Polyethylene powder and molded body

Abstract

The invention relates to a polyethylene powder and a molded body. A polyethylene powder in which when a free induction decay curve obtained by the Carr Purcell Meiboom Gill method in pulsed NMR is subjected to three-component approximation, the relaxation time T of each component and the presence ratio R of the component satisfy < Condition (1) > and < Condition (2) >. < Condition (1) > The entanglement index as determined from formula I at 180 DEG C is 12-25 milliseconds. (Entanglement Index) = T [alpha] * R [alpha] / (R [alpha] + R [beta]) + T [beta] * R [beta] / (R [alpha] + R [beta])... (Formula I) T [alpha] is the relaxation time (milliseconds) of the low-motility component [alpha]; r [alpha] is the presence ratio (%) of the component [alpha] having low motility; t [beta] is the relaxation time (millisecond) of the motility-centered component [beta]; and R [beta] is the presence ratio (%) of the motility-centered component [beta]. < Condition (2) > At 180 DEG C, the ratio of the motility-centered component determined from formula II is 0.25-0.5. (the motility-centered component ratio) = R [beta] / (R [alpha] + R [beta])... (formula II).

Description

[0001] This application is a divisional application of a Chinese patent application with an application date of November 15, 2021 and an application number of 202180075515.6. Technical Field

[0002] The present invention relates to polyethylene powder and molded articles. Background Art

[0003] Ultra-high molecular weight polyethylene powder is molded by various molding methods such as melt stretching, injection molding, extrusion molding, and compression molding, and is used for various applications such as films, sheets, microporous membranes, fibers, foams, and tubes.

[0004] In recent years, the demand for polyethylene powder in applications such as microporous membranes and fibers has increased, and in particular, the demand for raw materials for diaphragms, which are important components of lithium-ion batteries, lead-acid batteries, etc., has rapidly expanded.

[0005] Ultra-high molecular weight polyethylene powder has a high viscosity when melted and poor moldability, so in the case of manufacturing microporous membranes and high-strength fibers, wet extrusion processing in which it is dissolved in a specified solvent and then extrusion processed is usually used. During this wet extrusion processing, when the dispersibility of polyethylene powder in the solvent is poor, high molecular weight bodies are locally present in the molded article, resulting in dimensional unevenness in terms of width, thickness, etc., or the generation of unmelted matter, leading to deterioration of the physical properties and appearance of the molded article. Therefore, it is required to improve the dispersibility of polyethylene powder in the solvent.

[0006] In addition, when a microporous membrane made of polyethylene powder is used as a battery separator, it is required to have a function of isolating the positive and negative electrodes to prevent short circuits and only allowing ions to pass through, a shut-off function for blocking the passage of ions by melting through the pore portion when a large current flows to prevent the battery reaction from getting out of control, that is, a function of closing the pores at a temperature lower than the thermal runaway temperature, a so-called fusing effect, and high mechanical strength.

[0007] In recent years, centered on in-vehicle batteries, the requirements for high capacity and high output power have rapidly increased. Along with this, further improvement in mechanical strength and dimensional stability is required for battery separators. In addition, as the electrodes become higher in capacity, the expansion and contraction of the electrodes during charge and discharge become larger. Therefore, creep resistance, which can withstand long-term stress, has become even more important for battery separators.

[0008] Patent Document 1 discloses a technique for obtaining a film and a microporous membrane with high permeability, small thermal shrinkage rate, and excellent mechanical strength and heat resistance by using a polyolefin resin containing an ultra-high molecular weight ethylene polymer having a specific intrinsic viscosity and melting point.

[0009] In addition, Patent Document 2 discloses a technique for obtaining a microporous membrane having excellent moldability, high gas permeability, and excellent mechanical strength by using a polyethylene resin composition containing a homopolymer of ethylene having a specific melt flow rate, a specific molecular weight distribution, and a specific elution amount measured by cross-fractionation chromatography.

[0010] Prior Art Documents

[0011] Patent Documents

[0012] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2018-090744

[0013] Patent Document 2: Japanese Patent No. 5840743 Summary of the Invention

[0014] Problems to be Solved by the Invention

[0015] However, in the technique disclosed in Patent Document 1, although the obtained microporous membrane has excellent mechanical strength and dimensional stability, there are the following problems: no research has been conducted to improve moldability and creep resistance, there may be unevenness in mechanical strength, and in addition, it may not be able to withstand long-term stress caused by the expansion and contraction of the electrode accompanying charge and discharge.

[0016] In addition, in the technique disclosed in Patent Document 2, although moldability and mechanical strength are achieved simultaneously, there are the following problems: no research has been conducted to improve dimensional stability and creep resistance.

[0017] Therefore, an object of the present invention is to provide a polyethylene powder capable of achieving both excellent moldability and high mechanical strength and obtaining a microporous membrane having excellent dimensional stability and creep resistance.

[0018] Means for Solving the Problems

[0019] The present inventors conducted in-depth research to solve the above problems and found that polyethylene powder in which the relaxation time T and the component ratio R of each component satisfy a specified relationship when performing a three-component approximation on the free induction decay curve obtained by the Carr Purcell Meiboom Gill method in pulsed NMR can solve the problems of the above prior art, thereby completing the present invention.

[0020] That is, the present invention is as follows. [1]

[0022] A polyethylene powder, wherein, when performing a three-component approximation on the free induction decay curve obtained by the Carr Purcell Meiboom Gill method in pulsed NMR, the relaxation time T of each component and the proportion R of each component present satisfy the following <Requirement (1)> and <Requirement (2)>.

[0023] <Requirement (1)>

[0024] At 180 °C, the entanglement index obtained by the following (Equation I) is 12 milliseconds or more and 25 milliseconds or less.

[0025] (Entanglement index) = T α ×R α / (R α +R β ) + T β ×R β / (R α +R β ) ……(Equation I)

[0026] T α : Relaxation time (milliseconds) of the component α with low mobility

[0027] R α : Proportion of the component α with low mobility present (%)

[0028] T β : Relaxation time (milliseconds) of the component β with medium mobility

[0029] R β : Proportion of the component β with medium mobility present (%)

[0030] <Requirement (2)>

[0031] At 180 °C, the proportion of the component with medium mobility obtained by the following (Equation II) is 0.25 or more and 0.5 or less.

[0032] (Proportion of the component with medium mobility) = R β / (R α +R β ) ……(Equation II) [2]

[0034] The polyethylene powder as described in the above [1], wherein, regarding the proportion R of the components present obtained by performing a three-component approximation on the free induction decay curve obtained by the Carr Purcell Meiboom Gill method in pulsed NMR,

[0035] The rate of change of the proportion of the component with low mobility at 180 °C is -5% or more and 10% or less. [3]

[0037] The polyethylene powder as described in [1] or [2] above, wherein, regarding the proportion R of the components obtained by three-component approximation of the free induction decay curve obtained by the Carr Purcell Meiboom Gill method in pulsed NMR,

[0038] The change rate of the proportion of the component with high mobility at 180°C is 50% or less. [4]

[0040] The polyethylene powder as described in any one of [1] to [3] above, wherein the isothermal crystallization time of the polyethylene powder at 125°C is 5 minutes or less. [5]

[0042] The polyethylene powder as described in any one of [1] to [4] above, wherein the viscosity-average molecular weight of the polyethylene powder is 200,000 or more and 10,000,000 or less. [6]

[0044] The polyethylene powder as described in any one of [1] to [5] above, wherein the median particle size of the polyethylene powder is 50 μm or more and 250 μm or less. [7]

[0046] The polyethylene powder as described in any one of [1] to [6] above, wherein the polyethylene powder is used for a battery separator. [8]

[0048] A molded article, wherein the molded article is a molded article of the polyethylene powder as described in any one of [1] to [7] above. [9]

[0050] The molded article as described in [8] above, wherein the molded article is a microporous membrane.

[10]

[0052] The molded article as described in [8] above, wherein the molded article is a fiber.

[11]

[0054] The molded article as described in [8] above, wherein the molded article is a battery separator.

[0055] Advantages of the Invention

[0056] According to the present invention, it is possible to provide a polyethylene powder that can achieve both excellent moldability and high mechanical strength, and can obtain a microporous membrane with excellent dimensional stability and creep resistance. Detailed Description of the Invention

[0057] Hereinafter, the mode for implementing the present invention (hereinafter also referred to as "the present embodiment") will be described in detail.

[0058] It should be noted that the following present embodiment is an exemplification for explaining the present invention and is not intended to limit the present invention to the following content. The present invention can be implemented with various modifications within the scope of its gist.

[0059] [Polyethylene powder]

[0060] The polyethylene powder of the present embodiment is characterized in that when the free induction decay curve obtained by the Carr Purcell Meiboom Gill method in pulsed NMR is approximated by three components, the relaxation time T of each component and the proportion R of each component's existence satisfy the following <Requirement (1)> and <Requirement (2)>.

[0061] It should be noted that for the proportion R (%), the total of the three components is set to 100%.

[0062] <Requirement (1)>

[0063] At 180 °C, the entanglement index calculated by the following (Equation I) is 12 milliseconds or more and 25 milliseconds or less.

[0064] (Entanglement index) = T α × R α / (R α + R β ) + T β × R β / (R α + R β ) ……(Equation I)

[0065] T α : Relaxation time (milliseconds) of the component α with low mobility

[0066] R α : Proportion of the component α with low mobility (%)

[0067] T β : Relaxation time (milliseconds) of the component β with medium mobility

[0068] R β : Proportion of the component β with medium mobility (%)

[0069] <Requirement (2)>

[0070] At 180 °C, the proportion of the component with medium mobility calculated by the following (Equation II) is 0.25 or more and 0.5 or less.

[0071] (Proportion of the component with medium mobility) = Rβ / (R α +R β ) ……Formula (II)

[0072] The polyethylene powder of the present embodiment has the above-mentioned structure, and thus can achieve the effect of achieving both excellent molding processability and high mechanical strength and obtaining a microporous membrane having excellent dimensional stability and creep resistance.

[0073] Hereinafter, the structure of the polyethylene powder according to the present embodiment will be described.

[0074] The polyethylene powder (hereinafter sometimes simply referred to as “powder”) of the present embodiment is composed of an ethylene-based polymer.

[0075] Examples of the ethylene-based polymer include ethylene homopolymers and copolymers (for example, binary or ternary copolymers) of ethylene and other comonomers copolymerizable with ethylene.

[0076] The bonding form of the copolymer can be random or block.

[0077] The other comonomers are not particularly limited, and examples thereof include α-olefins, vinyl compounds, etc. The other comonomers may be used alone or in combination of two or more.

[0078] There are no particular restrictions on the α-olefins, and examples thereof include α-olefins having 3 to 20 carbon atoms, and specifically include propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-tridecene, 1-tetradecene, etc. Among them, from the viewpoint of further improving the heat resistance and strength of the microporous membrane, the other comonomer is preferably propylene and / or 1-butene.

[0079] The vinyl compound is not particularly limited, and examples thereof include vinylcyclohexane, styrene, and derivatives thereof.

[0080] Furthermore, as other comonomers, non-conjugated polyenes such as 1,5-hexadiene and 1,7-octadiene may be used as necessary.

[0081] (Ratio of components with intermediate entanglement index and mobility at 180°C)

[0082] Evaluation of dynamic viscoelasticity is a known index for estimating entanglement of molecular chains in polyethylene powder.

[0083] In the evaluation of dynamic viscoelasticity, since the entanglement degree of molecular chains is evaluated based on the responsiveness when stress is applied to the resin, the average entanglement degree of the molecular chains of the entire resin can be obtained. However, when controlling multiple physical properties such as mechanical properties and moldability simultaneously, it is preferable to separately treat the multiple entanglement components present in the resin. Therefore, using only the average entanglement degree of molecular chains as an index is insufficient.

[0084] In order to clarify the raw materials suitable for a molded body with well-controlled physical properties such as mechanical properties and moldability, the present inventors used the entanglement index calculated from the measurement of pulsed NMR at 180 °C and the proportion of components with medium mobility together as an index capable of separately evaluating the entanglement components of multiple molecular chains present in the resin, and accurately evaluated the entanglement degree of polyethylene powder.

[0085] In the measurement of pulsed NMR, the Carr Purcell Meiboom Gill method, which is a measurement method suitable for evaluating the mobility of polymers such as polymers with active molecular chain movement, such as in the rubber state, was used.

[0086] As a result, it was found that when approximating the free induction decay curve obtained by the Carr Purcell Meiboom Gill method in pulsed NMR with three components, polyethylene powder in which the relaxation time T and the component ratio R of each component simultaneously satisfy the following <Requirement (1)> and <Requirement (2)> is surprisingly suitable as a raw material for microporous membranes from the viewpoints of mechanical properties and moldability.

[0087] <Requirement (1)>

[0088] At 180 °C, the entanglement index calculated by the following (Equation I) is 12 milliseconds or more and 25 milliseconds or less.

[0089] (Entanglement index) = T α × R α / (R α + R β ) + T β × R β / (R α + R β ) …… (Equation I)

[0090] T α : Relaxation time (milliseconds) of the component α with low mobility

[0091] R α : Proportion of the component α with low mobility (%)

[0092] T β : Relaxation time (milliseconds) of the component β with medium mobility

[0093] R β : Proportion (%) of the component β with medium motility

[0094] <Requirement (2)>

[0095] At 180 °C, the proportion of the component with medium motility obtained from the following (Formula II) is 0.25 or more and 0.5 or less.

[0096] (Proportion of the component with medium motility) = R β / (R α +R β ) ……(Formula II)

[0097] The range of the entanglement index of the polyethylene powder of the present embodiment obtained from the above (Formula I) at 180 °C is 12 milliseconds or more and 25 milliseconds or less, preferably 13 milliseconds or more and 22 milliseconds or less, more preferably 14 milliseconds or more and 20 milliseconds or less.

[0098] For the polyethylene powder of the present embodiment, when performing a three-component approximation on the free induction decay curve obtained by the Carr Purcell MeiboomGill method in pulsed NMR, the component α with low motility corresponds to the part with strong molecular chain entanglement in the polyethylene powder, and is considered to be the component that is not easily untangled during the molding process and is likely to remain in the microporous membrane. On the other hand, the component β with medium motility in the polyethylene powder of the present embodiment corresponds to the part with weaker molecular chain entanglement than the above-mentioned component α with low motility, and is considered to be the component that is easily untangled during the molding process. In addition, the stronger the entanglement degree of each component, the smaller the value of the relaxation time T.

[0099] Since the entanglement index obtained from the above formula (I) at 180 °C is 12 milliseconds or more, the stress remaining after the molding process can be reduced, and thus there is a tendency to obtain a microporous membrane with excellent dimensional stability.

[0100] On the other hand, since the entanglement index obtained from the above formula (I) at 180 °C is 25 milliseconds or less, the entanglement degree of the molecular chains in the polyethylene powder becomes stronger, and thus there is a tendency that the microporous membrane obtained by the molding process has high mechanical strength and exhibits excellent creep resistance.

[0101] For the polyethylene powder of the present embodiment, when performing a three-component approximation on the free induction decay curve obtained by the Carr Purcell MeiboomGill method in pulsed NMR, the proportion of the component with medium motility at 180 °C obtained from the above (Formula II) is 0.25 or more and 0.5 or less, preferably 0.25 or more and 0.45 or less, more preferably 0.3 or more and 0.4 or less.

[0102] The proportion of the component with medium mobility at 180 °C obtained from the above (Formula II) is 0.25 or more, and there is a tendency to improve the molding processability of the polyethylene powder and to obtain a microporous membrane with excellent appearance.

[0103] On the other hand, when the proportion of the component with medium mobility at 180 °C is 0.5 or less, an appropriate amount of entanglement points of molecular chains remains in the microporous membrane obtained by molding, so stress is easily transmitted, and there is a tendency to have excellent creep resistance.

[0104] Generally, when the entanglement degree of the molecular chains of a polymer is strong, the mechanical strength of the obtained microporous membrane increases, but due to the low dispersibility of the molecular chains of the polymer, the molding processability deteriorates, and unevenness in thickness and the like occurs when manufacturing the microporous membrane. When there is unevenness in the thickness and the like of the microporous membrane like this, a part with weak mechanical strength is generated, which easily becomes a starting point for deterioration.

[0105] On the other hand, when the entanglement degree of the molecular chains of a polymer is weak, although the molding processability is good, the mechanical strength decreases.

[0106] Since the polyethylene powder of the present embodiment well controls the strength of the entanglement degree of the molecular chains of the polymer, when manufacturing a microporous membrane, the mechanical strength and the molding processability can be improved simultaneously.

[0107] In addition, when there are many entanglement points of the molecular chains of the polymer in the microporous membrane, the mechanical strength is high and stress is easily transmitted, so the creep resistance is excellent, but due to the large residual stress, there is a tendency for the dimensional stability to deteriorate. When the microporous membrane is used as a separator for a battery, the deterioration of the dimensional stability may cause short circuit and deterioration.

[0108] On the other hand, when there are few entanglement points of the molecular chains of the polymer, the dimensional stability becomes excellent, but there is a tendency not to exhibit sufficient mechanical strength. In addition, since stress is difficult to transmit, local load is easily applied, and when the microporous membrane is used for a battery separator, there is a tendency not to withstand the volume change of the electrode accompanying charge and discharge.

[0109] Since the polyethylene powder of the present embodiment well controls the amount of entanglement points of the molecular chains of the polymer, excellent dimensional stability, sufficient mechanical strength, and creep resistance can be achieved.

[0110] In order for the entanglement index at 180 °C obtained from the above (Formula I) and the proportion of the component with medium mobility obtained from the above (Formula II) to show values within the above specified ranges, in the polyethylene powder, the entanglement degree of the strongly entangled molecular chains needs to have a certain strength, and the proportion of the weakly entangled molecular chains is large.

[0111] Moreover, as characteristics of the polyethylene powder satisfying these requirements, it can be cited: containing various polymer components with different entanglement states, etc.

[0112] As methods for controlling the entanglement index at 180 °C obtained from the above (Formula I) and the proportion of the component with medium mobility obtained from the above (Formula II), it can be cited: changing the state of the catalyst during the polymerization of polyethylene, methods of mixing various catalyst components with greatly different polymerization behaviors, etc.

[0113] Specifically, it can be cited: using a polymerization catalyst containing a carrier with large pores and easy to break, performing polymerization under high-pressure conditions in the first half of the polymerization, and then adjusting the slurry concentration in the polymerization vessel to 40% by mass or more; pre-polymerizing a polymerization catalyst containing a carrier with large pores and easy to break, and then setting the stirring speed in the polymerization vessel to 300 rpm or more; using a mixture of various catalysts with greatly different distributions of active substances on the carrier surface, etc.

[0114] When synthesizing a polymerization catalyst for use in the polymerization reaction of polyethylene, by using a carrier with large pores, the loading amount of the active substance in the pores increases, and in the polymerization reaction of polyethylene, the polymerization of polyethylene in the above pores can be promoted. In addition, in the narrow space of the pores, the molecular chains of the growing polyethylene are easily intertwined with each other, so that a component with a strong degree of entanglement of molecular chains can be polymerized.

[0115] On the other hand, since the carrier used in the polymerization catalyst has an easily breakable structure, the catalyst is easily broken due to the increase in pressure in the pores accompanying the growth of the molecular chains of polyethylene during the polymerization of polyethylene.

[0116] In addition, when the catalyst is broken by increasing the stirring intensity, the molecular chains of the growing polyethylene become less likely to be intertwined with each other, and a component with a weak degree of entanglement of molecular chains can be polymerized.

[0117] Furthermore, by adding a thickener after the synthesis of the carrier and adjusting during the catalyst transportation to make the pressure difference between the transportation source and the transportation destination smaller, it is possible to prevent the catalyst carrier from breaking before the polymerization process and to generate various polyethylene components with different degrees of entanglement of molecular chains during the polymerization.

[0118] The measurement of pulsed NMR applied in the measurement of the polyethylene powder of the present embodiment is specifically carried out by the following method.

[0119] First, a sample tube filled with polyethylene powder to a height of 1 cm from the bottom is put into a TD-NMR apparatus (model: minispec mq20) manufactured by Bruker Corporation set so that the internal temperature of the sample tube is 30 °C, and the sample tube is heated according to the <heating conditions> shown below.

[0120] The temperature shown in the following <Temperature Rising Conditions> is the value obtained by measuring the internal temperature of the sample using a thermocouple.

[0121] <Temperature Rising Conditions>

[0122] (1) Set to 30 °C and let stand for 5 minutes.

[0123] (2) Raise the temperature to 180 °C at a rate of 5 °C per minute.

[0124] (3) After raising the temperature to 180 °C, let stand for 25 minutes.

[0125] After the temperature rising is completed according to the above steps, measure the spin-spin relaxation time (T 2 of polyethylene powder according to the <Measurement Conditions> shown below. Sometimes it is simply referred to as "relaxation time T" in this specification.

[0126] Then, after the measurement is completed, repeat the same measurement 3 times for a total of 4 measurements.

[0127] <Measurement Conditions>

[0128] Magnetic field strength: 0.47 T

[0129] Nuclear species to be measured: 1 H (20 MHz)

[0130] Measurement method: Carr Purcell Meiboom Gill method

[0131] Number of accumulations: 256 times

[0132] Repetition time: 3 seconds

[0133] Interval (τ) between the initial 90° pulse and 180° pulse: 0.04 milliseconds

[0134] Total number of echo signals: 6400

[0135] For the free induction decay (FID) obtained from the fourth measurement among the above 4 measurements in total, use the analysis program TD-NMR-A manufactured by Bruker Corporation for curve fitting.

[0136] Use the function shown in the following <Equation 1> for fitting.

[0137] <Equation 1>

[0138] f(t)=R α exp(-t / T α )+R β exp(-t / T β )+Rγ exp(-t / T γ )

[0139] (where R α +R β +R γ = 100)

[0140] t: variable (elapsed time counted from the start of pulsed radiation)

[0141] T α : relaxation time of the less motile component α (milliseconds)

[0142] R α : proportion of the less motile component α (%)

[0143] T β : relaxation time of the moderately motile component β (milliseconds)

[0144] R β : proportion of the moderately motile component β (%)

[0145] T γ : relaxation time of the highly motile component γ (milliseconds)

[0146] R γ : proportion of the highly motile component γ (%)

[0147] Finally, based on the relaxation time T and the proportion R obtained by curve fitting of the free induction decay, the entanglement index and the proportion of the moderately motile component are calculated by (Equation I) and (Equation II) shown below.

[0148] (Entanglement index) = T α ×R α / (R α +R β ) + T β ×R β / (R α +R β (Equation I)

[0149] (Proportion of the moderately motile component) = R β / (R α +R β (Equation II)

[0150] Generally, in the case of a polymer in the rubbery state where the molecular chains are actively moving, the free induction decay obtained by pulsed NMR measurement can be represented by an exponential function. Therefore, in this measurement, the obtained free induction decay can also be fitted in the form of the sum of three different components that can be represented by an exponential function as shown in <Equation 1> above.

[0151] In addition, it is known that 1 the higher the mobility of H, that is, the higher the mobility of the molecular chain, the slower the attenuation rate of the free induction decay. The relaxation time T in each exponential function is in the relationship of T α < T β < T γ . Therefore, the component with the lowest mobility is designated as α, the component with the medium mobility is designated as β, and the component with the highest mobility is designated as γ.

[0152] In addition, component α corresponds to the part with strong molecular chain entanglement in the polyethylene powder, component β corresponds to the part with weak molecular chain entanglement, and component γ is the part where the molecular chains are not entangled.

[0153] More specifically, the entanglement index and the proportion of the component with medium mobility at 180 °C of the present embodiment can be measured by the method described in the examples.

[0154] (Rate of change of the proportion of the component with low mobility at 180 °C)

[0155] For the polyethylene powder of the present embodiment, regarding the proportion R of the components obtained by three-component approximation of the free induction decay curve obtained by the Carr Purcell Meiboom Gill method in pulsed NMR, as the range of the rate of change of the proportion of the component α with low mobility at 180 °C, it is preferably -5% or more and 10% or less, more preferably -2% or more and 8% or less, and further preferably 0% or more and 6% or less.

[0156] The rate of change of the proportion of the component with low mobility at 180 °C of the polyethylene powder of the present embodiment is obtained by the method shown below.

[0157] When calculating the above (entanglement index and the proportion of the component with medium mobility at 180 °C), for the free induction decay (FID) obtained by the first measurement and the fourth measurement in the pulsed NMR measurement specifically shown above, curve fitting is performed using the analysis program TD-NMR-A manufactured by Bruker Corporation. The function shown in the above <Equation 1> is used in the fitting.

[0158] Based on the proportion R obtained by the fitting, the rate of change (%) of the proportion of the component with low mobility is calculated by the following (Equation III).

[0159] (Rate of change of the proportion of the component with low mobility) = ((R α4 - R α1 ) / R α1 ) × 100 …… (Equation III)

[0160] Rα1 : Proportion of component α with low motility at the first measurement

[0161] R α4 : Proportion of component α with low motility at the fourth measurement

[0162] Regarding this change rate, a negative value is shown when the entanglement of the molecular chains of the component with strong entanglement is untied under heating conditions, and a positive value is shown when the molecular chains of the component with weak entanglement are strongly entangled under heating conditions.

[0163] When the change rate of the proportion of the component with low motility is -5% or more, components with strong entanglement tend to remain easily even after molding processing, and a microporous membrane with more excellent mechanical strength and creep resistance can be obtained. On the other hand, when the change rate of the proportion of the component with low motility is 10% or less, the proportion of molecular chains with weak entanglement and unentangled molecular chains can be maintained above a certain value, and there is a tendency for excellent moldability.

[0164] Specifically, the change rate of the proportion of the component with low motility of the polyethylene powder of the present embodiment at 180 °C can be measured by the method described in the examples.

[0165] Regarding the change rate of the proportion of the component with low motility of the polyethylene powder of the present embodiment at 180 °C, it can be controlled within the above numerical range by adjusting the concentration and temperature during the synthesis of the catalyst carrier to a certain value or more.

[0166] (Change rate of the proportion of the component with high motility at 180 °C)

[0167] For the polyethylene powder of the present embodiment, regarding the proportion R of the components obtained by three-component approximation of the free induction decay curve obtained by the Carr Purcell Meiboom Gill method in pulsed NMR, as the range of the change rate of the proportion of the component with high motility at 180 °C, it is preferably 50% or less, more preferably 10% or less, and further preferably 5% or less. In addition, there is no particular limitation on the lower limit value, and it is usually 0% or more.

[0168] The change rate of the proportion of the component with high motility in the polyethylene powder of the present embodiment is obtained by the method shown below.

[0169] When calculating the above (entanglement index and proportion of the component with medium motility at 180 °C), for the free induction decay (FID) obtained by the first measurement and the fourth measurement in the pulsed NMR measurement specifically shown above, curve fitting is performed using the analysis program TD-NMR-A manufactured by Bruker Corporation.

[0170] Use the function shown in the above <Equation 1> in the fitting.

[0171] Based on the occupancy ratio R obtained by fitting, calculate the change rate (%) of the occupancy ratio of the highly motile component shown in the following (Equation IV).

[0172] (Change rate of the occupancy ratio of the highly motile component) = ((R γ4 - R γ1 ) / R γ1 ) × 100 …… (Equation IV)

[0173] R γ1 : Occupancy ratio of the highly motile component γ at the first measurement

[0174] R γ4 : Occupancy ratio of the highly motile component γ at the fourth measurement

[0175] The more the entanglement of molecular chains is unraveled under heating conditions, the larger the value of this change rate.

[0176] When the change rate of the occupancy ratio of the above-mentioned highly motile component is 50% or less, even after molding processing, components with entangled molecular chains are likely to remain, and a microporous membrane with more excellent mechanical strength and creep resistance can be obtained.

[0177] Specifically, the change rate of the occupancy ratio of the highly motile component of the polyethylene powder of the present embodiment at 180 °C can be measured by the method described in the examples.

[0178] Regarding the change rate of the occupancy ratio of the highly motile component of the polyethylene powder of the present embodiment at 180 °C, it can be controlled within the above numerical range by adjusting the slurry concentration and stirring speed during polymerization to an appropriate range, etc.

[0179] (Isothermal crystallization time at 125 °C)

[0180] The isothermal crystallization time of the polyethylene powder of the present embodiment is preferably 5 minutes or less, more preferably 4.5 minutes or less, and further preferably 4 minutes or less.

[0181] In addition, there is no particular limitation on the lower limit value of the isothermal crystallization time, and it is usually 0 minutes or more.

[0182] The isothermal crystallization time of the polyethylene powder of the present embodiment at 125 °C is obtained by the following method using a differential scanning calorimeter (DSC).

[0183] First, place an aluminum disk filled with polyethylene powder into a heating furnace and perform a heating operation according to the following (heating and cooling conditions). Here, the heating operation is carried out in a nitrogen atmosphere.

[0184] <Heating and Cooling Conditions>

[0185] (1) Hold at 50 °C for 1 minute.

[0186] (2) Raise the temperature to 180 °C at a rate of 200 °C / minute.

[0187] (3) Hold at 180 °C for 5 minutes.

[0188] (4) Lower the temperature to 125 °C at a rate of 80 °C / minute.

[0189] Then, take the time when the temperature reaches 125 °C as the starting point (0 minute), and take the time when the peak of the exothermic peak caused by crystallization is obtained as the isothermal crystallization time at 125 °C.

[0190] When the isothermal crystallization time at 125 °C is 5 minutes or less as described above, components with molecular chain entanglements are likely to be uniformly present in the molded body, so stress is easily transmitted, and a microporous membrane with more excellent creep resistance can be obtained.

[0191] As a method for controlling the isothermal crystallization time at 125 °C of the polyethylene powder in this embodiment, methods such as uniformly loading active sites on the carrier of the catalyst used in the polymerization process of the polyethylene powder and uniformly adjusting the temperature in the polymerization reactor can be cited.

[0192] Specifically, the isothermal crystallization time at 125 °C of the polyethylene powder in this embodiment can be measured by the method described in the examples.

[0193] (Viscosity-average molecular weight (Mv))

[0194] The viscosity-average molecular weight (Mv) of the polyethylene powder in this embodiment is preferably 200,000 or more and 10,000,000 or less, more preferably 250,000 or more and 3,000,000 or less, and still more preferably 300,000 or more and 2,000,000 or less.

[0195] The viscosity-average molecular weight (Mv) of the polyethylene powder can be controlled within the above numerical range by appropriately adjusting the polymerization conditions and the like described later.

[0196] Specifically, the viscosity-average molecular weight (Mv) can be controlled within the above numerical range by making hydrogen, which is a chain transfer agent, present in the polymerization system or changing the polymerization temperature, etc.

[0197] The viscosity-average molecular weight (Mv) of the polyethylene powder of the present embodiment is 200,000 or more, and the microporous membrane containing the polyethylene powder of the present embodiment has sufficient mechanical strength.

[0198] On the other hand, since the viscosity-average molecular weight (Mv) is 10,000,000 or less, the polyethylene powder of the present embodiment tends to have excellent moldability such as dispersibility and stretchability in a solvent. Therefore, the microporous membrane formed using the polyethylene powder of the present embodiment has less thickness unevenness and less unmolten matter, is less likely to deteriorate, and has excellent appearance.

[0199] The viscosity-average molecular weight (Mv) of the polyethylene powder of the present embodiment can be calculated by the following formula from the intrinsic viscosity [η] (dL / g) determined according to ISO1628-3 (2010).

[0200] More specifically, it can be measured by the method described in the examples.

[0201] Mv = (5.34 × 10 4 ) × [η] 1.49

[0202] (Median particle size)

[0203] The range of the median particle size of the polyethylene powder of the present embodiment is preferably 50 μm or more and 250 μm or less, more preferably 60 μm or more and 200 μm or less, and still more preferably 70 μm or more and 150 μm or less.

[0204] The median particle size of the polyethylene powder of the present embodiment is the particle size (D50) when the cumulative mass reaches 50%.

[0205] When the median particle size is 50 μm or more, the ease of handling (such as improvement of fluidity and suppression of dust) of the polyethylene powder in the manufacturing process and the extrusion process is improved.

[0206] On the other hand, when the median particle size is 250 μm or less, the plasticizer easily penetrates into the polyethylene powder, and the moldability tends to be improved.

[0207] As a method for controlling the median particle size of the polyethylene powder of the present embodiment within the above numerical range, for example, a method of controlling the particle size of the polymerization catalyst, a method of adjusting the polymerization conditions described later to suppress the rapid progress of the polymerization reaction (hereinafter sometimes referred to as rapid polymerization), etc. can be cited.

[0208] Specifically, the median particle size of the polyethylene powder of the present embodiment can be measured by the method described in the examples below.

[0209] [Manufacturing method of polyethylene powder]

[0210] Hereinafter, the method for manufacturing the polyethylene powder of the present embodiment will be described.

[0211] (Catalyst component)

[0212] There is no particular limitation on the catalyst component used in the production of the vinyl polymer constituting the polyethylene powder of the present embodiment, and a Ziegler-Natta catalyst or a metallocene catalyst produced by the methods described in Japanese Patent No. 5782558 and Japanese Unexamined Patent Application Publication No. 2019-19265 can be used. A Ziegler-Natta catalyst is particularly preferably used.

[0213] As the Ziegler-Natta catalyst used in the production of the polyethylene powder of the present embodiment, for example, an olefin polymerization catalyst is preferably used, which comprises a solid catalyst component [A] and an organometallic compound component [B]. The solid catalyst component [A] is produced by loading an organomagnesium compound [A-4] represented by the following (Formula iii) and a titanium compound [A-5] represented by the following (Formula iv) on a carrier [A-3] prepared by the reaction of an organomagnesium compound [A-1] soluble in an inert hydrocarbon solvent represented by the following (Formula i) and a chlorinating agent [A-2] represented by the following (Formula ii).

[0214] (A-1): (M 1 ) γ (Mg) δ (R 1 ) e (R 2 ) f (OR 3 ) g ......(Formula i)

[0215] (In Formula i, M 1 is a metal atom belonging to any one of the groups consisting of Group 12, Group 13, and Group 14 of the Periodic Table of the Elements, and R 1 , R 2 and R 3 are each a hydrocarbon group having 1 or more and 20 or less carbon atoms, and γ, δ, e, f, and g are real numbers satisfying the following relationships.

[0216] 0≤γ, 0<δ, 0≤e, 0≤f, 0≤g, 0<e + f, 0≤g / (γ + δ)≤2, kγ + 2δ = e + f + g (here, k represents the valence of M 1 ).)

[0217] (A-2): H h SiCl i R 4(4-(h+i)) ......(Formula (ii))

[0218] (In formula (ii), R 4 is a hydrocarbon group having 1 or more and 12 or less carbon atoms, and h and i are real numbers satisfying the following relationship. 0 < h, 0 < i, 0 < h + i ≤ 4)

[0219] (A - 4): (M 2 ) α (Mg) β (R 4 ) a (R 5 ) b Y 1 c ......(Formula (iii))

[0220] (In formula (iii), M 2 is a metal atom belonging to any one of the groups consisting of Group 12, Group 13, and Group 14 of the periodic table, R 4 and R 5 are hydrocarbon groups having 2 or more and 20 or less carbon atoms, Y 1 is a hydrocarbon oxy group, a silanol oxy group, an allyloxy group, an amino group, an amide group, -N = C - R 6 , R 7 , -SR 8 (Herein, R 6 , R 7 and R 8 represent hydrocarbon groups having 1 or more and 20 or less carbon atoms. When c is 2, Y 1 can be different from each other) and any one of β - keto acid residues, and α, β, a, b, and c are real numbers satisfying the following relationship.)

[0221] 0 ≤ α, 0 < β, 0 ≤ a, 0 ≤ b, 0 ≤ c, 0 < a + b, 0 ≤ c / (α + β) ≤ 2, nα + 2β = a + b + c (Herein, n represents the valence of M 2 .))

[0222] (A - 5): Ti(OR 9 ) d X 1 (4-d) ......(Formula (iv))

[0223] (In formula (iv), d is a real number of 0 or more and 4 or less, R 9 is a hydrocarbon group having 1 or more and 20 or less carbon atoms, and X 1 is a halogen atom.)

[0224] First, the organomagnesium compound (A - 1) will be described.)

[0225] Although the organomagnesium compound (A-1) is shown in the form of an organomagnesium complex soluble in an inert hydrocarbon solvent, it includes all of dialkylmagnesium compounds and complexes of such compounds with other metal compounds.

[0226] The above relationship kγ + 2δ = e + f + g of the symbols γ, δ, e, f, and g in the above (Formula i) represents the valence of the metal atom and the stoichiometry of the substituents.

[0227] In the above (Formula i), there is no particular limitation on the hydrocarbon group represented by R 1 , R 2 , and for example, they are each independently an alkyl group, a cycloalkyl group, or an aryl group. Examples thereof include: methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, decyl, cyclohexyl, phenyl, and the like.

[0228] Among them, R 1 and R 2 are preferably each an alkyl group.

[0229] When γ > 0, as the metal atom M 1 , a metal atom belonging to any one of the groups consisting of Group 12, Group 13, and Group 14 of the periodic table of elements can be used. Examples thereof include: zinc, boron, aluminum, etc. Aluminum and zinc are particularly preferred.

[0230] There is no particular limitation on the ratio δ / γ of magnesium to the metal atom M 1 , but it is preferably 0.1 or more and 30 or less, and more preferably 0.5 or more and 10 or less.

[0231] In addition, when a specified organomagnesium compound with γ = 0 is used as (A-1), for example, when R 1 is 1-methylpropyl or the like, it is soluble in an inert hydrocarbon solvent, and such a compound also gives preferable results in the production of the polyethylene powder of the present embodiment.

[0232] In the above (Formula i), when γ = 0, the hydrocarbon groups R 1 , R 2 are preferably any one of the following three groups (1), (2), and (3).

[0233] Group (1):

[0234] At least one of R 1 and R 2 is a secondary or tertiary alkyl group having 4 or more and 6 or less carbon atoms. Preferably, both R 1 and R 2 are alkyl groups having 4 or more and 6 or less carbon atoms, and at least one of them is a secondary or tertiary alkyl group.

[0235] Group (2):

[0236] R 1 and R 2 are alkyl groups with different numbers of carbon atoms. Preferably, R 1 is an alkyl group with 2 or 3 carbon atoms, and R 2 is an alkyl group with 4 or more carbon atoms.

[0237] Group (3):

[0238] R 1 and R 2 at least one of them is a hydrocarbon group with 6 or more carbon atoms. Preferably, it is an alkyl group with a total number of carbon atoms of 12 or more contained in R 1 and R 2 .

[0239] Hereinafter, the hydrocarbon groups R 1 , R 2 in the case of γ = 0 in the above (Formula i) are specifically shown.

[0240] As the secondary or tertiary alkyl group with 4 or more and 6 or less carbon atoms in Group (1), for example, 1-methylpropyl, 2-methylpropyl, 1,1-dimethylethyl, 2-methylbutyl, 2-ethylpropyl, 2,2-dimethylpropyl, 2-methylpentyl, 2-ethylbutyl, 2,2-dimethylbutyl, 2-methyl-2-ethylpropyl, etc. can be cited. 1-Methylpropyl is particularly preferred.

[0241] In addition, as the alkyl group with 2 or 3 carbon atoms in Group (2), for example, ethyl, 1-methylethyl, propyl, etc. can be cited.

[0242] Ethyl is particularly preferred.

[0243] In addition, as the alkyl group with 4 or more carbon atoms, there is no particular limitation, and for example, butyl, pentyl, hexyl, heptyl, octyl, etc. can be cited.

[0244] Butyl and hexyl are particularly preferred.

[0245] Furthermore, as the hydrocarbon group with 6 or more carbon atoms in Group (3), there is no particular limitation, and for example, hexyl, heptyl, octyl, nonyl, decyl, phenyl, 2-naphthyl, etc. can be cited. Among the hydrocarbon groups, alkyl groups are preferred, and among the alkyl groups, hexyl and octyl are more preferred.

[0246] Generally, when the number of carbon atoms contained in the alkyl group increases, it tends to be easily soluble in an inert hydrocarbon solvent and the viscosity of the solution tends to increase. Therefore, in the above (Formula i), as the hydrocarbon groups R 1 , R 2, from the perspective of processing, it is preferred to use an alkyl group with a moderately long chain. It should be noted that the above-mentioned organomagnesium compound (A-1) is used in the form of an inert hydrocarbon solution, but even if it contains or remains a trace amount of Lewis basic compounds such as ether, ester, amine, etc. in the solution, it can be used without problems.

[0247] Next, the alkoxy group (OR 3 ) in the formula (i) of the organomagnesium compound (A-1) will be described.

[0248] As the hydrocarbon group represented by R 3 , an alkyl group or an aryl group having 1 or more and 12 or less carbon atoms is preferred, and an alkyl group or an aryl group having 3 or more and 10 or less carbon atoms is more preferred.

[0249] As R 3 , there is no particular limitation, and examples thereof include: methyl, ethyl, propyl, 1-methylethyl, butyl, 1-methylpropyl, 1,1-dimethylethyl, pentyl, hexyl, 2-methylpentyl, 2-ethylbutyl, 2-ethylpentyl, 2-ethylhexyl, 2-ethyl-4-methylpentyl, 2-propylheptyl, 2-ethyl-5-methyloctyl, octyl, nonyl, decyl, phenyl, naphthyl, etc.

[0250] Particularly more preferred are butyl, 1-methylpropyl, 2-methylpentyl and 2-ethylhexyl.

[0251] There is no particular limitation on the method for synthesizing the organomagnesium compound (A-1). For example, the following methods can be cited: making any one of the organomagnesium compounds belonging to the group consisting of the formula: R 1 MgX 1 and the formula: R 1 2 Mg(R 1 As described above, X 1 is a halogen atom) and any one of the organometallic compounds belonging to the group consisting of the formula: M 1 R 2 k and the formula: M 1 R 2 (k-1) H (M 1 , R 2 and k are as described above) react in an inert hydrocarbon solvent at a temperature of 25°C or higher and 150°C or lower, and then, if necessary, react with an alcohol having a hydrocarbon group represented by R 2 (R 2 is as described above) or a magnesium alkoxide compound and / or an aluminum alkoxide compound having a hydrocarbon group represented by R 2 that is soluble in the inert hydrocarbon solvent, thereby synthesizing the organomagnesium compound (A-1).

[0252] In the above method, in the case of reacting an organomagnesium compound soluble in an inert hydrocarbon solvent with an alcohol, there is no particular limitation on the order of the reaction, and any one of the methods of adding an alcohol to the organomagnesium compound, adding the organomagnesium compound to the alcohol, or adding both at the same time can be used.

[0253] There is no particular limitation on the reaction ratio of the organomagnesium compound soluble in an inert hydrocarbon solvent to the alcohol, but as a result of the reaction, the molar composition ratio g / (γ + δ) of the alkoxy group in the obtained alkoxy-containing organomagnesium compound to all metal atoms is 0 ≤ g / (γ + δ) ≤ 2, preferably 0 ≤ g / (γ + δ) < 1.

[0254] Next, the chlorinating agent (A-2) will be described.

[0255] The chlorinating agent (A-2) is a silicon chloride compound having at least one Si-H bond represented by (Formula ii).

[0256] (A-2): H h SiCl i R 4 (4-(h+i)) ......(Formula ii)

[0257] (In Formula ii, R 4 is a hydrocarbon group having 1 or more and 12 or less carbon atoms, and h and i are real numbers satisfying the following relationship. 0 < h, 0 < i, 0 < h + i ≤ 4)

[0258] In the above (Formula ii), there is no particular limitation on the hydrocarbon group represented by R 4 , and examples thereof include: aliphatic hydrocarbon groups, alicyclic hydrocarbon groups, and aromatic hydrocarbon groups. Specifically, examples include: methyl, ethyl, propyl, 1-methylethyl, butyl, pentyl, hexyl, octyl, decyl, cyclohexyl, phenyl, etc.

[0259] An alkyl group having 1 or more and 10 or less carbon atoms is particularly preferred, and an alkyl group having 1 to 3 carbon atoms such as methyl, ethyl, propyl, and 1-methylethyl is more preferred. In addition, h and i are numbers greater than 0 satisfying the relationship h + i ≤ 4, and i is preferably 2 or more and 3 or less.

[0260] As the chlorinating agent (A-2), there is no particular limitation, and examples thereof include: HSiCl 3 , HSiCl 2 CH 3 , HSiCl 2 C 2 H 5 , HSiCl 2 (C 3 H 7 )、HSiCl 2(2-C 3 H 7 )、HSiCl 2 (C 4 H 9 )、HSiCl 2 (C 6 H 5 )、HSiCl 2 (4-Cl-C 6 H 4 )、HSiCl 2 (CH=CH 2 )、HSiCl 2 (CH 2 C 6 H 5 )、HSiCl 2 (1-C 10 H 7 )、HSiCl 2 (CH 2 CH=CH 2 )、H 2 SiCl(CH 3 )、H 2 SiCl(C 2 H 5 )、HSiCl(CH 3 ) 2 、HSiCl(C 2 H 5 ) 2 、HSiCl(CH 3 )(2-C 3 H 7 )、HSiCl(CH 3 )(C 6 H 5 )、HSiCl(C 6 H 5 ) 2 etc.

[0261] As the chlorinating agent (A-2), a silicon chloride compound containing these compounds or a mixture of two or more selected from these compounds is used.

[0262] HSiCl 3 、HSiCl 2 CH 3 、HSiCl(CH 3 ) 2 、HSiCl 2 (C 3 H 7 ) are particularly preferred, and HSiCl 3 、HSiCl 2CH 3 。

[0263] Next, the reaction of the organomagnesium compound (A-1) with the chlorinating agent (A-2) will be described.

[0264] During the reaction, it is preferable to dilute the chlorinating agent (A-2) in advance with an inert hydrocarbon solvent, a chlorinated hydrocarbon such as 1,2-dichloroethane, o-dichlorobenzene, or dichloromethane, an ether solvent such as diethyl ether or tetrahydrofuran, or a mixed solvent thereof before use. Among them, from the perspective of the performance of the catalyst, it is more preferable to use an inert hydrocarbon solvent.

[0265] There is no particular limitation on the reaction ratio of the organomagnesium compound (A-1) and the chlorinating agent (A-2), but the molar number of silicon atoms contained in (A-2) is preferably 0.01 mol or more and 100 mol or less, more preferably 0.1 mol or more and 10 mol or less, relative to 1 mol of magnesium atoms contained in (A-1).

[0266] There is no particular limitation on the reaction method of the organomagnesium compound (A-1) and the chlorinating agent (A-2), and any of the following methods can be used: a method of adding while reacting while simultaneously introducing (A-1) and (A-2) into the reactor; a method of previously charging (A-2) into the reactor and then introducing (A-1) into the reactor; or a method of previously charging (A-1) into the reactor and then introducing (A-2) into the reactor.

[0267] Particularly preferably, a method of previously charging (A-2) into the reactor and then introducing (A-1) into the reactor is used.

[0268] The support (A-3) obtained by the above reaction is preferably separated by filtration or decantation, and then washed thoroughly with an inert hydrocarbon solvent to remove unreacted substances or by-products, etc.

[0269] There is no particular limitation on the reaction temperature of the organomagnesium compound (A-1) and the chlorinating agent (A-2), but from the viewpoints of increasing the pores of the support (A-3) and making the support (A-3) easily broken, it is preferably 75 °C or higher and 150 °C or lower, more preferably 80 °C or higher and 120 °C or lower, and further preferably 80 °C or higher and 100 °C or lower.

[0270] In the method of adding while reacting while simultaneously introducing (A-1) and (A-2) into the reactor, it is preferable to adjust the temperature of the reactor to a specified temperature in advance and adjust the temperature inside the reactor to the specified temperature while performing the simultaneous addition.

[0271] In the method of first charging (A-2) into the reactor and then introducing (A-1) into the reactor, it is preferred to adjust the temperature of the reactor charged with the chlorinating agent (A-2) to a specified temperature, and while introducing the organomagnesium compound (A-1) into the reactor, adjust the temperature inside the reactor to the specified temperature.

[0272] In the method of first charging (A-1) into the reactor and then introducing (A-2) into the reactor, it is preferred to adjust the temperature of the reactor charged with (A-1) to a specified temperature, and while introducing (A-2) into the reactor, adjust the temperature inside the reactor to the specified temperature.

[0273] There is no particular limitation on the concentration of (A-1) (magnesium concentration) in the reaction system of the organomagnesium compound (A-1) and the chlorinating agent (A-2), but from the viewpoint of increasing the pores of the carrier (A-3) and making the carrier (A-3) liable to break, it is preferably 0.8 mol / L or more and 2.5 mol / L or less, more preferably 1.0 mol / L or more and 2.0 mol / L or less.

[0274] Next, the organomagnesium compound (A-4) will be described.

[0275] As (A-4), a compound represented by the aforementioned (Formula iii) is preferred.

[0276] (A-4): (M 2 ) α (Mg) β (R 4 ) a (R 5 ) b Y 1 c ......(Formula iii)

[0277] (In Formula iii, M 2 is a metal atom belonging to any one of the group consisting of Group 12, Group 13, and Group 14 of the Periodic Table of the Elements, R 4 and R 5 are hydrocarbon groups having 2 or more and 20 or less carbon atoms, Y 1 is a hydrocarbyloxy group, a silyloxy group, an allyloxy group, an amino group, an amide group, -N=C-R 6 ,R 7 、-SR 8 (here, R 6 、R 7 and R 8 represent hydrocarbon groups having 1 or more and 20 or less carbon atoms. When c is 2, Y 1Either of the α-keto acid residue (which may be different from each other) and the β-keto acid residue, and α, β, a, b, and c are real numbers satisfying the following relationships.

[0278] 0 ≤ α, 0 < β, 0 ≤ a, 0 ≤ b, 0 ≤ c, 0 < a + b, 0 ≤ c / (α + β) ≤ 2, nα + 2β = a + b + c (where n represents the valence of M 2 .))

[0279] Regarding the usage amount of the organomagnesium compound (A-4), the molar ratio of the magnesium atoms contained in the organomagnesium compound (A-4) to the titanium atoms contained in the titanium compound (A-5) is preferably 0.1 or more and 10 or less, more preferably 0.5 or more and 5 or less.

[0280] There is no particular limitation on the reaction temperature of the organomagnesium compound (A-4) and the titanium compound (A-5), and it is preferably -80°C or more and 150°C or less, more preferably -40°C or more and 100°C or less.

[0281] There is no particular limitation on the concentration during the use of the organomagnesium compound (A-4). Based on the magnesium atoms contained in the organomagnesium compound (A-4), it is preferably 0.1 mol / L or more and 2 mol / L or less, more preferably 0.5 mol / L or more and 1.5 mol / L or less. It should be noted that an inert hydrocarbon solvent is preferably used when diluting the organomagnesium compound (A-4).

[0282] Next, the titanium compound (A-5) will be described.

[0283] As described above, the titanium compound (A-5) is a titanium compound represented by the following formula iv.

[0284] (A-5): Ti(OR 9 ) d X 1 (4-d) ……(Formula iv)

[0285] (In formula iv, d is a real number from 0 or more and 4 or less, R 9 is a hydrocarbon group having 1 or more and 20 or less carbon atoms, and X 1 is a halogen atom.)

[0286] In the above (formula iv), d is preferably 0 or more and 1 or less, and d is further preferably 0.

[0287] In (formula iv), as R 9The represented hydrocarbon group is not particularly limited. For example, the following can be listed: aliphatic hydrocarbon groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, 2-ethylhexyl, heptyl, octyl, decyl, allyl; alicyclic hydrocarbon groups such as cyclohexyl, 2-methylcyclohexyl, cyclopentyl; aromatic hydrocarbon groups such as phenyl, naphthyl, etc. An aliphatic hydrocarbon group is particularly preferred.

[0288] As the halogen represented by X 1 The represented halogen is not particularly limited. For example, the following can be listed: chlorine, bromine, iodine. Chlorine is particularly preferred.

[0289] The titanium compound (A-5) can be used alone as a single kind, or two or more kinds can be used in combination.

[0290] Regarding the usage amount of the titanium compound (A-5), there is no particular limitation. However, from the viewpoint of increasing the loading amount in the pores of the carrier, in terms of the molar ratio of titanium to the magnesium atoms contained in the carrier (A-3) (Ti / Mg), it is preferably 0.15 or more and 20 or less, more preferably 0.2 or more and 10 or less.

[0291] There is no particular limitation on the reaction temperature of the titanium compound (A-5). It is preferably -80°C or more and 150°C or less, more preferably -40°C or more and 100°C or less.

[0292] There is no particular limitation on the method of loading the titanium compound (A-5) on the carrier (A-3). A method of reacting an excessive amount of the titanium compound (A-5) relative to the carrier (A-3), or a method of effectively loading the titanium compound (A-5) by using a third component can be used. A method of loading the titanium compound (A-5) on the carrier (A-3) by reacting the titanium compound (A-5) with an organomagnesium compound (A-4) is particularly preferred.

[0293] There is no particular limitation on the order of adding the organomagnesium compound (A-4) and the titanium compound (A-5) to the carrier (A-3). Any one of the following methods can be used: adding the titanium compound (A-5) after adding the organomagnesium compound (A-4), adding the organomagnesium compound (A-4) after adding the titanium compound (A-5), or adding the organomagnesium compound (A-4) and the titanium compound (A-5) simultaneously.

[0294] A method of adding the organomagnesium compound (A-4) and the titanium compound (A-5) simultaneously is particularly preferred.

[0295] The reaction of the organomagnesium compound (A-4) and the titanium compound (A-5) is carried out in an inert hydrocarbon solvent. An aliphatic hydrocarbon solvent such as hexane or heptane is preferably used.

[0296] The catalyst obtained as described above is used in the form of a slurry solution using an inert hydrocarbon solvent.

[0297] When transporting the slurry solution, from the perspective of preventing the obtained catalyst from cracking before the polymerization step, it is preferable to add a thickening agent or control it in a manner that reduces the pressure difference between the transport source and the transport destination.

[0298] As the above-mentioned thickening agent, there is no particular limitation, but from the perspective of maintaining the performance of the catalyst, saturated hydrocarbons are preferred. Specifically, liquid paraffin, polyolefin waxes, etc. can be cited.

[0299] As the pressure difference between the above-mentioned transport source and the transport destination, there is no particular limitation, but it is preferably 0.1 MPa or more and 0.5 MPa or less, and more preferably 0.1 MPa or more and 0.3 MPa or less.

[0300] Next, the organometallic compound component [B] used as the catalyst component in the polymerization of the polyethylene powder of the present embodiment will be described.

[0301] As the catalyst used in the polymerization of the polyethylene powder of the present embodiment, by combining the above-mentioned solid catalyst component [A] and the organometallic compound component [B], a highly active solid catalyst for polymerization is formed.

[0302] The organometallic compound component [B] is sometimes also referred to as a "cocatalyst".

[0303] As the organometallic compound component [B], a compound containing any metal belonging to the group consisting of Group 1, Group 2, Group 12, and Group 13 of the periodic table is preferred, and an organoaluminum compound and / or an organomagnesium compound is particularly preferred.

[0304] As the organoaluminum compound, it is preferable to use alone or in combination a compound represented by the following (Formula v).

[0305] AlR 10 j Z 1 (3-j) ……(Formula v)

[0306] (In Formula v, R 10 is a hydrocarbon group having 1 to 20 carbon atoms, Z 1 is any group belonging to the group consisting of hydrogen, halogen, alkoxy, allyloxy, and silanyloxy, and j is a number of 2 or more and 3 or less.)

[0307] In the above (Formula v), for R 10The hydrocarbon group having 1 to 20 carbon atoms is not particularly limited, and examples thereof include a hydrocarbon group including an aliphatic hydrocarbon group, an aromatic hydrocarbon group, or an alicyclic hydrocarbon group. Specifically, examples include: trialkylaluminums such as trimethylaluminum, triethylaluminum, tripropylaluminum, tributylaluminum, tris(2-methylpropyl)aluminum (or triisobutylaluminum), tripentylaluminum, tris(3-methylbutyl)aluminum, trihexylaluminum, trioctylaluminum, and tridecylaluminum; aluminum halide compounds such as diethylaluminum chloride, ethylaluminum dichloride, bis(2-methylpropyl)aluminum chloride, ethylaluminum sesquichloride, and diethylaluminum bromide; alkoxyaluminum compounds such as ethoxydiethylaluminum and butoxybis(2-methylpropyl)aluminum; silyloxyaluminum compounds such as dimethylhydrosilyloxydimethylaluminum, ethylmethylhydrosilyloxydiethylaluminum, and ethyldimethylsilyloxydiethylaluminum; and mixtures thereof as preferred substances.

[0308] Particularly more preferably, a trialkylaluminum compound.

[0309] As the organomagnesium compound, an organomagnesium compound represented by the above (Formula i) and soluble in an inert hydrocarbon solvent is preferred.

[0310] Regarding γ, δ, e, f, g, M in the above (Formula i) 1 , R 1 , R 2 , OR 3 , as described above, but preferably the organomagnesium compound has high solubility in an inert hydrocarbon solvent, so β / α is preferably in the range of 0.5 to 10. Additionally, more preferably, M 1 is a compound of aluminum.

[0311] There is no particular limitation on the method of adding the solid catalyst component [A] and the organometallic compound component [B] to the polymerization system under polymerization conditions. The two can be added to the polymerization system separately, or they can be reacted in advance and then added to the polymerization system.

[0312] In addition, there is no particular limitation on the ratio of the two in combination. Relative to 1 g of the solid catalyst component [A], the organometallic compound component [B] is preferably 1 mmol or more and 3000 mmol or less.

[0313] (Polymerization method of vinyl polymer)

[0314] As the polymerization method of the vinyl polymer constituting the polyethylene powder of the present embodiment, examples include: a method of polymerizing ethylene or copolymerizing ethylene with a comonomer by suspension polymerization or gas phase polymerization.

[0315] Among them, the suspension polymerization method capable of effectively removing the heat of polymerization is preferred.

[0316] In suspension polymerization, an inert hydrocarbon medium can be used as a solvent, and an olefin itself can also be used as a solvent.

[0317] There is no particular limitation on the above-mentioned inert hydrocarbon medium. For example, aliphatic hydrocarbons such as propane, butane, isobutane, pentane, isopentane, hexane, heptane, octane, decane, dodecane, and kerosene can be cited; cycloaliphatic hydrocarbons such as cyclopentane, cyclohexane, and methylcyclopentane; aromatic hydrocarbons such as benzene, toluene, and xylene; halogenated hydrocarbons such as chloroethane, chlorobenzene, and dichloromethane; or mixtures thereof, etc.

[0318] In the polymerization of the vinyl polymer in the method for producing the polyethylene powder of the present embodiment, there is no particular limitation on the method of adding the above [catalyst component] into the polymerization reactor. However, from the viewpoints of polymerizing inside the pores of the catalyst to obtain a component having strongly entangled molecular chains and making the catalyst easily broken in the polymerization system, it is preferable to add the [catalyst component] that has been pre-polymerized in advance.

[0319] As the polymerization temperature of the vinyl polymer in the method for producing the polyethylene powder of the present embodiment, it is preferably 40°C or higher and 100°C or lower, more preferably 45°C or higher and 95°C or lower, and still more preferably 50°C or higher and 90°C or lower.

[0320] When the polymerization temperature is 40°C or higher, industrially effective production can be carried out. On the other hand, when the polymerization temperature is 100°C or lower, the formation of block fouling caused by the melting of a part of the polymer can be suppressed, and continuous and stable production can be carried out without clogging the pipeline.

[0321] The polymerization pressure of the vinyl polymer in the method for producing the polyethylene powder of the present embodiment is preferably normal pressure or higher and 2 MPaG or lower, more preferably 0.2 MPaG or higher and 1.5 MPaG or lower, and still more preferably 0.3 MPaG or higher and 0.9 MPaG or lower.

[0322] When the polymerization pressure is normal pressure or higher, industrially effective production can be carried out. On the other hand, when the polymerization pressure is 2 MPaG or lower, there is a tendency to be able to stably produce without generating block fouling caused by rapid polymerization in the polymerization reactor.

[0323] Generally, when polymerizing a vinyl polymer, in order to suppress the electrostatic adhesion of the polymer to the polymerization reactor, antistatic agents such as Stadis and STATSAFE manufactured by Innospec (agent Maruwa Sangyo Co., Ltd.) can also be used.

[0324] For antistatic agents such as Stadis and STATSAFE, the antistatic agent diluted in an inert hydrocarbon medium can be added to the polymerization reactor using a pump or the like. The addition of the antistatic agent can be carried out by methods such as pre-adding it to the solid catalyst or adding it to the polymerization reactor. With respect to the production amount of the vinyl polymer per unit time, the addition amount of the antistatic agent is preferably 1 ppm or more and 500 ppm or less, more preferably 10 ppm or more and 100 ppm or less.

[0325] The regulation of the molecular weight of the vinyl polymer can be carried out by the presence of hydrogen in the polymerization system or by changing the polymerization temperature as described in the specification of German Patent Application Publication No. 3127133.

[0326] Specifically, by adding hydrogen as a chain transfer agent into the polymerization system, the molecular weight of the vinyl polymer can be controlled within an appropriate range. When adding hydrogen into the polymerization system, as the range of the mole fraction of hydrogen, it is preferably 0 mol% or more and 30 mol% or less, more preferably 0 mol% or more and 25 mol% or less.

[0327] In addition, hydrogen can also be pre-contacted with the catalyst and then added into the polymerization system from the catalyst introduction pipeline. After the catalyst is just introduced into the polymerization system, the catalyst concentration near the outlet of the introduction pipeline becomes high, so rapid polymerization occurs, and the possibility of generating a local high-temperature state increases. On the other hand, by contacting hydrogen with the catalyst before introducing it into the polymerization system, the initial activity of the catalyst can be inhibited, and the generation of block fouling caused by rapid polymerization, the deactivation of the catalyst at high temperature, etc. can be inhibited.

[0328] As the range of the concentration of the polymerization slurry in the method for producing the vinyl polymer constituting the polyethylene powder of the present embodiment, from the viewpoint of the easy breakage of the catalyst in the polymerization system, it is preferably 30% by mass or more and 60% by mass or less, more preferably 40% by mass or more and 50% by mass or less.

[0329] As the range of the stirring speed in the method for producing the vinyl polymer constituting the polyethylene powder of the present embodiment, from the viewpoint of the easy breakage of the catalyst in the polymerization system, it is preferably 300 rpm or more and 600 rpm or less, more preferably 400 rpm or more and 500 rpm or less.

[0330] The polymerization reaction can be carried out in any of the batch, semi-continuous, and continuous modes, and is preferably carried out in the continuous mode.

[0331] By continuously supplying ethylene gas, a solvent, a catalyst, etc. into the polymerization system and continuously discharging them together with the produced vinyl polymer, it is possible to suppress the locally high-temperature state caused by the rapid ethylene reaction, and the polymerization system becomes more stable. When ethylene reacts in a uniform state in the system, it is possible to suppress the formation of branches, double bonds, etc. in the polymer chain, or to suppress the generation of low-molecular-weight components and ultra-high-molecular-weight bodies due to the decomposition and crosslinking of the vinyl polymer, and it is easy to generate the crystalline component of the vinyl polymer. Thus, in the film, microporous film, etc. using the polyethylene powder of this embodiment, it is easy to obtain a sufficient amount of the crystalline component required for strength.

[0332] In addition, the polymerization reaction can be a single-stage polymerization method using one polymerization reactor, or a multi-stage polymerization method in which continuous polymerization is sequentially carried out in two or more polymerization reactors connected in series.

[0333] Specifically, the production of the vinyl polymer using the multi-stage polymerization method is carried out by the method shown below.

[0334] First, a vinyl polymer X is produced in the polymerization reactor of the first stage using the above production conditions, the vinyl polymer X withdrawn from the polymerization reactor of the first stage is transported to an intermediate flash tank, and unreacted ethylene, hydrogen, and comonomer (only in the case of copolymerization in the polymerization reactor of the first stage) are separated. Then, the suspension containing the vinyl polymer X is transported to the polymerization reactor of the second stage, and a vinyl polymer Y is produced using the above production conditions.

[0335] As the range of the polymerization pressure in the polymerization reactor of the first stage, from the viewpoint of polymerizing inside the pores of the catalyst to obtain a component with a strong degree of entanglement of molecular chains, it is preferably 0.6 MPaG or more and 2.0 MPaG or less, more preferably 0.7 MPaG or more and 1.5 MPaG or less, and still more preferably 0.8 MPaG or more and 1.0 MPaG or less.

[0336] As the range of the concentration of the polymerization slurry in the polymerization reactor of the first stage, from the viewpoint of controlling so that the catalyst does not break in the polymerization reactor of the first stage, it is preferably 10% by mass or more and 30% by mass or less, more preferably 10% by mass or more and 20% by mass or less.

[0337] As the range of the stirring speed in the polymerization reactor of the first stage, from the viewpoint of controlling so that the catalyst does not break in the polymerization reactor of the first stage, it is preferably 100 rpm or more and 300 rpm or less, more preferably 150 rpm or more and 250 rpm or less.

[0338] As the concentration range of the polymerization slurry in the polymerization reactor in the second stage, from the viewpoint of facilitating the breakdown of the catalyst in the polymerization system, it is preferably 30% by mass or more and 60% by mass or less, more preferably 40% by mass or more and 50% by mass or less.

[0339] As the range of the stirring speed in the polymerization reactor in the second stage, from the viewpoint of facilitating the breakdown of the catalyst in the polymerization system, it is preferably 300 rpm or more and 600 rpm or less, more preferably 400 rpm or more and 500 rpm or less.

[0340] As the proportion of the vinyl polymer X contained in the polyethylene powder produced by the above multi-stage polymerization method, that is, the production amount range in the polymerization reactor in the first stage, from the viewpoint of controlling the breakdown of the catalyst in the polymerization reactor in the second stage, it is preferably 10% by mass or more and 50% by mass or less, more preferably 15% by mass or more and 45% by mass or less, and still more preferably 20% by mass or more and 40% by mass or less.

[0341] As the physical property values of the vinyl polymer Y, the above-mentioned viscosity-average molecular weight and density can be obtained by measuring the physical property values of the vinyl polymer X extracted from the polymerization reactor in the first stage and the finally produced polyethylene powder, and then calculating according to the additivity based on the production amount in each polymerization reactor.

[0342] The suspension containing the vinyl polymer constituting the polyethylene powder of the present embodiment is quantitatively extracted from the polymerization reactor and transported to a flash tank to separate unreacted ethylene, hydrogen, and comonomer (only in the case of copolymerization in the reactor).

[0343] Any of the decantation method, centrifugation method, filter filtration method, etc. can be applied as the solvent separation method in the polymerization process of the polyethylene powder of the present embodiment, and the centrifugation method with good separation efficiency of the vinyl polymer and the solvent is more preferably used.

[0344] There is no particular limitation on the method for deactivating the catalyst used in the polymerization process of the vinyl polymer constituting the polyethylene powder of the present embodiment. The deactivation of the catalyst is preferably carried out after separating the vinyl polymer and the solvent.

[0345] By introducing a reagent for deactivating the catalyst after separating the polyethylene powder and the solvent, precipitation of low molecular weight components, catalyst components, etc. contained in the solvent in the vinyl polymer can be inhibited.

[0346] Examples of the reagent for deactivating the catalyst include oxygen, water, alcohols, diols, phenols, carbon monoxide, carbon dioxide, ethers, carbonyl compounds, alkynes, etc.

[0347] In the method for producing the polyethylene powder of the present embodiment, it is preferable to perform a drying step after separating the vinyl polymer from the solvent. In the drying step, it is preferable to use a rotary kiln method, a paddle method, a fluidized dryer, etc. Further, as the drying temperature, it is preferably 50°C or higher and 150°C or lower, more preferably 70°C or higher and 110°C or lower.

[0348] In addition, it is also effective to introduce an inert gas such as nitrogen into the dryer to promote drying. At this time, a method accompanied by steam or the like as a reagent for deactivating the catalyst is more effective.

[0349] After drying the vinyl polymer constituting the polyethylene powder of the present embodiment, in order to remove the coarse powder, sieving can be performed.

[0350] The polyethylene powder of the present embodiment may be a mixture of a plurality of polyethylene powders containing the vinyl polymer obtained by the above production method.

[0351] In addition, it can be used in combination with known additives such as a slip agent, a neutralizing agent, an antioxidant, a light stabilizer, an antistatic agent, a pigment, etc. as needed.

[0352] There is no particular limitation on the slip agent or the neutralizing agent, and examples thereof include: aliphatic hydrocarbons, higher fatty acids, metal salts of higher fatty acids, fatty acid esters of alcohols, waxes, higher fatty acid amides, silicone oils, rosin, etc. Specifically, stearates such as calcium stearate, magnesium stearate, and zinc stearate can be cited as appropriate additives.

[0353] There is no particular limitation on the antioxidant, and for example, phenolic compounds or phenolic phosphorus-containing compounds are preferred. Specifically, phenolic antioxidants such as 2,6-di-tert-butyl-4-methylphenol (butylated hydroxytoluene), n-octadecyl 3-(4-hydroxy-3,5-di-tert-butylphenyl)propionate, and tetrakis[methylene(3,5-di-tert-butyl-4-hydroxyhydrocinnamate)]methane; phenolic phosphorus-containing antioxidants such as 6-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propoxy]-2,4,8,10-tetra-tert-butyldibenz[d,f][1,3,2]dioxaphosphepin; phosphorus-containing antioxidants such as tetra(2,4-di-tert-butylphenyl) 4,4'-biphenylene diphosphonate, tris(2,4-di-tert-butylphenyl) phosphite, and cyclic neopentanetetrayl bis(2,4-di-tert-butylphenyl phosphite) can be cited.

[0354] As the light stabilizer, there is no particular limitation. For example, it can include: benzotriazole light stabilizers such as 2-(5-methyl-2-hydroxyphenyl)benzotriazole, 2-(3-tert-butyl-5-methyl-2-hydroxyphenyl)-5-chlorobenzotriazole; hindered amine light stabilizers such as bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, poly[{6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl}{(2,2,6,6-tetramethyl-4-piperidyl)imino)hexamethylene}{(2,2,6,6-tetramethyl-4-piperidyl)imino}].

[0355] As the antistatic agent, there is no particular limitation. For example, it can include: aluminum silicate, kaolin, clay, natural silica, synthetic silica, silicates, talc, diatomaceous earth, etc.; fatty acid glycerides, etc.

[0356] [Use]

[0357] The polyethylene powder of the present embodiment can be used as a raw material for various molded articles such as microporous membranes, fibers, especially high-strength fibers, sintered bodies, compression molded articles, and plunger extrusion molded articles.

[0358] It is particularly suitable as a raw material for the microporous membrane used for the battery separator.

[0359] [Molded article]

[0360] The molded article of the present embodiment is the molded article of the polyethylene powder of the present embodiment described above.

[0361] As the molded article, it can include: microporous membranes, especially microporous membranes used as battery separators, fibers, especially high-strength fibers, sintered bodies, compression molded articles, plunger extrusion molded articles, etc.

[0362] As the manufacturing method of the molded article, it can include: a molding method through the processes of extrusion, stretching, extraction, and drying of the resin using the wet extrusion method.

[0363] As the above-mentioned battery separator, it can include: separators for lithium-ion secondary batteries, separators for lead-acid batteries, etc.

[0364] Examples

[0365] Hereinafter, the present embodiment will be described in more detail through specific examples and comparative examples, but the present invention is not limited by any of the following examples and comparative examples.

[0366] First, the evaluation method of the physical properties of the polyethylene powder will be described.

[0367] [Physical properties of polyethylene powder]

[0368] (Proportion of components with intermediate entanglement index and mobility at 180 °C)

[0369] First, a sample tube filled with polyethylene powder to a height of 1 cm from the bottom was inserted into a TD-NMR apparatus (model: minispec mq20) manufactured by Bruker and set to maintain the internal temperature of the sample tube at 30 °C, and the sample tube was heated according to the <heating conditions> shown below.

[0370] The temperature shown in the following <heating conditions> is the value obtained by measuring the internal temperature of the sample using a thermocouple.

[0371] <Heating conditions>

[0372] (1) Set to 30 °C and left standing for 5 minutes.

[0373] (2) Heat up to 180 °C at a rate of 5 °C per minute.

[0374] (3) After heating up to 180 °C, left standing for 25 minutes.

[0375] After the heating is completed according to the above steps, the spin-spin relaxation time (T 2 , sometimes simply referred to as "relaxation time" in this specification) of the sample was measured according to the <measurement conditions> shown below.

[0376] Then, after the measurement is completed, the same measurement is repeated 3 times for a total of 4 measurements.

[0377] <Measurement conditions>

[0378] Magnetic field strength: 0.47 T

[0379] Nuclear species to be measured: 1 H (20 MHz)

[0380] Measurement method: Carr Purcell Meiboom Gill method

[0381] Number of accumulations: 256 times

[0382] Repetition time: 3 seconds

[0383] Interval (τ) between the first 90° pulse and 180° pulse: 0.04 milliseconds

[0384] Total number of echo signals: 6400

[0385] For the free induction decay (FID) obtained from the fourth measurement in all the above 4 measurements, curve fitting was performed using the analysis program TD-NMR-A manufactured by Bruker.

[0386] The following function shown in <Equation 1> was used in the fitting.

[0387] <Equation 1>

[0388] f(t)=R α exp(-t / T α )+R β exp(-t / T β )+R γ exp(-t / T γ )

[0389] (where R α +R β +R γ =100)

[0390] t: variable (elapsed time counted from the start of pulse radiation)

[0391] T α : relaxation time (milliseconds) of the component α with low motility

[0392] R α : proportion of the component α with low motility (%)

[0393] T β : relaxation time (milliseconds) of the component β with medium motility

[0394] R β : proportion of the component β with medium motility (%)

[0395] T γ : relaxation time (milliseconds) of the component γ with high motility

[0396] R γ : proportion of the component γ with high motility (%)

[0397] Finally, based on the relaxation time T and the proportion R obtained by curve fitting of the free induction decay, the entanglement index (milliseconds) and the proportion of the component with medium motility are calculated according to (Equation I) and (Equation II) shown below.

[0398] (Entanglement index)=T α ×R α / (R α +R β )+T β ×R β / (R α +R β ) ……(Equation I)

[0399] (Proportion of the component with medium motility)=R β / (R α +Rβ ) ……(Formula II)

[0400] (Rate of change in the proportion of components with low mobility at 180 °C)

[0401] For the free induction decay (FID) obtained from the first and fourth measurements in the pulsed NMR measurement when determining the above-mentioned (entanglement index and proportion of components with medium mobility at 180 °C), curve fitting was performed using the analysis program TD-NMR-A manufactured by Bruker Corporation.

[0402] The function shown in the above <Formula 1> was used in the fitting.

[0403] The rate of change (%) of the proportion of components with low mobility was calculated from the proportion R obtained by fitting according to the following (Formula III).

[0404] (Rate of change in the proportion of components with low mobility) = ((R α4 - R α1 ) / R α1 ) × 100 ……(Formula III)

[0405] R α1 : Proportion (%) of components α with low mobility at the first measurement

[0406] R α4 : Proportion (%) of components α with low mobility at the fourth measurement

[0407] (Rate of change in the proportion of components with high mobility at 180 °C)

[0408] For the free induction decay (FID) obtained from the first and fourth measurements in the pulsed NMR measurement when determining the above-mentioned (entanglement index and proportion of components with medium mobility at 180 °C), curve fitting was performed using the analysis program TD-NMR-A manufactured by Bruker Corporation.

[0409] The function shown in the above <Formula 1> was used in the fitting.

[0410] The rate of change (%) of the proportion of components with high mobility was calculated from the proportion R obtained by fitting according to the following (Formula IV).

[0411] (Rate of change in the proportion of components with high mobility) = ((R γ4 - R γ1 ) / R γ1 ) × 100 ……(Formula IV)

[0412] R γ1: Proportion (%) of component γ with high motility at the first measurement

[0413] R γ4 : Proportion (%) of component γ with high motility at the fourth measurement

[0414] [Isothermal crystallization time]

[0415] The isothermal crystallization time of the polyethylene powder at 125 °C was determined by using a differential scanning calorimeter (manufactured by PerkinElmer, product name: DSC8000) according to the method shown below.

[0416] First, an aluminum pan containing 8.5 mg of polyethylene powder was placed in the heating furnace of the DSC device, and a heating operation was performed according to the <heating and cooling conditions> shown below.

[0417] Among them, all heating operations were carried out under a nitrogen atmosphere.

[0418] <Heating and cooling conditions>

[0419] (1) Hold at 50 °C for 1 minute.

[0420] (2) Heat up to 180 °C at a rate of 200 °C / minute.

[0421] (3) Hold at 180 °C for 5 minutes.

[0422] (4) Cool down to 125 °C at a rate of 80 °C / minute.

[0423] Then, taking the time when reaching 125 °C as the starting point (0 minute), the time when obtaining the peak top of the exothermic peak generated by crystallization was taken as the isothermal crystallization time (minute) at 125 °C.

[0424] (Viscosity-average molecular weight (Mv))

[0425] The viscosity-average molecular weight of the polyethylene powder was measured according to ISO1628-3 (2010) by the method shown below.

[0426] First, weigh the polyethylene powder in the range of 4.0 mg to 4.5 mg in a dissolution tube. Denote the weighed mass as "m (unit: mg)" in the following formula. Then, evacuate the air inside the dissolution tube using a vacuum pump and replace it with nitrogen, and then add 20 mL of decalin (added with 1 g / L of 2,6-di-tert-butyl-4-methylphenol, hereinafter referred to as naphthalane) that has been degassed using a vacuum pump and replaced with nitrogen, and stir at 150 °C for 90 minutes to dissolve the polyethylene powder, thereby preparing a naphthalane solution.

[0427] Then, the above-mentioned decalin solution was put into a Cannon-Fenske viscometer (manufactured by Shibata Scientific Instruments Co., Ltd. / viscometer number: 100) in a constant-temperature bath at 135°C, and the falling time (ts) between the calibration marks was measured.

[0428] In addition, the falling time (tb) of decalin alone without adding polyethylene powder, which was used as a blank, was measured, and the specific viscosity (ηsp) was calculated according to the following (Formula A).

[0429] ηsp = (ts / tb) - 1 (Formula A)

[0430] The intrinsic viscosity IV was calculated from the specific viscosity (ηsp) and the concentration (C) (unit: g / dL) using the following (Formula B) and (Formula C).

[0431] Concentration C = m / (20×γ) / 10 (unit: g / dL) (Formula B)

[0432] γ = (density of decalin at 20°C) / (density of decalin at 135°C)

[0433] = 0.888 / 0.802 = 1.107

[0434] Intrinsic viscosity IV = (ηsp / C) / (1 + 0.27×ηsp) (Formula C)

[0435] Substitute this intrinsic viscosity IV into the following (Formula D) to obtain the viscosity-average molecular weight (Mv).

[0436] Viscosity-average molecular weight (Mv) = (5.34×10 4 )×[η] 1.49 (Formula D)

[0437] (Median particle size)

[0438] The median particle size of the polyethylene powder was determined by the method shown below.

[0439] The polyethylene powder was classified using sieves according to JIS Z8801 standards. Sieves with sieve hole sizes of 425 μm, 300 μm, 212 μm, 150 μm, 106 μm, 75 μm, and 53 μm were used, and the mass of the polyethylene powder recovered in each fraction was measured. Then, the fraction (mass%) of each fraction relative to the total mass of the polyethylene powder before classification was calculated, and the cumulative undersize ratio (mass%) was obtained. A cumulative undersize distribution graph, i.e., a cumulative particle size distribution curve (cumulative curve starting from small particles), was plotted with the sieve hole size value on the horizontal axis and the cumulative undersize ratio on the vertical axis, and the particle size (D50 (μm)) at a cumulative undersize ratio of 50% was taken as the median particle size.

[0440] [Method for manufacturing microporous membrane]

[0441] 1 part by mass of pentaerythritol - tetra[3-(3,5 - di - tert - butyl - 4 - hydroxyphenyl)propionate] as an antioxidant was added to 25 to 50 parts by mass of the polyethylene powder in each of the following Examples and Comparative Examples, and dry - mixed using a drum mixer to obtain a powder mixture.

[0442] The obtained powder mixture was purged with nitrogen, and then fed into a twin - screw extruder through a feeder under a nitrogen atmosphere.

[0443] Then, liquid paraffin (manufactured by MORESCO Corporation, P - 350P (product name)) measured in such a way that the total with the polyethylene powder was 100 parts by mass was injected into the twin - screw extruder by side - feeding, kneaded at 200 °C, extruded from a T - die head provided at the front end of the extruder, and then immediately cooled and solidified using a casting roll cooled to 25 °C to form a gel - like sheet with a thickness of 1200 μm. The gel - like sheet was stretched 7×7 times at 115 °C to 125 °C using a synchronous biaxial stretching machine to obtain a stretched film. Then, the stretched film was immersed in methyl ethyl ketone for 30 minutes to extract and remove the liquid paraffin, and then dried. Then, it was heat - set at 115 °C to 125 °C for 3 minutes to obtain a microporous membrane.

[0444] Regarding the stretching temperature and the heat - setting temperature, within the specified temperature range, each microporous membrane was appropriately adjusted.

[0445] [Evaluation of microporous membrane]

[0446] (Evaluation of the formability of microporous membrane)

[0447] As an evaluation index of formability, the thickness uniformity of the microporous membrane was evaluated.

[0448] Specifically, for the microporous membrane obtained by the above - mentioned [Method for manufacturing microporous membrane], 8 membranes of 100 mm×50 mm were punched out from 250 mm×250 mm, and the film thickness of each membrane was measured at 23 °C using a micro - thickness gauge (model: KBM) manufactured by Toyo Seiki Seisaku - sho, Ltd.

[0449] The film thickness of one punched - out membrane was measured at 3 places.

[0450] Then, the standard deviation of the measurement values at a total of 24 points was calculated, and the formability was evaluated according to the following evaluation criteria.

[0451] (Evaluation criteria)

[0452] ◎(Good): Less than 0.5 μm

[0453] ○ (Normal): greater than or equal to 0.5 μm and less than 1 μm

[0454] × (Poor): 1 μm or more

[0455] (Evaluation of the mechanical strength of the microporous membrane)

[0456] As an evaluation index of the mechanical strength, the puncture strength of the microporous membrane was evaluated.

[0457] Specifically, for the microporous membrane obtained by the above [manufacturing method of the microporous membrane], 8 membranes of 100 mm × 50 mm were punched out from 250 mm × 250 mm, and the puncture strength of each membrane was measured using a compression testing machine (model: KES-G5) manufactured by Kato Tech Co., Ltd. under the conditions of a needle tip curvature radius of 0.5 mm, a puncture speed of 2 mm / second, and 23°C. The measurement was carried out at 3 locations on one punched membrane.

[0458] In addition, the mass of each punched membrane was measured to obtain the basis weight (membrane mass [g] per 1 m 2 ), and the puncture strength converted by the basis weight was calculated by the following formula.

[0459] Then, the average value of the measurement values at a total of 24 points was calculated, and the mechanical strength was evaluated according to the following evaluation criteria.

[0460] (Puncture strength converted by the basis weight) = (Puncture strength [N]) / (Basis weight [g / m 2 )

[0461] (Evaluation criteria)

[0462] ◎ (Good): 0.85 N / (g / m 2 ) or more

[0463] ○ (Normal): greater than or equal to 0.7 N / (g / m 2 ) and less than 0.85 N / (g / m 2 )

[0464] × (Poor): less than 0.7 N / (g / m 2 )

[0465] (Evaluation of the dimensional stability of the microporous membrane)

[0466] As an evaluation index of the dimensional stability, the thermal shrinkage rate of the microporous membrane was evaluated.

[0467] Specifically, for the microporous membrane obtained by the above [manufacturing method of the microporous membrane], 8 membranes of 100 mm × 50 mm were punched out from 250 mm × 250 mm and left standing in an oven set at 120°C for 60 minutes.

[0468] After heating and standing still, it is cooled at room temperature for 15 minutes, then the size of the microporous membrane is measured, and the thermal shrinkage rate (%) is calculated by the following formula.

[0469] Then, the average value of the measured values at a total of 8 points is calculated, and the dimensional stability is evaluated according to the following evaluation criteria.

[0470] (Thermal shrinkage rate) = (Thermal shrinkage rate in the MD direction) + (Thermal shrinkage rate in the TD direction)

[0471] (Thermal shrinkage rate in the MD direction) = (1 - D MD120 / D MD23 ) × 100

[0472] (Thermal shrinkage rate in the TD direction) = (1 - D TD120 / D TD23 ) × 100

[0473] D MD120 : Size in the MD direction at 120°C [mm]

[0474] D MD23 : Size in the MD direction at 23°C [mm]

[0475] D TD120 : Size in the TD direction at 120°C [mm]

[0476] D TD23 : Size in the TD direction at 23°C [mm]

[0477] (Evaluation criteria)

[0478] ◎ (Good): Less than 15%

[0479] ○ (Normal): Greater than or equal to 15% and less than 25%

[0480] × (Poor): 25% or more

[0481] (Evaluation of the creep resistance of the microporous membrane)

[0482] A sample with a width of 20 mm × a length of 100 mm is cut out from the microporous membrane obtained by the above [Manufacturing method of microporous membrane], and is installed in a Tensilon manufactured by A&D Company Limited with the chuck spacing set to 50 mm. It is kept for 12 hours under the conditions of a temperature of 23°C and a load of 10 N, then the length of the microporous membrane is measured, and the tensile elongation rate (%) is calculated by the following formula.

[0483] Then, the creep resistance is evaluated according to the following evaluation criteria.

[0484] (Tensile elongation rate) = {(L12h × 100 / (( - 1) × 100)

[0485] L 12h : Length of the microporous membrane after 12 hours [mm]

[0486] (Evaluation criteria)

[0487] ◎ (Good): Less than 5%

[0488] ○ (Normal): Greater than or equal to 5% and less than 10%

[0489] × (Poor): 10% or more

[0490] [Preparation of Ziegler - Natta catalyst]

[0491] (Preparation of Ziegler - Natta catalyst (A))

[0492] <(1) Synthesis of raw material (a - 1)>

[0493] Charge 2.5 mol / L of Mg in an 8 - L stainless - steel autoclave after sufficient nitrogen replacement 6 (C 4 H 9 ) 12 Al(C 2 H 5 ) 3 800 mL of a hexane solution (equivalent to 2000 mmol in total of magnesium and aluminum), while stirring at 50 °C, drop - wise add 146 mL of a 5.47 mol / L n - butanol hexane solution over 3 hours. After completion, wash the pipeline with 200 mL of hexane. Then, continue stirring at 50 °C for 2 hours to carry out the reaction.

[0494] After the reaction is completed, cool the substance to room temperature and use it as raw material (a - 1). The concentration of magnesium in raw material (a - 1) is 1.5 mol / L.

[0495] <(2) Synthesis of raw material (a - 2)>

[0496] Charge 1 mol / L of Mg in an 8 - L stainless - steel autoclave after sufficient nitrogen replacement 6 (C 4 H 9 ) 12 Al(C 2 H 5 ) 3 2000 mL of a hexane solution (equivalent to 2000 mmol in total of magnesium and aluminum), while stirring at 80 °C, pump in 240 mL of a hexane solution of 8.33 mol / L methylhydrogenpolysiloxane (manufactured by Shin - Etsu Chemical Co., Ltd.), and then continue stirring at 80 °C for 2 hours.

[0497] After the reaction is completed, the substance cooled to room temperature is used as raw material (a-2).

[0498] The raw material (a-2) has a total concentration of magnesium and aluminum of 0.786 mol / L.

[0499] <(3) Synthesis of carrier (a-3)>

[0500] Into an 8 L stainless steel autoclave that has been thoroughly purged with nitrogen, 333 mL of a 3 mol / L hexane solution of hydroxychlorosilane is charged. While maintaining the temperature at 80°C, 629 mL of a hexane solution of the organomagnesium compound of raw material (a-1) (equivalent to 943 mmol of magnesium) is added dropwise over 3 hours. Then, the reaction is continued while stirring at 80°C for 1 hour.

[0501] After the reaction is completed, the supernatant is removed, and the residue is washed four times with 1,800 mL of hexane to obtain the carrier (a-3).

[0502] Analysis of this carrier shows that it contains 7.5 mmol of magnesium per 1 g of solid.

[0503] <(4) Preparation of Ziegler-Natta catalyst (A)>

[0504] Into an 8 L stainless steel autoclave that has been thoroughly purged with nitrogen, while stirring 1,970 mL of a hexane slurry containing 110 g of the above-mentioned carrier (a-3) at 10°C, 103 mL of a 1 mol / L hexane solution of titanium tetrachloride and 131 mL of the above-mentioned raw material (a-2) are added simultaneously over 3 hours.

[0505] After the addition, the reaction is continued at 10°C for 1 hour. After the reaction is completed, the supernatant is removed, and the unreacted raw material components are removed by washing four times with hexane. Then, 10% by volume (volume ratio: liquid paraffin / (liquid paraffin + hexane)) of liquid paraffin (manufactured by MORESCO Corporation, P-350P (product name)) as a thickening agent is added to prepare the Ziegler-Natta catalyst (A).

[0506] When transporting this Ziegler-Natta catalyst (A), the pressure difference between the transport source and the transport destination is adjusted to 0.3 MPa.

[0507] (Preparation of Ziegler-Natta catalyst (B))

[0508] Prepolymerization of 20 g of the above-mentioned Ziegler-Natta catalyst (A) was carried out using a 1.6 L autoclave. 800 mL of n-hexane was used as a solvent, 0.4 mmol of triisobutylaluminum and diisobutylaluminum hydride (9:1 mixture) were used as cocatalysts, and 20 mol% (molar ratio: hydrogen / (ethylene + hydrogen)) of hydrogen was supplied. The polymerization temperature was set at 20 °C, and ethylene was supplied in such a way that 5 g of polyethylene was polymerized per 1 g of the Ziegler-Natta catalyst (A). After the polymerization was completed, the supernatant was removed, and unreacted raw material components were removed by washing 4 times with hexane, thereby preparing the Ziegler-Natta catalyst (B). When transporting this Ziegler-Natta catalyst (B), the pressure difference between the transport source and the transport destination was adjusted to 0.8 MPa.

[0509] (Preparation of Ziegler-Natta catalyst (C))

[0510] <(5) Synthesis of carrier (c-3)>

[0511] Except that the reaction temperature was set at 65 °C, the same operations as those for the synthesis of the above-mentioned carrier (a-3) were carried out, thereby obtaining the carrier (c-3). The carrier (c-3) was analyzed, and as a result, the magnesium content per 1 g of the solid was 7.5 mmol.

[0512] <(6) Preparation of Ziegler-Natta catalyst (C)>

[0513] Using the carrier (c-3) instead of the above-mentioned carrier (a-3) and without adding liquid paraffin, the same operations as those for the preparation of the Ziegler-Natta catalyst (A) were carried out, thereby preparing the Ziegler-Natta catalyst (C). When transporting this Ziegler-Natta catalyst (C), the pressure difference between the transport source and the transport destination was adjusted to 0.3 MPa.

[0514] (Preparation of Ziegler-Natta catalyst (D))

[0515] <(7) Synthesis of raw material (d-1)>

[0516] Using a 2000 mL hexane solution of 1 mol / L Mg 6 (C 4 H 9 ) 12 Al(C 2 H 5 ) 3 and adjusting the amount of n-hexane used for cleaning the pipeline to 300 mL, the same operations as those for the synthesis of the above-mentioned raw material (a-1) were carried out, thereby obtaining the raw material (d-1). The raw material (d-1) had a magnesium concentration of 0.7 mol / L.

[0517] <Synthesis of carrier (d-3)>

[0518] Using 1340 mL of raw material (d-1) instead of 629 mL of the above raw material (a-1), and setting the reaction temperature to 65 °C, otherwise, the same operations as the synthesis of the above carrier (a-3) were carried out to obtain carrier (d-3). Analyzing this carrier (d-3), the result shows that the magnesium content per 1 g of solid is 7.5 millimoles.

[0519] <Synthesis of Ziegler-Natta catalyst (D)>

[0520] Using carrier (d-3) instead of the above carrier (a-3), and without adding liquid paraffin, otherwise, the same operations as the preparation of Ziegler-Natta catalyst (A) were carried out to prepare Ziegler-Natta catalyst (D). When transporting this Ziegler-Natta catalyst (D), the pressure difference between the transport source and the transport destination was adjusted to 0.8 MPa.

[0521] (Preparation of Ziegler-Natta catalyst (E))

[0522] Except for using Ziegler-Natta catalyst (D) instead of Ziegler-Natta catalyst (A), the same polymerization operations as the preparation of Ziegler-Natta catalyst (B) were carried out to prepare Ziegler-Natta catalyst (E). When transporting this Ziegler-Natta catalyst (E), the pressure difference between the transport source and the transport destination was adjusted to 0.3 MPa.

[0523] (Preparation of Ziegler-Natta catalyst (F))

[0524] In an 8 L stainless steel autoclave after sufficient nitrogen replacement, when stirring 1600 mL of hexane at 5 °C, a 1 mol / L hexane solution of 786 mL of titanium tetrachloride and 1000 mL of the above raw material (a-2) were added simultaneously over 4 hours.

[0525] After the addition, the temperature was slowly raised, and the reaction was continued at 10 °C for 1 hour.

[0526] After the reaction was completed, the supernatant was removed, and the unreacted raw material components were removed by washing 4 times with hexane to prepare Ziegler-Natta catalyst (F).

[0527] When transporting this Ziegler-Natta catalyst (F), the pressure difference between the transport source and the transport destination was adjusted to 0.8 MPa.

[0528] (Preparation of Ziegler-Natta catalyst (G))

[0529] 10% by volume (volume ratio: liquid paraffin / (liquid paraffin + hexane)) of liquid paraffin (manufactured by MORESCO CORPORATION, P-350P (product name)) as a thickener was added to the above-mentioned Ziegler-Natta catalyst (F) to prepare a Ziegler-Natta catalyst (G).

[0530] When transporting the Ziegler-Natta catalyst (G), the pressure difference between the transport source and the transport destination was adjusted to 0.8 MPa.

[0531] [Manufacture of polyethylene powder and microporous membrane]

[0532] (Example 1)

[0533] As described below, an ethylenic polymer (X A ) was polymerized in the polymerization reactor of the first stage, and an ethylenic polymer (Y A ) was polymerized in the polymerization reactor of the second stage to obtain polyethylene powder (A).

[0534] The viscosity-average molecular weight of the polyethylene powder (A) was 300,000, and the median particle diameter was 101 μm.

[0535] The results of carrying out the above various evaluations on the polyethylene powder (A) and the microporous membrane of the polyethylene powder (A) manufactured by the above [method for manufacturing a microporous membrane] are shown in Table 1.

[0536] <(1) Polymerization of ethylenic polymer (X A )>

[0537] The polymerization of the ethylenic polymer was carried out using a 300 L vessel-type polymerization reactor with a stirring blade having 3 retreat blades and 3 baffles. n-Hexane as a solvent was supplied at a flow rate of 40 L / hour, and the total liquid volume was adjusted so that the slurry concentration was 16% by mass. The stirring speed was set to 200 rpm. The Ziegler-Natta catalyst (A) was used as the polymerization catalyst and was supplied in such a way that the production rate of the ethylenic polymer was 9.0 kg / hour. In the polymerization catalyst, STATSAFE 3000 (90 g / L) diluted with n-hexane was added in an amount of 20 mass ppm relative to the production rate of the ethylenic polymer. Triisobutylaluminum and diisobutylaluminum hydride (9:1 mixture) were used as the cocatalyst components and were supplied at 10 mmol / hour. 26% by mole (mole ratio: hydrogen / (ethylene + hydrogen)) of hydrogen was supplied. The polymerization temperature was set to 60 °C, the polymerization pressure was set to 0.7 MPaG, and the average residence time was set to 3.3 hours.

[0538] The ethylenic polymer (X A) has a viscosity-average molecular weight of 300,000. Additionally, the polymerization activity in the polymerization reactor in the first stage is 12,000 g per 1 g of catalyst.

[0539] The polymerization slurry in the polymerization reactor is introduced into an intermediate flash tank at a pressure of 0.05 MPaG and a temperature of 70 °C in such a way that the liquid level height in the polymerization reactor remains constant, and unreacted ethylene and hydrogen are separated in this intermediate flash tank.

[0540] <(2) Polymerization of vinyl polymer (Y A )

[0541] The polymerization slurry containing vinyl polymer (X A ) is transferred from the above intermediate flash tank to a 300 L polymerization reactor of container type with a stirring blade having 3 retreating blades and 3 baffles, and then the polymerization of vinyl polymer (Y A ) is carried out.

[0542] The total liquid volume is adjusted so that the slurry concentration is 40% by mass, the stirring speed is set at 450 rpm, and triisobutylaluminum and diisobutylaluminum hydride (9:1 mixture) as cocatalyst components are supplied at 10 mmol / h. 10 mol% (molar ratio: hydrogen / (ethylene + hydrogen)) of hydrogen is supplied. The polymerization temperature is set at 78 °C, the polymerization pressure is set at 0.75 MPaG so that the production rate is 11.1 kg / h, and the average residence time is set at 0.75 h.

[0543] The vinyl polymer (Y A ) obtained in such a way has a viscosity-average molecular weight of 300,000. Additionally, the polymerization activity in the polymerization reactor in the second stage is 14,700 g per 1 g of catalyst.

[0544] The polymerization slurry in the polymerization reactor is introduced into a final flash tank at a pressure of 0.05 MPaG and a temperature of 70 °C in such a way that the liquid level height in the polymerization reactor remains constant, and unreacted ethylene and hydrogen are separated in this final flash tank. Then, the polymerization slurry is continuously fed into a centrifuge by a pump, the polymer is separated from the solvent in this centrifuge, and then the separated polyethylene powder is fed into a rotary kiln dryer controlled at 90 °C and dried while spraying nitrogen, thereby obtaining polyethylene powder (A). It should be noted that in this drying process, steam is sprayed onto the polyethylene powder to deactivate the catalyst and cocatalyst.

[0545] (Example 2)

[0546] As shown below, vinyl polymer (X is polymerized in the polymerization reactor in the first stageB ) is polymerized in the polymerization reactor in the second stage to obtain an ethylenic polymer (Y B ), and thus polyethylene powder (B) is obtained.

[0547] The polyethylene powder (B) has a viscosity-average molecular weight of 900,000 and a median particle size of 99 μm.

[0548] The results of carrying out the above various evaluations on the microporous membrane of the polyethylene powder (B) and the polyethylene powder (B) produced by the above [method for producing a microporous membrane] are shown in Table 1.

[0549] <(3) Polymerization of ethylenic polymer (X B )>

[0550] Except that the supply amount of hydrogen is adjusted to 16 mol%, polymerization is carried out in the same manner as in the above (Example 1) for (X A ), thereby obtaining an ethylenic polymer (X B ). The viscosity-average molecular weight of the obtained ethylenic polymer (X B ) is 900,000. In addition, the polymerization activity in the polymerization reactor in the first stage is 13,000 g per 1 g of catalyst.

[0551] <(4) Polymerization of ethylenic polymer (Y B )>

[0552] Except that the stirring speed is adjusted to 550 rpm and the supply amount of hydrogen is adjusted to 2 mol%, polymerization is carried out in the same manner as in the above (Example 1) for (Y A ), thereby obtaining an ethylenic polymer (Y B ).

[0553] The viscosity-average molecular weight of the obtained ethylenic polymer (Y B ) is 900,000. In addition, the polymerization activity in the polymerization reactor in the second stage is 15,900 g per 1 g of catalyst.

[0554] The same separation and drying operations as in the above (Example 1) are carried out on the polymerization slurry in the polymerization reactor, thereby obtaining polyethylene powder (B).

[0555] (Example 3)

[0556] <(5) Polymerization of polyethylene powder (C)>

[0557] Polymerization of polyethylene powder was carried out using a 300L container-type polymerization reactor with a stirring blade having 3 backward blades and 3 baffles. n-Hexane as a solvent was supplied at a flow rate of 40 L / hour, the total liquid volume was adjusted so that the slurry concentration was 40 mass%, and the stirring speed was set at 550 rpm. Ziegler-Natta catalyst (B) was used as the polymerization catalyst, and it was supplied in such a way that the production rate of polyethylene powder was 13 kg / hour. In the polymerization catalyst, STATSAFE3000 (90 g / L) diluted with n-hexane was added in an amount of 20 mass ppm relative to the production rate of polyethylene powder. Triisobutylaluminum and diisobutylaluminum hydride (9:1 mixture) were used as cocatalyst components and supplied at 10 mmol / hour. Hydrogen was supplied at 2.9 mol% (molar ratio: hydrogen / (ethylene + hydrogen)). The polymerization temperature was set at 78 °C, the polymerization pressure was set at 0.3 MPaG, and the average residence time was set at 3.0 hours. The polymerization slurry in the polymerization reactor was introduced into a flash tank at a pressure of 0.05 MPaG and a temperature of 70 °C in such a way that the liquid level height in the polymerization reactor was kept constant, and unreacted ethylene and hydrogen were separated in the flash tank. Then, the polymerization slurry was continuously fed from the flash tank into a centrifuge by a pump to separate the polymer from the solvent, and then the separated polyethylene powder was fed into a rotary kiln dryer controlled at 90 °C and dried while spraying nitrogen. It should be noted that in this drying process, steam was sprayed onto the polyethylene powder to deactivate the catalyst and cocatalyst.

[0558] The polyethylene powder (C) obtained in this way had a viscosity-average molecular weight of 900,000 and a median particle diameter of 110 μm. In addition, the polymerization activity in the polymerization reactor was 20,000 g per 1 g of catalyst.

[0559] The results of carrying out the above various evaluations on the microporous membranes of the polyethylene powder (C) and the polyethylene powder (C) of the microporous membrane manufactured by the above [manufacturing method of microporous membrane] are shown in Table 1.

[0560] (Example 4)

[0561] As follows, an ethylenic polymer (X D ) was polymerized in the polymerization reactor in the first stage, and an ethylenic polymer (Y D ) was polymerized in the polymerization reactor in the second stage, whereby polyethylene powder (D) was obtained. The polyethylene powder (D) had a viscosity-average molecular weight of 300,000 and a median particle diameter of 105 μm.

[0562] The results of carrying out the above various evaluations on the microporous membranes of the polyethylene powder (D) and the polyethylene powder (D) of the microporous membrane manufactured by the above [manufacturing method of microporous membrane] are shown in Table 1.

[0563] <(6) Polymerization of vinyl polymer (X D )>

[0564] Except for changing the polymerization catalyst to a Ziegler - Natta catalyst (C), polymerization was carried out in the same manner as in the above (Example 1) for (X A ) to obtain a vinyl polymer (X D ). The viscosity - average molecular weight of the obtained vinyl polymer (X D ) was 300,000. In addition, the polymerization activity in the polymerization reactor in the first stage was 11,500 g per 1 g of catalyst.

[0565] <(7) Polymerization of vinyl polymer (Y D )>

[0566] Polymerization was carried out in the same manner as in the above (Example 1) for (Y A ) to obtain a vinyl polymer (Y D ). The viscosity - average molecular weight of the obtained vinyl polymer (Y D ) was 300,000. In addition, the polymerization activity in the polymerization reactor in the second stage was 14,000 g per 1 g of catalyst.

[0567] The same separation and drying operations as in the above (Example 1) were carried out on the polymerization slurry in the polymerization reactor to obtain polyethylene powder (D).

[0568] (Example 5)

[0569] <(8) Polymerization of polyethylene powder (E)>

[0570] Except for adjusting the flow rate of n - hexane to 80 L / hour, the production rate to 10 kg / hour, the slurry concentration to 16 mass%, and the average residence time to 1.75 hours, polymerization was carried out in the same manner as in the above (Example 3) to obtain polyethylene powder (E).

[0571] The viscosity - average molecular weight of the polyethylene powder (E) obtained in this way was 900,000, and the median particle size was 108 μm. In addition, the polymerization activity in the polymerization reactor was 19,000 g per 1 g of catalyst.

[0572] The results of carrying out the above various evaluations on the polyethylene powder (E) and the microporous membrane of polyethylene powder (E) manufactured by the above [Manufacturing method of microporous membrane] are shown in Table 1.

[0573] [Example 6]

[0574] As shown below, an ethylenic polymer (X F ) is polymerized in the polymerization reactor in the first stage, and an ethylenic polymer (Y F ) is polymerized in the polymerization reactor in the second stage, whereby polyethylene powder (F) is obtained.

[0575] The polyethylene powder (F) has a viscosity-average molecular weight of 300,000 and a median particle diameter of 95 μm.

[0576] The results of carrying out the various evaluations described above on the microporous membranes of the polyethylene powder (F) and the polyethylene powder (F) produced by the above [method for producing a microporous membrane] are shown in Table 1.

[0577] <(9) Polymerization of ethylenic polymer (X F )>

[0578] Polymerization was carried out in the same manner as (X A ) in the above (Example 1), whereby an ethylenic polymer (X F ) was obtained. The obtained ethylenic polymer (X F ) has a viscosity-average molecular weight of 300,000. In addition, the polymerization activity in the polymerization reactor in the first stage is 12,000 g per 1 g of catalyst.

[0579] <(10) Polymerization of ethylenic polymer (Y F )>

[0580] Polymerization was carried out in the same manner as (Y A ) in the above (Example 1), except that the slurry concentration was adjusted to 30% by mass and the stirring speed was adjusted to 230 rpm, whereby an ethylenic polymer (Y F ) was obtained. The obtained ethylenic polymer (Y F ) has a viscosity-average molecular weight of 300,000. In addition, the polymerization activity in the polymerization reactor in the second stage is 14,500 g per 1 g of catalyst.

[0581] The polymerization slurry in the polymerization reactor was separated and dried in the same manner as in the above (Example 1), whereby polyethylene powder (F) was obtained.

[0582] (Example 7)

[0583] <(11) Polymerization of polyethylene powder (G)>

[0584] Polymerization was carried out in the same manner as in the above (Example 3), except that the production rate was adjusted to 9 kg / hour, the slurry concentration was adjusted to 30% by mass, and the supply amount of hydrogen was adjusted to 1 mol%, whereby polyethylene powder (G) was obtained.

[0585] The polyethylene powder (G) obtained in this way has a viscosity-average molecular weight of 2,000,000 and a median particle diameter of 103 μm. In addition, the polymerization activity in the polymerization reactor is 18,000 g per 1 g of catalyst.

[0586] The results of carrying out the above various evaluations on the microporous membrane of the polyethylene powder (G) and the polyethylene powder (G) produced by the above [method for producing a microporous membrane] are shown in Table 1.

[0587] (Example 8)

[0588] As follows, an ethylenic polymer (X H ) was polymerized in the polymerization reactor in the first stage, and an ethylenic polymer (Y H ) was polymerized in the polymerization reactor in the second stage, whereby polyethylene powder (H) was obtained. The polyethylene powder (H) has a viscosity-average molecular weight of 900,000 and a median particle diameter of 99 μm. The results of carrying out the above various evaluations on the microporous membrane of the polyethylene powder (H) and the polyethylene powder (H) produced by the above [method for producing a microporous membrane] are shown in Table 1.

[0589] <(12) Polymerization of ethylenic polymer (X H )>

[0590] Polymerization was carried out in the same manner as in (Example 2) for (X B ) except that the stirring speed was adjusted to 300 rpm and the slurry concentration was adjusted to 30% by mass, thereby obtaining an ethylenic polymer (X H ). The obtained ethylenic polymer (X H ) has a viscosity-average molecular weight of 900,000. In addition, the polymerization activity in the polymerization reactor in the first stage is 13,000 g per 1 g of catalyst.

[0591] <(13) Polymerization of ethylenic polymer (Y H )>

[0592] Polymerization was carried out in the same manner as in (Example 2) for (Y B ) except that the stirring speed was adjusted to 450 rpm, thereby obtaining an ethylenic polymer (Y H ). The obtained ethylenic polymer (Y H ) has a viscosity-average molecular weight of 900,000. In addition, the polymerization activity in the polymerization reactor in the second stage is 15,900 g per 1 g of catalyst.

[0593] The same separation and drying operations as in (Example 1) were carried out on the polymerization slurry in the polymerization reactor, thereby obtaining polyethylene powder (H).

[0594] (Comparative Example 1)

[0595] <(14) Polymerization of Polyethylene Powder (I)>

[0596] Polymerization was carried out in the same manner as in the above (Example 5), except that the stirring speed was adjusted to 230 rpm and the polymerization catalyst was changed to Ziegler-Natta catalyst (E), to obtain polyethylene powder (I).

[0597] The viscosity-average molecular weight of the polyethylene powder (I) thus obtained was 900,000, and the median particle diameter was 111 μm.

[0598] In addition, the polymerization activity in the polymerization reactor was 18,000 g per 1 g of the catalyst.

[0599] The results of the above various evaluations on the microporous membranes of polyethylene powder (I) and the polyethylene powder (I) produced by the above [Method for Producing Microporous Membrane] are shown in Table 2.

[0600] (Comparative Example 2)

[0601] <(15) Polymerization of Polyethylene Powder (J)>

[0602] Polymerization was carried out in the same manner as in the above (Example 3), except that the polymerization catalyst was changed to Ziegler-Natta catalyst (D), to obtain polyethylene powder (J).

[0603] The viscosity-average molecular weight of the polyethylene powder (J) thus obtained was 900,000, and the median particle diameter was 113 μm. In addition, the polymerization activity in the polymerization reactor was 18,500 g per 1 g of the catalyst.

[0604] The results of the above various evaluations on the microporous membranes of polyethylene powder (J) and the polyethylene powder (J) produced by the above [Method for Producing Microporous Membrane] are shown in Table 2.

[0605] (Comparative Example 3)

[0606] As shown below, an ethylenic polymer (X K ) was polymerized in the polymerization reactor in the first stage, and an ethylenic polymer (Y K ) was polymerized in the polymerization reactor in the second stage, to obtain polyethylene powder (K).

[0607] The viscosity-average molecular weight of the polyethylene powder (K) was 900,000, and the median particle diameter was 94 μm.

[0608] The results of carrying out the various evaluations described above on the polyethylene powder (K) and the microporous membrane of the polyethylene powder (K) produced by the above [method for producing a microporous membrane] are shown in Table 2.

[0609] <(16) Polymerization of vinyl polymer (X K )

[0610] Polymerization was carried out in the same manner as in (Example 2) above for (X B ) except that the stirring speed was adjusted to 450 rpm and the slurry concentration was adjusted to 30% by mass, thereby obtaining a vinyl polymer (X K ).

[0611] The obtained vinyl polymer (X K ) had a viscosity-average molecular weight of 900,000. In addition, the polymerization activity in the polymerization reactor in the first stage was 12,500 g per 1 g of catalyst.

[0612] <(17) Polymerization of vinyl polymer (Y K )

[0613] Polymerization was carried out in the same manner as in (Example 2) above for (Y B ) except that the stirring speed was adjusted to 230 rpm and the slurry concentration was adjusted to 20% by mass, thereby obtaining a vinyl polymer (Y K ). The obtained vinyl polymer (Y K ) had a viscosity-average molecular weight of 900,000. In addition, the polymerization activity in the polymerization reactor in the second stage was 15,400 g per 1 g of catalyst.

[0614] The polymerization slurry in the polymerization reactor was separated and dried in the same manner as in (Example 1) above, thereby obtaining polyethylene powder (K).

[0615] (Comparative Example 4)

[0616] <(18) Polymerization of polyethylene powder (L)>

[0617] Polymerization was carried out in the same manner as in (Example 5) above except that the stirring speed was adjusted to 230 rpm and the polymerization catalyst was changed to Ziegler-Natta catalyst (D), thereby obtaining polyethylene powder (L).

[0618] The polyethylene powder (L) obtained in this way had a viscosity-average molecular weight of 900,000 and a median particle diameter of 99 μm. In addition, the polymerization activity in the polymerization reactor was 19,000 g per 1 g of catalyst.

[0619] The results of the above various evaluations on the polyethylene powder (L) and the microporous membrane of the polyethylene powder (L) produced by the above [method for producing a microporous membrane] are shown in Table 2.

[0620] (Comparative Example 5)

[0621] As follows, an ethylenic polymer (X M ) was polymerized in the polymerization reactor of the first stage, and an ethylenic polymer (Y M ) was polymerized in the polymerization reactor of the second stage, whereby a polyethylene powder (M) was obtained.

[0622] The polyethylene powder (M) had a viscosity-average molecular weight of 600,000 and a median particle diameter of 87 μm.

[0623] The results of the above various evaluations on the polyethylene powder (M) and the microporous membrane of the polyethylene powder (M) produced by the above [method for producing a microporous membrane] are shown in Table 2.

[0624] <(16) Polymerization of ethylenic polymer (X M )>

[0625] Except that the flow rate of n-hexane was adjusted to 20 L / hour, the slurry concentration was adjusted to 40 mass%, the polymerization catalyst was changed to Ziegler-Natta catalyst (F), the production rate was adjusted to 13 kg / hour, the supply amount of hydrogen was adjusted to 6 mol%, the polymerization temperature was adjusted to 80 °C, and the polymerization pressure was adjusted to 0.5 MPaG, polymerization was carried out in the same manner as in (Example 2) for (X B ), whereby an ethylenic polymer (X M ) was obtained.

[0626] The obtained ethylenic polymer (X M ) had a viscosity-average molecular weight of 800,000. In addition, the polymerization activity in the polymerization reactor of the first stage was 70,000 g per 1 g of catalyst.

[0627] <(17) Polymerization of ethylenic polymer (Y M )>

[0628] Except that the stirring speed was adjusted to 230 rpm, the production rate was adjusted to 7 kg / hour, the supply amount of hydrogen was adjusted to 25 mol%, the polymerization temperature was adjusted to 80 °C, and the polymerization pressure was adjusted to 0.5 MPaG, polymerization was carried out in the same manner as in (Example 2) for (Y B ), whereby an ethylenic polymer (Y M ) was obtained. The obtained ethylenic polymer (Y MThe viscosity-average molecular weight of is 150,000. In addition, the polymerization activity in the polymerization reactor in the second stage is 38,000 g per 1 g of the catalyst.

[0629] The same separation and drying operations as those in the above (Example 1) were performed on the polymerization slurry in the polymerization reactor, and thus polyethylene powder (M) was obtained.

[0630] (Comparative Example 6)

[0631] As shown below, an ethylenic polymer (X N ) was polymerized in the polymerization reactor in the first stage, and an ethylenic polymer (Y N ) was polymerized in the polymerization reactor in the second stage, and thus polyethylene powder (N) was obtained.

[0632] The viscosity-average molecular weight of the polyethylene powder (N) is 600,000, and the median particle diameter is 89 μm.

[0633] The results of performing the above various evaluations on the polyethylene powder (N) and the microporous membrane of the polyethylene powder (N) produced by the above [method for producing a microporous membrane] are shown in Table 2.

[0634] <(16) Polymerization of ethylenic polymer (X N )>

[0635] Polymerization was carried out in the same manner as in the above (Comparative Example 5) for (X M ) except that the polymerization catalyst was changed to a Ziegler-Natta catalyst (G), and thus an ethylenic polymer (X N ) was obtained.

[0636] The viscosity-average molecular weight of the obtained ethylenic polymer (X N ) is 800,000. In addition, the polymerization activity in the polymerization reactor in the first stage is 70,000 g per 1 g of the catalyst.

[0637] <(17) Polymerization of ethylenic polymer (Y N )>

[0638] Polymerization was carried out in the same manner as in the above (Comparative Example 5) for (Y M ), and thus an ethylenic polymer (Y N ) was obtained. The viscosity-average molecular weight of the obtained ethylenic polymer (Y N ) is 150,000. In addition, the polymerization activity in the polymerization reactor in the second stage is 38,000 g per 1 g of the catalyst.

[0639] The same separation and drying operations as those in the above (Example 1) were performed on the polymerization slurry in the polymerization reactor, and thus polyethylene powder (N) was obtained.

[0640] [Table 1]

[0641]

[0642] [Table 2]

[0643]

[0644] This application is based on Japanese Patent Application (Japanese Patent Application No. 2020-196103) filed with the Japan Patent Office on November 26, 2020, the content of which is incorporated herein by reference.

[0645] Industrial Applicability

[0646] The polyethylene powder of the present invention has industrial applicability as a raw material for various molded articles, microporous membranes, battery separators, and fibers.

Claims

1. A microporous membrane comprising polyethylene powder, in, The viscosity average molecular weight of the polyethylene powder is 300,000 or more and 10,000,000 or less, When a three-component approximation is performed on a free induction decay curve of the polyethylene powder obtained by the Carr Purcell Meiboom Gill method in pulse NMR, the relaxation time T of each component and the abundance ratio R of each component satisfy the following <Requirement (1)> and <Requirement (2)>, The uniformity of the thickness of the microporous membrane is less than 1 μm, <Requirements (1)> At 180° C., the entanglement index determined by the following (Formula I) is 12 milliseconds or more and 25 milliseconds or less, (Tangle Index) = T α ×R α / (R α +R β )+T β ×R β / (R α +R β )...(Formula I) T α : relaxation time of the component α with low mobility, the unit of the relaxation time is milliseconds, R α : The existence ratio of the component α with low mobility, the unit of the existence ratio is %, T β : relaxation time of the component β with medium mobility, the unit of relaxation time is milliseconds, R β : The proportion of the component β with medium mobility, the unit of the proportion is %, <Requirements (2)> At 180°C, the ratio of the component having intermediate mobility determined by the following (Formula II) is 0.25 or more and 0.5 or less, (Ratio of components with moderate mobility) = R β / (R α +R β ) ……(Formula II) The relaxation time T and the abundance ratio R are obtained by curve fitting the free induction decay obtained by the fourth pulse NMR measurement using the function represented by the following <Formula 1>: <Formula 1> f(t)=R α exp(-t / T α )+R β exp(-t / T β )+R γ exp(-t / T γ ) Among them, R α +R β +R γ =100, t: variable, i.e. the time elapsed from the start of the pulse radiation T α : relaxation time of the component α with low mobility, the unit of the relaxation time is milliseconds, R α : The existence ratio of the component α with low mobility, the unit of the existence ratio is %, T β : relaxation time of the component β with medium mobility, the unit of relaxation time is milliseconds, R β : The proportion of the component β with medium mobility, the unit of the proportion is %, T γ : relaxation time of the highly mobile component γ, the unit of the relaxation time is milliseconds, R γ : The abundance ratio of the component γ with high mobility, the unit of the abundance ratio is %.

2. The microporous membrane according to claim 1, in, The puncture strength of the microporous membrane is 0.7N / (g / m 2 )above.

3. The microporous membrane according to claim 1 or 2, in, The heat shrinkage rate of the microporous film is less than 25%.

4. The microporous membrane according to claim 1 or 2, in, The creep resistance of the microporous membrane is less than 10%.

5. The microporous membrane according to claim 1, in, The microporous membrane is a separator for batteries.

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