DE102017107655A1 - Use of an acid-containing sizing composition in the foundry industry - Google Patents

Abstract

The present invention describes the use of a sizing composition comprising an aqueous phase having a pH of at most 5 and one or more refractories in the foundry industry, as well as sized waterglass-bound foundry molds, especially foundry molds and / or foundry cores, each comprising such an aforementioned sizing composition , Furthermore, the invention describes a method for producing a sized, water glass-bound foundry molded body. Also, the invention describes a kit, i.a. containing an aforesaid sizing composition comprising aqueous acid and one or more refractory materials.

Description

The present invention relates to the use of a sizing composition, in particular comprising an aqueous phase having a pH of at most 5 and one or more refractory materials in the foundry, as well as sized, waterglass bound foundry moldings, in particular foundry molds and / or foundry cores, each of which used according to the invention Sizing composition. Furthermore, the invention relates to a method for producing a sized, glass-bound foundry molded body (mold or core). Also, the invention relates to a kit, i.a. containing a sizing composition used according to the invention. The invention is defined in the appended claims.

Casting in a lost form is a common process for producing near-net shape components, especially in metal casting. After casting, the mold is destroyed and the casting is removed. Shapes are negatives, they contain the emptying cavity, which results in the casting to be produced. The inner contours of the future casting can be formed by cores. In the manufacture of the mold, the cavity can be formed into the molding material by means of a model of the casting to be manufactured. Cores are usually formed in a separate core box.

For foundry molds (also referred to as "molds" for the purposes of the present invention) and foundry cores (also referred to as "cores" for purposes of the present invention), predominantly refractory granular materials such as e.g. washed, classified quartz sand used. Further suitable molding materials which are known per se are e.g. Zirconsande, Chromitsande, chamois, olivine sands, feldspathaltige sands and Andalusitsande. A molding material may also be a mixture of various of the above or other preferred molding materials. The refractory molding base material is preferably in free-flowing form, so that it can be filled into a suitable mold and compacted therein. The molding base material or the corresponding molding material mixture (molding material) is compacted in order to increase the strength of the casting mold. For the production of the foundry molds, the mold bases are bound with inorganic or organic molding binders (binders). By the molding material binder a firm cohesion between the particles of the molding material is generated, so that the foundry mold obtains the required mechanical stability.

For the production of foundry molds both organic and inorganic molding material binders can be used, the curing of which can be carried out in each case by cold or hot processes. The skilled worker refers to processes which are carried out essentially at room temperature without heating the foundry mold. The curing is usually carried out by a chemical reaction, which is triggered for example by the fact that a gas is passed as a catalyst after molding through the molding mixture to be cured, which contains the molding material and the molding material binder. In hot processes, the molding material mixture is heated to a sufficiently high temperature after molding to expel, for example, the solvent contained in the molding material binder and / or to initiate a chemical reaction by which the molding material binder is cured, for example, by crosslinking.

Regardless of the curing mechanism is common to all organic molding binders that they decompose thermally when filling liquid metal into the mold and thereby pollutants such. As benzene, toluene, xylenes, phenol, formaldehyde and other, partially unidentified, thermolysis or cracking products can release. Although various measures have succeeded in minimizing these emissions, they are currently not completely avoidable with organic molding binders.

In order to minimize or avoid the emission of decomposition products during the casting process, it is possible to use molding material binders which are based on inorganic materials and at most contain a very low proportion of organic compounds. Such molding material binder systems have been known for some time, for example from the documents GB 782205 A . US 6972059 B1 . US 5582232A . US 5474606 A and US 7022178 ,

Hereinafter, the term "inorganic molding material binder" denotes a molding material binder, which consists entirely predominantly, preferably more than 95 wt .-%, preferably more than 99 wt .-%, most preferably completely of water and inorganic materials, so that the proportion on organic compounds in such an inorganic molding material binder is preferably less than 5 wt .-%, preferably less than 1 wt .-% and most preferably 0 wt .-%.

The term "inorganically bound" in the context of the present text means that a mold or a core has been bonded with an inorganic molding material binder (as defined above).

Of particular importance as a component of inorganic molding binders is alkali water glass. As the alkali water glass from a melt solidified, glassy, ie amorphous, water-soluble sodium, potassium and lithium silicates, their mixtures and the corresponding aqueous solutions are called. Hereinafter, the term "water glass" refers to such amorphous, water-soluble sodium, potassium and / or lithium silicates and / or their aqueous solutions and / or mixtures of the aforementioned silicates and / or their solutions, each having a molar modulus (molar ratio) of SiO ₂ to M ₂ O in the range of 1.6 to 4.0, preferably in the range of 1.8 to 2.5, wherein M ₂ O denotes the total amount of lithium, sodium and potassium oxide. The term "water-glass bound" means that a foundry shaped body, in particular a mold or a core, has been produced or can be produced using a molding material binder which comprises water glass or consists of water glass. For example, in the Scriptures US 7770629 B2 proposed a molding material mixture which comprises, in addition to a refractory molding material, a water glass-based molding material binder and a particulate metal oxide, wherein precipitated silica or fumed silica is preferably used as the particulate metal oxide.

Inorganic molding material binders, however, also have disadvantages compared to organic molding material binders. For example, foundry molds or cores produced with known inorganic molding material binders have a relatively low or lower stability to atmospheric moisture or to water or aqueous moisture. This is e.g. a storage of such foundry molds or cores over a longer period of time, as usual with organic molding binders, not reliable possible.

• - Verbesserung der Glätte der Gussstückoberfläche;
• - Möglichst vollständige Trennung von flüssigem Metall und Form bzw. Kern;
• - Vermeidung von chemischen Reaktionen zwischen Bestandteilen von Form/Kern und Schmelze, dadurch Erleichterung der Trennung zwischen Form/Kern und Gussstück und/oder
• - Vermeidung von Oberflächenfehlern am Gussstück wie z.B. Gasblasen, Penetrationen, Blattrippen und/oder Schülpen.

Usually, especially in steel and cast iron, the surfaces of foundry moldings, in particular of molds and cores, are coated with a coating called "sizing", in particular those surfaces which come into contact with cast metal. Finishes form a boundary or barrier layer between the shape / core and the metal, including the targeted suppression of failure mechanisms at these sites or the use of metallurgical effects. In general, finishing in foundry technology should fulfill the following functions:

• - improvement of the smoothness of the casting surface;
• - As complete as possible separation of liquid metal and form or core;
• Avoidance of chemical reactions between mold / core and melt components, thereby facilitating the separation between mold / core and casting and / or
• - Prevention of surface defects on the casting such as gas bubbles, penetrations, leaf ribs and / or slugs.

The abovementioned and, if appropriate, further functions are generally set and optimized by the exact composition of the size or the size composition to be applied to the mold or the core or adapted to the respective intended purpose.

Coating compositions for use in the foundry usually contain or consist of the following components: (i) one or more fine-grained refractories, i. fine-grained, refractory to highly refractory inorganic materials, (ii) a carrier liquid comprising one or more compounds (water, alcohols, etc.) and (iii) as further constituents, e.g. one or more sizing binders (hereinafter also referred to as "binders" for short) and / or biocides and / or wetting agents and / or rheological additives. Accordingly, ready-to-use sizing compositions for coating molds and cores are mostly suspensions of fine-grained, refractory to highly refractory inorganic materials (refractories) in a carrier liquid, e.g. an aqueous (water-containing) carrier liquid or a non-aqueous (non-water-containing) carrier liquid; for details regarding the carrier liquid, see below.

The size or the size composition is applied by a suitable application method, for example spraying, dipping, flooding or brushing on the inner contour of the casting mold or on the core and dried there, so that a size coat or size film is formed. The drying of the size coat can be done by supplying heat or radiant energy, for example by microwave radiation, or by drying in the room air. In the case of sizing compositions, which contain combustible compounds in the carrier liquid, the drying can also be done by burning these compounds.

As "refractory" in the present text in accordance with the usual expert understanding of masses, materials and minerals are referred to, at least for a short time the temperature load during casting or during the solidification of molten iron, usually cast iron, can withstand. As "high-fire" masses, materials and minerals are referred to, which can withstand the pouring heat of a steel melt in the short term. The temperatures that can occur when casting molten steel, are usually higher than the temperatures that can occur during the casting of iron or cast iron melts. Refractory materials, materials and minerals (refractories) and high-refractory masses, materials and minerals are known in the art, for example from the DIN 51060: 2000-06 ,

The refractory materials used in sizing compositions are usually mineral oxides, silicates or clay minerals. Examples of refractory materials which are also suitable for the purposes of the present invention are quartz, aluminum oxide, zirconium dioxide, aluminum silicates, phyllosilicates, zirconium silicates, olivine, talc, mica, graphite, coke, feldspar, diatomite, kaolins, calcined kaolins, metakaolinite, iron oxide, chromite and bauxite. each of which can be used individually or in any combination with each other. The refractory material serves, inter alia, to close the pores in a foundry mold or a core against the penetration of the liquid metal. Next is achieved by the refractory thermal insulation between the foundry mold or core and liquid metal. The refractory material is usually provided in powder form. Unless otherwise stated, pulverulent refractories then have an average particle size (preferably measured by means of light scattering) ISO 13320: 2009-10 ) in the range of 0.1 to 500 μm, preferably in the range of 1 to 200 μm. Suitable refractory materials are in particular those materials which have melting points which are at least 200 ° C. above the temperature of the particular molten metal used and / or which do not react with the molten metal.

The refractories are usually dispersed in a carrier liquid. The carrier liquid is one or the constituent of a sizing composition which is preferably liquid under normal conditions (20 ° C and 1013.25 hPa) and / or vaporizable at 160 ° C and normal pressure (1013.25 hPa). Preferred carrier liquids which are also suitable for the purposes of the present invention are selected from the group consisting of water and organic carrier liquids and mixtures thereof with one another and / or with further constituents. Suitable organic carrier liquids are preferably alcohols, including polyalcohols and polyether alcohols. Preferred alcohols are ethanol, n-propanol, isopropanol (2-propanol), n-butanol and glycol. Water and aqueous mixtures (including aqueous solutions) are often preferred as a carrier liquid.

Sizing binders (binders) are primarily used to fix the refractory materials contained in a sizing composition on the molding material. Examples of binders which are also suitable in the context of the present invention are synthetic resins (organic polymers) or synthetic resin dispersions, such as polyvinyl alcohols, polyacrylates, polyvinyl acetates and / or corresponding copolymers of the abovementioned polymers. Polyvinyl alcohols are preferred. Natural resins, dextrins, starches and peptides are also suitable as binders.

Biocides prevent bacterial infestation. Examples of biocides which are also suitable in the context of the present invention are formaldehyde, 2-methyl-4-isothiazolin-3-one (MIT), 5-chloro-2-methyl-4-iosthiazolin-3-one (CIT) and 1,2 -Bisisothiazolin-3-one (BIT). The biocides, preferably the individual biocides mentioned, are usually used in a total amount of 10 to 1000 ppm, preferably in an amount of 50 to 500 ppm, in each case based on the total mass of the ready-to-use sizing composition (intended to be applied directly to a casting mold or to a casting mold) to apply a core).

Rheological additives (adjusting agents) are used to adjust the flowability of the size desired for processing. Also suitable in the context of the present invention, inorganic adjusting agents are, for example, swellable clays, such. Sodium bentonite or Attapulgit (Palygorskit). As well as in the context of the present invention suitable organic adjusting agents are, for example, swellable polymers such as cellulose derivatives, in particular carboxymethyl, methyl, ethyl, hydroxyethyl and hydroxypropyl cellulose; Mucilages, polyvinylpyrrolidone, pectin, gelatin, agar agar, polypeptides and / or alginates. The aforementioned rheological additives or setting agents are preferred ingredients of the sizing composition used according to the invention.

In particular, in the case of aqueous (ie as the carrier liquid or component of the carrier liquid containing water) sizing compositions, wetting agents can be used to achieve better wetting of the molding material. The person skilled in the art is familiar with ionic and nonionic wetting agents. For example, dioctylsulfosuccinates are used as ionic wetting agents and alkynediols or ethoxylated alkynediols are used as nonionic wetting agents. The aforementioned wetting agents are also preferred ingredients of the aqueous sizing composition used in the invention.

A sizing composition may further contain defoamers, pigments and / or dyes. As defoamers, for example, silicone or mineral oil can be used. Examples of pigments are red and yellow iron oxide and graphite. Examples of dyes are commercially available dyes known to the person skilled in the art. The abovementioned defoamers, pigments and / or dyes are also preferred ingredients of the sizing composition used according to the invention

In order to meet the increasing demands in the area of environmental and emission protection, inorganic mold material binders, in particular water-glass-containing molding material binders, should become more important in the production of molds and cores in the area of steel and iron casting. In order to achieve the desired or necessary casting quality, it is, as stated above, usually necessary or advantageous to coat inorganically bound forms and cores with a size. Consequently, for the purposes of environmental and emission control, it is also desirable in the choice of sizing to dispense as far as possible with the use of organic carrier liquids, and preferably water-based sizing, i. Use of sizing with water as the sole carrier liquid or as at least predominant proportion of the carrier liquid.

However, as indicated above, foundry moldings, in particular molds and cores, which have been produced with inorganic molding material binders, in particular with water-glass-containing molding material binders, have low stability against the action of water or aqueous moisture. Consequently, the water contained in water-based sizing compositions can damage the thus treated (sized) inorganically bonded forms and cores. As a result, in particular the strength of the molds and cores thus sized can be disadvantageously reduced. This particular problem known in foundry technology (cf. WO 00 / 05010A1 ) can be met with previously used agents, including, for example, a particularly intensive curing of the molds and cores, consuming process for drying the applied size or the adaptation of the molding material mixture, so far only inadequate.

In document WO 00/05010 It is stated that a water-based coating can be applied in particular to carbon dioxide fumed and sodium silicate-bound cores and molds when the composition of the coating used is a water-soluble or water-miscible specific additive such as polyvalent esters Alcohols, carbonates, esters or lactones contains. The individual constituents of the coating system are preferably mixed together only immediately before the coating process.

In document WO 2013/044904 A1 It is stated that by combining certain clays as ingredients of a hydrous sizing, sizing with an unusually high solids content can be made, but whose viscosity is still comparable to commercially available ready-to-use sizings, the quality of cores coated with these sizings bonded to inorganic molding binders and shapes could be improved.

In the documents DE 10 2011 115 025 A1 and WO 2013/050022 A2 it is stated that the addition of certain salts in a certain concentration range to an aqueous sizing composition improves the quality of the sized inorganic cores and molds, in particular their storage stability can be increased. The salts are salts of magnesium and / or manganese, in particular their sulfates and chlorides.

The documents DE 10 2011 115 024 A1 and WO 2013/050023 A2 indicate that the addition of certain additives to an aqueous sizing composition improves the quality of the sized inorganic cores and molds, in particular their storage stability can be increased. As an additive component of the sizing composition, esters of formic acid (methanoic acid) are used, the chain length of the alcohol or the alcohol mixture used in the esterification in particular being on average less than six, and more preferably less than three, carbon atoms.

The document DE 27 30 753A1 describes a composition for coating molds used in the processing of molten metals and molds coated with this composition. The aforementioned composition may contain, for example, formic acid or its salts.

However, the above-mentioned problems, as their own studies have shown, even in a procedure according to the cited prior art still relevant extent.

• - die Festigkeit der damit herstellbaren geschlichteten Formen und/oder Kerne soll gegenüber mit bekannten wasserhaltigen Schlichten bzw. Schlichtezusammensetzungen geschlichteten Formen und Kernen erhöht werden, insbesondere soweit die Formen und Kerne mit anorganischen Formstoffbindemitteln, insbesondere mit wasserglashaltigen Formstoffbindemitteln, hergestellt wurden;
• - die Lagerstabilität sowie die Beständigkeit gegenüber Luftfeuchtigkeit der damit herstellbaren geschlichteten Formen und/oder Kerne soll gegenüber mit bekannten wasserhaltigen Schlichten bzw. Schlichtezusammensetzungen geschlichteten Formen und/oder Kernen erhöht werden;
• - die Lagerstabilität der Schlichtezusammensetzung selbst soll gegenüber bekannten wasserhaltigen Schlichtezusammensetzungen nicht signifikant verschlechtert sein oder sogar gesteigert werden;
• - die Applikation der Schlichtezusammensetzung auf heiße Formen und/oder Kerne (d.h. insbesondere auf solche Formen und/oder Kerne, welche Temperaturen von mehr als 50 °C, vorzugsweise Temperaturen im Bereich von 50 bis 100 °C, aufweisen) soll ermöglicht oder zumindest verbessert werden;
• - die damit herstellbaren geschlichteten Formen und Kerne sollen eine hohe Abgussgüte und Glätte der Gussstückoberfläche, vorzugsweise eine fehlerarme Abgussgüte, besonders bevorzugt eine fehlerfreie Abgussgüte, ermöglichen;
• - der Einsatz von anorganisch gebundenen, insbesondere wasserglasgebundenen Gießereiformkörpern, insbesondere Formen und/oder Kernen, soll auch für den Eisen- und/oder Stahlguss ermöglicht bzw. die Möglichkeit des Einsatzes für diese Zwecke soll erweitert werden.

Based on the prior art, therefore, there is a need for further improved sizing compositions for use in the foundry, which should or should have one or more, preferably all, of the following advantageous properties:

• the strength of the sized forms and / or cores produced thereby is to be increased compared to shapes and cores sized with known aqueous-containing sizes or sizing compositions, in particular insofar as the forms and cores have been produced with inorganic molding material binders, in particular with water-glass-containing molding material binders;
• - The storage stability and the resistance to humidity of the thus produced scalloped shapes and / or cores should be increased compared with known water-containing sizes or sizing compositions sized forms and / or cores;
• the storage stability of the sizing composition itself should not be significantly worsened or even increased compared with known aqueous sizing compositions;
• the application of the sizing composition to hot molds and / or cores (ie in particular to those molds and / or cores which have temperatures of more than 50 ° C., preferably temperatures in the range of 50 to 100 ° C.) is intended or at least improved become;
• - The thus produced scalloped shapes and cores should allow a high cast quality and smoothness of the casting surface, preferably a low-quality cast quality, particularly preferably a flawless Abgußgüte;
• - The use of inorganically bound, in particular water glass bonded foundry moldings, in particular molds and / or cores, should also be possible for iron and / or cast steel and the possibility of use for these purposes should be extended.

It has generally been an object of the present invention to provide a sizing composition for use in the foundry which has one or more or all of the aforementioned properties.

It was a primary object of the present invention to enable the use of a sizing composition in the foundry, which can be used on inorganically bound foundry moldings, preferably molds and / or cores, without adversely affecting their properties, in particular their strengths.

A further object of the present task was to provide sized inorganically bonded foundry moldings, in particular foundry molds and / or foundry cores, which in each case comprise a sizing composition to be specified according to the invention.

A further object of the present invention was to provide a corresponding process for the preparation of an inorganic bound foundry molded body sized with a water-containing size.

In addition, an object of the present invention was a kit, i.a. containing a sizing composition to be given according to the invention.

The invention is defined or described in more detail in the appended claims. Specific and / or preferred embodiments of the invention are described in more detail below. Unless otherwise stated, preferred aspects or embodiments of the invention may be combined with other aspects or embodiments of the invention, particularly with other preferred aspects or embodiments. The combination of respective preferred aspects or embodiments with each other again results in preferred aspects or embodiments of the invention. Embodiments, aspects or properties described in connection with the present invention for the size composition used according to the invention or described as being preferred, apply mutatis mutandis correspondingly or mutatis mutandis, for inventive method, for inventive sized forms or cores and kits according to the invention.

If in the following used sizing compositions, inventive method, coated forms or cores according to the invention and kits according to the invention are described, which "closer" certain embodiments, components or features "include" or should be understood in each case to a narrower extent corresponding variant of said uses, methods, sized molds or cores or kits, which "consists" of these specific embodiments, components or features.

1. (a) einen oder mehrere Feuerfeststoffe, und
2. (b) eine wässrige Phase mit einem pH-Wert von höchstens 5,

zur Herstellung eines Überzugs auf einer wasserglasgebundenen Form bzw. einem wasserglasgebundenen Kern, zur Verwendung in der Gießerei.According to the invention, the primary object and other aspects of the general object given above are achieved by the use of a sizing composition comprising

1. (a) one or more refractories, and
2. (b) an aqueous phase having a pH of at most 5,

for the production of a coating on a water-glass-bonded mold or a water-glass bonded core, for use in the foundry.

As refractory substances (see component (a)), one or more substances are preferably selected from the group consisting of quartz, aluminum oxide, zirconium dioxide, aluminum silicates, phyllosilicates, zirconium silicates, olivine, talc, mica, graphite, coke, feldspar, diatomite, kaolins, calcined kaolins, metakaolinite, iron oxide and bauxite.

For the purposes of the present invention, the pH in a sizing composition is determined in each case from the suspension or a suspension, preferably according to the standard method DIN 19260: 2012-10 ,

The foundry moldings which can be coated with the size composition of the invention can be prepared in any manner known per se, for example by firing, pouring or by 3D printing techniques.

Without guarantee of correctness, it is presumed that with the appropriate use of the aqueous sizing composition according to the invention, binding structures in the alkali silicate framework of the water-glass-bound, sifted foundry shaped body (mold or core) are attacked, however, possibly resulting weakening of the bonding structure by a further chemical reaction , such as an acid-base reaction, are again removed, as a result of which an increased strength of such sized, water-glass bonded foundry moldings is achieved in comparison with the prior art.

Preference is given to using a sizing composition according to the invention, wherein the water-glass-bonded form or the water-glass-bonded core contains particulate, amorphous silicon dioxide.

The term "particulate, amorphous silica" in the context of the present invention means particulate synthetic silica, preferably precipitated silica and / or pyrogenic silicic acids. Fumed silicas are preferred.

Precipitated silica is known per se and may be e.g. be obtained in a conventional manner by reaction of an aqueous alkali metal silicate solution with mineral acids: the resulting precipitate is then separated, dried and optionally ground. Fumed silicas are also known per se and can preferably be obtained in known manner at high temperatures by coagulation from the gas phase. The production of fumed silica may e.g. by flame hydrolysis of silicon tetrachloride, or for the purposes of the present invention preferably in the electric arc furnace by reduction of silica sand with coke or anthracite to silicon monoxide gas followed by oxidation to silica. Another preferred form of amorphous particulate silica of the present invention is that of zirconia production. Another, known per se, possibility of producing particulate amorphous silica is the spraying of a silicon dioxide melt: the primary, amorphous silicon dioxide particles do not arise here (as in other preferred production processes) through a milling process.

The primary amorphous silica particles ("primary particles") are often agglomerated, ie as agglomerates of primary particles, according to the abovementioned production processes. The particle shape of the primary particles of the particulate amorphous silica is preferably spherical. The spherical shape of the primary particles can be determined, for example, by means of scanning electron microscopy.

Water glass bonded shapes and cores, including those containing particulate amorphous silica, and their preparation are known per se, for example from the documents WO 2006/024540 and WO 2009/056320 , The aforementioned forms and cores known per se are suitable for the purposes of the present invention.

• (b1) Wasser, und
• (b2) eine oder mehrere Säuren, vorzugsweise mit einem pKa < 5, bevorzugt mit einem pKa < 4,

umfasst,
wobei vorzugsweise das Verhältnis der Masse des Bestandteils (b1) zur Masse des Bestandteils (b2) im Bereich von 10:1 bis 200: 1, besonders bevorzugt im Bereich von 10:1 bis 100:1 liegt.Also preferred according to one embodiment is an inventive or preferred use according to the invention of a sizing composition, wherein the aqueous phase (b)

• (b1) water, and
• (b2) one or more acids, preferably with a pKa <5, preferably with a pKa <4,

includes,
wherein preferably the ratio of the mass of the component (b1) to the mass of the component (b2) is in the range from 10: 1 to 200: 1, particularly preferably in the range from 10: 1 to 100: 1.

The one or more acids may be used in the preparation of the sizing composition of the invention in the usual form, i. solid or liquid and optionally diluted, preferably diluted with water, with other constituents of the sizing composition are mixed (ie in particular with refractory according to component (a) and water according to component (b1)) so that the desired pH is set or achieved.

Preferably, the stated preferred ratio of the compositions (b1) to (2) applies, provided that the one or more acids of the component (b2) are selected from the group of organic acids, as described in more detail below; the mass of the component (b2) in each case refers to the total mass of the pure (i.e., without adhesions or water of crystallization, etc.) organic acid or organic acids. When an acid has several pKa values (e.g., citric acid), for purposes of the present invention, it is meant the lowest (first) pKa value, respectively.

In a further embodiment of the inventive or preferred use of a sizing composition according to the invention, the ratio of the mass of constituent (b1) to the total mass of aqueous phase (b) is preferably greater than 50%, preferably greater than 70%, particularly preferably greater than 90%.

In a further preferred embodiment of the inventive or preferred use of a sizing composition according to the invention, the aqueous phase preferably has a pH of at most 4.

Preferred is generally a use according to the invention, in which two or more of the preferred embodiments are realized simultaneously.

Particularly preferred combinations of preferred parameters, properties and components of the invention are generally set forth in the appended claims.

A particularly preferred variant is an inventive or preferred use according to the invention of a sizing composition, wherein component (b2) comprises one or more acids selected from the group consisting of inorganic and organic acids. The aforementioned organic acids are preferably selected from the group consisting of mono-, di- and tricarboxylic acids, preferably at 25 ° C and 1013 mbar (or 1013 hPa) solid mono-, di- and tricarboxylic acids. The organic acids are particularly preferably selected from the group consisting of citric acid and oxalic acid. The aforementioned inorganic acids are preferably selected from the group consisting of hydrochloric acid, nitric acid, phosphoric acid and acidic phosphates, e.g. Aluminum phosphate, particularly preferably from the group consisting of hydrochloric acid, nitric acid and phosphoric acid.

The use of organic acids in combination with one or more inorganic acids in or as component (b2) is preferred. Particularly preferred is the use of organic acids in or as component (b2).

In the aforementioned preferred variant of the inventive use of a sizing composition, the ratio of the total mass of inorganic and organic acids of the component (b2) to the total mass of the sizing composition is preferably in the range of 0.1 to 10% (ie in the range of 0.1 to 10 wt %), more preferably in the range of 0.5 to 5% (ie in the range of 0.5 to 5% by weight), even more preferably in the range of 1 to 5% (ie in the range of 1 to 5 Wt .-%), more preferably in the range of 1 to 3.5% (ie in the range of 1 to 3.5 wt .-%) and most preferably in the range of 2.5 to 3.5% (ie im Range from 2.5 to 3.5% by weight).

Further preferred is a use according to the invention of a sizing composition, preferably a use according to the invention, wherein component (a) comprises particulate amorphous silica, preferably particulate, amorphous silica whose primary particles (i) are spherical and / or have a D90 value <10 .mu.m, preferably a D90 value of <1 .mu.m, have, as determined by means of laser diffraction, particularly preferably particulate, amorphous silicon dioxide which as minor component (i) zirconium dioxide and / or (ii) a Lewis acid, very particularly preferably zirconium dioxide, includes

In addition, particular preference is given to a use according to the invention of a sizing composition, preferably a use according to the invention, wherein component (a) comprises one or more substances selected from the group consisting of quartz, aluminum oxide, zirconium dioxide, aluminum silicates, layered silicates, zirconium silicates , Olivine, talc, mica, graphite, coke, feldspar, diatomite, kaolins, calcined kaolins, metakaolinite, iron oxide and bauxite.

The "D90 value" of the primary particles of the particulate amorphous silicon silicon dioxide denotes their particle size distribution. The particle size distribution is determined in a conventional manner by laser diffraction, preferably according to the standard method according to DIN ISO 13320: 2009-10 , Hereby determined D90 values of the cumulative frequency distribution of the volume-averaged size distribution function indicate that 90% by volume of the primary particles have a particle size which is equal to or less than the stated value (eg 10 μm). Suitable devices for the determination of the particle size distribution are laser diffraction devices known per se, for example of the "Mastersizer 3000" type from Malvern, Great Britain, preferably of the "Coulter LS 230" type from Beckman Coulter, USA, the measurement preferably being carried out with the aid of "Polarization Intensity Differential Scattering"("PIDS") technology. The evaluation of the scattered light signals is carried out in the aforementioned laser diffraction methods in each case preferably according to the Mie theory, which also takes into account the refractive and absorption behavior of the primary particles.

If the primary particles of the particulate, amorphous silicon dioxide are present as agglomerates and / or aggregates and / or otherwise as a combination of a plurality of primary particles, they are preferably mechanically or similarly separated in a manner known per se prior to carrying out the determination of the particle size distribution of the primary particles. in order to exclude a falsification of the result as far as possible.

The term "minor constituent" in the context of the present invention means that the particulate amorphous silica of constituent (a) contains only minor amounts of such minor constituents which may still be present as impurities or adhesions from previous production and / or processing processes of the particulate, amorphous Silicon dioxide can originate. The minor components mentioned are preferably in an amount of not more than 18% by weight (or by mass), more preferably in an amount of not more than 12% by weight, most preferably in an amount of not more than 8% by weight .-% present, each based on the total mass of the particulate amorphous silica of component (a).

One of the aforementioned minor components in component (a) may be a Lewis acid. However, several Lewis acids and / or mixtures thereof may also be included. By "Lewis acid" in the context of the present invention is meant an acid according to the concept proposed by GN Lewis, according to which an acid is an electron pair acceptor, ie a molecule or ion with incomplete noble gas configuration, which is an electron pair provided by a Lewis base absorb and form with this a so-called Lewis adduct. A Lewis acid is electrophilic, while a Lewis acid Base is nucleophilic. Thus, molecules and ions can be considered as acids, which according to classical ideas are not acids.

In addition to the above ingredients, the sizing compositions used in the present invention may contain other ingredients, e.g. Esters, lactones and / or acid anhydrides, for example methyl formate, ethyl formate, propylene carbonate, γ-butyrolactone, diacetin, triacetin, "dibasic esters" known per se (a mixture of several dimethyl esters of dicarboxylic acids, in particular of glutaric acid, succinic acid and adipic acid), acetic anhydride, Methyl carbonate and e-caprolactone.

• - ein oder mehrere Biozide,
• - ein oder mehrere Netzmittel,
• - ein oder mehrere rheologische Additive, und
• - ein oder mehrere Bindemittel, vorzugsweise Polyvinylalkohol.

In one embodiment, preference is given to an inventive or inventively preferred use of a sizing composition, wherein the sizing composition comprises one or more or all of the following constituents:

• - one or more biocides,
• - one or more wetting agents,
• one or more rheological additives, and
• - One or more binders, preferably polyvinyl alcohol.

Suitable biocides are customary biocides such as microbicides, in particular bactericides, algicides and / or fungicides. Preferably, the biocides specified above can be used. Suitable wetting agents are preferably the wetting agents mentioned above. As rheological additives are preferably the above-mentioned rheological additives. Suitable binders are preferably the abovementioned binders. Polyvinyl alcohol is a particularly preferred binder.

In a further embodiment, the use according to the invention of a sizing composition is preferred, the sizing composition having a solids content of less than 80% by weight, preferably less than 45% by weight, in each case based on the total mass of the sizing composition.

The sizing composition to be used according to the invention is preferably ready for use, ie it is intended to be applied directly to a casting mold or to a core. However, the sizing composition to be used according to the invention can also be in the form of a concentrate and is then intended to be diluted to a casting mold or a core before application, in particular by adding water or an aqueous mixture. This applies to all embodiments of the present invention, unless stated otherwise or specified. The expert decides in each case whether a sizing composition is ready for use or should still be diluted.

According to a further embodiment, a use according to the invention or preferred according to the invention is particularly preferred, wherein the sizing composition comprises one or more binders, preferably comprising polyvinyl alcohol, in a total amount of not more than 2% by weight, preferably in an amount in the range of from 0.05 to 0.80 wt .-%, each based on the total mass of the sizing composition comprises.

The determination of the solids content of a sizing composition to be used according to the invention is carried out in the context of the present invention in accordance with leaflet P79 of the Association of German Foundry Experts in the version of 1976, item 6.

According to another embodiment, the use of a sizing composition according to the invention or preferably according to the invention is particularly preferred, the application of the sizing composition on a water-glass-bonded form or a water-glass bonded core for use in casting a molten metal having a temperature of> 900 ° C., preferably> 1250 ° C., takes place, preferably for use in casting a molten metal comprising iron and / or steel.

In addition, the use of a sizing composition according to the invention or preferred according to the invention is particularly preferred, the application of Sizing composition on a waterglass-bonded or waterglass bonded core for use in iron or steel casting.

According to a further embodiment, the use of a sizing composition according to the invention or preferred according to the invention is particularly preferred, the application of the sizing composition on a water-glass-bonded form or a water-glass bonded core at a temperature of the water-glass-bonded core or the water-glass bonded form of> 50 ° C., preferably> 70 ° C, particularly preferably at a temperature <100 ° C. Surprisingly, under these conditions or remains under these conditions a useful for subsequent processing or processing steps form or a useful core obtained.

The invention further relates to the use of acid for adjusting a pH of at most 5, preferably a pH of at most 4, in the aqueous phase of a sizing composition for application to a water-glass-bonded form or a water-glass bonded core. Preferably, the aforesaid acid is selected from the group consisting of inorganic and organic acids. The organic acids are preferably selected from the group consisting of mono-, di- and tricarboxylic acids, preferably at 25 ° C and 1013 mbar solid mono-, di- and tricarboxylic acids, more preferably citric acid and oxalic acid. The inorganic acids are preferably selected from the group consisting of hydrochloric acid, nitric acid, phosphoric acid and acidic phosphates, e.g. Aluminum phosphate, particularly preferably from the group consisting of hydrochloric acid, nitric acid and phosphoric acid. In a preferred variant of the abovementioned use of acid according to the invention, the water-glass-bonded form or the water-glass-bonded core comprises particulate, amorphous silicon dioxide, the acid preferably being used to set a pH of at most 4.

1. (1) Bereitstellen oder Herstellen einer Schlichtezusammensetzung wie vorstehend im Rahmen der erfindungsgemäßen Verwendung einer Schlichtezusammensetzung definiert,
2. (2) Bereitstellen oder Herstellen einer ungeschlichteten, wasserglasgebundenen Form oder eines ungeschlichteten, wasserglasgebundenen Kerns, und
3. (3) Auftragen der bereitgestellten oder hergestellten Schlichtezusammensetzung aus Schritt (1) auf die in Schritt (2) bereitgestellte oder hergestellte Form bzw. den bereitgestellten oder hergestellten Kern.

The invention likewise provides a process for producing a sized, water-glass-bonded form, preferably having a high storage stability, or a sized, water-glass bonded core, preferably having a high storage stability, for use in the foundry, comprising the following steps:

1. (1) providing or preparing a sizing composition as defined above within the scope of the inventive use of a sizing composition,
2. (2) providing or producing an unsized, water-glass bonded or unglazed, water glass bonded core, and
3. (3) applying the provided or prepared sizing composition from step (1) to the form provided or prepared in step (2), or the core provided or manufactured.

The sizing composition provided or prepared in step (1) of the process of the invention may be prepared by methods known in the art. For example, water may be initially charged in an appropriate amount and the further ingredients used to prepare the sizing composition may then be added to this receiver in any desired amount while stirring with a suitable stirrer such as a high shear stirrer, e.g. a gear stirrer or a dissolver stirrer. If necessary, ingredients may be digested before or during the addition in a manner known per se. Thus, e.g. optionally one or more rheological additives are digested using a high shear stirrer, before or after addition to the water receiver, and individually or together with one or more refractory materials. Unless the one or more refractory solids are digested together with the optionally added rheological additives, they may also be individually digested and added to the water feed. Subsequently, then, e.g. the further constituents of the sizing composition are added to the water template, optionally containing rheological additives and / or refractories, in any order and preferably with stirring, preferably with a high shear stirrer, such as one or more acids, optionally one or more sizing binders, optionally one or more biocides, optionally one or more wetting agents, optionally one or more defoamers, optionally one or more pigments and / or optionally one or more dyes.

The sizing composition provided or prepared in step (1) of the process of the invention may be ready for application to foundry moldings, that is, for example, in a concentration suitable for use as a dipping bath for molds or cores. Likewise, the abovementioned sizing composition can also be prepared first in a manner known per se as a concentrate, which is diluted later, eg only shortly before the use of the sizing composition, eg by further addition of water to a ready-to-use concentration (or consistency) then suitable for application to molds and / or cores. If quantities or ratios are specified in the context of the present invention with respect to the size composition used according to the invention, in each case a ready-to-use size composition (intended to be applied directly to a casting mold or a core) is meant, unless expressly stated otherwise. It is not necessary for the individual components of the sizing composition to be used according to the invention to be applied to molds or cores until immediately prior to an intended coating process rather, the mixing can be carried out much earlier because the storage stability of the sizing composition to be used according to the invention is high.

The unclad, water-glass bound form provided or prepared in step (2) of the process of the invention or the provided or prepared unsized, water-glass bonded core can be prepared in a manner known per se, for example as in the documents WO 2006/024540 or WO 2009/056320 described.

The application in step (3) of the prepared or prepared sizing composition from step (1) to the prepared or prepared form or the prepared core after step (2) of the method according to the invention can be carried out in a manner known per se, preferably according to the above application method specified as being suitable, particularly preferably by dipping the mold or the core in a sizing composition used according to the invention as a dipping bath. Preferred is an embodiment of the aforementioned method according to the invention, wherein the provided or prepared form or the prepared or manufactured core contains particulate amorphous silicon dioxide.

In a further preferred embodiment of the abovementioned process according to the invention or preferred according to the invention, application to the mold takes place at a temperature of the core or the mold of> 50 ° C., preferably> 70 ° C., more preferably at a temperature of <100 ° C.

• (X) eine wasserglasgebundene Form bzw. einen wasserglasgebundenen Kern, und
• (Y) einen Überzug umfassend eine Schlichtezusammensetzung wie vorstehend im Rahmen der erfindungsgemäßen Verwendung einer Schlichtezusammensetzung definiert.

A further subject of the present invention is also a sized mold or a sized core for use in the foundry,
each comprehensive

• (X) a water glass bonded form or a water glass bonded core, and
• (Y) a coating comprising a sizing composition as defined above within the scope of the inventive use of a sizing composition.

In a preferred embodiment of this last-mentioned article according to the invention, the sized form or the sized core can be prepared according to an abovementioned inventive or inventively preferred process.

Preference is given to such a sized form according to the invention or a previously disclosed inventive sized core, wherein the water-glass-bonded form and / or the water-glass-bonded core each contain particulate, amorphous silicon dioxide.

The mold according to the invention disclosed above and / or the core disclosed above is preferably used for casting a molten metal having a temperature of> 900 ° C., preferably during casting of a molten metal comprising iron and / or steel, more preferably casting a molten metal comprising iron and / or steel with a temperature> 1250 ° C.

• (U) eine Schlichtezusammensetzung umfassend
  1. (a) einen oder mehrere Feuerfeststoffe, und
  2. (b) eine wässrige Phase mit einem pH-Wert von höchstens 5
  zur Herstellung eines Überzugs auf einer wasserglasgebundenen Form bzw. einem wasserglasgebundenen Kern, zur Verwendung in der Gießerei,
• (V) ein Bindemittel umfassend Wasserglas, und
• (W) partikuläres, amorphes Siliziumdioxid.

The invention likewise provides a kit comprising in separate components

• (U) comprising a sizing composition
  1. (a) one or more refractories, and
  2. (b) an aqueous phase having a pH of at most 5
  for the production of a coating on a water-glass-bonded mold or a water-glass-bonded core, for use in the foundry,
• (V) a binder comprising water glass, and
• (W) particulate, amorphous silica.

In a preferred alternative, the kit according to the invention comprises, as component (U), a sizing composition, wherein the sizing composition is defined as above within the scope of the inventive use of a sizing composition.

• - eine verbesserte Festigkeit der damit herstellbaren geschlichteten wasserglasgebundenen Formen und/oder Kerne, vorzugsweise wasserglasgebundener Formen und/oder Kerne, welche partikuläres, amorphes Siliziumdioxid enthalten;
• - eine verbesserte Lagerstabilität der damit herstellbaren geschlichteten wasserglasgebundenen Formen und/oder Kerne, vorzugsweise wasserglasgebundener Formen und/oder Kerne, welche partikuläres, amorphes Siliziumdioxid enthalten;
• - eine verbesserte Beständigkeit gegenüber Luftfeuchtigkeit der damit herstellbaren geschlichteten wasserglasgebundenen Formen und/oder Kerne, vorzugsweise wasserglasgebundener Formen und/oder Kerne, welche partikuläres, amorphes Siliziumdioxid enthalten;
• - eine verbesserte Möglichkeit der Applikation auf heiße Formen und/oder Kerne (d.h. vorzugsweise auf solche Formen und/oder Kerne, welche Temperaturen von mehr als 50 °C, vorzugsweise Temperaturen im Bereich von 50 bis 100 °C, aufweisen), vorzugsweise auf wasserglasgebundene Formen und/oder Kerne, insbesondere auf wasserglasgebundene Formen und/oder Kerne, welche partikuläres, amorphes Siliziumdioxid enthalten; und/oder
• - eine verbesserte Einsatzmöglichkeit von wasserglasgebundenen Gießereiformkörpern, insbesondere von Formen und/oder Kernen, vorzugsweise von wasserglasgebundenen Formen und/oder Kernen, welche partikuläres, amorphes Siliziumdioxid enthalten, für den Eisen- und/oder Stahlguss, durch erfindungsgemäße Verwendung der beschriebenen Schlichtenzusammensetzung.

It has been found that the use according to the invention of the sizing composition described above has, in particular, the following advantages over the prior art has comparable or comparably used sizing compositions and / or - depending on the aspect considered - justified:

• improved strength of the sized water-glass bonded molds and / or cores, preferably water glass bonded molds and / or cores, which contain particulate, amorphous silicon dioxide;
• improved storage stability of the sized water-glass-bound forms and / or cores, preferably water-glass bonded forms and / or cores, which contain particulate, amorphous silicon dioxide;
• improved resistance to atmospheric moisture of the sized water-glass bonded molds and / or cores, preferably water glass bonded molds and / or cores, which contain particulate, amorphous silicon dioxide;
• an improved possibility of application to hot molds and / or cores (ie preferably to those molds and / or cores which have temperatures of more than 50 ° C., preferably temperatures in the range from 50 to 100 ° C.), preferably to water glass bonded Molds and / or cores, in particular on water-glass-bonded molds and / or cores, which contain particulate, amorphous silica; and or
• an improved possible use of water-glass-bound foundry moldings, in particular of molds and / or cores, preferably of water-glass-bonded molds and / or cores containing particulate, amorphous silicon dioxide, for iron and / or cast steel, by the inventive use of the sizing composition described.

These advantages apply mutatis mutandis to the further aspects of the present invention.

Examples:

The examples given below are intended to further describe and explain the invention without limiting its scope.

Example 1: Preparation of sizing compositions.

The sizing composition ("SZ1") according to the invention and the non-inventive comparative sizing compositions ("SZ2" or "SZ3") were prepared in a manner known per se by mixing the constituents indicated in each case:

For this purpose, the required amount of water was initially introduced into a beaker (batch size in each case about 2 kg of sizing composition as "concentrate", see Table 1), the rheological additives and the refractory materials (phyllosilicates, zirconium flour, graphite) added and then with a high shear Dissolver stirrer 3 min. long unlocked in a known manner. The further constituents of the size compositions (see Table 1) were then added in the stated proportions and the mixture was stirred for a further 2 minutes with a high-shear dissolver stirrer. Each of the dilutable concentrates of sizing compositions given in Table 1 was obtained.

The statements on "DIN-Vermahlungen" in Table 1 mean that the particular constituent of the size composition is in the ground state, after screening a sample of this component with a test sieve with a nominal mesh size in microns, which corresponds to the numerical value specified (eg: "80" means "sieve with mesh size 80 μm") (according to DIN ISO 3310-1: 2001-09), in each case a residue in the range of 1 to 10 wt .-% remains, based on the amount of sample used. Table 1: Inventive and non-inventive sizing compositions, each obtained as dilutable "concentrates" Sizing compositions ("concentrates"): SZ1 SZ2 SZ3 Ingredients: [Wt .-%] [Wt .-%] [Wt .-%] water 44.1 46.0 47.1 Rheological additive 1.5 5.0 1.5 Phyllosilicate (pyrophyllite, DIN 140 grinding) ./. 26.0 11.0 Phyllosilicate (mica, DIN 160 grinding) 25.0 ./. 18.0 Zirconium flour (zirconium silicate, DIN 60 grinding) 14.0 9.0 10.0 Graphite (DIN 80 grinding) 11.0 8.0 11.0 Polyvinyl acetate ./. 0.9 ./. Biocide (benzisothiazolinone, 10% solution w / w in water) 0.3 0.3 0.3 Modified strength ./. 0.3 ./. polyvinyl alcohol 0.4 ./. 0.4 Iron oxide (yellow) ./. 1.2 ./. wetting agent 0.6 0.3 0.6 defoamers 0.1 ./. 0.1 propylene carbonate ./. 3.0 ./. citric acid 3.0 ./. ./. TOTAL: 100.0 100.0 100.0

The dilutable concentrates of sizing compositions given above in Table 1 were then diluted with water to prepare sizing compositions (for application to cores by means of a dipping process, preferably in the form of a dipping bath) ready for use for the intended purpose. The particular dilution used, as well as other properties of the ready-to-use size compositions resulting from the dilution used, are given below in Table 1a: TABLE 1a Preparation and properties of ready-to-use (for dip or dip) size compositions Impact Compositions (ready to use for dip tanks or immersion baths): SZ1 SZ2 SZ3 Concentrate (according to Table 1), parts by weight: 100.0 100.0 100.0 Water, parts by weight 40.0 30.0 40.0 Properties of the ready-to-use size compositions resulting from the above dilution: Density [g / ml] 1.32 1.36 1.35 Flow time [s] 13.5 13.7 13.3 PH value 2.1 7.2 6.7

As can be seen from Table 1a, the sizing compositions were prepared for the purpose intended here, application to test cores by means of a dip application or a dipping bath in such a way that good comparability (i) of their respective properties when applied to the test cores and (ii) the respective resulting properties of the coated test cores was ensured (densities and flow times which were as similar as possible were adjusted, but deviating pH for the size composition SZ1 according to the invention compared to non-inventive sizing compositions SZ2 and SZ3).

The densities of the ready-to-use sizing compositions shown in Table 1a were determined according to the standard test method DIN EN ISO 2811-2 (Method A).

The flow-out times of ready-to-use sizing compositions shown in Table 1a were determined according to the standard test method DIN 53211 (1974) measured by determination with the DIN cup 4.

The pH values of ready-to-use sizing compositions shown in Table 1a were determined according to the standard test method DIN 19260: 2012-10 each measured from the suspension.

The sizing compositions SZ1 and SZ3 each contained attapulgite as the rheological additive. Sizing composition SZ2 is from that in document WO00 / 05010 described type.

Example 2: Investigation of the softening of foundry cores

To determine the softening of foundry cores (ie the maximum drop in flexural strength) test cores (specimens) were prepared in a known manner (according to the "core system 1" shown in Table 4) in a core shooter of the company Multiserw (type LUT, fumigation pressure: 2 bar, shot time: 3.0 s, shooting pressure 4.0 bar). One hour after the core production, the experimental kernels were equipped with the o.g. Ready-to-use sizing compositions "SZ1", "SZ2" or "SZ3" (see Table 1a) at room temperature (25 ° C.) by immersion (conditions: 1 s immersion, 3 s hold time in sizing composition, 1 s expiration). The wet layer thickness of the sizes was adjusted to about 250 μm in each case. Subsequently, the sized test cores were dried in a circulating air oven under the conditions given below (1 hour at 120 ° C.), and in each case the change in their flexural strength under the drying conditions was investigated.

The sized test cores were each dried over a period of one hour, with their flexural strengths (in N / cm ² , as defined in the leaflet R 202 of the Association of German foundry professionals, issue October 1978) at different times during drying and then again one hour after the end of the drying process was measured by a standard test apparatus of the type "Multiserw-Morek LRu-2e", each with a standard measuring program "Rg1v_B 870.0 N / cm ^2" (3-point bending strength).

Table 2 shows in each case the values for the maximum drop in flexural strength under drying conditions in% for the investigated sized test cores, in each case based on the flexural strength of the respective freshly painted (still wet) test core before the start of drying (initial value). Table 2: Strength decrease of sized test cores under drying conditions Finishing type on experimental kernel Maximum drop in flexural strength during drying, to% of initial value Observation of nuclear failure during drying SZ 1 80 No SZ 2 25 No SZ 3 0 Yes

The term "core failure" herein and in each case means that a sized core became unusable during the drying process, i. The sized core was unusable for the measurement of flexural strength as well as for a subsequently intended casting.

Among other things, it can be seen from the values given in Table 2 that the maximum drop in the flexural strength of a test core which was finished with a sizing composition according to the invention (SZ1) was significantly lower than with non-inventive comparative sizing compositions (SZ2 or SZ3). , Furthermore, it can be seen from the values in Table 2 that with the non-inventive comparative size composition SZ3 no useful sized cores could be prepared under the chosen conditions.

Example 3: Investigation of the storage stability of sized and unsized foundry cores

To determine the storage stability, water glass bound test cores (test specimens) were prepared in known manner (analogously as described in Example 2) and their flexural strengths were respectively unsatisfied shortly after their preparation (one hour of storage, relative humidity in the range of 30 to 60%, storage temperature in the range of 20 to 25 ° C) as stated above, cf. Table 3 (entry "Unhatched after 1 h").

In addition, corresponding test cores as indicated below in Table 3 were heated at room temperature (25 ° C) at room temperature (25 ° C) with the sizing compositions SZ1 and SZ3, respectively, one hour after core preparation (ie at equal time intervals from their preparation) by immersion (conditions: 1 s immersion, 3 s Holding time in the size composition, 1 s Austauchen) (designation of the sizing compositions as in Example 1) and each dried for one hour at 120 ° C in a convection oven. The sized, dried test kernels were then subjected to a storage test for a period of four days (as far as the production of the sized core was possible or not previously the failure of the core was detected). The temperature during storage was 35 ° C, the relative humidity was 75%. After completion of the storage test, the flexural strengths of the test cores were determined as indicated above. The results of this storage test are given below in Table 3. Experimental cores ("core system 1") were used for all experiments in example 3, the production conditions of which are given below in table 4. Table 3: Determination of the storage stability of sized and unsealed foundry cores core system Ungeschlichtet after 1 h Treated with type SZ1 after storage (4d) Treated with type SZ3 after storage (4d) Unscaled during storage Bending strength [N / cm ² ] 1 300 149 not definable Core failure after 131 min.

From the values given in Table 3, it can be seen, inter alia, that a waterglass-bonded test core sized with a sizing composition (SZ1) according to the invention still had> 40% of the initial strength after storage for four days, whereas a tester sized with a non-inventive comparative sizing composition (SZ3) Experimental kernel was unusable under comparable conditions; its bending strength was no longer determinable under the conditions defined above, as it broke during aging. An uncoated control core failed under the experimental conditions after only 131 minutes, ie the application of a size composition according to the invention to a test core already led to a stabilization of the test core under drying conditions. Table 4: Manufacturing conditions for core system 1 parameter Core system 1 Molding material (100 parts by weight) quartz sand Binders (2.2 parts by weight) Alkali water glass solution, 25-35% by weight of water glass content in water (w / w) Additive (1.0 part by weight) Particulate, amorphous silica Core box temperature 120 ° C Begasungstemperatur 150 ° C curing 30 s

The core system 1 consisted only of the components molding material, binder and additive, as indicated in Table 4:

The binder specified for the core system 1 in Table 4 here was a commercially available alkali-water glass binder "Cordis® 8511" (Hüttenes-Albertus Chemische Werke GmbH).

The additive specified for the core system 1 in Table 4 here was a commercially available binder additive with the main constituent (≥ 95% by weight) of particulate, amorphous silicon dioxide, "Anorgit® 8396" (Hüttenes-Albertus Chemische Werke GmbH).

Example 4: Investigation of the flexural strength of sized foundry cores

In a manner known per se (analogously to Example 2, but after interim maintenance of the core shooter used), water-glass-bonded test cores (test specimens) were respectively produced with and without a content of particulate, amorphous silicon dioxide, and their flexural strengths were uncoated shortly afterwards for comparison purposes their production (one hour of storage at a temperature in the range of 20 to 25 ° C, relative humidity 30 to 60%) determined as indicated above (for the production conditions of the test cores see Table 6).

In addition, test cores were classified by dipping (conditions: immersing for 1 second, holding for 3 s in the sizing composition, immersing for 1 s) as described below in Table 5 (designation of the sizing compositions as in Example 1) and drying in an air-circulating oven for one hour each at 120 ° C. After cooling to room temperature and a storage time of 24 hours (relative humidity in the range of 30 to 60%, temperature in the range of 20 to 25 ° C), the flexural strengths were then determined on the sized, dried test cores as indicated above.

The results of the bending strength determinations are shown in Table 5 below. In each case, three different test cores (core systems A, B and C) were used, whose production conditions are given below in Table 6. Table 5: Determination of the bending strengths of sized and unfinished foundry cores Ungeschlichtet after 1 h Treated with type SZ1 Treated with type SZ3 core system Bending strength [N / cm ² ] A 401 335 Production of a sized core not possible B 413 * 317 Production of a sized core not possible C (without particulate, amorphous SiO2) 347 269 Production of a sized core not possible * Deviation of the measured value from the corresponding value in Table 3 for core system 1 is considered essentially as an effect of the maintenance of the core shooter.

From the values given in Table 5 it can be seen that foundry cores sized with a sizing composition according to the invention achieve high flexural strengths. Furthermore, the values given in Table 5 show that foundry cores produced successfully under various conditions with a sizing composition (SZ1) according to the invention successfully (high Bending strengths) can be finished. By contrast, a comparable sized sizing composition (SZ3) was unable to produce useful sized cores under comparable conditions. Table 6: Manufacturing conditions for core systems A, B and C parameter Core system A Core system B Core system C molding Quartz sand (100.0 parts by weight) Quartz sand (100.0 parts by weight) Quartz sand (100.0 parts by weight) binder Alkali water glass solution, 25-35% by weight of water glass content in water (w / w) (2.2 parts by weight) Alkali water glass solution, 25-35% by weight of water glass content in water (w / w) (2.2 parts by weight) Alkali water glass solution, 25-35% by weight of water glass content in water (w / w) (3.2 parts by weight) additive Particulate amorphous silica (1.0 part by weight) Particulate amorphous silica (1.0 part by weight) None Core box temperature 120 ° C 120 ° C 120 ° C Begasungstemperatur 150 ° C 150 ° C 150 ° C curing 50 s 30 s 50 s

The binders and additives indicated for core systems A, B and C in Table 6 corresponded in each case to the binders ("Cordis® 8511") or additives ("Anorgit® 8396") given in Table 4.

The above-mentioned core systems A, B and C consisted in each case only of the constituents molding material, binder and optionally additive, as indicated in Table 6.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been 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.

Cited patent literature

• GB 782205 A [0006]
• US Pat. No. 6,972,059 B1 [0006]
• US 5582232A [0006]
• US 5474606 A [0006]
• US7022178 [0006]
• US 7770629 B2 [0009]
• WO 0005010 A1 [0024]
• WO 0005010 [0025, 0099]
• WO 2013/044904 A1 [0026]
• DE 102011115025 A1 [0027]
• WO 2013/050022 A2 [0027]
• DE 102011115024 A1 [0028]
• WO 2013/050023 A2 [0028]
• DE 2730753 A1 [0029]
• WO 2006/024540 [0048, 0079]
• WO 2009/056320 [0048, 0079]

Cited non-patent literature

• DIN 51060: 2000-06 [0015]
• ISO 13320: 2009-10 [0016]
• DIN 19260: 2012-10 [0041, 0098]
• DIN ISO 13320: 2009-10 [0061]
• DIN EN ISO 2811-2 [0096]
• DIN 53211 [0097]

Claims (19)

Use of a sizing composition comprising (a) one or more refractories, and (b) an aqueous phase having a pH of at most 5, for the preparation of a coating on a waterglass-bonded or waterglass-bonded core, for use in the foundry. Use after Claim 1 , wherein the water-glass-bonded form or the water-glass-bonded core contains particulate, amorphous silicon dioxide. Use according to one of Claims 1 or 2 wherein the aqueous phase comprises (b) (b1) water, and (b2) one or more acids, preferably with a pKa <5, preferably with a pKa <4, wherein preferably the ratio of the mass of the component (b1) to Mass of the component (b2) in the range of 10: 1 to 200: 1, more preferably in the range of 10: 1 to 100: 1, and / or preferably wherein the ratio of the mass of the component (b1) to the total mass of the aqueous phase (b) greater than 50%, preferably greater than 70%, more preferably greater than 90%, and / or wherein preferably the aqueous phase has a pH of at most 4. Use after Claim 3 wherein component (b2) comprises one or more acids selected from the group consisting of inorganic and organic acids, - wherein the organic acids are preferably selected from the group consisting of mono-, di- and tricarboxylic acids, preferably at 25 ° C and 1013 mbar solid mono-, di- and tricarboxylic acids, more preferably citric acid and oxalic acid, and / or - wherein the inorganic acids are preferably selected from the group consisting of hydrochloric acid, nitric acid, phosphoric acid and acidic phosphates, more preferably from the group consisting of hydrochloric acid, nitric acid and phosphoric acid and / or - wherein the ratio of the total mass of inorganic and organic acids of the component (b2) to the total mass of the sizing composition in the range of 0.1 to 10%, preferably in the range of 0.5 to 5% more preferably in the range of 1 to 5%, more preferably in the range of in the range of 1 to 3.5% and g is particularly preferably in the range from 2.5 to 3.5%, Use according to any one of the preceding claims wherein component (a) is particulate amorphous silica, preferably particulate, amorphous silicon dioxide whose primary particles (i) are spherical and / or have a D90 value <10 μm, preferably a D90 value of <1 μm, determined by means of laser diffraction, particular preference is given to particulate, amorphous silicon dioxide which comprises as minor constituent (i) zirconium dioxide and / or (ii) a Lewis acid and or one or more substances selected from the group consisting of quartz, alumina, zirconia, aluminum silicates, phyllosilicates, zirconium silicates, olivine, talc, mica, graphite, coke, feldspar, diatomite, kaolins, calcined kaolins, metakaolinite, iron oxide and bauxite. Use according to one of the preceding claims, wherein the sizing composition comprises one or more or all of the following constituents: - one or more biocides, - one or more wetting agents, one or more rheological additives, and - One or more binders, preferably polyvinyl alcohol. Use according to one of the preceding claims, wherein the sizing composition has a solids content of less than 80% by weight, preferably less than 45% by weight, based on the total mass of the sizing composition and / or wherein the sizing composition comprises one or more binders, preferably comprising polyvinyl alcohol, in a total amount of not more than 2% by weight, preferably in an amount ranging from 0.05 to 0.80% by weight, based on the total weight of the sizing composition. Use according to one of the preceding claims, wherein the application of the sizing composition on a water-glass-bonded form or a water glass bonded core for use in casting a molten metal having a temperature> 900 ° C, preferably> 1250 ° C, preferably for use in casting a molten metal comprising iron and / or steel and or wherein the application of the sizing composition takes place on a water-glass-bonded form or a water-glass-bonded core for use in iron or steel casting and / or wherein the application of the sizing composition on a water-glass-bonded form or a water-glass-bonded core at a temperature of the water-glass bonded core or the water-glass bonded form of> 50 ° C, preferably> 70 ° C, more preferably at a temperature <100 ° C. Use of acid for adjusting a pH of at most 5 in the aqueous phase of a sizing composition for application to a water glass bonded or water glass bonded core. Use after Claim 9 wherein the acid is selected from the group consisting of inorganic and organic acids, wherein the organic acids are preferably selected from the group consisting of mono-, di- and tricarboxylic acids, preferably at 25 ° C and 1013 mbar solid mono-, di- and tricarboxylic acids, particularly preferably citric acid and oxalic acid, and / or wherein the inorganic acids are preferably selected from the group consisting of hydrochloric acid, nitric acid, phosphoric acid and acidic phosphates, more preferably from the group consisting of hydrochloric acid, nitric acid and phosphoric acid, and / or the water glass bonded or water glass bonded core comprises particulate amorphous silica, the acid preferably being used to set a pH of at most 4. A process for the preparation of a sized, water glass bonded, high storage stability or sized, water glass bonded core having high storage stability, for use in the foundry, comprising the steps of: (1) providing or preparing a sizing composition as in any one of Claims 1 to 7 (2) providing or forming an unsized, waterglass-bonded or uncoated, waterglass-bonded core, and (3) applying the provided or prepared sizing composition of step (1) to the provided or prepared mold or core. Method according to Claim 11 , wherein the provided or manufactured mold or core provided or contains particulate amorphous silica. Method according to one of Claims 11 or 12 , wherein the application to the mold at a temperature of the core or the form of> 50 ° C, preferably> 70 ° C, more preferably at a temperature <100 ° C. A sized or sized core for use in the foundry, each comprising (X) a water glass bonded or water glass bonded core, and (Y) a coating comprising a sizing composition as in any one of Claims 1 to 7 Are defined. Slanted shape or sized core after Claim 14 , preparable according to a method according to one of Claims 11 to 13 , Sliced shape or sized core after one of Claims 14 or 15 , wherein the water glass bonded form and / or the water glass bonded core contains particulate, amorphous silica. Sliced shape or sized core after one of Claims 14 to 16 for use in casting a molten metal having a temperature> 900 ° C, preferably for use in casting a molten metal comprising iron and / or steel. Kit containing in separate components (U) comprising a sizing composition (a) one or more refractories, and (b) an aqueous phase having a pH of at most 5 for the preparation of a coating on a water-glass bonded or waterglass bonded core, for use in the foundry, (V) a binder comprising water glass, and (W) particulate, amorphous silica. Kit after Claim 18 composition comprising as component (U) a sizing composition, wherein the sizing composition is as in one of Claims 1 to 7 is defined.