JP6656192B2 - Polyamide imide solution, porous polyamide imide film, and method for producing the same - Google Patents

Description

  The present invention relates to a polyamideimide solution and a method for producing the same, and a porous polyamideimide film obtained from the polyamideimide solution and a method for producing the same (hereinafter, polyamideimide may be abbreviated as “PAI”).

  Polyimide-based porous films utilize their excellent heat resistance and high porosity to produce electronic and optical materials, industrial materials such as lithium secondary battery separators, filters, separation membranes, wire coatings, and medical materials. It is used in fields such as materials. Among the polyimide-based porous films, for a thermosetting polyimide (PI) utilizing a polyimide precursor (polyamic acid), as a method for producing this porous film, an amide-based solvent and an ether-based solvent are used. A PI precursor solution containing as a solvent is applied on a substrate having heat resistance of 300 ° C. or higher, and then dried to induce a phase separation phenomenon. A method of obtaining a high quality PI film (hereinafter, this method may be abbreviated as “dry porous process”) has been proposed (Patent Document 1). This method is different from a wet-type porous process in which a coating film formed on a substrate is immersed in a coagulating liquid containing a poor solvent to produce a porous film when a porous PI film is manufactured. There is no need to use a coagulation bath for the formation. Therefore, during the production of the porous PI film, no waste liquid is generated from the coagulation bath, so that the dry porous process is an excellent method with good environmental compatibility. However, in order to produce a thermosetting porous polyimide film, the PI precursor coating film formed on the base material shrinks during thermosetting, and therefore, in some cases, its application range is limited. There was something.

  Therefore, a method of manufacturing a porous film or coating using PAI that does not cause shrinkage during the manufacturing of a coating film as described above has been proposed. For example, Patent Documents 2 to 4 disclose that a PAI solution containing an amide-based solvent and an ether-based solvent as a solvent is applied on a base material such as a copper wire or an aluminum strip and then heat-treated at a high temperature of about 500 ° C. Thus, a method for obtaining a porous PAI coating or film has been proposed. These methods attempt to obtain a porous PAI coating by utilizing a foaming phenomenon caused by decomposition and volatilization of a solvent at a high temperature. The PAI solution had an extremely low content of the ether solvent.

Japanese Patent No. 4947989 JP 2013-187029 A JP 2013-210493 A WO 2013/133333

  However, when a known PAI solution is applied to a dry porosity process utilizing a phase separation phenomenon that can easily be made porous at a low temperature, a film having a low porosity and a large number of independent porosity has a low permeability. I could only get it. Further, it was difficult to form pores on the film surface. Therefore, it has been difficult to use the lithium secondary battery as a separator or a filter for a lithium secondary battery that requires high permeability. Furthermore, the porous PAI film obtained by peeling the porous PAI coating from the substrate by utilizing the foaming phenomenon was inferior in uniformity of pores and low in mechanical strength.

  Therefore, the present invention is to solve the above-mentioned problem, and it is possible to obtain a porous PAI film which is adaptable to a dry porosity process, has excellent heat resistance, has high porosity, and has excellent permeability. It is an object to provide a PAI solution and a method for producing the same, a porous PAI film obtained from the solution, and a method for producing the same.

  The present inventors have found that the aforementioned problems can be solved by using a PAI solution having a specific composition, particularly a specific solvent content, and have completed the present invention.

The present invention aims at the following.
<1> A PAI solution containing a nitrogen-containing polar solvent and an ether solvent,
The solid content concentration of the PAI is 25% by mass or less based on the mass of the PAI solution;
The content of the nitrogen-containing polar solvent is 15% by mass or more based on the mass of the PAI solution;
The PAI solution, wherein the content of the ether solvent is more than 30% by mass based on the mass of the PAI solution.
<2> The method for producing a PAI solution according to <1>, wherein the solid PAI is dissolved in a mixed solvent containing a nitrogen-containing polar solvent and an ether-based solvent.
<3> Production of a porous PAI film, characterized in that after applying the PAI solution described in <1> on a substrate, it is dried at a temperature of 200 ° C. or less to induce a phase separation phenomenon to make it porous. Method.
<4> The method for producing a porous PAI film according to <3>, wherein the substrate is a polyester film.
<5> A porous PAI film produced by the method according to <3> or <4>.

  From the PAI solution of the present invention, a porous PAI film can be easily obtained by a simple process at a low temperature. The resulting porous PAI film is excellent in heat resistance, high in porosity, excellent in permeability, and has good mechanical properties based on excellent uniformity of pores. It can be suitably used in the fields of industrial materials such as separators for secondary batteries, filters, separation membranes, and electric wire coatings, and materials of medical materials.

It is a SEM image of the cross section of the porous PAI film of the present invention. 2 is an enlarged SEM image of a cross section of the porous PAI film in FIG. 1. It is a SEM image of the porous PAI film surface of the present invention.

Hereinafter, the present invention will be described in detail.
The present invention relates to a PAI solution and a method for producing the same, a porous PAI film obtained from the PAI solution, and a method for producing the same.

[PAI solution]
PAI is a heat-resistant polymer having both an imide bond and an amide bond in the main chain, and can be obtained by, for example, performing a polycondensation reaction between a tricarboxylic acid component and a diamine component, which are raw materials.

  The tricarboxylic acid component of the PAI is an organic compound having three carboxyl groups (including derivatives thereof) and one or more aromatic or aliphatic rings per molecule, and at least one of the three carboxyl groups. Two carboxyl groups are arranged at a position where both can form an acid anhydride form. The tricarboxylic acid component is used in a concept including an aromatic tricarboxylic acid component and an alicyclic tricarboxylic acid component.

  Examples of the aromatic tricarboxylic acid component include a benzene tricarboxylic acid component and a naphthalene tricarboxylic acid component.

  Specific examples of the benzenetricarboxylic acid component include, for example, trimellitic acid, hemi-mellitic acid, their anhydrides and their monochlorides.

  Specific examples of the naphthalene tricarboxylic acid component include, for example, 1,2,3-naphthalene tricarboxylic acid, 1,6,7-naphthalene tricarboxylic acid, 1,4,5-naphthalene tricarboxylic acid, and anhydrides and monochlorides thereof. Is mentioned.

  Specific examples of the alicyclic tricarboxylic acid component include, for example, 1,2,4-cyclopentanetricarboxylic acid, 1,2,3-cyclohexanetricarboxylic acid, 1,2,4-cyclohexanetricarboxylic acid, 1,3,5- Examples thereof include cyclohexanetricarboxylic acid, 1,2,4-decahydronaphthalenetricarboxylic acid, 1,2,5-decahydronaphthalenetricarboxylic acid, anhydrides thereof and monochlorides thereof.

Among the tricarboxylic acid components, an aromatic tricarboxylic acid component is preferred.
Among the aromatic tricarboxylic acid components, trimellitic acid and trimellitic anhydride chloride (TAC) are preferred.

  The tricarboxylic acid component may be used alone or in combination of two or more. As the tricarboxylic acid component, a component partially substituted with a component such as pyromellitic acid, benzophenonetetracarboxylic acid, or biphenyltetracarboxylic acid may be used.

  The diamine component of PAI is an organic compound having two primary amino groups (including derivatives thereof) and one or more aromatic or aliphatic rings per molecule. The diamine component is used in a concept including an aromatic diamine component and an alicyclic diamine component.

  Specific examples of the aromatic diamine component include, for example, 4,4'-diaminodiphenyl ether (DADE), m-phenylenediamine (MDA), p-phenylenediamine, 4,4'-diphenylmethanediamine (DMA), 4,4 ' Diphenyl ether diamine, diphenyl sulfone-4,4'-diamine, diphenyl-4,4'-diamine, o-tolidine, 2,4-tolylenediamine, 2,6-tolylenediamine, xylylenediamine, naphthalenediamine, and These diisocyanate derivatives are mentioned.

  Specific examples of the alicyclic diamine component include, for example, 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, and diisocyanate derivatives thereof.

Among the diamine components, an aromatic diamine component is preferred.
Among the aromatic diamine components, DADE, MDA and DMA are preferred.

  The diamine components may be used alone or in combination of two or more.

  PAI typically has a glass transition temperature of 200 ° C. or higher. As the glass transition temperature, a value measured by DSC (differential thermal analysis) is used.

  Among PAIs, aromatic PAI having excellent mechanical properties and heat resistance is preferable. Aromatic PAI can be obtained by performing a polycondensation reaction between the aromatic tricarboxylic acid component and the aromatic diamine component. The aromatic PAI may be thermoplastic or non-thermoplastic, but aromatic PAI having the above-mentioned glass transition temperature can be preferably used.

  In the present invention, by removing the solvent at a temperature of 200 ° C. or less from a PAI solution in which PAI is dissolved in a solvent, a heat-resistant film having excellent mechanical properties can be easily formed. Obtainable. In this respect, PAI is different from thermosetting polyimide which requires a high temperature of about 300 ° C. in order to imidize a polyamic acid as a precursor at the time of molding.

  The PAI solution of the present invention is a solution containing a mixed solvent containing a nitrogen-containing polar solvent and an ether-based solvent, wherein the solid content of the PAI is 25% by mass or less based on the mass of the PAI solution, The content of the polar solvent is 15% by mass or more based on the mass of the PAI solution, and the content of the ether solvent is more than 30% by mass based on the mass of the PAI solution.

  If the solid content of PAI is too high, a uniform solution cannot be obtained, and it cannot be used for film formation. From the viewpoint of further increasing the porosity of the film, the solid content concentration of PAI is preferably 20% by mass or less based on the mass of the PAI solution. However, if the solid content concentration of PAI is reduced more than necessary, productivity decreases. Therefore, the solid content concentration of PAI is preferably 5% by mass or more.

  If the content of the nitrogen-containing polar solvent is too small, a uniform PAI solution cannot be obtained. In order to obtain a uniform PAI solution, the content of the nitrogen-containing polar solvent is preferably 17% by mass or more based on the mass of the PAI solution. In the present invention, the upper limit value of the content of the nitrogen-containing polar solvent is not particularly limited, but from the viewpoint of further increasing the porosity in the film, 50% by mass or less, particularly 30% by mass or less based on the PAI solution mass. It is preferred that

  If the content of the ether solvent is too small, a film having a sufficient porosity cannot be obtained. From the viewpoint of further increasing the porosity of the film, the content of the ether solvent is preferably more than 40% by mass, more preferably more than 50% by mass, especially more than 60% by mass based on the mass of the PAI solution. . In the present invention, the upper limit of the content of the ether solvent is not particularly limited, but from the viewpoint of further increasing the porosity in the film, the upper limit is 80% by mass or less, particularly 75% by mass or less based on the mass of the PAI solution. Preferably, there is.

  When the coating composition obtained from the PAI solution is dried and solidified by setting the solvent composition as described above, the ether-based solvent (poor solvent) remaining in the coating film acts at a temperature of 200 ° C. or less. Phase separation occurs efficiently. Accordingly, a PAI film having a high porosity can be obtained.

  Amide solvents and urea solvents can be used as the nitrogen-containing polar solvent used in the present invention. Examples of the amide solvent include N-methyl-2-pyrrolidone (NMP boiling point: 202 ° C.), N, N-dimethylformamide (boiling point: 153 ° C.), and N, N-dimethylacetamide (DMAc boiling point: 166 ° C.). No. Examples of the urea-based solvent include tetramethyl urea (TMU boiling point: 177 ° C.) and dimethyl ethylene urea (boiling point: 220 ° C.). These nitrogen-containing polar solvents may be used alone or in combination of two or more. Among these, NMP and DMAc are preferably used, and NMP is particularly preferred.

  As the ether solvent used in the present invention, it is preferable to use a solvent having a boiling point higher than that of the nitrogen-containing polar solvent, and the boiling point difference is preferably 5 ° C or higher, more preferably 20 ° C or higher, and 50 ° C or higher. More preferred. These ether solvents alone are poor solvents that cannot dissolve PAI. Examples of ether solvents include diethylene glycol dimethyl ether (DEGM boiling point: 162 ° C), triethylene glycol dimethyl ether (TRGM boiling point: 216 ° C), tetraethylene glycol dimethyl ether (TEGM boiling point: 275 ° C), diethylene glycol (DEG boiling point: 244 ° C). And a solvent such as triethylene glycol (TEG boiling point: 287 ° C.). These may be used alone or in combination of two or more. Among these, TRGM and TEGM are preferably used, and TEGM is particularly preferred.

  The mixed solvent may contain another solvent as needed, as long as the effects of the present invention are not impaired.

  The PAI solution of the present invention is preferably produced, for example, by the following production method. That is, the solid PAI is dissolved in the mixed solvent to obtain a PAI solution. As the solid PAI, for example, commercially available PAI powder (for example, Torlon 4000T series, Torlon 4000TF, Torlon AI-10 series, etc., manufactured by Solvay Advanced Polymers Co., Ltd.) can be used. By using solid PAI, a PAI solution having the composition of the present invention can be easily obtained.

  In order to obtain the PAI solution of the present invention, the method of producing using the solid PAI as described above is preferable, but the tricarboxylic acid component and the diamine component, which are the raw materials, are mixed in approximately equimolar amounts, and A solution obtained by performing a polymerization reaction in a mixed solvent can also be used. Also, a method in which a polymerization reaction is carried out only in a nitrogen-containing polar solvent to obtain a solution, and then an ether solvent is added thereto, or a polymerization reaction is carried out only in an ether solvent to obtain a suspension, which is then contained therein Although a PAI solution can be obtained by a method of adding a nitrogen polar solvent, a method of producing using a solid PAI as described above is preferable.

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

[Porous PAI film]
The porous PAI film of the present invention can be manufactured by a low-temperature dry-type porous process using the PAI solution. That is, the PAI solution of the present invention is applied to the surface of a substrate and dried at 80 to 200 ° C., preferably 100 to 160 ° C. for 10 to 60 minutes to obtain a porosity of 40 to 90% by volume. A high quality PAI film can be formed. Thereafter, the porous PAI film can be peeled off from these substrates to form a single porous PAI film. Further, the porous PAI film formed on the substrate can be used by being laminated and integrated with the substrate without peeling off from the substrate. Since the porous PAI film has excellent heat resistance, a heat treatment may be performed at a temperature of 200 ° C. or more, for example, about 300 ° C. after the drying.

  Examples of the substrate include a metal foil, a metal wire, a glass plate, a thermoplastic resin film (a thermoplastic resin film having a melting point or softening point of 300 ° C. or less such as polyester, polypropylene, and polycarbonate), and a thermosetting resin such as polyimide. Examples include films, various woven fabrics, and various nonwoven fabrics. As the metal, gold, silver, copper, platinum, aluminum and the like can be used. The substrate may be porous or non-porous. Among these, a polyester film is preferable, and a polyethylene terephthalate (PET melting point: 260 ° C.) film is particularly preferable. The PET film may have been subjected to a surface treatment such as a corona discharge treatment. As a method of applying the coating liquid to these substrates, a dip coater, a bar coater, a spin coater, a die coater, a spray coater or the like can be used to apply the coating liquid in a continuous or batch manner.

The porosity of the porous PAI film obtained by the production method is preferably from 40 to 90% by volume, more preferably from 45 to 85% by volume, and still more preferably from 60 to 85% by volume. . The porous PAI film having the porosity set as described above can ensure good mechanical properties and permeability at the same time, and thus can be used for a separator, a filter, and the like for a lithium secondary battery. The porosity of the porous PAI film is a value calculated from the apparent density of the porous PAI film and the true density (specific gravity) of PAI constituting the porous PAI film. Specifically, the porosity (volume%) is calculated by the following equation when the apparent density of the porous PAI film is A (g / cm ³ ) and the true density of PAI is B (g / cm ³ ).

  The average pore diameter of the pores of the porous PAI film is preferably from 0.1 to 10 μm, more preferably from 0.5 to 5 μm.

  The pores formed may be continuous pores or independent pores, but are preferably continuous pores. Further, it is preferable that pores are formed on the film surface.

  The thickness of the porous PAI film is preferably from 1 to 300 μm, more preferably from 10 to 100 μm.

  In the above process, the porosity and the pore diameter can be adjusted by selecting the type and the amount of the mixed solvent (the nitrogen-containing polar solvent and the ether-based solvent) in the PAI solution.

  As described above, a porous PAI film can be easily obtained from the PAI solution of the present invention. Since this method for producing a porous PAI film is based on a dry porous process, no waste liquid is generated from a coagulation bath containing a poor solvent during pore formation. Therefore, the environmental compatibility is good and the process is extremely simple. The resulting porous PAI film has high porosity and good mechanical properties.

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

<Example 1>
15 g of PAI powder (Toron 4000T-HV manufactured by Solvay Advanced Polymers Co., Ltd., glass transition temperature: 280 ° C.) obtained by copolymerizing TAC, DADE and MDA (copolymerization molar ratio: DADE / MDA = 7/3) Was dissolved in a mixed solvent consisting of 25 g of NMP and 60 g of TEGM at 30 ° C., the solid content concentration of PAI was 15% by mass relative to the PAI solution ratio, and the content ratio of the ether solvent was 60% by mass relative to the PAI solution ratio. % PAI solution (A-1) was obtained.

  This solution was applied on a PET film (100 μm thick, manufactured by Unitika) whose surface was subjected to corona discharge treatment, dried at 130 ° C. for 30 minutes, and then peeled off from the PET film to form a 50 μm thick porous film. A quality PAI film was obtained. Table 1 shows the measurement results of the porosity of this porous PAI film. 1 to 3 show SEM images of the cross section and the surface (the PET film contact surface) of the porous PAI film. It can be seen that uniform continuous pores having a pore diameter of about 2 to 3 μm are formed over the entire cross section, and pores are also formed on the surface. When the mechanical properties of the porous PAI film were evaluated based on the provisions of JIS-C-2151, the porous PAI film had good mechanical properties of 14.1 MPa and an elongation of 38.8%. Was confirmed. Furthermore, when the Gurley value of this porous PAI film was measured based on the provisions of JIS-P8117, it was 1580 seconds, and it was confirmed that the porous PAI film exhibited good permeability based on continuous pores.

<Examples 2 to 8>
In the same manner as in Example 1, PAI solutions (A-2 to A-8) were prepared with the compositions shown in Table 1. From these solutions, a porous PAI film was obtained under the same conditions as in Example 1. Table 1 shows the porosity measurement results of these porous PAI films.

<Example 9>
The same procedure as in Example 1 was carried out except that PAI powder (Toron AI-10, manufactured by Solvay Advanced Polymers Co., Ltd., glass transition temperature: 272 ° C.) obtained by polymerizing TAC and DMA was used as the PAI powder. Thus, a PAI solution (A-9) was prepared. From this solution, a porous PAI film was obtained under the same conditions as in Example 1. Table 1 shows the results of measuring the porosity of this porous PAI film.

<Comparative Examples 1 to 6>
In the same manner as in Example 1, PAI solutions (B-1 to B-6) having the compositions shown in Table 1 were prepared. From these solutions, a porous PAI film was obtained under the same conditions as in Example 1. Table 1 shows the porosity measurement results of these porous PAI films.

<Comparative Examples 7 to 9>
An attempt was made to prepare PAI solutions (B-7 to B-9) in the same manner as in Example 1 with the compositions shown in Table 1, but no uniform solution could be obtained.

<Comparative Example 10>
JP-A-2013-187029 (Patent Document 2) A PAI solution (B-10) was prepared as described in Example 1. That is, by adding 51.2 g of TRGM to 200 g of a commercially available PAI solution (manufactured by Hitachi Chemical Co., Ltd .: HI-406, PAI solid content: 32% by mass, solvent: NMP, glass transition temperature of PAI: 288 ° C.), A homogeneous PAI solution (B-10) having a solid content concentration of about 25% by mass relative to the PAI solution and an ether solvent content of about 21% by mass relative to the PAI solution ratio was obtained. From this solution, a porous PAI film was obtained under the same conditions as in Example 1. Table 1 shows the porosity measurement results of the PAI film.

<Comparative Example 11>
JP-A-2013-210493 (Patent Document 3) A PAI solution (B-10) was prepared as described in Example 2. That is, 15 g of NMP, 10 g of TRGM, and 30 g of TEGM are added to 200 g of a commercially available PAI solution (manufactured by Hitachi Chemical Co., Ltd .: HI-406, solid content of PAI: 32% by mass, solvent: NMP, glass transition temperature of PAI: 288 ° C.). As a result, a uniform PAI solution (B-11) having a PAI solid content concentration of about 25% by mass relative to the PAI solution and an ether solvent content of approximately 16% by mass relative to the PAI solution ratio was obtained. From this solution, a porous PAI film was obtained under the same conditions as in Example 1. Table 1 shows the porosity measurement results of the PAI film.

  As shown in the examples, the porosity (40% by volume or more) of the porous PAI film obtained from the PAI solution of the present invention is high and can be suitably used for a secondary battery separator, a filter, and the like. It turns out there is. On the other hand, the porosity (less than 40% by volume) of the porous PAI film obtained from the PAI solution shown in the comparative example is low, which indicates that application to a secondary battery separator, a filter, or the like is difficult.

  The porous PAI film obtained by using the PAI solution of the present invention is used in the fields of electronic materials, optical materials, industrial materials such as lithium secondary battery separators, filters, separation membranes, electric wire coatings, and medical material materials. Useful in

Claims (4)

As the diamine component, the solid content concentration of the polyamideimide containing at least one selected from the group consisting of 4,4′-diaminodiphenyl ether, m-phenylenediamine and 4,4′-diphenylmethanediamine is 25 mass with respect to the mass of the polyamideimide solution. % Or less, and containing a uniformly dissolved polyamideimide solution containing a nitrogen-containing polar solvent that is a good solvent for polyamideimide and an ether solvent that is a poor solvent , applied on a substrate, and then heated at a temperature of 200 ° C or less. the method of manufacturing a porous polyamide-imide by drying to that dry-type pore formation process, a manufacturing method of a porous polyamide-imide, characterized in that the ether solvent and 50 wt percent relative to the polyamide-imide solution weight. By selecting the type and amount of the nitrogen - containing polar solvent and ether-based solvents, porosity and porous method for producing the polyamideimide according to claim 1, wherein adjusting the pore diameter.   3. The method for producing a porous polyamideimide according to claim 1, wherein the substrate is a nonwoven fabric. As the diamine component, the solid content concentration of the polyamideimide containing at least one selected from the group consisting of 4,4′-diaminodiphenyl ether, m-phenylenediamine and 4,4′-diphenylmethanediamine is 25 mass with respect to the mass of the polyamideimide solution. % Or less, containing a nitrogen-containing polar solvent that is a good solvent for polyamideimide and an ether solvent that is a poor solvent , and containing the ether solvent in an amount of more than 50% by mass based on the mass of the polyamideimide solution. Use of a porous polyamide-imide as a separator for a lithium secondary battery by a dry-porous process, wherein the imide solution is applied on a substrate and then dried at a temperature of 200 ° C. or less.