JP2017102204A - Method for producing porous elastic member - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a porous elastic member which hardly causes hardness unevenness.SOLUTION: A method for producing a porous elastic member, which has a base 21, a porous silicone rubber elastic layer 23 and a surface layer of a fluororesin tube 49, includes the following steps (1) to (7): (1) tightly fixing the fluororesin tube 49 to the inner surface of a cylindrical outer die 30; (2) fixing the base 21 to the inner part of the cylindrical outer die 30 to form a cavity among the base 21, the fluororesin tube 49 and the two caps; (3) injecting an emulsified substance of a specific liquid silicone rubber mixture into the cavity; (4) sealing the inner part of the cavity and then heating the cavity to form a silicone rubber layer and to obtain a laminate; (5) removing the caps, and then evaporating water in the silicone rubber layer to obtain an elastic laminate containing the porous silicone rubber elastic layer 23; (6) taking out the elastic laminate from the cylindrical outer die 30; and (7) secondary working the elastic laminate.SELECTED DRAWING: Figure 6

Description

  The present invention relates to a method for producing a porous elastic member used in an electrophotographic copying apparatus, a printer, or the like.

  In general, a fixing device used in an electrophotographic toner image forming apparatus has a function in which a pair of members including a rotating body such as a roller and a roller heated by a heating body, a film and a roller, and a belt and a roller are pressed against each other. It has the composition to do. Here, a pair of members in pressure contact is referred to as a nip. When an image support such as paper to which toner is transferred passes through the nip, the unfixed toner image is heated and softened in the nip, pressed against the image support by the applied pressure, and then cooled and solidified to be fixed. A toner-fixed image is formed.

  In these fixing devices, an elastic member in which a heat-resistant elastic molded body is laminated in a single layer or multiple layers on a substrate formed of a metal or a heat-resistant resin is often used as a rotating body. Hereinafter, a layer made of an elastic molded body constituting the elastic member is referred to as an elastic layer. As a constituent material of the elastic layer, silicone rubber is widely used because of its excellent heat resistance and weather resistance.

  In recent years, attempts have been made to increase heating efficiency in the fixing device for the purpose of energy saving. For example, an elastic member using a porous silicone rubber molding for the elastic layer may be used for the purpose of efficiently supplying heat to the image support while preventing heat dissipation. In general, a porous silicone rubber molded body has a large number of pores inside and has a function of hindering the transfer of heat from a heating source because the thermal conductivity of air is low. For example, an uncured material of addition-curable liquid silicone rubber and water are mixed with a thickener, an emulsifier, etc. to make an emulsion, and then the silicone rubber component is crosslinked in a water-containing state to become porous. A porous silicone rubber molded body can be obtained by forming a rubber precursor and then dehydrating the precursor.

  Here, in order to arrange pores in the entire area of the porous silicone rubber molded body, it is desirable to prevent evaporation of the water-containing component during the formation of the precursor, and to crosslink the rubber component while containing moisture. In order to prevent moisture from evaporating from the precursor, it is effective to crosslink the container containing the precursor in a sealed state. In order to fabricate an elastic member used in the fixing device in a sealed state, a technique called a casting method is generally used. That is, a fluid molding material (emulsion) is poured into a cavity formed by an outer mold and a substrate, sealed, and then cured by heating, a curing agent, or the like.

  In Patent Document 1, an elastic member made of porous silicone rubber is manufactured by injecting an emulsion into a cylindrical cavity in which a rod serving as a shaft is arranged and heating in an oven set at 80 ° C. for 90 minutes. ing. In order to use this porous elastic member for a fixing device, a surface layer is generally provided on the surface of the porous silicone rubber layer.

  When a surface layer is installed on the porous silicone rubber layer described in Patent Document 1, a method of fixing a resin tube serving as a surface layer using an adhesive on the outer periphery of the porous silicone rubber layer, or a resin paint is sprayed There is a method in which a surface layer is formed by baking after coating. In the former, since the adhesive penetrates into the porous silicone rubber layer and solidifies, the porous property is partially lost and the product hardness tends to increase. In the latter case, high temperature is required for baking the paint, which may cause problems in rubber properties. When the elastic member is formed by a casting method as in Patent Document 1, there is a method in which a resin tube serving as a surface layer is arranged in advance on the inner surface of a cylindrical outer mold. In other words, by applying a primer made of a silane coupling agent having adhesiveness to the silicone rubber material in advance to the resin tube, the silicone rubber component can be cured and the resin tube can be integrated to form a surface layer. is there. According to this method, since the adhesive does not permeate, the porous portion of the porous silicone rubber layer is not lost during the formation of the surface layer, and a high temperature is not required to impair the properties of the silicone rubber.

  However, when the resin tube is installed in the cavity described in Patent Document 1, the elastic layer and the resin tube may expand and be damaged by the vapor pressure of water when moisture evaporates. In order to deal with such a problem, Patent Document 2 proposes a method of manufacturing a fixing roller in which a hole is inserted through the end face of the elastic layer after the rubber component is crosslinked to remove water.

WO09 / 142151 JP 2008-241739 A

  However, inserting the hole into the elastic layer may cause unevenness in roller hardness in the circumferential direction. Since unevenness in hardness in the circumferential direction causes unevenness in the pressure applied to the toner on the support and causes deterioration of the fixed image, the porous silicone rubber layer and the surface layer not depending on the method described in Patent Document 2 There is a demand for a method of integrating the two. The present invention is directed to providing a method for producing a porous elastic member in which hardness unevenness is unlikely to occur.

The present invention is a method for producing a porous elastic member comprising a substrate, an elastic layer containing porous silicone rubber on the peripheral surface of the substrate, and a fluororesin tube as a surface layer, the following (1) To (7), and the steps (1), (2), (3), (4), (5), (6) and (7) are performed in this order. It is a manufacturing method of a porous elastic member.
(1) A step of closely fixing a fluororesin tube to the inner surface of the cylindrical outer mold,
(2) fixing the base inside the cylindrical outer mold and forming a cavity between the base, the fluororesin tube and two caps;
(3) Emulsification of a liquid silicone rubber mixture containing polyorganosiloxane having two or more alkenyl groups in one molecule, polyorganosiloxane having two or more silicon-bonded hydrogen atoms in one molecule, and water Injecting an object into the cavity;
(4) A step of forming a silicone rubber layer by heating the emulsion after the inside of the cavity is sealed to obtain a laminate in which the substrate, the silicone rubber layer, and the fluororesin tube are laminated. ,
(5) After removing the cap, the laminated body is heated in the cylindrical outer mold to evaporate water in the silicone rubber layer, and the substrate, the porous silicone rubber elastic layer, and the fluorine Obtaining an elastic laminate comprising a resin tube;
(6) A step of taking out the elastic laminate from the cylindrical outer mold, and (7) a step of secondary processing the elastic laminate.

  According to the present invention, it is possible to obtain a porous elastic member in which the occurrence of hardness unevenness is suppressed.

It is a figure which shows typically the elastic layer of the porous elastic member of this invention. (A) is the schematic of the pressure roller of the fixing device as a porous elastic member of the present invention. FIG. 5B is a schematic cross-sectional view taken along the line A-A ′ in FIG. It is the schematic of the cylindrical outer mold | type used by this invention. It is the schematic for demonstrating the casting method used by this invention. It is the schematic which shows the state by which the fluororesin tube is return | folded and fixed to the opening both ends of the cylindrical outer mold | type used by this invention. It is the schematic explaining the process of evaporating a water | moisture content from the crosslinked porous rubber precursor used by this invention.

  Examples of the porous elastic member according to the present invention include a pressure roller and a fixing roller used in a fixing device.

  The details of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram of an elastic layer (porous silicone rubber layer). The elastic layer 1 is mainly composed of silicone rubber 2 and pores 3. The pores have a spherical shape or an indefinite shape, and have a diameter or a size of about 10 μm on one side. The holes do not exist independently, but exist as so-called open bubbles connected by a fine communication path (not shown). Silicone rubber is produced by reacting a polyorganosiloxane having two or more alkenyl groups and a polyorganosiloxane having at least two silicon-bonded hydrogen atoms in one molecule through a hydrosilylation reaction (crosslinking reaction) catalyst. Can be obtained by: If the state in which the hydrosilylation reaction has not progressed sufficiently is referred to as an uncrosslinked state, the elastic layer 1 is prepared by mixing an uncrosslinked material with water, an emulsifier, a thickener and the like to obtain an emulsified state, and then heating or the like. A porous rubber precursor (silicone rubber layer) in which a hydrosilylation reaction (crosslinking reaction) has proceeded and cured by means of a water-containing state by means, and then water is removed from the porous rubber precursor.

  FIG. 2A is an example of a porous elastic member obtained by the manufacturing method according to the present invention, and is a schematic diagram of a roller-shaped porous member that can be used as a pressure roller in a fixing device, for example. FIG. 2B is a schematic cross-sectional view taken along the line A-A ′ of FIG. In FIG. 2, 10 is a pressure roller, 21 is a base, 23 is an elastic layer, and 24 is a surface layer made of a fluororesin tube. Reference numeral 25 denotes a primer layer that integrates the base 21 and the elastic layer 23, and reference numeral 26 denotes a primer layer that integrates the surface layer 24 and the elastic layer 23. Each of the primer layers 25 and 26 contains a silane coupling agent having a function of integrating different materials.

  The constituent materials, raw materials, and manufacturing method of the porous elastic member of the present invention will be specifically described below using a pressure roller as an example.

[Substrate]
In order to apply an appropriate pressing force as a pressure roller of the fixing device, it is preferable to use a base made of a metal material. When the pressure roller is rotated in the circumferential direction by a motor or the like for paper passing, it is common to provide a bearing portion at the longitudinal end portion of the base and to rotate it by a motor via a gear. In response to such requirements, for example, a free-cutting steel (SUM material) excellent in pressurization and workability is used, and a substrate processed into a desired shape including a bearing portion is preferably employed.

[Elastic layer]
The elastic layer of the porous elastic member is a layer made of porous silicone rubber. The material for forming the elastic layer is a polyorganosiloxane having two or more alkenyl groups in one molecule, a polyorganosiloxane having two or more silicon-bonded hydrogen atoms in one molecule, and water. It is an emulsion of the liquid silicone rubber mixture containing. For example, a polyorganosiloxane having two or more alkenyl groups in one molecule (hereinafter sometimes referred to as “liquid A”), a polyorganosiloxane having two or more silicon-bonded hydrogen atoms in one molecule ( Hereinafter, it may be referred to as “Liquid B”), C liquid composed of water and an inorganic thickener, and emulsifier D for dispersing these A to C liquids.

[Liquid A]
Liquid A is a composition mainly composed of a polysiloxane compound having an alkenyl group, which is one of the addition reaction sites. A small amount of a platinum compound which is a hydrosilylation reaction (crosslinking reaction) catalyst can be previously contained in the liquid A. In addition, since A liquid is a colorless and transparent and highly viscous liquid, and it may be difficult to distinguish from B liquid, it is possible to mix in advance a coloring material such as Bengala that does not impair the function of the silicone rubber.

[Liquid B]
Liquid B is a composition containing a polysiloxane compound having silicon atom-bonded hydrogen, which is another addition reaction site, and other polyorganosiloxane compounds. The polysiloxane compound having silicon atom-bonded hydrogen is composed of a polyorganosiloxane having at least two silicon atom-bonded hydrogen atoms in one molecule, and acts as a crosslinking agent. In addition, since B liquid is a colorless and transparent and highly viscous liquid, and it may be difficult to distinguish it from the A liquid, a coloring material such as bengara that does not impair the function of the silicone rubber can be mixed in advance.

[C liquid]
Water, which is the main component of the liquid C, is for making the silicone rubber layer porous by removing it in the curing and dehydrating step after crosslinking the emulsion. The water may be clean, but ion exchange water is generally used. Here, since water has a lower viscosity than liquid A and liquid B, it is preferable to use a thickener to facilitate mixing and dispersion. As the thickener, there are various types of inorganic and organic types. In the present invention, an inorganic thickener is preferably used. Among these, it is preferable to use an inorganic thickener (Bengel W-200U, manufactured by Hojun Co., Ltd.) made of an organic polymer composite hydrophilic purified bentonite containing a smectite clay mineral because the viscosity of the liquid C can be easily adjusted. For example, C liquid can be used as a gel-like liquid material obtained by adding 99 to 97 parts by mass of ion-exchanged water to 1 to 3 parts by mass of Bengel W-200U and sufficiently stirring.

[Liquid D] Emulsifier In order to form an emulsion containing three liquids of liquid A, liquid B, and liquid C, emulsifier D is blended into a mixed liquid obtained by mixing these three liquids in a desired ratio. Various types of emulsifiers D can be employed, and any of anionic, cationic, zwitterionic and nonionic types may be used. Among them, it is particularly preferable to employ a nonionic surfactant because it has little influence on the hydrosilylation reaction catalyst. The emulsifier preferably has an HLB (Hydrophile-Lipophile Balance) value of 1.5 or more and less than 6. Moreover, the compounding quantity of an emulsifier is 0.2-3 mass parts with respect to 100 mass parts of C liquids, for example.

[Emulsion]
The components of the liquids A to D are weighed, and an emulsion in which an uncrosslinked component of silicone rubber and water are emulsified and dispersed is prepared using a known stirrer such as a planetary mixer. Here, the density of the elastic layer can be determined by controlling the ratio of the C liquid to the A liquid and the B liquid. The density of the elastic layer is designed according to the thermal characteristics and mechanical characteristics, but considering the mixing and dispersibility of the emulsion and the ease of water removal in the dehydration process described later, liquid A, liquid B, liquid C Each mixing ratio (mass%) is determined.

  In general, a blending ratio corresponding to “A liquid: B liquid: C liquid = 50: 50: 100 (porosity 50%)” is preferably used, but “A liquid: B liquid” in which the ratio of C liquid is reduced. : C liquid = 99: 99: 2 (porosity 1%) ”or“ liquid A: B liquid: C liquid = 40: 40: 120 (porosity 60%) ”with the ratio of C liquid increased. It can also be used at a blending ratio. These raw materials are put into a planetary mixer, a predetermined amount of liquid D is added, and the mixture is sufficiently stirred to obtain an emulsion for an elastic layer. In addition, after adding D liquid which is an emulsifier to any one or several components of A liquid, B liquid, or C liquid previously, three liquids, A liquid, B liquid, and C liquid, can also be mixed.

  Further, in order to improve the thermal characteristics of the elastic layer, it is also possible to add other fillers, for example, acicular fillers, to the above components to obtain an emulsion. In this case, it is necessary to employ a filler that does not affect the emulsification characteristics. Specifically, a carbon fiber filler having excellent thermal conductivity can be used as the needle filler.

[Fluoropolymer tube (surface layer)]
Examples of the material constituting the fluororesin tube include PFA (tetrafluoroethylene perfluoroalkyl vinyl ether copolymer) and the like. The material of the fluororesin tube is appropriately selected in consideration of the tight fixability to the inner surface of the cylindrical outer mold at the time of attachment, the releasability from the cylindrical mold at the time of molding removal, and the like. The fluororesin tube is a thin cylindrical part having both ends opened, and its size and shape are determined by the specifications of the electrophotographic copying apparatus, manufacturing restrictions, and the like. For example, a transparent fluororesin tube having an inner diameter of 29 mm, a length of 435 mm, and a thickness of 0.050 mm is used to manufacture an electrophotographic elastic member having an outer diameter of 30 mm and a total length of the paper passing portion of 330 mm. In addition, since the fluororesin generally has poor adhesiveness with different materials, it is generally used at the interface with different materials after surface treatment. For example, a fluororesin tube wet-treated with a liquid material such as liquid ammonia or sodium naphthalene, or a fluororesin tube dry-treated with a laser or the like is preferably used.

[Casting molding method]
Next, as an example of the method for producing the porous elastic member of the present invention, a method for producing a pressure roller used in the fixing device by a casting method will be described with reference to FIGS.

[Cylindrical outer mold]
FIG. 3 is a schematic diagram of the cylindrical outer mold 30. As the cylindrical outer mold, a thick metal material made of stainless steel or the like is used in consideration of the outer diameter accuracy of the product, deformation during use of the mold, deformation due to heating, and the like. For example, when an electrophotographic elastic member having an outer diameter of 30 mm is manufactured, the center of the diameter cross section of the cylindrical body having an outer diameter of 40 mm and a length of 372 mm is dug out. Pipe shape is adopted. The inner diameter of the cylindrical outer mold is appropriately set according to the degree of expansion / contraction during the process of the material to be used, but is about 30 mm when an electrophotographic roller having an outer diameter of 30 mm is manufactured. The shape of the both ends of the cylindrical outer mold is preferably a structure that can be fitted with a cap to be attached in a later process and maintain a hermetic seal. In addition, in order to maintain the sealed state securely, an O-ring is arranged on either the surface of the cylindrical outer mold or the cap surface at the fitting part with the cap to prevent leakage of the injected material, and at the time of heating. It is good also as a seal structure corresponding to internal pressure rise.

[cap]
A cap is a member arrange | positioned at the both ends of a cylindrical outer mold | type, and two caps form a cavity with a cylindrical outer mold | type. As the material of the cap, the same material as that of the cylindrical outer mold can be used.

[Primer between substrate and elastic layer]
The primer is a liquid containing a silane coupling agent, additives, various solvents and the like, and has a function of integrating the two by applying to the interface of different materials and drying. The silane coupling agent has two or more kinds of reactive groups in the molecule, that is, a hydrolyzable group (eg, alkoxyl group) that is compatible with an inorganic substance, and an organic functional group imparting adhesion to an organic component. . It can be combined with an organic component by an organic functional group that reacts and bonds with an inorganic component such as glass or metal by a hydrolyzable group and imparts adhesion to the organic component.

  In consideration of adhesiveness to silicone rubber, examples of the organic functional group include a vinyl group, a methacryl group, an epoxy group, and a SiH group. Various types of adhesive layers composed of silane coupling agents applicable to the present invention can be applied. For example, an alkoxyl group that hydrolyzes and condenses with the metal or metal oxide constituting the substrate and an SiH group that adheres to the vinyl group of the liquid uncrosslinked silicone rubber by an addition reaction in the molecule. At the same time.

[Primer between surface layer and elastic layer]
The primer between the surface layer and the elastic layer is a liquid containing the same silane coupling agent, additive, various solvents, etc. as the primer between the base layer and the elastic layer. Has the function of integrating. In order to develop an adhesive function by applying and drying the inner surface of the fluororesin tube fixed to the inner surface of the cylindrical outer mold, a primer that easily undergoes a condensation reaction with the surface-treated fluororesin interface is used. For example, a molecule that has an alkoxyl group that adheres by hydrolysis and condensation and a silicon atom-bonded alkenyl group (SiVi group) that adheres to the hydride group of liquid uncrosslinked silicone rubber by an addition reaction. It is.

〔Manufacturing process〕
The present invention is a method for producing a porous elastic member having a base, an elastic layer made of porous silicone rubber formed on the peripheral surface of the base, and a surface layer made of a fluororesin tube, It includes at least the steps (1) to (7), and the steps (1), (2), (3), (4), (5), (6) and (7) are performed in this order. It is characterized by.

[Step (1): Tightening and fixing tube]
This is a step of closely fixing the fluororesin tube to the inner surface of the cylindrical outer mold. As shown in FIG. 5, the fluororesin tube 49 inserted along the inner peripheral surface of the cylindrical outer mold 30 is folded back and fixed to the outer peripheral surface of the outer mold at the openings 31 and 32 at both ends of the cylindrical outer mold. It is fixed in the state. It is preferable that a primer between the surface layer and the elastic layer is applied on the entire inner surface of the fluororesin tube after being folded back and dried.

[Step (2): Formation of cavity]
In this step, the base is fixed inside the cylindrical outer mold, and a cavity is formed between the base, the fluororesin tube, and the caps at both ends of the cylindrical outer mold. In FIG. 4, a cavity 40 filled with a molding material (emulsion) includes a cylindrical outer mold 30, caps 33 and 34 that seal openings 31 and 32 at both ends of the cylindrical outer mold, and a cap 33, 34 is a space constituted by a metal base 41 having bearings 46 and 47 fixed to 34. The outer peripheral surface of the metal substrate is preferably subjected to primer treatment to form a primer layer.

[Step (3): Injection of emulsion]
An emulsion of a liquid silicone rubber mixture comprising a polyorganosiloxane having two or more alkenyl groups in one molecule, a polyorganosiloxane having two or more silicon-bonded hydrogen atoms in one molecule, and water. This is a step of injecting into the cavity. As an emulsion, what contains the above-mentioned AD liquid can be used. An acicular filler can be further contained in the emulsion.

  In FIG. 4, reference numeral 42 denotes an emulsion mainly composed of an uncrosslinked material and water, and reference numeral 43 denotes a pipe for filling the cavity with the emulsion, which is connected to the measuring instrument 50 through a valve 52. The emulsion containing the liquids A to D described above is introduced into a measuring instrument having an inner diameter of 40 mm by a method (not shown), and then the pusher 51 attached to the measuring instrument is pushed down, so that the inlet 45 is connected via the pipe 43. Can be injected into the cavity 40.

[Step (4): Formation of Laminate]
After the cavity is sealed, the emulsion is heated to form a silicone rubber layer to obtain a laminate in which the substrate, the silicone rubber layer, and the fluororesin tube are laminated. After confirming that the emulsion injected into the cavity has flowed out from the opening 44 provided in the cap 33 at the cavity end opposite to the injection port 45, the opening 44 can be sealed with a sealing plug member (not shown). it can. Then, after the piping 43 is removed, the cap 34 on the inlet 45 side can also be provided with a sealing member so that the inside of the cavity can be sealed.

  Next, the emulsion in the cavity is heated using a heating means such as a hot air circulating furnace to form a silicone rubber layer to obtain a laminate. In order to crosslink the rubber component in a state where moisture is retained, the heating temperature is preferably lower than the boiling point of water, for example, less than 100 ° C. at normal pressure. Further, although depending on the volume of the material and the heat capacity of the substrate to be used and the cylindrical outer mold, the heating time is generally from 30 minutes to 150 minutes.

[Step (5): Formation of elastic laminate]
After removing the cap, the laminated body is heated in the cylindrical outer mold to evaporate water in the silicone rubber layer to obtain an elastic laminated body comprising the base, the porous silicone rubber elastic layer, and the fluororesin tube. It is a process.

  By removing the caps 33 and 34 at both ends, as shown in FIG. 6, both ends of the cylindrical outer mold are opened, and the inside of the cylindrical outer mold has a base, a water-containing silicone rubber layer, a fluororesin tube, It will be in the state in which the laminated body in which was integrated. Next, by placing these in a heating space such as a hot air circulating furnace and heating the laminate, moisture can be evaporated from the crosslinked water-containing silicone rubber layer. As a result, the silicone rubber layer changes to a porous silicone rubber elastic layer. In the present invention, since water is evaporated while being externally regulated by the cylindrical outer mold, it is possible to prevent expansion of the elastic layer due to the vapor pressure of water and damage to the fluororesin tube.

  In the present invention, it is important to appropriately set the temperature and time of the dehydration step. When moisture evaporates during the process of making the silicone rubber layer porous, the water vapor passes through the fine communication passages in the silicone rubber, or the water vapor itself forms a communication passage, and from both ends of the member where the fluororesin tube does not exist. It is discharged into an open space. The heating conditions vary depending on the diameter and length of the elastic member and the thickness of the elastic member, but it is preferable to carry out the heating at a temperature of 100 ° C. or higher and 230 ° C. or lower. If the temperature is lower than 100 ° C., that is, lower than the boiling point of water at normal pressure, it takes a long time to evaporate water. If the temperature is higher than 230 ° C., the silicone rubber may be deteriorated.

  By the way, in the temperature measurement of the silicone rubber layer inside the cylindrical outer mold, the temperature may rise to the dehydration temperature after being held at around 120 ° C. for a certain time. For this reason, it is assumed that the inside of the cylindrical outer mold is in a positive pressure state due to the influence of water vapor. Therefore, a more preferable lower limit of the dehydration temperature is preferably a temperature higher than the boiling point of water at normal pressure, and a temperature higher than 120 ° C.

  On the other hand, for the purpose of promoting the generation and discharge of water vapor, if the ambient temperature is set to a high temperature, the entire length of the elastic member may be extended and protrude from both ends of the cylindrical outer mold to increase the total length. This is probably because the volume of water vapor increases and the rubber stretches toward the open ends. As a result of the examination, it has been found that the protrusion is large when the ambient temperature of the outer mold is 200 ° C. or more, and remains protruding without contracting to the original length after cooling. For this reason, the upper limit of the ambient temperature of more preferable dehydration is less than 200 ° C. The time required for dehydration can be determined by measuring the mass of each cylindrical outer mold. If the point at which the mass does not decrease with the progress of dehydration is taken as the end point of dehydration, the necessary dehydration time is within 4 hours at 125 ° C. and within 1.5 hours at 195 ° C. Further, if a transparent fluororesin tube is used, the completion of dehydration of the molded body taken out from the cavity can be determined by the color of the silicone rubber layer. That is, the water-containing silicone rubber layer is dark, while the portion where dehydration has progressed is light.

[Step (6): Removal of elastic laminate]
This is a step of taking out the elastic laminate from the cylindrical outer mold. Since the releasable fluororesin tube is in contact with the inner surface of the cylindrical outer mold, the elastic laminate can be easily taken out from the cylindrical outer mold.

[Step (7): Secondary processing]
This is a step of secondary processing of the elastic laminate. The elastic laminate taken out from the cylindrical outer mold is subjected to secondary processing. “Secondary processing” includes, for example, processing including shape processing of an elastic member such as secondary cross-linking for volatilizing low molecular components from silicone rubber, and end cutting for use in a fixing device. It is. Of these, the secondary crosslinking is desirably performed at a temperature higher than the dehydration temperature and at a temperature at which the rubber properties are not impaired, and can be generally performed by heating at 200 ° C. to 230 ° C. for 2 to 4 hours. Through the secondary processing, the porous elastic member of the present invention can be obtained. In the porous elastic member, the porosity of the porous silicone rubber layer is preferably 1% or more and less than 60%.

  EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these examples. In this example, the porous elastic member of the present invention was manufactured as a pressure roller for a fixing device for A3 paper. Prior to the examples, the following preparation operations [1] to [5] were performed.

[1] Preparation of metal substrate A free-cutting steel (SUM) processed into the following shape was obtained and used as a substrate.
First bearing part: outer diameter 8 mm, length 22 mm,
Parts other than the bearing part: outer diameter 24.5 mm, length 330 mm,
Second bearing part: outer diameter 8 mm, length 53 mm.

[2] Formation of Primer Layer on Substrate A primer (trade name: DY35-051, Toray Dow Corning Co., Ltd.) is applied to an elastic body forming portion (portion other than the bearing portion) of the substrate by a known method. The primer layer was formed by baking and fixing at 0 ° C.

[3] Preparation of cylindrical outer mold to which a fluororesin tube is fixed A transparent inner surface treated inside the cylindrical outer mold (inner diameter: 30.4 mm, outer diameter: 40.0 mm, length: 372 mm) shown in FIG. A fluororesin tube (outer diameter: 29.0 mm, length: 435 mm, thickness: 0.05 mm; manufactured by Gunze Co., Ltd.) is evenly inserted, and both ends of the tube (each length is 26) from both ends in the longitudinal direction of the cylindrical outer mold. .5 mm) protruded.

  A pair of diameter-enlarging claws (not shown), which is composed of a plurality of claws and whose diameter is larger than the inner diameter of the fluororesin tube by operation, was inserted into one end of the fluororesin tube in a reduced diameter state. Next, the diameter expansion claw was operated to expand the diameter of the fluororesin tube so that the inner diameter of the fluororesin tube was larger than the outer diameter of the cylindrical outer mold. At this point, the one end of the fluororesin tube and the diameter-enlarging claw were engaged by frictional force.

  While maintaining the expanded state, one end of the fluororesin tube was folded back to the outer peripheral surface of the outer mold by changing the relative positional relationship between the cylindrical outer mold and the fluororesin tube in the longitudinal direction. Next, an operation of moving the end face of the fluororesin tube engaged with the diameter-enlarging claw was performed, the engagement was canceled, and one end of the fluororesin tube was transferred to the outer peripheral surface of the mold and fixed in a folded state. The same operation was performed at the other end, and as shown in FIG. 5, the inserted fluororesin tube was folded back and fixed at both ends of the cylindrical outer mold.

[4] Formation of primer layer on fluororesin tube Primer (trade name: DY35-067, Toray Dow Corning Co., Ltd.) is applied to the inner surface of fluororesin tube 49 fixed to a cylindrical outer mold by a known method. After drying, a primer layer was formed.

[5] Preparation of Emulsion Liquid A rubber (trade name: DY35-561; Toray Dow Corning Co., Ltd.) was prepared as liquid A and liquid B. As a liquid C, 99 parts by mass of deionized water was added to 1 part by mass of Bengel W-200U, and the mixture was sufficiently stirred to prepare a gel-like liquid material in advance. A nonionic surfactant (sorbitan fatty acid ester, trade name: Ionette HLB4.3; Sanyo Chemical Industries, Ltd.) was prepared as the D liquid (emulsifier). Emulsions 1 to 3 for porous silicone rubber were prepared by adding the A to D liquids in a planetary mixer at the blending amounts (parts by mass) shown in Table 1 and sufficiently stirring them.

[Example 1]
1. Cavity formation, emulsion injection (steps (1) to (3))
A cavity was formed using the members and materials obtained in the preparation operations of [1] to [5], and set in the apparatus shown in FIG. Subsequently, the meter 1 was operated to introduce the emulsion 1 of Preparation Example 1 into the cavity from the pipe. After confirming that the emulsion had flowed out of the opening 44, both the opening 44 and the inlet 45 were sealed and the set of molds was removed from the pipe 43.

2. Emulsion heating, laminate formation (step (4))
The cavity was hermetically sealed, the mold assembly filled with the emulsion was placed in a hot air circulating furnace set at a temperature of 90 ° C., heated for 100 minutes, and then taken out.

3. Cap removal, water evaporation, elastic laminate formation (step (5))
The caps 33 and 34 disposed at both ends in the longitudinal direction of the cylindrical outer mold were removed, and both ends were opened as shown in FIG. 6, and a laminate of the base, the silicone rubber layer, and the fluororesin tube was included. A cylindrical outer mold was obtained. Next, the laminated body that was in a state regulated by the cylindrical outer mold was placed in a hot air circulating furnace at a temperature of 180 ° C., and the mass was measured as needed. The mass gradually decreased and eventually became a constant value. Finally, after 120 minutes, it was judged that moisture evaporation from the silicone rubber layer was completed.

4). Removal of the elastic laminate and secondary curing (steps (6) to (7))
When the elastic laminate including the substrate, the porous silicone rubber elastic layer, and the fluororesin tube was taken out from the cooled cavity, the porous silicone rubber elastic layer inside the fluororesin tube exhibited a light reddish brown color over the entire surface. Then, it put into the hot-air circulation furnace, hold | maintained at the temperature of 200 degreeC for 4 hours, adjusted the shape of the taken-out member, and completed the elastic member. The finished elastic member was not chipped or damaged, and as a result of observation, it was confirmed that the porous elastic body had pores formed in the porous silicone rubber elastic layer near the interface with the fluororesin tube. .

[Comparative Example 1]
The same steps (1) to (4) as in Example 1 were performed. Next, the caps 33 and 34 at both ends in the longitudinal direction were removed, and a laminate composed of the substrate, the silicone rubber layer, and the fluororesin tube was taken out from the cylindrical outer mold. Next, when this laminated body was placed in a hot air circulating furnace set at a temperature of 150 ° C. without restriction by a cylindrical outer mold, after 40 minutes from the placement, fluorine was deposited at a site 50 mm from the end of the laminated body. Damage to the resin tube and the silicone rubber layer was observed.

[Example 2]
Emulsion 1 of Preparation Example 1 is placed in a planetary mixer, blended so that the pitch-based carbon fiber (XN-100-25M; Nippon Graphite Fiber Co., Ltd.) is 5% by volume, and mixed to obtain Emulsion 4. It was. Steps (1) to (7) were carried out in the same manner as in Example 1 except that the emulsion 4 was used as the emulsion.

  In step (5), as in Example 1, it was determined that the evaporation of moisture from the silicone rubber layer was completed after 120 minutes. Further, in the elastic laminate taken out in the step (6), the porous silicone rubber elastic layer inside the fluororesin tube had a light reddish brown color over the entire surface. The finished elastic member taken out in step (7) has no chipping or breakage, and as a result of observation, pores exist in the vicinity of the interface with the fluororesin tube, and the porous elasticity coexists with the carbon fiber. It was confirmed to be a body.

[Comparative Example 2]
Steps (1) to (7) were performed in the same manner as in the example except that the temperature of the hot air circulating furnace in step (5) was 120 ° C. In the measurement of the mass in the step (5), the mass showed a tendency to gradually decrease and did not become constant after 240 minutes.

  As for the elastic laminated body taken out in the step (6), it was found that the central part of the porous silicone rubber elastic layer was dark and moisture remained. In this state, in the step (7), when placed in a hot air circulating furnace and heated to 200 ° C., damage to the fluororesin tube and the porous silicone rubber elastic layer was observed at the center of the elastic member after 30 minutes.

[Comparative Example 3]
Steps (1) to (7) were carried out in the same manner as in Example 1 except that the temperature of the hot air circulating furnace in step (5) was 200 ° C. In step (5), the mass gradually decreased and eventually became a constant value. Finally, after 100 minutes, it was judged that the evaporation of moisture from the silicone rubber layer was completed. When taken out from the hot air circulation furnace, the rubber molded body protruded from the cylindrical outer mold by about 20 mm.

  No damage was confirmed in the elastic laminate taken out in the step (6). In addition, the porous silicone rubber elastic layer inside the fluororesin tube had a light reddish brown color over the entire surface. When the shape of the elastic member taken out in step (7) was confirmed, it was found that the outer diameter and the hardness were different on the left and right of the member.

Example 3
Steps (1) to (7) were carried out in the same manner as in Example 1 except that the emulsion 2 of Preparation Example 2 was used as the emulsion and the temperature of the hot-air circulating furnace in Step (5) was 130 ° C. did. In step (5), the mass gradually decreased and eventually became a constant value. Finally, after 100 minutes, it was judged that the evaporation of moisture from the silicone rubber layer was completed.

  In the elastic laminate taken out in the step (6), the porous silicone rubber elastic layer inside the fluororesin tube had a light reddish brown color over the entire surface. The finished elastic member taken out in the step (7) is a porous elastic body in which no chipping or breakage is observed, and as a result of microscopic observation, pores are formed near the interface with the fluororesin tube. confirmed.

Example 4
Steps (1) to (7) were carried out in the same manner as in Example 1 except that the emulsion 3 of Preparation Example 3 was used as the emulsion, and the temperature of the hot-air circulating furnace in Step (5) was 160 ° C. did. In step (5), the mass gradually decreased and eventually became a constant value. Finally, after 150 minutes, it was judged that the evaporation of water from the rubber precursor was completed.

  In the elastic laminate taken out in the step (6), the porous silicone rubber elastic layer inside the fluororesin tube had a light reddish brown color over the entire surface. The finished elastic member taken out in the step (7) was not found to be chipped or damaged, and as a result of observation, it was confirmed that the porous elastic body had pores formed near the interface with the fluororesin tube. It was done.

  The above results are summarized in Table 2.

DESCRIPTION OF SYMBOLS 1 Elastic member 2 Silicone rubber 3 Hole 10 Pressure roller 21 Base | substrate 23 Porous silicone rubber elastic layer 24 Surface layer 25 Base | substrate-elastic layer primer 26 Surface layer-elastic layer primer 30 Cylindrical outer type | molds 31 and 32 Cylindrical shape Caps 40 Cavity 41 Base 42 with primer layer Emulsion 43 Piping 44 Cavity opening 45 Cavity inlet 46, 47 Bearing 49 Fluororesin tube 50 Measuring instrument 51 Pusher 52 Valve

Claims (4)

A method for producing a porous elastic member comprising a substrate, an elastic layer containing porous silicone rubber on the peripheral surface of the substrate, and a fluororesin tube as a surface layer,
The following steps (1) to (7) are included, and the steps (1), (2), (3), (4), (5), (6) and (7) are performed in this order. A method for producing a porous elastic member, characterized in that:
(1) A step of closely fixing a fluororesin tube to the inner surface of the cylindrical outer mold,
(2) fixing the base inside the cylindrical outer mold and forming a cavity between the base, the fluororesin tube and two caps;
(3) Emulsification of a liquid silicone rubber mixture containing polyorganosiloxane having two or more alkenyl groups in one molecule, polyorganosiloxane having two or more silicon-bonded hydrogen atoms in one molecule, and water Injecting an object into the cavity;
(4) A step of forming a silicone rubber layer by heating the emulsion after the inside of the cavity is sealed to obtain a laminate in which the substrate, the silicone rubber layer, and the fluororesin tube are laminated. ,
(5) After removing the cap, the laminated body is heated in the cylindrical outer mold to evaporate water in the silicone rubber layer, and the substrate, the porous silicone rubber elastic layer, and the fluorine Obtaining an elastic laminate comprising a resin tube;
(6) A step of taking out the elastic laminate from the cylindrical outer mold, and (7) a step of secondary processing the elastic laminate.   The method for producing a porous elastic member according to claim 1, wherein in the step (3), a needle-like filler is further added to the emulsion.   The method for producing a porous elastic member according to claim 1, wherein the porosity of the porous silicone rubber layer is 1% or more and less than 60%. 2. The method for producing a porous elastic member according to claim 1, wherein in the step (5), the heating temperature is higher than 120 ° C. and lower than 200 ° C. 3.

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