JPH0571292B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a dispersant for metal magnetic powder, and more particularly to a dispersant for metal magnetic powder comprising long-chain 1,2-glycol. Metal magnetic powder is widely used as a material for magnetic tapes and floppy disks, as well as for high-performance plastic magnets used in automobile parts, micromotors, and developing rolls of copying machines. For example, metal magnetic powder such as iron powder and cobalt-containing iron oxide magnetic powder have high coercive force and are used as storage elements in high-performance magnetic recording media that require high-density recording. When preparing paints, there is a difficulty in uniformly dispersing them in the binder. In order to improve these drawbacks, higher fatty acids, alkyl esters of these fatty acids, metal salts, acid amides, sulfuric esters and phosphoric esters, lecithin, higher alcohols, higher amines, etc. have been proposed as dispersants. However, these dispersants were not always satisfactory. For example, higher alcohols, lower glycols, etc.
The effect as a dispersant was insufficient and there were problems with workability. The object of the present invention is to improve the dispersibility of magnetic particles in a magnetic coating material, and also to provide a dispersant for metal magnetic powder suitable for use in plastic magnets and the like. That is, the present invention provides a dispersant for metal magnetic powder comprising a compound represented by the following general formula ().

[Chemical Formula] (In the formula, R ₁ and R ₂ each represent a hydrogen atom or an alkyl group having 1 to 50 carbon atoms, and the total number of carbon atoms of R ₁ and R ₂ is 6 to 50.) The present invention having the above-mentioned summary will be explained in detail. Typical examples of long-chain 1,2-glycols that are dispersants of the present invention include octanediol, decanediol, dodecanediol, tetradecanediol, hexadecanediol, octadecanediol, eicosandiol, docosandiol, and tetracosandiol. , triacontanediol, tetracontanediol, pentacontanediol, etc. Among these, those having 12 carbon atoms
The above are highly effective and preferred. Examples of the metal magnetic powder to which the dispersant of the present invention can be applied include iron oxide magnetic powder, cobalt-containing iron oxide magnetic powder, Mn-based magnetic material, rare earth magnetic material, Ba-based ferrite, Sr-based ferrite, rare earth intermetallic compound magnet, Examples include carbonyl iron powder, other metal or alloy powders, and soft magnetic ferrite. The amount of the dispersant used is generally 0.01 to 10 parts by weight, preferably 0.1 to 3 parts by weight, per 100 parts by weight of the magnetic powder. EXAMPLES The present invention will be explained below with reference to Examples, but the present invention is not limited to these Examples. Example 1 A magnetic paint was prepared with the following composition, and this paint was applied onto a polyester film and dried to produce a magnetic tape. Cobalt-containing iron oxide magnetic powder 800g PVC/vinyl acetate/vinyl alcohol copolymer 120g Polyurethane prepolymer 80g Dispersant (see table) 5g Liquid paraffin 5g Toluene/methylisobutylene mixed solvent (volume ratio 1:1) 1010g Obtained Regarding magnetic tape: square (Br/Bm),
The orientation ratio, frequency characteristics, and coercive force (Hc) were measured. The results obtained are shown in Table 1. The square shape, orientation ratio, and frequency characteristics are indicators of the dispersibility of the magnetic powder, and the higher the value of each of these, the better the dispersibility.

[Table] Example 2 The following components were sufficiently premixed using a Henschel mixer, and the mixture was melt-kneaded using a mixing roll while heating to about 120°C. Epoxy resin 35 parts by weight Magnetic iron oxide powder 60 Carbon black 4 1,2-tetradecanediol 1 The kneaded material was cooled and solidified, and pulverized, and the pulverized material was classified to 20 μm or less. A magnetic toner was obtained by adding and mixing silica as a resistance adjusting agent to the classified particles of 20 μm or less. The obtained magnetic toner had good fluidity and excellent storage stability. Example 3 The following ingredients were kneaded in a Brabender at 240℃,
The torque was measured. The results are shown in Table 2. Barium ferrite (Nippon Bengara Kogyo, DNP,
1.2~1.4μ) 80 parts by weight Nylon 12 powder 20 Dispersant (Table 2) 0.4

【table】

[Table] Maximum torque by adding glycol,
The fact that both the minimum torque decreased indicates that the fluidity was improved, and the small deviation of the torque curve indicated that uniform dispersion became easier.

Claims (1)

[Claims] 1. A dispersant for metal magnetic powder comprising a compound represented by the following general formula (). [Chemical Formula] (In the formula, R ₁ and R ₂ each represent a hydrogen atom or an alkyl group having 1 to 50 carbon atoms, and the total number of carbon atoms of R ₁ and R ₂ is 6 to 50.)