JPH1015968A - Production of polyimide tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily separate a core member from a tubular article in a method for producing a polyimide tube by bonding a polyimide precursor soln. to the surface of the core member in substantially uniform thickness and subsequently performing imide conversion reaction to form the tubular article and separating the tubular article from the core member. SOLUTION: A cylindrical core member 1 made of porous ceramics is used. After the completion of imide conversion, a tubular article 4 is separated from the core member 1. In this case, a liquid 5 not reacting with the tubular article 4 and the core member is injected into the opening end of the core member to be exuded from the pores of the outer peripheral surface of the core member and the bonding force of the outer peripheral surface of the core member and the tubular article 4 is weakened by the exuded liquid 5 to separate the tubular article. The core member may be used on the way of the imide conversion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a polyimide resin tube suitable for use in a heat fixing section of an electronic copying machine or the like.

[0002]

2. Description of the Related Art Conventionally, a plain paper copying machine of the electrophotographic system, that is, a so-called electronic copying machine, forms an electrostatic latent image by using a photosensitive member that generates electric charges by light, and forms the electrostatic latent image on the electrostatic latent image. There is known a system in which a toner, which is a colored charged powder, is adhered to develop, that is, a visible image, and the image is fixed on recording paper by heat. For fixing, a system using a heat fixing roller having a heater therein is generally used. In this method, a pressure roller is provided in pressure contact with a heat fixing roller, and a recording paper on which a toner image is formed is sequentially fed between the two rollers to heat and melt the toner, thereby fixing the toner image on the recording paper. It is a method to make it.

[0003] With the remarkable spread of copying machines in recent years, demands for simplification and miniaturization of devices, as well as high speed and energy saving have been further increased. In order to meet such a demand, a heat fixing method without using a heat fixing roller has been developed. As one of such systems, there is a so-called film fixing system in which a seamless tube made of polyimide or a polyimide resin film, that is, a polyimide tube is used instead of the heat fixing roller.

A fixing device according to this method has a structure in which a heater and a driving roll are provided inside a tube made of a thin film polyimide film, and a pressure roll is provided outside a portion pressed against the heater. A tension roller for stabilizing the endless running of the film, a heater holder, and the like are provided as needed inside the tube. In fixing, the recording paper on which the toner image is formed is supplied between the polyimide tube and the pressure roll, and the toner image is sequentially fixed by heating from the heater inside the polyimide tube.

In this fixing device, a heater provided inside a thin polyimide film heats and melts toner on a recording paper passing over the outer surface to perform heat fixing. It has the feature that thermal fixing can be started as soon as the power switch is turned on, without requiring time for preheating the fixing roller. Further, since there is no need to heat a roller having a large heat capacity, there is an advantage that the electric capacity of the heater is small and the power consumption is small.

In such a polyimide tube,
If the thickness varies, the toner cannot be melted uniformly, and an offset phenomenon occurs. In addition, the difference in the circumferential length of the tube, that is, the variation in the inner diameter in the length direction of the tubular object causes meandering in the length direction of the tube when rotating the thin film tube in two or three axes. . Therefore, a highly accurate cylindricity is required for use of the polyimide tube as a seamless belt for thermal fixing. Also, in order to smoothly transmit the driving force from the driving pulley to the tube, the inner surface of the tube needs to have a certain roughness depending on the application.

Therefore, various methods have been proposed to obtain a polyimide seamless tube having a uniform thickness suitable for use as a heat fixing film. When producing a polyimide tube, there is a problem that extrusion molding, inflation or vacuum molding cannot be performed unlike a tube made of a thermoplastic resin. Therefore, for example, Japanese Patent Application Laid-Open Nos.
As disclosed in JP-A-261518, a metal tube or a glass tube having a smooth surface is used as a core, and a polyimide precursor solution such as a polyamic acid solution is adhered to the outer surface of the core in a uniform thickness. After drying and imidation, a method of separating a tubular material from a core has been developed as a typical production method.

However, polyimide resin is a resin used as an adhesive. When a polyamic acid solution is applied to a mold and converted into imide by heating, the polyimide tube shrinks and adheres or adheres to the core body. The force makes it more difficult to remove the core and the polyimide tube.

Therefore, various methods have been proposed so far to facilitate release from the core. For example, as disclosed in JP-A-3-110137, after a polyimide precursor solution is applied to a core, the solvent is released from the core when about 1 to 30% of the solvent remains, and then the tube is removed. A method using two types of cores has been proposed, in which the core is reinserted into a core having a diameter smaller than the inner diameter of the core, and then fired to convert the imide into an imide, that is, to close the imide, and release the tube from the core. . In Japanese Patent Application Laid-Open Nos. 6-143512, 6-344360, and 6-298952, a small hole is provided in a core, and a polyimide precursor solution is applied to the core. A method has also been proposed in which air is pressure-fed from inside the core through a small hole to release the tube from the core.

As a method of lowering the adhesive energy on the surface of the core in order to smoothly separate the tube from the core, Japanese Patent Application Laid-Open No. Hei 6-344360 discloses a method in which silicone oil is applied to the surface of the core in advance as a release agent. A method is disclosed for doing so. Alternatively, a method has been proposed in which a core made of a release resin such as a fluororesin is used, or a metal core whose surface is coated with such a resin is used.

On the other hand, after the polyimide precursor solution is applied to the core, heating is performed, and the imide ring closure is incomplete or incomplete, but is separated from the core when it reaches a strength that can be retained as a tubular material. Further, a method has been proposed in which a polyimide tube is obtained by heating and drying to completely close the imide ring.

[0012]

However, each of the above-mentioned improved methods has its own drawbacks. At present, it is still difficult to say that it is easy to release the tube from the core. For example, in the method using two types of cores, the size of the second core needs to be set in anticipation of the inner diameter of the tube that contracts when the imide is completely closed, and the process is complicated. Not only that, since the tube is taken out and re-inserted at an intermediate stage of imidization, there is a problem that the product yield is reduced.

On the other hand, the method of providing a small hole in a core formed to form a film on the outside has a drawback that the cost of manufacturing the core increases because the structure becomes complicated by providing the air hole. Was. In addition, since the tube shrinks after firing, if air is pumped to counter the binding force, the film is likely to peel or bend, resulting in reduced product quality and reduced yield. Was.

When the adhesive energy on the surface of the core is reduced, the surface of the core becomes less wettable. Therefore, when the liquid polyimide precursor solution is applied to the surface of the core, the viscosity of the solution is reduced. In particular, when the film thickness is low, many undesired phenomena such as a repelling phenomenon and a flowing phenomenon are newly generated, and pinholes are easily generated. Thus, it has been difficult to obtain a coating film having a uniform thickness without unevenness. Furthermore, since it is difficult to say that these releasable materials can withstand the high temperature of 380 to 400 ° C. required for complete imide ring closure of the polyimide precursor solution, it is taken out in the intermediate stage of imidization and separated. In some cases, it was attached to a metal core.

In the method of separating the imide from the core at an incomplete imide ring closure stage, the separation is easy, but there is a problem that the tube is easily deformed, for example, it shrinks and generates wrinkles upon heating. . Furthermore, since the imide ring closure is incomplete at the stage where the imide ring closure is incomplete, even if the film thickness is uniform when separated from the core, there is a disadvantage that the film is not uniform in the subsequent heating stage. Quality tended to decrease.

The present invention has been made in view of such a conventional situation, and a method of manufacturing a polyimide tube suitable for use as a fixing film, more specifically,
An object of the present invention is to provide a method for producing a polyimide tube in which a core and a tube can be easily separated and a high-quality tube can be easily obtained.

[0017]

According to the method for producing a polyimide tube of the present invention, a polyimide precursor solution is adhered to the outer peripheral surface of a porous ceramic cylindrical core with a substantially uniform thickness, and then heated. The first feature is that a tube-like material is formed by performing an imide conversion reaction according to the present invention, and then this tube-like material is separated from the core. A second feature of the method for producing a polyimide tube of the present invention is that, when the imide conversion reaction is completed, the formed tubular material is separated from the core, and the liquid that does not react with the tubular material and the core is used. Is injected from the open end of the core body and exudes from pores on the outer peripheral surface of the core body, and after the liquid that has exuded reduces the adhesive force between the outer peripheral surface of the core body and the tubular material, The tubular member is separated from the core.

Further, a third feature of the method for producing a polyimide tube of the present invention is that a polyimide precursor solution is adhered to the outer peripheral surface of a metal core in a substantially uniform thickness, and then the imide conversion reaction is carried out by heating. To form a tubular intermediate in which imide conversion has not been completed, and then separate the tubular intermediate from the core, attach it to the outer peripheral surface of the porous ceramic cylindrical core, and further heat The imide conversion reaction is completed to form a tubular material, and then the tubular material and a liquid that does not react with the porous ceramic cylindrical core are injected from the open end of the core to form the porous material. The liquid is leached from the pores on the outer peripheral surface of the ceramic cylindrical core, and the leached liquid makes contact between the outer peripheral surface of the porous ceramic cylindrical core and the tubular material. After weakening the force is to the tubular article was to separate from the porous ceramic cylindrical core body.

The polyimide precursor that can be used in the present invention is not particularly limited. Examples thereof include those obtained by reacting an aromatic diamine with an aromatic tetracarboxylic acid. Examples of the aromatic diamine include: 3,3′-dimethyl-4,4′-diaminobiphenyl,
Examples of aromatic tetracarboxylic acids such as 3,3'-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether and p-phenylenediamine include 3,3
', 4,4'-biphenyltetracarboxylic dianhydride,
Pyromellitic dianhydride, benzophenone-3,3 ',
4,4'-tetracarboxylic dianhydride and the like. The reaction between the aromatic diamine and the aromatic tetracarboxylic acid is performed in an organic polar solvent such as dimethylacetamide, dimethylformamide, and N-methyl-2-pyrrolidone.

In the present invention, in order to obtain a desired thickness, the polyimide precursor solution will be used at a relatively high viscosity as described above. Therefore, any method may be used to adhere the entire periphery of the core with a uniform thickness. For example, a predetermined amount is attached to the upper periphery of the core by a general coating method such as dipping or coating. rear,
A so-called die coat method or the like, in which a through-die outer mold having a predetermined clearance is fitted to the outside of the core body having its longitudinal direction held vertically, and the outer mold is lowered by its own weight, is particularly suitable.

In the present invention, the porous ceramic cylindrical core 1 schematically shown in FIG.
Those having through pores having a pore size of 50 μm and a porosity of 90 to 40% can be used. The cylindrical core body 1 made of porous ceramics has a through-hole 3 at the center of the cylindrical portion 2, and a tube-shaped material 4 made of a polyimide resin is formed on the outer periphery of the cylindrical portion 2. When the liquid 5 is injected from the open end of the through hole 3, the liquid 5 oozes from the outer peripheral surface of the cylindrical portion 2,
Because the adhesive force between the outer periphery of the tube and the tubular material 4 is impaired,
The tubular article 4 can be easily separated from the cylindrical section 2. In the figure, the liquid 5 oozing from the outer peripheral surface is represented by a plurality of thin arrows, and the support portion 6 supports the cylindrical portion 2 without impeding the oozing of the liquid 5 from the outer peripheral surface, and injects the liquid 5. Is mounted on the open end of the through hole 3 to facilitate the operation.

When a polyimide precursor solution is applied to the cylindrical portion 2 and heated as it is to complete the imide conversion, in order to obtain a smoother tube inner surface, the pore diameter should be relatively small within the above range. It is preferred to use On the other hand, if the tubular intermediate is formed on the metal core in advance and then removed and attached to the porous ceramic cylindrical core and heating is continued, the separation after the imide conversion is completed is easy. With an emphasis on the above, those having a larger pore diameter within the above range can be used. This is because, when it is mounted on the porous ceramic cylindrical core, it has already been heat-formed until it has the strength to hold it as a tube, so irregularities on the surface of the core affect the smoothness of the inner surface of the tube. This is because there is no possibility of exerting the following.

When the tubular intermediate formed on the metal core in advance is removed and mounted, the outer diameter of the second porous ceramic cylindrical core used is:
It may be the same as the outer diameter of the metal core used first.
As in the conventional method, there is no need for a complicated procedure for setting the outer diameter of the second core to a small value in anticipation of the inner diameter of the tube that shrinks when complete imide conversion is completed. Because the tubing that has contracted when the imide conversion is completed at the outer diameter of the first core can be sufficiently reduced by the method of the present invention to such an extent that the tube can be separated from the core. It is.

In the present invention, when the above liquid is injected into a hollow portion which is a through hole of a porous ceramic cylindrical core, the liquid is effectively or efficiently exuded from pores on the outer peripheral surface of the core. If it is a method, there is no particular limitation. For example, the longitudinal direction of the cylindrical core body can be held vertically, and the liquid can be injected from the upper open end. At this time, the liquid may be stored in the hollow portion by closing the lower opening end, and the liquid may ooze out from the pores on the outer peripheral surface.

In the present invention, the liquid which is injected from the open end of the porous ceramic cylindrical core and which does not react with the tubular material or the core is, for example, a hydrophobic solvent such as xylene or paraffin, or water or alcohol. And a hydrophilic solvent. Furthermore, solutions obtained by dissolving a release material in these solvents can also be used. Since such a liquid leaks out from the pores of the porous ceramic cylindrical core, the adhesive force between the outer peripheral surface of the core and the tubular material is weakened and the adhesion is impaired. Becomes easier.

In the present invention, the step of removing the tubular intermediate formed on the first metal core includes:
There is no particular limitation as long as the strength as a tubular material can be maintained and imide conversion is not completed yet. However, as the imide conversion proceeds by heating, the tube shrinks and becomes difficult to remove. Therefore, it is preferable to remove the tube as soon as possible so that the strength as a tubular material can be maintained.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to embodiments.

Example 1 Polyamic acid (trade name: u-varnish S, manufactured by Ube Industries, Ltd.) was coated on the outer peripheral surface of a porous ceramic cylindrical core having an outer diameter of 25 mm, a length of 350 mm, and a thickness of 3 mm with a solvent of dimethylacetamide. / Naphtha (9/1) to prepare a polyimide precursor solution having a viscosity of 1500 poise, which was applied to the upper part of the outer peripheral surface of the core with a spatula. In addition, this cylindrical core body made of porous ceramics has an average pore diameter of 5 μm,
The porosity was 65%.

Then, an outer mold that is movable in the longitudinal direction and is disposed with a predetermined clearance is fitted on the upper portion of the core body, and naturally falls due to the weight of the outer mold and the viscosity of the polyimide precursor solution. Then, a thin film of the polyimide precursor solution was formed on the outer peripheral surface of the core. The thin film was formed at room temperature.

Thereafter, the core having the thin film formed thereon is heated at a temperature of 3 ° C.
After heating and firing in a firing furnace at 50 ° C. for 25 minutes, it was taken out of the furnace and cooled. Thereafter, one opening end of the cylindrical core was closed, and 150 ml of ethanol was injected from the other end to exude from pores on the outer peripheral surface. After that, when the tube was removed from the core, it could be easily removed. The inner diameter was 25 mm, the wall thickness was 50 μm, and the effective length was 330 mm.
However, a polyimide tube having a uniform thickness without deformation was obtained.

Example 2 Polyamic acid (trade name: u-varnish S, manufactured by Ube Industries, Ltd.) was applied to the outer peripheral surface of a metal core having an outer diameter of 30 mm and a length of 350 mm.
Was dissolved in a solvent dimethylacetamide / naphtha (9/1) to prepare a polyimide precursor solution having a viscosity of 1650 poise, which was applied to the upper portion of the outer peripheral surface of the core with a spatula.

Then, an outer mold which is movable in the longitudinal direction and is disposed with a predetermined clearance is fitted on the upper portion of the core body, and naturally falls due to the weight of the outer mold and the viscosity of the polyimide precursor solution. Then, a thin film of the polyimide precursor solution was formed on the outer peripheral surface of the core. The thin film was formed at room temperature.

Thereafter, the metal core having the thin film formed thereon is
The film was kept in a firing furnace at a temperature of 230 ° C. for 30 minutes, and was removed from the furnace when the thin film was able to maintain the strength as a tubular material at a stage where the imide conversion was not completed yet.

Next, the tube-like material intermediate taken out is mounted on the outer peripheral surface of a porous ceramic cylindrical core, held in a firing furnace at a temperature of 360 ° C. for 30 minutes, and heated and fired to complete the imide conversion. I let it. The porous ceramic cylindrical core had an outer diameter of 30 mm and a length of 350 m.
m, wall thickness 5 mm, average pore diameter 15 μm, porosity 6
It was 0%.

Thereafter, one open end of the cylindrical core was closed and 170 ml of water was injected from the other end to exude from the pores on the outer peripheral surface. Thereafter, when the tube was removed from the core, the tube could be easily removed, and a polyimide tube having an inner diameter of 30 mm, a wall thickness of 50 μm, an effective length of 330 mm, and a uniform thickness without deformation was obtained.

Comparative Example 1 A polyimide tube was produced in the same manner as in Example 1 except that a SUS core was used in place of the porous ceramic cylindrical core. Since the obtained tube was firmly adhered to the core, it could not be separated.

Comparative Example 2 The same procedure as in Example 2 was carried out except that the tubular intermediate product taken out at the stage when the imide conversion was not completed was not attached to the outer peripheral surface of the porous ceramic cylindrical core, but was heated and baked as it was. Thus, a polyimide tube was produced. The obtained tube had a nonuniform film thickness and was deformed, and could not be used as a fixing film.

[0038]

As described above, according to the present invention,
Provided is a method for manufacturing a polyimide tube in which a core and a tube can be easily separated and a high-quality tube can be easily obtained.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a porous ceramic cylindrical core according to a production method of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Porous ceramic cylindrical core 2 ... Cylindrical part 3 ... Through-hole 4 ... Tubular material 5 ... Liquid 6 ... Support part

──────────────────────────────────────────────────続 き Continuation of the front page (51) Int.Cl. ⁶ Identification code Agency reference number FI Technical display location // B29K 79:00 B29L 23:00 (72) Inventor Yuji Suzuki Sakae Oda, Kawasaki-ku, Kawasaki-ku, Kawasaki-shi, Kanagawa 2-1-1, Showa Electric Wire & Cable Co., Ltd. (72) Inventor Toshimitsu Iwata 2-1-1, Oda Sakae, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture Showa Electric Wire & Cable Co., Ltd. (72) Inventor Junichi Nishioka Kawasaki-shi, Kanagawa Prefecture Inside Showa Electric Wire & Cable Co., Ltd. 2-1-1 Oda Sakae, Kawasaki-ku (72) Inventor Kimiki Kobayashi Inside 2-1-1 Oda Sakae Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture Showa Electric Wire & Cable Co., Ltd.

Claims (4)

[Claims] 1. A polyimide precursor solution having a substantially uniform thickness is adhered to the outer peripheral surface of a porous ceramic cylindrical core, and then the imide conversion reaction is completed by heating to form a tubular material. A method for producing a polyimide tube, wherein the tubular material is separated from the core. 2. The method according to claim 1, wherein the step of separating the tubular material formed after the completion of the imide conversion reaction from the core body includes the step of removing the liquid that does not react with the tubular body and the core body.
After being injected from the open end of the core body and exuding from the pores on the outer peripheral surface of the core body, the exuded liquid weakens the adhesive force between the outer peripheral surface of the core body and the tubular material,
The method for producing a polyimide tube according to claim 1, wherein the tube-shaped material is separated from the core. 3. A tube precursor intermediate in which the polyimide precursor solution is adhered to the outer peripheral surface of the metal core in a substantially uniform thickness, and then the imide conversion reaction is performed by heating to complete the imide conversion. Then, the tubular intermediate is separated from the metal core, and then attached to the outer peripheral surface of the porous ceramic cylindrical core, and further heated to complete the imide conversion reaction to form a tubular. Thereafter, a liquid that does not react with the tubular material and the porous ceramic cylindrical core is injected from the open end of the core and pores on the outer peripheral surface of the porous ceramic cylindrical core are then injected. After the liquid that has leached out and weakened the adhesive force between the outer peripheral surface of the porous ceramic cylindrical core body and the tubular material, the tubular material is removed from the porous ceramic. A method for producing a polyimide tube, characterized in that the tube is separated from a cylindrical core made of fiber. 4. The porous ceramic cylindrical core has an average pore diameter of 2 to 50 μm and a porosity of 90 to 40%.
The method for producing a polyimide tube according to claim 1, 2, or 3, wherein the method comprises a porous ceramic having through-pores of (1).