MXPA00001428A - Thermoplastic polymer blends of isotactic polypropylene and alpha-olefin/propylene copolymers - Google Patents

Abstract

Thermoplastic polymer blend compositions comprising an isotactic polypropylene component and an alpha-olefin and propylene copolymer, said copolymer comprising crystallizable alpha-olefin sequences. In a preferred embodiment, improved thermoplastic polymer blends are provided comprising from about 35%to about 85%isotactic polypropylene and from about 30%to about 70%of an ethylene and propylene copolymer, wherein said copolymer comprises isotactically crystallizable propylene sequences and is predominantly propylene. The resultant blends manifest compatibility characteristics, increased tensile strength, and improved process characteristics, e.g., a single melting point.

Description

POLYMERIC, THERMOPLASTIC, POLYPROPYLENE AND ISOTACTIC PHYSICAL MIXTURES AND COPOLYMERS ALPHA-OLEFINE / PROPYLENE Field of the Invention The invention relates to polymeric physical blends of at least two polymers having surprising properties when compared to the properties of the individual polymers prior to physical blending. More specifically, the invention relates to physical blends of thermoplastic polymers, for example, according to one embodiment, isotactic polypropylene and an olefin copolymer. The invention further relates to polymeric, thermoplastic physical blends comprising isotactic polypropylene and, according to one embodiment, a copolymer of ethylene and propylene, wherein the copolymer comprises isotactically crystallizable alpha-olefin sequences. In addition, the invention relates to methods for making the above polymers and their physical mixtures. BACKGROUND OF THE INVENTION Although physical mixtures of isotactic polypropylene and ethylene and propylene rubber are well known in the state of the art, Ziegler-Natta catalyst systems can only produce ethylene and propylene rubber compositions with more than 30% by weight. ethylene under practical, economical polymerization conditions. There is a need for polymeric materials that have advantageous processing characteristics while still providing adequate final properties to the articles formed therefrom, for example resistance to stress and impact. Copolymers and physical mixtures of polymers have been developed to try to satisfy the above needs. U.S. Patent No. 3,882,197, issued to Fritz et al., Discloses physical blends of stereo-regular propylene / alpha-olefin copolymers, stereo-regular propylene, and ethylene copolymer rubbers. In U.S. Patent No. 3,888,949 to Chi-Kai Shih, assigned to E.l. DuPont, shows the synthesis of physical mixture compositions containing isotactic polypropylene and copolymers of propylene and an alpha-olefin, containing between 6 and 20 carbon atoms, having improved elongation and tensile strength on either the isotactic copolymer or polypropylene. Propylene and alpha-olefin copolymers are disclosed wherein the alpha-olefin is hexene, octene or dodecene. However, the copolymer is made with a heterogeneous titanium catalyst that makes copolymers that are non-uniform in positional and typically broad distribution in molecular weight distribution. The compositional distribution is a property of the copolymers where there is a statistically significant intermolecular or intramolecular difference in the composition of the polymer. The methods to measure the compositional distribution are described later. The presence of intramolecular compositional distribution is described in U.S. Patent No. 3,888,949 by the use of the term "block" in the polymer description, where the copolymer is described as having "different alpha-olefin content sequences". In the context of the invention described above, the term "sequences" describes various residues of olefin monomer linked by chemical bonds and obtained by a polymerization process. In U.S. Patent No. 4,461,872, A. C.L. His improved the properties of the physical mixtures described in U.S. Patent No. 3,888,949 using another heterogeneous catalyst system. However, the properties and compositions of the copolymer with respect to either the nature and type of monomers (alpha-olefin containing 6 to 20 carbon atoms) or heterogeneous inter / intra molecular distribution, in blocks, of the alpha-olefin in the polymer, they have not been resolved because it is expected that the catalysts used for these propylene and alpha-olefin polymerizations form copolymers having statistically significant intermolecular and intramolecular compositional differences. In two successive publications in the magazine Macromole-cules1989 22, pp. 3851-3866, J.W. Collette de E.l. DuPont has described physical blends of isotactic polypropylene and partially atactic polypropylene that have desirable tensile elongation properties. However, partially atactic propylene has a broad molecular weight distribution, as shown in Figure 8 of the first publication. Partially atactic polypropylene is also composed of various fractions, which differ in the level of tacticity of the propylene units, as shown by differences in solubility in different solvents. This is shown by the corresponding physical decomposition of the physical mixture that is separated by extraction with different solvents to yield individual components of uniform solubility characteristics, as shown in Table IV of the previous publications. In U.S. Patent Nos. 3,853,969 and 3,378,606, E.G. Kontos discloses the formation of in situ physical mixtures of isotactic polypropylene and "stereo block" copolymers of propylene and another olefin of 2 to 12 carbon atoms, including ethylene and hexene. The copolymers of this invention are necessarily heterogeneous in intermolecular and intramolecular compositional composition. This is demonstrated by the synthesis methods of these copolymers, which involve sequential injection of mixtures of monomers of different compositions to synthesize polymer portions of analogously different compositions. Furthermore, Figure 1 of both patents shows that the "stereo block" character, which is intramolecular or intermolecular compositional differences in the context of the description of the present invention, is essential for the benefit of the elongation and stress properties of the physical mixture. Physical mixtures in isotactic polypropylene and random, compositionally uniform ethylene and propylene copolymers have poor properties. Moreover, all these compositions either do not satisfy all the properties desired for various applications or involve expensive and cumbersome process steps to achieve the desired results. Similar results are anticipated by R. Holzer and K. Mehnert in U.S. Patent No. 3,262,992, assigned to Hercules, where the authors disclose that the addition of a stereo block copolymer of ethylene and propylene to isotactic polypropylene leads to improved mechanics of the physical mixture compared to isotactic polypropylene alone. However, these benefits are only described for stereo block copolymers of ethylene and propylene. The synthesis of these copolymers is designed around polymerization conditions where the polymer chains are generated in different ethylene and propylene compositions achieved by changing, over time, the concentrations of monomers in the reactor. This is shown in Examples 1 and 2. The character of stereo blocks of the polymer is shown graphically in the molecular description (column 2, line 65) and contrasted with the undesirable random copolymer (column 2, line 60). The presence of the character of stereo blocks in these polymers is shown by the high melting point of these polymers, which is much higher than the melting point of the second polymeric component in the present invention, shown in Table 1, as well as the poor solubility of these heterobloc materials, as a function of the weight percent ethylene of the material as shown in Table 3. It would be desirable to produce a physical mixture of a crystalline polymer, hereinafter referred to as the "first polymeric component", and a crystallizable polymer, hereinafter referred to as the "second polymeric component", having advantageous processing characteristics while still providing final products made from the physical blend composition having the desired properties, ie resistance to stress, elongation and global toughness increased. The first polymer component (abbreviated as "FPC" in the Tables below) and the second polymeric component (abbreviated as "SPC" in the Tables below). In fact, there is a need for a fully polyolefin composition that is thermally stable, heat resistant, light resistant and generally suitable for thermoplastic elastomer (TPE) applications having advantageous processing characteristics. Such a completely polyolefin composition would be most beneficial if the combination of the first polymer component and the second polymer component were significantly different in properties than the compositionally heavy average of the corresponding properties of the first polymer component and the second polymer component alone. It is anticipated, although it is not desired to be limited by this, that the power of the second polymer component can be increased only if it consists of one or two polyolefin copolymer materials defined by intramolecular and intermolecular composition and microstructure. The term "crystalline", as used herein for the first polymeric component, characterizes those polymers which possess high degrees of inter- and intramolecular order, and which melt at a temperature greater than 110 ° C and preferably greater than 115 °. C and have a heat of fusion of at least 75 J / g, as determined by DSC analysis. And the term "crystallizable", as used herein for the second polymeric component, describes those polymers or sequences which are primarily amorphous in an undeformed state, but which upon stretching or quenching, crystallization occurs. Crystallization can also occur in the presence of the crystalline polymer such as the first polymer component. These polymers have a melting point of less than 105 ° C, or preferably less than 100 ° C, and a heat of fusion of less than 75 J / g, as determined by DSC. SUMMARY OF THE INVENTION The present invention, according to one embodiment, is directed to the use of chiral metallocene catalysts to (1) easily produce the second polymeric component which is ethylene and propylene rubber compositions with about 4 to about 25% by weight of ethylene, and (2) easily produce second polymer component compositions containing isotactic propylene sequences long enough to crystallize. In this way, the invention is directed, according to one embodiment, to semi-crystalline materials (second polymer component), which when physically mixed with isotactic polymers (first polymeric component), show an increased level of compatibility between the two. phases of ethylene propylene and isotactic polypropylene. Although not intended to be limited by this, it is believed that the increased compatibility is due to the similarity of the composition of the first polymer component and the entire second polymer component. In this way, the uniformity of the intra and intermolecular composition of the second polymer component is of importance. In particular, it is important that substantially all of the components of the second polymer component be within the narrow range of ethylene and propylene composition defined above. In addition, the presence of isotactic propylene sequences in the second polymer component is of benefit for the improved adhesion of the domains of the first polymer component and the second polymer component in the polymeric physical blend composition. As a result, physical blends of isotactic polypropylene with ethylene propylene copolymers according to the invention have improved physical properties compared to physical blends of isotactic polypropylene with ethylene and propylene rubbers of the state of the art. According to one embodiment, a composition of the present invention comprises a physical mixture of at least a first polymer component and a second polymer component. The physical mixture comprises more than about 2% by weight of the first polymeric component comprising an alpha-olefin and propylene copolymer containing isotactic polypropylene crystallinity "with a melting point of about 115 to about 170 ° C. The physical component also contains a second polymeric component comprising a copolymer of propylene and at least one other alpha-olefin having less than 6 carbon atoms, and preferably 2 carbon atoms The copolymer of the second polymeric component of the invention, in accordance with a embodiment, comprises isotactic crystallizable propylene sequences and more than 75% by weight of propylene and preferably more than 80% by weight of propylene In accordance with another embodiment, a physical blend composition of thermoplastic polymer of the invention It comprises a first polymer component and a second polymer component The first polymer component comprises isotactic polypropylene is present in an amount of from about 2 to about 95% by weight, and more preferably 2 to 70% by weight of the total weight of the physical mixture. The first polymeric component may also be comprised of commonly available isotactic polypropylene compositions, referred to as impact copolymer or reactor copolymer. However, these variations in the identity of the first polymer component are acceptable in the physical mixture only insofar as all the components of the first polymer component are substantially similar in composition and the first polymer component is within the limitations of the crystallinity and the melting point indicated above. This first polymer component may also contain additives such as flow improvers, nucleators and anti-oxidants that are normally added to isotactic polypropylene to improve or retain properties. All these polymers are referred to as the first polymer component. The second polymeric component is a thermoplastic comprising a random copolymer of ethylene and propylene having a melting point by DSC of 25 to 105 ° C, preferably in the range of 25 to 90 ° C, more preferably in the range of 40. at 90 ° C, and an average propylene content by weight of at least 75%, and more preferably at least 80%. The second polymer component is made with a polymerization catalyst that forms essential or substantially isotactic polypropylene, when all or substantially all of the propylene sequences in the second polymer component are isotactically arranged.This copolymer contains crystallizable propylene sequences due to polypropylene isotactic The second polymeric component is statistically random in the distribution of ethylene and propylene residues along the chain The quantitative evaluation of the randomness of the distribution of ethylene and propylene sequences can be obtained by considering the experimentally determined reactivity ratios of the second polymeric component It is believed that the second polymeric component is random in the distribution of ethylene and propylene sequences as (1) it is made with a single-site metallocene catalyst that allows only a minimum The addition of ethylene and propylene is performed statistically and (2) is carried out in a well-mixed monomer continuous feed stirred tank polymerization reactor, which only allows one polymerization environment for substantially all the polymer chains of the second polymeric component. In this way, there is substantially no statistically significant difference in the composition of the second polymeric component either between two polymer chains or along a single chain. The ratio of the first polymer component to the second polymer component of the physical mixture composition of the present invention can vary in the range of 2:98 to 95: 5 by weight and more preferably in the range of 2:98 to 70:30 in weigh. According to another embodiment of the present invention, the second polymeric component may contain small amounts of a non-conjugated diene to aid in vulcanization and other chemical modification of the physical mixture of the first polymer component and the second polymer component. The amount of diene is limited to not more than 10% by weight and preferably not greater than 5% by weight. The diene may be selected from the group consisting of those which are used for the vulcanization of ethylene and propylene rubbers and preferably ethyldiene norbornene, vinyl norbornene and dicyclopentadiene. According to still another embodiment, the invention is directed to a process for preparing thermoplastic polymeric physical mixture compositions. The process includes: (a) polymerizing propylene or a mixture of propylene and one or more monomers selected from C2 or C4-C10 alpha-olefins in the presence of a polymerization catalyst, wherein a substantially isotactic propylene polymer containing at least about 90% by weight of polymerized propylene is obtained; (b) polymerizing a mixture of ethylene and propylene in the presence of a metallocene chiral catalyst, where an ethylene-propylene copolymer comprising up to about 25% by weight of ethylene, and preferably up to 20% by weight of ethylene and containing propylene sequences crystallizable in an isotactic manner; and (c) physically mixing the propylene polymer of step (a) with the copolymer of step (b) to form a physical mixture. Detailed Description of the Preferred Embodiments of the Invention The physical mixture compositions of the present invention are generally comprised of two components: (1) a first polymeric component comprising isotactic polypropylene, and (2) a second polymeric component comprising a alpha-olefin copolymer (other than propylene) and propylene. The First Polymer Component (FPC) According to the present invention, the first thermoplastic polymer component (first polymer component), ie the polypropylene polymer component, can be homopolypropylene, or propylene copolymers, or some physical mixtures thereof. The polypropylene used in the present physical blends can vary widely in form. For example, substantially isotactic polypropylene homopolymer can be used or the polypropylene can be in the form of a copolymer containing equal to or less than about 10% by weight of another monomer, ie at least about 90% by weight of propylene. In addition, the polypropylene can be present in the form of a graft or block copolymer, in which the polypropylene blocks have substantially the same stereo regularity as the copolymer of propylene and alpha-olefin, while the graft copolymer or blocks have a melting point of about 110 ° C, and preferably above 115 ° C, and more preferably above 130 ° C, characteristic of regular stereo propylene sequences. The first polymer component of the present invention is predominantly crystalline, ie it has a melting point generally greater than about 110 ° C, preferably greater than about 115 ° C, and most preferably greater than about 130 ° C. . The polymer component of propylene can be a combination of homopolypropylene and / or random and / or block copolymers, as described herein. When the above propylene polymer component is a random copolymer, the percentage of alpha-olefin copolymerized in the copolymer is, in general, up to about 9% by weight, preferably about 2 to about 8% by weight, with the highest preference around 2 to about 6% by weight. Preferred alpha-olefins contain 2 or 4 to about 12 carbon atoms. The most preferred alpha-olefin is ethylene. One, two or more alpha-olefins can be copolyzed with propylene. Exemplary alpha-olefins may be selected from the group consisting of ethylene; butene-1; pentene-1,2-methylpentene-1,3-methylbutene-1; Hexene-1,3-methylpentene-1, 4-methylpentene-1,3,3-dimethylbutene-1; hepteno-1; hexene-1; methylhexene-1; dimethylpentene-1 trimethylbutene-1; ethylpentene-1; octene-1; methylpentene-1; dimethylhexene-1; trimethylpyntene-1; ethylhexene-1; methylethylpentene-1; diethylbutene-1; propylpentane-1; decene-1; methylnonne-1; noneno-1; dimethylcytene-1; trimethylheptene-1; ethyl-ketene-1; methylethylbutene-1; diethylhexene-1; dodecene-1, and hexadodecene-1. The thermoplastic polymeric physical blend compositions of the present invention may comprise from about 2 to about 95% by weight of the first polymer component. According to a preferred embodiment, the thermoplastic polymeric physical blend composition of the present invention may comprise from about 2 to about 70% by weight of the first polymer component. According to the most preferred embodiment, the compositions of the present invention may comprise from about 5 to about 70% by weight of the first polymer component. There is no particular limitation on the method for preparing this polymeric propylene component of the invention. However, in general, the polymer is a propylene homopolymer obtained by homopolymerization of propylene in a single-stage or multi-stage reactor. The copolymers can be obtained by copolymerizing propylene and an alpha-olefin having 2 or 4 to about 20 carbon atoms, preferably ethylene, in a single-stage or multi-stage reactor. Polymerization methods include high pressure, slurry, gas, bulk, or solution phase, or a combination thereof, using a traditional Ziegler-Natta catalyst or a single-site metallocene catalyst system. The catalyst used is preferably one that has a high iso-specificity. The polymerization can be carried out by a continuous or batch process and can include the use of chain transfer agents, despoilers, or other such additives that are considered applicable. The Second Polymer Component (SPC) The second polymer component of the polymeric physical blend compositions of the present invention comprises a copolymer of propylene and another alpha-olefin having less than 6 carbon atoms, preferably ethylene. Optionally, the second component of the composition of the present invention may additionally comprise, in addition to the aforementioned, amounts of a diene. The second polymer component of the present * composition preferably, according to one embodiment, comprises a random copolymer having a narrow compositional distribution. Although it is not intended to be limited by this, it is believed that the narrow compositional distribution of the second polymer component is important. The intermolecular distribution of the polymer composition is determined by thermal fractionation in a solvent. A typical solvent is a saturated hydrocarbon such as hexane or heptane. This thermal fractionation process is described below. Typically, about 75% by weight, and more preferably 85% by weight of the polymer, the remainder of the polymer is isolated as one or two adjacent, soluble fractions in immediately preceding or successive fractions. Each of these fractions has a composition (containing ethylene in percent by weight) with a difference of not more than 20% by weight (relative) and more preferably 10% by weight (relative) of the ethylene content in percentage by weight Average of the entire second polymer component. The second polymeric component is narrow in compositional distribution if it satisfies the fractionation test indicated above. Throughout the second component, the number and distribution of ethylene residues is consistent with the random statistical polymerization of ethylene, propylene, and optional amounts of diene. In regular stereo structures, the number of monomer residues of any type adjacent to each other is greater than that predicted from a statistical distribution in random copolymers with a similar composition. Historical polymers with stereo block structures have a distribution of ethylene residues consistent with these block structures rather than a random statistical distribution of the monomer residues in the polymer. The intramolecular distribution of the polymer composition can be determined by C13 NMR which locates the ethylene residues relative to the neighboring propylene residue. A more practical and consistent evaluation of the randomness of the distribution of the ethylene and propylene sequences can be obtained by means of the following consideration. It is believed that the second polymer component is random in ethylene and propylene sequence distribution since (1) is made with a single-site metallocene catalyst that allows only a statistical mode of addition of ethylene and propylene and (2) is made in a stirred tank polymerization reactor with continuous monomer feed, well mixed, which allows only one polymerization environment for substantially all of the polymer chains of the second polymer component. The second polymer component, according to one embodiment of the invention, preferably has a single melting point. The melting point is determined by DSC. Generally, the second copolymer component of the present invention has a melting point below the first polymer component of the physical mixture, typically between about 105 and 25 ° C. Preferably, the melting point of the second polymer component is between about 90 and 25 ° C. More preferably, according to an embodiment of the present invention, the melting point of the second polymeric component of the composition of the present invention is between 90 and 40 ° C. The second polymer component preferably has a narrow molecular weight distribution (MWD) of between about 1.8 to about 5-.0, with a MWD of between about 2.0 and about 3.2 being preferred. The second polymer component of the composition herein comprises isotactically crystallizable alpha-olefin sequences, for example, preferably propylene (NMR) sequences. The crystallinity of the second polymer component is preferably, according to one embodiment, from about 2 to about 65% of the homoisotactic polypropylene, preferably between 5 and 40%, as measured by the heat of sample fusion. tempered of the polymer. According to another embodiment of the present invention, the second polymer component of the composition comprises from about 5 to about 25% by weight of alpha-olefin, preferably from about 6 to about 20% by weight of α-olefin, and more preferably, comprises from about 6 to about 18% by weight of alpha-olefin and even more preferably between 10 and 16% by weight of alpha-olefin. These composition ranges for the second polymeric component are dictated by the object of the present invention. In alpha-olefin compositions lower than the above lower limits for the second polymer component, the physical blends of the first polymer component and the second polymer component are hard and do not have the favorable elongation properties of the physical blends of the present invention. In alpha-olefin compositions above the above upper limits for the second polymer component, the physical blends of the second polymer component and the first polymer component do not have the favorable tensile properties of the physical blends of the present invention. It is believed, without wishing to be limited thereto, that the second polymeric component needs to have the optimum amount of isotactic polypropylene crystallinity to crystallize with the first polymeric component for the beneficial effects of the present invention. As discussed above, the preferred alpha-olefin is ethylene. The compositions of the present invention may comprise from about 5 to about 98% by weight of the second polymer component. According to a preferred embodiment, the compositions of the present invention may comprise from about 30 to about 98% by weight of the second polymer component. More preferably, the compositions of the present invention may comprise from about 30 to about 95% by weight of the second polymer component. Generally, without limiting the scope of the invention in any way, means for carrying out a process of the present invention for the production of the second copolymer polymer component are as follows: (1) liquid propylene is introduced into a tank reactor agitated, (2) the catalyst system is introduced via nozzles in either the vapor phase or the liquid phase, (3) the ethylene gas feed is introduced either into the vapor phase of the reactor, or sprayed in the liquid phase, as is well known in the art, (4) the reactor contains a liquid phase composed substantially of propylene, together with dissolved alpha-olefin, preferably ethylene, and a vapor phase containing vapors of all the monomers, (5) the temperature and pressure of the reactor can be controlled via reflux of vaporizing propylene (self-cooling), as well as by cooling coils, liners, etc., (6) the rate or speed of polymerization is controlled by the catalyst concentration, the temperature, and (7) the ethylene (or other alpha-olefin) content of the polymer product is determined by the ratio of ethylene to propylene in the reactor, which is controlled by manipulating the relative rates of feeding these "components to the reactor." For example, a typical polymerization process consists of a polymerization in the presence of a catalyst comprising a bis (cyclopentadienyl) meta compound. l and either 1) a compatible, non-coordinating anionic activator, or 2) an alumoxane activator. According to one embodiment of the invention, this comprises the steps of contacting ethylene and propylene with a catalyst in a suitable polymerization diluent, said catalyst comprising, for example, according to a preferred embodiment, a catalyst of chiral metallocene, for example a bis (cyclopentadienyl) metal compound, as described in U.S. Patent No. 5,198,401, which is incorporated herein by reference, and an activator. The activator used can be an activator of alumoxane or a compatible, non-coordinating anionic activator. The alumoxane activator is preferably used in an amount to provide a molar ratio of aluminum to metallocene of from about 1: 1 to about 2,000: 1 or more. The compatible, non-coordinating anionic activator is preferably used in an amount to provide a molar ratio of metal biscyclopentadienyl compound to non-coordinating anion of 10: 1 to about 1: 1. The above polymerization reaction is conducted by reacting such monomers in the presence of such catalyst system at a temperature of about -100 to about 3L_00 ° C for a time of about 1 second to about 10 hours to produce a copolymer having a heavy average molecular weight of about 5,000, or less than about 1,000,000 or more and a molecular weight distribution of about 1.8 to about 4.5. Although the process of the present invention includes using a catalyst system in the liquid phase (slurry, solution, suspension or bulk phase or combinations thereof), according to other embodiments, high-pressure polymerization in the fluid phase can also be used. gas phase polymerization. When used in a gas phase polymerization, slurry phase or suspension phase, the catalyst systems will preferably be supported catalyst systems. See, for example, U.S. Patent No. 5,057,475, which is incorporated herein by reference. Such catalyst systems may also include other well-known additives such as, for example, stripping agents. See, for example, U.S. Patent No. 5,153,157, which is incorporated herein by reference. These processes can be employed without limitation of the type of reaction vessels and the manner of conducting the polymerization. As mentioned before, and although it is also true for systems using a supported catalyst system, the liquid phase process comprises the steps of contacting ethylene and propylene with the catalyst system in a suitable polymerization diluent and reacting the monomers in presence of the catalyst system for a time and at a temperature sufficient to produce an ethylene-propylene copolymer of the desired molecular weight and composition. It will be understood in the context of the present invention that, in one embodiment, more than one second polymer component can be used in a single physical mixture with a first polymer component. Each of the components of the second polymer component is described above and the number of components of the second polymer component in this embodiment is less than three and, more preferably, two. In this embodiment of the invention, the second polymeric components differ in the alpha-olefin content, one being in the range of 5 to 9% by weight of alpha-olefin, while the other is in the range of 10 to 22% by weight alpha-olefin. The preferred alpha-olefin is ethylene. It is believed that the use of two second polymeric components in conjunction with a single first polymeric component leads to beneficial improvements in the tensile-elongation properties of the physical mixtures. The Physical Mixture of the First and Second Polymer Components The physical blends of the copolymer of the first polymer component and the second polymer component of the present invention can be prepared by any process that ensures intimate mixing of the components. For example, the components can be combined by melt-pressing the components together in a Carver press to a thickness of about 0.5 mm (20 mils) and a temperature of about 180 ° C, winding the resulting ingot, bending together the ends, and repeating the pressing, rolling and bending operation about 10 times. Particularly useful are internal mixers for physical mixtures in solution or in the molten state. Physical mixing at a temperature of about 180 to 240 ° C in a Brabender plastometer for about 1 to 20 minutes has been found to be satisfactory. Still another method that can be used to mix components involves physically mixing the polymers in an internal Banbury mixer over the flow temperature of all the components, for example 180 ° C for about 5 minutes. The complete mixing of the polymeric components is indicated by the narrowing of the crystallization and the melting transitions characteristic of the crystallinity of the polypropylene of the components to give a single range or small range of crystallization and melting points for the physical mixture. These batch mixing processes are typically supplanted by the continuous mixing processes in the industry. These processes are well known in the art and include twin screw and twin screw extruders, static mixers for mixing melt streams of low viscosity polymer, shock mixers, as well as other machines and other processes, designed to disperse the first polymer component and the second polymer component in intimate contact. The polymeric physical blends of the present invention exhibit a remarkable combination of desirable physical properties. The incorporation of as little as 5% of the first polymer component in the propylene / alpha-olefin copolymers increases the melting point of the propylene sequence or the softening point of the polymer but, more significantly, reduces the range in comparison with the propylene / alpha-olefin copolymer. In addition, the incorporation of the first polymer component according to the present invention almost eliminates the stickiness caused by the propylene / alpha-olefin copolymer. In addition, the thermal characteristics of the physical copolymer blends are markedly improved over those of the second polymer component which is that of the propylene / alpha-olefin copolymers. The crystallization temperature and the melting point of the physical mixtures are changed as a result of the physical mixing operation. In one embodiment of the invention, the physical mixture of the first polymer component and the second polymer component has a single crystallization temperature and a single melting point. These temperatures are greater than the corresponding aspects for the second polymer component and close to those of the first polymer component. In other embodiments, the second polymer component and the first polymer component have different melting and crystallization temperatures but have these temperatures closer than would be expected for a combination of the second polymer component and the first polymer component. In all these cases, the glass transition temperature of the second polymeric component is conserved in the polymeric physical mixture. This favorable combination of thermal properties allows its satisfactory use in injection molding operations without the orientation previously found. The injection molded articles prepared from the physical blends of copolymers herein therefore exhibit excellent long-term dimensional stability. The aforementioned advantages are obtained without the need for an elaborate purification of the propylene / alpha-olefin copolymer or the tedious preparation of a carefully structured block copolymer. In addition, by using the second polymer component and the first polymer component, a physical mixture with a lower glass transition temperature than would be expected from a random copolymer of the same composition as the physical mixture can be obtained. In particular, the glass transition temperature of the physical mixture is closer to that of the second polymer component and is lower than the glass transition temperature of the first polymer component. This can be achieved without an exceptionally high alpha-olefin content in the polymeric physical mixture, which we believe, without wanting to be limited thereby, would lead to the degradation of the tensile-elongation properties of the physical mixture. The mechanism by which the desirable characteristics of the physical copolymer blends of the present are obtained is not fully understood. However, it is believed that a similar co-crystallization phenomenon between stereo propylene sequences involves similar regularity in the various polymeric components, which results, in one embodiment, in a single crystallization temperature and a single temperature. of the physical mixture of copolymer which are greater than those of the second polymer component, which is the propylene / alpha-olefin component of the physical mixture In another embodiment, the combination of the first polymer component and the second polymer component it has a melting point closer than would be expected from a comparison of those of individual components alone.It is surprising that in the embodiment, the physical mixture has a single crystallization temperature and a single melting temperature, since the technicians in the matter would expect that the physical mixture of two crystalline polymers would result in a double tempe crystallization ratio as well as a double melting temperature, reflecting the two polymeric components. However, the intimate physical mixture of the polymers having the requisite crystallinity characteristics apparently results in a crystallization phenomenon that modifies other physical properties of the propylene / alpha-olefin copolymer, thereby measurably increasing its commercial utility and the range of applications. Although the above discussion has been limited to the description of the invention in relation to having only components one and two, as will be apparent to those skilled in the art, the polymeric physical mixture compositions of the present invention may comprise other additives. Various additives may be present in the composition of the invention to augment a specific property or may be present as a result of the processing of the individual components. The additives that can be incorporated include, for example, fire retardants, anti-oxidants, plasticizers and pigments.

Other additives that can be used to improve properties include anti-blocking agents, coloring agents, stabilizers and oxidation, thermal and ultraviolet light inhibitors. Lubricants, mold release agents, nucleating agents, reinforcers and fillers (including granular, fibrous or powder-like) can also be employed. Nucleating agents and fillers tend to improve the stiffness of the article. The list described herein is not intended to be inclusive of all types of additives that may be employed with the present invention. Upon reading this disclosure, those skilled in the art will appreciate that other additives may be employed to improve the properties of the composition. As will be understood by those skilled in the art, the polymeric physical blend compositions of the present invention may be modified to adjust the characteristics of the physical mixture, as desired. As used herein, the Mooney viscosity was measured as ML (1 + 4) at 125 ° C in Mooney units, according to the ASTM DI646 method. The composition of the ethylene and propylene copolymers, which are used as comparative examples, was measured with weight percentage of ethylene, according to the ASTM D3900 method. The composition of the second polymer component was measured as a percentage by weight of ethylene, according to the following technique. A thin, homogeneous film of the second polymer component, pressed at a temperature of around or greater than 150 ° C was mounted on a Perkin Elmer infrared spectrophotometer PE 1760. A full spectrum of the sample of 600 to 400 cm "1 was recorded and the weight percentage of ethylene of the second polymer component was calculated according to equation 1, as follows: weight percentage of ethylene = 82.585 - 111.987X + 30.045X2 where X is the ratio of the peak height to 1.155 cm -1 and the height of the peak at either 722 or 732 cm-1, whichever is greater.The techniques for determining molecular weight (Mn and Mw) and the molecular weight distribution (MWD) are found in the United States patent No. 4,540,753 (Cozewith, Ju and Verstrate) (which is incorporated herein by reference), and references cited therein and in Macromoiecules, 1988, vol.21, p.3360 (Verstrate et al.) (Incorporated herein) in this by reference) and ref cited in this one. The procedure for differential scanning calorimetry is described as follows. About 6 to 10 mg of a sheet of the pressed polymer at about 200 to 230 ° C are removed with a punch die. This is tempered at room temperature for 80 to 100 hours. At the end of this period, the sample is placed in a differential scanning calorimeter (Perkin Elmer Series 7 thermal analysis system) and cooled to around -50 to around -70 ° C. The sample is heated at a rate of 20 ° C / min to reach a final temperature of around 200 to about 220 ° C. The thermal output is recorded as the area under the melting peak of the sample which typically has peaks at around 30 to about 175 ° C and occurs between temperatures of around 0 and about 200 ° C, measured in Joules as a measurement of the heat of fusion. The melting point is recorded as the temperature of highest heat absorption within the melting range of the sample. Under these conditions, the melting point of the second polymer component and the heat of fusion is better than the first polymer component, as outlined in the above description. The compositional distribution of the second polymer component was measured as described below. About 30 g of the second polymeric component were cut into small cubes about 1/8"on each side, which were placed in a thick-walled glass bottle, closed with a screw cap together with 50 mg of Irganox 1076, a anti-oxidant commercially available from Ciba-Geigy Corporation., 425 ml of hexane (a main mixture of normal and iso isomers) are added to the contents of the bottle and the sealed bottle is maintained at about 23 ° C for 24 hours. At the end of this period, the solution is decanted and the residue is treated with additional hexane for an additional 24 hours. At the end of this period, the two hexane solutions are combined and evaporated to give a soluble polymer residue at 23 ° C. To the residue, sufficient hexane is added to bring the volume to 425 ml and the bottle is maintained at about 31 ° C for 24 hours in a circulating water bath. The soluble polymer is decanted and the additional hexane is added for another 24 hours at about 31 ° C before decanting. In this way, fractions of the second polymeric component soluble at 40, 48, 55 and 62 ° C are obtained at temperature increments of about 8 ° C between stages. In addition, temperature increases can be accommodated at 95 ° C, if heptane is used instead of hexane as the solvent for all temperatures above about 60 ° C. The soluble polymers are dried, weighed and analyzed in terms of the composition, as weight percentage of ethylene content, by the infrared technique described above. Soluble fractions obtained in the adjacent temperature increments are the adjacent fractions in the previous specification. EPR in the data tables below is Vistalon 457, sold by Exxon Chemical Company, of Houston, Texas, United States. The invention, while not intended to be limited thereto, is further illustrated by the following specific examples. EXAMPLES Example 1: Copolymerization of ethylene / propylene to form the second polymer component The polymerizations were conducted in a 1 liter, continuous, thermostated stirred tank reactor using hexane as the solvent. The polymerization reactor was filled with liquid. The residence time in the reactor was typically 7 to 9 minutes and the pressure was maintained at 400 kPa. The hexane, ethene and propene were dosed in a single stream and cooled before introduction to the bottom of the reactor. The solutions of all reagents and polymerization catalysts were continuously introduced to the reactor to initiate the exothermic polymerization. The temperature of the reactor was maintained at 41 ° C by changing the temperature of the hexane feed and circulating water in the outer jacket. For a typical polymerization, the temperature of the feed was around 0 ° C. Ethene was introduced at a rate of 45 g / min and propene was introduced at a rate of 480 g / min. The polymerization catalyst, bis-indenyl hafnium dimethyl bridged with dimethyl silyl, activated at a 1: 1 molar ratio with N ', N' -dimethyl anilinium-tetrakis (pentafluorophenyl) borate, was introduced at a rate of 0.00897 g / hr. A dilute solution of triisobutyl aluminum was introduced into the reactor as a stripping agent for catalyst terminators: a rate of approximately 28.48 moles of stripping agent per mole of catalyst was adequate for this polymerization. After five residence times of stable polymerization, a representative sample of the polymer produced in this polymerization was collected. The polymer solution was removed from the top, and then distilled with steam to isolate the polymer. The polymer formation rate was 285.6 g / hr. The polymer produced in this polymerization had an ethylene content of 13%, MLT125 (1 + 4) of 12.1 and had isotactic propylene sequences. Variations in polymer composition were obtained mainly by changing the ratio of ethene to propene. The molecular weight of the polymer could be increased by a greater amount of ethene and propene compared to the amount of polymerization catalyst. Dienes such as norbornene and vinyl norbornene can be incorporated into the polymer, adding them continuously during the polymerization. Example 2: Comparative ethylene / propylene polymerization where propylene residues are atactic Polymerizations were conducted in a stirred tank reactor, of continuous feeding, with thermostat, of 1 liter, using hexane as solvent. The polymerization reactor was filled with liquid. The residence time in the reactor was typically 7 to 9 minutes and the pressure was maintained at 400 kPa. Hexane, ethene and propene were dosed in a single stream and cooled before introduction to the bottom of the reactor. Solutions of all reagents and polymerization catalysts were continuously introduced into the reactor to initiate the exothermic polymerization. The temperature of the reactor was maintained at 45 ° C by changing the temperature of the hexane feed and using cooling water in the outer jacket of the reactor. For a typical polymerization, the temperature of the feed was around -10 ° C. Ethene was introduced at a rate of 45 g / min and propene was introduced at a rate of 310 g / min. The polymerization catalyst, (tetramethylcyclopentadienyl) cyclododecylamido titanium dimethyl, activated at a 1: 1 molar ratio with N ', N' -dimethyl anilinium-tetra-quis (pentafluorophenyl) borate, was introduced at a rate of 0.002780 g / hr. A dilute solution of triisobutyl aluminum was introduced to the reactor as a stripping agent for catalyst terminators: a rate of about 36.8 moles per mole of catalyst was adequate for this polymerization. After five residence times of stable polymerization, a representative sample of the polymer produced in this polymerization was collected. The polymer solution was removed from the top, and then distilled in water vapor to isolate the polymer. The polymer formation rate was 258 g / hr. The polymer produced in this polymerization had an ethylene content of 14.1% by weight, ML0125 (1 + 4) of 95.4. Variations in polymer composition were obtained mainly by changing the ratio of ethene to propene. The molecular weight of the polymer could be increased by a greater amount of ethene and propene compared to the amount of the polymerization catalyst. These polymers are described as aePP in the tables below.

Example 3: Analysis and solubility of several second polymeric components In the manner described in Example 1 above, several second polymeric components of the above description were synthesized. These are described in the following table. Table 1 describes the results of the GPC, composition, ML and DSC analyzes for the polymers. Table 1 Table 1: Analysis of the second polymer component and the comparative polymers Table 2 describes the solubility of the second polymer component.

Table 2 Table 2: solubility of fractions of the second polymer component. The sum of the fractions adds up slightly more than 100 due to imperfect drying of the polymer fractions. Table 3 describes the composition of the fractions of the second polymer component obtained in Table 2. Only the fractions that have more than 4% of the total mass of the polymer have been analyzed in terms of their composition.

Table 3 Table 3: fraction composition of the second polymer component obtained in Table 2. The experimental inaccuracy in determining the ethylene content is believed to be about 0.4% by absolute weight. Example 4: A total of 72 g of the first polymer component and the second polymer component, as shown in Table 4, column 2, was mixed in a Brabender intensive mixer for 3 minutes at a controlled temperature to be within 185 and 220 ° C. High shear roller knives were used for mixing and approximately 0.4 g of Irganox 1076, an anti-oxidant available from Novartis Corporation, were added to the physical mixture. At the end of mixing, the mixture was removed and pressed into a 6 x 6 inch mold on a 0.25"thick pad at 215 ° C for 3 to 5 minutes.At the end of this period, the pad was cooled and removed and allowed to temper for 3 to 5 days Test specimens of the required geometry were removed from this pad and evaluated in an Instron tester to produce the data shown in Table 4. The first polymeric component was Escorene 4292, a commercially available homoisotactic polypropylene from Exxon Chemical Company, Houston, Texas, United States The second polymeric component was SPC-1, as characterized in Tables 1, 2 and 3 above.

Table 4 Table 4: stress versus extension data (E) for physical blends of the first polymer component and the second polymer component, where the second polymer component is the SPC-1 component in the above tables. The shaded areas represent broken samples. The light areas represent lack of data due to extension beyond the limits of the machine. Example 5: The first polymeric component was Escorene 4292, a homoisotactic polypropylene commercially available from Exxon Chemical Company, of Houston, Texas, United States. The second polymeric component was the SPC-2 component as characterized in Tables 1, 2 and 3 above. These components were mixed in the same manner as described for Example 4.

Table 5 Table 5: stress versus extension data (E) for physical mixtures of the first polymer component and the second polymer component, where the second polymer component is the SPC-2 component in the above tables. Shaded areas without data represent broken samples. The light areas represent lack of data due to extension beyond the limits of the machine. Example 6: The first polymeric component was Escorene 4292, a homoisotactic polypropylene commercially available from Exxon Chemical Company. The second polymeric component was the SPC-3 component, as characterized in Tables 1, 2 and 3 above. These components were mixed in the same manner described for Example 4.

Table 6 Composition in grams of FPC and SPC-3 Effort (psi.

Table 6: stress versus extension data (E) for physical blends of the first polymer component and the second polymer component where the second polymer component is the SPC-3 component in the above tables. Shaded areas without data represent broken samples. The light areas represent lack of data due to extension beyond the limits of the machine. Example 7: The first polymeric component was Escorene 4292, a homoisotactic polypropylene commercially available from Exxon Chemical Company, of Houston, Texas, United States. The second polymer component was the SPC-4 component, as characterized in Tables 1, 2 and 3 above. These components were mixed in the same manner described for Example 4.

Tabl 7 Table 7: Stress versus extension data (E) for physical blends of the first polymer component and the second polymer component, where the second polymer component is the SPC-4 component in the above tables. Shaded areas without data represent broken samples. The light areas represent lack of data due to extension beyond the limits of the machine. Example 8: The first polymeric component was Escorene 4292, a homoisotactic polypropylene commercially available from Exxon Chemical Company, of Houston, Texas, United States. The second polymer component was a mixture of the SPC-1 component and the SPC-5 component, as characterized in Tables 1, 2 and 3 above. These components were mixed in the same manner described for Example 4.

Table 8 Table 8: Effort versus extension data (E1 for physical mixtures of the first polymeric component and EPR in the above tables: The shaded areas without data represent broken samples Example 9 (comparative): The first polymeric component was Escorene 4292, a polypropylene homoisotactic commercially available from Exxon Chemical Company, of Houston, Texas, United States The second polymeric component was the EPR component, as characterized in the above Tables 1, 2 and 3. These components were mixed in the same manner described for Example Four.

Table 9 Table 9: effort versus extension data (E) for physical mixtures of the first polymer component and EPR in the above tables. Shaded areas without data represent broken samples. Example 10 (comparative): The first polymeric component was Escorene 4292, a homoisotactic polypropylene commercially available from Exxon Chemical Company, of Houston, Texas, United States. The second polymer component was the aePP component, as characterized in Tables 1, 2 and 3 above. These components were mixed in the same manner described for Example 4.

Table 10 Although exemplary embodiments of the invention have been described with particularity, it will be understood that other modifications will be apparent and readily apparent to those skilled in the art without departing from the spirit and scope of the invention. Accordingly, it is not intended that the scope of the appended claims be limited to the examples and descriptions set forth herein, but rather the claims should be construed as encompassing all aspects of patentable novelty that reside in the present invention, including all aspects that would be treated as their equivalents by the technicians in the matter to which the invention belongs.

Claims (20)

1. CLAIMS 1. A composition comprising a physical mixture of at least a first psimérico component and a second polymeric component, said physical mixture comprising: more than 2% by weight of said first polymeric component comprising isotactic polypropylene, and a second polymeric component comprising a copolymer of propylene and at least one other alpha-olefin having less than 6 carbon atoms, said copolymer comprising crystallizable propylene sequences and at least 75% by weight of propylene. The composition of claim 1, wherein the first polymer component further comprises a co-monomer. The composition of claim 1, wherein the first polymeric component is predominantly crystalline with a DSC melting point equal to or greater than 115 ° C. The composition of claim 1, wherein the alpha-olefin of the second polymer component comprises ethylene. The composition of claim 1, wherein the second polymer component comprises from about 5 to about 25% by weight of alpha-olefin. 6. The composition of claim 5, wherein the alpha-olefin of the second polymer component comprises ethylene. The composition of claim 1, wherein the second polymer component comprises from about 6 to about 18% by weight of ethylene. The composition of claim 1, wherein the crystallizable propylene sequences comprise isotactic propylene sequences. The composition of claim 1, wherein the first polymeric component has a melting point greater than or equal to 130 ° C and the second polymeric component has a melting point less than or equal to about 105 ° C. The composition of claim 9, wherein the resulting physical mixture has a glass transition temperature closer to that of the second polymer component and less than the glass transition temperature of the first polymer component. The composition of claim 1, wherein the second polymer component has a molecular weight distribution of from about 2.0 to about 3.
2. 2. The composition of claim 1, wherein the second polymer component has a DSC melting point between about 30 and about 100 ° C. 13. A thermoplastic polymer physical blend composition, comprising: from about 2 to about 95% by weight of a first thermoplastic polymer component comprising isotactic polypropylene, and from about 5 to about 98% by weight of a second a thermoplastic polymer component comprising a random copolymer of ethylene and propylene having a DSC melting point between about 30 and about 100 ° C, said copolymer comprising crystallizable propylene sequences and up to about 25% by weight of ethylene. The composition of claim 3, wherein said first thermoplastic polymer component further comprises a copolymer of propylene and alpha-olefin. 15. The composition of claim 13, wherein the second thermoplastic polymer component comprises from about 6 to about 18% ethylene. The composition of claim 13, wherein the physical blend composition has a glass transition temperature closer to that of the second polymeric component and less than the glass transition temperature of the first polymeric component. The composition of claim 13, wherein the second thermoplastic polymer component has a molecular weight distribution of from about 2.0 to about 3.2. 18. A thermoplastic polymeric physical blend composition, comprising: a) from about 2 to about 95% by weight of a first thermoplastic polymer component selected from the group consisting of isotactic polypropylene and isophatic propylene and alpha-olefin copolymer , and b) a second composition comprising a physical mixture of two copolymers of propylene and alpha-olefin, wherein one of said copolymers has an alpha-olefin content of 5 to 9% by weight and the other copolymer has an alpha-olefin content of 10 to 22% by weight. 19. The thermoplastic polymer physical blend of claim 18, wherein the alpha-olefin in the second polymer component is ethylene. 20. A process for preparing a thermoplastic polymer physical blend composition, comprising: a. polymerizing propylene or a mixture of propylene and one or more monomers selected from the group consisting of C2 or C4-C10 alpha-olefins in the presence of a polymerization catalyst, where a substantially isotactic propylene polymer containing at least about 90 is obtained % by weight of polymerized propylene; b. polymerizing a mixture of ethylene and propylene, wherein an ethylene-propylene copolymer is obtained comprising up to about 25% by weight of ethylene and containing isotactically crystallizable propylene sequences; and c. physically mix the propylene polymer from step a. with the copolymer of step b. to form a physical mixture. The process of claim 20, wherein the isotactic propylene polymer has a melting point greater than 130 ° C. 22. The process of claim 20, wherein the copolymer comprises from about 6 to about 18% by weight of ethylene. 23. The process of claim 20, wherein the copolymer has a DSC melting point of between about 30 and about 100 ° C. 24. The physical mixture resulting from the process of claim 20, wherein the physical mixture has a glass transition temperature closer to that of the second polymer component and less than the glass transition temperature of the first polymer component. The process of claim 20, wherein the ethylene-propylene copolymer is a random copolymer having a molecular weight distribution of from about 2.0 to about 3.2. 26. The process of claim 20, wherein ethylene and propylene are polymerized in the presence of the isotactic propylene polymer composition of step a. in a reactor where the physical mixture is formed. 27. The process of claim 20, wherein ethylene and propylene are polymerized in the presence of a metallocene catalyst. The process of claim 20, wherein the propylene is polymerized in the presence of a metallocene or a Ziegler-Natta catalyst. 29. The process of claim 20, wherein from about 2 to about 95% by weight of isotactic propylene polymer is physically mixed with about 5 to about 98% by weight of ethylene-propylene copolymer. 30. The thermoplastic polymer physical blend composition produced by the process of claim 20.