MXPA99001531A - Composition of flame retarder carbonate polymer with better hydrolytic stability - Google Patents

Abstract

A thermoplastic resin composition, which contains a thermoplastic resin comprising at least one aromatic polycarbonate resin and a flame retardant amount of an organophosphorus flame retardant compound, wherein any acid initially present in the compound and any acid generating impurity initially present in the compound, they do not exceed a level at which the combined amount of any of these acids, and any acid that can be generated under hydrolytic conditions from said acid-generating impurities, is equivalent to a titratable acid level of less than about 1.0 milligram of potassium hydroxide per gram of the organophosphorus compound

Description

COMPOSITION OF FLAME RETARDANT CARBONATE POLYMER WITH IMPROVED HYDROLYTIC STABILITY FIELD OF THE INVENTION This invention relates to a flame retardant polymer composition having improved hydrolytic stability.

BACKGROUND OF THE INVENTION It is known to use organophosphorus flame retardants to impart flame retardant properties to thermoplastic resins. For example, the US patent. No. 5,204,394 discloses thermoplastic resin compositions containing an aromatic polycarbonate resin, a graft copolymer containing styrene and an oligomeric organophosphorus flame retardant. A thermoplastic resin composition which exhibits suitable flame retardant properties and which maintains a general balance of physical properties under hydrolytic conditions is desired.

BRIEF DESCRIPTION OF THE INVENTION In a first embodiment, the present invention is directed to a thermoplastic flame retardant resin composition comprising: (a) one or more thermoplastic resins comprising at least one aromatic carbonate resin; and (b) a flame retardant amount of a flame retardant organic compound, wherein any acid initially present in the compound, and any acid generating impurity initially present in the compound, do not exceed a level at which the amount The combination of any of these acids and any acid that can be generated under hydrolytic conditions from any of these acid generating impurities is equivalent to a titratable acid level of less than about 1.0 ml of potassium hydroxide per gram of the compound of organophosphorus In a second embodiment, the present invention is directed to a process for preparing a thermoplastic flame retardant resin composition, which comprises combining a thermoplastic resin, this resin comprises at least one aromatic polycarbonate resin, and a retardant amount of 11ama. of an organophosphorus flame retardant compound as described above. As used herein, the term "hydrolytic conditions" means conditions that favor the hydrolysis of any acid and any acid generating impurity that are present, and the term "equivalent" means chemically equivalent in the sense of being neutralized by the same number of molar equivalents of KOH. The hydrolytic conditions include the conditions under which the composition of the present invention is exposed to moisture, typically in the form of high ambient humidity such as, for example, a relative humidity of more than about 50%. The hydrolytic conditions become more severe each time the temperature and humidity increase, and the hydrolytic stability of the composition of the present invention can be predicted based on accelerated aging tests carried out at high heat and humidity, such as, for example, 100 ° C and 100% relative humidity. The composition of the present invention exhibits improved hydrolytic stability. As used herein, the term "hydrolytic stability" means a tendency of the composition not to undergo any change in molecular weight of the components of the thermoplastic resin of the composition, particularly the polycarbonate resin, when the resin composition is exposed to hydrolytic conditions. < \ DETAILED DESCRIPTION OF THE INVENTION In a preferred embodiment, the composition of the present invention comprises 75 to 98 parts by weight ("pep"), preferably 80 to 95 pbw, and preferably 85 to 92 pbw, of the thermoplastic resin, and 2 pbw. at 25 pbw, preferably 5 to 20 pbw and most preferably 8 to 15 pbw of the organophosphoric compound, each based on 100 pbw of the combined amount of thermoplastic resin and organophosphorus compound. Suitable aromatic carbonate resins include aromatic polycarbonate resins and aromatic copolyester-carbonate resins. Aromatic polycarbonate resins are known compounds, as well as the properties and methods for manufacturing polycarbonate resins are also known. Typically, these are prepared by reacting a dihydric phenol with a carbonate precursor, such as a phosgene, a haloformate or a carbonate ester and generally in the presence of an acid receptor and a molecular weight regulator. Generally speaking, said carbonate polymers can be typified as having recurring structural units of the formula (I): 0 O (I) wherein A is a divalent aromatic radical of the dihydric phenol used in the reaction of the polymer. The dihydric phenol which can be used to provide said aromatic carbonate polymers are the mononuclear or polynuclear aromatic compounds which contain as functional groups two hydroxyl radicals, each of which can be directly linked to a carbon atom of an aromatic nucleus. Typical dihydric phenols are: 2,2-bis (4-hydroxyphenyl) propane; hydroquinone; resorcinol; 2,2-bis (4-hydroxyphenyl) -ethane; 2, 4 '- (dihydroxydiphenyl) methane; bis (2-hydroxyphenyl) methane; bis (4-hydroxyphenyl) methane; 1,1-bis (4-hydroxyphenyl) -3,3,5-trimethylcyclohexane; fluorenone bisphenol, 1,1-bis (4-hydroxyphenyl) ethane; 3,3-bis (4-hydroxyphenyl) pentane; 2, 2'-dihydroxydiphenyl; 2,6-dihydroxynaphthalene; bis (4-hydroxydiphenyl) sulfone; bis (3,5-diethyl-4-hydroxyphenyl) sulfone; 2, 2-bis (3, 5-dibromo-4-hydroxyphenyl) propane; 2, 2-bis (3,5-dimethyl-4-hydroxyphenyl) propane; 2, 4 '-dihydroxydiphenylsulfone; 5'-chloro-2, '-dihydroxydiphenylsulfone; ether 4, -dihydroxydiphenyl; ether 4, 4 '-dihydroxy-3, 3'-dichlorodiphenyl, spirobiindane bisphenol and the like. These aromatic polycarbonates can be manufactured by known methods, such as, for example, and as mentioned above, by reacting a dihydric phenol with a carbonate precursor, such as a phosgene, according to methods established in the literature including the process of fusion polymerization. In general, in the melt polymerization process, a diphenyl carbonate is reacted with a bisphenol. The carbonate precursor used to prepare the polycarbonate of this invention can be a carbonyl halide or a haloformate. Carbonyl halides that can be used herein are, for example, carbonyl bromide, carbonyl chloride, etc .; or mixtures thereof. Haloformates suitable for use herein include bishaloformates of dihydric phenols (Bisphenol A bischloroformates, hydroquinone, etc.) or glycols (ethylene glycol bishaloformates, neopentyl glycol, polyethylene glycol, etc.). Although other carbonate precursors will occur to those skilled in the art, carbonyl chloride, also known as phosgene, is preferred. The reaction described above is preferably known as an interfacial reaction between the dihydric compound and a carbonyl chloride such as a phosgene. Another process for preparing the aromatic polycarbonate employed in this invention is the transesterification process which includes the transesterification of an aromatic dihydroxy compound and a diester carbonate. This process is known as the melt polymerization process. In the practice of this invention, the process for producing the aromatic polycarbonate is not critical. As used herein, the term "aromatic carbonate polymer" will mean and include any of the aromatic polycarbonates, mixtures thereof with another polymer, copolymers thereof, copolyester carbonates and mixtures thereof. It is also possible to employ two or more different dihydric phenols or a copolymer of a dihydric phenol with a glycol or with a hydroxy or acidic polyester, or with a dibasic acid or hydroxy acid in case it is desired to use a copolymer or interpolymer of carbonate instead of a homopolymer in the preparation of the polycarbonate blends of the invention. Polyarylates and polyester-carbonate resins or mixtures thereof can also be used. Branched polycarbonates are also useful and are suitably described in the literature. Likewise, linear polycarbonate blends and a branched polycarbonate can also be used herein. Moreover, mixtures of any of the above materials can be employed in the practice of this invention to provide the aromatic polycarbonate component of the carbonate polymer composition. In any case, the aromatic polycarbonate which is preferred to be used in the practice of the present invention is a homopolymer, for example, a homopolymer derived from commercially available 2,2-bis (4-hydroxyphenyl) propane (bisphenol-A) and phosgene. Aromatic carbonate polymers also suitable for use in this invention include polyester carbonates, also known as copolyester-polycarbonates, i.e., resins containing, in addition to recurring polycarbonate chain units of the formula (II): 0 O D O: ID wherein D is a divalent aromatic radical of the dihydric phenol used in the polymerization reaction, repeating or recurring carboxylate units, for example of the formula (III): 0 or O or D (III) wherein D is as defined above and T is an aromatic radical such as phenylene, naphthylene, biphenylene, substituted phenylene and the like; a divalent aliphatic-aromatic hydrocarbon radical such as an alkaryl or alkaryl radical (sic); or two or more aromatic groups connected through aromatic linkages such as are known in the art. The copolyester-polycarbonate resins are also prepared by the interfacial polymerization technique, well known to those skilled in the art (see, for example, U.S. Patent No. 3,169,121 and 4,487,896). In general, any dicarboxylic acid conventionally used in the preparation of linear polyesters can be used in the preparation of the copolyester-carbonate resins of the present invention. In general, the dicarboxylic acids that can be used include the aliphatic dicarboxylic acids; the aromatic dicarboxylic acids and the aliphatic-aromatic dicarboxylic acids. These acids are well known and are described, for example, in the US patent. No. 3,169,121 which is incorporated herein by way of reference. Mixtures of dicarboxylic acids can be used. Therefore, when the term "dicarboxylic acid" is used herein, it is to be understood that this term includes mixtures of two or more dicarboxylic acids. Very preferred as the aromatic dicarboxylic acids are isophthalic acid, terephthalic acid and mixtures thereof. A particularly useful difunctional carboxylic acid comprises a mixture of isophthalic acid and terephthalic acid wherein the weight ratio of terephthalic acid to isophthalic acid ranges from about 10: 1 to about 0.2: 9: 8. Instead of using the dicarboxylic acid per se, it is possible, and sometimes even preferred, to employ the reactive derivatives of said acid. Examples of these reactive derivatives are the acid halides. Acid halides are acid dichlorides and acid dibromides. Thus, for example, instead of using isophthalic acid, terephthalic acid or mixtures thereof, it is possible to employ isophthaloyl dichloride, terephthaloyl dichloride and mixtures thereof. The aromatic polycarbonate resins can be linear or branched and will generally have a weight average molecular weight of from about 10,000 to about 200,000 grams per mole ("g / mol"), preferably from about 20,000 to about 100,000 g / mol, measured by gel permeation chromatography. Said resins typically exhibit an intrinsic viscosity, determined in chloroform at 25 ° C, from about 0.3 to about 1.5 deciliters per gram (dl / gm), preferably about 0.45 to about 1.0 dl / gm. The branched polycarbonates can be prepared by adding a branching agent during the polymerization. These branching agents are well known and can comprise polyfunctional organic compounds containing at least three functional groups which may be hydroxyl, carboxyl, carboxylic anhydride, haloformyl and mixtures thereof. Specific examples include trimellitic acid, trimellitic anhydride, trimellitic trichloride, tris-p-hydroxyphenylethane, isatin-bis-phenol, tris-phenol TC (1,3,5-tris ((p-hydroxyphenyl) isopropyl) benzene), tris-phenol PA (4 (1, 1-bis (p-hydroxyphenyl) -ethyl) alpha, alpha-dimethylbenzyl) -phenol), 4-chloroformylphthalic anhydride, trimesic acid and benzophenone tetracarboxylic acid. The branching agent can be added at a level of about 0.05-2.0 weight percent. All types of polycarbonate end groups are contemplated as being within the scope of the present invention with respect to the polycarbonate component of a carbonate polymer composition. The thermoplastic resin component of the composition of the present invention may optionally further comprise one or more thermoplastic resins in addition to the aromatic carbonate resin, such as, for example, polyphenylene ether resins, aromatic vinyl graft copolymer resins, styrenic resins, polyester resins, polyamide resins, polyesteramide resins, polysulfone resins, polyimide resins and polyetherimide resins. In a preferred embodiment, the composition of the present invention comprises an aromatic polycarbonate resin and an aromatic vinyl graft copolymer. In a preferred embodiment, the thermoplastic resin component of the composition of the present invention comprises, based on 100 pbw of the thermoplastic resin component, 30 to 99 pbw, most preferably 50 to 95 pbw and still more preferably 60 pb 90 pep of an aromatic polycarbonate resin, and from 1 to 70 pbw, most preferably from 50 to 95 pbw and still more preferably from 10 to 40 pbw of an aromatic vinyl graft copolymer. Suitable aromatic vinyl graft copolymers comprise (i) a rubber modified aromatic monovinylidene graft copolymer component and (ii) a non-grafted rigid copolymer component, and are generally prepared by graft polymerization of a mixture of a monomer of monovinylidene aromatics and one or more comonomers in the presence of one or more polymeric substrates. Depending on the amount of rubber present, a separate matrix or continuous rigid phase of a rigid ungrafted (co) oligomer can be obtained simultaneously with the rubber modified aromatic monovinylidene graft polymer. The resins can also be produced by combining a rigid aromatic monovinylidene copolymer with one or more rubber modified aromatic monovinylidene graft copolymers. Typically, the rubber-modified resins comprise the rubber modified graft copolymer at a level of 5 to 100 weight percent, based on the total weight of the resin, preferably 10 to 90 weight% thereof and most preferably from 30 to 80% by weight thereof. The resin modified with rubber comprises the rigid non-grafted polymer at a level of 95 to 0% by weight; based on the total weight of the resin, preferably 90 to 10% by weight thereof and most preferably 70 to 20% by weight thereof. The aromatic monovinylidene monomers that may be employed include styrene, alpha-methylstyrene, haloestyrenes, ie, dibromostyrene, mono- or dialkyl, alkoxy or hydroxyl substitution groups in the nuclear ring of the monovinylidene aromatic monomer, i.e. vinyltoluene, vinylxylene, butyl styrene, parahydroxystyrene or methoxystyrene or mixtures thereof. The aromatic monovinylidene monomers used are described generically by the following formula (IV): wherein each R ^ _ is independently H, C ^ -Cg, cycloalkyl, aryl, alkaryl, aralkyl, alkoxy, aryloxy or halogen alkyl, for example, such as bromine and chlorine, and R2 is selected from the group consisting of H , C ^ -Cg alkyl and halogen. As used herein, the annotation "(Cx-Cy)" in reference to an organic portion means that the organic portion contains x carbons and carbons. Examples of substituted aromatic vinyl compounds include styrene, 4-methylstyrene, 3,5-diethylstyrene, 4-n-propylstyrene, alpha-methylstyrene, alpha-methylvinyltoluene, alpha-chlorostyrene, alpha-bromostyrene, dichlorostyrene, dibromostyrene, tetrachlorostyrene, mixtures of the same and similar. The aromatic monovinylidene monomers that are preferred to use are styrene and / or alpha-methylstyrene. Comonomers which can be used with the monovinylidene aromatic monomer include acrylonitrile, methacrylonitrile, acrylate substituted with alkyl or aryl of Ci-Cg, methacrylate substituted with alkyl, aryl or halogenaryl of C ^ -Cg, acrylic acid, methacrylic acid, itaconic acid, N-substituted acrylamide, acrylamide or methacrylamide, maleic anhydride, maleimide, maleimide substituted with N-alkyl, aryl or haloaryl, glycidyl (meth) acrylates, hydroxyalkyl (meth) acrylates or mixtures thereof. The esters of acrylonitrile, substituted acrylonitrile or acrylic acid are described generically by the following formula (V): wherein R 3 is H or C 4 -Cg alkyl and R 4 is selected from the group consisting of cyano and C 1 -C 6 alkoxycarbonyl. Examples of such monomers include acrylonitrile, ethacrylonitrile, methacrylonitrile, alpha-chloroacrylonitrile, alpha-bromoacrylonitrile, methyl acrylate, methyl methacrylate, ethyl acrylate, butyl acrylate, propyl acrylate, isopropyl acrylate, and mixtures thereof. The preferred monomer is acrylonitrile and the acrylic acid esters which are preferred are ethyl acrylate and methyl methacrylate. It is also preferred that the acrylic acid esters, when included, are used in combination with styrene or acrylonitrile. The rubber-modified graft copolymer preferably comprises (i) the rubber substrate and (ii) a portion of a rigid polymeric superstrate grafted to the rubber substrate. The rubber substrate is preferably present in the graft copolymer at a level of 5 to 80% by weight, based on the total weight of the graft copolymer, most preferably 10 to 70% by weight thereof. The rigid superstrate is preferably present at a level of 95 to 20% by weight, based on the total weight of the graft copolymer, and most preferably 90 to 30% by weight thereof. Examples of rubberized polymers for the substrate include: conjugated dienes, copolymers of a diene with styrene, acrylonitrile, methacrylonitrile or CI-CQ alkyl acrylate, which contain at least 50% (preferably at least 65% by weight) of conjugated dienes , polyisoprene or mixtures thereof; olefin rubbers, i.e., ethylene-propylene copolymers (EPR) or ethylene-propylene non-conjugated diene copolymers (EPDM); silicone rubbers or homopolymers or copolymers of Ci-Cg alkyl acrylate with butadiene and / or styrene. The acrylic polymer may also contain up to 5% of one or more polyfunctional crosslinking agents such as alkylene diol methylene acrylates, alkylenetriol tri (meth) acrylates, polyester di (meth) acrylates, divinylbenzene, trivinylbenzene, butadiene, isoprene. and optionally gradable monomers such as triallyl cyanurate, triallyl isocyanurate, allyl (meth) acrylate, diallyl maleate, diallyl fumarate, diallyl adipate, triallyl citric acid esters or mixtures of these agents. The diene rubbers can preferably be polybutadiene, polyisoprene and butadiene copolymers with up to 35% by weight C 1 -Cg alkyl acrylate, which are produced by aqueous radical emulsion polymerization. The acrylate rubbers can be particulate and entangled emulsion copolymers of substantially C ^ -Cg alkyl acrylate., in particular C alqu-Cg alkyl acrylate, optionally combined with up to 15% by weight of comonomers such as styrene, methylmethacrylate, butadiene, vinylmethyl ether or acrylonitrile and optionally up to 5% by weight of a polyfunctional crosslinking comonomer, for example, divinylbenzene, glycolbis-acrylates, bisacrylamides, triallyl ester of phosphoric acid, triallyl ester of citric acid, allyl esters or acrylic acid or methacrylic acid, triallylcyanurate, triallylisocyanurate. Also suitable are mixtures of diene and alkyl acrylate rubbers and rubber having a so-called core / shell structure, for example a diene rubber core and an acrylate shell or vice versa. The specific conjugated diene monomers that are commonly used to prepare the rubber substrate of the graft polymer are generically described by the following formula (VI) R5 R ^ CH CH C / \ * 5 (vi; wherein each R5 is independently H, alkyl of C] _-Cg, chlorine or bromine. Examples of dienes that can be used are butadiene, isopropene, 1,3-heptadiene, il-1,3-pentadiene, 2,3-dimethylbutadiene, 2-ethyl-1,3-pentadiene, 1,3- and 2,4 -hexadienes, chlorinated and bromo substituted butadienes such as dichlorobutadiene, bromobutadiene, dibromobutadiene, mixtures thereof and the like. A conjugated diene that is preferred is 1,3-butadiene. The substrate polymer, as mentioned, is preferably a conjugated diene polymer such as polybutadiene or polyisoprene, or a copolymer, such as butadiene-styrene, butadiene-acrylonitrile, or the like. The portion of the polymerized substrate substrate must exhibit a glass transition temperature (Tg) of less than about 0 ° C. Mixtures of one or more of the above-described rubbery polymers may also be used to prepare monovinylidene aromatic graft polymers, or mixtures of one or more rubber-modified monovinylidene aromatic graft polymers described herein. In addition, the rubber may comprise a block or random copolymer. The particle size of the rubber used in this invention measured by simple light transmission methods or capillary hydrodynamic chromatography (CHDF) can be described as a weight average particle size of 0.05 to 1.2 microns, preferably 0.2 to 0.8 microns, for crystalline networks emulsion polymerized rubber bases, or from 0.5 to 10 microns, preferably 0.6 to 1.5 microns, for bulk polymerized rubber substrates which also include graft monomer occlusions. The rubber substrate is preferably a moderately entangled particulate diene or an alkyl acrylate rubber, and preferably has a gel content of more than 70%. Preferred graft superstrates include copolymers of styrene and acrylonitrile, copolymers of alpha-methylstyrene and acrylonitrile and polymers or copolymers of methylmethacrylate with up to 50% by weight of Ci-C, acrylonitrile or styrene alkyl acrylates. Specific examples of aromatic monovinylidene graft copolymers include but are not limited to the following: acrylonitrile-butadiene-styrene (ABS), acrylonitrile-styrene-butylacrylate (ASA), methylmethacrylate-acrylonitrile-butadiene-styrene (MABS), acrylonitrile-ethylene -propylene-non-conjugated diene-styrene (AES). Rigid non-grafted polymers (typically rubber-free) are thermoplastic resins polymers of styrene, alpha-methylstyrene, styrenes substituted in the core such as para-methylstyrene, methylacrylate, methylmethacrylate, acrylonitrile, methacrylonitrile, maleic anhydride, N-substituted maleimide , vinyl acetate or mixtures thereof. Preferred are styrene / acrylonitrile, alpha-methylstyrene / acrylonitrile and methylmethacrylate / acrylonitrile copolymers. Ungrafted rigid copolymers are known and can be prepared by radical polymerization, in particular by emulsion, suspension, solution or bulk polymerization. They preferably have number average molecular weights of 20,000 to 200,000 g / mol and limiting viscosity numbers of 20 to 110 ml / g (determined in dimethylformamide at 25 ° C). The number average molecular weight of the rigid grafted superstrate of the monovinylidene aromatic resin is designed to be in the range of 20,000 to 350,000 g / mol. The ratio of aromatic monovinylidene monomer to the second and optionally third monomer may be in the range of 90/10 to 50/50, preferably 80/20 to 60/40. The third monomer can optionally replace 0 to 50 percent of one or both of the first and second monomers. These rubber modified aromatic monovinylidene graft polymers can be polymerized either by mass polymerization, emulsion, suspension, solution or combined procedures such as bulk suspension, bulk emulsion, bulk solution or other techniques well known in the art. Moreover, these rubber modified aromatic monovinylidene graft copolymers can be produced by continuous, semi-intermittent or intermittent processes. In a preferred embodiment, the organophosphorus compound comprises one or more compounds according to structural formula (VII): Rg-- (O) • (0) d -] n - R9 'wherein Rg, R7, Rg and R9 are each independently aryl, optionally substituted with halogen or C-C alkyl, X is arylene, optionally substituted with halogen or C ^ -Cg alkyl, a, b, c and d are each one independently 0 or 1, and n is an integer from 0 to 5, most preferably from 1 to 5. As used herein, the term "aryl" means a monovalent radical containing one or more aromatic rings per radical, which may be optionally substituted on the aromatic ring (s) with one or more alkyl groups, each preferably being C ^ -Cg alkyl and which, in case the radical contains two or more rings, can be fused rings. As used herein, the term "arylene" means a divalent radical containing one or more aromatic rings per radical, which may be optionally substituted on one or more aromatic rings with one or more alkyl groups, each preferably being C ^ alkyl. - CQ, and in which, in case the divalent radical contains two or more rings, the rings can be fused or they can be bound by non-aromatic bonds, such as, for example, an alkylene or alkylidene, and any of them can to be substituted at one or more sites of the aromatic ring with a halogen group or an alkyl group of C ^ -Cg. In a preferred embodiment, the organophosphorus compound comprises a mixture of oligomers of organophosphorus compounds according to formula (8), wherein n for each oligomer is an integer from 1 to 5 and the mixture has an average n value of more than 1. less than 5, most preferably more than 1 to less than 3, still more preferably more than 1 to less than 2. In a highly preferred embodiment, the organophosphorus compound comprises one or more resorcinol diphosphate ("RDP") esters according to the formula (8), wherein Rg, 7 R-8 Y ^ 9 are a-da one phenyl, a, b, c and d are each 1, X is 1,3-phenylene and n is an integer of 1 5. Most preferably, the organophosphorus compound comprises a mixture of RDP oligomers, wherein n for each oligomer is an integer from 1 to 5 and the mixture has an average n value from more than 1 to less than 5, very preferably from more than 1 to less than 3, still more preferably from more than 1 to less than 2. In a mo Further preferred, the organophosphorus compound comprises one or more bisphenol A diphosphate esters ("BPA-DP") according to formula (8), wherein Rg, R7, Rg and R9 are each phenyl, a, b, c and d are each 1, and X is a divalent aromatic radical of the structural formula (VIII): CH3 CH3 (HIV) and n is an integer from 1 to 5. Most preferably, the organophosphorus compound comprises a mixture of BPA-DP oligomers, wherein n for each oligomer is an integer from 1 to 5 and the mixture has an average n value of more than 1. less than 5, most preferably more than 1 to less than 3, and still more preferably more than 1 to less than 2. In another preferred embodiment, the organophosphorus compound component of the composition of the present invention comprises a mixture of about 1 to about 99% by weight of one or more BPA-DP esters, and about 1 to about 99% by weight of one or more RDP esters. It has been found that acid species and / or acid precursors, which, under conditions of high heat and humidity lead to in situ formation of acid species, are typically present as impurities in the organophosphorus compounds described above. Such impurities can originate from sources such as, for example, catalyst residues, unreacted starting materials such as, for example, phosphoryl halides or phosphoric acid derivatives, or from non-stable phosphate esters of decomposition products. It has also been discovered that the use of an organophosphoric compound having a high level of said acid species and / or said acid precursors as a flame retardant additive in a thermoplastic resin composition, compromises the hydrolytic stability of the thermoplastic resin composition. These acid species can be titratable species and / or acid generating species that are not titratable but determinable by alternative analytical methods. In a preferred embodiment, the organophosphorus compound is characterized by high purity, such that any acid or acid generating impurity present in the compound, does not exceed a level at which the combined amount of any acid initially present in the compound and any acid that can be generated in situ under hydrolytic conditions from any acid generating impurity present in the compound, is equivalent to a titratable acid level of less than about 1.0 milligram ("mg"), preferably from 0 to about 0.5 mg and preferably from 0 to about 0.15 mg of potassium hydroxide per gram of the organophosphorus compound. At a lower level of acid and acid generating impurities present in the organophosphate flame retardant component of the thermoplastic resin composition of the present invention, the hydrolytic stability of the thermoplastic resin composition will be better. In a preferred embodiment, the organophosphorus compound exhibits an acid level that is neutralizable by a titration addition of 0 to the equivalent of about 1.0 mg, most preferably from 0 to about 0.5 mg, even most preferably from 0 to about 0.1 mg, of potassium hydroxide ("KOH") per gram of organophosphorus compound. The acid level of the organophosphorus compound is measured by dissolving a sample of the organophosphorus compound in isopropanol and then titrating the resulting solution with a 0.1 N aqueous solution of KOH to a bromophenol blue endpoint. In a highly preferred embodiment, the organophosphorus compound has a hydrolyzable chlorine content of from 0 to 100 parts per million ("ppm"), preferably from 0 to 50 ppm, and preferably from 0 to 20 ppm, based on the weight of the compound organophosphoric The chlorine content of the organophosphorus compound is measured by conventional gas or liquid chromatographic techniques. In a highly preferred embodiment, the organophosphorus compound has an alkenylphenyl diphenyl phosphate content of from 0 to 2000 ppm, preferably from 0 to 1000 ppm, and preferably from 0 to 500 ppm, based on the weight of the organophosphorus compound. Alkenylphenyl diphenyl phosphates include for example isopropyl phenyl diphenyl phosphate and isobutenyl phenyl diphenyl phosphate. The content of alkenylphenyl defenylphosphate of the organophosphorus compound is measured by conventional chromatographic techniques, preferably by means of reverse phase high pressure liquid chromatography. In a highly preferred embodiment, the organophosphorus compound has a magnesium content of from 0 to 1000 ppm, preferably from 0 to 500 ppm, and preferably from 0 to 250 ppm, based on the weight of the organophosphorus compound. The magnesium content of the organophosphorus compound is measured by conventional atomic absorption techniques. In a preferred embodiment, the composition of the present invention includes a fluoropolymer, in an amount typically from 0.01 to 0.5 pb of fluoropolymer per 100 pbw of the thermoplastic resin composition, which is effective to provide anti-drip properties to the resin composition. Suitable fluoropolymers and methods for making such fluoropolymers are known, for example, from the US patents. Nos. 3,671,487, 3,723,373 and 3,383,092. Suitable fluoropolymers include homopolymers and copolymers comprising structural units derived from one or more fluorinated olefin monomers. The term "fluorinated olefin monomer" means an olefin monomer that includes at least one fluorine atom substituent. Suitable fluorinated olefin monomers include, for example, fluoroethylenes such as, for example, CF = CF2, CHF = CF2, CH2 = CF2, CH = CHF, CC1F = CF2, CC12 = CF2, CClF = CClF, CHF = CC12, CH2 = CC1F and CC12 = CC1F and fluoropropylenes such as for example CF3CF = CF2, CF3CF = CHF, CF3CH = CF2, CF3CH = CH2, CF3CF = CHF, CHF2CH = CHF and CF3CH = CH2. In a preferred embodiment, the fluorinated olefin monomer is one or more of tetrafluoroethylene (CF2 = CF2), chlorotrichloroethylene (CC1F = CF2), vinylidene fluoride (CH2 = CF2) and hexafluoropropylene (CF2 = CFCF3). Suitable fluorinated olefin homopolymers include, for example, poly (tetrafluoroethylene) and poly (hexafluoroethylene). Suitable fluorinated olefin copolymers include copolymers comprising structural units derived from two or more fluorinated olefin copolymers such as for example poly (tetrafluoroethylene-hexafluoroethylene) and copolymers comprising structural units derived from one or more fluorinated monomers and one or more monoethylenically monomers non-fluorinated unsaturates which are copolymerizable with the fluorinated monomers such as for example poly (tetrafluoroethylene-ethylene-propylene) copolymers. The non-fluorinated monoethylenically unsaturated monomers include, for example, olefin monomers such as, for example, ethylene and propylenebutene.; acrylate monomers such as for example methyl methacrylate and butylacrylate; vinyl ethers such as, for example, cyclohexyl vinyl ether, ethyl vinyl ether, n-butyl vinyl ether; vinyl esters such as, for example, vinyl acetate and vinyl versatate. In a preferred embodiment, the fluoropolymer particles range in size from 50 to 500 nm, as measured by electron microscopy. In a highly preferred embodiment, the fluoropolymer is a poly (tetrafluoroethylene) homopolymer ("PTFE"). Since the direct incorporation of a fluoropolymer in a thermoplastic resin composition tends to be difficult, it is preferred that the fluoropolymer be pre-mixed in a certain way with a second polymer such as, for example, an aromatic polycarbonate resin or a styrene-resin. Acrylonitrile Methods for making suitable premixes are known. For example, an aqueous dispersion of fluoropolymer and a polycarbonate resin can be precipitated by vapor to form a fluoropolymer concentrate to be used as a drip inhibitor additive in thermoplastic resin composition, as described in, for example, the USA No. 5,521,230 or, alternatively, an aqueous emulsion of styrene-acrylonitrile resin or an aqueous emulsion of acrylonitrile-butadiene-styrene resin, and then precipitating and drying the thermoplastic resin-co-coagulated fluoropolymer composition to provide a resin powder PTFE thermoplastic as described, for example, in the US patent No. 4,579,906. In a preferred embodiment, the fluoropolymer additive comprises from 30 to 70% by weight, most preferably 40 to 60% by weight of the fluoropolymer, and from 30 to 70% by weight, most preferably 40 to 60% by weight, of the second polymer . In a preferred embodiment, a fluoropolymer additive is prepared by emulsion polymerization of one or more monoethylenically unsaturated monomers in the presence of the aqueous fluoropolymer dispersion of the present invention to form a second polymer in the presence of the fluoropolymer. Suitable monoethylenically unsaturated monomers are described above. Afterwards the emulsion is precipitated, for example, by adding sulfuric acid. The precipitate is dehydrated, for example, by centrifugation and then dried to form a fluoropolymer additive comprising fluoropolymer and a second associated polymer. The dry emulsion polymerized fluoropolymer additive is in the form of a free flowing powder. In a preferred embodiment, the monoethylenically unsaturated monomers that are emulsion polymerized to form the second polymer comprise one or more monomers selected from vinyl aromatic monomers, monoethylenically unsaturated nitrile monomer, and C ^ -C ^ alkyl (meth) acrylate monomers. The aromatic vinyl monomers, monoethylenically unsaturated nitrile monomer and suitable C 1 -C 4 alkyl (meth) acrylate monomers are described above. In a highly preferred embodiment, the second polymer comprises structural units derived from styrene and acrylonitrile. Most preferably, the second polymer comprises from 60 to 90% by weight of structural units derived from styrene, and from 10 to 40% by weight of structural units derived from acrylonitrile. The emulsion polymerization reaction mixture may optionally include emulsified or dispersed particles of a third polymer, such as, for example, an emulsified butadiene rubber latex. The emulsion polymerization reaction is initiated using a conventional free radical initiator such as for example an organic peroxide compound such as, for example, benzoyl peroxide, a persulfate compound such as, for example, potassium persulfate, an azonitrile compound such as, for example, 2, 2'-azobis-2, 3, 3-trimethylbutyronitrile or a reduction oxide initiator system such as, for example, a combination of eumeno hydroperoxide, ferrous sulfate, tetrasodium pyrophosphate and a reducing sugar or sodium formaldehyde sulfoxylate. To reduce the molecular weight of the second polymer, a chain transfer agent such as, for example, a C9-C13 alkyl mercaptan compound such as nonylmercaptan, t-dodecyl mercaptan, can optionally be added to the reaction vessel during the polymerization reaction. In a preferred embodiment, chain transfer agent is not used. In a preferred embodiment, the dispersion of the stabilized fluoropolymer is charged to a reaction vessel and heated with stirring. The initiator system, and the monoethylenically unsaturated monomer (s), are then charged to the reaction vessel and heated to polymerize the monomers in the presence of the fluoropolymer particles in the dispersion to then form the second polymer. Suitable fluoropolymer additives and emulsion polymerization methods are described in EP 0 739 914 A1. In a preferred embodiment, the second polymer exhibits a number average molecular weight of 30,000 to 200,000 g / mol. The thermoplastic resin composition of the present invention may also optionally contain various conventional additives such as for example: antioxidants such as organophosphites, for example, tris (nonylphenyl) phosphite, (2,4,6-tri-tert-butylphenyl) (2-butyl-2-ethyl-1, 3-propanediol) -phosphite, bis (2,4-di-t-butylphenyl) pentaerythritol diphosphite or distearyl pentaerythritol diphosphite, as well as alkylated monophenols, polyphenols, alkylated reaction products of polyphenols with dienes, such as, for example, butylated reaction products of para-cresol and dicyclopentadiene, alkylated hydroquinones, hydroxylated thiodiphenyl ethers, alkylidene bisphenols, benzyl compounds, acylaminophenols, esters of beta- (3, 5-di- tert-butyl-4-hydroxyphenyl) -propionic with monohydric or polyhydric alcohols, esters of beta- (5-tert-butyl-4-hydroxy-3-methylphenyl) -propionic acid with monohydric or polyhydric alcohols, beta-beta esters (5-tert-butyl-4-hydroxy-3-methylphenyl) propionic with monohydric or polyhydric alcohols, esters of thioalkyl or thioaryl compounds such as for example, distearylthiopropionate, dilaurylthiopropionate, ditridecylthiodi propionate, beta-3-acid amides 5-di-tert-butyl-4-hydroxyphenol) ropionic; UV light absorbers and light stabilizers such as, for example, 2- (2'-hydroxyphenyl) benzotriazoles, 2-hydroxybenzophenones; esters of substituted and unsubstituted benzoic acids, acrylates; fillers and reinforcing agents such as, for example, silicates, IO2, glass fibers, carbon black, graphite, calcium carbonate, talc, mica; other additives such as for example lubricants such as, for example, pentaerythritol tetrastearate, EBS wax, silicone fluids, plasticizers, optical brighteners, pigments, dyes, dyes, flameproofing agents; antistatic agents; blowing agents, as well as other flame retardants in addition to the organosphosphoric compounds described above.

EXAMPLES 1-4 The compositions of Examples 1-4 were prepared by combining the following components in the indicated relative amounts, in pep, in Table 1.

PC A linear polycarbonate resin derived from bisphenol A and phosgene, and having an intrinsic viscosity of 0. 50 deciliters per gram. ABS Acrylonitrile-butadiene-styrene graft copolymer ("ABS") polymerized in emulsion comprising 50 pbw of a discontinuous elastomer phase (polybutadiene with an average particle size of about 300 nm) and 50 pbw of a rigid thermoplastic phase (copolymer of 75 pbw of styrene and 25 pbw of acrylonitrile). SAN Styrene-acrylonitrile copolymer (75 pbw styrene / 25 pbw acrylonitrile). RDP Mixture of resorcinol diphosphate oligomers with an average degree of polymerization of n = 1.13 and with an acid level of less than 0.1 mg of KOH per gram. TSAN: Additive made by copolymerizing styrene and acrylonitrile in the presence of an aqueous dispersion of PTFE (50% by weight of PTFE and 50% by weight of a copolymer of 75% by weight of styrene and 25% by weight of acrylonitrile). BPA-DP-1 A mixture of bisphenol A diphosphate oligomers with an average degree of polymerization of 1.08. BPA-DP-2 A mixture of bisphenol A diphosphate oligomers with an average polymerization degree of 1.08. BPA-DP-3 A mixture of bisphenol A diphosphate oligomers with an average degree of polymerization of 1.08. The acid level, the hydrolyzable chloride content, the magnesium content and the isopropylphenyl diphenylphosphate content of BPA-DP-1, BPA-DP-2 and BPA-DP-3 were determined. The results are indicated below in Table I.

TABLE I BPA-DP-1 BPA-DP-2 BPA-DP-3 Acid level (mg KOH / g) < 0.01 < 0.01 < 0.02 Hydrogenizable chloride content 1450 22 (ppm) Magnesium content (ppm) 576 1296 < 60 Content of isopropenylphenyl diphenyl phosphate (% p) > 1% > l < l The following general procedure was followed to prepare and test the compositions of Examples 1-4. Well-mixed dry mixtures of the components of the compositions were prepared by dispersing the components in a Henschel mixer. These dry mixes were extruded in a twin laboratory worms extruder at a temperature of about 250 ° C to about 300 ° C, and test specimens were molded in a 30 ton Engel injection moulder with a nominal melting temperature of about 240 ° C. ASTM strain bars type I of each of the compositions were molded and tested. The hydrolytic stability was measured by exposing part of a tension bar at 100 ° C and at 100% relative humidity for several periods ("t"). A part of the bar was then cut and the weight average molecular weight ("PMp") of the polycarbonate was determined by gel permeation chromatography (CPG). All molecular weights are reported in relation to monodisperse polystyrene standards of known molecular weight. Table II shows the results of the determination of the weight average molecular weight of the specimens under exposure to temperature and humidity for several times ("PMp (g / mol x 10 ~ 3), after aging at 100 ° C and 100% relative humidity (RH) for the residence time t (hr) "), for each of the examples 1-4.

TABLE II PC 70.05 67.75 67.75 67.75 ABS 9 9 9 9 SAN 9.3 8.3 8.3 8.3 PTFE / PC 0.4 0.4 0.4 0.4 RDP 11.5 BPA-DP-1 13.8 BPA-DP-2 13.8 BPA-DP-3 13.8 Stabilizers and Lubricants 0.75 0.75 0.75 0.75 PMp (g / mol x 10 ~ 3), after aging at 100 ° C and 100% RH for a residence time t (hr) t = 0 52.7 44 52.9 53.3 t = 3.75 52.1 42.4 48.8 52.1 t = 6.5 48.8 41.2 47.5 51.5 t = 12 46.8 41.6 45.1 49.3 t = 15 43.5 40 41.6 50.2 t = 19 39.5 38.8 38.3 48.7 t = 24 32.2 36.4 34.1 47.9 The The composition of Example 4 exhibited improved stability, as shown by the relatively small change in molecular weight under the aging conditions.

Claims (16)

NOVELTY OF THE INVENTION CLAIMS

1. - A thermoplastic resin composition comprising: (a) a thermoplastic resin containing at least one aromatic polycarbonate resin, and (b) a flame retardant amount of an organophosphorus flame retardant compound, wherein any acid initially present in the the compound, and any acid generating impurity initially present in the compound, does not exceed a level at which the combined amount of said acids and any acid that can be generated under hydrolytic conditions from said acid-generating impurities, is equivalent to a titratable acid level of less than about 1.0 milligram of potassium hydroxide per gram of the organophosphorus compound.

2. The composition according to claim 1, characterized in that the organophosphorus compound has a titratable acid level of 0 to 1.0 milligram of potassium hydroxide per gram of the organophosphorus compound.

3. The composition according to claim 1, characterized in that the organophosphorus compound has a hydrolyzable chloride content of from 0 to 100 parts by weight per million parts by weight of the organophosphorus compound.

4. - The composition according to claim 1, characterized in that the organophosphoric compound has a magnesium content of 0 to 1000 parts by weight per million parts by weight of the organophosphorus compound.

5. The composition according to claim 1, characterized in that the organophosphoric compound is of the following structural formula: Rg-- (0) • (0) d -] n - R9 wherein Rg, R7, Rg and R9 are each independently aryl, optionally substituted with halogen or C ^-Cß alkyl; X is arylene, optionally substituted with halogen or C] _-Cg alkyl; a, b, c and d are each independently 0 or 1; and n is an integer from 0 to 5.

6. The composition according to claim 5, characterized in that X is a divalent radical containing 2 or more aromatic rings joined by means of a non-aromatic bond, any of which may be substituted at one or more sites on the aromatic ring with a halogen group or a C? -Cg alkyl group, and wherein the organophosphorus has an alkenylphenyl diphenyl phosphate content of from 0 to 2000 parts by weight per million parts by weight of the organophosphoric compound.

7. The composition according to claim 1, characterized in that the aromatic polycarbonate resin is derived from bisphenol and phosgene.

8. The composition according to claim 1, characterized in that the component (a) of the composition further comprises an aromatic vinyl graft copolymer.

9. The composition according to claim 8, characterized in that the aromatic vinyl graft copolymer comprises an acrylonitrile-butadiene-styrene graft copolymer.

10. The composition according to claim 9, further characterized in that it comprises a styrene-acronitrile copolymer.

11. The composition according to claim 1, further characterized in that it comprises a fluoropolymer, in an amount effective to provide anti-drip properties to the resin composition.

12. The composition according to claim 5, characterized in that Rg, R7, Rg and R9 are each phenyl; each of a, b, c and d is 1, and X is a divalent aromatic radical of the structural formula: and n is an integer from 1 to 5.

13. A shaped article made by molding the composition of claim 1.

14. A process for preparing a thermoplastic flame retardant resin composition, which comprises combining a thermoplastic resin, said resin comprises at least one aromatic polycarbonate resin, and a flame retardant amount of an organophosphorus flame retardant compound, wherein any acid initially present in the compound, and any acid generating impurity initially present in the compound, does not exceed a level at which the combined amount of any of these acids and any acid that can be generated under hydrolytic conditions from said acid generating impurities, is equivalent to a titratable acid level of less than about 1.0 milligram of potassium hydroxide per gram of the organophosphorus compound.

15. A thermoplastic resin composition prepared by the process of claim 14.

16. A shaped article made by molding a thermoplastic resin composition prepared by the process of claim 14.