SMOKE AND FIRE RETARDANT PLENUM COMPOSITIONS

Abstract: This invention, in one aspect, relates to an extruded or extrudable flame and smoke retardant composition comprising the residue of: a) polyvinyl chloride; b) at least one carboxylate ester plasticizer compound having no halogenated aromatic or phosphate residues; c) a zinc compound; and d) a magnesium compound.

Description: SMOKE AND FIRE RETARDANT PLENUM COMPOSITIONS CROSS REFERENCE TO RELATED APPLICATIONS This application claims priority to United States provisional patent application serial number 60/166,668, filed November 19, 1999, which is hereby incorporated herein by reference, in its entirety. FIELD OF THE INVENTION This invention relates generally to flame and smoke resistant compositions, having electrically insulating properties and sufficient low temperature flexibility to be suitable as jacketing material for covering insulated conductors, and plenum wiring. The invention also relates to processes for producing the compositions, and melt extruding the compositions to form articles. BACKGROUND OF THE INVENTION The growth of computer-related equipment, and the Internet, is exponentially increasing the need for integrated communications systems, and electronic data transmission, and telecommunications equipment. Such communication systems are increasingly installed in confined areas such as in high rise buildings, watercraft, aircraft, trains, drilling platforms and in mines. In order to link the electronic components, it is necessary to install thousands of feet of wire and cable throughout these structures and areas. It is convenient to install the wire and cable through air handling plenums and wire and cable raceways, without installing conduit piping to protect the wire and cable. Because of concerns that flame and smoke could travel along the extent the electrical conductors and cable in a plenum area in the event of a fire, in 1975 the National Fire Protection Association ("NFPA") developed a standard to diminish the potential of the insulating and jacket materials from spreading flames and evolving smoke to adjacent plenum areas and more distant areas throughout a building. This standard, commonly referred to as "the Plenum Cable Standard", permits the use of cable without conduit, so long as the cable exhibits low smoke and flame retardant characteristics. The NFPA test method for measuring these smoke and flame retardant characteristics provides for the test burning of cables according to the following test protocols: NFPA 262; Underwriters Laboratories (U.L.) 910 ( the Steiner Tunnel Test); or Canadian Standards Association (CSA) FT-6. In plenum applications for voice and data transmission, insulated electrical conductors and cables should exhibit low smoke evolution, low flame spread, and favorable electrical and physical properties. Materials selected for plenum wire insulation applications should exhibit a balance of properties. In this regard, most commonly employed materials have a unique combination of desirable characteristics and practical limitations. Polyvinyl chloride (PVC) has traditionally been the base material of choice for wire and cable insulation because of its inherent flame resistant properties. PVC is one of the least ignitable and flammable of commonly available polymeric materials. Other desirable attributes of PVC include good mechanical toughness, corrosion resistance, good dielectric properties, and low cost. Unfortunately, pure PVC is rigid and lacks flexibility, especially at low temperatures, where it is brittle. At the high temperatures required for melt processing, pure PVC is highly viscous, and difficult to process. Accordingly, plasticizers and other additives such as flame and smoke retardants, flexiblizers, and fillers are added to PVC during processing to improve the processing characteristics and the physical properties and flexibility of the end product at both high and low temperatures. As more stringent fire and safety standards are enacted and adopted in countries outside the United States, wire and cable insulation will require enormously improved fire and smoke performance, while maintaining superior physical properties and low cost. There is therefore a continuing need for a low cost wire and cable insulation compositions having improved flame spread and smoke evolution characteristics while simultaneously having superior physical properties, and simultaneously low costs. SUMMARY OF THE INVENTION The instant invention is capable of providing new low cost compositions which can have superior smoke and flame retardancy characteristics, and good mechanical and flexibility characteristics at low temperatures. These compositions may serve as either direct insulation for conductors, wires, and cables, or as a smoke and flame retardant jacketing material to cover other insulating materials, such as fluoropolymers or polyolefins, as are standardly applied in plenum cable and wiring constructions. In accordance with the purpose(s) of this invention, as embodied and broadly described herein, this invention, in one aspect, relates to an extruded or extrudable flame and smoke retardant composition comprising: a. polyvinyl chloride; b. at least one carboxylate ester plasticizer compound having no halogenated aromatic or phosphate residues; c. a zinc compound; and d. a magnesium compound. In another aspect, the invention relates to an extruded or extrudable flame and smoke retardant composition produced by the process of mixing: a. polyvinyl chloride; b. at least one carboxylate ester plasticizer compound having no halogenated aromatic or phosphate residues; c. a zinc compound; and d. a magnesium compound. In yet another aspect, the invention relates to an extruded or extrudable flame and smoke retardant composition comprising: a. polyvinyl chloride resin; b. a trimellitate ester compound, c. a zinc compound, d. a magnesium compound, e. chlorinated polyethylene, f. antimony trioxide, g. aluminum trihydrate, h. a lead compound, and i. calcium carbonate; wherein the composition has, at most, a minor amount of a brominated aromatic plasticizer compound or an organo-phosphate plasticizer compound. In still other aspects, the invention the invention relates to an extruded or extrudable flame and smoke retardant composition comprising: a. polyvinyl chloride resin; b. a trimellitate ester compound, c. a zinc compound, d. a magnesium compound, e. chlorinated polyethylene, f. antimony trioxide, g. aluminum trihydrate, h. a calcium-zinc thermal stabilizer compound, and i. an ethylene acrylate copolymer; wherein the composition has less than about 20 phr of a brominated aromatic plasticizer compound or an organo-phosphate plasticizer compound, and less than about 0.5 phr of any lead compound. The invention also provides articles comprising the compositions of the invention. Additional advantages of the invention will be set forth in part in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The advantages of the invention will be realized and attained by means of the elements and combinations particularly pointed out in the appended claims. It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention, as claimed. DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention may be understood more readily by reference to the following detailed description of preferred embodiments of the invention and the Examples included therein and to the Figures and their previous and following description. Before the present compounds, compositions and methods are disclosed and described, it is to be understood that this invention is not limited to specific synthetic methods, as such may, of course, vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. It must be noted that, as used in the specification and the appended claims, the singular forms "a," "an" and "the" include plural referents unless the context clearly dictates otherwise. Thus, for example, reference to "an aromatic compound" includes mixtures of aromatic compounds, reference to "a pharmaceutical carrier" includes mixtures of two or more such carriers, and the like. Ranges are often expressed herein as from "about" one particular value, and/or to "about" another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent "about," it will be understood that the particular value forms another embodiment. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint. In this specification and in the claims which follow, reference will be made to a number of terms which shall be defined to have the following meanings: References in the specification and concluding claims to parts by weight, of a particular element or component in a composition or article, denotes the weight relationship between the element or component and any other elements or components in the composition or article for which a part by weight is expressed. Thus, in a compound containing 2 parts by weight of component X and 5 parts by weight component Y, X and Y are present at a weight ratio of 2:5, and are present in such ratio regardless of whether additional components are contained in the compound. References in the specification and concluding claims to "Parts per hundred parts resin" ('phr') are a particular kind of "parts by weight" reference, as described immediately above . A reference to the "phr" of a component of a polyvinylchloride- based resin composition is a specialized reference to the parts by weight of that component as related to 100 parts by weight of polyvinylchloride resin, within the same composition. For example, in a PVC based-resin containing 4.0 phr of zinc oxide, the zinc oxide and PVC are present at a weight ratio of 4.0 : 100.0.; or stated alternatively, 4 parts zinc oxide as compared to 100 parts PVC. In another example, in a PVC based- resin containing 40 phr of a trimellitate plasticizer contains 40 parts trimellitate as compared to 100 parts PVC. A weight percent of a component, unless specifically stated to the contrary, is based on the total weight of the formulation or composition in which the component is included. A residue of a chemical species, as used in the specification and concluding claims, refers to the moiety that is the resulting product of the chemical species in a particular reaction scheme, or subsequent formulation of a chemical product, regardless of whether the moiety is actually obtained from the chemical species. Thus, an ethylene glycol residue in a polyester refers to one or more -OCH 2 CH 2 O- units in the polyester, regardless of whether ethylene glycol was used to prepare the polyester. Similarly, a sebacic acid residue in a polyester refers to one or more -CO(CH 2 ) 8 CO- moieties in the polyester, regardless of whether the residue is obtained by reacting sebacic acid or an ester thereof to obtain the polyester. A residue of a chemical formulation or composition, as used in the specification and concluding claims, refers to the final composition or product that is produced by a process for preparing the composition or product from starting materials of identifiable composition, regardless of whether the residue contains, after its formation, identifiable amounts of the starting materials. In other words, a residue of a chemical formulation or composition may refer to the product produced by the relevant process, even though the starting materials of the process may dissociate, mix, react, or otherwise become changed during the process for preparing the residue. For example, the residue of a composition formed by a process of mixing an aqueous solution comprising HC1 and aqueous solution comprising NaOH would refer to the final composition formed (comprising water and salt (NaCl)), regardless of whether the final composition contained HC1 or NaOH. In a further example, the residue of a composition formed by a process of mixing PVC, zinc acetate, and magnesium oxide would refer to the composition formed, regardless of whether the final composition contained zinc acetate or magnesium oxide, or regardless of the formation of some zinc oxide and/or magnesium acetate. The term "alkyl" as used herein refers to a branched or unbranched saturated hydrocarbon group of 1 to 24 carbon atoms, such as methyl, ethyl, «-propyl, isopropyl, «-butyl, isobutyl, t-butyl, octyl, decyl, tetradecyl, hexadecyl, eicosyl, tetracosyl and the like. Preferred alkyl groups herein contain from 1 to 12 carbon atoms. The term "lower alkyl" intends an alkyl group of from one to six carbon atoms, preferably from one to four carbon atoms. The term "cycloalkyl" intends a cyclic alkyl group of from three to eight, preferably five or six carbon atoms. The term "alkoxy" as used herein intends an alkyl group bound through a single, terminal ether linkage; that is, an "alkoxy" group may be defined as -OR where R is alkyl as defined above. A "lower alkoxy" group intends an alkoxy group containing from one to six, more preferably from one to four, carbon atoms. The term "alkene" as used herein intends a mono-unsaturated or di-unsaturated hydrocarbon group of 2 to 24 carbon atoms. Preferred groups within this class contain 2 to 12 carbon atoms. Asymmetric structures such as (AB)C=C(CD) are intended to include both the E and Z isomers. This may be presumed in structural formulae herein wherein an asymmetric alkene is present, or it may be explicitly indicated by the bond symbol =. The term "aliphatic" as used herein describes branched or unbranched hydrocarbon chains or groups containing 1 to 24 carbon atoms which are saturated, i.e., they have no double bonds between the carbon atoms. The term "aromatic" as used herein describes substituted or unsubstituted benzene-like compounds of six to twenty five carbon atoms having at least one 6- membered ring residue of carbon atoms, with alternating (conjugated) double bonds which have 4n + 2 π electrons, wherein n is a positive integer. "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. For example, the phrase "optionally substituted lower alkyl" means that the lower alkyl group may or may not be substituted and that the description includes both unsubstituted lower alkyl and lower alkyl where there is substitution. By the term "effective amount" of a compound or property as provided herein is meant such amount as is capable of performing the function of the compound or property for which an effective amount is expressed. As will be pointed out below, the exact amount required will vary from process to process, depending on recognized variables such as the compounds employed and the processing conditions observed. Thus, it is not possible to specify an exact "effective amount." However, an appropriate effective amount may be determined by one of ordinary skill in the art using only routine experimentation. As previously described above, the invention, in one aspect, relates to an extruded or extrudable flame and smoke retardant composition comprising: a. polyvinyl chloride; b. at least one carboxylate ester plasticizer compound having no halogenated aromatic or phosphate residues; c. a zinc compound; and d. a magnesium compound. The compositions of the invention can be applied as insulating or jacketing materials for wire or cable conductors or devices, by extruding the compositions in their hot molten state onto the wire or cable. Preferably, the combination of components is provided in amounts effective provide a compositions that is melt extrudable without significant thermal degradation, in the sense that they can be extruded from their hot molten state without the occurrence of unacceptable amounts thermally induced undesirable phenomena, including color changes, formation of embrittled or charred material or surfaces, and without the formation of gas bubbles in the resin resulting from decomposition of the materials comprising the composition. It is understood by those of skill in the art that the definition of an unacceptable amount of thermally induced undesirable phenonmena will vary with the nature of the composition, the nature of the intended application, and many other variables. Nevertheless, the definition of such unacceptable amounts of thermally induced undesirable phenomena are within the level of ordinary skill in the art, without excessive experimentation. The compositions of the invention typically contain polyvinylchloride (PVC) resin or polymers as a base material. Many variations of PVC base resin or polymer are suitable in the invention, and most ranges of molecular weight, and degrees of crosslinking can be acceptable. Preferably, the polyvinyl chloride is a commercially available polyvinyl chloride resin. Copolymers produced by the copolymerization of vinyl chloride and certain other mono, di, or multifunctional ethylenically unsaturated monomers (such as tetrafluoroethylene, ethylene, propylene, vinyl acetate, acrylates, styrenes, and the like) are also suitable polymers for the practice of the invention. Additionally, the PVC resins suitable for the invention may be have been post-treated after their formation by polymerization, by further halogenation, functionalization, crosslinking, or other similar chemical or physical treatments. The quantity of PVC resin or polymer used to prepare the compositions of the invention can be arbitrarily assigned a value of 100 parts by weight, relative to the parts by weight of any other components of the composition. In this way, the relative weight proportion of any other component of the composition may be conveniently expressed in terms well known in the art, i.e., in "phr", (parts per hundred parts resin), as defined hereinabove. For example, the compositions of the invention can comprise greater than about 10 phr of at least one carboxylate ester plasticizer compound having no halogenated aromatic or phosphate residues. In other words, for each 100 grams of polyvinylchloride resin, the composition additionally contains about 10 grams of the carboxylate ester plasticizer compounds (which will be more fully described below). The compositions of the invention additionally comprise a zinc compound or salt. Suitable zinc compounds include any metal alloys containing zinc, any inorganic or organic zinc compounds, any zinc containing complexes, or any zinc-containing salts. The zinc compound can comprise at least one zinc cation. Zinc cations may be present as either Zn 1+ mono-cations, or more typically as Zn 2+ di-cations, which is a zinc atom from which two electrons have been removed. Salts are defined as materials comprising at least one positively charged cation, and at least one negatively charged anion. Zinc-containing salts are zinc compounds comprising zinc cations in combination with at least one anion. Zinc-containing salts may or may not be soluble in water or any other liquid or solvent. Other cations may be also present in the zinc- containing salts, especially chemically similar cations such as magnesium cations, calcium cations, or other alkali-earth metal or transition metal di-cations. The anion for the zinc salts may comprise any chemically stable anion, of which many classes and species are known to those of skill in the art of chemical synthesis. Zinc complexes are zinc compounds in which a zinc atom or zinc cation is coordinately bonded to an external ligand, such as an amine, a phosphine, or some other ligand, many varieties of which are well-known to those of skill in the art . The zinc-containing salts can, e.g., have at least one anion comprising an oxide, a hydroxide, a halide, a sulfide, a carbonate, an organic carboxylate, a borate, a molybdate, a phosphate, a phosphite, a silicate, a sulfate, an organic sulfonate, a stannate, or mixtures thereof. A suitable class of zinc compounds are the organic carboxylates of zinc, in which the carboxylate anion is derived from a C 2 -C 20 carboxylic acid. The organic carboxylate groups may be substituted or unsubstituted, linear or branched, and may be aliphatic or aromatic. Zinc acetate and zinc stearate are preferred organic carboxylates of zinc. In certain embodiments, the zinc compound is zinc oxide, zinc hydroxide, or zinc acetate. Preferably, the zinc compound is present in the compositions in an amount effective to retard the rate of burning of the composition, and/or suppress the formation of smoke as the composition is burned or exposed to fire or extreme heat. Preferably, the zinc compounds are present in a concentration greater than at least about 0.5 phr, or more preferably greater than at least about 1, 2, or 3 phr. Preferably, the magnesium compound is present at less than about 20 phr, or more preferably at less than about 15 phr, 10 phr, or 8 phr. The lower and upper ranges of concentration of the zinc compound may be selected in any combination of the above described upper and lower limits. The compositions of the invention can additionally comprise a magnesium compound or salt. Suitable magnesium compounds include any metal alloys containing magnesium, any inorganic or organic magnesium compounds, any magnesium- containing complexes, or any magnesium-containing salts. Preferably, the magnesium compound comprises at least one magnesium cation. Magnesium cations may be present as either Mg 1+ mono-cations, or more typically as Mg 2+ di-cations, which comprises a magnesium atom from which two electrons have been removed. The magnesium-containing compound can have at least one anion. More preferably, the anion is an oxide, a hydroxide, a halide, a sulfide, a carbonate, an organic carboxylate, a borate, a molybdate, a phosphate, a phosphite, a silicate, a sulfate, an organic sulfonate, a stannate, or mixtures thereof. A suitable class of magnesium compounds are organic carboxylates of magnesium, in which the carboxylate anion is derived from a C 2 -C 20 carboxylic acid. The organic carboxylate groups may be substituted or unstubstituted, linear or branched, and may be aliphatic or aromatic. Magnesium acetate and magnesium stearate are preferred organic carboxylates of magnesium. In certain highly preferred embodiments, the magnesium compound is magnesium oxide, magnesium hydroxide, and/or magnesium chloride. Preferably, the magnesium compound is present in the compositions in an amount effective to retard burning of the composition, and/or suppress the formation of smoke as the composition is burned, or exposed to fire or extreme heat. Preferably, the magnesium compounds are present in a concentration greater than at least about 0.5 phr, or more preferably, at least about 1, 2, or 3 phr. Preferably, the magnesium compound is present at less than about 40 phr, or more preferably, less than about 35 phr, 30 phr, or 25 phr. The lower and upper ranges of concentration of the magnesium compound may be selected in any combination of the above described upper and lower limits. The compositions of the invention can comprise both a zinc compound and a magnesium compound. Preferably, both compounds are independently present in an amount effective to retard burning of the composition, and/or suppress the formation of smoke as the composition is burned or exposed to fire or extreme heat. Nevertheless it is observed that there is some synergism related to the presence of certain ratios of the zinc and magnesium compounds. Preferably the zinc compound and magnesium compound are present in weight ratios between about 1 :5 to about 5:1. More preferably, the zinc compound and magnesium compound are present in weight ratios between about 1 :4 to about 4:1. Most preferably, the weight ratio of the zinc compound to the magnesium compound is between about 1 :2 to about 2: 1. U.S. Patent No. 4,360,624 teaches that certain solid solutions of zinc oxide and magnesium oxide (nowadays available commercially under the tradename Ongard II™) are superior to physical mixtures of zinc oxide and magnesium oxide. The physical mixtures of zinc oxide and magnesium oxide are taught therein to (at least at higher concentrations) degrade the thermal stability of PVC-based resin compositions. No such effect has been observed with the present PVC-based compositions, as may be seen below in Example 2. In fact, in the present compositions, addition of a solid solution of zinc oxide and magnesium oxide can be decidedly inferior to separate addition of zinc oxide and magnesium oxide to the compositions of the invention. Therefore, in certain embodiments of the invention, the compositions do not comprise a solid solution of zinc oxide and magnesium oxide. As described hereinabove, the compositions of the invention can preferably include greater than about 10 phr of at least one carboxylate ester plasticizer compound having no halogenated aromatic or phosphate residues. The carboxylate ester plasticizer compounds are necessary to the composition in order to decrease the rigidity of pure solid PVC resins and increase the flexibility of the solid plenum compositions, especially at room temperature and lower. The carboxylate ester plasticizer compounds of the invention are esters which may be derived from the condensation of organic carboxylic acids with organic alcohols (though other methods of making esters are known), wherein neither the organic carboxylic acid or the organic alcohol comprises a halogenated aromatic residue or a phosphate residue. Although plasticizer compounds comprising halogenated aromatic residues (particularly brominated benzene or brominated phthalate residues), or phosphate residues (such as triphenyl phosphate, or mono-alkyl, diaromatic phosphates) increase the fire & smoke retardancy of a plenum composition, they are generally less environmentally acceptable, and much more expensive to make or purchase than the carboxylate ester plasticizer compounds of the invention. Therefore, the instant invention can employ relatively large quantities (at least about 10 phr) of carboxylate ester plasticizer compounds which do not comprise a halogenated aromatic residue or a phosphate residue. Such carboxylate ester plasticizer compounds preferably comprise from about five to about twenty-five carbon atoms. The organic carboxylic acids which may be used to form the ester may comprise a straight or branched, substituted or unsubstituted aliphatic or aromatic residue attached to its carboxylic acid group. Preferably, the organic carboxylic acid has an aromatic residue attached to its carboxylic acid group. Preferred organic carboxylic acids for formation of carboxylate ester plasticizer compounds include trimellitic acid, phthalic acid, isophthalic acid, adipic acid, and azelaic acid. The organic alcohols which may be used to form the carboxylate ester plasticizer compounds may comprise a straight or branched, substituted or unsubstituted aliphatic or aromatic residue attached to its alcoholic hydroxyl group, which condenses with the carboxylic acid to form an ester having an alkoxy residue formed from the organic alcohol. There may be more than one ester group, more than one carboxylate residue, or more than one alkoxy residue per molecule of the carboxylate ester plasticizer compounds. For example, tri- carboxylate esters of pentaerythritol are preferred carboxylate ester plasticizer compounds. Prefered carboxylate ester plasticizer compounds also encompass trimellitate ester compounds, phthalate ester compounds, adipic acid ester compounds, and azelaic ester compounds. Preferably, the majority of the alkoxy residues attached to the ester group or groups of the carboxylate ester plasticizer compounds comprise linear (rather than branched) alkyl groups. Preferably, the alkoxy residues have from about six to about 14 carbon atoms. Even more preferably, the alkoxy residues comprise mixtures of linear C7 and C9 alkoxy groups, or mixtures of linear C6, C8, or CIO alkoxy groups. In certain embodiments of the invention, the carboxylate ester plasticizer compound utilized is a trimellitate ester compound, a phthalate ester compound, or a mixture thereof. In other preferred embodiments of the invention, the carboxylate ester plasticizer compound utilized is a tri-ester of trimellitic acid. As described above, the at least one carboxylate ester plasticizer compound having no halogenated aromatic or phosphate residues is preferbly present at a concentration greater than about 10 phr. Preferably, the range of concentration of the carboxylate ester plasticizer compound is from about 10 to about 100 phr. At the highest ranges of the carboxylate ester plasticizer compound, the composition becomes so fluid that it exhibits "plastisol" behaviour, and become difficult to extrude easily. Therefore, more preferably, the range of concentration of the carboxylate ester plasticizer compound is from about 15 to about 60 phr. Even more preferably, the the range of concentration of the carboxylate ester plasticizer compound is from about 20 to about 50 phr. Most preferably, the carboxylate ester plasticizer compound is from about 25 to about 40 phr. While the four basic components of the extruded or extrudable flame and smoke retardant compositions of the invention have been described hereinabove (PVC, a zinc compound, a magnesium compound, and at least one carboxylate ester plasticizer compound), it is to be understood that the extruded or extrudable flame and smoke retardant compositions may optionally also contain various other additives and filler compounds or compositions, in order to further improve the flame and smoke retardance, extrudability, or other physical properties of the extrudable compositions. The following describes various additives that can be optionally incorporated in the composition. It will be understood that the relative number of parts assigned to any particular additive refers to the number of parts of the additive that can be incorporated into the composition regardless of what other additives are present. It will also be understood that any combination of the following additives can be present in the compositions of the invention. The extruded or extrudable flame and smoke retardant compositions of the invention may optionally comprise minor amounts of a halogenated aromatic plasticizer compound or an organo-phosphate plasticizer compound, or a mixture thereof. Although such plasticizer compounds improve flame and smoke retardance, extrudability, and other desirable physical properties, such additives are expensive, and their use at relatively high concentrations is undesirably expensive, especially at levels as high as 30, 20, 15, or 10 phr. Therefore, in preferred embodiments, the optional halogenated aromatic plasticizer compound or organo-phosphate plasticizer compound comprises less than about 5 phr of the extruded or extrudable flame and smoke retardant compositions. Even more preferably, the optional halogenated aromatic plasticizer compound or organo-phosphate plasticizer compound comprises less than about 4 phr, or less than about 3 phr, or less than about 2 phr, or less than about 1 phr, or less than about 0.5 phr of the extruded or extrudable flame and smoke retardant compositions. In a similar manner, the extruded or extrudable flame and smoke retardant compositions of the invention may optionally comprise a variety of flexibilizing agents. Flexibilizing agents generally comprise certain halogenated organic polymers and copolymers (other than polyvinylchloride), whose molecular weight and other characteristics are selected to enhance certain physical properties of polyvinylchloride, such as low temperature flexibility and/or elongation. Examples of flexibilizing agents suitable for the instant invention include chlorinated polyethylene, and chlorinated copolymers of ethylene and vinyl acetate. Chlorinated polyethylene is a highly preferred flexibilizing agent. Preferably, the flexibilizing agents are present in the extruded or extrudable flame and smoke retardant compositions of the invention from about 1 phr to about 30 phr. Another class of organic flexibilizing agents are ethylene acrylate copolymers, as can be exemplified by the ELVALOY series of ethylene acrylated co-polymers available from Dupont, of Wilmington Delaware. Suitable members of the ELVALOY family of copolymers include EP 4015, EP 4015B, EP 4051, EP 6797, HP 553, HP 441, HP441WP, HP 443, HP 661, HP 662, and HP 663. Ethylene acrylate copolymers are typically added to the compositions of this invention in a quantity sufficient to flexibilize the compositions, and to aid char formation on burning. Typically the ethylene acrylate copolymers are employed at a concentration from about 10 to about 100 phr Preferably, the ethylene acrylate copolymer are present in quantities from about 20 phr to about 50 phr. In other embodiments, the extruded or extrudable flame and smoke retardant compositions further comprise greater than about 5 phr of a molybdenum compound. Suitable molybdenum compounds are any compounds, complexes, or salts containing molybdenum atoms or molybdenum ions, which improve the flame and/or smoke retardancy, or any other physical properties of the compositions of the invention. Preferred molydenum compounds are MoO 3 , or a salt having a molybdate anion and at least one cation. Preferred molybdate anions have the formula Mo x O y n \ wherein x is an integer from 1 to about 10, y is an integer from 1 to about 25, and n is an integer from 1 to about 10. Even more preferably, the molybdate anion comprises an octomolybdate anion having the formula Mo 2 O g 2 \ Preferably, the cations associated with the above-described molybdate anions comprise hydrogen, ammonium cations, phosphonium cations, metal cations such as lithium, sodium, potassium, Mg 2+ , Ca 2+ , Zn 2+ , and the like. More preferred classes of molybdenum compounds include an ammonium molybdate compounds, and zinc molybdate compounds. Preferably, the molybdenum compounds of the invention are present in the extruded or extrudable flame and smoke retardant compositions in quantities from about 5 phr to about 25 phr. In other embodiments, the extruded or extrudable flame and smoke retardant compositions optionally further comprise at least one thermal stabilizer, which inhibit thermal degradation of the PVC during melt processing. One known class of preferred thermal stabilizer compounds include mixed metal salts, such as salts containing mixtures of metal cations (such as barium-cadmium, barium-cadmium-zinc, calcium- magnesium-tin-zinc, barium-zinc, calcium zinc, magnesium zinc, strontium zinc, and potassium-zinc) and suitable anions. Examples of suitable anions include but are not limited to an oxide, a hydroxide, a halide, a sulfide, a carbonate, an organic carboxylate, a borate, a molybdate, a phosphate, a phosphite, a silicate, a sulfate, an organic sulfonate, a stannate, or mixtures thereof. A suitable class of mixed metal salt thermal stabilizers are compositions comprising calcium and zinc compounds, and/or calcium and zinc cations. Such compositions include, for example, CG-1390, a proprietary thermal stabilizer / lubricant composition containing calcium and zinc compounds, available from the Chemical Group Inc, of Newtown Pennsylvania. CG-1390, and similar compositions, may be used to thermally stabilize PVC compositions while minimizing or avoiding the use of lead thermal stabilizers. Such calcium-zinc thermal stabilizer compositions are typically employed at a concentration from about 1 to about 20 phr, or preferably from about 5 to about 15 phr. In some embodiments, the thermal stabilizers of the invention are a lead compound. Lead compounds include metallic lead alloys, lead complexes, and lead salts. Preferred lead salts include tribasic lead sulfate, dibasic lead sulfate, dibasic lead stearate, dibasic leased phosphite, dibasic lead phthalate, lead fumarate, and mixtures thereof. Tribasic lead sulfate is a highly preferred thermal stabilizer. Typically, the above-described thermal stabilizers of the invention are utilized in a quantity sufficient to stabilize the extruded or extrudable flame and smoke retardant compositions during melt extrusion of the composition, so that no significant amount of discoloration, gassing, or charring of the composition occurs. Typically the thermal stabilizer compositions are employed at a concentration from about 1 to about 20 phr. Preferably, the thermal stabilizer compounds or compositions are present in quantities from about 5 phr to about 15 phr. Another thermal stabilizer comprises epoxidized soybean oil ("EPO"), utilized at concentrations from about 0.5 phr to about 15 phr. At higher concentrations, EPO also produces a plasticizing effect and/ or a lubricating effect in the compositions of the invention. Yet another optional thermal stabilizer comprises antimony trioxide, Sb 2 O 3 . Antimony trioxide is particularly effective as a thermal stabilizer when used in combination with the zinc compounds contained in the compositions of the invention. Preferably, antimony trioxide is utilized in concentrations ranging from about 0.5 phr to about 12 phr. In certain embodiments, the extruded or extrudable flame and smoke retardant compositions optionally further comprise certain fillers, which are inexpensive, and are selected to either improve or not effect flame and smoke retardance, and/or thermal stability of the compositions. Aluminum compounds are one class of such fillers. Particularly preferred aluminum filler compounds are aluminum trihydrate, and/or aluminum silicate. Aluminum silicate is present in many electrical grade clays, which are preferred fillers of the invention. Aluminum filler compound may be utilized in concentrations from about 0.5 phr to about 75 phr. Because of their inert behavior and low cost, relatively higher concentrations of aluminum trihydrate are generally preferable in many plenum compositions. Another class of filler compounds which may be utilized in the extruded or extrudable flame and smoke retardant compositions of the invention comprise magnesium carbonate, magnesium hydroxide, calcium carbonate, magnesium oxide, or a mixture thereof. A particularly preferred class of optional filler compounds are partially hydrated mixtures of magnesium and calcium carbonate, which provide a flame and smoke retardant effect by means of endothermically decomposition to produce magnesium oxide, magnesium hydroxide, calcium oxide, and an inert gas, CO 2 , which reduces flame temperatures. A particularly preferable example of a partially hydrated mixture of magnesium and calcium carbonates are the commercially available "Ultracarb" proprietary mixtures. These types of filler compounds which are preferably utilized in concentrations ranging from about 0.5 phr to about 75 phr, with higher ranges of concentrations being generally preferred. The above-described optional stabilizers, flexibilizers, additives, and fillers may be added to the extruded or extrudable flame and smoke retardant compositions of the invention either singly, or in mixtures. In many embodiments of the invention, several of the optional stabilizers, flexibilizers, additives, and fillers are employed in a single composition. In one example, the invention provides an extruded or extrudable flame and smoke retardant composition comprising: a. polyvinyl chloride resin; b. a trimellitate ester compound, c. a zinc compound, d. a magnesium compound, e. chlorinated polyethylene, f antimony trioxide, g. aluminum trihydrate, h. a lead compound, and i. calcium carbonate; wherein the composition has less than about 20 phr of a brominated aromatic plasticizer compound or an organo-phosphate plasticizer compound. In another example, the invention relates to an extruded or extrudable flame and smoke retardant composition comprising: a. polyvinyl chloride resin; b. a trimellitate ester compound, c. a zinc compound, d. a magnesium compound, e. chlorinated polyethylene, f. antimony trioxide, g. aluminum trihydrate, h. a calcium-zinc thermal stabilizer compound, and i. an ethylene acrylate copolymer; wherein the composition has less than about 20 phr of a brominated aromatic plasticizer compound or an organo-phosphate plasticizer compound, and less than about 0.5 phr of any lead compound. It is to be understood that the extruded or extrudable flame and smoke retardant compositions of the invention are typically residues produced by a process of mixing, compounding, and/or extruding mixtures of the above described starting materials, as described in the Experimental section below. Some of the materials (such as PVC and/or the plasicizer compounds) and/or additives are known to at least partially retain their individual chemical identities once compounded into the compositions, but it is not known whether all of the components do so. Some of the components, particularly the salts and/or fillers may dissolve and/or react to form solutions and/or new compounds once mixed, or solution residues derived from the mixtures. Individual analysis and/or identification of each original components mixed to form the compositions may or may not be possible in a given case. Therefore, the invention provides processes for preparing extruded or extrudable flame and smoke retardant compositions and/or their residues, by mixing the above-described components. In another example, the invention provides extruded or extrudable flame and smoke retardant composition produced by the process of mixing: a. 100 parts polyvinyl chloride; b. greater than about 10 phr of at least one carboxylate ester plasticizer compound having no halogenated aromatic or phosphate residues; c. a zinc compound; and d. a magnesium compound. Moreover, the above-described optional stabilizers, flexibilizers, additives, and fillers may be mixed or added to the above described basic ingredients singly or in groups, to produce the desired extruded or extrudable flame and smoke retardant compositions. In one exemplary process, in addition to the components a-d described immediately above, the process further comprises mixing; e. chlorinated polyethylene; f. antimony trioxide; g. aluminum trihydrate; and h. a lead compound. In another exemplary process, in addition to the components a-d described immediately above, the process further comprises mixing; e. a molybdate salt; f. epoxidized soybean oil; g. magnesium carbonate; and h. calcium carbonate. In yet another exemplary process, in addition to the components a-d described immediately above, the process further comprises mixing e. a molybdate salt, f. epoxidized soybean oil, g. magnesium carbonate, and h. a calcium-zinc thermal stabilizer compound. The extruded or extrudable flame and smoke retardant compositions can be produced in the form of a powder or a pellet. The powders or pellets are typically extruded to form articles. Preferably the compositions, in the form of powders or pellets are extruded to form suitable insulating materials or jacketing materials for articles such as fluoropolymer or polyolefm insulated conductors for telecommunication or data transmission. Such insulated conductors are preferrably sufficiently smoke and flame retardant to pass the UL 910 tests, and certain other tests required qualify as "Category 5" conductors, as defined by certain suppliers of insulated conductors, such as The Anixter Brothers Incorporated of Skokie Illinois. Such insulated conductor articles can comprise a conductor having a jacket comprising the extruded or extrudable flame and smoke retardant composition, wherein the conductor is a cable or wire. The articles may further comprise an insulating layer of polymeric or other material between the conductor and the jacket. Preferably, the insulating layer of polymeric material comprises a polyfluorinated organic polymer, such as polytetrafluoroethylene ("PTFE"), or fluorinated ethylene propylene ("FEP"). The component polymer compounds and/or stabilizers, plasticizers, flexibilizers, and fillers, of the invention may be readily synthesized using techniques generally known to industrial chemists. Suitable experimental methods for making and derivatizing polymeric compounds are described, for example, in the references cited in the Background section herein above, the disclosures of which are hereby incorporated by reference for their general teachings and for their synthesis teachings. Methods for making specific and preferred compositions of the present invention are described in detail in the Experimental section below. Experimental The following examples are put forth so as to provide those of ordinary skill in the art with a complete disclosure and description of how the compounds claimed herein are made and evaluated, and are intended to be purely exemplary of the invention and are not intended to limit the scope of what the inventors regard as their invention. Efforts have been made to ensure accuracy with respect to numbers (e.g., amounts, temperature, etc.) but some errors and deviations should be accounted for. Unless indicated otherwise, parts are parts per hundred resin (phr), temperature is in °C, or is at room temperature, and pressure is at or near atmospheric. Compounding of the compositions of the examples below may be accomplished by the following exemplary and non-limting protocol. First, base PVC polymer resin and a thermal stabilizer (which may include lead, or not include lead) is added to an operating high intensity mixer or ribbon blender, followed by liquid plasticizers. Next, metal-containing fire and smoke suppressants and fillers, then any non-metallic fillers or additives are added, with any lubricants being added last. When the plasticizer liquids have been completely absorbed into the solid composition, and a dry powder is obtained, the batch is dropped from the mixer and conveyed to a compounding machine. Compounding of the dry blend may be achieved using, for example, a Farrel Continuous Mixer, Buss Kneader, single or twin screw extruders, or Banbury Mixers. The compounded composition is then extruded, pelletized, and packaged for customer shipment. Customers feed the pellets into conventional extruders (typically in a single screw configuration), and extrude the compounded composition onto a conductor insulation or jacketing material for conductors. Example 1 Using the above-described protocol, the following composition of the invention (EX 1159) was prepared: Table 1. Compounding of EX - 1159 After compounding, the EX 1159 was extruded onto a wire conductor, as was a sample of a currently commercially available PVC jacketing material (01540), and several other experimental compositions (EX 1129, EX 1130, EX 1157, and EX 1160, each of which has a significantly higher raw materials cost than that of EX 1159. Example 2 In another seπes of expeπments, certain of the metal-containmg components of the EX 1159 composition were replaced with other metal containing mateπals, to the extent necessary to replace the metal content of the EX 1159 composition, as shown in Table 3, and the smoke generation charactenstics of the replacement compositions was tested in the 2' tunnel test As can be seen m Table 2 below, zmc oxide appears to be a supeπor zmc compound, but it can be replaced with compounds such as zmc acetate without substantial loss of smoke suppressant properties The smoke suppressant properties of the compostion can be significantly improved by the substitution of magnesium chloride for magnesium oxide Calcium carbonate can effectively substitute for aluminum tπhydrate and Ultracarb U5 Surpπsmgly (m view of the contrary teachings of U S Patent No 4,360,624), replacement of zmc oxide and magnesium oxide with a commercially available solid solution of zmc and magnesium oxides (Ongard II) actually substantially worsened the smoke generation charactenstics of the compositions Table 2. Selective Replacement of Metallic Components of EX 1159 Example 3 Using the above-described protocols, the following composition (similar to EX 1159 except for the non-lead Calcium / zinc thermal stabilizers ) was prepared as shown in Table 3 : Table 3. Compounding of a Lead Free Plenum Composition # 01561 After compounding, the above-described compositions were extruded onto a wire conductor, a nd tested for smoke generation characteristics, as illustrated below. The NFPA test method for measuring the smoke and flame retardant characteristics of cable insulation and jacketing materials provides for the test burning of cables according Underwriters Laboratories (U.L.) 910 ( the Steiner Tunnel Test). The test conditions for the U.L. 910 test are a 300,000 BTU/hour flame applied for 20 minutes to ten 24-foot lengths of test cables mounted on a horizontal tray within a tunnel. The criteria for passing the UL 910 Test are as follows: A. Flame spread— flame travel less than 5.0 feet. B. Smoke generation: 1. Maximum optical density of smoke less than 0.5. 2. Average optical density of smoke less than 0.15. Limited testing of the above-described compositions was carried out in a locally available 2' tunnel (which yields smoke generation results comparable obtained to those obtained in a 24' tunnel), and testing was limited to measurement of Maximum optical density of smoke ("Peak Smoke"), and average optical density of smoke ("Total Smoke"). The results of the Peak Smoke and Total Smoke Testing in the 2' tunnel are shown below in Table 4. The EX 1159 and # 01561compositions had both the lowest raw materials cost, and the best smoke generation characteristics. Measurements of various physical properties of some of the resins were also carried out, and EX 1159 had the second best low temperature brittle point (-10 °C versus -18 °C for EXl 160), and had the best high temperature stability observed (equalled only by EX 1157). Table 2. Smoke Generation Measurement Results for Plenum Cable Compositions Throughout this application, various publications are referenced. The disclosures of these publications in their entireties are hereby incorporated by reference into this application in order to more fully describe the state of the art to which this invention pertains. It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. Other embodiments of the invention will be apparent to those skilled in the art from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the invention being indicated by the following claims.

Claims: What is claimed is: 1. An extruded or extrudable flame and smoke retardant composition comprising the residue of: a. 100 parts polyvinyl chloride; b. greater than about 10 phr of at least one carboxylate ester plasticizer compound having no halogenated aromatic or phosphate residues; c. a zinc compound; and d. a magnesium compound. 2. The composition of Claim 1, wherein the zinc compound comprises at least one zinc cation and at least one anion. 3. The composition of Claim 3, wherein the at least one anion comprises an oxide, a hydroxide, a halide, a sulfide, a carbonate, an organic carboxylate, a borate, a molybdate, a phosphate, a phosphite, a silicate, a sulfate, an organic sulfonate, a stannate, or a mixture thereof. 4. The composition of Claim 1, wherein the zinc compound is zinc oxide, zinc hydroxide, or zinc acetate. 5. The composition of Claim 1, comprising from about 0.5 phr to about 20 phr of the zinc compound. 6. The composition of Claim 1 , wherein the magnesium compound comprises at least one magnesium cation and at least one anion. 7. The composition of Claim 6, wherein the at least one anion comprises an oxide, a hydroxide, a halide, a sulfide, a carbonate, an organic carboxylate, a borate, a molybdate, a phosphate, a phosphite, a silicate, a sulfate, an organic sulfonate, a stannate, or a mixture thereof. 8. The composition of Claim 1, wherein the magnesium compound is magnesium oxide, magnesium hydroxide, and/or magnesium chloride. 9. The composition of Claim 1, comprising from about 0.5 phr to about 40 phr of the magnesium compound 10. The composition of Claim 1, wherein the weight ratio of the zinc compound to the magnesium compound is from about 1 :2 to about 2:1. 11. The composition of Claim 1 , which does not comprise a solid solution of zinc oxide and magnesium oxide. 12. The composition of Claim 1 , wherein the carboxylate ester plasticizer is a trimellitate ester compound, a phthalate ester compound, or a mixture thereof. 13. The composition of Claim 1, wherein the carboxylate ester plasticizer is a tri- ester of trimellitic acid. 14. The composition of Claim 1, wherein the carboxylate ester plasticizer comprises alkoxy residues having from about six to about 14 carbon atoms. 15. The composition of Claim 1 , wherein the carboxylate ester plasticizer comprises alkoxy residues, and the majority of alkoxy residues have a linear structure. 16. The composition of Claim 1, further comprising greater than about 5 phr of a molybdenum compound. 17. The composition of Claim 1, further comprising MoO 3 . 18. The composition of Claim 1, further comprising a salt having a molybdate anion and at least one cation. 19. The composition of Claim 1, further comprising an octomolybdate. 20. The composition of Claim 1, further comprising an ammonium molybdate. 21. The composition of Claim 1 , further comprising a zinc molybdate. 22. The composition of Claim 1 , comprising a total of less than about 5 phr of a halogenated aromatic plasticizer compound, an organo-phosphate plasticizer compound, or a mixture thereof. 23. The composition of Claim 1, further comprising a flexibilizing agent. 24. The composition of Claim 1, further comprising an ethylene acrylate copolymer. 25. The composition of Claim 22, further comprising an ethylene acrylate copolymer. 26. The composition of Claim 1, further comprising chlorinated polyethylene. 27. The composition of Claim 1, further comprising a thermal stabilizer. 28. The composition of Claim 27, wherein the thermal stabilizer is a composition comprising calcium and zinc compounds. 29. The composition of claim 28, wherein the composition comprising calcium and zinc compounds is present in a concentration of from about 1 to about 20 phr. 30. The composition of claim 29 that does not contain more than about 0.5 phr of lead compounds. 31. The composition of Claim 1 , further comprising a lead compound. 32. The composition of Claim 1, further comprising tribasic lead sulfate or lead fumarate. 33. The composition of Claim 1, further comprising epoxidized soybean oil. 34. The composition of Claim 1, further comprising antimony trioxide. 35. The composition of Claim 1, further comprising an aluminum compound. 36. The composition of Claim 35, wherein the aluminum compound is aluminum trihydrate, or aluminum silicate. 37. The composition of Claim 1, further comprising magnesium carbonate, magnesium hydroxide, calcium carbonate, magnesium oxide, or a mixture thereof. 38. The composition of Claim 1, further comprising a partially hydrated mixture of magnesium and calcium carbonate. 39. The composition of Claim 1, wherein the composition is melt extrudable without significant thermal degradation. 40. The composition of Claim 1, wherein the composition is suitable as a jacketing material for fluoropolymer or polyolefin insulated conductors for telecommunication or data transmission. 41. An extruded or extrudable flame and smoke retardant composition comprising: a. polyvinyl chloride resin; b. a trimellitate ester compound, c. a zinc compound, d. a magnesium compound, e. chlorinated polyethylene, f. antimony trioxide, g. aluminum trihydrate, h. a lead compound, and i. calcium carbonate; wherein the composition has less than about 20 phr of a brominated aromatic plasticizer compound or an organo-phosphate plasticizer compound. 42. An extruded or extrudable flame and smoke retardant composition comprising: a. polyvinyl chloride resin; b. a trimellitate ester compound, c. a zinc compound, d. a magnesium compound, e. chlorinated polyethylene, f. antimony trioxide, g. aluminum trihydrate, h. a calcium-zinc thermal stabilizer compound, and i. an ethylene acrylate copolymer; wherein the composition has less than about 20 phr of a brominated aromatic plasticizer compound or an organo-phosphate plasticizer compound, and less than about 0.5 phr of any lead compound. 43. The composition of Claim 1, wherein the composition is a powder. 44. The composition of Claim 1, wherein the composition is a pellet. 45. An article comprising the composition of Claim 1. 46. The article of Claim 45, wherein the article comprises a conductor having a jacket comprising the extruded or extrudable flame and smoke retardant composition. 47. The article of Claim 46, wherein the conductor is a Category 5 cable or wire. 48. The article of Claim 46, further comprising an insulating layer between the conductor and the jacket. 49. The article of Claim 48, wherein the insulating layer comprises a polyfluorinated organic polymer. 50. An extruded or extrudable flame and smoke retardant composition produced by the process of mixing: a. 100 parts polyvinyl chloride; b. greater than about 10 phr of at least one carboxylate ester plasticizer compound having no halogenated aromatic or phosphate residues; c. a zinc compound; and d. a magnesium compound. 51. The composition of Claim 50, wherein the mixing is by melt extrusion. 52. An article comprising the composition of Claim 50. 53. The composition of Claim 50, wherein the process further comprises mixing; a. chlorinated polyethylene, b. antimony trioxide, c. aluminum trihydrate, d. a lead compound. 54. The composition of Claim 50, wherein the process further comprises mixing; a. a molybdate salt, b. epoxidized soybean oil, c. magnesium carbonate, and d. a calcium-zinc thermal stabilizer compound.

Inventors: MOORE JERMAINE L, PORRAS SAL E, MOORE, JERMAINE, L., PORRAS, SAL, E.
Applicants: GEORGIA GULF CORP, GEORGIA GULF CORPORATION
Application year: 2000
Main classification: C08K13
IPC codes: C08K3, C08K5, C08L27