JPH0588657B2 - - Google Patents

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a method for manufacturing a white rubber roll, and in particular, by forming a white conductive silicone rubber layer on the surface of the roll, it is easy to read characters and symbols from a document. The present invention relates to a method for manufacturing a white rubber roll useful as a facsimile reading roll.

(Prior art) Conventionally, heat-resistant materials such as acrylic rubber, butyl rubber, and nitrile rubber have been used for paper feed rolls in various copying machines and communication equipment because of their excellent compression set, temperature dependence, weather resistance, and heat resistance. Rubber rolls, particularly silicone rubber rolls, are widely used.

However, in the following, we will mainly explain the silicone rubber roll.This silicone rubber roll is a black roll that has antistatic properties using carbon black as a conductive agent to prevent paper from wrapping around due to static electricity and adhering to paper dust. However, when used as a facsimile reading roll, for example, it had the disadvantage that the characters and symbols on the original document were difficult to read.

Therefore, for this type of rubber roll, we are considering using a white conductive rubber roll in which a white pigment such as titanium oxide is added to a white or transparent metal oxide such as tin oxide or zinc oxide as a conductivity imparting agent. However, these white metal oxides and white pigments are two to three times more expensive than carbon black, so if the entire rubber roll was made of conductive white, the roll would be extremely expensive. The disadvantage is that it becomes uneconomical. Therefore, the present inventors developed a two-layer structure consisting of a black conductive silicone rubber layer using conventionally known carbon black and a white conductive silicone rubber layer using the above-mentioned metal oxide and white pigment. We focused on the fact that it would be possible to obtain an inexpensive rubber roll by doing this, and considered making this white conductive silicone rubber layer by press molding. A predetermined amount of black conductive rubber containing uncured carbon black is placed or wrapped around a metal shaft made of aluminum, stainless steel, brass, phosphor bronze, chrome-plated iron, etc., and cured by heating and pressure. Then, the mold is removed from the cooled half-split mold, the parting line that occurs at the boundary between the half-split molds is removed (deburred), and then polished to a perfect circle (e.g. 30mm±
20μm), and then in another half mold,
Since white conductive silicone rubber had to be provided and deburring and polishing had to be performed again, the process was complicated, there was a lot of loss, and the raw material yield was poor.

(Structure of the Invention) The present invention relates to a method for manufacturing a white rubber roll that solves the above disadvantages, and includes providing a carbon-containing black conductive rubber layer on the shaft, and then coating the surface with tin oxide and/or zinc oxide. It is also characterized by being coated with a titanium oxide-containing white conductive silicone rubber layer by extrusion molding.

That is, as a result of various studies on methods for whitening the surface of a rubber roll using a black rubber layer, the present inventors found that a black rubber roll formed using black conductive rubber using carbon black made by a conventionally known method. If the surface is coated with a white conductive silicone rubber layer using tin oxide and/or zinc oxide as a conductivity imparting agent and titanium oxide as a white pigment, the desired surface will be a white conductive silicone rubber layer. The white conductive silicone rubber layer can be easily and efficiently prepared from a silicone rubber compound containing tin oxide and zinc oxide as conductivity-imparting agents and titanium oxide as a white pigment. Since extrusion molding can be performed with good dimensional accuracy and almost no loss, we discovered that if a black rubber roll is coated with a white conductive silicone rubber layer by extrusion molding, there will be no problem in economic efficiency. A method for coating a black conductive rubber layer with white conductive silicone rubber used in
The present invention was completed through research on adhesion.

As described above, the production of a white rubber roll by the method of the present invention involves coating the black conductive rubber layer of a black rubber roll using black conductive rubber with a white conductive silicone rubber layer by extrusion molding. The black rubber roll using conductive rubber may be made by a conventionally known method or the polishing method described above.

That is, this black rubber roll is made by applying a primer to the surface of a metal shaft, and then adding 100 parts by weight of a commercially available silicone raw rubber whose main material is dimethylmethylvinylpolysiloxane to 5 to 5 parts of carbon black, especially acetylene black or butcher black. 100 parts by weight and dicumyl peroxide, 2,5-bis(t-butylperoxy) 2,
A silicone rubber compound obtained by adding 0.5 to 3.0 parts by weight of an organic peroxide-based vulcanizing agent such as 5-dimethylhexane and mixing uniformly is heated at 170°C to
The silicone rubber molded body may be made by press molding or the like under conditions of 180×15 to 50 kg/cm ² and then polished using a polishing machine or the like.

In manufacturing a white rubber roll by the method of the present invention, the roll surface of the black rubber roll thus produced is coated with white conductive silicone rubber by extrusion molding. 100 parts by weight of silicone raw rubber based on dimethylmethylvinylpolysiloxane, which is the same as that used in making the black roll, and 50 to 200 parts by weight of tin oxide and/or zinc oxide as a white conductive agent. and 20 to 200 parts by weight of titanium oxide powder as a white pigment,
and organic peroxide-based vulcanizing agent for extrusion vulcanization 0.8
A silicone rubber compound obtained by adding ~3.0 parts by weight and mixing uniformly may be used. However, regarding this organic peroxide, benzoyl peroxide, which is known for extrusion molding,
When 2,4-dichlorobenzoyl peroxide is used, in this case, the interface between the surface of the black conductive rubber roll containing carbon black and this white conductive silicone rubber layer becomes uncured.
Although there is a risk that foaming may occur and the adhesion may be incomplete, it is even better to use 2-chlorobenzoyl peroxide because this disadvantage can be overcome.

The extrusion coating of the white conductive silicone rubber on the surface of the black conductive rubber roll is carried out by continuously or intermittently feeding the black conductive rubber roll made by the method described above from the crosshead die of the extruder at a desired speed. The outer peripheral surface of this black conductive rubber roll was coated with the uncured white conductive silicone rubber described above by extrusion molding at 250 to 400°C for 20 to 180 seconds, and then this white conductive silicone rubber layer was coated at 150°C. It may be cured by heating at ~250°C for 1 to 20 hours, and by this method, a rubber roll with a white surface can be easily and reliably obtained. In this case, the thickness of the incandescent conductive silicone rubber layer must be at least 0.3 mm since the entire white roll of the present invention is white, but if it is too thick, Since it is economically disadvantageous, it may be within the range of 0.3 to 2.0 mm.

Further, when the white conductive silicone rubber layer and the black rubber roll are both made of silicone rubber, the white conductive silicone rubber layer and the black rubber roll can be bonded by reaction by heating for curing the white conductive silicone rubber layer as described above.

Furthermore, when this black conductive rubber roll is made of silicone rubber and a stronger adhesion is required, the above-mentioned addition reaction type organosiloxane composition (CH ₃ ) ₃ is used as the adhesive.
Siloxane-based rubber with the addition of so-called MQ siloxane, consisting of _0.5 units of SiO, (CH ₃ ) ₂ (CH ₂ =CH) _0.5 units of SiO and ₂ units of SiO, as well as tin oxide or zinc oxide and oxidation as a white pigment. A material to which titanium is added may be extruded and used.

This adhesive can be used by brushing it onto a black rubber roll or using a roll coater to coat it to a thickness of 5.
The roll may be coated to a thickness of ~30 μm, but the roll may be immersed in an adhesive solution, and the adhesive may be diluted with xylene, toluene, low molecular weight cyclic siloxane, etc. to adjust the viscosity as necessary. May be used. Note that this adhesive exhibits its adhesive effect by curing through an addition reaction, so after coating the adhesive surface with a white conductive silicone rubber layer by extrusion molding, the adhesive is heated to, for example, 60 to 250°C. It is preferable to cure the adhesive layer, thereby ensuring that the white conductive silicone rubber layer is firmly adhered to the black rubber roll to obtain the desired white roll. In the above description, the black rubber roll is made of silicone rubber, but there is no problem in using conventionally known heat-resistant rubber such as acrylic rubber or butyl rubber.

Next, examples of the present invention will be given, in which parts are parts by weight and viscosity is a value measured at 25°C.

Example 1 Stainless steel with a diameter of 10 mm and a length of 400 mm.
Primer No. 4 [trade name manufactured by Shin-Etsu Chemical Co., Ltd.] diluted to 10% with toluene was applied with a brush to the surface of the SUS304 shaft, and after air-drying for 30 minutes,
Baking treatment was carried out at ℃ for 5 minutes.

Next, on the surface of this shaft, 100 parts of methyl vinyl polysiloxane with a viscosity of 1,000,000 cS containing 0.3 mol% of vinyl siloxane units, 25 parts of acetylene black and 2,5-bis(t-butylperoxy) were added.
A silicone rubber compound obtained by adding 1.2 parts of 2,5-dimethylhexane and mixing uniformly was press-molded to an outer diameter of 32 mm, and polished using a polishing machine to obtain an outer diameter of 30 mmφ x length. length 360mm
A black conductive rubber roll was made.

Next, this black rubber roll is intermittently sent out from the crosshead die of the extruder at a speed of 200 cm/min.
On the surface of this roll, 100 parts of the methyl vinyl polysiloxane with a viscosity of 1,000,000 cS containing 0.3 moles of the vinyl siloxane unit used above was mixed with 200 parts of titanium oxide W-300 [trade name manufactured by Ishihara Sangyo Co., Ltd.] as a white conductivity imparting agent. 1.0 parts of 2-monochlorobenzoyl peroxide and 1.0 parts of 2-monochlorobenzoyl peroxide were added and mixed uniformly to obtain a silicone rubber compound, which was coated and extruded to a thickness of 0.8 mm.
When cured by heating for a period of time, a white rubber roll whose surface was coated with white conductive silicone rubber was obtained, and the resistance between the center of the roll and the shaft was 5×10 ⁶ Ω. This completed white rubber roll was installed as a reading roll in the fax machine Panafax UF-1000 manufactured by Matsushita Densen Co., Ltd., and when tested, it read 100,000 sheets (A4 size equivalent).
However, no reading errors occurred.

Claims (1)

[Scope of Claims] 1. A carbon-containing black conductive rubber layer is provided on the shaft, and then a white conductive silicone rubber layer containing tin oxide and/or zinc oxide and titanium oxide is coated on the surface by extrusion molding. A method for producing a white rubber roll, characterized by: 2 The white conductive silicone rubber layer has a thickness of 0.3 to 2.0
The method for manufacturing a white rubber roll according to claim 1, wherein the roll is made of a white rubber roll of mm.