Rotational molding composition having low relative elasticity

Abstract

High-density polyethylene compositions with high flow index and bimodal composition provide an outstanding combination of processability, stiffness, and ductility in rotationally molded articles. The compositions have a low relative modulus (G' / G", measured at 0.05 radians / second) of less than 0.03.

Description

[Technical Field]

[0001] The present disclosure relates to high-density polyethylene compositions for use in rotationally molded products. The compositions have high stiffness and ductility. The compositions also have a high flow index that facilitates molding, especially for parts having complex shapes and geometries. The compositions have a low relative modulus (G' / G"). [Background technology]

[0002] There are many different considerations in producing a resin suitable for use in making rotomolded articles, non-limiting examples of which include: the resin must be capable of being produced at commercially acceptable production rates; the resin must be suitable for use in the rotomolding process (e.g., have a suitable sintering temperature and a suitable cooling rate for removal from the mold); and the resulting rotomolded part must have properties suitable for the end use application.

[0003] U.S. Patent Nos. 5,382,630 and 5,382,631, issued to Stehling on January 17, 1995, and assigned to Exxon, teach bimodal resins with excellent physical properties. The patents require that the blend have two or more components, each with a polydispersity (Mw / Mn) of less than 3, that the blend have a polydispersity greater than 3, and that the blend does not contain a component with a relatively high molecular weight and low comonomer content (i.e., reversed by the incorporation of comonomer).

[0004] U.S. Patent No. 6,969,741, issued November 29, 2005 to Lustiger et al. and assigned to ExxonMobil, teaches polyethylene blends suitable for rotational molding. The patent describes blends of polyethylenes in which the density of each component differs by 0.030 g / cm. 3 The difference in density of the constituent polymers in the composition of the present disclosure is 0.030 g / cm or more. 3 is less than.

[0005] U.S. Patent No. 8,486,323, issued July 16, 2013, in the name of Davis and assigned to Dow Global Technologies Inc., teaches polymer blends for use in rotationally molded products that have high impact resistance. The blends have a residual unsaturation content of less than 0.06 per 1000 carbon atoms. Summary of the Invention [Means for solving the problem]

[0006] One embodiment of the present invention provides: 1) Molecular weight distribution Mw / Mn of 2.3 to 5.5; 2) Density of 0.940~0.957g / cc; 3) a melt index, I2, of 4 to 10 grams per 10 minutes, measured according to ASTM D1238 at 190°C with a 2.16 kg load; and 4) Relative modulus, G' / G" less than 0.03 rad / sec, measured at 190°C and 0.05 rad / sec 1. A bimodal polyethylene composition having The bimodal polyethylene composition comprises the following A and B: A. 10 to 70 wt. % of a first ethylene copolymer having the following Ai to A.iii: A melt index I2 of 0.4 to 5 grams per 10 minutes measured by AiASTM D1238 at 190°C with a load of 2.16 kg; A.ii. a molecular weight distribution Mw / Mn of 1.8 to 3.0; and A.iii.Density of 0.920-0.950 g / cc; B. 90 to 30 wt. % of a second ethylene copolymer having the following Bi to B.iii: Melt index I2 of 4 to 1500 grams per 10 minutes measured by BiASTM D1238 at 190°C with a 2.16 kg load; B.ii. A molecular weight distribution Mw / Mn of 2.3 to 6.0; and B.iii. A density greater than the density of said first ethylene copolymer but less than 0.967 g / cc; It contains provided that the density of the first ethylene copolymer is lower than the density of the second ethylene copolymer by an amount of 0.010 to 0.035 g / cc; Bimodal polyethylene compositions.

[0007] Another embodiment provides: 1. A process for producing a polyolefin hollow product, comprising: filling a mold with the bimodal polyethylene composition of claim 1 of the accompanying claims; heating the mold in an oven to above 280°C to melt the stabilized polyolefin; rotating the mold on at least two axes to cause the plastic material to spread on the walls; cooling the mold while rotating; opening the mold; and removing the resulting hollow product.

[0008] Another embodiment provides: in the presence of a single-site catalyst comprising a phosphinimine ligand in combination with one or more activators in a first reactor, and in the presence of a Ziegler-Natta (ZN) catalyst in a second reactor, ethylene and one or more C 4-8 A process for producing the bimodal polyethylene composition as described above, comprising feeding comonomers to two successive solution phase reactors.

[0009] In one embodiment, the single catalyst is defined by the following formula: [ka] wherein M is selected from the group consisting of Ti, Zr, and Hf; Pl is a phosphinimine ligand of the formula: [ka] (In the formula, each R 21is a hydrogen atom; a halogen atom; a halogen atom that is not substituted with a halogen atom or is further substituted with a halogen atom, typically C 1-10 Hydrocarbyl groups of C 1-8 Alkoxy group; C 6-10 aryl or aryloxy groups; amide groups; silyl groups of the formula: [ka] (In the formula, each R 22 are independently hydrogen, C 1-8 Alkyl or alkoxy groups, and C 6-10 aryl or aryloxy groups; and germanyl groups of the formula: [ka] (In the formula, R 22 are as defined above; are independently selected from the group consisting of: L is a monoanionic cyclopentadienyl-type ligand independently selected from the group consisting of cyclopentadienyl-type ligands; Y is independently selected from the group consisting of activatable ligands; m is 1 or 2; n is 0 or 1; p is an integer, and the sum of m+n+p equals the valence state of M.

[0010] A further embodiment provides a rotomolded part consisting essentially of the bimodal polyethylene composition described above. In another embodiment, the rotomolded part made from the bimodal polyethylene composition exhibits ductile fracture. One embodiment of the present invention will be described below, but the present invention is not limited thereto. [Invention 1] 1) Molecular weight distribution Mw / Mn of 2.3 to 5.5; 2) Density of 0.940~0.957g / cc; 3) A melt index (I) of 4 to 10 grams per 10 minutes measured according to ASTM D1238 at 190°C with a 2.16 kg load. 2 and 4) Relative elasticity G' / G" of less than 0.03 rad / sec, measured at 190°C and 0.05 rad / sec 1. A bimodal polyethylene composition having The bimodal polyethylene composition comprises the following A and B: A. 10 to 70 wt. % of a first ethylene copolymer having the following Ai to A.iii: Melt index I of 0.4 to 5 grams per 10 minutes measured according to ASTM D1238 at 190°C with a 2.16 kg load 2 ; A.ii. a molecular weight distribution Mw / Mn of 1.8 to 3.0; and A.iii.Density of 0.920-0.950 g / cc; B. 90 to 30 wt. % of a second ethylene copolymer having the following Bi to B.iii: Melt index I of 4 to 1500 grams per 10 minutes measured by ASTM D1238 at 190°C with a 2.16 kg load 2 ; B.ii. A molecular weight distribution Mw / Mn of 2.3 to 6.0; and B.iii. A density greater than the density of said first ethylene copolymer but less than 0.967 g / cc; It contains provided that the density of the first ethylene copolymer is lower than the density of the second ethylene copolymer by an amount of 0.010 to 0.035 g / cc; Bimodal polyethylene compositions. [Invention 2] the first ethylene copolymer is A.iv.Number average molecular weight Mn of 35,000 to 80,000; Weight average molecular weight Mw of 70,000 to 150,000; A.vi. 120,000-250,000 Mz; A.vii.Mw / Mn of 2-3; A. viii. Number of short chain branches (SCB1) between 1 and 5 per 1000 carbon atoms; and A.ix. Melt index I of 0.5 to 4.0 grams per 10 minutes, measured according to ASTM D1238 at 190°C with a load of 2.16 kg 2 2. The polyethylene composition according to claim 1, further characterized by having: [Invention 3] the second ethylene copolymer is A.iv.Number average molecular weight Mn of 12,000 to 30,000; Weight average molecular weight Mw of Av28,000-72,000; A. vi. 70,000-150,000 Mz; A.vii.Mw / Mn of 2.3-5.0; A.viii. Number of short chain branches (SCB2) of 0.1-2 per 1000 carbon atoms; B.ix. A density greater than the density of the first ethylene copolymer but less than 0.965 g / cc; BxMelt index I of 4 to 100 grams per 10 minutes measured according to ASTM D1238 at 190°C with a 2.16 kg load 2 ; However, the density of the first ethylene copolymer is lower than the density of the second ethylene copolymer by an amount of 0.010 to 0.030 g / cc. 3. The polyethylene composition according to claim 1 or 2, further characterized by: [Invention 4] A rotationally molded part produced using the polyethylene composition according to invention 1, 2 or 3. [Invention 5] 5. A rotationally molded part according to claim 4, having a ductility index of 80 to 100%. [Invention 6] 6. The rotationally molded part of claim 5, having an average energy to fracture of greater than 120 ft·lbs for 0.250 inch thick specimens tested in accordance with ASTM D5628 at a test temperature of −40° C. [Invention 7] 6. A rotomoulded part according to claim 4 or 5, wherein the first ethylene copolymer is prepared using a single-site catalyst and the second ethylene copolymer is prepared using a Ziegler-Natta catalyst. [Invention 8] 2. The polyethylene composition according to claim 1, wherein the bimodal polyethylene composition has a comonomer content of less than 1.2 mol % as measured by FTIR methods. [Invention 9] 2. The polyethylene composition according to claim 1, wherein the first and second ethylene copolymers are copolymers of ethylene and 1-octene. [Invention 10] 2. The polyethylene composition according to claim 1, wherein the bimodal polyethylene composition is prepared by contacting ethylene and an α-olefin with a polymerization catalyst under solution polymerization conditions in at least two polymerization reactors. [Invention 11] A process for producing a polyolefin hollow product, comprising: Filling a mold with the bimodal polyethylene composition of invention 1, heating the mold in an oven to above 280°C to melt the stabilized polyolefin, rotating the mold on at least two axes to spread the plastic material on the walls, cooling the mold while rotating, opening the mold, and removing the resulting hollow product. The process includes: [Brief explanation of the drawings]

[0011] [Figure 1] Figure 1 shows the deconvolution of Example 1. The experimentally measured GPC chromatograms were deconvoluted into the first and second ethylene interpolymers based on kinetic model predictions. [Figure 2] Figure 2 shows the deconvolution of Example 2. The experimentally measured GPC chromatograms were deconvoluted into 1 and 2 ethylene interpolymers based on kinetic model predictions. [Figure 3] FIG. 3 is a plot of the molecular weight distribution obtained by gel permeation chromatography (GPC) of the resins of Examples 1, 2, 3 and 4. [Figure 4] FIG. 4 is a plot of the molecular weight distribution obtained by gel permeation chromatography (GPC) of the resins of Examples 1, 8, 9 and 10. [Figure 5] FIG. 5 is a plot of the molecular weight distribution obtained by gel permeation chromatography (GPC) of the resins of Examples 3 and 4, as well as the short chain branching distribution determined from GPC-FTIR. [Figure 6]FIG. 6 is a plot of the molecular weight distributions obtained by gel permeation chromatography (GPC) of the resins of Examples 5, 6, 8 and 9, as well as the short chain branching distributions determined from GPC-FTIR. DETAILED DESCRIPTION OF THE INVENTION

[0012] Numeric range Except in the experimental examples or where otherwise indicated, all numerical values ​​or expressions referring to quantities of ingredients, reaction conditions, and the like used in the specification and claims should be understood to be modified in all instances by the term "about." Accordingly, unless indicated to the contrary, the numerical parameters set forth in the following specification and appended claims are approximations that may vary depending upon the desired properties of the disclosed embodiments. At the very least, each numerical parameter should be construed in light of the number of reported significant digits and by applying ordinary rounding techniques, but rather as an attempt to limit the application of the doctrine of equivalents to the scope of the claims.

[0013] Notwithstanding that the numerical ranges and parameters setting forth the broad scope of the present disclosure are approximations, the numerical values ​​set forth in the specific examples are reported as precisely as possible, however, any numerical values ​​inherently contain certain errors necessarily resulting from the standard deviation found in their respective testing measurements.

[0014] It should also be understood that any numerical range recited herein is intended to encompass all subranges encompassed therein. For example, a range of "1 to 10" is intended to encompass all subranges between the recited minimum value of 1 and the recited maximum value of 10, inclusive; that is, to encompass all subranges having a minimum value of 1 or more and a maximum value of 10 or less. Because the disclosed numerical ranges are continuous, they include all values ​​between the minimum and maximum values. Unless otherwise specified, the various numerical ranges specified in this application are approximations (round numbers).

[0015] All composition ranges set forth herein are limited to and do not actually exceed a total of 100 percent (volume percent or weight percent). Where multiple components may be present in a composition, the sum of the maximum amounts of each component may exceed 100 percent, with the understanding, and as one of ordinary skill in the art would readily understand, that the amounts of multiple components actually used will equal a maximum of 100 percent.

[0016] The compositions of the present disclosure are bimodal polyethylenes that can be deconvoluted into two distinct components. Typically, this is evidenced by the presence of a "shoulder" on the right side of the gel permeation chromatography (GPC) curve (see Figure 1). In this case, as shown in Figure 2, there is a small shoulder on the right side of the GPC curve, which points to a small amount of a higher molecular weight, lower density component.

[0017] The high molecular weight component has a melt index of 0.4 to 5 and is present in an amount of about 10 to about 70% by weight of the total composition, preferably about 15 to about 50% by weight, and the low molecular weight component is present in a corresponding amount of about 90 to about 30% by weight of the total composition, preferably about 85 to about 50% by weight based on the weight of the total composition.

[0018] In one embodiment, the high molecular weight component has a weight average molecular weight (Mw) of about 70,000 to about 150,000 as measured by gel permeation chromatography (GPC). The high molecular weight component has a polydispersity index (Mw / Mn: weight average molecular weight / number average molecular weight) of 1.8 to 3.0. The melt index I2 of the entire composition is about 4 to 10.

[0019] The high molecular weight component has a lower density than the low molecular weight component. The density of the high molecular weight component in the composition is about 0.920 to about 0.950 g / cm 3 The density of this component, or any other component or the total composition, is a function of the degree of comonomer incorporation. The high molecular weight component preferably does not have any long chain branching.

[0020] The low molecular weight component has a melt index of 4 to 1500. In one embodiment, its Mw is from about 28,000 to about 72,000 as measured by gel permeation chromatography (GPC), and the polydispersity (Mw / Mn) is from 2.3 to 5.0.

[0021] The low molecular weight component has a density 0.010 to 0.030 g / cc higher than that of the high molecular weight component.

[0022] The catalyst used to produce the bimodal polyethylene composition preferably does not produce long chain branching.

[0023] The overall properties of the bimodal polyethylene composition may include: Approximately 0.940~approximately 0.957g / cm 3 density of; a melt index (I2) of about 4 to about 10, as measured by ASTM D1238 at 190°C using a 2.16 kg load; and A relative elasticity G' / G" of less than 0.03 (especially 0.01 to 0.03), measured at 190°C and 0.05 rad / s.

[0024] In one embodiment, the overall polyethylene composition has a comonomer content of less than 1.2 mole % as measured by Fourier transform infrared spectroscopy (FTIR).

[0025] The polymers can be produced using solution polymerization techniques. In the solution polymerization of ethylene with one or more comonomers, non-limiting examples of the comonomers include C 3-8 In some cases, 1-hexene or 1-octene is preferred; in other cases, 1-octene is preferred. Generally, the monomers are typically unsubstituted or C 1 -substituted olefins such as pentane, methylpentane, hexane, heptane, octane, cyclohexane, methylcyclohexane, and hydrogenated naphtha. 1-4 C optionally substituted with an alkyl group 5-12It is dissolved in an inert hydrocarbon solvent such as a hydrocarbon. An example of a suitable commercially available solvent is "Isopar E" (C 8-12 Aliphatic solvents (Exxon Chemical Co.).

[0026] The catalyst and activator may also be dissolved in a solvent or suspended in a diluent that is miscible with the solvent under the reaction conditions.

[0027] In one embodiment, the single-site catalyst is a compound of the formula: [ka] wherein M is selected from the group consisting of Ti, Zr, and Hf; Pl is a phosphinimine ligand of the formula: [ka] (In the formula, each R 21 is a hydrogen atom; a halogen atom; a halogen atom that is not substituted with a halogen atom or is further substituted with a halogen atom, typically C 1-10 Hydrocarbyl group of C 1-8 Alkoxy group; C 6-10 aryl or aryloxy groups; amide groups; silyl groups of the formula: [ka] (In the formula, each R 22 are independently hydrogen, C 1-8 Alkyl or alkoxy groups, and C 6-10 aryl or aryloxy groups; and germanyl groups of the formula: [ka] (In the formula, R 22 are as defined above; are independently selected from the group consisting of: L is a monoanionic cyclopentadienyl-type ligand independently selected from the group consisting of cyclopentadienyl-type ligands; Y is independently selected from the group consisting of activatable ligands; m is 1 or 2; n is 0 or 1; p is an integer, and the sum of m+n+p equals the valence state of M.

[0028] Suitable phosphinimines are those in which each R 21 is a hydrocarbyl group, preferably C 1-6 Hydrocarbyl groups, most preferably C 1-4 It is a hydrocarbyl group.

[0029] The term "cyclopentadienyl" refers to a five-membered carbon ring with a delocalized bond within the ring, typically bonded by an η-5 bond to an active catalytic site, generally a Group 4 metal (M). The cyclopentadienyl ligand may be unsubstituted or may contain one of the following groups: unsubstituted or may contain halogen atoms and C 1-4 C substituted with one or more substituents selected from the group consisting of alkyl groups 1-10 Hydrocarbyl group; halogen atom; C 1-8 Alkoxy group; C 6-10 Aryl or aryloxy groups; unsubstituted or containing up to two C 1-8 Amide groups substituted with alkyl groups; unsubstituted or with up to two C 1-8 phosphido groups substituted with alkyl groups; groups of the formula -Si-(R)3, where each R is independently hydrogen, C 1-8 alkyl or alkoxy groups, and C 6-10 aryl or aryloxy groups; silyl groups of the formula (R); and germanyl groups of the formula Ge-(R)3, where R is as defined above.

[0030] The cyclopentadienyl-type ligand may be selected from the group consisting of cyclopentadienyl, indenyl, and fluorenyl groups, which may be unsubstituted or may contain fluorine atoms, chlorine atoms; 1-4 an alkyl group; which may be unsubstituted or partially or completely substituted with one or more substituents selected from the group consisting of a phenyl group or a benzyl group substituted with one or more fluorine atoms;

[0031] The activatable ligand Y is a halogen atom, C 1-4 Alkyl group, C 6-20 Aryl group, C 7-12 Arylalkyl groups, C 6-10 Phenoxy group, up to two C 1-4 an amide group optionally substituted with an alkyl group, and C 1-4 Optionally, Y is selected from the group consisting of a chlorine atom, a methyl group, an ethyl group, and a benzyl group.

[0032] Suitable phosphinimine catalysts are Group 4 organometallic complexes containing one phosphinimine ligand (described above), one cyclopentadienyl-type (L) ligand, and two activatable ligands. These catalysts are unbridged.

[0033] activator Activators for the catalyst are typically selected from the group consisting of aluminoxanes and ionic activators.

[0034] Alumoxanes (also known as "aluminoxanes") Suitable alumoxanes have the formula: 4 )2AlO(R 4 AlO) m Al(R 4 )2, where each R 4 is independently C 1-20 hydrocarbyl groups, m is 0 to 50, and preferably R 4 is C 1-4is an alkyl group, and m is 5 to 30. One non-limiting example of a suitable alumoxane is methylalumoxane (or "MAO"), where each R is methyl.

[0035] Alumoxanes are well known as cocatalysts (promoter catalysts), especially for metallocene-type catalysts. Alumoxanes are also readily available commercial products.

[0036] The use of an alumoxane cocatalyst generally requires that the molar ratio of aluminum to transition metal in the catalyst be from about 20:1 to about 1000:1, and in other cases from about 50:1 to about 250:1.

[0037] Commercially available MAO typically contains free aluminum alkyls (e.g., trimethylaluminum or "TMA") that can reduce catalyst activity and / or broaden the molecular weight distribution of the polymer. When a narrow molecular weight distribution polymer is required, it is preferable to treat such commercially available MAO with an additive capable of reacting with TMA. Non-limiting examples of suitable additives include alcohols or hindered phenols.

[0038] "Ionic Activator" Cocatalyst So-called "ionic activators" are also well known for metallocene catalysts. See, for example, U.S. Patent No. 5,198,401 (Hlatky, Turner) and U.S. Patent No. 5,132,380 (Stevens, Neithamer).

[0039] Without wishing to be bound by any theory, it is believed by those skilled in the art that "ionic activators" first cause the abstraction of one or more activatable ligands in a manner that ionizes the catalyst to a cation and then provides a bulky, unstable, non-coordinating anion that stabilizes the catalyst in its cationic form. The bulky, non-coordinating anion allows olefin polymerization to proceed at the cationic catalyst center, presumably because the non-coordinating anion is sufficiently unstable to be displaced by a monomer that coordinates to the catalyst. Non-limiting examples of ionic activators are boron-containing ionic activators such as: Formula [R 5 ] + [B(R 7 )4] - Compounds of (wherein B is a boron atom, and R 5 is an aromatic hydrocarbyl (e.g., a triphenylmethyl cation), and each R 7 are independently an unsubstituted phenyl group, a fluorine atom, an unsubstituted or fluorine-substituted C 1-4 Alkyl or alkoxy groups and groups of the formula -Si-(R 9 ) 3 silyl groups (wherein each R 9 are independently a hydrogen atom and C 1-4 alkyl groups); The expression [(R 8 ) t ZH] + [B(R 7 )4] - Compounds of (wherein B is a boron atom, H is a hydrogen atom, Z is a nitrogen atom or a phosphorus atom, t is 2 or 3, and R 8 is C 1-8 Alkyl groups, unsubstituted or up to 3 C 1-4 phenyl groups substituted with alkyl groups, or one R 8 may combine with the nitrogen atom to form an anilinium group, and R 7 is as defined above; ); and Formula B(R 7 )3 Compound (In the formula, R 7 is as defined above.)

[0040] In the above compounds, preferably, R 7 is a pentafluorophenyl group, and R 5 is a triphenylmethyl cation, Z is a nitrogen atom, and R 8 is C 1-4 R is an alkyl group or R together with the nitrogen atom 8 The two C's 1-4 An anilinium group substituted with an alkyl group is formed.

[0041] An "ionic activator" is capable of abstracting one or more activatable ligands, thereby ionizing the catalytic center to a cation but not covalently bonding to the catalyst, and providing sufficient distance between the catalyst and the ionized activator to allow entry of a polymerizable olefin into the resulting active site.

[0042] Examples of ionic activators include triethylammonium tetra(phenyl)boron; tripropylammonium tetra(phenyl)boron; tri(n-butyl)ammonium tetra(phenyl)boron; trimethylammonium tetra(p-tolyl)boron; trimethylammonium tetra(o-tolyl)boron; tributylammonium tetra(pentafluorophenyl)boron; tripropylammonium tetra(o,p-dimethylphenyl)boron; tributylammonium tetra(m,m-dimethylphenyl)boron; tributylammonium N,N-Dimethylanilinium tetra(phenyl)boron;N,N-Diethylanilinium tetra(phenyl)boron;N,N-Diethylanilinium tetra(phenyl)boron;N,N-Diethylanilinium tetra(phenyl)n-butylboron;N,N-2,4,6-Pentamethylanilinium tetra(phenyl)boron;Di(isopropyl)ammonium tetra(pentafluorophenyl)boron;Dicyclo Hexylammonium tetra(phenyl)boron;Triphenylphosphonium tetra(phenyl)boron;Tri(methylphenyl)phosphonium tetra(phenyl)boron;Tri(dimethylphenyl)phosphonium tetra(phenyl)boron;Tropylium tetrakispentafluorophenylborate;Triphenylmethylium tetrakispentafluorophenylborate;Benzene(diazonium)tetrakispentafluorophenylborate;Tropylium phenyltrispentafluorophenylborate;Triphenylmethylium phenyl Trispentafluorophenylborate;Benzene(diazonium)phenyl trispentafluorophenylborate;Tropylium tetrakis(2,3,5,6-tetrafluorophenyl)borate;Triphenylmethylium tetrakis(2,3,5,6-tetrafluorophenyl)borate;Benzene(diazonium)tetrakis(3,4,5-trifluorophenyl)borate;Tropylium tetrakis(3,4,5-trifluorophenyl)borate;Benzene(diazonium)tetrakis(3,4,5-trifluorophenyl)borateTropylium tetrakis(1,2,2-trifluoroethenyl)borate; triphenylmethylium tetrakis(1,2,2-trifluoroethenyl)borate; benzene(diazonium) tetrakis(1,2,2-trifluoroethenyl)borate; tropylium tetrakis(2,3,4,5-tetrafluorophenyl)borate; triphenylmethylium tetrakis(2,3,4,5-tetrafluorophenyl)borate; benzene(diazonium) tetrakis(2,3,4,5-tetrafluorophenyl)borate.

[0043] Readily available commercially available ionic activators include N,N-dimethylanilinium tetrakispentafluorophenylborate; triphenylmethylium tetrakispentafluorophenylborate; and trispentafluorophenylborane.

[0044] The ionic activator can be used at a few molar equivalents of boron relative to the Group IV metal in the catalyst. Suitable molar ratios of Group IV metal to boron from the catalyst can range from about 1:1 to about 3:1, and in other cases from about 1:1 to about 1:2.

[0045] In some cases, ionic activators can be used in combination with alkylating activators (which may also act as scavengers). 3 ) p MgX 2-p (X is a halide, and each R 3 is independently C 1-10 alkyl groups, and p is 1 or 2; R 3 Li(R 3 is as defined above. );(R 3 ) q ZnX 2-q (R 3 is as defined above, X is a halogen, and p is 1 or 2. );(R 3 ) s AlX 3-s (R 3is as defined above, X is a halogen, and s is an integer from 1 to 3. Preferably, in the above compound, R 3 is C 1-4 is an alkyl group and X is chlorine. Commercially available compounds include triethylaluminum (TEAL), diethylaluminum chloride (DEAC), dibutylmagnesium ((Bu)Mg), and butylethylmagnesium (BuEtMg or BuMgEt).

[0046] When the phosphinimine catalyst is activated with a combination of an ionic activator (e.g., a boron compound) and an alkylating agent, the molar ratio of Group IV metal from the catalyst:metalloid (boron) from the ionic activator:metal from the alkylating agent may range from about 1:1:1 to about 1:3:10, and in other cases may range from about 1:1.3:5 to about 1:1.5:3.

[0047] Second Catalyst In one embodiment, a ZN catalyst is used in the second reactor. Any ZN catalyst system that works well for the solution polymerization of ethylene (optionally with one or more alpha-olefin comonomers, particularly 1-butene; 1-hexene; or 1-octene) may be suitable. The ZN catalysts disclosed in U.S. Patent Nos. 10,023,706 and 9,695,309 are specific (but non-limiting) examples.

[0048] Polymerization Process The temperature of the reactor(s) in a high-temperature solution process is about 80°C to about 300°C, and in other cases about 120°C to 250°C. The upper temperature limit is influenced by considerations well known to those skilled in the art, such as the desire to maximize operating temperature (so as to reduce solution viscosity) while maintaining good polymer properties (since increasing polymerization temperatures generally result in a decrease in polymer molecular weight). Generally, the upper polymerization temperature limit can be about 200 to about 300°C. A two-reactor process can be carried out at two temperatures, with the temperature of the second reactor being higher than that of the first reactor. The most preferred reaction process is a "medium pressure process," meaning that the pressure in the reactor(s) is preferably less than about 6,000 psi (about 42,000 kilopascals or kPa). The preferred pressure is about 10,000 to about 40,000 kPa (1450 to 5800 psi), and most preferably about 14,000 to about 22,000 kPa (2,000 psi to 3,000 psi).

[0049] In some reaction schemes, the pressure within the reactor system should be high enough to maintain the polymerization solution as a single-phase solution and provide the upstream pressure necessary to feed the polymer solution from the reactor system through a heat exchanger system to a devolatilization system. Other systems allow for the separation of the solvent into a polymer-rich and polymer-lean stream to facilitate polymer separation.

[0050] Solution polymerization processes can be carried out in a stirred reactor system containing one or more stirred-tank reactors, or in one or more loop reactors, or in a mixed system of loop and stirred-tank reactors. The reactors can be operated in tandem or parallel. In a dual-tandem reactor system, the first polymerization reactor preferably operates at a lower temperature. The residence time in each reactor varies depending on the reactor design and capacity. Generally, the reactors should be operated under conditions that achieve complete mixing of the reactants. Furthermore, it is preferred that about 20 to about 60 weight percent of the final polymer be polymerized in the first reactor, with the remainder polymerized in the second reactor.

[0051] A useful solution polymerization process employs at least two polymerization reactors in series. The polymerization temperature in the first reactor is from about 80°C to about 180°C (also from about 120°C to 160°C), while the second reactor is typically operated at a higher temperature (up to about 220°C). The most preferred reaction process is a "medium pressure process," meaning that the pressure in each reactor is preferably less than about 6,000 psi (about 42,000 kilopascals or kPa), most preferably from about 2,000 psi to about 3,000 psi (about 14,000 to about 22,000 kPa). [Example]

[0052] Test Method Mn, Mw, and Mz (g / mol) were measured by high temperature gel permeation chromatography (GPC) with differential refractive index detection using universal calibration (ASTM-6467). Molecular weight distribution (MWD), also known to those skilled in the art as "polydispersity" or "polydispersity index," is the ratio of the weight average molecular weight (Mw) to the number average molecular weight (Mn).

[0053] GPC coupled with Fourier transform infrared spectroscopy ("GPC-FTIR") was used to measure comonomer content as a function of molecular weight. After separation of the polymer by GPC, online FTIR measures the concentration of polymer and methyl end groups. The methyl end groups are used to calculate the degree of branching. By conventional calibration, the molecular weight distribution can be calculated.

[0054] Mathematical deconvolution was performed to estimate the relative amounts, molecular weights, and comonomer contents of the component polymers produced in each reactor.

[0055] The short-chain branching (SCB per 1000 carbon atoms) of the copolymer samples was measured by Fourier transform infrared spectroscopy (FTIR) according to ASTM D6645-01 using a Thermo-Nicolet 750 Magna-IR spectrophotometer. FTIR was also used to measure the internal, side-chain, and terminal levels of unsaturation (also conveniently referred to as "unsats").

[0056] Comonomer content can also be measured by carbon-13 nuclear magnetic resonance (NMR) techniques as discussed in Randall Rev. Macromol. Chem. Phys., C29(2&3), p. 285; U.S. Pat. No. 5,292,845; and WO 2005 / 121239.

[0057] Information about the compositional distribution was also obtained by temperature-rising elution fractionation (TREF). A polymer sample (80–100 mg) was introduced into the reaction vessel of a Polymer Char crystal-TREF unit. The reaction vessel was filled with 35 mL of 1,2,4-trichlorobenzene (TCB) and heated to the desired dissolution temperature (e.g., 150 °C) for 2 h. This solution (1.5 mL) was then loaded into a TREF column packed with stainless steel beads. After equilibration at a given stabilization temperature (e.g., 110 °C) for 45 min, the polymer solution was crystallized by ramping the temperature from the stabilization temperature to 30 °C (0.09 °C / min). After equilibration at 30 °C for 30 min, the crystallized sample was eluted with TCB (0.75 mL / min) at a ramp rate of 0.25 °C / min from 30 °C to the stabilization temperature. At the end of the 30 min run at the dissolution temperature, the TREF column was cleaned. Data were processed using in-house developed Polymer Char software, an Excel spreadsheet, and TREF software.

[0058] CDBI is defined as the percentage of polymers whose composition is within 50% of the median comonomer composition, and is calculated from the composition distribution hardness curve and the normalized cumulative integral of the composition distribution curve, as shown in U.S. Patent No. 5,376,439.

[0059] Density (g / cm) of the polyethylene composition 3 ) was measured according to ASTM D792.

[0060] The melt index of the polyethylene composition is 12, 16 and I 21 was measured according to ASTM D1238. For clarity: I2 was measured at 190°C with a 2.16 kilogram load; I 21 is measured at the same temperature with a load of 21.6 kilograms.

[0061] The densities and melt indices of the first and second ethylene polymers constituting the polyethylene composition were determined based on a composition model. The density and melt index I2 were calculated using the following equations (see U.S. Patent No. 8,022,143 B2 to Wang, assigned to NOVA Chemicals, issued September 20, 2011):

number

[0062] The first melting peak (°C), heat of fusion (J / g), and crystallinity (%) were determined using differential scanning calorimetry (DSC) as follows: the instrument was first calibrated with indium; then, the polymer specimen was equilibrated at 0°C; heated to 200°C at a heating rate of 10°C / min; the melt was then held at that temperature for 5 minutes; the melt was then cooled to 0°C at a cooling rate of 10°C / min and held at 0°C for 5 minutes; the specimen was heated again to 200°C at a heating rate of 10°C / min. The reported melting peak (Tm), heat of fusion, and crystallinity are calculated based on the second heat.

[0063] Rheology - Melt Strength by Capillary Rheometry Molten polymer is extruded through a capillary die at a constant extrusion rate. The extruded strand is drawn at increasing haul-off speeds. The force drawing the melt is continuously monitored, and the maximum steady-state force level at or before filament breakage is defined as the melt strength. The ratio of the draw rate at the die exit to the extrusion rate is defined as the stretch ratio.

[0064] Melt strength is measured at 190°C using a capillary rheometer (barrel diameter = 15 mm) equipped with a 2 mm diameter flat die with an L / D ratio of 10:1. Pressure transducer: 10,000 psi (68.95 MPa). Piston speed: 5.33 mm / min. Haul-off angle: 52°. Pull speed increment: 50-80 m / min. 2 or 65±15m / min 2 The polymer melt is extruded through a capillary die at a constant rate, and the polymer strand is then stretched at increasing rates of pull until it breaks. The maximum steady-state force in the plateau region of the force versus time curve is defined as the melt strength of the polymer. The melt draw ratio is defined as the ratio of the speed at the pulley to the speed at the die exit.

[0065] Rheology - DMA The rheological properties were measured using frequency sweep test measurements on a rotational rheometer.

[0066] The sample, in the form of a compression-molded disk, was placed in an environmental test chamber between two test geometries: an upper geometry mounted on the drive shaft and a lower geometry mounted on the base. The analysis was carried out over a range of frequencies at fixed strain and constant temperature. The rheometer was a commercially available instrument (sold by TA Instruments under the name DHR-3).

[0067] This testing technique offers the opportunity to study various properties of polymer melts, thereby determining the elastic and viscous moduli (G' and G"), complex viscosity, complex modulus (G * ), loss tangent, dynamic viscosity, out-of-phase component of complex modulus, phase angle, and other rheological properties as a function of vibration frequency are generated, providing information on rheological behavior that correlates with molecular structure.

[0068] The rheological parameters obtained from the test data are as follows: crossover frequency, crossover modulus, three Ellis Model constants: Ellis constant C1 (or zero shear viscosity), Ellis constant C2 (or the inverse of the characteristic relaxation time), Ellis constant C3 (or the power exponent), Dow Rheological Index (DRI), Relaxation Spectral Index (RSI), melt elastic index (G'@G"=500 Pa), viscosity ratio, Cole-Cole and VGP plots.

[0069] Relative elasticity is defined as the ratio of G' to G" at a frequency of 0.05 rad / sec. Without wishing to be bound by theory, it has been observed that a relatively low relative elasticity correlates with powder densification during the rotational molding process.

[0070] Izod impact testing was performed according to ASTM D256-10E1. Tensile impact testing was performed according to ASTM D1822-13.

[0071] Rotational molded parts were prepared in a rotational molding machine sold by Ferry Industries Inc. under the trade name Rotospeed RS3-160. This machine has two arms that rotate around a central axis within an enclosed oven. The arms are fitted with plates that rotate around an axis approximately perpendicular to the arm's axis of rotation. Each arm is fitted with six cast aluminum molds that produce plastic cubes measuring 12.5 inches (31.8 cm) x 12.5 inches x 12.5 inches. The arm rotation was set at approximately 8 revolutions per minute (rpm), and the plate rotation was set at approximately 2 rpm. These molds, when initially filled with a standard charge of approximately 3.7 kg of powdered polyethylene resin (35 US mesh size), produce parts with a nominal thickness of approximately 0.25 inches (0.64 cm). The temperature within the enclosed oven was maintained at 560°F (293°C). The molds and their contents were heated for the specified period until complete powder densification was achieved. These molds were then cooled in a controlled environment before the parts were removed. Test specimens were taken from the molded parts for density and color measurements. ARM impact testing was performed according to ASTM D5628 at a test temperature of -40°C.

[0072] Test specimens for impact testing should be from rotationally molded parts. Test specimens should be conditioned so that the cross section of the specimen is uniformly cooled to at least -40°F ± 3.5°F (-40°C ± 2°C).

[0073] Impact testing techniques for rotationally molded parts are commonly referred to as the Bruceton Staircase Method or the Up-and-Dow Method. This procedure establishes a specific dart height that will cause 50% failure of the specimen. Percentage ductility represents the percentage of failure (fA.ilure), thereby demonstrating ductile properties. Samples are impact tested using a falling weight impact tester. If the sample does not fail at a given height / weight, either the height or weight is increased in increments until failure occurs. Once failure occurs, the height / weight is decreased by the same increment, and the process is repeated until all samples are utilized. The falling dart should impact the surface of the part that was in contact with the mold during molding. For polyethylene, ductile failure is the desired failure mode, typically occurring in properly processed samples. Brittle or shattering failure generally indicates that the process parameters used did not produce optimal properties.

[0074] Ductile fracture: Rather than cracking outward from the point of failure, this is indicated by a dart penetrating the specimen, leaving a hole containing thread-like fibers at the point of failure. The area under the dart stretches and thins at the point of failure.

[0075] Brittle fracture: This is indicated by the part physically breaking or cracking at the point of impact. The sample has little to no elongation. As used herein, the term "ductility index" refers to the percentage of parts in a multi-part test that exhibit ductile failure. For example, if 10 parts are tested and 8 of them exhibit ductile failure (i.e., 80% of the parts exhibit ductile failure), the test results would be reported as having a ductility index of 80%.

[0076] resin A bimodal polyethylene composition was prepared in a dual reactor pilot plant. In this dual reactor process, the contents of the first reactor flow into the second reactor, and both are thoroughly mixed. The process is operated using a continuous feed stream. The catalyst (cyclopentadienyltri(t-butyl)phosphinimine titanium dichloride) [Note: This catalyst is referred to as "PI-cat" in tables describing the experimental polymerizations] along with an activator was fed into the first reactor, and the ZN catalyst was fed into the second reactor. The overall production rate was approximately 90 kg / h.

[0077] The polymerization conditions are shown in Table 1.

[0078] The polymer compositions prepared in the pilot plant were stabilized using a conventional additive package for rotomolding applications before conducting plaque test trials. Rotomolding compositions typically contain an additive package to protect the polyethylene from degradation during the processing process and subsequently protect the rotomolded part from exposure to the atmosphere. The compositions of the present disclosure are not intended to be limited to the use of any particular additive package. The compositions of the invention illustrated in the examples contained the following additives (all amounts in parts per million by weight, based on the weight of polyethylene): 500 ppm hindered phenol (CAS Registry Number 2082-79-3); 550 ppm phosphite (CAS Registry Number 31570-04-4); 450 ppm diphosphite (CAS Registry Number 154862-43-8); 250 ppm hydroxylamine (CAS Registry Number 143925-92-2); 750 ppm hindered amine light stabilizer (HALS)-1 (CAS Registry Number 70624-18-9); 750 ppm HALS-2 (CAS Registry Number 65447-77-0); and 750 ppm zinc oxide.

[0079] Table 2 discloses the GPC deconvolution results, in which Examples 1 and 2 were mathematically deconvoluted into a first ethylene polymer (synthesized in reactor 1) and a second ethylene polymer (synthesized in reactor 2). The densities and melt indices of the first and second ethylene polymers were calculated based on a basic kinetic model (with specific kinetic constants for each catalyst formulation) and the feed and reactor conditions. The equations used to calculate the density and melt index are described above (and in U.S. Pat. No. 8,022,143). Simulations were performed based on the dual reactor solution pilot plant configuration described above. The first ethylene interpolymer was fitted to a distribution based on a basic kinetic model describing the behavior of a single-site catalyst formulation. The second ethylene interpolymer was fitted to a distribution based on a basic kinetic model describing the behavior of a heterogeneous catalyst formulation. As shown in Table 2, in the case of Example 1, the first and second ethylene polymers constituted 88 wt. % of Example 1; the remainder of Example 1 (12 wt. %) was synthesized in the tubular reactors 1 and 2 prior to the addition of the catalyst deactivator (less than 3 wt. %, having the same composition as the first ethylene polymer) and further in the tubular reactor following reactor 2 (less than 10 wt. %, having the same composition as the second ethylene polymer).

[0080] The properties of compressed (pressed) plaques of the rotomolding resins disclosed herein (Examples 1-4) are shown in Table 3a; comparative resins are shown in Table 3b (Comparative Examples 5-8). The properties of rotomolded parts and compressed plaques made from the polyethylene compositions disclosed herein are shown in Table 4a; comparatives are shown in Tables 4b and 4c. Higher density resins typically do not perform well in rotomolding applications that also require good toughness. Examples 1 and 2 demonstrate superior performance over the comparative examples due to a combination of high density, good toughness (greater than 50% ductility), and high average fracture energy at optimal molding conditions. Without wishing to be bound by theory, higher density results in higher stiffness, allowing for the use of less material to achieve equivalent structural strength in the molded part.

[0081] [Table 1a]

[0082] [Table 1b]

[0083] [Table 2]

[0084] [Table 3a]

[0085] [Table 3b]

[0086] [Table 3c]

[0087] [Table 4a]

[0088] [Table 4b]

[0089] [Table 4c] [Industrial Applicability]

[0090] High-density polyethylene compositions are provided that offer high stiffness and ductility and may be useful in preparing rotomolded articles.

Claims

1. 1) a molecular weight distribution Mw / Mn of 2.3 to 5.5, where Mw and Mn are measured according to ASTM-6467; 2) a density of 0.940 to 0.957 g / cc, measured in accordance with ASTM-D792; 3) A melt index I of 4 to 10 grams per 10 minutes, measured according to ASTM D1238 at 190°C with a load of 2.16 kg. ２ and 4) A relative elasticity G' / G" of less than 0.03 rad / sec, measured at 190°C and 0.05 rad / sec 1. A bimodal polyethylene composition having The bimodal polyethylene composition comprises the following A and B: A. 10 to 70 wt. % of a first ethylene copolymer having the following A.i to A.iii: A. i. A melt index I of 0.4 to 5 grams per 10 minutes, calculated according to the method described in the specification ２ ; A. ii. a molecular weight distribution Mw / Mn of 1.8 to 3.0; and A. iii. Density of 0.920 to 0.950 g / cc; B. 90 to 30 wt. % of a second ethylene copolymer having the following B. i to B. iii: B. i. A melt index I of 4 to 1500 grams per 10 minutes, calculated according to the method described in the specification. ２ ; B. ii. a molecular weight distribution Mw / Mn of 2.3 to 6.0; and B. iii. a density greater than the density of said first ethylene copolymer but less than 0.967 g / cc; It contains provided that the density of the first ethylene copolymer is less than the density of the second ethylene copolymer by an amount of 0.010 to 0.035 g / cc; Bimodal polyethylene compositions.

2. the first ethylene copolymer is A. iv. number average molecular weight Mn of 35,000 to 80,000; A. v. weight average molecular weight Mw of 70,000 to 150,000; A. vi. Mz of 120,000 to 250,000; and A. vii. a number of short chain branches (SCB1) per 1000 carbon atoms of from 1 to 5; the first ethylene copolymer has a Mw / Mn of 2 to 3; the melt index I of the first ethylene copolymer, calculated according to the method described herein; ２ is 0.5 to 4.0 grams per 10 minutes, Bimodal polyethylene compositions.

3. the second ethylene copolymer is B. iv. number average molecular weight Mn of 12,000 to 30,000; B. v. weight average molecular weight Mw of 28,000 to 72,000; B. vi. Mz of 70,000 to 150,000; B. vii. The number of short chain branches (SCB2) per 1000 carbon atoms is 0.1 to 2; and B. viii. a density greater than the density of said first ethylene copolymer but less than 0.965 g / cc; 10. The bimodal polyethylene composition of claim 1, further characterized by having: the second ethylene copolymer has a Mw / Mn of 2.3 to 5.0; and the melt index I of the second ethylene copolymer, calculated according to the method described herein ２ is between 4 and 100 grams per 10 minutes, provided that the density of the first ethylene copolymer is less than the density of the second ethylene copolymer by an amount of 0.010 to 0.030 g / cc; Bimodal polyethylene compositions.

4. A rotomolded part comprising the bimodal polyethylene composition of claim 1, 2 or 3.

5. 5. The rotomolded part of claim 4, having an average energy to fracture of greater than 120 ft-lbs (162.7 J) for 0.250 inch (6.35 mm) thick specimens tested according to ASTM D5628 at a test temperature of -40°C.

6. 10. The bimodal polyethylene composition of claim 1, wherein the bimodal polyethylene composition has a comonomer content of less than 1.2 mol % as measured by FTIR methods.

7. 2. The bimodal polyethylene composition of claim 1, wherein the first and second ethylene copolymers are copolymers of ethylene and 1-octene.

8. 10. A process for producing the bimodal polyethylene composition of claim 1, comprising contacting ethylene and an α-olefin with a polymerization catalyst under solution polymerization conditions in at least two polymerization reactors.

9. A process for producing a polyolefin hollow product, comprising:

10. A method for producing a mold comprising: filling the bimodal polyethylene composition of claim 1 into a mold; heating the mold in an oven to above 280°C to melt the stabilized polyolefin; rotating the mold on at least two axes to cause the plastic material to spread to the walls; cooling the mold while rotating; opening the mold; and removing the resulting hollow article. The process includes:

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