JP3390114B2 - Conductive silicone rubber roll - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive silicone rubber roll having improved conductivity stability (uniformity). BACKGROUND OF THE INVENTION Various conductive rubbers obtained by blending a conductive material with a rubber-like substance having electrical insulation properties have been known in the art. For example, carbon black and the like as conductive materials have been known. The electric resistance is 10 ⁵ ~
10 ⁰ Ω · cm conductive rubbers within the range of are applied in various fields. [0003] On the other hand, silicone rubber, which is 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 carbon black to the silicone rubber, 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, copper, etc .; Known are those treated with metal, those mixed with carbon fiber, metal fiber and the like.
These do not impair the properties of silicone rubber,
It is frequently used because the volume resistivity of silicone rubber can be reduced to about 10 ¹⁰ to 10 ⁻³ Ω · cm depending on the type and filling amount of the conductive material. 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. Have been. However, when a conductive silicone rubber is used as the above-mentioned roll, about 10 ³ to 10 ¹⁰ Ω · cm, particularly
In the range of 10 ⁶ to 10 ¹⁰ Ω · cm, it is necessary that the electric resistivity in the roll is uniform (for example, within one order). On the other hand, when the conductive carbon black is compounded, the amount of the compounded carbon black becomes small, so that there is a problem that the dispersion becomes large depending on molding conditions and kneading conditions, and a uniform roll cannot be obtained. Therefore, in order to attain conductivity stability (uniformity), a method of preparing a conductive silicone rubber powder in advance and blending it with an insulating silicone rubber (JP-A-61-108661).
No., JP-A-63-156858, JP-A-63-251464),
Further, a method has been proposed in which a conductive silicone rubber composition containing carbon black and an insulating silicone rubber composition containing no carbon black are prepared in advance, and these are mixed and macrodispersed (Japanese Patent Laid-Open No. 3-190964). . Furthermore, a method of blending carbon black having a higher specific resistance than conductive carbon black (Japanese Patent Laid-Open No. 4-32)
A method of blending a 8162 JP), conductive zinc oxide and conductive tin oxide (JP-A-3-190964) has also been proposed, in 10 ³ ~10 ⁵ Ω · cm level with these Although a stable roll can be obtained, there is a problem that the dispersion is increased when the roll is 10 ⁶ Ω · cm or more. SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a conductive silicone rubber roll having conductive stability (uniformity) in a range of 10 ⁶ to 10 ¹⁰ Ω · cm. Aim. [0011] SUMMARY OF THE INVENTION The present inventors have result of extensive studies in order to achieve the above object, formed of a conductive silicone rubber composition containing a powder specific iron oxide powder to the specific polyorganosiloxane The inventors have found that the roll is effective, and have completed the present invention. 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 C 1-10 carbon atom) Or 100 parts by weight of a polyorganosiloxane represented by a different monovalent hydrocarbon group, a = 1.95 to 2.05), (b) a general formula (FeO) _x (Fe ₂ O ₃ ) _y (where x + y = 1, 0.5 ≦ x ≦ 1, 0 ≦ y ≦ 0.5)
Is characterized in iron oxide powder powder 50 to 500 parts by weight shown in the (c) electrically conductive silicone rubber composition containing a curing agent required amount that was uniformly coated on the core metal. 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. R group in the above formula (1) is an alkyl group such as a methyl group, an ethyl group, a propyl group, a butyl group,
Alkenyl groups such as vinyl group, allyl group, butaniel group,
Aryl groups such as phenyl group and tolyl group, and chloromethyl group, chloropropyl group, in which part or all of hydrogen atoms bonded to carbon atoms of these groups are substituted with halogen atoms or cyano groups, 3,3,3 -Trifluoropropyl group, 2
-An unsubstituted or substituted monovalent hydrocarbon group such as a cyanoethyl group; 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 formula (1) is a positive number selected from the range of 1.90 to 2.05 for obtaining a rubber-like elastic body. As a part of the R group, an alkenyl group such as a vinyl group is used depending on the curing reaction of the rubber-like elastic body, as described later in detail. 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. Also,
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 methyldiphenylsilyl group. , A methyldivinylsilyl group, a trivinylsilyl group, and the like. In this case, in order to further reduce the surface tack, it is desirable that both ends of the molecular chain have a multifunctional group such as (CH ₂ = CH) ₂ RSi-, (CH ₂ = CH) ₃ Si- . The degree of polymerization of the polyorganosiloxane used in the present invention is not particularly limited. However, the degree of polymerization is 100 to 2,000 for liquid silicone rubber, and 2,000 to 2,000 for millable silicone rubber. 10000 is preferred. [0017] (b) component is represented by the general formula _{(FeO) x (Fe 2 O} 3) is indicated by _y, x + _y = 1 in 0.5 ≦ x ≦ 1,0 ≦ y ≦ 0.5 and iron oxide powder powder that is a Is done. Since this Fe ₂ O _3, commonly referred to as a red Benkara for iron oxide powder is conductive poor, this x value in FeO content Ru der should be more than 0.5. These iron oxide powder powder had a particle size 0.01~15μ
m, preferably 0.1 to 5 μm. [0018] Iron oxide Powder above, a volume resistivity of 10
³ to 10 ⁵ Ωcm and 10 ^-2 to 10 ^{-1 of} carbon black
Ωcm or higher than 10 ¹ to 10 ² Ωcm such as conductive zinc oxide
In the region of ^{6 ~10 10 Ω} · cm in which stable (uniform) was conductivity. The amount of these components is 100
50 to 500 parts by weight per part by weight is preferred. If the amount is less than 50 parts by weight, conductivity cannot be obtained, and if the amount exceeds 500 parts by weight, the mechanical strength may be reduced. More preferably 1
00 to 300 parts by weight. The curing agent (C) is appropriately selected according to the reaction mechanism for obtaining the rubber-like elastic material.
As the reaction mechanism, (1) a crosslinking reaction with an organic peroxide vulcanizing agent, and (2) an addition reaction are known. The polyorganosiloxane of the component (a) and the curing agent of the component (c) in the respective reaction mechanisms (1) and (2) will be described below. First, when the crosslinking reaction of the above (1) is applied, the polyorganosiloxane of the component (a) is usually an organic group R bonded to a silicon atom in one molecule.
Among them, a polyorganosiloxane in which at least two are alkenyl groups such as a vinyl group, a propenyl group, a butenyl group, and a hexenyl group is used. In particular, a vinyl group is preferable among the above groups because of ease of synthesis and availability of raw materials. In addition, as the curing agent of the component (c), benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, dicumyl peroxide, cumyl-t-butyl peroxide, 2,5-dimethyl-2,5-di- Since various organic peroxides such as t-butylperoxyhexane and di-t-butyl peroxide are used as vulcanizing agents and give particularly 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. The compounding amount of the organic peroxide as the curing agent of the component (c) is 100 parts by weight of the polyorganosiloxane of the component (a).
It is preferably in the range of 0.05 to 15 parts by weight based on 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. When the addition reaction of the above (2) is applied, the same polyorganosiloxane as the component (a) as described in the above (1) is used, and the curing agent of the component (c) is An addition reaction catalyst and a crosslinking agent are used. For example, as an addition reaction (curing) catalyst, a platinum catalyst such as chloroplatinic acid, a platinum olefin complex, a platinum vinyl siloxane complex, platinum black, and a platinum triphenylphosphine complex is used. A polyorganosiloxane having an average of at least two hydrogen atoms in one molecule bonded to an atom is used. Of the curing agents of the above-mentioned component (c), the amount of the curing catalyst is determined by the amount of the polyorganosiloxane of the component (a).
An amount which is in the range of 1 to 1000 ppm in terms of the amount of platinum element per 100 parts by weight is preferable. If the amount of the curing catalyst is less than 1 ppm in terms of platinum element, curing will not proceed sufficiently and
Even if the amount is more than 00 ppm, no improvement in the curing speed can be expected. The amount of the cross-linking agent is preferably such that the number of hydrogen atoms bonded to silicon atoms in the cross-linking agent is 0.5 to 5.0, and more preferably one alkenyl group in the component (a). The quantity is 1.0 to 4.0. When the amount of hydrogen atoms is less than 0.5, curing of the composition does not proceed sufficiently, and the hardness of the composition after curing becomes low. Physical properties and heat resistance are reduced. The conductive silicone rubber composition of the present invention may contain, if necessary, a filler other than the above components (A) to (C), for example, a reinforcing filler such as fumed silica or precipitated silica, 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 as a dispersant, cerium oxide or the like as a heat resistance improver, a platinum compound or the like as a flame retardant, or azodicarbonate to obtain a sponge-like rubber. An organic blowing agent such as amide and azobisisobutyronitrile may be blended. The conductive silicone rubber roll of the present invention comprises:
The conductive silicone rubber composition obtained by kneading the aforementioned components (a) to (c) 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, it may be coated on a core during the above molding, and then heat-molded. May be inserted. The conductive silicone rubber roll thus obtained is excellent in the stability (uniformity) of electric resistance, so that the charging roll, developing roll, transfer roll, cleaning roll, etc. of OA equipment such as PPC, printer, facsimile, etc. It is effective for Embodiments of the present invention will be described below.
The parts in the examples are parts by weight. Example 1 A vinyl group-containing polydimethylsiloxane containing 0.1 mol% of a methylvinylsiloxane unit whose end is blocked with a trimethylsilyl group (average degree of polymerization = 7000) 100 parts of Fe ₃ O
₄ (iron trioxide), that is, 200 parts of Fe ^(II) Fe ₂ ^(III) O ₄ are uniformly blended and kneaded with an open kneader, and then, as a vulcanizing agent, 2,5-dimethyl-2,5-di ( t-butyl peroxy)
Mix 1.5 parts of hexane with two rolls and then 6m in diameter
m, press-formed at 170 ° C for 10 minutes so as to cover the stainless steel core metal with a thickness of 6mm uniformly at a thickness of 250mm.
mm of a conductive silicone rubber roll was obtained. Then 200
Post-vulcanization was performed in an oven at 4 ° C. × 4 hours. This was polished by a cylindrical grinder until the diameter became 11 mm. The obtained conductive silicone rubber roll is
Using Hyresta IP (manufactured by Mitsubishi Yuka), the volume resistivity of the core metal and the roll surface was measured at 10 points at a voltage of 100V. Example 2 Example 2 was repeated except that the amount of the iron oxide powder was changed to 150 parts. Comparative Example 1 The procedure of Example 1 was repeated, except that the iron oxide powder was replaced with conductive carbon black (Denka Black, manufactured by Denki Kagaku Kogyo), and the blending amount was changed to 15 parts. Comparative Example 2 In Example 1, the iron oxide powder was replaced with conductive zinc oxide (23-
K, manufactured by Hakusui Chemical Industry Co., Ltd.). Comparative Example 3 The same procedure as in Example 1 was carried out except that the iron oxide powder was changed to conductive zinc oxide and the compounding amount was changed to 150 parts. Table 1 shows the results. [Table 1] Example 3 A terminal was capped with a dimethylvinylsilyl group, and 100 parts of a vinyl group-containing polydimethylsiloxane containing 0.2 mol% of methylvinylsiloxane units (average degree of polymerization = 8000) was added to
250 parts of iron tetroxide used in Example 1 was mixed with an open kneader, and 2 parts of 2,4-dichlorobenzoyl peroxide were further mixed with two rolls, and the diameter was 6 mm and the length was adjusted using an extruder. The resultant was extruded together with a 250 mm stainless steel core so as to have an outer diameter of 15 mm, and was then cured by heating in an oven at 250 ° C. for 10 minutes, and then vulcanized in an oven at 200 ° C. for 4 hours. This was polished to an outer diameter of 13 mm with a cylindrical grinder. The volume resistivity of the obtained conductive silicone rubber roll was measured in the same manner as in Example 1. Comparative Example 4 The procedure of Example 4 was repeated, except that conductive zinc oxide (as described above) was used instead of ferric oxide. Comparative Example 5 In Example 4, conductive carbon black (DENKA BLACK HS-100 manufactured by Denki Kagaku Kogyo) was used instead of iron tetroxide.
The procedure was the same as in Example 4, except that 16 parts were used. Table 2 shows the results. [Table 2]

Claims (1)

(57) [Claims] [Claim 1] (A) Average composition formula R _a SiO _{(4-a) / 2} ... (1) (where R is an unsubstituted or substituted C 1-10 carbon atom) (B) 100 parts by weight of a polyorganosiloxane represented by the same or different monovalent hydrocarbon groups, a = 1.95 to 2.05), (b) the general formula (FeO) _x (Fe ₂ O ₃ ) _y (where x + y = 1) , 0.5 ≦ x ≦ 1, 0 ≦ y ≦ 0.5)
In conductive silicone rubber roll, characterized in that the iron oxide powder powder 50 to 500 parts by weight of (c) a conductive silicone rubber composition containing a curing agent required amount was uniformly coated on the metal core indicated.