JPH11349177A - Cross-linked rubber composition, rubber roller and its manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a cross-linked rubber composite capable of providing comparatively low hardness and a high friction coefficient without blooming of a compounding agent and having excellent abrasion resistance. SOLUTION: This cross-linked rubber composite is cross-linked by kneading rubber with EPDM rubber as a main component, a cross linking agent of a 1-20 pts.wt. per this rubber 100 pts.wt. and zinc oxide of a 0.01-10 pts.wt. per this rubber 100 pts.wt. Consequently, it is possible to provide a cross-linked rubber composite having proper hardness and excellent abrasion resistance without blooming of a compounding agent, and it is possible to provided paper feeding performance stable for a long period of time by using it as a paper feeding roller of a paper feeding mechanism of an OA apparatus and an automatic deposit paying machine (ATM) by molding it into a roll shape.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crosslinked rubber composition having a suitable hardness and excellent abrasion resistance without the compounding agent blooming. OA equipment such as copiers and plain paper facsimile machines, and automatic teller machines (ATMs)
When used as a paper feed roller of a paper feed mechanism, stable paper feed performance can be obtained for a long time.

[0002]

2. Description of the Related Art Electrostatic copying machines, laser printers,
Rubber compositions used for OA equipment such as facsimile machines and paper feed rollers for automatic teller machines are required to have high abrasion resistance and a high coefficient of friction. In particular, in recent years, OA equipment for personal use has increased, and various types of paper have been passed. In order to obtain stable paper feedability even for various types of paper, a high friction coefficient and excellent In addition, it is required to ensure abrasion resistance. This is because when the roller surface is worn by repeated use, the coefficient of friction is reduced, which causes slipping and greatly reduces the paper gripping force. In addition, ozone is generated when an image is formed on an electrostatic copying machine, a laser printer, a facsimile, or the like. Therefore, it is required that the rubber composition used for these paper feed rollers is not easily deteriorated by ozone.

[0003] Conventionally, as a rubber composition used for these paper feed rollers, a rubber composition using EPDM rubber excellent in abrasion resistance and ozone resistance is often used. Further, when a paper feed roller, so as to obtain a high coefficient of friction between the paper, a softening agent such as process oil in the composition for the purpose of lowering the hardness,
In order to further improve the abrasion resistance, oil-extended EPDM rubber, which is a high molecular weight polymer, is used as the EPDM rubber.

The above rubber component is usually used by vulcanizing (crosslinking) in order to improve its physical properties (particularly mechanical properties), and sulfur or an organic peroxide is used as a vulcanizing (crosslinking) agent. However, in a system containing the above oil or softener,
Since the reaction of organic peroxides is inhibited by these oils and softeners, sulfur is often used in practice. However, the main chain of the EPDM rubber often used as a main component of the rubber component for the above-mentioned reason has no double bond, and the double bond is a DCPD compounded as a diene component.
(Dicyclopentadiene), 1,4-HD (1,4-hexadiene), ENB (ethylidene norbornene), etc. exist only in the third component, and the technology of polymerizing these third components into polymers There is a limit. Therefore, even if cross-linking with sulfur using EPDM rubber having the largest iodine value (iodine value 35) among existing EPDM rubbers,
Compared with diene polymers such as NR (natural rubber) and BR (butadiene rubber), there is a problem that the vulcanization rate is slow and the mechanical properties of the rubber component cannot be sufficiently improved. Therefore, conventionally, a vulcanization accelerator has been blended together with sulfur as a vulcanizing agent, and the type and amount of the vulcanization accelerator have been optimized to improve the vulcanization rate.

However, vulcanization accelerators have a high polarity,
It is unlikely to be present in EPDM rubber with low polarity. For this reason, the vulcanization accelerator is not uniformly dispersed in the unvulcanized (crosslinked) EPDM rubber, and the vulcanization accelerator and the reaction product of the vulcanization accelerator bloom in the vulcanized product. Occurred. The blooming in such a vulcanized product is caused by the fact that such a product (rubber composition) is formed into a roll and used as a paper feed roller of the OA device or the automatic teller machine (ATM). And reduced the coefficient of friction.

Therefore, a method of suppressing blooming by blending a filler such as silica with good adsorbability into EPDM rubber or the like has been attempted. However, in this case, although the blooming of the vulcanization accelerator or the reaction product of the vulcanization accelerator can be suppressed, the hardness of the rubber composition increases as the amount of the filler increases. Therefore, even when this rubber composition is formed into a roll and used as a paper feed roller, the friction coefficient between the roller and the paper cannot be increased.

Further, JP-A-57-73035 and JP-A-57-180647 disclose that a small amount of polyalkylene glycol or ethylene alkyl ether is added to EPDM rubber to suppress blooming of a vulcanization accelerator. Proposed. However, even if this method is used, a satisfactory blooming inhibitory effect has not been obtained, and polyalkylene glycol and ethylene alkyl ether precipitate from the rubber composition after vulcanization, causing a new problem. Sometimes.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides a crosslinked rubber composition having no blooming of a compounding agent, a relatively low hardness, a high coefficient of friction, and excellent abrasion resistance. The challenge is to provide
For example, when a paper feed roller of a paper feed mechanism of an electrostatic copying machine, a plain paper facsimile machine, an automatic teller machine (ATM) or the like is used, stable paper feed characteristics can be obtained for a long time. Another object of the present invention is to make it possible to manufacture a rubber roller made of the crosslinked rubber composition having the above excellent physical properties with high productivity.

[0009]

In order to solve the above-mentioned problems, according to the present invention, the amount of 0.1 to 20 parts by weight of a resin crosslinking agent per 100 parts by weight of a rubber containing EPDM rubber as a main component is used. The present invention provides a crosslinked rubber composition which is obtained by mixing and crosslinking zinc oxide in an amount of from 0.01 to 10 parts by weight.

That is, the present invention uses a resin crosslinking agent,
When a specific amount of zinc oxide is blended together with a specific amount of a resin cross-linking agent with a rubber containing EPDM rubber as a main component and crosslinked,
It has been found that a crosslinked rubber composition having no blooming, a high coefficient of friction, and excellent wear resistance and ozone resistance can be obtained with high productivity.

In the crosslinked rubber composition of the present invention, the EP
The amount of EPDM rubber, which is a rubber mainly composed of DM rubber, is 50
When the content is not less than% by weight, the ozone resistance of the obtained crosslinked rubber composition is further improved (claim 3).

In the crosslinked rubber composition of the present invention, a thiazole-based vulcanization accelerator, a sulfenamide-based vulcanization accelerator, a thiuram-based vulcanization accelerator having poor compatibility with conventional EPDM rubbers, and Since an organic vulcanization accelerator such as a dithiocarbamate vulcanization accelerator is not used, blooming of the vulcanization accelerator can be prevented. As the resin crosslinking agent, a phenol resin, a halogenated phenol resin, or the like can be used, and these are polymers having good compatibility with the EPDM rubber, and a phenol and an aldehyde copolymerized uniformly,
Since it is excellent in uniformity of molecular weight, physical properties and reactivity, the rubber mainly composed of EPDM rubber is uniformly crosslinked. Therefore, by blending the resin crosslinking agent in the above-described specific amount, the crosslinked rubber composition can have good mechanical properties (abrasion resistance) without becoming too hard. Zinc oxide (Z
nO) acts as a reaction catalyst for the resin crosslinking agent, and by blending the above specific amount, the crosslinking reaction rate is increased, and a crosslinked rubber composition having a more uniform crosslinked structure is obtained. The characteristics (wear resistance) are further improved, and the cross-linking reaction time is shortened to reduce the production cost.

The crosslinked rubber composition of the present invention is used after forming into a shape suitable for a desired application before or simultaneously with the crosslinking. For example, a rubber roller formed by molding into a cylindrical roll or a solid roll is used as an OA device such as an electrostatic copying machine or a paper feed roller of an automatic teller machine (ATM).

The phenol resin as the resin crosslinking agent is obtained by a two-step reaction of an addition reaction and a condensation reaction of phenols and aldehydes.
It is called what. Further, the halogenated phenol resin is obtained by bonding at least one halogen atom to the aldehyde unit in the above-mentioned phenol resin, and is represented by the following structural formula (Formula 1).

[0015]

Embedded image

Specific examples of the above-mentioned phenolic resin include various types of phenols such as phenols, alkylphenols, cresols, xylenols, resorcinols, and aldehydes such as formaldehyde, acetaldehyde, and furfural (addition reaction and condensation reaction). A phenol resin and its modified resin can be used.

As the phenols, alkylphenols having at least one alkyl group bonded to a benzene ring are preferred. This is because the alkylphenol has particularly good compatibility with the EPDM rubber. Formaldehyde is preferred as the aldehyde. This is because a phenol resin using formaldehyde has particularly high reactivity and low cost, and can reduce the cost of the rubber composition (product). Therefore, it is preferable to use an alkylphenol-formaldehyde resin as the phenol resin. The alkyl group of the alkylphenol is usually an alkyl group having 1 to 10 carbon atoms, and specific examples include a methyl group, an ethyl group, a propyl group, and a butyl group.

Further, the halogenated phenol resin is more reactive than the phenol resin, and more preferable results can be obtained. For the halogenated phenol resin, after synthesizing a normal phenol resin containing no halogen atom as described above, the aldehyde unit in the phenol resin is reacted with hydrogen halide (HX) to replace the hydroxyl group and the halogen atom in the aldehyde unit. What was made can be used. In addition, a halogen-donating substance such as a metal halide is compounded together with the above-mentioned normal phenol resin containing no halogen atom in the rubber composition, and a hydroxyl group and a halogen atom in an aldehyde unit in the phenol resin are substituted at a crosslinking step. It may be a halogenated phenol resin.

The halogen atom in the halogenated phenol resin is often chlorine, but may be other halogen atoms other than chlorine, such as bromine, fluorine and iodine. Also,
Examples of the halogen-donating substance include halogenated metals such as tin chloride (stannic chloride), iron chloride (ferric chloride) and copper chloride (cupric chloride), and halogenated resins such as chlorinated polyethylene. Can be used.

The polymerization degree n (the number of repeating units) of the phenol resin and the halogenated phenol resin is generally from 1 to 10, preferably from 3 to 6. This is because if the degree of polymerization is too small, the reactivity becomes too high (crosslinking reaction rate becomes too fast), and if it is too large, the reactivity becomes too low (crosslinking reaction rate becomes too slow).

In the present invention, as described above, the resin crosslinking agent is
1-2 per 100 parts by weight of rubber mainly composed of DM rubber
0 parts by weight are blended. If the amount of the resin crosslinking agent is less than 1 part by weight per 100 parts by weight of the rubber (polymer component), insufficient crosslinking occurs, and excellent abrasion resistance cannot be imparted to the crosslinked rubber composition. If the resin cross-linking agent exceeds 20 parts by weight with respect to 100 parts by weight of the rubber (polymer component), the cross-linked rubber composition becomes too hard and has high friction with paper when formed into a roll and used as a paper feed roller. The coefficient cannot be obtained. Therefore, the resin crosslinking agent is preferably used in an amount of 3 to 18 parts by weight, more preferably 5 to 15 parts by weight, based on 100 parts by weight of the rubber (polymer).

The amount of the resin crosslinking agent is 100 parts by weight of the non-oil-extended EPDM rubber or the sum of the non-oil-extended EPDM and the other rubber when the EPDM rubber of the rubber mainly composed of EPDM rubber is non-oil-extended. The value is based on 100 parts by weight of the weight,
When EPDM rubber is oil-extended, the oil component is oil-extended EPD
EPDM rubber (polymer) component 1 subtracted from M rubber
The value is based on 100 parts by weight or 100 parts by weight of the total weight of the EPDM rubber (polymer) component and the other rubber.

The rubber containing EPDM rubber as a main component may be a non-oil-extended or / and oil-extended EPDM rubber alone or a mixture of non-oil-extended or / and oil-extended EPDM rubber and another rubber other than EPDM rubber. Can be used. Other rubbers include, for example, butyl rubber, butadiene rubber (BR),
Isoprene rubber, styrene butadiene rubber (SBR),
Chloroprene rubber (CR), natural rubber (NR), chlorosulfonated polyethylene rubber (CSM), epichlorohydrin-ethylene oxide copolymer rubber (CIIC), homopolymerized epichlorohydrin rubber (CHR), hydride of nitrile rubber (NBR), chlorination Polyethylene, urethane rubber, silicon-ethylene propylene mixed rubber, 1,2
One or more selected from polybutadiene, acrylonitrile-butadiene rubber, ethylene propylene rubber (EPM), acrylic rubber, and chlorosulfonated polyethene can be used.

The crosslinked rubber composition is used in an OA such as an electrostatic copying machine.
When used for a paper feed roller in an apparatus, the crosslinked rubber composition is required to have ozone resistance and heat resistance. Therefore, in order to satisfy such requirements, the proportion of EPDM rubber having excellent ozone resistance and heat resistance is preferably 50% by weight based on the whole rubber (polymer) (claim 2), and preferably 80% by weight. And more preferably 95% by weight or more. In the best mode, the whole rubber (polymer) is preferably made of EPDM rubber.

The diene component of the EPDM rubber is not particularly limited, and ethylidene norbornene (ENB), dichloropentadiene (DCPD) and the like can be used.

As described above, zinc oxide as a reaction catalyst blended with the resin crosslinking agent is blended in an amount of 0.01 to 10 parts by weight per 100 parts by weight of the rubber mainly composed of EPDM rubber. If the amount of zinc oxide is less than 0.01 parts by weight per 100 parts by weight of rubber containing EPDM rubber as a main component,
The cross-linking reaction rate is low, and the productivity is low. Also, if the crosslinking time is shortened to improve productivity, insufficient crosslinking occurs,
The mechanical strength (abrasion resistance) of the crosslinked rubber composition is not sufficiently improved. When the amount of zinc oxide is more than 1.0 part by weight per 100 parts by weight of the rubber containing EPDM rubber as a main component, the crosslinking reaction speed becomes too fast. For example, the kneaded rubber composition is heated by injection molding, press molding or the like. When a molded product of a crosslinked rubber composition is obtained by filling in a molded mold and crosslinking at the same time as molding to obtain a molded product of a crosslinked rubber composition, a crosslinking reaction proceeds before the rubber composition is filled into the mold without gaps, and molding failure occurs. Etc. easily occur. Therefore, zinc oxide is used for rubber (polymer content) 10
It is preferable to add 0.1 to 8 parts by weight, more preferably 1 to 5 parts by weight, based on 0 parts by weight.

In order to reduce the hardness of the crosslinked rubber composition, an oil or a plasticizer may be added to the composition as necessary. Examples of the oil include paraffinic, naphthenic and aromatic oils. Known per se synthetic oils composed of mineral oils and hydrocarbon oligomers, or process oils can be used. Examples of the synthetic oil include an α-olefin oligomer, a butene oligomer, an ethylene and α-olefin oligomer, and an amorphous oligomer of ethylene and α-olefin is particularly preferable. Examples of the plasticizer include dioctyl phthalate (DOP), dibutyl phthalate (DBP), dioctyl sepate (DOS), and dioctyl adipate (D
OA) or the like can be used.

When compounding oil, rubber 100
When blending about 1 to 200 parts by weight per part by weight and adding a plasticizer, usually about 1 to 20 parts by weight is blended per 100 parts by weight of rubber.

[0029] In order to improve the strength of the crosslinked rubber composition, a filler can be blended if necessary. Examples of the filler include powders of silica, carbon black, clay, talc, calcium carbonate, dibasic phosphite (DLP), basic magnesium carbonate, and alumina. When compounding a filler,
The filler is preferably not more than 10% by weight based on the whole rubber composition. This is because, although the compounding of the filler is effective in improving the tensile strength and tearing strength of the rubber, if the compounding is too much, the flexibility of the rubber roller tends to decrease and the friction coefficient of the roller tends to decrease.

Further, in addition to the above-mentioned compounding agents, an antioxidant, a wax and the like can be added to the rubber composition, if necessary. Examples of the antioxidant include imidazoles such as 2-mercaptobenzimidazole, phenyl-α-naphthylamine, N, N-di-β-naphthyl-p-phenylenediamine, N-phenyl-N′-isopropyl-p-. Examples include amines such as phenylenediamine, phenols such as di-tert-butyl-p-cresol, and styrenated phenol.

The crosslinked rubber composition of the present invention is usually
It is manufactured by melt-kneading a rubber mainly composed of M rubber, a resin cross-linking agent, and zinc oxide, and various compounding agents to be compounded as necessary, and cross-linking the kneaded product. The kneading can be carried out by a usual method, for example, by using a known rubber kneading device such as an open roll or a Banbury mixer at 80 ° C to 1 ° C.
It is preferable to knead at 50 ° C. for about 5 to 20 minutes.

When a molded article of the crosslinked rubber composition is obtained, the crosslinking of the above kneaded material may be performed before or after molding the kneaded material.
Further, the kneading may be performed simultaneously with the molding of the kneaded material in order to shorten the working time.

For example, when a rubber roller (molded product) is manufactured by a method of crosslinking after molding the kneaded material, as shown in FIG. 1, a shaft S is inserted into a molded product R in which the kneaded portion is molded into a roller shape. Then, the shaft S is rotatably supported by the support C, and the roller-shaped molded product R is rotated at a predetermined rotation speed around the shaft S by the electron beam irradiation device E.
The surface layer of the roll-shaped molded article R is preliminarily cross-linked by irradiating an electron beam with a predetermined absorbed dose, and then the roller-shaped molded article R is put into a cross-linking can to perform full cross-linking.

When a rubber roller (molded product) is manufactured by a method of performing crosslinking at the same time as molding of the kneaded material, a mold having a desired roll shape in a mold portion is heated, and the above-described kneading is carried out in the heated mold. The preformed product obtained by preforming the product is filled and subjected to compression molding (press molding). In this case, the crosslinking of the kneaded material starts at the same time as charging the preformed product obtained by preforming the kneaded material into a heated mold, and is completed before the end of the molding step. Also,
A mold having a desired roll shape in the mold portion is heated, and the kneaded material is injection-molded in the heated mold. In this case, the crosslinking of the kneaded material starts from the stage of preheating the kneaded material before injecting the kneaded material into the heated mold, and is completed before the end of the molding step.

In the present invention, the crosslinking temperature and time of the rubber composition (kneaded material) vary depending on the type of the resin crosslinking agent used, but proceed at a temperature of 150 ° C. to 180 ° C. for about 5 to 40 minutes.

When the rubber roller made of the crosslinked rubber composition of the present invention is used as a paper feed roller for OA equipment, it can be used as a paper feed roller, a paper transport roller, a paper discharge roller after a fixing device, and the like. Fluctuation in the coefficient of friction greatly affects the paper feeding performance, and a great effect can be obtained when used for a paper feeding roller that needs to maintain the paper feeding performance for a long period of time.

FIG. 2 is a schematic diagram in which the rubber roller of the present invention is applied to a paper feed roller of an electrostatic copying machine. A shaft core 2 is inserted into the center cylindrical portion of the rubber roller 1 and is provided opposite to the rubber roller 1. Pad 3 is provided. When the shaft core 2 is rotated in the direction of the arrow, the rubber roller 1 also rotates, and the paper 4 near the rubber roller 1 is entrained.
The paper 4 is supplied to the inside of the copier through the gap between the paper 4 and the pad 3.

FIG. 3 is a schematic diagram in which the rubber roller of the present invention is applied to a paper feed roller (upper roller and lower roller) for feeding paper while separating paper in an electrostatic copying machine. The shaft core 2 is inserted into the central cylindrical portion of the rubber roller 10a, and a torque 11 in the direction opposite to the paper feeding direction is always applied to the lower rubber roller 10a integrally with the shaft core 2. On the other hand, the shaft core 2 is inserted into the central cylindrical portion of the upper rubber roller 10b, and the rotation of the shaft core 2 rotates the upper rubber roller 10b in the direction of arrow A. The upper rubber roller 10b has an arrow A
Direction, the torque 1 is applied to the lower rubber roller 10a.
1, the uppermost sheet 13 of the sheet bundle 12 is separated from the sheet below it, passes between the upper roller 10b and the lower roller 10a, and enters the inside of the copier.
Is supplied.

As the shaft core 2, a round bar made of metal or resin is usually used, and the round bar is used as a rubber roller 10a (10
b) into the internal through hole. Further, an adhesive layer or the like may be provided between the shaft core 2 and the rubber roller 10a (10b). In this case, the thickness of the rubber roller is 0.5 mm
If less, the elasticity is insufficient and the paper feeding performance tends to decrease.
It is good to be 0.5 mm-20 mm.

[0040]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.

The crosslinked rubber compositions of Examples 1 to 7 and Comparative Examples 1 to 7 having the formulations shown in the upper part of Table 1 below were produced. A plate sample was prepared. The numerical values in the upper part of Table 1 are parts by weight.

As the high cis polybutadiene rubber, BR11 (trade name) manufactured by Japan Synthetic Rubber was used. As the oil-extended EPDM rubber, Esplen E670F (trade name) which is an ENB-based oil-extended EPDM rubber manufactured by Sumitomo Chemical Co., Ltd. was used. Halogenated alkyl phenol resin is Taoka Chemical's Tacquilol 25
0III (alkylphenol-formaldehyde resin, the number of carbon atoms in the alkyl group of the alkylphenol: 5, degree of polymerization: 4) was used. Zinc oxide (ZnO) manufactured by Mitsui Mining & Smelting was used. The sulfur used was made by Tsurumi Chemical Industry. As the vulcanization accelerator, Noxeller M (trade name) and Noxeller TET (trade name) manufactured by Ouchi Shinko Chemical Co., Ltd. were used. Noxeller M is Mercaptobanzothiazole, Noxeller TE
T is tetraethylthiuram disulfide.

The oil-extended EPDM rubber (Esprene 670F) contains 100 parts by weight of process oil with respect to 100 parts by weight of EPDM polymer. Therefore, half of the numerical values in the table are actual polymer components (rubber components).

All the raw materials were kneaded with a kneader (55 L kneader) at 100 ° C. for 15 minutes, and the obtained kneaded material was pressed at 160 ° C. under a pressure of 20 kg / cm.
Cross-linking was carried out simultaneously with molding over 30 minutes under the conditions of ² , to prepare a rubber roller having an outer diameter of 20 mm, an inner diameter of 9 mm, and a width of 10 mm.

Further, as a sample for bloom test, the above kneaded material was heated at 160 ° C. under a pressure of 100 kg /
cross-linking at the same time as molding over 20 minutes under the condition of cm ² ,
A rubber plate having a length of 100 mm, a width of 100 mm and a thickness of 2 mm was prepared.

The following tests were performed for each of all the examples and comparative examples.

[Molding processability] Using a vibratory cross-linking tester, a curast meter (Curast meter V type manufactured by Shimadzu Corporation), at a temperature of 170 ° C. and a sample shape (φ44)
mm x thickness 2mm), amplitude angle ± 1 degree, cycle 100cp
Under the condition of m (100 reciprocations per minute), the sample (the above kneaded material) was crosslinked, and the stress (torque) in response to the vibration applied to the sample was measured. As shown in FIG.
Drawing a crosslinking curve axis of ordinate graph torque value (torque curve), the torque value at which the torque value crosslinking has been completed is maximized and _{T M ax, T 10 = T} Max from the starting crosslinking
Time t before the torque value of × 0.1 is reached
₁₀ (minutes) was obtained and used as the result for each sample.

[0048] t ₁₀ indicates the speed of the crosslinking reaction, which is now too the crosslinking reaction too fast small, the kneaded material into a mold when crosslinked at the same time as molding the kneaded product in the mold is no gap filling Before the crosslinking, the crosslinking proceeds, and the rubber is burnt and molding failure is likely to occur. Conversely too slow crosslinking reaction with t ₁₀ is too long, it takes time to crosslink the entire kneaded product, the productivity is deteriorated. Further, if the time of the crosslinking step is shortened in order to increase the productivity, the crosslinking becomes insufficient, the strength of the rubber composition becomes insufficient, and the abrasion resistance and the like decrease.

[Hardness Measurement Test] The hardness of the rubber roller was determined by JI
It measured with the A-type hardness meter of S6301.

[Abrasion Resistance Test] A rubber roller was attached to a commercially available copying machine, and at a temperature of 22 ° C. and a humidity of 55%,
A paper passing test was conducted in which 1,000,000 A4 size paper (PPC paper manufactured by Fuji Xerox Office Supply Co., Ltd.) was passed over 5 hours. Then, the wear amount (mg) was obtained by measuring the weight of each rubber roller before and after the paper passing test.

[Friction Coefficient Measurement Test] In the above-described paper passing test, the friction coefficient of the roller was measured by the method shown in FIG. That is, as shown in FIG.
A4 size PP connected to load cell 25
As shown by black arrows in the figure, a load W (W = 250) is applied to the shaft center (rotation shaft) 22 of the rubber roller 21.
g) was added, and the rubber roller 21 was pressed against the plate 23. Then, under the conditions of a temperature of 23 ° C. and a humidity of 55%, the rubber roller 21 is rotated at a peripheral speed of 300 mm / sec in a direction indicated by a solid arrow a in the figure, and before and after paper passing, a white arrow in the figure indicates The force F (g) generated in the indicated direction was measured by the load cell 25. And this measured value F (g)
And the load W (250 g), the friction coefficient ν was determined from the following equation (Equation 1).

[0052]

Ν = F (g) / W (g)

Further, in order to examine the change over time in the friction coefficient, after the initial friction coefficient was measured, the paper was not subjected to the paper-passing test, and the temperature was changed to 2 degrees.
Leave the rubber roller under the conditions of 3 ° C. and 55% humidity,
The coefficient of friction at 3, 6, and 6 months was measured in the same manner as above.

[Evaluation of Blooming] Temperature 23
The rubber roller was allowed to stand under the conditions of a temperature of 55 ° C. and a humidity of 55%, and the presence / absence of a precipitate on the surface of the rubber roller after one month, three months and six months was visually judged. Good, Good: Very small amount of surface precipitates, good
：: Four levels of evaluation were performed, in which the amount of surface precipitates was slightly large but no problem, and ×: the amount of surface precipitates was very large and defective. The rubber roller was left under the conditions of a temperature of 23 ° C. and a humidity of 55%,
After 6 months, the presence or absence of a precipitate on the surface of the rubber roller was visually judged, and ：: extremely good without any surface precipitate,
：: Very small amount of surface precipitates and good; Δ: Slightly large amount of surface precipitates but at a level that does not cause any problems. ×: Many surface precipitates and poor, XX: Very large number of surface precipitates and very poor.
Grading was performed.

The results of the above tests and evaluations are shown in the lower part of Table 1.

[0056]

[Table 1]

As can be seen from Table 1, the crosslinked rubber compositions of all Examples were excellent in moldability, and no blooming was observed in the molded product (rubber plate). Rubber rollers have relatively low hardness and excellent wear resistance.
A high coefficient of friction was obtained over a long period, and good paper transportability was obtained. Also, no decrease in friction coefficient with time was observed.

On the other hand, Comparative Example 1 was a crosslinked rubber composition obtained by crosslinking with sulfur and a crosslinking accelerator without using a resin crosslinking agent, and the crosslinking time was longer than that of Examples. In addition, the molded product had severe blooming, and the coefficient of friction after passing 1,000,000 sheets and passing over time with a rubber roller was significantly reduced.

In Comparative Example 2, oil-extended EPDM rubber 8 was used as the rubber.
This is a crosslinked rubber composition prepared in the same manner as in Comparative Example 1 except that 0 parts by weight and 20 parts by weight of butadiene rubber were used. As in Comparative Example 1, the crosslinking time was long. Also,
The molded product was severely bloomed, and the coefficient of friction after passing 1,000,000 sheets and passing over time with a rubber roller was greatly reduced. Further, the abrasion resistance was poor.

The crosslinked rubber composition of Comparative Example 3 was obtained by further increasing the compounding amount of butadiene rubber than that of Comparative Example 2. However, the molded product was unsuitable as a paper feed roller because of severe blooming and excessive hardness. Met.

Comparative Example 4 is different from Example 1 only in that zinc oxide is not blended. Is T ₁₀ becomes long in order not contain zinc oxide, it was inferior in productivity. In addition, the crosslinked rubber composition actually produced had poor abrasion resistance due to insufficient crosslinking, and the coefficient of friction after passing 1,000,000 sheets through the rubber roller was greatly reduced.

Comparative Example 5 is different from Example 1 only in that the amount of zinc oxide was changed to 15 parts by weight. Was assumed that T ₁₀ is prone to too short molding failure for the content of zinc oxide is too much beyond 10 parts by weight.

Comparative Example 6 is different from Example 1 only in that the compounding amount of the halogenated alkylphenol resin is 0.5 part by weight. Since the compounding amount of the halogenated alkylphenol resin was less than 1 part by weight, the abrasion resistance was poor due to insufficient crosslinking, and the surface of the rubber roller was greatly worn down after passing 1,000,000 sheets. Therefore, 1,000,000
It was difficult to use for a longer time than a sheet.

Comparative Example 7 is different from Example 1 only in that the compounding amount of the halogenated alkylphenol resin is 22 parts by weight. Since the compounding amount of the halogenated alkylphenol resin was too large exceeding 20 parts by weight, excessive crosslinking occurred, and the hardness was significantly increased. Therefore, in the case of the rubber roller, only a low coefficient of friction could be obtained from the beginning.

[0065]

As is apparent from the above description, according to the present invention, a crosslinked rubber composition having no blooming of a compounding agent, a relatively low hardness, a high friction coefficient and excellent wear resistance can be obtained. You can get things. Therefore, when formed into a roll and used as a paper feed roller of a paper feed mechanism of, for example, an electrostatic copying machine, a plain paper facsimile machine, an automatic teller machine (ATM), etc. A stable paper feed performance can be obtained, and a paper feed roller with a small performance change over time can be obtained.

In addition, the crosslinking reaction rate during the crosslinking reaction is high,
A crosslinked rubber composition in which the entire rubber composition is uniformly crosslinked can be obtained without causing insufficient crosslinking in a short time, and the production cost can be reduced.

[0067]

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of a step of forming a kneaded rubber composition into a roller shape and crosslinking.

FIG. 2 is a schematic diagram showing a state in which a rubber roller molded from the crosslinked rubber composition of the present invention is applied to a feed roller of an electrostatic copying machine.

FIG. 3 is a schematic view showing a state in which a rubber roller molded from the crosslinked rubber composition of the present invention is applied to a paper feed roller for feeding paper while separating paper in an electrostatic copying machine.

FIG. 4 shows a cross-linking curve (torque curve) obtained by a cross-linking reaction of a cross-linked rubber composition from the start of cross-linking T ₁₀ = T _Max ×
Time t to reach 0.1 (T _Max : maximum torque value)
It is a figure explaining ₁₀ (minute).

FIG. 5 is a schematic view showing a method for measuring a friction coefficient of a rubber roller.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Paper feed roller 2 Shaft 3 Pad 4 Paper 10a Lower roller 10b Upper roller 11 Torque 12 Paper bundle 13 Paper 21 Rubber roller 22 Rotating shaft 23 Plate 24 PPC paper 25 Load cell

Claims (5)

[Claims] 1. A rubber 100 containing EPDM rubber as a main component.
0.1 to 20 parts by weight of resin crosslinking agent per part by weight.
A cross-linked rubber composition obtained by mixing and cross-linking from 0.01 to 10 parts by weight of zinc oxide. 2. The crosslinked rubber composition according to claim 1, wherein the resin crosslinking agent is a phenol resin or a halogenated phenol resin. 3. The rubber containing EPDM rubber as a main component contains at least 50% by weight of EPDM rubber.
Or the crosslinked rubber composition according to claim 2. 4. A rubber roller formed by molding the crosslinked rubber composition according to claim 1 into a roll. 5. After kneading a rubber mainly composed of EPDM rubber, 1 to 20 parts by weight of a resin crosslinking agent and 0.01 to 10 parts by weight of zinc oxide per 100 parts by weight of the rubber, the kneaded composition is mixed. A method for producing a rubber roller, wherein the rubber roller is filled in a mold, molded into a roll, and crosslinked at the same time.