JP5437361B2 - Rubber composition for paper feed roll and paper feed roll - Google Patents

Description

  The present invention relates to a rubber composition for a paper feed roll (hereinafter sometimes simply referred to as “rubber composition”) and a paper feed roll provided with a rubber layer made of the rubber composition.

  Paper feed rolls used in OA equipment such as electrostatic copying machines, laser printers, facsimiles, or automatic deposit payment machines include natural rubber (NR), urethane rubber, ethylene propylene-diene copolymer (hereinafter “ EPDM ”), polynorbornene rubber, silicone rubber, chlorinated polyethylene rubber or the like is used. Among them, EPDM is often used because it is inexpensive and has excellent weather resistance. Such paper feed rolls are required to have a coefficient of friction retention, and the requirements are becoming increasingly sophisticated as the types of paper are diversified. As a technique developed so far, the technique of patent documents 1-6 is mentioned, for example.

  Patent Document 1 describes a rubber composition containing EPDM rubber as a main component, having a JISA hardness in a range of 20 to 30 degrees, and a loss tangent tan δ in a range of 0.02 to 0.035.

  Patent Document 2 describes a rubber roller obtained by vulcanizing and molding a rubber composition containing an oil-extended EPDM rubber. In this rubber composition, no filler is blended, or the blending amount of the filler is 15 parts by weight or less with respect to 100 parts by weight of the rubber component of the rubber composition.

  Patent Document 3 describes a rubber roller obtained by vulcanizing and molding a rubber composition containing EPDM and added with a softening agent. In this rubber roller, the ratio of the aromatic organic compound contained in the softening agent is 1 to 20% by weight. Patent Document 3 discloses a ratio tan δ (0 ° C.) / Tan δ (50 ° C.) of a loss tangent tan δ (0 ° C.) at 0 ° C. and a loss tangent tan δ (50 ° C.) at 50 ° C. Is preferably in the range of 0.7 to 2.0.

  Patent Document 4 describes a rubber material for a paper sheet transport member having a dynamic elastic modulus E ′ of 0.9 to 1.9 MPa under conditions of a temperature of 25 ° C., a frequency of 15 Hz, and an elongation rate of 15 ± 2%. Has been.

  Patent Document 5 describes a rubber composition for a paper feed roller whose main component is an EP rubber having an average molecular weight of 300,000 or more and an ethylene content of 60 to 80% by weight. In this rubber composition, the softener is blended in the range of 90 to 190 parts by weight with respect to 100 parts by weight of the EP rubber, and the blended amount of the elemental sulfur is suppressed to 0.2% by weight or less. ing.

Patent Document 6 discloses a low-hardness rubber composition obtained by blending a low-molecular material and a thermoplastic high-molecular material into a rubber composition mainly composed of oil-extended EPDM or mixed rubber of oil-extended EPDM and non-oil-extended EPDM. Things are listed. This Patent Document 6 describes the following. This low molecular weight material has a viscosity of 5 × 10 ⁵ centipoise or less at 100 ° C. The difference in solubility parameter value between the low molecular weight material and the thermoplastic polymer material, and the difference in solubility parameter value between the oil-extended EPDM extended oil and the thermoplastic polymer material are all 3 or less. The difference in solubility parameter value between the low molecular weight material and the rubber component of the rubber composition, and the difference in solubility parameter value between the oil-extended EPDM extended oil and the rubber component of the rubber composition are all 4 or less. The blending amount of the low molecular weight material and the oil-extended EPDM extended oil is 10 to 200 parts by weight with respect to 100 parts by weight of the rubber component in the rubber composition. The compounding quantity of a thermoplastic polymer material is 2-40 weight part with respect to 100 weight part of rubber components in a rubber composition.

JP-A-10-279115 JP 09-254275 A Japanese Patent Laid-Open No. 08-244139 JP 2001-171851 A Japanese Patent Laid-Open No. 07-242799 Japanese Patent Laid-Open No. 10-194512

  However, with the techniques described in Patent Documents 1 to 6, it is difficult to provide a paper feed roll having excellent friction coefficient retention. For example, if a low molecular weight material is used as in the technique described in Patent Document 6, it is possible to expect improvement in the retention coefficient of the paper feed roll. However, according to the study of the present inventor, when a thermoplastic polymer is blended with a rubber composition for the purpose of retaining a softener and a low molecular weight material as in the technique described in Patent Document 6, the glass transition point is increased. For this reason, it is difficult to provide a paper feed roll having excellent friction coefficient retention.

  The present invention has been made in view of the above points, and an object of the present invention is to provide a paper feed roll having excellent friction coefficient retention, and thus to realize long-term stabilization of the paper feed roll paper feed performance. It is to provide a rubber composition for a paper feed roll that is possible.

  The rubber composition according to the present invention contains at least a polymer component, and has a maximum value of loss tangent tan δ (hereinafter referred to as “tan δ max”) of 1.1 or less in the temperature dispersion measurement of dynamic viscoelasticity. The temperature at which the tangent tan δ is maximized (hereinafter referred to as “Tmax”) is −40 ° C. or lower, and the dynamic elastic modulus E1 (22 ° C.) is 2.1 MPa or lower. The dynamic elastic modulus E1 (22 ° C.) is the dynamic elastic modulus E1 at a measurement temperature of 22 ° C.

  The polymer component is preferably composed mainly of EPDM. Here, “having EPDM as the main component” means that the polymer component contains 80% by mass or more of EPDM. EPDM preferably contains 60% by mass or more and 72% by mass or less of ethylene units.

  The rubber composition according to the present invention preferably contains 70 parts by weight or more and 150 parts by weight or less of a softening agent with respect to 100 parts by weight of the polymer component.

The softening agent is preferably at least one of a paraffinic petroleum-based blended oil and a hydrocarbon-based synthetic oil. The softener preferably has a kinematic viscosity at 40 ° C. of 10 mm ² / s to 500 mm ² / s. When using a paraffinic petroleum blended oil, a paraffinic petroleum blended oil having a kinematic viscosity at 40 ° C. of 10 mm ² / s to 110 mm ² / s is more preferable. Here, the kinematic viscosity of the softener at 40 ° C. is measured according to JIS K 2283 (crude oil and petroleum products—kinematic viscosity test method).

  The rubber composition according to the present invention preferably contains 1 part by mass or more and 6 parts by mass or less of sulfur as a crosslinking agent with respect to 100 parts by mass of the polymer component.

  The paper feed roll according to the present invention includes a rubber layer made of the rubber composition according to the present invention. Here, the paper feed roll can transport not only paper but also various sheet materials such as an OHP sheet and a plastic sheet.

  With the rubber composition according to the present invention, it is possible to provide a paper feed roll having excellent friction coefficient retention, and thus it is possible to achieve long-term stabilization of the paper feed conveyance performance of the paper feed roll.

It is a top view which shows one form of the paper feed roll which concerns on this invention. It is a figure explaining the measuring method of a friction coefficient. It is a graph which shows the relationship between tan-deltamax and Tmax in an Example and a comparative example. It is a graph which shows the relationship between the dynamic elastic modulus E1 (22 degreeC) and tan-deltamax in an Example and a comparative example. It is a graph which shows the relationship between the dynamic elastic modulus E1 (22 degreeC) and Tmax in an Example and a comparative example. It is the graph which investigated the relationship between temperature and loss tangent tan-delta.

  Below, it shows about the rubber composition and paper feeding roll which concern on this invention. In addition, this invention is not limited to the matter shown below.

<Rubber composition>
The rubber composition according to the present invention constitutes a rubber layer of a paper feed roll, has a tan δmax of 1.1 or less, a Tmax of −40 ° C. or less, and a dynamic viscoelasticity temperature dispersion measurement. The elastic modulus E1 (22 ° C.) is 2.1 MPa or less. Thereby, since the paper feed roll excellent in the retention property of the friction coefficient can be provided, the long-term stabilization of the paper feed conveyance performance of the paper feed roll can be realized. Here, “the paper feed roll has excellent friction coefficient retention” means that the paper feed roll maintains a predetermined coefficient of friction even after a predetermined number of sheets have been conveyed. To do.

  Conventionally, it has been known that the viscoelastic properties of rubber are important factors affecting the friction properties and wear resistance. However, conventionally, attention has been focused only on viscoelastic characteristics in a frequency region (1 to several hundred Hz) corresponding to one deformation per rotation of a paper feed roll in an OA device or the like. Control of viscoelastic properties in the frequency range of 1 to several hundred Hz in the temperature range where OA equipment is normally used has shown some effect in improving friction properties and wear resistance, but maintaining the friction coefficient Regarding sex, it was not possible to achieve a sufficient effect. Accordingly, the inventor has generated vibrations in a higher frequency region (several hundreds to several millions Hz) in addition to vibrations having a frequency corresponding to one deformation per one rotation of the roll. Therefore, we thought that the viscoelastic characteristics in this high frequency region might affect the retention of the friction coefficient. However, a normal viscoelasticity measuring machine cannot measure such viscoelastic characteristics in the high frequency region. Therefore, the concept of a known time-temperature conversion rule was applied, and viscoelastic properties in the high frequency region were substituted with viscoelastic properties in the low temperature region. As a result of the experiment, in the temperature dispersion measurement of dynamic viscoelasticity, tan δmax, which is a viscoelastic characteristic in a low temperature region, is 1.1 or less, Tmax is −40 ° C. or less, and a dynamic elastic modulus in a room temperature region. It has been found that if a rubber layer of a paper feed roll is produced using a rubber composition having an E1 (22 ° C.) of 2.1 MPa or less, a paper feed roll having excellent friction coefficient retention can be obtained.

  tan δmax is the maximum value of the graph showing the relationship between the loss tangent tan δ obtained by dynamic viscoelastic temperature dispersion measurement and temperature, and Tmax is the loss tangent tan δ obtained by dynamic viscoelastic temperature dispersion measurement. Is a temperature at which tan δ takes a maximum value (tan δmax). tan δmax is 1.1 or less, preferably 0.90 or less, and more preferably 0.77 or less. Tmax is −40 ° C. or lower, preferably −44 ° C. or lower, and more preferably −47 ° C. or lower.

  The dynamic elastic modulus E1 (22 ° C.) is a value of the dynamic elastic modulus E1 obtained when the measurement temperature is 22 ° C. obtained by temperature dispersion measurement of dynamic viscoelasticity. The dynamic elastic modulus E1 (22 ° C.) is 2.1 MPa or less, preferably 1.45 MPa or less, more preferably 1.15 MPa or less. The dynamic elastic modulus E1 (22 ° C.) is preferably 0.4 MPa or more. If the dynamic elastic modulus E1 (22 ° C.) is 2.1 MPa or less, a sufficient contact area can be secured between the paper feed roll and the sheet material, and a high friction coefficient suitable for the paper feed roll can be obtained. When the dynamic elastic modulus E1 (22 ° C.) exceeds 2.1 MPa, the contact area between the paper feed roll and the sheet material becomes small, and a sufficient friction coefficient cannot be ensured. Further, when the dynamic elastic modulus E1 (22 ° C.) is less than 0.4 MPa, the wear resistance of the rubber layer of the paper feed roll may be lowered.

The combination of tan δmax, Tmax and E1 (22 ° C.) is more preferably any of the following (1) to (6). (1) tan δmax is 0.90 or less, Tmax is −47 ° C. or less, E1 (22 ° C.) is 2.1 MPa or less. (2) tan δmax is 0.77 or less, Tmax is −44 ° C. or less, and E1 (22 ° C.) is 2.1 MPa or less. (3) tan δmax is 0.90 or less, Tmax is −40 ° C. or less, and E1 (22 ° C.) is 1.45 MPa or less. (4) tan δmax is 0.90 or less and Tmax is −40 ° C. or less. And E1 (22 ° C.) is 1.15 MPa or less. (5) tan δmax is 1.1 or less, Tmax is −44 ° C. or less, and E1 (22 ° C.) is 1.45 M. (6) tan δmax is 1.1 or less, Tmax is −44 ° C. or less, and E1 (22 ° C.) is 1.15 MPa or less.

  In order to realize such a rubber composition having dynamic viscoelasticity, the rubber composition according to the present invention preferably comprises the following composition.

<Polymer component>
The polymer component may be a rubber material, and preferably contains EPDM as a main component. The polymer component is a rubber material other than EPDM, such as natural rubber, isoprene rubber, butadiene rubber, butyl rubber, styrene butadiene rubber, polynorbornene rubber, butadiene-nitrile rubber, chloroprene rubber, halogenated butyl rubber, acrylic rubber, and epichlorohydrin. It may include at least one such as rubber. When EPDM is used as the polymer component, the EPDM may be non-oil-extended grade, oil-extended grade, or a mixture of non-oil-extended grade and oil-extended grade.

  In this invention, it is preferable that EPDM contains 60 mass% or more and 72 mass% or less of ethylene units. If the content of the ethylene unit is less than 60% by mass, the loss tangent tan δ in the temperature region (hereinafter referred to as “low temperature region”) in the vicinity of the glass transition point of the rubber composition including Tmax may increase. Therefore, there is a case where a paper feed roll having excellent friction coefficient retention cannot be provided. In addition, the wear resistance of the rubber layer of the paper feed roll may be reduced. On the other hand, when the content of the ethylene unit exceeds 72% by mass, it is difficult for the rubber composition to exhibit rubber elasticity, and it may be difficult to secure a friction coefficient necessary for the paper feed roll.

  The diene unit contained in EPDM is not particularly limited, and may be, for example, ethylidene norbornene, 1,4-hexadiene, dicyclopentadiene, etc., and is preferably ethylidene norbornene.

  In the present invention, the polymer component may contain only one type of EPDM, or may contain two or more types of EPDM. When the polymer component contains two or more types of EPDM, the ethylene unit content is evaluated as an average value calculated from the content ratio of various EPDMs. Specifically, the characteristic values of various EPDMs and the content ratio of the EPDMs Is evaluated as the sum of the products of That is, when two or more types of EPDM are used in combination, EPDM that satisfies the above characteristic value and EPDM that does not satisfy the above characteristic value may be mixed.

<Softener>
The softening agent is not particularly limited, but preferably has a kinematic viscosity at 40 ° C. of 10 mm ² / s to 500 mm ² / s. If this kinematic viscosity is less than 10 mm ² / s, the rubber composition may easily cause oil bleeding. On the other hand, when the kinematic viscosity exceeds 500 mm ² / s, there is a case where the loss tangent tan δ in the low temperature region including Tmax and the Tmax increase may be caused. It may not be provided.

The softening agent satisfying such kinematic viscosity is not particularly limited, but is not limited to paraffinic oil-based blended oil or hydrocarbon-based synthetic oil (for example, ethylene and α-olefin) having a small content of naphthene component and aromatic component. Are preferred. When using a paraffin-based petroleum-based blended oil, the kinematic viscosity is more preferably 10 mm ² / s to 110 mm ² / s. Further, when the extension oil is contained in the polymer component, the softening agent may be the extension oil contained in the polymer component.

  The rubber composition according to the present invention may contain only one kind of softening agent, or may contain two or more kinds of softening agents. When the rubber composition contains two or more kinds of softeners, the kinematic viscosity of the softener at 40 ° C. is evaluated as an average value calculated from the content ratio of the various softeners, specifically, the various softeners at 40 ° C. It is evaluated as the total value of the product of the kinematic viscosity and the content of the softener. That is, when two or more softeners are used in combination, a softener having a kinematic viscosity within the above range and a softener having a kinematic viscosity outside the above range may be mixed.

  Such a softening agent is preferably contained in an amount of 70 to 150 parts by mass with respect to 100 parts by mass of the polymer component. If the blending amount of the softening agent is less than 70 parts by mass, it is difficult to set the dynamic elastic modulus E1 (22 ° C.) of the rubber composition to 2.1 MPa or less, and an increase in Tmax may be caused. . Therefore, there is a case where a paper feed roll having a large coefficient of friction and excellent retainability cannot be provided. On the other hand, if the blending amount of the softening agent exceeds 150 parts by mass, the abrasion resistance of the rubber layer of the paper feed roll may be lowered. More preferably, the softening agent is contained in an amount of 80 to 140 parts by mass with respect to 100 parts by mass of the polymer component. When the extension oil is included in the polymer component, the mass of the extension oil is handled as the blending mass of the softener.

-Crosslinking agent-
Although a crosslinking agent is not specifically limited, Sulfur-type organic compounds, such as sulfur and tetraalkyl tyrium-disulfide, Metal compounds, such as magnesium oxide, an organic peroxide, or a resin crosslinking agent is mentioned. Among these, sulfur is used in that it can be obtained inexpensively and easily, a tan δmax is low, and a crosslinked chain having a structure of “—Sx— (x is an integer of 1 or more)” having excellent wear resistance can be formed. It is preferable to use it.

  Although the compounding quantity of a crosslinking agent is not specifically limited, When using sulfur, it is preferable that it is 1 mass part or more and 6 mass parts or less with respect to 100 mass parts of polymer components, if it is 1 mass part or more and 5 mass parts or less. More preferred. If the amount of sulfur is less than 1 part by mass, the abrasion resistance or compression set characteristics of the rubber layer of the paper feed roll may be reduced, and the crosslink density may be reduced, resulting in bleeding of the softener. On the other hand, if the amount of sulfur exceeds 6 parts by mass, sulfur may bloom.

-Vulcanization accelerator-
When the rubber composition according to the present invention contains sulfur as a crosslinking agent, the rubber composition preferably contains a vulcanization accelerator. The vulcanization accelerator is not particularly limited, and is a thiazole such as dibenzothiazyl disulfide, a sulfenamide such as N-cyclohexyl-2-benzothiazole sulfenamide, a thyrium such as tetramethyltylium disulfide, or dimethyl Any dithiocarbamate such as zinc dithiocarbamate may be used. These materials may be used alone, or two or more of these materials may be used in combination. The blending amount of the vulcanization accelerator is not particularly limited and may be set as appropriate.

-Vulcanization accelerator-
The rubber composition according to the present invention may contain a vulcanization acceleration aid. As the vulcanization accelerating aid, an appropriate one can be selected from known metal oxides such as zinc oxide, fatty acids such as stearic acid or oleic acid, or zinc stearate depending on the crosslinking system. The blending amount of the vulcanization acceleration aid is not particularly limited and may be set as appropriate.

-Filler-
If necessary, a filler can be added to the rubber composition according to the present invention. The filler is not particularly limited, and may be carbon black, silica, calcium carbonate, magnesium carbonate, aluminum hydroxide, clay, talc, diatomaceous earth, mica, wood chips, cork, straw, bamboo, metal, glass Or a fiber made of a polymer. These may be used alone or in combination. Thereby, the mechanical strength of the rubber layer of the paper feed roll can be improved. Among these, since carbon black and silica are excellent in the effect of reinforcing the rubber layer, it is preferable to use at least one of carbon black and silica when a filler is used.

  Although the compounding quantity of a filler is not specifically limited, It is preferable that it is 20 mass parts or less with respect to 100 mass parts of polymer components, and it is more preferable that it is 10 mass parts or less. When the blending amount of the filler exceeds 20 parts by mass, the loss tangent tan δ increases as compared with the same dynamic elastic modulus E1 (22 ° C.) and the blending amount of the filler of 20 parts by mass or less, and the friction coefficient. In some cases, it is not possible to provide a paper feed roll excellent in retentivity.

  As a method for blending the rubber composition according to the present invention, in order to lower the maximum value (tan δmax) of the loss tangent tan δ, a softener with a low kinematic viscosity is used, and EPDM having a high ethylene unit content is selected as a polymer component. It is considered effective to do. In order to lower the temperature (Tmax) when the loss tangent tan δ is maximized, it is considered effective to use a softener with a low kinematic viscosity and to increase the blending amount of the softener. Furthermore, in order to lower the dynamic elastic modulus E1 (22 ° C.), it is considered effective to increase the amount of the softening agent and to decrease the amount of the filler.

<Method for producing rubber composition>
The rubber composition according to the present invention comprises a predetermined amount of a polymer component, a softening agent, a crosslinking agent, a predetermined amount of a filler as required, other vulcanization accelerators, vulcanization acceleration assistants, and antiaging agents. An unvulcanized rubber composition can be obtained by kneading a composition comprising additives such as these, and vulcanized and molded under predetermined heating conditions. Examples of the vulcanization molding method for the rubber composition include extrusion molding and transfer molding. For example, by introducing an unvulcanized rubber composition into a predetermined transfer molding die and heating it at a temperature of 150 ° C. to 180 ° C. for about 5 to 30 minutes, It can be formed into a tube at the same time. The molded tube may be subjected to secondary vulcanization for about 30 to 180 minutes at a temperature of 150 ° C. to 180 ° C., if necessary. When secondary vulcanization is performed in this manner, low molecular components that easily bleed can be volatilized. Therefore, a thermoplastic polymer material for preventing bleeding as described in Patent Document 6 is added separately. It is not necessary. Thereafter, the molded rubber tube is polished to a desired outer diameter with, for example, a cylindrical polishing machine and cut to a desired length to obtain a crosslinked rubber composition having a shape suitable for a paper feed roll. I can do it.

<Paper feed roll>
The paper feed roll according to the present invention is configured such that an axial core is inserted into a rubber layer made of the rubber composition according to the present invention, or both are bonded with an adhesive. Of the configuration of the paper feed roll, the configuration other than the material of the rubber layer, for example, the shape of the paper feed roll (for example, cylindrical shape or D-shape), the surface processing method (for example, polishing, knurling, embossing, or uneven pattern) ), The thickness of the rubber layer, the material of the shaft core, the diameter of the shaft core, etc., as long as the configuration is normally used as the configuration of the paper feed roll, the rubber layer is the outermost roll layer in contact with the sheet material It is preferable to comprise. Such a paper feed roll can be used as a pick-up roll, a feed roll, a retard roll or the like in an OA device or an automatic deposit payment machine.

  EXAMPLES Hereinafter, although an Example is given and this invention is demonstrated in detail, this invention is not limited to these.

<Preparation of paper feed roll>
FIG. 1 is a diagram showing the shape of the paper feed roll. The compounding components shown in Table 1 and Table 2 are kneaded using a kneader, vulcanized and molded in a predetermined mold at 160 ° C. for 30 minutes, and further at 160 ° C. for 60 minutes. Secondary vulcanized. Thereby, a rubber molded body for a cylindrical paper feed roll having an outer diameter of 21 mm, an inner diameter of 9 mm, and a length of 50 mm was obtained. This rubber molded body was fitted into a core having a diameter of 10 mm and cut into a width of 10 mm. This was inserted as a rubber layer 11 into a shaft 12 made of polyacetal resin as shown in FIG. Next, the surface of the rubber layer 11 was polished to an outer diameter of 20 mm, and paper feed rolls of Examples and Comparative Examples including the rubber layer 11 and the shaft core 12 were produced. The polished rubber layer 11 has an outer diameter of 20 mm, an inner diameter of 10 mm, and a length of 10 mm.

<Measurement of viscoelastic properties>
The compounding ingredients shown in Table 1 and Table 2 are kneaded using a kneader, vulcanized using a sheet-shaped mold at 160 ° C. for 30 minutes, and further 2 at 160 ° C. for 60 minutes. Next vulcanized. Thereby, a sheet-like rubber cross-linked product was obtained. A strip-shaped sample having a width of 5 mm, a length of 20 mm, and a thickness of 2 mm was punched from this sheet. Using a dynamic viscoelasticity measuring device (UBM, Rheogel E4000FHP), the viscoelastic properties (temperature dispersion) of the punched sample were measured under the following measurement conditions: -84 ° C to 120 ° C
Rate of temperature increase: 2 ° C / min
Measurement temperature interval: 1 ° C
Measurement frequency: 10Hz
Initial strain: 1.3mm
Amplitude: 2 μm
Deformation mode: Tensile chuck distance 10mm
Waveform: Sine wave.

  With respect to the sample prepared above, the value of the dynamic elastic modulus E1 (22 ° C.) was read from the measurement result, and tan δmax and Tmax were read from the graph showing the relationship between the obtained temperature and the loss tangent tan δ.

<Paper test>
Each paper feed roll of the example and the comparative example was mounted on a color composite machine DocuCentre C6550I (manufactured by Fuji Xerox Co., Ltd.), and “Xerox 4200” manufactured by Fuji Xerox Co., Ltd. was passed through. The measurement was performed in a temperature 22 ° C. and humidity 55% environment. The paper feed roll, the measurement paper, and the paper passing tester were left in this environment for 24 hours or more, and then the paper passing test was started.

<Measurement of friction coefficient μ>
The friction coefficient μ was measured by the method shown in FIG. FIG. 2 is a diagram for explaining a method of measuring a friction coefficient. The coefficient of friction was measured in an environment with a temperature of 22 ° C. and a humidity of 55%. The paper feed roll, measurement paper, and measurement jig were allowed to stand for 24 hours or more in this environment, and then measurement was started. First, 80 mm × 210 mm size paper 24 (“Xerox 4200” manufactured by Fuji Xerox Co., Ltd.) connected to a load cell 25 between a paper feed roll composed of a rubber layer 21 and a shaft core 22 and a Teflon (registered trademark) plate 23. ) And the paper feed roll was pressed against the Teflon (registered trademark) plate 23 with a vertical load W (W = 250 gf) as indicated by a vertical arrow W in the figure. Next, a force that pulls the paper while rotating the paper feed roll in the direction indicated by an arrow a in the drawing at a peripheral speed of 300 mm / sec, that is, a frictional force generated (force F indicated by a white arrow in the drawing). Was measured with a load cell. From F [gf] and load W [gf], the friction coefficient μ was determined by the following equation (1). Note that the coefficient of friction was measured initially and after a predetermined number of sheets were passed.
Friction coefficient μ = F [gf] / W [gf] (1).

<Evaluation of viscoelastic properties and paper passing performance>
The paper passing performance was evaluated by the viscoelasticity measurement, the paper passing test, and the measurement of the friction coefficient μ. The results are shown in Tables 5 to 6 and FIGS. Table 3 summarizes the ethylene unit content of each EPDM, and Table 4 summarizes the kinematic viscosity of each softener at 40 ° C. In the “sheet passing performance” in Tables 5 to 6, when the remaining friction coefficient μ at the time when the number of passing sheets reaches 20000 is 1.5 or more, S is written, and the number of passing sheets is When the residual friction coefficient μ at the time of reaching 20000 sheets is 1.2 or more and less than 1.5, it is indicated as A, and the residual friction coefficient μ at the time of reaching 20000 sheets is 1.2. If the remaining friction coefficient μ when the number of sheets passed reaches 15000 sheets is 1.2 or more, it is indicated as B, and the remaining friction coefficient μ when the number of sheets passed reaches 15000 sheets is When it is less than 1.2, it is written as C. 3 is a graph showing the relationship between tan δmax and Tmax in Examples and Comparative Examples, and FIG. 4 is a graph showing the relationship between dynamic elastic modulus E1 (22 ° C.) and tan δmax in Examples and Comparative Examples. FIG. 5 is a graph showing the relationship between the dynamic elastic modulus E1 (22 ° C.) and Tmax in Examples and Comparative Examples. FIG. 6 is a graph obtained by examining the relationship between the temperature and the loss tangent tan δ in Example 9 and Comparative Example 8.

The annotations in Tables 1 to 4 are as follows.
(1) ESPRENE 512F is an EPDM (non-oil exhibition) manufactured by Sumitomo Chemical Co., Ltd. (2) EP98 is an EPDM (75 parts oil exhibition) manufactured by JSR (3) 4770R is an EPDM manufactured by DuPont (3) EP103AF is a non-oil extended EPDM manufactured by JSR (5) PW32 is a paraffinic petroleum-based blended oil (process oil) manufactured by Idemitsu Kosan Co., Ltd. (6) PW90 is a paraffinic petroleum compounded oil (process oil) manufactured by Idemitsu Kosan Co., Ltd. (7) PW380 is a paraffinic petroleum compounded oil (process oil) manufactured by Idemitsu Kosan Co., Ltd. (8) Sansen 4240 is a naphthenic petroleum-based blended oil (process oil) manufactured by Nippon San Oil Co., Ltd. (9) LUCANT HC-40 is carbonized by Mitsui Chemicals. (10) Nip-seal VN3 is a silica made by Tosoh Silica Co., Ltd. (11) Denka Black is acetylene black produced by Electrochemical Co., Ltd. (12) Stearic acid is a product made by Kao Corporation. The name is “Lunac S-30” (13) Zinc Hana is Zinc Oxide (trade name “Zinc Hana 1”) manufactured by Shodo Chemical Co., Ltd. (14) Shiraka Hana CC is calcium carbonate manufactured by Shiroishi Kogyo Co., Ltd. (15) Sulfur is a trade name “Salfax A” manufactured by Tsurumi Chemical Co., Ltd. (16) DM is a trade name “Noxeller DM” manufactured by Ouchi Shinsei Chemical Co., Ltd. (17) TRA is (18) TTTE is a product name "Noxeller TTTE" made by Ouchi Shinsei Chemical Co., Ltd. (19) BZ is a product made by Ouchi Shinsei Chemical Co., Ltd. Name “Noxeller B "It is.

  From the results shown in Tables 5 to 6 and FIGS. 3 to 5, in the temperature dispersion measurement of dynamic viscoelasticity, tan δmax is 1.1 or less, Tmax is −40 ° C. or less, and the dynamic elastic modulus E1. If (22 degreeC) is 2.1 Mpa or less, it turned out that it is excellent in paper passing performance.

  In Comparative Example 1, since a petroleum-based blended oil having a relatively high kinematic viscosity is used as a softening agent, tan δmax is larger than 1.1 and Tmax is higher than −40 ° C. As a result, the friction coefficient is retained. Seems to have gotten worse. The use of naphthenic petroleum blended oil as a softening agent is also considered to be the cause of poor friction coefficient retention.

  In Comparative Example 2, since no softener was blended, Tmax was higher than −40 ° C. and E1 (22 ° C.) was higher than 2.1 MPa. As a result, the retention of the friction coefficient was considered to be worse. It is done.

  Comparative Example 3 and Comparative Example 4 use a paraffinic petroleum-based blended oil having a relatively low kinematic viscosity as a softening agent. However, since the blending amount is as small as 35 parts by mass, Tmax is higher than −40 ° C. And E1 (22 degreeC) became larger than 2.1 MPa, and it is thought that the retention property of a friction coefficient worsened as a result.

  In Comparative Example 5, a petroleum-based blended oil having a relatively high kinematic viscosity is used as a softening agent, and since its blending amount is as small as 35 parts by mass, Tmax is higher than −40 ° C. and E1 (22 ° C.). Is larger than 2.1 MPa, and as a result, the retention of the friction coefficient is considered to have deteriorated.

  In Comparative Example 6, a petroleum-based blended oil having a relatively high kinematic viscosity is used as a softening agent, and the blending amount is relatively small as 70 parts by mass, so that Tmax is higher than −40 ° C., resulting in friction. It is considered that the coefficient retention has deteriorated.

  In Comparative Example 7, since a petroleum-based blended oil having a relatively high kinematic viscosity is used as a softening agent, Tmax is higher than −40 ° C., and as a result, the retention of the friction coefficient is considered to be deteriorated.

  In Comparative Example 8, since EPDM having a high ethylene unit content was used as the polymer, tan δmax was larger than 1.1, and as a result, it was considered that the retention of the friction coefficient was deteriorated.

  As shown in FIG. 6, it can be seen that even if the loss tangent tan δ in the room temperature region (near 22 ° C.) is equal or low, the loss tangent tan δ in the low temperature region including Tmax may be large. Therefore, it is important to control the loss tangent tan δ in the low temperature region, thereby improving the retention of the friction coefficient.

  It should be understood that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  11, 21 Rubber layer, 12, 22 shaft core, 23 Teflon (registered trademark) board, 24 paper, 25 load cell.

Claims (9)

A rubber composition for a paper feed roll containing at least a polymer component,
In the temperature dispersion measurement of dynamic viscoelasticity, the maximum value of the loss tangent tan δ is 1.1 or less, the temperature when the loss tangent tan δ is maximum is −40 ° C. or less, and the dynamic elastic modulus E1 (22 C.) is a rubber composition for paper feed rolls of 2.1 MPa or less.   The rubber composition for a paper feed roll according to claim 1, wherein the polymer component is mainly composed of an ethylene propylene-diene copolymer.   The rubber composition for paper feed rolls according to claim 2, wherein the ethylene propylene-diene copolymer contains 60 mass% or more and 72 mass% or less of ethylene units.   The rubber composition for paper feed rolls according to any one of claims 1 to 3, comprising a softening agent of 70 parts by mass or more and 150 parts by mass or less with respect to 100 parts by mass of the polymer component.   The rubber composition for paper feeding rolls according to claim 4, wherein the softening agent is at least one of a paraffinic petroleum-based blended oil and a hydrocarbon-based synthetic oil. The rubber composition for a paper feed roll according to claim 5, wherein the softener has a kinematic viscosity at 40 ° C of 10 mm ² / s to 500 mm ² / s. The rubber composition for paper feed rolls according to claim 5, wherein the softening agent is a paraffinic petroleum-based oil having a kinematic viscosity at 40 ° C of 10 mm ² / s to 110 mm ² / s.   The rubber composition for paper feed rolls according to any one of claims 1 to 7, comprising 1 to 6 parts by mass of sulfur as a crosslinking agent with respect to 100 parts by mass of the polymer component.   A paper feed roll provided with a rubber layer comprising the rubber composition for a paper feed roll according to claim 1.

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