipped with a pair of roller-type blades positioned with a head provided with heat transfer means. The resultant mixtures were heated to a tempera-ture of about 205 degrees centigrade; at this temperature they were in a molten state. Each formulation was discharged from the mixer, cooled, and ground into chips. The chips were injection molded in a one-ounce Newbury Injection Molder ~t.~3~?S
(Model HI-30 RS, Newbury Indus-tries, Inc., Newbury, Ohio); a 60 second molding cycle with a ~am pressure of 2,000 p.s.i. was utilized; these chips were subjected to heat, melted, and then injected into a mold in order to provide solid samples for testing.
The s~mples prepared in Examples 16-19 contained 15 percent (by weight of total composition) of one of the flame retardants prepared in Examples 2-15, 3 percent (by weight of total composition) of antimony trioxide, and 6 percent (by weight of total composition) of "Solprene 411P" (a styrene-butadiene copolymer useful as an impact modifier which is available from the Phillips Petroleum Company). The injection molded samples were tested for Izod impact and heat distortion temperature (unannealed).

They were also tested for flammability in accordance with Underwriters' Laboratory Subject No. 94 test (U.L.
Tests for Flammabllity of Plastic Materials, U.L. 94, February 1, 1974). The results of these experiments are summarized in Table II.
TABLE II

PRIOR
EXAMPLE HEAT
DESCRIBING IZOD IMPACT, DISTORTION
FLAME FOOT-POUNDS TEMPERATURE U.L. U.L.
EXAMPLE RETARDANT PER INCH (UNANNEALED) 94, 94, NUMBER USED (NoTcH) _ DEGREES F. 1/8" 1/16 16 4 1.32 163 V-O V-O
17 2 1.55 166 V-O V-O
18 7 1.34 154 V-O V-O
19 8 1.50 161 V-O V-l EXAMPLES 20_AND 21 In substantial accordance with the procedure de-scribed in Examples 16 through 19, high impact poly-styrene composition containing 13 percent (by weight) of the flame retardant of Example 2 and Shell 335 high impact polystyrene were prepared and evaluated. The composition of Example 20 contained 13.0 percent of said flame retardant, 2.6 percen-t of antimony trioxide, and 6.0 percent of Solprene 411P. The composition of Example 21 contained 13.0 percent of said flame retar-dant, 3.25 perce~t of antimony trioxide, and 6.0 per-cent of said Solprene 411P. Samples prepared from the former composition were evaluated and found to have a U.L. 94 1/8" rating of V-O, a notched Izod impact of 1.63 foot-pounds per inch, a Gardner impact of 7~, and an unannealed heat distortion temperature of 164 degrees Fahrenheit. Samples prepared from the latter compo-sition were evaluated and found to have a U.L. 94 1/8"
rating of V-O, a notched impact of 1.55 foot-pounds per inch, a Gardner impact of 60, and unannealed heat distortion temperature of 165 degrees Fahrenheit.

The procedure of Examples 16 through 19 was re-peated with the exception that Dow Styron 49~ high im-pact polystyrene (available from the Dow Chemical Com-pany of Midland, Michigan) was used.
In Examples 22 and 23, the flame retardant de-scribed in Example 7 was used. The average Izod impact was 1.48 foot-pounds per inch, and the heat distortion temperature was 159 degrees Fahrenheit. The U.L. 94 1/8" flammability ratings were V-O.

The procedure described in Examples 22 and 23 was followed with the exception that the flame retardant of Example 4 was used. The I~od impact was 1.60 foot-pounds ` ~Lt:j3~S
per inch, the he~t distor-tion -tefnperature was 161 degrees Fahrenheit, the U.L. 94 1/8" flammability rating was V-O and the U.L. 94 1/16" flammability rating was V-l.

_ _ In substantial accordance with the procedures described in Examples 1 and 23, poly(brominated pheny-lene oxide) compositions of varying molecular weights were prepared and incorporated into Shell 335 high impact polystyrene; these styrene compositions con-tained 15 percent (by weight of total composition) of flame retardant, 3 percent (by weight of total composi-tion) of antimony trioxide, and 6 percent (by weight of total composition) of Solprene 411P. Samples of the high impact polystyrene compositions obtained were prepared and tested for flammability with the U.L.
test. The results of this experiment are shown below in Table III wherein the molecular weight of each flame retardant as well as the U.L. 94 1/16" flammability rating and the average number of seconds it took the samples tested to self extinguish after the igniting flame was removed from them is indicated.
TABLE III
V.P.O.
EXAMPLE MOLECULAR U.L. 94 NUMBERWEIGHT Mn Mw 1/16" RATING
25> 10,000 7395 12340 V-l (7.2 seconds) 26> 10,000 4287 9387 V-l (4.3 seconds) 27 7,390 4328 9480 V-l (5.8 seconds) 28 4,670 3832 8125 V-G (2.2 seconds) 29 3,855 3302 4460 V-O (1.4 seconds~
30 3,200 3189 5733 V-O (2.2 seconds) 31 2;480 2837 5327 V-O ~0.8 seconds) 32 1,875 2833 4028 V-O (0.7 seconds) s In substantial accordance with the procedures described in Examples 1 and Z3, poly(brominated pheny-lene oxide) compositions of high molecular weight were prepared and incorporated into Shell 35 high impact polystyrene; these compositions contained 15 percent (by weight of total composition) of flame retardant, 3 percent (~y weight of total composition) of an-timony trioxide, and 6 percent (by weight of total composition) of Solprene 411P.
The flame retardant additive used in Example 33 had a molecular weight in excess of 10,000 and a soften-ing point range of from about 225 to about 240 degrees centigrade; it was soluble in both tetrahydrofuran (at 25 degrees centigrade) and chloroform (at 25 degrees centigrade). The flame retardant additive used in Example 34 had a molecular weight in excess of lO,000 and a sofetning point range of from about 245 to about 290 degrees centigrade; it was insoluble in both tetra-hydrofuran (at 25 degrees centigrade) and chloroform (at 25 degrees centigrade).
Injection modled samples of the polystyrene com-positions of these Examples were prepared for testing and evaluated.
The polystyrene composition of Example 33 had a U.L. 94 l/16" rating of V-l (7.2 seconds). The Izod impact of the test specimen was 1.35 foot-pounds per inch.
The polystyrene composition of Example 34 had a U.L. 94 l/16" rating of V-l (6.7 seconds). The Izod - impact of the test specimen was 0.86 foot-pounds per inch.

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In substantial accordance with the procedure described in Example 1, poly(brominated phenylene oxides) were prepared from 2,~,6-tribromophenoli the molecular weight of this composition tas determined by the vapor phase osmometry method described in test AST~l D2503~67) was about 3830. The number average molecular weight (as determined by the gel permeation chromatography method described in this specification) was about 3302.
In substantial accordance with the procedure described in Example 16, high impact polystyrene com-positions containing 15 percent (by weight of total composition) of the poly(brominated phenylene oxide) described in the first paragraph of this Example, 3 percent (by weight of total composition) of antimony trio~ide, and 6 percent (by weight of total composition) of Solprene 411P were prepared; injection molded samples were prepared for testing.
One sample was subjected to accelerated aging by being exposed to a temperature of 150 degrees Fahrenheit for 48 hours; the other sample, the control, was not subjected to these conditions.
The surface area for the top and bottom surfaces of each of the samples was measured; for each sample, the combined surface area for the top and bottom surfaces was about 5.89 square inches.
The control sample and the sample subjected to accelerated aging conditions were each wiped with sepa-rate pieces of filter paper. The fil-ter paper used was then subjected to spectometric anal~sis with the General ~/~~

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Electric XRD S Fluorescence Spectrometer. The analytical procedure used was essentially the same as the procedure described in a paper entitled "The Determination of Sulfur, Lead, and Silicon in Atmospheric Aerosols--An Application of X-ray Fluorescence and Confined Spot Paper-Techniques"; this paper, which was prepared by J. L. Johnson, A. C. Ottolini, F. A. Forster, and R. B. Loranger and was published by the Research Labora-tories of General Motors Corporation as llResearch Publi-cation GMR-1128" on or about October oE 1972 and was presented at the ANACHEMS Conference held in Dearborn, Michigan, in October of 1972.
No surface bromine (in the form of polyCbrominated phenylene oxide~ ) was detected in the control sample.
lS No surface bromine (in the form of poly Cbrominated phenylene oxide~j was detected in the sample which had been subjected to a temperature of 150 degrees Fahren-heit for 48 hours.

... . .. . . , _ High impact polystyrene plastic compositions were prepared by incorporating either Noryl ~ (a composition containing poly [2,6-dimethyl-1,4-phenylene ether~ which is available from the General Electric Company) and/or flame retardant prepared in accordance with the procedure of Example 1 and/or antimony trioxide into "Cosden Polystyrene 825 TVPl, a high impace polystyrene avail-able from the Cosden Oil and Chemical Company: in the Table accompanying these Examples, the former composi-- tion is referred to as "poly(phenylene oxide)" and the latter composition is referred to as "poly(brominated phenylene oxide)".

34~5 Two con-trol polystyrene plastic compositions were prepared. The first of these contained only Cosden Polystyrene 825 TVPl; the second contained 6 percent (by weight) of antimony trioxide and 94 percent (by weight) of Cosden Polystyrene 825 TVPl.
The additives were admixed with the polystyrene by addition to a Brabender Prep Center Mixer ("Measuring Head", Model R6, C. W. Brabender Instruments, Inc., South Hackensack, N.J.); the mixer was equipped with a pair of roller-type blades positioned with a head pro-vided with heat transfer means. The resultant mixtures were heated to a temperature of 205 degrees centigrade;
at this temperature they were in a molten state. Each formulation was discharged from the mixer, cooled, and ground into chips. The chips were injection molded in a one-ounce Newbury Injection Molder (Model HI-30 RS, Newbury Industries, Inc., Newbury, Ohio); a 60 second molding cycle with a ram pressure of 2,000 p.s.i. was utilized~ and these chips were subjected to heat, melted, and then injected into a mold in order to provide solid samples for testing.
Thè samples so prepared were tested for flammability in accordance with the Underwriters' Laboratory Subject No. 94 test referred to in Example 16.
The results obtained in these tests are shown in Table IV. In each case the samples tested contained only Cosden Polystyrene 825 TVPl and tle speciied amount(s~ of antimony trioxide and/or poly(phenylene oxide) and/or poly(brominated phenylene oxide). The concentrations Gf these additives are indicated as a ~6 3~
weight~percent, and ~hey were calculated as a function of the combined weights of the polystyrene, antimony trioxide, and phenylene oxide polymers which were used in each Example.

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SUPPI.EMI~,NTARY l):l:SCLOSURT~
_ _ ____ ____ __ __ As previously indicated in the principal disclosure, it is preferred that the flame retardant condensation product of this invention be derived from tri~romophenol. It has been found that the condensati.on product of tribromophenol. in accordance with the present invention has a novel molecular structure exhibiting desirable properties over closely related compositions.
More specifically, the pre~erred flame retarding condensation product of this invention is a branched polymer having a hydroxy]. number of from 2.8 to about 30 and the structural formula _ _ (Br) ~ ~ =

( )q m wherein each repeating unit set out within the brackets of the structural formula is attached in an ortho or para configuration to its adjacent phenyl and phenoxy moiety; and wherein E is an end group of the formula Br -O ~ Br Y is a side chain of the same structure and configuration as said repeating unit; the substituents Br, E and Y on each phenyl ring are attached only to the ortho or para positions relative the hydroxyl group in the structural Eormula and the oxygen atom in . - 1 9 s the repeating unit; each t, p and q are independently the integer 0 or 1, provided that the sum of ~ plus p plus q equals 2, and provided that from about 10 to about 80 percent of the repeating units have the side chain and end uni-t -~-E attached thereto; and m i5 an integer such that the total molecular weight of the polymer ranges from about 2,000 to about 20,000.
The novelty and unexpected desired properties of the polymer described above are attributed to both the chemical as well as its structural configuration. First the polymer, because it is a condensation product of a phenol, necessarily has a residual hydroxyl group. This group can be titrated and accor-dingly the polymer has a hydroxyl number dependent on its molecular weight. As stated, this hydroxyl number typically ranges from 2.8 to about 30 mg per gram of sample.
It has also been found that the condensation of tribromophenol as described herein results in a 1-2 and 1-4 sub-stitution of bromine relative the phenolic moiety. Therefore, each repeating phenoxy group in the polymer is attached to an ortho or para position relative the phenolic group on the adjacent ring.
Thus7 any two repeating units have the following structural configuration (Br)t (Br)t _ 0 ~ 0 ~ / ~ or ( ) (y) ( ) (I) (: ~)q (Oq I~. `(Y-E)q /,J\
` (Br)t t ~ P
(Y-E) wherein Y, E, t, p and q are as heretofore described. Similarly, the side chains represented by Y and the end groups represented by E are attached to the ortho or para position of the respecti~e phenoxy ring.
An important aspect of the preferred fire retardant condensation product is its branching i.e. the existence of side groups on otherwise linear polymer backbone. These side groups can be one or more repeating units as in the backbone of the polymer terminated by an end group or simply an end group by -itself. The degree of branching in the preferred product can vary such that at least one in ten of the phenoxy units are substituted by a side chain or end group and as many as eight in 10 are so substituted. It is believed that this degree of branching significantly contributes to the non-blooming properties of polyester compositions containing the preferred product.
The preferred condensation product of the present invention has a number average molecular weight that ranges from about 2000 to about 20,000, and most preferably from about 2000 to about 12,000 as determined by vapor phase osmometry (VPO).
The preferred condensation product of tribtomophenol of the present invention can be prepared by the yeneral procedure heretofore described. A further more specific exemplary preparation is set forth in the followiny example.

Sodium tribromophenate (387 grams) dissolved in water to obtain a 37 percent by weight solution is charged into a reaction vessel equipped with stirring and heating means. Hydro-chloric acid (1.9 grams; 31.5~ concentration) is added and the resulting mixture is warmed to 40C with stirring. Potassium per-sulfate (2.3 grams) is added to the reaction vessel and stirring is continued for a period of about 30 minutes. A reaction tem-perature of 55 to 60C is maintained during this period. After this time the pH of the reaction mi~ture is adjusted to about 13 by the addition of 50% aqueous caustic soda and thereafter hydrazine (1 gram; 64~ conc.) is added with stirring. Stirring is continued for a period of 15 minutes and the reaction mixture is thereafter heated to a temperature of 95 to 100C with further stirring for a period of 4 hours. After this time the mixture is cooled to room temperature and the desired product is recovered by filtration and dried.

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Claims (17)

The embodiments of the invention in which an exclusive property or privilege is claimed are as fol-lows :

1. A polystyrene composition comprised of at least about 50 percent (by combined weight of polystyrene, poly [brominated phenylene oxide], and enhancing agent) of polystyrene, from about 9 to about 22 percent (by combined weight) of poly(brominated phenylene oxide),, and from about 1 to about 10 percent (by combined weight) of enhancing agent, wherein:
a) said poly(brominated phenylene oxide) is a condensation product derived from a bromi-nated phenol selected from the group consis-ting of tribromophenol, tetrabromophenol, and pentabromophenol;
b) said condensation product has a repeating structural unit of the formula wherein a is an integer of from about 1 to about 4, b is an integer of from about O to about 2, c is an integer of from about 1 to about 5, a plus b plus c equals 5, Q is a monovalent bond from a carbon atom in the aromatic nucleus of said repeating structural unit to an oxygen atom bonded to an aromatic nucleus, and the polymeric units containing said repeating structural unit comprise at least about 80 percent (by weight) of said product.
c) said condensation product contains from about 17 to about 31 percent (by weight) of elemental carbon, from about 0 to about 1.0 percent (by weight) of elemental hydrogen, from about 3 to about 8 percent (by weight) of elemental oxygen, and at least about 60 percent (by weight) of elemental bromine;
and d) said condensation product has a molecular weight of at least about 750, and one or more polymeric units containing at least four arc-matic nuclei per unit comprise at least about 80 percent (by weight) of said product.

2. The polystyrene composition of claim 1, where-in said poly(brominated phenylene oxide) has a number average molecular weight of less than about 100,000.

3. The polystyrene composition of claim 2, wherein said enhancing agent is antimony trioxide.

4. The polystyrene composition of claim 3, wherein said composition contains at least about 65 percent (by combined weight) of polystyrene.

5. The polystyrene composition of claim 4, wherein said poly(brominated phenylene oxide) conden-sation product has a number average molecular weight of less than about 10,000 and contains from about 62 to about 66 percent (by weight) of elemental bromine.

6. The polystyrene composition of claim 5, wherein said poly(brominated phenylene oxide) conden-sation product has a number average molecular weight of less than about 4,500, a notched Izod impact strength of less than about 0.5 foot-pounds per inch, an elongation of less than about 2.0 percent, and a tensile strength of less than about 200 pounds per square inch.

7. The polystyrene composition of claim 1, wherein said composition contains at least 50 percent (by combined weight) of high impact poly-styrene.

8. A flame retardant additive composition con-sisting essentially of at least about 50 percent (by combined weight of poly brominated phenylene oxide and enhancing agent) of the poly(brominated phenylene oxide) described in claim 1 and enhancing agent.

9. The flame retardant additive composition of claim 8, wherein said poly(brominated phenylene oxide) has a number average molecular weight of less than 100,000.

10. The flame retardant additive composition of claim 9, wherein said enhancing agent is antimony trioxide.

CLAIMS SUPPORTED BY THE SUPPLEMENTARY DISCLOSURE

11. A branched polymer having a hydroxyl number of from 2.8 to about 30 of the structural formula wherein each repeating unit set out within the brackets of the structural formula is attached in an ortho or para configuration to its adjacent phenyl and phenoxy moiety; and wherein E is an end group of the formula Y is a side chain of the same structure and configuration as said repeating unit; the substituents Br, E and Y each phenyl ring are attached only to the ortho or para positions relative the hydroxyl group in the structural formula and the oxygen atom in the repeating unit; each t, p and q are independently the integer 0 or 1, provided that the sum of t plus p plus q equals 2, and provided that from about 10 to about 80 percent of the repeating units have the side chain and end unit -Y-E attached thereto; and m is an integer such that the total molecular weight of the polymer ranges from 2000 to 20,000.

12. The branched polymer of claim 11 wherein its molecular weight ranges from 2000 to about 12,000.

13. A flame retarded polystyrene composition com-prising from about 50 to about 90 parts by weight polystyrene, from about 9 to about 22 parts by weight of a branched polymer of claim 11, and from about 1 to about 10 parts by weight fire retarding enhancing agent comprising an oxide or chloride of antimony, arsenic, bismuth, tin, lead or germanium.

14. The flame retarded polystyrene composition of claim 13, wherein the branched polymer has a molecular weight of from 2000 to 12,000.

15. The flame retarded polystyrene composition of claim 13, wherein the fire retarding enhancing agent is an oxide of antimony, arsenic or bismuth.

16. The flame retarded polystyrene composition of claim 13, wherein the fire retarding enhancing agent is antimony trioxide.

17. The flame retarded polystyrene composition of claim 13, wherein the polystyrene is high impact polystyrene.