RU2829446C2 - Blow moulding polymers treated with peroxide, with increased weight swelling and constant swelling of extruded stream - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: group of inventions relates to an ethylene polymer, a method for production thereof, which involves treatment of a polyolefin base resin with peroxide to obtain an ethylene polymer, and subsequent use of the ethylene polymer to produce articles. Ethylene polymer has an HLMI of less than or equal to 12 g/10 min, Mw in range of 200,000 to 550,000 g/mol, Mn in range from 18,000 to 48,000 g/mol, parameter CY-a less than or equal to 0.12, tan δ at 0.1 s^-1 in range from 0.5 to 0.9 degrees, tan δ at 100 s^-1 in range from 0.5 to 0.75 degrees and viscosity at 0.001 s^-1 in range of 1.3×10⁶ to 1×10⁷ Pa⋅s. Method of producing an ethylene polymer includes steps of bringing a base resin into contact with a peroxide compound to obtain an ethylene polymer, where the step for bringing the base resin into contact with the peroxide compound comprises moulding the mixture of the base resin and the peroxide compound at a suitable temperature of moulding from the melt, where the amount of the peroxide compound ranges from more than 200 to 500 ppm wt. peroxide groups per weight of base resin. Also described are articles containing an ethylene polymer with said characteristics.

EFFECT: providing an ethylene polymer with differentiation of swelling of the extruded flow and weight swelling, which makes it possible to independently control the weight of the part; besides, treatment with peroxide increases strength of the polymer melt.

20 cl, 8 dwg, 3 tbl, 12 ex

Description

AREA OF TECHNOLOGY

The present invention generally relates to peroxide treatment of a bimodal polyolefin base resin to form an ethylene polymer and subsequent use of the ethylene polymer to form blow molded products with a favorable combination of both die swell and weight swell.

LEVEL OF TECHNOLOGY

Polyolefins, such as high-density polyethylene (HDPE) homopolymer and linear low-density polyethylene (LLDPE) copolymer, can be produced using various combinations of catalyst systems and polymerization processes. Using metallocene-based catalyst systems, it is possible, for example, to produce ethylene polymers that have excellent impact resistance and toughness properties, but often at the expense of poor extrusion processability, melt strength, and bubble stability. Using Ziegler-Natta and chromium-based catalyst systems, it is possible, for example, to produce ethylene polymers that have good extrusion processability, polymer melt strength, and bubble stability in blown film applications, typically due to their broad molecular weight distribution (MWD).

In some end-use applications, such as blow molding, it may be difficult to produce ethylene polymers, regardless of the catalyst system, that have acceptable levels of both die swell and weight swell. Accordingly, the present invention is generally directed to these purposes.

ESSENCE OF THE INVENTION

This Summary of the Invention is provided to present in a simplified form a selection of concepts that are further described below in the Detailed Description of the Invention. This Summary of the Invention is not intended to identify necessary or essential features of the claimed subject matter. This Summary of the Invention is also not intended to be used to limit the scope of the claimed subject matter.

The present invention generally relates to ethylene polymers (e.g., ethylene-alpha-olefin copolymers) characterized by a high load melt index (HLMI) of less than or equal to 12 g/10 min, a weight average molecular weight (Mw) in the range of 200,000 to 550,000 g/mol, a number average molecular weight (Mn) in the range of 18,000 to 48,000 g/mol, a CY-a parameter of less than or equal to 0.12, a tan δ (tan d or tan delta) at 0.1 s ^-1 in the range of 0.5 to 0.9 degrees, a tan δ at 100 s ^-1 in the range of 0.5 to 0.75 degrees, and a viscosity at 0.001 s ^-1 (eta @ 0.001 s ^-1 or η @ 0.001 s ^-1 ) in the range from 1.3×10 ⁶ to 1×10 ⁷ Pa s. These ethylene polymers can be used for the production of various industrial products, such as blow molded bottles and other blow molded products.

Ethylene polymers can be produced, for example, by a process comprising contacting a base resin (e.g., an ethylene copolymer) with a peroxide compound to produce an ethylene polymer. In some aspects, the contacting step may comprise a melt-processing step of a mixture of the base resin and the peroxide compound at a suitable melt-processing temperature, and often the amount of peroxide groups is in the range of 10 to 500 ppm, 25 to 400 ppm, or 50 to 350 ppm, based on the weight of the base resin. Without limitation, the base resin may often be characterized by an HLMI in the range of 2 to 40 g/10 min, a Mw in the range of 250,000 to 550,000 g/mol, a CY-a parameter in the range of 0.12 to 0.3, a tan δ at 0.1 s ^-1 in the range of 0.8 to 1.05 degrees, a tan δ at 100 s ^-1 in the range of 0.4 to 0.6 degrees, and a viscosity at 0.001 s ^-1 in the range of 1 x 10 ⁵ to 3 x 10 ⁶ Pa s.

Both the above Summary and the following Detailed Description provide examples that are illustrative only. Accordingly, the above Summary and the following Detailed Description are not intended to be limiting. Furthermore, features or variations may be provided in addition to what is set forth herein. For example, certain aspects and embodiments of the invention may be directed to various combinations and subcombinations of the features described in the Detailed Description.

BRIEF DESCRIPTION OF GRAPHIC MATERIALS

Fig. 1 illustrates a graph of the molecular weight distribution of the ethylene polymers of Examples 1-6.

Fig. 2 illustrates a graph of the molecular weight distribution of the ethylene polymers of Examples 7-12.

Fig. 3 illustrates a graph of the molecular weight distribution of the ethylene polymers of Examples 13-17.

Fig. 4 is a differential dynamic rheology plot at 190°C illustrating the rheological differences between Examples 2-6 and the baseline of Example 1 at different shear rates.

Fig. 5 is a differential dynamic rheology plot at 190°C illustrating the rheological differences between Examples 8-12 and the baseline of Example 7 at different shear rates.

Fig. 6 is a differential dynamic rheology plot at 190°C illustrating the rheological differences between Examples 14-17 and the baseline of Example 13 at different shear rates.

Fig. 7 illustrates a graph of extrudate flow swelling and weight swelling as a function of peroxide loading in Examples 1-6.

Fig. 8 illustrates a graph of extrudate flow swelling and weight swelling as a function of peroxide loading in Examples 7-12.

DEFINITIONS

To more clearly define the terms used herein, the following definitions are provided. Unless otherwise noted, the definitions below apply to this disclosure. When a term is used in this disclosure but is not specifically defined herein, the definition in the IUPAC Compendium of Chemical Terminology, 2nd edition (1997) may apply, provided that the definition does not conflict with any other disclosure or definition used herein, or does not undefined or prohibit any claim to which the definition applies. To the extent that any definition or usage set forth in any document incorporated by reference herein conflicts with a definition or usage set forth herein, the definition or usage set forth herein shall control.

This document describes features of the subject matter of the invention, such that combinations of different features may be envisaged within specific aspects. For each aspect and/or feature disclosed herein, all combinations that do not adversely affect the embodiments, compositions and/or methods described herein are contemplated with or without explicit description of the specific combination. Furthermore, unless explicitly stated otherwise, any aspect and/or feature disclosed herein may be combined to describe claimed features consistent with this disclosure.

Although compositions and methods are described herein in the context of “comprising” various components or steps, said compositions and methods may also “consist essentially of” or “consist of” the various components or steps, unless otherwise indicated.

The reference to the singular is intended to include a plurality of alternatives, such as at least one, unless otherwise indicated. For example, a description of an "additive" or "comonomer" is intended to cover one, or mixtures or combinations of more than one additive or comonomer, respectively, unless otherwise indicated.

Generally, groups of elements are designated using the numbering scheme given in the version of the periodic table of the elements published in Chemical and Engineering News , 63(5), 27, 1985. In some cases, a group of elements may be referred to using the common name assigned to the group; for example, alkali metals for group 1 elements, alkaline earth metals for group 2 elements, transition metals for group 3–12 elements, and halogens or halides for group 17 elements.

For any particular compound disclosed herein, the general structure or name provided is also intended to encompass all structural isomers, conformational isomers, and stereoisomers that may arise from the specified set of substituents, unless otherwise specified. Thus, a general reference to a compound includes all structural isomers unless explicitly stated otherwise; for example, a general reference to pentane includes n-pentane, 2-methylbutane, and 2,2-dimethylpropane, while a general reference to a butyl group includes an n-butyl group, a sec-butyl group, an isobutyl group, and a tert-butyl group. Furthermore, a reference to a general structure or name encompasses all enantiomers, diastereomers, and other optical isomers, whether in enantiomeric or racemic forms, as well as mixtures of stereoisomers, as the context or requirements require. For any specific formula or name provided, any general formula or name provided also encompasses all conformational isomers, regioisomers, and stereoisomers that may arise from a particular set of substituents.

The term "polymer" is used herein generally to include olefin homopolymers, copolymers, terpolymers and the like, as well as alloys and blends thereof. The term "polymer" also includes impact, block, graft, random and alternating copolymers. A copolymer is prepared from an olefin monomer and one olefin comonomer, and a terpolymer is prepared from an olefin monomer and two olefin comonomers. Accordingly, "polymer" encompasses copolymers and terpolymers prepared from any of the olefin monomer and comonomer(s) described herein. Likewise, the term "polymerization" includes homopolymerization, copolymerization and terpolymerization. Thus, an ethylene polymer includes ethylene homopolymers, ethylene copolymers (e.g., ethylene-α-olefin copolymers), ethylene terpolymers and the like, as well as blends thereof. Thus, the ethylene polymer encompasses polymers often referred to in the art as linear low density polyethylene LLDPE and high density polyethylene HDPE. For example, an olefin copolymer, such as an ethylene copolymer, can be derived from ethylene and a comonomer, such as 1-butene, 1-hexene or 1-octene. If the monomer and comonomer were ethylene and 1-hexene, respectively, then the resulting polymer can be categorized as a copolymer of ethylene and 1-hexene. The term "polymer" also includes all possible geometric configurations, unless otherwise specified, and such configurations can include isotactic, syndiotactic and random symmetries. In addition, the "polymers" (e.g., ethylene polymers, base resins) disclosed herein can also be referred to herein as "polymer compositions".

The term "contacting" is used herein to refer to materials or components that may be mixed, stirred, suspended, dissolved, reacted, processed, compounded, or otherwise brought into contact or combined in any other manner or by any suitable method. The materials or components may be contacted with each other in any order, in any manner, and for any period of time, unless otherwise specified.

Although any methods, devices, and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, exemplary methods, devices, and materials are described herein.

All publications and patents mentioned in this document are herein incorporated by reference for the purpose of describing and disclosing, for example, structures and methods that are described in the publications and that may be applied, as appropriate, to the invention described herein.

The present invention discloses several types of ranges. In the event that a range of any type is disclosed or claimed, the intent is to individually disclose or claim each possible number that can sufficiently cover such a range, including the end points of the range, as well as any sub-ranges and combinations of sub-ranges included in the range. As a representative example, the Mw/Mn ratio of the ethylene polymer can be in certain ranges in various aspects of the present invention. The disclosure that the Mw/Mn ratio can be in the range from 6.5 to 20 is intended to indicate that the Mw/Mn ratio can be any ratio in the stated range and, for example, can include any range or combination of ranges from 6.5 to 20, such as from 7 to 17, from 7.5 to 15, or from 8 to 13, and so on. Likewise, all other ranges described herein should be interpreted similarly to this example.

Generally, a quantity, size, composition, parameter, range or other value or characteristic is approximate, regardless of whether it is explicitly stated. Regardless of whether it is modified by the term "about" or "approximately", the claims include equivalents for the stated values or characteristics.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is generally directed to high molecular weight ethylene-based polymers having excellent melt strength and a wide range of molecular weight distributions. Such polymers can be converted in blow molding equipment into various industrial articles.

The swelling characteristics of the polymer as it exits the accumulation die are critical to blow molding equipment operation. Proper swelling is necessary to ensure proper mold filling as well as proper part weight (e.g., proper wall thickness). The swelling characteristics of the polymer encompass two different swelling properties: die swell and weight swell. It is known in the industry that changing the polymer structure to increase swelling simultaneously increases both die swell (e.g., how much the polymer parison expands in diameter as it exits the accumulation die) and weight swell (e.g., how much the polymer penetrates the parison on its own and increases the parison wall thickness relative to the die gap opening). Regardless of whether the polymer is a unimodal chromium-based resin or a bimodal dual metallocene-based resin, changes in the polymer structure, such as molecular weight distribution, simultaneously increase or simultaneously decrease both die swell and weight swelling.

Surprisingly and advantageously, the disclosed ethylene polymers (which have been treated with 10-300 ppm of active peroxide groups) exhibit a divergence or separation of the flow swell and weight swell characteristics. Specifically, although the flow swell is held constant, the weight swell can be unexpectedly increased by increasing the amount of peroxide. Thus, the weight swell can be unexpectedly increased or decreased without affecting the flow swell, allowing blow molding machine operators to independently control the part weight (e.g., part wall thickness).

ETHYLENE POLYMERS

In general, the polymers described herein are ethylene-based polymers or ethylene polymers, including ethylene homopolymers, as well as copolymers, terpolymers, etc. of ethylene and at least one olefin comonomer. Comonomers that can be copolymerized with ethylene can often have from 3 to 20 carbon atoms in their molecular chain. For example, typical comonomers can include, but are not limited to, propylene, 1-butene, 1-pentene, 1-hexene, 1-heptene, 1-octene and similar comonomers or combinations thereof. In one aspect, the olefin comonomer can comprise a C ₃ -C ₁₈ olefin; alternatively, the olefin comonomer can comprise a C ₃ -C ₁₀ olefin; Alternatively, the olefin comonomer may comprise a _C4 - _C10 olefin; Alternatively, the olefin comonomer may comprise a _C3 - _C10 α-olefin; Alternatively, the olefin comonomer may comprise a _C4 - _C10 α-olefin; Alternatively, the olefin comonomer may comprise 1-butene, 1-hexene, 1-octene, or any combination thereof; or, Alternatively, the comonomer may comprise 1-hexene.

In one aspect, the ethylene polymer of the present invention may comprise a copolymer of ethylene and an α-olefin, while in another aspect, the ethylene polymer may comprise an ethylene homopolymer, and in yet another aspect, the ethylene polymer of the present invention may comprise a copolymer of ethylene and an α-olefin and an ethylene homopolymer. For example, the ethylene polymer may comprise a copolymer of ethylene and 1-butene, a copolymer of ethylene and 1-hexene, a copolymer of ethylene and 1-octene, a homopolymer of ethylene, or any combination thereof; alternatively, a copolymer of ethylene and 1-butene, a copolymer of ethylene and 1-hexene, a copolymer of ethylene and 1-octene, or any combination thereof; or, alternatively, a copolymer of ethylene and 1-hexene.

An illustrative and non-limiting example of an ethylene polymer (e.g., an ethylene-alpha-olefin copolymer) described herein has a high load melt index (HLMI) of less than or equal to 12 g/10 min, a weight average molecular weight (Mw) in the range of 200,000 to 550,000 g/mol, a number average molecular weight (Mn) in the range of 18,000 to 48,000 g/mol, a CY-a parameter of less than or equal to 0.12, a tan δ (tan d or tan delta) at 0.1 sec ^-1 in the range of 0.5 to 0.9 degrees, a tan δ (tan d or tan delta) at 100 sec ^-1 in the range of 0.5 to 0.75 degrees, and a viscosity at 0.001 s ^-1 (eta @ 0.001 s ^-1 or η @ 0.001 s ^-1 ) in the range of 1.3×10 ⁶ to 1×10 ⁷ Pa s. This illustrative and non-limiting example of an ethylene polymer may also have any of the polymer properties listed below, and in any combination, unless otherwise noted.

The ethylene polymer has a very low melt index, as indicated by a high load melt index (HLMI), which is less than or equal to 12 g/10 min. In some aspects, the HLMI of the ethylene polymer can be less than or equal to 10 or less than or equal to 8 g/10 min. Typical ranges for HLMI include from 1 to 12 g/10 min, from 1 to 10 g/10 min, from 1 to 8 g/10 min, from 2 to 12 g/10 min or from 2 to 10 g/10 min and similar ranges.

In one aspect, the ethylene polymer may have a Mw in the range of 200,000 to 500,000 g/mol, 250,000 to 550,000 g/mol, 250,000 to 500,000 g/mol, 250,000 to 475,000 g/mol, 275,000 to 550,000 g/mol, or 275,000 to 475,000 g/mol. In a further or alternative embodiment, the ethylene polymer may have a Mw/Mn ratio that is in the range of 6.5 to 20, such as 7 to 17, 7.5 to 15, or 8 to 13. In a further or alternative embodiment, the ethylene polymer may have a Mz/Mw ratio that is in the range of 4 to 9, such as 4 to 8, 4.5 to 7.5, or 5 to 7.

In one aspect, the ethylene polymers may have an Mp in the range of 60,000 to 110,000 g/mol, 65,000 to 105,000 g/mol, or 70,000 to 100,000 g/mol. Additionally or alternatively, the ethylene polymer may have an Mn in the range of 20,000 to 46,000 g/mol, 22,000 to 46,000 g/mol, 20,000 to 42,000 g/mol, or 22,000 to 40,000 g/mol. Additionally or alternatively, the ethylene polymers according to some aspects of the present invention may often have a bimodal molecular weight distribution (as determined using gel permeation chromatography (GPC) or other related analytical method). Typically, a bimodal molecular weight distribution has a valley between peaks, and the peaks may be separated or deconvoluted. Typically, a bimodal molecular weight distribution may be characterized as having an identifiable high molecular weight component (or distribution) and an identifiable low molecular weight component (or distribution). Exemplary unimodal MWD curves and bimodal MWD curves are shown in U.S. Patent No. 8,383,754, incorporated herein by reference in its entirety.

The density of the ethylene-based polymers disclosed herein is often greater than or equal to 0.935 g/ ^cm3 , and less than or equal to about 0.965 g/ ^cm3 . Also, in particular aspects, the density can be in the range of 0.94 to 0.965 g/ ^cm3 , 0.945 to 0.965 g/ ^cm3 , 0.94 to 0.96 g/ ^cm3 , 0.945 to 0.96 g/ ^cm3 , 0.95 to 0.965 g/ ^cm3 , or 0.95 to 0.96 g/ ^cm3 .

The ethylene polymers described herein have high viscosity at low shear rates, which is reflected in excellent polymer melt strength. The viscosity at 0.001 s ^-1 (eta @ 0.001 s ^-1 or η @ 0.001 s ^-1 ) at 190 °C is typically in the range of from 1.3 x 10 ⁶ to 1 x 10 ⁷ Pa s, such as from 1.3 x 10 ⁶ to 6 x 10 ⁶ Pa s; alternatively from 1.3 x 10 ⁶ to 5 x 10 ⁶ Pa s; alternatively from 1.5 x 10 ⁶ to 1 x 10 ⁷ Pa s; alternatively from 1.5 x 10 ⁶ to 6 x 10 ⁶ Pa s; alternatively from 1.5×10 ⁶ to 5×10 ⁶ Pa s; alternatively from 2×10 ⁶ to 6×10 ⁶ Pa s; or alternatively from 2×10 ⁶ to 5×10 ⁶ Pa s. In some aspects, the ethylene polymer may have a zero shear viscosity (η ₀ ) at 190°C in the range of from 1×10 ⁸ to 1×10 ³⁰ Pa s, from 1×10 ⁸ to 1×10 ²⁸ Pa s, from 1 x 10 ¹⁰ to 1 x 10 ³⁰ Pa s, from 1 x 10 ¹⁰ to 1 x 10 ²⁷ Pa s, or from 1 x 10 ¹² to 1 x 10 ²⁷ Pa s, and similar ranges. In an additional or alternative embodiment, the ethylene polymer may have a relaxation time ( τ _η ) in the range of from 5 x 10 ³ to 1 x 10 ²⁵ s, such as from 6 x 10 ³ to 1 x 10 ²³ s, from 1 x 10 ⁵ to 1 x 10 ²⁵ s, from 1 x 10 ⁵ to 1 x 10 ²³ s, or from 1 x 10 ⁷ to 1 x 10 ²³ s, and similar ranges. The zero-shear viscosity and relaxation time are determined from viscosity data measured at 190 °C and using the empirical Carreau-Yasuda (CY) model as described herein, with a creep correction.

The ethylene polymer may have a CY-a parameter of less than or equal to 0.12, such as less than or equal to 0.11, less than or equal to 0.1, less than or equal to 0.08, or less than or equal to 0.06. Typically, ranges include from 0.01 to 0.12, from 0.01 to 0.1, from 0.01 to 0.08, or from 0.01 to 0.06, and similar values. In a further or alternative embodiment, the ethylene polymer may have a tan δ at 0.1 s ^-1 in the range of from 0.5 to 0.9 degrees in one aspect, from 0.5 to 0.85 degrees in another aspect, from 0.5 to 0.8 degrees in another aspect, from 0.55 to 0.9 degrees in another aspect, from 0.55 to 0.85 degrees in another aspect, from 0.6 to 0.9 degrees in another aspect, from 0.6 to 0.85 degrees in yet another aspect, and from 0.6 to 0.8 degrees in yet another aspect. In a further or alternative embodiment, the ethylene polymer may have a tan δ at 100 sec ^-1 in the range of from 0.5 to 0.75 degrees in one aspect, from 0.5 to 0.72 degrees in another aspect, from 0.5 to 0.7 degrees in another aspect, from 0.52 to 0.75 degrees in another aspect, from 0.52 to 0.72 degrees in another aspect, from 0.52 to 0.7 degrees in another aspect, from 0.55 to 0.75 degrees in yet another aspect, and from 0.55 to 0.72 degrees in yet another aspect. In an additional or alternative embodiment, the ethylene polymers may have a viscosity at 100 s ^-1 (eta @ 100 or η @ 100) at 190 °C in the range of 1700 to 3300, 1800 to 3200, 1900 to 3100, or 2000 to 3000 Pa s. These rheological parameters are determined from viscosity data measured at 190 °C and using the empirical Carreau-Yasuda (CY) model as described herein, with a creep correction.

In addition, the ethylene polymers may have an inverse comonomer distribution, typically the higher molecular weight components of the polymer having a higher comonomer incorporation than the lower molecular weight components. Typically, as the molecular weight increases, the comonomer incorporation increases. In one aspect, the amount of short chain branches (SCB) per 1000 total carbon atoms of the polymer may be greater at Mw than at Mn. In another aspect, the amount of SCB per 1000 total carbon atoms of the polymer may be greater at Mz than at Mw. In another aspect, the amount of SCB per 1000 total carbon atoms of the polymer may be greater at Mz than at Mn.

In one aspect, the ethylene polymer described herein may be a reactor product (e.g., a product of one reactor), for example, rather than a blend of two reactor polymers, for example, having different molecular weight characteristics. As one skilled in the art will readily appreciate, physical blends of two different polymer resins may be prepared, but this requires additional processing and complexity not required for a reactor product.

In addition, the ethylene polymer can be obtained from a base resin that can be obtained using a dual metallocene catalyst system. Ziegler-Natta and chromium-based catalyst systems are not required. Therefore, the ethylene polymer can contain an immeasurable amount of chromium, or titanium, or vanadium, or magnesium (catalytic residue), i.e., less than 0.1 ppm by weight. In some aspects, the ethylene polymer can independently contain less than 0.08 ppm, less than 0.05 ppm, or less than 0.03 ppm of chromium (or titanium, or vanadium, or magnesium).

The ethylene polymer may be in any suitable form, such as flakes, powder, granules, pellets, and similar forms. Often, the ethylene polymer is in the form of pellets. The ethylene polymer may contain one or more additives, non-limiting examples of which may include an antioxidant, an acid scavenger, an anti-blocking agent, a slippery additive, a colorant, a filler, a processing aid, an ultraviolet inhibitor, and similar additives, as well as combinations thereof.

Aspects of this invention are also directed to the performance of these ethylene polymers (e.g., ethylene-1-hexene copolymers) on typical blow molding equipment, as described below. Advantageously, the ethylene polymers can have a weight swell (quantified by partial weight in grams) that is unrelated to the extrudate swell (quantified by flat bottom in inches), and the difference between the two can be dependent on the amount of peroxide used to produce the ethylene polymer. In one aspect, for example, the ethylene polymer may have a weight swell to flow swell ratio (weight swell is quantified by partial weight in grams and flow swell is quantified by flat bottom in inches) in the range of 200 to 280, 210 to 270 in another aspect, 230 to 280 in another aspect, and 230 to 270 in yet another aspect. It is also advantageous for the ethylene polymers to have exceptional melt strength in a blow molding process, which can be quantified by a hang time of at least 40 s, and more often at least 50 s or at least 100 s.

According to aspects of the present invention, an ethylene polymer can be produced from a base resin (discussed herein below) by a process comprising contacting the base resin with a peroxide compound to produce an ethylene polymer (any ethylene polymer described herein). Typically, the amount (parts per million by weight) of peroxide compound used in the process is of less concern because the amount of peroxide groups is more important and the molecular weight and the number of peroxide groups per peroxide compound are not the same for all suitable peroxide compounds. Typically, the amount of peroxide groups based on the weight of the base resin can be in the range of from 10 to 500 ppm, from 25 to 400 ppm, from 50 to 400 ppm, from 50 to 350 ppm, from 75 to 400 ppm, or from 10 to 500 ppm. or from 100 to 300 ppm of peroxide groups based on the weight of the base resin.

Thus, the base resin and the peroxide compound can be brought into contact at a temperature sufficient to form peroxide groups in the range of 10 to 500 ppm, 25 to 400 ppm, 50 to 400 ppm, 50 to 350 ppm, 75 to 400 ppm, or 100 to 300 ppm peroxide groups based on the weight of the base resin.

In one aspect, the step of contacting the base resin with the peroxide compound may comprise melt-forming the mixture of the base resin and the peroxide compound at any suitable melt-forming temperature, such as at a temperature in the range of 120 to 300°C, at a temperature in the range of 150 to 250°C, at a temperature in the range of 175 to 225°C, and so on. The suitable temperature may depend on the composition of the peroxide compound and the temperature at which it releases peroxide groups. Prior to contacting with the peroxide compound, the base resin may be in any suitable form, including, for example, flakes, powder, granulate, granules, solution, suspension, emulsion, and the like. Likewise, the peroxide compound may be in solid form, liquid form, solution, or suspension. One particular method utilizes a masterbatch of a peroxide compound and brings it into contact with a base resin (in flake form) during a melt spinning process. The masterbatch of the peroxide compound may comprise any suitable organic or inorganic carrier, but often comprises a carrier resin with high melt flowability, such as polyethylene or polypropylene.

The present invention is not limited to any particular method of contacting and melt forming the base resin and the peroxide compound. Various mixing and/or compounding methods may be used and should be known to those skilled in the art. In one aspect, the melt forming of the base resin and the peroxide compound may be performed in a single-screw extrusion system. In another aspect, the melt forming of the base resin and the peroxide compound may be performed in a twin-screw extrusion system (e.g., a counter-rotating mixer or a co-rotating twin-screw extrusion system). The twin-screw extrusion system may include any combination of feeding, melting, mixing, and transporting elements. For example, the twin-screw extrusion system may include all or most of the mixing elements.

The peroxide compound may be any compound containing one or more peroxide (O-O) groups, suitable examples of which may include, but are not limited to, 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, dicumyl peroxide, tert-butylcumyl peroxide, n-butyl-4,4'-di(tert-butylperoxy)valerate and the like. The peroxide compound may be added, for example, as a solid granule dissolved in mineral oil or in liquid form.

One or more additives may also be added during the conversion of the base resin (and peroxide compound) into an ethylene polymer. Non-limiting examples of suitable additives may include an antioxidant, an acid scavenger, an anti-blocking agent, a slip additive, a colorant, a filler, a processing aid, an ultraviolet inhibitor, and similar additives. Combinations of two or more additives may be contacted with the base resin and peroxide compound, if desired.

PRODUCTS AND PRODUCTS

Articles of manufacture may be formed from and/or may comprise the ethylene polymers (e.g., ethylene copolymers) of the present invention and are accordingly included herein. For example, articles that may comprise the ethylene polymers of the present invention may include, but are not limited to, an agricultural film, an automotive part, a bottle, a chemical container, a drum, a fiber or fabric, a food packaging film or container, a food service article, a fuel tank, a geomembrane, a household container, a liner, a molded product, a medical device or material, an outdoor storage article (e.g., outdoor shelter wall panels), outdoor play equipment (e.g., kayaks, basketball goal bases), a pipe, sheet or tape, a toy or road barrier, and similar articles. Various methods may be used to make these articles. Non-limiting examples of these processes include injection molding, blow molding, rotomolding, film extrusion, sheet extrusion, profile extrusion, thermoforming and the like. In addition, additives and modifiers are often added to these polymers in order to provide effective processing properties of the polymer or end-use product. Such processes and materials are described in Modern Plastics Encyclopedia , Mid-November 1995 Issue, Vol. 72, No. 12; and Film Extrusion Manual - Process, Materials, Properties , TAPPI Press, 1992; the disclosures of which are incorporated herein by reference in their entirety. In some aspects of the present invention, an article of manufacture may comprise any of the ethylene polymers described herein, and the article of manufacture may be or may comprise a blow molded product, such as a blow molded bottle.

BASE RESINS

In general, the base resin used to produce the ethylene polymer may be any homopolymer of ethylene or a copolymer, terpolymer, etc. of ethylene and at least one olefin comonomer described above for the ethylene polymer. Thus, the base resin may comprise a copolymer of ethylene and an α-olefin, while in another aspect, the base resin may comprise an ethylene homopolymer, and in yet another aspect, the base resin may comprise an ethylene and α-olefin copolymer and an ethylene homopolymer. Accordingly, the base resin may comprise a copolymer of ethylene and 1-butene, a copolymer of ethylene and 1-hexene, a copolymer of ethylene and 1-octene, an ethylene homopolymer, or any combination thereof; alternatively, a copolymer of ethylene and 1-butene, a copolymer of ethylene and 1-hexene, a copolymer of ethylene and 1-octene, or any combination thereof; or alternatively, a copolymer of ethylene and 1-hexene. Typically, for example, if the base resin is a copolymer of ethylene and 1-hexene, then the ethylene polymer produced from the base resin is also a copolymer of ethylene and 1-hexene, although blends and combinations of different types of homopolymers and copolymers may be used.

To obtain an ethylene polymer having the properties and advantages disclosed herein, a suitable base resin is used. An illustrative and non-limiting example of a base resin (e.g., an ethylene copolymer) according to the present invention may have an HLMI in the range of 2 to 40 g/10 min, a Mw in the range of 250,000 to 550,000 g/mol, a CY-a parameter in the range of 0.12 to 0.3, a tan δ at 0.1 s ^-1 in the range of 0.8 to 1.05 degrees, a tan δ at 100 s ^-1 in the range of 0.4 to 0.6 degrees, and a viscosity at 0.001 s ^-1 in the range of 1×10 ⁵ to 3×10 ⁶ Pa s. This illustrative and non-limiting example of a base resin according to the present invention may also have any of the polymer properties listed below, and in any combination, unless otherwise indicated.

The base resin used to produce the ethylene polymer may, in some aspects, have an HLMI in the range of 2 to 20 g/10 min, 2 to 12 g/10 min, 4 to 40 g/10 min, 4 to 20 g/10 min, 4 to 15 g/10 min, or 4 to 12 g/10 min and similar values.

In one aspect, the base resin may have a Mw in the range of 250,000 to 500,000 g/mol, 250,000 to 475,000 g/mol, 300,000 to 550,000 g/mol, or 300,000 to 500,000 g/mol. Additionally or alternatively, the base resin may have a Mw/Mn ratio that is in the range of 9 to 20, such as 11 to 19, 12 to 18, or 13 to 16. Additionally or alternatively, the base resin may have a Mz/Mw ratio that is in the range of 4 to 9, such as 5 to 8, 5 to 7.5, or 6 to 8.

In one aspect, the base resins can have an Mp in the range of 60,000 to 110,000 g/mol, 65,000 to 105,000 g/mol, or 65,000 to 100,000 g/mol. Additionally or alternatively, the base resin can have an Mn in the range of 18,000 to 48,000 g/mol, 20,000 to 42,000 g/mol, or 22,000 to 38,000 g/mol. Additionally or alternatively, the base resin used to produce the ethylene polymer can often have a bimodal molecular weight distribution (as determined using gel permeation chromatography (GPC) or other related analytical method). Typically, a bimodal molecular weight distribution has a valley between peaks, and the peaks may be separated or deconvoluted. Typically, a bimodal molecular weight distribution may be characterized as having an identifiable high molecular weight component (or distribution) and an identifiable low molecular weight component (or distribution). Exemplary unimodal MWD curves and bimodal MWD curves are shown in U.S. Patent No. 8,383,754, incorporated herein by reference in its entirety.

The density of the base resin used to produce the ethylene polymers disclosed herein is often greater than or equal to about 0.935 g/ ^cm3 , and less than or equal to about 0.965 g/ ^cm3 . Also, in particular aspects, the density can be in the range of 0.94 to 0.965 g/ ^cm3 , 0.945 to 0.965 g/ ^cm3 , 0.94 to 0.96 g/ ^cm3 , 0.945 to 0.96 g/ ^cm3 , 0.95 to 0.965 g/ ^cm3 , or 0.95 to 0.96 g/ ^cm3 .

For the base resin, the viscosity at 0.001 s ^-1 (eta @ 0.001 s ^-1 or η @ 0.001 s ^-1 ) at 190°C is typically in the range of from 1 x 10 ⁵ to 2 x 10 ⁶ Pa s; alternatively from 1 x 10 ⁵ to 1.8 x 10 ⁶ Pa s; alternatively from 8 x 10 ⁵ to 3 x 10 ⁶ Pa s; alternatively from 8 x 10 ⁵ to 2 x 10 ⁶ Pa s; or, alternatively from 8 x 10 ⁵ to 1.8 x 10 ⁶ Pa s. In some aspects, the base resin may have a zero shear viscosity (η ₀ ) at 190 °C in the range of 1 x 10 ⁶ to 1 x 10 ⁹ Pa s, 1 x 10 ⁶ to 2 x 10 ⁸ Pa s, 4 x 10 ⁶ to 1 x 10 ⁹ Pa s, or 4 x 10 ⁶ to 2 x 10 ⁸ Pa s, and similar ranges. As with the ethylene polymer, the viscosity data are measured at 190 °C for the base resin and using the empirical Carreau-Yasuda (CY) model as described herein, with a creep correction.

Typical ranges of the CY-a parameter for the base resin include from 0.12 to 0.25, from 0.13 to 0.3, from 0.13 to 0.25, or from 0.14 to 0.25 and similar ranges. In an additional or alternative embodiment, the base resin can have a tan δ at 0.1 s ^-1 in the range of from 0.5 to 0.85 degrees in one aspect, from 0.8 to 1 degree in another aspect, from 0.83 to 1.05 degrees in another aspect, from 0.83 to 1 degree in another aspect, from 0.85 to 1.05 degrees in another aspect, and from 0.85 to 1 degree in yet another aspect. In an additional or alternative embodiment, the base resin may have a tan δ at 100 sec ^-1 in the range of from 0.4 to 0.58 degrees in one aspect, from 0.4 to 0.55 degrees in another aspect, from 0.45 to 0.6 degrees in another aspect, from 0.45 to 0.58 degrees in another aspect, and from 0.45 to 0.55 degrees in another aspect. These rheological parameters are determined from viscosity data measured at 190 °C and using the empirical Carreau-Yasuda (CY) model as described herein, with a creep correction.

The base resins described herein may have an inverse comonomer distribution, typically the higher molecular weight components of the polymer having a higher comonomer incorporation than the lower molecular weight components. Typically, as the molecular weight increases, the comonomer incorporation increases. In one aspect, the amount of short chain branches (SCB) per 1000 total carbon atoms of the polymer may be greater at Mw than at Mn. In another aspect, the amount of SCB per 1000 total carbon atoms of the polymer may be greater at Mz than at Mw. In another aspect, the amount of SCB per 1000 total carbon atoms of the polymer may be greater at Mz than at Mn.

In one aspect, the base resin may be a reactor product (e.g., a product of one reactor), for example, rather than a blend of two reactor polymers, for example, having different molecular weight characteristics. As one skilled in the art will readily appreciate, physical blends of two different polymer resins may be prepared, but this requires additional processing and complexity not required for a reactor product.

The base resin can be prepared using a dual metallocene catalyst system, so that Ziegler-Natta and chromium-based catalyst systems are not required. Accordingly, the base resin can contain an immeasurable amount of chromium, or titanium, or vanadium, or magnesium (catalytic residue), i.e., less than 0.1 ppm by weight. In some aspects, the base resin can independently contain less than 0.08 ppm, less than 0.05 ppm, or less than 0.03 ppm of chromium (or titanium, or vanadium, or magnesium).

Although one or more additives may be added during the process of converting the base resin into an ethylene polymer or during the process of converting the ethylene polymer into a blow molded article (or other manufactured articles), the base resin may also contain one or more suitable additives. Non-limiting examples of suitable additives may include an antioxidant, an acid scavenger, an anti-blocking additive, a slip additive, a colorant, a filler, a processing aid, an ultraviolet inhibitor, and similar additives. Combinations of two or more additives may be present in the base resin.

The performance of the base resin on the representative blow molding equipment described herein may be characterized in one aspect by a weight swell to flow swell ratio (W:Flow) in the range of 150 to 225, 180 to 225, or 170 to 200. In another aspect, the base resin may be characterized by a hang time in the range of 10 to 45 s, 15 to 45 s, or 20 to 45 s.

According to aspects of the present invention, the base resin can be prepared using a dual metallocene catalyst system. Without limitation, catalyst component I can include a suitable non-bridged metallocene compound, catalyst component II can include a suitable bridged metallocene compound, and the catalyst system can also include a suitable activator and, optionally, a suitable cocatalyst.

First, we turn to the catalyst component I, which can include a non-bridged metallocene compound based on zirconium or hafnium, containing two cyclopentadienyl groups, two indenyl groups, or a cyclopentadienyl and indenyl groups. In one aspect, the catalyst component I can include a non-bridged metallocene compound based on zirconium or hafnium, containing two cyclopentadienyl groups. In another aspect, the catalyst component I can include a non-bridged metallocene compound based on zirconium or hafnium, containing two indenyl groups. In yet another aspect, the catalyst component I can include a non-bridged metallocene compound based on zirconium or hafnium, containing a cyclopentadienyl group and an indenyl group.

Now turning to the catalyst component II, which can be a bridged metallocene compound. In one aspect, for example, the catalyst component II can include a bridged metallocene compound based on zirconium or hafnium. In another aspect, the catalyst component II can include a bridged metallocene compound based on zirconium or hafnium with an alkenyl substituent. In another aspect, the catalyst component II can include a bridged metallocene compound based on zirconium or hafnium with an alkenyl substituent and a fluorenyl group. In another aspect, the catalyst component II can include a bridged metallocene compound based on zirconium or hafnium with a cyclopentadienyl group, a fluorenyl group, and with an alkenyl substituent in the bridge group and/or in the cyclopentadienyl group. In addition, the catalyst component II may comprise a bridged metallocene compound having an aryl group as a substituent in the bridging group.

In addition, the two-component catalyst system comprises an activator. For example, the catalyst system may comprise an activator support, an aluminoxane compound, an organoboron or organoborate compound, an ionizing ionic compound, and similar compounds, or any combination thereof. The catalyst system may comprise one or more activators. The cocatalyst, if present, may include, but is not limited to, alkylboron, alkylaluminum, and alkylzinc compounds such as tri-n-butylborane, tripropylborane, triethylborane, trimethylaluminum, triethylaluminum, tri-n-propylaluminum, tri-n-butylaluminum, triisobutylaluminum, tri-n-hexylaluminum, tri-n-octylaluminum, diisobutylaluminum hydride, diethylaluminum ethoxide, diethylaluminum chloride, dimethylzinc, diethylzinc, dipropylzinc, dibutylzinc, dineopentylzinc, and similar compounds or combinations thereof. Representative catalyst systems that can be used to prepare the base resin are disclosed in U.S. Patent Nos. 9,169,337, 9,273,170, 9,493,589, and 9,650,459, which are incorporated herein by reference in their entirety.

The base resins can be prepared from these catalyst systems using any suitable olefin polymerization process using various types of polymerization reactors, polymerization reactor systems, and polymerization reaction conditions. One such olefin polymerization process for polymerizing olefins in the presence of the catalyst composition of this invention can include contacting the catalyst composition with ethylene and, optionally, one or more olefin comonomers in a polymerization reactor system under polymerization conditions to produce a base resin.

As used herein, the term "polymerization reactor" includes any polymerization reactor capable of polymerizing olefin monomers and comonomers (one or more comonomers) to produce homopolymers, copolymers, terpolymers, and similar compounds. Various types of polymerization reactors include a batch reactor, a slurry reactor, a gas phase reactor, a solution reactor, a high pressure reactor, a tubular reactor, an autoclave reactor, and similar reactors or combinations thereof; or alternatively, a polymerization reactor system may comprise a slurry reactor, a gas phase reactor, a solution reactor, or a combination thereof. Polymerization conditions for various reactor types are well known to those skilled in the art. Gas phase reactors may include fluidized bed reactors or staged horizontal reactors. Slurry reactors may comprise vertical or horizontal loops. High pressure reactors may include autoclave or tubular reactors. Reactor types may include batch or continuous processes. Continuous processes may employ batch or continuous product discharge. Polymerization reactor systems and processes may also include partial or complete continuous recirculation of unreacted monomer, unreacted comonomer, and/or diluent.

The polymerization reactor system may include one reactor or multiple reactors (2 reactors, more than 2 reactors, etc.) of the same or different types. For example, the polymerization reactor system may include a slurry reactor, a gas phase reactor, a solution reactor, or a combination of two or more of these reactors. The production of polymers in multiple reactors may include multiple stages in at least two separate polymerization reactors interconnected by a transfer device that allows the polymers produced in the first polymerization reactor to be transferred to the second reactor. The desired polymerization conditions in one of the reactors may differ from the operating conditions in the other reactor(s). Alternatively, polymerization in multiple reactors may include manual transfer of polymer from one reactor to subsequent reactors to continue polymerization. Multiple reactor systems may include any combination, including but not limited to, multiple loop reactors, multiple gas phase reactors, a combination of loop and gas phase reactors, multiple high pressure reactors, or a combination of high pressure reactors with loop and/or gas phase reactors. Multiple reactors may operate in series, in parallel, or in both modes. Accordingly, the present invention encompasses polymerization reactor systems comprising one reactor, comprising two reactors, and comprising more than two reactors. The polymerization reactor system may comprise a slurry reactor, a gas phase reactor, or a solution reactor in certain aspects of the invention, as well as combinations thereof with multiple reactors.

According to one aspect, the polymerization reactor system may comprise at least one loop slurry reactor comprising vertical or horizontal loops. Monomer, diluent, catalyst and comonomer may be continuously fed to the loop reactor where polymerization occurs. Typically, continuous processes may include continuously introducing monomer/comonomer, catalyst and diluent into the polymerization reactor and continuously withdrawing a slurry comprising polymer particles and diluent from the reactor. The reactor effluent may be flashed to remove solid polymer from liquids that contain diluent, monomer and/or comonomer. Various technologies may be used for this separation step, including, but not limited to, flashing, which may include any combination of heat addition and pressure reduction, separation by cyclonic action in a cyclone or in a hydrocyclone, or separation by centrifugation.

A typical suspension polymerization process (also known as a particle forming process) is described, for example, in U.S. Patent Nos. 3,248,179, 4,501,885, 5,565,175, 5,575,979, 6,239,235, 6,262,191, 6,833,415, and 8,822,608, each of which is incorporated herein by reference in its entirety.

Suitable diluents used in suspension polymerization include, but are not limited to, the monomer being polymerized and hydrocarbons that are liquid under the reaction conditions. Examples of suitable diluents include, but are not limited to, hydrocarbons such as propane, cyclohexane, isobutane, n-butane, n-pentane, isopentane, neopentane, and n-hexane. Some loop polymerization reactions can occur under bulk conditions where no diluent is used.

According to another aspect, the polymerization reactor system can comprise at least one gas phase reactor (e.g., a fluidized bed reactor). Such reactor systems can employ a continuous recycle stream comprising one or more monomers continuously circulating through a fluidized bed in the presence of a catalyst under polymerization conditions. The recycle stream can be withdrawn from the fluidized bed and returned to the reactor. Simultaneously, the polymer product can be withdrawn from the reactor and new or fresh monomer can be added to replace the polymerized monomer. In such gas phase reactors, a multistage gas phase polymerization process of olefins can occur, in which olefins are polymerized in the gas phase in at least two independent gas phase polymerization zones by feeding the catalyst-containing polymer formed in the first polymerization zone to the second polymerization zone. Typical gas phase reactors are disclosed in U.S. Patents 5,352,749, 4,588,790, 5,436,304, 7,531,606, and 7,598,327, each of which is incorporated herein by reference in its entirety.

According to another aspect, the polymerization reactor system may comprise a high-pressure polymerization reactor, such as a tubular reactor or an autoclave reactor. Tubular reactors may have multiple zones where fresh monomer, initiators or catalysts are added. The monomer may be entrained in an inert gas stream and introduced into one zone of the reactor. The initiators, catalysts and/or catalyst components may be entrained in a gas stream and introduced into another zone of the reactor. The gas streams may be mixed for polymerization. Heat and pressure may be used appropriately to obtain optimal polymerization reaction conditions.

According to another aspect, the polymerization reactor system may comprise a solution polymerization reactor in which the monomer/comonomer is contacted with the catalyst composition by suitable mixing or other means. A support containing an inert organic diluent or an excess of monomer may be used. If desired, the monomer/comonomer may be contacted in the vapor phase with the catalyst reaction product in the presence or absence of a liquid material. The polymerization zone may be maintained at a temperature and pressure that will result in the formation of a polymer solution in the reaction medium. Mixing may be used to obtain better temperature control and to maintain homogeneity of the polymerization mixtures throughout the polymerization zone. Suitable means are used to remove the exothermic heat of polymerization.

The polymerization reactor system may further comprise any combination of at least one feedstock feed system, at least one catalyst or catalyst component feed system, and/or at least one polymer recovery system. Suitable reactor systems may further comprise systems for feedstock purification, catalyst storage and preparation, extrusion, reactor cooling, polymer recovery, fractionation, recycling, storage, unloading, laboratory analysis, and process control. Depending on the desired properties of the olefin polymer, hydrogen may be added to the polymerization reactor as needed (e.g., continuously, intermittently, etc.).

Polymerization conditions that can be effectively controlled to provide the desired polymer properties may include temperature, pressure, and concentrations of various reactants. The polymerization temperature may affect catalyst productivity, polymer molecular weight, and molecular weight distribution. Various polymerization conditions may be maintained substantially constant, for example, to produce a particular grade of olefin polymer (or ethylene polymer). A suitable polymerization temperature may be any temperature below the depolymerization temperature according to the Gibbs free energy equation. Typically, it includes from 60°C to 280°C, for example, or from 60°C to 120°C, depending on the type of polymerization reactor(s). In some reactor systems, the polymerization temperature may generally range from 70°C to 100°C or from 75°C to 95°C.

The appropriate pressure will also vary depending on the reactor and the type of polymerization. Liquid phase polymerization pressures in a loop reactor are typically less than 1000 psig (6.9 MPa). Pressures for gas phase polymerizations are typically 200 to 500 psig (1.4 MPa to 3.4 MPa). High pressure polymerization in tubular or autoclave reactors typically operates at pressures of 20,000 to 75,000 psig (138 to 517 MPa). Polymerization reactors can also be operated in the supercritical region, which occurs generally at higher temperatures and pressures. Operating above the critical point of the pressure/temperature diagram (in the supercritical phase) can provide advantages to the polymerization reaction process.

According to aspects of the present invention, the olefin monomer used in the polymerization process is ethylene and the comonomer may comprise a _C3 - _C10 alpha-olefin; alternatively, the comonomer may comprise 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, styrene, or any combination thereof; alternatively, the comonomer may comprise 1-butene, 1-hexene, 1-octene, or any combination thereof; alternatively, the comonomer may comprise 1-butene; alternatively, the comonomer may comprise 1-hexene; or, alternatively, the comonomer may comprise 1-octene.

EXAMPLES

The invention is further illustrated by the following examples, which should in no way be construed as limiting the scope of the invention. Various other aspects, embodiments of the invention, modifications and equivalents thereof may be realized by a person skilled in the art after reading the description herein, without departing from the spirit of the invention or the scope of the appended claims.

High shear melt index (HLMI, I ₂₁ , g/10 min) was determined according to ASTM D1238 at 190 °C on a 21.6 kg sample. Density was determined in grams per cubic centimeter (g/cm ³ ) on a mold pressed specimen cooled at 15 °C per hour and aged for 40 hours at room temperature according to ASTM D1505 and ASTM D4703.

Molecular weights and molecular weight distributions were obtained using a PL-GPC 220 system (Polymer Labs, Agilent Company) equipped with an IR4 detector (Polymer Char, Spain) and three (3) Styragel HMW-6E GPC columns (Waters, MA) operated at 145°C. The flow rate of the mobile phase 1,2,4-trichlorobenzene (TCB) containing 0.5 g/L 2,6-di-tert-butyl-4-methylphenol (BHT) was set at 1 mL/min and the polymer solution concentrations were approximately 1 mg/mL, depending on the molecular weight. Sample preparation was performed at 150°C for nominally 4 hours with occasional gentle shaking before the solutions were transferred to sample vials for injection. An injection volume of approximately 400 µL was used. The integral calibration method was used to determine the molecular weight and molecular weight distribution using Chevron Phillips Chemical Company MARLEX BHB5003 HDPE polyethylene resin as a standard. The integral table of the standard was previously determined in a separate SEC-MALS experiment. Mn is the number average molecular weight, Mw is the weight average molecular weight, Mz is the z-average molecular weight, and Mp is the maximum molecular weight (the location, in molecular weight, at the highest point of the molecular weight distribution curve).

The melt rheology was determined as follows. Low strain (10%) oscillatory shear measurements were performed on an Anton Paar MCR 501 rheometer using parallel plate geometry. All rheological tests were performed at 190°C. The complex viscosity | η* | versus frequency ( ω ) data were then curve fitted using a modified three-parameter empirical Carreau-Yasuda (CY) model to obtain the zero-shear viscosity, η ₀ , the characteristic viscous relaxation time, τ _{η ,} and the rheological width parameter, a (CY-a parameter). The simplified empirical Carreau-Yasuda (CY) model is presented below.

,

where: | η* ( ω ) |= the value of complex viscosity under shear;

η ₀ = zero shear viscosity;

τ _η = viscous relaxation time (Tau(η) in seconds);

a = parameter of “rheological width” (parameter CY-a);

n = adjusts the final slope of the power function, given by 2/11; and

ω = angular frequency of deformation during oscillatory shear.

Details of the meaning and interpretation of the CY model and derived parameters can be found in C. A. Hieber and H. H. Chiang, Rheol. Acta , 28, 321 (1989); C. A. Hieber and H. H. Chiang, Polym. Eng. Sci., 32, 931 (1992); and R. B. Bird, R. C. Armstrong and O. Hasseger, Dynamics of Polymeric Liquids, Volume 1, Fluid Mechanics , 2nd edition, John Wiley & Sons (1987); the contents of each of which are incorporated herein by reference in their entirety.

Creep correction was used to extend the low frequency range of the rheological properties to 10 ^-4 s ^-1 (except for the differential dynamic rheology plots, which were plotted without creep correction). In the creep test, a constant shear stress σ ₀ was applied to the specimen and the shear strain γ was recorded as a function of creep time t . Although the time-dependent data obtained from the creep and creep recovery tests look different from the frequency-dependent data measured in the dynamic frequency sweep tests, provided that the measurements are performed in the linear viscoelastic regime, the two sets of experimental data contain the same rheological information, thus the time-dependent creep compliance data can be transformed into frequency-dependent dynamic data, and thus the long-term creep measurement can complement the low frequency data of the dynamic frequency sweep measurement. Details of the test method and analysis can be found in YW Inn and DC Rohlfing, “Application of creep test to obtain the linear viscoelastic properties at low frequency range for polyethylene melts,” Applied Rheology 22 (2012), which is incorporated herein by reference in its entirety.

The generalized Voigt model was used to model the time-dependent creep compliance J ( t )= γ ( t )/ σ ₀ in the context of a discrete spectrum J _k of lag time τ _k and zero-shear-rate viscosity η ₀ ,

.

While the discrete delay spectrum accurately describes the compliance data, the theory of linear viscoelasticity allows one to quantitatively describe other types of experimental data, such as accumulation and compliance of losses, calculated as

, .

From the relationship between the complex modulus and the complex compliance, the data accumulation and loss modulus of the dynamic frequency sweep can be obtained as

, .

As a simple numerical approach to obtain the discrete time lag spectrum, Microsoft Excel Solver can be used by minimizing the following objective function O .

To reliably transform time-dependent creep data into frequency-dependent dynamic data, the frequency range must be limited by the test time of the creep measurement. If it is possible to obtain accurate experimental data over the entire creep time range until the creep compliance reaches the steady state, then it is also possible to calculate an accurate function of the retardation spectra over the entire time scale range. However, it is often impractical to obtain such data for high-molecular-weight polymers that have a very long relaxation period. Creep data contain information only within a limited time range, thus the frequency range is limited by the duration time t _N of the creep test, i.e. the reliable information for frequencies is in the range ω > t _N ^-1 , and extrapolated data outside this frequency range may be affected by unwanted fitting effects.

For rheological measurements including creep correction, polymer samples were compression molded at 182°C for 3 min. The samples were allowed to melt at a relatively low pressure for 1 min and then molded at high pressure for an additional 2 min. The molded samples were then quenched in a press at room temperature and then the molded plates were stamped into 25.4 mm diameter discs for measurements in a rotational rheometer. The measurements were carried out on 25 mm diameter parallel plates at 190°C using a variable stress rheometer equipped with an air bearing system (Physica MCR-501, Anton Paar). The rheometer test chamber was purged with nitrogen to minimize oxidative degradation. After thermal equilibration, the samples were compressed between plates to a thickness of 1.6 mm and the excess was trimmed. A total of 8 minutes elapsed between the specimen insertion and the start of the test. Small strain (1~10%) oscillatory shear in the linear viscoelastic regime at angular frequencies from 0.0316 to 316 s ^-1 was used to measure the dynamic frequency sweep. The creep test was carried out for 10,200 s (170 min) to limit the total test time to 4 hours since specimen throughput and thermal stability were of concern. By converting the time-dependent creep data into frequency-dependent dynamic data, the low frequency range was extended to 10 ^-4 rad/s, which is two orders of magnitude lower than the frequency range of the dynamic test. The complex viscosity (| η* |) data were plotted against frequency ( ω ) using the Carreau-Yasuda model.

One of the major challenges in performing creep testing, as with any measurement on a long time scale, was that the sample does not undergo appreciable changes during the measurement, which may take several hours. If a polymer sample is heated for a long period of time without proper thermal stabilization (e.g., using antioxidants), changes may occur in the polymer that can have a significant impact on the rheological behavior of the polymer and its performance. The polymers being tested must be thermally stable for at least 4-5 hours at 190°C under nitrogen; for example, ethylene polymers containing at least 0.4 wt.% antioxidants have been shown to be stable enough to provide reliable creep correction data.

For rheological measurements in parallel plates, the specimen was compressed between the plates to a thickness of 1.6 mm and then the excess was trimmed. When the specimen was trimmed with high forces in one direction, some residual stress was generated, causing strain drift. Therefore, creep testing should be avoided immediately after specimen trimming, since the residual stress may affect the subsequent creep measurement, especially for high-viscosity resins with long relaxation times. If the applied stress in the creep test is not high enough, the resulting strain may be so small that the creep results may be affected by the undesirable effect of strain drift. In order to minimize this effect, specimens were trimmed as gently as possible and the creep test was performed after a waiting period of 2000 s to allow any residual stress to relax.

An appropriate value of the applied stress σ ₀ is important for obtaining reliable creep data. The stress σ ₀ should be small enough to keep the strain within the linear viscoelastic regime, and it should be large enough to ensure that the strain signal is strong enough to provide satisfactory data resolution with good accuracy. Although not limited to this, a suitable applied stress is equal to the total modulus | G* | at a frequency of 0.01 rad/s multiplied by 0.04.

The viscosity of the polymer at 0.001 s ^-1 (denoted as η (0.001) or eta (0.001)) at 190 °C was determined using an Anton Paar MCR 501 rheometer using parallel plate geometry.

The short-chain branching (SCB) content and short-chain branching distribution (SCBD) by molecular weight distribution could be determined using a GPC/SEC system with IR5 detection (IR5-GPC), where the GPC/SEC system was a PL220 GPC/SEC system (Polymer Labs, an Agilent company) equipped with three Styragel HMW-6E columns (Waters, MA) for polymer separation. A detailed description of the method can be found in the literature (Y. Yu, A Short-Chain Branching Distribution Determination Technique for Polyethylene Using IR5-Detected GPC, Macromolecular Symposia , 2020, 390 , 1900014). Briefly, a thermoelectrically cooled IR5 MCT detector (IR5) (Polymer Char, Spain) was connected to the GPC columns via a hot transfer line. Chromatographic data were acquired from the two output ports of the IR5 detector. The analog signal was first sent from the analog output port to a digital converter before being connected to computer “A” for molecular weight determination using Cirrus software (Polymer Labs, now an Agilent company) and an integral calibration method using MARLEX BHB5003 wide-range HDPE resin (Chevron Phillips Chemical) as a wide-range molecular weight standard. Digital signals, on the other hand, were sent via a USB cable directly to computer “B” where they were acquired using LabView data acquisition software provided by Polymer Char. The following chromatographic conditions were set: column oven temperature 145°C; flow rate 1 mL/min; injection volume 0.4 mL; and polymer concentration around 2 mg/mL, depending on the molecular weight of the sample. The temperatures for both the hot transfer line and the IR5 detector sample cell were set to 150 °C and the IR5 detector electronics temperature was set to 60 °C. The short chain branching content was determined in-house using the intensity ratio of _CH3 (I _CH3 ) to _CH2 (I _CH2 ) in combination with a calibration curve. The calibration curve was a plot of the SCB content (x _SCB ) versus the intensity ratio I _CH3 /I _CH2 . A panel of polyethylene resins (at least 5) with SCB levels ranging from zero to approximately 32 SCB/1000 total carbon atoms (SCB standards) was used to generate the calibration curve. All of these SCB standards have known SCB levels and flat SCBD profiles previously determined separately using NMR and solvent gradient fractionation coupled to NMR (SGF-NMR). Using the SCB calibration curves thus constructed, short chain branching molecular weight distribution profiles were obtained for resins fractionated using the IR5-GPC system under exactly the same chromatographic conditions as for these SCB standards. The relationship between the intensity ratio and the elution volume was converted to an SCB distribution as a function of MWD using a given SCB calibration curve (i.e., I _CH3 /I _CH2 intensity ratio versus SCB content) and an MW calibration curve (i.e., molecular weight versus elution time) to convert I _CH3 /I _CH2 intensity ratio and elution time to SCB content and molecular weight, respectively. Although not tested, it was expected that the number of short chain branches (SCB) per 1000 total carbon atoms of the ethylene polymer (or base resin) at Mw (or Mz) would be greater than at Mn.

Metal content, such as the amount of catalyst residue in the ethylene polymer or article, can be determined by ICP analysis on a PerkinElmer Optima 8300. Polymer samples can be ashed in a Thermolyne oven using sulfuric acid overnight, followed by acid digestion in a HotBlock using HCl and _HNO3 (3:1 v:v).

EXAMPLES 1-17

Fig. 1 illustrates the bimodal molecular weight distribution (amount of polymer versus logarithm of molecular weight) of the polymers of Examples 1-6, Fig. 2 illustrates the bimodal molecular weight distribution of the polymers of Examples 7-12, Fig. 3 illustrates the broad molecular weight distribution of the polymers of Examples 13-17, Table I provides the HLMI for the polymers and some molecular weight properties of the polymers of Examples 1-17, and Table II provides some rheological properties at 190°C for the polymers of Examples 1-12.

Example 13 was the base resin (without peroxide) for Examples 14-17 and is a wide range ethylene copolymer resin having a nominal HLMI of 9 and a density of 0.95 (Chevron-Phillips Chemical Company LP). The base resin of Example 1 (for Examples 1-6; nominal HLMI of 8-12 and a density of 0.955-0.96) and the base resin of Example 7 (for Examples 7-12; nominal HLMI of 4.5-6.5 and a density of 0.95-0.955) were prepared using a dual metallocene catalyst system with an activator support as described below.

The silica-coated fluorinated alumina activator supports used to prepare the base resins of Examples 1 and 7 were prepared as follows. Bohemite was obtained from W. R. Grace & Company under the name "Alumina A" having a surface area of about 300 ^m2 /g, a pore volume of about 1.3 ml/g, and an average particle size of about 100 microns. The alumina was first calcined in dry air at about 600°C for about 6 hours, cooled to ambient temperature, and then contacted with tetraethyl orthosilicate in isopropanol to 25 wt.% _SiO2 . After drying, the silica-coated alumina was calcined at 600°C for 3 hours. A silica-coated fluorinated alumina (7 wt.% F) was prepared by impregnating calcined silica-coated alumina with a methanolic ammonium bifluoride solution, drying, and then calcining for 3 hours at 600°C in dry air. The silica-coated fluorinated alumina was then collected and stored under dry nitrogen and used without exposure to the atmosphere.

The pilot plant polymerization was carried out in a 30 gallon (113.6 L) slurry loop reactor with a throughput of approximately 33 pounds (15 kg) of polymer per hour. The polymerization was carried out under continuous particulate loop reactor process conditions (also called a slurry process) by contacting a double metallocene solution in isobutane, an organoaluminum solution (triisobutylaluminum, TIBA), and an activator support (silica-coated fluorinated alumina) in a 1 L stirred autoclave with a continuous outlet into the loop reactor. The TIBA and double metallocene solutions were fed in separate streams into a tee prior to the autoclave where they came into contact with each other. The activator carrier was washed with isobutane at a location after the above tee, brought into contact with the organoaluminum/metallocene mixture and sent together to the autoclave. The isobutane wash used to transfer the activator carrier to the autoclave was set at a rate that provided a residence time in the autoclave of approximately 30 minutes. The entire flow from the autoclave was then sent to the loop reactor.

The ethylene used was polymerization grade ethylene obtained from AirGas, which was purified through a column of zeolite alumina adsorbent (activated at 230-290°C in nitrogen). Hexene-1 (obtained from Chevron Phillips Chemical Company) was purified by distillation and passed through a column of zeolite alumina adsorbent activated at 230-290°C in nitrogen. The loop reactor was filled with liquid, had a diameter of 15.2 cm, and a volume of 30 gallons (113.6 L). Liquid isobutane was used as a diluent. Hydrogen was added at a rate of about 0.001-0.004 lb/hr (0.454-1.814 g/hr) to adjust the molecular weight and/or HLMI of the polymer product. Isobutane was grade Isobutane (obtained from Enterprise) which was further purified by distillation and then passed through a column of alumina (activated at 230-290°C in nitrogen). The TIBA cocatalyst was prepared as a 10-12 wt% solution in hydrocarbon and further diluted to 2 wt% with isobutane. The cocatalyst was added at a concentration in the range of 125 ppm based on the weight of diluent in the polymerization reactor.

The reactor conditions included a reactor pressure of about 590 psig (40.68 bar), an ethylene mole % of 11-13% (based on isobutane diluent), and a polymerization temperature of 93-100°C. The reactor was operated such that the residence time was about 0.8-1.3 hours. Metallocene concentrations in the reactor ranged from about 1.5 to 2.5 parts per million (ppm) by weight of diluent. Activator support (silica-coated fluorinated alumina) was fed to the reactor at a rate of about 0.015-0.03 lb/hr (6.8-13.6 g/hr). Polymer was withdrawn from the reactor at a rate of about 33 lb/hr (15 kg/hr) and passed through a flash chamber and a purge column. Nitrogen was fed into the purge column to ensure that the flocs were free of hydrocarbons. The structural formulas for MET 1 and MET 2 used in Examples 1 and 7 are shown below:

For Example 1, the MET2:MET1 ratio was 0.67, the pounds of hydrogen per 1000 pounds of ethylene was 0.063, and the pounds of 1-hexene per pounds of ethylene was 1.14, while for Example 7, the MET2:MET1 ratio was 0.63, the pounds of hydrogen per 1000 pounds of ethylene was 0.031, and the pounds of 1-hexene per pounds of ethylene was 1.14.

The ethylene polymers of Examples 2-6, 8-12, and 14-17 were prepared by mixing the respective base resins of Examples 1, 7, and 13 with a masterbatch comprising a carrier polymer resin and 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane. The amount of peroxide groups ranged from 10 to 300 ppm by weight of peroxide groups based on the weight of the base resin, as shown in Table I and Table II . The mixture of the base resin and the peroxide masterbatch was compounded using a twin-screw extrusion system (ZSK-300) and then pelletized to form the ethylene polymers of Examples 2-6, 8-12, and 14-17.

Some properties of the polymers of Examples 1-17 are shown in Table I and Table II . Many of the peroxide-treated polymers had HLMI values of less than 12 g/10 min, Mw values of 200,000 to 550,000 g/mol, Mn values of 18,000 to 48,000 g/mol, CY-a parameters of less than 0.12, tan δ values at 0.1 s ^-1 of 0.5 to 0.9 degrees, tan δ values at 100 s ^-1 of 0.5 to 0.75 degrees, and viscosities at 0.001 s ^-1 of 1.3 x 10 ⁶ to 1 x 10 ⁷ Pa s, such as Examples 4-6 and Examples 9-12. In general, as the amount of peroxide increased, the zero-shear viscosity, relaxation time, and viscosity at 0.001 s ^-1 increased, while the CY-a parameter and tan δ at 0.1 s ^-1 decreased.

Figure 4 illustrates the rheological differences between Examples 2-6 and the Example 1 baseline (no peroxide); Figure 5 illustrates the rheological differences between Examples 8-12 and the Example 7 baseline (no peroxide), and Figure 6 illustrates the rheological differences between Examples 14-17 and the Example 13 baseline (no peroxide). Figure 6 shows the expected effect of peroxide treatment on viscosity, in particular the steady increase in viscosity in the low shear regions as the amount of peroxide added increases. Conversely, the effect of peroxide treatment shown in Figures 4-5 is unexpected and, without wishing to be bound by theory, may be the result of varying degrees of chain scission versus crosslinking in the very high molecular weight fractions of the polymer; also note the unexpected change in the shape of the MWD profile in Figure 6. 1-2 at the high molecular weight end (eg Log M from about 5.5 to 7).

Blow molding evaluations of Examples 1-6 were performed on a Sterling blow molding machine with the following specifications. This particular equipment and processing conditions were chosen because the blow molding characteristics and properties thus obtained are generally typical of those achieved in larger commercial scale blow molding operations. The extruder screw diameter was 3 inches, the L/D ratio was 24:1, the drive motor was a 75 hp DC drive, and the maximum plasticizing capacity was approximately 350 lb (159 kg) of polyethylene per hour. The extruder was equipped with a dynicso pressure indicator, four air-cooled heating zones, and a liquid-cooled smoothbore barrel in the feed zone.

The accumulator head (FIFO design) had a maximum shot capacity of 10 pounds (4.5 kg), maximum and minimum diameters of the extruder nozzle outer ring of 8 inches (20.3 cm) and 1 inch (2.5 cm) (respectively), where 1 to 3½ inches (8.9 cm) converges and 4 (10.2 cm) to 8 inches diverges. The blow molder was also equipped with a 100-point MACO programming device.

For Examples 1-6, all zones of the extruder and die were set to 390°F (199°C). The mold was a 9-gallon bottle (Fremont Plastics Mold, 42 in. (106.7 cm) circumference) and used a 4.5 in. (11.4 cm) diameter diverging die with a 30 degree face angle. A constant ejection speed was used. The mold temperature was 50-60°F (10-15.6°C). The timer settings were 0.5 sec purge delay, 0 sec pre-purge, and 0.25 sec clamp close delay. The air pressure was approximately 90 psi (0.62 MPa). The minimum part wall thickness was in the range of 45-50 mils and the die gap was 0.196 in. (0.5 cm). The parts were produced at an extruder speed of 30 rpm and a blowing time of 90 s.

The weight of the resulting part (part weight) was recorded, and the width of the flash at the bottom of the part (flat bottom) was measured. Polymer weight swelling could be quantified from the part weight (in grams), and extrudate swell could be quantified from the flat bottom (in inches). The melt strength of the polymers was compared by means of a hang-up time test using a die gap of 0.089 in. (0.22 cm) and an extruder speed of 20 rpm. The parison was extruded and allowed to hang; the extruder speed was set to zero while the parison was hanging. The time from the end of the shot to the moment the parison lifted off the outer ring of the extruder nozzle was recorded as the hang-up time.

Blow molding evaluations of Examples 7-12 were performed on a Kautex KB-25 blow molding machine with the following specifications. This particular equipment and processing conditions were chosen because the blow molding characteristics and properties thus obtained are generally typical of those achieved in larger commercial scale blow molding operations. The extruder screw diameter was 80 mm, the L/D ratio was 20:1, the drive motor was a 60 hp DC drive, and the maximum plasticizing capacity was approximately 330 lb (149.7 kg) of polyethylene per hour. The extruder was equipped with a dynicso pressure indicator, three air-cooled heating zones, and a liquid-cooled grooved liner in the feed zone for processing high molecular weight polyethylene pellets and powder resins.

The accumulator head (FIFO design) had a maximum shot capacity of 8.5 pounds (3.9 kg), and a maximum and minimum extruder nozzle outer ring diameter of 8 inches and 2 inches (5.1 cm) (respectively), with 2 to 3½ inches converging and 4 to 8 inches diverging. The blow molder was also equipped with a 100-point Hunkar programming device.

For Examples 7 through 12, all zones of the extruder and die were set to 405°F (207°C). The mold was a 9-gallon bottle (Fremont Plastics Mold) and used a 4.5-inch diameter divergent die with a 30-degree face angle. Constant extrusion pressure was used. The mold temperature was 50°F to 60°F. The timer settings were 0.5 second purge delay, 0 second pre-purge, and 0 second mold close delay. The air pressure was 90 psi. The minimum part wall thickness was in the range of 45-50 mils and the die gap was 0.196 in. The parts were produced at an extruder speed of 30 rpm and a blow time of 90 seconds.

The weight of the resulting part (part weight) was recorded, and the width of the burr on the bottom of the part (flat bottom) was measured. The polymer weight swelling could be quantified from the part weight (in grams), and the extrudate swell could be quantified from the flat bottom (in inches). The melt strength of the polymers was compared by means of a hang-up time test using a die gap of 0.089 inches and an extruder speed of 20 rpm. The parison was extruded and allowed to hang. The time from the end of the shot until the parison lifted off the outer ring of the extruder nozzle was recorded as the hang-up time.

Table III provides blow molding performance for the polymers of Examples 1-12, Figure 7 illustrates the flow swell and weight swell properties for Examples 2-6 compared to Example 1 (no peroxide), and Figure 8 illustrates the flow swell and weight swell properties for Examples 8-12 compared to Example 7 (no peroxide). Surprisingly, the table and figures demonstrate a separation of the flow swell and weight swell. In particular, the flow swell (as measured by the flat bottom) was essentially the same for Examples 2-6 compared to Example 1 and was essentially the same for Examples 8-12 compared to Example 7, while the weight swell (as measured by the weight of the part) unexpectedly increased with increasing peroxide loading. Accordingly, the ratio of part weight (in grams) to flat bottom (in inches) was much greater for Examples 5-6 and Examples 11-12 compared to Examples 1 and 7, respectively, which were not peroxide treated. Additionally, and appropriately, peroxide treatment increases the melt strength of the polymer, as evidenced by the increase in hang time with increasing amounts of peroxide added.

Table I

Example HLMI
(g/10 min) Peroxide
m.d. Mn/1000
g/mol Mw/1000
(g/mol) Mz/1000
(g/mol) Mp/1000
(g/mol) Mw/Mn Mz/Mw IB 1 - 0 23.3 363 2590 69.4 15.6 7.14 1.41 2 9.53 10 30.6 337 2409 79.7 11.0 7.14 1.34 3 9.11 25 30.8 319 2192 75.8 10.4 6.86 1.34 4 7.69 50 30.2 328 2274 76.8 10.9 6.93 1.35 5 - 100 26.4 318 2064 73.0 12.1 6.49 1.42 6 - 300 25.1 306 1867 76.8 12.2 6.10 1.45 7 - 0 33.3 450 3148 94.0 13.5 7.00 1.34 8 4.78 10 44.1 487 3323 90.2 11.1 6.82 1.33 9 4.42 25 35.6 459 3100 100.8 12.9 6.76 1.35 10 3.82 50 41.8 446 2898 99.6 10.7 6.50 1.31 11 3.04 150 36.6 306 1713 96.4 8.4 5.59 1.34 12 2.50 300 35.3 287 1476 95.2 8.1 5.14 1.35 13 8.91 0 7.5 264 1502 133.1 35.3 5.69 2.55 14 8.28 15 7.6 268 1558 138.2 35.0 5.82 2.53 15 7.83 25 7.5 252 1470 160.7 33.7 5.82 2.51 16 - 50 7.6 240 1348 141.7 31.7 5.62 2.49 17 - 100 7.6 225 1226 156.7 29.4 5.45 2.46

Table II

Example Peroxide
m.d. η ₀
Pass τ _η
With CY-a η (0.001) Pa s Tan d@0,1
degrees η (100)
Pass Tan d@100
degrees 1 0 6.00E+06 9.52E+01 0.217 9.73E+05 0.978 2052 0.472 2 10 1.09E+08 9.29E+02 0.119 9.32E+05 0.948 1973 0.609 3 25 5.84E+08 4.59E+03 0.101 1,10E+06 0.903 2020 0.622 4 50 1.31E+11 9.13E+05 0.069 1.51E+06 0.822 2083 0,640 5 100 7.46E+15 2.57E+11 0.047 2.96E+06 0.681 2202 0.582 6 300 1.30E+26 2.59E+22 0.027 4.53E+06 0.626 2616 0.575 7 0 1.00E+08 1.09E+03 0.141 1.66E+06 0.883 2690 0.541 8 10 2.90E+08 3.02E+03 0.125 1.87E+06 0.857 2765 0.555 9 25 5.74E+08 6.03E+03 0.116 1.98E+06 0.841 2767 0,560 10 50 1.17E+12 1.20E+07 0.067 2.67E+06 0.758 2824 0.602 11 150 2.89E+20 3.25E+14 0.029 2.53E+06 0.769 2925 0.691 12 300 1.18E+24 4.05E+18 0.025 3.14E+06 0.723 2933 0.662

Table III

Example Peroxide,
m.d. Mass of the part,
grams % Change in mass of part
compared to no peroxide Flat bottom,
inches % Change in flat bottom compared to no peroxide Hang time,
seconds Part to flat bottom ratio, grams/inch 1 0 1996 0 10.08 0 21 198 2 10 2095 5 9.97 -1 22 210 3 25 2120 6 10.06 0 28 211 4 50 2131 7 10.05 0 42 212 5 100 2139 7 9.95 -1 93 215 6 300 2285 14 10.13 0 180 226 7 0 2269 0 10.05 0 42 226 8 10 2269 0 10.06 0 48 226 9 25 2337 3 10.09 0 72 232 10 50 2420 7 10,11 1 180 239 11 150 2521 11 10.06 0 180 251 12 300 2630 16 10.07 0 180 261

The invention has been described above with reference to numerous aspects and specific examples. Many variations will occur to those skilled in the art in light of the above detailed description. All such obvious variations are within the full scope of the appended claims. Other aspects of the invention may include, but are not limited to, (aspects are described as "comprising" but may alternatively "consist essentially of" or "consist of") the following:

Aspect 1. A polymer of ethylene having (or characterized by):

melt index at high shear stress less than or equal to 12 g/10 min;

average molecular weight in the range from 200,000 to 550,000 g/mol;

number average molecular weight in the range from 18,000 to 48,000 g/mol;

parameter CY-a less than or equal to 0.12;

tan δ at 0.1 s ^-1 in the range from 0.5 to 0.9 degrees;

tan δ at 100 s ^-1 in the range from 0.5 to 0.75 degrees; and

viscosity at 0.001 s ^-1 in the range from 1.3 x 10 ⁶ to 1 x 10 ⁷ Pa s.

Aspect 2. The polymer of aspect 1, wherein said ethylene polymer has an HLMI in any range disclosed herein, such as less than or equal to 10, less than or equal to 8, from 1 to 12, from 1 to 10, from 1 to 8, from 2 to 12, from 2 to 10 g/10 min, etc.

Aspect 3. The polymer of aspect 1 or 2, wherein said ethylene polymer has a Mw in any range disclosed herein, such as from 200,000 to 500,000, from 250,000 to 550,000, from 250,000 to 500,000, from 250,000 to 475,000, from 275,000 to 550,000, from 275,000 to 475,000 g/mol, etc.

Aspect 4. The polymer of any of the preceding aspects, wherein said ethylene polymer has a CY-a parameter in any range disclosed herein, such as less than or equal to 0.11, less than or equal to 0.1, less than or equal to 0.08, less than or equal to 0.06, from 0.01 to 0.12, from 0.01 to 0.1, from 0.01 to 0.08, from 0.01 to 0.06, etc.

Aspect 5. The polymer of any of the preceding aspects, wherein said ethylene polymer has a tan δ at 0.1 s ^-1 in any range disclosed herein, such as from 0.5 to 0.85 degrees, from 0.5 to 0.8 degrees, from 0.55 to 0.9 degrees, from 0.55 to 0.85 degrees, from 0.6 to 0.9 degrees, from 0.6 to 0.85 degrees, from 0.6 to 0.8 degrees, etc.

Aspect 6. The polymer of any of the preceding aspects, wherein said ethylene polymer has a tan δ at 100 s ^-1 in any range disclosed herein, such as from 0.5 to 0.72 degrees, from 0.5 to 0.7 degrees, from 0.52 to 0.75 degrees, from 0.52 to 0.72 degrees, from 0.52 to 0.7 degrees, from 0.55 to 0.75 degrees, from 0.55 to 0.72 degrees, etc.

Aspect 7. The polymer of any of the preceding aspects, wherein said ethylene polymer has a viscosity at 0.001 s ^-1 in any range disclosed herein, such as from 1.3 x 10 ⁶ to 5.5 x 10 ⁶ Pa s, from 1.3 x 10 ⁶ to 5 x 10 ⁶ Pa s, from 1.5 x 10 ⁶ to 1 x 10 ⁷ Pa s, from 1.5 x 10 ⁶ to 6 x 10 ⁶ Pa s, from 1.5 x 10 ⁶ to 5 x 10 ⁶ Pa s, from 2 x 10 ⁶ to 6 x 10 ⁶ Pa s, from 2 x 10 ⁶ to 5 x 10 ⁶ Pa s, etc.

Aspect 8. The polymer of any of the preceding aspects, wherein said ethylene polymer has a viscosity at 100 s ^-1 in any range disclosed herein, such as from 1700 to 3300, from 1800 to 3200, from 1900 to 3100, from 2000 to 3000 Pa s, etc.

Aspect 9. The polymer of any of the preceding aspects, wherein said ethylene polymer has a zero shear viscosity in any range disclosed herein, such as from 1×10 ⁸ to 1×10 ³⁰ Pa s, from 1×10 ⁸ to 1×10 ²⁸ Pa s, from 1×10 ¹⁰ to 1×10 ³⁰ Pa s, from 1×10 ¹⁰ to 1×10 ²⁷ Pa s, from 1×10 ¹² to 1×10 ²⁷ Pa s, etc.

Aspect 10. The polymer of any of the preceding aspects, wherein said ethylene polymer has a density in any range disclosed herein, such as from 0.935 to 0.965, from 0.94 to 0.965, from 0.945 to 0.965, from 0.94 to 0.96, from 0.945 to 0.96 g/ ^cm3 , etc.

Aspect 11. The polymer of any of the preceding aspects, wherein said ethylene polymer has an inverse comonomer distribution, such as an amount of short chain branches (SCB) per 1000 total carbon atoms of the polymer at Mw greater than at Mn, an amount of SCB per 1000 total carbon atoms of the polymer at Mz greater than at Mw, an amount of SCB per 1000 total carbon atoms of the polymer at Mz greater than at Mn, etc.

Aspect 12. The polymer of any of the preceding aspects, wherein said ethylene polymer has an Mp in any range disclosed herein, such as from 60,000 to 110,000, from 65,000 to 105,000, from 70,000 to 100,000 g/mol, etc.

Aspect 13. The polymer of any of the preceding aspects, wherein said ethylene polymer has a Mn in any range disclosed herein, such as from 20,000 to 46,000, from 22,000 to 46,000, from 20,000 to 42,000, from 22,000 to 40,000 g/mol, etc.

Aspect 14. The polymer of any of the preceding aspects, wherein said ethylene polymer has a Mw/Mn ratio in any range disclosed herein, such as from 6.5 to 20, from 7 to 17, from 7.5 to 15, from 8 to 13, etc.

Aspect 15. The polymer of any of the preceding aspects, wherein said ethylene polymer has a Mz/Mw ratio in any range disclosed herein, such as from 4 to 9, from 4 to 8, from 4.5 to 7.5, from 5 to 7, etc.

Aspect 16. The polymer of any of the preceding aspects, wherein said ethylene polymer has a relaxation time ( τ _η ) in any range disclosed herein, such as from 5×10 ³ to 1×10 ²⁵ s, from 6×10 ³ to 1 x 10 ²³ s, from 1 x 10 ⁵ to 1 x 10 ²⁵ s, from 1 x 10 ⁵ to 1 x 10 ²³ s, from 1 x 10 ⁷ to 1 x 10 ²³ s, etc.

Aspect 17. The polymer of any of the preceding aspects, wherein said ethylene polymer has a weight swell to die swell ratio (weight:die) in any range disclosed herein, such as from 200 to 280, from 210 to 270, from 230 to 280, from 230 to 270, etc., and/or said ethylene polymer has a hang-up time in any range disclosed herein, such as at least 40 s, at least 50 s, at least 100 s, etc.

Aspect 18. A polymer according to any of the preceding aspects, wherein said ethylene polymer has a bimodal molecular weight distribution.

Aspect 19. A polymer according to any of the preceding aspects, wherein said ethylene polymer is a single reactor product, for example, and not a post-reactor mixture of two polymers, for example, having different molecular weight characteristics.

Aspect 20. A polymer according to any of the preceding aspects, wherein said ethylene polymer comprises a copolymer of ethylene and an α-olefin.

Aspect 21. A polymer according to any of the preceding aspects, wherein said ethylene polymer comprises an ethylene homopolymer, an ethylene-1-butene copolymer, an ethylene-1-hexene copolymer and/or an ethylene-1-octene copolymer.

Aspect 22. The polymer according to any of the preceding aspects, wherein said ethylene polymer comprises a copolymer of ethylene and 1-hexene.

Aspect 23. The polymer of any of the preceding aspects, wherein said ethylene polymer comprises, independently, less than 0.1 ppm (wt), less than 0.08 ppm, less than 0.05 ppm, less than 0.03 ppm, etc. of Mg, V, Ti or Cr.

Aspect 24. The polymer according to any of the preceding aspects, wherein said ethylene polymer further comprises at least one additive selected from an antioxidant, an acid scavenger, an anti-blocking additive, a slip additive, a colorant, a filler, a polymer processing aid, a UV stabilizing additive, etc., or any combination thereof.

Aspect 25. An article (eg, a blow molded product) comprising an ethylene polymer according to any of the preceding aspects.

Aspect 26. An article comprising an ethylene polymer according to any one of aspects 1-24, wherein said article is an agricultural film, an automobile part, a bottle, a chemical container, a drum, a fiber or fabric, a film or container for food packaging, a food service article, a fuel tank, a geomembrane, a household container, a liner, a molded product, a medical device or material, an outdoor storage product, an outdoor play equipment, a pipe, a sheet or tape, a toy or a road barrier.

Aspect 27. A method for producing an ethylene polymer comprising contacting a base resin with a peroxide compound to produce an ethylene polymer according to any one of aspects 1-24.

Aspect 28. The method of aspect 27, wherein the base resin is contacted with peroxide groups in an amount of from 10 to 500 ppm, from 25 to 400 ppm, from 50 to 350 ppm, etc., based on the weight of the base resin.

Aspect 29. The method according to aspect 27 or 28, wherein the contacting step comprises melt-forming the mixture of the base resin and the peroxide compound at any melt-forming temperature disclosed herein, such as in the range of 120 to 300°C, in the range of 150 to 250°C, in the range of 175 to 225°C, etc.

Aspect 30. The method according to aspect 29, wherein the melt forming is carried out in a twin-screw extrusion system.

Aspect 31. The method according to aspect 29, wherein the melt forming is carried out in a single-screw extrusion system.

Aspect 32. The method according to any of aspects 27-31, wherein the peroxide compound comprises any suitable peroxide compound or any peroxide compound disclosed herein, such as 2,5-dimethyl-2,5-di(tert-butylperoxy)hexane, dicumyl peroxide, tert-butylcumyl peroxide, n-butyl-4,4'-di(tert-butylperoxy)valerate, etc., or any combination thereof.

Aspect 33. The method according to any of aspects 27-32, wherein the base resin has (or is characterized by):

high shear melt index in the range from 2 to 40 g/10 min;

average molecular weight in the range from 250,000 to 550,000 g/mol;

parameter CY-a in the range from 0.12 to 0.3;

tan δ at 0.1 s ^-1 in the range from 0.8 to 1.05 degrees;

tan δ at 100 s ^-1 in the range from 0.4 to 0.6 degrees; and

viscosity at 0.001 s ^-1 in the range from 1 x 10 ⁵ to 3 x 10 ⁶ Pa s.

Aspect 34. The method of aspect 33, wherein the base resin has an HLMI in any range disclosed herein, such as from 2 to 20, from 2 to 12, from 4 to 40, from 4 to 20, from 4 to 15, from 4 to 12 g/10 min, etc.

Aspect 35. The method according to aspect 33 or 34, wherein the base resin has a Mw in any range disclosed herein, such as from 250,000 to 500,000, from 250,000 to 475,000, from 300,000 to 550,000, from 300,000 to 500,000 g/mol, etc.

Aspect 36. The method according to any of aspects 33-35, wherein the base resin has a CY-a parameter in any range disclosed herein, such as from 0.12 to 0.25, from 0.13 to 0.3, from 0.13 to 0.25, from 0.14 to 0.25, etc.

Aspect 37. The method of any one of aspects 33-36, wherein the base resin has a tan δ at 0.1 s ^-1 in any range disclosed herein, such as from 0.5 to 0.85 degrees, from 0.8 to 1 degree, from 0.83 to 1.05 degrees, from 0.83 to 1 degree, from 0.85 to 1.05 degrees, from 0.85 to 1 degree, etc.

Aspect 38. The method according to any one of aspects 33-37, wherein the base resin has a tan δ at 100 s ^-1 in any range disclosed herein, such as from 0.4 to 0.58 degrees, from 0.4 to 0.55 degrees, from 0.45 to 0.6 degrees, from 0.45 to 0.58 degrees, from 0.45 to 0.55 degrees, etc.

Aspect 39. The method of any one of aspects 33-38, wherein the base resin has a viscosity at 0.001 s ^-1 in any range disclosed herein, such as from 1 x 10 ⁵ to 2 x 10 ⁶ Pa s, from 1 x 10 ⁵ to 1.8 x 10 ⁶ Pa s, from 8 x 10 ⁵ to 3 x 10 ⁶ Pa s, from 8 x 10 ⁵ to 2 x 10 ⁶ Pa s, from 8 x 10 ⁵ to 1.8 x 10 ⁶ Pa s, etc.

Aspect 40. The method of any one of aspects 33-39, wherein the base resin has a zero shear viscosity in any range disclosed herein, such as from 1×10 ⁶ to 1×10 ⁹ Pa s, from 1×10 ⁶ to 2×10 ⁸ Pa s, from 4×10 ⁶ to 1×10 ⁹ Pa s, from 4×10 ⁶ to 2×10 ⁸ Pa s, etc.

Aspect 41. The method according to any one of aspects 33-40, wherein the base resin has a density in any range disclosed herein, such as from 0.935 to 0.965, from 0.94 to 0.965, from 0.945 to 0.965, from 0.94 to 0.96, from 0.945 to 0.96 g/ ^cm3 , etc.

Aspect 42. The method according to any of aspects 33-41, wherein the base resin has an inverse comonomer distribution, for example, the amount of short chain branches (SCB) per 1000 total carbon atoms of the polymer at Mw greater than at Mn, the amount of SCB per 1000 total carbon atoms of the polymer at Mz greater than at Mw, the amount of SCB per 1000 total carbon atoms of the polymer at Mz greater than at Mn, etc.

Aspect 43. The method according to any one of aspects 33-42, wherein the base resin has an Mp in any range disclosed herein, such as from 60,000 to 110,000, from 65,000 to 105,000, from 65,000 to 100,000 g/mol, etc.

Aspect 44. The method according to any of aspects 33-43, wherein the base resin has a Mn in any range disclosed herein, such as from 18,000 to 48,000, from 20,000 to 42,000, from 20,000 to 38,000 g/mol, etc.

Aspect 45. The method according to any of aspects 33-44, wherein the base resin has a Mw/Mn ratio in any range disclosed herein, such as from 9 to 20, from 11 to 19, from 12 to 18, from 13 to 16, etc.

Aspect 46. The method according to any one of aspects 33-45, wherein the base resin has a Mz/Mw ratio in any range disclosed herein, such as from 4 to 9, from 5 to 8, from 5 to 7.5, from 6 to 8, etc.

Aspect 47. The method of any one of aspects 33-46, wherein the base resin has a weight swell to die swell ratio (weight:die) in any range disclosed herein, such as from 150 to 225, from 180 to 225, from 170 to 200, etc.

Aspect 48. The method according to any of aspects 33-47, wherein the base resin has a hang time in any range disclosed herein, such as from 10 to 45 s, from 15 to 45 s, from 20 to 45 s, etc.

Aspect 49. The method according to any of aspects 33-48, wherein the base resin has a bimodal molecular weight distribution.

Aspect 50. The method according to any of aspects 33-49, wherein the base resin is a single reactor product, for example, and not a post-reactor mixture of two polymers, for example, having different molecular weight characteristics.

Aspect 51. The method according to any of aspects 33-50, wherein the base resin comprises a copolymer of ethylene and an α-olefin.

Aspect 52. The method according to any one of aspects 33-51, wherein the base resin comprises an ethylene homopolymer, an ethylene-1-butene copolymer, an ethylene-1-hexene copolymer and/or an ethylene-1-octene copolymer.

Aspect 53. The method according to any of aspects 33-52, wherein the base resin comprises a copolymer of ethylene and 1-hexene.

Aspect 54. The method according to any one of aspects 33-53, wherein the base resin comprises, independently, less than 0.1 ppm (wt), less than 0.08 ppm, less than 0.05 ppm, less than 0.03 ppm, etc. of Mg, V, Ti or Cr.

Aspect 55. The method according to any one of aspects 33-54, wherein the base resin further comprises at least one additive selected from an antioxidant, an acid scavenger, an anti-blocking additive, a slip additive, a colorant, a filler, a polymer processing aid, a UV stabilizing additive, etc., or any combination thereof.

Claims (38)

1. A polymer of ethylene having: HLMI less than or equal to 12 g/10 min; Mw in the range of 200,000 to 550,000 g/mol; Mn in the range of 18,000 to 48,000 g/mol; CY-a parameter less than or equal to 0.12; tan δ at 0.1 s ^-1 in the range of 0.5 to 0.9 degrees; tan δ at 100 s ^-1 in the range of 0.5 to 0.75 degrees; and viscosity at 0.001 s ^-1 in the range of 1.3×10 ⁶ to 1×10 ⁷ Pa⋅s. 2. An industrial product containing a polymer according to paragraph 1. 3. The polymer according to claim 1, in which: HLMI ranges from 1 to 10 g/10 min; Mw ranges from 250000 to 500000 g/mol; Mn ranges from 22000 to 46000 g/mol; CY-a parameter ranges from 0.01 to 0.1; tan δ at 0.1 s ^-1 ranges from 0.6 to 0.85 degree; tan δ at 100 s ^-1 ranges from 0.52 to 0.72 degree; and viscosity at 0.001 s ^-1 ranges from 1.5×10 ⁶ to 6×10 ⁶ Pa⋅s. 4. The polymer according to claim 3, which comprises a copolymer of ethylene and 1-butene, a copolymer of ethylene and 1-hexene, a copolymer of ethylene and 1-octene, an ethylene homopolymer, or a combination thereof. 5. The polymer according to claim 3, which has a density in the range from 0.94 to 0.96 g/ ^cm3 . 6. The polymer according to claim 1, which has: zero-shear viscosity (η ₀ ) in the range from 1×10 ⁸ to 1×10 ³⁰ Pa⋅s; and relaxation time (τ _η ) in the range from 5×10 ³ to 1×10 ²⁵ s. 7. The polymer according to claim 1, which contains a copolymer of ethylene and an α-olefin. 8. The polymer of claim 7, which contains less than 0.1 ppm by weight, independently, Mg, V, Ti and Cr. 9. An industrial product containing a polymer according to paragraph 8. 10. The polymer according to claim 8, which has: zero-shear viscosity (η ₀ ) in the range from 1×10 ¹⁰ to 1×10 ²⁷ Pa⋅s; and relaxation time (τ _η ) in the range from 1×10 ⁵ to 1×10 ²³ s. 11. Polymer according to claim 1, containing a copolymer of ethylene and 1-butene, a copolymer of ethylene and 1-hexene, a copolymer of ethylene and 1-octene, an ethylene homopolymer, or a combination thereof. 12. The polymer according to claim 11, which has: viscosity at 100 s ^-1 in the range from 1700 to 3300 Pa⋅s; and Mr in the range from 65000 to 105000 g/mol. 13. The polymer according to claim 11, which has: Mw/Mn ratio in the range from 7 to 17; and Mz/Mw ratio in the range from 4.5 to 7.5. 14. The polymer according to claim 11, in which: HLMI ranges from 1 to 10 g/10 min; Mw ranges from 250000 to 500000 g/mol; Mn ranges from 22000 to 46000 g/mol; CY-a parameter ranges from 0.01 to 0.1; tan δ at 0.1 s ^-1 ranges from 0.6 to 0.85 degree; tan δ at 100 s ^-1 ranges from 0.52 to 0.72 degree; and viscosity at 0.001 s ^-1 ranges from 1.5×10 ⁶ to 6×10 ⁶ Pa⋅s. 15. An industrial product containing a polymer according to paragraph 14. 16. The polymer according to claim 1, which has: a weight swell to flow swell ratio in the range of 200 to 280; and a hang time of at least 40 s, where the weight swell is quantified by the part weight in grams and the flow swell is quantified by the flat bottom in inches and wherein the hang time is quantified by a hang time test using a die gap of 0.089 inches (0.22 cm) and an extruder speed of 20 rpm, in which the parison is extruded and left to hang; the extruder speed is set to zero while the parison is hanging; and the time from the end of the shot to the moment the parison breaks away from the outer ring of the extruder nozzle is recorded as the hang time. 17. The polymer of claim 1, which has an SCB amount per 1000 total carbon atoms at Mw greater than Mn, or an SCB amount per 1000 total carbon atoms of the polymer at Mz greater than Mn, or both. 18. A method for producing an ethylene polymer, comprising: contacting a base resin with a peroxide compound to produce an ethylene polymer, wherein the step of contacting the base resin with the peroxide compound comprises melt forming a mixture of the base resin and the peroxide compound at a suitable melt forming temperature; and the amount of peroxide compound is from more than 200 to 500 ppm by weight of peroxide groups based on the weight of the base resin; and In this case, the ethylene polymer is characterized by: HLMI less than or equal to 12 g/10 min; Mw in the range from 200,000 to 550,000 g/mol; Mn in the range from 18,000 to 48,000 g/mol; CY-a parameter less than or equal to 0.12; tan δ at 0.1 s ^-1 in the range from 0.5 to 0.9 degrees; tan δ at 100 s ^-1 in the range from 0.5 to 0.75 degrees; and viscosity at 0.001 s ^-1 in the range from 1.3×10 ⁶ to 1×10 ⁷ Pa⋅s. 19. The method according to item 18, wherein: the step of bringing the base resin into contact with the peroxide compound comprises melt molding a mixture of the base resin and the peroxide compound in a twin-screw extrusion system. 20. The method according to paragraph 18, wherein: the base resin comprises an ethylene homopolymer, an ethylene-1-butene copolymer, an ethylene-1-hexene copolymer, an ethylene-1-octene copolymer, or a combination thereof; and The base resin is produced using a dual metallocene catalyst system.