Abstract:
The present invention pertains to improved alkenyl aromatic polymer foams (and processes for their preparation) having increased heat distortion temperature and improved dimensional stability while maintaining good tensile/tear, creep and environmental dimensional change properties. 
     The closed cell low density alkenyl aromatic polymer foams exhibit increased heat distortion temperature, when substantially random interpolymers of about 21 to about 65 mol % styrene are blended in. When these same alkenyl aromatic polymer foams are made without these interpolymers, the heat distortion temperature is not improved.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     Not Applicable 
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not Applicable 
     FIELD OF THE INVENTION 
     This invention describes a method for increasing the heat distortion temperature of alkenyl aromatic foams by blending polymers which comprise (A) alkenyl aromatic polymers, and (B) vinyl or vinylidene aromatic and/or sterically hindered aliphatic or cycloaliphatic vinyl or vinylidene substantially random interpolymers. Suitable alkenyl aromatic polymers include alkenyl aromatic homopolymers and copolymers of alkenyl aromatic compounds and copolymerizable ethylenically unsaturated comonomers. A preferred alkenyl aromatic polymer is polystyrene. The substantially random interpolymers comprise polymer units derived from ethylene and/or one or more α-olefin monomers with specific amounts of one or more vinyl or vinylidene aromatic monomers and/or sterically hindered aliphatic or cycloaliphatic vinyl or vinylidene monomers. A preferred substantially random interpolymer is an ethylene/styrene interpolymer. Incorporation of the substantially random interpolymer in the blend with the alkenyl aromatic polymer results in an increase of the heat distortion temperature of the resulting foam. 
     BACKGROUND OF THE INVENTION 
     Foams made from alkenyl aromatic polymers such as polystyrene typically exhibit changes in dimension as the temperature is raised significantly above room temperature. Consideration of the heat distortion temperature of alkenyl aromatic foam is very important when it is being used in a relatively high temperature application close to the service temperature limit of the foam (about 165° F. for a conventional polystyrene foam). If the heat distortion temperature of a foam is too low, it may be subject to disfigurement and/or rupture. The stresses set up during foam manufacture are dissipated as the temperature is raised and the linear dimensions of the foams increase or decrease (depending on foam orientation and whether the cell gas pressure is above or below ambient pressure). The temperature at which significant expansion or shrinkage occurs depends on the glass transition temperature of the polymer matrix, which can be depressed due to plasticization by residual blowing agent and other additives which are soluble in the polymer. These effects can also limit the upper service temperature of the foam. One measure of the upper service temperature, and a test to determine the dimensional stability of the foam as a function of temperature, is the Heat Distortion Temperature Test (ASTM D2126-94) which measures the linear change in three dimensions of a foam when exposed to different temperatures. 
     A common high temperature application for alkenyl aromatic foams is in roofing. In roofing, the foam is typically employed below a roofing membrane, which is dark and rubber-like, and may reach service temperature limits when underneath a membrane exposed to direct sun-light in the summer months. If the foam becomes distorted, the membrane and the foam may separate to form void pockets, which leaves the membrane with less mechanical support on its under surface. The lack of under-surface support renders the membrane more subject to rupture, which results in water leaking in the roof. 
     U.S. Pat. Nos. 5,411,687; 5,434,195; 5,557,896; 5,693,687; 5,784,845; and 5,824,710, (the entire contents of which are herein incorporated by reference), disclose open cell foams (i.e. containing 30% or more open cells) as a means of obtaining high heat distortion temperatures. However the high open cell content of these foams can result in inferior thermal insulation performance (due to rapid loss of insulating blowing agent) as well as increased water absorption, both of which are undesirable. 
     Thus it would be desirable to have a closed cell alkenyl aromatic foam with increased heat distortion temperature and improved dimensional stability which also exhibits good vapor resistance, water resistance, and mechanical strength. Uses for such a foam would include insulation in building and construction, as well as in the preparation of foam film labels for bottles and other containers, where the improved dimensional stability of such labels would minimize any shrinkage or warpage of the label when the labeled bottle cools after fabrication. 
     We have surprisingly found that foams made from blends of alkenyl aromatic polymers and specific types and amounts of substantially random interpolymers, exhibit increased heat distortion temperatures relative to analogous alkenyl aromatic polymer foams made without substantially random interpolymers even when the foams are predominantly closed cell (i.e., open cell content of 20 volume % or less). Furthermore, compared with corresponding foams made without the interpolymers, the foams of the present invention exhibit similar or better performance in creep tests (such as DIN 18164 and ASTM 3575 suffix BB) and environmental dimensional change (ASTM C578-83) tests, as well as improved tensile strength/elongation (ASTM D614-91) and tear strength/elongation (ASTM D412-87). 
     BRIEF SUMMARY OF THE INVENTION 
     The present invention pertains to improved alkenyl aromatic polymer foams (and processes for their preparation) having increased heat distortion temperature and improved dimensional stability while maintaining excellent tensile/tear, creep and environmental dimensional change properties. 
     The foams comprise; 
     (A) from about 80 to about 98 percent by weight (based on the combined weight of Components A and B) of one or more alkenyl aromatic polymers, and wherein at least one of said alkenyl aromatic polymers has a molecular weight (M w ) of from about 100,000 to about 500,000; and; 
     (B) from about 2 to about 20 percent by weight (based on the combined weight of Components A and B) of one or more substantially random interpolymers having an I 2  of about 0.1 to about 1000 g/10 min, an M w  /M n  of about 1.5 to about 20; comprising; 
     (1) from about 21 to about 65 mol % of polymer units derived from; 
     (a) at least one vinyl or vinylidene aromatic monomer, or 
     (b) at least one hindered aliphatic or cycloaliphatic vinyl or vinylidene monomer, or 
     (c) a combination of at least one aromatic vinyl or vinylidene monomer and at least one hindered aliphatic or cycloaliphatic vinyl or vinylidene monomer, and 
     (2) from about 35 to about 79 mol % of polymer units derived from at least one of ethylene and/or a C 3-20  α-olefin; and 
     (3) from 0 to about 20 mol % of polymer units derived from one or more of ethylenically unsaturated polymerizable monomers other than those derived from (1) and (2); and 
     (C) optionally, one or more nucleating agents and 
     (D) optionally one or more other additives; and 
     (E) one or more blowing agents present in a total amount of from about 0.2 to about 5.0 gram-moles per kilogram (based on the combined weight of Components A and B); wherein 
     the heat distortion temperature of said foam is increased by about 2° C. or more relative to a corresponding foam without the substantially random interpolymer. 
     In a preferred embodiment the foam having increased heat distortion temperature and dimensional stability is also a closed cell foam (i.e., with 20 vol % or less open cells). 
     This combination allows the manufacture of low density alkenyl aromatic polymer foams of increased heat distortion temperature, when substantially random interpolymers of about 21 to about 65 mol % styrene are used. When these same alkenyl aromatic polymer foams are made without these interpolymers, the heat distortion temperature is not improved. In addition, we have unexpectedly found that the tensile and tear properties of the foam may be improved by using substantially random interpolymers. 
     Definitions 
     All references herein to elements or metals belonging to a certain Group refer to the Periodic Table of the 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 of the 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 numerical 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 &#34;hydrocarbyl&#34; as employed herein means any aliphatic, cycloaliphatic, aromatic, aryl substituted aliphatic, aryl substituted cycloaliphatic, aliphatic substituted aromatic, or aliphatic substituted cycloaliphatic groups. 
     The term &#34;hydrocarbyloxy&#34; means a hydrocarbyl group having an oxygen linkage between it and the carbon atom to which it is attached. 
     The term &#34;copolymer&#34; as employed herein means a polymer wherein at least two different monomers are polymerized to form the copolymer. 
     The term &#34;interpolymer&#34; 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 &#34;increased heat distortion temperature&#34; is used herein to indicate an increase in the heat distortion temperature of a foam of the present invention of about 2° C. or more, preferably about 3° C. or more, and more preferably about 5° C. or more, relative to a corresponding foam without the substantially random interpolymer. 
     DETAILED DESCRIPTION OF THE INVENTION 
     The invention especially covers foams comprising blends of one or more alkenyl aromatic homopolymers, or copolymers of alkenyl aromatic monomers, and/or copolymers of alkenyl aromatic monomers with one or more copolymerizeable ethylenically unsaturated comonomers (other than ethylene or linear C 3  -C 12  α-olefins) with at least one substantially random interpolymer. The foams of this invention have increased heat distortion temperatures relative to corresponding foams of similar density made without the substantially random interpolymer. 
     The alkenyl aromatic polymer material may further include minor proportions of non-alkenyl aromatic polymers. The alkenyl aromatic polymer material may be comprised solely of one or more alkenyl aromatic homopolymers, one or more alkenyl aromatic copolymers, a blend of one or more of each of alkenyl aromatic homopolymers and copolymers, or blends of any of the foregoing with a non-alkenyl aromatic polymer. Regardless of composition, the alkenyl aromatic polymer material comprises greater than 50 and preferably greater than 70 weight percent alkenyl aromatic monomeric units. Most preferably, the alkenyl aromatic polymer material is comprised entirely of alkenyl aromatic monomeric units. 
     Suitable alkenyl aromatic polymers include homopolymers and copolymers derived from alkenyl aromatic compounds such as styrene, alphamethylstyrene, ethylstyrene, vinyl benzene, vinyl toluene, chlorostyrene, and bromostyrene. A preferred alkenyl aromatic polymer is polystyrene. Minor amounts of monoethylenically unsaturated compounds such as C 2-6  alkyl acids and esters, ionomeric derivatives, and C 4-6  dienes may be copolymerized with alkenyl aromatic compounds. Examples of copolymerizable compounds include acrylic acid, methacrylic acid, ethacrylic acid, maleic acid, itaconic acid, acrylonitrile, maleic anhydride, methyl acrylate, ethyl acrylate, isobutyl acrylate, n-butyl acrylate, methyl methacrylate, vinyl acetate and butadiene. 
     The term &#34;substantially random&#34; (in the substantially random interpolymer comprising polymer units derived from ethylene and one or more α-olefin monomers with one or more vinyl or vinylidene aromatic monomers and/or aliphatic or cycloaliphatic vinyl or vinylidene monomers) as used herein means that the distribution of the monomers of said interpolymer can be described by the Bernoulli statistical model or by a first or second order Markovian statistical model, as described by J. C. Randall in POLYMER SEQUENCE DETERMINATION, Carbon-13 NMR Method, Academic Press New York, 1977, pp. 71-78. Preferably, substantially random interpolymers do not contain more than 15 percent of the total amount of vinyl aromatic monomer in blocks of vinyl aromatic monomer of more than 3 units. More preferably, the interpolymer is not characterized by a high degree of either isotacticity or syndiotacticity. This means that in the carbon -13  NMR spectrum of the substantially random interpolymer 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 of the total peak area of the main chain methylene and methine carbons. 
     The interpolymers used to prepare the foams of the present invention include the substantially random interpolymers prepared by polymerizing i) ethylene and/or one or more α-olefin monomers and ii) one or more vinyl or vinylidene aromatic monomers and/or one or more sterically hindered aliphatic or cycloaliphatic vinyl or vinylidene monomers, and optionally iii) other polymerizable ethylenically unsaturated monomer(s). Suitable α-olefins include for example, α-olefins containing from 3 to about 20, preferably from 3 to about 12, more preferably from 3 to about 8 carbon atoms. Particularly suitable are ethylene, propylene, butene-1, 4-methyl-1-pentene, hexene-1 or octene-1 or ethylene in combination with one or more of propylene, butene-1, 4-methyl-1-pentene, hexene-1 or octene-1. These α-olefins do not contain an aromatic moiety. 
     Other optional polymerizable ethylenically unsaturated monomer(s) include norbornene and C 1-10  alkyl or C 6-10  aryl substituted norbornenes, with an exemplary interpolymer being ethylene/styrene/norbornene. 
     Suitable vinyl or vinylidene aromatic monomers which can be employed to prepare the interpolymers include, for example, those represented by the following formula: ##STR1## wherein R 1  is selected from the group of radicals consisting of hydrogen and alkyl radicals containing from 1 to about 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 about 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, C 1-4  -alkyl, and C 1-4  -haloalkyl; and n has a value from zero to about 4, preferably from zero to 2, most preferably zero. Exemplary vinyl aromatic monomers include styrene, vinyl toluene, α-methylstyrene, t-butyl styrene, chlorostyrene, including all isomers of these compounds, and the like. Particularly suitable such monomers include styrene and lower alkyl- or halogen-substituted derivatives thereof. Preferred monomers include styrene, α-methyl styrene, the lower alkyl-(C 1  -C 4 ) or phenyl-ring substituted derivatives of styrene, such as for example, ortho-, meta-, and para-methylstyrene, the ring halogenated styrenes, para-vinyl toluene or mixtures thereof, and the like. A more preferred aromatic vinyl monomer is styrene. 
     By the term &#34;&#34;sterically hindered aliphatic or cycloaliphatic vinyl or vinylidene compounds&#34;, it is meant addition polymerizable vinyl or vinylidene monomers corresponding to the formula: ##STR2## wherein A 1  is a sterically bulky, aliphatic or cycloaliphatic 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 about 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 about 4 carbon atoms, preferably hydrogen or methyl; or alternatively R 1  and A 1  together form a ring system. Preferred aliphatic or cycloaliphatic vinyl or vinylidene compounds are monomers in which one of the carbon atoms bearing ethylenic unsaturation is tertiary or quaternary substituted. Examples of such substituents include cyclic aliphatic groups such as cyclohexyl, cyclohexenyl, cyclooctenyl, or ring alkyl or aryl substituted derivatives thereof, tert-butyl, norbornyl, and the like. Most preferred aliphatic or cycloaliphatic vinyl or vinylidene compounds are the various isomeric vinyl-ring substituted derivatives of cyclohexene and substituted cyclohexenes, and 5-ethylidene-2-norbornene. Especially suitable are 1-, 3-, and 4-vinylcyclohexene. Simple linear non-branched α-olefins including for example, α-olefins containing from 3 to about 20 carbon atoms such as propylene, butene-1, 4-methyl-1-pentene, hexene-1 or octene-1 are not examples of sterically hindered aliphatic or cycloaliphatic vinyl or vinylidene compounds. 
     One method of preparation of the substantially random interpolymers includes polymerizing a mixture of polymerizable monomers in the presence of one or more metallocene or constrained geometry catalysts in combination with various cocatalysts, as described in EP-A-0,416,815 by James C. Stevens et al. and U.S. Pat. No. 5,703,187 by Francis J. Timmers, both of which are incorporated herein by reference in their entirety. Preferred operating conditions for such 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 of the 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 interpolymers are disclosed in U.S. application Ser. No. 702,475, filed May 20, 1991 (EP-A-514,828); as well as U.S. Pat. Nos. 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; 5,470,993; 5,703,187; and 5,721,185 all of which patents and applications are incorporated herein by reference. 
     The substantially random α-olefin/vinyl aromatic interpolymers can also be prepared by the methods described in JP 07/278230 employing compounds shown by the general formula ##STR3## 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 substantially random α-olefin/vinyl aromatic interpolymers can also be prepared by the methods described by John G. Bradfute et al. (W. R. Grace &amp; 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 incorporated herein by reference in their entirety. 
     Also suitable are the substantially random interpolymers which comprise at least one α-olefin/vinyl aromatic/vinyl aromatic/α-olefin tetrad disclosed in U.S. application Ser. No. 08/708,869 filed Sep. 4, 1996 and WO 98/09999 both by Francis J. Timmers et al. These interpolymers contain additional signals in their carbon-13 NMR spectra 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. Specifically, 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. 
     It is believed that these new signals are due to sequences involving two head-to-tail vinyl aromatic monomer insertions preceded and followed by at least one α-olefin insertion, e.g. an ethylene/styrene/styrene/ethylene tetrad wherein the styrene monomer insertions of said tetrads occur exclusively in a 1,2 (head to tail) manner. It is understood by one skilled in the art that for such tetrads involving a vinyl aromatic monomer other than styrene and an α-olefin other than ethylene that the ethylene/vinyl aromatic monomer/vinyl aromatic monomer/ethylene tetrad will give rise to similar carbon-13 NMR peaks but with slightly different chemical shifts. 
     These interpolymers can be prepared by conducting the polymerization at temperatures of from about -30° C. to about 250° C. in the presence of such catalysts as those represented by the formula ##STR4## wherein: each Cp is independently, each occurrence, a substituted cyclopentadienyl group π-bound to M; E is C or Si; M is a group IV metal, preferably Zr or Hf, most preferably Zr; each R is independently, each occurrence, H, hydrocarbyl, silahydrocarbyl, or hydrocarbylsilyl, containing up to about 30 preferably from 1 to about 20 more preferably from 1 to about 10 carbon or silicon atoms; each R 1  is independently, each occurrence, H, halo, hydrocarbyl, hyrocarbyloxy, silahydrocarbyl, hydrocarbylsilyl containing up to about 30 preferably from 1 to about 20 more preferably from 1 to about 10 carbon or silicon atoms or two R 1  groups together can be a C 1-10  hydrocarbyl substituted 1,3-butadiene; m is 1 or 2; and optionally, but preferably in the presence of an activating cocatalyst. Particularly, suitable substituted cyclopentadienyl groups include those illustrated by the formula: ##STR5## wherein each R is independently, each occurrence, H, hydrocarbyl, silahydrocarbyl, or hydrocarbylsilyl, containing up to about 30 preferably from 1 to about 20 more preferably from 1 to about 10 carbon or silicon atoms or two R groups together form a divalent derivative of such group. Preferably, R independently each occurrence is (including where appropriate all isomers) hydrogen, methyl, ethyl, propyl, butyl, pentyl, hexyl, benzyl, phenyl or silyl or (where appropriate) two such R groups are linked together forming a fused ring system such as indenyl, fluorenyl, tetrahydroindenyl, tetrahydrofluorenyl, or octahydrofluorenyl. 
     Particularly preferred catalysts include, for example, racemic-(dimethylsilanediyl)-bis-(2-methyl-4-phenylindenyl) zirconium dichloride, racemic-(dimethylsilanediyl)-bis-(2-methyl-4-phenylindenyl) zirconium 1,4-diphenyl-1,3-butadiene, racemic-(dimethylsilanediyl)-bis-(2-methyl-4-phenylindenyl) zirconium di-C1-4 alkyl, racemic-(dimethylsilanediyl)-bis-(2-methyl-4-phenylindenyl) zirconium di-C1-4 alkoxide, or any combination thereof and the like. 
     It is also possible to use the following titanium-based constrained geometry catalysts, [N-(1,1-dimethylethyl)-1,1-dimethyl-1-[(1,2,3,4,5-η)-1,5,6,7-tetrahydro-s-indacen-1-yl]silanaminato(2-)-N]titanium dimethyl; (1-indenyl)(tert-butylamido)dimethyl-silane titanium dimethyl; ((3-tert-butyl)(1,2,3,4,5-η)-1-indenyl)(tert-butylamido) dimethylsilane titanium dimethyl; and ((3-iso-propyl)(1,2,3,4,5-η)-1-indenyl)(tert-butyl amido)dimethylsilane titanium dimethyl, or any combination thereof and the like. 
     Further preparative methods for the interpolymers used in the present invention have been described in the literature. Longo and Grassi (Makromol. Chem., Volume 191, pages 2387 to 2396 [1990]) and D&#39;Anniello et al. (Journal of Applied 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 4  /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 4  /NdCl 3  /MgCl 2  /Al(Et) 3  catalyst. Sernetz and Mulhaupt, (Macromol. Chem. Phys., 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 4  Cp)(N-tert-butyl)TiCl 2  /methylaluminoxane Ziegler-Natta catalysts. Copolymers of ethylene and styrene produced by bridged metallocene 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 U. S. Pat. No. 5,652,315, issued to Mitsui Toatsu Chemicals, Inc. The manufacture of α-olefin/vinyl aromatic monomer interpolymers such as propylene/styrene and butene/styrene are described in U.S. Pat. No. 5,244,996, issued to Mitsui Petrochemical Industries Ltd or U.S. Pat. No. 5,652,315 also issued to Mitsui Petrochemical Industries Ltd or as disclosed in DE 197 11 339 Al to Denki Kagaku Kogyo KK. All the above methods disclosed for preparing the interpolymer component are incorporated herein by reference. Also, although of high isotacticity and therefore not &#34;substantially random&#34;, 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 of the present invention. 
     While preparing the substantially random interpolymer, an amount of atactic vinyl aromatic homopolymer may be formed due to homopolymerization of the vinyl aromatic monomer at elevated temperatures. The presence of vinyl aromatic homopolymer is in general not detrimental for the purposes of the present invention and can be tolerated. The vinyl aromatic homopolymer may be separated from the interpolymer, if desired, by extraction techniques such as selective precipitation from solution with a non solvent for either the interpolymer or the vinyl aromatic homopolymer. For the purpose of the present invention it is preferred that no more than 30 weight percent, preferably less than 20 weight percent based on the total weight of the interpolymers of atactic vinyl aromatic homopolymer is present. 
     Preparation of the Foams of the Present Invention 
     The compositions of the present invention may be used to form extruded thermoplastic polymer foam, expandable thermoplastic foam beads or expanded thermoplastic foams, and molded articles formed by expansion and/or coalescing and welding of those particles. 
     The foams may take any known physical configuration, such as extruded sheet, rod, plank, films and profiles. The foam structure also may be formed by molding expandable beads into any of the foregoing configurations or any other configuration. 
     Foam structures may be made by a conventional extrusion foaming process. The present foam is generally prepared by melt blending in which the alkenyl aromatic polymer material and one or more substantially random interpolymers are heated together 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 extruding from the die, the gel is cooled to an optimum temperature. To make a foam, the optimum temperature is at or above the blends glass transition temperature or melting point. For the foams of the present invention the optimum foaming temperature is in a range sufficient to produce an open cell content in the foam of 20 vol % or less and to optimize physical characeristics of the foam structure. The blowing agent may be 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 of the melt polymer material and to generally disperse the blowing agent homogeneously therein. Optionally, a nucleator may be blended in the polymer melt or dry blended with the polymer material prior to plasticizing or melting. The substantially random interpolymers may be dry-blended with the polymer material prior to charging to the extruder, or charged to the extruder in the form of a polymer concentrate or a interpolymer/color pigment carrier material. The foamable gel is typically cooled to a lower temperature to optimize physical characteristics of the foam structure. The gel may be cooled in the extruder or other mixing device or in separate coolers. 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 formable gel is maintained prior to extrusion through the die. The lower pressure may be superatmospheric or subatmospheric (vacuum), but is preferably at an atmospheric level. 
     The present foam structures may be formed in a coalesced strand form by extrusion of the compositions of the present invention through a multi-orifice die. The orifices are arranged so that contact between adjacent streams of the 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. 
     The present foam structures may also be 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 of the compositions of the present invention and a blowing agent at a temperature at which the viscosity of the 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. 
     The present foam structures may also be formed into non-crosslinked foam beads suitable for molding into articles by expansion of pre-expanded beads containing a blowing agent. The beads may be molded at the time of expansion to form articles of various shapes. Processes for making expanded beads and molded expanded beam foam articles are described in Plastic Foams, Part II, Frisch And Saunders, pp. 544-585, Marcel Dekker, Inc. (1973) and Plastic Materials, Brydson, 5 th  Ed., pp. 426-429, Butterworths (1989)), which are incorporated herein by reference. 
     Expandable and expanded beads can be made by a batch or by an extrusion process. The batch process of making expandable beads is essentially the same as for manufacturing expandable polystyrene (EPS). The granules of a polymer blend, made either by melt blending or in-reactor blending, are impregnated with a blowing agent in an aqueous suspension or in an anhydrous state in a pressure vessel at an elevated temperature and pressure. The granules are then either rapidly discharged into a region of reduced pressure to expand to foam beads or cooled and discharged as unexpanded beads. The unexpanded beads are then heated to expand with a proper means, e.g., with steam or with hot air. The extrusion method is essentially the same as the conventional foam extrusion process as described above up to the die orifice. The die has multiple holes. In order to make unfoamed beads, the foamable strands exiting the die orifice are immediately quenched in a cold water bath to prevent foaming and then pelletized. Or, the strands are converted to foam beads by cutting at the die face and then allowed to expand. 
     The foam beads may then be molded by any means known in the art, such as charging the foam beads to the mold, compressing the mold to compress the beads, and heating the beads such as with steam to effect coalescing and welding of the beads to form the article. Optionally, the beads may be impregnated with air or other blowing agent at an elevated pressure and temperature prior to charging to the mold. Further, the beads may be heated prior to charging. The foam beads may then be molded to blocks or shaped articles by a suitable molding method known in the art. (Some of the methods are taught in U.S. Pat. Nos. 3,504,068 and 3,953,558.) Excellent teachings of the above processes and molding methods are seen in C. P. Park, supra, p. 191, pp. 197-198, and pp. 227-229, which are incorporated herein by reference. 
     To make the foam beads, blends of alkenyl aromatic polymers with one or more substantially random interpolymer are formed into discrete resin particles such as granulated resin pellets and are: suspended in a liquid medium in which they are substantially insoluble such as water; impregnated with a blowing agent by introducing the blowing agent into the liquid medium at an elevated pressure and temperature in an autoclave or other pressure vessel; and rapidly discharged into the atmosphere or a region of reduced pressure to expand to form the foam beads. This process is well taught in U.S. Pat. Nos. 4,379,859 and 4,464,484, which are incorporated herein by reference. 
     A process for making expandable thermoplastic beads comprises: providing an alkenyl aromatic monomer and optionally at least one additional monomer, which is different from, and polymerizable with said alkenyl aromatic monomer; and dissolving in at least one of said monomers the substantially random interpolymers; polymerizing the first and second monomers to form thermoplastic particles; incorporating a blowing agent into the thermoplastic particles during or after polymerization; and cooling the thermoplastic particles to form expandable beads. The alkenyl aromatic monomer is present in an amount of at least about 50, preferably at least about 70, more preferably at least about 90 wt % based on the combined weights of the polymerizeable monomer(s). 
     Another process for making expandable thermoplastic beads comprises: heating the blends of alkenyl aromatic polymers with one or more substantially random interpolymers to form a melt polymer; incorporating into the melt polymer material at an elevated temperature a blowing agent to form a foamable gel; cooling the gel to an optimum temperature which is one at which foaming will not occur, extruding through a die containing one or more orifices to form one or more essentially continuous expandable thermoplastic strand(s); and pelletizing the expandable thermoplastic strand(s) to form expandable thermoplastic bead(s). Alternatively expanded thermoplastic foam beads may be made if, prior to extruding from the die, the gel is cooled to an optimum temperature which in this case is at or above the blends glass transition temperature or melting point. For the expanded thermoplastic foam beads of the present invention, the optimum foaming temperature is in a range sufficient to produce an open cell content in the foam of 20 vol % or less. 
     The present foam structures may also be used to make foamed films for bottle labels and other containers using either a blown film or a cast film extrusion process. The films may also be made by a co-extrusion process to obtain foam in the core with one or two surface layers, which may or may not be comprised of the polymer compositions used in the present invention. 
     Blowing agents useful in making the present foams include inorganic blowing agents, organic blowing agents and chemical blowing agents. Suitable inorganic blowing agents include nitrogen, sulfur hexafluoride (SF 6 ), argon, water, air and helium. Organic blowing agents include carbon dioxide, aliphatic hydrocarbons having 1-9 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, n-butane, 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), fluoroethane (HFC-161), 1,1,1-trifluoroethane (HFC-143a), 1,1,1,2-tetrafluoroethane (HFC-134a), 1,1,2,2 tetrafluoroethane (HFC-134), 1,1,1,3,3-pentafluoropropane, pentafluoroethane (HFC-125), difluoromethane (HFC-32), 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-trichloro-ethane, 1,1-dichloro-1-fluoroethane (HCFC-141b), 1-chloro-1,1-difluoroethane (HCFC-142b), chlorodifluoromethane (HCFC-22), 1,1-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), trichloro-trifluoroethane (CFC-113), dichlorotetrafluoroethane (CFC-114), chloroheptafluoropropane, and dichlorohexafluoropropane. Chemical blowing agents include azodicarbonamide, azodiisobutyro-nitrile, benzenesulfonhydrazide, 4,4-oxybenzene sulfonyl-semicarbazide, p-toluene sulfonyl semi-carbazide, barium azodicarboxylate, N,N&#39;-dimethyl-N,N&#39;-dinitroso-terephthalamide, trihydrazino triazine and mixtures of citric acid and sodium bicarbonate such as the various products sold under the name Hydrocerol™ (a product and trademark of Boehringer Ingelheim). All of these blowing agents may be used as single components or any mixture of combination thereof, or in mixtures with other co-blowing agents. 
     The amount of blowing agent incorporated into the polymer melt material to make a foam-forming polymer gel is from about 0.2 to about 5.0 gram-moles per kilogram of polymer, preferably from about 0.5 to about 3.0 gram-moles per kilogram of polymer, and most preferably from about 1.0 to 2.5 gram-moles per kilogram of polymer. 
     In addition, a nucleating agent may be added in order to control the size of foam cells. Preferred nucleating agents include inorganic substances such as calcium carbonate, talc, clay, silica, barium stearate, diatomaceous earth, mixtures of citric acid and sodium bicarbonate, and the like. The amount of nucleating agent employed may range from 0 to about 5 parts by weight per hundred parts by weight of a polymer resin. The preferred range is from 0 to about 3 parts by weight. 
     Various additives may be incorporated in the present foam structure such as inorganic fillers, pigments, antioxidants, acid scavengers, ultraviolet absorbers, flame retardants, processing aids, extrusion aids, other thermoplastic polymers, antistatic agents, and the like. Examples of other thermoplastic polymers include alkenyl aromatic homopolymers or copolymers (having molecular weight of about 2,000 to about 50,000) and ethylenic polymers. 
     The foam has a density of from about 10 to about 150 and most preferably from about 10 to about 70 kilograms per cubic meter according to ASTM D-1622-88. 
     The foam has an average cell size of from about 0.05 to about 5.0 and preferably from about 0.1 to about 1.5 millimeters according to ASTM D3576-77. 
     The present foam is particularly suited to be formed into a plank or sheet, desirably one having a cross-sectional area of 30 square centimeters (cm) or more and a thickness or minor dimension in cross-section of 0.95 cm or more, preferably 2.5 cm or more. 
     The present foam is closed cell. The closed cell content of the present foams is greater than or equal to 80 percent according to ASTM D2856-94. 
     The present foam&#39;s heat distortion temperature is increased about 2° C. or more, preferably about 3° C. or more, and more preferably about 5° C. or more, relative to the heat distortion temperature of a corresponding foam made without the substantially random interpolymer. 
     The present foam structures may be used to insulate a surface by applying to the surface an insulating panel fashioned from the present structure, as used in for example, external wall sheathing (home thermal insulation), foundation insulation, and residing underlayment. Such panels are useful in any conventional insulating applications such as roofing, buildings, refrigerators and the like. Other applications include floating docks and rafts (buoyancy applications) as well as various floral and craft applications. 
     Properties of the Interpolymers and Blend Compositions Used to Prepare the Foams of the Present Invention. 
     The polymer compositions used to prepare the foams of the present invention comprise from about 80 to about 98, preferably from about 85 to about 97, more preferably from about 90 to about 95 wt %, (based on the combined weights of substantially random interpolymer and the alkenyl aromatic homopolymers or copolymer) of one or more alkenyl aromatic homopolymers or copolymers. 
     The molecular weight distribution (M w  /M n ) of the alkenyl aromatic homopolymers or copolymers used to prepare the foams of the present invention is from about 2 to about 7. 
     The molecular weight (Mw) of the alkenyl aromatic homopolymers or copolymers used to prepare the foams of the present invention is from about 100,000 to about 500,000, preferably of from about 120,000 to about 350,000, more preferably 130,000 to 325,000. 
     The alkenyl aromatic polymer material used to prepare the foams of the present invention comprises greater than 50 and preferably greater than 70 weight percent alkenyl aromatic monomeric units. Most preferably, the alkenyl aromatic polymer material is comprised entirely of alkenyl aromatic monomeric units. 
     The polymer compositions used to prepare the foams of the present invention comprise from about 2 to about 20, preferably from about 3 to about 15, more preferably from about 5 to about 10 wt %, (based on the combined weights of substantially random interpolymer and the alkenyl aromatic homopolymers or copolymers) of one or more substantially random interpolymers. 
     These substantially random interpolymers used to prepare the foams of the present invention usually contain from about 21 to about 65, preferably from about 29 to about 52, more preferably from about 29 to about 45 mole percent of at least one vinyl or vinylidene aromatic monomer and/or aliphatic or cycloaliphatic vinyl or vinylidene monomer and from about 35 to about 79, preferably from about 48 to about 71, more preferably from about 55 to about 71 mole percent of ethylene and/or at least one aliphatic α-olefin having from 3 to about 20 carbon atoms. 
     The melt index (I 2 ) of the substantially random interpolymer used to prepare the foams of the present invention is from about 0.1 to about 1000, preferably of from about 0.3 to about 30, more preferably of from about 0.5 to about 10 g/10 min. 
     The molecular weight distribution (M w  /M n ) of the substantially random interpolymer used to prepare the foams of the present invention is from about 1.5 to about 20, preferably of from about 1.8 to about 10, more preferably of from about 2 to about 5. 
     In addition, minor amounts of alkenyl aromatic homopolymers or copolymers having a molecular weight of about 2,000 to about 50,000, preferably from about 4,000 to about 25,000 can be added in an amount not exceeding about 20 wt % (based on the combined weights of substantially random interpolymer and the various alkenyl aromatic homopolymers or copolymers). 
     The following examples are illustrative of the invention, but are not to be construed as to limiting the scope thereof in any manner. 
    
    
     EXAMPLES 
     Test Methods 
     a) Melt Flow and Density Measurements 
     The molecular weight of the substantially random interpolymers used in the present invention is conveniently indicated using a melt index measurement according to ASTM D-1238, Condition 190° C./2.16 kg (formally known as &#34;Condition (E)&#34; and also known as I 2 ) was determined. Melt index is inversely proportional to the molecular weight of the polymer. Thus, the higher the molecular weight, the lower the melt index, although the relationship is not linear. 
     Also useful for indicating the molecular weight of the substantially random interpolymers used in the present invention is the Gottfert melt index (G, cm 3  /10 min) which is obtained in a similar fashion as for melt index (I 2 ) using the ASTM D1238 procedure for automated plastometers, with the melt density set to 0.7632, the melt density of polyethylene at 190° C. 
     The relationship of melt density to styrene content for ethylene-styrene interpolymers was measured, as a function of total styrene content, at 190° C. for a range of 29.8% to 81.8% by weight styrene. Atactic polystyrene levels in these samples was typically 10% or less. The influence of the atactic polystyrene was assumed to be minimal because of the low levels. Also, the melt density of atactic polystyrene and the melt densities of the samples with high total styrene are very similar. The method used to determine the melt density employed a Gottifert melt index machine with a melt density parameter set to 0.7632, and the collection of melt strands as a function of time while the I 2  weight was in force. The weight and time for each melt strand was recorded and normalized to yield the mass in grams per 10 minutes. The instrument&#39;s calculated I 2  melt index value was also recorded. The equation used to calculate the actual melt density is 
     
         δ=δ.sub.0.7632 ×I.sub.2 /I.sub.2 Gottfert 
    
     where δ 0 .7632 =0.7632 and I 2  Gottfert=displayed melt index. 
     A linear least squares fit of calculated melt density versus total styrene content leads to an equation with a correlation coefficient of 0.91 for the following equation: 
     
         δ=0.00299×S+0.723 
    
     where S=weight percentage of styrene in the polymer. The relationship of total styrene to melt density can be used to determine an actual melt index value, using these equations if the styrene content is known. 
     So for a polymer that is 73% total styrene content with a measured melt flow (the &#34;Gottfert number&#34;), the calculation becomes: 
     
         x=0.00299*73+0.723=0.9412 
    
     where 0.9412/0.7632=I 2  /G# (measured)=1.23 
     b) Styrene Analyses 
     Interpolymer styrene content and atactic polystyrene concentration were determined using proton nuclear magnetic resonance ( 1  H N.M.R). All proton NMR samples were prepared in 1, 1, 2, 2-tetrachloroethane-d 2  (TCE-d 2 ). The resulting solutions were 1.6-3.2 percent polymer by weight. Melt index (I 2 ) was used as a guide for determining sample concentration. Thus when the I 2  was greater than 2 g/10 min, 40 mg of interpolymer was used; with an I 2  between 1.5 and 2 g/10 min, 30 mg of interpolymer was used; and when the I 2  was less than 1.5 g/10 min, 20 mg of interpolymer was used. The interpolymers were weighed directly into 5 mm sample tubes. A 0.75 mL aliquot of TCE-d 2  was added by syringe and the tube was capped with a tight-fitting polyethylene cap. The samples were heated in a water bath at 85° C. to soften the interpolymer. To provide mixing, the capped samples were occasionally brought to reflux using a heat gun. 
     Proton NMR spectra were accumulated on a Varian VXR 300 with the sample probe at 80° C., and referenced to the residual protons of TCE-d 2  at 5.99 ppm. The delay times were varied between 1 second, and data was collected in triplicate on each sample. The following instrumental conditions were used for analysis of the interpolymer samples: 
     Varian VXR-300, standard  1  H: 
     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 about 10 minutes. 
     Initially, a  1  H NMR spectrum for a sample of the polystyrene, having a molecular weight (Mw) of about 192,000, was acquired with a delay time of one second. The protons were &#34;labeled&#34;: b, branch; a, alpha; o, ortho; m, meta; p, para, as shown in FIG. 1. ##STR6## 
     Integrals were measured around the protons labeled in FIG. 1; the `A` designates aPS. Integral A 7 .1 (aromatic, around 7.1 ppm) is believed to be the three ortho/para protons; and integral A 6 .6 (aromatic, around 6.6 ppm) the two meta protons. The two aliphatic protons labeled α resonate at 1.5 ppm; and the single proton labeled b is at 1.9 ppm. The aliphatic region was integrated from about 0.8 to 2.5 ppm and is referred to as A al . The theoretical ratio for A 7 .1 :A 6 .6 :A al  is 3:2:3, or 1.5:1:1.5, and correlated very well with the observed ratios for the polystyrene sample for several delay times of 1 second. The ratio calculations used to check the integration and verify peak assignments were performed by dividing the appropriate integral by the integral A 6 .6 Ratio A r  is A 7 .1 /A 6 .6. 
     Region A 6 .6 was assigned the value of 1. Ratio Al is integral A al  /A 6 .6. All spectra collected have the expected 1.5:1:1.5 integration ratio of (o+p): m: (α+b). The ratio of aromatic to aliphatic protons is 5 to 3. An aliphatic ratio of 2 to 1 is predicted based on the protons labeled α and b respectively in FIG. 1. This ratio was also observed when the two aliphatic peaks were integrated separately. 
     For the ethylene/styrene interpolymers, the  1  H NMR spectra using a delay time of one second, had integrals C 7 .1, C 6 .6, and C al  defined, such that the integration of the peak at 7.1 ppm included all the aromatic protons of the copolymer as well as the o &amp; p protons of aPS. Likewise, integration of the aliphatic region C al  in the spectrum of the interpolymers included aliphatic protons from both the aPS and the interpolymer with no clear baseline resolved signal from either polymer. The integral of the peak at 6.6 ppm C 6 .6 is resolved from the other aromatic signals and it is believed to be due solely to the aPS homopolymer (probably the meta protons). (The peak assignment for atactic polystyrene at 6.6 ppm (integral A 6 .6) was made based upon comparison to the authentic sample of polystyrene having a molecular weight (Mw) of about 192,000, This is a reasonable assumption since, at very low levels of atactic polystyrene, only a very weak signal is observed here. Therefore, the phenyl protons of the copolymer must not contribute to this signal. With this assumption, integral A 6 .6 becomes the basis for quantitatively determining the aPS content. 
     The following equations were then used to determine the degree of styrene incorporation in the ethylene/styrene interpolymer samples: 
     
         (CPhenyl)=C.sub.7.1 +A.sub.7.1 -(1.5×A.sub.6.6) 
    
     
         (CAliphatic)&#39;=C.sub.al -(1 5×A.sub.6.6) 
    
     
         s.sub.c =(CPhenyl)/5 
    
     
         e.sub.c =(CAliphatic-(3×s.sub.c))/4 
    
     
         E=e.sub.c /(e.sub.c +s.sub.c) 
    
     
         S.sub.c =s.sub.c /(e.sub.c +s.sub.c) 
    
     and the following equations were used to calculate the mol % ethylene and styrene in the interpolymers. ##EQU1## 
     where: s c  and e c  are styrene and ethylene proton fractions in the interpolymer, respectively, and S c  and E are mole fractions of styrene monomer and ethylene monomer in the interpolymer, respectively. 
     The weight percent of aPS in the interpolymers was then determined by the following equation: ##EQU2## 
     The total styrene content was also determined by quantitative Fourier Transform Infrared spectroscopy (FTIR). 
     Preparation of Ethylene/Styrene Interpolymers (ESI&#39;s) Used in Examples and Comparative Experiments of Present Invention 
     1) Preparation of ESI #&#39;s 1-3 
     ESI #&#39;s 1-3 are substantially random ethylene/styrene interpolymers prepared using the following catalyst and polymerization procedures. 
     Preparation of Catalyst A;(1H-cyclopenta[1]phenanthrene-2-yl)dimethyl(t-butylamido)-silanetitanium 1,4-diphenylbutadiene) 
     1) Preparation of lithium 1H-cyclopenta[1]phenanthrene-2-yl 
     To a 250 ml round bottom flask containing 1.42 g (0.00657 mole) of 1H-cyclopenta[1]phenanthrene and 120 ml of benzene was added dropwise, 4.2 ml of a 1.60 M solution of n-BuLi in mixed hexanes. The solution was allowed to stir overnight. The lithium salt was isolated by filtration, washing twice with 25 ml benzene and drying under vacuum. Isolated yield was 1.426 g (97.7 percent). 1H NMR analysis indicated the predominant isomer was substituted at the 2 position. 
     2) Preparation of (1H-cyclopenta[1]phenanthrene-2-yl)dimethylchlorosilane 
     To a 500 ml round bottom flask containing 4.16 g (0.0322 mole) of dimethyldichlorosilane (Me 2  SiCl 2 ) and 250 ml of tetrahydrofuran (THF) was added dropwise a solution of 1.45 g (0.0064 mole) of lithium 1H-cyclopenta[1]phenanthrene-2-yl in THF. The solution was stirred for approximately 16 hours, after which the solvent was removed under reduced pressure, leaving an oily solid which was extracted with toluene, filtered through diatomaceous earth filter aid (Celite™), washed twice with toluene and dried under reduced pressure. Isolated yield was 1.98 g (99.5 percent). 
     3. Preparation of (1H-cyclopenta[1]phenanthrene-2-yl)dimethyl(t-butylamino)silane 
     To a 500 ml round bottom flask containing 1.98 g (0.0064 mole) of (1H-cyclopenta[1]phenanthrene-2-yl)dimethylchlorosilane and 250 ml of hexane was added 2.00 ml (0.0160 mole) of t-butylamine. The reaction mixture was allowed to stir for several days, then filtered using diatomaceous earth filter aid (Celite™), washed twice with hexane. The product was isolated by removing residual solvent under reduced pressure. The isolated yield was 1.98 g (88.9 percent). 
     4. Preparation of dilithio (1H-cyclopenta[1]phenanthrene-2-yl)dimethyl(t-butylamido)silane 
     To a 250 ml round bottom flask containing 1.03 g (0.0030 mole) of (1H-cyclopenta[1]phenanthrene-2-yl)dimethyl(t-butylamino)silane) and 120 ml of benzene was added dropwise 3.90 ml of a solution of 1.6 M n-BuLi in mixed hexanes. The reaction mixture was stirred for approximately 16 hours. The product was isolated by filtration, washed twice with benzene and dried under reduced pressure. Isolated yield was 1.08 g (100 percent). 
     5. Preparation of (1H-cyclopenta[1]phenanthrene-2-yl)dimethyl(t-butylamido)silanetitanium dichloride 
     To a 250 ml round bottom flask containing 1.17 g (0.0030 mole) of TiCl 3 .3THF and about 120 ml of THF was added at a fast drip rate about 50 ml of a THF solution of 1.08 g of dilithio (1H-cyclopenta[1]phenanthrene-2-yl)dimethyl(t-butylamido)silane. The mixture was stirred at about 20° C. for 1.5 h at which time 0.55 gm (0.002 mole) of solid PbCl 2  was added. After stirring for an additional 1.5 h the THF was removed under vacuum and the reside was extracted with toluene, filtered and dried under reduced pressure to give an orange solid. Yield was 1.31 g (93.5 percent). 
     6. Preparation of (1H-cyclopenta[1]phenanthrene-2-yl)dimethyl(t-butylamido)silanetitanium 1,4-diphenylbutadiene 
     To a slurry of (1H-cyclopenta[1]phenanthrene-2-yl)dimethyl(t-butylamido)silanetitanium dichloride (3.48 g, 0.0075 mole) and 1.551 gm (0.0075 mole) of 1,4-diphenyllbutadiene in about 80 ml of toluene at 70° C. was add 9.9 ml of a 1.6 M solution of n-BuLi (0.0150 mole). The solution immediately darkened. The temperature was increased to bring the mixture to reflux and the mixture was maintained at that temperature for 2 hrs. The mixture was cooled to about -20° C. and the volatiles were removed under reduced pressure. The residue was slurried in 60 ml of mixed hexanes at about 20° C. for approximately 16 hours. The mixture was cooled to about -25° C. for about 1 h. The solids were collected on a glass frit by vacuum filtration and dried under reduced pressure. The dried solid was placed in a glass fiber thimble and solid extracted continuously with hexanes using a soxhlet extractor. After 6 h a crystalline solid was observed in the boiling pot. The mixture was cooled to about -20° C., isolated by filtration from the cold mixture and dried under reduced pressure to give 1.62 g of a dark crystalline solid. The filtrate was discarded. The solids in the extractor were stirred and the extraction continued with an additional quantity of mixed hexanes to give an additional 0.46 gm of the desired product as a dark crystalline solid. 
     Polymerization for ESI #&#39;s 1-3 
     ESI&#39;s 1-3 were prepared in a continuously operating loop reactor (36.8 gal. 139 L). An Ingersoll-Dresser twin screw pump provided the mixing. The reactor ran liquid full at 475 psig (3,275 kPa) with a residence time of approximately 25 minutes. Raw materials and catalyst/cocatalyst flows were fed into the suction of the twin screw pump through injectors and Kenics static mixers. The twin screw pump discharged into a 2&#34; diameter line which supplied two Chemineer-Kenics 10-68 Type BEM Multi-Tube heat exchangers in series. The tubes of these exchangers contained twisted tapes to increase heat transfer. Upon exiting the last exchanger, loop flow returned through the injectors and static mixers to the suction of the pump. Heat transfer oil was circulated through the exchangers&#39; jacket to control the loop temperature probe located just prior to the first exchanger. The exit stream of the loop reactor was taken off between the two exchangers. The flow and solution density of the exit stream was measured by a MicroMotion. 
     Solvent feed to the reactor was supplied by two different sources. A fresh stream of toluene from an 8480-S-E Pulsafeeder diaphragm pump with rates measured by a MicroMotion flowmeter was used to provide flush flow for the reactor seals (20 lb/hr (9.1 kg/hr). Recycle solvent was mixed with uninhibited styrene monomer on the suction side of five 8480-5-E Pulsafeeder diaphragm pumps in parallel. These five Pulsafeeder pumps supplied solvent and styrene to the reactor at 650 psig (4,583 kPa). Fresh styrene flow was measured by a MicroMotion flowmeter, and total recycle solvent/styrene flow was measured by a separate MicroMotion flowmeter. Ethylene was supplied to the reactor at 687 psig (4,838 kPa). The ethylene stream was measured by a Micro-Motion mass flowmeter. A Brooks flowmeter/controller was used to deliver hydrogen into the ethylene stream at the outlet of the ethylene control valve. 
     The ethylene/hydrogen mixture combined with the solvent/styrene stream at ambient temperature. The temperature of the entire feed stream as it entered the reactor loop was lowered to 2° C. by an exchanger with -10° C. glycol on the jacket. Preparation of the three catalyst components took place in three separate tanks: fresh solvent and concentrated catalyst/cocatalyst premix were added and mixed into their respective run tanks and fed into the reactor via variable speed 680-S-AEN7 Pulsafeeder diaphragm pumps. As previously explained, the three component catalyst system entered the reactor loop through an injector and static mixer into the suction side of the twin screw pump. The raw material feed stream was also fed into the reactor loop through an injector and static mixer downstream of the catalyst injection point but upstream of the twin screw pump suction. 
     Polymerization was stopped with the addition of catalyst kill (water mixed with solvent) into the reactor product line after the Micro Motion flowmeter measuring the solution density. A static mixer in the line provided dispersion of the catalyst kill and additives in the reactor effluent stream. This stream next entered post reactor heaters that provided additional energy for the solvent removal flash. This flash occurred as the effluent exited the post reactor heater and the pressure was dropped from 475 psig (3,275 kPa) down to 450 mmHg (60 kPa) of absolute pressure at the reactor pressure control valve. 
     This flashed polymer entered the first of two hot oil jacketed devolatilizers. The volatiles flashing from the first devolatizer were condensed with a glycol jacketed exchanger, passed through the suction of a vacuum pump, and were discharged to the solvent and styrene/ethylene separation vessel. Solvent and styrene were removed from the bottom of this vessel as recycle solvent while ethylene exhausted from the top. The ethylene stream was measured with a MicroMotion mass flowmeter. The measurement of vented ethylene plus a calculation of the dissolved gases in the solvent/styrene stream were used to calculate the ethylene conversion. The polymer and remaining solvent separated in the devolatilizer was pumped with a gear pump to a second devolatizer. The pressure in the second devolatizer was operated at 5 mm Hg (0.7 kPa) absolute pressure to flash the remaining solvent. This solvent was condensed in a glycol heat exchanger, pumped through another vacuum pump, and exported to a waste tank for disposal. The dry polymer (&lt;1000 ppm total volatiles) was pumped with a gear pump to an underwater pelletizer with 6-hole die, pelletized, spin-dried, and collected in 1000 lb boxes. 
     The various catalysts, co-catalysts and process conditions used to prepare the various individual ethylene styrene interpolymers (ESI #&#39;s 1-3) are summarized in Table 1 and their properties are summarized in Table 2. 
     
                                           TABLE 1__________________________________________________________________________Preparation Conditions for ESI #&#39;s 1-3    Reactor   Solvent       Ethylene            Hydrogen                 Styrene                     Ethylene  ESI Temp Flow Flow Flow Flow Conversion B/Ti MMAO                                        .sup.d /Ti  Co-  # ° C. lb/hr lb/hr sccm lb/hr % Ratio Ratio Catalyst Catalyst__________________________________________________________________________ESI 1-    73  445 33   432  115 92    6.0                              13.0  A.sup.a                                        B.sup.b  ESI 2 100 470 64 998 55 95 6.0 16.0 A.sup.a B.sup.b  ESI-3 61 386 20 0 100 88 3.50 2.5 A.sup.a B.sup.b__________________________________________________________________________ *N/A = not available .sup.a Catalyst A is; (1Hcyclopenta[l]phenathrene2-yl)dimethyl(t-butylamido)-silanetitanium 1,4diphenylbutadiene) .sup.b Cocatalyst B is tris(pentafluorophenyl)borane, (CAS# 00110915-5),. .sup.c a modified methylaluminoxane commercially available from Akzo Nobe as MMAO3A (CAS# 14690579-5) 
    
     
                       TABLE 2______________________________________Properties of ESI #&#39;s 1-3.     Copolymer Copolymer        Melt Index,   Styrene Styrene atactic PS I.sub.2  ESI # (wt. %) (mol. %) (wt %) (g/10 min)______________________________________ESI-1 68.1      19.5        3.0    0.96  ESI-2 38.8 37.5 0.4 0.74  ESI-3 69.5 38.0 8.9 0.94______________________________________ 
    
     Polystyrene Blend Components 
     PS 1 is a granular polystyrene having a weight average molecular weight, Mw, of 296,000 and a polydispersity, M w  /M n , of 2.7. 
     PS 2 is a granular polystyrene having a weight average molecular weight, Mw, of 148,700 and a polydispersity, M w  /M n , of 5.5. 
     Examples 1-2. 
     A foaming process comprising a single-screw extruder, mixer, coolers and die was used to make foam sheets. HCFC-22 was used as the blowing agent at a level of 5.7 part-per-hundred resin (phr) to foam PS and PS/ESI blends. Talc was used as nucleator. All foams were made at 140° C. Table 3 summarizes the foam properties: 
     Example 3 
     A foaming process comprising a single-screw extruder, mixer, coolers and die was used to make foam planks. Carbon dioxide (CO 2 ) was used as the blowing agent at a level of 4.7 phr, to foam polystyrene and a blend of polystyrene with ESI. The other additives were: hexabromocyclododecane=2.5 phr; barium stearate=0.2 phr; blue pigment=0.15 phr; tetrasodiumpyrophosphate=0.2 phr; linear low density polyethylene=0.4 phr. The foaming temperature was 123° C. 
     The data from Examples 1-3 show that the heat distortion temperatures of the foams of the present invention were significantly higher than those of the Comparative foams made without the substantially random interpolymer blend component. Additionally, the other physical and mechanical properties of the foams were generally similar to, or better than, those of the comparative foams. 
     
                                           TABLE 3__________________________________________________________________________Increased heat distortion temperatures with PS/ESI blends, using HCFC-22as Blowing Agent.                               Tear Tear Tensile                                              Tensile                                                   Compression                                                     Blend   foam                                                   Ht Distn.                                                   Strength Elongatio                                                   n strength                                                   Elongation Creep                                                   (%)   Composition Talc thickness density % open av cell Temp (kN/m) (%)                                                   (MPa) (%) ASTM                                                   D3575  Ex #  wt % (phr) mm kg/m3 cells size mm ° C. MD (CD) MD (CD) MD                                                   (CD) MD (CD)                                                   suffix BB__________________________________________________________________________Ex 1    85% PS1/15%      0.5         3.2  72.9                  13.6                      0.84                          85   6.5(6.6)                                    4.6(4.5)                                         1.89(1.54)                                              10.3(7.8)                                                   4.0   ESI 1  Ex 2 85% PS1/15% 0.9 2.5 74.9 14.0 0.68 85 8.5(7.5) 4.0(3.4) 2.57(1.78)                                                   10.9(9.3) 2.6                                                     ESI 1  Comp 1 100 wt % PS1 0.5 2.6 68.4 7.7 0.49 74 5.9(5.9) 2.4(3.0) 2.31(1.83                                                   )  7.5(7.3) 4.2                                                    Comp 2 85%                                                   PS1/15% 0.9 2.3                                                   82.9 14.7 0.70 74                                                   8.8(7.9) 4.0(3.4)                                                   2.45(1.96)                                                   8.6(9.2) 2.8                                                     ESI 2__________________________________________________________________________ 
    
     
                                           TABLE 4__________________________________________________________________________Increased heat distortion temperatures with PS/ESI blends, using CO.sub.2as Blowing Agent.                             Ht Distn.  EDC (%)                                           thickness foam density %                                        open av cell size Temp WD                                        (%) ASTM  Ex # Blend Composition mm kg/m.sup.3 cells mm ° C. DIN 18164                                        C578-83__________________________________________________________________________Ex 3    95% PS2/5% ESI 3        37   40.9  18.8                       0.34  97   1.9   Pass  Comp 3 100 wt % PS2 48 37.9 4.1 0.28 82 1.3 Pass__________________________________________________________________________