JP5774084B2 - Polyethylene powder - Google Patents

Description

  The present invention relates to polyethylene powder.

High molecular weight polyethylene powders are used in a wide variety of applications such as films, sheets, microporous membranes, fibers, foams and pipes. In particular, high molecular weight 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 reasons why the high molecular weight polyethylene powder is used in these applications include excellent stretch processability, high strength, high chemical stability, and excellent long-term reliability. The high molecular weight polyethylene powder generally has a high viscosity and is difficult to process by injection molding or the like. Therefore, the high molecular weight polyethylene powder is often molded by dissolving the high molecular weight polyethylene powder in a solvent. The microporous membrane for a secondary battery separator is produced by kneading high molecular weight polyethylene powder in a state of being dissolved in a solvent, for example, in a solvent at a high temperature, and then stretching and removing the solvent and the like.

  Thus, a microporous membrane for a secondary battery separator obtained by dissolving a high molecular weight polyethylene powder in a solvent is required to improve molding operation stability, productivity, and film quality. An excellent solubility is desired so that unmelted high molecular weight polyethylene powder does not remain as particles in the melt-kneading step.

As a technique for increasing the solubility of polyethylene powder in a solvent, for example, in Patent Document 1, polyethylene having an average particle diameter of 1 to 150 μm and a powder specific surface area of 0.7 m ² / g or more is used as one of the raw materials. It is disclosed.
In Patent Document 2, the microporous membrane of the ethylene polymer composition powder as a raw material for the bulk density 0.30 g / cm ³ or more 0.45 g / cm ³ or less is disclosed.
Further, Patent Document 3 discloses a polyethylene microporous membrane using a high-density polyethylene having a low molecular weight of 1 × 10 ⁴ or less and a low molecular weight as a raw material.

Japanese Patent No. 4799179 JP 2007-119751 A JP 2011-208144 A

  However, in recent years, in particular, the demand for microporous membranes for secondary battery separators has grown significantly, and it is strongly desired to improve productivity and produce at low cost. Specifically, from the viewpoint of improving productivity, there is a demand for continuous and stable production at high speed without stopping an extruder or the like, that is, formation of a uniform microporous film. Further, from the viewpoint of improving production efficiency, further improvement in solubility in the kneading process of polyethylene powder is desired, but further improvement of the above-described known technology is desired.

  Accordingly, an object of the present invention is to provide a polyethylene powder that is excellent in solubility even during high-speed production.

  As a result of conducting extensive research to solve the above-mentioned problems, the present inventor has found that a high-molecular-weight polyethylene powder having a predetermined specific surface area and pore volume can solve the above-mentioned problems. It came.

That is, the present invention is as follows.
[1]
The specific surface area determined by the BET method is 0.10 m ² / g or more and 0.30 m ² / g or less, the pore volume determined by the mercury intrusion method is 0.85 mL / g or less, and the viscosity average molecular weight (Mv ) Is a polyethylene powder having 100,000 to 1,000,000,
[2]
The polyethylene powder according to [1], wherein there is no maximum value in a pore size of 30 μm or less in a pore distribution determined by a mercury intrusion method,
[3]
The average particle size is 1 to 200 μm, and 60% or more of the total number of measured particles has an unevenness degree (UD) defined by the formula (1) of 0.90 or more and 0.95 or less, [1] or [2] polyethylene powder according to
UD = A / (A + B) (1)
(In the formula (1), A represents the projected area of the target particle, and A + B represents the projected area surrounded by the envelope connecting the convex portions of the target particle.)
[4]
The polyethylene powder according to any one of [1] to [3], comprising 1 ppm or more and 200 ppm or less of titanium,
[5]
The polyethylene powder according to any one of [1] to [4], which is for a secondary battery separator,
[6]
The polyethylene powder according to any one of [1] to [5], which is for a lithium ion secondary battery separator.

  According to the present invention, polyethylene powder having excellent solubility can be obtained even during high-speed production.

It is drawing explaining unevenness measurement of polyethylene powder.

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

[Polyethylene powder]
The polyethylene powder of this embodiment has a specific surface area determined by the BET method of 0.1 m ² / g to 0.3 m ² / g and a pore volume determined by the mercury intrusion method of 0.85 mL / g or less. The polyethylene powder has a viscosity average molecular weight (Mv) of 100,000 to 1,000,000.

Examples of the polyethylene powder of the present embodiment include an ethylene homopolymer or a copolymer of ethylene and another comonomer.
Although it does not specifically limit as another comonomer, For example, an alpha olefin, a vinyl compound, etc. are mentioned.
Although it does not specifically limit as an alpha olefin, For example, a C3-C20 alpha olefin is mentioned, Specifically, a propylene, 1-butene, 4-methyl- 1-pentene, 1-hexene, 1 -Octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-tridecene, 1-tetradecene and the like. Among these, propylene and 1-butene are preferable from the viewpoint of heat resistance and strength of a molded body represented by a film or fiber.
Although it does not specifically limit as a vinyl compound, For example, vinylcyclohexane, styrene, its derivative (s), etc. are mentioned.
Further, as the other comonomer, a non-conjugated polyene such as 1,5-hexadiene or 1,7-octadiene may be used as necessary. The copolymer may be a ternary random polymer.
Another comonomer may be used individually by 1 type, and may use 2 or more types together.

The polyethylene powder is preferably an ethylene homopolymer from the viewpoint of heat resistance. When the polyethylene powder contains a copolymer of ethylene and another comonomer, the copolymer is preferably copolymerized with another comonomer so long as the heat resistance does not deteriorate. Specifically, as polyethylene powder, the molar ratio of ethylene in the copolymer is preferably 50% or more and less than 100%, more preferably 80% or more and less than 100%, and even more preferably 90% or more. Less than 100%.
The amount of other comonomers in the copolymer when the polyethylene powder is a copolymer can be confirmed by infrared analysis, NMR, or the like.

  The polyethylene powder of this embodiment may contain additives such as a neutralizing agent, an antioxidant, and a light stabilizer.

The neutralizing agent is used as a halogen catcher such as chlorine contained in polyethylene powder or a molding processing aid.
The neutralizing agent is not particularly limited, and examples thereof include stearates of alkaline earth metals such as calcium, magnesium and barium. Although content of a neutralizing agent is not specifically limited, For example, it is 5000 ppm or less, Preferably it is 4000 ppm or less, More preferably, it is 3000 ppm or less.
An ethylene polymer obtained by a slurry polymerization method using a metallocene catalyst can exclude a halogen component from catalyst components without using a neutralizing agent.

  Although it does not specifically limit as antioxidant, For example, dibutylhydroxytoluene, pentaerythryl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate], octadecyl-3- (3 , 5-di-t-butyl-4-hydroxyphenyl) propionate and the like. Although content of antioxidant is not specifically limited, For example, it is 5000 ppm or less, Preferably it is 4000 ppm or less, More preferably, it is 3000 ppm or less.

  The light-resistant stabilizer is not particularly limited, and examples thereof include 2- (5-methyl-2-hydroxyphenyl) benzotriazole and 2- (3-t-butyl-5-methyl-2-hydroxyphenyl) -5-chloro. Benzotriazole-based light stabilizers such as benzotriazole; bis (2,2,6,6-tetramethyl-4-piperidine) 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- Hindered amine light stabilizers such as piperidyl) imino}] and the like. Although content of a light-resistant stabilizer is not specifically limited, For example, it is 5000 ppm or less, Preferably it is 4000 ppm or less, More preferably, it is 3000 ppm or less.

  The content of the additive contained in the polyethylene powder is obtained by extracting the additive in the polyethylene powder by Soxhlet extraction with tetrahydrofuran (THF) for 6 hours, and separating and quantifying the extract by liquid chromatography. Can do.

  The polyethylene powder of this embodiment can be blended with ethylene polymers having different viscosity average molecular weights, molecular weight distributions, etc., and other resins such as low density polyethylene, linear low density polyethylene, polypropylene and polystyrene are blended. You can also.

[Specific surface area determined by BET method]
Specific surface area determined by the BET method of the polyethylene powder of the present embodiment is less 0.10 m ² / g or more 0.30 m ² / g, preferably 0.15 m ² / g or more 0.30 m ² / g or less There is more preferably 0.20 m ² / g or more 0.30 m ² / g or less.
When the specific surface area determined by the BET method is 0.10 m ² / g or more and 0.30 m ² / g or less, a polyethylene powder having excellent solubility in a solvent can be obtained.
In general, the specific surface area is related to the surface and the internal structure of the polyethylene powder, and the polyethylene powder with a small specific surface area has a smooth surface and pores penetrating from the surface to the inside, and the inside is isolated from the outside. And there are fewer voids. When the solvent and polyethylene powder are melt-kneaded, the area of the polyethylene powder that comes into contact with the solvent is reduced and the solubility in the solvent is deteriorated. On the other hand, polyethylene powder having a large specific surface area has more voids that are present from the outside than the surface of the polyethylene powder. Therefore, when melt-kneading with a solvent, it becomes difficult for the solvent to impregnate the inside of the polyethylene powder, and further, the void portion prevents heat conduction, so that the solubility is deteriorated.
Therefore, in this embodiment, polyethylene powder having excellent solubility can be obtained by setting the specific surface area obtained by the BET method within the above range.
The specific surface area calculated | required by BET method can be measured using the measuring apparatus according to BET method, Although it does not specifically limit as a measuring apparatus, For example, Yuasa Ionics autosorb 3MP etc. are mentioned. The specific surface area according to the BET method can be obtained by performing deaeration treatment using the autosorb 3MP manufactured by Yuasa Ionics Co., Ltd. as a pretreatment for the measurement sample and using nitrogen as the adsorption gas at a measurement temperature of −196 ° C. Can be measured.

In this embodiment, the method for controlling the specific surface area determined by the BET method within the above range includes, for example, controlling the synthesis conditions of the catalyst, controlling the method of adding the catalyst to the polymerization machine, and after polymerization. And controlling the post-treatment method of the polyethylene slurry.
Specifically, the catalyst synthesis conditions can be controlled by the concentration of raw materials in the catalyst synthesis reactor and the addition rate. By diluting the raw material concentration and slowing the raw material addition rate, it is possible to synthesize a solid catalyst in which the active sites of the catalyst are uniformly arranged. By producing polyethylene powder using this solid catalyst, it is possible to obtain a polyethylene powder having an appropriate specific surface area in which internal voids are suppressed while the particle surface has irregularities.
Polymer chain growth using a solid catalyst depends on the active sites on the surface of the solid catalyst. On the surface of the solid catalyst synthesized at a high concentration and at a high addition rate, the active sites may be poorly dispersed, and the active sites may be present locally on the catalyst surface in an aggregated form. Therefore, polymer chains also grow locally on the surface of such a solid catalyst. In this case, the growth of the polymer chain is non-uniform according to the degree of aggregation of the active sites, and the surface irregularities are also unstable and distorted. In addition, when the active sites are not dispersed, the aggregated catalyst mass grows large until it comes into contact with the adjacent polymer chain, so that the isolated cavity inside becomes large accordingly.
By using a solid catalyst in which the active sites of the catalyst are uniformly arranged, a polyethylene powder having an appropriate specific surface area can be obtained.

[Pore volume required by mercury intrusion method]
The pore volume calculated | required by the mercury intrusion method of the polyethylene powder of this embodiment is 0.85 mL / g or less, Preferably it is 0.80 mL / g or less.
When the pore volume determined by the mercury intrusion method is 0.85 mL / g or less, the solubility of the polyethylene polymer in the solvent is improved.
The pore volume is related to the internal structure of the polyethylene powder and the aggregation state of the polyethylene powder. The pore volume penetrating from the surface to the inside and the inside of the aggregated particles present when the particles of the polyethylene powder are closely aggregated It means space volume.
In general, when the pore volume increases, 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 form, so polyethylene powder dissolves Sex worsens.
Therefore, in the present embodiment, the solubility of the polyethylene polymer in the solvent is improved by setting the pore volume determined by the mercury intrusion method within the above range.
The pore volume calculated | required by the mercury intrusion method can be measured using a mercury porosimeter, and although it does not specifically limit as a measuring apparatus, For example, Shimadzu Corporation auto pore IV9500 type etc. are mentioned. Using a Shimadzu Autopore IV9500 model, etc., the sample was degassed as a pretreatment, and after filling the sample container with mercury, the pressure was gradually increased (high pressure part) to inject mercury into the pores of the sample. Thus, the pore volume can be measured by mercury porosimetry.

In the present embodiment, examples of a method for controlling the pore volume determined by the mercury intrusion method within the above range include controlling the synthesis conditions of the catalyst.
Specifically, the catalyst synthesis conditions can be controlled by the concentration of raw materials in the catalyst synthesis reactor and the addition rate. By diluting the raw material concentration and slowing down the raw material addition rate, the active sites of the catalyst are dispersed, and aggregation of the active sites in the solid catalyst can be suppressed. When the active sites in the solid catalyst are dispersed in this way, polymer chain growth does not occur locally, and the polymer chain is uniformly coated on the surface of the solid catalyst, so that a polyethylene powder having a small pore volume can be obtained.
By using a solid catalyst in which the active sites of the catalyst are dispersed, a polyethylene powder having an appropriate pore volume can be obtained.

The polyethylene powder of this embodiment has a specific surface area determined by the BET method of 0.10 m ² / g or more and 0.30 m ² / g or less, and a pore volume determined by the mercury intrusion method of 0.85 mL / g or less. As a result, there are irregularities on the particle surface of the polyethylene powder, and there are few hollow parts isolated from the outside inside the particle, so it has excellent solubility when kneaded with a solvent, and high-speed production In this case, undissolved polyethylene powder does not remain. By using the polyethylene powder of the present embodiment, a continuously uniform microporous membrane for a secondary battery separator can be stably produced even during high-speed production.

[Viscosity average molecular weight (Mv)]
The polyethylene powder of this embodiment has a viscosity average molecular weight (Mv) of 100,000 to 1,000,000, preferably 150,000 to 800,000, more preferably 200,000 to 700,000.
When the viscosity average molecular weight (Mv) is 100,000 or more and 1,000,000 or less, it is excellent in productivity, and when molded, the polyethylene powder 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.

Viscosity average molecular weight (Mv) is obtained from intrinsic viscosity [η] (dL / g) obtained by dissolving polyethylene polymer in decahydronaphthalene solution at different concentrations and extrapolating reduced viscosity obtained at 135 ° C. to 0 concentration. It can be calculated by the following formula A.
Mv = (5.34 × 10 ⁴ ) × [η] ^1.49 (Formula A)

In the present embodiment, as a method for controlling the viscosity average molecular weight (Mv) within the above range, for example, changing the polymerization temperature of the reactor when polymerizing the polyethylene polymer can be mentioned. 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 of the polyethylene polymer produced even at the same polymerization temperature tends to be low.
In the present embodiment, it is preferable to control the viscosity average molecular weight (Mv) of the polyethylene polymer by combining both methods.

[Pore distribution required by mercury intrusion method]
In the polyethylene powder of this embodiment, in the pore distribution determined by the mercury intrusion method, there is preferably no maximum value at a pore diameter of 30 μm or less.
When the maximum value is larger than the pore diameter of 30 μm, it is possible to obtain a polyethylene powder having a large pore diameter present on the particle surface of the polyethylene powder, which can be easily impregnated inside the particle such as a solvent and has good solubility.
The pore distribution can be measured by mercury porosimetry. The pore diameter corresponding to the mercury pressure can be measured from the balance between the surface tension of mercury and the pressure acting on the pore cross section.

  In this embodiment, as a method for controlling the pore distribution determined by the mercury intrusion method to the above range, for example, suppressing deformation / melting of the particle surface in the production process of polyethylene powder can be mentioned. In other words, in the polymerization, catalyst deactivation, and drying processes, the surface of the polyethylene powder is subjected to a load and can be controlled by suppressing the pores from being blocked or narrowed by melting, abrasion, aggregation, or the like. Specifically, in order to increase the maximum value of the pore diameter in the pore distribution determined by the mercury intrusion method, the polymerization temperature is lowered or the catalyst slurry concentration is lowered, in the process tank of the catalyst deactivation or drying process. Examples thereof include lowering the temperature and the stirring speed.

[Average particle size]
The average particle diameter of the polyethylene powder of the present embodiment is preferably 1 μm or more and 200 μm or less, more preferably 50 μm or more and 180 μm or less, and further preferably 120 μm or more and 160 μm or less.
When the average particle size is 1 μm or more, the bulk density and fluidity of the polyethylene powder are sufficiently high, and therefore handling properties such as charging into the hopper and measurement from the hopper tend to be better. When the average particle diameter is 200 μm or less, the processing applicability such as productivity and / or stretchability tends to be more excellent when processing secondary battery separators and fibers.
An average particle diameter can be measured by the method as described in an Example.

  In the present embodiment, as a method for controlling the average particle size within the above range, for example, it can be controlled by the particle size of the catalyst used, and can be controlled by the productivity of polyethylene powder per unit catalyst amount. Is also possible. 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.

[Unevenness (UD)]
The degree of unevenness (UD) of the polyethylene powder of the present embodiment is preferably that the polyethylene powder having a form with a UD of 0.90 or more and 0.95 or less is 60% or more of the total number of particles, more preferably UD. The polyethylene powder having a form of 0.91 or more and 0.94 or less is 60% or more of the total number of particles.
When the unevenness degree (UD) is within such a range, the solubility of the polyethylene powder in the solvent can be improved.
The degree of unevenness (UD) is 0 <UD ≦ 1, and the closer the UD is to 1, the smoother the surface is such that the particles are not uneven.
The unevenness degree (UD) can be measured using, for example, a dynamic image method particle size distribution / particle shape evaluation apparatus QICPIC manufactured by Japan Laser Corporation. Using the apparatus or the like, the measurement sample can be dispersed by an airflow type dry disperser, and images of dispersed particles can be continuously captured and measured from the captured image information using image analysis software.
As shown in FIG. 1, when the projected area of the obtained target particle is A and the projected area surrounded by the envelope connecting the convex portions of the target particle is A + B, the degree of unevenness (UD) is expressed by the following formula (1). Defined by
UD = A / (A + B) (1)

In this embodiment, as a method of controlling the degree of unevenness (UD) within the above range, for example, controlling the synthesis conditions of the catalyst can be mentioned.
Specifically, the catalyst synthesis conditions can be controlled by the concentration of raw materials in the catalyst synthesis reactor and the addition rate. By diluting the raw material concentration and slowing the raw material addition rate, it is possible to synthesize a solid catalyst in which the active sites of the catalyst are uniformly arranged. By suppressing the generation of a heterogeneous catalyst in which active sites are locally concentrated, it is possible to suppress the polymer chain from growing in a strain.

[Titanium content in polyethylene powder]
The amount of titanium contained in the polyethylene powder of the present embodiment is preferably 1 ppm or more and 200 ppm or less, more preferably 1 ppm or more and 12 ppm or less, and further preferably 1 ppm or more and 10 ppm or less.
The amount of titanium contained in the polyethylene powder is derived from the catalyst component used in the polymerization step.
When the amount of titanium is 1 ppm or more, when used as a rechargeable ion secondary battery separator, it tends to adsorb hydrogen fluoride which is caused by decomposition of the electrolytic salt and adversely affects the battery reaction. When the amount of titanium is 200 ppm or less, polyethylene powder that is more excellent in thermal stability is obtained. In addition, when a battery separator or fiber is used, the long-term stability thereof is further improved.
The amount of titanium contained in the polyethylene powder can be measured by the method described in the examples.

  The amount of titanium contained in the polyethylene powder can be controlled by the productivity of the polyethylene powder per unit catalyst. The productivity of polyethylene powder can be controlled by the polymerization temperature, polymerization pressure, and polyethylene slurry concentration in the reactor during production. Examples of the method for increasing the productivity of polyethylene powder include increasing the polymerization temperature, increasing the polymerization pressure, and / or increasing the polyethylene slurry concentration. The catalyst to be used is not particularly limited, and a general Ziegler-Natta catalyst can be used, but a catalyst described later is preferably used.

[Production method of polyethylene powder]
In the present embodiment, the polyethylene powder is not particularly limited, but can be produced using a general Ziegler-Natta catalyst, and it is preferable to use the Ziegler-Natta catalyst described below.
The Ziegler-Natta catalyst is a catalyst comprising a solid catalyst component [A] and an organometallic compound component [B], and the solid catalyst component [A] is soluble in the inert hydrocarbon solvent represented by Formula 1. What is the catalyst for olefin polymerization manufactured by making the organomagnesium compound (A-1) which is and the titanium compound (A-2) represented by Formula 2 react is preferable.
(A-1): (M ¹ ) α (Mg) β (R ² ) _a (R ³ ) _b Y ¹ _c Formula 1
(In Formula 1, M ¹ is a metal atom belonging to the group consisting of Groups 12, 13, and 14 in the periodic table, and R ² and R ³ are hydrocarbon groups having 2 to 20 carbon atoms. , Y ¹ is alkoxy, siloxy, allyloxy, amino, amide, —N═CR ⁴ R ⁵ , —SR ⁶ and β-keto acid residues (wherein R ⁴ , R ⁵ and R ⁶ have 1 carbon atom) And a hydrocarbon group of 20 or less, and when c is 2, Y ¹ may be different from each other.), Α, β, a, b, and c are real numbers that satisfy the following relationship: 0 ≦ α, 0 <β, 0 ≦ a, 0 ≦ b, 0 ≦ c, 0 <a + b, 0 ≦ b / (α + β) ≦ 2, nα + 2β = a + b + c (where n represents the valence of M ¹ . ))
(A-2): Ti (OR ⁷ ) _d X ¹ _(4-d) Formula 2
(In Formula 2, d is a real number of 0 or more and 4 or less, R ⁷ is a hydrocarbon group of 1 to 20 carbon atoms, and X ¹ is a halogen atom.)

  Although it does not specifically limit as an inert hydrocarbon solvent used for reaction of (A-1) and (A-2), For example, aliphatic hydrocarbons, such as butane, pentane, hexane, heptane; benzene, toluene, xylene And alicyclic hydrocarbons such as cyclopentane, cyclohexane, methylcyclohexane, decalin, and the like.

  (A-1) is shown as a complex form of organomagnesium soluble in an inert hydrocarbon solvent, but includes all dihydrocarbylmagnesium compounds and complexes of this compound with other metal compounds. Is. The relational expression nα + 2β = a + b + c of the symbols α, β, a, b, c indicates the stoichiometry between the valence of the metal atom and the substituent.

In Formula 1, the hydrocarbon group having 2 to 20 carbon atoms represented by R ² and R ³ is not particularly limited, and examples thereof include alkyl, cycloalkyl, and aryl groups. Specifically, Examples include ethyl, propyl, butyl, propyl, hexyl, octyl, decyl, cyclohexyl, and phenyl groups. Among these, an alkyl group is preferable.

In Formula 1, when α> 0, the metal atom M ¹ is not particularly limited as long as it is a metal atom belonging to the group consisting of Group 12, Group 13, and Group 14 of the Periodic Table. For example, zinc, Examples include boron and aluminum. Among these, aluminum and zinc are preferable.
The ratio β / α of magnesium to the metal atom M ¹ is not particularly limited, but is preferably 0.1 or more and 30 or less, more preferably 0.5 or more and 10 or less.

In Formula 1, when α = 0, R ² and R ³ are preferably any one of the following three groups (1), (2), and (3).

Group (1):
At least one of R ² and R ³ is a secondary or tertiary alkyl group having 4 to 6 carbon atoms, preferably R ² and R ³ are both alkyl groups having 4 to 6 carbon atoms, At least one is a secondary or tertiary alkyl group.
Group (2):
R ² and R ³ are alkyl groups different from each other, preferably R ² is an alkyl group having 2 or 3 carbon atoms, and R ³ is an alkyl group having 4 or more carbon atoms.
Group (3):
At least one of R ² and R ³ is a hydrocarbon group having 6 or more carbon atoms, preferably an alkyl group that becomes 12 or more when the number of carbon atoms contained in R ² and R ³ is added.

The secondary or tertiary alkyl group having 4 to 6 carbon atoms in the group (1) is not particularly limited, and examples thereof include 1-methylpropyl, 2-methylpropyl, 1,1-dimethylethyl, 2- Examples include methylbutyl, 2-ethylpropyl, 2,2-dimethylpropyl, 2-methylpentyl, 2-ethylbutyl, 2,2-dimethylbutyl, and 2-methyl-2-ethylpropyl group. Among these, a 1-methylpropyl group is preferable.
In Formula 1, when α = 0, for example, when R ² is 1-methylpropyl or the like, the compound is soluble in an inert hydrocarbon solvent, and such a compound also gives preferable results to this embodiment.

In group (2), the alkyl group having 2 or 3 carbon atoms is not particularly limited, and examples thereof include ethyl, 1-methylethyl, and propyl groups. Among these, an ethyl group is preferable.
The alkyl group having 4 or more carbon atoms is not particularly limited, and examples thereof include a butyl group, a pentyl group, a hexyl group, a heptyl group, and an octyl group. Of these, butyl and hexyl groups are preferred.

  In group (3), the hydrocarbon group having 6 or more carbon atoms is not particularly limited, and examples thereof include hexyl, heptyl, octyl, nonyl, decyl, phenyl, and 2-naphthyl group. Among these, an alkyl group is preferable, and among the alkyl groups, hexyl and octyl groups are more preferable.

  In general, when the number of carbon atoms contained in the alkyl group increases, it tends to be soluble in an inert hydrocarbon solvent, and the viscosity of the solution tends to increase. Therefore, it is preferable in handling to use an appropriate long-chain alkyl group. (A-1) can be used by diluting with an inert hydrocarbon solvent. However, a trace amount of Lewis basic compounds such as ethers, esters, and amines may be contained or remain in the solution. Can be used without

In Formula 1, Y ¹ is any of an alkoxy, siloxy, allyloxy, amino, amide group, —N═CR ⁴ R ⁵ , —SR ⁶ and a β-keto acid residue. Here, R ⁴ , R ⁵ and R ⁶ are each independently a hydrocarbon group having 1 to 20 carbon atoms.

TMI: The position is moving.
Y ¹ is preferably an alkoxy or siloxy group.
Examples of the alkoxy group include, but are not limited to, methoxy, ethoxy, propoxy, 1-methylethoxy, butoxy, 1-methylpropoxy, 1,1-dimethylethoxy, pentoxy, hexoxy, 2-methylpentoxy, 2-ethyl. Examples include butoxy, 2-ethylpentoxy, 2-ethylhexoxy, 2-ethyl-4-methylpentoxy, 2-propylheptoxy, 2-ethyl-5-methyloctoxy, octoxy, phenoxy and naphthoxy groups. Among these, butoxy, 1-methylpropoxy, 2-methylpentoxy and 2-ethylhexoxy groups are preferable.
The siloxy group is not particularly limited, and examples thereof include hydrodimethylsiloxy, ethylhydromethylsiloxy, diethylhydrosiloxy, trimethylsiloxy, ethyldimethylsiloxy, diethylmethylsiloxy, triethylsiloxy group and the like. Among these, hydrodimethylsiloxy, ethylhydromethylsiloxy, diethylhydrosiloxy, and trimethylsiloxy groups are preferable.

R ⁴ , R ⁵ and R ⁶ are preferably an alkyl or aryl group having 1 to 12 carbon atoms, and more preferably an alkyl or aryl group having 3 to 10 carbon atoms. The alkyl or aryl group having 1 to 12 carbon atoms is not particularly limited, 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 Groups and the like. Of these, butyl, 1-methylpropyl, 2-methylpentyl and 2-ethylhexyl groups are preferred.

In the present embodiment, the synthesis method of (A-1) is not particularly limited. For example, formula R ² MgX ¹ or formula R ² ₂ Mg (R ² has the above-mentioned meaning, and X ¹ is a halogen atom. And an organometallic compound represented by the formula M ¹ R ³ _n or M ¹ R ³ _(n-1) H (M ¹ , R ³ and n are as defined above). The compound is allowed to react at 25 ° C. or more and 150 ° C. or less in an inert hydrocarbon solvent, and if necessary, the compound represented by the formula Y ¹ -H (Y ¹ has the above-mentioned meaning) is subsequently obtained. It can be synthesized by reacting or reacting an organomagnesium compound and / or organoaluminum compound having a functional group represented by Y ¹ . Among these, when the organomagnesium compound soluble in the inert hydrocarbon solvent and the compound represented by the formula Y ¹ -H are reacted, the order of the reaction is not particularly limited, but the formula is contained in the organomagnesium compound. how will the addition of a compound represented by Y ¹ -H, using any of the methods of the formula Y ¹ way going adding an organic magnesium compound into a compound represented by -H, or a method of gradually adding simultaneously both be able to.

The range of the molar composition ratio c / (α + β) of Y ¹ with respect to all metal atoms in (A-1) is 0 ≦ c / (α + β) ≦ 2, and preferably 0 ≦ c / (α + β) <1. . When the molar composition ratio of Y ^{1 to} all metal atoms is 2 or less, the reactivity of (A-1) to (A-2) tends to be improved.

(A-2) is a titanium compound represented by Formula 2.
(A-2): Ti (OR ⁷ ) _d X ¹ _(4-d) Formula 2
(In Formula 2, d is a real number of 0 or more and 4 or less, R ⁷ is a hydrocarbon group of 1 to 20 carbon atoms, and X ¹ is a halogen atom.)

d is preferably a real number of 0 or more and 1 or less, and more preferably 0.
The hydrocarbon group having 1 to 20 carbon atoms represented by R ⁷ is not particularly limited. For example, methyl, ethyl, propyl, butyl, pentyl, hexyl, 2-ethylhexyl, heptyl, octyl, decyl, allyl group An aliphatic hydrocarbon group such as cyclohexyl, 2-methylcyclohexyl, and cyclopentyl group; and an aromatic hydrocarbon group such as phenyl and naphthyl group. Among these, an aliphatic hydrocarbon group is preferable.
Examples of the halogen represented by X ¹ include chlorine, bromine, iodine and the like. Among these, chlorine is preferable.
In the present embodiment, (A-2) is preferably titanium tetrachloride. In this embodiment, it is possible to use a mixture of two or more types as (A-2).

The reaction between (A-1) and (A-2) is preferably carried out in an inert hydrocarbon solvent, more preferably in an aliphatic hydrocarbon solvent such as hexane or heptane. The molar ratio of (A-1) to (A-2) in the above reaction is not particularly limited, but the molar ratio of Ti atoms contained in (A-2) to Mg atoms contained in (A-1) ( Ti / Mg) is preferably 0.1 or more and 10 or less, more preferably 0.3 or more and 3 or less.
Although it does not specifically limit about reaction temperature, For example, it is the range of -80 degreeC or more and 150 degrees C or less, Preferably it is the range of -40 degreeC-100 degreeC.
The order of addition of (A-1) and (A-2) is not particularly limited, but (A-2) is added following (A-1), (A-1) is followed by (A-1) Any method of adding (A-1) and (A-2) at the same time is possible, but (A-1) and (A-2) are preferably added at the same time.
Moreover, although it does not specifically limit about the space | interval which adds (A-1) and (A-2), Although any method of adding continuously and adding intermittently is possible, 3 minutes or more 20 It is preferable to intermittently add at a cycle of 5 minutes or less, and more preferably intermittent addition at a cycle of 5 minutes to 15 minutes. Although it does not specifically limit about the time to add (A-1) and (A-2), 1 hour or more and 10 hours or less are preferable, and 2 hours or more and 5 hours or less are more preferable. The time for aging (A-1) and (A-2) is not particularly limited, but it is preferably in the range of 1 hour to 10 hours, and more preferably 2 hours to 5 hours. By performing the reaction of (A-1) and (A-2) as described above, the active sites of the catalyst can be more uniformly dispersed, and further, aggregation of the active sites in the solid catalyst can be suppressed. Therefore, polymer chain growth does not occur locally, and the polymer chain uniformly covers the surface of the catalyst particles, so that polyethylene powder with a small pore volume can be obtained, and internal voids are suppressed while having surface irregularities. A polyethylene powder having an appropriate specific surface area is obtained.

  In this embodiment, it is preferable to remove unreacted (A-1) and (A-2) after the reaction of (A-1) and (A-2). Unreacted (A-1) and (A-2) can be removed, and generation of amorphous polymers such as lumps, adhesion to the reactor wall surface, clogging of the extraction piping, etc. can be suppressed. It tends to be excellent in production. Removal of unreacted (A-1) and (A-2) can be reduced by repeatedly removing the supernatant liquid while the catalyst slurry is settled and adding a fresh inert hydrocarbon solvent. . It can also be removed by filtration using a filter or the like. It is preferable that the residual chlorine concentration derived from (A-2) is 1 mmol / L or less.

  In the present embodiment, the solid catalyst component [A] obtained by the above reaction is used as a slurry solution using an inert hydrocarbon solvent.

Another example of the Ziegler-Natta catalyst component used in the present embodiment includes a solid catalyst component [C] and an organometallic compound component [B], and the solid catalyst component [C] is represented by Formula 3. A carrier (C-3) prepared by reacting an organomagnesium compound (C-1) soluble in an inert hydrocarbon solvent with a chlorinating agent (C-2) represented by formula 4 contains A catalyst for olefin polymerization produced by supporting an organomagnesium compound (C-4) soluble in an inert hydrocarbon solvent represented by formula (2) and a titanium compound (C-5) represented by formula (2) Is mentioned.
(C-1): (M ² ) γ (Mg) δ (R ⁸ ) _e (R ⁹ ) _f (OR ¹⁰ ) _g Formula 3
(In Formula 3, M ² is a metal atom belonging to the group consisting of Groups 12, 13 and 14 of the periodic table, and R ⁸ , R ⁹ and R ¹⁰ are each a carbon atom having 1 to 20 carbon atoms. Γ, δ, e, f, and g are real numbers that satisfy the following relationship: 0 ≦ γ, 0 <δ, 0 ≦ e, 0 ≦ f, 0 ≦ g, 0 <e + f, 0 ≦ g / (γ + δ) ≦ 2, kγ + 2δ = e + f + g (where k represents the valence of M ² ))
(C-2): H _h SiCl _i R ¹¹ _{(4- (h + i))} Formula 4
(In Formula 4, R ¹¹ is a hydrocarbon group having 1 to 12 carbon atoms, and h and i are real numbers satisfying the following relationship: 0 <h, 0 <i, 0 <h + i ≦ 4)
(C-4): (M ¹ ) α (Mg) β (R ² ) _a (R ³ ) _b Y ¹ _c Formula 1
(In Formula 1, M ¹ is a metal atom belonging to the group consisting of Groups 12, 13, and 14 in the periodic table, and R ² and R ³ are hydrocarbon groups having 2 to 20 carbon atoms. Y ¹ is an alkoxy, siloxy, allyloxy, amino, amide group, —N═C—R ⁴ R ⁵ , —SR ⁶ and β-keto acid residues (where R ⁴ , R ⁵ and R ⁶ are Represents a hydrocarbon group having 1 to 20 carbon atoms, and when c is 2, Y ¹ may be different from each other.), Α, β, a, b, and c are real numbers that satisfy the following relationship: 0 ≦ α, 0 <β, 0 ≦ a, 0 ≦ b, 0 ≦ c, 0 <a + b, 0 ≦ b / (α + β) ≦ 2, nα + 2β = a + b + c (where n is the valence of M ¹ Represents)))
(C-5): Ti (OR ⁷ ) _d X ¹ _(4-d) Formula 2
(In Formula 2, d is a real number of 0 or more and 4 or less, R ⁷ is a hydrocarbon group of 1 to 20 carbon atoms, and X ¹ is a halogen atom.)
In this embodiment, as (C-4), the same organomagnesium compound as (A-1) can be used, and as (C-5), the same titanium compound as (A-2) can be used. Can be used. Formulas 1 and 2 in (C-4) and (C-5) are as described above for (A-1) and (A-2).

  (C-1) is shown as a complex form of organomagnesium soluble in an inert hydrocarbon solvent, but includes all dihydrocarbylmagnesium compounds and complexes of this compound with other metal compounds Is. The relational expression kγ + 2δ = e + f + g of the symbols γ, δ, e, f, and g in Formula 3 indicates the stoichiometry between the valence of the metal atom and the substituent.

In Formula 3, the hydrocarbon group having 1 to 20 carbon atoms represented by R ⁸ and R ⁹ is not particularly limited, and examples thereof include alkyl, cycloalkyl, and aryl groups. Specifically, Examples include methyl, ethyl, propyl, butyl, propyl, hexyl, octyl, decyl, cyclohexyl, and phenyl groups. Among these, an alkyl group is preferable.

In Formula 3, when α> 0, the metal atom M ² is not particularly limited as long as it is a metal atom belonging to the group consisting of Group 12, Group 13, and Group 14 of the Periodic Table. For example, zinc, Examples include boron and aluminum. Among these, aluminum and zinc are preferable.
The ratio δ / γ of magnesium to the metal atom M ² is not particularly limited, but is preferably 0.1 or more and 30 or less, more preferably 0.5 or more and 10 or less.

In Formula 3, when γ = 0, R ⁸ and R ⁹ are preferably any one of the following three groups (4), (5), and (6).

Group (4):
At least one of R ⁸ and R ⁹ is a secondary or tertiary alkyl group having 4 to 6 carbon atoms, preferably both R ⁸ and R ⁹ are alkyl groups having 4 to 6 carbon atoms, At least one is a secondary or tertiary alkyl group.
Group (5):
R ⁸ and R ⁹ are alkyl groups having different carbon numbers, preferably R ⁸ is an alkyl group having 2 or 3 carbon atoms, and R ⁹ is an alkyl group having 4 or more carbon atoms.
Group (6):
At least one of R ⁸ and R ⁹ is a hydrocarbon group having 6 or more carbon atoms, preferably an alkyl group that becomes 12 or more when the number of carbon atoms contained in R ⁸ and R ⁹ is added.

In the group (1), the secondary or tertiary alkyl group having 4 to 6 carbon atoms is not particularly limited, and examples thereof include 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 group and the like. Among these, a 1-methylpropyl group is preferable.
In Formula 3, when γ = 0, for example, when R ⁸ is 1-methylpropyl or the like, it is soluble in an inert hydrocarbon solvent, and such a compound also gives favorable results to this embodiment.

In group (2), the alkyl group having 2 or 3 carbon atoms is not particularly limited, and examples thereof include ethyl, 1-methylethyl, and propyl groups. Among these, an ethyl group is preferable.
The alkyl group having 4 or more carbon atoms is not particularly limited, and examples thereof include a butyl group, a pentyl group, a hexyl group, a heptyl group, and an octyl group. Of these, butyl and hexyl groups are preferred.

  In group (3), the hydrocarbon group having 6 or more carbon atoms is not particularly limited, and examples thereof include hexyl, heptyl, octyl, nonyl, decyl, phenyl, and 2-naphthyl group. Among these, an alkyl group is preferable, and among the alkyl groups, hexyl and octyl groups are more preferable.

  In general, when the number of carbon atoms contained in an alkyl group increases, it tends to be easily dissolved in an inert hydrocarbon solvent, and the viscosity of the solution tends to increase. Therefore, it is preferable in handling to use an appropriate long-chain alkyl group. (C-1) can be used by diluting with an inert hydrocarbon solvent, but the solution may contain a trace amount of Lewis basic compounds such as ethers, esters, and amines, or may remain. Can be used without

In Formula 3, the hydrocarbon group having 1 to 20 carbon atoms represented by R ¹⁰ is preferably an alkyl or aryl group having 1 to 12 carbon atoms, and more preferably an alkyl or aryl group having 3 to 10 carbon atoms.
The hydrocarbon group having 1 to 20 carbon atoms is not particularly limited, 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 groups Etc. Of these, butyl, 1-methylpropyl, 2-methylpentyl and 2-ethylhexyl groups are preferred.

In the present embodiment, the synthesis method of (C-1) is not particularly limited. For example, formula R ⁸ MgX ¹ or formula R ⁸ ₂ Mg (R ⁸ has the above-mentioned meaning, and X ¹ is a halogen atom. And an organic magnesium compound represented by the formula M ² R ⁹ _k or the formula M ² R ⁹ _(k-1) H (M ² , R ⁹ and k are as defined above). Reaction with a metal compound in an inert hydrocarbon solvent at a temperature of 25 ° C. or more and 150 ° C. or less, and if necessary, a hydrocarbon represented by R ⁹ (where R ⁹ has the above-mentioned meaning) A method of reacting with an alkoxymagnesium compound and / or an alkoxyaluminum compound having a hydrocarbon group represented by R ⁹ soluble in an alcohol having a group or an inert hydrocarbon solvent is preferred. Among these, when reacting an organomagnesium compound soluble in an inert hydrocarbon solvent with an alcohol, the order of the reaction is not particularly limited, but the method of adding alcohol to the organomagnesium compound, organic in the alcohol Any method of adding a magnesium compound or adding both at the same time can be used.
The reaction ratio between the organomagnesium compound and the alcohol is not particularly limited, but the molar composition ratio g / (γ + δ) of alkoxy groups to all metal atoms in the resulting alkoxy group-containing organomagnesium compound as a result of the reaction is 0 ≦ g / It is preferable that (γ + δ) ≦ 2 and 0 ≦ g / (γ + δ) <1.

(C-2) is a chlorinating agent represented by Formula 4, and at least one is a silicon chloride compound having a Si—H bond.
(C-2): H _h SiCl _i R ¹¹ _{(4- (h + i))} Formula 4
(In Formula 4, R ¹¹ is a hydrocarbon group having 1 to 12 carbon atoms, and h and i are real numbers satisfying the following relationship: 0 <h, 0 <i, 0 <h + i ≦ 4)

In Formula 4, the hydrocarbon group having 1 to 12 carbon atoms represented by R ¹¹ is not particularly limited, and examples thereof include an aliphatic hydrocarbon group, an alicyclic hydrocarbon group, and an aromatic hydrocarbon group. Specific examples include methyl, ethyl, propyl, 1-methylethyl, butyl, pentyl, hexyl, octyl, decyl, cyclohexyl, and phenyl groups. Among these, an alkyl group having 1 to 10 carbon atoms is preferable, and an alkyl group having 1 to 3 carbon atoms such as methyl, ethyl, propyl, and 1-methylethyl group is more preferable. H and i are real numbers larger than 0 satisfying the relationship of h + i ≦ 4, and i is preferably a real number of 2 or more and 3 or less.

(C-2) as is not particularly limited, _{specifically, 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 and the} like. Among these, HSiCl ₃ , HSiCl ₂ CH ₃ , HSiCl (CH ₃ ) ₂ , and HSiCl ₂ (C ₃ H ₇ ) are preferable, and HSiCl ₃ and HSiCl ₂ CH ₃ are more preferable. In this embodiment, it is possible to use a mixture of two or more types as (C-2).

In the reaction between (C-1) and (C-2), (C-2) is preliminarily inert hydrocarbon solvent; chlorinated hydrocarbon such as 1,2-dichloroethane, o-dichlorobenzene, dichloromethane, etc. It is preferably used after diluting with an ether solvent such as diethyl ether or tetrahydrofuran; or a mixed solvent thereof. Among these, an inert hydrocarbon solvent is more preferable in terms of catalyst performance.
Although the reaction ratio of (C-1) and (C-2) is not particularly limited, the silicon atom contained in (C-2) with respect to 1 mol of magnesium atom contained in (C-1) is 0.01 mol or more and 100 mol. Or less, more preferably 0.1 mol or more and 10 mol or less.

  The reaction method of (C-1) and (C-2) is not particularly limited, and a method of simultaneous addition in which (C-1) and (C-2) are reacted while being simultaneously introduced into the reactor, A method in which (C-1) is introduced into the reactor after C-2) is charged to the reactor in advance, or (C-2) is charged into the reactor after (C-1) is charged in the reactor in advance. Any of the methods of introduction can be used. Among these, the method of introducing (C-1) into the reactor after charging (C-2) into the reactor in advance is preferable. The carrier (C-3) obtained by the reaction is preferably separated by filtration or decantation, and then thoroughly washed with an inert hydrocarbon solvent to remove unreacted products or by-products. .

Although it does not specifically limit about the reaction temperature of (C-1) and (C-2), For example, it is 25 to 150 degreeC, Preferably it is 30 to 120 degreeC, More preferably, it is 40 degreeC The temperature is 100 ° C. or higher.
In the method of simultaneous addition in which (C-1) and (C-2) are simultaneously introduced into the reactor and reacted, the temperature of the reactor is adjusted to a predetermined temperature in advance, The reaction temperature is preferably adjusted to the predetermined temperature by adjusting the temperature to the predetermined temperature. In a method in which (C-1) is introduced into the reactor after (C-2) is charged into the reactor in advance, the temperature of the reactor charged with (C-2) is adjusted to a predetermined temperature, It is preferable to adjust the reaction temperature to the predetermined temperature by adjusting the temperature in the reactor to the predetermined temperature while introducing -1) into the reactor. In the method of introducing (C-2) into the reactor after charging (C-1) into the reactor in advance, the temperature of the reactor charged with (C-1) is adjusted to a predetermined temperature, The reaction temperature is adjusted to a predetermined temperature by adjusting the temperature in the reactor to a predetermined temperature while introducing -2) into the reactor.

  The amount of (C-4) used is preferably 0.1 or more and 10 or less in terms of a molar ratio of magnesium atoms contained in (C-4) to titanium atoms contained in (C-5). More preferably, it is 5 or less.

  Although it does not specifically limit about the temperature of reaction with (C-4) and (C-5), For example, they are -80 degreeC or more and 150 degrees C or less, Preferably they are -40 degreeC or more and 100 degrees C or less.

  The concentration when (C-4) is used is not particularly limited. For example, it is 0.1 mol / L or more and 2 mol / L or less, preferably 0.5 mol based on the titanium atom contained in (C-4). / L or more and 1.5 mol / L or less. An inert hydrocarbon solvent is preferably used for the dilution of (C-4).

The order of addition of (C-4) and (C-5) to (C-3) is not particularly limited, but (C-5) is added following (C-4), (C-5) is followed. (C-4) and (C-4) and (C-5) can be added at the same time. Among these, the method of adding (C-4) and (C-5) simultaneously is preferable. Although the reaction of (C-4) and (C-5) is carried out in an inert hydrocarbon solvent, it is preferable to use an aliphatic hydrocarbon solvent such as hexane or heptane as the inert hydrocarbon solvent.
The interval at which (C-4) and (C-5) are added is not particularly limited, but any method of adding continuously or intermittently can be used, but 3 minutes or more and 20 minutes or less. It is preferable to intermittently add at a period of 5 minutes, and it is more preferable to add intermittently at a period of 5 minutes to 15 minutes. Although it does not specifically limit about the time to add (C-4) and (C-5), 1 hour or more and 10 hours or less are preferable, and 2 hours or more and 5 hours or less are more preferable. The time for aging (C-4) and (C-5) is not particularly limited, but is preferably 1 hour or longer and 10 hours or shorter, and more preferably 2 hours or longer and 5 hours or shorter. The catalyst obtained by the above reaction is used as a slurry solution using an inert hydrocarbon solvent.

  Although the usage-amount of (C-5) is not specifically limited, 0.01-20 is preferable in molar ratio with respect to the magnesium atom contained in a support | carrier (C-3), and 0.05-10 is more preferable.

  Although it does not specifically limit about reaction temperature of (C-5), For example, they are -80 degreeC or more and 150 degrees C or less, Preferably they are -40 degreeC or more and 100 degrees C or less. In this embodiment, the method of supporting (C-5) with respect to (C-3) is not particularly limited, but a method of reacting excess (C-5) with (C-3), A method of efficiently supporting (C-5) by using components may be used, but a method of supporting by (C-5) and an organomagnesium compound (C-4) is preferable.

The Ziegler-Natta catalyst used in the present embodiment becomes a highly active polymerization catalyst by combining the solid catalyst component [A] or the solid catalyst component [C] with the organometallic compound component [B]. The organometallic compound component [B] is sometimes called a “promoter”.
Although it does not specifically limit as organometallic compound component [B], For example, the compound etc. which contain the metal which belongs to the group which consists of a periodic table 1st group, 2nd group, 12th group, and 13th group are mentioned. Among these, an organoaluminum compound and / or an organomagnesium compound are preferable.

As the organoaluminum compound, the compound represented by Formula 5 is preferably used alone or in combination.
AlR ¹² _j Z ¹ _(3-j) Formula 5
(In Formula 5, R ¹² is a hydrocarbon group having 1 to 20 carbon atoms, Z ¹ is a hydrogen, halogen atom, alkoxy, allyloxy, or siloxy group, and j is a real number of 2 to 3)

In Formula 5, the hydrocarbon group having 1 to 20 carbon atoms represented by R ¹² is not particularly limited, and examples thereof include aliphatic hydrocarbons, aromatic hydrocarbons, and alicyclic hydrocarbons.
The compound represented by Formula 5 is not particularly limited. For example, trimethylaluminum, triethylaluminum, tripropylaluminum, tributylaluminum, tri (2-methylpropyl) aluminum (also referred to as triisobutylaluminum), and tripentylaluminum. , Trialkylaluminum compounds such as tri (3-methylbutyl) aluminum, trihexylaluminum, trioctylaluminum, tridecylaluminum; diethylaluminum chloride, ethylaluminum dichloride, bis (2-methylpropyl) aluminum chloride, ethylaluminum sesquichloride, Aluminum halide compounds such as diethylaluminum bromide; diethylaluminum ethoxide, bis (2-methylpro Le) alkoxy aluminum compounds such as aluminum butoxide; dimethylhydrosiloxy aluminum dimethyl, ethyl methyl hydro siloxy aluminum diethyl, siloxy aluminum compounds such as ethyl dimethylsiloxy aluminum diethyl and the like. Among these, a trialkylaluminum compound is preferable.

As the organomagnesium compound, it is preferable to use an organomagnesium compound that is soluble in an inert hydrocarbon solvent represented by Formula 3 also represented by (C-1), alone or in combination.
(M ² ) γ (Mg) δ (R ⁸ ) _e (R ⁹ ) _f (OR ¹⁰ ) _g Formula 3
(In Formula 3, M ² is a metal atom belonging to the group consisting of Groups 12, 13 and 14 of the periodic table, and R ⁸ , R ⁹ and R ¹⁰ are each a carbon atom having 2 to 20 carbon atoms. Γ, δ, e, f, and g are real numbers that satisfy the following relationship: 0 ≦ γ, 0 <δ, 0 ≦ e, 0 ≦ f, 0 ≦ g, 0 <e + f, 0 ≦ g / (γ + δ) ≦ 2, kγ + 2δ = e + f + g (where k represents the valence of M ² ))

The organomagnesium compound as the organometallic compound component [B] is the same as the organomagnesium compound represented by Formula 3 as described above as (C-1), but the organomagnesium compound is dissolved in an inert hydrocarbon solvent. Since higher properties are preferable, β / α is preferably in the range of 0.5 to 10, and a compound in which M ² is aluminum is more preferable.

  The method of adding the solid catalyst component [A] or the solid catalyst component [C] and the organometallic compound component [B] into the polymerization system under the polymerization conditions is not particularly limited, but both are separately added to the polymerization system. It may be added, or may be added to the polymerization system after reacting both in advance. Moreover, although the ratio of both to combine is not specifically limited, It is preferable that an organometallic compound component is 1 mmol or more and 3000 mmol or less with respect to 1 g of solid catalyst components.

  In the present embodiment, examples of the polymerization method in the method for producing polyethylene powder include a method of (co) polymerizing ethylene or a monomer containing ethylene by a suspension polymerization method or a gas phase polymerization method. Among these, the suspension polymerization method that can efficiently remove the heat of polymerization is preferable. In the suspension polymerization method, an inert hydrocarbon medium can be used as a medium, and α-olefin itself may be used as a solvent.

  The inert hydrocarbon medium is not particularly limited, but examples thereof include aliphatic hydrocarbons such as propane, butane, isobutane, pentane, isopentane, hexane, heptane, octane, decane, dodecane, and kerosene; cyclopentane, cyclohexane, methylcyclo Examples thereof include alicyclic hydrocarbons such as pentane; aromatic hydrocarbons such as benzene, toluene and xylene; halogenated hydrocarbons such as ethylene chloride, chlorobenzene and dichloromethane, or mixtures thereof.

  Although the polymerization temperature in the manufacturing method of polyethylene powder is not specifically limited, For example, they are 30 degreeC or more and 100 degrees C or less, Preferably they are 35 degreeC or more and 90 degrees C or less, More preferably, they are 40 degreeC or more and 80 degrees C or less. If the polymerization temperature is 30 ° C. or higher, industrially efficient production is possible. If the polymerization temperature is 100 ° C. or lower, continuous operation is possible.

  The polymerization pressure in the method for producing polyethylene powder is not particularly limited, but is, for example, from 0.1 MPa to 2.0 MPa, preferably from 0.1 MPa to 1.5 MPa, and more preferably from 0.1 MPa to 1. 0 MPa or less.

  The polymerization reaction in the method for producing polyethylene powder can be carried out in any of batch, semi-continuous and continuous methods, but it is preferable to carry out polymerization in a continuous manner. By continuously supplying ethylene gas, solvent, catalyst, etc. into the polymerization system and continuously discharging it together with the generated ethylene (co) polymer, it is possible to suppress partial high-temperature conditions due to rapid ethylene reaction. And the inside of the polymerization system becomes more stable. In addition, it is preferable that ethylene gas, a solvent, a catalyst, and the like before being supplied to the polymerization reactor are supplied at the same temperature as in the reactor in order to stabilize the system. When ethylene reacts in a uniform state in the system, the formation of branches and double bonds in the polymer chain is suppressed, and the surface deformation of the polyethylene powder is caused by the decomposition and crosslinking of the ethylene (co) polymer. Etc. are suppressed. Therefore, a continuous system in which the inside of the polymerization system becomes more uniform is preferable. It is also possible to carry out the polymerization in two or more stages having different reaction conditions.

  It is described in West German Patent Publication No. 3127133 that molecular weight can be controlled within an appropriate range by adding hydrogen as a chain transfer agent in the polymerization system. Adding hydrogen to the polymerization system can suppress the growth of the polymer chain by preventing the growth of the polymer chain by preventing the growth of the polymer chain by promoting the chain transfer of the catalyst in addition to controlling the molecular weight. It becomes possible. When hydrogen is added into the polymerization system, the molar fraction of hydrogen is preferably 0 mol% or more and 30 mol% or less, more preferably 3 mol% or more and 25 mol% or less, and more preferably 5 mol% or more and 20 mol% or less. More preferably.

  Moreover, it is preferable to add hydrogen into the polymerization system from the catalyst introduction line after contacting the catalyst in advance. Immediately after the catalyst is introduced into the polymerization system, the concentration of the catalyst near the outlet of the introduction line is high, and there is an increased possibility of partial high temperatures due to the rapid reaction of ethylene. By bringing it into contact before introduction, it is possible to suppress the initial activity of the catalyst, and it is possible to suppress the shape change of the initial polymerization particle shape of the polyethylene powder that has become a high temperature state due to rapid polymerization.

The deactivation method of the Ziegler-Natta 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. By introducing an agent for deactivating the catalyst after separation from the solvent, the low molecular weight component remaining in the solvent is reduced, and the low molecular component in the particle is dissolved by the heat of reaction of deactivation so that the particle surface pores It is possible to suppress deformation of the particle surface such as blocking the particle.
In the solvent separation step, the liquid content remaining in the polyethylene slurry is preferably 10 wt% or more and 60 wt% or less, more preferably 15 wt% or more and 55 wt% or less, and further preferably 20 wt% or more and 50 wt% or less. When the liquid content is less than 10 wt%, the particle surface tension of the polyethylene powder is increased, and it becomes difficult for the deactivating agent to penetrate into the particles in the catalyst deactivation process, thereby increasing the possibility of unevenness in deactivation. When the liquid content is higher than 60 wt%, the low molecular weight component remaining in the polyethylene powder increases, and as a result, the shape of the powder progresses as a result of an increase in dissolution sites.

  Although it does not specifically limit as a chemical | medical agent which deactivates a catalyst system, For example, oxygen, water, alcohols, glycols, phenols, carbon monoxide, carbon dioxide, ethers, a carbonyl compound, alkynes, etc. are mentioned.

Although the drying temperature in the manufacturing method of polyethylene powder is not specifically limited, For example, it is 50 to 150 degreeC, Preferably it is 50 to 140 degreeC, More preferably, it is 50 to 130 degreeC.
If the drying temperature is 50 ° C. or higher, efficient drying is possible. When the drying temperature is 150 ° C. or lower, it is possible to dry in a state in which decomposition and crosslinking of the ethylene polymer are suppressed. On the other hand, when the drying temperature is 150 ° C. or higher, the surface of the polyethylene powder is dissolved, so that the surface pores are blocked or reduced. Furthermore, since the particles of polyethylene powder collide and move while the surface dissolves, the unevenness of the particle surface is leveled and approaches a true sphere, so that the surface is blocked and polyethylene powder is generated that is difficult for the solvent to penetrate inside. It will be.

[Use]
The polyethylene powder of the present embodiment can be processed by various processing methods. Molded articles obtained using polyethylene powder can be used for various applications. For example, a molded product obtained using polyethylene powder is suitable as a microporous membrane for a secondary battery separator, among others, a microporous membrane for a lithium ion secondary battery separator, high-strength fibers, gel spinning, and the like.
As a method for producing a microporous membrane, specifically, a wet method using a solvent and a processing method through extrusion, stretching, extraction, and drying in an extruder equipped with a T die can be mentioned. Since the polyethylene powder of this embodiment is excellent in solubility with a solvent, it can be suitably used as a microporous membrane for battery separators. Such a microporous membrane can be suitably used for a secondary battery separator represented by a lithium ion secondary battery or a lead storage battery, particularly for a lithium ion secondary battery separator. In the present embodiment, the molded body or rechargeable ion secondary battery separator or the like obtained by using polyethylene powder may be a molded body or rechargeable ion secondary battery separator or the like containing polyethylene powder.

  EXAMPLES Hereinafter, although this invention is demonstrated further in detail using an Example and a comparative example, this invention is not limited at all by the following examples. In addition, the evaluation method and measurement method used for a present Example are as follows.

(1) Specific surface area calculated | required by BET method The specific surface area was measured using the autosorb 3MP by Yuasa Ionics. As a pretreatment, 1 g of polyethylene powder was put into a sample cell, and heated and deaerated with a sample pretreatment apparatus at 80 ° C. and 0.01 mmHg or less for 12 hours. Then, it measured by BET method on the conditions of measurement temperature-196 degreeC using nitrogen as adsorption gas.

(2) Pore volume and pore distribution determined by mercury porosimetry The pore volume and pore distribution were measured using an Autopore IV9500 model manufactured by Shimadzu Corporation as a mercury porosimeter. As a pretreatment, 0.5 g of polyethylene powder was placed in a sample cell, and after deaeration and drying at room temperature in a low-pressure measuring section, mercury was filled in the sample container. The pressure was gradually increased (high pressure part), and mercury was pressed into the pores of the sample.
The pressure conditions were set as follows.
・ Low pressure part: measured at 69 Pa (0.01 psia) N ₂ pressure ・ High pressure part: 21 to 228 MPa (3,000 to 33,000 pisa)

(3) Viscosity average molecular weight (Mv)
About the viscosity average molecular weight (Mv) of polyethylene powder, it calculated | required by the method shown below according to ISO1628-3 (2010).
First, 20 mg of polyethylene powder was weighed in a melting tube, and the melting tube was purged with nitrogen, and then 20 mL of decahydronaphthalene (added with 1 g / L of 2,6-di-t-butyl-4-methylphenol) was added. The polyethylene powder was dissolved by stirring at 150 ° C. for 2 hours. The solution was measured for the drop time (t _s ) between the marked lines in a thermostatic bath at 135 ° C. using a Canon-Fenske viscometer (manufactured by Shibata Kagaku Kikai Kogyo Co., Ltd .: product number-100). Similarly, the fall time (t _s ) between the marked lines was measured in the same manner for samples in which the amount of polyethylene powder was changed to 10 mg, 5 mg, and 2 mg. The dropping time (t _b ) of only decahydronaphthalene without polyethylene powder as a blank was measured. By plotting the reduced viscosity (η _sp / C) of polyethylene powder obtained according to the following formula, the linear expression of concentration (C) (unit: g / dL) and reduced viscosity (η _sp / C) of polyethylene powder is derived. The intrinsic viscosity ([η]) extrapolated to a concentration of 0 was determined. η _sp / C = (t _s / t _b −1) /0.1 (unit: dL / g)
Next, using the following formula A, the viscosity average molecular weight (Mv) was calculated using the value of the intrinsic viscosity [η].
Mv = (5.34 × 10 ⁴ ) × [η] ^1.49 (Formula A)

(4) Average particle diameter The average particle diameter of the polyethylene powder is 10 types of sieves (openings: 710 μm, 500 μm, 425 μm, 355 μm, 300 μm, 212 μm, 150 μm, 106 μm, 75 μm, 53 μm) defined in JIS Z8801. Thus, in the integral curve obtained by integrating the weight of the polyethylene powder remaining on each sieve obtained when classifying 100 g of polyethylene powder from the side having a large mesh opening, the particle diameter at 50% weight was defined as the average particle diameter.

(5) Degree of unevenness (UD)
The degree of unevenness (UD) was a dynamic imaging method particle size distribution / particle shape evaluation apparatus QICPIC manufactured by Nippon Laser. The sample was dispersed with an airflow type dry disperser, and images of dispersed particles were taken continuously and measured from the captured image information using image analysis software.
Sample measurement conditions were set as follows.
Airflow disperser: RODOS ^TM
Compressed air flow dispersion pressure: 1.0 bar
Analysis mode: EQPC (circle area equivalent diameter)
Analysis measurement range: M6 (minimum pixel is 5 μm)
When the projected area of the obtained target particle is A and the projected area surrounded by the envelope connecting the convex portions of the target particle is A + B, UD represented by the following formula (1) is the degree of unevenness of the particle. did.
UD = A / (A + B) (1)

(6) Titanium content Polyethylene powder is pressure-decomposed using a microwave decomposing apparatus (model ETHOS TC, manufactured by Milestone General Co.), and ICP-MS (inductively coupled plasma mass spectrometer, model X is used) by an internal standard method. In series X7, manufactured by Thermo Fisher Scientific Co., Ltd.), the elemental concentration of titanium in the polyethylene powder was measured to obtain the amount of titanium contained.

(7) Solubility Evaluation 14 g of polyethylene powder, 0.4 g of pentaerythryl-tetrakis [3- (3,5-di-t-butyl-4-hydroxyphenyl) propionate] as an antioxidant, and liquid paraffin ( A mixture of 36 g of Matsumura Oil Co., Ltd. (P-350) was put into a small kneader (LABYLASTOMILL30C150 manufactured by TOYOSEIKI) and kneaded at 200 ° C. with a screw rotation of 50 rpm. The kneading time was two conditions of 2 minutes and 10 minutes. These kneaded materials are sandwiched between metal plates and heat-pressed at 190 ° 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 then 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 was determined by visually counting the foreign matter of 50 μm or more existing in the obtained microporous membrane 250 mm × 250 mm (observed as black spots when the microporous membrane was observed with transmitted light). Based on the following evaluation criteria.
(Solubility evaluation criteria)
○: The number of foreign matters is 1 or less.
(Triangle | delta): There are less than five foreign materials.
X: There are 5 or more foreign substances.

[Production example]
[Preparation of solid catalyst component [A-1]]
1600 mL of hexane was added to an 8 L stainless steel autoclave thoroughly purged with nitrogen. While stirring at 10 ° C., 800 mL of a 1 mol / L titanium tetrachloride hexane solution and 800 mL of a hexane solution of an organomagnesium compound represented by 1 mol / L composition formula AlMg ₅ (C ₄ H ₉ ) ₁₁ (OSiH) ₂ were mixed. The addition and the stop of the addition were repeated at a period of 4 minutes and added simultaneously over 4 hours. After the addition, the temperature was slowly raised and the reaction was continued at 10 ° C. for 1 hour. After completion of the reaction, 1600 mL of the supernatant was removed, and the solid catalyst component [A-1] was prepared by washing 5 times with 1600 mL of hexane. The amount of titanium contained in 1 g of this solid catalyst component [A-1] was 3.05 mmol.

[Preparation of solid catalyst component [A-2]]
1600 mL of hexane was added to an 8 L stainless steel autoclave thoroughly purged with nitrogen. While stirring at 10 ° C., 800 mL of a 1 mol / L titanium tetrachloride hexane solution and 800 mL of a hexane solution of an organomagnesium compound represented by 1 mol / L compositional formula AlMg ₅ (C ₄ H ₉ ) ₁₁ (OSiH) ₂ were continuously added. For 4 hours. After the addition, the temperature was slowly raised and the reaction was continued at 10 ° C. for 1 hour. After completion of the reaction, 1600 mL of the supernatant was removed, and the solid catalyst component [A-2] was prepared by washing 5 times with 1600 mL of hexane. The amount of titanium contained in 1 g of this solid catalyst component [A-2] was 3.12 mmol.

[Preparation of solid catalyst component [A-3]]
1600 mL of hexane was added to an 8 L stainless steel autoclave thoroughly purged with nitrogen. While stirring at 10 ° C., 800 mL of a 1 mol / L titanium tetrachloride hexane solution and 800 mL of a hexane solution of an organomagnesium compound represented by 1 mol / L compositional formula AlMg ₅ (C ₄ H ₉ ) ₁₁ (OSiH) ₂ were continuously added. For 0.5 hour. After the addition, the temperature was slowly raised and the reaction was continued at 10 ° C. for 1 hour. After completion of the reaction, 1600 mL of the supernatant was removed, and the solid catalyst component [A-3] was prepared by washing 5 times with 1600 mL of hexane. The amount of titanium contained in 1 g of this solid catalyst component [A-3] was 3.10 mmol.

[Example 1]
(Ethylene polymer polymerization process)
Hexane, ethylene, hydrogen, and catalyst were continuously supplied to a vessel type 300 L polymerization reactor equipped with a stirrer. The polymerization pressure was 0.5 MPa. The polymerization temperature was kept at 83 ° C. by jacket cooling. Hexane was fed from the bottom of the polymerizer at 40 L / hr. Solid catalyst component [A-1] and triisobutylaluminum were used as a cocatalyst. Solid catalyst component [A-1] was added to the polymerizer at a rate of 0.2 g / hr, and triisobutylaluminum was added to the polymerizer at a rate of 10 mmol / hr. The production rate of the ethylene polymer was 10 kg / hr. Hydrogen was continuously supplied by a pump so that the hydrogen concentration with respect to ethylene in the gas phase was 14 mol%. In addition, hydrogen was supplied from the catalyst introduction line in order to contact with the catalyst in advance, and ethylene was supplied from the bottom of the polymerization vessel. The catalytic activity was 80,000 g-PE / g-solid catalyst component [A-1]. The polyethylene slurry was continuously drawn into a flash drum 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 and hydrogen were separated.
Next, the polyethylene slurry was continuously sent to a centrifuge so that the level of the polymerization reactor was kept constant, and the polymer and other solvents were separated. The liquid content of the solvent and the like with respect to the polymer at that time was 45%.
The separated polyethylene powder was dried at 85 ° C. while blowing nitrogen. In this drying step, the catalyst and the cocatalyst were deactivated by spraying steam on the polymerized 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 obtained polyethylene powder using a sieve having an opening of 425 μm and not passing through the sieve.

About the polyethylene powder obtained in Example 1, it measured according to the method mentioned above, (1) specific surface area by BET method, (2) pore volume by mercury intrusion method, (3) viscosity average molecular weight (Mv), (4) Peak maximum value in pore distribution by mercury intrusion method, (4) average particle diameter, (5) degree of unevenness (UD) ratio of all measured particles of 0.90 to 0.95, (7) contained The amount of titanium was measured. The results are shown in Table 1.
Regarding the solubility, according to the method described above, (8) foreign matters in the microporous membrane obtained by kneading for 2 minutes and (9) foreign matters in the microporous membrane obtained by kneading for 10 minutes were evaluated. Is shown in Table 1.

[Example 2]
In the polymerization step, polyethylene powder of Example 2 was obtained by the same operation as Example 1 except that the solid catalyst component [A-2] was used without using the solid catalyst component [A-1]. The evaluation results of the polyethylene powder and the microporous membrane are shown in Table 1.

[Example 3]
A polyethylene powder of Example 3 was obtained in the same manner as in Example 1 except that the hydrogen concentration was 3 mol% in the polymerization step. The evaluation results of the polyethylene powder and the microporous membrane are shown in Table 1.

[Example 4]
A polyethylene powder of Example 4 was obtained by the same operation as in Example 1 except that the drying temperature was 140 ° C. in the drying step. The evaluation results of the polyethylene powder and the microporous membrane are shown in Table 1.

[Comparative Example 1]
In the polymerization step, a polyethylene powder of Comparative Example 1 was obtained by the same operation as in Example 1 except that the solid catalyst component [A-3] was used without using the solid catalyst component [A-1]. The evaluation results of the polyethylene powder and the microporous membrane are shown in Table 1.

[Comparative Example 2]
In the drying step, a polyethylene powder of Comparative Example 2 was obtained in the same manner as in Example 1 except that the drying temperature was 160 ° C. The evaluation results of the polyethylene powder and the microporous membrane are shown in Table 1.

[Comparative Example 3]
The ethylene polymer powder of Comparative Example 3 was treated in the same manner as in Example 1 except that the solvent content for the polymer was 70% in the solvent centrifugation to separate the polymer and the other solvent before the drying step. Got. The evaluation results of the polyethylene powder and the microporous membrane are shown in Table 1.

[Comparative Example 4]
The same operation as in Example 1 was performed except that the polymerization pressure was 1.2 MPa. The catalytic activity was 120,000 g-PE / g-solid catalyst component [A-1]. Thus, a polyethylene powder of Comparative Example 4 was obtained. The evaluation results of the polyethylene powder and the microporous membrane are shown in Table 1.

[Comparative Example 5]
In the polymerization step, ethylene polymer powder of Comparative Example 5 was obtained in the same manner as in Example 1 except that hydrogen was supplied to the polymerization vessel without contacting the catalyst in advance, except that it was supplied from the bottom of the polymerization vessel. . The evaluation results of the polyethylene powder and the microporous membrane are shown in Table 1.

  The polyethylene powder of the present invention can be used for lithium ion battery separators, lead storage battery separators, high-strength fibers, molding applications, and the like.

Claims (6)

The specific surface area determined by the BET method is 0.10 m ² / g or more and 0.30 m ² / g or less, the pore volume determined by the mercury intrusion method is 0.85 mL / g or less, and the viscosity average molecular weight (Mv ) Is a polyethylene powder having 100,000 to 1,000,000.   2. The polyethylene powder according to claim 1, wherein a maximum value does not exist at a pore diameter of 30 μm or less in a pore distribution determined by a mercury intrusion method. The average particle diameter is 1 to 200 μm, and 60% or more of the total number of measured particles has a form having an unevenness degree (UD) defined by the formula (1) of 0.90 or more and 0.95 or less. 2. Polyethylene powder according to 2.
UD = A / (A + B) (1)
(In the formula (1), A represents the projected area of the target particle, and A + B represents the projected area surrounded by the envelope connecting the convex portions of the target particle.)   The polyethylene powder according to any one of claims 1 to 3, comprising titanium of 1 ppm or more and 200 ppm or less.   The polyethylene powder according to any one of claims 1 to 4, which is used for a secondary battery separator.   The polyethylene powder according to any one of claims 1 to 5, which is for a lithium ion secondary battery separator.