JP2010163498A - Polyimide-based resin porous film or coating and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyimide-based resin porous film or coating which is thin but has a large number of pores, high porosity and a large water contact angle. <P>SOLUTION: A polymer solution includes an organic solvent mixture containing 30-99 wt.% of a cyclic ether (A) and 1-40 wt.% of a cyclic alcohol (B) which is a nonsolvent for a polyimide-based resin and has a boiling point higher than that of the cyclic ether (A), and 1-20 pts.wt. of a polyimide-based resin based on 100 pts.wt. of the organic solvent mixture. The polymer solution is cast into film or applied to a base material, then heated to remove an organic solvent to provide the polyimide-based resin porous film or coating. In the film or coating, porosity is 20-80%, an average pore size in the film or coating section is 0.1-10 μm, thickness is more than twice the average pore size and 1-100 μm, and water contact angle is 65°or larger. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a porous film or coating having a large number of continuous micropores and having strength, or a coating coated with the coating, and a method for producing the same.

  Polyimide resin with various excellent properties such as physical properties such as strength, chemical properties such as heat resistance and electrical properties such as relative dielectric constant, is useful by taking advantage of these properties by processing this into a porous body. It has been studied for various industrial uses as a material.

  As one method for producing a polyimide-based resin porous body, a technique for creating a porous body by molding a resin composition to which a chemical foaming agent has been added in advance (Japanese Patent Laid-Open No. 61-148244) has been disclosed. It was necessary to heat melt process at a high temperature using a special foaming agent, and it was not a method suitable for obtaining a thin porous body having fine pores uniformly and having a thickness of 100 μm or less as a processing method. There is also a problem that a residue of the chemical foaming agent remains. Alternatively, as a method of using an organic solvent or the like as a foaming agent regardless of a chemical foaming agent, an organic solvent having an affinity for a polyimide resin body that has been molded and processed in advance is impregnated and then heat-treated to remove the organic solvent. Although there is a disclosure of means for obtaining a porous body by foaming (Japanese Patent Laid-Open No. Sho 61-126146), it is severe such as forcibly impregnating an organic solvent under heat and pressure in a resin composition processed in advance by extrusion molding or the like. It was necessary to expose to various conditions, and the foaming of the solvent was severely restricted depending on the conditions, such as heterogeneity and cracks.

  On the other hand, a polymer solution obtained by dissolving a polyimide resin in an aprotic good solvent or the like is contacted with a non-solvent such as water having compatibility with the aprotic good solvent to obtain a porous material by a method commonly called dry-wet spinning. Phases of polymer solution, such as a technology for forming a film (Japanese Patent Laid-Open No. 11-537) and a technology using a heat-induced phase separation method that makes a polymer solution porous by giving a temperature change (Japanese Patent Laid-Open No. 6-166116) A method using a separation phenomenon is also performed. Furthermore, according to this method, a polyimide resin porous film having a porous structure and excellent surface wettability can be provided by devising a phase separation method of a polymer solution (Japanese Patent Laid-Open No. 2007-126638). Publication). However, in both cases, the solvent and additives are finally extracted and washed with water, so that a large amount of waste water is generated by extraction and washing, and water must be evaporated and dried from the obtained porous polyimide resin. There was a problem. Moreover, since the pores of the obtained porous body or porous membrane are in a wet state filled with water, there is a problem that water must be evaporated and dried to obtain a dried polyimide resin porous body. .

  As a method for forming a porous body without extraction of a solvent with a non-solvent (such as water) of such a polymer, there is a method of heating and evaporating a polymer solvent (dry phase separation method). However, in the case of polyimide resin, surface roughness is obtained by absorbing moisture in the air while evaporating the solvent from a polymer solution dissolved in a low-boiling chlorine solvent (which is difficult to use due to environmental problems). A porous body having sufficiently large pores and a high porosity has not been obtained to the extent that a technology for whitening by forming is disclosed (JP-A-60-139413). This is presumably because a polymer solution that causes a phase separation phenomenon only due to evaporation of the solvent cannot be obtained in a stable and homogeneous state. A technology for obtaining a homogeneous polyimide resin film that does not contain voids containing inorganic fillers by casting a homogeneous polymer solution dissolved in a good polymer solvent and removing the solvent by heating after molding -213805) and an organic solvent having a specific composition containing cyclic diethers can be used to obtain a stable and homogeneous polymer solution, which is cast and heated after molding to remove the solvent. However, a technique for obtaining a polyimide resin film (Japanese Patent Laid-Open No. 2006-291179) is disclosed, but until a polyimide resin porous body having sufficiently large pores and a high porosity is obtained. It was not reached.

JP 61-148244 A JP 61-126146 A Japanese Patent Laid-Open No. 11-537 JP-A-6-166116 JP 2007-126638 A JP-A-60-139413 JP 2006-213805 A JP 2006-291179 A

  An object of the present invention is to provide a polyimide-based resin porous film or coating film that is thin and has a large number of pores even when it is thin, has a high porosity, and has a large contact angle with water.

  Another object of the present invention is to provide a method for easily and efficiently producing a polyimide-based resin porous film or coating having a small thickness and a large number of pores even when the thickness is small, and a high porosity. .

  Still another object of the present invention is a method for producing a coating coated with a polyimide-based resin porous coating that is thin, has a large number of pores even if it is thin, has a high porosity, and has a large contact angle with water. And providing a coating obtained by the method.

  As a result of intensive studies to achieve the above object, the present inventors have found that the cyclic ether (A), the cyclic alcohol (B) which is a non-solvent for the polyimide resin and has a higher boiling point than the cyclic ether (A), and the polyimide After casting a polymer solution containing a specific resin in a specific ratio into a film or applying it to a substrate, the organic solvent is removed by heating, resulting in an efficient polyimide resin film with a thin thickness and high porosity The present invention has been completed by finding that it can be obtained well.

  That is, the present invention is an organic containing 30 to 99% by weight of cyclic ether (A), 1 to 40% by weight of cyclic alcohol (B) which is a non-solvent of polyimide resin and has a boiling point higher than that of cyclic ether (A). A solvent solution and a polymer solution containing 1 to 20 parts by weight of a polyimide resin with respect to 100 parts by weight of the organic solvent mixture are cast into a film or applied to a substrate, and then the organic solvent is removed by drying. The porosity is 20 to 80%, the average pore diameter of the film or coating cross section is 0.1 to 10 μm, the thickness is twice or more the average pore diameter and 1 to 100 μm, and the contact angle with water is Provided is a polyimide-based resin porous film or coating film having an angle of 65 ° or more.

  In the polyimide resin porous film or coating, the organic solvent mixed solution is a non-solvent of the polyimide resin in addition to the cyclic ether (A) and the cyclic alcohol (B) and has a higher boiling point than the cyclic ether (A) and is cyclic. An organic solvent having a boiling point lower than that of alcohol (B) and containing 1 to 40% by weight of at least one organic solvent (C) selected from the group consisting of cyclic ethers, cyclic ketones and cyclic alkanes. May be.

  The boiling point of the cyclic ether (A) may be less than 110 ° C, and the boiling point of the cyclic alcohol (B) may be 110 ° C or more.

  It is preferable that the organic solvent mixture does not substantially contain a halogen atom-containing solvent.

  The viscosity of the polymer solution is preferably in the range of 5 to 10,000 mPa · s.

  The present invention also includes 30 to 99% by weight of cyclic ether (A), 1 to 40% by weight of cyclic alcohol (B) which is a non-solvent of polyimide resin and has a boiling point higher than that of cyclic ether (A). Porosity obtained by applying a solvent mixture and a polymer solution containing 1 to 20 parts by weight of a polyimide-based resin to 100 parts by weight of the organic solvent mixture and drying and removing the organic solvent. Is a polyimide-based resin porous film having an average pore diameter of 0.1 to 10 μm, a thickness of 1 to 100 μm and a contact angle with water of 65 ° or more. A coating coated with a coating is provided.

  The present invention further includes 30 to 99% by weight of cyclic ether (A), 1 to 40% by weight of cyclic alcohol (B) which is a non-solvent of polyimide resin and has a boiling point higher than that of cyclic ether (A). A solvent solution and a polymer solution containing 1 to 20% by weight of a polyimide resin with respect to 100 parts by weight of the organic solvent solution are cast into a film or applied to a substrate, and then the organic solvent is removed by drying. Provided is a method for producing a polyimide-based resin porous film or film.

  In the method for producing the polyimide resin porous film, after casting or coating a polymer solution having a liquid temperature of −30 ° C. to 50 ° C., (liquid temperature at casting or coating −20 ° C.) to (liquid at casting or coating) The organic solvent may be removed by holding at a temperature in the range of (temperature + 50 ° C.) for 1 second or longer and then heating at a temperature not higher than the glass transition point of the polyimide resin.

  The present invention further contains 30 to 99% by weight of cyclic ether (A) and 1 to 40% by weight of cyclic alcohol (B) which is a non-solvent for polyimide resin and has a boiling point higher than that of cyclic ether (A). A polyimide characterized in that an organic solvent mixed solution and a polymer solution containing 1 to 20% by weight of a polyimide resin with respect to 100 parts by weight of the organic solvent mixed solution are applied to a substrate, and then the organic solvent is dried and removed. A method for producing a coating coated with a porous resin porous coating is provided.

  In the manufacturing method of the coating material coat | covered with the said polyimide resin porous film, after apply | coating the polymer solution of liquid temperature-30 degreeC-50 degreeC to a base material, (liquid temperature at the time of application | coating -20 degreeC)-(liquid at the time of application | coating) The organic solvent may be removed by holding at a temperature in the range of (temperature + 50 ° C.) for 1 second or longer and then heating at a temperature not higher than the glass transition point of the polyimide resin.

  ADVANTAGE OF THE INVENTION According to this invention, even if it is thin, even if it is thin, it has many void | holes, the porosity is high, and the polyimide resin porous film with a large contact angle with respect to water is provided.

  According to the method for producing a polyimide-based resin porous film of the present invention, since a specific organic solvent is used in combination in the dry phase separation method, the thickness is thin, even if it is thin, it has a large number of pores and has a high porosity. A polyimide resin porous film can be produced easily and efficiently. In addition, a polyimide resin porous film having a large contact angle with water can be produced easily and efficiently. Furthermore, according to the production method of the present invention, it is not necessary to use a highly toxic chlorine-based solvent as in the conventional dry phase separation method, and an additive such as a low-volatile solvent, a water-soluble polymer, or lithium chloride is used. Since it is not necessary to provide an extraction process, it is excellent in that it can be manufactured with simple equipment. In addition, in the conventional wet / dry wet method, an additive component serving as an opening aid such as a water-soluble polymer or lithium chloride is added to make it porous, but in the method of the present invention, an arbitrary amount of additive component is added. By doing so, it is possible to control wettability from water repellency to hydrophilicity. In conventional wet / dry wet methods, it is difficult to control the concentration properly in the coagulation tank because the wettability is controlled by the degree of extraction of the added water-soluble polymer and opening aid such as lithium chloride. However, in the present invention, the wettability can be easily controlled by adjusting the addition amount.

  In the conventional wet method, the dope for forming the porous body (porous film or coating) is guided to a coagulation tank such as water, and the good solvent is replaced with a poor solvent such as water. It becomes about 1/3 of the dope coating thickness to the dope coating thickness. In order to create a thin porous body, it is necessary to reduce the coating thickness of the dope, but in order to create a thin porous body of 50 μm or less, it is necessary to increase the mechanical accuracy of the coating part and an expensive apparatus is required. It becomes. On the other hand, the production method of the present invention is characterized in that the solvent volatilizes after drying, and solvent substitution is not performed, so that the porous body becomes 1/3 to 1/10 of the dope coating thickness. For this reason, even when a thin porous body having a thickness of 50 μm or less is prepared, the dope is thickly applied, and a special apparatus with high mechanical accuracy is not required, which is advantageous for producing a thin porous film or coating.

  The polyimide-based resin porous film or coating of the present invention has excellent heat resistance, heat insulation, low dielectric properties, sound absorption, printability, substance filling property, etc. It can be used for low dielectric constant insulating layers, gas / liquid separation membranes, and the like. Specific examples of applications include wire coating and laminated circuit coating. Moreover, since the polyimide resin porous film or coating of the present invention has a high porosity, the dielectric constant is low and the contact angle is also high, so that the liquid is difficult to penetrate. Therefore, the polyimide resin porous film or coating of the present invention is also suitable as a printing substrate and an image receiving layer for ink, and is excellent in fine line drawing printed on the porous film or coating of the present invention. It is also useful as a base material for use. Some porous bodies in the wet / dry wet process have a high porosity and a low dielectric constant. However, since the contact angle is low and the liquid easily permeates, a short circuit is likely to occur between the circuits due to the liquid contact.

2 is an electron micrograph (SEM) of a cross section of the porous film obtained in Example 1. FIG. 4 is an electron micrograph (SEM) of a cross section of the porous film obtained in Example 4.

  The polyimide-based resin porous film or coating of the present invention has a cyclic ether (A) of 30 to 99% by weight, a non-solvent of the polyimide-based resin and a cyclic alcohol (B) having a boiling point higher than that of the cyclic ether (A). After casting an organic solvent mixed solution containing 40% by weight and a polymer solution containing 1 to 20 parts by weight of a polyimide-based resin with respect to 100 parts by weight of the organic solvent mixed solution, or after applying to a substrate The porosity obtained by removing the organic solvent by heating is 20 to 80%, the average pore diameter of the hole in the cross section of the film or film is 0.1 to 10 μm, the thickness is at least twice the average pore diameter, and 1 to It is a polyimide resin porous film or film having a contact angle of 100 μm and water of 65 ° or more.

  Examples of the cyclic ether (A) include 5-membered cyclic ethers such as tetrahydrofuran, 1,2-dioxolane, 1,3-dioxolane, 1,2-dioxole, 1,3-dioxole; 1,3-dioxane, 1, Examples include 5- to 10-membered cyclic ethers such as 4-dioxane, 1,4-dioxene, and 6-membered cyclic ethers such as 1,4-dioxin. The cyclic ether (A) may be any of cyclic monoether, cyclic diether, etc., but cyclic diether is more preferable. The cyclic ether (A) functions as a good solvent for the polyimide resin. As cyclic ether (A), the solvent whose solubility of the said polyamide-type resin is 5 g / 100g or more is preferable.

These cyclic ethers may have a substituent. Examples of the substituent include a hydroxyl group, a hydroxyalkyl group (such as a hydroxy C _1-6 alkyl group such as a methylol group), an alkyl group (such as a C _1-6 alkyl group such as methyl, ethyl, propyl, butyl, etc.), alkoxy Groups (such as C _1-6 alkoxy groups such as methoxy, ethoxy and butoxy), alkoxyalkyl groups (such as C _1-6 alkyl C _1-6 alkoxy groups such as methoxymethyl and ethoxymethyl), acyloxyalkyl groups (acetyloxymethyl) C _2-4 acyloxy C _1-6 alkyl group such as a group) and the like.

  The cyclic ether (A) may have a plurality of these substituents, and may further have two substituents on the same carbon. In particular, for 1,3-dioxolane, many derivatives (substitutes) are known. In addition, it is preferable that cyclic ether (A) does not contain a halogen atom from an environmental pollution property or a corrosive point.

  These cyclic ethers can be used singly or in combination of two or more. Of these cyclic ethers, 5- to 8-membered cyclic ethers, particularly 5-membered cyclic ethers (5-membered cyclic diethers such as 1,3-dioxolane or derivatives thereof) are preferable.

  The cyclic ether (A) preferably has a boiling point (normal pressure) of less than 110 ° C. The boiling point of the cyclic ether (A) is more preferably less than 100 ° C, particularly preferably less than 80 ° C. When the boiling point of the cyclic ether (A) exceeds 110 ° C., the boiling point of the cyclic alcohol (B) is further increased, and the temperature for drying the cyclic ether (A) and the cyclic alcohol (B) is also increased. For example, at a temperature of about 240 ° C., the polyimide resin often melts and does not become porous. When the boiling point of the cyclic ether (A) is less than 30 ° C., the volatility is high and the composition of the mixed solvent is likely to change, so that it is difficult to form a porous body.

  The cyclic alcohol (B) is not particularly limited as long as it is a non-solvent for a polyimide resin and has a boiling point higher than that of the cyclic ether (A) (an alcohol in which a hydroxyl group is directly bonded to an alicyclic ring). The cyclic alcohol may have a substituent, and examples of the substituent include the substituents exemplified in the cyclic ether (A). The cyclic alcohol (B) preferably does not contain a halogen atom from the viewpoint of environmental pollution and corrosivity. In addition, the non-solvent of a polyamide-type resin means the solvent whose solubility of the said polyamide-type resin is 1 g / 100g or less.

  Examples of the cyclic alcohol (B) include 5- to 10-membered cyclic alcohols such as cyclopentanol, methylcyclopentanol, cyclohexanol, methylcyclohexanol, dimethylcyclohexanol, cyclohexanediol, and cycloheptanol.

  The cyclic alcohol (B) preferably has a boiling point (normal pressure) of 110 ° C. or higher. The boiling point of the cyclic alcohol (B) is more preferably 120 ° C. or higher, further preferably 130 ° C. or higher, and particularly preferably 150 ° C. or higher. When the boiling point of the cyclic alcohol (B) is low, it is difficult to form a porous body. The boiling point of the cyclic alcohol (B) is preferably lower than the glass transition point of the polyimide resin. If it is higher than the glass transition point of the polyimide-based resin, the resin is melted and it is difficult to make it porous.

  In the present invention, the organic solvent mixed solution may contain another organic solvent in addition to the cyclic ether (A) and the cyclic alcohol (B). Another organic solvent is a polyimide-based resin non-solvent, an organic solvent having a boiling point higher than that of the cyclic ether (A) and lower than that of the cyclic alcohol (B), and the group consisting of a cyclic ether, a cyclic ketone, and a cyclic alkane The at least 1 sort (s) of organic solvent (C) selected more is mentioned.

  As the organic solvent (C), any polyimide resin can be used as long as it does not dissolve the polyimide resin alone but does not precipitate and gel the polyimide resin in the mixed solvent. The boiling point of the organic solvent (C) is preferably less than 110 ° C, more preferably less than 100 ° C, and particularly preferably less than 80 ° C. If the boiling point of the organic solvent (C) is high, it may remain after drying and the formation of the porous body may be impaired. In addition, when the boiling point of the organic solvent (C) is less than 30 ° C., the volatility is high and the composition of the mixed solvent is likely to fluctuate, so that it is difficult to form a porous body.

  Examples of the cyclic ether include 5-membered cyclic ethers such as tetrahydrofuran, 1,2-dioxolane, 1,3-dioxolane, 1,2-dioxole, 1,3-dioxole; 1,3-dioxane, 1,4- And 5- to 10-membered cyclic ethers such as 6-membered cyclic ethers such as dioxane, 1,4-dioxene and 1,4-dioxin. Examples of the cyclic ketone include 5- to 15-membered cyclic ketones such as cycloalkanones such as cyclopentanone and cyclohexanone. Examples of the cyclic alkane include 4- to 15-membered cyclic alkanes such as cyclobutane, cyclopentane, and cyclohexane.

These cyclic ethers, cyclic ketones, and cyclic alkanes may have a substituent in the ring. Examples of the substituent include a hydroxyl group, a hydroxyalkyl group (such as a hydroxy C _1-6 alkyl group such as a methylol group), an alkyl group (such as a C _1-6 alkyl group such as methyl, ethyl, propyl, butyl, etc.), alkoxy Groups (such as C _1-6 alkoxy groups such as methoxy, ethoxy and butoxy), alkoxyalkyl groups (such as C _1-6 alkyl C _1-6 alkoxy groups such as methoxymethyl and ethoxymethyl), acyloxyalkyl groups (acetyloxymethyl) C _2-4 acyloxy C _1-6 alkyl group such as a group) and the like. The cyclic ether, cyclic ketone, and cyclic alkane may have a plurality of these substituents, and may further have two substituents on the same carbon. Examples of the cyclic alkane having a substituent in the ring include methylcyclobutane, methylcyclopentane, and methylcyclohexane. Cyclic ethers, cyclic ketones, and cyclic alkanes preferably do not contain halogen atoms from the viewpoint of environmental pollution and corrosivity.

  Cyclic ether, cyclic ketone, and cyclic alkane can be used singly or in combination of two or more. As the organic solvent (C), among these, a 5- to 8-membered cyclic ether (particularly tetrahydrofuran), a 5- to 8-membered cyclic ketone (particularly cyclopentanone), and a 5- to 8-membered cyclic alkane (particularly cyclopentane). Etc.) are preferred.

  It is preferable that the organic solvent mixed solution does not substantially contain a halogen atom-containing solvent. The phrase “substantially free of a halogen atom-containing solvent” means that the content of the halogen atom-containing solvent is 1% by weight or less.

Preferred examples of the organic solvent mixture include the following.
(1) A mixed solution (for example, 1,3-dioxolane) containing a 5-membered cyclic diether as the cyclic ether (A) and a 5- to 10-membered cyclic alcohol (particularly a 6-membered cyclic alcohol) as the cyclic alcohol (B) And liquid mixture containing cyclohexanol, liquid mixture containing 1,3-dioxolane and methylcyclohexanol)
(2) 5-membered cyclic diether as cyclic ether (A), 5- to 10-membered cyclic alcohol (particularly 6-membered cyclic alcohol) as cyclic alcohol (B), and 5- to 8-membered as organic solvent (C) A liquid mixture containing a cyclic ketone (particularly a 5-membered cyclic ketone) (for example, a liquid mixture containing 1,3-dioxolane, cyclohexanol (or methylcyclohexanol) and cyclopentanone)
(3) 5-membered cyclic diether as cyclic ether (A), 5- to 10-membered cyclic alcohol (particularly 6-membered cyclic alcohol) as cyclic alcohol (B), and 5- to 8-membered as organic solvent (C) Liquid mixture containing cyclic ketone (especially tetrahydrofuran) (for example, liquid mixture containing 1,3-dioxolane, cyclohexanol (or methylcyclohexanol) and tetrahydrofuran)
(4) 5-membered cyclic diether as cyclic ether (A), 5- to 10-membered cyclic alcohol (particularly 6-membered cyclic alcohol) as cyclic alcohol (B), and 5- to 8-membered as organic solvent (C) Liquid mixture containing cyclic alkane (particularly 5-membered cyclic alkane) (for example, liquid mixture containing 1,3-dioxolane, cyclohexanol (or methylcyclohexanol) and cyclopentane)

  The content of the cyclic ether (A) in the organic solvent mixed solution is 30 to 99% by weight, preferably 60 to 98% by weight, more preferably 70 to 97% by weight. The content of the cyclic alcohol (B) in the organic solvent mixture is 1 to 40% by weight, preferably 2 to 35% by weight, and more preferably 3 to 30% by weight. Content of the organic solvent (C) in the said organic solvent liquid mixture is 1 to 40 weight%, for example, Preferably it is 2 to 35 weight%, More preferably, it is 3 to 20 weight%.

  As the polyimide resin, an imide polymer, an amideimide polymer, a polyetherimide polymer, or the like is preferably used. Each polymer may be a homopolymer or a block, graft, or random copolymer containing other monomer components. These polymers may be used alone or as a mixture of a plurality of polymers.

  As the amidoimide-based polymer, conventionally known polymers can be used, but they can usually be produced by imidization after polymerization by reaction of trimellitic anhydride and diisocyanate or reaction of trimellitic anhydride chloride and diamine. it can. For example, “Toron 4000T” of Amoco Japan product having a repeating unit represented by the following formula (1), “Viromax” of Toyobo Co., Ltd., etc. are used.

  Although a conventionally well-known thing can be used for an imide type polymer, it can manufacture by obtaining polyamic acid by reaction with a tetracarboxylic-acid component and a diamine component, and imidating it further. The imide polymer is also heat resistant and has the same properties as the above-mentioned amide imide polymer.

  As the polyetherimide polymer, a conventionally known polymer can be used, and examples thereof include a polyetherimide polymer containing a repeating unit represented by the following formula (2).

In the formula, R ¹ and R ² are the same or different and each represents a divalent organic group containing an aromatic hydrocarbon ring. The aromatic hydrocarbon ring includes a monocyclic or polycyclic aromatic carbocyclic ring and aromatic heterocyclic ring. Examples of the monocyclic aromatic hydrocarbon ring include a benzene ring. Examples of the polycyclic aromatic hydrocarbon ring include those having a condensed ring structure in which two or more aromatic rings such as naphthalene ring and anthracene ring each share two or more atoms; biphenyl ring, biphenylene ring, fluorene Examples thereof include a structure in which two or more aromatic rings such as a ring and a stilbene ring are bonded via a linking group such as a single bond. These rings may have a substituent as long as the properties of the reaction and the crosslinked polymer are not impaired. Examples of the substituent include an alkyl group (such as an alkyl group having 1 to 4 carbon atoms such as methyl and ethyl groups), a haloalkyl group (such as a haloalkyl group having 1 to 4 carbon atoms such as trifluoromethyl group), an aryl group (phenyl, Naphthyl groups, etc.), halogen atoms (fluorine atoms, chlorine atoms, bromine atoms, etc.), alkoxy groups (such as alkoxy groups having 1 to 4 carbon atoms such as methoxy and ethoxy groups), hydroxyl groups, carboxyl groups, cyano groups, nitro groups Etc.

  Specific examples of the divalent organic group containing an aromatic hydrocarbon ring include a valent organic group represented by the following formula.

  In formula, n shows the integer of 1-10. The benzene ring contained in the organic group may have a substituent (for example, the exemplified substituent) as long as the physical properties of the reaction and polymer crosslinked product are not impaired.

Preferable R ¹ is, for example, a divalent organic group represented by the following formula.

Particularly preferred R ¹ is a divalent organic group represented by the following formula.

Preferable R ² includes, for example, a divalent organic group represented by the following formula.

  Actually, a commercially available product, for example, General Electric product “ULTEM1000” having a repeating unit represented by the following general formula can be used as it is.

  The amount of the polyimide resin in the polymer solution is 1 to 20 parts by weight, preferably 3 to 18 parts by weight, and more preferably 5 to 15 parts by weight with respect to 100 parts by weight of the organic solvent mixed solution. If the amount of the polyimide resin exceeds 20 parts by weight with respect to 100 parts by weight of the organic solvent mixture, the liquid becomes unstable and easily solidifies, and the amount of the polyimide resin is 100 parts by weight of the organic solvent mixture. If it is less than 1 part by weight, the thickness after coating and drying becomes thin and it is difficult to form a porous body.

  As a method for preparing the polymer solution, a general method can be adopted. There is no limitation on the method for dissolving and mixing the cyclic ether (A), the cyclic alcohol (B), the organic solvent (C), and the polyimide resin, and it can be carried out using a conventionally known apparatus. The mixture may be stirred and dissolved at room temperature and normal pressure, or may be returned to the casting or coating temperature after stirring and dissolving under heating and pressure. The material may be mixed at once to prepare a solution, or the polyimide resin may be a kind of organic solvent mixed liquid formulation of cyclic ether (A), cyclic alcohol (B), or organic solvent (C). You may pass through the melt | dissolution process in the multistage which adds the remaining solvent, after mixing a part quantity. Moreover, all the polyimide resins may be added all at once, or may be added in multiple times.

  The polymer solution further contains conventional additives such as crosslinking or curing agents, antifoaming agents, coatability improving agents, thickeners, lubricants, stabilizers (antioxidants, UV absorbers, heat stabilizers, light stabilizers). Etc.), dyes, pigments, antistatic agents, antiblocking agents, organic and inorganic fillers, and hydrophilizing agents (hydrophilic polymers, etc.).

  It is also useful to make the porous film or the coating surface hydrophilic for the purpose of imparting water permeability. In the production method of the present invention, a small amount of the hydrophilizing agent is previously added to the mixed solution of the cyclic ether (A) and the cyclic alcohol (B) or the mixed solution of the cyclic ether (A), the cyclic alcohol (B), and the organic solvent (C). By adding (for example, 0.1 to 2 parts by weight with respect to 100 parts by weight of the organic solvent mixed solution), the porous film or the coating surface can be hydrophilized.

  Conventionally, in porous bodies and hollow fibers by a manufacturing method called wet, the hydrophilicity was controlled by the degree to which the added hydrophilizing agent was extracted in a coagulation tank such as water. Since the added amount of the agent remains reliably in the porous body, it is excellent in that the added amount of the hydrophilizing agent can be easily controlled.

  Examples of preferred hydrophilizing agents include water-soluble polymers. Examples thereof include polyethylene glycol, polyvinyl pyrrolidone, polyethylene oxide, polyvinyl alcohol, polyacrylic acid, polysaccharides, derivatives thereof, and mixtures thereof. These water-soluble polymers can be used singly or in combination of two or more.

  The polymer solution (polyimide-based resin solvent composition) is liquid and preferably has a viscosity of 5 to 10,000 mPa · s, more preferably 20 to 800 mPa · s, and particularly preferably 30 to 100 mPa · s. In a polymer solution containing 1 part by weight or more of polyimide resin with respect to 100 parts by weight of the organic solvent mixed solution, the viscosity is usually 5 mPa · s or more. A high-viscosity liquid having a viscosity exceeding 10,000 mPa · s is not preferable because uniform coating becomes difficult and formation of a porous body having a uniform thickness becomes difficult.

  The casting and coating method of the polymer solution (polyimide resin solvent composition) is not particularly limited, and is a conventional method of continuous / single-plate coating by a coater, printing by various printing machines (gravure, offset, inkjet, screen, metal) Mask, etc.), dipping, drawing with a dispenser, etc., extruding a hollow or other shapes, spray coating, painting with a brush, etc. can be used. Moreover, the porous film of this invention can also be formed on the surface of a to-be-coated object by the general method used for coating-film formation, such as brush coating, spraying, and immersion pulling.

  Particularly preferred casting and coating methods from the viewpoint of productivity are coater methods such as roll coaters, air knife coaters, blade coaters, rod coaters, reverse coaters, bar coaters, comma coaters, dip squeeze coaters, and die coaters. , Gravure coater, silk screen coater and the like.

  A well-known material can be used for the board | substrate used in the case of casting, and a coating base material (to-be-coated object). Specific examples include paper, woven fabric, nonwoven fabric (polypropylene nonwoven fabric, polyamide nonwoven fabric, etc.), mesh (polyester fiber mesh, SUS mesh, etc.), plastic, glass, ceramics, metal, and the like. Preferred substrates and base materials are glass plates, metal foils (copper foil, aluminum foil, SUS film, etc.), plastic films (polyethylene terephthalate film, polyimide film, resin film having the same composition as the resin forming the porous body), metal, etc. Wire (such as copper wire). The substrate and the base material may have holes. Examples of the film having pores include a biaxially stretched polytetrafluoroethylene film (PTFE film), a biaxially stretched polyethylene film, and a film obtained by solidifying polyethylene particles.

  There is no limitation on the shape of the coated substrate, and it may be flat (continuous roll, plate), three-dimensional, thread, or linear. The surface may be smooth, may have a roughened structure or unevenness, or may have a structure with a hole.

  When the coated substrate is paper, cloth, porous substrate, etc., a porous film in which a part of the polymer solution enters the substrate and is integrated is often formed. After the film is formed, only the porous film peeled off from the substrate or the porous film integrated with the substrate can be used as appropriate.

  The temperature during casting or application of the polymer solution (polyimide resin solvent composition) is preferably -30 ° C to 50 ° C. When the liquid temperature at the time of casting or coating is less than −30 ° C., the liquid is easily solidified, and long-term storage becomes difficult. Further, when the temperature of the liquid at the time of casting or coating exceeds 50 ° C., the volatilization of the solvent is severe and uniform coating is difficult, and the equipment cost for safety measures such as prevention of ignition is high, which is not preferable.

  The porous body (porous film or porous coating) formed by casting or drying after coating may be in a state of adhering to the surface of the substrate or base material, and peeled off from the substrate or base material, and the porous body alone (no support) The self-supporting porous film may be peeled off. When peeling as a single porous body, industrially, a dope is continuously extruded from a die onto a substrate on a belt-like or drum-like base material, cast, dried, and then belt-like or drum-like base material. The method of peeling and winding from is common. What formed the porous film in the base-material surface corresponds to the coating of this invention.

  There is no limitation on the drying conditions after casting or coating, but as conditions for easily forming a porous structure, after casting or coating, (liquid temperature at casting or coating −20 ° C.) to (liquid at casting or coating). It is preferable to hold at a temperature in the range of (temperature + 50 ° C.) for 1 second or longer, and then heat-dry at a temperature not higher than the glass transition point of the polyimide resin.

  After casting or coating, cooling to a temperature lower than (liquid temperature at casting or coating −20 ° C.) is not preferable because it takes a long time to form a porous structure. Further, when the temperature is rapidly raised to a temperature exceeding 50 ° C. from the liquid temperature at the time of casting or coating, the low boiling point solvent is volatilized rapidly and the pore diameter of the porous body becomes 100 μm or more, and it is difficult to obtain a desired porous body. It becomes. The time for holding at a temperature in the range of (liquid temperature at casting or coating −20 ° C.) to (liquid temperature at casting or coating + 50 ° C.) is preferably 1 second or more, more preferably 5 seconds or more, particularly preferably. 10 seconds or more. During this time, wind may be blown or may be held under no wind. As a guide, casting or whitening of the coating solution may be confirmed. In the heat drying after passing through such holding conditions, the drying temperature and time can be arbitrarily set depending on the amount of residual solvent, but it is preferable to dry at a temperature not higher than the glass transition point of the polyimide resin. The heating and drying temperature is, for example, 30 ° C to 200 ° C, preferably 50 to 180 ° C, and particularly preferably 80 to 150 ° C.

  In the polyimide resin porous film or coating of the present invention, at least two or more pores of 0.1 to 10 μm are observed in the thickness direction in the cross section of the coating after drying. That is, the thickness of the porous film or coating is at least twice the average pore diameter. The hole is not a so-called finger type, but has a sponge type structure with a uniform hole diameter. The front and back surfaces of the porous film or coating may be opened or may not be opened. The holes may be independent holes or continuous holes. A hole can be easily observed by using an electron micrograph (SEM).

  It is preferable that the average hole diameter of the hole of the cross section of a porous film or a film is 0.1-10 micrometers. More preferably, it is 0.5-7 micrometers, Most preferably, it is 1-5 micrometers. When the average pore diameter exceeds 10 μm, it tends to be in a mesh shape, which is not preferable.

An electron micrograph can be used for the measurement of the pore diameter. The area of 10 or more arbitrary holes in the cross section of the film or coating was measured, and the average value was defined as the average hole area Save. Next, it converted into the hole diameter when it assumed that the hole was a perfect circle from the following formula, and the value was made into the average hole diameter. Here, π represents a circumference ratio.
Average pore diameter = 2 × (Save / π) ^1/2

  The thickness of the porous film or coating is 1 to 100 μm, more preferably 2 to 50 μm, and particularly preferably 5 to 30 μm. When the thickness of the porous film or coating exceeds 100 μm, it becomes difficult to dry the solvent, and it becomes difficult to form a porous body. Moreover, if the thickness of the porous film or coating is less than 1 μm, uneven coating tends to occur.

In the porous film or coating of the present invention, the porosity (porosity) is 20 to 80%. The porosity is more preferably 20 to 70%, particularly preferably 30 to 70%. If the porosity is higher than 80%, the strength of the porous body is inferior. If the porosity is less than 20%, the merit of the porous body is hardly obtained. The porosity can be obtained from the following equation. Here, V is the volume of the film (coating film), W is the weight of the film (coating film), and D is the density of the film (coating film) material. The density of polyamideimide was 1.45 (g / cm ³ ), and the density of polyimide was 1.35 (g / cm ³ ).
Porosity (%) = 100−100 × W / (D · V)

  In the polyimide resin porous film or coating of the present invention, the contact angle of the surface with respect to water is 65 ° or more, preferably 65 to 90 °. For the measurement of the contact angle, a contact angle measuring device “Drop Master 700” manufactured by Kyowa Interface Science Co., Ltd. can be used. Using distilled water as a test solution, the solution is dropped on the surface of the film or coating, and the contact angle of the droplet is measured.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited to these examples. These results are shown in Table 1. The average pore diameter, porosity, and contact angle with water were determined by the methods described above.

Example 1
In 153 parts by weight of 1,3-dioxolane and 27 parts by weight of cyclohexanol, 20 parts by weight of a polyimide resin (“Ultem 1000” manufactured by SABIC Innovative Plastics Japan GK, glass transition point 217 ° C.) is dissolved at room temperature to obtain a polymer solution ( Polyimide solution) was prepared. This polymer solution had a solid content of 10% by weight and a viscosity of 60 mPa · s, and the liquid state was good without gelation.
This polyimide solution was cast on a glass substrate to a thickness of 127 μm using a Baker type applicator. The liquid temperature and the ambient temperature during casting were 25 ° C. For drying, a hair dryer was used, and air at 25 ° C. was applied for 1 minute, followed by drying in an oven at 120 ° C. for 3 minutes. The thickness of the porous film after drying was 12 μm, the porosity was 38%, the contact angle with water was 85 °, and the average pore diameter of the holes in the film cross section was 2 μm. FIG. 1 shows an SEM photograph of the film cross section.

Example 2
20 parts by weight of polyimide resin (SABIC Innovative Plastics Japan “Ultem 1000”, glass transition point 217 ° C.) 20 parts by weight are dissolved in 247 parts by weight of 1,3-dioxolane, 38 parts by weight of cyclohexanol and 95 parts by weight of tetrahydrofuran at room temperature. To prepare a polymer solution (polyimide solution). This polymer solution had a solid content of 5% by weight and a viscosity of 47 mPa · s, and the liquid state was good without gelation.
This polyimide solution was cast on a glass substrate to a thickness of 127 μm using a Baker type applicator. The liquid temperature and the ambient temperature during casting were 25 ° C. For drying, a hair dryer was used, and air at 25 ° C. was applied for 1 minute, followed by drying in an oven at 120 ° C. for 3 minutes. The thickness of the porous film after drying was 7 μm, the porosity was 33%, the contact angle with water was 90 °, and the average pore diameter of the holes in the film cross section was 1 μm.

Example 3
To 126 parts by weight of 1,3-dioxolane, 27 parts by weight of cyclohexanol, and 27 parts by weight of cyclopentanone, 20 parts by weight of a polyimide resin (“Ultem 1000” manufactured by SABIC Innovative Plastics Japan GK, glass transition point 217 ° C.) To prepare a polymer solution (polyimide solution). The solid content of this polymer solution was 10% by weight, the viscosity was 58 mPa · s, and the liquid state was good without gelation.
This polyimide solution was cast on a glass substrate to a thickness of 127 μm using a Baker type applicator. The liquid temperature and the ambient temperature during casting were 25 ° C. For drying, a hair dryer was used, and air at 25 ° C. was applied for 1 minute, followed by drying in an oven at 120 ° C. for 3 minutes. The thickness of the porous film after drying was 17 μm, the porosity was 72%, the contact angle with water was 83 °, and the average pore diameter of the holes in the film cross section was 5 μm.

Example 4
In 144 parts by weight of 1,3-dioxolane, 18 parts by weight of cyclohexanol, and 18 parts by weight of tetrahydrofuran, 20 parts by weight of a polyimide resin (“Ultem 1000” manufactured by SABIC Innovative Plastics Japan GK, glass transition point 217 ° C.) are dissolved at room temperature. To prepare a polymer solution (polyimide solution). This polymer solution had a solid content of 10% by weight and a viscosity of 55 mPa · s, and the liquid state was good without gelation.
This polyimide solution was cast on a glass substrate using a Baker type applicator so as to have a thickness of 256 μm. The liquid temperature and the ambient temperature during casting were 25 ° C. For drying, a hair dryer was used, and air at 25 ° C. was applied for 1 minute, followed by drying in an oven at 120 ° C. for 3 minutes. The thickness of the porous film after drying was 15 μm, the porosity was 64%, the contact angle with water was 91 °, and the average pore diameter of the holes in the film cross section was 2 μm. FIG. 2 shows an SEM photograph of the film cross section.

Example 5
In 144 parts by weight of 1,3-dioxolane, 18 parts by weight of cyclohexanol, and 18 parts by weight of tetrahydrofuran, 20 parts by weight of a polyimide resin (“Ultem 1000” manufactured by SABIC Innovative Plastics Japan GK, glass transition point 217 ° C.) are dissolved at room temperature. To prepare a polymer solution (polyimide solution). This polymer solution had a solid content of 10% by weight and a viscosity of 55 mPa · s, and the liquid state was good without gelation.
This polyimide solution was cast on a glass substrate to a thickness of 127 μm using a Baker type applicator. The liquid temperature and the ambient temperature during casting were 25 ° C. For drying, a hair dryer was used, and air with an ambient temperature of 25 ° C. was applied for 3 minutes, and then left at 25 ° C. for 24 hours to be dried. The thickness of the porous film after drying was 14 μm, the porosity was 66%, the contact angle with water was 87 °, and the average pore diameter of the holes in the film cross section was 2 μm.

Example 6
In 144 parts by weight of 1,3-dioxolane, 18 parts by weight of cyclohexanol, and 18 parts by weight of tetrahydrofuran, 20 parts by weight of a polyimide resin (“Ultem 1000” manufactured by SABIC Innovative Plastics Japan GK, glass transition point 217 ° C.) are dissolved at room temperature. To prepare a polymer solution (polyimide solution). This polymer solution had a solid content of 10% by weight and a viscosity of 55 mPa · s, and the liquid state was good without gelation.
This polyimide solution was cast on a glass substrate to a thickness of 127 μm using a Baker type applicator. The liquid temperature and the ambient temperature during casting were 25 ° C. Drying was performed by placing in an oven at 60 ° C. for 3 minutes. The thickness of the porous film after drying was 17 μm, the porosity was 59%, the contact angle with water was 90 °, and the average pore diameter of the holes in the film cross section was 2 μm.

Example 7
20 parts by weight of polyimide resin (SABIC Innovative Plastics Japan “Ultem XH6050”, glass transition point 247 ° C.) is added to 144 parts by weight of 1,3-dioxolane, 18 parts by weight of cyclohexanol and 18 parts by weight of cyclopentanone at room temperature. To prepare a polymer solution (polyimide solution). The solid content of this polymer solution was 10% by weight, the viscosity was 35 mPa · s, and the liquid state was good without gelation.
This polyimide solution was cast on a glass substrate to a thickness of 127 μm using a Baker type applicator. The liquid temperature and the ambient temperature during casting were 25 ° C. For drying, a hair dryer was used, and air at 25 ° C. was applied for 1 minute, followed by drying in an oven at 120 ° C. for 3 minutes. The thickness of the porous film after drying was 16 μm, the porosity was 48%, the contact angle with water was 84 °, and the average pore diameter of the holes in the film cross section was 2 μm.

Example 8
To 144 parts by weight of 1,3-dioxolane, 10 parts by weight of cyclohexanol, and 10 parts by weight of cyclopentane, 20 parts by weight of a polyimide resin (“Ultem 1000” manufactured by SABIC Innovative Plastics Japan GK, glass transition point 217 ° C.) is used at room temperature. The polymer solution (polyimide solution) was prepared by dissolution. The solid content of this polymer solution was 10% by weight, the viscosity was 48 mPa · s, and the liquid state was good without gelation.
This polyimide solution was cast on a glass substrate to a thickness of 127 μm using a Baker type applicator. The liquid temperature and the ambient temperature during casting were 25 ° C. For drying, a hair dryer was used, and air at 25 ° C. was applied for 1 minute, followed by drying in an oven at 120 ° C. for 3 minutes. The thickness of the porous film after drying was 13 μm, the porosity was 43%, the contact angle with water was 88 °, and the average pore diameter of the holes in the film cross section was 2 μm.

Comparative Example 1
In 144 parts by weight of 1,3-dioxolane and 36 parts by weight of cyclopentanone, 36 parts by weight of a polyimide resin (“Ultem 1000” manufactured by SABIC Innovative Plastics Japan GK, glass transition point 217 ° C.) are dissolved at room temperature to obtain a polymer solution. (Polyimide solution) was prepared. The solid content of this polymer solution was 10% by weight, the viscosity was 42 mPa · s, and the liquid state was good without gelation.
This polyimide solution was cast on a glass substrate to a thickness of 127 μm using a Baker type applicator. The liquid temperature and the ambient temperature during casting were 25 ° C. For drying, a hair dryer was used, and air at 25 ° C. was applied for 1 minute, followed by drying in an oven at 120 ° C. for 3 minutes. The thickness of the porous film after drying was 5 μm, the porosity was 4%, the contact angle with water was 85 °, and no holes were observed in the film cross section.

Comparative Example 2
In 50 parts by weight of 1,3-dioxolane, 40 parts by weight of cyclohexanol, and 10 parts by weight of cyclopentanone, 10 parts by weight of a polyimide resin (SABIC Innovative Plastics Japan “Ultem 1000”, glass transition point 217 ° C.) are dissolved. However, the solution gelled and could not be cast on the substrate.

Comparative Example 3
75 parts by weight of 1,3-dioxolane, 9.35 parts by weight of cyclohexanol, 9.35 parts by weight of tetrahydrofuran, 25 parts by weight of polyimide resin (“Ultem 1000” manufactured by SABIC Innovative Plastics Japan LLC, glass transition point 217 ° C.) However, the solution gelled and could not be cast on the substrate.

Comparative Example 4
In 80 parts by weight of N-methylpyrrolidone and 20 parts by weight of cyclohexanol, polyimide resin (“Ultem 1000” manufactured by SABIC Innovative Plastics Japan GK, glass transition point 217 ° C.) is dissolved at room temperature, and the solid content is 10% by weight. A polymer solution (polyimide solution) was prepared. The viscosity of this polymer solution was 68 mPa · s, and the liquid state was good without gelation.
This polyimide solution was cast on a glass substrate to a thickness of 127 μm using a Baker type applicator. The liquid temperature and the ambient temperature during casting were 25 ° C. For drying, a hair dryer was used, and air at an ambient temperature of 25 ° C. was applied for 1 minute, followed by drying in an oven at 200 ° C. for 3 minutes. The thickness of the porous film after drying was 5 μm, the porosity was 2%, the contact angle with water was 91 °, and no holes were observed in the film cross section.

Claims (10)

  30 to 99% by weight of cyclic ether (A), an organic solvent mixture containing 1 to 40% by weight of cyclic alcohol (B) which is a non-solvent of polyimide resin and has a boiling point higher than that of cyclic ether (A), A polymer solution containing 1 to 20 parts by weight of a polyimide resin with respect to 100 parts by weight of an organic solvent mixed solution is cast into a film or applied to a substrate, and then obtained by drying and removing the organic solvent. Polyimide having a porosity of 20 to 80%, an average pore diameter of the film or coating cross section of 0.1 to 10 μm, a thickness of 2 to 100 μm and a contact angle with water of 65 ° or more of the average pore diameter. Based resin porous film or coating.   The organic solvent mixed solution is a non-solvent of polyimide resin in addition to the cyclic ether (A) and the cyclic alcohol (B) and has a higher boiling point than the cyclic ether (A) and lower boiling point than the cyclic alcohol (B). 2. The polyimide-based resin porous film according to claim 1, which is a mixed solution containing 1 to 40% by weight of at least one organic solvent (C) selected from the group consisting of cyclic ethers, cyclic ketones and cyclic alkanes. Or coating.   The polyimide resin porous film according to claim 1 or 2, wherein the cyclic ether (A) has a boiling point of less than 110 ° C, and the cyclic alcohol (B) has a boiling point of 110 ° C or higher.   The polyimide resin porous film or coating according to any one of claims 1 to 3, wherein the organic solvent mixed solution does not substantially contain a halogen atom-containing solvent.   The polyimide resin porous film or coating according to any one of claims 1 to 4, wherein the polymer solution has a viscosity of 5 to 10,000 mPa · s.   30 to 99% by weight of cyclic ether (A), an organic solvent mixture containing 1 to 40% by weight of cyclic alcohol (B) which is a non-solvent of polyimide resin and has a boiling point higher than that of cyclic ether (A), After applying a polymer solution containing 1 to 20 parts by weight of a polyimide resin to 100 parts by weight of an organic solvent mixed solution on a substrate, the porosity obtained by drying and removing the organic solvent is 20 to 80%, Coating covered with a polyimide-based resin porous film coating having an average pore diameter of 0.1 to 10 μm, a thickness of 1 to 100 μm and a contact angle with water of 65 ° or more of the average pore diameter of the cross section of the coating object.   30 to 99% by weight of cyclic ether (A), an organic solvent mixture containing 1 to 40% by weight of cyclic alcohol (B) which is a non-solvent of polyimide resin and has a boiling point higher than that of cyclic ether (A), A polymer solution containing 1 to 20% by weight of a polyimide resin with respect to 100 parts by weight of an organic solvent mixed solution is cast into a film or applied to a substrate, and then the organic solvent is dried and removed. A method for producing a polyimide-based resin porous film or coating.   After casting or coating a polymer solution having a liquid temperature of −30 ° C. to 50 ° C., the temperature is in the range of (liquid temperature at casting or coating—20 ° C.) to (liquid temperature at casting or coating + 50 ° C.) for 1 second. The manufacturing method of the polyimide resin porous film or film of Claim 7 which hold | maintains above and then heats at the temperature below the glass transition point of a polyimide resin, and removes an organic solvent.   30 to 99% by weight of cyclic ether (A), an organic solvent mixture containing 1 to 40% by weight of cyclic alcohol (B) which is a non-solvent of polyimide resin and has a boiling point higher than that of cyclic ether (A), A polymer solution containing 1 to 20% by weight of a polyimide resin with respect to 100 parts by weight of an organic solvent mixed solution is applied to a substrate, and then the organic solvent is dried and removed. A method for producing a coating.   After a polymer solution having a liquid temperature of −30 ° C. to 50 ° C. is applied to the substrate, it is held for 1 second or more at a temperature in the range of (liquid temperature at application −20 ° C.) to (liquid temperature at application + 50 ° C.), and then polyimide The manufacturing method of the coating body coat | covered with the polyimide resin porous film of Claim 9 which heats at the temperature below the glass transition point of a resin, and removes an organic solvent.