Multimodal polyethylene screw cap

Abstract

A multimodal polyethylene composition and screw cap having improved mechanical properties such as Charpy values, crystallization times, and spiral flow lengths are provided. [Solution] The multimodal polyethylene composition comprises: (A) 35 to 65 parts by weight of a low molecular weight polyethylene having a weight average molecular weight (Mw) of 20,000 to 90,000 g / mol; (B) 5 to 40 parts by weight of a first high molecular weight polyethylene having a weight average molecular weight (Mw) of more than 150,000 to 1,000,000 g / mol; and (C) 20 to 60 parts by weight of a second high molecular weight polyethylene having a weight average molecular weight (Mw) of more than 150,000 to 1,000,000 g / mol, wherein the molecular weight distribution is 10 to 25; the isothermal crystallization half time of the multimodal polyethylene composition at a temperature of 123°C is 7 minutes or less; and the spiral flow length at a temperature of 220°C is at least 200 mm.

Description

[Technical Field]

[0001] The present invention relates to a multimodal polyethylene composition for producing screw caps. [Background technology]

[0002] The demand for polyethylene resin is increasing due to its use in various applications. The high performance of polymers required for relatively new plastics has led to the development of new polymerisation process technology. Developed to aid in the manufacturing of polymeric materials. To balance these properties, developments in multimodal polymerization processes were investigated.

[0003] In the prior art, multimodal polyethylene polymerization is used to produce each resin fraction in a separate reactor. By performing the above steps, polymers with different molecular weights are produced. The low molecular weight fraction is used to produce the final polymer. Excess hydrogen is added to control the molecular weight of the polymer to give good processability of the polymer. The high molecular weight fraction affects the physical properties and the low hydrogen concentration A low molecular weight polymer is preferably produced in the first reactor under polymerization conditions. In order to obtain a multimodal polymer with good physical properties, first All hydrogen from the reactor is used to produce high molecular weight polymer. It should be removed before being transferred to the second reactor where production takes place.

[0004] The object is to overcome the drawbacks of the prior art, in particular to provide improved mechanical properties, e.g., Charpy values. To provide a multimodal polyethylene composition having a crystallization time and a spiral flow length is.

[0005] Screw caps, e.g., beverage screw caps and other closures, are used to seal beverage bottles. The invention relates to a method for capping bottles, particularly those for capping carbonated soft drink bottles, and is well known in the art. In particular, various polyethylene compositions for preparing such screw caps are available. exist. WO 2009 / 077142 describes an injection molded screw cap and closure. Polyethylene molding composition for manufacturing containers, particularly for use with carbonated beverage product containers The composition is disclosed.

[0006] WO 2007 / 003530 describes a method for producing injection-molded finished parts using a polyester resin. A polyethylene molding composition is disclosed. This composition is useful for the manufacture of, for example, closures and bottles. Further described is a multimodal polyethylene composition suitable for the manufacture of The use of things.

[0007] U.S. Pat. No. 8,759,448 describes a polyethylene molding composition having a multimodal molecular weight distribution. For the preparation of caps and closures, transport packaging, household goods and thin-wall packaging applications It is proposed to use the disclosed compositions for

[0008] European Patent No. 2365995 describes a multimodal polyethylene composition and a single piece polyethylene composition. The multimodal polyethylene composition is also disclosed for use in preparing a torcap. Nucleating agents were added to obtain faster crystallization rates and alter stress crack resistance.

[0009] However, still in light of the above-mentioned prior art, an improved cap, especially a screw cap, is required. and a polymer for preparing the cap that overcomes the drawbacks of the prior art. - composition, in particular, better processability, excellent flowability, high stiffness and high environmental stress crack resistance ( It is still necessary to provide a polymer composition for preparing a cap having ESCR. It is needed. [Prior art documents] [Patent documents]

[0010] [Patent Document 1] International Publication No. 2009 / 077142 [Patent Document 2] International Publication No. 2007 / 003530 [Patent Document 3] U.S. Patent No. 8,759,448 [Patent Document 4] European Patent No. 2365995 Summary of the Invention [Problem to be solved by the invention]

[0011] It is therefore an object of the present invention to provide an improved cap and multimodal polyethylene composition. The purpose is to provide. [Means for solving the problem]

[0012] This object is achieved according to the invention by the subject matter of the independent claims. Further aspects follow from the dependent claims.

[0013] The object is to provide a multimodal polyethylene composition comprising: (A) 35 to 65 parts by weight, preferably 45 to 65 parts by weight, most preferably 50 to 60 parts by weight A portion of the low molecular weight polymer having a weight average molecular weight (Mw) of 20,000 to 90,000 g / mol Low molecular weight polyethylene; (B) 5 to 40 parts by weight, preferably 5 to 30 parts by weight, most preferably 5 to 20 parts by weight , having a weight average molecular weight (Mw) of more than 150,000 to 1,000,000 g / mol First high molecular weight polyethylene or more than 1,000,000 to 5,000,000 g / mol a first ultra-high molecular weight polyethylene having a weight average molecular weight (Mw) of (C) 20 to 60 parts by weight, preferably 25 to 60 parts by weight, most preferably 35 to 55 parts by weight A weight average molecular weight (Mw) of more than 150,000 to 1,000,000 g / mol A second high molecular weight polyethylene having a molecular weight of more than 1,000,000 to 5,000,000 g / A second ultra-high molecular weight polyethylene having a weight average molecular weight (Mw) of 100 mol Including, Molecular weight distributions of multimodal polyethylene compositions determined by gel permeation chromatography. is 10 to 25, preferably 10 to 20; Isothermal Behavior of Multimodal Polyethylene Compositions at 123°C by Differential Scanning Calorimetry The crystallization half time is 7 minutes or less, preferably 6 minutes or less, preferably 2 to 6 minutes. Yes; and The spiral flow length at a temperature of 220°C is at least 200 mm, preferably 2 50~400mm, This is achieved by the multimodal polyethylene composition.

[0014] In a preferred embodiment, the multimodal polyethylene composition is 80,000 to 250,000 g / mol, preferably 80,00 It has a weight average molecular weight of 0 to 200,000 g / mol.

[0015] Furthermore, the multimodal polyethylene composition is characterized by the following properties as measured by gel permeation chromatography: , 5,000 to 30,000 g / mol, preferably 5,000 to 20,000 g / mol It is preferred that the copolymer has a number average molecular weight of 1.

[0016] Preferably, the multimodal polyethylene composition has a molecular weight of 1000 or more as measured by gel permeation chromatography. 700,000 to 2,500,000 g / mol, preferably 700,000 to 2 ,000,000 g / mol, more preferably 700,000 to 1,500,000 g / mol It has a Z-average molecular weight of 1.0 mol.

[0017] Preferably, the multimodal polyethylene composition has a modulus of elasticity of 0.950 to 0.950 by ASTM D1505. 0.965g / cm 3 , preferably 0.953 to 0.960 g / cm 3 density and / or According to ASTM D1238, 0.1 to 20 g / 10 min, preferably 0.3 to 17 g / It has an MI2 of 10 min.

[0018] Preferably, the multimodal polyethylene composition has a molecular weight of 15 to 25, preferably 15 to 20. It has a quantity distribution.

[0019] Preferably, the spiral flow length at a temperature of 220°C is 250 to 370 mm. .

[0020] This object is further provided by a screw cap comprising the multimodal polyethylene composition according to the invention. This is achieved by:

[0021] In this regard, screw caps (or screw closures) are used to "finish" containers. This is a mechanical device that twists the "finish" open and closed. (and barrier), compatible with the contents, easy for the consumer to open and, in many cases, reclose. The device must be designed to be compatible with the product and its packaging. Clew caps are a common type of closure for bottles, jars, and tubes. is.

[0022] Most preferably, the screw cap is obtained by injection molding or compression molding.

[0023] Regarding the screw cap of the present invention, the screw cap is made of the multimodal polyester of the present invention. Preferably, the composition contains primarily polyethylene, which is a screw cap that can be used to add other ingredients to the container. This affects cap performance in terms of workability (especially cycle time), flow, stiffness, and stress crack resistance. Most preferably, the screw cap contains only a non-destructive amount of the The invention comprises a multimodal polyethylene composition.

[0024] The reactor system of the present invention, the process of the present invention and the multimodal polyethylene composition of the present invention In a preferred embodiment, "comprising" becomes "consisting of "

[0025] In a preferred embodiment, "parts by weight" is "weight percent."

[0026] This object is further achieved by producing a multimodal polyethylene composition in the reactor system of the present invention. A process for: (a) in a first reactor, a catalyst selected from a Ziegler-Natta catalyst or a metallocene; In the presence of the system and in the gas phase in the first reactor, 0.1 to 95 mol % of hydrogen in an inert hydrocarbon medium to produce low molecular weight polyethylene. obtaining polyethylene or medium molecular weight polyethylene; (b) in the hydrogen removal unit, a first pressure in the range of 103 to 145 kPa (abs); The hydrogen content of the slurry mixture obtained from the reactor was 98.0 to 99.8 wt. %. and transferring the resulting residual mixture to a second reactor; (c) in a second reactor, a catalyst selected from a Ziegler-Natta catalyst or a metallocene; In the presence of the system and in the presence of hydrogen in the amount obtained in step (b), ethylene and optionally Choice C 4~12 polymerizing an α-olefin comonomer to form a first high molecular weight polyethylene or A first ultra-high molecular weight polyethylene in the form of a homopolymer or copolymer is obtained, and the obtained transferring the resulting mixture to a third reactor; and (d) in a third reactor, a catalyst selected from a Ziegler-Natta catalyst or a metallocene; In the presence of the system, and the amount of hydrogen in the third reactor is Hydrogen in the range of 0.1 to 70 mol %, preferably 0.1 to 60 mol %, based on the total weight or optionally in the substantial absence of hydrogen, ethylene and optionally C 4~1 2. Polymerizing an α-olefin comonomer to form a second high molecular weight polyethylene or a second ultra-high molecular weight polyethylene. A process for obtaining low molecular weight polyethylene homopolymer or copolymer This is achieved by a process that includes (in this order):

[0027] "Substantial absence" in this respect means that hydrogen is not introduced into the third reactor by technical means. This means that the amount contained is so small that it cannot be detected.

[0028] The slurry obtained from the first reactor and subjected to a step of removing hydrogen in a hydrogen removal unit. The mixture is a mixture of solid and liquid components obtained in the first reactor, in particular low molecular weight polyethylene. Further, the slurry obtained from the first reactor contains all of the polyethylene and the medium molecular weight polyethylene. - The mixture is saturated with hydrogen regardless of the amount of hydrogen used in the first reactor.

[0029] Preferably, the removal is 98.0 to 99.8% by weight, more preferably 98.0 to 99.5%. The removal of hydrogen is preferably 98.0 to 99.1% by weight.

[0030] Preferably, the α-comonomer contained in the second reactor and / or the third reactor is 1- It is selected from butene and / or 1-hexene.

[0031] Preferably, the operating pressure of the hydrogen removal unit is 103 to 145 kPa (abs), more preferably Preferably 104 to 130 kPa (abs), most preferably 105 to 115 kPa (abs) bs).

[0032] Preferably, step (a) results in a low molecular weight polyethylene or a medium molecular weight polyethylene; Step (c) produces high molecular weight polyethylene or ultra-high molecular weight polyethylene, and step (d) , resulting in high molecular weight polyethylene or ultra-high molecular weight polyethylene.

[0033] The low molecular weight polyethylene, medium molecular weight polyethylene, and high molecular weight polyethylene described herein The weight average molecular weight (Mw) of polyethylene and ultra-high molecular weight polyethylene is 20,000 to 90,000, respectively. 0,000g / mol (low), over 90,000~150,000g / mol (medium), 15 Over 0,000 to 1,000,000 g / mol (high) and over 1,000,000 to 5,0 00,000 g / mol (ultra-high).

[0034] Regarding the screw cap of the present invention, the screw cap is made of the multimodal polyester of the present invention. Preferably, the composition contains primarily polyethylene, which is a screw cap that can be used to add other ingredients to the container. This affects cap performance in terms of workability (especially cycle time), flow, stiffness, and stress crack resistance. Most preferably, the screw cap contains only a non-destructive amount of the The invention comprises a multimodal polyethylene composition. DETAILED DESCRIPTION OF THE INVENTION

[0035] The reactor system of the present invention, the process of the present invention and the multimodal polyethylene composition of the present invention In a preferred embodiment, "comprising" becomes "consisting of "

[0036] In a preferred embodiment, "parts by weight" is "weight percent."

[0037] The above-mentioned preferred embodiments further enhance the properties of the resulting multimodal polyethylene composition. This resulted in improved mechanical properties and screw caps prepared therefrom. The results can be obtained by combining two or more of the above preferred embodiments. Likewise, the embodiments described above as more preferred or most preferred are those that provide the best mechanical properties. It has improved significantly.

[0038] Surprisingly, the use of certain multimodal polyethylene compositions allows for the formation of screw caps. and excellent properties of the closure, especially processability (fast cycle time), flowability, rigidity and It was found that stress crack resistance was improved.

[0039] The catalyst for producing the multimodal polyethylene resin of the present invention is a Ziegler-Natta catalyst, Single-site catalysts, including metallocene and non-metallocene catalysts, or chromium-based A conventional Ziegler-Natta catalyst or a single-site catalyst is preferably used. The catalyst is typically used in conjunction with a co-catalyst as is well known in the art.

[0040] The inner hydrocarbon is preferably hexane, isohexane, heptane, isohexane, aliphatic hydrocarbons including butane; preferably hexane (most preferably n-hexafluorobutane); A coordination catalyst, ethylene, hydrogen, and optionally an α-olefin comonomer are used. is polymerized in the first reactor. The total product obtained from the first reactor is then Hydrogen removal to remove 0 to 99.8 wt% hydrogen, unreacted gases, and some volatiles After being transferred to the unit, it is fed to a second reactor to continue the polymerization. The polyethylene obtained from the reactor was the product obtained from the first reactor and the product obtained from the second reactor. This bimodal polyethylene is then The final product obtained from the third reactor is fed to the third reactor to continue the polymerization. Multimodal (trimodal) polyethylene is a mixture of polymers from the first, second and third reactors. is.

[0041] The polymerizations in the first, second and third reactors are carried out under different process conditions. These are the changes in the concentrations of ethylene and hydrogen in the gas phase, the temperature of the comonomer fed to each reactor, and the The degree or amount of each homopolymer or copolymer of the desired properties, particularly of the desired molecular weight, may be Suitable conditions for obtaining the above are well known in the art. As a result, the polymers obtained in each reactor can be The polyethylene has different molecular weights. Preferably, low molecular weight polyethylene or medium molecular weight polyethylene. Polyethylene is produced in the first reactor, while high molecular weight polyethylene or ultra high molecular weight polyethylene is produced in the second reactor. A quantity of polyethylene is produced in the second and third reactors, respectively. The term first reactor refers to a reactor containing low molecular weight polyethylene (LMW) or medium molecular weight polyethylene. The term second reactor refers to the stage where the first high molecular weight or This refers to the stage where ultra-high molecular weight polyethylene (HMW1) is produced. The term third reactor refers to the stage where the second high molecular weight polyethylene or ultra-high molecular weight (HMW2) is produced.

[0042] The term LMW refers to the 20,000-90,000 g / refers to a low molecular weight polyethylene polymer having a weight average molecular weight (Mw) of 100 mol.

[0043] The term MMW refers to the >90,000 to 150,000 polymerized in the first reactor. Refers to a medium molecular weight polyethylene polymer having a weight average molecular weight (Mw) of g / mol.

[0044] The term HMW1 refers to the 150,000 to 5,000 polymerized in the second reactor. High molecular weight or ultra-high molecular weight polyethylene having a weight average molecular weight (Mw) of 1,000 g / mol refers to polyethylene polymers.

[0045] The term HMW2 refers to the 150,000 to 5,000 polymerized in the third reactor. High molecular weight or ultra-high molecular weight polyethylene having a weight average molecular weight (Mw) of 1,000 g / mol refers to polyethylene polymers.

[0046] LMW or MMW is prepared by the absence of comonomer in the first reactor to obtain a homopolymer. Manufactured below.

[0047] To obtain the improved polyethylene properties of the present invention, the ethylene is preferably 0.965 g / cm 3 The above density and LMW are 10 to 1000g / 10min, and MMW are High density LMW polyethylene or M with MI2 in the range of 0.1 to 10 g / 10 min In the first reactor, the copolymer is polymerized in the absence of comonomers to obtain MW polyethylene. The polymerization conditions are controlled and adjusted to obtain the target density and MI in the first reactor. The temperature in the reactor is in the range of 70 to 90°C, preferably 80 to 85°C. Ethylene is fed to the first reactor to control the molecular weight. The first reactor is The reactor is operated at a pressure between 0 and 900 kPa, preferably between 400 and 850 kPa. The amount of hydrogen present in the gas phase of the reactor is 0.1 to 95 mol%, preferably 0.1 to 90 mol%. ol% range.

[0048] Before being fed to the second reactor, the LMW or MMW polyethylene is preferably mixed in hexane. The slurry obtained from the first reactor containing hydrogen is transferred to a hydrogen removal unit, The removal unit is configured to remove volatiles, unreacted gases, and hydrogen from the slurry stream. Among the vacuum pumps, compressors, blowers and ejectors that reduce the pressure inside the rush drum A flash drum connected to a pressure reducing device preferably including one or a combination of The operating pressure of the hydrogen removal unit is typically 98.0 to 99.8 wt.%, preferably or 98.0 to 99.5 wt. %, most preferably 98.0 to 99.1 wt. % of hydrogen removed. 103 to 145 kPa (abs), preferably 104 to 130 kPa (abs) ) range.

[0049] In the present invention, under these hydrogen content conditions, 98.0 to 99.8% by weight of hydrogen is removed. When polymerization occurs, a very high molecular weight polymer is thus obtained, Surprisingly, the impact and flexural modulus of the 98.0 to 99.8 wt. % water Operating outside the range of oxygen removal results in very high molecular weight polymers, which can cause Charpy impact and bending It was found that the effect of the present invention in improving the bending modulus was not observed to the same extent. , was more pronounced within the range described as favorable.

[0050] The polymerization conditions in the second reactor are significantly different from the polymerization conditions in the first reactor. The temperature in the reaction vessel is in the range of 65 to 90°C, preferably 68 to 80°C. The mole ratio of hydrogen to ethane is not controlled in this reactor because hydrogen is introduced into the second reactor. The hydrogen in the second reactor is flashed in the hydrogen removal unit. This is the residual hydrogen from the first reactor that remains in the slurry stream after being pumped through the second reactor. The polymerization pressure is 100 to 3000 kPa, preferably 150 to 900 kPa, more preferably The pressure is generally in the range of 150 to 400 kPa.

[0051] Hydrogen removal is measured by comparing the amount of hydrogen present in the slurry mixture before and after passing through the hydrogen removal unit. The calculation of hydrogen removal was performed by gas chromatography in the first and second reactors. This is carried out according to the measurement of the gas composition.

[0052] After a significant amount of hydrogen has been removed, the concentrated slurry from the hydrogen removal unit continues polymerization. In this reactor, ethylene is transferred to a second reactor for conversion to α-olefin mono-olefins. The LMW polyethylene or M obtained from the first reactor was polymerized with or without a monomer. In the presence of MW polyethylene, HMW1 polyethylene can be produced. -Olefin comonomers include C 4-12 , preferably 1-butene and 1- Contains hexene.

[0053] After polymerization in the second reactor, the resulting slurry is transferred to a third reactor to continue polymerization. Be transferred.

[0054] HMW2 is the total of the LMW or MMW obtained from the first and second reactors and the presence of HWM1. The third reaction is carried out by copolymerizing ethylene, optionally with an α-olefin comonomer. α-olefin comonomers useful for copolymerization include C 4-12 , Preferably, 1-butene and / or 1-hexene is included.

[0055] The polymerization conditions are controlled and adjusted to obtain the target density and target MI in the third reactor. However, the polymerization conditions in the third reactor are significantly different from those in the first and second reactors. The temperature in the reactor is in the range of 68 to 90°C, preferably 68 to 80°C. Ethylene is fed to the third reactor to control the molecular weight. Polymerization in the third reactor The pressure is in the range of 150 to 900 kPa, preferably 150 to 600 kPa. It is controlled by the addition of a gas, for example nitrogen.

[0056] The amount of LMW or MMW present in the multimodal polyethylene composition of the present invention is 30 to 65 parts by weight. The HMW1 present in the polyethylene of the present invention is 5 to 40 parts by weight, and the HMW2 present in the polyethylene of the present invention is 10 to 60 parts by weight. Depending on the polymerization conditions used, it is possible that HMW1 > HMW2 or HMW1 < HMW2. The final (free-flowing) multimodal polyethylene composition is obtained by separating hexane from the slurry discharged from the third reactor. The obtained polyethylene powder may then be extruded and mixed with an antioxidant and optionally additives before being pelletized.

[0057] : The melt flow index (MI) of the polymer was measured according to ASTM D1238, which measures the fluidity of the polymer under test conditions of 190 °C, loads of 2.16 kg (MI2), 5 kg (MI5), and 21.6 kg (MI ), and was expressed in g / 10 min.

[0058] : The density of the polyethylene was measured by observing the level at which the pellet sinks in a liquid column gradient tube compared to a standard of known density. This method is a measurement of solid plastics after annealing at 120 °C according to ASTM D1505. : The weight average molecular weight (Mw), number average molecular weight (Mn)

[0059] Definition and measurement method Melt Flow Index : and Z average molecular weight (M )(g / mol) were determined by gel permeation chromatography (GPC). 21 ): : / 10 min.

[0060] density : The density of the polyethylene was measured by observing the level at which the pellet sinks in a liquid column gradient tube compared to a standard of known density. This method is a measurement of solid plastics after annealing at 120 °C according to ASTM D1505. :

[0061] Molecular weight and polydispersity index (PDI) : Weight average molecular weight (Mw), number average molecular weight (Mn) and Z average molecular weight (M Z )(g / mol) were determined by gel permeation chromatography (GPC). The polydispersity index was calculated by Mw / Mn. Approximately 8 mg of sample was added to 8 ml of 1, The sample solution was dissolved in 2,4-trichlorobenzene at 160°C for 90 minutes. 10 μl was added to a high-performance liquid chromatography column equipped with an IR5 infrared detector (Polymer Char, Spain). The temperature in the column zone was 145°C, and the temperature in the detector zone was 160°C. The flow rate was 0.5 ml / m The injection was performed at a flow rate of 1000 kJ / min. Data were analyzed using GPC One® software (Poly The samples were processed by Mer Char (Spain).

[0062] Intrinsic viscosity (IV) This test method is for polyethylene at 135°C or ultra-high molecular weight polyethylene at 150°C. The purpose of this study is to measure the viscosity of dilute solutions of ultra-high molecular weight polyethylene (UHMWPE). Decalin containing 0.2% wt / vol stabilizer (Irganox 1010 or equivalent) The polymer was prepared by dissolving the polymer in a IV solution according to ASTM D2515. The measurement of

[0063] Comonomer Content : Comonomer content is high resolution 13 The carbon monoxide content was determined by C-NMR. C-NMR spectra were obtained using a 500 MHz ASCEND™ (Bruker) The measurements were recorded using a cryogenic 10 mm probe. TCB was used as the main solvent, and TCE-d2 was used as the probe. The NMR experiments were carried out at 120 °C and pulsed. A 13C reverse gate (zgig) was used with a pulse angle of 90°. The delay time (D1) for the spin recovery was set to 10 seconds.

[0064] CrystallinityCrystallinity is often measured by differential scanning calorimetry according to ASTM D3418. The sample is characterized by peak temperature and enthalpy. The crystallinity was calculated from the peak area.

[0065] Shear Thinning Index (SHI) This gives an indication of the molecular weight distribution of the material. A typical measurement is performed using a dynamic rheometer with a 25 mm diameter plate and a 1 mm gap. The viscosity is 190°C using a plate shape of 1 mm. SHI (1 / 100) is 1 kP The viscosity was calculated at a constant shear stress of 100 kPa and a constant shear stress of 100 kPa. Having this means better flowability of the material.

[0066] Viscosity (η) at angular frequency 0.01 [1 / s] 0.01 ) : Rheological parameters are Measured using an Anton-Paar stress-controlled rheometer model MCR-301 The geometry is a plate-plate 25mm diameter with a measurement gap of 1mm. The dynamic oscillatory shear is The test is carried out at an angular frequency (ω) of 0.01 to 600 rad / s at 190°C in a nitrogen atmosphere. Sample preparation is carried out on 25 mm discs by compression molding at 190°C. 1 / s](η 0.01 ) is the viscosity of a compound at a specific shear rate of 0.01 [1 / s]. It is obtained from the base viscosity.

[0067] Isothermal crystallization half time (ICHT) and crystal growth rate constant (K) : Differential scanning calorimetry (D The isothermal crystallization half time at 123°C was measured by SC to determine the crystallization rate of the sample. The sample was heated from 30°C to 200°C at a heating rate of 50°C / min and held for 5 minutes. The sample was then cooled to 123°C at a cooling rate of 50°C / min and held for 60 minutes. The logarithmic data was fitted to the Avrami equation to determine the crystal growth rate constant (K) and n. It was determined.

[0068] Spiral Flow Length Spiral flow test: Fanuc Roboshot S2 000i 100B injection molding machine (screw diameter 36 mm) using a spiral mold The test was carried out at a temperature of 220°C and a constant injection pressure of 1000 bar. The thickness of the test piece was 1 mm. After conditioning the sample for 24 hours, the spiral flow length (mm) was measured. It was determined.

[0069] Charpy impact strength Compression test specimens were prepared according to ISO 293. Charpy impact strength The strength is measured at 23°C according to ISO 179 and is expressed in kJ / m 2 It is shown as follows.

[0070] Flexural modulus Compression test specimens were prepared according to ISO 1872-2 and ISO 178. The bending test was carried out using a universal testing machine equipped with a three-point bending jig.

[0071] Full Notch Creep Test (FNCT) The full notch creep test according to ISO 16770 was the preferred method for determining the stress crack resistance of polymers (N=100) at a constant stress of 6 MPa at 50°C in a 2% Arkopal solution. Samples were cut from 6 mm thick compression molded plaques according to ISO 1872-2. The specimen (Type C) dimensions were 90 mm x 6 mm x 6 mm, with a notch depth of 1 mm. The time to failure is recorded in hours. The present invention includes the following aspects. Section 1. 1. A multimodal polyethylene composition comprising: (A) 35 to 65 parts by weight, preferably 45 to 65 parts by weight, and most preferably 50 to 60 parts by weight of a low-molecular-weight polyethylene having a weight-average molecular weight (Mw) of 20,000 to 90,000 g / mol; (B) 5 to 40 parts by weight, preferably 5 to 30 parts by weight, and most preferably 5 to 20 parts by weight of a first high molecular weight polyethylene having a weight average molecular weight (Mw) of more than 150,000 to 1,000,000 g / mol or a first ultra-high molecular weight polyethylene having a weight average molecular weight (Mw) of more than 1,000,000 to 5,000,000 g / mol; and (C) 20 to 60 parts by weight, preferably 25 to 60 parts by weight, most preferably 35 to 55 parts by weight of a second high-molecular-weight polyethylene having a weight-average molecular weight (Mw) of more than 150,000 to 1,000,000 g / mol or a second ultra-high-molecular-weight polyethylene having a weight-average molecular weight (Mw) of more than 1,000,000 to 5,000,000 g / mol Including, the molecular weight distribution of the multimodal polyethylene composition, as determined by gel permeation chromatography, is 10 to 25, preferably 10 to 20; the isothermal crystallization half time of the multimodal polyethylene composition at a temperature of 123°C as measured by differential scanning calorimetry is 7 minutes or less, preferably 6 minutes or less, preferably 2 to 6 minutes; and The spiral flow length at a temperature of 220°C is at least 200 mm, preferably 250 to 400 mm. Multimodal polyethylene composition. Section 2. Item 2. The multimodal polyethylene composition according to Item 1, wherein the molecular weight distribution is 15 to 25, preferably 15 to 20. Section 3. Item 3. The multimodal polyethylene composition according to Item 1 or 2, wherein the spiral flow length at a temperature of 220°C is 250 to 370 mm. Section 4. Item 4. The multimodal polyethylene composition according to any one of Items 1 to 3, having an average molecular weight of 80,000 to 250,000 g / mol, preferably 80,000 to 200,000 g / mol, as measured by gel permeation chromatography. Section 5. Item 5. The multimodal polyethylene composition according to any one of Items 1 to 4, having a number average molecular weight of 5,000 to 30,000 g / mol, preferably 5,000 to 20,000 g / mol, as measured by gel permeation chromatography. Section 6. Item 6. The multimodal polyethylene composition according to any one of items 1 to 5, having a Z-average molecular weight, as measured by gel permeation chromatography, of 700,000 to 2,500,000 g / mol, preferably 700,000 to 2,000,000 g / mol, and most preferably 700,000 to 1,500,000 g / mol. Section 7. The multimodal polyethylene composition has a viscosity of 0.950 to 0.965 g / cm according to ASTM D1505. 3 , preferably 0.953 to 0.960 g / cm 3 and / or an MI2 according to ASTM D1238 of 0.1 to 20 g / 10 min, preferably 0.3 to 17 g / 10 min. Section 8. Item 8. A screw cap comprising the multimodal polyethylene composition according to any one of items 1 to 7. Section 9. Item 9. The screw cap according to item 8, which can be obtained by injection molding or compression molding. [Example]

[0072] Composition Examples The preparation of medium or high density polyethylene was carried out in three reactors in series. , hydrogen, hexane, catalyst, and TEA (triethylaluminum) cocatalyst in a first reactor. The catalyst was prepared by the following methods: , as described, for example, in Hungarian Patent Application No. 0800771r.

[0073] Polymerization in the first reactor is carried out to produce low molecular weight polyethylene or medium molecular weight polyethylene. All of the polymerized slurry polymer from the first reactor was then dehydrogenated. The polymer was then transferred to a removal unit to remove unreacted gases and a portion of the hexane from the polymer. The operating pressure in the removal unit was changed within the range of 100 to 115 kPa (abs), and the second Residual hydrogen is converted from hexane to a concentration of more than 98% by weight, but not more than 98% by weight, before being transferred to the polymerization reactor. No more than 9.8 wt.% was removed. Some fresh hexane, ethylene and / or co Monomers are fed into a second reactor to produce a first high molecular weight polyethylene (HMW1). All of the polymerized polymer from the second reactor was transferred to a second high molecular weight polyethylene The ethylene, comonomer, hexane and propylene glycol were fed into a third reactor to produce HMW2. and / or hydrogen was fed into the third reactor.

[0074] Examples of screw caps of the polymer composition of the present invention for multimodal polyethylene and for screw caps Examples were polymerized as shown in Tables 1, 2, 3 and 4.

[0075] Comparative example 1 (CE1) A homopolymer is produced in the first reactor and such polymer is sent to a hydrogen removal unit. Before transfer, the low molecular weight fraction was obtained. The reaction mixture was introduced into a hydrogen removal unit to remove unreacted The mixture was separated from the polymer. The hydrogen removal unit was operated at a pressure of 150 kPa (abs). When operated, 97.6 wt% of residual hydrogen was removed. The final polymer from the second reactor was transferred to the second reactor to produce the first high molecular weight polymer. The polymer produced was transferred to a third reactor to produce a second high molecular weight polymer. Third, copolymerization was carried out by feeding 1-butene as the comonomer. As can be seen in Figures 1 and 2, the final melt flow rate of CE1 is approximately 1 / 2 the final melt flow rate of E1. The decrease in Charpy impact and flexural modulus was similar to that of CE1. It was shown compared to E1, but also showed a lower density of E1.

[0076] Example 1 (E1) of the present invention Example 1 (E1) was carried out in the same manner as Comparative Example 1 (CE1), except that the hydrogen removal unit The reactor was operated at a pressure of 115 kPa (abs). The residual components were removed to the extent of 98.5% by weight. The melt flow rate of the polymer is 48g / 10ml, which is lower than that obtained from CE1. As can be seen in Table 2, the percentage of residual hydrogen removed was When increased compared to the properties of Example 1, an improvement in stiffness-impact balance is evident.

[0077] The properties of the present invention according to Inventive Example E1 were compared with the properties of Comparative Example CE1.

[0078] Comparative Example 2 (CE2) Comparative Example 2 (CE2) is a bimodal polyethylene produced with a Ziegler-Natta catalyst. The weight ratio between ethylene homopolymer and ethylene copolymer is 45:55 to 55: 45. The polymer composition contains a comonomer in an amount of at least 0.40 mol %. Includes:

[0079] Comparative Example 3 (CE3) Comparative Example 3 (CE3) is a commercially available multimodal high density polyethylene, Hostalen® )ACP5331 UVB plus.

[0080] Inventive Examples 2 and 3 (E2 and E3) The multimodal polyethylene compositions of inventions 2 and 3 (E2 and E3) were prepared under the polymerization conditions shown in Table 3. The reactors were prepared according to the process of the present invention. Different weight fractions were defined in each reactor, 1- Butene was used as the comonomer in the second and third reactor components. The properties of the present invention according to Examples 2 and 3 (E2 and E3) are compared with those of Comparative Examples 2 and 3 (CE2 and CE3). The characteristics were compared with those of CE3).

[0081] The characteristics and properties of these multimodal polyethylenes are shown in Table 4. Comparison between different polymerization processes was shown. Surprisingly, higher Mz and higher The multimodal polyethylene according to the invention with shear thinning is shown in Comparative Examples 2 and 3 (CE2, CE 3) compared to Examples 2 and 3 (E2 and E3) of the present invention, and to Comparative Example 1 (CE1). Both Inventive Example 1 (E1) show significant improvements in processability and stiffness.

[0082] Better processability can be explored in terms of both faster cycle times and higher flowability. Faster cycle times result in lower crystallization half times (ICHT) and The results were judged by the higher crystal growth rate (K). Comparative Examples 1, 2 and 3 (CE1, CE2 and CE3) had lower ICHT and and exhibits a higher crystal growth rate (K). The resulting ultra-high molecular weight acts as a backbone for easier nucleation, resulting in faster crystallization rates. It is assumed that the fluidity is usually determined by the spiral flow length at a temperature of 220°C. The spiral flow length of Example E1 of the present invention is higher than that of Comparative Example 1 (CE1), Examples 2 and 3 (E2 and E3) of the present invention are better than Comparative Examples 2 and 3 (CE2 and CE3). Moreover, the inventive examples have lower MI than the comparative examples.

[0083] The improvement in stiffness compared to CE2 and CE3 was also investigated. These Inventive Example 2 (E2) The multimodal polyethylene composition has better bending elasticity than Comparative Examples 2 and 3 (CE2 and CE3). Furthermore, Example 1 (E1) of the present invention has a higher bending elasticity than Comparative Example (CE1). The multimodal polyethylene according to the present invention with a higher Mz has a significant improvement in stiffness. Show goodness.

[0084] This is because the multimodal polyethylene compositions of the present invention have better processability and It has been shown that this provides a good balance between higher stiffness and stress crack resistance. The invention significantly enhances the improvement of the properties of screw caps and closures.

[0085] [Table 1]

[0086] [Table 2]

[0087] [Table 3]

[0088] Table 4

Claims

1. 1. A multimodal polyethylene composition comprising: (A) 35 to 65 parts by weight of a low molecular weight polyethylene having a weight average molecular weight (Mw) of 20,000 to 90,000 g / mol; (B) 5 to 40 parts by weight of a first high molecular weight polyethylene having a weight average molecular weight (Mw) of greater than 150,000 to 1,000,000 g / mol; and (C) 20 to 60 parts by weight of a second high molecular weight polyethylene having a weight average molecular weight (Mw) of more than 150,000 to 1,000,000 g / mol Including, the first high molecular weight polyethylene and the second high molecular weight polyethylene are different; the molecular weight distribution of the multimodal polyethylene composition as determined by gel permeation chromatography is 10 to 25; the isothermal crystallization half time of the multimodal polyethylene composition at a temperature of 123°C by differential scanning calorimetry is 7 minutes or less; the spiral flow length of the multimodal polyethylene composition at a temperature of 220°C is at least 200 mm; and the multimodal polyethylene composition has a Z-average molecular weight of 700,000 to 2,500,000 g / mol as measured by gel permeation chromatography; Multimodal polyethylene composition.

2. 2. The multimodal polyethylene composition of claim 1, wherein the molecular weight distribution is from 15 to 25.

3. 3. The multimodal polyethylene composition according to claim 1 or 2, wherein the spiral flow length at a temperature of 220°C is from 250 to 370 mm.

4. 4. The multimodal polyethylene composition according to any one of claims 1 to 3, having a weight average molecular weight of 80,000 to 250,000 g / mol, as measured by gel permeation chromatography.

5. 5. The multimodal polyethylene composition according to any one of claims 1 to 4, having a number average molecular weight of 5,000 to 30,000 g / mol, as measured by gel permeation chromatography.

6. The multimodal polyethylene composition has a modulus of elasticity of 0.950 to 0.965 g / cm according to ASTM D1505 ３ and / or MI according to ASTM D1238 of 0.1 to 20 g / 10 min ２ 6. The polyethylene composition according to claim 1, having

7. A screw cap comprising the multimodal polyethylene composition of any one of claims 1 to 6.

8. 8. Screw cap according to claim 7, obtainable by injection molding or compression molding.

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