AS MAGNETIC AND/OR ELECTROCONDUCTIVE DEVICE

The present invention relates to the use of a non-sintered object as magnetic and/or electroconductive device, which is obtainable by a process for producing a non-sintered object by means of 3D printing comprising providing a filament comprising at least 90 wt.-% of at least a magnetic material, at least one thermoplastic polymer, at least one plasticizer and optionally at least one additive, 3D printing of the filament to a 3D printed object; removing at least partially the at least one plasticizer from the 3D printed object to obtain a non-sintered object; using said non-sintered object as magnetic and/or electroconductive object.

BACKGROUND OF THE INVENTION

In modem technology, magnetic materials are used in a variety of applications. On the one hand, there are permanent magnets, which are made of hard magnetic materials and can be permanently magnetized, and on the other hand bodies for electrical coils, which are made of soft magnetic materials and change their magnetic properties in the electrical field. These components are usually formed by pressing or injection molding with subsequent sintering. Huber, Grbnefeld, Suss in “Permanent Magnets from the 3D Printer” have published a method to produce permanent magnets by 3D printing. The hard magnetic material, an isotropic neodymium-iron-boron powder in a thermoplastic binder (polyamide) is processed with a standard 3D printer. The content of magnetic material is indicated with less than 90 wt.-% and the printing temperature with less than 260 °C. The use of this thermoplastic material of course means that the usage temperature must be lower than the printing temperature, otherwise the component would melt. It therefore remains thermoplastic.

The yet unpublished patent application PCT/EP2019/058256 addresses sinterable feedstock for use in 3D printing devices which comprise ceramic powder. The yet unpublished patent application PCT/EP2019/058265 addresses sinterable feedstock for use in 3D printing devices which comprise metallic powder. The printed devices are sintered at temperatures above 900 °C to obtain a shaped body. The present invention addresses drawbacks of existing devices and processed. For example, a combination of a polyamide and a plasticizer as a binding system results in more than 100 °C lower printing temperatures, a normal 3D printer can be used and the articles have less mechanical tension. After finishing the printing, the plasticizer is removed by solvent extraction. This results in the higher loading of magnetic material in the final article and the final article lost the thermoplastic properties, means it is dimensions stable also far over 150 °C.

SUMMARY OF THE INVENTION

The present invention is directed to the use of a non-sintered object as magnetic and/or electroconductive device, which is obtainable by a process by means of 3D printing, comprising

(a) providing a filament comprising

- at least 80 wt.-% of at least a magnetic material,

- at least a thermoplastic polymer,

- at least a plasticizer,

- and optional at least an additive;

(b) 3D printing of the filament to a 3D printed object;

(c) removing the at least partially the at least one plasticizer from the 3D printed object to obtain a non-sintered object;

(d) using said non-sintered object as magnetic and/or electroconductive object.

A further aspect of the present invention are non-sintered objects obtainable by the process disclosed herein, where the content of the least a magnetic material is at least 90 wt.-% based on the weight of the object.

The present invention eliminates the disadvantages of known processes. It results in material and objects having a high proportion of magnetic material in the finished product (preferably at least 90 %) to achieve the lowest possible printing temperature and to achieve the highest possible useful temperature in the finished product. This is achieved by using a binder system consisting of polyamide and a plasticizer. This system enables thermoplastic processing at low temperatures and after printing the plasticizer is dissolved out by extraction with a solvent. This significantly increases the heat resistance of the article and it no longer behaves thermoplastic.

The process according to the invention allows magnets to be manufactured for industrial applications. It is particularly suitable for the production of prototypes or small series, since complex pressing tools or injection molds are not required. Of particular interest is the production of core materials for coils in electrical engineering and electronics. The mostly soft magnetic material is brought into the mold for various coil bodies and then extracted. This core material changes the properties of the coil. For example, by using iron or other ferrites with the same number of turns, a higher inductance can be achieved. But also frequency range, quality or coil losses play a role. Polyamide is typically used as the material for coil bodies.

The process for manufacturing magnetic moldings or cores for electric coils via thermoplastic filaments, which is in accordance with the invention, even allows the use of conventional 3D printers, since it can be operated in a low temperature range of 60 to 250 °C. In this process, the hard or soft magnetic material is embedded in a thermoplastic binder, which can then be processed thermoplastically in the specified temperature range. It also allows the creation of particularly thin-walled and filigree structures. In addition to the magnetic material, the formulation contains a polyamide or copolyamide and one or more suitable plasticizers. Other processing aids such as release agents, lubricants and pigments may also be included.

An advantage of the present invention is for example that a combination of a polyamide and a plasticizer as a binding system results in more than 100 °C lower printing temperatures, a normal 3D printer can be used and the articles have less mechanical tension. After finishing the printing, the plasticizer is removed by solvent extraction. This results in the higher loading of magnetic material in the final article and the final article lost the thermoplastic properties, means it is dimensions stable also far over 150 °C.

The present invention enables an easy production of permanent magnets, several cores for the electronic industry, electro mobility and prototyping. The usage of common 3D printer for plastic filaments without heat controlled printing chamber is possible. This enables also do it yourself people to use this technology. DETAILED DESCRIPTION OF THE INVENTION

Before the present invention is described in detail below, it is to be understood that this invention is not limited to the particular methodology, protocols and reagents described herein as these may vary. It is also to be understood that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of the present invention which will be limited only by the appended claims. Unless defined otherwise, all technical and scientific terms used herein have the same meanings as commonly understood by one of ordinary skill in the art.

In the following passages different aspects of the invention are defined in more detail. Each aspect so defined may be combined with any other aspect or aspects unless clearly indicated to the contrary. In particular, any feature indicated as being preferred or advantageous may be combined with any other feature or features indicated as being preferred or advantageous.

In the following definitions of some chemical terms are provided. These terms will in each instance of its use in the remainder of the specification have the respectively defined meaning and preferred meanings.

The term “alkyl” refers to a saturated straight or branched carbon chain. Preferably, an alkyl as used herein is a C1-C36 alkyl and more preferably is a C8-C36 alkyl, i.e. having 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35 or 36 carbon atoms, e.g. is selected from methyl, ethyl, propyl, isopropyl, butyl, zso-butyl, tert-butyl, pentyl or hexyl, heptyl, octyl, 2-ethylhexyl, nonyl, decyl, behenyl, isostearyl and stearyl. Alkyl groups are optionally substituted.

The term “alcohol” refers to a compound having one or more hydroxyl groups. For example a C8-C36 alkyl alcohol is a C8-C36 alkyl substituted with one or more hydroxyl groups. A fatty alcohol as used herein refers to a linear aliphatic primary alcohol.

The present invention provides novel filaments suitable to be used in a 3D printing device such as a fused deposition modelling device. It was unexpectedly found that the filaments exhibit an ideal combination of viscosity and hardness properties as well as sufficient adhesion when printed. The present invention is directed to the use of a non-sintered object as magnetic and/or electroconductive device, which is obtainable by a process by means of 3D printing, comprising

(a) providing a filament comprising

- at least 80 wt.-% of at least a magnetic material,

- at least a thermoplastic polymer,

- at least a plasticizer,

- and optional at least an additive;

(b) 3D printing of the filament to a 3D printed object;

(c) removing the at least partially the at least one plasticizer from the 3D printed object to obtain a non-sintered object;

(d) using said non-sintered object as magnetic and/or electroconductive object.

The 3D printing of the process may be any known and suitable 3D printing process. Preferably, the 3D printing of the process comprises fused deposition modeling (FDM) or fused filament fabrication (FFF).

Preferably, the filament used in the process comprises at least one hard or soft magnetic material that comprises at least one of iron (Fe), nickel (Ni), cobalt (Co). Preferably, the amount of iron (Fe), nickel (Ni), cobalt (Co) is at least 10 wt.-%, based on the total filament.

The filament comprising a magnetic material usually results in a magnetic object. Preferably, the non-sintered object is magnetic and thus, the amount of magnetic material in the filament is chosen in an appropriate amount.

Preferably, the filament used in the process comprises at least one hard or soft magnetic material that is an alloy comprising iron (Fe), nickel (Ni), and/or cobalt (Co) and at least one element selected from the elements Al, B, Ba, C, Co, Cr, Cu, Mn, Nd, Ni, O, Pt, Si, Sm, Sr, Zn.

Preferred hard magnetic materials are preferably selected from samarium cobalt magnets (SmCos, SrmCon, Sm(Co,Cu,Fe,Zr)), neodymium iron boron (NdFeB), aluminum nickel cobalt alloys, strontium ferrites (SrFenOig), barium ferrites (BaFenOig), cobalt ferrites (CoFe2O4), platinum cobalt alloys, copper nickel iron alloys, copper nickel cobalt alloys, iron cobalt chromium alloys, manganese aluminum carbon alloys, magnetite (FesCft), hematite (Fe20s).

Preferred soft magnetic materials are preferably selected from iron, steels, carbon steels, alloy steels such as silicon steels and electrical steels, nickel iron alloys, cobalt iron alloys, iron aluminum alloys, iron aluminum silicon alloys, manganese zinc ferrites (Mn _a Zn(i-a)Fe2O4), nickel zinc ferrites (Ni _a Zn(i. _a )Fe2O4).

The present invention allows common thermoplastic polymers to be used. Preferably, the thermoplastic polymer is selected from polyurethane, polyamide, polyvinylpyrrolidon, polyethylene glycol, polyvinyl butyral, polystyrene, polyacrylate, polymethacrylate, polyolefin and mixtures thereof and copolymers thereof. More preferably, the thermoplastic polymer is selected from copolyamide, polyamide 11, polyamide 12, polyamide 6,6, polyamide 6,12, a polyether block amide and a mixture thereof.

The present invention allows common of plasticizer to be used. The plasticizer must be preferably well tolerated in the polymer. For the extraction step, the plasticizer should be (readily) soluble and the polymer poorly soluble or insoluble in the extraction solvent.

Preferably, the plasticizer is selected from substituted or non-substituted aromatic or heteroaromatic carboxylic acid esters or a mixture thereof, more preferably, hydroxybenzoic acid esters. In a specific preferred embodiment, the at least one plasticizer is a hydroxybenzoic acid ester or a mixture of hydroxybenzoic acid esters, especially if a polyamide is used as thermoplastic polymer.

In a preferred embodiment the hydroxybenzoic acid esters are esters of hydroxybenzoic acid and a branched or linear alcohol, wherein the alcohol is selected from the group consisting of a branched or linear C8-C22 alcohol and mixtures thereof and preferably selected from 2-propyl heptyl alcohol, isodecyl alcohol, 1 -docosanol, 1 -octadecanol, 1 -dodecanol, 2-ethylhexyl alcohol, fatty alcohol, and a mixture thereof. Preferably, the fatty alcohol is an isostearyl, stearyl and/or behenyl alcohol.

In a preferred embodiment the hydroxybenzoic acid ester is a p-hydroxybenzoic acid ester. In a more preferred embodiment of the filament, said at least one plasticizer is an ester mixture produced from p-hydroxybenzoic acid and a mixture of alcohols, wherein the alcohol mixture preferably comprises 2-propyl heptyl alcohol, isodecyl alcohol, 1 -docosanol, 1 -octadecanol, 1-dodecanol, isostearyl alcohol and/or 2-ethylhexyl alcohol.

In a preferred embodiment of the filament of the invention said at least one plasticizer is an ester which is solid at 20 °C and/or an ester that is liquid at 20 °C or comprises only esters that are solid at 20 °C. It was unexpectedly found that including such a mixture in the plasticizer allowed the filament of the invention in particular for filaments based on magnetic materials to stay elastic for a longer time, while at the same time providing sufficient bonding capability upon printing.

In a preferred embodiment, the filament comprises 80 to 98 wt.-%, preferably 85 to 98 wt.-%, more preferably 90 to 98 wt.-%, of magnetic material(s), where the wt.-% refer to the total weight of the filament.

In another preferred embodiment, the filament comprises 1 to 15 wt.-%, preferably 1 to 10 wt.-%, more preferably 1 to 5 wt.-%, of thermoplastic polymer(s), where the wt.-% refer to the total weight of the filament.

In another preferred embodiment, the filament comprises 1 to 15 wt.-%, preferably 1 to 10 wt.-%, preferably 1 to 5 wt.-%, of plasticizer(s), where the wt.-% refer to the total weight of the filament.

In another preferred embodiment, the filament optionally comprises up to 10 wt-%, preferable up to 5 wt.-% of additive(s), where the wt.-% refer to the total weight of the filament.

Preferably, the filament comprises

- 80 to 98 wt.-%, preferably 85 to 98 wt.-%, more preferably 90 to 98 wt.-%, of magnetic material(s),

- 1 to 15 wt.-%, preferably 1 to 10 wt.-%, more preferably 1 to 5 wt.-%, of thermoplastic polymer(s),

- 1 to 15 wt.-%, preferably 1 to 10 wt.-%, preferably 1 to 5 wt.-%, of plasticizer(s), where the wt.-% refer to the total weight of the filament. In another preferred embodiment, the filament comprises

- 80 to 98 wt.-%, preferably 85 to 98 wt.-%, more preferably 90 to 98 wt.-%, of magnetic material(s),

- 1 to 15 wt.-%, preferably 1 to 10 wt.-%, more preferably 1 to 5 wt.-%, of thermoplastic polymer(s),

- 1 to 15 wt.-%, preferably 1 to 10 wt.-%, preferably 1 to 5 wt.-%, of plasticizer(s),

- 0 to 10 wt-%, preferable up to 5 wt.-% of additive(s), where the wt.-% refer to the total weight of the filament.

Preferably, if present, the at least one additive is selected from the group consisting of montan waxes, amide waxes, paraffin waxes, fatty acids, esters of fatty acids and any mixture thereof.

In another preferred embodiment, the filament does not comprise an additive.

The filament usually has a diameter of 1 mm to 5 mm, preferably 1.1 to 3 mm, preferably 1.75 or 2.85 mm.

The 3D printing is can be done by any known 3D printing processes that is compatible with the filaments disclosed herein. Preferably, the process comprises fused deposition modeling (FDM) or fused filament fabrication (FFF).

In a preferred embodiment, the 3D printing is done under at least one of the following conditions:

- The temperature of the extruder is preferably 130 to 200 °C.

- The temperature of the printing nozzle is preferably 130 to 200 °C.

- The temperature of the printing bed is preferably 20 to 100 °C.

- The diameter of the printing nozzle is preferably 0.4 to 2.0 mm.

From the 3D printed object, the at least one plasticizer is at least partially removed. Preferably, after the removing step, the plasticizer content is lower than 5 wt.-%, preferably lower than 2 wt.-%, based on the weight of the object. More preferably, the at least one plasticizer is essentially removed, so that the plasticizer content is lower than 1 wt.-%, more preferably lower than 0.1 wt.-%, based on the weight of the object. The at least one plasticizer is preferably removed by contacting the printed body with at least one organic solvent, preferably at a temperature of 20 °C or higher. More preferably, the extraction is done at a temperature in the range of 20 to 150 °C, more preferably in the range of 20 to 100 °C, more preferably in the range of 20 to 60 °C. Preferably, the solvent is acetone, ethylacetate, hydrocarbons, and/or methylethylketone. Preferably, this step is carried out two or more times, preferably by using different solvents. Preferably, a solvent is used, wherein the at least one plasticizer is (readily) soluble and the thermoplastic polymer is poorly soluble or insoluble.

After removing the solvent, the objects will not be sintered and/or treated at temperatures above 900 °C. More preferably, the objects will not be sintered and/or treated at temperatures above 500 °C, more preferably above 250 °C. The objects obtained from the process described herein are used as non-sintered objects.

Particularly preferred, the non-sintered objects obtained are magnetic and optionally electroconductive. In a specific preferred embodiment, the objects are both magnetic and electroconducti ve .

The non-sintered objects obtained are in particular suitable to be used as magnetic and/or electroconductive devices.

Another embodiment of the present invention are non-sintered objects which are obtainable by the process disclosed herein, where the content of the magnetic material(s) is at least 90 wt.-%, preferably at least 95 wt.-%., more preferably at least 98 wt.-%, based on the weight of the object.

More preferably, the content of plasticizer(s) of these non-sintered objects is lower than 5 wt.-%, preferably lower than 2 wt.-%, more preferably lower than 1 wt.-%, based on the weight of the object.

Various modifications and variations of the invention will be apparent to those skilled in the art without departing from the scope of the invention. Although the invention has been described in connection with specific preferred embodiments, it should be understood that the invention as claimed should not be unduly limited to such specific embodiments. The following examples are merely illustrative of the present invention and should not be construed to limit the scope of the invention as indicated by the appended claims in any way.

EXPERIMENTAL SECTION

1. Filament with carbonyl iron

Material wt.-%

Carbony iron 92,5

Polyamide (Griltex of Ems-Chemie) 2,22

Plasticizer (Loxiol 2472 of Emery Oleochemicals GmbH) 4,35

Release agent 0,93

An exemplary release agent consists of 20 % Loxiol EBS (from Emery), 30 % paraffin wax (from Sasol) and 50 % Loxiol G 20 (from Emery).

The individual components were combined and processed into a homogeneous mixture in a Coperion laboratory kneader (approx. 200 g per batch) for 1 h at 130 °C. This homogeneous mixture was then ground at room temperature to a 1-3 mm granulate and then extruded in a single-screw extruder at 120 °C to a filament with a diameter of 1.75 mm (suitable for conventional 3D printers). The filament was wound onto suitable bobbins and could then be used in the 3D printing process.

2. Printing

The filaments of example 1 were printed on a FELIX 3D printer (model FELIX pro 2) is processed. As printed cylinders had a diameter of 6.4 mm and a height of 30 mm.

The following settings were used

Extruder / muzzle temperature: 170 °C

Pressure bed temperature: 60 °C

Nozzle diameter: 0.6 mm

Printing speed: 10 mm/s

Layer thickness: 0.15 mm The green bodies obtained by 3D printing as described had the following properties: diameter: 6.4 mm; height: 30 mm; weight: 5.46 g.

3. Removal of the plasticizer / debindering

The specimen was placed in 150 ml acetone for 20 h at 36 °C and then dried at room temperature for 24 h. The obtained body hat a weight pf 5.21 g, corresponding to a weight loss of approx. 4.5 %.

4. Heat resistance

The sample was then slowly heated up in a drying oven where it has been heated up to 200 °C with a heating rate of 1.5 °C/min.

The test specimen with plasticizer (green body) is softened at approx. 130 °C and fallen over. The extracted sample without plasticizer is stable up to 200 °C remained. The extracted sample without plasticizer was then placed in a Nabertherm furnace (type B 180) heated to 300°C. Also at this temperature it retained its shape.

5. Preparation of the U-cores

According to the specified process, U-cores for coils made of binder and carbonyl iron have been prepared. Characteristics: height 43.6 mm and width 33.8 mm of the U, crosssection: 5x6 mm

6. Filament with MnZn powder

Material wt.-%

MnZnP powder 86.8

Polyamide (Griltex from Ems-Chemie) 3.6

Plasticizer (Loxiol 2472 from Emery Oleochemicals GmbH) 9.0

Release agent 0.6

From the filament a test specimen with a length of 30 mm and a diameter of 8,3 mm manufactured, mass 5.88g. 7. Determination of the AL values of the core material

The printed coil cores were measured in comparison to the printed and debound materials. The determination of the AL- values was done in a wire coil with 1000 turns, whereby the inductance of the empty coil and the inductance of the coil with core was measured. Coil length 30 mm, average diameter 25 mm. The inductance was measured with a universal multimeter UT70 A from UNI-T determined.

The AL value is then calculated: AL = L/n ² [nH/n ² ]

Sample Material Weight extruded coil AL value

1 carbonyl iron 5.46 g no 25.1 mH 25.1 nH/n ²

2 carbonyl iron 5.21 g yes 26.5 mH 26.5 nH/n ²

3 MnZnP 5.88 g no 24.4 mH 24.4 nH/n ²

4 MzZnP 5.36 g yes 27.0 mH 2.0 nH/n ²

Air 12.1 mH

The measurements show that the coils (1000 turns) with the printed cores provide a higher inductance than the air-core coil without core and the extraction can again increase the measured inductance and the AL value of the core material.

The same was also found with the U-shaped coil cores:

Sample Material extruded coil AL value

U1 carbonyl iron yes 25.6 mH 25.6 nH/n ²

U2 carbonyl iron no 24.6 mH 24.6 nH/n ²

U3 carbonyl iron no 24.7 mH 24.7 nH/n ²

U4 carbonyl iron yes 25.5 mH 25.5 nH/n ²

Air 12.2 mH

U1+U4 carbonyl iron yes 26.7 mH 26.7 nH/n ²

U2+U3 carbonyl iron no 25.3 mH 25.3 nH/n ²