RU2825643C2 - Polypropylene copolymer composition having impact resistance at temperatures below zero - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to a polypropylene composition and can be used to produce various articles, such as packaging or containers. Polypropylene composition for producing moulded articles contains a first phase polymer containing a random polypropylene copolymer containing ethylene, wherein the copolymer has content of xylene-soluble substances from more than 0.5% to less than 10% by weight and has a melt flow rate from 20 g/10 min to 50 g/10 min, measured in accordance with ASTM D 1238, at 230 °C with load of 2.16 kg; second phase polymer in combination with first phase polymer, wherein the second phase polymer contains a propylene and ethylene copolymer. Polypropylene composition has a melt flow rate of 10 g/10 min to 30 g/10 min, measured in accordance with ASTM D 1238, at 230 °C with load of 2.16 kg, and the ratio of the melt flow rate of the polymer of the first phase to the melt flow rate of the polypropylene composition is greater than or equal to 1 and less than or equal to 2. Also, the polypropylene composition has a xylene-soluble part and a xylene-insoluble part, wherein the polypropylene composition has a total content of xylene-soluble substances from 12% to 25% by weight, xylene-soluble portion contains ethylene in an amount of about 55% to about 70% by weight, the xylene-insoluble portion contains ethylene in amount of 15% to 40% by weight. In addition, the invention relates to a moulded article made from a polypropylene composition and a storage container made from the polypropylene composition.

EFFECT: creation of polypropylene polymer compositions with improved balance of properties, for example, with excellent properties of transparency in combination with properties of impact resistance at temperatures below zero.

24 cl, 1 dwg, 5 tbl, 3 ex

Description

Related applications

This application is based on and claims priority from U.S. Provisional Patent Application No. 62/829,932, filed April 5, 2019, the contents of which are incorporated herein by reference.

Prerequisites for the creation of an invention

Transparency and impact resistance are highly desirable properties for many polymer applications. For example, polymers can be used to produce various products such as packaging or containers, where transparency can be very useful for the user. For example, in many situations, it is very useful to see the contents of the package or container through the walls of the package or container. On the other hand, high impact resistance properties make the containers durable.

One type of polymer that can be made very clear is the semicrystalline homopolymers of polypropylene. Homopolymers of polypropylene are inherently very clear due to their high crystallinity and large spherulites. The clarity of polypropylene polymers can be improved by incorporating ethylene or another alpha-olefin into the polymer chain to form a random copolymer of polypropylene. Nucleating agents and/or clarifiers can also be included in the polymer to further reduce crystal size and improve clarity.

Although random copolymers of polypropylene have excellent transparency properties, these polymers have relatively low impact resistance, especially in sub-zero ambient conditions. Thus, refrigerated or freezer storage containers and/or long-term storage containers require higher impact resistance. However, when attempts are made to improve the impact resistance of polypropylene polymers, other properties of these polymers may be degraded.

Impact-resistant polypropylene copolymers have been developed previously that contain a homopolymer matrix mixed with a rubber-like propylene-alpha-olefin copolymer phase. The copolymer phase is intended to increase impact resistance, for example at cold temperatures. The propylene-alpha-olefin copolymer may be predominantly amorphous and thus have elastomeric properties, forming a rubber phase within the polymer composition. The introduction of propylene-alpha-olefin copolymer increases impact resistance, but leads to a decrease in transparency.

In order to increase the clarity of heterophasic polypropylene compositions containing a rubber phase, those skilled in the art have attempted to reduce the size of the rubber phase. For example, adding ethylene to the matrix polymer and minimizing the ethylene content of the rubber phase can be used to improve compatibility between the matrix phase and the rubber phase. However, past attempts have failed to adequately produce a polymer composition having the desired combination of clarity and impact strength. More specifically, past attempts have failed to produce a polypropylene polymer composition having adequate impact strength at sub-zero temperatures.

Statement of the essence of the invention

In general, the present invention relates to polypropylene polymer compositions having an improved balance of properties. For example, polypropylene polymer compositions made in accordance with the present disclosure can be formulated to provide excellent transparency properties in combination with excellent impact properties at sub-zero temperatures. In one embodiment, the polypropylene polymer composition includes a polypropylene polymer in combination with a propylene-alpha-olefin copolymer containing relatively large amounts of an alpha-olefin. The content of the alpha-olefin (such as ethylene) in the polymer of each phase can be controlled within desired limits. In addition, the relative amounts of the polymer of each phase can be selected to maximize certain properties. In one embodiment, both polymers mixed together are made using a Ziegler-Natta catalyst system, which allows for careful control of various parameters and variables during polymer production.

For example, in one embodiment, the present disclosure relates to a polypropylene composition comprising a first phase polymer combined or blended with a second phase polymer. The first phase polymer comprises a polypropylene polymer, such as a polypropylene random copolymer. The polypropylene random copolymer may comprise an alpha-olefin, such as ethylene or butylene, in an amount of up to about 4% by weight, such as in an amount of from about 1% to about 4% by weight. The polypropylene random copolymer may have a xylene soluble fraction of less than about 10% by weight, such as less than about 8% by weight. The polypropylene random copolymer is substantially present in the polymer composition in an amount greater than about 50% by weight, such as in an amount greater than about 60% by weight, such as in an amount greater than about 65% by weight. The melt flow rate of the first phase polymer may be substantially from about 20 g/10 min to about 50 g/10 min.

The second phase polymer blended with the first phase polymer essentially comprises a copolymer of propylene and an alpha-olefin, such as a copolymer of propylene and ethylene, containing relatively large amounts of an alpha-olefin, such as ethylene. It has been found that increasing the amount of ethylene in the elastomeric or rubber-like copolymer can significantly and unexpectedly improve the impact properties of the polymer composition at subzero temperatures, such as at temperatures below 0°C, such as at a temperature of -20°C. The amount of ethylene contained in the copolymer can be characterized by the amount of ethylene in the xylene-soluble portion and the amount of ethylene in the xylene-insoluble portion of the polypropylene composition. For example, the polypropylene composition (both the first phase polymer and the second phase polymer) can have a total xylene-soluble content of from about 12% to about 25% by weight. The xylene soluble portion may comprise ethylene in an amount of from about 55% by weight to about 70% by weight, such as from about 60% by weight to about 70% by weight. Ethylene may be present in the xylene insoluble portion in an amount of from about 15% by weight to about 40% by weight, such as from about 20% by weight to about 38% by weight. In this regard, the propylene-ethylene copolymer in the second phase polymer substantially comprises ethylene in an amount greater than about 75% by weight, such as greater than about 80% by weight, and substantially in an amount less than about 95% by weight, such as less than about 92% by weight. In one embodiment, ethylene is present in the second phase polymer in an amount of from about 75% by weight to about 85% by weight, such as from about 77% by weight to about 83% by weight.

The above heterophasic polypropylene composition has an excellent combination of physical properties. For example, when tested at a temperature of -20 °C, the polypropylene composition can have a Gardner impact strength of more than about 200 inch-lbs, such as more than 250 inch-lbs, such as more than about 300 inch-lbs, such as more than about 350 inch-lbs, and substantially less than about 500 inch-lbs. Typically, the polymer composition can have a flexural modulus of less than about 1000 MPa, such as less than about 800 MPa, and substantially more than about 500 MPa, such as more than about 650 MPa. In addition, the polypropylene composition can have a haze per 1 mm of less than about 45%. For example, the haze can be from about 5% to about 45%. In addition, the polymer composition can have a relatively high transparency. For example, the transparency of a composition may be greater than about 90%, such as greater than about 92%.

The polypropylene composition can substantially have a melt flow rate of more than about 3 g/10 min, such as more than about 5 g/10 min, such as more than about 10 g/10 min, and substantially less than about 50 g/10 min. In one embodiment, the melt flow rate can be from about 15 g/10 min to about 25 g/10 min. The ratio of the melt flow rate of the first phase polymer to the melt flow rate of the polypropylene composition is substantially greater than or equal to 1. The second phase polymer is contained in the polypropylene composition substantially in an amount of from about 15% to about 50% by weight. In one embodiment, the composition can further comprise a clarifier to improve transparency properties.

The polymer composition of the present disclosure can be used to make a variety of different types of articles. In one embodiment, the polymer composition can be used to create various molded articles, such as injection molded articles. In one embodiment, the polymer composition can be used to mold containers, such as storage containers. Storage containers, for example, can be designed to hold food or can be used to mold long-term storage containers for warehouses, attics, garages, and the like. The polymer composition of the present disclosure is particularly well suited for making storage containers and other packaging for use in a freezer or for use in which the container must be exposed to sub-zero temperatures.

Other features and aspects of the present description are described in more detail below.

Brief description of graphic materials

A full and complete description of the present invention is more particularly set forth in the remainder of the specification, including reference to the accompanying figures.

Fig. 1 is a perspective view of one embodiment of a container manufactured in accordance with the present description.

Reuse of reference numbers throughout the present specification and drawings is intended to represent the same or similar features or elements of the present invention.

Definitions and testing procedures

As used herein, the term "propylene-ethylene copolymer" means a copolymer comprising propylene monomer in a predominant weight percentage relative to ethylene monomer as a secondary constituent. "Propylene-ethylene copolymer" (which is also sometimes referred to as polypropylene random copolymer, PPR, PP-R, RCP or RACO) is a polymer having individual repeating units of ethylene monomer present in a random or random distribution in the polymer chain.

Melt flow rate (MFR) as used herein is measured in accordance with the test method described in ASTM D 1238 at 230°C with a 2.16 kg load for propylene based polymers.

Xylene solubles (XS) are defined as the weight percent of resin remaining in solution after a sample of the random propylene copolymer resin is dissolved in hot xylene and the solution is cooled to 25°C. This method is also referred to as the gravimetric XS method according to ASTM D5492-06 using a 90-minute settling time, and is also referred to herein as the "wet method". XS content can also be measured according to the Viscotek method as follows: Dissolve 0.4 g of polymer in 20 ml of xylenes with stirring at 130°C for 60 minutes. Subsequently, the solution is cooled to 25°C, and after 60 minutes, the insoluble polymer fraction is filtered off. The resulting filtrate is analyzed by polymer flow injection analysis using a Viscotek ViscoGEL H-100-3078 column with a THF mobile phase flowing at 1.0 mL/min. The column is coupled to a Viscotek Model 302 triple detector array equipped with a light scattering detector, viscometer, and refractometer, all operated at 45°C. The instrument is calibrated using Viscotek PolyCAL™ polystyrene standards. A polypropylene (PP) homopolymer, such as Dow 5D98 biaxially oriented polypropylene (BOPP), is used as a reference standard to ensure that the Viscotek instrument and sample preparation procedures give reproducible results when 5D98 is used as a method performance check control. The XS value for 5D98 was originally obtained from testing using the ASTM method noted above.

The above mentioned ASTM D5492-06 method can be adapted for the determination of the xylene soluble fraction. In general, the procedure consists of weighing a 2 g sample and dissolving the sample in 200 mL of o-xylene in a 400 mL flask with a 24/40 joint. The flask is attached to a water-cooled condenser and the contents are stirred and heated under nitrogen (N ₂ ) until condensation occurs and then maintained at reflux for an additional 30 minutes. The solution is then cooled in a water bath maintained at 25°C for 90 minutes to allow the xylene insoluble fraction to crystallize. After cooling the solution and allowing the insoluble fraction to precipitate from the solution, the xylene-soluble portion (XS) is separated from the xylene-insoluble portion (XI) by filtration through filter paper with a pore size of 25 microns. One hundred milliliters of the filtrate are collected in a pre-weighed aluminum cup and o-xylene is evaporated from the aforementioned 100 ml of the filtrate in a stream of nitrogen. After evaporation of the solvent, the tray and contents are placed in a vacuum oven at 100°C for 30 minutes or until dry. The tray is then allowed to cool to room temperature and weighed. The xylene-soluble content is calculated using the formula: XS (wt.%) = [( _m3 − _m2 ) * 2/ _m1 ] * 100, where _m1 is the initial mass of the sample used, _m2 is the mass of the empty aluminum tray, and _m3 is the mass of the tray and residue (here and throughout the description, the asterisk (*) symbol means the product of the terms or values given).

The ethylene content of the xylene soluble fraction (XS) and the xylene insoluble fraction (XI) are measured by ¹³ C NMR. Samples are prepared by adding approximately 2.7 g of a 50/50 mixture of tetrachloroethane-d2/ortho-dichlorobenzene containing 0.025 M Cr(AcAc)3 to 0.20 g of sample in a 10 mm Norell 1001-7 NMR tube. Samples are dissolved and homogenized by heating the tube and its contents to 150 °C using a heating block. Each sample is inspected to ensure homogeneity. Data are collected using a Bruker 400 MHz spectrometer equipped with a Bruker Dual DUL CryoProbe high temperature probe. Data are collected using 500 transitions per data file, a 6 s pulse repetition delay, 90 degree magnetization vector deflection angles, and reverse decoupling with the sample temperature turned off at 120°C. All measurements are performed on non-rotating samples in the blocking mode. Samples are allowed to reach thermal equilibrium for 10 minutes before data collection.

The ethylene content was calculated based on the triad distribution. The triad chemical shift assignment is shown in Table 1.

PPP = (F + A - 0.5D)/2

PPE = D

EPE = C

EEE = (E - 0.5G)/2

PEE = G

PEP = H

Ethylene content is based on the following calculations:

mol P = sum of P-centered triads

mol E = sum of E-centered triads

Table 1. Assignment of chemical shift to the triad for ethylene-propylene copolymer

Chemical shift, δ (ppm) Triad Type of carbon atom Chemical shift range Region 1 44–49 PPE CH ₂ 44.0–49.0 A 2 PPP CH ₂ 3 37.8 EPE(P) CH ₂ 36.0–39.0 B 4 37.4 EPE(E) CH ₂ 5 33.2 EPE SN 32.8–34.0 C 6 31.0 PPE SN 31,00 D 7 30.8 PEE(P) CH ₂ 29.7–30.8 E 8 30.4 PEE(E) CH ₂ 9 30.0 EEE CH ₂ 10 28.8 PPP SN 28.0–29.7 F 11 27.3 EEP CH ₂ 26.0–28.3 G 12 24.6 PEP CH ₂ 24.0–26.0 H 13 21.6 PPP CH ₃ 19.0–23.0 I 14 20.8 PPE CH ₃ 15 20.0 EPE CH ₃

The Koenig B value, which is a measure of the randomness or blockiness in the copolymer, is calculated using the formula: Koenig B value = [EP]/(2[P][E]), where EP is the total mole fraction of EP dimers (EP + PE). (Spectroscopy of Polymers" 2nd edition, Jack L. Koenig, 1999, Elsevier; pp 17–18).

The flexural modulus is determined in accordance with ASTM D790-10 Method A at 1.3 mm/min using an ASTM 3641 Type 1 specimen cast in accordance with ASTM D4101.

The Mw/Mn ratio (also called MWD) and Mz/Mw are measured by GPC according to the gel permeation chromatography (GPC) analytical method for polypropylene. The polymers are analyzed on a PL-220 series high-temperature gel permeation chromatography (GPC) unit equipped with a RI detector and four PLgel Mixed-A (20 μm) columns (Polymer Laboratory Inc.). The oven temperature is set at 150°C and the hot and warm zone temperatures of the autosampler are set at 135°C and 130°C, respectively. The solvent is nitrogen-purged 1,2,4-trichlorobenzene (TCB) containing ˜200 ppm 2,6-di-t-butyl-4-methylphenol (BHT). The flow rate is 1.0 mL/min and the injection volume is 200 µL. A 2 mg/mL sample is prepared by dissolving the sample in _N2 -purged, pre-warmed TCB (containing 200 ppm BHT) for 2.5 h at 160°C with gentle stirring.

A set of GPC columns is calibrated by passing twenty polystyrene standards with a narrow molecular weight distribution. The molecular weight (MW) of the standards ranges from 580 to 8,400,000 g/mol, and the standards are contained in 6 "cocktail" mixtures. Each mixture based on the standard is characterized by at least a decimal place separating the individual molecular weights. The polystyrene standards are prepared at 0.005 g in 20 mL of solvent for molecular weight values equal to or greater than 1,000,000 g/mol and 0.001 g in 20 mL of solvent for molecular weight values less than 1,000,000 g/mol. The polystyrene standards are dissolved at 150 °C for 30 min with stirring. Narrow distribution mixtures of the standards are run first and in descending order of the component with the highest molecular weight to minimize the effect of sensitivity degradation. Logarithmic molecular weight calibration is performed using a fourth-order polynomial fit depending on the elution volume. Equivalent molecular weight values for polypropylene are calculated using the following equation using the validated Mark-Houwink coefficients for polypropylene (Th. G. Scholte, N. L. J. Meijerink, H. M. Schoffeleers, and A. M. G. Brands, J. Appl. Polym. Sci., 29, 3763–3782 (1984)) and polystyrene (E. P. Otocka, R. J. Roe, N. Y. Hellman, and P. M. Muglia, Macromolecules, 4, 507 (1971)):

where M _pp is the equivalent MW PP, M _PS is the equivalent MW PS, log K and the values of the Mark-Houwink coefficients for PP and PS are given below in Table 2.

Table 2

Polymer A log K Polypropylene 0.725 -3,721 Polystyrene 0.702 -3,900

Izod impact strength is measured in accordance with ASTM D 256.

Gardner impact test measurements are carried out in accordance with ASTM D5420.

Turbidity and clarity are measured in accordance with ASTM Test Procedure A D1003 and D1746 using a BYK Gardner Haze-Gard Plus 4725 apparatus using a 1 mm thick injection molded plate.

Tangent δ is measured by DMA test using TA Q800 dual cantilever fixture. The specimen is cut from 12.7mm*3.2mm*60mm flexural modulus test piece. The specimens are first equilibrated at -150°C and isothermally for 5 min, then heated to 100°C at a heating rate of 3°C/min.

The designation β/α refers to the ratio of the molecular weight of the dispersed phase copolymer to the molecular weight of the propylene-based polymer in the continuous phase, where β and α are the intrinsic viscosity values of the copolymer and the propylene-based polymer fractions, respectively, when measured in decalin at 135°C. (ASTM D 1601). For the purposes of this specification, the β/α value is calculated from the MFR of the matrix polymer, the MFR of the total impact copolymer, and the Fc before visbreaking as follows:

The rubber particle size is measured using a scanning electron microscope (SEM) in the form of a Hitachi Tabletop Microscope TM3030Plus machine. The specimen is first cut from the center of the Izod test fragments (ASTM D4101) along the flow direction, and then cryosectioned on a microtome at -20°C, stained with RuO ₄ and further cryosectioned on a microtome at -20°C. SEM images are observed in backscatter mode (BSE), in which the strongly stained area (EPR rubber) is the lighter phase and the slightly stained area is the darker phase. The particle size is recorded and analyzed using Image-Pro® Premier software. D50 is calculated from the average particle size in the fraction with a total volume of 50%.

Detailed description

One of ordinary skill in the art should understand that this text is intended to be a description of embodiments only and is not intended to limit the broader aspects of the present disclosure.

In general, the present description relates to a polypropylene composition having a unique combination of physical properties. For example, in one embodiment, the polymer composition can be formulated to have not only excellent transparency properties, but also excellent impact resistance properties. In addition, the polymer composition can be formulated to have good flow properties. Thus, the polymer composition is particularly well suited for molding injection molded articles. For example, in one embodiment, the polymer composition can be used to mold containers, in particular storage containers, in which a product or item placed in the container can be viewed through the walls of the container or package. The polypropylene composition of the present description is particularly well suited for producing freezer packages and containers.

In general, the polypropylene composition of the present description comprises a heterophasic composition. In particular, the polypropylene composition includes a first phase polymer mixed with a second phase polymer. The polymers of both phases are formed from a polypropylene copolymer containing controlled amounts of an alpha-olefin, such as ethylene or butylene. For example, in one embodiment, the first phase polymer comprises a polypropylene random copolymer containing ethylene in an amount of up to about 4% by weight. The first phase polymer is substantially present in the polymer composition in an amount greater than the second phase polymer and, therefore, forms a matrix polymer. On the other hand, the second phase polymer comprises a polypropylene copolymer having elastomeric or rubber-like properties. According to the present description, the second phase polymer contains a greater amount of ethylene than propylene. It has been found that substantially increasing the ethylene concentrations in the second phase polymer can significantly improve the impact properties of the polymer composition at subzero temperatures. Unexpectedly improved stiffness properties at lower temperatures, combined with excellent clarity properties, make the polypropylene composition well suited for the manufacture of containers that will be used in sub-zero ambient conditions.

For example, when tested in accordance with the Gardner Impact Test, the polymeric composition may exhibit a Gardner Impact Strength at a temperature of -20°C of greater than about 200 inch-lbs, such as greater than about 225 inch-lbs, such as greater than about 250 inch-lbs, such as greater than about 275 inch-lbs, such as greater than about 300 inch-lbs, such as greater than about 325 inch-lbs, and substantially less than about 500 inch-lbs.

As described above, in addition to excellent impact strength properties, the polymer composition of the present disclosure can also have very good transparency properties. For example, the polymer composition can have a turbidity per mm of less than about 45%, such as less than about 40%, such as less than about 35%, such as even less than about 30%. The turbidity per mm is substantially greater than about 10%.

In addition to the relatively low haze, the polypropylene composition of the present disclosure can exhibit excellent transparency characteristics. For example, the polymer composition can exhibit a haze of greater than about 80%, such as greater than about 85%, such as greater than about 90%, such as even greater than about 92%.

The flexible nature of the polymer composition may vary depending on various factors, including the relative amounts of the first phase polymer and the second phase polymer and the amount of comonomer in the first and second phases. Typically, the polymer composition of the general description may have a flexural modulus of less than about 1000 MPa, such as less than about 850 MPa, such as less than about 800 MPa, such as less than about 750 MPa. In general, the flexural modulus is greater than about 500 MPa, such as greater than about 550 MPa, such as greater than about 600 MPa.

The designation β/α refers to the ratio of the molecular weight of the copolymer to the molecular weight of the matrix polymer or the polymer from the first phase polymer. The molecular weight of each polymer is proportional to the intrinsic viscosity of each polymer. Intrinsic viscosity indicates the viscosity of a solution of the polymer in a given solvent and at a given temperature. For example, the polymer composition of the present description can have a β/α ratio greater than about 1, such as greater than or equal to 1.1. For example, the β/α ratio can be greater than about 1.2, such as greater than about 1.3. Typically, the β/α ratio is less than about 2, such as less than about 1.8, such as less than about 1.6.

The polymer compositions formulated according to the present disclosure may also have excellent flow properties while maintaining a relatively high impact strength. For example, the polymer composition of the present disclosure may have a melt flow rate of greater than about 3 g/10 min, such as greater than about 15 g/10 min, such as greater than about 17 g/10 min, such as greater than about 18 g/10 min. The melt flow rate is substantially less than about 80 g/10 min, such as less than about 70 g/10 min, such as less than about 50 g/10 min, such as less than about 35 g/10 min, such as less than about 30 g/10 min. Due to the flow properties described above, the polymer composition is well suited for use in injection molding.

As described above, the polypropylene composition of the present description essentially includes a first phase polymer combined with a second phase polymer. The first phase polymer comprises a polypropylene polymer, such as a random copolymer of polypropylene. For example, the random copolymer can be a copolymer of propylene and an alpha-olefin, such as ethylene or butylene. The random copolymer of polypropylene forms a matrix polymer in the polypropylene composition and can contain an alpha-olefin in an amount of up to about 4% by weight, such as in an amount of less than about 3.8% by weight, such as in an amount of less than about 3.5% by weight, and substantially in an amount of greater than about 0.5% by weight, such as in an amount of greater than about 1% by weight, such as in an amount of greater than about 1.5% by weight, such as in an amount of greater than about 2% by weight. The first phase polymer may have a xylene solubles content of substantially less than about 12% by weight, such as less than about 10% by weight, such as less than about 8% by weight, such as less than about 7% by weight. The xylene solubles content is substantially greater than about 0.5% by weight, such as greater than about 3% by weight.

As will be described in more detail below, the first phase polymer may comprise a Ziegler-Natta catalyzed polymer and may have a relatively broad molecular weight distribution. For example, the molecular weight distribution (Mw/Mn) is greater than about 3.8, such as greater than about 4, such as greater than about 4.3, such as greater than about 4.5, such as greater than about 4.8, such as greater than about 5, such as greater than about 5.2, such as greater than about 5.5, such as greater than about 5.7, such as greater than about 6, and substantially less than about 9, such as less than about 8.5, such as less than about 8. The weight average molecular weight (as determined by GPC) of the first phase polymer is substantially greater than about 100,000, such as greater than about 120,000.

The random copolymer of polypropylene that constitutes the first phase polymer has, in one embodiment, a relatively high melt flow rate. For example, the first phase polymer may have a melt flow rate of greater than about 15 g/10 min, such as greater than about 18 g/10 min, such as greater than about 20 g/10 min, such as greater than about 22 g/10 min, such as greater than about 25 g/10 min. The melt flow rate of the first phase polymer is substantially less than about 80 g/10 min, such as less than about 50 g/10 min.

The second phase polymer is a copolymer of propylene and alpha-olefin. Additionally, the second phase polymer has elastomeric or rubber-like properties. Thus, the second phase polymer can significantly improve the impact strength of the polymer composition.

According to the present description, the second phase polymer contains relatively large amounts of alpha-olefin relative to the amount of propylene contained in the second phase polymer. For example, in one embodiment, the second phase polymer contains ethylene in amounts greater than the amount of propylene present. It has been found that increasing the ethylene content of the second phase polymer unexpectedly and significantly improves the impact properties of the polymer composition at sub-zero temperatures.

The amount of ethylene contained in the second phase polymer can be characterized or quantified by analyzing the amount of ethylene in xylene solubles and xylene insolubles. For example, the polypropylene composition of the present description can have a total xylene solubles content of substantially greater than about 12% by weight, such as greater than about 15% by weight, such as greater than about 18% by weight, such as greater than about 20% by weight, and substantially less than about 40% by weight, such as less than about 30% by weight, such as less than about 25% by weight, such as less than about 21% by weight. Thus, the polypropylene composition includes a xylene soluble portion and a xylene insoluble portion. According to the present description, ethylene may be present in the xylene soluble portion in an amount greater than about 55% by weight, such as greater than about 58% by weight, such as greater than about 60% by weight, and substantially less than about 70% by weight, such as less than about 68% by weight. On the other hand, the amount of ethylene present in the xylene insoluble portion may be substantially greater than about 15% by weight, such as greater than about 18% by weight, such as greater than about 20% by weight, and substantially less than about 50% by weight, such as less than about 40% by weight, such as less than about 38% by weight.

Based on the above ranges, it is believed that ethylene may be present in the second phase polymer in an amount greater than about 75% by weight, such as greater than about 80% by weight, such as greater than about 85% by weight, and substantially in an amount less than about 95% by weight, such as less than about 90% by weight.

The second phase polymer may have a weight average molecular weight of at least about 130,000, such as at least about 140,000, such as at least about 150,000, and substantially less than about 500,000.

The first phase polymer essentially forms a matrix, and the second phase polymer forms particles within the matrix. Various efforts have been made previously to reduce the particle size of the second phase polymer. However, in the polymer composition of the present disclosure, the second phase polymer particles have a relatively large size. Surprisingly, it has been found that excellent physical properties, including transparency and turbidity, can be achieved while maintaining relatively large second phase polymer particles. For example, the second phase polymer particles can have an average particle size (D50) of more than about 1 μm, such as more than about 1.1 μm, and substantially less than about 8 μm, such as less than about 6 μm, such as less than about 4 μm. The average particle size, for example, can be more than about 1.5 μm, such as more than about 2 μm, such as more than about 2.5 μm, such as even more than 3 μm. The average particle size, for example, in one embodiment, can be from about 1 μm to about 5 μm. In one embodiment, more than 50% of the particles contained in the second phase polymer may be greater than about 2 μm, such as greater than about 3 μm, based on volume fraction. For example, in one embodiment, 50% of the particles have a particle size of from about 3 μm to about 5 μm based on volume fraction.

The relative amounts of the various phases contained in the polymer composition may vary depending on various factors and the desired result. As such, the second phase polymer may be present in the polypropylene composition in an amount greater than about 15% by weight, such as greater than about 20% by weight, such as greater than about 25% by weight, such as greater than about 30% by weight, such as greater than about 35% by weight, and as such in an amount less than about 60% by weight, such as less than about 50% by weight, such as less than about 40% by weight, such as less than about 35% by weight. For example, the second phase polymer may be present in the composition in an amount greater than about 15% by weight and in an amount less than about 60% by weight, including all 1% by weight increments therebetween.

In addition to the first phase polymer and the second phase polymer, the polypropylene composition of the present disclosure may comprise various other additives and ingredients. For example, the polypropylene composition may comprise nucleating agents, mold release agents, slip agents, antiblocking agents, UV stabilizers, a heat stabilizer (e.g., DSTDP), colorants/tints, and the like. In one embodiment, the polymer composition may comprise an antioxidant, such as a hindered phenolic antioxidant. The polymer composition may also comprise an acid scavenger. Each of the additives may be present in the polymer composition in an amount substantially less than about 3% by weight, such as in an amount substantially less than about 2% by weight, such as in an amount substantially less than about 1% by weight, such as in an amount substantially less than about 0.5% by weight, and substantially greater than about 0.001% by weight.

In one embodiment, the polypropylene composition may further comprise a clarifying agent. The clarifying agent may be added to further improve the transparency properties of the composition. For example, the clarifying agent may comprise a compound for forming a gel-like network in the composition.

In one embodiment, the clarifying agent may comprise a sorbitol compound, such as a sorbitol acetal derivative. For example, in one embodiment, the clarifying agent may comprise dibenzyl sorbitol.

With respect to sorbitol acetal derivatives that can be used as an additive in some embodiments, a sorbitol acetal derivative is shown in formula (I):

where R1–R5 contain the same or different functional groups selected from hydrogen and C1–C3 alkyl.

In some embodiments, R1-R5 are hydrogen, such that the sorbitan acetal derivative is 2,4-dibenzylidene sorbitol (DBS). In some embodiments, R1, R4, and R5 are hydrogen and R2 and R3 are methyl groups, such that the sorbitan acetal derivative is 1,3:2,4-di-p-methyldibenzylidene-D-sorbitol (MDBS). In some embodiments, R1-R4 are methyl groups and R5 is hydrogen, such that the sorbitan acetal derivative is 1,3:2,4-bis(3,4-dimethylobenzylidene)sorbitol (DMDBS). In some embodiments, R2, R3, and R5 are propyl groups (–CH2–CH2–CH3) and R1 and R4 are hydrogen, such that the sorbitol acetal derivative is 1,2,3-trideoxy-4,6:5,7-bis-O-(4-propylphenylmethylene)nonitol (TBPMN).

Other embodiments of lightening agents that can be used include:

1,3:2,4-dibenzylidene sorbitol;

1,3:2,4-bis(p-methylbenzylidene)sorbitol;

di(p-methylbenzylidene)sorbitol;

di(p-ethylbenzylidene)sorbitol;

bis(5', 6', 7', 8'-tetrahydro-2-naphthylidene)sorbitol.

In one embodiment, the lightening agent may also comprise a bisamide, such as benzene trisamide. The lightening agents described above may be used individually or in combination.

When clarifying agents are present in the polymer composition, one or more clarifying agents are substantially added in an amount greater than about 200 ppm, such as in an amount greater than about 1800 ppm, such as in an amount greater than about 2000 ppm, such as in an amount greater than about 2200 ppm. One or more clarifying agents are substantially present in an amount less than about 5000 ppm, such as less than about 4000 ppm, such as less than about 3000 ppm, such as less than about 2000 ppm. The amount of clarifying agent present in the composition may depend on various factors, including the type of clarifying agent used.

The first phase polymer and the second phase polymer can be prepared using various polymerization methods and procedures. In one embodiment, a Ziegler-Natta catalyst is used to prepare the polymer composition. For example, the polymerization of olefins can occur in the presence of a catalytic system that includes a catalyst, an internal electron donor, a cocatalyst and, optionally, an external electron donor. Olefins of the formula _CH2 =CHR, where R is hydrogen or a hydrocarbon radical containing from 1 to 12 atoms, can be contacted with the catalytic system under suitable conditions to form polymer products. The copolymerization can occur in a stepwise process method to create a heterophasic composition of the present description. The polymerization process can be carried out using known technologies in the gas phase using fluidized or stirred bed reactors or in the slurry phase using an inert hydrocarbon solvent or diluent or a liquid monomer.

In one embodiment, the first phase polymer and the second phase polymer can be produced in a two-stage process, which includes a first stage, in which a random propylene copolymer is produced from a continuous polymer phase, and a second stage, in which a propylene copolymer is produced. The first polymerization stage can be carried out in one or more block reactors or in one or more gas-phase reactors. The second polymerization stage can be carried out in one or more gas-phase reactors. The second polymerization stage is usually carried out immediately after the first polymerization stage. For example, the polymerization product recovered in the first polymerization stage can be sent directly to the second polymerization stage. In this regard, the polymerization can be carried out according to a sequential polymerization process. A heterophasic copolymer composition is obtained.

In one embodiment of the present disclosure, the polymerization is carried out in the presence of a stereoregular olefin polymerization catalyst. For example, the catalyst can be a Ziegler-Natta catalyst. For example, in one embodiment, the catalyst sold under the trade name CONSISTA, commercially available from W. R. Grace & Company, can be used. In one embodiment, electron donors that do not contain phthalates are selected.

In one embodiment, the catalyst includes a procatalyst composition that comprises a titanium functional group, such as titanium chloride, a magnesium functional group, such as magnesium chloride, and at least one internal electron donor.

The procatalyst precursor may comprise (i) magnesium, (ii) a compound of a transition metal of an element from Groups IV through VII of the periodic table of the elements, (iii) a halide, oxyhalide and/or alkoxide of (i) or (i) and/or (ii), and (iv) a combination of (i), (ii), and (iii). Non-limiting examples of suitable procatalyst precursors include halides, oxyhalides, alkoxides of magnesium, manganese, titanium, vanadium, chromium, molybdenum, zirconium, hafnium, and combinations thereof.

In one embodiment, the procatalyst precursor comprises magnesium as the only metal component. Non-limiting examples include anhydrous magnesium chloride and/or its alcohol adduct, magnesium alkoxide or aryloxide, mixed magnesium alkoxyhalide, and/or carboxylated magnesium dialkoxide or aryloxide.

In one embodiment, the procatalyst precursor is an alcohol adduct of anhydrous magnesium chloride. The anhydrous magnesium chloride adduct is essentially defined as MgCl ₂ -nROH, where n is in the range of 1.5-6.0, preferably 2.5-4.0 and most preferably 2.8-3.5 moles of total alcohol. ROH is a C ₁ -C ₄ alcohol, a linear or branched alcohol or an alcohol mixture. Preferably, ROH is ethanol or a mixture of ethanol and a higher alcohol. If ROH is a mixture, the molar ratio of ethanol to higher alcohol is at least 80:20, preferably 90:10 and most preferably at least 95:5.

In one embodiment, the substantially spherical _MgCl2 -nEtOH adduct can be formed by a spray crystallization process. In one embodiment, the spherical _MgCl2 precursor has an average particle size (Malvern _d50 ) of about 15-150 μm, preferably 20-100 μm, and most preferably 35-85 μm.

In one embodiment, the procatalyst precursor comprises a transition metal compound and a magnesium metal compound. The transition metal compound has the general formula TrX _x , where Tr is a transition metal, X is a halogen or a C _1-10 hydrocarbyl group, and x is the number of such X groups in the compound in combination with the magnesium metal compound. Tr can be a metal from group IV, V, or VI. In one embodiment, Tr is a metal from group IV, such as titanium. X can be a chloride, a bromide, a C _1-4 alkoxide, or a phenoxide, or a mixture thereof. In one embodiment, X is a chloride.

The precursor composition can be obtained by chlorinating the above-mentioned mixed magnesium compounds, titanium compounds or mixtures thereof.

In one embodiment, the precursor composition is a mixed magnesium/titanium compound of the formula Mg _d Ti(OR ^e ) _f X _g , wherein R ^e is an aliphatic or aromatic hydrocarbon radical containing from 1 to 14 carbon atoms, or COR', wherein R is an aliphatic or aromatic hydrocarbon radical containing from 1 to 14 carbon atoms; all OR ^e groups may be the same or different; X is independently chlorine, bromine, or iodine; D is from 0.5 to 56; or 2-4, or 3; F is from 2 to 116, or from 5 to 15; and g is from 0.5 to 116, or from 1 to 3.

According to the present invention, the above-described procatalyst precursor is combined with at least one internal electron donor. The internal electron donor may be a substituted phenylene aromatic diester.

In one embodiment, the first internal electron donor comprises a substituted phenylene aromatic diester with the following structure (I):

where R ₁ -R ₁₄ may be the same or different. Each of the groups R ₁ -R ₁₄ is selected from hydrogen, a substituted hydrocarbon group having from 1 to 20 carbon atoms, an unsubstituted hydrocarbon group having from 1 to 20 carbon atoms, an alkoxy group having from 1 to 20 carbon atoms, a heteroatom, and combinations thereof. At least one of R ₁ -R ₁₄ is not hydrogen.

In one embodiment, the substituted phenylene aromatic diester may be any substituted phenylene aromatic diester as described in U.S. Patent Application Ser. No. 61/141,959, filed December 31, 2008, the contents of which are incorporated herein by reference in their entirety.

In one embodiment, the substituted phenylene aromatic diester may be any substituted phenylene aromatic diester described in WO12088028, filed December 20, 2011, the entire contents of which are incorporated herein by reference.

In one embodiment, at least one (or two, or three, or four) R group(s) of R ₁ -R ₄ is(are) selected from a substituted hydrocarbon group having from 1 to 20 carbon atoms, an unsubstituted hydrocarbon group having from 1 to 20 carbon atoms, an alkoxy group having from 1 to 20 carbon atoms, a heteroatom, and combinations thereof.

In one embodiment, at least one (or some, or all) of the R group(s) of R ₅ -R ₁₄ is(are) selected from a substituted hydrocarbon group having from 1 to 20 carbon atoms, an unsubstituted hydrocarbon group having from 1 to 20 carbon atoms, an alkoxy group having from 1 to 20 carbon atoms, a heteroatom, and combinations thereof. In another embodiment, at least one of the R ₅ -R ₉ groups and at least one of the R ₁₀ -R ₁₄ groups are selected from a substituted hydrocarbon group having from 1 to 20 carbon atoms, an unsubstituted hydrocarbon group having from 1 to 20 carbon atoms, an alkoxy group having from 1 to 20 carbon atoms, a heteroatom, and combinations thereof.

In one embodiment, at least one of the R ₁ -R ₄ groups and at least one of the R ₅ -R ₁₄ groups are selected from a substituted hydrocarbon group having from 1 to 20 carbon atoms, an unsubstituted hydrocarbon group having from 1 to 20 carbon atoms, an alkoxy group having from 1 to 20 carbon atoms, a heteroatom, and combinations thereof. In another embodiment, at least one of the R ₁ -R ₄ groups, at least one of the R ₅ -R ₉ groups, and at least one of the R ₁₀ -R ₁₄ groups are selected from a substituted hydrocarbon group having from 1 to 20 carbon atoms, an unsubstituted hydrocarbon group having from 1 to 20 carbon atoms, an alkoxy group having from 1 to 20 carbon atoms, a heteroatom, and combinations thereof.

In one embodiment, any consecutive R groups in R ₁ -R ₄ , and/or any consecutive R groups in R ₅ -R ₉ , and/or any consecutive R groups in R ₁₀ -R ₁₄ may be linked to one another to form an intermolecular cyclic or intramolecular cyclic structure. Such an inter- or intramolecular cyclic structure may or may not be aromatic. In one embodiment, the inter- or intramolecular cyclic structure is a C ₅ - or C ₆ -membered ring.

In one embodiment, at least one of the groups R ₁ -R ₄ is selected from a substituted hydrocarbon group having from 1 to 20 carbon atoms, an unsubstituted hydrocarbon group having from 1 to 20 carbon atoms, and combinations thereof. At least one of R ₅ -R ₁₄ can optionally be a halogen atom or an alkoxy group having from 1 to 20 carbon atoms. The groups R ₁ -R ₄ , and/or R ₅ -R ₉ , and/or R ₁₀ -R ₁₄ can optionally be linked to each other to form an intermolecular cyclic or intramolecular cyclic structure. Such an intermolecular cyclic structure and/or intramolecular cyclic structure can be or not be aromatic.

In one embodiment, any consecutive R groups in R ₁ –R ₄ , and/or in R ₅ –R ₉ , and/or in R ₁₀ –R ₁₄ can be included in a C ₅ –C ₆ membered ring.

In one embodiment, structure (I) includes groups R ₁ , R ₃ and R ₄ that are hydrogen. R ₂ is selected from a substituted hydrocarbon group having from 1 to 20 carbon atoms, an unsubstituted hydrocarbon group having from 1 to 20 carbon atoms, and combinations thereof. Groups R ₅ -R ₁₄ can be the same or different, and each of the groups R ₅ -R ₁₄ is selected from hydrogen, a substituted hydrocarbon group having from 1 to 20 carbon atoms, an unsubstituted hydrocarbon group having from 1 to 20 carbon atoms, an alkoxy group having from 1 to 20 carbon atoms, a halogen, and combinations thereof.

In one embodiment, the R ₂ group is selected from a C ₁ -C ₈ alkyl group, a C ₃ -C ₆ cycloalkyl group, or a substituted C ₃ -C ₆ cycloalkyl group. R ₂ can be a methyl group, an ethyl group, an n-propyl group, an isopropyl group, a tert-butyl group, an isobutyl group, a sec-butyl group, a 2,4,4-trimethylpentan-2-yl group, a cyclopentyl group, and a cyclohexyl group.

In one embodiment, structure (I) includes an R ₂ group that is methyl and each of the R ₅ –R ₁₄ groups is hydrogen.

In one embodiment, structure (I) includes an R ₂ group that is ethyl and each of the R ₅ –R ₁₄ groups is hydrogen.

In one embodiment, structure (I) includes an R ₂ group that is tert-butyl and each of the R ₅ –R ₁₄ groups is hydrogen.

In one embodiment, structure (I) includes an R ₂ group that is ethoxycarbonyl and each of the R ₅ –R ₁₄ groups is hydrogen.

In one embodiment, structure (I) includes groups _R2 , _R3 , and _R4 , each of which is hydrogen, and the group _R1 is selected from a substituted hydrocarbon group having from 1 to 20 carbon atoms, an unsubstituted hydrocarbon group having from 1 to 20 carbon atoms, and combinations thereof. The groups _R5 - _R14 can be the same or different, and each of them is selected from hydrogen, a substituted hydrocarbon group having from 1 to 20 carbon atoms, an unsubstituted hydrocarbon group having from 1 to 20 carbon atoms, an alkoxy group having from 1 to 20 carbon atoms, a halogen, and combinations thereof.

In one embodiment, structure (I) includes an R ₁ group that is methyl and each of the R ₅ –R ₁₄ groups is hydrogen.

In one embodiment, structure (I) includes groups _R2 and _R4 , which are hydrogen, and groups _R1 and _R3 may be the same or different. Each of groups _R1 and _R3 is selected from a substituted hydrocarbon group having from 1 to 20 carbon atoms, an unsubstituted hydrocarbon group having from 1 to 20 carbon atoms, and combinations thereof. Groups _R5 - _R14 may be the same or different, and each of groups _R5 - _R14 is selected from a substituted hydrocarbon group having from 1 to 20 carbon atoms, an unsubstituted hydrocarbon group having from 1 to 20 carbon atoms, an alkoxy group having from 1 to 20 carbon atoms, a halogen, and combinations thereof.

In one embodiment, structure (I) includes R ₁ and R ₃ groups, which may be the same or different. Each of R ₁ and R ₃ groups is selected from a C ₁ -C ₈ alkyl group, a C ₃ -C ₆ cycloalkyl group, or a substituted C ₃ -C ₆ cycloalkyl group. The R ₅ -R ₁₄ groups may be the same or different, and each of R ₅ -R ₁₄ groups is selected from hydrogen, a C ₁ -C ₈ alkyl group, and halogen. Non-limiting examples of suitable C ₁ -C ₈ alkyl groups include methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, isopentyl, neopentyl,

tert-pentyl, n-hexyl and 2,4,4-trimethylpentan-2-yl groups. Non-limiting examples of suitable _C3 - _C6 cycloalkyl groups include cyclopentyl and cyclohexyl groups. In a further embodiment, at least one of the _R5 - _R14 groups is a _C1 - _C8 alkyl group or a halogen.

In one embodiment, structure (I) includes an R ₁ group that is a methyl group and an R ₃ group that is a tert-butyl group. Each of the R ₂ , R ₄ , and R ₅ -R ₁₄ groups is hydrogen.

In one embodiment, structure (I) includes R ₁ and R ₃ groups, each of which is an isopropyl group. Each of the R ₂ , R ₄ , and R ₅ -R ₁₄ groups is hydrogen.

In one embodiment, structure (I) includes R ₁ , R ₅ , and R ₁₀ groups, each of which is a methyl group, and an R ₃ group, which is a tert-butyl group. Each of the R ₂ , R ₄ , R ₆ -R ₉ , and R ₁₁ -R ₁₄ groups is hydrogen.

In one embodiment, structure (I) includes _R1 , _R7 , and _R12 groups, each of which is a methyl group, and an _R3 group, which is a tert-butyl group. Each of the _R2 , _R4 , _R5 , _R6 , _R8 , _R9 , _R10 , _R11 , _R13 , and _R14 groups is hydrogen.

In one embodiment, structure (I) includes an R ₁ group that is a methyl group and an R ₃ group that is a tert-butyl group. Each of the R ₇ and R ₁₂ groups is an ethyl group. Each of the R ₂ , R ₄ , R ₅ , R ₆ , R ₈ , R ₉ , R ₁₀ , R ₁₁ , R ₁₃ and R ₁₄ groups is hydrogen.

In one embodiment, structure (I) includes groups R ₁ , R ₅ , R ₇ , R ₉ , R ₁₀ , R ₁₂ and R ₁₄ , each of which is a methyl group, and a group R ₃ , which is a tert-butyl group. Each of the groups R ₂ , R ₄ , R ₆ , R ₈ , R ₁₁ and R ₁₃ is hydrogen.

In one embodiment, structure (I) includes an R ₁ group that is a methyl group and an R ₃ group that is a tert-butyl group. Each of the R ₅ , R ₇ , R ₉ , R ₁₀ , R ₁₂ and R ₁₄ groups is an isopropyl group. Each of the R ₂ , R ₄ , R ₆ , R ₈ , R ₁₁ and R ₁₃ groups is hydrogen.

In one embodiment, the substituted phenylene aromatic diester has structure (II), which includes an R ₁ group that is a methyl group and an R ₃ group that is a tert-butyl group. Each of the R ₂ and R ₄ groups is hydrogen. The R ₈ and R ₉ groups are included in a C ₆ -membered ring to form a 1-naphthoyl moiety. The R ₁₃ and R ₁₄ groups are included in a C ₆ -membered ring to form another 1-naphthoyl moiety. Structure (II) is shown below.

In one embodiment, the substituted phenylene aromatic diester has structure (III), which includes an R ₁ group that is a methyl group and an R ₃ group that is a tert-butyl group. Each of the R ₂ and R ₄ groups is hydrogen. The R ₆ and R ₇ groups are included in a C ₆ -membered ring to form a 2-naphthoyl moiety. The R ₁₂ and R ₁₃ groups are included in a C ₆ -membered ring to form a 2-naphthoyl moiety. Structure (III) is shown below.

In one embodiment, structure (I) includes an R ₁ group that is a methyl group and an R ₃ group that is a tert-butyl group. Each of the R ₇ and R ₁₂ groups is an ethoxy group. Each of the R ₂ , R ₄ , R ₅ , R ₆ , R ₈ , R ₉ , R ₁₀ , R ₁₁ , R ₁₃ and R ₁₄ groups is hydrogen.

In one embodiment, structure (I) includes an R ₁ group that is a methyl group and an R ₃ group that is a tert-butyl group. Each of the R ₇ and R ₁₂ groups is a fluorine atom. Each of the R ₂ , R ₄ , R ₅ , R ₆ , R ₈ , R ₉ , R ₁₀ , R ₁₁ , R ₁₃ and R ₁₄ groups is hydrogen.

In one embodiment, structure (I) includes an R ₁ group that is a methyl group and an R ₃ group that is a tert-butyl group. Each of the R ₇ and R ₁₂ groups is a chlorine atom. Each of the R ₂ , R ₄ , R ₅ , R ₆ , R ₈ , R ₉ , R ₁₀ , R ₁₁ , R ₁₃ and R ₁₄ groups is hydrogen.

In one embodiment, structure (I) includes an R ₁ group that is a methyl group and an R ₃ group that is a tert-butyl group. Each of the R ₇ and R ₁₂ groups is a bromine atom. Each of the R ₂ , R ₄ , R ₅ , R ₆ , R ₈ , R ₉ , R ₁₀ , R ₁₁ , R ₁₃ and R ₁₄ groups is hydrogen.

In one embodiment, structure (I) includes an R ₁ group that is a methyl group and an R ₃ group that is a tert-butyl group. Each of the R ₇ and R ₁₂ groups is an iodine atom. Each of the R ₂ , R ₄ , R ₅ , R ₆ , R ₈ , R ₉ , R ₁₀ , R ₁₁ , R ₁₃ and R ₁₄ groups is hydrogen.

In one embodiment, structure (I) includes an R ₁ group that is a methyl group and an R ₃ group that is a tert-butyl group. Each of the R ₆ , R ₇ , R ₁₁ , and R ₁₂ groups is a chlorine atom. Each of the R ₂ , R ₄ , R ₅ , R ₈ , R ₉ , R ₁₀ , R ₁₃ , and R ₁₄ groups is hydrogen.

In one embodiment, structure (I) includes an R ₁ group that is a methyl group and an R ₃ group that is a tert-butyl group. Each of the R ₆ , R ₈ , R ₁₁ , and R ₁₃ groups is a chlorine atom. Each of the R ₂ , R ₄ , R ₅ , R ₇ , R ₉ , R ₁₀ , R ₁₂ , and R ₁₄ groups is hydrogen.

In one embodiment, structure (I) includes an R ₁ group that is a methyl group and an R ₃ group that is a tert-butyl group. Each of the R ₂ , R ₄ , and R ₅ -R ₁₄ groups is a fluorine atom.

In one embodiment, structure (I) includes an R ₁ group that is a methyl group and an R ₃ group that is a tert-butyl group. Each of the R ₇ and R ₁₂ groups is a trifluoromethyl group. Each of the R ₂ , R ₄ , R ₅ , R ₆ , R ₈ , R ₉ , R ₁₀ , R ₁₁ , R ₁₃ and R ₁₄ groups is hydrogen.

In one embodiment, structure (I) includes an R ₁ group that is a methyl group and an R ₃ group that is a tert-butyl group. Each of the R ₇ and R ₁₂ groups is an ethoxycarbonyl group. Each of the R ₂ , R ₄ , R ₅ , R _6, R ₈ , R ₉ , R ₁₀ , R ₁₁ , R ₁₃ and R ₁₄ groups is hydrogen.

In one embodiment, the R ₁ group is a methyl group and the R ₃ group is a tert-butyl group. Each of the R ₇ and R ₁₂ groups is an ethoxy group. Each of the R ₂ , R ₄ , R ₅ , R ₆ , R ₈ , R ₉ , R ₁₀ , R ₁₁ , R ₁₃ and R ₁₄ groups is hydrogen.

In one embodiment, structure (I) includes an R ₁ group that is a methyl group and an R ₃ group that is a tert-butyl group. Each of the R ₇ and R ₁₂ groups is a diethylamine group. Each of the R ₂ , R ₄ , R ₅ , R ₆ , R ₈ , R ₉ , R ₁₀ , R ₁₁ , R ₁₃ and R ₁₄ groups is hydrogen.

In one embodiment, structure (I) includes an R ₁ group that is a methyl group and an R ₃ group that is a 2,4,4-trimethylpentan-2-yl group. Each of the R ₂ , R ₄ , and R ₅ -R ₁₄ groups is hydrogen.

In one embodiment, structure (I) includes R ₁ and R ₃ groups, each of which is a sec-butyl group. Each of the R ₂ , R ₄ , and R ₅ -R ₁₄ groups is hydrogen.

In one embodiment, the substituted phenylene aromatic diester has structure (IV), wherein the R ₁ and R ₂ groups are included in a C ₆ -membered ring to form a 1,2-naphthalene moiety. Each of the R ₅ -R ₁₄ groups is hydrogen. Structure (IV) is shown below.

In one embodiment, the substituted phenylene aromatic diester has the structure (V), wherein the R ₂ and R ₃ groups are included in a C ₆ -membered ring to form a 2,3-naphthalene functional group. Each of the R ₅ -R ₁₄ groups is hydrogen. The structure (V) is shown below.

In one embodiment, structure (I) includes R ₁ and R ₄ groups, each of which is a methyl group. Each of the R ₂ , R ₃ , R ₅ -R ₉ and R ₁₀ -R ₁₄ groups is hydrogen.

In one embodiment, structure (I) includes an R ₁ group that is a methyl group. The R ₄ group is an isopropyl group. Each of the R ₂ , R ₃ , R ₅ -R ₉ , and R ₁₀ -R ₁₄ groups is hydrogen.

In one embodiment, structure (I) includes R ₁ , R ₃ , and R ₄ groups, each of which is an isopropyl group. Each of the R ₂ , R ₅ -R ₉ , and R ₁₀ -R ₁₄ groups is hydrogen.

In one embodiment, each of R ₁ and R ₄ is selected from a methyl group, an ethyl group, and a vinyl group. Each of the R ₂ and R ₃ groups is selected from hydrogen, a secondary alkyl group, or a tertiary alkyl group, wherein R ₂ and R ₃ are not both hydrogen. In other words, if R 2 is hydrogen, R 3 is not hydrogen (and vice versa).

In one embodiment, a second internal electron donor can be used that essentially comprises a polyether that can coordinate bidentately. In one embodiment, the second internal electron donor is a substituted 1,3-diether of structure VI:

where R ₁ and R ₂ are the same or different, methyl, C ₂ –C ₁₈ linear or branched alkyl, C ₃ –C ₁₈ cycloalkyl, C ₄ –C ₁₈ cycloalkyl-alkyl, C ₄ –C ₁₈ alkyl-cycloalkyl, phenyl, organosilicon, C ₇ –C ₁₈ arylalkyl or C ₇ –C ₁₈ alkylaryl radicals; and R ₁ or R ₂ may also represent a hydrogen atom.

In one embodiment, the second internal electron donor may comprise a 1,3-diester with a cyclic or polycyclic structure VII:

where R ₁ , R ₂ , R ₃ and R ₄ are as described for R ₁ and R ₂ of structure VI or may be combined to form one or more C ₅ –C ₇ fused aromatic or non-aromatic ring structures optionally containing an N, O or S heteroatom. Specific examples of the second internal electron donor include

4,4-bis(methoxymethyl)-2,6-dimethylheptane, 9,9-bis(methoxymethyl)fluorene or mixtures thereof.

The precursor is converted into a solid procatalyst by subsequent reaction (halogenation) with an inorganic halide compound, preferably a titanium halide compound, and incorporation of internal electron donors.

One suitable method for halogenating the precursor is to react the precursor at elevated temperature with a tetravalent titanium halide, optionally in the presence of a hydrocarbon or halohydrocarbon diluent. A preferred tetravalent titanium halide is titanium tetrachloride.

The resulting procatalyst composition may substantially comprise titanium in an amount of from about 0.5% to about 6% by weight, such as from about 1.5% to about 5% by weight, such as from about 2% to about 4% by weight. The solid catalyst may substantially comprise magnesium in an amount greater than about 5% by weight, such as greater than about 8% by weight, such as greater than about 10% by weight, such as greater than about 12% by weight, such as greater than about 14% by weight, such as greater than about 16% by weight. Magnesium is present in the catalyst in an amount of less than about 25% by weight, such as less than about 23% by weight, such as less than about 20% by weight. The internal electron donor may be present in the catalyst composition in an amount of less than about 30% by weight, such as in an amount of less than about 25% by weight, such as in an amount of less than about 22% by weight, such as in an amount of less than about 20% by weight, such as in an amount of less than about 19% by weight. The internal electron donor is substantially present in an amount of greater than about 5% by weight, such as in an amount of greater than about 9% by weight.

In one embodiment, the procatalyst composition is combined with a cocatalyst to form a catalyst system. The catalyst system is a system that forms an olefin-based polymer when contacted with an olefin under polymerization conditions. The catalyst system may optionally include an external electron donor, a catalyst activity limiting agent, and/or various other components.

As used herein, the term "cocatalyst" means a substance capable of converting a procatalyst into an active polymerization catalyst. The cocatalyst may comprise hydrides, alkyls or aryls of aluminum, lithium, zinc, tin, cadmium, beryllium, magnesium and combinations thereof. In one embodiment, the cocatalyst is a hydrocarbyl aluminum cocatalyst represented by the formula _R3Al , wherein each R group is an alkyl, cycloalkyl, aryl or hydrogen radical; at least one R is a hydrocarbon radical; two or three R radicals may be joined into a cyclic radical to form a heterocyclic structure; each R may be the same or different; and each R that is a hydrocarbyl radical has from 1 to 20 carbon atoms and preferably from 1 to 10 carbon atoms. In a further embodiment, each alkyl radical may be a straight or branched chain, and such a hydrocarbyl radical may be a mixed radical, i.e., the radical may contain alkyl, aryl and/or cycloalkyl groups. Non-limiting examples of suitable radicals are methyl, ethyl, n-propyl, isopropyl, n-butyl, isobutyl, tert-butyl, n-pentyl, neopentyl, n-hexyl, 2-methylpentyl, n-heptyl, n-octyl, isooctyl, 2-ethylhexyl, 5,5-dimethylhexyl, n-nonyl, n-decyl, isodecyl, n-undecyl, n-dodecyl.

Non-limiting examples of suitable hydrocarbyl aluminum compounds are triisobutylaluminum, tri-n-hexylaluminum, diisobutylaluminum hydride, di-n-hexylaluminum hydride, isobutylaluminum dihydride, n-hexylaluminum dihydride, diisobutylhexylaluminum, isobutyldihexylaluminum, trimethylaluminum, triethylaluminum, tri-n-propylaluminum, triisopropylaluminum, tri-n-butylaluminum, tri-n-octylaluminum, tri-n-decylaluminum, tri-n-dodecylaluminum. In one embodiment, preferred cocatalysts are selected from triethylaluminum, triisobutylaluminum, tri-n-hexylaluminum, diisobutylaluminum hydride and di-n-hexylaluminum hydride, and the most preferred cocatalyst is triethylaluminum.

In one embodiment, the cocatalyst is an organoaluminum compound represented by the formula _{RnAlX3 -n} , where n=1 or 2, R is alkyl, and X is a halide or alkoxide. Non-limiting examples of suitable compounds are methylaluminoxane, isobutylaluminoxane, diethylaluminum ethoxide, diisobutylaluminum chloride, tetraethyldialuminoxane, tetraisobutyldialuminoxane, diethylaluminum chloride, ethylaluminum dichloride, methylaluminum dichloride, and dimethylaluminum chloride.

In one embodiment, the catalyst composition includes an external electron donor. As used herein, the term "external electron donor" means a compound added independently of the formation of the procatalyst and containing at least one functional group that is capable of donating a pair of electrons to a metal atom. Without intending to be limited by any particular theory, it is believed that the external electron donor improves the stereoselectivity of the catalyst (i.e., reduces the amount of xylene-soluble material in the polymer formant).

In one embodiment, the external electron donor can be selected from one or more of the following compounds: an alkoxysilane, an amine, an ether, a carboxylate, a ketone, an amide, a carbamate, a phosphine, a phosphate, a phosphite, a sulfonate, a sulfone, and/or a sulfoxide.

In one embodiment, the external electron donor is an alkoxysilane. The alkoxysilane has the following general formula: SiR _m (OR') _4-m (I), wherein each of the R groups is independently hydrogen, or a hydrocarbon group, or an amino group, optionally substituted with one or more substituents containing one or more heteroatoms from Group 14, 15, 16, or 17, said R' group containing up to 20 atoms, not counting hydrogen and halogen; R' is a C _1-4 alkyl group; and m is 0, 1, 2, or 3. In one embodiment, R is C _6-12 aryl, alkyl, or aralkyl, C _3-12 cycloalkyl, C _3-12 branched alkyl, or C _3-12 cyclic or acyclic amino, R' is C _1-4 alkyl, and m is 1 or 2. Non-limiting examples of suitable silane-based compositions include dicyclopentyldimethoxysilane, di-tert-butyldimethoxysilane, methylcyclohexyldimethoxysilane, methylcyclohexyldiethoxysilane, ethylcyclohexyldimethoxysilane, diphenyldimethoxysilane, diisopropyldimethoxysilane, di-n-propyldimethoxysilane, diisobutyldimethoxysilane, diisobutyldiethoxysilane, isobutylisopropyldimethoxysilane, di-n-butyldimethoxysilane, cyclopentyltrimethoxysilane, isopropyltrimethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, ethyltriethoxysilane, tetramethoxysilane, tetraethoxysilane, diethylaminotriethoxysilane, cyclopentylpyrrolidinodimethoxysilane, bis(pyrrolidino)dimethoxysilane, bis(perhydroisoquinolino)dimethoxysilane and dimethyldimethoxysilane. In one embodiment, the silane-based composition is dicyclopentyldimethoxysilane (DCPDMS), methylcyclohexyldimethoxysilane (MChDMS), diisopropyldimethoxysilane (DIPDMS), n-propylmethoxysilane (NPTMS), diethylaminotriethoxysilane (DATES) or n-propyltriethoxysilane (PTES), and any combination thereof.

In one embodiment, the external donor may be a mixture of at least 2 alkoxysilanes. In a further embodiment, the mixture may comprise dicyclopentyldimethoxysilane and methylcyclohexyldimethoxysilane, dicyclopentyldimethoxysilane and tetraethoxysilane, or dicyclopentyldimethoxysilane and n-propyltriethoxysilane.

In one embodiment, the external electron donor is selected from one or more of a benzoate and/or a diol ester. In another embodiment, the external electron donor is 2,2,6,6-tetramethylpiperidine. In yet another embodiment, the external electron donor is a diether.

In one embodiment, the catalyst composition includes an activity limiting agent (ALA). As used herein, the term "activity limiting agent" (ALA) refers to a material that reduces the activity of the catalyst at elevated temperature (i.e., above about 85°C). The ALA inhibits or otherwise prevents disruption of the polymerization reactor and ensures continuity of the polymerization process. Typically, as the reaction temperature increases, the activity of Ziegler-Natta catalysts increases. Ziegler-Natta catalysts also typically maintain high activity near the softening point temperature of the resulting polymer. The heat generated during the exothermic polymerization reaction can cause the formation of agglomerates of polymer particles and, ultimately, disrupt the continuity of the polymer production process. The ALA reduces the activity of the catalyst at elevated temperature, thereby preventing disruption of the reactor, reduces (or prevents) agglomeration of particles and ensures continuity of the polymerization process.

The activity limiting agent may be a carboxylic acid ester, a diester, a poly(alkene glycol), a poly(alkene glycol) ester, a diol ester, and combinations thereof. The carboxylic acid ether may be an aliphatic or aromatic ether of a mono- or polycarboxylic acid. Non-limiting examples of suitable monocarboxylic acid esters include ethyl and methyl benzoate, ethyl p-methoxybenzoate, methyl p-ethoxybenzoate, ethyl p-ethoxybenzoate, ethyl acrylate, methyl methacrylate, ethyl acetate, ethyl p-chlorobenzoate, hexyl p-aminobenzoate, isopropyl naphthenate, n-amyl toluate, ethyl cyclohexanoate, and propyl pivalate.

In one embodiment, the external electron donor and/or the activity limiting agent may be added to the reactor separately. In another embodiment, the external electron donor and the activity limiting agent may be pre-mixed and then added to the reactor as a mixture. More than one external electron donor or more than one activity limiting agent may be used in the mixture. In one embodiment, the mixture consists of dicyclopentyldimethoxysilane and isopropyl myristate, dicyclopentyldimethoxysilane and poly(ethylene glycol) laurate, dicyclopentyldimethoxysilane and isopropyl myristate with poly(ethylene glycol) dioleate, methylcyclohexyldimethoxysilane and isopropyl myristate, n-propyltrimethoxysilane and isopropyl myristate, dimethyldimethoxysilane and methylcyclohexyldimethoxysilane with isopropyl myristate, dicyclopentyldimethoxysilane and n-propyltriethoxysilane with isopropyl myristate, dicyclopentyldimethoxysilane and tetraethoxysilane, isopropyl myristate, pentyl valerate, and combinations thereof.

In one embodiment, the catalyst composition comprises any of the above-mentioned external electron donors in combination with any of the above-mentioned activity limiting agents.

It has been found that the above-described catalyst system is particularly well suited for producing the heterophasic polymer composition of the present disclosure.

Due to the physical properties of the polypropylene composition of the present disclosure, especially the flow properties of the composition, the composition is well suited for producing molded articles. For example, the polypropylene composition can be used for injection molding, blow molding and rotational molding.

The polypropylene polymer composition of the present description can be used to manufacture a variety of different articles and products. Since the polymer composition has high transparency in combination with excellent impact resistance properties, the polymer composition is particularly well suited for the manufacture of storage containers. For example, the storage container can be a food packaging. Due to the impact resistance properties of the polymer, the storage container can be used, for example, to place products in a freezer. For example, Fig. 1 shows one embodiment of a storage container manufactured in accordance with the present description. As shown, the storage container 10 includes a container portion 14 that forms a hollow interior space for receiving one or more items. The container portion 14 can correspond to a lid 12. The lid 12 can include a channel and a flange that engage with the rim of the container portion 14. According to the present description, the contents of the container 10 can be viewed through the walls of the container.

In addition to food containers, various other storage containers can be made according to the present disclosure. For example, larger storage containers can be made using the polymer composition of the present disclosure. For example, larger storage containers can be designed to store various items in an attic, garage, or other storage area where temperature fluctuations may occur.

The present description can be better understood by reference to the following examples.

Examples

Two different samples of heterophasic polypropylene copolymers according to the present description were prepared and their various properties were tested, including impact strength and turbidity. A comparative example containing lower amounts of ethylene in the second phase polymer was also prepared. The heterophasic copolymers were prepared essentially using the above-described method in combination with the above-described catalyst. In particular, the copolymers were prepared in a two-reactor setup in which the matrix polymer was prepared in a first gas-phase reactor and then the contents of the first reactor were transferred to a second gas-phase reactor. Ethylene was used as a comonomer. The ethylene content was controlled in the first phase polymer and the second phase polymer.

Polymer pellet samples were prepared and incorporated into the specimens by injection molding. An additive package was added to the polymer containing 1000 ppm pentaerythritol tetrakis(3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate); 1000 ppm tris(2,4-di-tert-butylphenyl)phosphite; 180 ppm acid scavenger (hydrotalcite); 2000 ppm glycerol monostearate, and 4000 ppm clarifying agent. For example, the specimens were prepared in accordance with ASTM test D4101 for producing bend and Izod specimens.

The polymerization conditions for the three samples are given below. Gas-phase reactors were used to obtain the polymers.

Sample No. 1 Sample No. 2 Sample No. 3 Reactor 1 Temperature, °C 72 65 65 Al/Ti catalyst 49 35 35 Duration of stay, h 2.8 1.7 1,1 Reactor 2 Temperature, °C 65 65 65 Catalyst residence time 3.1 2.8 1.8

The following polypropylene compositions were obtained.

Sample No. 1 Sample No. 2 Sample No. 3 First phase polymer MFR1, g/10 min 44 37 26 XS1, % 1.5 6 6 Polymer of the first and second phases MFR2, g/10 min 16 18 21 XS2, % 30 18.4 19.2 Ethylene in XS,% 42 65.2 61.8 Ethylene in XI,% - 36 22 Koenig's B-value for XS 0.9 0.7 0.75 B-value according to Koenig for XI - 0.15 0.19

The above compositions were tested for various properties. The following results were obtained.

Sample No. 1 Sample No. 2 Sample No. 3 Modulus of elasticity in bending, MPa 970 708 721 Gardner at 0°C, inch-pounds 300 227 246 Gardner at -20°C, inch-pounds 230 338 374 Turbidity per 1 mm, % > 99 42 21 Transparency at 1 mm, % < 50 92 98 Peak tangent δ, °C -45, 0 -105, -40, 5 -100, -45, 5 Degree of crystallinity < 3 58.3 42.3 Average particle size 1,2 3.4 2,2

Sample No. 2 and Sample No. 3 described above were prepared in accordance with this description. These samples demonstrated significantly better impact resistance properties at a temperature of -20°C.

These and other modifications and variations of the present invention may be made by those of ordinary skill in the art without departing from the spirit and scope of the present invention, which are more particularly set forth in the appended claims. It should also be understood that aspects of the various embodiments may be interchanged, either in whole or in part. Moreover, those skilled in the art will appreciate that the foregoing description is provided by way of example only and is not intended to limit the invention, which is further described in the appended claims.

Claims (32)

1. A polypropylene composition for producing cast products, containing: a first phase polymer comprising a random copolymer of polypropylene containing ethylene, the copolymer having a xylene solubles content of greater than 0.5% to less than 10% by weight and having a melt flow rate of 20 g/10 min to 50 g/10 min, measured according to ASTM D 1238, at 230°C with a load of 2.16 kg; a second phase polymer in combination with a first phase polymer, wherein the second phase polymer comprises a copolymer of propylene and ethylene; and Where the polypropylene composition has a melt flow rate of 10 g/10 min to 30 g/10 min, measured in accordance with ASTM D 1238, at 230°C with a load of 2.16 kg, and the ratio of the melt flow rate of the first phase polymer to the melt flow rate of the polypropylene composition is greater than or equal to 1 and less than or equal to 2, the polypropylene composition has a xylene-soluble portion and a xylene-insoluble portion, wherein the polypropylene composition has a total content of xylene-soluble substances from 12% to 25% by weight, the xylene-soluble portion contains ethylene in an amount of 55% to 70% by weight, the xylene-insoluble portion contains ethylene in an amount of 15% to 40% by weight. 2. A polypropylene composition according to claim 1, wherein the composition additionally contains a clarifier and wherein the polypropylene composition has a turbidity per 1 mm of less than 45%. 3. A polypropylene composition according to claim 1 or 2, wherein the polymer of the second phase is presented in the form of polymer particles dispersed in the polymer of the first phase, wherein the polymer particles have an average particle size that is greater than or equal to 1 μm and less than 8 μm. 4. The polypropylene composition according to claim 1, wherein the ethylene content in the xylene-soluble portion of the polypropylene composition is from 60% to 70% by weight. 5. The polypropylene composition according to claim 1, wherein the ethylene content in the xylene-insoluble portion of the polypropylene composition is from 20% to 38% by weight. 6. A polypropylene composition according to any of the preceding claims, wherein the composition has a flexural modulus of elasticity from 500 MPa to 1000 MPa. 7. A polypropylene composition according to any one of the preceding claims, wherein the composition has a Gardner impact strength at -20°C of from 300 inch-lbs to 500 inch-lbs. 8. The polypropylene composition according to claim 4, wherein the random copolymer of polypropylene in the first phase polymer contains ethylene in an amount of 1% to 4% by weight. 9. A polypropylene composition according to claim 4, wherein the copolymer of propylene and ethylene in the second phase polymer contains ethylene in an amount of more than 75% and less than 95% by weight. 10. A polypropylene composition according to any one of the preceding claims, wherein the second phase polymer is present in the polypropylene composition in an amount of from 15% to 50% by weight. 11. A polypropylene composition according to any one of the preceding claims, wherein the polypropylene composition has a total xylene solubles content of from 15% to 21% by weight. 12. A polypropylene composition according to any one of the preceding claims, wherein the polypropylene composition has a turbidity at 1 mm of from 15% to 45%. 13. A polypropylene composition according to any of the preceding claims, wherein the polypropylene composition has a transparency of greater than 90%. 14. A polypropylene composition according to any one of the preceding claims, wherein the polypropylene composition has a transparency of greater than 92%. 15. A polypropylene composition according to any one of the preceding claims, wherein the polypropylene composition has a melt flow rate of from 15 g/10 min to 30 g/10 min, measured according to ASTM D 1238, at 230°C with a load of 2.16 kg. 16. A polypropylene composition according to any one of the preceding claims, wherein the polypropylene polymer in the first phase polymer is obtained by Ziegler-Natta catalysis, and wherein the copolymer of propylene and ethylene in the second phase polymer is also obtained by Ziegler-Natta catalysis. 17. A polypropylene composition according to claim 16, wherein the Ziegler-Natta catalyst used to produce a polypropylene polymer from a first phase polymer and a propylene-ethylene copolymer from a second phase polymer includes an internal electron donor containing a substituted phenylene aromatic diester. 18. The polypropylene composition according to claim 16, wherein the second phase polymer is formed in the presence of the first phase polymer. 19. A polypropylene composition according to any one of the preceding claims, wherein the polypropylene composition exhibits at least three tan delta peaks at three different temperatures. 20. A polypropylene composition according to any one of the preceding claims, wherein the composition further comprises an antacid and an antioxidant. 21. A molded article made from a polypropylene composition according to any of the preceding claims. 22. A cast product according to item 21, wherein the cast product is a product obtained by injection molding. 23. A storage container made from a polypropylene composition according to any one of paragraphs 1-20. 24. The storage container of claim 23, wherein the storage container is a food container.