JP6969772B2 - Method for manufacturing soluble polyimide solution - Google Patents

Description

The present invention relates to a method for producing a soluble polyimide (SPI) solution used in the fields of electricity and electronics, energy, and the like.

Polyimide (PI), which has excellent heat resistance, chemical stability, and electrical insulation, is used to reduce the size, weight, and flexibility of equipment in the electrical and electronic fields and the energy field such as lithium secondary batteries. Widely used for adhesion, insulation, protection, etc. PI is usually supplied in the form of a polyamic acid solution (PAA) which is a precursor thereof, and in order to obtain PI from this solution, it is necessary to imidize the PAA solution after molding, so that the temperature is 300 ° C. The above heating is required. The PI obtained by such high-temperature treatment is called a thermosetting PI, and since it does not dissolve in a normal solvent, there is a problem that it lacks moldability.

To solve such a problem, a soluble polyimide (SPI) having good moldability has been developed. Since the SPI is dissolved in a general-purpose solvent, the SPI solution can be formed into a film or a film simply by removing the solvent. Therefore, although the moldability is good, there is a problem that the heat resistance of the molded product is lowered. To solve such a problem, Patent Documents 1 and 2 disclose a method for improving heat resistance by using SPI using an aliphatic diamine such as dimadiamine.

The SPI solution disclosed in Patent Documents 1 and 2 is subjected to a polymerization reaction and an imidization reaction using a solvent containing an amide solvent as a polymerization solvent to obtain an SPI solution, and then this solution is molded to obtain SPI. It is intended to form a film or coating film of. Here, the reason why the amide-based solvent is used as the solvent is that the polymerization reaction and the imidization reaction proceed efficiently due to the action of the amide-based solvent. Since the SPI solution obtained by using the amide-based solvent contains a high concentration of the amide-based solvent having a high boiling point and being strongly solvated with the SPI, the amide-based solvent is used as a film or a film during molding. There was a problem that it remained in. Since the amide-based solvent has high hygroscopicity, if it remains in the molded product, the electrical and mechanical properties due to hygroscopicity deteriorate.

As a method for avoiding such a problem of an amide-based solvent, a method is known in which a SPI solution is obtained by using an amide-based solvent as a reaction solvent, and then the solvent in the SPI solution is replaced with another solvent. For example, Patent Documents 3 and 4 describe SPI obtained by adding an SPI solution containing an amide-based solvent to a solvent that serves as a precipitating agent for SPI such as methanol, filtering the SPI, and drying the SPI. A method of dissolving in the solvent of the above and performing solvent substitution is disclosed.

Japanese Unexamined Patent Publication No. 2013-155329 Japanese Unexamined Patent Publication No. 2015-180750 International Publication 1998/29471 JP-A-2007-254615

In the method of performing solvent replacement by precipitation as described in the above-mentioned document, since a large amount of solvent as a precipitating agent is used, it causes an increase in cost and has a problem in environmental compatibility. In addition, complicated processes such as precipitation, filtration, drying, and redissolution are required, which causes a problem of increasing the process cost.

Therefore, an object of the present invention is to solve the above-mentioned problems and to provide a method for producing an SPI solution having a small residual amount of an amide-based solvent economically and ensuring high environmental compatibility.

The present inventors have found that the solvent extraction method is effective in SPI having a specific chemical structure and solves the above-mentioned problems, and has reached the completion of the present invention.

The present invention has the following object.

The present invention is a method for producing a polyimide solution having an amide-based solvent content of 5% by mass or less with respect to a polyimide mass, and is characterized by including the following process.
1) In a solvent containing an amide-based solvent, the aromatic tetracarboxylic dianhydride is reacted with a diamine to prepare an SPI solution.
2) The amide-based solvent in the SPI solution is removed by a solvent extraction method to obtain an SPI solution in which the content of the amide-based solvent in the SPI solution is 5% by mass or less with respect to the polyimide mass.

The method for producing an SPI solution of the present invention can economically obtain an SPI solution having excellent environmental compatibility and a reduced residual amide solvent content.

Hereinafter, the present invention will be described in detail.

In the method for producing an SPI solution of the present invention, first, an aromatic tetracarboxylic acid dianhydride is reacted with an aliphatic diamine in a solvent containing an amide solvent to obtain a soluble polyimide solution. By using an aromatic tetracarboxylic dianhydride as the tetracarboxylic dianhydride and an aliphatic diamine as the diamine, heat resistance as an SPI can be ensured.

Specific examples of the aliphatic diamine include 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 2-methyl-1,5-diaminopentane, 1,7-diaminoheptane, and the like. 1,8-Diaminooctane, 1,3-bis (aminomethyl) cyclohexane, 1,4-bis (aminomethyl) cyclohexane, 1,9-diaminononane, 1,10-diaminodecane, 1,11-diaminoundecane, 1 , 12-Diaminododecane, 4,4'-methylenebiscyclohexylamine, dimadiamine (aliphatic diamine derived from dimaic acid having 24-48 carbon atoms, sometimes abbreviated as "DDA") and the like. I can get it. These may be used alone or in combination of two or more. Of these, DDA is preferred. As the DDA, commercially available products such as trade names "Priamine 1074, 1075" (manufactured by Croda Japan) and "Versamine 551, 552" (trade name manufactured by Cognis Japan) can be used.

Aliphatic diamines can also be used in admixture with aromatic diamines (including heterocyclic diamines). Specific examples of the aromatic diamine include 4,4'-diaminodiphenyl ether, 2'-methoxy-4,4'-diaminobenzanilide, 1,4-bis (4-aminophenoxy) benzene, and 1,3-bis (. 4-Aminophenoxy) benzene, 2,2'-bis [4- (4-aminophenoxy) phenyl] propane, 2,2'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dihydroxy-4, 4'-diaminobiphenyl, 4,4'-diaminobenzanilide, bisaniline fluorene, 2,2-bis- [4- (3-aminophenoxy) phenyl] propane, bis [4- (4-aminophenoxy) phenyl] Sulfon, bis [4- (3-aminophenoxy) phenyl] sulfone, bis [4- (4-aminophenoxy)] biphenyl, bis [4- (3-aminophenoxy) biphenyl, bis [1- (4-aminophenoxy)] )] Biphenyl, bis [1- (3-aminophenoxy)] biphenyl, bis [4- (4-aminophenoxy) phenyl] methane, bis [4- (3-aminophenoxy) phenyl] methane, bis [4- ( 4-Aminophenoxy) phenyl] ether, bis [4- (3-aminophenoxy) phenyl] ether, bis [4- (4-aminophenoxy)] benzophenone, bis [4- (3-aminophenoxy)] benzophenone, bis [4,4'-(4-aminophenoxy)] benzanilide, bis [4,4'-(3-aminophenoxy)] benzanilide, 9,9-bis [4- (4-aminophenoxy) phenyl] fluorene, 9 , 9-Bis [4- (3-aminophenoxy) phenyl] fluorene, 2,2-bis- [4- (4-aminophenoxy) phenyl] hexafluoropropane, 2,2-bis- [4- (3- (3-) Aminophenoxy) phenyl] hexafluoropropane, 4,4'-methylenedi-o-toluidine, 4,4'-methylenedi-2,6-xylidine, 4,4'-methylene-2,6-diethylaniline, 4,4 ′ -Diaminodiphenylpropane, 3,3′-diaminodiphenylpropane, 4,4′-diaminodiphenylethane, 3,3′-diaminodiphenylethane, 4,4′-diaminodiphenylmethane, 3,3′-diaminodiphenylmethane, 4 , 4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfide, 4,4'-diaminodiphenylsulfone, 3,3'-diaminodi Phenylsulfone, 3,3-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, benzidine, 3,3'-diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminobiphenyl, 3,3'-dimethoxybenzidine , 4,4 ″ -diamino-p-terphenyl, 3,3 ″ -diamino-p-terphenyl, m-phenylenediamine, p-phenylenediamine, 2,6-diaminopyridine, 1,4-bis (4-bis) Aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 4,4'-[1,4-phenylenebis (1-methylethylidene)] bisaniline, 4,4'-[1,3-phenylene" Bis (1-methylethylidene)] bisaniline, bis (p-aminocyclohexyl) methane, bis (p-β-amino-t-butylphenyl) ether, bis (p-β-methyl-δ-aminopentyl) benzene, p -Bis (2-methyl-4-aminopentyl) benzene, p-bis (1,1-dimethyl-5-aminopentyl) benzene, 1,5-diaminonaphthalene, 2,6-diaminonaphthalene, 2,4-bis (Β-Amino-t-butyl) Toluene, 2,4-diaminotoluene, m-xylene-2,5-diamine, p-xylene-2,5-diamine, m-xylylene diamine, p-xylylene diamine, 2,6-diaminopyridine, 2,5-diaminopyridine, 2,5-diamino-1,3,4-oxadiazole and the like can be mentioned. These may be used alone or in combination of two or more.

Specific examples of the tetracarboxylic acid dianhydride include pyromellitic acid dianhydride (PMDA), 3,3', 4,4'-biphenyltetracarboxylic acid dianhydride (BPDA), 2,3,3',. 4'-biphenyltetracarboxylic acid dianhydride, 3,3', 4,4'-benzophenone tetracarboxylic acid dianhydride, 4,4'-oxydiphthalic acid anhydride, 3,3', 4,4'-diphenyl Examples thereof include sulfonetetracarboxylic acid dianhydride. These may be used alone or in combination of two or more. Of these, PMDA and BPDA are preferred.

In order to react the aromatic tetracarboxylic acid dianhydride with the aliphatic diamine in a solvent containing an amide solvent to obtain a soluble polyimide solution, for example, a known method disclosed in Patent Documents 1 and 2 is used. be able to. That is, in an amide-based solvent such as DMF, DMAc, NMP, etc., a substantially equal molar amount of tetracarboxylic acid dianhydride was reacted with diamine at a temperature of 0 ° C. to 50 ° C. to obtain a polyamic acid, and then continued. This can be obtained by dehydration ring closure and imidization at a temperature of 50 ° C to 200 ° C.
Among the amide-based solvents, NMP is preferable. The amide-based solvent should be mixed with a hydrocarbon-based solvent such as xylene (o-xylene, m-xylene, p-xylene), ethylbenzene, mesitylene, or a ketone solvent such as methylisobutylketone or cyclohexanone to prepare a mixed solvent. Can be done. As the solvent for SPI synthesis, it is preferable to use a mixed solvent thereof, and a mixed solvent of an amide-based solvent and a hydrocarbon-based solvent is particularly preferable. When dehydrating and ring-closing, water generated by imidization may be removed from the reaction system by azeotropic or the like. Further, when dehydrating and ring-closing, a known dehydrating agent such as acetic anhydride or dicyclohexylcarbodiimide may be used.

The concentration of the SPI solution in the polymerization reaction is not limited, but is preferably 1 to 70% by mass, more preferably 5 to 40% by mass.

The amide-based solvent in the SPI solution obtained as described above is removed by a solvent extraction method. In solvent extraction, the SPI solution obtained as described above is optionally mixed with a hydrocarbon solvent such as n-hexane, cyclohexane, n-heptane, petroleum ether, benzene, toluene, etc., and a ketone of methyl ethyl ketone and methyl isobutyl ketone. Add a solvent that is a good solvent for SPI, such as a solvent, an ether solvent such as diethyl ether, tetrahydrofuran, dimethoxyethane, and dioxane, and an ester solvent such as methyl acetate, ethyl acetate, isopropyl acetate, and butyl acetate, and add a SPI solution. The concentration of the solvent can be adjusted.

As the solvent extractant, a solvent that is a poor solvent for SPI is used. Specific examples of the solvent extractant include water, methyl alcohol, ethyl alcohol, acetone and the like. Of these, water and methyl alcohol are preferable. These may be used alone or in combination of two or more.

The amount of the solvent extractant used is preferably 10 to 300 parts by mass, more preferably 20 to 200 parts by mass with respect to 100 parts by mass of the SPI solution. If the amount of the solvent extractant used exceeds 300 parts by mass, the SPI may precipitate or precipitate. Further, if the amount of the solvent extractant used is less than 10 parts by mass, the two phases may not be separated in a uniform state.

The temperature at the time of solvent extraction is usually about 5 ° C to 60 ° C, preferably 10 ° C to 30 ° C.

The solvent extraction operation can be performed once or more than once.

In the solvent extraction operation, the SPI solution and the solvent extractant may be mixed, stirred, allowed to stand for two-phase separation, and then the solvent extractant and the SPI solution may be separated. As a result, the amide-based solvent used in the polymerization reaction of SPI shifts to the solvent extractant side. In the solvent extraction operation, the solvent composition may be appropriately adjusted so that an emulsion or the like is not generated, but when an emulsion or the like is generated, two-phase separation may be performed by centrifugation or the like. In this way, the amide-based solvent coexisting in the SPI solution is removed from the SPI solution by solvent extraction.

The content of the amide solvent in the SPI solution from which the amide solvent has been removed is 5% by mass or less, preferably 3% by mass or less, and more preferably 1% by mass or less, based on the polyimide mass.

The weight average molecular weight (Mw) of SPI is preferably 5000 or more and 200,000 or less, and more preferably 20000 or more and 80,000 or less. By setting Mw in such a range, good moldability of the SPI solution can be ensured. In addition, good mechanical properties and high heat resistance of the SPI film and the SPI film can be ensured. Here, the weight average molecular weight (Mw) can be confirmed, for example, by measuring GPC under the following conditions.
<GPC measurement conditions>
Column: Showa Denko's Shodex (R) GPC KF-803 x 1 piece, GPC KF-804 x 2 pieces (3 pieces connected)
Eluent: THF
Temperature: 40 ° C
Flow rate: 1.0 mL / min Detector: UV detector

The SPI may be completely or partially sealed with a crosslinkable component such as a maleimide group, a nadiimide group, a vinyl group, an acetylene group, or a silanol group.

By applying the purified SPI solution thus obtained to the surface of the base material and drying it, an SPI film can be formed on the surface of the base material. The type of base material to be applied is not limited, but may be porous or non-porous.
The SPI coating can be used in a state of being laminated and integrated with the base material. Further, the SPI film can be peeled off from the substrate and used as an SPI film.

Since the SPI solution obtained by the production method of the present invention has a reduced solvent content of the amide-based solvent, it is possible to form a film in which the residual amount of the amide-based solvent is reduced.
As a method for applying the SPI solution to the surface of the substrate, a known application method can be used. Specifically, for example, the gravure coater method, the reverse roll coater method, the transfer roll coater method, the kiss coater method, the dip coater method, the knife coater method, the air doctor coater method, the blade coater method, the rod coater method, the squeeze coater method, and the cast coater method. A method such as a method, a die coater method, a screen printing method, or a spray coating method can be used.

Hereinafter, examples of the present invention will be described in detail, but the present invention is not limited to these examples.

A crude SPI solution was obtained by the method described in the following reference example.

<Reference example 1>
A crude SPI solution was obtained according to the method described in Example 2 of Patent Document 2. That is, 0.60 mol (177 g) of BPDA, 0.59 mol of DDA (priamine 1075: 325 g), 300 g of NMP, and 800 g of p-xylene were added to the reaction vessel, and the mixture was stirred at 40 ° C. for 1 hour. , A polyamic acid solution was obtained. The temperature of this solution was raised to 140 ° C., and the generated water was removed by azeotropic heating while heating and stirring for 15 hours to complete imidization. After cooling to room temperature, 600 g of p-xylene was added to obtain a crude SPI (SPI-1) solution having a solid content concentration of 29% by mass. The weight average molecular weight (Mw) of SPI-1 was 48500. The NMP content in the SPI-1 solution was 62% by mass with respect to the mass of SPI-1.

<Reference example 2>
A crude SPI (SPI-2) solution having a solid content concentration of 27% by mass was obtained in the same manner as in Example 1 except that BPDA was used as PMDA. The weight average molecular weight (Mw) of SPI-2 was 59100. The NMP content in the SPI-2 solution was 69% by mass with respect to the mass of SPI-2.

<Example 1>
To 100 g of the crude SPI (SPI-1) solution obtained in Reference Example 1, 50 g of methanol was added as an extraction solvent, and the mixture was stirred at 20 ° C. for 60 minutes to obtain a suspension. The suspension was allowed to stand to be in a two-phase separated state, and then the extraction solvent layer was separated and removed. This operation was repeated twice more to obtain a purified SPI (SPI-3) solution. The NMP content in the SPI-3 solution was 1.5% by mass with respect to the mass of SPI-3.

<Example 2>
A purified SPI (SPI-4) solution was obtained in the same manner as in Example 1 except that the extraction solvent was a mixed solvent of 30 g of methanol and 20 g of acetone. The NMP content in the SPI-4 solution was 1.2% by mass with respect to the mass of SPI-4.

<Example 3>
To 100 g of the crude SPI (SPI-1) solution obtained in Reference Example 1, 70 g of water was added as an extraction solvent, and the mixture was stirred at 20 ° C. for 60 minutes to obtain a suspension. The suspension was allowed to stand and centrifuged to achieve a two-phase separation state, and then the extraction solvent layer was separated and removed. This operation was repeated twice more to obtain a purified SPI (SPI-5) solution. The NMP content in the SPI-5 solution was 0.8% by mass with respect to the mass of SPI-5.

<Example 4>
A purified SPI (SPI-6) solution was obtained in the same manner as in Example 3 except that 100 g of the crude SPI (SPI-2) solution obtained in Reference Example 2 was used. The NMP content in the SPI-6 solution was 1.2% by mass with respect to the mass of SPI-6.

<Comparative Example 1>
When 500 g of methanol was added to 100 g of the crude SPI (SPI-1) solution obtained in Reference Example 1 and stirred, a solid SPI precipitate was generated, and solvent extraction could not be performed. After filtering this precipitate, the dried product was redissolved in p-xylene to obtain a purified SPI (SPI-7) solution. The NMP content in the SPI-7 solution was 1.5% by mass with respect to the mass of SPI-7, but a large amount of methanol waste liquid containing NMP was generated.

<Comparative Example 2>
When 700 g of acetone was added to 100 g of the crude SPI (SPI-2) solution obtained in Reference Example 1 and stirred, solid SPI was generated and solvent extraction could not be performed. After filtering this precipitate, the dried product was redissolved in p-xylene to obtain a purified SPI (SPI-8) solution. The NMP content in the SPI-8 solution was 1.1% by mass with respect to the mass of SPI-8, but a large amount of acetone waste liquid containing NMP was generated.

<Comparative Example 3>
When 5 g of methanol was added to 100 g of the crude SPI (SPI-2) solution obtained in Reference Example 2 and stirred, solvent extraction could not be performed because the two phases were not separated in the solution state.

As shown in Examples and Comparative Examples, the method for producing a SPI solution of the present invention can efficiently reduce residual NMP with a small amount of extraction solvent by a solvent extraction method. It is clear that the method for purifying the SPI solution by the solvent extraction method of the present invention is superior in economic efficiency and environmental compatibility as compared with the conventionally known redissolution method through precipitation formation.

Since the SPI solution produced by the method of the present invention has a reduced amide solvent content in the SPI solution, the equipment can be made smaller and lighter in the electric / electronic field and the energy field such as a lithium secondary battery. , For flexibility and the like, it can be suitably used as an SPI solution for adhesion, insulation, protection and the like.

Claims (2)

A method for producing a soluble polyimide solution having a weight average molecular weight (Mw) of 20,000 or more and 80,000 or less, which comprises the following steps.
1) In a solvent containing an amide-based solvent, approximately equimolar aromatic tetracarboxylic acid dianhydride is reacted with an aliphatic diamine containing dimadiamine to prepare a soluble polyimide solution.
2) The amide-based solvent in the soluble polyimide solution is removed by a solvent extraction method to obtain a soluble polyimide solution in which the content of the amide-based solvent in the soluble polyimide solution is 5% by mass or less with respect to the soluble polyimide mass. The method for producing a soluble polyimide solution according to claim 1, wherein in the solvent extraction method, the amount of the solvent extractant used is 20 to 200 parts by mass with respect to 100 parts by mass of the soluble polyimide solution.