JP2012099574A - Method of producing film and film produced by that production method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a film having properties susceptible to soaking and penetration of electrolytic solution in which thermal shrinkage is reduced, and excellent handleability is ensured, and which is visible even in electrolytic solution.SOLUTION: The method of producing a film includes following steps (1A), (2A), (3) and (4), or the steps (1B), (3) and (4). Step (1A): a step for bringing a drawing polytetrafluoroethylene film into contact with a solution containing an inorganic powder, step (2A): a step for bringing a film obtained in the step (1A) into contact with a solution containing a resin having a hydrophilic group, step (1B): a step for bringing a drawing polytetrafluoroethylene film into contact with a solution containing an inorganic powder and a resin having hydrophilic group, step (3): a step for making silane coupling agent adhere to a film obtained by the step (2A) or step (1B), step (4): a step for heating a film obtained in the step (3) at 50-200°C and drying.

Description

  The present invention relates to a film production method and a film obtained by the production method.

  As a separator for an electric double layer capacitor, a mixed paper obtained by mixing and papermaking an olefin resin (for example, polyethylene, polypropylene, etc.) and fibers such as cellulose, polyester, aramid, etc. has been used.

  In recent years, in order to increase the capacity of electric double layer capacitors, an organic solvent such as propylene carbonate having a high withstand voltage is used as a solvent for the electrolytic solution. It is desirable that the separator used in such a large-capacity electric double layer capacitor has sufficient heat resistance. Generally, separators formed from heat-resistant aramid resin or polyester resin are widely produced and used. ing.

  However, since aramid resins and polyester resins are hydrophobic, there is a problem that wettability is lowered with respect to an electrolytic solution using propylene carbonate, which is an aprotic polar solvent, as a solvent.

  Therefore, Patent Document 1 discloses that a separator including a fiber containing glass fiber and an inorganic compound that forms a hydrosol attached to the surface of the fiber has good wettability with respect to an electrolyte solution and is flexible. It is disclosed that it has sex.

However, the separator described in Patent Document 1 is inferior in mechanical strength, chemical resistance, and the like.
Here, fluorine-containing resins such as polytetrafluoroethylene are known as resins having excellent heat resistance, chemical resistance, etc., and Patent Document 2 discloses porous polyethylene terephthalate as a separator for electronic components. ing.

JP 2004-349586 A JP 2006-344506 A

  However, since fluorine-containing resins such as polytetrafluoroethylene have water and oil repellency, they have low wettability with respect to an electrolytic solution containing water or propylene carbonate as an aprotic polar solvent. There was a problem.

  The present invention has been made in view of such problems, and has a property that the electrolytic solution is likely to permeate and permeate using a stretched polytetrafluoroethylene film as a base material, is difficult to heat shrink, and has excellent handleability. Furthermore, it aims at providing the film which can be visually recognized also in electrolyte solution, and its manufacturing method.

The film production method of the present invention includes the following step (1A), step (2A), step (3) and step (4), or includes the following step (1B), step (3) and step (4). It is characterized by that.

Step (1A): a step of bringing the stretched polytetrafluoroethylene film into contact with a solution containing inorganic powder,
Step (2A): a step of bringing the film obtained in Step (1A) into contact with a solution containing a resin having a hydrophilic group,
Step (1B): a step of bringing a stretched polytetrafluoroethylene film into contact with a solution containing an inorganic powder and a resin having a hydrophilic group,
Step (3): a step of attaching a silane coupling agent to the film obtained in the step (2A) or the step (1B),
Step (4): A step of heating and drying the film obtained in the step (3) at 50 to 200 ° C.

The step (1A) is a step of immersing the stretched polytetrafluoroethylene film in a solution containing an inorganic powder, and the immersion time is preferably 5 to 60 seconds.
The stretched polytetrafluoroethylene membrane is a porous membrane, and its maximum pore size (Galwick having a surface tension of 16 dynes / cm is used, and is measured and measured based on the ASTM F316-86 method; PERM-POROMETER measuring instrument manufactured by PMI ) Is preferably 0.01 to 10 μm.

The silane coupling agent includes a vinyl silane coupling agent, an epoxy silane coupling agent, a styryl silane coupling agent, a (meth) acryloxy silane coupling agent, an amino silane coupling agent, and a ureido silane coupling. Selected from the group consisting of an agent, a chloropropyl silane coupling agent, a polysulfide silane coupling agent, an isocyanate silane coupling agent, a mercapto silane coupling agent, a triazine silane coupling agent and an imidazole silane coupling agent. Preferably at least one compound,
Furthermore, it is preferably at least one compound selected from the group consisting of 3-methacryloxypropyltrimethoxysilane, 3-aminopropyltrimethoxysilane and 3-glycidoxypropyltrimethoxysilane.

  The inorganic powder is preferably a powder obtained by coating the surface of titanium oxide with silica, and is preferably at least one compound selected from the group consisting of silica, titanium oxide and alumina, and measured by the dynamic light scattering method. The average particle diameter is preferably not more than the maximum pore diameter of the stretched polytetrafluoroethylene membrane to be used.

  The resin having a hydrophilic group is preferably at least one resin selected from the group consisting of a hydroxyl group-containing resin, a carboxylic acid group-containing resin, a sulfonic acid group-containing resin, an epoxy group-containing resin, and an amino group-containing resin. More preferred is polyvinyl alcohol.

The film of the present invention is obtained by the above production method.
The film preferably has a shrinkage rate at 275 ° C. of 10% or less, and is preferably visible in the electrolytic solution.

  The film is preferably a separator, and more preferably an electric double layer capacitor separator.

  According to the production method of the present invention, an electrolyte (electrolyte) easily permeates and permeates, is resistant to thermal shrinkage, has excellent handleability, and is easily visible in the electrolyte. Can be manufactured.

FIG. 1 is a digital camera photograph of a film obtained in Example 1 immersed in an electrolytic solution or an untreated ePTFE film. FIG. 2 is a graph showing the transmittance curve of the film obtained in Example 1 or Reference Example 1 after being immersed in water.

Hereinafter, the film production method according to the present invention and the film obtained by the production method will be described in more detail.
≪Film production method≫
The method for producing a film according to the present invention includes the following step (1A), step (2A), step (3) and step (4), or includes step (1B), step (3) and step (4). A method for producing a film.

Step (1A): a step of bringing the stretched polytetrafluoroethylene film into contact with a solution containing inorganic powder,
Step (2A): a step of bringing the film obtained in Step (1A) into contact with a solution containing a resin having a hydrophilic group,
Step (1B): a step of bringing a stretched polytetrafluoroethylene film into contact with a solution containing an inorganic powder and a resin having a hydrophilic group,
Step (3): a step of attaching a silane coupling agent to the film obtained in the step (2A) or the step (1B),
Step (4): A step of heating and drying the film obtained in the step (3) at 50 to 200 ° C.

  According to such a film production method, it has excellent wettability with respect to the electrolytic solution, has a property that the electrolytic solution can easily permeate and penetrate, is difficult to heat shrink, has excellent handleability, and is visible even in the electrolytic solution. A film having certain properties can be easily and inexpensively manufactured.

<Step (1A), Step (2A), Step (1B)>
In the step (1A), an ePTFE membrane as described later is brought into contact with a solution containing the inorganic powder (a). In the step (2A), the film obtained in the step (1A) is brought into contact with the solution containing the resin (b) having a hydrophilic group.

  In this ePTFE membrane, there are a large number of voids (spaces, pores) between fibers forming the membrane, and these voids (pores) are obtained by uniaxially or biaxially stretching an unstretched PTFE membrane, and at least a part of the voids (pores). It is defined (formed) by fiberizing. These voids (holes) penetrate the front and back surfaces and side surfaces of the film or exist inside the film.

  By the step (1A) and the step (2A), the inorganic powder (a) and the resin (b) having a hydrophilic group are attached (adsorbed) or bonded (chemically) to the surface and / or pores of the ePTFE membrane. It is considered that a film having a desired physical property can be obtained.

  In the method for producing a film according to the present invention, it is possible to obtain a film that is less likely to occur such as “powder falling”, which is a phenomenon in which the inorganic powder or the like is dropped, including the step (1A) and the step (2A). However, the step (1A) + the step (2A) may be a step (1B) in which the ePTFE membrane is brought into contact with a mixed liquid containing an inorganic powder and a resin having a hydrophilic group. By the step (1B), the inorganic powder (a) and the resin (b) having a hydrophilic group are attached (adsorbed) or bonded (chemically or physically) to the surface and / or pores of the ePTFE membrane. It is thought that the obtained film can be obtained.

Method of contacting an ePTFE membrane with a solution containing an inorganic powder (a), contacting the membrane obtained in the step (1A) with a solution containing a resin (b) having a hydrophilic group The method and the method of bringing the ePTFE membrane into contact with the solution containing the inorganic powder (a) and the resin (b) having a hydrophilic group are not particularly limited.
(X) A method of bringing the solution into contact with the film, specifically, a method of dropping the solution on the film, a method of applying the solution to the film, etc.
(Y) A method of bringing a film into contact with a solution, specifically, a method of immersing a film in a solution, etc.
(Z) A method in which a film and a solution are simultaneously added to a container and both are brought into contact with each other can be mentioned.

  Among these, the method in which the ePTFE membrane is immersed in a solution containing the inorganic powder (a), and the solution obtained by the step (1A) containing the resin (b) having a hydrophilic group The method of immersing in is preferable.

  The solutions used in the step (1A), the step (2A) and the step (1B) include the solvent (c) and the like in the inorganic powder (a) and / or the resin (b) having a hydrophilic group, respectively. It is preferable that the composition further contains an additive or the like as long as the effects of the present invention are not impaired. Examples of the additive that may be contained in the solution include a crosslinking agent.

  In the present invention, providing the step (0) of immersing the ePTFE membrane in a solution containing the solvent (c) or the like before the step (1A) or the step (1B) provides a film as a base material and a step ( It is preferable from the viewpoint of obtaining a film that can improve the contact with the solution used in 1A) or the step (1B) and that the inorganic powder is easily attached or bonded. It is preferable that the solution used in step (0) consists essentially of the same solvent as the solvent in the solution used in step (1A) or step (1B).

  In the present invention, after step (1A) and / or step (2A), that is, between step (1A) and step (2A), or between step (2A) and step (3), and step ( It is preferable to provide the process (1 ') which dries the film | membrane (wet film) obtained at the process (1A), the process (2A), or the process (1B) after 1B).

  In the present invention, after the step (2A), the step (1B) or the step (1 ′), the film obtained in the step (2A), the step (1B) or the step (1 ′) is converted into a solution containing a crosslinking agent. It is preferable to provide a step (2 ′) of immersing in the substrate. By providing this step, it is possible to obtain a film that is less likely to occur, such as “powder falling”, which is a phenomenon in which inorganic powder and the like fall off. In addition, it is preferable that the solvent etc. are contained in the solution used at a process (2 '), and the following solvent (c) is preferable as said solvent. The usage-amount of a crosslinking agent will not be restrict | limited especially if it is a range which does not impair the effect of this invention.

  Further, it is preferable to provide a step (2 ″) of crosslinking the crosslinking agent after the step (2 ′). The method of crosslinking the crosslinking agent is appropriately selected according to the characteristics of the crosslinking agent used, and is not particularly limited, and a known method can be used.

(Temperature, pressure and time conditions of step (1A), step (2A) and step (1B))
The step (1A), the step (2A) and the step (1B) may be usually performed at room temperature (15 to 25 ° C.) and normal pressure (standard atmospheric pressure, 101.25 hPa), but heating (preferably 25 to 90). ° C) or under normal pressure, preferably under a pressure of about 400 to 2000 Pa. By carrying out under pressure, the inorganic powder may be more fitted into the pores of the ePTFE membrane and a film with less powder falling may be obtained.

  The immersion time in the case where the step (1A) and the step (1B) are a method of immersing the ePTFE membrane in the solution is not particularly limited as long as the inorganic powder (a) is attached or bonded, but preferably 5 to 60 seconds. More preferably, it is 5 to 30 seconds. If the immersion time is in the above range, excess inorganic powder (a) does not adhere or bind, so that a film with less powder falling off can be obtained, and productivity can be improved by shortening the process time. It is done.

[Stretched polytetrafluoroethylene membrane (ePTFE membrane)]
The stretched polytetrafluoroethylene film (ePTFE film) used in the present invention is a film formed by stretching polytetrafluoroethylene, and may be either a uniaxially stretched film or a biaxially stretched film. However, considering the mechanical strength of the resulting film, a biaxially stretched membrane is preferred, and a porous membrane is preferred.

  This ePTFE film is a film that has holes due to stretching, has high flexibility, and has high mechanical strength in addition to the properties such as heat resistance, chemical resistance, weather resistance and electrical insulation properties of PTFE It is.

  The ePTFE membrane used in the present invention has a large number of holes on the surface thereof, and the ePTFE membrane has communication holes. Among them, the maximum pore size (measured using a Galwick having a surface tension of 16 dynes / cm, based on the ASTM F316-86 method, measuring device; PRM-POREMETER measuring instrument manufactured by PMI) is preferably 0.01 to 10 μm, more Preferably it is 0.05-2.0 micrometers, More preferably, it is 0.1-1.3 micrometers, The porosity (The total (volume) ratio of the hole (void | void) which exists in the predetermined volume of an ePTFE film | membrane is said. Measurement method: (true density of PTFE−apparent density) × 100 / true density of PTFE) is preferably 10 to 90%.

  When the maximum pore diameter of the “hole” existing on the surface of the ePTFE membrane and communicating with the inside and the back of the membrane and the porosity of the ePTFE membrane are within the above ranges, the silane coupling agent, inorganic The powder (a), the resin (b) having a hydrophilic group and the like can be firmly held on the surface and / or pores of the ePTFE membrane, and the inorganic powder can be removed from the surface of the ePTFE membrane and the pores present on the surface. It is possible to obtain a film that is less prone to “powder falling”, which is a phenomenon in which etc. fall off. In addition, when the maximum pore diameter of the ePTFE membrane is in the above range, ions in the electrolytic solution can be smoothly transmitted even after the inorganic powder (a) is attached or bonded. It can be suitably used as a separator for multilayer capacitors.

  The thickness of the ePTFE membrane used in the present invention can be appropriately changed according to the desired application, but is preferably 3 to 100 μm, more preferably 3 to 30 μm, considering the strength of the obtained film and the like. It is. When the thickness of the ePTFE film is within the above range, the electrodes can be prevented from contacting each other and ions in the electrolytic solution can be smoothly transmitted. Therefore, the obtained film is suitable as a separator or a separator for an electric double layer capacitor. Can be used for

As the ePTFE membrane used in the present invention, a conventionally manufactured method (manufactured product) or a commercially available product can be used.
As a manufactured product, for example, emulsion-polymerized PTFE can be obtained by extruding and calendering to form a preformed product, and stretching and heat-treating the preformed product (for example, 100 to 370 ° C.).
Examples of commercially available products include sa-PTFE ^™ (average pore diameter: 0.3 μm, porosity: 90%) manufactured by Nippon Valqua Industries, Ltd.

[Inorganic powder (a)]
The inorganic powder (a) used in the present invention is not particularly limited. For example, inorganic particles having a titanium oxide surface coated with silica or the like, silica, titanium oxide, alumina, and carbon (carbon nanotubes (CNT), Carbon microcoil (CMC), nanodiamond, etc.). These inorganic powders may be used alone or in combination of two or more.

  By using the inorganic powder (a), the film obtained in the step (1A), the step (2A), the step (1B) and the step (3) and the film obtained in the step (4) are less likely to be thermally contracted. Therefore, the waist of the obtained film can be strengthened, and the handling property (handleability) and visibility of the film can be improved.

Among these, an inorganic powder that can be combined with the silane coupling agent (d) is preferable, and at least one selected from the group consisting of powder obtained by coating the surface of titanium oxide with silica, silica powder, titanium oxide, and alumina. A seed compound is preferred, and silica powder or titanium oxide powder is more preferred. When silica powder or titanium oxide powder is used, the resulting film is less susceptible to heat shrinkage, and the resulting film appears stiff (excellent elasticity), improving handling and further improving the visibility of the resulting film. Can be made. Moreover, it has the property that electrolyte solution permeates and penetrates into the film.
Here, “visibility” refers to the property of visually confirming the presence of the film when the film is left in the electrolyte.

  The average particle size measured by the dynamic light scattering method of the inorganic powder used in the present invention is not particularly limited as long as it is not more than the maximum pore size of the surface of the ePTFE membrane and the pores existing from the surface toward the inside, Preferably it is 0.01-1 micrometer. When the pore diameter of the inorganic powder is in the above range, a film that is less likely to fall off powder can be obtained.

  The content of the inorganic powder (a) in 100 parts by weight of the solution used in the step (1A) and the step (1B) is preferably 0.01 to 30 parts by weight, more preferably 0.1 to 5 parts. Parts by weight. When the amount of the inorganic powder is in the above range, powder falling off hardly occurs and a film having excellent visibility can be obtained.

[Resin having a hydrophilic group (b)]
The resin (b) having a hydrophilic group used in the present invention is not particularly limited as long as it is a resin having a hydrophilic group, but can be chemically or physically bonded to the silane coupling agent (d). It is preferable that

Examples of the resin having a hydrophilic group include a hydroxyl group-containing resin, a carboxylic acid group-containing resin, a sulfonic acid group-containing resin, an epoxy group-containing resin, and an amino group-containing resin.
These resins may be used alone or in combination of two or more.

  The hydroxyl group-containing resin is not particularly limited. For example, polyvinyl alcohol (PVA), a copolymer of vinyl alcohol and a vinyl group-containing monomer (eg, vinyl alcohol-vinyl acetate copolymer, ethylene-vinyl). Alcohol copolymers, etc.), acrylic polyols, fluorine-containing polyols, polyoxyalkylenes and polyester polyols.

The carboxylic acid group-containing resin is not particularly limited. For example, olefinic monomers such as ethylene, propylene, and butylene; diene monomers such as butadiene; aromatic group-containing monomers such as styrene; Any one or more monomers (i) of (meth) acrylic acid ester monomers such as methacrylic acid ester;
A copolymer with a monomer (ii) having a carboxylic acid group (—COOH) such as acrylic acid and methacrylic acid;
Homopolymers of monomers (ii) having carboxylic acid groups such as acrylic acid and methacrylic acid;
Is mentioned.

The sulfonic acid group-containing resin is not particularly limited. For example, a copolymer of styrene and acrylamide-2-methylpropanesulfonic acid (salt);
A terpolymer of styrene, n-butyl acrylate and acrylamide-2-methylpropanesulfonic acid (salt);
A terpolymer of styrene, 2-ethylhexyl acrylate, and acrylamide-2-methylpropanesulfonic acid (salt);
Is mentioned.

  The epoxy group-containing resin is not particularly limited. For example, an epoxy resin, a modified epoxy resin, an acrylic (co) polymer resin having an epoxy group, a polybutadiene resin having an epoxy group, and a polyurethane having an epoxy group Examples thereof include resins and adducts or condensates of these resins.

  The amino group-containing resin is not particularly limited, and examples thereof include polyethyleneimine, polyvinylamine, polyamide polyamine, polyamidine, polydimethylaminoethyl methacrylate, and polydimethylaminoethyl acrylate.

These resins having a hydrophilic group may be used alone or in combination of two or more.
Among these resins having a hydrophilic group, polyvinyl alcohol is preferable because it has many hydroxyl groups.

  In the resin (b) having a hydrophilic group, the concentration of the resin (b) having a hydrophilic group in the solution used in the step (2A) and the step (1B) is preferably 0.001 to 5% by weight, more preferably It is used in an amount of 0.1 to 2% by weight.

If the amount of the resin having a hydrophilic group is within the above range, even if the water- and oil-repellent ePTFE is a base material, a film that can easily penetrate and penetrate the electrolyte can be obtained, and the inorganic powder can be peeled off. It is possible to obtain a film that is difficult to cause.
Although the weight average molecular weight (Mw) of resin (b) which has a hydrophilic group used by this invention is not specifically limited, The range of about 500-100000 is preferable.

(Solvent (c))
The solvent (c) is preferably a solvent that can disperse the inorganic powder (a) and dissolve the resin (b) having the hydrophilic group and is easy to dry, and is not particularly limited. Specifically, alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, t-butyl alcohol and isobutyl alcohol;
Esters such as methyl acetate, ethyl acetate and butyl acetate;
Ketones such as acetone and methyl ethyl ketone;
Aromatic hydrocarbons such as toluene and xylene;
Ethers such as diethyl ether, dibutyl ether, tetrahydrofuran and dioxane;
Etc.

  These solvents can be used alone or in combination of two or more. Among these, since it can easily penetrate into the ePTFE membrane, the resin (b) having the hydrophilic group can be dissolved, and the inorganic powder (a) and the resin (b) having the hydrophilic group can be uniformly mixed. Alcohol is preferred.

In addition, the solvent used by a process (1A), a process (2A), and a process (1B) may be the same or different.
Although the usage-amount of the solvent (c) in a process (1A) and a process (1B) is not restrict | limited in particular, Preferably it is 70-99.99 with respect to 100 weight part of solutions used by a process (1A) and a process (1B). It is preferable to use it in an amount of parts by weight, more preferably 95 to 99.9 parts by weight.

  Although the solvent (c) in the step (2A) is not particularly limited, it is preferably used in such an amount that the concentration of the resin (b) having a hydrophilic group in the solution used in the step (2A) falls within the above range.

  The amount of the solvent (c) used is such that the viscosity of the solution used in step (1A), step (2A) and step (1B) is 0.00001 to 2 Pa · s, and further 0.0001 to 0.01 Pa · s. It is preferable to use it in the quantity which becomes s.

When the amount of the solvent (c) used is in the above range, the ePTFE membrane is easily immersed in the solution.
The solvent (c) is a film in which the inorganic powder (a) and the resin (b) having a hydrophilic group are attached or bonded (chemically and / or physically) to the surface and / or pores of the ePTFE membrane. (Membrane) is used to obtain the film, the membrane after Step (1A), Step (2A) and Step (1B), and the film finally obtained, the solvent (c) is It is preferable that substantially no residue remains.

(Crosslinking agent)
The crosslinking agent is not particularly limited and may be appropriately selected according to the type of resin having a hydrophilic group to be used. Aldehyde compounds such as formaldehyde and glutaraldehyde; Ketone compounds such as diacetyl and chloropentanedione A compound having a reactive halogen such as bis (2-chloroethylurea) -2-hydroxy-4,6-dichloro-1,3,5 triazine; a compound having a reactive olefin such as divinylsulfone; N-methylol Compounds; Isocyanates; Aziridine compounds; Carbodiimide compounds; Epoxy compounds; Halogen carboxaldehydes such as mucochloric acid; Dioxane derivatives such as dihydroxydioxane; Chromium alum, zirconium sulfate, boric acid, borate, phosphate 1,1-bis (diazo Cetyl) -2-phenyl-diazo compounds such as ethane; disuccinimidyl CHILLY compounds containing succinimidyl ester; and the like bifunctional maleic acid imide. Of these, glutaraldehyde is preferred. These crosslinking agents may be used alone or in combination of two or more. The cross-linking agent is a compound capable of cross-linking the resin (b) having a hydrophilic group. By using the cross-linking agent, the inorganic powder (a) is present on the surface and / or inside of the ePTFE membrane. It is possible to obtain a film that can be firmly held in the pores, hardly cause powder falling off from the film, and hardly crack.

<Process (1 ')>
In step (1 ′), the film (wet film) obtained in step (1A), step (2A) or step (1B) is dried. Although it does not restrict | limit especially as a method to dry, It is preferable to air-dry the film | membrane obtained at the process (1A), the process (2A), and the process (1B).

  The conditions of the step (1 ′) are not particularly limited as long as the solvent in the wet coating film can be diffused and removed while maintaining the stretched state of the ePTFE film, and conditions such as temperature, time, and pressure can be appropriately set. However, the drying temperature is preferably 25 to 200 ° C. When blown and dried, the gas sent from the nozzle is preferably in this temperature range. Further, the drying time at the above temperature is preferably 10 sec to 30 min, and the normal pressure is usually adopted as the pressure in many cases.

<Step (3)>
In step (3), the silane coupling agent (d) is adhered to the film obtained in step (2A) or step (1B) (or the dried film obtained in step (1 ′)).

  By carrying out the step (3), the surface of the membrane obtained in the step (2A) or the step (1B) or the dry membrane obtained in the step (1 ′) and / or the silane cup It is considered that a film to which a ring agent or the like is attached or bonded (chemical or physical) can be obtained.

  The step (3) may be performed substantially using only the silane coupling agent (d) or may be performed using a solution (D) containing an additive such as a solvent. From the viewpoint of obtaining a film in which a silane coupling agent or the like is uniformly attached or bonded (chemically or physically) to the surface and / or pores thereof, a solution (D) containing the silane coupling agent It is preferable to carry out using. Examples of the solvent include the same solvent (c) as described above.

  The method of attaching the solution containing the silane coupling agent to the film obtained in the step (2A) or the step (1B) (the dried film obtained in the step (1 ′)) is not particularly limited. For example, a method of dropping a solution on the film, a method of applying the solution to the film, a method of immersing the film in the solution, and the like can be mentioned.

The method for dropping the solution and the method for applying the solution may be performed by a conventionally known method. In addition, the method similar to the above is mentioned as the method of immersing a film | membrane in a solution.
In the case of using a solution containing the solvent (c), the film obtained in the step (2A) or the step (1B) (or the step (1 ′)) is immersed in the solution to obtain the step (3 ) Is performed for a short time, preferably 5 minutes or less, more preferably 30 seconds or less.

  The step (3) may be usually performed at room temperature (15 to 25 ° C.) and normal pressure (standard atmospheric pressure, 101.25 hPa), but may be performed under heating (preferably 25 to 90 ° C.). You may carry out under the pressure pressurized about 400-2000 Pa further preferably.

[Silane coupling agent (d)]
Although it does not restrict | limit especially as a silane coupling agent used by this invention, A vinyl type silane coupling agent, an epoxy type silane coupling agent, a styryl type silane coupling agent, a (meth) acryloxy type silane coupling agent, an amino type Silane coupling agent, ureido silane coupling agent, chloropropyl silane coupling agent, polysulfide silane coupling agent, isocyanate silane coupling agent, mercapto silane coupling agent triazine silane coupling agent and imidazole silane Can be selected from coupling agents, etc.
It is preferably at least one compound selected from the group consisting of an epoxy silane coupling agent, an amino silane coupling agent, and a (meth) acryloxy silane coupling agent. Moreover, it is preferable that it is a compound which can be couple | bonded chemically or physically with inorganic powder (a) and resin (b) which has a hydrophilic group. These silane coupling agents can be used alone or in combination of two or more.

Examples of vinyl-based silane coupling agents include vinyltrichlorosilane (KA-1003, manufactured by Shin-Etsu Silicone), vinyltrimethoxysilane (KMB-1003, manufactured by the company), and vinyltriethoxysilane (KBE-1003, manufactured by the company). Vinylphenyltrimethoxylane,
Examples of the epoxy silane coupling agent include 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane (KBM-403, manufactured by Shin-Etsu Silicone), 3-glycid Xyloxymethyldiethoxysilane, 3-glycidoxypropyltriethoxysilane, 4-glycidylbutyltrimethoxysilane,
Examples of the styryl silane coupling agent include p-styryltrimethoxysilane.
Examples of the (meth) acryloxy-based silane coupling agent include 3-methacryloxypropylmethyldimethoxysilane (KBM-502, manufactured by Shin-Etsu Silicone), 3-methacryloxypropyltrimethoxysilane (KBM-503, manufactured by the same company), 3-methacryloxypropyltriethoxysilane (KBE-503, manufactured by the company), 3-methacryloxypropylmethyldiethoxysilane (KBE-502, manufactured by the company), 3-acryloxypropyltrimethoxysilane (KBM-5103, manufactured by the company) )
Examples of amino-based silane coupling agents include 3-aminopropyltrimethoxysilane (γ-aminopropyltrimethoxysilane, KBM-903, manufactured by Shin-Etsu Silicone), N-3- (4- (3-aminopropoxy) Butoxy) propyl-3-aminopropyltrimethoxysilane, N-2- (aminoethyl) -3-aminopropylmethyldimethoxysilane (KBM-502, manufactured by the same company), N-2- (aminoethyl) -3-aminopropyl Trimethoxysilane (N-β (aminoethyl) γ-aminopropyltrimethoxysilane, KBM-603, manufactured by the company), N-2- (aminoethyl) -3-aminopropyltriethoxysilane (KBE-603, manufactured by the company) ) 3-Triethoxysilyl-N- (1,3-dimethyl-butylidene) propylamine and its partial hydrolyzate, N-phenyl- - aminopropyltrimethoxysilane (KBM-573, manufactured by the company), N- (vinylbenzyl) -2-aminoethyl-3-aminopropyltrimethoxysilane hydrochloride (KBM-575, manufactured by the company), with
Examples of the ureido silane coupling agent include 3-ureidopropyltriethoxysilane (KBE-585, manufactured by Shin-Etsu Silicone),
Examples of the chloropropyl silane coupling agent include 3-chloropropyltrimethoxysilane (KBM-703, manufactured by Shin-Etsu Silicone),
Examples of the polysulfide-based silane coupling agent include bis (triethoxysilylpropyl) tetrasulfide,
Examples of the isocyanate-based silane coupling agent include 3-isocyanatopropyltriethoxysilane,
Examples of the mercapto-based silane coupling agent include γ-mercaptopropyltrimethoxysilane (KBM-803, manufactured by Shin-Etsu Silicone) and 3-mercaptopropylmethyldimethoxysilane (KBM-802, manufactured by the same company).

  In addition, triazine-based triazine silane, imidazole-based imidazole silane (manufactured by Nikko Metal Co., Ltd.):

Etc.

  Among these silane coupling agents, for example, 3-methacryloxypropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, 3-glycidoxypropyltrimethoxysilane, vinyltrimethoxysilane, vinylphenyltrimethoxylane, 4-glycidylbutyltrimethoxysilane, N-β (aminoethyl) γ-aminopropyltrimethoxysilane, N-3- (4- (3-aminopropoxy) ptoxy) propyl-3-aminopropyltrimethoxysilane, imidazolesilane Triazinesilane and γ-mercaptopropyltrimethoxysilane are preferably mentioned in view of the point that the inorganic powder can be favorably retained and fixed on the surface and / or pores of the ePTFE membrane.

  Among these, at least one compound selected from the group consisting of 3-methacryloxypropyltrimethoxysilane, 3-aminopropyltrimethoxysilane and 3-glycidoxypropyltrimethoxysilane is preferable from the same point. .

  Moreover, although the said silane coupling agent is based also on the kind of electrolyte solution to be used, it is preferable that it has an ether group from the point which can improve the wettability with respect to the electrolyte solution of the film obtained.

The silane coupling agent is not particularly limited as long as it is used in such an amount that the silane coupling agent adheres to the resulting film without impairing the effects of the present invention. However, the step (3) includes an additive such as a solvent. When performing using a solution (D), as for a silane coupling agent, the density | concentration of the silane coupling agent in this solution (D) becomes like this. Preferably it is 0.001-20 weight%, More preferably, it is 0.5-15. Used in an amount of% by weight. When the amount of the silane coupling agent is within the above range, the inorganic powder and the resin having a hydrophilic group can be firmly held in the pores existing on the surface and / or inside of the ePTFE membrane, It is possible to obtain a film that is less prone to powder falling from the film and has excellent visibility.
As the silane coupling agent used in the present invention, those produced by a conventionally known method or commercially available products can be used.

<Process (4)>
In step (4), the film obtained in step (3) is heated and dried. The temperature applied in this step (4) is not particularly limited as long as it can dry the solvent that may be contained in the film obtained in step (3), but it is 50 to 200 ° C., preferably 100. It is -200 degreeC, More preferably, it is 100-120 degreeC. Further, the temperature is preferably a temperature at which the surface and / or pore-attached or bonded (chemical and / or physical) silane coupling agent (d) of the ePTFE membrane reacts.

  By performing the step (4), the silane coupling agent (d) and the like react with the inorganic powder (a) and the resin (b) having a hydrophilic group, and the surface of the ePTFE membrane and / or the membrane from the surface. When the inorganic powder (a), the resin (b) having a hydrophilic group, or the like is firmly attached or bonded (chemically or physically) in the pores existing toward the inside can be obtained. Conceivable.

  As a result, it has excellent physical properties, such as excellent visibility in the electrolyte, low stiffness, excellent handleability, low heat shrinkage, and the ability to impregnate the electrolyte with the ePTFE membrane in a short time. It is considered that a film that can be suitably used as a separator for an electric double layer capacitor or a battery separator can be obtained as a separator.

The drying time is not particularly limited, but is preferably 30 seconds to 300 minutes.
Drying may be performed in the above temperature range under normal pressure (standard atmospheric pressure, 101.25 hPa), but may be performed under pressure.

  In the present invention, after step (4), a resin (b) having a solvent and an unreacted hydrophilic group that may be present in the film obtained in step (4), a crosslinking agent, and a silane coupling agent (d) It is preferable to provide a step (4 ′) for dissolving the like. The method in the step (4 ′) is not particularly limited.

  By performing this step, elution of unreacted hydrophilic group-containing resin (b), crosslinking agent, silane coupling agent (d), etc. that can be an impurity in the use environment when the film finally obtained is used The amount can be reduced.

≪Film≫
The film of this invention is obtained with the said manufacturing method.
In the film, inorganic powder, a resin having a hydrophilic group, a silane coupling agent, or the like is firmly attached or bonded (chemically and / or physically) to the surface and / or pores of the ePTFE membrane. It is thought that there is.

This film
(A) The contact angle with water is preferably 0 to 30 °, and the color of the film changes within 1 second after the dropping, so that the water permeability is very good.

(B) Electrolytic solution (product name TEMA-BF ₄ / SLF: DMC, manufactured by Toyo Gosei Co., Ltd., composition (weight ratio); 0.9 M triethylmethylammonium borofluoride (TEMA-BF ₄ ) / tetrahydrothiophene 1,1-dioxide Since the contact angle with (SLF): dimethyl carbonate (DMC) = 8: 2) is 0 to 30 ° and the color of the film changes within 10 seconds after the dropping, the permeability is very good.

(C) The shrinkage at 275 ° C. is preferably 10% or less, more preferably 8% or less.
(2) Visible even in the electrolyte. (Visibility can be confirmed using a colorimeter, spectrophotometer, etc.)
In particular, an electrolytic solution (product name TEMA-BF ₄ / SLF: DMC, manufactured by Toyo Gosei Co., Ltd., composition (weight ratio); 0.9 M triethylmethylammonium borofluoride (TEMA-BF ₄ ) / tetrahydrothiophene 1,1-dioxide ( SLF): preferably visible in dimethyl carbonate (DMC) = 8: 2).

  For this reason, the film of the present invention has the characteristics that ePTFE has excellent heat resistance, chemical resistance, weather resistance, electrical insulation and mechanical strength, and is excellent in wettability with respect to the electrolyte. It has properties such as easy penetration and penetration. In addition, since the film of the present invention does not easily shrink, is stiff and excellent in handleability, and can be visually recognized even in an electrolytic solution, for example, when manufacturing an electric double layer capacitor, an electrolysis is used as a separator for the capacitor. It is easy to set (inspect / check) whether or not this film (separator) is set (attached) in the proper position, and it is easy to work and handle when manufacturing capacitors. Excellent in properties.

  Since the film of the present invention has the characteristics described above, it can be suitably used as a separator for an electric double layer capacitor, a lithium ion secondary battery, a polymer lithium battery, an aluminum electrolytic capacitor, a fuel cell material, and the like. .

In an electric double layer capacitor, the electrolyte is an aqueous, organic (aprotic polar solvent such as propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, acetonitrile, sulfolane, tetraethylammonium tetrafluoroborate or tetraethylammonium hexafluoro. Cations such as organic solutes such as phosphate and tetrabutylammonium perchlorate, or tetraalkylammonium such as lithium, quaternary phosphonium and triethylmethylammonium, and BF ₄ ⁻ , PF ₆ ⁻ , ClO ₄ ⁻ , CF ₃ SO ₃ ^- inorganic solutes such as those dissolved) and ionic liquids (imidazolium consisting anions such as, pyridium-based, alicyclic amine-based, aliphatic amine, aliphatic phospho Cations such as nium and inorganic ions such as BF ₄ ⁻ and PF ₆ ⁻ , and fluorine and other anions such as CF ₃ SO ₂ ⁻ , (CF ₃ SO ₂ ) ₂ N ⁻ and CF ₃ CO ₂ ⁻ The film of the present invention is excellent in wettability with respect to either electrolyte solution (electrolyte) and easily permeates and penetrates. Therefore, when such a film of the present invention is used as a separator for an electric double layer capacitor, the production time of the electric double layer capacitor can be shortened and productivity can be improved. Moreover, since the base material consists of polytetrafluoroethylene, the film of the present invention hardly corrodes even various types of electrolytes. Therefore, various electrolyte solutions can be selected, and a long-life separator can be obtained.

  The maximum pore size of the film according to the present invention (measurement and measurement apparatus based on ASTM F316-86 method using Galwick having a surface tension of 16 dynes / cm; PERM-POROMETER manufactured by PMI) is preferably 0.01 to 10 μm. It is.

  When the pore diameter of the film according to the present invention is in the above range, ions in the electrolytic solution can be smoothly transmitted, and thus can be suitably used as a separator for an electric double layer capacitor.

  The thickness of the film according to the present invention can be appropriately changed according to the desired application, but is preferably 3 to 100 μm, and more preferably 3 to 30 μm, considering the strength of the obtained film and the like. . When the thickness of the film according to the present invention is in the above range, the electrodes can be prevented from contacting each other, and ions in the electrolytic solution can be smoothly transmitted. Therefore, the film is preferably used as a separator for an electric double layer capacitor. Can do.

[Example]
EXAMPLES Hereinafter, although the manufacturing method of this invention is demonstrated in detail by an Example, this invention is not limited at all by these Examples.

[Example 1]
An average pore diameter of 0.3 μm, a thickness of 25 μm, a maximum pore diameter (measured based on ASTM F316-86 method using Galwick having a surface tension of 16 dynes / cm, measuring device; PERM-POROMETER measuring instrument manufactured by PMI) 0.4 μm ePTFE membrane (Nippon Valqua Industries, Ltd., sa-PTFE ^™ ) was immersed in an isopropyl alcohol solution (hereinafter also referred to as “IPA”). CIK NANOTEC Co., RTIPA15WT% -G0 (slurry liquid rutile TiO ₂ was dispersed in IPA, TiO ₂ concentration: 15 wt%) to the vat containing the solution 500ml diluted 50 times with IPA, IPA solution The ePTFE membrane after immersion in was immersed for 30 seconds. The obtained film was immersed in 500 ml of an aqueous solution of polyvinyl alcohol (made by Wako Pure Chemical Industries, Ltd., degree of polymerization 1500, hereinafter also referred to as “PVA”) adjusted to a concentration of 1% by weight, and then 500 ml of glutaraldehyde 5% solution (Wako Pure Chemical Industries, Ltd.). A 25% glutaraldehyde aqueous solution manufactured by Yakuhin Co., Ltd. was diluted with pure water and adjusted to a 5% solution) and immersed for several seconds. Then, it was immersed for several seconds in hydrochloric acid (concentration 0.05N aqueous solution) in order to cross-link glutaraldehyde.

  The obtained film was immersed in an IPA diluted solution of a silane coupling agent (manufactured by Shin-Etsu Chemical Co., Ltd., IPA solution adjusted to 10 vol% concentration of 3-glycidoxypropyltrimethoxysilane, KBM-403), and then Dry at 110 ° C. for 10 minutes. Drying was performed in a dryer. Next, the dried sample was put in water, boiled at 95 ° C. for 30 minutes, and unreacted PVA, glutaraldehyde, a silane coupling agent, and IPA were dissolved to obtain a film (hereinafter “treated product”). Also called.).

The film thus produced was evaluated by the following method.
[Reference Example 1]
The same as Example 1 except that the step of immersing the ePTFE membrane after being immersed in the IPA solution for 30 seconds in a vat containing 500 ml of a solution obtained by diluting 50 times of IPTA15WT% -G0 with IPA, manufactured by CIK Nanotech Co., Ltd., is not performed. Thus, a film was obtained (hereinafter also referred to as “inorganic-free product”).

(Contact angle evaluation)
Using a contact angle meter (manufactured by Kyowa Interface Science Co., Ltd., contact angle meter, CA-X type), the permeability of the following electrolyte was examined.

Electrolyte (TEMA-BF ₄ / SLF: DMC, manufactured by Toyo Gosei Co., Ltd., composition (weight ratio); 0.9 M triethylmethylammonium borofluoride (TEMA-BF ₄ ) / tetrahydrothiophene 1,1-dioxide (SLF): Dimethyl carbonate (DMC) = 8: 2)
In addition, the evaluation of permeability was carried out by using the treated product obtained in Example 1 and sa-PTFE ^™ (average pore diameter 0.3 μm, thickness 25 μm ePTFE membrane manufactured by Nippon Valqua Industries, Ltd., hereinafter “untreated product”. ")" If it penetrates within 10 seconds after being immersed in the above electrolyte solution, "「 "if it penetrates within 10 seconds for more than 10 seconds," O "if it penetrates within 30 seconds for more than 10 seconds, within 60 seconds for more than 30 seconds In this case, “Δ” indicates the case where it penetrates into the sample, and “x” indicates that the sample does not penetrate even after 60 seconds.

(Examination of shrinkage 1)
A sample cut out in the vertical (A) and horizontal (B) sizes shown in Table 2 below was placed on a hot plate at 275 ° C., and a heat shrink test was performed. The thermal shrinkage was calculated from the size of the sample used and the size of the sample (vertical (a), horizontal (b)) after being placed on a hot plate for 30 seconds. The “shrinkage rate” was calculated by an expression represented by − (a−A) × 100 / A or − (b−B) × 100 / B.

  When compared with the untreated product, the heat shrinkage rate was improved from 27% to 7% and from 25% to 5%.

(Examination of shrinkage 2)
The treated product or the untreated product of Example 1 was punched into a circle having a diameter of 15 mm and immersed in the following electrolytic solution. The electrolytic solution penetrated into the treated product several seconds after immersion.

Electrolyte (TEMA-BF ₄ / SLF: DMC, manufactured by Toyo Gosei Co., Ltd., composition (weight ratio); 0.9 M triethylmethylammonium borofluoride (TEMA-BF ₄ ) / tetrahydrothiophene 1,1-dioxide (SLF): Dimethyl carbonate (DMC) = 8: 2)
The treated product after permeation of the electrolytic solution was placed on a metal plate, left in an electric furnace set at 275 ° C., taken out after 30 seconds, and the shrinkage rate was measured.

Further, the untreated product was immersed in the electrolytic solution, left in an electric furnace set at 275 ° C., taken out after 30 seconds, and the shrinkage rate was measured.
The treated product had little change in dimensions.

The “shrinkage rate” was calculated by an expression represented by − (x−X) × 100 / X or − (y−Y) × 100 / Y.
The film of the present invention is a film that can sufficiently withstand the reflow process because the dimensions hardly change even at a high temperature of 275 ° C. Therefore, since the film of the present invention is not easily shrunk, thermally melted and damaged even at high temperatures, it can be used for a long time at high temperatures and can be suitably used for separators and separators for electric double layer capacitors. Moreover, an electric double layer capacitor can be easily manufactured by using the separator of the present invention.

(Color evaluation)
The sample being immersed in the electrolytic solution in the examination 2 of the shrinkage rate was photographed using a digital camera.
The results are shown in FIG. An unprocessed product is in the portion surrounded by the leftmost dotted line, and the middle and right circular products are the processed products obtained in Example 1. The black part around the circle is the electrolyte.

The treated product obtained in Example 1 can be visually confirmed to be present in the electrolytic solution, but the untreated product could not be visually confirmed in the electrolytic solution. .
Further, there is a difference between the processed product and the unprocessed product when represented by RGB numerical values.

(Evaluation of visibility (transmittance))
In order to examine visibility, it measured using U-3000 type spectrophotometer (made by Hitachi High-Tech). Specifically, using the sample obtained by immersing the membrane obtained in Example 1 or Reference Example 1 in water for 10 minutes, the transmittance of the sample after water impregnation was measured in the wavelength range of 340 to 900 nm.

  The inorganic non-containing product obtained in Reference Example 1 after water impregnation showed a relatively high transmittance in the wavelength range of 340 to 900 nm. On the other hand, the transmittance of the processed product obtained in Example 1 decreased as the wavelength decreased, and the transmittance became substantially zero near the ultraviolet region.

Claims (14)

The manufacturing method of the film characterized by including following process (1A), process (2A), process (3), and process (4), or including process (1B), process (3), and process (4).
Step (1A): a step of bringing the stretched polytetrafluoroethylene film into contact with a solution containing inorganic powder,
Step (2A): a step of bringing the film obtained in Step (1A) into contact with a solution containing a resin having a hydrophilic group,
Step (1B): a step of bringing a stretched polytetrafluoroethylene film into contact with a solution containing an inorganic powder and a resin having a hydrophilic group,
Step (3): a step of attaching a silane coupling agent to the film obtained in the step (2A) or the step (1B),
Step (4): A step of heating and drying the film obtained in the step (3) at 50 to 200 ° C.   The step (1A) is a step of immersing the stretched polytetrafluoroethylene film in a solution containing inorganic powder, and the immersion time is 5 to 60 seconds. A method for producing a film.   The stretched polytetrafluoroethylene membrane is a porous membrane, and its maximum pore size (Galwick having a surface tension of 16 dynes / cm is used, and is measured and measured based on the ASTM F316-86 method; PERM-POROMETER measuring instrument manufactured by PMI ) Is 0.01 to 10 μm. The method for producing a film according to claim 1 or 2.   The silane coupling agent is a vinyl silane coupling agent, an epoxy silane coupling agent, a styryl silane coupling agent, a (meth) acryloxy silane coupling agent, an amino silane coupling agent, or a ureido silane coupling. Selected from the group consisting of an agent, a chloropropyl silane coupling agent, a polysulfide silane coupling agent, an isocyanate silane coupling agent, a mercapto silane coupling agent, a triazine silane coupling agent and an imidazole silane coupling agent. It is at least 1 type of compound, The manufacturing method of the film of any one of Claims 1-3 characterized by the above-mentioned.   The silane coupling agent is at least one compound selected from the group consisting of 3-methacryloxypropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, and 3-glycidoxypropyltrimethoxysilane. The manufacturing method of the film of any one of Claims 1-4 to do.   The inorganic powder is at least one compound selected from the group consisting of powder obtained by coating the surface of titanium oxide with silica, silica, titanium oxide, and alumina. The method for producing a film according to claim 1.   The average particle diameter measured by the dynamic light scattering method of the inorganic powder is equal to or less than the maximum pore diameter of the stretched polytetrafluoroethylene film to be used. A method for producing a film.   The resin having a hydrophilic group is at least one resin selected from the group consisting of a hydroxyl group-containing resin, a carboxylic acid group-containing resin, a sulfonic acid group-containing resin, an epoxy group-containing resin, and an amino group-containing resin. The manufacturing method of the film of any one of Claims 1-7.   The method for producing a film according to claim 1, wherein the resin having a hydrophilic group is polyvinyl alcohol.   The film obtained by the manufacturing method of any one of the said Claims 1-9.   The film according to claim 10, wherein a shrinkage rate of the film at 275 ° C. is 10% or less.   The film according to claim 10 or 11, wherein the film is visible in an electrolytic solution.   The film according to claim 10, wherein the film is a separator.   The film according to claim 13, wherein the separator is an electric double layer capacitor separator.