JP2005169916A - Manufacturing method of foam roller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a foam roller having a dense foam diameter, reduced in the irregularity of the foam diameter/foam wall thickness, having no hardness irregularity, easy to demold and producing no parting line, and a manufacturing method of the foam roller having uniform quality using the foam manufactured by the foam manufacturing method. <P>SOLUTION: A molded article containing a foaming agent before vulcanization and foaming is molded into a columnar shape so as to be incorporated in the cavity of a mold and the columnar molded object is arranged in the cavity of the mold and foamed by heating the mold. Thereafter, a lid body is detached to form a through-hole to the almost center of the inner paripheral surface of a mold main body before taking the cylindrical foam out of the mold. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for producing a foam by vulcanizing and foaming using a mold having a cylindrical inner peripheral surface, and more specifically, an electronic device such as a copying machine, a laser beam printer, or an LED printer. The present invention relates to a foam production method that can be used to produce a foam roller used in a photographic or electrophotographic plate making system, for example, a cylindrical foam used to produce a conductive foam roller. The present invention also relates to a method of manufacturing a foam roller such as a conductive foam roller using the produced cylindrical foam.

  Conventionally, in electrophotographic apparatuses such as copying machines, laser beam printers, and LED printers, and electrophotographic plate making system apparatuses, there are elastic rollers in a form suitable for each application, such as a charging roller, a developing roller, and a transfer roller. in use. As shown in FIG. 4, the elastic roller used in these electrophotographic apparatuses has an elastic roller main body 51 and a cored bar 52 at the center thereof, and a core penetrating the cylindrical hole of the cylindrical roller main body. A part of the gold 52 protrudes from both ends. The elastic roller main body 51 is composed of an elastic body made of a foamed material such as rubber or elastomer in order to uniformly press the roller surface against an image carrier or the like like a charging roller. In addition, in a charging roller, a transfer roller, and the like, a charged object is charged by applying a bias voltage to be used for charging, so that the foam used for the elastic body is given conductivity, and the conductive foam is used. It is a body roller. In addition, it is also possible to use a conductive roller having a shape of a two-layer structure in which the roller resistance is adjusted by applying a conductive paint on the surface of the conductive foam. is there.

  FIG. 5 schematically shows an apparatus configuration of an electrophotographic apparatus in which various elastic rollers are used. The image forming process in the electrophotographic apparatus will be outlined with reference to the apparatus configuration schematically shown in FIG. The photosensitive member 53 used in the drum-type electrophotographic process is an image carrier as a member to be charged. For example, the photosensitive member 53 includes a conductive base layer using aluminum and a photoconductive layer formed on the outer peripheral surface thereof. ing. In the apparatus configuration shown in FIG. 3, a charging roller in the shape of a conductive roller is used as the charging member 54 that contacts the photosensitive member 53 and uniformly charges the surface of the photosensitive member to a predetermined potential. For example, in the charging roller 54, in addition to the cored bar 52 at the center and the conductive foam layer provided on the outer periphery thereof, the outer surface of the conductive foam layer is filled with conductive particles such as resin. It is possible to make a structure from a two-layered roller portion that is coated.

  The charging roller 54 is pressed against the drum-type photosensitive member 53 with a predetermined pressing force by a pressing means such as a spring. For example, the charging roller 54 can be driven to rotate as the photosensitive member 53 rotates. By applying a direct current + alternating current (or direct current only) bias to the cored bar portion 52, the surface of the photoreceptor 53 is contact-charged to a predetermined potential. Therefore, in order to achieve a uniform charging potential on the surface of the photoreceptor 53 necessary for obtaining a good copy image, the charging roller 54 needs to have a uniform contact state and conductivity. Next, the surface of the photosensitive member 53 charged to a predetermined potential by the charging roller 54 is exposed using an exposure unit 55 such as a laser or LED, thereby forming an electrostatic latent image corresponding to target image information. .

  Thereafter, a toner image is applied to the formed electrostatic latent image by using a developing roller 56 that is in pressure contact with the photosensitive member 53 as a developing unit, thereby developing the toner image into a visible image. . This toner image is then transferred to the transfer portion 58, that is, the photosensitive member, with respect to the surface of the transfer material 58 conveyed to the transfer portion at an appropriate timing synchronized with the rotation of the photosensitive member 53 from a paper supply unit (not shown). In the gap between the transfer unit 57 and the transfer unit 57, the image is sequentially transferred from the surface of the photoreceptor 53 to the transfer material 58 surface. In the configuration example shown in FIG. 5, a transfer roller 7 made of a conductive foam roller is used as the transfer means 57. A bias voltage is applied to the transfer roller 57 that rotates at a constant speed, and charging is performed with a polarity opposite to that of the toner 59 from the back surface of the transfer material 58, whereby the toner image on the surface of the photoreceptor 53 is transferred to the surface of the transfer material 58.

  The transfer material 58 to which the toner image has been transferred is separated from the photoconductor 53 and is fixed by being heated and pressurized by the fixing member 60 and fixed to the surface of the transfer material 58. On the other hand, after the image transfer, the photosensitive member 53 is cleaned by the cleaning unit 61 to remove the remaining toner and the like remaining on the surface after the transfer, and is repeatedly used for image formation.

  Also, in recent years, instead of the conventionally used DC + AC bias, only a DC voltage is applied to the charging roller 54 to provide a peripheral speed difference from the photoconductor 53, and a charge is directly injected to charge the photoconductor 53. A method of making it happen is being studied. For this purpose, the charging roller 54 is made of a foam, the surface thereof is polished to expose the bubble diameter, and the surface of the polished charging roller is electrically conductive to improve contact chargeability. The foam roller is coated with particles. The charging roller that coats the conductive particles is required to have a high retention property of the conductive particles during close contact sliding with the photosensitive member 53 and to uniformly distribute a large amount of the conductive particles. In addition, in order to widen the contact width with the photosensitive member 53, it is preferable that the bubble wall of the foam is thin, the bubble diameter is appropriately small and uniformly distributed, and has low hardness.

  Further, in recent years, with respect to the above-described image forming process, an increase in image forming speed and a higher definition of the image itself have been promoted. In order to obtain a high-quality image at high speed, for example, in the transfer roller 57 using a conductive foam roller, when rotating at high speed, the photosensitive member 53 and the transfer material 58 are uniformly contacted, and The ability to accurately convey the transfer material (paper) 58 is required. For this purpose, a foam roller with low hardness and little hardness variation is desired as the transfer roller 57.

An appropriate voltage is applied to the transfer roller 57 in order to satisfactorily attract the toner 59 to the surface of the transfer material (paper) 58 by the electrostatic force. The resistance value of the transfer roller 57 is 1 × 10 ⁶ to 1 × 10 ^{10 to} Ω semiconductive at an applied voltage of 1000 V for the purpose of preventing breakdown of the applied voltage due to excessive current or current leakage to the body 53). Selected in the area. In addition, with the increase in speed and definition, it is necessary to move the charge from the transfer roller 57 to the transfer material (paper) 58 in a short time, that is, as the current increases, the uniformity of image quality is governed. The uniformity of the current density is easily affected by the resistivity distribution on the roller surface, and is easily affected by, for example, variations in the diameter of bubbles contained in the foam constituting the transfer roller 57. Therefore, in order to obtain a high-quality image at a high speed, the foam constituting the transfer roller 57 is not limited to controlling the average resistivity. It is also necessary to be.

  Conventionally, in order to obtain a foam having a fine and uniform fine cell diameter and low hardness, there is a method using a mold, or a method in which a mold is not vulcanized and foamed by direct steam, hot air, microwave, etc. there were.

  The method that does not use a mold to obtain a cylindrical foam does not regulate the inner and outer diameters of the molded body that has been cylindrical before vulcanization foaming, so the polishing allowance to adjust the outer diameter after vulcanization foaming is compared Since it is difficult to increase the accuracy of eccentricity of the inner and outer diameters, a method using a mold that can control the outer diameter and easily obtain a low hardness foam with a fine bubble diameter has been used. Yes. Conventionally, as a method using a mold for molding a cylindrical foam, a method using a cylindrical mold having a circumferential cavity surface as shown in FIG. 6 is known. In these, a kneaded raw material composition containing a foaming agent is formed on an unvulcanized unfoamed cylindrical molded body 103 on a core metal 102 coated with an adhesive 101 with an extruder or the like, and the core metal is formed at both ends. The unvulcanized and unfoamed cylindrical molded body that is discharged is inserted into the molding die body 104 having a cylindrical inner peripheral surface, fitted into both ends of the core metal 102, and the cylindrical shape of the molding die body 104 There is known a method of forming a foam roller shape by holding the inner peripheral surface of the metal core 102 and the cored bar 102 in a molding die by a lid 105 that holds the core metal 102 substantially concentrically and heating the molding die.

  Japanese Patent Laid-Open No. 2001-191349 proposes a method that uses a split mold and that the finishing accuracy of the mating surface of the split mold is 25 μm or less (10-point average roughness).

  However, the conventional method has a problem that, when the expansion ratio is high, it is difficult to remove the foam from the mold. In addition, in the method using a split mold that does not cause any problems in mold removal, even if there is no problem at the beginning, the finishing accuracy of the split mold mating surface wears down during repeated use, and the split mold mating surface There was a risk that a parting line would occur in the portion corresponding to. Further, when a vulcanizing pressure is applied from one direction using a split mold, the core metal may be deformed, and the foam may have a banana shape.

  The present invention solves the above-mentioned problems, and the object of the present invention is to reproduce a highly accurate foam having a fine bubble diameter, less variation in the bubble diameter and bubble wall thickness, and no unevenness in hardness. It is in providing the method of manufacturing by sex. More specifically, the object of the present invention is to produce a foam having a dense bubble diameter, little variation in bubble diameter and bubble wall thickness, no hardness unevenness, and easy demolding and no parting line. It is an object of the present invention to provide a method and a method for producing a foam roller having high quality uniformity using the foam produced by such a method.

  A mold body having a cylindrical inner peripheral surface and forming a cavity with the mold body without using a split mold that causes parting line generation and core metal deformation. Using a mold having both ends of the mold, a molded product containing a foaming agent before vulcanization and foaming is molded into a cylindrical shape so as to be incorporated into the cavity of the mold, and the cylindrical molded body is formed into a cavity of the mold. After placing the mold inside and heating the mold to foam the molded product, the lid is removed and a through hole is made at the approximate center of the cylindrical inner peripheral surface of the mold body, and then the cylindrical foam is formed. A method for producing a foam characterized in that a body is taken out of a mold.

  The foam produced according to the present invention can be a foam having a dense cell diameter, little variation in cell diameter and cell wall thickness, and no hardness unevenness. Further, the foam can be easily taken out from the cylindrical mold body, and a foam without a parting line can be produced.

  A foam roller manufactured by using the foam produced by the method of the present invention, for example, a conductive foam roller, has little variation in bubble diameter and bubble wall thickness in the circumferential direction, and uneven hardness. In addition, there is an advantage that the resistance value can be reduced.

  Below, the manufacturing method of the foam concerning this invention, especially this invention is demonstrated in detail.

  Examples of polymer raw materials that can be used in the foam produced in the present invention include EPDM (ethylene-propylene-diene copolymer), polybutadiene, natural rubber, polyisoprene, SBR (styrene-butadiene rubber), and CR (chloroprene). , Rubber materials such as NBR (acrylonitrile-butadiene rubber), silicon rubber, urethane rubber, epichlorohydrin rubber; polystyrene polymer materials such as RB (butadiene resin) and SBS (styrene-butadiene-styrene elastomer); polyolefin-based materials Polymer material; Polyester polymer material; Polyurethane polymer material; Thermoplastic elastomer such as RVC, polyurethane, polystyrene, PE, PP, PVC, acrylic resin, styrene-vinyl acetate copolymer, butadiene-acrylonitrile copolymer Polymeric materials such as body; may further include these rubbers, elastomers, mixtures of a resin material. From these exemplified polymer raw materials, for example, it is desirable to appropriately select a polymer raw material suitable for the end use according to the use of the foam roller produced using the produced foam.

Moreover, when making the foam to produce into a conductive foam, a conductive substance is added to the said polymer raw material, and desired electroconductivity is provided. The conductive material used is not particularly limited, and conductive particles such as conductive carbon black, TiO ₂ , SnO ₂ , ZnO, a metal oxide such as a solid solution of SnO ₂ and SbO ₃ , Cu, Ag, etc. It is like the metal powder, and as an ion conductive _agent, LiClO 4, NaSCN, and the like. The addition ratio of the conductive material can be appropriately selected for the polymer raw material in accordance with the target resistivity and also taking into account the target expansion ratio. In addition, in some cases, the polymer raw material itself may be introduced by modifying and adding molecules having a polar group or atomic group in the polymer main chain or in the side chain of the polymer raw material itself. It is also possible to make itself conductive.

In addition, the charging roller that coats the conductive particles needs to have elasticity and obtain a sufficient contact state, and at the same time have a sufficiently low resistance to charge the moving charged object. However, on the other hand, it is necessary to prevent voltage leakage in the case where a defect site such as a pinhole exists in the member to be charged. Therefore, when an electrophotographic photosensitive member is used as the member to be charged, it is desirable that the applied voltage has a resistance of 1 × 10 ⁴ to 1 × 10 ⁷ Ω at 100 V in order to obtain sufficient chargeability and leakage resistance. .

  In the present invention, in order to make the bubbles contained in the foam dense, the foaming agent to be used needs to be uniformly mixed and dispersed in the polymer raw material. Are suitable. Examples of usable organic blowing agents include A.I. D. C. A (azodicarbonamide) system, D.I. P. T (dinitrosopentamethylenetetraamine) type, T.I. S. H (p-toluenesulfonyl hydrazide) system, O.D. B. S. H (oxybisbenzene sulfenyl hydrazide) system etc. are mentioned, It can also use individually or in mixture of multiple types.

  For the organic foaming agent, urea compounds, metal oxides such as zinc oxide and lead oxide, and compounds mainly composed of salicylic acid, stearic acid, and the like can be used as foaming aids. Depending on the type of foaming agent, a corresponding foaming aid can be selected and added in an appropriate amount.

  On the other hand, examples of the vulcanizing agent include sulfur and metal oxides, and examples of the vulcanization accelerator include thiazole-based, sulfenamide-based, thiuram-based, carbamate-based, and the like. It is preferable to select a vulcanization accelerator corresponding to the type of vulcanizing agent to be used as appropriate.

  In addition to the above-mentioned components used for vulcanization / foaming, known vulcanization accelerators may be added as necessary. Furthermore, known softeners, reinforcing agents, inorganic fillers, and the like can be appropriately added as necessary according to properties such as elasticity and hardness required for the obtained foam.

  In the foam production method of the present invention, it is necessary to harmonize the progress of the vulcanization reaction with the thermal decomposition reaction rate of the foaming agent in order to uniformize the generation of dense bubbles and the bubble diameter. Yes, thus also controlling the temperature at which thermal decomposition of the blowing agent begins to occur. Therefore, when it is necessary to lower the temperature at which the thermal decomposition of the foaming agent starts to occur, the thermal decomposition temperature can be increased by adding a foaming aid such as urea resin or zinc oxide and adjusting the addition ratio. It is preferable to control the lowering range of.

  In the charging roller for coating the conductive particles, the specific gravity of the foam is preferably in the range of 0.2 to 0.5 from the viewpoint of holding power of the conductive particles due to the bubble diameter and efficient and uniform injection charging.

  Further, by increasing the expansion ratio, the hardness of the roller is lowered, and the nip width necessary for the charging roller to charge the member to be charged (photosensitive member) can be secured, so that the charging efficiency can be increased. On the other hand, if the expansion ratio is increased too much, the charging roller is insufficient in strength and thus easily deforms and the charging performance deteriorates. Therefore, the expansion ratio is preferably 2 to 5 times.

The expansion ratio was calculated by an equation using specific gravity (g / cm ³ ) before and after foaming as shown below.

Foaming ratio = (specific gravity before vulcanization foaming) / (specific gravity after vulcanization foaming)
Furthermore, if the hardness is too low, the shape will not be stable, resulting in poor contact. If it is too high, not only will the charging nip be secured, but the micro contact to the surface of the photoreceptor will be poor. 15 to 40 degrees is a preferable range.

  Next, a mold used in the present invention will be described with reference to FIG.

  11 is a mold body having a cylindrical inner peripheral surface for forming the outer diameter of the foam, and the outer peripheral surface is also formed in a cylindrical shape, and the concentricity of the inner peripheral surface and the outer peripheral surface is 0.05 mm or less. It has become. The length of the inner peripheral surface of the mold body 11 is determined by the foam length to be obtained and the expansion ratio.

  Further, the inner peripheral surface of the mold main body may be configured to have a surface treatment excellent in heat resistance and releasability, such as fluororesin, silicon resin, and a mixture of releasable resin and metal. As a process for preventing sticking of the surface of the molded body, dust may be applied to the molded body. As the dusting powder, fine powders such as talc, clay, magnesium carbonate, calcium carbonate, and carbon are preferably applied as a slurry. It is also possible to use both, for example, an anti-sticking treatment on the surface of the molded body and a surface of the inner peripheral surface of the mold body made of a material having good releasability and low surface energy.

  Both ends of the mold body have a shape that fits with the lids 13a and 13b so that the cracked decomposition gas does not escape from inside the cavity 12. The lid 13a is fitted with the straight part and the lid 13b is fitted with the tapered part. To do.

  Further details of the method of manufacturing the foam roller will be described with reference to the process flow diagram of FIG. 2 and the heating method of the mold of FIG.

  A kneading machine such as a known Banbury mixer or kneader can be used as a means for mixing the above-mentioned additive components with the polymer raw material and kneading the raw material composition. After uniformly kneading, the unvulcanized raw material composition is sheeted with a roll.

In the method for producing a foam roller according to the present invention,
(A) As the molded product which is an unvulcanized unfoamed product subjected to vulcanization / foaming treatment, a product obtained by molding the unvulcanized raw material composition into a cylindrical shape is used. The outer diameter of the columnar molded body 14 can be appropriately selected in consideration of the target foaming ratio in accordance with the target outer diameter of the cylindrical foam to be produced. As a means for forming an unvulcanized raw material composition into a cylindrical shape, an extrusion molding machine is used, and the size of a die (die) used for extrusion molding into a cylindrical shape is selected according to the previously selected outer diameter. Then, an unvulcanized raw material composition is formed into a cylindrical shape. Next, in accordance with the roller length of the foam roller to be manufactured, the target foaming ratio is taken into consideration, and the product is cut into a predetermined length by a cutting machine to obtain a cylindrical unvulcanized unfoamed molded body 14. . Next, a cylindrical shaped body is incorporated into the mold body.

  (B) The lids 13a and 13b are fitted into the opening portions at both ends of the mold body in which the columnar molded body 14 is incorporated to form a mold cavity. The hermetically sealed mold can easily confine foaming decomposition gas in the cavity. The volume of the cylindrical unvulcanized unfoamed molded body 14 may be 70 to 95% with respect to the volume in the cavity. This is because if it is 70% or less, the hardness of the foam varies, and if it is 95% or more, a bubble diameter that is too small is formed.

  (C) shows a closed mold.

Next, a method of heating the sealed mold will be described with reference to FIG.
21a is an upper heating board and 21b is a lower heating board. In order to heat the mold, a heater (not shown) is embedded in the upper heating plate 21a and the lower heating plate 21b. In addition, the upper heating platen 21a and the lower heating platen 21b are in close contact with the outer peripheral surface of the sealed mold, and transmit the heat of the heating plate. The shape is opposite to the outer peripheral surface of the mold so as to be in close contact with the outer peripheral surface.

  The heat sources of the upper and lower heating plates, which are the heating elements, are not limited to these as long as the heating element can be heated using electric heat, steam or the like as the heat source and the desired temperature is obtained.

  The heating temperature is 120 to 200 ° C., and the time is 5 to 60 minutes. Preferably, the heating temperature is 130 to 180 ° C. and the time is 10 to 30 minutes. Thereafter, secondary vulcanization may be performed as necessary. The heating temperature for secondary vulcanization is usually 130 to 220 ° C. and 20 to 240 minutes.

  When the mold is heated, the cylindrical molded body placed in the cavity in the sealed mold expands and expands, and a large amount of cracked decomposition gas is generated. A foam is formed which is pressed inside by internal pressure.

  (D) attaches and detaches the lid bodies 13a and 13b from the mold body 11 after heating the cylindrical shaped body and vulcanizing and foaming.

  When the lids 13a and 13b are detached from the mold body 11, the internal pressure is released and both ends of the foam 15 are discharged from the mold body 11.

  (E) Next, the discharge part of the cylindrical foam 15 discharged to the lid 13a side is cut with a known cutter.

  (F) A columnar foam that is in pressure contact with the inner peripheral surface of the cylindrical mold body 11 is subjected to cutting or grinding with reference to the outer peripheral surface of the cylindrical mold body 11 to thereby obtain a columnar foam. Form the inner diameter.

  Reference numeral 16 denotes a gun drill. While rotating the gun drill 16 at the position of the substantially central axis of the inner peripheral surface of the mold body 11, the cylindrical foam body is cut by cutting the inner diameter of the cylindrical foam body in the thrust direction. Let it be the body.

A well-known deep hole process such as a method using a gun drill method as a cutting process and a method using a cylindrical grindstone having a diameter smaller than a desired inner diameter can be used as a grinding process.
The inner diameter accuracy and eccentricity accuracy of the cylindrical foam can be improved by matching the central axis of rotation of the gun drill 16 with the central axis of the cylindrical mold body. Alternatively, the gun drill 16 may be rotated in the thrust direction of the mold body 11 by rotating the mold body 11 without rotating the gun drill 16.

  (G) Next, the discharge part of the cylindrically formed foam 16 discharged to the lid 13b side is pulled out of the mold body 11 and taken out. By pulling out from the mold body 11, the foam 16 has a thin outer diameter and is more easily deformed because it is cylindrical, and the foam 16 that is highly foamed and press-contacted to the inner peripheral surface of the mold body can be easily removed. It is possible.

  (H) The cylindrical foam is completely removed from the mold body 11.

  Next, in the method for manufacturing a foam roller according to the present invention, after the above-described cylindrical foam is produced in advance, the core metal 2 in which a hot melt adhesive is applied to the foam whose inner diameter has been processed is press-fitted. A foam roller is obtained by applying a temperature at which the melt is melted to adhere the cored bar 52 and the inner peripheral surface of the foam 16.

  Hereinafter, the present invention will be described more specifically with reference to examples. These examples are examples of the best mode of the present invention, but the present invention is not limited to such examples.

(Examples 1 and 2 and Comparative Examples 1 and 2)
The unvulcanized raw material composition comprises 100 parts by mass of EPDM as a polymer raw material, 8 parts by mass of an ADCA (azodicarbonamide) -based foaming agent as a foaming agent, 8 parts by mass of urea resin as a foaming aid, and 1.5% of sulfur as a vulcanizing agent. 1 part by mass, 1 part by mass of mercaptobenzothiazole (2-sulfanylbenzothiazole) as a vulcanization accelerator, 2 parts by mass of tetraethylthiuram disulfide, 60 parts by mass of carbon black as a conductive agent, 10 parts by mass of calcium carbonate as a filler, acceleration of vulcanization It contains 5 parts by weight of zinc white (zinc oxide) as an auxiliary agent, 2 parts by weight of stearic acid, and 50 parts of paraffinic process oil as a softening agent, and these are kneaded uniformly using a kneader that is a conventional kneading method. Seated.

  Next, Examples 1 and 2 will be described. The kneaded raw material composition is formed into a cylindrical (unvulcanized) molded body by an extrusion molding machine, and then cut by a cutting machine to obtain a full length dimension. .

  The dimensions of the prepared cylindrical unvulcanized molded body were an outer diameter of 11.5 mm and a length of 197 mm. This cylindrical unvulcanized molded body was used as an unvulcanized molded body to be subjected to the vulcanization / foaming treatment of Examples 1 and 2.

In the configuration shown in FIG. 1, the cavity size of the mold in Example 1 was set to an inner diameter of 12.7 mm and a length of 200 mm, and the charging rate in the cavity was 81%. The cylindrical mold body has a configuration in which the inner peripheral surface is surface-treated by coating with a fluororesin.
In Example 2, the cavity size of the mold was 11.8 mm inside diameter and 200 mm long, and the charging rate in the cavity was 94%. The cylindrical mold body was structured such that the inner peripheral surface was surface-treated with a coating of fluororesin as in Example 1.

  As for the heating conditions, primary vulcanization was carried out at 150 ° C. for 15 minutes using the heating plate shown in FIG.

  Next, Examples 1 and 2 will be described. A cylindrical foam was obtained using the process flow shown in FIG.

  A gun drill was used to process the inner diameter of the foam that was in pressure contact with the inner peripheral surface of the mold body. In Example 1, a gun drill having an outer diameter of 3.8 mm and a length of 250 mm is set with a gun drill center set to a concentricity of 0.02 mm based on the outer diameter of the mold body, and at a rotational speed of 2500 rpm and a feed speed of 200 mm / min. A through-hole was provided in the foam that was in pressure contact with the inner peripheral surface of the main body. The cylindrical foam body end could be easily removed by pulling the cylindrical foam discharge part from the lid 13-b side.

  In Example 2, the dimensions of the gun drill were changed to an outer diameter of 3.3 mm and a length of 250 mm, and through holes were made in the foam under the same conditions as in Example 1. As in Example 1, the cylindrical foam was easily removed from the cylindrical mold body.

  In Examples 1 and 2, secondary vulcanization was performed on a cylindrical foam taken out from the mold using a hot air oven at 180 ° C. for 30 minutes.

  Then, when the density of the cylindrical foam taken out from the mold body was measured, it was 0.37 in Example 1 and 0.31 in Example 2. When the cross section of the foam was cut at five places and the cut surface was observed with an optical microscope at a magnification of 100, the average diameter of the major axis and minor axis was 120 μm in Example 1, and the variation was 15 μm. When the bubble diameter was evaluated in the same manner as in Example 1, in Example 2, the average was 80 μm and the variation was 10 μm.

  Further, in Examples 1 and 2, a cored bar having an outer diameter of Φ6.0 mm and a length of 245 mm was press-fitted into the cylindrical hole of the obtained cylindrical foamed body. The cylindrical foam into which the metal core was press-fitted was heated using a hot air oven at 170 ° C. for 10 minutes, and heat-bonded with a hot-melt conductive adhesive. Next, after the core metal is press-fitted and bonded, the outer diameter of the foam roller with the skin layer is polished with a cylindrical grinder, and both ends of the foam are cut off to obtain an outer diameter of Φ16. A conductive foam roller for a charging roller having a length of 5 mm and a length of 225 mm was prepared.

  Next, the hardness and resistance of the obtained conductive foam roller for the charging roller were evaluated as follows.

  When the hardness of the foam roller was measured with a load of 500 gr using a hardness meter of Asker C, in Example 1, the hardness unevenness in one was as good as 1.6 degrees (average of N number of 50). In Example 2, the hardness unevenness in one was as good as 1.8 degrees (average of N number of 50).

  Further, as shown in FIG. 7, the foam roller 121 is subjected to a load of 500 gr at both ends and brought into contact with the cylindrical φ30 mm metal drum 122, and the metal drum is rotated to be driven and rotated by the foam roller. A voltage 123 of 100 V DC was applied between the metal core part and the metal drum, an internal resistance of 1 KΩ was arranged on the ground side of the metal drum 122, and the voltage applied to the internal resistance 124 was measured and converted into a resistance. When the resistance value of the foam roller was measured, the resistance value was 3.0 to 5.0E + 05Ω, and the ratio of the minimum and maximum resistance values in the radial direction was defined as uneven resistance. In Example 1, the resistance unevenness was 1.67, and in Example 2, it was 1.6.

  Next, Comparative Examples 1 and 2 will be described.

  The above-mentioned kneaded raw material composition is formed into a cylindrical (unvulcanized) molded body on the surface of the core metal to which the adhesion has been applied by a cross extrusion molding machine, and then cut by a cutting machine. Dimensioned out.

  The dimensions of the cylindrical unvulcanized molded bodies of Comparative Examples 1 and 2 were an outer diameter of 12.5 mm and a length of 232 mm, and the dimensions of the cored bar were an outer diameter of φ6.0 and a length of 245 mm.

  This cylindrical unvulcanized molded body was used as an unvulcanized molded body subjected to the vulcanization / foaming treatment of Comparative Example 1 and Comparative Example 2.

  In Comparative Examples 1 and 2, a mold having the configuration shown in FIG. 6 was used. In addition, the cylindrical mold body was structured such that the inner peripheral surface was surface-treated with a coating of fluororesin as in Examples 1 and 2.

  In Comparative Example 1, the cavity size of the mold was 12.8 mm in inner diameter and 235 mm in length, and the charging rate in the cavity was 93%. In Comparative Example 2, the cavity size of the mold was 13.5 mm inside diameter and 235 mm long, and the charging rate in the cavity was 81%.

  The heating conditions were the same as in Examples 1 and 2, and both Comparative Examples 1 and 2 were subjected to primary vulcanization at 150 ° C. for 15 minutes using the heating plate shown in FIG.

  The mold was cooled to 50 ° C. after vulcanization and foaming under the heating conditions described above, the lid 105 was removed, and the foam roller was removed from the mold body. 2 could not be removed.

  Then, when the density of the cylindrical foam produced in Comparative Example 1 was measured in the same manner as in Examples 1 and 2, it was 0.38. When the cross section of the foam was cut at five places and the cut surface was observed with an optical microscope at a magnification of 100, the average diameter of the major axis and the minor axis was 125 μm and the variation was 25 μm.

Further, when the hardness of the foam roller of Comparative Example 1 was measured with a load of 500 gr using an Asker C hardness meter in the same manner as in Examples 1 and 2, the hardness unevenness in one was 3.5 degrees (N number of 50). As compared with Examples 1 and 2, the unevenness became larger.
When the resistance value of the foam roller of Comparative Example 1 was measured, the resistance value was 3.0 to 9.0E + 05Ω, and the resistance unevenness was 3.0.

  When the hardness unevenness and resistance unevenness portions were broken and visually observed, the adhesion with the core metal portion was peeled off.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a view for explaining a cross section of a mold applied to Examples 1 and 2 of the present invention. It is a process flow figure explaining typically a process of producing a cylindrical foam in a manufacturing method of a foam concerning the present invention. It is a figure which illustrates typically the heating method of the shaping | molding die used for a vulcanization | cure and foaming process process in the manufacturing method of the foam concerning this invention. It is a figure which shows typically the structure of a conductive foam roller. It is a side view which outlines the structure of an electrophotographic apparatus. It is a figure explaining the cross section of the conventional shaping | molding die applied to the comparative examples 1 and 2. FIG. It is a side view which outlines the structure which measures the resistance of a conductive foam roller.

Explanation of symbols

11 Cylindrical mold body
12 Cavity 13-a, 13-b Lid 14 Cylindrical molded body 15 Cylindrical foam 16 Cylindrical foam 21a Upper heating plate 21b Lower heating plate 51 Roller body 52, 102 Core metal 53 Photoconductor 54 Charging roller 55 Exposure light 56 Developing roller 57 Transfer roller 58 Transfer material (paper)
59 Toner 60 Fixing roller 61 Cleaning blade 103 Cylindrical molded body 104 Cylindrical mold body 105 Lid body 121 Foam roller 122 Metal drum

Claims (3)

  A method for producing a foam by vulcanization foaming, comprising a step of subjecting a molded product which is an unvulcanized unfoamed product to vulcanization foaming to form a foam, and the molding body has a cylindrical inner periphery A mold having a surface and forming a cavity with the mold body at both ends of the mold body can be used to incorporate a molded product containing a foaming agent before vulcanization and foaming into the cavity of the mold. The columnar molded body is placed in the cavity of the mold, the mold is heated to foam the molded product, and then the lid is removed to form the cylindrical shape of the mold body. A method for producing a foam, characterized in that a through-hole is provided at substantially the center of the inner peripheral surface and the cylindrical foam is then removed from the mold.   A foam roller using a cylindrical foam for a roller portion of a foam roller produced by the foam manufacturing method according to claim 1 and press-fitting a cored bar into a cylindrical hole of the cylindrical foam. Forming a foam roller.   The method for producing a foam roller according to claim 2, wherein the foam roller is a conductive foam roller.

Images