EP3060362A2

EP3060362A2 - Molding material mixtures containing an oxidic boron compound and method for the production of molds and cores

Info

Publication number: EP3060362A2
Application number: EP14796675.8A
Authority: EP
Inventors: Heinz DETERS; Martin Oberleiter; Henning ZUPAN
Original assignee: ASK Chemicals GmbH
Current assignee: ASK Chemicals GmbH
Priority date: 2013-10-22
Filing date: 2014-10-21
Publication date: 2016-08-31
Anticipated expiration: 2034-10-21
Also published as: SI3060362T1; EP3060362B1; CN105828973B; BR112016008892B1; KR20160088315A; HUE048328T2; DE102013111626A1; PL3060362T3; RU2016118813A3; ES2778075T3; WO2015058737A3; RU2016118813A; US9901975B2; WO2015058737A2; RU2703746C2; JP6594308B2; US20160361756A1; CN105828973A; MX2016005300A; MX359164B

Abstract

The invention relates to molding material mixtures containing a molding base material, water glass, amorphous silicon dioxide and an oxidic boron compound, and to the production of molds and cores, in particular for metal casting.

Description

Mixtures of molding materials containing an oxidic boron compound and methods for producing molds and cores

The invention relates to molding mixtures for the foundry industry containing one or more powdery oxidic boron compounds in combination with refractory molding materials, a water glass-based binder system and amorphous particulate silica, in particular for the production of castings of aluminum, and a method for producing molds and cores from the molding material mixtures , which easily break up after metal casting.

State of the art

Molds are essentially composed of cores and molds, which represent the negative molds of the casting to be produced. These

Cores and molds are made of a refractory material, such as quartz sand, and a suitable binder that gives the mold after removal from the mold sufficient mechanical strength. Thus, for the production of casting molds, a refractory molding base material is used, which is coated with a suitable binder. The refractory molding base material is preferably present in a free-flowing form, so that it can be filled into a suitable mold and compacted there. The binder produces a firm cohesion between the particles of the molding base material, so that the casting mold obtains the required mechanical stability.

Molds must meet different requirements. In the casting process itself, they must first have sufficient strength and temperature resistance in order to be able to absorb the liquid metal in the cavity formed from one or more casting molds. After the start of the solidification process, the mechanical stability of the casting is ensured by a solidified metal layer which forms along the walls of the casting mold. The material of the casting mold must now decompose under the influence of the heat given off by the metal in such a way that it loses its mechanical strength, that is to say the cohesion between individual particles of the refractory material is removed. Ideally, the mold decays back to a fine sand that can be easily removed from the casting.

Confirmation copy | More recently, more and more frequently, it is required that, during the production of the casting molds and during the production of the casting and cooling, as far as possible no emissions in the form of C0 ₂ or hydrocarbons arise in order to protect the environment and the odor nuisance of the environment by hydrocarbons , mainly due to aromatic hydrocarbons. In order to meet these requirements, inorganic bonding systems have been developed or developed in recent years, the use of which results in that emissions of CO ₂ and hydrocarbons in the production of metal molds can be avoided or at least significantly minimized. However, the use of inorganic binder systems is often associated with other disadvantages, which are described in detail in the following.

Inorganic binders have the disadvantage, in comparison to organic binders, that the casting molds produced therefrom have relatively low strengths. This is especially evident immediately after the removal of the mold from the tool. Good strength at this time, however, are particularly important for the production of complicated and / or thin-walled moldings and their safe handling. The resistance to air humidity is also significantly reduced compared to organic binders.

EP 1802409 B1 discloses that higher immediate strengths and higher resistance to atmospheric moisture can be achieved by using a refractory molding base, a water glass based binder and additions of particulate amorphous silica. This addition ensures a safe handling of even complicated casting molds.

Inorganic binder systems have the further disadvantage over organic binder systems that the coring behavior, ie the ability of the casting mold to disintegrate rapidly (under mechanical stress) into a readily pourable form after casting metal, in purely inorganically produced casting molds (for example, the waterglass as Binder) is often inferior to molds made with an organic binder. This latter property, a poor Entkernverhalten is particularly disadvantageous when thin-walled or filigree or complex molds are used, which can be difficult to remove after casting in principle. As an example, so-called water jacket cores can be attached here, which are necessary in the production of certain areas of an internal combustion engine.

Attempts have already been made to add organic components to the molding material mixture which pyrolyze / react under the influence of the hot metal and thereby facilitate the disintegration of the casting mold after casting by pore formation. An example of this is the DE 2059538 (= GB 1299779 A). However, the amounts of glucose syrup added here are very large and are therefore associated with a significant emission of C0 ₂ and other pyrolysis products.

Problems of the prior art and task

The previously known inorganic binder systems for foundry purposes still have room for improvement. Above all, it is desirable to develop an inorganic binder system which:

(a) producing no or at least a significantly reduced amount of emissions of CO2 and organic pyrolysis products (gaseous and / or aerosol, e.g., aromatic hydrocarbons, smoke) during metal casting,

(b) achieves a corresponding level of strength required in the automated manufacturing process (especially hot strengths and strengths after storage),

(C) allows a very good surface quality of the casting concerned, so that no or at least only a small post-processing is necessary, and

(D) leads to a very good disintegration property of the mold after the metal casting, so that the casting in question can be easily and without residue separated from the mold. The invention therefore an object of the invention to provide a molding material for the production of molds for metal processing is available, which particularly effectively improves the decay properties of the mold after the metal casting and at the same time reaches a strength level, which is necessary in the automated manufacturing process.

Furthermore, the production of molds with complex geometry is to be made possible, which may include, for example, thin-walled sections. Also, the mold should have a high storage stability and remain stable even at higher temperature and humidity.

Summary of the invention

The above objects are achieved by the molding material mixture, the multi-component system or the method having the features of the independent patent claims. Advantageous developments of the molding material mixture according to the invention are the subject of the dependent claims or described below. Surprisingly, it has been found that casting molds based on inorganic binders can be prepared by the addition of at least one pulverulent, oxidic boron compound to the molding material mixture, which have high strength both immediately after production and during prolonged storage.

A decisive advantage lies in the fact that the addition of pulverulent borates leads to significantly improved disintegration properties of the casting mold after the metal casting. This advantage is associated with significantly lower costs for the manufacture of a casting, in particular for castings which have a complex geometry with very small cavities, from which the casting mold must be removed.

According to one embodiment of the invention, the molding material mixture contains organic components with a proportion of up to a maximum of 0.49 wt.%, In particular up to a maximum of 0.19 wt.%, So that only very small amounts of emissions of CO2 and other pyrolysis products. For this reason, workplace exposure to employees and those living in the area can be reduced by harmful emissions. Also, the use of the form of substance mixture according to the invention makes a contribution to the reduction of climate-damaging emissions by CO2 and other organic pyrolysis products.

The molding material mixture according to the invention for the production of casting molds for metalworking comprises at least:

· A refractory base molding material; such as

• a water glass based binder and

Particulate amorphous silica; and

• one or more powdery oxidic boron compound (s). Detailed description of the invention

As a refractory molding base material, conventional and known materials can be used for the production of casting molds. Suitable examples are quartz, zirconium or chrome ore, olivine, vermiculite, bauxite, chamotte and artificial mold base materials, in particular more than 50 wt.% Quartz sand based on the refractory molding material. It is not necessary to use only new sands. In terms of resource conservation and to avoid landfill costs, it is even advantageous to use the highest possible proportion of regenerated used sand, as it is available from used forms by recycling.

A refractory base molding material is understood to mean substances which have a high melting point (melting temperature). Preferably, the melting point of the refractory base molding material is greater than 600 ° C, preferably greater than 900 ° C, more preferably greater than 1200 ° C and particularly preferably greater than 1500 ° C.

The refractory molding base material preferably makes up more than 80% by weight, in particular greater than 90% by weight, particularly preferably greater than 95% by weight, of the molding material mixture. A suitable sand is described, for example, in WO 2008/101668 A1 (= US 2010/173767 A1). Likewise suitable are regenerates which are obtainable by washing and subsequent drying of comminuted used molds. As a rule, the regenerates can make up at least about 70% by weight of the refractory molding base material, preferably at least about 80% by weight and more preferably greater than 90% by weight.

The average diameter of the refractory mold bases is generally between 100 μιη and 600 μιη, preferably between 120 μιη and 550 μιη and more preferably between 150 μιη and 500 μιη. The particle size can be e.g. determined by sieving according to DIN ISO 3310. Particularly preferred are particle shapes with the greatest length extension to the smallest linear extension (perpendicular to each other and in each case for all spatial directions) of 1: 1 to 1: 5 or 1: 1 to 1: 3, i. such as e.g. are not fibrous ig.

The refractory molding base material preferably has a free-flowing state, in particular in order to be able to process the molding material mixture according to the invention in conventional core shooting machines. The water glasses contain dissolved alkali silicates and can be prepared by dissolving glassy lithium, sodium and potassium silicates in water. The water glass preferably has a molar modulus SiO ₂ / M ₂ O (cumulative with different M's, ie in the sum) in the range of 1.6 to 4.0, in particular 2.0 to less than 3.5, where M is for Lithium, sodium and / or potassium is. The binders can also be based on water glasses which contain more than one of the alkali metal ions mentioned, for example the lithium-modified water glasses known from DE 2652421 A1 (= GB1532847 A). Furthermore, the water glasses can also contain polyvalent ions, for example the aluminum-modified water glasses described in EP 2305603 A1 (= WO 2011/042132 A1). According to a particular embodiment, a proportion of lithium ions, in particular amorphous lithium silicates, lithium oxides and lithium hydroxide, or a ratio of [Li ₂ O] / [M ₂ O] or [Li ₂ Oaktiv] / [M ₂ O] as in DE 102013106276 A1 described used. The water glasses have a solids content in the range from 25 to 65% by weight, preferably from 30 to 55% by weight, in particular from 30 to 50% by weight and very particularly preferably from 30 to 45% by weight. The solids content refers to the amount of S1O2 and M2O contained in the water glass. Depending on the application and the desired strength level, between 0.5% by weight and 5% by weight of the waterglass-based binder is used, preferably between 0.75% by weight and 4% by weight, more preferably between 1% by weight and 3.5% by weight and particularly preferably 1 to 3% by weight, in each case based on the molding base material. The data relate to the total amount of the waterglass binder, including the (in particular aqueous) solvent or diluent and the (possible) solids content (together = 100 wt.%). For the purposes of calculating the preferred total amount of waterglass, the above values are based on a solids content of 35% by weight (see examples), regardless of the actual solids content.

The term "powdery or particulate" is understood in each case to mean solid powder (including dust) or else granules which is pourable and thus also capable of sieving.

The molding material mixture according to the invention contains one or more powdery, oxidic boron compounds. The mean particle size of the oxide boron compounds is preferably less than 1 mm, preferably less than 0.5 mm, particularly preferably less than 0.25 mm. The particle size of the oxide boron compounds is preferably greater than 0.1 .mu.m, preferably greater than 1 .mu.m and more preferably greater than 5 .mu.m.

The mean particle size can be determined using a sieve analysis. The sieve residue on a sieve with a mesh size of 1.00 mm is preferably less than 5% by weight, more preferably less than 2.0% by weight and particularly preferably less than 1.0% by weight. Particularly preferably, the sieve residue, independently of the above information, is preferably less than 20% by weight, preferably less than 15% by weight, more preferably less than 10% by weight, and in particular, on a sieve with a mesh width of 0.5 mm preferably less than 5% by weight. Particularly preferably, the sieve residue, independently of the above information, is preferably less than 50% by weight, preferably less than 25% by weight and particularly preferably less than 15% by weight, on a sieve with a mesh width of 0.25 mm. The sieve residue is determined according to the machine screen method described in DIN 66165 (Part 2), wherein additionally a chain ring is used as screen aid. By oxide boron compounds are meant compounds in which the boron is present in the oxidation state +3. Furthermore, the boron is coordinated with oxygen atoms (in the first coordination sphere, ie as nearest neighbors) - either from 3 or from 4 oxygen atoms.

The oxidic boron compound is preferably selected from the group of borates, boric acids, boric anhydrides, borosilicates, borophosphates,

Borophosphosilikate and mixtures thereof, wherein the oxidic boron compound preferably contains no organic groups.

Boric acids are understood to mean orthoboric acid (empirical formula H3BO3) and meta- or polyboronic acids (empirical formula (HBO ₂ ) _n ). Orthoboric acid occurs, for example, in sources of steam and as a mineral sassolin. It can also be prepared from borates (eg borax) by acid hydrolysis. Meta- or polyboric acids can be prepared, for example, from orthoboric acid by intermolecular condensation by heating.

Boric anhydride (empirical formula B ₂ O ₃ ) can be prepared by annealing boric acids. Boric anhydride is obtained as the usually glassy, hygroscopic mass, which can then be comminuted.

Borates are derived in principle from the boric acids. They can be both natural and synthetic. Among other things, borates are built up from borate structural units in which the boron atom is surrounded by either 3 or 4 oxygen atoms as nearest neighbors. The individual structural units are usually anionic and can either be isolated within a substance, for example in the case of the orthoborate [BO ³ ] ^{3 "} , or be linked to one another, such as metaborates [BO ₂ ] ^n" _n , whose units are linked to rings or chains If one considers such a linked entity with corresponding BOB bonds, then such an entity is anionic in the overall view.

Borates containing linked BOB units are preferably used. Orthoborates are suitable but not preferred. Examples of counterions to the anionic borate units are alkali metal and / or alkaline earth cations, but also, for example, zinc cations. In the case of mono- or divalent cations, the molar molar ratio between cation and boron can be described in the following manner: ΜχΟ: B2O3, where M is the cation and x is divalent cation 1 and monovalent cation 2. The molar molar ratio of M _x O (x = 2 for M = alkali metals and x = 1 for M = alkaline earth metals): B2O3 can vary within wide limits, but it is preferably less than 10: 1, preferably less than 5: 1 and especially preferably less than 2: 1. The lower limit is preferably greater than 1:20, preferably greater than 1:10, and most preferably greater than 1: 5.

Also suitable are borates in which trivalent cations serve as counterions to the anionic borate units, for example aluminum cations in the case of aluminum borates. Natural borates are mostly hydrated, ie water is contained as structure water (as OH groups) and / or as water of crystallization (H ₂ O molecules). As an example, borax or borax decahydrate (di-sodium tetraborate decahydrate) may be considered, its empirical formula being referred to in the literature either as [Na (H ₂ O) 4] 2 [B ₄ O 5 (OH) 4] or for the sake of simplicity Na ₂ B ₄ O ₇ * 0H ₂ O is given. Both hydrated and non-hydrated borates can be used, but preferably the hydrated borates are used.

Both amorphous and crystalline borates can be used. As amorphous borates, for example, alkali or Erdalkaliboratgläser understood.

Perborates are not preferred because of their oxidative properties. In principle, the use of fluoroborates is also conceivable, but not particularly preferred in aluminum casting due to the fluorine content. Since the use of ammonium borate with an alkaline waterglass solution produces significant amounts of ammonia which endangers the health of people working in the foundry, such a substance is not preferred.

By Borosilikaten, Borophosphaten and Borophosphosilikaten connections are understood, which are usually amorphous / vitreous. In the structure of these compounds are not only neutral and / or anionic boron-oxygen coordination (eg neutral B0 ₃ units or anionic BO ^- units), but also neutral and / or anionic silicon oxygen and / or phosphorus Oxygen Coordination - the silicon is in the +4 oxidation state and the phosphorus is in the +5 oxidation state. The coordinations can be linked by bridging oxygen atoms, such as Si-OB or POB. In the structure of the borosilicates, borophosphates and borophosphosilicates metal oxides, in particular alkali and alkaline earth metal oxides may be incorporated, which are known as

Network modifiers serve. The proportion of boron (calculated as B2O3) in the borosilicates, borophosphates and borophosphosilicates is preferably greater than 15% by weight, preferably greater than 30% by weight, particularly preferably greater than 40% by weight, based on the total mass of the corresponding borosilicate , Borophosphate or borophosphosilicate.

Of the group of borates, boric acids, boric anhydride, borosilicates, borophosphates and / or borophosphosilicates, however, the borates, borophosphates and borophosphosilicates and in particular the alkali and Erdalkaliborate, are clearly preferred. One reason for this selection is due to the strong hygroscopicity of the boric anhydride, which impairs the possible use as a powder additive during prolonged storage of the same. In addition, casting experiments with an aluminum melt have shown that borates lead to significantly better casting surfaces than the boric acids, so the latter are less preferred. Particular preference is given to using borates. Particular preference is given to using alkali metal and / or alkaline-earth borates, of which sodium borates and / or calcium borates are preferred.

Surprisingly, it has been found that even very minor additions to the molding material mixture reduce the disintegration capability of the mold after exposure to temperature, i. after metal casting, especially after aluminum casting, significantly improve. The proportion of the oxidic boron compound, based on the refractory molding base material, is preferably less than 1.0% by weight, preferably less than 0.4% by weight, more preferably less than 0.2% by weight, particularly preferably less than 0.1% by weight and especially more preferably less than 0.075% by weight. The lower limit is preferably greater than 0.002 in each case

% By weight, preferably greater than 0.005% by weight, more preferably greater than 0.01% by weight and particularly preferably greater than 0.02% by weight. It has also surprisingly been found that alkaline earth borates, particularly calcium metaborate, increase the strengths of molds and / or cores cured with acidic gases such as CO2. It has also surprisingly been found that the moisture resistance of the molds and / or cores is improved by the addition of oxidic boron compounds according to the invention.

The molding material mixture according to the invention contains a proportion of a particulate amorphous silicon dioxide in order to increase the strength level of the casting molds produced with such molding material mixtures. An increase in the strength of the casting molds, in particular the increase of the hot strengths, can be advantageous in the automated production process. Synthetically produced amorphous silica is particularly preferred.

The particle size of the amorphous silicon dioxide is preferably less than 300 μm, preferably less than 200 μm, particularly preferably less than 00 μm, and has e.g. an average primary particle size between 0.05 μιη and 10 pm. The sieve residue of the particulate amorphous S1O2 when passing through a 125 μm sieve (120 mesh) is preferably not more than 10% by weight, more preferably not more than 5% by weight, and most preferably not more than 2% by weight. , Regardless thereof, the sieve residue on a sieve with a mesh size of 63 μιη less than 10 wt .-%, preferably less than 8 wt.%. The sieve residue is determined according to the machine screen method described in DIN 66165 (Part 2), whereby a chain ring is additionally used as screen aid.

The particulate amorphous silica preferably used according to the present invention has a water content of less than 15% by weight, in particular less than 5% by weight and particularly preferably less than 1% by weight. The particulate amorphous S1O2 is used as a powder (including dusts).

As amorphous S1O2 both synthetically produced and naturally occurring silicas can be used. The latter are known, for example, from DE 102007045649, but are not preferred, since they usually contain not inconsiderable crystalline fractions and are therefore classified as carcinogenic. Synthetic is understood to mean non-naturally occurring amorphous S1O2, that is to say the production of which comprises a consciously conducted chemical reaction, as is caused by a human, for example, the preparation of silica sols by ion exchange processes from alkali silicate solutions, the precipitation from alkali silicate solutions, the flame hydrolysis of silicon tetrachloride, the reduction of quartz sand with coke in an electric arc furnace in the production of ferrosilicon and silicon. The amorphous Si0 ₂ prepared by the latter two methods is also referred to as pyrogenic Si0 ₂ .

Occasionally, synthetic amorphous silica is understood to mean only precipitated silica (CAS No. 1 12926-00-8) and Si0 ₂ produced by flame hydrolysis (Pyrogenic Silica, Fumed Silica, CAS No. 1 12945-52-5), while in the case of ferrosilicon or silicon-produced product only as amorphous silica (Silica Fume, Microsilica, CAS No. 69012-64-12) is called. For the purposes of the present invention, the product formed in the production of ferrosilicon or silicon is also understood as amorphous SiO ₂ .

Preference is given to using precipitated silicas and pyrogenic silicon dioxide, ie flame-hydrolysis or arc-prepared silica. Particular preference is given to using amorphous silicon dioxide produced by thermal decomposition of ZrSiO ₄ (described in DE 102012020509) and SiO ₂ produced by oxidation of metallic Si by means of an oxygen-containing gas (described in DE 102012020510). Also preferred is quartz glass powder (mainly amorphous silicon dioxide), which has been prepared by melting and rapid re-cooling of crystalline quartz, so that the particles are spherical and not splintered (described in DE 10201202051 1). The mean primary particle size of the particulate amorphous silicon dioxide can be between 0.05 μm and 10 μm, in particular between 0.1 μm and 5 μm, particularly preferably between 0.1 μm and 2 μm. The primary particle size can be determined, for example, by means of dynamic light scattering (eg Horiba LA 950) and checked by scanning electron microscope images (SEM images with, for example, Nova NanoSEM 230 from FEI). Furthermore, details of the primary particle shape up to the order of 0.01 μm could be visualized with the aid of SEM images. The silica samples were dispersed in distilled water for SEM measurements and then coated on a copper tape-bonded aluminum holder before the water was evaporated. Furthermore, the specific surface area of the particulate amorphous silicon dioxide was determined by means of gas adsorption measurements (BET method) according to DIN 66131. The specific surface area of the particulate amorphous SiO 2 is between 1 and 200 m ² / g, in particular between 1 and 50 m ² / g, particularly preferably between 1 and 30 m ² / g. If necessary. The products can also be mixed, for example to obtain specific mixtures with certain particle size distributions.

Depending on the production method and producer, the purity of the amorphous S1O2 can vary greatly. Suitable grades having a content of at least 85% by weight of silicon dioxide have proven to be suitable, preferably of at least 90% by weight and more preferably of at least 95% by weight. Depending on the application and the desired strength level, between 0.1% by weight and 2% by weight of the particulate amorphous SiO 2 are used, preferably between 0.1% by weight and 1.8% by weight, particularly preferably between 0.1% by weight. and 1, 5 wt.%, Each based on the molding material.

The ratio of water glass binder to particulate amorphous silica can be varied within wide limits. This offers the advantage of greatly improving the initial strength of the cores, ie the strength immediately after removal from the tool, without significantly affecting the ultimate strengths. This is of great interest especially in light metal casting. On the one hand, high initial strengths are desired in order to be able to easily transport the cores after their production or to assemble them into whole core packages; on the other hand, the final strengths should not be too high to avoid difficulties in core decay after casting, ie the molding material should be able to be easily removed from the cavities of the mold after casting. Based on the total weight of the binding agent of water glass (including diluent or solvent), the amorphous SiO 2 is preferably present in a proportion of from 1 to 80% by weight, preferably from 2 to 60% by weight, more preferably from 3 to 55% by weight. and more preferably between 4 to 50% by weight. Or, independently of this, based on the ratio of solids content of the water glass (based on the oxides, ie total mass of alkali metal oxide and silicon dioxide) to amorphous S1O2 of 10: 1 to 1: 1, 2 (parts by weight) preferred. The addition of the amorphous silicon dioxide can be carried out according to EP 1802409 B1 both before and after the binder addition directly to the refractory material, but it can also, as described in EP 1884300 A1 (= US 2008/029240 A1), first a premix of S1O2 with at least one Part of the binder or sodium hydroxide solution are prepared and then added to the refractory material. The binder or binder portion which may still be present and which is not used for the premix can be added to the refractory material before or after the addition of the premix or together with it. Preferably, the amorphous S1O2 is added to the refractory prior to binder addition.

In a further embodiment, barium sulfate may be added to the molding material mixture in order to further improve the surface of the casting, in particular of aluminum. The barium sulfate can be synthetically produced as well as natural

Barium sulfate, i. be added in the form of minerals containing barium sulfate, such as barite or barite. This as well as other features of the suitable barium sulfate and of the molding material mixture produced therewith are described in greater detail in DE 102012104934 and the disclosure content thereof is hereby also incorporated herein by reference

Property rights. The barium sulfate is preferably used in an amount of 0.02 to 5.0% by weight, more preferably 0.05 to 3.0% by weight, particularly preferably 0.1 to 2.0% by weight, or 0.3 to 0 , 99% by weight, in each case based on the entire molding material mixture added.

In a further embodiment, at least aluminum oxides and / or aluminum / silicon mixed oxides in particulate form or metal oxides of aluminum and zirconium in particulate form in concentrations between 0.05 wt.% And 4.0 wt.%, Preferably between 0.1 Wt.% And 2.0 wt.%, Particularly preferably between 0.1 wt.% And 1, 5 wt.% And particularly preferably between 0.2 wt.% And 1, 2 wt.%, Each based on the molding material , the molding material mixture according to the invention are / are added, in particular via the additive component (A), as described in more detail in DE 1020121 13073 and DE 1020121 13074. In this respect, these references are also made by referencing as a revelation of the present intellectual property right. Through such additions castings, in particular made of iron or steel with very high surface quality can be obtained after the casting of metal, so that after the removal of the casting mold little or no post-processing of the surface of the casting is required.

In a further embodiment, the molding material mixture according to the invention may comprise a phosphorus-containing compound. This addition is preferred for very thin-walled sections of a mold. These are preferably inorganic phosphorus compounds in which the phosphorus is preferably present in the oxidation state +5.

The phosphorus-containing compound is preferably in the form of a phosphate or phosphorus oxide. The phosphate can be present as alkali metal or as alkaline earth metal phosphate, with alkali metal phosphates and especially the sodium salts being particularly preferred.

As phosphates, both orthophosphates and polyphosphates,

Pyrophophates or metaphosphates are used. The phosphates can be prepared, for example, by neutralization of the corresponding acids with a corresponding base, for example an alkali metal base, such as NaOH, or optionally also an alkaline earth metal base, wherein not necessarily all negative charges of the phosphate must be saturated by metal ions. It is possible to use both the metal phosphates and the metal hydrogen phos- phates as well as the metal dihydrogen phosphates, for example Na ₃ PO ₄ , Na ₂ HPO ₄ , and NaH ₂ PO ₄ . Likewise, the anhydrous phosphates as well as hydrates of the phosphates can be used. The phosphates can be incorporated in the molding material mixture both in crystalline and in amorphous form.

Polyphosphates are understood in particular to be linear phosphates which comprise more than one phosphorus atom, the phosphorus atoms being connected to one another via oxygen bridges in each case. Polyphosphates are obtained by condensation of orthophosphate ions with elimination of water, so that a linear chain of P0 ₄ tetrahedra is obtained, which are each connected via corners. Polyphosphates have the general formula (0 (PO ₃ ) n) ^{(n + 2) "} where n is the chain length

Polyphosphate may comprise up to several hundred P0 ₄ tetrahedra. However, polyphosphates with shorter chain lengths are preferably used. N preferably has values of 2 to 100, particularly preferably 5 to 50. It is also possible to use higher-condensed polyphosphates, ie

Polyphosphates in which the P0 ₄ tetrahedra are connected to each other over more than two corners and therefore exhibit polymerization in two or three dimensions.

Metaphosphates are understood to mean cyclic structures composed of P0 ₄ tetrahedra linked together by vertices. Metaphosphates have the general formula ((P0 ₃ ) n) ^{n "} , where n is at least 3. Preferably, n has values of from 3 to 10.

Both individual phosphates and mixtures of different phosphates and / or phosphorus oxides can be used.

The preferred proportion of the phosphorus-containing compound, based on the refractory molding material, is between 0.05 and 1.0% by weight. The proportion of the phosphorus-containing compound is preferably selected to be between 0.1 and 0.5% by weight. The phosphorus-containing inorganic compound preferably contains between 40 and 90% by weight, particularly preferably between 50 and 80% by weight, of phosphorus, calculated as P2O5. The phosphorus-containing compound may be added per se in solid or dissolved form of the molding material mixture. The phosphorus-containing compound is preferably added to the molding material mixture as a solid. According to an advantageous embodiment, the molding material mixture according to the invention contains a proportion of platelet-shaped lubricants, in particular graphite or MoS ₂ . The amount of added platelet-shaped lubricant, in particular graphite, is preferably 0.05 to 1 wt.%, Particularly preferably 0.05 to 0.5 wt.%, Based on the molding material. According to a further advantageous embodiment, it is also possible to use surface-active substances, in particular surfactants, which improve the flowability of the molding material mixture. Suitable representatives of these compounds are described, for example, in WO 2009/056320 (= US 2010/0326620 A1). Anionic surfactants are preferably used for the molding material mixture according to the invention. Mentioned here are in particular surfactants with sulfuric acid or sulfonic acid groups. In the novel molding material mixture, the pure surface-active substance, in particular the surfactant, based on the weight of the refractory molding base material is preferably present in a proportion of 0.001 to 1 wt .-%, particularly preferably 0.01 to 0.2 wt .-% ,

The molding material mixture according to the invention represents an intensive mixture of at least the constituents mentioned. In this case, the particles of the refractory molding material are preferably coated with a layer of the binder. By evaporating the water present in the binder (about 40-70 wt.%, Based on the weight of the binder) can then be a solid cohesion between the particles of the refractory mold base material can be achieved.

Despite the high strengths which can be achieved with the binder system according to the invention, the casting molds produced with the molding material mixture according to the invention surprisingly show a very good disintegration after the casting, in particular during aluminum casting. As already explained, it has also been found that casting molds can be produced with the molding material mixture according to the invention, which also show a very good disintegration during iron casting, so that the molding material mixture can easily be poured out again from narrow and crooked sections of the casting mold after casting , The use of the molded articles produced from the molding material mixture according to the invention is therefore not limited to light metal casting and / or non-ferrous metal casting. The molds are generally suitable for casting metals, such as non-ferrous metals or ferrous metals. However, the molding material mixture according to the invention is particularly preferably suitable for the casting of aluminum. The invention further relates to a method for the production of molds for metal processing, wherein the molding material mixture according to the invention is used. The method according to the invention comprises the steps:

Providing the above-described molding material mixture by bringing together and mixing at least the above-mentioned obligatory components;

Forms of the molding material mixture;

Curing the molded molding material mixture, wherein the cured mold is obtained.

In the production of the molding material mixture according to the invention, the procedure is generally such that initially the refractory molding base material (component (F)) is initially introduced and then the binder or component (B) and the additive or component (A) are added with stirring. The additives described above may be added per se in any form of the molding material mixture. They can be added individually or as a mixture. According to a preferred embodiment, the binder is provided as a two-component system, wherein a first liquid component contains the water glass and optionally a surfactant (see above) (components (B)) and a second but solid component one or more oxidic boron Compounds and the particulate silica (components (A)) and all other above-mentioned solid additives, except the molding materials, in particular the particulate amorphous silica and optionally a phosphate and optionally one

platelet-shaped lubricant and optionally barium sulfate or optionally other components as described comprise.

In the preparation of the molding material mixture, the refractory molding base material is placed in a mixer and then preferably first the solid component (s) of the binder is added and mixed with the refractory molding base material. The mixing time is chosen so that an intimate mixing of refractory base molding material and solid binder component takes place. The mixing time depends on the amount of the molding mixture to be produced and on the mixing unit used. Preferably, the mixing time is between 1 and 5 minutes chosen. Preferably, with further agitation of the mixture, the liquid component of the binder is then added and then the mixture is further mixed until a uniform layer of the binder has formed on the grains of the refractory base molding material.

Again, the mixing time of the amount of the molding mixture to be produced as well as the mixing unit used depends. Preferably, the duration for the mixing process is selected between 1 and 5 minutes. A liquid component is understood to mean both a mixture of different liquid components and the totality of all individual liquid components, the latter also being able to be added individually. Likewise, a solid component is understood as meaning both the mixture of individual or all of the solid components described above and the entirety of all solid individual components, the latter being able to be added to the molding material mixture jointly or else successively. According to another embodiment, the liquid component of the binder may also first be added to the refractory base molding material and only then be fed to the solid component of the mixture. According to a further embodiment, 0.05 to 0.3% by weight of water, based on the weight of the basic molding material, is first added to the refractory molding base material and only then the solid and liquid components of the binder are added.

In this embodiment, a surprising positive effect on the processing time of the molding material mixture can be achieved. The inventors believe that the dehydrating effect of the solid components of the binder is thus reduced and the curing process is thereby delayed. The molding material mixture is then brought into the desired shape. The usual methods of shaping are used. For example, the molding material mixture can be shot by means of a core shooting machine with the aid of compressed air into the mold. The molding material mixture is then cured using all methods known in waterglass binders, eg, heat curing, gasification with CO ₂ or air, or a combination of both, and curing by liquid or solid catalysts. Hot curing is preferred. During the hot curing process, water is removed from the molding material mixture. As a result, condensation reactions between silanol groups are presumably also initiated, so that crosslinking of the water glass occurs. The heating can be carried out, for example, in a mold, which preferably has a temperature of 100 to 300 ° C, particularly preferably a temperature of 120 to 250 ° C. It is possible to fully cure the mold already in the mold. But it is also possible to cure the mold only in its edge region, so that it has sufficient strength to be removed from the mold can. The casting mold can then be completely cured by removing further water. This can be done for example in an oven. The dehydration can for example also be done by the water is evaporated at reduced pressure.

The curing of the molds can be accelerated by blowing heated air into the mold. In this embodiment of the method, a rapid removal of the water contained in the binder is achieved, whereby the mold is solidified in suitable periods for industrial use. The temperature of the injected air is preferably 100 ° C to 180 ° C, particularly preferably 120 ° C to 150 ° C. The flow rate of the heated air is preferably adjusted to cure the mold in periods suitable for industrial use. The periods depend on the size of the molds produced. It is desirable to cure in less than 5 minutes, preferably less than 2 minutes. For very large molds, however, longer periods may be required.

The removal of the water from the molding material mixture can also be carried out in such a way that the heating of the molding material mixture is effected or assisted by irradiation of microwaves. It would be conceivable, for example, to mix the basic molding material with the solid, pulverulent component (s), to apply this mixture in layers on a surface and to print the individual layers with the aid of a liquid binder component, in particular with the aid of a waterglass, wherein the layered application of the

Solid mixture followed by a printing process using the liquid binder. At the end of this process, ie after completion of the last printing process, the entire mixture can be heated in a microwave oven.

The processes according to the invention are in themselves suitable for the production of all casting molds customary for metal casting, that is to say, for example, of cores and molds. It is also particularly advantageous to produce casting molds which comprise very thin-walled sections.

The casting molds produced from the molding material mixture according to the invention or the method according to the invention have a high strength immediately after production, without the strength of the casting molds after curing being so high that difficulties arise after the casting is removed when the casting mold is removed , Furthermore, these molds have a high stability at elevated humidity, i. Surprisingly, the casting molds can also be easily stored for a long time. As an advantage, the mold has a very high stability under mechanical stress, so that even thin-walled portions of the mold can be realized without these being deformed by the metallostatic pressure during the casting process. Another object of the invention is therefore a mold, which was obtained by the inventive method described above.

Furthermore, the invention will be explained in more detail by means of examples without being limited thereto. The fact that only the heat curing is described as the curing process is not limited.

Examples

1) A flow of various powdery oxidic boron compounds on the flexural strengths

For testing a molding material mixture, so-called Georg Fischer test bars were produced. Georg Fischer test bars are cuboid test bars measuring 150 mm x 22.36 mm x 22.36 mm. The compositions of the molding material mixtures are given in Table 1. The Georg Fischer test bars were prepared as follows: • The components listed in Table 1 were mixed in a laboratory paddle mixer (Vogel & Schemmann AG, Hagen, DE). For this purpose, the quartz sand was initially introduced and the water glass was added with stirring. As a water glass, a sodium water glass was used, the proportions of

Had potassium. In the following tables, the modulus is therefore given by Si0 ₂ : M ₂ 0, where M is the sum of sodium and potassium. After the mixture had been stirred for one minute, amorphous SiO 2 and, if necessary, powdery oxidic boron compounds were added with further stirring. The mixture was then added for another

Stirred the minute;

• The molding material mixtures were transferred to the storage bunker of a H 2.5 hot-box core shooter from Röperwerk-Gießereimaschinen GmbH, Viersen, DE, whose mold was heated to 180 ° C.;

• The molding material mixtures were introduced into the mold by means of compressed air (5 bar) and remained in the mold for a further 35 seconds; · To accelerate the curing of the mixtures, hot air (2 bar, 100 ° C on entering the mold) was passed through the mold during the last 20 seconds;

• The mold was opened and the test bars removed.

To determine the flexural strengths, the test bars were placed in a Georg Fischer strength tester equipped with a 3-point bending device (DISA Industrie AG, Schaffhausen, CH) and the force was measured which resulted in the breakage of the test bars. The flexural strengths were measured according to the following scheme:

• 10 seconds after removal (hot strength)

• 1 hour after removal (cold strength)

• 24 hours after storage of the cores in the climatic chamber at 30 ° C and 60% relative humidity, whereby the cores were placed in the climatic chamber only after cooling (1 hour after removal). Table 1

Compositions of the molding material mixtures

Verg eich = not according to the invention

The indices in Table 1 each have the following meaning:

a ⁾ alkali water glass with a molar modulus SiO ₂ : M ₂ O of about 2.2; based on the entire water glass. Solids content of approx. 35%

b ⁾ Microsilica POS BW 90 LD (amorphous SiO2, Possehl Erzkontor company, formation in the thermal decomposition of ZrSiO ₄ ) ^c) boric acid technical (99.9% H ₃ B0 ₃ , Cofermin Chemicals GmbH & Co. KG) ^d) Etibor 48 (borax pentahydrate, Na ₂ B ₄ 0 ₇ ^* 5H ₂ 0, Fa. Eti Maden Isletmeleri) ^e) Sodium metaborate 8mol (Na ₂ 0-B ₂ 0 ₃ * 8H ₂ 0, from borax Europe Limited) ^f) borax decahydrate SP (Na ₂ B ₄ O ₇ * 10H ₂ O -. powder, from borax Europe Limited). ⁹⁾ borax decahydrate (Na ₂ B ₄ O ₇ * 10H ₂ O - granulated, Fa. Eti Maden Isletmeleri) ^h) lithium tetraborate (99.998% Li ₂ B ₄ 0 ₇ , Alfa Aesar)

Calcium metaborate (Sigma Aldrich)

k ⁾ alkali water glass with a molar modulus Si0 ₂ : M ₂ 0 of about 2.2; based on the entire water glass. Solids content of about 35% - in this waterglass 0.05 GT Borax decahydrate ⁹⁾ pre-dissolved before use, so that a clear solution is formed.

The measured flexural strengths are summarized in Table 2. Examples 1.01 and 1.02 illustrate that the addition of amorphous Si0 ₂ can achieve a significantly improved strength level (according to EP 1802409 B1 and DE 102012020509 A1). A comparison of Examples 1.02 to 1.14 shows that the addition of powdery oxidic boron compounds does not appreciably affect the strength level.

Examples 1 .06 and 1.1 1 to 1.14, a slight deterioration in the strength levels can be determined with increasing proportion of inventive additive. The effect is very weak. Comparison of Examples 1.01, 1.15 and 1.16 shows that the addition of boron compounds of the invention alone, i. without the addition of the amorphous silica, has a negative impact on the strengths, especially hot strengths and cold strengths. Also, the hot strengths for automated mass production are too low.

A comparison of Examples 1.02, 1 .06 and 1.09 shows that the addition of boron compounds of the invention exerts little influence on the hot and cold strengths when the molding material mixture contains amorphous silica as a powdery additive. Surprisingly, however, the addition of the boron compound according to the invention to the molding material mixture improves the moisture stability of the cores produced therewith. Table 2

flexural strengths

Comparison = not according to the invention

2) Improvement of decomposition behavior

The influence of different powdered oxidic boron compounds on the coring behavior was investigated. For this purpose, the procedure was as follows:

· Georg Fischer test bars of the molding substance mixtures 1 .01 to 1 .14 in Table 1 were examined with regard to the flexural strengths (analogously to Example 1 - there were no differences from the values summarized in Table 2).

• Subsequently, the Georg Fischer test bars were broken in half in two parts across the largest length in a muffle furnace

(Naber Industrieofenbau) at a temperature of 650 ° C for 45 minutes thermally stressed.

• After removing the bars from the muffle furnace and after a subsequent cooling process to room temperature, the bars were placed on a so-called vibrating screen (sieve placed on the vibration sieving machine AS 200 digit, Retsch GmbH) with a mesh width of 1, 25 mm.

• The bars were then shaken for 60 seconds at a fixed amplitude (70% of the maximum possible setting (100 units)).

• Both the residue on the sieve and the shredded amount in the drip tray (cored portion) were determined by means of a balance. Table 3 shows the cored portion in percent. The respective values, which in each case reflect mean values of a quadruple determination, are summarized in Table 3.

A comparison of Examples 1.01 and 1.02 shows that the decomposition behavior of the molds produced therewith deteriorates markedly by addition of a particulate, amorphous silicon dioxide to the molding material mixture. A comparison of

By contrast, Examples 1.02 to 1.09 clearly show that the use of powdered oxidic boron compounds leads to significantly improved disintegration properties of the forms bound with waterglass. A comparison of Examples 1.07 and 1.10 shows that it makes a difference whether the borate (in this case) was pre-dissolved in the binder prior to use in the molding material mixture or whether the borate was added to the molding compound as a solid powder. Such an effect is surprising. Examples 1.06 and 1.11 to 1.14 illustrate that the decomposition behavior can be significantly increased with increasing proportion of the additive according to the invention. It also becomes clear that even small additions are sufficient to significantly increase the disintegration capability of the cured molding material mixture after thermal exposure.

Table 3

Entkernverhalten

Comparison = not according to the invention

Claims

claims

1 . Molding material mixture for the production of molds or cores comprising at least:

a refractory base molding material;

- water glass as a binder;

particulate amorphous silica; and

- One or more powdery oxidic boron compounds.

2. molding material mixture according to claim 1, wherein the molding material mixture by sammenbringen a multi-component system of at least the following spatially separate components (A), (B) and (F) can be produced:

(A) comprising a powdery additive component (A)

- particulate amorphous Si0 ₂ and

- One or more powdery oxidic boron compounds and

- no water glass,

(B) comprising a binder component (B)

- Water glass and as part of the water glass of water and

no particulate amorphous Si0 ₂ and

(F) comprising a free-flowing refractory component (F)

a refractory base molding material and

- no water glass.

3. Multi-component system for producing molds or cores comprising at least the following spatially separate components (A), (B) and (F):

(A) a powdery additive component comprising at least

one or more powdery oxidic boron compounds and

particulate amorphous silica and

- no water glass,

(B) a liquid binder component (B) comprising at least

- Water glass containing water, and

(F) comprising a free-flowing refractory component (F)

a refractory base molding material and

- no water glass.

4. molding material mixture and / or multi-component system according to at least one of the preceding claims, wherein the oxide boron compound is selected from the group consisting of borates, borophosphates,

Borophosphosilikaten and mixtures thereof and in particular a borate, preferably an alkali and / or Erdalkaliborat such as sodium borate and / or

Calcium borate, wherein the oxide boron compound more preferably contains no organic groups.

5. molding material mixture and / or multi-component system according to at least one of the preceding claims, wherein the oxidic boron compound of

B-O-B structural elements is constructed.

6. molding material mixture and / or multi-component system according to at least one of the preceding claims, wherein the oxidic boron compound has an average particle size of greater than 0.1 μιη and less than 1 mm, preferably greater than 1 μιη and less than 0.5 mm , and more preferably has greater than 5 μιη and less than 0.25 mm.

7. Form material mixture and / or multi-component system according to at least one of the preceding claims, wherein the oxidic boron compound, based on the refractory base molding material to greater than 0.002 wt.% And less than 1, 0 wt.%, preferably greater than 0.005% by weight and less than 0.4% by weight, particularly preferably greater than 0.01% by weight and less than 0.1% by weight and particularly preferably greater than 0.02% by weight , and less than 0.075 wt.% is added.

8. molding mixture and / or multi-component system according to at least one of the preceding claims, wherein the refractory molding material comprises quartz, zirconium or chrome ore, olivine, vermiculite, bauxite, chamotte, glass beads, glass granules, Aluminiumiumsilikatmikrohohlkugeln and mixtures thereof and preferably to more than 50 wt.% Of quartz sand based on the refractory base molding material.

9. Form Substance mixture and / or multi-component system according to at least one of the preceding claims, wherein greater than 80 wt.%, Preferably greater than 90 wt.%, And particularly preferably greater than 95 wt.%, Of the molding material mixture or the multicomponent system refractory molding material are.

10. molding material mixture and / or multi-component system according to at least one of the preceding claims, wherein the refractory molding base material average particle diameter of 100 μιη to 600 μιη, preferably between 120 μιη and 550 μιη, determined by sieve analysis.

1 1. Molding material mixture and / or multi-component system according to at least one of the preceding claims, wherein the particulate amorphous

Silica is a BET specific surface area between 1 and 200 m ² / g, preferably greater than or equal to 1 m ² / g and less than or equal to 30 m ² / g, more preferably of less than or equal to 15 m ² / g. having.

12. molding material mixture and / or multi-component system according to at least one of the preceding claims, wherein the particulate amorphous

Silica, based on the total weight of the binder, in a proportion of 1 to 80 wt.%, Preferably between 2 and 60 wt.%, Is used.

13. molding material mixture and / or multi-component system according to at least one of the preceding claims, wherein the particulate amorphous

Silica has a mean determined by dynamic light scattering primary particle diameter between 0.05 μιη and 10 μιη, in particular between 0.1 μιη and 5 μιη and more preferably between 0.1 μιη and 2 μιη.

14. Formstoffmischung and / or multi-component system according to at least one of the preceding claims, wherein the particulate amorphous silica from the group consisting of: precipitated silica, flame-hydrolysed or produced in the arc fumed silica, by thermal decomposition of ZrSiO ₄ produced amorphous silica, by Oxi dation of metallic silicon by means of an oxygen-containing gas produced silica, quartz glass powder with spherical particles, which was prepared by melting and rapid re-cooling of crystalline quartz, and their mixtures is selected.

15. molding material mixture and / or multi-component system according to at least one of the preceding claims, wherein the molding material mixture and the multi-component system in addition to particulate amorphous S1O2 further particulate metal oxides, preferably aluminas, contains, in particular selected from one or more members of groups a) to d ): a) corundum plus zirconium dioxide,

b) zircon mullite,

c) zirconium corundum and

d) aluminum silicates plus zirconium dioxide,

preferably as a component of component (A).

16. molding material mixture or multi-component system according to at least one of the preceding claims, wherein the molding material mixture and the multi-component system, the particulate amorphous silica

In amounts of from 0.1 to 2% by weight, preferably from 0.1 to 1.5% by weight, based in each case on the mold base,

and regardless of this

From 2 to 60% by weight, particularly preferably from 4 to 50% by weight, based on the weight of the binder (including water) or components (B), wherein the solids content of the binder is from 20 to 55% by weight, preferably from 25 to 50% by weight.

17. molding material mixture or multi-component system according to at least one of the preceding claims, wherein the particulate amorphous silica used has a water content of less than 5 wt.% And particularly preferably less than 1 wt.% Has.

18. Molding material mixture or multicomponent system according to at least one of the preceding claims, wherein the water glass (including the water) in an amount of 0.75 wt.% And 4 wt.%, Particularly preferably between 1 wt.% And 3, 5 wt.%, Soluble alkali silicates, relative to the molding material in the molding material mixture is contained and more preferably independently, but preferably in combination with the above values, the solids content of water glass from 0.2625 to 1, 4 wt.%, Preferably 0 , 35 to 1, 225 wt.% Is, relative to the molding base material in the molding material mixture.

19. molding material mixture or multi-component system according to at least one of the preceding claims, wherein the water glass is a molar module

S1O2 / M2O in the range of 1.6 to 4.0, in particular 2.0 to less than 3.5, having M = lithium, sodium and / or potassium.

20. molding material mixture or ehrkomponenten system according to at least one of the preceding claims, wherein the molding material mixture further contains at least one phosphorus-containing compound, preferably from 0.05 and 1, 0 wt.%, Particularly preferably 0.1 and 0.5 wt.%, based on the weight of the refractory molding base material, preferably as a constituent of component (A) and also independently thereof, the phosphorus-containing compound is preferably added as a solid and not in dissolved form.

21. Molding material mixture or multi-component system according to at least one of the preceding claims, wherein the molding material mixture is added to a curing agent, in particular at least one ester or phosphate compound, preferably as a component of component (A) or as a further component.

22. A process for producing molds or cores comprising:

Providing the molding material mixture by bringing together and mixing the substances or components according to claims 1 to 21,

• introducing the molding material mixture into a mold, and

Hardening of the form substance mixture by heat curing with heating and removal of water, preferably by exposure of the molding material mixture at a temperature of 100 to 300 ° C.

23. The method of claim 22, wherein the molding material mixture is introduced by means of a core shooter with the aid of compressed air into the mold and the mold is a mold and the mold with one or more gases is flowed through, in particular C0 ₂ , or gases containing C0 ₂ , preferably heated to above 60 ° C C0 ₂ and / or heated to above 60 ° C air.

24. The method of claim 22 or 23, wherein the molding material mixture for curing a temperature of 100 to 300 ° C, preferably from 120 to 250 ° C is exposed, preferably for less than 5 min, more preferably the temperature at least partially by blowing heated Air is produced in a mold.

25. mold or core to produce according to at least one of claims 22 to 24 for the metal casting, in particular the aluminum casting.

26. A method of layering bodies comprising:

Mixing at least the pulverulent additive component (A) and the free-flowing refractory component (F) according to claims 2 to 21, among other possible further optional constituents according to these claims, to form a mixture,

layer by layer application of the mixture on a surface in the form of layers and

- Printing the layers using the liquid binder component (B), wherein the layered application of the mixture each followed by a printing operation using the liquid binder component (B), and the curing is preferably carried out with microwaves.