CN113201174B

CN113201174B - Rubber composition, conductive roller, and image forming apparatus

Info

Publication number: CN113201174B
Application number: CN202011440083.8A
Authority: CN
Inventors: 小坂圭亮; 谷尾勇祐
Original assignee: Sumitomo Rubber Industries Ltd
Current assignee: Sumitomo Rubber Industries Ltd
Priority date: 2020-01-31
Filing date: 2020-12-11
Publication date: 2024-03-29
Anticipated expiration: 2040-12-11
Also published as: CN113201174A; JP2021124120A; JP7402413B2

Abstract

The invention provides a rubber composition capable of forming a roller body of a conductive roller with small variation of roller resistance value, a conductive roller comprising the roller body formed by using the rubber composition, and an image forming device comprising the conductive roller. In the rubber composition, 0.8 to 1.2 parts by mass of sulfur and 0.5 to 1 part by mass of 4,4' -dithiodimorpholine are blended with respect to 100 parts by mass of the total amount of the rubber, in a rubber containing a diene rubber, an ethylene-propylene rubber and an ion-conductive rubber. The conductive roller (1) comprises a roller body (2) containing a crosslinked product of the rubber composition. The image forming apparatus includes the conductive roller (1).

Description

Rubber composition, conductive roller, and image forming apparatus

Technical Field

The present invention relates to a rubber composition, a conductive roller including a roller body formed using the rubber composition, and an image forming apparatus including the conductive roller.

Background

In an image forming apparatus using an electrophotographic method, there is a case where a conductive roller including a roller body formed by foaming and crosslinking a conductive rubber composition is used (see patent document 1, patent document 2, and the like). However, the conventional conductive roller has a problem that the roller resistance value varies greatly.

[ Prior Art literature ]

[ patent literature ]

Patent document 1 Japanese patent laid-open No. 2015-034878

Patent document 2 Japanese patent laid-open publication No. 2014-119546

Disclosure of Invention

[ problem to be solved by the invention ]

The invention aims to provide a rubber composition capable of forming a roller body of a conductive roller with small roller resistance value placement variation.

Another object of the present invention is to provide a conductive roller including a roller body formed using the rubber composition, and an image forming apparatus including the conductive roller.

[ means of solving the problems ]

The present invention is a rubber composition for forming a roller body of a conductive roller, and the rubber composition comprises: a rubber containing a diene rubber, an ethylene propylene rubber, and an ion conductive rubber; and a crosslinking component for crosslinking the rubber, wherein the crosslinking component contains 0.8 to 1.2 parts by mass of sulfur per 100 parts by mass of the total amount of the rubber and 0.5 to 1 part by mass of 4,4' -dithiodimorpholine per 100 parts by mass of the total amount of the rubber.

The present invention also provides a conductive roller comprising a roller body containing the crosslinked product of the rubber composition of the present invention.

The present invention also provides an image forming apparatus including the conductive roller of the present invention.

[ Effect of the invention ]

According to the present invention, a rubber composition capable of forming a roller body of a conductive roller having a small variation in roller resistance value in the placement can be provided.

Further, according to the present invention, there can be provided a conductive roller including a roller body formed using the rubber composition, and an image forming apparatus including the conductive roller.

Drawings

Fig. 1 is a perspective view showing an example of an embodiment of a conductive roller according to the present invention.

Fig. 2 is a diagram for explaining a method of measuring a roller resistance value of a conductive roller.

[ description of symbols ]

1: conductive roller

2: roller body

3: through hole

4: shaft

5: an outer peripheral surface

6: aluminum roller

7: an outer peripheral surface

8: DC power supply

9: resistor

10: measuring circuit

F: load of

V: the voltage is detected.

Detailed Description

As described above, the rubber composition of the present invention is characterized by comprising: a rubber containing a diene rubber, an ethylene propylene rubber, and an ion conductive rubber; and a crosslinking component for crosslinking the rubber, wherein the crosslinking component contains 0.8 to 1.2 parts by mass of sulfur per 100 parts by mass of the total amount of the rubber and 0.5 to 1 part by mass of 4,4' -dithiodimorpholine per 100 parts by mass of the total amount of the rubber.

The conductive roller of the present invention is characterized by comprising a roller body containing a crosslinked product of the rubber composition.

If the conductive roller is stored (left to stand) for a long period of time without being used after the production of the conductive roller, aged deterioration such as oxidation deterioration occurs, and a phenomenon in which the roller resistance value increases is observed.

When the roll resistance value exceeds the upper limit of the specification value of the conductive roll due to the placement fluctuation, an image formed by the image forming apparatus incorporating the conductive roll may be defective.

In particular, in recent years, further longer life is demanded of image forming apparatuses, and therefore, in order to extend the product life of image forming apparatuses, it is demanded that the placement fluctuation of the roller resistance value is small also for conductive rollers stored for replacement purposes.

As a general countermeasure for reducing the variation in the placement of the roller resistance value, blending of an anti-aging agent in a rubber composition or increasing the proportion of rubber which is not easily oxidized and deteriorated is considered.

However, if these measures are taken, there is a problem that the degree of freedom in selecting the materials of the rubber composition is limited.

In contrast, according to the present invention, by using sulfur and 4,4' -dithiodimorpholine as the crosslinking agents in the above-described predetermined ratio with respect to the rubber, the variation in placement of the roll resistance value can be reduced without reducing the degree of freedom in the selection of the materials of the rubber composition.

The above-described cases are also clear from the results of examples and comparative examples described later.

Rubber composition

[ rubber ]

As the rubber, at least a diene rubber, an ethylene propylene rubber and an ion conductive rubber are used in combination.

Diene rubber

The diene rubber functions to impart good properties as rubber to the roll body, that is, soft and has a small compression set and less tendency to collapse.

Since the diene rubber has a double bond in the main chain and sulfur crosslinkability, various diene rubbers that can be crosslinked by a combination system of sulfur and 4,4' -dithiodimorpholine can be used as described above.

Examples of the diene rubber include natural rubber, isoprene Rubber (IR), acrylonitrile butadiene rubber (nitrile butadiene rubber, NBR), styrene butadiene rubber (styrene butadiene rubber, SBR), butadiene Rubber (BR), and chloroprene rubber (chloroprene rubber, CR).

Of these, the diene rubber is preferably one obtained by using both NBR and SBR.

(NBR)

As the NBR, a low nitrile NBR having an acrylonitrile content of 24% or less, a medium nitrile NBR of 25% to 30%, a medium and high nitrile NBR of 31% to 35%, a high nitrile NBR of 36% to 42% and an extremely high nitrile NBR of 43% or more can be used.

In addition, as the NBR, there are an oil-filled type NBR in which an extender oil is added to adjust flexibility and a non-oil-filled type NBR not added, but in the present invention, in order to prevent contamination of a photoreceptor or the like, a non-oil-filled type NBR containing no extender oil which can be an exuded substance is preferably used.

One or two or more of these NBRs may be used.

(SBR)

As SBR, various SBR synthesized by copolymerizing styrene and 1, 3-butadiene by various polymerization methods such as emulsion polymerization and solution polymerization can be used.

As SBR, there are SBR of high styrene type, medium styrene type and low styrene type classified according to styrene content, and any of these can be used.

Further, as SBR, there are oil-filled SBR in which an extender oil is added to adjust flexibility and non-oil-filled SBR in which no extender oil is added, but in the present invention, it is preferable to use non-oil-filled SBR containing no extender oil which can be exuded in order to prevent contamination of a photoreceptor or the like.

One or two or more of these SBR may be used.

Ethylene propylene rubber

Since the ethylene-propylene rubber is excellent in ozone resistance and weather resistance, the use of the ethylene-propylene rubber in combination can suppress oxidation degradation of the roll body and further reduce the variation in the roll resistance value.

Examples of the ethylene-propylene rubber include an ethylene-propylene rubber (Ethylene Propylene Monomer, EPM) which is a copolymer of ethylene and propylene, and an ethylene-propylene diene rubber (Ethylene Propylene Diene Monomer, EPDM) which is a copolymer of ethylene, propylene and diene.

In particular, EPDM which has sulfur crosslinkability and can be crosslinked by a combination system of sulfur and 4,4' -dithiodimorpholine is preferable.

As EPDM, various copolymers obtained by copolymerizing ethylene, propylene and diene can be used.

Examples of the diene include ethylidene norbornene (ethylidene norbornene, ENB) and dicyclopentadiene (DCPD).

In addition, as the EPDM, there are an oil-filled EPDM in which an oil is added to adjust flexibility, and a non-oil-filled EPDM in which no oil is added, but in the present invention, in order to prevent contamination of a photoreceptor or the like, it is preferable to use a non-oil-filled EPDM in which no oil that can be exuded is used.

One or two or more of these EPDM may be used.

Ion conductive rubber

The ion conductive rubber is a conductive rubber that imparts moderate ion conductivity to the rubber composition and includes a crosslinked product of the rubber composition, and functions by adjusting the roller resistance value of the conductive rubber within a range suitable for assembly into an image forming apparatus.

The conductive roller of the present invention can be incorporated into an image forming apparatus as, for example, a transfer roller, a charging roller, a developing roller, a cleaning roller, or the like.

Examples of the ion conductive rubber include epichlorohydrin rubber and polyether rubber.

Among them, examples of the epichlorohydrin rubber include epichlorohydrin homopolymers, epichlorohydrin-ethylene oxide binary copolymers (epichlorohydrin ethylene oxide dipolymer, ECO), epichlorohydrin-propylene oxide binary copolymers, epichlorohydrin-allyl glycidyl ether binary copolymers, epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymers (epichlorohydrin ethylene oxide allyl glycidyl ether terpolymer, GECO), epichlorohydrin-propylene oxide-allyl glycidyl ether terpolymers, and epichlorohydrin-ethylene oxide-propylene oxide-allyl glycidyl ether tetrapolymers.

Examples of the polyether rubber include ethylene oxide-allyl glycidyl ether binary copolymer and ethylene oxide-propylene oxide-allyl glycidyl ether ternary copolymer.

Among them, a copolymer containing ethylene oxide, particularly GECO which has sulfur crosslinkability and can be crosslinked by a system of sulfur and 4,4' -dithiodimorpholine in combination, is preferable.

The ethylene oxide content in GECO is preferably 30 mol% or more, particularly 50 mol% or more, and preferably 80 mol% or less.

As described above, ethylene oxide imparts ionic conductivity to a rubber composition and plays a role of reducing a roller resistance value of a conductive roller including a roller body including a crosslinked product of the rubber composition.

However, if the ethylene oxide content is less than the above range, the above effect cannot be sufficiently obtained, and thus the roll resistance value may not be sufficiently reduced.

On the other hand, when the ethylene oxide content exceeds the above range, crystallization of ethylene oxide occurs, and the chain segment movement of the molecular chain is hindered, so that the roll resistance tends to increase.

In addition, the roll body after crosslinking may become too hard, or the viscosity of the rubber composition before crosslinking may increase upon heating and melting, and the processability and foamability of the rubber composition may be lowered.

The allyl glycidyl ether content in GECO is preferably 0.5 mol% or more, particularly 2 mol% or more, and preferably 10 mol% or less, particularly 5 mol% or less.

The allyl glycidyl ether functions to secure a free volume as a side chain, thereby inhibiting crystallization of ethylene oxide and reducing a roll resistance value.

However, if the allyl glycidyl ether content is less than the above range, the effect cannot be sufficiently obtained, and thus the roll resistance value may not be sufficiently reduced.

On the other hand, allyl glycidyl ether functions as a crosslinking point at the time of crosslinking of GECO.

Therefore, when the allyl glycidyl ether content exceeds the above range, the crosslinking density of GECO becomes too high, whereby the segment movement of the molecular chain is hindered, and instead the roll resistance value tends to increase.

The epichlorohydrin content in GECO is the residual amount of the ethylene oxide content and the allyl glycidyl ether content.

That is, the epichlorohydrin content is preferably 10 mol% or more, particularly 19.5 mol% or more, and preferably 69.5 mol% or less, particularly 60 mol% or less.

Further, as GECO, there is known a modified product obtained by modifying an epichlorohydrin-ethylene oxide binary copolymer (ECO) with allyl glycidyl ether, in addition to a copolymer in the narrow sense of copolymerizing three monomers as described above.

In the present invention, any of the GECO's may be used.

One or two or more of these ion-conductive rubbers may be used.

Other rubbers

Further, as the rubber, a rubber having a polarity may be used in combination to finely adjust the roller resistance value of the conductive roller.

Examples of the rubber having polarity include an Acrylic rubber (ACM) and CR in the diene rubber.

Further, since the ACM has high heat resistance, the use of the ACM in combination can further effectively suppress oxidation degradation of the roller body and further reduce the variation in the placement of the roller resistance value.

(ACM)

As the ACM, various ACMs synthesized by copolymerizing a halogen-containing monomer such as acrylonitrile or 2-chloroethyl vinyl ether, a glycidyl acrylate, allyl glycidyl ether, ethylidene norbornene, or the like, with an alkyl acrylate such as ethyl acrylate or butyl acrylate as a main component, can be used.

One or two or more of these ACMs may be used.

(CR)

CR is synthesized by emulsion polymerization of chloroprene and is classified into a sulfur-modified type and a non-sulfur-modified type depending on the type of molecular weight regulator used at that time.

Among them, sulfur-modified CR can be synthesized by plasticizing a polymer obtained by copolymerizing chloroprene and sulfur as a molecular weight regulator with thiuram disulfide or the like, and adjusting the polymer to a predetermined viscosity.

The non-sulfur-modified CR is classified into, for example, a thiol-modified CR and a xanthogen-modified CR.

Wherein the thiol-modified CR is synthesized in the same manner as the sulfur-modified CR except that an alkyl mercaptan such as n-dodecyl mercaptan, t-dodecyl mercaptan, or octyl mercaptan is used as the molecular weight regulator.

Further, the xanthogen-modified CR was synthesized in the same manner as the sulfur-modified CR, except that an alkyl xanthogen compound was used as a molecular weight regulator.

CR is classified into slow crystallization rate type, intermediate type and fast crystallization rate type based on the crystallization rate.

Any type of CR may be used in the present invention, but among them, CR which is not sulfur-modified and has a slow crystallization rate is preferable.

As CR, a copolymer of chloroprene and another copolymerization component may be used.

Examples of the other copolymerizable component include: one or more of 2, 3-dichloro-1, 3-butadiene, 1-chloro-1, 3-butadiene, styrene, acrylonitrile, methacrylonitrile, isoprene, butadiene, acrylic acid ester, methacrylic acid, and methacrylic acid ester.

Further, as CR, there are an oil-filled CR in which an extender oil is added to adjust flexibility and a non-oil-filled CR in which no extender oil is added, but in the present invention, in order to prevent contamination of the photoreceptor, it is still preferable to use a non-oil-filled CR in which no extender oil that can be an exuding substance is used.

One or two or more of these CRs may be used.

Rubber ratio

The proportion of the ion conductive rubber is 5 parts by mass or more, preferably 10 parts by mass or more, particularly 15 parts by mass or more, and 35 parts by mass or less, particularly 30 parts by mass or less, particularly 25 parts by mass or less, based on 100 parts by mass of the total amount of the rubber.

In the case where the proportion of the ion conductive rubber is less than the range or exceeds the range, the roller resistance value of the conductive roller may not be adjusted to a range suitable for assembly into an image forming apparatus in any case.

In addition, in the ionic conductivity of rubber ratio beyond the range, sometimes in the diene rubber or ethylene propylene rubber ratio relatively becomes smaller, and the use of these rubbers to obtain the effect.

In contrast, by setting the proportion of the ion conductive rubber to the above range, the roller resistance value of the conductive roller can be adjusted to a range suitable for assembly into an image forming apparatus.

Further, the effect of the combination of the diene rubber or the ethylene-propylene rubber can be sufficiently exhibited.

The proportion of the ethylene-propylene rubber is preferably at least 5 parts by mass, particularly at least 10 parts by mass, and at most 30 parts by mass, and at most 25 parts by mass, particularly at most 20 parts by mass, based on 100 parts by mass of the total amount of the rubber.

If the proportion of the ethylene-propylene rubber is less than the above range, the effect of suppressing the oxidation degradation of the roll body and further reducing the variation in the roll resistance value due to blending of the ethylene-propylene rubber may not be sufficiently obtained.

On the other hand, when the ratio of ethylene propylene rubber exceeds the above range, the ion conductive rubber or diene rubber ratio is relatively reduced, also sometimes not fully obtained by using these rubbers and the effect.

In contrast, when the ratio of the ethylene-propylene rubber is within the above range, the roll body can be prevented from being oxidized and deteriorated, and the variation in the roll resistance value can be further reduced.

In addition, can also fully show by using ion conductive rubber or diene rubber and brought by the effect.

The proportion of the other rubber such as ACM or CR is preferably 10 parts by mass or less, particularly 5 parts by mass or less, based on 100 parts by mass of the total amount of the rubber.

The other rubber may not be blended, that is, the ratio of the other rubber may be 0 parts by mass.

The proportion of NBR and/or SBR as the diene rubber is the residual amount of the ion conductive rubber, the ethylene-propylene rubber and other rubbers.

That is, when the ion conductive rubber, ethylene propylene rubber and other rubber ratio set to the range of the specified value, as long as the total rubber to 100 parts by mass of NBR and/or SBR ratio.

[ crosslinking component ]

Crosslinking agent

As a crosslinking component, sulfur and 4,4' -dithiodimorpholine are used as a crosslinking agent for crosslinking rubber as described above.

Wherein the ratio of sulfur is defined to be 0.8 parts by mass or more and 1.2 parts by mass or less relative to 100 parts by mass of the total amount of rubber.

The proportion of 4,4' -dithiodimorpholine is defined to be 0.5 to 1 part by mass based on 100 parts by mass of the total amount of the rubber.

These reasons are as described previously.

That is, when either of the sulfur and the 4,4' -dithiodimorpholine is out of the above range, the effect due to the combination of the two crosslinking agents cannot be obtained, and the variation in the roll resistance value becomes large.

In contrast, by using both of the above-mentioned crosslinking agents in the above-mentioned predetermined ratio, the variation in the placement of the roll resistance value can be reduced even if the ratio of the blended rubber is arbitrarily changed.

That is, the roller body of the conductive roller having small variation in the placement of the roller resistance value can be formed without reducing the degree of freedom in the selection of the material of the rubber composition.

(Sulfur)

Examples of sulfur include various sulfur that can function as a crosslinking agent for rubber.

As the sulfur, for example, one or more of powdered sulfur as a general form of sulfur for rubber, oil-treated sulfur in which the powdered sulfur is treated with oil for the purpose of improving dispersibility, preventing scattering, etc., dispersible sulfur in which the powdered sulfur is treated with an organic dispersant or an inorganic dispersant for the purpose of improving dispersibility, etc., precipitated sulfur, colloidal sulfur, insoluble sulfur, etc. are used.

In particular, in view of improving dispersibility in rubber, improving processability and productivity of the rubber composition and the conductive roller, etc., oil-treated sulfur is preferable as sulfur.

As the oil-treated sulfur, various grades of sulfur are known depending on the oil content, and either of them can be used.

Even if the oil-treated sulfur has different oil contents, the effect of the present invention can be exhibited by defining the total amount of the oil-treated sulfur so as to be within the above range in terms of the amount of sulfur as an active ingredient.

(4, 4' -dithiodimorpholine)

Specific examples of the 4,4' -dithiodimorpholine include barnok (VULNOC) (registered trademark) R manufactured by the large-scale advanced chemistry (strand).

Crosslinking accelerator

As the crosslinking component, a so-called crosslinking accelerator having a function of adjusting the crosslinking reaction of the rubber caused by the two crosslinking agents may be used together with the two crosslinking agents.

Examples of the crosslinking accelerator include one or more of thiazole-based accelerators, thiuram-based accelerators, sulfenamide-based accelerators, and dithiocarbamate-based accelerators.

Among them, a combination of a thiazole-based accelerator and a thiuram-based accelerator is preferable.

(thiazole-based accelerator)

Examples of the thiazole-based accelerator include one or more of 2-mercaptobenzothiazole, di-2-benzothiazolyl disulfide, zinc salt of 2-mercaptobenzothiazole, cyclohexylamine salt of 2-mercaptobenzothiazole, and 2- (4' -morpholinodithio) benzothiazole, and particularly preferably di-2-benzothiazolyl disulfide.

(thiuram series accelerator)

Examples of the thiuram-based accelerator include one or more of tetramethylthiuram monosulfide, tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, and dipentamethylenethiuram tetrasulfide, and particularly tetramethylthiuram monosulfide is preferable.

Ratio of crosslinking accelerator

In view of sufficiently exhibiting a function of adjusting the crosslinking reaction of the rubber by the two crosslinking agents, the proportion of the thiuram-based accelerator is preferably 0.3 parts by mass or more, and preferably 2 parts by mass or less, relative to 100 parts by mass of the total amount of the rubber.

The proportion of the thiazole-based accelerator is preferably 0.3 parts by mass or more, and more preferably 3 parts by mass or less, based on 100 parts by mass of the total amount of the rubber.

[ foaming component ]

The roll body may be of a non-porous structure or a porous structure, and it is preferable to blend a foaming component into the rubber composition to crosslink the rubber and foam the rubber before and after crosslinking in order to make the roll body of a porous structure.

As the foaming component, various foaming agents that decompose and generate gas by heating can be used.

In addition, a foaming auxiliary agent that reduces the decomposition temperature of the foaming agent and promotes the decomposition thereof may be combined.

Foaming agent

Examples of the foaming agent include: one or more of azodicarbonamide (azo dicarbonamide, ADCA), 4 '-oxybis (benzenesulfonyl hydrazide) (4, 4' -oxy bis (benzenesulfonyl hydrazide), OBSH), N-dinitroso pentamethylene tetramine (N, N-dinitroso pentamethylenetetramine, DPT), and the like.

In particular, ADCA is preferable as the foaming agent.

The proportion of ADCA is preferably 0.5 parts by mass or more, and more preferably 5 parts by mass or less, relative to 100 parts by mass of the total amount of rubber.

Foaming aid

As the foaming aid, various foaming aids that exert the effect of reducing the decomposition temperature of the combined foaming agent and promoting its decomposition can be used as described above, and for example, urea (H ₂ HCONH ₂ ) Is a foaming auxiliary agent.

The proportion of the foaming auxiliary may be arbitrarily set according to the kind of the foaming agent to be combined, and is preferably 0.1 parts by mass or more, and preferably 5 parts by mass or less, based on 100 parts by mass of the total amount of the rubber.

[ others ]

Various additives may be further formulated in the rubber composition as needed.

Examples of the additive include: acid absorbing agents, inorganic fillers, and the like.

The acid absorber is functional to trap chlorine in chlorine-based gas generated from epichlorohydrin rubber or CR during crosslinking, and to prevent chlorine-based gas from remaining in the roller body in a free state, or to prevent crosslinking, contamination of photoreceptor, and the like.

As the acid acceptor, various substances that function as acid acceptors can be used, among which hydrotalcite-like compounds or migrater (maggarat) having excellent dispersibility are preferable, and hydrotalcite-like compounds are particularly preferable.

In addition, when hydrotalcite or the like is used in combination with magnesium oxide or potassium oxide, a higher acid absorption effect can be obtained, and contamination of a photoreceptor or the like can be prevented more surely.

The proportion of the acid absorber is preferably 0.2 parts by mass or more, and more preferably 5 parts by mass or less, based on 100 parts by mass of the total amount of the rubber.

The inorganic filler functions to improve mechanical strength of the roll body or to reduce the blending unit price of the rubber blending without affecting the properties of the roll body.

Examples of the inorganic filler include one or more of zinc oxide, silica, carbon black, talc, calcium carbonate, clay, magnesium carbonate, and aluminum hydroxide.

In particular, in order to reduce the blending unit price of the rubber blending without affecting the properties of the roll body, it is preferable to use one or more of talc, calcium carbonate, clay, magnesium carbonate, aluminum hydroxide, and the like.

The proportion of the inorganic filler is preferably 15 parts by mass or more, and more preferably 25 parts by mass or less, based on 100 parts by mass of the total amount of the rubber.

In addition, by using conductive carbon black as a filler, electron conductivity can be imparted to the roller body.

As the conductive carbon black, highly abrasion resistant carbon black (High abrasion furnace black, HAF) is preferable.

The HAF can be uniformly dispersed in the rubber composition, and therefore can impart uniform electron conductivity to the roller body as much as possible.

The proportion of the conductive carbon black is preferably 5 parts by mass or more, and more preferably 15 parts by mass or less, relative to 100 parts by mass of the total amount of the rubber.

Further, as the additive, various additives such as a crosslinking assistant, a deterioration inhibitor, an anti-scorch agent, a plasticizer, a lubricant, a pigment, an antistatic agent, a flame retardant, a neutralizing agent, a nucleating agent, and a co-crosslinking agent may be blended in any ratio.

The rubber composition of the present invention containing the above-described components can be prepared in the same manner as before.

First, a rubber is blended in a predetermined ratio and masticated, then various additives other than a foaming component and a crosslinking component are added and kneaded, and finally the foaming component and the crosslinking component are added and kneaded, thereby obtaining a rubber composition.

As the kneading, for example, a kneader, a Banbury mixer, an extruder or the like can be used.

Conductive roller

Fig. 1 is a perspective view showing an example of an embodiment of a conductive roller 1 according to the present invention.

Referring to fig. 1, the conductive roller 1 of the example includes a roller body 2, wherein the roller body 2 includes a crosslinked product of a rubber composition containing the above components, is formed in a porous and single-layer cylindrical shape, and a shaft 4 is inserted and fixed into a through hole 3 in the center of the roller body 2.

The shaft 4 is integrally formed of a material having good electrical conductivity, for example, a metal such as iron, aluminum alloy, or stainless steel.

The shaft 4 is electrically engaged and mechanically fixed with the roller body 2, for example, via an adhesive having conductivity, or with the roller body 2 by pressing a shaft having an outer diameter larger than an inner diameter of the through hole 3 into the through hole 3.

Alternatively, the shaft 4 may be electrically coupled to the roller body 2 and mechanically fixed by both methods.

Roll resistance measurement

Fig. 2 is a diagram for explaining a method of measuring the roller resistance value of the conductive roller 1.

Referring to fig. 1 and 2, in the above measurement method, an aluminum drum 6 rotatable at a fixed rotation speed is prepared, and an outer peripheral surface 5 of a roller body 2 of a conductive roller 1 for measuring a roller resistance value is brought into contact with an outer peripheral surface 7 of the prepared aluminum drum 6 from above.

A dc power supply 8 and a resistor 9 are connected in series between the shaft 4 of the conductive roller 1 and the aluminum cylinder 6 to form a measurement circuit 10.

The (-) side of the DC power supply 8 is connected to the shaft 4, and the (+) side is connected to the resistor 9.

The resistance value r of the resistor 9 was set to 100deg.C.

Then, a load F of 4.9N (approximately500 gf) was applied to each of the opposite ends of the shaft 4, and the aluminum drum 6 was rotated at 30rpm in a state where the roller body 2 was pressed against the aluminum drum 6.

Then, while continuing the rotation, an applied voltage E of 1000V was applied from the dc power supply 8 between the conductive roller 1 and the aluminum drum 6, and after 30 seconds, a detection voltage V applied to the resistor 9 was measured.

Based on the measured detection voltage V and the applied voltage E (=1000v), the roller resistance value R of the conductive roller 1 basically uses the formula (i'):

R＝r×E/V-r (i')

and the result was obtained.

Wherein one term of-r in formula (i') can be regarded as minute, and thus the present invention utilizes the formula (i):

R＝r×E/V (i)

the obtained value is the roller resistance value of the conductive roller 1.

The measurement was performed in a normal temperature and humidity environment at a temperature of 23℃and a relative humidity of 55%.

Manufacturing of conductive roller 1

In order to manufacture the conductive roller 1 of the present invention, a rubber composition containing the above components is first extruded into a tube shape using an extrusion molding machine, then cut into a predetermined length, and then pressurized and heated by pressurized steam in a vulcanizing tank to foam and crosslink the rubber composition.

Then, the cylindrical body subjected to foaming and crosslinking is heated by an oven or the like, is subjected to secondary crosslinking, is cooled, and is further ground to a predetermined outer diameter to form the roller body 2.

The shaft 4 may be inserted and fixed into the through hole 3 at any time point from the cutting to the polishing of the cylindrical body.

Among them, it is preferable that after cutting, the shaft 4 is first subjected to secondary crosslinking and polishing in a state of being inserted into the through hole 3.

This suppresses warpage, deformation, etc. of the tubular body due to expansion and contraction at the time of secondary crosslinking.

Further, polishing is performed while rotating about the shaft 4, so that the workability of the polishing is improved and runout of the outer peripheral surface 5 can be suppressed.

As described above, the shaft 4 may be inserted into the through hole 3 of the tubular body before the secondary crosslinking via an adhesive having conductivity, particularly a conductive thermosetting adhesive, and then subjected to the secondary crosslinking, or may be pressed into the through hole 3 by a shaft having an outer diameter larger than an inner diameter of the through hole 3.

In the former case, the cylindrical body is secondarily crosslinked by heating in the oven, and at the same time, the thermosetting adhesive is cured, and the shaft 4 is electrically coupled and mechanically fixed to the roller body 2.

In the latter case, the electrical connection and the mechanical fixing are performed simultaneously with the press-in.

In addition, as described above, the shaft 4 and the roller body 2 may be electrically joined and mechanically fixed by both the above-described methods.

Image Forming apparatus

The image forming apparatus of the present invention is characterized in that the conductive roller of the present invention is incorporated as, for example, a transfer roller, a charging roller, a developing roller, a cleaning roller, or the like.

The image forming apparatus according to the present invention includes: various image forming apparatuses using an electrophotographic method, such as a laser printer, an electrostatic copier, a plain paper facsimile machine, or a combination thereof, are used.

Examples (example)

The present invention will be further described below with reference to examples and comparative examples, but the structure of the present invention is not necessarily limited to these examples.

Example 1

(rubber composition)

As the rubber, 40 parts by mass of JSR (registered trademark) N250SL manufactured by NBR [ JSR (strand), low nitrile NBR, acrylonitrile content 20%, non-oil-filled ], 23.5% by mass of alumni SBR1502 manufactured by SBR [ alumni chemistry (strand), 30 parts by mass of styrene content, ai Puen (esprene) (registered trademark) EPDM 505A manufactured by EPDM [ alumni chemistry (strand), ethylene content: 50%, diene content: 9.5% of a non-oil-filled resin, 10 parts by mass of a sea de lin (HYDRIN) (registered trademark) T3108 manufactured by GECO (Japanese rayleigh (ZEON) (Stroke)), 20 parts by mass.

Further, each of the components shown in table 1 below was first added to a banbury mixer to carry out mastication of 100 parts by mass of the total amount of each rubber.

TABLE 1

Composition of the components	Parts by mass
		Filler I	10
Filler II	20
		Acid absorbing agent	1

The components in Table 1 are as follows. The mass parts in table 1 are 100 mass parts with respect to the total amount of rubber.

Filler I: carbon black HAF [ Hitt (Seast) (registered trademark) 3 manufactured by conductive carbon black, donghai carbon (Strand) ]

Filler II: wheatstone (registered trademark) BF-100 manufactured by heavy calcium carbonate [ Bai Dangai (Strand) ]

Acid absorber: hydrotalcite like compound (DHT-4A (registered trademark) -2 manufactured by the Co-ordination chemical industry (Strand))

Then, the foaming component and the crosslinking component shown in table 2 were added, and further kneaded to prepare a rubber composition.

TABLE 2

Composition of the components	Parts by mass
		Oil-treated sulfur	1
4,4' -dithiodimorpholine	0.5
		Crosslinking accelerator DM	2
Crosslinking accelerator TS	1
		Foaming agent	4
Foaming auxiliary agent	4

The components in table 2 are as follows. The mass parts in table 2 are 100 mass parts with respect to the total amount of rubber.

Oil treatment sulfur: the oil content was 5% by mass and the sulfur content as an active ingredient was 95% by mass

4,4' -dithiodimorpholine: barnok (VULNOC) R manufactured by large interior emerging chemistry (strand)

Crosslinking accelerator DM: di-2-benzothiazolyl disulfide (trade name Sunsine) MBTS manufactured by Shandong province county chemical (Shandong Shanxian Chemical Co. Ltd.)

Crosslinking accelerator TS: tetramethyl thiuram monosulfide [ Su Xile (SANCELER) (registered trademark) TS manufactured by Sanxin chemical industry (Co., ltd.) ]

Foaming agent: ADCA (trade name of Vinefu (vinyl for) AC #3 manufactured by Yong He Chemie industry (Co., ltd.))

Foaming auxiliary agent: urea foaming aid (product name of siraite (celpaste) 101 manufactured by immortalization chemical industry (strand))

The amount of sulfur as an active ingredient was 0.95 parts by mass based on 100 parts by mass of the total amount of rubber.

(conductive roller)

The prepared rubber composition was fed to an extrusion molding machine, extruded into a tube having an outer diameter of 10mm and an inner diameter of 3.0mm, cut into a predetermined length, and mounted on a temporary shaft for crosslinking having an outer diameter of 2.2 mm.

Then, the tube was foamed and the rubber was crosslinked by the gas generated by the decomposition of the foaming agent by pressurizing and heating the tube in a vulcanizing tank with pressurized steam at 120℃for 10 minutes and then at 160℃for 20 minutes.

Then, the cylindrical body was reattached to the shaft 4 having an outer diameter Φ5mm, to which the conductive thermosetting adhesive was applied, and the shaft 4 was electrically bonded and mechanically fixed by being heated in an oven at 160 ℃ for 60 minutes to perform secondary crosslinking, and the thermosetting adhesive was cured.

After shaping both ends of the cylindrical body, the outer peripheral surface 5 was ground longitudinally using a cylindrical grinding plate, and the outer diameter was finished to a diameter of 12.5mm (tolerance ±0.1 mm) to form a roller body 2, and a conductive roller 1 was manufactured.

Example 2

A rubber composition was prepared in the same manner as in example 1 except that the amount of 4,4' -dithiodimorpholine was set to 0.8 parts by mass, and a conductive roller 1 was produced.

Example 3

A rubber composition was prepared in the same manner as in example 1 except that the amount of the oil-treated sulfur was 1.2 parts by mass, and a conductive roller 1 was produced.

The amount of sulfur as an active ingredient was 1.14 parts by mass relative to 100 parts by mass of the total amount of rubber.

Example 4

A rubber composition was prepared in the same manner as in example 1 except that the amount of oil-treated sulfur was 1.2 parts by mass and the amount of 4,4' -dithiodimorpholine was 1 part by mass, and a conductive roller 1 was produced.

Example 5

A rubber composition was produced in the same manner as in example 1, except that the amount of NBR as the rubber was 30 parts by mass, the amount of SBR was 40 parts by mass, the amount of oil-treated sulfur was 1.2 parts by mass, and the amount of 4,4' -dithiodimorpholine was 1 part by mass, and a conductive roller 1 was produced.

Example 6

A rubber composition was produced in the same manner as in example 1, except that the amount of NBR as the rubber was 30 parts by mass, the amount of EPDM was 20 parts by mass, the amount of oil-treated sulfur was 1.2 parts by mass, and the amount of 4,4' -dithiodimorpholine was 1 part by mass, and a conductive roller 1 was produced.

Comparative example 1

A rubber composition was prepared in the same manner as in example 1 except that the amount of the oil-treated sulfur was 0.5 part by mass and the amount of 4,4' -dithiodimorpholine was 3 parts by mass, and a conductive roller 1 was produced.

The amount of sulfur as an active ingredient was 0.48 parts by mass relative to 100 parts by mass of the total amount of rubber.

Comparative example 2

A rubber composition was prepared in the same manner as in example 1 except that the amount of 4,4' -dithiodimorpholine was set to 0.3 parts by mass, and a conductive roller 1 was produced.

Comparative example 3

A rubber composition was prepared in the same manner as in example 1 except that the amount of oil-treated sulfur was 1.3 parts by mass and the amount of 4,4' -dithiodimorpholine was 1 part by mass, and a conductive roller 1 was produced.

The amount of sulfur as an active ingredient was 1.24 parts by mass relative to 100 parts by mass of the total amount of rubber.

Comparative example 4

A rubber composition was prepared in the same manner as in example 1 except that the amount of 4,4' -dithiodimorpholine was 2 parts by mass, and a conductive roller 1 was produced.

Comparative example 5

A rubber composition was prepared in the same manner as in example 1 except that the amount of the oil-treated sulfur was 0.8 part by mass and the amount of 4,4' -dithiodimorpholine was 1 part by mass, and a conductive roller 1 was produced.

The amount of sulfur as an active ingredient was 0.76 parts by mass relative to 100 parts by mass of the total amount of rubber.

Comparative example 6

A rubber composition was prepared in the same manner as in example 1 except that the amount of oil-treated sulfur was 0.32 part by mass and the amount of 4,4' -dithiodimorpholine was 0.4 part by mass, and a conductive roller 1 was produced.

The amount of sulfur as an active ingredient was 0.3 parts by mass relative to 100 parts by mass of the total amount of rubber.

Comparative example 7

A rubber composition was prepared in the same manner as in example 1 except that the amount of the oil-treated sulfur was 2.1 parts by mass and the amount of 4,4' -dithiodimorpholine was 0.3 parts by mass, and a conductive roller 1 was produced.

The amount of sulfur as an active ingredient was 2 parts by mass relative to 100 parts by mass of the total amount of rubber.

Roll resistance value placement variation evaluation

The roller resistance value R (Ω) of the conductive roller 1 produced in the examples and comparative examples was measured in a normal temperature and normal humidity environment at a temperature of 23℃and a relative humidity of 55% as an initial value R of the roller resistance value according to the measurement method described above ₀ 。

Then, after the conductive roller 1 was left to stand in a high-temperature and high-humidity environment at a temperature of 60℃and a relative humidity of 85% for 3 days, the roller resistance value was measured again in a normal-temperature and normal-humidity environment at a temperature of 23℃and a relative humidity of 55%, and the roller resistance value R after the standing was obtained ₁ 。

Then, find the log R of the usual log value of the initial value of the roller resistance value ₀ Log R, a common log value of the resistance of the roller after placement ₁ As a roll resistance value, a roll displacement value Δlog r was used, and the magnitude of the roll displacement was evaluated according to the following criteria.

O: Δlog r is 0.1 or less.

X: Δlog r exceeds 0.1.

The results are shown in tables 3 and 4.

TABLE 3

TABLE 4

From the results of examples 1 to 6 and comparative examples 1 to 7 in tables 3 and 4, it is apparent that the use of sulfur in an amount of 0.8 to 1.2 parts by mass and 4,4' -dithiodimorpholine in an amount of 0.5 to 1 part by mass in combination with respect to 100 parts by mass of the total amount of rubber as a crosslinking agent can reduce the variation in the roll resistance value of the conductive roll including the roll body without reducing the degree of freedom in selecting the materials of the rubber composition forming the roll body.

Claims

1. A rubber composition for forming a roller body of a conductive roller, and comprising: a rubber containing a diene rubber, an ethylene propylene rubber, and an ion conductive rubber; and a crosslinking component for crosslinking the rubber, wherein the crosslinking component contains sulfur as an active ingredient in an amount of 0.8 to 1.2 parts by mass relative to 100 parts by mass of the total amount of the rubber and 4,4' -dithiodimorpholine in an amount of 0.5 to 1 part by mass relative to 100 parts by mass of the total amount of the rubber, and the ion-conductive rubber is an epichlorohydrin rubber or a polyether rubber.

2. The rubber composition according to claim 1, further comprising azodicarbonamide as a foaming agent in a proportion of 0.5 parts by mass or more and 5 parts by mass or less relative to 100 parts by mass of the total amount of the rubber.

3. The rubber composition according to claim 1 or 2, wherein the diene rubber is at least one selected from the group consisting of acrylonitrile butadiene rubber and styrene butadiene rubber.

4. The rubber composition according to claim 1 or 2, wherein the ethylene propylene-based rubber is an ethylene propylene diene rubber.

5. The rubber composition according to claim 1 or 2, wherein the ion-conductive rubber is an epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer.

6. The rubber composition according to claim 1 or 2, wherein the sulfur as an active ingredient is sulfur derived from oil treatment.

7. A conductive roller comprising a roller body of the crosslinked product of the rubber composition according to any one of claims 1 to 6.

8. The conductive roller according to claim 7, wherein the roller body contains a porous body of the crosslinked material.

9. An image forming apparatus comprising the conductive roller according to claim 7 or 8.