JP4307323B2 - Conductive roll and method for producing the same - Google Patents

Description

  The present invention relates to a conductive roll made of a low hardness rubber imparted with conductivity and excellent in low compression set, and a manufacturing method for manufacturing the same inexpensively and easily in an electrophotographic apparatus such as a printer. It is used in contact with a photosensitive member such as a developing roll, a charging roll, or a transfer roll, and is suitable for a member that is used by applying a bias potential to a shaft.

  Conventionally, conductive fine powder is generally added as a means for imparting conductivity to rubber. As the conductive fine powder, carbon (carbon black), metal, metal oxide and the like are generally used.

  On the other hand, the bias application roll in the electrophotographic apparatus is required to be non-staining to the photoreceptor and toner. In order to prevent physical, chemical, and electrical contamination, a conductive coating such as polyamide (nylon) or alkyd resin is generally applied to the rubber roll surface layer (Patent Document 1, Patent Document 2, Patent). Reference 3 etc.).

  However, when such a structure is adopted, there is a disadvantage that the process becomes complicated and the manufacturing cost increases.

  As a means for easily solving these problems, a method of chemically treating the inside of the roll surface has been proposed (see Patent Document 4).

  Although this treatment method is effective, there is a problem that it is easily affected by the surface resistance of the substrate. When the electric resistance of the substrate is controlled by ionic conduction, variation in electric resistance is not recognized even in the micro region, but there is a problem that the electric resistance changes depending on the environment such as temperature and humidity.

  On the other hand, when the resistance value of the substrate is controlled by the dispersion of conductive fine particles such as carbon black, the variation due to the dispersion of the conductive fine particles becomes a problem, although the fluctuation due to the environment such as temperature and humidity is small. . This effect was not emphasized in the low-resolution area, but improvement has been demanded as the image quality of electrophotographic apparatuses such as printers and copiers is improved.

  A characteristic that is commonly required for a functional roll related to image formation incorporated in an electrophotographic apparatus is that the compression set is small. In particular, since the developing roll is required to have stable contact pressure with respect to the photoreceptor and the developing blade, low compression set is an important required characteristic.

  The properties actually required are slightly different from permanent set. An advantage of using a rubber roll is that it can absorb mechanical variations during incorporation into a product. This utilizes the characteristic that rubber is easily deformed when it receives an external force and can be instantly restored to its original shape when the external force is removed. Taking the developing roll as an example, it is in pressure contact with the photoreceptor and the developing blade, and is in a deformed state. When the apparatus is started from a state where it has been deformed for a long time, such as after a holiday, if the deformation does not recover within a predetermined time, image unevenness occurs. That is, it is practically a problem whether permanent deformation is not a direct measure but returns to the original shape in a short time (within several seconds). Therefore, the rubber compression set test method (JIS K6262) defined by JIS is a necessary condition but is not necessarily a sufficient condition. Recent high-quality printers are required to have a level at which compression set cannot be measured by measurement according to JIS (specifically, less than 0.5%: in JIS, measured values are rounded to the nearest 1%). Yes.

  Since polyurethane has a molecular design that is easy, it can produce a low hardness rubber with a relatively low compression set. Patent Document 5 discloses a carbon conductive polyurethane having a hardness (Shore A) of about 30 degrees and a compression set of 1.2 to 1.5%.

Japanese Patent Application Laid-Open No. 64-066674 JP-A-4-67067 Japanese Patent Laid-Open No. 7-020684 JP-A-5-158341 JP-A-3-249675

  In summary, the bias-applied rubber roll involved in image formation in a high-quality electrophotographic apparatus has a microscopic (toner particle size or less) uniform conductivity from the surface to the contact member. It is required to have all the characteristics that there is no contamination and the deformation from the pressure contact member is recovered in a short time.

  However, a production method that can easily produce a single-layer conductive roll satisfying all of these characteristics has not been realized.

  In view of such circumstances, the present invention provides a conductive roll having the above-described characteristics even in a substantially single-layer roll without using a conventional multilayer structure such as tube coating or coating, and the like. It is an object of the present invention to provide a method for manufacturing a conductive roll that can be manufactured at low cost.

  In order to solve the above-mentioned problems, the present inventors have repeatedly studied, and as a result, the base material is a thermosetting polyurethane, and the addition amount of carbon imparting conductivity is 2.5 wt% or more and 5 wt% or less to constitute the polyurethane. It becomes a non-plasticizer low-hardness conductive roll with extremely excellent strain recovery by curing the polyol to be a polyether having a functionality of 2.5 or more and an isocyanate compound having a functionality greater than 2 and NCO / OH being less than 1. As a result, the present invention has been completed.

According to a first aspect of the present invention, in the method for producing a conductive roll in which a conductive elastic layer formed by dispersing fine carbon powder in a thermosetting elastomer is formed on a core metal, the thermosetting elastomer per molecule. A polyurethane obtained by reacting a polyether polyol having an average functional group number of 2.5 or more with a polyisocyanate compound having an average functional group number greater than 2 at an NCO / OH molar ratio of less than 1. A curable elastomer is mixed with 2.5 to 8% by weight of carbon fine powder to form a molding material. A heating means for heating the molding member is provided around the molding member defining the molding cavity, and the thermal conductivity is 5 W / Between the heating means and the molding material in the molding cavity, a resin tube having a thickness of 0.05 to 1.00 mm which becomes a low thermal conductivity layer of m · K or less At least one layer is interposed, and the molding member is heated to 100 ° C. or higher and the molding material is heated via the low thermal conductivity layer, whereby an initial reaction until carbon fine particles reaggregate is 70 ° C. or lower. By fixing the carbon fine particles re-aggregated by reacting at a low temperature and then reacting by raising the temperature of the molding material, the compression set is 1% or less, and the range of 10 ⁴ to 10 ⁸ Ωcm. In addition, the present invention provides a method for producing a conductive roll, characterized in that a conductive roll having an electrical resistance value of not more than one digit in the axial and circumferential variations of the electrical resistance value is obtained.

According to a second aspect of the present invention, in the first aspect, the heat conductivity of the low thermal conductivity tube is 0.1 W / m · K to 5 W / m · K. Is in the way.

  In the present invention, the amount of carbon imparting conductivity is 2.5 wt% or more and 8 wt% or less, preferably 2.5 wt% or more and 5 wt% or less, and the polyol constituting the polyurethane is a 2.5 or more functional polyether. It is an isocyanate compound larger than bifunctional, NCO / OH is less than 1, and is cured in a state where carbon is uniformly dispersed, thereby producing a non-plasticizer low-hardness conductive roll with extremely excellent strain recovery. is there.

  That is, the conductive roll of the present invention is different from the one in which carbon called so-called conductive carbon is added in a small amount such as 2 wt% or less, and more than 5 wt% of carbon that is not highly conductive is 10 wt%. It is different from the one that is added to the extent or more to obtain stable conductivity.

  Carbon black having various properties is commercially available and is selected according to the application. For example, when conductive carbon having a large specific surface area and oil absorption (for example, Ketjen Black EC; manufactured by Lion Corporation) is used, it is possible to impart conductivity necessary for an electrophotographic image forming roll even at 2 wt% or less. The present invention is different from this. In this case, it is presumed that a micro-network structure is formed when the dispersed carbon re-aggregates. However, if the amount of carbon added is less than 2.5 wt%, the microscopic variation in conductivity is controlled. Is difficult. In addition, carbon black having a small specific surface area can be blended in a relatively large amount, and in the case of a product with small variation, if it exceeds 5 wt% in a state where conductivity is developed, the compression set becomes larger than 1%, This is also different from the present invention. Note that the compression set in this case is not due to the polymer as a matrix, and it is thought that the macroscopic chain structure of carbon black does not reversibly recover.

  In the present invention, the dispersibility of carbon can be remarkably improved. In this case, the conductivity is less likely to be exhibited as compared with the conventional case. In this case, carbon may be added up to about 8% by weight. In addition, when the dispersibility of carbon is good, the compression set is difficult to increase, and when adding a large amount of carbon in this way, the compression set is hardly affected. It is preferable to use a small size, a large particle size, or a material that is difficult to form a structure.

  As a result of examining polyurethane used as a matrix, a base material in which compression set is hardly observed at a low hardness of about 60 degrees (JISA) or less required as an image forming roll for electrophotography by selecting a limited molecular structure. We found a technique to make Furthermore, it has been found that by selecting the above-mentioned amount of carbon, it becomes a material having an unprecedented characteristic of 1% or less compression set even in a state where conductivity by carbon is expressed. Furthermore, this material is not only excellent in permanent strain, but also excellent in instantaneous recovery from strain itself, and thus is suitable for applications requiring high-speed start-up properties.

  That is, the matrix used in the present invention is a polyurethane mainly composed of a polyether-based polyol, preferably a polyether-based polyol having an average number of functional groups per molecule of 2.5 or more and an average number of functional groups greater than 2. It is a thermosetting polyurethane obtained by reacting a polyisocyanate with an NCO / OH molar ratio of less than 1.

  The ether-based polyurethane suitably used as the rubber elastic layer of the present invention is a so-called cast type polyurethane obtained by reacting a polyol mainly composed of an ether-based polyol with a polyisocyanate. This is to reduce the compression set. If ether type polyurethane is a millable type, the compression set cannot be sufficiently reduced. On the other hand, when ester polyurethane is used, the hydrolysis characteristics are poor and it cannot be used stably over a long period of time.

  On the other hand, as the isocyanate to be reacted with the polyol, for example, trifunctional isocyanate alone such as triphenylmethane triisocyanate, tris (isocyanate phenyl) thiophosphate, bicycloheptane triisocyanate, nurate-modified polyisocyanate of hexamethylene diisocyanate (trimer: Mixtures such as trifunctional, pentamer: tetrafunctional) and polymeric MDI can be used. Moreover, it is good also as a mixture of these polyfunctional isocyanates more than trifunctional and a general bifunctional isocyanate compound. Examples of the bifunctional isocyanate compound include 2,4-toluene diisocyanate (TDI), 4,4′-diphenylmethane diisocyanate (MDI), paraphenylene diisocyanate (PPDI), 1,5-naphthalene diisocyanate (NDI), 3,3- Examples include dimethyldiphenyl-4,4'-diisocyanate (TODI), and modified products and multimers such as prepolymers having these isocyanates at both ends.

In addition, stability of an electric resistance value is required as an electrical characteristic in an electrophotographic image forming roll. In particular, in a developing roll expressing photographic gradation, a partial resistance variation is required within one digit. It is very difficult to stably form a medium resistance region of 10 ⁴ to 10 ⁸ Ωcm by dispersing carbon black having a specific resistance of about 0.1 to 10 Ωcm in an elastomer (10 ¹² to 10 ¹⁶ Ωcm) that can be called an insulator. It is difficult to. The smallest unit for forming an image is a toner having a size of several microns.

  What has a stable resistance value in this region is limited to ionic conduction that can be expected to be dispersed at the molecular level, but in the present invention, it is formed by heating and curing while maintaining the dispersed state of carbon. It was found that the stability of the electrical resistance value can be secured in the whole body. The important point is to control the process in which the carbon dispersed in the polyurethane raw material is re-agglomerated and the process in which the liquid polyurethane raw material reacts to increase the viscosity and the carbon cannot move.

  Conventional polyurethane elastomers other than foam systems are molded by injecting raw materials into a metal mold having a high temperature of about 100 ° C. or higher connected to a heat medium. This is to advance the reaction by quickly heating the raw material, and is a very general method for curing the thermosetting elastomer. However, it has been found that when such a rapid thermal gradient occurs, carbon aggregation accelerates near the mold surface where the viscosity has decreased, and the microscopic electrical resistance varies.

  The present invention cures the carbon-dispersed raw material filled in the molded member without causing local agglomeration of carbon, and has been devised to maintain the same curing time as before. That is, in the present invention, in the state where the fine carbon powder is dispersed in the matrix, the initial stage of polyurethane production is relatively low, for example, 70 ° C. or lower, while maintaining the viscosity to the extent that the flow of the fine carbon powder is inhibited. After the reaction is performed and the reaction proceeds to a region where the reaggregation of carbon is fixed, the resistance is stabilized by heating slowly. Such reaction control is possible by controlling the mold temperature, but it is inefficient in energy and the apparatus becomes large.

  In the present invention, even if a constant temperature control mold similar to the conventional one is used, the initial temperature of the raw material injected into the mold is devised so as not to rise for a certain period of time, such as a thermosetting elastomer raw material and a molding die. A member having a low thermal conductivity between the heating means, for example, a material having at least one low thermal conductive layer of 5 W / m · K or less, which is heated from the outside and cured so as not to lower the viscosity It is.

  That is, in a method for manufacturing a conductive roll in which a conductive elastic layer formed by dispersing carbon fine powder in a thermosetting elastomer is formed on a cored bar, the molded member is heated around a molded member that defines a molding cavity. And a low thermal conductivity layer having a thermal conductivity of 5 W / m · K or less is interposed between the heating means and the molding material in the molding cavity for molding.

  Here, the low thermal conductivity layer having a thermal conductivity of 5 W / m · K or less is, for example, a low thermal conductivity tube having a thermal conductivity that is one digit or more lower than that of a molding die as a member having a small thermal conductivity. It is preferable to mold using as a molding member. Further preferred is a resinous tube that is two orders of magnitude lower. Examples of the thermal conductivity of the metal used in the mold are 48.5 W / m · K for carbon steel, 72 W / m · K for iron, and 240 W / m · K for aluminum (thermal conductivity at 100 ° C. : Quoted from the 2001 scientific chronology).

  Here, as the low thermal conductivity tube, various resin tubes such as polyethylene, polypropylene, polyamide, and polytetrafluoroethylene can be generally used. Further, the thickness of the low thermal conductivity tube is, for example, 0.05 to 1.00 mm, and the thermal conductivity of the low thermal conductivity tube is 0.1 W / m · K to 5 W / m · K. The thermal conductivity of the single resin is about 0.2 to 0.4, which is 2-3 orders of magnitude lower than that of metal. In addition, the thermal conductivity is further reduced by an order of magnitude by foaming the resin.

  Further, when such a low thermal conductivity tube is used as a molding member, the molding die may be disposed in close contact with the molding member as a heating means as described above, but between the molding member and the molding die. In this case, the air layer also functions as a low heat conductive layer. Furthermore, when such an air layer is provided, in order to support the molded member, a support member that intermittently contacts the molded member with points or lines may be provided. Note that the shape and material of such a support member are not particularly limited. For example, the material may be a metal or a low thermal conductivity material.

  Furthermore, you may form a shaping | molding member with materials, such as a metal. However, in this case, it is necessary to interpose at least one low thermal conductivity layer outside the molded member. Examples of such a low thermal conductivity layer include an air layer and a resin layer.

  In addition, although a molding die is exemplified as the heating means, the molded member may be heated in an electric furnace or the like. In this case, the electric furnace serves as the heating means.

  According to the present invention, it is possible to provide a carbon conductive low-hardness elastomer having a stable electric resistance value in the entire molded body, which has been difficult to achieve conventionally. It has become possible to provide a conductive roll having a resistance value that is stable up to the vicinity of the surface of the molded body and a small resistance variation. Using a 2 mm wide electrode as a measure of resistance variation, and using the ratio of the maximum resistance value to the minimum resistance value in multipoint measurement in the circumferential direction and the axial direction, the ratio of maximum resistance value / minimum resistance value is 10 or less. It is possible to easily adjust the conductive roll.

  Thus, since the base material with little variation in resistance does not require a coating layer whose conductivity is strictly adjusted, it is possible to effectively utilize the surface hardening treatment for treating the inside of the base material with an isocyanate compound or the like. By the surface curing treatment, contamination of the elastomer roll with respect to the photoreceptor and the toner is avoided.

  Moreover, it is preferable to add carbon to the surface hardening treatment liquid in order to further stabilize the resistance of the surface layer. In this case, it is preferable to add a small amount of a binder resin as a carbon binder. In this case, since the binder resin does not need to be provided with a function of preventing the migration of contaminants generated from the roll, the selection conditions are relaxed. Therefore, it is possible to select from materials considering not the stain resistance but the chargeability of the toner.

  Particularly when used for a developing roll, a polymer having a low water absorption rate for preventing toner charge leakage and further having an atomic group for stably charging the toner is suitably selected. Examples of the binder resin having good solubility include modified acrylic polymers. In particular, an acrylic polymer modified with a fluorine resin or a silicone resin is preferably used.

  Here, an example of the metal mold | die for shape | molding the electroconductive roll of this invention is shown in FIG.

  The mold 30 includes a cylindrical mold 31 made of a metal pipe member whose inner diameter is defined with high accuracy, and a top 32 that holds both ends of the core metal 11. The cylindrical mold 31 and the top 32 are the same. It is held by a pressing mold 33 that is a split mold so as to be in a core state. A low thermal conductivity tube 34 is disposed in the cylindrical mold 31.

  Such a mold 30 is heated to about 100 ° C., and a mixture 40 in which carbon is dispersed in a polyurethane raw material adjusted to about 60 ° C. is injected into the low thermal conductivity tube 34. In the first stage, the low thermal conductivity tube 34 prevents uneven carbon aggregation due to local thermal diffusion. After the initial reaction is performed in a thermally uniform state, the raw material is slowly heated by the presence of the low thermal conductivity tube, and the curing reaction proceeds quickly.

  In addition, in the metal mold | die 30 mentioned above, although the metal pipe member was used as the cylindrical mold 31, it is not necessary to use this, and you may make it heat directly with a hot air from the outer side of the cylindrical mold 31, The cylindrical mold 31 may be omitted and heated with hot air directly from the outside of the low thermal conductivity tube 34, and the mold structure is not particularly limited.

  The conductive roll manufactured in this manner can be used without substantially polishing the surface because carbon agglomeration does not substantially occur even near the surface of the molded roll. That is, when the conventional manufacturing method according to the prior art is used, agglomeration of carbon occurs in the vicinity of the surface. Therefore, unless the vicinity of the surface is polished at least about 3 to 4 mm, a stable surface resistance value cannot be obtained. However, in the conductive roll of the present invention, it is not necessary to substantially polish, and a stable surface resistance value can be obtained only by polishing only the surface layer of 0.5 to 2 mm as compared with the conventional one. In general, outer diameter polishing is performed to adjust the outer diameter dimension and the longitudinal variation of the outer diameter, and surface polishing of 1 to 2 mm is necessary for this purpose.

  The conductive roll of the present invention may be provided with a coating layer after being polished, but is preferably subjected to a surface treatment capable of maintaining a surface state and performing a predetermined friction coefficient and friction charging.

  Here, the surface treatment refers to an isocyanate treatment in which an isocyanate compound is impregnated and cured. As the surface treatment liquid to be used, a solution obtained by dissolving an isocyanate compound in an organic solvent, or a solution obtained by adding carbon black to this can be used. In addition, a surface treatment liquid containing at least one polymer selected from an acrylic fluorine-based polymer and an acrylic silicone-based polymer, a conductivity imparting agent, and an isocyanate component can also be used.

  Examples of the isocyanate compound used in the surface treatment liquid include 2,4-toluene diisocyanate (TDI), 4,4′-diphenylmethane diisocyanate (MDI), paraphenylene diisocyanate (PPDI), 1,5-naphthalene diisocyanate (NDI), and 3,4. Examples thereof include 3-dimethyldiphenyl-4,4′-diisocyanate (TODI) and the above-described multimers and modified products.

  Here, when the surface treatment layer surface-treated with the surface treatment liquid containing isocyanate is provided on the surface of the conductive roll as described above, a predetermined surface state and a friction coefficient are obtained by this surface treatment. Further, the variation in electric resistance value is reduced, and there is also an effect that a conductive roll having a predetermined electric resistance value can be obtained.

  As described above, in the present invention, the base material is thermosetting polyurethane, the amount of carbon imparting conductivity is 2.5 wt% or more and 5 wt% or less, and the polyol constituting the polyurethane is 2.5 functional or more. When the NCO / OH is less than 1 and is cured with an isocyanate compound having a functionality greater than 2 and a non-plasticizer low-hardness conductive roll having an extremely excellent strain recovery property, an effect is provided.

  EXAMPLES Hereinafter, although this invention is demonstrated based on an Example, this invention is not limited to this.

Example 1
<Method for producing roll> To 100 parts by weight of GP-3000 (manufactured by Sanyo Chemical Co., Ltd.), which is a trifunctional polyether-based polyol, 5 parts by weight of Toka Black # 5500 (manufactured by Tokai Carbon Co., Ltd.) is added, and the particle size becomes 10 μm or less. Disperse to the extent that the temperature was adjusted to 60 ° C. to obtain Liquid A. On the other hand, 70 parts by weight of bifunctional prepolymer adiprene L100 (made by Uniroyal Corporation) with an NCO concentration of 4.2% was added to coronate C-HX (made by Nippon Polyurethane Co., Ltd.) with an average of 3.7 functionalities and an NCO concentration of 21.3%. 30 parts by weight were added and mixed, and the temperature was adjusted to 60 ° C. to obtain a liquid B. The average functional group number of B liquid is 2.9, and NCO density | concentration is 9.3%. This liquid A and liquid B are mixed at a weight ratio of 105: 36 (NCO / OH = 0.8) so that the shaft (φ: 8 mm, l: 270 mm) is arranged in advance and is in close contact with the inner wall surface. A polypropylene extruded tube (outer diameter 23 mm, thickness 0.2 mm) is inserted, poured into a φ23 mm steel pipe mold preheated to 110 ° C., heated at 110 ° C. for 120 minutes, and both ends are removed. A roll having a conductive polyurethane layer formed on the shaft surface was obtained. The concentration of carbon black is 3.5 wt%.

  The conductive roll of Example 1 was prepared by polishing the surface of this conductive roll for 1.5 mm and adjusting the outer diameter to 20 mm.

  Moreover, in order to measure hardness (JIS K6253) and compression set (JIS K6262), it injected into the metal mold | die which has an internal volume of (phi) 30mm and height 13mm, and heat-hardened on the same conditions.

(Example 2)
In a ball mill, 100 parts by weight of ethyl acetate, 4 parts by weight of acetylene black (manufactured by Denki Kagaku), and 2 parts by weight of an acrylic silicone polymer (Modiper FS700; manufactured by Nippon Oil & Fats Co., Ltd.) were used. After dispersing and mixing for 3 hours, surface treatment was performed using a surface treatment liquid in which 20 parts by weight of an isocyanate compound (MDI) was added, mixed and dissolved to form a surface treatment layer. That is, the conductive roll of Example 2 was formed by immersing the rubber roll for 30 seconds while maintaining the surface treatment liquid at 23 ° C., and then forming the surface treatment layer by heating in an oven maintained at 120 ° C. for 1 hour. did.

(Example 3)
The surface of the roll of Example 1 was treated in the same manner as in Example 2 to obtain a conductive roll of Example 3.

(Example 4)
<Production Method of Roll> 4 parts by weight of Toka Black # 5500 (manufactured by Tokai Carbon Co.) and 100 parts by weight of GP-3000 (manufactured by Sanyo Chemical Co., Ltd.), a trifunctional polyether polyol, and VULCAN XC305 (manufactured by Cabot) 3 Part by weight was added and dispersed until the particle size became 10 μm or less, and the temperature was adjusted to 60 ° C. to obtain liquid C. On the other hand, the same B liquid as in Example 1 was prepared, and this C liquid and B liquid were mixed at a weight ratio of 105: 36 (NCO / OH = 0.85), and then preheated to 120 ° C. with an inner diameter of 28 mm. Inserted into an aluminum mold with a hole depth of 350 mm, and extruded with polypropylene with both ends of the shaft fixed with a polypropylene resin cap so that the shaft (φ: 8 mm, l: 270 mm) is placed in the center in advance. It was poured into a tube (outer diameter 24 mm, thickness 0.3 mm) and heated at 120 ° C. for 120 minutes to obtain a roll having a conductive polyurethane layer formed on the shaft surface excluding both ends. A sample for measuring hardness and permanent compression strain was prepared in the same manner as in Example 1. The concentration of carbon black is 5.2 wt%.

  The surface of this conductive roll was polished 1.5 mm and the outer diameter was adjusted to 20 mm, and the surface was treated in the same manner as in Example 2 to obtain a conductive roll of Example 4.

(Comparative Example 1)
Production was carried out in the same manner as in Example 1 except that a polypropylene-based extruded tube on the inner wall surface of the iron pipe mold used in Example 1 was used and a silicone release agent was applied as the release layer. The conductive roll of Comparative Example 1 was polished to a thickness of 1.5 mm and the outer diameter was adjusted to 20 mm.

(Comparative Example 2)
The surface of the unpolished roll of Comparative Example 1 was treated in the same manner as in Example 2 to obtain a conductive roll of Comparative Example 2.

(Comparative Example 3)
The surface of the roll of Comparative Example 1 was treated in the same manner as in Example 2 to obtain a conductive roll of Comparative Example 3.

(Comparative Example 4)
The unpolished product of Comparative Example 1 was used as the conductive roll of Comparative Example 4.

(Comparative Example 5)
The unpolished product of Example 1 was used as the conductive roll of Comparative Example 5.

(Test Example 1)
The hardness of the test pieces prepared in Example 1 and Example 2 was 51 degrees and 53 degrees (durometer A), and the compression set after standing at 25% 70 ° C. for 72 hours was 0.3% and 0.4%. It was. In JIS K6262, the average value is rounded by JIS Z8401 and expressed in integers. According to this example, it was found that a low-hardness elastomer material that was almost completely restored was obtained.

(Test Example 2)
Evaluation was made for variations in electrical resistance values. In order to evaluate the variation in the axial direction and the circumferential direction in one roll, as shown in FIG. 2, a stainless steel electrode 51 having an electrode width of 2 mm is adhered to the surface of the elastic layer 12 of the conductive roll, and the core metal The resistance value at that position was measured while rotating the roll between the two. This was measured at six locations in the longitudinal direction. The results are shown in Table 1.

The maximum value (R _max ), the minimum value (R _min ) of the resistance value at each measurement position, and the ratio between the maximum value and the minimum value (R _max / R _min ) are shown. Conventionally formed rolls made of metal molds have a small variation in electrical resistance values due to polishing (Comparative Examples 1 and 3) and surface treatment (Comparative Example 4), but very large variations on the surface of the molded body. Was found to be large. On the other hand, a roll formed by inserting a PP tube having a low thermal conductivity has a very small variation in resistance value. Even in an unpolished state (Comparative Example 5), the variation is very small. By polishing only the surface layer (Example) 1) The variation of the electric resistance value was within one digit. Moreover, when this roll base material is used, even if a simpler and lower-cost surface hardening treatment is used without using a conventional method of applying a coating agent with adjusted conductivity, the variation in electric resistance value is within one digit. (Examples 3 and 4), and in this case, it was found that even in an unpolished state, the variation in electric resistance value was within one digit (Example 2).

(Test Example 3)
FIG. 3 shows the results of measuring the change over time in the raw material temperature during the thermosetting process. The measurement is performed in Example 4 and Comparative Example 1, and the measurement position is a point at the center of the shaft and an outer diameter of 20 mm.

  In Comparative Example 1 in direct contact with the iron pipe mold via the silicone mold release agent, the liquid temperature reached 100 ° C. within 1 minute, whereas in Example 4 it was confirmed that 3 minutes or more were required. It was done.

It is a figure explaining one manufacture example of the electroconductive roll concerning one Embodiment. It is a figure which shows the mode of the measurement of the electrical resistance value of the electroconductive roll concerning one Embodiment. It is a figure which shows the result of having measured the time-dependent change of the raw material temperature in the electroconductive roll concerning one Embodiment.

Explanation of symbols

11 Core 12 Elastic layer 30 Mold 31 Cylindrical 34 Low thermal conductivity tube

Claims (2)

In the method for producing a conductive roll in which a conductive elastic layer formed by dispersing carbon fine powder in a thermosetting elastomer is formed on a core metal, the average number of functional groups per molecule of the thermosetting elastomer is 2.5 or more. Is a polyurethane obtained by reacting a polyisocyanate compound having a mean number of functional groups of greater than 2 with an NCO / OH molar ratio of less than 1, and 2 carbon fine powders are added to the thermosetting elastomer. A low thermal conductive layer having a thermal conductivity of 5 W / m · K or less provided with a heating means for heating the molded member around the molded member that defines a molding cavity by mixing 5 to 8% by weight to form a molding material At least one layer of a resin tube having a thickness of 0.05 to 1.00 mm is interposed between the heating means and the molding material in the molding cavity. By heating the molding material to 100 ° C. or higher and heating the molding material through the low thermal conductivity layer, the initial reaction until the carbon fine particles re-aggregate is allowed to react at a low temperature of 70 ° C. or lower. Then, by fixing the carbon fine particles that have been re-aggregated by reacting with the temperature of the subsequent molding material rising, the compression set is 1% or less, and the electric resistance value is in the range of 10 ⁴ to 10 ⁸ Ωcm. And a conductive roll having a variation in the axial direction and the circumferential direction of the electrical resistance value within one digit. The method of manufacturing a conductive roll according to claim 1 , wherein the low thermal conductivity tube has a thermal conductivity of 0.1 W / m · K to 5 W / m · K.

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