Flame retardant polymer-polyelectrolyte complex (PEC) composite

Abstract

A flame retardant composite including a polymeric resin and a polyelectrolyte complex obtained by contacting a polycation comprising an amino group and a polyanion comprising a phosphate group. The flame retardant composite may be used to form various flame retardant articles.

Description

FLAME RETARDANT POLYMER-POLYELECTROLYTE COMPLEX (PEC) COMPOSITEFIELD

[0003] The present disclosure is generally directed to a flame retardant composite comprising a polymeric resin and a polyelectrolyte complex obtained by contacting a polycation comprising an amino group and a polyanion comprising a phosphate group.BACKGROUND

[0004] Because of their chemical composition, many plastics materials are highly combustible. In order to be able to achieve the high requirements that are made in terms of fire retardancy by plastics processors, plastics materials must generally further include flame retardants. A large number of different flame retardants and flame retardant synergists are known for this purpose and are also available commercially.

[0005] For example, intumescent compositions can be mixed with the plastic material and extruded. When such materials are subjected to a flame, charring and swelling can occur which can provide a degree of insulation against continued combustion. The intumescent flame retardants can also produce non-flammable gasses created during the intumescent reaction.

[0006] However, intumescent flame retardant systems can be reactive at relatively low temperatures. The relatively low activation temperature of many intumescent flame retardant systems can also limit their usefulness in polymer processing techniques, for example, melt extrusion which can require temperatures that are higher than the activation temperature of the intumescent flame retardant system. While the temperature stability of intumescent systems can be improved by employing complex and / or exotic chemistries, such intumescent systems can be relatively expensive. Accordingly, their use can increase manufacturing costs. Furthermore, many intumescent flame retardant systems may be unsuitable for human contact or handling and thuscan have limited applicability. Still further, many intumescent flame retardant systems can generate harmful or toxic gases, which can further limit the applications of such systems.

[0007] Accordingly, there is a continued need to develop new, cost effective flame retardant additives which can be added to various polymers to produce flame retardant composites which are easy to process and which exhibit good flame retardant properties and mechanical properties.SUMMARY

[0008] The present disclosure describes a flame retardant composite comprising a polymeric resin and a polyelectrolyte complex obtained by contacting a polycation comprising an amino group and a polyanion comprising a phosphate group.

[0009] In another embodiment, there is provided a method for improving the flame retardancy of a polymeric resin comprising compounding the polyelectrolyte complex with the polymeric resin.

[0010] In yet another embodiment, there is provided a method for producing an article by molding, extruding or shaping the flame retardant composite and also to an article produced by such molding, extruding or shaping of the flame retardant composite.BRIEF DESCRIPTION OF THE DRAWINGS

[0011] FIG. 1 depicts micro-cone calorimeter (MCC) analysis of a polypropylene impact copolymer vs. polypropylene impact copolymer + polyelectrolyte complex composite.

[0012] FIG. 2 depicts polypropylene-based bars after burning that contain a polyelectrolyte complex (left) and an intumescent flame retardant (right).DETAILED DESCRIPTION

[0013] If appearing herein, the term "comprising" and derivatives thereof are not intended to exclude the presence of any additional component, step or procedure, whether or not the same is disclosed herein. In order to avoid any doubt, all compositions claimed herein through use of the term "comprising" may include any additional additive, adjuvant, or compound, unless stated to the contrary. In contrast, the term, "consisting essentially of" if appearing herein, excludes from the scope of any succeeding recitation any other component, step or procedure, except those that are not essential to operability and the term "consisting of", if used, excludes any component, step or procedure not specifically delineated or listed. The terms "or" and “and / or”, unless stated otherwise, refer to the listed members individually as well as in any combination. For example, the expression A and / or B refers to A alone, B alone, or to both A and B.

[0014] The articles "a" and "an" are used herein to refer to one or to more than one (i.e. to at least one) of the grammatical objects of the article. By way of example, "a polymer" means one polymer or more than one polymer. The phrases "in one embodiment", "according to one embodiment" and the like generally mean the particular feature, structure, or characteristic following the phrase is included in at least one embodiment of the present disclosure, and may be included in more than one embodiment of the present disclosure. Importantly, such phrases do not necessarily refer to the same embodiment. If the specification states a component or feature "may", "can", "could", or "might" be included or have a characteristic, that particular component or feature is not required to be included or have the characteristic.

[0015] The terms “preferred” and “preferably” refer to embodiments that may afford certain benefits, under certain circumstances. However, other embodiments may also be preferred, under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that otherembodiments are not useful, and is not intended to exclude other embodiments from the scope of the present disclosure.

[0016] The term “about” as used herein can allow for a degree of variability in a value or range, for example, it may be within 10%, within 5%, or within 1 % of a stated value or of a stated limit of a range.

[0017] Values expressed in a range format should be interpreted in a flexible manner to include not only the numerical values explicitly recited as the limits of the range, but to also include all of the individual numerical values or sub-ranges encompassed within that range as if each numerical value and sub-range is explicitly recited. For example, a range such as from 1 to 6, should be considered to have specifically disclosed sub-ranges, such as, from 1 to 3, from 2 to 4, from 3 to 6, etc., as well as individual numbers within that range, for example, 1 , 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range.

[0018] The term “optional” or “optionally” means that the subsequently described event or circumstance may or may not occur, and that the description includes instances where said event or circumstance occurs and instances where it does not.

[0019] The term “polycation” refers to a polyelectrolyte possessing a net positive charge. While the polycation can contain monomer units that have a positive, a neutral, or a negative charge, the net charge of the polymer is positive.

[0020] The term “polyanion” refers to a polyelectrolyte containing a net negative charge. While the polyanion can contain monomer units that have a negative, neutral, or positive charge, the net charge on the polymer is negative.

[0021] The term “polyelectrolyte complex” means the interaction between polyanion and polycation molecules or portions of the same molecule through noncovalent interactions such as coordination bonds, electrostatic interactions, hydrogen bonding interactions, and hydrophobic interactions.

[0022] The term “composite” means a multi-component material comprising at least two immiscible components (e.g., the polymeric resin and the polyelectrolyte complex).

[0023] The term “substantially free” refers to a composition in which a particular constituent or moiety is present in an amount that has no material effect on the overall composition. In some embodiments, “substantially free” may refer to a composition in which the particular constituent or moiety is present in the composition in an amount of less than about 5 wt.%, or less than about 4 wt.%, or less than about 3 wt.% or less than about 2 wt.% or less than about 1 wt.%, or less than about 0.5 wt.%, or less than about 0.1 wt.%, or less than about 0.05 wt.%, or even less than about 0.01 wt.% based on the total weight of the composition, or that no amount of that particular constituent or moiety is present in the respective composition.

[0024] “Flame retardant article or composite” means an article or composite in which basic flammability has been reduced by some modification as measured by one of the accepted test methods such as, but not limited to, the UL 94 Vertical Bum test or the DIN 4102 Vertical Burn test.

[0025] According to one embodiment, the present disclosure provides a flame retardant composite comprising a polyelectrolyte complex obtained by contacting a polycation comprising an amino group and a polyanion comprising a phosphate group and a polymeric resin.

[0026] According to one embodiment, the polycation may have at least one positively chargeable and / or positively charged moiety selected from the group consisting of a primary, secondary or tertiary amino group, a quaternary ammonium group, a guanidine group, a biguanide group, an imidazole group, an imino group, and a pyridyl group.

[0027] In one embodiment, the polycation may be a homopolymer or a copolymer. The term “copolymer” is understood to mean both copolymers obtained from two kinds of monomers and those obtained from more than two kinds of monomers, such as terpolymers obtained from three kinds of monomers. Additionally, the polycation may be a natural polymer or synthetic polycationic polymer. Non-limiting examples of polycations include, but are not limited to:(1 ) Homopolymers and copolymers derived from acrylic or methacrylic esters and amides and comprising at least one unit chosen from units of the following formulas:where R1 and R2, which may be identical or different, are chosen from hydrogen and alkyl groups comprising from 1 to 6 carbon atoms, for example, methyl and ethyl groups;R3, which may be identical or different, is chosen from hydrogen and CH3;the symbols A, which may be identical or different, are chosen from linear or branched alkyl groups comprising from 1 to 6 carbon atoms, for example, from 2 to 3 carbon atoms and hydroxyalkyl groups comprising from 1 to 4 carbon atoms;R4, R5, and R6, which may be identical or different, are chosen from alkyl groups comprising from 1 to 18 carbon atoms and benzyl groups, and in at least one embodiment, alkyl groups comprising from 1 to 6 carbon atoms; andX is an anion derived from an inorganic or organic acid, such as methosulphate anions and halides, for example chloride and bromide.The copolymers of (1 ) may also comprise at least one unit derived from comonomers which may be chosen from acrylamides, methacrylamides, diacetone acrylamides, acrylamides and methacrylamides substituted on the nitrogen atom with (C1-C4) lower alkyl groups, groups derived from acrylic or methacrylic acids and esters thereof, vinyllactams such as vinylpyrrolidone and vinylcaprolactam, and vinyl esters.Examples of copolymers of family (1 ) include, but are not limited to: copolymers of acrylamide and of dimethylaminoethyl methacrylate quatemized with dimethyl sulphate or with a dimethyl halide, copolymers of acrylamide and of methacryloyloxyethyltrimethylammonium chloride, copolymers of acrylamide and of methacryloyloxyethyltrimethylammonium methosulphate, quatemized or nonquaternized vinylpyrrolidone / dialkylaminoalkyl acrylate or methacrylate copolymers, dimethylaminoethyl methacrylate / vinylcaprolactam / vinylpyrrolidone terpolymers, vinylpyrrolidone / methacrylamidopropyldimethylamine copolymers, quatemized vinylpyrrolidone / dimethylaminopropylmethacrylamide copolymers, and crosslinked methacryloyloxy(C1-C4)alkyltri(C1-C4)alkylammonium salt polymers such as the polymers obtained by homopolymerization of dimethylaminoethyl methacrylate quatemized with methyl chloride, or bycopolymerization of acrylamide with dimethylaminoethyl methacrylate quaternized with methyl chloride, the homopolymerization or copolymerization being followed by crosslinking with a compound containing an olefinic unsaturation, for example, methylenebisacrylamide(2) Cationic cellulose derivatives such as cellulose ether derivatives comprising quaternary ammonium groups. These polymers may be defined as quaternary ammoniums of hydroxyethylcellulose that have reacted with an epoxide substituted with a trimethylammonium group.(3) Cationic cellulose derivatives, such as cellulose copolymers and cellulose derivatives grafted with a water-soluble monomer of quaternary ammonium, such as hydroxyalkylcelluloses, for instance, hydroxymethyl-, hydroxyethyl-, and hydroxypropylcelluloses grafted, for example, with a salt chosen from methacryloylethyltrimethylammonium, methacrylamidopropyltrimethylammonium, and dimethyldiallylammonium.(4) Non-cellulose-based cationic polysaccharides, such as guar gums comprising cationic trialkylammonium groups, cationic hyaluronic acid, and dextran hydroxypropyl trimonium chloride. Guar gums modified with a salt, for example the chloride, of 2,3-epoxypropyltrimethylammonium (guar hydroxypropyltrimonium chloride) may also be used.(5) Polymers comprising piperazinyl units and divalent alkylene or hydroxyalkylene groups comprising straight or branched chains, optionally interrupted with at least one entity chosen from oxygen, sulphur, nitrogen, aromatic rings, and heterocyclic rings, and also the oxidation and / or quaternization products of these polymers.(6) Water-soluble polyamino amides prepared, for example, by polycondensation of an acidic compound with a polyamine; these polyamino amides possibly being crosslinked with an entity chosen from epihalohydrins;diepoxides; dianhydrides; unsaturated dianhydrides; bisunsaturated derivatives; bishalohydrins; bisazetidiniums; bishaloacyldiamines; bisalkyl halides; oligomers resulting from the reaction of a difunctional compound which is reactive with an entity chosen from bishalohydrins, bisazetidiniums, bishaloacyldiamines, bisalkyl halides, epihalohydrins, diepoxides, and bisunsaturated derivatives; the crosslinking agent being used in an amount ranging from 0.025 to 0.35 mol per amine group of the polyamino amide; these polyamino amides optionally being alkylated or, if they comprise at least one tertiary amine function, they may be quaternized.(7) Polyamino amide derivatives resulting from the condensation of polyalkylene polyamines with polycarboxylic acids, followed by alkylation with difunctional agents, for example, adipic acid / dialkylaminohydroxyalkyldialkylenetriamine polymers in which the alkyl group comprises from 1 to 4 carbon atoms, such as methyl, ethyl, and propyl groups, and the alkylene group comprises from 1 to 4 carbon atoms, such as an ethylene group. Such polymers are described, for instance, in French Patent No. 1 583 363. In at least one embodiment, these derivatives may be chosen from acid / dimethylaminohydroxypropyldiethylenetriamine polymers.(8) Polymers obtained by reaction of a polyalkylene polyamine comprising two primary amine groups and at least one secondary amine group, with a dicarboxylic acid chosen from diglycolic acid and saturated aliphatic dicarboxylic acids comprising from 3 to 8 carbon atoms. The molar ratio of the polyalkylene polyamine to the dicarboxylic acid may range from 0.8:1 to 1.4:1 ; the polyamino amide resulting therefrom being reacted with epichlorohydrin in a molar ratio of epichlorohydrin relative to the secondary amine group of the polyamino amide ranging from 0.5:1 to 1.8:1.(9) Cyclopolymers of alkyldiallylamine and cyclopolymers of dialkyldiallyl- ammonium, such as homopolymers and copolymers comprising, as the mainconstituent of the chain, at least one unit chosen from units of formulas (la) and (lb)where k and t, which may be identical or different, are equal to 0 or 1 , the sum k+t being equal to 1 ; R12 is chosen from hydrogen and methyl groups; R10 and R11 , which may be identical or different, are chosen from alkyl groups comprising from 1 to 6 carbon atoms, hydroxyalkyl groups in which the alkyl group comprises, for example, from 1 to 5 carbon atoms, and lower (C1-C4) amidoalkyl groups, or R and R11 may form, together with the nitrogen atom to which they are attached, heterocyclic groups such as piperidinyl and morpholinyl; and Y1is an anion such as bromide, chloride, acetate, borate, citrate, tartrate, bisulphate, bisulphite, sulphate, and phosphate.In one embodiment, R10 and R11 , which may be identical or different, are chosen from alkyl groups comprising from 1 to 4 carbon atoms. Examples of such polymers include, but are not limited to, (co)polydiallyldialkyl ammonium chloride such as the dimethyldiallylammonium chloride homopolymer and the copolymers of diallyldimethylammonium chloride and of acrylamide.(10) Quaternary diammonium polymers comprising at least one repeating unit of formula (II):(ii)where R13, R14, R15, and Rw, which may be identical or different, are chosen from aliphatic, alicyclic, and arylaliphatic groups comprising from 1 to 20 carbon atoms and lower hydroxyalkyl aliphatic groups, or alternatively R13, R14, R15, and R may form, together or separately, with the nitrogen atoms to which they are attached, heterocycles optionally comprising a second heteroatom other than nitrogen, or alternatively R13, R14, R15, and R , which may be identical or different, are chosen from linear or branched Ci-Ce alkyl groups substituted with at least one group chosen from nitrile groups, ester groups, acyl groups, amide groups, — CO — 0 — R17-E groups, and — CO — NH — R17-E groups, where R17 is an alkylene group and E is a quaternary ammonium group;A1 and Bi , which may be identical or different, are chosen from polymethylene groups comprising from 2 to 20 carbon atoms, which may be linear or branched, saturated or unsaturated, and which may comprise, linked or intercalated in the main chain, at least one entity chosen from aromatic rings, oxygen, sulphur, sulphoxide groups, sulphone groups, disulphide groups, amino groups, alkylamino groups, hydroxyl groups, quaternary ammonium groups, ureido groups, amide groups, and ester groups, andX- is an anion derived from an inorganic or organic acid;A1 , R13, and R15 may form, together with the two nitrogen atoms to which they are attached, a piperazine ring;if Ai is chosen from linear or branched, saturated or unsaturated alkylene or hydroxyalkylene groups, Bi may be:where E’ is chosen from a) glycol residues of formula — 0 — Z — 0 — , where Z is chosen from linear or branched hydrocarbon-based groups and groups of the following formulas:where x and y, which may be identical or different, are chosen from integers ranging from 1 to 4, which represent a defined and unique degree of polymerization, and numbers ranging from 1 to 4, which represent an average degree of polymerization; b) bis-secondary diamine residue such as piperazine derivatives; c) bis-primary diamine residues of formula — NH — Y — NH — , wherein Y is chosen from linear or branched hydrocarbon-based groups and the divalentd) ureylene groups of formula — NH — CO — NH — .In one embodiment, X’ is an anion, for example, chloride or bromide.Non-limiting examples of such polymers include those comprising at least one repeating unit of formula (III):where R13, R14, R15, and Rw, which may be identical or different, are chosen from alkyl and hydroxyalkyl groups comprising from 1 to 4 carbon atoms, n and p, which may be identical or different, are integers ranging from 2 to 20, and X- is an anion derived from an inorganic or organic acid(11 ) Polyquaternary ammonium polymers comprising units of formula (IV):where R18, R19, R20, and R21 , which may be identical or different, are chosen from hydrogen, methyl groups, ethyl groups, propyl groups, [3-hydroxyethyl groups, [3-hydroxypropyl groups, — CH2CH2(OCH2CH2)POH groups, wherein p is chosen from integers ranging from 0 to 6, with the proviso that R18, R19, R20, and R21 are not simultaneously hydrogen; r and s, which may be identical or different, are chosen from integers ranging from 1 to 6; q is chosen from integers ranging from 0 to 34;X- is an anion such as a halide, andA is chosen from radicals of dihalides and — CH2 — CH2 — 0 — CH2 — CH2 — .(12) Quaternary polymers of vinlypyrrolidone and of vinylimidazole.

[0028] Other examples of suitable polycations include, but are not limited to, cationic proteins and cationic protein hydrolysates, polyalkyleneimines, such as polyethyleneimines, polymers comprising units chosen from vinylpyridine and vinylpyridinium units, condensates of polyamines and of epichlorohydrin, quaternary polyureylenes, and chitin derivatives.

[0029] In one particular embodiment, the polycation is selected from a poly(allylamine), polyethyleneimine, polydiallyldimethylammonium, poly (melamine-co-formaldehyde), polymelamine, polyetheramine, a copolymer of polymelamine, polyvinylpyridine, a copolymer of polyvinylpyridine and any combination thereof.

[0030] In still another embodiment, the polycation may be a co(polyamine). The (co)polyamine may be a homopolymer or copolymer with a plurality of amino groups. The amino group may be a primary, secondary, tertiary or quaternary amino group. The amino group may be present in a polymer backbone or a pendent group, if present, of the (co)polyamine.

[0031] Examples of (co)polyamines include, but are not limited to, chitosan, (co)polyallylamines, (co)polyvinylamines, (co)polyanilines,(co)polyvinylimidazoles, (co)polydimethylaminoethylenemethacrylates,(co)polyvinylpyridines such as (co)poly-1 -methyl-2-vinylpyridines, (co)polyimines such as (co) polyethyleneimines, (co)polypyridines such as (co)poly(quaternary pyridines), (co)polybiguanides such as (co)polyaminopropyl biguanides, (co)polylysines, (co)polyornithines, (co)polyarginines, (co)polyhistidines, aminodextrans, aminocelluloses, amino(co)polyvinylacetals, and salts thereof.

[0032] In some embodiments, the polyanion comprising a phosphate group is an inorganic phosphate. In other embodiments, the inorganic phosphate is selected from polysodium phosphate (PSP), disodium hydrogen phosphate, sodium dihydrogen phosphate, sodium phosphate, dihydrogen phosphate potassium, potassium dihydrogen phosphate, potassium phosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate ammonium phosphate, ammonium polyphosphate, sodium hexametaphosphate, sodium trimetaphosphate, sodium tripolyphosphate, sodium pyrophosphate,potassium tripolyphosphate, potassium pyrophosphate and any combination thereof.

[0033] The polyelectrolyte complex may be obtained by methods known to those skilled in the art. For example, in one embodiment, it involves preparing individual polyanion and polycation solutions, adjusting the pH of the solutions based on the pKa values of the polyanion and polycation, combining the polyanion and polycation solutions with vigorous mixing to form a precipitate and optionally washing the precipitate to expel any counterions to produce the polyelectrolyte complex solid. The polyelectrolyte complex may then be subsequently ground into a powder form.

[0034] In one embodiment, the polyanion solution and polycation solution can be prepared by dissolving the polyanion and the polycation in aqueous solutions, such as water. The pH’s for each of the polyanion and polycation solutions may be adjusted by adding a base, for example NaOH to the polyanion solution (pH=about 7-9) and an acid, for example, lactate, hydrochloric acid, phosphorous acid and / or ascorbic acid, to the polycation solution (pH=about 5-7). The amount of base and acid will depend on the polyanion and polycation as is known to the skilled person. The temperatures of each of the solutions may be between about 0°-100°C, or between about 10°-60°C, or at ambient temperature (about 15°- 25°C). The solutions can then be combined and the resulting mixture mixed vigorously during formation of the polyelectrolyte complex precipitate and then allowing the polyelectrolyte complex to settle. Following settlement, the polyelectrolyte complex may be washed with water and then ground into a fine powder, by milling or grinding, to produce a powder form of the polyelectrolyte complex.

[0035] In one embodiment, the polyelectrolyte complex of the present disclosure may be present in the flame retardant composite in an amount of between about 0.05-35 wt. % based on the total weight of the flame retardantcomposite. In another embodiment, the polyelectrolyte complex of the present disclosure may be present in the flame retardant composite in an amount of between about 1 -27.5 wt. %, or between about 2.5-25 wt. %, or between about 5- 22.5 wt. %, or between about 7.5-20 wt. %, or between about 10-18 wt. % or between about 12-16 wt. %.

[0036] According to one embodiment, the polymeric resins useful for the purposes of this disclosure are polymers of alpha-olefins, including, but not limited to, ethylene, propylene, isobutylene, butene-1 and copolymers thereof. Homopolymers and copolymers of polyolefins are commercially available in a wide range of molecular weights and densities, and in general all will be useful for forming the flame retardant composites of this disclosure.

[0037] In one particular embodiment, the polymeric resin is a polypropylene- based polymer. The polypropylene-based polymer may be a propylene homopolymer or a propylene alpha-olefin copolymer including random copolymers and (multi)block copolymers. In another particular embodiment, the copolymer is preferably a random copolymer. The copolymer may consist of at least 70 wt. % of propylene and up to 30 wt. % of a second alpha-olefin, based on the total weight of the copolymer. Preferably, the second alpha-olefin in the propylene-alpha-olefin copolymer is selected from the group of alpha-olefins having 2 or 4-10 carbon atoms, for example ethylene, 1 -butene, 1 -pentene, 4-methyl-1 -pentene, 1 -hexen, 1 -heptene or 1 -octene, and in one particular embodiment is preferably ethylene.

[0038] In some embodiments, the amount of the alpha-olefin in the propylene alpha-olefin copolymer is about 1-15 wt. %, or about 1-10 wt. %, or about 1-6 wt. %, or even about 1 -4 wt. %, based on the total weight of the copolymer.

[0039] In one particular embodiment, the propylene alpha-olefin copolymer is a propylene-ethylene random copolymer where the amount of ethylene is about 1 - 15 wt. %, or about 1 -10 wt. %, or about 1 -6 wt. %, or about 1 -4 wt. % based on the total weight of the copolymer.

[0040] In some embodiments, the melt flow index (MFI) of the polypropylene homopolymer or propylene alpha-olefin copolymer may be for example at least 0.1 dg / min, at least 0.5 dg / min, at least 1 dg / min, at least 5 dg / min, at least 10 dg / min, at least 20 dg / min. at least 30 dg / min or at least 40 dg / min, at least 50 dg / min, or at least 100 and / or at most 200 dg / min, at most 180 dg / min, at most 160 dg / min or at most 150 dg / min measured according to ISO1133 (2.16 kg / 230°C).

[0041] In still another embodiment, the polypropylene-based polymer may be a heterophasic propylene copolymer. Heterophasic propylene copolymers, also known as impact propylene copolymers or propylene block copolymers, are an important class of polymers due to their attractive combination of mechanical properties, such as impact strength over a wide temperature range and their low cost. These copolymers find a wide range of applications ranging from the consumer industry (for example packaging and housewares), the automotive industry to electrical applications.

[0042] Heterophasic propylene copolymers are generally prepared in one or more reactors, by polymerization of propylene in the presence of a catalyst and subsequent polymerization of a propylene-alpha-olefin mixture. The resulting polymeric materials are heterophasic, but the specific morphology usually depends on the preparation method and monomer ratios used.

[0043] The heterophasic propylene copolymers employed in the present disclosure can be produced using any conventional technique known to the skilled person, for example multistage process polymerization, such as bulk polymerization, gas phase polymerization, slurry polymerization, solution polymerization or any combinations thereof. Any conventional catalyst systems, for example, Ziegler-Natta or metallocene may be used. Such techniques and catalysts are described, for example, in W006 / 010414 and U.S. Pat. Nos. 4,399,054 and 4,472,524, the contents of which are incorporated herein byreference. Preferably, the heterophasic propylene copolymer is made using a Ziegler-Natta catalyst.

[0044] Thus, in one embodiment, the heterophasic propylene copolymer may be prepared by a process comprising: polymerizing propylene and optionally an alpha-olefin in the presence of a catalyst system to obtain the propylene-based matrix and subsequently polymerizing ethylene and alpha-olefin in the propylene- based matrix in the presence of a catalyst system to obtain the dispersed ethylene- alpha-olefin copolymer.

[0045] These steps are preferably performed in different reactors. The catalyst systems for the first step and for the second step may be different or the same.

[0046] One heterophasic propylene copolymer useful in the present disclosure consists of a propylene-based matrix and a dispersed ethylene-alpha-olefin copolymer. The propylene-based matrix typically forms the continuous phase in the heterophasic propylene copolymer. The amounts of the propylene-based matrix and the dispersed ethylene-alpha-olefin copolymer may be determined by13C-NMR spectroscopy, as is well known in the art.

[0047] The propylene-based polymer may be one type of heterophasic propylene copolymer or a mixture of different types of heterophasic propylene copolymers, e.g. a mixture of a first type of a heterophasic propylene copolymer and a second type of heterophasic propylene copolymer at any weight ratio, e.g., between about 1 :99-99: 1 , or between about 25:75-75:25, or between about 40:60- 60:40, or about 50:50.

[0048] In another embodiment, the heterophasic propylene copolymer consists of (a) a propylene-based matrix wherein the propylene-based matrix consists of a propylene homopolymer and / or a propylene-alpha-olefin copolymer consisting of at least about 70 wt. % of propylene and at most 30 wt. % of an alpha- olefin, based on the total weight of the propylene-based matrix and where thepropylene-based matrix is present in an amount of about 60-95 wt. %, with respect to the heterophasic propylene copolymer; and (b) a dispersed ethylene-alpha- olefin copolymer wherein the dispersed ethylene-alpha-olefin copolymer is present in an amount of about 5-40 wt. %, with respect to the heterophasic propylene copolymer and where the sum of the total amount of propylene-based matrix and total amount of the dispersed ethylene-alpha-olefin copolymer in the heterophasic propylene copolymer is 100 wt. % with respect to the heterophasic propylene copolymer.

[0049] Preferably, the alpha-olefin in the propylene-alpha-olefin copolymer is selected from the group of alpha-olefins having 2 or 4 to 10 carbon atoms, for example ethylene, 1 -butene, 1 -pentene, 4-methyl-1 -pentene, 1 -hexene, 1 -heptene or 1 -octene, and is preferably ethylene.

[0050] The melt flow index (MFI) of the propylene-based matrix (before the heterophasic propylene copolymer is mixed in), may be for example at least 0.1 dg / min, at least 0.2 dg / min, at least 0.3 dg / min, at least 0.5 dg / min, at least 1 dg / min, at least 1.5 dg / min, and / or for example at most 250 dg / min, at most 200 dg / min, at most 150 dg / min, at most 100 dg / min, at most 50 dg / min or at most 20 dg / min, measured according to ISO1133 (2.16 kg / 230°C). The MFI may be in the range of, for example, 0.1 to 250 dg / min, or from 0.2 to 200 dg / min, or from 0.3 to 150 dg / min, or from 0.5 to 100 dg / min, or from 1 to 50 dg / min or from 1.5 to 20 dg / min, or from 2 to 10 dg / min, measured according to ISO1133 (2.16 kg / 230°C).

[0051] The propylene-based matrix may be present in an amount of about 60- 95 wt. %, with respect to the heterophasic propylene coplymer. Preferably, the propylene-based matrix is present in an amount of about 60-80 wt. %, for example from about 65-75 wt. % and / or at most 78 wt. %, with respect to the heterophasic propylene copolymer.

[0052] The propylene-based matrix is preferably semi-crystalline, that is it is not 100% amorphous, nor is it 100% crystalline. For example, the propylene-based matrix is at least 40% crystalline, for example at least 50%, for example at least 60% crystalline and / or for example at most 80% crystalline, for example at most 70% crystalline. For example, the propylene-based matrix has a crystallinity of 60-70%. For purpose of this disclosure, the degree of crystallinity of the propylene-based matrix is measured using differential scanning calorimetry (DSC) according to ISO11357-1 and ISO11357-3 of 1997, using a scan rate of 10°C / min, a sample of 5 mg and the second heating curve using as a theoretical standard for a 100% crystalline material 207.1 J / g.

[0053] Besides the propylene-based matrix, the heterophasic propylene copolymer also comprises a dispersed ethylene-alpha-olefin copolymer. The dispersed ethylene-alpha-olefin copolymer is also referred to herein as the dispersed phase. The dispersed phase is embedded in the heterophasic propylene copolymer in a discontinuous form. The particle size of the dispersed phase is typically in the range of 0.05 to 2.0 microns, as may be determined by transmission electron microscopy (TEM). The amount of the dispersed ethylene- alpha-olefin copolymer in the heterophasic propylene copolymer may herein be sometimes referred as RC.

[0054] In some preferred heterophasic propylene copolymers, the amount of ethylene in the ethylene-alpha-olefin copolymer is in the range of about 20-65 wt. %, for example at least about 30 wt. %, at least about 35 wt. %, at least 40 wt. % or at least 45 wt. %, and / or at most 60 wt. % or at most 55 wt. %, with respect to the ethylene-alpha-copolymer. The amount of ethylene in the dispersed ethylene- alpha-olefin copolymer in the heterophasic propylene copolymer may herein be sometimes referred as RCC2.

[0055] The alpha-olefin in the ethylene-alpha-olefin copolymer is preferably chosen from the group of alpha-olefins having 3 to 8 carbon atoms. Examples of suitable alpha-olefins having 3 to 8 carbon atoms include, but are not limited to, propylene, 1 -butene, 1 -pentene, 4-methyl-1 -pentene, 1 -hexene, 1 -heptene and 1 -octene. More preferably, the alpha-olefin in the ethylene-alpha-olefin copolymer is chosen from the group of alpha-olefins having 3 to 4 carbon atoms and any mixture thereof, more preferably the alpha-olefin is propylene, in which case the ethylene-alpha-olefin copolymer is ethylene-propylene copolymer.

[0056] The MFI (or MFIEPR ) of the dispersed ethylene alpha-olefin copolymer (before the heterophasic propylene copolymer is mixed in) may be for example at least 0.001 dg / min, at least 0.01 dg / min, at least 0.1 dg / min, at least 0.3 dg / min, at least 0.7 dg / min, at least 1 dg / min, and / or for example at most 30 dg / min, at most 20 dg / min, at most 15 dg / min at most 10 dg / min, at most 5 dg / min or at most 3 dg / min. The MFIEPR may be in the range for example from 0.001 to 30 dg / min, or from 0.01 to 20 dg / min, or from 0.1 to 15 dg / min, or from 0.3 to 10 dg / min, or from 0.7 to 5 dg / min, or from 1 to 3 dg / min. MFIEPR is calculated taking into account the MFI of the propylene-based matrix (MFIpp) measured according to ISO1133 (2.16 kg / 230°C), the MFI of the heterophasic propylene copolymer (MFIheterophasic) measured according to ISO1133 (2.16 kg / 230°C) and the amount of the propylene- based matrix in the heterophasic propylene copolymer (matrix content) and the amount of the dispersed phase in the heterophasic propylene copolymer (rubber content (RC)) according to the following formula:MFIEPR = 10A((Log MFIheterophasic-matrix content*Log MFIpp) / rubber content).

[0057] In some embodiments, the dispersed ethylene-alpha-olefin copolymer is present in an amount of about 5-40 wt. %, with respect to the heterophasic propylene copolymer. In some preferred heterophasic propylene copolymers, the dispersed ethylene-alpha-olefin copolymer is present in an amount of at least about 10 wt. %, for example at least about 15 wt. % or at least about 17 wt. %, and / or at most about 35 wt. %, for example at most about 30 wt. % or at most about 25 wt. %, with respect to the heterophasic propylene copolymer.

[0058] In the heterophasic propylene copolymer, the sum of the total weight of the propylene-based matrix and the total weight of the dispersed ethylene-alpha-olefin copolymer is 100 wt. % with respect to the heterophasic propylene copolymer.

[0059] In some embodiments, the amount of ethylene in the heterophasic propylene copolymer (sometimes referred as TC2) is in the range of about 3-20 wt. %, with respect to the heterophasic propylene copolymer. For example, the amount of ethylene in the heterophasic propylene copolymer may be at least about 5 wt. % or at least about 7 wt. % and / or at most about 15 wt. % or at most about 13 wt. %.

[0060] The MFI of some preferred heterophasic propylene copolymers may be for example at least 0.1 dg / min, at least 0.5 dg / min, at least 1 dg / min, at least 5 dg / min, at least 10 dg / min or at least 15 dg / min and / or at most 100 dg / min, or at most 80 dg / min, or at most 50 dg / min or at most 40 dg / min, measured according to ISO1133 (2.16 kg / 230°C). The MFI of some preferred heterophasic propylene copolymers may be for example at least 0.1 dg / min, at least 0.2 dg / min, at least 0.3 dg / min, at least 0.5 dg / min, at least 1 dg / min at least 1.5 dg / min, and / or for example at most 8 dg / min or at most 5 dg / min, measured according to ISO1133 (2.16 kg / 230°C).

[0061] The values of the MFI of the propylene-based matrix (MFIpp) and the MFI of the dispersed ethylene-a-olefin elastomer (MFIEPR) mentioned herein are understood as the values before the heterophasic propylene copolymer is mixed with the polyelectrolyte complex and optional additives to obtain the flame retardant composite according to the present disclosure. The value of the MFI of the heterophasic propylene copolymer (MFIheterophasic) refers to the final MFI of the heterophasic propylene copolymer.

[0062] Preferably, in the heterophasic propylene copolymer according to the present disclosure,the alpha-olefin in the propylene-a-olefin copolymer is selected from the group of a-olefins having 2 or 4 to 10 carbon atoms and the alpha-olefin in the ethylene-alpha-olefin copolymer is selected from the group of alpha-olefins having 3 to 8 carbon atoms.

[0063] In some preferred embodiments, the propylene-based polymer is a mixture of heterophasic propylene copolymers, wherein the mixture comprises a heterophasic propylene copolymer having an MF I heterophasic of 10 to 50 dg / min measured according to ISO1133 (2.16 kg / 230°C), preferably wherein the amount of the dispersed ethylene-alpha-olefin copolymer is about 10-35 wt. %, with respect to the heterophasic propylene copolymer and preferably wherein the amount of ethylene in the ethylene-alpha-olefin copolymer is about 30-55 wt. %, with respect to the ethylene-alpha-olefin copolymer. Preferably, the mixture of the heterophasic propylene copolymers further comprises a heterophasic propylene copolymer having an MFIheterophasic of 0.1 to 8 dg / min measured according to ISO1133 (2.16 kg / 230°C), preferably wherein the amount of the dispersed ethylene-alpha-olefin copolymer is about 10-35 wt. %, with respect to the heterophasic propylene copolymer and preferably wherein the amount of ethylene in the ethylene-alpha-olefin copolymer is about 30-55 wt. %, with respect to the ethylene-alpha-olefin copolymer.

[0064] The propylene-based polymer may also be a combination of any of the propylene-based polymers mentioned above, for e.g., a mixture of a propylene homopolymer and a heterophasic propylene copolymer at a weight ratio of 1 :99- 99:1 or 50:50 or a mixture of a propylene homopolymer and a random propylene- ethylene copolymer at a weight ratio of between about 1 :99-99:1 , or about 25:75- 75:25, or about 40:60-60:40, or about 50:50.

[0065] Other polymeric resins useful in the present disclosure include, but are not limited to, polytrimethylene terephthalate, acrylonitrile butadiene styrene,acetal, cellulosics, Nylon, polycarbonate, polyester, like polyethylene terephthalate and polybutylene terephthalate, polyurethane, polyphenylene oxide / polyphenylene-ether, styrene acrylonitrile, styrene maleic anhydride, thermoplastic acrylic resin, thermoplastic elastomers, and ultra-high molecular weight polyethylene, polyetherimide (PEI), polyethyleneimine, polyvinyl chloride (PVC), epoxy polymers, polyether ether ketone, poly(phenylene oxide), polyether ketone ketone, polysulfone sulfonate, polyphenylene sulfide, sulfonates of polysulfones, thermoplastic elastomer, terephthalic acid elastomers, acrylonitrile butyldiene styrene, poly(methyl methacrylate), blend of polycarbonate and polybutylene terephthalate (PBT), blend of polycarbonate-acrylonitrile butadiene styrene (ABS), elastomeric block co-polymers, blend of polycarbonate- polyethylene terephthalate (PET), polyamide, polystyrene (PS), engineered thermoplastic compositions, or blends or copolymers thereof.

[0066] The amount of polymeric resin present in the flame retardant composite may be at least about 50 wt. %, or at least about 60 wt. %, or at least about 70 wt. %, or at least about 80 wt. %, or at least about 90 wt. % or at least about 95 wt. %, based on the total weight of the flame retardant composite. In another embodiment, the amount of polymeric resin present in the flame retardant composite may be from about 50-99 wt. %, or from about 55-97 wt. %, or from about 60-90 wt. %, based on the total weight of the flame retardant composite

[0067] The flame retardant composite according to the present disclosure may optionally comprise at least one optional additive. The amount of each of the optional additives may be present in an amount of up to about 30 wt. % of the total weight of the composite.

[0068] Examples of additives include, but are not limited to, nucleating agents, stabilizers, e.g. heat stabilizers, anti-oxidants, UV stabilizers; colorants, like pigments and dyes; clarifiers; surface tension modifiers; lubricants; mould-release agents;; flow improving agents; plasticizers; anti-static agents; externalelastomeric impact modifiers; blowing agents; inorganic fillers, such as glass fiber or talc and reinforcing agents; and / or components that enhance interfacial bonding between polymeric resin and filler, such as a maleated polypropylene, and mixtures thereof.

[0069] In some embodiments, the amount of the additives depends on their type and function and can typically be present in an amount of from about 0 to 50 wt. %, or from about 0.1 -40 wt.%, or from about 1 -20 wt. %, or from about 2-10 wt. % or from about 3-5 wt. %, based on the total weight of the composite.

[0070] The compounding of the polyelectrolyte complex with the polymer and optional additives may be accomplished by any of the conventional compounding processes including powder blending, Banbury mixing and melt extrusion. Those skilled in the art will recognize that the particular polyelectrolyte complex selected for use with a particular polymer resin will necessarily be stable at the processing temperature when melt processing is to be carried out.

[0071] Thus, according to one embodiment, a method for improving the flame retardancy of a polymeric resin includes the step of compounding the polyelectrolyte complex of the present disclosure and optional additives with the polymeric resin.

[0072] According to another embodiment, the flame retardant composite of the present disclosure may be obtained by a method including melt-mixing the polyelectrolyte, polymeric resin and optional additives.

[0073] Preferably, the flame retardant composite is made in a form that allows easy processing into a shaped article in a subsequent step, for example it is made in pellet or granular form. The composite can be a mixture of different particles or pellets like a blend of the heterophasic propylene copolymer and a masterbatch of additives. In some embodiments, the composite is in pellet or granular form as obtained by mixing all components in an apparatus like an extruder.

[0074] With melt-mixing it is meant that the polyelectrolyte complex and optional additives are mixed with the polymeric resin at a temperature that exceeds the melting point of the polymeric resin.

[0075] Melt-mixing may be done using techniques known to the skilled person, for example in an extruder. Generally, in the method of the present disclosure, melt-mixing is performed at a temperature in the range from about 150-350°C.

[0076] Suitable conditions for melt-mixing, such as temperature, pressure, amount of shear, screw speed and screw design when an extruder is used are known to the skilled person.

[0077] When using an extruder, a conventional extruder such as a twin-screw extruder may be used. The temperature can vary through the different zones of the extruder as required. For example, the temperature may vary from about 100°C in the feed zone to about 300°C at the die. Preferably, the temperature in the extruder varies from about 150-265°C. Likewise, the screw speed of the extruder may be varied as needed. Typical screw speed may range from about 100 rpm to about 600 rpm.

[0078] The flame retardant composite according to the present disclosure may be further processed by any conventional technique known in the art into an article. Suitable examples of processing techniques include injection moulding, injection blow moulding, injection stretch blow moulding, rotational moulding, compression moulding, extrusion, extrusion compression moulding, extrusion blow moulding, sheet extrusion, film extrusion, cast film extrusion, foam extrusion, foam injection moulding, thermoforming and thin-walled injection moulding.

[0079] Thus, the present disclosure further relates to an article comprising the flame retardant composite according to the present disclosure. In some embodiments, the article is in the form of a pellet, powder or molded part. In some embodiments, the article is an extrusion molded article, an injection molded article,a compression molded article, a rotational molded article, a blow molded article, an injection blow molded article, a thermoformed article, or solvent cast film Thus, the present disclosure relates to an article comprising the flame retardant composite according to the present disclosure, wherein the article is made by one of the processing techniques mentioned above. Injection moulding is widely used to produce articles such as, for example, caps and closures, battery covers pails, containers, external and internal parts in appliances, such as a printed circuit board holder, circuit breaker cover, drain pan in refrigerator and deflection coil of a TV, stadium seats, automotive exterior parts, such as bumpers, automotive interior parts, such as instrument panels, or automotive parts under the hood. Extrusion is for example widely used to produce articles, such as rods, sheets, films and pipes. Thin wall injection moulding may, for example, be used to make thin wall packaging.

[0080] The present disclosure is now elucidated by way of the following examples, without however being limited thereto.Examples

[0081] Example 1. Micro-cone calorimeter (FAA Micro Calorimeter) analysis per ASTM D7309 was done on a polypropylene copolymer (MFI 22 @ 230 °C and 2.16 kg) with and without an 18 wt. % loading of a polyelectrolyte complex prepared from polyvinyl amine and sodium hexametaphosphate. As shown in Figure 1 , incorporating the polyelectrolyte complex lowered the HR capacity and PHRR of the composite by about 15%, a 19% reduction in total HR and increased the temperature at PHRR by > 5°C. In addition, the polypropylene-polyelectrolyte complex composite rendered a dense char after combustion with minimal expansion to give superior char strength as compared to a polypropylene- intumescent flame retardant composite.

[0082] Example 2. A torch test was conducted on injection molded bars to compare the burning behavior of neat polypropylene vs. a polypropylene-polyelectrolyte complex (made from polyvinyl amine and sodium hexametaphosphate) composite. Standard 3-mmUL94 bars of neat polypropylene and polypropylene with 25 wt. % polyelectrolyte complex composite were prepared and subjected to > 10 seconds of burning with a butane micro-torch. The neat polypropylene sample had significant structural deterioration after fully igniting and produced flaming drips during the torch test. In comparison, the polypropylene-polyelectrolyte complex composite not only retained its original morphology with immediate charring, but it was observed to: exhibit self- extinguishing behavior; never fully ignited; and, did not produce any drips. FIG. 2 shows a polypropylene-polyelectrolyte complex UL94 bar (left) and a polypropylene-intumescent flame retardantUL94 bar (right) after being subjected to >10 seconds of burning. In general, no dripping or fracturing of the polypropylene-polyelectrolyte complexUL94 bar was observed even, and even after scraping away the black char, an in-tact inner core of polymer was recovered (FIG. 2, left) that was not observed in the polypropylene-intumescent flame retardanUtL94 bar which rendered a brittle char without any polymer core (FIG. 2, right).

[0083] While the foregoing is directed to embodiments of the present disclosure, other and further embodiments of the disclosure may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims

CLAIMS:

1. A flame retardant composite comprising a polymeric resin and a polyelectrolyte complex obtained by contacting a polycation comprising an amino group and a polyanion comprising a phosphate group, wherein the polyanion is an inorganic phosphate selected from polysodium phosphate (PSP), disodium hydrogen phosphate, sodium dihydrogen phosphate, sodium phosphate, dihydrogen phosphate potassium, potassium dihydrogen phosphate, potassium phosphate, diammonium hydrogen phosphate, ammonium dihydrogen phosphate, ammonium phosphate, sodium hexametaphosphate, and any combination thereof.

2. The flame retardant composite of claim 1 , wherein the polycation is selected from a poly(allylamine), polyvinyl amine, polyethyleneimine, polydiallyldimethylammonium, poly (melamine-co-formaldehyde)ny, polymelamine, polyetheramine, a copolymer of polymelamine, polyvinylpyridine, a copolymer of polyvinylpyridine and a combination thereof.

3. The flame retardant composite of claim 1 , further comprising one or more additives.

4. The flame retardant composite of claim 1 , wherein the polymeric resin comprises ethylene, propylene, isobutylene, butene-1 and copolymers thereof.

5. The flame retardant composite of claim 4, wherein the polymeric resin comprises a propylene homopolymer, a propylene alpha-olefin copolymer or a mixture thereof.

6. The flame retardant composite of claim 1 , wherein the polymeric resin comprises polytrimethylene terephthalate, acrylonitrile butadiene styrene, acetal, cellulosics, Nylon, polycarbonate, polyester, polyurethane, polyphenylene oxide / polyphenylene- ether, styrene acrylonitrile, styrene maleic anhydride, thermoplastic acrylic resin, thermoplastic elastomers, polyetherimide, polyethyleneimine, polyvinyl chloride (PVC), an epoxy polymer, polyether ether ketone, poly(phenylene oxide), polyether ketone ketone, polysulfone sulfonate, polyphenylene sulfide, a sulfonate of polysulfones, thermoplastic elastomer, a terephthaalic acid elastomer, acrylonitrileouiyioiene styrene, poly(methyl methacrylate), a blend of polycarbonate and polybutylene terephthalate (PBT), a blend of polycarbonate-acrylonitrile butadiene styrene (ABS), an elastomeric block co-polymer, a blend of polycarbonate- polyethylene terephthalate (PET), polyamide, polystyrene (PS), an engineered thermoplastic composition or a mixture thereof.

7. A method for improving the flame retardancy of a polymeric resin comprising compounding a polyelectrolyte complex and optionally one or more additives with the polymeric resin wherein the polyelectrolyte complex is obtained by contacting a polycation comprising an amino group and a polyanion comprising a phosphate group.

8. The method of claim 7, wherein the compounding comprises melt extrusion.

9. The method of claim 8, wherein the melt extrusion is performed in an extruder.

10. The method of claim 7, wherein the compounding of the polyelectrolyte complex with the polymeric resin is performed at a temperature of 150°C to 350°C.

11. An article comprising the flame retardant composite of claim 1 .

12. The article of claim 11 , wherein the article is in the form of a pellet, a powder, or a molded part.

13. The article of claim 12, wherein the article is an extrusion molded article, an injection molded article, a compression molded article, a rotational molded article, a blow molded article, an injection blow molded article, a thermoformed article, or solvent cast film.

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