JPH0426522B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a magnet composition that can be used for various purposes as a permanent magnet and has excellent flexibility, solvent resistance, heat resistance, and impact resistance. More specifically, the present invention relates to a magnet composition that uses an acrylic elastomer as a binder component to improve its flexibility and impact resistance, and also improves its solvent resistance and thermal integrity by incorporating a polyamide resin. Prior Art Until now, rubber magnets in which ferromagnetic powder is bonded with natural rubber or synthetic rubber, and plastic magnets in which ferromagnetic powder is bonded with plastics such as ethylene-vinyl acetate copolymer, polyolefin, and polyamide, have been known. However, rubber magnets generally have good flexibility but have the disadvantage of poor solvent resistance and heat resistance.
On the other hand, plastic magnets have excellent solvent resistance and heat resistance, but are inferior in flexibility and impact resistance, and when punched using a cutting die, cracks and chips occur, resulting in a large amount of loss, which limits the processing methods available. have. In recent years, as the applications of permanent magnets have diversified,
There has been a demand for the development of permanent magnets that have flexibility, solvent resistance, heat resistance, and impact resistance, and can be applied to any processing method. things are still unknown. Problems to be Solved by the Invention The purpose of the present invention is to provide a magnet that combines the flexibility and impact resistance that are the strengths of rubber magnets with the solvent resistance and heat resistance that are the strengths of plastic magnets, and that also has good workability. An object of the present invention is to provide a novel magnet composition. Means for Solving the Problems As a result of extensive research in order to achieve the above object, the present inventor discovered that certain acrylic elastomers and polyamide resins have good compatibility, and that a certain type of acrylic elastomer and polyamide resin have good compatibility, In this case, a homogeneous resin composition is formed, and if ferromagnetic powder is combined with this resin composition as a binder, a magnet composition with excellent flexibility, impact resistance, solvent resistance, and heat resistance can be obtained. Based on this knowledge, we have developed the present invention. That is, the present invention comprises (A) 10 to 80% by weight of at least one elastomer selected from ethylene-alkyl acrylate elastomer, alkyl acrylate elastomer, and alkoxyalkyl acrylate elastomer, and 90 to 20% by weight of polyamide resin. A magnet composition comprising (B) ferromagnetic powder mixed in a resin mixture with % and ferromagnetic powder in a ratio such that the weight ratio of (B) to the total amount of (A) and (B) is in the range of 0.70 to 0.93. It is something that provides something. The ethylene-alkyl acrylate elastomer used in component (A) of the present invention is ASTM
Mooney viscosity (ML ₁₊₄ a100°C) measured according to -1646 is preferably in the range of 10 to 60, examples of which include ethylene-
Mention may be made of polymers of methyl acrylate or ethylene-butyl acrylate and copolymers thereof. The alkyl acrylate elastomer preferably has a Mooney viscosity of 30 to 70, and examples of such elastomers include polymers of ethyl acrylate or butyl acrylate, and copolymers thereof. Furthermore, the alkoxyalkyl acrylate elastomer preferably has a Mooney viscosity of 30 to 70, and examples of such elastomers include polymers of methoxyethyl acrylate or ethoxyethyl acrylate, and copolymers thereof.These elastomers may contain a reactive functional group, such as a carboxyl group, in an amount of up to 5% by weight, if necessary. These elastomers may be used alone or in combination of two or more. Examples of polyamide resins used in combination with these elastomers include polylactams such as nylon 6, nylon 11, and nylon 12;
Condensates of dicarboxylic acids and diamines such as nylon 66, nylon 610, nylon 612, nylon 6/66, nylon 6/610, nylon 6/12, nylon 6/612, nylon 6/66/610, nylon 6/ Mention may be made of copolyamides such as 66/12, nylon 12/polyether. These may be used alone or in combination of two or more. As the component (A) of the present invention, the above-mentioned elastomer
10-80% by weight, preferably 50-70% by weight and polyamide resin 90-20% by weight, preferably 50-30% by weight
It is necessary to use a mixture of If the amount of the elastomer is less than 10% by weight, the impact resistance will be insufficient, and if the amount of the polyamide resin is less than 20% by weight, the solvent resistance and heat resistance will be insufficient. If you are simply trying to improve impact resistance without adding flexibility, please adjust the amount of elastomer.
It is preferably in the range of 10 to 40% by weight, preferably 20 to 30% by weight. Next, the ferromagnetic powder of component (B) of the present invention is:
For example, ferrite magnet powder, cobalt magnet powder,
Any materials that have been commonly used as ferromagnetic powders for rubber magnets and plastic magnets may be used, such as rare earth cobalt magnet powder, alnico magnet powder, manganese/aluminum/carbon magnet powder, soft ferrite powder, and permalloy powder. I can do it. In general rubber magnets and plastic magnets, in order to obtain magnets with excellent magnetic properties, it is preferable to increase the amount of ferromagnetic powder blended as much as possible. Since it is also required to have physical properties, there is naturally a limit to its amount. Therefore, in the present invention, the blending amount of component (B) is determined by the weight ratio (B)/based on the total amount of components (A) and (B).
It is necessary to select a range such that (A)+(B) is 0.7 to 0.93, preferably 0.8 to 0.88. This percentage
If it is smaller than 0.7, the magnetic properties will be poor.
Moreover, if it is larger than 0.93, molding becomes difficult and the strength decreases. In addition to the above-mentioned components (A) and (B), the composition of the present invention may optionally contain additives commonly used in ordinary rubber magnets and plastic magnets, such as lubricants, heat stabilizers, plasticizers, Softeners, colorants, and anti-aging agents can be added as appropriate. The composition of the present invention can be formed into a suitable shape by extrusion molding, rolling molding, compression molding, or injection molding after mixing the above-mentioned components, heating and melting the resin components, and thoroughly kneading the mixture. The heating temperature at this time is preferably about 1 to 30°C higher than the melting point of the polyamide resin used. Also,
When preparing the composition of the present invention, scraps of plastic magnets made of polyamide resin and ferromagnetic powder or rubber magnets made of acrylic elastomer and ferromagnetic powder are used, and the necessary amount of acrylic elastomer or It is also possible to mix a polyamide resin and heat-knead it. When an anisotropic ferromagnetic powder is used as component (B) in the composition of the present invention, in the case of a magnetically oriented type, extrusion molding, injection molding, or compression molding may be performed while oriented in a magnetic field. I can do it. In addition, in the case of a mechanically oriented type, the material can be oriented and molded by mechanical force during rolling or extrusion molding. Furthermore, when an elastomer containing a reactive functional group is used as the elastomer in component (A), the physical properties can be modified by reacting with a crosslinking agent as desired. Effects of the Invention The composition of the present invention has excellent solvent resistance, heat resistance, impact resistance, and flexibility, and has good processability, so it can be used not only in fields where conventional rubber magnets and plastic magnets are used, but also in fields where conventional rubber magnets and plastic magnets are used. It can be widely used even in fields where these magnets cannot be used. For example, hard magnetic materials used as ferromagnetic powder are used in masking magnetic sheets used during painting processes, reed switch magnets used in chemical atmospheres, and signage magnetic sheets used in relatively high temperatures. It is suitable for fixed magnets for micro motors used at relatively high temperatures, multi-polar magnetized magnets for rotational speed detection, etc. Also, those using soft magnetic materials are suitable for use as radio wave absorbing materials for ovens and microwave ovens, and color tone adjustment for color TVs. It is suitable for centering magnets, etc. Examples Next, the present invention will be explained in more detail with reference to Examples. Example 1 60 parts by weight of ethylene-methyl acrylate elastomer (Mooney viscosity 16, carboxyl group content 5% by weight or less), 1.2 parts by weight of substituted diphenylamine (antiaging agent), and stearic acid (lubricant).
A mixture of 1.2 parts by weight and 383 parts by weight of anisotropic barium ferrite powder (mechanically oriented type, average particle size 1.3μ) was kneaded using two rolls with a surface temperature of about 70°C, and then a plate of about 4 mm thickness was mixed. It is shaped into a shape and then pelletized using a pelletizer. Then nylon 12
(Weight: 100) powder and 244 parts by weight of anisotropic barium ferrite powder (mechanically oriented type, average particle size 1.3μ) were added and mixed, and mixed using a single-screw extruder (screw diameter 40 mm, L/ D15), extruded into a sheet at a cylinder temperature of 200-230°C and a die temperature of 190-200°C, and then at a surface temperature of 80-90°C.
It was rolled through two rolls at ℃ and formed into a sheet with a cross section of 2 x 50 mm. Comparative Example 1 (Non-vulcanized rubber magnet) Without using nylon 12 in Example 1, the amount of ethylene-methyl acrylate was 100 parts by weight, and the cylinder temperature of the extruder was 80 to 90°C,
Example 1 except that the die temperature was 110 to 120°C and the surface temperature of the two rolls used for rolling after extrusion was 60 to 70°C.
A sheet was molded in exactly the same manner as above. Example 2 Except for using anisotropic strontium ferrite powder (magnetic field oriented type, average particle size 1μ) in place of the anisotropic barium ferrite powder in Example 1,
A 2 mm thick sheet was molded in exactly the same manner as in Example 1. Next, punch this into a disc with a diameter of 25 mm,
Three of these discs were stacked together and pressed using a magnetic field press machine for 5 minutes at a pressing temperature of 200°C, a pressing pressure of 1 Kg/cm ² , and a magnetic field strength of 15,000 oersteds. A disc-shaped magnet was molded. Comparative Example 2 (Non-vulcanized rubber magnet) A disc-shaped magnet was molded in the same manner as in Example 2, using 100 parts by weight of ethylene-methyl acrylate elastomer without using nylon 12. Comparative example 3 (non-vulcanized rubber magnet) 100 parts by weight of chlorinated polyethylene, stearic acid
2.0 parts by weight, dibasic lead phosphite (heat stabilizer) 1.0
633 parts by weight of anisotropic barium ferrite powder (mechanically oriented type, average particle size 1.3 μm) were kneaded using two rolls with a surface temperature of about 80°C, and the same procedure as in Comparative Example 1 was carried out to form a 2 mm thick powder. It was formed into a sheet. Comparative Example 4 (Vulcanized rubber magnet) 100 parts by weight of butadiene acrylonitrile rubber (Mooney viscosity 40, bonded acrylonitrile 34%) and 682 parts by weight of anisotropic barium ferrite powder (mechanically oriented type, average particle size 1.3μ) were placed on the surface. After kneading with two rolls at a temperature of about 80°C, draw it out into a plate shape, and after cooling to room temperature, add 5.0 parts by weight of activated zinc white (activator) and dipentamethylenethiuram hexasulfide (vulcanizing agent).
1.5 parts by weight, 1.5 parts by weight of dibenzothiazyl disulfide (vulcanization accelerator) and 1.0 parts by weight of substituted diphenylamine (anti-aging agent) were added, and kneaded again with a roll. Next, this was rolled to a thickness of 0.8mm, and the three sheets were piled up and press-cured at 150℃ for 15 minutes to create a thickness of 2mm.
A thick sheet was obtained. Comparative Example 5 (Plastic magnet) A sheet with a thickness of 2 mm was obtained in the same manner as in Example 1 except that 100 parts by weight of nylon 12 was used without using the ethylene-methyl acrylate elastomer. Example 3 25 parts by weight of the same ethylene-methyl acrylate elastomer used in Example 1, 75 parts by weight of the same nylon 12 powder used in Example 1, 0.5 part by weight of substituted diphenylamine, and 0.5 part by weight of steric acid. 681 parts by weight of isotropic barium ferrite powder (average particle size 2μ) was added to the mixture with 0.75 parts by weight of magnesium stearate, stirred, extruded into a rod shape with a diameter of about 5 mm using an extruder, and then crushed.
Then cylinder temperature 280~290℃, mold temperature 120℃
Injection molded under the conditions of ℃ and injection pressure of 900Kg/ ^cm2 ,
A disc with a diameter of 25 mm and a thickness of 5 mm, an outer diameter of 74 mm, and an inner diameter of 68.7 mm.
Two types of rings were obtained: mm and 5 mm thick. Comparative Example 6 Discs and rings of the same dimensions were molded in exactly the same manner as in Example 3, except that the ethylene-methyl acrylate elastomer in Example 3 was not used and the amount of nylon 12 powder was increased to 100 parts by weight. did. Example 4 Exactly the same as Example 1 except that an ethyl acrylate-butyl acrylate-methoxyethyl acrylate copolymer elastomer (Mooney viscosity 50, epoxy group content 5% or less) was used instead of the ethylene-methyl acrylate elastomer in Example 1. A magnet composition was prepared under these conditions and formed into a sheet. Example 5 The same ethyl acrylate-butyl acrylate-methoxyethyl acrylate copolymer elastomer used in Example 4 was used in place of the ethylene-methyl acrylate elastomer in Example 2, and a magnet was prepared under exactly the same conditions as in Example 2. A composition was prepared and formed into a disc-shaped magnet. Example 6 The same ethyl acrylate-butyl acrylate-methoxyethyl acrylate copolymer elastomer used in Example 4 was used in place of the ethylene-methyl acrylate elastomer in Example 3, and the magnet composition was made under exactly the same conditions as in Example 3. The material was prepared and molded into disks and rings of the same size. Example 7 60 parts by weight of the same ethylene-methyl acrylate used in Example 1 and 1.2 parts by weight of substituted diphenylamine
Parts by weight of stearic acid, 1.2 parts by weight of stearic acid, and 376 parts by weight of anisotropic barium ferrite powder (mechanically oriented) were kneaded with two rolls to form a plate shape with a thickness of about 4 mm, and then pelletized with a pelletizer. Next, 291 parts by weight of the molding scrap powder produced in Comparative Example 5 was added to the pellets thus obtained, and the pellets were mixed by stirring.
It was formed into a sheet of mm. Reference Example 1 The samples obtained in each Example and Comparative Example were tested for organic solvent resistance, flexibility, heat aging resistance, and tensile strength by the methods shown below, and the results are shown in Table 1. (1) Organic solvent resistance test: In accordance with the method specified in ASTM D543, a 2 mm thick sample was immersed in gasoline, toluene, ethyl acetate, or acetone maintained at 20°C.
The volume change rate after 7 days was determined. (2) Flexibility test: Using 16 types of round rods ranging from 110 mm in diameter to 2 mm in diameter, wrap the sample sequentially from the thickest to the thinnest at 20°C, continue to do this until cracks or cracks occur, and test to prevent cracks or cracks. It is expressed by the smallest diameter value that does not occur. (3) Heat aging test: The sample was placed in a gear oven maintained at 150°C, and after 4 to 120 hours had passed, the flexibility test was conducted. (4) Tensile strength test; According to the method specified in JIS K6301, a sample with a thickness of 2 mm was
The tensile strength was measured when it was pulled at a speed of mm.
In addition, in the case of 100°C, the rate of change (%) is also written.

[Table] As is clear from this table, the magnet composition of the present invention has superior organic solvent resistance not only to non-vulcanized rubber magnets but also to vulcanized rubber magnets, and has significantly superior resistance to organic solvents compared to plastic magnets. It exhibits flexibility comparable to that of magnets, and thermal stability significantly superior to non-vulcanized rubber magnets and vulcanized rubber magnets. Furthermore, it exhibits higher tensile strength with less change in tensile strength due to temperature than either specific vulcanized rubber or vulcanized rubber. Reference Example 2 Using the compositions of Example 2, Example 5, and Comparative Example 2, magnetic field press molding was performed to form a mold with a diameter of 25 mm and a thickness of 5.5 mm.
A disk was prepared and its maximum energy product was measured using a BH curve tracer (manufactured by Denshi Magnetic Co., Ltd.), and the maximum energy product was 1.3 M・G・oe for those using the compositions of Example 2 and Example 5, Comparative Example The result using composition No. 2 was 1.2 M·G·oe. This shows that the magnet composition of the present invention can be more easily oriented in a magnetic field than a rubber magnet. Reference Example 3 In order to compare the impact resistance and thermal shock resistance of the composition of the present invention and conventional plastic magnets, the following tests were conducted and the results are shown in Table 2. (1) Impact test: A disk sample with a diameter of 25 mm and a thickness of 5 mm was tested using a Dupont impact tester by changing the height of the falling weight from low to high in 5 cm increments until cracking occurred. The highest height without cracking was taken as the measured value. The weight of the falling weight at this time was 300g, and 1/4 was used as the striking core. (2) Heat cycle test; A ring sample with an outer diameter of 74 mm, an inner diameter of 68.7 mm, and a thickness of 5 mm was made of stainless steel (SUS304).
Insert it into a disk with a diameter of 68.68 mm and a thickness of 10 mm, and heat it for 5 to 60 cycles from -30℃ to +70℃ for 2 hours each.
The cycle was repeated. At this time, the sample was observed to see if there were any cracks.

【table】

[Table] As is clear from this table, the magnet composition of the present invention is superior to conventional ones in both impact resistance and thermal shock resistance.

Claims (1)

[Claims] 1 (A) 10 to 80% by weight of at least one elastomer selected from ethylene-alkyl acrylate elastomer, alkyl acrylate elastomer, and alkoxyalkyl acrylate elastomer, and 90 to 20% by weight polyamide resin.
A magnet composition comprising (B) ferromagnetic powder mixed in a resin mixture with (B) in such a proportion that the weight ratio of (B) to the total amount of (A) and (B) is in the range of 0.70 to 0.93. .