MXPA00002021A

MXPA00002021A - Cross-linking of polymers and foams thereof

Info

Publication number: MXPA00002021A
Application number: MXPA/A/2000/002021A
Authority: MX
Inventors: V Karande Seema; H Ho Thoi; Kao Chei; H Cummins Clark; J Mullins Michael; Craig Silvis H; I Chaudhary Bharat; H Terbrueggen Robert; A Babb David
Original assignee: A Babb David; I Chaudhary Bharat; H Cummins Clark; H Ho Thoi; Kao Chei; V Karande Seema; J Mullins Michael; Craig Silvis H; H Terbrueggen Robert; The Dow Chemical Company
Priority date: 1997-08-27
Filing date: 2000-02-25
Publication date: 2001-05-17

Abstract

The invention includes a process comprising (a) forming a polymeric admixture including at least one polyolefin which has been prepared using a single site catalyst and at least a cross-linking amount of at least one poly(sulfonyl azide) cross-linking agent;(b) shaping the resulting admixture;and (c) heating the resulting shaped admixture to a temperature at least the decomposition temperature of the cross-linking agent. The steps take place in any sequence and optionally include substeps. The single site catalystis preferably a constrained geometry or metallocene catalyst, but optionally another transition metal catalyst which is not a traditional Ziegler Natta Ti/MgC12 catalyst such as a vanadium catalyst. At least one polyolefin is preferably a polyethylene homopolymer;an ethylene copolymer also having at least one alpha olefin comonomer selected from monomers of from 3 to 20 carbon atoms;an elastomeric polymer;an ethylene/alpha olefin/diene terpolymer or interpolymer;a substantially linear ethylene polymer or a combination thereof. At least one polyolefin preferably has a molecular weight distribution less than about 3.5;more preferably all of the polyolefins have that MWD. The polymeric admixture is preferably a blend comprising at least about 5 weight percent of at least one polyolefin made using a single site catalyst and at least one other polymer which differs from the polyolefin by having a different density, a different molecular weight, a different catalyst used in polymerization, a different chemical composition or combination thereof. The invention futher includes all compositions obtainable by the process of the invention as well as all articles formed from these compositions. The articles are preferably thermoformed, compression molded, injection molded, extruded, cast, blow molded, blown, profile extruded, spun, foamed or molded of any composition of the invention. The invention includes a use of any composition of the invention in any process of thermoforming, injection molding, extrusion, casting, blow molding, spinning, blowing, profile extrusion, foaming, compression molding or a combinationthereof.

Description

RETICULATION OF POLYMERS AND FOAMS OF THEM This invention is relates to the cross-linking of polyolefins, more specifically the cross-linking of polyolefins using the insertion within the carbon-hydrogen bonds (C-H). As used herein, the term "crosslinking" means the formation of bonds between polymer chains, such that gels insoluble in xylene are formed to a degree of at least 10 percent, as measured in accordance with the ASTM. 2765-84. Polyolefins are frequently crosslinked using non-selective chemistries that involve free radicals generated, for example, using peroxides or high energy radiation. However, chemistries that involve the generation of free radicals at elevated temperatures also degrade molecular weight, especially in polymers containing tertiary hydrogen, such as polystyrene, polypropylene, polyethylene copolymers, and so on. Other methods of crosslinking are also known. The teachings of the Patents of the United States of North America Nos. 3,058,944; 3,336,268; and 3,530,108 include the reaction of certain poly (sulfonyl azide) compounds with certain polyolefins. It would be desirable to have a crosslinking method, especially for polyolefins, especially for those prepared using single site catalysts, more particularly for ethylene and its copolymers, more preferably narrow molecular weight distribution (MWD), which avoids the effects of cleavage chain of free radicals, and more desirably that also avoids the need for functional groups in the polymers for the reactive sites for the crosslinking agents. Desirably, the crosslinking method would be initiated by heat, most desirably the temperatures normally found in polymer processes, within the skill in the art, such as extrusion and other industrial heat processes, for example, as described by J.A. Brydson, Rubber Materials and their Compounds, page 348, Chapter 18, Elsevier Applied Science, New York, 1988. (For example, the decomposition temperature of the crosslinking agent is conveniently matched to the melting temperature of the polymer, in such a way that the decomposition temperature be sufficiently high to be melt-blended, and in a shaping step with prior cure, and that the decomposition temperature be conveniently low so that it has a desirably short cure time in a cure step). The polymers, in the case of high density polyethylene, especially when the polymer produced by means of the single-site catalysts, and preferably with a density greater than 0.945 grams / milliliter (hereinafter HDPE produced using catalysts from a site only), would desirably have a higher firmness, flexibility and / or elongation than a crosslinked high density polyethylene, prepared using the Ziegler Natta catalyst (which would generally be of a wider molecular weight distribution); HDPE produced using cross-linked single site catalysts using the same equivalents of a free radical crosslinking agent. Conveniently, the compositions would have a less undesirable odor than the same crosslinked starting material using the same chemical equivalents of the free radical generating agents. Preferably, a process of the invention would result in a more consistent crosslinking than crosslinking methods involving free radicals, that is, the use of the same reagents, amounts and conditions would result in consistent amounts of crosslinking, or changes in properties. consistent (reproducible), especially consistent amounts of gel formation. Preferably, a process would be less subject to the effects by the presence of oxygen, than a cross-linking involving agents that generate free radicals. further, for a comparatively high melting polymer such as HDPE (about 140 ° C), it is desirable to avoid premature crosslinking during the melt mixing process. This is, desirably, a process 9 i would provide a wider processing window for crosslinking, than that observed with the peroxides. In the case of polyethylenes of medium and lower density (ie, polymers having a density of from about 0.94 grams / cubic centimeter to about 0.90 grams / cubic centimeter), also produced using single-site catalysts, which are conveniently copolymers of ethylene in which the comonomer percentage is preferably from about 0.5 to 5 mole percent of comonomer, based on the total polymer, as determined by ASTM 5017, the polymers would desirably display a combination of service temperature operation high top (measured by the mechanical thermal analysis described hereinafter), and slip resistance (measured in accordance with ASTM-D-2990-77), as compared to the non-crosslinked polymer. In the case of elastomeric polymers containing ethylene repeating units, in which the preferred density is less than about 0.89 grams / milliliter, and more preferably with a monomer content greater than about 5, more preferably about 5. -25 mole percent as determined by ASTM 5017, also produced using single-site catalysts, it would be desirable to have better mechanical properties such as elongation and flexibility, strength, and less setting by compression than would be achieved by means of of the crosslinking using the same chemical equivalents of the free radical generating agent as a peroxide. Desirably, the crosslinked material would have better organoleptic qualities, especially less pestilent odor, than the same crosslinked starting material using peroxides. It has been found that crosslinking polyolefins using poly (sulfonyl azide) produce polymer products having surprisingly useful properties, when the polyolefin has been prepared using a single site catalyst, such as a vanadium catalyst, a metallocene catalyst or a restricted geometry catalyst. The invention includes a process comprising (a) forming a polymer blend that includes at least one polyolefin that has been prepared using a single site catalyst, and at least one amount of crosslinking of at least one poly (sulfonylazide) crosslinking agent. ), - (b) shape the resulting mixture; and (c) heating the resulting shaped mixture to a temperature of at least the decomposition temperature of the crosslinking agent. The steps take place in any sequence, and optionally include substeps. Preferably in step (b) the polymer mixture is in a softened or molten condition for shaping; or step (b) comprises thermoforming, compression molding, injection molding, extrusion, casting, blow molding, blowing, profile extrusion, rotation, other molding or combinations thereof; or step (c) comprises foaming; or step (a) includes forming a foamable molten polymer material, by mixing and heating a decomposable chemical blowing agent, and other components of the polymer blend; and step (b) includes extruding the foamable molten polymer material through a die; or step (a) comprises the substeps of (i) suspending discrete polyolefin particles in a liquid medium, in which they are insoluble; (ii) impregnating the particles with a crosslinking amount of poly (sulfonyl azide) crosslinking agent and a blowing agent, at a superatmospheric pressure, and at a temperature above the softening point of the polymer; and the step (b), (c) or a combination thereof includes (iii) rapidly discharging the particles within a lower pressure than that in the sub-step (ii) to form foam beads, or (iv) cooling the particles and subsequently expanding them. with at least one heated gas; or step (a) includes mixing at least one polyolefin, a crosslinking amount of a poly (sulfonyl azide) crosslinking agent, and a chemical blowing agent to form a mixture; step (b) comprises a first sub-step forming a plate of the mixture; step (c) includes heating the mixture in a mold, such that the crosslinking agent crosslinks the polymer material and the blowing agent decomposes; and any of step (b), step (c) or a combination thereof, includes expanding the plate formed in the first sub-step of step (b), by releasing the pressure in the mold; or step (b) comprises a first sub-step of forming a sheet of the polymer mixture containing a cross-linking amount of poly (sulfonylazide) cross-linking agent; step (c) comprises heating the sheet enough to result in crosslinking; step (b) further includes a second sub-step of impregnating the sheet with N2 at a temperature above the softening point of the polymer, and at a pressure, and a third sub-step of releasing the pressure to result in the nucleation of the bubbles , and some expansion in the sheet, or a combination thereof. More preferably, the crosslinking agent is introduced into the polymer mixture in melt processing equipment, which is preferably an extruder. The single site catalyst is preferably a restricted geometry or metallocene catalyst, but optionally is another transition metal catalyst that is not a traditional Ti / MgCl2 catalyst of Ziegler Natta, such as a vanadium catalyst. At least one polyolefin is preferably a polyethylene homopolymer; an ethylene copolymer also having at least one alpha olefin comonomer selected from monomers of from 3 to 20 carbon atoms; an elastomeric polymer; a terpolymer or interpolymer of ethylene / alpha olefin / diene; a substantially linear ethylene polymer, or a combination thereof. At least one polyolefin preferably has a molecular weight distribution of less than about 3.5; most preferably all polyolefins have that molecular weight distribution. The polymer blend is preferably a combination comprising at least about 5 weight percent of at least one polyolefin made using a single site catalyst, and at least one other polymer that differs from the polyolefin by having a different density, a weight different molecular, a different catalyst used in the polymerization, a different chemical composition, or a combination thereof. The polyolefin is made using the single-site catalyst, and is preferably present in an amount of at least about 10 weight percent of the blend, is a polyethylene or an ethylene-alpha olefin copolymer, and the other polymer of preference differs in density, in weight molecules (Mn) by the largest molecular weight being at least about 10 percent greater than the smallest, or is selected from the group consisting of ethylene-vinyl acetate copolymer, copolymers of styrene-diene block, natural rubber, isoprene rubber, or a combination thereof. At least one poly (sulfonyl azide) preferably has an X-R-X structure, wherein each X is S02N3, and R represents an unsubstituted or inertly substituted hydrocarbyl group, hydrocarbyl ether, or silicon-containing; wherein the poly (sulfonyl azide) has at least 3, and less than about 50 carbon atoms, silicon or oxygen between the sulfonylazide groups; and wherein R includes at least one aryl group between the sulfonyl groups, or is preferably used in an amount greater than about 0.5 weight percent, based on the total weight of the total polymer blends, or reacts at a temperature of at least the decomposition temperature and greater than about 185 ° C. The invention also includes all compositions obtainable by the process of the invention, as well as all articles formed from these compositions. The articles are preferably thermoformed, compression molded, injection molded, extruded, cast, blow molded, blown, profile extruded, rotated, foamed or molded of any composition of the invention. The invention includes a use of any composition of the invention, in any process of thermoforming, injection molding, extrusion, casting, blow molding, rotation, blow molding, extrusion by extrusion, foaming, compression molding or a combination thereof. The practice of the invention is applicable to any olefin polymer (also referred to as polyolefin) that has been prepared using a single-site catalyst, and which has at least one CH bond that can react with a compound capable of insertion within a carbon-hydrogen bond (CH), including homopolymers and copolymers (including interpolymers, terpolymers, oligomers and other polymeric types), preferably with narrow comonomer distribution, narrow molecular weight distribution or a combination thereof, such as copolymers of ethylene with one or more alpha-olefins (of 3 to 20 carbon atoms), including LLDPE (linear low density polyethylene), ethylene copolymers with unsaturation (EPDM or EODM, which is ethylene-propylene-diene) or ethylene-octene-diene), or other polymers such as linear high density polyethylene. The practice of this invention is also applicable to combinations of two or more polymers, especially polyethylene, ethylene-alpha olefin copolymers or a combination thereof, at least one of which is prepared using a single-site catalyst, whose polymers they have different average molecular weights. The highest average molecular weight is preferably more than about 10 percent greater than the lowest average molecular weight, in a combination of two polymer components. When there are more than two polymer components, the highest and the lowest molecular weight are about 10 percent different from the molecular weight of the average molecular weight component. The resulting combination, optionally therefore has an Mw / Mn greater than 3.0 or 3.5, although at least one component individually has a molecular weight distribution of less than about 3. If the highest average molecular weight of a polymer component is approximately 30 percent or more greater than that of the other component of the combination, often the combination exhibits more than one peak in a gel permeation chromatography (GPC) curve analysis. The term "bimodal" is used to refer to polymers that exhibit two peaks in a graphical representation of appropriate analysis data to measure the property discussed, in this case the curve (GPC). These distributions are seen statistically, that is, as statistical distributions. In this way where there is a peak, the distribution has a mode and is unimodal. Two peaks are bimodal. Two or more are multimodal. The combination is optionally a reactor combination, or a combination formed by passing a first polymer made in a first reactor, into a second reactor, where the second polymer is produced. Alternatively, optionally, the combination is made using a mixture of two or more single-site catalysts. Those skilled in the art recognize that peaks often have overlapping areas, and that mathematical analysis is sometimes needed to distinguish multimodal curves from irregular wide curves. In this invention, where the preferred molecular weight distributions (MWD) (Mw / Mn) are given, those distributions refer to the molecular weight distribution of at least one component, which is preferably represented by a peak of the curve GPC Preferred polymers for use in the practice of the invention are polymers prepared from ethylene, conveniently ethylene in combination with other monomers polymerizable therewith. These monomers include alpha-olefins and other monomers having at least one double bond. Alpha-olefins having more than 2 carbon atoms include propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, as well as 4 -methyl-1-pentene, 4-methyl-1-hexene, 5-methyl-1-hexene, vinylcyclohexene. Interpolymers useful in the practice of the invention optionally, and in a preferred embodiment, include monomers having at least two double bonds that are preferably dienes or triphenyls. Suitable diene and triene comonomers include 7-methyl-l, 6-octadiene, 3,7-dimethyl-1,6-octadiene, 5,7-dimethyl-l, 6-octadiene, 3, 7, 11-trimethyl- 1, 6,10-octatriene, 6-methyl-l, 5-heptadiene, 1,3-butadiene, 1,6-heptadiene, 1,7-octadiene, 1,8-nonadiene, 1,9-decadiene, 1, 10-undecadiene, bicyclo [2.2.1] epta-2-5-diene (norbornadiene), tetracyclododecene, or mixtures thereof, preferably butadiene, hexadienes, and octadienes, most preferably 1,4-hexadiene, 4-methyl -1, -hexadiene, 5-methyl-l, 4-hexadiene, dicyclopentiene, bi c icl or [2.2.1] hept a - 2 - 5-di ene (norbornadiene) and 5-ethylidene-2-norbornene (ENB ). Polyolefins are formed by means within the skill of the art. The alpha-olefin monomers and optionally other polymerizable addition monomers are polymerized under conditions within the skill in the art, using metallocene and other single-site catalysts, as exemplified by means of US Pat. Numbers 3,645,992 (Elston), 4,937,299 (Ewen et al.), 5,218,071 (Tsutsui et al.), 5,278,272, 5,324,800, 5,084,534, 5,405,922, 4,588,794, 5,204,419. Preferred polymers for use in the practice of the present invention are elastomeric. "Elastomeric polymer" means a polymer that can be stretched with the application of tension, up to at least twice its length, and after the release of tension, returns to its approximate original dimensions and shape. The elastic recovery of an elastomeric polymer before vulcanization is generally at least 40 percent, preferably at least 60 percent, and most preferably at least 80 percent, after the sample is lengthened 100 percent of an original dimension at 20 ° C, in accordance with the procedures of ASTM 4649. Suitable elastomeric polymers for use in this invention include ethylene / α-olefin interpolymers. "cv-olefin" means a hydrocarbon molecule or a substituted hydrocarbon molecule (that is, a hydrocarbon molecule comprising one or more atoms other than hydrogen and carbon, eg, halogen, oxygen, nitrogen, etc.), the molecule of hydrocarbon comprising (i) only an ethylenic unsaturation, this unsaturation located between the first and second carbon atoms, and (ii) at least 3 carbon atoms, preferably from 3 to 20 carbon atoms, in some cases preferably from 4 to 10 carbon atoms, and in other cases preferably from 4 to 8 carbon atoms. Examples of the preferred α-olefins from which the elastomers which are used in this invention are prepared include propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-dodecene, and mixtures thereof. two or more of these monomers.

Preferred among the elastomeric polymers useful in the practice of this invention are the ethylene / cy-on interpolymers, particularly those having a density of less than about 0.9 grams / cubic centimeter. Preferred ethylene interpolymers include ethylene / α-on copolymers; ethylene / α-on / diene terpolymers; and interpolymers of ethylene and one or more monomers that are copolymerizable with ethylene. These polymers include homogeneous linear ethylene polymers such as (a) those described in U.S. Patent Number 3,645,992, and (b) those made using so-called single-site catalysts in a batch reactor, having relatively high on, as described, for example, in U.S. Patent Nos. 5,026,798 and 5,055,438. These polymers are commercially available. Representatives of the commercially available homogeneous linear ethylene polymers are the TAFMER1 ^ polymers, made by Mitsui Petrochemical Industries, Ltd. and the EXACTMR polymers made by Exxon Chemical Co. .. The elastomeric polymer is preferably substantially amorphous. The term "substantially amorphous" means that the polymer has a degree of crystallinity of less than about 25 percent. The elastomeric polymer most preferably has a crystallinity of less than about 15 percent. The elastomeric polymer can be the product of a single polymerization reaction, or it can be a combination of polymers that is the result of the physical combination of polymers obtained from different polymerization reactions and / or that is the result of the use of a catalyst. mixed polymerization. Especially preferred ethylene / α-on interpolymers are the copolymers of ethylene / l-octene, ethylene / l-hexene, ethylene / l-butene and ethylene / propylene, produced by means of a single site catalyst, of restricted geometry . In U.S. Patent No. 5,272,236, and in U.S. Patent No. 5,278,272, a process for making those copolymers is described. These ethylene interpolymers are preferably substantially linear on polymers, which have long chain branching. The substantially linear on polymers can be made by means of gas phase, solution phase, high pressure or slurry polymerization. These polymers are preferably made by means of solution polymerization. The substantially linear ethylene polymers (SLEP's) are commercially available from The Dow Chemical Co., under the registered trademark AFFINITY ™, and with DuPont Dow Elastomers LLC, under the registered trademark ENGAGE. ™ In one embodiment, the polyons from the The starting materials are preferably substantially linear ethylene polymers (SLEP's). The substantially linear ethylene polymers (SLEP's) are homogeneous polymers having long chain branching. These are described in the Patents of the United States of North America Nos. 5,272,236 and 5,278,272. Substantially linear ethylene polymers include the polyon plastomers (POPs) Affinity1 ^ 11 commercially available from The Dow Chemical Company, and the polyon elastomers (POEs) Engage ™ commercially available from DuPont Dow Elastomers LLC, as polymers made by Process I if e1 ^ and Catalyst Technology. Specific examples of the useful Engage1 polyon elastomers include the SM 8400, EG 8100, and CL 8001, and specific examples of the Affinity111 polyon plastomers include the FM-1570, HM 1100, and SM 1300, each of the which is somercialmente available with The Dow Chemical Company. Substantially linear ethylene polymers can be prepared by means of solution phase, slurry or gas, preferably solution phase, polymerization of ethylene and one or more optional α-olefin comonomers, in the presence of a constrained geometry catalyst, such as described in European Patent Application 416,815-A. The substantially linear ethylene / α-olefin polymers are made by means of a continuous process, using suitable restricted geometry catalysts, preferably restricted geometry catalysts as described in U.S. Patent No. 5,132,380 and the Application for U.S. Patent Serial Number 545,403, filed July 3, 1990. The monocyclopentadienyl transition metal olefin polymerization catalysts taught in U.S. Patent Number 5,026,798 are also suitable for use in the preparation of the polymers of the present invention, as long as the reaction conditions are as specified below. Suitable cocatalysts for use herein include, but are not limited to, for example, polymeric or oligomeric aluminoxanes, especially methyl aluminoxane, as well as inert, compatible, non-coordinating ion formation compounds. Preferred cocatalysts are inert, noncoordinating boron compounds. The term "continuous process" means a process in which reagents are continuously added, and the product is continuously removed, such that an approximation of an uninterrupted state is achieved (ie, a substantially constant concentration of reagents and product, while the process is done). The polymerization conditions for the manufacture of the substantially linear ethylene / c-olefin polymers of the present invention are generally those useful in the solution polymerization process, although the application of the present invention is not limited thereto. It is also believed that slurry and gas phase polymerization processes are useful, provided that the catalysts and the appropriate polymerization conditions are employed. Polymerization processes of multiple reactors may also be used to make the substantially linear olefin polymers and copolymers to be crosslinked in accordance with the present invention, such as those described in U.S. Patent No. 3,914,342. The multiple reactors can be operated in series or in parallel, with at least one catalyst of restricted geometry used in one of the reactors. The term "substantially linear" means that, in addition to the short chain branches that can be attributed to the incorporation of the homogeneous comonomer, the ethylene polymer is further characterized as having long chain branches, in the sense that the base structure of the polymer is replaced with an average of 0.01 to 3 branches of long chain / 1000 carbons. Preferred substantially linear polymers for use in the invention are substituted with from 0.01 long chain branching / 1000 carbons, up to 1 long chain branching / 1000 carbons, and more preferably from 0.05 long chain branching / 1000 carbons up to 1 branching long chain / 1000 carbons. In contrast to the term "substantially linear", the term "linear" means that the polymer lacks long chain branches that can be measured or can be demonstrated, that is, the polymer is replaced with an average of less than 0.01 branching. long chain / 1000 carbons. For ethylene / α-olefin interpolymers. "Long chain branching" (LCB) means a chain length longer than the short chain branching which is the result of the incorporation of the α-olefin (s) within the base structure of the polymer. Each long chain branch has the same comonomer distribution as the base structure of the polymer, and can be as long as the base structure of the polymer to which it is attached. The empirical effect of the presence of long chain branching on the substantially linear ethylene / α-olefin interpolymers which are used in the invention is manifested in their improved rheological properties, which are quantified and expressed herein in terms of the results of the gas extrusion rheometry (GER) and / or increases of the fusion flow, I10 / l2. The presence of short-chain branching of up to 6 carbon atoms in length in ethylene polymers can be determined by the use of 13-carbon nuclear magnetic resonance (NMR) spectroscopy, and quantified using the method described by Randall ( Rev. Macromol, Chem. Phys., C.29, V. 2 and 3, pages 285-297). As a practical matter, 13-carbon nuclear magnetic resonance spectroscopy can not distinguish the length of a long-chain branch in excess of six carbon atoms. However, other known techniques exist, useful for determining the presence of long chain branches in ethylene polymers, including ethylene / 1-octene interpolymers. Two of these methods are gel permeation chromatography coupled with a low angle laser light scattering detector (GPC-LALLS), and gel permeation chromatography coupled with a differential viscometer detector (GPC-DV). The use of these techniques for the detection of long-chain branching and the underlying theories has been well documented in the literature. See, for example, Zimm, G.H. and Stockmayer, W.H. , J. Chem. Phys., 17,1301 (1949) and Rudin, A., Modern Methods of Polymer Characterization, John Wiley & amp;; Sons, New York (1991), pages 103-112. A. Willem deGroot and P. Steve Chum, both of The Dow Chemical Company, at the October 4, 1994 conference of the Federation of Analytical Chemistry and Spectroscopy Society (FACSS) in St. Louis, Missouri, presented data demonstrating that GPC-DV is a useful technique for quantifying the presence of long chain branches in substantially linear ethylene polymers. In particular, deGroot and Chum found that the level of long-chain branches in homogeneous substantially linear homopolymer samples, measured using the Zimm-Stockmayer equation, correlated well with the level of long-chain branches measured using nuclear magnetic resonance 13 carbons. In addition, deGroot and Chum found that the presence of octene does not change the hydrodynamic volume of the polyethylene samples in solution and, as such, one can take into account the molecular weight increase that can be attributed to the short chain branches of octene. , by means of knowing the mole percentage of the octene in the sample. By deconvoluining the contribution to the molecular weight increase that can be attributed to the short chain branches of 1-octene, deGroot and Chum showed that GPC-DV can be used to quantify the level of long chain branches in the copolymers ethylene / octene substantially linear. deGroot and Chum also showed that a graph of the Log (I2) as a function of the Log (Mw), as determined by GPC, illustrates that aspects of the long-chain branching (but not the extent of the long branch) of the Substantially linear ethylene polymers can be compared to those of high-density, high-branched polyethylene (LDPE), highly branched, and are clearly distinct from ethylene polymers produced using Ziegler-type catalysts, such as titanium complexes, and catalysts ordinary to make homogeneous polymers such as hafnium and vanadium complexes. The substantially linear ethylene polymers are also characterized as having: (a) a melt flow ratio, I10 / l2 > 5.63, (b) a molecular weight distribution, Mw / Mn, as determined by gel permeation chromatography, and defined by the equation: (Mw / Mn) < (I10 / I2) - 4.63, (c) a critical shear stress at the start of the raw melt fracture, as determined by gas extrusion rheometry, of more than 4 x 106 dynes / square centimeter, or a rheology by gas extrusion such that the critical shear stress coefficient at the beginning of the surface melt fracture for the substantially linear ethylene polymer is at least 50 percent greater than the critical shear coefficient at the beginning of the surface melt fracture for a linear ethylene polymer, wherein the substantially linear ethylene polymer and the linear ethylene polymer comprise the same comonomer or comonomers, the linear ethylene polymers have an I2, Mw / Mn and density that are, each, within ten percent of the substantially linear ethylene polymer, and wherein the respective critical shear rates of the substantially linear ethylene polymer and the linear ethylene olimer, are measured at the same melting temperature, using a gas extrusion rheometer, and (d) a single differential scanning calorimetry melting peak, DSC, between -30 and 150 ° C. Generally, the ratio of for linear ethylene polymers is at least about 5.63, preferably at least about 7, especially at least about 8 or more. For the substantially linear ethylene / α-olefin polymers that are used in the compositions of the invention, the ratio of I 10 / l 2 indicates the degree of long chain branching, that is, the higher the ratio of I 10 / l 2, There is more long chain branching in the polymer. Generally, the ratio of I10 / I2 ^ to the substantially linear ethylene / α-olefin polymers is at least about 5.63, preferably at least about 7, especially at least about 8 or more, and as high as about 25. The melt index for substantially linear olefin polymers, useful herein, is preferably at least about 0.1 gram / 10 minutes (gram / 10 minutes), more preferably at least about 0.5 grams / 10 minutes, and especially at least about 1 gram / 10 minutes), preferably about 100 grams / 10 minutes, more preferably up to about 50 grams / 10 minutes, and especially up to about 20 grams / 10 minutes. The determination of the critical shear stress coefficient and the critical shear stress with respect to the melt fracture, as well as other rheology properties, such as the rheological processing index (Pl), is performed using a gas extrusion rheometer (GER) The gas extrusion rheometer is described by M. Shida, R.N. Shroff and L.V. Cancio in Polymer Engineering Science, Volume 17, Number 11, page 770 (1977), and in Rheometers for Molten Plastics by John Dealy, published by Van Nostrand Reinhold Co. (1982) on pages 97-99. GER experiments are generally performed at a temperature of 190 ° C, at nitrogen pressures between 250 to 5500 psig (1724 to 37921 kPa), using a diameter of 0.0754 millimeters, a die of 20: 1 L / D at an angle input 180 °. For the substantially linear ethylene polymers described herein, Pl is the apparent viscosity (in kpoise) of a material, measured by GER at an apparent shear stress of 2.15 x 10 d dynes / square centimeter. Substantially linear ethylene polymers for use in the invention include ethylene interpolymers, and have a Pl in the range of 0.01 kpoise (1 Pa / S) to 50 kpoise (5000 Pa / S), preferably 15 kpoise (1500 Pa / S). S) or less. The substantially linear ethylene polymers that are used herein have a Pl of less thanor equal to 70 percent of the Pl of a linear ethylene polymer (either a Ziegler polymerized polymer, or a uniformly branched linear polymer as described by Elston in U.S. Patent Number 3,645,992) having an I2 , Mw / Mn and density, each within ten percent of the substantially linear ethylene polymers. The rheological behavior of substantially linear ethylene polymers can also be characterized by means of the Dow Rheology Index (DRI), which expresses "a normalized polymer relaxation time, as the result of long chain branching". (See, S. Lai and G.W. Knight ANTEC '93 Proceedings, INSITEMR Technology Polyolefins (SLEP) - New Rules in the Structure / Rheology Relationship of Ethylene a-Olefin Copolymers, New Orleans, La., May 1993). DRI values vary from 0 for polymers that do not have any long-chain branching that can be measured (for example, the Tafmer ™ products available with Mitsui Petrochemical Industries, and the Exact1® products available with the Exxon Chemical Company), for polymers from low to medium pressure ethylene (particularly at lower densities), the DRI provides improved correlations to fuse the elasticity and high shear fluidity in relation to the correlations of the same with the melt flow rates. For the substantially linear ethylene polymers useful in this invention, the DRI is preferably at least 0.1, and especially at least 0.5, and more especially at least 0.8. The DRI can be calculated from the equation: DRI = (3652879 * tc 1- 00449 /? 0-l) / 10 where tc is the characteristic relaxation time of the material, and? 0 is the shear viscosity zero of the material. Both tc and? 0 are the values that "best fit" the Crusade equation, that is,? /? 0 = 1 / (1 + (? • t0) 1"n) where n is the low index of energy of the material, and? and? are the viscosity and the shear stress coefficient measured, respectively.The baseline determination of the viscosity data and the shear stress coefficient are obtained using a Rheometric Mechanical Stimulator (RMS-800). ) under dynamic sweep mode from 0.1 to 100 radians / second at 190 ° C, and a Gas Extrusion Rheometer (GER) at extrusion pressures from 1,000 psi to 5,000 psi (6.89 to 34.5 MPa), which corresponds to the shear stress of 0.086 to 0.43 MPa, using a diameter of 0.0754 millimeters, a die of 20: 1 L / D at 190 ° C. Specific determinations of material can be made from 140 to 190 ° C, as required for accommodate the variations of the melt index, using a graph of apparent shear stress versus apparent shear stress coefficient, to identify melting fracture phenomena, and quantify the critical shear stress coefficient and the critical shear stress of ethylene polymers. According to Ramamurthy in the Journal of Rheology, 30 (2), 337-357, 1986, above a certain critical flow velocity, the observed irregularities of the extrudate can be clearly classified into two main types: fracture of superficial fusion and fracture of gross fusion. The surface fusion fracture occurs under seemingly uninterrupted flow conditions, and varies in detail from loss of specular film brightness to the more severe form of "shark skin". Here, as determined using the GER described above, the onset of the surface melt fracture (OSMF) is defined as the loss of extrudate gloss. The loss of gloss of the extrudate is the point at which the surface roughness of the extrudate can only be detected by means of a 40X amplification. The critical shear stress coefficient at the start of the surface melt fracture for the substantially linear ethylene polymers is at least 50 percent greater than the critical shear coefficient at the beginning of the surface melt fracture of a polymer. linear ethylene having essentially the same I2 and Mw / Mn. The raw melt fracture occurs under non-uninterrupted extrusion flow conditions, and varies in detail from regular distortions (alternating rough and smooth, helical, etc.) to random. For commercial acceptability, to maximize the performance properties of films, coatings and mounds, surface defects should be minimal, if not absent. The critical shear stress at the start of the gross melt fracture for substantially linear ethylene polymers, especially those having a density >0.910 grams / cubic centimeter, which is used in the invention, is greater than 4 x 106 dynes / square centimeter. The coefficient of critical shear stress at the beginning of the surface melt fracture (OSMF) and at the beginning of the raw melt fracture (GFMO) will be used in the present based on the changes in roughness and surface configurations of the extruded extrudates by means of of a GER. The substantially linear ethylene polymers that are used in the invention are also characterized by a single DSC melting peak. The unique melting peak is determined using a differential scanning calorimeter, standardized with indium and deionized water. The method involves sample sizes of 3-7 milligrams, a "first heated" at approximately 180 ° C, which is maintained for 4 minutes, a cooling at 10 ° C / minute up to -30 ° C which is maintained for 3 minutes , and a heating at 10 ° C / minute up to 140 ° C for the "second heated". The only melting peak is taken from the heat flow of the "second heated" against the temperature curve. The total heat of the polymer melt is calculated from the area under the curve. For polymers having a density of 0.875 grams / cubic centimeter to 0.910 grams / cubic centimeter, the single melting peak may show, depending on the sensitivity of the equipment, a "shoulder" or a "hump" on the low melting side , which constitutes less than 12 percent, typically, less than 9 percent, and more typically less than 6 percent of the total heat of fusion of the polymer. That artifact can be observed for other homogeneously branched polymers such as Exact1 ^ resins, and is discerned on the basis of the inclination of the single melting peak that varies monotonously across the melting region of the artifact. This artifact occurs within 20 ° C of the melting point of the single fusion peak. The heat of fusion that can be attributed to an artifact can be determined separately by the specific integration of its associated area below the curve of heat flow versus temperature. The substantially linear ethylene polymers are analyzed by gel permeation chromatography (GPC) in a Waters 150 ° C high temperature chromatographic unit, equipped with a differential refractometer and three columns of mixed porosity. The columns are supplied by Polymer Laboratories, and are commonly packaged with pore sizes of 103, 104, 105 and 106. The solvent is 1, 2, 4-trichlorobenzene, from which 0.3 percent by weight solutions are prepared. the samples, for injection. The flow rate is 1.0 milliliter / minute, the operating temperature of the unit is 140 ° C, and the size of the injection is 100 microliters. The determination of the molecular weight with respect to the base structure of the polymer is deduced by the use of narrow molecular weight distribution polystyrene standards (from Polymer Laboratories), in conjunction with their levigation volumes. The equivalent molecular weights of polyethylene are determined by the use of Mark-Houwink coefficients for polyethylene and polystyrene (as described by Williams and Ward in Journal of Polymer Science, Polymer Letters, Volume 6, page 621, 1968), to derive the equation ^ olietileno = a '^ polystyrene' • In this equation, a = 0.4316 and b = 1.0. The weight average molecular weight, Mw, is calculated in the usual manner, according to the formula M, ((w ± x Mi #) where w and Mj_ are the weight fraction and the molecular weight, respectively, of the fraction ith to be levigated from the GPC column. The density of linear or substantially linear ethylene polymers (as measured in accordance with ASTM D-792) for use in the present invention is generally less than about 0.95 grams / cubic centimeter. The density is preferably at least about 0.85 grams / cubic centimeter, and especially at least about 0.86 grams / cubic centimeter, and preferably up to about 0.94 grams / cubic centimeter, most preferably up to about 0.92 grams / cubic centimeter . When the crosslinked resins are to be used for extrusion and injection molding, the density of the polymer is preferably at least 0.855 grams / cubic centimeter, more preferably at least 0.865 grams / cubic centimeter, and even more preferred when less 0.870 grams / cubic centimeter, preferably up to 0.900 grams / cubic centimeter, more preferably 0.885 grams / cubic centimeter, and even more preferably up to 0.880 grams / cubic centimeter. The most preferred density is determined primarily by means of the modulus of elasticity or flexibility desired in the molded article. The density remains substantially constant during crosslinking, in accordance with this invention. Ethylene polymers that are conveniently crosslinked in accordance with the practice of this invention are optionally any interpolymers of ethylene and at least one α-olefin. Suitable α-olefins are represented by the following formula: CH 2 = CHR wherein R is a hydrocarbyl radical. R generally has from one to twenty carbon atoms. Suitable α-olefins for use as comonomers in a solution, gas phase or slurry polymerization process, or combinations thereof, include 1-propylene, 1-butene, 1-isobutylene, 1-pentene, 1-hexene, 4-methyl-1-pentene, 1-heptene and 1-octene, as well as other types of monomers such as tetrafluoroethylene, benzocyclobutane vinyl, and cycloalkenes, for example, cyclopentene, cyclohexene, cyclooctene, and norbornene (NB). Preferably, the α-olefin will be 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1-octene or NB, or mixtures thereof. More preferably, the α-olefin will be 1-hexene, e-heptene, 1-octene, or mixtures thereof. More preferably, α-olefin will be i-octene. The cross-linked ethylene polymer according to this invention is preferably a substantially linear ethylene polymer. These interpolymers preferably contain at least about 2 weight percent, more preferably at least about 5 weight percent of the α-olefin. The polyolefin is a homopolymer, copolymer, or interpolymer. Preferably the homo or copolymers contain ethylene repeating units. In polyethylene copolymers, the comonomer content is greater than about 1 weight percent, as determined by 13 C NMR (13 carbon nuclear magnetic resonance), and more preferably greater than about 3 weight percent by weight. any monomer copolymerizable with ethylene, preferably an alpha-olefin or cyclic olefin, more preferably an olefin of less than about 20 carbon atoms, more preferably from about 2 to about 18 carbon atoms. The comonomer content is at least one comonomer polymerizable with ethylene, preferably less than about 4 comonomers polymerizable with ethylene, more preferably less than 2 of those comonomers. In one embodiment, the preferred polymers for the starting materials useful in the practice of this invention are high density polyethylene homopolymers in slurry, conveniently made using single site catalysts.

When the polymer has a narrow molecular weight distribution (MWD), that MWD is preferably less than about 3.5 Mw / Mn, more preferably less than 3.0, more preferably less than 2.5, more preferably with a density greater than about 0.945 grams / milliliter. In a combination of two or more polymers, which includes at least one HDPE made using a single site catalyst, at least one of the components, preferably all components, have a MWD preferably less than 3.5, more preferably less 3.0, more preferred less than 2.5. In these cases the composition, although it is a preferred embodiment, optionally has an overall MWD greater than 3.5. Polymer combinations are optionally formed, for example, to optimize processability and mechanical properties. The formation of the combination compositions is within the skill in the art, for example, two or more polymers of different molecular weight can be combined with a single catalyst in a reactor. The melt index (MI) of the starting material is preferably at least about 0.01, more preferably at least about 0.1 gram / 10 minutes, because an MI less than 0.01 gram / 10 minutes is generally associated with a viscosity so high enough to make it difficult to merge articles. Preferably the MI is less than about 100 grams / 10 minutes, more preferably less than about 20 grams / 10 minutes, because the polymer with a melt index greater than 100 grams / 10 minutes frequently has a poor firmness. These polymers have a good balance of (a) mechanical properties of a resulting article, which is also referred to herein as a final part, and (b) processability of the polymer in the forming step (s). The most preferred polymers as starting materials for this invention are copolymers of ethylene with a narrow MWD (that is, an Mw / Mn of less than 3.5, preferably less than 3.0, more preferably less than 2.5) of a combined composition, or at least one component of a combined composition. These can be produced using at least one olefin comonomer of 3 to 20 carbon atoms. The most preferred one for the copolymer is from 3 to 10 carbon atoms. About 0.5-40 mole percent comonomer is preferred in the starting material, as determined by ASTM 5017. The preferred melt index of the starting material depends on the applications; however, the preferred melt index is from about 0.01 to about 20 grams / 10 minutes. Polymers commercially available in this category are known as the polymer TAFMER1 ^, commercially available from Mitsui Petrochemical Industries, the polymer EXACT1 ^ commercially available from the Exxon Chemical Company, the polyolefin plastomer AFFINITY ™ commercially available from The Dow Chemical Company, the elastomer from Polyolefin E GAGE ^ commercially available with DuPont-Dow Elastomers. For thermoplastic applications such as film and injection molding, the most preferred comonomer content is between about 3-25 weight percent. For elastomeric applications, the preferred comonomer content is between about 20-40 weight percent. The most preferred terpolymer is an EPDM such as the ethylene / propylene / diene polymer NORDEL IPMR, commercially available with DuPont-Dow Elastomers. The melt index is measured in accordance with the condition of 190 ° C / 2.16 kg (formerly known as Condition E) of ASTM D-1238. In a particularly preferred embodiment the polymer is an ethylene / α-olefin / diene terpolymer. Suitable a-olefins include the a-olefins described above as suitable for making ethylene / α-olefin copolymers. Suitable dienes as monomers for the preparation of these terpolymers are dienes either conjugated or non-conjugated, typically non-conjugated, having from 6 to 15 carbon atoms. Representative examples of suitable non-conjugated dienes that can be used to prepare the terpolymer include: a) straight chain acyclic dienes such as 1,4-hexadiene, 1,5-heptadiene, and 1,6-octadiene; b) branched chain acyclic dienes such as 5-methyl-1,4-hexadiene, 3,7-dimethyl-1,6-octadiene, and 3,7-dimethyl-1,7-octadiene; c) single ring alicyclic dienes such as 4-vinylcyclohexene, l-allyl-4-isopropylidenecyclohexane, 3-allylcyclopentene, 4-allylcyclohexene, and l-isopropenyl-4-butenylcyclohexane; d) alicyclic dienes of multiple fused rings and bridged ring, such as dicyclopentadiene; alkenyl, alkylidene, cycloalkenyl and cycloalkylidene norbornenes such as 5-methylene-2-norbornene, 5-methylene-6-methyl-2-norbornene, 5-methylene-6,6-dimethyl-2-norbornene, 5-propenyl-2 -norbornene, 5- (3-cyclopentenyl) -2-norbornene, 5-ethylidene-2-norbornene, and 5-cyclohexylidene-2-norbornene. The preferred dienes are selected from the group consisting of 1,4-hexadiene, dicyclopentadiene, 5-ethylidene-2-norbornene, 5-methylene-2-norbornene, 7-methyl-1, 6-octadiene, piperylene, 4- vinylcyclohexene, et cetera. Preferred terpolymers for the practice of the invention are terpolymers of ethylene, propylene and a non-conjugated diene (EPDM). These terpolymers are or will be commercially available from companies such as DuPont Dow Elastomers L.L.C. The total diene monomer content in the terpolymer can suitably vary from about 0.1 to about 15 weight percent, preferably from 0.5 to about 12 weight percent, and most preferably from about 1.0 to about 6.0 weight percent . Both the ethylene copolymers and the ethylene terpolymers comprise from about 20 to about 90 weight percent, preferably from about 30 to about 85 weight percent ethylene, with the other comonomers comprising the equilibrium. The ethylene copolymers and terpolymers preferably have a weight average molecular weight (Mw) of at least about 10,000, and more preferably of at least about 15,000, and may have an Mw of up to about 1,000,000 or more, preferably up to approximately 500,000. The ethylene homo- and copolymers which are used as starting materials of the invention, especially high density polyethylene (density greater than about 0.94 grams / cubic centimeter), are preferably made using single-site catalysts, and preferably they are narrow molecular weight distribution (MWD), that is an Mw / Mn preferably less than about 3.5, more preferably less than about 2.5, and more preferably less than about 2. Polyolefins previously described, especially preferred species, and more preferably ethylene homopolymers and copolymers, more preferably elastomers, are optionally used in combinations comprising at least one of the polyolefins (first polymer), and at least one polymer other than the first polymer (second polymer). The second polymer is any thermoplastic, preferably selected from polyvinyl chloride, polypropylene, polyethylene terephthalate, polystyrene or other aromatic vinyl polymer, and styrenic block copolymers. Ethylene homopolymers and copolymers, produced using single-site catalysts, are optionally combined with polyolefin-carbon monoxide (CO) copolymers, such as ethylene-carbon monoxide copolymers, propylene-carbon monoxide copolymers, and copolymers of ethylene-propylene-carbon monoxide. Polymers having carbon monoxide are within the skill in the art, and are commercially available from The Dow Chemical Company and the Shell Oil Company. Alternatively, these are prepared by means within the skill in the art, such as those described in U.S. Patent Nos. 3,835,123; 3,984,388; 4,970,294; 5,554,777 and 5,565,547. Suitable polymers for the combinations also include, but are not restricted to, different ethylenic polymers or other natural or synthetic polymers. The various suitable ethylene polymers include low polyethylenes (LDPE) (e.g., formed using techniques of free radical polymerization, high pressure), medium (MDPE), and high (HDPE) density (for example, those made using Ziegler catalysts, as in United States Patent Number 4,076,698) , ethylene / ester copolymers, ethylene / vinyl acetate copolymers, copolymers of ethylene and ethylenically unsaturated carboxylic acid, homo and copolymers of alpha-olefins. In each combination that is used in the practice of the present invention, at least one of the polymer components is formed using a single-site catalyst. When used in the polyolefin combinations that are formed using single-site catalysts, these are conveniently used in sufficient amounts to result in improved properties (detailed later herein), which can be attributed to their presence, as compared to the presence of a polymer of the same composition, number average molecular weight (Mn), and monomer density. Preferably, the polyolefins that are prepared using single site catalysts constitute at least about 5 weight percent of any combination that is used as the starting material of the present invention, more preferably at least about 10 percent by weight. weight, more preferably at least about 20 weight percent. In a more preferred embodiment the combination contains 100 percent polyolefins made using single site catalysts, preferably metallocene catalysts. More specifically, for the purpose of improving impact resistance, elastomers made using single-site catalysts are preferably present in amounts of less than about 30 weight percent, more preferably from about 5 to about 30 weight percent. cent in weight. In a combination of an HDPE and an elastomer, the elastomer made using the single-site catalyst is preferably present in amounts of up to about 90 weight percent, and more preferably from about 70 to about 90 percent in weigh. The addition of HDPE facilitates the configuration of the mixture, before crosslinking (green state). Preferred combinations include Combinations (1): combinations of two or more polyolefins, made using single-site catalysts; Combinations (2): combinations of at least one polyolefin, made using a single site catalyst with at least one polyolefin, preferably ethylene polymer made using a Ziegler-Natta or free radical catalyst, or a combination thereof; Combinations (3): combinations of at least one polyolefin made using a single-site catalyst, with at least one elastomer not included in the description of Combinations (1) or Combinations (2); Combinations (4): at least one polyolefin made using a single-site catalyst with at least one thermoplastic polymer. In each case, the polyolefin (s) made using single site catalysts are preferably ethylene polymers or copolymers. Within the Combinations (1) and the Combinations (2) are combinations of polymers that have different molecular weights, but similar densities. These are conveniently formed for the purpose of balancing mechanical properties, such as lower compression setting (ASTM D-395 (60 ° C, 25 percent compression)), and high tensile strength (ASTM D-412) of the resulting crosslinked product, and the processability as indicated by the ratio of 12/110, measured by the procedures of ASTM-1238 to 190 ° C, to 2.16 kilograms for 12, and 10 kilograms for 110, of the mixture of the material of split in the green state (mixture containing poly (sulfonyl azide) and polymer (s) before crosslinking). In these combinations, a preferred embodiment is a combination of at least two HDPE polymers. An alternative preferred embodiment is a bimodal molecular weight combination that includes at least one ethylene-alpha-olefin elastomer, useful, for example, for wire ropes, gaskets, profile extrusion, and roof membranes. In another embodiment a bimodal density combination is formed, to obtain balanced mechanical properties, such as hardness, as measured by ASTM D2240-91, and firmness as measured by ASTM D412-87 of the crosslinked polymers. In this case, the combination is preferably a combination of HDPE with less than about 30 weight percent elastomer, for building construction materials, household appliances and automotive parts. In yet another embodiment, a preferred combination including elastomeric polymers combined with less than about 30 weight percent HDPE or LDPE, improves processability such as to reduce tackiness with the mold, during the shaping step of the part for Applications such as wire or cable sleeves, gaskets, profile extrusion, and roof membrane. In Combinations (3), suitable elastomers include ethylene-vinyl acetate copolymer (EVA), copolymers of ethylene and ethylenically unsaturated carboxylic acid, styrene-butadiene block copolymers, natural rubber, isoprene rubber and combinations thereof . Combinations of single-site ethylene / alpha-ethylene elastomer with EVA for wire and cable jacketing, packaging, and profile extrusion are preferred embodiments.

In Combinations (4), suitable thermoplastics include polyvinyl chloride, chloride, polypropylene, polyethylene terephthalate, polystyrene or other vinyl aromatic polymer, polyolefin-carbon monoxide copolymers. The polyolefin prepared using a single site catalyst is preferably an elastomer. Preferably, the combination contains less than 30 weight percent elastomer, to increase the firmness of the thermoplastic component; the elastomer preferably has a viscosity close enough to the thermoplastic component to achieve homogeneous mixing and dispersion of the elastomer in the thermoplastics. These combinations are useful, for example, for building construction materials, household appliances and automotive parts. In one embodiment, the component of the thermoplastic blend is preferably a polymer having tertiary carbon-hydrogen bonds such as a propylene polymer. The term "propylene polymers" is used to mean propylene homopolymers, copolymers and interpolymers, preferably having at least about 50 weight percent propylene. The practice of the invention is especially useful with polymers having tertiary C-H bonds, because the use of free radical generating crosslinking agents, such as peroxides, frequently induces cleavage at those tertiary sites; therefore, by comparison, the practice of the invention results in less chain scission than the use of peroxides or other free radical crosslinking elements. Preferred olefinic polymers for the production of the foam structures of this invention include linear high density polyethylene (HDPE), linear low density polyethylene (LLDPE) made using single site catalysts. These olefinic polymers include, for example, polymers commercially available from the Dow Chemical Company, under the registered trade designation Affinity polyolefin plastomers; polymers commercially available with the Mitsui Petrochemicals Company Limited, under the registered trade designation of polymers TAFMERMR; polymers commercially available from the Exxon Chemical Company, under the registered trade designation of EXACTMR polymers; and polymers commercially available with DuPont Dow Elastomers LLC, under the registered trade designation of ENGAGEMR and Nordel IP EPDM polymers. Polymers previously described as suitable and preferred for use in the practice of the invention, to form cross-linked polymers, are also those suitable and preferred, respectively, for use in making cross-linked foams, except that the most preferred combinations for making foams are combinations of an elastomer made using single-site catalysts with at least one other elastomer such as EVA, natural rubber, styrene-butadiene block copolymers, ethylene-styrene interpolymer, or a combination thereof. For the purposes of crosslinking, the polymer is reacted with a polyfunctional compound, capable of insertion reactions within the C-H bonds. These polyfunctional compounds have at least two, preferably 2, functional groups capable of C-H insertion reactions. Those skilled in the art are familiar with the insertion reactions of C-H, and the functional groups capable of those reactions. For example, carbenes are generated from diazo compounds, as Mathur, N.C .; Snow, M.S .; Young, K.M.; and Pincock, J.A.; Tetrahedron, (1985), 41 (8), pages 1509-1516, and nitrenes are generated from azides, as quoted by Abramovitch, R.A.; Chellathurai, T .; Holcomb, W.D.; McMaster, I.T .; and Vanderpool, D.P .; J. Org. Chem., (1977), 42 (17), 2920-6, and Abramovitch, R.A. , Knaus, G.N. , J. Org. Chem., (1975), 40 (7), 883-9. In the present reference is made to the compounds having at least two functional groups capable of insertion of C-H, under reaction conditions, as cross-linking agents. Some of these agents include alkyl and arylazides (R-N3), acylazides (RC (0) N3), azidoformates (R-0-C (0) -N3), phosphorylazides ((RO) 2- (PO) -N3) , phosphinic azides (R2-P (0) -N3) and silylazides (R2-Si-N3).

Polyfunctional compounds capable of insertions within the C-H bonds include poly (sulfonyl azide) s. The poly (sulfonyl azide) is any compound having at least two sulfonyl azide groups (-S02N3), reactive with the polyolefin. Preferably the poly (sulfonylazide) s have an XRX structure, wherein each X is S02N3, and R represents an unsubstituted or inertly substituted hydrocarbyl, hydrocarbyl ether or silicon-containing group, preferably having sufficient carbon, oxygen or silicon, preferably carbon, to separate the sulfonylazide groups sufficiently to allow an easy reaction between the polyolefin and the sulfonylazide, more preferably at least 1, more preferably at least 2, more preferably at least 3 carbon atoms, oxygen or silicon, preferably carbon, between the functional groups. Although there is no critical limit to the length of R, each R conveniently has at least one carbon or silicon atom among the X's, and preferably has less than about 50., more preferably less than about 30, more preferably less than about 20 carbon atoms, oxygen or silicon. Within these limits, the longer is better for reasons that include thermal stability and shock. When R is a straight-chain alkyl hydrocarbon, there are preferably less than 4 carbon atoms between the sulfonylazide groups, to reduce the propensity of nitrene to fold back and react with itself. Groups that include silicon include silanes and siloxanes, preferably siloxanes. The term "inertly substituted" refers to the substitution with atoms or groups that do not undesirably interfere with the desired reaction (s) or the desired properties of the resulting crosslinked polymers. These groups include fluorine, aliphatic or aromatic ether, siloxane, as well as sulfonylazide groups, when more than two polyolefin chains are to be joined. Suitable structures include R as aryl, alkyl, arylalkyl, arylalkyl, siloxane or heterocyclic groups, and other groups which are inert, and separate the sulfonylazide groups as described. More preferably R includes at least one aryl group between the sulfonyl groups, more preferably at least two aryl groups (such as when R is 4,4'-diphenyl or 4,4'-biphenyl ether). When R is an aryl group, it is preferred that the group has more than one ring, as in the case of naphthylene bis (sulfonyl azides). The poly (sulfonyl) azides include compounds such as bis (sulfonyl azide) 1,5-pentane, bis (sulfonyl azide) 1,8-octane, bis (sulfonyl azide) 1,10-decane, bis (sulfonyl azide) 1. 10-Octadecane, tris (sulfonyl azide) of l-octyl-2,4,6-benzene, 4,4'-bis (benzenesulfonyl azide), 1,6-bis (4'-sulfonazidophenyl) hexane, bis (sulfonylazide) 2 , 7-naphthalene, and mixed sulfonylazides of chlorinated aliphatic hydrocarbons containing an average of 1 to 8 chlorine atoms, and of about 2 to 5 sulfonyl azide groups per molecule, and mixtures thereof. The poly (sulfonyl azide) s include oxy-bis (4-sulfonyl-azidobenzene), bis (sulfonylazido) of 2,7-naphthalene, 4,4'-bis (sulfonylazido) biphenyl, 4,4'-oxybis (benzenesulfonyl azide) and bis (4-sulfonylazidophenyl) methane, and mixtures thereof. The sulfonylazides are conveniently prepared by the reaction of sodium azide with the corresponding sulfonyl chloride, although the oxidation of sulfonylhidazines with different reagents (nitrous acid, dinitrogen tetroxide, nitrosonium tetrafluoroborate) has been used. Polyfunctional compounds capable of insertions within the CH bonds also include carbene-forming compounds, such as salts of alkyl and aryl hydrazones, and diazo compounds, and nitrene-forming compounds, such as alkyl and arylazides (R-N3), acylazides (RC (0) N3), azidoformates (ROC (O) -N3), sulfonyl azides (R-S02-N3), phosphorylazides ((RO) 2- (PO) -N3), phosphinic azides (R2-P (0) -N3) and silylasides (R2-Si-N3). Some of the crosslinking agents of the invention are preferred, due to their propensity to form a greater abundance of carbon-hydrogen insertion products. These compounds, such as the hydrazone salts, the diazo compounds, the azidoformates, the sulfonyl azides, the phosphorylazides and the silylazides are preferred because they form stable singlet state electron products (carbenes and nitrenes), which perform efficient carbon-hydrogen insertion reactions , instead of substantially 1) reconfiguring by means of mechanisms such as the Curtius type reconfiguration, as in the case with acylazides and phosphinic azides, or 2) rapidly converting to the triplet state electron configuration, which preferentially undergoes the reactions of abstraction of hydrogen atoms, which is the case with the alkyl and arylazides. In addition, the selection of preferred crosslinking agents is conveniently possible due to differences in the temperatures at which different classes of crosslinking agents are converted to the active carbene or nitrene products. For example, those skilled in the art will recognize that carbenes are formed from diazo compounds, efficiently at temperatures below 100 ° C, while salts of hydrazones, azide-formates and sulfonyl azide compounds react at a convenient rate at temperatures above 100 ° C. 100 ° C, up to temperatures of approximately 200 ° C. (By convenient rates it is meant that the compounds react at a rate that is fast enough to make commercial processing possible, while reacting slowly enough to allow mixing and formation of suitable compounds, to result in a product end with the crosslinking agent suitably dispersed, and substantially localized at the desired position in the final product.This location and dispersion may be different from product to product, depending on the desired properties of the final product). The phosphorylazides can be reacted at temperatures in excess of 180 ° C to about 300 ° C, while the silylazides react preferentially at temperatures of from about 250 ° C to 400 ° C. To crosslink a polymer, the crosslinking agent is used in a crosslinking amount, that is, an effective amount to result in at least about 10 weight percent gel, as measured by ASTM D2765-procedure A. In the practice of the invention, preferably at least about 30 percent gel, more preferably at least about 50 percent, more preferably about 90 percent gel, is preferably achieved. That is, the polymer is most preferably converted from a thermoplastic to a thermoset polymer. Although those skilled in the art will recognize that the amount of poly (sulfonyl azide) sufficient to crosslink, and result in at least about 10 weight percent gel, will depend on the molecular weight of the azide used, the level of gel desired and the characteristics of the polymer, the amount is conveniently at least about 0.5 percent, preferably at least about 1 percent, more preferably at least about 2 percent, even more preferably at least about 5 percent of poly (sulfonylazide), based on the total weight of the polymer, when the poly (sulfonyl azide) has a molecular weight of from about 200 to about 2000. To avoid bubbles from the release of nitrogen by means of the poly (sulfonyl azide), in excess of that amount that reacts with the polymer (when bubbles are not desired), the amount of poly (sulfonyl azide) and s preferably of less than about 15, more preferably less than about 10, more preferably less than about 5 weight percent, based on the total polymer. To achieve crosslinking, the poly (sulfonyl azide) is heated in the presence of the polymer, at least the decomposition temperature of the sulfonyl azide. The decomposition temperature of the poly (sulfonyl azide) is the temperature at which the azide is converted to the sulfonyl nitrene, eliminating the nitrogen, and the heat in the process, as determined by differential scanning calorimetry (DSC). The poly (sulfonyl azide) starts reacting at a kinetically significant rate (convenient for use in the practice of the invention), at temperatures of about 130 ° C, and is reacted almost completely at about 160 ° C in a DSC (scanning at 10 ° C / minute). The ARC (scanning at 2 ° C / minute) shows that the onset of decomposition is at approximately 100 ° C. The degree of reaction is a function of time and temperature. The temperatures for use in the practice of the invention are also determined by the softening or melting temperatures of the polymer starting materials. For these reasons, the temperature is conveniently greater than about 90 ° C, preferably greater than about 120 ° C, more preferably greater than about 180 ° C, more preferably greater than 180 ° C. Preferred times at decomposition temperatures are times that are sufficient to result in the reaction of the crosslinking agent with the polymer (s), without the undesirable thermal degradation of the polymer matrix. Preferred reaction times in terms of the half-life of the crosslinking agent, that is, the time that is required for about half the agent to be reacted at a pre-selected temperature, whose half-life can be determined by DSC , is about 5 half lives of the crosslinking agent. In the case of a bis (sulfonyl azide), for example, the reaction time is preferably at least about 4 minutes at 200 ° C. When a larger mass of polymer or a coarse article is produced, often longer periods of time are required for adequate heat to penetrate the polymer; those times are conveniently around 20 minutes. The process of the invention preferably includes the steps of (a) mixing a polyolefin and at least a crosslinking amount of at least one crosslinking agent, which reacts with the polyolefin by inserting C-H; (b) forming the resulting mixture; and (c) heating the resulting shaped mixture at least to the decomposition temperature of the crosslinking agent, such that a crosslinked polyolefin is formed. The mixing of the polymer and the crosslinking agent is conveniently achieved by any means within the skill of the art. The preferred processes of the mixed step (a) of the polyolefin and the crosslinking agent include at least one of (a) dry blending the crosslinking agent with the polymer, preferably to form a substantially uniform mixture and adding this mixture to the equipment Fusion processing, for example a melting mixer or forming device, in which mixing is carried out, at a temperature lower than the decomposition temperature of the crosslinking agent; (b) introducing, for example by injection, a crosslinking agent in liquid form, for example dissolved in a solvent therefor, or in a slurry of the crosslinking agent in a liquid, inside a device containing the polymer, of preferably a softened, melted or melted polymer, most preferably in a fusion processing equipment (within the art, it is usually said that the polymer absorbs the liquid); (c) forming a first mixture of a first quantity of a first polymer and a crosslinking agent, conveniently at a temperature of less than about the decomposition temperature of the crosslinking agent, preferably by melt mixing, and then forming a second mixture of the first mixture with a second amount of a second polymer (eg, a concentrate of a crosslinking agent mixed with at least one polymer and, optionally, other additives, is conveniently mixed within a second polymer or combination thereof, optionally with other additives, to crosslink the second polymer); (d) feeding at least one crosslinking agent, preferably in solid form, preferably finely pulverized, eg powder, directly into the softened or melted polymer, for example in the melt processing equipment, for example in an extruder; or combinations thereof. Among processes (a) to (d), processes (b) and (c) are preferred, with (c) being most preferred. For example, process (c) is conveniently used to make a concentrate with a first polymer composition having a lower melting temperature, conveniently at a temperature below the decomposition temperature of the crosslinking agent, and the The concentrate is melt-blended into a second polymer composition having a higher melting temperature. Concentrates are especially preferred when temperatures are high enough to result in a loss of the crosslinking agent by evaporation or decomposition, without leading to a reaction with the polymer, or other conditions would result in that effect. When the crosslinking agent is added in a dry form, it is preferred to mix the agent and the polymer in a softened or melted state below the decomposition temperature of the crosslinking agent, and then to shape the resulting mixture. In this way, the steps to form a mixture frequently include at least two steps, a first step of mixing the polymer in particulate form, for example pellets with the crosslinking agent and optionally other additives after a melting step, which includes optionally and preferably additional mixing. Alternatively, the forming step preferably includes a melting step of the polymer mixture. The term "melt processing" is used to indicate any process in which the polymer is softened or melted, such as extrusion, pelletizing, molding, thermoforming, film blowing, polymer melt composition, spinning fiber, and combinations thereof. The polyolefin (s) and the crosslinking agent are suitably combined in a manner which ultimately results in the desired reaction thereof, preferably by means of mixing the crosslinking agent with the polymer (s). ) under conditions that allow sufficient mixing, prior to the reaction, most preferably before forming, to avoid uneven amounts of localized reaction, and then subjecting the resulting mixture to heat sufficient for the reaction. Preferably, a substantially uniform mixture of crosslinking agent and polymer is formed, prior to exposure to the conditions under which the chain crosslinking is performed. A substantially uniform mixture is one in which the distribution of the crosslinking agent in the polymer is sufficiently homogeneous, as evidenced by a polymer having consistent stress and elongation properties in different samples of the polymer, and having neither gel particles nor bubbles that can be observed in the cured samples. This mixing is preferably obtained with the polymer in a molten or melted state, which is above the crystalline melting temperature, or in a dissolved or finely dispersed condition rather than a solid or particulate mass form. The molten or melted form is the most preferred to ensure homogeneity, rather than the concentrations located on the surface. Any equipment is used properly, preferably equipment that provides sufficient mixing and temperature control in the equipment. The advantageous practice of the invention is carried out in devices such as an extruder, or a static polymer mixing device, such as a Brabender mixer or a Banbury mixer. In the mixing step, other additives are also optionally mixed within the skill in the art, in the polymer. The crosslinked polymers of the invention optionally include different additives, such as carbon black, silica, titanium dioxide, colored pigments, clay, zinc oxide, stearic acid, accelerators, curing agents, sulfur, stabilizers, coagents, antidegradants, aids of processing, adhesives, viscosity agents, plasticizers, wax, pre-crosslinking inhibitors, staple fibers (such as wood cellulose fibers), and diluting oils. These additives are optionally provided either before, during, or subsequent to the crosslinking (cure) of the polyolefin elastomers. Frequently, the polyolefin elastomers are mixed with a filler, an oil, and a curing agent, preferably at an elevated temperature (above room temperature, but preferably below the decomposition temperature of the drying agent). crosslinking), to compose them. The composite material is subsequently cured at a temperature which is typically higher than that used during the composition. Coagents such as tralyl cyanurate and trimethylpropanetrimethacrilate are optionally used to improve the efficiency of crosslinking. The amount of the coagent is from about 0.2 to 15 weight percent (based on the weight of the polymer), and preferably from 1 weight percent to 5 weight percent. Preferably, the carbon black is added to the polyolefin elastomers before curing. Carbon black is typically added to improve the tensile strength or firmness of the composite product, but it can also be used as a diluent or to disguise the color of the composite product. Carbon black is preferably present in an amount from 0 to 80 weight percent, more preferably from 0.5 to 50 weight percent, based on the total weight of the formulation. When carbon black is used to increase the firmness and / or to decrease the cost of the formulation, it is conveniently employed in amounts greater than 10 weight percent, based on the weight of the formulation. In addition, preferably one or more diluent oils will also be added to the polymer, before crosslinking. Diluent oils are conveniently added to improve processability and flexibility at low temperature, as well as to lower cost. Suitable diluent oils are within the skill in the art and are listed for example in the Rubber World Blue Book, 1975 edition, Materials and Compounding Ingredients for Rubber, pages 145-190. Typical classes of diluent oils include aromatic, naphthenic, and paraffinic diluent oils. The diluent oils are conveniently used in an amount of from 0 to 50 weight percent. When employed, the diluting oil is conveniently present in an amount of at least 5 percent by weight, more conveniently in an amount of from 15 to 25 percent by weight, based on the total weight of the formulation . After mixing, the polymer is preferably shaped before crosslinking. The forming is within the skill in the art and includes processes such as wire or cable sheathing, compression molding, thermoforming blow molding, fiber making, foaming, profile extrusion in forms such as gaskets or weather stripping. Within the skill in the art there are many types of molding operations, which are useful for forming useful manufactured articles or parts from the formulations described herein, including different injection molding processes (e.g. which is described in the Modern Plastics Encyclopedia / 89, mid-October number, 1988, volume 65, number 11, pages 264-268, "Introduction to Injection Molding" and on pages 270-271, "Injection Molding Thermoplastics") and blow molding processes (eg, the one described in the Modern Plastics Encyclopedia / 89, mid-October number, 1988, volume 65, number 11, pages 264-268, "Extrusion-Blow Molding"), extrusion profile, satin, and pultrusion. Conveniently, after being formed, the polymer is heated at least to the decomposition temperature of the crosslinking agent for a sufficient time to result in the desired crosslinking. The heating is within the skill in the art, such as by furnace, water bath, sand bath or the like. In this manner, the process of the invention comprises: (a) forming a polymer blend that includes at least one polyolefin which has been prepared using a single-site catalyst and at least one cross-linking amount of at least one cross-linking agent poly (sulfonyl azide); (b) shaping the resulting mixture; and (c) heating the resulting formed mixture to a temperature, which is at least the decomposition temperature of the crosslinking agent. These steps occur optionally in any order, which results in a cross-linked product. The preferred order is alphabetical, but especially in the case of foams, the steps are, optionally, completely or partially in another order or are simultaneous. For example, optionally some heating occurs at the decomposition temperature before or during forming, for example, to increase the melt strength. In another embodiment, the forming can proceed and follow heating to the decomposition temperature, for example in a foam where a thick sheet is formed before heating, and the pressure is decreased after heating. All variations of the steps that result in a cross-linked polymer are within the scope of the invention. The practice of the processes of the invention for crosslinking polymers produces crosslinked polymers, that is, polymers having a crosslinking of sulfonamide between the different chains of the polymer. Cross-linked HDPE (density greater than 0.94 grams / cc) made using the single site catalyst, preferably with narrow molecule distribution, is useful in pipes, fuel tanks, chemical tanks and agricultural tanks. The resulting crosslinked polymers conveniently exhibit a higher slip resistance, according to the ASTM D-290-77 measurement and a higher upper service temperature, according to the TMA measurement (as described later in the present), than the starting material polymer, due to the crosslinking of the polymer chains. After both have been crosslinked as taught herein, the articles and fibers of the HDPE which is made using the single-site catalyst conveniently have a higher firmness, as measured by the methods of ATSM D-412, than those of an HDPE which is made using a Ziegler Natta catalyst and which was treated in accordance with the practice of the invention. The crosslinked HDPE is useful in fibers including woven and nonwoven fibers. The medium density polyethylene copolymer which is made using the single site catalyst and which is crosslinked in accordance with the practice of the invention, is useful in films, wire-cable insulation, fibers, chemical tanks, lamination. The articles that are made from the crosslinked polyethylene copolymer which was made using single site catalysts, preferably having a narrow molecular weight distribution of at least one and more preferably all the components, have better firmness in accordance with the measurement of ASTM D-412, elongation in accordance with the measurement of ASTM D-412, and tensile strength according to the measurement of ASTM D-412, that the corresponding articles are made from the corresponding polymer that was made using the Ziegler Natta catalyst, using the poly (sulfonyl azide) or a corresponding article that was made using the polyethylene copolymer which was made using the single site catalyst and which was crosslinked using the peroxide crosslinking agent. A crosslinked polyolefin which was made using the single-site catalyst and which is cross-linked in accordance with the practice of the invention, has better organoleptic properties, better oxidative stability (ASTM 573-88), and better weather resistance (ASTM D -2565), than a corresponding polymer that cross-links using a peroxide as a cross-linking agent. A corresponding polymer is one that has the same density and average number of molecular weight. The crosslinked polyolefin elastomers of the invention are also useful in many applications such as wire and cable coating, roof membranes, floor coverings, gaskets, hoses, boots, automotive parts, provision of weather stripping and other parts that require elastomeric materials. The roofing membrane, gaskets, boots, and weather strips that are made from the crosslinked elastomers of this invention have better compression setting according to the ASTM-D-395 measurement, better weather resistance (ASTM 2565). ), and better oxidative stability (ASTM D 573-88) than the corresponding article which is made using the peroxide crosslinking agent, according to what is described in the prior art (U.S. Patent Number 5,580,920) . The cable insulation of this invention can be filled or not filled. If it is filled, then the amount of filler present should not exceed the amount that would cause the degradation of the electrical and / or mechanical properties of the crosslinked elastomers. Advantageously, the amount of filler present is between 20 and 80, preferably between 50 and 70 weight percent, which is based on the weight of the polymer. Representative fillers include kaolin clay, magnesium hydroxide, silica, calcium carbonate. In a preferred embodiment of this invention, in which a filler is present, the filler is coated with a material that will prevent or retard any tendency that the filler may have to interfere with the crosslinking reaction. Other additives are useful in the preparation of, and are present in the isolation of this invention, and include antioxidants, processing aids, pigments and lubricants. The cable insulation of this invention can be applied to a cable in known amounts and by known methods (for example, with the equipment and methods described in U.S. Patent Nos. 5,246,783 and 4,144,202). Conveniently, the cable insulation is prepared in a reactor-extruder equipped with a cable coating die and after the components of the insulation are formulated, the insulation composition is extruded on the cable as the cable is pulled through the die. The purity marks of this cable insulation include: improved tree strength according to the measurement of ASTM-D 3756, improved tensile strength according to the ASTM-D-412 measurement, improved elongation according to the measurement of ASTM-D-412, and improved compression setting according to the measurement of ASTM-D-395, compared to cross-linked peroxide polyolefin elastomers. In another embodiment of this invention, substantially linear ethylene polymers that are crosslinked in accordance with the present invention are configured as automotive drills. This provision of barletes is useful as a sealing system for doors, trunks, band lines, engine covers, and similar items. Preferably, the resulting materials are transparent and can be processed in conventional thermoplastic equipment. The drills of this invention have better weather resistance than conventional sulfur cured EPDM drills. In yet another embodiment of this invention, the substantially linear ethylene polymers that are crosslinked are given fiber form. These fibers crosslink easily after heating to crosslinking temperatures (at least the decomposition temperature of the crosslinking agent). These elastic fibers have utility in manufactured articles such as woven and nonwoven fabrics (e.g., washable clothing), elastic cord (e.g., woven elastic strips), elastic filters for air / water filtration (e.g., air cleaners not fabrics), and fiber mats (for example, non-woven carpet sub-floor). The cross-linked ethylene polymers, the processes to make them and the intermediaries to make them, of this invention, are useful in the automotive area such as in fuel tanks, applications for the lower part of engine covers (including packages and hoses), industrial goods such as instrument parts (including the housing thereof), Building and construction applications such as pipes, drainage tiles, and electrical insulation (for example, coating / insulation of wires and cables) and rim products. Some of the manufactured items include automotive hoses, single-ply roofing, and insulation and voltage coverage of wire and cable. One type of formation and crosslinking is foaming, where the polymer is formed into a foam and reticulated. The crosslinking is optionally simultaneous with the formation of the foam, after the formation of the foam or a combination thereof where some crosslinking occurs during the formation of the foam and further crosslinking occurs in a subsequent manner. All variations herein are referred to as crosslinking during foaming. The practice of the process of the invention for crosslinking polymers during forming produces reticulated polymer foams, that is, polymers having crosslinking of sulfonamide between the different polymer chains. The crosslinked polyolefins prepared using the Ziegler Natta or free radical catalysts, which preferably have a broad molecular weight distribution, (MWD of 3.5 or more), show a larger foam cell size, less size distribution homogeneous cell, less tensile and compressive strength, and less firmness than that noted in the foams of the corresponding cross-linked polymers that were made using the single-site catalysts, which preferably have narrow molecular weight distribution polymers (MWD less than 3.5, preferably about 2.0 or less). The term "crosslinking" is used to refer to foams with gel greater than 10 percent, according to what was determined by extraction of xylene. Cross-linked polyolefin foams, which include foams or blends that include polyolefins, are used in a variety of applications where cushioning under high or dynamic load is needed. Usually these foams are made using a chemical blowing agent, for example azodicarbonamide, in combination with the crosslinking typically induced by peroxide decomposition or electron beam irradiation. When exposed to high temperature (greater than 130 ° C), the blowing agent decomposes in a gas, for example nitrogen, and the polyolefin matrix is crosslinked simultaneously, for example by the decomposition of the peroxide. By attaining the optimum level of tensile properties at elevated temperatures by cross-linking, the decomposed gas is allowed to expand in a controllable manner to produce foams with desirable cell sizes. The crosslinking and blowing of the foam are optionally carried out either sequentially or simultaneously. Foams of very small cell size, approximately 100 μm in diameter, are produced by simultaneous crosslinking and decomposition of the blowing agent under pressure as, for example, in compression molding or by high temperature injection. Those skilled in the art will recognize that foaming processes within the skill in the art that use crosslinking by free radical generating agents can be adapted to crosslinking using poly (sulfonyl azide) and other methods of crosslinking by insertion.

According to the present invention, one embodiment of a process for making a cross-linked ethylene polymer foam structure is as follows: First, a meltable polymer material that can be foamed is formed by combining and heating a blowing agent corruptible chemical and an ethylene polymer material.

Second, crosslinking is induced in the foamable molten polymer material. Third, the foamable molten polymer material is expanded by exposing it to an elevated temperature to form the foam structure. The resultant foam structure is conveniently in any physical configuration known in the art, such as a sheet, panel, injection molded article or bow support. Other useful forms are expandable or foamable particles, moldable foam particles or beads, and articles that are formed by expansion and / or conglutination and welding of those particles. In C.P. Park, "Polyolefin Foam", chapter 9, Handbook of Polymer Foams and Technology, edited by D. Klempner and K.C. Frisch, Hanser Publishers, Munich, Vienna, New York, Barcelona (1991), excellent teachings are seen on the processes for manufacturing the foam structures of ethylene polymers and for processing them. The resultant foam structure is optionally prepared by combining and heating a polyolefin polymer material and a corruptible chemical blowing agent to form a foamed or molten polymerized plastic material, extruding the foamable molten polymer material. through a die, induce crosslinking in the molten polymer material by the poly (sulfonyl azide) compound, and expose the molten polymer material at an elevated temperature to release the blowing agent to form the foam structure. The polymer and the chemical blowing agent are optionally blended and combined by mixing by any means known in the art, such as with an extruder, blender, blender, or the like. Preferably, the chemical blowing agent is mixed dry with the polymer material, before heating the polymer material to a molten form, but it can also be added when the polymer material is in the melt phase. Crosslinking is induced by the addition of poly (sulfonyl azide) crosslinking agent. Induction of crosslinking and exposure to a high temperature to effect foaming or expansion may occur simultaneously or sequentially. The crosslinking agent is incorporated into the polymer material in the same manner as the chemical blowing agent. In addition, the foamable molten polymer material is heated or exposed to a temperature of preferably less than 150 ° C to prevent decomposition of the crosslinking agent or blowing agent, and to prevent premature crosslinking. The foamable molten polymer material is extruded or transported through a die of the desired shape, to form a foamable structure. Then, the structure is reticulated and expanded at a high or high temperature (conveniently 150 ° C-250 ° C), such as in an oven, to form a foam structure. The present structure can be conveniently made in sheet or panel form, in accordance with the above process. The resulting foam structure is optionally made as a continuous panel structure by the extrusion process using a long surface die, as described in GB 2,145,961A. In that process, the polymer, the corruptible blowing agent and the crosslinking agent are mixed in an extruder, heating the mixture to allow the polymer to crosslink and decompose the blowing agent in a long surface die; and it is shaped and driven away from the foam structure through the die by lubricating the foam structure and contacting the die with an appropriate lubricating material. The resulting foam structure can also be formed as cross-linked foam pellets suitable for molding into articles. To make the foam pellets, discrete resin particles such as pellets of granulated resin are suspended in a liquid medium in which they are substantially insoluble, such as water; they are impregnated with a crosslinking agent and a blowing agent at a high pressure and temperature in a sterilizer or other pressure chamber, and rapidly discharged into an atmosphere or a region of reduced pressure to expand and form the foam pellets. One version is that the polymer pellets are impregnated with the blowing agent, cooled, discharged from the chamber and then expanded by heating or steam. In a derivative of the above process, a styrene monomer is optionally impregnated within the suspended pellets together with the crosslinking agent, to form a graft interpolymer with the ethylene polymer material. The blowing agent optionally impregnates within the resin pellets while in suspension or, alternatively, in a non-hydrated state. The expandable pellets are then expanded by steam heating and molded by the conventional molding method for the expandable polystyrene foam pellets. The foam pellets are then optionally molded by any means within the skill in the art, such as loading the foam pellets into the mold, compressing the mold to compress the pellets, and heating the pellets as with steam to effect conglutination and the welding of the balls to form the article. Optionally, the pellets are preheated with air or another blowing agent before being loaded into the mold. In C.P. Park, Supra, pages 227-233, U.S. Patent Number 3,886,100, Number 3,959,189, Number 4,168,353, and Number 4,429,059, the excellent teachings of the above processes and molding methods are seen. The foam pellets can also be prepared by preparing a mixture of the polymer, the crosslinking agent, and the corruptible mixtures in a suitable mixing device or extruder, and forming the mixture as pellets, and heating the pellets to crosslink and expand them. . The resulting foam structure is optionally made in the form of a bow support by mixing the polyolefin polymer material, a crosslinking agent, and a chemical blowing agent, to form a thick sheet, heating the mixture in a mold so that the crosslinking agent can crosslink the polymer material and the blowing agent can be decomposed, and expanded by releasing pressure in the mold. Optionally, the bow support that is formed after the release of the pressure is optionally reheated to effect additional expansion. The crosslinked polymer sheet is manufactured by heating a polymer sheet containing the chemical crosslinking agent. The crosslinked polymer sheet is cut into the desired shapes and impregnated with N2 at a temperature above the softening point of the polymer and at a pressure sufficient to result in sufficient impregnation of N2 to result in the previously selected foam density; the release of the pressure affects the nucleation of the bubbles and some expansion in the lamina. The sheet is reheated in a low pressure chamber with a pressure above the softening point and the pressure is released so that the foam can expand. Blowing agents useful in making the resulting foam structure include corruptible chemical blowing agents. These chemical blowing agents decompose at elevated temperatures to form gases or vapors to blow the polymer into a foam form. The agent preferably takes a solid form, so that it conveniently combines dry with the polymer material. Chemical blowing agents include azodicarbonamide, azodi-isobutyronitrile, barium azodicarboxylate, N, N'-dimethyl-N, N'-dinitrosoterephthalamide, N, N'-dinitrosopentamethylenetetramine, benzenesulfonhydrazide, 4,4-oxybenzenesulfonylsemicarbazide, and p-toluenesulfonylsemicarbazide. Azodicarbonamide is preferred. In C.P. Park, Supra, pages 205-208, and F. A. Shutov, "Polyolefin Foam", Handbook of Polymer Foams and Technology, pages 382-402, D. Klemper and K.C. Frisch, Hanser Publishers, Munich, Vienna, New York, Barcelona (1991) can be seen additional teachings about chemical blowing agents. The chemical blowing agent is combined with the polymer material in an amount sufficient to conveniently emit from about 0.2 to about 5.0, preferably from about 0.5 to 3.0, and more preferably from about 1.0 to 2.50 moles of gas or vapor per kilogram of polymer. In some processes for manufacturing the present structure, a physical blowing agent is optionally used. Physical blowing agents include organic and inorganic agents. Convenient inorganic blowing agents include carbon dioxide, nitrogen, argon, water, air, nitrogen, and helium. Organic blowing agents include aliphatic hydrocarbons having from 1-9 carbon atoms, aliphatic alcohols having from 1-3 carbon atoms, and partially or fully halogenated aliphatic hydrocarbons having from 1-4 carbon atoms. The aliphatic hydrocarbons include methane, ethane, propane, n-butane, isobutane, n-pentane, isopentane, and neopentane. The aliphatic alcohols include methanol, ethanol, n-propanol, and isopropanol. The total or partially halogenated aliphatic hydrocarbons include fluorocarbons, chlorocarbons, and chlorofluorocarbons. Examples of fluorocarbons include methyl fluoride, perfluoromethane, ethyl fluoride, 1,1-difluoroethane (HFC-152a), 1,1-trifluoroethane (HFC-143a), 1,1,1-tetrafluoroethane (HFC) -134a), pentafluoroethane, difluoromethane, perfluoroethane, 2, 2-difluoropropane, 1,1-trifluoropropane, perfluoropropane, dichloropropane, difluoropropane, perfluorobutane, perfluorocyclobutane. Chlorocarbons and partially halogenated chlorofluorocarbons for use in this invention include methyl chloride, methylene chloride, ethyl chloride, 1,1-trichloroethane, 1,1-dichloro-1-fluoro-ethane (HCFC-141b), 1-chloro-l, 1-difluoroethane (HCFC-142b), chlorodifluoro-methane (HCFC-22), 1,1-dichloro-2,2,2-trifluoroethane (HCFC-123) and chloro-1,2, 2 , 2-tetrafluoroethane (HCFC-124). Chlorofluorocarbons include trichloromonofluoromethane (CFC-11), dichlorodifluoromethane (CFC-12), trichlorotrifluoroethane (CFC-113), 1,1-trifluoroethane, pentafluoroethane, dichlorotetrafluoroethane (CFC-114), chlorheptafluoropropane, and dichlorohexafluoropropane. The amount of blowing agent that is incorporated into the molten material of the polymer to make a foam-forming polymer gel is advantageously from about 0.2 to about 5.0, preferably from about 0.5 to about 3.0, and most preferably, from about 1.0. up to 2.50 moles per kilogram of polymer. The resulting foam structure conveniently has a crosslinked density of from 5 to 90 percent and more preferably from 30 to 80 percent, in accordance with ASTM D-2765-84, method A. The resulting foam structure conveniently has a density of less than 500, more preferably less than 250 and more preferably from about 10 to about 150 kilograms per cubic meter. The foam has an average cell size of from about 0.05 to about 5.0, more preferably from about 0.1 to about 2.0, and more preferably from 0.2 to about 1.0 millimeter, in accordance with ASTM D3576. The resulting foam structure optionally has closed cell or open cell, in accordance with ASTM D2856-A. Other components that are optionally added to the foam mixture include fillers, such as calcium carbonate, talc, clay, magnesium carbonate, and mica; the foaming agent activators include transition metal salts (especially those of lead, cadmium and zinc), polyols, urea, alcohol amines and organic acids. Zinc oxide and zinc stearate are preferred. The pigments include carbon black, titanium dioxide, pigments based on cadmium or other inorganic or organic based pigments. The nucleators of the foam include talc, silicon dioxide, titanium dioxide, and clay. Antioxidants, for example phenolic, phosphite, etc., may also be included to improve the shelf life of the finished article. Process aids such as low molecular weight polyethylene waxes, ester waxes, paraffin waxes, paraffin oils, mineral oils, naphthenic oils, biesteramides, stearamides, calcium stearate, and stearic acid can also be used. Other additives, for example ultraviolet absorbers, flame retardants, etc., can also be included in the polymer mixture. The foams which are prepared from ethylene copolymers which are crosslinked in accordance with the practice of the invention exhibit higher tensile strength, strength and tear resistance than foams made from the same polymers of starting material that were crosslinked with free radical generating crosslinking agents. The foams are conveniently formed into finished articles by processes such as compression molding, injection molding, extrusion, vertical and horizontal oven expansion, and oven curing and combinations thereof. When used in combination, the processes are optionally used sequentially or simultaneously as is done within the skill in the art.

There are many types of molding operations that can be used to form articles or fabricated parts useful from the formulations described herein, including different injection molding processes (e.g., that described in the Modern Plastics Encyclopedia / 89, mid-October, number of 1988, volume 65, number 11, pages 264-268, "Introduction to Injection Molding" and on pages 270-271, "Injection Molding Thermoplastics"), and blow molding processes ( for example, the one described in the Modern Plastics Encyclopedia / 89, mid-October, 1988 issue, volume 65, number 11, pages 217-218, "Extrusion-Blow Molding"), outlines extrusion, satin, and pultrusion . The following examples are to illustrate this invention and do not limit it. The proportions, parts, and percentages are by weight, unless otherwise stated. The examples (Ej) of the invention are designated numerically, while the comparative samples (M.C) are designated alphabetically and are not examples of the invention.

Test Methods: The extraction of xylene was performed by weighing 1 gram samples of the polymer. The samples were transferred to a mesh basket which was then placed in boiling xylene for 12 hours. After 12 hours, the sample baskets were removed and placed in a vacuum oven at 150 ° C and 28 in. Hg vacuum for 12 hours. After 12 hours, the samples were removed, allowed to cool to room temperature for a period of 1 hour, and then weighed. The results are reported as percentage of polymer extracted. Percentage removed = (initial weight - final weight) / initial weight, in accordance with ASTM D-2765, Procedure A. Samples were prepared using either a HaakeBuchler Rheomix 600 mixer with roller style blades, coupled to a torque rheometer of HaakeBuchler Rheocord 9000 torsion, or using a Brabender mixer (REE type Number A-19 / SB) with a mixing bowl of 50 grams. A Perkin Elmer thermomechanical analyzer was used Model TMA 7 to measure the higher service temperature (UST, for its acronym in English). Probe strength of 102 grams and heating rate of 5 ° C / min was used. The test specimen was a disk with a thickness of approximately 2 millimeters and diameter, which was prepared by melt pressing at 190 ° C and cooled with air at room temperature. The UST that should have been taken when the probe had penetrated the 1.0-mm sample was taken. Tension properties including elongation, rupture stress, and firmness were determined by compression molding of 1/16 inch plates. After they cut voltage specimens from those plates and were tested in an Instron voltage tester, in accordance with ASTMS D-1708, tensioned at 5 inches / minute. This procedure was used in the examples of the invention because it accommodates smaller sample sizes. ASTM 412 is also useful for evaluating the stress properties of larger samples. It is believed that the results are comparable, but in the rare cases where these are not comparable, the values that were obtained by the method of ASTM 412 for the evaluation of the products of the invention are preferred. All instruments were used according to the manufacturer's instructions. Samples were prepared using a roll style mixer which are commercially available from Haake, Inc., under the registered trade designation of HaakeBuchler Rheomix 600 mixer, attached to a rheometer commercially available from Haake Inc., under the trade designation registered rheometer Rheometer HaakeBuchler Rheocord 9000. The following materials were used: Dicumyl peroxide - Used as received from Hercules Corporation and sold under the registered trade designation of peroxide DI-CUP R lot 43HR-233. 4,4'-oxybis (benzenesulfonyl azide CAS # [7456-68-0]). This bis (benzenesulfonyl azide) was prepared by the reaction of sodium azide with the corresponding bis (sulfonyl) chloride, which is commercially available. Solid sodium azide was added to the acetone solution of the bis (sulfonyl) chloride, and the product was isolated by precipitation with excess water.

EXAMPLES 1-3 A 40.0 gram sample of a commercially available ethylene / octene copolymer was added with DuPont Dow Elastomers LLC under the registered trade designation ENGAGE D-8190 (0.858 grams / cm3, 0.5MI, 2.0 MWD) to an available rheometer commercially with Haake Inc., under the registered trade designation of Haake Rheocord System 9000 torque rheometer, equipped with a Haake 600 mixing bowl with roller style blades. The temperature of the bowl was 120 ° C, and the sample was mixed at 75 rpm. Once the polymer melted, 0.40 grams (1.0 weight percent, 1.05 mmol) of 4,4 '-oxibis (benzenesulfonyl azide CAS # [7456-68-0]) were added to the mixing bowl and the clock started. marching. The sample was mixed for 8 minutes. The polymer was removed and compression molded at 120 ° C for 3 minutes at 20,000 pounds of force. After 3 minutes, the sample was removed and placed in a press at 190 ° C for 10 minutes, during which time the sulfonyl azide reacts to cross-link the polymer. The sample was removed from the press and allowed to cool. In Example 2, the procedure of Example 1 was repeated, using 0.6 grams (1.5 weight percent, 1.5 mmol) of the 4,4'-oxybis (benzenesulfonyl azide CAS # [7456-68-0]). In Example 3, the procedure of Example 1 was repeated, using 0.8 grams (2.0 weight percent, 2.1 mmol) of the 4,4'-oxybis (benzenesulfonyl azide CAS # [7456-68-0]). Tension properties and TMA performance of the samples were measured and reported in Table 1.

Comparative Samples A-C: A 40.0 gram sample of an ethylene / octene copolymer, commercially available from DuPont Dow, was added.

Elastomers LLC under the registered trade designation ENGAGE D-8190 (0.858 grams / cm3, 0.5MI, 2.0 MWD), to a rheometer commercially available with Haake Inc., under the registered commercial designation of HaakeBuchler Rheocord 9000 torque rheometer, equipped with a commercially available mixing bowl with the Haake Inc., under the registered trade designation of Haake 600 mixing bowl with roller style blades. The temperature of the bowl was 120 ° C, and the sample was mixed at 75 rpm. Once the polymer melted, 0.28 grams (0.7 weight percent, 1.05 mmol) of dicumyl peroxide were added. The sample was mixed for 5 minutes. The polymer was removed and compression molded at 20 ° C for 3 minutes at 20,000 pounds of force. After 3 minutes, the sample was removed and placed in a press at 180 ° C for 10 minutes, during which time the peroxide reacted to cross-link the polymer. The sample was removed from the press and allowed to cool. For Comparative Sample B, the procedure that was used for Comparative Sample A was repeated, using 0.4 grams (1.0 weight percent, 1.5 mmol) of the dicumyl peroxide. For Comparative Sample C, the procedure that was used for Comparative Sample A was repeated, using 0.56 grams (1.4 weight percent, 2.1 mmol) of the dicumyl peroxide. The tensile properties and TMA performance of the samples were measured and recorded in Table 1.

Comparative Sample D: Comparative Sample D was a sample of the same ethylene / octene copolymer commercially available from DuPont Dow Elastomers LLC under the registered commercial designation ENGAGE D-8190 (0.858 grams / cm3, 0.5MI, 2.0 MWD) non-crosslinked, conformity with the practice of the invention. The sample was compression molded to make a test specimen without going through the mixing process.

Table 1. Comparison of the Mechanical Properties of the Crosslinked Polymer, using Azide and Peroxide They are not examples of the invention. 15 Firmness was measured by the procedure of ASTM D-1708. The Peak Effort was measured by the procedure of ASTM D-1708. Elongation was measured by the procedure of ASTM D-1708.

The data in Table 1 indicate that at a given molar concentration of the crosslinking agent, the difunctional sulfonyl azide provides improved strength and improved temperature resistance, according to the TMA measurement, as compared to cross-linked peroxide samples.

Process for Examples 4, 5 and 6: For Example 4, a 200.0 gram sample of an ethylene / propylene / diene terpolymer commercially available from DuPont Dow Elastomers LLC, under the trade designation registered from Nordel IP hydrocarbon rubber, was added. NDR 3720 (0.88 grams / cm3, viscosity of Mooney 20 (per ASTM D 1646-92), 2.0 MWD), to a rheometer commercially available with Haake Inc., under the registered trade designation of torque rheometer HaakeBuchler Rheocord System 9000 equipped with a mixing bowl commercially available with Haake Inc., under the registered trade designation of Haake 3000 mixing bowl with roller style blades. Reportedly, the ethylene-propylene-diene terpolymer was made using a single-site catalyst. The temperature of the bowl was 120 ° C, and the sample was mixed at 20 RPM (revolutions per minute) for 3 minutes, then increased to 40 RPM for 6 minutes, then the poly (sulfonyl azide) was added. Once the polymer melted, 1.0 gram (1.0 weight percent) of 4,4'-disulfonylazidophenyl ether was added to the mixing bowl and the running clock was started. The sample was mixed for 8 minutes. The polymer was removed and molded by compression at 130 ° C for 3 minutes at 20,000 pounds of force (88964 Newtons). After 3 minutes, the sample was removed and placed in a press at 190 ° C and 300 pounds of force (1334 Newtons) for 15 minutes, at which time the sulfonyl azide reacted to cross-link the polymer. The sample was removed from the 190 ° C press and placed in a press of 32 ° C and 300.00 pounds of force (1344 Newtons) for 6 minutes. In Example 5, the procedure of Example 4 was repeated, using 200.00 grams of the ethylene-propylene copolymer with Mw / Mn = 2.02, Mw = 122.00, melt index 1.1 grams / 10 minutes and density of 0.87 g / cc commercially available from Mitsui Petrochemical Industries, under the trade designation Tafmer polymer P0480. Reportedly, the Tafmer polymer P0480 was made using a single-site catalyst. In Example 6, the procedure of Example 4, using an ethylene-octene copolymer with melt index 1.0 grams / 10 minutes and density of 0.87 g / cc commercially available with DuPont Dow Elastomers LLC, under the registered trade designation of Engage 8100 polyolefin elastomer, which is reports, was done using a single-site catalyst.

Process for Comparative Sample E: For Comparative Sample E, a 40.0 gram sample of an ethylene / propene copolymer commercially available from Exxon Chemical Company was added under the registered trade designation Vistalon 707 (0.872 grams / cc, 0.5MI g / 10 minutes), to a commercially available rheometer with Haake Inc., under the registered trade designation of Haake Rheocord System 9000 torque rheometer, equipped with a mixing bowl commercially available from Haake Inc., under the registered trade designation of Haake 600 mixing bowl with roller style blades. The temperature of the bowl was 120 ° C, and the sample was mixed at 20 rpm. Once the polymer melted, 1.6 grams (4 weight percent, 1.05 mmol) of dicumyl peroxide were added. The sample was mixed for 5 minutes. The polymer was removed and compression molded at 138 ° C for 1 minute at 20,000 pounds (88964 Newtons) strength in plates of 15.2 centimeters x 15.2 centimeters x 1.27 millimeters (6 inches x 6 inches x 60 thousand) and then cooled immediately on cylinders cooled with water at room temperature. Each of these plates was cut into four 7.6 cm x 7.6 cm x 1.27 mm (3 inch x 3 inch x 50 mil) plates. These smaller plates were compression molded at 138 ° C for 2 minutes at 12,000 pounds of force (53378 Newtons) into 15.2 centimeters x 15.2 centimeters x 0.51 millimeters (6 inches x 6 inches x 20 mil) plates and then cooled as described above. The second step of molding was done to remove the air bubbles. The 15.2 centimeter x 15.2 centimeter x 0.51 millimeter (6 inch x 6 inch x 20 mil) plates were cured at 182 ° C for 10 minutes in the press. The tensile properties of the samples were measured.

Table 2. Properties that were measured for Examples 4-6 and M.C. AND.

N / M means that it was not measured The results in Table 3 indicate that a variety of elastomers can be crosslinked which are prepared using single site catalysts, using the poly (sulfonyl azide).

The strength was greater for a polymer that was made using a single site catalyst that was crosslinked in accordance with the practice of the invention, than the corresponding Ziegler Natta catalyzed polymer (of similar density and melt index), using the peroxide as a healing agent (MC E).

Example 7 and Comparative Sample F: Reagent Mixing Procedure: In Example 7, an ethylene-octene copolymer with melt index of 1.0 grams / 10 minutes and density of 0.87 g / cc commercially available with DuPont Dow Elastomers was used. LLC, under the registered trade designation of polyolefin elastomer Engage 8100, an azodicarboamide blowing agent commercially available with the Uniroyal Chemical Company under the registered trade designation of blowing agent Celogen AZ 130, the activator of zinc oxide blowing agent commercially available with CP Hall Chemical Inc. Engage 8100 polyolefin elastomer, Celogen AZ 130 blowing agent, and zinc oxide were weighed and mixed in a commercially available mixer with the Farrel Corporation under the registered trade designation Banbary BR at 100 ° C. 120 ° C for 3 minutes. 4,4'-Oxybis (benzenesulfonyl azide) CAS # [7456-68-01] was added and mixed for an additional 3 minutes. The mixture was then laminated in a roller mill which was heated to 80 ° C in a thick sheet of 1/4 inch thick (0.63 centimeters). The method of Example 7 was repeated for Comparative Sample F, except that 20.2 grams of 40 percent active dicumyl peroxide were used in clay commercially available with the Hercules Corporation under the registered commercial designation of peroxide DiCup 40 KE, instead of the poly (sulfonyl azide).

Table 3. Foam formulation Process for Making the Foam for Example 7; The coarse coarse sheet was cut by resulting roll into cubic pieces of approximately 0.25 x 0.25 x 0. 25 inches (0.635 x 0.635 x 0.635 centimeters). Then about 12 grams of these cut pieces were weighed and placed in a slot (a mold frame) with an opening of 1 inch (2.54 centimeters) in diameter and 1/4 inch (0.635 centimeters) in thickness. The mold frame was then placed into a compression molding press at 120 ° C with 25,000 pounds (111,205 Newtons) of applied pressure for 20 minutes. The plate was then foamed at 180 ° C with an applied pressure of 50,000 pounds of force (222,410 Newtons) for 7 minutes. The press was opened and the foam expanded.

Process for Making Foam for Comparative Sample F: The procedure of Example 7 was repeated, except that the thick sheet resulting from Comparative Sample F was used and the foaming temperature was 160 ° C for 9 minutes instead of 180 ° C for 7 minutes. The density of the foam was measured at 20 ° C, in accordance with ASTM D 792-86, using isopropanol as a liquid medium. The size of the cell was determined by scanning electron microscopy.

Table 4. Properties of the Foams of Example 7 and Comparative Sample F Good quality, low density foam (8.39 lb / ft3) (136 kg / m3) and small cell size (0.175 millimeters in diameter) was achieved using the poly (sulfonyl azide) in Example 7. The foam was very flexible , firm, and resilient (based on the sample that was squeezed, folded and manually torn). The data in Table 4 indicate that the foam that was made from the elastomer that was prepared using the single site catalyst and a poly (sulfonyl azide) crosslinking agent, in accordance with the practice of the invention, had a size of cell much smaller than the corresponding Comparative Sample F which was cross-linked using the peroxide. The smaller cell size of Example 7 had more desirable foam properties, such as a lower hardness that was measured in accordance with the procedures of ASTM D2240-91, higher tear strength in accordance with ASTM D-procedures. 3574 (Test F), higher tensile strength and greater elongation, which was measured in accordance with the procedures of ASTM D-1708, and lower compression setting that was measured in accordance with the procedures of ASTM D-395 (50 ° C, 50 percent compression, 6 hours) than the larger cell size foam of Comparative Sample F. The foam of Comparative Sample F also had an undesirable odor that is believed to be the result of decomposition products. of peroxide. The foam of Example 7, in contrast, was odorless, which is desirable for applications such as footwear foam, foam for building construction, and foams for automobile interiors.

Example 8 and Comparative Sample G: The procedure of Example 7 was repeated for Example 8, except that a large coarse sample (185 grams) and a slot with an opening of 6 x 6 x 0.5 inches (0.15 x 0.15) were used. x 0.013 m). The procedure of Comparative Sample F for Comparative Sample G was repeated, except that a large coarse sample (185 grams) and a slot with an opening of 6 x 6 x 0.5 inches (0.15 x 0.15 x 0.013 m) were used. . The properties of the foams of Example 8 and Comparative Sample G were measured and recorded in Table 5.

Table 5. Properties of the Foams of Example 8 and the Comparative Sample G The data in Table 5 indicate that the foam that was made from an elastomer that was prepared using a single site catalyst and a poly (sulfonyl azide) crosslinking agent, in accordance with the practice of the invention, had a lower hardness (it is more flexible), a lower density, a greater firmness, and a greater resilience than Comparative Sample G that was cross-linked using peroxide.

Claims

1. A process comprising (a) forming a polymer blend including at least one polyolefin, which has been prepared using a single site catalyst and at least one crosslinking amount of at least one poly (sulfonylazide) crosslinking agent; (b) shaping the resulting mixture; and (c) heating the resulting formed mixture to a temperature of at least the decomposition temperature of the crosslinking agent.

2. The process according to claim 1, wherein in step (b), the polymer blend is in a softened or molten condition to form it; wherein step (b) comprises thermoforming, compression molding, injection molding, extrusion, casting, blow molding, blow molding, profile extrusion, rotation, other molding or combinations thereof; wherein step (c) comprises foaming; wherein step (a) includes forming a foamable molten polymer material by mixing and heating a corruptible chemical blowing agent and other components of the polymer blend; and step (b) includes extruding the foamable molten polymer material through a die; wherein step (a) comprises the substrates of (i) suspending discrete polyolefin particles in a liquid medium in which they are insoluble, (ii) impregnating the particles with a crosslinking amount of the poly (sulfonyl azide) crosslinking agent and a blowing agent at superatmospheric pressure and a temperature above the softening point of the polymer; and step (b), (c) or a combination thereof, includes (iii) rapidly discharging the particles in at a lower pressure than in sub-step (ii), to form pellets or (iv) cooling the particles and expanding them subsequently with at least one heated gas; wherein step (a) includes mixing at least one polyolefin, a crosslinking amount of a poly (sulfonyl azide) crosslinking agent, and a chemical blowing agent, to form a mixture; step (b) comprises a first sub-step forming a thick sheet of the mixture; step (c) includes heating the mixture in a mold, so that the crosslinking agent crosslinks the polymer material and the blowing agent decomposes; and either step (b) or (c) or a combination thereof, includes the expansion of the thick sheet that formed in the first sub-step of step (b) by releasing the pressure in the mold; or wherein step (b) comprises a first sub-step of forming a sheet of the polymer mixture containing a cross-linking amount of the cross-linking agent of poly (sulfonyl azide); step (c) comprises heating the sheet enough to result in crosslinking; step (b) further includes a second sub-step of impregnation of the sheet with N2 at a temperature above the softening point of the polymer and at a pressure and a third sub-step of pressure release to result in the nucleation of the bubbles and some expansion in the plate.

3. The process in accordance with the claim 1, wherein the crosslinking agent is introduced into the polymer mixture in an extruder or other fusion processing equipment.

4. The process according to claim 1, wherein the single site catalyst is a restricted geometry or metallocene catalyst.

5. The process according to claim 1, wherein at least one polyolefin is a polyethylene homopolymer; an ethylene copolymer which also has at least one alpha olefin comonomer selected from monomer of from 3 to 20 carbon atoms; an elastomeric polymer; an ethylene / olefin / diene terpolymer or interpolymer; a substantially linear ethylene polymer, wherein at least one polyolefin has a molecular weight distribution of less than about 3.5, or a combination thereof. The process according to claim 1, wherein the polymer blend is a combination comprising at least about 5 weight percent of at least one polyolefin that is manufactured using a single-site catalyst and at least one other polymer, which differs from the polyolefin because it has a different density, a different molecular weight, a different catalyst used in the polymerization, a different chemical composition or combinations thereof. The process according to claim 1, wherein at least one poly (sulfonyl azide) has an XRX structure, wherein each X is S02N3 and R represents an unsubstituted or substituted hydrocarbyl, hydrocarbyl ether or a group that contains silicon; wherein the poly (sulfonyl azide) has at least 3 and less than about 50 carbon atoms, silicon or oxygen between the sulfonyl azide groups; and wherein R includes at least one aryl group between the sulfonyl groups and wherein the poly (sulfonyl azide) is present in an amount greater than about 0.5 weight percent, based on the total weight of the polymer blends and wherein the agent of crosslinking and the polyolefin react at a temperature of at least the decomposition temperature and greater than about 185 ° C. 8. A composition obtainable by the process of any of claims 1-7. 9. An article that is manufactured from a composition of claim 8. 10. A use of any of the compositions of claim 9 in any process of thermoforming, injection molding, extrusion, casting, blow molding, rotation, blown, profile extrusion, foaming, compression molding or a combination thereof.