JPH0587092B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention is applicable to laser beam printers used as OA equipment, toner conveyance rolls and paper feed rolls (paper feed rolls, conveyance rolls) used in the developing section of copying machines, etc. The present invention relates to a composition for conductive sponge rolls and a method for producing the same. [Prior Art] Conventionally, toner transport rolls (toner transport rolls, transfer rolls, photosensitive drum cleaning rolls, charging rolls, developing rolls), etc., and paper transport rolls used in laser beam printers and developing units of copying machines, etc. Conductive materials having a volume resistivity of 10 ³ to ^{10 9} Ωcm are used in view of the ability to convey toner, etc. This conductive roll requires a larger contact area at low pressure in order to make the equipment that uses it smaller and lighter, as well as to improve the quality of developability. A conductive sponge roll is used instead of rubber. [Problems to be Solved by the Invention] The volume resistivity of the rubber material used in the conductive sponge roll is generally adjusted by adjusting the amount of carbon black, which is the conductivity imparting agent. However, in the volume resistivity range of 10 ³ to ^{10 9} Ωcm, for example, various conditions such as foaming conditions, foam cell diameter, foaming uniformity, and the amount of conductivity imparting agent such as carbon black may be slightly changed. However, the resistance value changes greatly. Since this is a very unstable region, it is difficult to set the resistance value and obtain a stable product. Therefore, to supplement this, conductive powder is baked on a synthetic rubber sponge rubber molded body, and conductive sponge rolls coated with conductive paint and baked are also used, but the amount of baking Not only does the conductivity become unstable due to variations in the coating amount, but also the manufacturing process becomes complicated, resulting in high costs. In addition, since the sponge rubber that is the base of the conductive sponge roll is a synthetic rubber such as so-called CR or urethane, its physical properties change greatly depending on the environment, and in particular, its strain characteristics against compression are very poor. Therefore, research has been conducted on conductive silicone rubber sponge rolls that have small changes in physical properties due to the environment and particularly excellent strain characteristics against compression. However, it is difficult to obtain a product with stable physical properties, resulting in large variations in volume resistivity. Therefore, the problem of the present invention is to reduce the volume resistivity 10 ³
It is easy to set the resistance value within the range of ~ ¹⁰⁹ Ωcm,
An object of the present invention is to provide a physically stable composition for a conductive sponge roll that has a highly stable resistance value and a uniform cell diameter, and a method for producing a conductive sponge roll using the composition. . [Means for Solving the Problems] In order to solve the above problems, the present inventors conducted extensive research and found that 100 parts by weight of vinyl group-containing organopolysiloxane, 0.1 to 20 parts by weight of organohydrodiene polysiloxane, carbon black 3
A composition containing ~50 parts by weight, 0.5 to 10 parts by weight of a blowing agent, and a catalytic amount of a platinum catalyst is formed into a uniform layer on the surface of a core metal, and heated to a temperature of 150 to 400°C. It has been found that by foaming with sulfur, it is possible to obtain a conductive sponge roll with uniform cell diameter and very stable conductivity. The present invention will be specifically explained below. The vinyl group-containing organopolysiloxane used in the present invention has the general formula:

[Formula] (where R is a methyl group, an ethyl group, a vinyl group,
The same or different one selected from phenyl groups
Examples include compounds represented by a valent hydrocarbon group (l is an integer from 100 to 10,000). This organopolysiloxane preferably has a vinyl group content of, for example, about 0.05 to 3.0 mol%. Further, the organohydrodiene polysiloxane used in the present invention has the general formula:

[Formula] (where R is a group selected from a hydrogen group, a methyl group, an ethyl group, and a phenyl group, and m is an integer from 10 to 1000), which have at least two molecules in the molecule. It has a hydrogen atom bonded to an elementary atom. Typical blowing agents used in the present invention are 2,2'-azobisisobutyronitrile (hereinafter abbreviated as AIBN) and azodicarbonamide (hereinafter abbreviated as ADCA), for purposes of illustration only and not limitation. However, other commonly known blowing agents may also be used. Platinum-based catalysts used in the present invention include commonly used platinum chloride, chloroplatinic acid, reaction products of chloroplatinic acid and monohydric alcohols, complexes of chloroplatinic acid and olefins, and complexes of chloroplatinic acid and vinyl siloxane. Includes complexes, etc. Representative examples of the carbon black as the conductivity imparting agent used in the present invention include acetylene black, ketone black, and furnace black. The composition of the present invention includes, per 100 parts by weight of the vinyl group-containing organopolysiloxane, 0.1 to 20 parts by weight of organohydrodiene polysiloxane, 3 to 50 parts by weight of carbon black, and 0.5 parts by weight of a blowing agent.
It contains ~10 parts by weight of a platinum-based catalyst in a catalytic amount. In the composition, if the amount of organohydrodiene polysiloxane added is less than 0.1 part by weight, it will be difficult to cure and it will be difficult to obtain the desired rubber physical properties.
If the amount exceeds 1 part by weight, the rubber strength will decrease due to overcure, which is not preferable. Furthermore, the above range ratio of organopolysiloxane and organohydrodienepolysiloxane is such that the hydrogen group concentration (H) in the organohydrogenpolysiloxane is H/V=1.0 to the vinyl group concentration (V) contained in the organopolysiloxane. It is preferable to set it to be in the 8.0 range. If this H/V is smaller than 1.0, it will be difficult to heat cure and obtain the desired rubber physical properties.
If it exceeds 8.0, overcuring occurs and the rubber strength tends to decrease, which is not preferable. Furthermore, if the amount of carbon black added is less than 3 parts by weight, the rubber will not have electrical conductivity, and if it exceeds 50 parts by weight, the physical properties of the rubber will deteriorate significantly. Further, if the amount of the foaming agent added is less than 0.5 parts by weight, foaming will not occur, and if it exceeds 10 parts by weight, abnormal foaming will occur and a foam having a uniform cell diameter will not be obtained. The platinum-based catalyst is usually used in a known catalytically effective amount, e.g. 0.01 to 0.5 based on the total amount of polysiloxane.
Weight percent range amounts are preferably used, but can vary somewhat depending on foam curing temperature and time. In addition to the composition of the present invention, other additives may be mixed and used to the extent that the desired physical properties of the present invention are not impaired. In particular, it is effective to add reinforcing fillers to improve the strength of foam-molded conductive sponge rolls. Such reinforcing fillers include dry silica, wet silica,
This includes diatomaceous earth and those treated with hydrophobic treatment. The amount added is preferably 10 to 120 parts by weight per 100 parts by weight of the vinyl group-containing organopolysiloxane. If the amount is less than 10 parts by weight, the strength of the resulting conductive sponge roll cannot be sufficiently improved, and if it is more than 120 parts by weight, the elasticity of the conductive sponge roll is likely to be lost, which is disadvantageous. In some cases, the vulcanization rate may be adjusted by using an addition reaction rate retardant, such as an organic nitrogen compound, an alkyne compound, or a tin compound, or by using a non-acyl organic peracid. It may be used in combination to further improve compression set characteristics. In the present invention, by selecting the amount of carbon black added (3 to 50 parts by weight), the amount of blowing agent added (0.5 to 10 parts by weight), and the temperature and time of heat treatment, the volume resistivity can be adjusted to 10 ³ to 10. Conductive sponge rolls can be prepared with a desired volume resistivity in the range of 10 ⁹ Ωcm. To obtain a conductive sponge roll with a small volume resistivity, the amount of carbon black added is relatively large; conversely, to obtain a conductive sponge roll with a large volume resistivity, a small amount of carbon black is added. In manufacturing the conductive sponge roll of the present invention, the foaming ratio is preferably between 1.2 times and 10 times. If it is smaller than 1.2 times, it cannot be called a foam.
Moreover, if it exceeds 10 times, the elastic strength of the rubber material decreases significantly and the conductivity tends to exceed 10 ⁹ Ωcm. The above-mentioned method for adjusting the foaming ratio is carried out by adjusting the amount of the foaming agent added, as is conventionally known. In other words, increasing the amount added increases the foaming ratio and decreasing it lowers the foaming ratio, or using a mold and forcibly controlling the foaming ratio by adjusting the dimensions of the mold, or A method may be used in which the heating temperature during vulcanization is adjusted, that is, foaming and vulcanization at a low temperature lowers the expansion ratio, while foaming and vulcanization at a relatively high temperature increases the expansion ratio. Heating temperature is usually 150
~400°C is preferred. In the present invention, the volume resistivity can be easily set to a specific value within the range of 10 ³ to ^{10 9} Ωcm by combining the amount of carbon black added and the expansion ratio. A conductive sponge roll with little variation in resistance value can be obtained. The conductive sponge roll of the present invention is manufactured by continuously extruding the composition together with a core metal using an extruder equipped with a cross-head die, and applying unfoamed, unvulcanized silicone of uniform thickness onto the core metal. After forming a rubber layer, this is heated, foamed, and vulcanized. The above-mentioned core bar may be subjected to a primer treatment in advance as known prior to extrusion molding of silicone rubber, and heating means include a hot air drying oven, infrared, far infrared, vulcanizing oven, etc. A UHF wave vulcanization furnace, etc. is used. [Example] Example 1 Organohydrodiene polysiloxane (trade name, C-
153A) 3 parts by weight, platinum catalyst (Cat-PL-2)
A foaming agent AIBN is added to a conductive silicone rubber composition containing 0.5 parts by weight and 10 parts by weight of carbon black (product name: Ketchien Black EC manufactured by Lion Corporation).
After mixing and kneading, the mixture was divided into sheets with a thickness of 2 mm. This was heated in a hot air drying oven at 250℃ for 10 minutes.
After foaming and vulcanization, it was heated again in a drying oven at 200℃ for 4 hours.
Processed after hours. Amount of the above blowing agent added (parts by weight)
Sheets were produced in the same manner for various compositions with different values, heated and foamed, and various physical properties were measured. As a result, the foaming ratio changed depending on the amount added, and the volume resistivity also changed accordingly, but each sponge had a uniform cell diameter and its resistance value had little variation. The results are summarized in Table 1 below (all amounts added are parts by weight). Example 2 Same formulation as Example 1, but with the added amount of blowing agent AIBN 5
When the foaming ratio was adjusted by changing the heating conditions while fixing the parts by weight, the measured values shown in Table 2 below were obtained. Example 3 When 1 part by weight of the organic peroxide dicumyl peroxide was added to the formulation of Example 2 and the physical properties were compared, various physical properties were improved, particularly compression set characteristics. The results are shown in Table 3 below. Example 4 Organohydrodiene polysiloxane (trade name, C-
153A) 2.5 parts by weight, platinum catalyst (Cat-PL-
2) 0.05 part by weight, carbon black (Lion Corporation)
A foaming agent is added to a conductive silicone rubber composition containing 6 parts by weight of KETSUTIEN BLACK EC.
Using an extruder, a mixture with varying amounts of AIBN was extruded together with a stainless steel core (φ10 mm x 300 ^L mm) that had been primed in advance to form a rubber outer diameter of φ15 mm, and then dried with hot air. It was heated in a furnace at 250°C for 30 minutes to cause foaming and vulcanization. Next, this was put into the drying oven again and heat-treated at a temperature of 200° C. for 4 hours. After measuring the foaming ratio of the obtained conductive sponge roll, it was ground using a cylindrical grinder to an outer diameter of 16 mm, and cut to a length of 260 mm. Place this conductive sponge roll on a metal plate, apply a load of 100g to both core plates, and measure the resistance between the core metal plate and the metal plate while pressing the conductive sponge roll against the metal plate. did. The results are shown in Table 4 below. From Table 4, it can be seen that as the expansion ratio changes, the resistance value as a conductive sponge roll product changes easily, and a conductive sponge roll with a uniform cell diameter can be obtained.

【table】

【table】

【table】

【table】

【table】

[Table] [Effects of the Invention] Since the conductive sponge roll manufactured using the composition of the present invention is a foam roll having a uniform cell diameter, a stable product can be obtained with a hard rubber conductive roll. Volume resistivity 10 ³ to 10 ⁹
A conductive sponge roll having stable conductivity in the Ωcm range can be easily obtained. Furthermore, compared to the conventional method of imparting conductivity in a post-processing process after molding the sponge, it can be obtained at a lower cost. Furthermore, the conductive sponge roll of the present invention is a conductive sponge roll characterized in that its conductivity is controlled by adjusting its foaming ratio, and the amount of carbon black, which is a conventionally known conductivity imparting agent, is added. By adjusting the , it is possible to obtain a product with stable conductivity in the volume resistivity range of 10 ³ to ^{10 9} Ωcm compared to the method of controlling conductivity. In addition, since the conductive sponge roll of the present invention is based on silicone rubber, it is less susceptible to changes due to the environment, and has particularly good strain characteristics against compression.

Claims (1)

[Scope of Claims] 1 100 parts by weight of vinyl group-containing organopolysiloxane, organohydrodiene polysiloxane
0.1 to 20 parts by weight, 3 to 50 parts by weight of carbon black,
1. A composition for a conductive sponge roll, comprising 0.5 to 10 parts by weight of a blowing agent and a catalytic amount of a platinum catalyst. 2. A method for producing a conductive sponge roll, which comprises uniformly forming a layer of the composition according to claim 1 on the surface of a core metal, and heating the composition to a temperature of 150 to 400°C to vulcanize and foam the composition. 3. The method for manufacturing a conductive sponge roll according to claim 2, wherein the volume resistivity is controlled by adjusting the amount of carbon black added and the expansion ratio.