GB2597898A

GB2597898A - Fire retardant composition

Info

Publication number: GB2597898A
Application number: GB1917836.7A
Authority: GB
Inventors: Phillip Houlder Grahame; Blair Stephen
Original assignee: Polymer Compounders Ltd
Current assignee: Polymer Compounders Ltd
Priority date: 2019-12-05
Filing date: 2019-12-05
Publication date: 2022-02-16
Also published as: GB201917836D0

Abstract

A fire retardant polymer blend comprises: a) at least 20% by weight of a poly(phosphonate-co-carbonate); b) at least 5% by weight of a polycarbonate polymer; and c) at least 5% by weight of an acrylonitrile styrene polymer. The polymer blend may be used as the major component in a fire retardant polymer composition which comprises one or more further polymer additives. These polymer compositions may form moulded articles, for instance by extrusion of injection moulding. Moulded articles may be used as casings for electronic devices and as exterior or interior building cladding.

Description

FIRE RETARDANT COMPOSITION

Field of the Invention

The present invention relates to fire retardant compositions and, in particular, to fire retardant compositions which comprise blends of polymers. The fire retardant compositions are highly 5 suited to applications where polycarbonate/acrylonitrile butadiene styrene and polycarbonate/acrylonitrile styrene acrylate polymer blends have traditionally been used.

Background to the Invention

Fire retardant compositions are desirable for a variety of domestic, commercial and industrial applications. Such compositions reduce the risk of fire-related injuries to both people and property, either by preventing a fire from developing altogether or by slowing the progress of the fire to allow the fire to be brought under control time before significant injuries occur.

Polycarbonate/acrylonitrile butadiene styrene (PC/ABS) and polycarbonate/acrylonitrile styrene acrylate (PC/ASA) are widely used polymer blends, which combine ease of processability with high impact strength, chemical resistance, and heat resistance. Common applications include, but are not limited to, automotive exteriors, electrical device casings, industrial equipment, interior wall cladding for buildings, outdoor furniture and safety helmets.

However, neither PC/ABS nor PC/ASA is sufficiently fire retardant intrinsically to be used in applications where fire is a potential risk without inclusion of fire-retardant additives. These fire-retardant additives may reduce the strength, chemical resistance and processability of the blends.

It has therefore long been desired to produce polymer compositions which exhibit good levels of fire retardancy, but without compromising the advantageous properties of PC/ABS and PC/ASA compositions.

One technology well known in the art is the provision of a PC/ABS or PC/ASA polymer composition comprising brominated fire retardants, and optionally antimony (III) oxide or red phosphorus as a synergic agent. Such materials have good fire resistance, and retain most functional properties of the base polymer blend. -2 -

However, brominated fire retardants may cause chronic toxicity in human subjects and nonhuman animals, and their presence in industrial waste has resulted in persistent pollution and associated environmental damage in affected areas. Antimony (III) oxide also has high acute toxicity and is suspected to be carcinogenic at lower levels of exposure.

Therefore, the current industrial preference is to treat PC/ABS and PC/ASA with aryl bis(diphenyl phosphate) fire retardants, such as resorcinol bis(diphenyl phosphate) and bisphenol A bis(diphenyl phosphate). Although significantly less toxic than their brominated predecessors, the aryl bis(diphenyl phosphate) fire retardants suffer from several drawbacks.

This is largely due to their liquid nature at room temperature and pressure.

For instance, including aryl bis(diphenyl phosphate) fire retardants in PC/ABS and PC/ASA blends results in unwanted plasticization, reducing the heat deflection performance of the polymer blend. The presence of liquid aryl bis(diphenyl phosphate) in the blend can also render injection moulding of the blend difficult, due to the tendency for the liquid components to migrate to the surface of the blend during moulding. As a consequence, the quantity of aryl bis(diphenyl phosphate) additives that can be used in a polymer blend may be limited, thereby also limiting the extent to which the additives can be used to improve the fire rating of the blend. Furthermore, the liquid additives often require the use of significant amounts of PTFE to prevent dripping during extrusion, but this has the disadvantage of reducing the visual clarity of the extruded material.

There is therefore a need for a polymer composition which retains the excellent functional properties of PC/ABS and PC/ASA polymer blends, yet which exhibits high levels fire 25 retardancy thereby rendering it suitable for a wide range of uses.

Summary of the Invention

The present invention is based on the surprising discovery that, by using a poly(phosphonate-co-carbonate) polymer in conventional polycarbonate/acrylonitrile butadiene styrene (PC/ABS) and polycarbonate/acrylonitrile styrene acrylate (PC/ASA) type polymers, a high level of fire resistance may be obtained without compromising the advantageous properties typically associated with PC/ABS and PC/ASA blends, including ease of processability, impact strength and heat resistance, in combination with excellent fire retardancy. -3 -

Accordingly, the present invention provides a fire retardant polymer blend comprising: a) at least 20 % by weight of a poly(phosphonate-co-carbonate); b) at least 5 % by weight of a polycarbonate polymer; and c) at least 5 % by weight of an acrylonitrile styrene polymer.

Also provided is a fire retardant polymer composition comprising: i) at least 50 % by weight of a fire retardant polymer blend of the present invention; and ii) one or more polymer additives.

The present invention further provides a moulded article, e.g. an extruded or injection moulded article, comprising a polymer composition of the present invention, as well as a method for preparing a moulded article, said method comprises subjecting a polymer composition of the present invention to moulding, e.g. extrusion or injection moulding, to form the moulded article.

Detailed Description of the Invention

For the purposes of the present invention, the following terms as used herein shall, unless otherwise indicated, be understood to have the following meanings which are standard in the 20 art.

The terms "alkyl" and "alkylene" refer to saturated groups which may be branched or unbranched. The terms refer to groups which may contain or consist of cyclic structures, though for the purposes of the present invention acyclic groups are preferred. Unless otherwise specified, the terms alkyl and alkylene refer to groups that are optionally substituted alkyl and alkylene groups.

The terms "aryl" and "arylene" refer to aromatic groups, which may be aromatic hydrocarbon groups or heteroaromatic groups (Le. aromatic groups in which one or more ring members is a heteroatom such as, but not limited to, N, 0, and S). The terms encompass fused ring species. Unless otherwise specified, the terms aryl and arylene refer to groups that are optionally substituted alkyl and alkylene groups.

The terms "hydrocarbyl" and "hydrocarbylene" refer to groups that consist only of carbon and 35 hydrogen. The terms refer to groups which may be branched or unbranched and which may contain, consist or be free of cyclic structures. The groups may be saturated or unsaturated -4 -groups. Unless otherwise specified, the terms hydrocarbyl and hydrocarbylene refer to groups that are optionally substituted hydrocarbyl and hydrocarbylene groups.

It will be appreciated that the suffix "-y1" refers to monovalent groups, and the suffix "-ylene" 5 refers to divalent groups.

The term "optionally substituted" means unsubstituted or substituted.

The term "substituted" means that one or more (e.g. 1, 2, 3, 4 or 5) of the hydrogen atoms in that group are replaced independently of each other by a corresponding number of substituents, including hydrocarbyl or non-hydrocarbyl substituents. It will, of course, be understood that the one or more substituents may only be at positions where they are chemically possible, i.e. that any substitution is in accordance with permitted valence of the substituted atom and the substituent and that the substitution results in a stable compound.

The term is contemplated to include all permissible substituents of a chemical group.

Fire retardant polymer blend The polymer blend of the present invention comprises a) at least 20 % by weight of a 20 poly(phosphonate-co-carbonate); b) at least 5 % by weight of a polycarbonate polymer; and c) at least 5 % by weight of an acrylonitrile styrene polymer. Each of components a) to c) is described in greater detail below.

The polymer blend preferably comprises the polycarbonate and the acrylonitrile styrene polymer components in a total amount of at least 30 %, preferably at least 40 %, and more preferably at least 50 %, by weight. The polymer blend preferably comprises the poly(phosphonate-co-carbonate), the acrylonitrile styrene polymer and the polycarbonate polymer components in a total amount of at least 80 %, preferably at least 90 %, and more preferably at least 95 % by weight. It will be appreciated that, where more than one type of poly(phosphonate-co-carbonate), acrylonitrile styrene polymer and/or polycarbonate polymer is used in the polymer blend, these values refer to the total amount of poly(phosphonate-cocarbonate), acrylonitrile styrene polymer and/or polycarbonate polymer that may be present.

Most preferred is for the polymer blend to consist of the poly(phosphonate-co-carbonate), the 35 acrylonitrile styrene polymer and the polycarbonate polymer components. -5 -

Poly(phosphonate-co-carbonate) The fire retardant polymer blend used in the present invention comprises a poly(phosphonate-co-carbonate) (PPCC). These materials, though known for their fire 5 retardancy, have been found to be highly suitable for use in the polymer blends of the present invention, since they may allow the advantageous properties typically associated with PC/ABS and PC/ASA type materials, such as melt processability, heat resistance and impact strength, to be retained. In particular, since PPCC is a solid at room temperature, ease of processability of the polymer blend of the present invention may be significantly 10 better than that observed in prior art blends containing liquid fire retardant additives.

PPCCs are copolymers derived from phosphonate and carbonate monomers, and optionally further monomers. The PPCC may be derived from at least 20 %, preferably at least 40 %, and more preferably at least 55 %, by weight of phosphonate monomer. The PPCC may be derived from up to 80 %, preferably up to 70 %, and more preferably up to 65 % by weight of phosphonate monomer. Thus, the PPCC may be derived from 20 to 80 % by weight phosphonate monomer, preferably from 40 to 70 % by weight of phosphonate monomer, and more preferably from 55 to 65 % by weight of phosphonate monomer.

Typically, the PPCC will be derived from up to 10 %, preferably up to 5 %, and more preferably up to 1 °/0, by weight of monomer other than phosphonate and carbonate monomers. The PPCC may be derived solely from phosphonate and carbonate monomers.

The PPCC may have a weight average molecular weight, Mw, of at least 10,000 g/mol, preferably at least 12,000 g/mol, and more preferably at least 15,000 g/mol. The PPCC may have a weight average molecular weight of up to 100,000 g/mol, preferably up to 90,000 g/mol, and more preferably up to 80,000 g/mol. Thus, the PPCC may have a weight average molecular of from 10,000 to 100,000 g/mol, preferably from 12,000 to 90,000 g/mol and more preferably from 15,000 to 80,000 g/mol. The weight average molecular weights referred to herein may be measured using light scattering techniques such as static light scattering.

The proportion of phosphorus in the PPCC may be at least 1 %, preferably at least 2%, and more preferably at least 3 %, by weight. The proportion of phosphorus in the PPCC may be up to 8 %, preferably up to 6 %, and more preferably up to 5 %, by weight. Thus, the proportion of phosphorus in the PPCC may be from 1 to 8 %, preferably from 2 to 6 ck, and more preferably from 3 to 5 %, by weight. -6 -

The PPCC may be any form of copolymer, however preferably the PPCC is in the form of a random copolymer or a block copolymer. Block copolymers are known in the art as comprising homopolymer subunits linked by covalent bonds. Thus, the PPCC block copolymer would be a copolymer in which blocks of polyphosphonate are alternately linked to blocks of polycarbonate.

Though a variety of PPCC chemistries may be adopted in the polymer blends of the present invention, the phosphonate monomers from which the PPCCs are derived are preferably arylphosphonate or alkylphosphonates.

Preferred phosphonate monomers, once in the polymer, may have the structure: where: R1 is an arylene or alkylene group; and R2 is an alkyl group.

IR1 may be a 06.20 group, and is preferably an arylene group, for instance a phenyl-containing group.

R2 may be a Ci_B group, for instance a methyl or ethyl group.

Preferably, R1 and R2 are hydrocarbylene and hydrocarbyl groups respectively, i.e. they consist of just hydrogen and carbon.

Particularly preferred is the following monomer unit: -7 -Preferred carbonate monomers, once in the polymer, may have the structure: RTh 0 0 0 _ where: R3 is an arylene or alkylene group.

R3 may be a C6_20 group, and is preferably an arylene group, for instance a phenyl-containing group.

Preferably, R3 is a hydrocarbylene group, Le. it consists of just hydrogen and carbon.

Particularly preferred is the following monomer unit: Suitable PPCC polymers may be obtained from FRX Polymers, Inc. For instance, Nofia® 15 C03500 or C06000, and preferably C06000, may be used.

The PPCC is used in the polymer blend in an amount of at least 20 % by weight. Preferably, the PPCC is used in the polymer blend in an amount of at least 30 %, preferably at least 35 %, and more preferably at least 40 %, by weight. These amounts of PPCC may provide excellent fire retardancy. It is surprising that PPCC may be used in these high amounts without significantly compromising the other properties of the base polymer. It will be appreciated that, where more than one type of PPCC is used in the polymer blend, these values refer to the total amount of PPCC that may be present.

Polycarbonate polymer The fire retardant polymer blend used in the present invention also comprises a polycarbonate (PC). A wide range of polycarbonates may be used in the polymer blend to -8 -adjust the properties of the polymer blend. As such, the polycarbonate polymer may be seen as a tuneable component in the polymer blend.

Typically, the PC will be derived from at least 90 %, preferably at least 95 To, and more 5 preferably at least 99 % by weight of carbonate monomers The PPCC may be derived solely from carbonate monomers.

The PC may have a weight average molecular weight, M," of at least 5,000 g/mol, preferably at least 10,000 g/mol, and more preferably at least 15,000 g/mol. The PPCC may have a weight average molecular weight of up to 60,000 g/mol, preferably up to 50,000 g/mol, and more preferably up to 45,000 g/mol. Thus, the PPCC may have a weight average molecular of from 5,000 to 60,000 g/mol, preferably from 10,000 to 50,000 g/mol and more preferably from 15,000 to 45,000 g/mol.

Varying the molecular weight is one method by which the PC can be used to tune the properties of the resulting polymer blend. For instance, lower molecular weights (i.e. those ranges given above, but with an upper bound of 25,000 g/mol) may be preferred for where the polymer is to be used in small consumer products, such as mobile phones. Higher molecular weights (i.e, those ranges given above, but with a lower bound of 35,000 g/mol) may be preferred for where the polymer is to be used in larger structures, such as in building materials, where it is important that brittleness is minimised.

The rigidity of the polymer blend may also be modulated by the degree of branching in the PC. Though a wide range of PCs may be used, preferred carbonate monomers, once in the 25 PC, may have the structure: o 0 _ where: R4 is an arylene or alkylene group.

R4 may be a C6.20 group, and is preferably an arylene group, for instance a phenyl-containing group.

Preferably, R4 is a hydrocarbylene group, i.e. it consists of just hydrogen and carbon. -9 -

Particularly preferred is the following monomer unit: Suitable PCs may be obtained from Lotte Advanced Materials Co. Ltd. For instance, Infinio® SC-1100UR may be used. Other suitable materials include Lexan® 161R, available from SABIC.

The PC is used in the polymer blend in an amount of at least 5 % by weight. Preferably, the PC is used in the polymer blend in an amount of at least 10 %, preferably at least 20 %, and more preferably at least 30 %, by weight. These amounts of PC provide excellent mechanical properties. It will be appreciated that, where more than one type of PC is used in the polymer blend, these values refer to the total amount of PC that may be present.

Actylonitrile styrene polymer The fire retardant polymer blend used in the present invention also comprises an acrylonitrile styrene polymer. The acrylonitrile styrene polymers are used in the present invention as they impart a rubber-like quality, thereby providing the polymer blend with impact resistance and 20 toughness.

Acrylonitrile styrene polymers are polymers derived from acrylonitrile and styrene monomers, and optionally further monomers. As such, they can alternatively be referred to as acrylonitrile styrene co-polymers Preferred acrylonitrile monomers, once in the polymer, may have the structure: -10 -Preferred styrene monomers, once in the polymer, may have the structure: The acrylonitrile styrene polymer may have a weight average molecular weight, Mw, of at 5 least 50,000 g/mol, preferably at least 70,000 g/mol, and more preferably at least 80,000 g/mol. The acrylonitrile styrene polymer may have a weight average molecular weight of up to 300,000 g/mol, preferably up to 200,000 g/mol, and more preferably up to 150,000 g/mol. Thus, the acrylonitrile styrene polymer may have a weight average molecular of from 50,000 to 300,000 g/mol, preferably from 70,000 to 200,000 g/mol and more preferably from 80,000 10 to 150,000 g/mol.

The acrylonitrile styrene polymer will typically be an amorphous polymer.

A range of acrylonitrile styrene polymer chemistries may be used in the polymer blends of the present invention. However, preferred polymers include acrylonitrile butadiene styrene (ABS), acrylonitrile styrene acrylate (ASA), styrene acrylonitrile, methyacrylate-acrylonitrilebutadiene-styrene, acrylonitrile-(ethylene-propylene-diene)-styrene, acrylonitrile-(chlorinated polyethylene)-styrene, and acrylonitrile ethylene styrene. Particularly preferred are ABS and ASA.

ABS and ASA are derived from acrylonitrile monomers, styrene monomers and a tertiary monomer which is a 1,3-butadiene monomer in the case of ABS or an acrylate monomer in the case of ASA.

Preferred tertiary monomers, once in the polymer, may have the structure: _.0 Or for ABS, and for ASA.

It will be appreciated that the butadiene monomer structures allow for cross-linking.

The ABS and ASA may be derived by polymerising the styrene and acrylonitrile polymers in the presence of pre-formed polymers of the tertiary monomer, thereby providing chains of tertiary monomer interspersed with poly(styrene-co-acrylonitrile).

The ABS and ASA may be derived from at least 15 % by weight of acrylonitrile, at least 40 % by weight of styrene, and at least 5 % by weight of the tertiary monomer. Preferably, none of the monomers are used in an amount of greater than 60 % by weight.

Typically, ABS and ASA will be derived from up to 10 %, preferably up to 5 %, and more 10 preferably up to 1 %, by weight of monomer other than acrylonitrile, styrene and tertiary monomers. ABS and ASA may be derived solely from the acrylonitrile, styrene and tertiary monomers.

Whether ABS or ASA is preferred will depend on the application. Where the polymer 15 composition is to be directly exposed to daylight, then ASA may be preferred due to its enhanced UV stability. However, ABS may have slightly superior low temperature strength properties than ASA, making ABS the preferred option for use in a cold environment.

Suitable acrylonitrile styrene polymers may be obtained from INEOS Ltd or Chi Mei 20 Corporation. For instance, Terluran HI-10 (INEOS) may be used as the ABS and Kibilac0 PW-957 (Chi-Mei) may be used as the ASA.

The acrylonitrile styrene polymer is used in the polymer blend in an amount of at least 5 % by weight. Preferably, the acrylonitrile styrene polymer is used in the polymer blend in an amount of at least 7.5 %, preferably at least 10 %, and more preferably at least 12.5 %, by weight. These amounts of acrylonitrile styrene polymer may impart excellent mechanical properties to the blend. It will be appreciated that, where more than one type of acrylonitrile styrene polymer is used in the polymer blend, these values refer to the total amount of acrylonitrile styrene polymer that may be present.

Fire retardant polymer compositions The fire retardant polymer blends of the present invention may be used in a fire retardant polymer composition. According, the present invention also provides a fire retardant polymer 35 composition comprising: i) at least 50 % by weight of fire retardant polymer blend of the present invention; and -12 -one or more polymer additives.

Typically, the polymer composition will comprise at least 70 %, preferably at least 80 %, and more preferably at least 90 %, by weight of the polymer blend.

Advantageously, and unlike some prior art compositions, the polymer compositions of the present invention may be free from bromine and chlorine.

Suitable additives for use in the polymer composition include anti-drip agents, anti-oxidants, 10 colourant, UV stabilisers and flame retardant additives. Preferably, the polymer composition comprises as additives at least an anti-drip agent, an anti-oxidant and colourant.

In some embodiments, colourant may be present. Colourants for polymers are widely known, and a large variety may be adopted in the present invention. Common colourants 15 include titanium dioxide and carbon black which impart a white and black colour, respectively.

The amount of colourant that is required depends greatly on the target colour. For instance, bright white polymers may comprise a relatively high level of colourant, whereas other colours may be achieved using just a small amount of colourant. Typically, colourant will be used in an amount of up to 10 %, preferably up to 8 %, and more preferably up to 6 % by weight of the polymer composition. It will be appreciated that these values refer to the total amount of colourant that may be present.

In some embodiments, an anti-oxidant may be present. These components enhance the stability of the polymer composition by preventing degradation by reaction with atmospheric oxygen. A primary antioxidant (radical scavenger) or a secondary antioxidant (hydroperoxide scavenger) may be used. Preferably both a primary and second anti-oxidants are present in the polymer compositions of the present invention. Suitable primary anti-oxidants include sterically hindered phenolic antioxidants, such as octadecy1-3-[3,5-di-ter-butyl-4-hydroxyphenyl]propionate, which is widely commercially available, e.g. in formulations such as Kingnox® 76 from Hubron Speciality Limited, or as Irganox® 1076 from BASF SE. Suitable secondary antioxidants include tris(2,4-di-tert-butylphenyl) phosphite, which is widely commercially available e.g. in formulations such as KingFos® 168 from Hubron Speciality Limited or as Irgafose 168 from BASF SE.

-13 -The anti-oxidant may be used in an amount of at least 0.4 %, preferably at least 0.6 %, and more preferably at least 0.7 %, by weight of the polymer composition. The anti-oxidant may be used in an amount of up to 1.5 %, preferably up to 1.2 %, and more preferably up to 0.9 %, by weight of the polymer composition. Thus, the anti-oxidant may be used in an amount of from 0.4 to 1.5 %, preferably from 0.6 to 1.2 %, and more preferably from 0.7 to 0.9 °A), by weight of the polymer composition. It will be appreciated that, where more than one type of anti-oxidant is used in the polymer composition, these values refer to the total amount of antioxidant that may be present.

Where a primary and secondary anti-oxidant are both adopted, these are preferably used in a weight ratio of from 2:1 to 1:2, preferably from 1.5:1 to 1:1.5, and more preferably from 1.25:1 to 1:1.25.

In some embodiments, an anti-drip agent may be present. Anti-drip agents are widely used 15 in the field to prevent molten material from dripping from the polymer composition during a fire by forming a matrix during burning. Suitable anti-drip agents include polytetrafluoroethylene (PTFE), which is preferably used in the form of a micronised powder. Suitable grades of PTFE are widely available from the speciality chemical industry, e.g. Polymiste from Solvay S.A.

The anti-drip agent may be used in relatively low amounts as compared to prior art compositions, since liquid fire retardants are generally not used in the polymer compositions of the present invention. The anti-drip agent may be used in an amount of at least 0.1 %, preferably at least 0.2 %, and more preferably at least 0.3 %, by weight of the polymer composition. The anti-drip agent may be used in an amount of up to 0.8 %, preferably up to 0.6 %, and more preferably up to 0.5 %, by weight of the polymer composition. Thus, the anti-drip agent may be used in an amount of from 0.1 to 0.8%, preferably from 0.2 to 0.6%, and more preferably from 0.3 to 0.5 %, by weight of the polymer composition. It will be appreciated that, where more than one type of anti-drip agent is used in the polymer composition, these values refer to the total amount of anti-drip agent that may be present.

In some embodiments, the polymer composition may comprise a UV stabiliser. Suitable UV stabilisers include 2-(2H-benzotriazol-2-y1)-4,6-bis(1-methyl-1-phenylethyl)phenol.

The UV stabiliser may be used in an amount of at least 0.05 %, preferably at least 0.1 %, and more preferably at least 0.2 %, by weight of the polymer composition. The UV stabiliser -14 -may be used in an amount of up to 0.8 °/0, preferably up to 0.5 %, and more preferably up to 0.4 %, by weight of the polymer composition. Thus, the UV stabiliser may be used in an amount of from 0.05 to 0.8 °/0, preferably from 0.1 to 0.5%, and more preferably from 0.2 to 0.4 % by weight of the polymer composition. It will be appreciated that, where more than one type of UV stabiliser is used in the polymer composition, these values refer to the total amount of UV stabiliser that may be present.

In some embodiments, the polymer composition may comprise fire retardant additives, such as bis(diphenyl phosphate) fire retardants. However, since the polymer blends used in the compositions of the present invention already exhibit excellent fire retardancy properties, these additives are preferably not used or are only used in small amounts of up to 5 %, preferably up to 3 %, and more preferably up to 1 %, by weight of the polymer composition, though in some instances may be used in an amount of up to 15 %, such as from 10 to 15 %, by weight of the polymer composition.

Oil may also be used in the polymer composition, though will typically be used in just a small amount (e.g. of up to 1 %, for instance from 0.25 to 0.75 %, by weight of the polymer composition).

The polymer compositions of the present invention preferably exhibit a V-0 flammability rating with a sample thickness of 1.6 mm, preferably 1 mm, and more preferably 0.8 mm. Flammability rating may be determined using the method described in the Examples.

The polymer compositions of the present invention may exhibit a high melt-volume flow rate, 25 e.g. of at least 12 cm3/10 mins, preferably at least 14 cm3/10 mins, and more preferably at least 16 cm3/10 mins. Flow rate may be determined using the method described in the Examples.

The polymer compositions of the present invention may exhibit excellent notched impact 30 resistance, e.g. of at least 40 kJ/m2, preferably at least 43 kJ/m2, and more preferably greater than 46 kJ/m2. Notched impact resistance may be determined using the method described in the Examples.

The polymer compositions of the present invention may exhibit a high softening point, e.g. of 35 at least 120 °C, preferably at least 122 °C, and more preferably at least 125 °C. Softening point may be determined using the method described in the Examples.

-15 -The polymer compositions of the present invention may exhibit a low specific gravity, e.g. of up to 1.8 g/cm3, preferably up to 1.5 g/cm3, and more preferably up to 1.3 g/cm3. Specific gravity may be determined using the method described in the Examples.

In particular embodiments, the polymer composition of the present invention may also exhibit a desirable combination of the above-mentioned properties.

Applications The polymer compositions of the present disclosure may be used in a wide range of different applications, thanks to their advantageous properties, in particular their low flammability, high impact strength, low specific gravity and ease of processing.

The polymer composition may be used as a material, e.g. a protective coating, in leisure and 15 outdoor equipment. Outdoor equipment may include gardening equipment such as lawnmowers, strimmers and hedgetrimmers. As mentioned above, for equipment that is used outside, ASA is preferably used in the polymer composition.

The polymer compositions may also be advantageously used to provide electronic device casings, also commonly referred to as electronic enclosures. Such casings may include casings for telephones such as mobile telephones, fire and safety equipment, computing devices, radio-frequency receiving systems, satellite navigation receivers and electronic cigarettes.

The polymer compositions may be used in automotive transportation application. For instance, the polymer composition may be used as part of the internal fittings in a vehicle, and in electric batteries.

The polymer compositions of the present disclosure may be advantageously used in exterior or interior building cladding for residential, commercial and industrial use. This cladding may be provided in the form of a sheet which is fixable onto a wall or other building element by adhesion or mechanical means. The cladding may comprise further materials in addition to a polymer composition of the present invention, e.g. metal panel sheets (such as aluminium or steel) which surround a core filled with a polymer composition of the present invention.

-16 -Preparation methods for preparing the polymer blends and compositions The polymer blends and polymer compositions of the present invention may be prepared using conventional methods. For instance, each of the components in the blend or composition may be mixed to prepare the polymer blend or composition. Where a polymer composition is prepared, the polymer blend may be pre-mixed before it is combined with the remaining components in the composition, preferably in an extruder.

In some embodiments, the polymer blend and composition are in the form of a compounded 10 preparation, e.g. a granular mixture, which is ready for moulding e.g. via extrusion or injection moulding. Polymer compositions of the present invention are, compared to prior art compositions, particularly suitable for injection moulding.

In other embodiments, the polymer composition may be in a moulded form, e.g. an extruded 15 or injection moulded form.

The present invention provides a method for preparing a moulded article, said method comprising subjecting a polymer composition of the present invention to moulding, e.g. by extrusion or injection moulding, to form the article.

Typically, the polymer compositions of the present invention exhibit superior moulding performance than compositions based on PPCC alone, which tend to exhibit a dripping effect during processing thereby necessitating the use of high temperature jacketing and/or dosing pumps.

Examples

The present invention will now be illustrated by way of the following non-limiting examples.

In the examples, flammability of polymer compositions was tested according to industry standard method UL 94, as set out in the sixth edition dated 28 March 2013 (see section 8 for vertical burn classifications, V; and section 6 for horizontal burn classifications, HB). Unless otherwise specified, the thickness of the samples used in the tests was 1.6 mm.

Other properties of polymer compositions were measured using the following methods: Melt Volume Flow Rate: ISO 1133-1:2011 (260 °C, 5 kg load) -17 -Density and Specific Gravity: Notched Impact: ISO 1183-1 (method A) Vicat Softening Temperature: ISO 180:2000 (method 1A; temperature 23 °C Izod notched impact test) ISO 306:2013 (method B50) Example 1: Preparation of polymer compositions Four different polymer blends, A to D, were prepared in accordance with the present invention. Specifically, a poly(phosphonate-co-carbonate) polymer, a polycarbonate and acrylonitrile butadiene styrene were combined in different amounts to give a polymer base blend. 25 kg of base blend was combined with 1.4 of additives to give Polymer Compositions A to D. By weight, colourants represented about 76.4 % of the additives; an anti-drip agent (micronised PTFE), a first antioxidant (Kingnoxe 76) and a second antioxidant (KingFose 168) each represented about 7.4 % of the additives; and the balance was made up by oil which can help with binding of the colourants and additives to the base blends.

The resulting polymer compositions were tested to determine their Flammability, as well as their Melt Volume Flow Rate, Notched Impact and VICAT Softening Point Temperature.

The results are shown in the following table:

A B C D

Base Blend (13/0 by weight) Poly(phosphonate-co-carbonate)1 45% 37% 29% 21% Polycarbonate2 40% 48% 56% 64% Acrylonitrile butadiene styrene3 15% 15% 15% 15% Properties of Polymer Composition Flammability V-0 V-0 V-0 V-1 Melt Volume Flow Rate (cm3/10 minutes) 18 16 10 11 Notched Impact (kJ/m2) 48 45 45 42 VICAT Softening Point (°C) 126 126 128 130 -18 -It can be seen that each of polymer compositions A to D exhibits a good flammability rating, in combination with excellent properties. The level of flammability observed in the polymer compositions was lower for the blends containing a higher proportion of the poly(phosphonate-co-carbonate) polymer.

A further polymer composition was prepared having the same composition as composition A, but in which the acrylonitrile butadiene styrene (ABS) was replaced with acrylonitrile styrene acrylate (ASA). This composition also exhibited a V-0 flammability rating.

Example 2: Flammability compared to commercially available polymer blends The minimum thickness of polymer composition A from Example 1 required to achieve a V-0 flammability rating was measured and compared with that required by nine different commercially available fire resistant PC/ABS polymer compositions.

The results are shown in the following table: It can be seen that polymer composition A exhibited superior fire retardancy to the majority of 20 the commercially available compositions, without using conventional fire retardant technology.

Example 3: Other properties compared to commercially available polymer compositions The polymer compositions from Example 2 were further tested to determine whether the use of a significant amount of poly(phosphonate-co-carbonate) to improve the fire retardancy of a polymer composition jeopardises other properties.

Polymer Composition A 1 2 3 4 5 6 7 8 9 0.75 2 1.2 0.75 1.2 1.5 0.75 1.5 1.2 0.75 Sample thickness -19 -The results are shown in the following table: Polymer Composition A 1 2 3 4 5 6 7 8 9 Melt-Volume Flow Rate (cm3/10 mins) 18 12 21 15 21 14 15 41 25 19 Notched Impact (kJ/m2) 48 45 15 40 15 40 25 30 11 50 VICAT Softening Point (° C) 126 124 102 110 102 105 110 115 128 105 Specific Gravity (g/cm3) 1.15 1.2 1.19 1.19 1.19 1.18 1.19 1.18 1.22 1.2 It can be seen that polymer composition A exhibited: a superior Melt-Volume Flow Rate to five of the commercially available polymer compositions; a superior Notched Impact to eight of the commercially available polymer compositions, and a similar Notched Impact to highest performing polymer composition 9 which is an impact modified composition; and a superior Softening Point to eight of the commercially available polymer compositions.

It is particularly noteworthy that this combination of excellent properties is exhibited by polymer composition A, which exhibits a lower Specific Gravity -Le. is lightweight -15 compared to all of the commercially available polymer compositions.

A composition similar to polymer composition A, but not containing any PPCC, is commercially available PCABSCOM B300.

-20 -The properties of this material are shown in the following table: PPCC-free polymer UL94 (1.5 mm sample thickness) H B Melt-Volume Flow Rate (cm3/10 mins) 18 Notched Impact (kJ/m2) 50 VICAT Softening Point (° C) 128 Specific Gravity (g/cm3) 1.14 Thus, it can be seen that the use of PPCC may significantly increase the flame resistance of 5 a polymer composition, without significantly jeopardising the other properties of the material.

Claims

-21 -Claims 1. A fire retardant polymer blend comprising: d) at least 20 % by weight of a poly(phosphonate-co-carbonate); e) at least 5 % by weight of a polycarbonate polymer; and at least 5 c/c, by weight of an acrylonitrile styrene polymer.
2. The polymer blend of claim 1, wherein the poly(phosphonate-co-cocarbonate) comprises elemental phosphorus in an amount of from 1 to 8 %, preferably from 2 to 6 %, and more preferably from 3 to 5 %, by weight.
3. The polymer blend of claim 1 or claim 2, wherein the poly(phosphonate-co-cocarbonate) comprises: phosphonate monomers which, once in the polymer, have the structure: R2IAwhere: R1 is an arylene or alkylene group; and R2 is an alkyl group; and/or: carbonate monomers which, once in the polymer, have the structure: o"-^ -*"o R3 o where: R3 is an arylene or alkylene group.
4. The polymer blend of any preceding claim, wherein the poly(phosphonate-co-carbonate) has a weight average molecular weight, M, of from 10,000 to 100,000 g/mol, preferably from 12,000 to 90,000 g/mol and more preferably from 15,000 to 80,000 g/mol.
-22 -The polymer blend of any preceding claim, wherein the polymer blend comprises at least 30 °/0, preferably at least 35 °/0, and more preferably at least 40 %, by weight of the polyphosphonate copolymer.
The polymer blend of any preceding claim, wherein the polycarbonate polymer comprises monomers which, once in the polymer, have the structure: where: R4 is an arylene or alkylene group.
7. The polymer blend of any preceding claim, wherein the polycarbonate polymer has a weight average molecular weight, NA, of from 5,000 to 60,000 g/mol, preferably from 10,000 to 50,000 g/mol and more preferably from 15,000 to 45,000 g/mol.
The polymer blend of any preceding claim, wherein the polymer blend comprises at least 10 %, preferably at least 20 %, and more preferably at least 30 %, by weight of the polycarbonate polymer.
The polymer blend of any preceding claim, wherein the acrylonitrile styrene polymer is selected from the group comprising acrylonitrile butadiene styrene (ABS), acrylonitrile styrene acrylate (ASA), styrene acrylonitrile, methyacrylate-acrylonitrilebutadiene-styrene, acrylonitrile-(ethylene-propylene-diene)-styrene, acrylonitrile(chlorinated polyethylene)-styrene, acrylonitrile ethylene styrene, and preferably from ABS and ASA.
10. The polymer blend of any preceding claim, wherein the acrylonitrile styrene polymer has a weight average molecular weight, NA," of from 50,000 to 300,000 g/mol, preferably from 70,000 to 200,000 g/mol and more preferably from 80,000 to 150,000 g/mol.
11. The polymer blend of any preceding claim, wherein the polymer blend comprises at least 7.5 °/0, preferably at least 10 c/c, and more preferably at least 12.5 %, by weight of the acrylonitrile styrene polymer.
-23 - 12. The polymer blend of any preceding claim, wherein: the polymer blend comprises the polycarbonate and the acrylonitrile styrene polymer components in a total amount of at least 30 %, preferably at least 40 %, and more preferably at least 50 %, by weight; and/or the polymer blend comprises the polyphosphonate copolymer, the acrylonitrile styrene polymer and the polycarbonate polymer components in a total amount of at least 80 WO, preferably at least 90 %, and more preferably at least 95 % by weight.
13. The polymer blend of any preceding claim, wherein the polymer blend consists of the polyphosphonate copolymer, the acrylonitrile styrene polymer and the polycarbonate polymer components.
14. A fire retardant polymer composition comprising: i) at least 50 % by weight of a fire retardant polymer blend as defined in any of claims 1 to 13; and ii) one or more polymer additives.
15. The polymer composition of claim 14, wherein the polymer composition comprises at least 70 %, preferably at least 80 %, and more preferably at least 90 %, by weight of the polymer blend.
16. The polymer composition of claim 14 or claim 15, wherein the polymer composition comprises one or more polymer additives selected from anti-drip agents, antioxidants, colourant, UV stabilisers and flame retardant additives, and preferably wherein the polymer composition comprises an anti-drip agent, an anti-oxidant and colourant.
17. The polymer composition of any of claims 14 to 16, wherein the polymer composition has a V-0 flammability rating with a sample thickness of 1.6 mm, preferably 1 mm, and more preferably 0.8 mm.
18. The polymer composition of any of claims 14 to 17, wherein the polymer composition exhibits: a melt-volume flow rate of at least 12 cm3/10 mins, preferably at least 14 cm3/10 mins, and more preferably at least 16 cm3/10 mins; -24 -a notched impact resistance of at least 40 kJ/m2, preferably at least 43 kJ/m2, and more preferably greater than 46 kJ/m2; a softening point of at least 120 °C, preferably at least 122 °C, and more preferably at least 125 °C; and/or a specific gravity of up to 1.8 g/cm3, preferably up to 1.5 g/cm3, and more preferably up to 1.3 g/cm3.
19. A moulded article, e.g. an extruded or injection moulded article, comprising the polymer composition of any of claims 14 to 18.
20. A method for preparing a moulded article, said method comprises subjecting a polymer composition of any of claims 14 to 18 to moulding, e.g. extrusion or injection moulding, to form the moulded article.