JP2006256323A - Tubular object and its manufacturing process - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a tubular object of high durability and low production cost and its manufacturing process, by lowering a coefficient of dynamic friction especially on the exterior surface of the tubular object. <P>SOLUTION: A tubular object (31) comprises a molded and heat cured composite containing polyimide and fluororesin particles, wherein at least a part of the fluororesin particles residing near the surface of the tubular object (31) precipitates by melt flowing to the exterior surface or inner and outer surfaces of the tubular object and forms a fluororesin coating film partially or fully. The tubular object (31) can be manufactured by aplying a liquid mixture, in which the fluororesin particle is added into a polyimide precursor solution, on the outer surface of a die and cast molding into a predetermined thickness; heating it to imidize, setting a maximum imidization temperature to exceed fusion point of the fluororesin; and separating the die and the tubular object after cooling off. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a tubular object made of a heat-resistant resin for thermally fixing an unfixed toner image in an image forming apparatus using an electrophotographic system such as a copying machine, a printer, and a facsimile machine. More specifically, the present invention relates to the inner and outer surfaces of a tubular object. The present invention relates to a tubular object having a low dynamic friction coefficient and high durability, and a method for manufacturing the same.

  Polyimide resins have excellent properties such as heat resistance, dimensional stability, mechanical properties, and electrical properties, and are used in a wide range of fields such as electronic and electrical equipment, insulating materials, and aerospace. As an example of the application, an electrophotographic image forming apparatus is used as many members in electrophotographic processes such as charging, photosensitivity, intermediate transfer, and fixing.

  Here, an example of a polyimide tubular object used as a fixing member of an image forming apparatus will be described. In an image forming apparatus such as a copying machine or a laser beam printer, in a final stage of printing or copying, a toner image on a sheet-like transfer material such as paper is heated and melted and fixed on the transfer material.

  As an example of using a polyimide resin tubular object as a fixing belt of an image forming apparatus, there is a belt fixing method proposed in Patent Documents 1 to 3, etc., and a toner image formed on a copy paper as shown in FIG. It is used as a fixing belt for heat fixing. In this application, a copy paper 37 having a belt guide 32 and a ceramic heater 33 inside a fixing belt 31 (polyimide resin tubular object) and having a toner image formed between a pressure roll 34 having a driving source in pressure contact with the heater is used. While sequentially feeding, the toner 38 is heated and melted and fixed on the copy paper. In the belt fixing method, since the heater substantially directly heats the toner through a polyimide tubular object (fixing belt) having an extremely thin film-like film, the heating unit instantaneously reaches a predetermined fixing temperature and the power is turned on. There is no waiting time until the fixing state is reached, and the power consumption is small and it has an excellent feature.

  An example in which a polyimide tubular object is used as a pressure belt of a fixing device in a full-color image forming apparatus is proposed in Patent Document 4. As shown in FIG. 7, the fixing device includes a rotatable fixing roll 54 having a driving source having a heat source 55, a pressure belt 51 (polyimide resin tubular object) pressed against the roll, and an inner side of the pressure belt. The pressure pad 53 and the pressure guide 52 are arranged on the surface of the fixing roll. The pressure belt is pressed against the surface of the fixing roll, and the pressure belt is rotated by the driving force of the fixing roll. In this method, the formed copy paper 57 is sequentially fed and the toner image 56 is thermally fixed on the surface of the fixing roll. Polyimide resin tubular objects used in these applications are generally formed from a polyimide precursor solution obtained by reacting tetracarboxylic dianhydride and diamine in a polar polymerization solvent, and imidized. Can be obtained.

  A method of manufacturing a tubular body from the polyimide precursor solution is, as known in Patent Documents 5 to 6, after forming a polyimide precursor solution with a predetermined thickness on the outer surface or inner surface of a molding die, A method has been proposed in which imidization is chemically completed and a tubular object is obtained by separation from a mold.

  The fixing belt or pressure belt has a two-layer structure in which a release layer such as a fluororesin is formed on the outer surface of the polyimide tubular object (the surface in contact with the toner), or has an adhesive property between the polyimide tubular object and the fluororesin layer. A three-layer belt having a primer layer for improvement is used.

  In recent years, there has been a high demand for miniaturization and high speed of OA equipment, and a fixing belt or pressure belt for meeting such demands has a low dynamic friction coefficient on the inner surface as well as a releasability of the outer surface of the belt, or a high thermal conductivity. Such characteristics are required.

  That is, the fixing belt shown in FIG. 6 or the pressure belt shown in FIG. 7 is a mechanism that is transmitted and rotated by a pressure roll or a fixing roll having a drive source. When the roll having the drive source and the belt are in direct contact with such a mechanism, the rotational force of the drive roll is transmitted to the belt as it is and rotates relatively smoothly. However, when the copy paper is inserted between the drive roll and the belt and the toner is substantially fixed, the rotational force to the belt is transmitted from the drive roll to the belt via the transfer paper. And slip is likely to occur on the surface of the belt.

  In particular, the outermost layer of the fixing or pressure belt is laminated with a release layer such as fluororesin to prevent adhesion of melted toner (offset phenomenon), making it easy to slide with a low coefficient of dynamic friction, and high speed copying machines and printers. Slip is more likely to occur. As described above, when slip occurs on the fixing surface (nip part), the release layer on the belt surface is worn by the copy paper due to repeated minute slips on the copy paper and the belt surface, and the fluffing release layer surface Becomes rough and causes offset.

  In addition, the polyimide resin and the fluororesin laminated on the outer surface have a low thermal conductivity from the beginning, and since it has a multilayer structure, it has a problem that it has a poor thermal conductivity to cope with a higher speed.

In order to cope with these required characteristics, for example, Patent Documents 7 to 9 have been proposed. In Patent Document 7, the inner surface of a polyimide tubular object is roughened to hold a lubricant. In Patent Document 8, a polyimide precursor is added with a heat conductive inorganic filler and a fluororesin powder such as polytetrafluoroethylene, heated at 250 ° C., and then coated with a fluororesin on the outer surface to form a film. . In Patent Document 9, a polyimide precursor added with fluororesin powder is spread on an inner peripheral surface of a cylindrical mold, and heated to cause a curing reaction.
JP 7-178741 A Japanese Patent Laid-Open No. 3-25471 JP-A-6-258969 Japanese Patent Application Laid-Open No. 11-133776 JP-A-6-23770 Japanese Patent Laid-Open No. 1-156017 JP 2001-341143 A JP 2001-040102 A JP 2001-056615 A

  However, Patent Documents 7 to 9 of the conventional proposals all aim at lowering the frictional resistance of the inner surface of the tubular object, and the surface of the surface layer in contact with the paper is the conventional release layer of the fluororesin layer as it is. Adopted or not improved. In addition, since it has a two-layer structure having a polyimide tubular object and a fluororesin release layer or a three-layer structure having a primer layer between the polyimide layer and the fluororesin layer, it has a multilayer structure particularly when used in the fixing device of FIG. The thickness is large and the thermal conductivity is reduced. Also, the manufacturing method requires three types of raw materials and three different processes, making the manufacturing process complicated, and the adhesion between layers formed of each material. There was a problem.

  The present invention solves the problems of the conventional example, and the inner surface of the tubular object has low frictional resistance, and at the same time, the outer surface of the tubular object has sufficient releasability as a fixing belt and a pressure belt, and has high durability and manufacturing cost. A low-pipe tubular object and a method for manufacturing the same are provided.

  The tubular object of the present invention is a tubular object obtained by molding and heat-curing a mixture containing polyimide and fluororesin particles, and at least a part of the fluororesin particles present in the vicinity of the surface layer of the tubular object is the tubular object It is characterized by being melt-flowed and deposited on the outer surface or inner / outer surface of the film, and forming a fluororesin film partially or entirely.

  In the method for producing a tubular object of the present invention, a mixed solution of a polyimide precursor solution and melt-flowing fluororesin particles is applied to the outer surface of a mold, cast to a predetermined thickness, heated to imidize, The maximum temperature is set to a temperature exceeding the melting point of the fluororesin, and after cooling, the mold and the tubular object are separated, so that at least a part of the fluororesin particles present in the vicinity of the surface layer of the tubular object is removed from the outer surface of the tubular object or It is characterized by being melt-flowed and deposited on the inner and outer surfaces, and forming a fluororesin film partially or entirely.

  In the present invention, at least a part of the fluororesin particles present in the vicinity of the surface layer of the tubular object is melted and deposited on the outer surface or the inner and outer surfaces of the tubular object, and the melted and precipitated fluororesin is integrated with the polyimide, and the tubular Since the film that flows on the surface of the object is formed, the coefficient of dynamic friction on the inner surface of the tubular object is low, and the outer surface of the tubular object is also formed of a fluororesin film. Unlike the fixing belt, there is no need to newly form a fluororesin release layer in a separate process, and it can be used for a fixing member or transfer belt of an image forming apparatus, an intermediate transfer / heat fixing belt, or the like. Further, a mixed solution obtained by adding fluororesin particles to a polyimide precursor solution is applied to the outer surface or inner surface of a molding die, cast-molded to a predetermined thickness, heated to imidize, and the maximum temperature of the imidization is set to the maximum temperature of the fluororesin. By setting the temperature exceeding the melting point, at least a part of the fluororesin particles existing in the vicinity of the surface layer of the tubular object can be melted and deposited on at least the outer surface of the tubular object. Molded products with a structure in which a fluororesin melts and precipitates on one or both sides of a polyimide substrate. In the form of a film, the heat-resistant sliding material or release film, or in the form of a tube, the chemical stability of the fluororesin and the mechanical properties of the polyimide. It has characteristics and can be suitably used for medical catheters and various medical tubes inserted into the body.

  The basic components of the tubular object of the present invention are polyimide and fluororesin particles. There is no compatibility between the polyimide and the fluororesin particles, and the fluororesin melts and precipitates on the outer surface or inner and outer surfaces of the polyimide tubular body, and the melt-deposited surface forms a fluidized film on the surface.

  When the polyimide precursor solution containing fluororesin particles cast on the outer surface of the mold is heated and imidized, the maximum temperature of imidization is set to a temperature exceeding the melting point of the fluororesin. Thereby, the fluororesin particles melt and precipitate on at least the outer surface of the polyimide, whereby a polyimide tubular body having an inner surface having a low friction coefficient and an outer surface characteristic having a high releasability can be obtained.

  The fluororesin coating surface preferably has a granular pattern resulting from the fluororesin particles. This is observed as a state of fine bubbles with a part of the fluororesin particles remaining.

  The fluororesin particles include polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), polychlorotrifluoroethylene (PCTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP). ) Or at least one fluororesin selected from tetrafluoroethylene-ethylene copolymer (PETFE).

  In order to thermally flow the fluororesin deposited on the surface of the tubular body and form a fluororesin coating, a thermoplastic fluororesin such as PFA or FEP is preferable. These fluororesins flow at a temperature equal to or higher than the melting point, and can be formed as a film-like film on the inner and outer surfaces of the tubular object.

  In addition, when a fluororesin such as PTFE resin, which has a high melt viscosity and is difficult to heat flow even when heated to a temperature higher than the melting point, the state of the inner and outer surfaces of the tubular object is as follows. This is a so-called sea-island structure. Such a structure is optimal for applications such as an intermediate transfer belt used in an image forming apparatus. That is, the transfer belt is a belt that is used for the purpose of intermediately transferring a toner image from a photosensitive member and then retransferring the toner image onto a copy paper. When the toner powder remaining on the surface is scraped off with a blade, the sliding resistance with the blade is low, which is a preferable structure.

  The polyimide used in the present invention is a thermosetting resin, a mixed solution of a polyimide precursor solution and a fluororesin is cast on, for example, the outer surface or the inner surface of a mold, dried and heated to complete imidization, A polyimide / fluororesin composite tubular object in which a fluororesin is deposited on at least the outer surface or the inner / outer surface of the tubular object can be manufactured.

  In the tubular body manufactured by the above method, the fluororesin is likely to be melted and deposited on the surface where the coating is in contact with air. That is, the fluororesin powder exists in a mixed and dispersed state in the polyimide precursor solution. However, the heat treatment causes the molten fluororesin to move toward the outermost layer in contact with the air in the thickness direction of the tubular object by performing heat treatment to a temperature exceeding the melting point of the fluororesin during the process of imidization. It is conceivable to do.

  Although the detailed mechanism of the phenomenon in which the fluororesin moves in the tubular body is not clear, the present inventors have continued numerous experiments and researches, and as a result, mixed polyimide precursor solution and fluororesin. The solution is cast on a glass plate, cast-molded, dried and heated to complete imidization, and in the production of a polyimide / fluorine resin composite film, the surface where the film is in contact with the glass surface is also treated with fluorine. It was found that the resin melted and precipitated, and a confirmation experiment was conducted on the tubular object of the present invention.

  As a result, it has been found that the fluororesin can be deposited also on the inner surface of the tubular object that is not in contact with the air layer. Further, it has been found that the phenomenon in which the fluororesin precipitates on both surfaces of the tubular object is different depending on the difference in the type of fluororesin and the temperature in the imidization process.

  That is, the phenomenon in which the fluororesin precipitates is affected by the melting point of the fluororesin and the imidization temperature of the polyimide precursor. In the detailed experimental results, fluororesin was mixed with rigid polyimide using biphenyltetracarboxylic dianhydride (BPDA) as aromatic tetracarboxylic dianhydride and paraphenylenediamine (PPD) as aromatic diamine. In this case, when the maximum temperature of imidization is lower than the melting point of the fluororesin, the fluororesin does not appear remarkably on any surface of the tubular object. The fluororesin melted and deposited on both sides, and a tubular object having low frictional resistance could be obtained.

  Moreover, it discovered that it was preferable in order to melt-precipitate a fluororesin that the polyimide has a large thermal contraction rate obtained by imidizing a polyimide precursor solution consisting of the aromatic tetracarboxylic dianhydride and an aromatic diamine. . That is, the polyimide precursor solution is cast on a glass plate, dried, heated to 300 ° C stepwise to advance imidization, and after cooling, the polyimide film is peeled off from the glass plate and the melting point of the fluororesin is increased from 300 ° C. Fluorine resin tends to melt and precipitate in polyimide having a large thermal shrinkage when heated to a temperature of, for example, 400 ° C.

  As a result of the test, the heat shrinkage rate of the film prepared from the polyimide precursor composed of BPDA as the aromatic tetracarboxylic dianhydride component and PPD as the aromatic diamine component was 0.9%, and PMDA and ODA were used. The heat shrinkage rate of the film obtained from the polyimide precursor was 0.09%. The relationship between the value of the heat shrinkage rate of the polyimide film and the phenomenon in which the fluororesin melts and precipitates was found to be a phenomenon in which the fluororesin easily precipitates from the polyimide film as the heat shrinkage rate at 300 ° C. to 400 ° C. increases.

  A detailed test method for the heat shrinkage will be described below. “TMA-50” manufactured by Shimadzu Corporation was used for the measurement of the heat shrinkage rate. The polyimide film was prepared by casting a polyimide precursor solution obtained from the above monomer onto a glass plate so that the thickness upon completion of imidization was 50 μm, dried at 150 ° C. for 40 minutes, then 200 ° C. for 40 minutes, and further 250 ° C. And heated at 300 ° C. for 20 minutes to produce a polyimide film.

  This film was cut into strips having a length of 10 mm and a width of 3.5 mm, and a load of 2.0 g was applied to one of the films and the film was attached to “TMA-50”. The state of heat shrinkage was observed from room temperature to 400 ° C. at a rate of temperature increase of 10 ° C./min, and the heat shrinkage rate from 300 ° C. to 400 ° C. was calculated.

  In addition, as a result of an experiment with a polyimide precursor solution using FEP (melting point: 250 ° C.) having a melting point lower than that of PTFE (melting point: 327 ° C.), the maximum temperature of imidization is 300 ° C. Fluororesin (FEP) was deposited on the outer surface, and the surface was heat-flowed to form a coating state, and a tubular object having a low frictional resistance could be obtained.

  As described above, the phenomenon in which the fluororesin precipitates on the inner and outer surfaces of the tubular object of the present invention is achieved by selecting the melting point of the fluororesin, the imidization temperature of the polyimide precursor, etc., and setting them to predetermined conditions. It became possible to deposit a fluororesin on.

  The tubular object of the present invention may be a single layer or may be formed in multiple layers as necessary. In the case of a multilayer, the inner layer does not contain fluororesin particles, or the polyimide layer can be formed with a relatively small amount of the inner layer as compared with the outer layer, so that the mechanical properties of the tubular object can be further improved. Moreover, it can also be made into a multilayer by the layer which changed the kind of polyimide or fluororesin, or the mixing amount of fluororesin. Furthermore, after casting into a mold using a polyimide precursor mixed with a fluororesin, the temperature during the imide reaction can be controlled to melt and deposit the fluororesin only on the outer surface of the tubular object. This is because there may be a case where only the surface of the outer layer needs to have a good friction characteristic as in an intermediate transfer belt.

  The fluororesin mixed polyimide precursor solution includes boron nitride, potassium titanate, mica, titanium oxide, talc, calcium carbonate, aluminum nitride, alumina, silicon carbide, silicon, silicon nitride, silica, graphite, carbon fiber, metal Thermally conductive fillers such as powder, beryllium oxide, magnesium and magnesium oxide can be added. Addition of these thermally conductive fillers is preferable because the thermal conductivity of the tubular object coating is improved and high-speed fixing can be supported.

  In the present invention, as the fluororesin, fluororesins such as PTFE, PFA, FEP, and CPTFE can be used alone or as a mixture. PTFE, PFA, and FEP are preferable materials that have excellent heat resistance and releasability and can be used in the present invention. In addition, a conductive material such as carbon black, carbon fiber, metal powder or an antistatic agent can be added to the polyimide precursor solution mixed with the fluororesin.

  Use of a fluororesin in which a conductive or antistatic agent is mixed and dispersed is preferable because it can improve the deterioration of image quality due to electrostatic offset or the like generated in the image forming process, or the state of ghosting on the image.

  Moreover, it is preferable to set the mixing amount of the said fluororesin to 10-90 mass% with respect to solid content of a polyimide precursor solution. Most preferably, it is 20-80 mass%.

  When the content of the fluororesin is less than 10% by mass, the fluororesin that melts and precipitates tends to be less effective to reduce the frictional resistance, and when it exceeds 90% by mass, the mechanical strength decreases. The smoothness of the surface of the tubular object is also impaired and cracking tends to occur.

  Moreover, the said fluororesin is a preferable form which is easy to mix a powdery thing, and the average particle diameter has the preferable range of 0.1-100 micrometers. A more preferable average particle diameter is in the range of 0.5 to 50 μm. Within such a range, it is preferable because the particles can be dispersed uniformly with little aggregation.

  If the average particle size is less than 0.1 μm, the particles are likely to agglomerate. If the average particle size is more than 100 μm, irregularities due to the fluororesin particles are likely to occur on the inner surface or outer surface of the tubular object. In addition, the measuring method of the average particle diameter of the said fluororesin powder is a laser diffraction type particle size measuring device (ASLD-2100: manufactured by Shimadzu Corporation) or a laser diffraction / scattering type particle size distribution measuring device (LA-920: Horiba, Ltd.). Manufactured).

  In order to adjust the size of the fluororesin particles, before applying the mixed solution of the polyimide precursor solution and the fluororesin particles to the outer surface of the mold, the mixed solution is filtered with a filter, and the coarse particles of the fluororesin particles are removed. It is preferable to remove.

  Moreover, the tubular body of the present invention is a tubular body having polyimide as a main component, and is obtained by mixing a fluororesin and a polyimide precursor solution, casting seamlessly, and then heating imidization. The polyimide precursor solution can be obtained by reacting approximately equimolar amounts of an aromatic tetracarboxylic dianhydride and an aromatic diamine in an organic polar solvent.

  Representative examples of the aromatic tetracarboxylic dianhydride include 3,3 ′, 4,4′-benzophenonetetracarboxylic dianhydride, pyromellitic dianhydride, 2,3,3 ′, 4- Biphenyltetracarboxylic dianhydride, 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride, 1,2,5,6-naphthalenetetracarboxylic dianhydride, 1,4,5,8- Naphthalenetetracarboxylic dianhydride, 2,3,6,7-naphthalenetetracarboxylic dianhydride, 2,2'-bis (3,4-dicarboxyphenyl) propane dianhydride, perylene-3,4, Examples include 9,10-tetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, and the like.

  Representative examples of the aromatic diamine include 4,4'-diaminodiphenyl ether, p-phenylenediamine, m-phenylenediamine, 1,5-diaminonaphthalene, 3,3'-dichlorobenzidine, 3,3'- Diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 3,3'-dimethyl-4,4'-biphenyldiamine, 4,4'-diaminodiphenyl sulfide-3,3'-diaminodiphenylsulfone, benzidine, 3,3 ' -Dimethylbenzidine, 4,4'-diaminophenylsulfone, 4,4'-diaminodiphenylpropane, m-xylylenediamine, hexamethylenediamine, diaminopropyltetramethylene, 3-methylheptamethylenediamine and the like.

  These aromatic tetracarboxylic dianhydrides and aromatic diamines can be used alone or in combination. It is also possible to complete the polyimide precursor solution and use the precursors mixed.

  Among the combinations of the aromatic tetracarboxylic dianhydride and the aromatic diamine, a combination of biphenyltetracarboxylic dianhydride and paraphenylenediamine is preferable. The polyimide obtained from this precursor has a rigid polymer structure and has a structure in which the fluororesin can be easily extruded outward at the melting temperature of the fluororesin.

  Examples of the organic polar solvent for reacting the aromatic tetracarboxylic dianhydride and the aromatic diamine include N-methyl-2-pyrrolidone, N, N-dimethylformamide, N, N-dimethylacetamide, N, N-diethylformamide. N, N-diethylacetamide, dimethyl sulfoxide, hexamethyl phosphortriamide, pyridine, dimethyltetramethylene sulfone, tetramethylene sulfone and the like. These organic polar solvents can also be mixed with phenol, xylene, hexane, toluene and the like.

  The polyimide precursor solution is obtained by reacting the aromatic tetracarboxylic dianhydride and the aromatic diamine in an organic polar solvent usually at 90 ° C. or lower, and the solid content concentration in the solvent is the final concentration. Although it can be set according to the specifications and processing conditions of the polyimide tubular object, it is 10 to 30% by mass.

  In addition, when aromatic tetracarboxylic dianhydride and aromatic diamine are reacted in an organic polar solvent, the viscosity of the solution increases depending on the polymerization conditions. Can do. It is usually used at a viscosity of 1 to 5000 poise depending on manufacturing conditions and working conditions.

  In the production method of the present invention, the temperature at which the fluororesin layer can be deposited on at least the outer surface of the tubular object needs to be heated to a temperature exceeding the melting point of the fluororesin. It is preferable that the imidization is completed at a temperature that is 10 ° C. or more higher than the melting point of the mixed fluororesin.

  Further, the heating time necessary for precipitating the fluororesin on the inner and outer surfaces of the tubular body is preferably within 30 minutes after the maximum temperature of imidization reaches a temperature exceeding the melting point of the fluororesin. . If the heating time is 30 minutes or longer, the thermal decomposition of the fluororesin or the mechanical properties of the polyimide may be reduced.

  The tubular object of the present invention can be obtained, for example, by the following method. A fluororesin mixed polyimide precursor solution is applied to a mold surface having a predetermined outer diameter (a diameter corresponding to the inner diameter of a tubular object), casted using a die on the outside, guided to a heating device, and heated at 100 to 150 ° C. The polymerization solvent is dried at a relatively low temperature, and then the imidization reaction proceeds. Finally, the imidization is completed by heating at a temperature exceeding the melting point of the fluororesin for a predetermined time. Thereafter, the tube is cooled and the tubular object is removed from the mold.

  FIG. 1 is a schematic enlarged cross-sectional view of a tubular object 10 when a polyimide precursor solution is mixed with a polyimide precursor solution, cast-molded, and the polyimide imidization temperature is 300 ° C. in one embodiment of the present invention. . Up to this stage, the fluororesin powder 12 is dispersed inside the polyimide film layer 11, and the surface layer is almost covered with the polyimide layer. At this stage, the water contact angle is also low. Reference numeral 15 denotes a mold.

  Next, when the imidization temperature is set to 400 ° C., as shown in FIG. 2, the fluororesin powder is melted and deposited on the air-side surface layer so as to exude from the polyimide surface. Reference numeral 13 denotes a fluororesin that melts and exudes. 14 is a fluororesin which is melted and deposited on the inner surface side on the mold side. In this state, the water contact angle increases. In the relationship with the polyimide, the fluororesin is incompatible and has a sea-island structure (the sea is polyimide and the island is fluororesin), and the molten fluororesin is partially deposited from the polyimide surface.

  FIG. 3 is a schematic enlarged cross-sectional view of a tubular object when only FEP (melting point: 260 ° C.) particles are mixed alone with a polyimide precursor solution, cast-molded, and the imidization temperature of polyimide is 400 ° C. The FEP powder 22 is dispersed inside the polyimide film layer 21, and FEP melts and flows on the outer surface layer surface to form a fluororesin coating 23 partially or entirely. Reference numeral 30 denotes an FEP resin melt-deposited on the inner surface. Reference numeral 28 denotes a mold.

  FIG. 4 shows a tubular structure when PTFE (melting point: 327 ° C.) particles and FEP (melting point: 260 ° C.) particles are mixed in a ratio of 50:50 in a polyimide precursor solution, cast-molded, and the polyimide imidization temperature is set to 400 ° C. It is a general | schematic expanded sectional view of an object. The FEP powder 22 and the PTFE powder 24 are dispersed inside the polyimide film layer 21, and FEP and PTFE are melt-flowed and deposited on the surface layer to form a fluororesin coating (23, 25) partially or entirely. ing. Reference numeral 28 denotes a mold.

  Hereinafter, the present invention will be described in more detail based on examples. In addition, this invention is not limited to the following Example.

  In the following Examples and Comparative Examples, biphenyltetracarboxylic dianhydride is abbreviated as “BPDA”, paraphenylenediamine is abbreviated as “PPD”, and pyromellitic dianhydride is abbreviated as “PMDA”. , 4′-diaminodiphenyl ether is abbreviated as “ODA” and N-methyl-2-pyrrolidone is abbreviated as “NMP”.

Moreover, the dynamic friction coefficient of the tubular object obtained by this invention and the contact angle with respect to the pure water of the film obtained by these materials were measured with the following method.
(1) Method for measuring coefficient of dynamic friction (shown in FIG. 12)
The dynamic friction coefficient was measured according to JISK7125. A test film 62 having a width of 80 mm and a length of 200 mm was fixed on a horizontal table 64. A test film 62 fixed to a size of 63 mm in width and 63 mm in length (area 40 cm ² ) is overlaid thereon, and a test film 61 made of the same material as that of the test film 62 is stacked thereon, and further, 63 mm in width and 63 mm in length (area 40 cm ² ) A weight 63 having a weight of 200 g was placed, the stacked test films were slid horizontally at a speed of 100 mm / min, the load (dynamic friction force) was measured, and the dynamic friction coefficient was calculated by the following equation. 65 is a wire, 66 is a pulley, 67 is a load cell of a tensile tester, and is wound in the Z direction.
Coefficient of dynamic friction μ _D = F _D / F _P
F _D : Dynamic friction force (N)
F _P : A linear force generated by the mass of the sliding piece (= 1.96 N)
(2) Measurement of contact angle The contact angle with respect to 23 degreeC pure water was measured using the "FACE CA-Z" measuring device by Kyowa Interface Chemical Co., Ltd.

Example 1
(1) Production of fluororesin mixed polyimide precursor solution 39 parts by mass of PPD is dissolved in NMP (monomer concentration: 18.2% by mass) in a flask with respect to 100 parts by mass of BPDA, and the reaction is performed while stirring at a temperature of 23 ° C. for 6 hours. To obtain a polyimide precursor solution. The rotational viscosity of this polyimide precursor solution was 1200 poise. The rotational viscosity is a value measured with a B-type viscometer at a temperature of 23 ° C. Next, a PTFE powder having an average particle size of 3.0 μm (melting point: 327 ° C., trade name “Zonyl MP1100” manufactured by DuPont) is added to the polyimide precursor solution at a ratio of 20% by mass with respect to the solid content in the polyimide precursor solution. The FEP powder having an average particle size of 35 μm (melting point: 260 ° C., trade name “532-8110” manufactured by DuPont) is further added to the solid content in the polyimide precursor solution to 4.0 mass. % Was added and stirred, and uniformly dispersed. Thereafter, coarse foreign matters were filtered using a 250 mesh stainless steel wire mesh to prepare a fluorine resin powder mixed polyimide precursor solution.
(2) Production of tubular object A silicon oxide coating agent was coated on the surface of an aluminum mold having an outer diameter of 24 mm and a length of 500 mm by a dipping method and baked to coat a silicon oxide film.

  Next, as shown in FIG. 5, the mold 1 is immersed in the fluororesin powder mixed polyimide precursor solution 4 from the tip to a 400 mm portion and coated, and then a ring-shaped die 2 having an inner diameter of 25 mm is applied from the top of the mold. The cast film 3 having a thickness of 500 μm was formed on the surface of the mold.

  Thereafter, the mold 1 is placed in an oven at 120 ° C. and dried for 60 minutes, then heated to a temperature of 200 ° C. over 40 minutes, held at the same temperature for 20 minutes, and as a final imidization treatment at a temperature of 250 ° C. for 10 minutes. After heating, the temperature was raised to a temperature of 400 ° C. over 15 minutes, heated at the same temperature for 10 minutes to complete imidization, and after cooling to room temperature (25 ° C.), the tubular object was removed from the mold.

  The thickness of the obtained tubular object was 55 μm, and both ends were cut to obtain a tubular object having a length of 240 mm (A4 size) and an inner diameter of 24 mm.

  The measurement results of the dynamic friction coefficients of the inner and outer surfaces of this tubular object are shown in Table 1 below. Further, FIG. 9 shows an observation photograph of the outer surface of 1000 times with a digital microscope (VHX-100 manufactured by Keyence Corporation). The portion of the outer surface that appears white and spotted is PTFE resin particles, and the portion that is precipitated in a state of flowing around it is FEP resin. It can be confirmed that the fluororesin coating surface as a whole has a granular pattern due to the fluororesin particles. Moreover, the same photograph of the inner surface of this tubular object is shown in FIG. A black spot-like portion is a precipitate of PTFE resin, and a surrounding white portion is a portion where the FEP resin melts and flows.

  This polyimide tubular object was mounted as a fixing belt of a laser beam printer capable of fixing 10 sheets per minute as shown in FIG. 6 and image fixing was performed. As a result, a good image was obtained.

(Comparative Example 1)
A polyimide tubular body was obtained under the same conditions as in Example 1 except that the fluororesin powder was not mixed with the polyimide precursor solution under the conditions of Example 1. Table 1 below shows the measurement results of the dynamic friction coefficient of the inner surface of this tubular object.

(Example 2)
Only the FEP powder (trade name “532-8110” manufactured by DuPont) having an average particle size of 35 μm as a fluororesin powder was added to the polyimide precursor single solution composed of BPDA / PPD prepared in Example 1 as a solid content in the polyimide precursor solution. It added and mixed so that it might become a ratio of 23 mass% with respect to the fluororesin mixed polyimide precursor solution.

  Thereafter, a polyimide precursor solution is applied to the surface of the mold in the same manner as in Example 1, cast, and imidized in the same manner as in Example 1, and heated at a temperature of 250 ° C. for 10 minutes as the final imidized treatment. Then, the temperature was raised to a temperature of 300 ° C. in 5 minutes, heated at a temperature of 350 ° C. for 15 minutes, and cooled to obtain a polyimide tubular body.

  Table 1 shows the measurement results of the dynamic friction coefficient of this tubular object. Further, 10 images can be fixed per minute as shown in FIG. 6. As a result of mounting the image as a fixing belt of a laser beam printer and fixing the image, a good image was obtained. In FIG. 6, 31 is a fixing belt (polyimide resin tubular object), 32 is a belt guide, 33 is a ceramic heater, 34 is a pressure roll having a drive source, 35 is a thermistor, 36 is a core metal of the pressure roll, 37 is Copy paper, 38 is a toner image before fixing, 39 is a toner image after fixing, and N is a nip point.

(Example 3)
Only a PFA resin powder (trade name: PFA MP102, manufactured by Mitsui DuPont Fluoro Chemical Co., Ltd.) having an average particle size of 28 μm as a fluororesin powder was added to the polyimide precursor single solution composed of BPDA / PPD prepared in Example 1 in the polyimide precursor solution. It added and mixed so that it might become a ratio of 24 mass% with respect to minutes, and prepared the fluororesin mixed polyimide precursor solution.

  Thereafter, a mold surface polyimide precursor solution was cast and molded in the same manner as in Example 1 and treated at 400 ° C. under the same conditions as in Example 1 to obtain a polyimide tubular body. However, a mold having an outer diameter of 30 mm was used as the mold.

  Table 1 shows the measurement results of the dynamic friction coefficient of this tubular object. Further, the fixing of 6 sheets per minute shown in FIG. 7 was possible. As a result of image fixing by mounting as a pressure belt of a laser beam printer, a good image was obtained. In FIG. 7, 51 is a pressure belt, 52 is a pressure guide, 53 is a pressure pad, 54 is a fixing roll, 55 is a heat source, 56 is a toner image before fixing, and 57 is a copy paper.

Example 4
75 parts by mass of ODA was dissolved in NMP (monomer concentration: 18.0% by mass) in a flask with respect to 100 parts by mass of PMDA, and reacted with stirring at a temperature of 23 ° C. for 6 hours to obtain a polyimide precursor solution. The rotational viscosity of this polyimide precursor solution was 1500 poise. The rotational viscosity is a value measured with a B-type viscometer at a temperature of 23 ° C. Next, only FEP powder having an average particle diameter of 35 μm (melting point: 270 ° C., product name “532-8110” manufactured by DuPont) is added and mixed in a proportion of 26 mass% with respect to the solid content in the polyimide precursor solution. A fluororesin mixed polyimide precursor solution was prepared.

  Thereafter, in the same manner as in Example 1, a polyimide precursor solution was liquid molded on the surface of the mold. Then, it is dried in an oven at 120 ° C. for 60 minutes, heated to 200 ° C. for 20 minutes, heated at the same temperature for 20 minutes, and heated at 250 ° C. for 10 minutes as the final imidization treatment, and then to 400 ° C. The temperature was raised in 10 minutes, heated at a temperature of 400 ° C. for 10 minutes, and then cooled to obtain a polyimide tubular body.

  Table 1 shows the measurement results of the dynamic friction coefficient of this tubular object. In addition, it was possible to fix 6 sheets per minute as shown in FIG. 6 and as a fixing belt of a laser beam printer, image fixing was performed. As a result, a good image was obtained.

(Comparative Example 2)
A polyimide tubular body was obtained under the same conditions as in Example 1 except that the final imidization temperature was changed to 250 ° C. under the conditions of Example 1. Table 1 shows the measurement results of the dynamic friction coefficients of the inner and outer surfaces of this tubular object.

  The fluororesin mixed polyimide precursor solution prepared in each example and each comparative example was cast on a 300 mm □ (length: 300 mm, width: 300 mm) glass plate to a thickness of 80 μm, and the maximum imidization shown in Table 1 Imidization was completed at temperature to obtain a polyimide film. Then, the result of having measured the contact angle with respect to the pure water of each film is shown in Table 1.

(Example 5)
The tubular object molding apparatus shown in FIG. 8 is used, and a discharge slit head 70 having a discharge slit opening 72 having a discharge slit opening width of 1.4 mm and an inner diameter of a discharge slit portion 72 of polyimide precursor is attached to the molding apparatus. did. In addition, an aluminum mold having an outer diameter of 229 mm and a length of 500 mm is prepared as the molding mold 71, and a mold in which a silicon oxide coating agent is coated and baked by a dipping method on the mold surface and coated with a silicon oxide film is used. The mold was installed so that the upper end of the mold was inside the discharge slit. The average surface roughness of the mold was (Rz) 2.2 μm.

  Next, PTFE powder having an average particle diameter of 3.0 μm (melting point: 327 ° C .: trade name “Zonyl MP1100” manufactured by DuPont) was added to the polyimide precursor single solution composed of BPDA / PPD prepared in Example 1 in the polyimide precursor solution. The mixture was added so as to have a ratio of 23% by mass with respect to the solid content and stirred to be uniformly dispersed. Thereafter, coarse foreign matters were filtered using a 250 mesh stainless steel wire mesh to prepare a PTFE powder mixed polyimide precursor solution.

Thereafter, acidic carbon black (trade name “MA78”, manufactured by Mitsubishi Chemical Corporation), DBP absorption: 70 cm ³ , volatile content per specific surface area of 100 m ² / g: 2.6 was added to the PTFE powder mixed polyimide precursor solution. (1 wt%) was added to the polyimide resin in an amount of 14.5% by mass to prepare a polyimide precursor in which three components of polyimide, PTFE, and carbon black were mixed and dispersed.

  Thereafter, the PTFE mixed precursor solution 74 is put into the storage tank 73, the slurry pump 77 is rotated, a predetermined amount of the polyimide precursor solution is distributed to 24 locations by the branch unit 78, and pipes 79 and 80 (the other pipes are connected). (Not shown) was connected to the pipe connector of the discharge slide head 70 and was pumped to the discharge slit opening. At the same time, the mold is raised vertically in the direction of the arrow Y, and when the position of 50 mm downward from the uppermost part of the mold 71 passes through the discharge slit portion, the polyimide precursor solution is pumped from the slurry pump 77, and the mold A polyimide precursor solution 81 was cast on the outer surface of 71 with a thickness of 600 μm. 75 is a liquid feed pipe, and 76 is a valve. The pumping speed of the slurry pump 77 and the ascending speed of the mold 71 were calculated in advance from data such as the viscosity of the polyimide precursor solution, the outer diameter of the mold 71, and the liquid molding thickness, and predetermined conditions were set. When the position of 50 mm from the lowermost end of the mold 71 passed through the discharge slit, the pumping from the slurry pump was stopped, and liquid molding was completed on the surface of the mold 71 with a length of about 400 mm. Thereafter, the mold was placed in an oven as it was, dried at 120 ° C. for 60 minutes, heated to a temperature of 200 ° C. over 40 minutes, and held at that temperature for 20 minutes. Next, the temperature is raised to 300 ° C. for 20 minutes, held for 30 minutes, further heated to 340 ° C. for 15 minutes, heated at the same temperature for 20 minutes to complete imidization, taken out from the oven, cooled, and then removed from the mold Thus, a polyimide resin tubular body was produced.

The thickness of this tubular object was 57 μm, and the volume resistivity at an applied voltage of 500 v was 1.1 × 10 ⁸ Ω · cm. The PTFE resin mixed in the precursor solution melted and precipitated on the inner and outer surfaces of the tubular body. However, the dynamic friction coefficient data showed that the PTFE resin was precipitated more on the outer surface than on the inner surface.

  FIG. 11 shows an observation photograph of the outer surface of this tubular object with a digital microscope (VHX-100 manufactured by Keyence Corporation) at a magnification of 1000 times. It can be confirmed that the white spots appear to be PTFE resin particles and have a granular pattern due to the fluororesin particles.

  Table 1 shows the measurement results of the dynamic friction coefficient and the contact angle of this tubular object. As a result of using this tubular object as an intermediate transfer belt for a full-color tandem laser beam printer, the color toner image formed on the belt surface is transferred to copy paper, and then the toner remaining on the transfer belt is removed with a urethane rubber blade. In this case, the remaining toner having a low sliding resistance between the blade and the transfer belt surface can be surely removed, and a clear image and sufficient durability can be obtained. Further, since the fluororesin is hardly deposited on the inner surface of the tubular object, the rotation can be reliably transmitted between the driving rolls arranged on the inner surface of the transfer belt without slipping, the toner image is not disturbed, and the image blurring is not caused. Occurrence could be prevented. The volume resistivity was measured at an application time of 30 seconds using a digital ultrahigh resistance / microammeter R8340 / R8340A manufactured by Advantest Corporation according to the method of JIS C2151.

(Example 6)
(1) Production of first layer (inner layer) of multilayer structure tubular object Boron nitride powder (Mitsui Chemicals, Inc., MBN-010T) was added to the polyimide precursor single solution consisting of BPDA / PPD prepared in Example 1. 30% by mass with respect to the solid content concentration of the precursor solution was mixed to prepare a boron nitride powder mixed polyimide precursor solution. Next, the surface of the mold used in Example 1 was applied using a ring die so that the film thickness after imidization was 35 μm, cast-molded, dried at 120 ° C., and then subjected to an imidation intermediate treatment at a temperature of 250 ° C. The first layer of a tubular object made of a polyimide film mixed with boron nitride powder was formed.
(2) Manufacture of polyimide precursor solution used for second layer (outer layer) of multilayer structure tubular product PTFE powder having an average particle size of 3.0 μm was added to the polyimide precursor single solution composed of BPDA / PPD prepared in Example 1 ( Melting point 327 ° C .: “SP-Powdered PTFE” manufactured by SUMMIT PRECISION POLYMERS CORPORATION) is 70% by mass with respect to the solid content in the polyimide precursor solution, and 5% by mass of carbon fiber (“VGCF-H” manufactured by Showa Denko KK). The mixture was added at a ratio of and stirred and dispersed uniformly. Thereafter, coarse foreign matters were filtered using a 250 mesh stainless steel wire mesh to prepare a fluororesin powder and a carbon fiber mixed polyimide precursor solution.
(3) Completion of molding and imidization of the second layer (outer layer) of the multi-layered tubular object The fluororesin powder prepared in the above (2) and the surface of the first layered tubular object manufactured in the above (1) The carbon fiber mixed polyimide precursor solution is cast using a ring die so that the film thickness after imidization is 20 μm, dried at a temperature of 120 ° C., and then subjected to a primary imidization treatment at a temperature of 250 ° C. Further, the temperature is raised to a temperature of 400 ° C. in 15 minutes, heated at the same temperature for 20 minutes to complete imidization, and an inner layer in which boron nitride powder is mixed with polyimide, and fluorine resin powder and carbon fiber are also mixed with polyimide. A two-layer polyimide tubular body having a mixed outer layer was obtained. The tubular body had an inner diameter of 24 mm and a total thickness of 54 μm. The first and second layers were firmly bonded by imidization and could not be peeled off. Further, the mixed fluororesin melted and deposited on the outer surface of the tubular body, and had excellent release properties and low friction characteristics of the fluororesin. Table 1 shows the measurement results of the dynamic friction coefficients of the inner and outer surfaces of this tubular object. This tubular object has a structure in which the first layer and the second layer are integrated by imidization, and the first layer (inner layer) has mechanical properties required as a tubular object, and the second layer (outer layer). In this case, the fluororesin mixed in a large amount melts and precipitates, and a release layer having a sufficient thickness is obtained, resulting in excellent durability.

  Further, the boron nitride mixed in the first layer and the carbon fiber mixed in the second layer improve the thermal conductivity in the thickness direction of the tubular body, and at the same time, the surface resistance of the fluororesin layer deposited on the outermost layer is 800Ω / □. As a result of attaching the fixing belt of the laser beam printer shown in FIG. 6 capable of fixing 14 sheets per minute and performing image fixing, a good image was obtained without occurrence of offset.

(Example 7)
(1) Production of first layer (inner layer) of multilayer structure tubular object PTFE powder having an average particle size of 3.0 μm (melting point: 327 ° C .: DuPont) was added to the polyimide precursor single solution made of BPDA / PPD prepared in Example 1. A mixed solution of a fluororesin and a polyimide precursor was prepared by mixing 15% by mass of a product name “Zonyl MP1100”). Next, the surface of the mold used in Example 3 was coated with a ring die so that the film thickness after imidization was 35 μm, cast-molded, dried at 120 ° C., and then imidized at a temperature of 250 ° C. Processing was performed to form a first layer film composed of the mixed solution.
(2) Manufacture of a polyimide precursor solution used for the second layer (outer layer) of the multilayer structure tubular material PTFE powder (melting point) having an average particle size of 3.0 μm was added to the polyimide precursor single solution made of BPDA / PPD prepared in Example 1. 327 ° C .: “SP-Powdered PTFE” manufactured by SUMMIT PRECISION POLYMERS CORPORATION at a ratio of 55% by mass with respect to the solid content in the polyimide precursor solution, and carbon fiber (“VGCF-H” manufactured by Showa Denko KK) at a ratio of 5% by mass. The mixture was stirred and dispersed uniformly, and then coarse foreign matters were filtered using a 250 mesh stainless steel wire mesh to prepare a fluororesin powder and a carbon fiber mixed polyimide precursor solution.
(3) Molding of second layer (outer layer) of multilayer structure tubular object and completion of imidization Fluorine resin prepared in (2) above on the surface of first layer tubular object manufactured in (1) above The powder and carbon fiber mixed polyimide precursor solution is cast using a ring die so that the film thickness after imidization is 20 μm, dried at a temperature of 120 ° C., and then primary imidized at a temperature of 250 ° C. Then, the temperature is raised to a temperature of 400 ° C. in 15 minutes, heated at the same temperature for 20 minutes to complete imidization, and an inner layer in which a fluororesin is mixed with polyimide, and a fluororesin powder and carbon are also mixed with polyimide. A polyimide tubular body having a two-layer structure having an outer layer mixed with fibers was obtained. The tubular body had an inner diameter of 24 mm and a total thickness of 55 μm, and the first and second layers were firmly bonded by imidization. Further, the fluororesin melted and precipitated on the outer surface and the inner surface of the tubular body, and had excellent release properties and low friction characteristics of the fluororesin. Table 1 shows the measurement results of the dynamic friction coefficients of the inner and outer surfaces of this tubular object. The surface resistance of the fluororesin layer deposited on the outermost layer of this tubular object is 815Ω / □, and as a result of image fixing using a pressure belt of a laser beam printer equipped with the fixing device shown in FIG. A good image was obtained without occurrence.

  As is apparent from Table 1, the tubular object of the present invention had a low coefficient of dynamic friction and a low contact angle of the film-like molded product. Moreover, it has confirmed that the fluororesin had deposited on the surface of the polyimide tubular body from the observation result by an electron micrograph. Furthermore, as a result of fixing as a fixing belt of a laser beam printer and performing image fixing, a good image was obtained.

FIG. 1 is a schematic cross-sectional view of a tubular object before imidization is completed in an embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of a tubular object after imidization is completed in an embodiment of the present invention. FIG. 3 is a schematic cross-sectional view showing film formation when FEP is added in one embodiment of the present invention. FIG. 4 is a schematic cross-sectional view showing comparative formation in the case of FEP and PTFE mixed addition in one example of the present invention. FIG. 5 is a cross-sectional view showing a casting method in one embodiment of the present invention. FIG. 6 is a schematic sectional view showing a laser beam printer fixing device used in one embodiment of the present invention. FIG. 7 is a schematic sectional view showing a laser beam printer fixing device used in another embodiment of the present invention. FIG. 8 is a cross-sectional view showing a casting method according to another embodiment of the present invention. FIG. 9 is a photomicrograph of the outer surface of the polyimide tubular object in Example 1 of the present invention. FIG. 10 is a photomicrograph of the inner surface of the polyimide tubular object in Example 1 of the present invention. FIG. 11 is a photomicrograph of the outer surface of a polyimide tubular object in Example 5 of the present invention. FIG. 12 is a schematic sectional view showing a dynamic friction coefficient measuring apparatus used in one embodiment of the present invention.

Explanation of symbols

1,15,28,71 Mold 2, Die 3,81 Cast film 4,74 Fluororesin powder mixed polyimide precursor solution 10,51 Polyimide tubular object 11,21 Polyimide film layer 12,24 PTFE particles 13,25 Outer surface PTFE melted and deposited on the side
14,29 PTFE melted and precipitated on the inner surface side
22 Thermoplastic fluororesin particles 23 Thermoplastic fluororesin particles 30 melted and precipitated on the outer surface Thermoplastic fluororesin particles 31 melted and precipitated on the inner surface 31 Fixing belt 32 Belt guide 33 Ceramic heater 34 Pressure roll 35 Thermistor 36 Pressure roller Core metal 37 Copy paper 38 Toner 39 Toner image

Claims (15)

A tubular object molded and heat-cured of a mixture containing polyimide and fluororesin particles,
At least some of the fluororesin particles present in the vicinity of the surface layer of the tubular object are melt-flowed and deposited on the outer surface or inner / outer surface of the tubular object, and a fluororesin coating is formed partially or entirely. A tubular object.   The tubular object according to claim 1, wherein the fluororesin coating surface has a granular pattern resulting from the fluororesin particles.   The tubular object according to claim 1 or 2, wherein the tubular object is a single layer containing polyimide and fluororesin particles.   The tubular body is formed of an inner layer that does not contain fluororesin particles, or an inner layer that contains less fluororesin than the outer layer, and an outer layer that contains greater fluororesin than the inner layer. A tubular object according to claim 1.   The tubular object according to any one of claims 1 to 4, wherein the amount of the fluororesin particles in the layer containing the polyimide and the fluororesin particles is 10 to 90% by mass.   The fluororesin particles include polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), polychlorotrifluoroethylene (PCTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP). The tubular object according to claim 1, which is at least one fluororesin selected from tetrafluoroethylene-ethylene copolymer (PETFE).   The tubular object according to any one of claims 1 to 6, wherein an average particle diameter of the fluororesin is 0.1 to 100 µm.   The tubular according to claim 1, 3 or 5, wherein the polyimide is a polyimide obtained by heating and imidizing a polyimide precursor solution comprising at least one aromatic tetracarboxylic dianhydride and at least one aromatic diamine. object. A mixed solution of a polyimide precursor solution and melt-flowing fluororesin particles is applied to the outer surface of the mold and cast to a predetermined thickness,
Heating to imidize, the maximum temperature of the imidization exceeds the melting point of the fluororesin,
After cooling, by separating the mold and the tubular object,
At least a part of the fluororesin particles existing in the vicinity of the surface layer of the tubular object is melt-flowed and deposited on the outer surface or the inner / outer surface of the tubular object to form a fluororesin film partially or entirely. A method for manufacturing an object. Before the mixed solution is applied to the outer surface of the mold and cast to a predetermined thickness, the polyimide precursor solution is applied to the outer surface of the mold in advance and cast to a predetermined thickness,
The method for producing a tubular object according to claim 9, wherein the mixed solution is applied to an outer surface of a mold and cast to a predetermined thickness before or after imidization.   The method for producing a tubular object according to claim 9 or 10, wherein the amount of the fluororesin particles in the layer containing the polyimide and the fluororesin particles is 10 to 90% by mass.   The fluororesin particles include polytetrafluoroethylene (PTFE), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), polychlorotrifluoroethylene (PCTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP). ), A method for producing a tubular object according to any one of 9 to 11, which is at least one fluororesin selected from tetrafluoroethylene-ethylene copolymer (PETFE).   The method for producing a tubular object according to any one of claims 9 to 12, wherein an average particle diameter of the fluororesin is 0.1 to 100 µm.   12. The polyimide according to claim 9, wherein the polyimide is a polyimide obtained by heating and imidizing a polyimide precursor solution composed of at least one aromatic tetracarboxylic dianhydride and at least one aromatic diamine. A method for manufacturing a tubular object.   The method for producing a tubular object according to claim 14, wherein the polyimide is a polyimide obtained by heating and imidizing a polyimide precursor solution composed of biphenyltetracarboxylic dianhydride and paraphenylenediamine.

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