JP2012225990A - Polyimide tube and fixing belt - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a polyimide tube having an excellent fixing property and superior strength with high rigidity hardly causing collapse by twist deformation or buckling during driving and hardly causing cracks or breakage even when paper feeding is repeated, and to provide a fixing belt using the polyimide tube as a substrate.SOLUTION: The polyimide tube is made of a polyimide resin composition comprising a polyimide resin and graphite and acicular titanium oxide dispersed in the resin, in which the sum of the compounded amount of the graphite and acicular titanium oxide compounded is 15 vol.% or more on the basis of the whole volume of the polyimide resin composition, the compounded amount of the graphite is 28 vol.% or less on the basis of the whole volume of the composition, and the compounding ratio of the acicular titanium oxide is 15 to 60 vol.% with respect to the sum of the graphite and acicular titanium oxide. The fixing belt comprises the above polyimide tube as a substrate.

Description

  The present invention relates to a polyimide tube used for a fixing belt or the like of an image forming apparatus. More specifically, the present invention relates to a polyimide tube that gives excellent fixability when used in a fixing belt and is excellent in rigidity and strength (durability). The present invention also relates to a fixing belt using the polyimide tube as a belt base material.

  In general, in an image forming process in an electrophotographic copying machine, a laser beam printer, etc., this unfixed toner is formed after a toner image is formed on a transfer material such as a recording paper through an exposure process, a development process, and a transfer process. A fixing step for fixing the image on the transfer material is performed. As a fixing method, a method in which an unfixed toner image is heated and pressurized to be fused onto a transfer material is generally used. As the heating / pressurizing means, the fixing roller and the pressure roller are opposed to each other, and a transfer material on which an unfixed toner image is placed is allowed to pass between the rollers. A method of heating with a heating source is widely adopted.

  As a fixing roller, a SUS tube is disclosed in Patent Document 1 and the like. However, a SUS tube has a high material cost and a high processing cost and has a problem in price. There was a problem that it was likely to occur. Therefore, in recent years, the unfixed toner image 5 on the transfer material 4 is heated by the heating means (heater) 2 through the thin endless belt 1 (fixing belt) as shown in FIG. A method of forming a fixed toner image 6 by applying pressure by 3 has been developed.

  As a base material for such a fixing belt, polyimide having excellent heat resistance, mechanical strength, tear strength, flexibility and the like is widely used. And to improve the thermal conductivity of the polyimide tube and improve the fixability, to reduce the waiting time after power-on, reduce power consumption, increase the fixing speed, etc. A method of containing an excellent filler (high thermal conductive filler) is known.

  Inorganic fillers such as carbon black, silicon carbide, silica (Patent Document 2), boron nitride (Patent Document 3), and carbon nanotube (Patent Document 4) have been proposed as the high thermal conductive filler. Further, in Patent Document 5, a needle-shaped high thermal conductive filler such as carbon nanotube or needle-shaped titanium oxide is dispersed in a predetermined volume% or more, and the degree of orientation of the needle-shaped high thermal conductive filler is a predetermined value or more. Is disclosed. This polyimide tube has a high thermal conductivity and excellent mechanical strength, as well as excellent compressive strength (indentation load). The fixing belt made of this polyimide tube has excellent offset properties and It is stated that a clear image can be obtained by using a fixing belt.

JP-A-5-40425 Japanese Patent Laid-Open No. 3-25478 JP-A-8-80580 JP 2004-123867 A JP 2009-156965 A

  However, in recent years, the demand for fixing belts has become more advanced. In addition to the above-described excellent fixing properties, high thermal conductivity, excellent compressive strength, offset properties, etc., for example, it has high rigidity and is driven when used as a fixing belt substrate. There is a demand for a property that can effectively suppress the torsional deformation and collapse due to buckling. In addition, a higher level of properties that do not cause tearing or tearing even when paper is repeatedly passed is desired.

  An object of the present invention is to have a high thermal conductivity, and when used as a base material for a fixing belt, it has excellent fixing properties, is highly rigid and hardly undergoes torsional deformation or buckling during driving, and paper passing The object is to provide a polyimide tube having an excellent strength that is difficult to tear or tear even if the above is repeated. Another object of the present invention is to provide a fixing belt that uses a polyimide tube having excellent characteristics as described above as a base material, is less likely to be crushed due to torsional deformation or buckling during driving, and is less susceptible to tearing or tearing. .

  As a result of intensive research to solve the above problems, the present inventors have found that the above object can be achieved by dispersing a predetermined amount of acicular titanium oxide together with a predetermined amount of graphite in a polyimide resin. The headline and the present invention were completed.

  The present invention provides a polyimide tube comprising a polyimide resin composition in which graphite and acicular titanium oxide are dispersed in a polyimide resin, wherein the total amount of graphite and acicular titanium oxide is the polyimide resin. 15 vol% or more based on the total volume of the composition, the blending amount of graphite is 28 vol% or less based on the total volume of the composition, and the blending ratio of acicular titanium oxide is graphite and acicular titanium oxide The polyimide tube characterized by being 15-60 volume% with respect to the sum total.

This polyimide tube is composed of a polyimide resin composition in which graphite and acicular titanium oxide are dispersed in a polyimide resin.
The blending amount of graphite and acicular titanium oxide is a total of graphite and acicular titanium oxide, and is 15% by volume or more based on the total volume of the composition.
The blending ratio of graphite is 28% by volume or less based on the total volume of the composition, and the blending ratio of acicular titanium oxide is 15 to 60% by volume with respect to the total of graphite and acicular titanium oxide. And

  Here, the blending amount of graphite and acicular titanium oxide is 15% by volume or more on the basis of the total composition volume. The graphite and needle with respect to the total capacity of the polyimide resin composition containing polyimide resin and graphite and acicular titanium oxide. This means that the total capacity of the titanium oxide is 15% or more, and this capacity% is a value obtained based on the true specific gravity measured by the underwater substitution method defined in the JIS K7112A method.

  By dispersing graphite and acicular titanium oxide in the above proportion and blending amount in polyimide resin, it has high thermal conductivity and excellent fixability, and has high rigidity, and it is difficult to tear or tear even when paper is repeatedly passed. A polyimide tube having excellent strength is obtained. Due to the high rigidity of the polyimide tube, when used as a base material for a fixing belt, it becomes difficult to cause torsional deformation or crushing due to buckling during driving, and a fixing belt having high so-called buckling strength can be obtained.

  When the blending amount of graphite and acicular titanium oxide is too small, high thermal conductivity cannot be obtained. As a result, the fixing property of the fixing belt is lowered. Further, when the ratio of acicular titanium oxide in the graphite and acicular titanium oxide is too large, the fixing property of the fixing belt is lowered. On the other hand, if the proportion of acicular titanium oxide in the graphite and acicular titanium oxide is too small, the rigidity decreases, the buckling strength decreases, and the twist deformation during driving when used as a base material for a fixing belt It tends to be crushed by buckling.

  When the blending amount of graphite is increased, the rigidity is improved, and it is possible to obtain a desired rigidity even when acicular titanium oxide is not blended or when the ratio is small. However, in this case, the strength of the polyimide tube is reduced, and tearing and tearing are likely to occur due to repeated paper feeding.

  The blending amount of graphite and acicular titanium oxide is 15% by volume or more, the blending ratio of graphite is 28% by volume or less, and the blending ratio of acicular titanium oxide is 15 to 60 with respect to the total of graphite and acicular titanium oxide. By setting the volume%, it is possible to obtain a polyimide tube and a fixing belt that have excellent fixing properties and rigidity, and that are not easily torn or torn by repeated paper passing. The blending amount of graphite and acicular titanium oxide is preferably 20% by volume or more, and the blending ratio of acicular titanium oxide is preferably 18 to 50% by volume with respect to the total of graphite and acicular titanium oxide.

  The invention according to claim 2 is the polyimide tube according to claim 1, wherein the graphite has an average particle size of 0.3 μm or more and 30 μm or less.

  Graphite is usually an elemental mineral in which sheets of carbon atoms bonded in a plane are laminated, and means a hexagonal hexagonal plate crystal. In the present invention, it is commercially available as graphite, graphite, etc. Can also be used. As such graphite, graphite having an average particle diameter of 0.3 μm or more and 30 μm or less is preferable. If the average particle size is smaller than 0.3 μm, the surface area of graphite increases and the interface with the resin increases, so when mixed with the polyimide precursor, the viscosity may rise extremely and cause problems in the manufacturing process. There is. On the other hand, when the average particle diameter is larger than 30 μm, the thickness of the polyimide used for the fixing roller is preferably 10 to 150 μm and is often around 50 μm as described later. ) May get worse. The average particle diameter of graphite is more preferably 0.5 μm or more and 10 μm or less, and further preferably 1 μm or more and 5 μm or less. The average particle size refers to the particle size (D50) at which the weight ratio is 50% in the particle size distribution measured with a laser diffraction particle size distribution analyzer. As graphite, commercially available products such as BF-3AK manufactured by Chuetsu Graphite Co., Ltd. can also be used.

  The invention according to claim 3 is characterized in that the acicular titanium oxide has an average diameter of 0.3 μm or more and 30 μm or less, and an average length of 0.10 μm or more and 1000 μm or less. It is a polyimide tube of Claim 2.

  The acicular titanium oxide is a titanium oxide particle having a sufficiently large length compared to its diameter (thickness). Here, the average of the diameters of the particles is referred to as the average diameter, and the average of the particle lengths is referred to as the average length. As the titanium oxide, anatase type or brucite type titanium oxide can be used in addition to the rutile crystal structure titanium oxide used as a white pigment. The diameter of the particles and the length of the particles are measured from an electron micrograph or an SEM photograph, and an average value of values measured by arbitrarily selecting 30 particles is an average diameter and an average length, respectively.

  The average diameter of acicular titanium oxide is preferably 0.01 μm or more and 30 μm or less. When the average diameter is smaller than 0.01 μm, the surface area of the acicular titanium oxide increases and the interface with the resin increases. Therefore, when mixed with the polyimide precursor, the viscosity is extremely increased, resulting in problems in the manufacturing process. there is a possibility. On the other hand, when the average particle diameter is larger than 30 μm, the thickness of the polyimide used for the fixing roller is preferably 10 to 150 μm and is often around 50 μm, as will be described later. Can get worse. The average diameter of acicular titanium oxide is more preferably 0.05 μm or more and 10 μm or less, and still more preferably 0.10 μm or more and 1 μm or less.

  The average length of acicular titanium oxide is preferably 0.10 μm or more and 1000 μm or less. When the average length is less than 0.10 μm, the surface area of acicular titanium oxide increases and the interface with the resin increases. Therefore, when mixed with the polyimide precursor, the viscosity rises extremely, causing problems in the manufacturing process. It can happen. On the other hand, when the average length is larger than 1000 μm, the surface condition (surface property) of the fixing roller may be deteriorated. The average length of acicular titanium oxide is more preferably 0.50 μm or more and 100 μm or less, and still more preferably 1 μm or more and 50 μm or less.

  In addition, since the average diameter and average length of acicular titanium oxide are preferably within the above range, (average length / average diameter) is preferably in the range of 5 to 300, more preferably in the range of 10 to 100. . As the acicular titanium oxide, commercially available products such as FTL-300 manufactured by Ishihara Sangyo Co., Ltd. can be used.

  In the polyimide tube of the present invention, a filler other than graphite and acicular titanium oxide may be blended within a range that does not impair the spirit of the present invention. Such fillers include high thermal conductive fillers such as boron nitride, carbon nanotubes, alumina, silicon carbide, and metallic silicon, and conductive materials such as carbon black, ketjen black, and metal powder (nickel, aluminum, copper, silver, etc.) Can be mentioned.

  A fourth aspect of the present invention is the polyimide tube according to any one of the first to third aspects, wherein the thickness is 10 to 150 μm.

  The thickness, outer diameter, length, etc. of the polyimide tube can be appropriately selected according to the desired mechanical strength and application. When the polyimide tube of the present invention is used as a base material for a fixing belt in an electrophotographic image forming apparatus, the thickness of the polyimide tube is usually 10 to 150 μm, preferably 20 to 120 μm, more preferably 30 to 100 μm. The outer diameter is usually 5 to 100 mm, preferably 10 to 50 mm. The length of the polyimide tube can be appropriately set according to the size of the transfer material such as copy paper.

  As the polyimide resin constituting the polyimide tube of the present invention, either a thermosetting polyimide resin (also referred to as “condensation type polyimide resin”) or a thermoplastic polyimide resin can be used, but it is formed from a thermosetting polyimide resin. It is preferable from the viewpoint of heat resistance, tensile strength, tensile elastic modulus, and the like.

  The thermosetting polyimide resin is preferably a condensation type wholly aromatic polyimide resin from the viewpoint of heat resistance, mechanical strength, and the like. For example, acid dianhydrides such as pyromellitic dianhydride, 3,3 ′, 4,4′-diphenyltetracarboxylic dianhydride, oxydiphthalic dianhydride, 4,4′-diaminodiphenyl ether, p- Examples thereof include a polyimide precursor synthesized by a polymerization reaction of a diamine such as phenylenediamine, 4,4'-diaminobenzanilide, resorcinoxydianiline, etc. in an organic solvent, and dehydrated and closed by heating.

  The polyimide resin used in the present invention may be a homopolymer or a copolymer. Specific examples of the polyimide resin include those whose chemical structures are described in Patent Document 5.

  A polyimide tube made of a thermosetting polyimide resin is made of graphite or acicular oxidation in an organic solvent solution (hereinafter referred to as “polyimide precursor varnish”) of a polyimide precursor (also referred to as “polyamic acid” or “polyamic acid”). A material in which titanium or the like is added and dispersed (hereinafter referred to as “polyimide varnish”) is formed into a tube shape and then heated to produce a polyimide precursor by dehydrating and ring-closing the polyimide. Can do. As the polyimide precursor varnish, commercially available products can be used in addition to those synthesized independently.

  Examples of the method for shaping the tube shape include a method in which a polyimide varnish is applied to the outer surface of a cylindrical core or the outer surface or inner surface of a cylindrical core and dried. After drying the coating layer of the polyimide varnish, it may be heat-cured (imidized) in a state of adhering to the core surface, or from the core surface when solidified to a strength that can maintain the structure as a tubular product. The coating layer may be removed and heat cured in the next step. When the polyimide precursor is heated from a maximum temperature of 350 ° C. to 450 ° C., the polyamic acid is dehydrated and closed to form a polyimide.

  As a method of applying the polyimide varnish to the outer surface of the cylindrical core or the outer surface (outer surface) or inner surface of the cylindrical core, a method of forming a coating layer by spirally winding using a dispenser (dispenser method) ).

Specifically, in the dispenser method,
The discharge port of the dispenser supply part is close to or in contact with the outer surface of the cylindrical core, or the outer surface or inner surface of the cylindrical core,
While rotating the core body and relatively moving the discharge port in the rotation axis direction of the core body,
A step of forming a coating layer by continuously supplying polyimide varnish on the outer surface of the cylindrical core body or on the outer surface or inner surface of the cylindrical core body from the discharge port,
A step of solidifying or curing the coating layer after the formation of the coating layer; and a step of demolding the coating layer from the core after the solidification or curing,
Is done.

  The polyimide tube of the present invention can be used as a base material for a fixing belt. According to a fifth aspect of the present invention, the polyimide tube of the present invention is used as a belt base material, and a fluororesin layer is provided directly or via an adhesive layer on the outer peripheral surface of the belt base material. A fixing belt is provided. This fixing belt is suitably used for a fixing unit or the like in an electrophotographic image forming apparatus.

  When using the polyimide tube of the present invention as a base material for a fixing belt, a method of applying a fluororesin varnish to the outer peripheral surface and sintering at a high temperature may be employed, but the polyimide resin, polyimide copolymer, And these blends have heat resistance sufficient to withstand sintering at such high temperatures.

  The polyimide tube of the present invention has high heat conductivity and excellent fixability when used as a fixing belt, and has high rigidity, is less likely to be crushed due to torsional deformation or buckling at the time of driving, and repeats paper passing. It has excellent strength that prevents tearing and tearing. The fixing belt of the present invention is a fixing belt that is less likely to be crushed due to torsional deformation or buckling during driving, and is less likely to be torn or torn, and has an excellent image quality and strength. It is suitably used for a fixing unit or the like.

FIG. 4 is an explanatory diagram illustrating a fixing method using a fixing belt. It is explanatory drawing which shows the coating method by a dispenser method. FIG. 3 is a cross-sectional view illustrating a layer configuration of an example of a fixing belt. FIG. 6 is a cross-sectional view illustrating a layer configuration of another example of a fixing belt.

  Next, the form for implementing this invention is demonstrated concretely. In addition, this invention is not limited to this form, It can change into another form, unless the meaning of this invention is impaired.

  FIG. 2 is an explanatory view of a dispenser method that can be applied to the production of the polyimide tube of the present invention. As shown in FIG. 2, the polyimide varnish is continuously supplied from the supply unit 21 of the dispenser to the outer surface of the cylindrical core body 24 while rotating the cylindrical core body 24 in the circumferential direction. The discharge port 22 of the supply unit is brought into contact with the outer surface of the core body 24. As the core body, a cylindrical core body can be used instead of the columnar core body 24. In this case as well, polyimide varnish can be supplied to the outer surface of the core body as in the case of FIG. However, the polyimide varnish can also be supplied to the inner surface of the core body by bringing the discharge port of the supply part of the dispenser into contact with the inside of the core body.

  When the polyimide varnish is continuously supplied from the discharge port 22 of the supply unit 21 of the dispenser 1 and the supply unit 21 is relatively moved in the rotation axis direction of the core body, the supplied polyimide varnish is spirally wound. Thus, the coating layer 23 is formed. The rotation speed and the movement speed are such that the polyimide varnish is applied to the surface of the core body 24 without a gap, and adjacent portions of the polyimide varnish wound in a spiral shape are combined to form a uniform coating layer.

  After this coating step, when the coated polyimide varnish is heat-cured (imidized) by a conventional method, a strong thin tube-like film is generated. Then, a polyimide tube can be obtained by taking out the tube from the core. After the coating process, the solidified tube is removed until the coating layer has sufficient strength to maintain the structure of the tube without being completely imidized, and the tube is heated and cured (imidized) after demolding. Also good.

  The viscosity of the polyimide varnish used in this production method at 25 ° C. is preferably 100 to 15000 poise. If the viscosity of the polyimide varnish is too high, the portion of the polyimide varnish that is spirally wound and applied in contact with each other becomes thinner than the other portions, resulting in irregularities on the surface of the coating layer. If the viscosity of the polyimide varnish is too low, dripping or repelling occurs during coating or drying, making it difficult to form a tube.

  The shape of the core used is a columnar shape or a cylindrical shape. Materials for the core used in the present invention include metals such as aluminum, aluminum alloys, iron, and stainless steels; ceramics such as alumina and silicon carbide; heat-resistant resins such as polyimide, polyamideimide, polybenzimidazole, and polybenzoxazole. Can be mentioned.

  The polyimide tube of the present invention can be used as a base material for a fixing belt mounted on a fixing unit in an electrophotographic image forming apparatus. The fixing belt of the present invention has a structure in which the polyimide tube of the present invention is used as a belt base material and a fluororesin layer is provided on the outer peripheral surface of the belt base material directly or via an adhesive layer. The fluororesin layer is provided to impart releasability to the fixing belt and prevent the toner on the transfer material such as recording paper from adhering to the surface of the fixing belt.

  As the fluororesin forming the fluororesin layer, in order to enable continuous use of the fixing belt at a high temperature, a resin excellent in heat resistance is preferable. Specific examples thereof include, for example, tetrafluoroethylene (PTFE), Examples thereof include tetrafluoroethylene / perfluoroalkyl vinyl ether copolymer (PFA) and tetrafluoroethylene / hexafluoropropylene copolymer (FEP).

  The fixing belt of the present invention can be produced by forming a fluororesin layer directly or via an adhesive layer on the outer peripheral surface of a heat-cured (imidized) polyimide tube. When forming the fluororesin layer, when sintering the fluororesin at a high temperature, a tube is formed by drying and removing the solvent in the polyimide tube manufacturing process, and then directly or via an adhesive layer. After forming the fluororesin layer, the polyimide tube may be heated and cured simultaneously with the sintering of the fluororesin. As another method of forming the fluororesin layer, a method of covering the fluororesin tube can be employed. The thickness of the fluororesin layer is usually about 1 to 30 μm, preferably about 5 to 15 μm.

  The fluororesin layer can be formed using only a fluororesin, but preferably contains a conductive filler in order to prevent offset due to charging. The conductive filler is not particularly limited, and examples thereof include conductive carbon black such as ketjen black, metal powder such as aluminum, and the like.

  In the fixing belt, an adhesive layer can be provided as an intermediate layer in order to improve the adhesion between the polyimide tube and the fluororesin layer. The adhesive layer may contain a conductive filler as desired. The adhesive layer is preferably composed of a heat resistant resin from the viewpoint of heat resistance. Although it does not specifically limit as resin which comprises an contact bonding layer, For example, the mixture of a fluororesin and a polyamidoimide resin, the mixture of a fluororesin and a polyether sulfone resin, etc. are preferable.

  FIG. 3 is a cross-sectional view showing a two-layer fixing belt in which a fluororesin layer 13 is formed on the outer peripheral surface of the polyimide tube 11. FIG. 4 is a cross-sectional view showing a fixing belt having a three-layer structure in which a fluororesin layer 13 is formed on the outer peripheral surface of the polyimide tube 11 via an adhesive layer 12. Furthermore, a resin layer or a rubber layer other than the adhesive layer may be additionally disposed in the intermediate layer as long as the gist of the present invention is not impaired.

  Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples. However, the scope of the present invention is not limited to the examples.

Examples 1-10, Comparative Examples 1-4
<Manufacture of polyimide varnish>
The polyimide precursor varnish, graphite, and acicular titanium oxide shown in the column of “used raw material” below are pre-stirred with a stirrer at the blending ratios shown in Tables 1 to 3, and blended with a three-roll mill, and then vacuum degassed. The polyimide varnish was obtained.

"Raw material"
[Polyimide precursor varnish]
“U-Varnish S-301” manufactured by Ube Industries, Ltd., specific gravity 1.446: a polyimide precursor that forms a polyimide having a repeating unit represented by the following formula (A), in a solvent (N-methylpyrrolidone) at a concentration of 18 % Varnish (hereinafter, abbreviated as “U varnish S”),
I. S. “Pyre ML RC-5019” manufactured by T Company: a varnish (hereinafter referred to as “polyimide precursor”) that forms a polyimide having a repeating unit represented by the following formula (B) in a solvent (N-methylpyrrolidone) at a concentration of 15% , Abbreviated as “Pyre ML”)
Varnish mixed at 80:20 (weight ratio).

[Graphite] Manufactured by Chuetsu Graphite Co., Ltd .: BF-3AK (average particle size 3 μm, scale-like)

[Acicular titanium oxide] manufactured by Ishihara Sangyo Co., Ltd .: FTL-300 (average diameter × length: 0.27 μmφ × 5.15 μm needle)

<Preparation of polyimide tube>
The nozzle (discharge port) set in the supply part of the dispenser is brought into contact with the outer surface of an aluminum cylinder having an outer diameter of 20 mmφ whose outer surface is coated with ceramics, the core is rotated, and the nozzle is moved to the core The polyimide varnish was quantitatively supplied from the nozzle to the outer surface of the core while being moved at a constant speed in the direction of the rotation axis, and the polyimide varnish was applied. After coating, the core was heated stepwise to 400 ° C. while being cooled, and after cooling, the solidified polyimide resin coating film was removed from the core as a tube. The polyimide tube thus obtained had a thickness of 60 μm, an outer diameter of 24.2 mm, and a length of 233 mm.

  The obtained polyimide tube was subjected to a fixability test, rigidity evaluation, and strength evaluation by the following methods. The results are shown in Tables 1-3.

(1) Fixability test Using a commercially available laser beam printer, printing was carried out at a printing speed of 20 sheets / min, and toner dropout was visually confirmed and evaluated according to the following criteria.
A: Almost no toner falls off.
○: The toner has fallen off, but is slight and acceptable.
X: Toner is often dropped and causes problems.

(2) Rigidity Evaluation Using a commercially available laser beam printer, printing 100K sheets at a printing speed of 20 sheets / minute, confirming the state of the roller after 100K sheets passed, and evaluating according to the following criteria.
A: Almost no buckling or twisting of the roller occurs at 100K.
○: Roller buckling does not occur at 100K. Twist is also acceptable.
X: Roller buckling occurs at 100K. Or a twist occurs and causes a problem.

(3) Evaluation of roller strength (occurrence of tearing and tearing) Using a commercially available laser beam printer, printing 100K sheets at a printing speed of 20 sheets / min. Evaluation was made according to the criteria shown in.
A: Almost no tearing or tearing occurs at 100K.
○: Slight tearing or tearing occurs at 100K, but is acceptable.
X: A tear or tear occurs at 100K of paper passing, causing a problem.

  In Examples 1 to 10 and Comparative Examples 1 to 4, the total blending amount of graphite and acicular titanium oxide is 15% by volume or more. However, the polyimide tube obtained in Comparative Example 1 in which the blending amount of graphite is 30% by volume (exceeding 28% by volume) is inferior in strength and causes problems such as tearing and tearing at 100K. That is, this result indicates that the graphite content should be 28% by volume or less.

  In addition, the polyimide tubes obtained in Comparative Examples 2 and 3 that do not contain acicular titanium oxide (the blending ratio of acicular titanium oxide is less than 15%) are inferior in rigidity, and the fixing roller is buckled or twisted. Yes. Therefore, it has been shown that the addition of acicular titanium oxide is necessary to obtain an excellent buckling strength.

  On the other hand, the polyimide tube obtained in Comparative Example 4 containing only acicular titanium oxide without blending graphite (the blending ratio of acicular titanium oxide exceeds 60% by volume) has poor fixability and strength. Therefore, it has been shown that in order to obtain excellent fixing properties and strength, graphite should be added together with acicular titanium oxide.

  The polyimide tube of the present invention can be used as a base material for a fixing belt disposed in a fixing unit of an electrophotographic image forming apparatus.

DESCRIPTION OF SYMBOLS 1 Fixing belt 2 Heater 3 Pressure roller 4 Transfer material 5 Unfixed toner image 6 Fixing toner image 11 Polyimide tube 12 Adhesive layer 13 Fluororesin layer 21 Dispenser 22 Supply part 23 Applied polyimide varnish 24 Core body

Claims (5)

  A polyimide tube comprising a polyimide resin composition in which graphite and acicular titanium oxide are dispersed in a polyimide resin, wherein the total amount of graphite and acicular titanium oxide is 15 based on the total capacity of the polyimide resin composition. The blending amount of graphite is 28% by volume or less based on the total volume of the composition, and the blending ratio of acicular titanium oxide is 15 to 60 with respect to the total of graphite and acicular titanium oxide. A polyimide tube characterized by a volume%.   2. The polyimide tube according to claim 1, wherein an average particle diameter of the graphite is 0.3 μm or more and 30 μm or less.   3. The polyimide according to claim 1, wherein an average diameter of the acicular titanium oxide is 0.3 μm or more and 30 μm or less, and an average length is 0.10 μm or more and 1000 μm or less. tube.   The polyimide tube according to any one of claims 1 to 3, wherein the polyimide tube has a thickness of 10 to 150 µm.   A polyimide tube according to any one of claims 1 to 4 is used as a belt base material, and a fluororesin layer is provided on the outer peripheral surface of the belt base material directly or via an adhesive layer. Features a fixing belt.

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