JPWO2015012329A1 - Magnetic rubber composition, magnetic rubber molded product, and magnetic encoder - Google Patents

Abstract

Contains 100 parts by mass of hydrogenated nitrile rubber (A) containing a carboxyl group or carboxylic acid anhydride group, 0.5 to 10 parts by mass of polyamine-based crosslinking agent (B), and 200 to 1500 parts by mass of rare earth magnet powder (C). The magnetic rubber composition is heated and crosslinked to obtain a magnetic rubber molded product. As a result, a magnetic rubber molded article containing hydrogenated nitrile rubber and rare earth magnet powder and excellent in heat resistance and magnetic properties is provided. The hydrogenated nitrile rubber (A) preferably contains an α, β-ethylenically unsaturated dicarboxylic acid monoester monomer unit.

Description

  The present invention relates to a magnetic rubber composition containing hydrogenated nitrile rubber and rare earth magnet powder, and a magnetic rubber molded article obtained by crosslinking it. The present invention also relates to a magnetic encoder including the magnetic rubber molded product.

  Magnetic rubber molded products containing magnet powder in rubber are used for various applications. Ferrite magnet powder and rare earth magnet powder are used as the magnet powder contained in the magnetic rubber molded product. In general, it is known that the use of rare earth magnet powder improves the magnetic properties rather than the use of ferrite magnet powder, and rare earth magnet powder is used for applications that require high magnetic properties. For example, rare earth magnet powder may be used in magnetic encoders used in various sensors.

  There are various types of rubber used in magnetic rubber molded products, and they are appropriately selected according to the application. For example, nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR), fluorine rubber (FKM), and the like are properly used for magnetic encoder applications according to required performance. In the case of magnetic rubber molded products using nitrile rubber and rare earth magnet powder, the heat resistance may be insufficient, and the use is limited depending on the application. On the other hand, magnetic rubber molded products using fluororubber and rare earth magnet powder (for example, Patent Document 1) are excellent in heat resistance, oil resistance, and chemical resistance, but they are expensive and use is limited depending on applications. The On the other hand, hydrogenated nitrile rubber has better heat resistance than nitrile rubber and is less expensive than fluororubber. Therefore, there is a demand to use a magnetic rubber molded product using the same because of its good balance. Magnetic rubber molded articles containing hydrogenated nitrile rubber and ferrite magnet powder are widely used (for example, Patent Document 2), but their magnetic properties are insufficient depending on the application.

  Patent Document 3 describes a rotation sensor using a sheet magnet obtained by blending a rare earth magnet powder with a rubber material. The example describes an example in which rare earth magnet powder (Nd-Fe-B) having a mass 24 times the mass of the hydrogenated nitrile rubber is blended. The cross-linking agent used in this example is not clarified, but is considered to be one of these because only the peroxide and sulfur are exemplified in the specification.

  Patent Document 4 describes a rubber composition containing hydrogenated carboxylated nitrile rubber, hydrogenated nitrile rubber, and magnet powder. The only crosslinking agent specifically described in the specification is peroxide, and peroxide is also used in the examples. As magnet powder, both ferrite magnet powder and rare earth magnet powder are exemplified, but only strontium ferrite magnet powder is used in the examples, and examples using rare earth magnet powder are described. Absent.

  Patent Document 5 describes a crosslinkable rubber composition containing a nitrile group-containing highly saturated copolymer rubber containing an ethylenically unsaturated dicarboxylic acid monoalkyl ester monomer unit, a polyamine crosslinking agent and a basic crosslinking accelerator. Has been. There is no description of blending magnet powder with the crosslinkable rubber composition.

JP 2006-214775 A WO01 / 41162 JP 2004-279102 A JP 2005-68432 A WO01 / 14469

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a magnetic rubber molded product excellent in heat resistance and magnetic properties. Moreover, it aims at providing the magnetic rubber composition used as the raw material. Furthermore, it aims at providing a high performance magnetic encoder.

  The above-mentioned problems include 100 parts by mass of hydrogenated nitrile rubber (A) containing a carboxyl group or a carboxylic acid anhydride group, 0.5 to 10 parts by mass of polyamine-based crosslinking agent (B), and 200 to 1500 parts by mass of rare earth magnet powder (C). This is solved by providing a magnetic rubber composition containing parts.

  At this time, the hydrogenated nitrile rubber (A) is preferably a hydrogenated nitrile rubber containing an α, β-ethylenically unsaturated dicarboxylic acid monoester monomer unit. The polyamine crosslinking agent (B) is also preferably an aliphatic polyamine compound. Furthermore, it is also preferable that the rare earth magnet powder (C) is neodymium iron-based magnet powder, samarium iron-based magnet powder, or samarium cobalt-based magnet powder.

  The above-mentioned problem can also be solved by providing a magnetic rubber molded article obtained by heating and crosslinking the above magnetic rubber composition. A magnetic encoder including the magnetic rubber molded product is a preferred embodiment of the present invention.

  A magnetic rubber molded product obtained by crosslinking the magnetic rubber composition of the present invention is excellent in heat resistance and magnetic properties, and can be suitably used for a magnetic encoder or the like.

  The present invention relates to 100 parts by mass of hydrogenated nitrile rubber (A) containing a carboxyl group or a carboxylic acid anhydride group, 0.5 to 10 parts by mass of a polyamine-based crosslinking agent (B), and 200 to 1500 parts by mass of rare earth magnet powder (C). Part of a magnetic rubber composition. By using a hydrogenated nitrile rubber (A) containing a carboxyl group or a carboxylic acid anhydride group and a polyamine-based cross-linking agent (B), the cross-linking reaction proceeds well even when the rare-earth magnet powder (C) is contained. A molded product can be obtained.

  The inventors of the present invention have attempted to produce a magnetic rubber molded article in which rare earth magnet powder is blended with a hydrogenated nitrile rubber that does not contain a carboxyl group or a carboxylic acid anhydride group. As described in Comparative Example 3 of the present specification, the hydrogenated nitrile rubber having a relatively high iodine value (a large amount of residual double bonds) was tried to be crosslinked using sulfur, but almost crosslinked. I could not. It is a formulation that naturally crosslinks if rare earth magnet powder is not included, and it is known that crosslinking occurs even when ferrite magnet powder is included. However, when rare earth magnet powder is included, the progress of the crosslinking reaction is hindered. I have.

  Further, as described in Comparative Example 4 of the present specification, rare earth magnet powder is blended with a hydrogenated nitrile rubber having a relatively low iodine value (low residual double bond content), and a peroxide is used. Attempts were made to crosslink, however, foaming was remarkable and a good molded product could not be obtained. It is known that if the rare earth magnet powder is not included, the crosslinking reaction proceeds without problems, and it is known that there is no problem even if the ferrite magnet powder is included. Could not be controlled.

  The reason why such a phenomenon has occurred is not necessarily clear at this time. Ferrite magnets are composed of stable oxides, whereas rare earth magnets are composed of relatively active alloys, so when proceeding with the crosslinking reaction of hydrogenated nitrile rubber at high temperatures, rare earth magnets May affect the reaction.

  Therefore, as a result of intensive studies by the present inventors, as a hydrogenated nitrile rubber, a material containing a carboxyl group or a carboxylic acid anhydride group is used, and a polyamine-based crosslinking agent is used as a crosslinking agent, whereby a rare earth magnet powder is obtained. It has been found that even if it is contained, the crosslinking reaction proceeds well and a good molded product can be obtained. In addition, as shown in Comparative Examples 1 and 2 of the present specification, even when hydrogenated nitrile rubber containing a carboxyl group or a carboxylic anhydride group is used, sulfur or peroxide is used as a crosslinking agent. However, a good molded product could not be obtained.

  The present inventors have repeated the trial and error as described above to obtain a hydrogenated nitrile rubber (A) containing a carboxyl group or a carboxylic anhydride group, a polyamine-based crosslinking agent (B), and a rare earth magnet powder (C). It contained the magnetic rubber composition of the present invention.

  The hydrogenated nitrile rubber (A) used in the present invention contains a carboxyl group or a carboxylic anhydride group. A method for introducing a carboxyl group or a carboxylic acid anhydride group is not particularly limited, but a monomer containing these functional groups or precursors thereof is copolymerized with acrylonitrile and 1,3-butadiene, and then hydrogenated. Is preferred. Suitable examples of such monomers include α, β-ethylenically unsaturated dicarboxylic acid monoester monomers. In this case, the hydrogenated nitrile rubber (A) is a hydrogenated nitrile rubber containing an α, β-ethylenically unsaturated dicarboxylic acid monoester monomer unit. The content of the α, β-ethylenically unsaturated dicarboxylic acid monoester monomer unit is preferably 1 to 10% by mass.

  As the α, β-ethylenically unsaturated dicarboxylic acid monoester monomer, maleic acid monoalkyl esters such as monomethyl maleate, monoethyl maleate, monopropyl maleate, mono n-butyl maleate; monocyclopentyl maleate, Maleic acid monocycloalkyl esters such as monocyclohexyl maleate and monocycloheptyl maleate; Monoalkyl cycloalkyl esters of maleic acid such as monomethylcyclopentyl maleate and monoethylcyclohexyl maleate; Monomethyl fumarate, monoethyl fumarate and monofumarate Monoalkyl esters of fumaric acid such as propyl and mono-n-butyl fumarate; mono-fumaric acid such as monocyclopentyl fumarate, monocyclohexyl fumarate and monocycloheptyl fumarate Cycloalkyl esters; fumaric acid monoalkyl cycloalkyl esters such as monomethylcyclopentyl fumarate and monoethylcyclohexyl fumarate; citraconic acid monoalkyl esters such as monomethyl citraconic acid, monoethyl citraconic acid, monopropyl citraconic acid and mono n-butyl citraconic acid Citraconic acid monocycloalkyl ester such as citraconic acid monocyclopentyl, citraconic acid monocyclohexyl, citraconic acid monocycloheptyl, etc .; citraconic acid monomethylcyclopentyl, citraconic acid monoethylcyclohexyl citraconic acid monoalkyl cycloalkyl ester; itaconic acid monomethyl itacon Monoalkyl itaconate such as monoethyl acrylate, monopropyl itaconate, mono n-butyl itaconate Esters; itaconic acid monocyclopentyl, itaconic acid monocyclohexyl, itaconic acid monocycloheptyl, etc. itaconic acid monocycloalkyl ester; itaconic acid monomethylcyclopentyl, itaconic acid monoethylcyclohexyl, etc. .

  The content of acrylonitrile units in the hydrogenated nitrile rubber (A) is preferably 15 to 49% by mass. Moreover, it is preferable that content of a 1, 3- butadiene unit is 50-84 mass% including what was hydrogenated. The iodine value of the hydrogenated nitrile rubber (A) is preferably 50 g / 100 g or less, and more preferably 20 g / 100 g or less.

The polyamine-based crosslinking agent (B) used in the present invention is particularly a compound that has two or more amino groups or can be in the form of a compound having two or more amino groups during crosslinking. It is not limited. A compound in which a plurality of hydrogen atoms of an aliphatic hydrocarbon or an aromatic hydrocarbon is substituted with an amino group or a hydrazide group (—CONHNH ₂ ) is preferable. Specific examples of the polyamine crosslinking agent (B) include aliphatic polyamine compounds such as hexamethylene diamine, hexamethylene diamine carbamate, tetramethylene pentamine, hexamethylene diamine-cinnamaldehyde adduct, hexamethylene diamine-dibenzoate salt and the like. 2,2-bis {4- (4-aminophenoxy) phenyl} propane, 4,4′-methylenedianiline, m-phenylenediamine, p-phenylenediamine, 4,4′-methylenebis (o-chloroaniline); Aromatic polyamine compounds such as isophthalic acid dihydrazide, adipic acid dihydrazide, and compounds having two or more hydrazide structures such as sebacic acid dihydrazide. Among these, aliphatic polyamine compounds are preferable, and hexamethylenediamine carbamate is particularly preferable.

  The rare earth magnet powder (C) is a magnet powder made of an alloy containing a rare earth metal. Preferred are neodymium iron-based magnet powders typified by Nd-Fe-B alloys, samarium iron-based magnet powders typified by Sm-Fe-N alloys, and samarium cobalt-based magnet powders typified by Sm-Co alloys. As an example. In the above alloy, other elements may be contained in addition to the above elements as long as the performance as a magnet powder is not impaired. Two or more kinds of such rare earth magnet powders may be used simultaneously. Moreover, you may use simultaneously with another kind of magnet powder. As the rare earth magnet powder (C), there are an anisotropic magnet powder having magnetic anisotropy and an isotropic magnet powder having no magnetic anisotropy. In the magnetic rubber composition of the present invention, any of them is used. It doesn't matter. From the standpoint of magnetism, it is preferable to use isotropic magnet powder.

  The particle size of the rare earth magnet powder (C) is not particularly limited, but the proportion of particles that do not pass through a sieve having a nominal aperture of 500 μm when sieved by a sieve according to JIS Z8801-1 is 10% by weight or less. The proportion of particles passing through a sieve having an opening of 20 μm is preferably 12% by weight or less.

  Content of polyamine type crosslinking agent (B) with respect to 100 mass parts of hydrogenated nitrile rubber (A) is 0.5-10 mass parts. When the content of the polyamine crosslinking agent (B) is less than 0.5 parts by mass, the crosslinking reaction does not proceed sufficiently, and a molded product with good mechanical properties cannot be obtained. The content of the polyamine crosslinking agent (B) is preferably 1 part by mass or more. On the other hand, when the content of the polyamine crosslinking agent (B) exceeds 10 parts by mass, the elongation of the obtained magnetic rubber molded product is significantly reduced. The content of the polyamine crosslinking agent (B) is preferably 5 parts by mass or less.

  Content of rare earth magnet powder (C) with respect to 100 mass parts of hydrogenated nitrile rubber (A) is 200-1500 mass parts. When the content of the rare earth magnet powder (C) is less than 200 parts by mass, the magnetic flux density is lowered, and a molded product having good magnetic properties cannot be obtained. The content of the rare earth magnet powder (C) is preferably 400 parts by mass or more. On the other hand, when the content of the rare earth magnet powder (C) exceeds 1500 parts by mass, the strength and flexibility of the obtained molded product are lowered. The content of the rare earth magnet powder (C) is preferably 1000 parts by mass or less.

  The magnetic rubber composition of the present invention preferably further contains a basic crosslinking accelerator (D). By including a basic crosslinking accelerator, the crosslinking reaction further proceeds.

  Specific examples of basic crosslinking accelerators include guanidine-based basic crosslinking accelerators such as tetramethylguanidine, tetraethylguanidine, 1,3-diphenylguanidine, 1,3-di-ortho-tolylguanidine, orthotolylbiguanide; 1 , 8-diazabicyclo [5,4,0] undecene-7,1,5-diazabicyclo [4,3,0] nonene-5, 1-methylimidazole, 1-ethylimidazole, 1-phenylimidazole, 1-benzylimidazole 1,2-dimethylimidazole, 1-ethyl-2-methylimidazole, 1-methoxyethylimidazole, 1-phenyl-2-methylimidazole, 1-benzyl-2-methylimidazole, 1-methyl-2-phenylimidazole, 1-methyl-2-benzylimidazole, 1,4-dimethyli Dodazole, 1,5-dimethylimidazole, 1,2,4-trimethylimidazole, 1,4-dimethyl-2-ethylimidazole, 1-methyl-2-methoxyimidazole, 1-methyl-2-ethoxyimidazole, 1-methyl -4-methoxyimidazole, 1-methyl-2-methoxyimidazole, 1-ethoxymethyl-2-methylimidazole, 1-methyl-4-nitroimidazole, 1,2-dimethyl-5-nitroimidazole, 1,2-dimethyl -5-aminoimidazole, 1-methyl-4- (2-aminoethyl) imidazole, 1-methylbenzimidazole, 1-methyl-2-benzylbenzimidazole, 1-methyl-5-nitrobenzimidazole, 1-methylimidazoline 1,2-dimethylimidazoline, 1,2,4-trimethyl Midazoline, 1,4-dimethyl-2-ethylimidazoline, 1-methyl-phenylimidazoline, 1-methyl-2-benzylimidazoline, 1-methyl-2-ethoxyimidazoline, 1-methyl-2-heptylimidazoline, 1-methyl A basic crosslinking accelerator having a cyclic amidine structure such as 2-undecylimidazoline, 1-methyl-2-heptadecylimidazoline, 1-methyl-2-ethoxymethylimidazoline, 1-ethoxymethyl-2-methylimidazoline; n -Aldehyde amine basic crosslinking accelerators such as butyraldehyde aniline and acetaldehyde ammonia; Among these, a guanidine-based basic crosslinking accelerator and a basic crosslinking accelerator having a cyclic amidine structure are preferable, and a guanidine-based basic crosslinking accelerator is more preferable.

  The content of the basic crosslinking accelerator (D) in the magnetic rubber composition of the present invention is 0.5 to 10 parts by mass with respect to 100 parts by mass of the hydrogenated nitrile rubber (A). When the content of the basic crosslinking accelerator (D) is less than 0.5 parts by mass, the crosslinking rate becomes slow, and as a result, the crosslinking density of the resulting molded product may be lowered. The content of the basic crosslinking accelerator (D) is preferably 1 part by mass or more. On the other hand, when the content of the basic cross-linking accelerator (D) exceeds 10 parts by mass, the cross-linking speed becomes too fast, which may cause scorch or decrease workability. The content of the basic crosslinking accelerator (D) is preferably 5 parts by mass or less.

  The magnetic rubber composition of the present invention may contain a rubber other than the hydrogenated nitrile rubber (A) as long as the effects of the present invention are not impaired. Suitable examples of such rubbers include hydrogenated nitrile rubbers that do not contain carboxyl groups or carboxylic anhydride groups. In addition, styrene-butadiene copolymer rubber, polybutadiene rubber, ethylene-propylene copolymer rubber, ethylene-propylene-diene terpolymer rubber, urethane rubber, silicone rubber, natural rubber, polyisoprene rubber, etc. Can be mentioned. The content of rubber other than the hydrogenated nitrile rubber (A) is preferably 60 parts by mass or less, more preferably 30 parts by mass or less, and still more preferably 10 parts by mass with respect to 100 parts by mass of the hydrogenated nitrile rubber (A). It is as follows. Moreover, in addition to each component mentioned above, you may mix | blend the other compounding agent normally used in a rubber composition with the crosslinkable rubber composition of this invention.

  The magnetic rubber composition of the present invention is produced by mixing the above components. The mixing method is not particularly limited, and kneading can be performed using an open roll, a kneader, a Banbury mixer, an intermixer, an extruder, and the like. Especially, it is preferable to knead | mix using an open roll or a kneader. The temperature of the rubber composition during kneading is preferably 20 to 120 ° C.

  The magnetic rubber molded article of the present invention is obtained by forming the magnetic rubber composition into a desired shape and crosslinking it by heating. Examples of the molding method of the magnetic rubber composition include injection molding, extrusion molding, compression molding, roll molding and the like. At this time, it may be crosslinked after being molded in advance, or may be crosslinked simultaneously with the molding. The molding temperature is usually 10 to 200 ° C, preferably 25 to 120 ° C. The crosslinking temperature is usually 100 to 250 ° C, preferably 110 to 220 ° C, more preferably 120 to 200 ° C. The crosslinking time is usually 1 minute to 24 hours, preferably 2 minutes to 12 hours, and more preferably 3 minutes to 6 hours. Further, depending on the shape and size of the magnetic rubber molded product, even if the surface is cross-linked, it may not be sufficiently cross-linked to the inside. Therefore, secondary cross-linking may be performed by heating. As a heating method for crosslinking, general methods used for crosslinking of rubber, such as compression heating, steam heating, oven heating, hot air heating, and the like are used. Residual magnetic flux density can be increased by cross-linking in a magnetic field.

  The magnetic rubber molded article of the present invention obtained in this way is excellent in mechanical properties, heat resistance and oil resistance, while having the properties inherent in hydrogenated nitrile rubber and excellent in magnetic properties. is there. Therefore, it can be used for various applications that require magnetic properties and rubber elasticity. For example, it can be molded into a form such as a rubber magnet sheet and used for various applications.

  Among them, a particularly suitable application is a magnetic encoder. The magnetic encoder includes a multipolar magnet in which magnetic poles are alternately arranged, and includes a support member that supports the multipolar magnet as necessary. The support member is preferably a metal plate. In manufacturing a magnetic encoder, a method in which the magnetic rubber composition of the present invention is press-molded together with a support member, and crosslinked and integrated is preferable. After molding, the magnetic encoder is magnetized in a magnetic field.

  Among the magnetic encoders, one including an annular or disk-shaped multipolar magnet in which magnetic poles are alternately arranged in the circumferential direction is used as a sensor for detecting rotational motion. For example, it is used for an axle rotation speed detection device, a crank angle detection device, a motor rotation angle detection device, and the like. Moreover, what contains the multipolar magnet by which the magnetic pole is alternately arrange | positioned in a linear direction is used for the sensor which detects a linear motion. For example, it is used for a linear guide device, a power window, a power seat, a brake depression amount detection device, office equipment, and the like.

  The raw materials used in the following examples are as follows.

(1) Rubber / carboxyl group-containing hydrogenated nitrile rubber “ZPT 136” manufactured by Nippon Zeon Co., Ltd.
Hydrogenated acrylonitrile / 1,3-butadiene / α, β-ethylenically unsaturated dicarboxylic acid monoester copolymer (acrylonitrile content 35 wt%, iodine value 12 g / 100 g or less)
・ Hydrogenated nitrile rubber “Zetpol 2020” manufactured by Nippon Zeon Co., Ltd.
Hydrogenated acrylonitrile / 1,3-butadiene copolymer (acrylonitrile content 36% by weight, iodine value 28 g / 100 g)
・ Hydrogenated nitrile rubber “Zetpol 2010” manufactured by Nippon Zeon Co., Ltd.
Hydrogenated acrylonitrile / 1,3-butadiene copolymer (acrylonitrile content 36% by weight, iodine value 11 g / 100 g)

(2) Cross-linking agent / polyamine-based cross-linking agent Hexamethylenediamine carbamate (HDC)
"Diak-1" made by DuPont
・ Sulfur "Fine sulfur 500 mesh" manufactured by Hosoi Chemical Co., Ltd.
・ Organic peroxide "Parkadox 14R-P" manufactured by Kayaku Akzo Corporation

(3) Cross-linking accelerator, 1,3-di-o-tolylguanidine (DOTG)
"Noxeller DT" made by Ouchi Shinsei Chemical Co., Ltd.
・ 1,3-Diphenylguanidine (DPG)
“Noxeller D” manufactured by Ouchi Shinsei Chemical Co., Ltd.
・ 2,2'-Dibenzothiazolyl disulfide (MBTS)
"Sunseller DM" manufactured by Sanshin Chemical Industry Co., Ltd.
・ Tetraethylthiuram disulfide (TETD)
"Sunceller TET-G" manufactured by Sanshin Chemical Industry Co., Ltd.

(4) Crosslinking aid, metaphenylene bismaleimide "Sumifine BM" manufactured by Sumika Chemtex Co., Ltd.

(5) Rare earth magnet powder / Nd-Fe-B system (isotropic powder)
"MQP-14-12" manufactured by Magnequench
Particle size distribution:
40 mesh (nominal opening 425 μm) ON: less than 0.1 wt% 60 mesh (nominal opening 250 μm) ON: less than 25 wt% 270 mesh (nominal opening 53 μm) Pass: less than 12 wt%

Example 1
100 parts by mass of carboxyl group-containing hydrogenated nitrile rubber “ZPT 136”, 2 parts by mass of hexamethylenediamine carbamate (HDC), 3 parts by mass of 1,3-di-o-tolylguanidine (DOTG) and Nd—Fe—B system Using an open roll, 700 parts by mass of magnet powder was kneaded for 40 minutes at a temperature of the rubber composition of 40 ° C. to prepare an unvulcanized rubber sheet. The blending ratio is shown in Table 1.

  Vulcanization characteristics were evaluated using the obtained rubber sheet. Vulcanization characteristics were measured according to JIS K6300-2. Using the unvulcanized rubber sheet after kneading as a sample, measurement was performed using a “Curast Meter 7” manufactured by JSR Corporation. A vulcanization curve for 5 minutes at a measurement temperature of 180 ° C. is measured, and the minimum value ML (kgf · cm), maximum value MH (kgf · cm), MH of the torque in the graph with the vertical axis representing torque and the horizontal axis representing time. A time t10 (min) until a torque of 10% and a time t90 (min) until a torque of 90% of MH were obtained. The results are shown in Table 1.

  Also, a disk-shaped sample having a diameter of 18 mm and a thickness of 6 mm was prepared from the mixture obtained by kneading with an open roll, and was crosslinked by heating at 180 ° C. for 3 minutes while applying pressure with a vulcanizing press. A molded product was obtained. The obtained molded product was sufficiently cross-linked, had high strength, and had a good appearance. The magnetic properties of the obtained molded product were measured with a DC magnetization measuring device manufactured by Metron Giken Co., Ltd. As a result, the magnetic flux density was 390 mT, indicating good magnetic properties. This magnetic flux density was at a level that was not problematic for manufacturing a magnetic encoder.

Example 2
In Example 1, the test was conducted and evaluated in the same manner as in Example 1 except that the crosslinking accelerator was changed from 1,3-di-o-tolylguanidine (DOTG) to 3 parts by mass of diphenylguanidine (DPG). The obtained molded product was sufficiently cross-linked, had high strength, and had a good appearance. The results are shown in Table 1.

Comparative Example 1
In Example 1, 0.5 parts by mass of sulfur was used instead of the polyamine-based crosslinking agent, 2 parts by mass of 2,2′-dibenzothiazolyl disulfide (MBTS) and tetraethylthiuram disulfide (TETD) as a crosslinking accelerator. A test was conducted and evaluated in the same manner as in Example 1 except that 5 parts by mass was used. The obtained molded product was hardly crosslinked. Further, since the sample was almost unvulcanized, a sample for magnetic measurement could not be prepared in a predetermined shape, and the magnetic characteristics could not be measured. The results are shown in Table 1.

Comparative Example 2
In Example 1, instead of the polyamine-based crosslinking agent, 3 parts by mass of the peroxide crosslinking agent “Parkadox 14R-P” was used, and 1 part by mass of “Sumifine BM” was used as a crosslinking aid. The test was conducted in the same manner as above and evaluated. The obtained molded product was markedly foamed and did not form a flat sheet. Therefore, a sample for magnetic measurement could not be prepared with a predetermined shape, and the magnetic characteristics could not be measured. The results are shown in Table 1.

Comparative Example 3
In Comparative Example 1, tests were conducted and evaluated in the same manner as in Comparative Example 1 except that 100 parts by mass of hydrogenated nitrile rubber “Zetpol 2020” was used instead of carboxyl group-containing hydrogenated nitrile rubber “ZPT 136”. The obtained molded product was hardly crosslinked. Further, since the sample was almost unvulcanized, a sample for magnetic measurement could not be prepared in a predetermined shape, and the magnetic characteristics could not be measured. The results are shown in Table 1. In addition, it confirmed that what remove | excluded magnet powder from the mixing | blending prescription of the comparative example 3 bridge | crosslinks favorably.

Comparative Example 4
In Comparative Example 2, tests were conducted and evaluated in the same manner as in Comparative Example 2 except that 100 parts by mass of hydrogenated nitrile rubber “Zetpol 2010” was used instead of carboxyl group-containing hydrogenated nitrile rubber “ZPT 136”. The obtained molded product was markedly foamed and did not form a flat sheet. Therefore, a sample for magnetic measurement could not be prepared with a predetermined shape, and the magnetic characteristics could not be measured. The results are shown in Table 1. In addition, it confirmed that what remove | excluded magnet powder from the mixing | blending prescription of the comparative example 4 bridge | crosslinks favorably.

Claims (6)

  Contains 100 parts by mass of hydrogenated nitrile rubber (A) containing a carboxyl group or carboxylic acid anhydride group, 0.5 to 10 parts by mass of polyamine-based crosslinking agent (B), and 200 to 1500 parts by mass of rare earth magnet powder (C). Magnetic rubber composition.   The magnetic rubber composition according to claim 1, wherein the hydrogenated nitrile rubber (A) is a hydrogenated nitrile rubber containing an α, β-ethylenically unsaturated dicarboxylic acid monoester monomer unit.   The magnetic rubber composition according to claim 1 or 2, wherein the polyamine crosslinking agent (B) is an aliphatic polyamine compound.   The magnetic rubber composition according to any one of claims 1 to 3, wherein the rare earth magnet powder (C) is neodymium iron-based magnet powder, samarium iron-based magnet powder, or samarium-cobalt magnet powder.   A magnetic rubber molded article obtained by heating and crosslinking the magnetic rubber composition according to claim 1.   A magnetic encoder comprising the magnetic rubber molded product according to claim 5.