JPH08104813A - Conductive silicone rubber composition and silicone rubber roll - Google Patents

Abstract

PURPOSE: To obtain the subject composition minimized in unreacted siloxane components oozing from the cured rubber therefrom, thus suitably usable for rubber rolls, etc., among others. CONSTITUTION: This electrically conductive silicone rubber composition is obtained by incorporating (A) 100 pts.wt. of a specific polyorganosiloxane with (B) 3-1000 pts.wt. of an electrical conductivity-imparting agent, (C) 1-150 pts.wt. of a finely powdered precipitated silica-based filler with >=150cc/100g oil absorption or inorganic fine powder having micropores with >=300cc/100g oil absorption (except precipitated silica), and (D) a necessary amount of a curing agent.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive silicone rubber composition having a very small amount of a component exuded from a rubber after molding, and by utilizing its characteristics, it can be used for a photosensitive drum used in a dry copying machine, a printer or the like. The present invention relates to a conductive silicone rubber roll and a conductive silicone rubber sponge roll that prevent contamination and contact failure.

[0002]

TECHNICAL BACKGROUND OF THE INVENTION AND ITS PROBLEMS Conventionally, various conductive rubbers in which a conductive material (conductivity-imparting agent) is mixed with a rubber-like substance exhibiting electrical insulation are known. For example, carbon is used as the conductive material. Black resistance is mixed, and the electric resistance is 10 ⁵ to 10
Conductive rubber in the range of Ω · cm is applied in a wide range of fields. On the other hand, silicone rubber, one of the electrically insulating rubbery substances, has excellent heat resistance, cold resistance, and weather resistance, and is widely used as an electrically insulating rubber. By adding a material, it has been put to practical use as a conductive silicone rubber. In this case, as the conductive material added to the conductive silicone rubber, for example, various metal powders such as carbon black, graphite, silver, nickel and copper, various non-conductive powders and short fiber surfaces are treated with a metal such as silver. However, the volume resistivity of silicone rubber is 10 ¹³ -10 ^-3 Ω depending on the type and filling amount of the conductive material without impairing the unique properties of silicone rubber.・ It is often used because it can be reduced to about cm, especially when obtaining highly conductive silicone rubber of 10 ⁵ Ω ・ cm or less, among these, metal powder such as carbon black, silver, nickel, etc., especially Carbon black is often used because of its cost. In addition, conductive silicone rubber is widely used for contacts of electric / electronic devices, sheet heating elements, dry copying machines, printers, rolls for fax machines, and the like. In recent years, the mechanism of printers, fax machines, copiers, etc. is changing from magnetic toners to one-component electrostatic toners. Further, due to the problem of ozone generation, the corona discharge is being changed to a conductive roll, and the utilization of silicone is increasing from the viewpoint of characteristics. However, 4 to 5 rolls are usually used around a so-called photosensitive member such as a charging roll, a developing roll, a transfer roll, and a cleaning roll of a dry copying machine or a printer, but 2 to 3 of them are photosensitive members. Is in contact with.
For this reason, when it is not operating, unreacted siloxane components present in the cured rubber, which is the roll material, oozes out, contaminates the photoconductor, and problems such as white spots that prevent reliable printing occur There was a problem that the obtained image could not be obtained. To solve this problem, a method of coating the roll surface so that the unreacted siloxane component does not exude, a method of removing the unreacted siloxane component in a high temperature atmosphere, a method of extracting with a solvent and the like have been performed. However, there are problems that the method of coating is costly and that it is difficult to obtain a stable coating layer. Further, a method of removing in a high temperature atmosphere or with a solvent is effective for removing low-molecular siloxanes having a degree of polymerization of 20 or less, but there is a problem that it is not effective for siloxanes having a degree of polymerization of more than that. there were.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above problems and provide a conductive silicone rubber composition containing an extremely small amount of unreacted siloxane component exuding from a cured rubber, and a conductive silicone rubber roll using the same. And

[0004]

DETAILED DESCRIPTION OF THE INVENTION As a result of intensive studies to achieve the above object, the present inventors have found that a fine powdery precipitated silica filler having an oil absorption amount of 150 cc / 100 g or more or fine pores having an oil absorption amount of 300 cc / 100 g or more. It has been found that it is effective to blend an inorganic fine powder other than precipitated silica, and the present invention has been completed. That is, the present invention provides (A) a polyorganosiloxane represented by the average composition formula (1).
100 parts by weight of R _a SiO _{(4-a) / 2} (1) (wherein R is a substituted or unsubstituted monovalent hydrocarbon group, a
Is a positive number from 1.95 to 2.05. ) (B) Conductivity-imparting agent 3 to 1000 parts by weight (C) Fine powdery precipitated silica filler with oil absorption of 150 cc / 100 g or more or inorganic other than precipitated silica having fine pores with oil absorption of 300 cc / 100 g or more 1 to 150 parts by weight of fine powder (D) A conductive silicone rubber composition containing a necessary amount of a curing agent, a conductive silicone rubber roll using the conductive silicone rubber composition, and a conductive silicone rubber sponge roll.

The present invention will be described in detail below. The component (A) constituting the composition of the present invention is an organopolysiloxane represented by the general formula (1), wherein R is a methyl group,
Alkyl groups such as ethyl group, propyl group and butyl group, alkenyl groups such as vinyl group, allyl group and butaniel group,
A phenyl group, an aryl group such as a tolyl group, or a chloromethyl group in which a part or all of hydrogen atoms bonded to carbon atoms of these groups are substituted with a halogen atom, a cyano group, a chloropropyl group, 3,3,3- Trifluoropropyl group, 2
The same or different unsubstituted or substituted monovalent hydrocarbon group selected from cyanoethyl group and the like, preferably having 1 to 10 carbon atoms, more preferably 1 to 8 carbon atoms. or,
a is a positive number from 1.90 to 2.05. This compound preferably has a linear molecular structure, but there is no problem even if it partially contains a branched molecular structure. Further, this may have a molecular chain terminal blocked with a triorganosilyl group or a hydroxyl group, and the triorganosilyl group may be a trimethylsilyl group, a dimethylvinylsilyl group, a methylphenylvinylsilyl group, or a methyldiphenyl group. Examples thereof include a silyl group, a methyldivinylsilyl group and a trivinylsilyl group. The degree of polymerization of this product is not limited, but when the liquid silicone rubber is used, the degree of polymerization is 100-
2000, degree of polymerization when using millable silicone rubber
2000-10000 is preferable.

As the conductivity-imparting agent as the component (B), metal powders, metal fibers, metal flakes, metal-based conductive agents such as conductive metal oxides, carbon black and the like can be used. Here, the powder, the fiber, the metal used in the flakes,
Examples thereof include silver, copper, nickel, stainless steel, and aluminum, and examples of the conductive metal oxide include conductive zinc oxide and conductive titanium oxide. As the carbon black, those commonly used in conductive rubber compositions can be used. For example, acetylene black, conductive furnace black (CF), super conductive furnace black (SCF), extra conductive furnace black (XCF), conductive channel black (CC), and furnace black or channel black heat-treated at a high temperature of about 1500 ° C are available. Can be mentioned. Specific examples of acetylene black include electrified acetylene black (manufactured by Denki Kagaku Co., Ltd.) and Shawnigan acetylene black (manufactured by Shawnigan Chemical Co., Ltd.), and specific examples of conductive furnace black include Continex CF (Continental Carbon Co., Ltd.). Company), Vulcan C (manufactured by Cabot Co., Ltd.), and specific examples of Super Conductive Furnace Black are Continex SCF (manufactured by Continental Carbon Co., Ltd.) and Vulcan SC (manufactured by Cabot Co., Ltd.). As a specific example of Asahi HS-500
(Asahi Carbon Co., Ltd.), Vulcan XC-72 (manufactured by Cabot Co., Ltd.) and the like are Kolux L (manufactured by Degussa Co., Ltd.) as a conductive channel black.
And the like, and Ketjen Black EC and Ketjen Black EC-, which are types of furnace black.
600 JD (Ketjen Black International Co., Ltd.) can also be used. The metal-based conductivity-imparting agent is added in an amount of 50 to 1000 parts by weight, preferably 100 to 500 parts by weight, based on 100 parts by weight of the polyorganosiloxane as the component (A). If it is less than 50 parts by weight, conductivity cannot be obtained, and if it is mixed in excess of 1000 parts by weight,
Not only the effect is not improved, but the mechanical strength may be reduced. The carbon black content is 3 to 150 parts by weight, more preferably 5 to 100 parts by weight. If the amount is less than 3 parts by weight, it is difficult to obtain conductivity, and if the amount exceeds 150 parts by weight, the effect is not improved and the mechanical strength may be deteriorated.

The component (C), a finely powdered precipitated silica filler, is for preventing the unreacted siloxane component from oozing out. In this precipitated silica-based filler, primary particles are aggregated to form an aggregate, and a large number of voids are present in the aggregate. Therefore, unreacted siloxane is adsorbed in the voids to prevent bleeding. Further, the precipitated silica-based filler may not be surface-treated, or may be surface-treated with organosilane, organosiloxane, organosiloxane or the like.
In addition, in order to prevent the exudation of unreacted siloxane components, this product has an oil absorption amount specified in JIS K 5101.
It should be 150cc / 100g or more, preferably
180cc / 100g or more. Inorganic fine powders having fine pores other than precipitated silica are also effective, but in this case, unlike the precipitated silica filler, the affinity with siloxane is weak,
It is necessary that the oil absorption is 300cc / 100g or more. Examples of such inorganic fine powders include jaolite-type calcium silicate (for example, Tokuyama fluorite), zeolite, and shirasu balloon. In addition, the inorganic fine powder having fine pores may also act on the polymer of the component (A) to increase the viscosity of the composition and reduce the moldability. In this case, before mixing the component (C) and the component (A), 10 to 50 parts by weight of a cyclic or linear dimethylsiloxane having 2 to 6 siloxane units per 100 parts by weight of the component (C) should be prepared in advance.
The problem can be solved by supporting 0 part by weight. Also (C)
If the blending amount of the components is too small, it is not possible to prevent the unreacted siloxane component from oozing out, and if it is too large, the mechanical strength of the silicone rubber obtained by curing this will decrease, so (A)
The amount is 1 to 150 parts by weight, more preferably 3 to 100 parts by weight, based on 100 parts by weight of the component.

The curing agent as the component (D) is appropriately selected according to the reaction mechanism for obtaining the rubber elastic body. As the reaction mechanism, (1) a crosslinking method using an organic peroxide vulcanizing agent, (2) a condensation reaction method, (3) an addition reaction method, etc. are known.
It is well known that the preferred combination of component (A) and component (D), i.e. a curing catalyst or crosslinking agent, and the amount of component (D) are determined. The (A) organopolysiloxane and (D) curing agent in the respective reaction mechanisms (1) to (3) will be described below. First, in the case of applying the cross-linking method of (1), usually, as the organopolysiloxane of the component (A), at least two of the organic groups bonded to the silicon atom in one molecule are vinyl, propenyl, An organopolysiloxane which is an alkenyl group such as butenyl or hexenyl is used. Of these groups, the vinyl group is particularly preferred because it is easy to synthesize and the raw materials are easily available.
Further, as the curing agent of the component (C), benzoyl peroxide, 2,4-dichlorobenzoyl peroxide, dicumyl peroxide, cumyl-t-butyl peroxide, 2,
Various organic peroxide vulcanizing agents such as 5-dimethyl-2,5-di-t-butylperoxyhexane and di-t-butylperoxide are used, and since they give particularly low compression set, dicumyl peroxide is used. , Cumyl-t-butylperoxide, 2,5-dimethyl-2,5-di-t-butylperoxyhexane, di-t-butylperoxide are preferred. In addition, these organic peroxide vulcanizing agents are used as one kind or as a mixture of two or more kinds. The blending amount of the organic peroxide as the curing agent of the component (D) is preferably 0.05 to 15 parts by weight with respect to 100 parts by weight of the organopolysiloxane of the component (A). If the compounding amount of the organic peroxide is less than 0.05 part by weight, the vulcanization is not sufficiently performed, and if the compounding amount exceeds 15 parts by weight, there is no particular effect, and the conductive silicone rubber This is because the physical properties may be adversely affected.

When the condensation reaction of (2) is applied, an organopolysiloxane having hydroxyl groups at both ends is used as the organopolysiloxane of the component (A). As the curing agent for the component (D), first, as a crosslinking agent, ethyl silicate, propyl silicate, methyltrimethoxysilane, vinyltrimethoxysilane, methyltriethoxysilane, vinyltriethoxysilane, methyltris (methoxyethoxy) silane, vinyltris ( Alkoxy type such as methoxyethoxy) silane and methyltripropenoxysilane; acetoxy type such as methyltriacetoxysilane and vinyltriacetoxysilane; methyltri (acetoneoxime) silane, vinyltri (acetoneoxime) silane, methyltri (methylethylketoxime) silane, Examples thereof include vinyltri (methylethylketoxime) silane and the like, and partial hydrolysates thereof. Hexamethyl-bis (diethylaminoxy)
Cyclotetrasiloxane, tetramethyldibutyl-bis (diethylaminoxy) cyclotetrasiloxane, heptamethyl (diethylaminoxy) cyclotetrasiloxane, pentamethyl-tris (diethylaminoxy) cyclotetrasiloxane, hexamethyl-bis (methylethylaminoxy) cyclotetrasiloxane, Cyclic siloxanes such as tetramethyl-bis (diethylaminoxy) -mono (methylethylaminoxy) cyclotetrasiloxane are also exemplified. As described above, the cross-linking agent may have any of a silane and siloxane structure, and the siloxane structure may be any of linear, branched and cyclic structures. Furthermore, when using these, it is not necessary to be limited to one type, and two or more types can be used in combination. Further, among the curing agents of the component (D), as a curing catalyst, iron octoate, cobalt octoate, manganese octoate, tin naphthenate, tin caprylate, tin carboxylic acid metal salts such as oleate; dimethyltin dioleate,
Organic tin compounds such as dimethyltin dilaurate, dibutyltin diacetate, dibutyltin dioctoate, dibutyltin dilaurate, dibutyltin dioleate, diphenyltin diacetate, dibutyltin oxide, dibutyltin dimethoxide, dibutylbis (triethoxysiloxy) tin, dioctyltin dilaurate are available. Used. In the curing agent as the component (D), the amount of the cross-linking agent is preferably 0.1 to 20 parts by weight based on 100 parts by weight of the organopolysiloxane as the component (A). If the amount of the cross-linking agent used is less than 0.1 part by weight, sufficient strength cannot be obtained for the cured rubber,
Further, if it exceeds 20 parts by weight, the obtained rubber becomes brittle, and any of them cannot be put to practical use. Also, the compounding amount of the curing catalyst is (A)
0.01 to 100 parts by weight of the component organopolysiloxane
5 parts by weight is preferred. If the amount is less than this, it is insufficient as a curing catalyst, and it takes a long time to cure, and the curing in the interior far from the contact surface with air becomes poor. On the other hand,
If it is more than this, the storage stability will decrease. A more preferable range of blending amount is 0.1 to 3 parts by weight.

(A) when applying the addition reaction of (3) above
As the component organopolysiloxane, those similar to the organopolysiloxane in (1) above are used. Further, as the curing agent for the component (D), a platinum catalyst such as chloroplatinic acid, a platinum olefin complex, a platinum vinyl siloxane complex, platinum black, or a platinum triphenylphosphine complex is used as a curing catalyst. An organopolysiloxane having at least an average of more than 2 hydrogen atoms bonded to silicon atoms in one molecule is used. Among the curing agents of component (D), the amount of the curing catalyst blended is
The amount of elemental platinum is preferably in the range of 1 to 1000 ppm with respect to 100 parts by weight of the organopolysiloxane as the component (A). If the compounding amount of the curing catalyst is less than 1 ppm of platinum element,
Curing does not proceed sufficiently, and even if it exceeds 1000 ppm, no particular improvement in the curing rate can be expected. The amount of the cross-linking agent to be blended is preferably such that 0.5 to 4.0 hydrogen atoms bonded to silicon atoms in the cross-linking agent per one alkenyl group in the component (A), and more preferably 1.0. The amount is about 3.0. 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. The physical properties and heat resistance of the composition are reduced.

In the composition of the present invention, if necessary, a dispersant such as a low molecular weight siloxane having a degree of polymerization of 100 or less, a silanol group-containing silane, an alkoxy group-containing silane, iron oxide, cerium oxide, iron octylate, etc. Heat resistance improver,
Flame retardants such as platinum compounds, iron oxides, azo compounds, titanium oxides, pigments, etc., and fumed silica from the aspect of reinforcement,
Fumed silica whose surface is hydrophobized, quartz fine powder,
Finely powdered silica such as diatomaceous earth may be blended with polyorganosilsesquioxane, and saturated aliphatic hydrocarbons such as isoparaffin solvent for the purpose of imparting processability and moldability to the composition, and other ordinary silicones. Other additives that are added to the rubber composition can also be added. As a method for producing the composition of the present invention, compounding and kneading may be carried out by a conventionally used apparatus such as a kneader, Banbury mixer, mixing roll or the like. Further, the conductive silicone rubber composition of the present invention can be molded and processed by a usual method such as pressure molding, extrusion molding, injection molding, calender molding or the like to be cured to obtain a product. Particularly, the conductive silicone rubber composition of the present invention is useful as a silicone rubber roll material, and the conductive silicone rubber composition of the present invention is uniformly coated on a roll core metal and cured as in a conventional method, It is possible to obtain a silicone rubber roll having excellent performance. Further, as a foaming agent, organic compounds such as azobisisobutyronitrile, dinitrosopentamethylenetetramine, p, p-oxybis (benzenesulfonylhydrazide), N, N-dinitroso-N, N-dimethylterephthalamide, and azodicarbonamide. A conductive silicone rubber composition containing a foaming agent or a foaming agent composed of a plastic micro hollow body that expands by heat with a volatile substance contained in a plastic shell is uniformly coated on a roll core metal in the same manner, and foamed. -By curing, a silicone rubber sponge roll with excellent performance can be obtained.

[0012]

EXAMPLES The present invention will be described below with reference to examples.
In the examples, all parts are parts by weight. Example 1 100 parts of dimethylvinylpolysiloxane containing 0.2 mol% of methylvinylsiloxane unit and having a degree of polymerization of about 7000, 15 parts of acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd.), and a fine powder having an oil absorption of 250 cc / 100 g. Precipitated silica filler (Nips
15 parts of il HD, manufactured by Nippon Silica Industry Co., Ltd., were kneaded with a kneader until uniform, and then 1.0 part of 2,5-dimethyl-2,5-di (tert-butylperoxy) hexane was added to the mixture to obtain 2 parts. The conductive silicone composition was obtained by uniformly mixing with this roll. This composition was press-vulcanized at 170 ° C for 10 minutes,
200 ℃ × 200 after vulcanization at 200 ℃ × 4 hours in the oven
A rubber sheet of mm × 2 mm was obtained. The volume resistivity of the obtained rubber sheet was measured with Hiresta IP (manufactured by Mitsubishi Petrochemical Co., Ltd.) at an applied voltage of 100V. Further, this sheet was placed on a polycarbonate plate, a load of 1 kg / cm ² was applied, and the sheet was left at room temperature for 1 day. After standing, it was examined using an infrared spectrophotometer whether or not the silicone component was attached to the polycarbonate plate, and bleeding of unreacted siloxane was evaluated. Example 2 In Example 1, instead of Nipsil HD, oil absorption 235cc
/ 100g of finely powdered precipitated silica filler (Nipsil HD-2,
A rubber sheet was prepared and evaluated in the same manner as in Example 1 except that Nippon Silica Industry Co., Ltd. was used. Example 3 In Example 1, instead of Nipsil HD, the average particle size was 25 μm.
A rubber sheet was prepared and evaluated in the same manner as in Example 1 except that calcium silicate having an oil absorption of 500 cc / 100 g (Florite R manufactured by Tokuyama Corporation) was used. Comparative Example 1 A rubber sheet was prepared and evaluated in the same manner as in Example 1 except that Nipsil HD was not added. Comparative Example 2 In Example 1, the finely powdered precipitated silica-based filler (Nips
oil powder absorption 140cc / 100g instead of il HD) Nipsil E-75 (Nippsil Silica Industry Co., Ltd.)
A rubber sheet was prepared and evaluated in the same manner as in Example 1 except that the rubber sheet was used.

Comparative Example 3 In Example 3, instead of the Fluorite R, the oil absorption 1
A rubber sheet was prepared and evaluated in the same manner as in Example 3 except that 3 parts of 50 cc / 100 g of calcium silicate (Solex CM (manufactured by Tokuyama Soda Co., Ltd.)) was used. The results are shown in Table 1.

[0014]

[Table 1]

Example 4 100 parts of dimethylvinylpolysiloxane having a degree of polymerization of about 8000 containing 0.15 mol% of methylvinylsiloxane units, 20 parts of acetylene black used in Example 1, and Nipsil HD 15 used in Example 1 Partially blended, methylhydrogenpolysiloxane containing 50 mol% methylhydrogensiloxane units as a curing agent (average degree of polymerization about 30)
1.5 parts, 1 part of triazine isocyanurate and 0.001 part of chloroplatinic acid were mixed, and a sheet was prepared and evaluated in the same manner as in Example 1. Comparative Example 4 Instead of Nipsil HD in Example 4, an oil absorption amount of 260 cc
A sheet was prepared and evaluated in the same manner as in Example 4 except that / 100 g of the dry silica filler Aerosil 130 (manufactured by Nippon Aerosil Co., Ltd.) was used. Table 2 shows the results.

[0016]

[Table 2]

Example 5 The silicone rubber composition of Example 1 was press-vulcanized at a temperature of 4 mm at 170 ° C. for 15 minutes on a core metal for a developing roll of a page printer “MICROLINE 400” manufactured by Oki Electric Co., Ltd. And 200 ℃ ×
After post-vulcanization in an oven for 4 hours, it was polished by a polishing machine to a thickness of 3 nm. Install the produced roll on the MICROLINE 400,
After left for one week, the entire surface was printed in black and white blank was evaluated. No white blank was observed. Comparative Example 5 When a roll was prepared from the silicone rubber composition of Comparative Example 1 and evaluated in the same manner as in Example 5, white spots were remarkably observed. Comparative Example 6 When a roll was prepared from the silicone rubber composition of Comparative Example 2 and evaluated in the same manner as in Example 5, white spots were remarkably observed.

Claims (5)

[Claims] (A) 100 parts by weight of the polyorganosiloxane represented by the average composition formula (1) is added to R _a SiO _{(4-a) / 2} (1) (wherein R is a substituted or unsubstituted group). Monovalent hydrocarbon group, a is
It is a positive number between 1.95 and 2.05. ) (B) Conductivity-imparting agent 3 to 1000 parts by weight (C) Fine powdery precipitated silica filler with oil absorption of 150 cc / 100 g or more or inorganic other than precipitated silica having fine pores with oil absorption of 300 cc / 100 g or more 1 to 150 parts by weight of fine powder (D) A conductive silicone rubber composition containing the necessary amount of a curing agent. 2. The conductive silicone rubber composition according to claim 1, wherein the conductivity-imparting agent (B) is carbon black. 3. A fine inorganic powder other than precipitated silica as the component (C).
The conductive silicone rubber composition according to claim 1 or 2, wherein 100 parts by weight of 10 to 500 parts by weight of cyclic or linear dimethylsiloxane having 2 to 6 siloxane units are supported. 4. A conductive silicone rubber roll comprising a cored bar coated and cured with the conductive silicone rubber composition according to any one of claims 1 to 3. 5. A composition obtained by further adding a foaming agent to the conductive silicone rubber composition according to claim 1.
A conductive silicone rubber sponge roll characterized by being coated on a cored bar, foamed and cured.