JP2015076515A - Molded product with magnetic rubber layer glued to support member, and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a molded product with a magnetic rubber layer superior in magnetic property and durability glued to a support member; and a method for manufacturing such a molded product.SOLUTION: A molded product comprises: a support member; and a magnetic rubber layer glued to the support member. The magnetic rubber layer is produced by vulcanizing a rubber composition including magnetic powder. The rubber composition includes: a rubber (A); rare earth magnet powder (B); and ferrite magnet powder (C). The content of the rare earth magnet powder (B) is 200-1000 pts.mass to 100 pts.mass of the rubber (A). The mass ratio (B/C) of the rare earth magnet powder (B) to the ferrite magnet powder (C) is 4/6 to 8/2. In a skin layer ranging from the surface of the magnetic rubber layer to a depth of 50 μm, the content of the rare earth magnet powder (B) is less than one-half of the content of the rare earth magnet powder (B) in the whole magnetic rubber layer. In the skin layer, the content of the ferrite magnet powder (C) is over one-half of the content of the ferrite magnet powder (C) in the whole magnetic rubber layer.

Description

  The present invention relates to a molded article, in particular a magnetic encoder, in which a magnetic rubber layer formed by vulcanizing a rubber composition containing magnetic powder is bonded to a support member. Moreover, it is related with the manufacturing method of such a molded article.

  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.

  Patent Document 1 describes a rubber composition for a magnetic encoder containing fluororubber having a Mooney viscosity in a certain range and rare earth magnet powder. And the magnetic encoder using the said rubber composition is said to be excellent in magnetic characteristics, heat resistance, oil resistance, and chemical resistance. However, when such a magnetic encoder is used for a long time in an environment exposed to the atmosphere, the rare earth magnet powder contained in the rubber composition may rust and may be restricted to use in a sealed environment. There were many.

  Patent Document 2 describes a rubber magnet composition containing rare earth magnet powder having a surface coated with a phosphate coating. The rare earth magnet powder is said to have excellent weather resistance because it is coated with phosphate. At this time, it is also described that an inexpensive ferrite magnet powder may be mixed for cost reasons. However, it is not always easy to use magnet powder coated with a special salt, including the cost.

JP 2006-214775 A JP 2003-297618 A

  The present invention has been made to solve the above-described problems, and provides a molded product, particularly a magnetic encoder, in which a magnetic rubber layer having excellent magnetic characteristics and excellent durability is bonded to a support member. It is the purpose. Moreover, the manufacturing method suitable for manufacturing such a molded article is provided.

The above-described problem is a molded article in which a magnetic rubber layer formed by vulcanizing a rubber composition containing magnetic powder is bonded to a support member;
The rubber composition contains a rubber (A), a rare earth magnet powder (B), and a ferrite magnet powder (C), and the content of the rare earth magnet powder (B) with respect to 100 parts by mass of the rubber (A) is 200. ~ 1000 parts by mass, the mass ratio (B / C) of the rare earth magnet powder (B) and the ferrite magnet powder (C) is 4/6 to 8/2,
The content of the rare earth magnet powder (B) in the skin layer from the surface of the magnetic rubber layer to 50 μm is less than half of the content of the rare earth magnet powder (B) in the entire magnetic rubber layer,
The problem is solved by providing a molded product characterized in that the content of ferrite magnet powder (C) in the skin layer exceeds half of the content of ferrite magnet powder (C) in the entire magnetic rubber layer.

  At this time, the rubber (A) is preferably at least one rubber selected from the group consisting of fluorine rubber, hydrogenated nitrile rubber, nitrile rubber and acrylic rubber. The rare earth magnet powder (B) has an average particle diameter of 2 to 300 μm, the ferrite magnet powder (C) has an average particle diameter of 0.5 to 5 μm, and the rare earth magnet powder (B) has an average particle diameter of It is also preferable that the average particle diameter of the ferrite magnet powder (C) is larger. A preferred embodiment of the molded article is a magnetic encoder.

The above-mentioned subject is a kneading step of kneading a rubber composition containing rubber (A), rare earth magnet powder (B) and ferrite magnet powder (C);
An extrusion step of extruding the kneaded rubber composition from a nozzle; and the extruded rubber composition is compression-molded under heating conditions together with a support member to crosslink the rubber composition and adhere a magnetic rubber layer to the support member Compressing step;
It is solved also by providing the manufacturing method of the said molded article characterized by including this.

At this time, in the extrusion step, the ratio (v / d) of the diameter d (mm) of the inscribed circle of the nozzle to the average speed v (mm / sec) of the rubber composition when passing through the nozzle is 1 to 100 ( Second- ¹ ) is preferable.

  The molded article of the present invention has excellent magnetic properties and excellent durability. Therefore, it is suitable as a magnetic encoder. Moreover, the manufacturing method of this invention is a method suitable for manufacturing such a molded article.

2 is a photograph of a cross section of a molded product obtained in Example 1. FIG. 2 is a photograph of a cross section of a molded product obtained in Comparative Example 1.

  The present invention relates to a molded article in which a magnetic rubber layer formed by vulcanizing a rubber composition containing magnetic powder is bonded to a support member. Here, the rubber composition contains rubber (A), rare earth magnet powder (B), and ferrite magnet powder (C), and contains rare earth magnet powder (B) with respect to 100 parts by mass of rubber (A). It is important that the ratio is 200 to 1000 parts by mass, and the mass ratio (B / C) of the rare earth magnet powder (B) and the ferrite magnet powder (C) is 4/6 to 8/2. Further, the content of the rare earth magnet powder (B) in the skin layer from the surface of the magnetic rubber layer to 50 μm is less than half of the content of the rare earth magnet powder (B) in the entire magnetic rubber layer, and the skin layer It is also important that the content of ferrite magnet powder (C) in is more than half the content of ferrite magnet powder (C) in the entire magnetic rubber layer.

  The present inventors have found that the magnetic rubber layer contains both rare earth magnet powder (B) and ferrite magnet powder (C), and the rare earth magnet powder in the skin layer formed on the surface of the magnetic rubber layer ( It has been found that when the content of B) is small, rust can be prevented from occurring in the molded product, and the durability of the molded product is improved.

  The rubber (A) used in the present invention is not particularly limited, but is preferably at least one rubber selected from the group consisting of fluorine rubber, hydrogenated nitrile rubber, nitrile rubber and acrylic rubber. Among these, fluororubber and hydrogenated nitrile rubber are preferable from the viewpoint of the heat resistance, chemical resistance, durability and the like of the rubber itself.

  The fluororubber used in the present invention is not particularly limited, and is a copolymer of vinylidene fluoride (VDF) and hexafluoropropylene (HFP), a copolymer of VDF and trichlorofluoroethylene (CTFE), VDF and HFP, Copolymer of tetrafluoroethylene (TFE), copolymer of TFE and propylene, copolymer of TFE and fluorine-containing vinyl ether, copolymer of hydrocarbon-based diene monomer and fluorine-containing monomer In particular, binary fluororubber composed of VDF and HFP is preferable. As long as the gist of the present invention is not impaired, a constitutional unit derived from another copolymerizable monomer may be included. The method for vulcanizing the fluororubber is not particularly limited, and polyol vulcanization, peroxide vulcanization, polyamine vulcanization, and the like can be employed. In vulcanizing the polyol, it is preferable to add an acid acceptor such as magnesium oxide or calcium hydroxide in addition to the polyol. The polyol can be blended in advance in the fluororubber.

  The acrylic rubber used by this invention is not specifically limited, What is necessary is just the rubber | gum which has acrylic acid ester as a main component. As the acrylate ester, methyl acrylate, ethyl acrylate, butyl acrylate, methoxyethyl acrylate and the like are preferably used. Examples of the monomer copolymerized with the acrylate ester include acrylonitrile, ethylene, 2-chloroethyl vinyl ether and the like. As long as the gist of the present invention is not impaired, a constitutional unit derived from another copolymerizable monomer may be included. The method for vulcanizing the acrylic rubber is not particularly limited, and peroxide vulcanization, polyamine vulcanization, and the like can be employed.

  The nitrile rubber used in the present invention is not particularly limited, and a copolymer of acrylonitrile and 1,3-butadiene can be used. The 1,3-butadiene unit after polymerization has a double bond, but is not particularly hydrogenated. As long as the gist of the present invention is not impaired, a constitutional unit derived from another copolymerizable monomer may be included. The nitrile rubber vulcanization method is not particularly limited, and peroxide vulcanization, polyamine vulcanization, and the like can be employed.

  The hydrogenated nitrile rubber used in the present invention is not particularly limited, and hydrogenated nitrile rubber can be used. However, in the present invention, it is preferable that the hydrogenated nitrile rubber contains a carboxyl group or a carboxylic anhydride group. The reason will be described in detail below.

  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 a result, the hydrogenated nitrile rubber having a relatively high iodine value (a large amount of residual double bonds) was attempted to be crosslinked using sulfur, but it was hardly crosslinked. 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.

  In addition, the inventors of the present invention blended rare earth magnet powder with a hydrogenated nitrile rubber having a relatively low iodine value (low residual double bond amount) and attempted crosslinking using a peroxide. A remarkably 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.

  On the other hand, as a result of intensive studies by the present inventors, rare earth magnet powder was obtained by using a hydrogenated nitrile rubber containing a carboxyl group or a carboxylic anhydride group and using a polyamine compound as a crosslinking agent. It has been found that the cross-linking reaction proceeds well and a good molded product can be obtained even if it contains. That is, by using a rubber composition containing a hydrogenated nitrile rubber containing a carboxyl group or a carboxylic acid anhydride group and a polyamine-based crosslinking agent, the crosslinking reaction proceeds well even if rare earth magnet powder is blended. The examples shown in Examples 2 to 4 and Comparative Examples 2 to 4 in the present specification are in accordance with the prescription.

  A method for introducing a carboxyl group or a carboxylic acid anhydride group into the hydrogenated nitrile rubber is not particularly limited, but a monomer containing these functional groups or precursors thereof is copolymerized with acrylonitrile and 1,3-butadiene. Thereafter, hydrogenation is preferably performed. Suitable examples of such monomers include α, β-ethylenically unsaturated dicarboxylic acid monoester monomers. In this case, the hydrogenated nitrile rubber 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 esters such as citraconic acid monocyclopentyl, citraconic acid monocyclohexyl, citraconic acid monocycloheptyl; citraconic acid monomethylcyclopentyl, citraconic acid monoethylcyclohexyl, etc .; 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 is preferably 15 to 49% by mass. Moreover, it is preferable that the content rate of a 1, 3- butadiene unit is 50-84 mass% including what was hydrogenated. The iodine value of the hydrogenated nitrile rubber is preferably 50 g / 100 g or less, and more preferably 20 g / 100 g or less.

The polyamine-based crosslinking agent used here is not particularly limited as long as it is a compound having two or more amino groups, or can be in the form of a compound having two or more amino groups during crosslinking. 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 include aliphatic polyamine compounds such as hexamethylenediamine, hexamethylenediamine carbamate, tetramethylenepentamine, hexamethylenediamine-cinnamaldehyde adduct, hexamethylenediamine-dibenzoate salt; Fragrances such as 2-bis {4- (4-aminophenoxy) phenyl} propane, 4,4′-methylenedianiline, m-phenylenediamine, p-phenylenediamine, 4,4′-methylenebis (o-chloroaniline) Group polyamine compounds; compounds having two or more hydrazide structures such as isophthalic acid dihydrazide, adipic acid dihydrazide, sebacic acid dihydrazide; and the like. Among these, aliphatic polyamine compounds are preferable, and hexamethylenediamine carbamate is particularly preferable.

  The rubber composition of the present invention contains rare earth magnet powder (B). By using the rare earth magnet powder (B), the magnetic properties are remarkably improved as compared with the case of using only the ferrite magnet powder (C). The rare earth magnet powder (B) used here 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. As the rare earth magnet powder (B), there are anisotropic magnet powder having magnetic anisotropy and isotropic magnet powder having no magnetic anisotropy, and any of them is used in the magnetic rubber composition of the present invention. It doesn't matter. From the standpoint of magnetism, it is preferable to use isotropic magnet powder.

  The rubber composition of the present invention contains ferrite magnet powder (C) in addition to rare earth magnet powder (B). It is possible to suppress rusting of the rare earth magnet powder (B) by containing the ferrite magnet powder (C) and expressing the distribution of the magnet powder as described later in the magnetic rubber layer. The ferrite magnet powder (C) used in the present invention is not particularly limited, but those having a high coercive force per se are preferable, and magnet powder made of strontium ferrite or barium ferrite is preferably used.

  The particle size of the rare earth magnet powder (B) is not particularly limited, but the average particle size is preferably 2 to 300 μm. When the average particle diameter of the rare earth magnet powder (B) is less than 2 μm, the surface area is large, and the handleability is likely to be deteriorated due to easy oxidation. Moreover, since the content rate of the rare earth magnet powder (B) in a skin layer becomes small, the one where the particle size compared with a ferrite magnet powder (C) is large is suitable also from this point. The average particle diameter of the rare earth magnet powder (B) is more preferably 10 μm or more, and even more preferably 50 μm or more. On the other hand, when the average particle size of the rare earth magnet powder (B) exceeds 300 μm, the magnetic properties in the magnetic rubber layer are likely to vary, and it is difficult to form a fine magnetization pattern. The average particle size is more preferably 250 μm or less.

  The particle diameter of the ferrite magnet powder (C) is not particularly limited, but the average particle diameter is preferably 0.5 to 5 μm. When the average particle diameter of the ferrite magnet powder (C) is less than 0.5 μm, the handleability may be deteriorated. On the other hand, since the content of the rare earth magnet powder (B) in the skin layer is smaller when the particle diameter is smaller than that of the rare earth magnet powder (B), the average particle diameter of the ferrite magnet powder (C) is preferably It is 5 μm or less, more preferably 3 μm or less, and even more preferably 2 μm or less.

  In order to reduce the content of the rare earth magnet powder (B) in the skin layer, the average particle diameter of the rare earth magnet powder (B) is preferably larger than the average particle diameter of the ferrite magnet powder (C). More preferably, the average particle size of the rare earth magnet powder (B) is at least twice the average particle size of the ferrite magnet powder (C), more preferably at least 5 times, particularly preferably at least 10 times. It is.

  In the rubber composition of the present invention, the content of the rare earth magnet powder (B) with respect to 100 parts by mass of the rubber (A) is 200 to 1000 parts by mass. When the content of the rare earth magnet powder (B) is less than 200 parts by mass, the magnetic properties of the obtained molded product are insufficient. The content of the rare earth magnet powder (B) is preferably 250 parts by mass or more. On the other hand, when the content rate of rare earth magnet powder (B) exceeds 1000 mass parts, the mechanical strength of the molded product obtained becomes inadequate. The content of the rare earth magnet powder (B) is preferably 800 parts by mass or less.

  In the rubber composition of the present invention, the mass ratio (B / C) of the rare earth magnet powder (B) and the ferrite magnet powder (C) is 4/6 to 8/2. When the mass ratio (B / C) is less than 4/6, the magnetic properties are insufficient. The mass ratio (B / C) is preferably 5/5 or more, and more preferably 55/45 or more. On the other hand, when the mass ratio (B / C) exceeds 8/2, the content of the rare earth magnet powder (B) in the skin layer cannot be reduced, and the durability of the molded product becomes insufficient. The mass ratio (B / C) is preferably 75/25 or less.

  The rubber composition of the present invention may contain components other than rubber (A), rare earth magnet powder (B) and ferrite magnet powder (C) as long as the effects of the present invention are not impaired. Various additives such as a vulcanizing agent, a vulcanization accelerator, a vulcanization aid, an acid acceptor, a colorant, a filler, and a plasticizer, which are usually used in a rubber composition, can be included.

  The manufacturing method of the molded article of the present invention is not particularly limited. The magnetic rubber layer contains both rare earth magnet powder (B) and ferrite magnet powder (C), and the content of the rare earth magnet powder (B) in the skin layer formed on the surface of the magnetic rubber layer is Any method can be used as long as it can produce a product having the characteristics of the molded product of the present invention. A suitable production method includes a kneading step of kneading a rubber composition containing rubber (A), rare earth magnet powder (B) and ferrite magnet powder (C); an extrusion step of extruding the kneaded rubber composition from a nozzle; And a compression step of compression-molding the extruded rubber composition together with the support member under heating conditions to crosslink the rubber composition and adhere the magnetic rubber layer to the support member. By manufacturing by such a method, the content rate of the rare earth magnet powder (B) of the skin layer is reduced, and a molded product having excellent durability can be obtained.

  First, in the kneading step, a rubber composition containing rubber (A), rare earth magnet powder (B) and ferrite magnet powder (C) is kneaded. The method of kneading 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.

  Subsequently, in the extrusion process, the kneaded rubber composition is extruded from a nozzle. As an apparatus used at this time, an extruder equipped with a cylinder and a screw can be used. The shape of the nozzle is not particularly limited, and may be circular, elliptical, square, or slit-shaped. The temperature of the rubber composition during extrusion is preferably 50 to 100 ° C.

In the extrusion step, the ratio (v / d) of the diameter d (mm) of the inscribed circle of the nozzle to the average speed v (mm / second) of the rubber composition when passing through the nozzle is 1 to 100 (seconds). ^-1 ). Generally, the shear stress in the tube wall when a fluid flows in the tube is proportional to the ratio (v / d) multiplied by the viscosity. Therefore, in the production method of the present invention, it is preferable that the shear stress on the inner wall of the nozzle when discharging from the nozzle is high. By applying such shear stress to the rubber composition from the inner wall of the nozzle, it is presumed that the rare earth magnet powder (B) having a particle size larger than that of the ferrite magnet powder (C) is separated from the inner wall of the nozzle.

  The rubber composition extruded from the nozzle is placed on the support member. The shape of the support member is not particularly limited, but is preferably a plate-like body. In this case, the support member is a substrate. The material of the support member is not particularly limited, but is preferably a metal. When the rubber composition is placed on the support member, the side surface of the extruded rubber composition, that is, the surface that touches the inner wall of the nozzle is brought into contact with the surface of the support member and the mold facing it. At this time, it arrange | positions so that the cross-linked magnetic rubber layer of predetermined thickness may be formed in a subsequent compression process.

  Subsequently, in the compression step, the extruded rubber composition is compression-molded together with the support member under heating conditions to crosslink the rubber composition and adhere the magnetic rubber layer to the support member. The temperature at the time of compression molding 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. Depending on the shape and dimensions of the molded product, even if the surface is cross-linked, there is a case where the surface is not fully cross-linked. 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.

  In the molded product of the present invention thus obtained, the content of the rare earth magnet powder (B) in the skin layer from the surface of the magnetic rubber layer to 50 μm is half the content of the rare earth magnet powder (B) in the entire magnetic rubber layer. Is less than. By reducing the content of the rare earth magnet powder (B) in the skin layer, oxidation deterioration of the rare earth magnet powder (B) can be prevented, and a molded product having excellent durability can be obtained. The content of the rare earth magnet powder (B) in the skin layer is preferably 1/3 or less of the content of the rare earth magnet powder (B) in the entire magnetic rubber layer. Moreover, it is preferable that the rare earth magnet powder (B) is not substantially exposed on the surface of the magnetic rubber layer.

  In the molded product of the present invention, the content of ferrite magnet powder (C) in the skin layer exceeds half of the content of ferrite magnet powder (C) in the entire magnetic rubber layer. When the content rate of the ferrite magnet powder (B) in the skin layer is large, the content rate of the rare earth magnet powder (B) in the skin layer can be reduced. Moreover, by containing ferrite magnet powder (C), oxidation deterioration of the rare earth magnet powder (B) covered with the rubber (A) containing the ferrite magnet powder (C) can be prevented, and the molded article has excellent durability. Can do. Suitably, the content rate of the ferrite magnet powder (C) in a skin layer is 2/3 or more of the content rate of the ferrite magnet powder (C) of the whole magnetic rubber layer.

  Although the use of the molded article of the present invention is not particularly limited, the preferred use 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. When manufacturing a magnetic encoder, a method in which the magnetic rubber composition of the present invention is compression-molded together with a support member, and cross-linked and integrated is preferred. After molding, the magnetic encoder is magnetized in a magnetic field. Since the encoder of the present invention is excellent in rust prevention, it can be used in an environment where it is in direct contact with the atmosphere or in a place where it is hot and humid, and its application is expected to expand.

  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 / Fluoro rubber “DAIEL G716” manufactured by Daikin Industries, Ltd.
Binary polyol vulcanization type Mooney viscosity (ML _{1 + 10} , 100 ° C.): 63
・ Hydrogenated nitrile rubber “ZPT136” manufactured by Nippon Zeon Co., Ltd.
Hydrogenated product of acrylonitrile / 1,3-butadiene / α, β-ethylenically unsaturated dicarboxylic acid monoester copolymer Acrylonitrile content: 35% by mass
Iodine value: 12g / 100g or less

(2) Acid acceptor / Ca (OH) ₂
“Caldic # 2000” manufactured by Omi Chemical Co., Ltd.
・ MgO
"Kyowa Mug 150" manufactured by Kyowa Chemical Industry Co., Ltd.
(3) Cross-linking agent / polyamine-based cross-linking agent Hexamethylenediamine carbamate (HDC)
"Diak-1" made by DuPont

(4) Crosslinking accelerator 1,3-diphenylguanidine (DPG)
“Noxeller D” manufactured by Ouchi Shinsei Chemical Co., Ltd.

(5) Magnet powder / Nd-Fe-B system (isotropic powder: large particle size)
"MQP-14-12" manufactured by Magnequench
Particle size distribution (sieving):
40 mesh (nominal opening 425 μm) ON: less than 0.1% by weight 60 mesh (nominal opening 250 μm) ON: less than 25% by weight 270 mesh (nominal opening 53 μm) pass: less than 12% by weight Particles observed with a microscope The diameter is mainly 100 to 200 μm.
・ Nd-Fe-B system (isotropic powder: small particle size)
"MQFP-14-12" manufactured by Magnequench
Particle size distribution (Microtrack particle analyzer):
Particle size 11 μm or more: less than 0.1% by mass Particle size 5.5 μm or more: less than 36% by mass Particle size 1.95 μm or less: less than 10% by mass The particle size observed with a microscope is mainly 3 to 5 μm.
・ Strontium ferrite (anisotropic powder)
"FH-801" manufactured by Toda Industry Co., Ltd.
Average particle size 1.2μm

Example 1
Fluoro rubber “DAIEL G716” 100 parts by mass, Ca (OH) ₂ 6 parts by mass, MgO ₂ parts by mass, Nd—Fe—B based magnet powder “MQP-14-12” (large particle size) 350 parts by mass and strontium ferrite magnet 200 parts by mass of the powder “FH-801” was kneaded for 40 minutes using an open roll at a temperature of the rubber composition of 40 ° C. to obtain an unvulcanized rubber sheet having a thickness of 2 mm. The roll diameter of the open roll used was 8 inches, the rotation speed of the roll was 20 rpm, and the gap between rolls was 2 mm. The blending ratio at this time 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, a vulcanization curve was measured 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 the torque reaches 10% and a time T90 (min) until the torque reaches 90% of MH were obtained. The results are shown in Table 1.

  Also, using the resulting rubber sheet, a disk-shaped sample having a diameter of 18 mm and a thickness of 6 mm was prepared, and the molded product was crosslinked by heating at 180 ° C. for 3 minutes while applying pressure with a vulcanizing press. Obtained. 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 residual magnetic flux density was 350 mT, indicating good magnetic properties. This residual magnetic flux density was at a level that was not problematic for manufacturing a magnetic encoder.

The obtained unvulcanized rubber sheet was introduced into a rubber extrusion molding machine “EMR-30” manufactured by EM Giken Co., Ltd., kneaded by rotating a screw (L / D = 12), and having a diameter of 2.8 mm. A strand of the rubber composition at 80 ° C. was discharged from the circular nozzle at a speed of 3 m / min (50 mm / sec). The ratio (v / d) of the average speed v (mm / second) of the rubber composition when passing through the nozzle to the diameter d (mm) of the inscribed circle of the nozzle was 18 (second ⁻¹ ).

The strand thus extruded was manually shaped into a ring shape and placed on a SUS430 substrate having an outer diameter of 66 mm, an inner diameter of 56 mm, and a thickness of 0.6 mm. The substrate on which the strand is placed is attached to a mold of a vulcanizing press (50 tons), and is vulcanized and magnetically vulcanized by compressing it at 190 ° C. for 5 minutes at a pressure of 100 kgf / cm ^2. A molded product adhered to the substrate was obtained. The thickness of the magnetic rubber layer was 0.75 mm. The obtained molded product was sufficiently cross-linked and had high strength.

  The photograph which observed the cross section of the obtained molded article with the stereomicroscope is shown in FIG. It can be seen that rare earth magnet powder is hardly observed in the skin layer from the surface to 50 μm. Specifically, it can be seen that the rare earth magnet powder content in the skin layer is approximately 1/5 or less of the rare earth magnet powder content in the entire magnetic rubber layer. On the other hand, rare earth magnet powder was contained in the vicinity of the interface with the substrate at the same content as the central portion of the magnetic rubber layer. The ferrite magnet powder could not be observed because of its small particle size.

  About the cross section of the obtained molded article, the map which showed element distribution of the magnetic rubber layer was obtained using the electron beam microanalyzer "JXA-8500FS" by JEOL Ltd. As a result, the neodymium content was reduced in the vicinity of the surface, and this point was consistent with the knowledge obtained from the cross-sectional photograph. On the other hand, it was found that strontium was distributed almost uniformly over the entire area of the magnetic rubber layer, and the strontium ferrite magnet powder was present in the skin layer at the same content as that in the central portion.

The obtained molded product was subjected to a salt spray test (based on JIS Z2371). Specifically, salt water spray was performed for 33 hours at 35 ° C. using a salt spray tester “STP-90V-2” manufactured by Suga Test Instruments Co., Ltd. The surface condition of the magnetic rubber layer of the molded product after the test was visually observed and evaluated according to the following evaluation criteria.
A: The generation | occurrence | production of the slight rust was recognized for a very small part.
B: The generation | occurrence | production of the slight rust was recognized partially.
C: Generation of rust was partially observed.
D: The generation | occurrence | production of remarkable rust was recognized partially.
E: The generation | occurrence | production of remarkable rust was recognized by the whole.

Comparative Example 1
In Example 1, only 350 parts by mass of Nd—Fe—B magnet powder “MQP-14-12” was used as the magnet powder, and the strontium ferrite magnet powder was not used. An unvulcanized rubber sheet was obtained. The blending ratio at this time is shown in Table 1. Using the obtained rubber sheet, vulcanization characteristics and magnetic characteristics were evaluated in the same manner as in Example 1. The results are shown in Table 1. The obtained unvulcanized rubber sheet was molded under the same conditions as in Example 1 to obtain a molded product in which the vulcanized magnetic rubber layer was bonded to the substrate. The thickness of the magnetic rubber layer was 0.75 mm. The obtained molded product was sufficiently cross-linked and had high strength. The photograph which observed the cross section of the obtained molded article with the stereomicroscope is shown in FIG. It can be seen that the rare earth magnet powder is distributed in the skin layer as well as in the vicinity of the interface with the substrate in the same manner as in the central portion. The obtained molded product was subjected to a salt spray test in the same manner as in Example 1, and the state of the surface of the magnetic rubber layer of the molded product after the test was visually observed to be “E” determination.

Example 2
Carboxyl group-containing hydrogenated nitrile rubber “ZPT136” 100 parts by mass, hexamethylenediamine carbamate (HDC) 3 parts by mass, 1,3-diphenylguanidine (DPG) 2 parts by mass, Nd—Fe—B magnet powder “MQP-14” -12 "(large particle size) 540 parts by mass and strontium ferrite magnet powder" FH-801 "360 parts by mass using an open roll for 40 minutes at a temperature of the rubber composition of 40 ° C., and unvulcanized rubber A sheet was produced. The blending ratio is shown in Table 2. Using the obtained rubber sheet, vulcanization characteristics and magnetic characteristics were evaluated in the same manner as in Example 1. The results are shown in Table 2. The obtained unvulcanized rubber sheet was molded under the same conditions as in Example 1 to obtain a molded product in which the vulcanized magnetic rubber layer was bonded to the substrate. The thickness of the magnetic rubber layer was 0.75 mm. The obtained molded product was sufficiently cross-linked and had high strength.

  When a cross section of the obtained molded product was observed, rare earth magnet powder was hardly observed in the skin layer from the surface to 50 μm, and the content of rare earth magnet powder in the skin layer was determined based on the rare earth magnet in the entire magnetic rubber layer. The content of powder was approximately 1/5 or less. On the other hand, rare earth magnet powder was contained in the vicinity of the interface with the substrate at the same content as the central portion of the magnetic rubber layer. Further, as in Example 1, an element distribution map of the cross section of the magnetic rubber layer was obtained using an electron beam microanalyzer. As a result, strontium was distributed almost uniformly over the entire area of the magnetic rubber layer. It was also found that strontium ferrite magnet powder was present in the layer at the same content as the central part. The obtained molded product was subjected to a salt spray test in the same manner as in Example 1. When the condition of the surface of the magnetic rubber layer of the molded product after the test was visually observed, it was “A” judgment.

Example 3
In Example 2, the Nd—Fe—B magnet powder “MQP-14-12” was added to 630 parts by mass, and the strontium ferrite magnet powder was changed to 270 parts by mass. In the same manner as in Example 2, an unvulcanized rubber sheet was produced. The blending ratio is shown in Table 2. Using the obtained rubber sheet, the vulcanization characteristics and magnetic characteristics were evaluated in the same manner as in Example 2. The results are shown in Table 2. The obtained unvulcanized rubber sheet was molded under the same conditions as in Example 2 to obtain a molded product in which the vulcanized magnetic rubber layer was bonded to the substrate. The thickness of the magnetic rubber layer was 0.75 mm. The obtained molded product was sufficiently cross-linked and had high strength.

  When a cross section of the obtained molded product was observed, rare earth magnet powder was hardly observed in the skin layer from the surface to 50 μm, and the content of rare earth magnet powder in the skin layer was determined based on the rare earth magnet in the entire magnetic rubber layer. The content of powder was approximately 1/5 or less. On the other hand, rare earth magnet powder was contained in the vicinity of the interface with the substrate at the same content as the central portion of the magnetic rubber layer. Further, as in Example 1, an element distribution map of the cross section of the magnetic rubber layer was obtained using an electron beam microanalyzer. As a result, strontium was distributed almost uniformly over the entire area of the magnetic rubber layer. It was also found that strontium ferrite magnet powder was present in the layer at the same content as the central part. The obtained molded product was subjected to a salt spray test in the same manner as in Example 1. When the condition of the surface of the magnetic rubber layer of the molded product after the test was visually observed, it was “A” judgment.

Example 4
In Example 2, instead of Nd—Fe—B magnet powder “MQP-14-12”, Nd—Fe—B magnet powder “MQFP-14-12” having a small particle diameter was used. In the same manner as in Example 2, an unvulcanized rubber sheet was produced. The blending ratio is shown in Table 2. Using the obtained rubber sheet, the vulcanization characteristics and magnetic characteristics were evaluated in the same manner as in Example 2. The results are shown in Table 2. The obtained unvulcanized rubber sheet was molded under the same conditions as in Example 2 to obtain a molded product in which the vulcanized magnetic rubber layer was bonded to the substrate. The thickness of the magnetic rubber layer was 0.75 mm. The obtained molded product was sufficiently cross-linked and had high strength.

  In the same manner as in Example 1, using an electron beam microanalyzer, a map of the element distribution of the magnetic rubber layer of the obtained molded product was obtained. In the skin layer, the content of neodymium was half of that in the central portion. It was about 1/3 less. Further, strontium was distributed almost uniformly throughout the entire magnetic rubber layer. The obtained molded product was subjected to a salt spray test in the same manner as in Example 1, and when the condition of the surface of the magnetic rubber layer of the molded product after the test was visually observed, it was “B”.

Comparative Example 2
Raw materials were blended in the same formulation as in Example 2, and an unvulcanized rubber sheet was produced using an open roll in the same manner as in Example 2. The obtained sheet was cut into an annular shape and placed on a SUS430 substrate having an outer diameter of 66 mm, an inner diameter of 56 mm, and a thickness of 0.6 mm. The substrate on which the annular sheet is placed is mounted on a mold of a vulcanizing press (50 tons), and is compressed and crosslinked at 190 ° C. for 5 minutes at a pressure of 100 kgf / cm ² to vulcanize the magnetic rubber. A molded product with the layer adhered to the substrate was obtained. The thickness of the magnetic rubber layer was 0.75 mm. The obtained molded product was sufficiently cross-linked and had high strength.

  When the cross section of the obtained molded product was observed, the content of the rare earth magnet powder in the skin layer from the surface to 50 μm was less than the content of the rare earth magnet powder in the entire magnetic rubber layer, but more than half of the content. Moreover, when the element distribution map of the magnetic rubber layer was obtained using an electron beam microanalyzer in the same manner as in Example 1, strontium was distributed almost uniformly over the entire area of the magnetic rubber layer. In addition, it was found that strontium ferrite magnet powder was present in the vicinity of the interface with the substrate at the same content as the central portion. The obtained molded product was subjected to a salt spray test in the same manner as in Example 1. When the condition of the surface of the magnetic rubber layer of the molded product after the test was visually observed, it was “C” judgment.

Comparative Example 3
Raw materials were blended in the same formulation as in Example 2, and an unvulcanized rubber sheet was produced using an open roll in the same manner as in Example 2. The obtained sheet was finely broken by hand, and then placed on a SUS430 substrate having an outer diameter of 66 mm, an inner diameter of 56 mm, and a thickness of 0.6 mm. The substrate on which the strips of the sheet were placed was mounted on a mold of a vulcanizing press (50 tons), compressed and crosslinked at 190 ° C. for 5 minutes at a pressure of 100 kgf / cm ² and vulcanized. A molded product having a magnetic rubber layer adhered to the substrate was obtained. The thickness of the magnetic rubber layer was 0.75 mm. The obtained molded product was sufficiently cross-linked and had high strength.

  When the cross section of the obtained molded product was observed, the content of rare earth magnet powder in the skin layer from the surface to 50 μm was smaller than the content of rare earth magnet powder in the entire magnetic rubber layer, but the molded product of Comparative Example 2 It was more. Moreover, when the element distribution map of the magnetic rubber layer was obtained using an electron beam microanalyzer in the same manner as in Example 1, strontium was distributed almost uniformly over the entire area of the magnetic rubber layer. In addition, it was found that strontium ferrite magnet powder was present in the vicinity of the interface with the substrate at the same content as the central portion. The obtained molded product was subjected to a salt spray test in the same manner as in Example 1, and the state of the surface of the magnetic rubber layer of the molded product after the test was visually observed to be “D” determination.

Comparative Example 4
In Example 2, only 700 parts by mass of Nd—Fe—B-based magnet powder “MQP-14-12” was used as magnet powder, and strontium ferrite magnet powder was not used. An unvulcanized rubber sheet was obtained. The blending ratio at this time is shown in Table 2. Vulcanization characteristics were evaluated in the same manner as in Example 2 using the obtained rubber sheet. The results are shown in Table 2. The obtained unvulcanized rubber sheet was molded under the same conditions as in Example 2 to obtain a molded product in which the vulcanized magnetic rubber layer was bonded to the substrate. The thickness of the magnetic rubber layer was 0.75 mm. The obtained molded product was sufficiently cross-linked and had high strength.

  When the cross section of the obtained molded product was observed, the rare earth magnet powder was distributed in the skin layer from the surface to 50 μm and in the vicinity of the interface with the substrate as in the central portion. The obtained molded product was subjected to a salt spray test in the same manner as in Example 1, and the state of the surface of the magnetic rubber layer of the molded product after the test was visually observed to be “E” determination.

Comparative Example 5
In Example 2, only 700 parts by mass of strontium ferrite magnet powder “FH-801” was used as the magnet powder, and no Nd—Fe—B magnet powder was used. A vulcanized rubber sheet was obtained. The blending ratio at this time is shown in Table 2. Using the obtained rubber sheet, the vulcanization characteristics and magnetic characteristics were evaluated in the same manner as in Example 2. The results are shown in Table 2. The obtained unvulcanized rubber sheet was molded under the same conditions as in Example 2 to obtain a molded product in which the vulcanized magnetic rubber layer was bonded to the substrate. The thickness of the magnetic rubber layer was 0.75 mm. The obtained molded product was sufficiently cross-linked and had high strength. The obtained molded product was subjected to a salt spray test in the same manner as in Example 1. When the condition of the surface of the magnetic rubber layer of the molded product after the test was visually observed, it was “A” judgment.

As shown in Tables 1 and 2, in Examples 1 to 4 in which a strand obtained by extruding a rubber composition containing a rare earth magnet powder (B) and a ferrite magnet powder (C) was compression molded, the rare earth magnet in the skin layer The content of the powder (B) was reduced, and the generation of rust was suppressed. At this time, when the particle size of the rare earth magnet powder (B) was larger (Examples 1 to 3), the rust resistance was better than when the particle size was smaller (Example 4). In Comparative Example 2 using a sheet that applies only a momentary shearing force at the roll contact point, the rust prevention property is reduced as compared with the Example, and in Comparative Example 3 using a sheet strip, the rust prevention property is further reduced. did. On the other hand, when the ferrite magnet powder (C) is not included (Comparative Examples 1 and 4), the rare earth magnet powder (B) is distributed in the skin layer and in the vicinity of the interface with the substrate as in the central portion. The occurrence of rust was remarkable. Further, when only the ferrite magnet powder (C) was included (Comparative Example 5), the magnetic properties were insufficient.

Claims (6)

A molded article in which a magnetic rubber layer formed by vulcanizing a rubber composition containing magnetic powder is bonded to a support member;
The rubber composition contains a rubber (A), a rare earth magnet powder (B), and a ferrite magnet powder (C), and the content of the rare earth magnet powder (B) with respect to 100 parts by mass of the rubber (A) is 200. ~ 1000 parts by mass, the mass ratio (B / C) of the rare earth magnet powder (B) and the ferrite magnet powder (C) is 4/6 to 8/2,
The content of the rare earth magnet powder (B) in the skin layer from the surface of the magnetic rubber layer to 50 μm is less than half of the content of the rare earth magnet powder (B) in the entire magnetic rubber layer,
A molded product characterized in that the content of ferrite magnet powder (C) in the skin layer exceeds half of the content of ferrite magnet powder (C) in the entire magnetic rubber layer.   The molded article according to claim 1, wherein the rubber (A) is at least one rubber selected from the group consisting of fluoro rubber, hydrogenated nitrile rubber, nitrile rubber, and acrylic rubber.   The rare earth magnet powder (B) has an average particle diameter of 2 to 300 μm, the ferrite magnet powder (C) has an average particle diameter of 0.5 to 5 μm, and the rare earth magnet powder (B) has an average particle diameter of a ferrite magnet. The molded product according to claim 1 or 2, wherein the molded product is larger than the average particle size of the powder (C).   The molded article according to claim 1, which is a magnetic encoder. A kneading step of kneading a rubber composition containing rubber (A), rare earth magnet powder (B) and ferrite magnet powder (C);
An extrusion step of extruding the kneaded rubber composition from a nozzle; and the extruded rubber composition is compression-molded under heating conditions together with a support member to crosslink the rubber composition and adhere a magnetic rubber layer to the support member Compressing step;
The method for producing a molded product according to any one of claims 1 to 4, further comprising: In the extrusion step, the ratio (v / d) of the diameter d (mm) of the inscribed circle of the nozzle and the average speed v (mm / second) of the rubber composition when passing through the nozzle is 1 to 100 (second ⁻¹ ). The method for producing a molded article according to claim 5.

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