JP2006332431A - Rubber magnet and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rubber magnet with requested property including fire resistance while reducing the use of chlorinated polyethylene. <P>SOLUTION: In the rubber magnet containing rubber material and magnetic powder, the rubber material consists of 5 to 45 wt% acryl-based copolymer and the residual part consisting of chlorinated polyethylene. The manufacturing method of the rubber magnet is provided with a process for obtaining a kneaded matter containing the rubber material consisting of the acryl-based copolymer and the chlorinated polyethylene and magnetic powder, and a process for obtaining a molded body by extrusion molding of the kneaded matter. In the process for obtaining the kneaded body, it is desirable that only a part of the magnetic powder to be added (including 0) is added before the rubber material consisting of the acryl-based copolymer and the chlorinated polyethylene comes into a prescribed kneaded state, and that the remaining magnetic powder is added and kneading is kept after the rubber material comes into the prescribed kneaded state. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a rubber magnet, and more particularly to a rubber magnet containing flame retardant chlorinated polyethylene as a rubber material.

  Conventionally, ferrite permanent magnets are used in various fields as sintered magnets, plastic magnets, or rubber magnets because raw materials are inexpensive. Specifically, it is incorporated in motors and actuators and is widely used in the automotive field from AV equipment and OA equipment. Currently, with the downsizing of motors and the like, permanent magnet bodies are required to have a smaller diameter and a thinner wall and to improve dimensional accuracy.

  Sintered magnets shrink greatly during the sintering process, and high dimensional accuracy cannot be obtained. A processing process is required after sintering. A magnet (a permanent magnet body formed by mixing magnetic powder and a rubber material) is used. Among these, when a permanent magnet is incorporated into a motor device or the like, a rubber magnet that does not easily cause a crack during press-fitting and does not require an adhesion step is preferably used.

  An example of a conventional method for producing an anisotropic rubber magnet is shown below. First, ferrite magnet powder and a rubber material are pressure-kneaded to obtain a composition having a certain viscosity, and then extrusion molding is performed in a magnetic field to prepare an anisotropic composition. Furthermore, after demagnetizing the anisotropic composition, crosslinking treatment (heat treatment) is performed as necessary to obtain a rubber magnet precursor. Then, after cutting into a required size, a rubber magnet is obtained by performing a magnetization process. There is also a method for producing an anisotropic composition by molding a composition of a ferrite magnet powder and a rubber material by roll rolling. In this case as well, a rubber magnet precursor is obtained by cutting a sheet having a uniform thickness obtained by roll rolling into a required size. For convenience of handling, transactions are often made at the precursor stage of rubber magnets, and products at the precursor stage are also called rubber magnets.

  By the way, many of the components incorporated into the resin member are required to have flame retardancy, and the rubber magnet is also required to have flame retardancy. In order to obtain flame retardancy, it is effective to use chlorinated polyethylene as the rubber material of the rubber magnet (for example, Patent Document 1).

JP-A-11-111518

However, when only chlorinated polyethylene is used as a rubber material, it is desirable that the amount be reduced as much as possible because chlorinated polyethylene may release harmful substances by combustion.
An object of the present invention is to provide a rubber magnet having required characteristics including flame retardancy while reducing the amount of chlorinated polyethylene used.

  In order to reduce the use of chlorinated polyethylene, substitution substances were examined, and it was found that a predetermined amount of acrylic copolymer was effective. Accordingly, the present invention provides a rubber magnet comprising a rubber material and a magnetic powder, wherein the rubber material comprises an acrylic copolymer: 5 to 45 wt%, and the balance: chlorinated polyethylene. To do.

  In the process of producing the rubber magnet of the present invention, when two types of rubber materials, chlorinated polyethylene and acrylic copolymer, are used, the rubber materials are uniform compared to the case of using a single rubber material. It was found that kneading was not easy. It has been found that this problem can be solved by limiting the amount of magnetic powder added in the initial stage of rubber material kneading. The method for producing a rubber magnet of the present invention based on this knowledge includes a step of obtaining a kneaded product containing different types of rubber materials and magnetic powders, and a step of extruding the kneaded product to obtain a molded body. The step of obtaining the product is limited to the addition of a part of the magnetic powder to be added (however, including 0) until a plurality of different types of rubber materials are in a predetermined kneaded state. After the kneading state is reached, the remaining magnetic powder is added and kneading is continued.

  The manufacturing method of the rubber magnet of the present invention does not limit different types of rubber materials, but when manufacturing the rubber magnet of the present invention described above, the different types of rubber materials include chlorinated polyethylene and An acrylic copolymer will be included.

  In the method for producing a rubber magnet of the present invention, whether or not different types of rubber materials are in a predetermined kneaded state can be determined by the temperature of the kneaded product. In the present invention, when the temperature of the kneaded product reaches 50 ° C. or more, it is considered that different types of rubber materials are in a predetermined kneaded state, and the remaining magnetic powder is added to continue kneading. preferable.

  In the present invention, it is preferable to knead a plurality of types of rubber materials without adding magnetic powder until a predetermined kneading state is achieved, in order to quickly knead a plurality of types of rubber materials, The addition of magnetic powder is not avoided until the kneaded state is reached. If the added weight of the magnetic powder is 120 parts by weight or less with respect to the total weight of the plurality of types of rubber materials, the kneading of the plurality of types of rubber materials is not hindered.

  As described above, according to the present invention, it is possible to provide a rubber magnet having required characteristics including flame retardancy while reducing the amount of chlorinated polyethylene used. In addition, according to the present invention, it is possible to provide a rubber magnet in which different types of rubber materials ensure a predetermined kneading state, and different types of rubber materials are uniformly dispersed.

Hereinafter, the present invention will be described in detail based on embodiments.
<Rubber magnet>
The rubber magnet of the present invention contains chlorinated polyethylene and an acrylic copolymer as a rubber material.
Chlorinated polyethylene having excellent flame retardancy is obtained by chlorinating polyethylene and has a structure of a ternary copolymer of ethylene-vinyl chloride-1,2-dichloroethylene. Depending on the addition conditions of chlorine, the physical properties can be arbitrarily adjusted from hard plastic to complete rubber. In the present invention, rubber-like chlorinated polyethylene is preferably used, but a plastic-like one can also be used depending on the application. Specific examples of chlorinated polyethylene include Showa Denko's “Elaslene” series, Daiso's “Daisolac” series, and DuPont Dow Elastomer Japan's “Tyrin” series.

The rubber magnet of the present invention uses an acrylic copolymer as a rubber material together with chlorinated polyethylene. This is because, as shown in Example 1 to be described later, the rubber magnet has the requirements for manufacturing. As the acrylic copolymer, nitrile rubber (NBR) is preferable. NBR is a copolymer rubber obtained by copolymerization of acrylonitrile and butadiene. The acrylonitrile content in NBR is 18 to 50%, preferably 26 to 42%. NBR preferably has a high Mooney viscosity (high molecular weight) of ML _{1 + 4} (100 ° C.) of 25 or more. More preferable Mooney viscosity is 30-60.
Specific examples of NBR include, for example, “Nipol” series “1041”, “1031”, “1001” from ZEON Corporation, “Perbunan” series from Bayer, “JSR N240S” from Nippon Synthetic Rubber, Polymer "Polycer Clinac 802" and ICI "Butacon XA-1300". The rubber material is usually provided as a lump.
Further, as the acrylic copolymer, hydrogenated nitrile rubber (HNBR) and acrylic rubber (ACM) can also be suitably used.

  In the rubber magnet of the present invention, when the amount of the acrylic copolymer with respect to the entire rubber material is less than 5 wt%, the effect of substituting part of the chlorinated polyethylene is insufficient. On the other hand, if the amount of the acrylic copolymer exceeds 45 wt%, flame retardancy cannot be ensured. Therefore, in the present invention, the amount of the acrylic copolymer in the rubber material is set to 5 to 45 wt%. The amount of the acrylic copolymer in a preferable rubber material is 8 to 35 wt%.

As the magnetic powder used in the rubber magnet of the present invention, a ferrite magnet powder, which is a ferromagnetic material represented by MO · 6Fe ₂ O ₃ (M = Sr, Ba, Pb, etc.), RCo ₅ , R ₂ Co ₁₇ ( A rare earth cobalt-based magnet powder represented by R = Sm, Y, La, Ce or the like), an R—Fe—B based magnet powder having R ₂ Fe ₁₄ B as a main phase, Manganese-bismuth-based magnet powder, manganese-aluminum-based magnet powder, cobalt-based magnet powder (for example, Al—Ni—Co-based, Fe—Cr—Co-based, etc.) can be used. In particular, Sr · ferrite is preferably used. For example, Sr · ferrite is prepared by mixing and mixing 6 mol of iron oxide (Fe ₂ O ₃ ) and 1 mol of strontium carbonate (SrCO ₃ ), granulating it into pellets, performing reaction firing, cooling, and ball milling. It is obtained by pulverizing to 0.5 to 3.0 μm.

  The magnetic powder preferably has a volume ratio of 60 to 80 vol% with respect to the entire rubber magnet. This is because if the magnetic powder ratio is less than 60 vol%, the magnetic properties (particularly the residual magnetic flux density Br) will be insufficient, and if it exceeds 80 vol%, it will be difficult to extrude the mixture. The volume ratio of the magnetic powder with respect to the rubber material is 80 to 90 parts by weight.

As shown in FIG. 1, the rubber magnet according to the present embodiment can be manufactured through a kneading step, a pulverizing step, a forming step, a rolling step, a crosslinking treatment step, and a cutting step.
<Kneading process>
Usually, in the kneading step, the rubber material and the magnetic powder are added together and kneaded from the beginning. However, as shown in FIG. 2, the present invention has a plurality of types of rubber materials (for example, rubber material A and rubber material B). Is characterized in that, after the two rubber materials are in a predetermined kneaded state, the magnetic powder is added and further kneaded. This is because, as described above, when two types of rubber materials and magnetic powder are added together and kneaded from the beginning, it is difficult to sufficiently knead the two types of rubber materials. It is understood that the magnetic powder prevents kneading between the rubber materials. Therefore, when only the rubber material was kneaded without adding the magnetic powder together with the rubber material, a good kneaded state could be obtained quickly, and the magnetic powder was added to the kneaded material and kneaded. However, it was possible to obtain a kneaded material in a good state containing a rubber material and magnetic powder.

  In the present invention, it is most preferable to add the magnetic powder after bringing the two types of rubber materials into a predetermined kneaded state. However, the present invention does not exclude adding magnetic powder together with a rubber material from the beginning of kneading. As shown in FIG. 3, if it is a part of the amount to be finally added, even if the magnetic powder is added together with the rubber material from the beginning of kneading, the tendency of hindering the kneading of the two types of rubber materials is small. Specifically, the magnetic powder can be added together with the rubber material from the beginning of the kneading as long as it is equal to or less than the rubber material. Then, after the two types of rubber materials have obtained a predetermined kneaded state, the remaining magnetic powder can be added. The temperature of the kneaded product is an important factor in grasping the kneaded state, and whether or not two types of rubber materials have obtained a predetermined kneaded state can be determined by the temperature of the kneaded product. Therefore, in the present invention, it is allowed to add magnetic powder in an amount of 120 parts by weight or more with respect to the total weight of the rubber material when the temperature reaches 50 ° C or higher. In other words, when the temperature of the kneaded material containing two types of rubber materials is less than 50 ° C., the amount of magnetic powder added is set to a range of less than 120 parts by weight with respect to the total weight of the rubber materials.

  The form of adding the magnetic powder is not limited to that shown in FIGS. For example, as shown in FIG. 4, rubber material A (rubber material B) and a part of the magnetic powder to be added are kneaded, and rubber material B (rubber material A) is further added and kneaded to obtain a predetermined kneading. After the state is reached, the remaining magnetic powder may be added. Further, as shown in FIG. 5, the rubber material A and a part of the magnetic powder to be added are kneaded, and the rubber material B and a part of the magnetic powder to be added are kneaded. It is good also as a form which knead | mixes, after combining each kneaded material and adding the remaining magnetic powder. In addition to this, it can be set as the form which does not deviate from the meaning of this invention.

<Additives>
Various additives can be added during kneading. Additives include plasticizers, coupling agents, cross-linking agents, cross-linking aids, lubricants and anti-aging agents.
The plasticizer plays a role of softening the rubber material during kneading or molding. Examples of the plasticizer used in the present invention include phthalic acid esters such as dibutyl phthalate, dioctyl phthalate, and diethyl phthalate. Various trimellitic esters can also be used suitably. The addition amount of the plasticizer is 10 to 30 parts by weight, preferably 15 to 25 parts by weight per 100 parts by weight of the rubber material.

The coupling agent plays a role of modifying the surface of the magnetic powder, which is an inorganic substance, and improving the adhesion with a rubber material, which is an organic substance. As coupling agents, silane-based, titanate-based, aluminate-based and zirconate-based ones are known. In the present invention, silane-based coupling agents are suitable. The silane coupling agent is represented by the general formula: X—R—Si (OR) ₃ and has two different functional groups (X and OR) in the molecule. One functional group (X) is a functional group chemically bonded to an organic material (for example, vinyl group, epoxy group, amino group, methacryl group, mercapto group, etc.), and the other functional group (OR) is an inorganic material. A functional group (methoxy group, ethoxy group, etc.) The coupling agent is preferably 0.1 to 3% by weight with respect to the magnetic powder.

The cross-linking agent forms a three-dimensional structure in the chain rubber molecule by a cross-linking operation and imparts properties as an elastic body. As the crosslinking agent in the present invention, sulfur or peroxide is preferably used. Examples of the peroxide include “Kayamek A”, “Trigonox TMBH” manufactured by Kayaku Akzo, “Park Mill D”, “Perhexa 25B” manufactured by Nippon Oil & Fats. The compounding amount of the crosslinking agent is 0.4 to 3.0 parts by weight, preferably 0.6 to 2.4 parts by weight per 100 parts by weight of the rubber material.
Examples of the crosslinking assistant (crosslinking accelerator) include zinc oxide, magnesium oxide, dibenzothiazyl sulfide and the like. Two or more of these may be used in combination. The amount of the crosslinking aid is 0.1 to 15 parts by weight, preferably 1.0 to 10 parts by weight per 100 parts by weight of the rubber material.

  The lubricant functions to improve the fluidity of the rubber material itself and to increase the fluidity and improve the moldability by reducing the frictional resistance acting on the interface between the rubber material and the molding machine. Therefore, it is generally desirable that the lubricant has a nonpolar group that can soften the rubber material and a polar group that acts as a lubricant interposed between the molding machine and the rubber material. Examples of the lubricant used in the present invention include waxes such as paraffin wax, liquid paraffin, polyethylene wax, and microcristan wax; fatty acids such as stearic acid, myristic acid, lauric acid, palmitic acid, oleic acid, and behenic acid; Metal soaps such as calcium phosphate, magnesium stearate, lithium stearate, zinc stearate, calcium laurate; fatty acid amides such as stearic acid amide, oleic acid amide, erucic acid amide, lauric acid amide; stearyl alcohol, lauryl alcohol, meli Higher alcohols such as sil alcohol; fatty acid esters such as butyl stearate and methyl stearate. Among these, metal soaps are preferable, and zinc stearate is particularly preferable.

  The addition amount of the lubricant (total of metal soap and fatty acid) is preferably 3 to 25 parts by weight with respect to 100 parts by weight of the rubber material. A more preferable amount of the lubricant is 5 to 20 parts by weight. If the amount of the lubricant added is small, the orientation at the time of molding in a magnetic field is lowered, and further, the molded article is cracked after molding. Moreover, when it adds excessively, the adhesive force of the molded object surface will increase, and it will become a cause of adhesion to a roll in the rolling process after shaping | molding.

Rubber has high oxygen diffusivity due to active thermal motion of molecular chains, and is therefore more easily oxidized than plastic. In addition, the main chain cleavage reaction (ozone degradation) due to ozone and fatigue degradation due to repeated elongation accompanied by breakage of the cross-linked chain are also easily received. Anti-aging agents are added to prevent these series of degradations.
As the antioxidant, aldehydes, ketones, amine-reactive organisms and derivatives thereof, amines and derivatives thereof, imidazoles, phenols and derivatives thereof, and the like can be used. The addition amount of the anti-aging agent is preferably 0.5 to 3.0 parts by weight, more preferably 1.0 to 2.5 parts by weight with respect to 100 parts by weight of the rubber material.
Additives are appropriately added depending on the type of rubber material and the use of the rubber magnet, and it is not essential for the present invention to add all types of additives described above.

<Crushing and molding process>
The composition (kneaded material) obtained in the kneading step is pulverized into pellets, and the pellets are molded by, for example, an extrusion method to obtain a molded body formed into an arbitrary shape such as a sheet. In the case of extrusion molding, the temperature of the molded body immediately after extrusion is 80 to 120 ° C.
In addition, shaping | molding can be performed in a magnetic field or a non-magnetic field. In order to perform extrusion molding in a magnetic field, an extruder in which a magnetic coil is disposed around a mold is used, and for example, the molding may be performed under conditions of a magnetic field intensity of 1100 to 1600 kA / m.

Anisotropy can be imparted to the rubber magnet by orienting the magnetic powder by molding in a magnetic field. The lubricant improves the degree of orientation by facilitating the movement of the magnetic powder in the rubber material during molding.
Even when the molding is not performed in a magnetic field, the rubber magnet can be made anisotropic by molding by using plate-like magnetic powder. Even in this case, it goes without saying that lubricants, particularly fatty acids, are effective for improving the degree of orientation.

<Rolling process>
The formed body is rolled and a magnetic sheet having a desired thickness is obtained. For roll rolling, for example, a calendar roll can be used.
The rolling reduction during rolling is not particularly limited, but if the rolling reduction is too small, the number of rolling increases. On the other hand, if the rolling reduction is too large, the residual magnetic flux density (Br) decreases. Therefore, the rolling reduction may be 5 to 60%, preferably 5 to 30%.

  The rolling conditions may be set based on the hardness of the magnetic sheet during rolling. For example, when ferrite powder is used as the magnetic powder and chlorinated polyethylene and NBR are used as the rubber material, the hardness of the magnetic sheet during rolling is set to 27 or less, preferably 15 to 26, and more preferably 15 to 23. When rolled at room temperature, the magnetic sheet has a hardness of about 28.

<Crosslinking process>
In the crosslinking treatment step, the rolled magnetic sheet is held at 160 to 230 ° C. for 5 to 60 minutes. When the temperature of the crosslinking treatment is lower than 160 ° C., the time required for the crosslinking treatment is undesirably increased. On the other hand, it is difficult to stably obtain a rubber magnet having desired strength and flexibility by a crosslinking treatment at a high temperature exceeding 230 ° C.

<Cutting process>
In the cutting step, the magnetic sheet cured by crosslinking is cut into a desired size. The cut magnetic sheet is magnetized and used as a rubber magnet. The rubber magnet of the present invention is used in various fields, for example, fields of electric machines such as small motors, timers, generators, reed switches, fields of office automation equipment such as copiers, calculators, printers, telephones, keyboards, chucks, It is suitably used in the field of using adsorption force such as stickers and educational materials.

Hereinafter, the present invention will be described based on specific examples.
As magnetic powder, anisotropic Sr ferrite powder (manufactured by Nippon Valve Industry Co., Ltd., NF56, average particle size 1.1 μm) was prepared.
Moreover, the following rubber materials A and B (8 types) were prepared as rubber materials. In addition, the rubber material shall use two kinds of convenience of any one of the rubber material A and the rubber material B.
A: Chlorinated polyethylene (manufactured by Showa Denko KK, elastane)
B: Nitrile rubber NBR (manufactured by JSR Corporation, N230S)
Hydrogenated nitrile rubber HNBR (manufactured by Nippon Zeon Co., Ltd., Nipol AR71)
Acrylic rubber ACM (manufactured by Nippon Zeon Co., Ltd., Zetpol 2010)
Styrene butadiene rubber SBR (manufactured by JSR Corporation, 1714)
Ethylene propylene rubber EPDM (manufactured by Chukyo Rubber Co., Ltd., EB270N)
Urethane rubber AU (manufactured by Chukyo Rubber Co., Ltd., TR100-50)
Silicon rubber Si (manufactured by Chukyo Rubber Co., Ltd., SRS151)

A rubber magnet was manufactured using the above magnetic powder and rubber material.
The kneading was performed in the following two forms using a kneader (kneader). During kneading, myristic acid: 10 wt% and zinc oxide: 5 wt% were added as additives. Kneading was completed when the kneaded product reached 120 ° C. After completion of the kneading, the amount of magnetic powder remaining in the kneader was measured to evaluate the compatibility. Evaluation criteria are shown below. The smaller the amount of magnetic powder remaining in the kneader after completion of kneading, the better the compatibility between the magnetic powder and the rubber material.
Form 1: Magnetic powder and rubber material are added from the beginning Form 2: Two kinds of rubber materials are kneaded in advance, and when the kneaded material reaches 60 ° C., magnetic powder is added and kneaded.

Using the composition obtained by kneading, a rubber magnet was molded by an extrusion die (opening area: 15 × 2 mm). For a rubber magnet that has been subjected to crosslinking treatment at 200 ° C. for 30 minutes, the magnetic properties (residual magnetic flux density (Br), maximum energy product ((BH) _max )) are measured, and shape retention, oil resistance, and combustibility are measured. And dispersibility was evaluated. The evaluation results are shown in Table 1. When urethane rubber (AU) or silicon rubber (Si) was used as the rubber material B, it could not be molded. Although the evaluation criteria of shape retention property are as follows, it is preferable that the cross-sectional area of the mold coincides with or approximates the cross-sectional area of the molded body. The evaluation criteria for oil resistance are as follows, and the resistance is evaluated by immersing a rubber magnet in the test oil. The evaluation criteria of combustibility are as shown in Table 2, and V-0 is the most excellent in flame retardancy. The dispersibility is evaluated by visually observing whether or not the two types of rubber materials are unevenly distributed.

Compatibility Evaluation 1: Remaining magnetic powder None Evaluation 2: Remaining magnetic powder 50 g or less Evaluation 3: Remaining magnetic powder 50-100 g
Shape retention evaluation 1: 98-100%
Evaluation 2: 90-98%
Evaluation 3: 90% or less * Cross-sectional area of molded body / opening area of mold × 100
Oil resistance Evaluation: Less than 1: 1% Evaluation 2: 1-5%
Evaluation 3: 5% or more * Dimensional change after immersion in ethanol for 24 hours

Dispersibility Evaluation 1: No uneven distribution of rubber material Evaluation 2: Uneven distribution of rubber material

Looking at the magnetic properties (residual magnetic flux density (Br), maximum energy product ((BH) _max )) for Table 1, acrylic copolymer nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR) and acrylic A rubber magnet using rubber (ACM or ethylene propylene rubber (EPDM) as the rubber material B obtains a residual magnetic flux density (Br) of 250 mT or more and a maximum energy product ((BH) _max ) of 11 kJ / m ³ or more. However, when butadiene rubber (BR) or styrene butadiene rubber (SBR) is used as the rubber material B, such magnetic characteristics cannot be obtained.

  Next, regarding compatibility, when nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR), and acrylic rubber (ACM), which are acrylic copolymers, are used as rubber material B, magnetic powder is mixed in the kneader. Does not remain. It can also be seen that when nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR) and acrylic rubber (ACM), which are acrylic copolymers, are used as rubber material B, excellent oil resistance is exhibited. Furthermore, when nitrile rubber (NBR), hydrogenated nitrile rubber (HNBR) and acrylic rubber (ACM), which are acrylic copolymers, are used as the rubber material B, it can be seen that they have flame retardancy. However, when the amount of nitrile rubber (NBR) reaches 50 wt%, it burns, so in the present invention, the amount of acrylic copolymer relative to the rubber material is limited to 45 wt% or less.

  In terms of the flammability of nitrile rubber (NBR), the evaluation results of flammability differ depending on the kneading mode. That is, rather than adding magnetic powder and a rubber material from the beginning and kneading them (form 1), the two types of rubber materials are kneaded in advance, and then added and kneaded (form 2) show flame retardancy. . This is because the rubber material according to the form 1 is easy to burn because the nitrile rubber (NBR) is unevenly distributed, whereas the rubber material according to the form 2 is difficult to burn because the nitrile rubber (NBR) is not unevenly distributed. It is understood that it has become. The same applies to hydrogenated nitrile rubber (HNBR) and acrylic rubber (ACM). From the above results, in the present invention, it is recommended to limit the amount of magnetic powder added together with the rubber material from the beginning of kneading.

  As rubber material A (chlorinated polyethylene): 70 wt% as rubber material, nitrile rubber (NBR): 30 wt% as rubber material B, and the kneading form shown in Table 3 is the same as in Example 1. Thus, a rubber magnet was manufactured. The combustibility of the obtained rubber magnet and the dispersibility of the rubber material A and the rubber material B were evaluated in the same manner as in Example 1. The results are shown in Table 3. In addition, in the kneading form of Table 3, “magnetic powder tip addition amount” means the amount of magnetic powder added to the rubber material added from the beginning of kneading together with the rubber material, and “magnetic powder post-addition amount” means that the kneaded product of Table 3 The amount of magnetic powder added to the rubber material when the “post-addition temperature” is reached. Incidentally, the addition amount of the magnetic powder of 100 parts by weight means that the same amount of magnetic powder as that of the rubber material is added. The total amount of magnetic powder added to the rubber material is 1000 parts by weight.

No. in Table 3 As shown in FIG. 16, when all the magnetic powders are added to the rubber material from the beginning of kneading, a rubber magnet exhibiting flame retardancy cannot be obtained because the dispersibility of the two types of rubber materials is poor.
No. As shown in FIG. 21, when the magnetic powder is added at a low temperature of 40 ° C. after the magnetic powder is added, that is, the kneading of the rubber materials is not progressing, the dispersibility of the rubber material is inferior. No. 20, no. 23, no. As shown in FIG. 24, when the amount of magnetic powder initially added is larger than the amount of rubber material, the dispersibility of the rubber material is also inferior.
Based on the above results, in the present invention, when the kneaded material is less than 50 ° C., it is recommended to restrict the addition of the magnetic powder to 120 parts by weight or less with respect to the total weight of the rubber material. When the kneaded product is less than 50 ° C., the amount of magnetic powder added is more preferably 100 parts by weight (equal) or less, and still more preferably 70 parts by weight or less, based on the total weight of the rubber material. . Most preferably, when the kneaded material is less than 50 ° C., no magnetic powder is added.

It is a flowchart which shows the manufacturing process of the rubber magnet in this Embodiment. It is a figure which shows the addition timing of the magnetic powder in this Embodiment. It is a figure which shows the addition timing of the magnetic powder in this Embodiment. It is a figure which shows the addition timing of the magnetic powder in this Embodiment. It is a figure which shows the addition timing of the magnetic powder in this Embodiment.

Claims (6)

A rubber magnet containing a rubber material and magnetic powder,
The rubber material is made of an acrylic copolymer: 5-45 wt%, and the balance: chlorinated polyethylene. Obtaining a kneaded product containing different types of rubber materials and magnetic powder;
A step of extruding the kneaded product to obtain a molded body,
The step of obtaining the kneaded product includes
Until the plurality of different rubber materials are in a predetermined kneaded state, the amount of the magnetic powder to be added is not more than a part of the magnetic powder (however, including 0),
After the predetermined kneading state is reached, the remaining magnetic powder is added to continue the kneading.   The method for producing a rubber magnet according to claim 2, wherein the different types of rubber materials include chlorinated polyethylene and an acrylic copolymer.   4. The method for producing a rubber magnet according to claim 2, wherein when the temperature of the kneaded product reaches 50 ° C. or more, the plurality of different types of rubber materials are regarded as being in a predetermined kneaded state. .   The added weight of the magnetic powder until reaching the predetermined kneading state is 120 parts by weight or less with respect to the total of the plurality of types of rubber materials. Method for producing rubber magnets.   The method for producing a rubber magnet according to any one of claims 2 to 4, wherein the plurality of types of rubber materials are kneaded without adding the magnetic powder until the predetermined kneading state is reached.

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