MX2014003804A - Coating compositions for inorganic casting moulds and cores and use thereof and method for sizing. - Google Patents

Abstract

The invention relates to coating compositions, comprising specific clays, an aqueous carrier fluid and refractory materials in powder form, and to the use thereof for casting moulds and cores, in particular those that are produced using water glass as a binder. The invention further relates to a method for producing the sizing agents and for applying same to inorganically bound casting moulds and cores.

Description

COATING COMPOSITIONS FOR INORGANIC CAST MOLDS AND MOLDS AND USE OF THEM AND METHOD FOR GLASSING DESCRIPTION The invention relates to a coating composition for casting molds and the use thereof. The coating composition is suitable for casting molds and cores, in particular, those which are produced using water glass as a binder. The coating composition comprises certain clay materials. A gluing method is also claimed.

Previous technique The casting molds can be produced from a refractory material, for example quartz sand, by shaping in a casting mold and agglomeration using a suitable binder to ensure adequate mechanical strength. Therefore, the molds castings are produced using a refractory base material and a suitable binder. The refractory basic mold material is preferably present in free flowing form, so that it can be packed in a suitable hollow mold and compacted there. The binder produces firm cohesion between the particles of the mold base material, so that the mold form achieves the necessary mechanical stability.

Both organic and inorganic binders can be used for the production of casting molds, and can be cured by cold or hot processes. The cold processes are those that are carried out essentially at room temperature without heating the casting molds. In these cases, the curing is usually carried out by a chemical reaction, initiated, for example, by passing a gas as catalyst through the mold to be cured. In hot processes, the molding mixture, after forming, can be heated to a sufficiently high temperature, for example, to expel the solvent present in the binder or to initiate a chemical reaction by which the binder is cured, by example by crosslinking.

Regardless of the curing mechanism, all organic systems share the fact that they undergo thermal decomposition when the liquid metal It enters the casting mold and in this process can release toxic materials, such as benzene, toluene, xylene, phenol, formaldehyde and other cracking products, some of which have not been identified.

It has become possible to minimize these emissions by various measures, but they can not be completely avoided in the case of organic binders. To minimize or avoid the emission of decomposition products during the smelting process, the binders can be used which are based on inorganic materials or which contain a very small fraction of the organic compounds. Such binder systems have been known for a long time.

The binder systems have been developed which can be cured by passing the gases in them. A system of this type is described, for example, in GB 782 205, in which an alkaline water glass is used as a binder and can be cured by the passage of C02. In E.U. No. 6972059 Bl discloses an exothermic feedstock containing an alkali silicate as a binder. In addition, binder systems that are self-curing at room temperature have been developed. One such system, based on phosphoric acid and metal oxides, is described, for example, in E.U. 5,582,232. Finally, the binder systems Inorganic ones that are cured at higher temperatures, for example in a hot tool, are also known. Such hot cure binder systems are known, for example, from E.U. 5,474,606, in which a binder system consisting of alkaline water glass and aluminum silicate is described.

In E.U. No. 7022178 Bl describes a binder system for molding sands for the production of cores. The binder system, based on the water glass, is composed of an aqueous solution of alkali silicate and a hygroscopic base, for example sodium hydroxide, which is added in a ratio of 1: 04-1: 06. Soluble glass has a SiO2 / M20 modulus of 2.5 to 3.5 and a solids fraction of 20 to 40%. To obtain a mixture of flow-free molding material, which can also be packaged in complicated mold shapes, and to control hygroscopicity, the binder system also contains a surface active material, such as silicone oil, having a boiling point 250 >; ° C. The binder system is mixed with a suitable refractory material, such as quartz sand, and then it can be fired in a core box using a core shooting machine. The curing of the molding material mixture is carried out by removing the remaining water. The drying or curing of the casting mold also They can take place with the help of microwaves.

However, the inorganic binders also have drawbacks compared to organic binders, for example, the known inorganic binders result in a low stability of the casting molds produced by using them towards high atmospheric humidity and towards water. Therefore, the storage of the molded parts over a long period of time, as usual with organic binders, is definitely not possible. To achieve higher initial strengths, better resistance of the casting molds towards atmospheric humidity and better results on the surface of the casting, in E.U. 7770629 B2 a molding mixture is suggested which, in addition to a refractory basic mold material, contains a binder based on water glass. A fraction of a particulate metal oxide is added to the mixture of mold material. Preferably, the precipitated silica or pyrogenic silica is used as the particulate metal oxide.

The methods described for the production of casting molds and cores generally also include the application of a refractory mold coating, also known as a sizing agent, to at least the surfaces of the base mold that come into contact with the mold. molten metal. The mold coatings are mainly intended to influence the surface of the castings, to improve the appearance of the casting, to influence the casting metallurgically, and / or to avoid casting defects.

The sizing agents used generally contain as their basic materials, for example, clays, quartz, diatomaceous earth, cristobalite, tridymite, aluminum silicate, zirconium silicate, mica, refractory clay and also coke and graphite. These basic materials are the parts that define the sizing agent, which cover the surface of the mold and close the pores against the penetration of the casting metal.

With the help of these coatings, therefore, the surface of the casting mold can be modified and adapted to the properties of the metal being processed. For example, the sizing agent can improve the appearance of the casting by producing a smooth surface, since the sizing agent softens the irregularities caused by the different sizes of the granules of the molding material. In addition, the sizing agent can metallurgically influence the casting in that, for example, through the sizing agent, the additives on the surface of the casting are selectively transferred into the workpiece. melted, improving the surface properties of the casting.

In addition, the sizing agents form a layer that chemically isolates the casting mold during the casting of liquid metal. In this way, any adhesion between the casting and the casting mold is prevented, so that the casting can be removed from the casting mold and without problems. However, the sizing agent can also be used to control the transfer of heat between the liquid metal and the casting mold, in order, for example, to carry out the formation of a certain metal microstructure through the speed Cooling.

Nowadays, the curing of the inorganic binders used is carried out increasingly through a condensation reaction initiated by high temperatures, in which the formation of the binder bridges occurs through dissociation of the water. Like many chemical reactions, this is a reversible reaction, that is, the bonds can be broken by contact and reaction with water, in which the degree of this reaction depends to a large extent on the process parameters for production of macho. Under the process parameters typically used in mass production (fast cycle, high temperatures), the casting molds lose their strength due to contact with water and to some extent also, get in contact with alcohol; the surface softens and the casting mold loses its shape.

Problem Statement The invention is based on the task of proposing a sizing agent through which the most possible defect-free coating, especially of the inorganic cores and molds, can be ensured, without negatively impacting the stability of the cores or molds and therefore its processing and storage.

BRIEF DESCRIPTION OF THE INVENTION This task is achieved with the features of claim 1; the advantageous embodiments form the subject matter of the dependent claims or are described below.

In a preferred embodiment, the sizing composition according to the invention is prepared in the form of a paste or a suspension. In this form of embodiment, the sizing composition contains a carrier fluid.

Surprisingly, it has been found that through from the combination of certain clays as constituents of sizing agents, sizing agents with an unusually high solids content can be produced, the viscosity of which is however comparable to that of commercial sizing agents ready for used such as Trioflex WK-LS-1. The quality of cores and molds coated with these sizing agents and bonded with inorganic binders was permanently improved by the combination of clays according to the invention and, for example, in this way The stability of storage of several days of the cores and molds can be achieved. It should be particularly emphasized that despite the high solids content unusually, the viscosity of the sizing agent is in the usual range for sizing agents with substantially lower solids contents. Gluing agents can be brought into ready-to-use condition without the use of special additives or large amounts of water.

Detailed description of the invention The clay material used was a combination of (Al) 1 to 10 parts by weight, especially 1 to 5 parts by weight, of paligorskite (A2) 1 to 10 parts by weight, especially 1 to 5 parts by weight, of hectorite Y (A3) 1 to 20 parts by weight, especially 1 to 5 parts by weight, sodium bentonite (in each case with respect to the other), especially in a weight ratio of paligorskite to hectorite of 1: 0.5 to 2, especially 1: 0.8 to 1.2 and a ratio of paligorskite sodium bentonite of 1: 0.5 to 3, especially 1 : 0.8 to 1.2 and sodium bentonite hectorite from 1: 0.5 to 2, especially 1: 0.8 to 2.

The total content of the aforementioned clays in the sizing agent amounts to 0.1 to 4.0% by weight, preferably 0.5 to 3.0% by weight, and particularly preferably 1.0 to 2.0% by weight.

Paligorskite is a magnesium-aluminum hydrosilicate mentioned in CAS N2 8031-18-3. Paligorskita is a component of commercial products sold as attapulgite. Atapulgite contains paligorskite, but should not be used due to other interference constituents and the absence of rod-shaped crystals.

There is paligorskite in the form of rod-shaped crystals. The particles have the following dimensions: 1 to 3 μp ?, especially 1.5 to 2 μ? of length with a diameter of 1 to 5 nm, especially of about 3 nm.

Paligorskita has different properties of attapulgite. Paligorskite does not swell or shrink, is stable to shear, and in a suspension with water or water-based liquids with A (2) or A (3), for example, at low rates of addition such as 0.01 to 3% by weight , produces a structurally viscous or thixotropic fluid.

Once the shearing effect ceases, the higher initial viscosity is quickly restored. The viscosity is low in the presence of shear. Atapulgite contains smectite, SIO2, and / or CaCO3 and other contaminants.

For example, the product Acti-Gel®208 from the company "active minerals" can be used as the paligorskite. For example, Bentone CT of the company "Elementis" can be used as the hectorite.

For example, Volclay from the company "Südchemie" can be used as sodium bentonite. This natural raw material consists mainly (> 80%) of montmorillonite; Accompanying minerals can be quartzite, calcite, feldspar and mica.

Depending on the intended use of the sizing composition, for example, as a base layer or top layer, and the desired layer thickness of the coating produced from the sizing composition, the Additional characteristic parameters of the sizing composition can be adjusted.

The carrier fluid may be composed partially or completely of water. The carrier fluid is the component that can be evaporated at 160 ° C and the normal pressure and in this sense, by definition, it is mainly the component that is not the solids content. The carrier fluid contains water in the measure of more than 50% by weight, preferably 75% by weight, especially more than 80% by weight, and, optionally, greater than 95% by weight of water.

The additional components in the carrier fluid can be organic solvents. Suitable solvents are alcohols, including polyalcohols and polyether alcohols. Examples of alcohols are ethanol, n-propanol, isopropanol, butanol and glycol.

The solids content of the ready-to-use sizing composition is preferably adjusted to the range of 10 to 90% by weight, especially more than 80% by weight to 85% by weight.

In addition to the components already mentioned, the sizing agent according to the invention can contain additional customary components for sizing agents.

Therefore, the sizing composition according to the invention contains at least one refractory material in dust. This refractory material serves to block the pores in a casting mold against the penetration of the liquid metal. In addition, the refractory material achieves thermal insulation between the casting mold and the liquid metal. Examples of suitable refractory materials are quartz, aluminum oxide, zirconium oxide, aluminum silicates such as pyrophilite, kyanite, andalusite or refractory clay, zirconium sands, zirconium silicates, olivine, talc, mica, graphite, coke, feldspar , diatomite, kaolins, calcined kaolins, kaolinite, metakaolinite, iron oxide and / or bauxite.

The refractory material is prepared in powder form. The particle size is selected in such a way that a stable structure is formed in the coating and that the sizing agent can preferably be distributed without problems in the wall of the casting mold using a spraying device. Suitably, the refractory material has an average particle size (measured by light scattering according to DIN / ISO 13320) in the range of 0.1 to 500 μm, particularly preferably in the range of 1 to 200 μ ?t ?. Particularly suitable refractory materials are those that have a melting point that is at least 200 ° C above the temperature of the liquid metal and independently of this, do not react with the metal.

The fraction of the refractory material (in each case only contribute to the solids content), for example, in the commercial form of a paste, in relation to the solids fraction of the sizing material composition, is favorably more than 70% in weight, preferably more than 80% by weight, and particularly preferably more than 85% by weight.

According to another form of mode (in each case they only contribute to the solids content), the fraction of the refractory material is selected for the application case after dilution (for example, of the paste) with water to be less than 80 % by weight, according to a form of additional embodiment of less than 70% by weight and according to an additional embodiment of less than 60% by weight.

In another embodiment, the sizing material according to the invention may contain at least one suspending agent. The suspending agent produces an increase in the viscosity of the sizing agent, so that the solid components of the sizing agent do not fall to the bottom in the suspension, or do so only to a slight degree. Organic or inorganic materials or mixtures thereof can be used to increase the viscosity. Suitable inorganic suspending agents are, for example, strongly clay swelling, such as sodium bentonite.

Alternatively or additionally, the suspending agent may also include organic thickeners, since after application of the protective coating, they may dry to such an extent that they barely release the water after the application of the protective layer. Possible organic suspending agents are, for example, swellable polymers such as carboxymethyl-, methyl-, ethyl-, hydroxyethyl- and hydroxypropylcelluloses, plant mucilages, polyvinyl alcohols, polyvinylpyrrolidone, pectin, gelatin, agar-agar, polypeptides and / or alginates.

The fraction of the suspending agent, based on the total sizing composition, is advantageously selected as 0.1 to 5% by weight, preferably 0.5 to 3% by weight, particularly preferably 1 to 2% by weight.

According to a preferred embodiment, the sizing agent according to the invention contains at least one binder as an additional component. The binder makes possible a better fixation of the sizing agent or the individual protection coating of the sizing agent on the wall of the casting mold. In addition, the binder increases the mechanical stability of the protective layer, so that less erosion is observed under the influence of liquid metal. Preferably, the binder is cured irreversibly, so that an abrasion-resistant coating is obtained. In particular, binders that do not soften again under contact with atmospheric moisture are preferred. Fundamentally any binder used in sizing agents may be present. Both inorganic and organic binders can be used. Suitable binders for use include, for example, clays, especially bentonite.

The binder fraction is preferably selected in the range of 0.1 to 20% by weight, particularly preferably 0.5 to 5% by weight, based on the solids content of the size composition.

According to a further preferred embodiment form, the sizing agent contains a graphite fraction. This supports the formation of lamellar carbon at the interface between the foundry and the casting mold. The graphite fraction is preferably selected in the range of 1 to 30% by weight, especially preferably 5 to 15% by weight, based on the solids content of the sizing agent. In cast iron, graphite has a beneficial effect on the quality of the surface of the casting.

Optionally, the sizing composition of According to the invention, it can contain other customary components in sizing agents, for example wetting agents, defoamers, pigments, dyes or biocides. The fraction of these additional components in the ready-to-use coating composition is advantageously less than 10% by weight, preferably less than 5% by weight and particularly preferably less than 1% by weight.

For example, wetting agents may include anionic and non-anionic surfactants, especially those with an HSB value of at least 7. An example of such a wetting agent is disodium dioctylsulfosuccinate. The wetting agent is preferably used in an amount of 0.01 to 1% by weight, preferably 0.05 to 0.3% by weight, based on the sizing composition-ready for use.

Defoamers, also known as defoamers, can be used to prevent foaming during the production or application of the sizing composition. The formation of foam during the application of the sizing composition can lead to a lack of uniformity in the thickness of the layer and to the holes in the coating. For example, mineral oil or silicone oil can be used as an antifoam. The antifoam is present advantageously in an amount of 0.01 to 1% by weight, preferably 0.05 to 3% by weight, based on the sizing composition-ready for use.

In the sizing composition according to the invention, customary pigments and dyes can be used if desired. These are added to achieve contrast, for example, between the different sizing agents, or to create a stronger separation effect of the casting sizing agent.

Examples of pigments are red and yellow iron oxide and graphite. Examples of dyes are commercial dyes, such as the Luconyl® dye series from BASF AG, Ludwigshafen, DE. The dyes and pigments are preferably present in an amount of 0.01 to 10% by weight, preferably 0.1 to 5% by weight, based on the solids content of the size composition.

According to a form of additional embodiment, the sizing composition contains a biocide to prevent the attack of bacteria and therefore avoid a negative effect on the rheology and agglomeration force of the binder. This is especially preferred when the carrier fluid contained in the sizing composition is composed essentially (on a weight basis) of water, and therefore the sizing agent according to the invention it is supplied in the form of a so-called aqueous sizing agent. Examples of suitable biocides are formaldehyde, 2-ethyl-4-isothiazolin-3-one (MIT), 5-chloro-2-methyl-4-isothiazolin-3-one (CIT) and 1,2-benzisothiazolin-3-. ona (BIT). Preferably, the MIT, bits or a mixture thereof are used. The biocides are generally used in an amount of 10 to 1000 ppm, preferably 50 to 500 ppm, based on the weight of the sizing composition ready for use.

The sizing composition according to the invention can be made by the usual methods. For example, a sizing composition according to the invention can be prepared by initially taking water and then dispersing the clay, which acts as a suspending agent, therein using a high shear stirrer. Next, the refractory components, pigments and dyes, as well as the metal additive are mixed in until a homogeneous mixture is formed. Finally, wetting agents, defoamers, biocides and binders are mixed.

The sizing composition according to the invention can be prepared and sold as a ready-for-use formulating agent. However, the sizing agent can also be prepared and sold in concentrated form. In this case, to produce a sizing agent-ready for use, the amount of fluid is added carrier necessary to establish the viscosity and density of the desired sizing agent. In addition, the sizing agent according to the invention can also be prepared and sold in the form of a packet, in which for example the solid component (s) and the solvent component (s) are present side by side in containers separated .

The solid component (s) can be supplied as a mixture of powdered solids in a separate container. The additional liquid component (s) optionally to be used, for example, binders, surfactants, wetting / defoaming agents, pigments, dyes and biocides, may also be present in this package, once again in a separate container. The solvent component (s) may include any of the optional additional components for use, for example, in a single container, or which may be present separately from other optional components in a separate container. To produce a ready-for-use sizing agent, suitable quantities of the solid components, the optional additional components and the solvent components are mixed together.

The sizing compositions according to the invention are suitable for the coating of casting molds. The term "casting mold" that is used here it includes all the types of solid bodies necessary for the production of a casting, for example, cores, molds and dies. The use of the sizing agent according to the invention also includes partial coating of casting molds.

The sizing agents are used for casting molds for metal processing, which can be obtained from inorganic molding material mixtures containing at least one basic refractory material, a binder based on water glass and preferably a fraction of a metal oxide selected from the group of silicon dioxide, especially amorphous silicon dioxide, aluminum oxide, titanium oxide or zinc oxide and mixtures thereof, wherein this is preferably present in particulate form and especially has particle sizes less than 300 ¡im (screen analysis). For example, amorphous silicon dioxide can be obtained through precipitation processes from water glass, which can be obtained by solubilization of quartz with sodium carbonate or potassium carbonate. Depending on the process conditions, Si02 obtained in this way is called precipitated silica. Another important manufacturing variant is the production of the so-called pyrogenic Si02 in a detonating gas flame, from chlorosilanes liquids such as silicon tetrachloride.

Mixtures of molding material and a method for the production of casting molds for metal processing using mixtures of cured molding material are described in WO 2006/024540 (+ EU 7770629 B2), and this publication is incorporated in the content of this request to this measure. Mixtures of preferred molding materials are the subject matter of patent claims WO 2006/024540.

Therefore the casting molds to be coated typically comprise a) More than 80% by weight of a basic refractory mold material (including additives that behave as basic refractory mold materials). b) 0.01 to 5% by weight of cured water glass as a binder, and c) optionally from 0 to 5% by weight of the aforementioned metal oxide or metal oxides.

Furthermore, the invention relates to a method for the production of smelting molds of a size for the metal processing with the application of sizing agents to the aforementioned inorganic mixtures, partially or completely curing the molding material. The application or preparation of the sizing agents is You can perform as follows: In the case of immersion as an application method, the casting mold, in the mold cavity from which a base layer of sizing agent is applied, is immersed for about 2 seconds to 2 minutes in a container that is filled with a gluing composition ready for use according to the invention.

The casting mold is then removed from the sizing composition and the excess sizing composition is allowed to function outside the smelting mold. The time required for the excess sizing composition to be exhausted after immersion depends on the runoff behavior of the sizing composition used.

In the case of spraying as the application method, commercial pressure tank spraying devices are used. In this process the sizing composition, in a diluted state, is introduced into a spray tank. Through the positive pressure when applied, the sizing agent can be forced to a spray gun, where it is sprayed with the help of controllable atomisation air separately. During spraying, the conditions are selectively sold in such a way that the pressure of the sizing composition and the atomization air is selected in the spray gun is configured so that the sizing composition that is sprayed atomizing air hits the mold or the core, while said sizing composition is still wet, but results in a uniform application.

In the case of flow coating such as the application method, the casting mold, optionally with a base layer applied in the mold cavity, is covered with a composition ready for the use of sizing with the aid of a tube, a spear or similar instruments.

In this process, the casting mold is completely covered with the sizing composition and the excess sizing composition is left without the casting mold. The time necessary for the sizing composition to drain after flow coating depends on the flow behavior of the sizing composition used.

In addition, the sizing agent can also be applied by painting.

The carrier fluid contained in the sizing agent is then evaporated, so that a layer of dry sizing agent is obtained. The drying methods used can include all conventional drying methods, for example, allowing it to dry in air, drying with dehumidified air, drying with microwave or infrared radiation, drying in a convection oven and comparable methods. In a preferred embodiment of the invention, the coating casting mold is dried in a convection oven at 20 to 250 ° C, preferably 50 to 180 ° C.

When alcohol-based sizing agents are used, the sizing composition according to the invention is preferably dried by burning the alcohol or the mixture of alcohols. In this case, the coating casting mold is further heated by the combustion heat. In a further preferred embodiment form, the coating casting mold is dried in the air without further treatment or the use of microwaves.

The sizing agent can be applied in the form of a single layer or in the form of several layers arranged one on top of the other. In this process, the individual layers may be the same or different in terms of their composition. For example, first a base layer can be produced from a conventional commercial sizing agent that does not contain any metallic additive according to the invention. For example, water-based sizing agents or alcohol-based sizing agents can be used. It is also possible to prepare all the layers of the size composition according to the invention. The layer that later come into contact With the liquid metal, however, it is always produced from the sizing agent according to the invention. When multiple layers are applied, each individual layer may be completely or partially dried after the application.

The coating prepared from the sizing composition advantageously has a dry layer thickness of at least 0.1 mm, preferably at least 0.2 mm, particularly preferably at least 0.45 mm, especially preferably at least 0.55 mm. According to one form of embodiment, the thickness of the coating to be less than 1.5 mm is selected. The thickness of the dry layer in this case is the layer thickness of the dry coating obtained by essentially completely removing the solvent component and, optionally, curing it afterwards. The dry layer thickness of the base layer and the top layer are preferably determined by measuring with the wet layer comb thickness. The casting mold can be assembled completely if desired. The casing is advantageously made to make pieces of iron and steel.

Example 1: In this example, the effect of increasing the solids content of the sizing agents used In the hardening of the size males was tested. The male glueing agents 1 and 2 have the compositions and physical properties indicated in Tables 1 and 2.

Table 1: Composition of the sizing agents The mold casting sizing agent was produced as follows: the water is placed in a container and the clay (s) broken using a high shear unit and a helicopter disk for at least 15 minutes. Next, the refractory components, pigments and dyes are mixed in at least 15 minutes until a homogeneous mixture is formed. Finally, the additives such as wetting agents, defoamers and preservatives, as well as the binder are mixed for 5 minutes.

For the experiments that follow, the sizing agents were adjusted to a viscosity in the range of 0.6 Pas, suitable for the application. The adjustment is made by adding appropriate amounts of water to the original composition and then homogenizing. The main characteristic in this case is the viscosity, measured with a Brookfield viscometer (DIN EN ISO 2555) and with an adapter DIN 4 rtim flow cup viscosity (DIN EN ISO 2431), at 20 ° C in each case.

Table 2: Application parameters It was observed that less water penetrates the molds and males of size compared to conventional sizing agents. Consequently, as a result, the range of effect of the carrier fluid, water, in the inorganic binder can be reduced decisively and the stability of the produced cores and molds can be increased.

The products of the company ASK Chemicals, Trioflex® WK-HP or Solitec® W 3 can be cited as additional examples of sizing agents not in accordance with the patent.

In the following, the performance of the corresponding series of experiments, which served as a basis for the presented results, will be described.

Produce and test the test pieces of molding materials Two different male geometries were investigated for experimental purposes. One geometry, the so-called Georg Fischer test bar, illustrates the behavior of the size test pieces on thicker male geometries, while the other geometry, the long so-called males, illustrates the behavior of the test pieces in size in the thin geometries. The Georg Fischer test bars are defined as rectangular test bars with dimensions of 150 mm x 22.36 mm x 22.36 mm. The long males have dimensions of 13 mm x 20 mm x 235 mm.

The composition of the molding material mixture is shown in Table 3. The following procedure was used for the production of the Georg Fischer test bar: the components listed in Table 3 are mixed in a vane-type laboratory pallet mixer (Vogel &Schemmann AG, Hagen DE).

For this purpose, first the quartz sand was placed in a container and the water glass while stirring. Soluble glass of sodium that contains some potassium is used as water glass. The Si02: M20 water glass module was approximately 2.2, where M is the sum of sodium and potassium. After the mixture was stirred for one minute, amorphous silicon dioxide is optionally added under further stirring. Amorphous silicon dioxide is pyrogenic silica from the company RW Silicium. Then, the mixture was stirred for an additional minute.

The molding composition mixture was transferred to the storage bunker, a H 2.5 Thermal Box male shotgun from Róperwerk-Giessereimaschinen GmbH, Viersen, DE, the molding tool of which was heated to 180 ° C. The mixture of the molding composition is introduced into the molding tool using compressed air (5 bar) and kept in the molding tool for an additional 35 seconds. To accelerate the curing of the mixture, hot air (2 bar, 150 ° C at the entrance to the tool) was passed through the molding tool for the last 20 seconds. The molding tool was opened and the test bar was removed.

The coating compositions were applied to the dipstick; the parameters of the application are listed in Table 2. The test bars were coated either immediately after the removal of the molding tool or after a cooling time of 30 minutes.

After application of the coating, the coated test rods were carried out in a drying oven for 30 min at 150 ° C.

To determine the flexural strengths, the test rods were placed in a Georg Fischer resistance test apparatus equipped with a 3-point bending device (DISA Industrie AG, Schaffhausen, CH) and the resulting force was measured at the rupture of the test bar.

The uncoated flexural strengths were measured according to the following plan: - 10 seconds after removal (heat resistance) - 1 hour after the elimination (resistance to cold).

The resistance to bending was coated according to the following scheme: Coating 1 minute after removal (hot coating) - Coating 30 minutes after removal (cold coating) The resistance to bending coating was measured according to the following plan: - 10 seconds after the elimination of the drying oven (hot hardening, hot coating) - Coating 30 minutes after the elimination (cold hardening, hot coating, immediately after removing it from the furnace) - 10 seconds after the elimination of the drying oven (hot hardening, cold coating, room temperature 20 ° C - Coating 30 minutes after removal (cold hardening, cold coating) Table 3: Composition of the molding mixtures Table 4: Hardening in Georg Fischer test rods Table 5: Hardening in long males Results The use of a coating containing the alcohol is not desirable due to the drawback presented by the release of the emissions during the casting process. The use of standardized water-based coating agents, test tubes made of agents Molding materials containing water glass loses considerable strength (sizing agent 2).

Surprisingly, it was found that by using a combination of certain clays, sizing agents with an unusually high solids content can be produced, the viscosity of which is comparable to that of commercial ready-to-use sizing agents such like Trioflex ® K-LS 1.

The quality of the inorganic cores and the molds coated with these sizing agents is improved in a lasting manner, and thus for example, the storage stability of the cores and molds for several days can be achieved. It should be mentioned, in particular, that despite the unusually high solids content, the viscosity of the sizing agents is in a usual range for sizing agents. The agents can be put in the proper condition for the application without the need to use special additives or large amounts of water.

The high resistances of cores coated with sizing agent 2 according to the invention provide evidence of the positive effect.

Claims (14)

1. Sizing composition comprising (A) at least the following clays: (Al) 1 to 10 parts by weight of paligorskite (A2) 1 to 10 parts by weight of hectorite and (A3) 1 to 20 parts by weight of sodium bentonite, based on the ratio of the components (Al), (A2) and (A3) relative to another, and (B) a carrier fluid comprising water that can be completely evaporated up to 160 ° C and 1013 mbar, and (C) refractory materials other than (A), wherein paligorskite is a magnesium-aluminum hydrosilicate and is present in the form of rod-shaped crystals with particle sizes of 1 to 3 fim in length and 1 to 5 nm in diameter.

2. Sizing composition according to claim 1, comprising, independently of one another, (Al) from 1 to 5 parts by weight of paligorskite (A2) 1 to 5 parts by weight of hectorite and (A3) from 1 to 10 parts by weight of sodium bentonite.

3. Sizing composition in accordance with Claim 1 or 2, characterized in that the total clay content of Al, A2 and A3 of the sizing agents combined amounts of 0.1 to 4.0% by weight, preferably 0.5 to 3.0% by weight and particularly preferably 1.0 to 2.0. % by weight, based on the solids content of the sizing composition.

4. Sizing composition according to one or more of the preceding claims, characterized in that the carrier fluid comprises more than 50% by weight of water and also preferably comprises alcohols, including polyalcohols and polyether alcohols.

5. Sizing composition according to one or more of the preceding claims, characterized in that the solids content of the sizing composition amounts to 20 to 90% by weight, especially more than 80% by weight to 85% by weight.

6. Sizing composition according to one or more of the preceding claims, characterized in that the sizing composition comprises from 10 to 85% by weight of refractory material, based on the solids content of the sizing composition.

7. Sizing composition according to one or more of the preceding claims, characterized in that the refractory materials are quartz, aluminum oxide, zirconium dioxide, aluminum silicates, sands of zirconium, zirconium silicates, olivine, talc, mica, graphite, coke, feldspar, diatomite, kaolin, calcined kaolin, kaolinite, metakaolinite, iron oxide, bauxite and / or mixtures thereof.

8. Gluing composition according to one or more of the preceding claims, characterized in that the refractory materials have particle sizes of 0.1 to 500 μm, especially 1 to 200 μm, measured by light scattering in accordance with the standard DIN / ISO 13320.

9. Sizing composition according to one or more of the preceding claims, characterized in that the sizing composition comprises 0.1 to 20% by weight, especially 0.5 to 5% by weight, of at least the binder, based on the solids content of the gluing composition.

10. Sizing composition according to one or more of the claims, characterized in that the sizing composition is used as a concentrate and the fraction of the refractory solid (C) in the sizing composition is more than 70% by weight, preferably more than 80 % by weight, in each case based on the solids fraction of the sizing composition.

11. Use of the sizing composition according to one or more of the claims above for mixtures of coating molding materials which are cured with an inorganic binder, especially water glass as binder, especially in the presence of silicon dioxide, aluminum oxide, titanium oxide or zinc oxide and / or mixtures thereof in the mixtures of molding composition and amorphous silicon dioxide especially.

12. Method for dimensioning molds and males cured with an inorganic binder, comprising the steps: a) provide a sizing composition by the combination of at least (A) the following clays (Al) 1 to 10 parts by weight of paligorskite (A2) 1 to 10 parts by weight of hectorite and (A3) 1 to 20 parts by weight of sodium bentonite, based on the ratio of the components (Al), (A2) and (A3) in relation to another and (B) a carrier fluid comprising water that can be completely evaporated up to 160 ° C and 1013 mbar, and (C) Refractory materials other than (A), in which the paligorskite is a magnesium-aluminum hydrosilicate and is present in the form of crystals in the form of a rod and with particle sizes of 1 to 3 μp? of length and i of from 1 to 5 nm in diameter, and b) size molds and cores with the sizing composition, wherein the molds and cores consist of mixtures of molding materials cured with an inorganic binder.

13. Method according to claim 12, characterized in that the sizing composition is characterized by the features of claims 1 to 10.

14. Method according to claim 12 or 13, characterized in that the binder is a water glass and the mixtures of the molding material comprise particulate silicon dioxide, particulate aluminum oxide, particulate titanium oxide or particulate zinc oxide. / or mixtures thereof, especially amorphous silicon dioxide particles.