Soft and flexible foams made from blends of alkenyl aromatic polymers and alpha-olefin/vinyl or vinylidene aromatic and/or sterically hindered aliphatic or cycloaliphatic vinyl or vinylidene interpolymers

[0013] Not Applicable

[0014] Not Applicable

[0015] This invention describes a method for making soft and flexible foams by expanding blends of polymers comprising (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.

[0016] 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 in the softness and flexibility of the resulting foam.

[0017] Crosslinked olefinic foams are typically made from ethylenic polymers such as low density polyethylene, ethylene vinylacetate copolymer, homogeneous ethylene and/or α-olefin homopolymers or interpolymers comprising ethylene and/or C₃-C₂₀α-olefins including the substantially linear ethylene/α-olefin interpolymers. These include the polyolefin plastomers, such as those marketed by The Dow Chemical Company under the AFFINITY™ tradename and polyethylene elastomers, such as those marketed under the ENGAGE™ tradename by Du Pont Dow Elastomers PLC.

[0018] Crosslinking is achieved by conventional means such as peroxides, silane and/or radiation. Some of the advantages of crosslinked foam over noncrosslinked foams are smaller cell sizes (typically less than about 1 mm), smooth skin and thermoformability. However, there are several disadvantages of crosslinked foams, such as: (1) the chemical blowing agents used (for example, azodicarbonamide) are expensive; (2) crosslinked foams expanded with nitrogen are made in energy intensive equipment at high pressures (typically about 10,000 to 30,000 psi); (3) the processes used to make the foams are typically batch processes which are expensive to operate; and (4) the foams cannot be recycled. On the other hand, non-crosslinked olefinic foams are made in continuous processes at relatively high production rates using less expensive physical blowing agents (such as isobutane) and the foams can be recycled (which is environmentally desirable), but these foams are difficult to thermoform.

[0019] It is desirable to make soft and flexible non-crosslinked foams with small cell sizes and good aesthetics that could be used as alternatives to crosslinked foams without the disadvantages listed above. We have surprisingly found that non-crosslinked foams made from blends of alkenyl aromatic polymers and specific types and amounts of substantially random interpolymers are soft and flexible with small cell sizes. Furthermore, the foams are thermoformable and can be recycled.

[0020] The present invention pertains to soft and flexible foams having an Asker C hardness of less than about 65 (and processes for their preparation), comprising;

[0021] (A) from about 30 to about 70 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

[0022] (B) from about 30 to about 70 percent by weight (based on the combined weight of Components A and B) of one or more substantially random interpolymers having an I₂of about 0.1 to about 50 g/10 min, and an M_w/M_nof about 1.5 to about 20; comprising

[0023] (1) from about 8 to about 45 mol % of polymer units derived from;

[0024] (a) at least one vinyl or vinylidene aromatic monomer, or

[0025] (b) at least one hindered aliphatic or cycloaliphatic vinyl or vinylidene monomer, or

[0026] (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

[0027] (2) from about 55 to about 92 mol % of polymer units derived from at least one of ethylene and/or a C_3-20α-olefin; and

[0028] (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

[0029] (C) optionally, one or more nucleating agents; and

[0030] (D) optionally, one or more other additives; and

[0031] (E) one or more blowing agents present in a total amount of from about 0.4 to about 5.0 gram-moles per kilogram (based on the combined weight of Components A and B).

[0032] This combination allows the manufacture of soft and flexible low density foams when 30 to 70 wt % of substantially random interpolymers of about 8 to about 45 mol % styrene are blended with alkenyl aromatic polymers. When similar foams are made from blends containing less than 30 wt % of the substantially random interpolymer, the resulting foams are not as soft and flexible as traditional crosslinked olefinic foams. Also when foams are made from blends containing more than 70 wt % of the substantially random interpolymer, the foams collapse at the temperatures required to avoid solidification of the alkenyl aromatic polymer fraction.

[0033] Definitions

[0034] 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.

[0035] 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 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.

[0036] The term “hydrocarbyl” as employed herein means any aliphatic, cycloaliphatic, aromatic, aryl substituted aliphatic, aryl substituted cycloaliphatic, aliphatic substituted aromatic, or aliphatic substituted cycloaliphatic groups.

[0037] The term “hydrocarbyloxy” means a hydrocarbyl group having an oxygen linkage between it and the carbon atom to which it is attached.

[0038] The term “copolymer” as employed herein means a polymer wherein at least two different monomers are polymerized to form the copolymer.

[0039] 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.

[0040] The term “soft foam” is used herein to indicate a foam having an Asker C hardness of less than about 65, preferably less than about 60, more preferably less than about 55 at a foam density of about 95 kg/m³or less.

[0041] The term “small cell size” is used herein to indicate a foam having a cell size of less than about 1.8 mm.

[0042] 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 C₃-C₁₂α-olefins) with at least one substantially random interpolymer. The foams of this invention have softness and flexibility comparable to traditional cross linked olefinic foams of similar densities.

[0043] 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.

[0044] 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_2-6alkyl acids and esters, ionomeric derivatives, and C₄, 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.

[0045] The term “substantially random” (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 SEOUENCE 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⁻¹³NMR 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.

[0046] 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.

[0047] Other optional polymerizable ethylenically unsaturated monomer(s) include norbomene and C₁alkyl or C_6-10aryl substituted norbomenes, with an exemplary interpolymer being ethylene/styrene/norbomene.

[0048] Suitable vinyl or vinylidene aromatic monomers which can be employed to prepare the interpolymers include, for example, those represented by the following formula:

[0049] wherein R¹is 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 R²is 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, ax-methyl styrene, the lower alkyl-(C₁-C₄) 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.

[0050] By the term ““sterically hindered aliphatic or cycloaliphatic vinyl or vinylidene compounds”, it is meant addition polymerizable vinyl or vinylidene monomers corresponding to the formula:

[0051] wherein A¹is a sterically bulky, aliphatic or cycloaliphatic substituent of up to 20 carbons, R¹is 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 R²is 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 R¹and A¹together 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 carbon atoms such as propylene, butene-1,4-methyl-1-pentene, hexene-l or octene-1 are not examples of sterically hindered aliphatic or cycloaliphatic vinyl or vinylidene compounds.

[0052] 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.

[0053] 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 now abandoned (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.

[0054] 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

[0055] where Cp¹and Cp²are cyclopentadienyl groups, indenyl groups, fluorenyl groups, or substituents of these, independently of each other; R¹and R²are 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 R³is an alkylene group or silanediyl group used to crosslink Cp¹and Cp²).

[0056] 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 & 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.

[0057] 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 now abandoned 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.

[0058] 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.

[0059] 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

[0060] 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′ 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′ groups together can be a C_1-10hydrocarbyl 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:

[0061] 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 examnple, 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.

[0062] 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.

[0063] 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'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 (CpTiCl₃) 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 MgCl₂/TiCl₄/NdCl₃/Al(iBu)₃catalyst 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 TiCl₄/NdCl₃/MgCl₂/Al(Et)₃catalyst. 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 Me₂Si(Me₄Cp)(N-tert-butyl)TiCl₂/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 A1 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 “substantially random”, 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.

[0064] 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.

[0065] Preparation of the Foams of the Present Invention

[0066] 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.

[0067] 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.

[0068] The foams may, if required for fast cure purposes and to attain accelerated blowing agent release, be modified by introducing a multiplicity of channels or perforations into the foam extending from a surface into the foam, the channels being free of direction with respect to the longitudinal extension of the foam. Excellent teachings of such modifications are disclosed in U.S. Pat. No. 5,424,016, WO 92/19439 and WO 97/22455, the entire contents of which are herein incorporated by reference.

[0069] 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 in which the foam does not collapse. 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.

[0070] 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.

[0071] 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.

[0072] The present foam structures may also be formed into 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^thEd., pp. 426-429, Butterworths (1989).

[0073] 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.

[0074] 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.

[0075] 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.

[0076] U.S. Pat. No. 4,168,353, the entire contents of which are incorporated herein by reference, describes a process in which foamed beads are prepared from a graft polymer of polyethylene and polystyrene. Styrene monomer may also be used to form a graft polymer with one or more substantially random interpolymers and be used to prepare foam beads. The process involves

[0077] (I) impregnation of styrene monomer into suspended pellets of one or more substantially random interpolymer(s) in a vessel at elevated temperature in the presence of a peroxide initiator to form a grafted polymer of polystyrene with the substantially random polymer;

[0078] (II) impregnation of the product of step I with one or more blowing agents;

[0079] (III) cooling and discharging the product from step II to form unexpanded beads; and

[0080] (IV) expanding and molding the beads of step III to form a foam.

[0081] Another 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).

[0082] 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 prevent foam collapse.

[0083] 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.

[0084] 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 (SF₆), 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-141 b), 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′-dimethyl-N,N′-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.

[0085] The amount of blowing agent incorporated into the polymer melt material to make a foam-forming polymer gel is from about 0.4 to about 5.0 gram-moles per kilogram of polymer, preferably from about 0.6 to about 3.0 gram-moles per kilogram of polymer, and most preferably from about 0.8 to 2.5 gram-moles per kilogram of polymer.

[0086] 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.

[0087] 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, permeability modifiers, antistatic agents, other thermoplastic polymers and the like. Examples of permeability modifiers include but are not limited to glycerol monoesters. These monoesters may also serve to reduce static during foam manufacture. 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.

[0088] The foam has a density of from about 10 to about 95 and most preferably from about 10 to about 80 kilograms per cubic meter according to ASTM D-1622-88.

[0089] The foam has an average cell size of from about 0.05 to about 5, preferably from about 0.1 to about 2.0, and more preferably from about 0.2 to about 1.8 millimeters according to ASTM D3576-77.

[0090] The present foam is particularly suited to be formed into a plank or sheet, desirably one having a thickness or minor dimension in cross-section of 1 mm or more, preferably 2 mm or more, or more preferably 2.5 mm or more. The foam width could be as large as about 1.5 meter.

[0091] The present foams have an open cell content ranging from 0 to 100 percent according to ASTM D2856-94.

[0092] The hardness of the present foams was measured using an Asker C durometer for cellular rubber and yarn in accordance with ASTM D2240-97 (but with a spherical indentor of about 5 mm diameter). The Asker C hardness was less than about 65, preferably less than about 60, more preferably less than about 55.

[0093] The foams of the present invention may be used in a variety of applications such as cushion packaging, athletic and recreational products, egg cartons, meat trays, building and construction (e.g., thermal insulation, acoustical insulation), pipe insulation, gaskets, vibration pads, luggage liners, desk pads shoe soles, gymnastic mats, insulation blankets for greenhouses, case inserts, display foams, etc. Examples of building and construction applications include external wall sheathing (home thermal insulation), roofing, foundation insulation, and residing underlayment. Other applications include insulation for refrigeration, buoyancy applications (e.g., body boards, floating docks and rafts) as well as various floral and craft applications. It should be clear, however, that the foams of this invention will not be limited to the above mentioned applications.

[0094] Properties of the Interpolymers and Blend Compositions Used to Prepare the Foams of the Present Invention.

[0095] The polymer compositions used to prepare the foams of the present invention comprise from about 30 to about 70, preferably from about 32 to about 68, more preferably from about 35 to about 65 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.

[0096] 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.

[0097] 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.

[0098] 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.

[0099] The polymer compositions used to prepare the foams of the present invention comprise from about 30 to about 70, preferably from about 32 to about 68, more preferably from about 35 to about 65 wt %, (based on the combined weights of substantially random interpolymer and the alkenyl aromatic homopolymers or copolymers) of one or more substantially random interpolymers.

[0100] These substantially random interpolymers used to prepare the foams of the present invention usually contain from about 8 to about 45, preferably from about 10 to about 43, more preferably from about 13 to about 40 mole percent of at least one vinyl or vinylidene aromatic monomer and/or aliphatic or cycloaliphatic vinyl or vinylidene monomer and from about 55 to about 92, preferably from about 57 to about 90, more preferably from about 60 to about 87 mole percent of ethylene and/or at least one aliphatic α-olefin having from about 3 to about 20 carbon atoms.

[0101] The melt index (I₂) of the substantially random interpolymer used to prepare the foams of the present invention is from about 0.1 to about 50, preferably of from about 0.3 to about 30, more preferably of from about 0.5 to about 10 g/10 min.

[0102] The molecular weight distribution (M_m/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.

[0103] 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).

[0104] The following examples are illustrative of the invention, but are not to be construed as to limiting the scope thereof in any manner.

[0105] Test Methods

[0106] a) Melt Flow and Density Measurements

[0107] 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 “Condition (E)” and also known as I₂) 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.

[0108] Also useful for indicating the molecular weight of the substantially random interpolymers used in the present invention is the Gottfert melt index (G, cm³/10 min) which is obtained in a similar fashion as for melt index (I₂) using the ASTM D1238 procedure for automated plastometers, with the melt density set to 0.7632, the melt density of polyethylene at 190° C.

[0109] 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 Gottfert 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 I₂weight 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's calculated I₂melt index value was also recorded. The equation used to calculate the actual melt density is

[0110] δ=δ_0.7632×I₂/I₂Gottfert

[0111] where δ_0.7632=0.7632 and I₂Gottfert=displayed melt index.

[0112] 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:

[0113] δ=0.00299×S+0.723

[0114] 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.

[0115] So for a polymer that is 73% total styrene content with a measured melt flow (the “Gottfert number”), the calculation becomes:

[0116] x=0.00299*73+0.723=0.9412

[0117] where 0.9412/0.7632=I₂/G#(measured)=1.23

[0118] b) Styrene Analyses

[0119] Interpolymer styrene content and atactic polystyrene concentration were determined using proton nuclear magnetic resonance (¹H N.M.R). All proton NMR samples were prepared in 1,1,2,2-tetrachloroethane-d₂(TCE-d₂). The resulting solutions were 1.6-3.2 percent polymer by weight. Melt index (I₂) was used as a guide for determining sample concentration. Thus when the I₂was greater than 2 g/10 min, 40 mg of interpolymer was used; with an I₂between 1.5 and 2 g/10 min, 30 mg of interpolymer was used; and when the I₂was 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-d₂was 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.

[0120] 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-d₂at 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:

[0121] Varian VXR-300, standard ¹H:

[0122] Sweep Width, 5000 Hz

[0123] Acquisition Time, 3.002 sec

[0124] Pulse Width, 8 μsec

[0125] Frequency, 300 MHz

[0126] Delay, 1 sec

[0127] Transients, 16

[0128] The total analysis time per sample was about 10 minutes.

[0129] Initially, a ¹H 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 “labeled”: b, branch; a, alpha; o, ortho; m, meta; p, para, as shown in Figure 1.

[0130] Integrals were measured around the protons labeled in Figure 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 ax 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_a1. The theoretical ratio for A_7.1:A_6.6:A_a1is 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_6.6Ratio A_ris A_7.1/A_6.6.

[0131] Region A_6.6was assigned the value of 1. Ratio A1 is integral A_a1/A_6.6. All spectra collected have the expected 1.5:1:1.5 integration ratio of (o+p):m: (a+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 a and b respectively in Figure 1. This ratio was also observed when the two aliphatic peaks were integrated separately.

[0132] For the ethylene/styrene interpolymers, the ¹H NMR spectra using a delay time of one second, had integrals C_7.1, C_6.6, and C_a1defined, such that the integration of the peak at 7.1 ppm included all the aromatic protons of the copolymer as well as the o & p protons of aPS. Likewise, integration of the aliphatic region C_a1in 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_6.6is 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_6.6becomes the basis for quantitatively determining the aPS content.

[0133] The following equations were then used to determine the degree of styrene incorporation in the ethylene/styrene interpolymer samples:

[0134] (CPhenyl)=C_7.1+A_7.1−(1.5×A_6.6)

[0135] (CAliphatic)=C_a1−(1 5×A_6.6)

[0136] s_c=(CPhenyl)/5

[0137] e_c=(CAliphatic−(3×s_c))/4

[0138] E=e_c/(e_c+s_c)

[0139] S_c=s_c/(e_c+s_c)

[0140] and the following equations were used to calculate the mol % ethylene and styrene in the interpolymers. $\begin{array}{c}\text{Wt}\%E=\frac{E*28}{\left(E*28\right)+\left(S_c*104\right)}\left(100\right)\\ \text{and}\\ \text{Wt}\%S=\frac{S_c*104}{\left(E*28\right)+\left(S_c*104\right)}\left(100\right)\end{array}$

[0141] where: s_cand e_care styrene and ethylene proton fractions in the interpolymer, respectively, and S_cand E are mole fractions of styrene monomer and ethylene monomer in the interpolymer, respectively.

[0142] The weight percent of aPS in the interpolymers was then determined by the following equation: $\text{Wt}\%\mathrm{aPS}=\frac{\left(\text{Wt}\%S\right)*\left(\frac{A_{6.6}/2}{S_c}\right)}{100+\left[\left(\text{Wt}\%S\right)*\left(\frac{A_{6.6}/2}{S_c}\right)\right]}*100$

[0143] The total styrene content was also determined by quantitative Fourier Transform Infrared spectroscopy (FTIR).

[0144] Preparation of Ethylene/Styrene Interpolymers (“ESI's”) Used in Examples and Comparative Experiments of Present Invention

[0145] 1) Preparation of ESI #'s 1-7

[0146] ESI #'s 1-7 are substantially random ethylene/styrene interpolymers prepared using the following catalysts.

[0147] Preparation of Catalyst A (dimethy[N-(1,1-dimethylethyl)-1,1-dimethyl-1-[(1,2,3,4,5-η)-1,5,6,7-tetrahydro-3-phenyl-s-indacen-1-yl]silanaminato(2-)-N]-titanium)

[0148] 1) Preparation of 3,5,6,7-Tetrahydro-s-Hydrindacen-1 (2H)-one

[0149] Indan (94.00 g, 0.7954 moles) and 3-chloropropionyl chloride (100.99 g, 0.7954 moles) were stirred in CH₂Cl₂(300 μL) at 0° C. as AlCl₃(130.00 g, 0.9750 moles) was added slowly under a nitrogen flow. The mixture was then allowed to stir at room temperature for 2 hours. The volatiles were then removed. The mixture was then cooled to 0° C. and concentrated H₂SO₄(500 mL) slowly added. The forming solid had to be frequently broken up with a spatula as stirring was lost early in this step. The mixture was then left under nitrogen overnight at room temperature. The mixture was then heated until the temperature readings reached 90° C. These conditions were maintained for a 2 hour period of time during which a spatula was periodically used to stir the mixture. After the reaction period crushed ice was placed in the mixture and moved around. The mixture was then transferred to a beaker and washed intermittently with H₂O and diethylether and then the fractions filtered and combined. The mixture was washed with H₂O (2×200 mL). The organic layer was then separated and the volatiles removed. The desired product was then isolated via recrystallization from hexane at 0° C. as pale yellow crystals (22.36 g, 16.3% yield).

[0150] ¹H NMR (CDCl₃): d2.04-2.19 (m, 2H), 2.65 (t, ³J_HH=5.7 Hz, 2H), 2.84-3.0 (m, 4 H), 3.03 (t, ³J_HH=5.5 Hz, 2H), 7.26 (s, 1H), 7.53 (s, 1H).

[0151] ¹³C NMR (CDCl₃): d25.71, 26.01, 32.19, 33.24, 36.93, 118.90, 122.16, 135.88, 144.06, 152.89, 154.36, 206.50.

[0152] GC-MS: Calculated for C₁₂H₁₂O 172.09, found 172.05.

[0153] 2) Preparation of 1,2,3,5-Tetrahydro-7-phenyl-s-indacen. 3,5,6,7-Tetrahydro-s-Hydrindacen-1(2H)-one (12.00 g, 0.06967 moles) was stirred in diethyl ether (200 mL) at 0° C. as PhMgBr (0.105 moles, 35.00 mL of 3.0 M solution in diethyl ether) was added slowly. This mixture was then allowed to stir overnight at room temperature. After the reaction period the mixture was quenched by pouring over ice. The mixture was then acidified (pH=1) with HCl and stirred vigorously for 2 hours. The organic layer was then separated and washed with H₂O (2×100 mL) and then dried over MgSO₄. Filtration followed by the removal of the volatiles resulted in the isolation of the desired product as a dark oil (14.68 g, 90.3% yield).

[0154] ¹H NMR (CDCl₃): d2.0-2.2 (m, 2H), 2.8-3.1 (m, 4H), 6.54 (s, 1H), 7.2-7.6 (m, 7H).

[0155] GC-MS: Calculated for C₁₈H₁₆232.13, found 232.05.

[0156] 3) Preparation of 1,2,3,5-Tetrahydro-7-phenyl-s-indacene, dilithium salt.

[0157] 1,2,3,5-Tetrahydro-7-phenyl-s-indacen (14.68 g, 0.06291 moles) was stirred in hexane (150 mL) as nBuLi (0.080 moles, 40.00 mL of 2.0 M solution in cyclohexane) was slowly added. This mixture was then allowed to stir overnight. After the reaction period the solid was collected via suction filtration as a yellow solid which was washed with hexane, dried under vacuum, and used without further purification or analysis (12.2075 g, 81.1% yield).

[0158] 4) Preparation of Chlorodimethyl(1,5,6,7-tetrahydro-3-phenyl-s-indacen-1-yl)silane.

[0159] 1,2,3,5-Tetrahydro-7-phenyl-s-indacene, dilithium salt (12.2075 g, 0.05102 moles) in THF (50 mL) was added dropwise to a solution of Me₂SiCl₂(19.5010 g, 0.1511 moles) in THF (100 mL) at 0° C. This mixture was then allowed to stir at room temperature overnight. After the reaction period the volatiles were removed and the residue extracted and filtered using hexane. The removal of the hexane resulted in the isolation of the desired product as a yellow oil (15.1492 g, 91.1% yield).

[0160] ¹H NMR (CDCl₃): d0.33 (s, 3H), 0.38 (s, 3H), 2.20 (p, ³J_HH=7.5 Hz, 2H), 2.9-3.1 (m, 4H), 3.84 (s, 1H), 6.69 (d, ³J_HH=2.8 Hz, 1H), 7.3-7.6 (m, 7H), 7.68 (d, ³J_HH=7.4 Hz, 2H).

[0161] ¹³C NMR (CDCl₃): d0.24, 0.38, 26.28, 33.05, 33.18, 46.13, 116.42, 119.71, 127.51, 128.33, 128.64, 129.56, 136.51, 141.31, 141.86, 142.17, 142.41, 144.62.

[0162] GC-MS: Calculated for C₂₀H₂₁ClSi 324.11, found 324.05.

[0163] 5) Preparation of N-(1,1-Dimethylethyl)-1,1-dimethyl-1-(1,5,6,7-tetrahydro-3-phenyl-s-indacen-1-yl)silanamine.

[0164] Chlorodimethyl(1,5,6,7-tetrahydro-3-phenyl-s-indacen-1-yl)silane (10.8277 g, 0.03322 moles) was stirred in hexane (150 mL) as NEt₃(3.5123 g, 0.03471 moles) and t-butylamine (2.6074 g, 0.03565 moles) were added. This mixture was allowed to stir for 24 hours. After the reaction period the mixture was filtered and the volatiles removed resulting in the isolation of the desired product as a thick red-yellow oil (10.6551 g, 88.7% yield).

[0165] 1H NMR (CDCl₃): d0.02 (s, 3H), 0.04 (s, 3H), 1.27 (s, 9H), 2.16 (p, ³J_HH=7.2 Hz, 2H), 2.9-3.0 (m, 4H), 3.68 (s, 1H), 6.69 (s, 1H), 7.3-7.5 (m, 4H), 7.63 (d, ³J_HH=7.4 Hz, 2H).

[0166] ¹³C NMR (CDCl₃): d−0.32, −0.09, 26.28, 33.39, 34.11, 46.46, 47.54, 49.81, 115.80, 119.30, 126.92, 127.89, 128.46, 132.99, 137.30, 140.20, 140.81, 141.64, 142.08, 144.83.

[0167] 6) Preparation of N-(1,1-Dimethylethyl)-1,1-dimethyl-1-(1,5,6,7-tetrahydro-3-phenyl-s-indacen-1-yl) silanamine, dilithium salt.

[0168] N-(1,1-Dimethylethyl)-1,1-dimethyl-1-(1,5,6,7-tetrahydro-3-phenyl-s-indacen-1-yl)silanamine (10.6551 g, 0.02947 moles) was stirred in hexane (100 mL) as nBuLi (0.070 moles, 35.00 mL of 2.0 M solution in cyclohexane) was added slowly. This mixture was then allowed to stir overnight during which time no salts crashed out of the dark red solution. After the reaction period the volatiles were removed and the residue quickly washed with hexane (2×50 mL). The dark red residue was then pumped dry and used without further purification or analysis (9.6517 g, 87.7% yield).

[0169] 7) Preparation of Dichloro[N-(1,1-dimethylethyl)-1,1-dimethyl-1-[(1,2,3,4,5-μ)-1,5,6,7-tetrahydro-3-phenyl-s-indacen-1-yl]silanaminato(2-)-N]titanium

[0170] N-(1,1-Dimethylethyl)-1,1-dimethyl-1-(1,5,6,7-tetrahydro-3-phenyl-s-indacen-1-yl)silanamine, dilithium salt (4.5355 g, 0.01214 moles) in THF (50 mL) was added dropwise to a slurry of TiCl₃(THF)₃(4.5005 g, 0.01214 moles) in THF (100 mL). This mixture was allowed to stir for 2 hours. PbCl₂(1.7136 g, 0.006162 moles) was then added and the mixture allowed to stir for an additional hour. After the reaction period the volatiles were removed and the residue extracted and filtered using toluene. Removal of the toluene resulted in the isolation of a dark residue. This residue was then slurried in hexane and cooled to 0° C. The desired product was then isolated via filtration as a red-brown crystalline solid (2.5280 g, 43.5% yield).

[0171] ¹H NMR (CDCl₃): d0.71 (s, 3H), 0.97 (s, 3H), 1.37 (s, 9H), 2.0-2.2 (m, 2H), 2.9-3.2 (m, 4H), 6.62 (s, 1H), 7.35-7.45 (m, 1H), 7.50 (t, ³J_HH=7.8 Hz, 2H), 7.57 (s, 1 H), 7.70 (d, JJ_HH=7.1 Hz, 2H), 7.78 (s, 1H).

[0172] ¹H NMR (C₆D₆): d0.44 (s, 3H), 0.68 (s, 3H), 1.35 (s, 9H), 1.6-1.9 (m, 2H), 2.5-3.9 (m, 4H), 6.65 (s, 1H), 7.1-7.2 (m, 1H), 7.24 (t, ³J_HH=7.1 Hz, 2H), 7.61 (s, 1H), 7.69 (s, 1H), 7.77-7.8 (m, 2H).

[0173] ¹³C NMR(CDCl₃): d1.29, 3.89, 26.47, 32.62, 32.84, 32.92, 63.16, 98.25, 118.70, 121.75, 125.62, 128.46, 128.55, 128.79, 129.01, 134.11, 134.53, 136.04, 146.15, 148.93.

[0174] ¹³C NMR (C₆D₆): d0.90, 3.57, 26.46, 32.56, 32.78, 62.88, 98.14, 119.19, 121.97, 125.84, 127.15, 128.83, 129.03, 129.55, 134.57, 135.04, 136.41, 136.51, 147.24, 148.96.

[0175] 8) Preparation of Dimethyl[N-(1,1-dimethylethyl)-1,1-dimethyl-1-[(1,2,3,4,5-η)-1,5,6,7-tetrahydro-3-phenyl-s-indacen-1-yl]silanaminato(2-)-N]titanium

[0176] Dichloro[N-(1,1-dimethylethyl)-1,1-dimethyl-1-[(1,2,3,4,5-η)-1,5,6,7-tetrahydro-3-phenyl-s-indacen-1-yl]silanaminato(2-)-N]titanium (0.4970 g, 0.001039 moles) was stirred in diethylether (50 mL) as MeMgBr (0.0021 moles, 0.70 mL of 3.0 M solution in diethylether) was added slowly. This mixture was then stirred for 1 hour. After the reaction period the volatiles were removed and the residue extracted and filtered using hexane. Removal of the hexane resulted in the isolation of the desired product as a golden yellow solid (0.4546 g, 66.7% yield).

[0177] ¹H NMR (C₆D₆): d0.071 (s, 3H), 0.49 (s, 3H), 0.70 (s, 3H), 0.73 (s, 3H), 1.49 (s, 9 H), 1.7-1.8 (m, 2H), 2.5-2.8 (m, 4H), 6.41 (s, 1H), 7.29 (t, ³J_HH=7.4 Hz, 2H), 7.48 (s, 1H), 7.72 (d, ³J_HH=7.4 Hz, 2H), 7.92 (s, 1H).

[0178] ¹³C NMR (C₆D₆): d2.19, 4.61, 27.12, 32.86, 33.00, 34.73, 58.68, 58.82, 118.62, 121.98, 124.26, 127.32, 128.63, 128.98, 131.23, 134.39, 136.38, 143.19, 144.85.

[0179] Preparation of Catalyst B:(1H-cyclopenta[1]phenanthrene-2-yl)dimethyl(t-butylamido)-silanetitanium 1,4-diphenylbutadiene)

[0180] 1. Preparation of lithium 1H-cyclopenta[1]phenanthrene-2-yl

[0181] 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.

[0182] 2. Preparation of (1H-cyclopenta[1]phenanthrene-2-yl)dimethylchlorosilane

[0183] To a 500 ml round bottom flask containing 4.16 g (0.0322 mole) of dimethyldichlorosilane (Me₂SiCl₂) 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).

[0184] 3. Preparation of (1H-cyclopenta[1]phenanthrene-2-yl)dimethyl(t-butylamino)silane

[0185] 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).

[0186] 4. Preparation of dilithio (1H-cyclopenta[1]phenanthrene-2-yl)dimethyl(t-butylamido)silane

[0187] 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).

[0188] 5. Preparation of (1H-cyclopenta[I]phenanthrene-2-yl)dimethyl(t-butylamido)silanetitanium dichloride

[0189] To a 250 ml round bottom flask containing 1.17 g (0.0030 mole) of TiCl₃.0.3THF 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 PbCl₂was 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).

[0190] 6. Preparation of (1H-cyclopenta[l]phenanthrene-2-yl)dimethyl(t-butylamido)silanetitanium 1,4-diphenylbutadiene

[0191] 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.

[0192] Polymerization for ESI #'s 1-2

[0193] ESI's 1-2 were prepared in a 6 gallon (22.7 L), oil jacketed, Autoclave continuously stirred tank reactor (CSTR). A magnetically coupled agitator with Lightning A-320 impellers provided the mixing. The reactor ran liquid full at 475 psig (3,275 kPa). Process flow was in at the bottom and out of the top. A heat transfer oil was circulated through the jacket of the reactor to remove some of the heat of reaction. At the exit of the reactor was a micromotion flow meter that measured flow and solution density. All lines on the exit of the reactor were traced with 50 psi (344.7 kPa) steam and insulated.

[0194] Toluene solvent was supplied to the reactor at 30 psig (207 kPa). The feed to the reactor was measured by a Micro-Motion mass flow meter. A variable speed diaphragm pump controlled the feed rate. At the discharge of the solvent pump, a side stream was taken to provide flush flows for the catalyst injection line (1 lb/hr (0.45 kg/hr)) and the reactor agitator (0.75 lb/hr (0.34 kg/hr)). These flows were measured by differential pressure flow meters and controlled by manual adjustment of micro-flow needle valves. Uninhibited styrene monomer was supplied to the reactor at 30 psig (207 kpa). The feed to the reactor was measured by a Micro-Motion mass flow meter. A variable speed diaphragm pump controlled the feed rate. The styrene stream was mixed with the remaining solvent stream.

[0195] Ethylene was supplied to the reactor at 600 psig (4,137 kPa). The ethylene stream was measured by a Micro-Motion mass flow meter just prior to the Research valve controlling flow. A Brooks flow meter/controller was used to deliver hydrogen into the ethylene stream at the outlet of the ethylene control valve. The ethylene/hydrogen mixture combines with the solvent/styrene stream at ambient temperature. The temperature of the solvent/monomer as it enters the reactor was dropped to ˜5° C. by an exchanger with −5° C. glycol on the jacket. This stream entered the bottom of the reactor.

[0196] The three component catalyst system and its solvent flush also entered the reactor at the bottom but through a different port than the monomer stream. Preparation of the catalyst components took place in an inert atmosphere glove box. The diluted components were put in nitrogen padded cylinders and charged to the catalyst run tanks in the process area. From these run tanks the catalyst was pressured up with piston pumps and the flow was measured with Micro-Motion mass flow meters. These streams combine with each other and the catalyst flush solvent just prior to entry through a single injection line into the reactor.

[0197] Polymerization was stopped with the addition of catalyst kill (water mixed with solvent) into the reactor product line after the micromotion flow meter measuring the solution density. Other polymer additives can be added with the catalyst kill. 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 provide 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 ˜250 mm of pressure absolute at the reactor pressure control valve. This flashed polymer entered a hot oil jacketed devolatilizer. Approximately 85 percent of the volatiles were removed from the polymer in the devolatilizer. The volatiles exited the top of the devolatilizer. The stream was condensed with a glycol jacketed exchanger and entered the suction of a vacuum pump and was discharged to a glycol jacket solvent and styrene/ethylene separation vessel. Solvent and styrene were removed from the bottom of the vessel and ethylene from the top. The ethylene stream was measured with a Micro-Motion mass flow meter and analyzed for composition. The measurement of vented ethylene plus a calculation of the dissolved gasses in the solvent/styrene stream were used to calculate the ethylene conversion. The polymer separated in the devolatilizer was pumped out with a gear pump to a ZSK-30 devolatilizing vacuum extruder. The dry polymer exits the extruder as a single strand. This strand was cooled as it was pulled through a water bath. The excess water was blown from the strand with air and the strand was chopped into pellets with a strand chopper.

[0198] Polymerization for ESI's 3-7

[0199] ESI's 3-7 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″ 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' 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.

[0200] 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 flowineter. Ethylene was supplied to the reactor at 687 psig (4,838 kPa). The ethylene stream was measured by a Micro-Motion mass flowineter. A Brooks flowmeter/controller was used to deliver hydrogen into the ethylene stream at the outlet of the ethylene control valve.

[0201] 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.

[0202] 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.

[0203] This flashed polymer entered the first of two hot oil jacketed devolatilizers.

[0204] 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 (<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.

[0205] The various catalysts, co-catalysts and process conditions used to prepare the various individual ethylene styrene interpolymers (ESI #'s 1-7) are summarized in Table 1 and their properties are summarized in Table 2.

[0206] Additional Blend Components

[0207] PS 1 is a granular polystyrene having a weight average molecular weight, M_w, of about 192,000 and a polydispersity, M_w/M_n, of about 2. PS 2 is a granular polystyrene having a weight average molecular weight, M_w, of about 305,000 and a polydispersity, M of about 2. LDPE 1 is a low density polyethylene having a melt index, I₂, of 1.8 g/10 min, a weight-average molecular weight of 117,600, a number-average molecular weight of 17,200 and a density of 0.9230 g/cm³.

[0208] LDPE 2 is a low density polyethylene having a melt index, I2, of 2.4 g/10 min, a weight-average molecular weight of 98,300, a number-average molecular weight of 13,300 and a density of 0.9241 g/cm³.

[0209] A foaming process comprising a single-screw extruder, mixer, coolers and die was used to make foam. Isobutane was used as the blowing agent at a level of 7.5 part-per-hundred resin (phr) to foam LDPE and PS/ESI blends. Table 3 summarizes the foam properties, all of which foams were soft and flexible to the touch while having small cell size, smooth skin, good dimensional stability, and a wide range of open cell contents. The foams of the present invention (Ex. 1-4) did not shrink significantly as measured by volume change (computed from measurements of foam mass and density) when cured at room temperature unlike the comparative non-crosslinked foam made form LDPE (Comp. Ex 1).

[0210] A foaming process comprising a single-screw extruder, mixer, coolers and die was used to make foam planks. Isobutane and HCFC-142b were used as blowing agents to foam LDPE and blends of polystyrene with ESI. For Examples 5-9 and Comparative Example 2, Irganox ^Tm1010 (a product and trademark of Ciba-Geigy) was used at a loading of 0.06 phr. In the case of Comparative Example 2, additional additives were 0.2 phr of Hydrocerol^tm(a product and trademark of Boehringer Ingelheim) CF40E as nucleator, and 0.5 phr of glycerol monostearate as permeability modifier. For Comparative Example 3, the additives used 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 examples in Table 4 were soft and flexible, close in Asker C hardness to a conventional LDPE foam used for cushion packaging (Comparative Example 2) and much softer than a foam made from an 80120 blend of polystyrene/ESI (Comparative Example 3).

[0211] A foaming process comprising a single-screw extruder, mixer, coolers and die was used to make foam planks. Isobutane or isobutane/carbon dioxide mixtures were used as blowing agents to foam blends of polystyrene with ESI. The foams were soft and flexible with smooth skin, small cells and Asker C hardness of about 50 or less.