JPH10268627A - Foamed conductive polyuretane roll - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a foamed conductive polyurethane roll that is constituted of only a foamed polyurethane molding body having no special conductive layer on the surface of the roll, that has uniform volume resistance and has a hardness lower than the conventional one. SOLUTION: This foamed conductive polyurethane roll is constituted of a shaft 10a made of a metal and a columnar roll main body 10b provided around the shaft 10a; and the roll main body 10b is the foaming polyurethane molding body to which conductivity is imparted by carbon block. In such a case, ASKER hardness F is 10 deg. to 80 deg. and the volume resistance is 10<4> to 10<9> Ωcm. Especially, the roll is suitable as a toner carrying roll or a transfer roll.

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.

Further, as described in the above-mentioned Japanese Patent Application Laid-Open No. Hei 5-188774, when carbon black is added to and mixed with a polyol, the viscosity is remarkably increased, so that it cannot be injected into a molding die or foaming occurs. There are drawbacks such as difficulty in dispersing the carbon black, making it difficult to evenly disperse the carbon black, and making it impossible to make the volume resistance of the entire roll uniform. In order to eliminate these disadvantages, it is only necessary to reduce the amount of carbon black to be added, but in that case, there is a problem that it is difficult to obtain the required conductivity.

[0008]

As described above, it has been extremely difficult to reduce the hardness of a conductive roll made of foamed polyurethane while imparting necessary conductivity by adding carbon black. Therefore, the developing roll described in JP-A-5-188774 also includes
In order to satisfy the conflicting requirements of lowering the hardness of the roll and imparting conductivity, the conductive surface of the roll of foamed polyurethane is coated with a conductive paint.

The present invention has been made in view of such conventional circumstances,
A foamed conductive polyurethane roll consisting only of a foamed polyurethane molded article without a special conductive layer on the roll surface, having the necessary and uniform conductivity, and having a lower hardness than conventional and suitable for higher speed and improved 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 molded article of foamed polyurethane provided with conductivity by carbon black, and has an Asker hardness F of 10 ° to 80 ° and a volume resistance of 10 ⁴ to 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 ° and a volume resistance (or volume resistivity) of 10 ⁴ to 10 ⁹ Ωcm, and is extremely low in hardness. At the same time, it has the necessary conductivity. Therefore, the foamed conductive polyurethane roll of the present invention can be used as a toner transporting roll requiring an Asker hardness F of 10 ° to 40 ° and a volume resistance of 10 ⁴ to 10 ⁶ Ωcm.
It is particularly useful as a transfer roll 0 ⁷ to 10 ⁹ [Omega] cm is required.

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,
Since the toner is deteriorated, it becomes difficult to meet the demands for higher speed and higher image quality, which is not preferable. In order to obtain a hardness in this range, the density of the foamed polyurethane is preferably 0.05 to 0.20 g / cm ³ . Further, the foamed polyurethane has a compression set of 20 to ensure the durability as a roll body and the required dimensional accuracy.
% Is preferable.

The foamed conductive polyurethane roll of the present invention maintains the volume resistance of 10 ⁴ to 10 ⁹ Ωcm as the required conductivity and at the same time has the extremely low hardness of 10 to 80 ° as Asker hardness F as described above. What can be achieved is that by appropriately selecting the polyol which is the main raw material of the foamed polyurethane, it is possible to reduce the amount of carbon black for imparting the necessary conductivity, and as a result, the viscosity of the premix polyol can be reduced. This is because the moldability is improved by the decrease and the hardness of the foamed polyurethane molded article is significantly decreased by the high foaming.

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 available, for example, from EP 550N from Mitsui Toatsu Chemicals, Inc., and HF from Daiichi Kogyo Seiyaku.
It is commercially available as 445.

As the polyisocyanate which forms a polyurethane by reacting with the premix polyol, toluene diisocyanate is preferred. Toluene diisocyanate includes 2,4-toluene diisocyanate and 2,6-toluene diisocyanate
TDI-
Although there are various types such as 80/20 and TDI-65 / 35, particularly when a foamed polyurethane of low hardness is obtained,
TDI with 100% 2,4-toluene diisocyanate
The use of 100 is preferred. The equivalent ratio of the polyisocyanate to the premix polyol is such that the ratio of the premix polyol / polyisocyanate is 100/100 to
It is preferably in the range of 100/120.

The method of producing the foamed polyurethane molded article itself is the same as the conventional method. Specifically, first, a polyoxypropylene as a 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, toluene 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 various other 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, organic tin compounds and the like can be used. The addition amount of the tertiary amine is preferably 0.1 to 1.0 part by weight based on 100 parts by weight of the polyol, and the organotin compound is preferably 0.05 to 0.3 part by weight based on 100 parts by weight of the polyol. As the foam stabilizer, a modified 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 foaming agent is preferably 1.0 to 2.5 parts by weight based on 100 parts by weight of the polyol.

[0021]

Example 1 A toner transport roll was produced as follows using polyoxypropylene EP550N manufactured by Mitsui Toatsu Chemicals Co., Ltd. or HF445 manufactured by Daiichi Kogyo Seiyaku Co., Ltd. as a polyol. did. For comparison, EP828 and EP240 manufactured by Mitsui Toatsu Chemicals, Inc., or ND5 manufactured by Daiichi Kogyo Seiyaku Co., Ltd. were prepared in place of the above polyoxypropylene. The molecular weight, number of functional groups, and terminal primary alcohol group concentration of each of these polyoxypropylenes are shown in Table 1 below.

[0022]

[Table 1] Type of sample polyol Molecular weight number of functional groups Alcohol group 1 HF445 3700 3.0 60% 2 EP550N 3100 3.0 70% 3 * ND5 2500 3.0 55% 4 * EP828 6100 3.0 75% 5 * EP240 7100 3.0 77% Samples marked with * are comparative examples.

With respect to 100 parts by weight of each of these polyoxypropylenes, Ketjen Black E manufactured by Ketjen Black International Co., Ltd. was used as carbon black.
1.6 parts by weight of C (1.3% by weight as a content in the final product), 1.8 parts by weight of water as a foaming agent, and 0 parts of a surfactant L5366 manufactured by Nippon Unicar Co., Ltd. as a foam stabilizer. As a curing catalyst, 0.2 part by weight of triethylenediamine manufactured by Kao Corporation was added and mixed to obtain a premix polyol. The viscosity at room temperature of each of the obtained premix polyols is shown in Table 2 below.

Next, to each of the above premix polyols,
As a polyisocyanate, TDI-100 composed of 100% 2,4-toluene diisocyanate is used in an equivalent ratio of premix polyol / TDI-100 of 100/1.
The mixture was added and mixed so as to obtain a mixture of 10, and poured into a mold having a shaft inserted therein. The mixture was heated in an oven at 60 ° C. for 30 minutes to foam and harden. Thereafter, the mold was removed to obtain a toner transport roll.

For each of the obtained toner transport 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 DC50
At 0 V, the compression set is a value measured under the conditions of 50 ° C. × 50% compression × 72 hours (the same applies hereinafter).

[0026]

[Table 2] Plastic Mixor density Density Asker Volume resistance Compression permanent sample viscosity (cp) (g / cm ³ ) Hardness F (Ωcm) Strain (%) 1 5100 0.11 30 ° 2.0 × 10 ⁵ 15 2 4800 0.12 40 ° 1.5 × 10 ⁵ 18 3 * 4100 0.12 87 ° 1.0 × 10 ¹⁰ 23 4 * 6500 0.14 24 ° 1.0 × 10 ¹⁰ 14 5 * 6800 0.13 18 ° 1.0 × 10 ¹⁰ 22 (Note) Samples marked with * in the table are It is a comparative example.

As can be seen from the above results, in each sample of the present invention, characteristics suitable for a toner transport roll having an Asker hardness F of 10 ° to 40 ° and a volume resistance of 10 ⁴ to 10 ⁶ Ωcm were obtained. However, each sample of the comparative example has a volume resistivity exceeding 10 ⁹ Ωcm at the same carbon black content, and it is understood that the sample is unsuitable as a toner transport roll. As can be seen from the viscosity of the premix polyol, Samples 1 to 3 are excellent in moldability.
In Nos. 5 and 5, the injection into the mold was difficult.

Example 2 Using the same polyoxypropylene as in Example 1, EP550N manufactured by Mitsui Toatsu Chemicals Co., Ltd. or HF445 manufactured by Daiichi Kogyo Seiyaku Co., Ltd. Rolls were manufactured. For comparison, as in Example 1, EP828 and EP made by Mitsui Toatsu Chemicals, Inc.
240 and ND5 manufactured by Daiichi Kogyo Seiyaku Co., Ltd. were also prepared. In addition, the molecular weight of each polyoxypropylene, the number of functional groups,
The concentration of the terminal primary alcohol group is as shown in Table 1 above.

With respect to 100 parts by weight of each of these polyoxypropylenes, Ketjen Black E manufactured by Ketjen Black International Co., Ltd. was used as carbon black.
1.8 parts by weight of water as a foaming agent and surfactant as a foam stabilizer as in Example 1, except that 0.9 parts by weight of C (0.7% by weight as a content in the final product) was added. Agent L5366
And 0.2 parts by weight of triethylenediamine as a curing catalyst were added and mixed to obtain a premix polyol. The viscosity at room temperature of each of the obtained premix polyols is shown in Table 3 below.

Next, to each of the above premix polyols,
80% of 2,4-toluene diisocyanate and 20 of 2,6-toluene diisocyanate as polyisocyanates
% Of TDI-80 / 20, the equivalent ratio of premix polyol / TDI-80 / 20 is 100/110.
The mixture was added and mixed so as to obtain the mixture, poured into a mold having a shaft inserted, and heated in an oven at 60 ° C. for 30 minutes to foam and harden. Thereafter, the mold was released to obtain a transfer roll.

For each of the transfer rolls obtained, the density, Asker hardness F, volume resistance, and compression set of the polyurethane molded body constituting the roll body were measured in the same manner as in Example 1, and the results are shown in Table 3 below. Was.

[0032]

[Table 3] Premix polyol Density Asker Volume resistance Compression permanent sample viscosity (cp) (g / cm ³ ) Hardness F (Ωcm) Strain (%) 6 1800 0.16 62 ° 6.0 × 10 ⁸ 15 7 1500 0.19 76 ° 9.0 × 10 ⁷ 18 8 * 4100 0.12 87 ° 1.0 × 10 ¹⁰ 23 9 * 6500 0.14 24 ° 1.0 × 10 ¹⁰ 15 10 * 6800 0.13 18 ° 1.0 × 10 ¹⁰ 22 (Note) Samples marked with * in the table It is a comparative example.

[0033] As can be seen from the above results, in the samples of the present invention, the Asker hardness F is 40 ° to 80 ° and a volume resistivity suitable properties are obtained as a transfer roll 10 ⁷ ~10 ⁹ Ωcm. However, each sample of the comparative example has a volume resistance exceeding 10 ⁹ Ωcm at the same carbon black content, and it is understood that the sample is unsuitable as a transfer roll. In addition, as can be seen from the viscosity of the premix polyol, samples 6 to
Sample 8 was excellent in moldability, but Samples 9 and 10 were difficult to inject into a mold.

[0034]

According to the present invention, even if the amount of carbon black as a conductivity-imparting agent is reduced, a desired conductivity can be obtained, and at the same time, a premix polyol having low viscosity and excellent moldability. Thus, foamed conductive polyurethane rolls having high hardness by molding and having a lower hardness than before 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 molded article of foamed polyurethane provided with conductivity by carbon black, comprising a shaft and a cylindrical roll body provided around the shaft. Is 10 ° -8
A foamed conductive polyurethane roll having 0 ° and a volume resistance of 10 ⁴ to 10 ⁹ Ωcm. 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 roll according to claim 1, wherein the foamed conductive polyurethane roll is mainly composed of toluene diisocyanate. 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. .