Polyethylene composition, article and film.

Abstract

SUMMARY "POLYETHYLENE, ARTICLE AND FILM COMPOSITION" A polyethylene composition comprising at least 95 weight percent ethylene derived units is provided; less than 5 weight percent of units derived from one or more ?-olefin comonomers; said polyethylene composition having a density in the range of 0.930 to 0.945 g / cm 3 , a molecular weight distribution defined by the ratio of z-average molecular weight to weight-average molecular weight (Mz / Mw) of less than 5, a melt index, I2 (measured at 190oC, 2.16 kg), in the range of 0.08 to 0.5 g / 10 minutes, and a high flow melt index, I21 (measured at 190oC, 21.6 kg ), in the range of 10 to 20 g / 10 minutes; and wherein the polyethylene composition is produced using a chromium oxide catalyst.

Description

"POLYETHYLENE COMPOSITION, ARTICLE AND FILM" Technical field

[0001] The present invention relates to a polyethylene composition and to articles made therefrom. Prior art

[0002] Chromium-containing catalysts are typically used to produce polyethylene compositions having high density, wide molecular weight distributions, and fractional melt indices. With such properties, good operability is achieved during the polymerization process (e.g., no fouling in the reactor, low static). Medium-density polyethylene compositions tend to maintain good operability, but also do not exhibit sufficient optical improvement for such end uses. Low-density polyethylene compositions provide improved optics, but polymerization reactors experience greater fouling and static. Summary

[0003] The present invention is a composition of polyethylene and articles made therefrom.

[0004] In one embodiment, the present invention provides a polyethylene composition comprising: at least 95 percent by weight of ethylene-derived units; less than 5 percent by weight of units derived from one or more α-olefin comonomers; said polyethylene composition having a density in the range of 0.930 to 0.945 g / cm3, a molecular weight distribution defined by the ratio of average molecular weight z to weight-average molecular weight (Mz / Mw) of less than 5, a melt index, I2 (measured at 190°C, 2.16 kg), in the range of 0.08 to 0.5 g / 10 Petition 870200033903, dated 03 / 13 / 2020, page 12 / 47 2 / 30 minutes, and a high-charge melting index, I21 (measured at 190°C, 21.6 kg), in the range of 10 to 20 g / 10 minutes; and the polyethylene composition is produced using a chromium oxide catalyst. Description of the drawings

[0005] For the purpose of illustrating the invention, an exemplary form is shown in the drawings; it being understood, however, that this invention is not limited to the precise arrangements and instrumentation shown.

[0006] Figure 1 is a graph illustrating the casting strength of Inventive Examples 1-5 and Comparative Examples 14. Detailed description

[0007] The present invention is a composition of polyethylene and articles made therefrom.

[0008] The polyethylene composition according to the present invention comprises: at least 95 percent by weight of ethylene-derived units; less than 5 percent by weight of units derived from one or more α-olefin comonomers; wherein said polyethylene composition has a density in the range of 0.930 to 0.945 g / cm3, a molecular weight distribution defined by the ratio of average molecular weight z to weight-average molecular weight (Mz / Mw) of less than 5, a melting index, I2 (measured at 190°C, 2.16 kg), in the range of 0.08 to 0.5 g / 10 minutes, and a high-load melting index, I21 (measured at 190°C, 21.6 kg), in the range of 10 to 20 g / 10 minutes; and wherein the polyethylene composition is produced using a chromium oxide catalyst.

[0009] Articles according to the present invention include articles comprising the composition according to any Petition 870200033903, dated 03 / 13 / 2020, page 13 / 47 3 / 30 implementation described here.

[00010] The polyethylene composition according to the present invention comprises: at least 95 percent by weight of ethylene-derived units. All individual values ​​and sub-ranges of at least 95 percent by weight are included herein and disclosed herein. For example, the amount of ethylene-derived units may be at least 95 percent by weight or, alternatively, the amount of ethylene-derived units may be at least 96 percent by weight or, alternatively, the amount of ethylene-derived units may be at least 97 percent by weight or, alternatively, the amount of ethylene-derived units may be at least 98 percent by weight or, alternatively, the amount of ethylene-derived units may be at least 99 percent by weight.

[00011] The polyethylene composition according to the present invention comprises: at least 95 percent by weight of units derived from less than 5 percent by weight of units of one or more α-olefin comonomers. All individual values ​​and sub-ranges of less than 5 percent by weight are included herein and disclosed herein. For example, the amount of units derived from one or more α-olefin comonomers may be less than 5 percent by weight or, alternatively, the amount of units derived from one or more α-olefin comonomers may be less than 4 percent by weight or, alternatively, the amount of units derived from one or more α-olefin comonomers may be less than 3 percent by weight or, alternatively, the amount of units derived from one or more α-olefin comonomers may be less than 2 percent by weight or, alternatively Petition 870200033903, dated 03 / 13 / 2020, page 14 / 47 4 / 30 Alternatively, the amount of units derived from one or more α-olefin comonomers may be less than 1 percent by weight.

[00012] The polyethylene composition has a density in the range of 0.930 to 0.945 g / cm3. All individual values ​​and sub-ranges from 0.930 to 0.945 g / cm3 are included herein and disclosed herein; for example, the polyethylene composition may have a density from a lower limit of 0.930, 0.934, 0.938, 0.941, or 0.944 g / cm3 to an upper limit of 0.931, 0.925, 0.939, 0.942, or 0.945 g / cm3. For example, the density could be from 0.930 to 0.945 g / cm3, or alternatively, the density could be from 0.934 to 0.942 g / cm3, or alternatively, the density could be from 0.930 to 0.940 g / cm3, or alternatively, the density could be from 0.938 to 0.945 g / cm3.

[00013] The polyethylene composition has a molecular weight distribution defined by the ratio of the average molecular weight z to the weight-average molecular weight (Mz / Mw) of less than 5. All individual values ​​and subranges of less than 5 are included herein and disclosed herein. For example, Mz / Mw could be less than 5 or, alternatively, Mz / Mw could be less than 4.5 or, alternatively, Mz / Mw could be less than 4.

[00014] The polyethylene composition has a melt index, I2 (measured at 190°C, 2.16 kg), in the range of 0.08 to 0.5 g / 10 minutes. All individual values ​​and sub-ranges from 0.08 to 0.5 g / 10 minutes are included here and disclosed here; for example, I2 can range from a lower limit of 0.08, 0.1, 0.2, 0.3, or 0.4 g / 10 min to an upper limit of 0.1, 0.2, 0.32, 0.44, or 0.5 g / 10 min. For example, I2 can range from Petition 870200033903, dated 03 / 13 / 2020, p. 15 / 47 5 / 30 0.08 to 0.5 g / 10 min or, alternatively, I2 may vary 0.08 to 0.25 g / 10 min or, alternatively, I2 may vary 0.25 to 0.5 g / 10 min or, alternatively, I2 may vary 0.1 to 0.4 g / 10 min.

[00015] The polyethylene composition has a high-load melt index, I21 (measured at 190°C, 21.6 kg), in the range of 10 to 20 g / 10 minutes. All individual values ​​and sub-ranges of 10 to 20 g / 10 minutes are included here and disclosed here; for example, I21 can range from a lower limit of 10, 12, 14, 16, or 18 g / 10 min to an upper limit of 11, 13, 15, 17, 19, or 20 g / 10 min. For example, the I21 of the polyethylene composition can vary from 10 to 20 g / 10 min or, alternatively, the I21 of the polyethylene composition can vary from 15 to 20 g / 10 min or, alternatively, the I21 of the polyethylene composition can vary from 10 to 15 g / 10 min or, alternatively, the I21 of the polyethylene composition can vary from 12 to 18 g / 10 min.

[00016] The polyethylene composition is produced using a chromium oxide-based catalyst. Chromium oxide-based catalysts useful for producing the polyethylene composition according to the embodiments disclosed herein include those disclosed in U.S. Patent No. 4,011,382, the disclosure of which is incorporated herein by reference in its entirety. Such chromium oxide (CrO3)-based catalysts may be formed by depositing a suitable chromium compound, a titanium compound, and optionally a fluorine compound onto a dry support, and then activating the resulting composition by heating it in air or oxygen at a temperature of 300°C to 900°C for at least 2 hours. Chromium compounds that may be used include CrO3 and Petition 870200033903, dated 03 / 13 / 2020, page 16 / 47 6 / 30 other chromium-containing compounds that are convertible to CrO3 under the catalyst preparation conditions, including, for example, chromic acetyl acetonate, chromic nitrate, chromic acetate, chromic chloride, chromic sulfate, and ammonium chromate. Other chromium compounds include those disclosed in U.S. Patents Nos. 2,825,721 and 3,622,521, the disclosures of which are incorporated herein by reference in full. In some embodiments, the chromium oxide catalyst comprises from more than zero to 2.5 percent by weight of fluorine. All individual values ​​and sub-ranges of more than zero to 2.5 percent by weight of fluorine are included herein and disclosed herein; For example, when present, fluorine may range from a lower limit of 0.01, 0.1, 0.5, 1, 1.5, 2, or 2.25 percent by weight to an upper limit of 0.1, 0.5, 1, 1.5, 2, or 2.5 percent by weight based on the total weight of the support and catalyst.The chromium oxide-based catalyst could contain from 0.05 to 3.0 percent by weight of chromium oxide based on the total weight of the support and the catalyst. All individual values ​​and subranges from 0.05 to 3.0 percent by weight are included here and disclosed here; for example, the amount of chromium could range from a lower limit of 0.05, 0.1, 0.5, 1, 1.5, 2, or 2.5 percent by weight to an upper limit of 0.1, 0.5, 1, 1.5, 2, 2.5, or 3.0 percent by weight based on the total weight of the support and the catalyst. The chromium oxide-based catalyst could contain from 1.5 to 9.0 percent by weight of titanium based on the total weight of the support and the catalyst. All individual values ​​and subranges from 1.5 to 9.0 percent by weight are included here and disclosed here; For example, the amount of titanium could... Petition 870200033903, dated 03 / 13 / 2020, p. 17 / 47 7 / 30 being from a lower limit of 1.5, 2.5, 3.5, 4.5, 6.5, 7.5, or 8.5 percent by weight to an upper limit of 2, 3, 4, 5, 6, 7, 8, or 9 percent by weight based on the total weight of the carrier and the catalyst.

[00017] In an alternative embodiment, the present invention provides a polyethylene composition and articles made therefrom, according to any of the embodiments disclosed herein, except that the polyethylene composition has a vinyl unsaturation of less than 1 vinyl per thousand carbon atoms present in the polyethylene backbone. All individual values ​​and subranges of less than 1 vinyl per thousand carbon atoms present in the polyethylene backbone are included herein and disclosed herein.For example, the vinyl unsaturation may be less than 1 vinyl per thousand carbon atoms present in the polyethylene backbone or, alternatively, the vinyl unsaturation may be less than 0.95 vinyl per thousand carbon atoms present in the polyethylene backbone or, alternatively, the vinyl unsaturation may be less than 0.93 vinyl per thousand carbon atoms present in the polyethylene backbone or, alternatively, the vinyl unsaturation may be less than 0.9 vinyl per thousand carbon atoms present in the polyethylene backbone. In an alternative embodiment, the present invention provides a polyethylene composition and articles made therefrom, according to any of the embodiments disclosed herein, except that the polyethylene composition has a vinyl unsaturation of at least 0.5 vinyl per thousand carbon atoms present in the polyethylene backbone.

[00018] In an alternative embodiment, the present Petition 870200033903, dated 03 / 13 / 2020, p. 18 / 47 8 / 30 The invention provides a polyethylene composition and articles made therefrom, according to any of the embodiments disclosed herein, except that the polyethylene composition has a complex viscosity (η*), determined at 0.02 s-1 and 190°C, of ​​at least 100,000 Pa-s. All individual values ​​and sub-ranges of at least 100,000 Pa-s will be included herein and disclosed herein. For example, the polyethylene composition could have a η* at 0.02 s-1e 190oC of at least 100,000 Pa-s or, alternatively, the polyethylene composition could have a η* at 0.02 s-1e 190oC of at least 105,000 Pa-s or, alternatively, the polyethylene composition could have a η* at 0.02 s-1e 190oC of at least 110,000 Pa-s or, alternatively, the polyethylene composition could have a η* at 0.02 s-1e 190oC of at least 112,000 Pa's.In an alternative embodiment, the present invention provides a polyethylene composition and articles made therefrom, according to any of the embodiments disclosed herein, except that the polyethylene composition has a η* at 0.02 s-1e 190oC of not more than 300,000 Pa^s.

[00019] In an alternative embodiment, the present invention provides a polyethylene composition and articles made thereof, according to any of the embodiments disclosed herein, except that the polyethylene composition has a ratio of η* at 0.02 s⁻¹e⁻¹ 190°C to η* at 200 s⁻¹e⁻¹ 190°C of more than 85. All individual values ​​and sub-ranges of more than 90 are included herein and disclosed herein. For example, the polyethylene composition has a ratio of η* at 0.02 s⁻¹e⁻¹ 190°C to η* at 200 s⁻¹e⁻¹ 190°C of more than 85 or, alternatively, the polyethylene composition has a ratio of η* at 0.02 s⁻¹e⁻¹ 190°C to η* at 200 s⁻¹e⁻¹ 190°C of more than 90 Petition 870200033903, dated 03 / 13 / 2020, p. 19 / 47 9 / 30 or, alternatively, the polyethylene composition has a ratio of η* at 0.02 s-1 and 190°C to η* at 200 s-1 and 190°C of more than 94 or, alternatively, the polyethylene composition has a ratio of η* at 0.02 s-1 and 190°C to η* at 200 s-1 and 190°C of more than 96. In an alternative embodiment, the present invention provides a polyethylene composition and articles made therefrom, according to any of the embodiments disclosed herein, except that the polyethylene composition has a ratio of η* at 0.02 s-1 and 190°C to η* at 200 s-1 and 190°C of less than 250.

[00020] In an alternative embodiment, the present invention provides a polyethylene composition and articles made thereof, according to any of the embodiments disclosed herein, except that the article exhibits one or more of the following properties: a 45-degree gloss of at least 10%, a total haze of less than 60%. All individual values ​​and sub-ranges of at least 10% are included herein and disclosed herein. For example, the item could have a 45-degree gloss of at least 10% or, alternatively, the item could have a 45-degree gloss of at least 12% or, alternatively, the item could have a 45-degree gloss of at least 14% or, alternatively, the item could have a 45-degree gloss of at least 15%. All individual values ​​and sub-ranges of less than 60% total haze are included herein and disclosed herein.For example, the article may have a haze of less than 60%, or alternatively, the article may have a haze of less than 58%, or alternatively, the article may have a haze of less than 55%, or alternatively, the article may have a haze of less than 50%, or alternatively, the article may have a haze of... Petition 870200033903, dated 03 / 13 / 2020, p. 20 / 47 10 / 30 less than 45% or, alternatively, the article may have a haze of less than 44%.

[00021] In an alternative embodiment, the present invention provides a polyethylene composition and articles made therefrom, according to any of the embodiments disclosed herein, except that the article is an extrusion-blow molded article.

[00022] In an alternative embodiment, the present invention provides a polyethylene composition and articles made therefrom, according to any of the embodiments disclosed herein, except that the article is a film comprising at least one layer comprising a polyethylene composition according to any of the embodiments described herein.

[00023] In an alternative embodiment, the present invention provides a polyethylene composition and articles made therefrom, according to any of the embodiments disclosed herein, except that the article is a film that is a shrink film.

[00024] In an alternative embodiment, the present invention provides a polyethylene composition and articles made therefrom, according to any of the embodiments disclosed herein, except that the article is a film that is a high-strength transport bag.

[00025] In an alternative embodiment, the present invention provides a polyethylene composition and articles made therefrom, according to any of the embodiments disclosed herein, except that the article is a film wherein the polyethylene composition additionally comprises one or more additives selected from the group consisting of adjuvants. Petition 870200033903, dated 03 / 13 / 2020, p. 21 / 47 11 / 30 processing agents, acid neutralizers, UV stabilizers, antioxidants, process stabilizers, metal deactivators, additives to improve oxidative or chlorine resistance, pigments and dyes.

[00026] Any conventional ethylene (co)polymerization reaction may be employed to produce the inventive polyethylene composition. Such conventional ethylene (co)polymerization reactions include, but are not limited to, a gas-phase polymerization process, a paste-phase polymerization process, a liquid-phase polymerization process, and combinations thereof using one or more conventional reactors, e.g., fluidized bed gas-phase reactors, loop reactors, stirred tank reactors, parallel batch reactors, series reactors, and / or any combination thereof. Alternatively, the inventive polyethylene composition may be produced in a high-pressure reactor by means of a coordination catalyst system.For example, the inventive polyethylene composition according to the present invention may be produced by a gas-phase polymerization process in a gas-phase reactor; however, the present invention is not limited to this, and any of the above polymerization processes may be employed. In one embodiment, the polymerization reactor may comprise two or more reactors in series, in parallel, or combinations thereof. Preferably, the polymerization reactor is, e.g., a fluidized bed gas-phase reactor. In another embodiment, the polymerization reactor is a continuous polymerization reactor comprising a feed stream or gas cycle comprising ethylene and... Petition 870200033903, dated 03 / 13 / 2020, page 22 / 47 12 / 30 optionally one or more comonomers such as one or more αolefins flowing continuously through the polymerization reactor by any suitable means.

[00027] In production, a chromium oxide catalyst, as described in more detail below, ethylene, optionally one or more alpha-olefin comonomers, hydrogen, optionally O2, optionally one or more inert gases and / or liquids, e.g., N2, isopentane, hexane, and optionally one or more continuity additives, e.g., ethoxylated stearyl amine, are continuously fed to a reactor, e.g., a fluidized bed gas phase reactor. The reactor may be in fluid communication with one or more discharge tanks, accumulation tanks, purge tanks, and / or recycle compressors. The temperature in the reactor is typically in the range of 70 to 115°C, preferably 75 to 110°C, more preferably 75 to 100°C, and the pressure is in the range of 15 to 30 atmospheres (atm), preferably 17 to 26 atm. A distributor plate at the bottom of the polymer bed provides a uniform flow of the monomer, comonomer, and inert gases in an upward flow.A mechanical agitator may also be provided to ensure contact between the solid particles and the comonomer gas stream. The fluidized bed, a vertical cylindrical reactor, may have a bulbous shape at the top to facilitate the reduction of gas velocity, thus allowing granular polymer to separate from the ascending gases. The unreacted gases are then cooled to remove the heat of polymerization, re-compressed, and then recycled to the bottom of the reactor. Once the residual hydrocarbons have been removed, and the resin has been transported under N2 to a purge box... Petition 870200033903, dated 03 / 13 / 2020, page 23 / 47 13 / 30 Moisture may be introduced in order to reduce the presence of any residual O2-catalyzed reactions before the inventive polyethylene composition is exposed to oxygen. The inventive polyethylene composition could then be transferred to an extruder to be pelletized. Such pelletizing techniques are generally known. The inventive polyethylene composition could additionally be sieved under molten heat. Subsequent to the melting process in the extruder, the molten composition is passed through one or more active sieves (positioned in series of more than one) with each active sieve having a retention size in microns of about 2 to about 400 (2 to 4 x 10⁻⁵ m), more preferably about 2 to about 300 (2 to 3 x 10⁻⁵ m), and most preferably about 2 to about 70 (2 to 7 x 10⁻⁶ m), at a mass flow rate of about 1.0 to about 20 kg / s / m² (about 5 to about 100 lb / h / in²).Such additional melt screening is disclosed in U.S. Patent No. 6,485,662, which is incorporated herein by reference to the extent that it discloses melt screening.

[00028] In one embodiment of a fluidized bed reactor, a monomer stream is passed to a polymerization section. The fluidized bed reactor may include a reaction zone in fluid communication with a rate-reducing zone. The rate-reducing zone includes a bed of growing polymer particles, formed polymer particles, and catalyst composition particles fluidized by the continuous flow of polymerizable gaseous components and modifiers in the form of replenishment feed and recycled through the reaction zone. Preferably, the replenishment feed includes monomer. Petition 870200033903, dated 03 / 13 / 2020, page 24 / 47 14 / 30 polymerizable, more preferably ethylene and at least one other α-olefin, and may also include condensing agents as is known in the art and disclosed, for example, in US patent no. 4,543,399, US patent no. 5,405,922 and US patent no. 5,462,999.

[00029] The fluidized bed has the general appearance of a dense mass of individually moving particles, preferably polyethylene particles, as created by the percolation of gas through the bed. The pressure drop across the bed is equal to or slightly greater than the weight of the bed divided by the cross-sectional area. Therefore, this is dependent on the reactor geometry. To maintain a viable fluidized bed in the reaction zone, the superficial gas velocity through the bed must exceed the minimum flow rate required for fluidization. Preferably, the superficial gas velocity is at least twice the minimum flow rate. Generally, the superficial gas velocity does not exceed 1.5 m / s and in some embodiments, no more than 0.76 ft / s is sufficient.

[00030] In general, the height-to-diameter ratio of the reaction zone may vary from about 2:1 to about 5:1. The range, of course, may vary to higher or lower ratios and depends on the desired production capacity. The cross-sectional area of ​​the speed-reducing zone is typically within the range of about 2 to about 3 times the cross-sectional area of ​​the reaction zone.

[00031] The velocity-reducing zone has a larger internal diameter than the reaction zone, and may be conically tapered in shape. As the name suggests, the velocity-reducing zone reduces the gas velocity due to the area of Petition 870200033903, dated 03 / 13 / 2020, page 25 / 47 15 / 30 increased cross-section. This reduction in gas velocity loosens the entrained particles into the bed, reducing the amount of entrained particles flowing out of the reactor. The gas exiting the top of the reactor is the recycled gas stream.

[00032] The recycled stream is compressed in a compressor and then passed through a heat exchange zone where heat is removed before the stream is returned to the bed. The heat exchange zone is typically a heat exchanger, which can be horizontal or vertical. If desired, several heat exchangers can be employed to lower the temperature of the cycle gas stream stages. It is also possible to position the compressor downstream of the heat exchanger or at an intermediate point between several heat exchangers. After cooling, the recycled stream is returned to the reactor through a recycled inlet line. The cooled recycled stream absorbs the heat of reaction generated by the polymerization reaction.

[00033] Preferably, the recycled stream is returned to the reactor through a gas distribution plate. A gas baffle is preferably installed at the reactor inlet to prevent contained polymer particles from settling and agglomerating into a solid mass and to prevent liquid accumulation at the bottom of the reactor, as well as to facilitate easy transitions between processes containing liquid in the cycle gas stream and those that do not, and vice versa. Such baffles are described in US Patent No. 4,933,149 and US Patent No. 6,627,713. Petition 870200033903, dated 03 / 13 / 2020, page 26 / 47 16 / 30

[00034] The chromium oxide-based catalyst system used in the fluidized bed is preferably stored for service in a reservoir under a blanket of gas that is inert to the stored material, such as nitrogen or argon. The chromium oxide-based catalyst system can be added to the reaction system, or reactor, at any point and by any suitable means, and is preferably added to the reaction system either directly to the fluidized bed or downstream of the last heat exchanger, i.e., the heat exchanger furthest downstream relative to the flow, in the recycle line, in which case the activator is fed to the bed or the recycle line from a dispenser. The chromium oxide-based catalyst system is injected into the bed at a point above the distributor plate. Preferably, the chromium oxide-based catalyst system is injected at a point in the bed where good mixing with the polymer particles occurs.Injecting the chromium oxide-based catalyst system at a point above the distribution plate provides satisfactory operation of a fluidized bed polymerization reactor.

[00035] Monomers can be introduced into the polymerization zone in several ways including, but not limited to, direct injection through a nozzle positioned in the bed or in the cycle gas line. Monomers can also be sprayed onto the bed through a nozzle positioned over the bed, which may help to eliminate some entrainment of fines by the cycle gas stream.

[00036] The makeup fluid can be added to the bed via a separate line to the reactor. The composition of the makeup stream is determined by a gas analyzer. Petition 870200033903, dated 03 / 13 / 2020, page 27 / 47 17 / 30 The gas analyzer determines the composition of the recycled stream, and the replacement composition is adjusted accordingly to maintain an essentially steady-state gas composition within the reaction zone. The gas analyzer may be a conventional gas analyzer that determines the composition of the recycled stream in a way that maintains the component proportions of the feed stream. Such equipment is commercially available from a wide variety of sources. The gas analyzer is typically positioned to receive gas from a sampling point located between the velocity-reducing zone and the heat exchanger.

[00037] The production rate of the inventive polyethylene composition can be conveniently controlled by adjusting the injection rate of the catalyst composition, the injection rate of the activator, or both. Since any change in the catalyst injection rate will change the reaction rate and thus the rate at which heat is generated in the bed, the temperature of the recycling stream entering the reactor is adjusted to accommodate any change in the rate of heat generation. This ensures the maintenance of an essentially constant temperature in the bed. Complete instrumentation for both the fluidized bed and the recycling stream cooling system is, of course, useful for detecting any temperature change in the bed so as to enable either the operator or a conventional automatic control system to make an appropriate adjustment to the recycling stream temperature.

[00038] Under a given set of operating conditions, the fluidized bed is maintained at an essentially high height. Petition 870200033903, dated 03 / 13 / 2020, p. 28 / 47 18 / 30 constant collecting a portion of the bed as product at a rate of formation of the particulate polymeric product. Since the rate of heat generation is directly related to the rate of product formation, a measure of the temperature rise of the fluid through the reactor, i.e., the difference between the temperature of the inlet fluid and the temperature of the outlet fluid, is indicative of the rate of formation of the inventive polyethylene composition at a constant fluid velocity if no vaporizable liquid is present or a negligible amount is present in the inlet fluid.

[00039] When discharging particulate polymer product from the reactor, it is desirable and preferable to separate the fluid from the product and return the fluid to the recycled line. There are numerous ways known in the art to accomplish this separation. Product discharge systems that may alternatively be employed are disclosed and claimed in U.S. Patent No. 4,621,952. Such a system typically employs at least one (parallel) pair of tanks comprising a sedimentation tank and a transfer tank, arranged in series and having the separated gas phase returned from the top of the sedimentation tank to a point in the reactor near the top of the fluidized bed.

[00040] In the implementation of the fluidized bed gas phase reactor, the fluidized bed process temperature varies from 70°C or 75°C, or 80°C to 90°C or 95°C or 100°C or 110°C or 115°C, with a desirable temperature comprising any upper limit combined with any lower limit described herein. In general, the reactor temperature is operated at the highest feasible temperature, leading Petition 870200033903, dated 03 / 13 / 2020, page 29 / 47 19 / 30 taking into account the sintering temperature of the inventive polyethylene composition within the reactor and the fouling that may occur in the reactor or in the recycling line(s).

[00041] The process of the present invention is suitable for the production of homopolymers comprising ethylene-derived units, or copolymers comprising ethylene-derived units and at least one or more olefin-derived units.

[00042] In order to maintain adequate catalyst productivity in the present invention, it is preferable that ethylene be present in the reactor at a partial pressure of or greater than 1100 kPa (160 psia), or 1300 kPa (190 psia), or 1380 kPa (200 psia), or 1450 kPa (210 psia), or 1515 kPa (220 psia).

[00043] The comonomer, e.g., one or more αolefin comonomers, if present in the polymerization reactor, is present at any level that achieves the desired percentage incorporation level by weight of the comonomer into the finished polyethylene. This is expressed as a molar ratio of comonomer to ethylene as described herein, which is the ratio of the gaseous concentration of moles of comonomer in the cycle gas to the gaseous concentration of moles of ethylene in the cycle gas.

[00044] Gaseous hydrogen may also be added to the polymerization reactor(s) to control the final properties (e.g., I21 and / or I2) of the inventive polyethylene composition. Examples

[00045] The following examples illustrate the present invention, but are not intended to limit the scope of the invention. Inventive Examples 1-5 and Examples 6-7 have been prepared. Petition 870200033903, dated 03 / 13 / 2020, page 30 / 47 20 / 30 Comparative Examples 1-4. Reactor conditions and catalyst types are shown in Table 1A for the Inventive Examples. Table 1B provides reactor conditions and catalyst type for Comparative Example 3. Table 1C provides reactor conditions and catalyst type for Comparative Example 1, and Table 1D provides reactor conditions and catalyst type for Comparative Example 4. The UCATMR G-150, UCATMR B-300, UCATMR B-375, and UCATMR B-400 catalysts are commercially available from Univation Technologies. The resins in the Inventive and Comparative Examples were stabilized with antioxidants. Table 1A CATALYST UCATMR B-375 UCATMR B-375 UCATMR B-300 UCATMR B-300 UCATMR B-400 EXAMPLE Ex.Inv.1 Ex.Inv.2 Ex.Inv.3 Ex.Inv.4 Ex.Inv.5 REACTION CONDITIONS Temperature, °C 94.6 94.5 95.4 95.4 97.7 Pressure, psig 348 348 349 348 348 Partial Pressure C2, psi 220 220 220 220 220 Molar Ratio H2 / C2 0.050 0.050 0.050 0.050 0.050 Molar Ratio C6 / C2 0.013 0.013 0.013 0.013 0.011 Isopentane, mol% 2.0 2.0 2.0 2.0 2.0 O2 / C2 (ppbv) 90 90 175 175 175 Production Rate, lb / h 25.6 28.5 29.2 29.3 37.5 Bed Weight, lb 126 125 140 140 160 FBD (fluidized apparent density), lb / ft3 15.5 15.9 17.5 17.9 19.4 Bed Volume, ft3 8.1 7.9 8.0 7.8 8.2 Residence Time, h 4.9 4.4 4.8 4.8 4.3 STY (space yield) time), lb / h / ft3 3.2 3.6 3.7 3.7 4.6 Petition 870200033903, dated 03 / 13 / 2020, page 31 / 47 21 / 30 Table 1B UCATMR G-150 CATALYST EXAMPLE Ex. Comp. 3 REACTION CONDITIONS Temperature, °C 93.5-99.5 Pressure, psig 348 Partial Pressure C2, psi 210-260 Molar Ratio H2 / C2 0.050 Molar Ratio C6 / C2 0.011 - 0.021 Isopentane, mol% 0.0 - 4.0 O2 / C2 (ppbv) 20 Production Rate, lb / h 40,000 - 60,000 FBD, lb / ft3 20.0 - 23.0 Bed Height, ft 48 - 50 Residence Time, h 3.25 - 4.5 STY, lb / h / ft3 4.5 - 6.0 Table 1C UCAT JMR CATALYST EXAMPLE Ex. Comp. 1 REACTION CONDITIONS Reactor 1 Reactor 2 Temperature, °C 80 95 Pressure, psig 268 324 Partial Pressure C2, psi 40 75 Molar Ratio H2 / C2 0.03 0.6 Molar Ratio C6 / C2 0.066 0.025 Isopentane, mol% 12.75 12.5 Production Rate, lb / h 48.3 43.0 FBD, lb / ft³ 14.5 19.0 Bed Height, ft 34 47 Residence Time, h 1.9 2.0 STY, lb / h / ft³ 7.9 5.0 Petition 870200033903, dated 03 / 13 / 2020, pp. 32 / 47 22 / 30 Table 1D UCATMR G-150 CATALYST EXAMPLE Ex. Comp. 4 REACTION CONDITIONS Temperature, °C 93.8 Pressure, psig 348 Partial Pressure C2, psi 220 Molar Ratio H2 / C2 0.050 Molar Ratio C6 / C2 0.018 Isopentane, mol% 2.0 O2 / C2 (ppbv) 0 Production Rate, lb / h 34.0 Bed Weight, lb 159 FBD, lb / ft3 20.0 Bed Volume, ft3 7.9 Residence Time, h 4.7 STY (space-time yield), lb / h / ft3 4.3

[00046] Tables 2 and 3 provide the polymer characteristics of each of the Inventive Examples 1-5 and Comparative Examples 1-4, respectively. Table 2 Sample Ex.Inv.1 Ex.Inv.2 Ex.Inv.3 Ex.Inv.4 Ex.Inv.5 Reactor Configuration Simple Simple Simple Simple Process Gas Phase Gas Phase Gas Phase Gas Phase Gas Phase Catalyst UCATMR B-375 UCATMR B-375 UCATMR B-300 UCATMR B-300 UCATMR B-400 Density, g / cm3 0.9372 0.9369 0.9367 0.9366 0.9364 I2, g / 10 min 0.11 0.11 0.12 0.13 0.14 I5, g / 10 min 0.61 0.67 0.73 0.98 0.68 I10, g / 10 min 2, 64 2, 62 2.51 2, 62 2.77 I21, g / 10 min 14.02 15, 65 15, 36 15, 31 13, 67 Tc, oC 113, 9 114.0 113, 8 113, 9 114.3 Δη christ., J / g 175, 7 174.9 174.5 168, 3 175, 1 Tm, oC 125, 4 125, 1 125, 6 125, 5 125, 4 Δη fusion, J / g 176, 5 176, 8 175, 4 172.2 176.5 Vinyls / 1000 carbons (ASTM D6248) 0.941 0.944 0.927 0.93 0.853 Petition 870200033903, dated 03 / 13 / 2020, pp. 33 / 47 23 / 30 Table 3 Sample Ex.Comp.1 Ex.Comp.2 Ex.Comp.3 Ex.Comp.4 Reactor Configuration Double Single Single Single Process Gas Phase Gas Phase Gas Phase Catalyst Type or Catalyst ZieglerNatta UCATMR G-150 UCATMR G-150 Density, g / cm3 0.9407 0.937 0.9398 0.9366 I2, g / 10 min 0.15 0.25 0.14 0.20 I5, g / 10 min 0.52 1.09 0.85 1.04 I10, g / 10 min 1.87 3.82 2.94 3.92 I21, g / 10 min 8.75 19.26 18.59 22.54 Tc, oC 115. 186.2 180.6 184.7 175.6 Vinyls / 1000 carbons (ASTM D6248) 0.168 1.031 1.3 0.952

[00047] Ex.Comp.2 is a commercially available medium-density polyethylene resin from Chevron Phillips Chemical Company LP, under the trade name MARFFLEX HHM TR-130. Film Production Conditions

[00048] Single-layer blown films were manufactured from the comparative and inventive resins on a 3 ½ inch Sterling extruder, C / D of 30:1. The extrusion line is equipped with internal bubble cooling. Additional manufacturing conditions include: Die diameter: 8 inches Die clearance: 70 mil Rate: 15-16 lb / h / inch BUR: 2.5:1 Film thickness: 2 mil Lay flat thickness: 31.4 inches Additional conditions are provided in Table 4. Petition 870200033903, dated 03 / 13 / 2020, pp. 34 / 47 24 / 30 Table 4 Sample Melt Temperature (°F) Melt Pressure Sieve (psi) Melt Pressure Adapter (psi) Speed / rpm Rate (lb / h) Ex. Comp. 2 502 4,480 1,810 6.5 387 Ex. Comp. 3 497 4,090 1,590 5.9 387 Ex. Comp. Inv. Ex. 387 Ex. Inv. 4 500 4,240 1,850 6, 4 385 Ex. Inv. 5 502 4,370 1,480 6, 6 386

[00049] Molecular weight data for each of the Examples Comparative and Inventive Examples are shown in Table 5. Table 6 provides viscoelastic property data for each of the Comparative and Inventive Examples. Table 7 provides optical property data for each of the Inventive Examples and Comparative Examples 2-4. Table 5 Conventional GPC Mn Mw Mz Mw / Mn Mz / Mn Ex. Comp. 1 19,720 184,160 724,500 9.3 3.9 Ex. Comp. 2 11,420 150,030 756,800 13.1 5.0 Ex. Comp. 3 8,390 161,420 996,800 19.2 6.2 Ex. Comp. 4 9,480 163,350 1,031,000 17.2 6, 3 Ex. Inv. 1 9,530 121,580 493,700 12.8 4.1 Ex. Inv. 3 10,560 125,380 519,100 11, 9 4.1 Ex. Inv. Petition 870200033903, dated 03 / 13 / 2020, pp. 35 / 47 25 / 30 Table 6 Sample η* at 0.02s1, 190oC (Pa^s) (η* at 0.02s1, 190oC) / (n*a 200s-1, 190oC) tan delta 0, 02s1, 190oC) (tan delta 0.02s 1, 190oC) / (tan delta 200 s-1,190oC) Ex.Comp.1 71,395 45 3, 33 5, 56 Ex.Comp.2 60,975 54 2, 11 3, 14 Ex.Comp.3 96,313 105 1, 38 2.23 Ex.Comp.4 83,071 83 1, 61 2.47 Ex.Inv.1 144,818 136 1, 31 2, 10 Ex.Inv.2 140,184 134 1, 31 2.09 Ex.Inv.3 119,469 109 1, 42 2.22 Ex.Inv.4 114,078 104 1, 45 2.24 Ex.Inv.5 112,019 98 1.47 2.27 Table 7 Sample Total Fog External Fog Brightness at 45° ASTM D1003 ASTM D1003 ASTM D2457 0% 0% 0% Ex. Comp.2 63 56 9 Ex. Comp.3 67 60 11 Ex. Comp.4 71 63 8 Ex. Inv.1 39 35 16 Ex. Inv.2 38 34 17 Ex. Inv.3 40 35 16 Ex. Inv.4 41 36 15 Ex. Inv.5 40 36 16

[00050] As can be seen from the above and Figures 1-3, the inventive composition results in a molded article with a balance of good optical properties, e.g., low haze and high clarity, and melt strength. Test Methods

[00051] Test methods include the following: Density

[00052] Resin density was measured using the Archimedes displacement method, ASTM D792, Method B in isopropanol. Test specimens were measured within one hour of molding, after being conditioned in an isopropanol bath at 23°C for eight minutes to achieve thermal equilibrium before measurement. The test specimens were molded Petition 870200033903, dated 03 / 13 / 2020, pp. 36 / 47 26 / 30 by compression according to ASTM D4703, Annex A-1, according to Procedure C. Melt Flow Rate by Extrusion Plastomer

[00053] Melt flow rate measurements were performed according to ASTM D1238, Condition 190°C, 2.16 kg, Condition 190°C, 5 kg, Condition 190°C, 10 kg, and Condition 190°C, 21.6 kg, which are known as I2, I5, I10, and I21, respectively. The melt flow rate is inversely proportional to the molecular weight of the polymer. Therefore, the higher the molecular weight, the lower the melt flow rate, although the relationship is not linear. Differential Scanning Calorimetry (DSC)

[00054] The peak melting temperature (Tm), heat of fusion (AHm), peak crystallization temperature (Tc), and heat of crystallization (ΔHο) were generated by a TA Instruments Model Q1000 DSC equipped with an RCS (refrigerated cooling system) accessory and an autosampler. A nitrogen purge gas flow of 50 mL / min was used throughout. The sample was compressed into a thin film using a press at 175°C and 10.3 MPa (1500 psi) maximum pressure for approximately 15 seconds, then air-cooled to room temperature and atmospheric pressure. A 6 mm diameter disc (approximately 3 to 10 mg) was cut from the film using a paper punch, weighed to the nearest 0.001 mg, placed in a lightweight aluminum pan (approximately 50 mg), and then sealed by crimping.

[00055] The thermal behavior of the sample was investigated with the following temperature profile. The sample was rapidly heated to 180°C and held isothermally. Petition 870200033903, dated 03 / 13 / 2020, pages 37 / 47 The sample was heated to 27 / 30 for three minutes to remove any previous thermal history. The sample was then cooled to -40°C at a cooling rate of 10°C / min and held at -40°C for three minutes. The sample was then heated to 150°C at a heating rate of 10°C / min. The cooling and second heating curves were recorded. Tc and ΔHc were determined from the cooling curve, and Tm and ΔHm were determined from the second heating curve. Determination of Molecular Weight (Mw) and Molecular Weight Distribution (MWD) by GPC Conventional Data from Triple Detector GPC

[00056] A high-temperature triple detector gel permeation chromatography (GPC-3D) system was used, consisting of a Waters (Milford, MA) 150°C high-temperature chromatograph equipped with an infrared detector (IR4 from PolymerChar, Valencia, Spain). Concentration was measured with an infrared detector.

[00057] Data collection was performed using Viscotek TriSEC Version 3 software and a 4-channel Viscotek Data Manager DM400. The carrier solvent was 1,2,4-trichlorobenzene (TCB). The system was equipped with a degassing device from Polymer Laboratories. The carousel compartment was operated at 150°C, and the column compartment was operated at 150°C. The columns were four Mixed-A 30 cm, 20 micron columns from Polymer Laboratories. The samples were prepared at a concentration of 0.1 gram of polymer in 50 mL of TCB.The chromatographic solvent (TCB) and the sample preparation solvent contained 200 ppm of butylated hydroxytoluene (BHT), and both solvent sources were sprayed. Petition 870200033903, dated 03 / 13 / 2020, pages 38 / 47 28 / 30 with nitrogen. The polyethylene samples were gently agitated at 160°C for 4 hours. The injection volume was 200 μL, and the flow rate was 1.0 mL / minute. The calibration of the GPC column array was performed with 21 polystyrene standards with narrow molecular weight distribution. The molecular weights of the standards ranged from 580 to 8,400,000 g / mol, and were arranged into 6 cocktail mixtures, with at least a decade of separation between individual molecular weights. The peak molecular weights of the polystyrene standards were converted to polyethylene molecular weights using the following equation: (as described by Williams and Ward, J. Poly, Sci., Polym. Let., 6, 621 (1968) : Mpolyethylene A Mpolyethylene)(1)here, B has a value of 1.0, and the experimentally determined value is about 0.38.

[00058] A first-order polynomial was used to fit the respective calibration points for polyethylene equivalents obtained from equation (1) to their observed elution volumes. The effective polynomial fit was obtained by relating the logarithm of the polyethylene equivalent molecular weights to the observed elution volumes (and associated energies) for each polystyrene standard.

[00059] The numerical, weight-based, and average z-weights were calculated according to the following equations: - twf. (2) _ i(Wf.·M) (3) _ t (W·M 1) (4) Mn = Mw =-.Mz = tWf / MiJ iWf i Wf · M.) where Wfi is the weight fraction of the i-th component and M is the molecular weight of the i-th component.

[00060] The MWD molecular weight distribution was expressed Petition 870200033903, dated 03 / 13 / 2020, pp. 39 / 47 29 / 30 as the ratio of the weight-average molecular weight (Mw) to the number-average molecular weight (Mn) or the ratio of the z-average molecular weight (Mz) to the weight-average molecular weight (Mw).

[00061] The value A was determined by adjusting the value A in equation (1) up to Mw, the weight-average molecular weight calculated using equation (3) and the corresponding retention volume polynomial, consistent with the independently determined value of Mw obtained according to the known molecular weight linear homopolymer reference of 115,000 g / mol. Rheology by DMS

[00062] Each sample was compression molded into a disc for rheology measurement. The discs were prepared by pressing the samples into plates 3.0 mm thick, and were subsequently cut into discs 25 mm in diameter. The compression molding procedure was as follows: 177°C (350°F) for five minutes, at 10.3 MPa (1500 psi), under N2 purge protection, then the frame was transferred to an oven at room temperature, with N2 purge, until the sample plate solidified, and then the plate was removed from the frame.

[00063] The rheology of resin was measured using the TA Instruments ARES-LS model rheometer. The ARES is a strain-controlled rheometer. A rotary actuator (servomotor) applies a shear strain in the form of stress to a sample. In response, the sample generates torque, which is measured by the transducer. Stress and torque are used to calculate dynamic mechanical properties such as modulus and viscosity. The viscoelastic properties of the sample were Petition 870200033903, dated 03 / 13 / 2020, pp. 40 / 47 30 / 30 measurements were taken in the melt, using a set of parallel plates with a diameter of 25 mm, at 190°C, and as a variable frequency function (range from 0.01 s⁻¹ to 500 s⁻¹). A small constant deformation (5%) was applied to ensure that the measurement was in the linear viscoelastic region. The storage modulus (G'), loss modulus (G), tan delta (G / G'), and complex viscosity (eta* or η*) of the resin were determined using Rheometrics Orchestrator software (v.6.5.8). Casting Resistance

[00064] The strength measurement of Rheotens casting (Goettfert Inc., Rock Hill, SC, USA) was performed at 190°C. The casting was produced by a Goettfert Rheotester 2000 capillary rheometer with a 30 / 2 flat die, at a shear rate of 38.2 s⁻¹. The rheometer cylinder (diameter: 12 mm) was filled in less than one minute. A 10-minute delay was allowed for proper melting. The winding speed of the Rheotens wheels was varied, with a constant acceleration of 2.4 mm / s². The tension in the wound filament was monitored over time until the filament broke. The steady-state force and the speed at break were reported.

[00065] The present invention may be carried out in other ways without departing from the spirit and essential attributes thereof, and, consequently, reference should be made to the appended claims, instead of to the preceding description, as indicative of the scope of the invention.

Claims

1. Polyethylene composition, comprising: - at least 95 percent by weight of ethylene-derived units; - less than 5 percent by weight of units derived from one or more α-olefin comonomers; - said polyethylene composition having a density in the range of 0.930 to 0.945 g / cm3, a molecular weight distribution characterized by having a ratio of average molecular weight z to weight-average molecular weight (Mz / Mw) less than 5, a melt index, I2 (measured at 190°C, 2.16 kg), in the range of 0.08 to 0.5 g / 10 minutes, and a high-flow melt index, I21 (measured at 190°C, 21.6 kg), in the range of 10 to 20 g / 10 minutes; and - wherein the polyethylene composition is produced using a chromium oxide catalyst, and wherein the polyethylene composition has a vinyl unsaturation of at least 0.5 less than 1 vinyl per thousand carbon atoms present in the main chain of said composition, wherein the vinyl unsaturation is measured in accordance with ASTM D6248.

2. Polyethylene composition according to claim 1, characterized in that the polyethylene composition has a density of 0.934 to 0.942 g / cm3.

3. Polyethylene composition, according to any one of claims 1 or 2, characterized in that the polyethylene composition has a complex viscosity (η*), determined at 0.02 s-1 and 190oC, of ​​at least 100,000 Pa's.

4. Polyethylene composition, according to any one of claims 1 to 3, characterized in that the polyethylene composition has a complex viscosity ratio, η* at 0.02 s-1 and 190oC, for η* at 200 s-1 and 190oC, greater than 90.

5. Article, characterized by comprising a polyethylene composition, as defined in any one of claims 1 to 4, wherein the article exhibits one or more of the following properties: a gloss at 45° of at least 10%, a total haze of less than 60%.

6. Article according to claim 5, characterized in that the article is an extrusion-blow molded article.

7. Article according to claim 5, characterized in that the article is a film comprising at least one layer comprising a polyethylene composition.

8. Film, as defined in claim 7, characterized in that the film is a shrinkable film.

9. Polyethylene composition, according to any one of claims 1 to 4, characterized in that the polyethylene composition exhibits improved processability as shown by having a melt strength of 10 cN or greater, measured at 190°C.

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