PREPARATION OF A MACROCELLULAR ACOUSTIC FOAM

Abstract: A process for making a macrocellular acoustic foam is disclosed in which a foamable gel comprising a blowing agent and a polymeric resin composition is subjected to an extrusion process characterized by a die pressure greater than the prefoaming critical die pressure but less than or equal to four times that of said prefoaming critical die pressure and macrocellular foams are disclosed obtainable by that process which are made of: A) one ore more homopolymers of ethylene, one ore more C3-C20 alpha -olefin polymers, or a combination thereof; B) one or more halogenated flame retardants; C) optionally, one or more polymers other than that of Component A; and D) optionally, one or more flame retardant synergists.

Description: PREPARATION OF A MACROCELLULAR ACOUSTIC FOAM BACKGROUND OF THE INVENTION Foams and foamed articles often find utility in acoustic systems for sound absorption and insulation. Such foams, when developed for different market segments (appliance, automotive, building & construction, etc) often need to meet certain acoustic performance requirements and applicable fire test codes. To achieve the desired fire rating, a variety of flame retardants are often added to such foam resin formulations. Unfortunately, the typical flame retardants and other additives added to the formulation cause a number of foam problems. Flame retardants cause poor cell structure and cell collapse due to their effects on the polymer gel viscosity and melt strength. Flame retardants also act as nucleating agents in the foaming process and provide additional nucleation sites, resulting in the formation of a large number of small cells with variable properties. Unfortunately, small cell foam is not as acoustically active as large cell foam for sound absorption. US Patent No. 4,277,569 teaches the preparation of flame retardant polyolefin foams for thermal insulation and padding. However, the patent does not describe macrocellular foams or flame retardant macrocellular foams for acoustic applications or their preparation. Copending U.S. Application No. 60/178,516 filed on January 19, 2000 in the name of Martin Reimers et al., teaches the composition of macrocellular foams useful in sound management and a process to make the same. Copending U.S. Application No. 60/168844 filed on December 3, 1999, in the name of Bharat Chaudhary et al., teaches the use of flame retardants and synergists in the preparation of fabricated articles from substantially random ethylene styrene interpolymers and blends. However, a significant market need still exists for a large cell, acoustically active foam with good flame retardancy. This disclosure teaches a composition and a method of preparation of such macrocellular acoustic foam having both good flame retardancy and acoustic properties, suitable for several commercial applications. The key to the invention is the selection of a low nucleating foam composition, combining it with a selected flame retardant and extruding the formulation at a specific die pressure. The formulations are based on one or more ethylene or α-olefin homopolymer resins or their blends. The formulation optionally includes, a second polymer component, cell-enlarging agents, and organic or inorganic flame retardant synergists. BRIEF SUMMARY OF THE INVENTION. One aspect ofthe present invention is macrocellular acoustic foam comprising: A) one or more homopolymers of ethylene, one or more C3,-C 2 o α-olefin polymers, or a combination thereof; B) one or more halogenated flame retardants; C) optionally, one or more polymers other than that of Component A; and D) optionally, one or more flame retardant synergists. Another aspect ofthe present invention is a process for making macrocellular acoustic foam, such as those described below, comprising subjecting a foamable gel comprising at least one blowing agent and at least one polymeric resin composition to a die pressure greater than the prefoaming critical die pressure but less than or equal to four times that of said prefoaming critical die pressure. Another aspect of this invention is macrocellular acoustic foams obtainable, or prepared, by the above process of this invention, particularly those comprising; A) one or more homopolymers of ethylene, one or more C -C?o α-olefin polymers, or a combination thereof; B) one or more halogenated flame retardants; C) optionally, one or more polymers other than that of Component A; and D) optionally, one or more flame retardant synergists, as such or preferably in the form of an office partition, automotive decoupler, domestic appliance sound insulation, sound proofing panel or machine enclosure.. Another aspect of this invention is the use ofthe above macrocellular acoustic foam as an acoustic absorption or acoustic insulation material, particularly in environments in which fire retardancy is required. DETAILED DESCRIPTION OF THE INVENTION. Definitions. All references herein to elements or metals belonging to a certain Group refer to the Periodic Table ofthe Elements published and copyrighted by CRC Press, Inc., 1989. Also any reference to the Group or Groups shall be to the Group or Groups as reflected in this Periodic Table ofthe Elements using the IUPAC system for numbering groups. Any numerical values recited herein include all values from the lower value to the upper value in increments of one unit provided that there is a separation of at least 2 units between any lower value and any higher value. As an example, if it is stated that the amount of a component or a value of a process variable such as, for example, temperature, pressure, time and the like is, for example, from 1 to 90, preferably from 20 to 80, more preferably from 30 to 70, it is intended that values such as 15 to 85, 22 to 68, 43 to 51, 30 to 32 etc. are expressly enumerated in this specification. For values which are less than one, one unit is considered to be 0.0001, 0.001, 0.01 or 0.1 as appropriate. These are only examples of what is specifically intended and all possible combinations of njmerical values between the lowest value and the highest value enumerated are to be considered to be expressly stated in this application in a similar manner. The term " flame retardant " is used herein to indicate a flame retardant which can be any halogen-containing compound or mixture of compounds which imparts flame resistance to the compositions ofthe present invention. The term " flame retardant synergist" is used herein to indicate inorganic or organic compounds which enhance the effectiveness of flame-retardants, especially halogenated flame retardants. The term "interpolymer" is used herein to indicate a polymer wherein at least two different monomers are polymerized to make the interpolymer. This includes copolymers, terpolymers, etc. The term "macrocellular acoustic foam" is used herein to indicate a foam having an average cell size according to ASTM D3576 of from 1.5 mm to 15 mm, with cell sizes of from 2 mm to 10 mm being preferred, from 3 mm to 10 mm being more preferred, and from 4 mm to 8 mm being particularly preferred, and which, at a thickness of 35 mm, has an average sound absorption coefficient (measured via ASTM E-1050 at 250, 500, 1000 and 2000 Hz) of greater than 0.15, preferably greater than 0.20, more preferably greater than 0.25, even more preferably greater than 0.30. The term "prefoaming critical die pressure" is best determined empirically by observation ofthe foaming process, and is defined herein as the minimum die pressure at which popping is heard at the die and the resulting foam takes on a rough surface caused by premature nucleation and expansion ofthe foam inside the die lip. Preparation of Foams Excellent teachings to processes for making ethylenic polymer foam structures and processing them can be found in C. P. Park. "Polyolefin Foam", Chapter 9, Handbook of Polymer Foams and Technology, edited by D. Klempner and K. C. Frisch, Hanser Publishers, Munich, Vienna, New York, Barcelona (1991), which is incorporated here in by reference. The present process for making the macrocellular foam involves for the most part a conventional extrusion foaming process. The foam is advantageously prepared by heating an ethylenic polymer material to form a plasticized or melt polymer material, incorporating therein a blowing agent to form a foamable gel, and extruding the gel through a die to form the foam product. Prior to mixing with the blowing agent, the polymer material is heated to a temperature at or above its glass transition temperature or melting point. The blowing agent is optionally incorporated or mixed into the melt polymer material by any means known in the art such as with an extruder, mixer, blender, or the like. The blowing agent is mixed with the melt polymer material at an elevated pressure sufficient to prevent substantial expansion ofthe melt polymer material and to advantageously disperse the blowing agent homogeneously therein. Optionally, a nucleator is optionally blended in the polymer melt or dry blended with the polymer material prior to plasticizing or melting. The foamable gel is typically cooled to a lower temperature to optimize physical characteristics ofthe foam structure. The gel is then extruded or conveyed through a die of desired shape to a zone of reduced or lower pressure to form the foam structure. The zone of lower pressure is at a pressure lower than that in which the foamable gel is maintained prior to extrusion through the die. The lower pressure is optionally superatmospheric or subatmospheric (vacuum), but is preferably at an atmospheric level. However, what is critical to the process ofthe present invention is that the preparation ofthe macrocellular foam involves using a low die pressure for extrusion which is greater than the prefoaming critical die pressure but can only go as high as four times, more preferably three times, even more preferably two times the prefoaming critical die pressure. The range ofthe prefoaming critical die pressure can be estimated from a calculation based on solubility data for the blowing agent in the polymer melt as a function of temperature and pressure. For interpolation or extrapolation, the Flory-Huggins equation or the Eyring and Henry equations can be used. The Flory Huggins theory provides an implicit relationship for solubility as a function of temperature and pressure and requires a trial and error solution procedure. The Eyring equation and Henry equation provide an explicit relationship for solubility as a function of temperature and pressure that is easier to implement. The solubility of isobutane (and other blowing agents) in low density polyethylene as a function of temperature and pressure has been experimentally determined by B.I. Chaudhary & A.I. Johns and reported in Journal of Cellular Plastics, volume 34, number 4, pages 312-328 (1998). Experimental data is presented at three temperatures: 145°C, 160°C, and 200°C. Using the equations described below, the solubility curve at 108°C (foaming temperature) is predicted and the pressure corresponding to the solubility at 9% (weight), i.e. 90 mg/g polymer is read off as the prefoaming critical die pressure. At constant pressure, the Eyring equation is given by S = So*exp(-ΔH/RT) where S is the solubility ofthe gas at temperature, So is the solubility at the reference condition, ΔH is enthalpy and T is temperature, in K At constant temperature, the Henry equation is given by p = K*S where p is the partial pressure ofthe gas, K is a constant and S is the solubility At a fixed pressure, the solubility ofthe gas in the melt at any temperature is calculated from the solubilities at the two experimental temperatures. Thus, the solubility at 108°C (foaming temperature) and say 40 bar can be calculated from the solubility's at say 145°C and 160°C at 40 bar, using the Eyring equation. Knowing the solubility at 108°C and say 40 bar, the Henry equation can be used to calculate the pressure corresponding to the 9 % by weight isobutane solubility in polyethylene. This is the minimum pressure to keep the isobutane solubilized in the polymer melt and is therefore the prefoaming critical die pressure. Due to scatter in the experimental data, extrapolation to 108°C resulted in varying values for the prefoaming critical die pressure, depending on the data points chosen. Thus the prefoaming critical die pressure obtained by extrapolation ofthe experimental data is therefore not reliable. Thus, it is recommended that the experimental procedure cited in the reference be used to generate the solubility curve at 108°C and the pressure corresponding to the solubility of 9 pph isobutane be determined directly without extrapolation to obtain the prefoaming critical die pressure. The prefoaming critical die pressure is best determined experimentally for formulations comprising not only the polymer components but also additional additives such as flame retardants, synergists and cell enlarging agents. This is typically accomplished by preparing foams at several prefoaming die pressures and determining the effect of changes in the die pressure on the foam cell size and appearance. Below the prefoaming critical die pressure, the quality ofthe foam deteriorates sharply, rough skin is observed on the foam due to rupture of surface cells and typically a crackling noise is heard at the die due to rapid degassing ofthe blowing agent. At too high die pressures, the foam tends to nucleate significantly causing a loss in cell size upper limit which typically corresponds to a value of up to four times, the prefoaming critical die pressure. In another embodiment ofthe present invention, the resulting foam structure is optionally formed in a coalesced strand form by extrusion ofthe ethylenic polymer material through a multi-orifice die and wherein the die pressure for extrusion is greater than the prefoaming critical die pressure but can only go as high as four times, preferably three times, more preferably two times the prefoaming critical die pressure. The orifices a/e arranged so that contact between adjacent streams ofthe molten extrudate occurs during the foaming process and the contacting surfaces adhere to one another with sufficient adhesion to result in a unitary foam structure. The streams of molten extrudate exiting the die take the form of strands or profiles, which desirably foam, coalesce, and adhere to one another to form a unitary structure. Desirably, the coalesced individual strands or profiles should remain adhered in a unitary structure to prevent strand delamination under stresses encountered in preparing, shaping, and using the foam. Apparatuses and method for producing foam structures in coalesced strand form are seen in U.S. Pat. Nos. 3,573,152 and 4,824,720, both of which are incorporated herein by reference. Alternatively, the resulting foam structure is conveniently formed by an accumulating extrusion process as seen in U.S. Pat. No. 4,323,528, which is incorporated by reference herein. In this process, low density foam structures having large lateral cross-sectional areas are prepared by: 1) forming under pressure a gel ofthe ethylenic polymer material and a blowing agent at a temperature at which the viscosity ofthe gel is sufficient to retain the blowing agent when the gel is allowed to expand; 2) extruding the gel into a holding zone maintained at a temperature and pressure which does not allow the gel to foam, the holding zone having an outlet die defining an orifice opening into a zone of lower pressure at which the gel foams, and an openable gate closing the die orifice; 3) periodically opening the gate; 4) substantially concurrently applying mechanical pressure by a movable ram on the gel to eject it from the holding zone through the die orifice into the zone of lower pressure, at a rate greater than that at which substantial foaming in the die orifice occurs and less than that at which substantial irregularities in cross-sectional area or shape occurs; and 5) permitting the ejected gel to expand unrestrained in at least one dimension to produce the foam structure, and 6) wherein the die pressure for extrusion is greater than the prefoaming critical die pressure where prefoaming occurs but can only go as high as four times, more preferably three times, even more preferably two times the prefoaming critical die pressure. Blowing agents useful in making the resulting foam structure include inorganic agents, organic blowing agents and chemical blowing agents. Suitable inorganic blowing agents include carbon dioxide, nitrogen, argon, water, air, nitrogen, and helium. Organic blowing agents include aliphatic hydrocarbons having 1 -6 carbon atoms, aliphatic alcohols having 1 -3 carbon atoms, and fully and partially halogenated aliphatic hydrocarbons having 1-4 carbon atoms. Aliphatic hydrocarbons include methane, ethane, propane. : utane, isobutane, n-pentane, isopentane, neopentane, and the like. Aliphatic alcohols include methanol, ethanol, n-propanol, and isopropanol. Fully and partially halogenated aliphatic hydrocarbons include fluorocarbons, chlorocarbons, and chlorofluorocarbons. Examples of fluorocarbons include methyl fluoride, perfluoromethane, ethyl fluoride, 1 , 1-difluoroethane (HFC-152a), 1,1,1-trifluoroethane (HFC-143a), 1,1,1,-2-tetrafluoro-ethane (HFC-134a), pentafluoroethane, difluoromethane, perfluoroethane, 2,2-difluoropropane, 1,1,1- trifluoropropane, perfluoropropane, dichloropropane, difluoropropane, perfluorobutane, perfluorocyclobutane. Partially halogenated chlorocarbons and chlorofluorocarbons for use in this invention include methyl chloride, methylene chloride, ethyl chloride, 1,1,1- trichloroethane, 1 , 1 -dichloro- 1 fluoroethane (HCFC-141b), 1 -chloro 1 , 1 -difluoroethane (HCFC-142b), l-dichloro-2,2,2-trifluoroethane (HCFC-123) and 1 -chloro- 1,2,2,2- tetrafluoroethane (HCFC-124). Fully halogenated chlorofluorocarbons include trichloromonofluoromethane (CFC-11), dichlorodifluoromethane (CFC-12), trichlorotrifluoroethane (CFC- 113), 1,1,1 -trifluoroethane, pentafluoroethane, dichlorotetro fluoroethane (CFC-114), chloroheptafluoropropane, and dichloro- hexafluoropropane. Chemical blowing agents include azodicarbonamide, azodiisobutyro- nitrile, barium azodicarboxylate, n,n'-dimethyl-n,n'-dinitrosoterephthalamide, and benzenesulfonhydrazide, 4,4-oxybenzene sulfonyl semicarbazide, and p-toluene sulfonyl semicarbazide trihydrazino triazine. Preferred blowing agents include propane, n-butane, isobutane, HCFC-142b, HFC- 152a, carbon dioxide and mixtures ofthe foregoing. The amount of blowing agent incorporated into the polymer melt material to make a foam-foπriing polymer gel is typically from 0.2 to 5.0, preferably from 0.5 to 3.0, and most preferably from 1.0 to 2.50 gram moles per kilogram of polymer. However, these ranges should not be taken to limit the scope ofthe present invention. The foam of this invention preferably has perforation channels, more preferably a multiphcity of perforation channels extending from the at least one surface into the foam such that there is an average of at least one, preferably at least 5, more preferably at least 10, even more preferably at least 20, and even more preferably at least 30, perforation channel(s) per 10 square centimeters (cm 2 ) area ofthe at least one surface. The term "multiphcity" as used herein means at least two. In a preferred embodiment, the foam of this invention contains at least seven perforation channels. The perforation channels preferably have an average diameter at the at least one surface of at least 0.1 mm, more preferably at least 0.5 mm, and even more preferably at least 1 mm and preferably up to about the average cell size ofthe foam measured according to ASTM D 3756. One or more surfaces ofthe foam preferably has an average of at least four perforation channels per square centimeter extending from the at least one surface into the foam. The polymer foam preferably has an average thickness perpendicular to the surface perforated of at least 25 mm and the polymer foam is preferably perforated to an average depth of at least 5 mm below the surface ofthe polymer foam. Typically, perforation comprises puncturing the base foam with one or more pointed, sharp objects. Suitable pointed, sharp objects include needles, spikes, pins, or nails. In addition, perforation may comprise αΗlling, laser cutting, high pressure fluid cutting, air guns, or projectiles. A description of how to create suitable perforation channels for a different purpose, namely to accelerate release of blowing agent from the foam, is provided in U.S. Patent No. 5,585,058, which is incorporated herein by reference. In addition, the base foam may be prepared to have elongated cells by pulling the foam during expansion. Such pulling results in elongated cells without changing or often, increasing the cell size in the horizontal direction. Thus, pulling results in an increased average cell size in the direction perpendicular to the vertical direction (EH average) and facilitates perforation. Perforation ofthe base foam may be performed in any pattern, including square patterns and triangular patterns. Although the choice of a particular diameter ofthe sharp, pointed object with which to perforate the base foam is dependent upon many factors, including average cell size, intended spacing of perforations, pointed, sharp objects useful in the preparation of certain foams ofthe present invention will typically have diameters of from 1 mm to 4 mm. Compression may be used as an additional means of opening cells. Compression may be performed by any means sufficient to exert external force to one or more surfaces ofthe foam, and thus cause the cells within the foam to burst. Compression during o: after perforation is especially effective in rupturing the cell walls adjacent to the channels created by perforation since a high pressure difference across the cell walls can be created. In addition, unlike needle punching, compression can result in rupturing cell walls facing in all directions, thereby creating tortuous paths desired for sound absorption. The mechanical opening of closed-cells ofthe base foam lowers the airflow resistivity ofthe base foam by creating large- size pores in the cell walls and struts. In any event, regardless ofthe particular means by which it does so, such mechanical opening of closed- cells within the base thermoplastic polymer foam serves to enhance the usefulness ofthe foam for sound absorption and sound insulation applications. Of course, the percentage of cells opened mechanically will depend on a number of factors, including cell size, cell shape, means for opening, and the extent ofthe application of the means for opening applied to the base foam. The resulting foam structure preferably exhibits good dimensional stability. Preferred foams recover 80 or more percent of initial volume within a month with initial volume being measured within 30 seconds after foam expansion. Volume is measured by a suitable method such as cubic displacement of water. In addition, a nucleating agent may optionally be added in order to control the size of foam cells. Preferred nucleating agents include inorganic substances such as calcium carbonate, talc, clay, titanium oxide, silica, barium sulfate, diatomaceous earth, mixtures of citric acid and sodium bicarbonate, and the like. The amount of nucleating agent employed may range from 0 to 5 parts by weight per hundred parts by weight of a polymer resin. The resulting foam structure may be substantially noncrosslinked or uncrosslinked. The polymer material comprising the foam structure is substantially free of crosslinking. The foam structure may also be substantially cross-linked. Cross-linking may be induced by addition of a cross-linking agent or by radiation. Induction of cross-linking and exposure to an elevated temperature to effect foaming or expansion may occur simultaneously or sequentially. If a cross-linking agent is used, it is incorporated into the polymer material in the same manner as the chemical blowing agent. Further, if a cross- linking agent is used, the foamable melt polymer material is heated or exposed to a temperature of preferably less than 150°C to prevent decomposition of the cross-linking agent or the blowing agent and to prevent premature cross-linking. If radiation cross-linking is used, the foamable melt polymer material is heated or exposed to a temperature of preferably less than 160°C to prevent decomposition ofthe blowing agent. The foamable melt polymer material is extruded or conveyed through a die of desired shape to form a foamable structure. The foamable structure is then cross-linked and expanded at an elevated or high temperature (typically, 150°C-250°C) such as in an oven to form a foam structure. If radiation cross-Unking is used, the foamable structure is irradiated to cross-link the polymer material, which is then expanded at the elevated temperature as described above. The present structure can advantageously be made in sheet or thin plank form according to the above process using either cross-linking agents or radiation. The present foam structure may also be made into a continuous plank structure by an extrusion process utilizing a long-land die as described in GB 2,145,961A. In that process, the polymer, decomposable blowing agent and cross-linking agent are mixed in an extruder, heating the mixture to let the polymer cross-link and the blowing agent to decompose in a long-land die; and shaping and conducting away from the foam structure through the die with the foam structure and the die contact lubricated by a proper lubrication material The resulting foam structure may be either closed-celled or open-celled. The open cell content will range from 0 to 100 volume % as measured according to ASTM D2856-A. The resulting foam structure preferably has a density of less than 300, preferably less than 100, more preferably less than 60 and most preferably from 10 to 50 kilograms per cubic meter. The macrocellular foams exhibit an average cell size of from 1.5 mm to 15 mm, with cell sizes of from 2 mm to 10 mm being preferred, from 3 mm to 10 mm being more preferred, and from 4 mm to 8 mm being particularly preferred, according to ASTM D3576. The preferred ranges of density and cell size should not be taken as limiting the scope of this invention. The macrocellular foams made by the process ofthe present invention can be prepared from any combination of polymers for which the prefoaming critical die pressure can be determined. Preferably the resin to be foamed comprises an ethylene or α-olefin homopolymer resin or a blend of one or more of said ethylene or α-olefin hcrru- polymers. The resin to be foamed can also comprise a blend of one or more of said ethylene or α-olefin homopolymers with a second polymer component. This second polymer component can include, but is not limited to, ethylene/alpha olefin interpolymers (including polyolefin elastomers, and polyolefin plastomers) or one or more substantially random interpolymers, or combinations thereof. The α-Olefin Homopolymer The homopolymer resins include polyethylene or Cτ,-C 2 o α-olefin homopolymers or combinations thereof, preferably polyethylene or C 3 - Cio α-olefin homopolymers or combinations thereof, most preferably interpolymers comprising polyethylene or propylene polymers, or combinations thereof. One such class of polyethylene resins is generally produced by a high pressure polymerization process using a free radical initiator resulting in the traditional long chain branched low density polyethylene (LDPE). LDPE employed in the present composition usually has a density of less than or equal to 0.935 g/cc (ASTM D 792) and a melt idex of from 0.01 to 100, and preferably from 0.05 to 50, more preferably from 0.1 to 20 grams per 10 minutes (as determined by ASTM Test Method D 1238, Condition 190 2.16). The term "propylene polymer" as used herein means a polymer in which at least 50 weight percent of its monomeric units are derived directly from propylene. Suitable ethylenically unsaturated monomers other than propylene that may be included in the propylene polymer, include olefins, vinylacetate, methylacrylate, ethylacrylate, methyl methacrylate, acrylic acid, itaconic acid, maleic acid, and maleic anhydride. Appropriate propylene interpolymers include random, block, and grafted copolymers or inteφolymers of propylene and an olefin selected from the group consisting of ethylene, C4-C10 1 -olefins, and C4-C10 dienes. Propylene inteφolymers also include random teφolymers of propylene and 1 -olefins selected from the group consisting of ethylene and C4-C8 1 -olefins. The C4- CJO 1 -olefins include the linear and branched C4- 0 1 -olefins such as, for example, 1- butene, isobutylene, 1-pentene, 3-methyl-l-butene, 1-hexene, 3,4-dimethyl-l-butene, 1- heptene, 3 -methyl- 1-hexene, and the like. Examples of C4-C10 dienes include 1,3- butadiene, 1 ,4-pentadiene, isoprene, 1,5-hexadiene, and 2,3-dimethyl-l,3-hexadiene. As used herein, the term "inteφolymers" means polymers derived from the reaction of two of more different monomers and includes, for example, copolymers and teφolymers. The propylene polymer material may be comprised solely of one or more propylene homopolymers, one or more propylene copolymers, and blends of one or more of each of propylene homopolymers and copolymers. The polypropylene preferably comprises at least 70, even more preferably at least 90, and even more preferably 100, weight percent propylene monomer derived units (i.e., the propylene homopolymers are preferred). The propylene polymer preferably has a weight average molecular weight (M w ) of at least 100,000. M w can be measured by known procedures. The propylene polymer also preferably has a branching index less than 1. The branching index is an approach to quantifying the degree of long chain branching selected for this particular invention. The definition of branching index and procedure for determining the same is described in column 3, line 65 to column 4, line 30, of U.S. Patent 4,916,198, which is incoφorated herein by reference. The branching index is more preferably less than 0.9, and even more preferably less than 0.4. The propylene polymer has a tan δ value not greater than 1.5, preferably not greater than 1.2, even more preferably not greater than 1.0, and even more preferably not greater than 0.8. Tan δ may be calculated from g"/g', where g" is the loss modulus ofthe propylene polymer and g' is storage modulus ofthe propylene polymer melt using a 2.5 mm thick and 25 mm diameter specimen ofthe propylene polymer at 190 C at a one Radian per second oscillating frequency. These parameters may be measured using a mechanical spectrometer, such as a Rheometrics Model RMS-800 available from Rheometrics, Inc., Piscataway, New Jersey, U.S.A. Further details of how to carry out this determination ofthe tan δ, g' and g" values is provided in column 5, lines 59 to 64, and column 6, lines 4 to 29, of U.S. Patent 5,527,573, which is incoφorated herein by reference. In addition or in the alternative, the propylene polymer preferably has a melt tension of at least 7 centiNewtons (cN), more preferably at least 10 cN, and even more preferably at least 15 cN, and even more preferably at least 20 cN. Preferably, the propylene polymer has a melt tension not greater than 60 cN, more preferably not greater than 40 cN. The term "melt tension" as used throughout this description refers to a measurement ofthe tension in cN of a strand of molten polymer material at extruded from a capillary die with an diameter of 2.1 mm and a length of 40 mm at 230°C at an extrusion speed of 20 mm/minute (min.) and a constant take-up speed of 3.14 meter/minute using an apparatus known as a Melt Tension Tester Model 2 available from Toyo Seiki Seisaku-sho, Ltd. This method for determining melt tension is sometimes referred to as the "Chisso method". In addition or in the alternative, the propylene polymer preferably has a melt strength of at least 10 centiNewtons (cN), more preferably at least 20 cN, and even more preferably at least 25 cN, and even more preferably at least 30 cN. Preferably, the propylene polymer has a melt strength not greater than 60 cN, more preferably not greater than 55 cN. The term "melt strength" throughout this description refers to a measurement ofthe tension in cN of a strand of molten polymer material extruded from a capillary die with an diameter of 2.1 mm and a length of 41.9 mm at 190°C at a rate of 0.030 cc/sec. and stretched at a constant acceleration to determine the limiting draw force, or strength at break, using an apparatus known as a Gottfert Rheotens™ melt tension apparatus available from Gottfert, Inc. The propylene polymer used in the process ofthe invention preferably also has a melt elongation of at least 100 percent, more preferably at least 150 percent, most preferably at least 200 percent as measured by the same Rheotens™ melt tension apparatus and general procedure described above. The propylene polymer material preferably also has a melt flow rate of at least 0.01 more preferably at least 0.05, even more preferably at least 0.1 g/10 min., and even more preferably at least 0.5 g/10 min. up to 100, more preferably up to 50, even more preferably up to 20, and even more preferably up to 10, g/10 min. Throughout this description, the term "melt flow rate" refers to a measurement conducted according to American Society for Testing and Materials (ASTM) D-1238 condition 230°C/2.16 kg. (aka Condition L). Preferred propylene polymers include those that are branched or lightly cross-linked. Branching (or light cross-linking) may be obtained by those methods generally known in the art, such as chemical or irradiation branching/light cross-linking. One such resin which is prepared as a branched/lightly cross-linked polypropylene resin prior to using the polypropylene resin to prepare a finished polypropylene resin product and the method of preparing such a polypropylene resin is described in U.S. Patent No. 4,916,198, which is hereby incoφorated by reference. Another method to prepare branched/lightly cross-linked polypropylene resin is to introduce chemical compounds into the extruder, along with a polypropylene resin and allow the branching/lightly cross-linking reaction to take place in the extruder. This method is illustrated in U.S. Patent Nos. 3,250,731 with a polyfunctional azide, U.S. Patent 4,714,716 (and published Intemational Application WO 99/10424) with an azidofunctional silane and EP 879,844-Al with a peroxide in conjunction with a multi- vinyl functional nomoner. The aforementioned U.S. patents are incoφorated herein by reference. Irradiation techniques are illustrated by U.S Patent Nos. 5,605,936 and 5,883,151, which are also incoφorated by reference. The polymer composition used to prepare the foam preferably has a gel content of less than 10 percent, more preferably less than 5 percent, per ASTM D2765-84, Method A. If the ethylene homopolymer is blended with the propylene polymer, the weight ratio ofthe propylene polymer to the ethylene homopolymer is at least 35:65. The Second Polymer Blend Component In addition to the olefin homoplymer component, the polymer compositions used to prepare the foams of the present invention optionally can also comprise a second polymer component, which must be foamable in its unblended state, and must also, when blended with the olefin homoplymer component, yield a macrocellular acoustic foam. The olefin homoplymer or blend component is typically the majority component of a blend with a second polymer blend component, although this depends on their relative melting points and/or Tg's.. In any such blend, it is critical that the component having the highest melting point or Tg be present in an amount greater than 35 wt%, preferably greater than 40 wt %, more preferably greater than 50 wt % in the final blend This second polymer component can comprise one or more of; heterogeneous ethylene/α-olefin inteφolymers, preferably a heterogenous ethylene/ C^-d. α-olefin inteφolymer, most preferably a heterogenous ethylene/ octene- 1 inteφolymer; or homogeneous ethylene/α-olefin inteφolymers, including the substantially linear ethylene/α- olefin inteφolymers, most preferably a substantially linear ethylene/C 3 -C 8 α-olefin inteφolymer; or a substantially random inteφolymer, preferably a substantially random ethylene/styrene inteφolymer; or a thermoplastic olefin, preferably an ethylene/propylene rubber (EPM) or ethylene/propylene diene monomer teφolymer (EPDM); or a styreneic block copolymer, preferably styrene-butadiene (SB), styrene-isoprene(SI), styrene- butadiene-styrene (SBS), styrene-isoprene- styrene (SIS) or styrene-ethylene/cutene-styrene (SEBS) block copolymer, most preferably a styrene-butadiene-styrene (SBS) copolymer; or styrenic homopolymers or copolymers, preferably polystyrene, high impact polystyrene, copolymers of styrene and at least one of acrylonitrile, methacrylonitrile, maleic anhydride, or α-methyl styrene, most preferably polystyrene; or elastomers, preferably polyisoprene, polybutadiene, natural rubbers, ethylene/propylene rubbers, ethylene/propylene diene (EPDM) rubbers, styrene/butadiene rubbers, thermoplastic polyurethanes; or vinyl halide homopolymers and copolymers, preferably homopolymers or copolymers of vinyl chloride or vinylidene chloride or the chlorinated derivatives therefrom, most preferably poly (vinyl chloride) and poly (vinylidene chloride); or engineering thermosplastics, preferably poly(methylmethacrylate) (PMMA), cellulosics, nylons, poly(esters), poly(acetals); poly(amides),the poly(arylate), aromatic polyesters, poly(carbonate), poly(butylene) and polybutylene and polyethylene terephthalates, most preferably poly(methylmethacrylate) (PMMA), and poly(esters); and any and all combinations thereof. The ethylene/α-olefin inteφolymers can be further characterized by their degree of long or short chain branching and the distribution thereof. Linear olefin polymers which have an absence of long chain branching, such as the traditional linear low density polyethylene polymers (heterogeneous LLDPE) or linear high density polyethylene polymers (HDPE) made using Ziegler polymerization processes (for example, U.S. Patent No. 4,076,698 (Anderson et al.), are sometimes called heterogeneous polymers. HDPE consists mainly of long linear polyethylene chains. The HDPE employed in the present composition usually has a density of at least 0.94 grams per cubic centimeter (g/cc) as determined by ASTM D 792, and a melt index of from 0.01 to 1000, and preferably from 0.01 to 100, more preferably from 0.05 to 50 grams per 10 minutes (as determined by ASTM Test Method D 1238, Condition 190 2.16). The heterogeneous LLDPE employed in the present composition generally has a density of from 0.85 to 0.94 g/cc (ASTM D 792), and melt index of from 0.01 to 1000, and preferably from 0.01 to 100, more preferably from 0.05 to 50 grams per 10 minutes (as determined by ASTM Test Method D 1238, Condition 19072.16). Preferably the LLDPE is an inteφolymer of ethylene and one or more other α-olefins having from 3 to 18 carbon atoms, more preferably from 3-8 carbon atoms. Preferred comonomers include 1-butene, 4-methyl-l-pentene, 1-hexene, and 1-octene. A further class is that ofthe uniformly branched or homogeneous polymers (e.g. homogeneous polyethylene). The homogeneous polymers contain no long chain branches and have only branches derived from the monomers (if having more than two carbon atoms). Homogeneous polymers include those made as described in U.S. Patent 3,645,992 (Elston), and those made using so-called single site catalysts in a batch reactor having relatively high olefin concentrations (as described in U.S. Patent Nos. 5,026,798 and 5,055,438 (Canich). The uniformly branched/homogeneous polymers are those polymers in which the comonomer is randomly distributed within a given inteφolymer molecule and wherein the inteφolymer molecules have a similar ethylene/comonomer ratio within that inteφolymer. The homogeneous LLDPE employed in the present composition generally has a density of from 0.85 to 0.94 g/cc (ASTM D 792), and a melt index of from 0.01 to 1000, and preferably from 0.01 to 100, more preferably from 0.05 to 50 grams per 10 minutes (as determined by ASTM Test Method D 1238, Condition 19072.16). Preferably the LLDPE is an inteφolymer of ethylene and one or more other α- olefins having from 3 to 18 carbon atoms, more preferably from 3-8 carbon atoms. Preferred comonomers include 1-butene, 4-methyl-l-pentene, 1-hexene, and 1-octene. Further, there is the class of substantially linear olefin polymers that may advantageously be as a component (B) ofthe blends used to prepare the foams ofthe present invention. These polymers have processability similar to LDPE, but the strength and toughness of LLDPE. Substantially linear olefin polymers are disclosed in U.S. Patent Nos. 5,272,236 and 5,278,272, the entire contents of which are incoφorated herein by reference. The density ofthe substantially linear olefin polymers as measured in accordance with ASTM D-792 is generally from 0.85 g/cc to 0.97 g/cc, preferably from 0.85 g/cc to 0.955 g/cc, and especially from 0.85 g/cc to 0.92 g/cc and a melt index of from 0.01 to 1000, and preferably from 0.01 to 100, more preferably from 0.05 to 50 grams per 10 minutes (as determined by ASTM Test Method D 1238, Condition 19072.16). Also, included are the ultra low molecular weight ethylene polymers and ethylene/α- olefin inteφolymers described in the U. S. Patent Application No. 784,683 entitled Ultra- Low Molecular Weight Polymers, filed January 22, 1997 M. J. Guest, et al., which is incoφorated herein by reference. These ethylene/α-olefin inteφolymers have I 2 melt indices greater than 1,000, or a number average molecular weight (Mn) less than 11,000. Especially preferred olefinic polymers comprise HDPE, heterogeneous LLDPE, homogeneous linear polyethylene, substantially linear olefin polymer, polypropylene (PP), especially isotactic polypropylene, syndiotactic polypropylene and rubber toughened polypropylenes, or ethylene-propylene inteφolymers (EP), or chlorinated polyolefins (CPE), or ethylene-vinyl acetate copolymers (EVA), the polymeric ionomer compositions or ethylene-acrylic acid copolymers, or any combination thereof. Also included in the second polymer component are the so called substantially random inteφolymers which comprise polymer units derived from one or more α-olefin monomers with one or more vinyl or vinylidene aromatic monomers and/or a hindered aliphatic or cycloaliphatic vinyl or vinylidene monomers. The term substantially random as used herein means that the distribution ofthe monomers of said inteφolymer can be described by the Bernoulli statistical model or by a first or second order Markovian statistical model, as described by J. C. RandaU in POLYMER SEOUENCE DETERMINATION. Carbon- 13 NMR Method. Academic Press New York, 1977, pp. 71-78. Preferably, substantiaUy random inteφolymers do not contain more than 15 percent ofthe total amount of vinyl or vinyUdene aromatic monomer in blocks of vinyl or vinylidene aromatic monomer of more than 3 units. More preferably, the inteφolymer is not characterized by a high degree ofeither isotacticity or syndiotacticity. This means that in the carbon "13 NMR spectrum of the substantiaUy random inteφolymer the peak areas corresponding to the main chain methylene and methine carbons representing either meso diad sequences or racemic diad sequences should not exceed 75 percent ofthe total peak area ofthe main chain methylene and methine carbons. Suitable α-olefins include for example, α-olefins containing from 2 to 20, preferably from 2 to 12, more preferably from 2 to 8 carbon atoms. Particularly suitable are ethylene, propylene, butene-1, pentene-1, 4-methyl-l-pentene, hexene-1 or octene-1 or ethylene in combination with one or more of propylene, butene-1, 4-methyl-l-pentene, hexene-1 or octene- 1. These α-olefins do not contain an aromatic moiety. Suitable vinyl or vinyUdene aromatic monomers which can be employed to prepare the inteφolymers include, for example, those represented by the following formula: Ar I (CH 2 ) n R l _ c = C(R ) 2 wherein R 1 is selected from the group of radicals consisting of hydrogen and alkyl radicals containing from 1 to 4 carbon atoms, preferably hydrogen or methyl; each R 2 is independently selected from the group of radicals consisting of hydrogen and alkyl radicals containing from 1 to 4 carbon atoms, preferably hydrogen or methyl; Ar is a phenyl group or a phenyl group substituted with from 1 to 5 substituents selected from the group consisting of halo, G--i-alkyl, and G-4-haloalkyl; and n has a value from zero to 4, preferably from zero to 2, most preferably zero. Exemplary vinyl or vinylidene aromatic monomers include styrene, vinyl toluene, α-methylstyrene, t-butyl styrene, chlorostyrene, including aU isomers of these compounds, and the Uke. Particularly suitable such monomers include styrene and lower alkyl- or halogen-substituted derivatives thereof. Preferred monomers include styrene, α-methyl styrene, the lower alkyl- (G - C 4 ) or phenyl-ring substituted derivatives of styrene, such as for example, ortho-, meta-, and para-metbylstyrene, the ring halogenated styrenes, para-vinyl toluene or mixtures thereof, and the Uke. A more preferred aromatic vinyl monomer is styrene. By the term "hindered aUphatic or cycloahphatic vinyl or vinylidene compounds", it is meant addition polymerizable vinyl or vinylidene monomers corresponding to the formula: A' I R i _ C = C(R2) 2 wherein A 1 is a stericaUy bulky, aliphatic or cycloahphatic substituent of up to 20 carbons, R 1 is selected from the group of radicals consisting of hydrogen and alkyl radicals containing from 1 to 4 carbon atoms, preferably hydrogen or methyl; each R 2 is independently selected from the group of radicals consisting of hydrogen and alkyl radicals containing from 1 to 4 carbon atoms, preferably hydrogen or methyl; or alternatively R 1 and A 1 together form a ring system. By the term "stericaUy bulky" is meant that the monomer bearing this substituent is normaUy incapable of addition polymerization by standard Ziegler-Natta polymerization catalysts at a rate comparable with ethylene polymerizations. Preferred hindered aUphatic or cycloahphatic vinyl or vinyUdene compounds are monomers in which one ofthe carbon atoms bearing ethylenic unsaturation is tertiary or quaternary substituted. Examples of such substituents include cycUc aUphatic groups such as cyclohexyl, cyclohexenvi. . clooctenyl, or ring alkyl or aryl substituted derivatives thereof, tert-butyl, norbornyl, and the Uke. Most preferred hindered aUphatic or cycloahphatic vinyl or vinyUdene compounds are the various isomeric vinyl- ring substituted derivatives of cyclohexene and substituted cyclohexenes, and 5-ethylidene-2-norbornene. EspeciaUy suitable are 1-, 3-, and 4-vinylcyclohexene. Other optional polymerizable ethylenically unsaturated monomer(s) include norbornene and C M O alkyl or C6-10 aryl substituted norbornenes. Exemplary substantiaUy random inteφolymers include ethylene/styrene, ethylene/styrene/propylene, ethylene/styrene/octene, ethylene/styrene/butene, and ethylene/styrene/norbornene inteφolymers. The substantially random inteφolymers may be modified by typical grafting, hydrogenation, fiinctionalizing, or other reactions well known to those skilled in the art. The polymers may be readily sulfonated or chlorinated to provide functionalized derivatives according to estabUshed techniques. The substantiaUy random inteφolymers may also be modified by various cross- Unking processes including, but not limited to peroxide-, silane-, sulfur-, radiation-, or azide-based cure systems. A full description ofthe various cross-Unking technologies is described in copending U.S. Patent AppUcation Nos. 08/921,641, now issued as US-A-5, 869,591, and 08/921,642, now issued as US-A-5,977,271, both filed on August 27, 1997, the entire contents of both of which are herein incoφorated by reference. Dual cure systems, which use a combination of heat, moisture cure, and radiation steps, may be effectively employed. Such dual cure systems are disclosed and claimed in U. S. Patent Application Serial No. 536,022, filed on September 29, 1995, in the names of K. L. Walton and S. V. Karande, now issued as US-A-5, 911,940, which is incoφorated herein by reference. For instance, it may be desirable to employ peroxide crosslinking agents in conjunction with silane crossUnking agents, peroxide crossUnking agents in conjunction with radiation, sulfur-containing crossUnking agents in conjunction with silane crossUnking agents, etc. The substantiaUy random inteφolymers may also be modified by various cross-Unking processes including, but not limited to the incoφoration of a diene component as a termonomer in its preparation and subsequent cross Unking by the aforementioned methods and further methods including vulcanization via the vinyl group using sulfur for example as the cross linking agent. The substantially random inteφolymers include the pseudo-random inteφolymers as described in EP-A-0,416,815 by James C. Stevens et al. and US Patent No. 5,703,187 by Francis J. Timmers, both of which are incoφorated herein by reference in their entirety. The substantiaUy random inteφolymers also include the substantially random teφolymers as described in US Patent No. 5,872,201 which is incoφorated herein by reference in their entirety. The substantiaUy random inteφolymers are best prepared by polymerizing a mixture of polymerizable monomers in the presence of one or more metaUocene or constrained geometry catalysts in combination with various cocatalysts. Preferred operating conditions for the polymerization reactions are pressures from atmospheric up to 3000 atmospheres and temperatures from -30°C to 200°C. Polymerizations and unreacted monomer removal at temperatures above the autopolymerization temperature ofthe respective monomers may result in formation of some amounts of homopolymer polymerization products resulting from free radical polymerization. Examples of suitable catalysts and methods for preparing the substantially random inteφolymers are disclosed in EP-A-416,815; EP-A-514,828; EP-A-520,732; and EP-B- 705,269; as weU as U.S. Patents: 5,055,438; 5,057,475; 5,096,867; 5,064,802; 5,132,380; 5,189,192; 5,321,106; 5,347,024; 5,350,723; 5,374,696; 5,399,635; and 5,470,993, all of which patents and apphcations are incoφorated herein by reference. The substantially random α-olefin/ vinyl or vinylidene aromatic inteφolymers can also be prepared by the methods described in JP 07/278230 employing compounds shown by the general formula Cp 1 R l R ; 3 \ / M \ / \ Cp R 2 where Cp 1 and Cp 2 are cyclopentadienyl groups, indenyl groups, fluorenyl groups, or substituents of these, independently of each other; R 1 and R 2 are hydrogen atoms, halogen atoms, hydrocarbon groups with carbon numbers of 1-12, alkoxyl groups, or aryloxyl groups, independently of each other; M is a group IV metal, preferably Zr or Hf, most preferably Zr; and R 3 is an alkylene group or silanediyl group used to cross-link Cp 1 and Cp 2 ). The substantiaUy random α-olefin/ vinyl or vinyUdene aromatic inteφolymers can also be prepared by the methods described by John G. Bradfute et al. (W. R. Grace & Co.) in WO 95/32095; by R. B. Pannell (Exxon Chemical Patents, Inc.) in WO 94/00500; and in Plastics Technology, p. 25 (September 1992), all of which are incoφorated herein by reference in their entirety. Also suitable are the substantially random inteφolymers which comprise at least one α-olefin/vinyl aromatic/vinyl aromatic/α-olefin tetrad disclosed in WO 98/0999. These inteφolymers contain additional signals with intensities greater than three times the peak to peak noise. These signals appear in the chemical shift range 43.70-44.25 ppm and 38.0-38.5 ppm. SpecificaUy, major peaks are observed at 44.1 , 43.9 and 38.2 ppm. A proton test NMR experiment indicates that the signals in the chemical shift region 43.70-44.25 ppm are methine carbons and the signals in the region 38.0-38.5 ppm are methylene carbons. Further preparative methods for the inteφolymers used in the present invention have been described in the Uterature. Longo and Grassi (Makromol. Chem.. Volume 191, pages 2387 to 2396 [ 1990]) and D'AnniePo et al. (Journal of AppUed Polymer Science, Volume 58, pages 1701-1706 [1995]) reported the use of a catalytic system based on methylalumoxane (MAO) and cyclopentadienyltitanium trichloride (CpTiCl 3 ) to prepare an ethylene-styrene copolymer. Xu and Lin (Polymer Preprints. Am. Chem. Soc. Div. Polym. Chem.) Volume 35, pages 686,687 [1994]) have reported copolymerization using a MgCl 2 /TiCL/NdCl 3 / Al(iBu) 3 catalyst to give random copolymers of styrene and propylene. Lu et al (Journal of Applied Polymer Science. Volume 53, pages 1453 to 1460 [1994]) have described the copolymerization of ethylene and styrene using a TiCL/NdCy MgCl 2 /Al(Et) 3 catalyst. Sernetz and Mulhaupt. (Macromol. Chem. Phvs.. v. 197, pp. 1071-1083, 1997) have described the influence of polymerization conditions on the copolymerization of styrene with ethylene using Me 2 Si(Me Cp)(N-tert-butyl)TiCl 2 /methylaluminoxane Ziegler-Natta catalysts. Copolymers of ethylene and styrene produced by bridged metaUocene catalysts have been described by Arai, Toshiaki and Suzuki (Polymer Preprints. Am. Chem. Soc. Div. Polym. Chem.) Volume 38, pages 349, 350 [1997]) and in United States patent number 5,652,315, issued to Mitsui Toatsu Chemicals, Inc. The manufacture of α-olefin/vinyl aromatic monomer inteφolymers such as propylene/styrene and butene/styrene are described in United States patent number 5,244,996, issued to Mitsui Petrochemical Industries Ltd or United States patent number 5,652,315 also issued to Mitsui Petrochemical Industries Ltd or as disclosed in DE 197 11 339 Al and U.S. patent No. 5,883,213 to Denki Kagaku Kogyo KK. All the above methods disclosed for preparing the inteφolymer component are incoφorated herein by reference. Also, the random copolymers of ethylene and styrene as disclosed in Polymer Preprints Vol 39, No. 1, March 1998 by Toru Aria et al. can also be employed as blend components for the foams ofthe present invention. The substantiaUy random inteφolymers usuaUy contain from 0.5 to 65, preferably from 1 to 55, more preferably from 1 to 50 mole percent of at least one vinyl or vinylidene aromatic monomer and/or hindered aUphatic or cycloahphatic vinyl or vinyUdene monomer and from 35 to 99.5, preferably from 45 to 99, more preferably from 50 to 99 mole percent of ethylene and/or at least one aUphatic α-olefin having from 3 to 20 carbon atoms. The substantiaUy random inteφolymer(s) appUcable to the present invention can have a melt index of from 0.01 to 1000, and preferably from 0.01 to 100, more preferably from 0.05 to 50 grams per 10 minutes (as determined by ASTM Test Method D 1238, Condition 19072.16). While preparing the substantiaUy random inteφolymer, a * , amount of atactic vinyl or vinyUdene aromatic homopolymer may be formed due to homopolymerization ofthe vinyl or vinyUdene aromatic monomer at elevated temperatures. The presence of vinyl or vinyUdene aromatic homopolymer is in general not detrimental for the puφoses ofthe present invention and can be tolerated. The vinyl or vinyUdene aromatic homopolymer may be separated from the inteφolymer, if desired, by extraction techniques such as selective precipitation from solution with a non solvent for either the inteφolymer or the vinyl or vinylidene aromatic homopolymer. For the puφose ofthe present invention it is preferred that no more than 20 weight percent, preferably less than 15 weight percent, most preferably less than 10 weight percent based on the total weight ofthe inteφolymers of atactic vinyl or vinylidene aromatic homopolymer is present. Most preferred as the second polymer component are the substantiaUy random inteφolymers such as those marketed by The Dow Chemical Company under the INDEX™ tradename, the polyolefin plastomers, such as those marketed by The Dow Chemical Company under the AFFINITY™ tradename and polyethylene elastomers, such as those marketed by Du Pont Dow Elastomers LLC under the ENGAGE™ tradename. Flame Retardant As the foam wiU be used as acoustical insulation in buildings, it will also contain a flame retardant which functions to extinguish flames or at least slow the spread of fire in the foam. Suitable flame retardants are weU-known in the art and include but are not Umited to hexahalodiphenyl ethers, tetrabromobisphenol A bis (2,3-dibromopropyl ether) octahalodiphenyl ethers, decahalodiphenyl ethers, decahalobiphenyl ethanes, 1 ,2- bis(trihalophenoxy)ethanes, 1 ,2-bis(pentahalophenoxy)ethanes, hexahalocyclododecane, a tetrahalobisphenol-A, ethylene(N, N')-bis-tetrahalophthalimides, tetrahalophthahc anhydrides, hexahalobenzenes, halogenated indanes, halogenated phosphate esters, halogenated paraffins, halogenated polystyrenes, and polymers of halogenated bisphenol-A and epichlorohydrin, or mixtures thereof. Preferably, the flame retardant is a bromine or chlorine containing compound. The halogenated flame-retardants may include one or more of hexabromocycledodecane (HBCD), tetrabromobisphenol-A- (TBBA), chlorowax and may be used with or without flame retardant synergists. Commercially available products suitable for use as flame retardants in the present invention include PE-68™ (a trademark and product ofthe Great Lakes Chemical Coφoration). Suitable flame retardants are well known, and include brominated organic compounds such as are described in US-A- 4,446,254 and US-A- 5,171,757, the entire contents of which are herein incoφorated by reference. For foams, the halogen content in the final foams should be 0.05-20 wt%, preferably 0.1-15 wt% and most preferably 0.2-10 wt%. In a preferred embodiment, the flame retardant is a hexahalocyclododecane, preferably hexabromocyclododecane (HBCD), or tetrabromobisphenol A bis (2,3- dibromopropyl ether), PE™-68, or a combination with any other halogenated or non- halogenated flame-retardants, which can include, but are not Umited to phosphorous based flame retardants such as triphenyl phosphate and encapsulated red phosphorous. In the case of halogenated flame retardants, preferred loadings or amounts depend on the apphcation and the desired level of flame retardants but are those which typically yield halogen contents of 0.05 to 20 phr in foamed structures Flame Retardant Synergist Optionally a flame retardant synergist may be added along with the flame retardant. Examples of inorganic flame retardant synergists include, but are not limited to, metal oxides, e.g. iron oxide, tin oxide, zinc oxide, aluminum trioxide, alumina, antimony trioxide and antimony pentoxide, bismuth oxide, molybdenum trioxide, and tungsten trioxide, boron compounds such as zinc borate, antimony siUcates, zinc stannate, zinc hydroxystannate, ferrocene and mixtures thereof. Examples of organic flame retardant synergists include, but are not limited to organic peroxides, such as dicumyl peroxide and polycumyl peroxide. Synergistic combinations, such as mixtures of one or more halogenated compounds and one or more flame retardant synergists, typically are used preferably at a ratio of 0.25 to 25, preferably 0.5 to 15, more preferably from 0.5 to 10 parts by weight flame retardant halogen to 1 part by weight of flame retardant synergist. StabiUty Control Agent or Cell Size Enlarging Agent A stabiUty control agent or ceU size enlarging agent is optionally added to the present foam to enhance dimensional stabiUty. Preferred agents include amides and esters of C 10-24 fatty acids. Such agents are seen in U.S. Pat. Nos. 3,644,230 and 4,214,054, which arel08°C incoφorated herein by reference. Most preferred agents include stearyl stearamide, glycerol monostearate (available from ICI Americas Inc., under the trademark Atmer™ 129), glycerol monobehenate, and sorbitol monostearate. Typically, such stability control agents are employed in an amount ranging from 0.1 to 10 parts per hundred parts of the polymer. Other Additives. Additives such as antioxidants such as hindered phenols (e.g, Irganox™ 1010), and phosphites (e.g., Irgafos™ 168) both of which are trademarks of and available from the Ciba Geigy coφoration), UN. Stabilizers, cling additives (e.g., polyisobutylene), antiblock additives, colorants, pigments, fiUers, acid scavengers (including, but not limited to, zeolite, organic carboxylates and hydrotalcite) and the like can optionaUy also be included in the compositions and fabricated articles ofthe present invention, to the extent that they do not interfere with their enhanced properties. The additives are advantageously employed in functionaUy equivalent amounts known to those skiUed in the art. For example, the amount of antioxidant employed is that amount which prevents the polymer or polymer blend from undergoing oxidation at the temperatures and environment employed during storage and ultimate use ofthe polymers. Such amount of antioxidants is usuaUy in the range of from 0.01 to 10, preferably from 0.05 to 5, more preferably from 0.1 to 2 percent by weight based upon the weight ofthe polymer or polymer blend. Similarly, the amounts of any ofthe other enumerated additives are the functionaUy equivalent amounts such as the amount to render the polymer or polymer blend antiblocking, to produce the desired amount of filler loading to produce the desired result, to provide the desired color from the colorant or pigment. Such additives are advantageously employed in the range of from 0 to 50, preferably from 0 to 35, more preferably from 0 to 20 percent by weight based upon the weight ofthe polymer or polymer blend. Preferred examples of fillers are talc, carbon black, carbon fibers, calcium carbonate, alumina trihydrate, glass fibers, marble dust, cement dus:. clay, feldspar, silica or glass, fumed siUca, alumina, magnesium oxide, magnesium hydroxide, antimony oxide, zinc oxide, barium sulfate, aluminum siUcate, calcium siUcate, titanium dioxide, titanates, glass microspheres or chalk. Of these fillers, barium sulfate, talc, calcium carbonate, siUca/glass, glass fibers, alumina and titanium dioxide, and mixtures thereof are preferred. The most preferred inorganic fiUers are talc, calcium carbonate, barium sulfate, glass fibers or mixtures thereof. These fillers could be employed in amounts from 0 to 90, preferably from 0 to 80, more preferably from 0 to 70 % by weight based on the weight ofthe polymer or polymer blend. One type of additive found useful in the polymer compositions used to prepare the foams ofthe present invention are lubricating agents. Such additives are better known by a variety of more common names such as shp agent or release agent which seem to depend upon the particular property modification contemplated for the additive. IUustrative lubricating agents, preferably soUd lubricating agents, include organic materials such as sihcones, particularly dimethylsiloxane polymers, fatty acid amides such as ethylene bis (stearamides), oleamides and erucamide; and metal salts of fatty acids such as zinc, calcium, or lead stearates. Also suitable are inorganic materials such as talc, mica, fumed siUca and calcium siUcate. Particularly preferred are the fatty acid amides, oleamides, and erucamide. Quantities of lubricating agent of from 0 to 5 % by weight based on the total weight ofthe mixture are satisfactory, more preferred are quantities of from 0 to 4 % by weight. Applications for the macroceUular flame resistant acoustic compositions ofthe present invention include articles made by aU the various extrusion processes. Such articles may be used in automotive and other transportation devices, building and construction, household and garden appliances, power tool and apphance and electrical supply housing, connectors, and aircraft as acoustic systems for sound absoφtion and insulation. The materials are especiaUy suited to apphcations where, in addition to meeting the relevant acoustic performance standards, they must also meet any applicable fire test codes, for example office partitions, automotive decouplers, domestic appUance sound insulation, and sound proofing panels and machine enclosures. The foams ofthe present invention have exceUent acoustic absoφtion capabiUties. One way to measure the abihty to absorb sound is to measure the acoustic absoφtion coefficient ofthe foam according to ASTM E-1050 at 25, 500, 1000 and 2000 Hz and then calculate the arithmetic average of those sound absoφtion coefficients. When that determination is made with the foams ofthe present invention, the average sound absoφtion coefficient is greater than 0.15, preferably greater than 0.20, more preferably greater than 0.25, even more preferably greater than 0.30. Thus the foams of this invention are useful for absorbing sound in the range from 250 to 2000 Hz such that the sound absoφtion capabiUty is equivalent to the foregoing preferred average sound absoφtion coefficients. For example, the foam may be located in the presence of a sound intensity of at least 50 decibels, such as on a vehicle equipped with a combustion engine. The foregoing Ust merely iUustrates a number of suitable appUcations. SkiUed artisans can readily envision additional appUcations without departing from the scope or spirit ofthe present invention. The following examples iUustrate, but do not in any way limit the scope ofthe present invention. EXAMPLES. Test Methods. a) Melt Flow Measurements. The molecular weight ofthe polymer compositions for use in the present invention is conveniently indicated using a melt index measurement according to ASTM D-1238, Condition 190°C/2.16 kg (formaUy known as "Condition (E)" and also known as 12) was determined. Melt index is inversely proportional to the molecular weight ofthe polymer. Thus, the higher the molecular weight, the lower the melt index, although the relationship is not linear. b) Styrene Analyses Inteφolymer styrene content and the concentration of atactic polystyrene homopolymer impurity in the ESI inteφolymers was determined using proton nuclear magnetic resonance (Η NMR). AU proton NMR samples were prepared in 1, 1, 2, 2- tetrachloroethane-d 2 (cce-d 2 ). The resulting solutions contained approximately 1 - 3 weight percent polymer. The inteφolymers were weighed directly into 5-mm sample tubes. A 0.75-ml ahquot of tce-d 2 was added by syringe and the tube sealed with a tight-fitting cap. The samples were heated at 85°C to soften the inteφolymer. To provide mixing, the capped samples were occasionaUy brought to reflux using a heat gun. Proton NMR spectra were accumulated with the sample probe at 80°C, and referenced to the residual protons of tce-d 2 at 5.99 ppm. Data was coUected in tripUcate on each sample using the foUowing instrumental conditions: Sweep width, 5000 hz Acquisition time, 3.002 sec Pulse width, 8 μsec Frequency, 300 mhz Delay, 1 sec Transients, 16 The total analysis time per sample was 10 minutes. Initially, a spectrum for a sample of polystyrene (192,000 M w ) was acquired. Polystyrene has five different types of protons that are distinguishable by proton NMR. In Figure 1, these protons are labeled b, branch; α, alpha; o, ortho; m, meta; p, para, as shown in figure 1. For each repeating unit in the polymer, there are one branch proton, two-alpha protons, two ortho protons, two meta protons and one para proton. The NMR spectrum for polystyrene homopolymer includes a resonance centered around a chemical shift of 7.1 ppm, which is beUeved to correspond to the three ortho and para protons. The spectrum also includes another peak centered around a chemical shift of 6.6 ppm. That peak corresponds to the two meta protons. Other peaks at about 1.5 and 1.9 ppm correspond to the three aUphatic protons (alpha and branch). The relative intensities ofthe resonances for each of these protons were determined by integration. The integral corresponding to the resonance at 7.1 ppm was designated PS 7 1 below. That corresponding to the resonance at 6.6 ppm was designated PSό.β, and that corresponding to the aUphatic protons (integrated from 0.8-2.5 ppm) was designated PSai. The theoretical ratio for PS 7 ] : PSai is 3:2:3, or 1.5: 1 : 1.5. For atactic polystyrene homopolymer, aU spectra coUected had the expected 1.5: 1: 1.5 integration ratio. An aUphatic ratio of 2 to 1 is predicted based on the protons labeled α and b respectively in figure 1. This ratio was also observed when the two aUphatic peaks were integrated separately. Further, the ratio of aromatic to aliphatic protons was measured to be 5 to 3, as predicted from theoretical considerations. The Η NMR spectrum for the ESI inteφolymer was then acquired. This spectrum showed resonances centered at about 7.1 ppm, 6.6 ppm and in the aliphatic region. However, the 6.6 ppm peak was relatively much weaker for the ESI inteφolymer than for the polystyrene homopolymer. The relative weakness of this peak is believed to occur because the meta protons in the ESI copolymer resonate in the 7.1 ppm region. Thus, the only protons that produce the 6.6 ppm peak are meta protons associated with atactic polystyrene homopolymer that is an impurity in the ESI. The peak centered at about 7.1 ppm thus includes ortho, meta and para protons from the aromatic rings in the ESI inteφolymer, as weU as the ortho and para protons from the aromatic rings in the polystyrene homopolymer impurity. The peaks in the aliphatic region include resonances of aUphatic protons from both the ESI inteφolymer and the polystyrene homopolymer impurity. Again, the relative intensities ofthe peaks were determined by integration. The peak centered around 7.1 ppm is referred to below as I 1, that centered around 6.6 ppm is ^ nd that in the aUphatic regions is Iai. I 1 includes a component attributable to the aromatic protons ofthe ESI inteφolymer and a component attributable to the ortho and para protons ofthe aromatic rings ofthe polystyrene homopolymer impurity. Thus, where I c7 1 is the intensity ofthe 7.1 ppm resonance attributable to the aromatic protons in the inteφolymer and 1 is the intensity ofthe 7.1 ppm resonance attributable to the ortho and meta protons ofthe polystyrene homopolymer. From theoretical considerations, as confirmed by the Η NMR spectrum ofthe polystyrene homopolymer, the intensity ofthe 7.1 ppm resonance attributable to the polystyrene homopolymer impurity (I pS 7 1), equals 1.5 times the intensity ofthe 6.6 ppm resonance. This provides a basis for determining I c7 1 from measured values, as foUows: I c7 1 = I 7 1 - 1.5(I 66 ). Similarly, 1^ can be resolved into resonances attributable to the ESI and the polystyrene homopolymer impurity using the relationship wherein I ca ι is the intensity attributable to the aliphatic protons on the inteφolymer and I psa ι is the intensity attributable to the aUphatic protons ofthe polystyrene homopolymer impurity. Again, it is known from theoretical considerations and the spectrum from the atactic polystyrene homopolymer that wiU equal 1.5 times I 6 6- Thus the foUowing relationship provides a basis for determining I ca ι from measured values: The mole percent ethylene and styrene in the inteφolymer are then calculated as foUows: E = e c /(s c + e c ), and S = s c /(s c + e c ), wherein E and S are the mole fractions of copolymerized ethylene and styrene, respectively, contained in tl'e inteφolymer. Weight percent ethylene and styrene were calculated using the equations Wt % E = 100 % * 28 E and (28 E + 104 S) Wt% S = 100 % * 104 S . (28 E + 104 S) The weight percent of polystyrene homopolymer impurity in the ESI sample was then determined by the foUowing equation: Wt% PS = 100% * Wt% S * f 2S). 100 - [Wt% S * (I 66 /2S)] The total styrene content was also determined by quantitative Fourier transform infrared spectroscopy (FTIR). Materials Used to Prepare the Foams ofthe Present Invention. 1. LDPE 1 is commerciaUy available as LDPE 400R which is a low density polyethylene (LDPE) with a density of 0.925 g/cm 3 and melt index of 1.0 dg/min and available from The Dow Chemical Company. 2. LDPE 2 is commerciaUy available as LDPE 620i which is a low density polyethylene (LDPE) with a density of 0.924 g/cc and melt index of 1.8 dg/min (according to ASTM D1238, 190°C/2.16 kg) and available from The Dow Chemical Company. 3. ESI 1 is commercially available as.DS201 which is a substantially random ethylene styrene inteφolymer (ESI) with a nominal styrene content of 37.5 mol % (69 wt %) and melt index of 1 dg/min (according to ASTM D1238, 190°C/2.16 kg) and available from The Dow Chemical Company. 4. HMS PP 1 is commerciaUy available us Profax PF814 which is a high melt strength polypropylene with a melt index of 3 dg/min (according to ASTM D1238, 230°C/2.16 kg) and available from MonteU. 5. PE-68™ is a brominated fire retardant having 68 wt % bromine content (tetrabromobisphenol A bis (2,3-dibromopropyl ether) 30% concentrate in LDPE) and is a trademark of and available from The Great Lakes Chemical Coφoration. 6. TRUTINT™ 50 is antimony trioxide, SbO 3 of average particle size of 3 microns (used as an 80% concentrate in LDPE) and is a trademark of and available from The Great Lakes Chemical Coφoration. 7. TMS™ is antimony trioxide, SbO 3 of average particle size of 1.5 microns (used as an 80% concentrate in LDPE) and is a trademark of and available from The Great Lakes Chemical Coφoration. 8. CHLOREZ™ 700 is chlorinated paraffin containing 70 wt % chlorine and is a trademark of and available from the Dover Chemical Coφoration. 9. CHLOREZ™ 760 is chlorinated paraffin containing 74 wt % chlorine and :s a trademark of and available from the Dover Chemical Coφoration. 10. SAYTEX™ HP-900 is hexabromocyclododecane containing about 75 wt % bromine and is a trademark of and available from the Albemarle Coφoration. Example 1 This example iUustrates the experimental method for deteπriining the critical prefoaming die pressure a flame retardant polyethylene formulation. The foams Usted in Table 1 were prepared in commercial extrusion equipment. The laboratory scale single screw extruder consisted of a feeding zone for soUd additives and resins, a melting zone and a metering zone. In addition, there was a mixing zone with a port to inject the blowing agent and Uquid additives, a cooling zone to uniformly cool the melt to the foaming temperature and a die body. The foaming temperature is the optimal gel temperature for foaming when the melt strength is high enough to stabilize the foam and prevent ceU coUapse. The melt is extruded through a die to room temperature and pressure to expand tlie gel and stabiUze the resulting foam. Low density polyethylene (LDPE 1) with a density of 0.925 g/cm 3 and melt index of 1.0 dg/min (according to ASTM D1238, 190°C/2.16 kg) was fed from a feed hopper to the extruder. The levels of additives used in the formulation are reported in parts by weight per hundred parts by weight ofthe polymer resin blend (pph). The foUowing additives were added : 0.3 pph glycerol monostearate, 4 pph ofthe brominated flame retardant (PE-68, tetrabromobisphenol A bis (2,3-dibromopropyl ether) 30% concentrate in LDPE) and 2 pph ofthe synergist (Trutint™ 50, antimony trioxide 80% concentrate in LDPE). Isobutane at 9 pph was injected into the mixing zone. The temperature ofthe cooling zone and die block was graduaUy reduced to the foaming temperature range to produce stable foam. At a die temperature of 108°C, the die opening was changed to vary the pressure at the die. The results ofthe change in die pressure on ceU size and foam appearance are shown in Table 1. At high die pressure (>3000 kPa), the foam nucleated significantly and ceU size was smaU. As the die pressure was reduced, the foam quaUty improved and the ceU size became larger. FinaUy, at the prefoaming pressure, the quaUty ofthe foam deteriorated shaφly (very rough skin due to rupture of surface ceUs) and a crackling noise was heard at the die due to rapid degassing ofthe blowing agent. The prefoaming critical die pressure this formulation is 650 kPa. Table 1 1 die width: 6 mm 2 3-d average ceU size measured by ASTM D3576 Example 2 This example also iUustrates the experimental method for determining the prefoaming critical die pressure for a flame retardant polyethylene formulation. A formulation similar to that used in Example 1 was foamed using a higher level of glycerol mono stearate (GMS). The levels of additives used in the formulation are reported in parts by weight per hundred parts by weight ofthe polymer resin blend (pph). The level of GMS used was 1.3 pph. AU other process conditions were the same as Example 1. The foaming temperature was 108-°C. The prepared foams are Usted in Table 2. In this case, the prefoaming critical die pressure for this formulation is between 350 kPa and 720 kPa. Table 2 1 die width: 6 mm 2 3-d average ceU size measured by ASTM D3576 3 ceU size not measured due to very poor quality foam Example Three The foUowing example also illustrates the experimental method for determining the prefoaming critical die pressure for a non flame retardant polyethylene formulation. A formulation similar to that used in Example 2 without the brominated flame retardant and the synergist. The foaming temperature was 108°C, all other process conditions were the same as before. The prepared foams are Usted in Table 3. In this case, the prefoaming critical die pressure for this formulation is 760 kPa. /70859 Table 3 ie width: 6 mm -d average ceU size measured by ASTM D3576 Example 4 This example describes the formulation and the process conditions to make large ceU acoustic foam with flame retardants and synergists. The foams were prepared in commercial extrusion equipment. The pilot scale single screw extruder consisted of a feeding zone for soUd additives and resins, a melting zone and a metering zone. In addition, there was a mixing zone with a port to inject the blowing agent and Uquid additives, a cooling zone to uniformly cool the melt to the foaming temperature and a die body. A gear pump between the metering and mixing zones stabilized the melt flow rate. The foaming temperature is the optimal gel temperature for foaming when the melt strength is high enough to stabilize the foam and prevent cell coUapse. The melt is extruded through a die to room temperature and pressure to expand the gel and stabiUze the resulting foam. For this Example 4, low density polyethylene with a density of 0.925 g/cm 3 and melt index of 1.0 dg/min (according to ASTM D1238, 190°C/2.16 kg) was fed to the extruder. The levels of additives used in the formulation are reported in parts by weight per hundred parts by weight ofthe polymer resin blend (pph). For the comparative foam (Comp Ex 1) the following additive was used: 0.1 pph Irganox 1010 antioxidant (Tetrakis [methylene(3,5-di- tert-butyl-4-hydroxyhydrocinnamate)] methane. Isobutane at 8.5 pph was injected into the mixing zone and glycerol monostearate at 1.5 pph was melt injected. For the flame retardant foam of Example 4, the following ingredients were added to the formulation : 5 pph ofthe brominated flame retardant (PE-68, tetrabromobisphenol A bis (2,3-dibromopropyl ether) 30% concentrate in LDPE) and 1.4 pph ofthe synergist (TMS™ antimony trioxide 1.5 micron average particle size 80% concentrate in LDPE). The gel residence time in the extrusion line was 45 min. The gel temperature was the highest in the mixing zone (200°C) and the gel pressure was highest at the gear pump outlet (18540 kPa). The hot gel was cooled to the foaming temperature (104°C). The gel temperature ofthe adjustable die (50 mm wide x 3.3 mm high) was maintained at 104°C and the gel pressure at the die was kept at 1300 kPa. Note the die pressure is approximately 2X the prefoaming critical die pressure. MacroceUular foam of exceUent quaUty was obtained. For the comparative foam (Comp Ex 1 ) made with no flame retardant package, the average ceU size was 11.7 mm and the fresh density was 47.8 kg/m3. For the foam of Example 4 made with the flame retardant package, the average ceU size was 10.4 mm and the fresh density was 33.5 kg/m3. The comparative foam (Comp Ex 1) failed the DIN-4102 B2 flame test and the UL-94 flame test. The flame retardant (Example 4) foam passed the DIN-4102 test with B2 rating (with paper burning) and passed the UL-94 test with 94 HF-2 rating (with burning droplets). The comparative (Comp Ex 1) and the flame retardant foam (Example 4) both with skin, no perforations and 25 mm thickness were tested for acoustic performance using ASTM E— 1050 (Impedance Tube Method). The acoustic results, tabulated below, show that the comparative (Comp Ex 1) and the flame retardant foam (Example 4) are very comparable. Table 4 1 Frequency corresponding to the maximum sound absoφtion 2 Average SAC is the mean SAC ofthe following frequencies: 250 Hz, 500 Hz, 1000 Hz, and 2000 Hz Example 5 This example details the effect of nucleators that are used in the formulation on foam ceU size and hence acoustic properties. The formulation was made in the same commercial extrusion equipment as described in Example 4. For this example, a 85/15 wt% blend of low density polyethylene (LDPE 1) with a density of 0.925 g/cm 3 and melt index of 1.0 dg/min (according to ASTM D1238, 190°C/2.16 kg) and a substantiaUy random ethylene styrene inteφolymer (ESI 1) with a nominal styrene content of 69 wt % and melt index of 1 dg/min (according to ASTM D1238, 190°C/2.16 kg) was fed to the extruder. The levels of additives used in the formulation are reported in parts by weight per hundred parts by weight ofthe polymer resh tl nd (pph). The ESI 1 resin contained approximately 1 pph of dusted talc as an anti-block agent that acts as a powerful nucleator. Isobutane at 8.5 pph was injected into the mixing zone and glycerol monostearate at 1.5 pph was melt injected. 0.1 pph Irganox™ 1010 antioxidant (Tetrakis [methylene(3,5-di-tert-butyl-4-hydroxyhydrocinnamate)] methane and 3.2 pph carbon black concentrate were fed into the extruder. The flame retardant package comprised 5.5 pph of the brominated flame retardant (PE-68, tetrabromobisphenol A bis (2,3-dibromopropyl ether) 30% concentrate in LDPE) and 0.55 pph ofthe synergist (TMS™ antimony trioxide, 1.5 micron average particle size, 80% concentrate in LDPE). The gel residence time in the extrusion line was 45 min. The gel temperature was the highest in the mixing zone (197°C) and the gel pressure was highest at the gear pump outlet (17000 kPa). The hot gel was cooled to the foaming temperature (106°C). The gel temperature ofthe adjustable die (50 mm wide x 3 mm high) was maintained at 103.4°C and the pressure at the die was kept at 1170 kPa. Note the die pressure is approximately 2X the prefoaming critical die pressure. MacroceUular foam of exceUent quality was obtained. For the run made with the flame retardant package (Ex 5), the average cell size was 5.5 mm and the fresh density was 31.7 kg/m3. The ceU size is significantly smaUer than that of Example 4. The flame retardant foam passed the UL-94 test with 94 HBF rating and the ASTM E-84 Steiner Tunnel test with Class A rating The flame retardant foam with skin, no perforations and 25 mm thickness was tested for acoustic performance using ASTM E-1050 (Impedance Tube Method). The results are tabulated below: Table 5 Frequency corresponding to the maximum sound absoφtion 2 Average SAC is the mean SAC ofthe foUowing frequencies: 250 Hz, 500 Hz, 1000 Hz, 2000 Hz.The flame retardancy ofthe foam is adequate. The acoustics ofthe smaUer ceU foam is not as good as that ofthe larger cell foam of Example 4. Cell size clearly has a big impact on sound absoφtion performance. Thus, foam formulations should contain low, preferably zero, levels of nucleating agents such as talc (magnesium siUcate), calcium stearate, barium stearate, etc. Example 6 This example iUustrates the effect of additives Uke glycerol monostearate and propylene glycol/ethanol mixtures on foam cell size and hence acoustic performance. Trials were made using the equipment and process conditions detailed in Example 1. The levels of additives used in the formulation are reported in parts by weight per hundred parts by weight ofthe polymer resin blend (pph). The foUowing formulation was used: low density polyethylene (LDPE 1 ) with a density of 0.925 g/cmT and melt index of 1.0 dg/min (according to ASTM D1238, 190°C/2.16 kg), 9 pph isobutane, 5 pph ofthe brominated flame retardant (PE-68, tetrabromobisphenol A bis (2,3-dibromopropyl ether) 30% concentrate in LDPE) and 2 pph ofthe synergist (Trutint™ 50 antimony trioxide 80% concentrate in LDPE). The glycerol mono stearate (GMS) level (percent by weight based on polymer) was varied with aU other conditions kept the same. The results are presented in Table 6 and show that an increase in GMS level results in an increase in cell size but that beyond a critical value, increase in GMS level results in a decrease in cell size. Note that GMS increases cell size during foaming and provides dimensional stabiUty during aging. Table 6 1 parts by weight per hundred parts by weight polymer 2 3-d average cell size measured by ASTM D3576 Example 7 Trials were made using the equipment and process conditions detailed in Example 4. The foUowing formulation was used: 70/30 wt % blend of low density polyethylene (LDPE 1) with a density of 0.925 g/cm 3 and melt index of 1.0 dg/min (according to ASTM D1238, 190°C/2.16 kg) and a substantiaUy random ethylene styrene inteφolymer (ESI i) with a nominal styrene content of 69 wt % and melt index of 1 dg/min (according to ASTM D1238, 190°C/2.16 kg), 9 pph isobutane, 0.4 pph glycerol mono stearate, 0.1 pph Irganox 1010 antioxidant (Tetrakis [methylene(3,5-di-tert-butyl-4-hydroxyhydrocinnamate)] methane and 1.5 pph carbon black concentrate. The level ofthe 75/25 polypropylene glycol/ethanol (PPG/EtOH) mixture was varied with aU other conditions kept the same and the results are presented in Table 7 A. The results show that an increase in the level ofthe polypropylene glycol ethanol mixture over the range studied results in an increase in ceU size and counteracts some ofthe nucleating tendencies ofthe flame retardancy additives. TABLE 7A parts by weight per hundred parts by weight polymer 2 3-d average ceU size measured by ASTM D3576 The foUowing resin formulation comprising polyethylene, polypropylene and ethylene styrene inteφolymers was also used: 28/2/70 wt % blend of low density polyethylene (LDPE 1) with a density of 0.925 g/cm 3 and melt index of 1.0 dg/min (according to ASTM D1238, 190°C/2.16 kg) and a substantially random ethylene styrene inteφolymer (ESI 1) with a nominal styrene content of 69 wt % and melt index of 1 dg/min (according to ASTM D1238, 190°C/2.16 kg) and a polypropylene high melt strength (HMS PP 1) with a melt flow rate of 3g/10min (according to ASTM D1238, 230°C/2.16 kg). The levels of additives used in the formulation are reported in parts by weight per hundred parts by weight ofthe polymer resin blend (pph). 8 pph isobutane, 0.3 pph glycerol mono stearate, 0.1 pph Irganox 1010 antioxidant (Tetrakis [methylene(3,5-di-tert-butyl-4- hydroxyhydrocinnamate)] methane and 1.5 pph carbon black concentrate. The flame retardant package comprising 3.8 pph tetrabromobisphenol A bis 2,3-dibromopropyl ether (PE™-68) and 1.5 pph TRUTINT™ 50 antimony trioxide. The level ofthe 75/25 polypropylene glycol/ethanol (PPG/EtOH) mixture was varied with aU other conditions kept the same and the results are presented in Table 7B. The results show that an increase in the level ofthe polypropylene glycol/ethanol mixture over the range studied results in an increase in ceU size and counteracts some ofthe nucleating tendencies ofthe flame retardancy additives. TABLE 7B 1 parts by weight per hundred parts by weight polymer 2 3-d average ceU size measured by ASTM D3576 The foams of Ex7d and 7e made with the PE-68/ St^O;* FR package passed the DIN-4102 test with B2 rating. Example 8 This example describes the formulation and process conditions to make large cell foam with flame retardants and synergists. Trials were made using equipment and process conditions similar to that used in Example 4. The foUowing resins were used: 85/15 wt %blend of low density polyethylene (LDPE 1) with a density of 0.925 g/cm 3 and melt index of 1.0 dg/min (according to ASTM D1238, 190°C/2.16 kg) and a substantially random ethylene styrene inteφolymer (ESI 1) with a nominal styrene content of 69 wt % and melt index of 1 dg/min (according to ASTM D1238, 190°C/2.16 kg). The levels of additives used in the formulation are reported in parts by weight per hundred parts by weight ofthe polymer resin blend (pph). 0.1 pph Irganox antioxidant (Tetrakis [methylene(3,5-di-tert-butyl-4-hydroxyhydrocinnamate)] methane was metered into the extruder. The flame retardants used included brominated agents (PE™-68, (tetrabromobisphenol A bis (2,3-dibromopropyl ether) 30% concentrate in LDPE; and chlorinated agents (Chlorez™700). The inorganic synergist used was antimony trioxide (TMS™, 80% concentrate in LDPE) and the organic synergist used was polycumyl (poly 1,4- diisopropyl benzene). Isobutane at 8.5 pph was injected into the mixing zone and glycerol monostearate at 1.5 pph was melt injected. The first four runs used no color concentrates for a white foam but the last two runs used 3.2 pph of black concentrate for a black foam The control foam (Comparative Ex 2) used no flame retardant or synergist. The gel residence time in the extrusion line was 45 min. The gel temperature was the highest in the mixing zone (about 197°C) and the gel pressure was highest at the gear pump outlet (about 18200 kPa). The hot gel was cooled to the foaming temperature (105°C). The temperature ofthe adjustable die (50 mm wide x 3.2 mm high) was maintained at 105°C and the pressure at the die was kept at 1260 kPa. Note the die pressure is approximately 2X the prefoaming critical die pressure. Table 8 1 parts by weight per hundred parts by weight polymer 2 3-d average ceU size measured by ASTM D3576 3 density measured by ASTM D3575 suffix W method B The foam properties are presented in Table 8. AU the flame retardant packages produced moderate to large ceU foam of exceUent quaUty, which indicates that the formulations have low nucleating potential. The control foam (Comp Ex 2) failed the DIN-4102 test (B2 rating). The foams of Ex 8 made with the PE-68/Sb 2 O 3 FR package passed the UL-94 test with HBF rating. The foams of Ex 8 made with Chlorez™700/Sb 2 O 3 passed the ASTM E-84 test with Class A rating. Example 9 This example describes the formulation and process conditions to make large ceU foam with a binary blend of brominated and chlorinated flame retardants and a flame retardant synergist. Trials were made using equipment and process conditions were very similar to that used in Example 4. Low density polyethylene (LDPE 1) with a density of 0.925 g/cm 3 and melt index of 1.0 dg/min (according to ASTM D1238, 190°C/2.16 kg) was used. The levels of additives used in the formulation are reported in parts by weight per hundred parts by weight ofthe polymer resin blend (pph). 0.1 pph Irganox antioxidant (Tetrakis [methylene(3,5-di-tert-butyl-4-hydroxyhydrocinnamate)] methane was metered into the extruder. The flame retardants used included a ternary blend of brominated agent 4.1 pph PE™-68, (tetrabromobisphenol A bis (2,3-dibromopropyl ether) 30% concentrate in LDPE with chlorinated agent 2 pph Chlorez™700 with an inorganic synergist 2 pph antimony trioxide (TMS™ concentrate in LDPE). Isobutane at 9 pph was injected into the mixing zone and glycerol monostearate at 0.2 pph was melt injected. The runs used 1.5 pph of black concentrate for a black foam. The gel residence time in the extrusion line was 45 min. The gel temperature was the highest in the mixing zone (about 197°C) and the gel pressure was highest at the gear pump outlet (about 12106 kPa). The hot gel was cooled to the foaming temperature (108°C). The temperature ofthe adjustable die (50 mm wide) was maintained at 106°C. Table 9 Example # Flame retardant, pph 1 Synergist, pph 1 Av cell size 2 , mm Density 3 , kg m3 Ex 9 PE-68, 4.1 Sb 2 0 3 , 2 6.3 33.9 Chlorez™700, 2 parts by weight per hundred parts by weight polymer 2 3-d average ceU size measured by ASTM D3576 3 density measured by ASTM D3575 suffix W method B The foam properties are presented in Table 9. This flame retardant package produced large ceU foam of exceUent quaUty, which indicates that the formulation has low nucleating potential. The foam of Ex 9 made with the PE-68/ Chlorez™700/Sb 2 O 3 FR package passed the UL-94 test with HF-1 rating and passed the DIN-4102 test with B2 rating. Example 10 This example describes the formulation and process conditions to make large ceU foam using a blend of polyethylene and polypropylene with flame retardants and synergists. Trials were made using equipment and process conditions were very similar to that used in Example 4. The foUowing resins were used: 40/60 wt %blend of low density polyethylene (LDPE 1) with a density of 0.925 g/cm 3 and melt index of 1.0 dg/min (according to ASTM D1238, 190°C/2.16 kg) and a polypropylene high melt strength (HMS PP 1) with a melt flow rate of3g/10min (according to ASTM D1238, 230°C/2.16 kg). The levels of additives used in the formulation are reported in parts by weight per hundred parts by weight ofthe polymer resin blend (pph). 0.1 pph Irganox antioxidant (Tetrakis [methylene(3,5-di- tert-butyl-4-hydroxyhydrocinnamate)] methane was metered into the extruder. The flame retardants used included brominated agents (PE™-68, (tetrabromobisphenol A bis (2,3- dibromopropyl ether) 30% concentrate in LDPE; and chlorinated agents (Chlorez™700). The inorganic synergist used was antimony trioxide (TMS™, 80% concentrate in LDPE). Isobutane at 10 pph was injected into the mixing zone. The runs used 1.5 pph of black concentrate for a black foam The control foam used no flame retardant or synergist. The gel residence time in the extrusion line was 45 min. The gel temperature was the highest in the mixing zone (about 225°C) and the gel pressure was highest at the gear pump outlet (about 21474 kPa). The hot gel was cooled to the foaming temperature (155°C). The temperature ofthe adjustable die (50 mm wide) was maintained at 152°C. Table 10 parts by weight per hundred parts by weight polymer 3-d average cell size measured by ASTM D3576 density measured by ASTM D3575 suffix W method B The foam properties are presented in Table 10. AU the flame retardant packages produced moderate to large ceU foam of exceUent quaUty, which indicates that the formulations have low nucleating potential. The control foam (Comp ) failed the DIN-4102 test (B2 rating) and failed UL-94 test. The foams of Ex 10 made with the PE-68/Sb 2 O 3 FR package passed the DIN-4102 test with B2 rating and passed UL-94 test with HF-1 rating. The foams of Ex 10 made with PE-68/Chlorez™700/Sb O 3 passed the the DIN-4102 test with B2 rating and passed UL-94 test with HF-1 rating. Example 11 Example 11 iUustrates the effect of nucleating agents on ceU size. This example also compares the foam properties obtained with flame retardant packages comprising inorganic and organic synergists. The formulation and process conditions were very similar to that used in the earlier section. The ESI 1 resin is typicaUy dusted with talc to prevent blocking (agglomeration of peUets). Batch to batch variations exist in the talc level ofthe dusted resin. Nucleating agents Uke talc (magnesium siUcate), calcium stearate, barium stearate, etc., increase the number of nuclei that are created during foaming and produce smaU ceUs. The ceU size decreases as the level of nucleator increases until a critical level, beyond which no effect is observed. The foam properties are presented in Table 11. The flame retardant package comprising 3 pph tetrabromobisphenol A bis 2,3-dibromopropyl ether (PE™-68) and 1 pph TRUTINT™ 50 antimony trioxide at the same ratio (3: 1) as used in the earUer section produced smaU ceU foam (<3mm) that is acoustically inactive. A higher level of dusted talc in the formulation is responsible for this ceU size reduction. The flame retardant package comprising 3.5 pph of SAYTEX™ HP-900 hexabromocyclo-dodecane (HBCD) with 0.3 pph of poly 1 ,4-diisoproplbenzene (polycumyl) was added to the formulation. A foam with moderate ceU size was obtained (>3 mm). Synergists with a low level of insoluble particles are preferred for making large ceU acoustic foam because of their lower nucleation tendency. The flame retardant package also comprising 4.6 pph tetrabromobisphenol A bis 2,3- dibromopropyl ether (PE™-68) and 1.9 pph TRUTINT™ 50 antimony trioxide with increasing percentage of ESI. For a fixed flame retardant composition (4.6 pph tetrabromobisphenol A bis 2,3- dibromopropyl ether (PE™-68) and 1.9 pph TRUTINT™ 50 antimony trioxide), the level of ESI (and hence, the level of talc) in the formulation was varied and the results are presented in Table 11. The results show that an increase in the level of ESI in the blend caused a reduction in the ceU size due to the nucleation caused by the dusted talc. However, no negative effect on flame retardancy was observed in the range studied as all foams passed the DIN 4102 fire test with B2 rating 01/7 TABLE 11 1 parts by weight per hundred parts by weight polymer 2 3-d average ceU size measured by ASTM D3576 The flame retardant foam passed the DIN 4102 fire test with B2 rating. Example 12 This example describes the formulation and the process conditions to make large ceU acoustic foam with flame retardants and synergists. The foams were prepared in commercial extrusion equipment. The large scale single screw extruder consisted of a feeding zone for solid additives and resins, a melting zone and a metering zone. In addition, there was a mixing zone with a port to inject the blowing agent and hquid additives, a cooling zone to uniformly cool the melt to the foaming temperature and a die body. A gear pump between the metering and mixing zones stabilized the melt flow rate. A static mixer in the cooling zone aided in gel temperature uniformity. The foaming temperature is the optimal gel temperature for foaming when the melt strength is high enough to stabilize the foam and prevent ceU collapse. The melt is extruded through a die to room temperature and pressure to expand the gel and stabilize the resulting foam. The levels of additives used in the formulation are reported in parts by weight per hundred parts by weight ofthe polymer resin blend (pph). For Comparative Example 3, low density polyethylene (LDPE 2) with a density of 0.924 g/cc and melt index of 1.8 dg/min (according to ASTM D1238, 190°C/2.16 kg) was fed along with 0.3 pph Irganox antioxidant (Tetrakis [methylene(3,5-di-tert-butyl-4-hydroxyhydrocinnamate)] methane and 1.5 pph of black concentrate (25% carbon black in the same LDPE resin ). Isobutane at 8.5 pph was injected into the mixing zone and glycerol monostearate at 1.5 pph was melt injected. For the flame retardant run, the compounded FR package was dosed at 3.5 pph Chlorez™ 760 and 3.5 pph antimony trioxide. The gel residence time in the extrusion line was 45 min. The gel temperature was the highest in the mixing zone (192°C) and the gel pressure was highest at the gear pump outlet (8800 kPa). The hot gel was cooled to the foaming temperature (112.5°C). The temperature ofthe fixed, variable cross-section die was maintained at 112.5°C. The die body was not equipped with a pressure transducer for determining the die pressure. Knowing the die geometry's, the die pressure in the large scale extruder can be estimated from the die pressure in the pilot scale extruder by the following procedure. The procedure assumes that the viscosity ofthe polymer melt, the gel foaming temperature and the formulation are the same for both lines. The shear rates for the non-Newtonian fluid (γ°) in the two lines are therefore the same and given by the Rabinowitsch equation: γ° = {(2n+ 1 )/3n} *6Q/(w*h*h) where n is the power law index (t = γ° n ), Q is the flow rate and w and h are the width and height ofthe die. For the pilot line, the flow rate was 60 kg/hr = 132 lb/hr. The die pressure was determined at two die sUt settings. When the slit die dimensions were 50 mm width (1.97") and 3.3 mm (0.13") height, the die pressure was 1390 kPa (2X prefoaming critical die pressure) and shear rate calculated from the above equation (for n=l) is 215 sec "1 When the sht die dimensions were 50 mm width (1.97") and 0.85 mm (0.13") height, the die pressure was 3130 kPa (4.5X prefoaming critical die pressure) and shear rate calculated from the above equation (for n= 1 ) is 3341 sec "1 For the large line, the flow rate was 1180 kg/hr = 2600 lb/hr. The cross-section ofthe die is non-uniform and a representative gap needs to be determined. This was done by dividing the die into sections from the center ofthe die to the ends and by calculating the incremental and cumulative areas for each section. The cumulative area was then plotted against the section distance from the center ofthe die, resulting in a very non- linear curve. Different average gaps were assumed and the cumulative area was then plotted against the section distance from the centerline resulting in a linear curve with different slopes. The best fit line was obtained with the average gap which corresponded to the cumulative area ofthe section at 2/3 the fuU width divided by the section distance from the center ofthe die. For the large die, the average gap as calculated as 3.22 mm and the effective width ofthe die was 332mm. The shear rate calculated from the above equation was 670 sec "1 . The die pressure ofthe large line was estimated at 2.4X the prefoaming critical die pressure. For Comparative Example 3 made with no flame retardant package, the ceU size was 7 mm and the fresh density was 30.4 kg/m 3 . For Example 11 made with the flame retardant package, the cell size was 4 mm (horizontal) x 12 mm (vertical) and the fresh density was 30.4 kg/m 3 . The foam of Comparative Example 3 failed the DIN-4102 fire test and the UL-94 fire test. The flame retardant foam of Example 12 passed the DIN-4102 fire test with B2 fire rating and passed the UL-94 fire test with HF1 rating. The foams of Example 12 and Comparative Example 3 both with no skin, no perforations and 35 mm thickness were tested for acoustic performance using ASTM E— 1050 (Impedance Tube Method). The acoustic results are comparable as summarized in Table 12: Table 12 1 Frequency corresponding to the maximum sound absoφtion 2 Average SAC is the mean SAC ofthe foUowing frequencies: 250 Hz, 500 Hz, 1000 Hz, 2000 Hz, Example 13. This example describes the formulation and the process conditions to make large ceU acoustic foam made with a different flame retardant/synergist package. Runs were made in commercial extrusion equipment on a different large line. For the flame retardant foam run, a 97/3 blend of low density polyethylene (LDPE 2) with a density of 0.924 g/cm 3 and melt index of 1.8 dg/min (according to ASTM D1238, 190°C/2.16 kg) and ethylene styrene inteφolymer (ESI 1) with a nominal styrene content of 69% and melt index of 1 dg/min (according to ASTM D1238, 190°C/2.16 kg) was fed. 0.5 pph Irganox antioxidant (Tetrakis [methylene(3,5-di-tert-butyl-4-hydroxyhydrocinnamate)] methane and 2 pph of black concentrate (25% carbon black in LDPE 2) were also fed to the extruder. Isobutane at 9 pph was injected into the mixing zone and glycerol mono stearate at 0.75 pph was melt injected. The first flame retardant formulation (FR1) comprised 5 pph of PE-68 (tetrabromobisphenol A bis (2,3-dibromopropyl ether) 30% concentrate in LDPE) and 1.5 pph of antimony trioxide (Trutint™ 50, 3 micron paricle size, 80% concentrate in LDPE). The second flame retardant formulation (FR2) comprised 4 pph of PE-68 (tetrabromobisphenol A bis (2,3-dibromopropyl ether) 30% concentrate in LDPE) and 2 pph of antimony trioxide (Trutint™ 50, 80% concentrate in LDPE). The gel residence time in the extrusion line was 45 min. The gel temperature was the highest in the mixing zone (190°C). The hot gel was cooled to the foaming temperature (112.5°C). The temperature ofthe fixed, variable cross-section die was maintained at 112.5°C. The die body was not equipped with a pressure transducer for determining the die pressure. For the large line, the flow rate was 680 kg/hr = 1500 lb/hr. For the large die, the average gap was calculated as 3.22mm and the effective width ofthe die was 332mm. The shear rate was obtained as 386 sec "1 when calculated using the procedure detailed in the earher section. The die pressure ofthe large line was estimated at 2. IX the prefoaming critical die pressure. Large ceU foam with ceU size of 6 mm (horizontal) x 6 mm (extrusion) x 8 m (vertical) was obtained. The first flame retardant formulation passed the UL-94 fire test with HBF rating and passed the DIN-4102 fire test with B2 fire rating. The second flame retardant formulation passed only the UL-94 fire test with HBF rating. The flame retardant foams were tested using ASTM E-1050 (Impedance Tube Method). The foams were tested without skins, unperforated and 35 mm in thickness. The acoustic results are summarized in Table 13. Table 13. 1 Frequency corresponding to the maximum sound absoφtion 2 Average SAC is the mean SAC ofthe foUowing frequencies: 250 Hz, 500 Hz, 1000 Hz, 2000 Hz,

Claims: CLAIMS 1. A process for preparing a macroceUular acoustic foam from a polymeric resin composition, said process comprising subjecting a foamable gel comprising at least one blowing agent and at least one polymeric resin composition to an extrusion process, wherein said polymeric resin composition comprises A) one or more homopolymers of ethylene, one or more C -C 20 α-olefin polymer, or a combination thereof; B) one or more halogenated flame retardants; C) optionally, one or more polymers other than that of Component A; and D) optionaUy, one or more flame retardant synergists, characterized by conducting the extrusion process at a die pressure greater than the prefoaming critical die pressure but less than or equal to four times that of said prefoaming critical die pressure. 2. The process of Claim 1 ; wherein A) Component A is one or more homopolymers of ethylene, or one or more C 3 -Cιo α-olefin polymers, or a combination thereof; B) said halogenated flame retardant, Component B comprises one or more of hexahalodiphenyl ethers, octahalodiphenyl ethers, decahalodiphenyl ethers, decahalobiphenyl ethanes, 1 ,2-bis(trihalophenoxy) ethanes, 1 ,2- bis(pentahalophenoxy) ethanes, hexahalocyclododecane, a tetrahalobisphenol-A, ethylene(N, N')-bis-tetrahalophthalimides, tetrabromobisphenol A bis (2,3- dibromopropyl ether) tetrahalophthahc anhydrides, hexahalobenzenes, halogenated indanes, halogenated phosphate esters, halogenated paraffins, halogenated polystyrenes, polymers of halogenated bisphenol-A and epichlorohydrin, or a combination thereof; C) Component C when present comprises one or more of; a substantiaUy random inteφolymer, a heterogeneous ethylene/α-olefin inteφolymer, a homogeneous ethylene/α-olefin inteφolymer, a thermoplastic olefin, a styrenic block copolymer, a styrenic homopolymer or copolymer, an elastomer, a thermoplastic polymer, a thermoset polymer; a vinyl or vinylidene haUde homopolymer or copolymer, an engineering thermoplastic, or a combination thereof; and D) Component D when present comprises one or more metal oxides, boron compounds, and organic peroxides, or a combination thereof. 3. The process of Claim 1 ; wherein A) Component A is one or more homopolymers of ethylene, or one or more propylene polymers, or a combination thereof; B) said halogenated flame retardant, Component B, comprises hexabromocyclododecane (HBCD), tetrabromobisphenol A bis (2,3-dibromopropyl ether), PE™-68, or a combination thereof; C) Component C when present comprises one or more of; a substantiaUy random inteφolymer, a heterogeneous ethylene/α-olefin inteφolymer, a homogeneous ethylene/α-olefin inteφolymer, or a combination thereof; and D) said flame retardant synergist, Component D when present, comprises one or more of; iron oxide, tin oxide, zinc oxide, aluminum trioxide, alumina, antimony trioxide, antimony pentoxide, bismuth oxide, molybdenum trioxide, tungsten trioxide, zinc borate, antimony sihcates, zinc stannate, zinc hydroxystannate, ferrocene, dicumyl peroxide, and polycumyl peroxide, or a combination thereof. 4. The process of Claim 3 ; wherein A) Component A is LDPE, polypropylene, or a combination thereof; B) Component B is hexabromocyclododecane (HBCD), tetrabromobisphenol A bis (2,3-dibromopropyl ether), PE™-68, or a combination thereof; C) Component C when present is a substantiaUy random ethylene/styrene inteφolymer, a substantiaUy linear ethylene/ 1-octene copolymer; or a combination thereof; and D) Component D when present is antimony trioxide. 5. The process of any one ofthe preceding claims in which the die pressure is less than or equal to three times that of said prefoaming critical die pressure. 6. The process of any one ofthe preceding claims in which the die pressure is less than or equal to two times that of said prefoaming critical die pressure. 7. A macroceUular acoustic foam comprising; E) one or more homopolymers of ethylene, one or more C3-C20 α-olefin polymers, or a combination thereof; F) one or more halogenated flame retardants; G) optionaUy, one or more polymers other than that of Component A; and H) optionaUy, one or more flame retardant synergists. 8. The macroceUular acoustic foam of Claim 7; wherein A) Component A is one or more homopolymers of ethylene, or one or more C 3 -Cι 0 α-olefin polymers, or a combination thereof; B) said halogenated flame retardant, Component B comprises one or more of hexahalodiphenyl ethers, octahalodiphenyl ethers, decahalodiphenyl ethers, decahalobiphenyl ethanes, l,2-bis(trihalophenoxy) ethanes, 1,2- bis(pentahalophenoxy) ethanes, hexahalocyclododecane, a tetrahalobisphenol-A, ethylene(N, N')-bis-tetrahalophthaUmides, tetrabromobisphenol A bis (2,3- dibromopropyl ether), tetrahalophthaUc anhydrides, hexahalobenzenes, halogenated indanes, halogenated phosphate esters, halogenated paraffins, halogenated polystyrenes, polymers of halogenated bisphenol-A and epichlorohydrin, or a combination thereof; C) Component C when present comprises one or more of; a substantiaUy random inteφolymer, a heterogeneous ethylene/α-olefin inteφolymer, a homogeneous ethylene/α-olefin inteφolymer, a thermoplastic olefin, a styrenic block copolymer, a styrenic homopolymer or copolymer, an elastomer, a thermoplastic polymer, a theπnoset polymer; a vinyl or vinyUdene haUde homopolymer or copolymer, an engineering thermoplastics, or a combination thereof; and D) Component D when present comprises one or more metal oxides, boron compounds, and organic peroxides, or a combination thereof. 9. The macroceUular acoustic foam of Claim 7; wherein A) Component A is a homopolymer of ethylene, or a propylene polymer, or a combination thereof; B) said halogenated flame retardant, Component B comprises hexabromocyclododecane (HBCD), tetrabromobisphenol A bis (2,3-dibromopropyl ether), PE™-68, or a combination thereof; C) Component C when present comprises a substantiaUy random inteφolymer, a heterogeneous ethylene/α-olefin inteφolymer, a homogeneous ethylene/α-olefin inteφolymer, or a combination thereof; and D) said flame retardant synergist, Component D when present, comprises one or more iron oxide, tin oxide, zinc oxide, aluminum trioxide, alumina, antimony trioxide, antimony pentoxide, bismuth oxide, molybdenum trioxide, and tungsten trioxide, zinc borate, antimony siUcates, zinc stannate, zinc hydroxystannate, ferrocene, dicumyl peroxide, and polycumyl peroxide, or a combination thereof. 10. The macroceUular acoustic foam of Claim 9; wherein A) Component A is LDPE or polypropylene, or a combination thereof; B) Component B is hexabromocyclododecane (HBCD), tetrabromobisphenol A bis (2,3-dibromopropyl ether), PE™-68, or a combination thereof; C) Component C when present is a substantiaUy random ethylene/styrene inteφolymer, a substantiaUy linear ethylene/ 1-octene copolymer; or a combination thereof; and D) Component D when present is antimony trioxide. 11. A macroceUular acoustic foam obtainable by the process according to any one of claims 1 to 6. 12. The macroceUular acoustic foam of any one of claims 7 to 11 having an average ceU size according to ASTM D3576 in the range from 3 mm to 10 mm. 13. The macroceUular acoustic foam of Claims 7 - 11, in the form of an office partition, automotive decoupler, domestic appUance sound insulation, sound proofing panel or machine enclosure. 14. Use ofthe macroceUular foam of any one of claims 7 to 12 as an acoustic absoφtion material.

Inventors: GILG SANDRINE, PARK CHUNG P, SUBRAMONIAN SURESH, GILG, SANDRINE, PARK, CHUNG, P., SUBRAMONIAN, SURESH
Applicants: DOW CHEMICAL CO, GILG SANDRINE, PARK CHUNG P, SUBRAMONIAN SURESH, GILG, SANDRINE, PARK, CHUNG, P., SUBRAMONIAN, SURESH, THE DOW CHEMICAL COMPANY
Application year: 2001
Main classification: C08J9
IPC codes: B60R13, C08J9, C08K5, C08L23