CN108864523B

CN108864523B - Polyethylene powder, and molded article and fiber thereof

Info

Publication number: CN108864523B
Application number: CN201710335008.7A
Authority: CN
Inventors: 妯借胺娣崇ク; 樽谷淳祯
Original assignee: Asahi Kasei Corp
Current assignee: Asahi Kasei Corp
Priority date: 2017-05-12
Filing date: 2017-05-12
Publication date: 2021-04-06
Anticipated expiration: 2037-05-12
Also published as: CN108864523A

Abstract

The invention relates to polyethylenePowder, and molded articles and fibers thereof. The invention provides a polyethylene powder which is quickly dissolved in a solvent and generates little undissolved substance. A polyethylene powder having a specific surface area of 0.20m as determined by the BET method²0.80 m/g or more²A pore volume of 0.95mL/g or less as determined by mercury intrusion, a full width at half maximum of a melting endothermic peak in differential scanning calorimetry of 6.00 ℃ or less, a viscosity-average molecular weight of 10 to 1000 ten thousand, and an average particle diameter of 100 to 300 μm.

Description

Polyethylene powder, and molded article and fiber thereof

Technical Field

The present invention relates to a polyethylene powder, and a molded article and a fiber thereof.

Background

Polyethylene powder is used as a raw material for various products such as films, sheets, microporous films, fibers, foams, and pipes. In particular, high molecular weight polyethylene powder is suitably used as a raw material for microporous films and high-strength fibers for separators of secondary batteries typified by lead-acid batteries and lithium-ion batteries. The reason why the high molecular weight polyethylene powder is used for these purposes is as follows: excellent tensile processability, high tensile strength, high chemical stability and the like.

Since high molecular weight polyethylene powder is generally difficult to process by injection molding or the like due to its high viscosity, it is often molded by dissolving it in a solvent. For example, in the case of processing into fibers, ultra-high molecular weight polyethylene is dissolved in a solvent, and the resulting thin solution is spun and drawn. Thus, a highly oriented high-strength fiber having a high elastic modulus and tensile strength can be obtained.

Further, as for high molecular weight polyethylene, a technique of reducing defects generated at the time of molding thereof and making the structure thereof uniform is disclosed. For example, patent document 1 discloses: the defects of the polyethylene crystal structure can be reduced by optimizing the solvent reduction rate at the time of removing the solvent in the spinning step. Further, patent document 2 discloses: by adding a poor solvent as a solvent, the expansion of the polyethylene molecular chain is suppressed, the entanglement of the molecular chain causing defects is reduced, and the nonuniform structure is suppressed. Further, patent document 3 discloses: by making the solvent evaporation rate uniform when the polyethylene solution is discharged from the nozzle and further uniformly cooling the gel discharged from the spinning port to reduce the crystal size, a molded body having a uniform crystal structure can be obtained.

In addition, patent document 4 discloses: polyethylene was uniformly dissolved by using paraffin-based wax instead of liquid solvent. Further, patent document 5 discloses: the use of dialkyl ketone as an additive suppresses the formation of a gel-like substance having a high viscosity due to nonuniform dissolution. Although patent documents 1 to 5 describe the properties of the polyethylene solution, they do not describe the improvement of the properties of the polyethylene powder as a raw material.

In recent years, there has been an increasing demand for higher performance of high-strength fibers molded from ultrahigh molecular weight polyethylene. Patent document 6 describes the following technique: the carbon nanotubes are mixed in the ultra-high molecular weight polyethylene, and sufficiently drawn to be aligned in the fiber axis direction and uniformly dispersed. Disclosed is a method for producing: the carbon nanotube-oriented ultrahigh molecular weight polyethylene fiber described above can improve the brittleness of heat resistance, which is unavoidable in the properties of polyethylene, and particularly can improve the heat resistance of the elastic modulus in the fiber axis direction, thereby reducing the decrease in mechanical properties. In this patent document, various conditions such as properties of carbon nanotubes, a solvent for mixing, a pre-dispersion treatment of each component before kneading, and an extrusion apparatus for applying high shear are described for dispersion of carbon nanotubes, but evaluation of intra-fiber dispersion of carbon nanotubes is not performed at all, and it is not clear to what extent uniform dispersion is achieved. There is no description about improvement in dispersibility of a filler-containing material obtained from characteristics of a polyethylene powder as a raw material.

Documents of the prior art

Patent document

Patent document 1: japanese patent No. 5327488

Patent document 2: japanese laid-open patent publication No. 2007-297763

Patent document 3: japanese patent No. 3666635

Patent document 4: japanese examined patent publication (Kokoku) No. 7-29372

Patent document 5: japanese patent laid-open publication No. 2011-

Patent document 6: japanese patent laid-open publication No. 2004-124277

Disclosure of Invention

Problems to be solved by the invention

However, in polyethylene using conventional polyethylene powder, if the draw ratio at the time of molding polyethylene is increased in order to increase the tensile strength, there is a problem that the load applied increases and breakage (filament breakage) occurs when fibers are produced by molding. On the other hand, in the step of dissolving polyethylene in a solvent, if the undissolved polyethylene powder remains as particles, there is a problem that yarn breakage occurs during spinning after molding and the tensile strength of the fiber is locally reduced. In addition, when the polyethylene is kneaded with a filler such as carbon nanotubes for the purpose of improving the performance of the polyethylene, there are problems as follows: the dispersion of the filler is not uniform, and the functional performance of the ultra-high molecular weight polyethylene composite material is hindered. Therefore, in order to improve the tensile strength and the elastic modulus, it is important to uniformly dissolve the polyethylene in the solvent to obtain a molded article having few defects.

Accordingly, an object of the present invention is to provide a polyethylene powder which can be rapidly dissolved in a solvent, generates little undissolved matter, and can improve filler dispersibility in a drawn fiber obtained when a filler is added.

Means for solving the problems

The present inventors have conducted intensive studies to solve the above problems of the prior art, and as a result, have found that: the present inventors have found that a polyethylene powder having a specific surface area, a pore volume, a half height width of a melting endothermic peak, a viscosity-average molecular weight and an average particle diameter in a predetermined range is rapidly dissolved in a solvent, generation of undissolved matter is small, and dispersion of a filler in a mixture when the filler is mixed is improved, thereby completing the present invention.

Namely, the present invention is as follows.

[1]

A polyethylene powder, wherein the polyethylene powder

The specific surface area determined by the BET method was 0.20m²0.80 m/g or more²Per gram of the total amount of the components,

A pore volume of 0.95mL/g or less as determined by mercury porosimetry,

The half width of the melting endothermic peak in differential scanning calorimetry is 6.00 ℃ or less,

A viscosity average molecular weight of 10 to 1000 ten thousand and

the average particle diameter is 100 to 300 μm.

[2]

The polyethylene powder according to [1], wherein the polyethylene powder has a viscosity-average molecular weight of 100 to 950 ten thousand.

[3]

The polyethylene powder according to [1] or [2], wherein the ratio of the number of particles having an aspect ratio (アスペクト ratio) of 0.66 or more and 0.84 or less to the number of all particles is 50% or more.

[4]

The polyethylene powder according to [1] to [3], wherein,

the ratio of the number of particles having an unevenness of 0.95 or more defined by the following formula (1) to the number of all the particles is 25% or more.

UD＝A/(A+B) (1)

(in the formula (1), UD represents the degree of concavity and convexity, A represents the projected area of the target particle, and (A + B) represents the projected area surrounded by the envelope of the convex part connecting the target particle.)

[5]

The polyethylene powder according to any one of [1] to [4], wherein the angle of repose of the polyethylene powder is 34 to 45 degrees.

[6]

The polyethylene powder according to any one of [1] to [5], which is used for fibers.

[7]

A fiber produced by using the polyethylene powder according to [6 ].

[8]

A molded article obtained by molding the polyethylene powder according to any one of [1] to [5 ].

Effects of the invention

According to the polyethylene powder of the present invention, a molded article having a rapid solubility in a solvent and little generation of undissolved matter can be obtained.

Drawings

Fig. 1 is a schematic diagram illustrating a method of obtaining the unevenness according to the present embodiment.

Detailed Description

Hereinafter, specific embodiments of the present invention (hereinafter, referred to as "the present embodiment") will be described in detail. The following embodiments are illustrative of the present invention, and are not intended to limit the present invention to the following. The present invention can be suitably modified and implemented within the scope of the gist thereof.

[ polyethylene powder ]

The polyethylene powder (hereinafter also simply referred to as "powder" or "particle") of the present embodiment has a specific surface area of 0.20m as determined by the BET method²0.80 m/g or more²A pore volume of 0.95mL/g or less as determined by mercury intrusion, a full width at half maximum of a melting endothermic peak in differential scanning calorimetry of 6.00 ℃ or less, a viscosity average molecular weight of 100 to 1000 ten thousand, and an average particle diameter of 100 to 300 μm. The polyethylene powder is not particularly limited, and examples thereof include: ethylene homopolymers, copolymers of ethylene with other comonomers.

The ethylene homopolymer is a polymer comprising ethylene in an amount of 99.5 mol% or more of the repeating unit. Since the polyethylene powder is an ethylene homopolymer, it tends to be drawn in a highly oriented manner and to obtain a fiber excellent in tensile strength. Further, since the polyethylene powder is a copolymer of ethylene and another comonomer, side reactions during polymerization are suppressed, the polymerization rate is increased, and the creep characteristics of the obtained fiber tend to be improved.

The other comonomers are not limited to the following ones, and examples thereof include: alpha-olefins, vinyl compounds. The α -olefin is not particularly limited, and examples thereof include: more specifically, the α -olefin having 3 to 20 carbon atoms includes: propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene, 1-nonene, 1-decene, 1-undecene, 1-dodecene, 1-tridecene, 1-tetradecene. Among these, propylene and 1-butene are preferable from the viewpoint of heat resistance and strength of molded articles typified by films and fibers. One kind of the comonomer may be used alone, or two or more kinds may be used in combination.

From the viewpoint of the tensile strength of the fiber, the molar ratio of ethylene in the copolymer is preferably 50% or more and less than 99.5%, more preferably 80% or more and less than 99.2%, and still more preferably 90% or more and less than 99%. The amount of other comonomer in the copolymer in the case where the polyethylene powder is a copolymer can be measured by, for example, NMR.

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

The neutralizing agent functions as a scavenger for chlorine and the like contained in the polyethylene powder, a molding processing aid, and the like. The neutralizing agent is not limited to the following, and examples thereof include: stearates of alkaline earth metals such as calcium, magnesium, and barium. The content of the neutralizing agent is not particularly limited, but is preferably 5000 mass ppm or less, more preferably 4000 mass ppm or less, and still more preferably 3000 mass ppm or less. The halogen component can be removed from the catalyst component by using a polyethylene powder obtained by a slurry polymerization method using a metallocene catalyst without using a neutralizing agent.

The antioxidant is not limited to the following, and examples thereof include: phenol compounds such as dibutylhydroxytoluene, pentaerythrityl tetrakis [3- (3, 5-di-t-butyl-4-hydroxyphenyl) propionate ], and octadecyl 3- (3, 5-di-t-butyl-4-hydroxyphenyl) propionate. The content of the antioxidant is not particularly limited, but is preferably 5000 mass ppm or less, more preferably 4000 mass ppm or less, and further preferably 3000 mass ppm or less.

The light stabilizer is not limited to the following, and examples thereof include: benzotriazole-based light stabilizers such as 2- (5-methyl-2-hydroxyphenyl) benzotriazole and 2- (3-tert-butyl-5-methyl-2-hydroxyphenyl) -5-chlorobenzotriazole; bis (2,2,6, 6-tetramethyl-4-piperidyl) sebacate, poly [ {6- (1,1,3, 3-tetramethylbutyl) amino-1, 3, 5-triazine-2, 4-diyl } { (2,2,6, 6-tetramethyl-4-piperidyl) imino } hexamethylene { (2,2,6, 6-tetramethyl-4-piperidyl) imino } ], and the like. The content of the light stabilizer is not particularly limited, but is preferably 5000 mass ppm or less, more preferably 4000 mass ppm or less, and still more preferably 3000 mass ppm or less.

The content of the additive in the polyethylene powder can be determined, for example, by extracting the polyethylene powder for 6 hours by soxhlet extraction using Tetrahydrofuran (THF), separating the extract by liquid chromatography, and quantifying the fraction.

[ specific surface area ]

The specific surface area of the polyethylene powder as determined by the BET method was 0.20m²0.80 m/g or more²A ratio of 0.25m or less in terms of/g²0.60 m/g or more²A value of less than or equal to g, more preferably 0.30m²0.40 m/g or more²The ratio of the carbon atoms to the carbon atoms is less than g. The specific surface area of the polyethylene powder of the present embodiment is a specific surface area obtained by a BET method (specific surface area method), and can be obtained by a method described in examples described later.

Passing specific surface area of 0.20m²0.80 m/g or more²(ii) at most/g, the dissolution of the powder surface and the dissolution of the powder interior proceed simultaneously. This can suppress the occurrence of undissolved matter due to uneven dissolution.

The specific surface area is related to the surface and internal structure of the polyethylene powder. For a specific surface area of 0.20m²Polyethylene powder having a surface smoothness of at least one gram is small, and many pores penetrating from the surface to the inside and many voids isolated from the outside and existing inside are present. Such polyethylene powder has a large area in contact with a solvent when dissolved in the solvent. Therefore, the time taken until a uniform solution is formed is reduced by improving the solubility, and the production efficiency is improved.

On the other hand, the specific surface area was 0.80m²At most,/g, the number of voids present inside the polyethylene powder isolated from the outside is not greater than the number of pores penetrating from the surface to the inside, and the solvent easily penetrates into the polyethylene powder. In addition, since the voids present inside are also suppressed from interfering with heat conduction, the solubility is not lowered. Therefore, the vicinity of the particle surface is dissolved and swollen, and the interior of the particle is suppressedProducing undissolved particles. As a result, the particles are less likely to fuse with each other on the outer surface to form large aggregated particles, and the formation of defects due to the generation of insoluble matter is suppressed.

The method of controlling the specific surface area within the above range may be exemplified by: controlling the synthesis conditions of the catalyst used in the polymerization of the polyethylene and controlling the method of post-treatment of the polyethylene slurry after polymerization. In order to adjust the specific surface area to 0.20m²The drying temperature may be set to 150 ℃ or lower in the post-treatment of the polyethylene slurry after polymerization. In addition, in order to adjust the specific surface area to 0.80m²The catalyst may be prepared, for example, under the conditions for synthesizing the catalyst so that a solid catalyst having active sites uniformly arranged can be obtained, and in addition, the drying temperature may be set to 60 ℃ or higher in the post-treatment of the polyethylene slurry after polymerization.

The conditions for synthesizing the catalyst include, for example: the concentration of the catalyst raw material in the catalyst synthesis, the addition rate of the raw material, and the stirring rate during the synthesis. Specifically, the concentration of the catalyst raw material is diluted to reduce the rate of addition of the catalyst raw material and increase the stirring rate during synthesis, thereby enabling synthesis of a solid catalyst in which active sites are uniformly arranged.

The extent of the growth of the polymer chains using the solid catalyst depends on the distribution of active sites on the surface of the solid catalyst. The raw material is slowly added at a low concentration, and the active sites on the surface of the solid catalyst obtained by synthesis tend to be dispersed sufficiently and uniformly present without aggregation. On the surface of such a solid catalyst, the growth of polymer chains is uniform. As a result, unevenness is less likely to occur on the surface of the obtained powder. By using a solid catalyst in which active sites are uniformly arranged, it tends to be possible to obtain a polyethylene powder having an appropriate specific surface area.

The catalyst to be used is not particularly limited, and a usual ziegler-natta catalyst or a metallocene catalyst can be used, and a catalyst specified below is preferably used.

The control of the process of the post-treatment of the polymerized polyethylene slurry can be performed by varying the drying temperature. When the drying temperature is increased, the surface of the polyethylene powder melts during drying, and pores present on the surface tend to be clogged or irregularities tend to be uniformized. Thereby enabling a reduction in surface area.

[ pore volume ]

The polyethylene powder of the present embodiment has a pore volume of 0.95mL/g or less, preferably 0.90mL/g or less, and more preferably 0.85mL/g or less as determined by mercury porosimetry. The pore volume of the polyethylene powder of the present embodiment is the pore volume determined by the mercury intrusion method, and can be determined by the method described in the examples described later.

The solubility of the polyethylene powder is improved by the pore volume of 0.95mL/g or less. The pore volume is related to the internal structure and aggregation state of the polyethylene powder. Specifically, the volume of pores penetrating from the surface to the inside is referred to, and when particles of the polyethylene powder are aggregated, the volume of the space existing in the aggregated particles is referred to. When the pore volume is 0.95mL/g or less, the number of pores penetrating from the surface does not become too large, and the solvent can sufficiently reach the inside of the particles during dissolution, thereby suppressing the formation of particles in which gas is entrapped. Therefore, the solubility of the polyethylene powder becomes good.

The method of controlling the pore volume within the above range may be exemplified by: controlling the synthesis conditions of the catalyst used in the polymerization of the polyethylene and controlling the polymerization conditions of the polyethylene. In order to adjust the pore volume to 0.95mL/g or less, for example, the polymerization pressure may be set to 0.1MPa or more under the polymerization conditions of polyethylene; or the content of the solvent before drying the polymer may be set to 60% by mass or less; alternatively, the position at which the catalyst is supplied into the polymerization apparatus and the position at which ethylene is supplied may be separated from each other by a predetermined distance or more so that the catalyst and ethylene are sufficiently diffused in the polymerization apparatus and then brought into contact with each other to carry out polymerization.

The conditions for synthesizing the catalyst include, for example: the concentration of the catalyst raw material in the catalyst synthesis reaction, and the rate of addition of the raw material. Specifically, the concentration of the catalyst raw material is diluted to slow the rate of addition of the catalyst raw material, thereby suppressing the aggregation of active sites in the solid catalyst. Without aggregation of active sites, a polymer growing from a uniformly present active site does not grow substantially before coming into contact with a polymer growing from another, isolated active site. Therefore, the internal hollow portion is inhibited from increasing before the growing polymers contact each other, so that the pore volume does not increase.

The catalyst to be used is not particularly limited, and a usual Ziegler-Natta catalyst and a metallocene catalyst can be used, and a catalyst specified below is preferably used.

The polymerization conditions of ethylene may be exemplified by: the polymerization temperature is lowered, the outlet of the catalyst introduction line and the outlet of the ethylene introduction line are set at positions distant from each other within a possible range, and the catalyst slurry concentration is lowered. This tends to suppress the volume expansion of the polyethylene powder due to the vigorous polymerization, and to obtain a polyethylene powder having a dense structure with few pores.

[ half-height Width of melting endothermic Peak ]

The polyethylene powder of the present embodiment has a half-height width of a melting endothermic peak in differential scanning calorimetry of 6.00 ℃ or less, preferably 5.50 ℃ or less, and more preferably 5.25 ℃ or less. The half width of the melting endothermic peak of the polyethylene powder of the present embodiment is the half width of the melting endothermic peak determined by differential scanning calorimetry, and can be determined by the method described in the examples described later.

The solubility of the polyethylene powder is improved by setting the half-height width of the melting endothermic peak to 6.00 ℃ or less. This is presumably because: the dissolution of the polyethylene powder in the solvent is ended in a short time by the melting transition of the polymer taking place vigorously. Further, since the half width of the melting endothermic peak is 6.00 ℃ or less, occurrence of unevenness in melting transition of the polymer is suppressed, and thus, if the dissolution conditions are strictly controlled to be constant, the rapidly dissolved portion and the hardly dissolved portion do not exist in a mixed state, the polyethylene powder is uniformly dissolved, and the production stability is improved. In addition, the filler dispersibility when producing the nanocomposite composite is also improved. This is believed to be due to: since the polyethylene can be uniformly dissolved in a short time when dissolved, the dispersion of the filler component during kneading is also good, and the transition of the polyethylene is likely to occur sharply during cooling gelation (solidification) in the molding step of the nanocomposite-dissolved product, and there is no time lag in solidification, that is, crystallization of the polyethylene, and thus, the change in the arrangement of the uniformly dispersed filler can be suppressed. Although not yet determined, it is presumed that the solution is uniformly swollen and that a certain structural memory effect derived from the raw material is present in the polyethylene after dissolution. It is noted that the heat of fusion in high molecular weight polyethylene depends on the thickness of the crystalline lamellae. That is, it is considered that the full width at half maximum of the melting endothermic peak is uniformly related to the crystal structure of polyethylene.

As a method of controlling the full width at half maximum of the melting endothermic peak to 6.00 ℃ or less, for example, a method of disposing the outlet of the line for introducing the catalyst and the outlet of the line for introducing the ethylene monomer in the reactor as far as possible in the polymerization of ethylene is mentioned. Further, there is a method of suppressing temperature unevenness in the reactor from immediately after introduction until diffusion occurs by making the introduction temperature of each component the same as the temperature in the reactor. By these methods, vigorous polymerization of polyethylene is suppressed as much as possible, the growth rate of molecular chains is kept constant, and the crystal structure of polyethylene powder tends to be able to be made uniform. Further, there is also a method of reducing the amount of the solvent remaining in the polymer after the polymerization of ethylene. By promoting the diffusion of molecular chains in the polymer and reducing the content of the solvent, the change in the crystal structure such as crystallization of the amorphous portion can be suppressed. Further, a method of suppressing a temperature difference in the steps from polymerization to drying of the polyethylene powder may be mentioned. In particular, by keeping the drying temperature low, it is possible to suppress structural changes such as melting of the crystals of the polyethylene powder or thickening of the sheet layer due to recrystallization, and it is likely to be possible to maintain the crystal structure uniformly.

[ viscosity average molecular weight (Mv) ]

The polyethylene powder of the present embodiment has a viscosity average molecular weight (Mv) of 10 to 1000 ten thousand, preferably 100 to 900 ten thousand, and more preferably 300 to 800 ten thousand. The viscosity average molecular weight (Mv) of the present embodiment can be measured by the method described in the examples described later.

By setting the viscosity-average molecular weight (Mv) to 10 ten thousand or more, a molded article excellent in mechanical strength such as tensile strength can be obtained.

On the other hand, when the viscosity-average molecular weight (Mv) is 1000 ten thousand or less, the solubility of the polyethylene powder is improved, and a uniform solution containing no undissolved matter can be produced in a short time. Thereby, the production stability and mechanical strength of the fiber are improved. In addition, the stretchability is also improved.

As a method of controlling the viscosity average molecular weight (Mv) within the above range, for example: the temperature at which the ethylene was polymerized was varied. The molecular weight tends to decrease as the polymerization temperature is increased, and the molecular weight tends to increase as the polymerization temperature is decreased. In addition, as another method for controlling the viscosity average molecular weight (Mv) to 1000 ten thousand or less, a chain transfer agent such as hydrogen may be added at the time of polymerizing ethylene. By adding a chain transfer agent, the molecular weight of the polyethylene produced tends to decrease even at the same polymerization temperature. The viscosity average molecular weight (Mv) of the polyethylene is preferably controlled by combining the above two methods.

[ average particle diameter ]

The average particle diameter of the polyethylene powder of the present embodiment is preferably 100 μm or more and 300 μm or less, more preferably 120 μm or more and 280 μm or less, and further preferably 150 μm or more and 250 μm or less. The average particle diameter of the present embodiment can be measured by the method described in the examples described later.

Since the polyethylene powder has a sufficiently improved bulk density and flowability when the average particle diameter is 100 μm or more, handling properties such as charging into a hopper or the like and measurement from the hopper tend to be further improved.

Further, the solubility of the polyethylene powder is improved by the average particle diameter of 300 μm or less.

In the present embodiment, the average particle diameter can be controlled by, for example, the particle diameter of the catalyst used, and as the particle diameter of the catalyst is larger, polyethylene powder having a larger average particle diameter tends to be obtained, and as the particle diameter of the catalyst is smaller, polyethylene powder having a smaller average particle diameter tends to be obtained. In addition, the activity of the catalyst and the polymerization conditions of the polyethylene can be controlled. More specifically, in order to control the average particle diameter to 300 μm or less, for example, the polymerization pressure may be set to 0.1MPa or more under the polymerization conditions of polyethylene, or the content of the solvent before drying the polymer may be set to 60 mass% or less.

[ aspect ratio ]

In the polyethylene powder of the present embodiment, the ratio of the number of particles having an aspect ratio of 0.66 or more and 0.84 or less (hereinafter also referred to as "specific particles X") to the number of all particles is preferably 50% or more, more preferably 55% or more, and still more preferably 60% or more. The aspect ratio of the present embodiment can be measured by the method described in the examples described later, and the number ratio of the specific particles X can be determined at this time.

The specific particles X tend not to be easily aggregated and not to be easily undissolved. When the aspect ratio of the particles is 0.66 or more, that is, the particles are not excessively flattened, the surface contact between the particles is suppressed, and the particles tend to be less likely to fuse with each other. In addition, when the aspect ratio of the particles is 0.84 or less, that is, when the particles are not excessively close to a spherical shape, the particles are suppressed from being packed densely, and the particles tend to be less likely to fuse with each other.

As a method of controlling the number ratio of the specific particles X within the above range, for example, there can be mentioned: the synthesis conditions of the catalyst, particularly the synthesis conditions in the solid precipitation reaction during the synthesis of the catalyst, are controlled. When the solid precipitation reaction is carried out, the stirring speed is increased to control the shape of the carrier to a flat shape.

[ degree of concavity and convexity ]

In the polyethylene powder of the present embodiment, the ratio of the number of particles having an unevenness of 0.95 or more (hereinafter also referred to as "specific particles Y") to the number of all the particles is preferably 25% or more, more preferably 30% or more. The roughness of the present embodiment is a value defined by the following formula (1), and can be measured by the method described in the examples described later. The content of the specific particles Y may be determined at this time.

UD＝A/(A+B) (1)

In the formula (1), UD represents the degree of unevenness, a represents the projected area of the target particle, and (a + B) represents the projected area surrounded by the envelope of the convex portion connecting the target particle. The roughness is 0.00 or more and 1.00 or less, and means that the closer to 1.00, the particles have no roughness and have a smooth surface. Fig. 1 is a schematic diagram illustrating a method of obtaining the unevenness according to the present embodiment. For example, the projection area (a) of the target particle is obtained from the "particle projection region" as the left diagram in fig. 1. Next, the projected area (a + B) surrounded by the envelope of the convex portion connecting the particle projection regions is obtained as an area including the a portion and the B portion as the "convex hull" in the right diagram in fig. 1.

When the number ratio of the specific particles Y is 25% or more, the flowability of the polyethylene powder is more sufficiently improved, and therefore, the workability such as charging into a hopper or the like and measuring from the hopper tends to be more favorable.

As a method of controlling the number ratio of the specific particles Y within the above range, for example, there can be mentioned: the exothermic amount due to a severe polymerization reaction occurring when producing polyethylene powder is suppressed. As a specific method for suppressing the exothermic amount, for example, polymerization is carried out by continuous polymerization, in which ethylene gas, a solvent, a catalyst, and the like are continuously supplied into a polymerization system and continuously discharged together with the produced ethylene polymer. In addition, an effective method further comprises: the outlet of the introduction line for the catalyst is disposed at a position as far away as possible from the outlet of the introduction line for the ethylene monomer; reducing the catalyst feed concentration; an ethylene monomer inlet port was provided in the gas phase portion of the reactor. This can suppress a sharp polymerization reaction, and can suppress the generation of irregular shaped polyethylene powder and the generation of polyethylene powder aggregates. Further, there is also a method of positively colliding polyethylene powders in the step with each other. For example, by increasing the residence time in the drying step, the powders collide with each other to promote abrasion, thereby reducing unevenness.

[ angle of repose ]

The angle of repose of the polyethylene powder of the present embodiment is preferably 34 degrees or more and 45 degrees or less, and more preferably 38 degrees or more and 43 degrees or less. The angle of repose of the present embodiment can be measured by the method described in the examples described below.

The large angle of repose of the polyethylene powder of the present embodiment suggests that the particles are likely to stick when they come into contact with each other (see っ and hanging かり). The angle of repose is preferably 34 degrees or more from the viewpoint of promoting the release and release of the solvent and moisture from the polymer during drying. This tends to shorten the drying time as compared with conventional polyethylene, or to facilitate removal and drying of the solvent and moisture by low-temperature drying. It is also presumed that the penetration of the solvent into the powder is promoted as opposed to the release of the solvent from the inside, which is also thought to affect the improvement in the solubility of the powder.

Further, when the angle of repose of the polyethylene powder is 45 degrees or less, deterioration in flowability such as bridging (ブリッジ) of the powder in the hopper or the like due to increase in friction between particles can be suppressed.

The angle of repose is controlled within the above range under the conditions of catalyst synthesis, and examples thereof include: the concentration of the catalyst raw material in the catalyst synthesis reaction, and the rate of addition of the raw material. Specifically, the addition rate of the catalyst raw material is slowed by diluting the concentration of the catalyst raw material, thereby suppressing the aggregation of active sites in the solid catalyst. In the case where the active sites are not aggregated, the polymer particles of the catalyst particles grow on the support at equal intervals and in the form of fine particle polymers, and therefore, the surface area of the outermost surface can be increased, and the angle of repose of the particles of the polyethylene powder can be increased.

[ Process for producing polyethylene powder ]

The method for producing the polyethylene powder of the present embodiment is not particularly limited, and the polyethylene powder can be produced by using a usual ziegler-natta catalyst. In addition, a Ziegler-Natta catalyst specified below is preferably used.

The Ziegler-Natta catalyst is a catalyst for olefin polymerization which is a catalyst comprising a solid catalyst component [ A ] and an organometallic compound component [ B ]. The solid catalyst component [ A ] can be produced, for example, by reacting an organomagnesium compound (A-1) (hereinafter also referred to simply as "(A-1)") represented by the following formula (2) which is soluble in an inert hydrocarbon solvent with a titanium compound (A-2) (hereinafter also referred to simply as "(A-2)") represented by the following formula (3).

(M¹)_α(Mg)_β(R²)_a(R³)_bY¹ _c (2)

In the formula (2), M¹Represents a metal atom belonging to group 12, group 13 or group 14 of the periodic Table of the elements, R²And R³Each independently represents a hydrocarbon group having 2 to 20 carbon atoms, and Y¹Represents alkoxy, siloxy, allyloxy, amino, amido, -N ═ CR⁴R⁵、-SR⁶Or a beta-keto acid residue (wherein, R⁴、R⁵And R⁶Each independently represents a hydrocarbon group having 1 to 20 carbon atoms. When c is 2, plural Y¹Each may be different), α, β, a, b, and c are real numbers satisfying the following relationship. 0 < alpha, 0 < beta, 0 < a, 0 < b, 0 < c, 0 < a + b, 0 < b/(alpha + beta) 2, n alpha +2 beta ═ a + b + c (where n is M)¹The valence of (c). M in case of plural¹、R²、R³And Y¹Each independently.

Ti(OR⁷)_dX¹ _(4-d) (3)

In the formula (3), d is a real number of 0 to 4, R⁷Represents a hydrocarbon group having 1 to 20 carbon atoms, X¹Represents a halogen atom. R in case of plural⁷And X¹Each independently.

The inert hydrocarbon solvent used in the reaction of (A-1) and (A-2) is not limited to the following, and examples thereof include: aliphatic hydrocarbons such as butane, pentane, hexane, and heptane; aromatic hydrocarbons such as benzene, toluene, and xylene; alicyclic hydrocarbons such as cyclopentane, cyclohexane, methylcyclohexane, and decalin.

(A-1) is represented by formula (2) in the form of an organomagnesium complex soluble in an inert hydrocarbon solvent. However, (A-1) includes all dihydrocarbylmagnesium compounds and complexes of the compounds with other metal compounds.

In the formula (2), when α > 0, the metal atom M is¹The metal atom is not particularly limited as long as it is a metal atom belonging to group 12, group 13 or group 14 of the periodic table, and examples thereof include: zinc, boron, aluminum. Among these, aluminum and zinc are preferable. In addition, magnesium is relative to the metal atom M¹The ratio (β/α) is not particularly limited, but is preferably 0.1 or more and 30 or less, and more preferably 0.5 or more and 10 or less.

In the formula (2), from R²And R³The hydrocarbon group having 2 to 20 carbon atoms is not limited to the following groups, and examples thereof include: alkyl groups, cycloalkyl groups, aryl groups, and the like, and more specifically, there can be mentioned: ethyl, propyl, butyl, pentyl, hexyl, octyl, decyl, cyclohexyl, phenyl. Among these, an alkyl group is preferable.

In the formula (2), when α is 0, R²And R³It is preferable to satisfy any of the three groups (1), (2), and (3) shown below.

Group (1): r²And R³At least one of (a) represents a secondary alkyl group or a tertiary alkyl group having 4 to 6 carbon atoms; preferably R²And R³Each represents an alkyl group having 4 to 6 carbon atoms, and at least one represents a secondary alkyl group or a tertiary alkyl group.

Group (2): r²And R³Represents alkyl groups having different carbon atoms from each other; preferably R²Represents an alkyl group having 2 or 3 carbon atoms and R³Represents an alkyl group having 4 or more carbon atoms.

Group (3): r²And R³At least one of (a) represents a hydrocarbon group having 6 or more carbon atoms; preferably represents R²And R³And alkyl groups having a total of 12 or more carbon atoms contained in the hydrocarbon group.

In the group (1), a secondary or tertiary alkyl group having 4 to 6 carbon atoms is not presentExamples of the following groups include: 1-methylpropyl, 2-methylpropyl, 1-dimethylethyl, 2-methylbutyl, 2-ethylpropyl, 2-dimethylpropyl, 2-methylpentyl, 2-ethylbutyl, 2-dimethylbutyl, 2-methyl-2-ethylpropyl. Among these, 1-methylpropyl group is preferable. In the formula (2), when α is 0, for example, in R²In the case of 1-methylpropyl, (A-1) is soluble in an inert hydrocarbon solvent, and such (A-1) also tends to bring about preferable results in the present embodiment.

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

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

In general, as the number of carbon atoms contained in an alkyl group increases, it tends to become easily dissolved in an inert hydrocarbon solvent, and the viscosity of the solution tends to increase. Therefore, from the viewpoint of handling, it is preferable to use an alkyl group having an appropriate number of carbon atoms. The compound (A-1) may be used after dilution with an inert hydrocarbon solvent, and a slight amount of a Lewis basic compound such as ether, ester or amine may be contained or left in the solution.

In the formula (2), Y¹Represents alkoxy, siloxy, allyloxy, amino, amido, -N ═ CR⁴R⁵、-SR⁶And a β -keto acid residue. Wherein R is⁴、R⁵And R⁶Each independently represents a hydrocarbon group having 1 to 20 carbon atoms. Y is¹Alkoxy and siloxy are preferred.

The above alkoxy group is not limited to the following groups, and examples thereof include: methoxy, ethoxy, propoxy, 1-methylethoxy, butoxy, 1-methylpropoxy, 1-dimethylethoxy, pentyloxy, hexyloxy, 2-methylpentyloxy, 2-ethylbutoxy, 2-ethylpentyloxy, 2-ethylhexyloxy, 2-ethyl-4-methylpentyloxy, 2-propylheptyloxy, 2-ethyl-5-methyloctyloxy, octyloxy, phenoxy, naphthyloxy. Among these, preferred are butoxy, 1-methylpropoxy, 2-methylpentyloxy and 2-ethylhexyloxy.

The aforementioned siloxy group is not limited to the following groups, and examples thereof include: hydrodimethylsiloxy, ethylhydromethylsiloxy, diethylhydrosiloxy, trimethylsiloxy, ethyldimethylsiloxy, diethylmethylsiloxy, triethylsiloxy. Among these, preferred are hydrodimethylsiloxy, ethylhydrogenmethylsiloxy, diethylhydrosiloxy, and trimethylsiloxy groups.

R⁴、R⁵And R⁶Each independently represents an alkyl group or an aryl group having 1 to 12 carbon atoms, and more preferably an alkyl group or an aryl group having 3 to 10 carbon atoms. The alkyl group or aryl group having 1 to 12 carbon atoms is not limited to the following groups, and examples thereof include: methyl, ethyl, propyl, 1-methylethyl, butyl, 1-methylpropyl, 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. Among these, butyl, 1-methylpropyl, 2-methylpentyl and 2-ethylhexyl are preferred.

In the formula (2), (n α +2 β ═ a + b + c) as a relational expression of α, β, a, b, and c represents the stoichiometric properties of the valence of the metal atom and the substituent.

In (A-1), Y¹The molar composition ratio (c/(α + β)) to all metal atoms is in the range of 0 to 2, and preferably 0 to 1. When the molar composition ratio is 2 or less, the reactivity of (A-1) and (A-2) tends to be improved.

In the present embodiment, the method for synthesizing (A-1) is not particularly limited, and examples thereof includeThe formula: r²MgX¹Or by the formula: r² ₂Mg (wherein, R²Represents the same meaning as that represented in the formula (2), X¹Represents a halogen atom) with an organic magnesium compound represented by the formula: m¹R³n or a compound of formula: m¹R³ _(n-1)H (wherein, M)¹、R³And n represents the same meaning as that represented in formula (2) in an inert hydrocarbon solvent at 25 ℃ or higher and 150 ℃ or lower. Furthermore, if necessary, the following is performed by using the formula: y is¹-H (wherein, Y)¹Represents the same meaning as that represented in formula (2), or a compound having a structure represented by the formula: y is¹(A-1) can be synthesized by reacting the organomagnesium compound and/or the organoaluminum compound having the functional group shown above. Among these, an organomagnesium compound soluble in an inert hydrocarbon solvent is reacted with a compound represented by the formula: y is¹In the case of reacting the compound represented by-H, the order of the reaction is not particularly limited, and examples thereof include: adding to an organomagnesium compound a compound represented by the formula: y is¹-H to a compound represented by formula (la): y is¹A method of adding an organomagnesium compound to the compound represented by the formula-H and a method of simultaneously adding both.

(A-2) is preferably titanium tetrachloride. One kind of (A-2) may be used alone, or two or more kinds may be used in combination.

From R⁷The hydrocarbon group having 1 to 20 carbon atoms is not limited to the following groups, and examples thereof include: aliphatic hydrocarbon groups such as methyl, ethyl, propyl, butyl, pentyl, hexyl, 2-ethylhexyl, heptyl, octyl, decyl, and allyl; alicyclic hydrocarbon groups such as cyclohexyl, 2-methylcyclohexyl and cyclopentyl; and aromatic hydrocarbon groups such as phenyl and naphthyl. Among these, aliphatic hydrocarbon groups are preferred. d is a real number of 0 to 1, preferably 0. From X¹Examples of the halogen atom include: chlorine atom, bromine atom, iodine atom. Among these, chlorine is preferred.

The reaction of (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, and the molar ratio of the Ti atom contained in (A-2) to the Mg atom contained in (A-1) (Ti/Mg) is preferably 0.1 or more and 10 or less, more preferably 0.3 or more and 3.0 or less.

The reaction temperature is not particularly limited, but is preferably-80 ℃ or higher and 150 ℃ or lower, and more preferably-40 ℃ or higher and 100 ℃ or lower. The stirring speed of the reaction is not particularly limited, but is preferably 1.0X 10 in Reynolds number⁵Above and 5.0X 10⁶Hereinafter, more preferably 2.0 × 10⁵Above and 2.5X 10⁶The following.

The order of addition of (A-1) and (A-2) is not particularly limited, and examples thereof include: a method of adding (A-2) after the addition of (A-1), a method of adding (A-1) after the addition of (A-2), and a method of simultaneously adding (A-1) and (A-2), preferably a method of simultaneously adding (A-1) and (A-2). In addition, the interval between the addition of (A-1) and the addition of (A-2) may be either continuous addition or intermittent addition, and the addition is preferably intermittent addition at a period of 3 minutes to 20 minutes inclusive, and more preferably intermittent addition at a period of 5 minutes to 15 minutes inclusive. The time for adding (A-1) and (A-2) is not particularly limited, but is preferably 1.0 hour to 10 hours, more preferably 2.0 hours to 5 hours.

The time for aging (A-1) and (A-2) is not particularly limited, and for example, it is preferably in the range of 1.0 hour to 10 hours, more preferably 2.0 hours to 5.0 hours. By carrying out the reaction of (A-1) and (A-2) in the above manner, it tends to be possible to disperse the catalyst active sites obtained by the reaction more uniformly, and further to suppress aggregation of the active sites in the solid catalyst. Therefore, the growth of the polymer chains does not locally occur, and the polymer chains are covered on the entire surface of the catalyst particle, and therefore, there is a tendency to obtain a polyethylene powder having a small pore volume, to obtain a polyethylene powder having surface irregularities and having an appropriate specific surface area with suppressing internal voids.

It is preferable to remove unreacted (A-1) and (A-2) after the reaction of (A-1) with (A-2). By removing the unreacted (A-1) and (A-2), generation of an irregularly shaped polymer such as lumps, adhesion to the reactor wall surface, clogging of the extraction line, and the like can be suppressed, and thus there is a tendency to be excellent in continuous production. In order to remove the unreacted (A-1) and (A-2), for example, the unreacted amount can be reduced by repeating the operations of withdrawing the supernatant liquid while the catalyst slurry is settled and adding a new inert hydrocarbon solvent. Further, unreacted materials may be removed by filtration with a filter or the like. The residual amount after the removal is preferably, for example, a residual chlorine concentration derived from (A-2) of 1.0 mmol/L or less.

In the present embodiment, the solid catalyst component [ a ] obtained by the above reaction can be used in the form of a slurry solution using an inert hydrocarbon solvent.

The Ziegler-Natta catalyst as defined above may be a catalyst for olefin polymerization comprising the solid catalyst component [ C ] and the organometallic compound component [ B ]. The solid catalyst component [ C ] is produced, for example, by supporting an organomagnesium compound (C-4) (which is the same compound as (A-1); (hereinafter also abbreviated as "(C-4)") represented by the above formula (2) and a titanium compound (C-5) (which is the same compound as (A-2); (hereinafter also abbreviated as "(C-5)") represented by the above formula (3) on a carrier (C-3) (which is also abbreviated as "(C-3)") prepared by the reaction of the organomagnesium compound (C-1) (hereinafter also abbreviated as "(C-1)") represented by the below formula (4) and a chlorinating agent (C-2) (which is also abbreviated as "(C-2)") represented by the below formula (5) which are soluble in an inert hydrocarbon solvent.

(M²)_γ(Mg)_δ(R⁸)_e(R⁹)_f(OR¹⁰)_g (4)

In the formula (4), M²Represents a metal atom belonging to group 12, group 13 or group 14 of the periodic Table of the elements, R⁸、R⁹And R¹⁰Each independently represents a hydrocarbon group having 1 to 20 carbon atoms, and γ, δ, e, f and g are real numbers satisfying the following relationship. 0 is more than or equal to gamma, 0 is more than or equal to delta, 0 is more than or equal to e, 0 is more than or equal to f, 0 is more than or equal to g, 0 is more than or equal to e + f, 0 is more than or equal to g/(gamma + delta) is more than or equal to 2, and k gamma +2 delta is equal to e + f + g (wherein k is M²The valence of (c). Multiple M in Presence²、R⁸、R⁹And R¹⁰Each independently.

H_hSiCl_iR¹¹ _(4-(h+i)) (5)

In the formula (5), R¹¹Represents a hydrocarbon group having 1 to 12 carbon atoms, and h and i are real numbers satisfying the following relationship. H is more than 0, i is more than 0, and h + i is more than 0 and less than or equal to 4. R in the case of plural existence¹¹Each independently.

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. As to the formulae (2) and (3) in (C-4) and (C-5), the same as described above for (A-1) and (A-2) can be mentioned.

(C-1) although expressed in the form of an organomagnesium complex soluble in an inert hydrocarbon solvent, includes all dihydrocarbylmagnesium compounds and complexes of the compounds with other metal compounds.

In the formula (4), R⁸And R⁹The hydrocarbon group having 1 to 20 carbon atoms is not limited to the following groups, and examples thereof include: alkyl, cycloalkyl or aryl, more specifically, mention may be made of: methyl, ethyl, propyl, butyl, pentyl, hexyl, octyl, decyl, cyclohexyl, phenyl. Among these, an alkyl group is preferable.

In the formula (4), when α > 0, the metal atom M is²The metal atom is not particularly limited as long as it is a metal atom belonging to group 12, group 13 or group 14 of the periodic table, and examples thereof include: zinc atoms, boron atoms, aluminum atoms. Among these, aluminum atom and zinc atom are preferable.

Magnesium relative to metal atom M²The ratio (δ/γ) is not particularly limited, but is preferably 0.1 or more and 30 or less, and more preferably 0.5 or more and 10 or less.

In formula (4), R is 0⁸And R⁹Preferably, any one of the three groups of group (4), group (5) and group (6) shown below is satisfied.

Group (4): r⁸And R⁹At least one of them represents a secondary alkyl group or a tertiary alkyl group having 4 to 6 carbon atomsA group; preferably R⁸And R⁹Each represents an alkyl group having 4 to 6 carbon atoms, and at least one represents a secondary alkyl group or a tertiary alkyl group.

Group (5): r⁸And R⁹Represents alkyl groups having different carbon atoms from each other; preferably R⁸Represents an alkyl group having 2 or 3 carbon atoms and R⁹Represents an alkyl group having 4 or more carbon atoms.

Group (6): r⁸And R⁹At least one of them represents a hydrocarbon group having 6 or more carbon atoms; preferably represents R⁸And R⁹And alkyl groups having a total of 12 or more carbon atoms contained in the hydrocarbon group.

In the group (4), the secondary or tertiary alkyl group having 4 or more and 6 or less carbon atoms is not limited to the following groups, and examples thereof include: 1-methylpropyl, 2-methylpropyl, 1-dimethylethyl, 2-methylbutyl, 2-ethylpropyl, 2-dimethylpropyl, 2-methylpentyl, 2-ethylbutyl, 2-dimethylbutyl, 2-methyl-2-ethylpropyl. Among these, 1-methylpropyl group is preferable. In the formula (4), when γ is 0, for example, R⁸In the case of 1-methylpropyl or the like, (C-1) is soluble in an inert hydrocarbon solvent, and such (C-1) also tends to bring about preferable results in the present embodiment.

In the group (5), the alkyl group having 2 or 3 carbon atoms is not limited to the following groups, and examples thereof include: ethyl, 1-methylethyl, propyl. Among these, ethyl is preferred. The alkyl group having 4 or more carbon atoms is not limited to the following groups, and examples thereof include: butyl, pentyl, hexyl, heptyl, octyl. Among these, butyl and hexyl are preferable.

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

In general, when the number of carbon atoms contained in the alkyl group is increased, the carbon atoms tend to be easily dissolved in an inert hydrocarbon solvent, and the viscosity of the solution tends to be increased. Therefore, from the viewpoint of handling, it is preferable to use an alkyl group having an appropriate number of carbon atoms. The (C-1) may be used after dilution with an inert hydrocarbon solvent, and a slight amount of a Lewis basic compound such as ether, ester or amine may be contained or left in the solution.

In the formula (4), as represented by R¹⁰The hydrocarbon group having 1 to 20 carbon atoms is preferably an alkyl group or an aryl group having 1 to 12 carbon atoms, more preferably an alkyl group or an aryl group having 3 to 10 carbon atoms. The hydrocarbon group having 1 to 20 carbon atoms is not limited to the following groups, and examples thereof include: methyl, ethyl, propyl, 1-methylethyl, butyl, 1-methylpropyl, 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. Among these, butyl, 1-methylpropyl, 2-methylpentyl and 2-ethylhexyl are preferred.

The symbols γ, δ, e, f and g of formula (4): (k γ +2 δ ═ e + f + g) represents the valency of the metal atom and the stoichiometry of the substituent.

The method for synthesizing (C-1) is not particularly limited, and for example, a method represented by the formula: r⁸MgX¹Or by the formula: r⁸ ₂Mg(R⁸Represents the same meaning as that represented by the formula (4), X¹Represents a halogen atom) with an organic magnesium compound represented by the formula: m²R⁹ _kOr by the formula: m²R⁹ _(k-1)H(M²、R⁹And k represents the same meaning as that represented in formula (4) in an inert hydrocarbon solvent at a temperature of 25 ℃ or higher and 150 ℃ or lower. Further, if necessary, it is preferable to have R in succession⁹(R⁹An alcohol having a hydrocarbon group represented by the formula (4) or an inert hydrocarbon solvent-soluble alcohol having a hydrocarbon group represented by R⁹A method for reacting the above-mentioned magnesium alkoxide compound and/or aluminum alkoxide compound with a hydrocarbon group. Among these, the order of reacting the organomagnesium compound soluble in the inert hydrocarbon solvent with the alcohol is not particularly limited, and there may be mentioned: in the organic magnesium treatmentA method of adding an alcohol to the compound, a method of adding an organomagnesium compound to an alcohol, and a method of adding both at the same time.

The reaction ratio of the organomagnesium compound and the alcohol is not particularly limited, and as a result of the reaction, the molar composition ratio (g/(γ + δ)) of the alkoxy group to all the metal atoms in the obtained alkoxy group-containing organomagnesium compound is 0 or more and 2.0 or less, and preferably 0 or more and less than 1.0.

(C-2) is a chlorinating agent represented by the formula (5), which is a silicon chloride compound having at least one Si-H bond.

In the formula (5), from R¹¹The hydrocarbon group having 1 to 12 carbon atoms is not limited to the following group, and examples thereof include: aliphatic hydrocarbon group, alicyclic hydrocarbon group, and aromatic hydrocarbon group, and more specifically, there may be mentioned: methyl, ethyl, propyl, 1-methylethyl, butyl, pentyl, hexyl, octyl, decyl, cyclohexyl, phenyl. 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 a methyl group, an ethyl group, a propyl group, and a 1-methylethyl group is more preferable.

In addition, h and i are real numbers greater than 0 that satisfy the relationship of (h + i ≦ 4), and i is preferably a real number of 2 or more and 3 or less.

(C-2) is not limited to the following, and examples thereof include: HSiCl₃、HSiCl₂CH₃、HSiCl₂C₂H₅、HSiCl₂(C₃H₇)、HSiCl₂(2-C₃H₇)、HSiCl₂(C₄H₉)、HSiCl₂(C₆H₅)、HSiCl₂(4-Cl-C₆H₄)、HSiCl₂(CH＝CH₂)、HSiCl₂(CH₂C₆H₅)、HSiCl₂(1-C₁₀H₇)、HSiCl₂(CH₂CH＝CH₂)、H₂SiCl(CH₃)、H₂SiCl(C₂H₅)、HSiCl(CH₃)₂、HSiCl(C₂H₅)₂、HSiCl(CH₃)(2-C₃H₇)、HSiCl(CH₃)(C₆H₅)、HSiCl(C₆H₅)₂. Among these, HSiCl is preferred₃、HSiCl₂CH₃、HSiCl(CH₃)₂、HSiCl₂(C₃H₇) More preferably HSiCl₃、HSiCl₂CH₃. (C-2) may be used singly or in combination of two or more.

In the reaction of (C-1) with (C-2), it is preferable to use an inert hydrocarbon solvent in advance; chlorinated hydrocarbons such as 1, 2-dichloroethane, o-dichlorobenzene, and dichloromethane; ether solvents such as diethyl ether and tetrahydrofuran; or a mixed solvent thereof, and (C-2) is diluted and used. Among these, inert hydrocarbon solvents are more preferable from the viewpoint of the performance of the catalyst.

The reaction ratio of (C-1) and (C-2) is not particularly limited, but is preferably 0.01 to 100 moles, more preferably 0.1 to 10 moles, of silicon atom contained in (C-2) to 1 mole of magnesium atom contained in (C-1).

The method for reacting (C-1) and (C-2) is not particularly limited, and examples thereof include: a method of introducing (C-1) and (C-2) into a reactor at the same time and adding them while reacting, a method of introducing (C-1) into a reactor after (C-2) has been previously charged into the reactor, and a method of introducing (C-2) into a reactor after (C-1) has been previously charged into the reactor. Among these, a method in which (C-2) is charged into a reactor in advance and then (C-1) is introduced into the reactor is preferred. The carrier (C-3) obtained by the reaction is preferably sufficiently washed with an inert hydrocarbon solvent after separation by filtration or decantation to remove unreacted substances, by-products, and the like.

The reaction temperature of (C-1) and (C-2) is not particularly limited, but is preferably 25 ℃ to 150 ℃, more preferably 30 ℃ to 120 ℃, and still more preferably 40 ℃ to 100 ℃. The stirring speed of the reaction is not particularly limited, but is preferably 1.0X 10 in Reynolds number⁵Above and 5.0X 10⁶Hereinafter, more preferably 2.0 × 10⁵Above and 2.5X 10⁶The following.

In the method of introducing (C-1) and (C-2) simultaneously into the reactor and simultaneously adding them to the reactor for reaction, it is preferable that the temperature of the reactor is adjusted to a predetermined temperature in advance, and the temperature in the reactor is adjusted to a predetermined temperature while simultaneously adding them, thereby adjusting the reaction temperature to a predetermined temperature. In the method of introducing (C-1) into the reactor after (C-2) is previously charged into the reactor, it is preferable to adjust the reaction temperature to a predetermined temperature by adjusting the temperature of the reactor into which (C-2) is charged to a predetermined temperature and adjusting the temperature in the reactor to a predetermined temperature while (C-1) is introduced into the reactor. In the method of introducing (C-2) into the reactor after (C-1) is previously charged into the reactor, it is preferable to adjust the reaction temperature to a predetermined temperature by adjusting the temperature of the reactor into which (C-1) is charged to a predetermined temperature and adjusting the temperature in the reactor to a predetermined temperature while (C-2) is introduced into the reactor.

The amount of (C-4) used is preferably 0.1 to 10, more preferably 0.5 to 5, in terms of the molar ratio of the magnesium atom contained in (C-4) to the titanium atom contained in (C-5).

The reaction temperature of (C-4) and (C-5) is not particularly limited, but is preferably from-80 ℃ to 150 ℃, more preferably from-40 ℃ to 100 ℃.

The concentration of (C-4) in use is not particularly limited, but is preferably 0.1 mol/L to 2 mol/L, more preferably 0.5 mol/L to 1.5 mol/L, based on the magnesium atom contained in (C-4). The dilution of (C-4) is preferably carried out using an inert hydrocarbon solvent.

The order of adding (C-4) and (C-5) to (C-3) is not particularly limited, and any of (C-5) after the addition of (C-4), (C-4) after the addition of (C-5), and (C-4) and (C-5) may be added simultaneously. Among these, a method of adding (C-4) and (C-5) simultaneously is preferred. The reaction of (C-4) and (C-5) is carried out in an inert hydrocarbon solvent, preferably an aliphatic hydrocarbon solvent such as hexane or heptane is used as the inert hydrocarbon solvent.

The interval between addition of (C-4) and addition of (C-5) may be either continuous addition or intermittent addition, but from the viewpoint of controlling the surface area of the polyethylene powder particles, the addition is preferably intermittent at a cycle of 3.0 minutes to 20 minutes inclusive, and more preferably intermittent at a cycle of 5.0 minutes to 15 minutes inclusive. The time for adding (C-4) and (C-5) is not particularly limited, but is preferably 1.0 hour or more and 10 hours or less, and more preferably 2.0 hours or more and 5 hours or less. The time for aging (C-4) and (C-5) is not particularly limited, but is preferably 1.0 hour to 10 hours, more preferably 2.0 hours to 5 hours. The catalyst obtained by the above reaction may be used in the form of a slurry solution using an inert hydrocarbon solvent.

The amount of (C-5) used is not particularly limited, but is preferably 0.01 to 20, more preferably 0.05 to 10 in terms of a molar ratio to the magnesium atom contained in the carrier (C-3). The reaction temperature of (C-5) is not particularly limited, but is preferably-80 ℃ or higher and 150 ℃ or lower, and more preferably-40 ℃ or higher and 100 ℃ or lower. The method for loading (C-5) on (C-3) is not particularly limited, and there may be mentioned: a method of reacting (C-5) in an excess amount relative to (C-3), a method of efficiently supporting (C-5) by using the third component, and preferably a method of supporting (C-5) by a reaction with an organomagnesium compound (C-4).

The Ziegler-Natta catalyst according to the present embodiment is a highly active polymerization catalyst obtained 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 also referred to as a "cocatalyst".

The organometallic compound component [ B ] is not particularly limited, and examples thereof include: a compound containing a metal belonging to group 1, group 2, group 12 or group 13 of the periodic table. Among these, an organoaluminum compound and/or an organomagnesium compound is preferable.

As the organoaluminum compound, a compound represented by formula 6 is preferably used alone or in combination.

AlR¹² _jZ¹ _(3-j) (6)

In the formula (6), R¹²Z represents a hydrocarbon group having 1 to 20 carbon atoms¹Represents a hydrogen atom, a halogen atom, an alkoxy group, an allyloxy group or a siloxy group, and j is 2 or moreAnd real numbers below 3.

In the formula (6), from R¹²The hydrocarbon group having 1 to 20 carbon atoms is not limited to the following groups, and examples thereof include: aliphatic hydrocarbon groups, aromatic hydrocarbon groups, and alicyclic hydrocarbon groups.

The compound represented by formula (6) is not limited to the following, and examples thereof include: trialkylaluminum compounds such as trimethylaluminum, triethylaluminum, tripropylaluminum, tributylaluminum, tris (2-methylpropyl) aluminum (also referred to as triisobutylaluminum), tripentylaluminum, tris (3-methylbutyl) aluminum, trihexylaluminum, trioctylaluminum, and tridecylaluminum; aluminum halide compounds such as diethylaluminum chloride, ethylaluminum dichloride, bis (2-methylpropyl) aluminum chloride, ethylaluminum sesquichloride and diethylaluminum bromide; alkoxy aluminum compounds such as diethyl aluminum ethoxide and bis (2-methylpropyl) aluminum butoxide; siloxy aluminum compounds such as dimethylhydrogensiloxy dimethylaluminum, ethylmethylhydrosiloxy diethylaluminum, and ethyldimethylsiloxy diethylaluminum. Among these, trialkylaluminum compounds are preferred.

As the organomagnesium compound, those represented by the above formula (4) shown as (C-1) and soluble in an inert hydrocarbon solvent are preferably used alone or in combination.

As the organometallic compound constituent [ B]The organomagnesium compound of (2) is the same compound as the organomagnesium compound represented by the formula (4) described above as (C-1), but the higher the solubility of the organomagnesium compound in an inert hydrocarbon solvent, the more preferable the range of (β/α) is from 0.5 to 10, and further more preferable the M is²Represents a compound of aluminum.

The method for adding the solid catalyst component [ a ] or the solid catalyst component [ C ] and the organometallic compound component [ B ] to the polymerization system under polymerization conditions is not particularly limited, and both may be added to the polymerization system separately or may be added to the polymerization system after reacting both in advance. The ratio of the two components in combination is not particularly limited, and the organometallic compound component [ B ] is preferably 1 mmol or more and 3000 mmol or less with respect to 1g of the solid catalyst component [ A ] or [ C ].

Examples of the polymerization method include a method of (co) polymerizing ethylene or an ethylene-containing monomer by a suspension polymerization method or a gas phase polymerization method. Among these, the suspension polymerization method is preferable from the viewpoint of being able to effectively remove the heat of polymerization. In the suspension polymerization method, an inert hydrocarbon medium may be used as a medium, and an α -olefin itself used as a monomer may be used as a solvent.

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

The polymerization temperature is not particularly limited, and for example, is preferably 30 ℃ or more and 100 ℃ or less, more preferably 35 ℃ or more and 90 ℃ or less, and further preferably 40 ℃ or more and 80 ℃ or less. When the polymerization temperature is 30 ℃ or higher, the production tends to be industrially efficient. In addition, when the polymerization temperature is 100 ℃ or lower, continuous stable operation tends to be enabled.

The polymerization pressure is not particularly limited, but is preferably 0.1MPa or more and 2.0MPa or less, more preferably 0.1MPa or more and 1.5MPa or less, and further preferably 0.1MPa or more and 1.0MPa or less, from the viewpoint of the average particle diameter of the polyethylene powder.

The polymerization reaction may be carried out by any of a batch type, a semi-continuous type and a continuous type, and is preferably carried out by a continuous type. By carrying out the polymerization in a continuous manner, ethylene gas, a solvent, a catalyst, and the like are continuously supplied into the polymerization system and continuously discharged together with the produced ethylene (co) polymer, whereby a local high-temperature state due to a severe reaction of ethylene can be suppressed, and the inside of the polymerization system tends to be more stable. Further, it is preferable to supply the ethylene gas, the solvent, the catalyst, etc. before the supply to the polymerization reactor at the same temperature as the inside of the reactor to stabilize the system. When ethylene is reacted in a homogeneous state in the system, the formation of branched chains, double bonds, and the like in the polymer chain tends to be suppressed. In addition, it tends to be possible to suppress surface deformation and the like of the polyethylene powder caused by decomposition and crosslinking of the ethylene (co) polymer. Therefore, a continuous type which tends to become more uniform in the polymerization system is preferred. Further, the polymerization may be carried out in two or more stages under different reaction conditions.

By adding hydrogen as a chain transfer agent at an appropriate concentration in the polymerization system, the molecular weight tends to be able to be controlled within an appropriate range. By adding hydrogen to the polymerization system, it tends to be possible to promote chain transfer of the catalyst and suppress polymerization growth in addition to controlling the molecular weight. This tends to suppress the growth of a polymer chain, which is violent, and to prevent the generation of deformed particles. When hydrogen is added to the polymerization system, the molar fraction of hydrogen is preferably 0 mol% or more and 30 mol% or less, more preferably 3.0 mol% or more and 25 mol% or less, and still more preferably 5.0 mol% or more and 20 mol% or less, based on the whole system.

Further, it is more preferable that hydrogen is previously brought into contact with the catalyst and then added to the polymerization system from the catalyst introduction line. Immediately after the catalyst is introduced into the polymerization system, the catalyst concentration near the outlet of the introduction line is high, and ethylene reacts vigorously, so that the possibility of forming a locally high-temperature state is increased. Here, by bringing the hydrogen gas into contact with the catalyst before introducing the hydrogen gas into the polymerization system, the initial activity of the catalyst can be suppressed, and the change in particle shape of the polyethylene powder in a high-temperature state due to vigorous polymerization at the initial stage of polymerization can be suppressed.

The method of deactivating the ziegler-natta catalyst used for synthesizing the polyethylene powder is not particularly limited, and is preferably carried out after separating the polyethylene powder from the solvent to some extent. By introducing a medicine (a gentamicin) for inactivating the catalyst after separation from the solvent, the low molecular weight component remaining in the solvent tends to be reduced, and the crystal structure in the molecule tends to be uniform.

In the solvent separation step, the remaining liquid content in the slurry of polyethylene is preferably 10 mass% or more and 60 mass% or less, more preferably 15 mass% or more and 55 mass% or less, and still more preferably 20 mass% or more and 50 mass% or less, from the viewpoint of controlling the heat absorption for melting the polyethylene powder. When the liquid content is 10 mass% or more, the increase in the particle surface tension of the polyethylene powder is suppressed, and the possibility of the occurrence of unevenness in deactivation tends to be suppressed without making difficult the penetration of the deactivation chemical into the particles in the catalyst deactivation step. When the liquid content is 60 mass% or less, the increase of the low molecular weight component remaining in the polyethylene powder is suppressed, and the portion which is easily dissolved in the polymer is not localized, and therefore, uniform solubility and a gentle melting behavior tend to be obtained.

The catalyst-based deactivator is not particularly limited, and examples thereof include: oxygen, water, alcohols, glycols, phenols, carbon monoxide, carbon dioxide, ethers, carbonyl compounds, alkynes.

The drying temperature after the solvent separation is not particularly limited, but is preferably 60 ℃ to 150 ℃ inclusive, more preferably 70 ℃ to 140 ℃ inclusive, and further preferably 80 ℃ to 130 ℃ inclusive, from the viewpoint of controlling the surface area of the polyethylene powder. By the drying temperature being 60 ℃ or more, efficient drying tends to be enabled. In addition, by setting the drying temperature to 150 ℃ or lower, drying tends to be possible in a state in which decomposition and crosslinking of the ethylene polymer are suppressed, and there is no exposure to the ambient environment above the melting point of the polyethylene powder, which tends to suppress local melting of the particles. In addition, rearrangement of the crystal structure is less likely to occur in various portions of the polyethylene powder, particularly on the outer surface, and therefore the crystal structure in the molecule tends to be able to be uniformized. Further, particles of the polyethylene powder are suppressed from colliding with each other while the surface is melted and are transported while being fused, and therefore, an increase in the average particle diameter by generation of giant molecules tends to be suppressed.

[ fibers ]

The polyethylene powder of the present embodiment is preferably used for the fiber. The fiber produced using the polyethylene powder of the present embodiment can be processed into a fiber by a general spinning method as appropriate. The fibers can be obtained, for example, by the following method: the fibers are obtained by a processing method in which they are extruded into a gel form by an extruder equipped with a circular die using a wet method using a solvent, and then drawn, taken out, and dried to obtain filaments, and further drawn.

[ use ]

According to the polyethylene powder of the present embodiment, a rapid solubility in a solvent, a molded article with little generation of undissolved matter, and good flowability and spinning stability can be obtained. Therefore, the polyethylene powder of the present embodiment can be suitably used as a raw material for a battery separator requiring a high-strength fiber or a uniform thin microporous membrane structure. The fibers obtained from the polyethylene powder of the present embodiment can be used in high-performance textiles such as various sportswear materials, bulletproof protective clothing materials, protective gloves, various safety articles, and the like; various rope products such as tag ropes, mooring ropes, yacht ropes, and building ropes; various braid products such as fishing lines, hollow cables, and the like; net products such as fishing nets and ball nets; reinforcing materials such as chemical filter materials and battery separators; curtain materials such as various nonwoven fabrics and tents; for sports such as helmets and snowboards, reinforcing fibers for speaker cones, prepreg, concrete reinforcement, and the like.

Examples

The present embodiment will be described in further detail with reference to the following specific examples and comparative examples, but the present embodiment is not limited to the following examples and comparative examples as long as the gist of the present embodiment is not exceeded. Various physical properties and evaluations in examples and comparative examples described below were measured and evaluated by the following methods.

(Property 1) specific surface area

The specific surface area was determined by the BET method using a polyethylene powder as a sample. The specific surface area was measured by using "AUTOSOBE 3 MP" (trade name) manufactured by Yuasa-ionics Co., Ltd. As the pretreatment, 1g of polyethylene powder was put into a sample cell (specimen セル), and heated and degassed at 80 ℃ and 0.01mmHg or less for 12 hours by a sample pretreatment apparatus. Then, measurement was performed by the BET method using nitrogen as an adsorption gas at a measurement temperature of-196 ℃.

(Property 2) pore volume

The pore volume was determined by mercury porosimetry using polyethylene powder as a sample. The pore volume and the pore distribution were measured using "Autopore IV9500 type" (trade name) from Shimadzu corporation as a mercury porosimeter. As the pretreatment, 0.5g of polyethylene powder was put into a sample cell, degassed and dried at room temperature at a low-pressure measuring part, and then mercury was filled into a sample container. The pressurization is slowly carried out to press the mercury into the pores of the sample. The pressure conditions were set as follows.

Low-voltage part: 69Pa (0.01psia) and N₂The air pressure is measured

High-voltage part: 21 MPa-228 MPa (3000 psia-33000 psia)

(Property 3) half height Width of melting endothermic Peak

The half height width of the melting endothermic peak was measured using a Differential Scanning Calorimeter (DSC) (Perkin Elmer Pyrs 1DSC) using a polyethylene powder as a sample. An 8.4g (8.3g to 8.5g) sample was weighed by an electronic balance. Next, the sample was placed in an aluminum sample pan. An aluminum lid was mounted on the pan and set in a differential scanning calorimeter. The sample and the reference sample were kept at 50 ℃ for 1 minute while nitrogen purging was performed at a flow rate of 20 mL/minute, and then heated from 50 ℃ to 180 ℃ at a heating rate of 10 ℃/minute, kept at 180 ℃ for 5 minutes, and then cooled to 50 ℃ at a cooling rate of 10 ℃/minute. The melting curve obtained at this time was referenced from 60 ℃ to 155 ℃ as a baseline, and the half height width of the melting endothermic peak was derived by using analytical software "Pyris software (version 7)" (trade name).

(Property 4) viscosity average molecular weight (Mv)

The viscosity average molecular weight (Mv) of polyethylene powder was determined by the following method in accordance with ISO1628-3(2010) using polyethylene powder as a sample. First, 20mg of polyethylene powder was weighed in a melting tube, the melting tube was purged with nitrogen, 20mL of decalin (1 g/L of 2, 6-di-t-butyl-4-methylphenol) was added, and the mixture was stirred at 150 ℃ for 2 hours to dissolve the polyethylene powder. The solution was incubated at 135 ℃ in a thermostatic bath using cannon-FenskeType viscometer (manufactured by Kaita scientific instruments industries, Ltd., product No. 100) and measuring drop time (t) between calibration standards_s). Similarly, the fall time (t) between calibration lines was measured for samples obtained by changing the polyethylene powder amounts to 10mg, 5mg, and 2mg in the same manner as described above_s). In addition, the falling time (t) of decalin alone without adding polyethylene powder was measured as a blank_b). The reduced viscosity (. eta.) of the polyethylene powder obtained according to the following formula_sp/C) were plotted separately to derive the concentration (C) (unit: g/dL) and the reduced viscosity (. eta.) of polyethylene powder_spThe linear equation of/C) and the intrinsic viscosity ([ eta ] eta) obtained by extrapolation to a concentration of 0])。

η_sp/C＝(t_s/t_b-1)/0.1 (unit: dL/g)

Subsequently, the viscosity average molecular weight (Mv) was calculated using the value of the intrinsic viscosity [ η ] in the following formula.

Mv＝(5.34×10⁴)×[η]^1.49

(Property 5) average particle diameter

As for the average particle diameter of the polyethylene powder, the particle diameter at which the integrated value reached 50% by mass was taken as the average particle diameter in an integration curve obtained by integrating the mass of the polyethylene powder remaining in each sieve obtained when 100g of the polyethylene powder was classified by ten sieves (mesh opening: 710. mu.m, 500. mu.m, 425. mu.m, 355. mu.m, 300. mu.m, 212. mu.m, 150. mu.m, 106. mu.m, 75. mu.m, 53. mu.m) prescribed in JIS Z8801 from the side having the smaller mesh opening.

(Property 6) the number ratio of specific particles X (particles having an aspect ratio of 0.66 to 0.84) and the number ratio of specific particles Y (particles having an irregularity of 0.95 or more)

The number ratio of the specific particles X to the specific particles Y was determined as follows using a polyethylene powder as a sample. The aspect ratio and the roughness (UD) were measured by a dynamic image method particle size distribution and particle shape evaluation device "QICPIC" (trade name) manufactured by Japan Laser co. A sample is dispersed by an air-flow dry disperser described below, images of 4500 to 40000 particles are continuously captured and acquired, and the number ratio of specific particles X to specific particles Y is determined by image analysis software based on the acquired image information. When the number of particles is within the above range, the aspect ratio and the roughness (UD) do not vary depending on the number. Other measurement conditions were set as follows. Specific methods for obtaining the aspect ratio and the roughness are as follows.

An airflow disperser: RODOS^TM(trade name of Japan Laser Co., Ltd.)

Compressed air flow dispersion pressure: 1.0bar

Analysis mode: EQPC (equivalent circle area diameter)

Analytical measurement range: m6 (minimum pixel 5 μ M)

(aspect ratio)

In parallel lines in the constant direction sandwiching the obtained target particles, the aspect ratio of all the particles was determined by the following formula, with Fmax as the maximum value and Fmin as the minimum value. After the aspect ratios of all the particles were determined, the particles having an aspect ratio in a specific range (0.66 or more and 0.84 or less) were set as the specific particles X, and the number ratio thereof to the total number of the obtained target particles was determined.

Length-diameter ratio Fmin/Fmax

(degree of concavity and convexity)

When the projection area of the obtained target particle is a and the projection area surrounded by the envelope of the convex portion of the connection target particle is (a + B), UD represented by the following formula (1) is the degree of unevenness of the particle. After the unevenness of all the particles was obtained, the particles having the unevenness within a specific range (0.95 or more) were defined as specific particles Y, and the number ratio thereof to the total number of the obtained target particles was obtained.

UD＝A/(A+B) (1)

(Property 7) angle of repose

The angle of repose of the polyethylene Powder was measured under the following conditions using a Powder Tester PT-X manufactured by michigan corporation.

The procedure for measuring the angle of repose of the software is selected, and the accessory is installed in the main body device.

200ml of the powder was put on a sieve having a mesh size of 710 μm, and the vibration conditions were set to 1.5mm in amplitude, 170 seconds in vibration time, and 10 seconds in deceleration time.

The vibration was started, and the sample was passed through the sieve in its entirety, and it was confirmed that the angle of repose could be measured on the lower receiving table.

The angle measurement method is set to (r) ridge line Average to obtain the angle of repose in accordance with the instruction of the software.

(evaluation 1) dissolution Rate

A mixture of 14g of polyethylene powder, 0.4g of pentaerythritol tetrakis [3- (3, 5-di-t-butyl-4-hydroxyphenyl) propionate ] as an antioxidant and 36g of liquid paraffin (trade name "P-350" available from Sonmura oil Co., Ltd.) was charged into a small-sized kneader (trade name "LABPLASTOMILL 30C 150" available from Toyo Seiki Seisaku-Sho Ltd.) and kneaded at 200 ℃ at a screw rotation speed of 50 rpm. The kneading was carried out for 10 minutes. The kneaded product was sandwiched between metal plates, hot-pressed at 190 ℃ by a compression molding machine (trade name "SFA-37" manufactured by Marsdenia metal Co., Ltd.) to a thickness of 1mm to prepare a sheet, and then rapidly cooled at 25 ℃ to mold a gel-like sheet.

The obtained gel-like sheet was stretched 7 × 7 times at 120 ℃ by a simultaneous biaxial stretcher, and then liquid paraffin was removed by extraction with methylene chloride, followed by drying. The number of foreign matters of 50 μm or more (observed as black dots when the stretched sheet is observed by transmitted light) present in the obtained sheet molded product of 250mm × 250mm was visually counted for the undissolved polyethylene powder, and the number of foreign matters was evaluated based on the obtained number. The dissolution rate was evaluated by the following evaluation criteria.

(evaluation criteria)

Very good: the number of foreign matters is1 or less.

O: the number of foreign matters is 2 or more and 4 or less.

X: the number of the foreign matters is more than 5.

(evaluation 2) undissolved substance

A mixture of 14g of polyethylene powder, 0.4g of pentaerythritol tetrakis [3- (3, 5-di-t-butyl-4-hydroxyphenyl) propionate ] as an antioxidant and 36g of liquid paraffin (trade name "P-350" available from Sonmura oil Co., Ltd.) was charged into a small-sized kneader (trade name "LABPLASTOMILL 30C 150" available from Toyo Seiki Seisaku-Sho Ltd.) and kneaded at 200 ℃ at a screw rotation speed of 50 rpm. The kneading time was set to 20 minutes. The kneaded product was sandwiched between metal plates, hot-pressed at 190 ℃ by a compression molding machine (product name "SFA-37" manufactured by Marsdenia Tenacissima Co., Ltd.) to a thickness of 1mm to prepare a sheet, and then rapidly cooled at 25 ℃ to mold a gel-like sheet.

The obtained gel-like sheet was stretched 7 × 7 times at 120 ℃ by a simultaneous biaxial stretcher, and then liquid paraffin was removed by extraction with methylene chloride, followed by drying. The undissolved matter of the polyethylene powder was evaluated by the following evaluation criteria based on the number of foreign matters (observed as black dots when the stretched sheet was observed by transmitted light) of 50 μm or more present in the obtained sheet molded product of 250mm × 250mm as visually observed with the naked eye.

(evaluation criteria)

Very good: the number of foreign matters is1 or less.

O: the number of foreign matters is 2 or more and 4 or less.

X: the number of the foreign matters is more than 5.

(evaluation 3) flowability

Flowability of polyethylene powder was determined by using JIS K-6721: the time taken for 50g of the polyethylene powder to fall was measured with a funnel of the bulk specific gravity measuring apparatus described in 1997, and evaluated according to the following evaluation criteria.

(evaluation criteria)

Very good: the drop time was less than 30 seconds.

O: the falling time is 30 seconds or more and less than 40 seconds.

X: the falling time is 40 seconds or more and does not fall continuously or fall.

(evaluation 4) spinning stability

N-octadecyl 3- (4-hydroxy-3, 5-di-tert-butylphenyl) propionate was added as an antioxidant in an amount of 500 ppm by mass, and decalin (manufactured by kangdao and shinko corporation) (5% by mass relative to the total amount) was added to a polyethylene powder (95% by mass relative to the total amount) to prepare a slurry liquid. The prepared slurry-like liquid was fed into an extruder set at 280 ℃ to form a homogeneous solution. At this time, the retention time was set to 20 minutes. Then, the solution was spun through a spinneret having an aperture of 0.7mm set at 180 ℃ at a single-hole discharge rate of 1.1 g/min. The ejected solvent-containing yarn was put into a water bath at 10 ℃ through an air gap of 3cm, and was wound at a speed of 40 m/min while being quenched.

The spinning step was continuously performed for 2 hours, and when a yarn breakage occurred in the middle of the spinning, the number of yarn breakage was counted, and the spinning was continued again, and the time required for starting was removed from the 2 hours, so that the total time for which the continuous operation could be completed reached 2 hours. This series of 2-hour runs was carried out twice, and the average of the number of yarn breaks was taken. Using the average value of the number of yarn breakage times, the spinning stability was evaluated according to the following evaluation criteria.

(evaluation criteria)

Very good: the average number of filament breakage times was 0.

O: the average number of filament breakage exceeds 0 and is 1.5 times or less.

X: the average number of broken filaments exceeds 1.5.

(evaluation 5) CNT Dispersion of Carbon Nanotube (CNT) nanocomposite spinning Cross section

A mixture of 2.5g of polyethylene powder, 0.0125g of carbon nanotube Pyrrolraf III, 0.5g of pentaerythritol tetrakis [3- (3, 5-di-t-butyl-4-hydroxyphenyl) propionate ] as an antioxidant and 47.5g of liquid paraffin (trade name "P-350" manufactured by Sonmura oil Co., Ltd.) was charged into a small kneader (trade name "LABPLASTOMILL 30C 150" manufactured by Toyo Seiki Seisaku-Sho Ltd.), and kneading was carried out while changing the screw rotation speed to 50rpm and the kneading temperature in three steps. The 1 st step is to knead the polyethylene used at a temperature of Tc +10 ℃ for 15 minutes, the 2 nd step is to knead the polyethylene by changing the temperature so as to constantly raise the temperature from the set temperature of the 1 st step to 200 ℃ over 40 minutes, and the 3 rd step is to knead the polyethylene at 200 ℃ for 10 minutes. The kneaded product was passed through an orifice having a diameter of 1mm and a length of 9.99mm by a Toyo Seiki, Ltd., and wound into fibers at an extrusion rate of 10 mm/min and a take-up rate (speed of り pull) of 3 m/min. The extraction of liquid paraffin by immersing the obtained gel fiber in hexane for 1 hour was repeated twice, and then dried by leaving it at room temperature for one day. The obtained undrawn yarn was subjected to primary drawing at a draw-out speed of 20 mm/min at 120 ℃ and then secondary drawing at a draw-out speed of 10 mm/min at 140 ℃ by using an ORIENTECRTC-1310A thermostatic bath tensile tester manufactured by a & D corporation, to prepare a drawn yarn.

As a pretreatment for observing the cross section of the filaments, 20 bundled drawn filaments were bundled at two positions at an interval of about 5mm, and cut to produce bundled filaments (bundle ね) with one remaining bundled portion. Double-sided adhesive tapes 1mm wide were provided in parallel at intervals of 3mm on a cutting resin sheet (the front end of 1cm × 2cm × 0.5mm was trimmed so as to have a width of 2 mm), and the binding wires were fixed to the double-sided adhesive tapes so as to bridge (橋架けする). A fiber surface is hydrophilized by subjecting a tow including a sheet to a plasma treatment (hydrophilization treatment apparatus, Japanese electron), the whole of the filament is embedded with a photocurable resin (LCR D-800 (Tokyo synthesis)), and then irradiated with a halogen lamp (visible light irradiation) in a visible light irradiator LUXSPOT II (visible light irradiation) for 1 minute at the maximum irradiation level to photocure the filament, and after the curing, the cross section of the fiber is roughly ground with a glass cutter in a microtome, and when the cut surface is exposed, the contact diamond cutter is filled with water so that the continuous section floats on the water surface, and the cut surface is exposed at a thickness of 70 to 90 nm.

The cross sections of 20 drawn yarns of the obtained open section were observed and stored as images under the conditions of a normal mode, an acceleration voltage of 15kV and a magnification of 1000 times of a desktop electron microscope TM3030 manufactured by hitachi high and new technologies. The sectional image was subjected to image analysis using image analysis software "a image man" (manufactured by asahi Engineering). First, an image area of a part of a cross section is extracted by setting an area size to 2500 pixels in 50 × 50. A histogram of gradation (256 gradations) is acquired by a histogram acquisition program of a multivalued image processing for the extracted image, and degree distribution data is output from the histogram. The output gradation degree distribution data was developed in Excel manufactured by microsoft corporation, and the mean value and variance were calculated from the degree distribution, and the standard deviation was derived. Regarding the obtained standard deviation, the dispersibility of the carbon nanotubes was evaluated according to the following evaluation criteria.

(evaluation criteria)

Very good: the standard deviation of all 20 sections was less than 40.

O: the standard deviation of all 20 sections was less than 70.

X: among the 20 sections, there were sections having a standard deviation of 70 or more.

(evaluation 6) evaluation of moisture-containing Release amount of Polymer

150ml of water at 80 ℃ was mixed with 50g of polyethylene powder and stirred for 30 minutes, filtered through a Buchner funnel, and then allowed to stand at 50 ℃ for two hours under a nitrogen gas jet, and the weight Wa thereof was measured. The powder after standing was placed in a 200ml beaker, and vacuum-dried at 50 ℃ for 30 minutes by a vacuum dryer AVO-250NS-D manufactured by AS ONE under the condition that the operation was started at the time-lapse SV in the operation mode. The weight Wb after drying was measured, and the easiness of releasing the contained moisture was evaluated with Wb/Wa × 100 as a decrement value.

(evaluation criteria)

Very good: the decrement value is more than 80%.

O: the decrement value is 60% or more and less than 80%.

X: the decrement value is less than 60 percent

[ preparation example 1] solid catalyst component [ A-1]

1600mL of hexane was added to an 8L stainless steel autoclave sufficiently purged with nitrogen. Reynolds number of the fluid in the reactor at 10 ℃ was 1.5X 10⁶While stirring, the addition was repeated at a cycle of 5 minutes, the addition was stopped, and 1 mol was added over 4 hours800 mL/L of a hexane solution of titanium tetrachloride and 1 mol/L of a titanium tetrachloride having the composition formula AlMg₅(C₄H₉)₁₁(OSiH)₂The indicated hexane solution of the organomagnesium compound was 800 mL. After the addition, the temperature was slowly raised, and the reaction was continued at 10 ℃ for 1 hour. After completion of the reaction, 1600mL of the supernatant was removed, and the reaction mixture was washed 5 times with 1600mL of hexane to prepare [ A-1] as a solid catalyst component].1g of the solid catalyst component [ A-1]The amount of titanium contained in (1) was 3.05 mmol.

[ preparation example 2] solid catalyst component [ A-2]

1600mL of hexane was added to an 8L stainless steel autoclave sufficiently purged with nitrogen. Reynolds number of the fluid in the reactor at 10 ℃ was 1.48X 10⁶While stirring, 800mL of a hexane solution of titanium tetrachloride (1 mol/l) and 1 mol/l of a hexane solution of AlMg (composition formula) were added continuously and simultaneously for 0.5 hour₅(C₄H₉)₁₁(OSiH)₂The indicated hexane solution of the organomagnesium compound was 800 mL. After the addition, the temperature was slowly raised, and the reaction was continued at 10 ℃ for 1 hour. After completion of the reaction, 1600mL of the supernatant was removed, and the reaction mixture was washed 5 times with 1600mL of hexane to prepare [ A-2] as a solid catalyst component].1g of the solid catalyst component [ A-2]]The amount of titanium contained in (a) was 3.10 mmol.

[ preparation example 3] Carrier (B-1)

A2 mol/L hexane solution of hydroxytrichlorosilane (1000 mL) was charged into an 8L stainless steel autoclave sufficiently purged with nitrogen, and the Reynolds number of the fluid in the reactor at 65 ℃ was 1.55X 10⁶While stirring, AlMg of the composition formula was added dropwise over 4 hours₅(C₄H₉)₁₁(OC₄H₉)₂The reaction was continued while stirring the hexane solution of the organomagnesium compound (shown as 2550mL, corresponding to 2.68 mol of magnesium) at 65 ℃ for 1 hour. After the reaction was completed, the supernatant was removed and washed 4 times with 1800mL of hexane. The solid (carrier (B-1)) was decomposed under pressure using a microwave decomposition apparatus (model ETHOS TC, manufactured by Milestone General Co., Ltd.), and ICP-AES (inductively coupled plasma Mass Spectrometry apparatus, model number ICP-1) was used according to the internal standard methodX series X7, manufactured by seimer feishol scientific) was analyzed, and as a result, magnesium contained in 1g of the solid was 8.31 mmol.

Preparation example 4 solid catalyst component [ B ]

While stirring at 10 ℃ in 1970mL of a hexane slurry containing 110g of the above (B-1) carrier, the addition was repeated at a cycle of 5 minutes, the addition was stopped, and 110mL of a 1 mol/L titanium tetrachloride hexane solution and 1 mol/L of a composition formula AlMg were simultaneously added over 2 hours₅(C₄H₉)₁₁(OSiH)₂The indicated hexane solution of the organomagnesium compound was 110 mL. After the addition, the reaction was continued at 10 ℃ for 1 hour. After completion of the reaction, 1100mL of the supernatant was removed, and the reaction mixture was washed 2 times with 1100mL of hexane to prepare a solid catalyst component [ B ]].1g of the solid catalyst component [ B]The amount of titanium contained in (a) was 0.75 mmol.

[ example 1]

Hexane, ethylene, and a catalyst were continuously supplied to a vessel type 300L polymerization reactor equipped with a stirring device, to obtain a polymerization slurry. The polymerization temperature was maintained at 70 ℃ by jacket cooling. Hexane was supplied at 80L/hr from the bottom of the polymerizer. The catalyst used was the solid catalyst component [ A-1] and triisobutylaluminum as a co-catalyst. The solid catalyst constituent [ A-1] was fed at a rate of 0.2 g/hr from the middle between the liquid surface and the bottom of the polymerization vessel, and triisobutylaluminum was brought into contact with the solid catalyst constituent [ A-1] at a rate of 10 mmol/hr and then fed through the same introduction line as the solid catalyst constituent [ A-1 ]. The contact time of the solid catalyst component [ A-1] with triisobutylaluminum was adjusted to 30 seconds. The solid catalyst component [ A-1] and triisobutylaluminum were introduced from a storage tank at the start of introduction in a state of being kept at 70 ℃ equivalent to the reactor temperature in advance. Ethylene was supplied from the bottom of the polymerizer and the polymerization pressure was maintained at 0.2 MPa. The production rate of polyethylene was 10 kg/hr.

The resulting polymerization slurry was continuously withdrawn into a flash column at a pressure of 0.05MPa with the liquid level of the polymerization reactor kept constant, and unreacted ethylene was separated out. The polymerization slurry was continuously fed to a centrifugal separator in such a manner that the liquid level of the flash column was kept constant, and the polymer and the solvent and the like other than the polymer were separated. The content of the solvent and the like in this case was 45% by mass based on the polymer. In this case, the polymer cake was not present, and the slurry discharge pipe was not clogged, and the continuous operation was stable.

The separated polymer was dried while blowing nitrogen gas at 85 ℃ for 4 hours. In this drying, steam is sprayed to the polymer after polymerization to deactivate the catalyst and cocatalyst. For the dried polymer, the polymer which did not pass through the screen was removed by a screen having openings of 425 μm to obtain polyethylene powder PE 1.

The polyethylene powder obtained in example 1 was measured by the above-mentioned method, and the specific surface area (property 1), the pore volume (property 2), the half height width of the melting endothermic peak (property 3), the viscosity average molecular weight (property 4), the average particle diameter (property 5), the number ratio of specific particles X and Y (property 6), and the angle of repose (property 7) were determined. The results are shown in table 1. Further, the dissolution rate (evaluation 1), the undissolved matter (evaluation 2), the fluidity (evaluation 3), the spinning stability (evaluation 4), the filler dispersibility (evaluation 5), and the moisture releasability (evaluation 6) were evaluated. The results are also shown in table 1.

[ example 2]

Polyethylene powder PE2 was obtained in the same manner as in example 1, except that the solid catalyst component [ B-1] was used in place of the solid catalyst component [ A-1] as a catalyst. The physical properties and evaluation results of polyethylene powder PE2 are shown in table 1.

[ example 3]

A polyethylene powder PE3 was obtained in the same manner as in example 1, except that the polymerization reaction was adjusted so that the content of the solvent and the like before drying the polymer was changed from 45 mass% to 60 mass%. The physical properties and evaluation results of polyethylene powder PE3 are shown in table 1.

[ example 4]

Changing Reynolds number to 2.5X 10⁴Otherwise, a novel solid catalyst component [ A-3 ] was obtained in the same manner as in preparation example 1]. Then, as the catalyst, a solid catalyst is usedAgent component [ A-3]In place of the solid catalyst component [ A-1]Otherwise, polyethylene powder PE4 was obtained in the same manner as in example 1. The physical properties and evaluation results of polyethylene powder PE4 are shown in table 1.

[ example 5]

A polyethylene powder PE5 was obtained in the same manner as in example 1, except that the polymerization temperature was changed from 70 ℃ to 85 ℃. The physical properties and evaluation results of polyethylene powder PE5 are shown in table 1.

[ example 6]

A polyethylene powder PE6 was obtained in the same manner as in example 4, except that the polymerization temperature was changed from 70 ℃ to 85 ℃. The physical properties and evaluation results of polyethylene powder PE6 are shown in table 1.

[ example 7]

A polyethylene powder PE7 was obtained in the same manner as in example 1, except that the polymerization temperature was changed from 70 ℃ to 85 ℃ and 1 mol% of hydrogen gas was further added to the entire system in the polymerization reactor to carry out polymerization. The physical properties and evaluation results of polyethylene powder PE7 are shown in table 1.

Comparative example 1

Polyethylene powder PE8 of comparative example 1 was obtained in the same manner as in example 1 except that the drying temperature was changed from 85 ℃ to 160 ℃. The physical properties and evaluation results of polyethylene powder PE8 are shown in table 2.

Comparative example 2

Polyethylene powder PE9 of comparative example 2 was obtained in the same manner as in example 1 except that the drying temperature was changed from 85 ℃ to 55 ℃ and the drying time was changed from 4 hours to 12 hours. The physical properties and evaluation results of polyethylene powder PE9 are shown in table 2.

Comparative example 3

Polyethylene powder PE10 was obtained in the same manner as in example 1 except that both ethylene and the solid catalyst component [ a-1] were supplied from the introduction ports adjacent to the bottom of the polymerization vessel. The physical properties and evaluation results of polyethylene powder PE10 are shown in table 2.

Comparative example 4

A polyethylene powder PE11 was obtained in the same manner as in example 1, except that the solid catalyst component [ a-2] was used in place of the solid catalyst component [ a-1] as a catalyst. The physical properties and evaluation results of polyethylene powder PE11 are shown in table 2.

Comparative example 5

A polyethylene powder PE12 was obtained in the same manner as in example 1, except that the polymerization reaction was adjusted so that the content of the solvent and the like before drying the polymer was changed from 45 mass% to 65 mass%. The physical properties and evaluation results of polyethylene powder PE12 are shown in table 2.

Comparative example 6

A polyethylene powder PE13 was obtained in the same manner as in example 1, except that the polymerization pressure was changed from 0.2MPa to 0.05 MPa. The physical properties and evaluation results of polyethylene powder PE13 are shown in table 2.

Comparative example 7

Polyethylene powder PE14 was obtained in the same manner as in example 1, except that the solid catalyst component [ A-1] was replaced with the solid catalyst component [ A-2] and that both ethylene and the solid catalyst component [ A-2] were supplied from the inlet port adjacent to the bottom of the polymerization vessel as a catalyst. The physical properties and evaluation results of polyethylene powder PE14 are shown in table 2.

Comparative example 8

A polyethylene powder PE15 was obtained in the same manner as in example 1 except that the temperature of the storage tank for the solid catalyst component [ A-1] and triethylaluminum was not adjusted (actually measured value: 30 ℃ C.). The physical properties and evaluation results of polyethylene powder PE15 are shown in table 2.

TABLE 1

	Example 1	Example 2	Example 3	Example 4	Example 5	Example 6	Example 7
								Species of polyethylene powder	PE1	PE2	PE3	PE4	PE5	PE6	PE7
(Property 1) specific surface area [ m²/g]	0.34	0.50	0.42	0.61	0.50	0.64	0.55
								(Property 2) pore volume [ mL/g]	0.83	0.88	0.81	0.86	0.93	0.91	0.92
(Property 3) half height Width of melting endothermic Peak [. degree.C]	5.07	5.17	5.70	5.20	5.30	5.11	5.63
								(Property 4) viscosity average molecular weight (Mv) [ ten thousand]	400	330	450	600	370	350	90
(Property 5) average particle diameter [ mu.m ]]	101	115	102	122	116	138	230
								(Property 6) the number ratio [% of specific particles X]	65	60	63	45	61	48	63
(Property 6) the number ratio [% of specific particles Y]	33	31	30	29	20	22	26
								(Property 7) angle of repose [ °]	40.8	38.2	34.6	42.5	43.2	43.9	37.7
(evaluation 1) dissolution Rate	◎	◎	○	○	◎	○	○
								(evaluation 2) undissolved substance	◎	〇	◎	○	○	○	○
(evaluation 3) flowability	◎	◎	◎	◎	○	○	○
								(evaluation 4) spinning stability	◎	◎	◎	◎	◎	◎	◎
(evaluation 5) Filler dispersibility	◎	◎	○	◎	○	◎	○
								(evaluation 6) moisture Release Properties	◎	◎	○	◎	○	○	○

TABLE 2

	Comparative example 1	Comparative example 2	Comparative example 3	Comparative example 4	Comparative example 5	Comparative example 6	Comparative example 7	Comparative example 8
									Species of polyethylene powder	PE8	PE9	PE10	PE11	PE12	PE13	PE14	PE15
(Property 1) specific surface area [ m²/g]	0.18	1.02	0.56	1.07	0.62	0.45	0.90	0.26
									(Property 2) pore volume [ mL/g]	0.78	0.84	1.10	0.97	0.87	0.84	0.99	1.04
(Property 3) half height Width of melting endothermic Peak [. degree.C]	5.32	5.02	5.00	5.80	7.19	5.35	6.30	7.31
									(Property 4) viscosity average molecular weight (Mv) [ ten thousand]	500	550	410	300	660	510	340	380
(Property 5) average particle diameter [ mu.m ]]	170	150	130	120	210	50	180	110
									(Property 6) the number ratio [% of specific particles X]	62	60	64	64	62	67	37	58
(Property 6) the number ratio [% of specific particles Y]	26	25	30	27	27	31	20	24
									(Property 7) angle of repose [ °]	30.2	44.4	44	45	34.1	43.6	45.2	39.2
(evaluation 1) dissolution Rate	○	○	○	×	×	○	×	×
									(evaluation 2) undissolved substance	×	×	×	×	○	○	×	×
(evaluation 3) flowability	○	○	○	○	○	×	×	○
									(evaluation 4) spinning stability	○	○	○	×	×	○	×	×
(evaluation 5) fillingMaterial dispersibility	○	◎	◎	○	×	○	×	×
									(evaluation 6) moisture Release Properties	×	○	○	×	○	○	×	○

From the above results, it can be seen that: the polyethylene powder of the present invention has a small surface area and internal pores, and exhibits excellent solubility in an appropriate solvent, and therefore, the polyethylene powder has a small amount of dissolved residues of the powder which become defects when processed into fibers. In addition, it can be seen that: the half height width of the melting endothermic peak is narrow, so that the powder is uniformly dissolved in a short time without generating unevenness, and the carbon nanotubes in the carbon nanotube nanocomposite in the drawing process are well dispersed.

Industrial applicability

The polyethylene powder of the present invention is quickly dissolved in a solvent, generates little undissolved matter, has excellent fluidity and spinning stability, and has excellent strength of a molded product, and therefore, can be applied to a wide range of applications such as high-strength fibers used for ropes, nets, bulletproof and protective clothing, protective gloves, fiber-reinforced concrete products, helmets, and the like.

Claims

1. A polyethylene powder, wherein the polyethylene powder

A pore volume of 0.95mL/g or less as determined by mercury porosimetry,

A viscosity average molecular weight of 10 to 1000 ten thousand and

the average particle diameter is 100 to 300 μm.

2. The polyethylene powder according to claim 1, wherein the polyethylene powder has a viscosity average molecular weight of 100 to 950 ten thousand.

3. The polyethylene powder according to claim 1, wherein the ratio of the number of particles having an aspect ratio of 0.66 or more and 0.84 or less to the number of all particles is 50% or more.

4. The polyethylene powder according to claim 1, wherein,

the ratio of the number of particles having an unevenness of 0.95 or more defined by the following formula (1) to the number of all the particles is 25% or more,

UD＝A/(A+B) (1)

in the formula (1), UD represents the degree of unevenness, a represents the projected area of the target particle, and (a + B) represents the projected area surrounded by the envelope of the convex portion connecting the target particle.

5. The polyethylene powder according to claim 1, wherein the angle of repose of the polyethylene powder is 34 degrees or more and 45 degrees or less.

6. A polyethylene powder as claimed in any one of claims 1 to 5 for use in fibres.

7. A fiber produced by using the polyethylene powder according to claim 6.

8. A molded article obtained by molding the polyethylene powder according to any one of claims 1 to 5.