JP2017145306A - Polyethylene-based powder and manufacturing method thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide polyethylene-based powder excellent in solubility in a solvent at low-temperature molding, and capable of continuously and stably forming a uniform microporous film even when heterogeneous polyethylene-based powder is blended and molded at a low-temperature, and a manufacturing method thereof.SOLUTION: Polyethylene-based powder includes an ethylene homopolymer or a copolymer of ethylene and α-olefin of 3-6 C. The ratio of a median diameter and a modal diameter of pores is 0.80-1.20 when measured in a mercury penetration method, and the density is 920 kg/m-960 kg/m.SELECTED DRAWING: None

Description

  The present invention relates to a polyethylene powder and a method for producing the same.

  Ethylene homopolymers or ethylene-α-olefin copolymer powders (hereinafter collectively referred to as “polyethylene powders”) are a wide variety of films, sheets, microporous membranes, fibers, foams and pipes. Used for applications. In particular, polyethylene powder is used as a raw material for microporous membranes for secondary battery separators typified by lead-acid batteries and lithium-ion batteries and high-strength fibers.

  The reason why the polyethylene powder is used in these applications includes excellent stretch processability, high strength, high chemical stability, and excellent long-term reliability. The microporous membrane for a secondary battery separator is produced by kneading polyethylene powder in a state of being dissolved in a solvent, for example, in an extruder at a high temperature, and then stretching and removing the solvent and the like.

  A microporous membrane for a secondary battery separator obtained by dissolving polyethylene powder in a solvent is required to improve molding operation stability, productivity, and membrane quality. An excellent solubility is desired so that unmelted polyethylene-based powder does not remain as particles.

Conventionally, as a technique for increasing the solubility of polyethylene powder in a solvent, focusing on the shape, specific surface area, and pore volume of the powder, for example, in Patent Document 1, the average particle diameter is 1-150 μm and the powder specific surface area is It is disclosed that polyethylene of 0.7 m ² / g or more is used as a raw material. Moreover, in patent document 2, the powder specific surface area is 0.10 m < ² > / g or more and 0.30 m < ² > / g or less, and the polyethylene whose pore volume calculated | required by the mercury intrusion method is 0.85 mL / g or less is used as a raw material. It is disclosed to use.

Japanese Patent No. 4799179 Japanese Patent No. 5774084

  However, in recent years, development has been promoted aiming at higher energy density, higher capacity, higher output, and safety of secondary batteries, and as a result, separators also require high strength, high permeability, etc. In addition, there is an increasing demand for improvement in pore blocking properties and heat resistance, and it is extremely difficult to achieve a single polyethylene powder as a raw material for improving these properties. It is common to blend system powders and study their types and blending ratios to improve their properties.

  At that time, different types of polyethylene powders have different solubility in solvents due to differences in molecular weight and density, so there is a high possibility that unmelted polyethylene powder will remain as particles in the film. , Film uniformity may be reduced.

  Furthermore, the growth in demand for microporous membranes for secondary battery separators is remarkable, and it is strongly desired to improve productivity. Specifically, since it is possible to continuously and stably produce at a lower temperature without stopping the extruder or the like, that is, it is desired to form a uniform microporous film even at a lower temperature. Further improvement in solubility in the kneading step is desired.

  The present invention has been made in view of the above-mentioned problems, and is excellent in solubility in a solvent in low-temperature molding, and a uniform microporous membrane can be continuously and stably even when low-temperature molding is performed by blending different types of polyethylene powder. It is an object of the present invention to provide a polyethylene powder that can be molded and a method for producing the same.

  As a result of diligent research to solve the above-mentioned problems of the prior art, the present inventors have found that a polyethylene-based powder having a ratio of median diameter to mode diameter and density of pores measured by mercury porosimetry is within a predetermined range. The present inventors have found that the above-described problems can be solved, and have reached the present invention.

That is, the present invention is as follows.
[1]
An ethylene homopolymer, or a copolymer of ethylene and an α-olefin having 3 to 6 carbon atoms,
The ratio of pore median diameter and mode diameter measured by mercury porosimetry is 0.80 or more and 1.20 or less,
The density is 920 kg / m ³ or more and 960 kg / m ³ or less,
Polyethylene powder.
[2]
The pore volume measured by the mercury intrusion method is 0.85 mL / g or more and 1.40 mL / g or less,
The pore mode diameter measured by mercury porosimetry is 30 μm or more and 45 μm or less,
The polyethylene-based powder described in [1] above.
[3]
The average particle size measured by sieving particle size distribution measurement is 50 to 300 μm, and the proportion of powder less than 106 μm is 20% by mass or more and 50% by mass or less,
The polyethylene powder according to [1] or [2] above.
[4]
Bulk density is 0.30 g / cm ³ or more 0.45 g / cm ³ or less,
The polyethylene powder according to any one of [1] to [3] above.
[5]
The viscosity average molecular weight (Mv) is 10,000 or more and 3000000 or less,
The polyethylene powder according to any one of [1] to [4] above.
[6]
The polyethylene according to any one of [1] to [5] above, by homopolymerizing ethylene using a catalyst or copolymerizing ethylene and an α-olefin having 3 to 6 carbon atoms. Including a polymerization step to obtain a system powder,
Wherein the catalyst has an average particle diameter is at 1.0μm or 20μm or less and a pore volume not more than 1.0 mL / g or more 2.5 mL / g, specific surface area, 400 meters ² / g or more 800 m ² / g or less, having an inorganic support material as a catalyst support,
Production method of polyethylene powder.
[7]
For secondary battery separator,
The polyethylene powder according to any one of [1] to [5] above.
[8]
For lithium ion secondary battery separator,
The polyethylene powder according to any one of [1] to [5] above.
[9]
For lead-acid battery separator,
The polyethylene powder according to any one of [1] to [5] above.

  According to the present invention, a polyethylene powder excellent in solubility in a solvent in low temperature molding, and capable of forming a uniform microporous film even when low temperature molding is performed by blending different types of polyethylene powder, and its A manufacturing method can be provided. Surprisingly, it has excellent powder fluidity and suppresses compositional deviation in the molding machine caused by classification in the upper hopper of the molding machine when blending and molding different types of polyethylene powder. Therefore, a uniform microporous membrane can be produced continuously and stably.

  Hereinafter, a mode for carrying out the present invention (hereinafter also referred to as “the present embodiment”) will be described in detail. In addition, this invention is not limited to this embodiment, It can implement in various deformation | transformation within the range of the summary.

[Polyethylene powder]
The polyethylene-based powder of the present embodiment includes an ethylene homopolymer or a copolymer of ethylene and an α-olefin having 3 to 6 carbon atoms, and has a pore median diameter and mode measured by a mercury intrusion method. The diameter ratio is 0.80 or more and 1.20 or less, and the density is 920 kg / m ³ or more and 960 kg / m ³ or less.

  By having the above-mentioned configuration, the polyethylene powder has excellent solubility in a solvent during low-temperature molding, and even when blended with different types of polyethylene-based powder, it can form a uniform microporous film. It becomes. Surprisingly, it has excellent powder fluidity and suppresses compositional deviation in the molding machine caused by classification in the upper hopper of the molding machine when blending and molding different types of polyethylene powder. Therefore, a uniform microporous membrane can be produced continuously and stably. Moreover, the polyethylene powder which has such a characteristic can be used suitably for a secondary battery separator, a separator for lithium ion secondary batteries, and a lead storage battery separator.

  Hereinafter, each of the above requirements will be described in detail.

The polyethylene-based powder includes an ethylene homopolymer or a copolymer of ethylene and an α-olefin having 3 to 6 carbon atoms (hereinafter also simply referred to as “comonomer”). Although the comonomer which can be used by this embodiment is not specifically limited, For example, the alpha-olefin of a following formula is mentioned.
H ₂ C═CHR ²
(In the formula, R ² represents a linear or branched alkyl group having 1 to 4 carbon atoms.)

  Specific comonomers are not particularly limited, and examples include propylene, 1-butene, 1-pentene, 1-hexene, and 4-methyl-1-pentene. Among these, propylene and 1-butene are preferable from the viewpoint of economy and ease of handling. Further, by using an α-olefin having 6 or less carbon atoms, there is little entanglement between polymer chains, and the solubility in a solvent tends to be excellent.

  From the viewpoint of adjusting density, the mol% of ethylene in the polyethylene powder is preferably 80% or more and 100% or less, more preferably 85% or more and 99% or less, and still more preferably 90%. It is 98% or less.

  The ratio of the median diameter and mode diameter of the pores determined by the mercury intrusion method of the polyethylene powder is 0.80 or more and 1.20 or less, preferably 0.85 or more and 1.11 or less, more preferably 0. .90 or more and 1.06 or less. When the ratio of the median diameter and mode diameter of the pores determined by the mercury intrusion method is 0.80 or more and 1.20 or less, the solubility in a solvent in low temperature molding is excellent. The ratio between the median diameter and the mode diameter is an index representing the uniformity of the pore diameter existing in the polyethylene-based powder, and the closer to 1.0 is, the more uniform the pore diameter is. If the pore size is uniform, the solvent can easily penetrate into the pores of the powder, and part of the powder particles do not dissolve locally, and the inside of the pores and the outside of the surface dissolve simultaneously, It is thought that there is no undissolved residue when it is made into a film. Surprisingly, the polyethylene-based powder of this embodiment having a uniform pore diameter is also excellent in powder flowability.

  In the present embodiment, the method for controlling the ratio between the median diameter and the mode diameter of the pores determined by the mercury intrusion method to 0.80 or more and 1.20 or less is not particularly limited. It can be controlled by using a catalyst carrier whose diameter, pore volume, specific surface area and the like are controlled within a predetermined range. Regarding the adjustment of the production process, specifically, (1) after the polymerization vessel, after removing ethylene, hydrogen, and α-olefin in a flash tank, the buffer tank of a predetermined condition is held in a state where no raw material is supplied. (2) Decreasing the solvent separation efficiency so that the amount of solvent contained in the polyethylene powder increases after the solvent separation step.

  The reason why the ratio of the median diameter and the mode diameter of the pores required by the mercury intrusion method can be controlled within the above range through the above-mentioned process is not necessarily clear, but (1) a low-temperature / low-pressure buffer tank without raw material supply Since a small amount of raw material is present, a part of the active catalyst particles are polymerized to generate a powder of less than 106 μm (hereinafter also referred to as fine powder). (2) Solvent in a centrifuge By weakening the separation, a low molecular weight component (hereinafter also referred to as WAX) that is easily dissolved in hexane is incorporated into the powder, and then through a drying step, the WAX and the fine powder are aggregated in the powder to be uniform. It is assumed that pores are formed. The ratio of the median diameter to the mode diameter of the pores of the polyethylene powder is measured by the method described in the examples described later.

  The “median diameter” means the value of the X axis (pore diameter) corresponding to the middle between the minimum value and the maximum value of the Y axis (pore volume or pore specific surface area) of the curve in the integrated pore distribution, “Mode diameter” means the pore diameter at which the differential value is maximum in the differential pore distribution. The “pore volume” is a value obtained by dividing the integrated value of the pore volume into which mercury has been injected up to the maximum pressure at the time of measurement by the sample weight.

The density of polyethylene powder is at 920 kg / m ³ or more 960 kg / m ³ or less, preferably 925 kg / m ³ or more 955 kg / m ³ or less, more preferably at 930 kg / m ³ or more 950 kg / m ³ or less . When the density of the polyethylene powder is 920 kg / m ³ or more and 960 kg / m ³ or less, the solubility in a solvent in low temperature molding is excellent.

  The density of the polyethylene powder is not particularly limited, but can be adjusted by, for example, the amount of introduction with other α-olefin (also referred to as comonomer) mainly copolymerized with ethylene. The density of polyethylene-type powder is measured by the method as described in the Example mentioned later.

  The pore volume of the polyethylene powder measured by mercury porosimetry is preferably 0.85 mL / g or more and 1.40 mL / g or less, more preferably 0.90 mL / g or more and 1.35 mL / g or less. More preferably, it is 0.95 mL / g or more and 1.30 mL / g or less. When the pore volume is 0.85 mL / g or more, the solvent tends to penetrate and dissolve easily, and when it is 1.40 mL / g or less, the solvent easily penetrates and dissolves from the surface. Since the inside of the pores and the outside of the surface dissolve simultaneously, there is a tendency that undissolved residue is unlikely to occur when the film is formed.

  The pore volume is related to the internal structure of the polyethylene powder and the aggregation state of the polyethylene powder, and exists when the volume of the pores penetrating from the surface to the inside and the particles of the polyethylene powder are closely aggregated. It means the space volume inside the agglomerated particles.

  The pore volume of the polyethylene powder is not particularly limited in order to set the pore volume to 0.85 mL / g or more and 1.40 mL / g or less. For example, a catalyst carrier in which the average particle diameter, pore volume, specific surface area, etc. are controlled. By adjusting the slurry concentration calculated from the ratio of the amount of solvent and the amount of powder during polymerization, the introduction amount of other α-olefins (also referred to as comonomer) mainly copolymerized with ethylene, etc. Can be adjusted.

  In Japanese Patent No. 5774084, when the pore volume is increased, there are many internal pores that lead from the surface, and solvent impregnation during solvent kneading does not reach the inside of the particles sufficiently, so that particles that embed gas inside are formed. Therefore, although there is a description that the solubility of the polyethylene powder is deteriorated, in the present invention, since the pore diameter is controlled, excellent solubility is exhibited even in the above-mentioned range of the pore volume. The pore volume of the polyethylene powder is measured by the method described in Examples described later.

  The mode diameter of the pores measured by the mercury intrusion method of the polyethylene powder is preferably 30 μm or more and 45 μm or less, more preferably 31 μm or more and 44 μm or less, and further preferably 32 μm or more and 43 μm or less. When the mode diameter is 30 μm or more, the pore diameter present on the particle surface of the polyethylene powder is large, and the solvent tends to be easily impregnated into the inside of the particle and the solubility tends to be improved. The solvent easily permeates, does not start to dissolve from the surface, and the inside of the pores and the outside of the surface dissolve at the same time. The mode diameter of the pores of the polyethylene powder is measured by the method described in the examples described later.

  The average particle size of the polyethylene powder is preferably 50 μm or more and 300 μm or less, more preferably 60 μm or more and 250 μm or less, and still more preferably 70 μm or more and 200 μm or less. The average particle size of the polyethylene powder can be measured by sieving particle size distribution measurement. Specifically, multiple types of sieves and trays specified in JIS Z8801 are prepared, the sieves are stacked on the tray in ascending order of opening, and polyethylene powder is added to the uppermost sieve, followed by low-tap type sieve shaking In the integral curve obtained by integrating the mass of the powder remaining on each sieve and the saucer from the side having a large opening after setting in the machine and classifying, the average particle size can be 50%. As a method of controlling the average particle diameter within the above range, for example, it can be controlled by the particle diameter of the catalyst used, and can also be controlled by the productivity of polyethylene powder per unit catalyst amount. In addition, in the catalyst deactivation and drying processes, control is possible by suppressing the surface of the polyethylene powder from being subjected to a load and being melted and worn to be smooth. Specifically, it is possible to lower the liquid content of the solvent and the like remaining in the polyethylene powder during the catalyst deactivation and the drying step.

  In addition, the ratio of the powder of less than 106 μm (hereinafter also referred to as “fine powder”) measured by sieving particle size distribution measurement of the polyethylene powder is preferably 20% by mass or more and 50% by mass or less, and more preferably 22%. The content is not less than 50% by mass and not more than 49% by mass, more preferably not less than 23% by mass and not more than 48% by mass. When the ratio of particles of less than 106 μm is 20% by mass or more, the solubility tends to be high, and when it is 50% by mass or less, undissolved residue due to the presence of fine particles in the solvent in an aggregated state. It tends to be able to be suppressed.

  There are no particular limitations on the ratio of the powder of less than 106 μm in the polyethylene powder to 20% by mass or more and 50% by mass or less. For example, raising the temperature and pressure during polymerization, classifying with a sieve, etc. Can be adjusted by. The ratio of the powder (hereinafter also referred to as fine powder) of less than 106 μm of the polyethylene powder is measured by the method described in the examples described later.

The bulk density of polyethylene powder is preferably not more than 0.30 g / cm ³ or more 0.45 g / cm ^3, more preferably 0.31 g / cm ³ or more 0.44 g / cm ³ or less, more preferably 0 .32 g / cm ³ or more and 0.43 g / cm ³ or less. By bulk density is less than 0.30 g / cm ³ or more 0.45 g / cm ^3, good mixing condition when mixed with a solvent, in dissolved prone. The bulk density of the polyethylene powder to the 0.30 g / cm ³ or more 0.45 g / cm ³ or less is not particularly limited, for example, at the time of polymerization temperature and pressure, mainly ethylene copolymerized with other It can be adjusted by adjusting the slurry concentration calculated from the amount of α-olefin (also referred to as comonomer) introduced, the ratio of the solvent amount and the powder amount during polymerization, and the like. The bulk density of polyethylene-type powder is measured by the method as described in the Example mentioned later.

  The viscosity average molecular weight (Mv) of the polyethylene powder is preferably 10,000 or more and 3000000 or less, more preferably 20000 or more and 2000000 or less, further preferably 30000 or more and 1000000 or less, and most preferably 40000 or more and 500000 or less. When the viscosity average molecular weight (Mv) is 10,000 or more and 3,000,000 or less, it is excellent in solubility, and when molded, it tends to be a polyethylene powder that is excellent in stretchability and film strength. The polyethylene powder having such characteristics can be suitably used for a secondary battery separator, and can be suitably used for a lithium ion secondary battery separator.

  The method for controlling the viscosity average molecular weight (Mv) to 10,000 or more and 3000000 or less is not particularly limited, and examples thereof include changing the polymerization temperature of the reactor during polymerization. In general, the higher the polymerization temperature, the lower the molecular weight, and the lower the polymerization temperature, the higher the molecular weight. Another method for controlling the viscosity average molecular weight (Mv) within the above range includes, for example, adding a chain transfer agent such as hydrogen when polymerizing ethylene or the like. By adding a chain transfer agent, the molecular weight produced tends to be low even at the same polymerization temperature.

[Production method of polyethylene powder]
The polyethylene powder production method of the present embodiment uses a catalyst to homopolymerize ethylene, or copolymerize ethylene and an α-olefin having 3 to 6 carbon atoms to produce the polyethylene powder. Having a polymerization step. As the catalyst, an average particle diameter is at 1.0μm or 20μm or less and a pore volume not more than 1.0 mL / g or more 2.5 mL / g, specific surface area, 400 meters ² / g or more 800 m ² / g or less, as long as it has an inorganic carrier material as a catalyst carrier, the Ziegler-Natta catalyst described in Japanese Patent No. 5774084 and the supported geometrically constrained metallocene catalyst described later can be used. Of these, supported geometrically constrained metallocene catalysts are preferred.

<Supported geometrically constrained metallocene catalyst>
The supported geometrically constrained metallocene catalyst of the present embodiment is not particularly limited, but at least (a) an inorganic carrier material (hereinafter also referred to as “component (a)” or “(a)”), (a) organoaluminum. Compound (hereinafter also referred to as “component (a)” and “(a)”), (c) transition metal compound having a cyclic η-bonding anion ligand (hereinafter referred to as “component (c)”, “(c) ) ", And (d) an activator capable of reacting with the transition metal compound having the cyclic η-bonding anion ligand to form a complex that exhibits catalytic activity (hereinafter referred to as" component (d) "). And “(D)”).
(A) The inorganic carrier material is not particularly limited, and examples thereof include oxides such as SiO ₂ , Al ₂ O ₃ , MgO, and TiO ₂ ; halogen compounds such as MgCl ₂ . Of these, the preferred support material is SiO ₂ .

  The average particle size of the inorganic carrier material is 1.0 μm or more and 20 μm or less, preferably 2.0 μm or more and 15 μm or less, more preferably 3.0 μm or more and 10 μm or less. The average particle diameter of the inorganic carrier substance is an average particle diameter in terms of volume in a measuring method by a laser light scattering method. Specifically, it can be measured using “SALD-2100” manufactured by Shimadzu Corporation.

  The pore volume of the inorganic carrier material is 1.0 mL / g or more and 2.5 mL / g or less, preferably 1.2 mL / g or more and 2.0 mL / g or less, more preferably 1.4 mL / g or more. It is 2.0 mL / g or less. The pore volume of the inorganic carrier material is determined by the Barrett-Joyner-Halenda method (hereinafter also referred to as BJH method). Specifically, it can be measured using Tristar II3020 manufactured by Shimadzu Corporation.

The specific surface area of the inorganic carrier material is 400 m ² / g or more and 800 m ² / g or less, preferably 450 m ² / g or more and 800 m ² / g or less, more preferably 500 m ² / g or more and 750 m ² / g or less. is there. The specific surface area of the inorganic carrier material is determined by the Brunauer-Emmett-Teller method (hereinafter also referred to as BET method). Specifically, it can be measured using Tristar II3020 manufactured by Shimadzu Corporation.

  When the average particle diameter, pore volume, and specific surface area of the inorganic carrier material are within the above ranges, the polyethylene powder grows while the inorganic carrier material is crushed during the polymerization reaction. Tend to be uniform.

  (A) The inorganic carrier material is preferably treated with (a) an organoaluminum compound as necessary. Preferable (a) organoaluminum compound is not particularly limited, but, for example, alkylaluminum such as trimethylaluminum, triethylaluminum, triisobutylaluminum, trihexylaluminum, trioctylaluminum; Hydrides; aluminum alkoxides such as diethylaluminum ethoxide and dimethylaluminum methoxide; and alumoxanes such as methylalumoxane, isobutylalumoxane, and methylisobutylalumoxane. Of these, trialkylaluminum and aluminum alkoxide are preferable, and trimethylaluminum, triethylaluminum, and triisobutylaluminum are more preferable.

The supported geometrically constrained metallocene catalyst can include (c) a transition metal compound having a cyclic η-bonding anion ligand (hereinafter also simply referred to as “transition metal compound”). Although the transition metal compound of this embodiment is not specifically limited, For example, it can represent with following formula (1).
L _l MX _p X ' _q (1)

  In formula (1), M represents a transition metal belonging to Group 4 of the periodic table having an oxidation number of +2, +3, or +4 and having η5 bond with one or more ligands L.

  In the formula (1), each L independently represents a cyclic η-bonding anion ligand. The cyclic η-bonding anion ligand is a cyclopentadienyl group, an indenyl group, a tetrahydroindenyl group, a fluorenyl group, a tetrahydrofluorenyl group, or an octahydrofluorenyl group, and up to 20 of these groups. From a hydrocarbon group containing a non-hydrogen atom, a halogen, a halogen-substituted hydrocarbon group, an aminohydrocarbyl group, a hydrocarbyloxy group, a dihydrocarbylamino group, a hydrocarbylphosphino group, a silyl group, an aminosilyl group, a hydrocarbyloxysilyl group, and a halosilyl group Optionally having 1 to 8 substituents each independently selected, and two Ls containing up to 20 non-hydrogen atoms, hydrocabadiyl, halohydrocarbadiyl, hydrocarbyleneoxy, hydro Carbyleneamino, siladiyl, halosiladiyl, a It may be linked by a divalent substituent such as aminosilane.

  In formula (1), each X is independently a monovalent anionic σ-bonded ligand having up to 60 non-hydrogen atoms, or a divalent anionic σ-bonded bond that binds to M in a divalent manner. A ligand or a divalent anionic σ-bonded ligand that binds to M and L with a monovalent valence each is shown. X ′ each independently represents a neutral Lewis base coordination compound selected from phosphine, ether, amine, olefin and conjugated diene, each having 4 to 40 carbon atoms.

  In formula (1), l represents an integer of 1 or 2. p represents an integer of 0, 1 or 2, and X is a monovalent anionic σ-bonded ligand or a divalent anionic σ-bonded configuration in which M and L are each bonded with a monovalent valence. When a ligand is represented, p represents an integer one or more less than the formal oxidation number of M, and when X represents a divalent anionic σ-bonded ligand that binds to M in a divalent manner, p is , Represents an integer that is 1 + 1 or more less than the formal oxidation number of M. Q represents an integer of 0, 1 or 2. The transition metal compound is preferably a compound in which l is 1 in the formula (1).

A suitable example of the transition metal compound is a compound represented by the following formula (2).

In the formula (2), M represents titanium, zirconium or hafnium having a formal oxidation number of +2, +3 or +4. In formula (2), each R ¹ independently represents hydrogen, a hydrocarbon group, a silyl group, a germyl group, a cyano group, a halogen, or a composite group thereof, each of which is up to 20 non-hydrogens. It may have an atom, and adjacent R ¹ may combine to form a divalent derivative such as hydrocarbadiyl, siladiyl, germaniyl or the like to form a ring.

In formula (2), X ″ each independently represents a halogen, a hydrocarbon group, a hydrocarbyloxy group, a hydrocarbylamino group or a silyl group, each having up to 20 non-hydrogen atoms, Two X ″ may form a neutral conjugated diene or divalent derivative having 5 to 30 carbon atoms. Y represents —O—, —S—, —NR ³ — or —PR ³ —, and Z represents SiR ³ ₂ , CR ³ ₂ , SiR ³ ₂ SiR ³ ₂ , CR ³ ₂ CR ³ ₂ , CR ^3. = CR ³ , CR ³ ₂ SiR ³ ₂ or GeR ³ ₂ , wherein R ³ independently represents an alkyl group having 1 to 12 carbon atoms or an allyl group. Moreover, n shows the integer of 1-3.

More preferred examples of the transition metal compound are compounds represented by the following formula (3) and the following formula (4).

In formulas (3) and (4), each R ¹ independently represents hydrogen, a hydrocarbon group, a silyl group, a germyl group, a cyano group, a halogen, or a composite group thereof, each of up to 20 Can have non-hydrogen atoms. M represents titanium, zirconium or hafnium. Z and Y are the same as those shown in the formula (2). X and X ′ are the same as those indicated by X ″ in the formula (2).

  In formulas (3) and (4), p represents 0, 1 or 2, and q represents 0 or 1, respectively. When p is 2 and q is 0, the oxidation number of M is +4 and X is halogen, hydrocarbon group, hydrocarbyloxy group, dihydrocarbylamide group, dihydrocarbyl phosphide group, hydrocarbyl sulfide group, silyl group A group or a composite group thereof having up to 20 non-hydrogen atoms.

  In the formulas (3) and (4), when p is 1 and q is 0, the oxidation number of M is +3 and X is an allyl group, 2- (N, N-dimethylaminomethyl) phenyl A stabilized anionic ligand selected from the group and 2- (N, N-dimethyl) -aminobenzyl group; whether the oxidation number of M is +4 and X represents a derivative of a divalent conjugated diene M and X together form a metallocyclopentene group.

  In formulas (3) and (4), when p is 0 and q is 1, respectively, the oxidation number of M is +2, and X ′ is a neutral conjugated or non-conjugated diene, optionally It may be substituted with one or more hydrocarbon groups and X ′ may contain up to 40 carbon atoms, forming a π-type complex with M.

Further preferred examples of the transition metal compound are compounds represented by the following formulas (5) and (6).

In formulas (5) and (6), each R ¹ independently represents hydrogen or an alkyl group having 1 to 6 carbon atoms. M represents titanium, and Y represents —O—, —S—, —NR ³ —, or —PR ³ —. Z represents SiR ³ ₂ , CR ³ ₂ , SiR ³ ₂ SiR ³ ₂ , CR ³ ₂ CR ³ ₂ , CR ³ = CR ³ , CR ³ ₂ SiR ³ ₂ , or GeR ³ ₂ , wherein R ³ represents Independently represents hydrogen or a hydrocarbon group, hydrocarbyloxy group, silyl group, halogenated alkyl group, halogenated allyl group, or a composite group thereof, which may have up to 20 non-hydrogen atoms. and optionally, two R ³ together, or R ³ and R ³ in Y in Z may be a ring I coupled with in Z. X and X ′ are the same as those shown in the formula (3) or (4).

  In formulas (5) and (6), p represents 0, 1 or 2, and q represents 0 or 1, respectively. However, when p is 2 and q is 0, the oxidation number of M is +4 and each X independently represents a methyl group or a benzyl group. When p is 1 and q is 0, the oxidation number of M is +3 and X represents 2- (N, N-dimethyl) aminobenzyl, or the oxidation number of M is +4 and X Represents 2-butene-1,4-diyl. When p is 0 and q is 1, the oxidation number of M is +2 and X ′ is 1,4-diphenyl-1,3-butadiene or 1,3-pentadiene. These dienes are examples of asymmetric dienes that form metal complexes, and are actually a mixture of geometric isomers.

The supported geometrically constrained metallocene catalyst includes (d) an activator (hereinafter, also simply referred to as “activator”) capable of forming a complex that reacts with a transition metal compound and exhibits catalytic activity. Generally, in a metallocene catalyst, a transition metal compound and a complex formed by the above activator exhibit high olefin polymerization activity as a catalytically active species. In the present embodiment, the activator is not particularly limited, and examples thereof include a compound represented by the following formula (7).
[L−H] ^{d +} [M _m Q _p ] ^d− (7)

In the formula (7), [L—H] ^{d +} represents a proton-providing Bronsted acid, and L represents a neutral Lewis base. [M _m Q _p ] ^d− represents a compatible non-coordinating anion, M represents a metal or metalloid selected from Groups 5 to 15 of the periodic table, and Q is independently selected. Represents a hydride, a dialkylamide group, a halide, an alkoxy group, an allyloxy group, a hydrocarbon group, or a substituted hydrocarbon group having up to 20 carbon atoms, and Q as a halide is 1 or less. Further, m represents an integer of 1 to 7, p represents an integer of 2 to 14, d represents an integer of 1 to 7, and pm = d.

A more preferred example of the activator is a compound represented by the following formula (8).
[L−H] ^{d +} [M _m Q _n (G _q (T−H) _r ) _z ] ^d− (8)

In formula (8), [L-H] ^{d +} represents a proton-providing Bronsted acid, and L represents a neutral Lewis base. [M _m Q _n (G _q ( ^TH ) _r ) _z ] ^{d −} represents a compatible non-coordinating anion, and M is selected from Groups 5 to 15 of the periodic table. Q represents a metal or a metalloid, and each Q independently represents a hydride, a dialkylamide group, a halide, an alkoxy group, an allyloxy group, a hydrocarbon group, or a substituted hydrocarbon group having up to 20 carbon atoms. Is 1 or less. G represents a polyvalent hydrocarbon group having an r + 1 valence bonded to M and T, and T represents O, S, NR, or PR. Here, R represents hydrocarbyl, trihydrocarbylsilyl group, trihydrocarbylgermanium group or hydrogen. M represents an integer of 1 to 7, n represents an integer of 0 to 7, q represents an integer of 0 or 1, r represents an integer of 1 to 3, and z represents 1 The integer of -8 is shown, d shows the integer of 1-7, and is n + z-m = d.

A further preferred example of the activator is a compound represented by the following formula (9).
[LH] ⁺ [BQ ₃ Q ¹ ] ^- (9)

In the formula (9), [L—H] ⁺ represents a proton-providing Bronsted acid, and L represents a neutral Lewis base. [BQ ₃ Q ¹ ] ⁻ represents a compatible non-coordinating anion, B represents a boron element, Q independently represents a pentafluorophenyl group, and Q ¹ represents a substituent. As a substituted allyl group having 6 to 20 carbon atoms having one OH group.

  The proton-providing Bronsted acid is not particularly limited, and examples thereof include triethylammonium, tripropylammonium, tri (n-butyl) ammonium, trimethylammonium, tributylammonium, tri (n-octyl) ammonium, diethylmethylammonium. , Dibutylmethylammonium, dibutylethylammonium, dihexylmethylammonium, dioctylmethylammonium, didecylmethylammonium, didodecylmethylammonium, ditetradecylmethylammonium, dihexadecylmethylammonium, dioctadecylmethylammonium, diicosylmethylammonium, And trialkyl group-substituted ammonium carboxyls such as bis (hydrogenated tallow alkyl) methylammonium ON; N, N-, such as N, N-dimethylanilinium, N, N-diethylanilinium, N, N-2,4,6-pentamethylanilinium, and N, N-dimethylbenzylanilinium A dialkylanilinium cation; a triphenylcarbonium cation.

  The compatible non-coordinating anion is not particularly limited, and examples thereof include triphenyl (hydroxyphenyl) borate, diphenyl-di (hydroxyphenyl) borate, triphenyl (2,4-dihydroxyphenyl) borate, tri ( p-tolyl) (hydroxyphenyl) borate, tris (pentafluorophenyl) (hydroxyphenyl) borate, tris (2,4-dimethylphenyl) (hydroxyphenyl) borate, tris (3,5-dimethylphenyl) (hydroxyphenyl) Borate, tris (3,5-di-trifluoromethylphenyl) (hydroxyphenyl) borate, tris (pentafluorophenyl) (2-hydroxyethyl) borate, tris (pentafluorophenyl) (4-hydroxybutyl) borate Tris (pentafluorophenyl) (4-hydroxy-cyclohexyl) borate, tris (pentafluorophenyl) (4- (4′-hydroxyphenyl) phenyl) borate, and tris (pentafluorophenyl) (6-hydroxy-2-naphthyl) ) Borate. These compatible non-coordinating anions are also referred to as “borate compounds”. From the viewpoint of catalytic activity and the viewpoint of reducing the total content of Al, Mg, Ti, Zr and Hf, the activator of the supported geometrically constrained metallocene catalyst is preferably a borate compound. Preferred borate compounds include tris (pentafluorophenyl) (hydroxyphenyl) borate.

As the activator, an organometallic oxy compound having a unit represented by the following formula (10) can also be used.
(In the formula (10), M ² represents a metal of Group 13 to Group 15 of the periodic table, or a metalloid, and each R independently represents a hydrocarbon group or substituted hydrocarbon group having 1 to 12 carbon atoms. N represents the valence of the metal M ² , and m represents an integer of 2 or more.)

Another preferred example of the activator is an organoaluminum oxy compound containing a unit represented by the following formula (11).
(In formula (11), R represents an alkyl group having 1 to 8 carbon atoms, and m represents an integer of 2 to 60.)

A more preferred example of the activator is methylalumoxane containing a unit represented by the following formula (12).
(In formula (12), m represents an integer of 2 to 60.)

In addition to the components (a) to (d) described above, an organoaluminum compound can be used as a catalyst as required. Although it does not specifically limit as an organoaluminum compound, For example, the compound represented by following formula (13) is mentioned.
AlR _n X _3-n (13)

  In formula (13), R represents a linear, branched or cyclic alkyl group having 1 to 12 carbon atoms or an allyl group having 6 to 20 carbon atoms, X represents a halogen, hydrogen or alkoxyl group, n shows the integer of 1-3. The organoaluminum compound may be a mixture of compounds represented by formula (13).

  The catalyst can be obtained by supporting the component (a), the component (c), and the component (d) on the component (a). The method for supporting component (a), component (c), and component (e) is not particularly limited. For example, an inert solvent that can dissolve component (a), component (c), and component (d), respectively. A method in which the solvent is distilled off after being dissolved in and mixed with component (a); after dissolving component (b), component (c) and component (d) in an inert solvent, it is not in the range where no solid precipitates. A method of concentrating this, and then adding component (a) in such an amount that the entire amount of the concentrate can be retained in the particles; component (a) is first loaded with component (a) and component (e), and then component (C) A method of supporting (c); a method of supporting component (a), (a), (d), and (c) sequentially. The component (c) and the component (d) of the present embodiment are preferably liquid or solid. In addition, component (a), component (c), and component (d) may be used after being diluted with an inert solvent during loading.

  Examples of the inert solvent include, but are not limited to, aliphatic hydrocarbons such as hexane, heptane, octane, decane, dodecane, and kerosene; alicyclic hydrocarbons such as cyclohexane and methylcyclopentane; benzene, toluene, xylene Aromatic hydrocarbons such as, and the like; and mixtures thereof. Such an inert solvent is preferably used after removing impurities such as water, oxygen, and sulfur using a desiccant, an adsorbent, or the like.

Component (A) is preferably 1.0 × 10 ^{−5 to} 1.0 × 10 ⁻¹ mol in terms of Al atom, more preferably 1.0 × 10 ⁻⁴ to 1.0 g of component (A). 5.0 × 10 ⁻² mol and component (c) are preferably 1.0 × 10 ^{−7 to} 1.0 × 10 ⁻³ mol, more preferably 5.0 × 10 ^{−7 to} 5.0 × 10. ^-4 mol, the component (d) is preferably in the range of 1.0 × 10 ^{−7 to} 1.0 × 10 ⁻³ mol, more preferably in the range of 5.0 × 10 ^{−7 to} 5.0 × 10 ⁻⁴ mol. It is. The amount of each component used and the loading method are determined by activity, economy, powder characteristics, scale in the reactor, and the like. The obtained supported geometrically constrained metallocene catalyst was washed by a method such as decantation or filtration using an inert solvent for the purpose of removing organoaluminum compounds, borate compounds and titanium compounds not supported on the carrier. You can also

  The series of operations such as dissolution, contact, and washing are preferably performed at a temperature of −30 ° C. or higher and 80 ° C. or lower that is selected for each unit operation. A more preferable range of such temperature is 0 ° C. or more and 50 ° C. or less. The series of operations for obtaining the supported geometrically constrained metallocene catalyst is preferably performed in a dry inert atmosphere.

  The supported geometrically constrained metallocene catalyst can be used for homopolymerization of ethylene or copolymerization of ethylene and α-olefin, but an organoaluminum compound is added as an additional component to prevent poisoning of solvents and reactions. They can also be used together. Although it does not specifically limit as a preferable organoaluminum compound, For example, alkyl aluminum, such as trimethylaluminum, triethylaluminum, triisobutylaluminum, trihexylaluminum, trioctylaluminum; alkylaluminum hydride, such as diethylaluminum hydride and diisobutylaluminum hydride; Examples include aluminum alkoxides such as diethylaluminum ethoxide; alumoxanes such as methylalumoxane, isobutylaluminoxane, and methylisobutylalumoxane. Among these, trialkylaluminum and aluminum alkoxide are preferable. More preferred is triisobutylaluminum.

  The polymerization method of the polyethylene powder is preferably a slurry polymerization method. In the case of performing polymerization, generally, the polymerization pressure is preferably 0.1 MPaG or more and 10 MPaG or less, more preferably 0.3 MPaG or more and 3.0 MPaG or less. The polymerization temperature is preferably 20 ° C. or higher and 115 ° C. or lower, more preferably 50 ° C. or higher and 85 ° C. or lower.

  As the solvent used in the slurry polymerization method, the above-described inert solvent is preferable, and an inert hydrocarbon solvent is more preferable. Examples of the inert hydrocarbon solvent include hydrocarbon solvents having 6 to 8 carbon atoms, specifically, aliphatic hydrocarbons such as hexane, heptane and octane; alicyclic hydrocarbons such as cyclohexane and methylcyclopentane; Of the mixture.

  The polymerization method of the polyethylene powder is preferably a continuous polymerization. By continuously supplying ethylene gas, solvent, catalyst, etc. into the polymerization and continuously discharging together with the generated polyethylene powder, it becomes possible to suppress a partial high temperature state due to a sudden ethylene reaction, The polymerization system tends to be more stable. When ethylene reacts in a uniform state, the broadening of the molecular weight distribution tends to be suppressed.

  Further, after removing the ethylene, hydrogen, and α-olefin by a flash tank after the polymerization vessel, it is preferable to hold the buffer tank under predetermined conditions in a state where no raw material is supplied. The temperature of the buffer tank is preferably 65 ° C. or higher, more preferably 68 ° C. or higher, and particularly preferably 70 ° C. or higher. The upper limit is preferably 80 ° C. or lower, and more preferably 75 ° C. or lower.

  The solvent separation method in the method for producing polyethylene-based powder in the present embodiment can be performed by a decantation method, a centrifugal separation method, a filter filtration method, or the like, but a centrifugal separation method with good separation efficiency between the polyethylene-based powder and the solvent is available. More preferred. The amount of the solvent contained in the polyethylene powder after the solvent separation is not particularly limited, but is preferably 50% by mass to 90% by mass, and more preferably 55% by mass to 85% by mass with respect to the mass of the polyethylene powder. % Or less, and more preferably 60% by mass or more and 80% by mass or less.

  By passing through the above-mentioned process, the ratio of the median diameter and mode diameter of the pores determined by the mercury intrusion method can be controlled within the range described in the present application. The reason for this is not always clear, but (1) a small amount of raw material is present in a low-temperature / low-pressure buffer tank without raw material supply, so that only a part of the catalyst particles are polymerized and less than 106 μm. Powder is generated. (2) By weakening solvent separation in the centrifuge, a low molecular weight component (hereinafter also referred to as WAX) that is easily dissolved in hexane is taken into the powder, and then passed through a drying step. It is presumed that uniform pores are formed by aggregation of WAX and fine powder in the powder.

  The method for deactivating the catalyst used for synthesizing the polyethylene powder is not particularly limited, but it is preferably carried out after separating the polyethylene powder and the solvent.

  Although it does not specifically limit as a chemical | medical agent which deactivates a catalyst, For example, oxygen, water, alcohols are mentioned.

  The drying in the polyethylene powder production method is preferably performed in a state where an inert gas such as nitrogen or argon is circulated. Further, the drying temperature is preferably 50 ° C. or higher and 150 ° C. or lower, more preferably 50 ° C. or higher and 140 ° C. or lower, and further preferably 50 ° C. or higher and 130 ° C. or lower. If the drying temperature is 50 ° C. or higher, efficient drying tends to be possible. On the other hand, if the drying temperature is 150 ° C. or lower, drying tends to be possible in a state where the decomposition and crosslinking of the polyethylene powder are suppressed. In addition to the above components, other known components useful for the production of polyethylene powder can be included.

  Hereinafter, the present embodiment will be described in more detail based on examples, but the present embodiment is not limited to the following examples. First, the physical properties and measurement methods for evaluation and evaluation criteria will be described below.

(Physical property 1) Pore characteristics by mercury porosimetry For each of the polyethylene powders obtained in the examples and comparative examples, the median diameter, mode diameter and pore volume were measured by the mercury porosimetry. In addition, the apparatus and conditions used for the measurement were as follows.
Device: Shimadzu Autopore 9500
Sample amount: 500mg
1. Low pressure measurement Measurement pressure: 0 to 30 psia
Measurement pore diameter: 6 to 120 μm
2. High pressure measurement Measurement pressure: 30 to 33000 psia
Measurement pore diameter: 0.005 to 6 μm

  The median diameter means the value of the X axis (pore diameter) corresponding to the middle of the minimum value and maximum value of the Y axis (pore volume or pore specific surface area) of the curve in the integrated pore distribution, and the mode diameter is the differential. In the pore distribution, it means the pore diameter where the differential value is maximized. The pore volume is a value obtained by dividing the integrated value of the pore volume into which mercury has been injected up to the maximum pressure at the time of measurement by the sample weight.

(Physical property 2) Density The density of each polyethylene powder obtained in Examples and Comparative Examples was measured by a density gradient tube method in accordance with JIS K6760.

(Physical property 3) Average particle diameter of powder and proportion of powder less than 106 μm For each polyethylene powder obtained in Examples and Comparative Examples, eight types of sieves defined in JIS Z8801 (opening: 600 μm, 425 μm, (300 μm, 212 μm, 150 μm, 106 μm, 75 μm, 53 μm) and a tray, the sieves are stacked on the tray in ascending order of opening, and 100 g of polyethylene powder is put on the uppermost sieve, and then a low-tap type sieve. After setting on a shaker and classification, the mass of the powder remaining on each sieve and the saucer was measured, and the average particle size of the powder and the proportion of powder less than 106 μm were measured. The average particle diameter of the polyethylene powder was defined as an average particle diameter at 50% mass in an integral curve obtained by integrating the mass of the polyethylene powder remaining on each sieve and the saucer from the side having a large opening.

(Physical property 4) Bulk density The bulk density of each polyethylene-type powder obtained by the Example and the comparative example was measured based on JISK6891.

(Physical property 5) Viscosity average molecular weight (Mv)
The viscosity average molecular weight (Mv) of each polyethylene powder obtained in Examples and Comparative Examples was determined by the method shown below based on ISO1628-3 (2010).

First, 20 mg of polyethylene powder was weighed into a dissolution tube, and the dissolution tube was purged with nitrogen, and then 20 mL of decahydronaphthalene (with 1 g / L of 2,6-di-t-butyl-4-methylphenol added). In addition, the mixture was stirred at 150 ° C. for 2 hours to dissolve the polyethylene powder. The solution was measured in a thermostatic bath at 135 ° C. using a Canon-Fenske viscometer (manufactured by Shibata Kagaku Kikai Kogyo Co., Ltd .: product number-100) for the drop time (ts) between the marked lines. Similarly, the fall time (ts) between marked lines was similarly measured about the sample which changed the amount of polyethylene powder into 10 mg, 5 mg, and 2 mg. The dropping time (tb) of only decahydronaphthalene without polyethylene powder as a blank was measured. The reduced viscosity (ηsp / C) of the polyethylene powder was determined according to the following formula.
ηsp / C = (ts / tb−1) /0.1 (unit: dL / g)

The relationship between the concentration (C) (unit: g / dL) and the reduced viscosity (ηsp / C) of the polyethylene powder is plotted, and an approximate linear equation is derived by the least square method. [Η]) was determined. Next, the viscosity average molecular weight (Mv) was calculated from the value of the intrinsic viscosity [η] using the following formula A.
Mv = (5.34 × 10 ⁴ ) × [η] ^1.49 (Formula A)

(Physical property 6) Powder flowability About each polyethylene-type powder obtained by the Example and the comparative example, based on JISZ2502, the time (sec / 50g) for which the polyethylene-type powder 50g falls was measured.

(Evaluation 1 and 2) Solubility evaluation 7 g of each polyethylene powder obtained in Examples and Comparative Examples with respect to 7 g of Hi-Z Million (registered trademark) 030S manufactured by Mitsui Chemicals, Inc. Pentaerythryl as an antioxidant A mixture of 0.4 g of tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] and 36 g of liquid paraffin (P-350 manufactured by Matsumura Oil Co., Ltd.) was mixed with a small kneader (Toyo Seiki Co., Ltd.). LABPLASTOMILL 30C150) and kneaded for 2 minutes at a screw rotation of 50 rpm. The kneading temperature was carried out at two levels of 200 ° C. and 180 ° C. These kneaded materials are sandwiched between metal plates and heat-pressed at 170 ° C. until a thickness of 1 mm is obtained with a compression molding machine (SFA-37 manufactured by Shindo Metal Co., Ltd.), then rapidly cooled at 25 ° C. to form a gel sheet. did.

This gel sheet was stretched 7 × 7 times at 120 ° C. using a simultaneous biaxial stretching machine, and liquid paraffin was extracted and removed using methylene chloride, followed by drying. Furthermore, heat setting was performed at 125 ° C. for 3 minutes to obtain a microporous membrane. The solubility of the polyethylene powder is a particle mass of 50 μm or more present in the obtained microporous membrane 250 mm × 250 mm (what is observed as a black spot when the microporous membrane is observed with transmitted light, unmelted polyethylene Were considered by visual observation, and evaluated based on the following evaluation criteria based on the obtained number.
(Solubility evaluation criteria)
○: The number of particulate lumps is one or less.
(Triangle | delta): A particulate lump is 2-4 pieces.
X: There are 5 or more particulate lumps.

[Preparation of catalyst]
[Preparation of supported geometrically constrained metallocene catalyst [A]]
Silica for catalyst support (average particle size 6.5 μm, pore volume 1.70 mL / g, specific surface area 715 m ² / g) sufficiently washed with water and dried is calcined at 550 ° C. for 5 hours in a nitrogen atmosphere, and dehydrated. Silica was obtained. In a 1.8 L autoclave, 40 g of this dehydrated silica was dispersed in 800 mL of hexane to obtain a slurry. While maintaining the resulting slurry at 25 ° C. with stirring, 84 mL of a hexane solution of triethylaluminum (concentration: 1 mol / L) was added, and then stirred for 2 hours to react triethylaluminum with the surface hydroxyl group of silica to obtain the surface hydroxyl group of silica. A hexane slurry of component [a] capped with triethylaluminum was obtained.

  On the other hand, 200 mmol of [(Nt-butylamide) (tetramethyl-η5-cyclopentadienyl) dimethylsilane] titanium dimethyl (hereinafter referred to as “titanium complex”) was added to Isopar E (registered trademark) [Exxon Chemical Co., Ltd. (US) Hydrocarbon mixture product name] Dissolved in 1000 mL, added 20 mL of 1 mol / L hexane solution of n-butylethylmagnesium, further added hexane to adjust the titanium complex concentration to 0.1 mol / L, Component [b] was obtained.

  Further, 5.7 g of bis (hydrogenated tallow alkyl) methylammonium-tris (pentafluorophenyl) (4-hydroxyphenyl) borate (hereinafter referred to as “borate compound”) was added to 50 mL of toluene and dissolved, A 100 mmol / L toluene solution of the borate compound was obtained. To the toluene solution of the borate compound, 5 mL of a 1 mol / L hexane solution of diethylaluminum ethoxide was added at room temperature, and further hexane was added so that the borate compound concentration in the solution was 70 mmol / L. Then, it stirred at room temperature for 1 hour and obtained the reaction mixture containing a borate compound.

  46 mL of this reaction mixture containing a borate compound and 32 mL of the component [b] obtained above were simultaneously added to 800 mL of the slurry of the component [a] obtained above while stirring at 20 to 25 ° C., and further stirred for 3 hours. Then, the titanium complex and borate were reacted and precipitated, and physically adsorbed on silica. Thereafter, the supernatant containing the unreacted borate compound / titanium complex in the obtained reaction mixture is removed by decantation, whereby the supported geometrically constrained metallocene catalyst in which the catalytically active species is formed on the silica [ A] (simply indicated as “A” in the table).

[Supported geometrically constrained metallocene catalyst [B]]
The catalyst support silica was adjusted according to the preparation of the supported geometrically constrained metallocene catalyst [A], except that the average particle diameter was 22 μm, the pore volume was 0.85 mL / g, and the specific surface area was 325 m ² / g. A supported geometrically constrained metallocene catalyst [B] (simply indicated as “B” in the table) was obtained.

[Preparation of Ziegler-Natta catalyst [C]]
Ziegler-Natta catalyst [C] (simply indicated as “C” in the table) was obtained by the method described in [Preparation of Solid Catalyst Component [A-1]] of Japanese Patent No. 5774084.

[Example 1]
Polyethylene powder was obtained by the continuous slurry polymerization method shown below. Specifically, continuous polymerization was performed using a Bessel type 340L polymerization reactor equipped with a stirrer under conditions of a polymerization temperature of 80 ° C., a polymerization pressure of 0.98 MPa, and an average residence time of 1.8 hours. Dehydrated normal hexane 80 L / hour as a solvent, the supported metallocene catalyst [A] described above as a catalyst was supplied at 1.4 mmol / hour in terms of Ti atom, and triisobutylaluminum was fed at 20 mmol / hour. Also, hydrogen for molecular weight adjustment is supplied at 0.53 mol% with respect to the gas phase concentration of ethylene and 1-butene, and 1-butene is supplied at 0.17 mol% with respect to the gas phase concentration of ethylene. Ethylene and 1-butene were copolymerized. The catalyst was supplied from near the liquid level of the polymerization vessel, and ethylene and 1-butene were supplied from the bottom of the polymerization vessel. The polymerization slurry in the polymerization reactor was led to a flash tank having a pressure of 0.05 MPa and a temperature of 70 ° C. so that the level of the polymerization reactor was kept constant, and unreacted ethylene, 1-butene and hydrogen were separated. Next, the slurry was continuously sent to the centrifuge so that the level of the flash tank was kept constant, and the powder and other solvents were separated. The liquid content of the solvent, etc. with respect to the powder at that time was 60%. The separated polyethylene powder was dried while blowing nitrogen at 85 ° C. In this drying step, the catalyst and the cocatalyst were deactivated by spraying steam on the powder. To the obtained polyethylene powder, 1500 ppm of calcium stearate (manufactured by Dainichi Chemical Co., Ltd., C60) was added, and uniformly mixed using a Henschel mixer. The polyethylene powder obtained in Example 1 was obtained by removing the polyethylene powder that did not pass through the sieve using a sieve having an opening of 425 μm. The measurement results and evaluation results are shown in Table 1.

[Example 2]
Under conditions of a polymerization temperature of 75 ° C. and a polymerization pressure of 0.80 MPa, hydrogen is 0.25 mol% with respect to the gas phase concentration of ethylene and 1-butene, and 1-butene is 0.37 mol% with respect to the gas phase concentration of ethylene. A polyethylene powder of Example 2 was obtained in the same manner as in Example 1 except that this was achieved. The measurement results and evaluation results are shown in Table 1.

[Example 3]
Under conditions of a polymerization temperature of 80 ° C. and a polymerization pressure of 1.0 MPa, hydrogen is 0.31 mol% with respect to the gas phase concentration of ethylene and 1-butene, and 1-butene is 0.30 mol% with respect to the gas phase concentration of ethylene. A polyethylene powder of Example 2 was obtained in the same manner as in Example 1 except that this was achieved. The measurement results and evaluation results are shown in Table 1.

[Example 4]
A polyethylene powder of Example 4 was obtained in the same manner as in Example 2 except that the polymerization temperature was 80 ° C. and the polymerization pressure was 0.98 MPa. The measurement results and evaluation results are shown in Table 1.

[Example 5]
Using the above Ziegler-Natta catalyst [C] under conditions of a polymerization temperature of 83 ° C. and a polymerization pressure of 0.5 MPa, hydrogen is 3.0 mol% with respect to the gas phase concentration of ethylene, and 1-butene is not fed, It was led to a flash tank having a pressure of 0.05 MPa and a temperature of 70 ° C., and after separating unreacted raw materials, it was led to a buffer tank having a pressure of 0.30 MPa and a temperature of 65 ° C. under an average residence time of 1.0 hour. The polyethylene-based powder of Example 5 was obtained by the same operation as Example 1. The measurement results and evaluation results are shown in Table 1.

[Example 6]
The same operation as in Example 5 except that hydrogen was 7.0 mol% with respect to the gas phase concentration of ethylene and 1-butene and 1-butene was 0.30 mol% with respect to the gas phase concentration of ethylene. Thus, a polyethylene-based powder of Example 6 was obtained. The measurement results and evaluation results are shown in Table 1.

[Example 7]
A polyethylene powder of Example 7 was obtained in the same manner as in Example 5 except that the polymerization temperature was 86 ° C., the polymerization pressure was 0.21 MPa, and hydrogen was not fed. The measurement results and evaluation results are shown in Table 1.

[Example 8]
A polyethylene-based powder of Example 8 was obtained in the same manner as in Example 5 except that the polymerization temperature was 80 ° C., the polymerization pressure was 0.40 MPa, and hydrogen was 0.2 mol% with respect to the gas phase concentration of ethylene. The measurement results and evaluation results are shown in Table 1.

[Comparative Example 1]
Polyethylene powder of Comparative Example 1 was obtained by the method described in Example 1 of Japanese Patent No. 5774084. The measurement results and evaluation results are shown in Table 1. The ratio of the median diameter to the mode diameter was large because the liquid content of the solvent and the like with respect to the powder after separation with a centrifuge was set to 45% without being guided to the buffer tank. The solubility evaluation at 200 ° C. was “good”, but the solubility evaluation at 180 ° C. was “poor”.

[Comparative Example 2]
After separating unreacted raw materials, powder and other solvents after separation by a centrifuge without guiding to a buffer tank having a pressure of 0.30 MPa and a temperature of 65 ° C. under an average residence time of 1.0 hour The polyethylene powder of Comparative Example 2 was obtained in the same manner as in Example 7, except that the liquid content of the solvent and the like with respect to the powder was 45%. The measurement results and evaluation results are shown in Table 1. Since the liquid content of the solvent and the like with respect to the powder after separation with a centrifuge was set to 45% without being led to the buffer tank, the ratio of the median diameter to the mode diameter was larger than that in Example 7. The solubility evaluation at 200 ° C. was Δ, and the solubility evaluation at 180 ° C. was x.

[Comparative Example 3]
The above supported metallocene catalyst [B] is used under the conditions of a polymerization temperature of 70 ° C. and a polymerization pressure of 0.8 MPa, hydrogen is 200 ppm relative to the gas phase concentration of ethylene and 1-butene, and 1-butene is an ethylene gas. Except that the liquid content of the solvent, etc. with respect to the powder was 45% when the powder after separation by the centrifuge and the other solvent were separated so as to be 0.37 mol% with respect to the phase concentration. The polyethylene powder of Comparative Example 3 was obtained by the same operation as in Example 1. Using carrier materials with different average particle diameter, pore volume, and specific surface area, and the liquid content of the solvent etc. to the powder after separation with a centrifuge was 45%, so the ratio of median diameter and mode diameter was small, The density was low. The solubility evaluation at 200 ° C. was x, and the solubility evaluation at 180 ° C. was x.

[Comparative Example 4]
A polyethylene powder of Comparative Example 4 was obtained in the same manner as in Example 1 except that the supported metallocene catalyst [B] was used. The measurement results and evaluation results are shown in Table 1. Since carrier materials having different average particle diameter, pore volume, and specific surface area were used, the median diameter / mode diameter ratio was small and the density was high as compared with Example 1. The powder fluidity deteriorated, the solubility evaluation at 200 ° C. was Δ, and the solubility evaluation at 180 ° C. was x.

[Comparative Example 5]
After separating unreacted raw materials, powder and other solvents after separation by a centrifuge without guiding to a buffer tank having a pressure of 0.30 MPa and a temperature of 65 ° C. under an average residence time of 1.0 hour The polyethylene powder of Comparative Example 5 was obtained in the same manner as in Example 8, except that the liquid content of the solvent and the like with respect to the powder was 45%. The measurement results and evaluation results are shown in Table 1. Since the liquid content of the solvent and the like with respect to the powder after separation with a centrifuge was set to 45% without being guided to the buffer tank, the ratio of the median diameter to the mode diameter was larger than that in Example 8. The powder fluidity deteriorated, the solubility evaluation at 200 ° C. was x, and the solubility evaluation at 180 ° C. was x.

  As shown in Table 1, in the examples, foreign matter is hardly generated even at a low kneading temperature, excellent in solubility in a solvent in low temperature molding, and when low temperature molding is performed by blending different types of polyethylene powder. It was also possible to form a uniform microporous film.

  By using the polyethylene-based powder of the present invention, a uniform microporous film can be formed even when different types of polyethylene-based powders are blended and low-temperature molded. Therefore, the present invention has high industrial applicability.

Claims (9)

An ethylene homopolymer, or a copolymer of ethylene and an α-olefin having 3 to 6 carbon atoms,
The ratio of pore median diameter and mode diameter measured by mercury porosimetry is 0.80 or more and 1.20 or less,
The density is 920 kg / m ³ or more and 960 kg / m ³ or less,
Polyethylene powder. The pore volume measured by the mercury intrusion method is 0.85 mL / g or more and 1.40 mL / g or less,
The pore mode diameter measured by mercury porosimetry is 30 μm or more and 45 μm or less,
The polyethylene-based powder according to claim 1. The average particle size measured by sieving particle size distribution measurement is 50 to 300 μm, and the proportion of powder less than 106 μm is 20% by mass or more and 50% by mass or less,
The polyethylene-based powder according to claim 1 or 2. Bulk density is 0.30 g / cm ³ or more 0.45 g / cm ³ or less,
The polyethylene-type powder of any one of Claims 1-3. The viscosity average molecular weight (Mv) is 10,000 or more and 3000000 or less,
The polyethylene-type powder of any one of Claims 1-4. The polyethylene powder according to any one of claims 1 to 5 is obtained by homopolymerizing ethylene using a catalyst or copolymerizing ethylene and an α-olefin having 3 to 6 carbon atoms. A polymerization step to obtain,
Wherein the catalyst has an average particle diameter is at 1.0μm or 20μm or less and a pore volume not more than 1.0 mL / g or more 2.5 mL / g, specific surface area, 400 meters ² / g or more 800 m ² / g or less, having an inorganic support material as a catalyst support,
Production method of polyethylene powder. For secondary battery separator,
The polyethylene-type powder of any one of Claims 1-5. For lithium ion secondary battery separator,
The polyethylene-type powder of any one of Claims 1-5. For lead-acid battery separator,
The polyethylene-type powder of any one of Claims 1-5.