Method for producing abrasive particles
View Patent ↗A method for producing abrasive particles includes preparing a starting mixture containing at least aluminium hydroxide, which mixture can be converted at least into aluminium oxide by means of heat treatment; extruding the starting mixture to form an extrudate; separating the extrudate into intermediate particles; and heat-treating the intermediate particles. The intermediate particles are converted into abrasive particles that contain aluminium oxide, and the extrudate and/or the intermediate particles is/are subjected to an input of energy that is asymmetrical with respect to the geometry of the extrudate and/or the intermediate particles.
1 . A method of producing abrasive particles, the method comprising:
providing a starting mixture containing aluminum hydroxide convertible into at least aluminum oxide by heat treatment,
extruding the starting mixture to form an extrudate,
separating the extrudate into intermediate particles, and
heat-treating the intermediate particles, wherein the intermediate particles are converted into abrasive particles containing aluminum oxide,
wherein at least one of the extrudate and the intermediate particles is subjected to an energy input asymmetric with respect to a geometry of the at least one of the extrudate and the intermediate particles.
2 . The method according to claim 1 , wherein the asymmetric energy input is effected at an outlet opening of a nozzle body of an extrusion device and/or on a belt guiding device and/or in a device for asymmetric energy input.
3 . The method according to claim 2 , wherein the asymmetric energy input is effected at the outlet opening of the nozzle body of the extrusion device such that an extrudate strand hanging downwards under influence of gravity is subjected to the asymmetric energy input.
4 . The method according to claim 2 , wherein the asymmetric energy input is effected in the device for asymmetric energy input comprising a drum and/or roller.
5 . The method according to claim 1 , wherein the peptizer is nitric acid, and the additives include an acid and/or cobalt nitrate.
6 . The method according to claim 1 , wherein the asymmetric energy input:
is effected by contact with a heating device, and/or
is effected by introduction of an electric current into the extrudate and/or the intermediate particles, wherein at least a part of an energy of the electric current is converted into heat by an electrical resistance of the extrudate and/or the intermediate particles, and/or
is effected by convection, and/or
is effected by action of an electromagnetic radiation, and/or
is effected by induction, wherein ferromagnetic particles are incorporated in the starting mixture to be extruded.
7 . The method according to claim 6 , wherein the asymmetric energy input:
is effected by contact with the heating device formed at least partially plate-shaped, and/or
is effected by a fan heater device, and/or
is effected by action of the electromagnetic radiation.
8 . The method according to claim 7 , wherein the wavelength of the electromagnetic radiation is:
between 780 nm and 1 mm or 380 nm and 100 nm, and/or
emitted by a laser or a radiant heater.
9 . The method according to claim 1 , wherein the extrudate and/or the intermediate particles have a longitudinal direction and the asymmetric energy input is effected in a direction transverse to the longitudinal direction.
10 . The method according to claim 1 , wherein, during the extruding, the starting mixture is pressed through a nozzle body with a nozzle channel.
11 . The method according to claim 10 , wherein the nozzle channel is one of a plurality of nozzle channels running substantially parallel, and the nozzle body is produced using an additive manufacturing method.
12 . The method according to claim 10 , wherein the nozzle channel of the nozzle body has an inlet opening, through which the starting mixture enters the nozzle channel, and an outlet opening having a convex side or a concave side via which the extrudate exits from the nozzle channel.
13 . The method according to claim 12 , wherein the inlet opening is circular or elliptical, and the outlet opening is rectangular, square, triangular, drop-shaped, or star-shaped.
14 . The method according to claim 10 , wherein the nozzle channel has a funnel-shaped section following the inlet opening with a diameter decreasing in a direction of the outlet opening, whereby the pressure, the density, and/or the speed of the starting mixture to be extruded is increased.
15 . The method according to claim 1 , wherein the extrudate is separated into intermediate particles by a separator and/or by a laser, and/or by a water jet cutter, and/or by a plasma cutter.
16 . The method according to claim 15 , wherein the separator is a rotating or oscillating blade, and the extrudate to be separated by the separator is deposited on a conveyor before the separation.
17 . The method according to claim 1 , wherein, during the heat treatment, the intermediate particles generated by the separation:
are calcined, and/or
are sintered.
18 . The method according to claim 17 , wherein, during the heat treatment, the intermediate particles generated by the separation are pre-dried before the calcination and/or sintering.
19 . The method according to claim 18 , wherein the pre-drying of the intermediate particles before the calcination and/or the sintering is performed at a temperature of between 50° C. and 350° C.
20 . The method according to claim 19 , wherein the pre-drying of the intermediate particles before the calcination and/or the sintering is performed at a temperature of between 80° C. and 100° C.
21 . The method according to claim 17 , wherein:
the calcination is performed at a temperature of between 400° C. and 1200° C., and/or
the sintering is performed at a temperature of between 1200° C. and 1800° C.
22 . The method according to claim 1 , further comprising cooling the abrasive particles present after the heat treatment.
23 . The method according to claim 1 , wherein, during the providing of the starting mixture and/or during the extruding of the starting mixture, water, a peptizer and/or additives are added to the starting mixture.