JP2002001804A - Aromatic polyimide film and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an aromatic polyimide film having mechanical properties including tensile modulus of not less than 10 Gpa which has not been observed in conventional films and to provide its manufacturing method. SOLUTION: A method for manufacturing an aromatic polyimide film comprises a process of swelling a precursor film of a solvent-remaining aromatic polyimide with a swelling agent, a process of stretching the swollen film at least in a uniaxial direction, a process of removing the swelling agent from the stretched film and a process of fixing and heating the film to convert it into an imide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an aromatic polyimide film having improved mechanical properties by stretching an aromatic polyimide precursor film in a swollen state, and a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, polyimide has excellent heat resistance, mechanical properties, and electrical properties.
It is widely used in the fields of electric and electronic materials, heat-resistant fiber materials and the like. In particular, pyromellitic dianhydride and 4,4'-
Excellent heat resistance and mechanical properties from aromatic polyimide produced from diaminodiphenyl ether and aromatic polyimide produced from 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride and p-phenylenediamine Is known to be obtained.

These aromatic polyimides are formed into a thin film by polymerizing a combination of an acid (or amine) component exhibiting rigidity and an amine (or acid) component exhibiting flexibility as monomer components. It has a degree of moldability and expresses a high elastic modulus.

[0004]

However, since the tensile elastic modulus of the film is at most about 4 to 8 GPa, the fixing belt of an image forming apparatus which requires a high processing speed and a high image quality is required. In the case of a belt or the like, the numerical values do not sufficiently satisfy the required characteristics. In other words, a belt having a thin and strong tensile elastic modulus of 10 GPa or more is desired especially for an apparatus having a high processing speed or an apparatus for large-size printing. However, at present, a belt using an aromatic polyimide having the highest elastic modulus is required. Was difficult to manufacture when the tensile modulus exceeded 9 GPa without reinforcing the filler.

[0005] The present invention has been made in response to such a demand, and provides an aromatic polyimide film having mechanical properties of 10 GPa or more, which is unprecedented, and a method for producing the film. The purpose is to:

[0006]

Means for Solving the Problems The present inventors have paid attention to the orientation of rod-like polyimide molecules and studied a method for suitably orienting them. As a result, a film was prepared in a complete polyimide precursor state, and swelled. Then, it was found that an oriented film having a large tensile modulus was obtained by stretching at a low magnification, and the present invention was completed.

That is, the production method of the present invention comprises a step of swelling an aromatic polyimide precursor film in which a solvent remains, with a swelling agent, a step of stretching the swollen film in at least one direction, and a step of swelling the stretched film. It has a step of removing the agent and a step of fixing the film and thermally imidizing the film.

Further, a seamless tubular body is used as the precursor film, and the stretching is performed in the circumferential direction.

In the above, it is preferable that the remaining amount of the solvent in the precursor film is 25 to 40% by weight. Further, the stretching ratio of the stretching is preferably 5 to 20%. On the other hand, the aromatic polyimide film of the present invention can be produced by the above-mentioned production method (Claim 1), is composed of an aromatic polyimide having an aromatic dianhydride and an aromatic diamine as monomer components, and has a tensile elasticity in a stretching direction. Rate is 10GP
a is an aromatic polyimide film which is not less than a.

Further, the aromatic polyimide film of the present invention can be produced by the above another production method (Claim 2), and comprises an aromatic polyimide having an aromatic dianhydride and an aromatic diamine as monomer components, A seamless tubular aromatic polyimide film having a tensile modulus in the circumferential direction of 10 GPa or more.

[Effects] According to the production method of the present invention,
As shown in the results of the examples, since the precursor film of the aromatic polyimide is stretched in a swollen state, the tensile modulus of the obtained film can be significantly improved.
Although the details of the reason why stretching in the swollen state is effective are not clear, the swollen state has a microstructure in which the molecular chains are stretched in a microstructure compared to the case where the amount of the solvent is increased to increase the mobility of the molecular chains. It is assumed that the orientation effect is high. The use of the precursor film in which the solvent remains is effective in facilitating the swelling due to substitution, and removing the swelling agent before thermal imidization improves the mechanical properties of the obtained film. Is considered to be effective.

When a seamless tubular body is used as the precursor film and the stretching is performed in the circumferential direction, a seamless tubular aromatic polyimide film having significantly improved tensile modulus can be manufactured.

The residual amount of the solvent in the precursor film is 25 to
When the content is 40% by weight, the replacement between the solvent and the swelling agent can be performed more easily, and the strength and the like of the precursor film become moderate, and the handling becomes easier.

When the stretching ratio of the stretching is 5 to 20%, the effect of improving the elastic modulus by the stretching is sufficiently obtained, and the brittleness in the transverse direction (non-stretching direction) due to excessive stretching is less likely to occur.

On the other hand, since the aromatic polyimide film of the present invention has a structure in which the molecular chains are appropriately oriented as obtained by the above-mentioned production method, the tensile elastic modulus in the stretching direction is as high as 10 GPa or more, and the The strength in the stretching direction is also maintained to some extent.

Further, another aromatic polyimide film of the present invention has a structure in which the molecular chains are appropriately oriented in the same manner as described above, so that the tensile modulus in the circumferential direction is as high as 10 GPa or more, and the strength in the non-stretching direction is high. Also becomes a seamless tubular body maintained to some extent.

[0017]

Embodiments of the present invention will be described below. In the present invention, a precursor film of an aromatic polyimide in which a solvent remains is used, but such a precursor film is produced by an ordinary method using an aromatic dianhydride and an aromatic diamine as described below. be able to.

Examples of the aromatic acid anhydride include biphenyltetracarboxylic dianhydride and / or pyromellitic dianhydride. Examples of the biphenyltetracarboxylic dianhydride include 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and 2,3,3 ′, 4-biphenyltetracarboxylic dianhydride.

As the aromatic diamine, p-phenylenediamine, 2,2'-dimethylbenzidine, 3,3
3'-dihydroxy-4,4'-diaminobiphenyl,
Those having a linear structure such as 4,4'-diaminobenzanilide are exemplified.

Examples of the combination of the aromatic dianhydride and the aromatic diamine include biphenyltetracarboxylic dianhydride, p-phenylenediamine, 2,2'-dimethylbenzidine, and 3,3'-dihydroxy-4. The combination with 4,4'-diaminobiphenyl is preferred in view of the orientation of the molecular chain. The aromatic acid dianhydride and the aromatic diamine may be used in combination of two or more, and in that case, the obtained aromatic polyimide is a copolymer.

In the synthesis, organic polar solvents such as N, N-dialkylamides are suitably used. For example, N, N-dimethylformamide, N, N-dimethylacetamide,
N, N-diethylformamide, N, N-diethylacetamide, N, N-dimethylmethoxyacetamide, dimethylsulfoxide, hexamethylphosphortriamide, N-methyl-2-pyrrolidone, pyridine, dimethylsulfoxide, tetramethylenesulfone, dimethyltetra Methylene sulfone or the like is used. These may be used alone or in combination. Furthermore, phenols such as cresol, phenol and xylenol, benzonitrile, dioxane, butyrolactone, xylene, cyclohexane, hexane, benzene, toluene and the like can be used alone or in combination in the organic polar solvent. Since the polyamic acid produced by the presence of water is hydrolyzed to have a low molecular weight, the synthesis of the polyamic acid is preferably performed under substantially anhydrous conditions.

By reacting the aromatic dianhydride (a) and the aromatic diamine (b) in an organic polar solvent as described above, a polyamic acid can be obtained. In (a) + (b)) are set according to various conditions. The reaction temperature is 80 ° C.
It is preferable to set the following, particularly preferably 5 to 5
0 ° C. Although the solution viscosity increases with the progress of the reaction, the viscosity at 25 ° C. in the B-type viscometer is preferably adjusted to 0.01 to 1000 Pa · s from the viewpoint of processability and the like. The solution viscosity can also be adjusted by stirring under heating or the monomer concentration.

For forming the precursor film into a sheet-like film or a seamless tubular body, a known method can be adopted. Specifically, in the case of a sheet-like film, a method of casting on a substrate such as a glass plate, a stainless steel substrate, or a stainless steel belt, and then drying by heating is common. On the other hand, the seamless tubular body is applied to the inner surface and the outer surface of the cylindrical mold by immersion coating, spray coating, or the like, and then, using a tubular outer mold, a bullet-shaped traveling body, a scraper, etc. It is molded by removing a polyamide precursor solution or by a centrifugal molding method.

At this time, since the film thickness accuracy is determined by the monomer concentration and the solution viscosity, and the surface roughness of the inner surface of the mold determines the surface accuracy of the tubular body, these can be determined according to the design of the tubular body. The monomer concentration of the polyimide precursor solution is 3 to 50 wt%, preferably 5 to 40 wt%.
Further, the solution viscosity is 0.01 to 1000 Pa · s, preferably 0.05 to 700 Pa · s, and more preferably 0.1.
５００500 Pa · s. Solution viscosity is a major factor that affects dimensional accuracy such as film thickness accuracy of the tubular body.If the viscosity is less than the above viscosity, there is a tendency that uneven wall thickness tends to occur. Tends to be scarce.

Depending on the required properties such as conductivity, semi-conductivity, high thermal conductivity and high strength, desired organic powders, inorganic powders, inorganic oxides, metals, metal oxides, surfactants, fibers, etc. Can be used.

In the present invention, a precursor film in which a solvent remains is used, and the applied polyimide precursor solution is heated and dried at a temperature of 80 ° C. or less (for example, 60 ° C.) for an appropriate time to form a base material or the like. By peeling from a mold or the like, a precursor film in which a solvent in which imidization has not progressed remains can be obtained. In the present invention, the remaining amount of the solvent is 25 to 40.
% Of the precursor film is preferably used, but the remaining amount of the solvent can be adjusted by heating temperature and time. If the remaining amount of the solvent is less than 25%, swelling is difficult in a subsequent step, and stretching tends to occur. If it exceeds 40%, the film tends to be soft and deformed during peeling.

The polyimide precursor film thus manufactured is swollen with a swelling agent before stretching. Any swelling agent may be used as long as it replaces the solvent and swells (increases the volume without dissolving) the precursor film of the aromatic polyimide. Examples thereof include high boiling alcohols such as ethylene glycol, diethylene glycol, and glycerin. And ethylene glycol is particularly preferred. Swelling can be performed by immersing the precursor film in a swelling agent or applying a swelling agent. For efficient swelling, swelling is preferably performed under heating at 80 ° C. or lower. The time for swelling depends on the type of swelling agent and solvent, but is preferably about 1 to 10 minutes.

In the present invention, the swollen film is stretched at least uniaxially, and this stretching is performed in the swelling agent or after immersion in the swelling agent. Examples of the stretching method include a method using a rotation speed difference between a plurality of metal rolls, a method using a rotation speed difference between pinch rolls, and a method using a tenter type stretching machine (biaxial stretching is possible). When a seamless tubular body is used as the precursor film, the stretching is performed at least in the circumferential direction. In any stretching method, the stretching is preferably performed at a low temperature from room temperature to 50 ° C. When the temperature exceeds 50 ° C., the rigidity of the film is lost, and the moldability tends to be poor.

The stretching ratio at that time is preferably 5 to 20% in each stretching direction. If it is less than 5%, the effect of improving the elastic modulus by stretching tends to be insufficient. If it exceeds 20%, the film tends to have too strong an orientation and weakly tear.

In the present invention, the swelling agent is removed from the thus stretched film. The swelling agent may be removed by drying at room temperature, drying by heating, or the like, but removal by extraction with a liquid is preferable because the swelling agent can be removed in a short time without heating. As the liquid used at that time,
Water, ethanol, isopropyl alcohol and the like can be used.

In the present invention, the film from which the swelling agent has been removed is fixed and thermally imidized. The film may be fixed as long as it can prevent shrinkage in the direction opposite to the stretching direction.Examples include a method of fixing both ends, a method of conveying a roll at a constant speed, a method of holding between rolls, and a method of coating and fixing to a cylindrical mold. No.

The thermal imidization can be performed in the same manner as a conventional polyimide film. For example, the imidization can be advanced and completed by stepwise heating from about 100 ° C. to about 400 ° C.

The liquid used for removing the swelling agent may be dried immediately after use, or may be removed by evaporation by heating during thermal imidization.

The aromatic polyimide film of the present invention can be produced by the above-described production method, is composed of an aromatic polyimide having an aromatic dianhydride and an aromatic diamine as monomer components, and has a tensile modulus in the stretching direction. It is 10 GPa or more. The tensile modulus in the circumferential direction is 10 GPa.
The above is a seamless tubular aromatic polyimide film.

Further, the tear strength in the non-stretching direction (JIS
K 7128-3) is 150 to 600 N /
mm is preferred. If it is less than 150 N / mm, the durability when used for a belt or the like tends to be insufficient.

The aromatic polyimide resin film according to the present invention is not particularly limited in use, but is suitably used for a circuit board of an FPC, a base material of a heat-resistant tape, and the like. In addition, the seamless tubular body of the aromatic polyimide according to the present invention can be used in a wide range of fields, particularly a copying machine,
Functional belts such as fixing belts, transfer belts, transport belts, and photoreceptor belts used in image forming apparatuses such as laser beam printers; transport belts for transporting paper and cards such as ATMs and public telephones; Can be suitably used. In particular, according to the present invention, the fixing belt of a copying machine or a copying machine has a mechanical strength higher than that of a conventional fixing belt. Therefore, heat conduction is advantageous, and the speed can be increased by shortening the fixing time. Further, if the thickness is the same as before, it has higher mechanical strength than before, so that it can be widened and used for large-size printing.

[0037]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments and the like specifically showing the configuration and effects of the present invention will be described below. In addition, evaluation of the physical property in an Example and a comparative example was performed as follows.

1) Tensile modulus According to JIS K 7127 (1999), the test piece was taken to have a width of 10 mm and a length of 250 mm.
It was measured and calculated at mm / min.

2) Tear strength Test speed 200 m based on JIS K 7128-3
The measurement was performed at m / min, and the tear strength was calculated from the obtained result.

Example 1 Dimethylacetamide (380 g) and p-
Phenylenediamine (25.5 g) was charged and dissolved with stirring at room temperature. Then, 3,3 ', 4,4'-
Biphenyltetracarboxylic dianhydride (69.4 g) was added, and a polymerization reaction was performed at 25 ° C. with stirring for a certain period of time. As a result, the viscosity gradually increased. The obtained polyamic acid solution was heated and stirred at 75 ° C. for 24 hours to obtain a polyimide precursor solution (solid content concentration: 20 wt%) having a solution viscosity of 250 Pa · s measured by a B-type viscometer.

This polyimide precursor solution was applied on a glass plate, heated at 60 ° C. for 90 minutes, and peeled off.
A 2% polyimide precursor film having a thickness of 120 μm was obtained. Here, the solvent remaining amount was calculated by calculating the weight of the polyimide precursor from the weight of the polyimide as in the following equation.

Solvent residual amount (%) = (dry sample weight−polyimide precursor weight) / sample weight × 100 where polyimide precursor weight = polyimide weight + (polyimide weight / polyimide molecular weight) × 2 × (H ₂ O Molecular weight).

This polyimide precursor film was dipped in ethylene glycol at 50 ° C. for 5 minutes to swell, pulled up, stretched 10% in one axis direction, and then ethylene glycol was removed with isopropyl alcohol. After that, both ends are fixed and heated stepwise from 130 ° C. to 360 ° C. (isopropyl alcohol evaporates during heating)
Then, thermal imidization was carried out to obtain a 58 μm aromatic stretched polyimide film. The film surface precision is good, according to JIS K 7127 (1999), a _13. 5 GPa was measured tensile modulus in the stretching direction, was extended 13%. Further, the tear strength in the non-stretching direction was 440 N / mm.

[Example 2] The aromatic polyimide precursor solution obtained in Example 1 was coated with an inner diameter of about φ40 mm and a length of 500
15 mm from the top with a dispenser on the inner surface of a cylindrical mold
About 0 mm was applied. Next, the bullet-shaped traveling body is dropped from the upper part into the mold by its own weight, and a uniform film thickness (600 μm) is obtained.
And The mold was heated at 60 ° C. for 90 minutes. The mold was released from the cylindrical mold to obtain a seamless tubular body of the polyimide precursor (film thickness: 120 μm, solvent remaining: 35%).

This seamless tubular body was dipped in ethylene glycol at 50 ° C. for 5 minutes to swell, pulled up, stretched 5% in the circumferential direction between rolls, and then ethylene glycol was removed with isopropyl alcohol. Then, it was fixed to a cylindrical mold and heated stepwise from 130 ° C. to 360 ° C. to perform thermal imidization to obtain a 58 μm stretched polyimide seamless tubular body.

This seamless tubular body has a good surface accuracy, and the JISK 7127 (199)
According to 9), the tensile modulus in the circumferential direction was measured.
₀ GPa, and the elongation was 17%. Further, the tear strength in the non-stretching direction was 490 N / mm.

[Comparative Example 1] The aromatic polyimide precursor solution obtained in Example 1 was coated with an inner diameter of about φ40 mm and a length of 500
15 mm from the top with a dispenser on the inner surface of a cylindrical mold
About 0 mm was applied. Next, the bullet-shaped traveling body is dropped from the upper part into the mold by its own weight, and a uniform film thickness (600 μm) is obtained.
And The mold was heated and cured stepwise from room temperature to 360 ° C. to remove the solvent, remove the dehydrated ring-closing water and complete the imide conversion, and then cooled to room temperature. A cured seamless tubular body (film thickness: 74 μm) was obtained from a cylindrical mold. This tubular body has good surface accuracy on both the inner surface and the outer surface, and JIS K 7127 (19)
5. The tensile modulus in the circumferential direction was measured according to 99).
8 GPa and elongation was 20%. The tear strength in the width direction was 509 N / mm.

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Claims (6)

[Claims] 1. a step of swelling a precursor film of an aromatic polyimide in which a solvent remains with a swelling agent, a step of stretching the swollen film in at least one axial direction, and a step of removing the swelling agent from the stretched film; Fixing the film and thermally imidizing the film. 2. The method for producing an aromatic polyimide film according to claim 1, wherein a seamless tubular body is used as the precursor film, and the stretching is performed in a circumferential direction. 3. The residual amount of the solvent in the precursor film is 25.
3. The method for producing an aromatic polyimide film according to claim 1, wherein the amount is from 40 to 40 wt%. 4. The method for producing an aromatic polyimide film according to claim 1, wherein the stretching ratio of the stretching is 5 to 20%. 5. An aromatic material which can be produced by the production method according to claim 1 and is composed of an aromatic polyimide having an aromatic dianhydride and an aromatic diamine as monomer components, and having a tensile modulus in the stretching direction of 10 GPa or more. Polyimide film. 6. A seamless tube which can be produced by the production method according to claim 2, is made of an aromatic polyimide having an aromatic dianhydride and an aromatic diamine as monomer components, and has a tensile modulus in the circumferential direction of 10 GPa or more. Aromatic polyimide film.