JPH0820725A - Semiconducting silicone rubber member for business machine - Google Patents

Abstract

PURPOSE:To obtain the subject member which is stable to change in resistance under a high voltage, can withstand a long-term use, and is used for a roll or a belt by mixing a silicone rubber with zinc oxide in a large proportion. CONSTITUTION:This rubber member is obtd. by curing a semiconducting silicone rubber compsn. and has a resistivity of. 1X10<3> to 1X10<12>OMEGA.cm. The compsn. is prepd. by compounding 100 pts.wt. organopolysiloxane represented by the mean compsn. formula: R<1>nSiO(4-n)/2 (wherein R<1> is an optionally substd. monovalent hydrocarbon group; and (n) is 1.98-2.02) and having at least two aliph. unsatd. groups, 5-70 pts.wt. reinforcing silica powder having a specific surface area of 50m<2>/g or higher, 30-700 pts.wt. zinc white, 0-50 pts.wt. conductive carbon black, and a curative in an amt. capable of curing the organopolysiloxane. An organopolysiloxane having an average degree of polymn. of 100-10,000 is pref., and a conductive zinc white doped with aluminum is esp. pref.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to rolls and belts for office machines such as copiers and facsimiles, especially 1 × 10 ³ to
Semi-conductive silicone rubber member for office machines, which is especially useful for semi-conductive silicone rubber rolls such as charging rolls, transfer rolls, and developing rolls and semi-conductive silicone rubber belts, which have a specific resistance value of 1 × 10 ¹² Ω · cm. Regarding

[0002]

2. Description of the Related Art Roll materials are one of the rubber materials for office machines. Currently, rubber materials include silicone rubber, urethane elastomer, ethylene propylene rubber, natural rubber, etc. Various materials have been used, and composite materials thereof have also been proposed. These rubber materials have been used for various purposes as an electrically insulating material or as a conductive material mixed with a conductive material for the purpose of preventing static electricity or an electrical conduction path. 10 ³ to 1 x 10 ¹² Ω
-Semi-conductive materials in the medium resistance region of cm have come to be used as roll materials for copying machines and the like.

The semiconductive roll material has a very stable resistance value in order to control the electric current flowing by the resistance value of the rubber material itself in most of the use environment, for example, for the purpose such as transfer ability. Has become important. Further, in order to stabilize the current value flowing in the roll material, and further to effectively apply the electric charge on the OPC, 300V to
A voltage of 10 KV is often applied.

However, in such a high voltage use environment, most of the semiconductive roll materials do not have sufficient withstand voltage characteristics, and the resistance value deviates from the set resistance value when used for a long time. There is a problem, in particular, the higher the voltage becomes, and the more current is passed, the more this defect becomes noticeable.

The present invention has been made to improve the above circumstances, and by using a silicone rubber containing a high proportion of zinc white (ZnO) as a roll material,
Semi-conductive silicone rubber for office machines such as semi-conductive silicone rubber rolls and semi-conductive silicone rubber belts that stabilize the resistance value of rolls and belts used under high voltage and can withstand long-term use under high voltage. It is intended to provide a member.

[0006]

Means and Actions for Solving the Problems The present inventor has conducted diligent studies to achieve the above object, and as a result, rolls a silicone rubber containing a high proportion of zinc white (ZnO). It is used as a material for office machines such as belts and belts, and the presence of a large amount of zinc white on the surface of rolls and belts makes it stable against changes in resistance under high voltage and can be used for a long time. It was found that a semiconductive silicone rubber roll or a semiconductive silicone rubber belt can be obtained.

That is, a silicone rubber composition containing the organopolysiloxane represented by the above average composition formula (1), a reinforcing silica powder having a specific surface area of 50 m ² / g or more, zinc white, and, if necessary, a conductive carbon black. Is an organic peroxide or an organohydrogenpolysiloxane /
It can be cured with both platinum catalysts and organic peroxide catalysts in combination with organohydrogenpolysiloxane / platinum catalysts, and its molding and cured product is due to the presence of a large amount of zinc white on the roll or belt surface. It has been found that the semi-conductive member for office machines used under high voltage has little change in resistance value, can withstand long-term use, and is most suitable for rolls and belts for office machines. Came to make.

Therefore, according to the present invention, the specific resistance value obtained by curing the semiconductive silicone rubber composition is 1 × 10 ³ to 1 ×.
In a semiconductive silicone rubber member for office machines having a resistivity of 10 ¹² Ω · cm, the above composition (A) is an organopolysiloxane 100 represented by the following average composition formula (1) and having at least two aliphatic unsaturated groups. Parts by weight, R ¹ _n SiO _{(4-n) / 2} (1) (wherein R ¹ is the same or different, unsubstituted or substituted 1
And n is a positive number from 1.98 to 2.02. ) (B) 5 to 70 parts by weight of reinforcing silica powder having a specific surface area of 50 m ² / g or more, (C) 30 to 700 parts by weight of zinc white, (D) 0 to 50 parts by weight of conductive carbon black,
(E) A semiconductive silicone rubber member for an office machine, comprising an amount of a curing agent capable of curing the component (A).

The present invention will be described in more detail below. The organopolysiloxane which is the first essential component of the silicone rubber composition according to the present invention is represented by the following average composition formula (1).

R ¹ _n SiO _{(4-n) / 2} (1) (In the formula, R ¹ is the same or different and is unsubstituted or substituted 1
And n is a positive number from 1.98 to 2.02. )

In the above formula, R ¹ is an alkyl group such as methyl group, ethyl group, propyl group, butyl group, cycloalkyl group such as cyclohexyl group, vinyl group, allyl group,
Butenyl group, alkenyl group such as hexenyl group, phenyl group, aryl group such as tolyl group, or chloromethyl in which some or all of the hydrogen atoms bonded to carbon atoms of these groups are substituted with halogen atoms, cyano groups, etc. The same or different monovalent hydrocarbon groups having 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms, more preferably unsubstituted or substituted, selected from a group, a trifluoropropyl group and a cyanoethyl group. In this case, R ¹ needs to have at least two aliphatic unsaturated groups (alkenyl groups),
The content of the aliphatic unsaturated group in R ¹ is preferably 0.001 to 20 mol%, particularly 0.025 to 5 mol%. N is a positive number between 1.98 and 2.02. The organopolysiloxane of the above formula (1) is basically preferably linear, but one or two having different molecular structures may be used.
It may be a mixture of two or more species.

Further, the above-mentioned organopolysiloxane has an average degree of polymerization of 100 to 10,000, particularly 3,000 to 8,
It is preferably 000.

Next, the reinforcing silica powder, which is the second essential component of the silicone rubber composition, is essential for obtaining a silicone rubber having excellent mechanical strength. For this purpose, Has a specific surface area of 50 m ² / g or more,
It should preferably be 100 to 300 m ² / g.
If the specific surface area is less than 50 m ² / g, the mechanical strength of the cured product will be low.

Examples of such reinforcing silica powder include fumed silica and precipitated silica, and those whose surface is made hydrophobic with chlorosilane or hexamethyldisilazane are also preferably used.

The amount of the reinforcing silica powder added is 5 to 70 parts based on 100 parts of the first component organopolysiloxane,
In particular, it is preferably 10 to 50 parts, and if it is less than 5 parts, the reinforcing effect may not be obtained because the addition amount is too small,
If it exceeds 70 parts, the workability may deteriorate and the mechanical strength may decrease.

In the present invention, zinc white (ZnO) is added as the third essential component. The zinc white may be a commonly known one, and examples thereof include zinc white 1, zinc white 2, zinc white 3 (manufactured by Mitsubishi Metals Co., Ltd. and Honjo Chemical Co., Ltd.). Conductive zinc white is preferred.

As the electroconductive zinc white, an insulating zinc white is calcined at a high temperature in a vacuum to increase the electroconductivity, and aluminum zinc oxide is solid-dissolved in zinc white to make the electroconductive zinc white. Electrically conductive zinc white No. 1, conductive zinc white No. 2,
There are conductive zinc white FX (all manufactured by Honjo Chemical Co., Ltd.) and the like, but the above-mentioned conductive zinc white doped with aluminum is particularly preferable.

The amount of addition is 30 to 700 parts, preferably 1 to 100 parts of the first component organopolysiloxane.
00 to 400 parts is preferable, and it is preferable to add the maximum amount to such an extent that the required physical properties of the rubber member are not affected. If the added amount is less than 30 parts, sufficient zinc white may not appear on the surface of the rubber member and the desired effect may not be observed. If the added amount exceeds 700 parts, compounding becomes extremely difficult and physical (mechanical) The characteristics may deteriorate. If the amount of conductive zinc white exceeds 400 parts, the compoundability may be poor and the compound may not be integrated, but if the compounding is difficult, the low degree of polymerization (average polymerization of the first component organopolysiloxane) An appropriate amount of oil (degrees of 1,000 or less) may be added.

Fourth of silicone rubber composition according to the present invention
The conductive carbon black as a component is an optional component suitable for adjusting to a desired volume resistance value, and is not particularly limited, and it is possible to use a component that is usually blended with a silicone rubber composition. it can. Specifically, acetylene black, conductive furnace black (CF), super conductive furnace black (SCF), extra conductive furnace black (XCF), conductive channel black (CC), furnace black and channel heat-treated at a high temperature of about 1500 ° C. Black etc. can be mentioned.

Specific examples of acetylene black include electrified acetylene black (manufactured by Denki Kagaku), Shawnigan acetylene black (manufactured by Shawnigan Chemical), and specific examples of conductive furnace blacks are Continex CF (manufactured by Continental Carbon Co., Ltd.). ), Vulcan C (manufactured by Cabot), and Superconductive Furnace Black as specific examples, Continex SCF
(Continental Carbon), Vulcan SC (Cabot), and Extra Conductive Furnace Black as specific examples of Asahi HS-500 (Asahi Carbon), Vulcan XC-72 (Cabot), and Conductive Channel Black. , Kolux L
(Manufactured by Degussa) is exemplified. Further, Ketjen Black EC and Ketjen Black EC-600JD (manufactured by Ketjen Black International), which are one type of furnace black, can also be used.

Of these, acetylene black is excellent in conductivity because it has a small amount of impurities and has a developed secondary structure structure, and is particularly preferably used in the present invention. Also, due to its outstanding specific surface area, Ketjen Black EC and Ketjen Black EC-600JD exhibit excellent conductivity even with a low filling amount.
And the like can be preferably used.

The amount of the conductive carbon black added is 0 to 100 parts of the first component organopolysiloxane.
It is preferably 50 parts, especially 1 to 10 parts. If it exceeds 50 parts, the electric resistance of the obtained member may be 10 ² Ω or less, and the desired semiconductive region may not be obtained.

When zinc white is not conductive, the conductive carbon black is 1 to 50 in order to impart semiconductivity.
Part is an essential ingredient.

In the present invention, a known organohydrogenpolysiloxane / platinum-based catalyst (curing agent for addition reaction) or an organic peroxide catalyst can be used as the fifth essential component curing agent.

As the platinum-based catalyst, known catalysts can be used, and specifically, platinum element simple substance, platinum compound, platinum complex, chloroplatinic acid, alcohol compound of chloroplatinic acid, aldehyde compound, ether compound, various olefins. And the complex are exemplified. The amount of the platinum-based catalyst added is preferably in the range of 1 to 2,000 ppm as platinum atom with respect to the organopolysiloxane of the first component.

On the other hand, the organohydrogenpolysiloxane may be linear, branched or cyclic, but preferably has a degree of polymerization of 300 or less, and the end is blocked with a dimethylhydrogensilyl group. A diorganopolysiloxane, a copolymer of a dimethylsiloxane unit with a methylhydrogensiloxane unit and a terminal trimethylsiloxy unit, a low-molecular composition comprising a dimethylhydrogensiloxane unit (H (CH ₃ ) ₂ SiO _0.5 unit) and a SiO ₂ unit. Viscous fluid, 1,3,5,7-tetrahydrogen-1,3,5,7-tetramethylcyclotetrasiloxane, 1-propyl-3,5,7-trihydrogen-1,3,5,7 -Tetramethylcyclotetrasiloxane, 1,5-dihydrogen-3,7-dihexyl-1,3,5, - tetramethyl cyclotetrasiloxane and the like.

The addition amount of the organohydrogenpolysiloxane as the curing agent is 50 to 500 hydrogen atoms directly bonded to the silicon atom with respect to the aliphatic unsaturated group (alkenyl group) of the organopolysiloxane of the first component. Mol%
It is desirable to use it in a ratio such that

Examples of organic peroxide catalysts include benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, p-methylbenzoyl peroxide, 2,4-dicumyl peroxide and 2,5-dimethyl-bis. (2,5-t-butylperoxy) hexane,
Di-t-butyl peroxide, t-butyl perbenzoate, etc. are mentioned. The addition amount of the organic peroxide catalyst may be 0.1 to 5 parts with respect to 100 parts of the first component organopolysiloxane.

The silicone rubber composition according to the present invention comprises:
In addition to the above-mentioned essential components, other inorganic materials such as titanium oxide, silicone rubber powder, red iron oxide as a bulking agent, if necessary, as long as they do not impair the effects of the present invention as optional components.
Pulverized quartz, calcium carbonate, etc. may be added. Furthermore, an inorganic or organic foaming agent for forming a sponge may be added. Examples of the foaming agent include azobisisobutyronitrile, dinitropentamethylenetetramine, benzenesulfone hydrazide azodicarbonamide, and the addition amount thereof is 100% silicone rubber compound.
The range of 1 to 10 parts is suitable for the parts.

By thus adding the foaming agent to the composition of the present invention, a sponge-like silicone rubber can be obtained.

Further, it is optional to add various additives such as a colorant and a heat resistance improver, a reaction control agent, a releasing agent or a dispersant for a filler to the composition of the present invention, if necessary. However, the diphenylsilanediol, various alkoxysilanes, carbon functional silanes, silanol group-containing low molecular weight siloxanes, etc. used as the dispersant for the filler are added to the minimum amount so as not to impair the effects of the present invention. It is preferable.

Further, in order to make the silicone rubber composition of the present invention flame-retardant and fire-resistant, a platinum-containing material, a platinum compound and titanium dioxide, platinum and manganese carbonate, platinum and γ-Fe.
Known additives such as ₂ O ₃ , ferrite, mica, glass fiber and glass flakes may be added.

The silicone rubber composition according to the present invention is prepared by uniformly mixing the above-mentioned components using a rubber kneader such as a two-roll mill, Banbury mixer, dough mixer (kneader), and if necessary heat treatment. In this case, for example, the organopolysiloxane of the first component and the reinforcing silica powder of the second component are mixed in advance to adjust the base compound, and the zinc compound of the third component is added thereto. , The first component of the conductive carbon black of the fourth component
It may be prepared by mixing the organopolysiloxane as a component in advance with a three-roll process and mixing the dispersed components, or by adding and mixing the curing agent as the fifth component.

In this case, the zinc white is preferably subjected to a three-roll process in order to uniformly disperse it. If the dispersibility is not good, the resistance value of a certain portion may differ from the resistance value of the surrounding area, which may lead to white spots on the image of the copying machine or uneven printing.

The silicone rubber composition thus obtained is coated and laminated on the core metal of the roll or the belt base material, and then cured. For the curing, a commonly used vulcanizing method of silicone rubber such as press vulcanization, atmospheric pressure hot air vulcanization (HAV), steam vulcanization (CV) is used.
It can be performed at 0 ° C. for about 30 seconds to 5 hours.

In this case, it is preferable to use a primer or an adhesive in order to adhere the silicone rubber to the core metal or the belt base material.

The thickness of the silicone rubber layer coated on the roll core metal or the belt base material is appropriately selected, but is usually 0.2 to 20 mm, particularly 1 to 6 mm.

[0038]

EFFECT OF THE INVENTION The semiconductive silicone rubber member for office machines of the present invention uses the silicone rubber mixed with a high proportion of zinc white (ZnO), so that the rubber used under high voltage is Semi-conductive silicone rubber members such as rolls and belts for office machines, which are stable against changes in resistance value peculiar to materials and can withstand long-term use under high voltage, especially 1 × 10 ³ to 1 × 10 ¹² Ω ・It is used as a charging roll, a transfer roll, a developing roll, etc. having a specific resistance value of cm.

[0039]

EXAMPLES The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to the following examples.

Example 1 Dimethylsiloxane unit 9
9.825 mol%, methyl vinyl siloxane unit 0.1
100 parts of a rubber-like organopolysiloxane having an average degree of polymerization of about 5,000, composed of 5 mol% and a dimethylvinylsiloxane unit of 0.025 mol%, 3 parts of diphenylsilanediol as a dispersant, and a terminal silanol group dimethylpolysiloxane. (Polymerization degree n = 10) 4 parts and 30 parts of treated silica having a specific surface area of 200 m ² / g (manufactured by Nippon Aerosil Co., Ltd.) were added and kneaded with a kneader to give 16
A base compound was prepared by heat treatment at 0 ° C. for 2 hours.

100 parts of the above base compound, 50 parts of Zinc Hua No. 3 (manufactured by Honjo Chemical Co., Ltd.) and 6 parts of Denka acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd.) were kneaded with a pressure kneader, and then three A compound was prepared by evenly dispersing with a roll.

As a curing agent for the above compound, 2,5-
2 parts of dimethyl-2,5-di (t-butylperoxy) hexane were kneaded, and a diameter of 20 m was placed on a core metal having a diameter of 10 mm.
m roll (wall thickness 5 mm) was manufactured. Molding temperature is 16
The molding pressure was 5 kg / 10 minutes and the molding pressure was 30 kgf / cm ² .

[Examples 2-6, Comparative Examples 1-2] Example 1
Rolls were produced in the same proportions as shown in Table 1 in the same manner as.
However, the base compounds are all the same, carbon black is Denka acetylene black, zinc white is zinc white No. 3, organic peroxide is 2,5-dimethyl-2,5-di (t-butylperoxy) hexane, As the conductive zinc white, conductive zinc white FX (manufactured by Honjo Chemical Co., Ltd.) was used.

In the vulcanization method, methyl hydrogen siloxane / platinum was added in an amount of 0.5 g of an alcohol solution of chloroplatinic acid (platinum content 1.0%) to 100 parts of the compound,
1.2 parts of methylhydrogenpolysiloxane having a SiH content of 0.005 mol% was used.

The obtained silicone rubber roll is heated to 200 ° C.
/ 4 hour post-curing, roll 1 was placed on platinum electrode plate A placed on glass epoxy substrate B as shown in FIG. 1, and roll was performed at 50 Hz AC while moving electrode plate A back and forth by 10 mm. 1 core metal 2-
After passing 4 KV / 10 min between the platinum electrode plates A, the resistance value of the silicone rubber was measured and the rate of change was calculated.
The resistance value of the roll 1 was measured by bringing the roll 1 into contact with the electrode 3 as shown in FIG. 2 and measuring the electrical characteristics between the electrode 3 and the core metal 2. The measurement voltage was 100 V, and the measuring instrument 4 was Advantest Digital Super Resistance Meter R8340. The results are shown in Table 1.

[0046]

[Table 1]

[Brief description of drawings]

FIG. 1 is a perspective view showing an apparatus for applying a high voltage to a semiconductive silicone rubber roll.

FIG. 2 is a plan view of an apparatus for measuring the resistance of the same silicone rubber roll.

[Explanation of symbols]

 1 roll 2 core metal 3 electrode 4 measuring instrument

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number for FI Technical indication H01B 1/00 A 7244-5L 1/24 Z (72) Inventor Masaharu Takahashi Matsuida-cho, Usui-gun, Gunma Prefecture Daiji Hitomi 10 Shin-Etsu Chemical Co., Ltd. Silicone Electronic Materials Research Laboratory (72) Inventor Tomiyoshi Tsuchida Matsuida-cho, Usui-gun, Gunma Daiji Hitomi 10 Shin-Etsu Chemical Co., Ltd. Silicone Electronic Materials Research Laboratory

Claims (3)

[Claims] 1. A semiconductive silicone rubber member for office machines having a specific resistance of 1 × 10 ³ to 1 × 10 ¹² Ω · cm, which is obtained by curing a semiconductive silicone rubber composition. (A) Organopolysiloxane 1 represented by the following average composition formula (1) and having at least two aliphatic unsaturated groups
00 parts by weight, R ¹ _n SiO _{(4-n) / 2} (1) (wherein R ¹ is the same or different, unsubstituted or substituted 1
And n is a positive number from 1.98 to 2.02. ) (B) 5 to 70 parts by weight of reinforcing silica powder having a specific surface area of 50 m ² / g or more, (C) 30 to 700 parts by weight of zinc white, (D) 0 to 50 parts by weight of conductive carbon black,
(E) A semi-conductive silicone rubber member for office machines, comprising an amount capable of curing the component (A) of the curing agent. 2. The semiconductive silicone rubber member for office machines according to claim 1, wherein the zinc white is a conductive zinc white doped with aluminum. 3. The semiconductive silicone rubber member for an office machine according to claim 1, wherein the semiconductive silicone rubber member is a semiconductive silicone rubber roll or a semiconductive silicone rubber belt.