SU1191949A1 - Composite material for permanent magnets - Google Patents

Abstract

COMPOSITE MATERIAL FOR CONSTANT MAGNETS based on barium ferrite containing ethylene-vinyl acetate copolymer, characterized in that, in order to increase the strength and magnetic properties and improve the processability of the material, it also contains zinc stearate and dibutyl sebacate in the following ratio of components, May. %: Ethylene copolymer of vinyl acetate 9-18 Zinc stearate 0.6-1.0 Dibutylsebacate 0.3-0.5 Ferrite barium Rest

Description

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The invention relates to magnetic materials, in particular to composite materials for permanent magnets, and can be used in the manufacture of permanent magnets for electrical products.

The aim of the invention is to increase the strength and magnetic properties and improve the processability of processing composite material for permanent magnets.

The invention is based on the introduction of barium ferrite into a composite material containing ethylene / vinyl acetate copolymer, low molecular weight additives of zinc stearate and dibutyl sebacate as a binder. The increase in the magnetic and mechanical properties of the composite material and the improvement in the processability of its processing due to the reduced viscosity are associated with a decrease in the content of low molecular weight additives in the composite material, improved adhesion of the binder to the filler (barium ferrite), and improved dispersion of the magnetic filler particles and their orientation field.

The invention is illustrated by the examples in the table.

A copolymer of ethylene and vinyl acetate containing 12–23 w / v vinyl acetate (TU6-05-1636-78) is used as a copolymer of ethylene with vinyl acetate, and zinc stearate is a white amorphous powder with a melting weight of 117–27 ° C as additives. 110-220 kg / m (TU6-09-4262-76), dibutyl sebacate is a clear liquid with a molecular weight of 314, density of 933 kg / m (GOST 8728-66).

Compositions were prepared as follows. The components taken in predetermined ratios were mixed on rollers at 120-130 ° C for 15-20 minutes, and a copolymer of ethylene with vinyl acetate in the form of a powder with a dispersity of 500-800 microns or granules was first introduced into the rollers, then low molecular weight additives were introduced and barium ferrite powder with dispersion of 1.0-5.0 microns. The resulting composition in the form of a film cut off the rolls. The resulting films were pressed into plates from which samples were cut out for tensile testing according to GOST 11262-76. To measure the magnetic properties — the maximum magnetic energy (HV) L5x at 150–200 ° C and a pressure of 25 MPa, cylindrical samples with a diameter of 25–100 m and a height of 6–7 lO M were pressed. The magnitude (HV) of maize was measured when an external magnetic field was applied. 16 kOe on an EM8-6 hysteresisograph. To determine the viscosity of composite materials, the resulting film was crushed into pieces with an average size of 510z m. Viscosity

determined on a VPK-1 capillary viscometer at 170 ° C.

In addition, for a comprehensive assessment of the characteristics of a composite material, a dimensionless criterion was introduced:

 CB-H ax- p)

6

where is the maximum magnetic energy,

MGS E; b - destructive stress at races

current, MPa;

and viscosity at a shear rate of 100 s. Pa s.

For comparison, the table also shows the characteristics of the known 2 composite materials for permanent magnets with the same content of ferromagnetic filler (barium ferrite) as for the proposed material.

0 As can be seen from the table, the proposed material greatly exceeds the known 2 in magnetic and strength properties. So when the content of the ferromagnetic filler is 80 May. Yo (Example 1), the proposed material has the value (HV) ax 0.55 MGS E and the tensile stress Oo 12 MPa compared with the values of 0.40 MGS E and 8.3 MPa for the known 2 materials with the same content ferromagnetic filling of bodies (example 2). The corresponding values at 85% ferromagnetic filler content for the proposed material are 0.94 MGS E and 9.3 MPa (Example 3), for the known (2) - 0.78 MGS-E and 5.8 MPa (Example 4) , and at 90% content:

for the known - 1.14 and 7.5 MPa (example 5), for the proposed one - 0.8 MGgsE and 4.1 MPa (example 6), while the proposed material has more than 2 times lower viscosity than the known 2 material, which significantly improves its manufacturability during processing by extrusion. The proposed material exceeds more than 2 times also known by the criterion / (complexly taking into account the characteristics of the material.

When the lower limit of the ratio of the components is reached (Example 8), the purpose of the invention is not achieved, since the material has high (26-35-10 Pa-s) viscosity values, which makes it difficult to process it with extrusion methods. When the contents of the components are higher than the upper stated limit (Example 7), the magnetic properties of the material deteriorate, making it unsuitable for the manufacture of permanent magnets.

The improved technological properties of the composite material 5 in comparison with the known ones allow it to be processed on serial, high-performance equipment - extruders and injection molding machines for plastics processing or to introduce more ferromagnetic filler into the material.

Increasing the strength and magnetic properties of the magnets of the proposed material allows to expand their field of application. They can be widely used in household goods, television equipment, c. micro motor, etc.

Continued table.

Claims (1)

COMPOSITE MATERIAL FOR PERMANENT MAGNETS based on barium ferrite, containing ethylene vinyl acetate polymer, characterized in that, in order to increase the strength and magnetic properties and improve the processability of the material, it additionally contains zinc stearate and dibutylsebacinate in the following ratio of components, May. %: Ethylene Vinyl Acetate Copolymer Zinc Stearate Dibutyl Sebacinate Barium Ferrite 9-18 0.6-1.0 0.3-0.5 Else