JP2008145832A - Heat insulating roller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a heat insulating roller which has a remarkably low heat conductivity and is superior in thermal resistance and mechanical strength. <P>SOLUTION: The heat insulating roller includes a core bar and a cylinder layer formed on an outer periphery of the core bar, and the cylinder layer is made of a composite material of a porous base and an aerogel and is obtained by a method including a step of forming a cylinder layer of the porous base on the outer periphery of the core bar and a step of impregnating the cylinder layer of the porous base with an aerogel precursor and drying it in a super-critical area. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a heat insulating roller including a shaft core and a cylindrical body layer made of a composite material of a porous base material and an airgel formed on the outer periphery of the shaft core, and particularly mounted in an electrophotographic apparatus such as an electrophotographic copying machine or a printer. The present invention relates to a heat insulating roller used in a heat fixing apparatus.

  An electrophotographic apparatus such as an electrostatic copying machine or a laser printer projects an optical image onto a uniformly charged photoreceptor surface in the dark, and an electrostatic latent image corresponding to the optical image is formed on the photoreceptor surface. The image is developed by spraying charged toner, which is a developer, on the surface of the photoconductor and electrostatically adhering it, and the surface of the printing paper charged to the opposite polarity to the charge of the toner is superimposed on the surface of the photoreceptor. The image is copied by transferring it onto a paper surface and heating and melting the toner on the paper surface under pressure by a heat fixing roller and then heat-fixing the toner on the paper surface.

  As the heat fixing device portion for fixing the toner on the paper surface with the heat fixing roller, the heat fixing roller is usually composed of two rollers, a heat fixing roller and a pressure roller, or a heat fixing roller, a pressure roller and a conveying roller. And a roller having an endless belt wound between one of a heat fixing roller or a pressure roller and a conveying roller. That is, the printing paper is supported from the back side by a pressure roller or a pressure roller via an endless belt, and is pressed and heated by a heat fixing roller heated from the front side, so that the toner on the paper surface is fused. Heat fixing. The temperature of the heat fixing roller is generally about 150 to 200 ° C. However, when the temperature of the roller is increased, it may be temporarily reached due to overshoot.

  In order to fuse the toner on the paper surface by the heat fixing roller, it is heated to a high temperature capable of fusing, but when the heat fixing operation is performed, the printing paper or pressure roller, which is always much lower than the heat fixing temperature, Or since it contacts and rotates with the endless belt, a large amount of heat energy is taken away and cooled at that moment. For this reason, the heat fixing roller needs to be heated to a higher temperature in anticipation of cooling due to such contact, and power consumption increases. Therefore, the pressure roller is required to have a low thermal conductivity, that is, heat insulation. Further, since the pressure roller is in contact with the high-temperature heat fixing roller, heat resistance and mechanical strength are also required.

  As a solution to this problem, it is composed of a shaft core and a cylindrical body layer of porous ceramics formed on the outer periphery of the shaft core, and the cylindrical body layer is mainly composed of 100 parts by weight of an inorganic fiber binder and a heat-resistant inorganic material. And a heat insulating pressure roller having an average thermal conductivity of the cylindrical body layer of 0.05 to 0.5 W / m · K has been proposed (Japanese Patent Laid-Open No. 2005-173433).

On the other hand, Japanese translations of PCT publication No. 2004-517222 discloses a composite material product that acts as a flexible and durable lightweight insulating product including an airgel and a reinforcing structure, and the reinforcing structure is a A composite product comprising a lofty fiber vat that does not substantially reduce thermal performance when compared to an airgel body made of the same material but not reinforced is disclosed. The thermal conductivity of such composite material products is as low as 0.0124 to 0.0174 W / m · K.
JP 2005-173433 A JP 2004-517222 A

  Although the average heat conductivity of the heat insulating pressure roller disclosed in Japanese Patent Application Laid-Open No. 2005-173433 is generally low, in recent years, for example, there has been a demand for further shortening of the warm-up time of the fixing roller. It has been demanded. In addition, JP-A-2004-517222 does not disclose that the composite material is suitable for the cylindrical body layer of the heat insulating roller, and the fiber bat having a higher orientation is used as a base material, so that the mechanical strength is sufficient. However, there is a problem that it cannot be used for the cylindrical body layer of the heat insulating roller.

  Accordingly, an object of the present invention is to provide a heat insulating roller having a remarkably low thermal conductivity and excellent heat resistance and mechanical strength.

  In such a situation, the present inventors have intensively studied, and as a result, a roller comprising a shaft core and a cylindrical body layer formed on the outer periphery of the shaft core, the cylindrical body layer comprising a porous substrate and an airgel In the case of the heat insulating roller which is a composite material of the above, the present inventors have found that the thermal conductivity of the cylindrical body layer is remarkably low and excellent in heat resistance and mechanical strength, and the present invention has been completed.

  That is, the present invention is a roller including a shaft core and a cylindrical body layer formed on the outer periphery of the shaft core, wherein the cylindrical body layer is a composite material of a porous base material and an airgel. An insulating roller is provided.

  Moreover, this invention provides the manufacturing method of the heat insulation roller which has the process of winding the composite material of an airgel and a porous base material around an axial center.

  In addition, the present invention includes a step of forming a cylindrical layer of a porous substrate on the outer periphery of the shaft core, a step of impregnating the cylindrical layer of the porous substrate with an airgel precursor, and drying in a supercritical region. A method for manufacturing a heat insulating roller is provided.

  Since the heat conductivity of the heat insulating roller of the present invention is remarkably low, even when the roller is heated to a high temperature such as 150 ° C., heat is not taken away, and heat energy can be saved. The heat insulating property of the heat insulating roller of the present invention is far higher than that of a ceramic heat insulating roller, which has been conventionally considered to have a low thermal conductivity, and can greatly contribute to energy saving. Moreover, it is excellent in heat resistance and mechanical strength.

  The heat insulating roller of the present invention comprises an axial core and a cylindrical body layer in order from the center to the outside, and the cylindrical body layer is a composite material of a porous substrate and an airgel. As the shaft core, a metal shaft core such as iron, stainless steel, aluminum, copper, or brass is preferable in that it has rigidity to withstand use. The present invention exhibits a particularly remarkable effect when a metal shaft core is used as the shaft core. That is, since the thermal conductivity of the metal shaft core is much higher than that of the cylindrical body layer, the heat source from the heating roller or the like is easily lost through the cylindrical body layer. For this reason, the present invention is particularly advantageous in the case of the present invention in which the thermal conductivity of the cylindrical body layer is remarkably small. There may be an adhesive layer between the shaft core and the cylindrical body layer.

  The cylindrical body layer is made of a composite material of a porous substrate and an airgel. The porous substrate is a reinforcing material used to increase the strength of the cylindrical body layer, and examples thereof include porous ceramics, silicon rubber, and nonwoven fabric. Since such a porous substrate is included in the cylindrical body layer, the heat insulating roller of the present invention has high heat resistance and mechanical strength.

  As the porous ceramics, those having high heat insulation, high heat resistance, and high strength expressed by low thermal conductivity and low heat capacity are suitable. Specifically, ceramics mainly composed of an inorganic binder and a heat resistant inorganic material. (Hereinafter also referred to as a first ceramic) and ceramics mainly composed of calcium silicate (hereinafter also referred to as a second ceramic).

  The first ceramic is a known ceramic used for the cylindrical layer of the heat insulating roller, and is disclosed in, for example, Japanese Patent Application Laid-Open No. 2004-301293. The first ceramic is usually composed of 100 parts by mass of an inorganic binder and 0 to 500 parts by mass of a heat-resistant inorganic material.

  The inorganic binder is a material that itself becomes a ceramic component in the firing step and consolidates the inorganic materials. The inorganic binder is not particularly limited, and examples thereof include glass frit, colloidal silica, alumina sol, silica sol, sodium silicate, titania sol, lithium silicate, and water glass. These inorganic binders can be used alone or in combination of two or more.

  Examples of the heat resistant inorganic material include fibrous materials and particulate materials, and examples of the fibrous heat resistant inorganic material include alumina silica fiber, alumina fiber, chrysotile, carbon fiber, glass fiber, slag wool, silica fiber. Zirconia fiber, gypsum whisker, silicon carbide fiber, potassium titanate whisker, aluminum borate whisker, high silicate fiber, fused silica fiber and rock wool. In addition, these fibrous heat resistant inorganic materials can be used individually by 1 type or in combination of 2 or more types.

  Examples of the particulate heat-resistant inorganic material include clay, calcium carbonate, talc, silica, aluminum, magnesium oxide, calcium oxide, zirconia, titania, sepiolite, kaolin, zeolite, silicon nitride, aluminum nitride, aluminoborosilicate, aluminosilicate, and Examples thereof include porous carbon. Moreover, hollow materials, such as hollow ceramics and a glass balloon, can also be used as a particulate heat-resistant inorganic material. In addition, these particulate heat-resistant inorganic materials can be used individually by 1 type or in combination of 2 or more types.

  The length of the fibrous heat-resistant inorganic material or the long diameter of the particulate heat-resistant inorganic material is not particularly limited, and is preferably 3 mm or less in consideration of dispersibility in water, extrusion moldability, and the like. Further, the diameter of the fibrous heat-resistant inorganic material and the diameter of the particulate material are preferably slightly thick, for example, 1 to 15 μm, in order to reduce the internal heat capacity of the heat insulating roller as a product. Similarly, it is also preferable to use a hollow fibrous or particulate heat-resistant inorganic material having pores inside in order to further reduce the internal heat capacity.

  The heat-resistant inorganic material is an optional component, but is preferably used from the viewpoint of improving heat resistance and strength. The usage-amount of this heat resistant inorganic material is 0-500 mass parts with respect to 100 mass parts of inorganic binders, Preferably it is 100-300 mass parts. When the amount used exceeds 500 parts by mass, the strength of the obtained cylindrical body layer becomes insufficient.

The bulk density of the first ceramic is usually 0.2 to 1.5 g / cm ³ , preferably 0.2 to 1.0 g / cm ³ , and its heat capacity is 1 × 10 ^{−4 to} 1.5 ×. 10 ⁻³ KJ / K · cm ³ , and the thermal conductivity is 0.1 to 1.0 W / m · K, preferably 0.1 to 0.58 W / m · K.

  In the second ceramic, calcium silicate is not particularly limited, and is a compound formed by hydrothermal reaction of a siliceous raw material and a calcium raw material in the presence of water. Examples of calcium silicate crystals include zonotlite crystals, tobermorite crystals, and amorphous C—S—H crystals. These crystals may be single crystals or crystals in which two or more are mixed, but single crystals are preferred. In particular, a molded body made of zonotlite crystals is preferable because it is lightweight, has a very high specific strength, and is excellent in heat resistance and heat insulation. Zonotolite crystals are assembled and bonded to form secondary particles. Such a crystal can be easily identified by X-ray diffraction on the surface of the cylindrical body layer.

  The secondary particles of the zonotlite crystals have a clear spherical shape, and acicular zonotrite crystals are precipitated in the shape of chestnuts on the surface of the particles, and the inside is in the state of a cavity or close to it. Therefore, when it shape | molds using this secondary particle, it will be very bulky and will have a low thermal conductivity and heat capacity. Moreover, since it couple | bonds together by the self-hardening property of this secondary particle, it has the outstanding intensity | strength even if it is lightweight.

The bulk density of the second ceramic is 0.05 to 0.7 g / cm ³ , preferably 0.2 to 0.4 g / cm ³ . Further, the heat capacity of the ceramic of the cylindrical body layer is 0.04 to 0.65 J / K · cm ³ , preferably 0.04 to 0.4 J / K · cm ³ . Moreover, the thermal conductivity of the ceramic of the cylindrical body layer is 0.01 to 0.15 W / m · K, preferably 0.06 to 0.09 W / m · K.

As the silicon rubber, a known one can be used, and a sponge-like one is preferable. The silicon rubber has a bulk density of 0.4 to 1.0 g / cm ³ and a thermal conductivity of 0.08 to 0.18 W / m · K. Moreover, it does not restrict | limit especially as a nonwoven fabric, The nonwoven fabric which consists of an aramid fiber felt, a polyethylene terephthalate (PET), polyester, glass fiber, ceramic fiber etc. is mentioned. The nonwoven fabric has a bulk density of 0.1 to 0.6 g / cm ³ and a thermal conductivity of 0.05 to 0.12 W / m · K.

  Aerogels are created by removing the interstitial mobile solvent phase from the pores of a gel structure with open cells supported by a polymeric material at temperatures and pressures above the critical point of the solvent. . Therefore, the airgel has a low density and a cluster structure in which spherical fine particles having an average of 2 to 7 nm are fused. The airgel has an open cell structure having an average diameter of 2 to 7 nm and a large surface area. Airgel efficiently suppresses heat transfer due to convection because air cannot convect beyond the lattice structure. For this reason, it shows amazing heat insulation. The average size and density of the pores can be controlled during manufacture.

  Examples of the airgel include inorganic airgel and organic airgel. Inorganic aerogels are based on metal alkoxides and include materials such as silica, carbides and alumina. Organic airgel includes polymer airgel such as carbon airgel and polyimide. Among these, silica airgel is preferable because it has many production examples and is easily available. The manufacturing method of an airgel is described in Japanese translations of PCT publication No. 2004-517222, for example.

The structure of the composite material composed of the porous base material and the airgel is a composite structure of a porous base material structure and an airgel lattice structure. The bulk density of the cylindrical body layer is 0.05 to 0.5 g / cm ³ , preferably 0.1 to 0.3 g / cm ³ .

Moreover, the heat capacity of the cylindrical body layer is 0.04 to 1.5 J / K · cm ³ , and preferably 0.04 to 0.4 J / K · cm ³ . The cylindrical body layer has a thermal conductivity of 0.01 to 0.1 W / m · K, preferably 0.01 to 0.08 W / m · K.

The heat capacity (KJ / cm ³ ) can be calculated from the value of bulk density by pulverizing a sample, measuring 50 g of the sample using a high temperature sample dropping type specific heat measuring device, and measuring the specific heat. The thermal conductivity (W / m · K) is a rapid thermal conductivity meter in accordance with JIS R2618 unsteady hot wire method on the surface of a flat plate-shaped specimen having a width of 100 mm, a thickness of 20 mm, and a length of 50 mm. It is measured at room temperature using QTM-500 (manufactured by Kyoto Electronics Industry Co., Ltd.).

  As a method for producing a composite material composed of a porous substrate and an airgel, a production method (hereinafter referred to as “first method”) having a step of winding a composite material of an airgel and a porous substrate around a shaft core, and Examples of the production method include a step of forming a cylindrical body layer of a porous base material on the outer periphery of the shaft core, a step of impregnating an airgel precursor into the cylindrical body layer of the porous base material, and drying in a supercritical region ( Hereinafter, it is referred to as “second method”).

  In the first method, a composite material of an airgel and a porous base material (hereinafter also referred to as “airgel porous base material”) impregnates a porous base material such as a nonwoven fabric with an airgel precursor in a supercritical region. Obtained by drying. When the airgel is a silica airgel, first, after hydrolyzing a silane compound such as tetraethoxysilane, tetramethoxysilane, tetra-n-propoxysilane, etc., at a low pH as a polymer such as polysilicate ester, for example, polydiethoxysiloxane. A stabilized silica precursor is obtained. Next, a silica precursor and an alcohol such as ethanol are mixed and stirred for a predetermined time to obtain a silica precursor solution.

  Next, for example, a silica precursor solution is poured into a container containing a porous substrate, and the porous substrate is impregnated with the silica precursor solution. Gelation is caused by adding an acid such as hydrochloric acid, sulfuric acid or hydrofluoric acid to the silica precursor solution while stirring. As for the mixing | blending capacity ratio of a silica precursor and alcohol, the silica precursor 0.1-5.0 is suitable with respect to alcohol 1.0.

  When the gelled porous substrate is aged and then subjected to a supercritical drying treatment, and alcohol is removed from the gel, a silica airgel having the porous substrate as a reinforcing substrate, that is, an airgel porous substrate is formed. The supercritical drying process can be performed by first replacing the alcohol with liquid acetone and then placing carbon dioxide on the critical point. Good gradient elution can be achieved by using liquid acetone. Eventually, all the liquid in the gel is replaced with gas without compromising the structure of the gel.

  In order to wind the airgel porous substrate around the shaft core, as shown in FIG. 1, the tape-shaped porous substrate may be wound spirally so that the side end faces are abutted and the surface does not rise. In addition, the porous substrate may be formed into a tape shape before producing the airgel porous substrate, or the airgel porous substrate may be cut into a tape shape and used in the next step. The porous substrate used in the first method is flexible and is preferably a nonwoven fabric.

  In the second method, first, a step of forming a cylindrical body layer of a porous substrate on the outer periphery of the shaft core is performed. The step of forming the cylindrical body layer of the porous base material on the outer periphery of the shaft core can be performed by a known method. That is, when the porous substrate is the first ceramic, normally, in addition to the inorganic binder and the heat-resistant inorganic material, water is added to a mixture mainly composed of an organic binder and, if necessary, a water-resistant organic material. In addition, after the mixture obtained by the kneading step for preparing the aqueous mixture is subjected to steps including a forming step, a drying step and a firing step, the first ceramic is manufactured, and the product is processed into a predetermined shape, and then the shaft core The method of attaching to the outer periphery of is mentioned. Moreover, when a porous base material is sponge-like silicon rubber, the method of installing a shaft core in a shaping | molding die and attaching silicon rubber to the outer periphery of a shaft core by cast molding is mentioned.

  Further, when the porous substrate is the second ceramic, a crystallization step of obtaining calcium silicate crystals by heating the siliceous raw material and the calcareous raw material together with a large amount of water to a high temperature while stirring in an autoclave; The second ceramic is manufactured through a step including a forming step of forming a calcium silicate crystal-containing shaped body from the slurry containing the calcium silicate crystal, and after processing the product into a predetermined shape, the outer periphery of the shaft core The method of attaching to is mentioned. The method for producing the second ceramic is disclosed in detail in JP-A No. 2006-171170.

  Examples of the method of attaching the porous substrate to the outer periphery of the shaft core include, for example, a method of inserting a shaft core in which an adhesive has been applied in advance into a hollow portion of a cylindrical porous substrate, and a semi-cylindrical porous material. A method in which an adhesive is applied to the inner surface formed on the inner side of the porous base material, and a pair of semi-cylindrical porous base materials are fixed on the shaft core, or formed on the shaft core and the outer periphery of the shaft core. For example, a method of injecting an adhesive from a gap between the porous substrates may be used.

  In the second method, the step of impregnating the airgel precursor into the cylindrical layer of the porous substrate and then drying in the supercritical region is performed. The method for impregnating the airgel precursor into the cylindrical layer of the porous substrate can be performed by the same method as the method for producing the composite material of the airgel and the porous substrate. In the second method, the silica precursor solution is poured into a container that houses a structure in which a cylindrical porous substrate is attached to the outer periphery of the shaft core. The porous base material used in the second method is a first ceramic, a second ceramic, silicon rubber, and a nonwoven fabric, and preferably a first ceramic, a second ceramic, and a sponge-like silicon rubber. .

  In the heat insulating roller of the present invention, the outer circumference of the cylindrical body layer can be further coated with an inorganic layer such as a fluororesin layer such as a PFA resin film or a glass layer. Such a coating layer can be formed by a known method.

  The adhesive that bonds the shaft core and the cylindrical body layer is not particularly limited as long as it forms an adhesive layer exhibiting the above-described elasticity after curing, and a known one can be used. Examples of such an adhesive include what is generally referred to as liquid silicone rubber, including a soft paste and a fluid. Examples of the liquid silicone rubber include what is called a room temperature curing type and what is called a heat curing type. The liquid silicone rubber is a fluid liquid silicone rubber having a viscosity of 50 Pa · s or higher at 23 ° C., preferably 100 to 500 Pa · s at 23 ° C., or is difficult to measure the viscosity. There are those belonging to a certain soft paste-like liquid silicone rubber. If the viscosity of the liquid silicone rubber is too low, defects may easily occur when the pores of the cylindrical body layer are closed and filled with excessive penetration into the cylindrical body layer.

  Since the heat insulating roller of the present invention has a remarkably small bulk density and a remarkably small heat capacity and heat conductivity, the heat insulating property is remarkably excellent. Moreover, since the cylindrical body layer of the heat insulating roller includes a porous base material that has been conventionally used as a cylindrical body layer as a reinforcing material, it has high heat resistance and mechanical strength. Therefore, it can be used for rollers that are required for heat insulation used in a heat fixing device mounted on an electrophotographic apparatus such as an electronic copying machine or a printer. In other words, the heat insulating roller of the present invention can be used in various names, for example, a fixing roller, a pressure roller, a conveyance roller, an auxiliary roller, a drive roller, a peeling roller, a tension roller, a driving roller, A guide roller etc. are mentioned.

  EXAMPLES Next, although an Example is given and this invention is demonstrated more concretely, this is only an illustration and does not restrict | limit this invention. In Examples and Comparative Examples, each evaluation item shown in Table 1 was measured by the following test method.

(1) Bulk density (g / cm ³ ): Calculated from the mass of the test piece and the volume calculated from the shape dimensions.
(2) Thermal conductivity of the heat insulating roller: As shown in FIG. 2, a measurement probe is brought into contact with the surface (circumferential surface) of the heat insulating roller, and a rapid thermal conductivity meter QTM-500 according to JIS R2618 unsteady hot wire method. It was measured at room temperature (by Kyoto Electronics Co., Ltd.). The thermal conductivity of the heat insulating roller is calculated from ΔT for 30 to 60 seconds from the start of measurement.
(3) Heating rate test up to 180 ° C .; heat insulating roller in which a heat insulating layer 32 is provided around the shaft core 31 with a total load of 30 kgf on a heating roller 20 having an outer diameter of 40 mm using a halogen lamp 21 as shown in FIG. 30 was pressed, and the time (seconds) for the heating roller 20 to reach 180 ° C. at a rotation speed of 100 rpm was measured.

(Production of airgel nonwoven fabric)
The aramid fiber felt was prepared by impregnating a silica airgel precursor into a tape-shaped non-woven fabric having a thickness of 2 mm and a density of 0.1 g / cm ³ and drying in a supercritical region. That is, first, tetraethoxysilane was hydrolyzed, and then polydiethoxysiloxane (silica precursor) stabilized at a low pH was obtained. Next, the silica precursor and ethanol were mixed to obtain a silica precursor solution. Next, the silica precursor solution was poured into a container containing the tape-shaped nonwoven fabric, and the nonwoven fabric was impregnated with the silica precursor solution. The silica precursor solution was gelled by adding 2% by volume of hydrofluoric acid to the solution while stirring. The gelled nonwoven fabric was aged overnight in a 50 ° C. ethanol bath and sealed. Thereafter, a subcritical and supercritical carbon dioxide gas extraction treatment was performed, and alcohol was removed from the gel over 4 days to prepare a composite material of silica airgel and nonwoven fabric. A part of the tape-shaped silica airgel nonwoven fabric was cut and used for measurement of thermal conductivity.

(Production of heat insulation roller)
A silicone rubber adhesive (“KE45” (manufactured by Shin-Etsu Chemical Co., Ltd.)) was applied to the outer peripheral surface of a SUS shaft core having an outer diameter of 36 mm and a length of 300 mm, and a silica airgel nonwoven fabric was wound in a spiral shape. Next, a silicone rubber adhesive similar to that described above was applied to the outer peripheral surface of the silica airgel nonwoven fabric, and a PFA tube having a thickness of 30 μm was inserted to produce a heat insulating roller. The two adhesive layers were applied so that the thickness after curing was 50 μm.

  About the obtained heat insulation roller, roller thermal conductivity was measured and the temperature increase rate test to 180 degreeC was done. The results are shown in Table 1. In addition, the thermal conductivity of the heat insulating roller was also measured every time a fixed time elapses until 60 seconds after heating. When the thermal conductivity calculated from ΔT from the beginning to 60 seconds does not change, it can be said that the heat insulation is high without being influenced by the shaft core. The result is shown in FIG.

(Formation of zonotlite crystals)
Quick lime (150 mesh Adachi quick lime) as a calcareous raw material was put into 24 times amount of 90 ° C. hot water and digested for 30 minutes while stirring with a stirring blade rotating at 160 rpm to obtain lime milk. Subsequently, silica powder (Izu silica special powder D) as a siliceous raw material is added to the obtained lime milk so that the CaO / SiO ₂ molar ratio is 1.0, and at the same time, the total of quick lime and silica powder 30 times the amount of water was added to make a uniform slurry, and the mixture was hydrothermally reacted for 4 hours at a pressure of 16 kg / cm ² while stirring at 120 rpm in an autoclave. The solid in the obtained slurry was substantially composed of zonotolite crystals, and formed spherical secondary particles having a diameter of 30 to 130 μm in which a large number of needle crystals were aggregated.

(Slurry adjustment)
7 parts by weight of Portland cement ("ordinary Portland cement"; manufactured by Ube Mitsubishi Cement Co., Ltd.) and 5 parts by weight of glass fibers ("ECS131-33G"; manufactured by Nippon Electric Glass Co., Ltd.) are added to the slurry. Then, 100 ppm of a flocculant (“San Flock N-0P” manufactured by Sanyo Chemical Industries) was added and mixed to obtain a slurry for dehydration press molding. The slurry was poured into a mold, subjected to dehydration press molding at a molding pressure of 10 kgf / cm ² , dried at 100 ° C. for 12 hours, and a board having a length of 350 mm, a width of 350 mm, a thickness of 30 mm, and a density of 0.20 g / cm ³ A shaped molded body was obtained.

(Production of heat insulation roller intermediate)
A prismatic shaped piece having a length of 40 mm, a width of 40 mm and a length of 300 mm was cut out from the obtained board-like shaped body. A through hole having a diameter of 36.4 mm was formed at the center along the length direction of the molded body piece. A cold-curing silicone rubber adhesive (“KE422” manufactured by Shin-Etsu Chemical Co., Ltd.) was applied in advance to the through hole, and then a stainless steel shaft core was inserted. After confirming that the molded piece was fixed to the shaft core, the outer diameter of the molded piece was ground to obtain a cylindrical surface layer having a thickness of 2 mm.

(Production of heat insulation roller)
The cylindrical surface layer of the heat insulating roller intermediate was impregnated with a silica airgel precursor and dried in a supercritical region. That is, first, tetraethoxysilane was hydrolyzed, and then polydiethoxysiloxane (silica precursor) stabilized at a low pH was obtained. Next, the silica precursor and ethanol were mixed to obtain a silica precursor solution. Next, a silica precursor solution was poured into a container containing the heat insulating roller intermediate, and the cylindrical surface layer was impregnated with the silica precursor solution. The silica precursor solution was gelled by adding 2% by volume of hydrofluoric acid to the solution while stirring. The gelled heat insulating roller intermediate was aged overnight in a sealed state in an ethanol bath at 50 ° C. Thereafter, a subcritical and supercritical carbon dioxide extraction process was performed, alcohol was removed from the gel over 4 days, and a heat insulating roller having a heat insulating layer made of a composite material of silica airgel and calcium silicate was obtained. Next, the same room temperature curing type silicone rubber adhesive as that described above was applied to the surface of the heat insulating layer, and a 30 μm thick PFA tube was inserted to produce a heat insulating roller. The adhesive layer on the shaft core side was applied so that the thickness after curing was 200 μm, and the adhesive thickness on the outer peripheral surface was 50 μm. Two of these heat insulating rollers were produced, and one of the two was used for measuring the thermal conductivity of the heat insulating layer.

  About the obtained heat insulation roller, roller thermal conductivity was measured and the temperature increase rate test to 180 degreeC was done. The results are shown in Table 1.

Comparative Example 1
A heat insulating roller was produced in the same manner as in Example 1 except that an aramid fiber felt having a density of 0.26 g / cm ³ not subjected to the silica airgel treatment was used in place of the silica airgel treated aramid fiber felt. The results are shown in Table 1. Further, in the same manner as in Example 1, the thermal conductivity was measured every certain time. The result is shown in FIG.

Comparative Example 2
(Preparation of cylindrical body layer)
The composition of the composition is 100 parts by weight of glass fiber, 100 parts by weight of glass frit as an inorganic binder, 60 parts by weight of polyethylene particles as a flammable organic substance, and 20 parts by weight of methylcellulose as an organic binder in 125 parts by weight of water. The mixture was kneaded with a double-arm kneader to obtain a plastic mixture, and then the plastic mixture was extruded to obtain a cylindrical body. The obtained cylindrical molded body was dried and cured at 105 ° C. for 5 hours, and then heated in the range from 300 to 400 ° C. for a total of 24 hours to burn off the contained polyethylene particles and methylcellulose component, and then Furthermore, a cylindrical low bulk density ceramic having an outer diameter of 41 mm, an inner diameter of 36.4 mm, and a length of 300 mm, which is further fired in the atmosphere at 600 ° C. for 3 hours to fuse the inorganic binder and integrate the inorganic components. Two bodies were obtained.

(Production of heat insulation roller)
Paste room temperature curable silicone rubber adhesive on the outer peripheral surface of a SUS shaft core having an outer diameter of 36 mm and a length of 300 mm and the inner peripheral surface of one of the two cylindrical low bulk density ceramic bodies ("KE422" manufactured by Shin-Etsu Chemical Co., Ltd.) is applied, and then the shaft core is inserted into a hollow portion of a cylindrical low bulk density ceramic, and the outer diameter is ground to a diameter of 40 mm, and the shaft core, adhesive layer, and cylindrical body A heat insulating roller consisting of a layer was obtained. The shaft core adhesive layer was applied so that the thickness after curing was 200 μm. Next, the same room temperature curing type silicone rubber adhesive as that described above was applied to the surface of the heat insulating layer, and a 30 μm thick PFA tube was inserted to produce a heat insulating roller. In addition, it apply | coated so that the adhesive agent thickness of an outer peripheral surface might be set to 50 micrometers.

  For the remaining low bulk density ceramic body, the bulk density was measured by the above-described method, and for the ceramic roller, the roller thermal conductivity was measured, and a temperature increase rate test up to 180 ° C. was performed. The results are shown in Table 1. Further, in the same manner as in Example 1, the thermal conductivity was measured every certain time. The result is shown in FIG.

Comparative Example 3
(Production of heat insulation roller)
A primer is applied to the outer peripheral surface of a SUS shaft core having an outer diameter of 36 mm and a length of 300 mm, set with a 30 μm PFA tube in a casting mold, casted with silicon foam rubber, and heat-cured after casting. A heat insulating roller consisting of a shaft core and a cylindrical body layer was obtained. With respect to the silicon rubber roller, the roller thermal conductivity was measured, and a temperature increase rate test up to 180 ° C. was performed. The results are shown in Table 1.

  From the results shown in Table 1, Examples 1 and 2 showed surprisingly low values of the roller thermal conductivity of 0.05 W / mK and 0.08 W / mK. Moreover, the temperature increase rate up to 180 ° C. was remarkably short as 24 seconds and 28 seconds. Moreover, from the result of FIG. 4, in Example 1, the value of thermal conductivity did not change at all even after 60 seconds had elapsed from the start of heating. A metal having high thermal conductivity is used for the shaft core of the heat insulating roller of the example and the comparative example, and the thickness is as thin as 2 mm. Therefore, it can be seen that the result of Example 1 is surprising, considering that the results of Comparative Examples 1 and 2 which are said to have high heat insulation properties are deprived of heat. Further, all of the example products had sufficient mechanical strength as a heat insulating roller.

The figure explaining the method of winding a porous base material around a shaft in a spiral shape. The figure explaining the method to measure the heat conductivity of a heat insulation roller. The figure explaining a temperature increase rate test apparatus. The figure which shows the relationship between the time from a heating start, and heat conductivity in the heat conductivity measuring method of an heat insulation roller.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Axis core 2 Spiral porous base material 3 Cylindrical body layer 4 Measurement probe 10, 10a Heat insulation roller 20 Heating roller 21 Halogen lamp 30 Heat insulation roller 31 Axis core 32 Heat insulation layer

Claims (7)

  A heat insulating roller comprising a shaft core and a cylindrical body layer formed on an outer periphery of the shaft core, wherein the cylindrical body layer is a composite material of a porous substrate and an airgel.   The heat insulating roller according to claim 1, wherein the airgel is an open-cell structure having an average diameter of 2 to 7 nm.   The heat insulating roller according to claim 1, wherein the airgel is a silica airgel. The cylindrical body layer has a bulk density of 0.05 to 0.5 g / cm ³ and a thermal conductivity of 0.01 to 0.1 W / m · K. Insulating roller as described in.   The heat insulating roller according to claim 1, wherein the heat insulating roller is used in a heat fixing device of an electrophotographic apparatus.   A method for producing a heat insulating roller, comprising a step of winding a composite material of an airgel and a porous substrate around a shaft core.   Heat insulation comprising: forming a cylindrical body layer of a porous base material on an outer periphery of the shaft core; impregnating an airgel precursor into the cylindrical body layer of the porous base material and drying in a supercritical region Roller manufacturing method.

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