JPH0458681B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD This invention relates to a resin magnet composition used in magnet rolls used in copying machines, facsimile machines, and the like. Conventional structure and its problems The developing method used in copiers, facsimile machines, etc.
Magnetic toner (single-component developer) made of magnetic powder and developer made of non-magnetic toner and magnetic powder carrier (two-component developer) are stored in a built-in cylindrical magnet roll 1 with multiple magnetic poles as shown in the drawing. The developer on the rotated sleeve 2 is exposed to light, either by holding it on a cylindrical non-magnetic sleeve 2 and rotating the magnet roll 1, or by fixing the magnet roll 1 and rotating the sleeve 2. The mainstream is a magnetic brush development method in which the image is conveyed to the latent image surface and visualized. Sintered ferrite has conventionally been used as a magnet roll material, but it has drawbacks such as poor workability, heavy weight, and brittleness. In order to overcome these drawbacks, resin magnets based on resin or rubber have come into use. Resin magnets are small, lightweight, can be molded into any shape, are low cost, and can be easily finished, so they are used in a variety of shapes, including rolls, sheets, and rods. Therefore, there are various manufacturing methods such as rolling molding, injection molding, calendar molding, and extrusion molding. The manufacturing method of the magnet roll 1, which coats the shaft 3 with a resin magnet, is to knead magnetic ferrite, a binder, and additives in a heated pressure kneader, cool the kneaded material, and then knead it to a thickness of 1 to 2 mm. The ferrite powder is coarsely pulverized and mechanically oriented while being sheeted with a rolling roller to obtain a sheet-like resin magnet, which is wound around a rod-shaped shaft 3, magnetized to a predetermined size, and placed on a magnet roll 1. The most common method is rolling. Further, in order to improve the orientation efficiency, some measures have been taken, such as stacking several sheets of the above-mentioned rolled resin magnet sheets and press-molding them into a fan shape, and then fixing the separated fan-shaped pieces to the shaft 3 using an adhesive. In addition, using an injection molding method or a pressure molding method, an orienting magnetic field is applied to the thermoplasticized resin magnet composition in a mold to orient the ferrite, and the piece is molded into a predetermined shape and attached to the shaft 3 with an adhesive. I found a way to fix it. However, these were all produced in batches and were therefore inferior in productivity. In addition to these methods, there is an extrusion molding method that has excellent productivity, but it has not been put to practical use because sufficient magnetic force cannot be obtained because the resin magnet is continuously coated around the shaft 3 and extruded. . OBJECTS OF THE INVENTION An object of the present invention is to provide a resin magnet composition that can obtain sufficient magnetic force by extrusion molding with high productivity. Structure of the Invention The resin magnet composition of the present invention has a melt viscosity of 100 poise or less at 180°C and has a general formula HO-
[CO−R ₂ −CO・NH−R ₃ −NH・CO−R ₁ −
CO・NH−R ₃ −NH] _o It contains a polymerized fatty acid-based polyamide resin (hereinafter referred to as polyamide resin) represented by H and ferromagnetic ferrite powder. A cooling part is provided, and a resin magnet can be continuously coated around the shaft in a cylindrical shape and then extruded. Polyamide resins with a melt viscosity exceeding 100 voices at 180°C have a high melt viscosity in the plasticized state in an extruder, making it difficult to orient the ferrite powder in response to an applied magnetic field, resulting in poor magnetic properties. The content of the ferrite powder is based on the total weight
The content is preferably 70 to 92% by weight; when it exceeds 92% by weight, kneading and extrusion molding become extremely difficult.
If the content is less than 70% by weight, the orientation of the ferrite powder will be high with respect to the applied orientation magnetic field, but the amount will be insufficient and the magnetic properties will deteriorate. As the ferromagnetic ferrite powder, commercially available ferrites such as barium ferrite and strontium ferrite can be used. In addition, in order to improve the moldability during extrusion molding,
As in general plastic molding, fatty acid metal salts such as calcium stearate and barium stearate, higher fatty acids such as stearic acid and palmitic acid, and lubricants such as waxes can be used. Description of Examples Examples 1 to 8 Each composition shown in Table 1 was kneaded in a pressure kneader heated to 150 to 180°C, and after cooling, coarsely pulverized products of 2 to 5 mm were crushed by a coarse pulverizer. Obtained. Each composition was put into an extrusion molding machine equipped with a cooling part while applying an orienting magnetic field, and the shaft was coated with resin magnesium and continuously extruded to obtain a magnet roll. The outer diameter of this material was set to 20 mm, the magnetic flux density applied during extrusion was 10,000 Gauss, and the extrusion speed was 7.5 mm/sec.

[Table] The molded magnet roll is further magnetized using a magnetizer, and the surface magnetic flux density is determined by Denshi Porcelain Industry.
Measurements were made using a Gaussmeter manufactured by Co., Ltd. by contacting the surface of the magnet roll. The results are shown in Table 2. Comparative Examples 1 to 3 Magnet rolls were produced in the same manner as in Examples using each of the compositions shown below, and their surface magnetic flux densities were measured. The results are shown in Table 3. Comparative Example 1 (Ingredients) (Weight %) GP-825 (mentioned above) 91 Chlorinated polyethylene (not melted) (manufactured by Showa Denko K.K.)
8.73 Calcium stearate (manufactured by Sakai Chemical Industry Co., Ltd.) 0.27 Comparative example 2 (components) (wt%) GP-825 (mentioned above) 64 Tomide #1310 (mentioned above): Melt viscosity at 180°C is 48
Poise 35 Armowactus EBS (manufactured by Lion Akzo Co., Ltd.) 1 Comparative example 3 (Components) (% by weight) GP-825 (mentioned above) 85 EBR (high viscosity) (manufactured by Japan Synthetic Rubber Co., Ltd.) 15

【table】

[Table] As is clear from Tables 2 and 3, the magnet rolls obtained in Examples 1 to 8 all had smooth surfaces and surface magnetic flux densities of 1000 G or more, whereas Comparative Example 1 ~The magnet roll obtained in 3 is
The value was low, less than 1000G. Effects of the Invention According to the present invention, as a binder for ferrite powder, the general formula HO-[CO- _R2 -CO・NH- _R3 -NH・CO having a melt viscosity of 100 poise or less at 180°C
-R ₁ -CO.NH-R ₃ -NH] _o By using a polymerized fatty acid-based polyamide resin represented by H, a resin with low melt viscosity and low viscous resistance during orientation and high magnetic force can be obtained. Furthermore, since a magnet with high magnetic force can be obtained, continuous extrusion production is possible in addition to batch production, which is the conventional manufacturing method for magnets by mechanical orientation, and furthermore, extrusion production can stabilize the magnetic force in the axial direction. As a result, it is possible to produce a magnet roll with excellent magnetic properties by extrusion molding, which has not been possible with conventional resin magnet compositions.

[Brief explanation of the drawing]

The drawing is a cross-sectional view of an ordinary magnet roll. 1...Magnetic roll, 2...Nonmagnetic sleeve, 3...Shaft.

Claims (1)

[Claims] 1. Melt viscosity at 180°C is 100 poise or less and the general formula HO-[CO-R ₂ -CO・NH-R ₃ -NH・CO
-R ₁ -CO.NH-R ₃ -NH] _o A resin magnet composition containing a polymerized fatty acid-based polyamide resin represented by H and ferromagnetic ferrite powder. 2 The ferrite powder is 70 to 92% of the total weight
The resin magnet composition according to claim 1, wherein the resin magnet composition is contained in a proportion of % by weight.