Feedstock composition for producing permanent magnets

Abstract

The invention relates to a feedstock composition for producing a permanent magnet; to a method for producing a permanent magnet; to a permanent magnet that can be produced using the method according to the invention; and to devices having a permanent magnet according to the invention.

Description

[0001] DESCRIPTION

[0002] Feedstock composition for the production of permanent magnets

[0003] The invention relates to a feedstock composition for the production of a permanent magnet, a method for producing a permanent magnet, a permanent magnet that can be produced using the method according to the invention, and devices comprising a permanent magnet according to the invention.

[0004] Permanent magnets from the rare earth group are used in a wide variety of technical applications and are characterized by a particularly high energy product. Neodymium-iron-boron magnets (NdFeB magnets) are especially noteworthy in this regard, exhibiting energy products of up to -400 kJ / m. 3NdFeB magnets can exhibit very high energy density. This high energy density allows for significantly smaller magnetic systems than would be possible with other magnetic materials. Important applications for NdFeB magnets today include electric motors, sensors, loudspeakers, and other electronic components.

[0005] The production of high-performance NdFeB sintered magnets uses finely ground powder of a magnetic feedstock. When using a metal powder injection molding process to manufacture the magnets, the finely ground magnetic feedstock is mixed with organic binder components to create a feedstock. This feedstock can then be formed into a green body using processes such as metal powder injection molding, extrusion, or additive manufacturing. The organic binder components are then removed via a debinding process, and the resulting green body is sintered to produce a dense, metallic raw magnet. The raw magnet can then be magnetized in a strong magnetic field to create a permanent magnet.

[0006] To achieve maximum magnetic properties, an external magnetic field is typically applied during the shaping step, causing the fine magnetic particles in the feedstock melt to align along the field lines, i.e., along the direction of the magnetic flux. The molded green bodies then cool to a temperature below the melting point of the higher-melting-point components of the binder system and solidify.

[0007] An optimal feedstock must meet two fundamental parameters to be suitable for manufacturing injection-molded or extruded magnets. First, the feedstock melt should have a sufficiently low viscosity during the alignment process so that friction between the particles and the feedstock does not impede the alignment. If the melt viscosity is too high, the particles are in a "frozen" state, and alignment is impossible. Second, the green body obtained after cooling should exhibit high strength to allow for damage-free ejection from the mold.

[0008] Prior art feedstock compositions suitable for conventional metal injection molding (MIM) components are particularly inadequate in meeting the requirement of low viscosity during the alignment process. In conventional part production, the feedstock composition is adjusted to have a sufficiently low viscosity during injection to enable rapid and uniform mold filling. However, these feedstock compositions have a narrow melting temperature range and solidify rapidly after injection. Consequently, the "frozen state"—that is, the state in which the fine magnetic particles can no longer move sufficiently to align themselves in an applied magnetic field—is reached at relatively high temperatures. Below the melting temperature, particle alignment in the magnetic field is no longer possible.If cold shifting is required in the injection mold after solidification, this can still be achieved with such feedstock compositions. However, this process involves moving the cooled melt within the mold to completely fill it. During this movement, the material no longer flows properly, it leaves its plastic state, and can only be cold-formed. This narrow melting temperature range and the resulting frequent cold-forming during the injection process are extremely disadvantageous for the use of conventional feedstock compositions in the production of injection-molded magnets. In this process, the magnetic particles contained within the composition are intended to align along magnetic field lines during injection molding, and any cold shifting of the injection-molded material must be avoided.Due to the temperature-dependent viscosity of feedstock compositions, particle alignment is most effective during injection. As the flow path progresses, the temperature decreases, causing the viscosity of the feedstock composition to increase. Consequently, particle alignment in the magnetic field is no longer possible, or only partially possible, due to the higher frictional forces. Particularly with long flow paths and simultaneously changing magnetic field orientation along a cavity, and / or changes in the direction of the feedstock composition while the magnetic particles are in their non-plastic state, misalignments occur, significantly reducing the achievable remanence.

[0009] Conventional feedstock compositions for metal injection molding (MIM) typically consist of four different components: framework polymer, base polymer, additive (wetting aid), and metal powder. The melting temperature range of such feedstock compositions is usually around 40 K. This narrow range makes the successful production of homogeneously filled and simultaneously homogeneously magnetically aligned injection-molded parts impossible.

[0010] The present invention is therefore based on the objective of providing a feedstock composition for the production of a raw magnet, in particular for the production of a permanent magnet, with which the aforementioned disadvantages of conventional feedstock compositions are overcome, especially with regard to the correct and complete alignment of the magnetic particles in a magnetic field applied externally during the manufacturing process.

[0011] The problem is solved by providing the present technical teaching, in particular the teaching of the independent claims as well as the embodiments of the invention disclosed in the dependent claims and in the description.

[0012] The present invention relates in particular to a feedstock composition for the production of permanent magnets, comprising

[0013] 1 to 30 vol% of at least one framework polymer with a melting temperature of at least 100 °C,

[0014] 1 to 25 vol% of at least one base polymer with a melting temperature of 60 to 100°C; 0 to 10 vol% of at least one surfactant.

[0015] 0 to 25 vol.% of at least one wax with a melting point of 30 to 80 °C,

[0016] >0 to 25 vol% of at least one organic solvent, preferably at least one polar or non-polar organic solvent, with a melting point of -80 °C to 30 °C, in particular 1 to 25 vol% of at least one organic solvent, preferably at least one polar or non-polar organic solvent, with a melting point of -80 °C to 30 °C and

[0017] 40 to 80 vol% of at least one metal powder (vol% in each case based on the total volume of the feedstock composition).

[0018] The feedstock composition according to the invention advantageously has a wider melting temperature range than feedstock compositions from the prior art, which makes it possible for the particles of the metal powder in a feedstock melt to align themselves within an externally applied magnetic field during cooling and solidification of the melt over a long period of time.

[0019] According to a preferred embodiment of the present invention, the feedstock composition has a melting temperature range of at least 50 K, preferably at least 100 K, preferably at least 150 K, and particularly preferably at least 175 K.

[0020] In a preferred embodiment, the feedstock composition has a melting temperature range of at most 250 K, preferably at most 225 K, preferably at most 200 K.

[0021] According to the invention, it can also be provided that the feedstock composition has a melting temperature range of 50 to 250 K, preferably 75 to 225 K, preferably 100 to 200 K, preferably 150 to 200 K, preferably 160 to 200 K, preferably 170 to 190 K.

[0022] According to a preferred embodiment of the present invention, the metal powder comprises particles of an R x T y B z -alloy or consists of particles of an R x T y Bz -alloy, wherein: R = at least one rare-earth element, in particular at least one element selected from the group consisting of neodymium (Nd), samarium (Sm), praseodymium (Pr), dysprosium (Dy), terbium (Tb), gadolinium (Gd), yttrium (Y), cerium (Ce) and lanthanum (La); T = at least one metal with ferromagnetic properties, in particular at least one element from group 8, preferably iron (Fe) or cobalt (Co); B = boron (B); wherein x, y are each independently a number > 1; and z is 0 or 1.

[0023] The metal powder particularly preferentially exhibits particles of an R x T y B z -alloy and particles of a rare-earth-rich phase, in particular the metal powder preferably consists of particles of an R x T y B z -alloy and particles of a rare-earth-rich phase.

[0024] In particular, the elements iron (Fe) and cobalt (Co) substitute for each other in the R x T y B z -The alloy is partially or completely such that it consists of either only iron (Fe), only cobalt (Co), or any iron-cobalt mixture.

[0025] In a preferred embodiment, the R comprises x T y B z -Alloy additionally comprising at least one further element, preferably at least one metal, in particular a transition metal, preferably selected from a group consisting of aluminium (Al), copper (Cu), zirconium (Zr), gallium (Ga), hafnium (Hf), and niobium (Nb), preferably in traces.

[0026] Preferably, the rare-earth element R is the R x T y B z -alloy and / or the rare-earth-rich phase neodymium (Nd).

[0027] In a particularly preferred embodiment of the present invention, the R xT y B z -alloy around a neodymium-iron-boron (NdFeB) alloy, preferably around an Nd2Fe14B alloy.

[0028] Alternatively or additionally, according to the invention, the at least one rare-earth element, in particular neodymium (Nd), may be present in a hydrogenated form. Preferably, the rare-earth-rich phase, in particular the neodymium-rich phase, comprises NdH₂ and / or NdH₂. 2 7 on or consists of NdH2 and / or NdH 2 7 Alternatively, in a preferred embodiment, it is also possible that the rare-earth-rich phase, in particular the neodymium-rich phase, consists of at least one rare-earth element, in particular neodymium (Nd), or of a chemical compound of this rare-earth element, in particular a chemical compound of neodymium (Nd).

[0029] The rare-earth-rich phase, particularly the neodymium-rich phase, is preferably located at the grain boundaries of the raw magnet's microstructure. Preferably, the rare-earth-rich phase, particularly the neodymium-rich phase, is enriched at the grain boundaries of the microstructure. In particular, the rare-earth-rich phase, particularly the neodymium-rich phase, is inhomogeneously distributed within the microstructure.

[0030] According to one embodiment of the present invention, the metal powder comprises at least one compound selected from the group consisting of an aluminium nickel cobalt alloy, a samarium cobalt alloy, and a ferrite alloy.

[0031] According to the invention, the samarium-cobalt alloy may comprise SmCo5, preferably consisting entirely of SmCo5. In a further embodiment of the present invention, the samarium-cobalt alloy may comprise Sm2Coi7, iron, copper, and zirconium, preferably consisting entirely of Sm2Coi7, iron, copper, and zirconium.

[0032] According to the invention, the metal powder may comprise an iron oxide, in particular Fe2O3, and at least one metal oxide, in particular nickel oxide, zinc oxide, manganese oxide, cobalt oxide, copper oxide, magnesium oxide, cadmium oxide, barium oxide, or strontium oxide, or consist of an iron oxide, in particular Fe2O3, and at least one metal oxide, in particular nickel oxide, zinc oxide, manganese oxide, cobalt oxide, copper oxide, magnesium oxide, cadmium oxide, barium oxide, or strontium oxide.

[0033] In a further embodiment, the metal powder comprises at least one ferrite selected from the group consisting of a manganese-zinc ferrite, a nickel-zinc ferrite, a strontium ferrite, a barium ferrite, and a cobalt ferrite.

[0034] According to a preferred embodiment of the present invention, the particles of the metal powder have an average particle size of at least 0.01 pm, preferably at least 0.025 pm, at least 0.05 pm, preferably at least 0.075 pm, preferably at least 0.1 pm, preferably at least 0.25 pm, preferably at least 0.5 pm, preferably at least 0.75 pm, preferably at least 1 pm, preferably at least 2.5 pm, preferably at least 5 pm.

[0035] In a preferred embodiment of the present invention, the particles of the metal powder have an average particle size of at most 50 pm, preferably at most 45 pm, preferably at most 40 pm, preferably at most 35 pm, preferably at most 30 pm, preferably at most 25 pm, preferably at most 20 pm, preferably at most 15 pm, preferably at most 10 pm, preferably at most 9 pm, preferably at most 8 pm, preferably at most 7 pm, preferably at most 6 pm, preferably at most 5 pm, preferably at most 4 pm, preferably at most 3 pm, preferably at most 2 pm, preferably at most 1 pm.

[0036] Preferably the metal powder particles have an average particle size of 0.01 to 50 pm, preferably 0.05 to 25 pm, preferably 0.1 to 20 pm, preferably 0.5 to 15 pm, preferably 1 to 10 pm.

[0037] In a preferred embodiment, the feedstock composition comprises at least 40 vol.%, preferably at least 45 vol.%, preferably at least 50 vol.%, preferably at least 55 vol.%, preferably at least 60 vol.%, preferably at least 65 vol.%, preferably at least 70 vol.%, preferably at least 75 vol.% of the at least one metal powder (vol.% in each case based on the total volume of the feedstock composition).

[0038] In a preferred embodiment of the present invention, the feedstock composition comprises at most 80 vol.%, preferably at most 75 vol.%, preferably at most 70 vol.%, preferably at most 65 vol.%, preferably at most 60 vol.%, preferably at most 55 vol.%, preferably at most 50 vol.%, preferably at most 45 vol.%, of the at least one metal powder (vol.% in each case based on the total volume of the feedstock composition).

[0039] According to a preferred embodiment of the present invention, the feedstock composition comprises 45 to 80 vol.%, preferably 50 to 80 vol.%, more preferably 55 to 80 vol.%, more preferably 60 to 80 vol.%, of the at least one metal powder. Particularly preferably, the feedstock composition comprises 40 to 75 vol.%, more preferably 40 to 70 vol.%, more preferably 40 to 65 vol.%, more preferably 40 to 60 vol.%, more preferably 40 to 55 vol.%, more preferably 40 to 50 vol.%, more preferably 40 to 45 vol.%, of the at least one metal powder. In a particularly preferred embodiment of the present invention, the feedstock composition comprises 40 to 75 vol.%, more preferably 42.5 to 65 vol.%, more preferably 45 to 60, more preferably 45 to 57 vol.%, of the at least one metal powder (vol.% in each case based on the total volume of the feedstock composition).

[0040] In a further preferred embodiment of the present invention, the at least one metal powder is a recycled magnetic material, in particular a magnetic material obtained from recycled magnets, preferably from recycled rare-earth magnets. Preferably, the at least one metal powder is a recycled magnetic material obtained from recycled magnets, preferably from recycled rare-earth magnets, using hydrogen in the HPMS process by embrittlement and pulverization.

[0041] In a preferred embodiment of the invention, the at least one framework polymer is a thermoplastic polymer. Preferably, the at least one framework polymer is a polymer selected from the group consisting of: high-density polyethylene (HDPE), low-density polyethylene (LDPE), polypropylene (PP), polystyrene (PS), acrylonitrile butadiene styrene copolymer (ABS), and mixtures thereof.

[0042] The at least one framework polymer is particularly preferred to be nonpolar and / or oxygen-free.

[0043] Preferably, the feedstock composition comprises at least 1 vol.%, preferably at least 2.5 vol.%, preferably at least 5 vol.%, preferably at least 7.5 vol.%, preferably at least 10 vol.%, preferably at least 12.5 vol.%, preferably at least 15 vol.%, preferably at least 17.5 vol.%, preferably at least 20 vol.%, preferably at least 22.5 vol.%, preferably at least 25 vol.%, preferably at least 27.5 vol.% of the at least one framework polymer (vol.% in each case based on the total volume of the feedstock composition).

[0044] In a preferred embodiment of the present invention, the feedstock composition comprises at most 30 vol.%, preferably at most 27.5 vol.%, preferably at most 25 vol.%, preferably at most 22.5 vol.%, preferably at most 20 vol.%, preferably at most 17.5 vol.%, preferably at most 15 vol.%, preferably at most 12.5 vol.%, preferably at most 10 vol.%, preferably at most 7.5 vol.%, preferably at most 5 vol.% of the at least one framework polymer (vol.% in each case based on the total volume of the feedstock composition).

[0045] According to a preferred embodiment of the present invention, the feedstock composition comprises 2.5 to 30 vol.%, preferably 5 to 30 vol.%, preferably 7.5 to 30 vol.%, preferably 10 to 30 vol.%, preferably 12.5 to 30 vol.%, preferably 15 to 30 vol.%, preferably 17.5 to 30 vol.%, and preferably 20 to 30 vol.% of the at least one framework polymer (vol.% in each case based on the total volume of the feedstock composition). Particularly preferably, the feedstock composition comprises 1 to 27.5 vol.%, preferably 1 to 25 vol.%, preferably 1 to 22.5 vol.%, preferably 1 to 20 vol.%, preferably 1 to 17.5 vol.%, and preferably 1 to 15 vol.% of the at least one framework polymer (vol.% in each case based on the total volume of the feedstock composition).

[0046] In a further preferred embodiment of the present invention, the feedstock composition comprises 5 to 30 vol.%, preferably 7.5 to 27.5 vol.%, preferably 10 to 25 vol.%, preferably 12.5 to 22.5 vol.%, preferably 15 to 20 vol.%, of the at least one framework polymer (vol.% in each case based on the total volume of the feedstock composition).

[0047] According to a preferred embodiment, the at least one base polymer is a thermoplastic, low-melting, non-polar polymer. Preferably, the at least one base polymer is a polymer selected from the group consisting of: polypropylene-polyethylene (PP-PE) copolymer, polyethylene wax, and mixtures thereof.

[0048] The at least one base polymer is particularly preferred to be nonpolar and / or oxygen-free.

[0049] Preferably, the feedstock composition comprises at least 1 vol.%, preferably at least 2 vol.%, preferably at least 3 vol.%, preferably at least 4 vol.%, preferably at least 5 vol.%, preferably at least 7.5 vol.%, preferably at least 10 vol.%, preferably at least 12.5 vol.%, preferably at least 15 vol.%, preferably at least 17.5 vol.%, preferably at least 20 vol.%, preferably at least 22.5 vol.% of the at least one base polymer (vol.% in each case based on the total volume of the feedstock composition).

[0050] In a preferred embodiment of the present invention, the feedstock composition comprises at most 25 vol.%, preferably at most 22.5 vol.%, preferably at most 20 vol.%, preferably at most 17.5 vol.%, preferably at most 15 vol.%, preferably at most 12.5 vol.%, preferably at most 10 vol.%, preferably at most 7.5 vol.%, preferably at most 5 vol.%, preferably at most 2.5 vol.%, of the at least one base polymer (vol.% in each case based on the total volume of the feedstock composition). According to a preferred embodiment of the present invention, the feedstock composition comprises 2 to 25 vol.%, preferably 3 to 25 vol.%, preferably 4 to 25 vol.%, preferably 5 to 25 vol.%, preferably 7.5 to 25 vol.%, preferably 10 to 25 vol.%, preferably 12.5 to 25 vol.%, preferably 15 to 25 vol.%, preferably 17.5 to 25 vol.%, of the at least one base polymer (vol.% in each case based on the total volume of the feedstock composition).

[0051] The feedstock composition particularly preferably comprises 1 to 22.5 vol.%, preferably 1 to 20 vol.%, preferably 1 to 17.5 vol.%, preferably 1 to 15 vol.%, preferably 1 to 12.5 vol.%, of the at least one base polymer (vol.% in each case based on the total volume of the feedstock composition).

[0052] In a further preferred embodiment of the present invention, the feedstock composition comprises 2 to 22.5 vol.%, preferably 3 to 20 vol.%, preferably 4 to 17.5 vol.%, preferably 5 to 15 vol.%, preferably 7.5 to 12.5 vol.%, of the at least one base polymer (vol.% in each case based on the total volume of the feedstock composition).

[0053] In a preferred embodiment of the present invention, the feedstock composition comprises at least one surfactant. Preferably, the at least one surfactant is a non-ionic, anionic, cationic, or amphoteric surfactant. Particularly preferred is the at least one surfactant selected from the group consisting of: fatty acids or salts thereof, preferably stearic acid or magnesium stearate; polysorbates, preferably polysorbate 20, polysorbate 21, polysorbate 40, polysorbate 60, polysorbate 61, polysorbate 65, polysorbate 80, polysorbate 81, polysorbate 85, or polysorbate 120; and mixtures thereof.

[0054] The at least one surfactant advantageously serves to wet the polymers with the metal powder and the polymers with each other. In this way, the at least one surfactant supports the formation of a homogeneous and agglomerate-free feedstock melt.

[0055] In a preferred embodiment, the feedstock composition comprises at least 0.05 vol.%, preferably at least 0.1 vol.%, preferably at least 0.2 vol.%, preferably at least 0.3 vol.%, preferably at least 0.4 vol.%, preferably at least 0.5 vol.%, preferably at least 0.6 vol.%, preferably at least 0.7 vol.%, preferably at least 0.8 vol.%, preferably at least 0.9 vol.%, particularly preferably at least 1 vol.%, of the at least one surfactant (vol.% in each case based on the total volume of the feedstock composition).

[0056] According to a preferred embodiment of the present invention, the feedstock composition comprises at most 10 vol.%, preferably at most 9 vol.%, preferably at most 8 vol.%, preferably at most 7 vol.%, preferably at most 6 vol.%, preferably at most 5 vol.%, preferably at most 4 vol.%, preferably at most 3 vol.%, preferably at most 2 vol.%, preferably at most 1 vol.%, of the at least one surfactant (vol.% in each case based on the total volume of the feedstock composition).

[0057] In a preferred embodiment of the present invention, the feedstock composition comprises 0.05 to 10 vol.%, preferably 0.1 to 10 vol.%, preferably 0.5 to 10 vol.%, preferably 1 to 10 vol.%, preferably 2 to 10 vol.%, preferably 3 to 10 vol.%, preferably 4 to 10 vol.%, preferably 5 to 10 vol.%, of the at least one surfactant (vol.% in each case based on the total volume of the feedstock composition).

[0058] The feedstock composition particularly preferably comprises 0.05 to 10 vol.%, preferably 0.05 to 8 vol.%, preferably 0.05 to 6 vol.%, preferably 0.05 to 5 vol.%, preferably 0.05 to 4 vol.%, preferably 0.05 to 3 vol.%, preferably 0.05 to 2 vol.%, preferably 0.05 to 1 vol.%, preferably 0.05 to 0.5 vol.%, of the at least one surfactant (vol.% in each case based on the total volume of the feedstock composition).

[0059] In a further preferred embodiment of the present invention, the feedstock composition comprises 0.05 to 10 vol.%, preferably 0.1 to 7.5 vol.%, preferably 0.5 to 5 vol.%, preferably 1 to 4 vol.%, of the at least one surfactant (vol.% in each case based on the total volume of the feedstock composition).

[0060] According to the invention, it can also be provided that the feedstock composition does not contain a surfactant.

[0061] According to a preferred embodiment of the present invention, the feedstock composition comprises at least one wax. In a preferred embodiment, the at least one wax is a mineral, vegetable, animal, semi-synthetic, or synthetic wax. Preferably, the at least one wax is selected from the group consisting of: paraffin wax, camauba wax, wool wax, beeswax, and mixtures thereof. According to the invention, the at least one wax serves to improve the flowability of the feedstock melt. Furthermore, the at least one wax reduces the melt viscosity and thus improves the alignment of the magnetic particles in the feedstock melt in an externally applied magnetic field.In addition, the at least one wax advantageously extends the melting temperature range of the feedstock composition to lower temperatures, so that the plastic state in which the particles of the metal powder can align themselves along the field lines of an externally applied magnetic field persists for a longer period during the cooling of the feedstock melt.

[0062] Preferably, at least one wax should be nonpolar and oxygen-free.

[0063] Preferably, the feedstock composition comprises at least 0.05 vol.%, preferably at least 0.1 vol.%, preferably at least 0.5 vol.%, preferably at least 1 vol.%, preferably at least 2.5 vol.%, preferably at least 5 vol.%, preferably at least 7.5 vol.%, preferably at least 10 vol.%, preferably at least 12.5 vol.% of the at least one wax (vol.% in each case based on the total volume of the feedstock composition).

[0064] In a preferred embodiment of the present invention, the feedstock composition comprises at most 25 vol.%, preferably at most 22.5 vol.%, preferably at most 20 vol.%, preferably at most 17.5 vol.%, preferably at most 15 vol.%, preferably at most 12.5 vol.%, preferably at most 10 vol.%, preferably at most 7.5 vol.%, preferably at most 5 vol.%, preferably at most 4 vol.%, preferably at most 3 vol.%, preferably at most 2 vol.%, preferably at most 1 vol.%, preferably at most 0.5 vol.%, of the at least one wax (vol.% in each case based on the total volume of the feedstock composition).

[0065] According to a preferred embodiment of the present invention, the feedstock composition comprises 0.05 to 25 vol.%, preferably 0.1 to 25 vol.%, preferably 0.5 to 25 vol.%, preferably 1 to 25 vol.%, preferably 2.5 to 25 vol.%, preferably 5 to 25 vol.%, preferably 7.5 to 25 vol.%, preferably 10 to 25 vol.%, preferably 12.5 to 25 vol.%, preferably 15 to 25 vol.%, preferably 17.5 to 25 vol.%, preferably 20 to 25 vol.%, preferably 22.5 to 25 vol.%, of at least one wax (vol.% in each case based on the total volume of the feedstock composition). The feedstock composition particularly preferably comprises 0.05 to 25 vol.%, preferably 0.05 to 22.5 vol.%, preferably 0.05 to 20 vol.%, preferably 0.05 to 17.5 vol.%, preferably 0.05 to 15 vol.%, preferably 0.05 to 12.5 vol.%, preferably 0.05 to 10 vol.%, preferably 0.05 to 7.5 vol.%, preferably 0.05 to 5 vol.% of the at least one wax (vol.-% in each case based on the total volume of the feedstock composition).

[0066] In a further preferred embodiment of the present invention, the feedstock composition comprises 1 to 20 vol.%, preferably 2.5 to 17.5 vol.%, preferably 5 to 15 vol.%, of the at least one wax (vol.% in each case based on the total volume of the feedstock composition).

[0067] According to the present invention, it can also be provided that the feedstock composition does not contain wax.

[0068] According to the invention, the feedstock composition comprises at least one organic solvent, in particular at least one polar or nonpolar organic solvent.

[0069] In a preferred embodiment of the present invention, the at least one organic solvent of the feedstock composition is selected from the group consisting of: aromatic hydrocarbons, alkenes, fluorochlorohydrocarbons, fluorocarbons, chlorinated hydrocarbons, and mixtures thereof.

[0070] In a further preferred embodiment of the present invention, the at least one organic solvent of the feedstock composition may be a plasticizer, particularly preferably a plasticizer selected from the group consisting of: phthalic acid-based plasticizers, in particular di(2-ethylhexyl) phthalate (DEHP), diisodecyl phthalate (DIDP), diisononyl phthalate (DINP), dibutyl phthalate (DBP), diisobutyl phthalate (DIBP), and benzyl butyl phthalate (BBP), (Cio-C2i)alkanesulfonic acid phenyl esters (Mesamoll), 1,2-cyclohexanedicarboxylic acid diisononyl esters (DINCH), citric acid-based plasticizers, in particular triethyl citrate, adipic acid-based plasticizers, in particular diethylhexyl adipate and diethyl octyl adipate, and mixtures thereof.

[0071] Preferably, the at least one organic solvent of the feedstock composition is a polar organic solvent, particularly preferably a polar organic solvent selected from the group consisting of: alcohols, aldehydes, esters, ketones, ethers, carboxylic acids, glycols, fluorochlorohydrocarbons, nitriles, fluorocarbons, chlorinated hydrocarbons, pyridine, and mixtures thereof.

[0072] According to a preferred embodiment of the invention, the at least one organic solvent of the feedstock composition is a nonpolar organic solvent, particularly preferably a nonpolar organic solvent selected from the group consisting of: paraffin oils, white spirits, alkanes, and mixtures thereof.

[0073] According to the invention, the at least one organic solvent, in particular the at least one polar or nonpolar organic solvent, serves in the feedstock composition to optimize the alignment of the metal powder particles in the magnetic field. The organic solvent, in particular the polar or nonpolar organic solvent, possesses excellent wetting properties and protects the metal powder in the feedstock composition from oxidation during the permanent magnet production process. Preferably, the at least one organic solvent, in particular the at least one polar or nonpolar organic solvent, forms a very thin protective or lubricating film on the particles due to its very good wetting properties and the small contact angle of 0-25°.The formation of this thin lubricating film leads to a significant improvement in the magnetic alignment of the particles in the feedstock melt when an external magnetic field is applied. The protective or lubricating film formed by the at least one organic solvent, in particular the at least one polar or nonpolar organic solvent, protects the metal powder particles from oxidation before (during compounding, granulation), after (storage of the green bodies), and during molding, especially during injection molding (i.e., during conveying in the injection molding machine, during the injection process, and during the cooling process). Furthermore, the at least one organic solvent, in particular the at least one polar or nonpolar organic solvent, can act as a plasticizer and lower the melting temperature range of the feedstock system.

[0074] Particularly preferred is the at least one organic solvent, especially the at least one polar or nonpolar organic solvent, which is oxygen-free. According to a preferred embodiment of the present invention, the at least one organic solvent, especially the at least one polar or nonpolar organic solvent, is liquid at room temperature.

[0075] Preferably, the at least one organic solvent, in particular the at least one polar or non-polar organic solvent, has a melting point of at most 30 °C, preferably at most 25 °C, preferably at most 20 °C, preferably at most 15 °C, preferably at most 10 °C, preferably at most 5 °C, preferably at most 0 °C, preferably at most -5 °C, preferably at most -10 °C, preferably at most -20 °C, preferably at most -25 °C, preferably at most -30 °C.

[0076] In a particularly preferred embodiment of the present invention, the at least one organic solvent, in particular the at least one polar or non-polar organic solvent, has a melting temperature in the range of -70 to 20 °C, preferably -65 to 10 °C, preferably -60 to 0 °C.

[0077] According to a preferred embodiment of the present invention, the feedstock composition comprises at least 0.1 vol.%, preferably at least 0.2 vol.%, preferably at least 0.3 vol.%, preferably at least 0.4 vol.%, preferably at least 0.5 vol.%, preferably at least 0.6 vol.%, preferably at least 0.7 vol.%, preferably at least 0.8 vol.%, preferably at least 0.9 vol.%, in particular at least 1 vol.%, of the at least one organic solvent, in particular of the at least one polar or nonpolar organic solvent (vol.% in each case based on the total volume of the feedstock composition).

[0078] In a preferred embodiment, the feedstock composition comprises at least 1.5 vol%, preferably at least 2 vol%, preferably at least 2.5 vol%, preferably at least 5 vol%, preferably at least 7.5 vol%, preferably at least 10 vol%, preferably at least 12.5 vol%, preferably at least 15 vol%, preferably at least 17.5 vol%, preferably at least 20 vol%, and preferably at least 22.5 vol% of the at least one organic solvent, in particular the at least one polar or nonpolar organic solvent (vol% in each case based on the total volume of the feedstock composition). In a preferred embodiment of the present invention, the feedstock composition comprises at most 25 vol%, preferably at most 22.5 vol%, preferably at most 20 vol%, preferably at most 17.5 vol%, preferably at most 15 vol%, preferably at most 12.5 vol%, preferably at most 10 vol%, and preferably at most 7.5 vol%.-%, preferably at most 5 vol%, preferably at most 4 vol%, preferably at most 3 vol%, preferably at most 2 vol%, preferably at most 1 vol%, preferably at most 0.5 vol%, of the at least one organic solvent, in particular of the at least one polar or non-polar organic solvent (vol. -% in each case based on the total volume of the feedstock composition).

[0079] In a preferred embodiment of the present invention, the feedstock composition comprises 0.1 to 25 vol.%, preferably 0.2 to 25 vol.%, preferably 0.3 to 25 vol.%, preferably 0.4 to 25 vol.%, preferably 0.5 to 25 vol.%, preferably 0.6 to 25 vol.%, preferably 0.7 to 25 vol.%, preferably 0.8 to 25 vol.%, preferably 0.9 to 25 vol.%, in particular 1 to 25 vol.%, of the at least one organic solvent, in particular of the at least one polar or nonpolar organic solvent (vol.% in each case based on the total volume of the feedstock composition).

[0080] According to a preferred embodiment of the present invention, the feedstock composition comprises 1.5 to 25 vol.%, preferably 2 to 25 vol.%, preferably 2.5 to 25 vol.%, preferably 5 to 25 vol.%, preferably 7.5 to 25 vol.%, preferably 10 to 25 vol.%, preferably 12.5 to 25 vol.%, preferably 15 to 25 vol.%, preferably 17.5 to 25 vol.%, preferably 20 to 25 vol.%, preferably 22.5 to 25 vol.%, of the at least one organic solvent, in particular of the at least one polar or nonpolar organic solvent (vol.% in each case based on the total volume of the

[0081] Feedstock composition).

[0082] In a further preferred embodiment of the present invention, the feedstock composition comprises 0.1 to 22.5 vol.%, preferably 0.1 to 20 vol.%, preferably 0.1 to 17.5 vol.%, preferably 0.1 to 15 vol.%, preferably 0.1 to 12.5 vol.%, preferably 0.1 to 10 vol.%, preferably 0.1 to 7.5 vol.%, preferably 0.1 to 5 vol.%, preferably 0.1 to 2.5 vol.%, preferably 0.1 to 1 vol.%, of the at least one organic solvent, in particular of the at least one polar or nonpolar organic solvent (vol.% in each case based on the total volume of the feedstock composition). The feedstock composition most preferably comprises 1 to 22.5 vol.%, preferably 1 to 20 vol.%, preferably 1 to 17.5 vol.%, preferably 1 to 15 vol.%, preferably 1 to 12.5 vol.%, preferably 1 to 10 vol.%, preferably 1 to 7.5 vol.%, preferably 1 to 5 vol.%, preferably 1 to 2.5 vol.%.-% of the at least one organic solvent, in particular the at least one polar or non-polar organic solvent (vol% in each case based on the total volume of the feedstock composition).

[0083] In a further preferred embodiment of the present invention, the feedstock composition comprises 5 to 25 vol.%, preferably 7.5 to 22.5 vol.%, preferably 10 to 20 vol.%, of the at least one organic solvent, in particular of the at least one polar or non-polar organic solvent (vol.% in each case based on the total volume of the feedstock composition).

[0084] In a particularly preferred embodiment, the feedstock composition according to the invention comprises:

[0085] 5 to 30 vol% of the at least one framework polymer,

[0086] 5 to 15 vol% of the at least one base polymer,

[0087] 1 to 5 vol% of at least one surfactant,

[0088] 5 to 15 vol.% of the at least one wax,

[0089] 10 to 20 vol% of the at least one organic solvent, in particular the at least one polar or non-polar organic solvent, and

[0090] 45 to 57 vol% of the at least one metal powder (vol% in each case based on the total volume of the feedstock composition).

[0091] The present invention further relates to a method for producing a permanent magnet, comprising the steps of: a) providing a feedstock composition according to the invention, b) heating the feedstock composition to a temperature above the melting temperature of the at least one base polymer and the at least one base polymer of the feedstock composition, such that a feedstock melt is obtained, c) molding the feedstock melt obtained in step b), d) cooling the feedstock melt to a temperature below the melting temperature of the at least one base polymer and the at least one base polymer of the feedstock system, such that a solid, molded green body is obtained, e) at least partially debinding the green body obtained in step d) to obtain a browning, f) sintering the browning to obtain a raw magnet, and g) magnetizing the raw magnet to obtain a permanent magnet.where step c) and / or step d) takes place in a magnetic field that is applied externally, at least temporarily.

[0092] By using the feedstock composition according to the invention, it is advantageously possible to obtain very homogeneous and uniformly molded and aligned green bodies, particularly in the metal injection molding (MIM) process, whereas with conventional feedstock compositions, only inhomogeneously aligned green bodies are often obtained, resulting in very inhomogeneous sintered parts and, after final magnetization, in very inhomogeneous magnets with inhomogeneous magnetic flux density. Thus, without the use of the at least one organic solvent, in particular a polar or nonpolar organic solvent, present in the feedstock composition according to the invention, the magnetic particles in conventional feedstock compositions do not have sufficient time to align themselves in the rapidly solidifying melt.Furthermore, conventional feedstock compositions lacking at least one organic solvent, particularly polar or nonpolar organic solvents, a component that exhibits excellent wetting and sliding properties over a wide temperature range, even down to relatively low temperatures. This often results in significant local inhomogeneities in the orientation of individual particles in the molded green body.

[0093] According to a preferred embodiment of the present invention, the feedstock composition is heated in step b) to a temperature of at least 100 °C, preferably at least 105 °C, preferably at least 110 °C, preferably at least 115 °C, preferably at least 120 °C, preferably at least 125 °C, preferably at least 130 °C, preferably at least 135 °C, preferably at least 140 °C.

[0094] In a further preferred embodiment of the present invention, the feedstock composition is heated in step b) to a temperature of 100 to 160 °C, preferably at least 110 to 150 °C, preferably 120 to 140 °C.

[0095] Preferably, the feedstock composition is heated to a temperature above the melting temperature of the at least one base polymer and the at least one base polymer of the feedstock composition in step b) for a duration of at least 5 minutes, preferably at least 10 minutes, preferably at least 20 minutes, preferably at least 30 minutes, preferably at least 40 minutes, preferably at least 50 minutes, preferably at least 60 minutes.

[0096] The feedstock composition is particularly preferably mixed, especially kneaded, during heating in step b).

[0097] In a preferred embodiment of the present invention, the molding in step c) was carried out by means of metal injection molding (MIM), extrusion, or additive manufacturing (3D printing). Particularly preferably, the molding in step c) is carried out by means of metal injection molding (MIM).

[0098] If the molding of the feedstock melt obtained in step b) is provided for by extrusion in step c), it is preferably provided according to the invention that the feedstock composition provided in step a) preferably comprises at most 15 vol.%, preferably at most 10 vol.%, preferably at most 5 vol.%, preferably at most 4 vol.%, preferably at most 3 vol.%, preferably at most 2 vol.%, preferably at most 1 vol.%, of the at least one wax (vol.% in each case based on the total volume of the feedstock composition). Particularly preferably, the feedstock composition provided in step a) contains no wax if the molding of the feedstock melt obtained in step b) is carried out by extrusion in step c). In this way, the feedstock melt solidifies completely even at elevated temperature, so that dimensionally stable extrudates can be removed directly from the extruder die.

[0099] According to the invention, step c) and / or step d) is performed in an externally applied magnetic field, at least temporarily. Preferably, the molding of the feedstock melt obtained in step b) is performed in step c) in an externally applied magnetic field, at least temporarily. In a further embodiment of the present invention, the cooling of the feedstock melt in step d) is performed in an externally applied magnetic field, at least temporarily. According to the invention, it can also be provided that both step c) and step d) are performed in an externally applied magnetic field, at least temporarily. According to these embodiments of the present invention, the externally applied magnetic field can be present for the entire duration of step c) and / or d), for a limited period of time during step c) and / or d), or applied in the form of at least one magnetic pulse during step c) and / or step d).It is of particular importance that the external magnetic field is applied at a time when the feedstock melt is still in a plastic state, in particular at a time when the viscosity of the feedstock melt is sufficiently low so that the magnetic particles in the melt have a mobility that allows the particles to align themselves along the field lines of the applied magnetic field.

[0100] According to a preferred embodiment of the present invention, the external magnetic field is applied for only a short period of time during the molding process in step c). In a preferred embodiment of the present invention, the external magnetic field may be applied during the molding process in step c) in the form of at least one magnetic pulse, preferably in the form of a single magnetic pulse.

[0101] According to the invention, the cooling of the feedstock melt in step d) can take place in an externally applied magnetic field. Particularly preferably, the external magnetic field is applied in step d) at least until the melting temperature of the at least one framework polymer, preferably of the at least one framework polymer and the at least one base polymer, is undershot. According to the invention, it can also be provided that the external magnetic field is applied only for a short period during the cooling in step d). Thus, in a preferred embodiment, the external magnetic field can be applied during the cooling in step c) in the form of at least one magnetic pulse, preferably in the form of a single magnetic pulse.

[0102] In a further preferred embodiment of the present invention, both the molding of the feedstock melt in step c) and the cooling of the feedstock melt in step d) are carried out in an externally applied magnetic field. Preferably, the externally applied magnetic field in step c) and / or step d) is generated by a switchable electromagnet and / or a permanent magnet.

[0103] According to a preferred embodiment of the invention, the at least partial debinding of the green body to obtain a raw magnet in step e) comprises the steps: e) pre-debinding of the green body obtained in step d), and e) thermal debinding of the pre-debound green body obtained from step e).

[0104] Preferably, the organic components are at least partially removed from the green body in step el) by solvent extraction. According to the invention, it can also be provided that the organic components are chemically cleaved in step el).

[0105] In a preferred embodiment of the present invention, in step e) at least 80%, preferably at least 85%, preferably at least 90%, preferably at least 95%, preferably at least 96%, preferably at least 97%, preferably at least 98% of the organic compounds are removed from the green body obtained in step d).

[0106] According to a preferred embodiment of the present invention, the sintering of the browning material in step f) takes place at a temperature of at least 1000 °C, preferably at least 1050 °C, preferably at least 1100 °C, preferably at least 1150 °C, preferably at least 1200 °C.

[0107] In a further preferred embodiment of the present invention, the sintering of the browning material in step f) takes place at a temperature of at most 2200 °C, preferably at most 2000 °C, preferably at most 1800 °C, preferably at most 1600 °C, preferably at most 1400 °C.

[0108] Particularly preferably, the sintering of the browning material in step f) takes place at a temperature in the range of 1000 to 2200 °C, preferably 1050 to 2000 °C, preferably 1100 to 1800 °C, preferably 1150 to 1600 °C, preferably 1200 to 1400 °C.

[0109] In a preferred embodiment of the present invention, the raw magnet obtained by sintering in step f) has a relative density of at least 95%, preferably at least 95.5%, preferably at least 96%, preferably at least 96.5%, preferably at least 97%, preferably at least 97.5%, preferably at least 98%, preferably at least 98.5%, and preferably at least 99% (in each case based on the theoretically maximum achievable density). Here, the following applies: relative density [%] = 100% (theoretical maximum density) - porosity [%].

[0110] According to the invention, it can also be provided that the raw magnet obtained by sintering in step f) has a porosity of at most 5%, preferably at most 4.5%, preferably at most 4%, preferably at most 3.5%, preferably at most 3%, preferably at most 2.5%, preferably at most 2%, preferably at most 1.5%, preferably at most 1%.

[0111] In a preferred embodiment of the present invention, the raw magnet obtained from step f) has a volume that is at least 8%, preferably at least 10%, preferably at least 12%, preferably at least 14%, preferably at least 16%, preferably at least 18%, preferably at least 20% smaller than the volume of the solid, molded green body obtained from step d).

[0112] According to the present invention, it can also be provided that a further post-processing step of the raw magnet obtained from step f) and / or the permanent magnet obtained from step g) is carried out following step f) and before step g), or following steps f) and g). Preferably, the post-processing step is selected from the group consisting of hot isostatic pressing (HIP), heat treatment, boundary diffusion (GBD), machining, in particular CNC machining, laser processing, wire EDM, grinding, joining, and surface treatment, in particular surface finishing, such as vibratory finishing, sandblasting, polishing, and electroplating.

[0113] The steps of the process according to the invention, that is to say, in particular both the production and provision of the feedstock composition according to the invention, and the processing of the feedstock composition in steps b) to f), in particular the heating of the feedstock composition in step b), the molding of the feedstock melt in step c), the cooling of the molded feedstock melt in step d), the at least partial debonding of the resulting green body in step e), and / or the sintering of the brown body in step f), are preferably carried out under a protective gas atmosphere. In addition, transport between the individual process steps preferably also takes place under a protective gas atmosphere. The entire manufacturing process is particularly preferably carried out under a protective gas atmosphere.The present invention also relates to a permanent magnet that can be manufactured, in particular manufactured, using the method according to the invention.

[0114] According to a preferred embodiment, the permanent magnet has an energy product of at least 250 kJ / m². 3 , preferably at least 300 kJ / m² 3 , preferably at least 350 kJ / m² 3 , on.

[0115] Preferably, the permanent magnet according to the invention has an energy product of at least 250 to 500 kJ / m. 3 , preferably 275 to 475 kJ / m² 3 preferably 300 to 450 kJ / m² 3 , preferably 325 to 425 kJ / m² 3 preferably 350 to 400 kJ / m² 3 , on.

[0116] The invention also includes the use of a permanent magnet according to the invention in a device selected from the group consisting of an electric motor, a loudspeaker, a microphone, a generator, a hard disk drive, a holding magnet and a sensor.

[0117] The present invention further relates to a device selected from the group consisting of an electric motor, a loudspeaker, a microphone, a generator, a hard disk drive, a holding magnet and a sensor, characterized in that the device has a permanent magnet according to the invention.

[0118] The embodiments described and statements made in connection with the inventive feedstock composition also relate, mutatis mutandis, to the inventive method for manufacturing a permanent magnet, the inventive permanent magnet, the inventive use, and the inventive device, and vice versa.

[0119] According to the invention, the term "framework polymer" refers to a macromolecule composed of identical or different monomers that is responsible for the mechanical stability of a green body produced from the feedstock composition. The "framework polymer" is defined as the polymer in the feedstock composition with the highest melting point, in particular a polymer with a melting temperature of at least 100 °C. The mechanical stability of the green body obtained after solidification of the feedstock melt, achieved by the "framework polymer," enables subsequent machining, laser processing, and handling of the green body without mechanical damage or deformation.In the context of the present invention, the term "base polymer" refers to a macromolecule composed of identical or different monomers, which serves to make a feedstock melt produced from the feedstock composition by heating flowable. According to the invention, the "base polymer" has a melting point in the range of 60 to 100 °C and is preferably nonpolar and oxygen-free.

[0120] In the context of the present invention, the terms "comprising" and "comprising" are understood to mean that, in addition to the elements explicitly covered by these terms, further, unmentioned elements may be present. In the context of the present invention, these terms are also understood to mean that only the explicitly mentioned elements are covered and no further elements are present. In this particular embodiment, the meaning of the terms "comprising" and "comprising" is synonymous with the term "consisting of." Furthermore, the terms "comprising" and "comprising" also encompass compositions that, in addition to the explicitly mentioned elements, contain further unmentioned elements that are, however, of a functionally and qualitatively subordinate nature. In this embodiment, the terms "comprising" and "comprising" are synonymous with the term "essentially consisting of."

[0121] In the context of the present invention, the term "and / or" means that all members of a group connected by the term "and / or" are disclosed both alternatively to one another and cumulatively to one another in any combination. For the expression "A, B and / or C", this means that the following disclosure content is to be understood: a) A or B or C or b) (A and B) or c) (A and C) or d) (B and C) or e) (A and B and C).

[0122] Further preferred embodiments of the present invention are set forth in the dependent claims.

[0123] The invention is illustrated below, without limiting the general concept, by means of a figure and exemplary embodiments. The figures show:

[0124] Fig. 1 shows various examples of misalignments of the magnetic particles during the metal powder injection molding process using conventional feedstock compositions. Fig. 2 shows the measurement of the magnetic flux density of a permanent magnet produced by metal powder injection molding using a conventional feedstock composition (Fig. 2A) compared to a permanent magnet produced by metal powder injection molding using a feedstock composition according to the invention (Fig. 2B).

[0125] Figures 1A and 1B show that when using conventional feedstock compositions, the rapid cooling after injection of the feedstock melt within a cavity (1) of an injection mold leads to the formation of a non-plastic state in which the magnetic particles (3a, 3b) no longer have the opportunity to align themselves precisely along the field lines of an externally applied magnetic field (see 3b). Only in the region of the injection point (2) does the higher temperature result in a viscosity of the melt that allows for correct alignment of the magnetic particles (3a) present in this area. This results in an inhomogeneous alignment of the magnetic particles within the green body that solidifies in the cavity (1).

[0126] Figures IC and ID illustrate the alignment of the magnetic particles (3a, 3b) of a metal powder in an injection mold when an external magnetic field is applied using a conventional feedstock composition (Fig. IC) compared to using a feedstock composition according to the invention (Fig. ID). The extension of the melting temperature range of the feedstock composition according to the invention towards lower temperatures, and the associated increase in the time until the transition from a plastic state to a non-plastic state during the cooling of the melt, ensures that the magnetic particles (3b) present in the composition according to the invention have the opportunity to align themselves precisely along the field lines of the applied magnetic field before the non-plastic state is reached in the cavity of the injection mold (see Fig. ID).In contrast, the transition from the plastic to the non-plastic state in the cavity of the injection mold occurs at higher temperatures when using a conventional feedstock composition. As a result, not all magnetic particles (3a, 3b) can align along the field lines of the applied magnetic field before the melt solidifies. This inhomogeneous alignment of the magnetic particles in the resulting green body leads to lower magnetic remanence and an inhomogeneous magnetic flux density of the permanent magnet produced therefrom. Figures 2A and 2B show the magnetic flux densities measured with a 3D magnetic field scanner of a permanent magnet produced with a conventional feedstock composition by metal powder injection molding (Fig. 2A) and of a permanent magnet produced with a feedstock composition according to the invention by metal powder injection molding (Fig. 2B).Figure 2A shows that the permanent magnet produced by metal powder injection molding with a conventional feedstock composition exhibits an inhomogeneous magnetic flux density, which is due to the inhomogeneous magnetic orientation of the magnetic particles. The z-component of the magnetic field above the permanent magnet fluctuates considerably. In contrast, the permanent magnet produced by metal powder injection molding with a feedstock composition according to the invention (Figure 2B) shows a homogeneous magnetic flux density. It is evident that the z-component of the magnetic field above the permanent magnet is significantly more uniform.

[0127] Example 1: Production of permanent magnets

[0128] To investigate the magnetic flux densities of permanent magnets made from different feedstock compositions, the two feedstock formulations shown in Table 1 were prepared. Green bodies were molded from a feedstock melt using metal powder injection molding, thermally debound, and sintered. Finally, the resulting raw magnets were magnetized.

[0129] Table 1: Compositions of a control feedstock composition and a feedstock composition according to the invention The two feedstock compositions from Table 1 were first placed in a laboratory kneader and kneaded at a melt temperature of 130 °C for 60 minutes. The resulting feedstock melts were then removed from the kneader with the kneading hooks no longer rotating and at a temperature of approximately 50 °C. The feedstock melts were then cooled to room temperature in an inert gas atmosphere (argon). The cooled masses were granulated in a slow-running mill and subsequently injection molded. The injection mold used was one in which a magnetic field could be applied to the cavity to achieve a preferred magnetic orientation of the molded green body. The green bodies produced from the feedstock compositions were then thermally debound and densified to a density of > 7.5 g / cm³. 3Sintered. The sintered raw magnets were then magnetized with a pulse magnetizer in a magnetic field of ~3 T until magnetic saturation.

[0130] Example 2: Determination of magnetic flux density

[0131] The magnetic flux densities of the two permanent magnets produced according to Example 1 were subsequently determined using a 3D magnetic field scanner. For this purpose, the magnets were analyzed for inhomogeneities using a magnetic field camera (MagCam) and magnetically characterized in a hysteresis graph.

[0132] The magnetic field distributions shown in Figures 2A and 2B show that the z-component of the B-field fluctuated strongly over the control permanent magnet, whereas the permanent magnet produced with the feedstock composition according to the invention shows a significantly more uniform z-component of the B-field over the permanent magnet.

Claims

REQUIREMENTS 1. Feedstock composition for the manufacture of permanent magnets, comprising: 1 to 30 vol% of at least one framework polymer with a melting temperature of at least 100 °C, 1 to 25 vol.% of at least one base polymer with a melting temperature of 60 to 100 °C, 0 to 10 vol.% of at least one surfactant, 0 to 25 vol% of at least one wax with a melting point of 30 to 80 °C, >0 to 25 vol% of at least one organic solvent with a melting point of -80°C to 30 °C and 40 to 80 vol% of at least one metal powder (vol% in each case based on the total volume of the feedstock composition).

2. Feedstock composition according to claim 1, characterized in that the feedstock composition has a melting temperature range of at least 50 K, preferably at least 100 K, preferably at least 150 K, particularly preferably at least 175 K.

3. Feedstock composition according to claim 1 or 2, characterized in that the metal powder contains particles of a R x T y B z -alloy comprises, in particular, particles of an R x T y B z - alloy, wherein: R = at least one rare-earth element, in particular at least one element selected from the group consisting of neodymium (Nd), samarium (Sm), praseodymium (Pr), dysprosium (Dy), terbium (Tb), gadolinium (Gd), yttrium (Y), cerium (Ce) and lanthanum (La); T = iron (Fe) or cobalt (Co); B = boron (B); x, y are each independently a number > 1; and z = 0 or 1.

4. Feedstock composition according to claim 3, characterized in that the R x T y B z -alloy is a neodymium-iron-boron (NdFeB) alloy, preferably an Nd2Fei4B alloy.

5. Feedstock composition according to one of the preceding claims, characterized in that the particles of the metal powder have an average particle size of 1 to 20 pm, preferably 1 to 15 pm, preferably 1 to 10 pm.

6. Feedstock composition according to one of the preceding claims, characterized in that the at least one framework polymer is a thermoplastic polymer, in particular a polymer selected from the group consisting of: high-density polyethylene (HDPE), low-density polyethylene (LDPE), polypropylene (PP), polystyrene (PS), acrylonitrile butadiene styrene copolymer (ABS) and mixtures thereof.

7. Feedstock composition according to one of the preceding claims, characterized in that the at least one base polymer is a thermoplastic low-melting, non-polar polymer, in particular a polymer selected from the group consisting of: polypropylene-polyethylene (PP-PE) copolymer, polyethylene wax and mixtures thereof.

8. Feedstock composition according to one of the preceding claims, characterized in that the at least one surfactant is a non-ionic, anionic, cationic or amphoteric surfactant, in particular a surfactant selected from the group consisting of: fatty acids or salts thereof, preferably stearic acid or magnesium stearate, polysorbates, preferably polysorbate 20, polysorbate 21, polysorbate 40, polysorbate 60, polysorbate 61, polysorbate 65, polysorbate 80, polysorbate 81, polysorbate 85 or polysorbate 120, and mixtures thereof.

9. Feedstock composition according to one of the preceding claims, characterized in that the at least one wax is a mineral, vegetable, animal, partially synthetic or synthetic wax, in particular a wax selected from the group consisting of: paraffin wax, carnauba wax, wool wax, beeswax and mixtures thereof.

10. Feedstock composition according to one of the preceding claims, characterized in that the at least one organic solvent is a nonpolar organic solvent, preferably a nonpolar organic solvent selected from the group consisting of: paraffin oils, white spirits, alkanes, and mixtures thereof.

11. Feedstock composition according to any one of the preceding claims, comprising: 5 to 30 vol% of the at least one framework polymer, 5 to 15 vol% of the at least one base polymer, 1 to 5 vol% of at least one surfactant, 5 to 15 vol.% of the at least one wax, 10 to 20 vol% of at least one organic solvent and 45 to 57 vol% of the at least one metal powder (vol% in each case based on the total volume of the feedstock composition).

12. A method for producing a permanent magnet, comprising the steps of: a) providing a feedstock composition according to any one of claims 1 to 11, b) heating the feedstock composition to a temperature above the melting temperature of the at least one base polymer and the at least one base polymer of the feedstock composition to obtain a feedstock melt, c) molding the feedstock melt obtained in step b), d) cooling the feedstock melt to a temperature below the melting temperature of the at least one base polymer and the at least one base polymer of the feedstock system to obtain a solid, molded green body, e) at least partially debinding the green body obtained in step d) to obtain a brown body, f) sintering the brown body to obtain a raw magnet, and g) magnetizing the raw magnet to obtain a permanent magnet.where step c) and / or step d) takes place in a magnetic field that is applied externally, at least temporarily.

13. Method according to claim 12, characterized in that the molding in step c) is carried out by means of metal powder injection molding, extrusion or additive manufacturing.

14. Permanent magnet, manufactured by the method according to claim 12 or 13.

15. Permanent magnet according to claim 14, characterized in that the magnet has an energy product of at least 250 kJ / m 3 , preferably at least 300 kJ / m² 3 , preferably at least 350 kJ / m² 3 , exhibits.

16. Use of a permanent magnet according to claim 14 or 15 in a device selected from the group consisting of an electric motor, a loudspeaker, a microphone, a generator, a hard disk drive, a holding magnet and a sensor.

17. Device selected from the group consisting of an electric motor, a loudspeaker, a microphone, a generator, a hard disk drive, a holding magnet and a sensor, characterized in that the device has a permanent magnet according to claim 14 or 15.

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