GB2025427A

GB2025427A - Flame Retardant Polystyrene Plastic Compositions

Info

Publication number: GB2025427A
Application number: GB7902069A
Authority: GB
Original assignee: Velsicol Chemical LLC
Current assignee: Velsicol Chemical LLC
Priority date: 1978-07-14
Filing date: 1979-01-19
Publication date: 1980-01-23
Also published as: BE877525A; AU4458279A; IT1114725B; FR2435494B1; FR2435494A1; IT7948044A0; AU512088B2; DE2906035A1; NL7811907A; JPS5513772A

Abstract

Disclosed are plastic compositions comprising (i) a styrene polymer; (ii) a bis-phenoxy compound of the formula <IMAGE> wherein alkylene is a straight chain carbon group having 1 to 6 carbon atoms; (iii) a self condensation product of a tri-, tetra-, or pentabromo phenol; and (iv) an enhancing agent e.g. Sb2O3.

Description

SPECIFICATION Flame Retardant Additive Composition and Flame Retardant Polystyrene Plastic Compositions The present invention relates to a polystyrene plastic composition containing a three-component flame retardant system.

U.S. 3,658,634 discloses a conjugate sheath and core fiber comprising a thermoplastic sheath polymer and a thermoplastic core polymer (both of which are disclosed as being either polyester or polyamide). The core polymer contains a two-component fire retardant system i.e., (i) a halogenated aromatic fire retardant of the general formula

wherein X is bromine or chlorine, Y is -R', -OR', andOR"OR' (wherein R' is alkyl, aryl, aralkyl, alkaryl, and halogenated derivatives thereof and R" is an alkylene radical of from 1 to 6 carbon atoms) and n and m are positive integers satisfying the formula 62m2 1, 51nTO; and (ii) an organophosphorus compound. Bisphenoxyalkanes are disclosed as useful flame retardants in this patent.

Japanese patent publication 72/14500 teaches a flame retardant polyester composition comprising polyethylene terephthalate and a compound of the formula

wherein X represents bromine or chlorine, m and n are each integers of 1 to 5, and R represents a halogen-free alkylene, phenylene or R'OR"R"' group where R', R", and R"' are alkyl or phenyl groups.

U.S. 3,383,435 discloses a thermoplastic composition comprising a polyphenylene ether and a styrene resin.

U.S. 3,717,609 discloses a flame retardant polymer comprising propylene and a two-component flame retardant additive which consists of an organo-tin compound and a bromophenyl.

British patent No. 1 ,41 6,585 and German patent publication No. 2328520 disclose polystyrene compositions containing certain bisbromophenoxyalkane flame retardants and, optionally, enhancing agents such as antimony trioxide. While the bisphenoxy compounds disclosed therein are generally excellent flame retardants in polystyrene, they are less desirable when the flame retardant polymer is required to have a relatively high heat distortion temperature. These bisphenoxy compounds generally impart a relatively low heat distortion temperature to the polymeric system.

Other prior art also of interest in connection with this application include U.S. patents 3,71 7,609, 3,403,036, 3,819,761, 3,887,846, 3,883,613, 3,663,654, 3,660,531 and 3,639,506.

Polystyrene and uses therefor are well known in the art; see, e.g., Polystyrene, W. C. Teach and G.

C. Kiseeling (Reinhold Plastics Applications Series, Reinhold Publishing Corporation, New York, 1 Ui and Modern Plastics Encyclopedia 1972-1973, Vol. 49: No. 1 OA, October, 1972, pages 97-99, 161 and 261-272.

The need for flame retarding polystyrenes has also been recognized in the art as is shown by, e.g., U.S. patents 3,347,882 and 3,422,048 and Modern Plastics Encyclopedia, ibid, pages 221 , 222 and 456-458.

The prior art has specifically recognized that polymer systems differ substantially in both flammability characteristics and physical properties and there is no predictability whatsoever from one system to another. Thus, in the Norris et al. paper entitled "Toxicological and Environmental Factors Involved in the Selection of Decabromodiphenyl Oxide as a Fire Retardant Chemical", Applied Polymer Symposium No. 22, 195-219 (1973), the authors state: "a growing recognition of the high annual toll taken by fire is resulting in more stringent flamabiiity requirements for synthetic polymers in a variety of applications.Because of economic constraints and the need to produce flame resistant polymers without total replacement of existing manufacturing processes, increased flame resistance is generally achieved by incorporation of a fire retardant chemical in the finished product. This chemical is usually based on bromine, chlorine, phosphorus, or nitrogen and may either be chemically reacted or physically blended into the product. Since polymer systems differ markedly in both flammability characteristics and physical properties, selection of a suitable flame retardant depends on a variety of factors that severely limits the number of acceptable materials".

"...Some of the most important criteria for an acceptable flame retardant.. are: 1. It must be as effective as possible to minimize both cost and effect on polymer properties. Use levels may range up to 15% by weight.

2. It must have sufficient stability to withstand conditions encountered during polymer processing and use. Processing conditions (blending, extrusion, and molding) often involve temperatures exceeding 3000 C. The flame retardant must tolerate these conditions without degradation or volatilization. Also, attention must be given to hydrolytic stability and oxidative degradation, particularly under extended service at high temperatures.

3. It must be compatible with the base polymer and exert minimal adverse effect on those properties that give the polymer its value. Some of these critical properties are tensile strength, impact strength, heat deflection temperature, shear strength, and flexural modulus.

4. Finally, the flame retardant must not interfere with attainment of desired product esthetics and form".

"Because of the most stringent thermal stability requirements, only a very few compounds have been identified which can meet the necessary performance and economic criteria".

Disadvantages in the utilization of various prior art materials as flame retardants for plastic compositions include, without limitation, factors such as thermal migration, heat instability, light instability, non-biodegradability, toxicity, discoloration, the large amounts required for effectiveness, and the unpredictable end results obtained when using the same material in different plastics. For example, in Modern Plastics Encyclopedia, ibid, page 650, octabromobiphenyl is shown for use in polyolefins as a flame retardant but is not shown for use with the other 27 compositions listed.

The foregoing discussion is particularly applicable to the flame-retarding of polystyrene plastics. It is important that, in addition to retaining good physical characteristics, three properties of the polystyrene be within certain limitations in order to provide a functional product, viz., flame retardancy (as measured, for example, by UL 94), thermal stability (as measured, for example, by certain ASTM tests for decomposition and migration), and heat distortion temperature.

The prior art recognizes that prospective flame retardants must be adjudged on a case by case basis because of the unpredictable results obtained when an additive is incorporated into a polymeric system. For example, in U.S. patent 3,658,634, the patentee teaches (at column 1, lines 26-32), that "...the compounds containing chlorine or bromine atoms to be used as fire retardant agents are generally sublimated and therefore, the fire retardant agents are sublimated and lost in the process for producing fire retardant polymers or in after finishing processes; accordingly, deteriorations of fire retardancy or difficulties in use tend to occur more often than not".

The prior art problem of providing a flame retarded polystyrene composition having the desired chemical, physical and mechanical properties has now been substantially solved by the present invention.

It has now been found that the addition of a certain poly (brominated phenylene oxide), to a polystyrene composition which contains bisphenoxyalkane compound results in a composition which retains all of the excellent physical properties of a composition containing only those bisphenoxy compounds while additionally resulting in a significant improvement in the heat distortion temperature of said composition.

In accordance with this invention, there is provided a flame retardant plastic composition comprising: a polystyrene polymer and a flame retardant amount of a bis phenoxy compound of the formula

& e'3 wherein alkylene is a straight chain carbon group having from one to six carbon atoms; a flame retardant enhancing agent; and a poly(brominated phenylene oxide) condensation product derived from a brominated phenol selected from the group consisting of tribromophenol, tetrabromophenol, and pentabromophenol, wherein: 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 equal 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; 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 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.

The particular class of bis-tribromophenoxy compounds used in the present invention comDositions have the formula:

%O-(aikine)-0 wherein alkylene is a straight chain carbon group having from 1 to 6 carbon atoms, and includes, without limitation, groups such as -CH2-; -(CH2)2-; -(CH2)3-; -(CH2)4-; -(CH2)5-; and it is to be understood that all the compounds falling within formula I above and as heretofore defined are generically described herein as "bis-tribromophenoxy compounds".

Some non-limiting examples of compounds of formula I are 1,1 -bis(2,4,6-tribromophenoxy) methane; 1,2-bis (2,4,6-tribromophenoxy) ethane; 1,3bis (2,4,6-tribromophenoxy) propane; 1,4-bis (2,4,6-tribromophenoxy) butane; 1,5-bis (2,4,6-tribromophenoxy) pentane; 1,6-bis (2,4,6tribromophenoxy) hexane; 1 , 1 -bis (3,4,5-tribromophenoxy) methane; 1,2-bis (3,4,5-tribromophenoxy) ethane; 1,3-bis (2,4,5-tribromophenoxy) propane; 1,3-bis (2,3,4-tribromophenoxy) propane; and 1,1bis (2,3,6-tribromophenoxy) propane.

The bis-tribromophenoxy compounds containing bromine substituents in the 2,4,6 positions are preferred from the standpoint of ease of production.

In general, the bis-tribromophenoxy compounds are prepared by reacting a halogenated phenol with a halogenated alkane at elevated temperatures in the presence of a basic material such as alkali metal hydroxides, carbonates, bicarbonates, oxides and hydrides. The preferred alkali metals are potassium and sodium. Where one desires to increase, for example, ease of handling the reaction mass, solvents such as ketones (e.g., acetone, methyl ethyl ketone, and methyl iso-butyl ketone), alcohols (e.g., methanol, ethanol, iso-propyl alcohol, butyl alcohol and giycols), or aqueous solvents (e.g., water, a mixture of water and alcohol and a mixture of water and ketone) can be employed. The desired end products, i.e., the bis-tribromophenoxy compounds, can be recovered from the reaction mass via various methods known to those skilled in the art.Where the end product requires recovery via crystallization, various aromatic solvents, such as benzene, toluene, xylene, dichlorobenzene and the like, can be used.

Specifically, the bis-tribromophenoxy compounds are prepared according to the following reactions:

cm +XHaIky(eneHX Base Br eBr3 (aikylene) -o of sa(t or the base In the above reaction, X is halogen, preferably bromine.

The above reaction is conducted at temperatures ranging from the freezing point of the initial reaction mass to the boiling point thereof. Preferably the temperatures are from about 400C to about 2000C and more preferably from about 500C to about 1 750C. It is to be understood that the reaction can be conducted under subatmospheric (e.g., 1/10-8/10 atmospheres) pressure. Preferably, the reaction is carried out at atmospheric pressure.

The above described processes can be carried out with conventional, readily available chemical processing equipment. For example, a conventional glass-lined vessel provided with heat transfer means, a reflux condenser and a mechanical stirrer can be advantageously utilized in practicing any of the 1?referred embodiments of the invention described in preparing the bisphenoxy examples set forth herein.

The flame-retarded polystyrene compositions of this invention contain a 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 pius 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 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 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 "III"). The bond may exist at both the ortho and para positions when c is 2 (hereinafter referred to as "IV"); and it may exist ortho, ortho, and para to the carbon-oxygen bond when c is 3 (hereinafter referred to as "V"). The poly(bromophenylene oxide) condensation product contains at least one of the repeating structural units denoted II, III, IV, and V 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 pheylene oxide) compositions described in this specification, four Waters Associates, inc. stainless steel columns packed with Styragel are connected in series; these columns, each of which measured 48" longxO.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. Aflow 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 than about 4500.

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.

It is preferred that the poly(brominated phenylene oxide) product used in the composition of this invention, when fused to form test specimens 0.125" thick, have a notched Izod impact strength of less than about 0.5 foot-pounds per inch of notch (ASTM D256), an elongation of less than about 2.0 percent, and a tensile strength of less than about 200 pounds per square inch (ASTM D638).

The poly(brominated phenylene oxide) product may be prepared by any of several methods well known to those skilled in the art. Generally, the brominated phenol is contacted with an effective amount of activating agent and allowed to condense for a period of up to 48 hours at a temperature of up to about 300 degrees centigrade.Suitable activating agents include, without limitation, heat, light, organic and inorganic perioxides such as benzoyl peroxide, hydrogen peroxide, dimethane sulfonyl peroxide, lauroyl peroxide, caprylyl peroxide, succinic peroxide, acetyl peroxide, p-tertiarybutyl benzoyl peroxide, tertiary-butylperoxy isopropyl carbonate peroxide, hydroxyheptyl peroxide, cyclohexane peroxide, 2,5-dimethylhexane peroxide, di-tertiarybutyl diperphthalate peroxide, tertiary butyl perbenzoate peroxide, and the like; azo compounds, such as azobisisobutyronitrile, for example; persulfates, such as ammonium persulfate, potassium persulfate, and sodium persulfate; hypochlorites; ferricyanides; ferric chloride; copper salts wherein the copper has a valency of one or two such as, e.g.

cuprous-2,4,6-tribromophenate, cupric-2,4,6-tribromophenate, cuprous chloride, cupric chloride, cuprous nitrate, cupric nitrate, cuprous sulfate, cupric sulfate, mixtures of one or more of the aforementioned salts, etc.; metal oxides, such as lead oxide, mercury oxide, silver oxide, and the like; halogen, such as iodine, bromine, and chlorine; lead tetracetate; sodium bismuthate; etc. Generally, any of the activators known to promote free radical chain initiation may be used.

Alternatively, one may use a metal salt of the brominated phenol with the activating agents.

Suitable salts which may be utilized include, without limitation, the lithium, sodium, potassium, barium, zinc, and tin salts of the brominated phenol. Other phenolates well known to those skilled in the art may also be used.

The brominated phenol (or the metallic salt derived from it) may be contacted with the activating agent in the solid state. Alternatively, one may conduct the polymerization of the brominated phenol (or its salt) in a suitable inert solvent. In general, any of the inert aqueous or organic solvents in which phenol or its salt are known to be soluble may be used to prepare the flame retarding condensation product. Suitable solvents include, without limitation, water, dimethylsulfoxide, acetone, hexane, methanol, ethanol, propanol, butanol, benzene, toluene, tetrahydrofuran, etc. Aqueous salt solutions wherein the salt is selected from the group consisting of barium chloride, calcium chloride, magnesium chloride, strontium chloride, potassium chloride, lithium chloride, sodium chloride, and the like may also be utilized.Mixtures of organic solvents and water may be used; thus aqueous acetone solutions, benzene and water, aqueous alkaline solutions and organic compounds insoluble in water (such as octyl alcohol, toluene, and heptane), carbon tetrachioride and water, amyl alcohol and water, and the like are suitable.

One of many methods which may be used to prepare this product involves dissolving a metal hydroxide in water and, to the solution thus formed, adding activating agent and the brominated phenol; thereafter the reaction mixture is maintained at a specified temperature.

In this method, an emulsifying agent may be used to suspend the condensation product in aqueous media; when so used, from about 0.1 to about 5.0 percent of it (by weight of water in the hydroxide solution) should be present in the reaction mixture.

In this method, an alkali or alkaline earth metal hydroxide may be used. It is preferred to use a metal hydroxide selected from the group consisting of sodium hydroxide, potassium hydroxide, and lithium hydroxide; sodium hydoxide is the most preferred. From about 0.5 to about 5.0 moles of the hydroxide per liter of water is utilized. It is preferred to use from about 1 to about 3 moles of hydroxide per liter of water; it is most preferred to use about 2 moles of the hydroxide per liter of water.

The brominated phenol described hereinabove is added to the reaction mixture at a concentration of from about 0.5 to about 5 moles per liter of water to make up the hydroxide solution in this method.

It is preferred to use from about 1 to about 3 moles of phenol per liter of water. It is most preferred that the concentration be about 2 moles of phenol per liter of water.

In this method, although it is not essential, organic solvent may be added to the reaction mixture; any of the organic solvents listed hereinabove may be utilized. When organic solvent is used, it is preferred that from 1 to about 20 percent of it (by volume of water used to make up the hydroxide solution) be utilized. It is more preferred to use from about 3 to about 10 percent of organic solvent in this process; and it is most preferred to use from about 4 to about 8 percent of organic solvent. Some of the preferred organic solvents include toluene, benzene, chloroform, chlorinated benzenes, and the like.

Activating agent is contacted with the reaction mixture after all of the other components are present in this process. When the activating agent is solid, liquid, or gaseous, at least about 1 x10-5 males of it (based upon liters of water used to make up the hydroxide solution) is used; it is preferred to use from about 0.01 to about 0.1 moles of these activating agents.

The third component of the instant flame retardant plastic composition are certain compounds which when used with the bisphenoxy compounds, and the poly(brominated phenylene oxides) promote a cooperative effect therebetween and thus enhance the flame retardancy of the resultant plastic composition. These "enhancing agents" comprise e.g., the oxides and halides of groups IVA and VA of the Periodic Table such as, e.g., the oxides and halides of antimony, bismuth, arsenic, tin, lead and germanium; antimony oxychloride, antimony chloride, antimony oxide, stannic oxide, stannic chloride, arsenous oxide, arsenous chloride, and the like may be used. Organic and inorganic compounds of phosphorus, nitrogen, boron, and sulfur (such as e.g., triphenyl phosphate, ammonium phosphate, zinc borate, thiourea, urea, stannic sulfide, and the like) may also be utilized.Oxides and halides of titanium, vanadium, chrominum, manganese, iron, niobium, molybdenum, copper, zinc, magnesium (such as, e.g., titanium dioxide, titanium chloride, vanadium pentoxide, chromic bromide, manganous oxide, molybdenum, trioxide, ammonium molybdate) may also be utilized. Hydrates of the aforementioned such as, e.g., stannic oxide hydrate, and lead hydrate also are effective. The preferred enhancing agents are the oxides of antimony, arsenic and bismuth. However, any compound which on decomposition, as by ignition, yields these oxides would be suitable. Thus, some organic antimonates are preferred. The enhancing agents disclosed in U.S. 3,205,196 are also suitable for use.

Antimony oxide is the antimony compound that is preferred for use in the present invention.

However, many organic antimony compounds are suitable (such as the antimony salts of organic acids and their pentavalent derivatives disclosed in U.S. patent 2,996,528). Compound of this class include antimony butyrate, antimony valerate, antimony caproate, antimony heptylate, antimony caprylate, antimony pelargonate, antimony caprate, antimony cinnamate, antimony anisate, and their pentavalent dihalide derivatives. Likewise, the esters of antimonous acids and their pentavalent derivatives disclosed is U.S. patent 2,993,924 (such as tris [n-octyl] antimonite, tris [2-ethylhexyl] antimonite, tribenzyl antimonite, tris [2-chloroethyl] antimonite, tris [chloropropyl] antimonite, and tris [2chlorbutyl] antimonite) may be used.

These three components, i.e., the bis-phenoxy compound, the poly (brominated phenylene oxide), and the enhancing agent, when added to polystyrene copolymers, impart flame retardancy thereto. It is to be understood that the term polystyrene are used herein means polymers containing more than 60% styrene (phenylethylene, vinyl benzene, styrol, cinnamene) C6H5CH=CH2 or other unsaturated aromatic monomers comprised of variously substituted styrene derivatives. This term also includes rubber-modified impact-resistant polystyrene (HIPS) and copolymers of styrene such as styreneacrylonitrile (sometimes referred to in the trade as "SA" or "SAN"). Of these, rubber-modified high impact polystyrene is preferred.

It is to be understood that the polystyrene used in the composition of this invention can be a "virgin" material. Alternatively, the polystyrene can have additives already contained therein or added concurrently with or after the addition of the bisphenoxy compounds, poly(brominated phenylene oxides), and enhancing agents.

The bis-phenoxy compounds, poly(brominated phenylene oxides), and enhancing agents can be incorporated into the polystyrene at any processing stage in order to prepare the plastic compositions.

In general, this is undertaken prior to fabrication either by physical blending or during the process of forming polystyrene. Where one so desires, the bis-phenoxy compounds and/or poly (brominated phenylene oxides) and/or enhancing agents may be micronized into finely divided particles prior to incorporation into the polystyrene.

It is also within the scope of the present invention to employ other materials in the present invention compositions where one so desires to achieve a particular end result. Such materials include, without limitation, adhesion promoters, fillers, antioxidants, antistatic agents, antimicrobials, colorants, flame retardants such as those listed on pages 456-458, Modern Plastics Encyclopedia, ibid. (in addition to the new class of flame retardants described herein), heat stabilizers, light stabilizers, pigments, plasticizers, preservatives, ultraviolet stabilizers, fillers and additives, and the like.

Suitable fillers include, e.g., materials such as glass, carbon, cellulosic fillers (wood flour, cork and shell flour), calcium carbonate (chalk, limestone, and precipitated calcium carbonate), metal flakes, metallic oxides (aluminum, beryllium oxide and magnesia), metallic powders (aluminum, bronze, lead, stainless steel and zinc), polymers (comminuted polymers and elastomerplastic blends), silica products diatomaceous earth, novaculite, quartz, sand, tripoli, furned colloidal silica, silica aerogel, wet process silica), silicates (abestos, kaolinite, mica, nepheline syenite, talc, wollastonite, aluminum silicate and calcium silicate), and inorganic compounds such as barium ferrite, barium sulfate, molybdenum disulfide and silicon carbide.

The above mentioned materials, including filler, are more fully described in Modern Plastics Encyclopedia, ibid.

The amount of the above described materials employed in the present invention compositions can be any quantity which will not substantially adversely affect the desired results derived from the present invention compositions. Thus, the amount used can be zero (0) percent, based on the total weight of the composition, up to that percent at which the composition can still be classified as a plastic. In general, such amount will be from about 0%, to about 75% and, preferrably from about 1% to about 50%.

The polystyrene composition of the present invention contains an amount of bis-tribromophenoxy compound and poly(brominated phenylene oxide) and the enhancing agent which will effectively render said composition flame retardant In general, the amount of bis-tribromophenoxy compound plus: poly (brominated phenylene oxide) plus enhancing agent used is from about 2% to about 35% by weight (based on the total weight of the composition). Preferably, the amount employed is from about 5% to about 30% by weight, with an amount of from about 10% to about 20% being more preferred. It is to be understood that any amount can be used as long as it does not adversely effect the chemical and/or physical and/or mechanical properties of the plastic compositions.

The bis-tribromophenoxy compound and the poly (brominated phenylene oxide) are present in a ratio of from about one part by weight of the bis-tribromophenoxy compound to about nine parts by weight of poly (brominated phenylene oxide) to from about nine parts by weight of the bistribromophenoxy compound to about one part by weight of the poly (brominated phenylene oxide). It is preferred to use from about three parts by weight of the bis-tribromophenoxy compound to about one part by weight of the poly(brominated phenylene oxide) to from about one part by weight of the bistribromophenoxy compound to about three parts by weight of poly(brominated phenylene oxide).

Generally, the amount of enhancing agent used (based on the amount of bis-tribromophenoxy compound plus poly brominated phenylene oxide used) is from about one part (by weight) to about one-eighth part (by weight). It is preferred to use from about one-sixth part (by weight) to about onehalf part by weight.

Thus, for example, a typical preferred composition may contain 4% of the bis-tribromophenoxy compound,11 of the poly (brominated phenylene oxide), and 3% of the enhancing agent.

One of the critical features of the polystyrene cómposition of this invention is the unusually high flame retardancy thereof.

The significance of light stability of plastic compositions is recognized in the art; see, e.g., the book entitled "The Measurement of Appearance" by Mr. Richard S. Hunter (Hunter Associates Laboratory, Inc., 9529 Lee Highway, Fairfax, Virginia) 1973, which publication is hereby incorporated by reference.

The polystyrene compositions of the present invention are both flame retardant and nondiscolored, i.e., have a relatively low E value (the higher the E value the greater this discoloration).

Another critical feature of the present plastic composition described herein is the relatively high heat distortion temperature thereof. This feature is important when the plastic compositions are used close to sources of heat, such as when they are formed into television and radio cabinets. This feature is also important in demolding plastic articles of manufacture; when these articles contain polymers with high heat distortion temperatures, they can be removed from the mold at relatively high temperatures without having to cool them prior to demolding and with only a minimal amount of distortion.

Generally, compounds of formula I, when added to polystyrene, even with the aforedescribed enhancing agents, do not result in plastic compositions having the requisite heat distortion temperatures. However, when the aforedescribed poly(brominated phenylene oxides) are added to these compositions, the resultant plastic compositions have the requisite heat distortion temperatures and all of the aforedescribed desirable physical and flame retardant properties.

Another advantage of the present invention is that the fire retardant system, i.e., the bistribromophenoxy compound and poly (brominated phenylene oxide), can be readily compounded into polystyrene, particularly high impact polystyrene, using normally accessible single screw extrusion equipment since the bis-tribromophenoxy compound and the poly (brominated phenylene oxide) are melt blendable. With many other flame retardant systems, i.e., decabromobiphenyl oxide, it is essential to compound the flame retardant into polystyrene, particularly high impact polystyrene, using special, expensive, high intensity mixing equipment such as a twin screw extruder.This is necessitated by the high melting points of some of these prior art flame retardants such as decabromobiphenyl oxide (--3000C). If such equipment is not used, erratic flame retardancy and physical properties can result.

A second embodiment of the present invention is a three-component flame retardant additive composition for flame retarding polystyrene compositions. The additive mixture is comprised of a bistribromophenoxy compound of formula I, a poly(brominated phenylene oxide) described herein, and the aforementioned enhancing agent. Generally, the flame retardant additive composition contains in percent by weight, from about 5% to about 80% of the bis-tribromophenoxy compound, from about 5% to about 80% of the poly(brominated phenylene oxide) and from about 11- to about 50% of the enhancing agent; preferably it contains from about 1 6% to about 65% of the bis-tribromophenoxy compound, from about 16% to about 65% of the poly(brominated phenylene oxide), and rfrom about 14% to about 33% of the enhancing agent.

The flame retardant additive composition can be added to the polystyrene plastic composition either during the production of the polystyrene polymer itself or after the formation of the polystyrene polymer but during the formulation of the plastic composition. Incorporation of the additive composition is achieved by merely adding, with mixing, the additive to the composition containing the styrene monomer (if the additive composition is added during the polystyrene formation step) or the polystyrene-plastic containing composition (if the additive is added after the polymerization process).

The following examples illustrate the claimed invention but are not to be deemed limitative thereof. Unless otherwise specified, all parts are by weight, all temperatures are in degrees centigrade, all weights are in grams, and all volumes are in millimeters.

Examples High impact polystyrene plastic compositions were prepared according to the procedure set forth hereinafter and were subjected to the following tests in order to ascertain comparative properties of the resultant plastic compositions: (1) Flammability (a) Oxygen Index, 0.1.: ASTM Test No. D 2863-70 (b) UL 94: UL 94 procedure described hereinafter (2) Notch Izod Impact: ASTM Test No. D 256-70 (3) Heat Deflection Temperature (HDT): ASTM Test No. D 648-72 (4) Gardner Impact The plastic materials which were subject to the above described tests were prepared in the following manner.With the exception of the "base resin", the particular additive or additives were incorporated into the polystyrene polymer plastic material (Cosden 825 TV-PI, a product of Cosden Oil and Chemical Company) 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 mixture was heated to about 205 or; at this temperature it was in a molten state. Each formulation was discharged from the mixer and, upon cooling, solidified and was ground into chips.The chips were subjected to injection molding in a one (1) ounce Newbury Injection Molder (Model Hl-30 RS, manufactured by Newbury Industries, Inc., Newbury, Ohio) by placing said chips therein and utilizing a 60-second molding cycle with a ram pressure of 2000 psi. The chips contained in said molder were subjected to heat transfer means supplied thereto in order to melt said chips, and the molten plastic was then injected into a mold in order to provide solid samples (after cooling) for testing.

Portions of the molded specimens of each formulation of Example 1 thru 5 prepared according to the above described procedure were subjected to two different flammability tests, i.e., UL 94 and ASTM D 2863-70. The UL 94 test is fully described in Under-Writefs Laboratories bulletin entitled UL 94, Standard for Safety Safety, First Edition, September 1 972. ASTM No. D 2863-70 describes a flammability test which correlates ease of extinction of a plastic specimen to the avilable oxygen in its immediate environment; this correlation is stated as an Oxygen Index, ("0.1.") level which is predicated upon the percent of oxygen (by volume) in the gaseous medium which is required to just provide a steady state of continuous burning of the plastic specimen.This ASTM method is fully described in 1 971 Annual Book of ASTM Standards-Part 27 (published by the American Society for Testing and Materials, 1916 Race Street, Philadelphia, PA.).

Table I shows that the polystyrene/Sb203/bis-phenoxy compound/poly (dibromophenylene oxide) combination has excellent flame retardant properties, good heat deflection temperatures, and acceptable impact strength.

In examples 6 thru 8, molded specimens prepared substantially in accordance with the above described procedure were subjected to a color determination test (the Gardner Colorimeter Test) to determine discoloration. In the Gardner Colorimeter Test, a Gardner XL10-CDM colorimeter was used to measure the color development. The surface of each test specimen was measured prior to and following exposure to U.V. light. A couple of samples from each molding run were tested and results reported as an average of the two. Example 8 is a comparative example employing the prior art flame retardant decabromobiphenyl oxide. This well known flame retardant requires special equipment to be satisfactorily processed.By comparing the light stability results in Table II, is becomes apparent that the composition of Example 8 is visually unacceptable and was materially altered after only 25 hours of exposure.

The plastic compositions which incorporate the four-component polystyrene/enhancing agent/bis-phenoxy compound/poly (brominated phenlyene oxide) system possess characteristics which have been heretofor unobtainable in the prior art, i.e., good flame retardancy, good heat distortion temperature, and acceptable physical properties.

Table I I Example Base Resin 2 3 4 5 Additive 1 ,2-bis(2,4,6-tribromophenoxy) ethane Ot" 1 5 3.75 6 9 poly(dibromophenylene oxide) 0 0 11.25 9 6 Sb203 0 3 3 3 3 Flammability and Physical Property Data Izod Impact,ft-lb/in. (0.10" notch) 2.76 2.20 2.16 2.12 2.09 UL 94 Class, 1/8" thickness HB V-O V-O V-O V-O Heat Deflection Temperature, (Annealedi hr. at 1700F) OF at 264 psi 193 157 187 182 172 Oxygen Index % at 730F 18.0 24.0 23.5 23.5 24.0 Gardner Impact, in-lb. 110 115 50 50 60 (1) Percent by weight of Total composition Table II 6 8 Example Base Resin 7 Comparative Additive 1,2-bis(2,4,6-tribromophenoxy) ethane 0(1) 3.75 0 poly (dibromophenyiene oxide) 0 11.25 0 Sb2O3 0 3.0 2.4 Decabromobiphenyl oxide 0 0 12 Physical Data E Color Value Hours(2) 25 1.9 8.2 32.3 50 4.4 11.0 34.8 75 5.7 12.7 36.1 100 6.2 13.8 36.0 200 9.2 15.8 47.2 300 12 16.6 46.5 500 18 18.9 49.1 (1) Percent by weight of total composition (2) Exposure to UV light (Xenon Arc) The above examples have been described in the foregoing specification for the purpose of illustration and not limitation. Many other modifications and ramifications will naturally suggest themselves to those skilled in the art based on this disclosure. These are intended to be comprehended as within the scope of this invention.

Claims

1. A flame retardant additive composition for polystyrene plastic compositions comprising (i) a bis-phenoxy compound of the formula

Br3 ẏo -(aiAy(ene)-O wherein alkylene is a straight chain carbon group having from one to six carbon atoms; (ii) a flame retardant enhancing agent; and (iii) a poly(brominated phenylene oxide) condensation product derived from a brominated phenol selected from the group consisting of tribromophenol, tetrabromophenol and pentabromophenol, wherein: 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 equal 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; said condensation product containing 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 said condensation product has a molecular weight of at least about 750, and one or more polymer units containing at least for aromatic nuclei per unit comprise at least about 80 percent (by weight) of said product.

2. A composition as claimed in claim 1, wherein from about one-ninth to about nine parts (by weight) of said bis-phenoxy compound per part of said poly(brominated phenylene oxide) condensation product are contained in said flame retardant additive system.

3. A composition as claimed in claim 1 or 2, wherein said enhancing agent is selected from the group consisting of oxides and halides of Groups IV-A and V-A of the Periodic Table of Elements.

4. A composition as claimed in claim 3, wherein said enhancing agent is antimony trioxide.

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

6. A flame retardant plastics composition comprising polystyrene polymer and a flame retardant amount of a flame retardant additive system as claimed in any one of claims 1 to 5.

7. A composition as claimed in claim 6, wherein from about 2 to about 35 percent (by weight of said polystyrene, bis-phenoxy compound, enhancing agent, and poly brominated phenylene oxide) of the flame retardant additive system comprises said plastic composition.

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

9. A method of rendering polystyrene flame retardant which comprises adding to the polystyrene either during, or subsequent to production thereof a flame retardant amount of a composition as claimed in any one of claims 1 to 5.

10. A method as claimed in claim 9, substantially as hereinbefore described in any one of the foregoing Examples. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~