JP4429688B2 - Rubber composition, method for producing the rubber composition, and rubber member - Google Patents

Description

  The present invention relates to a rubber composition, a method for producing the rubber composition, and a rubber member using the composition, and more specifically, a paper having improved hardness and improved wear resistance, and having tensile strength and tear resistance. It is suitably used as a leaf double feed prevention member and a paper feed roller.

In a paper feeding mechanism of an OA device such as an ink jet printer, a laser printer, an electrostatic copying machine, a plain paper facsimile machine, or an automatic deposit payment machine (ATM), a paper sheet 3 conveyed as shown in FIG. The paper feed roller 2 and the plate-like double feed prevention rubber member 1 are disposed to face each other. Since the paper feed roller 2 and the plate-like double feed preventing rubber member 1 are repeatedly brought into contact with the paper sheet 3 , the rubber material used for these members is required to have a required hardness and wear resistance. Further, in recent years, the speed of OA equipment has been increased, and excellent tensile strength and tear strength have been demanded for members in a paper feed mechanism in order to cope with speedup of equipment.

  Conventionally, rubber materials having excellent wear resistance such as EPDM rubber, natural rubber, urethane rubber, northorex rubber, silicone rubber, chlorinated polyethylene rubber, and chloroprene rubber have been used as the rubber material for the member. Among these, rubbers with less unsaturated bonds such as EPDM are suitably used because they are excellent not only in abrasion resistance but also in oxidation resistance and light resistance. Such a rubber material is generally crosslinked by a crosslinking agent. Sulfur is widely used as a crosslinking agent, but a rubber roller for paper feeding made of a rubber material vulcanized by sulfur has a problem that foreign matter is deposited on the surface of the rubber roller to cause blooming that contaminates paper or the like. . In order to solve this problem, rubber compositions using a peroxide as a crosslinking agent other than sulfur have been proposed (Patent Document 1, Patent Document 2 and Patent Document 3).

  However, rubbers with few unsaturated bonds such as EPDM crosslinked with peroxides have low tensile strength and tear strength. Further, rubbers with few unsaturated bonds, such as EPDM, have few crosslinking points, so even if they are crosslinked with peroxide, the hardness is usually 90 degrees or less (Duro) and it is necessary to further improve the hardness. Hardness can be improved by increasing the blending amount of the filler to about 50 parts by weight with respect to 100 parts by weight of the rubber component, but when more fillers are added than usual, the dispersibility in the rubber is poor, There is a problem in that the quality of rubber parts that are likely to vary and which is produced deteriorates.

Japanese Patent Laid-Open No. 2002-19986 JP 2002-37472 A JP 2002-364630 A

  An object of the present invention is to provide a rubber composition which can be increased in hardness and excellent in wear resistance, tensile strength and tear strength, and a rubber part comprising the rubber composition.

In order to solve the above problems, the present invention firstly includes ethylene-propylene-diene rubber, magnesium oxide, methacrylic acid or an ionic compound thereof, and a peroxide as a crosslinking agent.
Together with the magnesium oxide is blended at 10 times or less than twice in molar ratio with respect to the methacrylic acid, the ethylene - propylene - are formulated below 150 parts by weight 60 parts by weight or more with respect to the diene rubber 100 parts by weight And
The ethylene - propylene - methacrylic acid in the main chain of the diene rubber and the above magnesium oxide and the methacrylic acid with being partially crosslinked provides a rubber composition characterized by being an ionic bond.

In the rubber composition of the present invention, methacrylic acid is partially crosslinked in the main chain of the rubber, and further magnesium oxide is used, whereby an ionic bond is generated between methacrylic acid and magnesium ions. For this reason, the dispersibility of a filler improves markedly and it becomes possible to mix | blend a much larger amount of filler than before. As a result, it is possible to increase the hardness of the rubber and thus improve the wear resistance of the rubber composition. Furthermore, due to the ionic bond between magnesium ions and methacrylic acid, the tensile strength and tear strength of the rubber composition are also improved.

As described above, the present invention uses ethylene-propylene-diene rubber (EPDM rubber) as the rubber component . EPDM includes a non-oil-extended EPDM composed of only a rubber component and an oil-extended EPDM containing a confidential oil together with a rubber component. Any type of EPDM can be used in the present invention. Since the main chain of the EPDM rubber is composed of a saturated hydrocarbon and does not contain a double bond in the main chain, even when exposed to a high-concentration ozone atmosphere or an environment such as light irradiation for a long time, the molecular main chain is hardly broken. Therefore, there is an advantage that the ozone resistance of the rubber composition can be increased.

In addition to the EPDM rubber , an acrylic rubber having an alkyl acrylate or alkyl methacrylate having an alkyl group having 2 to 12 carbon atoms, such as ethyl acrylate, butyl acrylate, 2-ethylhexyl acrylate, or n-octyl methacrylate, as a component, Urethane rubber, silicone rubber, epichlorohydrin rubber, fluororubber, etc. may be used in combination. These may be used alone or in combination of two or more.
In addition to non-diene rubbers, diene rubbers such as natural rubber (NR), butadiene rubber (BR), styrene butadiene rubber (SBR), isoprene rubber, acrylonitrile-butadiene rubber, butyl rubber, isoprene rubber, chloropropylene rubber One or more rubber components selected from (CR), acrylonitrile-butadiene rubber, acrylic rubber or ethylene propylene rubber (EPR) may be used in combination.
However, it is most preferable to use only EPDM rubber . When EPDM rubber and other rubber are blended, the ratio of EPDM rubber to the total rubber is preferably about 50% by weight or more, more preferably about 80% by weight or more. preferable.

As a filler containing metal ions for use in the present invention, comprises a metal ion, and is used contributes magnesium oxide to an increase in the hardness of the rubber composition.
Incidentally, as a filler comprising a metal ion, salt group magnesium carbonate, magnesium hydroxide, magnesium carbonate, magnesium sulfate, alumina, zinc oxide, titanium oxide, calcium oxide, iron oxide, tin oxide, antimony oxide, ferrites, water Calcium oxide, aluminum hydroxide, calcium carbonate, zinc carbonate, barium carbonate, calcium sulfate, barium sulfate, aluminum nitride, potassium titanate, lead zirconate titanate, aluminum borate, molybdenum sulfide, stainless fiber or zinc borate It is done . In kana, alumina, zinc oxide, titanium oxide, calcium oxide, magnesium oxide, iron oxide, tin oxide, preferably a metal oxide such as antimony oxide or ferrites, therefore, as described above in the present invention, acid magnesium Is used.
The rubber composition of the present invention uses magnesium oxide as a filler containing metal ions.

  Specific examples of methacrylic acid and its ionic compound used in the present invention include trimethylolpropane trimethacrylic sheet, ethylene dimethacrylate, polyethylene glycol dimethacrylate, cyclohexyl methacrylate, acrylic methacrylate, tetrahydrofurfuryl methacrylate, and isopreethylene dimethacrylate. , Triallyl isocyanurate, triallyl cyanurate, diallyl phthalate, diallyl taconate, vinyl toluene, vinyl pyridine, and divinyl benzene. Further examples include aluminum methacrylate, zinc methacrylate, calcium methacrylate, and magnesium methacrylate.

The production method of the present invention the rubber composition in the second, the ethylene - propylene - after kneaded with a peroxide as a diene rubber and the magnesium oxide and the following cross-linking agent, the reaction temperature of the methacrylic acid was charged with the methacrylic acid while being heated to 120 ° C., the ethylene - propylene - to ionic bond and the magnesium oxide and the methacrylic acid with the methacrylic acid in the main chain of the diene rubber is made to partially crosslinked It is set to the manufacturing method of the rubber composition characterized by the above-mentioned.

In the rubber composition produced by the above production method, the hardness of the rubber composition is adjusted by changing the blending amount of magnesium oxide or methacrylic acid.
The hardness varies depending on the type of rubber member formed from the rubber composition, but is preferably 80 or more and 95 or less in JIS K 6253 Shore A. In order to obtain this hardness, 60 parts by weight or more and 150 parts by weight or less, preferably 80 parts by weight to 120 parts by weight of magnesium oxide is blended with 100 parts by weight of rubber. If it is less than 60 parts by weight, the hardness is less than 80, and if it exceeds 150 parts by weight, there is a possibility that poor dispersion of the filler occurs.

In addition, magnesium oxide is used in a molar ratio of 2 to 10 times the methacrylic acid. If this is less than 2 times, the ionic bond between magnesium oxide and methacrylic acid is not sufficiently performed, and the tear strength and tensile strength do not reach the required values. On the other hand, if it exceeds 10 times, crosslinking is inhibited. .

  The rubber composition of the present invention has a tensile strength (Mpa) of 8 or more, preferably 10. The tear strength (N / mm) is 10 or more, preferably 15 or more. The tensile strength is measured according to JIS K 6251, and the tear strength is measured according to JIS K 6252.

The rubber composition of the present invention may contain a known component as long as it is not contrary to the object of the present invention, other than the above essential components.
The rubber composition of the present invention contains a cross-linking agent. The crosslinking agent in order to suppress the blanking rooming is Ru with peroxide. Benzoyl peroxide as an upper Symbol peroxide, 1-1-di -tert- butyl peroxy 3-3-5 trimethylcyclohexane, 2-5 dimethyl 2-5 di (benzoyl peroxy) hexane, di -tert- butyl peroxy Diisopropylbenzene, di-tert-butylperoxybenzoate, dicumyl peroxide, tert-butylcumyl peroxide, 2-5 dimethyl 2-5 di (tert-butylperoxy) hexane, di-tert-butyl peroxide and 2 -5 dimethyl 2-5 di (tert-butylperoxy) hexene-3 and the like can be used.

  Furthermore, a softening agent, a crosslinking activator, a crosslinking aid, an antiaging agent, a wax and the like can be blended. Examples of the softening agent include oils and plasticizers. As the oil, there can be used a paraffinic, naphthenic, aromatic or other mineral oil or a synthetic oil known per se made of a hydrocarbon orimer, or a process oil. As the synthetic oil, for example, an oligomer with α-olefin, an oligomer of butene, and an amorphous oligomer of ethylene and α-olefin are preferable. As the plasticizer, for example, dioctyl phthalate (DOP), dibutyl phthalate (DBP), dioctyl separate (DOS), dioctyl adipate (DOA) and the like can be used. Examples of the anti-aging agent include imidazoles such as 2-mercaptobenzimidazole, phenyl-α-naphthylamine, N, N′-di-6-naphthyl-p-phenylenediamine, N-phenyl-N′-isopropyl- Examples thereof include amines such as p-phenylenediamine.

  The rubber composition of the present invention described above can be used for various applications, but in OA equipment such as an ink jet printer, a laser printer, an electrostatic copying machine, a plain paper facsimile machine, or an automatic deposit payment machine (ATM). It is preferably used for a rubber member having hardness, and is particularly preferably applied to a double feed prevention rubber member (hereinafter simply referred to as “double feed prevention rubber member”) comprising a paper feed roller and a separation pad for paper sheets.

As a method of creating the above-mentioned multifeed rubber member, a known method can be employed. For example, it can be produced by the following method. Ethylene-propylene-diene rubber , magnesium oxide , and additives such as a crosslinking agent are put into a rubber kneading apparatus such as a twin-screw extruder, an open roll, a Banbury mixer, or a kneader and kneaded. Heat to about 120 ° C. or higher, add methacrylic acid, and knead.
The obtained mixture is set in a mold and press vulcanized at about 165 to 175 ° C. to produce a rubber sheet. After slicing this sheet to a desired thickness, the sheet is further cut into a rectangular shape having a desired size to form a multi-feed preventing rubber member for paper sheets.
In the case of the multi-feed preventing rubber member for the paper sheet, the rubber composition has a hardness of 80 to 95 as the JISA hardness.

Moreover, a well-known method can be employ | adopted as a method of producing a paper feed roller using the said rubber composition, For example, it can produce by the following method.
After obtaining a mixture in the same manner as the paper sheet multi-feed preventing member, the mixture is filled into an extruder and extruded as a continuous tube, then cut into a predetermined length, and a shaft core is attached. . Alternatively, the kneaded product is set in a mold and press vulcanized at about 165 to 175 ° C. to form a cylindrical body. This cylindrical body is polished by a cylindrical grinder and mounted on the shaft core in the hollow portion. The rubber roller for paper feeding includes a roller (nudger (used by one), a feed (used by a retarder and two sets described later)) that is rotated in the paper feeding direction for the purpose of feeding paper, and a weight of paper. There is a roller (retard) that is used by applying a torque in a direction opposite to the paper feeding direction for the purpose of preventing feeding, but the paper feeding roller of the present invention can be used for various types of rollers. The shape of the rubber roller can be various shapes such as a cylindrical shape and other irregularly shaped rollers such as a D-shape.

In the rubber composition of the present invention, methacrylic acid partially crosslinked to the main chain of rubber and magnesium ions in magnesium oxide are ionically bonded, so that the tensile strength and tear strength of the rubber composition can be increased. Thus, a larger amount of filler can be blended uniformly than before, and as a result, the hardness increases and the wear resistance can be improved.
Therefore, it can be suitably used for applications requiring friction resistance or durability, such as a paper feed roller or a double feed prevention rubber member in OA equipment. For example, when the rubber composition according to the present invention is used as a paper feed roller, generation of wear powder can be suppressed even if the paper runs out and slides on a separation pad or the like. As a result, it is possible to prevent the wear powder from adhering to the surface of the paper feed roller, and it is possible to prevent image formation in the ink jet printer from being hindered and occurrence of white spots in the image.

Embodiments of the present invention will be described below.
The rubber composition of the embodiment contains a rubber having no double bond made of EPDM, a filler containing metal ions made of magnesium oxide, and methacrylic acid.
Mixing ratio, magnesium oxide 60 to 150 parts by weight to EPDM100 parts by weight, preferably about 80 to 120 parts by weight dicumyl consists peroxide peroxide 10 parts by weight or less, and preferably 5 parts by weight hereinafter is doing. Methacrylic acid is 5 to 50 parts by weight, preferably 10 to 40 parts by weight, based on 100 parts by weight of EPDM. Further, methacrylic acid is about 0.5 mol or less per 1 mol of magnesium oxide.

  In the production of the rubber composition, after sufficiently mixing EPDM, magnesium oxide and a peroxide as a crosslinking agent, the temperature is raised to 120 ° C. or more, which is the reaction temperature of methacrylic acid, and methacrylic acid is added. Even after the addition, it is sufficiently kneaded.

The obtained kneaded material is set in a mold and subjected to press vulcanization at 165 to 175 ° C. for 10 to 20 minutes. From the separation pad provided in the paper feed mechanism in the image forming apparatus as shown in FIG. It is formed as a double-feed prevention rubber member 1 for the paper sheet.
The double feed prevention rubber member 1 is formed into a sheet of 50 mm × 200 mm × 2 mm, sliced into 1.2 mm, and then cut into a rectangle having a width of 10 mm and a length of 60 mm.

  Also, the kneaded material obtained by the same method as the rubber composition for forming the multifeed preventing rubber member 1 is put into a tube extruder, and a tube having an inner diameter of 9 mm, an outer diameter of 21 mm, and a length of 38 mm is formed. The tube is polished with a cylindrical grinder to an outer diameter of 20 mm, cut to a length of 10 mm, and attached to a hollow portion of the tube on a dedicated core to manufacture the feed roller 2 shown in FIG.

The multi-feed preventing rubber member 1 is urged by an urging means (not shown) to the opposite side of the paper feed roller 2 to rotate the paper feed roller 2 to feed the paper 3 one by one. Not in the direction of the arrow.
Since the hardness of the multifeed prevention rubber member 1 is set to be relatively hard, the amount of wear caused when the paper feed roller 2 and the multifeed prevention rubber member come into contact with the paper can be reduced as compared with the conventional case. In addition, the tensile strength and tearing force applied to the paper feed roller 2 and the multi-feed prevention rubber member 1 during paper feeding are both 8 Mpa or higher and the tear strength is 10 N / mm or higher, so that it is durable. Have sex.

EPDM, magnesium oxide, methacrylic acid, and dicumyl peroxide were mixed at the blending ratio shown in Table 1 and kneaded thoroughly, then heated to set the temperature at 120 ° C., and the amount of methacrylic acid shown in Table 1 was added. I put it in. After further kneading sufficiently, the kneaded product was press vulcanized at 170 ° C. for 20 minutes to form a 50 mm × 200 mm × 2 mm sheet, and this sheet was sliced into 1.2 mm, then 10 mm wide Cut into a rectangle with a length of 60 mm to produce a multifeed rubber member.
In Comparative Example 1, methacrylic acid was not added. The numerical unit of each formulation in the table is parts by weight.

The materials used are as follows.
(A) Rubber; EPDM (“Mitsui EPT 4070” manufactured by Mitsui Chemicals, Inc.)
(B) Filler; Magnesium oxide (“Magarat 150ST” manufactured by Kyowa Chemical Industry Co., Ltd.)
(C) Crosslinking agent: Dicumyl peroxide (“Park Mill D” manufactured by NOF Corporation)

The following tests were conducted using the sample sheets made of the rubber compositions obtained in Examples 1 to 3 and Comparative Example 1.
(i) Hardness measurement The hardness of the rubber composition was measured according to JIS K 6253 using an A-type hardness meter.
(Ii) Tensile strength Measured according to JIS K 6251 to determine the tensile strength (MPa).
(Iii) Tear strength Measured according to JIS K 6252 to determine tear strength (N / mm).

Further, a paper sheet multi-feed prevention member (separation pad) was formed from the rubber composition, and mounted on a printer to conduct a paper passing durability test.
The printer was a laser printer (“LBP-1310” manufactured by Canon Inc.), and the sheet was punched out into a CST separation pad shape and attached to the separation pad resin for LBP-1310. After passing 30,000 sheets of Canon PPC paper (A4 size), the change in weight of the separation pad was defined as the amount of wear.
The results of the above test are shown in Table 1.

The double-feed prevention rubber members prepared in Examples 1 to 3 had a Shore A hardness of 84 to 91, whereas the hardness of Comparative Example 1 in which no methacrylic acid was blended was 76, less than 80. Moreover, although the tensile strength of Examples 1-3 was 11.9-14.5 Mpa, the comparative example 1 was 6.8 Mpa less than 7 Mpa. Furthermore, the tear strengths of Examples 1 to 3 were 15.7 to 22.4 N / mm, but Comparative Example 1 was 9.9 N / mm, which was less than 10 N / mm.
Moreover, in the paper-passing test for actual machine mounting, the wear amount in Examples 1 to 3 was 20 mg or less, while that in Comparative Example 1 was 23 mg.
From the above test results, it was confirmed that Examples 1 to 3 had excellent wear resistance due to their high hardness, and were superior to Comparative Example 1 in both tensile strength and tear strength.

It is the schematic which shows the paper feed mechanism in OA apparatus.

Explanation of symbols

1 Double feed rubber member 2 Paper feed roller 3 Paper

Claims (6)

Containing ethylene-propylene-diene rubber, magnesium oxide, methacrylic acid or an ionic compound thereof, and a peroxide as a crosslinking agent;
Together with the magnesium oxide is blended at 10 times or less than twice in molar ratio with respect to the methacrylic acid, the ethylene - propylene - are formulated below 150 parts by weight 60 parts by weight or more with respect to the diene rubber 100 parts by weight And
The ethylene - propylene - rubber composition in the main chain of the diene rubber with methacrylic acid is partially crosslinked and the magnesium oxide and the methacrylic acid, characterized in that it is an ionic bond.   80 to 120 parts by weight of the magnesium oxide, 5 parts by weight or less of the peroxide made of dicumyl peroxide, and 10 to 40 parts by weight of the methacrylic acid are blended with 100 parts by weight of the ethylene-propylene-diene rubber. The rubber composition according to claim 1.   The rubber composition according to claim 1 or 2, wherein the Shore A hardness measured by JIS K 6253 is 80 or more and 95 or less, the tensile strength is 8 Mpa or more, and the tear strength is 10 N / mm or more. A method for producing a rubber composition according to any one of claims 1 to 3,
The ethylene - propylene - after kneaded with a peroxide as a diene rubber and the magnesium oxide and the crosslinking agent, was charged the above methacrylic acid while being heated to 120 ° C. reaction temperature of the methacrylic acid the ethylene - propylene - method for producing a rubber composition comprising the above-described magnesium oxide and the methacrylic acid to be ionic bond with is the backbone the methacrylic acid partially crosslinked in the diene rubber.   A rubber member comprising the rubber composition according to any one of claims 1 to 3 and having a Shore A hardness of 80 to 95 and formed as a multi-feed preventing member for paper sheets.   A rubber member formed as a paper feed roller using the rubber composition according to any one of claims 1 to 3.

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