KR101841513B1 - Microporous membranes, methods for making these membranes, and the use of these membranes as battery separator films - Google Patents

Abstract

The present invention relates to a microporous membrane having a high meltdown temperature and useful electrolyte affinity. The invention also relates to the manufacture of these films and the use of these films as battery separator films.

Description

TECHNICAL FIELD [0001] The present invention relates to a microporous membrane, a method for producing such a membrane, and a use of these membranes as a battery separator film. [0002] MICROPOROUS MEMBRANES, METHODS FOR MAKING THREE MEMBRANES, AND THE USE OF THESE MEMBRANES AS BATTERY SEPARATOR FILMS [

The present invention relates to a microporous membrane having a high meltdown temperature and an affinity useful for the polymer electrolyte of a lithium ion polymer battery. The present invention also relates to the production of these films and the use of these films as battery separator films.

The microporous membrane is useful as a battery separator film ("BSF") for primary batteries and secondary batteries. Examples of such a battery include a lithium ion secondary battery, a lithium ion polymer secondary battery, a nickel-hydrogen battery, a nickel-cadmium battery, a nickel-zinc battery, and a silver-zinc battery.

The microporous polymer membrane can be used, for example, as a battery separator film ("BSF") of a lithium ion battery. Such a film has high polymer mobility at high battery temperature and significantly decreases the durability. This effect is beneficial to BSF because it reduces the electrochemical activity of the cell due to reduced specularity at high temperatures, thereby reducing the risk of battery failure under overcharge, rapid discharge, or other high temperature battery conditions. Even if the electrochemical activity is lowered, the internal temperature of the battery may continue to increase (for example, from a temperature overshoot), thereby increasing the thermal stability of the membrane at high temperatures, thereby further reducing the risk of battery failure. This can be achieved by including a species of high melting point (e.g., polypropylene) in the polymer of the membrane. The difference in temperature of the melting point between polyethylene and polypropylene and their physical incompatibility makes it difficult to produce a film containing all of the polymer, especially when the film is thin.

For example, a lithium ion battery ("lithium ion polymer battery"), in which the electrolyte is contained in a polymer medium, is a gel electrolyte or a polymer electrolyte generally has polymer compatibility (e.g., affinity) with a polymer medium containing an electrolyte Use the included BSF. Generally, BSFs for lithium ion polymer batteries are significantly thinner than BSF, which is typically used for cylindrical and prismatic lithium ion cells, for example.

It is therefore desirable to produce a relatively thin polymer membrane having affinity for the polymer used as the electrolyte medium in the polymer cell and having dimensional stability at high temperatures.

In one embodiment, the wt% of the film based on the weight of the polymer in the invention is at least 4.0% by weight of polyethylene and having a Mw 5.0 × 10 ⁵ or more and more ΔHm 80.0J / g wt% to 20.0 wt.% Of a film comprising polypropylene; The membrane is microporous and has a thickness of 12.0 m or less.

In another embodiment, the present invention provides a process for producing a microporous membrane comprising:

(1) a step of extruding a mixture of a diluent and a polymer, wherein the polymer comprises the amount of A ₁ of polyethylene and the amount of A ₂ of the polypropylene, wherein the% by weight is based on the weight of the polymer in the polymer- A ₁ is at least 1.0% by weight, for example from 80.0% by weight to 96.0% by weight, and A ₂ is from 4.0% by weight to 20.0% by weight; (2) stretching the extrudate in at least one plane direction; And (3) removing at least a portion of the diluent from the stretched extrudate.

(Effects of the Invention)

The membranes of the present invention have both an improved meltdown temperature and a sufficient electrolyte affinity.

It was confirmed that the microporous membrane containing polyethylene and having a thickness of 12.0 占 퐉 or less had a meltdown temperature of usually less than 145.0 占 폚. It has also been found that when these polyethylenes are combined with polypropylene, these membranes increase the meltdown temperature, but also reduce the affinity for the polymer electrolyte. The invention at least in part, 4.0% by weight has a film basis weight in the least 1.0% by weight polyethylene and 5.0 × 10 ⁵ or more weight average molecular weight ( "Mw") and 80.0J / g or more of the heat of fusion ( "ΔHm") the% It is based on the discovery that these difficulties can be solved if the membrane comprises a mixture of polypropylene in weight percent to 20.0 weight percent (based on the weight of the membrane). These membranes have both an improved melt-down temperature and a sufficient electrolyte affinity for lithium ion polymer cells useful as BSF.

For purposes of this specification and the appended claims, the term "polymer" refers to a composition comprising a plurality of polymers comprising repeating units derived from one or more monomers. This polymer may vary in size, molecular structure, atomic content, and so on. The term "polymer" includes polymers such as copolymers, terpolymers, and the like. "Polyethylene" means a polyolefin comprising 50% or more (on a number basis) repeat units derived from ethylene, preferably a polyethylene copolymer wherein at least 85% (by number) of the polyethylene homopolymer and / or repeat units are ethylene units do. "Polypropylene" includes propylene-based repeat units of 50.0% or more (on a number basis), preferably polypropylene homopolymers and / or polypropylene copolymers wherein at least 85% Means polyolefin. The term isotactic polypropylene refers to polypropylene having a mesopentad fraction of mmmm pentads, preferably greater than 96.0 mole%, of at least about 50.0 mole percent (based on the total number of moles of isotactic polypropylene) . The "microporous film" is a thin film having micropores in which 90.0% or more (by volume) of the microporous volume of the microporous membrane having an average diameter in the range of 0.01 μm to 10.0 μm exists. For membranes made from extrudates, the machine direction ("MD") is defined as the direction in which extrudates are produced from the die. The transverse direction ("TD") is defined as the direction perpendicular to both the MD direction and the thickness direction of the extrudate. MD and TD are referred to as the plane direction of the film, and the term "plane" in this context refers to the direction that lies primarily in the plane of the film when the film is flat.

(Composition of microporous membrane)

In one or more embodiments, the present invention relates to a membrane comprising polyethylene and polypropylene, which is microporous and which has a thickness of 12.0 m or less. In one embodiment, the microporous membrane comprises an amount of polyethylene (A ₁ ) and an amount of polypropylene (A ₂ ) having an Mw of at least 5.0 × 10 ⁵ and ΔH m of at least 80.0 J / g. A ₁ and A ₂ may be expressed as weight% based on the weight of the polymer in the film. For example, the wt% can be, for example, A ₁ + A ₂ = 100 wt%, based on the combined weight of polyethylene and polypropylene in the film. In another embodiment, the weight percent is relative to the weight of the membrane, for example when the membrane consists essentially of polyethylene and polypropylene (or even polyethylene and polypropylene).

For example, in one or more embodiments, A ₁ ranges from 80.0 wt% to 96.0 wt%, A ₂ ranges from 4.0 wt% to 20.0 wt%, A ₁ and A ₂ wt% and will for the combined weight of the same a ₁ and a _2. If necessary, A ₁ is in the range of 84.5 wt.% To 95.5 wt.%, For example in the range of 94.75 wt.% To 95.25 wt.%. If necessary, A ₂ is in the range of 4.5 wt.% To 15.5 wt.%, For example in the range of 4.75 wt.% To 5.25 wt.%.

Selected embodiments of polyethylene and polypropylene are described in greater detail, but this description is not meant to exclude other embodiments that are within the broad scope of the invention.

(Polyethylene)

In certain embodiments, polyethylene ("PE") may comprise a mixture or reactor blend of polyethylene, such as a mixture of two or more polyethylenes ("PE1", "PE2", "PE3" . For example, the PE may include (i) a blend of a first PE (PE1) and / or a second PE (PE2) and (ii) a third PE (PE3).

(PE1)

In one embodiment, the first PE ("PE1") has a MW in the range of less than 1.0 x 10 ⁶ , such as about 1.0 x 10 ⁵ to about 0.90 x 10 ⁶ ; MWD in the range of about 50.0 or less, such as about 2.0 to about 20.0; And it may be a carbon atom to 1.0 × 10 ⁴ per one PE having a terminal unsaturation amount of less than 0.20. Optionally, PE1 has a Mw in the range of about 4.0 x 10 ⁵ to about 6.0 x 10 ⁵ , and a molecular weight distribution ("MWD", about 3.0 to about 10.0, divided by the number average molecular weight, Mw). If necessary, PE1 has a terminal unsaturation amount of the range of the carbon atom to 1.0 × 10 ⁴ per 0.14 or less, or the carbon atom to 1.0 × 10 ⁴ per 0.12 or less, for example, the carbon atom to 1.0 × 10 ⁴ per 0.05 ~ 0.14 (e.g. For example, below the detection limit of the measurement).

(PE2)

In one embodiment, the second PE ("PE2") has a MW in the range of, for example, less than 1.0 x 10 ⁶ , such as about 2.0 x 10 ⁵ to about 0.9 x 10 ⁶ , 2 or may be a PE having a MWD, and the carbon atom to 1.0 × 10 ⁴ or more per 0.20 terminal unsaturation amount ranging from about 50. If necessary, PE2 has an amount of terminal unsaturation in the range of 0.30 or more per 1.0 x 10 ⁴ carbon atoms, or 0.50 or more per 1.0 x 10 ⁴ carbon atoms, for example, 0.6 to 10.0 per 1.0 x 10 ⁴ carbon atoms. Non-limiting examples of PE2 are those having a MWD in the range of about 3.0 x 10 ⁵ to about 8.0 x 10 ⁵ , such as about 7.5 x 10 ⁵ , and an MWD of about 4 to about 15.

PE1 and / or PE2 may be an ethylene / alpha -olefin copolymer comprising, for example, up to 5.0 mole%, based on 100 mole% of the copolymer, of one or more comonomers, such as ethylene homopolymers or alpha-olefins have. Optionally, the? -Olefin is at least one of propylene, butene-1, pentene-1, hexene-1, 4-methylpentene-1, octene-1, vinyl acetate, methyl methacrylate or styrene. Such a PE may have a melting point of 132 캜 or higher. PE1 can be prepared, for example, by a process using a Ziegler-Natta catalyst or a single site polymerization catalyst, but this is not essential. The amount of terminal unsaturation can be measured, for example, according to the procedure described in PCT Patent Publication WO 97/23554. PE2 can be prepared, for example, using a chromium-containing catalyst.

(PE3)

In one embodiment, the third PE ("PE3") has a Mw of, for example, greater than or equal to 1.0 x 10 ⁶ , such as from about 1.0 x 10 ⁶ to about 5.0 x 10 ⁶ , MWD. ≪ / RTI > Non-limiting examples of PE3 include Mw of from about 1.0 x 10 ⁶ to about 3.0 x 10 ⁶ , such as about 2.0 x 10 ⁶ , and no greater than 20.0, such as from about 2.0 to about 20.0, preferably from about 4.0 to about And a MWD of 15.0. PE3 can be, for example, an ethylene / alpha-olefin copolymer comprising up to 5.0 mole percent, based on 100 mole percent of the copolymer, of one or more comonomers, such as ethylene homopolymers or alpha-olefins. The comonomer may be, for example, at least one of propylene, butene-1, pentene-1, hexene-1, 4-methylpentene-1, octene-1, vinyl acetate, methyl methacrylate or styrene. Such polymers or copolymers can be prepared using Ziegler-Natta catalysts or single site catalysts, but this is not necessary. Such a PE may have a melting point of 134 캜 or higher. The melting point of PE1-PE3 can be determined, for example, using the method disclosed in PCT Patent Publication No. WO 2008/140835.

In one or more embodiments, PE includes the amount of B ₂ of the PE1, and / or amount of the B ₁ of the PE2, and PE3. In one embodiment, B ₁ and the weight% of B ₂ is in the range of the basis is 60.0% to 96.0% by weight of B ₁ on the weight of polymer in the film, B ₂ is 0.0 wt.% To the range of 20.0% by weight to be. If necessary, B ₁ is in the range of 69.5 wt.% To 90.5 wt.%, For example, 80.0 wt.% To 85.0 wt.%, Based on the total polymer in the film. If necessary, B ₂ is in the range of 5.0 wt.% To 15.0 wt.%, Based on the total polymer in the film, for example, in the range of 9.75 wt.% To 15.25 wt.%. In one embodiment, B ₁ ranges from 79.0 wt% to 95.0 wt%, and B ₂ ranges from 0.0 wt% to 16.0 wt%. In one embodiment, when the B ₂ is less than about 7.5 wt%, the film has a melting point of 145 ° C or higher, for example 147 ° C or higher. In one embodiment, And a B ₂ of 8.0 wt% or more, such as 10.0 wt% or more.

(Polypropylene)

In one embodiment, polypropylene ( "PP") is about the same as the range of 6.0 × 10 ⁵ or more, or 7.5 × 10 ⁵ or more and the same 5.0 × 10 ⁵ or more, for example, ^{0.9 × 10 6 ~ 2.0 × 10} 6 And may have a Mw in the range of 0.8 x 10 < ⁶ > to about 3.0 x 10 < ⁶ >. If necessary, the PP has a Tm of 160.0 DEG C or higher and an Hm of 90.0 J / g or more, or 100.0 J / g or more, such as a range of 80.0 J / g or more, for example, 110 J / g to 120 J / g. Optionally, the PP has an MWD in the range of about 1.5 to about 10.0, such as in the range of about 20.0 or less, such as about 2.0 to about 8.5. If necessary, PP is a copolymer (random or block) of propylene and up to 5.0 mol% of a comonomer and the comonomer is, for example, ethylene, butene-1, pentene-1, hexene- 1, octene-1, vinyl acetate, methyl methacrylate, styrene and the like; Or diolefins such as butadiene, 1,5-hexadiene, 1,7-octadiene, 1,9-decadiene and the like.

In one embodiment, PP is isotactic polypropylene. In one embodiment, the PP comprises: (a) a meso pentad fraction of at least about 90.0 mole percent mmmm pentad, optionally at least 96.0 mole percent mmmm pentad, preferably at least 96.0 mole percent mmmm pentad; And (b) the carbon atom to 1.0 × 10 ⁴ per about 5.0 or less, for example, the carbon atom to 1.0 × 10 ⁴ per about 5.0 carbon atoms, such as less than 1.0 × 10 ⁴ per about 20 or less, or the carbon atom to 1.0 × 10 ⁴ per about And has a stereo defect amount of 10.0 or less. If necessary, PP has the following properties: (1) Tm of 162.0 DEG C or higher; (ii) an elongational viscosity of at least about 5.0 x 10 ⁴ Pa s at a temperature of 230 ° C and a strain rate of 25 sec ^-1 ; (iii) a Trouton ratio of about 15 or greater when measured at a temperature of about 230 < ⁰ > C and a strain rate of ²⁵ sec < ^-1 >; (iv) a melt index ("MFR") of less than or equal to about 0.1 dg / min, such as less than or equal to about 0.01 dg / min (ie, the value is such that the MFR is measurably low); ASTM D-1238 -95 condition L); Or (v) an amount of extractable species of not more than 0.5% by weight, such as not more than 0.1% by weight, such as not more than 0.1% by weight based on the weight of PP (extractable by contacting the PP with boiling xylene) .

In one embodiment, the PP has an Mw in the range of about 0.9 x 10 ⁶ to about 2.0 x 10 ⁶ , an MWD in the range of 8.5 or less, such as 2.0 to 8.5, such as 2.5 to 6.0, / RTI >< RTI ID = 0.0 > Hm. < / RTI > In general, these PP has a meso pentad fraction, the carbon atom to 1.0 × 10 ⁴ per stereo defect amount, and a Tm above 162.0 ℃ of about 5.0 or less of 94.0 mol% or more in mmmm penta de. In one embodiment, the weight percents are based on the weight of the PP PP is more than 6.0 × 10 ⁵ Mw, more than 90.0% by weight having a MWD, and 90.0J / g or more than 8.5 ΔHm of isotactic polypropylene including ticks do.

Non-limiting examples of PP and methods for determining the Tm, the meso pentad fraction, the stereoregularity, the intrinsic viscosity, the Trouton ratio, the stereo defect, and the amount of extractable species of PP are described in U.S. Pat. PCT Patent Publication No. WO2008 / 140835.

The? Hm of PP is measured by the method disclosed in PCT Patent Publication WO2007 / 132942, which is hereby incorporated by reference in its entirety. The Tm can be measured from differential scanning calorimetry (DSC) data obtained using a PerkinElmer Instrument product, Pyris 1 DSC. Weigh approximately 5.5 to 6.5 mg of the sample into an aluminum sample pan. DSC data is first recorded by heating a sample called first fusion (data not recorded) at a rate of 10 ° C / min to 230 ° C. The sample is held at 230 ° C for 10 minutes before applying the cooling heat cycle. The sample is then cooled from about 230 ° C to about 25 ° C at a rate of 10 ° C / min, referred to as "crystallization", held at 25 ° C for 10 minutes, and then heated to 230 ° C at a rate of 10 ° C / Second fusion "). Record the heat image in both the crystallization and the second melting. The melting temperature (T _m) is the peak temperature of the second melting curve, the crystallization temperature (T _c) is the peak temperature of the crystallization peak.

(Other species)

If desired, inorganic species (e.g., silica and / or species comprising silicon and / or aluminum atoms such as alumina) and / or PCT Patent Publication Nos. WO2007 / 132942 and PCT Patent Publication WO2008 / 016174 The entirety of which is incorporated herein by reference) may be present in the film. In one embodiment, the membrane comprises less than 1.0% by weight of such material based on the weight of the membrane.

For example, as processing aids, small amounts of diluent or other species may be present in the film in an amount generally less than 1.0 wt.%, Based on the weight of the film.

When the microporous membrane is prepared by extrusion, the final microporous membrane generally comprises the polymer used to make the extrudate. In addition, small amounts of diluent or other species introduced during the process may also generally be present in an amount of less than 1.0% by weight, based on the weight of the film. A small amount of polymer molecular weight degradation may occur during the process, but this is acceptable. In one aspect, when molecular weight degradation occurs during the process, the value of the MWD of the polymer in the membrane may be less than or equal to about 10%, or less than about 1%, for example, MWD of the polymer used to make the membrane Or less, or about 0,1% or less.

(Measurement of Mw and MWD)

The Mw and MWD of the polymer can be measured using "SEC" (GPC PL 220, Polymer Laboratories) equipped with high temperature size exclusion chromatography or differential refractive index detector (DRI). The measurement is carried out according to the procedure disclosed in "Macromolecules, Vol. 34, No. 19, pp. 6812-6820 (2001). Three PLgel Mixed-B columns (Polymer Laboratories) are used for Mw and MWD measurements. The nominal flow rate for PE is 0.5 cm3 / min; The nominal injection volume is 300 μl; The transfer line, column and DRI detector are contained in an oven maintained at 145 占 폚. The nominal flow rate for PP is 1.0 cm3 / min; The nominal injection volume is 300 μl; The transfer line, column, and DRI detector are contained in an oven maintained at 160 < 0 > C.

The GPC solvent used is filtered Aldrich reagent grade 1,2,4-trichlorobenzene (TCB) containing about 1000 ppm of butylated hydroxytoluene (BHT). The TCB is degassed with on-line degassing prior to input to the SEC. The same solvent is used as the SEC eluent. The polymer solution is prepared by placing the dried polymer in a glass container, adding a desired amount of the TCB solvent, and then heating the mixture at 160 DEG C with continuous stirring for about 2 hours. The concentration of the polymer solution is 0.25 to 0.75 mg / ml. Before injection into GPC, the sample solution is off-line filtered with a 2 탆 filter using SP260 Sample Prep Station (Polymer Laboratories).

The separation efficiency of the column set is calibrated to a calibration curve created using 17 polystyrene standards each having a range of from about 580 to about 10,000,000 in Mp ("Mp" is defined as the peak in Mw). Polystyrene standards are obtained from Polymer Laboratories (Amherst, MA). The calibration curve (1 gMp vs. storage volume) records the storage volume at the peak of the DRI signal for each PS standard and creates this data in a second order polynomial. Wave Metrics, Inc. Analyze the sample using IGOR Pro, the product.

(membrane)

The present invention is further illustrated by the following embodiments. This description is not meant to exclude other embodiments within the broad scope of the invention.

In one embodiment, the present invention relates to a film comprising 79.0 wt% to 86.0 wt% PE1, 9.0 wt% to 16.0 wt% PE3, and 4.0 wt% to 6.0 wt% PP, wherein i) PE1 is about 4.0 × 10 ⁵ ~ about 6.0 × 10 ⁵ range of the Mw, of about 3.0 ~ have about 10.0 of MWD, the carbon atom to 1.0 × 10 ⁴ per 0.14 terminal unsaturation amount of less than, and more than 132 ℃ melting point; (ii) PE3 has an Mw in the range of about 1.0 x 10 < ⁶ > to about 3.0 x 10 < ⁶ >, an MWD in the range of about 4.0 to about 15.0, (iii) PP has an Mw in the range of about 0.9 x 10 ⁶ to about 2.0 x 10 ⁶ , an MWD in the range of 8.5 or less, such as 2.0 to 8.5, such as 2.5 to 6.0, , Such as isotactic PP having an [Delta] Hm of greater than or equal to 100 J / g (wt% is based on the weight of the film); (iv) the membrane is microporous; The film (v) has a thickness of 12.0 占 퐉 or less, such as 8.0 占 퐉 or less. If necessary, the film is a single layer film. If desired, the membrane comprises not more than 1.0% by weight of PE2, based on the weight of the membrane. Such a film may have a melt down temperature of 148.0 DEG C or higher such as 145.0 DEG C or higher, for example, 150.0 DEG C or higher; 0.24 sec / ㎛ or less, for example 0.18 seconds / 0.20 seconds / ㎛ or less standardized electrolyte affinity for such ㎛ below: and 2.85 × 10 ² mN / ㎛ or more, for example, 2.90 × 10 standardized perforation least ² mN / ㎛ It has strength. In one embodiment, the membrane has a thickness of 9.0 μm or less, a normalized piercing strength of 2.85 × 10 ² mN / μm or more, an NEA of 0.18 sec / μm or less, and a porosity of 35.0% or more. Optionally, the combined weight of PE1, PE2 and PP is at least 98.0 wt%, such as at least 95.0 wt%, e.g., at least 99.0 wt%, of the weight of the film.

In another embodiment, the present invention relates to a film comprising 79.0 wt% to 86.0 wt% PE2, 9.0 wt% to 16.0 wt% PE3, and 4.0 wt% to 6.0 wt% PP, wherein (i ) PE2 is from about 3.0 × 10 ⁵ ~ about 8.0 × 10 ⁵ has a range of Mw, of about 4 or of from about 15 degrees MWD, the carbon atom to 1.0 × 10 ⁴ or more per 0.20 terminal unsaturation amount, and more than 132 ℃ melting point; (ii) PE3 has an Mw in the range of about 1.0 x 10 < ⁶ > to about 3.0 x 10 < ⁶ >, an MWD in the range of about 4.0 to about 15.0, (iii) PP has an MW in the range of about 0.9 x 10 ⁶ to about 2.0 x 10 ⁶ , an MWD in the range of 2.0 to 8.5 such as in the range of less than 8.5, such as 2.5 to 6.0, Is isotactic PP having? Hm of at least 100.0 J / g; (iv) the membrane is microporous; The film (v) has a thickness of 12.0 占 퐉 or less, for example, 8.0 占 퐉. The weight percent is based on the weight of the membrane. Optionally, the membrane comprises less than or equal to 1.0% by weight of PE1, based on the weight of the membrane. Such a membrane has a standardized electrolyte affinity of 145.0 DEG C or higher, for example 150.0 DEG C or higher, and a standardized electrolyte affinity of 0.16 sec / μm or lower, such as 0.14 sec / μm or lower, and a standardized puncture strength of 2.90x10 ² mN / . If necessary, the film is a single layer film. Optionally, the combined weight of PE1, PE2 and PP is at least 98.0 wt%, such as at least 95.0 wt%, e.g., at least 99.0 wt%, of the weight of the film.

Although not limited thereto, the present invention includes the use of a film of any of the above-described embodiments as a battery separator film in a lithium ion polymer battery, particularly, a secondary lithium ion polymer battery. While it is not desirable to be limited to any theory or model, it is believed that the use of PE2 in place of PE1 increases the affinity of the membrane to the polymer electrolyte, but decreases the strength of the membrane, while maintaining the relative amounts of PP and PE3 in the membrane .

Hereinafter, a method for producing a microporous membrane will be described in more detail. The present invention is described with respect to a single-layer film produced by extrusion, but the present invention is not limited thereto, and the description is not meant to exclude other embodiments within the broad scope of the present invention.

(Manufacturing Method of Membrane)

In one or more embodiments, a first polymer (i.e., PE) and a second polymer (i.e., PP) (e.g., by dry blending or melt mixing) are combined with optional components such as diluents and inorganic fillers The microporous membrane can be prepared by forming a mixture, and then extruding the mixture to form an extrudate. At least a portion of the diluent is removed from the extrudate to form a microporous membrane. For example, the blend of PE1 and / or PE2 and PE3 and PP may be combined with a diluent such as liquid paraffin to form a mixture, and the mixture may be extruded and processed to form a monolayer film having a thickness of 12.0 占 퐉 or less have. If desired, an additional layer may be applied to the extrudate to provide a final membrane with, for example, a low shutdown function. That is, a single-layer extrudate or a single-layered microporous membrane can be laminated or co-extruded to form a multilayered membrane.

In at least one embodiment, the manufacturing process of the film includes a step of stretching the extrudate in at least one direction prior to diluent removal. In these or other embodiments, the process includes a step of stretching the film in at least one direction after removal of the diluent. The manufacturing process of the film requires, for example, a step of removing at least a part of any residual volatile species from the film at any time after the removal of the diluting agent, a step of heat-treating the film (for example, heating setting or annealing) before or after removing the diluting agent And more. As described in PCT Patent Publication WO2008 / 016174, a selective solvent treatment, selective heating setting, crosslinking with selective ionizing radiation, and a hydrophilic treatment process can be carried out as needed. The order of the selection process is not critical.

(Preparation of polymer-diluent mixture)

In one or more embodiments, first and second polymers (e.g., PE1 (and / or PE2) as first polymer and PE3 as described above, and PP as second polymer) are placed with one or more diluents , To form a polymer-diluent mixture. For example, the first and second polymers can be combined to form a polymer blend, and the blend can be combined with a diluent (a mixture of diluents, such as a solvent mixture) to produce a polymer-diluent mixture. The mixing can be carried out in an extruder such as, for example, a reaction extruder. Such extruders include, without limitation, twin screw extruders, ring extruders and planetary extruders. The embodiment of the present invention is not limited to the kind of the extruder to be used. For example, optional species such as fillers, antioxidants, stabilizers and / or heat resistant polymers may be included in the polymer-diluent mixture. The types and amounts of these optional species can be the same as those described in PCT Patent Publication No. WO 2007/132942, PCT Patent Publication No. WO 2008/016174, and PCT Patent Publication No. WO 2008/140835, the entirety of which is incorporated herein by reference .

The diluent is generally compatible with the polymer used to make the extrudate. For example, the diluent may be any species or combination of species capable of forming a single phase with the resin at the extrusion temperature. Examples of diluents include at least one of aliphatic or alicyclic hydrocarbons such as nonane, decane, decalin, and paraffin oil, and phthalic esters such as dibutyl phthalate and dioctyl phthalate. For example, paraffin oil having a fluid viscosity of 20 to 200 cSt at 40 占 폚 can be used. The diluent may be the same as described in U.S. Patent Application Publication No. 2008/0057388 and U.S. Patent Application Publication No. 2008/0057389, all of which are incorporated by reference.

In one embodiment, the polymer blend in the polymer-diluent mixture comprises the amount of A ₁ of the first polymer (e.g., PE 1 and PE 3) and the amount of A ₂ of the second polymer (e.g., PP) . In one embodiment, A ₁ is in the range of 1.0 wt% or more, such as 80.0 wt% to 96.0 wt%, A ₂ is in the range of 4.0 wt% to 20.0 wt%, and A ₁ and A ₂ The weight percent is based on the weight of the polymer in the mixture. If necessary, A ₁ is in the range of 84.5 wt.% To 95.5 wt.%, For example in the range of 94.75 wt.% To 95.25 wt.%. Optionally, A < ₂ > is in the range of 4.5 wt% to 15.5%, for example, in the range of 4.75 to 5.25 wt%, based on the total weight of the polymer in the mixture. Optionally, the polymer-diluent mixture comprises up to 45.0 wt.% Polymer based on the weight of the mixture, for example, ranging from 30.0 wt.% To 40.0 wt.% Based on the total weight of polymer in the mixture. The remainder of the mixture can be a diluent.

In one or more embodiments, the amount of A _{1 in} the PE in the polymer-diluent mixture may include the amount of B ₁ of PE ₁ and / or PE _{2 and} the amount of B ₂ of PE ₃ . In one embodiment, B ₁ ranges from 60.0 wt% to 96.0 wt%, B ₂ ranges from 0.0 wt% to 20.0 wt%, and the weight percentages of B ₁ and B ₂ are based on the weight of the polymer in the mixture will be. If desired, B ₁ may range from 69.5 wt.% To 90.5 wt.%, For example from 80.0 wt.% To 85.0 wt.%, Based on the total polymer in the mixture. If necessary, B ₂ ranges from 5.0 wt% to 15.0 wt%, for example, from 9.75 wt% to 15.25 wt%, based on the total polymer in the mixture.

In one embodiment, the polymer-diluent mixture is exposed to a temperature in the range of 140 ° C to 250 ° C, for example 210 ° C to 230 ° C, during extrusion.

(Production of extrudate)

In one embodiment, the polymer-diluent mixture is extruded through a die to produce an extrudate. The extrudate should have a suitable thickness to produce a final film having a desired thickness (generally below 12.0 占 퐉) after the process step. For example, the extrudate may have a thickness in the range of about 1.0 占 퐉 to about 10.0 占 퐉, or about 3.0 占 퐉 to about 8.0 占 퐉. In at least one embodiment, the final film has a final film thickness (after processing) of 12.0 占 퐉 or less, for example, 10.0 占 퐉 or less.

Extrusion is generally carried out in a molten polymer-diluent mixture. When a sheet-forming die is used, the die lip is generally heated, for example, at a high temperature ranging from 180 ° C to 240 ° C. Suitable process conditions for achieving extrusion are disclosed in PCT Patent Publication Nos. WO2007 / 132942 and PCT Patent Publication WO2008 / 016174.

Optionally, the extrudate can be exposed to a temperature in the range of about 10 ° C to about 45 ° C to form a cooled extrudate. The cooling rate is not particularly important. For example, the extrudate may be cooled at a cooling rate of at least about 30 [deg.] C / min until the temperature of the extrudate (the cooled temperature) is approximately equal to (or less than) the gelling temperature of the extrudate. Process conditions for cooling may be the same as those disclosed in, for example, PCT Patent Publication No. WO 2007/132942, PCT Patent Publication No. WO 2008/016174, and PCT Patent Publication No. WO 2008/140835.

(Stretching of the extrudate (upstream stretching))

The extrudate or the cooled extrudate can be stretched in a plane direction such as MD or TD in at least one direction (referred to as "upstream stretching" or "wet stretching"). As a result of this stretching, it is believed that at least some of the polymers in the extrudate are oriented. This orientation is referred to as "upstream" orientation. The extrudate may be stretched by a tentering method, a roll method, an inflation method, or a combination thereof, for example, as described in PCT Patent Publication WO2008 / 016174. The stretching may be performed in a short axis or in two axes; In some embodiments, the extrudate is biaxially oriented. In the case of biaxial stretching, either biaxial stretching, sequential stretching or multistage stretching (for example, a combination of simultaneous biaxial stretching and sequential stretching) may be used; In some embodiments, the extrudate is simultaneously biaxially stretched. When biaxial stretching is used, the magnification need not be the same in each stretching direction.

For example, in the case of uniaxial stretching, the stretching magnification may be 2 times or more and 3 to 30 times. In the case of biaxial stretching, for example, the stretching magnification may be 3 times or more, that is, 9 times or more, for example, 16 times or more, 25 times or more, as an area multiplication factor in any direction. Examples of such a stretching process include stretching at an area ratio of about 9 times to about 49 times. Further, the stretching amounts in the respective directions are not necessarily the same. The magnification acts as a multiplication of the size of the film. For example, a film having an initial width (TD) of 2.0 cm which is stretched at a magnification of 4 times in TD will have a final width of 8.0 cm.

The stretching can be carried out while exposing the extrudate to a temperature in the range of about Tcd to Tm (upstream stretching temperature). In this case, Tcd and Tm are the crystallinity of the polyethylene used for producing the extrudate and the lowest melting point Is defined as the melting point of PE (generally PE, such as PE1 or PE3). The crystal dispersion temperature is determined by measuring the temperature characteristic of dynamic viscoelasticity according to ASTM D4065. In embodiments wherein the Tcd is in the range of about 90 ° C to about 100 ° C, the stretching temperature is 90.0 ° C to 122.0 ° C; For example, 108.0 DEG C to 116.0 DEG C, such as 110.0 DEG C to 114.0 DEG C, for example.

When a sample (e.g., extrudate, dried extrudate, membrane, etc.) is exposed to high temperatures, this exposure may be accomplished by heating the air and moving the heated air to the vicinity of the sample. In general, the temperature of the heated air is controlled to the same set point as the desired temperature, and then moved toward the sample, for example, through the plenum. Other methods of exposing a sample containing conventional methods, such as exposing a sample to a heated surface, infrared heating in an oven, or the like, may be used together with or instead of heated air.

(Removal of diluent)

In one embodiment, at least a portion of the diluent is removed (or replaced) from the stretched extrudate to form a dried film. For example, the diluent may be removed (cleaned or replaced) using a replacement (or "cleaning") solvent as described in PCT Patent Publication WO2008 / 016174.

In one embodiment, at least a portion of any remaining volatilization species (e.g., cleaning solvent) is removed from the dried film after removal of the diluent. Any method capable of removing the cleaning solvent can be used and includes conventional methods such as heat drying, air blow drying (air movement), and the like. Process conditions for removing volatile species such as cleaning solvents may be the same as those disclosed, for example, in PCT Patent Publication No. WO 2008/016174.

(Drawing of the selective film (downstream drawing))

The dried film can be stretched in at least one direction, e.g., MD and / or TD (called "downstream stretching" or "dry stretching" because at least a portion of the diluent has been removed or replaced). It is believed that such stretching results in the polymer being able to be performed in at least a predetermined orientation. This orientation is referred to as downstream orientation. The membrane dried prior to downstream drawing has an initial MD size (first drying length) and an initial TD size (first drying width). As used herein, the term "first dry width" refers to the TD size of the dried film prior to the start of dry stretching. The term "first dry length" refers to the MD size of the dried film prior to the start of dry stretching. For example, a tenter stretching device of the type described in WO2008 / 016174 can be used.

The dried film may have a MD by a magnification ("MD dry stretching magnification") ranging from a first drying length to a second drying length that is longer than the first drying length, ranging from about 1.0 to about 1.6, Lt; / RTI > If TD dry stretching is used, the dried film may be stretched in TD by a magnification ("TD dry stretch magnification") from a first dry width to a second dry width which is wider than the first dry width. If necessary, the TD dry stretching magnification is more than the MD dry stretching magnification. The TD dry stretch magnification may range from about 1.1 to about 1.6, for example, from about 1.1 to 1.5. The dry stretching may be sequential or simultaneous with MD and TD. When using two-axis dry stretching, dry stretching can be simultaneous or sequential to MD and TD. When the dry stretching is sequential, the MD stretching generally takes precedence, followed by the TD stretching.

In certain embodiments, dry stretching is to be avoided or minimized, particularly when implementing embodiments of the present invention in terms of the thickness of a particular film produced in accordance with the present invention. For example, the process step of producing a film having a desired thickness is free of any dry drawing step. In another embodiment, the process step includes dry drawing at a magnification of 1.1 or less, in other embodiments 1.08 or less, in another embodiment 1.05 or less, and in other embodiments 1.03 or less.

The dry stretching can be performed while exposing the dried film to a temperature of Tm or lower (downstream stretching temperature), for example, a temperature in the range of about Tcd-20 ° C to Tm. In one embodiment, the stretching temperature is from about 70.0 DEG C to about 135.0 DEG C, for example, from about 110.0 DEG C to about 132.0 DEG C, such as from about 120.0 DEG C to about 130.0 DEG C.

In one embodiment, the MD dry stretch magnification is about 1.0; TD dry stretch magnification is in the range of about 1.05 to about 1.5 such as 1.6 or less, such as about 1.1 to 1.5; The dry stretching is performed while exposing the film to a temperature in the range of about 120.0 ° C to about 130.0 ° C.

Dry drawing speed is not important. In one embodiment, the dry stretching speed is 1% / second or more in the stretching direction (MD or TD), and the speed can be selected independently for MD and TD stretching. If necessary, the stretching speed is not less than 2% / sec, for example, not less than 3% / sec, such as not less than 10% / sec. In one embodiment, the stretching speed is in the range of 2% / sec to 25% / sec. Although not particularly important, the upper limit of the stretching speed may be 50% / sec to prevent breakage of the film.

(Controlled reduction of membrane width)

Following the dry stretching, the dried film is subjected to a controlled width reduction from the second drying width to the third drying width as needed, and the third drying width is from about 0.9 times the first drying width to about 1.5 It is a range of ships. If necessary, the second drying width is in the range of 1.25 to 1.35 of the first drying width, and the third drying width is in the range of 0.95 to 1.05 of the first drying width. The width reduction is generally in the range of from about 110.0 DEG C to about 132.0 DEG C, such as about 120.0 DEG C to about 130.0 DEG C, such as a temperature in the range of from about 70.0 DEG C to about 135.0 DEG C, Lt; 0 > C.

The temperature during controlled width reduction may be the same as the downstream stretching temperature, but this is not essential, and in one embodiment, the temperature at which the film is exposed during controlled width reduction is at least 1.01 times the downstream stretching temperature, e.g., 1.05 times To 1.1 times. In one aspect, the film width reduction is performed while exposing the film to a temperature below 130.0 캜, and the third drying width is in the range of 0.95 to 1.05 of the first drying width.

(Heating set)

(Heat set) at least once after drying, for example after dry stretching if necessary, after dilution removal after a controlled width reduction, or both later. It is considered that crystals are stabilized by the heating set and a uniform layer is formed in the film. In one form, the heating setting may be at a temperature in the range of Tcd to Tm, such as in the range of about 70.0 DEG C to about 135.0 DEG C, for example, from about 110.0 DEG C to about 120.0 DEG C, such as from about 120.0 DEG C to about 130.0 DEG C Exposure is done.

The heat set temperature may be equal to the downstream draw temperature, but this is not necessary. In one embodiment, the temperature at which the film is exposed during the heating setting is in the range of 1.01 times or more, for example 1.05 times to 1.1 times, the downstream drawing temperature. Generally, the heating setting is performed for a time sufficient to form a uniform layered phase in the film, for example, a time in the range of 1000 seconds or less, for example, 1 to 600 seconds. In one embodiment, the heating setting is performed under conventional heating set "heat setting" conditions. The term "heat setting" refers to a heating setting that is performed, for example, while keeping the length and width of the film essentially constant by fixing the perimeter of the film using a tenter clip during the heating setting.

If necessary, the annealing process can be performed after the heat setting step. The annealing is a heat treatment not applying a load to the film, and can be performed using, for example, a drying chamber equipped with a belt conveyor or an air floating type drying chamber. The annealing can be performed continuously with the tenter relaxed after the heating setting. During annealing, the film may be exposed to a temperature in the range of Tm or less, such as in the range of about 60 ° C to about Tm-5 ° C. The annealing improves the permeability and strength of the microporous membrane.

Optional heating rollers, heating solvents, crosslinking, hydrophilic, and coating treatments can be performed as required, for example, as described in PCT Patent Publication No. WO 2008/016174.

(Characteristic of membrane)

In at least one embodiment, the membrane is a microporous membrane that is permeable to liquids (aqueous and nonaqueous) at atmospheric pressure. Therefore, the membrane can be used as a battery separator, a filtration membrane, and the like. The microporous membrane is particularly useful as a BSF for a secondary battery such as a nickel-hydrogen battery, a nickel-cadmium battery, a nickel-zinc battery, a silver-zinc battery, a lithium-ion battery, and a lithium-ion polymer battery. In one embodiment, the present invention relates to a lithium ion secondary cell comprising a BSF comprising a membrane. Such a battery is described in PCT Patent Publication WO2008 / 016174, the entirety of which is incorporated herein by reference.

In one or more embodiments, the microporous membrane is a monolayer useful as a BSF for a polymer battery, such as a lithium ion polymer cell. The term "polymer electrolyte" as used herein refers to an electrolyte in a polymer cell, which can be used in a conventional sense. As will be appreciated by those skilled in the art, polymer batteries include electrolytes that are dispersed, suspended or dissolved in polymeric media such as lithium ions. Thus, electrolyte affinity or permeability refers to the ability to permeate through a membrane of an electrolyte, such as a polymeric medium and / or lithium ion.

The membrane may have one or more of the following properties.

(thickness)

In one embodiment, the thickness of the final film is 12.0 占 퐉 or less, such as 10.0 占 퐉 or less, for example, in the range of about 1.0 占 퐉 to about 10.0 占 퐉. For example, the monolayer may have a thickness in the range of about 4.5 microns to about 9.5 microns. The thickness of the film can be measured, for example, by a contact thickness meter at intervals of 1 cm over a 10 cm width, and then averaged to obtain a film thickness. Matsun, Inc. 746-3, Kanjima, Fuji-shi, Shizuoka, Japan. A thickness gauge such as RC-1 Rotary Caliper or "Litematic" manufactured by Mitsutoyo Corporation is suitable. For the non-contact thickness measurement method, for example, an optical thickness measurement method is also suitable.

(Porosity)

The porosity of the membrane is measured by conventional methods by comparing the actual weight of the membrane to the weight of the same non-porous membrane of 100% polymer (the same in terms of polymer composition, length, width and thickness). W1 "is the actual weight of the membrane and" w2 "is the volume and thickness of the same polymer (expressed in%) = 99% x (w1 / w2) ) It is the weight of the non-sclera. In one embodiment, the porosity of the membrane is not less than 20.0%, for example not less than 31.0%, such as not less than 35.0%. For example, the porosity of the membrane may range from 20.0% to 80.0%, such as from 36.0% to 40.0%.

(Standardized speculative diagram)

In one embodiment, the film has a thickness of from about 10.0 sec / 100 cm < 3 > / um to about 45.0 / cm < 3 >, such as from about 15.0 sec / 100 cm / Sec / 100 cm 3 / 탆. The permeability value is normalized to a value for the same membrane having a membrane thickness of 1.0 mu m, so that the permeability value of the membrane is expressed in units of "sec / 100cm3 / mu m ". Normalized air permeability is measured according to JIS P8117, the result is equation A = 1.0㎛ * (X) / T ₁ and using the normalized value for the same film also having a thickness of speculation 1.0㎛, where X is the physical thickness and T ₁ is the measured air permeability of the membrane, a is an identical film normalized air permeability and having a thickness of 1.0㎛.

(Standardized puncture strength)

The pore strength of the membrane is expressed as the pore strength of the same membrane having a thickness of 1.0 탆 and a porosity of 30%, and has a unit of [mN / 탆]. The puncture strength is defined as the maximum load measured at ambient temperature when the membrane with thickness T ₁ is punctured at a speed of 2 mm / sec with a needle of 1 mm in diameter with a spherical surface (radius of curvature R: 0.5 mm). This puncture strength ("S") was measured using a formula S ₂ = [30% * 1.0 탆 * (S ₁ )] / [T ₁ * (100% Where S ₁ is the measured puncture strength, S ₂ is the normalized puncture strength, P is the measured porosity of the membrane, and T ₁ is the average thickness of the membrane. In one embodiment, the normalized puncture strength of the film is not less than 2.50 x 10 ² mN / 탆, for example, not less than 2.90 x 10 ² mN / 탆. If necessary, the normalized piercing strength of the film is 3.0 x 10 ² mN / 탆 or more, which is in the range of 3.05 x 10 ² mN / m to 4.5 x 10 ² mN / m.

(Shutdown temperature)

The shutdown temperature of the microporous membrane is measured by the method disclosed in PCT Patent Publication WO2007 / 052663, which is incorporated herein by reference in its entirety. In this method, the microporous membrane is exposed at an increasing temperature (5 ° C / min) starting at 25 ° C while measuring the permeability of the membrane starting at 25 ° C and increasing at a temperature of 5 ° C / min. The shutdown temperature of the microporous membrane is defined as the temperature at which the permeability (Gurley value) of the microporous membrane first exceeds 1.0 × 10 ⁵ sec / 100 cm 3. The permeability of the microporous membrane was measured using an air permeability meter (EGO-1T, manufactured by Asahi Seiko Co., Ltd.) according to JIS P8117. In one embodiment, the shutdown temperature is 136 占 폚 or less, for example, 132.5 占 폚 to 134.5 占 폚.

(Melt down temperature)

The shutdown temperature of the microporous membrane is measured using the same procedure as the measurement of the shutdown temperature. According to this method, the microporous membrane is exposed at an increasing temperature (5 DEG C / min) starting from 25 DEG C, which is a temperature exceeding the shutdown temperature of the membrane while measuring the permeability of the membrane. The film is continuously heated, and the meltdown temperature of the microporous membrane is defined as the temperature at which the permeability (Gurley value) of the microporous membrane is first reduced to a value of 1.0 × 10 ⁵ sec / 100 cm 3. The permeability of the microporous membrane was measured using an air permeability meter (EGO-1T, manufactured by Asahi Seiko Co., Ltd.) according to JIS P8117. In one embodiment, the meltdown temperature of the membrane of the present invention is at least 145.0 DEG C, such as at least 160.0 DEG C, for example. In one embodiment, the meltdown temperature is in the range of 146.0 占 폚 to 170.0 占 폚, for example, 150.0 占 폚 to 165 占 폚.

(105 deg. C heat shrinkage)

In one embodiment, the film has thermal shrinkage at 105 占 폚 in at least one planar orientation (e.g., MD or TD) of 6.0% or greater, such as in the range of 10.0% or less, e.g., 1.0% to 5.0%. The film shrinkage of MD and TD at 105.0 占 폚 is measured as follows: (i) the size of the specimen of the microporous membrane at both ambient temperature is measured both in MD and TD; (ii) The test piece of the microporous membrane was equilibrated at a temperature of 105 DEG C for 8 hours to the unloaded; (Iii) the size of the film is measured in both MD and TD. The heat (or "heat") contraction of MD and TD can be obtained by dividing the measurement result (i) by the measurement result and (ii) representing the obtained value as a percentage.

(The tensile strength)

In one embodiment, the membranes have MD and TD tensile strengths in the range of 1.4 x 10 ⁵ kPa or more, for example, 1.5 x 10 ⁵ kPa to 2.0 x 10 ⁵ kPa, respectively. Tensile strength is measured in MD and TD according to ASTM D-882A.

(Standardized electrolytic affinity)

A film sample of 50 mm x 50 mm (thickness: 12.0 m or less) was prepared and placed on a flat glass substrate having a larger area than the film. The film is irradiated from the top using visible light, and the film at the beginning of the measurement is opaque. 500.0 占 퐇 of a droplet of propylene carbonate (purity not less than 99% by volume) is applied to the surface of the film by using a film at 25 占 폚 and +/- 3 占 폚. The electrolyte affinity ("EA") of the membrane is defined as the average elapsed time from the time the droplet initially contacts the film until the film becomes transparent. The measurement is repeated five times to obtain an average value.

Standardized electrolyte affinity ("NEA") is defined as EA / (average film thickness in [mu] m). NEA has units of [sec / 탆]. In one embodiment, the membrane has an NEA in the range of less than or equal to 2.5 sec / 탆, such as less than or equal to 5.0 sec / 탆, such as 0.1 sec / m to 0.9 sec / m.

(Example)

The present invention will be explained in more detail without limiting the scope of the present invention with reference to the following examples.

(Example 1)

(1) Preparation of polymer-diluent mixture

The polymer-diluent mixture is prepared as follows by combining two kinds of polyethylenes, PE1 and PE3, and a polymer blend of PP and a diluent. Weight percents are based on the weight of the combined polymer polymer blend (a) having 5.6 × 10 ⁵ of the Mw, 4.0 of the MWD, the carbon atom to 1.0 × 10 ⁴ per 0.14 terminal unsaturation amount of less, and a Tm of 136.0 ℃ PE (PE1) of 90.0% by weight, (b) PE (PE3) of 5.0 wt% with 1.9 × 10 ⁶ of the Mw, 5.1 of MWD, and Tm of 136.0 ℃, and (c) of 5.3 × 10 ⁵ Mw and And 5.0 wt% of isotactic PP (PP2) having an [Delta] Hm of about 80 J / g.

35.0% by weight of the polymer blend was then charged into a strong blending twin screw extruder having an internal diameter of 58 mm and a L / D of 42, and 65.0% by weight liquid paraffin (50 cst at 40 캜) was fed through a side feeder to a twin screw extruder . Mixing is carried out at 220 캜 and 320 rpm to prepare a polymer-diluent mixture, the weight% being based on the weight of the polymer-diluent mixture.

(2) Production of membranes

The polymer-diluent mixture is extruded from a sheet-forming die (in the form of a sheet) to form an extrudate. The temperature of the die is about 210 占 폚 (or specifically as described above in Table 1). The extrudate is cooled by contact with a chilled roller controlled at 20 < 0 > C. The cooled extrudate is simultaneously biaxially stretched (up-stretched) 5 times in both MD and TD at about 112.5 DEG C (as specifically shown in the table) by a tenter stretcher. The stretched three-layered gel sheet is then immersed in a methylene chloride bath controlled at 25 캜 to remove the liquid paraffin in an amount of up to 1.0% by weight based on the weight of the liquid paraffin in the polymer-diluent mixture. Then, the film is dried by air flow at room temperature. The final microporous membrane is then prepared by heating the membrane at 128.8 [deg.] C for 10 minutes (as described in the table) while keeping the membrane size largely constant. Table 1 shows selected starting materials, process conditions and film properties.

(Example 2)

Example 1 other than those listed in Table 1 is repeated. The starting materials and process conditions are the same as those used in Example 1 except those listed in the table. For example, PP1 may be used instead of polypropylene (PP1) having Mw of 1.1 x 10 < ⁶ > and DELTA Hm of 114 J / g; PE1 may be used instead of PE1 (PE2) having an Mw of 7.46 × 10 ⁵ , a Tm of 134.0 ° C., and an end unsaturation value of at least 0.20 per 1.0 × 10 ⁴ carbon atoms. The membranes of Example 4 and Example 5 were stretched (downstream stretching) at a TD magnification of 1.4 downstream of the diluent removal, with exposure to temperatures of 130.2 占 폚 (Example 4) and 130.0 占 폚 (Example 5), respectively, before heat setting.

(Review)

A relatively thin microporous membrane having a useful meltdown temperature (e.g., greater than 145.0 DEG C) can be prepared from more than 4.0 wt.% PP based on the weight of PE and membrane. Such a membrane is useful as a BSF in a lithium ion battery such as a lithium ion polymer battery using a thin BSF. When the concentration of PP is increased as shown by Example 5, the NEA is significantly increased. For membranes containing 20.0 wt% or more PP, the larger the NEA value, the more difficult it becomes to use the membrane as the BSF for the polymer battery. On the other hand, the data for the limiting amount of PP are needed to achieve a useful meltdown temperature, while increasing the amount of PP has an undesirable effect on the NEA. Comparative Example 1 shows BSF without PP. In addition, such membranes have useful NEA but also have relatively low meltdown temperatures, relatively low porosity, and relatively low standardized pore strength.

All patents, test procedures, and other documents, including the priorities listed in the present invention, are fully incorporated by reference in their entirety and to the jurisdiction in which they are permitted to be incorporated.

Although the exemplary embodiments disclosed in the present invention have been specifically described, it will be apparent to those skilled in the art that various other changes can be made without departing from the spirit and scope of the present invention. Thus, while the scope of the claims appended hereto is not intended to be limited to the embodiments and descriptions set forth herein, the claims are intended to encompass all of the features of the patentable novelty present in the present invention, And the characteristics considered to be the same as those included in the second embodiment.

When the numerical lower limit and the upper numerical limit are described in the present invention, they are considered to be any lower limit to an arbitrary upper limit.

(Industrial availability)

The microporous membrane of the present invention is suitable for use as a battery separator film.

Claims (24)

As based on the weight of the film, the film comprising at least 1.0% by weight polyethylene and, 5.0 × 10 ⁵ or more and polypropylene Mw of 4.0 wt% to 20.0 wt% with 80.0J / g or more ΔHm:
Wherein the polyethylene comprises at least one of a first polyethylene and a second polyethylene and a third polyethylene,
The first polyethylene is 1.0 × 10 ⁶ less than the Mw, in the range of 2.0 ~ 20.0 MWD, the carbon atom to 1.0 × 10 ⁴ per one having a terminal unsaturation amount of less than 0.20, wherein the second polyethylene is 1.0 × 10 ⁶ less than the Mw, 2-50 have a terminal unsaturation amount of MWD, the carbon atom to 1.0 × 10 ⁴ per one or more of 0.20 in the range of said third polyethylene has an MWD in the range of 1.0 × 10 ⁶ or more Mw, 1.2 ~ 50.0, the third polyethylene The amount is at least 8.0 wt% based on the weight of the membrane,
It said polypropylene includes isotactic polypropylene having a meso pentad fraction of the amount of stereo defects and the carbon atom to 1.0 × 10 ⁴ or less per 5.0 mol of at least 90.0% mmmm pentads,
Wherein the membrane is microporous and has a thickness of 12.0 m or less. The method according to claim 1,
Wherein the amount of polypropylene is in the range of 4.5 wt.% To 15.5 wt.%, Based on the weight of the membrane, and the membrane has a thickness of 10.0 m or less. 3. The method according to claim 1 or 2,
A meltdown temperature of 145.0 占 폚 or higher and a normalized electrolyte affinity of 2.5 sec / 占 퐉 or less. 3. The method according to claim 1 or 2,
A porosity in the range of 20% to 80%, a standardized permeability of 50.0 sec / 100 cm 3 / 탆 or less, and a normalized puncture strength of 2.5 x 10 ² mN / 탆 or more. 3. The method according to claim 1 or 2,
Wherein the polypropylene has an Mw of at least 6.0 x 10 ⁵ , an MWD of at most 8.5 and an? Hm of at least 90.0 J / g, and comprises at least 90.0 wt% isotactic polypropylene based on the weight of the film. 3. The method according to claim 1 or 2,
(ii) said first polyethylene and said second polyethylene are present in an amount of B ₁ ranging from 69.5% to 90.5% by weight; (iii) said third polyethylene is present in an amount of B ₂ in the range of from 5.0 wt% to 20.0 wt% (wt% is the weight of the membrane). The method according to claim 6,
Wherein the amount of the first polyethylene and the second polyethylene is in the range of 72.0 wt% to 90.0 wt%, the amount of the third polyethylene is in the range of 5.0 wt% to 20.0 wt%, and the amount of the polypropylene is 5.0 wt% By weight to about 8.0% by weight. 8. The method of claim 7,
The first polyethylene and the second polyethylene is ^{4.0 × 10 5 ~ 6.0 × 10} 5 has a range of Mw and scope MWD of 3.0 ~ 10.0, the range of the third polyethylene is ^{1.0 × 10 6 ~ 3.0 × 10} 6 Mw and a MWD in the range of 4.0 to 15.0. 9. The method of claim 8,
Wherein said first polyethylene has a terminal unsaturation amount of less than 0.20 per 1.0 x 10 < ⁴ > of carbon atoms. A battery separator film comprising the microporous membrane according to any one of claims 1 to 5. (1) A process for extruding a mixture of a diluent and a polymer, wherein the polymer comprises an A ₁ amount of polyethylene and an A ₂ amount of polypropylene, wherein A ₁ is 1.0 weight%, based on the weight of the polymer in the polymer- %, And A < ₂ > is in the range of 4.0 wt% to 20.0 wt%;
(2) stretching the extrudate in at least one plane direction; and
(3) removing at least a portion of the diluent from the stretched extrudate,
Wherein the polyethylene comprises at least one of a first polyethylene and a second polyethylene and a third polyethylene,
The first polyethylene is 1.0 × 10 ⁶ less than the Mw, in the range of 2.0 ~ 20.0 MWD, the carbon atom to 1.0 × 10 ⁴ per one having a terminal unsaturation amount of less than 0.20, wherein the second polyethylene is 1.0 × 10 ⁶ less than the Mw, 2-50 have a terminal unsaturation amount of MWD, the carbon atom to 1.0 × 10 ⁴ per one or more of 0.20 in the range, and the third PE has an MWD in the range of 1.0 × 10 ⁶ or more Mw, 1.2 ~ 50.0, the third polyethylene The amount is at least 8.0 wt% based on the weight of the membrane,
Characterized in that said polypropylene comprises an isotactic polypropylene having a meso pentad fraction of mmmm pentads of not less than 90.0 mol% and a stereo defect quantity of not more than 5.0 per 1.0 x 10 ⁴ carbon atoms . 12. The method of claim 11,
Wherein A ₁ is in the range of 84.5 wt% to 95.5 wt% based on the weight of the polymer in the polymer-diluent mixture, and the polyethylene has a Mw of less than 1.0 x 10 ⁶ . 13. The method according to claim 11 or 12,
(i) the A ₂ ranges from 4.5 wt% to 15.5 wt%; (ii) the polypropylene comprises an isotactic polypropylene having an Mw of 6.0 x 10 < ⁵ > or more, an MWD of 8.5 or less and an [Delta] Hm of 90.0 J / g or more, A method for producing a microporous membrane. 13. The method according to claim 11 or 12,
(ii) the first polyethylene and the second polyethylene are present in an amount of B ₁ ranging from 69.5% to 90.5% by weight based on the weight of the membrane, (iii) the third polyethylene comprises 5.0% % ≪ / RTI _> of B _{2, based on} the total weight of the microporous membrane. 13. The method according to claim 11 or 12,
Further comprising a step of cooling the extrudate before the step (2). 13. The method according to claim 11 or 12,
Further comprising a step of stretching the film in at least one direction following the step (3), and a step of heat-treating the film following the step (3). 17. The method of claim 16,
And the stretching direction is TD. 13. The method according to claim 11 or 12,
Wherein the stretching in the step (2) is carried out biaxially at a magnification in the range of 9 to 49 times the area while exposing the extrudate to a temperature in the range of 90.0 占 폚 to 125.0 占 폚. 13. The method according to claim 11 or 12,
Further comprising the step of removing any volatile species remaining after the step (3) from the film. A membrane product produced by the method for producing a microporous membrane according to claim 11 or 12. A battery comprising a negative electrode, a positive electrode, an electrolyte, and a battery separator positioned between the negative electrode and the positive electrode,
Wherein the battery separator comprises the film according to any one of claims 1 to 3. [ 22. The method of claim 21,
Wherein the membrane has a thickness of 10.0 占 퐉 or less, and the battery is a lithium ion polymer battery. delete A battery comprising a negative electrode, a positive electrode, an electrolyte, and a battery separator positioned between the negative electrode and the positive electrode,
The battery separator comprises the film according to claim 10.