DE102021116139A1 - Abrasive and method of making the abrasive - Google Patents

Abstract

The invention relates to an abrasive (1) for grinding workpieces, which has: a carrier (2), e.g. B. a carrier disc or a carrier belt, abrasive grains (4) applied to the carrier (2), and a binder (6) applied to the carrier (2). In order to enable material-friendly and energy-efficient production, the binder (6) contains nanoparticles (8) included sid, which have a superparamagnetic, ferrimagnetic and / or ferromagnetic material that can be excited by one or more of the following measures: - an electric induction alternating field, - an alternating magnetic field microwave radiation, wherein the nanoparticles (8) by the excitation can be heated, and the binder (6) is cured thermally. A production method is also provided.

Description

The invention relates to an abrasive and a method for producing the abrasive.

Such abrasives are used in particular for processing metal workpieces and are available in different grits. The abrasive generally has a backing, e.g. B. a backing disk or a backing tape of a rigid or flexible material on which are coated a make coat and abrasive grains incorporated in the make coat. The abrasive grains can be made of α-aluminum oxide or other materials.

On the one hand, the abrasive grains can be broken abrasive grains; furthermore shaped abrasive grains are known which individually, e.g. B. by a sol-gel process, shaped, dried and fired, and their uniform shape with proper orientation allow for uniform abrasive engagement.

To produce the binder layer and the abrasive grains are applied, the abrasive grains z. B. gravitationally or electrostatically scattered, so that they are included in the binder layer. It can be used to align the abrasive grains, e.g. B. by means of an electrostatic DC field come. The binder layer is then cured. Here z. B. thermally initiated, radiation-curing, and chemical curing by appropriate binders or hardeners / initiators are known.

The magnetic curing of epoxy resins is known in "Magnetocuring of temperature failsafe epoxy adhesives, Chaudhary, Ramanujan, Steele, Applied Materials Today 21 (2020)". Thus z. B. soles of sneakers and other heat-sensitive materials can be attached by a binder layer, which has superparamagnetic nanoparticles with a defined Curie temperature. These superparamagnetic nanoparticles are specifically excited by an alternating magnetic field or alternating magnetic field and enable thermal curing of the binder layer.

The invention is based on the object of creating an abrasive and a method for producing an abrasive which enable the abrasive to be designed in a safe and material-friendly manner.

This object is achieved by an abrasive and the method for producing an abrasive according to the independent claims. The dependent claims describe preferred developments.

The abrasive according to the invention can be produced in particular by the production method according to the invention; the manufacturing method according to the invention serves in particular to form the grinding means according to the invention.

Thus, the abrasive is formed with at least one binder layer that includes a thermosetting binder and magnetic nanoparticles. Thus, the binder layer and the abrasive grains can first be applied in the usual way and with the known process parameters and tools. Curing does not take place subsequently, or not solely, through thermal exposure, but through targeted excitation of the magnetic nanoparticles, which thus heat up and/or heat up the surrounding binder due to their internal change in polarity, in particular heat up endogenously. The thermally curing binder can thus be specifically stimulated and cured without z. B. to affect the wearer. This means that carrier materials such as plastics, paper and textile fibers can also be used, which can usually be damaged by external thermal stress, e.g. in an oven, at the temperatures used. From an environmental point of view, this targeted curing is also advantageous compared to thermal curing, which is the industry standard.

Another advantage is the uniform temperature distribution during endogenous heating, as the heat emanates from the nanoparticles. In this way, temperature gradients within the layer can be kept low.

The magnetic nanoparticles have a primary particle size of 2-100 nm, in particular 10 nm to 70 nm, in particular 10 to 50 nm, preferably 10 to 30 nm. In particular, the range from 10 to 30 nm is special due to the complex relaxation behavior of the nanoparticles in the magnetic field well suited.

The primary particle size of a nanoparticle is to be understood here as meaning a sphere-equivalent diameter of an individually present nanoparticle. The sphere-equivalent diameter can also be referred to as the volume-equivalent diameter of a sphere.

The magnetic nanoparticles can in particular be ferromagnetic, ferrimagnetic or also superparamagnetic. Superparamagnetic nanoparticles are in particular made of a fer romagnetic or ferrimagnetic material that does not retain any permanent magnetization even at temperatures below the Curie temperature when a previously applied magnetic field has been switched off.

A particular advantage of the invention is that the Curie temperature of the magnetic nanoparticles, above which the magnetic nanoparticles lose their magnetic properties, is related to the process temperature for curing the binder, i. H. the curing temperature, can be adjusted. For example, the Curie temperature can be specifically above the curing temperature or process temperature, but below a critical upper temperature that can lead to damage. This guarantees a special process reliability (fail-safe), since overheating of the product is impossible. This is the case in particular because at a higher process temperature the magnetic nanoparticles can no longer be activated or excited and therefore no further heating can take place.

Instead of controlling using the Curie temperature, the energy quantity can also be regulated using the system parameters, i.e. in particular using the field strength and/or exposure time and/or frequency of the alternating magnetic field and/or the electric induction field.

Furthermore, the concentration of the nanoparticles can also be adjusted in a targeted manner. If several binder layers are formed with magnetic (particularly metallic) nanoparticles, the concentration and material, for example, can be adjusted differently. The concentration range of 3 to 30% by weight, preferably 10 to 25% by weight, has proven particularly advantageous for the invention.

The magnetic nanoparticles can be activated by an alternating magnetic field. However, electromagnetic microwave radiation, e.g. B. in the frequency range of 1 to 10 GHz, in particular 2 to 7 GHz, since the invention recognizes that such an electromagnetic field or electromagnetic radiation without additional alternating magnetic field, an activation of the magnetic nanoparticles achieved, which is sufficient to to stimulate heating, and in particular to heat the binder.

Alternatively or in addition, an induction field can be applied and used to change the polarity of the nanoparticles, e.g. with frequencies in the range 1 to 1500 kHz, e.g. 10 to 1000 kHz, in particular 20 to 800 kHz. According to the invention, this can also lead to heating of the binder.

The abrasive grains, in particular as shaped abrasive grains, can have a defined contact edge and a defined tip. Designs with triangular, in particular plane-parallel, triangular abrasive grains are particularly advantageous here, since these have a sufficient edge to rest on the backing and a suitable tip. Equilateral triangles are also particularly advantageous, since the same support is achieved on one of the three edges when scattering.

Furthermore, non-shaped abrasive grains can also be used.

• Mn_xZn_1-xFe₂O₄, Fe₃O₄, Fe₂O₃, z.B. mit x zwischen 0,2 und 0,6, z.B. 0.3 bis 0,5.

The magnetic material of the magnetic nanoparticles can contain in particular:

• Mn _x Zn _1-x Fe ₂ O ₄ , Fe ₃ O ₄ , Fe ₂ O ₃ , eg with x between 0.2 and 0.6, eg 0.3 to 0.5.

• 3 bis 30 Gew-%, vorzugsweise 10 bis 25 Gew-%

The concentration of the nanoparticles in the binder can be in the range:

• 3 to 30% by weight, preferably 10 to 25% by weight

Here, the concentration and the alternating magnetic field used can be adjusted to each other.

The magnetic nanoparticles can, for example, also be provided with a coating and/or functionalization, which is optionally included in the binder. The coating can consist in particular of oleic acid, silicon dioxide and/or a diglycidyl ether. This can improve properties such as dispersibility, stability against agglomeration and incorporation into the binder.

A suitable composition which has the suitable process temperature can be used as the thermally curing binder.

Advantageously, resins are mixed with a hardener as binders.

• - Bisphenol A Harze, z. B.:
  • o Hexion Epikote Resin 828
  • o Ipox ER 1022
• - Bisphenol F Harze, z. B.:
  • o Hexion Epikote Resin 862
  • o Ipox ER 1054

One or more of the following substances can be provided as the resin system:

• - Bisphenol A resins, e.g. e.g.:
  • o Hexion Epikote Resin 828
  • o IPox ER 1022
• - Bisphenol F resins, e.g. e.g.:
  • o Hexion Epikote Resin 862
  • o IPox ER 1054

• - Pulverförmige Amide und Polyamine, z. B.:
  • o Evonik Ancamine 2442 (modifiziertes Polyamin) mit 5-40 w% bezogen auf Harz
  • o Evonik DICYANEX 1400B (Dicyandiamid) mit 2-40 w% bezogen auf Harz
  • o Mischung der beiden vorgenannten Härter, wobei das Polyamin (2-19 w%) als Beschleuniger wirkt.
• - Polyamin flüssig, bei dem die Härtung wird durch Temperatur beschleunigt wird und ermöglicht eine höhere Glasübergangstemperatur ermöglicht, z.B.
  • o Hexion Epikure Curing Agent 3230 (z. B. 20-70 w% auf Harzbasis bezogen)

In particular, one or more of the following substances can be used as hardeners:

• - Powdered amides and polyamines, e.g. e.g.:
  • o Evonik Ancamine 2442 (modified polyamine) with 5-40% by weight based on resin
  • o Evonik DICYANEX 1400B (dicyandiamide) with 2-40% by weight based on resin
  • o Mixture of the two aforementioned hardeners, with the polyamine (2-19 w%) acting as an accelerator.
• - Polyamine liquid, in which the curing is accelerated by temperature and allows a higher glass transition temperature, e.g
  • o Hexion Epikure Curing Agent 3230 (e.g. 20-70 w% based on resin)

• - Polyurethane, besonders mit blockierten Isocyanaten (z. B. Adiprene BL16 Lanxess, Trixene BI7675 Lanxess)
• - Acrylate (z.B. Trimethylolpropantriacrylat: Laromer TMPTA) mit Azo- oder Peroxidinitiatoren (z. B. tert-Butylperoxy 2-ethylhexylcarbonat:
  • Peroxan BEC, Azobis(isobutyronitril): Vazo 64)
• - Phenolharze und Melaminharze (z. B. Bakelite PF7870SW)

One or more of the following systems can be provided as alternative resin systems

• - Polyurethanes, especially with blocked isocyanates (e.g. Adiprene BL16 Lanxess, Trixene BI7675 Lanxess)
• - Acrylates (e.g. trimethylolpropane triacrylate: Laromer TMPTA) with azo or peroxide initiators (e.g. tert-butylperoxy 2-ethylhexyl carbonate:
  • Peroxane BEC, Azobis(isobutyronitrile): Vazo 64)
• - phenolic resins and melamine resins (e.g. Bakelite PF7870SW)

• - Methode: Rakel (Walzenrakel, Luftrakel), Walzenbeschichtung (z.B. Kiss Coating), Spray (Airless, Druckluftspritzen)
• - Auftragsmenge: 20 bis 300 g/m2 je nach Körnung
• - Bei Streichmasse: 200 - 1600 g/m2 je nach Körnung
• - Deckbindung: 50- 1100 g/m2
• - Topsize: 50-600 g/m2

The binder application can advantageously be carried out by one of the following methods:

• - Method: doctor blade (roller blade, air blade), roll coating (e.g. kiss coating), spray (airless, compressed air spraying)
• - Application quantity: 20 to 300 g/m2 depending on the grain
• - For coating: 200 - 1600 g/m2 depending on the grain size
• - Cover weave: 50- 1100 g/m2
• - Top size: 50-600 g/m2

The grain scattering of the abrasive grains can advantageously be carried out according to one or more of the following methods, which can also be combined.

Variant 1 of grain scattering - electrostatic, in which the grain is electrostatically scattered in a constant or alternating electric field and aligns itself in flight and/or in the binder.

1. 1. Korn wird von oben auf den Träger gestreut.
2. 2. Korn richtet sich zufällig eher liegend aus.

Variant 2 of grain scattering - gravimetric or gravity, which is preferred for grain agglomerates or support grain scattering

1. 1. Grain is sprinkled onto the carrier from above.
2. 2. Grain happens to align more horizontally.

variant 3; the grain is applied together with the binder as a mass or mixture.

The grain scattering can thus take place using different methods and can in particular take place separately from the curing of the binder layer. The electrical or electrostatic scattering does not affect the magnetic nanoparticles either, so that according to the invention there is advantageously a high degree of freedom in the choice of materials and process parameters.

Furthermore, suitable fillers can be introduced into the binder, e.g. B. Chalk (20-70 wt%), cryolite (20-70 wt%), potassium tetrafluoroborate (20-80 wt%), wollastonite (1-10 wt%), fumed silica (0.1-5 wt%), Kaolin (0.5-10 w%)

Furthermore, suitable additives can be introduced into the binder, e.g. B. silanes (0.1-3 w%), film formers (0.05-2 w%), dispersing additives (0.1-5 w%), defoamers (0.1-2 w%), plasticizers (0, 5-10 w%), rheology additives (0.1-10 w%).

These supplementary fillers and additives as such do not show any particular magnetic properties and can therefore in principle be used in any way to supplement the magnetic nanoparticles without affecting the magnetic behavior.

• - Härtung im Wechselmagnetfeld eines Tunnelmagnetisierers
• - Z. B. Frequenz: 100-1000 kHz
• - Z. B. Feldstärke: 4000 bis 21000 A/m
• - Z. B. Temperaturkontrolle mittels IR Kamera
• - Vorzugsweise mit einem Array mehrerer Magnetspulen, um die Verweilzeit einzustellen.

The curing or hardening of the binder can take place through one or more of the following conditions:

• - Hardening in the alternating magnetic field of a tunnel magnetizer
• - E.g. frequency: 100-1000 kHz
• - Eg field strength: 4000 to 21000 A/m
• - For example, temperature control using an IR camera
• - Preferably with an array of multiple solenoids to set the dwell time.

• - Dicyandiamid (DICY): 5 Min. bis 2h bei z.B. 150° - 220°, z. B. 180°C Curie Temperatur
• - Ancamine 2442: 30min bei 100- 140, z. B. 120°C Curie Temperatur
• - Mischung: 30 min bei z.B. 120 - 160, z. B. 140 °C Curie Temperatur
• - Beschleunigung mit Imidazolen möglich (z. B. 2-Methylimidazol)

For the curing z. B. one or more of the following curing programs and process temperatures can be used:

• - Dicyandiamide (DICY): 5 minutes to 2 hours at e.g. 150° - 220°, e.g. B. 180°C Curie temperature
• - Ancamine 2442: 30min at 100-140, e.g. B. 120°C Curie temperature
• - Mixing: 30 min at e.g. 120 - 160, e.g. B. 140 °C Curie temperature
• - Acceleration possible with imidazoles (e.g. 2-methylimidazole)

The material of the abrasive grains is basically freely selectable. In particular, it can be α-alumina, e.g. B. with suitable additives, which are formed in particular in a sol-gel process. Furthermore, zirconium corundum and silicon carbide can also be used as material for the abrasive grains.

• - Physikalisches Verfahren (Physical Vapor Deposition - PVD)
  • ◯ Ferromagnetisches/ Paramagnetisches Material wird in die Gasphase überführt und auf dem Korn abgeschieden
• - Chemisches Verfahren (Chemical Vapor Deposition - CVD)
  • ◯ Ferromagnetisches/Paramagnetisches Material wird aus einem Precursor erzeugt und dabei auf dem Korn in einer chemischen Reaktion gebildet und abgeschieden.
• - Harzummantelung
  • ◯ Magnetische Partikel sind in einer Phenolharz- oder Melaminharz-/ Wasser Mischung zu dispergieren. Diese Dispersion wird in einem Mischer unter Temperatur auf den Körner verteilt.

In principle, all coatings of the abrasive grains are possible. According to the embodiments with additional magnetic coating, grain pretreatments can be provided, e.g. B.

• - Physical process (Physical Vapor Deposition - PVD)
  • ◯ Ferromagnetic/paramagnetic material is converted into the gas phase and deposited on the grain
• - Chemical process (Chemical Vapor Deposition - CVD)
  • ◯ Ferromagnetic/paramagnetic material is generated from a precursor and is formed and deposited on the grain in a chemical reaction.
• - Resin jacket
  • ◯ Magnetic particles are to be dispersed in a phenolic resin or melamine resin/water mixture. This dispersion is distributed over the grains in a mixer at elevated temperature.

According to a development, several binder layers can be provided, e.g. For example, the cover layer can also be formed without nanoparticles, i.e. with a concentration of zero.

According to the invention, a number of advantages are thus achieved:

A high level of energy efficiency is achieved. The energy introduced is converted into thermal energy directly in the binder and used there evenly for hardening. There is thus an in-situ hardening. The energy is thus introduced directly into the bond at the site of the chemical hardening reaction and not additionally in other areas such as e.g. B. the backing and the abrasive grains, or additional layers provided. This means that unnecessary thermal stress in other areas or process rooms/buildings/hangings can be avoided or reduced.

The Curie temperature of the magnetic nanoparticles limits the maximum process temperature, which means that overheating or overcuring is impossible.

The process is environmentally friendly because compared to thermal curing processes in z. B. an oven or autoclave, the magnetic hardening requires less energy. In this way, the devices for forming the magnetic fields can also be aligned in a targeted and effective manner.

According to one embodiment, the energy supply can be combined by excitation of the nanoparticles and also by another energy source, e.g. thermal heating from the outside with low power, with the thermal power preferably being dimensioned such that after the excitation of the nanoparticles has ended, e.g. above the Curie -Temperature, alone does not represent a relevant thermal load. Thus, for example, the effort for an alternating magnetic field can be kept low.

Aligned or positioned abrasive grains are quickly fixed by the process and can then no longer tip over on the carrier due to potential mechanical stresses on the system or from their contact edge.

In particular, in terms of process technology, hardening can be carried out at a specific point in time, i. H. on demand, to take place; the adjustment of the process parameters is possible in a short period of time, in particular within seconds.

The inventive method can be combined with conventional methods, z. B. also with thermal curing and/or radiation curing processes, i.e. thermal energy and/or radiation is additionally supplied for curing.

The magnetic particles are not influenced by grain scattering processes, e.g. electric fields, so that there is a high degree of freedom in the choice of process parameters.

• - Eine Trägerausrüstung: Foulardierung und Korn-, sowie Rückseitenstriche, Haftvermittelnde Striche
• - Eine Grundbindung: Gefüllt mit Kreide, Kryolith, KBF4, Wollastonit, Kaolin, Ruß, Schichtsilikate, pyrogene Kieselsäure, Farbpigmente oder ungefüllt
• - Kornummantelung mit z.B. Harzen
• - Erste Deckbindung (Sizecoat): Gefüllt mit Kreide, Kryolith, KBF4, Wollastonit, Kaolin, Ruß, Schichtsilikate, pyrogene Kieselsäure, Farbpigmente oder ungefüllt
• - Zweite Deckbindung (Supersizecoat oder Topsize) mit schleifaktiven Füllstoffen, wie z.B. KBF4 oder Kryolith
• - Gestrichene Schleifmittel und/oder strukturierte Schleifmittel: Phenolharz, Polyurethan, Epoxid und/oder Acrylatbasiert
• - Härtung von Schleifkornagglomeraten auf Harzbasis, z. B. Phenolharzen

Suitable applications include:

• - A carrier equipment: padding and grain, as well as backside coatings, adhesion-promoting coatings
• - A basic bond: Filled with chalk, cryolite, KBF4, wollastonite, kaolin, carbon black, layered silicates, fumed silica, colored pigments or unfilled
• - Grain coating with eg resins
• - First top coat (size coat): Filled with chalk, cryolite, KBF4, wollastonite, kaolin, carbon black, layered silicates, pyrogenic silica, color pigments or unfilled
• - Second top coat (Supersizecoat or Topsize) with abrasive fillers such as KBF4 or cryolite
• - Coated abrasives and/or structured abrasives: phenolic, polyurethane, epoxy and/or acrylate based
• - Hardening of resin-based abrasive grain agglomerates, e.g. B. phenolic resins

• 1 ein Schleifmittel gemäß einer Ausführungsform der Erfindung;
• 2 eine vergrößerte Darstellung des Schleifmittels;
• 3 ein Flussdiagramm des erfindungsgemäßen Verfahrens.

The invention is explained in more detail below with reference to the accompanying drawings of some embodiments. Show it:

• 1 an abrasive according to an embodiment of the invention;
• 2 an enlarged view of the abrasive;
• 3 a flowchart of the method according to the invention.

An abrasive 1 has a backing 2, e.g. B. a carrier tape or a carrier disk, z. B. made of a textile material, technical paper, in particular fiber, or plastic material, furthermore a binder layer 3 applied to the carrier 2, abrasive grains 4 and preferably an in 1 partially drawn top layer 5 on. The abrasive grains 4 are in particular ceramic abrasive grains, for example based on α-aluminum oxide. The abrasive grains 4 can in particular be shaped abrasive grains 4, e.g. B. as shown with a triangular, in particular triangular and plane-parallel shape. The abrasive grains 4 are thus aligned on the backing 2 and fixed in their position and orientation by the binder layer 3 .

The binder layer 3 comprises a thermosetting binder 6, in particular epoxy resin, e.g. a bisphenol A resin, e.g. B. Hexion Epikote Resin 828, Ipox ER 1022,
and/or a bisphenol F resin, e.g. E.g.: Hexion Epikote Resin 862 or Ipox 1054 (Bisphenol A/F resin).

Magnetic nanoparticles 8 are evenly distributed in the thermosetting binder 6, e.g. B. from Mn _x Zn _1-x Fe ₂ O ₄ , z. B. with x = 0.1 to 0.5, preferably 0.2 to 0.5. Other materials of the magnetic nanoparticles 8 can also be formed without manganese / zinc, z. B. based on iron oxide, z. B. as Fe ₃ O ₄ or alternatively as Fe ₂ O ₃ . The abrasive grains 4 are thus accommodated with their lower regions--in the direction of orientation, ie upwards in the figures--in the binding agent layer 3, lie with their respective underside 4a on the carrier 2 and protrude upwards with their tips 4b. Their orientation can be parallel as shown in the figures; however, they can generally be oriented with their tops and bottoms non-parallel to each other. Furthermore, the abrasive grains 4 can also be arranged inclined relative to the vertical, in particular inclined uniformly in a preferred direction in order to support a grinding action in this direction.

The production of the abrasive 1 takes place according to in 3 shown procedures:
Step ST1 of providing or producing the starting materials: The nanoparticles 8 can z. B. be prepared by a modified hydrothermal method, as such z. B. from Chaudhary, Ramanujan, Steele, Applied Materials today - Magnetocuring of temperature failsafe epoxy adhesives, 2020.

In particular, epoxy resins with DICY (dicyandiamide) can be used as the binder 6 .

According to step ST2, the nanoparticles 8 are introduced or mixed into the binder 6 in order to achieve uniform distribution.

In step ST3, the binder layer 3 is applied to the carrier 2. For this purpose, the binder layer 3 can be B. by means of a doctor blade, z. B. roller doctor blade or air doctor blade, or by roller coating, or by spray, z. B. compressed air spraying or airless can be applied. The order quantity can B. 20 to 300 g/m ² , depending on the grain size of the abrasive grains 4 to be introduced later, or in the case of a coating compound also 200 to 1,600 g/m ² , depending on the grain size.

In step ST4, the abrasive grains 4 are applied, i. H. the grain scatter. The abrasive grains 4 can be applied gravimetrically and/or electrostatically, i. H. than electrostatic scattering. In the case of electrostatic scattering and electrostatic alignment, a direct or alternating electric field E is applied.

According to step ST5, the abrasive grains 4 are aligned. Steps ST4 and ST5 can also be carried out in combination here, ie the abrasive grains 4 are scattered in an aligned manner.

When aligning the abrasive grains 4 in step ST5, the in 1 , 2 shown position of the abrasive grains 4 reached on an edge as a bottom 4a. In the case of the shaped abrasive grains 4 shown in particular, a firm support on the edges and also a uniform length are achieved, so that the tips 4b are arranged or run at approximately the same distance from the carrier 2, and thus a simultaneous abrasive intervention the processing of workpieces is achieved.

In step ST6, the binder 6 is hardened, whereby the solid binder layer 3 is formed. The hardening of the binder 6 to form the binder layer 3 takes place by applying an alternating magnetic field 10, which in principle can initially have any direction or orientation. The direction or orientation of the magnetic field can also change.

The nanoparticles 8 are heated directly by the alternating magnetic field 10 and heat is thereby generated, as a result of which the entire binder layer 3 is heated from the inside out. As a result, the binder 6 hardens so that the solid binder layer 3 forms.

The alternating magnetic field 10 can be formed in particular by means of a tunnel magnetizer. The frequency can e.g. 100 to 1000 kHz. The field strength can 4,000 to 21,000 A/m.

In the case of magnetic hardening, the process temperature T that is reached can preferably be defined by the Curie temperature T 8 of the magnetic nanoparticles 8 . As soon as the temperature T exceeds the Curie temperature T8, the magnetic nanoparticles 8 become non-magnetic or no longer ferromagnetic, ferrimagnetic or superparamagnetic, in particular the nanoparticles become paramagnetic and thus they do not heat the binder any further or at least not to the relevant extent.

Furthermore, when using the alternating magnetic field, the process can be controlled by means of energy quantity regulation, so that the Curie temperature may not be used, or not to a relevant extent.

According to one embodiment, the amount of energy can be regulated by measuring a surface temperature, e.g.

In order to achieve a sufficient dwell time, an array of several magnetic coils can be provided.

According to an alternative embodiment, the binder layer 3 is not cured by an alternating magnetic field, but by microwave radiation 11, e.g. B. in the frequency range of 1 to 5 GHz, z. B. at 2.4 GHz. In particular, an induced excitation and thus a change in polarity of the nanoparticles 8 can be achieved by the microwave radiation 11 , which thus represents electromagnetic radiation in this frequency range, which in turn leads to heating of the nanoparticles 8 themselves and of the binder 6 .

When using microwave radiation 11, a process-controlled power regulation can take place and/or the temperature of the binding agent 6 can be measured for the control function, e.g. by means of an infrared sensor.

A top layer can then be applied in a step ST7, so that the grinding means 1 is subsequently completed. This cover layer can be equipped with nanoparticles 8 as an alternative or, if appropriate, in addition. In this case, the endogenous hardening takes place in the same way as already described for the previous layers.

In the variant of grain scattering by means of gravity, the abrasive grains 4 are scattered from above onto the carrier 2 with the binder layer 3 . Thus, the abrasive grain 4 lays out rather randomly. Such configurations are relevant for grain agglomerates or support grain scattering, in which some of the abrasive grains 4 serve as support grains for the other abrasive grains 4 .

Here z. B. In addition, between the abrasive grains 4, smaller abrasive grain particles can also be introduced as so-called gravel, which supports the particularly shaped abrasive grains 4.

Alternatively or in addition to magnetically curing the binder layer that receives the abrasive grains, another binder layer, such as a top size coat, can also be magnetically cured. Thus, one or more layers, eg with different Curie temperatures, the process-related energy quantity regulation, and/or with ver different concentrations of the nanoparticles are cured.

Reference List

1

abrasives

2

carrier, e.g. B. carrier tape, carrier belt or carrier disc

3

binder layer

4

abrasive grains

5

top layer

6

binders, e.g. B. epoxy resin, the binder layer 3

8th

magnetic nanoparticles

10

alternating magnetic field

11

microwave radiation

T

temperature

T8

Curie temperature

ST1

Providing the starting materials

ST2

Introduction or mixing in of the nanoparticles 8 in the adhesive material 6

ST3

Application of the binder layer 3

ST4

grain spread

ST5

Orientation of the abrasive grains 4

ST6

Hardening of the binder layer 3

ST7

Applying the top layer 5

Claims (33)

Abrasive means (1) for grinding workpieces, the abrasive means (1) having: a backing (2), abrasive grains (4) applied to the backing (2), and at least one binder (6) applied to the backing (2), characterized in that nanoparticles (8) are accommodated in the binder (6), the nanoparticles (8) having a superparamagnetic, ferrimagnetic and/or ferromagnetic material which can be excited by one or more of the following measures: - an alternating electric induction field - An alternating magnetic field - microwave radiation, wherein the nanoparticles (8) can be heated by the excitation, and wherein the binder (6) is thermally cured. Abrasive (1) after claim 1 , characterized in that the binder (6) is at least partially endogenously thermally cured by heating the nanoparticles, for example by a polarity change of the nanoparticles (8). Abrasive (1) after claim 1 or 2 , characterized in that the nanoparticles (8) are formed exclusively from a material which can be excited in an alternating electric or magnetic field to change polarity, whereby heat energy can be induced in the binder. Abrasive (1) according to one of the preceding claims, characterized in that a concentration of the nanoparticles in the binder is in the range of 1 to 30% by weight, eg 5 to 25% by weight, preferably 10 to 20% by weight, based on the total weight of the binder layer (3). Abrasive (1) after claim 4 , characterized in that the binder (6) has a resin component and in particular further substances, eg fillers, the concentration of the nanoparticles (8) relative to the resin component being 3 to 30% by weight, preferably 10 to 25% by weight. Abrasive means (1) according to one of the preceding claims, characterized in that at least one binder layer (3) with the binder (6) is applied to the backing, and abrasive grains (4) are accommodated in the binder layer (3), in particular in a lower one , directly applied to the support binder layer (3). Abrasive (1) according to one of the preceding claims, characterized in that the binder (6) with the nanoparticles (8) is applied as a top layer (5) to one or more lower layers, eg a lower layer with abrasive grains (4). Abrasive means (1) according to one of the preceding claims, characterized in that several binder layers are provided, for example a lower binder layer (3) and a top layer (5), the several binder layers (3) having different concentrations of nanoparticles (8) and/or or different Curie temperatures of their nanoparticles (8). Abrasive means (1) according to one of the preceding claims, characterized in that the magnetic material of the magnetic nanoparticles (8) is one or more of the following materials: a metal oxide, in particular Mn _x Zn _1-x Fe ₂ O ₄ , with x= 0.2 to 0.6, for example 0.3 to 0.5, of an iron oxide, in particular Fe ₃ O ₄ and/or Fe ₂ O ₃ . Abrasive means (1) according to one of the preceding claims, characterized in that the magnetic nanoparticles have a primary particle size of 2 to 200 nm, in particular 10 nm to 150 nm, in particular 10 to 100 nm, preferably 10 to 30 nm. Abrasive means (1) according to one of the preceding claims, characterized in that the abrasive grains (4) are shaped abrasive grains. Abrasive (1) after claim 11 , characterized in that the abrasive grains (4) are designed to be plane-parallel and with a triangular upper side and lower side, and stand on an edge (4a) on the carrier (2), with their tips (4b) protruding upwards and/or inclined upwards . Abrasive means (1) according to one of the preceding claims, characterized in that the abrasive grains (4) are in the form of flakes and/or are plane-parallel. Abrasive means (1) according to one of the preceding claims, characterized in that the abrasive grains (4) are aligned in parallel such that their tips (4b) are arranged approximately at the same height above the backing (2). Abrasive means (1) according to one of the preceding claims, characterized in that the abrasive grains (4) are formed from one or more of the following materials: zirconium corundum, alpha aluminum oxide, silicon carbide, diamond, broken cubic boron nitride (CBN).. Abrasive means (1) according to any one of the preceding claims, characterized in that the carrier (2) is formed from a disc or a belt, e.g. B. from a textile fabric, paper, plastic. Abrasive means (1) according to one of the preceding claims, characterized in that the Curie temperature (T8) of the nanoparticles (8) is above a curing temperature (T6) of the binder (6), in particular within a range of 20° C, preferably 10 ° C, above the curing temperature (T6) of the binder (6), to avoid overheating of the binder (6). Abrasive (1) according to one of the preceding claims, characterized in that the binder (6) is formed by mixing one or more resins and one or more hardeners, the resin being selected, for example, from the following group: epoxy resins, acrylates, phenolic resins , polyurethanes. Method for producing an abrasive (1), in which at least one binder layer (3) and abrasive grains (4) are applied to a carrier (2) and a binder (6) of the binder layer (3) is cured, characterized in that in the Binding agent (6) nanoparticles (8) are added and the nanoparticles (8) are excited and/or alternately polarized during the curing of the binding agent (6) and thereby heat up, the binding agent (6) being at least partially caused by the heating of the nanoparticles ( 8) is cured. procedure after claim 19 , with at least the following steps: = providing the carrier (2), the abrasive grains (4), the binder (6) and the nanoparticles (8) (ST1 - preparation step), = applying the abrasive grains and the binder to the carrier (2) = Hardening of the binder (6) at least partially by activation and/or excitation of the nanoparticles (8) with the generation of heat, the binder (6) being at least partially hardened by the heat generated by the nanoparticles. (ST6 - binder hardening). procedure after claim 20 , characterized in that first the binder with the nanoparticles (8) is applied to the carrier (ST3 - binder application) and then the abrasive grains are applied to the binder by scattering. (ST4 - grain scattering) procedure after claim 20 , characterized in that the binder is applied with added abrasive grains, for example by a brushing process or a brush application (St3). Procedure according to one of claims 19 until 22 , characterized in that the nanoparticles (8) are introduced into the binder (6) in advance, for example mixed in. Procedure according to one of claims 19 until 23 , characterized in that the binder (6) is applied as a binder layer, eg as a lower binder layer (3) for receiving the abrasive grains, and/or as a top cover layer (5). Procedure according to one of claims 19 until 24 , characterized in that the binder (6) is at least partially cured by a Alternating magnetic field (10) for activating the nanoparticles (8), in particular with the properties: frequency 100 to 1,000 kHz, field strength 4,000 to 21,000 A/m, Procedure according to one of claims 19 until 25 , characterized in that the binder (6) is at least partially cured by microwave radiation, z. B. in the range of 1 to 10 GHz. Procedure according to one of claims 19 until 26 , characterized in that the binder (6) is at least partially cured by an electric induction field, for. B. in the range of 500 to 1500 kHz. Procedure according to one of claims 19 until 27 , characterized in that the step of aligning the abrasive grains (4) (ST4) is carried out by one or more of the following alignment methods: - electrostatic alignment in an applied electrostatic DC field (E) and / or alternating field, - gravitationally by sprinkling. Procedure according to one of claims 19 until 28 , characterized in that when the binder (6) hardens, additional thermal energy is supplied, for example in an oven. Procedure according to one of claims 19 until 29 characterized in that the magnetic nanoparticles (8) lose their magnetic properties when their Curie temperature (T8) is reached and this limits the process temperature (T) upwards, with the Curie temperature (T8) above the curing temperature (T6 ) of the binder (6). procedure after Claim 30 , characterized in that the Curie temperature (T8) is below a critical upper temperature at which the abrasive (1) can be damaged. Procedure according to one of claims 19 until 31 , characterized in that an amount of energy is regulated for curing the binder (6), the regulated amount of energy at least comprising the energy supplied by excitation of the nanoparticles (8). procedure after Claim 32 , characterized in that to regulate the amount of energy, a surface temperature, for example of the binder layer (3), is measured and the amount of energy introduced is deduced from a process time and the measured surface temperature.

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