JPH10130506A - Electroconductive silicone rubber roll - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject roll having electroconductive stability in a wide range of receptivity and capable of expressing excellent time-dependent stability in the receptivity by using a co-compounded composition comprising a specific polyorganosiloxane together and electroconductive carbon black and a specific powder iron oxide. SOLUTION: To 100 pts.wt. of (A) a polyorganosiloxane expressed by an average compositional formula: RaSiO(4-a)/2 [R is a 1-10C monovalent (substituted) hydrocarbon group; (a) is 1.95-2.05], 3-100pts.wt. of (B) electroconductive carbon black, 5-200 pts.wt. of (C) powdery iron oxide expressed by the formula: (FeO)x (Fe2 O3 )y [(x) is 0.5-1: (y) is 0-0.5: x+y=1] (e.g.; iron oxide having 0.01-15μm, preferably 0.1-5μm particle size] and 0.05-15 pts.wt. of (D) an organic peroxide vulcanizer are blended to obtain the electroconductive silicone rubber composition, which is uniformly coated on a core metal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a conductive silicone rubber roll having improved conductivity stability (uniformity) and long-term stability over time.

[0002]

TECHNICAL BACKGROUND OF THE INVENTION AND PROBLEMS There have been known various conductive rubbers in which a conductive material is blended with a rubber-like substance having electrical insulation properties. For example, carbon black or the like is blended as a conductive material. Depending on the electric resistance, 10 ⁵ ~
10 ⁰ Ω · cm conductive rubbers within the range of are applied in various fields. On the other hand, silicone rubber, one of the electrically insulating rubber-like substances, has excellent heat resistance, cold resistance, and weather resistance, and is widely used as an electrically insulating rubber. By adding a conductive material such as the above, it has been put to practical use as a conductive silicone rubber. Further, a conductive silicone rubber foam which is foamed and cured by adding a foaming agent is also known. In this case, as the conductive material to be added to the silicone rubber composition, for example, various metal powders such as carbon black, graphite, silver, nickel and copper, non-conductive powders and short fiber surfaces are treated with a metal such as silver. And those obtained by mixing carbon fibers, metal fibers, and the like. They without impairing the properties possessed by the silicone rubber, depending on the type and loading of conductive material, the volume resistivity of the silicone rubber ¹⁰ 10 ~10 ^-3 Ω · cm
It is frequently used because it can be reduced to a degree.
On the other hand, there are various rolls as one of the uses of the conductive silicone rubber, and the conductive silicone rubber roll is used as a developing roll, a transfer roll, a charging roll, a cleaning roll, etc. of OA equipment such as a PPC, a printer, and a facsimile. . However, when the conductive silicone rubber is used as the above-mentioned roll, when the electrical resistivity is uniform (for example, within one order) in the roll at about 10 ³ to 10 ¹⁰ Ω · cm, particularly about 10 ⁵ to 10 ¹⁰ Ω · cm. Something is needed. Further, it is necessary that the electric resistivity does not change even after long-term use. On the other hand, when the conductive carbon black is blended, the blending amount becomes small, and the dispersion becomes large due to molding conditions and kneading conditions, and a uniform roll cannot be obtained. There is a problem that the electrical resistivity increases with time. Therefore, in order to solve the above problem, a method of blending conductive zinc black with conductive carbon black (Japanese Patent Laid-Open No. 8-2072)
No. 5) has been proposed. However, in the case of this method, there is a problem that the dispersion of the initial resistance becomes large because the conductivity is obtained by carbon black, and even if conductive zinc white is used, the volume resistivity of the conductive zinc white is increased. Is as low as 10 ² Ωcm, so 10 ⁵ to 10 ⁸
There was a problem that it was difficult to obtain a stable resistivity of the Ω · cm level.

[0003]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has conductivity stability (uniformity) in a region of 10 ⁵ to 10 ¹⁰ Ω · cm, and changes in resistivity even after long-term use. It is an object of the present invention to provide a conductive silicone rubber roll free from any problems.

[0004]

The present inventors have conducted intensive studies to achieve the above object, and as a result, have found that a conductive silicone rubber composition in which conductive carbon black and a specific iron oxide powder are combined with a specific polyorganosiloxane is used. It has been found that such a roll is effective, and the present invention has been completed. That is, the conductive silicone rubber roll of the present invention comprises (a) an average composition formula R _a SiO _{(4-a) / 2} (1) (where R is an unsubstituted or substituted identical or different C 1-10 carbon atom) 100 parts by weight of polyorganosiloxane represented by a monovalent hydrocarbon group, a = 1.95 to 2.05) (b) conductive carbon black 3 to 100 parts by weight (c) general formula (FeO) _x (Fe ₂ O ₃ ) _y (Where x + y = 1, 0.5 ≦ x ≦ 1, 0 ≦ y ≦ 0.5)
(D) An electrically conductive silicone rubber composition containing 0.05 to 15 parts by weight of an organic peroxide vulcanizing agent is uniformly coated on a metal core.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail. The component (A) constituting the conductive silicone rubber composition used in the roll of the present invention is a polyorganosiloxane represented by the above formula (1), which serves as a base polymer. The R group in the above formula (1) is an alkyl group such as a methyl group, an ethyl group, a propyl group or a butyl group, an alkenyl group such as a vinyl group, an allyl group, a butaniel group, an aryl group such as a phenyl group or a tolyl group, And chloromethyl, chloropropyl, 3,3,3-trifluoropropyl, and 2-cyanoethyl groups in which some or all of the hydrogen atoms bonded to the carbon atoms of these groups have been substituted with halogen atoms, cyano groups, or the like. And unsubstituted or substituted monovalent hydrocarbon groups. The R groups may be the same or different, and the hydrocarbon group as the R group preferably has 1 to 10 carbon atoms, and more preferably is a monovalent hydrocarbon group having 1 to 8 carbon atoms. The value of a in the equation (1) is important for obtaining a rubber-like elastic body.
A positive number selected from the range of 1.90 to 2.05. It is necessary that at least two of the organic groups R bonded to the silicon atom in one molecule are alkenyl groups such as a vinyl group, a propenyl group, a butenyl group, and a hexenyl group. In particular, a vinyl group is preferable among the above groups because of ease of synthesis and availability of raw materials. As the polyorganosiloxane, those having a linear molecular structure are preferable, but there is no problem even if the molecule contains a partially branched one. The molecular chain end of the polyorganosiloxane may have a structure blocked with a triorganosilyl group or a hydroxyl group. Examples of the triorganosilyl group include a trimethylsilyl group, a dimethylvinylsilyl group, a methylphenylvinylsilyl group, and a methyldiphenyl group. Examples thereof include a silyl group, a methyldivinylsilyl group, and a trivinylsilyl group. In this case, in order to further reduce the surface tack,
It is desirable that both ends of the molecular chain have a polyfunctional group such as (CH ₂ = CH) ₂ RSi- and (CH ₂ = CH) ₃ Si-. The degree of polymerization of the polyorganosiloxane used in the present invention is not particularly limited.
In the case of 100 to 2000, and a millable silicone rubber, the polymerization degree is preferably 2000 to 10,000. As the conductive carbon black of the component (b), those commonly used in conductive rubber compositions can be used. For example, acetylene black, conductive furnace black (CF), superconductive furnace black (SCF),
Extra conductive furnace black (XC
F), conductive channel black (CC) and
Furnace black or channel black heat-treated at a high temperature of about 1500 ° C. can be used. Specific examples of acetylene black include electrified acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd.) and Shaunigan door acetylene black (manufactured by Shaunigan Chemical Co., Ltd.). Specific examples of the conductive furnace black include Continex CF ( Continental Carbon Co., Ltd.), Vulcan SC (Cabot Co., Ltd.) and the like are specific examples of extra-conductive furnace black. Asahi HS-500 (Asahi Carbon Co., Ltd.) and Vulcan XC-72 (Cabot Co., Ltd.) Specific examples of the conductive channel black include Colux L (manufactured by Degussa Co., Ltd.), and Ketjen Black EC and Ketjen Black EC-600 JD, which are a kind of furnace black.
(Made by Ketjen Black International)
Can also be used. (B) The addition amount of the conductive carbon black is preferably from 3 to 100 parts by weight, particularly preferably from 5 to 50 parts by weight, based on 100 parts by weight of the polyorganosiloxane base polymer as the component (A). . If the amount is less than 3 parts by weight, desired conductivity may not be obtained, and if it exceeds 100 parts by weight, the cured product may have poor mechanical strength.

The component (c) is an iron oxide powder represented by the general formula (FeO) _x (Fe ₂ O ₃ ) _y , wherein x + y = 1 and 0.5 ≦ x ≦ 1, 0 ≦ y ≦ 0.5. . These iron oxide powders have a particle size
The thickness may be in the range of 0.01 to 15 μm, preferably 0.1 to 5 μm. The above iron oxide powder has a volume resistivity of 10 ³ to 10 ⁵ Ωcm, and 10 ^{-2 of} carbon black.
~ 10 ^-1 Ωcm or higher than 10 ¹ -10 ² Ωcm such as conductive zinc white
Stable (uniform) conductivity is obtained in the region of 10 ⁵ to 10 ¹⁰ Ω · cm. The amount of these components is preferably 5 to 200 parts by weight based on 100 parts by weight of the component (A). If the amount is less than 5 parts by weight, conductivity cannot be obtained, and if it exceeds 200 parts by weight, the mechanical strength may be reduced. More preferably, it is 10 to 100 parts by weight.

The component (d) is an organic peroxide vulcanizing agent,
It is a curing agent for obtaining a rubber-like elastic body by a crosslinking reaction. (D) As components, benzoyl peroxide,
2,4-dichlorobenzoyl peroxide, dicumyl peroxide, cumyl-t-butyl peroxide, 2,
Since various organic peroxides such as 5-dimethyl-2,5-di-t-butylperoxyhexane and di-t-butyl peroxide are used as a vulcanizing agent and particularly give a low compression set, Dicumyl peroxide, cumyl-
T-butyl peroxide, 2,5-dimethyl-2,5-di-t-butylperoxyhexane and di-t-butyl peroxide are preferred. In addition, these organic peroxide vulcanizing agents are used as one kind or as a mixture of two or more kinds.
(D) The compounding amount of the organic peroxide as the curing agent of the component is
(A) 100 parts by weight of the component polyorganosiloxane
The content is preferably in the range of 0.05 to 15 parts by weight. If the amount of the organic peroxide is less than 0.05 part by weight, the vulcanization is not sufficiently performed.On the other hand, if the amount exceeds 15 parts by weight, there is no more special effect, and the obtained rubber-like elastic body (Conductive silicone rubber) may adversely affect the properties.

Incidentally, a method other than the crosslinking reaction by the component (d), for example, using a polyorganosiloxane having an average number of more than two hydrogen atoms bonded to a silicon atom in one molecule as a crosslinking agent, a platinum catalyst or the like When cured by a method of crosslinking with an addition reaction catalyst, the same volume resistivity as that obtained by crosslinking with the component (d) is obtained,
The value of the compression set is large, which makes the silicone rubber roll unsuitable.

The conductive silicone rubber composition of the present invention may contain, if necessary, a filler other than the above-mentioned components (a) to (d), for example, a reinforcing filler such as fumed silica, precipitated silica, or the like. Quartz powder, fused quartz powder, diatomaceous earth, talc, calcium carbonate, titanium oxide, aluminum oxide, clay, conductive metal oxides such as conductive zinc oxide, etc., which are blended in the rubber composition may be added. ,
Further, a low molecular siloxane ester or a silanol group-containing siloxane or the like as a dispersant, cerium oxide or the like as a heat resistance improver, a platinum compound or the like as a flame retardant, or azodicarbonamide when a sponge-like rubber is obtained. And an organic foaming agent such as azobisisobutyronitrile.

[0010] The conductive silicone rubber roll of the present invention comprises:
The conductive silicone rubber composition obtained by kneading the components (a) to (d) with a roll, kneader, Banbury mixer or the like in the same manner as a normal silicone rubber composition is subjected to press molding, transfer molding, injection molding, and extrusion molding. It can be obtained by hot molding under normal pressure or under pressure. In addition, since it is excellent in microwave absorbency, it can be vulcanized by UHF. However, after coating on the core metal at the time of the above molding, it may be heated and molded. May be inserted. The conductive silicone rubber roll thus obtained is
Since it is excellent in stability (uniformity) of electric resistance, it is effective for a charging roll, a developing roll, a transfer roll, a cleaning roll and the like of OA equipment such as a PPC, a printer and a facsimile.

[0011]

Embodiments of the present invention will be described below.
The parts in the examples are parts by weight. Example 1 Acetylene black (Denka Black; manufactured by Denki Kagaku Kogyo Co., Ltd.) was added to 100 parts of a vinyl group-containing polydimethylsiloxane containing 0.15 mol% of a methylvinylsiloxane unit and capped with a trimethylsilyl group (average degree of polymerization = 7000). 10 parts and 30 parts of iron oxide (Todacolor KN310; manufactured by Toda Kogyo Co., Ltd.) are uniformly mixed and kneaded with an open kneader, and then, as a vulcanizing agent, 2,5-dimethyl-2,5-di (t)
-Butyl peroxy) hexane was mixed with 1.5 rolls of two rolls, and then press-formed at 170 ° C. for 10 minutes so as to uniformly coat a 6 mm thick stainless steel core bar having a diameter of 6 mm and a length of 250 mm. A 12 mm conductive silicone rubber roll was obtained. Subsequently, post-curing was performed in an oven at 200 ° C. for 4 hours. This was polished by a cylindrical grinder until the diameter became 11 mm. Using a Hiresta IP (manufactured by Mitsubishi Yuka Co., Ltd.), the obtained conductive silicone rubber roll was measured for the resistance values of the core metal and the roll surface at 10 points at a voltage of 100 V. Furthermore, after fixing the electrode and applying a current for 3 hours with 500V applied, 100
The resistance value was measured at V, and the rate of change from the initial value was calculated. Examples 2 to 4 The same procedures as in Example 1 were carried out except that the amounts of the components were changed as shown in Table 1. Comparative Example 1 Example 1 was repeated except that iron oxide was not used. Comparative Example 2 The procedure of Example 3 was repeated, except that conductive zinc white was used instead of iron oxide. Table 1 shows the results.

[0012]

[Table 1]

Continued on the front page (51) Int.Cl. ⁶ Identification code FI G03G 15/08 501 G03G 15/08 501D

Claims (1)

[Claims] (1) Average compositional formula: R _a SiO _{(4-a) / 2} (1) (where R is an unsubstituted or substituted monovalent hydrocarbon group having 1 to 10 carbon atoms) , A = 1.95 to 2.05) 100 parts by weight of the polyorganosiloxane represented by (b) conductive carbon black 3 to 100 parts by weight (c) general formula (FeO) _x (Fe ₂ O ₃ ) _y (where x + Y = 1, 0.5 ≦ x ≦ 1, 0 ≦ y ≦ 0.5)
5 to 200 parts by weight of iron oxide powder represented by (d) Conductive silicone rubber composition comprising 0.05 to 15 parts by weight of an organic peroxide vulcanizing agent uniformly coated on a metal core. Silicone rubber roll.