Patent Publication Number: US-2003232933-A1

Title: Reactive blend ploymer compositions with thermoplastic polyurethane

Description:
FIELD OF THE INVENTION  
       [0001] The present invention relates to reactive blends of polymers made by melt blending and reacting a polymer having a hydroxyl, carboxylic acid, amine, amide, enamine, oxazolidine, epoxide, urethane, thioisocyanate, isocyanate, carbon dioxide, imine, thiol, acrylic, maleic anhydride, imide or ester functionality in the polymer with a thermoplastic polyurethane (TPU) polymer. The blending and reacting is accomplished by melt mixing the polymer to be reacted with a TPU in the presence of an isocyanate to form the polymer blend composition. The reactive blending may also be performed as the TPU is being made by adding the polymer to the TPU reaction mixture prior to reaction completion. This invention also relates to the process of reactive blending and articles made from the reactive blend polymers. Processes to compatibilize two or more normally immiscible TPU polymers are also disclosed. The compound formed via reactive blending can also be used to compatibilize immiscible polymer blends.  
       BACKGROUND OF THE INVENTION  
       [0002] It is known that various polymers can be blended, such as by melt mixing, to achieve a combination of desired properties. If the two polymers can be rendered compatible, the physical properties achieved by the blend should be proportional to the levels of the individual polymers in the blend. When the two polymers used in the blend are less miscible or not compatible with each other, the blend will frequently have physical properties that are inferior to those exhibited by either polymer used alone.  
       [0003] For a blend of polymers to have higher physical properties, such as tensile strength, than either polymers alone, there must be a synergistic result.  
       [0004] Blends of polymers are desired to achieve a certain desirable physical or chemical property. Some polymers that exhibit certain excellent characteristics, such as weathering resistance, might be blended with a second polymer that exhibits poor weathering properties to improve the second polymer&#39;s weatherability. The concept of blending is frequently used to improve a certain polymer&#39;s performance while retaining other good features of the polymer. The practice of blending will usually involve some trade-off in properties, i.e., some properties will be improved while other properties are harmed.  
       [0005] Sometimes the trade-off in properties can be solved by making copolymers where different monomers are copolymerized together to make one polymer having the desired properties. This approach requires that the monomers be copolymerizable with each other and copolymers are usually more expensive than homopolymers.  
       [0006] It would be desirable to have an inexpensive method to reactive blend a TPU polymer with a second polymer, to achieve unusual property enhancement. TPU polymers can have low melt strength, which can sometimes make them difficult to process. It would be desirable to increase the melt viscosity of a TPU composition to improve melt processing, particularly when melt processed by extrusion equipment.  
       BRIEF SUMMARY OF THE INVENTION  
       [0007] It is an object of the present invention to make a reactive blend composition of polymers with a thermoplastic polyurethane (TPU) polymer and at least one blend partner polymer which is capable of being chemically bonded with the TPU polymer by using an isocyanate-containing compound.  
       [0008] It is another object of the present invention to react a TPU polymer with at least one blend partner polymer having a hydroxyl, carboxylic acid, amine, amide, enamine, oxazolidine, epoxide, urethane, thioisocyanate, isocyanate, carbon dioxide, imine, thiol, acrylic, maleic anhydride, imide, ester or other isocyanate-reactive functional group present in said blend partner polymer.  
       [0009] It is a further object of the present invention to make a reactive blend of a TPU polymer and a blend partner polymer whereby the ultimate tensile strength of the reactive blend is greater than either the TPU polymer or the blend partner polymer when used alone.  
       [0010] It is another object of the present invention to provide a process for reacting a TPU polymer and a blend partner polymer.  
       [0011] It is another object of the present invention to provide articles made from reactive blends.  
       [0012] It is a further object of the present invention to provide a method to compatibilize two or more TPU polymers, which otherwise are not miscible with each other and to compatibilize TPU and non-TPU polymers.  
       [0013] These and other objects are accomplished by melt mixing the TPU polymer and at least one polyisocyanate compound with at least one blend partner polymer having a functional group that is capable of reacting with an isocyanate moiety or isocyanate-containing compound, where the polyisocyanate compound also reacts with the TPU polymer to chemically bond the TPU polymer and the blend partner polymer. The blend polymer preferably has a functionality group selected from the group consisting of hydroxyl, carboxylic acid, amine, amide, and ester.  
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0014] The first essential ingredient of the composition of this invention is at least one thermoplastic polyurethane (TPU for short) polymer.  
       [0015] TPU Polymer  
       [0016] The TPU polymer type used in this invention can be any conventional TPU polymer that is known to the art and in the literature. The TPU polymer is generally prepared by reacting a diisocyanate with an intermediate such as a hydroxyl terminated polyester, a hydroxyl terminated polyether, a hydroxyl terminated polycarbonate or mixtures thereof, with one or more chain extenders, all of which are well known to those skilled in the art.  
       [0017] The hydroxyl terminated polyester intermediate is generally a linear polyester having a number average molecular weight (Mn) of from about 500 to about 10,000, desirably from about 700 to about 5,000, and preferably from about 700 to about 4,000, an acid number generally less than 1.3 and preferably less than 0.8. The molecular weight is determined by assay of the terminal functional groups and is related to the number average molecular weight. The polymers are produced by (1) an esterification reaction of one or more glycols with one or more dicarboxylic acids or anhydrides or (2) by transesterification reaction, i.e., the reaction of one or more glycols with esters of dicarboxylic acids. Mole ratios generally in excess of more than one mole of glycol to acid are preferred so as to obtain linear chains having a preponderance of terminal hydroxyl groups. Suitable polyester intermediates also include various lactones such as polycaprolactone typically made from ε-caprolactone and a bifunctional initiator such as diethylene glycol. The dicarboxylic acids of the desired polyester can be aliphatic, cycloaliphatic, aromatic, or combinations thereof. Suitable dicarboxylic acids which may be used alone or in mixtures generally have a total of from 4 to 15 carbon atoms and include: succinic, glutaric, adipic, pimelic, suberic, azelaic, sebacic, dodecanedioic, isophthalic, terephthalic, cyclohexane dicarboxylic, and the like. Anhydrides of the above dicarboxylic acids such as phthalic anhydride, tetrahydrophthalic anhydride, or the like, can also be used. Adipic acid is the preferred acid. The glycols which are reacted to form a desirable polyester intermediate can be aliphatic, aromatic, or combinations thereof, and have a total of from 2 to 12 carbon atoms, and include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 2,2-dimethyl-1,3-propanediol, 1,4-cyclohexanedimethanol, decamethylene glycol, dodecamethylene glycol, hydroquinone di(hydroxyethyl)ether and the like, 1,4-butanediol is the preferred glycol.  
       [0018] Hydroxyl terminated polyether intermediates are polyether polyols derived from a diol or polyol having a total of from 2 to 15 carbon atoms, preferably an alkyl diol or glycol which is reacted with an ether comprising an alkylene oxide having from 2 to 6 carbon atoms, typically ethylene oxide or tetrahydrofuran or mixtures thereof. For example, hydroxyl functional polyether can be produced by first reacting propylene glycol with propylene oxide followed by subsequent reaction with ethylene oxide. Primary hydroxyl groups resulting from ethylene oxide are more reactive than secondary hydroxyl groups and thus are preferred. Useful commercial polyether polyols include poly(ethylene glycol) comprising ethylene oxide reacted with ethylene glycol, poly(propylene glycol) comprising propylene oxide reacted with propylene glycol, poly(tetramethylene glycol) comprising water reacted with tetrahydrofuran (PTMEG). PTMEG is the preferred polyether intermediate. Polyether polyols further include polyamide adducts of an alkylene oxide and can include, for example, a N,N 1 -dimethyl ethylenediamine adduct comprising the reaction product of ethylenediamine and propylene oxide, diethylenetriamine adduct comprising the reaction product of diethylenetriamine with propylene oxide, and similar polyamide type polyether polyols. Copolyethers can also be utilized in the current invention. Typical copolyethers include the reaction product of THF and ethylene oxide or THF and propylene oxide. These are available from BASF as Poly THF B, a block copolymer, and poly THF R, a random copolymer. The various polyether intermediates generally have a number average molecular weight (Mn), as determined by assay of the terminal functional groups which is an average molecular weight, of from about 250 to about 10,000, desirably from about 500 to about 5,000, and preferably from about 700 to about 3,000.  
       [0019] The polycarbonate-based polyurethane resin of this invention is prepared by reacting a diisocyanate with a blend of a hydroxyl terminated polycarbonate and a chain extender. The hydroxyl terminated polycarbonate can be prepared by reacting a glycol with a carbonate or phosgene.  
       [0020] U.S. Pat. No. 4,131,731 is hereby incorporated by reference for its disclosure of hydroxyl terminated polycarbonates and their preparation. Such polycarbonates are linear and have terminal hydroxyl groups with essential exclusion of other terminal groups. The essential reactants are glycols and carbonates. Suitable glycols are selected from cycloaliphatic and aliphatic diols containing 4 to 40, and preferably 4 to 12 carbon atoms, and from polyoxyalkylene glycols containing 2 to 20 alkoxy groups per molecular with each alkoxy group containing 2 to 4 carbon atoms. Diols suitable for use in the present invention include aliphatic diols containing 4 to 12 carbon atoms such as butanediol-1,4, pentanediol-1,4, neopentyl glycol, hexanediol-1,6, 2,2,4-trimethylhexanediol-1,6, decanediol-1,10, hydrogenated dilinoleylglycol, hydrogenated dioleylglycol; and cycloaliphatic diols such as cyclohexanediol-1,3, dimethylolcyclohexane-1,4, cyclohexanediol-1,4, dimethylolcyclohexane-1,3, 1,4-endomethylene-2-hydroxy-5-hydroxymethyl cyclohexane, and polyalkylene glycols. The diols used in the reaction may be a single diol or a mixture of diols depending on the properties desired in the finished product.  
       [0021] Polycarbonate intermediates which are hydroxyl terminated are generally those known to the art and in the literature. Suitable carbonates are selected from alkylene carbonates composed of a 5 to 7 membered ring having the following general formula:  
                 
 
       [0022] where R is a saturated divalent radical containing 2 to 6 linear carbon atoms. Suitable carbonates for use herein include ethylene carbonate, trimethylene carbonate, tetramethylene carbonate, 1,2-propylene carbonate, 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-ethylene carbonate, 1,3-pentylene carbonate, 1,4-pentylene carbonate, 2,3-pentylene carbonate, and 2,4-pentylene carbonate.  
       [0023] Also, suitable herein are dialkylcarbonates, cycloaliphatic carbonates, and diarylcarbonates. The dialkylcarbonates can contain 2 to 5 carbon atoms in each alkyl group and specific examples thereof are diethylcarbonate and dipropylcarbonate. Cycloaliphatic carbonates, especially dicycloaliphatic carbonates, can contain 4 to 7 carbon atoms in each cyclic structure, and there can be one or two of such structures. When one group is cycloaliphatic, the other can be either cycloaliphatic, alkyl or aryl. On the other hand, if one group is aryl, the other can be aryl, alkyl or cycloaliphatic. Preferred examples of diarylcarbonates, which can contain 6 to 20 carbon atoms in each aryl group, are diphenylcarbonate, ditolylcarbonate, and dinaphthylcarbonate.  
       [0024] The reaction is carried out by reacting a glycol with a carbonate, preferably an alkylene carbonate in the molar range of 10:1 to 1:10, but preferably 3:1 to 1:3 at a temperature of 100° C. to 300° C. and at a pressure in the range of 0.1 to 300 mm of mercury in the presence or absence of an ester interchange catalyst, while removing low boiling glycols by distillation.  
       [0025] More specifically, the hydroxyl terminated polycarbonates are prepared in two stages. In the first stage, a glycol is reacted with an alkylene carbonate to form a low molecular weight hydroxyl terminated polycarbonate. The lower boiling point glycol is removed by distillation at 100° C. to 300° C., preferably at 150° C. to 250° C., under a reduced pressure of 10 to 30 mm Hg, preferably 50 to 200 mm Hg. A fractionating column is used to separate the by-product glycol from the reaction mixture. The by-product glycol is taken off the top of the column and the unreacted alkylene carbonate and glycol reactant are returned to the reaction vessel as reflux. A current of inert gas or an inert solvent can be used to facilitate removal of by-product glycol as it is formed. When amount of by-product glycol obtained indicates that degree of polymerization of the hydroxyl terminated polycarbonate is in the range of 2 to 10, the pressure is gradually reduced to 0.1 to 10 mm Hg and the unreacted glycol and alkylene carbonate are removed. This marks the beginning of the second stage of reaction during which the low molecular weight hydroxyl terminated polycarbonate is condensed by distilling off glycol as it is formed at 100° C. to 300° C., preferably 150° C. to 250° C. and at a pressure of 0.1 to 10 mm Hg until the desired molecular weight of the hydroxyl terminated polycarbonate is attained. Molecular weight (Mn) of the hydroxyl terminated polycarbonates can vary from about 500 to about 10,000 but in a preferred embodiment, it will be in the range of 500 to 2500.  
       [0026] Suitable extender glycols (i.e., chain extenders) are lower aliphatic or short chain glycols having from about 2 to about 10 carbon atoms and include for instance ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, 1,4-butanediol, 1,6-hexanediol, 1,3-butanediol, 1,5-pentanediol, 1,4-cyclohexanedimethanol, hydroquinone di(hydroxyethyl) ether, neopentyglycol, and the like, with 1,4-butanediol being preferred.  
       [0027] The desired TPU polymer used as the TPU for the reactive blend composition of this invention is generally made from the above-noted intermediates such as a hydroxyl terminated polyesters, polyether, or polycarbonate, preferably polyester, which is further reacted with a polyisocyanate, preferably a diisocyanate, along with extender glycol desirably in a so-called one-shot process or simultaneous coreaction of polyester, polycarbonate or polyether intermediate, diisocyanate, and extender glycol to produce a high molecular weight linear TPU polymer. The preparation of the macroglycol is generally well known to the art and to the literature and any suitable method may be used. The weight average molecular weight (Mw) of the TPU polymer is generally about 10,000 to 500,000, and preferably from about 90,000 to about 250,000. The equivalent weight amount of diisocyanate to the total equivalent weight amount of hydroxyl containing components, that is the hydroxyl terminated polyester, polyether, or poycarbonate, and chain extender glycol, is from about 0.95 to about 1.10, desirably from about 0.96 to about 1.02, and preferably from about 0.97 to about 1.005. Suitable diisocyanates include aromatic diisocyanates such as: 4,4′-methylene bis-(phenyl isocyanate) (MDI); m-xylylene diisocyanate (XDI), phenylene-1,4-diisocyanate, naphthalene-1,5-diisocyanate, diphenylmethane-3,3′-dimethoxy-4,4′-diisocyanate and toluene diisocyanate (TDI); as well as aliphatic diisocyanates such as isophorone diisocyanate (IPDI), 1,4-cyclohexyl diisocyanate (CHDI), decane-1,10-diisocyanate, and dicyclohexylmethane-4,4′-diisocyanate. The most preferred diisocyanate is 4,4′-methylene bis(phenyl isocyanate), i.e., MDI.  
       [0028] In the one-shot polymerization process which generally occurs in-situ, a simultaneous reaction occurs between three components, that is the one or more intermediates, the one or more polyisocyanates, and the one or more extender glycols, with the reaction generally being initiated at temperatures of from about 100° C. to about 200° C. Inasmuch as the reaction is exothermic, the reaction temperature generally increases to about 220° C.-250° C.  
       [0029] The level of TPU polymer used in the reactive blend composition of this invention is from about 20 to about 95 weight parts based on 100 weight parts of the total weight of the TPU polymer and the blend partner polymer. Preferably the level of TPU polymer is from about 35 to about 85 weight parts. More preferably from about 50 to about 80 weight parts. A single TPU polymer can be used or a blend of two or more TPU polymers can be used to make the reactive blend composition of this invention. For most applications, it is preferred to use a single TPU polymer in the reactive blend composition. The selection of the particular TPU(s) used will depend on the desired end product application. TPU properties such as type of TPU (i.e., ester or ether), molecular weight, melting point and hardness are chosen depending on the end use application, as is well understood to those skilled in the art.  
       [0030] TPU polymers which are suitable for use in this invention are commercially available from several manufacturers such as Noveon, Inc., Dow Chemical, Huntsman Chemical, BASF and Bayer. Post industrial and post consumer recycle TPU may also be used in the compositions of this invention.  
       [0031] Blend Partner Polymer  
       [0032] The composition of the present invention comprises at least one blend partner polymer having a functionality group capable of reacting with an isocyanate compound. Examples of functional groups capable of reacting with an isocyanate include hydroxyl, carboxylic acid, amine, amide, enamine, oxazolidine, epoxide, urethane, thioisocyanate, isocyanate, carbon dioxide, imine, thiol, acrylic maleic anhydride, imide or ester. Polymers which have hydroxyl groups include polyvinyl alcohol (PVOH) polymers, hydroxy ethyl methacrylate polymers and its copolymers, ethylene vinylalcohol (EVOH) polymers, polyoxymethylene (POM) polymers, copolyesters, copolyamides, poly(acrylate), and poly(alkyl acrylate). An example of a polymer which contains carboxyl groups is polyacrylic acid polymers. An example of a polymer which contains an amine group is Nylon-6,6 polymers. An example of a polymer which contains an amide group is polyvinyl pyrrolidone (PVP) polymers. Ester groups are found in poly(ethylene-co-vinyl acetate) (EVA) polymers and poly(vinyl acetate) (PVAc) polymers. EVA is a preferred blend partner polymer. The blend partner polymer should contain greater than 2 mole percent of the repeat unit containing the functional group, preferably greater than 5 mole percent and more preferably greater than 10 mole percent of the repeat unit containing the functional group capable of reacting with an isocyanate.  
       [0033] The EVA used as the blend partner polymer in this invention has from about 2 to about 50 weight percent vinyl acetate, preferably 10-45 weight percent vinyl acetate, and more preferably from 18-33 weight percent vinyl acetate. The particular choice of the vinyl acetate content of the EVA will depend on the desired properties of the reactive blend composition.  
       [0034] The level of blend partner polymer used in the reactive blend composition of this invention is from about 5 to about 80 weight parts based on 100 weight parts of the total weight of the TPU polymer and the blend partner polymer. Preferably, the level of blend partner polymer is from about 15 to about 65 weight parts. More preferably, from about 20 to about 50 weight parts of blend partner polymer is used in the reactive blend composition. A single blend partner polymer can be used or a blend of two or more blend partner polymers can be used to make the reactive blend composition of this invention. For most applications, it is preferred to use a single blend partner polymer in the reactive blend composition of this invention. The selection of the particular blend partner polymer used will depend on the desired end product application. Blend partner polymer properties such as flame and smoke resistance, melt processing properties, solvent resistance, weathering properties, and heat distoration temperature are chosen depending on the end use application, as is well understood to those skilled in the polymer art.  
       [0035] The term “blend partner” as used in this specification, refers to a polymer, other than a miscible TPU polymer, which is capable of reacting with an isocyanate. TPU polymers have functional groups, such as hydroxyl, which can react with an isocyanate. It is not intended that the blend partner be a miscible TPU polymer. However, the blend partner polymer may be a TPU polymer which is not miscible with the other TPU polymer used. For example, if a polyester based TPU polymer is used, the blend partner polymer can be a polyether TPU polymer.  
       [0036] In the normal prior art method of melt blending, a polyester TPU polymer is not miscible with a polyether TPU polymer. However, by using the reactive blending process of this invention, the polyester and polyether TPU polymers can be reactive blended to form useful polymers.  
       [0037] Isocyanate Compound  
       [0038] The isocyanate compound used in the reactive blend composition of this invention is one which will react the TPU polymer with the blend partner polymer under melt mixing conditions to form the composition of this invention. Suitable isocyanates are polyisocyanates, preferably diisocyanates. Suitable diisocyanates include aromatic diisocyanates such as: 4,4′-methylene bis-(phenyl isocyanate) (MDI); m-xylylene diisocyanate (XDI), phenylene-1,4-diisocyanate, naphthalene-1,5-diisocyanate, diphenylmethane-3,3′-dimethoxy-4,4′-diisocyanate and toluene diisocyanate (TDI); as well as aliphatic diisocyanates such as isophorone diisocyanate (IPDI), 1,4-cyclohexyl diisocyanate (CHDI), decane-1,0-diisocyanate, and dicyclohexylmethane-4,4′-diisocyanate. Dimers and trimers of the above diisocyanate may also be used. The most preferred diisocyanate is 4,4′-methylene bis(phenyl isocyanate), i.e., MDI.  
       [0039] The polyisocyanate used in the reactive blend compositions of this invention may be in the form of a low molecular weight polymer or oligomer which is end capped with an isocyanate. For example, the hydroxyl terminated intermediate described above may be reacted with an isocyanate-containing compound to create a low molecular weight polymer end capped with isocyanate. In the TPU art, such materials are normally referred to as pre-polymers. Such pre-polymers normally have a number average molecular weight (Mn) of from about 500 to about 10,000.  
       [0040] Polyisocyanates having a functionality greater than 2.0, such as triisocyanates, may be used in sufficient amounts, especially if a crosslinked thermoset reactive blend composition is desired.  
       [0041] The level of polyisocyanate used in the composition of this invention is from about 0.1 to about 4.0 weight parts based on 100 weight parts of the combined weight of the TPU polymer and the blend partner polymer. The level and functionality of polyisocyanate used will determine whether a thermoplastic or thermoset reactive blend composition is produced. Above about 2 weight parts of polyisocyanate, the reactive blend composition becomes more like a thermoset in that it is more viscous and more difficult to melt process once the blend has reacted. At levels of about 4 weight parts of polyisocyanate, the reactive blend becomes a thermoset, even if a diisocyanate is used. If thermoplastic compositions are desired, the level of polyisocyanate used is from about 0.1 to about 2.0 weight parts. One or two or more different polyisocyanate may be used. Preferably, one polyisocyanate is used. Preferably, for a thermoplastic blend, the level of polyisocyanate used is from about 0.5 to about 1.75 weight parts and more preferably from about 0.75 to about 1.25 weight parts. The levels of polyisocyanate referred to in this paragraph are the levels added to the reactive blend and does not include the polyisocyanate which is used in making the base TPU polymer.  
       [0042] Reactive Processes  
       [0043] To produce the reactive blend compositions of this invention, the three essential ingredients [i.e., (1) at least one TPU polymer; (2) at least one blend partner polymer; and (3) at least one polyisocyanate] are reacted by melt blending. Any melt blending process known in the art and literature may be used to perform the reaction. Suitable processes include melt blending in a single screw extruder, a twin screw extruder, on a two roll mill, a screw feeding injection molding machine, or in an internal mixture such as a Banbury mixer. Preferably, an extruder is used to melt blend the ingredients to form the reactive blend composition. The process will be further described using the preferred extrusion process.  
       [0044] The polymer components (TPU and blend partner) are preferably fed to the extruder in pellet form, as is commercially available. The polyisocyanate can be fed in liquid or solid form (granulates or flakes) to the extruder. The mixing temperature of the melt in the extruder will be a temperature sufficient to melt the polymers such that they can be processed through an extruder. The exact temperature used will depend on the melt processing temperature of the highest melting point polymers used in the blend. Melt processing temperatures for a TPU/EVA blend will be from about 150° C. to about 250° C., preferably from about 170° C. to about 200° C., depending on the particular TPU and EVA used, as can be well understood by those skilled in the art of polymer blending. The ingredients are in the extruder for a very short time such as from about 5 seconds to about five minutes. The reaction does not need to be completed within the extruder, as it will continue after exiting the extruder. When blending a TPU with EVA, it is not necessary to pre-dry the polymers before reactive blending. The moisture in the atmosphere can go inside the pellets produced and the reaction can continue.  
       [0045] An alternate process to produce the reactive blend composition of this invention is to add the blend partner polymer in the process of making the TPU polymer. In this alternative process, the TPU precursor ingredients, i.e., (diisocyanate, hydroxyl terminated intermediate, and chain extender) are added to an extruder and the blend partner polymer is added to the extruder, much like a compounding ingredient. The level of polyisocyanate used is in excess of that required to produce the TPU polymer. The equivalent weight of polyisocyanate to the total equivalent weight amount of hydroxyl containing compounds, i.e., the hydroxyl terminated intermediate and chain extender is about 1.0 to produce the TPU polymer. From about 0.1 to about 4.0 weight parts based on 100 weight parts of the combined weight of the TPU polymer precursors and the blend partner polymer, of polyisocyanate is used in excess of the 1.0 equivalent weight to produce the TPU polymer. The excess polyisocyanate may be added with the blend partner polymer or with the TPU polymer precursor ingredients. The preferred alternate process is the one-shot process described above in this specification. The TPU polymer is substantially formed before the blend partner polymer is added. The TPU polymer should be at least 80% reacted, and preferably 90% reacted before the blend partner is added. The reaction to form the TPU polymer will continue to completion in the presence of the blend partner polymer. To allow the TPU polymer to be substantially reacted before addition of the blend partner polymer, the blend partner polymer is added down-stream in the extruder nearer the exit (die) end of the extruder. For example, in an extruder having four heat zones and entry ports, the blend partner polymer would be added in zone 3 or zone 4, whereas the TPU reactants would be added in zone 1. The alternate process may include any of the normal well known processes to make TPU polymer with the exception that a blend partner polymer is added to the normal TPU process.  
       [0046] After exiting the extruder, the reactive blend composition is normally pelletized and stored as is typical for TPUs and is ultimely sold in pellet form. It being understood that the composition would not always need to be pelletized, but rather could be extruded directly from the reaction extruder through a die into a final product profile.  
       [0047] Other Ingredients  
       [0048] The reactive blend compositions may contain other ingredients which are customary in polymer compositions. Ingredients such as flame retardants, colorants, antioxidants, antiozonates, light stabilizers, fillers, foaming agents, and the like may be used. The level of the other ingredients may be from 0 to about 100 weight parts based on 100 weight parts of the total weight of the TPU and blend partner polymer, depending on the desired end use application. If other ingredients are used, they may be mixed into the composition in the reactive melt blend or they may be added post-reaction in a compounding step. Compounding ingredients into polymer formulations is a well known art understood by those skilled in the art. Melt mixing equipment such as extruders, two roll mills, Banbury mixers and the like, may be used in the compounding step.  
       [0049] Flame retardants are particularly desirable ingredients to add to the compositions of this invention. Suitable flame retardants include melamine, melamine cyanurate, melamine borate, melamine phosphate, melamine derivatives, organic phosphates, organic phosphonates, halogenated compounds, and mixture thereof. Flame retardants are usually necessary for wire and cable end use applications. The level of flame retardants used for wire and cable jacketing is from about 10 to about 50 weight parts per 100 weight parts of the total weight of the TPU and blend partner polymer.  
       [0050] Uses  
       [0051] The reactive blend compositions of this invention have many uses where polymer compositions are currently used. Articles may be extruded into various profiles and shapes such as sheet, film, pipe, and other shaped articles. The compositions may be molded by injection molding, transfer molding or compression molding. The compositions may be calendered into sheet and film using conventional calendering equipment.  
       [0052] The reactive blend compositions may be used to compatibilize two or more immiscible polymers by proper selection of the blend partner polymer used. For example, the TPU/EVA reactive blend can be used to compatibilize TPU and polyethylene. The EVA component of the reactive blend is compatible with polyethylene. Likewise, the TPU/EVA reactive blend can compatibilize a blend of polyvinyl chloride (PVC) and polyethylene polymers, since the TPU component is compatible with PVC and the EVA component is compatible with polyethylene. PVC and polyethylene are normally immiscible when melt blended. As can be well understood by those skilled in the art, the proper selection of the blend partner polymer can allow numerous immiscible polymers to be compatibilized, by following the teachings of this disclosure.  
       [0053] When used as a compatiblizer for two or more immiscible polymers, the reactive blend composition is used at a level of from about 0.2 weight parts to about 20 weight parts, preferably about 2.0 to about 15.0 weight parts and more preferably about 5.0 to about 10.0 weight parts, based on 100 weight parts of the combined weight of the two or more immiscible polymers.  
       [0054] A particular desirable use for the TPU/EVA reactive blend is in wire and cable applications, such as jacketing for wire and cable. Wire and cable construction will have one or usually multiple metal conductors, such as wires. The metal conductors are insulated with a non conductive polymer. The complete package of insulated conductors are encased in a jacketing material. The TPU/EVA reactive blend increases the melt viscosity (melt strength) over a straight TPU polymer, such that processing is improved. Quite surprisingly, the TPU/EVA reactive blend composition has significantly greater tensile strength, as measured according to ASTM D412, than either the TPU polymer or the EVA polymer, when measured alone.  
       [0055] The invention will be better understood by reference to the following examples. 
     
    
    
     EXAMPLES  
     [0056] Examples 1-14 are presented to show the present invention in the embodiment of a reactive blend of TPU polymer and EVA as the blend partner polymer. Examples 1-3, 5-6, 8, 10-11 and 15-16 are comparative examples. The composition of each example was run through an extruder to melt mix the composition. A twin screw corotative extruder from Werner &amp; Pfleider, type ZSK 25 WLE with a screw diameter of 25 mm and a barrel length of 44 cm was used. The polymer components of the composition were fed to the extruder in pellet form and the polyisocyanate, when used, was fed to the extruder as a solid. The extruder was operated at a temperature of 190° C. and an RPM of 400 and a feed rate of 20 Kg per hour. The output of the extruder was pelletized and sample test specimens were molded from the pellets.  
     [0057] The test samples from each example were tested for ultimate tensile strength and ultimate elongation according to ASTM D 412. Abrasion loss was tested according to DIN 53516. The melt flow (MVR) was tested for Examples 1-9 according to ASTM D1238 at 210° C. under 8.7 Kg load.  
     [0058] The test results for the examples are shown in Table I below.  
     Example 1 (Comparative)  
     [0059] Example 1 is a comparative example to evaluate the physical properties of a polyester based TPU polymer. The TPU polymer used is Estane® 58213 available from Noveon, Inc. of Cleveland, Ohio U.S.A.  
     Example 2 (Comparative)  
     [0060] Example 2 is a comparative example to evaluate the physical properties of an EVA polymer. The EVA polymer used is Alcudia PA 538 available from Repsol YPF and has a vinyl acetate content of 18 wt. %.  
     Example 3 (Comparative)  
     [0061] Example 3 is a comparative example to evaluate the physical properties of a non-reactive melt blend of 70 weight parts TPU and 30 weight parts EVA. The TPU used is the same TPU as in Example 1 and the EVA is the same EVA as in Example 2.  
     Example 4  
     [0062] Example 4 is to show that the same composition (70% TPU/30% EVA) of Example 3 when made into a reactive blend by adding 1.0 weight part per 100 weight parts of total polymer (TPU &amp; EVA) of a polyissocyanate (MDI) has improved tensile strength and abrasion resistance over either the TPU of Example 1 or the EVA of Example 2 or the non-reactive blend of Example 3 and has higher melt viscosity than the TPU alone of Example 1.  
     Example 5 (Comparative)  
     [0063] Example 5 is a comparative example to evaluate the physical properties of a polyether based TPU polymer. The TPU polymer used is Estane® 5714 available from Noveon, Inc. of Cleveland, Ohio U.S.A.  
     Example 6 (Comparative)  
     [0064] Example 6 is a comparative example to evaluate the physical properties of a non-reactive melt blend of 70 weight parts TPU and 30 weight parts EVA. The TPU used is the same TPU of Example 5 and the EVA used is the same EVA as in Example 2.  
     Example 7  
     [0065] Example 7 is presented to show that the same composition of Example 6 when made into a reactive blend by adding 1.0 weight part per 100 weight parts of total polymer (TPU &amp; EVA) of a polyisocyanate (MDI) has improved tensile strength over either the TPU of Example 5 or the EVA of Example 2 or the non-reactive blend of Example 6 and improved abrasion resistance over the EVA of Example 2 and the non-reactive blend of Example 6 and has higher melt viscosity than the TPU alone of Example 5 or the non-reactive blend of Example 6.  
     Example 8 (Comparative)  
     [0066] Example 8 is a comparative example to evaluate the physical properties of a non-reactive melt blend of 60 weight parts TPU and 40 weight parts EVA. The TPU used is the same as in Example 5 and the EVA used is the same as in Example 2.  
     Example 9  
     [0067] Example 9 is presented to show that the same composition of Example 8 when made into a reactive blend by adding 1.0 weight part per 100 weight parts of total polymer (TPU &amp; EVA) of a polyisocyanate (MDI) has improved tensile strength and abrasion resistance and has a higher melt viscosity than the non-reactive blend of Example 8.  
     Example 10 (Comparative)  
     [0068] Example 10 is a comparative example to evaluate the physical properties of a polyester based TPU polymer. The TPU polymer used in Gemothane® 951D available from Gemoplast of Lyon, France.  
     Example 11 (Comparative)  
     [0069] Example 11 is a comparative example to evaluate the physical properties of a non-reactive melt blend of 60 weight parts TPU and 40 weight parts EVA. The TPU used is the same as in Example 10 and the EVA used is the same as in Example 2.  
     Example 12  
     [0070] Example 12 is presented to show that the same composition of Example 11 when made into a reactive blend by adding 1.0 weight part per 100 weight parts of total polymer (TPU &amp; EVA) of a polyisocyanate (MDI) has improved tensile strength and improved abrasion resistance as compared to the non-reactive blend of Example 11.  
     Example 13  
     [0071] Example 13 is presented to show a reactive blend of 70 weight parts of the TPU of Example 10 and 30 weight parts of the EVA of Example 2, reacted by using 1.0 weight part of polyisocyanate (MDI).  
     Example 14  
     [0072] Example 14 is presented to show a reactive blend of 80 weight parts of the TPU of Example 10 and 20 weight parts of the EVA of Example 2, reacted by using 1.0 weight part of polyisocyanate (MDI).  
                           TABLE I                                      Ingredient (Parts by Weight)   Property                                                                             Tensile   Ultimate   Abrasion   MVR       Ex.                       Strength   Elongation   Loss   g/10       No.   TPU 1     TPU 2     TPU 3     EVA 4     MDI 5     (MPA)   %   (mm 3 )   min.                                                             *1   100   —   —   —   —   22.5   1400%   15   140       *2   —   —   —   100   —   14.0    970%   31   44       *3   70   —   —   30   —   13.0   1130%   18   152       4   70   —   —   30   1.0   31.0   1400%   11   43       *5   —   100   —   —   —   20.0   1170%   13   101       *6   —   70   —   30   —   11.0   1030    39   105       7   —   70   —   30   1.0   22.0   980   25   65       *8   —   60   —   40   —   10.0   930   50   90       9   —   60   —   40   1.0   19.0   1010    34   54       *10   —   —   100   —   —   35.0   800   27   **       *11   —   —   60   40   —   14.0   700   100   **       12   —   —   60   40   1.0   24.0   600   60   **       13   —   —   70   30   1.0   35.0   800   34   **       14   —   —   80   20   1.0   39.0   800   40   **                                                                          
 
     [0073] From Table I, a comparison of Examples 3 and 4 shows that when a reactive blend of this invention (Example 4) is compared to a conventional melt blend (Example 3), the ultimate tensile strength is increased from 13 MPA to 31 MPA. The abrasion loss is also reduced (which is an improvement) from 18 mm 3  to 11 mm 3 . The melt viscosity is increased from 152 g/10 min. to 43 g/10 min. Also, the data show a synergy between the two polymers as the tensile strength and abrasion resistance is better than the two polymers taken individually. A simple melt blend of the two polymers (Example 3) does not give these enhanced results. In fact, the melt blend of Example 3 shows lower tensile strength than either of the two polymers individually contained in the blend.  
     [0074] The melt viscosity, as demonstrated by the MVR results, shows that a simple non-reactive melt blend of TPU and EVA (Example 3, 6, and 8) tends to have a melt viscosity similar to the base TPU used in the blend. This is not surprising, since the TPU is the largest polymer component and thus is the continuous phase. Thus, the difficulty in processing TPU is not improved by a non-reactive blend with EVA, as long as the major component is TPU. It was very unexpected that the reactive blends of this invention (Examples 4, 7, 9, 12, 13, and 14), showed a melt viscosity closer to the EVA component even though the EVA is present in lesser amounts than the TPU. This indicates that the reactive blend will process more like EVA than TPU, thus resulting in very good processability. It is believed that the reduction in the MVR results of the reactive blend indicates that the molecular weight of the polymer has been increased as a result of bonding the TPU with the EVA through the polyisocyanate compound.  
     [0075] While in accordance with the Patent statutes, the best most and preferred embodiment has been set forth, the scope of the invention is not limited thereto, but rather by the scope of the attached claims.