Process for reducing gel and increasing melt index potential of chromium catalysts

Abstract

The title of the invention is a method for reducing gel and increasing melt index potential of chromium catalyst activation. The invention discloses methods for making activated chromium catalysts such as titania-coated chromium / silica catalysts, and these methods employ a multi-step process involving exposure to inert and oxidizing atmospheres at specific temperature conditions. The activated chromium catalysts thus obtained have unexpectedly high melt index potential, and ethylene-based polymers with lower gel counts and higher melt indices can be made.

Description

[0001] This application is a divisional application of the patent application filed on April 30, 2024, with application number 2024800203949, entitled "Method for Activating a Chromium Catalyst to Reduce Gel and Improve Melt Index Potential".

[0002] Citation of relevant applications This application was filed on April 30, 2024 as a PCT international patent application and claims the benefit and priority of U.S. Provisional Patent Application No. 63 / 499,507, filed on May 2, 2023, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0003] This disclosure generally relates to methods for activating supported chromium precatalysts and the use of activated chromium catalysts in the polymerization of olefins. Background Technology

[0004] Supported chromium precatalysts are activated by exposing them to an oxygen-containing atmosphere (e.g., air) at high temperatures to convert at least a portion of the low-valent chromium to the +6 valent oxidation state (hexavalent chromium). However, in commercial practice, activation of large quantities of supported chromium catalysts typically results in relatively low Cr(VI) conversion, and the resulting activated chromium catalysts often fail to efficiently produce polymers with relatively high melt indexes and low film gel content. Overcoming these drawbacks with alternative catalyst activation methods would be beneficial; therefore, this invention is generally intended for these purposes. Summary of the Invention

[0005] This summary is provided to introduce, in a simplified form, a series of concepts that will be further described in the following detailed description. This summary is not intended to identify any essential or necessary features of the claimed subject matter. Nor is it intended to limit the scope of the claimed subject matter.

[0006] This invention relates to methods for manufacturing activated (or calcined) chromium catalysts, and such methods may include: (i) contacting a pre-catalyst with a first inert atmosphere at a temperature T1 in the range of 500℉ to 700℉ (260°C to 371°C), wherein the pre-catalyst comprises a silica support and 0.1 to 5 wt% chromium, 0.1 to 10 wt% titanium, and 1 to 5 moles of nitrogen per mole of titanium; (ii) subjecting the pre-catalyst to a cycle of exposure to a first oxidizing atmosphere at a temperature T2 in the range of 500℉ to 700℉ (260°C to 371°C) and exposure to a second inert atmosphere at a temperature T3 in the range of 700℉ to 900℉ (371°C to 482°C), wherein the first oxidizing atmosphere causes an exothermic temperature rise from T2 to T3, thereby triggering the introduction of the second inert atmosphere, resulting in cooling to T2 until the exothermic temperature rise in the first oxidizing atmosphere is less than or equal to 50℉ within 15 minutes. (iii) When heat must be added to maintain T3 in the presence of the first oxidizing atmosphere (28°C); (iv) the precatalyst is heated in a third inert atmosphere to a temperature T4 in the range of 1000°F to 1400°F (538°C to 760°C), and the precatalyst is held in the third inert atmosphere for a holding time t1 in the range of 1 hour to 15 hours at T4; (v) the precatalyst is cooled in a fourth inert atmosphere to a temperature T5 in the range of 900°F to 1200°F (482°C to 649°C), wherein T5 is lower than T4; (v) the precatalyst is exposed to a second oxidizing atmosphere at T5 for a holding time t2 in the range of 30 minutes to 10 hours; (vi) the precatalyst is cooled in a third oxidizing atmosphere to a temperature of 500°F to 700°F. Temperature T6 is applied within the range of 260°C to 371°C to produce an activated (calcined) chromium catalyst; and (vii) at T6, the activated (calcined) chromium catalyst is purged in a fifth inert atmosphere and cooled to ambient temperature.

[0007] This document also provides methods for olefin polymerization. These polymerization methods may include: (I) performing any method to produce the activated chromium catalyst disclosed herein; and (II) contacting the activated chromium catalyst and optional co-catalyst with olefin monomers and optional olefin comonomers under polymerization conditions in a polymerization reactor system to produce an olefin polymer.

[0008] Other aspects of the invention relate to ethylene polymers (typically in granule or bead form) characterized by a high load melt index (HLMI) in the range of 10 to 80 g / 10 min and a value in the range of 0.93 to 0.96 g / cm³. 3Density within the range of 0.1 to 1 g / 10 min (or melt index (MI) within the range of 0.93 to 0.96 g / cm³) 3 (Density within the range). These ethylene polymers may have a total membrane gel number (or catalyst particle gel number) of less than or equal to 100 gels per square foot with a thickness of 25 micrometers, wherein the membrane gels contain a size greater than 200 μm (and for the catalyst particle gel number, caused by the catalyst particles), and may contain 150 to 680 ppm of silica, 1.5 to 6.8 ppm of chromium, and 1.5 to 40 ppm of titanium.

[0009] The foregoing summary and the following detailed description are illustrative and should not be construed as limiting. Furthermore, features or variations may be provided in addition to those set forth herein. For example, certain aspects may be addressed to various combinations and sub-combinations of features described in the detailed description. Attached Figure Description

[0010] The following figures form part of this specification and are included to further illustrate certain aspects of the invention. The invention can be better understood by referring to one or more of these figures in conjunction with the detailed description of the specific embodiments presented herein.

[0011] Figure 1 A graph showing the temperature versus time for a representative activation method similar to activation method FG is shown.

[0012] Figure 2 It shows Figure 1 The graph shows the temperature change over time in the heat-exothermic elimination portion.

[0013] Figure 3 A graph showing the temperature change over time for a representative activation method similar to activation method H is shown.

[0014] While the invention disclosed herein is susceptible to various modifications and alternatives, only a few specific embodiments have been illustrated by way of example in the accompanying drawings and are described in detail below. The drawings and the detailed description of these specific embodiments are not intended to limit the breadth or scope of the inventive concept or the appended claims in any way. Rather, the drawings and detailed written description are provided to illustrate this disclosure to those skilled in the art and to enable such persons to acquire and use the inventive concept.

[0015] definition To more clearly define the terms used herein, the following definitions are provided. Unless otherwise specified, the following definitions apply to this disclosure. If a term is used in this disclosure but is not specifically defined herein, the definition in IUPAC Compendium of Chemical Terminology, 2nd Edition (1997) may be applied, provided that such definition does not conflict with any other disclosure or definition applied herein, or render any claim to which such definition is applied uncertain or invalid. If any definition or usage provided in any document incorporated herein by reference conflicts with the definition or usage provided herein, the definition or usage provided herein shall prevail.

[0016] In this document, the features of the subject matter are described such that combinations of different features are conceivable within a particular aspect. For each aspect and feature disclosed herein, all combinations are contemplated, whether explicitly described or not, that will not adversely affect the catalyst, composition, process, or method described herein. Furthermore, unless expressly stated otherwise, any aspect or feature disclosed herein may be combined to describe the catalyst, composition, process, or method of the invention consistent with this disclosure.

[0017] Generally speaking, elemental families use Chemical and Engineering News The numbering scheme indicated in the version of the periodic table published in 1985, 63(5), 27, indicates that a group of elements may be indicated by the common name assigned to that group; for example, alkali metals are indicated by Group 1 elements, alkaline earth metals by Group 2 elements, transition metals by Groups 3-12 elements, and halogens or halides by Group 17 elements.

[0018] Whenever used in this specification and claims, the term "hydrocarbon" refers to a compound containing only carbon and hydrogen, whether saturated or unsaturated. Other identifiers may be used to indicate the presence of a specific group in a hydrocarbon (e.g., a halohydrocarbon indicates the presence of one or more halogen atoms in a substituted hydrocarbon with an equal number of hydrogen atoms). Non-limiting examples of hydrocarbons include alkanes (straight-chain, branched, and cyclic alkanes), alkenes (olefins), and aromatic compounds, as well as other compounds.

[0019] For any particular compound or group disclosed herein, unless otherwise stated, any name or structure presented (generally or specifically) is intended to cover all conformational isomers, positional isomers, stereoisomers, and mixtures thereof that can be produced by a particular set of substituents. Unless otherwise stated, the name or structure (generally or specifically) also covers all enantiomers, diastereomers, and other optical isomers (if any), whether enantiomers or racemic forms, and mixtures of stereoisomers, as known to those skilled in the art. For example, pentane as commonly referred to includes n-pentane, 2-methylbutane, and 2,2-dimethylpropane; and butyl as commonly referred to includes n-butyl, sec-butyl, isobutyl, and tert-butyl.

[0020] Unless otherwise stated, the terms “contacting” and “subjecting” are used herein to describe catalysts, compositions, processes, and methods in which materials or components are combined in any order, in any manner, and for any duration. For example, materials or components may be blended, mixed, slurried, dissolved, reacted, treated, impregnated, compounded, or otherwise combined in some other manner or by any suitable method or technique.

[0021] As used herein, “BET surface area” means the surface area determined by the nitrogen adsorption Brunauer, Emmett, and Teller (BET) method according to ASTM D1993-91, and as described, for example, in Brunauer, S., Emmett, PH, and Teller, E., “Adsorption of gases in multimolecular layers,” J. Am. Chem. Soc., 60, 3, pp. 309-319.

[0022] The term "polymer" generally includes olefin homopolymers, copolymers, terpolymers, etc., as well as alloys and blends thereof. The term "polymer" also includes impact copolymers, block copolymers, graft copolymers, random copolymers, and alternating copolymers. Copolymers are derived from one olefin monomer and one olefin comonomer, while terpolymers are derived from one olefin monomer and two olefin comonomers. Thus, "polymer" encompasses copolymers and terpolymers derived from any olefin monomer and comonomer disclosed herein. Similarly, the term "polymerization" encompasses homopolymerization, copolymerization, and terpolymerization. Therefore, ethylene polymers include ethylene homopolymers, ethylene copolymers (e.g., ethylene / α-olefin copolymers), ethylene terpolymers, etc., as well as blends or mixtures thereof. Therefore, ethylene polymers encompass polymers commonly referred to in the art as linear low-density polyethylene (LLDPE) and high-density polyethylene (HDPE). As an example, olefin copolymers, such as ethylene copolymers, can be derived from ethylene and comonomers, such as 1-butene, 1-hexene, or 1-octene. If the monomer and comonomer are ethylene and 1-hexene, respectively, the resulting polymer can be classified as an ethylene / 1-hexene copolymer. Unless otherwise stated, the term "polymer" also includes all possible geometries, and these geometries may include isotactic, syndiotactic, and atactic symmetries. Furthermore, unless otherwise stated, the term "polymer" is also intended to include polymers of all molecular weights.

[0023] In this disclosure, although catalysts, compositions, processes, and methods are described as “comprising” various components or steps, unless otherwise stated, the catalysts, compositions, processes, and methods may also be “substantially composed of various components or steps” or “composed of various components or steps.” Unless otherwise specified, the terms “an (a),” “an (an),” and “the” are intended to include multiple (a) alternatives, such as at least one (a).

[0024] This invention discloses several types of ranges. When any type of range is disclosed or claimed, it is intended that each possible number reasonably covered by such range be disclosed or claimed individually, including the endpoints of the range and any sub-ranges and combinations thereof covered therein. For example, in aspects of this invention, an oxidizing atmosphere may contain a range of oxygen contents. By disclosing that an oxidizing atmosphere may contain 1 to 100 vol% oxygen, it is intended to indicate that the oxygen content can be any amount within that range, such as any range or combination of ranges from 1 to 100 vol%, for example, 1 to 50 vol%, 2 to 30 vol%, 3 to 25 vol%, or 4 to 21 vol% oxygen, etc. Similarly, all other ranges disclosed herein should be interpreted in a similar manner to this example.

[0025] Generally, quantities, sizes, formulations, parameters, ranges, or other quantities or characteristics are modified by “about” or “approximately”, whether or not explicitly stated otherwise. Regardless of whether modified by the terms “about” or “approximately”, claims include equivalents of the quantities or characteristics.

[0026] Although any methods, apparatus, and materials similar to or equivalent to those described herein may be used in the practice or testing of this invention, typical methods, apparatus, and materials are described herein.

[0027] All publications and patents mentioned herein are incorporated herein by reference in their entirety for the purpose of describing and disclosing, for example, the constructs and methods described in the publications and patents, which may be used in conjunction with the inventions described herein. Detailed Implementation

[0028] The present invention generally relates to the conversion of low-valent supported chromium precatalysts into activated (hexavalent) chromium catalysts for use in olefin polymerization processes.

[0029] One objective of this invention is to produce activated chromium catalysts with high Cr(VI) content and catalytic activity. Another objective is to produce activated chromium catalysts with high melt index potential, enabling the production of vinyl polymers with lower molecular weights and / or higher melt flow rates. Another objective is to produce activated catalysts with high melt index potential at relatively low calcination / activation temperatures. Another objective is to produce activated chromium catalysts that can produce vinyl polymers with a wide molecular weight distribution and low levels of long-chain branching. Another objective is to produce activated chromium catalysts that can produce vinyl polymers with extremely low levels of film gelation. Another objective is to produce activated chromium catalysts that can produce vinyl polymers with improved extrusion processing properties suitable for a variety of applications, including blown films, pipes, and blow-molded products. These and other benefits will be further described below.

[0030] Methods for activating chromium catalysts This document discloses a method for manufacturing an activated (or calcined) chromium catalyst. The method may include: (i) contacting a pre-catalyst with a first inert atmosphere at a temperature T1 in the range of 500℉ to 700℉ (260℃ to 371℃), wherein the pre-catalyst comprises a silica support and 0.1 to 5 wt% chromium, 0.1 to 10 wt% titanium, and 1 to 5 moles of nitrogen per mole of titanium; (ii) subjecting the pre-catalyst to a cycle of exposure to a first oxidizing atmosphere at a temperature T2 in the range of 500℉ to 700℉ (260℃ to 371℃) and exposure to a second inert atmosphere at a temperature T3 in the range of 700℉ to 900℉ (371℃ to 482℃), wherein the first oxidizing atmosphere causes an exothermic temperature rise from T2 to T3, thereby triggering the introduction of the second inert atmosphere, resulting in cooling to T2 until the exothermic temperature rise in the first oxidizing atmosphere is less than or equal to 50℉ within 15 minutes. (iii) When heat must be added to maintain T3 in the presence of the first oxidizing atmosphere (28°C); (iv) the precatalyst is heated in a third inert atmosphere to a temperature T4 in the range of 1000°F to 1400°F (538°C to 760°C), and the precatalyst is held in the third inert atmosphere for a holding time t1 in the range of 1 hour to 15 hours at T4; (v) the precatalyst is cooled in a fourth inert atmosphere to a temperature T5 in the range of 900°F to 1200°F (482°C to 649°C), wherein T5 is lower than T4; (v) the precatalyst is exposed to a second oxidizing atmosphere at T5 for a holding time t2 in the range of 30 minutes to 10 hours; (vi) the precatalyst is cooled in a third oxidizing atmosphere to a temperature of 500°F to 700°F. Temperature T6 in the range of 260°C to 371°C is used to produce an activated (calcined) chromium catalyst; and (vii) at T6, the activated (calcined) chromium catalyst is purged in a fifth inert atmosphere and cooled to ambient temperature (the ambient temperature is nominally 77°F or 25°C).

[0031] Generally, the characteristics of this method (e.g., pre-catalyst, activated chromium catalyst, oxidizing atmosphere, inert atmosphere, temperature, and holding time, etc.) are described independently herein, and these characteristics may be combined in any combination to further describe the disclosed method for producing an activated chromium catalyst. Furthermore, unless otherwise stated, additional method steps may be performed before, during, and / or after any step in any method disclosed herein, and may be used without limitation in any combination to further describe these methods. Moreover, any activated chromium catalyst produced according to the disclosed method is within the scope of this disclosure and is covered herein. Activated chromium catalysts may also be referred to herein as calcined chromium catalysts.

[0032] First, referring to step (i), the precatalyst is contacted with a first inert atmosphere at a temperature T1 ranging from 500℉ to 700℉ (260℃ to 371℃). The precatalyst comprises a silica support and 0.1 to 5 wt% chromium, 0.1 to 10 wt% titanium, and 1 to 5 moles of nitrogen per mole of titanium. Other suitable ranges for the amount of chromium present in the precatalyst (or activated chromium catalyst) include, but are not limited to, 0.1 to 4 wt%, 0.2 to 5 wt%, 0.5 to 3 wt%, 0.5 to 2 wt%, or 0.5 to 1.5 wt% chromium. These weight percentages are based on the proportion of chromium to the total weight of the precatalyst or activated chromium catalyst. Similarly, other suitable ranges for the amount of titanium present in the precatalyst (or activated chromium catalyst) include, but are not limited to, 0.5 to 10 wt%, 1 to 10 wt%, 2 to 8 wt%, or 2 to 6 wt% titanium. These weight percentages are also based on the proportion of titanium to the total weight of the precatalyst or activated catalyst.

[0033] The precatalyst may also contain nitrogen from the nitrogen-containing compound used to prepare the precatalyst. Generally, the precatalyst contains 1 to 5 moles of nitrogen per mole of titanium, and more typically, 1 to 4.5 moles, 1.5 to 5 moles, 1.5 to 4.5 moles, 2 to 5 moles, 2 to 4 moles, or 2 to 3 moles of nitrogen per mole of titanium.

[0034] The precatalyst can also be characterized by the presence of carboxylate groups / ligands before activation and the amount of carbon. In one aspect, the precatalyst may contain 1 to 5 moles of carboxylate per mole of titanium; in another, 1 to 4 moles of carboxylate per mole of titanium; in yet another, 1 to 3 moles of carboxylate per mole of titanium; in yet another, 1.5 to 5 moles of carboxylate per mole of titanium; in yet another, 1.5 to 4 moles of carboxylate per mole of titanium; and in yet another, 2 to 3 moles of carboxylate per mole of titanium. Examples of carboxylate (including dicarboxylate) include acetates, oxalates, citrates, malates, lactates, gluconates, glycolates, 2-hydroxybutyrates, glyoxylates, lactates, malates, malonates, phosphonoacetates, tartrates, etc.

[0035] Alternatively, the precatalyst may contain 0.5 to 10% by weight of carbon prior to activation, and more typically, 1 to 10% by weight, 1 to 5% by weight, 2 to 10% by weight, 2 to 8% by weight, or 2 to 6% by weight of carbon. These weight percentages are based on the proportion of carbon content relative to the total weight of the precatalyst.

[0036] The precatalyst in step (i), namely the precatalyst containing a silica support, 0.1 to 5 wt% chromium, 0.1 to 10 wt% titanium, and 1 to 5 moles of nitrogen per mole of titanium, can undergo activation alone or optionally be blended or mixed with a second precatalyst having a different catalyst composition. Any relative amount of the precatalyst and the second precatalyst in step (i) can be used. For example, the second precatalyst can be a chromium / silica precatalyst; or a chromium / silica-titanium dioxide cogel precatalyst; or a chromium oxide-silica-titanium dioxide ternary gel precatalyst.

[0037] In step (i), the temperature T1 ranges from 500℉ to 700℉ (260℃ to 371℃). On one hand, T1 can be in the range of 550℉ to 650℉ (288℃ to 343℃), and on the other hand, T1 can be in the range of 600℉ to 700℉ (315℃ to 371℃), and further still, T1 can be in the range of 600℉ to 650℉ (315℃ to 343℃). These and other temperature ranges disclosed herein are intended to cover cases where the corresponding steps in the method are performed at a series of different temperatures within the corresponding temperature range, rather than at a single fixed temperature.

[0038] In step (ii), the precatalyst undergoes the following cycle: exposure to a first oxidizing atmosphere at a temperature T2 in the range of 500℉ to 700℉ (260℃ to 371℃), and exposure to a second inert atmosphere at a temperature T3 in the range of 700℉ to 900℉ (371℃ to 482℃). The first oxidizing atmosphere causes an exothermic temperature rise from T2 to T3, thereby triggering the introduction of the second inert atmosphere, resulting in a cooling of the temperature to T2. Other illustrative and representative ranges for T2 include 600℉ to 700℉ (315℃ to 371℃), 500℉ to 650℉ (260℃ to 343℃), 625℉ to 700℉ (329℃ to 371℃), or 575℉ to 675℉ (302℃ to 357℃), while other illustrative and representative ranges for T3 include 700℉ to 850℉ (371℃ to 454℃), 700℉ to 800℉ (371℃ to 427℃), 725℉ to 900℉ (385℃ to 482℃), or 750℉ to 850℉ (399℃ to 454℃). For example, in the first cycle, the pre-catalyst is exposed to a first oxidizing atmosphere at a temperature T2 in the range of 500℉ to 700℉ (260℃ to 371℃), for example at 550℉ (288℃). Due to exothermic reactions, the temperature is raised to a temperature T3 in the range of 700℉ to 900℉ (371℃ to 482℃), for example, 775℉ (413℃), at which point the precatalyst is exposed to a second inert atmosphere. The precatalyst is then cooled to any suitable temperature in the range of 500℉ to 700℉ (260℃ to 371℃). In the second cycle, the precatalyst is exposed to a first oxidizing atmosphere at a temperature of, for example, 625℉ (329℃). Due to exothermic reactions, the temperature is raised to a temperature T3 in the range of 700℉ to 900℉ (371℃ to 482℃), for example, 750℉ (399℃), at which point the precatalyst is exposed to a second inert atmosphere. The precatalyst is then cooled to any suitable temperature in the range of 500℉ to 700℉ (260℃ to 371℃). Although not bound by theory, it is believed that limiting the temperature rise in step (ii) will prevent premature oxidation of chromium, while oxidizing organic matter and other residues present on the precatalyst.

[0039] The cycling of oxidizing and inert atmospheres continues until the exothermic temperature rise in the first oxidizing atmosphere is less than or equal to 50℉ (28°C) within 15 minutes, or until heat must be added to maintain T3 in the presence of the first oxidizing atmosphere. In some aspects, step (ii) may proceed until the exothermic temperature rise in the first oxidizing atmosphere is less than or equal to 40℉ (22°C) within 15 minutes; or less than or equal to 25℉ (14°C) within 15 minutes; or less than or equal to 10℉ (6°C) within 15 minutes. While not limited to these, the number of cycles in step (ii) is typically 2 to 10, but more commonly, the number of cycles in step (ii) is 2 to 6, 2 to 4, 2 to 3, 3 to 8, 3 to 5, 4 to 10, or 4 to 6.

[0040] The first oxidizing atmosphere in each cycle of step (ii) may be the same or different, and may independently comprise (or consist substantially of, or consist of) oxygen, air, mixtures of oxygen and inert gases (e.g., nitrogen), mixtures of air and inert gases (e.g., nitrogen), and any combination thereof. The first oxidizing atmosphere in each cycle of step (ii) may independently comprise any suitable oxygen volume percentage in the range of 1 to 100 vol%. On one hand, the oxygen volume percentage may be 1 to 50 vol%, on the other hand, it may be 2 to 30 vol%, on yet another hand, it may be 3 to 25 vol%, and on yet another hand, it may be 4 to 21 vol%.

[0041] Similar to the first oxidizing atmosphere in each cycle of step (ii), the second inert atmosphere in each cycle of step (ii) may be the same or different. The second inert atmosphere in each cycle of step (ii) may independently contain (or consist substantially of, or consist of) the following: nitrogen, argon, or a combination thereof; or nitrogen; or argon.

[0042] After step (ii) and the exothermic reaction, in step (iii), the precatalyst is heated in a third inert atmosphere to a temperature T4 in the range of 1000℉ to 1400℉ (538℃ to 760℃), and at T4, the precatalyst is held in the third inert atmosphere for a holding time t1 in the range of 1 hour to 15 hours. Any suitable heating rate can be used in step (iii), such as 1 to 5℉ / min (0.6 to 3℃ / min), 1.5 to 4℉ / min (0.8 to 2.2℃ / min), or 2 to 3.5℉ / min (1 to 2℃ / min), etc. In addition to the T4 range of 1000℉ to 1400℉ (538℃ to 760℃), other temperature ranges may be used, such as the following non-limiting ranges: 1000℉ to 1300℉ (538℃ to 704℃), 1100℉ to 1400℉ (593℃ to 760℃), 1100℉ to 1300℉ (593℃ to 704℃), or 1200℉ to 1300℉ (649℃ to 704℃), etc.

[0043] In step (iii), the pre-catalyst is held in a third inert atmosphere at T4 for a holding time t1 ranging from 1 hour to 15 hours. Other representative and non-limiting ranges for t1 include 1 hour to 8 hours, 2 hours to 10 hours, 3 hours to 15 hours, 3 hours to 8 hours, or 4 hours to 6 hours, etc. Although not bound by theory, it is believed that exposure to an inert atmosphere at high temperatures can dehydroxylate the catalyst without causing premature oxidation of chromium. Furthermore, it is believed that by using a relatively low T4 temperature, key polymer properties such as molecular weight distribution and low long-chain branching can be preserved.

[0044] Following step (iii), in step (iv), the pre-catalyst is cooled in a fourth inert atmosphere to a temperature T5 in the range of 900℉ to 1200℉ (482℃ to 649℃), provided that T5 is lower than T4. Any suitable heating rate can be used in step (iv), such as 1 to 4℉ / min (0.6 to 2.2℃ / min), 1.5 to 3.5℉ / min (0.8 to 2℃ / min), or 2 to 3℉ / min (1 to 1.7℃ / min), etc. In addition to the T5 range of 900℉ to 1200℉ (482℃ to 649℃), other temperature ranges may be used, such as the following non-limiting ranges: 900℉ to 1100℉ (482℃ to 593℃), 950℉ to 1150℉ (510℃ to 621℃), 1000℉ to 1200℉ (538℃ to 649℃) or 1000℉ to 1100℉ (538℃ to 593℃), etc.

[0045] After reaching temperature T5 in a fourth inert atmosphere, the atmosphere is changed, and in step (v), at T5, the pre-catalyst is exposed to a second oxidizing atmosphere for a holding time t2 ranging from 30 minutes to 10 hours. Generally, the holding time t2 is a period of time sufficient to form at least 30% by weight, more typically at least 50% by weight, 70% by weight, or at least 80% by weight of chromium (VI), based on the amount of chromium present on the activated chromium catalyst. In step (v), the holding time t2 can range from 30 minutes to 10 hours, but other representative and non-limiting ranges for t2 include 30 minutes to 8 hours, 1 hour to 10 hours, 1 hour to 8 hours, 2 hours to 6 hours, or 3 hours to 5 hours, etc. Typically, a balance can exist between chromium conversion and melt index potential, as longer t2 holding times and higher temperatures may reduce melt index potential.

[0046] In step (vi), the catalyst is cooled in a third oxidizing atmosphere to a temperature T6 in the range of 500℉ to 700℉ (260℃ to 371℃) to produce an activated chromium catalyst. In step (iv), any suitable cooling rate can be used, such as 1 to 4℉ / min (0.6 to 2.2℃ / min), 1.5 to 3.5℉ / min (0.8 to 2℃ / min), or 2 to 3℉ / min (1 to 1.7℃ / min), etc. In addition to the T6 range of 500℉ to 700℉ (260℃ to 371℃), other temperature ranges can be used, such as the following non-limiting ranges: 500℉ to 650℉ (260℃ to 343℃), 550℉ to 700℉ (288℃ to 371℃), 550℉ to 650℉ (288℃ to 343℃), or 600℉ to 675℉ (315℃ to 357℃), etc. Although not required, temperature T6 is typically within 50℉ (28℃), 25℉ (14℃), or 10℉ (6℃) of temperature T1. While not bound by theory, it is believed that switching to an inert atmosphere at relatively high temperatures would impair the conversion to Cr(VI).

[0047] Following step (vi), in step (vii), the activated (calcined) chromium catalyst is purged in a fifth inert atmosphere at T6, and then cooled to ambient temperature (nominal value 77℉ or 25°C). While not limited to this, in step (vii), the activated (calcined) chromium catalyst can be purged in a fifth inert atmosphere at T6 for a purging time t3 typically ranging from 2 minutes to 20 hours; or 5 minutes to 12 hours; or 5 minutes to 5 hours; or 15 minutes to 4 hours; or 30 minutes to 6 hours. Although not bound by theory, purging in an inert atmosphere is believed to be crucial for removing oxygen / air from the catalyst pores, thus preventing the poisoning effect of oxygen / air in the reactor during the polymerization reaction.

[0048] In the method for producing an activated chromium catalyst, the first, third, fourth, fifth, and sixth inert atmospheres may be the same or different. For example, on one hand, the third inert atmosphere may be the same as the fourth inert atmosphere, while on the other hand, the third inert atmosphere may be different from the fourth inert atmosphere. The first, third, fourth, fifth, and sixth inert atmospheres may independently comprise (or substantially consist of, or consist of) nitrogen, argon, or a combination thereof; or nitrogen; or argon.

[0049] Similarly, the second oxidizing atmosphere and the third oxidizing atmosphere may be the same or different. For example, in one aspect, the second oxidizing atmosphere and the third oxidizing atmosphere may be the same, while in another aspect, they may be different. The second oxidizing atmosphere and the third oxidizing atmosphere may independently comprise (or substantially consist of, or consist of) oxygen, air, mixtures of oxygen and inert gases (e.g., nitrogen), mixtures of air and inert gases (e.g., nitrogen), and any combination thereof. The second oxidizing atmosphere and the third oxidizing atmosphere may independently comprise any suitable oxygen volume percentage in the range of 1 to 100 vol%. In one aspect, the oxygen volume percentage may be 1 to 50 vol%, while in another aspect, the oxygen volume percentage may be 2 to 30 vol%, while in yet another aspect, the oxygen volume percentage may be 3 to 25 vol%, and in yet another aspect, the oxygen volume percentage may be 4 to 21 vol%.

[0050] Referring again to step (i) of the method for producing an activated chromium catalyst, in step (i) the precatalyst is contacted with a first inert atmosphere at a temperature T1 in the range of 500℉ to 700℉ (260°C to 371°C). Prior to step (i), the precatalyst may be loaded into a suitable container and then heated to T1. Therefore, the method disclosed herein may also include the step of loading the precatalyst and heating it to T1 in a first inert atmosphere prior to step (i). Prior to loading, the precatalyst may be at any suitable temperature, but is generally from ambient temperature to 120℉ (49°C), but is not limited thereto.

[0051] Loading the precatalyst prior to step (i) can be achieved by dividing the total amount of precatalyst into 2 to 10, 2 to 8, 3 to 10, or 3 to 6 portions and loading them into the container before proceeding to step (i). The number of portions may depend on the size of the container and the amount of catalyst to be activated, as well as other considerations. During each portion of the total precatalyst is loaded, the temperature is generally maintained in the range of 300 to 600℉ (149°C to 315°C), for example, 400 to 600℉ (204°C to 315°C). Typically, loading of each portion of the total precatalyst is stopped when the temperature drops below 400℉ (204°C) or below 300℉ (149°C) (which is usually a result of water evaporation). Alternatively or alternatively, loading of each portion of the total precatalyst can be stopped when the pressure rises above 1 psig, which is also largely a result of water evaporation (i.e., steam).

[0052] The total charge or total amount of the precatalyst may be at least 100 pounds, at least 200 pounds, at least 300 pounds, at least 500 pounds, at least 750 pounds, at least 1000 pounds, at least 1200 pounds, or at least 1500 pounds, and typically up to and including 1750 pounds, 2000 pounds, or 2500 pounds, but is not limited thereto.

[0053] In this document, the method for producing an activated chromium catalyst can be carried out in any suitable calcination or activation vessel, but the method is typically carried out in a fluidized bed vessel, or any one or more steps of the method can be carried out in a fluidized bed vessel. The fluidized bed reactor can be operated in batch or continuous operation, or any one or more steps of the method can be carried out in batch or continuous operation. The catalyst amount and fluidized bed depth can be any values ​​suitable for fluidized bed operation. In the method for producing an activated chromium catalyst, the pre-catalyst (or activated catalyst) can be contacted with the gas stream at any suitable linear velocity, typically in the range of 0.05 to 0.6 feet per second. For example, each step in the disclosed method can be performed by fluidizing a pre-catalyst (or, depending on the context, an activated catalyst) in an inert fluidizing gas (for an inert atmosphere) or an oxygen-containing fluidizing gas (for an oxidizing atmosphere), the linear velocity of which is independently in the range of 0.05 to 0.6 feet per second, and in some respects in the range of 0.05 to 0.3 feet per second or 0.1 to 0.4 feet per second, while in other respects in the range of 0.2 to 0.5 feet per second, 0.2 to 0.4 feet per second or 0.2 to 0.3 feet per second.

[0054] The diameter of the fluidized bed container can be at least 12 inches, at least 20 inches, at least 30 inches, at least 40 inches or at least 50 inches, and typically up to and including 55 inches, 60 inches or 70 inches, but is not limited thereto.

[0055] The activated catalyst produced by the disclosed activation method possesses many superior properties compared to catalysts that have not undergone the specific steps described above but are otherwise identical. For example, compared to a catalyst activated by exposure to an oxidizing atmosphere at temperature T4 for a holding time t1 but otherwise identical (often referred to as a control catalyst), the activated catalyst according to the invention may have a higher melt index potential (e.g., at least 10%, at least 25%, at least 50%, at least 75%, or at least 100% higher). Alternatively, the control catalyst may be Magnapore, available from WR Grace. ® The catalyst is calcined at 1200℉ (649℃) for 3 hours (for laboratory scale) or 8 hours (for large-scale). In making these comparisons, the polymerization reaction needs to be carried out under identical conditions. That is, the reaction temperature should be the same, the concentrations of ethylene and comonomers in the reaction zone should be the same, and the achieved productivity should also be the same, preferably in the range of 3000 gPE / gCat to 5000 gPE / gCat.

[0056] This potential for improved melt index can be achieved through melt index (MI, I2) or high-load melt index (HLMI, I2). 21 The MI potential of the activated catalyst of the present invention may be at least 0.2, at least 0.3, at least 0.4, at least 0.5, at least 0.6, at least 0.7, at least 0.8, at least 0.9, at least 1, or at least 1.2 g / 10 min. Alternatively, when the activated catalyst of the present invention is tested in isobutane at 105°C, 550 psig ethylene, and the time required to reach 3000 g PE / g Cat, its HLMI potential may be at least 20, at least 25, at least 30, at least 35, at least 40, at least 50, at least 60, at least 70, at least 80, or at least 100 g / 10 min.

[0057] While the activated catalysts described herein can significantly improve melt index potential, the resulting polymers are generally very similar to those produced using a control catalyst. Therefore, in some aspects, the activated catalysts according to the invention can produce a polymer under standard polymerization conditions where the Mw / Mn ratio (or Mz / Mw ratio, or CY-a parameter) is within 35% (or within 30%, 25%, 20%, 15%, 10%, or 5%) of the Mw / Mn ratio (or Mz / Mw, or CY-a parameter) of the polymer produced using the control catalyst as defined above. Standard polymerization conditions are described in detail in the following examples, but briefly, include isobutane diluent, a polymerization temperature of 105°C, an ethylene pressure of 550 psig, and the time required to achieve a productivity of 3000 grams of polymer per gram of catalyst.

[0058] Alternatively or concurrently, the activated catalyst according to the invention can produce a polymer under standard polymerization conditions that, when compared under the same or substantially the same MI (or HLMI), has a Mw that is 30% (or 25%, 20%, 15%, or 10%) smaller than that of a polymer produced using the control catalyst as defined above, depending on the context.

[0059] Surprisingly, the activated catalyst according to the invention can produce polymers with low gel content. In one aspect, the activated catalyst can produce polymers under standard polymerization conditions, wherein the total number of membrane gels (or catalyst particle gels) of the polymer is less than or equal to 100 gels per 25 micrometers thick membrane square feet (and in some cases, less than or equal to 80, or less than or equal to 60, or less than or equal to 40, or less than or equal to 30, or less than or equal to 20, or less than or equal to 10, or less than or equal to 8, or less than or equal to 5 gels per 25 micrometers thick membrane square feet), wherein the membrane gels contain a size (diameter) greater than 200 μm (and for catalyst particle gels, this is caused by the catalyst particles).

[0060] Generally, the disclosed methods are applicable to activating any supported chromium precatalyst containing a silica support, thereby forming an activated chromium catalyst in which at least a portion of the chromium is in a hexavalent oxidation state. Therefore, the supported chromium precatalysts covered herein include those prepared by contacting a silica support with a chromium-containing compound (chromium precursor, chromium source) and a titanium-containing compound (titanium precursor, titanium source). The precatalyst is generally referred to as a chromium titanate / silica precatalyst. The precatalyst can be formed by depositing a water-soluble titanium compound and a water-soluble chromium compound onto a pre-formed silica in the form of an aqueous slurry, followed by spray drying the slurry. Alternatively, the precatalyst can be formed by depositing a water-soluble titanium compound onto a pre-formed silica containing the desired chromium in the form of an aqueous slurry, followed by spray drying the slurry.

[0061] Typical titanium compounds include titanium carboxylate, which may also contain nitrogen compounds to help regulate pH, but is not limited thereto. Carboxylate salts can be dicarboxylic or tricarboxylic acids, as well as α-hydroxy monocarboxylic acids, examples of which include oxalic acid, citric acid, malic acid, lactic acid, glycolic acid, gluconic acid, 2-hydroxybutyric acid, glyoxylic acid, malonic acid, phosphonoacetic acid, tartaric acid, etc. Suitable nitrogen compounds include simple alkylamines, alkanolamines, cyclic amines, and more complex polynitrogen compounds, as well as amides and quaternary ammonium hydroxides. Examples include dimethylformamide (DMF), acetamide, acrylamide, allylamine, ammonia, methylamine, diethylamine, ethanolamine, diethanolamine, butylamine, tert-butylamine, N,N'-dibutylurea, tetraethylammonium hydroxide, ammonium hydroxide, dimethylethanolamine, creatine, creatine anhydride, 1,8-diazabicyclo[5.4.0]undec-7-ene (DBU), diethylhydroxylamine, diisopropanolamine, dimethylaminoethanol, dimethylcarbamate, di... Methylformamide, dimethylglycine, dimethylisopropanolamine, N,N'-dimethylurea, ethylamine, ethylene glycolamine, hexylamine, hydroxylamine, imidazole, isopropanolamine, methacrylamide, N-methylaniline, N-methyl-2-propanolamine, methyldiethanolamine, methylformamide, propylamine, 2-propanolamine, pyrazole, pyrrolidine, pyrrolidone, succinimide, tetraethylammonium hydroxide, tetramethylammonium hydroxide, triethanolamine, triisopropanolamine, trimethylamine, urea, etc. Typical chromium compounds include chromium acetate(III), basic chromium acetate(III), chromium formate(III), Cr₂O₃, Cr(OH)₃, Cr(NO₃)₃, etc. Generally, chromium compounds are trivalent, but hexavalent chromium compounds are also suitable, provided they are reduced to their trivalent form during catalyst manufacturing. The silica used in this invention can be any suitable pre-formed silica dry gel with an acceptable porosity, the grade of which is available from Asahi Glass and Grace (e.g., HA30W). A BET surface area of ​​300 to 500 m² is preferred. 2 / g, pore volume of 1.5 to 2.0 m³2 Silica with a d50 average particle size of 30 to 130 micrometers (e.g., about 1.6 mL / g) and a d50 average particle size of 30 to 130 micrometers (e.g., 40 to 70 micrometers), but not limited thereto. Additional information regarding precatalysts that can be activated as described herein and methods for preparing said precatalysts is provided in representative U.S. Patent Nos. 10,300,460, 10,323,109, 10,513,570, 10,543,480, 10,722,874, 10,858,456, 10,889,664, and 11,242,416.

[0062] Chromium polymerization catalysts generally require supports with relatively high porosity to allow for catalyst fragmentation and subsequent detachment of polymer chains from the fragments, some of which are hundreds of times longer than the catalyst's pore size. Therefore, the total pore volume of the pre-catalyst (or silica support, or activated chromium catalyst) is typically in the range of 0.5 to 5 mL / g, and more commonly in the ranges of 1 to 5 mL / g, 1 to 3 mL / g, or 1.5 to 2 mL / g, etc. The BET surface area of ​​the pre-catalyst (or silica support, or activated chromium catalyst) is not limited to any particular range, but is typically in the range of 100 to 700 m². 2 Within the range of / g, for example, in the range of 200 to 600 m 2 / g, 250 to 550 m 2 / g or 300 to 500 m 2 Within the range of / g, etc.

[0063] The precatalyst, silica support, and activated chromium catalyst can have any suitable shape or form, and this can depend on the type of polymerization method in which the chromium catalyst is used. However, in general, the precatalyst, silica support, and activated chromium catalyst have relatively small particle sizes, with representative ranges for the average (d50) particle size of the precatalyst (or silica support, or activated chromium catalyst) including, but not limited to, 10 to 500 micrometers, 15 to 250 micrometers, 30 to 130 micrometers, or 40 to 70 micrometers.

[0064] Similarly, there is no particular limitation on the amount of chromium in the precatalyst (before activation) in a +5 oxidation state or lower. The amount of chromium in the precatalyst in a +5 oxidation state or lower is at least 50% by weight, and more typically at least 60% by weight, at least 70% by weight, at least 80% by weight, at least 90% by weight, or at least 95% by weight. This percentage is expressed as the ratio of the amount of chromium in the precatalyst in a +5 oxidation state or lower to the total amount of chromium on the precatalyst.

[0065] Conversely, at least 40% by weight of chromium in the activated chromium catalyst is present in the hexavalent oxidation state after the activation step, and more typically at least 50% by weight of chromium is present as chromium (VI). In other respects, at least 60%, at least 70%, at least 80%, at least 90%, or at least 95% by weight of chromium in the activated chromium catalyst may be present in the +6 oxidation state. These weight percentages are based on the total amount of chromium present on the activated chromium catalyst. Conventional chromium (VI) catalysts typically exhibit an orange, yellow, or brownish hue, indicating the presence of chromium (VI).

[0066] Aggregation methods Olefin polymers (e.g., ethylene polymers) can be produced using any suitable olefin polymerization method and various types of polymerization reactors, polymerization reactor systems, and polymerization reaction conditions by an activated chromium catalyst. One such olefin polymerization method may include (I) performing any method to produce the activated chromium catalyst disclosed herein; and (II) contacting the activated chromium catalyst and optionally a co-catalyst with olefin monomers and optionally olefin comonomers under polymerization conditions in a polymerization reactor system including a circulating slurry reactor to produce the olefin polymer. The invention also covers any olefin polymer (e.g., ethylene polymer) produced by any polymerization method disclosed herein.

[0067] In polymerization methods, the co-catalyst can be used in conjunction with an activated chromium catalyst. In one aspect, the co-catalyst can comprise an aluminum oxane compound, an organoaluminum compound, or an organoboron compound, and this includes combinations of various co-catalyst compounds. Representative and non-limiting examples of aluminum oxanes include methylaluminoxane, modified methylaluminoxane, ethylaluminoxane, n-propylaluminoxane, isopropylaluminoxane, n-butylaluminoxane, tert-butylaluminoxane, sec-butylaluminoxane, isobutylaluminoxane, 1-pentylaluminoxane, 2-pentylaluminoxane, 3-pentylaluminoxane, isopentylaluminoxane, neopentylaluminoxane, etc., or any combination thereof. Representative and non-limiting examples of organoaluminum compounds include trimethylaluminum, triethylaluminum, tri-n-propylaluminum, tri-n-butylaluminum, triisobutylaluminum, tri-n-hexylaluminum, tri-n-octylaluminum, diisobutylaluminum hydride, diethylaluminum ethanol, diethylaluminum chloride, etc., or any combination thereof. Representative and non-limiting examples of organoboron compounds include tri-n-butylborane, tripropylborane, triethylborane, and any combination thereof. The cocatalysts that can be used are not limited to those described above. Other suitable cocatalysts (e.g., organomagnesium and organolithium) are well known to those skilled in the art, including, for example, those disclosed in U.S. Patent Nos. 3,242,099, 4,794,096, 4,808,561, 5,576,259, 5,807,938, 5,919,983, 7,294,599, 7,601,665, 7,884,163, 8,114,946, and 8,309,485.

[0068] As used herein, a “polymerization reactor” includes any polymerization reactor capable of polymerizing olefin monomers and comonomers (one or more comonomers) to produce homopolymers, copolymers, terpolymers, etc. Various types of polymerization reactors include those that may be referred to as batch reactors, slurry reactors, gas-phase reactors, solution reactors, high-pressure reactors, tubular reactors, autoclave reactors, etc., or combinations thereof; or alternatively, polymerization reactor systems may include slurry reactors, gas-phase reactors, solution reactors, or combinations thereof. The 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 include vertical and / or horizontal circulation. High-pressure reactors may include autoclaves and / or tubular reactors. Reactor types may include batch or continuous processes. Continuous processes may use batch and / or continuous product discharge. Polymerization reactor systems and processes may also include partial or complete direct recycling of unreacted monomers, unreacted comonomers, and / or diluents.

[0069] Polymerization reactor systems may include a single reactor or multiple reactors of the same or different types (two reactors, more than two reactors). For example, a 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. Polymer production in multiple reactors may include several stages in at least two separate polymerization reactors interconnected by transfer devices, making it possible to transfer polymer obtained from a first polymerization reactor to a second reactor. The polymerization conditions required in one reactor may differ from the operating conditions of the other reactors. Alternatively, polymerization in multiple reactors may include manually transferring polymer from one reactor to a subsequent reactor to continue polymerization. Multiple reactor systems may include any combination, including but not limited to multiple circulating reactors, multiple gas-phase reactors, a combination of circulating and gas-phase reactors, multiple high-pressure reactors, or a combination of high-pressure reactors with circulating and / or gas-phase reactors. Multiple reactors may operate in series, in parallel, or in a combination of series and parallel. Therefore, the present invention covers polymerization reactor systems including a single reactor, including two reactors, and including more than two reactors. In some aspects of the invention, a polymerization reactor system may include a slurry reactor, a gas-phase reactor, a solution reactor, and combinations thereof.

[0070] According to one aspect, the polymerization reactor system may include at least one circulating slurry reactor comprising vertical or horizontal circulation. Monomers, diluents, catalysts, and comonomers may be continuously fed into the circulating reactor where polymerization occurs. Typically, a continuous process may include the continuous introduction of monomers / comonomers, catalysts, and diluents into the polymerization reactor, and the continuous removal of a suspension containing polymer particles and diluents from the reactor. The reactor effluent may be flashed to remove solid polymers from the liquid containing diluents, monomers, and / or comonomers. Various techniques may be used for this separation step, including but not limited to flashing, which may include any combination of heating and depressurization, separation by cyclone action in a cyclone separator or hydrocyclone, or separation by centrifugation.

[0071] Typical slurry polymerization processes (also known as particle-forming processes) are disclosed, 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. Suitable diluents used in slurry polymerization include, but are not limited to, the monomers 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 cyclic polymerization reactions can occur under bulk conditions without the use of diluents.

[0072] According to another aspect, the polymerization reactor system may include at least one gas-phase reactor (e.g., a fluidized bed reactor). Such reactor systems may employ a continuous recycle stream containing one or more monomers, which is continuously circulated through a fluidized bed under polymerization conditions in the presence of a catalyst. The recycle stream can be discharged from the fluidized bed and recycled back into the reactor. Simultaneously, polymer products can be discharged from the reactor, and new or fresh monomers can be added to replace the monomers polymerized. These gas-phase reactors may comprise a multi-step gas-phase polymerization method for olefins, wherein the olefins are polymerized in the gas phase in at least two separate gas-phase polymerization zones, while a catalyst-containing polymer formed in the first polymerization zone is fed into a second polymerization zone. Representative gas-phase reactors are disclosed in U.S. Patent Nos. 5,352,749, 4,588,790, 5,436,304, 7,531,606, and 7,598,327.

[0073] According to another approach, the polymerization reactor system may include a high-pressure polymerization reactor, such as a tubular reactor or an autoclave reactor. The tubular reactor may have several zones in which fresh monomers, initiators, or catalysts are added. The monomers may be entrained in an inert gas stream and introduced in one zone of the reactor. The initiator, catalyst, and / or catalyst components may be entrained in the gas stream and introduced in another zone of the reactor. The gas streams may be intermixed for polymerization. Heat and pressure may be appropriately used to obtain optimal polymerization reaction conditions.

[0074] According to another aspect, the polymerization reactor system may include a solution polymerization reactor, in which the monomer / comonomer is contacted with the catalyst by suitable stirring or other means. A support containing an inert organic diluent or excess monomer may be used. If necessary, the monomer / comonomer may be contacted with the catalytic reaction products in the gas phase, with or without liquid material. The polymerization zone may be maintained at temperatures and pressures that allow a polymer solution to form in the reaction medium. Stirring may be used to obtain better temperature control and maintain a homogeneous polymerization mixture throughout the polymerization zone. Appropriate means are used to dissipate the exothermic reaction.

[0075] The polymerization reactor system may also include any combination of at least one feed system, at least one feed system for catalyst or catalyst components, and / or at least one polymer recovery system. Suitable reactor systems may also include systems for feedstock purification, catalyst storage and preparation, extrusion, reactor cooling, polymer recovery, fractionation, recycling, storage, loading output, 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 or pulsedly).

[0076] Polymerization conditions that can be controlled to improve efficiency and provide desired polymer properties can include temperature, pressure, and the concentrations of various reactants. Polymerization temperature can affect catalyst yield, polymer molecular weight, and molecular weight distribution. For example, to produce a specific grade of olefin polymer (or ethylene polymer), various polymerization conditions can be kept substantially constant. According to the Gibbs free energy equation, a suitable polymerization temperature can be any temperature below the depolymerization temperature. Typically, depending on the type of polymerization reactor, this includes, for example, 60°C to 280°C or 60°C to 120°C. In some reactor systems, polymerization temperatures are generally in the range of about 70°C to 105°C or 75°C to 100°C.

[0077] The appropriate pressure will also vary depending on the reactor and type of polymerization. Liquid-phase polymerization in a circulating reactor typically occurs at pressures less than 1000 psig (6.9 MPa). Gas-phase polymerization typically occurs at pressures of approximately 200 to 500 psig (1.4 MPa to 3.4 MPa). High-pressure polymerization in tubular reactors or autoclaves typically occurs at 20,000 to 75,000 psig (138 MPa to 517 MPa). Polymerization reactors can also be operated in the supercritical region, generally at higher temperatures and pressures. Operation above the critical point (supercritical phase) of the pressure / temperature diagram can provide advantages for the polymerization process.

[0078] Olefin monomers that can be used with the chromium catalyst and polymerization method of the present invention typically include olefin compounds having 2 to 30 carbon atoms per molecule and having at least one olefinic double bond, such as ethylene or propylene. In one aspect, the olefin monomer may contain C2-C... 20 Olefins; alternatively, C2-C 20 α-olefins; alternatively, C2-C 10 Olefins; alternatively, C2-C 10 α-olefin; alternatively, the olefin monomer may contain ethylene; or alternatively, the olefin monomer may contain propylene (e.g., to produce polypropylene homopolymers or propylene-based copolymers).

[0079] When copolymers (or alternatively, terpolymers) are required, the olefin monomers and olefin comonomers may independently contain, for example, C2-C. 20 α-olefins. In some respects, the olefin monomer may contain ethylene or propylene, which is comonomerized with at least one comonomer (e.g., C2-C). 20 α-olefins or C3-C 20 (α-olefin) copolymerization. According to one aspect of the invention, the olefin monomer used in the polymerization process may contain ethylene. In this aspect, the comonomer may contain C3-C... 10 α-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.

[0080] On the one hand, the polymerization method can be carried out in a commercial circulating reactor at a production rate of 2000 to 5000 grams of polymer per gram of catalyst and / or a space-time yield greater than or equal to 2, 2.5, 2.8, 3, or 4 (lb / h) / gallon and / or less than or equal to 6, 5.5, or 5 (lb / h) / gallon, to prepare an ethylene / 1-hexene copolymer with a density of at least 0.947 g / cc, said density being determined by ISO 1183 Part 2. The space-time yield can be in the range of any minimum to any maximum value listed above, and therefore representative and non-limiting ranges of space-time yield include 2 to 6, 2 to 5, 2.5 to 5.5, 2.8 to 6, 3 to 6, 3 to 5.5, 4 to 6, or 4 to 5 (lb / h) / gallon.

[0081] On the other hand, the polymerization method can be carried out in a commercial circulating reactor at a production rate of 2000 to 5000 grams of polymer per gram of catalyst and / or a space-time yield greater than or equal to 2, 2.5, 2.8, 3, or 4 (lb / h) / gallon and / or less than or equal to 6, 5.5, or 5 (lb / h) / gallon, to prepare an ethylene / 1-hexene copolymer with a density of at least 0.938 g / cc, said density being determined by ISO 1183 Part 2. As mentioned above, the space-time yield can be in the range of any minimum to any maximum value listed above, and therefore representative and non-limiting ranges of space-time yield include 2 to 6, 2 to 5, 2.5 to 5.5, 2.8 to 6, 3 to 6, 3 to 5.5, 4 to 6, or 4 to 5 (lb / h) / gallon.

[0082] Ethylene polymers and olefin polymers This invention also relates to and includes olefin polymers manufactured using any of the chromium catalysts and polymerization methods disclosed herein. The olefin polymers included herein may include any polymers manufactured from any olefin monomers and optional comonomers described herein. For example, olefin polymers may include ethylene homopolymers, ethylene copolymers (e.g., ethylene / α-olefin, ethylene / 1-butene, ethylene / 1-hexene, ethylene / 1-octene, etc.), propylene homopolymers, propylene copolymers, ethylene terpolymers, propylene terpolymers, etc., including any combination thereof. In one aspect, the olefin polymer may include ethylene homopolymers, ethylene / 1-butene copolymers, ethylene / 1-hexene copolymers, and / or ethylene / 1-octene copolymers, while in another aspect, the olefin polymer may include ethylene / 1-hexene copolymers.

[0083] If the resulting polymer produced according to the invention is, for example, an ethylene polymer, its properties can be characterized by various analytical techniques known and used in the polyolefin industry. Articles may be formed from and / or may contain the olefin polymers of the invention (e.g., ethylene polymers), the typical properties of which are provided below.

[0084] Illustrative and non-limiting examples of first ethylene polymers (e.g., ethylene / α-olefin copolymers) produced using the activated chromium catalyst disclosed herein may have high loading melt index (HLMI) in the range of 10 to 80 g / 10 min and in the range of 0.93 to 0.96 g / cm³. 3 The density within the range and the total number of membrane gels per square foot of 25 micrometers thick film, less than or equal to 100 gels (or less than or equal to 80, 60, 40, 30, 20, 10, 8, or 5 gels), where the membrane gels contain a size greater than 200 µm. Alternatively, the number of gels > 200 micrometers caused by undisturbed catalyst particles (e.g., undisturbed Cr / silica catalyst particles) can be less than or equal to 100 gels per square foot of 25 micrometers thick film, or less than or equal to 80, 60, 40, 30, 20, 10, 8, or 5 gels per square foot of 25 micrometers thick film. The ethylene polymer contains a total of 150 to 680 ppm of silica, 1.5 to 6.8 ppm of chromium, and 1.5 to 40 ppm of titanium (both decomposed and unfragmented).

[0085] Illustrative and non-limiting examples of second ethylene polymers (e.g., ethylene / α-olefin copolymers) may have a melt index (MI) in the range of 0.1 g / 10 min to 1 g / 10 min and a melt flow rate in the range of 0.93 to 0.96 g / cm³. 3 The density within the range and the total number of membrane gels per square foot of 25 micrometers thick film is less than or equal to 100 gels (or less than or equal to 80, 60, 40, 30, 20, 10, 8, or 5 gels per square foot of 25 micrometers thick film), wherein the membrane gels contain a size greater than 200 µm (and for catalyst particle gels, the number is caused by undisturbed catalyst particles). The ethylene polymer contains 150 to 680 ppm of silica, 1.5 to 6.8 ppm of chromium, and 1.5 to 40 ppm of titanium.

[0086] Furthermore, unless otherwise stated, these illustrative first and second ethylene polymers (generally in granule or bead form) according to the invention may also have any and any combination of the polymer properties listed below.

[0087] The density of ethylene-based polymers typically ranges from 0.93 to 0.96 or 0.93 to 0.956 g / cm³. 3 Within a certain range. On the one hand, the density can be in the range of 0.934 to 0.96; on the other hand, it can be in the range of 0.934 to 0.956; in yet another aspect, it can be in the range of 0.934 to 0.95; or in yet another aspect, it can be in the range of 0.945 to 0.958 g / cm³. 3 Within the range.

[0088] Ethylene polymers can exhibit a variety of melt flow characteristics, for example, expressed by a high load melt index (HLMI) in the range of 10 to 80 g / 10 min. In some respects, the HLMI of ethylene polymers can fall within the ranges of 10 to 70, 10 to 60, 10 to 50, 20 to 80, 20 to 50, or 30 to 50 g / 10 min, etc. Alternatively or additionally, these ethylene polymers can have a melt index (MI) of 0.1 to 1 g / 10 min, and more typically, have MIs of 0.1 to 0.75, 0.1 to 0.6, 0.2 to 1, 0.2 to 0.6, or 0.3 to 0.6 g / 10 min, etc.

[0089] On one hand, the ethylene polymer may have Mw in the range of 100,000 to 250,000 g / mol, 120,000 to 200,000 g / mol, or 140,000 to 180,000 g / mol. For example, Mw may be less than or equal to 180,000 g / mol, less than or equal to 170,000 g / mol, or less than or equal to 160,000 g / mol. Alternatively or additionally, the ethylene polymer may have Mn in the range of 3,000 to 25,000 g / mol, 8,000 to 20,000 g / mol, 10,000 to 18,000 g / mol, or 12,000 to 15,000 g / mol. For example, Mn may be less than or equal to 15,000 g / mol, less than or equal to 14,000 g / mol, or less than or equal to 13,000 g / mol. Alternatively or concurrently, the ethylene polymer may have an Mz of 500,000 to 2,000,000 g / mol, 500,000 to 1,800,000 g / mol, or 600,000 to 1,500,000 g / mol. For example, Mz may be less than or equal to 1,300,000 g / mol, less than or equal to 1,100,000 g / mol, or less than or equal to 1,000,000 g / mol. Not limited thereto, these ethylene polymers may have an Mw / Mn ratio in the range of 7 to 20, for example, 8 to 18, 9 to 17, 9 to 15, or 10 to 14. For example, Mw / Mn may be less than or equal to 14, less than or equal to 13, less than or equal to 12.5, or less than or equal to 11.5. Similarly, representative ranges for Mz / Mw ratios include 5 to 10, 5 to 9, 6 to 10, or 6 to 9. For example, Mz / Mw can be less than or equal to 8, less than or equal to 7.5, less than or equal to 7, less than or equal to 6.5, or less than or equal to 6.

[0090] Alternatively or concurrently, the CY-a parameter of these ethylene polymers may be 0.1 to 0.3 on one hand, 0.13 to 0.2 on another, 0.13 to 0.17 on another, 0.16 to 0.26 on another, 0.17 to 0.24 on yet another, and 0.18 to 0.22 on yet another. For example, the CY-a parameter may be less than or equal to 0.18, less than or equal to 0.17, less than or equal to 0.165, less than or equal to 0.16, less than or equal to 0.155, or less than or equal to 0.15. This rheological parameter is determined from viscosity data measured at 190 °C using the Carreau-Yasuda (CY) empirical model described herein.

[0091] Furthermore, as discussed herein, the ethylene polymer is produced in the presence of a supported active chromium catalyst. Ziegler-Natta catalyst systems and metallocene-based catalyst systems are not required. Therefore, the ethylene polymer may be free of measurable amounts of zirconium, hafnium, titanium, vanadium, or magnesium (catalyst residues), i.e., less than 0.1 ppm by weight. In some respects, the ethylene polymer may independently contain less than 0.08 ppm, less than 0.05 ppm, or less than 0.03 ppm of zirconium (or hafnium, or titanium, or vanadium, or magnesium). The amounts of these elements can be determined by ICP analysis on a PerkinElmer Optima 8300 instrument. The polymer sample can be ashed overnight in a Thermolyne furnace with sulfuric acid, followed by acid digestion in a HotBlock with HCl and HNO3 (3:1 v:v).

[0092] In practice, ethylene polymers typically contain 1.5 to 6.8 ppm of chromium, 1.5 to 40 ppm of titanium, and 150 to 680 ppm of silica (by weight). Other illustrative ranges for chromium content in these ethylene polymers include, but are not limited to, 1.8 to 6 ppm, 2 to 6.8 ppm, 2 to 6 ppm, 2 to 5 ppm, 2 to 4.5 ppm, 2 to 4 ppm, 1.5 to 6 ppm, 1.5 to 5.5 ppm, 1.5 to 5 ppm, or 3 to 6 ppm of chromium. Other illustrative ranges for titanium content in these ethylene polymers include, but are not limited to, 1.5 to 30 ppm, 2 to 40 ppm, 2 to 30 ppm, 2 to 10 ppm, 3 to 30 ppm, 3 to 20 ppm, 3 to 10 ppm, 4 to 20 ppm, 5 to 40 ppm, 5 to 25 ppm, 5 to 15 ppm, 7 to 17 ppm, or 8 to 16 ppm of titanium. The amounts of these elements can be determined by ICP analysis on a PerkinElmer Optima 8300 instrument. Other illustrative ranges for silica content in these ethylene polymers include, but are not limited to, 180 to 600 ppm, 200 to 680 ppm, 200 to 600 ppm, 200 to 500 ppm, 200 to 400 ppm, 150 to 600 ppm, 150 to 500 ppm, or 150 to 450 ppm silica. The silica content of the polymer is quantified by the ASTM ash test, as discussed below.

[0093] The amount of gel can be based on the total number of membrane gels (all membrane defects with a diameter greater than 200 micrometers) or the number of catalyst particle gels (membrane defects with a diameter greater than 200 micrometers caused by catalyst particles), i.e., the number of gels per 25 micrometers thick ethylene polymer membrane. Most gels in chromium-derived polymers are catalyst particle gels (hard gels) caused by supported catalyst particles. When using these supported chromium catalysts for ethylene polymerization, most catalyst particles break down or decompose into barely perceptible small fragments that are dispersed in the final polymer and do not cause problems, especially in thin-film products. However, depending on the polymerization conditions, some catalyst particles may be discharged from the reactor before becoming active and therefore before decomposing due to polymerization. These unbroken catalyst particles can cause visual defects on the surface of the final product or article, commonly referred to as “gels”, “hard gels”, or “catalyst gels,” and membrane grades are particularly sensitive to this problem (notably, such catalyst particle gels can also produce noticeable defects on the surface of thick parts, resulting in poor surface aesthetics of the final product or article, and this surface roughness can also interfere with printing operations). Therefore, polymer membrane grades typically have strict manufacturing specifications for gels with a diameter greater than 200 micrometers. During polymer manufacturing, the polymer forms a 25-micron film, and the gel count is automatically measured by an online camera specifically designed to count gels larger than 200 microns. The total gel count includes catalyst particle gels as well as gels formed due to contamination such as foreign matter, polymer particles, or additive particles.

[0094] Typically, to be considered a "gel," optical defects identified by the camera and computer on a gel analyzer must be recorded as gel sizes greater than 200 µm in diameter. Empirically, catalyst particles with diameters of 100+ µm are often recorded as 200+ µm gels because polymers sometimes adhere to the catalyst particles, thereby increasing their size, and also due to the "lens effect," where the catalyst particles appear larger due to the lenticular polymer coating. The latter is an optical magnification of the catalyst particle size because a convex lens made of transparent polymer forms around the catalyst particle. Therefore, catalyst particle gelation can be reduced by minimizing catalyst particles with a size of 100 μm or larger in the ethylene polymer.

[0095] Another unexpected benefit of using the supported chromium catalyst activated as described herein is the improved processability of the ethylene polymers compared to polymers produced using chromium catalysts activated in a conventional manner (control or comparative examples, discussed further below). In extrusion processing for blown films, pipes, blow molding, and other conversion applications, the extrusion pressure can be reduced by at least 3%, at least 5%, at least 8%, or at least 10%, or at least 15%, and in some cases by up to 20% or more. This improved processability can be measured or quantified on a granulating extruder that forms the ethylene polymer into granules or beads, or on an extruder used for film manufacturing. Therefore, this also applies to granulation performed during the manufacture of the polymers of this invention. Again, the extrusion pressure can be reduced by at least 3%, 5%, 8%, 10%, or 15%, or up to 20% or more.

[0096] Similarly, for the polymers of the present invention, the melt temperature is typically low during extrusion, molding, granulation, and other processes. The extrusion melt temperature can typically be reduced by at least 5℉, 8℉, 10℉, 15℉, or 20℉, or up to 25℉ (3℃, 4℃, 6℃, 8℃, or 11℃, or up to 14℃), or more. Furthermore, compared to polymers made with controlled catalysts, power consumption is also reduced during the corresponding extrusion process, measured as the current intensity of the extruder. Power consumption can typically be reduced by at least 5%, or at least 8%, or 10%, or 12%, or 15%. Additionally, the specific energy or work imparted to the polymer can be reduced by at least 1%, or 2%, or 3%, or 4%.

[0097] Another advantage of polymers prepared using the catalyst of this invention is that they typically exhibit enhanced mixing during extrusion. Evidence of this is the significant drop in melt index as the material passes through the extruder, indicating increased chain entanglement. The melt index change can be at least 0.21 g, or 0.22 g, or 0.23 g, or 0.24 g, or 0.25 g, or 0.26 g per 10 minutes. When expressed as a percentage, this can be a melt index decrease of at least 30%, 40%, 42%, 45%, or 48%, and a melt index decrease of up to 50%, 55%, or 60%, or more. HLMI may also decrease by a similar percentage.

[0098] Products and products Articles may be formed from the olefin polymers (e.g., ethylene polymers) of the present invention, and / or may contain the olefin polymers (e.g., ethylene polymers) of the present invention, and are therefore covered herein. For example, articles that may contain the polymers of the present invention may include, but are not limited to, agricultural films, geomembranes, packaging films, pallet wrapping films, automotive parts, bottles, chemical containers, barrels, fibers or fabrics, food packaging films or containers, food contact articles, fuel tanks, geomembranes, household containers, liners, molded products, medical devices or materials, outdoor storage products, outdoor recreational equipment, pipes, sheets or tapes, toys or traffic barriers, etc. Various processes can be used to form these articles. Non-limiting examples of these methods include injection molding, blow molding, rotational molding, film extrusion, sheet extrusion, profile extrusion, thermoforming, etc. Furthermore, additives and modifiers are typically added to these polymers to provide beneficial polymer processing or end-use product properties. A description of such methods and materials is provided in [link to description]. Modern Plastics Encyclopedia Mid-November 1995, Volume 72, Issue 12; and Film Extrusion Manual - Process, Materials, Properties , TAPPI Publishing, 1992. In some aspects of the invention, the article may comprise any of the olefin polymers (or ethylene polymers) described herein, and the article may be or may comprise a film (e.g., a blown film), a tube, or a blow-molded product.

[0099] Example The following embodiments further illustrate the present invention, and these embodiments should not be construed as limiting the scope of the invention in any way. After reading this description, those skilled in the art will realize various other aspects, modifications, and equivalents without departing from the spirit of the invention or the scope of the appended claims.

[0100] Standard catalyst activation for control or comparative catalysts in laboratory testing is performed as follows: Approximately 10 g of catalyst sample is placed in a 1.75-inch quartz tube with a sintered quartz disc at the bottom. While the catalyst is loaded onto the disc, dry air is blown through the disc at a linear rate of 1.6–1.8 standard cubic feet per hour (45–51 L / hr). The electric furnace around the quartz tube is then turned on, and the temperature is increased to the specified temperature at a rate of 400 °C / hour, typically reaching 650 °C. At this temperature, the catalyst is fluidized in dry air for 3 hours. Subsequently, the catalyst is collected and stored under dry nitrogen, protecting it from oxygen and moisture, until it is ready for polymerization testing.

[0101] The catalyst of this invention uses the same equipment as in a laboratory setting, but the procedure is significantly different. Typically, the catalyst is circulated between air and nitrogen at a low temperature, then heated to a maximum temperature in nitrogen. After holding this temperature for a period, the temperature is lowered to another temperature, at which point the gas flow is switched to air. After holding this temperature for a further period, the catalyst is cooled in air to 200-350°C. At this temperature, the gas flow is switched back to nitrogen, and the catalyst is purged in nitrogen for another 30 minutes. The catalyst is then cooled to ambient temperature in nitrogen and bottled for subsequent testing. This general activation procedure is used, but the specific temperature and time vary depending on the experiment.

[0102] Activation method A: Treat the catalyst according to the standard activation procedure of the control or comparative catalyst.

[0103] Activation method B: The same procedure as in activation A is used, but the final temperature is 704℃ instead of 650℃.

[0104] Activation Method C: The catalyst is added in two portions under nitrogen. The following cycle is performed three times: The temperature is raised to 350°C in air, then cooled to 150°C in nitrogen. Then, the temperature is raised to 704°C in nitrogen and held for 4 hours. The temperature is cooled to 550°C in nitrogen and then switched to air. The temperature is held in air for 1 hour. The temperature is cooled to 300°C in air, then purged with nitrogen for 30 minutes, cooled, and bottled.

[0105] Activation method D: The same procedure as in activation C is used, but the holding time at 550°C is 2 hours instead of 1 hour.

[0106] Other catalyst activation (method EH) was carried out in a large fluidized bed calciner with a diameter of 42 inches, where the gas flow rate was 0.1 ft / s at temperatures below 700°C and 0.2 ft / s at temperatures above that. The calciner was designed similarly to the quartz laboratory activator, only constructed on a larger scale. The temperatures (within the calciner) were the average of three (3) thermocouples located at the top, bottom, and middle of the fluidized bed calciner. The catalyst / pre-catalyst temperature was effectively the same as the calciner temperature.

[0107] Activation Method E: 600 pounds of catalyst are charged into nitrogen atmosphere at once, and then the atmosphere is changed to air. The temperature is increased to 1350℉ (732℃) at a heating rate of 2.7℉ / min (1.5℃ / min). The catalyst is held at this temperature for 8 hours, then cooled to 600℉ (315℃) in air, under which the catalyst is purged with nitrogen for 3 hours, and then vented.

[0108] Activation Method F: At a temperature of 600℉ (315℃), approximately 600 pounds of catalyst are loaded into a calcining furnace in four unequal portions under nitrogen atmosphere. The first portion is slightly smaller than each subsequent portion. With each portion loaded, the temperature is rapidly reduced to 450-500℉ (232-260℃), then restored to 600℉ (315℃). After all catalyst has been loaded, the atmosphere is changed to air, and the temperature begins to rise as volatile compounds on the catalyst are oxidized. When the temperature reaches 900℉ (482℃), the atmosphere is changed back to nitrogen, and the temperature is gradually reduced to approximately 600℉ (315℃). This cycle is repeated three times until no further exothermic reaction occurs. Then, under nitrogen atmosphere, the temperature is increased to 1300℉ (704℃) at a rate of 2.4℉ / min (1.3℃ / min) and maintained at this temperature for 5 hours. Next, the temperature was cooled to 1025℉ (552℃) in nitrogen. The atmosphere was then changed to air, and the catalyst was maintained at the stated temperature for 5 hours. Then, the catalyst was cooled to 650℉ (343℃) in air, and the atmosphere was changed back to nitrogen. After purging for 3 hours, the catalyst was discharged into an airtight metal container.

[0109] Activation method G: Follow the procedure of activation F, but load the catalyst into two equal portions and treat it in air at 1025℉ (552℃) for 2 hours. Figure 1 It is a representation of the time-temperature activation sequence similar to the activation method FG, and Figure 2 Further shown Figure 1 The heat-eliminating part in the process.

[0110] Activation method H: The catalyst is loaded into the air in a single step. The temperature is increased to 1200℉ (649℃) at a rate of 2.7℉ / min (1.5℃ / min) and maintained for 8 hours. Then, it is cooled to 600℉ (315℃) in the air and purged with nitrogen for 3 hours under these conditions before being discharged. Figure 3 A representation of a time-temperature activation sequence similar to activation method H is shown.

[0111] The catalyst, activated in both laboratory and large-scale processes, was tested in polymerization experiments as follows: A marine agitator rotating at 500 rpm was used in a 2.2-liter steel reactor. A steel jacket surrounded the reactor, through which a mixture of steam and water was passed, regulated by electronic controls to maintain a constant temperature of 105°C (+ / - 0.5°C). Unless otherwise stated, a small amount (typically 0.01 to 0.10 g) of solid catalyst was first added to the dry reactor under nitrogen atmosphere. Next, 1.2 L of liquid isobutane was added and the reactor was heated to the specified temperature (105°C). Finally, ethylene was added to the reactor to reach a fixed pressure of 550 psig, which was maintained during the experiment. Stirring continued until approximately 3000 g of polymer was produced per gram of catalyst, and the instantaneous reaction rate was recorded by recording the ethylene flow rate into the reactor to maintain the set pressure.

[0112] Once the desired productivity of 3000 g / g is reached, the ethylene flow is stopped, and the reactor is slowly depressurized and opened to recover the granular polymer powder. In all cases, the reactor is clean, showing no signs of scale, coatings, or other forms of fouling. The polymer powder is then removed and weighed. Activity is specified as the number of grams of polymer produced per gram of solid catalyst charged per hour.

[0113] Then, the melt index and high-load melt index of the recycled polymer were obtained. The melt index (MI, I², g / 10 min) was determined according to ASTM D1238-E, condition 190 / 2, at 190°C using a 2.16 kg weight. The high-load melt index (HLMI, I², g / 10 min) was... 21 The values ​​(g / 10 min) were determined according to ASTM D1238-E, condition 190 / 21.6, at 190°C using a 21.6 kg weight. These two values ​​were obtained from polymers prepared under standardized reactor conditions, and then used to compare the melt index potential (MIP) or high load melt index potential (HLMIP) of each catalyst. Density was determined according to ASTM D1505 and ASTM D4703 on compression-molded samples cooled at 15°C per minute and conditioned at room temperature for 40 hours, in grams per cubic centimeter (g / cm³). 3 ).

[0114] 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 Styragel HMW-6E GPC columns (Waters, MA) operating at 145 °C. The mobile phase of 1,2,4-trichlorobenzene (TCB) containing 0.5 g / L 2,6-di-tert-butyl-4-methylphenol (BHT) was flowed at a rate of 1 mL / min, and the polymer solution concentration ranged from 1.0 to 1.5 mg / mL, depending on the molecular weight. Sample preparation was performed at 150 °C, typically for 4 hours with occasional gentle stirring, followed by transfer of the solution to sample vials for injection. Injection volumes of approximately 400 μL were used. The HDPE polyethylene resin MARLEX from Chevron Phillips Chemical Company was used. ® BHB5003 serves as a broad standard, using an integral calibration method to derive molecular weight and molecular weight distribution. The integral table for the broad standard is pre-determined in a separate experiment using SEC-MALS. 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 peak molecular weight (the position of the highest point on the molecular weight distribution curve).

[0115] Melt rheological characterization was performed as follows. Small strain (less than 10%) oscillatory shear measurements were performed on an Anton Paar MCR rheometer using a parallel plate geometry. All rheological tests were performed at 190 °C. The complex viscosity || was then characterized using a modified three-parameter Carreau-Yasuda (CY) empirical model. η |With frequency ( ω Curve fitting was performed on the changing data to obtain the zero-shear viscosity. η 0 Characteristic viscous relaxation time τ η and width parameter a (CY-a parameters). A simplified Carreau-Yasuda (CY) empirical model is shown below: ,in: | η ( ω The modulus of complex shear viscosity is denoted as |. η 0 =Zero shear viscosity; τ η=Viscous relaxation time (τ(η)); a = "Width" parameter (CY-a parameter); n =The final power-law slope is fixed at 2 / 11; and ω = Angular frequency of oscillatory shear deformation.

[0116] Detailed information on the meaning and interpretation of the CY model and its derived parameters can be found at: CA Hieber and HHChiang. Rheol. Acta , 28, 321 (1989); CA Hieber and HH Chiang, Polym. Eng. Sci. , 32, 931 (1992); and RB Bird, RC Armstrong and O. Hasseger, Dynamics of Polymeric Liquids,Volume 1, Fluid Mechanics , 2nd ed., John Wiley & Sons (1987).

[0117] Six (6) different precatalysts were prepared, each with a slightly different preparation procedure. All procedures began with approximately 550 lbs of silica (dry weight) with a surface area of ​​450 m². 2 The pore volume was 1.9 mL / g. The average d50 particle size was 60 μm. Silica was loaded into a 1000-gallon reactor and mixed with 2750 lbs of deionized water. The slurry was stirred and the other components outlined in Table 1 were added. After adding all components, the mixture was spray-dried to form precatalysts 1-6. Precatalysts 1-6 nominally contained 1 wt% chromium and 3.5 wt% titanium, except for precatalyst 3, which contained 4 wt% titanium. A comparative commercially available catalyst, designated as type M (1 wt% chromium and 2.5 wt% titanium), was also tested, and this catalyst had a surface area of ​​500 m². 2 / g, the pore volume is 2.5 mL / g and the d50 average particle size is 130 micrometers.

[0118] Table 1 (Quantities in pounds) Tables 2-4 summarize the melt index potential of precatalysts 1-6 activated using comparative activation method AB and the activation method CD of the present invention. Each value shown in these tables is an average of several tests. High loading melt index potential (HLMIP) is listed in Table 2, and melt index potential (MIP) is listed in Table 3. In summary, the melt index and HLMI of polymers produced by activation using method CD of the present invention are generally higher than those produced by the comparative activation methods, even when activated at higher temperatures. This is advantageous during commercial operation. Advantageously, as shown below, the realization of this increased MI potential does not adversely affect other polymer properties.

[0119] Similar to Tables 2-4, Table 5 summarizes the melt index potential of precatalysts 1-5 and comparative catalyst M using comparative activation methods E and H, as well as the activation method FG (large-scale fluidized bed calcination) of the present invention. As mentioned above, the melt index and HLMI of polymers produced by the activation of the present invention using method FG are generally higher than those of polymers produced by comparative activation methods, even when activated at higher temperatures. The catalyst activated by methods F and G of this invention was then used in a large 18,000-gallon circulating reactor with isobutane as a diluent to prepare a series of polymers with a density of about 0.938 g / cc and a melt index of about 0.2 g / 10 min. The reaction conditions are shown in Table 6 below.

[0120] The rheological and gel permeation chromatography results are summarized in Table 7 below. Surprisingly, the polymers of this invention, i.e., those prepared using the catalyst activation procedure of this invention, have lower molecular weights and narrower molecular weight distributions (Mw / Mn or Mz / Mw) than the control polymers. The polymers of this invention exhibit lower CY-a parameters (i.e., the width of the relaxation time distribution) and significantly higher HLMI at the same melt index, but with lower molecular weights. Furthermore, the tan δ at a shear rate of 0.1 / sec is also lower. In summary, this is a unique and advantageous combination of rheological and molecular weight properties.

[0121] These molecular weights and rheological characteristics provide some processing advantages during granulation and extrusion / conversion operations. These polymers were then blow-molded into 25-micron films and compared. Physical properties, dart impact resistance, and MD and TD tear resistance were identical within the error range. However, the processing was significantly different. Table 8 summarizes the extrusion and film blow molding performance. The polymers of the present invention improve processing performance. Although MI and density are similar, the extruder current intensity is lower (less energy required) during film blow molding. In Table 8, the average power consumption (current) of the polymers of the present invention is reduced by 17.3%. Similarly, the extrusion pressure measured at the extruder head is lower, and similarly, the pressure at the screen is also lower. The polymers of the present invention require an average of 13.9% lower die head pressure and 15.2% lower screen pressure than the average control polymer. Therefore, the melt temperature is lower due to the improved extrusion processing performance. In the examples shown in Table 8, the average melt temperature of the polymers of the present invention is 6.8℉ (3.8℃) lower than the average melt temperature of the control polymer. These differences were observed even when the extruder speed and output rate were the same.

[0122] The improved extrusion ease of the polymers of this invention is also reflected in polymer granulation during the manufacturing process. Table 9 below summarizes this, comparing the granulation parameters of the polymers of this invention with those of the control polymer. Although the granulation rate and final melt index remained unchanged, the polymers of this invention were easier to extrude than the control polymer. This was reflected in a 9% reduction in pressure and a 4% reduction in specific energy, as well as a 24℉ (13℃) reduction in melt temperature. This means that less polymer is required during granulation, resulting in a lower melt temperature, reducing costs and minimizing mechanical and thermal degradation. However, the melt index of the polymers of this invention varied significantly during granulation. This is shown in Table 9 through absolute MI changes and percentage changes in MI. The decrease in melt index during granulation is a result of increased melt viscosity due to mixing (i.e., chain entanglement). Therefore, the increased decrease in melt index can be considered an indicator of the excellent mixing properties of the polymers of this invention.

[0123] Another surprising aspect of these inventive polymers is their extremely low gel number when forming 25-micron-thick films. During polymer fabrication, measurements of the 25-micron-thick films formed from the polymers were taken using an automated camera, revealing gels larger than 200 microns in diameter. While specifications typically show 170 gels / or less per square foot, these inventive polymers exhibited gel numbers far below that. The gel data are summarized in Table 8. Typical gel numbers during the fabrication of this grade of polymer (density 0.938 g / cc and melt index 0.2 g / 10 min) range from 60 to 120 gels / square foot. However, as shown in Table 8, all of the inventive polymers unexpectedly produced films with single-digit gel numbers. Individual hourly values ​​during fabrication often dropped to 3 gels / square foot, or even 2 gels / square foot. While not wishing to be bound by the following theories, it is believed that the unexpectedly low gel number is a result of a combination of factors: catalyst productivity, high catalyst activation / calcination temperatures, and catalyst particle size distribution. Table 10 summarizes the data on gel number, catalyst productivity, and ppm of ash, titanium, and chromium (ppm of silica is the ash content minus the sum of the chromium and titanium contents). For the polymer of this invention, the chromium content is 3-4 ppm, the titanium content is 12-14 ppm, and the silica content is 330-370 ppm, and as mentioned above, the gel number is less than 10 gels per square foot.

[0124] In addition, 20-25 other polymer samples of the present invention listed in Tables 6-10 were subjected to additional tests; the chromium content was in the range of 2.4-4.2 ppm, the titanium content was in the range of 8.5-14.8 ppm, the silica content was in the range of 233-403 ppm, and the number of gels was in the range of 3-17 gels per square foot (with an average number of about 6 gels per square foot).

[0125] Gel counting was performed on 25 µm thick films from the Killion 125 cast film production line, with a die width of 203 mm. A CR7 winding machine model was used, with a cooling bath temperature of 23°C. The gel inspection area was 3 square meters. The screw diameter was 1.24 inches, running at 10 rpm, with a linear speed of approximately 3 lb / hr, and all temperature zones were set at 400℉. The upper and lower take-up rollers were set to 35. The machine was purged for 120 minutes prior to measurement. The cooling roller speed was set to 23 rpm.

[0126] The number of membrane gels on a 25 µm thick membrane was measured using an automated camera-based gel counting machine; the camera model was FSA100, and the Optical Control System (OCS) software was used. The system consisted of a light source and a detector. The membrane was passed through the system located between the light source and the detector, with an examination width of 150 mm. A 3 m² membrane area was examined, and gels with a diameter greater than 200 µm were analyzed. The membrane was then normalized per square foot, resulting in the gel count measurements for a 25 µm thick membrane per square foot, as shown in Table 8.

[0127] As mentioned above, catalyst particles with a diameter of 100+ µm are typically recorded as 200+ µm gels because polymers sometimes adhere to the catalyst particles, thereby increasing their size, and also due to the "lens effect," where the catalyst particles appear larger due to the lenticular polymer coating. The latter is an optical magnification of the catalyst particle size, as convex lenses made of transparent polymer are formed around the catalyst particles. Therefore, catalyst particle gelation can be reduced by minimizing catalyst particles with a size of 100 μm or larger in the ethylene polymer.

[0128] To determine the amount of all gels present as catalyst particle gels, the composition of each gel (e.g., catalyst particles, cellulose, cross-linked polymers, additives, etc.) can be determined. Those skilled in the art can readily determine the cause of the gel using a variety of non-limiting techniques, such as hot-stage microscopy (and observation of melting behavior), infrared spectroscopy, and electron microscopy. For example, IR spectroscopy can be used to help determine whether the gel is a result of catalyst particles or other substances. In cases where multiple catalysts are used in a reactor to produce different grades of polymers, IR can even be used to determine which catalyst produced the gel.

[0129] The ash content in the polymer can be determined according to ASTM D5630-13 Procedure B). In this document, ASTM ash content includes the amounts of solid oxides (e.g., silica), chromium, and titanium. Since chromium and titanium constitute a very small proportion of the ash content, the ash content is very close to the solid oxide (e.g., silica) content; however, the solid oxide (e.g., silica) content in this document is equal to the ash content minus the sum of the chromium and titanium contents.

[0130] Most Cr polymerization catalysts nominally contain about 1% by weight of total Cr, which is typically present as Cr(III) before calcination. In this final preparation step, the catalyst is activated by calcination, thereby converting a portion of the initial Cr(III) to Cr(VI). The activation process disclosed herein converts most of the Cr to Cr(VI). The chromium(VI) content in the calcined catalyst or ash can be determined as follows. First, a small sample (typically about half a gram) is slurried in about 25 mL of deionized water and 25 mL of 18N sulfuric acid, to which 4 drops of indicator solution (1,10-phenanthroline ferrous(II) sulfate, 0.025 M in water) are added, all in a 250 mL beaker with a magnetic stir bar. The resulting mixture is typically yellow-green. This mixture is titrated with about 0.025 M ferrous ammonium sulfate solution (FAS) with stirring. The mixture should undergo several color changes, becoming greener and gradually turning blue, then finally rapidly turning reddish-orange. The titration is complete when the mixture turns reddish-orange. The weight percentage of Cr(VI) is determined by the following formula: Chromium weight % = 1.733% (FAS molar concentration) (FAS mL) / (sample in g). The invention has been described above with reference to numerous aspects and specific embodiments. Based on the detailed description above, many variations will occur to those skilled in the art. 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, the following aspects (each aspect is described as “comprising”, but alternatively may be “substantially constitutes” or “consisting of”): Aspect 1. A method for manufacturing an activated (calcined) chromium catalyst, the method comprising: (i) contacting a pre-catalyst with a first inert atmosphere at a temperature T1 in the range of 500℉ to 700℉ (260°C to 371°C), wherein the pre-catalyst comprises a silica support and 0.1 to 5 wt% chromium, 0.1 to 10 wt% titanium, and 1 to 5 moles of nitrogen per mole of titanium; (ii) subjecting the pre-catalyst to a cycle of exposure to a first oxidizing atmosphere at a temperature T2 in the range of 500℉ to 700℉ (260°C to 371°C) and exposure to a second inert atmosphere at a temperature T3 in the range of 700℉ to 900℉ (371°C to 482°C), wherein the first oxidizing atmosphere causes an exothermic temperature rise from T2 to T3, thereby triggering the introduction of the second inert atmosphere, resulting in cooling to T2 until the exothermic temperature rise in the first oxidizing atmosphere is less than or equal to 50℉ within 15 minutes. (iii) When heat must be added to maintain T3 in the presence of the first oxidizing atmosphere (28°C); (iv) the precatalyst is heated in a third inert atmosphere to a temperature T4 in the range of 1000°F to 1400°F (538°C to 760°C), and the precatalyst is held in the third inert atmosphere for a holding time t1 in the range of 1 hour to 15 hours at T4; (v) the precatalyst is cooled in a fourth inert atmosphere to a temperature of 900°F to 1200°F. (v) exposing the pre-catalyst to a second oxidizing atmosphere at T5, wherein T5 is lower than T4; (vi) cooling the pre-catalyst in a third oxidizing atmosphere to a temperature in the range of 500℉ to 700℉ (260℃ to 371℃) to produce an activated (calcined) chromium catalyst; and (vii) purging the activated (calcined) chromium catalyst in a fifth inert atmosphere at T6 and cooling it to ambient temperature.

[0131] Aspect 2. The method as defined in Aspect 1, wherein in step (vii), at T6, the activated (calcined) chromium catalyst is purged with the fifth inert atmosphere for a purging time t3 within any suitable range or any range disclosed herein, such as 2 minutes to 20 hours, 5 minutes to 12 hours, 5 minutes to 5 hours, 15 minutes to 4 hours, or 30 minutes to 6 hours.

[0132] Aspect 3. The method as defined in any of the preceding aspects, the method further comprising, prior to step (i), loading the pre-catalyst and heating it to T1 in the first inert atmosphere.

[0133] Aspect 4. The method as defined in aspect 3, wherein the temperature of the pre-catalyst prior to loading is ambient temperature to 120℉ (49°C).

[0134] Aspect 5. The method as defined in aspect 3 or 4, wherein loading the precatalyst into contact step (i) is performed by dividing the total amount of precatalyst into 2-10 portions.

[0135] Aspect 6. The method as defined in aspect 5, wherein during each portion of the total amount of the pre-catalyst, the temperature is maintained within a temperature range of 300 to 600℉ (149°C to 315°C) or 400 to 600℉ (204°C to 315°C).

[0136] Aspect 7. The method as defined in Aspect 5 or 6, wherein loading of each portion of the total pre-catalyst amount is stopped when the temperature drops below 400℉ (204°C) or below 300℉ (149°C).

[0137] Aspect 8. The method as defined in any of Aspects 5 to 7, wherein when the pressure rises above 1 psig, the loading of each portion of the total pre-catalyst quantity is stopped.

[0138] Aspect 9. The method as defined in any of the preceding aspects, wherein the first inert atmosphere, the third inert atmosphere, the fourth inert atmosphere, the fifth inert atmosphere, and the sixth inert atmosphere are the same or different and independently comprise (or substantially consist of, or consist of) nitrogen, argon, or combinations thereof.

[0139] Aspect 10. The method as defined in any of aspects 1 to 9, wherein the third inert atmosphere is the same as the fourth inert atmosphere.

[0140] Aspect 11. The method as defined in any of aspects 1 to 9, wherein the third inert atmosphere is different from the fourth inert atmosphere.

[0141] Aspect 12. The method as defined in any of the preceding aspects, wherein the second inert atmosphere in each cycle of step (ii) is the same or different, and independently comprises (or substantially consists of, or consists of) nitrogen, argon, or a combination thereof.

[0142] Aspect 13. The method as defined in any of the preceding aspects, wherein the second oxidizing atmosphere and the third oxidizing atmosphere independently comprise (or consist substantially of, or consist of) oxygen, air, a mixture of oxygen and an inert gas (e.g., nitrogen), or a combination thereof, having any suitable oxygen volume percentage, for example 1 to 100 volume%, 1 to 50 volume%, 2 to 30 volume%, 3 to 25 volume%, or 4 to 21 volume%.

[0143] Aspect 14. The method as defined in any of Aspects 1 to 13, wherein the second oxidizing atmosphere is the same as the third oxidizing atmosphere.

[0144] Aspect 15. The method as defined in any of aspects 1 to 13, wherein the second oxidizing atmosphere is different from the third oxidizing atmosphere.

[0145] Aspect 16. The method as defined in any of the preceding aspects, wherein the first oxidizing atmosphere in each cycle of step (ii) is the same or different and independently comprises (or substantially comprises, or consists of) oxygen, air, a mixture of oxygen and an inert gas (e.g., nitrogen), or a combination thereof, having any suitable oxygen volume percentage, for example 1 to 100 volume%, 1 to 50 volume%, 2 to 30 volume%, 3 to 25 volume%, or 4 to 21 volume%.

[0146] Aspect 17. The method as defined in any of the preceding aspects, wherein T1 is within any suitable range or any range disclosed herein, such as 550℉ to 650℉ (288℃ to 343℃), 600℉ to 700℉ (315℃ to 371℃) or 600℉ to 650℉ (315℃ to 343℃).

[0147] Aspect 18. The method as defined in any of the preceding aspects, wherein T2 is within any suitable range or any range disclosed herein, such as 600℉ to 700℉ (315℃ to 371℃), 500℉ to 650℉ (260℃ to 343℃), 625℉ to 700℉ (329℃ to 371℃), or 575℉ to 675℉ (302℃ to 357℃).

[0148] Aspect 19. The method as defined in any of the preceding aspects, wherein T3 is within any suitable range or any range disclosed herein, such as 700℉ to 850℉ (371℃ to 454℃), 700℉ to 800℉ (371℃ to 427℃), 725℉ to 900℉ (385℃ to 482℃), or 750℉ to 850℉ (399℃ to 454℃).

[0149] Aspect 20. The method as defined in any of the preceding aspects, wherein step (ii) is carried out until the exothermic rise in temperature in the first oxidizing atmosphere is less than or equal to 40℉ (22°C), less than or equal to 25℉ (14°C), or less than or equal to 10℉ (6°C) within 15 minutes.

[0150] Aspect 21. The method as defined in any of the preceding aspects, wherein step (ii) includes any suitable number of cycles or any number of cycles disclosed herein, such as 2 to 10, 2 to 6, 2 to 4, 2 to 3, 3 to 8, 3 to 5, 4 to 10, or 4 to 6.

[0151] Aspect 22. The method as defined in any of the preceding aspects, wherein any suitable heating rate or any heating rate disclosed herein is used in step (iii), such as 1 to 5℉ / min (0.6 to 3℃ / min), 1.5 to 4℉ / min (0.8 to 2.2℃ / min) or 2 to 3.5℉ / min (1 to 2℃ / min).

[0152] Aspect 23. The method as defined in any of the preceding aspects, wherein T4 is within any suitable range or any range disclosed herein, such as 1000℉ to 1300℉ (538℃ to 704℃), 1100℉ to 1400℉ (593℃ to 760℃), 1100℉ to 1300℉ (593℃ to 704℃), or 1200℉ to 1300℉ (649℃ to 704℃).

[0153] Aspect 24. The method as defined in any of the preceding aspects, wherein t1 is within any suitable range or any range disclosed herein, such as 1 hour to 8 hours, 2 hours to 10 hours, 3 hours to 15 hours, 3 hours to 8 hours or 4 hours to 6 hours.

[0154] Aspect 25. The method as defined in any of the preceding aspects, wherein any suitable cooling rate or any cooling rate disclosed herein is used in step (iv), such as 1 to 4℉ / min (0.6 to 2.2℃ / min), 1.5 to 3.5℉ / min (0.8 to 2℃ / min), or 2 to 3℉ / min (1 to 1.7℃ / min).

[0155] Aspect 26. The method as defined in any of the preceding aspects, wherein T5 is within any suitable range or any range disclosed herein, such as 900℉ to 1100℉ (482℃ to 593℃), 950℉ to 1150℉ (510℃ to 621℃), 1000℉ to 1200℉ (538℃ to 649℃) or 1000℉ to 1100℉ (538℃ to 593℃).

[0156] Aspect 27. The method as defined in any of the preceding aspects, wherein t2 is within any suitable range or any range disclosed herein, such as 30 minutes to 8 hours, 1 hour to 10 hours, 1 hour to 8 hours, 2 hours to 6 hours or 3 hours to 5 hours.

[0157] Aspect 28. The method as defined in any of the preceding aspects, wherein t2 is a time period sufficient, based on the amount of chromium present on the activated chromium catalyst, to form at least 30 wt%, at least 50 wt%, 70 wt%, or at least 80 wt% of chromium (VI).

[0158] Aspect 29. The method as defined in any of the preceding aspects, wherein T6 is within any suitable range or any range disclosed herein, such as 500℉ to 650℉ (260℃ to 343℃), 550℉ to 700℉ (288℃ to 371℃), 550℉ to 650℉ (288℃ to 343℃), or 600℉ to 675℉ (315℃ to 357℃).

[0159] Aspect 30. The method as defined in any of the preceding aspects, wherein T6 is within 50℉ (28℃), 25℉ (14℃), or 10℉ (6℃) of T1.

[0160] Aspect 31. The method as defined in any of the preceding aspects, wherein any suitable cooling rate or any cooling rate disclosed herein is used in step (vi), such as 1 to 4℉ / min (0.6 to 2.2℃ / min), 1.5 to 3.5℉ / min (0.8 to 2℃ / min), or 2 to 3℉ / min (1 to 1.7℃ / min).

[0161] Aspect 32. The method as defined in any of the preceding aspects, wherein, when measured by MI, HLMI or both, the melt index potential of the activated (calcined) catalyst is greater than that of a catalyst (or control catalyst) activated by exposure to an oxidizing atmosphere at a temperature of 1200℉ (649°C) for a period of 3 hours (or 8 hours) but otherwise identical (greater than any suitable amount or any amount disclosed herein, such as at least 10%, at least 25%, at least 50%, at least 75% or at least 100%).

[0162] Aspect 33. The method as defined in any of the preceding aspects, wherein the Mw / Mn (or Mz / Mw, or CY-a parameter) ratio of the polymer produced by the activated (calcined) catalyst under standard polymerization conditions is within 35% (or within 30%, 25%, 20%, 15%, 10% or 5%) of the Mw / Mn (or Mz / Mw, or CY-a parameter) ratio of the polymer produced by using a catalyst (or control catalyst) activated by exposure to an oxidizing atmosphere at a temperature of 1200℉ (649℃) for a period of 3 hours (or 8 hours) but otherwise identical.

[0163] Aspect 34. The method as defined in any of the preceding aspects, wherein the MI potential of the activated (calcined) catalyst is at least 0.2, at least 0.3, at least 0.4, at least 0.5, at least 0.6, at least 0.7, at least 0.8, at least 0.9, at least 1, or at least 1.2 g / 10 min.

[0164] Aspect 35. The method as defined in any of the preceding aspects, wherein the HLMI potential of the activated (calcined) catalyst is at least 20, at least 25, at least 30, at least 35, at least 40, at least 50, at least 60, at least 70, at least 80 or at least 100 g / 10 min.

[0165] Aspect 36. The method as defined in any of the preceding aspects, wherein the activated (calcined) catalyst produces a polymer under standard polymerization conditions, wherein the total number of membrane gels (or the number of catalyst particle gels) is less than or equal to 100 gels per 25 micrometers thick membrane square feet (or less than or equal to 80 gels per 25 micrometers thick membrane square feet, or less than or equal to 60 gels, or less than or equal to 40 gels, or less than or equal to 30 gels, or less than or equal to 20 gels, or less than or equal to 10 gels, or less than or equal to 8 gels, or less than or equal to 5 gels), wherein the membrane gels contain a size (diameter) greater than 200 μm (and for the number of catalyst particle gels, caused by the catalyst particles).

[0166] Aspect 37. The method as defined in any of the preceding aspects, wherein the pre-catalyst (or the activated catalyst) is contacted with the gas flow in a fluidized bed vessel (intermittent or continuous) at any suitable linear velocity or any linear velocity disclosed herein, such linear velocities as 0.05 to 0.6 ft / s, 0.05 to 0.3 ft / s, 0.1 to 0.4 ft / s, 0.2 to 0.5 ft / s, 0.2 to 0.4 ft / s, or 0.2 to 0.3 ft / s.

[0167] Aspect 38. An olefin polymerization method, the method comprising: (I) carrying out a method for producing the activated (calcined) chromium catalyst as defined in any one of aspects 1 to 37; and (II) in a polymerization reactor system, contacting the activated (calcined) chromium catalyst and optionally a co-catalyst with an olefin monomer and optionally an olefin comonomer under polymerization conditions to produce an olefin polymer.

[0168] Aspect 39. An olefin polymerization method as defined in Aspect 38, wherein a co-catalyst is used, and said co-catalyst comprises any suitable co-catalyst or any co-catalyst disclosed herein, such as an aluminoxane co-catalyst, an organoaluminum co-catalyst, or an organoboron co-catalyst, or any combination thereof.

[0169] Aspect 40. An olefin polymerization method as defined in Aspect 38 or 39, wherein the olefin monomer and the optional olefin comonomer independently comprise C2-C. 20 α-olefins.

[0170] Aspect 41. An olefin polymerization method as defined in any of Aspects 38 to 40, wherein the olefin monomer comprises ethylene.

[0171] Aspect 42. An olefin polymerization method as defined in any of Aspects 38 to 41, wherein the activated chromium catalyst is contacted with ethylene and an olefin comonomer comprising C3-C4. 10 α-olefins.

[0172] Aspect 43. An olefin polymerization method as defined in any of Aspects 38 to 42, wherein the activated chromium catalyst is contacted with ethylene and an olefin comonomer comprising 1-butene, 1-hexene, 1-octene, or a mixture thereof.

[0173] Aspect 44. An olefin polymerization method as defined in any of Aspects 38 to 43, wherein the polymerization reactor system comprises a slurry reactor, a gas-phase reactor, a solution reactor, or a combination thereof.

[0174] Aspect 45. An olefin polymerization method as defined in any of aspects 38 to 44, wherein the polymerization reactor system comprises a circulating slurry reactor.

[0175] Aspect 46. An olefin polymerization method as defined in any of aspects 38 to 45, wherein the polymerization reactor system comprises a single reactor.

[0176] Aspect 47. An olefin polymerization method as defined in any of Aspects 38 to 45, wherein the polymerization reactor system comprises two reactors.

[0177] Aspect 48. An olefin polymerization method as defined in any of Aspects 38 to 45, wherein the polymerization reactor system comprises more than two reactors.

[0178] Aspect 49. An olefin polymerization method as defined in any of aspects 38 to 48, wherein the olefin polymer comprises any olefin polymer disclosed herein.

[0179] Aspect 50. An olefin polymerization method as defined in any of Aspects 38 to 49, wherein the olefin polymer comprises ethylene homopolymer, ethylene / 1-butene copolymer, ethylene / 1-hexene copolymer, and / or ethylene / 1-octene copolymer.

[0180] Aspect 51. An olefin polymerization method as defined in any one of Aspects 38 to 50, wherein the polymerization conditions comprise a polymerization reaction temperature in the range of 60°C to 120°C and a reaction pressure in the range of 200 psig to 1000 psig (1.4 MPa to 6.9 MPa).

[0181] Aspect 52. An olefin polymerization method as defined in any of Aspects 38 to 51, wherein the polymerization conditions are substantially constant, for example, for a particular polymer grade.

[0182] Aspect 53. An olefin polymerization method as defined in any of aspects 38 to 52, wherein no hydrogen is added to the polymerization reactor system.

[0183] Aspect 54. An olefin polymerization method as defined in any of Aspects 38 to 52, wherein hydrogen is added to the polymerization reactor system.

[0184] Aspect 55. An olefin polymerization method as defined in any one of Aspects 38 to 54, wherein the method is carried out in a commercial circulating reactor at a production rate of 2,000 to 5,000 grams of polymer per gram of catalyst, and / or a space-time yield greater than or equal to 2, 2.5, 2.8, 3 or 4 (lb / h) / gallon and / or less than or equal to 6, 5.5 or 5 (lb / h) / gallon, to produce an ethylene / 1-hexene copolymer with a density of at least 0.947 g / cc, said density being determined according to ISO 1183 Part 2.

[0185] Aspect 56. An olefin polymerization method as defined in any one of Aspects 38 to 55, wherein the method is carried out in a commercial circulating reactor at a production rate of 2,000 to 5,000 grams of polymer per gram of catalyst, and / or a space-time yield greater than or equal to 2, 2.5, 2.8, 3 or 4 (lb / h) / gallon and / or less than or equal to 6, 5.5 or 5 (lb / h) / gallon, to produce an ethylene / 1-hexene copolymer with a density of at least 0.938 g / cc, said density being determined according to ISO 1183 Part 2.

[0186] Aspect 57. The method as defined in any of the preceding aspects, wherein the precatalyst (or the silica support, or the activated chromium catalyst) has any suitable pore volume (total) or a pore volume (total) within any range disclosed herein, such as 0.5 to 5 mL / g, 1 to 5 mL / g, 1 to 3 mL / g, or 1.5 to 2 mL / g.

[0187] Aspect 58. The method as defined in any of the preceding aspects, wherein the precatalyst (or the silica support, or the activated chromium catalyst) has any suitable BET surface area or a BET surface area within any range disclosed herein, for example, 100 to 700 m². 2 / g, 200 to 600 m 2 / g, 250 to 550 m 2 / g or 300 to 500 m 2 / g.

[0188] Aspect 59. The method as defined in any of the preceding aspects, wherein the precatalyst (or the silica support, or the activated chromium catalyst) has any suitable average (d50) particle size or an average (d50) particle size within any range disclosed herein, such as 10 to 500 micrometers, 30 to 130 micrometers, or 40 to 70 micrometers.

[0189] Aspect 60. The method as defined in any of the preceding aspects, wherein the pre-catalyst (or the activated chromium catalyst) has any suitable amount of titanium, or an amount within any range disclosed herein, based on the weight of the corresponding catalyst, such as 0.5 to 10 wt%, 1 to 10 wt%, 2 to 8 wt%, or 2 to 6 wt%.

[0190] Aspect 61. The method as defined in any of the preceding aspects, wherein the pre-catalyst (or the activated chromium catalyst) has any suitable amount of chromium or an amount within any range disclosed herein, based on the weight of the corresponding catalyst, for example, 0.1 to 4 wt%, 0.2 to 5 wt%, 0.5 to 3 wt%, 0.5 to 2 wt%, or 0.5 to 1.5 wt%.

[0191] Aspect 62. The method as defined in any of the preceding aspects, wherein the pre-catalyst (or the activated chromium catalyst) has any suitable amount or within any range of nitrogen disclosed herein, such as 1 to 4.5 moles, 1.5 to 5 moles, 1.5 to 4.5 moles, 2 to 5 moles, 2 to 4 moles, or 2 to 3 moles of nitrogen per mole of titanium.

[0192] Aspect 63. The method as defined in any of the preceding aspects, wherein the precatalyst has any suitable amount or within any range disclosed herein of a carboxylate group / ligand, such as 1 to 5 moles, 1 to 4 moles, 1 to 3 moles, 1.5 to 5 moles, 1.5 to 4 moles or 2 to 3 moles of carboxylate per mole of titanium.

[0193] Aspect 64. The method as defined in any of the preceding aspects, wherein the pre-catalyst has any suitable amount of carbon or an amount within any range disclosed herein, based on the weight of the catalyst, for example, 0.5 to 10 wt%, 1 to 10 wt%, 1 to 5 wt%, 2 to 10 wt%, 2 to 8 wt%, or 2 to 6 wt%.

[0194] Aspect 65. The method as defined in any of the preceding aspects, wherein the amount of chromium in the precatalyst in a +5 oxidation state or lower is at least 50% by weight, at least 60% by weight, at least 70% by weight, at least 80% by weight, at least 90% by weight, or at least 95% by weight, based on the total amount of chromium on the precatalyst.

[0195] Aspect 66. The method as defined in any of the preceding aspects, wherein the amount of chromium in the activated chromium catalyst in the hexavalent oxidation state is at least 40% by weight, at least 50% by weight, at least 60% by weight, at least 70% by weight, at least 80% by weight, at least 90% by weight, or at least 95% by weight, based on the total amount of chromium on the activated chromium catalyst.

[0196] Aspect 67. An olefin polymer (e.g., an ethylene polymer) produced by an olefin polymerization method as defined in any one of aspects 38 to 66.

[0197] Aspect 68. An ethylene polymer having (or characterized by) a high load melt index (HLMI) in the range of 10 to 80 g / 10 min; and a melt index in the range of 0.93 to 0.96 g / cm³. 3 The density within the range; and the total number of membrane gels of 100 or less per square foot of 25 micrometer-thick film (or 80 or less per square foot of 25 micrometer-thick film, or 60 or less per square foot of 25 micrometer-thick film, or 40 or less per square foot of 25 micrometer-thick film, or 30 or less per square foot of 25 micrometer-thick film, or 10 or less per square foot of 25 micrometer-thick film, or 5 or less per square foot of 25 micrometer-thick film), wherein the membrane gels contain a size (diameter) greater than 200 µm (and for the number of gels of the catalyst particles, caused by the catalyst particles); wherein the ethylene polymer contains 150 to 680 ppm of silica, 1.5 to 6.8 ppm of chromium and 1.5 to 40 ppm of titanium.

[0198] Aspect 69. An ethylene polymer having (or characterized by) a melt index (MI) in the range of 0.1 g / 10 min to 1 g / 10 min; and a melt index in the range of 0.93 to 0.96 g / cm³. 3The density within the range; and the total number of membrane gels of 100 or less per square foot of 25 micrometer-thick film (or 80 or less per square foot of 25 micrometer-thick film, or 60 or less per square foot of 25 micrometer-thick film, or 40 or less per square foot of 25 micrometer-thick film, or 30 or less per square foot of 25 micrometer-thick film, or 10 or less per square foot of 25 micrometer-thick film, or 5 or less per square foot of 25 micrometer-thick film), wherein the membrane gels contain a size (diameter) greater than 200 µm (and for the number of gels of the catalyst particles, caused by the catalyst particles); wherein the ethylene polymer contains 150 to 680 ppm of silica, 1.5 to 6.8 ppm of chromium and 1.5 to 40 ppm of titanium.

[0199] Aspect 70. A polymer as defined in any of aspects 67 to 69, wherein the ethylene polymer has an HLMI in any range disclosed herein, such as 10 to 70, 10 to 60, 10 to 50, 20 to 80, 20 to 50 or 30 to 50 g / 10 min.

[0200] Aspect 71. A polymer as defined in any of aspects 67 to 70, wherein the ethylene polymer has an MI in any range disclosed herein, such as 0.1 to 1, 0.1 to 0.75, 0.1 to 0.6, 0.2 to 1, 0.2 to 0.6 or 0.3 to 0.6 g / 10 min.

[0201] Aspect 72. A polymer as defined in any of Aspects 67 to 71, wherein said ethylene polymer has a density within any range disclosed herein, such as 0.93 to 0.956, 0.934 to 0.96, 0.934 to 0.956, 0.934 to 0.95, or 0.945 to 0.958 g / cm³. 3 The density.

[0202] Aspect 73. The polymer as defined in any of Aspects 67 to 72, wherein the ethylene polymer independently contains less than 0.1 ppm (by weight), less than 0.08 ppm, less than 0.05 ppm or less than 0.03 ppm of Mg, V, Zr or Hf.

[0203] Aspect 74. The polymer as defined in any one of Aspects 67 to 73, wherein the ethylene polymer contains 1.8 to 6 ppm, 2 to 6.8 ppm, 2 to 6 ppm, 2 to 5 ppm, 2 to 4.5 ppm, 2 to 4 ppm, 1.5 to 6 ppm, 1.5 to 5.5 ppm, 1.5 to 5 ppm or 3 to 6 ppm of chromium.

[0204] Aspect 75. The polymer as defined in any one of Aspects 67 to 74, wherein the ethylene polymer contains 1.5 to 30 ppm, 2 to 40 ppm, 2 to 30 ppm, 2 to 10 ppm, 3 to 30 ppm, 3 to 20 ppm, 3 to 10 ppm, 4 to 20 ppm, 5 to 40 ppm, 5 to 25 ppm, 5 to 15 ppm, 7 to 17 ppm, or 8 to 16 ppm of titanium.

[0205] Aspect 76. The polymer as defined in any one of Aspects 67 to 75, wherein the ethylene polymer contains 180 to 600 ppm, 200 to 680 ppm, 200 to 600 ppm, 200 to 500 ppm, 200 to 400 ppm, 150 to 600 ppm, 150 to 500 ppm or 150 to 450 ppm of silica.

[0206] Aspect 77. A polymer as defined in any of aspects 67 to 76, wherein the ethylene polymer has Mn in any range disclosed herein, such as 3,000 to 25,000, 8,000 to 20,000, 10,000 to 18,000 or 12,000 to 15,000 g / mol.

[0207] Aspect 78. A polymer as defined in any of aspects 67 to 76, wherein the ethylene polymer has a Mw in any range disclosed herein, such as 100,000 to 250,000, 120,000 to 200,000 or 140,000 to 180,000 g / mol.

[0208] Aspect 79. A polymer as defined in any of aspects 67 to 78, wherein the ethylene polymer has an Mz in any range disclosed herein, such as 500,000 to 2,000,000, 500,000 to 1,800,000 or 600,000 to 1,500,000 g / mol.

[0209] Aspect 80. A polymer as defined in any of Aspects 67 to 79, wherein the ethylene polymer has an Mw / Mn ratio in any range disclosed herein, such as 7 to 20, 8 to 18, 9 to 17, 9 to 15 or 10 to 14.

[0210] Aspect 81. A polymer as defined in any of Aspects 67 to 80, wherein the ethylene polymer has an Mz / Mw ratio in any range disclosed herein, such as 5 to 10, 5 to 9, 6 to 10 or 6 to 9.

[0211] Aspect 82. The polymer as defined in any of aspects 67 to 81, wherein the ethylene polymer has a CY-a parameter within any range disclosed herein, such as a CY-a parameter of 0.1 to 0.3, 0.13 to 0.2, 0.13 to 0.17, 0.16 to 0.26, 0.17 to 0.24 or 0.18 to 0.22.

[0212] Aspect 83. The polymer as defined in any one of aspects 67 to 82, wherein the ethylene polymer comprises ethylene homopolymer and / or ethylene / α-olefin copolymer.

[0213] Aspect 84. The polymer as defined in any of Aspects 67 to 83, wherein the ethylene polymer comprises ethylene homopolymer, ethylene / 1-butene copolymer, ethylene / 1-hexene copolymer, and / or ethylene / 1-octene copolymer.

[0214] Aspect 85. The polymer as defined in any one of aspects 67 to 84, wherein the ethylene polymer comprises an ethylene / 1-hexene copolymer.

[0215] Aspect 86. A polymer as defined in any of aspects 67 to 85, said polymer being produced by a method defined in any of aspects 38 to 66.

[0216] Aspect 87. An article comprising an ethylene polymer as defined in any one of aspects 67 to 86.

[0217] Aspect 88. An article comprising an ethylene polymer as defined in any one of Aspects 67 to 86, wherein the article is an agricultural film, geomembrane, packaging film, pallet wrapping film, automotive parts, bottles, chemical containers, barrels, fibers or fabrics, food packaging films or containers, food contact articles, fuel tanks, geomembranes, household containers, liners, molded products, medical devices or materials, outdoor storage products, outdoor recreational equipment, pipes, sheets or tapes, toys or traffic barriers.

Claims

1. An ethylene polymer, said ethylene polymer having: Melt index (MI) in the range of 0.1 to 1 g / 10 min and / or high load melt index (HLMI) in the range of 10 to 80 g / 10 min; Between 0.93 and 0.96 g / cm 3 Density within the range; and The total number of membrane gels is less than or equal to 40 gels per square foot of membrane with a thickness of 25 micrometers, wherein the diameter of the membrane gel is greater than 200 µm; The ethylene polymer comprises: 150 to 680 ppm of silica; Chromium ranging from 1.5 to 6.8 ppm; and Titanium content of 1.5 to 40 ppm.

2. The polymer according to claim 1, wherein the MI of the ethylene polymer is in the range of 0.1 to 1 g / 10 min.

3. The polymer according to claim 1, wherein the HLMI of the ethylene polymer is in the range of 10 to 80 g / 10 min.

4. The polymer according to claim 1, wherein the density is between 0.93 and 0.956 g / cm³. 3 Within the range.

5. The polymer of claim 1, wherein the total number of membrane gels is less than or equal to 10 gels per square foot of 25 micrometer-thick membrane.

6. The polymer of claim 1, wherein the catalyst particle gel number of the ethylene polymer is less than or equal to 10 gels per square foot of 25 micrometer-thick film, wherein the catalyst particle gel has a diameter dimension greater than 200 µm and is caused by catalyst particles.

7. The polymer of claim 1, wherein the ethylene polymer comprises: 200 to 600 ppm of silica; or 2 to 6 ppm of chromium; or 3 to 30 ppm titanium; or Any combination of them.

8. The polymer of claim 1, wherein the ethylene polymer independently contains less than 0.1 ppm of Mg, V, Zr or Hf by weight.

9. The polymer of claim 1, wherein the ethylene polymer comprises ethylene homopolymer, ethylene / 1-butene copolymer, ethylene / 1-hexene copolymer, and / or ethylene / 1-octene copolymer.

10. The polymer according to claim 1, wherein the ethylene polymer comprises: MI in the range of 0.1 to 0.75 g / 10 min; and HLMI in the range of 20 to 50 g / 10 min.

11. The polymer according to claim 10, wherein the ethylene polymer is further characterized in that: Mn in the range of 3,000 to 25,000 g / mol; Mw in the range of 100,000 to 250,000 g / mol; and Mz in the range of 500,000 to 2,000,000 g / mol.

12. The polymer of claim 11, wherein the ethylene polymer is further characterized by a CY-a parameter in the range of 0.13 to 0.

2.

13. The polymer according to claim 10, wherein the ethylene polymer is further characterized in that: The Mw / Mn ratio in the range of 7 to 20; and The Mz / Mw ratio is in the range of 5 to 10.

14. The polymer of claim 1, wherein the ethylene polymer comprises: 200 to 600 ppm of silica; 2 to 6 ppm of chromium; and Titanium content of 3 to 30 ppm.

15. The polymer according to claim 14, wherein the ethylene polymer is further characterized in that: Mn in the range of 10,000 to 18,000 g / mol; Mw in the range of 140,000 to 180,000 g / mol; and Mz in the range of 600,000 to 1,500,000 g / mol.

16. The polymer of claim 15, wherein the ethylene polymer is further characterized by a CY-a parameter in the range of 0.13 to 0.

17.

17. The polymer according to claim 14, wherein the ethylene polymer is further characterized in that: The Mw / Mn ratio in the range of 9 to 15; and The Mz / Mw ratio is in the range of 5 to 9.

18. The polymer of claim 1, wherein the ethylene polymer comprises: 200 to 400 ppm of silica; 2 to 5 ppm of chromium; and Titanium content of 7 to 17 ppm.

19. The polymer of claim 18, wherein the ethylene polymer comprises: MI in the range of 0.1 to 0.75 g / 10 min; and HLMI in the range of 20 to 50 g / 10 min.

20. The polymer of claim 19, wherein the total number of membrane gels is less than or equal to 20 gels per square foot of 25 micrometer-thick membrane.

21. An article comprising the polymer according to claim 1.

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