JP7567071B2 - Polyimide, polyimide solution, coating material and molding material - Google Patents

Description

The present invention relates to polyimides, polyimide solutions, coating materials and molding materials.

Polyimide (polyimide resin) not only has excellent heat resistance, but also has other properties such as chemical resistance, radiation resistance, electrical insulation, and excellent mechanical properties.
For this reason, polyimides are known as materials used for flexible printed wiring circuit boards, insulating coating paints, heat-resistant molding materials, and the like.

Most of the polyimides that are used industrially are insoluble in organic solvents and do not melt even at or above their glass transition temperature, so it is generally not easy to mold the polyimides themselves.
Generally, polyimides are synthesized, for example, as described in US Pat. No. 5,399,323.
That is, first, an aromatic tetracarboxylic dianhydride such as 3,3',4,4'-biphenyltetracarboxylic dianhydride is reacted with an aromatic diamine such as 1,4-phenylenediamine in an aprotic polar organic solvent such as N-methyl-2-pyrrolidone to obtain a polyamic acid (polyamic acid), which is a precursor of a polyimide.
Thereafter, the polyamic acid is heated at 250° C. to 400° C. to proceed with dehydration and cyclization (imidization) to obtain a polyimide.

Special Publication No. 60-42817

Many of the polyimides with industrially used structures dissolve in organic solvents in the form of polyamic acid, but when they become polyimide, they gel or precipitate immediately after synthesis or after being left for about a day, becoming insoluble and not soluble.
For this reason, in order to obtain a material containing polyimide (polyimide material), it is common to apply a solution of polyamic acid, volatilize the solvent, and then heat the resulting material to cause imidization.
However, condensation water is generated during the process of imidizing polyamic acid, which may cause voids in the polyimide material, and the polyimide material may shrink, causing changes in thickness, etc.

The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide a polyimide that has excellent solubility in a solvent (does not cause gelation or precipitation).
A further object of the present invention is to provide a polyimide solution, a coating material, and a molding material containing the above polyimide.

After extensive research, the inventors discovered that the above objective can be achieved by adopting the following configuration, and thus completed the present invention.

That is, the present invention provides the following [1] to [9].
[1] A polyimide obtained by polymerizing an acid component containing 3,3',4,4'-biphenyltetracarboxylic dianhydride and a diamine component containing 20.0 to 80.0 mol % of a compound A described below and 20.0 to 80.0 mol % of 2,2-bis-[4-(4-aminophenoxy)phenyl]propane.
[2] A polyimide obtained by polymerizing an acid component containing more than 70.0 mol% and less than 100.0 mol% of 3,3',4,4'-biphenyltetracarboxylic dianhydride and more than 0.0 mol% and less than 30.0 mol% of pyromellitic dianhydride, and a diamine component containing 20.0 to 80.0 mol% of a compound A described below and 20.0 to 80.0 mol% of 2,2-bis-[4-(4-aminophenoxy)phenyl]propane.
[3] A polyimide obtained by polymerizing an acid component containing 3,3',4,4'-biphenyltetracarboxylic dianhydride and a diamine component containing 15.0 to 80.0 mol % of a compound A described below, 15.0 to 80.0 mol % of 2,2-bis-[4-(4-aminophenoxy)phenyl]propane, and more than 0.0 mol % but less than 30.0 mol % of 2,4-diaminotoluene.
[4] A polyimide obtained by polymerizing an acid component containing more than 70.0 mol% and less than 100.0 mol% of 3,3',4,4'-biphenyltetracarboxylic dianhydride and more than 0.0 mol% and less than 30.0 mol% of pyromellitic dianhydride, and a diamine component containing 15.0 to 80.0 mol% of a compound A described below, 15.0 to 80.0 mol% of 2,2-bis-[4-(4-aminophenoxy)phenyl]propane, and more than 0.0 mol% and less than 30.0 mol% of 2,4-diaminotoluene.
[5] A polyimide obtained by polymerizing an acid component containing 3,3',4,4'-biphenyltetracarboxylic dianhydride and a diamine component containing 15.0 to 80.0 mol% of a compound A described below, 15.0 to 80.0 mol% of 2,2-bis-[4-(4-aminophenoxy)phenyl]propane, and more than 0.0 mol% and less than 30.0 mol% of 4,4'-oxydianiline and/or 3,4'-oxydianiline.
[6] A polyimide obtained by polymerizing an acid component containing more than 70.0 mol% and less than 100.0 mol% of 3,3',4,4'-biphenyltetracarboxylic dianhydride and more than 0.0 mol% and less than 30.0 mol% of pyromellitic dianhydride, and a diamine component containing 15.0 to 80.0 mol% of a compound A described below, 15.0 to 80.0 mol% of 2,2-bis-[4-(4-aminophenoxy)phenyl]propane, and more than 0.0 mol% and less than 30.0 mol% of 4,4'-oxydianiline and/or 3,4'-oxydianiline.
[7] A polyimide solution containing 5 to 50% by mass of the polyimide according to any one of [1] to [6] above in a polar organic solvent.
[8] A coating material containing the polyimide according to any one of [1] to [6] above.
[9] A molding material containing the polyimide according to any one of [1] to [6] above.

According to the present invention, a polyimide having excellent solubility in a solvent can be provided.
When a solution containing such a polyimide (polyimide solution) is used, the imidization has already progressed, so that the generation of voids and the like can be suppressed in the resulting polyimide material.
In other words, polyimide materials of any shape can be obtained simply by coating a polyimide solution and then volatilizing off the solvent. In addition, the mechanical strength and thermal properties are comparable to those of other materials.

[Polyimide]
The polyimide (polyimide resin) of the present invention will be described in detail below with respect to first to sixth embodiments. The polyimides of the first to sixth embodiments described below exhibit excellent solubility in a solvent (for example, a polar organic solvent described later).

First Embodiment
The polyimide of the first embodiment is obtained by polymerizing an acid component containing 3,3',4,4'-biphenyltetracarboxylic dianhydride and a diamine component containing 20.0 to 80.0 mol % of a compound A described below and 20.0 to 80.0 mol % of 2,2-bis-[4-(4-aminophenoxy)phenyl]propane.

Acid components
The acid component contains 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA).
The content of BPDA in the acid component is preferably 90.0 mol % or more, more preferably 95.0 mol % or more, and even more preferably 100.0 mol %, for the reason of achieving both strength and solubility.

Diamine component
The diamine component contains a compound A represented by the following formula (A).

In the above formula (A), R ¹ , R ² , R ³ and R ⁴ are each independently a methyl group or an ethyl group.

Suitable examples of compound A include 4,4'-methylenebis(2-ethyl-6-methylaniline) (MED) represented by formula (3) described below, 4,4'-methylenebis(2,6-dimethylaniline) (MMD) represented by formula (4) described below, and 4,4'-methylenebis(2,6-diethylaniline) (EED) represented by formula (5) described below.

In the diamine component, the content of compound A is 20.0 to 80.0 mol%, preferably 23.0 to 77.0 mol%, and more preferably 25.0 to 75.0 mol%, in order to achieve both strength and solubility.

The diamine component further contains 2,2-bis-[4-(4-aminophenoxy)phenyl]propane (BAPP).
The content of BAPP in the diamine component is 20.0 to 80.0 mol %, preferably 23.0 to 77.0 mol %, and more preferably 25.0 to 75.0 mol %, for the reason of achieving both strength and solubility.

Second Embodiment
The polyimide of the second embodiment is obtained by polymerizing an acid component containing more than 70.0 mol% and less than 100.0 mol% of 3,3',4,4'-biphenyltetracarboxylic dianhydride and more than 0.0 mol% and less than 30.0 mol% of pyromellitic dianhydride, and a diamine component containing 20.0 to 80.0 mol% of compound A and 20.0 to 80.0 mol% of 2,2-bis-[4-(4-aminophenoxy)phenyl]propane.

Acid components
The acid component contains 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA).
In order to achieve both strength and solubility, the content of BPDA in the acid component is more than 70.0 mol % and less than 100.0 mol %, preferably 73.0 to 97.0 mol %, and more preferably 75.0 to 90.0 mol %.

The acid component further contains pyromellitic dianhydride (PMDA).
The content of PMDA in the acid component is more than 0.0 mol % and less than 30.0 mol %, preferably 3.0 to 27.0 mol %, and more preferably 10.0 to 27.0 mol %, for the reason of achieving both strength and solubility.

Diamine component
The diamine component contains compound A.
The content of compound A in the diamine component is 20.0 to 80.0 mol %, preferably 23.0 to 77.0 mol %, and more preferably 25.0 to 75.0 mol %, for the reason of achieving both strength and solubility.

The diamine component further contains 2,2-bis-[4-(4-aminophenoxy)phenyl]propane (BAPP).
The content of BAPP in the diamine component is 20.0 to 80.0 mol %, preferably 23.0 to 77.0 mol %, and more preferably 25.0 to 75.0 mol %, for the reason of achieving both strength and solubility.

Third Embodiment
The polyimide of the third embodiment is obtained by polymerizing an acid component containing 3,3',4,4'-biphenyltetracarboxylic dianhydride and a diamine component containing 15.0 to 80.0 mol% of compound A, 15.0 to 80.0 mol% of 2,2-bis-[4-(4-aminophenoxy)phenyl]propane, and more than 0.0 mol% and less than 30.0 mol% of 2,4-diaminotoluene.

Acid components
The acid component contains 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA).
The content of BPDA in the acid component is preferably 90.0 mol % or more, more preferably 95.0 mol % or more, and even more preferably 100.0 mol %, for the reason of achieving both strength and solubility.

Diamine component
The diamine component contains compound A.
The content of compound A in the diamine component is 15.0 to 80.0 mol %, preferably 20.0 to 70.0 mol %, and more preferably 20.0 to 60.0 mol %, for the reason of achieving both strength and solubility.

The diamine component further contains 2,2-bis-[4-(4-aminophenoxy)phenyl]propane (BAPP).
In the diamine component, the content of BAPP is 15.0 to 80.0 mol %, preferably 20.0 to 70.0 mol %, and more preferably 25.0 to 60.0 mol %, for the reason of achieving both strength and solubility.

The diamine component further contains 2,4-diaminotoluene (DAT).
In order to achieve both strength and solubility, the content of DAT in the diamine component is more than 0.0 mol % and less than 30.0 mol %, preferably 5.0 to 28.0 mol %, and more preferably 10.0 to 27.0 mol %.

Fourth Embodiment
The polyimide of the fourth embodiment is obtained by polymerizing an acid component containing more than 70.0 mol% and less than 100.0 mol% of 3,3',4,4'-biphenyltetracarboxylic dianhydride and more than 0.0 mol% and less than 30.0 mol% of pyromellitic dianhydride, and a diamine component containing 15.0 to 80.0 mol% of compound A, 15.0 to 80.0 mol% of 2,2-bis-[4-(4-aminophenoxy)phenyl]propane, and more than 0.0 mol% and less than 30.0 mol% of 2,4-diaminotoluene.

Acid components
The acid component contains 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA).
In order to achieve both strength and solubility, the content of BPDA in the acid component is more than 70.0 mol % and less than 100.0 mol %, preferably 73.0 to 97.0 mol %, and more preferably 75.0 to 90.0 mol %.

The acid component further contains pyromellitic dianhydride (PMDA).
The content of PMDA in the acid component is more than 0.0 mol % and less than 30.0 mol %, preferably 3.0 to 27.0 mol %, and more preferably 10.0 to 25.0 mol %, for the reason of achieving both strength and solubility.

Diamine component
The diamine component contains compound A.
The content of compound A in the diamine component is 15.0 to 80.0 mol %, preferably 20.0 to 60.0 mol %, and more preferably 22.0 to 45.0 mol %, for the reason of achieving both strength and solubility.

The diamine component further contains 2,2-bis-[4-(4-aminophenoxy)phenyl]propane (BAPP).
The content of BAPP in the diamine component is 15.0 to 80.0 mol %, preferably 25.0 to 60.0 mol %, and more preferably 30.0 to 55.0 mol %, for the reason of achieving both strength and solubility.

The diamine component further contains 2,4-diaminotoluene (DAT).
In order to achieve both strength and solubility, the content of DAT in the diamine component is more than 0.0 mol % and less than 30.0 mol %, preferably 5.0 to 28.0 mol %, and more preferably 10.0 to 27.0 mol %.

Fifth embodiment
The polyimide of the fifth embodiment is obtained by polymerizing an acid component containing 3,3',4,4'-biphenyltetracarboxylic dianhydride and a diamine component containing 15.0 to 80.0 mol% of compound A, 15.0 to 80.0 mol% of 2,2-bis-[4-(4-aminophenoxy)phenyl]propane, and more than 0.0 mol% and less than 30.0 mol% of 4,4'-oxydianiline and/or 3,4'-oxydianiline.

Acid components
The acid component contains 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA).
The content of BPDA in the acid component is preferably 90.0 mol % or more, more preferably 95.0 mol % or more, and even more preferably 100.0 mol %, for the reason of achieving both strength and solubility.

Diamine component
The diamine component contains compound A.
The content of compound A in the diamine component is 15.0 to 80.0 mol %, preferably 20.0 to 60.0 mol %, and more preferably 23.0 to 52 mol %, for the reason of achieving both strength and solubility.

The diamine component further contains 2,2-bis-[4-(4-aminophenoxy)phenyl]propane (BAPP).
The content of BAPP in the diamine component is 15.0 to 80.0 mol %, preferably 20.0 to 60.0 mol %, and more preferably 23.0 to 52.0 mol %, for the reason of achieving both strength and solubility.

The diamine component further contains 4,4'-oxydianiline (ODA) and/or 3,4'-oxydianiline (DAPE).
In the diamine component, the total content of ODA and DAPE is more than 0.0 mol % and less than 30.0 mol %, preferably 5.0 to 28.0 mol %, and more preferably 10.0 to 27.0 mol %, in order to achieve both strength and solubility.

Sixth Embodiment
The polyimide of the sixth embodiment is obtained by polymerizing an acid component containing more than 70.0 mol% and less than 100.0 mol% of 3,3',4,4'-biphenyltetracarboxylic dianhydride and more than 0.0 mol% and less than 30.0 mol% of pyromellitic dianhydride, and a diamine component containing 15.0 to 80.0 mol% of compound A, 15.0 to 80.0 mol% of 2,2-bis-[4-(4-aminophenoxy)phenyl]propane, and more than 0.0 mol% and less than 30.0 mol% of 4,4'-oxydianiline and/or 3,4'-oxydianiline.

Acid components
The acid component contains 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA).
In order to achieve both strength and solubility, the content of BPDA in the acid component is more than 70.0 mol % and less than 100.0 mol %, preferably 73.0 to 97.0 mol %, and more preferably 75.0 to 90.0 mol %.

The acid component further contains pyromellitic dianhydride (PMDA).
The content of PMDA in the acid component is more than 0.0 mol % and less than 30.0 mol %, preferably 3.0 to 27.0 mol %, and more preferably 10.0 to 25.0 mol %, for the reason of achieving both strength and solubility.

Diamine component
The diamine component contains compound A.
The content of compound A in the diamine component is 15.0 to 80.0 mol %, preferably 20.0 to 60.0 mol %, and more preferably 22.0 to 55.0 mol %, for the reason of achieving both strength and solubility.

The diamine component further contains 2,2-bis-[4-(4-aminophenoxy)phenyl]propane (BAPP).
The content of BAPP in the diamine component is 15.0 to 80.0 mol %, preferably 20.0 to 60.0 mol %, and more preferably 23.0 to 55.0 mol %, for the reason of achieving both strength and solubility.

The diamine component further contains 4,4'-oxydianiline (ODA) and/or 3,4'-oxydianiline (DAPE).
In the diamine component, the total content of ODA and DAPE is more than 0.0 mol % and less than 30.0 mol %, preferably 5.0 to 28.0 mol %, and more preferably 10.0 to 27.0 mol %, in order to achieve both strength and solubility.

[Polyimide manufacturing method and polyimide solution]
Next, a method for producing the polyimides of the above-mentioned first to sixth embodiments (hereinafter, for convenience, also referred to as "the present production method") will be described.
The following description also covers a solution in which polyimide is dissolved in a solvent (polyimide solution). The polyimide solution is also a coating material containing polyimide.
The polyimide solution (coating material) can be used as an electrodeposition paint, an insulating paint, a heat-resistant paint, etc.

In general, this manufacturing method involves polymerizing (dehydration condensation) the above-mentioned diamine component and acid component in a solvent to obtain the above-mentioned polyimide (first to sixth embodiments).

The diamine component is as described above.
The diamine component may further include aromatic diamines such as 1,4-phenylenediamine, aliphatic diamines such as 1,2-diaminoethane, 1,3-diaminopropane, 1,5-diaminopentane, and 1,6-hexanediamine, and generally known polyamines. These may be used alone or in combination of two or more.

The acid component is as described above.
As the acid component, aromatic tetracarboxylic dianhydrides such as 4,4'-oxydiphthalic dianhydride (ODPA) and 3,3',4,4'-benzophenonetetracarboxylic dianhydride (BTDA), aliphatic tetracarboxylic dianhydrides such as cyclohexanetetracarboxylic dianhydride, etc. may be used. These may be used alone or in combination of two or more.

A diamine component and an acid component, which are mixed in an appropriate molar ratio, are reacted in a solvent to obtain a polyamic acid, i.e., a solution containing the polyamic acid (polyamic acid solution) is obtained.
In this case, the reaction temperature is preferably 30 to 70° C., more preferably 40 to 60° C. The reaction time is preferably 1 to 36 hours, more preferably 6 to 30 hours. The reaction is carried out, for example, under atmospheric pressure.

The polyamic acid solution is then heated to imidize (dehydrate and cyclize) the polyamic acid. This results in a solution containing polyimide (polyimide solution).

The temperature (heating temperature) when the polyamic acid (polyamic acid solution) is heated is not particularly limited as long as the temperature is selected so that the azeotropic solvent can be distilled off, but is preferably 140 to 220°C, and more preferably 160 to 200°C.
The holding time (heating time) at this heating temperature is preferably 0.5 to 10 hours, more preferably 2 to 7 hours. Temperature control may be performed in an inert gas blowing environment or in a reduced pressure environment, as necessary.

In this manufacturing method, it is preferable to use a container equipped with various cooling devices such as a Dean-Stark trap or a condenser. Then, the desired polyimide solution can be obtained while removing the moisture that is generated as the imidization proceeds.

The molar ratio of the acid component to the diamine component (acid component/diamine component) may be set arbitrarily depending on, for example, the viscosity of the polyimide solution to be applied, and is preferably 0.90 to 1.10, and more preferably 0.95 to 1.05.

The molecular structure of polyimide is not particularly limited. For example, depending on the polymerization conditions, it can be a random copolymer, an alternating copolymer, a block copolymer, etc.

The weight average molecular weight of the resulting polyimide is preferably at least 1,500. If the molecular weight is within this range, the polyimide solution exhibits sufficient viscosity, and it is easy to obtain a desired film thickness.
On the other hand, the molecular weight is preferably 200,000 or less. If the molecular weight is in this range, problems with the stirring equipment are suppressed, and the solvent can be easily and efficiently removed.

As the solvent used in this production method, it is preferable to use a polar organic solvent, since the resulting polyimide exhibits sufficient solubility.
When obtaining polyimide in a solvent, the water generated by imidization is removed, and for this purpose, it is preferable to remove the water by heating or the like in the presence of a known cosolvent (e.g., benzene, toluene, xylene, etc.) that is known to have an azeotropic effect with water.
Moreover, the polyimide solution preferably has a fluidity suitable for coating and is a homogeneous, transparent solution free of precipitates.
From these viewpoints, the polar organic solvent is preferably an amide solvent such as N,N-dimethylformamide, N,N-dimethylacetamide, or N-methyl-2-pyrrolidone.

The solids concentration of the polyimide solution is not particularly limited and is set appropriately depending on the desired viscosity, etc., for example, 5 to 50 mass%.

The viscosity of the polyimide solution can be set appropriately as long as the polyimide solution can be mixed by stirring or pumped and does not cause any problems in coating. Specifically, the viscosity at 25°C is preferably 0.3 to 200 Pa·s.

In the present production method, a dehydrating agent and an imidization catalyst may be blended in the solvent in order to promote imidization.
As the dehydrating agent, any commonly known agent may be used, and examples thereof include acid anhydrides such as acetic anhydride and oxalic anhydride; γ-valerolactone; and the like.
As the imidization catalyst, any commonly known one may be used, and examples thereof include tertiary amines such as isoquinoline, β-picoline, and pyridine.
A mixture of two or more kinds of dehydrating agents and imidization catalysts may be used.

Furthermore, a crosslinking agent, a coupling agent, etc. may be blended for the purpose of modifying the main chain of the polyimide to impart various properties to the polyimide, within the scope of not impairing the mechanical properties and electrical properties of the resulting polyimide.
As the crosslinking agent, any commonly known agent may be used, such as oxazolines, melamines, isocyanates, aziridines, benzoxazines, bismaleimides, etc., and a mixture of two or more types may be used.

From the viewpoint of industrial use, it is preferable that the state of the polyimide solution after polymerization (dehydration condensation) continues for two weeks or more, and it is more preferable that the viscosity does not change.
For this reason, a viscosity stabilizer may be added within a range that does not impair the mechanical properties and electrical properties of the resulting polyimide.

[Polyimide film (molding material)]
Next, a cured film (polyimide film) obtained by using the polyimide solution will be described.
Polyimide film is a molding material containing polyimide, and can be handled as a film, sheet, panel, etc. depending on the thickness. It can also be applied to seamless cylindrical tubes, belts, and molded parts using a mold.

Polyimide films can be used, for example, as heat-resistant molding materials in fields such as flexible printed circuits (FPCs), chip-on-film (COF), and electronic circuit boards for tape automated bonding (TAB).

The conditions for obtaining a polyimide film from a polyimide solution may vary depending on the polyimide composition, the type of solvent, the substrate to be coated, etc., but the method used may be any known method and is not particularly limited.

For example, a polyimide solution can be applied onto a substrate and then dried to obtain a cured polyimide film.

It is preferable that the substrate is not corroded by the solvent of the polyimide solution.
Specifically, examples of materials for the substrate include glass; wood; stone; resins such as triacetate cellulose (TAC), polyethylene terephthalate (PET), diacetyl cellulose, acetate butyrate cellulose, polyethersulfone, acrylic resins, polyurethane resins, polyester, polycarbonate, polysulfone, polyether, trimethylpentene, polyether ketone, and (meth)acrylonitrile; rubber; and metals such as SUS and copper.
When the substrate has excellent transparency, a composite of the substrate and the cured film can be used as a transparent material.
If the substrate is colored, it can be used without impairing the design of the substrate.

Any commonly known coating method may be used, such as roll coating, gravure coating, slide coating, spraying, dipping, screen printing, spraying, etc.

As the drying method, any commonly known method may be used, for example, hot air drying, a method using a far-infrared heating furnace, a ceramic heater, a muffle furnace, etc., and a combination of two or more methods may be used.
The drying temperature is set, for example, according to the boiling point of the solvent, taking into consideration the glass transition points of the polyimide and the substrate.
In the polyimide solution obtained by the above-mentioned production method, the imide ring closure has already progressed due to the heating of the solvent carried out in the production method. Therefore, in order to form a cured film, it is only necessary to volatilize and remove the solvent after coating the polyimide solution. If the time and pressure are appropriately set, a cured film can be obtained even under conditions below the boiling point of the solvent.

The resulting cured polyimide film does not require the dehydration condensation step required for typical polyimides, and is therefore free from the cure shrinkage that is characteristic of polyimides.
This makes it possible to omit the steps required for conventional polyimide, such as fixing the ends of the intermediate film and stretching it.

When a polyimide film is obtained from a polyimide solution, a filler may be added to the polyimide solution for the purpose of improving various properties of the cured film.
The filler may be any of the commonly known fillers, such as silica, titanium oxide, alumina, silicon nitride, boron nitride, calcium hydrogen phosphate, calcium phosphate, mica, carbon black, etc., and may be used in combination with a plurality of types. These may also contain conductive components, coloring components, adhesion-imparting components, etc.
In addition, known additives such as a mold release agent, an antifoaming agent, a leveling agent, an ion trapper, a polymerization inhibitor, an antioxidant, a viscosity modifier, and an antistatic agent may be added as necessary.

The polyimide film can be used for any of the conventionally known applications of polyimides.
For example, the substrate is used in electronic devices such as displays, touch panels, projectors, printers, earphones, speakers, antennas, etc. The substrate may be selected on the assumption that the substrate will be mounted in these electronic devices.
The polyimide obtained has excellent physical properties such as heat resistance and hardness as well as good mechanical properties, and can therefore be used, for example, as a binder for carbon fibers, glass fibers, metal nanowires, etc.
Because it reduces the heating load, it can be applied to electrodes of secondary batteries that use metal foil as a base material.
Since it does not shrink during hardening and its dimensions are stable, it can be used for porous materials with internal voids. Polyimide films can also be made into cylindrical shapes and used for tubes and belts.
The polyimide film obtained by ensuring thickness precision and smooth coating and drying can be peeled off and used as a film, sheet, panel, etc.

Polyimide films are expected to have sufficient durability against low-polarity solvents and moisture, and therefore can be used in applications that require water resistance and chemical resistance.
Furthermore, by utilizing this property, polyimide can be precipitated while mixing with a poor solvent such as alcohol, and then washed and dried as necessary to obtain a solid (powder) of polyimide.

The present invention will be specifically described below with reference to examples. However, the present invention is not limited to the examples described below.

Example 1
Preparation of polyimide solution
Under a nitrogen atmosphere, 7.62 g (27.00 mmol) of 4,4'-methylenebis(2-ethyl-6-methylaniline) (MED) as compound A, 3.70 g (9.01 mmol) of 2,2-bis-[4-(4-aminophenoxy)phenyl]propane (BAPP), and 10.60 g (36.01 mmol) of 3,3',4,4'-biphenyltetracarboxylic dianhydride (BPDA) were added to 78.77 g of N-methyl-2-pyrrolidone (NMP), and the mixture was stirred and reacted at 50°C and atmospheric pressure for 24 hours to obtain a polyamic acid solution.
To the resulting polyamic acid solution, γ-valerolactone (GVL), pyridine, and toluene were added, and the mixture was heated and stirred at 170° C. for 5 hours while removing the condensed water from the system, to obtain a polyimide solution. The resulting polyimide solution was reddish brown and transparent.

Solubility
The obtained polyimide solution was left at room temperature and atmospheric pressure for two weeks. If the solution showed good solubility and fluidity after the standing, it was rated "Good", and if abnormalities such as gelation or precipitation occurred immediately after synthesis or within one day after synthesis, it was rated "Bad" in Table 1 below. If the result was "Good", the polyimide in the obtained polyimide solution could be evaluated as having excellent solubility in the solvent.

<Preparation of polyimide film>
15 g of the obtained polyimide solution (synthesized within 1 day) was applied to a glass plate using a bar coater and heated at 100° C. for 30 minutes, 150° C. for 30 minutes, 200° C. for 90 minutes, and 220° C. for 30 minutes to obtain a polyimide film with a thickness of approximately 50 μm.

Mechanical strength
The obtained polyimide film was subjected to a tensile test in accordance with JIS K 7127:1999 (ISO 527-3:1995) under the following conditions to determine the tensile modulus (unit: MPa) and tensile strength (unit: MPa). The results are shown in Table 1 below.
Measuring device: Shimadzu AGS-J
Tensile speed: 102 mm/min
Chuck distance: 30 mm

Thermal properties
The polyimide film thus obtained was subjected to tests under the following conditions to determine its glass transition temperature (unit: ° C.), linear thermal expansion coefficient (unit: ppm/K), and thermal decomposition temperature (unit: ° C.). The results are shown in Table 1 below.

(Glass Transition Temperature)
Equipment: TA Instruments DMA Q800
Heating rate: 3°C/min
Temperature range: 50 to 450°C
Frequency: 1Hz

(Coefficient of linear thermal expansion)
Equipment: Shimadzu TMA-60
Temperature range: 50℃-200℃
Heating rate: 10° C./min

(Thermal decomposition temperature)
Equipment: Shimadzu DTG-60
Speed: 10℃/min
Thermal decomposition temperature: the temperature at which a 5% mass reduction occurs according to the measurement chart

Examples 2 to 25 and Comparative Examples 1 to 7
A polyimide solution was prepared and evaluated in the same manner as in Example 1 using the diamine component and acid component shown in Table 1 in the amounts shown in Table 1. The results are shown in Table 1.

For Examples 12 and 19, polyimide films were produced under the same conditions as in "Preparation of Polyimide Film" using samples stored at room temperature for two months after production, and mechanical strength and thermal properties were measured. The results are shown in Table 2 below. Even after storage for two months, the results were almost the same as those obtained immediately after synthesis.

For samples with "Bad" solubility (specifically, Comparative Examples 1 to 7), polyamic acid solutions were produced again. It was confirmed that there was no gelation or precipitation in any of the samples. Using the obtained polyamic acid solutions, polyimide films were produced under the same conditions as in "Preparation of Polyimide Film," and the mechanical strength and thermal properties were measured for reference.

The components shown in Table 1 below are as follows.
BPDA: 3,3',4,4'-biphenyltetracarboxylic dianhydride represented by the following formula (1) PMDA: pyromellitic dianhydride represented by the following formula (2) MED: 4,4'-methylenebis(2-ethyl-6-methylaniline) represented by the following formula (3)
MMD: 4,4'-methylenebis(2,6-dimethylaniline) represented by the following formula (4)
EED: 4,4'-methylenebis(2,6-diethylaniline) represented by the following formula (5):
MDA: 4,4'-methylenedianiline represented by the following formula (6) BAPP: 2,2-bis-[4-(4-aminophenoxy)phenyl]propane represented by the following formula (7) DAT: 2,4-diaminotoluene represented by the following formula (8) ODA: 4,4'-oxydianiline represented by the following formula (9) DAPE: 3,4'-oxydianiline represented by the following formula (10)

<Summary of evaluation results>
As shown in Table 1 above, the polyimides of Examples 1 to 25 had good solubility in solvents.
In contrast, the polyimides of Comparative Examples 1 to 7 had insufficient solubility in the solvent.

Claims (8)

A polyimide for a polyimide solution,
an acid component consisting of 3,3',4,4'-biphenyltetracarboxylic dianhydride;
A polyimide obtained by polymerizing 20.0 to 80.0 mol % of a compound A represented by the following formula (A) and a diamine component consisting of 20.0 to 80.0 mol % of 2,2-bis-[4-(4-aminophenoxy)phenyl]propane:
In the formula (A), R ¹ , R ² , R ³ and R ⁴ are each independently a methyl group or an ethyl group. A polyimide for a polyimide solution,
An acid component containing 3,3',4,4'-biphenyltetracarboxylic dianhydride;
A polyimide obtained by polymerizing a diamine component containing 15.0 to 80.0 mol % of a compound A represented by the following formula (A), 15.0 to 80.0 mol % of 2,2-bis-[4-(4-aminophenoxy)phenyl]propane, and more than 0.0 mol % and less than 30.0 mol % of 2,4-diaminotoluene:
In the formula (A), R ¹ , R ² , R ³ and R ⁴ are each independently a methyl group or an ethyl group. A polyimide for a polyimide solution,
An acid component containing more than 70.0 mol% and less than 100.0 mol% of 3,3',4,4'-biphenyltetracarboxylic dianhydride and more than 0.0 mol% and less than 30.0 mol% of pyromellitic dianhydride;
A polyimide obtained by polymerizing a diamine component containing 15.0 to 80.0 mol % of a compound A represented by the following formula (A), 15.0 to 80.0 mol % of 2,2-bis-[4-(4-aminophenoxy)phenyl]propane, and more than 0.0 mol % and less than 30.0 mol % of 2,4-diaminotoluene:
In the formula (A), R ¹ , R ² , R ³ and R ⁴ are each independently a methyl group or an ethyl group. A polyimide for a polyimide solution,
An acid component containing 3,3',4,4'-biphenyltetracarboxylic dianhydride;
A polyimide obtained by polymerizing a diamine component containing 15.0 to 80.0 mol % of a compound A represented by the following formula (A), 15.0 to 80.0 mol % of 2,2-bis-[4-(4-aminophenoxy)phenyl]propane, and more than 0.0 mol % and less than 30.0 mol % of 4,4'-oxydianiline and/or 3,4'-oxydianiline:
In the formula (A), R ¹ , R ² , R ³ and R ⁴ are each independently a methyl group or an ethyl group. A polyimide for a polyimide solution,
An acid component containing more than 70.0 mol% and less than 100.0 mol% of 3,3',4,4'-biphenyltetracarboxylic dianhydride and more than 0.0 mol% and less than 30.0 mol% of pyromellitic dianhydride;
A polyimide obtained by polymerizing a diamine component containing 15.0 to 80.0 mol % of a compound A represented by the following formula (A), 15.0 to 80.0 mol % of 2,2-bis-[4-(4-aminophenoxy)phenyl]propane, and more than 0.0 mol % and less than 30.0 mol % of 4,4'-oxydianiline and/or 3,4'-oxydianiline:
In the formula (A), R ¹ , R ² , R ³ and R ⁴ are each independently a methyl group or an ethyl group. A polyimide solution comprising 5 to 50% by mass of the polyimide according to any one of claims 1 to 5 in a polar organic solvent. A coating material comprising the polyimide according to any one of claims 1 to 5 . A molding material comprising the polyimide according to any one of claims 1 to 5 .