GB2023616A

GB2023616A - Flame-retardant Composition and Flame Retarded Polystyrene Composition

Info

Publication number: GB2023616A
Application number: GB7919077A
Authority: GB
Original assignee: Velsicol Chemical LLC
Current assignee: Velsicol Chemical LLC
Priority date: 1978-06-01
Filing date: 1979-05-31
Publication date: 1980-01-03
Also published as: JPS5742655B2; FR2427356A1; DE2922559A1; DE2948263C2; DE2948263A1; JPS54163943A; CA1153495A

Abstract

Flame retardant additives for polystyrene comprise at least 50 per cent of a poly(brominated phenylene oxide) of MW at least 750 and containing at least 60% of bromine and an enhancing agent, e.g. antimony trioxide. Flame-retarded compositions which do not bloom comprise at least 50 per cent of high impact polystyrene, from 9 to 22 per cent of the poly(brominated phenylene oxide), and from 1 to 10 percent of the enhancing agent.

Description

SPECIFICATION Flame-retardant Composition and Flame Retarded Polystyrene Composition 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 flameretarded 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, and it decreases the concentration of the flame retardant in the polystyrene.

Blends of polystyrene and poly(phenylene oxide) are well known to the art. These blends, however, are flammable. Thus, e.g., U.S. Patent 3,663,654 discloses that the "admixture of a polyphenylene ether with a styrene resin destroys flame retardant properties"; 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 Underwriters' Laboratory test... "described in Underwriters' Laboratories in its Bulletin No. 94. Thus, e.g., U.S.Patent 3,639,506 discloses that"... many blends comprising a styrene resin, even in low concentration, with a polyphenylene ether have poor flame retardant properties and are unable to meet the requirements 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 3 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.

The flame-retarded composition of this invention contains at least about 50 percent (by combined weight of polystyrene, poly[brominated phenylene oxide], and enhancing agent) of high impact polystyrene. It is preferred that the flame-retarded composition of this invention contains at least 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 contains polymer units derived from the compound of the formula

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[brominated phenylene oxide], 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

wherein a is an integer of from about 1 to about 4, b is an integer of from about 0 to about 2, c is an integer of from about 1 to about 5, a plus b plus c equal 5, and 0 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 nay exist any place on the aromatic 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 position para to the oxygen-carbon bond. One repeating structural unit which has this para bond may be represented by the formula

wherein x is 2, 3 or 4 (and preferably 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) condensation product contains at least one of the repeating structural units denoted I, II, Ill 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(brominated phenylene oxide) product has a molecular weight of at least about 750. The molecular weight of this product may be determined by the vapor phase osmometry method described in ASTM test D2503-67. It is preferred, however, to determine the molecular weight of this product by the gel permeation chromatography 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 Water Associates, Inc., stainless steel columns packed with Styragel are connected in series; these columns, each of which measures 48" longx0.375" in diameter, have pore sizes of 1 5,000-50,000 angstroms, 8,000 angstroms, 250 angstroms, and 250 angstroms, respectively. The solvent utilized is tetrahydrofuran; 33.5 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 available polystyrene standards, and the molecular weight values found are reported in terms of polystyrene.

It is preferred that the number average molecular weight of the poly(brominated phenylene oxide) compositions of this invention be less than about 100,000. It is more preferred that said number average molecular weight be less than about 10,000. In the most preferred embodiment, said number average molecular weight is less shat 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, tetrabromophenol, 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 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. It is preferred that this product contain from about 62 to about 66 percent (by weight) of elemental bromine.

The flame-retarded polystyrene composition of this invention contains from about 1 to about 10 percent (by combined weight) of enhancing agent. The enhancing agents known in the art may be used in the compositions of this invention; some of these are, e.g., the oxides and halides of the metals of groups IVA and VA of the Periodic Table such as the oxides and halides of antimony, bismuth, arsenic, tin, lead, and germanium; antimony 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 polystyrene composition of this invention contains poly(brominated phenylene oxide) and enhancing agent. Poly(brominated phenylene oxide) comprises at least about 50 percent (by combined weight of poly[brominated phenylene oxide] and enhacing agent) of the flame retardant additive. It is preferred that the poly(brominated phenylene oxide) comprise at least 70 percent (by combined weight of poly[brominated phenylene oxides and enhancing agent) of this additive.

The following 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 degrees centigrade, and all volumes are in milliliters.

Example 1 Two thousand milliliters of water, 1 64 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 2,4,6-tribromophenol were charged to a five-liter flask fitted with mechanical stirring, a thermometer, and a reflux condenser. The reaction mixture was first heated to 100 degrees centigrade and maintained at that temperature 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 reaction 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 1 5 liters of water, and the filter cake was dried to give 932 grams of product.

Examples 2-15 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 molecular 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 expressed as "Mw" (weight average molecular weight), "M," (number average molecular weight), and "H.I." (the "heterogeneity index" which is calculated by dividing the weight average molecular weight by the number average molecular weight). The results of these experiments are summarized in Table I.

Table I Softening Point V.P.O.

Example Range, Molecular Number Degrees C. Weight M Mw H,l.

2 210-225 8370 3531 8319 2.36 3 210-230 > 10,000 4542 8622- 1.90 4 188-200 3540 2741 4549 1.66 5 225-240 > 10,000 7395 12340 1.67 6 225-250 Insoluble 7 160-175 1735 2489 3630 1.46 8 210-227 > 10,000 4287 9387 2.19 9 205-220 3295 3277 6610 2.02 10 205-220 3735 3510 7150 2.04 11 205-220 4670 3832 8125 2.12 12 160-180 1875 2833 4028 1.42 13 190-205 2480 2837 5327 1.88 14 190-210 3855 3302 4460 1.35 15 200-215 3200 3189 5733 1.80 Examples 16-19 High impact polystyrene plastic compositions were prepared by incorporating one of the flame retardants described in Examples 2 through 1 5 and antimony trioxide into "Cosden Polystyrene 825 TVP1", a high impact polystyrene available from the Cosden Oil and Chemical Company. These 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 provided with heat transfer means. The resultant mixtures were heated to a temperature 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 (Model Hl-30 RS, Newbury Industries, Inc., Newbury, Ohio); a 60 second molding cycle with a ram 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 samples prepared in Examples 1 6-1 9 contained 1 5 percent (by weight of total composition) of one of the flame retardants prepared in Examples 2-1 5, 3 percent (by weight of total composition) of antimony trioxide, and 6 percent (by weight of total composition) of "Solprene 411 P" (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 Flammability 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 Izodimpact, 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-1 Examples 20 and 21 In substantial accordance with the procedure described in Examples 1 6 through 19, high impact polystyrene 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 percent of antimony trioxide, and 6.0 percent of Solprene 41 1P.The composition of Example 21 containd 13.0 percent of said flame retardant, 3.25 percent of antimony trioxide, and 6.0 percent of said Solprene 411 P. 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 70, and an unannealed heat distortion temperature of 1 64 degrees Fahrenheit. Samples prepared from the latter composition were evaluated and found to have a U.L 94-1/8" rating of V-O, a notched impact of 1.65 foot-pounds per inch, a Gardner impact of 60, and unannealed heat distortion temperature of 165 degrees Fahrenheit.

Examples 22 and 23 The procedure of Examples 1 6 through 1 9 was repeated with the exception that Dow Styron 492 high impact polystyrene (available from the Dow Chemical Company of Midland, Michigan) was used.

In Examples 22 and 23, the flame retardant described in Example 7 was used. The average Izod impact was 1.48 foot-pounds per inch, and the heat distortion temperature was 1 59 degrees Fahrenheit. The U.L 94-1/8" flammability ratings were V-O.

Example 24 The procedure described in Examples 22 and 23 was followed with the exception that the flame retardant of Example 4 was used. The Izod impact was 1.60 foot-pounds per inch, the heat distortion temperature 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-1.

Examples 2532 In substantial accordance with the procedures described in Examples 1 and 23, poly(brominated phenylene oxide) compositions of varying molecular weights were prepared and incorporated into Shell 335 high impact polystyrene; these styrene compositions contained 15 percent (by weight of total composition) of flame retardant, 3 percent (by weight of total composition) of antimony trioxide, and 6 percent (by weight of total composition) of Solprene 411 P. 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 Ill wherein the molecular weight of each flame retardant as well as the U.L. 94-1/1 6" 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 Ill V.P.O.

Example Molecular U.L. 94 Number Weight 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-1 (5.8 seconds) 28 4,670 3832 8125 V-O (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) Examples 33 and 34 In substantial accordance with the procedures described in Examples 1 and 23, poly(brominated phenylene 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 (by weight of total composition) of antimony trioxide, and 6 percent (by weight of total composition) of Solprene 411 P.

The flame retardant additive used in Example 33 had a molecular weight in excess of 10,000 and a softening point range of from about 225 to about 240 degrees centrigrade, 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 10,000 and a softening point range of from about 245 to about 290 degrees centrigrade; it was insoluble in both tetrahydrofuran (at 25 degrees centrigrade) and chloroform (at 25 degrees centrigrade).

Injection molded samples of the polystyrene compositions of these Examples were prepared for testing and evaluated.

The polystyrene composition of Example 33 had a U.L. 94 1/1 6" rating of V-1 (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 1/16" rating of V-1 (6.7 seconds). The Izod impact of the test specimen was 0.86 foot-pounds per inch.

Example 35 In substantial accordance with the procedure described in Example 1, poly(brominated phenylene oxides) were prepared from 2,4,6-tribromophenol; the molecular weight of this composition (as determined by the vapor phase osmometry method described in test ASTM D2503t67) 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 1 6; high impact polystyrene compositions containing 1 5 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 trioxide, and 6 percent (by weight of total composition) of Solprene 411 P were prepared; injection molded samples were prepared for testing.

One sample was subjected to accelerated aging by being exposed to a temperature of 1 50 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 separate pieces of filter paper. The filter paper used was then subjected to spectrometric analysis with the General Electric XRD 5 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 Laboratories of General Motors Corporation as "Research Publication GMR-1 1 28" on or about October of 1 972 and was presented at the Anachems Conference held in Dearborn, Michigan, in October of 1 972.

No surface bromine (in the form of poly[brominated phenylene oxide]) was detected in the control sample.

No surface bromine (in the form of poly[brominated phenylene oxide]) was detected in the sample which had been subjected to a temperature of 1 50 degrees Fahrenheit for 48 hours.

Examples 3641 High impact polystyrene plastic compositions were prepared by incorporating either Noryls (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 TVP1, a high impace polystyrene available from the Cosden Oil and Chemical Company; in the Table accompanying these Examples, the former composition is referred to as "poly(phenylene oxide)" and the latter composition is referred to as "poly(brominated phenylene oxide)".

Two control polystyrene plastic compositions were prepared. The first of these contained only Cosden Polystyrene 825 TVP1 the second contained 6 percent (by weight) of antimony trioxide and 94 percent (by weight) of Cosden Polystyrene 825 TVP1.

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 provided with heat transfer means. The resultant mixtures were heated to a temperature of 205 degrees centrigrade; 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 Hl-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.

The samples so prepared were tested for flammability in accordance with the Underwriters' Laboratory Subject No. 94 test referred to in Example 1 6.

The results obtained in these tests are shown in Table IV. In each case the samples tested contained only Cosden Polystyrene 825 TVP 1 and the specified amount(s) of antimony trioxide and/or poly(phenylene oxide) and/or poly(brominated phenylene oxide). The concentrations of these additives are indicated as a weight-percent, and they were calculated as a function of the combined weights of the polystyrene, antimony trioxide, and phenylene oxide polymers which were used in each Example.

Table IV Percent (by Percent (by Percent (by Percent (by weight) of weight) of weight) of weight) of Cosden Poly- poly(phenylene polyfbrominated antimony Example styrene 825 oxide) in sample phenylene oxide) trioxide in U.L. Rating Number TVP 1 in sample sample in sample sample (1/8" sample) 36 100 0 0 0 HB 37 94 0 0 6 HB 38 70 30 0 0 HB 39 67 30 0 3 HB 40 70 0 30 0 HB 41 82 0 15 3 V-O

Claims

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 brominated phenol selected from the group consisting 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 0 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 aromatic nuclei per unit comprise at least about 80 percent (by weight) of said product.

2. A polystyrene composition as claimed in claim 1, wherein said poly(brominated phenylene oxide) has a number average molecular weight of less than about 100,000.

3. A polystyrene composition as claimed in claim 1 or 2, wherein said enhancing agent is antimony trioxide.

4. A polystyrene composition as claimed in any one of the preceding claims, wherein said composition contains at least about 65 percent (by combined weight) of polystyrene.

5. A polystyrene composition as claimed in any one of the preceding claims, wherein said poly(brominated phenylene oxide) condensation product contains from about 62 to about 66 percent (by weight) of elemental bromine.

6. A polystyrene composition as claimed in any one of the preceding claims, wherein said poly(brominated phenylene oxide) condensation product has a number average molecular weight of less than about 4,500.

7. A polystyrene composition as claimed in claim 6, wherein said poly(brominated phenylene oxide) condensation product has 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.

8. A polystyrene composition as claimed in any one of the preceding claims, wherein said composition contains at least 50 percent (by combined weight) of high impact polystyrene.

9. A flame retardant additive composition comprising at least about 50 percent (by combined weight of poly brominated phenylene oxide and enhancing agent) of the poly(brominated phenylene oxide) defined in claim 1 and enhancing agent.

10. A flame retardant additive composition as claimed in claim 9, wherein said poly(brominated phenylene oxide) has a number average molecular weight of less than 100,000.

11. A flame retardant additive composition as claimed in claim 10, wherein said poly(brominated phenylene oxide) has a number average molecular weight of less than 4500.

12. A flame retardant composition as claimed in claim 11, wherein said poly(brominated phenylene oxide condensation product has a notched Izod impact strength of less than about 0.5 footpounds per inch, an elongation of less than about 2.0 percent, and a tensile strength of less than about 200 pounds per square inch.

13. A flame retardant additive composition as claimed in any one of claims 9 to 11, wherein said poly(brominated phenylene oxide) condensation product contains from about 62 to about 66 per cent (by weight) of elemental chlorine.

14. The flame retardant additive composition as claimed in any one of claims 9 to 13, wherein said enhancing agent is antimony trioxide.

1 5. A flame retarded composition substantially as hereinbefore described in any one of the foregoing Examples.

1 6. A flame retardant composition substantially as hereinbefore described in any one of the foregoing Examples.