JPH10268628A - Electrically conductive foamed polyurethane roll - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an electrically conductive foamed polyurethane roll made of a molded body of foamed polyurethane with no special electrically conductive layer on the surface and having lower hardness than the conventional hardness as well as controlled uniform electric conductivity. SOLUTION: This electrically conductive foamed polyurethane roll consists of a shaft 10a and a columnar roll body 10b formed around the shaft 10a. The roll body 10b is a molded body of foamed polyurethane obtd. using polyoxypropylene and a polyisocyanate mixture of toluene diisocyanate with hexamethylene diisocyanate and/or polymeric diphenylmethane diisocyanate as principal starting materials and provided with electric conductivity by carbon black. The molded body has 10-80 deg. ASKER hardness F and 10<4> -10<9> Ωcm volume resistivity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive roll used for office equipment such as a copying machine, a printer, a facsimile and the like utilizing electrophotography, and more particularly to a foamed conductive roll made of polyurethane foam.

[0002]

2. Description of the Related Art In a copying machine or the like utilizing an electrophotographic method, as shown in FIG. 2, a photosensitive drum 1 uniformly charged by a charging roll 2 is exposed to form an electrostatic latent image, and a toner box is formed. The toner 4 having the opposite charge supplied from the toner transport roll 5 to the photosensitive drum 1 is supplied by the developing roll 6.
To develop the toner image.

On the other hand, the paper 8 is supplied to the photosensitive drum 1 by a paper feed roll (not shown), and after the toner image on the photosensitive drum 1 is transferred to the paper 8 by the transfer roll 7, a fixing roll provided with a heating element is provided. (Not shown) to fix the image on the paper 8. Incidentally, reference numeral 9 in FIG. 2 denotes a cleaning unit for removing the toner 4 remaining on the photosensitive drum 1.

[0004] Various conductive rolls used in such an apparatus utilizing electrophotography are required to have even lower hardness in order to respond to the high speed of the apparatus and the improvement of image quality. Specifically, the toner transport roll has an Asker hardness F of 10 °.
At about to 40 °, the volume resistivity is about 10 ⁵ [Omega] cm, the transfer roll is about Asker hardness F is 40 ° to 80 °, it is desired volume resistivity of about 10 ⁸ [Omega] cm.

Therefore, as a method for reducing the hardness of the conductive roll, a roll made of a polyurethane foam has been proposed. Such a foamed polyurethane roll is prepared by adding carbon black for imparting conductivity to the polyol, further adding a foaming agent, a catalyst, and the like to form a premix polyol, and then mixing the premix polyol with a polyisocyanate. It is manufactured by injecting into a mold and solidifying and molding at the same time as foaming.

Japanese Patent Application Laid-Open No. Hei 5-188774 discloses an example of a conductive roll made of such foamed polyurethane, which is mainly composed of a polyol and a polyisocyanate, has an Asker hardness C of 10 ° to 70 °, and a volume resistance of 10 ^5. ~
There is disclosed a developing roll formed by coating a surface of a 10 ⁸ Ωcm polyurethane foam with a conductive paint having triboelectricity-imparting performance. However, even with such a conventional foamed polyurethane roll, it has been difficult to obtain a satisfactory level of low hardness.

[0007] In addition, carbon black is usually mixed to impart conductivity, but it is difficult to control the volume resistance of the foamed polyurethane roll. That is, since it is difficult to control the dispersibility of carbon black, there is a drawback that the volume resistance of the roll tends to fluctuate greatly. When the amount of carbon black is increased, the above-mentioned JP-A-5-188 is used.
As described in Japanese Patent No. 774, the viscosity is remarkably increased so that it cannot be injected into a molding die, foaming becomes difficult, and the hardness of the obtained foamed polyurethane roll becomes high. There was a disadvantage.

[0008]

As described above, it has been extremely difficult for a conductive roll made of foamed polyurethane to impart controlled conductivity by adding carbon black and at the same time reduce its hardness. . For this reason, the developing roll described in JP-A-5-188774 is also coated with a conductive paint on the roll surface of the foamed polyurethane in order to satisfy the conflicting requirements of lowering the hardness of the roll and imparting conductivity. is there.

The present invention has been made in view of such conventional circumstances,
A foamed conductive polyurethane roll consisting of a foamed polyurethane molded body that does not have a special conductive layer on the roll surface, has controlled and uniform conductivity, and has a lower hardness than before and is suitable for speeding up and improving image quality In particular, an object of the present invention is to provide a toner transport roll or a transfer roll used for a copying machine, a printer, a facsimile, and the like.

[0010]

In order to achieve the above object, a foamed conductive polyurethane roll provided by the present invention comprises a shaft and a cylindrical roll body provided around the shaft. The main body is a polyoxypropylene and a polyisocyanate obtained by mixing hexamethylene diisocyanate and / or polymeric diphenylmethane diisocyanate with toluene diisocyanate as a main raw material, and a molded article of foamed polyurethane provided with conductivity by carbon black, Asker hardness F of 10 ° to 80 ° and volume resistance of 10 ⁴ to
It is characterized by being 10 ⁹ Ωcm.

The foamed conductive polyurethane roll according to the present invention has a foamed polyurethane constituting the roll body having a density of 0.05 to 0.20 g / cm ³ and a compression set of 20% or less. Features. The compression set is a value measured according to JIS K6301 under the conditions of 50 ° C. × 50% compression × 72 hr.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS As shown in FIG. 1, a foamed conductive polyurethane roll 10 of the present invention has a cylindrical roll body 10b provided around a shaft 10a made of a metal rod. 10b is made of only a foamed polyurethane molded article having conductivity, and its surface is not provided with any special conductive layer or conductive coating for imparting conductivity.

The roll body made of the foamed polyurethane molded article has an Asker hardness F of 10 ° to 80 °, a volume resistance (or volume resistivity) of 10 ⁴ to 10 ⁹ Ωcm, and can be easily controlled. It has extremely low hardness and at the same time has necessary conductivity. Therefore, the foamed conductive polyurethane roll of the present invention has an Asker hardness of F10 ° to 4 °.
0 ° and a volume resistance of 10 ⁴ to 10 ⁶ Ωcm are required for the toner transporting roll.
It is particularly useful as a transfer roll requiring a degree and a volume resistance of 10 ⁷ to 10 ⁹ Ωcm.

If the Asker hardness F of the polyurethane foam constituting the roll body is less than 10 °, it is too soft to withstand use, and if it exceeds 80 °, the photosensitive drum may be damaged,
It is not preferable because it becomes difficult to meet the demand for higher speed and higher image quality. In order to obtain hardness in this range,
The density of the foamed polyurethane is 0.05 to 0.20 g / cm ³
It is preferred that Further, the foamed polyurethane preferably has a compression set of 20% or less in order to ensure the durability as a roll body and the required dimensional accuracy.

The foamed conductive polyurethane roll of the present invention maintains a required volume uniformity in the range of 10 ⁴ to 10 ⁹ Ωcm and at the same time has an extremely low Asker hardness F of 10 ° to 80 ° as described above. By properly selecting the polyol and polyisocyanate, which are the main raw materials of the foamed polyurethane, it is possible to reduce the amount of carbon black required for imparting conductivity and prevent uniform dispersion and sedimentation of the carbon black. Because it became possible. As a result, the moldability was improved by lowering the viscosity of the premix polyol, and the hardness of the foamed polyurethane molded article was significantly reduced by high foaming, and the conductivity could be easily controlled.

That is, in the present invention, the polyol which is one of the main raw materials of the foamed polyurethane has a molecular weight of 30.
A polyoxypropylene having a number of functional groups of 2.5 to 3.5 and a primary alcohol group concentration of 60 to 70% at the terminal is used. Can be reduced. Polyoxypropylene of such quality is commercially available, for example, as EP550N from Mitsui Toatsu Chemicals, Inc. and as HF445 from Daiichi Kogyo Seiyaku.

As the polyisocyanate which reacts with the premix polyol to form a polyurethane, a mixture of toluene diisocyanate, hexamethylene diisocyanate and / or polymeric diphenylmethane diisocyanate is used. By mixing hexamethylene diisocyanate and / or polymeric diphenylmethane diisocyanate with toluene diisocyanate, the dispersibility of carbon black can be improved and its sedimentation can be prevented. As a result, the volume resistance of the foamed polyurethane can be easily increased by the blend ratio of polyisocyanate. , It is possible to uniformly impart desired conductivity to the entire roll.

The mixing ratio of each polyisocyanate is preferably not more than 25 equivalents of hexamethylene diisocyanate and / or polymeric diphenylmethane diisocyanate in equivalent ratio to toluene diisocyanate. If the amount of toluene diisocyanate is less than 75 equivalents, it is difficult to control the volume resistance of the obtained foamed polyurethane, and it is likely to exceed 10 ⁹ Ωcm. The equivalent ratio of the polyisocyanate to the premix polyol is preferably in the range of 100/100 to 100/120 for the premix polyol / polyisocyanate.

The toluene diisocyanate includes 2,4-
TDI-80 / 20 or TD due to the difference in the blending of toluene diisocyanate and 2,6-toluene diisocyanate
There are various types such as I-65 / 35, but in particular, when obtaining a foamed polyurethane having a low hardness, it is preferable to use TDI-100 containing 100% 2,4-toluene diisocyanate.

The method of producing the foamed polyurethane molded article itself is the same as in the prior art. Specifically, first, a polyoxypropylene polyol is added to carbon black as a conductivity-imparting agent.
A foaming agent, a foam stabilizer, a curing catalyst, and other auxiliaries are added and mixed to obtain a premix polyol. Next, a mixture of toluene diisocyanate, hexamethylene diisocyanate and / or polymeric diphenylmethane diisocyanate is added and mixed as a polyisocyanate to the premix polyol, and the mixture is injected into a mold and foamed and cured.

The carbon black as a conductivity-imparting agent has a particle size of 20 to 50 nm and a DBP oil absorption of 100 to 5
Conductive carbon black in the range of 00 ml / 100 g is preferred. Specifically, Ketjen Black EC (particle size: 31 nm, DBP oil absorption: 350 ml / 100 g) manufactured by Ketjen Black International Co., Ltd., and acetylene black (particle size: 45 n) manufactured by Denki Kagaku Kogyo KK
m, DBP oil absorption 165 ml / 100 g). Further, the content of carbon black in the foamed polyurethane is preferably 0.5 to 3.0% by weight. Thus, a required volume resistance can be obtained even with a smaller amount of carbon black than in the conventional case.

As other various additives, conventionally known additives can be used. For example, as a curing catalyst, various tertiary amines such as triethylamine and triethylenediamine are used.
Secondary amines and the like can be used. The addition amount of the tertiary amine is 0.1 to 1.0 with respect to 100 parts by weight of the polyol.
0 parts by weight is preferred. As the foam stabilizer, a silicone oil or a surfactant can be used. In the present invention, it is preferable to use water as a foaming agent. The amount of water added as a blowing agent is 1.
0 to 2.5 parts by weight is preferred.

[0023]

Example 1 Polyoxypropylene HF445 manufactured by Daiichi Kogyo Seiyaku Co., Ltd. was used as a polyol, and TDI-100 and hexamethylene diisocyanate (HDI) or polymeric diphenylmethane diisocyanate (MDI-CR) were used as polyisocyanates. ) And
A foamed conductive polyurethane roll was produced as described below. HF445, which is polyoxypropylene, has a molecular weight of 3,700, a number of functional groups of 3.0, and a terminal primary alcohol group concentration of 60%.

1.6 parts by weight of Ketjen Black EC manufactured by Ketjen Black International Co., Ltd. as carbon black (1.3% by weight as a content in the final product) based on 100 parts by weight of the above polyoxypropylene. 1.8 parts by weight of water as a foaming agent, 0.2 parts by weight of a surfactant L5366 manufactured by Nippon Unicar Co., Ltd. as a foam stabilizer, and 0.2 parts by weight of triethylenediamine manufactured by Kao Corporation as a curing catalyst. And then mixed to obtain a premix polyol. The viscosity at room temperature of each of the obtained premix polyols was 5,100 cp, and was excellent in moldability.

Next, as a polyisocyanate, 2,4
-TDI consisting of 100% toluene diisocyanate-
To 100, HDI or MDI-CR was mixed at the equivalent ratio shown in Table 1 below. Each of the obtained polyisocyanate mixtures was added to and mixed with the above-mentioned premix polyol so that the equivalent ratio of the premix polyol / polyisocyanate mixture became 100/110. Was foam-cured by heating in an oven for 30 minutes. Thereafter, the mold was released to obtain a foamed conductive polyurethane roll.

[0026]

[Table 1] (Note) Samples marked with * in the table are comparative examples.

With respect to each of the obtained foamed polyurethane rolls, the density, Asker hardness F, volume resistance, and compression set of the foamed polyurethane molded article constituting the roll body were measured. The results are shown in Table 2 below. The volume resistance is D
C500V, compression set: 50 ° C x 50% compression x 7
This is a value measured under the condition of 2 hours.

[0028]

[Table 2] (Note) Samples marked with * in the table are comparative examples.

As can be seen from the above results, the foamed conductive polyurethane roll of each sample of the present invention has an Asker hardness F of 10 ° to 80 ° and a volume resistance of 10 ⁴ to 10 ⁹ Ω.
cm, and uniform conductivity could be stably obtained. However, each sample of the comparative example had a volume resistance exceeding 10 ⁹ Ωcm even with the same carbon black content, and it was found that the sample was unsuitable as a conductive roll.

[0030]

According to the present invention, since the dispersibility of carbon black as a conductivity-imparting agent is improved, a desired conductivity can be obtained with a small amount of carbon black, and the conductivity of polyisocyanate can be improved. It can be easily controlled by the blending ratio, and at the same time, a premix polyol with low viscosity and excellent moldability can be obtained. Can be obtained.

Therefore, even if a special conductive layer is not formed on the roll surface, the volume resistance is within a predetermined range and is uniform.
A foamed conductive polyurethane roll having a much lower hardness than before can be provided, and this foamed conductive polyurethane roll is particularly suitable as a toner transporting roll or a transfer roll used in a copying machine, a printer, a facsimile, and the like. is there.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing a foamed conductive polyurethane roll of the present invention.

FIG. 2 is an explanatory diagram of a developing method by an electrophotographic method.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photosensitive drum 2 Charging roll 3 Toner box 4 Toner 5 Toner transport roll 6 Developing roll 7 Transfer roll 8 Paper 9 Cleaning part 10 Foamed conductive polyurethane roll 10a Shaft 10b Roll body

Claims (4)

[Claims] 1. A polyisocyanate comprising a shaft and a cylindrical roll main body provided around the shaft, wherein the roll main body is obtained by mixing polyoxypropylene and toluene diisocyanate with hexamethylene diisocyanate and / or polymeric diphenylmethane diisocyanate. And a foamed polyurethane molded body having conductivity given by carbon black, having an Asker hardness F of 10 ° to 80 ° and a volume resistance of 10 ⁴ to 10 ⁹ Ωcm. Characteristic foamed conductive polyurethane roll. 2. The foamed polyurethane has a density of 0.05.
2. The foamed conductive polyurethane roll according to claim 1, wherein the foamed conductive polyurethane roll has a compression set of 20% or less and 0.20 g / cm ³ or less. 3. The foamed polyurethane has a molecular weight of 300.
A polyoxypropylene having 0 to 4000, a functional group number of 2.5 to 3.5, and a terminal primary alcohol group concentration of 60 to 70%;
The foamed conductive polyurethane according to claim 1 or 2, wherein the foamed conductive polyurethane is mainly composed of toluene diisocyanate and a polyisocyanate obtained by mixing hexamethylene diisocyanate and / or polymeric diphenylmethane diisocyanate in an equivalent ratio of 25 equivalents or less. roll. 4. The foamed polyurethane contains carbon black having a particle size of 20 to 50 nm and a DBP oil absorption of 1.
The foamed conductive polyurethane roll according to any one of claims 1 to 3, wherein the content of the foamed polyurethane is 0.5 to 3.0% by weight. .