JP6563632B2 - Rubber composition for semiconductive belt and semiconductive belt - Google Patents

Description

  The present invention relates to a transfer belt and a transfer conveyor belt in an image forming apparatus such as a plain paper copier, a color copier, a laser beam printer, a facsimile, and an OA apparatus having a combined function of these using the basic principle of electrophotography. The present invention relates to a semiconductive belt that can be used as an intermediate transfer belt and the like, and to a rubber composition used for the semiconductor belt.

  The transfer belt, transfer conveyance belt, and intermediate transfer belt in electrophotographic image forming apparatuses such as copying machines are semiconductive by adding conductive additives or fillers to elastomer materials such as rubber. A conductive belt is used.

  For example, Patent Document 1 discloses a conductive endless belt in which a base resin mainly composed of a polymer alloy of a polyphenylene sulfide resin and an olefin elastomer is blended with a polymer ion conductive agent. Patent Document 2 discloses that an organic metal salt having a fluoro group and a sulfonyl group is blended with nitrile rubber together with a polyether made of an ethylene oxide-propylene oxide copolymer. However, these polymer ionic conductive agents and organic metal salts are blended in order to develop a desired resistance value and improve antistatic properties, and mention is made of the effect of improving resistance variation in the belt surface. Not.

  On the other hand, in Patent Document 3, for a semiconductive roller, a base rubber composed of epichlorohydrin rubber and nitrile rubber is blended with an antistatic agent composed of a mixture of ethylene oxide-propylene oxide copolymer, lithium salt and adipic acid ester. A rubber composition is disclosed. In Patent Document 4, a conductive elastic layer of a conductive member such as a conductive roller is formed using any one of rubber, resin, and thermoplastic elastomer, and an ionic conductivity imparting agent such as a lithium salt is formed thereon. Is disclosed. However, the antistatic agent is blended in order to reduce the resistance variation of each roller or to reduce the change in electric resistance depending on the environmental change, and the ionic conductivity imparting agent is conductive to the conductive elastic layer. Both documents do not disclose the effect of improving resistance variation in the belt surface in combination with a specific base rubber.

JP 2007-171414 A JP 2008-031287 A JP 2008-197267 A JP 2009-108265 A

  A semiconductive belt used in electrophotographic technology is required to have uniform resistance in the belt surface so that image unevenness does not occur. In the transfer belt using a blend rubber of chloroprene rubber and ethylene propylene rubber as the base rubber, carbon black is blended in order to impart semiconductivity, but the resistance variation in the belt surface is large and image unevenness is caused. It is required to reduce resistance variation so as not to occur.

  An object of this invention is to provide the semiconductive belt which can reduce the resistance variation in a belt surface, and the rubber composition for it in view of the above point.

  The rubber composition for a semiconductive belt according to the present invention comprises 5 to 40 parts by mass of carbon black with respect to 100 parts by mass of base rubber including 30 to 90 parts by mass of chloroprene rubber and 10 to 70 parts by mass of ethylene propylene rubber. It contains 0.5 to 20 parts by mass of an ion conductive polymer composed of a mixture of an ethylene oxide-propylene oxide copolymer and a lithium salt. The semiconductive belt according to the present invention is a semiconductive belt for an image forming apparatus using the rubber composition.

  According to the present invention, an ion conductive polymer composed of a mixture of an ethylene oxide-propylene oxide copolymer and a lithium salt is added to a semiconductive rubber obtained by adding carbon black to a base rubber composed of chloroprene rubber and ethylene propylene rubber. By blending, resistance variation in the belt surface in the carbon black blending can be reduced.

  Hereinafter, matters related to the implementation of the present invention will be described in detail.

  The rubber composition for a semiconductive belt according to the present embodiment includes a base rubber made of chloroprene rubber and ethylene propylene rubber, an ion conductive polymer made of a mixture of carbon black, an ethylene oxide-propylene oxide copolymer, and a lithium salt. Are blended. The rubber composition has a sea-island structure. In one embodiment, the rubber composition has a structure in which chloroprene rubber is the sea (continuous phase) and ethylene propylene rubber is the island (dispersed phase). At this time, carbon black, which is a conductive filler, is dispersed in chloroprene rubber and ethylene propylene rubber when observed with an electron microscope, but is not evenly dispersed at a micro level (for example, electronic level). This is considered to be a cause of resistance variation in the belt surface. According to this embodiment, in the system in which a blend rubber of chloroprene rubber and ethylene propylene rubber is used as a base rubber, an ion conductive polymer composed of an ethylene oxide-propylene oxide copolymer to which a lithium salt is added is added. Insufficient resistance homogenization with black alone can be improved, and resistance variation in the belt surface can be reduced.

  In the rubber composition according to this embodiment, the base rubber is composed of chloroprene rubber (CR) and ethylene propylene rubber (EPDM). Flame retardancy can be improved by using chloroprene rubber, and ozone resistance can be improved by using ethylene propylene rubber. The ethylene-propylene rubber may be a two-component copolymer of ethylene and propylene, or an ethylene-propylene-diene copolymer rubber obtained by copolymerizing a non-conjugated diene as the third component. Propylene-diene copolymer rubber. The ratio of chloroprene rubber to ethylene propylene rubber is 30 to 90 parts by mass for chloroprene rubber and 10 to 70 parts by mass for ethylene propylene rubber in 100 parts by mass of the base rubber. As a preferred embodiment, when chloroprene rubber is a sea of sea-island structure and ethylene propylene rubber is an island, chloroprene rubber is preferably 50 to 90 parts by mass, more preferably 60 to 100 parts by mass in 100 parts by mass of base rubber. It is 85 mass parts, More preferably, it is 70-85 mass parts. Moreover, it is preferable that ethylene propylene rubber is 10-50 mass parts in 100 mass parts of base rubber, More preferably, it is 15-40 mass parts, More preferably, it is 15-30 mass parts.

  The base rubber is basically composed only of chloroprene rubber and ethylene propylene rubber, but may contain other rubber materials as long as the effect is not impaired. Examples of other rubber materials include natural rubber (NR), styrene butadiene rubber (SBR), isoprene rubber (IR), butadiene rubber (BR), nitrile rubber (NBR), butyl rubber (IIR), acrylic rubber, and epichlorohydrin rubber. , Urethane rubber, fluororubber, and at least one selected from silicone rubber.

  Carbon rubber is blended in the rubber composition according to this embodiment in order to impart semiconductivity. Examples of carbon black include EC (Extra Conductive Furnace) carbon, ECF (Extra Conductive Furnace) carbon, SCF (Super Conductive Furnace) carbon, CF (Conductive Furnace) carbon, acetylene black, SAF grade carbon black, ISAF grade carbon black, Examples include HAF grade carbon black, FEF grade carbon black, GPF grade carbon black, SRF grade carbon black and the like. These may be used alone or in combination of two or more. Among these, it is particularly preferable to use acetylene black.

  The compounding amount of carbon black is 5 to 40 parts by mass with respect to 100 parts by mass of the base rubber. By setting it as such a compounding quantity, suitable semiconductivity can be provided to a semiconductive belt. The compounding amount of carbon black is preferably 10 to 35 parts by mass, more preferably 15 to 30 parts by mass, and further preferably 15 to 25 parts by mass with respect to 100 parts by mass of the base rubber.

  The rubber composition according to this embodiment is blended with an ion conductive polymer composed of a mixture of an ethylene oxide-propylene oxide copolymer and a lithium salt. By blending such an ion conductive polymer, resistance variation in the belt surface can be reduced without impairing rubber physical properties. The ion conductive polymer can also be referred to as an ion conductive agent, but it means that the ion conductive polymer itself has conductivity, and even if it imparts conductivity to the rubber composition, it does not impart. There may be. That is, it is not always necessary to reduce the resistance value of the rubber composition by adding the ion conductive polymer. In this embodiment, since the resistance variation in the belt surface is reduced by the addition of the ion conductive polymer, the ion conductive polymer can be referred to as a resistance variation reducing agent.

  The ion conductive polymer is obtained by adding a lithium salt to an ethylene oxide-propylene oxide copolymer. Thus, since an ion conductive polymer consists of an ethylene oxide propylene oxide copolymer, the high dispersibility with respect to the base rubber which consists of CR / EPDM is acquired. The ethylene oxide-propylene oxide copolymer contains ethylene oxide and propylene oxide as monomer units, and has a plurality of ether structures in the main chain. Lithium ions are coordinated and stabilized by ether oxygen in the ethylene oxide monomer unit, and lithium ions are generated by local motion (segment motion) of the ethylene oxide monomer unit, which is a flexible polymer segment containing the ether oxygen. Therefore, the ethylene oxide-propylene oxide copolymer provided with a lithium salt is an ion conductive polymer and has conductivity due to ion conduction.

  The ratio of both monomer units in the ethylene oxide-propylene oxide copolymer is not particularly limited. For example, the ethylene oxide monomer unit is 50 to 99 mol% (more preferably 60 to 96 mol%), and propylene. The oxide monomer unit may be 0.5 to 49 mol% (more preferably 2 to 38 mol%).

  As an ethylene oxide-propylene oxide copolymer, a carbon-carbon double bond may be introduced into the molecule by copolymerizing a monomer having a carbon-carbon double bond. Examples of such unsaturated bond-containing monomers include allyl glycidyl ether. Therefore, the ethylene oxide-propylene oxide copolymer according to one embodiment may be an ethylene oxide-propylene oxide-allyl glycidyl ether copolymer. Content of an unsaturated bond containing monomer unit is not specifically limited, For example, 0.5-20 mol% may be sufficient and 1-10 mol% may be sufficient.

  The molecular weight of the ethylene oxide-propylene oxide copolymer is not particularly limited. For example, the number average molecular weight Mn may be 5,000 to 1,000,000, 10,000 to 500,000, or 30,000 to 200,000. In addition, Mn is the value of polystyrene conversion by GPC measurement.

As the lithium salt, an organic lithium salt having a fluoro group and a sulfonyl group is preferably used. As an anion which has a fluoro group and a sulfonyl group in a molecule | numerator, 1 type (s) or 2 or more types, such as a fluoroalkyl sulfonate ion, a bis (fluoroalkyl sulfonyl) imide ion, a tris (fluoro alkyl sulfonyl) methide ion, are mentioned, for example. Specific examples of the organic lithium salt include CF ₃ SO ₃ Li, C ₄ F ₉ SO ₃ Li, (CF ₃ SO ₂ ) ₂ NLi, (C ₂ F ₅ SO ₂ ) ₂ NLi, and (C ₄ F ₉ SO ₂ ) (CF ₃ SO ₂ ) NLi, (FSO ₂ C ₆ F ₄ ) (CF ₃ SO ₂ ) NLi, (C ₈ F ₁₇ SO ₂ ) (CF ₃ SO ₂ ) NLi, (CF ₃ CH ₂ OSO ₂ ) ₂ NLi, (CF ₃ CF ₂ CH ₂ OSO ₂ ) ₂ NLi, (HCF ₂ CF ₂ CH ₂ OSO ₂ ) ₂ NLi, [(CF ₃ ) ₂ CHOSO ₂ ] ₂ NLi, (CF ₃ SO ₂ ) ₃ CLi, CF ₃ CH ₂ OSO ₂ ) ₃ CLi and the like. Any one of these may be used, or two or more may be used in combination.

  Additives such as adipic acid ester may be contained in the ion conductive polymer composed of a mixture of an ethylene oxide-propylene oxide copolymer and a lithium salt. As such an ion conductive polymer, for example, trade names “Sanconol RBX-8310” and “Sanconol TBX-8310” manufactured by Sanko Chemical Industry Co., Ltd. are commercially available.

  The rubber composition according to this embodiment contains 0.5 to 20 parts by mass of the ion conductive polymer. By using such a compounding amount, the resistance variation in the belt surface can be improved without impairing the rubber physical properties. The compounding amount of the ion conductive polymer is more preferably 0.1 to 10 parts by mass, and still more preferably 0.2 to 8 parts by mass with respect to 100 parts by mass of the base rubber. In addition, the ion conductive polymer may be blended in an amount of 0.05 to 2 parts by mass, more preferably 0.1 to 1.0 part by mass with respect to 100 parts by mass of the base rubber as the amount of the lithium salt. More preferably, it is 0.2 to 0.8 parts by mass. The content of the ethylene oxide-propylene oxide copolymer and the lithium salt in the ion conductive polymer is 60 to 95% by mass of the ethylene oxide-propylene oxide copolymer and 5 to 40 lithium salt in one embodiment. The ethylene oxide-propylene oxide copolymer may be 80 to 93% by mass and the lithium salt may be 7 to 20% by mass in another embodiment. In still another embodiment, the ethylene oxide-propylene oxide copolymer may be May be 85 to 90 mass% and the lithium salt may be 10 to 15 mass%.

  In the rubber composition according to the present embodiment, in addition to the above components, oil, stearic acid, magnesium oxide, silica, silane coupling agent, processing aid, aluminum hydroxide, zinc oxide, sulfur, vulcanization acceleration Various additives such as an agent can be blended. The compounding quantity of a silica is not specifically limited, 1-15 mass parts may be sufficient with respect to 100 mass parts of said base rubbers, and 2-10 mass parts may be sufficient. The silane coupling agent is preferably used when silica is blended, and the blending amount may be 2 to 25% by mass of the amount of silica. Examples of sulfur include powdered sulfur, precipitated sulfur, colloidal sulfur, insoluble sulfur, and highly dispersible sulfur. The blending amount may be, for example, 0.1 to 10 parts by mass with respect to 100 parts by mass of the base rubber. It may be 0.5 to 5 parts by mass. Examples of the vulcanization accelerator include various vulcanization accelerators such as thiazole-based, thiourea-based, thiuram-based, dithiocarbamate-based, guanidine-based, sulfenamide-based, and any one or two of these. You may use in combination above, The compounding quantity may be 0.1-7 mass parts with respect to 100 mass parts of said base rubbers, for example, and may be 0.5-5 mass parts.

  The rubber composition can be prepared by kneading according to a conventional method using a commonly used Banbury mixer, kneader, roll, or other mixer. For example, in the first mixing stage, carbon black and the ion conductive polymer are added to the base rubber together with other additives except sulfur, vulcanization accelerator and zinc oxide, and then the resulting mixture is In the final mixing stage, a rubber composition can be prepared by adding and mixing a vulcanizing agent, a vulcanization accelerator and zinc oxide.

The rubber composition according to this embodiment is used for constituting a semiconductive belt, and becomes a semiconductive rubber by vulcanization. Semiconductivity means that the volume resistivity is in the range of 10 ⁵ to 10 ¹² Ω · cm. Here, the volume resistivity is 23 ° C. and relative humidity 50%, using “R8340A” manufactured by Advantest Corporation (HRS probe manufactured by Mitsubishi Chemical Analytech Co., Ltd.) as a measuring device, and measurement conditions: 500 V × 10 seconds. It is a measured value.

  The semiconductive belt according to the present embodiment is prepared by, for example, extruding the rubber composition prepared as described above into a tube shape to produce an unvulcanized belt, and vulcanizing and molding the unvulcanized belt. Can be manufactured. After the vulcanization molding, a polishing step for making the belt a predetermined thickness may be provided, or a surface layer having lubricity may be provided on the surface of the semiconductive belt by a coating step or the like.

  The semiconductive belt according to this embodiment can be used as a transfer belt, a transfer conveyance belt, an intermediate transfer belt, and the like in various image forming apparatuses using the basic principle of the electrophotographic system described above. It can also be used for a transfer drum in which the semiconductive belt is covered with a cylindrical drum to form a roll. Although the thickness of a semiconductive belt is not specifically limited, For example, 0.3-3.0 mm may be sufficient.

  Examples of the present invention will be described below, but the present invention is not limited to these examples.

[First embodiment]
Using a Banbury mixer, according to the composition (parts by mass) shown in Table 1 below, first, in the first mixing stage, components other than zinc oxide, sulfur and vulcanization accelerator are added and mixed (discharge temperature = 115 ° C.), Next, in the final mixing stage, zinc oxide, sulfur and a vulcanization accelerator were added and mixed to the obtained mixture (discharge temperature = 85 ° C.) to prepare a rubber composition for a semiconductive belt.

The details of each component in Table 1 are as follows.
・ CR: “SKYPRENE B12” manufactured by Tosoh Corporation
・ EPDM: “Esplen 505” manufactured by Sumitomo Chemical Co., Ltd.
-Acetylene black: Denka Black manufactured by Denki Kagaku Kogyo Co., Ltd.
・ Oil: “PW-380” manufactured by Idemitsu Kosan Co., Ltd.
Magnesium oxide: “Kyowa Mug # 150” manufactured by Kyowa Chemical Industry Co., Ltd.
・ Silica: Tosoh Silica Co., Ltd. “Nip seal VN3”
・ Processing aid: “Emaster 510P” manufactured by Riken Vitamin Co., Ltd.
Silane coupling agent: “Si69” manufactured by Degussa
Ion conductive polymer 1: Sanko Kogyo Co., Ltd. "Sankonoru TBX-8310" (ethylene oxide - propylene oxide - with allyl glycidyl ether copolymer, trifluoromethanesulfonic acid lithium (CF ₃ SO ₃ Li) and adipic acid Ester mixture, lithium salt content: 10% by mass)
Ion conductive polymer 2: “Sanconol RBX-8310” (ethylene oxide-propylene oxide-allyl glycidyl ether copolymer and lithium bis (trifluoromethanesulfonyl) imide ((CF ₃ SO ₂ )) manufactured by Sanko Chemical Co., Ltd. ₂ NLi) and adipic acid ester mixture, lithium salt content: 10% by mass)
・ Zinc oxide: Renogran ZnO-80 manufactured by Rhein Chemie
・ Sulfur: “Crytex HS OT20” manufactured by Akzo Nobel
・ Vulcanization accelerator 1: Renogran ETU-80 manufactured by Rhein Chemie
・ Vulcanization accelerator 2: "Sunseller TT" manufactured by Sanshin Chemical Industry Co., Ltd.

  About each obtained rubber composition, an unvulcanized sheet was produced with an open roll, and a vulcanized rubber sheet having a thickness of 2 mm was obtained by press vulcanization (185 ° C. × 7 minutes) using a mold. . In-plane variation of the surface resistance value Ω was measured using the obtained rubber sheet. The measuring method is as follows.

  -In-plane variation in surface resistance value: The surface resistance value Ω was measured at 25 x vertical = horizontal x 5 x 8 = 40 locations on the rubber sheet at 25 mm intervals. The measurement is performed using “R8340A” manufactured by Advantest as a measuring device, and a rubber sheet is set between the counter electrode (polytetrafluoroethylene sheet laminated insulating plate) and the probe (HRS probe manufactured by Mitsubishi Chemical Analytech). At a temperature of 23 ° C. and a relative humidity of 50%, an applied voltage of 500 V was applied for 10 seconds, and the resistance value was read. For the common logarithm log Ω of the surface resistance value Ω, the maximum value (Max), minimum value (Min), average value (Avg), range (difference between the maximum value and minimum value) (R) of the log Ω for the above 40 locations, and Standard deviation (s) was calculated.

  The results are as shown in Table 1, and in Comparative Examples 1 in which the ion conductive polymer was not added, in Examples 1 and 2 in which the ion conductive polymer was blended, the standard deviation (s) was small, and the surface resistance value was In-plane variation was reduced. In Example 1 and Example 2, the improvement effect of in-plane variation was larger in Example 2 in which the ion conductive polymer 2 containing lithium bis (trifluoromethanesulfonyl) imide as a lithium salt was blended.

[Second Embodiment]
Using a Banbury mixer, a rubber composition for a semiconductive belt was prepared in the same manner as in the first example according to the formulation (parts by mass) shown in Table 2 below, and a vulcanized rubber sheet was produced. Details of each component in Table 2 are the same as those in Table 1. In-plane variation of the surface resistance value Ω was measured using the obtained rubber sheet. Measurement is performed under three conditions: temperature 10 ° C. × 15% relative humidity (L / L), temperature 23 ° C. × relative humidity 50% (N / N), and temperature 28 ° C. × relative humidity 85% (H / H) The other steps are the same as in the first embodiment. In order to investigate the voltage dependence, the applied voltage was measured under three conditions of 100 V, 500 V and 1000 V in an N / N environment (all for 10 seconds), and the average value of log Ω (Avg) at the above 40 points. ), The difference between the maximum value and the minimum value under the above three conditions was determined as the voltage fluctuation R.

  The results are as shown in Table 2. In Examples 3 to 6 to which an ion conductive polymer was added, reduction in in-plane variation of the surface resistance value was recognized under any environment. Moreover, the voltage fluctuation R became small by adding an ion conductive polymer, and the improvement effect of voltage dependence was recognized. The voltage dependence showed almost the same behavior when the addition amount of the ion conductive polymer was 2.5 parts by mass or more.

[Third embodiment]
According to the composition (parts by mass) shown in Table 3 below, rubber mixing was performed with a 70 L kneader. The obtained rubber was coated with 0.8 mm thick rubber on a φ95 aluminum pipe with a crosshead extruder. The rubber-coated aluminum pipe was vulcanized by the direct vulcanization method. Vulcanization conditions are 185 ° C x 9 minutes. The obtained rubber belt was subjected to single-side polishing (double-side polishing if necessary) so as to have a thickness of 0.5 mm, thereby producing a transfer belt. The details of each component in Table 3 are the same as those in Table 1, except that “Hijilite H-32” manufactured by Showa Denko Co., Ltd. was used as the aluminum hydroxide. Moreover, in Example 7 to which the ion conductive polymer was added, the amount of each component was adjusted so that the carbon black content relative to the entire rubber composition was the same as that of Comparative Example 3 to which no ion was added.

  Using the obtained transfer belt, the in-plane variation of the volume resistance value Ω and the average value (Avg) of the volume resistivity were measured. As mechanical properties, tensile stress at 100% elongation (M100), breaking strength (TB), breaking elongation (EB), tear strength (TR), hardness (HS) and permanent elongation (PS) are measured. did. The measuring method is as follows.

  -In-plane variation in volume resistance value: The volume resistance value Ω was measured at vertical and horizontal = 5 × 12 = 60 locations on the transfer belt at intervals of 25 mm. Measurement is performed by using "R8340A" manufactured by Advantest Corporation (HRS probe manufactured by Mitsubishi Chemical Analytech) as a measuring device, applying an applied voltage of 500 V for 10 seconds at a temperature of 23 ° C and a relative humidity of 50%, and reading the resistance value. Went by. For the common logarithm logΩ of the volume resistance value, the maximum value (Max), the minimum value (Min), the average value (Avg), the range (R), and the standard deviation (s) of logΩ for the 60 locations were calculated.

  Mechanical properties: M100, TB and EB were measured by a tensile test based on JIS K6251 (dumbbell shape No. 3). TR was measured by a tear test in accordance with JIS K6252 (angle type without incision). HS was measured according to JIS K6253-3 (durometer A). PS conforms to JIS K6251 (dumbbell shape No. 1), stretches 100% between the marked lines, holds for 10 minutes, then releases the sample piece and measures the distance between the marked lines after 10 minutes to determine the residual strain. .

  The results are as shown in Table 3, and Example 7 to which the ion conductive polymer was added had substantially the same mechanical properties as that of Comparative Example 3 to which no ion was added, and the volume resistance value Ω itself was also substantially the same. However, the difference (R) between the maximum value and the minimum value of the volume resistance value Ω was small, the standard deviation (s) was small, and the in-plane variation of the volume resistance value Ω was significantly reduced.

Claims (2)

Basically, 5 to 40 parts by mass of carbon black and ethylene oxide-propylene oxide with respect to 100 parts by mass of base rubber comprising 50 to 90 parts by mass of chloroprene rubber and 10 to 50 parts by mass of ethylene - propylene -diene copolymer rubber. -A rubber composition for a semiconductive belt, comprising 0.5 to 20 parts by mass of an ion conductive polymer comprising a mixture of an allyl glycidyl ether copolymer and an organic lithium salt having a fluoro group and a sulfonyl group . A semiconductive belt for an image forming apparatus using the rubber composition according to claim 1 .