JP5500578B2 - Conductive rubber member - Google Patents

Description

The present invention is suitable for a charging roll / developing roll, a toner regulating roll, a transfer roll / intermediate transfer roll, a belt, etc. The present invention relates to a conductive rubber member used.

For example, in the case of a charging roll, the conductive rubber roll of an image forming apparatus such as an electrophotographic copying machine and a printer is required to have a volume resistivity of 10 ⁵ to 10 ⁸ Ω · cm. Therefore, conductive particles such as carbon black and ionic conductive agents are added to polyurethane, silicone rubber, ethylene propylene rubber (EPDM), nitrile butadiene rubber (NBR), styrene butadiene rubber (SBR), etc. A conductive rubber member to which is given is used.

  However, when a large amount of carbon black is blended in order to obtain a low electric resistance value, there is a problem that leakage tends to occur. Further, when a large amount of ionic conductive agent is blended, there is a possibility that the electrical resistance value becomes more dependent on the environment, or the ionic conductive agent bleeds out and contaminates the photoreceptor.

  On the other hand, epichlorohydrin rubber has a volume resistivity required for a conductive rubber roll as a specific resistance value. However, when chlorine is desorbed during vulcanization, vulcanization is hindered or the shaft is rusted. There was a problem to do. Then, the electroconductive roll which consists of a rubber composition which mix | blended a predetermined amount of acid acceptor with epichlorohydrin rubber is proposed (refer patent documents 1-2).

JP 2003-064244 A JP 2007-264557 A

  However, there is a problem that the resistance value tends to increase by adding an acid acceptor, and a desired volume resistivity cannot be obtained.

  This invention makes it a subject to provide the conductive rubber member which implement | achieved the fall of the volume resistivity which does not originate in an electroconductivity imparting agent in view of such a situation.

A first aspect of the present invention that solves the above-described problems is obtained by curing and molding a rubber composition containing a rubber base material mainly composed of epichlorohydrin rubber , zinc oxide, and alkaline silica and not containing an acid acceptor. The conductive rubber member is made of a rubber-like elastic body and contains 15 parts by mass or less of the alkaline silica with respect to 100 parts by mass of the rubber base material.

  A second aspect of the present invention is the conductive rubber member according to the first aspect, wherein the rubber composition does not contain stearic acid.

According to a third aspect of the present invention, in the conductive rubber member according to the first or second aspect, the rubber composition satisfies the following formula.
[Formula 1]
{Alkaline silica (parts by mass) / Zinc oxide (parts by mass)} ≦ 2

According to a fourth aspect of the present invention, in the conductive rubber member according to any one of the first to third aspects, the rubber composition further includes an ionic conductive agent. is there.

According to a fifth aspect of the present invention, in the conductive rubber member according to any one of the first to fourth aspects, the conductive rubber member has a volume resistivity of 1.0 × 10 ⁵ at an applied voltage of 500V. It is in the conductive rubber member characterized by -1.0 × 10 ⁷ Ω · cm.

According to a sixth aspect of the present invention, there is provided a conductive rubber member characterized in that the conductive rubber member according to any one of the first to fifth aspects has a roll shape or a belt shape.

  According to this invention, it becomes an electroconductive rubber member which implement | achieved the fall of the volume resistivity which does not originate in an electroconductivity imparting agent.

It is a figure which shows the result of Test Example 2. It is a figure which shows the result of Test Example 2. It is a figure which shows the result of Test Example 2.

  The present invention realizes a low volume resistivity by using zinc oxide and alkaline silica in combination without blending an acid acceptor. When various additives are blended with the rubber base material, the volume resistivity usually increases. However, in the present invention, the acid acceptor is not blended, and further, the rubber is obtained by using zinc oxide and alkaline silica in combination. Volume resistivity can be reduced as compared with the base material alone.

The conductive rubber member of the present invention comprises a rubber-like elastic body obtained by curing and molding a rubber composition containing a rubber base mainly composed of epichlorohydrin rubber , zinc oxide, and alkaline silica and not containing an acid acceptor. Thus, 15 parts by mass or less of alkaline silica is blended with 100 parts by mass of the rubber base material. When only alkaline silica is blended or an acid acceptor is used in combination, the volume resistivity is increased, but by using zinc oxide and alkaline silica in combination, the volume resistivity is decreased.

  The mechanism by which the volume resistivity decreases is expected as follows.

Zinc oxide desorbs a portion of the epichlorohydrin rubber , such as chlorine. The ions (for example, chlorine) released from the epichlorohydrin rubber react with the metal ions (M ⁺ ) of alkaline silica to form a salt. This salt acts as a conductive agent in the rubber base material to reduce the volume resistivity. Formula 2 shows the reaction formula when chlorine is eliminated.
[Formula 2]
SiO ⁻ M ⁺ + H ⁺ Cl ⁻ → SiOH + M ⁺ Cl ⁻

  As a result, it is possible to achieve a decrease in volume resistivity while preventing vulcanization inhibition and corrosion of the shaft and the like. As described above, when zinc oxide and alkaline silica are used in combination, dechlorination is promoted by zinc oxide, and at the same time, a large amount of salt that is highly effective as an ionic conductive agent is formed, so that the volume resistivity is lowered. This is presumably because the salt generated due to the alkali metal or alkaline earth metal contained in the alkaline silica is easily dissolved in the polymer. Moreover, when the excess amount of acid is produced | generated, it can neutralize with alkaline silica.

  In addition, when an acid acceptor is blended as in the past, the acid generated by the acid acceptor is captured and a salt is formed, but the salt generated from the acid acceptor does not dissolve sufficiently in the polymer, and resistance as an ionic conductive agent However, the specific volume resistivity of the acid acceptor increases the volume resistivity of the rubber member.

  On the other hand, when only alkaline silica is blended and zinc oxide is not blended, neutralization produces a highly effective salt as an ionic conductive agent and the resistance value decreases, but the resistance value of silica itself is high and acts as a conductive agent. The volume resistivity increases with the amount of silica added, probably because the amount of salt formed is small. In addition, when zinc oxide is blended and alkaline silica is not blended, dechlorination is promoted compared to the case where an acid acceptor is used, and the amount of salt produced is increased compared to the case where an acid acceptor is used. Although volume resistivity is lowered, measures against excess acid are required.

The rubber base material is mainly composed of an ion conductive polymer. The ion conductive polymer here has a polar group and is 1.0 × 10 ^{4 to} 1.0 × 10 ⁹ Ω · cm, preferably 1.0 × 10 ^{5 to} 1.0 × 10 ⁹ Ω. A polymer exhibiting a volume resistivity with a medium resistance of cm. The ion conductive polymer according to the present invention contains a halogen such as a chloromethyl group and a chloro group in the side chain. Examples of the main chain (main polymer skeleton) of the ion conductive polymer include acrylonitrile butadiene rubber (NBR), epichlorohydrin rubber, polymers containing alkylene oxide, and urethane, and epichlorohydrin rubber is preferable. The epichlorohydrin rubber includes epichlorohydrin homopolymer, epichlorohydrin-ethylene oxide copolymer, epichlorohydrin-allyl glycidyl ether copolymer, epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer, epichlorohydrin-ethylene oxide-propylene oxide-allyl. Examples thereof include glycidyl ether quaternary copolymers and derivatives thereof. Polymers containing alkylene oxide include ethylene oxide homopolymer, ethylene oxide-propylene oxide copolymer, ethylene oxide-allyl glycidyl ether copolymer, ethylene oxide-propylene oxide-allyl glycidyl ether terpolymer and derivatives thereof. And so on. Urethanes include polyurethanes prepared from ether-based, ester-based, or carbonate-based glycols. The ion conductive polymer may be used alone or in combination. Further, the rubber substrate may be one composed mainly of ion conductive polymer, as appropriate, other rubbers, for example, polyurethane, nitrile rubber (NBR), styrene rubber (SBR), a blend of chloroprene rubber or the like Also good.

  The conductive rubber member of the present invention does not contain an acid acceptor, but the acid acceptor here refers to accepting hydrotalcite, magnesium oxide, calcium oxide, calcium hydroxide, lead oxide, etc. It has a high acid capacity.

  Alkaline silica is wet silica having a pH of 7 or more, and volume resistivity decreases when used in combination with zinc oxide. Further, by adding alkaline silica, processability is improved and vulcanization time is shortened.

  Here, the alkaline silica is blended in an amount of 15 parts by mass or less, preferably 10 parts by mass or less based on 100 parts by mass of the rubber base material. When more than 15 parts by mass of alkaline silica is blended, the volume resistivity increases. It is preferable to blend 0.1 to 30 parts by mass of the total amount of zinc oxide with respect to 100 parts by mass of the rubber base material. Thereby, it can be set as a desired volume resistivity. In addition, there exists a possibility that volume resistivity may become high when the total amount of zinc oxide becomes more than 30 mass parts.

Further, the rubber composition preferably satisfies the following formula. Thereby, it can be easily set as a desired volume resistivity. If the proportion of the alkaline silica becomes too large, there is a possibility that the effect of lowering the volume resistivity due to the formation of salt cannot be obtained sufficiently.
[Formula 1]
(Alkaline silica (parts by mass) / Zinc oxide (parts by mass)) ≦ 2

  The rubber composition preferably does not contain stearic acid. This is because by not mixing stearic acid, the volume resistivity is further reduced as compared with the case where stearic acid is mixed. In addition, there is no possibility that stearic acid bleeds and contaminates the photoreceptor.

  As described above, the conductive rubber member of the present invention can reduce the volume resistivity without using an ion conductivity imparting agent or a conductivity imparting material such as carbon black. Carbon black or the like may be blended to further reduce the volume resistivity. At this time, volume resistivity falls more by mix | blending a small amount of ion conductivity-imparting agents and carbon black with the said rubber composition. That is, the conductive rubber member can obtain a desired volume resistivity by blending the rubber composition according to the present invention with a smaller amount of ionic conductivity-imparting agent and carbon black than before.

  The conductive rubber member of the present invention can reduce the volume resistivity without blending a conductivity imparting material such as an ion conductivity imparting agent or carbon black, and a small amount may be used even when a conductivity imparting material is blended. Therefore, there is no possibility that the ionic conductivity imparting agent bleeds out or the volume resistivity changes due to changes in temperature, humidity, or applied voltage, and it has excellent contamination resistance and environmental characteristics.

  When the conductivity imparting material is blended, an ion conductivity imparting material is preferable, but various carbon blacks, electronic conductivity imparting materials such as metal powder, or a mixture thereof can be used. Examples of the ion conductivity-imparting material include organic salts, inorganic salts, metal complexes, ionic liquids, and the like. Examples of organic salts and inorganic salts include lithium perchlorate, quaternary ammonium salts, and sodium trifluoride acetate. Moreover, as a metal complex, a halogenated ferric-ethylene glycol etc. can be mentioned, Specifically, the diethylene glycol-ferric chloride complex etc. which were described in patent 3655364 can be mentioned. On the other hand, the ionic liquid is a molten salt that is liquid at room temperature, and is also called a room temperature molten salt, and particularly refers to a melting point of 70 ° C. or lower, preferably 30 ° C. or lower. Specifically, 1-ethyl-3-methylimidazolium bis (trifluoromethylsulfonyl) imide, 1-butyl-3-ethylimidazolium trifluoromethylsulfonyl) imide described in JP-A No. 2003-202722, and the like Can be mentioned.

  The vulcanization of the rubber composition described above may be either peroxide vulcanization or sulfur vulcanization, and is not particularly limited.

The conductive rubber member of the present invention preferably has a volume resistivity of 1.0 × 10 ^{5 to} 1.0 × 10 ⁷ Ω · cm at an applied voltage of 500V. By curing and molding a rubber composition mainly comprising epichlorohydrin rubber , zinc oxide, and alkaline silica and not containing an acid acceptor, the above-described volume resistivity conductive rubber member and can do.

  The conductive rubber member according to the present invention is suitable for use in, for example, a roll or a belt. Specifically, suitable for charging rolls / developing rolls, toner regulating rolls, and transfer rolls / intermediate transfer rolls and belts of image forming apparatuses such as electrophotographic copying machines and printers, or toner jet copying machines and printers. Can be used.

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

Example 1
<Manufacture of rolls>
Epichlorohydrin rubber (1) (epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer; ECH / EO / AGE = 40/56/4), 100 parts by mass of zinc oxide, 5 parts by mass of zinc oxide, wet silica (Nipseal NA; Japan) 5 parts by mass of Silica Industry Co., Ltd., 2 parts by mass of carbon black (EC; manufactured by Mitsubishi Chemical Corporation), 1.5 parts by mass of Sunseller CZ (manufactured by Sanshin Chemical Industry Co., Ltd.), thiuram vulcanization accelerator (Sanshin Chemical Co., Ltd.) Manufactured by Suncellor TT) and 1 part by mass of sulfur and 0.5 part by mass of sulfur were added and kneaded with a roll mixer. After extrusion molding on a shaft, vulcanization was carried out at 180 ° C. for 15 minutes. A sex roll was obtained.

(Example 2)
In Example 1, the conductive roll of Example 2 was obtained in the same manner except that the wet silica was changed to 10 parts by mass.

(Example 3)
In Example 1, the conductive roll of Example 3 was obtained in the same manner except that the wet silica was changed to 15 parts by mass.

(Example 4)
In Example 1, instead of epichlorohydrin rubber (1), epichlorohydrin rubber (2) (epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer; ECH / EO / AGE = 27/70/3) was used. In the same manner, a conductive roll of Example 4 was obtained.

(Example 5)
A conductive roll of Example 5 was obtained in the same manner as in Example 2, except that epichlorohydrin rubber (2) was used instead of epichlorohydrin rubber (1).

(Example 6)
In Example 3, the conductive roll of Example 6 was obtained in the same manner except that the epichlorohydrin rubber (2) was used instead of the epichlorohydrin rubber (1).

(Example 7)
In Example 1, the electroconductive roll of Example 7 was obtained similarly except having made wet silica into 1 mass part.

(Example 8)
The conductive roll of Example 8 was obtained in the same manner as in Example 1 except that the wet silica was changed to 2.5 parts by mass.

Example 9
In Example 1, the conductive roll of Example 9 was obtained in the same manner except that 0.4 parts by mass of an ionic conductive agent (sodium trifluoroacetate) was further added.

(Comparative Example 1)
In Example 1, the electroconductive roll of the comparative example 1 was obtained similarly except not having mix | blended the wet silica.

(Comparative Example 2)
In Example 5, the electroconductive roll of the comparative example 2 was obtained similarly except not having mix | blended wet silica.

(Comparative Example 3)
In Example 1, the electroconductive roll of the comparative example 3 was obtained similarly except having made wet silica into 20 mass parts.

(Comparative Example 4)
In the comparative example 3, the conductive roll of the comparative example 4 was obtained similarly except having used the epichlorohydrin rubber (2) instead of the epichlorohydrin rubber (1).

(Comparative Example 5)
In Comparative Example 1, a conductive roll of Comparative Example 5 was obtained in the same manner except that 5 parts by mass of magnesium oxide was blended instead of zinc oxide.

(Comparative Example 6)
In Comparative Example 1, a conductive roll of Comparative Example 6 was obtained in the same manner except that 5 parts by mass of calcium oxide was added instead of zinc oxide.

(Comparative Example 7)
In Comparative Example 1, a conductive roll of Comparative Example 7 was obtained in the same manner except that 5 parts by mass of hydrotalcite was blended in place of zinc oxide.

(Comparative Example 8)
In Example 1, the electroconductive roll of the comparative example 8 was obtained similarly except having further mix | blended 5 mass parts of magnesium oxide.

(Comparative Example 9)
In Example 1, the electroconductive roll of the comparative example 9 was obtained similarly except having further mix | blended 5 mass parts of hydrotalcite.

(Comparative Example 10)
In Comparative Example 1, a conductive roll of Comparative Example 10 was obtained in the same manner except that zinc oxide was not blended.

(Comparative Example 11)
In Example 1, the electroconductive roll of the comparative example 11 was obtained similarly except not having mix | blended zinc oxide.

(Comparative Example 12)
In Example 2, the electroconductive roll of the comparative example 12 was obtained similarly except not having mix | blended zinc oxide.

(Comparative Example 13)
In Example 3, the electroconductive roll of the comparative example 13 was obtained similarly except not having mix | blended zinc oxide.

(Comparative Example 14)
In the comparative example 4, the electroconductive roll of the comparative example 14 was obtained similarly except not having mix | blended zinc oxide.

(Comparative Example 15)
In the comparative example 2, the electroconductive roll of the comparative example 15 was obtained similarly except not having mix | blended zinc oxide.

(Comparative Example 16)
In Example 4, the electroconductive roll of the comparative example 16 was obtained similarly except not having mix | blended zinc oxide.

(Comparative Example 17)
In Example 5, the electroconductive roll of the comparative example 17 was obtained similarly except not having mix | blended zinc oxide.

(Comparative Example 18)
In Example 6, the electroconductive roll of the comparative example 18 was obtained similarly except not having mix | blended zinc oxide.

(Comparative Example 19)
In Comparative Example 4, a conductive roll of Comparative Example 19 was obtained in the same manner except that zinc oxide was not blended.

(Comparative Example 20)
In Comparative Example 7, a conductive roll of Comparative Example 20 was obtained in the same manner except that 5 parts by mass of wet silica was further added.

(Test Example 1) Measurement of rubber hardness Using a rubber member used in the conductive roll of each example and each comparative example, a sample having a thickness of 12 mm was prepared, and the rubber hardness (type A) was 25 ° C according to JIS K6253. It was measured. The results are shown in Tables 1-4.

(Test Example 2) Volume Resistivity Measurement Using a rubber member used in the conductive rolls of each Example and each Comparative Example, a sheet-like sample having a thickness of 2 mm was separately produced by a flat plate press, and the volume resistivity was measured according to JIS K6271. It was measured. In addition, the measurement was performed using ULTRA HIGH RESISTANCE METER R8340A (made by Advantest Co., Ltd.) in a normal temperature and normal humidity environment (N / N: 25 ° C. × 55% RH). The applied voltage at this time was an applied voltage of 500V. The volume resistivity was determined from the volume resistance. The results are shown in Tables 1 to 4 and FIGS.

(Summary of results)
As shown in Tables 1 and 3, the conductive roll of Example 1 in which zinc oxide and alkaline silica are used in combination is the conductive roll of Comparative Example 1 in which only zinc oxide is blended, and Comparative Example 5 in which an acid acceptor is blended. Volume resistivity was lower than 7 conductive rolls.

  As shown in FIG. 1, the conductive rolls of Comparative Examples 11 to 14 and the conductive rolls of Comparative Examples 16 to 19 in which alkaline silica is blended but zinc oxide is not blended are blended with alkaline silica and zinc oxide, respectively. The volume resistivity was higher than those of Comparative Example 10 and Comparative Example 15 which were not performed. From this, it was found that when zinc oxide is not blended, the volume resistivity is increased by blending alkaline silica.

  In contrast, the conductive rolls of Examples 1 to 3 and the conductive rolls of Examples 4 to 6 in which zinc oxide and alkaline silica were used in combination had lower volume resistivity than Comparative Example 10 and Comparative Example 15, respectively. . From this, it was found that the volume resistivity is decreased by using zinc oxide and alkaline silica in combination. In particular, Examples 1-2, Examples 7-8, and Examples 4-5, which satisfy (alkaline silica / zinc oxide) ≦ 2 and blend 10 parts by mass or less of alkaline silica, have a decrease in volume resistivity. It was remarkable.

  In addition, as shown in FIG. 2, the conductive roll of Example 1 which uses zinc oxide and alkaline silica in combination and does not contain an acid acceptor is the conductive roll of Comparative Example 8 further mixed with magnesium oxide and further hydrotalc. The volume resistivity was significantly lower than that of the conductive roll of Comparative Example 9 containing the site. From this, it was found that a conductive roll containing no acid acceptor and using zinc oxide and alkaline silica in combination has a lower volume resistivity than a conductive roll containing an acid acceptor.

  Further, when the acid acceptor (hydrotalcite) and wet silica are used in combination (Comparative Example 20), the volume resistivity is higher than that obtained by adding the acid acceptor and not wet silica (Comparative Example 7). I found out that

  As shown in FIG. 3, the volume resistivity of the conductive roll of Example 1 in which zinc oxide and alkaline silica were blended was lower than that of Comparative Example 1 in which only zinc oxide was blended. Moreover, in addition to zinc oxide and alkaline silica, the conductive roll of Example 9 in which 0.4 parts by mass of an ionic conductive agent was further blended had a lower volume resistivity than the conductive roll of Example 1. From this, it was found that when zinc oxide and alkaline silica are used in combination, the volume resistivity is further reduced by adding a small amount of the ionic conductive agent.

As described above, the rubber base material is composed of a rubber-like elastic body obtained by curing and molding a rubber base material mainly composed of epichlorohydrin rubber , zinc oxide, and alkaline silica and containing no acid acceptor. It turned out that the conductive rubber member which mix | blended 15 mass parts or less of alkaline silica with respect to a part becomes a thing with a low volume resistivity.

Claims (6)

100 parts by mass of the rubber base material, comprising a rubber-like elastic body obtained by curing and molding a rubber composition mainly containing epichlorohydrin rubber , zinc oxide, and alkaline silica and not containing an acid acceptor. The conductive rubber member is characterized by containing 15 parts by mass or less of the alkaline silica.   The conductive rubber member according to claim 1, wherein the rubber composition does not contain stearic acid. 3. The conductive rubber member according to claim 1, wherein the rubber composition satisfies the following formula. 4.
[Formula 1]
{Alkaline silica (parts by mass) / Zinc oxide (parts by mass)} ≦ 2 The conductive rubber member according to any one of claims 1 to 3 , wherein the rubber composition further contains an ionic conductive agent. The conductive rubber member according to any one of claims 1 to 4 , wherein the conductive rubber member has a volume resistivity of 1.0 × 10 ^{5 to} 1.0 × 10 ⁷ Ω · cm at an applied voltage of 500V. A conductive rubber member. Conductive rubber member characterized by conductive rubber member according is roll-shaped or belt-shaped to any one of claims 1-5.

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