POLYCARBONATE CONTAINING AN AROMATIC SULFONAMTJDE AS AN
IGNITION DEPRESSANT
This invention relates to polycarbonates containing additives which inhibit combustion upon exposure of the polycarbonates to low temperature ignition sources. This invention relates particularly to ignition resistant polycarbonate compositions having a good balance of physical properties and rated V-2 in the Underwriters Laboratories Standard 94 (UL 94) flammability test.
Polycarbonates derived from reactions of dihydroxyorganic compounds, particularly the dihydric phenols, and carbonic acid derivatives such as phosgene have found extensive commercial application because of their excellent physical properties. These thermoplastic polymers appear to be particularly suitable for the manufacture of molded parts wherein impact strength, rigidity, toughness, heat resistance and excellent electrical properties are required. Unfortunately, however, these polymers exhibit a brief but definite burning time when contacted with an open flame or comparable low temperature ignition source. More importantly, as is often the case, the polycarbonates contain stabilizers and other additives which are often more combustible than the unmodified polycarbonate. As a result, the modified polycarbonate frequently exhibits substantially poorer resistance to combustion than does the unmodified polycarbonate.
In attempts to increase the combustion resistance of polycarbonates including modified forms thereof, it has been a common practice to employ monomeric phosphites, phosphoric acid esters, thiophosphoric acid esters containing halogenated alkyl radicals and halogenated organic compounds into the polycarbonate. However, in order to obtain any noticeable improvement in combustion resistance, these additives have been employed in such large quantities that they often adversely affect many of the desirable physical and mechanical properties of the polycarbonate.
More recently, for example as taught in USP 4,254,015 and JP 2000169693A, various organo sulfonamides have been employed as ignition resistant additives for polycarbonates. These materials generally must be employed in high concentrations in order to impart ignition resistance to the polycarbonate and it has been found that at higher levels, they too, can have a substantial deleterious effect on the physical properties, such as molecular weight degradation, of the polycarbonate. USP 6,197,854 and 6,350,798 teach
that insoluble saccharin in conjunction with other additives can improve thermal stability and/or reduce yellowing resulting from exposure to gamma radiation. However, they teach that traces of alkali compounds, alkaline-earth compounds or heavy metal compounds can result in molecular weight degradation.
In view of the deficiencies of conventional ignition resistant polycarbonate compositions, it would be highly desirable to provide a polycarbonate composition having a good balance of physical properties, molecular weight stability and improved resistance to burning when exposed to a low temperature ignition source.
The present invention is a polycarbonate composition comprising a carbonate polymer having dispersed therein a metal salt of a sulfur containing compound, such as an aromatic sulfonamide in an amount from equal to or greater than 0.001 to an amount equal to or less than 0.01 parts by weight based on the weight of the polycarbonate composition and sufficient to retard combustion when the composition is exposed to a low temperature ignition source. Hereinafter, such composition shall be refened to as an ignition resistant carbonate composition. The metal salt of an aromatic sulfonamide employed in the ignition resistant polycarbonate advantageously has at least one sulfonamide moiety represented by the formula:
wherein Ar is an aromatic group, M is a cation and n is a number conesponding to the valence of M. Preferably, the metal salt of the aromatic sulfonamide is the sodium salt of saccharin more preferably it is FDA approved sodium salt of saccharin.
The ignition resistant polycarbonate of the present invention is suitably employed in most applications which polycarbonates have been previously utilized. Applications of particular interest for the utilization of the ignition resistant polycarbonates of this invention are as follows: automobile parts, for example, air filters, fan housings, exterior components; housings for electrical motors, appliances, information technology equipment, and photographic equipment; lighting and aircraft applications. These compositions are particularly suited for use in thinwall instrument housings such as for power tools,
appliances, consumer electronic equipment such as TVs, VCRs, web appliances, electronic books, etc., or information technology equipment such as telephones, cell phones, computers, monitors, fax machines, battery chargers, scanners, copiers, printers, hand held computers, etc. Another application of particular interest for the utilization of the ignition resistant carbonate compositions of this invention is in food and beverage applications such as appliance housings or containers that may contact food wherein the appliance also contains some sort of electrical device; often times such applications are preferably transparent or translucent for example small kitchen appliances, water tanks for cleaning appliances, refrigerator light housings, etc. The migration of trace amounts of reaction and degradation byproducts, additives, oligomers, and monomers from food and beverage applications can affect consumer acceptance, product quality, and regulatory approval of candidate materials. In such applications, materials must meet tests conducted by, or be approved by, such agencies as the U.S. Food and Drug Admimstration (FDA).
In general, such ignition resistant carbonate compositions are particularly useful in applications wherein the polycarbonate part is likely to be exposed to low temperature ignition sources.
The carbonate polymers employed in the present invention are well known in the literature and can be prepared by known techniques, for example several suitable methods are disclosed in USP 3,028,365, 4,529,791, 4,677,162, and 6,380,303. The carbonate polymers that can be used in the present invention can be prepared from one or more multihydric compounds by reacting the multihydric compounds, such as an aromatic diol, with a carbonate precursor, such as phosgene, a haloformate or a carbonate ester such as diphenyl or dimethyl carbonate. Preferably the polycarbonate is prepared from one or more aromatic diols such as bisphenol A, tetrabromo bisphenol A, tetramethyl bisphenol A, l,l-bis(4-hydroxyphenyl)-l-phenylethane, 3,3-bis(para-hydroxyphenyl)phthalide, or bis hydroxyphenylfluorene. The carbonate polymers can be prepared from these raw materials by any of several known processes such as the known interfacial, solution or melt processes. The carbonate polymers of the present invention may be linear, branched or mixtures thereof. The carbonate polymers may be derived from (1) two or more different aromatic diols or (2) an aromatic diol and a glycol or a hydroxy- or acid-terminated polyester or a dibasic acid in the event a polycarbonate copolymer or heteropolymer rather than a homopolymer is desired. Also suitable for the practice of this invention are blends of one or more of the above polycarbonates. The particular polycarbonate chosen may depend upon
the application and desired properties, but where the end use is in contact with food, FDA approved polycarbonates are the material of choice. Also included in the term carbonate polymers are the poly(ester/carbonates). Preferably, the polycarbonate is opaque or translucent and more preferably it is transparent. Preferably, the carbonate polymer of the present invention is a linear aromatic carbonate polymer, a branched aromatic carbonate polymer or mixtures thereof. Branched aromatic carbonate polymers suitable for use in the present invention can be prepared by techniques known in the literature such as the known interfacial, solution or melt processes. Suitable types and amounts of chain terminators (typically monophenolic compounds) and/or branching agents (typically phenols having three or more hydroxy or condensation reactive groups) can be employed to obtain the desired molecular weight and branching degrees in the branched component. Suitable branching agents are generally one or more of the following: phloroglucin; phloroglucid; 2,6-dimethyl-2,4,6-tri(4-hydroxyphenyl)heptene- 3 ; 4,6-dimethyl-2,4,6-tri(4-hydroxyphenyl)heptene-2; 4,6-dimethyl-2,4,6-tri(4- hydroxyphenyl)pentene-2; 4,6-dimethyl-2,4,6-tri(4-hydroxyphenyl)pentane; l,3,5-tri(4- hydroxyphenyl)benzene; l,3,5-tri(2-hydroxyphenyl)benzol; l,l,l-tri(4- hydroxyphenyl)ethane; 2,6-bis(2-hydroxy-5-methylbenzyl)-4-methylphenol; tetra(4- hydroxy-phenyl)methane; trisphenol; bis(2,4-dihydroxyphenyl)ketone; l,4-bis(4,4- dihydroxytriphenylmethyl)benzene; α,α',α"-tri(4-hydroxyphenyl)- 1 ,3,5-tri- isopropylbenzene; 3,3-bis(4-hydroxyaryl)oxyindole;, isatinbisphenol; 5-chloroisatin; 5,7- dichloroisatin; 5-bromoisatin; trimellitic acid; pyromellitic acid; benzophenonetetracarboxylic acid; and including for the appropriate compounds, the acid chlorides or other condensation reactive derivatives thereof such as trimellitic trichloride, trimesoylchloride and trimellitic anhydride chloride. Specifically preferred branching agents include phloroglucin; phloroglucid; 1,1,1 -tri(4-hydroxyphenyι)ethane; trimellitic acid; trimellitic trichloride; pyromellitic acid; benzophenonetetracarboxylic acid and acid chlorides thereof; 2,6-bis(2-hydroxy-5-methylbenzyl)-4-methylphenol and l,3,5-tri(4- hydroxyphenyl)benzene.
The branched aromatic carbonate polymer according to the present invention can be prepared (a) directly from a polymerization process (b) by the blending of two or more separately prepared carbonate polymer components, (c) by the addition of one or more previously prepared carbonate polymer into the reaction process that is preparing or has prepared the other carbonate polymer, (d) by the appropriate operation of a sequence or
series of reactors to prepare one or more linear or branched carbonate polymer in the presence of the previously prepared other carbonate polymer prior to the recovery of the carbonate polymer from the reaction mixture or (e) the appropriate operation of parallel reactors to prepare one or more linear and branched carbonate polymers followed by combining the unrecovered reaction products prior to the recovery of the carbonate polymer blend from the reaction mixture.
Preferably, the branched aromatic carbonate polymer is a combination of two or more branched carbonate polymer components of different molecular weights and different melt flow rates that are blended to obtain the desired degree of branching, intermediate molecular weight and melt flow rate branched aromatic carbonate polymer. More preferably, the carbonate polymer of this invention comprises a branched aromatic carbonate polymer that is a combination of one or more branched carbonate polymer components having different molecular weights and different melt flow rates with one or more linear carbonate polymer components having different molecular weights and different melt flow rates to obtain the desired degree of branching, intermediate molecular weight and melt flow rate branched aromatic carbonate polymer. This type of system of blending carbonate polymer components of different molecular weights and different melt flow rates is practiced commercially to provide a broader range of polycarbonate resins of differing melt flow rate while reducing the overall number of different products the production facility must supply.
Unless otherwise indicated, the references to "molecular weight" herein refer to weight average molecular weights (Mw) determined on the carbonate polymers using gel permeation chromatography (GPC) with a bisphenol A polycarbonate standard. Otherwise, viscometry or light scattering can also be used to determine weight average molecular weight if similar results are obtained. It should be noted that various references refer to "viscosity average" molecular weight (Mv), which is not the same as "weight average" molecular weight but can be conelated or converted to Mw values.
It has been found that the carbonate polymer should have a weight average molecular weight of at least 10,000, preferably at least 15,000, more preferably at least 19,000, even more preferably at least 22,000 and most preferably at least 28,000. Further, it has been found that the linear carbonate polymer component for blending with the branched carbonate polymer component should have a weight average molecular weight of no more
than 45,000, preferably no more than 39,000, more preferably no more than 36,000, even more preferably no more than 32,000, most preferably no more than 28,000.
It has been found that the carbonate polymer component should have a melt flow rate of at least 1.2 grams per 10 minutes (g/10 min.), preferably at least 2 g/10 min., preferably at least 2.5 g/10 min., more preferably at least 3 g/10 min., more preferably at least 3.5 g/10 min., even more preferably at least 5 g/10 min. and most preferably at least 10.0 g/10 min. and preferably no more than 200 g/10 min., preferably no more than 80 g/10 min., more preferably no more than 40 g/10 min., more preferably no more than 22 g/10 min. and most preferably no more than 1 g/10 min. While the non-ionic aromatic sulfonamides are suitable in the practice of this invention, the salt form of aromatic sulfonamides are preferably employed and are those represented by the formula:
wherein Ar is a monovalent carbocyclic aromatic moiety, R is a monovalent organic moiety, especially one containing a sulfonyl or carbonyl which is bonded to the anionic nitrogen, or Ar and R are collectively a divalent aromatic moiety, especially one containing sulfonyl or carbonyl, both valencies of which divalent moiety are bonded to the anionic nitrogen, M is a cation, preferably a monovalent cation, and n is a number conesponding to the valence of M. Representative prefened sulfonamide salts are those in which Ar is phenyl, aromatically substituted phenyl, phenylene or aromatically substituted phenylene wherein the substituent(s) are halo, alkyl, aryl, amino, including N-alkyl amino and N, N-dialkyl amino, alkyl carbonyl, alkaryl, and aralkyl; R is carbonyl, aromatic carbonyl such as arylcarbonyl (for example, benzoyl), arylaminocarbonyl (for example, benzylaminocarbonyl); aromatic sulfonyl such as arylsulfonyl (for example, tolylsulfonyl), thiazolyl including alkylthiazolyl, pyrimidinyl including alkyl pyrimidinyl, quinolinyl and pynolidinyl, thiadiazolyl including alkyl thiadiazolyl and comparable monovalent organic moieties that are inert to the sulfonamide moiety; and M is ammonium or an alkali metal cation, preferably sodium or potassium. Alternatively, M is a divalent cation, preferably derived from the alkaline earth
metals, for example, calcium, magnesium, etc., or a multivalent cation obtained from iron, copper, and zinc.
Especially prefened aromatic sulfonamide salts include the heterocyclic sulfonamide salts wherein Ar and R taken collectively are phenylenecarbonyl
O
and AR-substituted phenylenecarbonyl such as AR-methylphenylenecarbonyl
and AR-chlorophenylenecarbonyl and M is sodium. A prefened example is:
metal salt of N- p-toylsufonyl)-p-toluenesulfonamide
Specific examples of preferred and other suitable sulfonamides include the salt forms (especially the sodium salt forms) of the following sulfonamides: (N- benzoyl)sulfanilamide, N-(2-thiazolyl)sulfanilamide, N-(2-(4- methylpyrimidinyl))sulfanilamide, N-(5-methyl- 1 ,3 ,4-thiadiazol-2-yl)sulfanilamide, N-(6- methoxy-2-methyl-4-pyrimidinyl)sulfanilamide, N-(5-methyl-3-isoxazolyl)sulfanilamide, N-(6-methoxy-3-pyridazinyl)sulfanilamide, N-(2-quinoxalinyl)sulfanilamide, N-(5-chloro- 2-pyrazinyl)sulfanilamide, saccharin
O
metal salt of saccharin O
metal salt of 5-methylsaccharin
Cl O
metal salt of 6-chlorosaccharin
with the saccharin and substituted saccharin being prefened. The particular aromatic sulfonamides chosen may depend upon the application and desired properties, but where the end use is in contact with food, FDA approved aromatic sulfonamides, such as FDA approved sodium saccharin, is the material of choice. While saccharin and other similar compounds having the sulfonamide moiety,
O
-N
0Θ ©M
embodied in a heterocyclic ring are technically sulfimides, they are included within the term "aromatic sulfonamide" for the purposes of this invention.
Methods for preparing the aromatic sulfonamides to be employed in the practice of this invention are described in Kirk-Othmer, Encyclopedia of Chemical Technology, 2nd
Edition, Vol. 19, Wiley & Sons Inc., New York (1969) at pp. 257-258 and Kharasch, Organic Sulfur Compounds, Pergamon Press Inc., New York (1961) at pp. 561-562.
Preferred amounts of the sulfonamide, metal salt of the sulfonamide or mixtures thereof are in the range from equal to or greater than 0.0001, preferably equal to or greater than 0.0005 and more preferably equal to or greater than 0.001 parts by weight based on the weight of the ignition resistant carbonate composition. Prefened amounts of the sulfonamide are in the range of from equal to or less than 0.01, more preferably equal to or less than 0.008 and more preferably equal to or less than 0.005 parts by weight based on the weight of the ignition resistant carbonate polymer composition. In addition to the aforementioned sulfonamide, other additives may be included in the ignition resistant polycarbonate of the present invention such as fillers, pigments, dyes, antioxidants, stabilizers, ultraviolet light absorbers, mold release agents, organic or inorganic sulfur containing and/or sulfur free buffers, additional ignition resistant additives such as halogen and/or non-halogen containing compounds and/or polytetrafluoroethylene polymers and other additives commonly employed in polycarbonate resin formulations.
Ester group-containing additives for thermoplastic polycarbonates are, in particular, plasticizers and mold release agents, as described in the literature and also used for processing thermoplastic polycarbonates.
The ester group-containing additives according to component may be completely esterified compounds or partial esters with non-esterified OH groups or non-esterified carboxyl groups.
The ester group-containing additives are synthesized from aliphatic monoalcohols, aliphatic dialcohols, aliphatic trialcohols, aliphatic tetrols, aliphatic pentols and/or aliphatic hexols having 1 to 15 C atoms, preferably 2 to 10 C atoms and particularly preferably 3 to 6 C atoms, and aliphatic monocarboxylic acids, aliphatic dicarboxylic acids and/or aliphatic tricarboxylic acids having 3 to 34 C atoms, preferably 10 to 24 C atoms and particularly preferably 12 to 18 C atoms.
The ester group-containing additives have average molecular weights n (number average, determined by end group assay) of from 100 to 3000, preferably from 300 to 1000. Examples of aliphatic alcohols are ethanol, propanol, butanol, ethylene glycol, glycerol, pentaerythritol, 1,4-butanediol, 1,6-hexanediol, 1,10-decanediol, hexanol, n-decyl alcohol, lauryl alcohol, myristyl glycol, t-amyl alcohol, 1,2,4-butanetriol, 1,2,6-hexanetriol, inositol, sorbitol, erythritol and xylitol.
Examples of aliphatic carboxylic acids are butyric acid, isovaleric, caproic, caprylic, capric, lauric, myristic, palmitic, stearic, arachidic, behenic, lignoceric and cerotic acid, malonic acid, succinic acid, glutaric acid, adipic acid, sebacic acid, dodecanedioic acid and thapsic acid. Examples of ester group-containing additives are ethyl stearate, glycerol monostearate, distearate and tristearate, butyl laurate, hexyl laurate, pentaerythritol tetralaurate, tetrapalmitate, tetra-stearale, pentaerythritol trilaurate, tripalmitate and tristearate, sebacic acid monobutyl ester and dibutyl ester together with dodecanedioic acid monobutyl ester and dibutyl ester. The ester group-containing additives are known from the literature or may be produced according to processes known from the literature. See for example USP 3,186,961, JA-Sho-47-41092, USP 3,784,595, JA-Sho-49-11949, JA-Sho-49-55752 and USP 4,131,575.
If present, preferred amounts of the ester group-containing additive are in the range from equal to or greater than 0.001 , preferably equal to or greater than 0.01, more preferably equal to or greater than 0.05 and even more preferably equal to or greater than 0.1 parts by weight based on the weight of the ignition resistant carbonate polymer composition. Prefened amounts of the ester group-containing additive are in the range of from equal to or less than 1, more preferably equal to or less than 0.75 and more preferably equal to or less than 0.5 parts by weight based on the weight of the ignition resistant carbonate polymer composition.
The structure of a preferred stabilizer contains at least one benzofuran-2-one group per molecule. This compound conforms structurally to
wherein in the embodiment where n is 1, Rj is an unsubstituted or substituted carbocyclic or heterocyclic aromatic ring system, and where in the embodiment where n is 2, Ri is
unsubstituted or C1- -alkyl or hydroxy substituted phenylene or naphthylene, and R2, R3 R4 and R5 independently of one another are hydrogen, C1-25 -alkyl groups or phenyl.
A prefened compound is represented by 5,7-di-tertiary-butyl-3-(3,4 di- methylphenyl)-3H-benzofuran-2-one which is depicted as:
CH3
Detailed description of suitable compounds and their preparation maybe found in USP 4,325,863, 5,175,312 and 5,607,624. Suitable compounds are available in commerce from Ciba Specialty Chemicals Limited as IRGANOX™ HP 136. Preferably, the stabilizer suitable in the context of the invention melts at a temperature equal to or lower than the melt temperature of polycarbonate. This characteristic enables the compounding of the stabilizer with the polycarbonate resin in their molten state.
If present, preferred amounts of the benzofuran-2-one containing stabilizer are in the range from equal to or greater than 0.001, preferably equal to or greater than 0.01 and more preferably equal to or greater than 0.05 parts by weight based on the weight of the ignition resistant carbonate polymer composition. Preferred amounts of the benzofuran-2-one containing stabilizer are in the range of from equal to or less than 1, more preferably equal to or less than 0.5 and more preferably equal to or less than 0.1 parts by weight based on the weight of the ignition resistant carbonate polymer composition. The ignition resistant polycarbonate of the present invention is suitably prepared by combining the carbonate polymer with an effective amount of sulfonamide and any additional additives using any one of a variety of blending procedures conventionally employed for incorporating additives into carbonate polymer resins. For example, dry particulates of the carbonate polymer and the sulfonamide may be dry blended and the resulting dry blend extruded into the desired shape. The ignition resistant polycarbonate compositions of the present invention are thermoplastic and are preferably translucent and
more preferably transparent. The ignition resistant carbonate polymer compositions of the present invention maybe compression molded, injection molded, blow molded or extruded into profile or sheet which can be further thermoformed or vacuum formed.
The following examples are given to further illustrate the invention and should not be construed as limiting its scope. In the following examples, all parts and percentages are by weight unless otherwise indicated.
EXAMPLES
Examples 1 and 2 and Comparative Example C were prepared by adding sodium saccharin powder to polycarbonate having a melt flow rate (MFR) of 3 grams per 10 minutes (g/10 min.). The two ingredients were dry blended by tumbling for about 10 minutes. The dry blended mixture was melt blended in a 30 millimeter (mm) Werner and Pfleider fully intermeshing corotating twin screw extruder. The following conditions were used on the Werner Pfleider extruder: The banel temperature zones were set at 325°C across the board. The RPM was set at 350, the torque was between 80 and 90 percent and the feed rate was set at 50 pounds per hour. The extrudate was cooled in the form of strands and chopped into pellets. The pellets were post blended for 10 minutes and were dried in an air draft oven for 3 hours at 125°C. The dried pellets were molded into 3.2 mm and 1.6 mm thick test bars on the 90 ton Toyo SI 90 injection molding machine. The following conditions were used on the Toyo injection molding machine: barrel temperatures were set at 320°C at all zones. The injection pressure was 18,000 pounds per square inch (psi), holding pressure was 15,000 psi, back pressure was 600 psi, screw speed was 200 millimeters per second (mm/sec), injection speed was 60 mm/sec, cycle time 25 seconds, cooling time was 15 seconds dosage was 85 mm and mold temperature was 40°C.
Comparative Example A was neat polycarbonate with a MFR of 3 g/10 min. used in Examples 1 to 3. Comparative Example B was the neat polycarbonate of Comparative Example A subjected to the same extrusion process (in the 30 mm Werner and Pfleider extruder) used in Examples 1 to 3. The formulation content and properties of Examples 1 and 2 and Comparative
Examples A, B and C are given in Table 1 below in parts by weight of the total composition. In Table 1 :
Table 1
*Not an Example of the present invention NR = not rated
PC" is a branched bisphenol-A polycarbonate homopolymer having a melt flow of
3 g/10 m tiinn..,, hhaavviinngg FFDDAA aapppprroovvaall aanndd ccoommmmeerrcciiaallllyy aavvaaiillaafcble as CALIBRE™ 200-03 polycarbonate resin from The Dow Chemical Company and
"NaS" is a FDA approved sodium saccharin available from Sigma- Aldrich Company as free flowing fine white crystals with 40 to 80 mesh.
The following tests were run on Examples 1 and 2 and Comparative Examples A, B and C and the results of these tests are shown in Table 1 :
"YI" yellowness index is determined according to ASTM D 1925 using a HunterLab UltraScan Xe spectrometer using total transmittance, large area of view and (1 inch port) UV filter;
"Mw" unless otherwise specified is weight average molecular weight and is measured by GPC;
"UL 94" flammability test is performed on 0.125 inch (3.2 mm) or 0.062 inch (1.6 mm) test specimens as identified hereinabove. UL 94 vertical (V) flammability test determines the upward-burning characteristics of a solid. Five test specimens, of a desired thickness measuring 0.5 inch (12.5 mm) by 5 inch (125 mm), suspended vertically over surgical cotton are ignited by a 0.75 inch (18.75 mm) Bunsen burner flame; two ignitions of 10 seconds each are applied to the samples. The rating criteria include the sum of after- flame times after each ignition, glow time after the second ignition, and whether the bar drips flaming particles that ignite the cotton. Table 2 lists the criteria for V-2 rating:
Table 2
^Rating criteria are reported in seconds
"MFR" is determined according to ASTM D 1238 on a Tinius Olsen plastometer at 230 °C and an applied load of 3.8 kg.; and "Izod" impact resistance as measured by the Notched Izod test is determined according to ASTM D 256-90-B at 23 °C. Specimens are cut from rectangular 5 inch (125 mm) by 0.5 (12.6 mm) inch bars and measure 0.125 inch (3.2 mm) in thickness and 0.64 inch (50.8 mm) in length. The specimens were notched with a TMI 22-05 notcher to give a
0.01 inch (0.254 mm) radius notch. A 48.5 pound (22 kilogram) pendulum is used, values are reported in Joules per meter (J/m).
As can be seen from the data presented in Table 1, the ignition resistant polycarbonate compositions of the present invention show a good balance of ignition resistance, impact strength, color stability and molecular weight stability.