JP2002070835A - Electroconductive roll - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electroconductive roll which has low hardness, low settling, and superior moldability. SOLUTION: The electroconductive roll comprises a shaft body 1 and a flexible urethane foam layer 2 formed around the outer surface of the shaft body 1. The flexible urethane foam layer 2 is formed by using urethane raw materials containing ingredients (A) a polyol which contains the component (A1) 50% by weight or more of the whole polyol [wherein, (A1) is a polyol having the number of functional group of 5 comprising a copolymer unit of ethylene oxide group and propylene oxide in molecular structure], (B) Isocyanate and (C) conductant agent, and the flexible urethane foam layer 2 has the following characteristics: (α) Asker hardness is F10 deg. to C50 deg.; (β) electric resistance is 1×103 to 1×109 Ω.cm; and (γ) compression permanent deformation is 2% or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a conductive roll such as a charging roll, a developing roll, a transfer roll, and a toner conveying roll used in an electrophotographic apparatus such as a copying machine, a printer, and a facsimile. The present invention relates to a conductive roll having a single-layer structure in which a soft urethane foam layer is formed on an outer peripheral surface of a shaft body.

[0002]

2. Description of the Related Art Conventionally, in an electrophotographic apparatus such as a copying machine, a printer, a facsimile or the like utilizing an electrophotographic method, an electrostatic latent image is formed on an image carrier made of an electrophotographic photosensitive member or an electrostatic recording dielectric. Is formed, and the electrostatic latent image is developed by a developing device to be visualized as a toner image. For example, as shown in FIG. 4, the photosensitive drum 31 uniformly charged by the charging roll 32 is exposed to form an electrostatic latent image, and the toner having the opposite charge supplied from the toner box 33 by the toner transporting roll 35 is formed. 34 is attached to the photosensitive drum 31 by the developing roll 36 to develop the toner image. On the other hand, the paper 38 is supplied to the photosensitive drum 31 by a paper feed roll (not shown), and the toner image on the photosensitive drum 31 is transferred to the paper 38 by the transfer roll 37, and then heated by the fixing roll 40 having a heating element. Image 38
To be established. In the drawing, reference numeral 39 denotes the photosensitive drum 3
This is a cleaning blade that removes the toner 34 remaining in 1.

The conductive rolls used in such electrophotographic apparatuses, such as charging rolls, developing rolls, transfer rolls, and toner conveying rolls, are required to have even lower hardness in order to respond to high-speed apparatus and improved image quality. Have been. Therefore, in order to reduce the hardness, a conductive roll having a foamed polyurethane layer formed on the outer peripheral surface of a shaft has been proposed. And
The foamed polyurethane layer is formed by injecting a premix polyol obtained by mixing a polyol with a conductive agent such as carbon black and an isocyanate into a mold in which a shaft is set, and foaming and curing the mixture.

[0004]

However, if a large amount of a conductive agent such as carbon black is mixed with the polyol, the viscosity of the premix polyol is significantly increased and the fluidity is reduced. Poor sex. In addition, since the foaming is not performed smoothly, the cells (cells) become non-uniform, the compression set of the foamed polyurethane layer is increased, and a satisfactory level of low hardness cannot be achieved.

[0005] The present invention has been made in view of such circumstances, and an object of the present invention is to provide a conductive roll having low hardness, low setability, and excellent moldability.

[0006]

In order to achieve the above object, the present invention provides a conductive roll comprising a shaft and a soft urethane foam layer formed on the outer peripheral surface of the shaft. In the soft urethane foam layer,
The soft urethane foam layer formed using a urethane raw material containing the following components (A) to (C),
A configuration is provided in which all of the following characteristics (α) to (γ) are provided. (A) A polyol containing the following (A1) in an amount of 50% by weight or more of the whole polyol. (A1) A polyol having 6 functional groups and having a copolymer unit of ethylene oxide and propylene oxide in the molecular structure. (B) Isocyanate. (C) a conductive agent. (Α) Asker hardness is F10 ° to C50 °. (Β) The electric resistance is 1 × 10 ³ to 1 × 10 ⁹ Ω · cm. (Γ) Compression set is 2% or less.

The inventors of the present invention have conducted intensive studies mainly on a material for forming a soft urethane foam layer in order to obtain a conductive roll having low hardness and low setability and excellent moldability. As a result, a special polyol having a copolymer unit of ethylene oxide and propylene oxide in the molecular structure (A
It has been found that the intended purpose can be achieved by using 1) at 50% by weight or more of the whole polyol, and the present invention has been achieved. That is, by using the special polyol (A1), the viscosity of the premix polyol can be reduced, the moldability can be improved, and a conductive roll having a low hardness or a low hardness can be obtained.

By using conductive carbon black or an ionic conductive agent as the conductive agent (component C) and setting the content thereof in a predetermined range, the conductivity required for the conductive roll can be easily obtained. Will be able to do it.

When tolylene diisocyanate (TDI) is used as the isocyanate (component B),
Low hardness becomes easy.

[0010]

Next, embodiments of the present invention will be described in detail.

The conductive roll of the present invention has, for example, a single-layer structure in which a soft urethane foam layer 2 is formed on the outer peripheral surface of a shaft 1 as shown in FIG.

The shaft 1 is not particularly limited.
For example, a metal core made of a solid metal body, a metal cylindrical body whose inside is hollowed out, and the like are used. Examples of the material include stainless steel, aluminum, and iron plated.

The urethane raw material for forming the flexible urethane foam layer 2 includes a specific polyol (A component).
, An isocyanate (B component) and a conductive agent (C component).

It is necessary to use the specific polyol (component A) containing the following (A1) in an amount of 50% by weight or more of the whole polyol. (A1) A copolymer unit of ethylene oxide (EO) and propylene oxide (PO) (hereinafter referred to as “E
A polyol having 6 functional groups having an O / PO copolymer unit ”).

That is, the above-mentioned special polyol (A1)
This is because if the content of is less than 50% by weight of the whole polyol (A component), the intended effect is small. The content of the special polyol (A1) is preferably 70% by weight or more of the whole polyol (A component).

The special polyol (A1) uses, for example, an active hydrogen-containing compound such as a hexahydric alcohol (sorbitol or the like) as an initiator, to which both ethylene oxide (EO) and propylene oxide (PO) are used. Can be obtained by addition polymerization. In addition,
As the special polyol (A1), those obtained by block copolymerizing EO and PO are preferable.

As shown in FIG. 2, the special polyol (A1) is a hexafunctional polyol having an EO / PO copolymer unit formed by copolymerizing EO and PO and having a hydroxyl group at a terminal. .

The copolymerization ratio (weight ratio) of the above ethylene oxide (EO) and propylene oxide (PO) is EO
/ PO = 95/5 to 50/50 is preferable, and 70/30 to 50/50 is particularly preferable. That is, when the copolymerization ratio of EO exceeds 95 (copolymerization ratio of PO is less than 5), the hardness changes greatly depending on temperature and humidity, and conversely, the copolymerization ratio of EO is less than 50 (PO If the copolymerization ratio exceeds 50), the molded article tends to shrink more.

The weight average molecular weight (MW) of the special polyol (A1) is preferably in the range of 500 to 10,000, particularly preferably 800 to 8,000.

The hydroxyl value of the special polyol (A1) is preferably in the range of 30 to 150 mgKOH / g, and particularly preferably 30 to 120 mgKOH / g.

The polyol other than the special polyol (A1) is not particularly limited, and examples thereof include olefin-based polyols such as polyether polyol, polyester polyol, polycarbonate polyol, polycaprolactone polyol, polybutadiene polyol and polyisoprene polyol. can give. These may be used alone or in combination of two or more.

As the above isocyanate (component B),
There is no particular limitation as long as it is a bifunctional or higher polyisocyanate. For example, tolylene diisocyanate (TDI)
[2,4-form, 2,6-form, mixture of 2,4-form and 2,6-form], hexamethylene diisocyanate (HD
I), 4,4'-diphenylmethane diisocyanate (MDI), carbodiimide-modified MDI, polymeric polyisocyanate, orthotoluidine diisocyanate (TODI), naphthylene diisocyanate (ND)
I), xylylene diisocyanate (XDI), polymethylene polyphenyl isocyanate and the like. These may be used alone or in combination of two or more. Among them, tolylene diisocyanate (TDI) is preferably used in terms of lowering hardness.

The amount of the isocyanate (component B) used with respect to the polyol (component A) is 90 to 90 as an isocyanate index (NCO index).
It is preferably set to a range of 120, particularly preferably 100 to 110. In addition, the NCO index means an isocyanate equivalent relative to a total equivalent 100 of the raw material components having a hydroxyl group that reacts with the isocyanate group.

As the above-mentioned conductive agent (component C), for example,
Examples include conductive carbon black, ionic conductive agents, graphite, and metal oxides. These may be used alone or in combination of two or more.

Examples of the conductive carbon black include Ketjen black, acetylene black, furnace black, channel black, thermal black, and color black. These may be used alone or in combination of two or more. Of these,
Ketjen black and acetylene black are preferably used.

The amount of the conductive carbon black is as follows:
It is preferable to use the conductive roll so that the content in the soft urethane foam layer is in the range of 0.5 to 10% by weight, preferably 0.5 to 3% by weight.

The conductive carbon black has a particle size of 2
Those having a range of 0 to 50 nm are preferable, and those having a DBP oil absorption of 100 to 500 ml / 100 g are preferable.

Examples of the ionic conductive agent include quaternary ammonium salts, borates, and surfactants.

The ionic conductive agent is used in such an amount that the content of the conductive roll in the soft urethane foam layer is in the range of 0.5 to 3% by weight, preferably 0.5 to 1% by weight. Is preferred.

The graphite can be appropriately selected from scale-like graphite, earth-like graphite and the like, and those having a particle size of 20 μm or less have relatively good conductivity.

The urethane raw materials include the above-mentioned A to C
In addition to the components, a foaming agent, a catalyst, a foam stabilizer, an antioxidant, a coloring agent, a flame retardant, and the like may be appropriately blended.

As the foaming agent, water is preferable. The mixing amount of water as the foaming agent is 0.3 part with respect to 100 parts by weight of the polyol (A component) (hereinafter abbreviated as “part”).
A range of .about.2.5 parts is preferred.

Examples of the catalyst include a tertiary amine catalyst, an organometallic compound and the like.

As the above tertiary amine catalyst, for example,
Monoamines such as triethylamine (TEA) and N, N-dimethylcyclohexylamine (DMEDA):
N, N ', N'-tetramethylethylenediamine (TM
Diamines such as EDA): N, N, N ', N ", N"-
Triamines such as pentamethyldiethylenetriamine (PMDETA): Cyclic amines such as triethylenediamine (TEDA): dimethylaminoethanol (DME)
Alcohol amines such as A): ether amines such as bis (2-dimethylaminoethyl) ether (BDMEE); These may be used alone or in combination of two or more.

The amount of the tertiary amine catalyst is preferably in the range of 0.1 to 3 parts based on 100 parts of the polyol (Component A).

Examples of the organometallic compound include stannas octoate, dibutyltin diacetate, dibutyltin dilaurate, dibutyltin thiocarboxyate and the like. These may be used alone or in combination of two or more.

The amount of the organometallic compound is preferably in the range of 0.05 to 0.5 part based on 100 parts of the polyol (component (A)).

Examples of the foam stabilizer include a silicone foam stabilizer (polyoxyalkylene-dimethylpolysiloxane copolymer) and a non-silicone foam stabilizer.

The conductive roll of the present invention can be manufactured, for example, by the following method. That is, first, as shown in FIG. 3, a cylindrical mold 21 having a length substantially equal to the axial length of the soft urethane foam layer 2 of the conductive roll.
And caps 22, 2 for closing both ends of the cylindrical mold 21.
3 is prepared. This mold is
In a state where the shaft 1 is positioned in the cylindrical mold 21, both ends of the cylindrical mold 21 are closed by caps 22 and 23, and the shaft 1 is supported by the caps 22 and 23. Molding cavity 2 that gives the final roll shape (outer diameter) of the desired conductive roll inside
4 are formed. Then, after preparing a premix polyol comprising the above specific polyol (component A), a conductive agent (component C) and, if necessary, a catalyst, a foaming agent and a foam stabilizer, an isocyanate ( The mixture of the (B component) is injected into the molding cavity 24, and the mixture is heated at a predetermined temperature (60 ° C.).
(Approximately 30 ° C.) in an oven for a predetermined time (approximately 30 minutes) to foam and cure. Thereafter, by removing the mold, a conductive roll having a single-layer structure in which the soft urethane foam layer 2 is formed on the outer peripheral surface of the shaft body 1 as shown in FIG. 1 can be obtained.

The thickness of the flexible urethane foam layer 2 is as follows:
Usually, it is 2 to 8 mm, preferably 3 to 6 mm.

In the conductive roll of the present invention thus obtained, the soft urethane foam layer 2 must have all of the following properties (α) to (γ). (Α) Asker hardness is F10 ° to C50 °. (Β) The electric resistance is 1 × 10 ³ to 1 × 10 ⁹ Ω · cm. (Γ) Compression set is 2% or less.

That is, if the Asker hardness is less than F10 °, it is too soft to withstand use. Conversely, if the Asker hardness exceeds C50 °, the photosensitive drum is damaged or the toner is deteriorated. This is because it becomes impossible to meet the demand for improvement. The Asker hardness indicates a value measured at 25 ° C. If the electric resistance is less than 1 × 10 ³ Ω · cm, the current cannot be controlled because the current flows too much, so that it cannot be used as a conductive roll. Conversely, if the electric resistance exceeds 1 × 10 ⁹ Ω · cm, This is because a considerably high voltage needs to be applied to supply a necessary current, which is not preferable. Furthermore, compression set is 2
If the amount exceeds%, traces will appear on the image after a long period of time.

In the conductive roll of the present invention, it is preferable that the flexible urethane foam layer 2 has the following property (δ) in addition to the above properties (α) to (γ). (Δ) The density is 0.05 to 0.50 g / cm ³ .

That is, when the density is out of the above range,
This is because it tends to be difficult to set the Asker hardness within the above-mentioned predetermined range.

The conductive roll of the present invention is used as a toner transport roll, a transfer roll, a charging roll, a developing roll and the like.

Next, examples will be described together with comparative examples.

First, prior to Examples and Comparative Examples, the following materials were prepared.

[Bifunctional polyol (component A)] ED28 [manufactured by Mitsui Chemicals, Inc.] [hydroxyl value: 28 mgKOH / g, M
W: 4000]

[Trifunctional polyol (component A)] EP240 manufactured by Mitsui Chemicals, Inc. [hydroxyl value: 24 mgKOH / g, M
W: 7000]

[Tetrafunctional polyol (component A)] EP3033 manufactured by Mitsui Chemicals, Inc. [hydroxyl value: 34 mgKOH / g,
MW: 6600]

[Hexafunctional polyol (A1)] Polyether polyol obtained by block addition polymerization of sorbitol with EO and PO at a ratio of 95/5 (weight ratio) [hydroxyl value: 1
00 mg KOH / g, MW: 3800]

[Hexafunctional polyol (A1)] Polyether polyol obtained by block addition polymerization of sorbitol with EO and PO at a ratio of 70/30 (weight ratio) [hydroxyl value:
100 mg KOH / g, MW: 3800]

[Hexafunctional polyol (A1)] Polyether polyol obtained by block addition polymerization of EO and PO with sorbitol at a ratio of 50/50 (weight ratio) [hydroxyl value:
100 mg KOH / g, MW: 3800]

[6-functional polyol (A1)] Polyether polyol obtained by block addition polymerization of sorbitol with EO and PO at a ratio of 30/70 (weight ratio) [hydroxyl value:
100 mg KOH / g, MW: 3800]

[Six-functional polyol] P is added to sorbitol
Polyether polyol obtained by block addition polymerization of O [hydroxyl value: 100 mgKOH / g, MW: 3800]

[Isocyanate (component B)] 2,4-toluene diisocyanate (TDI-10, manufactured by Mitsui Chemicals, Inc.)
0)

[Conductive agent (component C)] Conductive carbon black (Ketjen Black EC, manufactured by Ketjen Black International) [particle diameter: 31 nm, DBP oil absorption: 350 ml / 100 g]

[Conductive agent (component C)] Ionic conductive agent (quaternary ammonium salt)

[Conductive Agent (Component C)] Graphite

[Curing catalyst] Kaolyzer N manufactured by Kao Corporation
o. 31

[Foam stabilizer] Silicone foam stabilizer (manufactured by Nippon Unicar, L5366)

[0062]

Example 1 A conductive roll was produced using a urethane raw material obtained by mixing the components shown in Table 1 below in the proportions shown in the table according to the production method shown in FIG. That is, first, the mold shown in FIG. 3 was prepared, and a metal core (diameter: 5 mm, made of SUS304) serving as the shaft body 1 was set in the cylindrical mold 21. Then, polyol, conductive agent, curing catalyst,
After preparing a premix polyol by blending a foaming agent and a foam stabilizer at the ratios shown in Table 1 below, a mixture of the premix polyol and isocyanate at a predetermined ratio is added to the molding cavity 24 of the mold. The required amount was injected into the inside. This is heated in an oven at 60 ° C. for 30 minutes to foam and harden, and then removed from the mold to form a single-layer conductive film having a soft urethane foam layer (5.5 mm in thickness) formed on the outer peripheral surface of the shaft body. A flexible roll was produced (see FIG. 1).

[0063]

Examples 2 to 9 and Comparative Examples 1 to 6 Conductive rolls were prepared in the same manner as in Example 1 except that the urethane raw materials were changed to those shown in Tables 1 to 3 below.

[0064]

[Table 1]

[0065]

[Table 2]

[0066]

[Table 3]

Using the conductive rolls of the example product and the comparative example product thus obtained, each characteristic was evaluated according to the following criteria. These results are also shown in Tables 4 to 6 below.

[Electric Resistance] The electric resistance of the flexible urethane foam layer was measured at DC 500 V.

[Compression Set] The compression set of the flexible urethane foam layer was measured at a temperature of 50 ° C., a compressibility of 50%, and a test time of 72 hours in accordance with JIS K6301.

[Moldability] Premix polyols having high viscosity and difficult to inject into molding dies, or those having large shrinkage and difficult to mold were marked with X, and those in which premix polyols were somewhat difficult to inject into molding dies. Was evaluated as “△”, and those in which the premix polyol was easily injected into the mold were evaluated as “○”.

[0071]

[Table 4]

[0072]

[Table 5]

[0073]

[Table 6]

From the above results, it can be seen that all of the examples were low in hardness, low in compression set, low, and excellent in moldability.

On the other hand, the product of Comparative Example 1 had 6 functional groups.
Although the special polyol (A1) is used, it can be seen that the compression set is large and the set is large because the ratio of the polyol to the whole polyol (A component) is small. Also,
High viscosity and poor moldability. Comparative Examples 2 to 4 have high viscosity and poor moldability. Also, the compression set is large and the set is large. The products of Comparative Examples 5 and 6 have a small compression set, a low set, and a good viscosity, but have shrinkage.

[0076]

As described above, the conductive roll of the present invention comprises a polyol (A component) containing a predetermined amount of a special polyol having six functional groups (A1) having an EO / PO copolymer unit in the molecular structure. ) Is used to form a soft urethane foam layer, and the hardness, electric resistance and compression set of this soft urethane foam layer are set in specific ranges. Therefore, the conductive roll of the present invention has a low hardness,
Excellent in moldability with low set.

By using conductive carbon black, ionic conductive agent and graphite as the conductive agent (component C) and setting their contents within a predetermined range, the conductivity required for the conductive roll can be easily increased. You can get to.

When tolylene diisocyanate (TDI) is used as the isocyanate (component B),
Low hardness becomes easy.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of a conductive roll of the present invention.

FIG. 2 is a schematic diagram showing a schematic configuration of a special polyol (A1).

FIG. 3 is a cross-sectional view illustrating an example of a method for manufacturing a conductive roll of the present invention.

FIG. 4 is an explanatory diagram of a developing method by an electrophotographic method.

[Explanation of symbols]

 1 Shaft 2 Soft urethane foam layer

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference) C08L 75/08 C08L 75/08 4J002 G03G 15/02 101 G03G 15/02 101 4J034 15/08 501 15/08 501D 501A 15/16 103 15/16 103 // (C08G 18/48 (C08G 18/48 F 101: 00) 101: 00) (72) Inventor Kadai Takeyama 1-3-1, Higashi 3-chome, Komaki City, Aichi Prefecture Tokai Rubber Works F Term (Reference) 2H003 BB11 CC05 2H032 AA05 BA23 2H077 AC04 AD06 FA13 FA22 FA27 3J103 AA02 AA13 AA32 AA37 BA34 BA41 CA05 EA02 FA03 FA06 FA15 GA02 GA52 GA57 GA58 GA60 GA73 GA74 HA03 HA15 HA18 HA33 HA41 HA52 HA55 4F071 AA53 AA67 AB03 AB17 AB27 AC12 AE01 AE10 AE15 AF18Y AF26Y AF37Y AH17 BA02 BB01 BB12 BC07 BC10 BC11 4J002 CK041 CP18 2 DA036 DE027 DK006 EN136 FD116 FD316 FD322 FD327 GM00 4J034 BA03 BA07 DA01 DB05 DB07 DC50 DF01 DF02 DF12 DG03 DG04 DG09 DG12 DG14 DP19 HA01 HA02 HA07 HA11 HB06 HC03 HC12 HC13 HC52 HC61 HC02 HC02 MA02 KCA QB01 QB07 QB14 QB15 QC01 QC10 QD03 RA11 RA19

Claims (7)

[Claims] 1. A conductive roll comprising a shaft and a soft urethane foam layer formed on an outer peripheral surface of the shaft, wherein the soft urethane foam layer has the following (A) to
(C) formed using a urethane raw material containing the component,
A conductive roll, wherein the flexible urethane foam layer has all of the following properties (α) to (γ). (A) A polyol containing the following (A1) in an amount of 50% by weight or more of the whole polyol. (A1) A polyol having 6 functional groups and having a copolymer unit of ethylene oxide and propylene oxide in the molecular structure. (B) Isocyanate. (C) a conductive agent. (Α) Asker hardness is F10 ° to C50 °. (Β) The electric resistance is 1 × 10 ³ to 1 × 10 ⁹ Ω · cm. (Γ) Compression set is 2% or less. 2. The conductive roll according to claim 1, wherein the flexible urethane foam layer has the following property (δ) in addition to the properties (α) to (γ). (Δ) The density is 0.05 to 0.50 g / cm ³ . 3. The conductive roll according to claim 1, wherein in the polyol (A1), the proportion of ethylene oxide is 50% by weight or more based on the whole copolymerized units. 4. The conductive agent as the component (C) is conductive carbon black, and is contained in the soft urethane foam layer in an amount of 0.5 to 10% by weight. 4. The conductive roll according to item 1. 5. The conductive agent as the component (C) is graphite, and the soft urethane foam layer contains 10 to 3 times.
The conductive roll according to any one of claims 1 to 3, which contains 0% by weight. 6. The conductive agent as the component (C) is an ionic conductive agent, and 0.5 to 0.5%
The conductive roll according to any one of claims 1 to 3, which contains 3% by weight. 7. The conductive roll according to claim 1, wherein the isocyanate as the component (B) is tolylene diisocyanate.