JP2002113735A - Method of manufacturing foam roller - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for producing a foaming roller suitable for a transfer roller or the like used in an electrophotographic apparatus, which has a small variation in a bubble diameter, a dense bubble, and a small hardness unevenness. SOLUTION: A heating step of heating a raw material composition containing a vulcanizing agent and a foaming agent molded into a desired shape to expand and expand the foamed material into a foam is carried out by (1) the raw material composition. Heating to a temperature t1 selected below the decomposition temperature of the blowing agent,
When holding temporarily at this temperature t1, the holding time
A preheating step of selecting T2 in the range of 1 to 10 minutes;
(2) A temperature t2 selected to be equal to or higher than the decomposition temperature of the blowing agent at an average heating rate of 15 ° C./min or more, continuously to the preheating step
(3) temperature t2 for a predetermined time
A foaming vulcanization step of holding only T4, a method for manufacturing a foamed roller.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a foaming roller for forming a foam by heating, and more particularly to a method for manufacturing a foaming roller characterized by a heating step for forming the foam. More specifically, the present invention relates to a method for producing a foaming roller used for an electrophotographic apparatus or an electrophotographic plate making system such as a copying machine, a laser beam printer, and an LED printer. And a method for producing the same.

[0002]

2. Description of the Related Art Conventionally, various kinds of rollers such as a charging roller, a developing roller, and a transfer roller have been used in an electrophotographic apparatus. These rollers have a structure in which a core 2 is embedded in the center axis of the roller body 1 as shown in FIG. 1, and a part of the core 2 protrudes from the roller body 1. In addition, since the roller body 1 is used while being uniformly pressed against a photosensitive member or the like, the roller body 1 is formed of an elastic body made of a foam such as rubber or elastomer. In addition, in the case of a charging roller, a transfer roller, or the like, for example, a bias voltage is applied between the surface of the charging roller and the photosensitive member to charge the member to be charged, and the device is used in a state where a bias voltage is applied to the roller surface. For this reason, a roller having conductivity added to the foam itself is used. Further, there is a roller having a two-layer structure in which the roller resistance is adjusted by applying a conductive paint to the surface of the conductive foam.

FIG. 2 schematically shows an example of the configuration of an electrophotographic apparatus using these rollers as components.
The image forming process of the electrophotographic apparatus will be outlined with reference to a cross-sectional view showing the apparatus configuration shown in FIG.

Here, the photosensitive member 3 is a member to be charged, and is a drum composed of two layers, a conductive base layer made of aluminum and a photoconductive layer formed on the outer peripheral surface thereof. The charging roller 4 is a charging member that comes into contact with the photoconductor 3 and uniformly charges the photoconductive layer surface of the photoconductor 3 to a predetermined potential. In addition,
As the charging member, those having various shapes other than the roller illustrated in FIG. 2 are used.

The charging roller 4 has a structure in which a central metal core, a layer of a conductive foam provided on the outer periphery thereof, and a outermost layer of which is covered with a resin or the like filled with conductive particles. are doing. The charging roller 4 is pressed against the surface of the photoconductor 3 with a predetermined pressure by a spring or the like, and is rotated by the rotation of the photoconductor 3 in contact with the surface. In addition, an alternating current is superimposed on a direct current on the core metal of the charging roller (or
Bias (only DC current) is applied,
The surface is contact-charged to a predetermined potential.

At this time, in order to obtain a good electrophotographic image, the charging roller 4 and the photoreceptor 3 need to be in contact with a uniform pressure. In addition, in order to achieve uniform charging and prevent leakage. It is necessary that the charging roller 4 itself has a resistance value of 10 ⁴ to 10 ⁷ Ω.

On the surface of the photoconductor 3 charged to a predetermined potential,
Exposure of image information is performed by exposure means 5 such as a laser or an LED, and an electrostatic latent image corresponding to a target image is formed on the surface of the photoconductor 3. Next, the formed electrostatic latent image is visualized as a toner image by a developing roller 6 which is a developing unit pressed against the photoconductor 3.

Next, the toner image is sequentially transferred to the surface of the transfer material 8 by the transfer means 7. The transfer material 8 such as a paper sheet is conveyed from a paper feeding unit (not shown) to a transfer unit between the photoconductor 3 and the transfer unit 7 at an appropriate timing synchronized with the rotation of the photoconductor 3. . In the example shown in FIG. 2, the transfer means 7 is a transfer roller 7 made of a conductive foam. Transfer roller 7 rotating at a constant speed
By applying a bias voltage having a polarity opposite to the charge carried by the toner, the toner image on the surface of the photoconductor 3 is electrostatically transferred to the surface of the transfer material 8.

The transfer material 8 onto which the toner image has been transferred is separated from the photoreceptor 3 and is fixed by a fixing member 10 using heat and pressure. On the other hand, after the transfer of the image, the surface of the photoconductor 3 is cleaned by the cleaning unit 11 to remove extraneous matter such as residual toner at the time of transfer, and is repeatedly subjected to image formation.

In recent years, there has been an increasing demand for speeding up the above-described series of image forming processes and increasing the definition of the formed image itself, and various attempts have been made to improve an image forming apparatus for obtaining a high quality image. Has been done.

For example, regarding the transfer roller 7, even if the transfer roller 7 is rotated at a high speed as the paper passing speed is increased, the transfer material 8 is brought into contact with the photosensitive member 3 at a uniform pressure.
In addition, a performance capable of accurately transporting the transfer material (paper) 8 is required. For this reason, it is required that the transfer roller 7 be manufactured using a low-hardness foam and with less hardness unevenness than before.

Further, a predetermined voltage is applied to the transfer roller 7 in order to attract the toner 9 on the photosensitive member 3 to the surface of the transfer material 8 (paper) by electrostatic force. When the transfer roller 7 and the photosensitive member 3 is in direct contact, and electrical leakage may occur between them, in order to prevent the occurrence of breakdown due to the applied voltage, the transfer roller 7 itself, 1 × 10 ⁶ to 1 ×
Manufactured to have an electrical resistance of 10 ¹⁰ Ω. However, when the transfer roller 7 has uneven hardness, the nip width between the transfer roller 7 and the photoconductor 3 may greatly change depending on the location. At this time, even if the transfer roller 7 as a whole satisfies the above-described electric resistance, the transfer current partially varies, which may cause unevenness in the transferred image.

Further, with the increase in the speed of the apparatus, the transfer roller 7
The amount of current per unit time traveling through the device increases. Thus, when the amount of moving current increases,
It is known that the obtained image is easily affected by the bubble diameter of the foam. From this viewpoint, it is necessary that the foam used for the transfer roller 7 is formed of dense bubbles having little unevenness in the size of bubbles and an average diameter of 200 μm or less.

The foam used for these foam rollers is made of a raw material composition obtained by kneading a vulcanizing agent, a foaming agent, a filler, and the like into rubber, and is formed into an unvulcanized cylindrical molded product by a mold, an extruder, or the like. After that, the unvulcanized molded body was vulcanized and foamed by heating to prepare a cylindrical foam. Thereafter, a method is used in which a metal core is pressed into a cylindrical foam, and the outer diameter is cylindrically polished to form a roller shape.

The foaming of the raw material composition proceeds by thermal decomposition of the foaming agent contained therein. However, if the vulcanization reaction has not proceeded to an extent sufficient to maintain the structure of the bubbles generated in the raw material composition, the once formed bubble wall will burst, and the generated gas in the bubble wall will leak out. I will. As a result, at the time of forming the cylindrical foam, the foam shrinks from a desired diameter or has a variation in the diameter of the cells.

[0016] The foaming reaction is a reaction that proceeds at a stretch as the heating proceeds, but the vulcanization reaction is a reaction that proceeds slowly. In order to obtain a high vulcanization rate commensurate with the progress of the foaming reaction, various methods have hitherto been used. Attempts have been made. As one of the attempts, a method is known in which heating is performed in two stages in order to balance foaming and vulcanization.

As the two-stage heating method, the following method has been devised. A method in which a mold is filled with the kneaded raw material composition, preheated under pressure, and then put into a vulcanization mold and heated under normal pressure to perform vulcanization / foaming. Pre-heating, etc., followed by continuous vulcanization and foaming in a hot blast stove.

However, in the above-described method using preheating using a mold, since the raw material composition is cooled when the mold is taken in and out, it is difficult to uniformly transfer heat to the kneaded raw material composition. It is difficult to produce a densely packed foam with less variation in cell diameter with high reproducibility. Furthermore, if there is a leakage of the kneaded raw material composition at the parting part of the mold, there arises a problem that the conductivity changes at the parting part.

In the method using the above two types of heating means, the heating method must be changed between the preheating and the main heating, so that the process tends to be complicated, and the temperature gradient from the preheating to the main heating is reduced. Difficult to control. in addition,
Unlike means of direct heating using direct pressurized steam such as vulcanizing cans, far-infrared heaters, hot blast stoves, etc., are locally heated. .

[0020]

SUMMARY OF THE INVENTION The present invention has been made in view of the problems that various foaming rollers used in an electrophotographic apparatus have hitherto had. It is an object of the present invention to provide a method for producing a foaming roller having less unevenness and high reproducibility in a dense state of air bubbles and, as a result, having less unevenness in hardness, in particular, a conductive foaming roller used in an electrophotographic apparatus. I do.

[0021]

In order to solve the above-mentioned problems, the present invention uses a raw material composition containing at least a vulcanizing agent and a foaming agent, and heats the raw material composition molded into a desired shape. In the method for producing a foamed roller having at least a step of foaming and expanding to form a foam, the heating step of forming the foam of the raw material composition includes the steps of (1) forming a foaming agent contained in the raw material composition. When heating to a temperature t1 selected lower than the decomposition temperature and temporarily holding at this temperature t1, a preheating step of selecting the holding time T2 in the range of 1 to 10 minutes, and (2) continuous with the preheating step A temperature raising step of raising the temperature to a temperature t2 selected above the decomposition temperature of the blowing agent at an average temperature change rate of 15 ° C./min or more; and (3) after reaching the temperature t2, the temperature t2 For a predetermined time T4 And a foaming vulcanizing step.

In the method of the present invention, it is desirable that the temperature t1 be 100 ° C. or higher in the preheating step. Further, it is preferable to perform the above-mentioned steps (1) to (3) in a vulcanizer heated with pressurized steam. In addition,
As the raw material composition, a material containing a conductive substance can be used.

In addition, the present invention provides a foam roller manufactured by the above-described method of manufacturing a foam roller, and further provides an electrophotographic apparatus using such a foam roller as a component.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail.

The method of the present invention will be described with reference to FIG. 3 taking a more specific form as an example. In the example shown in FIG.
It is assumed that the production of the foaming roller is performed in a vulcanizer using heated steam. The horizontal axis in FIG. 3 is time (minutes),
The vertical axis is the temperature inside the vulcanizer (° C.). The temperature t1 is a set heating temperature in the preheating step, and the temperature t2 is a set heating temperature in the foam vulcanization step.

In this example, a method of heating the vulcanizer with heated steam is selected as the heating means, but as shown in FIG. 3, the temperature of the unvulcanized formed body can be changed in the heating step. The heating means is not limited to the vulcanizer as long as such means is used.

The time T1 is a time from the start of heating by the inflow of pressurized steam to the time when the set heating temperature t1 in the preheating step is reached, and the time T2 is thereafter used to hold the set heating temperature t1 in the preheating step. Time T3
Is the time required for raising the temperature of the vulcanization can from the temperature t1 to the temperature t2 in the temperature raising step performed subsequent to the preheating step. The time T4 is a time for maintaining the set heating temperature t2 in the foam vulcanization step.

First, an unvulcanized compact is placed in a vulcanization can and the vulcanization can is sealed. Thereafter, pressurized steam is introduced into the vulcanizing can, and the temperature is raised over time T1 so that the inside of the vulcanizing can is uniform up to the set heating temperature t1 in the preheating step.

When the temperature of the vulcanizing can reaches t1, the temperature of the vulcanizing can is maintained at that temperature for a time T2 to preheat the unvulcanized compact.

Subsequently, the temperature inside the vulcanization can is raised to the set heating temperature t2 in the foaming vulcanization step by injecting heated steam and increasing the pressure of the vulcanization can. The heating time at this time is T3.

When the temperature inside the vulcanizing can reaches t2, a foaming vulcanizing step of foaming and vulcanizing the molded body while holding the vulcanizing can at the temperature t2 for a time T4 is performed. After the end of the set heating time T4, the pressurized steam is exhausted, the vapor pressure in the vulcanizing can is reduced to atmospheric pressure, and the foamed and vulcanized molded body is taken out.

The reason that the set heating temperature t1 in the preheating step is selected to be lower than the decomposition temperature of the foaming agent is that vulcanization proceeds to some extent before foaming is started at this temperature. In addition, while holding at this temperature t1 for 1 to 10 minutes, the movement of gas inside the vulcanization can caused by the rapid injection of pressurized steam in the initial stage of heating is suppressed, and before the next foaming vulcanization step is performed. For reducing heating unevenness in the apparatus (effect)
It also has

At this time, the set heating temperature t1 in the preheating step
Is preferably 100 ° C. or higher at a temperature lower than the decomposition temperature of the foaming agent. When the temperature is 100 ° C. or higher, there is an advantage that the temperature in the vulcanizing can can be controlled with high accuracy by adjusting the pressure of the pressurized steam. Along with this, the temperature variation in the preheating step for each lot is reduced, and there is no difference in the progress of vulcanization between lots. Also, the temperature t
Desirably, 1 is significantly lower than the decomposition temperature of the blowing agent.

The set heating time T2 of the preheating step is 1 to
10 minutes is good. If the time is less than 1 minute, preliminary vulcanization does not sufficiently proceed, and thereafter, it is not possible to sufficiently suppress the variation in the bubble diameter generated in the foam vulcanization step,
Influence of temperature unevenness generated at the time of steam injection remains,
It also causes the occurrence of foam variation depending on the location. Meanwhile, 1
If the time exceeds 0 minutes, the preliminary vulcanization becomes excessive and the foaming and vulcanization in the foam vulcanization step cannot be balanced.

Next, the temperature inside the vulcanization can is increased while controlling the heating rate up to the set heating temperature t2 in the foam vulcanization step. If the average heating rate is 15 ° C./min or more, the preliminary vulcanization performed in the preheating step does not proceed to an excessive extent until the start of foaming, and the preliminary vulcanization in the foaming vulcanization step Foaming and vulcanization can be balanced.

The set heating temperature t2 in the foam vulcanization step is preferably equal to or higher than the decomposition temperature of the foaming agent and in the range of 130 to 180 ° C. If the temperature t2 is 130 ° C. or higher, it is a temperature sufficient to decompose the foaming agent, and vulcanization proceeds quickly. When the temperature t2 is 180 ° C. or lower, a stable temperature can be easily obtained even when heating using pressurized steam. Further, the temperature t2 is 150 ° C.
It is even more desirable to select a temperature in the range of -170 ° C.

The set heating time T4 in the foam vulcanization step is determined by the temperature t
5 to 120 minutes, preferably 10 to 100
It is preferable that the foaming and vulcanization treatment be performed in a range of minutes.

Although the heating means selected in this example uses pressurized steam, this method can rapidly change the temperature and also has good uniformity of the temperature in the vulcanizing can.

Further, the foam taken out from the vulcanizing can may be additionally heated in a hot blast stove if necessary. Here, "as needed" means that the foaming reaction and the vulcanization reaction have not completely proceeded in the vulcanizer placed under pressurized conditions. It is intended to completely react the foaming agent and / or the vulcanizing agent remaining in the foam by heating the foaming agent.

Thereafter, as described above, a core metal is pressed into a cylindrical foam by a known means, and the outer diameter is cylindrically polished to form a roller.

In the process of foaming and vulcanizing a rubber containing a vulcanizing agent and a foaming agent, two kinds of reactions occur inside the foaming rubber. One is a vulcanization reaction and the other is a foaming reaction. The vulcanization reaction is a reaction that proceeds gradually, and the reaction starts and proceeds at a lower temperature than the foaming reaction, but the reaction rate is slow. The other foaming reaction, once
When the thermal decomposition reaction of the blowing agent starts, the reaction rate is very fast, but the reaction does not proceed below the decomposition temperature of the blowing agent.

If the progress of the vulcanization reaction is insufficient at the time when the foaming reaction starts, and if the degree of vulcanization in the rubber is insufficient, the “bubbles” generated by the foaming reaction have the structure For example, as a result of being broken on the surface or coalescing with nearby bubbles to become large bubbles, irregularities are generated on the foam surface, so that uniform bubbles are included, and the surface is flat. However, it is difficult to obtain a good quality foam.

Conversely, if the vulcanization reaction proceeds excessively at the time the foaming reaction starts and the degree of vulcanization in the rubber is excessive, the rubber becomes too hard, and the desired diameter It is difficult for bubbles to form.

It is very important that the vulcanization reaction and the foaming reaction proceed in a well-balanced manner in order to obtain a foam having a small variation in cell diameter, dense cells, and less hardness unevenness.

The present invention is characterized in that two means are used for adjusting the balance of the progress of both reactions. One is to provide a preheating step of heating the raw material composition to a temperature t1, which is preferably selected to be 100 ° C. or higher and lower than the decomposition temperature of the foaming agent, and hold the temperature t1 for a predetermined time T2. It is. As described above, the vulcanization reaction proceeds even at a temperature lower than the decomposition temperature of the blowing agent at which the foaming reaction does not occur. Therefore, the degree of vulcanization of the raw material composition is increased in advance during this preheating step. By preliminarily increasing the degree of vulcanization of the raw material composition, a structure for retaining a large amount of “bubbles” generated in the initial stage of the foaming reaction is formed. Furthermore, the preheating step plays another important role. If the pre-heating step is not provided and the vulcanizing can is heated to a temperature equal to or higher than the foaming start temperature at a stretch, for example, pressure unevenness in the vulcanizing can caused by the introduction of pressurized steam is not sufficiently eliminated. Temperature unevenness occurs, as a result, distribution of the bubble density and the bubble diameter occurs,
The hardness of the foam roller is not uniform. In the present invention, once the temperature rise is stopped at a temperature lower than the foaming start temperature, and during the holding, for example, since the pressure in the vulcanizing can is made uniform, it becomes possible to make the temperature of the rubber uniform, Thereafter, even when the temperature is rapidly raised to the temperature t2 used in the foaming vulcanization step, the temperature can be raised while suppressing temperature unevenness.

When manufacturing a foaming roller used in an electrophotographic apparatus such as a transfer roller, a charging roller, and a developing roller, the holding time T2 of the preheating step is desirably 1 to 10 minutes. Although it depends on the temperature t1, if the holding time T2 is 1 minute or more, it is possible to obtain a sufficient degree of vulcanization in order to hold the bubbles generated in the initial stage of the foaming reaction. Further, if the holding time T2 is 10 minutes or less, it is possible to avoid a problem that the degree of vulcanization is excessively increased and foaming is suppressed. Further, when the temperature t1 is selected to be equal to or higher than 100 ° C., the holding time T2 can be preferably selected in the range of 1 to 4 minutes.

The holding temperature t1 of the raw material composition in the preheating step is not particularly limited as long as it is lower than the temperature at which decomposition of the foaming agent starts and a temperature at which a sufficient vulcanization reaction rate can be obtained. Considering the reaction speed of the sulfuric acid reaction, it is desirable that the temperature is at least 100 ° C. or higher. When the temperature is 100 ° C. or higher, a sufficient vulcanization reaction rate can be obtained, and the holding time T2 can be set in the above-mentioned preferable range.

When the holding temperature t1 is 100 ° C. or higher, the pressure of the steam is adjusted when the raw material composition is heated and foamed using a vulcanizer that changes the temperature by controlling the pressure of the steam under pressure. By doing so, the temperature of the vulcanizing can can be controlled with sufficient accuracy.

The other is to introduce a temperature increasing step of increasing the temperature of the raw material composition at a predetermined rate, following the preheating step. The average heating rate in this heating step is 15 ° C.
/ Min or more is desirable.

Here, the term "continuously" means that the temperature is raised "without lowering the temperature". Further, the “average heating rate” is a value obtained by dividing the temperature rise (t2−t1) during the time T3 required for this heating step;
It indicates the rate of temperature increase given by (t2−t1) / T3.

The foaming reaction starts when the temperature reaches the decomposition temperature of the foaming agent during the temperature raising step, and then proceeds rapidly while the temperature rises. In addition, it is difficult to maintain the structure of generated bubbles only by the progress of vulcanization in the preheating step. Therefore, in order to further advance the vulcanization reaction in accordance with the rapid progress of the foaming reaction, the average heating rate is selected to be 15 ° C./min or more, and the temperature t2 is quickly reached, and the vulcanization reaction rate is also rapidly increased. do. By selecting the heating rate in this manner, the raw material composition is foamed while maintaining the balance between the foaming reaction and the vulcanization reaction.

The average heating rate in the heating step is 15 ° C. /
If it is not less than minutes, the progress of the vulcanization reaction can be promoted as much as necessary to maintain the structure of the foam, and it is possible to obtain a foam having foams with a uniform diameter.

In the present invention, the raw material composition may contain a conductive substance. These transfer rollers,
Rollers such as a charging roller and a developing roller have different degrees of conductivity, but all are required to have conductivity, and even if the conductivity is adjusted by including a known conductive material in the raw material composition. good.

Therefore, the method for producing a foamed roller of the present invention is suitably used for producing a roller-shaped member of an electrophotographic apparatus. Specifically, a transfer roller used when transferring a toner image from a photoconductor carrying a toner image to a transfer material,
A charging roller for charging the photoconductor surface to a predetermined voltage,
It is suitably used for manufacturing a developing roller for developing the surface of a photosensitive drum carrying an electrostatic latent image by exposure.

The rubber used in the raw material composition of the present invention includes EPDM (ethylene-propylene-diene-copolymer), polybutadiene, natural rubber, polyisoprene, SB
R (styrene butadiene rubber), CR (chloroprene), N
Rubbers such as BR (acrylonitrile butadiene rubber), silicone rubber, urethane rubber, epichlorohydrin rubber, polystyrene-based polymer materials such as RB (butadiene resin), SBS (styrene-butadiene-styrene elastomer), polyolefin-based polymer materials, polyester -Based polymer materials: polyurethane-based polymer materials, thermoplastic elastomers such as RVC, polyurethane, polystyrene, PE
(Polyethylene), PP (polypropylene), PVC (polyvinyl alcohol), acrylic resin, styrene-vinyl acetate copolymer, butadiene-acrylonitrile copolymer, and other high-molecular materials, and rubbers, elastomers,
Mixtures of resins can be used.

Further, as the conductive substance added for imparting conductivity to the rubber, a known substance can be used. For example, as the conductive particles, conductive carbon black, TiO _2, SnO _2, ZnO, metal oxides such as solid solutions of SnO ₂ and SbO _3, Cu, metal powder or the like, such as Ag, also, as the ion conductive agent, Licio ₄ , NaSCN, etc., and it is possible to obtain a desired electric resistance by adding and dispersing the rubber alone or in combination. In addition, conductivity can be obtained by introducing a molecule having polarity into the rubber main chain or into the side chain.

As a foaming agent, an organic foaming agent such as AD
C. A (azodicarbonamide), DPT (dinitrosopentamethylenetetraamine), TSH (P. toluenesulfonyl hydrazide), OBS H (oxybisbenzenesulfenyl hydrazide), etc., alone or mixed It is possible to use it.

Examples of the foaming aid include urea compounds, metal oxides such as zinc oxide and lead oxide, and compounds containing salicylic acid and stearic acid as main components. it can.

Examples of the vulcanizing agent include sulfur and metal oxides, and examples of the vulcanizing accelerator include thiazole-based, sulfenamide-based, thiuram-based, and carbamate-based vulcanizing agents. It is selected accordingly.
In addition, known vulcanization accelerators, softeners, reinforcing agents, inorganic fillers, and the like are appropriately added as necessary.

The decomposition temperature of the foaming agent can be lowered by adding a foaming aid such as a urea resin or zinc oxide.

A predetermined amount of the above raw materials is mixed to obtain a raw material composition. As a kneading means for mixing the raw material compositions, kneading is uniformly performed by a kneading machine such as a known bumper mixer or kneader, and the unvulcanized raw material composition is sheeted by a roll.

As a means for forming the unvulcanized raw material composition into a cylindrical shape, a cylindrical shape required for the final shape is selected by an extruder by selecting the size of a die (die) and a mandrel (mandrel). The unvulcanized raw material composition is formed into a cylindrical shape, and a predetermined length is obtained by a cutting machine to obtain a cylindrical molded body.

Next, the heating means and the heating method used in the present invention will be described. As the heating means, it is desirable to use a vulcanizer that is heated directly by pressurized steam. This heating method controls the temperature by increasing or decreasing the pressure of the pressurized steam in the vulcanizing can, so that uniform heating is possible, the heat conduction is good, and the vulcanization can be quickly performed. It is very suitable as a heating means.

[0064]

The present invention will be described below in detail with reference to examples.

(Preparation of Unvulcanized Formed Body) NBR1 as rubber
00 parts by mass, 8 parts by mass of ADCA (azodicarbonamide) foaming agent, 8 parts by mass of urea resin as foaming aid, 1.5 parts by mass of sulfur, 1 part by mass of mercaprobenzothiazole as vulcanization accelerator, tetraethylthiuramdis 2 parts by mass of sulfide, 30 parts by mass of carbon black as a filler, 30 parts by mass of calcium carbonate, 5 parts by mass of zinc white as a vulcanization accelerator, 1 part by mass of stearic acid, and 20 parts of a naphthenic process oil as a softener. The mixture was uniformly kneaded with a kneader, which is a well-known method, and sheeting was performed with a roll.

The kneaded raw material composition was formed into a cylindrical unvulcanized molded product by an extruder and cut by a cutter to obtain a length.

At this time, the dimensions of the cylindrical unvulcanized compact were set to an inner diameter of 5.0 mm, an outer diameter of 14.5 mm, and a length of 320 mm. A vulcanized molded product was obtained.

(Examples 1, 2 and Comparative Example 1) Experiments of foaming and vulcanization were carried out at heating temperatures and holding times shown in Table 1 below.

The unvulcanized product used was the one described in the section (Preparation of unvulcanized product). The heating sequence is input to the vulcanizer temperature control device in advance, and after the start of heating, the temperature is automatically controlled and the foam vulcanization process is performed.

[0070]

[Table 1]

Under the conditions of Example 1, Example 2, and Comparative Example 1, 50 of the above-mentioned cylindrical unvulcanized molded articles were vulcanized and foamed.

In Table 1, at time T5, from the end of the holding period (foaming step) at the set heating temperature t2, the pressure is reduced until the vapor pressure in the vulcanizer becomes approximately 0 kgf / cm ² in gauge vapor pressure. (Decompression time).

The foam taken out of the vulcanizer was subjected to secondary vulcanization in a hot air oven at 180 ° C. for 20 minutes.

The obtained cylindrical foams of Example 1, Example 2 and Comparative Example 1 were cut at a pitch of 60 mm in the length direction, and the inner diameter was measured with a cylindrical gauge, respectively. The difference between the maximum inside diameter and the minimum inside diameter in the book was defined as the inside diameter unevenness. The same measurement was performed for each of ten pieces, and the average inner diameter unevenness of ten pieces was calculated.

Next, a φ8.0 mm core metal coated with a conductive adhesive was pressed into the cylindrical hole of the cylindrical foam, and the press-fitting property was evaluated. Table 2 shows the evaluation results of the average inner diameter unevenness (inner diameter variation) and the press fit.

Subsequently, the outer diameter of the foam roller provided with the press-fitted and adhered skin layer was polished by a cylindrical grinder, and both ends of the foam were cut off to obtain an outer diameter of 18.0 mm and a length of 304 mm.
Was obtained.

After polishing the outer diameter of these foaming rollers, the hardness of the transfer roller was measured using an Asker C hardness meter to a load of 50%.
It was measured at 0 gr. The evaluation was performed at two locations 10 mm from the both ends of the roller and three locations at the center, a total of five locations, and the difference between the maximum value and the minimum value was regarded as hardness unevenness. The same measurement was performed for each of ten pieces, and the average of ten pieces of hardness unevenness was calculated.
It was shown to.

[0078]

[Table 2]

In Comparative Example 1 in which the average of the inner diameter was small and the variation in the inner diameter was large, it was difficult to press-fit the core metal, and it took time to press-fit.

Next, an image actually output was evaluated using these transfer rollers. In the image evaluation, the transfer roller of the present invention manufactured as described above in the image forming process described above was applied to the photosensitive member surface with a total pressure of 1 kg.
The image was evaluated by a high-speed LBP (laser beam printer) having a process speed (peripheral speed of the OPC photosensitive member) of 145 mm / sec and a sheet passing speed of 32 sheets / min.

As a result, when the transfer rollers of Example 1 and Example 2 output a solid black image and a halftone image, both images were clear.

The same evaluation was performed on the transfer roller of Comparative Example 1. However, the skew of the transfer material did not occur in Example 1 and Example 2, but occurred on the transfer roller having the hardness unevenness of 3.5 degrees.

(Examples 3 and 4 and Comparative Example 2) Foamed rollers were manufactured under the conditions of Examples 3 and 4 and Comparative Example 2 shown in Table 1.

The obtained cylindrical foams of Example 3, Example 4, and Comparative Example 2 were cut, and the diameters of the cells in the cross sections were measured by an optical microscope. When the cross section of the bubble is not a perfect circle such as an elliptical shape, the average value of the major axis and the minor axis of the bubble is defined as the bubble diameter.

Next, in the same manner as in Examples 1 and 2, a core metal is pressed and bonded, and the outer periphery thereof is polished and cut off.
A transfer roller having an outer diameter of 18.0 mm and a length of 304 mm was obtained.

In Example 1, the hardness of the polished transfer roller was measured.
As in the case of Example 2, etc., 10 samples were measured, and 10 samples were measured.
The average hardness of the book was used. Table 3 shows the measurement results of the cell diameter and hardness.

[0087]

[Table 3]

In Examples 3 and 4, bubbles having a uniform diameter were obtained as shown in Table 3, but in Comparative Example 2, bubbles having a diameter of 180 to 220 μm were present in some places. This is presumably because during the foam vulcanization step, adjacent bubbles burst and were bonded, so that large-diameter bubbles were generated.

Next, using these transfer rollers, evaluation of images actually output was performed in the same manner as in Examples 1 and 2.

As a result, when the transfer rollers of Example 3 and Example 4 produced solid black and halftone images, they were all clear images.

When the same evaluation was performed on the transfer roller of Comparative Example 2, image unevenness due to air bubble unevenness that did not exist in Examples 3 and 4 was observed in the L / L environment (temperature: 15 ° C., relative humidity: 10%) occurred in the lower halftone image.

[0092]

As described above, when the roller manufacturing method of the present invention is used, an unvulcanized molded product is vulcanized and foamed in a vulcanization can directly heated in a foaming vulcanization step by pressurized steam. In the foamed roller, the unevenness in foaming is reduced and the unevenness in hardness is reduced. Further, a foam roller having a small bubble diameter can be manufactured.

A foamed roller can be easily manufactured by press-fitting a cylindrical foam, thereby improving the productivity.

In particular, when used as a transfer roller, partial image unevenness due to a large bubble diameter is eliminated. Further, it is possible to provide a transfer roller which is free from unevenness in hardness and excellent in transportability.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a conductive foam roller.

FIG. 2 is a side view illustrating the configuration of the electrophotographic apparatus.

FIG. 3 is a schematic diagram illustrating a method for heating in the foam vulcanization step of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Roller body 2 Core metal 3 Photoconductor 4 Charging roller 6 Developing roller 7 Transfer roller

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01B 13/00 501 B29K 105: 04 // B29K 105: 04 105: 24 105: 24 B29L 31:32 B29L 31 : 32 B29C 67/22 F term (reference) 2H003 BB11 CC05 2H032 AA05 BA23 2H077 AC04 AD06 AD14 FA22 FA25 4F203 AA09 AB02 AB03 AB13 AH04 AR06 AR11 DA11 DB01 DC04 DK02 DK07 DL10 DL14 DW06 4F212 AA09 AB02 AR03 AB03 AB03 UK01 UN09 UN13 UN27

Claims (6)

[Claims] 1. A method comprising using a raw material composition containing at least a vulcanizing agent and a foaming agent, and heating the raw material composition molded into a desired shape to expand and expand the foam to form a foam. In the method for manufacturing a foam roller, the heating step of forming a foam of the raw material composition includes: (1) heating the raw material composition to a temperature t1 which is lower than a decomposition temperature of a foaming agent contained in the raw material composition; In the case of temporarily holding in the above, a preheating step of selecting the holding time T2 in the range of 1 to 10 minutes, and (2) following the preheating step, at an average temperature change rate of 15 ° C./min or more. A temperature raising step of raising the temperature to a temperature t2 selected above the decomposition temperature of the blowing agent; and (3) a foam vulcanization step of maintaining the temperature t2 at the temperature t2 for a predetermined time T4 after reaching the temperature t2.
A method for producing a foamed roller, comprising at least: 2. The method according to claim 1, wherein the temperature t1 is set to 100 ° C. or higher in the preheating step. 3. The method according to claim 1, wherein the steps (1) to (3) are performed in a vulcanizer heated by pressurized steam.
The method for producing a foamed roller according to any one of claims 1 to 3. 4. The method according to claim 1, wherein the raw material composition contains a conductive material. 5. A foam roller manufactured by the method of manufacturing a foam roller according to claim 1. 6. An electrophotographic apparatus using the foam roller according to claim 6 as a part.