JP2657434C - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION       [0001]     [Industrial applications]   The present invention relates to a microporous polyethylene membrane, a method for producing the same, and a battery separator using the same.
With regard to the radiator, it has excellent permeability and mechanical strength, and
Polyethylene microporous membrane having a function of blocking, method for producing the same, and electrode using the same
It relates to a pond separator.       [0002]     2. Description of the Related Art   Microporous membranes include separators for batteries, diaphragms for electrolytic capacitors, and various filters
Used for various applications such as waterproof, moisture permeable clothing, reverse osmosis filtration membrane, ultrafiltration membrane, and microfiltration membrane.
Have been.       [0003]   Conventionally, as a method for producing a microporous polyolefin membrane, for example,
After mixing the pore-forming agent consisting of fine powder with the polyolefin and micro-dispersing it,
Mixed extraction method to extract the agent, micro phase separation of polyolefin phase with solvent Phase separation method with more porous structure, polyolefin synthesis with different solids micro-dispersed
By giving strains such as stretching to the shape, interfacial fracture between different types of solids is generated and voids are generated.
For example, a stretching method of making the film porous is used. However, these methods usually
Since a polyolefin having a molecular weight of less than 500,000 is used, it is thinned by stretching.
And there was a limit to the increase in strength.       [0004]   Recently, ultra-high molecular weight polyolefins that can be formed into high strength and high elasticity films
Various proposals have been made for the production of high-strength microporous membranes. For example,
No. 58-5228 dissolves an ultra-high molecular weight polyolefin in a non-volatile solvent,
Form a gel, such as a fiber or film, from the solution and make the gel containing this solvent volatile
It discloses a method of performing heat-stretching after extracting with a solvent. However, non-volatility
A gel with a porous structure highly swollen with a propellant tends to stretch in two directions
However, highly oriented stretching is not possible, and it is easy to break due to the expansion of the network structure.
Lum has the disadvantage of low strength and large pore size distribution.
. On the other hand, the gel dried after extracting the nonvolatile solvent with the volatile solvent has a network structure.
Although it densifies, warpage occurs in the film raw material due to uneven evaporation of volatile solvents.
There is a drawback that stretching at a high magnification cannot be easily performed due to shrinkage and densification.       [0005]   On the other hand, when the weight average molecular weight is 7 × 10^FiveUltra high molecular weight polyolefin
A gel-like sheet is formed from a solution obtained by heating and dissolving in a solvent,
After adjusting the amount of solvent by desolvation treatment and then heat drawing, remove the residual solvent
This produces a microporous membrane of ultra-high molecular weight polyolefin (polyethylene)
Various methods have been proposed (Japanese Patent Application Laid-Open Nos. 60-242035 and 61-495).
No. 132, JP-A-61-195133, JP-A-63-39602, JP-A-6
No. 3-273661).       [0006]   However, the production of the microporous ultra-high molecular weight polyolefin (polyethylene) film
In order to biaxially stretch the ultra-high molecular weight polyolefin,
Since a somewhat dilute solution of the olefin is prepared, the resulting solution is The swell and neck-in are large at the die exit for sheet forming, making sheet forming difficult.
is there. Further, since the sheet contains an excessive amount of solvent, it is stretched as it is.
The desired microporous membrane cannot be obtained, so remove the solvent and adjust the amount of solvent in the sheet
For example, a large amount of solvent is required, and there is a problem in productivity. Therefore
Polyol can be prepared from a highly concentrated solution of ultra-high molecular weight polyolefin without impairing stretchability.
It has become desirable to produce fin microporous membranes.       [0007]   For the purpose of solving such a problem, the present inventors have developed an ultra-high molecular weight polymer.
Contains olefins and the value of (weight average molecular weight / number average molecular weight) is within a specific range
A method for producing a microporous polyolefin membrane using a certain composition was proposed (Japanese Patent Laid-Open Publication No. Hei 3-
64334). By this method, the stretchability is good and a high concentration solvent can be used.
It is possible to produce microporous polyolefin membranes from functional polyolefin compositions
became.       [0008]   By the way, the above-mentioned microporous polyolefin membrane is used for a battery, for example, a separator for a lithium battery.
When the battery is used for heating, etc., when the electrode short-circuits and the temperature inside the battery rises,
It is necessary to prevent such accidents from occurring. As a result, melting occurs before lithium fires.
The separator has the function of clogging the hole and shutting down the current.
I need to help. However, in each of the above microporous membranes, permeation due to microporous occlusion
Temperature is not necessarily low enough in terms of safety.
For better performance, a separator that shuts down the current at lower temperatures
Is desirable.       [0009]   Therefore, an object of the present invention is to provide excellent permeation performance and mechanical strength as well as low temperature.
And to provide a microporous polyethylene membrane having a function of blocking permeability.       [0010]   Another object of the present invention is to efficiently produce the above microporous polyethylene membrane.
Is to provide a way to       [0011]   Further, another object of the present invention is to provide a battery using the above microporous polyethylene membrane.
The purpose of this is to provide a separator.       [0012]     [Means for Solving the Problems]   As a result of intensive studies in view of the above objects, the present inventors have found that ultra-high molecular weight polyethylene
Polyethylene comprising a composition containing high density polyethylene and low density polyethylene
The microporous membrane has excellent permeability and mechanical strength, and has low permeability at low temperatures.
I found out. We have also developed ultra high molecular weight polyethylene and low density
Polyethylene microporous membranes made of a composition containing polyethylene have almost the same properties
It was found to have the ability. The present invention has been made based on the above.       [0013]   That is, the first microporous polyethylene membrane of the present invention has a weight average molecular weight of 7 × 1.
0^Five5 to 30% by weight of the above ultra high molecular weight polyethylene and 93
~ 50% by weight and melt index of 0.1 ~ 20g / 10min by high pressure method
Low pressure method with branched polyethylene or melt index of 0.1 to 25 g / 10 min
2 to 20% by weight of a linear low density polyethylene according to
Weight average molecular weight of components containing polyethylene and high-density polyethylene / number plane
Consisting of a composition having an average molecular weight of 10 to 300, a thickness of 0.1 to 50 μm, and pores
Rate is 35 to 95%, average through hole diameter is 0.001 to 1 μm, and tensile breaking strength is 600.
kg / cm^TwoThat is, the permeability cutoff temperature is 100 to 130 ° C.
And       [0014]   The second microporous polyethylene membrane of the present invention has a weight average molecular weight of 7 × 10^FiveLess than
40 to 80% by weight of the above ultra high molecular weight polyethylene and a melt index of 0.1
Branched polyethylene or melt index by high pressure method of ~ 20 g / 10 min
Linear low density polyethylene 60-20 by low pressure method at 0.1-25g / 10min
% By weight, a thickness of 0.1 to 50 μm, and a porosity of 35 to
95%, average through hole diameter is 0.001 to 1 μm, tensile strength at break is 600 kg / cm
^TwoAs described above, the permeability blocking temperature is 90 to 130 ° C.       [0015]   The method of the present invention for producing the first polyethylene microporous membrane has a weight average molecular weight
Is 7 × 10^Five5 to 30% by weight of the above ultra high molecular weight polyethylene and high density polyethylene
93-50% by weight of ren and high pressure with melt index of 0.1-20g / 10min
Branched polyethylene or melt index of 0.1 to 25 g / 10 min.
2 to 20% by weight of a linear low-density polyethylene obtained by the low-pressure method of
Weight average molecules of components containing high molecular weight polyethylene and high density polyethylene
10 to 50% by weight of a composition having an amount / number average molecular weight of 10 to 300, and a solvent of 50 to 50% by weight.
A solution consisting of 90% by weight was prepared, and the solution was extruded from a die, cooled and gelled.
A gel composition is formed, and the gel composition is melted at the melting point of the polyethylene composition + 10 ° C.
It is characterized in that it is stretched at the following temperature, and then the remaining solvent is removed.       [0016]   Further, the method of the present invention for producing the second polyethylene microporous membrane, the weight average
Child quantity is 7 × 10^Five40 to 80% by weight of the above ultra high molecular weight polyethylene,
The branched polyethylene or polyester is prepared by a high-pressure method with an index of 0.1 to 20 g / 10 min.
Linear low density poly by low pressure method with a low index of 0.1 to 25 g / 10 min.
60 to 20% by weight of ethylene, the ultra high molecular weight polyethylene,
10 to 50% by weight of a composition comprising polyethylene and 50 to 90% by weight of a solvent.
A solution consisting of a mixture, extruding the solution through a die and cooling to form a gel composition
The gel composition is rolled at a temperature equal to or lower than the melting point of the polyethylene composition + 10 ° C.
Elongation, followed by removal of the remaining solvent.       [0017]   Further, the battery separator of the present invention, the first or second microporous polyethylene
It is characterized by comprising a film.       [0018]   The present invention will be described in detail below. First, the first polyethylene microporous membrane of the present invention was formed.
The composition to be formed will be described. The first polyethylene microporous membrane of the present invention has a weight
Average molecular weight 7 × 10^Five5-30% by weight of ultra high molecular weight polyethylene
93 to 50% by weight of polyethylene and melt index of 0.1 to 20 g / 1
0 0.1-25 g of branched polyethylene or melt index by high pressure method
2 to 20% by weight of linear low density polyethylene by low pressure method
The weight of the components containing the ultra-high molecular weight polyethylene and the high density polyethylene
It consists of a composition having an average molecular weight / number average molecular weight of 10 to 300.       [0019]   The ultra high molecular weight polyethylene has a weight average molecular weight of 7 × 10^FiveAbove, preferably
Is 1 × 10⁶~ 15 × 10⁶belongs to. Weight average molecular weight is 7 × 10^FiveLess than
And the maximum draw ratio is low, and the desired microporous membrane cannot be obtained. On the other hand, the upper limit is particularly limited
Not 15 × 10⁶In the formation of gel-like molded products,
Inferior. The density of the ultra high molecular weight polyethylene is usually 0.93 to 0.95 g / c.
m^ThreeIt is about.       [0020]   In the present invention, high-density polyethylene is usually 0.935 g / cm^Three
The above is polyethylene. Its weight average molecular weight is 7 × 10^FiveLess than
However, the lower limit of the molecular weight is 1 × 10^FourThe above are preferred. Weight average molecule
1 × 10^FourIf it is less than 10, it is not preferable because breakage easily occurs during stretching. Special
Has a weight average molecular weight of 1 × 10^FiveMore than 7 × 10^FiveLess than is preferred.       [0021]   Furthermore, the low-density polyethylene used in the present invention is a branched polyethylene obtained by a high-pressure method.
Polyethylene (LDPE) and linear low-density polyethylene (LL
DPE).       [0022]   In the case of LDPE, its density is usually 0.91 to 0.93 g / cm.^ThreeAbout
And its melt index (MI, 190 ° C., 2.16 kg load) is 0.1.
It is 1 to 20 g / 10 min, preferably 0.5 to 10 g / 10 min.       [0023]   In the case of LLDPE, its density is usually 0.91 to 0.93 g / cm^ThreeAbout
And its melt index (MI, 190 ° C., 2.16 kg load) is 0
. It is 1 to 25 g / 10 minutes, preferably 0.5 to 10 g / 10 minutes.       [0024]   The mixing ratio of the various components as described above is such that the ultra-high molecular weight polyethylene is 5 to 30 times
%, The high-density polyethylene is 93 to 50% by weight, and the low-density polyethylene is
2 to 20% by weight.       [0025]   Less than 5% by weight of ultra high molecular weight polyethylene contributes to improvement of stretchability
Entanglement of polyethylene chains is hardly formed, and a high-strength microporous membrane is formed.
I can't get it. On the other hand, if it exceeds 30% by weight, the solution of the polyethylene composition
It is difficult to achieve a high concentration. If the high-density polyethylene is less than 50% by weight,
It is difficult to achieve a high concentration of the ethylene composition.
Since the molecular weight of polyethylene is small, a high-strength microporous membrane cannot be obtained. Even lower
If the density polyethylene (LDPE or LLDPE) is less than 2% by weight,
No permeability barrier at low temperature (100-130 ° C) is achieved and more than 20% by weight
When it is stretched, cleavage between lamellas does not occur, making it difficult to form microporous, and permeability
And the mechanical strength is not sufficient.       [0026]   However, among the above components, ultra high molecular weight polyethylene and high density polyethylene
The weight-average molecular weight / number-average molecular weight when both are used as a composition is 10 to 3
00, preferably 12-250. Weight average molecular weight / number average molecule
If the amount is less than 10, the average molecular chain length is large, and the entanglement density of the molecular chains during dissolution.
Therefore, it is difficult to prepare a high concentration solution. If it exceeds 300, it will be stretched
Occasionally, the low molecular weight component is broken and the strength of the entire film is reduced.       [0027]   The weight average molecular weight / number average molecular weight is used as a measure of the molecular weight distribution.
And the width of the molecular weight distribution increases as the ratio of the molecular weights increases. sand
That is, in a composition composed of polyethylene having different weight average molecular weights,
The greater the ratio of the molecular weights, the greater the difference in the weight average molecular weight of the polyethylene compounded.
The smaller the weight average molecular weight, the smaller the difference.       [0028]   Such ultra high molecular weight polyethylene and high density polyethylene are
Child quantity is 7 × 10^FiveThe above ultra high molecular weight polyethylene and a weight average molecular weight of 7 × 10^Five
The weight-average molecular weight / number-average molecular weight of the high-density polyethylene of less than the above ranges
As described above.       [0029]   In the present invention, the ultra-high molecular weight polyethylene and high density polyethylene
A multi-stage high density polyethylene can also be used as a composition comprising Was
However, the multi-stage polymerized polyethylene has a weight average molecular weight of 7 × 10^FiveWith the above ingredients
Having a weight average molecular weight of 7 × 10^FiveLess than the components satisfy the relationship of the molecular weight distribution
And a weight average molecular weight of 7 × 10^FiveContains 5 to 30% by weight of the above components
It needs to be polymerized. Weight when using multi-stage polyethylene
Average molecular weight 7 × 10^FiveThe above components and a weight average molecular weight of 7 × 10^FiveWith less than ingredients
Are, respectively, the ultra-high molecular weight polyethylene and the high-density polyethylene in the above composition.
What is necessary is just to set the compounding ratio so that it may correspond to the above.       [0030]   Next, the composition for forming the second microporous membrane of the present invention will be described. The present invention
The second polyethylene microporous membrane has a weight average molecular weight of 7 × 10^FiveUltra high molecular weight
40 to 80% by weight of ethylene and a melt index of 0.1 to 20 g / 10 minutes
Branched polyethylene or melt index of 0.1 to 25 g /
It consists of 60 to 20% by weight of linear low density polyethylene by low pressure method for 10 minutes.
Consists of a composition.       [0031]   The ultra-high molecular weight polyethylene is the same as the composition for the first microporous membrane described above.
Can be used.       [0032]   Also, low-density polyethylene is the same as the composition for the first microporous membrane described above.
Can be used.       [0033]   Mixing ratio of ultra high molecular weight polyethylene as described above and low density polyethylene Is 40 to 80% by weight of ultra-high molecular weight polyethylene, and low-density polyethylene is
60 to 20% by weight.       [0034]   If the ultra-high molecular weight polyethylene is less than 40% by weight (low-density polyethylene
%, The cleavage between the lamellas does not occur even when the film is stretched, and microporosity is hardly formed.
And the transmission function and mechanical strength are not sufficient.
Exceeds 80% by weight (low-density polyethylene is less than 20% by weight),
It is difficult to achieve a high concentration of the styrene composition. Therefore, the target low temperature (90-1
(30 ° C.), it is difficult to obtain a microporous polyethylene membrane whose permeability can be blocked.       [0035]   In addition, the polyethylene for the first and second polyethylene microporous membranes as described above
The composition may optionally contain antioxidants, UV absorbers, lubricants, anti-blocking
Additives such as coloring agents, pigments, dyes, inorganic fillers, etc.
Can be added in box.       [0036]   Production of the microporous polyethylene membrane of the present invention using such a polyethylene composition
The method will be described.       [0037]   In the present invention, the solution of the polyethylene composition as a raw material is the above-described polyethylene.
It is prepared by heating and dissolving the composition in a solvent.       [0038]   As the solvent, particularly, any solvent capable of sufficiently dissolving the polyethylene composition can be used.
Not limited. For example, nonane, decane, undecane, dodecane, paraffin oil
Such as aliphatic or cyclic hydrocarbons or mineral oil fractions whose boiling points correspond to them
However, in order to obtain a gel-like molded product with a stable solvent content,
Non-volatile solvents such as oils are preferred.       [0039]   Heat dissolution is carried out while stirring at a temperature at which the polyethylene composition completely dissolves in the solvent.
Perform from. The temperature varies depending on the polymer and solvent used, for example, Composition consisting of polyethylene, high density polyethylene and low density polyethylene (
Hereinafter, it is referred to as a first polyethylene composition. ) In the range of 140-250 ° C
And a composition comprising ultra-high molecular weight polyethylene and low density polyethylene (hereinafter referred to as
It is referred to as a second polyethylene composition. )) Is in the range of 140 to 250 ° C.
The concentration of the polyethylene composition solution is 10 to 50% by weight in the case of the first composition.
, Preferably 10 to 40% by weight, and in the case of the second composition 10 to 50% by weight.
%, Preferably 10 to 30% by weight. When melting by heating,
It is preferable to add an antioxidant to prevent oxidation of the len.       [0040]   Next, the heated solution of the polyethylene composition is extruded from a die and molded. Da
As the chair, a sheet die with a flat mouthpiece is usually used, but a double cylindrical shape is used.
Hollow dies, inflation dies and the like can also be used. Sheet dies
The die gap when used is usually 0.1 to 5 mm, and is 1 mm at the time of extrusion molding.
Heat to 40-250 ° C. At this time, the extrusion speed is usually 20 to 30 cm / min.
To 2 to 3 m / min.       [0041]   The solution thus extruded from the die is cooled to a gel
Molded into Cooling is performed at a rate of 50 ° C./min or more at least until the gelling temperature or less.
It is preferred to do so. If the cooling rate is slow, the crystallinity will increase, making it a gel-like material suitable for stretching.
It is difficult to become. Cooling method includes direct contact with cold air, cooling water and other cooling media
And a method of contacting with a roll cooled by cooling.
The solution extruded from the die is preferably 1 to 10 before or during cooling.
Alternatively, it may be collected at a collection ratio of 1 to 5. Neck-in when the takeover ratio exceeds 10
Is undesirably increased, and breakage tends to occur during stretching.       [0042]   Next, this gel-like molded product is stretched. For stretching, the gel-like molded product is heated and
Method, roll method, inflation method, rolling method or a combination of these methods
At a predetermined magnification. Biaxial stretching is preferred, and vertical and horizontal simultaneous stretching or sequential stretching
Either stretching may be used, but simultaneous biaxial stretching is particularly preferred.       [0043]   The stretching temperature is not higher than the melting point of the polyethylene composition + 10 ° C, preferably the crystal dispersion temperature.
It is in the range from the temperature to below the crystal melting point. For example, in the case of the first polyethylene composition
90-135 ° C, more preferably in the range of 110-125 ° C,
In the case of the ethylene composition, it is 90 to 135 ° C., more preferably 110 to 125 ° C.
It is in the range of ° C. If the stretching temperature exceeds the melting point + 10 ° C, the
The molecular chains cannot be oriented by stretching. If the stretching temperature is lower than the crystal dispersion temperature,
The softening of the fat is insufficient, the film is easily broken in stretching, and high-magnification stretching cannot be performed.       [0044]   Although the stretching ratio varies depending on the thickness of the raw material, the stretching ratio is at least twice in the uniaxial direction.
Above, preferably 3 to 20 times, 10 times or more in area magnification, preferably 20 to 400 times
is there. If the area ratio is less than 10 times, stretching is insufficient and a highly elastic, high-strength microporous film is obtained.
Not. On the other hand, if the area magnification exceeds 400 times, the stretching apparatus, stretching operation, and the like are restricted.
About.       [0045]   The obtained stretch molded product is washed with a solvent to remove the remaining solvent. As a cleaning solvent
Hydrocarbons such as pentane, hexane, heptane, methylene chloride, carbon tetrachloride
Chlorinated hydrocarbons such as nitrogen, fluorinated hydrocarbons such as ethane trifluoride, diethyl ether
Easily volatile compounds such as ethers such as ter and dioxane can be used
. These solvents are appropriately selected according to the solvent used for dissolving the polyethylene composition,
Use alone or as a mixture. The cleaning method is a method of immersing and extracting in a solvent,
It can be done by a method of showering, a method of a combination of these, etc.
You.       [0046]   The washing as described above is performed until the residual solvent in the stretch molded product becomes less than 1% by weight.
. After that, the washing solvent is dried. The drying method of the washing solvent is heating drying, air drying, etc.
Can be done by law. The dried stretch molded product has a temperature range from the crystal dispersion temperature to the melting point.
It is desirable to heat-fix with.       [0047]   The polyethylene microporous membrane produced as described above has a porosity of 35 to 95%,
Average through-hole diameter is 0.001-1 μm, tensile strength at break is 600 kg / cm^TwoAbove
Yes, the permeability cutoff temperature is very high molecular weight polyethylene, high density polyethylene and
Branched polyethylene by high pressure method with a tilt index of 0.1 to 20 g / 10 min
Or a linear low density by a low pressure method having a melt index of 0.1 to 25 g / 10 min.
100-130 ° C in a three-component system consisting of polyethylene
Polyethylene and melt index of 0.1-20 g / 10 min by high pressure method
Low pressure, branched polyethylene or melt index of 0.1 to 25 g / 10 min
90 to 130 for a bicomponent yarn composed of linear low-density polyethylene by the
° C. Usually, fine-grained polyethylene
Since the permeability cut-off temperature of the porous material is 135 to 145 ° C., the power of a lithium battery or the like can be reduced.
It can be said that this has greatly improved in terms of safety as a pond separator and the like. Again
The thickness of the clear polyethylene microporous membrane can be appropriately selected depending on the application, but is generally 0
. It is 1 to 50 μm, preferably 5 to 40 μm.       [0048]   The obtained polyethylene microporous membrane may be further subjected to plasma irradiation as necessary.
Hydrophilization treatment can be performed by impregnation with a surfactant, surface grafting, or the like.       [0049] Example   Hereinafter, examples of the present invention will be described. In addition, the test method in an Example is as follows.
is there. (1) Molecular weight and molecular weight distribution: using a GPC device manufactured by Waters
Using GMH-6 manufactured by Tosoh Corporation and o-dichlorobenzene as a solvent at a temperature of 1
Gel permeation chromatography (35 ° C., flow rate 1.0 ml / min)
GPC) method. (2) Tensile breaking strength: measured according to ASTM D882. (3) Film thickness: The cross section was measured with a scanning electron microscope. (4) Air permeability: Measured according to JIS P8117. (5) Water permeability: incorporating microporous membrane into flat membrane module, mixed with distilled water / ethanol The liquid (50/50 volume ratio) is subjected to a hydrophilization treatment, and is sufficiently washed with distilled water.
It was determined by measuring the permeation amount of the filtrate when a water pressure of 0 mmHg was applied. (6) Average through-hole diameter: 380 mmH using the module described in (5) above
circulates an aqueous solution of 0.05% by weight pullulan (manufactured by Showa Denko KK) under a pressure difference of 0.05 g.
The concentration of pullulan contained in the filtrate was determined from the differential refractive index measurement,
From the value of the molecular weight of pullulan at which the rejection calculated by the above becomes 50%, as described later,
The pore size was calculated using the Flory's theory. Pullulan rejection = {1- (Pullulan concentration in filtrate / Pullulan concentration in stock solution)}
× 100 The chain polymer in a solution state is in the form of a spherical thread, and its diameter d is at both ends of the molecular chain.
Root mean square distance <γ^Two> [D / 2]^Two= <Γ^Two> ... (1) You can think of it as having a relationship. On viscosity and molecular chain spreading in polymer solutions
According to Flory's theory, regardless of the type of polymer [Η] M = 2.1 × 10^{twenty one}<Γ^Two>^3/2... (2) Is satisfied, the measured value of the intrinsic viscosity [η] is calculated by the equations (1) and (2).
From the molecular weight M at which the ratio becomes 50%, the diameter d of the chain polymer can be calculated.
This d was defined as the average pore size of the polyethylene microporous membrane. (7) Porosity: Measured by a mercury porosimeter. (8) Permeability cutoff temperature: The microporous membrane is fixed with a frame, left at a predetermined temperature for 2 minutes,
Temper 10^FourA temperature exceeding sec / 100 cc was measured. (9) Effective resistance: 1: of propylene carbonate and 1,2-dimethoxyethane
In one mixed solvent, LiC10_FourSolution of 1 mol / L
Is prepared using a separator between the positive and negative electrodes using this electrolyte and a stainless steel electrode.
(Microporous polyethylene membrane) was installed and measured at 25 ° C. in an argon atmosphere.
It was determined from a composite impedance plot.       [0050] Example 1   Weight average molecular weight 2.0 × 10⁶Ultra high molecular weight polyethylene (UHMWPE)
2 0% by weight and 3.9 × 10^Five66.7% by weight of high density polyethylene (HDPE)
And melt index (MI, 190 ° C., 2.16 kg load) 2.0 g / 10
Raw material resin mixed with 13.3% by weight of low density polyethylene (LDPE)
15 parts by weight of a polyethylene composition (melting point 132 ° C.) and liquid paraffin (64 c
(st / 40 ° C.) 85 parts by weight to prepare a solution of the polyethylene composition.
Next, 2,5-di-t-butyl- was added to 100 parts by weight of the solution of the polyethylene composition.
0.125 parts by weight of p-cresol (“BHT”, manufactured by Sumitomo Chemical Co., Ltd.)
Tolakis [methylene-3- (3,5-di-t-butyl-4-hydroxyphenyl)
-Propionate] methane (“Irganox 1010”, manufactured by Ciba-Geigy)
0.25 parts by weight) as an antioxidant. This mixed solution is auto-
The mixture was filled in a clave and stirred at 200 ° C. for 90 minutes to obtain a uniform solution.       [0051]   This solution was extruded from a T-die by an extruder having a diameter of 45 mm, and pulled by a cooling roll.
While taking, a gel-like sheet was formed.       [0052]   The obtained sheet was set on a biaxial stretching machine, and the temperature was 115 ° C. and the stretching speed was 0.5 m.
/ Min. Was simultaneously biaxially stretched 5 × 5 times. Wash the obtained stretched membrane with methylene chloride.
After removing the remaining liquid paraffin by extraction, heat set at 100 ° C for 30 seconds.
Thus, a microporous polyethylene membrane was obtained.       [0053]   Film thickness, tensile rupture strength, porosity, average through-pore diameter of the obtained microporous polyethylene membrane
, Air permeability, permeability cutoff temperature and effective resistance were measured. Polyethylene microporous membrane
Table 1 shows the composition and production conditions of the polyethylene, and Table 2 shows the physical properties of the polyethylene microporous membrane.
You.       [0054] Example 2   Weight average molecular weight 2.0 × 10⁶Ultra high molecular weight polyethylene (UHMWPE)
20% by weight and 3.9 × 10^FiveHigh density polyethylene (HDPE) 66.7 weight
% And melt index (MI, 190 ° C., 2.16 kg load) 1.5 g / 1
0 minutes Resin mixed with 13.3% by weight of linear low density polyethylene (LLDPE)
Example 1 was repeated except that a polyethylene composition (melting point 132 ° C.) was used.
To produce a polyethylene microporous membrane.       [0055]   Film thickness, tensile rupture strength, porosity, average through-pore diameter of the obtained microporous polyethylene membrane
, Air permeability, permeability cutoff temperature and effective resistance were measured. Polyethylene microporous membrane
Table 1 shows the composition and production conditions of the polyethylene, and Table 2 shows the physical properties of the polyethylene microporous membrane.
You.       [0056] Example 3   Weight average molecular weight 2.0 × 10⁶Ultra high molecular weight polyethylene (UHMWPE)
20% by weight and 3.9 × 10^Five77% by weight of high-density polyethylene (HDPE)
, Melt index (MI, 190 ° C., 2.16 kg load) 2.0 g / 10 min
Raw material resin mixed with 3% by weight of low-density polyethylene (LDPE)
A polyethylene was prepared in the same manner as in Example 1 except that a styrene composition (melting point: 134 ° C.) was used.
A microporous membrane was manufactured.       [0057]   Film thickness, tensile rupture strength, porosity, average through-pore diameter of the obtained microporous polyethylene membrane
, Air permeability, permeability cutoff temperature and effective resistance were measured. Polyethylene microporous membrane
Table 1 shows the composition and production conditions of the polyethylene, and Table 2 shows the physical properties of the polyethylene microporous membrane.
You.       [0058] Example 4   Weight average molecular weight 2.0 × 10⁶Ultra high molecular weight polyethylene (UHMWPE)
20% by weight and 3.9 × 10^Five77% by weight of high-density polyethylene (HDPE)
, Melt index (MI, 190 ° C., 2.16 kg load) 1.5 g / 10 min
Raw resin mixed with 3% by weight of linear low density polyethylene (LLDPE)
The same procedure as in Example 1 was repeated except that a polyethylene composition (melting point 134 ° C.) was used.
An ethylene microporous membrane was manufactured.       [0059]   Film thickness, tensile rupture strength, porosity, average through-pore diameter of the obtained microporous polyethylene membrane
, Air permeability, permeability cutoff temperature and effective resistance were measured. Polyethylene microporous membrane
Table 1 shows the composition and production conditions of the polyethylene, and Table 2 shows the physical properties of the polyethylene microporous membrane.
You.       [0060] Comparative Example 1   Weight average molecular weight 2.0 × 10⁶Ultra high molecular weight polyethylene (UHMWPE)
13% by weight and 3.9 × 10^Five87% by weight of high density polyethylene (HDPE)
And 15 parts by weight of a raw resin mixed with liquid paraffin (64 cst / 40 ° C.) 8
And 5 parts by weight to prepare a solution of the polyethylene composition. Then this polyethy
2,5-di-t-butyl-p-cresol (100 parts by weight of the solution of the
[BHT], manufactured by Sumitomo Chemical Co., Ltd.) 0.125 parts by weight and tetrakis [methyle
3- (3,5-di-tert-butyl-4-hydroxyphenyl) -propione
Methane] (“Irganox 1010”, manufactured by Ciba-Geigy) 0.25 parts by weight
And were added as antioxidants. This mixture is filled in an autoclave equipped with a stirrer.
And stirred at 200 ° C. for 90 minutes to obtain a uniform solution.       [0061]   This solution was extruded from a T-die by an extruder having a diameter of 45 mm, and pulled by a cooling roll.
While taking, a gel-like sheet was formed.       [0062]   The obtained sheet was set on a biaxial stretching machine, and the temperature was 115 ° C. and the stretching speed was 0.5 m.
/ Min. Was simultaneously biaxially stretched 5 × 5 times. Wash the obtained stretched membrane with methylene chloride.
After removing the remaining liquid paraffin by extraction, heat set at 115 ° C. for 30 seconds.
Thus, a microporous polyethylene membrane was obtained.       [0063]   Film thickness, tensile rupture strength, porosity, average through-pore diameter of the obtained microporous polyethylene membrane
, Air permeability, permeability cutoff temperature and effective resistance were measured. Polyethylene microporous membrane
Table 1 shows the composition and production conditions of the polyethylene, and Table 2 shows the physical properties of the polyethylene microporous membrane. You.       [0064] Comparative Example 2   Weight average molecular weight 2.0 × 10⁶Ultra high molecular weight polyethylene (UHMWPE)
10% by weight and 3.9 × 10^Five55% by weight of high-density polyethylene (HDPE)
, Melt index (MI, 190 ° C., 2.16 kg load) 2.0 g / 10 min
Of low-density polyethylene (LDPE) 35% by weight
Except for the above, a microporous polyethylene membrane was produced in the same manner as in Example 1.       [0065]   Film thickness, tensile rupture strength, porosity, average through-pore diameter of the obtained microporous polyethylene membrane
, Air permeability, permeability cutoff temperature and effective resistance were measured. Polyethylene microporous membrane
Table 1 shows the composition and production conditions of the polyethylene, and Table 2 shows the physical properties of the polyethylene microporous membrane.
You.       [0066] Comparative Example 3   Weight average molecular weight 2.0 × 10⁶Ultra high molecular weight polyethylene (UHMWPE)
10% by weight and 3.9 × 10^Five55% by weight of high-density polyethylene (HDPE)
, Melt index (MI, 190 ° C., 2.16 kg load) 1.5 g / 10 min
Raw resin mixed with 35% by weight of linear low density polyethylene (LLDPE)
A microporous polyethylene membrane was produced in the same manner as in Example 1 except for the difference.       [0067]   Film thickness, tensile rupture strength, porosity, average through-pore diameter of the obtained microporous polyethylene membrane
, Air permeability, permeability cutoff temperature and effective resistance were measured. Polyethylene microporous membrane
Table 1 shows the composition and production conditions of the polyethylene, and Table 2 shows the physical properties of the polyethylene microporous membrane.
You.       [0068]       [0069]       [0070]      [0071]       [0072]   Note) *: Not microporous. (1): The unit is μm. (2): Unit is%. (3): The unit is μm. (4): Unit is kg / cm^TwoTables for longitudinal direction (MD) and width direction (TD)
Shown. (5): The unit is sec / 100 cc. (6): The unit is ° C. (7): The unit is Ω · cm^Two.       [0073] Example 5   Weight average molecular weight 2.0 × 10⁶Ultra high molecular weight polyethylene (UHMWPE)
1. 50% by weight and melt index (MI, 190 ° C., 2.16 kg load)
Raw material tree mixed with 50% by weight of low density polyethylene (LDPE) at 0 g / 10 min
15 parts by weight of a polyethylene composition (melting point 128 ° C.) which is a fat and liquid paraffin (
64 cst / 40 ° C.) and prepare a solution of the polyethylene composition by mixing with 85 parts by weight.
did. Next, 2,5-di-tert-butyl was added to 100 parts by weight of the solution of the polyethylene composition.
0.125 parts by weight of chill-p-cresol ([BHT], manufactured by Sumitomo Chemical Co., Ltd.)
And tetrakis [methylene-3- (3,5-di-t-butyl-4-hydroxyl)
H Enyl) -propionate] methane ("Irganox 1010",
0.25 parts by weight) as an antioxidant. This mixed solution is
And stirred at 200 ° C. for 90 minutes to obtain a uniform solution.       [0074]   This solution was extruded from a T-die by an extruder having a diameter of 45 mm, and pulled by a cooling roll.
While taking, a gel-like sheet was formed.       [0075]   The obtained sheet was set on a biaxial stretching machine, and the temperature was 117 ° C. and the stretching speed was 0.5 m.
/ Min. Was simultaneously biaxially stretched 5 × 5 times. Wash the obtained stretched membrane with methylene chloride.
After removing the remaining liquid paraffin by extraction, heat set at 100 ° C for 30 seconds.
Thus, a microporous polyethylene membrane was obtained.       [0076]   Film thickness, tensile rupture strength, porosity, average through-pore diameter of the obtained microporous polyethylene membrane
, Air permeability, permeability cutoff temperature and effective resistance were measured. Polyethylene microporous membrane
Table 3 shows the composition and manufacturing conditions of the polyethylene, and Table 4 shows the physical properties of the microporous polyethylene membrane.
You.       [0077] Example 6   In Example 5, instead of low density polyethylene (LDPE), melt-in
Dex (MI, 190 ° C, 2.16kg load) 1.5g / 10min linear low density
Polyethylene composition (melt) which is a raw material resin mixed with polyethylene (LLDPE)
(129 ° C.) to produce a microporous polyethylene membrane in the same manner as in Example 5.
did. Table 3 shows the composition and manufacturing conditions of the polyethylene microporous membrane.
Table 4 shows the physical properties of the microporous membrane.       [0078]       [0079]      [0080]   Note) *: Not microporous. (1): The unit is μm. (2): Unit is%. (3): The unit is μm. (4): Unit is kg / cm^TwoTables for longitudinal direction (MD) and width direction (TD)
Shown. (5): The unit is sec / 100 cc. (6): The unit is ° C. (7): The unit is Ω · cm^Two.       [0081]   As is clear from this example, the microporous polyethylene membranes of Examples 1 to 4
Good tensile breaking strength, high air permeability, and a permeability cut-off temperature of 100
To 130 ° C., and the microporous polyethylene membranes of Examples 5 and 6 had a tensile strength at break. Good value, high air permeability, and a permeability cutoff temperature of 90 to 130 ° C.
Was. Further, the microporous polyethylene membranes of Examples 1 to 6 have sufficiently small effective resistance values.
It can be seen that this is suitable as a battery separator.       [0082]     【The invention's effect】   As described in detail above, the first microporous polyethylene membrane of the present invention is an ultra-high molecular weight polyethylene.
A composition containing ethylene, high density polyethylene, and low density polyethylene
Excellent in permeability and mechanical strength, and cut off permeability at low temperature
.       [0083]   Further, the second microporous polyethylene membrane of the present invention is made of
Excellent permeability and mechanical strength because it is composed of high density polyethylene
At the same time, the transmission performance is interrupted at low temperatures.       [0084]   Such a polyethylene microporous membrane of the present invention can be used as a battery separator, an electrolytic
Diaphragm for denser, light shutter, ultra precision filtration membrane, ultrafiltration membrane, various filters,
Suitable for various applications such as porous membrane for moisture-permeable waterproof clothing, especially for battery separator
It is suitable.

Claims (1)

Claims: 1. An ultrahigh molecular weight polyethylene 5 having a weight average molecular weight of 7 × 10 ⁵ or more.
-30% by weight, high-density polyethylene of 93-50% by weight, and a low-pressure method of branched polyethylene or a melt index of 0.1-25 g / 10 minutes by a high-pressure method with a melt index of 0.1-20 g / 10 minutes. Linear low-density polyethylene 2
And a weight-average molecular weight / number-average molecular weight of a component containing the ultrahigh-molecular-weight polyethylene and the high-density polyethylene is 10 to 300, and the thickness is 0.1 to 300%. 50 μm, porosity 35-95%, average through-hole diameter 0
. A microporous polyethylene membrane having 001 to 1 μm, a tensile strength at break of 600 kg / cm ² or more, and a permeability cutoff temperature of 100 to 130 ° C. 2. Ultra high molecular weight polyethylene 4 having a weight average molecular weight of 7 × 10 ⁵ or more.
0 to 80% by weight and a branched low-density polyethylene 60 having a melt index of 0.1 to 20 g / 10 min by a high-pressure method or a linear low-density polyethylene 60 having a melt index of 0.1 to 25 g / 10 min. And a thickness of 0.1 to 50 μm, a porosity of 35 to 95%, and an average through-hole diameter of 0.0 to 20% by weight.
A microporous polyethylene membrane having a tensile breaking strength of from 0.01 to 1 µm, a tensile breaking strength of at least 600 kg / cm ² , and a permeability cutoff temperature of from 90 to 130 ° C. 3. A high-pressure method wherein 5 to 30% by weight of ultrahigh molecular weight polyethylene having a weight average molecular weight of 7 × 10 ⁵ or more, 93 to 50% by weight of high density polyethylene, and a melt index of 0.1 to 20 g / 10 min. A low-pressure polyethylene having a melt index of 0.1 to 25 g / 10 min and a linear low-density polyethylene having a melt index of 0.1 to 25 g / 10 min. A solution composed of 10 to 50% by weight of a composition having a weight average molecular weight / number average molecular weight of 10 to 300 of a contained component and 50 to 90% by weight of a solvent is prepared, and the solution is extruded from a die and cooled. Forming a gel composition, stretching the gel composition at a temperature equal to or lower than the melting point of the polyethylene composition + 10 ° C, and then removing the residual solvent. Method for producing a microporous polyethylene membrane of claim 1, wherein. 4. Ultra high molecular weight polyethylene 4 having a weight average molecular weight of 7 × 10 ⁵ or more.
0 to 80% by weight and a branched low-density polyethylene 60 having a melt index of 0.1 to 20 g / 10 min by a high-pressure method or a linear low-density polyethylene 60 having a melt index of 0.1 to 25 g / 10 min. And a solution comprising 10 to 50% by weight of the composition comprising the ultrahigh molecular weight polyethylene and the low-density polyethylene, and 50 to 90% by weight of the solvent. Extrusion,
The polyethylene according to claim 2, wherein the composition is cooled to form a gel-like composition, and the gel-like composition is stretched at a temperature equal to or lower than the melting point of the polyethylene composition + 10 ° C, and thereafter the residual solvent is removed. 5. A method for producing a microporous membrane. 5. A battery separator comprising the polyethylene microporous membrane according to claim 1 or 2.