DE102019002802A1 - Sizing composition, method for coating a casting mold, use of the sizing composition for coating a casting mold and casting mold - Google Patents

Abstract

The present invention relates to a size composition comprising: a solid component which comprises a first solid which can split off CO2 in the temperature range from about 150 to about 1000 ° C. and which has a D50 value of at most about 10 μm. Furthermore, a method for coating a casting mold, the use of the size composition for coating a casting mold and the coated casting mold are disclosed.

Description

Technical area

The present invention relates to a sizing composition capable of suppressing veins in iron and heavy metal casting. The present invention further relates to a method for coating a casting mold, the use of the size composition for coating a casting mold, and the corresponding casting mold.

State of the art

Most products in the iron, steel and non-ferrous metal industries go through casting processes for initial shaping. The molten liquid materials, ferrous metals or non-ferrous metals, are converted into shaped objects with certain workpiece properties. For the shaping of the cast pieces, very complicated casting molds for receiving the molten metal must first be made. The casting molds are divided into lost molds, which are destroyed after each casting, and permanent molds, with each of which a large number of castings can be produced. The lost molds usually consist of a refractory, granular mold base material that is solidified with the help of a hardenable binder.

Molds are negatives, they contain the cavity to be poured, which results in the casting to be manufactured. The inner contours of the future casting are formed by cores. During the production of the mold, the cavity is formed in the mold base material by means of a model of the casting to be produced. Inner contours are represented by cores that are formed in a separate core box.

Both organic and inorganic binders can be used to produce the casting molds, and they can be hardened by cold or hot processes. Cold processes are processes in which curing takes place essentially at room temperature without heating the basic mold material mixture. The curing usually takes place by a chemical reaction, which can be triggered, for example, by passing a gaseous catalyst through the molding base mixture to be hardened, or by adding a liquid catalyst to the molding base mixture. In hot processes, the mold base material mixture is heated to a sufficiently high temperature after molding, for example to drive out the solvent contained in the binder, or to initiate a chemical reaction by which the binder is cured by crosslinking.

The production of the casting molds can proceed in such a way that the basic mold material is first mixed with the binder, so that the grains of the basic mold material are coated with a thin film of the binder. The basic molding material mixture obtained from the basic molding material and the binding agent can then be introduced into a corresponding mold and, if necessary, compacted in order to achieve sufficient stability of the casting mold. The casting mold is then hardened, for example by heating it or by adding a catalyst which causes a hardening reaction. If the casting mold has reached at least a certain initial strength, it can be removed from the mold.

As already mentioned, casting molds for the production of metal bodies are often composed of so-called cores and molds. Different requirements are placed on the cores and shapes. In the case of molds, a relatively large surface area is available to dissipate gases that arise during casting due to the action of the hot metal. With cores there is usually only a very small area available over which the gases can be discharged. In the event of excessive gas development, there is therefore the risk that gas will pass from the core into the liquid metal and lead to the formation of casting defects there. The inner cavities are therefore often created by sand cores that have been solidified by cold box binders, i.e. a binder based on polyurethane, while the outer contour of the casting is represented by cheaper shapes, such as a green sand mold, a furan resin or a phenolic resin bonded form or through a steel mold.

For larger molds, organic polymers are usually used as binders for the refractory, granular mold base material. Washed, classified quartz sand is often used as the refractory, granular mold base material, but other mold base materials such as. B. zircon sands, chromite sands, chamottes, olivine sands, feldspathic sands and andalusite sands can be used. The molding base mixture obtained from the molding base material and the binding agent is preferably in a free-flowing form.

At present, organic binders, such as. B. polyurethane, furan resin or epoxy-acrylate binders are used, in which the curing of the binder takes place by adding a catalyst.

The selection of the suitable binding agent depends on the shape and size of the casting to be produced, the production conditions and the material used for the casting. For example, polyurethane binders are often used in the production of small castings that are produced in large numbers, as these enable fast cycle times and thus also series production.

The use of two-component polyurethane binders for core production has gained great importance in the foundry industry. One component contains a polyol with at least two OH groups per molecule, the other a polyisocyanate with at least two NCO groups per molecule. In one form of core production, the so-called cold box process, the two components are first mixed with a suitable basic molding material, for example quartz sand, simultaneously or one after the other. This mixture, the so-called basic molding material mixture, is then transferred to the storage container of a core shooting machine, from there conveyed with the aid of compressed air into a molding tool and cured in this by introducing a gaseous low-boiling tertiary amine as a catalyst so that a solid, self-supporting core is obtained ( U.S. 3,409,579 ). The basic molding material can also contain additives as further constituents, such as those in EP 0 795 366 A1 are described.

For example, quartz, zirconium or chrome ore sand, olivine, chamotte and bauxite can be used as refractory mold base materials. Furthermore, synthetically produced molding raw materials can also be used, e.g. Aluminum silicate hollow spheres (so-called microspheres), glass beads, glass granulate or the spherical ceramic mold base materials known under the name “Cerabeads” or “Carboaccucast”. Mixtures of the molding raw materials mentioned are also possible.

In order to improve the surface finish of the castings, the cores and molds can be coated with a coating known as a size before use.

Sizing compositions conventionally contain at least one refractory material as the proportion determining the purpose. The purpose of this refractory material is mainly to influence the surface of the molded casting to be coated in order to meet the above-mentioned requirements with regard to the avoidance of sand defects, which lead to defects in the casting and to uncleanliness of the cast part.

For example, in foundry technology, the refractory material can close the sand pores of a core or molded part in order to prevent the casting metal from penetrating.

Examples of refractory materials are pyrophyllite, zirconium silicate, andalusite, chamotte, iron oxide, kyanite, bauxite, olivine, aluminum oxide, quartz, talc, calcined kaolins (metakaolin) and / or graphite alone or as mixtures thereof.

So describe WO 2004/083321 A1 and EP 2 364 795 A1 the use of fine-grained material such as metakaolin, which can impregnate the sand pores, and a platelet-shaped coarse pyrophyllite, which covers the sand surface and thus provides good protection against both veins and penetrations.

Conventionally, a sizing composition comprises a carrier liquid. The solid constituents of the size composition can form a suspension with the carrier liquid, whereby the solid constituents are processable and can be processed by a suitable method, e.g. Dip, can be applied to the body to be coated.

In general, when coating porous materials, the application behavior of the coating compound is influenced not only by the rheology of the coating compound, but also by the suction behavior of the porous body and by the retention capacity of the carrier liquid by the coating material. With regard to the suction behavior of porous bodies, it should be noted that substrates with hydraulic binders such as clay, cement and water glass usually soak up the carrier liquid particularly strongly.

In the case of coating compositions based on an aqueous system, the use of adjusting agents, such as natural slime or cellulose derivatives, is known. Although these result in a high water retention capacity of the coating material, the rheology of the system becomes negative influences that the coating compounds have unfavorable, lower pseudoplastic properties and run more viscously. This can lead to undesirable application features such as the formation of drops and curtains as well as uneven layer thicknesses. Particularly when dipping is used as an application method, the optimization of the run-off behavior of the coating compound to achieve contour formation, uniform layer thickness and low drop formation is important.

In principle, every coating compound should be kept in a homogeneous state during processing in order to prevent the solids of the suspension from settling. In connection with the required application behavior, the rheological character and the degree of thixotropy of the complex suspensions should meet the desired requirements.

For example, swellable activated phyllosilicates are used in numerous areas of technology as thickeners for water-containing systems. Using shear forces, the layered silicates are dispersed in finely divided form in the system, the individual layer platelets largely or completely separating from one another and forming a colloidal dispersion or suspension in the system, which leads to a gel structure.

A method for producing casting molds and cores from synthetic resin-bonded molding sand includes, for example, the production of a basic form or a base core from the molding sand and the application of a refractory coating containing inorganic constituents at least to those surfaces of the base form / base core that are in contact with the cast metal Come into contact. The purpose of the mold coatings is, on the one hand, to influence the surface of the molded part, to improve the appearance of the cast part, to influence the cast part metallurgically and / or to avoid casting defects. Furthermore, these coatings or finishes have the function of chemically isolating the mold from the liquid metal during casting, which prevents any adhesion and enables the later separation of the molded and cast part. In addition, the coating ensures a thermal separation of the molded and cast part. The heat transfer can be used in a targeted manner to influence the cooling of the casting. In the production of cold box cores, problems with expansion errors in the sand occur again and again in practice, which occur due to the so-called quartz jump of the conversion from α- to ß-quartz and a linear expansion of about 1% at approx. 580 ° C Cause tension in the core surface. This causes so-called leaf ribs (torn cores with penetrated metal) or scabs (blasted sand layer) that lead to a raised cast surface and to sand inclusions in other places.

Another topic is the increasing demand from automotive foundries for increasingly thin-walled cast parts of 3 to 5 mm with a high dimensional accuracy of 0.2 to 0.3 mm. Since commercially available coatings are typically applied with a dry layer thickness of 0.2 to 0.4 mm to avoid casting defects in automobile casting, the high layer thickness represents a limitation for improving the dimensional tolerance. So-called dripping noses or curtain formation also lead to dimensional problems when the coating is applied and tightness of thin-walled cast parts.

WO 2011/110798 A1 describes a foundry coating composition comprising a liquid carrier, a binder and a particulate refractory filler, wherein the particulate refractory filler comprises a first relatively coarse fraction with a particle size of d> 38 µm and a second relatively fine fraction with a particle size of d <38 µm wherein no more than 10% of the total particulate refractory filler has a particle size of 38 µm <d <53 µm and 0 to 50% of the second relatively fine fraction consists of calcined kaolin.

DE 10 2009 032 668 A1 describes a ready-to-use size for the production of mold coatings on lost molds or on cores for iron and steel casting, the size containing a weight-related proportion of 0.001% or more and less than 1% of inorganic hollow bodies, characterized in that the inorganic hollow bodies consist partially or entirely of crystalline material.

WO 2006/063696 A1 describes a sizing composition for casting molds, comprising a solvent component and a solid component, characterized in that the solid component comprises a mixture of metakaolinite and pyrophyllite as the main component.

EP 2 176 018 A1 describes a method for casting vermicular and spherical cast iron in an SO ₂ epoxy-bound sand, where the sulfur is prevented by carbonates from causing graphite degeneration in the edge zone of the metal. Alkaline earth carbonate is also called.

DE 10 2016 211 930 A1 describes the use of carbonates and / or phosphates in combination with refractory fillers, preferably on acid-bound sand molds to avoid the so-called white coating.

WO 2011/075220 A1 describes the use of carbonates as an additive against vein formation in the sand mixture, although there is no indication of the grain size distribution, but grain sizes of more than 50 μm are usually used to reduce losses in strength.

It was an object of the present invention to provide a sizing composition which enables the production of thin-walled cast parts with a high dimensional tolerance and ensures good protection against leaf ribs and penetrations.

Figure list

• 1 : Schematic side view of a step core
• 2 : Schematic view of a step core from above
• 3 : Schematic side view of a cathedral core

Summary of the invention

1. 1. Eine Schlichtezusammensetzung, umfassend:
   • eine Feststoffkomponente, die einen ersten Feststoff umfasst, der im Temperaturbereich von etwa 150 bis etwa 1000 °C CO₂ abspalten kann, und der einen D50 Wert von höchstens etwa 10 µm aufweist.
2. 2. Die Schlichtezusammensetzung gemäß Punkt 1, wobei der erste Feststoff einen D99 Wert von höchstens etwa 30 µm und einen D90 Wert von höchstens etwa 20 µm aufweist.
3. 3. Die Schlichtezusammensetzung gemäß Punkt 1 oder 2, wobei der erste Feststoff aus Carbonaten der Elemente der 2., 7., 8., 9., 10., 11. und 12. Gruppen des Periodensystems ausgewählt ist.
4. 4. Die Schlichtezusammensetzung gemäß Punkt 3, wobei der erste Feststoff aus Calciumcarbonat, Magnesiumcarbonat, Dolomit, oder Eisencarbonat oder deren Mischungen ausgewählt ist.
5. 5. Die Schlichtezusammensetzung gemäß Punkt 1 oder 2, wobei der erste Feststoff aus Stärke, insbesondere Reis- oder Haferstärke, ausgewählt ist.
6. 6. Die Schlichtezusammensetzung gemäß einem der Punkte 1 bis 5, wobei die Schlichtezusammensetzung ferner eine Trägerflüssigkeit umfasst und wobei die Trägerflüssigkeit bevorzugt Wasser umfasst.
7. 7. Die Schlichtezusammensetzung gemäß Punkt 6, wobei das Löslichkeitsprodukt des ersten Feststoffs in der Trägerflüssigkeit ausgedrückt als pK_L, bei 25 °C, mindestens etwa 4 beträgt.
8. 8. Ein Verfahren zur Beschichtung einer Gießform, wobei das Verfahren die Schritte umfasst:
   1. (a) Bereitstellen einer Gießform, gegebenenfalls mit einem oder mehreren Gießkernen bestückt, die eine Oberfläche umfasst, die einen Gießhohlraum definiert,
   2. (b) Bereitstellen einer Schlichtezusammensetzung gemäß einem der Punkte 1 bis 7; und
   3. (c) Aufbringen der Schlichtezusammensetzung auf mindestens einen Teil der Oberfläche, die den Gießhohlraum definiert.
9. 9. Verfahren gemäß Punkt 8, wobei die Schlichtezusammensetzung ferner eine Trägerflüssigkeit umfasst und die Schlichtezusammensetzung nach Schritt (c) getrocknet wird.
10. 10. Verfahren gemäß Punkt 8 oder 9, wobei die Schlichte mindestens 2 mm in die beschlichtete Oberfläche eindringt und die Schichtdicke der Schlichte nach dem Trocknen der Schlichte höchstens etwa 100 µm beträgt.
11. 11. Verwendung einer Schlichtezusammensetzung gemäß einem der Punkte 1 bis 7 zur Beschichtung einer Gießform, wobei die Gießform, gegebenenfalls mit einem oder mehreren Gießkernen bestückt, eine Oberfläche umfasst, die einen Gießhohlraum definiert, und die Schlichtezusammensetzung auf mindestens einen Teil der Oberfläche, die den Gießhohlraum definiert, aufgebracht wird.
12. 12. Verwendung gemäß Punkt 11, wobei die Schlichte mindestens 2 mm in die beschlichtete Oberfläche eindringt und die Schichtdicke der Schlichte nach dem Trocknen der Schlichte höchstens etwa 100 µm beträgt.
13. 13. Eine beschichtete Gießform, gegebenenfalls mit einem oder mehreren Gießkernen bestückt, erhältlich nach dem Verfahren gemäß einem der Punkte 8 bis 10.

Accordingly, the present invention is directed to the following points.

1. 1. A sizing composition comprising:
   • a solid component which comprises a first solid which can split off CO ₂ in the temperature range from about 150 to about 1000 ° C. and which has a D50 value of at most about 10 μm.
2. 2. The size composition according to point 1 wherein the first solid has a D99 value of at most about 30 μm and a D90 value of at most about 20 μm.
3. 3. The size composition according to point 1 or 2 , wherein the first solid consists of carbonates of the elements of 2 ., 7th ., 8th ., 9 ., 10 ., 11 . and 12 . Groups of the periodic table is selected.
4. 4. The size composition according to point 3 , wherein the first solid is selected from calcium carbonate, magnesium carbonate, dolomite, or iron carbonate or mixtures thereof.
5. 5. The size composition according to point 1 or 2 , wherein the first solid is selected from starch, in particular rice or oat starch.
6. 6. The size composition according to one of the points 1 to 5 wherein the size composition further comprises a carrier liquid and wherein the carrier liquid preferably comprises water.
7. 7. The size composition according to point 6 , wherein the solubility product of the first solid in the carrier liquid, expressed as pK _L , at 25 ° C, is at least about 4.
8. 8. A method of coating a casting mold, the method comprising the steps of:
   1. (a) Providing a casting mold, optionally equipped with one or more casting cores, which comprises a surface that defines a casting cavity,
   2. (b) Providing a size composition according to one of the points 1 to 7th ; and
   3. (c) applying the sizing composition to at least a portion of the surface defining the mold cavity.
9. 9. Procedure according to point 8th wherein the size composition further comprises a carrier liquid and the size composition is dried after step (c).
10. 10. Procedure according to point 8th or 9 , the size penetrating at least 2 mm into the coated surface and the layer thickness of the size after drying of the size being at most about 100 μm.
11. 11. Use of a size composition according to one of the points 1 to 7th for coating a casting mold, the casting mold, optionally equipped with one or more casting cores, comprising a surface that defines a casting cavity, and the sizing composition is applied to at least part of the surface that defines the casting cavity.
12. 12. Use according to point 11 , the size penetrating at least 2 mm into the coated surface and the layer thickness of the size after drying of the size being at most about 100 μm.
13. 13. A coated casting mold, optionally equipped with one or more casting cores, obtainable by the method according to one of the points 8th to 10 .

Detailed description of the invention

• eine Feststoffkomponente, die einen ersten Feststoff umfasst, der im Temperaturbereich von etwa 150 bis etwa 1000 °C CO₂ abspalten kann, und der einen D50 Wert von höchstens etwa 10 µm aufweist.

The present invention relates to a sizing composition comprising:

• a solid component which comprises a first solid which can split off CO ₂ in the temperature range from about 150 to about 1000 ° C. and which has a D50 value of at most about 10 μm.

Solid component

All components that are present as solids after drying of the ready-to-use size composition are referred to as solids components. In this context, for example, 120 ° C. can be specified as the drying temperature.

First solid

The grain size distribution of the individual constituents of the size composition and in particular of the first solid can be determined on the basis of the passage proportions D99, D90, D50 and D10. These are measures of the particle size distribution. The passage proportions D99, D90, D50 and D10 denote the proportions in 99%, 90%, 50% and 10% of the particles which pass through a sieve with a mesh size corresponding to the specified grain size fraction. With a D50 value of, for example, 10 μm, 50% of the particles are less than 10 μm in size. The grain size and the passage proportions D99, D90, D50 and D10 can be determined by means of laser diffraction granulometry according to ISO13320. The percentage of passage is given on a volume basis. In the case of non-spherical particles, a hypothetical spherical grain size is calculated and used as a basis.

In a preferred embodiment, the D10 value of the first solid is at most about 3 μm, more preferably from about 0.1 μm to about 3 μm, more preferably from about 0.1 μm to about 2 μm, particularly preferably from about 0.1 μm up to about 1 µm.

The D50 value of the first solid is at most about 10 μm, preferably from about 0.5 μm to about 10 μm, more preferably from about 0.5 μm to about 7 μm, particularly preferably from about 0.5 μm to about 6 μm.

In a preferred embodiment, the D90 value of the first solid is at most about 20 μm, more preferably from about 5 μm to about 20 μm, more preferably from about 5 μm to about 15 μm, particularly preferably from about 5 μm to about 10 μm.

In a preferred embodiment, the D99 value of the first solid is at most approximately 30 μm, more preferably from approximately 5 μm to approximately 30 μm, further preferably from approximately 5 μm to approximately 20 μm, particularly preferably from approximately 5 μm to approximately 15 μm.

In a preferred embodiment, one or more of the above-mentioned D10, D50, D99 and D90 values are fulfilled at the same time. In a particularly preferred embodiment, the above-mentioned D50, D99, D90 values and optionally the D10 value are fulfilled at the same time.

The desired grain size can be set by crushing the first solid until the desired grain size is achieved. Alternatively or additionally, the desired grain size can be provided by sieving. In the case of synthetic first solids, it is also possible to adjust the process parameters during production so that the desired grain size is achieved.

The first solid separates in the temperature range from about 150 to about 1000 ° C., preferably from about 300 to about 1000 ° C., CO ₂ . This can be determined by heating the first solid in a nitrogen atmosphere in a tube furnace and measuring by means of absorption in a washing bottle with milk of lime and subsequent filtration, drying and gravimetric determination whether CO _{2 is} emitted at at least one temperature in the range mentioned . The CO ₂ partial pressure should be below 0.01 bar, to avoid errors caused by influencing the balance. The splitting off of CO ₂ required according to the invention thus only comprises the decomposition of the first solid, with CO _{2 being} formed, and not combustion of the same.

The chemical composition of the first solid is not particularly restricted, provided that the first solid is able to split off CO ₂ , as required.

In one embodiment, the first solid is selected from carbonates of the elements of the 2nd, 7th, 8th, 9th, 10th, 11th and 12th groups of the periodic table. The first solid is preferably selected from carbonates of Mg, Ca, Sr, Ba, Mn, Fe, Co, Ni, Cu and Zn, preferably Mg, Ca, Mn, Fe, Cu and Zn, particularly preferably Mg, Ca, Mn and Fe, more preferably Mg, Ca and Fe.

Mixed carbonates of the above elements, such as, for example, calcium-magnesium carbonate, can also be used as carbonates. Mixtures of the aforementioned carbonates are also possible.

Furthermore, it goes without saying that the carbonates can be used not only in their pure form, but also in the form of natural minerals. In the case of natural minerals, the content of carbonates of the elements of the 2nd, 7th, 8th, 9th, 10th, 11th and 12th groups of the periodic table is preferably more than about 50% by weight, more preferably more than about 70 % By weight and particularly preferably more than 90% by weight.

Calcium carbonate

Calcium carbonate CaCO ₃ can be used in pure form or in the form of a natural mineral such as calcite (calcite, double spar), aragonite and vaterite. Well-known natural minerals that contain calcite, aragonite, or vaterite are chalk, limestone, and marble.

Calcium carbonate can be made synthetically by methods known in the art. Among other things, precipitation with carbon dioxide, the soda-lime process and the Solvay process, in which calcium carbonate is a by-product of ammonia production, are known.

Calcium carbonate occurs in several anhydrous and also two hydrate modifications as well as other amorphous forms. At around 600 ° C they break down into calcium oxide and carbon dioxide: CaCO ₃ → CaO + CO ₂

According to the present invention, the kind of calcium carbonate is not particularly limited. Any known calcium carbonate can be used. The calcium carbonate can preferably be selected from calcite and aragonite, more preferably the calcium carbonate is calcite.

Magnesium carbonate

Magnesium carbonate MgCO ₃ can be used in its pure form or in the form of a natural mineral such as magnesite (bitter spar ₎ , barringtonite, nesquehonite and lansfordite.

Magnesium carbonate can be synthesized using methods known in the art. Among other things, precipitation with carbon dioxide is known.

According to the present invention, the kind of magnesium carbonate is not particularly limited. Any known magnesium carbonate can be used. The magnesium carbonate can preferably be selected from magnesite, magnesia alba and upscalite, magnesite is particularly preferred.

Calcium Magnesium Carbonate

Calcium carbonates and magnesium carbonate can be used as mixed carbonates. A well-known calcium-magnesium carbonate is dolomite CaMg (CO ₃ ) ₂ , which also occurs as dolomite spar, rautenspat and pearl spar.

According to the present invention, the kind of calcium magnesium carbonate is not particularly limited, and dolomite can preferably be used.

Iron carbonate

Iron carbonate FeCO ₃ can be used in pure form or in the form of a natural mineral such as siderite, iron lime, iron spar, spate iron stone, chalybit and steel stone, siderite is preferred. Alternatively, iron carbonate can be made synthetically according to methods known in the art.

Manganese carbonate

Manganese carbonate MnCO ₃ can be used in its pure form or in the form of a natural mineral such as rhodochrosite. Alternatively, manganese carbonate can be synthesized using methods known in the art.

Zinc carbonate

Zinc carbonate ZnCO ₃ can be used in its pure form or in the form of a natural mineral such as smithsonite. Alternatively, zinc carbonate can be synthetically prepared according to methods known in the art.

Copper carbonate

Copper carbonate CuCO ₃ can be used in the form of basic compounds or in the form of a natural mineral such as malachite and azurite. Alternatively, copper carbonate can be synthetically made according to methods known in the art.

The table below gives an overview of the properties of preferred carbonate compounds. connection Separation of CO ₂ [° C] Solubility product pK _L Calcite 898 8.48 Magnesite 650 8.03 dolomite 800 17.09 Siderite 200 10.89 Zinc carbonate 180 10.00 Copper carbonate 280 9.63 Malachite* 350-384 33.16 Rhodochrosite 350 10.39 * as CuCO ₃ Cu (OH) ₂

In a preferred embodiment, the first solid is selected from calcium carbonate, magnesium carbonate, dolomite, or iron carbonate or mixtures thereof.

In a second embodiment, the first solid is selected from starch, in particular rice or oat starch. The starch should preferably be insoluble in the carrier liquid as described below.

In the ready-to-use form, the size composition preferably contains a carrier liquid. It is preferred if the first solid is insoluble in the carrier liquid. In the context of the present invention, “insoluble in the carrier liquid” is understood to mean that the first solid has a solubility product, expressed as pK _L , of at least about 4, preferably at least about 6, at 25 ° C. The solubility product can be measured by mixing a certain amount of substance to be measured (e.g. 100 g) into a certain amount of solvent (e.g. 1 liter) at a temperature of 25 ° C, filtering off the liquid, and either by evaporating the Solvent or by chemical analysis of the dissolved substance.

The amount of the first solid in the solid component is not particularly limited and can be from about 65 to about 99% by weight, preferably from about 80 to about 99% by weight, more preferably from about 90 to be about 99% by weight. The upper limit of the amount of the first solid in the solid component can be 90% by weight, preferably 95% by weight. Natural minerals often contain mixtures of various chemical compounds. If a natural mineral is used, the amount of the first solid specified above relates to the amount of the chemical compound (s) which can split off CO ₂ in the temperature range from about 150 to about 1000 ° C. In the case of dolomite rock, for example 90% by weight of calcium-magnesium-carbonate and 10% by weight of other constituents that cannot split off CO ₂ , only the 90% would be used when calculating the amount given above % By weight calcium magnesium carbonate must be taken into account. The 10% by weight of other constituents that cannot split off CO ₂ would thus be part of the solid component, provided that they remain as a solid residue during the defined drying process.

Second solid

In addition to the first solid, the solid component can also contain a second solid. A second solid is understood to mean any solid which is not able to split off CO ₂ in the temperature range from about 150 to about 1000.degree.

Examples of the second solid include graphite, mica, non-swellable aluminum silicates and swellable sheet silicates.

Graphite can be contained in an amount from 0 to about 20% by weight, preferably from 0 to about 10% by weight, based on the solid component.

One or more types of mica can be used. Examples are muscovite or phlogopite mica. Mica can be contained in an amount of from 0 to about 10% by weight, preferably from 0 to about 5% by weight, more preferably from 0 to about 2% by weight, based on the solid component.

The second solid can contain one or more non-swellable aluminum silicates. Examples of this are pyrophyllite, metakaolinite, mullite, kyanite or silimanite. Pyrophyllite and metakaolinite are preferred. Non-swellable aluminum silicates can be present in an amount from 0 to about 10% by weight, preferably from 0 to about 5% by weight, based on the solid component.

The D10 value of the second solid (with the exception of the swellable sheet silicates) is in a preferred embodiment at most about 15 μm, preferably from about 0.1 μm to about 10 μm, particularly preferably from about 0.1 μm to about 8 μm, especially preferably from about 0.1 µm to about 7 µm.

The D50 value of the second solid (excluding the swellable phyllosilicates) is in a preferred embodiment at most about 50 μm, more preferably from about 0.5 μm to about 30 μm, more preferably from about 0.5 μm to about 25 μm, particularly preferred from about 0.5 µm to about 20 µm.

The D90 value of the second solid (excluding the swellable phyllosilicates) is in a preferred embodiment at most about 100 μm, more preferably from about 5 μm to about 90 μm, more preferably from about 5 μm to about 80 μm, particularly preferably from about 5 μm up to about 75 µm.

The D99 value of the second solid (excluding the swellable phyllosilicates) is in a preferred embodiment at most about 250 μm), more preferably from about 5 μm to about 200 μm, further preferably from about 5 μm to about 150 μm, particularly preferably from about 5 µm to about 100 µm.

In a preferred embodiment, one or more of the above-mentioned D50, D99 and D90 values are fulfilled at the same time. In a particularly preferred embodiment, the above-mentioned D10, D50, D99 and D90 values are fulfilled at the same time.

Swelling is the property of dispersed solids in solvents to store them and thus to become more voluminous. This usually increases the viscosity very much.

In one embodiment, the second solid comprises one or more swellable sheet silicates in order to reduce the settling behavior of the size composition and to control the rheology. The swellable sheet silicates are not particularly restricted. Any swellable layered silicate known to the person skilled in the art can be used which is capable of storing water between the layers. The swellable sheet silicate made of attapulgite (palygorskite), ball clay, serpentines, kaolins, Smectites (such as saponite, montmorillonite, beidellite and nontronite), vermiculite, illite, sepiolite, synthetic lithium-magnesium layered silicate LAPONITE RD and mixtures thereof, particularly preferably attapulgite (palygorskite), serpentines, smectites (such as saponite, beidellite), and nontronite Vermiculite, illite, sepiolite, synthetic lithium-magnesium sheet silicate LAPONITE RD and mixtures thereof, particularly preferably the swellable sheet silicate can be attapulgite. Attapulgite is preferred because of the increased yield point.

Furthermore, the grain size of the swellable phyllosilicates is not particularly restricted; any customary grain size can be used. The D10, D50, D90 and D99 values given for the second solid also apply to the swellable sheet silicates.

In a preferred embodiment, the D10 value of the swellable phyllosilicates is at most about 5 μm, more preferably from about 0.1 μm to about 5 μm, more preferably from about 0.1 μm to about 4 μm, particularly preferably from about 0.1 µm to about 3 µm.

In a preferred embodiment, the D50 value of the swellable phyllosilicates is at most about 30 μm, more preferably from about 0.5 μm to about 25 μm, more preferably from about 0.5 μm to about 20 μm, particularly preferably from about 0.5 μm to about 15 µηι.

The D90 value of the swellable sheet silicates can preferably be at most about 50 μm, more preferably from about 5 μm to about 40 μm, more preferably from about 5 μm to about 30 μm, more preferably from about 5 μm to about 25 μm.

In a preferred embodiment, the D99 value of the swellable phyllosilicates is at most about 100 μm, more preferably from about 5 μm to about 90 μm, further preferably from about 5 μm to about 80 μm, particularly preferably from about 5 μm to about 75 μm.

In a preferred embodiment, one or more of the above-mentioned D50, D99 and D90 values are fulfilled at the same time. In a particularly preferred embodiment, the above-mentioned D50, D99 and D90 values are met at the same time.

The proportion of swellable phyllosilicates (especially attapulgite) in the sizing composition is not particularly limited; it can preferably be from about 0 to about 5 parts by weight, more preferably from about 0.1 to about 5 parts by weight, particularly preferably from about 0.1 to about 4 Parts by weight, even more preferably from about 0.1 to 2 parts by weight, based on the solid component.

Carrier liquid

The size composition can contain a carrier liquid to simplify application. All constituents which are volatilized by drying the ready-to-use size composition and are not present in the dried size are referred to as carrier liquid.

The sizing composition can be provided as a dry powder, as a concentrate which contains part of the required amount of carrier liquid and is to be diluted with further carrier liquid before use, or as a ready-to-use sizing composition which already contains the desired amount of carrier liquid.

The carrier liquid can be selected by one skilled in the art according to the intended application. The carrier liquid can preferably be selected from water, alcohols such as, for example, aliphatic C ₁ -C ₅ alcohols, or mixtures thereof. In a preferred embodiment, the carrier liquid is water, methanol, ethanol, n-propanol, iso-propanol, n-butanol, or mixtures thereof, particularly preferably water, ethanol, iso-propanol or mixtures thereof, more preferably the carrier liquid can be water.

Sizing compositions whose carrier liquid consists mainly of water are usually called water sizes. Sizing compositions whose carrier liquid consists mainly of alcohol or alcohol mixtures are called alcohol sizing agents. In one embodiment of the present invention, the carrier liquid comprises about 0 to about 100% by weight, preferably about 30 to about 100% by weight, more preferably about 60 to about 100% by weight, water, and about 100 as a further component to about 0% by weight, preferably about 70 to about 0% by weight, more preferably about 40 to about 0% by weight %, one or more alcohols defined above, based on the carrier liquid. According to the invention, both pure water-based sizes and pure alcohol-based sizes as well as water / alcohol mixtures can be used. In a particularly preferred embodiment, water is the sole carrier liquid. Alternatively, it is also possible to produce size compositions whose solvent component consists of alcohol or, in the case of so-called hybrid sizes, initially only consists of water. These sizes can be used as alcohol sizes by diluting them with an alcohol or an alcohol mixture. Ethanol, propanol, iso-propanol and mixtures thereof are preferably used here.

If necessary, other organic solvents can be used. Examples are alkyl acetate such as ethyl acetate and butyl acetate, and ketones such as acetone and methyl ethyl ketone. The proportion of further organic solvents is not particularly limited; it can preferably be from about 0 to about 10% by weight, more preferably from about 0 to about 5% by weight, particularly preferably from about 0 to about 1% by weight. , based on the carrier liquid.

The proportion of the carrier liquid in the size composition is not particularly limited; it can preferably be 80% by weight or less, more preferably 75% by weight or less, particularly preferably 70% by weight or less.

Accordingly, the proportion of the solid component in the size composition is preferably about 20% by weight or more, more preferably about 25% by weight or more, particularly preferably about 30% by weight or more.

In the ready-to-use size composition, the proportion of carrier liquid is preferably from about 40 to about 85% by weight, more preferably from about 45 to about 85% by weight, particularly preferably from about 50 to about 85% by weight.

Accordingly, the proportion of the solid component in the ready-to-use size composition is preferably from about 15 to about 60% by weight, more preferably from about 15 to about 55% by weight, particularly preferably from about 15 to about 50% by weight.

Optional additives

In addition to the above constituents, the size composition can contain customary additives such as binders, wetting agents, defoamers, pigments, dyes and biocidal active ingredients.

binder

The main task of a binder is to bind the solid component. The binder is preferably distinguished by an irreversible bond and thus results in an abrasion-resistant coating on the casting mold. The abrasion resistance is of great importance for the finished coating, since the coating can be damaged if the abrasion resistance is insufficient. In particular, the binder should not soften back due to humidity. According to the invention, it is possible to use all binders which are conventionally used, for example, in aqueous and / or water-alcohol systems. Water-soluble starches or dextrins, for example, whose D50 value is more than about 10 μm (preferably at least about 15 μm) and which are soluble in the carrier liquid, peptides, polyvinyl alcohol, polyvinyl acetate copolymers, polyacrylic acid, polystyrene, polyvinyl acetate-polyacrylate dispersions and mixtures thereof can be used as binders will. In a preferred embodiment of the invention, the binder comprises a dispersion of an alkyd resin which is soluble both in water and in lower (for example C _1-4 ) alcohols such as ethanol, propanol and isopropanol. Examples of alkyd resins are unmodified water-dispersible alkyd resins, based on a natural oil or their fatty acids with polyalcohols, as for example in U.S. 3,442,835 are described, or isocyanate-modified alkyd resins, as for example in U.S. 3,639,315 described and which are preferred, or epoxy-urethane-modified alkyd resins according to DE 43 08 188 . For example, products from the NECOWEL series from ASK Chemicals GmbH, 40721 Hilden, Germany, can be used. Further preferred binders are polyvinyl alcohols and polyvinyl acetate copolymers, in particular polyvinyl alcohols.

“Binder” is understood to mean the binding component, which can also be present as a solution or dispersion in diluted form.

The binders are preferably used in an amount of about 0.1 to about 5 parts by weight, more preferably about 0.2 to about 2 parts by weight, based on all ingredients of the size composition.

Wetting agents

Anionic and non-anionic surfactants of medium and high polarity (HLB value of 7 and higher) known to the person skilled in the art can preferably be used as wetting agents. Examples of wetting agents that can be used in the present invention are disodium dioctyl sulfosuccinate, ethoxylated 2,5,8,11-tetramethyl-6-dodecyn-5,8-diol, ethoxylated 2,4,7,9-tetramethyl 5-decyn-4,7-diol or combinations thereof, particularly preferably ethoxylated 2,4,7,9-tetramethyl-5-decyn-4,7-diol can be used.

The wetting agents are preferably used in an amount of from about 0.01 to about 1 part by weight, more preferably from about 0.05 to about 0.3 part by weight, even more preferably from about 0.1 to about 0.3 part by weight, based on all ingredients the size composition.

Defoamer

Defoamers or antifoam agents are used in order to prevent foam formation during the production of the size composition according to the invention and during the application of the same. Foam formation when applying the size composition can lead to an uneven layer thickness and holes in the coating. Silicone or mineral oil, for example, can be used as defoamers. The defoamer can preferably be selected from the FINASOL product range, commercially available from Total Deutschland GmbH.

In the present size composition, defoamers are used in an amount of from about 0.01 to about 1 part by weight, more preferably from about 0.05 to about 0.3 part by weight, even more preferably from about 0.1 to about 0.2 part by weight, based on all components of the sizing composition are used.

Pigments and dyes

Customary pigments and dyes can optionally be used in the size composition according to the invention. These are optionally added to provide a visible contrast, e.g. between different layers, or to bring about a stronger separation effect between the coating and the casting. Examples of pigments are red and yellow iron oxide. Examples of dyes are commercially available dyes such as the LUCONYL products from BASF SE.

The dyes and pigments are usually used in an amount of from about 0.01 to about 10 parts by weight, preferably from about 0.05 to about 5 parts by weight, based on all components of the size composition.

Biocidal active ingredients

The size composition can optionally (especially if the carrier liquid comprises water) contain one or more biocidal active ingredients in order to prevent bacterial infestation and thus to avoid a negative influence on the rheology and the binding force of the binding agent. The biocidal active ingredients are not particularly limited; they can preferably be selected from the group consisting of formaldehyde, glutaraldehyde, tetramethylolacetylenediurea, 2-methyl-4-isothiazolin-3-one (MIT), 5-chloro-2-methyl-4-isothiazolin-3- one (CIT), 1,2-benzisothiazolin-3-one (BIT), or mixtures thereof, more preferably from 2-methyl-4-isothiazolin-3-one (MIT), 1,2-benzisothiazolin-3-one ( BIT), or mixtures thereof, can be selected.

The proportion of biocidal active ingredients in the size composition is not particularly limited and depends on the selected biocidal active ingredient. The proportion can, for example, from about 0.001 to about 1.0 part by weight, preferably from about 0.005 to about 1.0 part by weight, more preferably from about 0.007 to about 1.0 part by weight, even more preferably from about 0.007 to about 0.9 part by weight , particularly preferably from about 0.007 to about 0.8 parts by weight, based on all constituents of the size composition.

In a preferred embodiment, a size composition according to the invention comprises about 10 to about 60 parts by weight of calcium carbonate, and about 0.1 to about 2 parts by weight of attapulgite, based on the solid component. Furthermore, the size composition contains about 0.2 to about 2 parts by weight of binder, about 0.1 to about 0.3 parts by weight of wetting agent, about 0.1 to about 0.2 part by weight of defoamer, about 0.005 to about 0.3 part by weight of biocidal active ingredient Difference to 100% by weight is the carrier liquid, particularly preferably water.

Manufacture of the size composition

The size compositions according to the invention are produced by customary processes. For example, a size composition according to the invention is prepared by introducing a large part of the carrier liquid (preferably the entire amount of the carrier liquid) and breaking up swellable sheet silicates (if used) using a high-shear stirrer (e.g. about 400 to about 2000 rpm) (premix B in the examples). Then further solid components, for example the first solid and (if used) pigments and dyes, are stirred in until a homogeneous mixture is formed. The order of addition plays no role or only a minor role and can easily be determined by a person skilled in the art. Finally (if used) wetting agents, defoamers, biocidal active ingredients and binding agents are stirred in. For example, the size composition is prepared at a temperature of preferably about 5 to about 50 ° C, more preferably about 10 to about 30 ° C, with a stirrer speed of preferably about 400 to about 2000 rpm, more preferably about 1000 to about 1500 rpm / min, and with a toothed disk with preferably d / D = about 0.3 to about 0.7, more preferably d / D = about 0.4 to about 0.6 (d is the diameter of the toothed disk of the stirrer; D is the diameter of the stirred tank).

The properties of the wash composition are preferably set as an impregnation wash so that the first solid can penetrate the surface of the casting mold. It is particularly preferred that the impregnation depth of the size composition is at least about 2 mm, preferably from about 2 mm to about 20 mm, more preferably from about 2 mm to about 6 mm. The impregnation depth can be measured by cutting.

The dry layer thickness of the dried coating that results from the size composition described above is the thickness of the layer of the dried size composition (“size”) which was obtained by drying the size composition by essentially completely removing the carrier liquid. Preferably, the dry layer thickness of the coating can be at most about 100 µm, more preferably from about 10 µm to about 100 µm, even more preferably from about 10 µm to about 50 µm. The dry layer thickness of the coating is determined either preferably by dimensioning bending bars before and after finishing (dried) with a micrometer screw or by measuring with a wet layer thickness comb. For example, you can use a comb to determine the dry film thickness by scratching away the coating at the end marks of the comb until the substrate appears. The dry layer thickness can then be read from the markings on the teeth. Instead, you can also determine the wet layer thickness in the matted state (hereinafter referred to as matt layer thickness) DIN EN ISO 2808 measure, in which case the dry layer thickness is 70 to 80% of the thickness of the matted layer. A “dulled” layer is a layer that is no longer flowable and in which the solvent content is so reduced that the surface no longer has a gloss.

The impregnation depth of the size composition is preferably at least about 2 mm and the dry layer thickness is at most about 100 μm. More preferably, the impregnation depth of the size composition is from about 2 mm to about 20 mm (more preferably from about 2 mm to about 6 mm) and the dry film thickness from about 10 µm to about 50 µm.

The viscosity of the ready-to-use size composition can be from about 10 seconds to about 16 seconds, preferably from about 10 seconds to about 13 seconds, determined in accordance with DIN 53211; Flow cup 4 mm, Ford Cup can be set.

The density of the ready-to-use size composition can, for example, from about 20 ° Be to about 50 ° Be, particularly preferably from about 25 ° Be to about 35 ° Be, determined by the Baume buoyancy method; DIN 12791.

Application of the size composition

1. (a) Bereitstellen einer Gießform, die eine Oberfläche umfasst, die einen Gießhohlraum definiert,
2. (b) Bereitstellen einer erfindungsgemäßen Schlichtezusammensetzung;
3. (c) Aufbringen der Schlichtezusammensetzung auf mindestens einen Teil der Oberfläche, die den Gießhohlraum definiert; und
4. (d) Trocknen der Schlichtezusammensetzung.

The wash composition according to the invention can be used for coating a casting mold. One possible process involves the following steps:

1. (a) providing a casting mold that includes a surface defining a casting cavity,
2. (b) providing a size composition according to the invention;
3. (c) applying the sizing composition to at least a portion of the surface defining the mold cavity; and
4. (d) drying the size composition.

All types of bodies that are necessary for the production of casting molds are referred to as casting molds. The casting molds are not particularly restricted; all casting molds customary in the iron, steel and non-metal industries can be used, for example cores, molds or chill molds. The casting molds can consist of a refractory, granular mold base material that is solidified with the aid of a hardenable binder. The refractory, granular molding base material is not particularly limited; any conventional molding base material can be used. The refractory, granular mold base material can preferably be quartz sand, zircon sand, chromite sand, chamotte, bauxite, olivine sand, sand containing feldspar, andalusite sand, aluminum silicate hollow spheres (also known as "microspheres"), glass beads, glass granules, which are known as "Cerabeads" or "Carboaccucast". known spherical ceramic mold base materials or mixtures thereof. The sizing composition according to the invention is particularly preferably used for casting molds which have used quartz sand or portions of quartz sand as the basic molding material.

The grain size of the sand should be from about 100 to about 600 µm, preferably from about 100 to about 500 µm, and most preferably from about 200 to about 400 µm.

The curable binder is not particularly limited. Any curable binder known to those skilled in the art can be used. Organic binders such as polyurethane, furan resin or epoxy-acrylate binders, inorganic binders such as water glass, or mixtures thereof can preferably be used; the binders based on PUR cold box, water glass CO ₂ , resol methyl formate can particularly preferably be used (MF), resol-CO ₂ , furan resin, phenolic resin or water glass ester binders, with polyurethane binders being particularly preferred. The proportion of the curable binder in the casting mold is not particularly limited; the binder can be present in any usual proportion. The proportion of the binder is preferably from about 0.2 to about 5 parts by weight, more preferably from about 0.3 to about 4 parts by weight, particularly preferably from about 0.4 to about 3 parts by weight, based on 100 parts by weight of refractory, granular molding base material. The wash compositions are suitable for all conceivable applications in which coating of casting molds with wash is desired. As examples of casting molds, ie for cores and forms in foundry use, sand cores can be mentioned, the PUR cold box, water glass-C0 ₂ -, resol-MF, resol-CO ₂ -, furan resin, phenolic resin or water glass Ester are bound. Other examples of preferred casting molds which can be coated with the size compositions according to the invention are, for example, in “Formstoffe und Formverfahren”, Eckart Flemming and Werner Tilch, Wiley-VCH, 1993, ISBN 3-527-30920-9 described.

The surfaces of the casting mold, optionally equipped with one or more casting cores, define a casting cavity into which the liquid metal is introduced. The surfaces of a casting mold can be the surfaces of a core or a hollow mold. According to the invention, the casting molds and cores can be coated in whole or in part. Preferably, the surfaces of the casting mold and cores that come into contact with the casting metal are coated.

The sizing composition is initially provided in a ready-to-use form. If it is available as a dry powder or as a concentrate, carrier liquid is added in order to achieve the consistency required for application.

In one embodiment, for example, the size composition can be in the form of a kit (multi-component pack which contains two or more containers for different components). The solid component and the carrier liquid can be present next to one another in separate containers. All constituents of the solid component can be present as a powdery solid mixture in a container. The constituents of the solid component can alternatively be provided as several separate components. Any further components to be used, such as binders, wetting agents, defoamers, pigments, dyes and biocidal active ingredients, can be present in this kit together with the above-mentioned components or in one or more separate containers. The carrier liquid can either comprise the additional components to be used if necessary, for example in a common container, or it can be separated from other optional components Ingredients in a separate container. To produce a ready-to-use size composition, the appropriate quantities of the components are mixed with one another.

Typically, the size composition can be in the form of a water size. Alternatively, a ready-to-use alcohol wash can also be prepared from this water wash by adding an alcohol.

The application and drying of at least one layer of a sizing composition on at least a portion of the surface defining the casting cavity is not particularly limited. All conventional application methods described in the art can be used for this purpose. Examples of preferred application methods are dipping, flooding, spraying and brushing. Conventional application methods are discussed, for example, in “Formstoffe und Formverfahren”, Eckart Flemming and Werner Tilch, Wiley-VCH, 1993, ISBN 3-527-30920-9.

In the case of dipping as an application process, the casting mold is immersed, for example, in a container with a ready-to-use sizing composition for about 1 second to about 2 minutes. The time it takes for the excess size composition to drain off after dipping depends on the drainage behavior of the size composition used. After a sufficient drainage time, the coated casting mold is subjected to drying.

All drying methods conventional in the art, such as, for example, drying in the air, drying with dehumidified air, drying with microwave or infrared radiation, drying in a convection oven, and the like can be used as the drying method. In a preferred embodiment of the invention, the coated casting mold is dried at about 100 to about 250 ° C., more preferably at about 120 to about 180 ° C., in a convection oven. When alcohol sizes are used, the size composition is preferably dried by burning off the alcohol or alcohol mixture. The coated casting mold is additionally heated by the heat of combustion. In a further preferred embodiment, the coated casting mold is air-dried without further treatment.

The size composition according to the invention can be used as a base layer. The dry layer thickness of the base layer is, for example, at most about 100 μm, more preferably from about 10 μm to about 80 μm, even more preferably from about 10 μm to 50 μm.

Casting molds coated according to the invention are preferably used for the production of metal bodies. They are particularly suitable for the manufacture of engine and engine components, brake discs, turbochargers, exhaust manifolds and general machine components.

In a casting process, a casting mold coated according to the invention is provided, liquid metal is poured in and the casting mold is removed after the metal has hardened.

The following examples illustrate the invention without restricting it.

EXAMPLES

Attapulgit

ATTAGEL 40 von BASF, 67063 Ludwigshafen, Deutschland D99 ca. 50 µm, D90 ca. 20 µm, D50 ca. 9 µm, D10 ca. 2 µm

Biozid

ACTICIDE F (N) (70 Gew:-% Tetramethylolacetylendiharnstoff) von Thor GmbH, 67346 Speyer, Deutschland

Entschäumer

FINASOL, Total Deutschland GmbH, 10117 Berlin, Deutschland

Netzmittel

SURFYNOL 440, Evonik Corporation, Allentown, PA 18195, USA

Bindemittel

POLYVIOL (25 Gew.-% Polyvinylalkohol)), Wacker AG, 81737 München, Deutschland

Graphit amorph

Georg H. Luh, 65396 Walluf, Deutschland D 99 ca. 90 µm, D90 ca. 60 µm, D50 ca. 18 µm, D10 ca. 7 µm

Glanzpudergraphit

Fa. Georg H. Luh GmbH, 65396 Walluf, Deutschland; C-Gehalt min. 85 Gew.-%, Asche max. 15 Gew.-% Kornverteilung bestimmt nach Laserbeugungsgranulometrie: D10 15 bis 30 µm, D50 80 bis 120 µm, D90 190 bis 250 µm

Ton

Kärlicher Blauton gelbbrennend T7001 KTS, Kärlicher Ton und Schamottewerke Mannheim GmbH & Co. KG, 56218 Mülheim-Kärlich, Deutschland; Chemische Analyse, in Gew.-% geglüht: SiO₂ 53,66, Al₂O₃ 37, TiO₂ 3,75, Fe₂O₃ 2,98, CaO 0,73, MgO 0,63, K₂O 0,75, Na₂O 0,07; Sedimentationsanalyse mittels Sedigraphmessung in Masse-%: <2,0 µm 95,7, Mineralanalyse in Masse-%: Kaolinit 70 bis 75, Illit 7,0, Montmorillonit 15 bis 20, Quarz 2,0, Fe-Ti-Minerale 3,0

Glimmer

Fa. Georg H. Luh GmbH, 65396 Walluf, Deutschland; chemische Analyse in Gew.-%: SiO₂ 43 bis 46, Al₂O₃ 33 bis 37, Fe₂O₃ 2 bis 5, K₂O 9 bis 11; Siebanalyse Durchgang durch Sieb 60 µm: 25 bis 64 Gew.-%

Calcinierter Kaolin

Satintone W, BASF Corporation, Charlotte, NC, USA D99 ca. 65,5 µm, D90 8,53 µm, D50 2,4 µm, D10 ca. 0,4 µm

The following components were used:

Attapulgite

ATTAGEL 40 from BASF, 67063 Ludwigshafen, Germany D99 approx. 50 µm, D90 approx. 20 µm, D50 approx. 9 µm, D10 approx. 2 µm

Biocide

ACTICIDE F (N) (70% by weight tetramethylolacetylenediurea) from Thor GmbH, 67346 Speyer, Germany

Defoamer

FINASOL, Total Deutschland GmbH, 10117 Berlin, Germany

Wetting agents

SURFYNOL 440, Evonik Corporation, Allentown, PA 18195, USA

binder

POLYVIOL (25% by weight polyvinyl alcohol)), Wacker AG, 81737 Munich, Germany

Amorphous graphite

Georg H. Luh, 65396 Walluf, Germany D 99 approx. 90 µm, D90 approx. 60 µm, D50 approx. 18 µm, D10 approx. 7 µm

Gloss powder graphite

Georg H. Luh GmbH, 65396 Walluf, Germany; C content min. 85% by weight, ash max. 15% by weight particle size distribution determined by laser diffraction granulometry: D10 15 to 30 μm, D50 80 to 120 μm, D90 190 to 250 μm

volume

Kärlicher blue tone, yellow-burning T7001 KTS, Kärlicher Ton und Schamottewerke Mannheim GmbH & Co. KG, 56218 Mülheim-Kärlich, Germany; Chemical analysis, calcined in% by weight: SiO ₂ 53.66, Al ₂ O ₃ 37, TiO ₂ 3.75, Fe ₂ O ₃ 2.98, CaO 0.73, MgO 0.63, K ₂ O 0 .75, Na ₂ O 0.07; Sedimentation analysis by means of Sedigraph measurement in% by mass: <2.0 µm 95.7, mineral analysis in% by mass: kaolinite 70 to 75, illite 7.0, montmorillonite 15 to 20, quartz 2.0, Fe-Ti minerals 3, 0

mica

Georg H. Luh GmbH, 65396 Walluf, Germany; chemical analysis in% by weight: SiO ₂ 43 to 46, Al ₂ O ₃ 33 to 37, Fe ₂ O ₃ 2 to 5, K ₂ O 9 to 11; Sieve analysis passage through a 60 µm sieve: 25 to 64% by weight

Calcined kaolin

Satintone W, BASF Corporation, Charlotte, NC, USA D99 approx. 65.5 µm, D90 8.53 µm, D50 2.4 µm, D10 approx. 0.4 µm

Calciumcarbonat

ETIQUETTE VIOLETTE von Omya GmbH, 50679 Köln, Deutschland D99 ca. 15 µm, D90 ca. 8 µm, D50 ca. 3 µm, D10 ca. 1 µm

Dolomit

HELADOL10, Helawit GmbH, D-23829 Wittenborn, Deutschland D99 ca. 15 µm, D90 ca. 8 µm, D50 ca. 3 µm, D10 ca. 1 µm

Eisencarbonat

Cofermin Chemicals GmbH & Co. KG, D-45130 Essen, Deutschland wie erhalten 100 mesh = 150 µm micronisiert durch Vermahlung auf D 99 etwa 5 µm, D90 etwa 1,4 µm , D50 etwa 0,5 µm , D10 etwa 0,2 µm

Reisstärke

Hermann Kröner GmbH, D-49479 Ibbenbüren, Deutschland D50 = etwa 5 µm

The following components were examined as the first solid:

Calcium carbonate

ETIQUETTE VIOLETTE from Omya GmbH, 50679 Cologne, Germany D99 approx. 15 µm, D90 approx. 8 µm, D50 approx. 3 µm, D10 approx. 1 µm

dolomite

HELADOL10, Helawit GmbH, D-23829 Wittenborn, Germany D99 approx. 15 µm, D90 approx. 8 µm, D50 approx. 3 µm, D10 approx. 1 µm

Iron carbonate

Cofermin Chemicals GmbH & Co. KG, D-45130 Essen, Germany as received 100 mesh = 150 µm micronized by grinding to D 99 about 5 µm, D90 about 1.4 µm, D50 about 0.5 µm, D10 about 0.2 µm

Rice starch

Hermann Kröner GmbH, D-49479 Ibbenbüren, Germany D50 = about 5 µm

A size composition for coating a casting mold was obtained as follows:

The first solid was combined with premix A and B and the size was adjusted with additional water to an outlet viscosity of approx. 13 seconds, determined using an immersed flow cup according to DIN 53211 with a 4 mm nozzle. Wt% Premix A Premix B water 99.4 85.1 Wetting agents 0.6 Biocide 1.0 binder 9.0 Attapulgite 4.0 Defoamer 0.9 All figures in% by weight

Dome core moldings with the dimensions diameter 50 mm and height 50 mm with an upper radius of 25 mm and step cores with the dimensions R ₁ = 63 mm / H ₁ = 25 mm, R ₂ = 54 mm / H ₂ = 25 mm, R ₃ = 45 mm / H ₃ = 25 mm, R ₄ = 37 mm / H ₄ = 25 mm, R ₅ = 28 mm / H ₅ = 25 mm, R ₆ = 21 mm / H ₆ = 25 mm and R ₇ = 12 mm / H ₇ = 43 mm (where R _{I is} the radius and H _{I is} the height of the i-th step) were made from sand H32 by the Quarzwerke Group with 0.8% by weight of ASKOCURE 388 (available from ASK Chemicals, Hilden, Germany) and 0.8% by weight of ASKOCURE 666, each based on the sand, produced in the polyurethane cold box process by amine gassing with dimethylethylamine. In the 1 Level 0 of the dome core shown is glued in and therefore does not come into contact with the metal.

The dome cores or step cores were then dipped into the stirred size by hand for 5 seconds and then dried in a drying oven at 120 ° C.

The dried cores were freed from the size by rubbing them off at the core marks and the mirror surface, so that no compressive stress arises, and glued into the casting mold made of water glass / ester hardened sand H32 using ASKOBOND RAPID A (available from ASK Chemicals, Hilden, Germany). After the mold package had been closed and clamped using screw clamps, the castings were made at 1420 ° C using GJL 200 gray cast iron.

After the castings had cooled and unpacked, the cavity of the core was sandblasted (2 bar pressure) and subjected to an evaluation.

• Stufenkern: in der nachfolgenden Tabelle wurde die Anzahl der Blattrippen auf den jeweiligen Stufen angegeben.
• Domkern: in der nachfolgenden Tabelle wurde die Blattrippenbildung mit Schulnoten von 1 bis 6 bewertet.

The leaf veins were rated as follows:

• Step kernel: the number of leaf veins on the respective steps was given in the table below.
• Dome core: in the table below, the vein formation was rated with school grades from 1 to 6.

Examples according to the invention Cathedral core

Examples according to the invention: step core

When using the step core, which is glued into a cylindrical sand mold with a cavity with a diameter of 150mm and a height of 200mm so that the "foot" is on top, the volume ratio of metal to sand core increases from the 1st step (the "foot", R = 63 mm) gradually. The mold is poured from the bottom. The "number of leaf veins Step n" indicates the number of leaf veins that are present in the step core cast on the nth stage.

Furthermore, a dome core and step core based on a patent application were used as a comparative example DE 10 2018 004 234.1 coated according to the manufacturer's instructions.

Example of a cathedral core not according to the invention

Example step core not according to the invention

The results show that the sizing composition according to the invention, with a very low matt layer thickness of only 25 to 100 μm, shows sufficiently high leaf vein protection in the dome core test and also in the step core test. For the evaluation, the steps were used in the step test 1 to 5 evaluated as this corresponds to the most common and demanding applications in foundries for automotive parts in terms of the wall thickness ratio of metal to sand. Here, the effect of the size composition according to the invention exceeds the effect of conventional size compositions against vein defects which are applied in thick layers of 300 to 500 μm.

It can be seen that the size composition according to the invention saves the process step of adding sand additive and provides a much higher active ingredient concentration in the zone where this concentration is required. In particular, the gas formation provides very good protection against so-called leaf ribs, which are often found in quartz sand due to the thermal expansion of the quartz sand (quartz crack) and the inadequate thermal strengths, especially in polyurethane cold box cores.

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• US 3409579 [0010]
• EP 0795366 A1 [0010]
• WO 2004/083321 A1 [0016]
• EP 2364795 A1 [0016]
• WO 2011/110798 A1 [0024]
• DE 102009032668 A1 [0025]
• WO 2006/063696 A1 [0026]
• EP 2176018 A1 [0027]
• DE 102016211930 A1 [0028]
• WO 2011/075220 A1 [0029]
• US 3442835 [0093]
• US 3639315 [0093]
• DE 4308188 [0093]
• DE 102018004234 [0136]

Non-patent literature cited

• DIN EN ISO 2808 [0107]
• "Formstoffe und Formverfahren", Eckart Flemming and Werner Tilch, Wiley-VCH, 1993, ISBN 3-527-30920-9 [0114]

Claims (13)

A sizing composition comprising: a solid component which comprises a first solid which can split off CO ₂ in the temperature range from about 150 to about 1000 ° C. and which has a D50 value of at most about 10 μm. The size composition according to Claim 1 wherein the first solid has a D99 value of at most about 30 μm and a D90 value of at most about 20 μm. The size composition according to Claim 1 or 2 , wherein the first solid is selected from carbonates of the elements of the 2nd, 7th, 8th, 9th, 10th, 11th and 12th groups of the periodic table. The size composition according to Claim 3 , wherein the first solid is selected from calcium carbonate, magnesium carbonate, dolomite, or iron carbonate or mixtures thereof. The size composition according to Claim 1 or 2 , wherein the first solid is selected from starch, in particular rice or oat starch. The size composition according to one of Claims 1 to 5 wherein the size composition further comprises a carrier liquid and wherein the carrier liquid preferably comprises water. The size composition according to Claim 6 , wherein the solubility product of the first component in the carrier liquid, expressed as pK _L , at 25 ° C, is at least about 4. A method for coating a casting mold, the method comprising the steps of: (a) providing a casting mold, optionally equipped with one or more casting cores, which comprises a surface which defines a casting cavity, (b) providing a size composition according to one of the Claims 1 to 7th ; and (c) applying the sizing composition to at least a portion of the surface defining the mold cavity. Procedure according to Claim 8 wherein the size composition further comprises a carrier liquid and the size composition is dried after step (c). Procedure according to Claim 8 or 9 , the size penetrating at least 2 mm into the coated surface and the layer thickness of the size after drying of the size being at most about 100 μm. Use of a size composition according to one of the Claims 1 to 7th for coating a casting mold, the casting mold, optionally equipped with one or more casting cores, comprising a surface that defines a casting cavity, and the sizing composition is applied to at least part of the surface that defines the casting cavity. Use according to Claim 11 , the size penetrating at least 2 mm into the coated surface and the layer thickness of the size after drying of the size being at most about 100 μm. A coated casting mold, optionally equipped with one or more casting cores, obtainable by the method according to one of the Claims 8 to 10 .

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