JP7224197B2 - Method for producing ultra-high molecular weight ethylene-based polymer - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for producing an ultra-high molecular weight ethylene-based polymer. Specifically, it relates to a method for producing an ultra-high molecular weight ethylene-based polymer by a continuous polymerization method. More particularly, it relates to a method for producing an ultra-high molecular weight ethylene-based polymer suitable for battery separators and the like by a continuous polymerization method.

Polyolefin microporous membranes include battery separators used in lithium secondary batteries, nickel-hydrogen batteries, nickel-cadmium batteries, polymer batteries, etc., separators for electrolytic capacitors, reverse osmosis filtration membranes, ultrafiltration membranes, microfiltration membranes, etc. It is widely used for various filters, moisture-permeable and waterproof clothing, medical materials, etc.
In recent years, there is a growing possibility that the spread of electric vehicles (EVs) will accelerate, and there is a growing demand for improvements in the production efficiency of batteries and battery components and establishment of inexpensive manufacturing methods.

When polyolefin microporous membranes are used as battery separators, especially lithium-ion battery separators, their performance is closely related to battery characteristics, battery productivity and battery safety. Therefore, polyolefin microporous membranes are required to have excellent mechanical properties, heat resistance, film appearance, permeability, dimensional stability, shutdown properties, meltdown properties, and the like. For example, if the mechanical strength is low, when it is used as a battery separator, the voltage of the battery may drop due to the short circuit of the electrodes.

Since a microporous membrane made of polyethylene alone generally has low mechanical strength, a microporous membrane made of an ultra-high-molecular-weight ethylene-based polymer has been proposed to improve the mechanical strength. Also, from the viewpoint of improving heat resistance, a technique of combining an ultra-high molecular weight ethylene polymer with other polymers has been disclosed. (For example, Patent Document 1)

In general, ultra-high molecular weight ethylene polymers tend to adhere and accumulate on the inner wall of the polymerization vessel due to their high molecular weight, so-called fouling phenomenon. In comparison, it is known that long-term stable operation tends to be difficult. On the other hand, as described above, there is a demand for establishment of a less expensive and highly efficient production method for ultra-high molecular weight ethylene-based polymers that are used as raw materials for battery separators.

International Patent Publication No. 2010/013467 Pamphlet

According to the studies of the present inventors, when an ultra-high molecular weight ethylene-based polymer is produced by a continuous polymerization method, depending on the polymerization conditions, the above-mentioned so-called fouling may occur in the vicinity of the portion where raw material gas such as ethylene is supplied to the polymerization vessel. It has been found that the ring phenomenon tends to occur easily. The supply part of the raw material gas is usually a pipe with a relatively small inner diameter, and if fouling occurs in that part, the pipe may be clogged and the polymerization operation may not be continued. tend to be relatively difficult to remove due to their high molecular weight.

The continuous polymerization method is a method of polymerizing olefins by appropriately combining recovery and recycling of unreacted olefins, and it is known that once the polymerization reaction reaches a steady state, a polymer can be obtained extremely efficiently. . It is also known that, depending on the conditions, for example, the relationship between the gas composition of the gas phase in the reactor and the composition of the raw material gas to be supplied may differ.
As a result of investigations by the present inventors, the case where such fouling occurs is mainly due to the composition of the raw material gas to be supplied (ethylene gas content) being higher than that of the gas phase in the reactor. was found to be quite high in many cases.

Based on these results, the present inventors considered the cause as follows.
"It will be particularly noticeable when performing operations such as increasing the catalyst concentration or increasing the ethylene concentration (partial pressure, etc.) for the purpose of increasing productivity, but the ethylene introduced into the reactor will not react sufficiently. Excessive polymerization reaction occurs near the supply port of the raw material gas before it diffuses uniformly in the system.This phenomenon becomes more pronounced as the scale becomes larger, because it is thought that it takes time for the gas to diffuse. In the polymerization of ethylene, the enthalpy of the reaction (corresponding to the heat of polymerization) is relatively high, and depending on the cooling state of the polymerization vessel, the ethylene polymer produced may not be sufficiently cooled, resulting in a semi-molten state / or It will be in a molten state, and the possibility of forming coarse particles due to agglomeration and adhesion to the inner wall of the polymerization apparatus will increase.
In the case of normal molecular weight level ethylene polymer production, even if the above phenomenon occurred, the cohesive force of the particles and the adhesion to the inner wall were relatively low. fits. ”
Therefore, in view of the various problems of the background art described above, the problem to be solved by the present invention is to suppress the fouling of the raw material gas supply part in particular, and to produce ultra high molecular weight polyethylene stably for a long time by a continuous polymerization method. The object is to provide a method that enables

The present inventors have made extensive studies to solve the above problems. As a result, the present inventors found that fouling is determined by the balance between the adhesion of particles to the inner wall and the detachment of the adhered particles due to stirring and collision of particles, and that the supply to the polymerization vessel is a factor that governs these balances. It was found that the raw material gas composition and the molecular weight of the resulting ultra-high molecular weight ethylene-based polymer are important factors. Based on this knowledge, when further investigation was carried out, when producing an ultra-high molecular weight ethylene-based polymer with a specific range of intrinsic viscosity, which is one of the indices of molecular weight, the composition of the raw material gas to be supplied to the polymerization vessel was specified. The present inventors have found that the above-mentioned problems are less likely to occur even in the continuous polymerization method, and long-term stable operation is facilitated, and thus the present invention has been accomplished.

That is, the method for producing an ultra-high molecular weight ethylene-based polymer of the present invention has the following aspects. (1) Polymerizing ethylene alone or ethylene and an α-olefin having 3 to 20 carbon atoms in the presence of a transition metal compound and an organometallic compound under conditions satisfying the following requirements (I) and (II). A method for producing an ultra-high molecular weight ethylene-based polymer characterized by
(I) in the presence of a transition metal compound and an organometallic compound, ethylene and (A) a gas selected from the group consisting of hydrogen, nitrogen, a group 18 element of the periodic table, and a saturated hydrocarbon gas [(A) gas] is provided in a molar ratio of 50/50 to 97/3;
(II) The intrinsic viscosity [η] of the ethylene polymer is 4.5 dl/g or more and 20 dl/g or less.
(2) An ultra-high molecular weight ethylene-based polymer is produced in a reactor having a liquid phase portion and a gas phase portion, and the molar ratio of the supplied ethylene and the (A) gas,
The method for producing an ultra-high molecular weight ethylene-based polymer according to (1), wherein the difference in molar ratio between ethylene in the gas phase and the (A) gas is 5 to 50.
(3) The method for producing an ultra-high molecular weight ethylene polymer according to (2), wherein the supplied ethylene and (A) gas are supplied in or near the liquid phase.

According to the method for producing ultra-high molecular weight polyethylene of the present invention, stoppage of operation due to troubles caused by fouling during continuous polymerization is less likely to occur. In particular, since clogging in the vicinity of the supply port of the source gas is unlikely to occur, troubles such as shutdown of operation are unlikely to occur. As described above, according to the present invention, an ultra-high molecular weight ethylene-based polymer can be stably produced for a long period of time, particularly by a continuous polymerization method. Therefore, the industrial utility value of the present invention is high.

1 is a configuration example of a production apparatus for carrying out the polymerization method for an ultra-high molecular weight ethylene-based polymer of the present invention.

The method for producing an ultra-high molecular weight ethylene-based polymer of the present invention comprises a step of (co)polymerizing ethylene alone or ethylene and an α-olefin having 3 to 20 carbon atoms in the presence of a transition metal compound and an organometallic compound. including. The present invention is characterized in that the polymerization of ethylene alone or ethylene with an α-olefin having 3 to 20 carbon atoms satisfies the following requirements (I) and (II). In this specification, even if not specified, the term "polymerization" includes copolymerization, and the term "polymer" includes copolymers.
(I) in the presence of a transition metal compound and an organometallic compound, ethylene and (A) a gas selected from the group consisting of hydrogen, nitrogen, a group 18 element of the periodic table, and a saturated hydrocarbon gas [(A) gas] is provided in a molar ratio of 50/50 to 97/3;
(II) The intrinsic viscosity [η] of the ethylene polymer is 4.5 dl/g or more and 20 dl/g or less.

The method for producing an ultra-high molecular weight ethylene-based polymer of the present invention comprises supplying ethylene alone or ethylene and an α-olefin having 3 to 20 carbon atoms in the presence of a transition metal compound and an organometallic compound to produce an ultra-high molecular weight polymer. Manufactures ethylene-based polymers.
The present inventor believes that the production method of the present invention enables the production of an ultra-high molecular weight ethylene-based polymer stably for a long period of time, particularly in continuous polymerization, as follows.
Conventionally, in the process of producing an ultra-high molecular weight ethylene-based polymer, depending on the polymerization conditions, for example, when the gas composition in the reactor and the gas composition to be supplied are stabilized under greatly different conditions, There are various cases, such as the case where the difference is small. Particularly in a continuous polymerization process, the difference between the gas composition in the reactor and the supplied gas composition may vary greatly depending on whether the method of circulating and reusing the unreacted gas is used or not. The difference is also affected by the conditions of reuse.

In the present invention, as in requirement (I) above, ethylene is supplied in a gas composition state in which the molar ratio of ethylene to the (A) gas is within the above specific range. It is difficult for the so-called olefin polymerization catalyst containing the metal catalyst and the organometallic compound to be excessively supplied (a state in which the ethylene concentration is high before the end of diffusion). Therefore, it is considered that the polymerization of ethylene proceeds relatively mildly even in the vicinity of the gas supply section, and fusion of the ethylene-based polymer due to the heat of the polymerization reaction hardly occurs. Therefore, even in the vicinity of the supply port of the raw material gas, as in the above requirement (II), the conditions must be such that a high-molecular-weight polymer with [η] of 4.5 dl/g or more is produced. Also, clogging due to polymer adhesion is unlikely to occur.
That is, by setting the above-mentioned requirements (I) and (II), fouling that hinders the long-term stable production of the ultra-high molecular weight ethylene-based polymer becomes difficult to occur, and the above-mentioned effects of the present invention are achieved. be done.

The production method of the present invention will be described in detail below. The ultra-high molecular weight ethylene-based polymer and its use will be described in order.

I. Monomers (α-olefins) that may be used in the production of the ethylene-based polymer of the present invention
In the present invention, α-olefins that may be copolymerized with ethylene include propylene, 1-butene, 1-pentene, 3-methyl-1-butene, 1-hexene, 4-methyl-1-pentene, 3- Linear or branched chain having 3 to 20 carbon atoms such as methyl-1-pentene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, 1-eicosene and vinylcyclohexane can be exemplified by α-olefins of The α-olefin is preferably a linear or branched α-olefin having 3 to 10 carbon atoms, more preferably propylene, 1-butene, 1-hexene and 1-octene. Propylene is most preferred from the standpoint of shear stability of the lubricating oil. These α-olefins can be used singly or in combination of two or more.

(Olefin other than α-olefin)
In the present invention, copolymerization may be carried out using other copolymerizable olefinic monomers in addition to ethylene and α-olefin. Examples of the olefinic monomer include polyenes, vinyl aromatic compounds, vinyl alicyclic compounds, cyclic olefins, and the like.

Polyenes include 1,4-hexadiene, 1,5-hexadiene, 1,5-heptadiene, 1,6-heptadiene, 1,6-octadiene, 1,7-octadiene, 1,7-nonadiene, 1,8- nonadiene, 1,8-decadiene, 1,9-decadiene, 1,12-tetradecadiene, 1,13-tetradecadiene, 3-methyl-1,4-hexadiene, 3-methyl-1,5-hexadiene, 3-ethyl-1,4-hexadiene, 3-ethyl-1,5-hexadiene, 3,3-dimethyl-1,4-hexadiene, 3,3-dimethyl-1,5-hexadiene, dicyclopentadiene, 5- ethylidene-2-norbornene, 5-vinyl-2-norbornene, 2,5-norbornadiene, 7-methyl-2,5-norbornadiene, 7-ethyl-2,5-norbornadiene, 7-propyl-2,5-norbornadiene, 7-butyl-2,5-norbornadiene, 7-pentyl-2,5-norbornadiene, 7-hexyl-2,5-norbornadiene, 7,7-dimethyl-2,5-norbornadiene, 7,7-methylethyl-2 ,5-norbornadiene, 7-chloro-2,5-norbornadiene, 7-bromo-2,5-norbornadiene, 7-fluoro-2,5-norbornadiene, 7,7-dichloro-2,5-norbornadiene, 1-methyl -2,5-norbornadiene, 1-ethyl-2,5-norbornadiene, 1-propyl-2,5-norbornadiene, 1-butyl-2,5-norbornadiene, 1-chloro-2,5-norbornadiene, 1-bromo -2,5-norbornadiene and the like.

Moreover, the compound of the following structure can also be mentioned as a polyene.

One or more polyenes may be used, preferably 5-ethylidene-2-norbornene, dicyclopentadiene, 5-vinylnorbornene and norbornadiene.
Examples of vinyl aromatic compounds include styrene, o-methylstyrene, m-methylstyrene and p-methylstyrene. Examples of vinyl alicyclic compounds include vinylcyclohexane, vinylcycloheptane, and vinylcyclooctane. Examples of cyclic olefins include cyclohexene and 2-norbornene.

((A) gas)
(A) the gas is selected from the group consisting of hydrogen, nitrogen, Group 18 elements of the periodic table and saturated hydrocarbon gases; Hydrogen is a chain transfer agent in olefin polymerization reactions. Nitrogen, the 18 elements of the periodic table, and saturated hydrocarbons are known as examples of inert gases and solvents in so-called olefin polymerization reactions. Among the 18th group elements of the periodic table, neon and argon are preferable examples. Examples of saturated hydrogen gas include saturated hydrocarbons having 1 to 6 carbon atoms such as methane, ethane, propane, butane, and pentane. preferable. Therefore, more preferred examples of saturated hydrocarbon gases are methane, ethane and propane, and even more preferably methane and ethane.
However, if the (A) gas that is not used in the reaction is used while circulating (recycling) the gas in a continuous polymerization process or the like, it accumulates over time in the reaction system, causing the ethylene content and partial pressure to increase more than necessary. It may be lowered. In such a case, it may be necessary to perform (A) the step of lowering the gas concentration in combination with an operation such as gas purging.
Among these (A) gases, hydrogen is preferably used mainly from the viewpoint of productivity.

II. Olefin Polymerization Catalyst In the present invention, a catalyst obtained by combining a transition metal compound and an organometallic compound can be used as the olefin polymerization catalyst. Such catalysts include, for example, the catalysts described in WO 2008/013144 pamphlet, specifically,
Olefin polymerization containing [A] a solid titanium catalyst component containing magnesium, halogen and titanium and [B] an organometallic compound catalyst component containing a metal element selected from Groups 1, 2 and 13 of the periodic table catalysts for Examples of these catalysts are detailed below.

[Solid titanium catalyst component [A]]
The above-mentioned solid titanium catalyst component [A] containing titanium, magnesium, and halogen is disclosed in JP-A-56-811, JP-A-57-63310, JP-A-57-63310, JP-A-56-811 and JP-A Solid titanium catalyst components described in JP-A-58-83006, JP-A-3-706, JP-A-2-255810 and JP-A-4-218509 can be exemplified. Such a solid titanium catalyst component can be obtained by contacting the following magnesium compound, titanium compound and, if necessary, an electron donor.

<Magnesium compound>
Specific examples of magnesium compounds include magnesium halides such as magnesium chloride and magnesium bromide;
Alkoxymagnesium halides such as methoxymagnesium chloride, ethoxymagnesium chloride, phenoxymagnesium chloride;
alkoxymagnesium such as ethoxymagnesium, isopropoxymagnesium, butoxymagnesium, 2-ethylhexoxymagnesium;
aryloxymagnesium such as phenoxymagnesium;
Known magnesium compounds such as magnesium carboxylates such as magnesium stearate can be mentioned.

These magnesium compounds may be used alone or in combination of two or more. These magnesium compounds may also be complex compounds with other metals, double compounds, or mixtures with other metal compounds.

Among these, halogen-containing magnesium compounds are preferred. Magnesium halides, especially magnesium chloride, are preferably used. In addition, alkoxymagnesium such as ethoxymagnesium is also preferably used. Further, the magnesium compound may be one derived from another substance, for example, one obtained by contacting an organomagnesium compound such as a Grignard reagent with a titanium halide, a silicon halide, a halogenated alcohol, or the like. good.

<Titanium compound>
As the titanium compound, for example, general formula (1);
Ti(OR) _g X _4-g (1)
(In general formula (1), R is a hydrocarbon group, X is a halogen atom, and g is 0≤g≤4.). More specifically,
Titanium tetrahalides such as _TiCl4 , _TiBr4 ;
Ti(OCH ₃ )Cl ₃ , Ti(OC ₂ H ₅ )Cl ₃ , Ti(On-C ₄ H ₉ )Cl ₃ , Ti(OC ₂ H ₅ )Br ₃ , Ti(O-isoC ₄ H ₉ ) trihalogenated alkoxytitanium such as _Br3 ;
Dihalogenated _alkoxy titanium such as Ti( _{OCH3 ) 2Cl2} , Ti( _OC2H5 ) _{2Cl2 ;}
monohalogenated alkoxy titaniums such as Ti(OCH ₃ ) ₃ Cl, Ti(On-C ₄ H ₉ ) ₃ Cl, Ti(OC ₂ H ₅ ) ₃ Br;
Tetraalkoxy titanium such as Ti(OCH ₃ ) ₄ , Ti(OC ₂ H ₅ ) ₄ , Ti(OC ₄ H ₉ ) ₄ and Ti(O-2-ethylhexyl) ₄ can be mentioned.
Among these, titanium tetrahalides are preferred, and titanium tetrachloride is particularly preferred. These titanium compounds may be used alone or in combination of two or more.

<Electron donor>
The solid titanium catalyst component [A] of the present invention may contain a known electron donor or a substitute thereof. Preferred examples of the electron donor include an electron donor selected from aromatic carboxylic acid esters, alicyclic carboxylic acid esters, compounds having two or more ether bonds via a plurality of carbon atoms, that is, polyether compounds ( a) can be mentioned.

When the solid titanium catalyst component [A] of the present invention contains an electron donor, it may be possible to control the molecular weight of the resulting polyolefin to a high value and to control the molecular weight distribution.
Specific examples of such aromatic carboxylic acid esters include benzoic acid esters, aromatic carboxylic acid monoesters such as toluic acid esters, and aromatic polyvalent carboxylic acid esters such as phthalic acid esters. . Among these, aromatic monocarboxylic acid esters are preferred, specifically ethyl benzoate, isobutyl benzoate, and hexyl benzoate. Examples include methyl p-toluate and ethyl p-toluate.

More specifically, the polyether compound includes compounds represented by the following general formula (2).

なお、上記一般式（２）において、ｍは１≦ｍ≦１０の整数、より好ましくは３≦ｍ≦１０の整数であり、Ｒ^１１～Ｒ^３６は、それぞれ独立に、水素原子、あるいは炭素、水素、酸素、フッ素、塩素、臭素、ヨウ素、窒素、硫黄、リン、ホウ素及びケイ素から選択される少なくとも１種の元素を有する置換基である。

In general formula (2) above, m is an integer of 1≦m≦10, more preferably an integer of 3≦m≦10, and R ¹¹ to R ³⁶ each independently represent a hydrogen atom, carbon, A substituent containing at least one element selected from hydrogen, oxygen, fluorine, chlorine, bromine, iodine, nitrogen, sulfur, phosphorus, boron and silicon.

When m is 2 or more, a plurality of R ¹¹ and R ¹² may be the same or different. Any of R ¹¹ to R ³⁶ , preferably R ¹¹ and R ¹² may together form a ring other than a benzene ring.

Some specific examples of such compounds include:
2,2-dicyclohexyl-1,3-dimethoxypropane,
2-methyl-2-isopropyl-1,3-dimethoxypropane,
2-cyclohexyl-2-methyl-1,3-dimethoxypropane,
2-isobutyl-2-methyl-1,3-dimethoxypropane,
2,2-diisobutyl-1,3-dimethoxypropane,
2,2-bis(cyclohexylmethyl)-1,3-dimethoxypropane,
2,2-diisobutyl-1,3-diethoxypropane,
2,2-diisobutyl-1,3-dibutoxypropane,
2,2-di-sec-butyl-1,3-dimethoxypropane,
2,2-dineopentyl-1,3-dimethoxypropane,
2-isobutyl-2-isopropyl-1,3-dimethoxypropane,
2-isopentyl-2-isopropyl-1,3-dimethoxypropane,
2-cyclohexyl-2-cyclohexylmethyl-1,3-dimethoxypropane,
2-methyl-2-n-propyl-1,3-diethoxypropane,
2-substituted dialkoxypropanes such as 2,-2-diethyl-1,3-diethoxypropane 2-methoxymethyl-2-methyl-1,3-dimethoxypropane,
2-cyclohexyl-2-ethoxymethyl-1,3-diethoxypropane,
trialkoxyalkanes such as 2-cyclohexyl-2-methoxymethyl-1,3-dimethoxypropane,
2,2-diisobutyl-1,3-dimethoxy-cyclohexane,
2-isoamyl-2-isopropyl-1,3-dimethoxycyclohexane,
2-cyclohexyl-2-methoxymethyl-1,3-dimethoxycyclohexane,
2-isopropyl-2-methoxymethyl-1,3-dimethoxycyclohexane,
2-isobutyl-2-methoxymethyl-1,3-dimethoxycyclohexane,
2-cyclohexyl-2-ethoxymethyl-1,3-dimethoxycyclohexane,
2-ethoxymethyl-2-isopropyl-1,3-dimethoxycyclohexane,
Examples include dialkoxycycloalkanes such as 2-isobutyl-2-ethoxymethyl-1,3-dimethoxycyclohexane.

Among these, 2-isobutyl-2-isopropyl-1,3-dimethoxypropane, 2,2-diisobutyl-1,3-dimethoxypropane, 2-isopentyl-2-isopropyl-1,3-dimethoxypropane, 2 ,2-dicyclohexyl-1,3-dimethoxypropane, 2,2-bis(cyclohexylmethyl)1,3-dimethoxypropane, 2-methyl-2-n-propyl-1,3-diethoxypropane, 2,2- Diethyl-1,3-diethoxypropane is preferred.

These compounds may be used individually by 1 type, and may be used in combination of 2 or more type.
The alicyclic carboxylic acid ester compound is represented by the following general formula (3).

一般式（３）において、ｎは、５～１０の整数、好ましくは５～７の整数であり、特に好ましくは６である。またＣ^ａは、炭素原子を表わす。

In general formula (3), n is an integer of 5-10, preferably an integer of 5-7, and particularly preferably 6. ^Ca represents a carbon atom.

R ² and R ³ are each independently COOR ¹ or R, and at least one of R ² and R ³ is COOR ¹ .
All of the bonds between carbon atoms in the cyclic skeleton are preferably single bonds, but any single bond other than the C ^a -C ^a bond in the cyclic skeleton may be replaced with a double bond. .

A plurality of R ¹ each independently has 1 to 20 carbon atoms, preferably 1 to 10 carbon atoms, more preferably 2 to 8 carbon atoms, still more preferably 4 to 8 carbon atoms, and particularly preferably 4 to 6 carbon atoms. It is a hydrogen group. Examples of the hydrocarbon group include ethyl group, n-propyl group, isopropyl group, n-butyl group, isobutyl group, hexyl group, heptyl group, octyl group, 2-ethylhexyl group, decyl group, dodecyl group, tetradecyl group, Hexadecyl group, octadecyl group, eicosyl group and the like can be mentioned, among which n-butyl group, isobutyl group, hexyl group and octyl group are preferred, and n-butyl group and isobutyl group are more preferred.

A plurality of R are each independently an atom selected from a hydrogen atom, a hydrocarbon group having 1 to 20 carbon atoms, a halogen atom, a nitrogen-containing group, an oxygen-containing group, a phosphorus-containing group, a halogen-containing group and a silicon-containing group. or is a group.

R is preferably a hydrocarbon group having 1 to 20 carbon atoms, and examples of the hydrocarbon group having 1 to 20 carbon atoms include methyl group, ethyl group, n-propyl group, iso-propyl group and n-butyl group. , iso-butyl group, sec-butyl group, n-pentyl group, cyclopentyl group, n-hexyl group, cyclohexyl group, vinyl group, phenyl group, aliphatic hydrocarbon group such as octyl group, alicyclic hydrocarbon group, An aromatic hydrocarbon group is mentioned. Among them, aliphatic hydrocarbon groups are preferred, and specifically, methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, iso-butyl group and sec-butyl group are preferred.

In addition, R may be bonded to each other to form a ring, the skeleton of the ring formed by bonding R to each other may contain a double bond, and the skeleton of the ring, When COOR ¹ contains 2 or more C ^a bonded thereto, the number of carbon atoms forming the skeleton of the ring is 5-10.
Such a ring skeleton includes a norbornane skeleton, a tetracyclododecene skeleton, and the like.

In addition, a plurality of R may be a carbonyl structure-containing group such as a carboxylic acid ester group, an alkoxy group, a siloxy group, an aldehyde group or an acetyl group, and these substituents include one or more hydrocarbon groups. It is preferable to be

Preferred examples of such alicyclic ester compounds include:
3,6-dimethylcyclohexane-1,2-dicarboxylic acid ester,
3-methyl-6-propylcyclohexane-1,2-dicarboxylic acid ester, cyclohexane-1,2-dicarboxylic acid ester, and the like.

Compounds having a diester structure as described above have isomers such as cis and trans derived from multiple COOR ¹ groups in general formula (3), but any structure can meet the object of the present invention. have the effect of From the viewpoint of polymerization activity, etc., it is particularly preferable that the trans isomer content is high.

In the present invention, among the above aromatic carboxylic acid esters, alicyclic carboxylic acid esters and ether compounds, aromatic monoesters, alicyclic polyvalent esters and ether compounds are preferred, and ether compounds are more preferred. Among the ether compounds, 1,3-diethers are preferred, particularly 2-isobutyl-2-isopropyl-1,3-dimethoxypropane, 2,2-diisobutyl-1,3-dimethoxypropane, 2-isopentyl-2- Isopropyl-1,3-dimethoxypropane, 2,2-dicyclohexyl-1,3-dimethoxypropane and 2,2-bis(cyclohexylmethyl)1,3-dimethoxypropane are preferred.

These electron donors (a) such as aromatic carboxylic acid esters, alicyclic carboxylic acid esters and ether compounds may be used alone or in combination of two or more. The electron donor may also be formed during the preparation of the solid titanium catalyst component [A]. Specifically, in the case of an ester compound as an example, when preparing the solid titanium catalyst component [A], the carboxylic acid anhydride or carboxylic acid halide corresponding to the above ester is brought into substantial contact with the corresponding alcohol. By providing a step, the ester compound can be included in the solid titanium catalyst component.

Known methods can be used without limitation for the preparation of the solid titanium catalyst component [A] used in the present invention. Specific preferred methods include, for example, the following methods (P-1) to (P-4).
(P-1) A solid adduct comprising a magnesium compound and an electron donor such as alcohol, the electron donor (a), and a liquid titanium compound are contacted in the presence of an inert hydrocarbon solvent in a suspended state. how to let
(P-2) A method of bringing a solid adduct comprising a magnesium compound and an electron donor such as alcohol into contact with the electron donor (a) and a liquid titanium compound in multiple steps.
(P-3) A solid adduct comprising a magnesium compound and an electron donor such as alcohol, the electron donor (a), and a liquid titanium compound are suspended in the presence of an inert hydrocarbon solvent. A method of contacting and contacting in a plurality of times.
(P-4) A method of contacting a liquid magnesium compound comprising a magnesium compound and an electron donor such as alcohol, a liquid titanium compound, and the electron donor (a).

A preferred reaction temperature is in the range of -30°C to 150°C, more preferably -25°C to 130°C, still more preferably -25°C to 120°C.

Moreover, the production of the above-mentioned solid titanium catalyst component can be carried out in the presence of a known medium, if necessary. Examples of the medium include slightly polar aromatic hydrocarbons such as toluene and o-dichlorotoluene, and known aliphatic hydrocarbons and alicyclic hydrocarbon compounds such as heptane, octane, decane, and cyclohexane. Among these, aliphatic hydrocarbons are preferred examples.

In the solid titanium catalyst component [A] used in the present invention, the halogen/titanium (atomic ratio) (that is, the number of moles of halogen atoms/the number of moles of titanium atoms) is 2 to 100, preferably 4 to 90. is desirable.

The magnesium/titanium (atomic ratio) (that is, the number of moles of magnesium atoms/the number of moles of titanium atoms) is desirably 2-100, preferably 4-50.
Electron donor (a) / titanium (molar ratio) (i.e., number of moles of electron donor selected from aromatic carboxylic acid ester, alicyclic carboxylic acid ester, polyether compound / number of moles of titanium atom) is 0 ~100, preferably 0.2-10.

[Organometallic compound catalyst component [B]]
The aforementioned olefin polymerization catalyst is
the solid titanium catalyst component [A] according to the present invention;
and an organometallic compound catalyst component [B] containing a metal element selected from Groups 1, 2 and 13 of the periodic table.
As the organometallic compound catalyst component [B], a compound containing a Group 13 metal, such as an organoaluminum compound, a complex alkylate of a Group 1 metal and aluminum, an organometallic compound of a Group 2 metal, etc., can be used. can. Among these, organoaluminum compounds are preferred.

Specific examples of the organometallic compound catalyst component [B] are described in the above-mentioned known documents.
R ^a _n AlX _3-n (4)
(In general formula (4), R ^a is a hydrocarbon group having 1 to 12 carbon atoms, X is halogen or hydrogen, and n is 1 ≤ n ≤ 3). can do. In the above general formula (4), R ^a is a hydrocarbon group having 1 to 12 carbon atoms, such as an alkyl group, a cycloalkyl group or an aryl group. -propyl group, isopropyl group, isobutyl group, pentyl group, hexyl group, octyl group, cyclopentyl group, cyclohexyl group, phenyl group, tolyl group and the like. Among these, trialkylaluminum with n=3, particularly triethylaluminum, triisobutylaluminum, and the like are preferable. These compounds can also be used in combination of two or more.

[Catalyst component [C]]
In addition, the olefin polymerization catalyst may contain a known catalyst component [C] together with the above organometallic compound catalyst component [B], if necessary. As the catalyst component [C], organic silicon compounds are preferred. Examples of the organosilicon compound include compounds represented by the following general formula (5).
_RnSi (OR') _4-n (5)

In general formula (5), R and R' are hydrocarbon groups, and n is an integer of 0<n<4. Preferred specific examples of the organosilicon compound represented by the general formula (5) include vinyltriethoxysilane, diphenyldimethoxysilane, dicyclohexyldimethoxysilane, cyclohexylmethyldimethoxysilane, and dicyclopentyldimethoxysilane.

Further, a silane compound represented by the following general formula (6) described in WO 2004/016662 pamphlet is also a preferred example of the organosilicon compound.
Si( ^ORa ) ₃ ( ^NRbRc ) ( ⁶ )

In general formula (6), R ^a is a hydrocarbon group having 1 to 6 carbon atoms, and examples of R ^a include unsaturated or saturated aliphatic hydrocarbon groups having 1 to 6 carbon atoms, Hydrocarbon groups having 2 to 6 carbon atoms are particularly preferred. Specific examples include methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, iso-butyl group, sec-butyl group, n-pentyl group, iso-pentyl group, cyclopentyl group, n- Examples include a hexyl group and a cyclohexyl group, and among these, an ethyl group is particularly preferred.

Further, in general formula (6), R ^b is a hydrocarbon group having 1 to 12 carbon atoms or hydrogen, and R ^b is an unsaturated or saturated aliphatic hydrocarbon group having 1 to 12 carbon atoms or hydrogen etc. Specific examples include hydrogen atom, methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, iso-butyl group, sec-butyl group, n-pentyl group, iso-pentyl group and cyclopentyl group. , n-hexyl group, cyclohexyl group, octyl group and the like, and among these, ethyl group is particularly preferred.

Further, in general formula (6), R ^c is a hydrocarbon group having 1 to 12 carbon atoms, and R ^c is an unsaturated or saturated aliphatic hydrocarbon group having 1 to 12 carbon atoms, hydrogen, or the like. mentioned. Specific examples include methyl group, ethyl group, n-propyl group, iso-propyl group, n-butyl group, iso-butyl group, sec-butyl group, n-pentyl group, iso-pentyl group, cyclopentyl group, n- A hexyl group, a cyclohexyl group, an octyl group, and the like can be mentioned, and among these, an ethyl group is particularly preferable.

Specific examples of the compound represented by the general formula (6) include:
dimethylaminotriethoxysilane,
diethylaminotriethoxysilane,
diethylaminotrimethoxysilane,
diethylaminotriethoxysilane,
diethylaminotri-n-propoxysilane,
di-n-propylaminotriethoxysilane,
methyl n-propylaminotriethoxysilane,
t-butylaminotriethoxysilane,
ethyl n-propylaminotriethoxysilane,
ethyl iso-propylaminotriethoxysilane,
Methylethylaminotriethoxysilane can be mentioned.

Other compounds useful as the catalyst component [C] include the above aromatic carboxylic acid esters, alicyclic carboxylic acid esters and/or multiple Polyether compounds described as examples of compounds having two or more ether bonds via the carbon atoms of are also preferred examples.

Among these polyether compounds, 1,3-diethers are preferred, particularly 2-isobutyl-2-isopropyl-1,3-dimethoxypropane, 2,2-diisobutyl-1,3-dimethoxypropane, 2-isopentyl -2-isopropyl-1,3-dimethoxypropane, 2,2-dicyclohexyl-1,3-dimethoxypropane, 2,2-bis(cyclohexylmethyl)1,3-dimethoxypropane, 2-methyl-2-n-propyl -1,3-diethoxypropane and 2,-2-diethyl-1,3-diethoxypropane are preferred.

These catalyst components [C] can be used alone or in combination of two or more.

In addition to these, the olefin polymerization catalysts that can be used in the present invention include metallocene compounds disclosed in JP-A-2004-168744 and the like, JP-A-2000-128931 and JP-A-2004-646097. Catalysts for olefin polymerization containing an organometallic complex having a phenoxyimine compound or the like as a ligand and an organometallic compound catalyst component disclosed in JP-A-2005-2244, JP-A-2005-2086, etc. can also be exemplified as a preferred olefin polymerization catalyst.

Among these, a preferable example is a method for polymerizing an ethylene polymer using a solid titanium catalyst component containing a halogen and containing a magnesium compound component, a titanium compound component and an aromatic carboxylic acid ester. Particularly preferred is a method for polymerizing an ethylene polymer using a solid titanium catalyst component containing a magnesium compound component, a titanium compound component and an aromatic monocarboxylic acid ester.

III. Other Components Used in Reaction In the present invention, the polymerization reaction is usually carried out in a hydrocarbon medium. Specific examples of such hydrocarbon media include aliphatic hydrocarbons such as propane, butane, pentane, hexane, heptane, octane, decane, dodecane, and kerosene, and alicyclic hydrocarbons such as cyclopentane, cyclohexane, and methylcyclopentane. Hydrogen, aromatic hydrocarbons such as benzene, toluene and xylene; halogenated hydrocarbons such as ethylene chloride, chlorobenzene and dichloromethane; and petroleum fractions such as gasoline, kerosene and light oil. Furthermore, olefins used for polymerization can also be used.

IV. Production Process and Polymerization Conditions In the present invention, the production of an ultra-high molecular weight ethylene-based polymer obtained by (co)polymerizing ethylene alone or ethylene with the α-olefin and/or other olefins includes the transition metal compound and in the presence of the above-mentioned organometallic compound, ethylene alone or ethylene and an α-olefin having 3 to 20 carbon atoms are (co)polymerized under conditions satisfying the above requirements (I) and (II). Except for the above, the same method as a conventionally known method for producing an ultrahigh molecular weight ethylene-based polymer can be employed as appropriate. Each condition and the like will be described below.

The ultra-high molecular weight ethylene-based polymer of the present invention can be polymerized in any of batch polymerization, continuous polymerization, and semi-continuous polymerization, but the production method of the present invention is particularly useful when a continuous polymerization process is used. is.
The polymerization mode of the present invention can be carried out in any of liquid phase polymerization methods such as bulk polymerization method, solution polymerization and suspension polymerization, and gas phase polymerization methods.

The reactor for polymerization is a reactor made of SUS or the like, and is equipped with a rotatable stirring shaft having stirring blades. Plate blades and the like are exemplified.

The size of the reactor or reactor used in the present invention is preferably in the range of 50 liters to 1000 cubic meters, more preferably in the range of 60 liters to 800 cubic meters, and still more preferably in the range of 70 liters to 800 cubic meters. Range.

(polymerization temperature)
In the present invention, the polymerization temperature for producing the ultra-high molecular weight ethylene polymer is preferably -20 to 200°C, more preferably 0 to 150°C, and particularly preferably 20 to 100°C.
The temperature within this range tends to produce the desired ultra-high molecular weight ethylene polymer with high polymerization activity, although this may be affected by the type of catalyst described above.

(polymerization pressure)
In the present invention, the polymerization pressure (P) when producing the ultra-high molecular weight ethylene polymer is preferably 0.1 to 10 MPa, more preferably 0.2 to 5 MPa, and particularly preferably 0.3 to 2 MPa. .
If the polymerization pressure is within such a range, there is a tendency that the desired ultra-high molecular weight ethylene copolymer can be produced with high polymerization activity.
(Regarding the supply of raw materials)

When hydrogen, which also functions as a chain transfer agent, is used as the [A] gas, the molar ratio of the amounts of hydrogen and ethylene used as the [A] gas is preferably 0-50. A more preferable lower limit is 1, and an even more preferable lower limit is 2. On the other hand, the upper limit is more preferably 45, more preferably 40. If the amount of hydrogen used is too large, there is a possibility that the molecular weight of the ethylene polymer produced will not increase, that is, [η] will not increase. A preferred residence time is 10 minutes to 2 hours, more preferably 15 minutes to 1.5 hours, even more preferably 20 minutes to 1 hour. When the production method of the ethylene-based copolymer is continuous polymerization, the residence time can be regarded as the polymerization time.

As the olefin polymerization catalyst, when using the olefin polymerization catalyst containing the solid titanium catalyst component [A] and the organometallic compound catalyst component [B] described in WO 2008/013144 pamphlet,
The solid titanium catalyst component [A] is usually used in an amount of 0.0001 mmol to 0.5 mmol, preferably 0.005 mmol to 0.1 mmol in terms of titanium atoms per liter of polymerization volume. be done. The amount of the organometallic compound catalyst component [B] is generally 1 mol to 2000 mol, preferably 5 mol to 500 mol, per 1 mol of the titanium atom in the preliminary polymerization catalyst component in the polymerization system. Used. When the catalyst component [C] is used, it is 0.001 mol to 50 mol, preferably 0.01 mol to 30 mol, particularly preferably 0.05 mol, relative to the organometallic compound catalyst component [B]. Used in amounts of ~20 molar. However, the amount of each component of the catalyst mentioned above is the amount used in the case of main polymerization excluding prepolymerization as referred to in the same document, and the amount of catalyst used and other conditions when performing prepolymerization etc. are the same. As described in the literature.

(One mode of reactor)
The production of the ultra-high molecular weight ethylene-based polymer described above is carried out, for example, in the reactor shown in FIG.
The reactor shown in FIG. 1 has a liquid phase portion (liquid phase) and a gas phase portion (gas phase), and is equipped with a rotatable stirring shaft having stirring blades in the reactor. is. Further, the reactor of FIG. 1 is provided with a line for circulating and reusing unreacted gas, and the raw material gas is supplied to the reactor together with all or part of this unreacted gas.

In the reactor of FIG. 1, the (A) gas such as ethylene and hydrogen is mixed in a molar ratio of 50/50 to 97/30, preferably 60/40 to 97/3, more preferably 70/30. Supplied in a molar ratio of ~96/4. If the molar ratio of ethylene to the (A) gas is less than 50/50, productivity may not be sufficient. On the other hand, if the molar ratio of ethylene to the (A) gas is greater than 97/3, fouling may occur.

In the reactor of FIG. 1, the difference between the molar ratio of the (A) gas and ethylene in the feed section and the molar ratio of the (A) gas and ethylene in the gas phase section of the reactor is preferably 0.5. 01 to 0.12, a more preferred lower limit is 0.02, and a further preferred lower limit is 0.04. On the other hand, a more preferable upper limit is 0.11, and more preferably 0.10. By controlling the composition of both gases within the above range, there is a tendency that fouling can be suppressed more effectively.

The reactor of FIG. 1 is provided with a line for circulating and reusing unreacted gas. (Hereinafter, this reused unreacted gas is also referred to as circulating gas). The circulating gas line is provided with a heat exchanger, a valve, and a compressor, and the (A) gas such as raw material ethylene and hydrogen gas is adjusted in heat quantity and pressure by the heat exchanger and the compressor. It is fed into the reactor together with some or all of the circulating gas. By adopting such a method, it is possible to easily control the supply gas composition within a preferable range, and to efficiently prevent fouling.

As described above, among the (A) gases, nitrogen, group 18 elements, and saturated hydrocarbon gases are inert gases, and hydrogen does not contribute to polymerization, so a continuous polymerization method that recycles unreacted gas is applied. In a reactor such as that shown in FIG. 1, these gases may accumulate in the reaction system over time. When the above accumulation is excessive, the concentrations of ethylene and the optionally used α-olefin relatively decrease, and the polymerization efficiency may decrease. In such a case, it is desirable to periodically remove part or all of the unreacted gas to maintain the ethylene concentration and α-olefin concentration at appropriate values.
These gases are introduced into the reactor together with the olefin mentioned above as the circulation gas mentioned above. The method generally includes a method of direct introduction from a supply port provided in the flange portion. It can be introduced into the gas phase part in addition to the part. In this case, as shown in FIG. 1, it is preferable to dispose the supply port in the vicinity of the liquid phase portion. The vicinity is usually within 50 cm, more preferably within 30 cm from the liquid phase, although it depends on the size of the reactor. Moreover, it is also one of preferred embodiments that the above gas is directly introduced into the liquid phase portion in the reaction system via an introduction pipe. In such cases, even if particles begin to adhere near the inlet. A liquid flow or a flow of suspended particles can be expected to impede adhesion by colliding with the adhering matter.

The method for producing the ultra-high molecular weight ethylene-based polymer of the present invention is often carried out by continuous suspension polymerization using a solvent as shown in FIG. In this case, it is important to select conditions that allow long-term continuous operation. Considering these, in addition to the above conditions, it is preferable to carry out the reaction system with a polymer concentration in the range of 50 to 500 g / l, more preferably 100 to 450 g / l, and still more preferably 150 to 400 g / l. be. If the polymer concentration is within the above range, adverse effects such as fouling are less likely to occur, which is advantageous for stable operation over a long period of time.

V. Ultra-high molecular weight ethylene-based polymer produced by the present invention and its use The ultra-high-molecular-weight ethylene-based polymer obtained by the method for producing an ultra-high-molecular-weight ethylene-based polymer of the present invention is a homopolymer of ethylene, or ethylene and propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 4-methyl-1-pentene, 3-methyl-1-pentene, etc. having 3 to 10 carbon atoms; It consists of a copolymer with one or more α-olefins selected from α-olefins.

Among these, ethylene is a homopolymer of ethylene or a copolymer of ethylene and the above α-olefin, and ethylene is 50% by mass or more, preferably 70% by mass or more, and further 90% by mass or more. It is preferable to use a polymer as the main component, because the microporous membrane obtained using the ultrahigh molecular weight ethylene-based polymer is excellent in permeability and shutdown characteristics.

The lower limit of the intrinsic viscosity [η] of the ultra-high molecular weight ethylene polymer measured in decalin at 135°C according to ASTM D4020 is 4.5 dl/g, preferably 5.0 dl/g, more preferably 6 0 dl/g, more preferably 8.0 dl/g, particularly preferably 10.0 dl/g. The upper limit of the intrinsic viscosity [η] is 35 dl/g, preferably 30 dl/g, more preferably 26 dl/g, more preferably 23 dl/g, particularly preferably 20 dl/g. If the intrinsic viscosity [η] is less than 4.5 dl/g, the strength of the film or microporous membrane obtained from the polyolefin resin composition is lowered. Further, when the intrinsic viscosity [η] is more than 35 dl/g, it becomes difficult to form a film or a microporous membrane containing the ultra-high molecular weight ethylene polymer.

Therefore, when the intrinsic viscosity [η] of the ultra-high molecular weight ethylene polymer is within the above range, the mechanical properties and dimensional stability of the ultra-high molecular weight ethylene polymer are more effectively applied to films and microporous membranes. can be granted.

<Film using ultra-high molecular weight ethylene polymer>
The ultra-high molecular weight polyethylene obtained by the method of the present invention can be formed into films. Specifically, it can be produced by film forming by a known method such as a press molding method, an extrusion molding method, an inflation method, a calendering method, or the like. The ultra-high molecular weight polyethylene can be used as it is, or can be molded after being gelled with a known solvent. For such molding, known methods can be used without limitation.

<Microporous membrane using ultra-high molecular weight ethylene polymer>
The ultra-high molecular weight polyethylene obtained by the method of the present invention can be molded into a microporous membrane, and the microporous membrane can be produced by a known method. Specifically, the following methods can be mentioned.

a) a step of melt-kneading the ultra-high molecular weight polyethylene and a plasticizer (also referred to as a solvent) to prepare a polyolefin composition;
b) extruding the polyolefin composition through a die and cooling to form a gel sheet;
c) stretching/plasticizer removal step d) drying and heat-treating the obtained film Each step will be described below.

a) Step of preparing polyolefin composition The polyolefin resin composition and plasticizer are melt-kneaded to prepare a polyolefin composition suitable for microporous membranes, particularly battery separators.

As the plasticizer, any known plasticizer can be used as long as it is liquid or solid, becomes liquid at high temperature, and can be extracted with the washing solvent described below.

For example, when a plasticizer that is liquid at room temperature is used, stretching at a relatively high magnification tends to be possible. Examples of such liquid plasticizers include, but are not limited to, aliphatic or cyclic hydrocarbons such as nonane, decane, decalin, paraxylene, undecane, dodecane, liquid paraffin, and mineral oil distillates having boiling points corresponding to these. phthalates that are liquid at room temperature, such as dibutyl phthalate and dioctyl phthalate. In order to obtain a gel sheet with a stable liquid plasticizer content, it is preferable to use a non-volatile liquid plasticizer such as liquid paraffin. In the present invention, it is also preferable to use a plasticizer that is solid and becomes liquid at high temperatures. In the heat-melt-kneading state, the plasticizer is mixed with the polyolefin resin composition, but the plasticizer that is solid at room temperature may be mixed with the plasticizer that is liquid. Examples of such plasticizers include paraffin waxes that are solid at room temperature, and higher aliphatic alcohols such as stearyl alcohol and ceryl alcohol.

Although the method of melt-kneading is not particularly limited, it is usually carried out by uniform kneading in a twin-screw extruder. This method is suitable for preparing highly concentrated solutions of polyolefins. The melting temperature is usually 160-300°C, preferably 180-280°C.

The mixing ratio of the polyolefin resin composition and the plasticizer in the polyolefin composition is 1 to 50 parts by mass, preferably 20 to 40 parts by mass, based on the total of 100 parts by mass.

b) Forming step of sheet The melt-kneaded polyolefin composition is extruded directly or through another extruder, or once cooled and pelletized, then extruded through the extruder again through a die. As the die, a sheet die is usually used, but a double cylindrical hollow die, an inflation die, or the like can also be used. The melting temperature during this extrusion is usually 140-280°C.

A molding is formed by cooling the solution extruded from the die in this way. In this way, a phase-separated structure in which the polyolefin phase is microphase-separated by the plasticizer can be fixed. In addition, as a molding, a gel-like thing is preferable.

c) Stretching/Plasticizer Removal Step Next, the obtained sheet is stretched and then the liquid solvent is extracted and removed, or the liquid solvent is extracted and removed from the sheet and then stretched, or the sheet is stretched and then the liquid is removed. Solvent is removed by extraction and further drawn. As the sheet, a gel sheet is preferable.

After the sheet is heated, stretching is performed at a predetermined magnification by a conventional tenter method, roll method, inflation method, rolling method, or a combination of these methods. The stretching may be uniaxial stretching or biaxial stretching, but biaxial stretching is preferred. In the case of biaxial stretching, simultaneous biaxial stretching, sequential stretching or multistage stretching (for example, a combination of simultaneous biaxial stretching and sequential stretching) may be used, but simultaneous biaxial stretching is particularly preferred. Stretching improves mechanical strength.

The draw ratio varies depending on the thickness of the sheet, but in the case of uniaxial drawing, it is preferably 2 times or more, more preferably 3 to 30 times. In the biaxial stretching, the film is stretched at least 3 times in any direction, preferably 9 times or more in terms of surface magnification, and more preferably 25 times or more in terms of surface magnification. By setting the surface magnification to 9 times or more, the piercing strength is improved. The stretching temperature is generally 100 to 140°C, preferably 110 to 120°C.

A washing solvent is used to remove (wash) the plasticizer. Since the polyolefin phase is phase separated from the plasticizer, extraction and removal of the plasticizer results in a porous membrane. Removal (washing) of the plasticizer can be performed using a known washing solvent. Examples of known washing solvents include chlorinated hydrocarbons such as methylene chloride and carbon tetrachloride; hydrocarbons such as pentane, hexane and heptane; fluorinated hydrocarbons such as ethane trifluoride; ethers such as diethyl ether and dioxane; Examples include easily volatile solvents such as methyl ethyl ketone.

The washing method can be carried out by a method of immersing the stretched film or sheet in a washing solvent, a method of showering the stretched film or sheet with a washing solvent, or a combination thereof. Washing with a washing solvent is preferably carried out until the amount of residual plasticizer is less than 1 part by mass based on the added amount.

d) Film Drying Process The film obtained by stretching and removing the plasticizer can be dried by a heat drying method, an air drying method, or the like. The drying temperature is preferably a temperature not higher than the crystal dispersion temperature of the ultrahigh molecular weight ethylene polymer (A), and more preferably a temperature lower than the crystal dispersion temperature by 5°C or more.

There is no particular problem as long as the membrane is dried by the drying treatment within a range that does not impair the purpose of the present invention. is preferably 5 parts by mass or less, more preferably 3 parts by mass or less. If drying is insufficient and a large amount of the washing solvent remains in the membrane, the porosity will decrease in subsequent heat setting, and the permeability will deteriorate, which is not preferable.

Furthermore, after drying, it is preferable to perform heat setting for the purpose of preventing shrinkage of the microporous membrane in the stretching direction due to residual stress applied during stretching. A preferable temperature for this heat setting is 80°C or higher and lower than 150°C. A method of thermally shrinking the length of the microporous membrane after heat setting by 10 to 50% (this method is hereinafter referred to as "relaxation"), a method of fixing so that the dimension in the stretching direction does not change, etc. be done.

The present invention will be explained more concretely by the following examples. However, the present invention is in no way limited by these examples and the like.

Example 1
A temperature-controllable jacketed pressure-resistant reactor with internal volume of 155 liters and a stirrer, a line for circulating unreacted gas, etc. (equipped with a heat exchanger, a compressor for circulating recovered gas, and a valve), a solvent feed line, raw materials Using an apparatus equipped with a gas feed line, a catalyst feed line, and a contents extraction line, ethylene and hydrogen are separated into a known Mg compound-supported solid titanium catalyst (described in Comparative Example 1 of WO2008/013144 Continuous polymerization of ethylene was carried out under the following conditions so as to achieve a steady state while circulating unreacted gas (ethylene, hydrogen) using a catalyst). As a result, an ultra-high molecular weight ethylene polymer having an intrinsic viscosity [η] of about 5 dl/g was obtained. As the intrinsic viscosity [η] of the ultra-high molecular weight ethylene polymer, [η] was measured in decalin at 135°C according to ASTM D4020.

(Polymerization conditions)
・Polymerization temperature: 75°C
Feed rate of each component Hexane: 36.5 liters/hour Catalyst (same component as in Comparative Example 1 of WO2008/013144): 0.9 mmol/hour as titanium atom Triisobutylaluminum: 11.25 mmol/hour Ethylene:8. 8 kg/hour Hydrogen: 60 NL/hour Pressure: 0.50 MPa
Extracted amount: 44.3 liters/hour The gas composition at that time was as follows.
(gas composition)
Hydrogen/ethylene ratio: 0.17 m. r. (gas phase)
Ethylene/hydrogen ratio: 5.88 m. r. (gas phase)
Hydrogen/ethylene ratio: 0.10 m. r. (Feedline)
Ethylene/hydrogen ratio: 10.1 m. r. (Feedline)
Ethylene concentration: 91.0 mol% (feed line)

Even if the continuous polymerization of the ultra-high molecular weight ethylene polymer was carried out under the above conditions for 40 hours, deposits near the feed line were not detected.

Comparative example 1
Continuous polymerization of ethylene was carried out in the same manner as in Example 1 except that the valve of the circulation line was closed and the operation was performed under the following conditions to obtain an ultrahigh molecular weight ethylene polymer having an intrinsic viscosity [η] of about 5 dl/g. rice field. As a result, there was a pronounced tendency for clumping near the ethylene feed line.

(polymerization temperature)
・Polymerization temperature: 75°C
Feed rate of each component Hexane: 36.5 liters/hour Catalyst (same component as in Example 1 of WO2008/013144): 0.9 mmol/hour Triisobutylaluminum: 11.25 mmol/hour Ethylene: 8.8 kg/hour Hydrogen: 60 NL/hour Pressure: 0.50 MPa
Extracted amount: 44.3 liters/hour The gas composition at that time was as follows.
(gas composition)
Hydrogen/ethylene ratio: 0.17 m. r. (gas phase)
Ethylene/hydrogen ratio: 5.88 m. r. (gas phase)
Hydrogen/ethylene ratio: 0.005 m. r. (Feedline)
Ethylene/hydrogen ratio: 200m. r. (Feedline)
Ethylene concentration: 99.5 mol% (feed line)

By comparing Example 1 and Comparative Example 1, Example 1 has a lower ethylene concentration in the feed line. This is considered to suggest the possibility that the ethylene concentration in the feed line, which is the point of the present invention, is one of the causes of fouling suppression.
From the above, it is considered that, according to the method for producing ultra-high molecular weight polyethylene of the present invention, shutdown due to troubles caused by fouling during continuous polymerization is unlikely to occur.

Claims (4)

In the presence of a transition metal compound and an organometallic compound, ethylene alone or ethylene and an α-olefin having 3 to 20 carbon atoms are continuously mixed in a hydrocarbon medium under conditions satisfying the following requirements (I) and (II). An ultra-high molecular weight ethylene polymer having an ethylene-derived unit of 50% by mass or more and having an intrinsic viscosity [η] of 4.5 dl / g or more and 20 dl / g or less in decalin at 135 ° C. according to ASTM 4020 standards, which is characterized by being polymerized. a method of manufacturing a coalesce,
(I) in the presence of a transition metal compound and an organometallic compound, ethylene and (A) a gas selected from the group consisting of hydrogen, nitrogen, a group 18 element of the periodic table, and a saturated hydrocarbon gas [(A) gas] is provided in a molar ratio of 50/50 to 97/3;
(II) The intrinsic viscosity [η] of the ethylene polymer is 4.5 dl/g or more and 20 dl/g or less. An ultra-high molecular weight ethylene-based polymer is produced in a reactor having a liquid phase portion and a gas phase portion, and the molar ratio of the supplied (A) gas and ethylene,
The difference in the molar ratio between the (A) gas and ethylene in the gas phase is
The method for producing an ultra-high molecular weight ethylene-based polymer according to claim 1, characterized in that it is 0.01 to 0.120. 2. The method for producing an ultra-high molecular weight ethylene-based polymer according to claim 1 , wherein the ethylene-derived unit is 70% by mass or more . 2. The method for producing an ultra-high molecular weight ethylene-based polymer according to claim 1, wherein the ethylene-derived units are 90% by mass or more.

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