Method for processing at least one three-dimensional green body - Patents.com

Abstract

The present invention relates to a method for treating at least one three-dimensional green body (GB), in which the at least one three-dimensional green body (GB) comprises an inorganic powder (IP) and a binder (B), the binder (B) comprising at least one polyoxymethylene (POM) as component (b1). In this method, 0.01 to 5.0% by weight of anhydrous oxalic acid, based on the total weight of the at least one three-dimensional green body (GB), is provided, with which the at least one three-dimensional green body (GB) is treated in the presence of an inert gas at a temperature (T1) below 140°C. The present invention further relates to a three-dimensional Brown body (BB) prepared by this method, and a three-dimensional sintered body (SB) prepared from the three-dimensional Brown body (BB). Furthermore, the present invention relates to an apparatus in which this method is carried out.

Description

[Technical field]

[0001] The present invention relates to a method for treating at least one three-dimensional green body (GB), in which the at least one three-dimensional green body (GB) comprises an inorganic powder (IP) and a binder (B), the binder (B) comprising at least one polyoxymethylene (POM) as component (b1). In this method, 0.01 to 5.0% by weight of anhydrous oxalic acid, based on the total weight of the at least one three-dimensional green body (GB), is provided, with which the at least one three-dimensional green body (GB) is treated in the presence of an inert gas at a temperature (T1) below 140°C. The present invention further relates to a three-dimensional Brown body (BB) prepared by this method, and a three-dimensional sintered body (SB) prepared from the three-dimensional Brown body (BB). Furthermore, the present invention relates to an apparatus in which this method is carried out. [Background technology]

[0002] A problem that is often encountered these days is the production of prototypes, spare parts or models of metal or ceramic bodies, especially those that show complex geometries. The production of prototypes in particular requires rapid manufacturing processes. For this so-called "rapid prototyping" different processes are known. One of the most economical is the Fused Filament Fabrication process (FFF), also known as "Fused Deposition Modeling" (FDM).

[0003] Fused Filament Fabrication (FFF) is an additive manufacturing technology. Three-dimensional objects are produced by extruding a thermoplastic material through a nozzle and hardening the thermoplastic material after extrusion to form layers. The nozzle is heated to heat the thermoplastic material above its melting and / or glass transition temperature, and then the extrusion head deposits the thermoplastic material on a base to form the three-dimensional object in layers. The thermoplastic material is typically selected and its temperature controlled to solidify substantially immediately upon extrusion or ejection onto a base on which multiple layers are built to form the desired three-dimensional object.

[0004] To form each layer, a drive motor is provided to move the base and / or the extrusion nozzle (discharge head) relatively in a predetermined pattern along the X, Y and Z axes. The FFF process was first described in US 5,121,329.

[0005] Typical materials for producing three-dimensional objects are thermoplastic materials. The production of three-dimensional metal or ceramic objects by fused filament manufacturing is only possible if the metal or ceramic material has a low melting point so that it can be heated and melted by the nozzle. If the metal or ceramic material has a high melting point, it is necessary to feed the metal or ceramic material to the extrusion nozzle in a binder composition. The binder composition usually comprises a thermoplastic material. When a mixture of metal or ceramic material in a binder is deposited on a base, the three-dimensional object formed is a so-called "green body" that contains the metal or ceramic material in the binder. To obtain the desired metallic or ceramic object, the binder must be removed and the object must finally be sintered. The three-dimensional object formed after the removal of the binder is the so-called "brown body" and the three-dimensional object formed after sintering is the so-called "sintered body". The removal of the binder is also called "debinding".

[0006] In the case of injection molded three-dimensional green bodies, the debinding process can be carried out catalytically, chemically, by solvent extraction or thermally. Industrially, catalytic debinding is preferred, preferably carried out with gaseous nitric acid, as this process is known to be the fastest debinding process. The acid acts as a catalyst, allowing a fast and complete gas-phase depolymerization of the thermoplastic binder.

[0007] However, working with concentrated nitric acid requires great safety efforts and should only be carried out by trained professionals. Mishandling can lead to serious personal injury and damage to the human body and the environment.

[0008] Moreover, nitric acid reacts with many inorganic materials, thus adversely altering the chemical composition of the resulting brown or sintered body, respectively. Moreover, nitric acid decomposes during the debinding process, reducing the effective concentration of the catalyst and therefore must be extracted from the system, thus necessitating a constant injection of acid, leading to an increased material consumption during the process. Moreover, the acid is highly corrosive, so the use of technologically sophisticated components and their continuous monitoring are essential.

[0009] To avoid concentrated nitric acid, the state of the art suggests oxalic acid, either as a solution or sublimated powder, for debinding green bodies containing polyoxymethylene (POM) raw materials.

[0010] WO 2015 / 185468 A1 describes a method for producing a sintered body, which comprises the following steps: shaping a mixture comprising a sinterable metal powder and a polyoxymethylene or a copolymer containing a majority of oxymethylene units as a binder to obtain a green body, removing the binder from the green body by treatment with a gaseous or liquid acid to obtain a brown part, and sintering the brown part, where the acid is selected from the group consisting of water, C 1~4 methanesulfonic acid or a solution of methanesulfonic acid, oxalic acid or mixtures thereof in a solvent selected from carboxylic acids and mixtures thereof.

[0011] WO 2011 / 120066 A1 describes a method for producing shaped bodies based on aluminum alloys by metal powder injection molding, which comprises the following steps: a) preparing a raw material by blending the metals contained in the desired alloy in the form of a metal powder and / or one or more metal alloy powders with a binder; b) preparing a green body by injection molding the raw material; c) preparing a brown body by at least partially removing the binder from the green body by catalytic and / or solvent and / or thermal debinding; d) sintering the at least partially debinding brown body to obtain the desired shaped body. In step c), the binder is completely removed and, optionally after carrying out one or more preceding debinding steps, a thermal debinding is carried out to remove the (residual) binder, carried out in an atmosphere containing at least 0.5% by volume of oxygen, after which the obtained completely debinding brown body is sintered.

[0012] WO 94 / 25205 A1 describes the production of sintered articles by forming a mixture of a sinterable ceramic or metal powder with a polyoxymethylene or copolymer containing a predominant proportion of oxymethylene units as binder to obtain a green body, treating with a gaseous acid to remove the binder, and sintering. To remove the binder, an acid is used, such as anhydrous or dehydrated oxalic acid, which is solid at room temperature and which sublimates or melts and evaporates at high temperatures.

[0013] US 5,695,697 A discloses a method for producing molded sintered articles by first molding a mixture of a) ceramic or metal powder or a mixture thereof with b) a thermoplastic polyoxymethylene binder, and c) a second moldable essentially inert thermoplastic polymer having a melting point between 90° C. and 220° C., such as a moldable thermoplastic composition containing bisphenol A and a polyether of an aliphatic diol. The binder is then removed from the molded article by exposure to a gaseous acid-containing atmosphere, preferably below its softening temperature, while the second inert thermoplastic polymer is retained as a source of elemental carbon in which the ceramic or metal powder is finely dispersed.

[0014] US 2016 / 0024293 A1 describes a method for treating a mixture (M) at a temperature (T M ), and depositing the mixture (M) in a build chamber using a layer-based additive technique to form the three-dimensional green body, where the mixture (M) comprises: (a) 40-70 volume % of an inorganic powder (IP) based on the total volume of the mixture (M), and (b) 30-60 volume % of a binder (B) based on the total volume of the mixture (M), where the binder (B) comprises at least one polyoxymethylene (POM). Removal of the binder (B) can include removal by acid treatment.

[0015] CN 106270506 A discloses a catalytic debinding furnace and a catalytic debinding method using oxalic acid as a catalyst.

[0016] US 2013 / 0101456 A1 discloses a method for producing molded articles based on aluminum alloys by metal injection molding.

[0017] However, in the above-mentioned latest debinding process involving oxalic acid, a debinding temperature of 140°C is proposed by using an excess of anhydrous oxalic acid. While such conditions do not pose any problem for debinding of injection molded or extruded three-dimensional bodies, such conditions are problematic for 3D printed bodies, since the 3D printed bodies tend to warp or distort during the debinding process at such temperatures. Moreover, heating at 140°C is also disadvantageous from a commercial point of view. Moreover, the use of excess oxalic acid results in waste and poses potential hazard problems for the operator of the debinding equipment. Another problem is the time required for debinding. According to Examples 5-10 of WO 2011 / 120066 A1, the debinding time is 24 hours, which is not attractive from a commercial point of view. [Prior art documents] [Patent documents]

[0018] [Patent Document 1] US 5,121,329 [Patent Document 2] WO 2015 / 185468 A1 [Patent Document 3] WO 2011 / 120066 A1 [Patent Document 4] WO 94 / 25205 A1 [Patent Document 5] US 5,695,697 A [Patent Document 6] US 2016 / 0024293 A1 [Patent Document 7] CN 106270506A [Patent Document 8] US 2013 / 0101456 A1 Summary of the Invention [Problem to be solved by the invention]

[0019] The object underlying the present invention is therefore to provide an improved method for the processing of three-dimensional green bodies which does not have the above-mentioned disadvantages of the prior art or only has them to a significantly reduced extent. [Means for solving the problem]

[0020] The objective is to provide at least the following steps: a) providing at least one three-dimensional green body (GB), said at least one three-dimensional green body (GB) comprising an inorganic powder (IP) and a binder (B), said binder (B) being (b1) at least one polyoxymethylene (POM) and b) providing 0.01 to 5.0 wt. % anhydrous oxalic acid based on the total weight of the at least one three-dimensional green body (GB); c) treating said at least one three-dimensional green body (GB) with anhydrous oxalic acid in the presence of an inert gas at a temperature (T1) below 140°C; This is achieved by at least one method of processing the three-dimensional green body (GB), comprising: DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Surprisingly, it has been found that no warping or distortion of the resulting brown body and sintered body, respectively, is observed by the method of the present invention, in particular by using a temperature (T1) below 140° C., which is lower than the sublimation temperature of anhydrous oxalic acid. Moreover, by using a temperature (T1) below 140° C., preferably below 135° C., more preferably below 130° C., the debinding rate is advantageously in the range of 1 mm to 2 mm per hour.

[0022] Furthermore, by using 0.01-5.0 wt. %, preferably 0.05-2.5 wt. %, more preferably 0.1-1.5 wt. % of anhydrous oxalic acid based on the total mass of the at least one three-dimensional green body (GB), the problem of using excessive anhydrous oxalic acid and thus waste and potential danger to the operator of the debinding equipment is avoided.

[0023] It has also surprisingly been found that the debinding process according to steps a) to c) and the sintering process according to step d) can be carried out in the same heating chamber (HC), allowing for a seamless single-step process flow.

[0024] In summary, the method of the present invention improves the overall effectiveness of the process for the production of sintered parts, reduces the risk of damage to the part and the operator, and produces sintered parts faster because no additional heating and cooling times are required and the parts are not transported from the debinding machine to the sintering machine.

[0025] For the purposes of the present invention, the term "three-dimensional green body" refers to a three-dimensional body comprising an inorganic powder (IP) and a binder (B), where the binder (B) comprises (b1) at least one polyoxymethylene (POM). The three-dimensional green body can be prepared by various processes, for example by additive manufacturing processes such as fused filament fabrication processes or by injection molding. The methods for producing three-dimensional green bodies have in common that a mixture that comprises an inorganic powder and a binder and is initially present in a solid state is heated to melt and then cooled, whereby the three-dimensional green body is formed during cooling. For the purposes of the present invention, the three-dimensional green body is preferably prepared by a fused filament fabrication process.

[0026] Therefore, the present invention also provides a method, wherein at least one three-dimensional green body (GB) is prepared by an injection moulding or fused filament fabrication process, preferably by a fused filament fabrication process.

[0027] The term "at least one three-dimensional green body" according to the present invention means exactly one three-dimensional green body as well as a mixture of two or more three-dimensional green bodies.

[0028] The present invention will now be described in more detail.

[0029] The method for treating at least one three-dimensional green body (GB) according to the present invention comprises at least steps a) to c).

[0030] Steps a) and b) can be carried out simultaneously, but it is also possible that step a) is carried out before step b) or step b) is carried out before step a). Step c) is preferably carried out after steps a) and b).

[0031] Process a) In step a), at least one three-dimensional green body (GB) is provided. The at least one three-dimensional green body (GB) comprises an inorganic powder (IP) and a binder (B), the binder (B) being (b1) contains at least one polyoxymethylene (POM).

[0032] Preferably, the at least one three-dimensional green body (GB) comprises 30-70 volume % of inorganic powder (IP) and 30-70 volume % of binder (B), based on the total volume of the at least one three-dimensional green body (GB), where the sum of the volume % of inorganic powder (IP) and binder (B) is generally 100%.

[0033] More preferably, the at least one three-dimensional green body (GB) comprises 45-65 volume % of inorganic powder (IP) and 35-55 volume % of binder (B), based on the total volume of the at least one three-dimensional green body (GB), where the sum of the volume % of inorganic powder (IP) and binder (B) is generally 100%.

[0034] Particularly preferably, the at least one three-dimensional green body (GB) comprises 48-60 vol.-% of inorganic powder (IP) and 40-52 vol.-% of binder (B), based on the total volume of the at least one three-dimensional green body (GB), where the sum of the vol.-% of inorganic powder (IP) and binder (B) is generally 100%.

[0035] In one embodiment of the present invention, at least one three-dimensional green body (GB) comprises at least one dispersant. Preferably, at least one three-dimensional green body (GB) comprises 0.1-5 vol. % of at least one dispersant, particularly preferably 0.2-4 vol. %, most preferably 0.5-2 vol. %, of at least one dispersant, based on the total volume of the at least one three-dimensional green body (GB).

[0036] It is clear to the skilled artisan that when at least one three-dimensional green body (GB) comprises at least one dispersant, the sum of the volume percentages of inorganic powder (IP), binder (B) and at least one dispersant is generally 100%.

[0037] "At least one dispersant" according to the present invention means exactly one dispersant, but also a mixture of two or more dispersants.

[0038] Examples of suitable dispersants include oligomeric polyethylene oxides with low molecular weights of 200 to 600 g / mol, stearic acid, stearamide, hydroxystearic acid, fatty alcohols, fatty acid esters, sulfonates, and block copolymers of ethylene oxide and propylene oxide, and also particularly preferably polyisobutylene.

[0039] The components of the at least one three-dimensional green body (GB) are described in detail below.

[0040] Inorganic powder (IP) At least one three-dimensional green body (GB) comprises an inorganic powder (IP).

[0041] As the inorganic powder (IP), a known inorganic powder (IP) can be used. Preferably, a sinterable inorganic powder (IP) is used. More preferably, the inorganic powder (IP) is a powder of at least one inorganic material selected from the group consisting of a metal, a metal alloy, and a ceramic material, most preferably, the inorganic powder (IP) is a metal or a metal alloy, and particularly preferably, the inorganic powder (IP) is a metal.

[0042] The present invention therefore also provides a method, wherein the inorganic powder (IP) is a powder of at least one inorganic material selected from the group consisting of metals, metal alloys and ceramic materials, preferably, the inorganic powder (IP) is a metal or a metal alloy, particularly preferably, the inorganic powder (IP) is a metal.

[0043] "Inorganic powder (IP)" means not only one type of inorganic powder (IP) but also a mixture of two or more inorganic powders (IP). The same applies to the term "inorganic material". "Inorganic material" means exactly one type of inorganic material and a mixture of two or more inorganic materials. "Metal" means exactly one type of metal and a mixture of two or more metals. The metal in the present invention can be selected from any metal of the periodic table of elements that is stable under the conditions of the fused filament manufacturing process and can form a three-dimensional object. Preferably, the metal is selected from the group consisting of aluminum, yttrium, titanium, zirconium, vanadium, niobium, chromium, molybdenum, tungsten, manganese, iron, carbonyl iron powder (CIP), cobalt, nickel, copper, silver, zinc, magnesium, tin and cadmium, more preferably, the metal is selected from the group consisting of titanium, niobium, chromium, molybdenum, tungsten, manganese, iron, carbonyl iron powder (CIP), nickel and copper. Particularly preferably, the metal is selected from the group consisting of titanium, iron and carbonyl iron powder (CIP).

[0044] Carbonyl iron powder (CIP) is a high purity iron powder prepared by the chemical decomposition of refined iron pentcarbide.

[0045] By "metal alloy" is meant exactly one metal alloy and mixtures of two or more metal alloys. In the context of the present invention, the term "metal alloy" means a solid solution or partial solid solution that exhibits metallic properties and contains a metal and other elements. By "metal" is meant exactly one metal and mixtures of two or more metals, as described above. The same is true for "another element". By "another element" is meant exactly one other element and mixtures of two or more other elements. A solid solution metal alloy exhibits a microstructure of a single solid phase, whereas a partial solid solution metal alloy exhibits two or more solid phases. These two or more solid phases may be homogeneously distributed in the metal alloy, but may also be heterogeneously distributed in the metal alloy. The metal alloy may be prepared according to any process known to the skilled person. For example, a metal may be melted and other elements may be added to the molten metal. However, it is also possible that an inorganic powder (IP) contains a metal and other elements without preparing a metal alloy. The metal alloy is formed during the preparation of a three-dimensional object.

[0046] For the metal, the above-mentioned embodiments and preferences apply. The other element may be selected from the above-mentioned metals. However, the other element is different from the metal contained in the metal alloy. The other element may be selected from any element of the periodic table that forms a stable metal alloy under the conditions of the molten filament production process or that is stable or forms a stable alloy with the metal under the conditions of the molten filament production process. In a preferred embodiment of the invention, the other element is selected from the group consisting of the above-mentioned metals, boron, carbon, silicon, phosphorus, sulfur, selenium and tellurium. Particularly preferably, at least one other element is selected from the group consisting of the above-mentioned metals, boron, carbon, silicon, phosphorus and sulfur. Preferably, the metal alloy according to the invention comprises a steel.

[0047] By "ceramic material" is meant both exactly one ceramic material and mixtures of two or more ceramic materials. In the context of the present invention, the term "ceramic material" means a non-metallic compound of a metal or a first metalloid with a non-metal or a second metalloid.

[0048] "Metal" means exactly one metal, and a mixture of two or more metals. The same applies to "nonmetal", "first metalloid", and "second metalloid". "Nonmetal" means exactly one nonmetal, and a mixture of two or more nonmetals. "First metalloid" means exactly one first metalloid, and a mixture of two or more first metalloids. "Second metalloid" means exactly one second metalloid, and a mixture of two or more second metalloids.

[0049] Nonmetals are known per se to those skilled in the art. The nonmetal according to the invention can be selected from any nonmetal of the periodic table. Preferably, at least one nonmetal is selected from the group consisting of carbon, nitrogen, oxygen, phosphorus and sulfur.

[0050] Metalloids are well known per se to those skilled in the art. The first metalloid and the second metalloid can be selected from any metalloid of the periodic table. Preferably, the first metalloid and / or the second metalloid are selected from the group consisting of boron and silicon. It will be clear that the first metalloid and the second metalloid are different from each other. For example, if the first metalloid is boron, the second metalloid is selected from other metalloids of the periodic table of elements other than boron.

[0051] In one embodiment of the present invention, the ceramic material is selected from the group consisting of oxides, carbides, borides, nitrides and silicides. In a preferred embodiment, the ceramic material is selected from the group consisting of MgO, CaO, SiO2, Na2O, Al2O3, ZrO2, Y2O3, SiC, Si3N4, TiB and AlN. Particularly preferably, the ceramic material is selected from the group consisting of Al2O3, ZrO2 and Y2O3.

[0052] To prepare the inorganic powder (IP), the inorganic material needs to be pulverized. Any method known to those skilled in the art can be used to pulverize the inorganic material. For example, the inorganic material can be pulverized. For example, the pulverization can be performed in a classifier mill, a hammer mill, or a ball mill.

[0053] Carbonyl iron powder (CIP) is prepared by chemical decomposition of purified carbonyl iron (Pentavalent).

[0054] The particle size of the inorganic powder (IP) used is preferably 0.1 to 80 μm, particularly preferably 0.5 to 50 μm, and more preferably 0.1 to 30 μm, as measured by laser diffraction.

[0055] Therefore, the present invention also provides a method, wherein the particle size of the inorganic powder (IP) is 0.1 to 80 μm.

[0056] Binder (B) The at least one three-dimensional green body (GB) also comprises a binder (B), wherein the binder (B) is (b1) at least one polyoxymethylene (POM) Includes.

[0057] Preferably, the binder (B) is (b1) 50 to 96% by weight of at least one polyoxymethylene (POM), based on the total weight of the binder (B); (b2) 2 to 35% by weight of at least one polyolefin (PO), based on the total weight of the binder (B); (b3) 2 to 40% by weight of at least one further polymer (FP), based on the total weight of the binder (B). wherein the sum of the weight percent of components (b1), (b2) and (b3) is generally 100%.

[0058] Therefore, the present invention relates to a binder (B) (b1) 50 to 96% by weight of at least one polyoxymethylene (POM), based on the total weight of the binder (B); (b2) 2 to 35% by weight of at least one polyolefin (PO), based on the total weight of the binder (B); (b3) 2 to 40% by weight of at least one further polymer (FP), based on the total weight of the binder (B). Also provided is a method comprising:

[0059] In a preferred embodiment, the binder (B) is, based on the total weight of the binder (B), As component (b1), 60 to 90% by weight of at least one polyoxymethylene (POM), As component (b2), 3 to 20% by weight of at least one polyolefin (PO), and as component (b3), 5 to 30% by weight of at least one further polymer (FP), wherein the sum of the weight percent of components (b1), (b2) and (b3) is typically 100%.

[0060] Particularly preferably, the binder (B) is As component (b1), 70 to 85% by weight of at least one polyoxymethylene (POM), As component (b2), 4 to 15% by weight of at least one polyolefin (PO), and as component (b3), 10 to 26% by weight of at least one further polymer (FP), wherein the sum of the weight percent of components (b1), (b2) and (b3) is 100%.

[0061] According to the invention, component (b1) is different from component (b2), which is different from component (b3), which is different from component (b1). However, components (b1), (b2) and (b3) may contain the same building blocks, e.g., different further building blocks and / or different molecular weights.

[0062] Components (b1), (b2) and (b3) of the binder (B) are described in detail below.

[0063] Component (b1) / Polyoxymethylene (POM) For purposes of the present invention, the terms "component (b1)" and "at least one polyoxymethylene (POM)" are synonymous and are used interchangeably throughout the present invention.

[0064] Preferably, the binder (B) comprises 50 to 96% by weight, more preferably 60 to 90% by weight, and most preferably 70 to 85% by weight of at least one polyoxymethylene (POM), based on the total weight of the binder (B).

[0065] "At least one polyoxymethylene (POM)" in the present invention means exactly one polyoxymethylene (POM) and mixtures of two or more polyoxymethylene (POM). For the purposes of the present invention, the term "polyoxymethylene (POM)" encompasses both polyoxymethylene (POM) itself, i.e. polyoxymethylene (POM) homopolymers, as well as polyoxymethylene (POM) copolymers and polyoxymethylene (POM) terpolymers. Polyoxymethylene (POM) homopolymers are usually prepared by polymerization of monomers selected from the formaldehyde source (b1a). The term "formaldehyde source (b1a)" relates to substances capable of releasing formaldehyde under the reaction conditions of the preparation of polyoxymethylene (POM). The formaldehyde source (b1a) is advantageously selected from the group of cyclic or linear formals, in particular from the group consisting of formaldehyde and 1,3,5-trioxane. 1,3,5-trioxane is particularly preferred.

[0066] Polyoxymethylene (POM) copolymers are known per se and commercially available. They are usually prepared by polymerization with trioxane as the main monomer. In addition, comonomers are used in combination. The main monomers are preferably selected from trioxane and other cyclic or linear formals or other formaldehyde sources (b1a). The expression "main monomers" is intended to indicate that the proportion of these monomers in the total amount of monomers, i.e. the sum of main monomers and comonomers, is greater than the proportion of comonomers in the total amount of monomers. Very generally, the polyoxymethylene (POM) according to the invention has at least 50 mol % of repeat units -CHO- in the main polymer chain. Suitable polyoxymethylene (POM) copolymers are in particular those which contain the repeat unit -CHO- and 0.01 to 20 mol %, in particular 0.1 to 10 mol %, very particularly preferably 0.5 to 6 mol % of repeat units of formula (I), [ka] (In the formula, R 1 ~R 4 are each independently selected from the group consisting of H, C1-C4-alkyl, and halogen-substituted C1-C4-alkyl; R 5 is a chemical bond, (-CR 5a R 5b -) group, and (-CR 5a R 5b O-) groups, Here, R 5a and R 5b are each independently selected from the group consisting of H and unsubstituted or at least monosubstituted C1-C4-alkyl, The substituents are selected from the group consisting of F, Cl, Br, OH and C1-C4-alkyl; where n is 0, 1, 2 or 3.

[0067] If n is 0, R 5 is a chemical bond between adjacent carbon and oxygen atoms. 5 (-CR 5a R5b -) group, (-CR 5a R 5b The oxygen atom (O) of the O- group is bonded to another carbon atom (C) of formula (I) and is not bonded to the oxygen atom (O) of formula (I). In other words, formula (I) does not include peroxide compounds. The same applies to formula (II).

[0068] In the context of the present invention, the definition of C1-C4-alkyl refers, for example, to the radical R 1 ~R 4 As defined above for , it means that the substituent (radical) is an alkyl radical having from 1 to 4 carbon atoms. The alkyl radical may be linear or branched, and optionally cyclic. Alkyl radicals having both cyclic and linear components fall under this definition as well. Examples of alkyl radicals include methyl, ethyl, n-propyl, iso-propyl, butyl, iso-butyl, sec-butyl, and tert-butyl.

[0069] In the context of the present invention, the definition of halogen-substituted C1-C4-alkyl refers, for example, to the radical R 1 ~R 4 means that the C1-C4-alkyl is substituted with at least one halogen, as defined above for Halogen is F (fluorine), Cl (chlorine), Br (bromine) and I (iodine).

[0070] The repeating units of formula (I) can advantageously be introduced into polyoxymethylene (POM) copolymers by ring opening of cyclic ethers as first comonomers (b1b). First comonomers (b1b) of general formula (II) are preferred: [ka] Here, R 1 ~R 5 and n have the meanings defined above for general formula (I).

[0071] As first comonomers (b1b), for example, ethylene oxide, 1,2-propylene oxide, 1,2-butylene oxide, 1,3-butylene oxide, 1,3-dioxane, 1,3-dioxolane and 1,3-dioxepane (=butanediol formal, BUFO), as cyclic ethers, and linear oligoformals or polyformals, such as polydioxolanes or polydioxepanes, are mentioned. 1,3-Dioxolanes and 1,3-dioxepanes are particularly preferred first comonomers (b1b), with 1,3-dioxepanes being very particularly preferred as first comonomer (b1b).

[0072] Likewise suitable are polyoxymethylene (POM) polymers obtained by reacting a formaldehyde source with a first comonomer (b1b) and a second comonomer (b1c). The addition of the second comonomer (b1c) in particular allows the preparation of polyoxymethylene (POM) terpolymers.

[0073] The second comonomer (b1c) is preferably selected from the group consisting of compounds of formula (III) and compounds of formula (IV), [ka] (wherein Z is a chemical bond, a (-O-) group, and a (-OR 6 -O-) groups, Here, R 6 is selected from the group consisting of unsubstituted C1-C8-alkylene and C3-C8-cycloalkylene.

[0074] In the context of the present invention, the definition C1-C8-alkylene means C1-C8-alkanediyl. C1-C8-alkylene is a hydrocarbon having two free valences and a number of carbon atoms from 1 to 8. C1-C8-alkylene according to the present invention may be branched or unbranched.

[0075] In the context of the present invention, the definition C3-C8-cycloalkylene means C3-C8-cycloalkanediyl. C3-C8-Cycloalkylene is a cyclic hydrocarbon having two free valences and a number of carbon atoms from 3 to 8. Hydrocarbons having two free valences, cyclic and linear components and a number of carbon atoms from 3 to 8 likewise fall under this definition.

[0076] Preferred examples of the second comonomer (b1c) include ethylene diglycidyl, diglycidyl ethers, and diethers prepared from a glycidyl compound and formaldehyde, dioxane or trioxane in a molar ratio of 2:1, and also diethers prepared from 2 moles of a glycidyl compound and 1 mole of an aliphatic diol having 2 to 8 carbon atoms, such as the diglycidyl ethers of ethylene glycol, 1,4-butanediol, 1,3-butanediol, 1,3-cyclobutanediol, 1,2-propanediol and 1,4-cyclohexanediol.

[0077] In a preferred embodiment, component (b1) is a polyoxymethylene (POM) copolymer prepared by polymerization of at least 50 mol % of a formaldehyde source, 0.01-20 mol % of at least one first comonomer (b1b) and 0-20 mol % of at least one second comonomer (b1c).

[0078] In a particularly preferred embodiment, component (b1) is a polyoxymethylene (POM) copolymer prepared by polymerization of 80 to 99.98 mol %, preferably 88 to 99 mol %, of a formaldehyde source, 0.1 to 10 mol %, preferably 0.5 to 6 mol %, of at least one first comonomer (b1b) and 0.1 to 10 mol %, preferably 0.5 to 6 mol %, of at least one second comonomer (b1c).

[0079] In a further preferred embodiment, component (b1) is a polyoxymethylene (POM) copolymer prepared by polymerization of at least 50 mol % of a formaldehyde source, 0.01-20 mol % of at least one first comonomer (b1b) of general formula (II), and 0-20 mol % of at least one second comonomer (b1c) selected from the group consisting of compounds of formula (III) and compounds of formula (IV).

[0080] Another subject of the invention is therefore a process, in which component (b1) is a polyoxymethylene (POM) copolymer prepared by polymerization of - at least 50 mol % of a formaldehyde source, - 0.01 to 20 mol % of at least one first comonomer (b1b) of general formula (II) [ka] (In the formula, R 1 ~R 4 are each independently selected from the group consisting of H, C1-C4-alkyl, and halogen-substituted C1-C4-alkyl; R 5 is a chemical bond, (-CR 5a R 5b -) group, and (-CR 5a R 5b O-) groups, Here, R 5a and R 5b are each independently selected from the group consisting of H and unsubstituted or at least monosubstituted C1-C4-alkyl, The substituents are selected from the group consisting of F, Cl, Br, OH and C1-C4-alkyl; n is 0, 1, 2 or 3); and - from 0 to 20 mol % of at least one second comonomer (b1c) selected from the group consisting of compounds of formula (III) and compounds of formula (IV) [ka] (wherein Z is a chemical bond, a (-O-) group, and a (-OR 6 -O-) groups, Here, R 6 is selected from the group consisting of unsubstituted C1-C8-alkylene and C3-C8-cycloalkylene.

[0081] In a preferred embodiment of the present invention, at least a portion of the OH end groups of the polyoxymethylene (POM) are capped. Methods for capping the OH end groups are known to those skilled in the art. For example, the OH end groups can be capped by etherification or esterification.

[0082] Preferred polyoxymethylene (POM) copolymers have a melting point of at least 150° C. and a weight average molecular weight M in the range of 5000 g / mol to 300000 g / mol, preferably 6000 g / mol to 150000 g / mol, particularly preferably 7000 g / mol to 100000 g / mol. W has.

[0083] Particularly preferred are polydispersities (M W / M n ) is a polyoxymethylene (POM) copolymer.

[0084] Mass average molecular weight (M W ) and number average molecular weight (M n The measurement of ) is commonly performed by gel permeation chromatography (GPC), also known as size exclusion chromatography (SEC).

[0085] Methods for preparing polyoxymethylene (POM) are known to those skilled in the art.

[0086] Component (b2) / Polyolefin (PO) Furthermore, the binder (B) may contain a component (b2).

[0087] Preferably, the binder (B) contains 2 to 35% by weight, more preferably 3 to 20% by weight, most preferably 4 to 15% by weight of component (b2).

[0088] Preferably, component (b2) is at least one polyolefin (PO). "At least one polyolefin (PO)" in the present invention means exactly one polyolefin (PO) and mixtures of two or more polyolefins (PO).

[0089] Polyolefins (PO) are known per se and commercially available. They are usually prepared by polymerization of C2-C8-alkene monomers, preferably C2-C4-alkene monomers.

[0090] In the context of the present invention, C2-C8-alkene means an unsubstituted or at least monosubstituted hydrocarbon having 2 to 8 carbon atoms and at least one carbon-carbon double bond (CC double bond). "At least one carbon-carbon double bond" means exactly one carbon-carbon double bond, and more than one carbon-carbon double bond.

[0091] In other words, C2-C8-alkene means that the hydrocarbon having 2-8 carbon atoms is unsaturated. The hydrocarbon may be branched or unbranched. Examples of C2-C8-alkene having one CC double bond include ethene, propene, 1-butene, 2-butene, 2-methyl-propene (=isobutylene), 1-pentene, 2-pentene, 2-methyl-1-butene, 3-methyl-1-butene, 1-hexene, 2-hexene, 3-hexene, and 4-methyl-1-pentene. Examples of C2-C8-alkene having two or more CC double bonds include allene, 1,3-butadiene, 1,4-pentadiene, 1,3-pentadiene, 2-methyl-1,3-butadiene (=isoprene).

[0092] When the C2-C8-alkene has one C-C double bond, the polyolefin (PO) prepared from those monomers is linear. When the C2-C8-alkene has two or more double bonds, the polyolefin (PO) prepared from those monomers can be crosslinked. Linear polyolefins (PO) are preferred.

[0093] It is also possible to use polyolefin (PO) copolymers, which are prepared by using different C2-C8-alkene monomers during the preparation of the polyolefin (PO).

[0094] Preferably, the polyolefin (PO) is selected from the group consisting of polymethylpentene, poly-1-butene, polyisobutylene, polyethylene and polypropylene. Particularly preferred are polyethylene and polypropylene and their copolymers known to those skilled in the art and commercially available.

[0095] Polyolefins (PO) can be prepared by any polymerization process known to those skilled in the art, preferably by free radical polymerization, such as emulsion polymerization, bead polymerization, solution polymerization or bulk polymerization. Initiators that can be used are free radical initiators, such as peroxide compounds and azo compounds, depending on the type of monomer and polymerization, and the amount of initiator is generally in the range of 0.001 to 0.5% by weight based on the monomer.

[0096] Component (b3) / further polymer (FP) The binder (B) may comprise a further polymer (FP) as component (b3).

[0097] For the purposes of the present invention, the terms "component (b3)" and "further polymer (FP)" are synonymous and are used interchangeably throughout the present invention.

[0098] Preferably, the binder (B) contains as component (b3) 2 to 40% by weight, more preferably 5 to 30% by weight, most preferably 10 to 26% by weight, based on the total weight of the binder (B).

[0099] Component (b3) according to the invention is at least one further polymer (FP). "At least one further polymer (FP)" in the present invention means exactly one further polymer (FP) and mixtures of two or more further polymers (FP).

[0100] As already mentioned above, the at least one further polymer (FP) is different from component (b1), the polyoxymethylene (POM), and from component (b2), the polyolefin (PO).

[0101] According to the invention, the at least one further polymer (FP) is preferably selected from the group consisting of polyethers, polyurethanes, polyepoxides, polyamides, vinyl aromatic polymers, poly(vinyl esters), poly(vinyl ethers), poly(alkyl(meth)acrylates) and copolymers thereof.

[0102] Another subject of the present invention is therefore a process, in which the further polymer (FP) is at least one further polymer (FP) selected from the group consisting of polyethers, polyurethanes, polyepoxides, polyamides, vinyl aromatic polymers, poly(vinyl esters), poly(vinyl ethers), poly(alkyl(meth)acrylates) and copolymers thereof.

[0103] Preferably, the at least one further polymer (FP) of component (b3) is selected from the group consisting of poly(C2-C6-alkylene oxides), aliphatic polyurethanes, aliphatic uncrosslinked epoxides, aliphatic polyamides, vinyl aromatic polymers, poly(vinyl esters) of aliphatic C1-C8-carboxylic acids, poly(vinyl ethers) of C1-C8-alkyl vinyl ethers, C 1~8 -alkyl poly(alkyl(meth)acrylates) and copolymers thereof.

[0104] The preferred at least one further polymer (FP) is described in more detail below.

[0105] The polyether comprises repeat units of formula (V) [ka] (In the formula, R 11 ~R 14 are each independently selected from the group consisting of H, C1-C4-alkyl, and halogen-substituted C1-C4-alkyl; R 15 is a chemical bond, (-CR 15a R 15b -) group, and (-CR 15a R 1515b O-) groups, Here, R 15a and R 15b are each independently selected from the group consisting of H and unsubstituted or at least monosubstituted C1-C4-alkyl, The substituents are selected from the group consisting of F, Cl, Br, OH and C1-C4-alkyl; where n is 0, 1, 2 or 3.

[0106] If n is 0, R 15 is a chemical bond between adjacent carbon and oxygen atoms. 15 (-CR 15a R 15b -) group, (-CR 15a R 15b The oxygen atom (O) of the O- group is bonded to another carbon atom (C) of formula (V), and is not bonded to the oxygen atom (O) of formula (V). In other words, formula (V) does not include peroxide compounds. The same applies to formula (VI).

[0107] Typical polyethers and their methods of preparation are known to those skilled in the art.

[0108] Preferred polyethers according to the invention are, for example, poly(alkylene glycols), also known as poly(alkylene oxides).

[0109] Polyalkylene oxides and their preparation are known to those skilled in the art. Polyalkylene oxides are usually synthesized by the interaction of water, dihydric or polyhydric alcohols and cyclic ethers of general formula (VI), i.e. alkylene oxides. The reaction is catalyzed by acidic or basic catalysts. This reaction is the so-called ring-opening polymerization of cyclic ethers of general formula (VI): [ka] (In the formula, R 11 ~R 15 has the meaning defined above for general formula (V).

[0110] A preferred poly(alkylene oxide) according to the present invention is derived from a monomer of general formula (VI) having 2 to 6 carbon atoms in the ring. In other words, the poly(alkylene oxide) is preferably a poly(C2-C6-alkylene oxide). Particularly preferred is a poly(alkylene oxide) derived from a monomer selected from the group consisting of 1,3-dioxolane, 1,3-dioxepane and tetrahydrofuran (IUPAC name: oxolane). In other words, particularly preferred is a poly(alkylene oxide) selected from the group consisting of poly-1,3-dioxolane, poly-1,3-dioxepane and polytetrahydrofuran.

[0111] In one embodiment, the poly(alkylene oxide) can include OH end groups. In another embodiment, at least a portion of the OH end groups of the poly(alkylene oxide) can be capped. Methods for capping the OH end groups are known to those skilled in the art. For example, the OH end groups can be capped by etherification or esterification.

[0112] The mass average molecular weight of the poly(alkylene oxide) is preferably in the range of 1,000 to 150,000 g / mol, particularly preferably in the range of 1,500 to 120,000 g / mol, and more preferably in the range of 2,000 to 100,000 g / mol.

[0113] Polyurethanes are polymers containing carbamate units. Polyurethanes and their preparation are known to those skilled in the art.

[0114] In the present invention, aliphatic polyurethanes are preferred. They can be prepared, for example, by polyaddition of aliphatic polyisocyanates with aliphatic polyhydroxy compounds. Among the polyisocyanates, diisocyanates of general formula (VII) are preferred: [ka] (In the formula, R 7 is a substituted or unsubstituted C1-C 20 -Alkylene or C4-C 20 -cycloalkylene, where the substituents are selected from the group consisting of F, Cl, Br and C1-C6-alkyl.

[0115] Preferably, R 7 is substituted or unsubstituted C2-C 12 -Alkylene or C6-C 15 -cycloalkylene.

[0116] In the context of the present invention, C1 to C 20 -Alkylene is defined as C1-C 20 -alkanediyl. C1-C 20 -Alkylene is a hydrocarbon having two free valences and a number of carbon atoms from 1 to 20. 20 The alkylene may be branched or unbranched.

[0117] In the context of the present invention, C4-C 20 -Cycloalkylene is defined as C4-C 20 -Cycloalkanediyl. C4~C 20 -Cycloalkylene is a cyclic hydrocarbon having two free valences and a number of carbon atoms between 4 and 20. Hydrocarbons having two free valences, cyclic and linear moieties, and a number of carbon atoms between 4 and 20 fall under this definition as well.

[0118] Preferred diisocyanates are selected from the group consisting of hexamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, 1,2-diisocyanatomethylcyclohexane, 1,4-diisocyanatomethylcyclohexane and isophorone diisocyanate (IUPAC name: 5-isocyanato-1-(isocyanatomethyl)-1,3,3-trimethylcyclohexane).

[0119] The diisocyanates can also be used in the form of oligomers, for example dimers or trimers. Instead of the polyisocyanates, it is also possible to use conventional blocked polyisocyanates which are obtained from the abovementioned isocyanates, for example by addition reaction with phenols or caprolactam.

[0120] Suitable polyhydroxy compounds for the preparation of aliphatic polyurethanes are, for example, polyesters, polyethers, polyesteramides or polyacetals or mixtures thereof.

[0121] Suitable chain extenders for the preparation of polyurethanes are low molecular weight polyols, especially diols and polyamines, especially diamines, or water.

[0122] The polyurethanes are preferably thermoplastic and therefore preferably essentially uncrosslinked, i.e. can be repeatedly melted without noticeable signs of decomposition. Their reduced specific viscosity, measured in dimethylformamide at 30°C, is as a rule 0.5-3 dL / g, preferably 1-2 dL / g.

[0123] A polyepoxide contains at least two epoxide groups, also known as glycidyl or oxirane groups. By "at least two epoxide groups" we mean exactly two epoxide groups, and more than two epoxide groups.

[0124] Polyepoxides and their preparation are known to those skilled in the art. For example, polyepoxides are prepared by the reaction of epichlorohydrin (IUPAC name: chloromethyloxirane) with diols, polyols, or dicarboxylic acids. Polyepoxides prepared in this manner are polyethers with epoxide end groups.

[0125] Another possibility for preparing polyepoxides is the reaction of glycidyl (meth)acrylate (IUPAC name: oxiran-2-ylmethyl-2-methylprop-2-enoate) with polyolefins or polyacrylates, which results in polyolefins or polyacrylates with epoxy end groups.

[0126] Preferably, aliphatic uncrosslinked polyepoxides are used. Copolymers of epichlorohydrin and 2,2-bis-(4-hydroxyphenyl)-propane (bisphenol A) are particularly preferred.

[0127] Component (b3) (the at least one further polymer (FP)) may also comprise a polyamide. Aliphatic polyamides are preferred.

[0128] Suitable polyamides generally have an intrinsic viscosity of 150 to 350 mL / g, preferably 180 to 275 mL / g, the intrinsic viscosity being measured here from a 0.5% by weight solution of the polyamide in 96% by weight sulfuric acid at 25° C. according to ISO 307.

[0129] Preferred polyamides are semi-crystalline or amorphous polyamides.

[0130] Examples of suitable polyamides as component (b3) are those derived from lactams having 7 to 13 ring members. Other suitable polyamides are those obtained by reaction of dicarboxylic acids with diamines.

[0131] Examples of polyamides derived from lactams include polyamides derived from polycaprolactam, polycaprylolactam, and / or polylaurolactam.

[0132] When using polyamides obtainable from dicarboxylic acids and diamines, the dicarboxylic acids which can be used are alkanedicarboxylic acids having 6 to 14 carbon atoms, preferably 6 to 10 carbon atoms. Aromatic dicarboxylic acids are also suitable.

[0133] Examples which may be mentioned here as dicarboxylic acids are adipic acid, azelaic acid, sebacic acid, dodecanedicarboxylic acid, and also terephthalic acid and / or isophthalic acid.

[0134] Examples of suitable diamines include alkanediamines having 4 to 14 carbon atoms, in particular alkanediamines having 6 to 8 carbon atoms, and also aromatic diamines such as m-xylylenediamine, di(4-aminophenyl)methane, di(4-aminocyclohexyl)methane, 2,2-di(4-aminophenyl)propane, 2,2-di(4-aminocyclohexyl)propane, and 1,5-diamino-2-methylpentane.

[0135] Other suitable polyamides are those obtainable by copolymerization of two or more of the monomers mentioned above and below, and mixtures of several polyamides in any desired mixing ratio.

[0136] Preferred polyamides are polyhexamethylene adipamide, polyhexamethylene sebacamide, polycaprolactam and also nylon 6 / 6,6, in particular having a proportion of caprolactam units of 75 to 95% by weight.

[0137] Particularly preferred are mixtures of nylon-6 with other polyamides, in particular nylon-6 / 6,6 (PA 6 / 66), and especially mixtures of 80 to 50% by weight of PA 6 and 20 to 50% by weight of PA 6 / 66, where the PA 6 / 66 contains 75 to 95% by weight of caprolactam units, based on the total weight of PA 6 / 66 in the mixture.

[0138] The following non-exclusive list includes the polyamides described above, as well as other suitable polyamides and monomers that may also be included: AB Polymer: PA 4 Pyrrolidone PA 6 ε-caprolactam PA 7 Ethanol Lactam PA 8 Caprylolactam PA 9 9-Aminopelargonic Acid PA 11 11-aminoundecanoic acid PA 12 Laurolactam AA / BB polymer: PA 46 Tetramethylenediamine, Adipic Acid PA 66 Hexamethylenediamine, Adipic Acid PA 69 Hexamethylenediamine, Azelaic Acid PA 610 Hexamethylenediamine, Sebacic acid PA 612 Hexamethylenediamine, Decanedicarboxylic acid PA 613 Hexamethylenediamine, undecanedicarboxylic acid PA 1212 1,12-Dodecanediamine, decanedicarboxylic acid PA 1313 1,13-Diaminotridecane, undecanedicarboxylic acid PA 6T Hexamethylenediamine, Terephthalic acid PA MXD6 m-Xylylenediamine, Adipic Acid PA 6I Hexamethylenediamine, Isophthalic acid PA 6-3-T Trimethylhexamethylenediamine, terephthalic acid PA 6 / 6T (see PA 6 and PA 6T) PA 6 / 66 (see PA 6 and PA 66) PA 6 / 12 (see PA 6 and PA 12) PA 66 / 6 / 610 (see PA 66, PA 6 and PA 610) PA 6I / 6T (see PA 6I and PA 6T) PA PACM 6 Diaminodicyclohexylmethane, Adipic Acid PA PACM 12 Diaminodicyclohexylmethane, Laurolactam PA 6I / 6T / PACMT PA 6I / 6T+Diaminodicyclohexylmethane PA 12 / MACMI Laurolactam, Dimethyldiaminodicyclohexylmethane, Isophthalic Acid PA 12 / MACMT Laurolactam, Dimethyldiaminodicyclohexylmethane, Terephthalic Acid PA PDA-T Phenylenediamine, Terephthalic Acid.

[0139] Preferred polyamides are PA 6, PA 66, and PA PACM 6.

[0140] Vinyl aromatic polymers are polyolefins having unsubstituted or at least monosubstituted styrene as monomer units. Suitable substituents are, for example, C1-C6 alkyl, F, Cl, Br and OH. Preferred vinyl aromatic polymers are selected from the group consisting of polystyrene, poly-α-methylstyrene and their copolymers with up to 30% by weight of a comonomer selected from the group consisting of acrylic acid esters, acrylonitrile and methacrylonitrile.

[0141] Vinyl aromatic polymers are commercially available and known to those skilled in the art, and the preparation of these polymers is also known to those skilled in the art.

[0142] Preferably, the vinyl aromatic polymer is prepared by free radical polymerization, such as emulsion polymerization, bead polymerization, solution polymerization or bulk polymerization. Possible initiators can be free radical initiators such as peroxy compounds and azo compounds, depending on the monomer and type of polymerization, the amount of initiator generally ranges from 0.001 to 0.5% by weight, based on the monomer.

[0143] Poly(vinyl ester) and its preparation are known to those skilled in the art. Poly(vinyl ester) is preferably prepared by polymerization of vinyl esters. In a preferred embodiment of the invention, the vinyl ester is a vinyl ester of an aliphatic C1-C6 carboxylic acid. Preferred monomers are vinyl acetate and vinyl propionate. These monomers form poly(vinyl acetate) and poly(vinyl propionate) polymers.

[0144] Poly(vinyl ether) is prepared by polymerization of vinyl ether monomers. Poly(vinyl ether) and its preparation are known to those skilled in the art. In a preferred embodiment, the vinyl ether is an aliphatic C1-C8 alkyl ether vinyl ether. Preferred monomers are methyl vinyl ether and ethyl vinyl ether, which form poly(methyl vinyl ether) and poly(ethyl vinyl ether) during polymerization.

[0145] Preferably, the poly(vinyl ether) is prepared by free radical polymerization, such as emulsion, bead, solution, suspension or bulk polymerization. Possible initiators can be free radical initiators such as peroxy compounds and azo compounds, depending on the monomer and type of polymerization, and the amount of initiator is generally in the range of 0.001 to 0.5% by weight based on the monomer.

[0146] The poly(alkyl(meth)acrylate) of the present invention includes poly(alkyl acrylate), poly(alkyl methacrylate) and copolymers thereof. The poly(alkyl(meth)acrylate) comprises units derived from a monomer of formula (VIII): [ka] Here, R 8 is selected from the group consisting of H and C1-C8 alkyl; R 9 is a radical of formula (IX), [ka] (In the formula, R 10 is C1~C 14 (It is alkyl).

[0147] Preferably, R 8 is selected from the group consisting of H and C1-C4-alkyl, particularly preferably R 8 is H or methyl. Preferably, R 10 is C1-C8-alkyl, particularly preferably R 10 is methyl or ethyl.

[0148] R in formula (VIII) 8 is H and R 9 is a radical of formula (IX), in which R 10 When is methyl, the monomer of formula (VIII) is methyl acrylate.

[0149] R in formula (VIII) 8 is H and R 9 is a radical of formula (IX), in which R 10 When is ethyl, the monomer of formula (VIII) is ethyl acrylate.

[0150] R in formula (VIII) 8 is methyl and R 9 is a radical of formula (IX), the monomer of formula (VI) is a methacrylic acid ester.

[0151] The poly(alkyl(meth)acrylate) contains, as a monomer, preferably 40 to 100 mass % of a methacrylic acid ester, particularly preferably 70 to 100 mass % of a methacrylic acid ester, and more preferably 80 to 100 mass % of a methacrylic acid ester, based on the total amount of the poly(alkyl(meth)acrylate).

[0152] In another preferred embodiment, the poly(alkyl(meth)acrylate) comprises as a monomer 20 to 100% by mass of methyl acrylate, ethyl acrylate or a mixture thereof, preferably 40 to 100% by mass of methyl acrylate, ethyl acrylate or a mixture thereof, particularly preferably 50 to 100% by mass of methyl acrylate, ethyl acrylate or a mixture thereof, each based on the total amount of the poly(alkyl(meth)acrylate).

[0153] Such polymers of monomers of formula (VIII) and further monomers can be prepared by conventional, preferably free radical, polymerization, for example emulsion, bead, solution or bulk polymerization (see: Kirk-Othmer, Encyclopedia of Chemical Technology, 3rd edition, Vol. 1, pp. 330-342, Vol. 18, pp. 720-755, J. Wiley; H. Rauch-Puntigam, Th. Voelker, Acryl- und Methacrylverbindungen). Depending on the type of monomer and polymerization, possible initiators are free radical initiators such as peroxy compounds and azo compounds. The amount of initiator is generally in the range of 0.001 to 0.5% by weight, based on the monomers.

[0154] Suitable initiators for emulsion polymerization are, for example, peroxodisulfates, and suitable redox systems for bulk polymerization are peroxides, such as dibenzoyl peroxide or dilauroyl peroxide, but also azo compounds, such as azobisisobutyrodinitrile, as well as for solution or bead polymerization. The molecular weight can be adjusted using conventional regulators, in particular mercaptans, such as dodecyl mercaptan.

[0155] Preferably, the polymerization is carried out at elevated temperatures, for example above 50° C. The weight average molecular weight (M W) is generally in the range of 2000 to 5,000,000 g / mol, preferably 20,000 to 3,000,000 g / mol (determination by light scattering; see HoubenWeyl, Methoden der Org. Chemie, 4th edition, volume 14 / 1, Georg Thieme-Verlag Stuttgart 1961).

[0156] Those skilled in the art know that the monomers mentioned above for the preparation of components (b1), (b2) and (b3) may change their structure during the polymerization reaction. As a result, the building blocks of the polymer are not the same as the monomers from which they are derived. However, those skilled in the art know which monomers correspond to which building blocks of the polymer.

[0157] Under compounding or processing conditions by injection molding or melt filament production, substantially no transacetalization occurs between the polyoxymethylene (POM) of component (b1) and the at least one further polymer (FP) of component (b3), i.e. substantially no exchange of comonomer units occurs.

[0158] 3D green body The at least one three-dimensional green body (GB) can be prepared by any method known to those skilled in the art, for example, an additive manufacturing process such as a fused filament fabrication process or injection molding. Preferably, the at least one three-dimensional green body (GB) is prepared by a fused filament fabrication process.

[0159] The fused filament fabrication process for producing at least one three-dimensional green body (GB) is well known in the art and described in detail in the above cited documents. The fused filament fabrication process is also called 3D printing process. The filament can include a continuous filament, as well as a rod, pellet and / or powder.

[0160] Preferably, the fused filament manufacturing process comprises the steps of: i) feeding a mixture (M) to a nozzle, the mixture (M) comprising an inorganic powder (IP) and a binder (B), the binder (B) comprising at least one polyoxymethylene (POM); ii) Mixture (M) at temperature (T M ) and iii) depositing the mixture (M) in a build chamber using layer-based additive techniques to form at least one three-dimensional green body (GB); Includes.

[0161] The above-mentioned embodiments and preferences regarding at least one three-dimensional green body (GB) comprising an inorganic powder (IP) and a binder (B), the binder (B) comprising at least one polyoxymethylene (POM), apply analogously to the mixture (M).

[0162] The mixture (M) can be prepared by any method known to those skilled in the art. Preferably, the mixture (M) is prepared by melting the binder (B) and mixing with the inorganic powder (IP) and, if necessary, at least one dispersant. For example, the binder (B) can be melted in a twin-screw extruder, preferably at a temperature of 150 to 220 ° C, in particular at 170 to 200 ° C. The inorganic powder (IP) is then metered in the required amount into the molten stream of the binder (B) at a temperature in the same range. The inorganic powder (IP) advantageously comprises at least one dispersant on its surface. However, the mixture (M) of the invention can also be prepared by melting the binder (B) and, optionally, at least one dispersant in the presence of the inorganic powder (IP) at a temperature of 150 to 220 ° C, preferably at 170 to 200 ° C.

[0163] A particularly preferred device for metering the inorganic powder (IP) comprises as an essential element a transport screw arranged in a heatable metal cylinder, which transports the inorganic powder (IP) into the melt of the binder (B). The process described above has the advantage over mixing the components at room temperature and then extruding at elevated temperature that degradation of the polyoxymethylene (POM) used as binder as a result of the high shear forces that occur in this variant is largely avoided.

[0164] Step b) In step b), 0.01-5.0 wt. % of anhydrous oxalic acid is provided, based on the total weight of the at least one three-dimensional green body (GB).

[0165] Preferably, in step b), 0.05 to 2.5 wt. % and more preferably 0.1 to 1.5 wt. % of anhydrous oxalic acid is provided, based on the total weight of the at least one three-dimensional green body (GB).

[0166] The anhydrous oxalic acid preferably has a purity of 95% or more, more preferably 98% or more.

[0167] Therefore, another object of the present invention is a process in which the anhydrous oxalic acid has a purity of at least 95%, preferably at least 98%.

[0168] Thus, the anhydrous oxalic acid preferably comprises at most 5% by weight, more preferably at most 2% by weight, most preferably at most 1% by weight and particularly preferably 0% by weight of water, based on the total weight of the anhydrous oxalic acid.

[0169] Further suitable acids which may preferably be provided in place of anhydrous oxalic acid in step b) are at least one acid selected from the group consisting of acetic acid, citric acid, malonic acid, succinic acid, maleic acid, glycolic acid and lactic acid.

[0170] However, it is also possible to provide in step b) 0.01 to 5.0% by weight of anhydrous oxalic acid, based on the total weight of the at least one three-dimensional green body (GB), together with at least one acid selected from the group consisting of acetic acid, citric acid, malonic acid, succinic acid, maleic acid, glycolic acid and lactic acid.

[0171] Process c) In step c) at least one three-dimensional green body (GB) is treated with anhydrous oxalic acid in the presence of an inert gas at a temperature (T1) below 140°C.

[0172] Preferably, in step c) the at least one three-dimensional green body (GB) is treated with anhydrous oxalic acid at a temperature (T1) between 110 and 135°C, more preferably at a temperature (T1) between 110 and 130°C.

[0173] However, in step c), it is also possible to treat at least one three-dimensional green body (GB) with at least one acid selected from the group consisting of acetic acid, citric acid, malonic acid, succinic acid, maleic acid, glycolic acid and lactic acid in the presence of an inert gas at a temperature (T1) below 140 ° C, preferably at a temperature (T1) between 110 and 135 ° C, more preferably at a temperature (T1) between 110 and 130 ° C. Furthermore, in step c), it is also possible to treat at least one three-dimensional green body (GB) with anhydrous oxalic acid and at least one acid selected from the group consisting of acetic acid, citric acid, malonic acid, succinic acid, maleic acid, glycolic acid and lactic acid in the presence of an inert gas at a temperature (T1) below 140 ° C, preferably at a temperature (T1) between 110 and 135 ° C, more preferably at a temperature (T1) between 110 and 130 ° C.

[0174] The inert gas can be any gas that is substantially free of oxygen and water, and is preferably selected from the group consisting of hydrogen, nitrogen and the noble gases, more preferably nitrogen and argon.

[0175] Therefore, another object of the present invention is a process, wherein the inert gas is selected from the group consisting of hydrogen, nitrogen and the noble gases.

[0176] Step c) is preferably carried out in a heating chamber (HC), which is for example comprised in a furnace.

[0177] The flow rate of the inert gas in step c) is preferably 0 to 5 V. HC h -1 where V HC is the volume of the heating chamber.

[0178] Preferably, the debinding time t 脱バインダー is calculated according to the following formula (X): t 脱バインダー = x -1 h mm -1 d mm (X) where x is 1 to 3 and d is the thickness of the thickest wall of the at least one three-dimensional green body.

[0179] In the context of the present invention, the term "thickest wall of at least one three-dimensional green body" means the thickest continuous volume from the exterior to the exterior of the at least one three-dimensional green body.

[0180] In a preferred embodiment, a furnace is used that includes at least two heating chambers. In this case, anhydrous oxalic acid is placed in a first heating chamber (HC1) and at least one three-dimensional green body is placed in a second heating chamber (HC2). Both heating chambers (HC1) and (HC2) are heated to a temperature (T1) below the sublimation temperature of anhydrous oxalic acid, below 140°C, preferably between 110 and 135°C, more preferably between 110 and 130°C.

[0181] In a particularly preferred embodiment, the temperature of the heating chamber (HC2) is 0 to 20°C, preferably 5 to 15°C, more preferably 7 to 12°C lower than the temperature of the heating chamber (HC1), provided that the temperatures of all the heating chambers are within the above ranges.

[0182] Therefore, another object of the present invention is an apparatus in which the method of the present invention is carried out, wherein this apparatus comprises a first heating chamber (HC1) and a second heating chamber (HC2), wherein the first heating chamber (HC1) contains anhydrous oxalic acid and the second heating chamber (HC2) contains at least one three-dimensional green body (GB), and wherein both the first and second heating chambers (HC1, HC2) are heated to a temperature (T1) below 140°C, the temperature of the heating chamber (HC2) being 0-20°C lower than the temperature of the heating chamber (HC1).

[0183] In a further preferred embodiment, a furnace containing only one heating chamber can also be used. In this case, anhydrous oxalic acid and at least one three-dimensional green body are placed in the same heating chamber, where the heating chamber is also heated to a temperature (T1) lower than the sublimation temperature of anhydrous oxalic acid, less than 140°C, preferably a temperature (T1) between 110 and 135°C, more preferably a temperature (T1) between 110 and 130°C. In this case, it is also possible to form an atmosphere with a controlled concentration of anhydrous oxalic acid.

[0184] In addition, in place of oxalic anhydride, at least one acid selected from the group consisting of acetic acid, citric acid, malonic acid, succinic acid, maleic acid, glycolic acid, and lactic acid can be placed in these furnaces. Furthermore, it is also possible to place oxalic anhydride and at least one acid selected from the group consisting of acetic acid, citric acid, malonic acid, succinic acid, maleic acid, glycolic acid, and lactic acid in the furnace.

[0185] By carrying out step c), a part of the binder (B) is preferably removed. Preferably, in step c), the binder (B) is removed to the extent of at least 90% by weight, more preferably at least 95% by weight, based on the total weight of the binder (B) contained in the at least one three-dimensional green body (GB) provided in step a).

[0186] After removal of the binder (B) in step c), the resulting three-dimensional object is called a "three-dimensional Brownian body". The three-dimensional Brownian body comprises the inorganic powder (IP) and the part of the binder (B) that was not removed during debinding. Those skilled in the art know that three-dimensional Brownian bodies that comprise ceramic materials as inorganic powder (IP) are also called three-dimensional white bodies. However, for the purposes of the present invention, the terms "three-dimensional Brownian body" and "three-dimensional white body" are used synonymously and are interchangeable.

[0187] Another object of the present invention is therefore also a three-dimensional Brownian body (BB) prepared by the method according to the invention comprising at least steps a) to c).

[0188] In a preferred embodiment, the at least one three-dimensional Brownian body (BB) formed in step c) comprises 90-100 vol. % of the inorganic powder (IP) and 0-10 vol. % of the binder (B), preferably 95-100 vol. % of the inorganic powder (IP) and 0-5 vol. % of the binder (B), based on the total volume of the at least one three-dimensional Brownian body (BB).

[0189] It is known to those skilled in the art that at temperature (T1) the inorganic powder (IP) contained in the at least one three-dimensional green body (GB) can undergo chemical and / or physical reactions, in particular the particles of the inorganic powder (IP) can fuse and the inorganic powder can undergo a solid-state phase transition.

[0190] The same applies to the binder (B). During step c), the composition of the binder (B) can change.

[0191] Consequently, in one embodiment of the invention, the inorganic powder (IP) and / or binder (B) contained in at least one three-dimensional green body (GB) is different from the inorganic powder (IP) and / or binder (B) contained in the three-dimensional Brownian body (BB) obtained in step c) of the method.

[0192] Step d) In one embodiment of the present invention, an additional step d) may be carried out.

[0193] Preferably, step c) is followed by step d), in which at least one three-dimensional Brownian body (BB) is sintered to form at least one three-dimensional sintered body (SB). Step d) is also called sintering. For the purposes of the present invention, the terms "step d) of the method" and "sintering" are synonymous and are used interchangeably throughout the present invention.

[0194] The three-dimensional object after sintering is a three-dimensional sintered body. The three-dimensional sintered body comprises the inorganic powder (IP) and is substantially free of the binder (B).

[0195] "Substantially free of binder (B)" according to the present invention means that the three-dimensional sintered body (SB) contains less than 5 vol. %, preferably less than 2 vol. %, particularly preferably less than 0.5 vol. %, and most preferably less than 0.01 vol. % of binder (B), based on the total volume of the three-dimensional sintered body.

[0196] Those skilled in the art know that during the sintering process, inorganic powders (IP) are sintered together to obtain sintered inorganic powders. Furthermore, during the sintering process, inorganic powders (IP) can undergo chemical and / or physical reactions. As a result, inorganic powders (IP) contained in a three-dimensional Brownian body are usually different from sintered inorganic powders contained in a three-dimensional sintered body.

[0197] In one embodiment of the present invention, after process step c) and before process step d), the three-dimensional Brownian body obtained in process step c) is heated preferably at a temperature of 250 to 700° C., particularly preferably at 250 to 600° C., preferably for 0.1 to 12 hours, particularly preferably for 0.3 to 6 hours, in order to completely remove residual binder (B).

[0198] The temperature, duration and atmosphere during step d) depend on the inorganic powder contained in the mixture (M). The temperature program, duration and atmosphere of the sintering process are generally adapted to the needs of the inorganic powder (IP) contained in the mixture (M). Suitable conditions for step d) of the method are known to the person skilled in the art.

[0199] Generally, step d) is carried out under an atmosphere of a gas inert with respect to the inorganic powder (IP) and the binder (B). Typical inert gases are, for example, nitrogen and / or argon.

[0200] Depending on the inorganic powder (IP) contained in the mixture (M), it is also possible to carry out step d) of the process in air, under vacuum or under a hydrogen atmosphere.

[0201] The temperature (T2) in step d) of the method is generally in the range from 750 to 1600°C, preferably from 800 to 1500°C, particularly preferably from 850 to 1450°C.

[0202] Preferably, step d) is carried out in a heating chamber, which is the same as the heating chamber (HC) in which step c) is carried out.

[0203] Therefore, another object of the present invention is to provide a method for producing ... cellular endothelial cell comprising at least the following steps: a) providing at least one three-dimensional green body (GB), said at least one three-dimensional green body (GB) comprising an inorganic powder (IP) and a binder (B), said binder (B) being (b1) at least one polyoxymethylene (POM) and b) providing 0.01 to 5.0 wt. % anhydrous oxalic acid based on the total weight of the at least one three-dimensional green body (GB); c) treating said at least one three-dimensional green body (GB) with anhydrous oxalic acid in the presence of an inert gas at a temperature (T1) below 140° C. to obtain a three-dimensional Brownian body (BB); c1) removing anhydrous oxalic acid; d) treating the three-dimensional Brownian body (BB) in a heating chamber (HC) at a temperature (T2) in the range of 750-1600°C to obtain at least one three-dimensional sintered body (SB), the heating chamber (HC) being the same as the heating chamber (HC) in which step c) is carried out; The method for producing at least one three-dimensional sintered body (SB) comprises:

[0204] The present invention will now be described with reference to examples, but is not limited thereto. EXAMPLES

[0205] Equipment: Furnace: Carbolite Gero, horizontal tube furnace, maximum temperature 1200℃, hydrogen KIT, capacity 2.7L Balance: KERN PCB 3500-2.

[0206] Materials and samples: Oxalic Acid Anhydrous: 98%, Water Free, Arco Organics, CAS:144-62-7.

[0207] 3D green bodies produced by the Fused Filament Fabrication (FFF) process (GB-FFF): For the production of three-dimensional green bodies in the form of cubes (25mm x 25mm x 25mm) by the fused filament manufacturing process, Ultrafuse 316L filament was used. Ultrafuse 316L filament is a metal-polymer composite filament containing 316L stainless steel and POM as binder. The printer used is based on a conventional FFF printing system (Ultimaker S5, AIM 3D ExAM255) with an extrusion system that allows the individual selection of extrusion parameters. The printing bed is coated with a thin layer of a water-soluble adhesion promoter (Magigoo ProMetal) like adhesive. The three-dimensional body is printed layer by layer, each layer consisting of lines that can be connected or disconnected. The nozzle diameter used was 0.2mm-0.8mm and the printing temperature was varied from 200°C to 260°C. The printed three-dimensional green body (GB-FFFF) was released from the printing bed by dissolving the adhesive and immersing the printing bed in water overnight.

[0208] 3D Green Body Manufactured by Metal Injection Molding (MIM) (GB-MIM): Three-dimensional green bodies produced by metal injection molding (MIM) (GB-MIM) are made from Catamold 17-4PH Plus, a moldable metal-polymer composite granule for the production of sintered parts of precipitation hardenable stainless steel type 17-4PH with POM as binder on an Arburg 270S under standard process conditions. Starting values ​​are shown in Table 1.

[0209] [Table 1]

[0210] nitrogen: Purity 5.0.

[0211] Test description: Inventive Examples 1a and 1b (I1a and I1b) Process a) Two such three-dimensional green bodies (GB-FFF; I1a) and two other three-dimensional green bodies (GB-MIM; I1b) were provided.

[0212] Total mass of two three-dimensional green bodies (GB-FFF): 150.0 g, Total mass of the two three-dimensional green bodies (GB-MIM): 25.6 g; Total mass of the three-dimensional body: 175.6g.

[0213] Step b) 5.2 g of anhydrous oxalic acid (corresponding to 2.96% by weight based on the total weight of the three-dimensional green body) was provided.

[0214] Process c) The three-dimensional green bodies (GB-FFF) and (GB-MIM) were treated with anhydrous oxalic acid for 12 h at a temperature (T1) of 120° C. using 14 L / h nitrogen in the heating chamber (HC) of a 2.7 L tube furnace.

[0215] Inventive Examples 2a and 2b (I2a and I2b) Process a) Two such 3D green bodies (GB-FFF; I2a) and two other 3D green bodies (GB-MIM; I2b) were provided.

[0216] Total mass of the two three-dimensional green bodies (GB-FFF): 150.7g, Total mass of the two three-dimensional green bodies (GB-MIM): 25.6 g; Total mass of the three-dimensional body: 176.3g.

[0217] Step b) 3.6 g of anhydrous oxalic acid (corresponding to 2.04% by weight based on the total weight of the three-dimensional green body) was provided.

[0218] Process c) The three-dimensional green bodies (GB-FFF) and (GB-MIM) were treated with anhydrous oxalic acid for 6 h at a temperature (T1) of 120° C. using 14 L / h nitrogen in the heating chamber (HC) of a 2.7 L tube furnace.

[0219] Inventive Examples 3a and 3b (I3a and I3b) Process a) Two such 3D green bodies (GB-FFF; I2a) and two other 3D green bodies (GB-MIM; I2b) were provided.

[0220] Total mass of the two three-dimensional green bodies (GB-FFF): 150.7g, Total mass of the two three-dimensional green bodies (GB-MIM): 25.6 g; Total mass of the three-dimensional body: 176.3g.

[0221] Step b) 1.8 g of anhydrous oxalic acid (corresponding to 1.02% by weight based on the total weight of the three-dimensional green body) was provided.

[0222] Process c) The three-dimensional green bodies (GB-FFF) and (GB-MIM) were treated with anhydrous oxalic acid for 6 h at a temperature (T1) of 120° C. using 14 L / h nitrogen in the heating chamber (HC) of a 2.7 L tube furnace.

[0223] Comparative Examples 4a and 4b (C4a and C4b) Process a) Two such 3D green bodies (GB-FFF; I2a) and two other 3D green bodies (GB-MIM; I2b) were provided.

[0224] Total mass of the two 3D green bodies (GB-FFF): 150.2g, Total mass of the two three-dimensional green bodies (GB-MIM): 25.6 g; Total mass of the three-dimensional body: 175.8g.

[0225] Step b) 29.8 g of anhydrous oxalic acid was provided, corresponding to 16.95% by weight based on the total weight of the three-dimensional green body.

[0226] Process c) The three-dimensional green bodies (GB-FFF) and (GB-MIM) were treated with anhydrous oxalic acid for 12 h at a temperature of 160° C. using 14 L / h nitrogen in the heating chamber (HC) of a 2.7 L tube furnace.

[0227] The results are shown in Table 2.

[0228] [Table 2]

Claims

1. At least the following steps: a) providing at least one three-dimensional green body (GB), said at least one three-dimensional green body (GB) comprising an inorganic powder (IP) and a binder (B), said binder (B) being (b1) at least one polyoxymethylene (POM); and b) providing 0.01 to 5% by weight of anhydrous oxalic acid based on the total weight of the at least one three-dimensional green body (GB); c) treating said at least one three-dimensional green body (GB) with anhydrous oxalic acid in the presence of an inert gas at a temperature (T1) below 140° C.; A method for treating at least one three-dimensional green body (GB), comprising:

2. i) the inorganic powder (IP) is a powder of at least one inorganic material selected from the group consisting of metals, metal alloys and ceramic materials, preferably the inorganic powder (IP) is a metal or a metal alloy, particularly preferably the inorganic powder (IP) is a metal, and / or ii) the particle size of said inorganic powder (IP) is between 0.1 and 80 μm, as measured by laser diffraction; The method of claim 1.

3. i) in step b), 0.05 to 2.5% by weight, preferably 0.1 to 1.5% by weight, of anhydrous oxalic acid is provided, based on the total weight of the at least one three-dimensional green body (GB); and / or ii) in step c) said at least one three-dimensional green body (GB) is treated with anhydrous oxalic acid at a temperature (T1) between 110 and 135°C, preferably between 110 and 130°C, The method according to claim 1 or 2.

4. The at least one three-dimensional green body (GB) i) comprising 30-70% by volume of said inorganic powder (IP) and 30-70% by volume of said binder (B), preferably 45-65% by volume of said inorganic powder (IP) and 35-55% by volume of said binder (B), based on the total volume of said at least one three-dimensional green body (GB); and / or ii) prepared by injection molding or a fused filament fabrication process, preferably a fused filament fabrication process; 4. The method according to any one of claims 1 to 3.

5. The binder (B) is (b1) 50 to 96% by weight of at least one polyoxymethylene (POM), based on the total weight of the binder (B); (b2) 2 to 35% by weight of at least one polyolefin (PO), based on the total weight of the binder (B); (b3) 2 to 40% by weight, based on the total weight of said binder (B), of at least one further polymer (FP); The method of any one of claims 1 to 4, comprising:

6. 6. The method of claim 1, wherein the inert gas is selected from the group consisting of hydrogen, nitrogen and the noble gases.

7. 7. The method according to any one of claims 1 to 6, wherein the anhydrous oxalic acid has a purity of 95% or more, preferably 98% or more.

8. 8. The method according to any one of claims 1 to 7, wherein step c) is carried out in a heating chamber (HC).

9. During step c), the gas flow rate of the inert gas is 0 to 5 V ＨＣ h －１ and V ＨＣ 9. The method according to claim 8, wherein: is the volume of the heating chamber (HC).

10. 10. The method according to claim 1, wherein in step c) at least one three-dimensional Brownian body (BB) is formed.

11. 11. The method according to any one of claims 1 to 10, wherein step c) is followed by step d), in which the at least one three-dimensional Brownian body (BB) is sintered to form at least one three-dimensional sintered body (SB).

12. 12. The method according to claim 11, wherein step d) is carried out in a heating chamber (HC), which is the same heating chamber (HC) in which step c) is carried out.

13. A three-dimensional Brownian body (BB) prepared by the method according to any one of claims 1 to 10.

14. 14. The three-dimensional Brownian body (BB) according to claim 13, comprising 90-100% by volume of inorganic powder (IP) and 0-10% by volume of binder (B), based on the total volume of the three-dimensional Brownian body (BB).

15. A three-dimensional sintered body (SB) prepared by the method according to claim 11.

16. An apparatus for carrying out the method according to any one of claims 1 to 10, comprising: The apparatus comprises at least a first heating chamber (HC1) and a second heating chamber (HC2), the first heating chamber (HC1) containing anhydrous oxalic acid and the second heating chamber (HC2) containing at least one three-dimensional green body (GB), both the first and second heating chambers (HC1, HC2) being heated to a temperature (T1) less than 140°C, the temperature of the heating chamber (HC2) being 0-20°C lower than the temperature of the heating chamber (HC1).

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