WO2008137722A1 - Bimodal polyethylene resins that have high stiffness and high escr - Google Patents
Bimodal polyethylene resins that have high stiffness and high escr Download PDFInfo
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- WO2008137722A1 WO2008137722A1 PCT/US2008/062474 US2008062474W WO2008137722A1 WO 2008137722 A1 WO2008137722 A1 WO 2008137722A1 US 2008062474 W US2008062474 W US 2008062474W WO 2008137722 A1 WO2008137722 A1 WO 2008137722A1
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F10/00—Homopolymers and copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
- C08F10/02—Ethene
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
- B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
- B29C49/00—Blow-moulding, i.e. blowing a preform or parison to a desired shape within a mould; Apparatus therefor
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F210/00—Copolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
- C08F210/16—Copolymers of ethene with alpha-alkenes, e.g. EP rubbers
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F4/00—Polymerisation catalysts
- C08F4/42—Metals; Metal hydrides; Metallo-organic compounds; Use thereof as catalyst precursors
- C08F4/44—Metals; Metal hydrides; Metallo-organic compounds; Use thereof as catalyst precursors selected from light metals, zinc, cadmium, mercury, copper, silver, gold, boron, gallium, indium, thallium, rare earths or actinides
- C08F4/60—Metals; Metal hydrides; Metallo-organic compounds; Use thereof as catalyst precursors selected from light metals, zinc, cadmium, mercury, copper, silver, gold, boron, gallium, indium, thallium, rare earths or actinides together with refractory metals, iron group metals, platinum group metals, manganese, rhenium technetium or compounds thereof
- C08F4/62—Refractory metals or compounds thereof
- C08F4/64—Titanium, zirconium, hafnium or compounds thereof
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- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08F—MACROMOLECULAR COMPOUNDS OBTAINED BY REACTIONS ONLY INVOLVING CARBON-TO-CARBON UNSATURATED BONDS
- C08F110/00—Homopolymers of unsaturated aliphatic hydrocarbons having only one carbon-to-carbon double bond
- C08F110/02—Ethene
Definitions
- the present invention relates to a process for the production of polyethylene, in particular high density polyethylene (HDPE), and relates more particularly in one non-iirniting embodiment to producing polyoiefin having a birrtodai molecular weight distribution, an improved environmental stress cracking resistance (ESCR) and improved stiffness.
- HDPE high density polyethylene
- ESCR environmental stress cracking resistance
- the MWD of a polyethylene resin may principally determine the physical, and in particular the mechanical, properties of the resin and that ihe provision of different molecular weight polyethylene molecules may significantly affect the rheologicai properties of ihe polyethylene as a whole.
- a high molecular weight polyethylene is one having a M n of at least 1 x 10 5 , typicaily from about 1 x 10 5 to about 1 x 10 7 .
- M n the high molecular weight molecules which render the polymers more difficult to process.
- a broadening of the molecular weight distribution tends to improve the flow of the poiymer when it is being processed at high rates of shear. Accordingly, in applications requiring a rapid transformation employing quite high throughputs of the materia!
- the broadening of the molecular weight distribution permits an improvement in the processing of polyethylene at high molecular weight relative to a !ow melt index of the polyethylene, which is known in the art. It is known that when the polyethylene has a high molecular weight and also a broad molecular weight distribution, the processing of the polyethylene is made easier as a result of the low molecular weight portion and also the high molecular weight portion contributes to a good impact resistance.
- a polyethylene of this type may be processed utilizing iess energy with higher processing yieids. [0004]
- a polymer comprising two groups of molecules with different average molecular masses is said to be bimodal.
- polymers of this type make it possible to combine, in the same material, the properties of each group of molecules from which it is composed.
- polymers of high mass introduce good mechanical strength
- low masses make it possible to retain, in the material, good fluidity at high temperature, which facilitates its processing.
- the high molecular weight fraction provides good mechanical properties to the high density polyethylene and the low molecular weight fraction is required to give good processability to the high density polyethylene.
- the high molecular weight fraction having relatively high viscosity may lead to difficulties in processing such a high molecular weight fraction.
- the mixture of the high and low molecular weight fractions is adjusted as compared to a monomoda! distribution to optimize both the quantity and the molecular weight of high molecular weight species in the polymer. This may provide improved mechanical properties and/or improved processability depending on the end use or the process used to fabricate the end use application.
- the invention is a process for producing a bimodal high density polyethylene in two reactors in series, the process including homopolymerizing in a first reactor a first polyethylene product from ethylene in the presence of hydrogen and a Ziegler-Natta polymerization catalyst; polymerizing In a second, serially connected, downstream reactor a second polyethylene product from ethylene and from about 0 to 3 wi% of an ⁇ -olefinic comonomer having from 3 to 8 carbon atoms, based on the total weight of ethylene monomer.
- the process also includes recovering bimodal polyethylene having a density ranging from about 0.955 to about 0.959 g/cc.
- HLMI high load meli index
- ESCR environmental stress cracking resistance
- 0.4% fiexural modulus from about 180.000 to about 260,000 psi (1.200 MPa to about 1.800 MPa).
- the invention is a bimodal high density polyethylene resin produced by a process including homopoiymerizing in a first reactor a first polyethylene product from ethylene in the presence of hydrogen and a Ziegier- Natta polymerization catalyst; polymerizing in a second, serially connected, downstream reactor a second polyethylene product from ethylene and from about 0 to 3 wt% of an ⁇ -olefinic comonomer having from 3 to 8 carbon atoms, based on the total weight of ethylene monomer.
- the process also includes recovering bimodal polyethylene having a density ranging from about 0.955 to abo ⁇ i 0.959 g/cc, a high load melt index (HLMI) of from about 2 and about 30 dg/min, an environmental stress cracking resistance (ESCR) of from about 400 to about 2500 hours, and a 0.4% fiexura! modulus of from about 180.000 to about 260,000 psi (1 ,200 MPa to about 1 ,800 MPa).
- HLMI high load melt index
- ESCR environmental stress cracking resistance
- the invention is an article made from a resin produced by a process including homopolymerizing in a first reactor a first polyethylene product from ethylene in the presence of hydrogen and a Ziegler- Natta polymerization catalyst; polymerizing in a second, serially connected, downstream reactor a second polyethylene product from ethylene and from about 0 to 3 wt% of an ⁇ -olefinic comonomer having from 3 to 8 carbon atoms, based on the totai weight of ethylene monomer.
- the process also includes recovering bimodal polyethylene having a density ranging from about 0.955 to about 0.959 g/cc.
- HLMI high load melt index
- ESCR environmental stress cracking resistance
- 0.4% flexural modulus of from about 180.000 to about 260 : 000 psi (1 ,200 MPa to about 1 ,800 MPa).
- the article is prepared by a process selected from the group of processes consisting of blow-molding, injeciion-moiding, extrusion, transfer compression molding, and thermoforming.
- FIG. 1 is a graph of ESCR results (at F50, condition B, 10% igepai) for experimental bimodal drum resins as a function of density, and compared to FINA TR-570 polyethylene;
- FIG. 2 is a graph of NCTL results for experimental bimodal drum resins as a function of density
- FIG. 3 is a graph of Flexural Modulus (at 0.4% strain) for experimental bimodal drum resins of Examples 1 , 2 and 4 as a function of density, and as compared to TR-570;
- FIG. 4 is a graph of Tensile Modulus for experimental bimodal drum resins of Examples 1 , 2 and 4 as a function of density, and as compared to TR-
- FIG, 5 is a graph of extrusion pressure as a function of throughput for the experimental bimodal drum resins of Examples 1 , 2 and 4, and as compared to TR-570;
- FIG. 6 is a graph of RPM as a function of throughput for the experimental bimodal drum resins of Examples 1 , 2 and 4, and as compared to
- FIG. 7 is a graph of pressure as a function of HLM! for a constant throughput of 700 g/min for the experimental bimodal drum resins of Examples
- FIG. 8 is a graph of meit strength by extruded strand method as a function of HLMl for the experimental bimodal drum resins of Examples 1 , 2 and
- FIG. 9 is a graph of the shear rate of the onset of melt fracture as a function of HLMI for the experimental bimodal drum resins of Examples 1 , 2 and
- the present invention relates to the production of polyethylene having a broad molecular weight distribution, and in particular a bimodal molecular weight distribution, which also has high stiffness and high ESCR.
- flexura! modulus is measured in psi (kPa) at 0.4% strain according to common procedures.
- ESCR evaluates the time a container can withstand an aggressive liquid ⁇ e.g. detergent, oil, agricultural chemicals, etc.) under mechanical stress (e.g. pressure, top load, deformation, molded in stress, etc.).
- Conditions of service e.g. temperature, stress, bottle molding conditions and container design
- F50 refers to the time taken (in hours) to achieve 50% failure under well-recognized Condition B 10% igepai.
- CSTRs continuous stirred tank reactors
- low and high molecular weight fractions of polyethylene in the first and second reactors in a series may unexpectedly yield high density polyethylene having a bimodal molecular weight distribution with improved mechanical properties, such as high stiffness and high ESCR.
- High stiffness which accompanies high molecular weight typically is observed with low ESCR properties where there is very little resistance to stress cracking.
- a polyethylene polymer having a bimodal molecular weight distribution will have a GPC curve showing either two separate peaks or a substantially broadened and asymmetrical peak.
- the low molecular weight distribution peak wilt occur at a range of from about 1 x 10 3 to about 1 x 10 5 and the high molecular weight peak will occur at a range of from about 1 X10 5 to about 1 x 10 7 .
- the high stiffness is at a constant density and higher than that of some unimodal resins, such as a Chromium catalyzed polymer.
- Bimodal polymers are desirable because such polymers generally exhibit both good mechanical properties, in particular impact strength (measured by the lzod and/or Charpy test, ISO Standard 180 and ISO Standard 179 respectively), and better performance at high temperatures, which is reflected by a high Vicat point and a higher heat deflection temperature or HDT (Vicat: ISO Standard 306, HDT: ISO Standard 75); the good mechanical properties deriving in particular from the population with high molecular weight portions, and. secondiy, are easy to process, in particular by conversion technologies known to a person skilled in the art (extrusion, injection molding, transfer compression moiding, thermoforming), due in this instance to the presence of the population with low molecular weight portions.
- the polymerization processes are carried out in the liquid phase in an inert diluent, the reactants including ethylene and hydrogen for homopolymerization and for copoiymerization ethylene and, as appropriate, an alpha-olefinic comonomer comprising from 3 to 8 carbon atoms.
- the comonomer may be selected from 1 -butene, 1-pentene, 1-hexene, 4-melhyi 1-pentene, 1-heptene and 1-octene.
- the inert diluent may comprise isob ⁇ tene or hexane or the like.
- the polymerization processes may be carried out at a temperature of from about 100 to about 250 °F (about 38 to about 93 °C), in one non-restrictive embodiment from about 150 to about 190°F (about 66 to about 88 °C), under an absolute pressure of about 100 to 10,000 kPa (about 14.5 to about 1 ,450 psi).
- the ethylene monomer may comprise from 0.1 to 3% by weight based on the total weight of the ethylene monomer in the inert diluent and the hydrogen may comprise from 0.1 to 5 mo!% on the same basis.
- the composition in the first reactor comprises 0.5% by weight ethylene and 0.1 mol% hydrogen.
- the polymerization product from the first reactor may have a melt index Ml5 of from about 50 to about 2000 dg/min, and in another non-limiting embodiment, from about 200 to about 800 dg/min.
- the melt index MI5 being measured determined using the procedures of ASTM D1238 using a load of 5 kg at a temperature of 190°C.
- the melt index MI5 is broadly inversely indicative of the molecular weight of the polymer.
- the relatively low molecular weight polyethylene fraction produced in the first reactor comprises from 30 to 70% by weight, more typically around 40 - 60% by weight, such as a split of about 49/51 to about 51/49. up to about 57/43 to about 43/57, of the total polyethylene produced in the first and second serially connected reactors.
- the comonomer as described above is introduced into the second reactor in relatively small amounts e.g.
- the comonomer which is typically 1 -hexene, 1 -butene or the like, is reacted with the ethylene monomer to form a relatively high molecular weight polyethylene fraction in the second reactor in a controllable manner.
- the temperature in the second reactor may be lower than that in the first reactor in, in one non-limiting example the temperature is from about 166 to about 186°F (about 74 to about 86 °C) in the second reactor as opposed to about 173 to about 193°F in the first reactor (about 78 to about 89 °C); and in another non-restrictive version from about 173 to about 179°F (about 78 to about 82 °C) in the second reactor as opposed to 180 to about 186°F (about 82 to about 86°C) in the first reactor.
- the ethylene monomer may comprise from about 0.1 to about 2% by weight, typically around 0.8% by weight based on the total weight of the monomer and comonomer and the inert diluent, and the comonomer comprises from 0 to about 5% by weight, typically around 0 to about 2% by weight of the total ethylene feed.
- the process of the invention is done at constant pressure, in such a process, the Ziegler-Natta catalyst is injected into the process stream in an amount sufficient to maintain the pressure.
- the final polyethylene comprising in admixture the low molecular weight polyethylene fraction produced in the first reactor and conveyed through the second reactor and the high molecular weight polyethylene fraction produced in the second reactor, may have a high load melt index (HLMl). determined using the procedures of ASTM D1238 using a load of 21.6 kg at a temperature of 190°C, of from about 2 to about 30 g/10rnins, and in another non-restrictive embodiment from about 3 to about 16 dg/min.
- HLMl high load melt index
- the bimodal polyethylene recovered has a density ranging from about 0.950 to about 0.965 g/cc. an ESCR of from about 400 to about 2500 hours, and a 0.4% fiexurai modulus of from about 180,000 to about 260,000 psi (1200 MPa to about 1 ,800 MPa).
- the bimodal polyethylene recovered has a density ranging from about 0.955 to about 0.959 g/cc, an ESCR of from about 400 to about 1200 hours, and a 0.4% flexural modulus of from about 220,000 to about 240000 psi (1 ,500 MPa to about 1 ,600 MPa).
- the final product may have a molecular weight distribution MWD (the ratio of Mw/Mn) of from 8 to 20, or in an alternative embodiment, from 10-18.
- the process herein may yield bimodal high density polyethylene having properties which make them particuiariy suitable for use as polyethylene resins for the manufacture of srna ⁇ and large parts, pipes, drums, tubes, profiles and the like, through known processes such as injection moiding, blow moiding, extrusion, transfer compression molding, thermoforming and the like. Since no comonomer is incorporated into the low moiecular weight fraction, even if the polymer as a whole has the same molecular weight distribution as in a known polymer the resultant polymer will have improved properties.
- the poiymerization catalysts suitable in this process may be those having stalwart morphoiogy and robust integrity in that their physical structure is maintained in feeding systems and under intense reactor conditions.
- the catalysts may have a good compromise between efficiency and sensitivity meaning a manageable response to changes in production variables (e.g. H 2 feed rates, aluminum alkyl co- catalysts, comonomer feed rates, temperatures, pressures, etc).
- the catalyst may have high miieage.
- the catalyst lifetime and activity may match residence times, and the catalyst may maximize productivity and lower costs, polymer residues, and additives, in one non- restrictive embodiment, the catalyst may provide appropriate powder morphology for products and processes. Powder replicates caiaiyst: thus, high bulk density and low fines are desired to allow powder to be readily cut from diluent and conveyed to finishing. Powder should not, however be too large; a small but uniform particle size distribution favors bimodal homogeneity.
- the catalyst may- yield PE with appropriate MWD and comonomer distribution. That is, for optimal final product properties, the catalyst may provide narrow polydispersity for uniform comonomer incorporation. Too narrow a MWD, however, will prevent good processing.
- the catalyst may provide high homopolymer densities.
- a linear polymer is desired, in one non-restrictive embodiment. This gives a high homopolymer density and allows better segregation of comonomer into property-enhancing high MW portion of bimodal distribution.
- the catalyst preparation can be generally described as comprising at least three steps: (1 ) preparation of a dialkoxide as the reaction product of a metal dialkyl and an alcohol; (2) preparation of a soluble catalyst precursor as the reaction product of the metal diaikoxide and a halogenating/titanating agent; and (3) combining the products from steps 1 and 2 and precipitation of a final solid catalyst component as the reaction product of the soluble caiaiyst precursor and a precipitating agent.
- the precipitating agent may in some embodiments also be a halogenating/titanating agent.
- the metal dialkyls may include Group HA metal dialkyls.
- the metal diaikyl can be, for example, a magnesium dialkyl. Suitable and non-limiting examples include diethyl magnesium, dipropyl magnesium, ddibutyl magnesium, butylethyl magnesium (BEM), and the like. In one embodiment butylethyl magnesium is employed.
- the alcohol can be, in one embodiment, any compound conforming to !he formula R 1 OH and yielding the desired metal dialkoxide upon reaction as described hereinabove may be utilized, in the given formula R 1 is an alkyl group of 2 to 20 carbon atoms.
- suitable alcohols include ethanol, prcpanoi, isopropanol, butanol, isobutanol, 2-methyl-pentanol, 2- ethylhexanol. and the like.
- the amount of alcohol relative to the metal dialkyl may vary over a wide range, provided that the result is the desired metal aikoxide.
- a level of from about 0.01 to about 10 equivalents of alcohol relative to the metal dialkyl may be employed, in some embodiments a level ranging from about 0.5 to about 6 equivalents may be used, and in other embodiments a level ranging from about 1 to about 3 equivalents may be selected.
- a problem that may be encountered when a selected metal diaikyl is added to a solution is a dramatic increase in the solution's viscosity.
- This undesirably high viscosity can be reduced in by adding an aluminum alkyl co- catalyst to the solution, such as, for example, triethyl aluminum (TEAI), which operates to disrupt the association between the individual alkyl metal molecules.
- TEAI triethyl aluminum
- alkyl aluminum in the practice of the invention, rather than use TEAl, other alkyl aluminums Known to those of ordinary skill to be useful may be used, such as, for example, triisobutyl aliminum (TIBAI); Al(n-octyl)(O-Bu) 2 ; tri-n-hexyl aluminum; tri-n-octyl aluminum (TNOAl); and the like. Mixtures of the cocataiysts may also be used, in some embodiments it is therefore desirable to include the alkyl aluminum, in an aikyi aiuminum-to-metal ratio of from 0.001 :1 to 1 :1.
- the ratio in other embodiments can be from 0.01 :1 to 0.5:1 ; and in still other embodiments the ratio can be from 0.03:1 to 0.2:1.
- an electron donor such as an ether, for example, diisoamyi ether (DSAE), may be used to further reduce the viscosity of the aikyi metal.
- the typical ratio of electron donor to metal ranges from 0:1 to 10:1 and can range from 0.1 :1 to 1 :1.
- the metal diaikoxide produced by the reaction of diaiky! metal and alcohol may be a magnesium compound of the genera! formula Mg(OR 2 ) 2 wherein R 2 is a hydrocarbyi or substituted hydrocarbyi of 1 to 20 atoms, in one embodiment the metal diaikoxide is non-reducing.
- Non-limiting examples of species of metal dialkoxides which can be used include magnesium di(2-ethyihexoxide) and other Group HA metal dialkoxides, may be produced by reacting an aikyi magnesium compound (MgR 3 R 4 , i.e., a metal diaikyl wherein R 3 and R 4 are each independently any aikyi group of 1 to 10 carbon atoms) with an aicohol (R 1 OH) and an aluminum aikyi (AIR 5 3 wherein R 5 is any aikyi group of 1 to 10 carbon atoms.
- MgR 3 R 4 i.e., a metal diaikyl wherein R 3 and R 4 are each independently any aikyi group of 1 to 10 carbon atoms
- R 1 OH aicohol
- AIR 5 3 aluminum aikyi
- Suitabie MgRR' compounds include, for example, diethyl magnesium, dipropy! magnesium : dibuty!
- the MgR 3 R 4 compound can be BEM, wherein the reaction products, in addition to ihe magnesium diaikoxide, are denoted as R 3 H and R 4 H and are butane and ethane, respectively.
- the metal diaikoxide is reacted with a haiogenating agent to form a soluble catalyst precursor, it is significant that this step can be accomplished in one or several parts, in this case a compound conforming to the formula CIAR ⁇ x may in some embodiments be selected as the haiogenating agent, in ⁇ he formula A is a nonreducing oxyphilic compound which is capable of exchanging one chioride for an alkoxide.
- R b is a hydrocarbyi or substituted hydrocarbyi
- x is the vaience of A minus 1. Examples of A inciude titanium, silicon, aluminum, carbon, tin and germanium, and In some embodiments titanium or silicon wherein x is 3.
- the agent is referred to as a haiogenating/titanating agent.
- Exampies of R f ⁇ include methyl, ethyl, propyl, isopropy! and the like having from 2 to 6 carbon atoms.
- a non-iimiting example of a haiogenating/titanating agent that can be used is GiTi(O 1 Pr) 3 and, as a halogenating agent, GISiMe 3 , wherein Me is methyl.
- the halogenation is generally conducted in a hydrocarbon solvent under an inert atmosphere.
- suitable solvents include toluene, heptane, hexane, octane and the like, in this haiogenating step, the mole ratio of metal alkoxide to haiogenating agent is, in some embodiments, in the range of about 6:1 to about 1 :3, and in other embodiments from about 3:1 to 1 :2, and in still other embodiments from about 2:1 to 1 :2, and in yet other embodiments is about 1 :1.
- Halogenalion can be carried out at a temperature from about O°C to about 100 c C and for a reaction time in the range of from about 0.5 to about 24 hours. In other embodiments a temperature of from about 20 0 C to about 90°C can be used, and the reaction time can range from about 1 hour to about 4 hours.
- the haiogenation in this case, chio ⁇ nation, that takes place results in a reaction product which is the soluble catalyst precursor, which may in some embodiments be of uncertain composition. Regardless of the constituents or the nature of their association, in this embodiment, the catalyst precursor is substantially soluble, which is defined herein as at least about 90 percent by- weight, and in desirable embodiments more than about 95 percent by weight, in the catalyst synthesis solution.
- a haiogenating/- titanating agent is used for the purpose of precipitating the desired final solid catalyst component, i.e., thereby providing a supported catalyst.
- this agent is herein referred to as the "precipitating agent" in order to more clearly separate ii. by virtue of its effect, from other haiogenating agents, some of which may contain Uianium and therefore double as titanating agents, that are used in forming the soluble catalyst precursor via reaction of that agent with the metal diaikoxide.
- the precipitating agent can be, in some embodiments, blends of two tetra-subsiiluted titanium compounds with ai! four substitue ⁇ ts being ⁇ he same and the s ⁇ bstiiuents being a halide.
- the precipitating agent may be a single compound, if a blend is chosen, a combination of a titanium haiide and an organic titanate may, in some embodiments, be selected.
- a blend of TiCi 4 and Ti(OBu) 4 wherein Bu is butyi, may be utilized, in some desirabie embodiments a blend of Ti(OBu)CI 3 and Ti(OBiOsCi ? is selected as the precipitating agent.
- the proportion of the constituents may vary over a range of from 0.5:1 to 6:1 , and in some embodiments from about 2:1 to 3:1.
- the support is generally composed of an inert solid, which is chemicaiiy unreactive with any of the components of the conventional Ziegfer-Natta catalyst.
- the support is often a magnesium compound. Examples of the magnesium compounds which can be used to provide a support source for the cataiysi component are magnesium haiides, diaikoxymagnesium.
- the amount of precipitating agent utilized is desirably sufficient to precipitate a solid product from the solution. Desirable embodiments include employing a precipitating agent concentration of from about 0.5:1 to about 5:1 , typically from about 1 :1 to about 4:1 , and in certain embodiments in the range of from about 1.5:1 to about 2.5:1.
- the precipitation is carried oui at room temperature.
- the solid catalyst component is then recovered by any suitable recovery technique known to those skilled in the art, and then desirably washed at room/ambient temperature with a solvent, such as hexane.
- a solvent such as hexane.
- the solid catalyst component is washed until the [Ti] is iess than about 100 mmoi/L
- [Ti] represents any titanium species capable of acting as a second generation Ziegler catalyst, which would comprise titanium species that are not part of the reaction producis as described herein.
- the resuiting catalyst component may ihe ⁇ : in some embodiments, be subjected to additional haiogenation/iitanatio ⁇ steps, if desired, to produce alternative and/or additional catalyst products.
- the solid product can be washed until the [Ti] is less than a desired amount, for example, iess than about 100 mmoi/L, less than about 50 mmoi/L, or less than about 20 mrnol/L
- the product can be washed until the [Ti] is less than a desired amount, for example, less than about 20 mmoi/L, iess than about 10 mmoi/L, or iess than about 1.0 mmoi/L.
- a titanium halide such as titanium tetrachloride (TiCU)
- TiCU titanium tetrachloride
- the haiogenation/titanation agent is added to the slurry. While this addition is often carried out at ambient/room temperature, it may also be carried out at other temperatures and pressures and under a variety of conditions.
- the amount of such additional agent may be in a titanium to magnesium ratio of from about 0.1 to 5.0 equivalents, in some embodiments desirably about 2,0, and In other embodiments from about 0.25 to about 4, in still other embodiments from about 0.3 to about 3 equivendings, and in still other embodiments from about 0.4 to about 2.0 equivendings.
- the amount of the halogenating/titanating agent utilized in post- precipitation steps may be from about 0.45 to about 1.5 equivendings.
- an electron donor may also be employed, during the haiogenation/titanation, to produce the soluble catalyst precursor; during the precipitation, to produce the (solid) catalyst component; or during subsequent halogenations/titanations, to produce alternative catalyst components.
- Electron donors useful in the preparation of poiyolefin catalysts are well known in the art, and any suitable electron donor that will provide a suitable catalyst may be used.
- Eiectron donors, aiso known as Lewis bases, are typicaiiy organic compounds of oxygen, nitrogen, phosphorus, or sulfur which are capable of donating an eiectron pair to the catalyst.
- Such an eiectron donor may be a monofunciionai or poiyfunctiona! compound, and can be seiected from among the aliphatic or aromatic carboxyiic acids and their alkyi esters, the aliphatic or cyclic ethers, ketones, vinyl esters, aery! derivatives,, particularly alkyl acrylates or methacrylates, and silanes.
- An exampie of a suitable electron donor is di-n-buty! phthalate.
- a generic example of a suitable electron donor is an alkylsilyialkoxide of the general formula RSi(OFT) 3 , e.g..
- An internal eiectron donor may be used in the synthesis of the catalysts and an external electron donor, or stereoselectivity control agent (SCA), to activate the cataiyst at polymerization.
- An internal electron donor may be used in the formation reaction of the catalyst during the halogenation or halogenation/titanation steps.
- esters suitable as internal eiectron donors for preparing conventional supported Ziegler-Natta catalyst components include ethers, diethers, ketones, lactones, electron donor compounds with nitrogen, phosphorus and/or suifur atoms, and specific classes of esters. Particularly suitable are the esters of phthalic acid, such as diisobutyi dioctyi, dipheny! and benzylbutyiphthaiate; esters of malonic acid, such as diisobutyi and diethyl malonate: aikyl and ary! pivaiates; aikyi, cycloalkyl and ary!
- External electron donors which may be utilized in the preparation of a cataiyst according to the present invention include organosiiane compounds such as aikoxysilanes of the general formula SiRm(ORVm wherein R is selected from the group consisting of alkyi, cycioaikyl, aryl and vinyl groups; R : is an atkyl group; and m is 0-3, wherein R may be the same as R'; and further wherein, when m is 0> 1 or 2, the R' groups may be the same or different; and when m is 2 or 3, the R groups may be the same or different.
- organosiiane compounds such as aikoxysilanes of the general formula SiRm(ORVm wherein R is selected from the group consisting of alkyi, cycioaikyl, aryl and vinyl groups; R : is an atkyl group; and m is 0-3, wherein R may be the same as R'; and
- the external electron donor useful in the invention can be selected from a siiane compound of the following formula:
- R 1 and R 4 are both an alkyi or cycloalkyl group containing a primary, secondary or tertiary carbon atom attached to the silicon, R 1 and R " being the same or different; and R 2 and R 3 are alky! or ary! groups.
- R 1 may be methyl, isopropyi, isopentyi, cyciohexyi, or t-butyi;
- R 2 and R 3 may be methyl, ethyl, propyl or butyl groups and are not necessarily the same; and R 4 may also be methyl. IsopropyL cyciopentyl, cyciohexyi or t-butyl.
- CMDS meihyidlmethoxy siiane
- DIDS diisopropyi dlmethoxys ⁇ ane
- CIDS cyciohexyi isopropyi dimethoxysiiane
- CPDS dicyclopentyi dimethoxysilane
- DTDS di-t-butyl dimethoxys ⁇ ane
- the catalyst component made as described hereinabove may be combined with an organometaliic catalyst component (a "preactivating agent ' ') to form a preactivated catalyst system suitable for the polymerization of olefins.
- organometaliic catalyst component a "preactivating agent ' '”
- the preactivating agents which are used together with the catalyst component of the invention are organometaliic compounds such as aluminum alkyis, aluminum alkyi hydrides, lithium aluminum alkyis, zinc aikyls, magnesium aSkyis and the like. Organoaiuminum compounds are used in some embodiments.
- the Ziegier-Naita catalysts of U.S. Pat. No. 6,174,971 are suitable for use in the instant process ; and this patent is incorporated herein by reference in its entirety, in one non-restrictive embodiment the synthesis of these Ziegier-Natta catalysts uses a multi-step preparation that Includes treating a soluble magnesium compound with successively stronger chiorinating-titanating reagents.
- the catalysts poiymerize olefins, particularly ethylene, to produce a polymer with low amount of fines, iarge average fluff particle size and narrow molecular weight distribution.
- the catalyst has high activity and good hydrogen response.
- the polymerization catalyst may be that described in U.S. Patent Application Publication 2004/0058803A1 , also incorporated herein in its entirety by reference.
- This document concerns a Ziegier-Natta type catalyst component that may be produced by a process involving contacting a magnesium dialkoxide compound with a halogenating agent to form a reaction product A, and contacting reaction product A with a first, second and third halogenating/titanating agents.
- the reaction products may be washed with a hydrocarbon solvent to reduce titanium species [Ti] content to less than about 100 mmoi/L in another non-limiting embodiment, these Ziegier- Natta polymerization catalysts are produced by a) generating a reaction product A by contacting a magnesium diaikoxide compound with a haiogenating agent; b) contacting reaction product A with a first haiogenating/titanating agent to form reaction product 8; c) contacting reaction product 8 with a second haiogenating/titanating agent to form reaction product C; and d) contacting reaction product C with a third haiogenating/titanating agent to form catalyst component D.
- NCTL Notched Constant Tensile Load
- ESCR is a slow crack growth resistance test (similar to ESCR) to see how fast a uniform notch spreads in contaci with high stress or aggressive liquids such as those described previously and run according to ASTM D5397.
- ESCR and NCTL testing results indicate that the bimodal resins show a signif cant improvement of slow crack growth resistance over FiNA TR- 570 polyethylene at an equivalent density.
- FfGS. 1. 2 and Table Il show the results.
- the relative melt strength of the bimodal drum resins relative to TR-570 was measured using an extruded strand method. This experiment was carried out using a Brabender bench top extruder fitted with a 15 L/D capillary die. A strand of a given length and weight was extruded, and then ihe time for the strand to sag a given distance was recorded. Although this test could be considered somewhat arbitrary, the relative melt strengths (resistance to sag) between resins may be accurately established. The results from this experiment are shown in FIG. 8. Similarly to the throughput-HLMi relationship, a roughly 1 HLM! unit offset in melt strength between the bimodal drum resin and TR-570 are observed.
- a bimodal drum resin at a HLMi of 5.2 has Ihe same meit strength as a TR-570 resin at a HLMI of 6.1.
- Targeting the TR-570 HLMI+1 in order to obtain equivalent pressure limited throughput as discussed above would result in a bimodal drum resin with equivalent meit strength to that of TR-570.
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Abstract
Description
Claims
Priority Applications (5)
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CA2669027A CA2669027C (en) | 2007-05-04 | 2008-05-02 | Bimodal polyethylene resins that have high stiffness and high escr |
JP2010506684A JP2010526186A (en) | 2007-05-04 | 2008-05-02 | Bimodal polyethylene resin with high rigidity and high ESCR |
EP08747536A EP2144955B1 (en) | 2007-05-04 | 2008-05-02 | Bimodal polyethylene resins that have high stiffness and high escr |
ES08747536T ES2398144T3 (en) | 2007-05-04 | 2008-05-02 | Bimodal polyethylene resins that have high hardness and high resistance to cracking due to environmental fatigue |
MX2009005475A MX2009005475A (en) | 2007-05-04 | 2008-05-02 | Bimodal polyethylene resins that have high stiffness and high escr. |
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US11/744,596 US8138264B2 (en) | 2007-05-04 | 2007-05-04 | Bimodal polyethylene resins that have high stiffness and high ESCR |
US11/744,596 | 2007-05-04 |
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PCT/US2008/062474 WO2008137722A1 (en) | 2007-05-04 | 2008-05-02 | Bimodal polyethylene resins that have high stiffness and high escr |
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US (1) | US8138264B2 (en) |
EP (1) | EP2144955B1 (en) |
JP (1) | JP2010526186A (en) |
KR (1) | KR20100016232A (en) |
CN (1) | CN101616963A (en) |
CA (1) | CA2669027C (en) |
ES (1) | ES2398144T3 (en) |
MX (1) | MX2009005475A (en) |
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WO2014043364A1 (en) | 2012-09-13 | 2014-03-20 | Dow Global Technologies Llc | Ethylene-based polymer compositions, and articles prepared from the same |
US9441062B2 (en) | 2013-05-09 | 2016-09-13 | Abu Dhabi Polymers Company Limited (Borouge), Llc | Multimodal polyethylene polymers and methods of making and using the same |
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US8168112B2 (en) * | 2008-12-20 | 2012-05-01 | Fina Technology, Inc. | Blown films and processes of forming the same |
US20100210797A1 (en) * | 2009-02-17 | 2010-08-19 | Fina Technology, Inc. | Polyethylene Films having Improved Barrier Properties |
US7951883B1 (en) * | 2009-12-04 | 2011-05-31 | Equistar Chemicals, Lp | Preparation of multimodal, high density, ethylene homopolymer barrier resins and films |
EP2354167A1 (en) * | 2010-02-05 | 2011-08-10 | Total Petrochemicals Research Feluy | Bimodal polyethylene for blow-moulding applications. |
EA025606B1 (en) * | 2010-02-05 | 2017-01-30 | Тотал Рисерч Энд Текнолоджи Фелюй | Process for preparing polyolefin |
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EP2878623B1 (en) * | 2013-11-28 | 2018-07-11 | Abu Dhabi Polymers Company Limited (Borouge) | Multimodal polymer |
US9624321B2 (en) * | 2014-06-13 | 2017-04-18 | Fina Technology, Inc. | Formation of a Ziegler-Natta catalyst |
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CN109438818B (en) * | 2018-09-07 | 2022-03-08 | 中国石油化工股份有限公司 | Special resin for cracking-resistant high-density polyethylene pipe and preparation method thereof |
CN116135892A (en) * | 2021-11-16 | 2023-05-19 | 中国石油化工股份有限公司 | Method for preparing bimodal polyethylene resin for pipe material and bimodal polyethylene resin thereof |
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EP2144955A1 (en) | 2010-01-20 |
MX2009005475A (en) | 2009-06-02 |
EP2144955A4 (en) | 2010-12-29 |
CA2669027C (en) | 2015-02-24 |
KR20100016232A (en) | 2010-02-12 |
CN101616963A (en) | 2009-12-30 |
CA2669027A1 (en) | 2008-11-13 |
ES2398144T3 (en) | 2013-03-13 |
US8138264B2 (en) | 2012-03-20 |
US20080275197A1 (en) | 2008-11-06 |
JP2010526186A (en) | 2010-07-29 |
EP2144955B1 (en) | 2012-11-28 |
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