Bimodal molecular weight low ethylene content propylene-based random copolymer compositions and methods

Abstract

Compositions, methods, and molded articles including bimodal molecular weight ethylene / propylene random copolymers, the bimodal molecular weight ethylene / propylene random copolymer includes a high molecular weight component having a melt flow rate at 230 DEG C of about 0.02 g / 10 min to about 0.5 g / 10 min and a low molecular weight component having a melt flow rate at 230 DEG C of about 1 g / 10 min to about 10 g / 10 min and an ethylene content of about 0.40 wt% to about 0.60 wt%.

Description

Technical Field

[0001] The present disclosure relates to bimodal molecular weight low ethylene content propylene-based random copolymer compositions and methods related thereto, and more particularly, to bimodal molecular weight low ethylene content propylene-based random copolymer compositions having improved strength and toughness (rigidity) and transparency, and methods related thereto. Background Art

[0002] Polypropylene is one of the most widely used thermoplastics for various applications due to its excellent physical properties. In particular, compared to other polyolefins, polypropylene exhibits excellent properties in, for example, chemical resistance to organic solvents, tensile strength, and processability. Conventional uses of polypropylene include packaging products (molded articles) such as food containers, beverage containers, storage containers, plastic cans, associated lids and covers, etc. These packaging products are generally desired to be rigid so that they can be formed into different shapes suitable for a particular application and maintain that shape. In addition, such packaging products are generally desired to be characterized by high transparency (low haze) so that the packaged article can be easily observed.

[0003] However, polypropylene specimens can be very brittle and thus may exhibit undesirable mechanical properties, particularly for packaging products. Therefore, polypropylene is typically compounded with an elastomeric polymer such as ethylene to form a random copolymer having improved impact strength and toughness. The ethylene content in polypropylene copolymers is used in product packaging due to this impact strength and toughness, as well as other advantages including favorable heat seal characteristics. However, as the ethylene content increases, undesirable side effects may result, such as a large amount of extractables, leading to processing difficulties and constraints in food and medical packaging product applications. Some of these processing difficulties, such as an increased tendency for oligomer / additive migration, can cause visible frosting signs that have a negative impact on transparency.

[0004] Accordingly, there remains a need for a low ethylene content ethylene / propylene copolymer for rigid packaging products that has favorable strength and toughness as well as transparency. Summary of the Invention Overview of the Invention

[0005] The present disclosure relates to bimodal molecular weight low ethylene content propylene-based random copolymer compositions and methods related thereto, and more particularly, to bimodal molecular weight low ethylene content propylene-based random copolymer compositions having improved strength and toughness as well as transparency, and methods related thereto.

[0006] In one or more aspects, the present disclosure provides a composition comprising a bimodal molecular weight ethylene / propylene random copolymer. The bimodal molecular weight ethylene / propylene random copolymer comprises a high molecular weight component having a melt flow rate at 230 °C of from about 0.02 g / 10 min to about 0.5 g / 10 min, a low molecular weight component having a melt flow rate at 230 °C of from about 1 g / 10 min to about 10 g / 10 min, and an ethylene content of from about 0.40 wt% to about 0.60 wt%.

[0007] In one or more aspects, the present disclosure provides a method for polymerizing ethylene and propylene monomers to produce a bimodal molecular weight ethylene / propylene random copolymer. The bimodal molecular weight ethylene / propylene random copolymer comprises a high molecular weight component having a melt flow rate at 230 °C of from about 0.02 g / 10 min to about 0.5 g / 10 min, a low molecular weight component having a melt flow rate at 230 °C of from about 1 g / 10 min to about 10 g / 10 min, and an ethylene content of from about 0.40 wt% to about 0.60 wt%.

[0008] In one or more aspects, the present disclosure provides a molded article comprising a bimodal molecular weight ethylene / propylene random copolymer. The bimodal molecular weight ethylene / propylene random copolymer comprises a high molecular weight component having a melt flow rate at 230 °C of from about 0.02 g / 10 min to about 0.5 g / 10 min, a low molecular weight component having a melt flow rate at 230 °C of from about 1 g / 10 min to about 10 g / 10 min, and an ethylene content of from about 0.40 wt% to about 0.60 wt%. DETAILED DESCRIPTION OF THE INVENTION

[0009] The present disclosure relates to bimodal molecular weight low ethylene content propylene-based random copolymer compositions and methods related thereto, and more particularly, to bimodal molecular weight low ethylene content propylene-based random copolymer compositions having improved strength, toughness, and transparency, and methods related thereto.

[0010] The propylene-based random copolymer compositions described herein comprise a polypropylene random copolymer having a low ethylene content and a high molecular weight polypropylene homopolymer. Such bimodal molecular weight propylene-based random copolymer compositions exhibit a high degree of strength / toughness (stiffness) and transparency.

[0011] As described above, ethylene / propylene random copolymers can be effectively used to manufacture packaging products, particularly rigid packaging products, but may suffer from a trade-off between strength / toughness and transparency. The present disclosure alleviates the foregoing difficulties and also provides related advantages. In particular, the present disclosure provides improvements in strength / toughness and transparency by utilizing the bimodal molecular weight distribution of ethylene / propylene random copolymers.

[0012] Exemplary aspects of the present disclosure include ethylene / propylene random copolymers, methods for preparing the same, and packaging products prepared therefrom. Definitions and Test Methods

[0013] All numerical values in the detailed description and claims herein are modified by the term "about" or "approximate" relative to the indicated values, and account for experimental error and deviation that would be expected by a person of ordinary skill in the art. Unless otherwise stated, the ambient temperature (room temperature or "RT") is about 25 °C.

[0014] The singular forms "a", "an", and "the" used in the present disclosure and the appended claims include plural referents unless the context clearly dictates otherwise.

[0015] The term "and / or" used in the phrase "A and / or B" is intended herein to include "A and B", "A or B", "A", and "B".

[0016] For the purposes of the present disclosure and its claims, the following definitions should be used.

[0017] As used herein, "copolymer" and its grammatical variants are composed of the polymerization comonomers of propylene and ethylene. The copolymers described herein are "random copolymers", wherein the ethylene monomer residues are randomly located within the polypropylene polymer. The term "copolypropylene polymer" as used herein will refer to a random copolymer of propylene and ethylene.

[0018] The term "melt flow rate" or "MFR" and its grammatical variants as used herein are the number of grams extruded in 10 minutes under a standard load and are inversely proportional to viscosity. A high MFR means low viscosity, and a low MFR means high viscosity. In addition, the copolymers described herein are shear thinning, which means that their flow resistance decreases as the shear rate increases. This is attributed to the molecular alignment in the direction of flow and disentanglement. The MFR (I2, 230 °C, 2.16 kg) provided herein is determined according to ASTM D-1238-E(20) and measured in grams per minute (g / min).

[0019] Unless otherwise stated, the term "melt temperature" or "Tm" and its grammatical variants refer to the copolymer melt temperature at the die of the extruder, and the unit is °C.

[0020] The term "crystallization temperature" or "Tc" and its grammatical variants refer to the temperature at which the copolymer melt transforms from the amorphous-liquid state to the crystalline state, and the unit is °C unless otherwise stated.

[0021] As used herein, the term "haze" and its grammatical variants refer to the scattering of light as it passes through the copolypropylene polymers of the present disclosure. Haze is measured based on a 1 mm sheet thickness in accordance with ASTM D1003B-21.

[0022] The term "flexural modulus" and its grammatical variants refer to the tendency of a material to bend in terms of the stress-strain ratio and is determined in accordance with ASTM D790A-17. The unit of flexural modulus is kilopounds per square inch (kpsi).

[0023] The term "tensile strength" and its grammatical variants refer to the plastic strength specifications of un-reinforced and reinforced polymers. The test method uses a standard dog-bone specimen with a thickness of 14 mm and is conducted in accordance with ASTM D638-22. The unit of tensile strength is pounds per square inch (psi).

[0024] As used herein, the term "notched Izod" and its grammatical variants refer to a measure of impact resistance from a swinging pendulum; it is the degree of kinetic energy required to initiate and continue a break in the material until the material fractures. Notched Izod is determined in accordance with ASTM D256A-10 and is measured in foot-pounds per inch (ft-lb / inch).

[0025] As used herein, "M" n is the number-average molecular weight and "M" w is the weight-average molecular weight. Unless otherwise stated, all molecular weight units (e.g., M w and M n ), including molecular weight data, are in kilograms per mole (kg / mol). Molecular weight is tested according to the GPC-4D method.

[0026] As used herein, the term "molecular weight distribution" or "MWD" and its grammatical variants are equivalent to the expression M w / M n , and is also referred to as the polydispersity index (PDI). The expression M w / M n is the ratio of M w to M n . M w is given as follows:

[0027] M n is given as follows: where n i in the foregoing equation is the mole fraction of molecules having a molecular weight M i .

[0028] As used herein, the term "bimodal molecular weight distribution" or "bimodal MWD" and grammatical variations thereof with respect to the copolymerized - polypropylene polymer refer to a copolymerized - polypropylene polymer having at least two components with different molecular weights, including a higher molecular weight (HMW) component and a lower molecular weight (LMW) component. The bimodal copolymerized - polypropylene polymers of the present disclosure are physically blended, for example, by extrusion compounding.

[0029] As used herein, the term "ethylene percentage" or "C2%" and grammatical variations thereof refer to the percentage of ethylene included in the copolymerized - polypropylene polymer.

[0030] As used herein, the terms "slurry polymerization", "slurry", and "slurry polymerization reactor" and grammatical variations thereof each refer to a process in which an olefin (e.g., propylene) is partially soluble or insoluble in a polymerization medium. During slurry polymerization, catalyst components, solvents, α - olefins, and hydrogen can be transferred under pressure to one or more slurry polymerization reactors. Typically, the catalyst components are fed into the slurry polymerization reactor as a mixture in an aliphatic hydrocarbon solvent, oil, a mixture thereof, or as a dry powder.

[0031] As used herein, the term "extruder" and grammatical variations thereof include any machine suitable for polyolefin extrusion. For example, the term includes machines that can extrude polyolefins in the form of powders or pellets, sheets, fibers, or other shapes and / or profiles, but is not limited thereto. Typically, an extruder operates by feeding a polymer material through a feed throat that contacts one or more rotating screws. The rotating screw(s) force the polyolefin forward into one or more heated barrels. In some processes, a heating profile can be set for the barrel, where one or more (e.g., three or more) independently proportional - integral - derivative (PID) - controlled heater zones can gradually increase the temperature of the barrel. The extruder can be a single - screw or twin - screw extruder. Copolymerized - polypropylene random copolymers, methods, and systems

[0032] Compositions and methods for producing copolymerized - polypropylene polymers include preparing a copolymerized - polypropylene polymer composition having a low ethylene content and a bimodal molecular weight, which exhibits enhanced flexural modulus values (stiffness) and tensile strength, as well as enhanced plate haze (transparency).

[0033] The compositions and methods disclosed herein include preparing a copolymerized - polypropylene polymer composition having a bimodal molecular weight and enhanced strength, toughness, and transparency by polymerization. The copolymerized - polypropylene polymer compositions disclosed herein can include a mixture of a polypropylene polymer and a low concentration of a second polyethylene polymer, as described herein.

[0034] The copolymerized - polypropylene polymers of the present disclosure may have an ethylene content of less than about 0.60 wt%, such as less than about 0.50 wt%, or in the range of about 0.40 wt% to about 0.60 wt%, covering any value and subgroup therebetween.

[0035] The copolymerized - polypropylene polymers of the present disclosure may have a flexural modulus greater than about 240 kpsi, such as in the range of about 240 kpsi to about 280 kpsi, covering any value and subgroup therebetween.

[0036] The copolymerized - polypropylene polymers of the present disclosure may have a tensile strength greater than about 5200 psi, such as greater than about 5300 psi, or in the range of about 5200 psi to about 5700 psi, covering any value and subgroup therebetween.

[0037] Based on a 1 - mm - thick sample, the copolymerized - polypropylene polymers of the present disclosure may have a haze of less than about 35%, such as less than about 30%, or in the range of about 20% to about 35%, covering any value and subgroup therebetween.

[0038] The copolymerized - polypropylene polymers of the present disclosure may have a 230°C MFR of about 1 g / 10 min to about 10 g / 10 min, such as about 1.5 g / 10 min to about 4 g / 10 min, covering any value and subgroup therebetween.

[0039] The copolymerized - polypropylene polymers of the present disclosure may have a melt temperature (Tm) in the range of about 150°C to about 170°C, such as about 155°C to about 165°C, covering any value and subgroup therebetween.

[0040] The copolymerized - polypropylene polymers of the present disclosure may have a crystallization temperature (Tc) of about 100°C - about 130°C, such as about 120°C - about 125°C, covering any value and subgroup therebetween.

[0041] The copolymerized - polypropylene polymers of the present disclosure described herein have a molecular weight (Mw) of about 300 kg / mol to about 700 kg / mol, such as about 400 kg / mol to about 600 kg / mol, covering any value and subgroup therebetween.

[0042] The copolymerized - polypropylene polymers of the present disclosure may have an MWD of about 5 to about 20, such as about 5 to about 16, or about 5 to about 14, covering any value and subgroup therebetween.

[0043] In one or more aspects, the copolymerized - polypropylene polymers of the present disclosure can comprise at least an HMW component having a 230 °C MFR of from about 0.02 g / 10 min to about 0.5 g / 10 min and an LMW component having a 230 °C MFR of from about 1 g / 10 min to about 10 g / 10 min, encompassing any values and subgroups therebetween. In one or more aspects, as described herein, the HMW component can comprise a polypropylene homopolymer and the LMW component can comprise a polypropylene / polyethylene random copolymer having a low ethylene concentration. The amount of the HMW component(s) can range from about 15 wt% to about 2 wt% of the LMW component(s), encompassing any values and subgroups therebetween.

[0044] The copolymerized - polypropylene polymers of the present disclosure can have a 23 °C notched Izod impact value of from about 0.5 ft - lb / inch to about 1 ft - lb / inch, such as from about 0.7 ft - lb / inch to about 0.9 J / m, encompassing any values and subgroups therebetween.

[0045] The methods disclosed herein can include single - stage or multi - stage polymerization methods having a first stage in which one or more polypropylene polymerization reactions produce a first and / or second polypropylene and a second stage that produces a second polyethylene polymer. The two polymers can be co - extruded to form the copolymerized - polypropylene polymers of the present disclosure. In one or more aspects, the co - extrusion compounding can be achieved using a screw extruder, such as a 30 mm Werner & Pfleiderer twin - screw extruder (New Jersey, USA).

[0046] The methods described herein can be used in combination with other techniques to modulate strength, toughness, and transparency, including post - reactor modification by cross - linking or blending with other additives such as antioxidants.

[0047] A method of preparing the copolymerized - polypropylene polymer composition can include polymerizing propylene and ethylene with a non - phthalate Ziegler - Natta catalyst system to form an ethylene / propylene random copolymer composition and extruding the ethylene / propylene random copolymer composition to form a copolymerized - polypropylene polymer composition.

[0048] A variety of Ziegler-Natta pre-catalysts can be used in the non-phthalate catalyst system, but other catalyst systems for the polymerization of propylene and ethylene can be used without departing from the scope of the present disclosure. For example, the Ziegler-Natta pre-catalyst composition can include a transition metal compound and a Group 2 metal compound. The transition metal compound can include a solid complex derived from a transition metal compound, such as a titanium-, zirconium-, chromium-, or vanadium-hydrocarbyloxide, hydrocarbylide, halide, or a mixture thereof. In one or more aspects, the Ziegler-Natta pre-catalyst composition contains a titanium transition metal, a magnesium Group 2 metal, and a chlorine halogen.

[0049] The polymerization process includes polymerizing ethylene (at a low concentration) and propylene in the presence of a non-phthalate catalyst system under reaction conditions sufficient to form the co-polypropylene polymer composition of the present disclosure.

[0050] Any type of polymerization process suitable for the preparation of polyolefins can be used with the catalyst system. The polymerization can be carried out, for example, in the bulk phase using a liquid monomer (such as propylene) as the reaction medium, in a slurry using an inert liquid (such as a hydrocarbon) as a diluent, in solution using a monomer or an inert hydrocarbon as a polymerization solvent, or in the gas phase, where it is operated in one or more fluidized or mechanically stirred bed reactors. In other aspects, the polymerization reaction can be carried out using melt extrusion, where the heat generated during the extrusion step provides the energy required for the reaction between the bimodal components described herein to form the co-polypropylene polymer composition described herein.

[0051] The co-polypropylene polymer composition disclosed herein can include one or more additives during one or more stages of the polymerization process and / or before or after polymerization. Suitable additives can include mechanical and rheological modifiers, such as carbon nanomaterials, including carbon nanotubes, graphene, fullerenes, diamond-like carbon, or carbon black, fibers, nanocrystalline cellulose, cellulose nanofibrils, silica, silica-alumina, alumina such as (pseudo)boehmite, gibbsite, titanium oxide, zirconium oxide, cationic clay, or anionic clay such as saponite, bentonite, kaolin, sepiolite, hydrotalcite, etc. The additives can also include metal oxides, such as aluminum trihydroxide (ATH), aluminum monohydrate, magnesium hydroxide, magnesium silicate, talc, silica (such as pyrogenic silica and precipitated silica), and calcium carbonate, calcium metasilicate, wollastonite, dolomite, perlite, hollow glass spheres, kaolin, etc.

[0052] Other additives can include fillers; antioxidants (e.g., hindered phenols, such as IRGANOX TM 1010 or IRGANOX TM1076); phosphites (such as Irgafos 168 available from Ciba-Geigy); nucleating agents (e.g., aromatic carboxylates, organic derivatives of dibenzylidene sorbitol, organic phosphates, inorganic materials lacking polymer solubility); anti-adhesion additives; tackifiers such as polybutene, terpene resins, aliphatic and aromatic hydrocarbon resins, alkali metal and glycerol stearates, and hydrogenated rosin; UV stabilizers such as titanium oxide, zinc oxide, benzophenone, benzotriazole, aryl esters, sterically hindered amines, etc.; heat stabilizers; anti-blocking agents; mold release agents; antistatic agents; pigments; colorants; dyes; waxes; silica; fillers; talc, etc. TM 168); nucleating agents (e.g., aromatic carboxylates, organic derivatives of dibenzylidene sorbitol, organic phosphates, inorganic materials lacking polymer solubility); anti-adhesion additives; tackifiers such as polybutene, terpene resins, aliphatic and aromatic hydrocarbon resins, alkali metal and glycerol stearates, and hydrogenated rosin; UV stabilizers such as titanium oxide, zinc oxide, benzophenone, benzotriazole, aryl esters, sterically hindered amines, etc.; heat stabilizers; anti-blocking agents; mold release agents; antistatic agents; pigments; colorants; dyes; waxes; silica; fillers; talc, etc.

[0053] In various aspects of the present disclosure, one or more polypropylene polymers having a low ethylene content can be compounded (e.g., in an extruder) together and can be further compounded with one or more polypropylene polymers having a complete lack of ethylene content (polypropylene homopolymers). Exemplary embodiments

[0054] Non-limiting exemplary embodiments of the present disclosure include:

[0055] Embodiment A: A composition comprising: a bimodal molecular weight ethylene / propylene random copolymer comprising a high molecular weight component having a melt flow rate at 230 °C of about 0.02 g / 10 min to about 0.5 g / 10 min and a low molecular weight component having a melt flow rate at 230 °C of about 1 g / 10 min to about 10 g / 10 min and an ethylene content of about 0.40 wt% to about 0.60 wt%.

[0056] Embodiment B: A method comprising: polymerizing ethylene and propylene monomers to produce a bimodal molecular weight ethylene / propylene random copolymer comprising a high molecular weight component having a melt flow rate at 230 °C of about 0.02 g / 10 min to about 0.5 g / 10 min and a low molecular weight component having a melt flow rate at 230 °C of about 1 g / 10 min to about 10 g / 10 min and an ethylene content of about 0.40 wt% to about 0.60 wt%.

[0057] Embodiment C: A molded article comprising a bimodal molecular weight ethylene / propylene random copolymer comprising a high molecular weight component having a melt flow rate at 230 °C of about 0.02 g / 10 min to about 0.5 g / 10 min and a low molecular weight component having a melt flow rate at 230 °C of about 1 g / 10 min to about 10 g / 10 min and an ethylene content of about 0.40 wt% to about 0.60 wt%.

[0058] Non-limiting exemplary embodiments A, B, or C may include one or more of the following elements:

[0059] Element 1: wherein the composition has a flexural modulus of from about 240 kpsi to about 280 kpsi.

[0060] Element 2: wherein the composition has a tensile strength of from about 5200 psi to about 5700 psi.

[0061] Element 3: wherein the composition has a plaque haze value of from about 20% to about 35% based on a 1 mm thick sample.

[0062] Element 4: wherein the composition has a molecular weight of from about 300 kg / mol to about 700 kg / mol.

[0063] Element 5: wherein the composition has a melt temperature of from about 150 °C to about 170 °C.

[0064] Element 6: wherein the composition has a crystallization temperature of from about 100 °C to about 130 °C.

[0065] Element 7: wherein the composition has a molecular weight distribution of from about 5 to about 20.

[0066] Element 8: wherein the composition has a 23 °C notched Izod impact value of from about 0.5 ft-lb / inch to about 1 ft-lb / inch.

[0067] Each of embodiments A, B, and C may include any one, more than one, or all of elements 1-8 in any combination.

[0068] Embodiment C may further include:

[0069] Element 9: wherein the molded article is a packaging product.

[0070] Embodiment C may have any one, more than one, or all of elements 1-9 in any combination.

[0071] To facilitate a better understanding of aspects of the present disclosure, the following examples of preferred or representative aspects are given. The following examples should in no way be construed as limiting, or defining the scope of the present disclosure. Examples

[0072] In the following examples, various experiments are conducted and measurements are made to evaluate and verify the improved strength, toughness, and transparency of the copolypropylene polymer compositions having a bimodal molecular weight distribution and low ethylene content described herein.

[0073] Samples EX1 - EX4 were prepared using a combination of one or more of the polymer “pellets” - G1, G2, and / or G3. G1 and G2 are random copolypropylene polymers with a low ethylene content, and G3 is a HMW polypropylene homopolymer. G1 and G2 further have a lower molecular weight compared to G3. The melt flow rate and ethylene content of each of G1 - G3 are provided in Table 1 below. Table 1

[0074] G1 and G2 were compounded with a certain amount of G3 (as provided in Table 2) with a nucleating agent masterbatch and an antioxidant masterbatch using a 30 mm Werner & Pfleiderer (Dinkelsbuhl, Germany) twin - screw extruder to form samples EX1 - EX4. The nucleating agent masterbatch consists of an α - nucleating agent for polypropylene, and the antioxidant masterbatch consists of both a phenolic primary antioxidant and a phosphite - based secondary antioxidant. Table 2

[0075] The properties of each of EX1 - EX4 were tested according to the method described herein and are provided in Table 3 below. Each of EX1 - EX4 was compared with a commercially available PP6272NE1 (a nucleated polypropylene homopolymer (ExxonMobi l TM , Texas), labeled “CT” in Table 3). “TDS” stands for Technical Data Sheet from which the values were obtained. Table 3

[0076] As shown in Table 3, as the MWD increases, the stiffness and transparency of the copoly - polypropylene polymers also increase. In each of EX1 - EX4, the transparency remains comparable to the CT sample. Thus, the copoly - polypropylene polymer composition of the present disclosure exhibits improved strength, toughness (stiffness), and transparency at low ethylene levels with a bimodal MWD. Such copoly - polypropylene polymer compositions can be particularly used in thermoforming, low molding, and injection molding applications, for example, for packaging products.

[0077] It is apparent from the foregoing general description and specific embodiments that, while the forms of the present disclosure have been illustrated and described, various modifications can be made without departing from the spirit and scope of the present disclosure. Accordingly, it is not intended that the present disclosure be limited thereby. For example, the compositions described herein may be free of any component or composition not specifically enumerated or disclosed herein. Any method may lack any step not enumerated or disclosed herein. Similarly, the term "comprising" is considered synonymous with the term "including". Whenever a method, composition, element, or group of elements is preceded by the transitional term "comprising", it should be understood that the same composition or group of elements is also contemplated wherein the transitional phrase "consisting essentially of", "consisting of", "selected from", or "is" precedes the recited composition, element, or each element.

[0078] Unless otherwise indicated, all numbers expressing quantities of ingredients, properties such as molecular weight, reaction conditions, and the like used in the specification and the appended claims are to be understood as being modified in all instances by the term "about". Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and attached claims are approximations that may vary depending upon the properties desired to be obtained by the embodiments of the present disclosure. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques.

[0079] Whenever a numerical range having a lower limit and an upper limit is disclosed, any number and any included range falling within the range are specifically disclosed. In particular, each range of values disclosed herein (of the form "from about a to about b" or equivalently "from approximately a to b" or equivalently "from approximately a - b") should be understood to set forth every number and range encompassed within the broader range of values. Additionally, the terms in the claims have their ordinary and customary meanings unless the patentee has otherwise clearly and expressly defined them. Further, the indefinite articles "a" or "an" used in the claims are defined herein as meaning one or more of the elements introduced thereby.

[0080] One or more illustrative embodiments are provided herein. For clarity, not all features of a physical implementation are described or shown in this application. It should be understood that in developing a physical implementation incorporating the present disclosure, numerous implementation - specific decisions must be made to achieve the developer's goals, such as compliance with system - related, business - related, government - related, and other constraints, which vary depending on the implementation and change over time. Although the efforts of developers may be time - consuming, such efforts are routine tasks for those of ordinary skill in the art who benefit from the present disclosure.

[0081] Accordingly, the present disclosure is fully suitable for attaining the mentioned objects and advantages as well as those inherent therein. The specific embodiments disclosed above are merely illustrative, as the present disclosure may be modified and practiced in different but equivalent ways that are obvious to those of ordinary skill in the art benefiting from the teachings herein. Moreover, there is no intention to limit the details of the construction or design shown herein other than as described in the following claims. Thus, it is evident that the specific illustrative embodiments disclosed above may be varied, combined, or modified, and all such variations are considered to be within the scope and spirit of the present disclosure. The embodiments illustratively disclosed herein may be suitably practiced in the absence of any element not specifically disclosed herein and / or any optional element disclosed herein.

Claims

1. A composition comprising: A bimodal molecular weight ethylene / propylene random copolymer comprising a high molecular weight component having a melt flow rate at 230 °C of from about 0.02 g / 10 min to about 0.5 g / 10 min, a low molecular weight component having a melt flow rate at 230 °C of from about 1 g / 10 min to about 10 g / 10 min, and an ethylene content of from about 0.40 wt% to about 0.60 wt%.

2. The composition of claim 1, wherein the composition has a flexural modulus of from about 240 kpsi to about 280 kpsi.

3. The composition of claim 1, wherein the composition has a tensile strength of from about 5200 psi to about 5700 psi.

4. The composition of claim 1, wherein the composition has a haze value of from about 20% to about 35% based on a 1 mm thick sample.

5. The composition of claim 1, wherein the composition has a molecular weight of from about 300 kg / mol to about 700 kg / mol.

6. The composition of claim 1, wherein the composition has a melt temperature of from about 150 °C to about 170 °C.

7. The composition of claim 1, wherein the composition has a crystallization temperature of from about 100 °C to about 130 °C.

8. The composition of claim 1, wherein the composition has a molecular weight distribution of from about 5 to about 20.

9. The composition of claim 1, wherein the composition has a 23 °C notched Izod impact value of from about 0.5 ft-lb / inch to about 1 ft-lb / inch.

10. A method comprising: Polymerizing ethylene and propylene monomers to produce a bimodal molecular weight ethylene / propylene random copolymer comprising a high molecular weight component having a melt flow rate at 230 °C of from about 0.02 g / 10 min to about 0.5 g / 10 min, a low molecular weight component having a melt flow rate at 230 °C of from about 1 g / 10 min to about 10 g / 10 min, and an ethylene content of from about 0.40 wt% to about 0.60 wt%.

11. The method of claim 10, wherein the bimodal molecular weight ethylene / propylene random copolymer has a flexural modulus of from about 240 kpsi to about 280 kpsi.

12. The method of claim 10, wherein the bimodal molecular weight ethylene / propylene random copolymer has a tensile strength of from about 5200 psi to about 5700 psi.

13. The method of claim 10, wherein the bimodal molecular weight ethylene / propylene random copolymer has a haze value of from about 20% to about 35% based on a 1 mm thick sample.

14. The method of claim 10, wherein the bimodal molecular weight ethylene / propylene random copolymer has a melt temperature of from about 150 °C to about 170 °C.

15. The method of claim 10, wherein the bimodal molecular weight ethylene / propylene random copolymer has a crystallization temperature of from about 100 °C to about 130 °C.

16. The method of claim 10, wherein the bimodal molecular weight ethylene / propylene random copolymer has a molecular weight of from about 300 kg / mol to about 700 kg / mol.

17. The method of claim 10, wherein the bimodal molecular weight ethylene / propylene random copolymer of the composition has a molecular weight distribution of about 5 to about 20.

18. The method of claim 10, wherein the bimodal molecular weight ethylene / propylene random copolymer has a 23 °C notched Izod impact value of about 0.5 ft-lb / inch to about 1 ft-lb / inch.

19. A molded article comprising a bimodal molecular weight ethylene / propylene random copolymer, the bimodal molecular weight ethylene / propylene random copolymer comprising a high molecular weight component having a melt flow rate at 230 °C of about 0.02 g / 10 min to about 0.5 g / 10 min and a low molecular weight component having a melt flow rate at 230 °C of about 1 g / 10 min to about 10 g / 10 min and an ethylene content of about 0.40 wt% to about 0.60 wt%.

20. The molded article of claim 19, wherein the molded article is a packaging product.

Images