Multimodal polyethylene

Abstract

The invention relates to an ethylene copolymer having a multimodal molecular weight distribution, comprising or consisting of: 40 - 80 wt% of an ethylene polymer component A, 5 - 40 wt% of an ethylene copolymer component B of ethylene and an olefin comonomer having a higher molecular weight Mn than the ethylene homopolymer component A and having a molar comonomer content C B and a density D B , and 5 - 40 wt% of an ethylene copolymer component C of ethylene and an olefin comonomer having a higher molecular weight Mn than the ethylene copolymer component B and having a molar comonomer content C C and a density D C , wherein the amounts of A, B and C are based on the total weight of the ethylene polymer, wherein the comonomer content of the ethylene copolymer is 0.10 - 3.00 mol%, and the difference between C B and C C is at most 0.10 mol%.

Description

Technical Field

[0001] This invention relates to a multi-peaked, preferably tri-peaked, ethylene copolymer and the use of such ethylene copolymer in articles. Background Technology

[0002] Trimodal ethylene copolymers are used in many applications, such as pipes.

[0003] WO 2013079180 discloses a polyethylene composition for pipes comprising three ethylene homopolymer or copolymer portions (A), (B), and (C), differing in their weight-average molecular weight Mw. Portion (A) is preferably an ethylene homopolymer. Portions (B) and (C) are preferably ethylene copolymers. The preferred olefin comonomer is 1-hexene. In Invention Example 1, trimodal polyethylene is produced by a multi-reactor system, consisting of 60 wt% portion (A), 21 wt% portion (B), and 19 wt% portion (C). The comonomer content and density of each portion of the trimodal polyethylene of Invention Example 1 are not mentioned. From the polyethylene density obtained from each reactor and the division of the portions, it can be calculated that the density of portion (C) is significantly lower than that of portion (B), and the comonomer content of portion (C) is higher than that of portion (B).

[0004] WO 2007022908 discloses a polyethylene composition for pipes comprising a low molecular weight ethylene homopolymer A, a high molecular weight ethylene copolymer B, and an ultra-high molecular weight ethylene copolymer C. In WO 2007022908, preferably, ethylene copolymer B contains 1-8 wt% of additional olefin monomer units, and ethylene copolymer C contains 1-8 wt% of additional olefin monomer units. A preferred olefin comonomer is 1-butene. In Example 1, trimodal polyethylene was produced using a multi-reactor system. The comonomer content and density of each fraction of the trimodal polyethylene in Example 1 are not mentioned. Based on the volumetric amounts of ethylene and 1-butene measured in the gas phase of each reactor, it can be calculated that the comonomer content of ethylene copolymer C in Example 1 is higher than that of ethylene copolymer B.

[0005] For a wide range of applications, including pipes, resistance to slow crack growth, as demonstrated by high strain hardening, is important. Impact properties, processability, melt strength, sag resistance, density, and stiffness are also important. While known polyethylene is satisfactory for some applications, there has been a ongoing need for ethylene copolymers with a combination of high strain hardening modulus and other mechanical properties. Summary of the Invention

[0006] One object of the present invention is to provide an ethylene polymer that satisfies the above and / or other requirements.

[0007] Therefore, the present invention provides an ethylene copolymer having a multi-peak molecular weight distribution, comprising or consisting of:

[0008] 40-80 wt% ethylene polymer component A,

[0009] Component B, an ethylene copolymer containing 5-40 wt% ethylene and olefin comonomers, has a higher molecular weight (Mn) than ethylene homopolymer component A, and also has a molar comonomer content (C). B and density D B ,and

[0010] Ethylene copolymer component C, containing 5-40 wt% ethylene and olefin comonomers, has a higher molecular weight (Mn) than ethylene copolymer component B, and also has a molar comonomer content of C. C and density D C ,

[0011] The amounts of A, B, and C are based on the total weight of the ethylene copolymer, wherein

[0012] The comonomer content of this ethylene copolymer is 0.10-3.00 mol%, and

[0013] C B and C C The difference is at most 0.10 mol%.

[0014] It has been surprisingly found that, according to the present invention, similar comonomer contents between copolymer components B and C result in high strain hardening moduli. Compared to multimodal ethylene copolymers with similar overall comonomer contents and similar MWD but different comonomer contents in the components, it has been surprisingly found that the ethylene copolymers of the present invention exhibit higher strain hardening moduli while retaining other mechanical properties.

[0015] The ethylene copolymer of the present invention is preferably a trimodal ethylene copolymer, i.e., it consists of components A, B, and C. However, the ethylene copolymer of the present invention may contain one or more other ethylene polymer components.

[0016] In other words, an ethylene copolymer containing a required amount of a component that satisfies the definition of component A, a required amount of a component that satisfies the definition of component B, and a required amount of a component that satisfies the relationship between components A, B, and C is considered an ethylene copolymer of the present invention, even if the ethylene copolymer contains one or more other ethylene polymer components.

[0017] When present, the additional ethylene polymer component is preferably an ethylene homopolymer. Preferably, the total amount of components A, B, and C relative to the ethylene copolymer of the present invention is at least 60 wt%, at least 70 wt%, at least 80 wt%, at least 90 wt%, at least 95 wt%, at least 98 wt%, or at least 99 wt%. Attached Figure Description

[0018] Figure 1 The MWD of polymer component A is shown;

[0019] Figure 2 The MWD and SCBD of polymer components B and D are shown;

[0020] Figure 3 The MWD and SCBD of polymer components C and E are shown;

[0021] Figure 4 The MWD and SCBD of the ethylene copolymers of Example 1 and Comparative Test 2 are shown. Detailed Implementation

[0022] ethylene copolymer

[0023] Ethylene copolymers refer to polymers whose majority weight is derived from ethylene monomer units. The comonomers in the ethylene copolymers of the present invention may be selected from C3-C20 α-olefins, more preferably C3-10 α-olefins, even more preferably propylene, 1-butene, 1-hexene and 1-octene, and most preferably 1-butene and / or 1-hexene.

[0024] Preferably, the ethylene copolymer of the present invention is high-density polyethylene.

[0025] Preferably, the density of the ethylene copolymer of the present invention is 920-970 kg / m³. 3 Preferred weight: 940-960 kg / m³ 3 .

[0026] The ethylene copolymers of the present invention have a melt flow index (sometimes referred to herein as MI5) of 0.05-20 dg / min, measured at 190°C and 5 kg according to ISO 1133-1:2011. The MI5 of the ethylene copolymers of the present invention can be 0.05-2.0 dg / min, making them particularly suitable for manufacturing tubes or films. The MI5 of the ethylene copolymers of the present invention can be 0.05-5.0 dg / min, making them particularly suitable for blow molding. The MI5 of the ethylene copolymers of the present invention can be 1.0-20 dg / min, making them particularly suitable for injection molding.

[0027] Preferably, the melt flow index (sometimes referred to herein as MI21.6) of the ethylene copolymer of the present invention, measured according to ISO 1133-1:2011 at 190°C and 21.6 kg, is 1.0-500 dg / min. The MI21.6 of the ethylene copolymer of the present invention can be 1.0-50 dg / min, which is particularly suitable for manufacturing tubes or films. The MI21.6 of the ethylene copolymer of the present invention can be 1.0-125 dg / min, which is particularly suitable for blow molding. The MI21.6 of the ethylene copolymer of the present invention can be 20-500 dg / min, which is particularly suitable for injection molding.

[0028] Methods for preparing ethylene copolymers

[0029] The ethylene copolymer of the present invention can be prepared by means of melt-blending or solution-blending components A, B, and C with optional additional ethylene polymer components produced in different reactors to obtain the ethylene copolymer. Melt-blending or solution-blending can be carried out in any conventional blending equipment. Components A, B, and C to be melt-blended or solution-blended, and optional additional ethylene polymer components, can be produced by any known method.

[0030] Optionally, the ethylene copolymer of the present invention can be prepared by a method comprising polymerizing component A, subsequently polymerizing component B in the presence of component A, and subsequently polymerizing component C in the presence of components A and B. Therefore, the present invention provides a method for preparing the ethylene copolymer of the present invention, wherein the method comprises a sequential polymerization method comprising at least three reactors in series, wherein the method includes the steps of:

[0031] - Component A is prepared using the first set of conditions in the first reactor.

[0032] - The component A and unreacted monomers from the first reactor are transferred to the second reactor.

[0033] - Feed the monomer into the second reactor.

[0034] - Component B is prepared in the second reactor in the presence of component A.

[0035] - The components A and B and the unreacted monomers from the second reactor are transferred to the third reactor.

[0036] - The monomer is fed into the third reactor.

[0037] - Component C is prepared in the third reactor in the presence of components A and B.

[0038] In such cases, the performance of the fractions produced in the second and third reactors can be inferred from the polymer produced in a single stage using the same polymerization conditions (e.g., the same temperature, reactant / diluent partial pressures, suspension medium, and reaction time) as in the multi-stage process, and using a catalyst on which the polymer was not previously produced. Alternatively, the performance of the fractions produced in the higher stages of the multi-stage process can also be calculated, for example, according to B. Hagström, Conference on Polymer Processing (The Polymer Processing Society), Extended Abstracts and Final Programme, Gothenburg, August 19-21, 1997, 4:13. The performance of the fractions produced in the higher stages of the multi-stage process can also be calculated according to KB McAuley, JFMcGregor, AIChE Journal, Vol. 37, No. 6, 825-835, June 1991.

[0039] Therefore, although the properties of the products of a multi-stage process cannot be directly measured, the performance of the portions produced in the higher stages of such a multi-stage process can be determined by applying any or both of the methods described above. Those skilled in the art will be able to select the appropriate method.

[0040] Ethylene polymer component A

[0041] Preferably, the density D of ethylene polymer component A is... A At least 954 kg / m 3 The preferred strength is 965-982 kg / m³. 3 More preferably 968-975 kg / m 3 .

[0042] Preferably, the melt flow index of component A, measured at 190°C and 1.2 kg according to ISO 1133-1:2011, is 0.5-500 dg / min, more preferably 40-250 dg / min.

[0043] Preferably, the Mn of component A is 2-50 kDa.

[0044] Preferably, the Mw of component A is 4-150 kDa.

[0045] Preferably, the Mz of component A is 20-4000 kDa.

[0046] Preferably, the Mw / Mn ratio of component A is 2-20.

[0047] Preferably, component A is an ethylene homopolymer. When component A is an ethylene copolymer, it can be a copolymer of ethylene and a comonomer selected from: C3-C20 α-olefins, more preferably C3-10 α-olefins, even more preferably propylene, 1-butene, 1-hexene and 1-octene, most preferably 1-butene and / or 1-hexene. Preferably, the amount of the comonomer unit in the ethylene polymer A is less than 0.1 mol%.

[0048] The amount of component A relative to the ethylene copolymer of the present invention is 40-80 wt%, preferably 45-60 wt%.

[0049] Ethylene copolymer component B

[0050] Preferably, the density D of ethylene copolymer component B is... B 910-940 kg / m 3 Preferred weight is 925-935 kg / m³. 3 .

[0051] Preferably, the melt flow index of component B, measured at 190°C and 21.6 kg according to ISO 1133-1:2011, is 0.01-50.0 dg / min, more preferably 0.1-5.0 dg / min.

[0052] Preferably, the Mn of component B is 15-300 kDa. Preferably, the Mn of component B is at least 20 kDa higher than the Mn of component A, for example, 30-100 kDa.

[0053] Preferably, the Mw of component B is 100-1000 kDa. Preferably, the Mw of component B is at least 100 kDa higher than the Mw of component A, for example, 300-500 kDa.

[0054] Preferably, the Mz of component B is 170-7000 kDa.

[0055] Preferably, the Mw / Mn ratio of component B is 2-10.

[0056] In some embodiments, component B has Mn of 15-300 kDa, Mw of 200-1000 kDa, Mz of 350-7000 kDa, and / or Mw / Mn of 2-10. These ranges of Mn, Mw, Mz, and Mw / Mn are particularly suitable when the ethylene copolymer of the present invention is used to manufacture tubes or membranes.

[0057] In some embodiments, component B has Mn of 15-300 kDa, Mw of 150-1000 kDa, Mz of 250-7000 kDa, and / or Mw / Mn of 2-10. These ranges of Mn, Mw, Mz, and Mw / Mn are particularly suitable when the ethylene copolymer of the present invention is used for blow molding.

[0058] In some embodiments, component B has Mn of 15-300 kDa, Mw of 100-700 kDa, Mz of 170-5000 kDa, and / or Mw / Mn of 2-10. These ranges of Mn, Mw, Mz, and Mw / Mn are particularly suitable when the ethylene copolymer of the present invention is used for injection molding.

[0059] Component B is an ethylene copolymer of ethylene and comonomers selected from the following: C3-C20 α-olefins, more preferably C3-10 α-olefins, more preferably propylene, 1-butene, 1-hexene and 1-octene, most preferably 1-butene and / or 1-hexene.

[0060] Preferably, the comonomer content of component B is C B It is 0.10-5.00 mol%, more preferably 0.50-3.00 mol%, and even more preferably 0.75-1.50 mol%.

[0061] The amount of component B relative to the ethylene polymer of the present invention is 5-40 wt%, preferably 10-30 wt%.

[0062] ethylene copolymer component C

[0063] Preferably, the density D of the ethylene copolymer component C is... C 910-940 kg / m 3 Preferred weight: 920-930 kg / m³ 3 D B and D C The difference is at most 10 kg / m 3 Preferred at most 5.0 kg / m 3 D B It can be lower than D C However, D is preferred. B Higher than or equal to D C .

[0064] Preferably, the melt flow index of component C, measured according to ISO 1133-1:2011 at 190°C and 21.6 kg, is 0.01-50.0 dg / min, more preferably 0.05-2.0 dg / min.

[0065] Preferably, the Mn of component C is 30-400 kDa. Preferably, the Mn of component C is at least 10 kDa higher than the Mn of component B, for example, 15-30 kDa.

[0066] Preferably, the Mw of component C is 170-1200 kDa. Preferably, the Mw of component C is at least 20 kDa higher than the Mw of component B, for example, 30-100 kDa.

[0067] Preferably, the Mz of component C is 300-10000 kDa.

[0068] Preferably, the Mw / Mn ratio of component C is 2-10.

[0069] In some embodiments, component C has Mn of 30-400 kDa, Mw of 350-1200 kDa, Mz of 500-10000 kDa, and / or Mw / Mn of 2-10. These ranges of Mn, Mw, Mz, and Mw / Mn are particularly suitable when the ethylene copolymer of the present invention is used to manufacture tubes or membranes.

[0070] In some embodiments, component C has Mn of 30-400 kDa, Mw of 200-1200 kDa, Mz of 400-10000 kDa, and / or Mw / Mn of 2-10. These ranges of Mn, Mw, Mz, and Mw / Mn are particularly suitable when the ethylene copolymer of the present invention is used for blow molding.

[0071] In some embodiments, component C has Mn of 30-400 kDa, Mw of 170-1000 kDa, Mz of 300-8000 kDa, and / or Mw / Mn of 2-10. These ranges of Mn, Mw, Mz, and Mw / Mn are particularly suitable when the ethylene copolymer of the present invention is used for injection molding.

[0072] Component C is an ethylene copolymer of ethylene and comonomers selected from the following: C3-C20 α-olefins, more preferably C3-10 α-olefins, more preferably selected from propylene, 1-butene, 1-hexene and 1-octene, most preferably 1-butene and / or 1-hexene.

[0073] Preferably, the comonomer content of component C is C C The concentration is 0.10-5.00 mol%, more preferably 0.50-3.00 mol%, and even more preferably 0.75-1.50 mol%. C B and C C The difference is at most 0.10 mol%, more preferably at most 0.05 mol%, and even more preferably at most 0.03 mol%. C C It can be higher than C B However, C is preferred.B Less than or equal to C C .

[0074] The amount of component C relative to the ethylene polymer of the present invention is 5-40 wt%, preferably 10-30 wt%.

[0075] catalyst

[0076] The ethylene polymer components A, B, and C and optionally additional ethylene polymer components can each be produced in the presence of known catalyst systems such as Ziegler-Natta catalyst systems or metallocene catalyst systems, preferably Ziegler-Natta catalyst systems. The polymerization can be carried out in the presence of, for example, an antistatic agent or an antifouling agent in an amount within the range of 1-500 ppm relative to the total amount of the reactor contents.

[0077] Preferably, the catalyst system comprises:

[0078] (I) A solid reaction product obtained by the reaction of:

[0079] a) A hydrocarbon solution containing:

[0080] 1) An organic oxygen-containing magnesium compound or a halogen-containing magnesium compound, and

[0081] 2) An organic oxygen-containing titanium compound, and

[0082] b) An aluminum halide of the formula AlR n X 3-n where R is a hydrocarbon moiety containing 1-10 carbon atoms, X is a halogen, and 0 < n < 3, and

[0083] (II) An aluminum compound of the formula AlR3, where R is a hydrocarbon moiety containing 1-10 carbon atoms.

[0084] Precipitation occurs during the reaction of the hydrocarbon solution containing the organic oxygen-containing magnesium compound and the organic oxygen-containing titanium compound with the solid catalyst precursor of component (I b), and after the precipitation reaction, the formed mixture is heated to complete the reaction.

[0085] The aluminum compound (II) is dosed before or during the polymerization and can be referred to as a cocatalyst.

[0086] The polymerization method can be a slurry polymerization method.

[0087] Preferably, the diluent in the slurry polymerization method is a diluent composed of aliphatic hydrocarbon compounds, which exhibits an atmospheric boiling point temperature of at least 35°C, more preferably higher than 55°C. Suitable diluents are hexane and heptane. The preferred diluent is hexane.

[0088] Suitable organo-oxygenated magnesium compounds include, for example, magnesium alkoxides such as methylated magnesium, ethylated magnesium and isopropylated magnesium, and magnesium alkyl alkoxides such as ethyl-ethylated magnesium and so-called carbonated magnesium alkoxides such as ethyl magnesium carbonate. Preferably, the organo-oxygenated magnesium compound is a magnesium alkoxide. A preferred magnesium alkoxide is magnesium ethoxide Mg(OC2H5)2.

[0089] Suitable halogen-containing magnesium compounds include, for example, magnesium dihalides and magnesium dihalide complexes, where the halide is preferably chlorine.

[0090] Preferably, the hydrocarbon solution contains an organo-oxygenated magnesium compound as (I)(a)(1).

[0091] Suitable organo-oxygenated titanium compounds can be represented by the general formula [TiO x (OR) 4-2x n where R represents an organic structural moiety, x is 0 - 1, and n is 1 - 6.

[0092] Suitable examples of organo-oxygenated titanium compounds include alkoxides, phenoxides, oxoalkoxides, condensed alkoxides, carboxylates and enolates. Preferably, the organo-oxygenated titanium compound is a titanium alkoxide. Suitable alkoxides include, for example, Ti(OC2H5)4, Ti(OC3H7)4, TiOC4H9)4 and Ti(OC8H 17 )4. Preferably, the organo-oxygenated titanium compound is Ti(OC4H9)4.

[0093] Preferably, the aluminum halide is a compound of the formula AlR n X 3-n where R is a hydrocarbon structural moiety containing 1 - 10 carbon atoms, X is a halogen, and 0.5 < n < 2. Examples of suitable aluminum halides of the formula AlR n X 3-n in (I) b) include ethylaluminum dibromide, ethylaluminum dichloride, propylaluminum dichloride, n-butylaluminum dichloride, isobutylaluminum dichloride, diethylaluminum chloride, diisobutylaluminum chloride. Preferably, X is Cl. Preferably, the organoaluminum halide in (I) b) is an organoaluminum chloride, more preferably the organoaluminum halide in (I) b) is selected from ethylaluminum dichloride, diethylaluminum dichloride, isobutylaluminum dichloride, diisobutylaluminum chloride or a mixture thereof.

[0094] Generally, the molar ratio of Al in I b):Ti in I a)2 is 3:1 to 16:1. According to a preferred embodiment of the present invention, the molar ratio of Al in I b):Ti in I a)2 is 6:1 to 10:1.

[0095] ​Suitable examples of cocatalysts of formula AlR3 include triethylaluminum, triisobutylaluminum, tri-n-hexylaluminum, and trioctylaluminum. Preferably, the aluminum compound of formula AlR3 in (II) is triethylaluminum or triisobutylaluminum.

[0096] Hydrocarbon solutions of organic oxygen-containing magnesium compounds and organic oxygen-containing titanium compounds can be prepared according to procedures disclosed, for example, in US 4178300 and EP 0876318. The solution is typically a clear liquid. In the presence of any solid particles, they can be removed by filtration before the solution is used for catalyst synthesis.

[0097] Typically, the magnesium:titanium molar ratio is less than 3:1, and preferably it is between 0.2:1 and 3:1.

[0098] Typically, the molar ratio of aluminum in (II) to titanium in (a) is from 1:1 to 300:1, and preferably the molar ratio of aluminum in (II) to titanium in (a) is from 3:1 to 100:1.

[0099] The catalyst can be obtained as follows: a first reaction between magnesium alkyl oxide and titanium alkyl oxide, followed by dilution with a hydrocarbon solvent, which forms a soluble complex consisting of magnesium alkyl oxide and titanium alkyl oxide, followed by a hydrocarbon solution of the complex and a reaction of the formula AlR. n X 3-n The reaction between organoaluminum halides.

[0100] Optionally, an electron donor may be added during the preparation of the solid catalytic complex (simultaneously with subsequent steps or in separate steps) or during the polymerization stage. The addition of an electron donor is disclosed, for example, in WO 2013087167.

[0101] Typically, the formula AlR n X 3-n Aluminum halides are used as hydrocarbon solutions. Any hydrocarbon that does not react with organoaluminum halides is suitable for use as this hydrocarbon.

[0102] The order of addition could be to add a hydrocarbon solution containing organic oxygen-containing magnesium compounds and organic oxygen-containing titanium compounds to formula AlR. n X 3-n Compounds, or vice versa.

[0103] The reaction can be performed at any temperature below the boiling point of the hydrocarbon used. Typically, the addition time is preferably less than 1 hour.

[0104] In hydrocarbon solutions of organic oxygen-containing magnesium compounds and organic oxygen-containing titanium compounds with formula AlR n X 3-nIn the organoaluminum halide reaction, the solid catalyst precursor precipitates. Following this precipitation reaction, the resulting mixture is heated for a period of time to complete the reaction. After the reaction, the precipitate is filtered and washed with hydrocarbons. Other methods, such as multiple decantation steps, are also used to separate the solid from the diluent and subsequently wash it. All steps should be carried out under an inert atmosphere of nitrogen or another suitable inert gas.

[0105] Other aspects

[0106] The present invention further relates to a composition comprising the ethylene polymer of the present invention. The composition may consist of the ethylene polymer of the present invention and additives such as pigments, nucleating agents, antistatic agents, fillers, antioxidants, etc. The amount of additives in the composition is typically up to 10% by weight, preferably up to 5% by weight.

[0107] The present invention further relates to an article comprising the ethylene polymer of the present invention or the composition of the present invention. Preferably, the article is selected from extruded articles such as tubes, blow-molded articles, films, and injection-molded articles.

[0108] It should be noted that this invention relates to all possible combinations of the features described herein, preferably, in particular, those combinations of features present in the claims. Therefore, it will be understood that this document describes all combinations of features relating to the compositions of the invention; all combinations of features relating to the methods of the invention; and all combinations of features relating to the compositions of the invention and the methods of the invention.

[0109] It should be further noted that the term "comprising / including" does not exclude the presence of other elements. However, it should also be understood that a description of a product / composition comprising certain components also discloses a product / composition composed of those components. A product / composition composed of these components can be advantageous because it provides a simpler and more economical method for preparing the product / composition. Similarly, it should be understood that a description of a method including certain steps also discloses a method composed of those steps. A method composed of these steps can be advantageous because it provides a simpler and more economical method.

[0110] When the lower and upper limits of a parameter are mentioned, it is also understood to mean that the range generated by the combination of the lower and upper limits is disclosed.

[0111] The invention will now be illustrated by the following embodiments, but is not limited thereto.

[0112] Example

[0113] Catalyst preparation

[0114] 100 g of granular Mg(OC2H5)2 and 150 mL of Ti(OC4H9)4 were placed in a 2 L round-bottom flask equipped with a reflux condenser and a stirrer. The mixture was heated to 180°C and then stirred for 1.5 hours while gently stirring. A clear liquid was obtained during this period. The mixture was cooled to 120°C and then diluted with 1480 mL of hexane. By adding hexane, the mixture was further cooled to 67°C. The mixture was held at this temperature for 2 hours, and then cooled to room temperature. The resulting clear solution was stored under a nitrogen atmosphere and used directly. Analysis of the solution showed a titanium concentration of 0.25 mol / L.

[0115] In a 1.0 L glass reactor equipped with baffles, a reflux condenser, and a stirrer, 286 mL of hexane and 170 mL of the complex obtained above were added. The stirrer was set to 1400 rpm. In a separate flask, 75 mL of a 50% ethyl aluminum dichloride (EADC) solution was added to 43 mL of hexane. The resulting EADC solution was fed into the reactor using a peristaltic pump over 15 minutes. The mixture was then refluxed for 2 hours. After cooling to ambient temperature, the resulting red / brown suspension was transferred to a glass P4 filter, and the solids were separated. The solids were washed four times with 500 mL of hexane. The solids were collected in 0.3 L of hexane, and the resulting slurry was stored under a nitrogen atmosphere. The solids content was 30 g / L.

[0116] Catalyst analysis results:

[0117] Ti 9.7wt%; Mg 10.4wt%; Al 4.6wt%; Cl 49wt%; OEt 9.0wt%; and OBu 12wt%.

[0118] Preparation of ethylene polymer components

[0119] Component A

[0120] Ethylene polymer component A was prepared using 40 mg of the catalyst prepared above in a 20 L autoclave reactor, with 10 L of purified hexane as a diluent. 8 mmol of TIBA was added to the 10 L of purified hexane. The catalyst was added at the start of polymerization. After catalyst injection, ethylene and hydrogen were continuously added to the reactor to maintain a constant total pressure and H2 / C2 ratio throughout the polymerization process. Polymerization was carried out at 85°C and a total pressure of 5.5 barg, with a hydrogen-to-ethylene ratio of 3.0 mol / mol in the reactor headspace.

[0121] Component B

[0122] Ethylene polymer component B was prepared using 15 mg of the catalyst prepared above in a 10 L autoclave reactor, with 5 L of purified hexane as a diluent. 8 mmol of TIBA was added to the 5 L of purified hexane. 80 mL of purified 1-hexene was added to the reactor. The catalyst was added at the start of polymerization. After catalyst injection, ethylene and hydrogen were continuously added to the reactor to maintain a constant total pressure and H2 / C2 ratio throughout the polymerization process. Polymerization was carried out at 68°C and a total pressure of 1.0 barg, with a hydrogen-to-ethylene ratio of 0.2 mol / mol in the reactor headspace.

[0123] Component C

[0124] Ethylene polymer component C was prepared using 15 mg of the catalyst prepared above in a 20 L autoclave reactor, with 10 L of purified hexane as a diluent. 8 mmol of TIBA was added to the 10 L of purified hexane. 100 mL of purified 1-hexene was added to the reactor. The catalyst was added at the start of polymerization. After catalyst injection, ethylene and hydrogen were continuously added to the reactor to maintain a constant total pressure and H2 / C2 ratio throughout the polymerization process. Polymerization was carried out at 78°C and a total pressure of 1.4 barg, with a hydrogen-to-ethylene ratio of 0.034 mol / mol in the reactor headspace.

[0125] Component D

[0126] Ethylene polymer component D was prepared using 15 mg of the catalyst prepared above in a 10 L autoclave reactor, with 5 L of purified hexane as a diluent. 8 mmol of TIBA was added to the 5 L of purified hexane. 20 mL of purified 1-hexene was added to the reactor. The catalyst was added at the start of polymerization. After catalyst injection, ethylene and hydrogen were continuously added to the reactor to maintain a constant total pressure and H2 / C2 ratio throughout the polymerization process. Polymerization was carried out at 78°C and a total pressure of 2.3 barg, with a hydrogen-to-ethylene ratio of 0.17 mol / mol in the reactor headspace.

[0127] Component E

[0128] Ethylene polymer component E was prepared using 15 mg of the catalyst prepared above in a 20 L autoclave reactor, with 10 L of purified hexane as a diluent. 8 mmol of TIBA was added to the 10 L of purified hexane. 200 mL of purified 1-hexene was added to the reactor. The catalyst was added at the start of polymerization. After catalyst injection, ethylene and hydrogen were continuously added to the reactor to maintain a constant total pressure and H2 / C2 ratio throughout the polymerization process. Polymerization was carried out at 78°C and a total pressure of 1.4 barg, with a hydrogen-to-ethylene ratio of 0.03 mol / mol in the reactor headspace.

[0129] Component F

[0130] Ethylene polymer component F was prepared using 15 mg of the catalyst prepared above in a 20 L autoclave reactor, with 10 L of purified hexane as a diluent. 8 mmol of TIBA was added to the 10 L of purified hexane. 14 mL of purified 1-hexene was added to the reactor. The catalyst was added at the start of polymerization. After catalyst injection, ethylene and hydrogen were continuously added to the reactor to maintain a constant total pressure and H2 / C2 ratio throughout the polymerization process. Polymerization was carried out at 78°C and a total pressure of 1.46 barg, with a hydrogen-to-ethylene ratio of 0.11 mol / mol in the reactor headspace.

[0131] Component G

[0132] Ethylene polymer component G was prepared using 20 mg of the catalyst prepared above in a 20 L autoclave reactor, with 10 L of purified hexane as a diluent. 8 mmol of TIBA was added to the 10 L of purified hexane. 225 mL of purified 1-hexene was added to the reactor. The catalyst was added at the start of polymerization. After catalyst injection, ethylene and hydrogen were continuously added to the reactor to maintain a constant total pressure and H2 / C2 ratio throughout the polymerization process. Polymerization was carried out at 78°C and a total pressure of 1.42 barg, with a hydrogen-to-ethylene ratio of 0.056 mol / mol in the reactor headspace.

[0133] The molecular weight, density, comonomer content, and MFI of each component were measured according to the following method and summarized in Table 1.

[0134] Table 1

[0135]

[0136] Preparation of trimodal ethylene polymer

[0137] Example 1

[0138] 11 g of component A, 5.5 g of component B, 5.5 g of component C, and 5 g / L di-tert-butyl-p-cresol in xylene were dissolved in 2.5 L of xylene. The mixture was stirred at 140°C for 3 hours, then precipitated in methanol and dried under vacuum. After drying, 1500 ppm of Irganox 1010 and 1500 ppm of Irgafos 168 relative to the polymer were added to the material in 120 ml of acetone and 30 ml of heptane. The slurry was stirred at room temperature for 12 hours, followed by further evaporation under vacuum at 45°C for another 12 hours.

[0139] Comparative Experiment 2

[0140] Repeat Example 1, except that 11g of component A, 5.5g of component D and 5.5g of component E are mixed.

[0141] Comparative Test 3

[0142] Repeat Example 1, except that 11g of component A, 5.5g of component F and 5.5g of component G are mixed.

[0143] The molecular weight, density, comonomer content, MFI and strain hardening of the composition were measured according to the methods described below and are summarized in Table 2.

[0144] Table 2

[0145]

[0146] The composition of the present invention (Ex1), with similar comonomer content and density to components B and C, exhibits higher strain hardening than the composition (CEx2), which has a higher comonomer content and lower density compared to the highest molecular weight component E and the medium molecular weight component D.

[0147] The composition of the present invention (Ex1), with similar comonomer content and density to components B and C, exhibits strain hardening higher than that of the composition (CEx3) with lower comonomer content compared to the highest molecular weight component F and the medium molecular weight component G.

[0148] from Figure 1-4 Given that Ex1 and CEx2 have similar molecular weight distributions and total monomer content, it can be understood that Ex1 and CEx2 have similar impact properties, processability, melt strength, sag resistance, and stiffness.

[0149] Therefore, the compositions of the present invention exhibit high strain hardening while maintaining different other mechanical properties.

[0150] Molecular weight distribution (MWD) and determination of MWD

[0151] Mw, Mn, and Mz are measured according to ASTM D 6474-12 (Routine test method for determining the molecular weight distribution and average molecular weight of polyolefins by high-temperature gel permeation chromatography). Mw represents the weight-average molecular weight, and Mn represents the number-average molecular weight. Mz represents the z-average molecular weight.

[0152] MWD and SCB as a function of molecular weight were determined at 160°C using a PolymerChar GPC-IR system (PolymerChar SA, Spain) equipped with an IR5 MCT detector and a PolymerChar viscometer. GPC separation was performed using three Polymer Laboratories 13µm PLgel Olexis columns (300 × 7.5 mm) in tandem. 1,2,4-trichlorobenzene (also known as 2,6-di-tert-butyl-4-methylphenol or BHT), stabilized with 1 g / L butylated hydroxytoluene, was used as the eluent at a flow rate of 1 mL / min. The sample concentration was approximately 0.7 mg / mL, and the injection volume was 300 µL. Molar amounts were determined based on the Universal GPC principle using corrections derived from narrow and wide PE standards (0.5–2800 kg / mol, Mw / Mn⁻⁴ to 15) combined with known Mark-Horwinkle constants (α = 0.725 and log K = -3.721) of the PE calibrators.

[0153] density

[0154] The density of the polymer component was measured using a 40×40×1.6 mm polymer test piece in a TP 200 Fontyne press according to ISO 17855-2. The compression cycle temperature was set at 180°C, using a contact pressure of 10 minutes. Cooling was performed as follows: no pressure increase for the first 30 seconds, followed by pressurization up to 200 kN, and maintaining the pressure level for the time required for the sample to reach 23°C at a cooling rate of 15±2°C / min. The mass of the test piece was determined in air (using an analytical balance XS104 Mettler Toledo). Subsequently, the test piece was immersed in 4 L of 100°C water (Toyo Seiki DH 100 automatic densitometer, equipped with a WMR-equipped MX7LR-20 thermostat) for 10 minutes, after which heating was turned off and the sample was cooled to room temperature. The density was then determined as follows:

[0155]

[0156] in:

[0157] =Density of the test piece (g / cm³)

[0158] =Mass of the test piece in air (g)

[0159] =Density of softened water at the test temperature (23°C) (g / cm³)

[0160] =Mass of the test piece and plumb bob in water (g)

[0161] =Mass of the plumb bob held in water (g)

[0162] Note: Because polyethylene has a lower density than water, a plumb bob is used to keep the test piece submerged.

[0163] The density of the copolymer is calculated from the density and proportion of the polymer components.

[0164] Comonomer content

[0165] The sample was dissolved at 125°C in C2D2Cl4 containing DBPC as a stabilizer. 13 C10 NMR spectra were recorded on a Bruker Avance 500 NMR spectrometer equipped with a 10 mm cryogenically cooled probe tip and operated at 125°C. Data were processed using a Bruker Topspin 3.6.

[0166] MFI

[0167] MFI is measured at 190°C under a load of 1.2 kg (MI1.2) or 21.6 kg (MI21.6) according to ISO 1133-1:2011.

[0168] strain hardening modulus

[0169] Strain hardening was determined according to ISO 18488.

[0170] Short chain branching distribution (SCBD)

[0171] The comonomer content of the polymer molecular weight fraction exiting the column was quantified using an infrared detector (IR5 MCT, Polymer Char SA, Spain) located at the GPC column exit, in units of short-chain branch number per 1000 carbon atoms (SCB / 1000C). The SCB / 1000C content was determined by measuring the response at the IR band ratio (methyl to methylene absorbance), corrected for this signal relative to known samples in the range of 1–75 SCB / 1000C. Correction for end groups was made when calculating the SCB number / 1000C from the total methyl end groups per thousand carbon atoms, assuming two end groups per polymer chain.

Claims

1. An ethylene copolymer with a multimodal molecular weight distribution, comprising or consisting of: 40-80 wt% ethylene polymer component A, Ethylene copolymer component B, containing 5-40 wt% ethylene and olefin comonomers, has a higher molecular weight (Mn) than ethylene polymer component A, and also has a molar comonomer content (C). B and density D B ,and Ethylene copolymer component C, containing 5-40 wt% ethylene and olefin comonomers, has a higher molecular weight (Mn) than ethylene copolymer component B, and also has a molar comonomer content of C. C and density D C , The amounts of A, B, and C are based on the total weight of the ethylene copolymer, wherein The comonomer content of this ethylene copolymer is 0.10-3.00 mol%, and C B and C C The difference is at most 0.10 mol%, where C B Less than or equal to C C And wherein the ethylene polymer component A is an ethylene homopolymer, wherein the density of the ethylene copolymer is 940-960 kg / m³. 3 D B and D C The difference is at most 5.0 kg / m 3 D B Higher than or equal to D C .

2. The ethylene copolymer according to claim 1, wherein the melt flow index of the ethylene copolymer, measured according to ISO 1133-1: 2011 at 190°C and 5 kg, is 0.05-20 dg / min, and / or the melt flow index, measured according to ISO 1133-1: 2011 at 190°C and 21.6 kg, is 1.0-500 dg / min.

3. The ethylene copolymer according to claim 1 or 2, wherein the density D of the ethylene polymer component A is... A At least 954 kg / m 3 And / or the melt flow index, measured at 190°C and 1.2 kg according to ISO 1133-1:2011, is 0.5-500 dg / min.

4. The ethylene copolymer according to claim 3, wherein the density D of the ethylene polymer component A is... A 965-982 kg / m 3 .

5. The ethylene copolymer according to claim 3, wherein the density D of the ethylene polymer component A is... A 968-975 kg / m 3 .

6. The ethylene copolymer according to claim 3, wherein the melt flow index of the ethylene polymer component A, measured according to ISO 1133-1:2011 at 190°C and 1.2 kg, is 40-250 dg / min.

7. The ethylene copolymer according to claim 1 or 2, wherein the density D of the ethylene copolymer component B is... B 910-940 kg / m 3 And / or the melt flow index, measured at 190°C and 21.6 kg according to ISO 1133-1:2011, is 0.01-50.0 dg / min.

8. The ethylene copolymer according to claim 7, wherein the density D of the ethylene copolymer component B is... B 925-935 kg / m 3 .

9. The ethylene copolymer according to claim 7, wherein the melt flow index of the ethylene copolymer component B, measured according to ISO 1133-1:2011 at 190°C and 21.6 kg, is 0.1-5.0 dg / min.

10. The ethylene copolymer of claim 7, wherein the ethylene copolymer component B is an ethylene copolymer of ethylene and 1-butene and / or 1-hexene.

11. The ethylene copolymer according to claim 1 or 2, wherein the density D of the ethylene copolymer component C is... C 910-940 kg / m 3 And / or the melt flow index, measured at 190°C and 21.6 kg according to ISO 1133-1:2011, is 0.01-50.0 dg / min.

12. The ethylene copolymer according to claim 11, wherein the density D of the ethylene copolymer component C is... C 920-930 kg / m 3 .

13. The ethylene copolymer of claim 11, wherein the melt flow index of the ethylene copolymer component C, measured according to ISO 1133-1:2011 at 190°C and 21.6 kg, is 0.05-2.0 dg / min.

14. The ethylene copolymer of claim 11, wherein the ethylene copolymer component C is an ethylene copolymer of ethylene and 1-butene and / or 1-hexene.

15. The ethylene copolymer according to claim 1 or 2, wherein the Mw of the ethylene polymer component A is 4-150 kDa, the Mw of the ethylene copolymer component B is 100-1000 kDa, and / or the Mw of the ethylene copolymer component C is 170-1200 kDa.

16. The ethylene copolymer of claim 15, wherein the Mw of the ethylene copolymer component B is at least 100 kDa higher than the Mw of the ethylene polymer component A, and / or the Mw of the ethylene copolymer component C is at least 20 kDa higher than the Mw of the ethylene copolymer component B.

17. The ethylene copolymer according to claim 1 or 2, wherein the comonomer content of component B is C. B The content of comonomers in component C is 0.10-5.00 mol%, and / or the content of comonomers in component C. C It ranges from 0.10 to 5.00 mol%.

18. The ethylene copolymer according to claim 17, wherein the comonomer content of component B is C. B It ranges from 0.50 to 3.00 mol%.

19. The ethylene copolymer according to claim 17, wherein the comonomer content of component B is C. B It ranges from 0.75 to 1.50 mol%.

20. The ethylene copolymer according to claim 17, wherein the comonomer content of component C is C C It ranges from 0.50 to 3.00 mol%.

21. The ethylene copolymer according to claim 17, wherein the comonomer content of component C is C C It ranges from 0.75 to 1.50 mol%.

22. The ethylene copolymer according to claim 1 or 2, wherein C B and C C The difference is at most 0.05 mol%.

23. The ethylene copolymer according to claim 22, wherein C B and C C The difference is at most 0.03 mol%.

24. The ethylene copolymer according to claim 1 or 2, wherein the ethylene copolymer comprises one or more additional ethylene polymer components.

25. The ethylene copolymer of claim 24, wherein the total amount of components A, B and C is at least 60 wt% relative to the ethylene copolymer.

26. The ethylene copolymer of claim 24, wherein the total amount of components A, B and C is at least 70 wt% relative to the ethylene copolymer.

27. The ethylene copolymer of claim 24, wherein the total amount of components A, B and C is at least 80 wt% relative to the ethylene copolymer.

28. The ethylene copolymer of claim 24, wherein the total amount of components A, B and C is at least 90 wt% relative to the ethylene copolymer.

29. The ethylene copolymer of claim 24, wherein the total amount of components A, B and C is at least 95 wt% relative to the ethylene copolymer.

30. The ethylene copolymer of claim 24, wherein the total amount of components A, B and C is at least 98 wt% relative to the ethylene copolymer.

31. The ethylene copolymer of claim 24, wherein the total amount of components A, B and C is at least 99 wt% relative to the ethylene copolymer.

32. A method for preparing an ethylene copolymer according to any one of claims 1-31, comprising melting or solution blending components A, B and C, wherein each of components A, B and C is prepared by slurry polymerization in the presence of a Ziegler-Natta catalyst system.

33. A method for preparing an ethylene copolymer according to any one of claims 1-31, wherein the copolymer is a multi-step slurry polymerization method carried out using a cascade reactor in the presence of a Ziegler-Natta catalyst system.

34. The method according to claim 32 or 33, wherein the catalyst system comprises: (I) Solid reaction product, which is obtained through the following reaction: a) A hydrocarbon solution containing: 1) Organic oxygen-containing magnesium compounds or halogenated magnesium compounds, and 2) Organic oxygen-containing titanium compounds, and b) Aluminum halide of the formula AlR n X 3-n where R is a hydrocarbon structural moiety having 1 to 10 carbon atoms, X is a halogen, and 0 < n < 3, and (II) Aluminum compounds of formula AlR3, wherein R is a hydrocarbon structural moiety containing 1-10 carbon atoms.

35. A composition comprising an ethylene copolymer according to any one of claims 1-31, and an additive.

36. An article comprising an ethylene copolymer according to any one of claims 1-31 or a composition according to claim 35.

37. The article of claim 36, wherein the article is selected from extruded articles, blow-molded articles, films and injection-molded articles.

38. The article of claim 37, wherein the extruded article is a tube.

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