EP0734412A1

EP0734412A1 - Flame retardant styrenic polymer compositions

Info

Publication number: EP0734412A1
Application number: EP95904228A
Authority: EP
Inventors: Claude T. E. Van Nuffel; Rik G. Vaneeckhoutte
Original assignee: Dow Chemical Co
Current assignee: Dow Chemical Co
Priority date: 1993-12-14
Filing date: 1994-11-28
Publication date: 1996-10-02
Also published as: AU1300395A; CA2178211A1; BR9408200A; WO1995016736A1; CO4440436A1; GB9325575D0; MY131694A

Abstract

The present invention relates to a styrenic polymer composition having a polymeric component and a flame retardant component, wherein the polymeric component is substantially oxygen-free, and wherein the flame retardant component is substantially halogen-free and comprises from 2 to 10 percent by weight (based on the composition) of triphenylphosphate (TPP), and optionally, one or more of flame retardant additives such as red phosphorus (P), ammonium polyphosphate (APP), melaminephosphate (MP), melaminecyanurate (MC), melaminepyrophosphate (MPP), resorcinol bis(diphenylphosphate) (RDP), magnesium hydroxide (MG), and a thermoplastic rubber (TPR). The resulting compositions are capable of attaining a 94-UL 'V-2' flammability rating and of passing the requirements of IEC-65 while still retaining acceptable physical properties.

Description

^:LAM E RETARDAN^X STYREN IC POLYMER COMPOSIT ONS ^τnιs invention relates to stvrenic polymer comoositions, tnat is compositions comprising polymers of styrene and optionally one or more comonomers In particular it relates to polystyrene compositions, including so called ' hign impact polystyrene (HIPS), containing various polymeric additives such as rubbers to improve mechanical properties, and acryionitπle/ butadiene/styrene (ABS)-tvpe compositions Styrenic resins are widely used for many purposes, because of their excellent mechanical properties, and ease of processing For example, rubber-reinforced styrenic polymers, such as high impact polystyrene (HIPS), are commonly used to produce molded consumer goods, for example in the production of certain parts of television cabinets ABS is commonly used in the production of parts requiring higher toughness and chemical resistance

One disadvantage of styrenic resins is their relatively high flammability, which limits their use in certain applications

Many attempts have been made to improve the flammability properties of polystyrene, oy the aααition of various tire ^retarαant additives Most fire retardant additives which have oeen used his'oπcally contain halogens, for example, hexadromoDenzene Although such additives can improve significantly the flame retardancy of polystyrene, they suffer trom the disadvantage that they can give rise to the production oτ undesirable combustion products Significant effort has therefore been expended in recent years to developing fire retardant additives for polystyrene which are free from halogens

Examples of fire retardant additives which have been employed are red phosphorus, polyphosphates such as ammonium polyphosphate, melaminephosphate, and various inorganic compounds such as magnesium hydroxide Red phosphorus-containing compositions are disclosed, for example, in U S Patent 3,546, 160

Triphenylphosphate (TPP) has been known for many years as a flame retardant additive for polymer compositions of various kinds Among numerous examples are U S Patent 4,526,917, U S Patent 4,684,682, and U S Patent 5,206,276 However, the use of TPP as a flame retardant additive has hitherto been understood to depend either upon the presence of oxygen in the polymer chain, or else the simultaneous use of halogen-

-contaming flame retardant additives The " International Plastics Flammabilitv Handbook" (Second Edition, Jurgen Troitzsch, Carl Hanserverlag, 1990, pp 47 to 49) puts ^forward a mechanistic explanation for the requirement either for oxygen in tne polyme^r molecule or the simultaneous presence of a halogen-containing flame retardant For this reason, TPP has rarely been used in preparation of styrenic-type polymer compositions, although it has been much more widely used in oxygen- -containing polymers, such as polycarbonates and poiyethers (see, ^tor example, U S Patent 4,526,917 and U S Patent 4,684,682) As inαicated aoove, a l imiteα numoer of proposals have Deen maαe to use TPP as a flame retarαant in styrenic compositions In ail of tnese (for example in U .S. Patent 3,879,345 and U.S Patent 4, 172,858), a nalogen-containing flame retardant additive is also believed to be essential. For example, in U S. Patent 3,879,345, an equimolar amount of tetrabromobisphenol-A is required to be used with tncresol and/or triphenyl phosphate. TPP has also been proposed as a plasticizer for polystyrene, for example in U.S. Patent 2,493,965. The amount of TPP required for such a purpose however is very large (between 20 and 50 percent), and no mention is made of any flame retardant effect of TPP.

Conventional fire retardant additives for polystyrene have various disadvantages associated with them Usually they have a deleterious effect on the physical properties of the polymer, for example in terms of impact strength or gloss, or else they affect adversely the ease with which the material can be processed. Certain fire retardant additives also increase significantly the cost of the molded product, or can limit the maximum temperature at which the product can be processed. There exists a need therefore for flame retardant additives for styrenic resins which do not have unacceptable effects on the physical properties of the resin, and do not rely on the presence of halogen-containing flame retardant additives.

In accordance with the present invention, there is provided a styrenic polymer composition, having a polymeric component and flame retardant component, wherein the polymeric component is substantially oxygen-

-free, and wherein the flame retardant component is substantially halogen-free and comprises from 2 to 10 percent by weight (based on the composition) of triphenyl phosphate (TPP), and, optionally, one or more of flame retardant additives (a) to (h) a. red phosphorus (P); b. ammonium polyphosphate (APP); c. meiaminephosphate (MP); d. melaminecyanurate (MC); e. melamιnepyrophosphate (MPP); f. resorcinol bis(diphenylphosphate) (RDP); g. magnesium hydroxide (MG); h. a thermoplastic rubber (TPR) wherein the concentration expressed as weight percent of the total composition of flame retardant additives satisfy the following conditions:

I) P < 6, APP < 15, MP ≤ 10, MC < 10, MPP ≤ 10, RDP < 10, MG < 20, TPR ≤ 10

II) 6 < [2xP + 0.5xAPP + 0.7xMP + 0.9xTPP + 0.5xMPP + 0.4xRDP +

0.3xMG] < 20

III) P + TPP ≥ 5 IV) ~PR > [0.3xP + 0.25xAPP ->- 0.25xMP ->- 0 40xMC + 0.25xMPP + 0 1 5xRDP

- 0.5xMG j Appropriate selection of the fire retardant additives within the ranges specified aoove can provide a resin material with acceptable physical properties (in particular, impact strength, stiffness, and heat distortion temperature), while also providing acceptable levels of flame retardancy.

The preferred amounts of the fire retardant (FR) additives to be employed depend upon the specific FR agents which are used. In general terms, the preferred amount of TPP employed is in the range of from 7 to 9 percent. When the FR agents TPP, P, and TPR, are employed (the others being absent), the preferred ranges (as percent by weight of the composition) are as follows: TPP: 2.5 - 5 P: 3 - 6 TPR: 1 - 4

When the FR agents TPP, P, TPR, and APP are employed (the others being absent), the preferred ranges (as percent by weight of the composition) are as follows: TPP: 2.5 - 5 ?: 2.5 - 5 TPR: 3 - 7

APP: 5 - 12

When the FR agents employed are TPP, P, TPR, and MP, the preferred amounts of FR agents are.

TPP: 2.5 - 5 P: 2.5 - 5 TPR: 2 - 6 MP : 3 - 8

When the compositions contain just the FR agents TPP, P, TPR, and MPP (the others being absent), the preferred amounts are:

TPP: 2.5 - 5 P: 2.5 - 5 TPR: 2 - 7

MPP: 4 - 10 The styrenic polymers of the present invention are prepared from one or more monoalkenyl aromatic compounds. Representative monoalkenyl aromatic compounds include styrene, alkyl substituted styrenes such as alpha-alkyl-styrenes (for example, alpha-methyl- -styrene and alpha-ethyl-styrene) and ring substituted styrenes (for example, o-ethyl-styrere, 2,4-dimethyl-styrene, and vinyltoluene, particularly, p-vinyl-toluene); vinyl anthracene; and mixtures thereof. In general, the polymer matrix preferably utilizes styrene and/or aipha-methyl-styrene as the monoalkenyl aromatic monomer, with styrene being the most preferred monoalkenyl aromatic compound. In addition to the monoalkenyl aromatic monomer, one or more additional comonomers, _ preferably in an amount of up to 40 percent by weight of the polymeπzable monomer mixture optionally nay be employed. Suitable comonomers include, for example, unsaturated nitπles, for example acrylonitπle. The styrenic polymer is the maior component of the composition of the invention. ~ne stvrenic polymer empioyeα ODτionailv can DΘ ruDber-moαiTied Diene- coπtaining ruobery poivmers are preTerreα as the ruooer ^_ne αiere-containing ru obe^ry polymer preterably employed is a rubbery polymer having at least one diene-containmg block Preferaply, said poiymer is a homoooiymer or copoiymer or an alkaoiene Advantageously, the ^rubber is a homopolymer of a

1 ,3-conjugated diene such as butadiene, isoprene, piperylene and chloroprene and the like, or a copoiymer, such as, for example, a block copoiymer, of said conjugated dienes with one or more compounds such as, for example, the monoalkenyl aromatic compounds, such as styrene, alpha, beta-ethylenically unsaturated nitπles such as acrylonitπie, alpha-olefms such as ethylene and propylene The diene-containmg rubbery polymer is advantageously employed in amounts such that the rubber-reinforced polymer product contains from about 5 to about 25 percent, preferably from about 6 to about 20 percent, more preferably from about 7 to about 16 weight percent rubber (expressed as rubber or rubber equivalent)

Mixtures of rubbery polymers can be employed For example, mixtures of rubbery polymers prepared by emulsion ana mass polymerization processes can oe employed The preparation of ABS using such mixtures is disclosed in U S Patent 4,713,420 These emulsion/mass mixtures are preferred for use in the preparation of ABS

The thermoplastic rubber which is preferably employed can oe a thermoplastic elastomeπc olock copoiymer compatible with the styrenic polymer Thermoplastic elastomeπc block copolymers are well known, and several are commercially available Additionally, the general type and preparation of some of these block copolymers are described in U S Patent Re 28,246, and in many other patents

Although the diene-containmg rubbery polymer may contain a small amount of a crosslinking agent, excessive crosslinking can result in loss of the rubbery characteristics and/or render the rubber insoluble in the monomer The rubber preferably employed in the preparation of the disperse rubber particles exhibits a second order glass transition temperature not higher than about 0°C and preferably not higher than aoout -20°C

The styrenic polymer component of the present invention can be selected from a wide variety of compositions comprising a styrenic polymer and, optionally, rubber These materials are commercially available and their composition is well known to those skilled in the art The methods for preparing styrenic polymers are well known to those skilled i n the art and include, for example, emulsion, suspension, mass, and mass-susoension polymerization methods A mass type polymerization is preferred when preparing polystyrene, HIPS or SAN The techniques of mass polymerization, and the conditions needed for producing desired average rubber particle sizes are well known to those skilled in the art In general, continuous methods are preferred for mass polymerizing the monoalkenyl aromatic compound in the reaction mixture It is generally preferred to utilize a stratified, linear flow, stirreo tower-type reactor, also referred to as a plug flow-type reactor wnen preparing polystyrene or HIPS Such reactors are well known See τor example U S Patent 2 727 884 Such a process may or may not comprise recircui ation ot a portion oτ the partially poivmeπzeα oroαuct

A suitable initiator may be employed in the preparation of the styrenic polymer Representative or such initiators include the peroxide initiators such as the peresters, for example, tertiary butyl peroxybenzoate and tertiary butyl peroxyacetate, αibenzoyi peroxide, dilauroyl peroxide, 1 , 1 -bis tertiary butyl peroxycyclohexane, 1-3-bιs tertiary butyl peroxy- -3,3,5-tπmethyl cyclohexane, dicumyl peroxide and photochemical initiation techniques Preferred initiators include dibenzoyl peroxide, tertiary butyl peroxy benzoate, 1 , 1 -bis tertiary butyl peroxy cyclohexane and tertiary butyl peroxy acetate As is known in the art, initiators o may be employed in a range of concentrations dependent on a variety of factors including the specific initiator employed, the desired levels of polymer grafting when rubber is employed, and the conditions at which the mass polymerization is conducted Specifically, in the preferred mass polymerization process for preparing rubber-reinforced polymers, from 50 to 2000, preferably from 100 to 1500, weight parts of the initiator are employed per million 5 weignt parts of monomer

In addition to the monomer, rubber and initiator, the mass polymerization mixture preferably contains a reaction diluent Reaction diluents advantageously employed include normally liquid organic materials which form a solution with the rubber reinforcing polymer, the polymerizable monomers and the polymer prepared therefrom Examples of such 0 organic liquid diluents include aromatic and substituted aromatic hydrocarbons such as benzene, ethyl benzene, toluene and xylene, saturated, substituted or unsubstituted, straight or branched, aliphatics having 5 or more carbon atoms, such as heptane, hexane or octane, and a cyclic or substituted ahcyclic hydrocarbons having 5 or 6 carbon atoms such as cyclohexane and the like Preferred organic liquid diluents employed herein are the substituted aromatics, 5 with ethylbenzene and xylene being most preferred If employed, the reaction diluent is generally employed in an amount up to about 25 weight percent, preferably from 2 to 25 weight percent, based on the total weight of rubber, monomer and diluent

As is conventional, the polymerization mixture used in preparing the styrenic polymer may also contain other materials such as one or more flow promoters, catalysts, lubricants, plasticizers or antioxidants

The temperatures at which mass polymerization is most advantageously conducted are dependent on the specific components, particularly the initiator, employed, but will generally vary from about 60°C to about 190°C

Tne polymer composition of the present invention can include commonly 5 employed additives such as, for example, fillers, pigments, stabilizers, lubricants and mold release agents Examples of common additives include, carbon black, polyethylene wax, glass fibers, . ass beads, talc, Tι0₂, phenolic antioxidants and mineral oil Additionally, the ruobery ooiymers of the invention may oe on exτendeα These aααitives are employed in amounts .vnicn are well Known to those sκn leα in the an

The polymer composition of the invention may oe prepared by batch or conti nuous olending of the individual components, with or without using a masteroatch, according to methods well known to those skil led in the art For example, the blending can be accomplished by extrusion.

A number of preferred embodiments of the invention are described in the following Examples. In the examples which follow, physical properties are measured in accordance with the following methods Melt Flow Rate (MFR)

Measured by Test Method ASTM D 1238 (200°C and a load of 5 kg). Vicat Heat Distortion Temperature (Vicat)

Measured in accordance with ASTM D1525B at a heating rate of 120°C/hour and a load of 1 kg. Notched Izod (Izod)

Measured in accordance with ASTM D256 Tensile Yield (TSY)

Measured in accordance with ASTM D638M.

For general use as components of electrical equipment, it is desirable for the above quantities to have the following values:

MFR > 5 g/10 mιn

Vicat > 75°C

Izod > 60 J/m

TSY ≥ 15 MPa The following are the additional fire retardant additives employed in the examples which follow.

Material Trade Mark (manufacturer)

APP: ammoniumpolyphosphate HOSTAFLAM AP422 (Hoechst) MP : melammephosphate AMGARD N H (Albright & Wilson) MPP: melaminepyrophosphate (Chemie Linz)

P : red phosphorus HOSTAFL.AM RP602 (Hoechst)

TPP: triphenylphosphate REOMOL TPP (FMC Corp)

TPR: thermoplastic rubber VECTOR 8508D (Dexco) RDP: resorcinol bιs(di- ohenyl phosphate) FYROLFLEX RDP (Akzo)

MG : Magnesium Hydroxide SECUROC B8S1 1.0 (Incemiπ)

EXAMPLES

Comparative Example 1 A hign impact polystyrene was oreoareα usi ng 8.5 weignt percent oτ low cis poiyDutaαiene Rubber 1 HX528 proαuceα by Bayer; in a mass ooiymeπzation process

Checking conditions I to III, it is seen that oniy conαition II I is fulfilleα

The HIPS material was injection moided into test bars for evaluation of physical properties and flammability. Injection molding was done on an Engel ES 330/80 injection molding machine. The processing conditions used were:

Barrel temperature: 250°C

Mold temperature : 45°C

Injection speed : 50 mm/sec Physical properties were tested according to the ASTM methods mentioned.

Flammability was determined according to IEC-65 and UL-94 V-2 on specimens naving a thickness of 2.0 mm. Prior to testing, samples were conditioned at 50 percent relative humidity at 23°C for 48 hours.

This HIPS resin has the following properties: M FR 4.5 g/10 mιn

Vicat : 105°C

Izod 1 15 J/m

TSY 23 MPa

IEC-65. 49 mm/mιn UL-94 : No rating

(To pass IEC-65, the flame propagation rate has to be below 40 mm/minute)

The HIPS resin therefore does not pass the flammability ratings.

Example 1

The HIPS resin from Comparative Example 1 was melt blended with the following additives:

HIPS : 85 weight percent

P : 5 weight percent

TPR : 5 weight percent

TPP . 5 weight percent on a Buss Ko-Kneader model MDK E 46B, having an L D of 1 1 and a screw diameter of 46 mm, at a speed of 220 rpm, with the following zone temperatures: Z1 200°C, Z2 190°C, die 200°C. The discharge extruder was used at 400 rpm. Vacuum was applied and the througnout was 15 kg/hr.

Substituting the additive levels into conditions I to IV reveals that all 4 conditions are satisfied.

(11) 6 < [Px2 + TPPxO.9] + [5x2 + 5x0.9] = 14.5 < 20

(lll) [P + TPP] = [5 + 5] = 10 > 5

(IV) TPR = 5 ≥ [Px0.30 + TPPxO.00] = [5x0.30 + 0] = 1.5 The material was evai uateα according to tne test proceαures as αescπoeα for Comparative Exampl e ' ana nas tne ^τoι l owιng prooerτi es MFR 13 0 g/10 mιn

Vicat : 89.5³C Izod 104 J/m

TSY 18 MPa

IEC-65: 31 mm/mm U L-94 : V-2 All reαuirements on flammability and physical properties are met. Example 2

An IR-HIPS resin was prepared according to the procedure as descri bed for

Example 1 and having the following composition: HIPS : 87.5 weight percent P : 5 weight percent TPR . 5 weight percent

TPP : 2.5 weignt percent

Substituti ng the additive levels into conditions I to IV reveals that all 4 conditions are satisfied.

(I I) 6 < [Px2 + TPPx0.9] + [5x2 + 2 5x0.9] = 12.25 < 20 O'D -P ⁺ TPP] = [5 ^■-^■ 2.5] = 7 5 > 5

(IV) TPR = 5 > [Px0.30] = [5x0.30] = 1.5

The material was evaluated according to the test procedures as described for Comparative Example 1 and has the following properties: MFR : 10.6 g/10 mιn Vicat : 97°C

Izod 98 J/m

TSY 18 MPa

IEC-65: 36 mm/mm U L-94 : V-2 All requirements on flammability and physical properties are met.

Example 3

An IR-HIPS resin was prepared according to the procedure as described for Example 1 and having the following composition: HIPS : 82.5 weignt percent P : 5 weight percent

MP : 5 weight percent TPR . 5 weight percent TPP : 2.5 weight percent Substituting the aαditive levels into conditions I to IV reveals that all 4 conditions are satisfied

(II) 6 < [Px2 + MPx0.7 + TPPx0.9] = [5x2 + 5x0.7 + 2.5x0 9] = 15.75 < 20

(II I) [P + TPP] = [5 + 2.5] = 7.5 > 5

(IV) TPR = 5 > [Px0.30 + MPx0.25] = [5x0.30 + 5x0.25] = 2.75

The material was evaluated according to the test procedures as descπoed for Comparative Example 1 and has the following properties:

MFR : 6.0 g/10 mιn

Vicat : 93°C

Izod 75 J/m

TSY 17 MPa

IEC-65: 27 mm/mm

U L-94 : V-2 All requirements on flammaDility and physical properties are met. Example 4

An IR-HIPS resin was prepared according to the procedure as descπbed for

Example 1 and having the following composition: HIPS : 78.5 weight percent P : 5 weight percent MP : 7.5 weight percent

TPP : 3 weight percent TPR : 6 weight percent

Substituting the additive levels into conditions I to IV reveals that all 4 conditions are satisfied. (ID 6 < [Px2 + MPPxO.5 + TPPx0.9] = [5x2 + 7.5x0.5 + 3x0.9] = 16.45 < 20

(III) [P + TPP] = [5 + 3] = 8 > 5

(IV) TPR = 6 > [Px0.30 + MPPx0.25] = [5x0.30 + 7.5x0.25] = 3.38

The material was evaluated according to the test procedures as described for Comparative Example 1 and has the following properties: MFR : 5.5 g/10 mιn

Vicat : 86°C Izod 70 J/m

TSY 17 MPa

IEC-65: 30 mm/min U L-94 : V-2

All requirements on flammability and physical properties are met. Example 5 An IR-HIPS resin was orepareα accorαi πg to the proceαure as αescπped for Example i ana having tne followi ng corriDOSition HIPS : 76.5 weight percent P : 5 weight percent APP : 10 weight percent

TPP : 2.5 weight percent TPR : 6 weight percent

(II) 6 < [Px2 + APPx0.5 + TPPx0.9] = [5x2 + 10x0.5 + 2.5x0.9] = 17.25 < 20

(III) [P + TPP] = [5 + 2.5] = 7.5 > 5

(IV) TPR = 6 > [Px0.30 + APPx0.25] = [5x0.30 + 10x0.25] = 4

The material was evaluated accorαing to the test procedures as described for Comparative Example 1 and has the following properties. MFR : 5.5 g/10 mιn Vicat : 92°C Izod 65 J/m

TSY 18 MPa IEC-65: 25 mm/mm

UL-94 : V-2 All requirements on flammability and physical properties are met. Comparative Example 2

An IR-HIPS resin was prepared according to the procedure as described for Example 1 and having the following composition: HIPS : 95 weight percent P : 5 weight percent

This composition is not in accordance with the invention, as there is no TPP present. Furthermore, condition IV is also not satisfied.

(II) 6 < [Px2] = [5x2] = 10 < 20

(III) [P + TPP] = [5 + 0] = 5 > 5

(IV) TPR = 0 ≥ [Px0.30] = [5x0.30] = 1.5 NOT fulfilled The material was evaiuateα according to the test procedures as described for

Comparative Example 1 and has the following properties: MFR . 4.3 g/10 mιn Vicat : 105°C

TSY 22 MPa

IEC-65: 37 mm/mιn U L-94 : V-2 All requirements on flammability are met, but the Izod Impact and the MFR are unsatisfactory. Comparative Example 3

An IR-HIPS resin was prepared according to the procedure as descri bed for Example 1 and having the following composition: HIPS : 95 weight percent

TPP : 5 weight percent This composition does not satisfy condition II. (II) 6 < [TPPx0.9] = [5x0.9] = 4.25 < 20

NOT fulfilled (III) [P + TPP] = [0 + 5] = 5 ≥ 5

(IV) TPR = 0 > [TPPxO.OO] = [5x0.00] = 0

The material was evaluated according to the test procedures as described for Comparative Example 1 and has the following properties: MFR : 1 1.9 g/10 mιn Vicat : 93.5°C

Izod 1 10 J/m

TSY 20 MPa

IEC-65: 45 mm/mm UL-94 : NO RATING Physical properties are satisfactory, but flammability ratings are unsatisfactory

Comparative Example 4

An IR-HIPS resin was prepared according to the procedure as described for Example 1 and having the following composition: HIPS : 85 weight percent TPP : 15 weight percent

Substituting the additive levels into conditions I to IV reveals that conditions It to IV are fulfilled, but the amount of TPP is greater than the requisite 10 weight percent upper TPP content limit.

(II) 6 < [TPPxO.9] = [15x0.9] = 13.5 < 20 (I II) [P + TPP] = [0 + 15] = 15 > 5

(IV) TPR = 0 > [TPPxO.OO] = [15x0.00] = 0

The material was evaluated according to the test procedures as described for Comparative Example 1 and has the following properties: MFR 50 3 g/10 mιn

Jicax ^• 66^"C Izod 103 J/m

TSY 13.5 IEC-65: 34 mm/mm

U L-94 : V-2 All requirements on flammability are met, but the Vicat Heat Distortion Temperature and Tensile Yield (Stiffness) are unsatisfactory. Example 6 An IR-HIPS resin was prepared according to the procedure as described for

Example 1 and having the following composition: P : 5 weight percent TPP : 2 weight percent TPR : 6 weight percent RDP : 5 weignt percent

HIPS : 82 weignt percent

The material was evaluated according to the test procedures as described for Comparative Example 1 and has the following properties:

MFR : 1 1 g/10 mιn

Vicat : 88°C Izod 73 J/m

TSY 17 MPa IEC-65: 25 mm/miπ

UL-94 : V-2 All requirements on flammability and physical properties are met. Example 7

An IR-HIPS resin was prepared according to the procedure as described for Example 1 and having the following composition: MG : 10 weight percent P : 5 weight percent TPP : 5 weignt percent TPR : 7 weight percent HIPS: 73 weight percent

Substituting the additive levels into conditions I to IV reveals that all 4 conditions are satisfied. The material was evaluated according to tne test procedures as αescπσed for Comparative Example 1 and nas the following prooerties. MFR : 9g/10mιn Vicat: 88°C Izod 75J/m

TSY 16 MPa

IEC-65: 28 mm/mm UL-94: V-2 All requirements on flammability and physical properties are met.

Claims

WHAT IS CLAIMED IS:

I A styrenic polymer composition, naving a ooiymeπc component ana flame retardant component, wherein the polymeric component is substantially oxygen- -free, and wherein the flame retardant component is substantially halogen-free and comprises from 2 to 10 percent by weight (based on the comppsition) of triphenylphosphate (TPP), and, optionally, one or more of flame retardant additives (a) to (h)

(a) red phosphorus (P);

(b) ammonium polyphospnate (APP);

(c) melaminephosphate (MP); (d) meiaminecyanurate (MC);

(e) melaminepyropnosphate (MPP);

(f) resorcmol bis(diphenylphosphate) (RDP);

(g) magnesium hydroxide (MG); (h) a thermoplastic rubber (TPR) wherein the concentration expressed as weight percent of the total composition of flame retardant additives satisfy the following conditions:

I) P ≤ 6, APP < 15, MP < 10, MC < 10, MPP ≤ 10, RDP < 10, MG ≤ 20, TPR ≤ 10

II) 6 ≤ [2xP + O.SxAPP + 0.7xMP + 0.9xTPP + 0.5xMPP + 0 4 RDP + 0.3 MG] < 20

III) P + TPP ≥ 5

IV) TPR ≥ [0.3xP + 0.25xAPP + 0.25xMP + 0.40xMC + 0.25xMPP + 0.15xRDP + 0.5 MG]

2. A composition as claimed in Claim 1 , wherein the amount of TPP present is from 7 to 9 percent by weight of the composition.

3. A composition as claimed in Claim 1 , wherein the amounts of flame retardant additives present are as follows:

TPP: 2.5-6; P: 3-6; TPR: 1-4 the remaining additives (a) to (h) being absent.

4. A composition as claimed in Claim 1 , wherein the amounts of flame retardant additives present are as follows:

TPP: 2.5-5; P: 2.5-5; TPR: 3-7; APP: 5- 12 the remaining additives (a) to (h) being aDsent.

5. A composition as claimed in Claim 1 , wherein the amounts of flame retardant additives present are as follows:

TPP: 2.5-5; P: 2.5-5; TPR: 2-6; MP: 3-8 the remaining additives (a) to (h) being absent.

6 A composition as claimed in Claim 1 , wherein the amounts of flame retardant additives present are as follows:

TPP: 2.5-5; P: 2.5-5, TPR: 2-7; MPP: 4-10 the remaining additives (a) to (h) being absent.

7. The use of triphenylphosphate as a flame retardant additive in a styrenic polymer composition, wherein the composition has a polymeric component and flame retardant component, wherein the polymeric component is substantially oxygen-free, and wherein the flame retardant component is substantially halogen-free and comprises from 2 to 10 percent by weight (based on the composition) of triphenylphosphate (TPP), wherein the flame retardant component optionally further comprises one or more of flame retardant additives (a) to (h)

(a) red phosphorus (P);

(b) ammonium polyphosphate (APP);

(c) melaminephosphate (MP); (d) meiaminecyanurate (MC);

(e) melamιnepyrophosphate (MPP);

(f) resorcinol bis(diphenylphosphate) (RDP);

(g) magnesium hydroxide (MG); (h) a thermoplastic rubber (TPR) and wherein the concentration expressed as weight percent of the total composition of flame retardant additives (a) to (h), if present, satisfy the following conditions:

I) P < 6, APP < 15, MP ≤ 10, MC < 10, MPP < 10, RDP < 10, MG < 20, TPR < 10

II) 6 < [2xP + 0.5xAPP + 0.7xMP + 0.9xTPP + 0.5xMPP + 0.4 RDP + 0.3 MG] < 20 lll) P + TPP ≥ 5

IV) TPR > [0.3xP + 0.25xAPP + 0.25xMP + 0.40xMC + 0.25xMPP + 0.15xRDP + 0.5 MG]

8. The use of a styrenic polymer composition as claimed in any one of Claims 1 to 6, in the production of a molded industrial part.

9. A moided industrial part produced from a styrenic polymer composition as claimed in any one of Claims 1 to 6.