JP2013522379A - Microporous membranes, methods for making these membranes, and 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 membranes and the use of these membranes as battery separator films.

Description

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

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

  The microporous polymer membrane can be used as a battery separator film (“BSF”) in lithium ion batteries and the like. Such membranes have high polymer mobility at high battery temperatures, leading to a significant decrease in air permeability. This effect can be attributed to the BSF, since lowering the air permeability at higher temperatures will reduce the electrochemical activity of the battery, thereby reducing the risk of battery failure under overcharge, rapid discharge, or other high temperature battery conditions. Is beneficial in. Since the internal temperature of the battery may continue to rise even when the electrochemical activity is reduced (eg, from temperature overshoot), it is desirable to further increase the thermal stability of the film at high temperatures to further reduce the risk of battery failure. This can be accomplished by including a high melting point species (eg, polypropylene) in the membrane polymer. Due to the temperature difference between the melting points of polyethylene and polypropylene and their physical incompatibility, it is difficult to produce membranes containing both polymers, especially when the membranes are thin.

  For example, in lithium ion batteries where the electrolyte is a gel electrolyte or a polymer electrolyte and the electrolyte is contained within a polymer medium (“lithium ion polymer battery”), compatibility (eg affinity) with the polymer medium containing the electrolyte BSF containing a polymer having) is usually used. BSFs for lithium ion polymer batteries are typically significantly thinner than BSFs commonly used in, for example, cylindrical and prismatic lithium ion batteries.

  Accordingly, it is desirable to produce a relatively thin polymer film that has an affinity for the polymer used as the electrolyte medium of a polymer battery and is dimensionally stable at high temperatures.

In certain embodiments, the present invention provides at least 1% by weight polyethylene and 4.0% to 20.0% by weight polypropylene having a Mw of 5.0 × 10 ⁵ or greater and a ΔHm of 80.0 J / g or greater. Wherein the weight percent is based on the weight of the polymer in the membrane, is microporous, and has a thickness of 12.0 micrometers or less.

In another embodiment, the present invention is a manufacturing process of the microporous film, (1) a step of extruding the mixture of diluent and polymer, the amount of polyethylene and A ₂ of the amount of polymer A ₁ by weight of polypropylene, and the _{a 1,} for example, 80.0 wt% ～96.0 wt% range, such as 1.0 wt% or more, _{a 2} is in the range of 4.0 wt% to 20.0 wt% (Weight percent is based on the weight of the polymer in the polymer-diluent mixture), (2) stretching the extrudate in at least one planar direction, and (3) stretching at least a portion of the diluent. The present invention relates to a process including a step of removing from an object.

  The membrane of the present invention has both an improved meltdown temperature and sufficient electrolyte affinity.

It has been observed that microporous membranes comprising polyethylene and having a thickness of 12.0 micrometers or less typically have a meltdown temperature of less than 145.0 degrees Celsius. It has also been observed that when this polyethylene is combined with polypropylene, these films have a higher meltdown temperature but a reduced affinity for the polymer electrolyte. The present invention is at least partially based on 1.0 weight percent polyethylene (based on the weight of the membrane) and 4.0 weight percent to 20.0 weight percent, 5.0 × 10 ⁵ weight average Overcoming these difficulties when the membrane contains a mixture of polypropylene (weight percent is based on the weight of the membrane) with a molecular weight (“Mw”) and a heat of fusion (“ΔHm”) greater than or equal to 80.0 J / g. Based on the discovery that you can. These membranes have both an improved meltdown temperature and sufficient electrolyte affinity to be useful as a BSF for lithium ion polymer batteries.

In this specification and the appended claims, the term “polymer” means a composition comprising a plurality of macromolecules comprising repeating units derived from one or more monomers. These polymers may be different in size, molecular structure, atomic content and the like. The term “polymer” includes polymers such as copolymers and terpolymers. “Polyethylene” contains 50% or more (number basis) of ethylene-derived repeat units, preferably polyethylene homopolymer, and / or polyethylene copolymer in which at least 85% (number basis) of repeat units are ethylene units. Means polyolefin. “Polypropylene” contains more than 50.0% (number basis) of propylene-derived repeating units, preferably polypropylene homopolymer, and / or polypropylene copolymer in which at least 85% (number basis) of repeating units are propylene units Means polyolefin. The term isotactic polypropylene (based on the total number of moles of isotactic polypropylene) is a polypropylene having a mesopentad fraction of about 50.0 mol% or more mmmm pentads, preferably 96.0 mol% or more mmmm pentads. Means. A “microporous membrane” is a thin film having pores, in which 90.0 percent or more (volume basis) of the pore amount of the membrane has an average diameter in the range of 0.01 to 10.0 micrometers. It is a pore. For membranes made from extrudates, the machine direction (“MD”) is defined as the direction in which the extrudates are made from a die. The transverse direction (“TD”) is defined as the direction perpendicular to both the MD and thickness directions of the extrudate. MD and TD may be referred to as the planar direction of the membrane, and in this context the term “planar” means a direction that is approximately in the plane of the membrane when the membrane is flat.
Composition of microporous membrane

In one or more embodiments, the present invention relates to a membrane comprising polyethylene and polypropylene that is microporous and has a thickness of 12.0 micrometers or less. In some embodiments, the microporous membrane comprises an amount of polyethylene (A ₁ ) and an amount of polypropylene (A ₂ ) having a Mw of 5.0 × 10 ⁵ or greater and a ΔHm of 80.0 J / g or greater. A ₁ and A ₂ can be expressed in weight percent based on the weight of the polymer in the membrane. For example, the weight percent can be based on the combined weight of polyethylene and polypropylene in the membrane, for example, A ₁ + A ₂ = 100 wt%. In other embodiments, the weight percent is based on the weight of the membrane, for example, as may be the case when the membrane consists essentially of polyethylene and polypropylene (or just consists of polyethylene and polypropylene).

For example, in one or more embodiments, A ₁ is in the range of 80.0 wt% to 96.0 wt%, A ₂ is in the range of 4.0 wt% to 20.0 wt%, weight percent of a ₁ and _{a 2} are weight based a combination of the _{a 1} and _{a 2} is equal to 100 wt%. Optionally, _{A 1} is in the range of 84.5 wt% ～95.5 wt%, such a range of, for example, 94.75 wt% ～95.25 wt%. Optionally, _{A 2} is in the range of 4.5 wt% ～15.5 wt%, such a range of, for example 4.75 wt% to 5.25 wt%.

In the following, selected embodiments of polyethylene and polypropylene will be described in more detail, but this description is intended to exclude other embodiments that are within the broader scope of the present invention.
polyethylene

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

In some embodiments, the first PE (“PE1”) has an Mw of less than 1.0 × 10 ⁶ , for example about 1.0 × 10 ⁵ to about 0.90 × 10 ⁶ , for example about PE having a MWD of 50.0 or less, such as in the range of 2.0 to about 20.0, and a terminal unsaturation amount of less than 0.20 per 1.0 × 10 ⁴ carbon atoms. Optionally, PE1 has a Mw in the range of about 4.0 × 10 ⁵ to about 6.0 × 10 ⁵ and a molecular weight distribution of about 3.0 to about 10.0 (“MWD”, Mw divided by number average molecular weight). Defined as). Optionally, PE1 is 1.0 × 10 ⁴ cells per 0.14 or less carbon atoms, or a carbon atom 1.0 × 10 ⁴ cells per 0.12 or less, for example, carbon atoms 1.0 × 10 ⁴ per 0.05 It has a terminal unsaturation in the range of ~ 0.14 (eg below the detection limit of measurement).
PE2

In some embodiments, the second PE (“PE2”) has a Mw of less than 1.0 × 10 ⁶ , eg, about 2.0 × 10 ⁵ to about 0.9 × 10 ⁶ , eg, about PE with a MWD of 50.0 or less, such as in the range of 2 to about 50, and terminal unsaturation greater than 0.20 per 1.0 × 10 ⁴ carbon atoms. Optionally, PE2 0.30 greater per 1.0 × 10 ⁴ carbon atoms, or 0.50 than carbon atoms 1.0 × 10 ⁴ per, for example, carbon atoms 1.0 × 10 ⁴ per 0.6 It has terminal unsaturation in the range of -10.0. Non-limiting examples of PE2 include those having a Mw in the range of about 3.0 × 10 ⁵ to about 8.0 × 10 ⁵ , such as about 7.5 × 10 ⁵ and an MWD of about 4 to about 15. is there.

PE1 and / or PE2 is an ethylene / α-olefin containing, for example, ethylene homopolymer or 5.0 or less mol% of one or more comonomers such as α-olefin based on 100% molar copolymer It may be a copolymer. Optionally, the α-olefin is one or more of propylene, butene-1, pentene-1, hexene-1, 4-methylpentene-1, octene-1, vinyl acetate, methyl methacrylate, or styrene. Such PE may have a melting point of 132 degrees Celsius or higher. PE1 can be produced, 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 Publication WO 97/23554. PE2 can be produced using, for example, a chromium-containing catalyst.
PE3

In some embodiments, the third PE (“PE3”) has a Mw of 1.0 × 10 ⁶ or greater, such as, for example, in the range of about 1.0 × 10 ⁶ to about 5.0 × 10 ⁶ and about 1 It may be a PE having an MWD of 2 to about 50.0. Non-limiting examples of PE3 include about 1.0 × 10 ⁶ to about 3.0 × 10 ⁶ Mw, such as about 2.0 × 10 ⁶ , and about 2.0 to about 20.0, for example. Some have an MWD of 20.0 or less, preferably from about 4.0 to about 15.0. PE3 is, for example, an ethylene homopolymer or an ethylene / α-olefin copolymer containing one or more comonomers, such as 5.0 mol% or less α-olefin, based on a 100% molar copolymer. Also good. The comonomer may be, for example, one or more 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 produced using Ziegler-Natta catalysts or single site catalysts, but this is not essential. Such PE may have a melting point of 134 degrees Celsius or higher. The melting points of PE1 to PE3 can be determined, for example, by the method disclosed in PCT Patent Publication No. WO2008 / 140835.

In one or more embodiments, the PE comprises PE ₁ and / or PE _{2 in} an amount of B 1 and PE 3 in an amount of B ₂ . In some embodiments, B ₁ is in the range of 60.0 wt% to 96.0 wt%, and B ₂ is in the range of 0.0 wt% to 20.0 wt% (of B ₁ and B ₂ The weight percent is based on the weight of the polymer in the membrane). Optionally, _{B 1} is in the range of 69.5 wt% ～90.5 wt% such total polymer the scope of example 80.0 wt% ～85.0 wt%, based in the film. If desired, _{B 2} is in the range of the total polymer for example, based on the 9.75 wt% ～15.25 such wt% in the range 5.0 wt% to 15.0 wt% in the film. In some embodiments, B ₁ ranges from 79.0 wt% to 95.0 wt% and B ₂ ranges from 0.0 wt% to 16.0 wt%. If B ₂ is less than about 7.5 wt%, for example because to produce a film having a meltdown temperature of more than 145 degrees Celsius, such as more than 147 degrees Celsius can become more difficult, in one embodiment, the membrane e.g. It has over meltdown temperature of 145 degrees Celsius such above 147 degrees Celsius, and having 8.0 wt% or more of _{B 2} which say for example 10.0 wt% or more.
polypropylene

In certain embodiments, polypropylene ( "PP"), for example, for example, 6.0 × 10 ⁵ or more, or 7.5 × 10 ⁵ or more, such as about 0.8 × 10 ⁶ ~ about 3.0 × 10 ⁶ A polypropylene having a Mw of 5.0 × 10 ⁵ or more, such as a range of 0.9 × 10 ^{6 to} 2.0 × 10 ⁶ , may be used. If desired, the PP has a Tm of 160.0 degrees Celsius or higher and a ΔHm of 80.0 J / g or higher, such as 90.0 J / g or higher, or 100.0 J / g or higher, such as 110 J / g to 120 J / g. Have. Optionally, the PP has an MWD of 20.0 or less, such as in the range of about 1.5 to about 10.0, such as in the range of about 2.0 to about 8.5. Optionally, PP is a copolymer (random or block) of propylene and up to 5.0 mole% comonomer, which may be, for example, ethylene, butene-1, pentene-1, hexene-1, 4-methylpentene- 1, one or more α-olefins such as octene-1, vinyl acetate, methyl methacrylate, and styrene, or one such as butadiene, 1,5-hexadiene, 1,7-octadiene, 1,9-decadiene, etc. Or a plurality of diolefins.

In some embodiments, PP is isotactic polypropylene. In certain embodiments, the PP comprises (a) a mesopentad fraction of about 90.0 mol% or more mmmm pentads, optionally 96.0 mol% or more mmmm pentads, preferably 96.0 mol% or more mmmm pentads. And (b) a steric defect amount of about 50.0 or less per 1.0 × 10 ⁴ carbon atoms, eg, about 20 × or less per 1.0 × 10 ⁴ carbon atoms, or 1.0 × 10 carbon atoms, for example ^The amount of steric defects is about 10.0 or less per 1.0 × 10 ⁴ carbon atoms, such as about 5.0 or less per ^four . Optionally, the PP has one or more of the following properties: (i) a Tm greater than or equal to 162.0 degrees Celsius, (ii) a temperature of 230 degrees Celsius and a strain rate of 25 seconds ⁻¹ at about 5.0. × 10 ⁴ Pa seconds or higher, (iii) Trought ratio of about 15 or more when measured at a temperature of about 230 degrees Celsius and a strain rate of 25 seconds ⁻¹ , (iv) about 0.1 dg / minute or less For example, melt flow rate ("MFR"; ASTM D-1238-95 Condition L, 230 degrees Celsius, and 2.16 kg) at about 0.01 dg / min or less (ie, low value and practically MFR cannot be measured) Or (v) 0.5 wt% or less of an extractable species amount, such as 0.2 wt% or less, for example 0.1 wt% or less, based on the weight of PP (contacting PP with boiling xylene) Letting More can be extracted).

In some embodiments, the PP has a Mw in the range of about 0.9 × 10 ⁶ to about 2.0 × 10 ⁶ , such as in the range of 2.0 to 8.5, such as in the range of 2.5 to 6.0. Isotactic PP having an MWD of 8.5 or less and a ΔHm of 90.0 J / g or more. Typically, such PP has a mesopentad fraction of mmmm pentads greater than or equal to 94.0 mol%, less than about 5.0 steric defects per 1.0 × 10 ⁴ carbon atoms, and greater than or equal to 162.0 degrees Celsius. Tm. In some embodiments, the PP comprises 90.0 wt% or more isotactic polypropylene (weight percent) having a Mw of 6.0 × 10 ⁵ or more, an MWD of 8.5 or less, and a ΔHm of 90.0 J / g or more. Is based on the weight of PP).

  Non-limiting examples of PP and methods for determining PP Tm, mesopentad fraction, stereoregularity, intrinsic viscosity, trouton ratio, steric defects, and amount of extractable species are hereby incorporated by reference in their entirety. PCT Patent Publication No. WO 2008/140835, which is incorporated into the document.

The ΔHm of the PP is determined by the method disclosed in PCT Patent Publication No. WO 2007/132294, which is incorporated herein by reference in its entirety. Tm can be determined from differential scanning calorimetry (DSC) data obtained by model Pyris 1 DSC manufactured by Perkin Elmer Instruments. A sample weighing approximately 5.5-6.5 mg is enclosed in an aluminum sample pan. DSC data is recorded by first heating the sample to 230 degrees Celsius at a rate of 10 degrees Celsius / minute, referred to as the first melt (no data recorded). The sample is held at 230 degrees Celsius for 10 minutes before applying the cooling heating cycle. The sample is then cooled (called “crystallization”) from about 230 degrees Celsius to about 25 degrees Celsius at a rate of 10 degrees Celsius / minute, then held at 25 degrees Celsius for 10 minutes, and then 10 degrees Celsius / minute Heat to 230 degrees Celsius at a rate (referred to as “second melt”). Record thermal events in both crystallization and second melt. The melting temperature (Tm) is the peak temperature of the second melting curve, and the crystallization temperature (Tc) is the peak temperature of the crystallization peak.
Other species

  Optionally, inorganic species (such as species containing silicon and / or aluminum atoms, such as silica and / or alumina, etc.), and / or PCT publications WO2007 / 132294 and WO2008 / 016174 (both herein incorporated by reference in their entirety). The heat-resistant polymer such as the polymer described in (1) may be present in the film. In certain embodiments, the membrane contains 1.0% or less by weight of such material, based on the weight of the membrane.

  For example, small amounts of diluents or other species as processing aids may also be present in the membrane in amounts usually less than 1.0% by weight, based on the weight of the membrane.

When the microporous membrane is made by extrusion, the final microporous membrane usually contains the polymer used to make the extrudate. Small amounts of diluent or other species introduced during processing may also be present, usually in an amount of less than 1.0% by weight, based on the weight of the membrane. During processing, the molecular weight of the polymer may be reduced by a small amount, which is acceptable. In some forms, even if there is a decrease in molecular weight during processing, the difference between the MWD value of the polymer in the membrane and the MWD of the polymer used to make the membrane (eg, before extrusion) is, for example, only about 10% Only about 1%, or only about 0.1%.
Determination of Mw and MWD

The Mw and MWD of the polymer can be determined using a high temperature size exclusion chromatograph equipped with a differential refractometer (DRI), ie “SEC” (GPC PL 220, Polymer Laboratories). The measurement is performed 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 the determination of Mw and MWD. For PE, the nominal flow rate is 0.5 cm ³ / min, the nominal injection volume is 300 microL, and the transfer line, column, and DRI detector are contained in an oven maintained at 145 degrees Celsius. Yes. For PP, the nominal flow rate is 1.0 cm ³ / min, the nominal injection volume is 300 microL, and the transfer line, column, and DRI detector are contained in an oven maintained at 160 degrees Celsius. Yes.

  The GPC solvent used is a filtered Aldrich reagent grade 1,2,4-trichlorobenzene (TCB) containing about 1000 ppm butylated hydroxytoluene (BHT). The TCB is degassed with an online degasser prior to introduction into the SEC. The same solvent is used as the SEC eluent. A polymer solution is prepared by placing the dried polymer into a glass container, adding the desired amount of TCB solvent, and then heating the mixture at 160 degrees Celsius with continuous stirring for about 2 hours. The concentration of the polymer solution is 0.25 to 0.75 mg / ml. The sample solution is filtered off-line with a 2 micrometer filter using a model SP260 Sample Prep Station (manufactured by Polymer Laboratories) before being injected into the GPC.

Calibrate the separation efficiency of the column set with a calibration curve generated using 17 individual polystyrene standards with Mp ("Mp" defined as the peak at Mw) in the range of about 580 to about 10,000,000. . Polystyrene standards are obtained from Polymer Laboratories (Amherst, Mass.). A calibration curve (logMp vs. retention capacity) is created by recording the retention capacity at the peak of the DRI signal for each PS standard and fitting this data set to a second order polynomial. Samples are analyzed using IGOR Pro manufactured by Wave Metrics, Inc.
film

  The invention is further described in the following embodiments. This description is not intended to exclude other embodiments within the broader scope of the invention.

In one embodiment, the present invention provides 79.0 wt.% To 86.0 wt.% PE1, 9.0 wt.% To 16.0 wt.% PE3, and 4.0 wt.% To 6.0 wt.%. Where: (i) PE1 has a Mw in the range of about 4.0 × 10 ⁵ to about 6.0 × 10 ⁵ , an MWD of about 3.0 to about 10.0, carbon atoms 1 A terminal unsaturation amount of 0.14 or less per 0.0 × 10 ⁴ , and a melting point of 132 ° C. or more; (ii) PE3 is about 1.0 × 10 ⁶ to about 3.0 × 10 ⁶ Having an Mw in the range, an MWD in the range of about 4.0 to about 15.0, and a melting point of 134 degrees Celsius or higher; (iii) PP is about 0.9 × 10 ⁶ to about 2.0 × 10 ⁶ Mw in the range of 8.5, for example in the range of 2.0 to 8.5, for example in the range of 2.5 to 6.0, MWD of 8.5 or less, and for example 100 Isotactic PP having a ΔHm of 90.0 J / g or greater, such as 0 J / g or greater (weight percent is based on the weight of the membrane), (iv) the membrane is microporous, and (v) The film has a thickness of 12.0 micrometers or less, for example 8.0 micrometers or less. If desired, the film is a single layer film. Optionally, the membrane contains 1.0 wt% or less of PE2 based on the weight of the membrane. Such a film has a meltdown temperature of, for example, 145.0 degrees Celsius or higher, such as 148.0 degrees Celsius or higher, such as 150.0 degrees Celsius or higher; such as 0.20 seconds / micrometer or lower, such as 0.18 seconds / Normalized electrolyte affinity of 0.24 seconds / micrometer or less, such as micrometer or less; and a standardized piercing of 2.85 × 10 ² mN / micrometer or more, eg, 2.90 × 10 ² mN / micrometer or more Has strength. In certain embodiments, the membrane has a thickness of 9.0 micrometers or less, a normalized puncture strength of 2.85 × 10 ² mN / micrometer or more, a NEA of 0.18 seconds / micrometer or less, and 35. It has a porosity of 0% or more. Optionally, the combined weight of PE1, PE2, and PP is 95.0% by weight or more, such as 98.0% by weight or more, for example 99.0% by weight or more, of the weight of the membrane.

In another embodiment, the present invention provides 79.0% to 86.0% PE2, 9.0% to 16.0% PE3, and 4.0% to 6.0% by weight. Where: (i) PE2 has a Mw in the range of about 3.0 × 10 ⁵ to about 8.0 × 10 ⁵ , an MWD in the range of about 4 to about 15; It has a terminal unsaturation amount of 0.20 or more per 0 × 10 ⁴ and a melting point of 132 ° C. or more, and (ii) PE3 ranges from about 1.0 × 10 ⁶ to about 3.0 × 10 ⁶ Having a MWD in the range of about 4.0 to about 15.0, and a melting point of 134 degrees Celsius or higher, (iii) PP is about 0.9 × 10 ⁶ to about 2.0 × 10 ⁶ Mw in the range, for example a MWD of 8.5 or less, such as in the range of 2.0 to 8.5, for example in the range of 2.5 to 6.0, and for example An isotactic PP having a ΔHm of 90.0 J / g or greater, such as 0 J / g or greater; (iv) the membrane is microporous; and (v) the membrane is, for example, 8.0 micrometers. It has a thickness of 0 micrometer or less. The weight percent is based on the weight of the membrane. Optionally, the membrane contains 1.0 wt% or less of PE1 based on the weight of the membrane. Such membranes have a melt down temperature of 145.0 degrees Celsius or higher, such as 150.0 degrees Celsius or higher, a normalized electrolyte affinity of 0.16 seconds / micrometer or lower, such as 0.14 seconds / micrometer or lower, and 2 It has a normalized puncture strength of less than 90 × 10 ² mN / micrometer. If desired, the film is a single layer film. Optionally, the combined weight of PE1, PE2, and PP is 95.0% by weight or more, such as 98.0% by weight or more, for example 99.0% by weight or more, of the weight of the membrane.

  Without being limited thereto, the present invention encompasses the use of the membrane of any of the previous embodiments as a battery separator film in a lithium ion polymer battery, particularly a secondary lithium ion polymer battery. Although not wishing to be bound by any theory or model, using PE2 instead of PE1 while maintaining the relative amounts of PP and PE3 in the membrane nearly constant increases the affinity of the membrane for the polymer electrolyte. It is believed that the strength of the film will decrease.

Hereinafter, the manufacturing method of a microporous film is demonstrated in detail. The present invention will be described with respect to a monolayer film produced by extrusion, but the present invention is not limited thereto and this description is intended to exclude other embodiments that are within the broader scope of the invention. Not what you want.
Membrane manufacturing method

  In one or more embodiments, the microporous membrane comprises a first polymer (ie, PE) and a second polymer (ie, PP), a diluent (eg, by dry or melt mixing), and an inorganic filler. Etc., can be produced by mixing with components that are optional to form 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, a blend of PE1 and / or PE2, PE3, and PP may be combined with a diluent such as liquid paraffin to form a mixture, and the mixture is extruded and processed to a thickness of 12.0 micrometers or less. A single layer film is formed. If desired, an additional layer may be applied to the extrudate, for example, to provide a final membrane with a low shutdown function. In other words, a multilayer film may be formed by laminating or coextruding a single layer extrudate or a single layer microporous film.

In one or more embodiments, the membrane manufacturing process includes stretching the extrudate in at least one direction prior to diluent removal. In these or other embodiments, the process includes stretching the film in at least one direction after diluent removal. The film manufacturing process may include, for example, removing at least a portion of any remaining volatile species from the film at any time after removal of the diluent, heat treating the film before or after the removal of the diluent (heat setting). Or an annealing step or the like. If desired, optional steps such as solvent treatment, heat setting, crosslinking with ionizing radiation, and hydrophilic treatment described in PCT Publication WO2008 / 016174 may be performed. The number or order of these optional steps is not critical.
Production of polymer-diluent mixture

  In one or more embodiments, the first and second polymers (as described above, eg, PE1 (and / or PE2) and PE3 as the first polymer, and PP as the second polymer) Introduced and mixed with one or more diluents to form a polymer-diluent mixture. For example, the first and second polymers may be combined to form a polymer blend, and this blend may be combined with a diluent (which may be a mixture of diluents, such as a solvent mixture) to form a polymer-diluent mixture. Manufacturing. Mixing may be performed in an extruder such as a reactive extruder. These extruders include, but are not limited to, twin screw extruders, ring extruders, and planetary multi-screw extruders. The practice of the present invention is not limited to the type of extruder used. Any optional species such as fillers, antioxidants, stabilizers, and / or heat resistant polymers may be included in the polymer-diluent mixture. The type and amount of these optional species may be the same as those described in PCT Publication Nos. WO 2007/132294, WO 2008/016174, and WO 2008/140835, all of which are The entirety of which is incorporated herein by reference.

  The diluent is usually compatible with the polymer used to produce the extrudate. For example, the diluent may be any species or combination of species that can combine with the resin at the extrusion temperature to form a single phase. Examples of diluents include one or more of aliphatic or cyclic hydrocarbons such as nonane, decane, decalin, and paraffin oil, and phthalates such as dibutyl phthalate and dioctyl phthalate. For example, paraffin oil having a kinematic viscosity of 20 to 200 cSt at 40 degrees Celsius may be used. The diluent may be the same as described in US Patent Publication Nos. 2008/0057388 and 2008/0057389, both of which are incorporated by reference in their entirety.

In some embodiments, the polymer blend in the polymer-diluent mixture includes an amount of A ₁ of the first polymer (eg, PE1 and PE3) and an amount of A ₂ of the second polymer (eg, PP). In some embodiments, A ₁ is greater than or equal to 1.0 wt%, for example in the range of 80.0 wt% to 96.0 wt%, and A ₂ is in the range of 4.0 wt% to 20.0 wt%. is (weight percentage of a ₁ and a ₂ are the weight of the polymer in the mixture is the reference). Optionally, _{A 1} is in the range of 84.5 wt% ～95.5 wt%, such a range of, for example, 94.75 wt% ～95.25 wt%. Optionally, _{A 2,} based on the total weight of the polymer in the mixture is in the range of 4.5 wt% ～15.5 such a range of, for example, 4.75 to 5.25 wt%. Optionally, the polymer-diluent mixture includes up to 45.0% by weight of polymer, based on the weight of the mixture, for example, 30.0% to 40.0% by weight, based on the total weight of polymer in the mixture. It is a range. The remaining part of the mixture may be a diluent.

In one or more embodiments, the polymer - PE in the amount of _{A 1} in the diluent mixture may include a PE3 amount of PE1 and / or PE2 and _{B 2} in an amount of _{B 1.} In some embodiments, B ₁ is in the range of 60.0 wt% to 96.0 wt%, and B ₂ is in the range of 0.0 wt% to 20.0 wt% (of B ₁ and B ₂ The weight percent is based on the weight of the polymer in the mixture). Optionally, B ₁ is in the range of 69.5 wt% to 90.5 wt%, such as in the range of 80.0 wt% to 85.0 wt%, based on the total polymer in the mixture. If desired, _{B 2} is such total polymer the range of, for example 9.75 wt% ～15.25 wt% based on the mixture, ranges from 5.0 wt% to 15.0.

In some embodiments, the polymer-diluent mixture during extrusion is exposed to a temperature in the range of 140 degrees Celsius to 250 degrees Celsius, such as 210 degrees Celsius to 230 degrees Celsius.
Extrudate manufacturing

  In some embodiments, the polymer-diluent mixture is directed from an extruder through a die to produce an extrudate. The extrudate should have an appropriate thickness to produce a final membrane having the desired thickness (usually 12.0 micrometers or less) after the processing step. For example, the extrudate may have a thickness in the range of about 1.0 micrometer to about 10.0 micrometers, or about 3.0 micrometers to about 8.0 micrometers. In one or more embodiments, the final film has a final film thickness (after processing) of 12.0 micrometers or less, such as 10.0 micrometers or less.

  Extrusion is usually performed using a molten polymer-diluent mixture. When using a sheet forming die, the die lip is typically heated to an elevated temperature, for example in the range of 180 degrees Celsius to 240 degrees Celsius. Suitable processing conditions for carrying out the extrusion are disclosed in PCT Publications WO2007 / 132294 and WO2008 / 016174.

If desired, the extrudate can be exposed to temperatures ranging from about 10 degrees Celsius to about 45 degrees Celsius 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 degrees Celsius / minute until the temperature of the extrudate (cooled temperature) is approximately the same as (or below) the gel temperature of the extrudate. . The cooling treatment conditions may be the same as those disclosed in, for example, PCT Publication No. WO2007 / 132294, WO2008 / 016174, and WO2008 / 140835.
Stretching of extrudate (upstream stretching)

  The extrudate or chilled extrudate may be stretched in at least one direction, for example a planar direction such as MD or TD (referred to as “upstream stretching” or “wet stretching”). Such stretching is believed to cause the polymer in the extrudate to stretch in at least some directions. This stretching is called “upstream” stretching. The extrudate can be stretched, for example, by the tenter method, roll method, inflation method, or combinations thereof as described in PCT Publication No. WO 2008/016174, for example. Stretching may be uniaxial or biaxial, and in certain embodiments the extrudate is stretched biaxially. In the case of biaxial stretching, either simultaneous biaxial stretching, sequential stretching, or multistage stretching (eg, a combination of simultaneous biaxial stretching and sequential stretching) may be used, and in certain embodiments, the extrudate is Stretch to the axis. When using biaxial stretching, the magnitude of the magnification need not be the same in each stretching direction.

  In the case of uniaxial stretching, the stretching ratio may be 2 times or more, for example, 3 to 30 times. In the case of biaxial stretching, the stretching ratio may be 3 times or more in any direction, that is, the area ratio may be 9 times or more, for example, 16 times or more, for example, 25 times or more. Examples of this stretching step include stretching at an area magnification of about 9 times to about 49 times. Again, the amount of stretching in each direction need not be the same. The magnification has a multiplicative effect on the size of the film. For example, a film having an initial width (TD) of 2.0 cm that is stretched by 4 times the TD has a final width of 8.0 cm.

  Stretching may be performed while subjecting the extrudate to temperatures in the range of approximately Tcd temperature to Tm (upstream stretching temperature), although Tcd and Tm are the crystal dispersion temperatures and most of the polyethylene used to produce the extrudate. It is defined as the melting point of PE having a low melting point (usually PE such as PE1 or PE3). The crystal dispersion temperature is determined by measuring the temperature characteristics of dynamic viscoelasticity according to ASTM D 4065. In embodiments where the Tcd ranges from about 90 degrees Celsius to about 100 degrees Celsius, the stretching temperature is, for example, 108.0 degrees Celsius to 116.0 degrees Celsius, such as 110.0 degrees Celsius to 114.0 degrees Celsius. 90.0 degrees Celsius to 122.0 degrees Celsius.

When a sample (eg, extrudate, dry extrudate, membrane, etc.) is exposed to high temperatures, such exposure can be done by heating the air and then carrying the heated air close to the sample. The temperature of the heated air is usually controlled to a set value equal to the desired temperature, and then directed toward the sample through a plenum or the like. Other methods of exposing the sample to high temperatures may be used with or in place of heated air, including conventional methods such as exposing the sample to a heated surface, infrared heating in an oven, and the like.
Diluent removal

  In some embodiments, at least a portion of the diluent is removed (or replaced) from the stretched extrudate to form a dry film. For example, as described in PCT Open Publication No. WO 2008/016174, a diluent (or “wash”) solvent may be used to remove (wash or replace) the diluent.

In some embodiments, at least a portion of any remaining volatile species (eg, cleaning solvent) is removed from the dry film after diluent removal. Any method capable of removing the cleaning solvent may be used, including conventional methods such as heat drying and air drying (moving air). The processing conditions for removing volatile species such as cleaning solvents may be the same as those disclosed, for example, in PCT Publication No. WO2008 / 016174.
Optional film stretching (downstream stretching)

  The dry membrane may be stretched in at least one direction, eg MD and / or TD (referred to as “downstream stretching” or “dry stretching” because at least a portion of the diluent is removed or moved). Such stretching is thought to cause the polymer in the film to stretch in at least some directions. This stretching is called downstream stretching. Prior to downstream stretching, the dry membrane has an initial size of MD (first dry length) and an initial size of TD (first dry width). As used herein, the term “first drying width” refers to the size of a dry film to TD before the start of dry stretching. The term “first dry length” refers to the size of the dry film to MD before the start of dry stretching. For example, a tenter stretching apparatus of the type described in WO2008 / 016174 can be used.

  The dried film is first dried at a magnification (“MD dry draw ratio”) in the range of about 1.0 to about 1.6, such as in the range of about 1.1 to 1.5, from the first dry length. You may extend to MD to the 2nd dry length longer than length. In the case of using TD dry stretching, the dry film may be stretched in TD from the first dry width to a second dry width wider than the first dry width at a certain ratio (“TD dry stretch ratio”). . If desired, the TD dry stretch ratio is greater than or equal to the MD dry stretch ratio. The TD dry draw ratio may be in the range of about 1.1 to about 1.6, for example about 1.1 to 1.5. Dry stretching may be sequential or simultaneous with MD and TD. If biaxial dry stretching is used, the dry stretching may be simultaneous with MD and TD or sequential. When dry stretching is sequential, MD stretching is usually performed first, followed by TD stretching.

  In certain embodiments, especially when considering the thickness of certain films produced according to the present invention, dry stretching is avoided or minimized when practicing embodiments of the present invention. For example, the process of producing a membrane film having a desired thickness does not include any dry stretching process. In other embodiments, the processing step includes dry stretching to a magnification of 1.1 or less, in other embodiments 1.08 or less, in other embodiments 1.05 or less, and other embodiments. Then, it is 1.03 or less.

  The dry stretching may be performed while subjecting the dry film to a temperature below Tm (downstream stretching temperature), for example, in the range of about Tcd—20 degrees Celsius to Tm. In some embodiments, the stretching temperature is about 70.0 degrees Celsius to about 135 degrees Celsius, such as about 110.0 degrees Celsius to about 132.0 degrees Celsius, such as about 120.0 degrees Celsius to about 130.0 degrees Celsius. Performed on membranes exposed to temperatures in the range of 0 degrees.

  In some embodiments, the MD dry draw ratio is about 1.0 and the TD dry draw ratio is 1.6 or less, such as in the range of about 1.05 to about 1.5, such as about 1.1 to 1.5. And the dry stretching is performed while subjecting the membrane to a temperature in the range of about 120.0 degrees Celsius to about 130.0 degrees Celsius.

The dry stretching speed is not critical. In some embodiments, the dry stretching speed is 1% / second or more in the stretching direction (MD or TD), and the speed can be independently selected for MD and TD stretching. Optionally, the stretching speed is 2% / second or more, such as 3% / second or more, for example 10% / second or more. In one embodiment, the stretch rate ranges from 2% / second to 25% / second. Although not particularly important, the upper limit of the stretching speed may be 50% / second in order to prevent rupture of the film.
Controlled film width reduction

  Following dry stretching, optionally into a dry film, from the second dry width to a third dry width that is in the range of 0.9 times the first dry width to about 1.5 times the first dry width. A controlled width reduction may be applied. If desired, 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. . Typically, the width reduction is about 70.0 degrees Celsius to about 135 degrees Celsius, for example, about 110.0 degrees Celsius to about 132.0 degrees Celsius, for example, about 120.0 degrees Celsius to about 130.0 degrees Celsius. The film is exposed to a temperature in the range of 0 ° C. while the film is exposed to a temperature that is Tcd−30 ° C. or more but Tm or less.

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 to which the film is exposed during controlled width reduction is: It is 1.01 times or more of the downstream stretching temperature, for example, a range of 1.05 times to 1.1 times. In some embodiments, the reduction in the width of the membrane is performed while subjecting the membrane to a temperature of 130.0 degrees Celsius or less, and the third drying width is in the range of 0.95 to 1.05 of the first drying width. .
Heat set

  Optionally, the film is heat treated (heat set) at least once following removal of the diluent, for example after dry stretching, after controlled width reduction, or both. It is considered that the crystal is stabilized by heat setting and a uniform thin layer is formed in the film. In one form, the heat set ranges from, for example, about 70.0 degrees Celsius to about 135.0 degrees Celsius, such as from about 110.0 degrees Celsius to about 132.0 degrees Celsius, such as from about 120.0 degrees Celsius to about 13 degrees Celsius. The film is exposed to a temperature in the range of Tcd to Tm, such as 130.0 degrees Celsius.

  The heat set temperature may be the same as the downstream stretching temperature, but this is not essential. In one embodiment, the temperature to which the film is exposed during heat setting ranges from 1.01 times the downstream stretching temperature, such as from 1.05 times to 1.1 times. Usually, the heat setting is performed for a time sufficient to form a thin layer in the film, such as a time in the range of 1000 seconds or less, for example 1 to 600 seconds. In some embodiments, the heat set is performed under typical heat set “heat set” conditions. The term “heat setting” refers to heat setting performed while maintaining the membrane length and width substantially constant, for example, by holding the outer periphery of the membrane with a tenter clip during heat setting.

  If desired, an annealing treatment may be performed after the heat setting step. Annealing is a heat treatment that does not apply a load to the film, and may be performed using, for example, a heating chamber equipped with a belt conveyor or an air-floating-type heating chamber. Annealing may be performed continuously with the tenter loosened after heat setting. During annealing, the membrane may be exposed to a temperature in the range of Tm or lower, such as in the range of about 60 degrees Celsius to about Tm—about 5 degrees Celsius. It is considered that the air permeability and strength of the microporous membrane are improved by annealing.

Optional hot roller treatment, hot solvent treatment, crosslinking treatment, hydrophilic treatment, and coating treatment may be performed if desired, as described, for example, in PCT Publication No. WO 2008/016174.
Membrane properties

  In one or more embodiments, the membrane is a microporous membrane that is permeable to liquids (aqueous and non-aqueous) at normal pressure. Therefore, the membrane can be used as a battery separator, a filtration membrane or the like. The membrane is particularly useful as a BSF for secondary batteries such as nickel metal hydride batteries, nickel cadmium batteries, nickel zinc batteries, silver zinc batteries, lithium ion batteries, lithium ion polymer batteries and the like. In one embodiment, the present invention relates to a lithium ion secondary battery containing BSF including a membrane. Such a battery is described in PCT Patent Publication No. WO 2008/016174, which is incorporated herein by reference in its entirety.

  In one or more embodiments, the microporous membrane is a single layer useful as a BSF for a polymer battery, such as a lithium ion polymer battery. As used herein, the term “polymer electrolyte” is used in its ordinary sense and refers to an electrolyte within a polymer battery. As will be appreciated by those skilled in the art, a polymer battery includes an electrolyte, such as lithium ion, that is dispersed, suspended, or dissolved in a polymer medium. Thus, electrolyte affinity or air permeability refers to the ability of polymer media and / or electrolytes such as lithium ions to permeate the membrane.

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

In some embodiments, the final film thickness is 12.0 micrometers or less, such as 10.0 micrometers or less, such as in the range of about 1.0 micrometers to about 10.0 micrometers. For example, the monolayer film may have a thickness in the range of about 4.5 micrometers to about 9.5 micrometers. The thickness of the film can be measured, for example, with a contact thickness meter over a width of 10 cm at intervals of 1 cm in the vertical direction, and then the average value can be obtained to obtain the film thickness. Thickness gauges such as 746-3 Gokanjima, Fuji City, Shizuoka Prefecture 416-0946, Model RC-1 rotary caliper manufactured by Meisho Co., Ltd., or “Lightmatic” manufactured by Mitutoyo Corporation are suitable. Non-contact thickness measurement methods such as optical thickness measurement methods are also suitable.
Porosity

The porosity of the membrane is to compare the actual weight of the membrane with the weight of an equivalent non-porous membrane of 100% polymer (equal in the sense of having the same polymer composition, length, width, and thickness) According to the conventional method. Next, the porosity is determined using the following formula: Porosity (expressed in percent) = 99% × (w1 / w2). Where “w1” is the actual weight of the membrane and “w2” is the weight of an equivalent non-porous membrane (of the same polymer) having the same size and thickness. In some embodiments, the porosity of the membrane is 20.0% or higher, such as 31.0% or higher, such as 35.0% or higher. For example, the porosity of the membrane may be in the range of 20.0% to 80.0%, such as 36.0% to 40.0%.
Standardized air permeability

In certain embodiments, the membrane is, for example, from about 10.0 seconds / 100 cm ³ / micrometer to about 45.0 seconds / 100 cm ³ / micrometer, such as from about 15.0 seconds / 100 cm ³ / micrometer to about 40. It has a normalized air permeability of 50.0 seconds / 100 cm ³ / micrometer or less, such as a range of 0 seconds / 100 cm ³ / micrometer. Since the air permeability value is normalized to the value of an equivalent film having a film thickness of 1.0 micrometers, the air permeability value of the film is expressed in units of “seconds / 100 cm ³ / micrometer”. The normalized air permeability is measured in accordance with JIS P8117, and the result is obtained from an equivalent film having a thickness of 1.0 micrometer, using the formula A = 1.0 micrometer × (X) / T _1. Normalize to the air permeability value. Where X is the measured value of the air permeability of the membrane having the actual thickness T ₁ and A is the normalized air permeability of an equivalent membrane having a thickness of 1.0 micrometers.
Standardized puncture strength

The puncture strength of the membrane is expressed as the puncture strength of an equivalent membrane having a thickness of 1.0 micrometers and a porosity of 30% and has a unit of [mN / micrometer]. Puncture strength, the thickness T ₁ ends spherical membrane having a (radius of curvature R: 0.5 mm) maximum load was measured at ambient temperature when piercing at a speed of 2 mm / sec in diameter 1mm needle is, as defined Is done. This puncture strength (“S”) is expressed as S ₂ = [30% * 1.0 micrometers * (S ₁ )] / [T ₁ * (100% −P)] (where S ₁ is the puncture strength. Measured values, S ₂ is the normalized puncture strength, P is the measured value of the membrane porosity, and T ₁ is the average thickness of the membrane). And a puncture strength value of an equivalent film having a thickness of 30% and a porosity of 30%. In some embodiments, the normalized puncture strength of the membrane is 2.50 × 10 ² mN / micrometer or greater, eg, 2.90 × 10 ² mN / micrometer or greater. If desired, the normalized puncture strength of the membrane is greater than or equal to 3.0 × 10 ² mN / micrometer, for example in the range of 3.05 × 10 ² mN / micrometer to 4.5 × 10 ² mN / micrometer. .
Shutdown temperature

The shutdown temperature of the microporous membrane is measured by the method disclosed in PCT Publication No. WO2007 / 052663, which is incorporated herein by reference in its entirety. According to this method, the microporous membrane is exposed to a temperature starting at 25 degrees Celsius and rising (5 degrees Celsius / minute), during which the air permeability of the membrane is measured. The shutdown temperature of the microporous membrane is defined as the temperature at which the air permeability (Gurley value) of the microporous membrane first exceeds 1.0 × 10 ⁵ seconds / 100 cm ³ . The air permeability of the microporous membrane is measured according to JIS P 8117 using an air permeability meter (Asahi Seiko Co., Ltd., EGO-1T). In some embodiments, the shutdown temperature is 136 degrees Celsius or less, such as in the range of 132.5 degrees Celsius to 134.5 degrees Celsius.
Meltdown temperature

The shutdown temperature of the microporous membrane is measured using a procedure similar to the measurement of the shutdown temperature. According to this method, the microporous membrane is exposed to a temperature (5 degrees Celsius / minute) that starts at 25 degrees Celsius and rises above the shutdown temperature of the film, during which time the air permeability of the film is measured. Membrane heating is continued, and the temperature at which the air permeability (Gurley value) of the microporous membrane first decreases to a value of 1.0 × 10 ⁵ seconds / 100 cm ³ is defined as the meltdown temperature of the microporous membrane. The air permeability of the microporous membrane is measured according to JIS P 8117 using an air permeability meter (Asahi Seiko Co., Ltd., EGO-1T). In some embodiments, the meltdown temperature of the films of the present invention is 145.0 degrees Celsius or higher, such as 150.0 degrees Celsius or higher, such as 160.0 degrees Celsius or higher. In some embodiments, the meltdown temperature is in the range of 146.0 degrees Celsius to 170.0 degrees Celsius, such as in the range of 150.0 degrees Celsius to 165 degrees Celsius.
105 degrees Celsius heat shrink

In certain embodiments, the membrane is in degrees Celsius in at least one planar direction (eg, MD or TD), for example in the range of 10.0% or less, 6.0% or more, eg, 1.0% to 5.0%. It has a thermal shrinkage at 105 degrees. The shrinkage of the membrane at 105.0 degrees Celsius to MD and TD is measured as follows: (i) The microporous membrane specimen size at ambient temperature is measured for both MD and TD; ) The microporous membrane specimen is allowed to equilibrate for 8 hours at a temperature of 105 degrees Celsius with no load, and then (iii) the membrane size is measured for both MD and TD. Thermal (ie, “thermal”) shrinkage to MD and TD can be obtained by dividing the measurement result (i) by the measurement result and (ii) expressing the resulting quotient as a percentage.
Tensile strength

In certain embodiments, the membrane has, like the range of, for example, ^{1.5 × 10 5 kPa~2.0 × 10 5} kPa, the MD and TD tensile strength of at least the 1.4 × ¹⁰ 5 kPa. Tensile strength is measured for MD and TD according to ASTM D-882A.
Standardized electrolyte affinity

  A film sample of 50 mm × 50 mm (thickness is 12.0 micrometers or less) is prepared and placed flat on a glass substrate having a larger area than the film. The film is irradiated from above using visible light, but the film is opaque at the start of measurement. A 500.0 microL drop of propylene carbonate (purity> 99% by volume) is applied to the surface of the film using a 25 degree Celsius +/- 3 degree Celsius film. The electrolyte affinity (“EA”) of a membrane is defined as the average elapsed time from when a droplet first contacts the film until the film becomes transparent. Repeat the measurement 5 times to obtain the average value.

  Normalized electrolyte affinity ("NEA") is defined as EA / (average film thickness, units: micrometers). NEA has [second / micrometer] as a unit. In some embodiments, the membrane has a NEA of 5.0 seconds / micrometer or less, such as 2.5 seconds / micrometer or less, such as in the range of 0.1 second / micrometer to 0.9 seconds / micrometer. Have.

The invention will now be described in more detail with reference to the following examples, without intending to limit the scope of the invention.
Example 1

(1) Preparation of polymer-diluent mixture A polymer-diluent mixture is prepared as follows by combining a polymer blend of two types of polyethylene, PE1 and PE3 and PP, and a diluent. The polymer blend has (a) 5.6 × 10 ⁵ Mw, 4.0 MWD, a terminal unsaturation amount of less than 0.14 per 1.0 × 10 ⁴ carbon atoms, and a Tm of 136.0 degrees Celsius. (B) 1.9 × 10 ⁶ Mw, 5.1 MWD, and 5.0 wt% PE (PE3 with a Tm of 136.0 degrees Celsius) ), And (c) 5.0 wt% isotactic PP (PP2) having a Mw of 5.3 × 10 ⁵ and a ΔHm of about 80 J / g (weight percentages are based on the weight of the combined polymers) including.

  Next, 35.0% by weight of the polymer blend was loaded into a strongly mixed twin screw extruder having an inner diameter of 58 mm and an L / D of 42, and 65.0% by weight liquid paraffin (50 cst at 40 degrees Celsius). ) To the twin screw extruder via the side feeder. Mixing is performed at 220 degrees Celsius and 320 rpm to produce a polymer-diluent mixture (weight percentages are based on the weight of the polymer-diluent mixture).

(2) Membrane preparation The polymer-diluent mixture is led from an extruder to a sheet forming die to form an extrudate (in the form of a sheet). The die temperature is about 210 degrees Celsius (as specifically shown in Table 1). The extrudate is cooled by contact with a cooling roller controlled at 20 degrees Celsius. The cooled extrudate is simultaneously biaxially stretched (upstream stretched) in a tenter stretcher at a magnification of 5 times for both MD and TD at approximately 112.5 degrees Celsius (as specifically shown in the table). The stretched three-layer gel-like sheet is then immersed in a methylene chloride bath controlled at 25 degrees Celsius to remove liquid paraffin and 1.0 weight based on the weight of liquid paraffin in the polymer-diluent mixture. % Or less. The membrane is then dried with a stream of room temperature. The membrane is then heat set at 128.8 degrees Celsius (as described in the table) for 10 minutes while maintaining the membrane size approximately constant to produce the final microporous membrane. Selected starting materials, processing conditions, and membrane properties are shown in Table 1.
Example 2

考察 Example 1 is repeated except as noted in Table 1. Starting materials and processing conditions are the same as those used in Example 1 except as noted in the table. For example, PP1 may be replaced with a polypropylene (PP1) having a Mw of 1.1 × 10 ⁶ and a ΔHm of 114 J / g, and PE1 is 7.46 × 10 ⁵ Mw, Tm of 134.0 degrees Celsius, and It may be replaced with PE (PE2) having a terminal unsaturation amount of 0.20 or more per ^four carbon atoms 1.0 × 10 ⁴ . The membranes of Examples 4 and 5 were exposed to a temperature of 130.2 degrees Celsius (Example 4) and 130.0 degrees Celsius (Example 5), respectively, prior to heat setting while downstream of diluent removal. Stretch to a TD magnification of 4 (downstream stretching).

Consideration

  From Examples 1-5, a relatively thin microporous membrane having a useful meltdown temperature (eg, 145.0 degrees Celsius or higher) is made from PE and 4.0 wt% or higher PP based on the weight of the membrane. I understand that I can do it. Such membranes are useful as BSFs for lithium ion batteries such as lithium ion polymer batteries that utilize thin BSF. As Example 5 shows, increasing the concentration of PP significantly increases NEA. For membranes containing more than 20.0 wt% PP, the higher the NEA value, the more difficult it is to use the membrane as a BSF for polymer batteries. In other words, the data shows that while a limiting amount of PP is necessary to achieve a useful meltdown temperature, increasing the PP amount has an undesirable effect on NEA. Comparative Example 1 shows BSF containing no PP. Such membranes have a useful NEA, but also have a relatively low meltdown temperature, a relatively low porosity, and a relatively low normalized puncture strength.

  All patents, test procedures, and other references cited herein, including priority documents, are fully incorporated by reference, and such incorporation is permitted, to the extent that such disclosure does not contradict the present invention. All permissions are fully integrated.

  Although the exemplary forms disclosed herein are described with particularity, various other modifications will be apparent to those skilled in the art and depart from the spirit and scope of the disclosure by those skilled in the art. It will be understood that this can be done easily without Accordingly, the scope of the claims appended hereto is not limited to the examples and descriptions set forth herein, which are claimed by those skilled in the art to which this disclosure belongs. It is intended to be construed as including all patentable, novel features provided herein, including all features treated as equivalents.

  Where numerical lower limits and numerical upper limits are listed herein, ranges from any lower limit to any upper limit are contemplated.

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

Claims (23)

1.0 wt% or more of polyethylene, 5.0 × 10 ⁵ or more of Mw and 80.0 J / g or more of ΔHm, 4.0 wt% to 20.0 wt based on the weight of the polymer in the membrane % Of polypropylene and is microporous and has a thickness of 12.0 micrometers or less.   The membrane of claim 1 wherein the amount of polypropylene ranges from 4.5 wt% to 15.5 wt%, based on the weight of the membrane, and the membrane has a thickness of 10.0 micrometers or less.   The membrane according to claim 1 or 2, having a meltdown temperature of 145.0 degrees Celsius or higher and a normalized electrolyte affinity of 2.5 seconds / micrometer or lower. Having a porosity in the range of 20% to 80%, a normalized air permeability of 50.0 sec / 100 cm ³ / micrometer or less, and a standardized puncture strength of 2.5 × 10 ² mN / micrometer or more, The membrane according to any one of claims 1 to 3. The polypropylene has an Mw of 6.0 × 10 ⁵ or more, an MWD of 8.5 or less, and a ΔHm of 90.0 J / g or more, and an isoform of 90.0% by weight or more based on the weight of the polymer in the film. The film according to any one of claims 1 to 4, comprising tactic polypropylene. (I) polyethylene, and a second polyethylene having a first polyethylene and 1.0 × 10 ⁶ Mw of at least having a Mw of less than 1.0 × 10 ^6, it is (ii) a first polyethylene 69 Present in an amount of B ₁ ranging from 5% to 90.5% by weight, and (iii) a second polyethylene is present in an amount of B ₂ ranging from 5.0% to 15.0% by weight. 6. A membrane according to claims 1-5 (weight percent is based on the weight of polymer in the membrane).   Based on the weight of the polymer in the membrane, the amount of the first polyethylene is in the range of 72.0 wt% to 90.0 wt%, and the amount of the second polyethylene is 5.0 wt% to 20.0 wt%. The membrane of claim 6, wherein the amount of polypropylene is in the range of 5.0 wt% to 8.0 wt%. The first polyethylene has an Mw in the range of 4.0 × 10 ^{5 to} 6.0 × 10 ⁵ and an MWD in the range of 3.0 to 10.0, and the second polyethylene is 1.0 × 10 ⁶ to 8. The membrane of claim 7, having a Mw in the range of 3.0 x 10 < ⁶ > and a MWD in the range of 4.0 to 15.0. 9. The membrane of claim 8, wherein the first polyethylene has a terminal unsaturation amount of less than 0.20 per 1.0 × 10 ⁴ carbon atoms.   The battery separator film containing the microporous film as described in any one of Claims 1-9. A manufacturing process of a microporous membrane,
(1) a step of extruding the mixture of diluent and polymer, the polymer comprises polypropylene in an amount of polyethylene and A ₂ in the amount of A _1, polymer - based on the weight of the polymer in the polymer in a diluent mixture step a ₁ is 1.0 wt% or more, _{a 2} is in the range of 4.0 wt% to 20.0 wt%;
(2) stretching the extrudate in at least one planar direction; and (3) removing at least a portion of the diluent from the stretched extrudate. A ₁ is a polymer - in the range of 84.5 wt% ～95.5 wt% based on the weight of the polymer in the diluent mixture, a polyethylene having a Mw of less than 1.0 × 10 ^6, in claim 11 The method described. (I) _{A 2} is in the range of 4.5 wt% ～15.5 wt%, (ii) polypropylene, the weight of more than 90.0% by weight, based on polypropylene, 6.0 × 10 ⁵ or more 13. The method of claim 11 or 12, comprising isotactic polypropylene having a Mw, an MWD of 8.5 or less, and a [Delta] Hm of 90.0 J / g or more. (I) polyethylene, and a second polyethylene having a first polyethylene and 1.0 × 10 ⁶ Mw of at least having a Mw of less than 1.0 × 10 ^6, the total of (ii) polymer in the mixture The first polyethylene is present in an amount of B ₁ in the range of 69.5% to 90.5% by weight, based on weight, and (iii) the second polyethylene is 5.0% to 15.0% by weight. present in an amount of B ₂ in the range a method according to any one of claims 11 to 13.   15. The method according to any one of claims 11 to 14, further comprising the step of cooling the extrudate prior to step (2).   16. The method according to any one of claims 11 to 15, further comprising the step of stretching the membrane in at least one direction following step (3) and the step of subjecting the membrane to a heat treatment following step (3).   The method according to claim 16, wherein the stretching direction is TD.   The stretching of step (2) is performed biaxially at a magnification ranging from 9 to 49 times in area, while subjecting the extrudate to a temperature ranging from 90.0 degrees Celsius to 125.0 degrees Celsius. The method according to any one of 11 to 17.   19. A method according to any one of claims 11 to 18, further comprising the step of removing any residual volatile species from the film after step (3).   The film product according to any one of claims 11 to 19.   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 membrane according to claim 1.   The battery of claim 21, wherein the membrane has a thickness of 10.0 micrometers or less and the battery is a lithium ion polymer battery.   An electric vehicle or a hybrid electric vehicle including power means electrically connected to the battery according to claim 21.