Methods for preparing magnetic powder material and magnet, process for prepartion of resin composition and process for producing a powder molded product

A method for preparing a magnetic powder material comprising 99.5 to 60% by volume (99.9 to 85% by weight) of magnetic powder and 0.5 to 40% by volume (0.1 to 15% by weight) of a polymer having a repeating unit represented by the formula:

• ##STR12## wherein Ar represents ##STR13## and a limiting viscosity (.eta.) in p-chlorophenol as a solvent at 60.degree. C. of 0.2 dl/g or more, which comprises volatilizing and evaporating N-methylpyrrolidone from a mixture containing the magnetic powder within a solution of the polymer dissolved in the N-methylpyrrolidone at a temperature of at least 190.degree. C., thereby precipitating the polymer onto the magnetic powder.

A method for preparing a magnetic powder material comprising 99.5 to 60% by volume (99.9 to 85% by weight) of magnetic powder and 0.5 to 40% by volume (0.1% to 15% by weight) of a polymer having a repeating unit represented by the formula:

• ##STR14## wherein Ar represents ##STR15## and a limiting viscosity (.eta.) in p-chlorophenol as a solvent at 60.degree. C. of 0.2 dl/g or more, which comprises preparing a mixture of the magnetic powder and a solution of the polymer by dissolving the polymer in N-methylpyrrolidone at a temperature of at least 190.degree. C. and by dispersing the magnetic powder within the solution, and then cooling the mixture of the polymer dissolved in the N-methylpyrrolidone and the magnetic powder dispersed therein thereby precipitating the polymer onto the magnetic powder.

A method for preparing a magnetic powder material comprising 99.5 to 60% by volume (99.9 to 85% by weight) of magnetic powder and 0.5 to 40% by volume (0.1 to 15% by weight) of a polymer having a repeating unit represented by the formula:

• ##STR16## wherein Ar represents ##STR17## and a limiting viscosity (.eta.) in p-chlorophenol as a solvent at 60.degree. C. of 0.2 dl/g or more, which comprises effecting dispersion, mixing and grinding of a gel prepared by dissolving the polymer in N-methylpyrrolidone and by heating at a temperature of at least 190.degree. C. and then cooling, with the magnetic powder, and simultaneously effecting volatilization and evaporation of the N-methylpyrrolidone.

A method for preparing a resin-bonded magnet which comprises effecting injection molding of a magnetic powder material comprising 99.5 to 60% by volume (99.9 to 85% by weight) of magnetic powder and 0.5 to 40% by volume (0.1 to 15% by weight) of a polymer having a repeating unit represented by the formula:

• ##STR18## wherein Ar represents ##STR19## and a limiting viscosity (.eta.) in p-chlorophenol as a solvent at 60.degree. C. of 0.2 dl/g or more;
• said magnetic powder being prepared by dissolving said polymer in N-methylpyrrolidone at a temperature of at least 190.degree. C., dispersing the magnetic powder within the polymer solution and, thereafter, treating the resulting mixture to remove the N-methylpyrrolidone and to adhere the polymer to the magnetic powder.