JP2012077220A - Method for producing polyolefin resin composition, and method for producing porous film made of polyolefin resin - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a uniformly-kneaded polyolefin resin composition, when producing a resin composition by using a high-molecular weight polyolefin.SOLUTION: In this method for producing a polyolefin resin composition, an ultra-high-molecular weight polyolefin (component A) whose weight-average molecular weight is one million or more, and polyolefin wax (component B) whose weight-average molecular weight is 500-3,000 are kneaded at the weight ratio of component A/component B=30/70-90/10, and then a polyolefin (component C) whose weight-average molecular weight is 50,000-800,000 is added and kneaded furthermore. In the method for producing the polyolefin resin composition, a filler is added and kneaded at an optional point of time.

Description

The present invention relates to a method for producing a polyolefin resin composition and a method for producing a polyolefin resin porous film.

Polyolefin resin porous films are used in various applications such as sanitary materials, medical materials, and battery separators. Among them, a polyolefin resin porous film used as a separator of a lithium ion secondary battery is required to have high strength, and therefore a film using ultrahigh molecular weight polyolefin is used.

As a method for producing a porous film using an ultrahigh molecular weight polyolefin, a high molecular weight polyolefin having a weight average molecular weight of 5 × 10 ⁵ or more, a thermoplastic resin having a weight average molecular weight of 2 × 10 ⁴ or less, and fine particles are used. A method for producing a porous film by kneading and forming into a sheet and then stretching the sheet is known (see Patent Document 1).

JP 2002-69221 A

However, when a homogeneous porous film is produced for a long time by the above-described method, it is necessary to strictly control the kneading conditions, and further improvement in workability is required.
In general, when a resin is processed, it is said that the wider the molecular weight distribution of the resin, the better the processability. On the other hand, when processing a resin composition having a broad molecular weight distribution obtained by mixing two or more types of resins having different molecular weights, it is said that the smaller the difference in the molecular weight of the components to be mixed, the easier it is to knead uniformly. It has been broken. Therefore, when kneading a high molecular weight polyolefin having a molecular weight of 500,000 or more and a thermoplastic resin having a molecular weight of 2000 or less as described in Patent Document 1, a polyolefin having a molecular weight intermediate between these two components is added. It is considered that this is easier to knead uniformly.
However, it is difficult to knead uniformly even if a high molecular weight polyolefin having a molecular weight of 500,000 or more, a polyolefin having a molecular weight of several thousand or less, two components having greatly different molecular weights, and a polyolefin having a molecular weight therebetween are kneaded at the same time. there were.

An object of the present invention is to produce a uniformly kneaded polyolefin-based resin composition when a resin composition is produced using a polyolefin having a high molecular weight, a porous film and a laminated porous material using the resin composition And a battery including a porous film or a laminated porous film obtained by the method.

That is, the present invention relates to [1] to [4].
[1] Ultra high molecular weight polyolefin (component A) having a weight average molecular weight of 1 million or more, and polyolefin wax (component B) having a weight average molecular weight of 500 to 3000, component A / component B = 30/70 to 90/10 A method for producing a polyolefin-based resin composition in which a polyolefin (component C) having a weight average molecular weight of 5 to 800,000 is added and further kneaded after kneading at a weight ratio of 1 to 5.
[2] The method for producing a polyolefin resin composition according to [1], wherein a filler is added and kneaded at an arbitrary time.
[3] A method for producing a polyolefin resin porous film in which a sheet is produced using the polyolefin resin composition obtained by the method of [2], and then the sheet is stretched at least in a uniaxial direction.
[4] A method for producing a polyolefin resin porous film through the following two steps after producing a sheet using the polyolefin resin composition obtained by the method of [2] above.
(1) Step of stretching the sheet in at least uniaxial direction (2) Step of removing inorganic filler from the sheet [5] Inorganic filler to polyolefin resin porous film obtained by the method of [3] or [4] The manufacturing method of the laminated porous film which laminates | stacks the porous layer containing this.
[6] A battery comprising a polyolefin resin porous film obtained by the method of [3] or [4], or a laminated porous film obtained by the method of [5].

  ADVANTAGE OF THE INVENTION According to this invention, when manufacturing a resin composition using polyolefin with high molecular weight, the polyolefin resin composition kneaded uniformly can be provided. By using this composition, a porous film or a laminated porous film can be provided, and a battery can be provided using these films.

  In the present invention, an ultra-high molecular weight polyolefin (component A) having a weight average molecular weight of 1,000,000 or more and a polyolefin wax (component B) having a weight average molecular weight of 500 to 3000 are mixed into component A / component B = 30/70 to 90 / This is a method for producing a polyolefin-based resin composition in which after kneading at a weight ratio of 10, a polyolefin (component C) having a weight average molecular weight of 5 to 800,000 is added and further kneaded.

  In the present invention, first, an ultrahigh molecular weight polyolefin (component A) having a molecular weight of 1 million or more and a polyolefin wax (component B) having a molecular weight of 500 to 3000 are mixed into component A / component B = 30/70 to 90/10, preferably 40. After kneading in advance at a weight ratio of / 60 to 80/20, a polyolefin (component C) having a molecular weight of 5 to 800,000 is added and further kneaded to produce a polyolefin resin composition.

After kneading component A and component B, as a method of adding component C and further kneading, (1) a method of kneading component A and component B once pelletized and component C, (2) A method of continuously kneading by mixing a device for kneading by adding component C to a device for kneading component A and component B, or (3) a component in the middle of kneading of a device for kneading component A and component B For example, a method of side-feeding C may be used.
The kneading temperature is preferably not lower than the melting point of the resin used and not higher than the thermal decomposition start temperature. When the kneading temperature is equal to or higher than the melting point, uniform kneading can be performed, and when the kneading temperature is equal to or lower than the thermal decomposition start temperature, deterioration of the resin during kneading can be suppressed. However, in order to adjust the molecular weight of the resin, it can be kneaded at a temperature higher than the thermal decomposition start temperature. The melting point can be measured by DSC, and the thermal decomposition starting temperature can be measured by TG / DTA.

The ultrahigh molecular weight polyolefin as component A in the present invention is a polyolefin having a weight average molecular weight of 1,000,000 or more. From the viewpoint of the strength of the porous film obtained using the polyolefin resin composition, when the total weight of the resin components used for producing the polyolefin resin composition is 100% by weight, the component A is 5% by weight. It is preferable to be contained above. Examples of ultrahigh molecular weight polyolefins include polymers obtained by polymerizing monomers such as ethylene, propylene, 1-butene, 4-methyl-1-pentene, and 1-hexene alone, and copolymerizing two or more of these. The obtained copolymer is mentioned. The ultrahigh molecular weight polyolefin is preferably an ethylene homopolymer or a copolymer of ethylene and the other monomers described above. Two or more types of ultrahigh molecular weight polyolefins may be used.

The polyolefin wax (component B) in the present invention is a polyolefin wax having a weight average molecular weight of 500 to 3,000. The weight average molecular weight of the polyolefin wax is preferably 500-2500. Polyolefin waxes include ethylene polymers, polyethylene polymers such as ethylene-α-olefin copolymers, polypropylene polymers such as propylene homopolymers, propylene-α-olefin copolymers, 4-methylpentene- 1 polymer, poly (butene-1), ethylene-vinyl acetate copolymer and the like. It is preferable to select a polyolefin wax having excellent compatibility with the ultrahigh molecular weight polyolefin. For example, when the ultrahigh molecular weight polyolefin is ultrahigh molecular weight polyethylene, an ethylene homopolymer or an ethylene-α-olefin copolymer is used. It is preferable to use polyethylene wax. Two or more types of polyolefin waxes may be used.

In the present invention, a polyolefin (component C) having a weight average molecular weight of 5 to 800,000, preferably 80,000 to 500,000 is used. Component C is obtained by polymerizing monomers such as ethylene, propylene, 1-butene, 4-methyl-1-pentene and 1-hexene alone, or by copolymerizing two or more of these. A copolymer is mentioned. It is preferable to select component C having excellent compatibility with component A and component B. For example, when the ultrahigh molecular weight polyolefin is ultra high molecular weight polyethylene and the polyolefin wax is polyethylene wax, an ethylene homopolymer or ethylene It is preferable to use polyethylene such as -α-olefin copolymer. As Component C, two or more kinds of polyolefins may be used.

  When the total weight of the resin components used for producing the polyolefin-based resin composition is 100% by weight, the content of component C is preferably 40 to 95% by weight, and 50 to 90% by weight or more. It is more preferable.

  The weight average molecular weight of each of component A, component B and component C can be generally determined by GPC measurement.

When producing a porous film using a polyolefin-based resin composition obtained by kneading Component A, Component B and Component C, it is preferable to use a filler in addition to the aforementioned components as a material. A porous film can be easily obtained by kneading Component A, Component B, Component C and a filler to produce a sheet, and further stretching the sheet using the sheet.
As a method for producing a polyolefin resin composition using Component A, Component B, Component C and a filler,
(1) Method of adding a filler to a kneaded product obtained by kneading component A, component B and component C and further kneading (2) After kneading component A, component B and filler, component C Method of adding and kneading (3) Method of adding a mixture of component C and filler in advance to the kneaded product of component A and component B and further kneading (4) Component A, component B and filler And a kneaded mixture obtained by adding a mixture of component C and filler in advance. Since the number of times of kneading is small, the method (2), (3) or (4) is preferred, and the method (4) is most preferred because the amount of filler to be kneaded at a time can be reduced.

  As the filler, inorganic or organic fine particles generally called a filler can be used. Inorganic fine particles include calcium carbonate, talc, clay, kaolin, silica, hydrotalcite, diatomaceous earth, magnesium carbonate, barium carbonate, calcium sulfate, magnesium sulfate, barium sulfate, aluminum hydroxide, magnesium hydroxide, calcium oxide, oxidation Fine particles such as magnesium, titanium oxide, alumina, mica, zeolite, glass powder, and zinc oxide can be used. As the organic fine particles, known resin fine particles are used. As the resin, a polymer obtained by polymerizing monomers such as styrene, acrylonitrile, methyl methacrylate, ethyl methacrylate, glycidyl methacrylate, methyl acrylate alone or in combination of two or more kinds. Examples include coalescence fine particles, polycondensation resin fine particles such as melamine and urea.

When manufacturing a porous film using the polyolefin-type resin composition containing a filler, the component A, the component B, and the component C, it is preferable that the process of manufacturing a film includes the process of removing a filler. That is, the porous film preferably contains no filler.
When removing the filler, a sheet is produced using the resin composition, the filler may be removed from the sheet, and then stretched, or the sheet may be produced using the resin composition, and then stretched. After that, the filler may be removed.
Therefore, it is preferable to use a filler that can be easily removed with an aqueous solution such as neutral, acidic, or alkaline. For example, among the above-mentioned fine particles, talc, clay, kaolin, diatomaceous earth, calcium carbonate, magnesium carbonate, barium carbonate, magnesium sulfate, calcium oxide, calcium oxide, magnesium hydroxide, calcium hydroxide, zinc oxide and silica can be mentioned. Among these, calcium carbonate is preferable.

The average particle size of the filler is preferably 0.01 to 3 μm, more preferably 0.02 to 1 μm, and most preferably 0.05 to 0.5 μm. When a filler having an average particle size of 3 μm or less is used, a film having excellent puncture strength can be obtained. Therefore, it is possible to obtain a porous film that is uniformly opened.

In order to facilitate dispersion of the filler in the resin components of component A, component B and component C, surface treatment is performed to facilitate separation of the resin component and the filler at the interface and to prevent absorption of moisture from the outside. It is preferable to use those subjected to. Examples of the surface treatment agent include higher fatty acids such as stearic acid and lauric acid, and metal salts thereof.

  The content of the filler in the resin composition is preferably 15 to 150 parts by volume with respect to the total volume of 100 parts by volume when the total volume of component A, component B and component C is 100 parts by volume. Preferably it is 25-100 volume parts. If it is 15 parts by volume or more, it can be sufficiently opened by stretching to obtain a good porous film, and if it is 150 parts by volume or less, a resin ratio is high, so that a porous film having excellent puncture strength is obtained. be able to.

  In addition, the resin composition used in the present invention contains additives (antistatic agents, plasticizers, lubricants, antioxidants, nucleating agents, etc.) that are generally used as long as they do not impair the purpose of the present invention. May be added.

  As a kneading apparatus for kneading Component A, Component B and Component C, and optionally a filler and other additives, it is preferable to carry out with a kneading apparatus having a high shearing force. Specifically, a roll, a Banbury mixer, A single screw extruder, a twin screw extruder, etc. are mentioned.

  A method for forming a sheet using the resin composition is not particularly limited, and examples thereof include inflation processing, calendar processing, T-die extrusion processing, and Skyf method. The resin kneaded product may be continuously fed from a kneader to a sheet molding machine, or the kneaded resin composition may be once pelletized and the pellets may be fed to the sheet molding machine.

The method of stretching the sheet obtained by molding the resin composition to form a porous film is not particularly limited, but can be produced by stretching using a known device such as a tenter, roll, or autograph. . The stretching may be uniaxial or biaxial, and the stretching may be performed in one step or in multiple steps. The draw ratio is preferably 2 to 12 times, and more preferably 4 to 10 times. The stretching temperature is usually carried out at a temperature not lower than the softening point and not higher than the melting point of the ultrahigh molecular weight polyolefin. When the ultrahigh molecular weight polyolefin is ultrahigh molecular weight polyethylene, it is preferably performed at 80 ° C. to 120 ° C. By stretching at such a temperature, the film hardly breaks during stretching and the ultrahigh molecular weight polyethylene is difficult to melt, so that the holes generated by the interface peeling between the resin and the filler are difficult to close.
In addition, after stretching, a heat setting treatment may be performed as necessary to stabilize the shape of the holes.

  After removing at least a part of the filler from the sheet obtained by molding the resin composition, the porous film may be produced by stretching in at least a uniaxial direction. Alternatively, a sheet obtained by molding the resin composition may be stretched at least in a uniaxial direction, and then at least a part of the filler may be removed to produce a porous film. Examples of the method for removing the filler include a method of immersing the sheet or the stretched film in a liquid capable of dissolving the filler.

  A laminated porous film can be produced by laminating a porous heat-resistant layer on at least one surface of a porous film obtained by the method as described above. The laminated porous film having such a heat-resistant layer is excellent in film thickness uniformity, heat resistance, strength, and ion permeability, and when a battery is used as a separator, when abnormal heat generation occurs due to overcharge, Even if the porous film is melted, the heat-resistant layer is preferable because it prevents the positive electrode and the negative electrode from contacting each other and is excellent in safety.

  The heat-resistant layer is a layer formed from a heat-resistant resin or a heat-resistant resin and an inorganic filler, and is preferably a layer formed from a heat-resistant resin and an inorganic filler.

  Examples of the heat-resistant resin constituting the heat-resistant layer include water-soluble polymers such as polyvinyl alcohol, polyethylene glycol, cellulose ether, sodium alginate, polyacrylic acid, polyacrylamide, and polymethacrylic acid, and aromatic polyaramid (hereinafter referred to as “aramid”). And nitrogen-containing aromatic polymers such as aromatic polyimide (hereinafter sometimes referred to as “polyimide”) and aromatic polyamideimide.

As the water-soluble polymer, polyvinyl alcohol, cellulose ether, and sodium alginate are preferable, and cellulose ether is more preferable. Specific examples of the cellulose ether include carboxymethyl cellulose (hereinafter sometimes referred to as CMC), hydroxyethyl cellulose, carboxyethyl cellulose, methyl cellulose, ethyl cellulose, cyanethyl cellulose, oxyethyl cellulose, and the like, and CMC that hardly deteriorates is most preferable.

  As the nitrogen-containing aromatic polymer, aramid is preferable because it is easy to form a porous heat-resistant layer having a uniform film thickness and excellent air permeability. Among aramids, para-aromatic polyamide (hereinafter referred to as “para-aramid”) is preferable. Most preferred).

  Para-aramid is obtained by condensation polymerization of a para-oriented aromatic diamine and a para-oriented aromatic dicarboxylic acid halide, and the amide bond is in the para position of the aromatic ring or an oriented position equivalent thereto (for example, 4,4′-biphenylene). , 1,5-naphthalene, 2,6-naphthalene, and the like, which are substantially composed of repeating units bonded in the opposite direction (orientation positions extending coaxially or in parallel). Specifically, poly (paraphenylene terephthalamide), poly (parabenzamide), poly (4,4′-benzanilide terephthalamide), poly (paraphenylene-4,4′-biphenylenedicarboxylic acid amide), poly ( (Paraphenylene 2,6-naphthalene dicarboxylic acid amide), poly (2-chloro-paraphenylene terephthalamide), paraphenylene terephthalamide / 2,6-dichloroparaphenylene terephthalamide copolymer, etc. Para-aramid having a similar structure is exemplified.

When providing the heat-resistant layer, a coating solution obtained by dissolving a heat-resistant resin in a solvent is usually used. When the heat resistant resin is a water-soluble polymer, water can be used as the solvent, and alcohol may be added to such an extent that the solubility is not impaired. In the case of para-aramid, a polar amide solvent or a polar urea solvent can be used as the solvent. Specifically, N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2- Examples include pyrrolidone and tetramethylurea.

When para-aramid is used as the heat-resistant resin, it is preferable to add an alkali metal or alkaline earth metal chloride during the para-aramid polymerization for the purpose of improving the solubility of para-aramid in a solvent. Specific examples include, but are not limited to lithium chloride or calcium chloride. The amount of the chloride added to the polymerization system is preferably 0.5 to 6.0 mol, more preferably 1.0 to 4.0 mol, per 1.0 mol of the amide group produced by condensation polymerization. If the chloride is 0.5 mol or more, the resulting para-aramid is sufficiently soluble, and if it is 6.0 mol or less, the chloride does not remain dissolved in the solvent. In general, the alkali metal or alkaline earth metal chloride is often 2% by weight or more and the solubility of para-aramid is often sufficient. At 10% by weight or less, the alkali metal or alkaline earth metal chloride is polar. In many cases, it is completely dissolved without being dissolved in a polar organic solvent such as an amide solvent or a polar urea solvent.

  In the present invention, the coating liquid used for forming the heat-resistant layer particularly preferably contains ceramic powder as an inorganic filler. By forming a heat-resistant layer using a coating solution in which ceramic powder is added to a solution having an arbitrary heat-resistant resin concentration, it is possible to form a heat-resistant layer having a uniform film thickness and a fine porosity. The air permeability can be controlled by the amount of ceramic powder added. In the ceramic powder of the present invention, the average particle diameter of the primary particles is preferably 1.0 μm or less, more preferably 0.5 μm or less, from the viewpoint of the strength of the porous film and the smoothness of the heat-resistant layer surface. More preferably, it is 0.1 μm or less.

  The content of the ceramic powder is preferably 1% by weight to 99% by weight in the heat resistant layer, and more preferably 5% by weight to 95% by weight. When it is 1% by weight or more, the ion permeability is excellent, and when it is 99% by weight or less, the film strength is excellent. The shape of the ceramic powder to be used is not particularly limited, and can be spherical or random.

  Examples of the ceramic powder in the present invention include ceramic powders made of electrically insulating metal oxides, metal nitrides, metal carbides, and the like. For example, powders of alumina, silica, titanium dioxide, zirconium oxide and the like are preferably used. The ceramic powders may be used alone, or two or more kinds thereof may be mixed, and the same or different ceramic powders having different particle sizes may be arbitrarily mixed and used.

As a method of laminating a heat-resistant layer on a porous film, a method of laminating a separately produced heat-resistant layer with a porous film, a coating solution containing a heat-resistant resin and optionally ceramic powder on at least one surface of the porous film A method of forming a heat-resistant layer by coating is preferred, but a method using a coating solution is preferred from the viewpoint of productivity. Specific examples of such a method include a method including the following steps.
(A) A slurry-like coating liquid in which 1 to 8000 parts by weight of ceramic powder is dispersed in 100 parts by weight of heat-resistant resin in a polar organic solvent solution containing 100 parts by weight of heat-resistant resin is prepared.
(B) The coating solution is applied to at least one surface of the porous film to form a coating film.
(C) The heat-resistant resin is deposited from the coating film by drying or removing the solvent, or immersed in a solvent that does not dissolve the heat-resistant resin, and then dried.
The coating liquid is preferably continuously applied to the porous film by a coating apparatus described in JP-A No. 2001-316006 and a method described in JP-A No. 2001-23602.

  The porous film of the present invention is excellent in permeability at the use temperature and can be quickly shut down at a low temperature when the use temperature is exceeded, and is suitable as a separator for non-aqueous batteries. Moreover, the laminated porous film obtained by laminating the heat-resistant layer on the porous film of the present invention is excellent in heat resistance, strength and ion permeability, and is preferably used as a separator for non-aqueous batteries, particularly a separator for lithium secondary batteries. Can do.

As the battery separator, the above-mentioned laminated porous film is preferably used because it has less shrinkage when heated and is superior in safety.

When the porous film of the present invention is used as a battery separator, the porosity of the porous film is preferably 30 to 80% by volume, more preferably from the viewpoint of electrolyte retention, film strength, and shutdown performance. 40 to 70% by volume. In addition, from the viewpoint of shutdown property, battery short circuit prevention during winding, and high battery capacity, the thickness of the porous film is preferably 5 to 50 μm, more preferably 10 to 50 μm, and still more preferably 10 to 10 μm. 30 μm. The pore diameter of the porous film is preferably 0.1 μm or less, and more preferably 0.08 μm or less.

When the laminated porous film of the present invention is used as a battery separator, among the laminated porous films, preferred porosity and pore diameter of the porous film are the same as those of the porous film. However, the film thickness is preferably 5 to 50 μm, more preferably 10 to 50 μm, and still more preferably 10 to 30 μm as the whole laminated porous film. Among the laminated porous films, the porosity of the heat-resistant layer is preferably 30 to 80% by volume, more preferably 40 to 70% by volume, from the viewpoint of the amount of electrolyte retained and the strength. The film thickness of the heat-resistant layer is preferably 0.5 μm to 10 μm, more preferably 1 μm to 5 μm, from the viewpoint of suppressing shrinkage during heating and load characteristics when a battery is formed.

The battery of the present invention includes the porous film or laminated porous film of the present invention as a battery separator. Below, when the battery of this invention is nonaqueous electrolyte secondary batteries, such as a lithium battery, components other than the battery separator are demonstrated in detail.

As the non-aqueous electrolyte solution, for example, a non-aqueous electrolyte solution in which a lithium salt is dissolved in an organic solvent can be used. Examples of lithium salts include LiClO ₄ , LiPF ₆ , LiAsF ₆ , LiSbF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (SO ₂ CF ₃ ) ₂ , LiC (SO ₂ CF ₃ ) ₃ , Li ₂ B ₁₀ Cl ₁₀ , One or a mixture of two or more of lower aliphatic carboxylic acid lithium salts, LiAlCl _{4 and the} like can be mentioned. The lithium salt is selected from the group consisting of LiPF ₆ containing fluorine, LiAsF ₆ , LiSbF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , and LiC (CF ₃ SO ₂ ) ₃ among these. It is preferable to use at least one selected from the above.

Examples of the organic solvent used in the nonaqueous electrolyte solution include propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, 4-trifluoromethyl-1,3-dioxolan-2-one, 1,2-di ( Carbonates such as methoxycarbonyloxy) ethane; 1,2-dimethoxyethane, 1,3-dimethoxypropane, pentafluoropropyl methyl ether, 2,2,3,3-tetrafluoropropyl difluoromethyl ether, tetrahydrofuran, 2-methyl Ethers such as tetrahydrofuran; esters such as methyl formate, methyl acetate and γ-butyrolactone; nitriles such as acetonitrile and butyronitrile; N, N-dimethylformamide, N, N-dimethylacetate Amides such as amide; Carbamates such as 3-methyl-2-oxazolidone; Sulfur-containing compounds such as sulfolane, dimethyl sulfoxide and 1,3-propane sultone, or those obtained by introducing a fluorine substituent into the above organic solvent Usually, a mixture of two or more of these is used.

Among these, a mixed solvent containing carbonates is preferable, and a mixed solvent of cyclic carbonate and acyclic carbonate or cyclic carbonate and ether is more preferable. As a mixed solvent of cyclic carbonate and non-cyclic carbonate, ethylene has a wide operating temperature range, excellent load characteristics, and is difficult to decompose even when a graphite material such as natural graphite or artificial graphite is used as the negative electrode active material. A mixed solvent containing carbonate, dimethyl carbonate and ethyl methyl carbonate is preferred. As the positive electrode sheet, a sheet in which a mixture containing a positive electrode active material, a conductive material, and a binder is supported on a current collector is usually used. Specifically, as the positive electrode active material, a material containing a material that can be doped / undoped with lithium ions, a carbonaceous material as a conductive material, and a thermoplastic resin as a binder can be used. Examples of the material that can be doped / undoped with lithium ions include lithium composite oxides containing at least one transition metal such as V, Mn, Fe, Co, and Ni. Among these, in view of high average discharge potential, lithium based on a layered lithium composite oxide based on an α-NaFeO2 type structure such as lithium nickelate and lithium cobaltate and a spinel type structure such as lithium manganese spinel is preferable. A composite oxide is mentioned.

The lithium composite oxide may contain various additive elements, particularly at least selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Cu, Ag, Mg, Al, Ga, In, and Sn. Composite nickel acid containing a metal such that the at least one metal is 0.1 to 20 mol% with respect to the sum of the number of moles of one metal and the number of moles of Ni in lithium nickelate Lithium is preferable because cycle characteristics in use at a high capacity are improved.

As the thermoplastic resin as the binder, polyvinylidene fluoride, vinylidene fluoride copolymer, polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene-perfluoroalkyl vinyl ether Copolymer, ethylene-tetrafluoroethylene copolymer, vinylidene fluoride-hexafluoropropylene-tetrafluoroethylene copolymer, thermoplastic polyimide, polyethylene, polypropylene and the like.

Examples of the carbonaceous material as the conductive material include natural graphite, artificial graphite, cokes, and carbon black. As the conductive material, each may be used alone, or for example, a composite conductive material system in which artificial graphite and carbon black are mixed and used may be used.

As the negative electrode sheet, for example, a material capable of doping and dedoping lithium ions, lithium metal, or a lithium alloy can be used. Materials that can be doped / undoped with lithium ions include carbonaceous materials such as natural graphite, artificial graphite, cokes, carbon black, pyrolytic carbons, carbon fibers, and fired organic polymer compounds, and lower potential than the positive electrode. And chalcogen compounds such as oxides and sulfides for doping and dedoping lithium ions. As a carbonaceous material, a carbonaceous material mainly composed of graphite materials such as natural graphite and artificial graphite, because it has a high potential flatness and a low average discharge potential, so that a large energy density can be obtained when combined with a positive electrode. Is preferred.

As the negative electrode current collector, Cu, Ni, stainless steel, or the like can be used. In particular, in a lithium secondary battery, Cu is preferable because it is difficult to form an alloy with lithium and it can be easily processed into a thin film. As a method of supporting the mixture containing the negative electrode active material on the negative electrode current collector, a method of pressure molding, or a method of pasting into a paste using a solvent or the like and applying pressure to the current collector by pressing after drying Is mentioned.

The shape of the battery of the present invention is not particularly limited, and may be any of a paper type, a coin type, a cylindrical type, a rectangular shape, and the like.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the present invention is not limited to the following examples.

(1) Tensile test of polyolefin resin composition The polyolefin resin composition was pressed at 200 ° C to obtain a sheet having a thickness of about 180 µm. This sheet was immersed in 3N hydrochloric acid overnight to remove the filler, washed with water and dried to obtain a porous sheet. A measurement sample was obtained from the obtained porous sheet, and the sample was stretched at a strain rate of 400% / min at room temperature and 110 ° C., and the breaking strain was measured.
(2) Film thickness Measured with Mitutoyo VL-50A according to JISK7130.
(3) Puncture strength The maximum stress (gf) when the porous film was fixed with a 12 mmφ washer and the pin was punctured at 200 mm / min was defined as the puncture strength of the film. A pin with a pin diameter of 1 mmΦ and a tip of 0.5R was used.
(4) Air permeability Measured using a Gurley type densometer manufactured by Toyo Seiki Co., Ltd.

Example 1
(Kneading conditions 1-1)
12.3 g of ultra high molecular weight polyethylene powder having a weight average molecular weight of about 3 million (340M, manufactured by Mitsui Chemicals), 12.3 g of polyethylene wax having a weight average molecular weight of 1000 (FNP-0115, manufactured by Nippon Seiki Co., Ltd.), average particle diameter 0.1 μm calcium carbonate (manufactured by Maruo Calcium Co., Ltd.) 39.6 g, antioxidant (Irg1010, manufactured by Ciba Specialty Chemicals Co., Ltd.) 0.17% by weight (P168, manufactured by Ciba Specialty Chemicals Co., Ltd.) 0.05 After mixing the weight percent in powder form, the mixture was kneaded for 3 minutes at 200 ° C. and 60 rpm in a lab plast mill (R-60H type). The obtained kneaded material is referred to as kneaded material A.
(Kneading conditions 1-2)
Polyethylene powder having a weight average molecular weight of about 500,000 (030S, manufactured by Mitsui Chemicals), 34.6 g of calcium carbonate (manufactured by Maruo Calcium) having an average particle diameter of 0.1 μm, antioxidant (Irg1010, Ciba Specialty) (Chemicals) 0.17g (P168, Ciba Specialty Chemicals) 0.05g were mixed in powder form and then lab plast mill (R-60H type) at 200 ° C, 60rpm for 3 minutes. Kneaded. The obtained kneaded material is referred to as kneaded material B.
(Kneading condition 2)
7.0 g of kneaded material A and 63.0 g of kneaded material B were kneaded for 3 minutes at 230 ° C. and 100 rpm using a lab plast mill (R-60H type) to obtain a polyolefin resin composition (1). Obtained.

Example 2
A polyolefin-based resin composition (2) was obtained under the same conditions as Example 1 except that the kneaded product A was 21.0 g and the kneaded product B was 49.0 g.

Example 3
The polyolefin resin composition (3) was obtained under the same conditions as Example 1 except that the kneaded product A was 35.0 g and the kneaded product B was 35.0 g.

Example 4
The kneading condition 1-1 of Example 1 is as follows: ultrahigh molecular weight polyethylene powder (340M, manufactured by Mitsui Chemicals), 17.2 g, weight average molecular weight 1000 polyethylene wax (FNP-0115, manufactured by Nippon Seiki Co., Ltd.) 7.4 g Kneading was carried out under the same conditions except that 21.0 g of the kneaded product A and 49.0 g of the kneaded product B were used in the same kneading condition 2 to obtain a polyolefin resin composition (4).

Example 5
The kneading condition 1-1 of Example 1 is as follows: ultrahigh molecular weight polyethylene powder (340M, Mitsui Chemicals) 22.1g, weight average molecular weight 1000 polyethylene wax (FNP-0115, Nippon Seiki Co., Ltd.) 2.5g Kneading was carried out under the same conditions except that 21.0 g of the kneaded product A and 49.0 g of the kneaded product B were used in the same kneading condition 2 to obtain a polyolefin resin composition (5).

Example 6
21.0 g of kneaded product A, 18.7 g of ultra high molecular weight polyethylene powder (030S, manufactured by Mitsui Chemicals) having a weight average molecular weight of about 500,000, 30.1 g of calcium carbonate (manufactured by Maruo Calcium) having an average pore size of 0.1 μm , 0.13 g of an antioxidant (Irg1010, manufactured by Ciba Specialty Chemicals), 0.04 g of (P168, manufactured by Ciba Specialty Chemicals) was used at 230 ° C. using a lab plast mill (R-60H type). The polyolefin resin composition (6) was obtained by kneading for 3 minutes at 100 rpm.

Comparative Example 1
3.7 g of ultra high molecular weight polyethylene powder (340M, manufactured by Mitsui Chemicals) having a weight average molecular weight of approximately 3 million, 17.2 g of ultra high molecular weight polyethylene powder (030S, manufactured by Mitsui Chemicals) having a weight average molecular weight of approximately 500,000, Polyethylene wax having a weight average molecular weight of 1000 (FNP-0115, manufactured by Nippon Seiki Co., Ltd.) 3.7 g, calcium carbonate having an average pore size of 0.1 μm (manufactured by Maruo Calcium Co., Ltd.) 39.6 g, antioxidant (Irg1010, Ciba Specialty) (Chemicals Co., Ltd.) 0.17% by weight (P168, Ciba Specialty Chemicals Co., Ltd.) 0.05% by weight were mixed in powder form and then mixed at 200 ° C. and 60 rpm with a lab plast mill (R-60H type). The mixture was kneaded for 3 minutes and then kneaded at 230 ° C. and 100 rpm for 3 minutes to obtain a polyolefin resin composition (7).

The tensile test results using the kneaded materials of Examples 1 to 5 and Comparative Examples 1 and 2 are summarized in Table 1.

Example 7
The polyolefin resin compositions (1), (2) and (3) were each pressed at 200 ° C. to obtain a sheet having a thickness of about 180 μm. The obtained sheet was immersed in 3N hydrochloric acid overnight to remove the filler, washed with water and dried to obtain a porous sheet. This porous sheet was stretched 4 × 4 times at 120 ° C. using a desktop biaxial stretching machine manufactured by Toyo Seiki Co., Ltd. to obtain porous films (1), (2) and (3).

Example 8
Synthesis of para-aramid (poly (paraphenylene terephthalamide)) Production of poly (paraphenylene terephthalamide) using a 3 liter separable flask with stirring blade, thermometer, nitrogen inlet tube and powder addition port went. The flask was sufficiently dried, charged with 2200 g of N-methyl-2-pyrrolidone (NMP), added with 151.07 g of calcium chloride powder vacuum-dried at 200 ° C. for 2 hours, heated to 100 ° C. and completely dissolved. . After returning to room temperature, 68.23 g of paraphenylenediamine was added and completely dissolved. While maintaining this solution at 20 ° C. ± 2 ° C., 124.97 g of terephthalic acid dichloride was added in 10 divided portions every about 5 minutes. Thereafter, the solution was aged for 1 hour while maintaining the temperature at 20 ° C. ± 2 ° C. with stirring. It filtered with the 1500 mesh stainless steel wire mesh. The resulting solution had a para-aramid concentration of 6%.
Preparation of coating liquid 100 g of the previously polymerized para-aramid solution was weighed into a flask, 300 g of NMP was added, and a solution having a para-aramid concentration of 1.5% by weight was prepared and stirred for 60 minutes. 6 g of alumina C (manufactured by Nippon Aerosil Co., Ltd.) and 6 g of advanced alumina AA-03 (manufactured by Sumitomo Chemical Co., Ltd.) were mixed with the above-mentioned solution having a para-aramid concentration of 1.5% by weight and stirred for 240 minutes. The obtained solution was filtered through a 1000 mesh wire mesh, then 0.73 g of calcium oxide was added, and the mixture was neutralized by stirring for 240 minutes, and defoamed under reduced pressure to obtain a coating solution on the slurry.
Coating on PE porous film After applying the coating solution to the porous film (2) obtained in Example 7 with a bar coater so as to have a thickness of 130 μm, the temperature was 50 ° C. and 70% RH. Aramid was deposited on the porous film by placing in an oven for 15 seconds. The obtained film was fixed on four sides with metal fittings and dried in an oven at 70 ° C. for 10 minutes to obtain a laminated porous film (2).

Various physical properties of the porous film obtained in Example 7 and the laminated porous film obtained in Example 8 are summarized in Table 2.

As shown in Table 1, the examples exhibited sufficient tensile strain at 110 ° C. This indicates that the components constituting the sheet are uniformly kneaded and a homogeneous sheet is obtained.
In addition, as shown in Table 2, it can be seen that a porous film and a laminated porous film suitable as a battery separator can be obtained by processing a sheet obtained using the polyolefin resin composition of the present invention.

Claims (6)

Weight ratio of component A / component B = 30/70 to 90/10 for ultra high molecular weight polyolefin (component A) having a weight average molecular weight of 1 million or more and polyolefin wax (component B) having a weight average molecular weight of 500 to 3000 And then kneading and adding a polyolefin (component C) having a weight average molecular weight of 5 to 800,000 and further kneading. 2. The method for producing a polyolefin resin composition according to claim 1, wherein a filler is added and kneaded at an arbitrary time. A method for producing a polyolefin resin porous film comprising producing a sheet using the polyolefin resin composition obtained by the method according to claim 2 and then stretching the sheet in at least a uniaxial direction. A method for producing a porous film made of polyolefin resin through the following two steps after producing a sheet using the polyolefin resin composition obtained by the method according to claim 2.
(1) Step of stretching the sheet in at least uniaxial direction (2) Step of removing inorganic filler from the sheet The manufacturing method of the laminated porous film which laminates | stacks the porous heat resistant layer containing an inorganic filler on the polyolefin resin porous film obtained by the method of Claim 3 or Claim 4. A battery comprising a polyolefin resin porous film obtained by the method according to claim 3 or 4, or a laminated porous film obtained by the method according to claim 5.