CN113201174A

CN113201174A - Rubber composition, conductive roller, and image forming apparatus

Info

Publication number: CN113201174A
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: 2021-08-03
Anticipated expiration: 2040-12-11
Also published as: CN113201174B; JP2021124120A; JP7402413B2

Abstract

The invention provides a rubber composition capable of forming a roller body of a conductive roller with small roll resistance value placement variation, a conductive roller comprising the roller body formed by using the rubber composition, and an image forming device comprising the conductive roller. A rubber composition comprising a diene rubber, an ethylene-propylene rubber and an ionic-conductive rubber, wherein 0.8 to 1.2 parts by mass of sulfur and 0.5 to 1 part by mass of 4,4' -dithiodimorpholine are blended per 100 parts by mass of the total amount of the rubbers. 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, a conductive roller including a roller body formed by foaming and crosslinking a rubber composition having conductivity is sometimes used (see patent documents 1 and 2). However, the conventional conductive roller has a problem that the roll resistance value is largely fluctuated.

[ Prior art documents ]

[ patent document ]

[ patent document 1] Japanese patent laid-open No. 2015-034878

[ patent document 2] Japanese patent laid-open No. 2014-119546

Disclosure of Invention

[ problems 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 roll resistance value placement variation.

Further, an 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 for solving 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, the crosslinking component containing 0.8 part by mass or more and 1.2 parts by mass or less of sulfur relative to 100 parts by mass of the total amount of the rubber and 0.5 part by mass or more and 1 part by mass or less of 4,4' -dithiodimorpholine relative to 100 parts by mass of the total amount of the rubber.

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

Further, the present invention is 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 with little variation in the roll resistance value 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 the conductive roller of the present invention.

Fig. 2 is a diagram illustrating a method of measuring a roller resistance value of the conductive roller.

[ description of symbols ]

1: conductive roller

2: roller body

3: through hole

4: shaft

5: peripheral surface

6: aluminum roller

7: peripheral surface

8: direct current power supply

9: resistance (RC)

10: measuring circuit

F: load(s)

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, the crosslinking component containing 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 before the above-described production is not used and stored (left to stand) for a long period of time, aged deterioration such as oxidation deterioration occurs, and a phenomenon in which the roller resistance value increases is observed.

This phenomenon is referred to as roll resistance variation, and if the roll resistance value exceeds the upper limit of the specification value of the conductive roller due to the roll resistance variation, a problem may occur in an image formed by an image forming apparatus incorporating the conductive roller.

In particular, in recent years, further increase in the lifetime of an image forming apparatus has been demanded, and therefore, in order to extend the product lifetime of the image forming apparatus, it is also demanded that the standing variation in the roller resistance value is small for a conductive roller stored for replacement.

As a general countermeasure for reducing the standing variation of the roller resistance value, it is considered to blend an antioxidant in the rubber composition or to increase the proportion of rubber which is less susceptible to oxidation deterioration.

However, these measures have a problem that the degree of freedom in selecting the material of the rubber composition is limited.

In contrast, according to the present invention, by using sulfur and 4,4' -dithiodimorpholine as a crosslinking agent in the prescribed ratio with respect to the rubber, the variation in the roll resistance value without reducing the degree of freedom in selecting the material of the rubber composition can be reduced.

The above-mentioned case is 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 ionic conductive rubber are used in combination as described above.

Diene rubber

The diene rubber functions to impart excellent properties as a rubber to a roll body, that is, properties of softness, small compression permanent strain, and resistance to collapse.

Since the diene rubber contains a double bond in the main chain and has sulfur-crosslinking properties, various diene rubbers capable of being crosslinked by a system in which sulfur and 4,4' -dithiodimorpholine are used in combination can be used as described above.

Examples of the diene rubber include natural rubber, Isoprene Rubber (IR), acrylonitrile butadiene rubber (NBR), Styrene Butadiene Rubber (SBR), Butadiene Rubber (BR), and Chloroprene Rubber (CR).

Among them, the diene rubber is preferably a combination of two types, NBR and SBR.

(NBR)

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

The NBR may be an oil-filled NBR in which an extender oil is added to adjust flexibility, or an oil-unfilled NBR in which an extender oil that may be a bleeding substance is not contained, in order to prevent contamination of the photoreceptor and the like.

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

(SBR)

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

As the SBR, any of high styrene type, medium styrene type, and low styrene type SBRs classified according to the styrene content can be used.

Further, as the SBR, there are oil-filled SBR in which flexibility is adjusted by adding an extender oil, and non-oil-filled SBR in which no extender oil that may be a bleeding substance is contained, but in the present invention, it is still preferable to use non-oil-filled SBR in which an extender oil that may be a bleeding substance is not contained, in order to prevent contamination of the photoreceptor and the like.

One or two or more of these SBRs can be used.

Ethylene propylene rubber

Since the ethylene propylene rubber is excellent in ozone resistance and weather resistance, the ethylene propylene rubber is used in combination with the roller body to suppress oxidative deterioration of the roller body and further reduce the variation in the roll resistance value during the standing.

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

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

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

Examples of the diene include Ethylidene Norbornene (ENB), dicyclopentadiene (DCPD), and the like.

Further, as the EPDM, there are oil-filled EPDM to which an extender oil is added to adjust flexibility and non-oil-filled EPDM to which the extender oil is not added, but in the present invention, it is still preferable to use non-oil-filled EPDM which does not contain an extender oil that may be a bleeding substance in order to prevent contamination of the photoreceptor and the like.

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

Ionic conductive rubber

The ion conductive rubber functions to impart appropriate ion conductivity to a rubber composition and to adjust the roller resistance value of the conductive rubber of a roller body including a crosslinked product of the rubber composition to a range suitable for assembly into an image forming apparatus.

The conductive roller of the present invention can be incorporated in 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.

Examples of the epichlorohydrin rubber include epichlorohydrin homopolymers, epichlorohydrin-ethylene oxide dipolymers (ECO), epichlorohydrin-propylene oxide dipolymers, epichlorohydrin-allyl glycidyl ether dipolymers, epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymers (GECO), epichlorohydrin-propylene oxide-allyl glycidyl ether terpolymers, epichlorohydrin-ethylene oxide-propylene oxide-allyl glycidyl ether tetrapolymers, and epichlorohydrin-ethylene oxide-propylene oxide-allyl glycidyl ether tetrapolymers.

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

Among these, preferred are copolymers containing ethylene oxide, in particular, GECO which has sulfur-crosslinking properties and can be crosslinked by a combined system of sulfur and 4,4' -dithiodimorpholine.

The ethylene oxide content in the 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 acts to reduce the 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-described effect cannot be sufficiently obtained, and therefore 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 motion of the molecular chain is inhibited, so that the roll resistance value tends to be increased on the contrary.

Further, the roller body after crosslinking becomes too hard, or the viscosity of the rubber composition before crosslinking at the time of heating and melting increases, and the processability or foamability of the rubber composition may be lowered.

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

Allyl glycidyl ether functions to secure a free volume as a side chain, thereby playing a role of suppressing crystallization of ethylene oxide and reducing a roll resistance value.

However, if the allyl glycidyl ether content is less than the above range, the above-described effect cannot be sufficiently obtained, and therefore 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 the GECO becomes too high, and the segmental motion of the molecular chain is inhibited, and the roll resistance value tends to be increased.

The epichlorohydrin content in the GECO is the remainder 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, preferably 69.5 mol% or less, particularly 60 mol% or less.

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

In the present invention, any of the above-mentioned GECOs may be used.

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

Other rubbers

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

Examples of the rubber having polarity include Acrylic rubber (ACM), CR in the above-mentioned diene rubber, and the like.

In addition, since the medium ACM has high heat resistance, by using the ACM in combination, oxidation deterioration of the roller body can be further effectively suppressed, and the variation in the roll resistance value in the standing position can be further reduced.

(ACM)

As the ACM, various ACMs synthesized by copolymerizing a halogen-containing monomer such as acrylonitrile or 2-chloroethyl vinyl ether, 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 chlorobutadiene, and is classified into sulfur-modified type and non-sulfur-modified type according to the kind of molecular weight modifier used at this time.

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

Further, the non-sulfur-modified CR is classified into, for example, a thiol-modified CR and a xanthane-modified CR.

Among them, the thiol-modified CR is synthesized in the same manner as the sulfur-modified CR, except that alkylthiols such as n-dodecylthiol, t-dodecylthiol, and octylthiol are used as a molecular weight modifier.

Further, the xanthate-modified CR is synthesized in the same manner as the sulfur-modified CR, except that an alkylxanthate compound is used as a molecular weight modifier.

CR is classified into a slow crystallization rate type, a medium crystallization rate type, and a fast crystallization rate type based on its crystallization rate.

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

Further, as CR, a copolymer of chloroprene and another copolymerization component may also be used.

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

Further, as CR, there are oil-filled CR in which filling oil is added to adjust flexibility and non-oil-filled CR in which filling oil is not added, but in the present invention, it is still preferable to use non-oil-filled CR not containing filling oil that may become a bleeding substance in order to prevent contamination of the photoreceptor.

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

Proportion of rubber

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, preferably 30 parts by mass or less, particularly 25 parts by mass or less, in 100 parts by mass of the total amount of the rubber.

When the ratio of the ionic-conductive rubber is less than the above range or exceeds the above range, the roller resistance value of the conductive roller may not be adjusted to a range suitable for incorporation into the image forming apparatus in any case.

When the proportion of the ion conductive rubber exceeds the above range, the proportion of the diene rubber or the ethylene propylene rubber is relatively small, and the effect of the combination of these rubbers may not be sufficiently obtained.

In contrast, by setting the ratio of the ionic conductive rubber to the above range, the roller resistance value of the conductive roller can be adjusted to a range suitable for incorporation into the image forming apparatus.

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

The proportion of the ethylene-propylene rubber is 1 part by mass or more, preferably 5 parts by mass or more, particularly 10 parts by mass or more, and 30 parts by mass or less, preferably 25 parts by mass or less, particularly 20 parts by mass or less, per 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 effects of suppressing the oxidation degradation of the roller body and further reducing the variation in the roll resistance value due to the blending of the ethylene-propylene rubber may not be sufficiently obtained.

On the other hand, when the proportion of the ethylene-propylene rubber exceeds the above range, the proportion of the ion-conductive rubber or the diene rubber is relatively decreased, and the above-described effects by the combined use of these rubbers may not be sufficiently obtained.

On the other hand, by setting the ratio of the ethylene-propylene rubber within the above range, the roll body can be inhibited from being oxidized and deteriorated, and the roll resistance value can be further reduced from being left unchanged.

Further, the effects of the combined use of the ion conductive rubber and the diene rubber can be sufficiently exhibited.

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

The ratio 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 proportions of the ion-conductive rubber, the ethylene propylene rubber, and the other rubber are set to the predetermined values in the above ranges, the proportions of the NBR and/or the SBR may be set so that the total amount of the rubbers is 100 parts by mass.

[ crosslinking component ]

Crosslinking agent

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

The proportion of sulfur is limited to 0.8 to 1.2 parts by mass relative to 100 parts by mass of the total amount of the rubber.

The ratio of 4,4' -dithiodimorpholine is limited to 0.5 parts by mass or more and 1 part by mass or less with respect to 100 parts by mass of the total amount of the rubber.

These reasons are as described above.

That is, when either of the proportions of sulfur and 4,4' -dithiodimorpholine is outside the above range, the effect of using both crosslinking agents together cannot be obtained, and the variation in the roll resistance value as a result of standing is large.

On the other hand, by using both of the crosslinking agents at the predetermined ratio, the variation in the roll resistance value in the standing state can be reduced even if the ratio of the rubber to be compounded is arbitrarily changed.

That is, the roller body of the conductive roller with less variation in the roll resistance value can be formed without lowering the degree of freedom in selecting the material of the rubber composition.

(Sulfur)

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

As the sulfur, for example, one or more of powdered sulfur, which is 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, or the like, dispersed sulfur in which the powdered sulfur is treated with an organic dispersant or an inorganic dispersant for the purpose of improving dispersibility, or the like, precipitated sulfur, colloidal sulfur, insoluble sulfur, or the like can be used.

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

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

Even when the oil-treated sulfur contains different amounts of oil, the effect of the present invention can be exhibited by defining the total amount of the oil-treated sulfur so that the amount is in the above range in terms of the amount of sulfur as an active ingredient.

(4,4' -Didithiodimorpholine)

Specific examples of 4,4' -dithiodimorpholine include Barnock (VULNOC) (registered trademark) R manufactured by Dai-Neighurian Chemicals (Ltd.).

Crosslinking accelerator

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

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

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

(thiazole-based accelerator)

Examples of the thiazole 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 di-2-benzothiazolyl disulfide is particularly preferable.

(thiuram series accelerator)

The thiuram-based accelerator includes, for example, one or more of tetramethylthiuram monosulfide, tetramethylthiuram disulfide, tetraethylthiuram disulfide, tetrabutylthiuram disulfide, dipentamethylenethiuram tetrasulfide, and the like, and tetramethylthiuram monosulfide is particularly preferable.

Proportion of crosslinking Accelerator

In view of sufficiently exhibiting the 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 accelerator is preferably 0.3 parts by mass or more, and preferably 3 parts by mass or less, relative to 100 parts by mass of the total amount of the rubber.

[ foaming component ]

The roller main body may have either a non-porous structure or a porous structure, and in order to make the roller main body have a porous structure, it is preferable to mix a foaming component in the rubber composition and crosslink the rubber and foam the rubber before and after crosslinking.

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

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

Foaming agent

Examples of the blowing agent include: azodicarbonamide (ADCA), 4 '-oxybis (benzenesulfonyl hydrazide) (4,4' -oxybis (benzenesulfonyl hydrazide), OBSH), N-Dinitrosopentamethylenetetramine (DPT), and the like.

Particularly, ADCA is preferable as the blowing agent.

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

Foaming aid

As the foaming aid, various foaming aids which lower the decomposition temperature of the combined foaming agent and promote the decomposition thereof can be used as described above, and for example, urea (H) can be mentioned as the foaming aid combined with ADCA₂HCONH₂) Is a foaming aid.

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

[ others ]

Various additives may be further compounded in the rubber composition as required.

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

Among them, the acid-absorbing agent functions to trap chlorine in chlorine-based gas generated from epichlorohydrin rubber or CR at the time of crosslinking, and to suppress chlorine-based gas from remaining in a free state in the roller body, or to inhibit crosslinking or contamination of the photoreceptor due to chlorine-based gas.

As the acid acceptor, various substances which function as acid acceptors can be used, and among them, hydrotalcite and magarat (magaraat) having excellent dispersibility are preferable, and hydrotalcite is particularly preferable.

Further, 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 the photoreceptor or the like can be more reliably prevented.

The proportion of the acid scavenger is preferably 0.2 parts by mass or more, and preferably 5 parts by mass or less, relative to 100 parts by mass of the total amount of the rubber.

The inorganic filler functions to improve mechanical strength of the roll body and the like, or to reduce the blending unit price of rubber 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 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 preferably 25 parts by mass or less, relative to 100 parts by mass of the total amount of the rubber.

Further, by using conductive carbon black as a filler, electronic conductivity can be imparted to the roller body.

As the conductive carbon black, High abrasion resistance carbon black (HAF) is preferable.

Since the HAF is uniformly dispersed in the rubber composition, the roller body can be provided with uniform electronic conductivity as much as possible.

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

Further, various additives such as a crosslinking aid, a deterioration inhibitor, a scorch retarder, a plasticizer, a lubricant, a pigment, an antistatic agent, a flame retardant, a neutralizer, a nucleating agent, and a co-crosslinking agent may be blended at an arbitrary ratio as the additive.

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

First, a rubber composition is obtained by blending a rubber at a predetermined ratio, kneading the rubber, adding various additives other than a foaming component and a crosslinking component, and kneading the kneaded mixture, and finally adding the foaming component and the crosslinking component.

The kneading may be carried out by, for example, a kneader, a Banbury mixer, an extruder, or the like.

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 above example includes a roller body 2, the roller body 2 is formed in a porous single-layer cylindrical shape including a crosslinked product of a rubber composition containing the above components, 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, an aluminum alloy, or stainless steel.

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

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

Measurement of roll resistance value

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

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

Further, a direct current power supply 8 and a resistor 9 are connected in series between the shaft 4 of the conductive roller 1 and the aluminum drum 6 to constitute 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 r of the resistor 9 is set to 100 Ω.

Then, a load F of 4.9N (≈ 500gf) is applied to both end portions of the shaft 4, and the aluminum drum 6 is rotated at 30rpm in a state where the roller body 2 is pressed against the aluminum drum 6.

While the rotation is continued, an applied voltage E of 1000V dc is applied from the dc power supply 8 between the conductive roller 1 and the aluminum drum 6, and a detection voltage V applied to the resistor 9 is measured 30 seconds later.

From 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 then the result is obtained.

Wherein one term of-r in the formula (i') may be regarded as minute, and therefore, the present invention utilizes a compound represented by the formula (i):

R＝r×E/V (i)

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

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

Production of conductive roller 1

In order to manufacture the conductive roller 1 of the present invention, first, the rubber composition containing the above components is extruded into a cylindrical shape by using an extruder, then cut into a predetermined length, pressurized and heated by pressurized steam in a vulcanizing tank, foamed and crosslinked.

Then, the foamed and crosslinked tubular body is heated in an oven or the like to be secondarily crosslinked, and then cooled, and further ground to have a predetermined outer diameter to form the roller body 2.

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

Among them, it is preferable that after the cutting, the secondary crosslinking and the polishing are performed in a state where the shaft 4 is inserted into the through hole 3.

This can suppress warpage, deformation, and the like of the cylindrical body due to expansion and contraction during secondary crosslinking.

Further, since the polishing is performed while rotating around the shaft 4, the workability of the polishing is improved and the run-out 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 secondary crosslinking via an adhesive having conductivity, particularly a thermosetting adhesive having conductivity, and then secondary crosslinking is performed, or a shaft having an outer diameter larger than the inner diameter of the through hole 3 may be pressed into 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 and mechanically fixed to the roller body 2.

In addition, in the latter case, the electrical bonding and the mechanical fixing are completed simultaneously with the press-fitting.

As described above, the shaft 4 and the roller body 2 may be electrically and mechanically fixed by the two methods.

Image forming apparatus

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

As the image forming apparatus of the present invention, there are mentioned: various image forming apparatuses using electrophotography, such as laser printers, electrostatic copiers, plain paper facsimile apparatuses, and multi-functional machines thereof.

[ examples ]

The present invention will be further described below based on 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, NBR [ JSR (registered trademark) N250SL manufactured by JSR (stock), low-nitrile NBR, acrylonitrile content 20%, non-oil-extended ]40 parts by mass, SBR1502 manufactured by SBR [ sumitomo chemical (stock), styrene content 23.5%, non-oil-extended ]30 parts by mass, EPDM 505A manufactured by EPDM [ eprene (registered trademark) EPDM manufactured by sumitomo chemical (stock), ethylene content: 50%, diene content: 9.5%, 10 parts by mass of a non-oil-extended oil, and 20 parts by mass of Hederin (HYDRIN) (registered trademark) T3108 manufactured by GECO [ Nippon Rukusho (ZEON) (Strand).

Then, the ingredients shown in table 1 below were first added and kneaded while masticating 100 parts by mass of the total amount of each rubber using a banbury mixer.

[ Table 1]

Composition (I)	Mass portion of
		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 mass parts per 100 mass parts of the total amount of the rubber.

Filler I: carbon black HAF [ conductive carbon black, Seast (registered trademark) 3 made of east China sea carbon (stock) ]

And (3) a filler II: ground calcium carbonate [ Whiton (registered trademark) BF-100 manufactured by Baishi calcium (stock) ]

Acid-absorbing agent: hydrotalcite (DHT-4A (registered trademark) -2 manufactured by Kyowa chemical industry (Strand)

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

[ Table 2]

Composition (I)	Mass portion of
		Oil treatment sulfur	1
4,4' -dithiodimorpholine	0.5
		Crosslinking accelerator DM	2
Crosslinking accelerator TS	1
		Foaming agent	4
Foaming aid	4

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

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

4,4' -dithiodimorpholine: barronock (VULNOC) R made by Dai Innovation Chemicals (Strand)

Crosslinking accelerator DM: di-2-benzothiazyl disulfide [ Suxin (SUNSINE) MBTS manufactured by Shandong province Single county Chemical (Shandong Shanxian Chemical Co. Ltd.) ]

Crosslinking accelerator TS: tetramethylthiuram monosulfide [ Suncelle (SANCELLER) (registered trademark) TS manufactured by Sanxin chemical industries (Ltd.) ]

Foaming agent: ADCA [ Vinyfo AC #3, trade name of Yonghe chemical industry (Strand Co.) ]

Foaming auxiliary agent: urea foaming aid [ Seapate (cellpate) 101, trade name of Yonghe chemical industry (Strand) ]

The amount of sulfur as an active ingredient was 0.95 part by mass with respect to 100 parts by mass of the total amount of rubber.

(conductive roll)

The prepared rubber composition was supplied to an extrusion molding machine and extrusion-molded into a cylindrical shape having an outer diameter of 10mm and an inner diameter of 3.0mm, and then cut into a predetermined length and attached to a temporary shaft for crosslinking having an outer diameter of 2.2 mm.

Then, the inside of the vulcanizing tank was pressurized and heated with pressurized steam at 120 ℃ for 10 minutes and then at 160 ℃ for 20 minutes, and the tubular body was foamed with the gas generated by decomposition of the foaming agent to crosslink the rubber.

Then, the cylindrical body was remounted on the shaft 4 having an outer diameter of 5mm and coated with a conductive thermosetting adhesive on the outer peripheral surface thereof, and heated in an oven at 160 ℃ for 60 minutes to perform secondary crosslinking, and the thermosetting adhesive was cured, electrically bonded to the shaft 4, and mechanically fixed.

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

EXAMPLE 2

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

EXAMPLE 3

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

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 and a conductive roller 1 was manufactured 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.

EXAMPLE 5

A rubber composition was prepared and a conductive roller 1 was manufactured in the same manner as in example 1, except that the amount of NBR as a 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.

EXAMPLE 6

A rubber composition was prepared and a conductive roller 1 was manufactured in the same manner as in example 1, except that the amount of NBR as a 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.

Comparative example 1

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

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 and a conductive roller 1 was manufactured in the same manner as in example 1, except that the amount of 4,4' -dithiodimorpholine was changed to 0.3 parts by mass.

Comparative example 3

A rubber composition was prepared and a conductive roller 1 was manufactured 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.

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 and a conductive roller 1 was manufactured in the same manner as in example 1, except that the amount of 4,4' -dithiodimorpholine was changed to 2 parts by mass.

Comparative example 5

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

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 and a conductive roller 1 was manufactured in the same manner as in example 1, except that the amount of oil-treated sulfur was 0.32 parts by mass and the amount of 4,4' -dithiodimorpholine was 0.4 parts by mass.

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

Comparative example 7

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

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

Evaluation of Placement Change in roll resistance value

The conductive roller 1 produced in the examples and comparative examples was measured as the initial value R of the roller resistance value by the measurement method described above, as the roller resistance value R (Ω) in the normal-temperature and normal-humidity environment at 23 ℃ and 55% relative humidity₀。

Then, 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, and then 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% as the roller resistance value R after the left to stand₁。

Then, a common logarithmic value logR of an initial value of the roll resistance value is obtained₀logR, which is a common logarithm of the resistance value of the roll after placement₁The difference in the values of (a) and (b) was used as the roll resistance value set fluctuation value Δ logR, and the magnitude of the set fluctuation was evaluated according to the following criteria.

O: Δ logR is 0.1 or less.

X: Δ logR exceeds 0.1.

The results are shown in tables 3 and 4.

[ Table 3]

[ Table 4]

As is clear from the results of examples 1 to 6 and comparative examples 1 to 7 in tables 3 and 4, by using 0.8 to 1.2 parts by mass of sulfur and 0.5 to 1 part by mass of 4,4' -dithiodimorpholine as a crosslinking agent in combination with 100 parts by mass of the total amount of rubber, the variation in the placement of the roller resistance value of the conductive roller including the roller body can be reduced without reducing the degree of freedom in selecting the material of the rubber composition forming the roller body.

Claims

1. A rubber composition for forming a roller body of a conductive roller, and the rubber composition comprising: a rubber containing a diene rubber, an ethylene-propylene rubber and an ion-conductive rubber; and a crosslinking component for crosslinking the rubber, the crosslinking component containing 0.8 part by mass or more and 1.2 parts by mass or less of sulfur relative to 100 parts by mass of the total amount of the rubber and 0.5 part by mass or more and 1 part by mass or less of 4,4' -dithiodimorpholine relative to 100 parts by mass of the total amount of the 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 with respect 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 any one of claims 1 to 3, wherein the ethylene propylene-based rubber is an ethylene propylene diene rubber.

5. The rubber composition according to any one of claims 1 to 4, wherein the ionic conductive rubber is an epichlorohydrin-ethylene oxide-allyl glycidyl ether terpolymer.

6. The rubber composition of any one of claims 1-5, wherein the sulfur is oil-treated sulfur.

7. A conductive roller comprising a roller body of a 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 comprises a porous body of the crosslinked substance.

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