JP5900868B2 - Porous polyimide and method for producing the same - Google Patents

Description

  The present invention relates to a porous polyimide, particularly a polyimide film having three-dimensionally ordered macroporous (hereinafter 3DOM). These porous membranes can be suitably used for battery membrane materials such as separators and ion exchange membranes, optical materials such as displays and optical waveguides, and catalyst supports.

  In recent years, studies have been made on polyimide porous membranes as fuel cell electrolyte membranes and low dielectric constant materials. For example, a method of heat imidizing a block copolymer or a graft copolymer of polyimide and an easily decomposable component to make it porous, and a technique of optically treating a polyimide film to form a continuous pore film are known (Patent Document 1). To 4).

Japanese Patent Laid-Open No. 2004-2865 JP 2003-147118 A JP 2007-92078 A JP 2004-171994 A

  The above-mentioned film has a problem in reproducibility and the like such that a portion which is not necessarily a communication hole is generated or the porosity is changed, and the physical property value varies in the application field and the application field.

  Accordingly, an object of the present invention is to provide a method capable of producing a 3DOM polyimide film having continuous micropores arranged three-dimensionally in a highly reproducible manner.

The present invention is a process for producing a porous silica mold, which is filled with silica particles having a particle size of 100 to 2000 nm and then sintered to obtain a porous silica mold,
After filling the voids of the porous silica mold obtained in the porous silica mold manufacturing process with a polyimide solution, the polyimide is filled with a polyimide filling process by removing the solvent, and the porous silica filled with the polyimide. The present invention relates to a method for producing a porous polyimide, comprising a silica removal step of removing silica from a mold to obtain a porous polyimide.

In the present invention, in the above-described manufacturing process of the porous silica mold, it is preferable that silica particles having a particle size of 100 to 2000 nm are closely packed and then sintered to obtain a porous silica mold.
In the polyimide filling step, the polyimide can be filled by ring-closing reaction of the polyamic acid after the polyamic acid is filled in the voids of the porous silica mold.
In the polyimide filling step, the polyimide can be filled by removing the solvent after filling the voids of the porous silica mold with the polyimide solution.
In the polyimide filling step, polyimide can be filled by filling the voids of the porous silica mold with a polyimide melt.
In the silica removal step, it is preferable that the porous silica mold filled with polyimide is immersed in an aqueous hydrogen fluoride solution to dissolve and remove the silica.
Preferably, the obtained porous polyimide is a film having an average film thickness of 10 to 300 μm.

The present invention is a membrane-like porous polyimide having micropores regularly arranged in three dimensions,
The porosity of the film is 70% or more,
The average diameter of the micropores is 100 to 2000 nm,
The micropores are in contact with each other to form a communication hole, and the diameter of the communication hole is 1000 nm or less.

  The present invention has an advantage that a porous polyimide having continuous micropores arranged in a three-dimensional order can be obtained by using a porous silica mold formed from regularly arranged and filled silica particles.

It is a figure which shows the diameter of a micropore and a communicating hole. 3 is a drawing-substituting photograph of the 3DOM polyimide porous membrane obtained in Example 1. FIG. 5 is a drawing-substituting photograph of the polyimide film obtained in Comparative Example 1. FIG.

  The porous silica mold is obtained by sintering after filling with silica particles. The silica particles are preferably colloidal silica or monodispersed spherical silica particles. Silica particles having a particle diameter (average diameter) of 100 to 2000 nm can be used.

  A porous silica mold can be obtained by preparing and sintering a regular array of silica particles as a mold. Silica particles can be arranged by a filtration method or the like, and preferably close-packed to produce a three-dimensional ordered porous silica mold.

  As the casting spherical particles, acrylic beads and polystyrene beads other than the silica particles can be used in combination with the silica particles. In addition, since things other than a silica particle may break easily at the time of polyamic acid (polyamic acid) filling, preferably only a silica particle is used.

  By filling the voids of the porous silica mold with polyimide, a silica-polyimide composite film can be obtained. The composite film can be manufactured with good reproducibility by dissolving the silica mold silica with low-concentration hydrogen fluoride water or the like to have a three-dimensionally ordered 3DOM polyimide film having continuous micropores.

  The template used in this method is preferably composed of silica spherical particles, and is preferably a structure in which spherical particles are three-dimensionally closely packed. Regularly arranged micropores and continuous pores can be obtained stably.

  As the silica monodispersed spherical particles, particles having a diameter of 100 to 2000 nm manufactured by Nippon Shokubai are suitable. In such a range, it is easy to obtain good performance in an application field, for example, in an electrolyte membrane. According to the diameter of the silica particles, the fine pore diameter and the communication pore diameter are affected, and an improvement in performance based on the same diameter can be expected.

  These particles can be stably dispersed in water. This can also be done by using a polycarbonate membrane filter, sucking the suspension as necessary, filtering, aligning and depositing particles on the filter, etc. It is possible to obtain a silica film as a mold by sintering.

  In the polyimide filling, the polyimide can be filled by performing a ring-closing reaction of the polyamic acid after the polyamic acid is filled into the voids of the porous silica mold. In the polyimide filling step, the polyimide can be filled by removing the solvent or filling the polyimide melt after filling the voids of the porous silica mold with the polyimide solution.

  The polyamic acid (polyamic acid) or polyimide solution used for filling is obtained from any tetracarboxylic dianhydride and diamine.

  Examples of the acid dianhydride include ethylenetetracarboxylic dianhydride, butanetetracarboxylic dianhydride, cyclopentanetetracarboxylic dianhydride, cyclohexanetetracarboxylic dianhydride, 1,2,4,5- Cyclohexanetetracarboxylic dianhydride, 1,2,3,4-cyclohexanetetracarboxylic dianhydride, pyromellitic dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride Bis (2,3-dicarboxyphenyl) methane dianhydride, bis (3,4-dicarboxyphenyl) methane dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 2,2,6,6-biphenyltetracarboxylic dianhydride, 2,2-bis (3,4-dicarboxyphenyl) propane dianhydride, 2,2-bis (2,3-dicarboxyphenyl) propane Dianhydride, 2,2-bis (3,4-dicarboxyphenyl) -1,1,1,3,3,3-hex Safluoropropane dianhydride, 2,2-bis (2,3-dicarboxyphenyl) -1,1,1,3,3,3-hexafluoropropane dianhydride, bis (3,4-dicarboxy) Phenyl) sulfone dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, bis (2,3-dicarboxyphenyl) ether dianhydride, 3,3 ', 4,4'-benzophenonetetracarboxylic Acid dianhydride, 2,2 ', 3,3'-benzophenonetetracarboxylic dianhydride, 4,4- (p-phenylenedioxy) diphthalic dianhydride, 4,4- (m-phenylenedioxy ) Diphthalic dianhydride, 1,2,5,6-naphthalene tetracarboxylic dianhydride, 1,4,5,8-naphthalene tetracarboxylic dianhydride, 2,3,6,7-naphthalene tetracarboxylic acid Dianhydride, 1,2,3,4-benzenetetracarboxylic dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, 2,3,6,7-anthracenetetraca Bon dianhydride, 1,2,7,8-phenanthrene tetracarboxylic acid dianhydride, 9,9-bis phthalic anhydride fluorene, and the like. These tetracarboxylic dianhydrides can be used alone or in admixture of two or more.

  As diamine, fatty acid diamine, aromatic diamine, etc. can be mixed and used. The aliphatic diamine has, for example, about 2 to 15 carbon atoms, and specific examples include pentamethylenediamine, hexamethylenediamine, and heptamethylenediamine. Examples of the aromatic diamine include diamino compounds in which one phenyl group or about 2 to 10 phenyl groups are bonded.

  Specifically, phenylenediamine and derivatives thereof, diaminodiphenyl compounds and derivatives thereof, diaminotriphenyl compounds and derivatives thereof, diaminonaphthalene and derivatives thereof, aminophenylaminoindane and derivatives thereof, diaminotetraphenyl compounds and derivatives thereof, diamino Xaphenyl compounds and derivatives thereof, cardo-type fluorenediamine derivatives.

  Phenylenediamine is m-phenylenediamine, p-phenylenediamine, etc., and the phenylenediamine derivative is a diamine to which an alkyl group such as methyl group or ethyl group is bonded, for example, 2,4-triphenylenediamine.

  The diaminodiphenyl compound is a compound in which two aminophenyl groups are bonded to each other via other groups. This bond includes an ether bond, a sulfonyl bond, a thioether bond, a bond by alkylene or a derivative group thereof, an imino bond, an azo bond, a phosphine oxide bond, an amide bond, a ureylene bond, and the like. The alkylene bond has about 1 to 6 carbon atoms, and the derivative group has one or more hydrogen atoms in the alkylene group substituted with halogen atoms or the like.

  Examples of diaminodiphenyl compounds include 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether, 3,3'-diaminodienyl sulfone, 3,4'-diaminodienyl Sulfone, 4,4'-diaminodienylsulfone, 3,3'-diaminodiphenylmethane, 3,4'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl sulfide, 3,3'- Diaminodienyl ketone, 3,4'-diaminodiphenyl ketone, 2,2-bis (p-aminophenyl) propane, 2,2'-bis (p-aminophenyl) hexafluoropropane, 4-methyl-2, 4-bis (p-aminophenyl) -1-pentene, 4-methyl-2,4-bis (p-aminophenyl) -2-pentene, iminodianiline, 4-methyl-2,4-bis (p- Aminophenyl) pentane, bis (p-a Nofeniru) phosphine oxide, 4,4'-aminoazobenzene, 4,4'-diaminodiphenyl urea, may be mentioned 4,4'-diaminodiphenyl amide.

  In the diaminotriphenyl compound, two aminophenyl groups and one phenylene group are both bonded via other groups, and the other groups are the same as the diaminodiphenyl compounds.

  Examples of diaminotriphenyl compounds include 1,3-bis (m-aminophenoxy) benzene, 1,3-bis (p-aminophenoxy) benzene, 1,4-bis (p-aminophenoxy) benzene, and the like. be able to.

  Examples of diaminonaphthalene include 1,5-diaminonaphthalene and 2,6-diaminonaphthalene.

  Examples of aminophenylaminoindanes include 5 or 6-amino-1- (p-aminophenyl) -1,3,3-trimethylindane.

  Examples of diaminotetraphenyl compounds include 4,4'-bis (p-aminophenoxy) biphenyl, 2,2'-bis [p- (p'-aminophenoxy) phenyl] propane and 2,2'-bis [ and p- (p′-aminophenoxy) biphenyl] propane, 2,2′-bis [p- (m-aminophenoxy) phenyl] benzophenone, and the like.

  Examples of the cardo type fluorene derivative include 9,9-bisaniline fluorene. A compound in which the hydrogen atom of these aromatic diamines is substituted with at least one substituent selected from the group such as a halogen atom, a methyl group, a methoxy group, a cyano group, and a phenyl group may be used.

  The means for producing the polyamic acid and the polyimide solution according to the present invention are not particularly limited. For example, (a.1) a method of reacting an acid and a diamine component in an organic solvent, (a.2) chemical imidization of the polyamic acid Alternatively, known methods such as a method of heating imidization and dissolving in an organic solvent can be used.

  Solvents used here include aprotic polar solvents such as N, N-dimethylformamide, N, N-dimethylacetamide, N-methyl-2-pyrrolidone, phenolic solvents such as cresols, glycols such as diglyme And system solvents. These solvents can be used alone or in admixture of two or more. Although there is no restriction | limiting in particular in the usage-amount of a solvent, It is desirable that content of the polyimide to produce | generate shall be 5-50 mass%.

The polymerization temperature is generally -10 to 120 ° C, preferably 5 to 30 ° C.
The polymerization time varies depending on the raw material composition to be used, but is usually 3 to 24 Hr (hour).

  The intrinsic viscosity of the polyimide precursor and polyimide organic solvent solution obtained under such conditions is in the range of 0.1 to 3.0 dl / g, more preferably 0.2 to 1.5 dl / g.

  After impregnating the polyamic acid or polyimide solution thus obtained into the gaps of the three-dimensional ordered array silica film as a template, removing the solvent contained at any temperature, and performing imidization treatment as necessary and curing Then, a polyimide porous membrane having continuous micropores arranged three-dimensionally by eluting the template with low concentration hydrogen fluoride water is manufactured with good reproducibility.

In a preferred example, the porous polyimide can be produced as follows.
100 to 2000 nm spherical silica particles are filtered under reduced pressure at 0 to 20 MPa, closely packed, and a porous silica mold obtained by firing at 500 to 1200 ° C. is used. The solvent solution and the melt are filled and immersed in an aqueous hydrogen fluoride solution to dissolve and remove the silica.

  The membrane-like porous polyimide obtained as described above has fine pores regularly arranged in three dimensions, and the porosity of the membrane is 70% or more, preferably 85% or less. The average diameter is 100 to 2000 nm, and the polyimide phase and the spatial phase form fine communication holes in the membrane or the like, and the diameter of the communication holes is 1000 nm or less, preferably 10 nm or more.

Further, in a preferred example of the porous polyimide, the polyimide filling the voids is obtained by thermally or chemically ring-closing the polyamic acid represented by the repeating unit represented by the formula (1), or the repeating represented by the formula (2). The unit polyimide is dissolved in a solvent, or is melted by heat and filled.

  The porous polyimide can be produced into a film having an average film thickness of 10 to 300 μm. Preferably, the porous polyimide has a mass loss of at least 5% in heat resistance of 350 ° C. or higher.

The physical properties of the polyimide porous membrane were determined by the following measurement method.
1) Porosity
Porosity [%] = 100− (W / (A × L × d)) × 100
(W is the mass of the film, A is the apparent area of the film, L is the film thickness, and d is the density of the polyimide.)
2) Micropore diameter The diameters D1 and D2 of the micropores P1 and P2 as shown in FIG. From the scanning electron microscope (SEM) photograph of the surface of the porous film, the diameter was measured for a plurality of apertures and calculated from the average value.
3) Diameter of communication hole The diameter D3 of the communication hole Q of the micro holes P1 and P2 as shown in FIG. From the scanning electron micrograph of the cross section of the porous film, the diameters of the apertures at a plurality of points were measured and calculated from the average value.
4) Td 5% (5% mass reduction temperature)
Using a Shimadzu TGA-60, the measured temperature R.P. T. T. et al. (Room temperature) -800 degreeC, temperature rising rate 10 degree-C / min, and measured in nitrogen atmosphere.

  550 nm diameter silica monodispersed spherical particles made by Nippon Shokubai Co., Ltd. were dispersed in distilled water to form a suspension, and vacuum filtration was performed using a membrane filter, and the finest packing was deposited on the filter with a thickness of 100 μm. Thereafter, the silica was dried, removed from the filter, and baked at 900 ° C. for high strength. On the other hand, as a polyimide precursor to be filled, 0.5 mol of pyromellitic acid (PMDA) and 0.5 mol of 4,4′-diaminodiphenyl ether (ODA) are reacted in dimethylacetamide, and the solid content concentration is 10% by mass. A polyamic acid was synthesized.

  The synthesized polyamic acid was filled in a three-dimensional particle ordered silica film (porous silica mold) as a template by a vacuum impregnation method, and imide was cured by heating imidization. The polyimide-silica composite film was immersed in a 10% by mass hydrogen fluoride aqueous solution to dissolve the silica to obtain a 3DOM polyimide film having continuous fine pores. A cross-sectional SEM image of the obtained polyimide film is shown in FIG. The physical properties are summarized in Table 1.

  The silica monodispersed spherical particles of Example 1 were made to have a particle diameter of 1500 nm, and the same treatment as in Example 1 was performed to obtain a polyimide porous membrane having continuous fine pores. The physical properties are summarized in Table 1.

  The silica monodispersed spherical particles of Example 1 were made to have a particle size of 280 nm, and the same treatment as in Example 1 was performed to obtain a polyimide porous membrane having continuous fine pores. The physical properties are summarized in Table 1.

  The polyimide raw material used was changed to 3,3,4,4'-biphenyltetracarboxylic dianhydride (S-BPDA) and paraphenylenediamine (PDA). The physical properties are summarized in Table 1.

  Uses oxydiphthalic dianhydride (ODPA) and 5 (6) -amino-1- (p-aminophenyl) -1,3,3-trimethylindane (DAIND) as polyimide raw materials and N-methylpyrrolidone as solvent And a dehydration ring-closing reaction at 180 ° C. to prepare a polyimide solution having a solid concentration of 10% by mass.

  The polyimide solution was filled in the porous silica mold produced in Example 1 using a vacuum impregnation method, dried under reduced pressure, the solvent was removed, and a polyimide-silica composite membrane was obtained.

  The polyimide-silica composite film was immersed in an aqueous hydrogen fluoride solution in the same manner as in Example 1 to dissolve the silica, thereby obtaining a 3DOM polyimide film. The physical properties are shown in Table 1.

Comparative Example 1

  Alkoxytitanium, which is easily decomposed at high temperature, was dispersed in polyamic acid, and imidized by heating at high temperature to prepare a polyimide porous film. A cross-sectional SEM image of the obtained polyimide film is shown in FIG.

  As shown in FIG. 2, Table 1, etc., the example provides a 3DOM porous polyimide having regular continuous micropores, which is useful for an electrolyte membrane. In the comparative example, almost no continuous fine pores were obtained, which was insufficient as a continuous fine pore porous membrane.

  3DOM porous polyimide provides a porous membrane having three-dimensional regular array of continuous micropores and a porosity of 70% or more, and is required to have stable physical properties such as a fuel cell electrolyte membrane and a low dielectric constant. It can also be used as a material.

P1, P2 Micro hole Q Communication hole D1, D2, D3 Diameter

Claims (4)

A process for producing a porous silica mold, which is filled with silica particles having a particle size of 100 to 2000 nm and then sintered to obtain a porous silica mold;
After filling the voids of the porous silica mold obtained in the porous silica mold manufacturing process with a polyimide solution, the polyimide is filled with a polyimide filling process by removing the solvent, and the porous silica filled with the polyimide. A method for producing porous polyimide, comprising a silica removal step of removing silica from a mold to obtain porous polyimide. It polyimide to fill the gap mentioned above is a polyimide showing a polyamic acid represented by the repeating unit represented by formula (1) those obtained by thermal or chemical ring closure reaction, or a repeating unit represented by formula (2) The method for producing a porous polyimide according to claim 1.
  3. The porous material according to claim 1, wherein in the silica removing step, a porous silica mold filled with polyimide is immersed in an aqueous hydrogen fluoride solution to dissolve and remove the silica. 4. A method for producing polyimide. The method for producing a porous polyimide according to any one of claims 1 to 3, wherein the obtained porous polyimide is a film having an average film thickness of 10 to 300 µm.