JP6983394B2 - Polyimide solution for forming porous polyimide film, manufacturing method of porous polyimide film and porous polyimide film - Google Patents

Description

The present invention relates to a PI solution for forming a porous polyimide (PI) film, a method for producing a porous PI film, and a porous PI film.

Porous PI film utilizes its excellent heat resistance and high porosity to be used as a material for electronic materials, optical materials, separators for lithium secondary batteries, filters, separation membranes, wire coatings and other industrial materials, and medical materials. It is used in such fields as. As a method for producing this porous PI film, Patent Documents 1 and 2 describe a solution containing a good solvent and a poor solvent for a PI precursor such as polyamic acid (hereinafter, may be abbreviated as "PAA"). , A method of obtaining a porous PI film by coating, drying and imidizing on a substrate (hereinafter, this method may be abbreviated as "dry porous process") has been proposed.

The dry porosification process is different from the wet porosification process in which the coating film formed on the substrate is immersed in a coagulating liquid containing a poor solvent to make the porous PI film porous. It is not necessary to use a coagulation bath for porosification. Therefore, no waste liquid is generated from the coagulation bath during the production of the porous PI film, which is an excellent method with good environmental compatibility.

Japanese Patent No. 4947989 Japanese Unexamined Patent Publication No. 2015-52061

However, since a PI precursor such as PAA is used in the PI solution for the dry porous process disclosed in the above patent document, when the coating film is dried and the PI precursor is converted to PI, In many cases, a high temperature of over 200 ° C. is required, and there are points to be improved from the viewpoint of process cost. Further, as the base material for coating, only a base material having heat resistance can be used, so that there is a point to be improved from the viewpoint of process compatibility.

Therefore, the present invention solves the above-mentioned problems, and an object of the present invention is to provide a PI solution for forming a porous PI film, a method for producing the same, and a porous PI film, which are highly economical and compatible with the process.

The present inventors have found that the above problems can be solved by specifying the chemical structure and composition of the PI solution for forming a porous PI film, and have completed the present invention.

The present invention has the following object.
<1> A PI solution containing a good solvent and a poor solvent for PI, wherein the PI contains at least one component selected from an oxyalkylene component, a siloxane component, and an alkylene component in the main chain. A PI solution for forming a porous PI film, which comprises a polyimide in which the ether solvent is a poor solvent.
<2> A method for producing a porous PI film, which comprises a step of forming a porous PI film by applying the PI solution to the surface of a substrate and then drying it at a temperature of 200 ° C. or lower.
<3> A porous PI film having a porosity of 20% by volume or more, 90% by volume or less, and an average pore diameter of 10 nm or more and 5000 nm or less, wherein the PI is an oxyalkylene component, a siloxane component, or an alkylene in the main chain. A porous PI film characterized by being a PI containing at least one component selected from the components.

Since the porous PI film obtained from the PI solution of the present invention has excellent heat resistance and high porosity, it is an industrial material such as an electronic material, an optical material, a separator for a lithium secondary battery, a filter, a separation membrane, and an electric wire coating. , Can be suitably used as a material for medical materials and the like.

Hereinafter, the present invention will be described in detail.

In the present invention, a PI solution containing at least one component selected from an oxyalkylene component, a siloxane component, and an alkylene component in the main chain is used. Here, PI is a heat-resistant polymer having an imide bond in the main chain, and refers to polyimide, polyamide-imide, polyesterimide, or the like. This solution can be obtained, for example, by polymerizing a diamine component, which is a monoma component, and a tetracarboxylic acid component in a solvent to form a PAA solution, and then thermally or chemically dehydrating and imidizing the solution in the solvent. .. As the solvent used here, it is preferable to use a solvent that is a good solvent for PI. The good solvent for PI means a solvent having a solubility in PI of 1% by mass or more at 25 ° C., and an amide-based solvent or a urea-based solvent is preferably used. Specific examples of the amide-based solvent include, for example, N-methyl-2-pyrrolidone (NMP boiling point: 202 ° C.), N, N-dimethylformamide (DMF boiling point: 153 ° C.), N, N-dimethylacetamide (DMAc boiling point: DMAc boiling point:). 166 ° C.) and the like. Specific examples of the urea solvent include tetramethylurea (TMU boiling point: 177 ° C.) and dimethylethylene urea (boiling point: 220 ° C.). These may be used alone or in combination of two or more. Of these, NMP and DMAc are preferred. The PI thus obtained needs to be a polyimide in which the ether solvent is a poor solvent. As the polymerization solvent, a mixed solvent containing a poor solvent for PI such as an ether solvent may be used. This poor solvent will be described later.

PAA contains at least one component selected from an oxyalkylene component, a siloxane component, and an alkylene component in the main chain. By doing so, at least one component selected from the oxyalkylene component, the siloxane component, and the alkylene component can be contained in the main chain of PI obtained by dehydration imidization.

Specific examples of the oxyalkylene component include an oxyethylene component, an oxypropylene component, and an oxybutylene component. The PAA containing an oxyalkylene component is, for example, a tetracarboxylic acid dianhydride having an oxyalkylene component (hereinafter, may be abbreviated as “TA-1”) and / or a diamine having an oxyalkylene component (hereinafter, “DA”). -1 ”), tetracarboxylic acid dianhydride having no oxyalkylene component (hereinafter, may be abbreviated as“ TA ”), and diamine having no oxyalkylene component (hereinafter,“ DA ”). It is a copolymerized PAA (hereinafter, may be abbreviated as "PAA-1") obtained by copolymerizing with (may be abbreviated as "PAA-1").

The PAA containing a siloxane component is, for example, a tetracarboxylic acid dianhydride having a siloxane component (hereinafter, may be abbreviated as “TA-2”) and / or a diamine having a siloxane component (hereinafter, “DA-2”). (Sometimes abbreviated) and a copolymerized PAA obtained by copolymerizing TA and DA (hereinafter, may be abbreviated as "PAA-2").

The PAA containing an alkylene component is, for example, a tetracarboxylic dianhydride having an alkylene component (hereinafter, may be abbreviated as “TA-3”) and / or a diamine having an alkylene component (hereinafter, “DA-3”). (May be abbreviated) and copolymerized PAA obtained by copolymerizing TA and DA (hereinafter, may be abbreviated as "PAA-3").

Two or more types of PAA-1, PAA-2, and PAA-3 can be mixed and used.

As the PAA-1 solution, TA-1 and / or DA-1 and TA and DA are blended so that the total of the tetracarboxylic dianhydride and the total of the diamine are approximately equimolar, and the solution is added. A solution obtained by polymerizing at a temperature of 10 to 70 ° C. in a mixed solvent can be used. Here, the amount of TA-1 or DA-1 used is preferably 1 to 20 mol%, more preferably 2 to 15 mol%. The mol% means a value calculated according to the following formula.
Amount of substance used for TA-1 (mol%) = (number of moles of TA-1 / (number of moles of TA-1 + number of moles of TA)) x 100
Amount of substance used (mol%) = (number of moles of DA-1 / (number of moles of DA-1 + number of moles of DA)) x 100

Specific examples of TA-1 include ethylene glycol bisanhydrotrimeritate (TMEG), diethylene glycol bisanhydrotrimerite, triethylene glycol bisanhydrotrimerite, tetraethylene glycol bisanhydrotrimerite, and polyethylene. Glycolbis Amhydrotrimeritate, Ethylene Glycol Bisuanhydrotrimeritamide, Diethylene Glycol Bisuanhydrotrimeritamide, Triethylene Glycol Bisuanhydrotrimeritamide, Tetraethylene Glycol Bisuanhydrotrimeritamide, Polyethylene Glycol Bisuanhydro Trimeritamide, Propylene Glycol Bis-Anhydro-Trimeritate, Dipropylene Glycol-Bis-Anhydro-Trimeritate, Tri-Propylene Glycol-Bis-Anhydro-Trimeritate, Tetrapropylene Glycol-Bis-Anhydro-Trimeritate, Polypropylene Glycol-Bis-Anhydrotrimeritate Tate, Propylene Glycol Bisuanhydrotrimeritamide, Dipropylene Glycol Bisuanhydrotrimeritamide, Tripropylene Glycol Bisuanhydrotrimeritamide, Tetrapropylene Glycol Bisuanhydrotrimeritamide, Polypropylene Glycol Bisuanhydrotrimeritamide, etc. Can be mentioned. These may be used alone or in combination of two or more. Of these, TMEG is preferred.

Specific examples of TA include pyromellitic acid dianhydride (PMDA), 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride (BPDA), 2,3,3', 4'-biphenyltetra. Carboxycide dianhydride, 3,3', 4,4'-benzophenonetetracarboxylic acid dianhydride (BTDA), 4,4'-oxydiphthalic acid anhydride (ODPA), and 3,3', 4,4'. -Diphenylsulfone tetracarboxylic acid dianhydride and the like can be mentioned. These may be used alone or in combination of two or more. Among these, BPDA, ODPA and BTDA are preferable.

Specific examples of DA-1 include ethylene glycol bis (2-aminoethyl) ether, diethylene glycol bis (2-aminoethyl) ether, triethylene glycol bis (2-aminoethyl) ether, and tetraethylene glycol bis (2-amino). Ethyl) ether, polyethylene glycol bis (2-aminoethyl) ether, propylene glycol bis (2-aminoethyl) ether, dipropylene glycol bis (2-aminoethyl) ether, tripropylene glycol bis (2-aminoethyl) ether, Examples thereof include tetrapropylene glycol bis (2-aminoethyl) ether and polypropylene glycol bis (2-aminoethyl) ether. These may be used alone or in combination of two or more. Among these, polyethylene glycol bis (2-aminoethyl) ether (PEGME) and polypropylene glycol bis (2-aminoethyl) ether (PPGME) are preferable. Commercially available products can be used for these compounds.

Specific examples of DA include 2,2-bis [4- (4-aminophenoxy) phenyl] propane (BAPP), 4,4'-diaminodiphenyl ether, p-phenylenediamine, m-phenylenediamine, 2,4-. Diaminotoluene, 4,4'-diaminobiphenyl, 4,4'-diamino-2,2'-bis (trifluoromethyl) biphenyl, 3,3'-diaminodiphenylsulphon, 4,4'-diaminodiphenylsulphon, 4 , 4'-diaminodiphenyl sulfide, 4,4'-diaminodiphenylmethane 3,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis ( 4-Aminophenoxy) Benzene, 1,3-bis (3-aminophenoxy) benzene, 4,4'-bis (4-aminophenoxy) biphenyl, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [ Examples thereof include 4- (3-aminophenoxy) phenyl] sulfone, 2,2-bis [4- (4-aminophenoxy) phenyl] hexafluoropropane and the like. These may be used alone or in combination of two or more. Of these, BAPP is preferred.

As the PAA-2 solution, TA-2 and / or DA-2 and TA and DA are blended so that the total of the tetracarboxylic dianhydride and the total of the diamine are approximately equimolar, and the solution is added. A solution obtained by polymerizing at a temperature of 10 to 70 ° C. in a mixed solvent can be used. Here, the amount of TA-2 or DA-2 used is preferably 1 to 20 mol%, more preferably 2 to 15 mol%. The mol% means a value calculated according to the following formula.
Amount of substance used for TA-2 (mol%) = (number of moles of TA-2 / (number of moles of TA-2 + number of moles of TA)) x 100
Amount of substance used (mol%) = (number of moles of DA-2 / (number of moles of DA-2 + number of moles of DA)) x 100

Specific examples of TA-2 include bis (3,4-dicarboxyphenyl) tetramethylsiloxane dianhydride, bis (3,4-dicarboxyphenyl) tetraethylsiloxane dianhydride, and acid anhydride groups at both ends. Examples thereof include siloxane oligomas having. These may be used alone or in combination of two or more. Examples of the siloxane oligoma having an acid anhydride group at both ends include "X22-168AS" (number average molecular weight 1,000), "X22-168A" (number average molecular weight 2,000), and "X22-168AS" manufactured by Shin-Etsu Chemical Co., Ltd. "X22-168B" (number average molecular weight 3,200), "X22-168-P5-8" (number average molecular weight 4,200), manufactured by Gerest, "DMS-Z21" (number average molecular weight 600-800), etc. Commercially available products can be used. Among these TA-2s, a siloxane oligoma having an acid anhydride group at both ends is preferable.

Specific examples of DA-2 include 1,3-bis (3-aminopropyl) -1,1,3,3-tetramethyldisiloxane and 1,3-bis (4-aminobutyl) -1,1,. 3,3-Tetramethyldisiloxane, bis (4-aminophenoxy) dimethylsilane, 1,3-bis (4-aminophenoxy) -1,1,3,3-tetramethyldisiloxane, etc., and the following general formula ( Those represented by 1) can be mentioned. These may be used alone or in combination of two or more. Among these, in the following general formula (1), R1 and R2 are trimethylene groups, R3, R4, R5 and R6 are methyl groups, and n is 3 to 100 (hereinafter, abbreviated as "DASM"). There is), and those having a number average molecular weight of 300 to 5000 are more preferable. DASM may be used alone or in combination of two or more. DASMs manufactured by Shin-Etsu Chemical Co., Ltd., KF8010 (number average molecular weight 860), X22-161A (number average molecular weight 1,600), X22-161B (number average molecular weight 3,000), KF8012 (number average molecular weight 4). , 400), manufactured by Toray Dow Corning, BY16-835U (number average molecular weight 900), manufactured by Chisso, Cilaplane FM3311 (number average molecular weight 1000), and the like can be used. Among these DA-2, DASM is preferable.

（ただし、式中ｎは１以上の整数を示す。また、Ｒ１およびＲ２は、それぞれ同一または異なった、低級アルキレン基またはフェニレン基を示し、Ｒ３、Ｒ４、Ｒ５およびＲ６は、それぞれ同一または異なった、低級アルキル基、フェニル基またはフェノキシ基を示す。）

(However, n in the formula indicates an integer of 1 or more. Further, R1 and R2 indicate the same or different lower alkylene group or phenylene group, respectively, and R3, R4, R5 and R6 are the same or different, respectively. , Lower alkyl group, phenyl group or phenoxy group.)

As the PAA-3 solution, TA-3 and / or DA-3 and TA and DA are blended so that the total amount of tetracarboxylic acid dianhydride and the total amount of diamine are approximately equimolar, and the above-mentioned solution is used. A solution obtained by polymerizing at a temperature of 10 to 70 ° C. in a mixed solvent can be used. Here, the amount of TA-3 or DA-3 used is preferably 1 to 20 mol%, more preferably 2 to 15 mol%. The mol% means a value calculated according to the following formula.
Amount of substance used for TA-3 (mol%) = (number of moles of TA-3 / (number of moles of TA-3 + number of moles of TA)) x 100
Amount of substance used (mol%) = (number of moles of DA-3 / (number of moles of DA-3 + number of moles of DA)) x 100

Specific examples of TA-3 include, for example, 1,2,3,4-butanetetracarboxylic acid dianhydride, 1,2,3,4-cyclobutanetetracarboxylic acid dianhydride, 1,3,3a, 4 , 5,9b-Hexahydro-8-methyl-5- (tetrahydro-2,5-dioxo-3-franyl) -naphtho [1,2-c] furan-1,3-dione, 1,3,3a, 4 , 5,9b-Hexahydro-5- (tetrahydro-2,5-dioxo-3-franyl) naphtho [1,2-c] furan-1,3-dione, bicyclo [3,3,0] octane-2, Examples thereof include 4,6,8-tetracarboxylic acid dianhydride and cyclohexanetetracarboxylic acid dianhydride (HPMDA). These may be used alone or in combination of two or more. Of these, HPMDA is preferred.

Specific examples of DA-3 include, for example, hexamethylenediamine, heptamethylenediamine, octamethylenediamine, nonamethylenediamine, decamethylenediamine, dodecamethylenediamine, 2,11-diaminododecane, 2,5-dimethylhexamethylenediamine. , 3-Methylheptamethylenediamine, 2,5-dimethylheptamethylenediamine, 4,4-dimethylheptamethylenediamine, 5-methylnonamethylenediamine, 3-methoxyhexamethylenediamine, dimadiamine (DDA) and other aliphatic diamines. Can be mentioned. These aliphatic diamines may be used alone or in combination of two or more. Of these, DDA is preferred. As the DDA, commercially available products such as those manufactured by Cognis Japan, trade names "Versamine 551" and "Versamine 552", and manufactured by Croda International, trade names "Priamine 1074" and "Priamine 1075" can be used.

The concentration in the PAA solution is preferably 3 to 45% by mass, more preferably 5 to 40% by mass.

The viscosity of the PAA solution at 30 ° C. is preferably in the range of 0.01 to 100 Pa · s, more preferably 0.1 to 50 Pa · s.

The PI solution can be obtained by thermally or chemically imidizing the PAA solution in the solution using a known method, but it is preferable to thermally imidize the PAA solution from the viewpoint of economy. For thermal imidization, it is preferable to carry out the reaction at a temperature of about 100 ° C. to 200 ° C. while removing the water produced by the imidization from the reaction system. As this method, a solvent such as toluene or xylene is added to the PAA solution, and water is removed from the system by using the azeotropic boiling of these solvents and water, or by bubbling nitrogen gas in the PAA solution. A method of removing water or the like can be used. For chemical imidization, a dehydrating agent such as dicyclohexylcarbodiimide or acetic anhydride may be added to the PAA solution for imidization.

In the imidization reaction, the imidization of PAA is substantially completed, but a part of the imidized portion may remain. Whether or not the imidization is completed can be determined by confirming the absorption based on the imide group of the infrared absorption spectrum, for example, as described in Japanese Patent No. 5825651 and Japanese Patent No. 293704.

The PI solution of the present invention can be obtained by mixing a PI solution (including a good solvent for PI) obtained as described above with a poor solvent for PI to prepare a mixed solvent. Here, the poor solvent means a solvent having a solubility in PI of less than 1% by mass at 25 ° C. The poor solvent preferably has a higher boiling point than the good solvent. The boiling point difference is preferably 5 ° C. or higher, more preferably 20 ° C. or higher, and even more preferably 50 ° C. or higher.

As the poor solvent, an alcohol solvent, an ester solvent, an ether solvent and the like are used, and an ether solvent is preferably used. Specific examples of the alcohol solvent include ethylene glycol (boiling point: 197 ° C.), decanol (boiling point: 233 ° C.), and the like. Specific examples of the ester-based solvent include dimethyl succinate (boiling point 200 ° C.), diethyl succinate (boiling point 218 ° C.), dimethyl glutarate (boiling point 210-215 ° C.), diethyl glutarate (boiling point 237 ° C.), and dimethyl adipate. (Boiling point 215 to 225 ° C.), diethyl adipate (boiling point 245 ° C.), ethylcarbinate acetate (ECA: boiling point 218 ° C.), butylcarbinate acetate (BCA: boiling point 247 ° C.) and the like can be mentioned. Specific examples of the ether solvent include, for example, diethylene glycol dimethyl ether (boiling point: 162 ° C.), triethylene glycol dimethyl ether (boiling point: 216 ° C.), tetraethylene glycol dimethyl ether (boiling point: 275 ° C.), diethylene glycol (boiling point: 244 ° C.), and the like. Examples thereof include solvents such as triethylene glycol (boiling point: 287 ° C.), tripropylene glycol dimethyl ether (boiling point: 215 ° C.), and dipropylene glycol dimethyl ether (boiling point: 175 ° C.). These may be used alone or in combination of two or more. Among these, triethylene glycol dimethyl ether (G3) and tetraethylene glycol dimethyl ether (G4) are preferable.

The blending amount of the poor solvent in the mixed solvent is preferably 20 to 95% by mass, more preferably 50 to 90% by mass, based on the mass of the mixed solvent. By doing so, in the drying step after coating on the substrate, phase separation occurs efficiently, and a porous PI film having a high porosity can be obtained.

If necessary, known additives such as various surfactants and silane coupling agents may be added to the PI solution as long as the effects of the present invention are not impaired. Further, if necessary, a polymer other than PI may be added to the PI solution as long as the effect of the present invention is not impaired.

A porous PI film can be formed by applying the PI solution to the surface of the substrate and drying it under normal pressure or reduced pressure. After that, the porous PI film can be peeled off from the base material to form a single porous PI film. Further, the porous PI film formed on the base material can be used by being laminated and integrated with the base material without peeling from the base material.

The drying step is a step of inducing phase separation by volatilizing the solvent contained in the coating film to form a porous PI film, and the drying temperature is preferably 200 ° C. or lower, preferably 120 ° C. or higher. , 180 ° C. or lower is more preferable.

Examples of the base material include metal foil, metal wire, glass plate, plastic film, various woven fabrics, various non-woven fabrics, and the like, and as the metal, gold, silver, copper, platinum, aluminum, and the like can be used. .. These may be porous or non-porous. As a method of applying the coating liquid to this substrate, a dip coater, a bar coater, a spin coater, a die coater, a spray coater or the like can be used, and the coating liquid can be applied continuously or in a batch manner.

The thickness of the porous PI film is usually about 1 to 800 μm, preferably about 10 to 500 μm.

The porosity of the porous PI film is 20% by volume or more and 90% by volume or less, preferably 30% by volume or more and 85% by volume or less, and more preferably 40% by volume or more and 80% by volume or less. As the porosity, a value calculated by using the following formula can be used.
Porosity (% by volume) = 100-100 × (W / D) / (S × T)
In the formula, S is the area of the porous PI film, T is the thickness thereof, W is the mass thereof, and D is the density of the corresponding non-porous PI film. By setting the porosity within such a range, it is possible to secure the excellent mechanical properties and heat resistance peculiar to the PI film.

The average pore diameter of the porous PI film is 10 nm or more and 5000 nm or less, preferably 20 nm or more and 3000 nm or less. The average pore diameter is obtained by acquiring an SEM (scanning electron microscope) image of the cross section of the porous PI film at a magnification of 1000 to 20000 times and analyzing it separately into the pore portion and the PI portion by commercially available image processing software. You can check. By setting the average pore diameter in such a range, excellent properties peculiar to the porous PI film such as air permeability and dielectric properties can be ensured. The pores of the porous PI film may be continuous pores or independent pores.

The Tg of PI constituting the porous PI film is preferably 150 ° C. or higher, more preferably 200 ° C. or higher. By setting Tg in this way, good heat resistance can be ensured. As Tg, a value measured by DSC (differential thermal analysis) can be used.

Hereinafter, the present invention will be described in more detail with reference to examples. The present invention is not limited to the examples.

[Example 1]
In a glass reaction vessel, BAPP (DA): 0.90 mol, PPGME (DA-1): 0.10 mol (molecular weight 2000: Jeffermin D2000 manufactured by Huntsman), and NMP were put into a glass reaction vessel and stirred. , Diamine was dissolved in NMP. While cooling this solution to 30 ° C. or lower with a jacket, BPDA (TA): 1.0 mol was gradually added and then polymerized at 40 ° C. for 5 hours to obtain a copolymerized PAA solution into which an oxypropylene component was introduced. rice field. Xylene was added to this solution and heated to 140 ° C. to proceed with the reaction while removing water generated by imidization of PAA from the reaction system by azeotrope to obtain a PI solution having a solid content concentration of 25% by mass. .. It was confirmed by measuring the infrared absorption spectrum that imidization of this PI was substantially completed. G4, which is a poor solvent for PI, was added to this solution to obtain a PI solution having a solid content concentration of 14% by mass with a solvent composition of NMP / G4 = 50/50 (mass ratio). This PI liquid was applied onto an aluminum foil (thickness: 150 μm) using a doctor blade, dried at 130 ° C. for 20 minutes, and laminated on the aluminum foil to form a porous PI film (P-1) having a thickness of about 50 μm. ) Was obtained. The porosity and average pore diameter of P-1 were 54% and 1200 nm, respectively.
Further, when the obtained laminate was heat-treated at 200 ° C. for 1 hour and the electric resistance value of the surface of the porous PI film (P-1) was measured, the electric resistance value was almost unchanged from that before the treatment. Good heat resistance was confirmed.

[Example 2]
As the diamine, "BAPP (DA): 0.90 mol, DASM (DA-2): 0.10 mol (number average molecular weight 860: KF-8010 manufactured by Shin-Etsu Chemical Co., Ltd.) was used, except that the same as in Example 1. In the same manner, a porous PI film (P-2) having a thickness of about 70 μm laminated on the aluminum foil was obtained. The pore ratio and the average pore diameter of P-2 were 58% and 1500 nm, respectively.

[Example 3]
As the diamine, "BAPP (DA): 0.90 mol, DASM (DA-2): 0.10 mol (number average molecular weight 860: KF-8010 manufactured by Shin-Etsu Chemical Co., Ltd.) was used, and the solvent composition was NMP / G4 = 45. A porous PI film (P-3) having a thickness of about 80 μm laminated on an aluminum foil was obtained in the same manner as in Example 1 except that the ratio was set to / 55 (mass ratio). The average pore diameter was 65% and 1200 nm, respectively.

[Example 4]
As the diamine, "BAPP (DA): 0.80 mol, DDA (DA-3): 0.20 mol (Priamine 1075 manufactured by Claude)" was used, and the solvent composition was NMP / G4 = 40/60 (mass ratio). Except for the above, the same procedure as in Example 1 was carried out to obtain a porous PI film (P-4) having a thickness of about 50 μm laminated on the aluminum foil. , 59%, 1700 nm.

[Example 5]
The same procedure as in Example 1 was carried out except that the polymerization solvent was DMAc, to obtain a porous PI film (P-5) having a thickness of about 50 μm laminated on the aluminum foil. The porosity and average pore diameter of P-5 were 57% and 2100 nm, respectively.

[Example 6]
As the tetracarboxylic acid dianhydride, "BPDA (TA): 0.40 mol, ODPA (TA): 0.40 mol, TMEG (TA-1): 0.2 mol" was used, and BAPP (DA) was used as the diamine. : 1.0 mol was used, and the same procedure as in Example 1 was carried out except that the solvent composition was NMP / G4 = 45/55 (mass ratio), and the porous PI having a thickness of about 50 μm laminated on the aluminum foil was used. A film (P-6) was obtained. The porosity and average pore diameter of P-6 were 59% and 1500 nm, respectively.

[Example 7]
As the tetracarboxylic acid dianhydride, "BPDA (TA): 0.80 mol, siloxane oligoma (TA-2) having an acid anhydride group at both ends: 0.20 mol (number average molecular weight 1,000: Shin-Etsu Chemical Co., Ltd.) X22-168AS) ”was used, BAPP (DA): 1.0 mol was used as the diamine, and the solvent composition was NMP / G4 = 40/60 (mass ratio), as in Example 1. This was performed to obtain a porous PI film (P-7) having a thickness of about 50 μm laminated on the aluminum foil. The porosity and average pore diameter of P-7 were 52% and 2500 nm, respectively.

[Example 8]
"BPDA (TA): 0.75 mol, HPMDA (TA-3): 0.25 mol" was used as the tetracarboxylic acid dianhydride, and BAPP (DA): 1.0 mol was used as the diamine, and the solvent composition was used. The same procedure as in Example 1 was carried out except that NMP / G4 = 35/65 (mass ratio) was used to obtain a porous PI film (P-8) having a thickness of about 50 μm laminated on an aluminum foil. The porosity and average pore diameter of P-8 were 51% and 2700 nm, respectively.

[Example 9]
The same procedure as in Example 1 was carried out except that the diamine was set to "BAPP (DA): 0.93 mol and PPGME (DA-1): 0.07 mol", and the porosity was laminated on the aluminum foil and had a thickness of about 50 μm. A quality PI film (P-9) was obtained. The pore ratio and average pore diameter of P-9 were 53% and 2800 nm, respectively.

[Example 10]
The same procedure as in Example 1 was carried out except that the diamine was set to "BAPP (DA): 0.85 mol, DASM (DA-2): 0.15 mol", and the thickness was about 50 μm laminated on the aluminum foil. A porous PI film (P-10) was obtained. The porosity and average pore diameter of P-10 were 51% and 2900 nm, respectively.

[Example 11]
The same procedure as in Example 1 was carried out except that the diamine was set to "BAPP (DA): 0.85 mol, DDA (DA-3): 0.15 mol", and the thickness was about 50 μm laminated on the aluminum foil. A porous PI film (P-11) was obtained. The porosity and average pore diameter of P-11 were 51% and 2200 nm, respectively.

[Example 12]
Except for the fact that the diamine was "BAPP (DA): 0.40 mol, 1,3-bis (3-aminophenoxy) benzene (DA): 0.40 mol, PPGME (DA-1): 0.20 mol". In the same manner as in Example 1, a porous PI film (P-12) having a thickness of about 50 μm laminated on an aluminum foil was obtained. The pore ratio and average pore diameter of P-12 were 61%, respectively. It was 1900 nm.

[Comparative Example 1]
An attempt was made to obtain a PI solution in the same manner as in Example 1 except that "BAPP (DA-2): 0.995 mol, PPGME (DA-1): 0.005 mol" was used as the diamine. It was not possible to obtain a uniform PI solution.

[Comparative Example 2]
An attempt was made to obtain a PI solution in the same manner as in Example 1 except that "BAPP (DA-2): 0.995 mol, DASM (DA-2): 0.005 mol" was used as the diamine. It was not possible to obtain a uniform PI solution.

[Comparative Example 3]
An attempt was made to obtain a PI solution in the same manner as in Example 1 except that "BAPP (DA-2): 0.995 mol, DDA (DA-3): 0.005 mol" was used as the diamine. It was not possible to obtain a uniform PI solution.

[Comparative Example 4]
The same procedure as in Example 1 was carried out except that G4, which is a poor solvent, was not added, to obtain a PI film having a thickness of about 40 μm, but no pores were formed in this film.

[Comparative Example 5]
The same procedure as in Example 2 was carried out except that G4, which was a poor solvent, was not added, to obtain a PI film having a thickness of about 40 μm, but no pores were formed in this film.

[Comparative Example 6]
A PI film having a thickness of about 40 μm was obtained in the same manner as in Example 3 except that G4, which was a poor solvent, was not added, but no pores were formed in this film.

As shown in the examples, it can be seen that the porous PI films P-1 to 12 obtained from the PI solution of the present invention have pores having an average pore diameter of 5000 nm or less uniformly formed. On the other hand, as shown in Comparative Examples 4 to 6, it can be seen that the porous PI film cannot be obtained from the PI solution containing no G4 which is a poor solvent.

A porous PI film can be obtained by applying the PI solution of the present invention on a substrate and drying the coating film obtained at a temperature of 200 ° C. or lower. Since this porous PI film has heat resistance and a large number of fine pores are formed, it is an industrial material such as an electronic material, an optical material, a separator for a lithium secondary battery, a filter, a separation membrane, and an electric wire coating. , Can be suitably used as a material for medical materials and the like.

Claims (3)

A polyimide solution used for forming a porous polyimide film having a pore ratio of 20% by volume or more and 90% by volume or less and an average pore diameter of 10 nm or more and 5000 nm or less by a dry porous process. , The polyimide contains a good solvent and a poor solvent for polyimide, and the polyimide is a polyimide containing at least one component selected from an oxyalkylene component, a siloxane component, and an alkylene component in the main chain, and the ether-based solvent is a poor solvent. A polyimide solution for forming a porous polyimide film, which is characterized by being a polyimide. A method for producing a porous polyimide film, which comprises a step of forming a porous polyimide film by applying the polyimide solution according to claim 1 to the surface of a substrate and then drying it at a temperature of 200 ° C. or lower. A porous polyimide film having a porosity of 20% by volume or more, 90% by volume or less, and an average pore diameter of 10 nm or more and 5000 nm or less, wherein the polyimide is selected from an oxyalkylene component, a siloxane component, and an alkylene component in the main chain. at least one component Ri Oh polyimide containing the monomer composition of the polyimide, a porous polyimide film and satisfies at least one of the following (1) to (3) to be.
(1) The amount of TA-1 or DA-1 used is 1 to 20 mol%.
(2) The amount of TA-2 or DA-2 used is 1 to 20 mol%.
(3) The amount of TA-3 or DA-3 used is 1 to 20 mol%.
Here, TA-1 is a tetracarboxylic dianhydride having an oxyalkylene component, DA-1 is a diamine having an oxyalkylene component, TA-2 is a tetracarboxylic dianhydride having a siloxane component, and DA-2 is a siloxane. Diamine having a component, TA-3 means a tetracarboxylic dianhydride having an alkylene component, and DA-3 means a diamine having an alkylene component.