KR102431208B1 - Use of coating compositions containing acids in the foundry industry - Google Patents

Abstract

The present invention relates to the use of a coating composition comprising an aqueous phase having a pH of up to 5 and at least one refractory material in the field of casting; And also described are coated waterglass-bonded molding elements for casting, in particular casting molds and/or casting cores, each comprising such above-mentioned coating compositions. The present invention also describes a method for manufacturing a molding element for a coated water glass-bonded casting. The present invention also describes a kit comprising the aforementioned coating composition, the contents of which include an aqueous acid and at least one refractory material.

Description

Use of coating compositions containing acids in the foundry industry

The present invention relates to the use of a coating composition comprising an aqueous phase having a pH of up to 5 and at least one refractories in particular in the field of casting; and also coated waterglass-bound foundry molding elements, in particular foundry molds and/or casting cores, each comprising a coating composition for use according to the invention ( about the foundry core). The invention also relates to a method for producing a molding element (mold or core) for a coated water glass-bonded casting. The invention also relates to a kit, the contents of which comprise a coating composition for use according to the invention. The invention is specified in the appended claims.

Casting in expendable molds is a widespread method for manufacturing near-net-shape components, especially in metal casting. After casting, the mold is broken and the casting is removed. The mold is negative: they contain the cavity from which the casting takes place and make the casting for which the manufacture is intended. The inner contour of the future casting may be formed by the core. In the manufacture of a mold, a cavity can be molded into a molding material by a model of the casting to be fabricated. The core is typically molded in a separate core box.

The mold base material used in the casting molds (also called "moulds" for the purposes of this invention) and casting cores (also called "cores" for the purposes of this invention) is mostly granular, such as washed fractionated silica sand. (granular) It is a fire-resistant material. Also suitable mold base materials known per se are, for example, zircon sand, chromite sand, chamotte, olivine sand, feldspar-containing sand, and andalusite sand. Also, the mold base material may be a mixture of mold base materials different from those described, or other preferred mold base materials. The refractory mold base material is preferably in free-flowing form so that it is introduced into a suitable cavity and compacted therein. The mold base material or the corresponding molding material mixture (molding material) is compacted to increase the strength of the casting mold. To produce a casting mold, the mold base material is bonded using an organic or inorganic molding material binder (binder). The molding material binder creates a strong cohesive force between the particles of the molding material, thereby providing the mechanical stability required for the casting mold. On an industrial level, the production of molds and cores is customarily and advantageously carried out in shooting machines or molding machines, in which the particulate components are minced and the binder is hardened; This also applies to the molds and cores used in the present invention.

The casting mold may be manufactured using an organic or inorganic molding material binder, and curing thereof may be performed by a cold or hot process, respectively. The low-temperature process, called by the technician, is carried out at substantially room temperature without heating of the casting mold. Curing in this case is generally achieved, for example, by a chemical reaction initiated by a catalyst gas passing through a molding material mixture to be cured comprising a mold base material and a molding material binder after molding. In the case of high temperature processes, after molding the molding material mixture is heated to a sufficiently high temperature to drive out solvents present in the molding material binder, for example, and/or a chemical reaction to harden the molding material binder, for example by crosslinking. to start

A characteristic common to all organic molding material binders is that, irrespective of their curing mechanism, when liquid metals are introduced into a casting mold, they undergo thermal decomposition, and thus, for example, benzene, toluene, xylene, phenol, contaminants such as formaldehyde, and other products of thermolysis and/or cracking, some of which are unknown. Although various measures have succeeded in minimizing these emissions, they are nonetheless completely unavoidable at present in the case of organic molding material binders.

In order to minimize or prevent the release of decomposition products during the casting process, molding material binders based on inorganic materials and containing as much as possible very low proportions of organic compounds can be used. Molding material binder systems of this kind have already been known for quite some time from the documents GB 782205 A, US 6972059 B1, US 5582232 A, US 5474606 A, and US 7022178, for example.

The term “inorganic molding material binder” refers to an inorganic molding material binder of this kind, mostly, preferably more than 95 wt %, more preferably more than 99 wt %, very preferably entirely composed of water and inorganic materials, It refers to a molding material binder in which the proportion of the organic compound is preferably less than 5 wt%, more preferably less than 1 wt%, and very preferably 0 wt%.

As used herein, the term “inorganically bound” means that a mold or core is bound with an inorganic molding material binder (as described above).

Of particular importance as a component of the inorganic molding material binder is alkali metal water glass. Alkali metal water glass refers to vitreous, in other words amorphous, water-soluble sodium, potassium and lithium silicates, which have been solidified from a melt into mixtures thereof and also into corresponding aqueous solutions. The term "waterglass" refers to amorphous, water-soluble sodium, potassium and/or lithium silicates and/or aqueous solutions thereof and/or mixtures and/or solutions of the aforementioned silicates and/or solutions thereof, in each case moles of SiO ₂ to M ₂ O The molar modulus (molar ratio) ranges from 1.6 to 4.0, preferably from 1.8 to 2.5, where M ₂ O represents the total amount of lithium oxide, sodium oxide and potassium oxide. The term "water glass-bonded" means that a molding element for casting, more specifically a mold or core, has been made or is producible using a molding material binder comprising or consisting of water glass. In the specification of US 7770629 B2, for example, the refractory mold base material comprises a waterglass-based molding material binder and a particulate metal oxide, and the particulate metal oxide used is preferably precipitated silica or fumed silica. A molding material mixture is proposed.

However, compared to organic molding material binders, inorganic molding material binders also have disadvantages. For example, casting molds or cores made using known inorganic molding material binders have a relatively low or lower stability to atmospheric moisture and/or to water or aqueous moisture. Thus, it is certainly not possible, for example, for such casting molds or cores to be stored over a long period of time, as is common in organic molding material binders.

In particular, in iron and steel castings, the surfaces of molding elements for casting, more specifically molds and cores, are usually coated with a coating called a “refractory coating”, in particular these surfaces are in contact with the cast metal. will do The refractory coating here forms a boundary or barrier layer between the mold/core and the metal, in particular for the purpose of controlled suppression of the defect mechanism at these points, or for the use of metallurgical effects. Generally speaking, fire-resisting coatings in casting technology are specifically intended to perform the following functions:

- to improve the smoothness of the surface of the casting;

- maximizing separation of liquid metal and mold or core;

- to facilitate separation between the mold/core and the casting by preventing chemical reactions between the components of the mold/core and the melt; and/or

- to avoid surface defects such as gas bubbles, intrusions, flashes and/or scabs on the casting.

The functions described above and also, where appropriate, other functions are generally established and optimized and/or adjusted for the particular intended purpose by means of the precise composition of the refractory coating or coating composition to be applied to the mold or core.

Coating compositions used in the foundry field generally comprise or consist of the following components: (i) at least one fine-grained refractory material, i.e. a fine-grained, refractory or highly-refractory inorganic material, (ii) one a carrier liquid comprising one or more compounds (water, alcohol, etc.), and (iii) as additional components, for example, one or more fire resistant coating binders (hereinafter also referred to as "binders" for short) and/or biocides ( biocide) and/or wetting and/or rheological additives. Thus, ready-to-use coating compositions for the coating of molds and cores are generally formulated in a carrier liquid, for example an aqueous (water-containing) carrier liquid or a non-aqueous (water-free) carrier liquid. is a suspension of fine-grained, refractory or highly-refractory inorganic materials (refractories); See below for a detailed description of the carrier liquid.

The refractory coating or coating composition is applied to the inner contour of the casting mold or to the core by a suitable application process such as, for example, spraying, dipping, flow coating or spreading and By drying, it provides a fire resistant coating, or a coating based on a fire resistant coating film. Coatings based on refractory coatings may be dried, for example, by the supply of heat or radiant energy, such as microwave radiation, or by drying in ambient air. In the case of coating compositions comprising combustible compounds in a carrier liquid, drying may be carried out by burning these compounds away.

The term "refractory material (refractory)" as used herein and according to the common understanding of the skilled artisan is used to refer to compositions, materials and minerals that can withstand, for at least a short time, the temperature exposure that accompanies the casting or solidification of iron melt, usually cast iron. . Compositions, materials and minerals referred to as "highly refractory" are those that can briefly withstand the casting heat of steel melt. The temperatures that may occur during casting of steel melts are generally higher than those that may occur during casting of iron or cast iron melts. Refractory compositions, materials and minerals (refractories) and highly-refractory compositions, materials and minerals are known to the person skilled in the art, for example from DIN 51060:2000-06.

The refractories used in the coating compositions are typically mineral oxides, silicates or clay minerals. Examples of suitable refractories in the present invention include quartz, aluminum oxide, zirconium dioxide, aluminum silicate, phyllosilicate, zirconium silicate, olivine, talc, mica, graphite, coke, feldspar, diatomaceous earth, kaolin, calcined kaolin, metakaolinite, iron oxide, chromite and bauxite, each of which may be used individually or in any desired combination with each other. The refractory material serves to seal the pores of the casting mold or core, in particular against penetration of liquid metal. The refractory material also forms a thermal insulation between the casting mold or core and the liquid metal. Refractories are generally provided in powder form. Unless otherwise stated, the refractory material in powder form in that case has an average particle (preferably measured by light scattering according to ISO 13320:2009-10) in the range from 0.1 to 500 μm, preferably in the range from 1 to 200 μm. have a size Particularly suitable as refractories are materials having a melting point that exceeds the temperature of the particular metal melt used by at least 200° C. and/or materials that do not participate in any reaction with the metal melt.

The refractory material is generally dispersed in a carrier liquid. The carrier liquid is preferably in liquid form at standard conditions (20° C. and 1013.25 hPa) and/or is a vaporizable component or component of the coating composition at 160° C. and standard pressure (1013.25 hPa). Preferred carrier liquids suitable also in the present invention are selected from the group consisting of water and organic carrier liquids and also mixtures thereof with each other and/or with other components. Suitable organic carrier liquids are preferably alcohols, including polyhydric alcohols 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 carrier liquids.

The primary purpose of a refractory coating binder (binder) is to hold the refractory material present in the coating composition overlying the molding material. Examples of suitable binders in the present invention are synthetic resins (organic polymers) or dispersions of synthetic resins such as polyvinyl alcohol, polyacrylate, polyvinyl acetate and/or corresponding copolymers of the aforementioned polymers. Polyvinyl alcohol is preferred. Also suitable as binders are natural resins, dextrins, starches and peptides.

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

Rheological additives (standardizing agents) are used to establish the desired refractory coating rheology for processing. Inorganic standardizers suitable for the present invention are also swellable clays, for example sodium bentonite or even for example attapulgite (palygorskite). Examples of organic standardizing agents suitable also in the present invention include cellulose derivatives, more specifically, swellable polymers such as carboxymethyl-, methyl-, ethyl-, hydroxyethyl- and hydroxypropylcellulose; plant mucilage, polyvinylpyrrolidone, pectin, gelatin, agar, polypeptide and/or alginate. The rheological additives or standardizers described above are preferred components of the coating compositions used according to the invention.

It is also possible to use a wetting agent to achieve more effective wetting of the molding material, especially when the coating composition is aqueous (ie comprising water as a carrier liquid or a component of the carrier liquid). The skilled person is aware of ionic and non-ionic wetting agents. Ionic wetting agents used are, for example, dioctylsulfosuccinates, and non-ionic wetting agents used are, for example, alkynediols or ethoxylated alkynediols. The aforementioned wetting agents are also preferred components of the aqueous coating compositions used in accordance with the present invention.

The coating composition may further comprise an anti-foaming agent, a pigment and/or a dye. The antifoaming agent used may be, for example, a silicone oil or a mineral oil. Examples of pigments are red and yellow iron oxides and also graphite. Examples of dyes are commercial dyes known to the person skilled in the art. Antifoams, pigments and/or dyes as described above are also preferred components of the coating composition used according to the invention.

In order to be able to meet the increasing demands in the sphere of environmental and emission protection, inorganic molding material binders, in particular water glass-containing molding material binders, must become of increasing importance in the future for the production of molds and cores in the sector of castings of iron and steel. It is generally necessary or advantageous to coat the inorganic bonding mold and core with a refractory coating, as described above, to achieve the desired or required casting quality. Therefore, for environmental and emission protection, when choosing a fire resistant coating, the use of organic carrier liquids should be avoided as far as possible, preferably water-based fire resistant coatings, i.e. water as the sole carrier liquid or at least as a predominant proportion of the carrier liquid. It is also logically worthwhile to use a fire resistant coating containing

However, as mentioned above, molding elements for casting, in particular molds and cores, made using an inorganic molding material binder, and more specifically using a waterglass-containing molding material binder, have low stability against exposure to water or aqueous moisture. has Thus, water present in water-based coating compositions can damage the inorganic bonding molds and cores treated (coated) with them. As a result, in particular, the strength of the molds and cores thus coated can be significantly reduced. This particular problem known heretofore in the casting technology (see, for example, WO 00/05010A1) has hitherto been an expensive and inconvenient process for, for example, particularly strong curing of molds and cores, drying of applied refractory coatings, or molding material mixtures. It was inadequately responded only to the means previously used, including the adjustment of

The document WO 00/05010 describes gas treatment with carbon dioxide, in particular when the coating composition used contains certain water-soluble or water-miscible adjuvants such as esters, carbonates, esters or lactones of polyhydric alcohols. It specifies how it is possible for a water-based coating to be applied to the mold and core combined with sodium silicate. The individual components of the coating system are preferably mixed with each other only immediately prior to the coating process.

Document WO 2013/044904 A1, through the combination of certain clays as a component of water-containing fire resistant coatings, has a very high solids content, but nevertheless has a viscosity comparable to that of commercial ready-to-use fire resistant coatings, thereby providing an inorganic molding material binder. and the possibility of producing fire resistant coatings which can obviously improve the quality of cores and molds coated with these fire resistant coatings.

Documents DE 10 2011 115 025 A1 and WO 2013/050022 A2 describe the improvement of the quality of coated inorganic cores and molds, and in particular of the storage stability of said cores and molds, when the aqueous coating composition is mixed with certain salts in certain concentration ranges. Specify an obvious increase. The salts discussed are the salts of magnesium and/or manganese, in particular the sulfates and chlorides thereof.

Documents DE 10 2011 115 024 A1 and WO 2013/050023 A2 show that when certain additives are added to the aqueous coating composition, the quality of the coated inorganic cores and molds is clearly improved, in particular their storage stability is increased. Used as additive component of the coating composition are esters of formic acid (methanoic acid), and the chain length of the alcohol or alcohol mixture used for esterification is in particular less than 6, more preferably less than 3 carbon atoms, on average.

Document DE 27, 30 30 753A1 describes a composition for coating a mold used in the processing of molten metal, and a mold coated with the composition. The composition described above may include, for example, formic acid or a salt thereof.

DE 10 10 2006 040 0 385 A1 discloses a temperature-stable BN mold release layer based on ceramic and vitreous binders; This document does not disclose the use for an inorganic bonding mold or core (based on a corresponding particulate mold base material) used in the casting field.

For the priority application of the present application, the German Patent and Trademark Office has searched the following prior art: DE 10 0 2006 0 40 0 385 A1, DE 10 10 2006 2006 0 002 A1 246 A1, and DE 10 0 2005 0 0 4 1 A 863 A1.

However, as self-examination has shown, the above-mentioned problems still exist to some extent even in the case of the procedure according to the prior art described.

Accordingly, starting from the prior art, there is a need for a further improved coating composition for use in the casting field, which has or enables one or more, preferably all, of the following advantageous properties:

- molds and cores coated with known water-containing refractory coatings or coating compositions, in particular molds and cores, are increased compared to those prepared using inorganic molding material binders, more particularly waterglass-containing molding material binders, through which the strength of the manufacturable coated mold and/or core;

- increased storage stability and also atmospheric moisture resistance of the coated molds and/or cores producible therethrough compared to molds and/or cores coated with the known water-containing fire resistant coatings or coating compositions;

- the storage stability of the coating composition itself, which is not significantly impaired or even increased, compared to known water-containing coating compositions;

- possible or at least improved application of the coating composition to a hot mold and/or core (ie molds and/or cores with a temperature in particular above 50° C., preferably in the range from 50 to 100° C.);

- coated molds and cores producible therewith capable of high casting quality and casting surface smoothness, preferably low-defect casting quality, more preferably defect-free casting quality;

- the use of molding elements, in particular molds and/or cores, for casting inorganic bonds, in particular water glass-bonding, which are also possible for the casting of iron and/or steel, or the possibility of their use for these purposes is expanded.

It is an object of the present invention to specify a coating composition for use in the foundry field, which generally possesses or enables one or more or all of the properties described above.

The main object of the present invention is here the use in the field of casting of coating compositions, so that they can be used in molding elements, preferably molds and/or cores for casting inorganic bonds, in particular water glass-bonding, without adversely affecting their properties, in particular strength. will make it possible

Another object of the present invention is to provide a coated molding element for inorganic bond casting, in particular a casting mold and/or a casting core, comprising in each case the coating composition to be specified according to the invention.

Another object of the present invention is to provide a corresponding method for producing a molding element for inorganic bond casting coated with a water-containing refractory coating.

It is also an object of the present invention to provide a kit, the contents of which comprise a coating composition specified according to the invention.

The invention is specified or described in more detail in the appended claims. Certain and/or preferred embodiments of the present invention are described more precisely below. Unless otherwise stated, a preferred aspect or embodiment of the invention may be combined with other aspects or embodiments of the invention, particularly other preferred aspects or embodiments. The combination of each preferred aspect or embodiment with one another in each case again forms a preferred aspect or embodiment of the invention. The embodiments, aspects or properties described according to the invention or described as preferred for the coating composition for use according to the invention are in each case in the method of the invention, the coated mold or core of the invention, and the kit of the invention It is also equivalently valid or has the same meaning.

A coating composition used according to the invention, a method of the invention, a coated mold or core of the invention, and a kit of the invention "comprising" or "containing" the embodiment, component or feature identified in more detail. It is also intended that, if described below, a corresponding variant, understood in a narrow scope, of the use, method, coated mold or core, or kit, is disclosed in each case, said variant being in more detail in each case. “consisting of” those embodiments, components, or features specified.

According to the present invention, the main object of the general purpose and other above-mentioned aspects are

For forming a coating on a waterglass-bonded mold or a waterglass-bonded core used in the casting field when the waterglass-bonded mold or waterglass-bonded core comprises particulate amorphous silicon dioxide;

(a) at least one refractory material, and

(b) an aqueous phase having a pH of at most 5, preferably at most 4

It is achieved by the use (method of use) of the coating composition comprising

In a waterglass-bonded mold or waterglass-bonded core, there is generally a relatively large amount of conventional molding base material, as well as particulate amorphous silicon dioxide. For selection of the preferred mold base material, see above.

The refractory material in the coating composition (see component (a)) is preferably quartz, aluminum oxide, zirconium dioxide, aluminum silicate, phyllosilicate, zirconium silicate, olivine, talc, mica, graphite, coke, feldspar, diatomaceous earth, kaolin, calcined kaolin , metakaolinite, iron oxide, at least one material selected from the group consisting of chromite and bauxite.

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

Molding elements for casting (coated) which can be coated with the coating composition of the invention can be produced in a desired manner known per se, for example by shooting, pouring or 3D printing techniques.

Without assurance of accuracy, when the aqueous coating composition of the present invention is used, the water proportion of the coating composition is determined by the water glass-bonding, the bonding structure being attacked in the alkali metal silicate backbone of the coated casting molding element (mold or core), and acid -Other chemical reactions, such as base reactions, possibly temporarily mean that they result in weakening of the bond structure that is being lost again, but strength as an end result in some of these coated water glass-bonded casting molding elements compared to the prior art. is thought to increase.

In a preferred application, a coated waterglass-bonded comparative mold or coated waterglass-bonded prepared under otherwise identical conditions using a comparative coating composition obtained from the coating composition by addition of sodium hydroxide until a pH of 7 is reached. Compared to the comparative example core, the coated waterglass-bonding mold or the coated waterglass-bonding core according to the present invention has a less decreasing flexural strength upon drying. Indeed, technically particularly relevant in industrial practice are "acidic" coating compositions (i.e., those comprising an aqueous phase having a pH of at most 5, preferably at most 4), the "alkaline" equivalents (pH of 7 and above) of which are dried resulting in a coated waterglass-bonded mold or core, which exhibits a large reduction in flexural strength upon time.

Also, in a preferred application, a coated waterglass-bonded comparative mold or coated waterglass prepared under otherwise identical conditions using a comparative coating composition obtained from the coating composition by addition of sodium hydroxide until pH 7 is reached. -Compared to the bonding comparative example core, the coated waterglass-bonding mold or the coated waterglass-bonding core according to the invention has an increased storage stability.

In the use of the coating composition, according to the invention, the waterglass-bonded mold or waterglass-bonded core comprises particulate amorphous silicon dioxide.

As used herein, the term "particulate amorphous silicon dioxide" refers to particulate synthetic silicon dioxide, preferably precipitated silica and/or fumed silica. Fumed silica is preferred.

Precipitated silica is known per se and can be obtained in a manner known per se, for example by reaction of an aqueous alkali metal silicate solution with an inorganic acid: the precipitate obtained is then separated, dried and, if appropriate, ground . Fumed silica is likewise known per se and can preferably be obtained in a manner known per se at high temperature by solidification from the gas phase. Fumed silica forms silicon monoxide gas, for example by flame hydrolysis of silicon tetrachloride, or for the purposes of the present invention, preferably by reduction of silica sand with coke or anthracite in an arc furnace and , can be prepared by forming silicon dioxide by subsequent oxidation. Another form of amorphous particulate silicon dioxide preferred according to the invention is obtained during the production of zirconium dioxide. For the production of particulate amorphous silicon dioxide, another possibility known per se is the spraying of silicon dioxide melt: in this case the primary amorphous silicon dioxide particles are not subjected to a grinding operation (and also another preferred production method). as in) is formed.

After the aforementioned manufacturing operations, the primary amorphous silicon dioxide particles (“primary particles”) are often present in aggregated form, ie as aggregates of primary particles. The particle shape of the primary particles of particulate amorphous silicon dioxide is preferably spherical. The spherical shape of the primary particles can be observed, for example, by scanning electron microscopy. Preferably the primary particles of particulate amorphous silicon dioxide are spherical and have a sphericity of 0.9 or greater as determined by evaluation of a two-dimensional microscope (preferably scanning electron microscope) image.

Water glass-bonded molds and cores, including those comprising particulate amorphous silicon dioxide (as well as conventional mold base materials), and their manufacture are known per se, for example from WO2006/024540 and WO2009/056320 documents. have. The above-mentioned molds and cores, which are known per se, are suitable for the purpose of the present invention.

According to one embodiment, the aqueous phase (b) is

(b1) water, and

(b2) one or more acids, preferably having a pKa<　5, more preferably a pKa<4;

the present invention or of a coating composition preferably in which the ratio of the mass of component (b1) to the mass of component (b2) is in the range of 10:1 to 200:1, more preferably in the range of 10:1 to 100:1; Preferred uses of the invention are likewise preferred.

In the preparation of the coating compositions used according to the invention, one or more acids are combined with other components of the coating composition (in other words, in particular with the refractory material of component (a) and water of component (b1)), so as to set or reach the desired pH. , can be mixed in conventional form, i.e. solid or liquid form, and optionally diluted, preferably diluted with water.

The specified preferred ratio of material (b1) to (b2) is, as described in more detail below, that one or more acids of component (b2) are from the group of organic acids (i.e. without water or adhering material such as crystallization). preferably effective as long as it is selected from; The mass of component (b2) in this case relates in each case to the total mass of the pure organic acid or of the organic acids. If the acid has more than one pKa value (eg citric acid), the pKa mentioned for the purposes of the present invention is in each case the lowest (first) pKa.

In another embodiment of the invention or preferred inventive use of the coating composition, the ratio of the mass of component (b1) to the total mass of the aqueous phase (b) is preferably greater than 50%, more preferably greater than 70%, highly preferred more than 90%.

In another preferred embodiment of the present invention or preferred use of the present invention of the coating composition, the aqueous phase preferably has a pH of at most 4.

Uses of the invention in which two or more preferred embodiments are implemented simultaneously are generally preferred.

Particularly preferred combinations of parameters, properties and components of the invention are generally apparent from the appended claims.

One particularly preferred variant is the invention or the preferred inventive use of a coating composition wherein component (b2) comprises at least one acid selected from the group consisting of inorganic and organic acids. The organic acids described above in this case are preferably mono-, di- and tricarboxylic acids, preferably from the group consisting of mono-, di- and tricarboxylic acids which are solid at 25° C. and 1013 hPa (or 1013 hPa). is selected from Particularly preferably, the organic acid is selected from the group consisting of citric acid and oxalic acid. The above-mentioned inorganic acid is preferably selected from the group consisting of hydrochloric acid, nitric acid, phosphoric acid, and acidic phosphates such as aluminum phosphate, more preferably from the group consisting of hydrochloric acid, nitric acid and phosphoric acid.

Preference is given to the use of organic acids in combination with one or more inorganic acids in component (b2) or as component (b2). Particular preference is given to the use of organic acids in component (b2) or as component (b2).

In the above-mentioned preferred variants of the inventive use of the coating composition, the ratio of the total mass of inorganic and organic acids of component (b2) to the total mass of the coating composition is preferably in the range of 0.1 to 10% (ie 0.1 to 10 wt. %), more preferably in the range of 0.5 to 5% (ie in the range of 0.5 to 5 wt%), even more preferably in the range of 1 to 5% (ie in the range of 1 to 5 wt%), very Preferably in the range of 1 to 3.5% (ie in the range of 1 to 3.5 wt%), particularly preferably in the range of 2.5 to 3.5% (ie in the range of 2.5 to 3.5 wt%).

More particularly preferably, in the present use of a coating composition, preferably in the present use designated as preferred, component (a) comprises particulate amorphous silicon dioxide, preferably its primary particles are (i) spherical and / or particulate amorphous silicon dioxide having a D90 < 10 μm, preferably D90 < 1 μ μm as determined by laser diffraction, more preferably as secondary component (i) zirconium dioxide and/or (ii) Lewis (Lewis) ) acids, very preferably particulate amorphous silicon dioxide including zirconium dioxide. Preferably, in the present use of the coating composition, the primary particles of particulate amorphous silicon dioxide of component (a) are (i) spherical and/or (ii) D90 < 10 µm as determined by laser diffraction, preferably It has a D90 < 1　㎛. Preferably, the primary particles of particulate amorphous silicon dioxide of component (a) are (i) spherical and have a sphericity of at least 0.9 as determined by evaluation of a two-dimensional microscopic image. Modern commercial electron or light microscopy systems enable digital image analysis and thus convenient measurement of particle morphology. Digital image analysis is preferred for the study of sphericity.

Also particularly preferably, in the present use of a coating composition, in the present use designated as preferably preferred, component (a) comprises quartz, aluminum oxide, zirconium dioxide, aluminum silicate, phyllosilicate, zirconium silicate, olivine, and at least one material selected from the group consisting of talc, mica, graphite, coke, feldspar, diatomaceous earth, kaolin, calcined kaolin, metakaolinite, iron oxide and bauxite.

The "D90" of the primary particles of particulate amorphous silicon dioxide represents their particle size distribution. The particle size distribution is determined in a manner known per se by means of laser diffraction, preferably by standard methods according to DIN ISO 13320:2009-10. The D90 value identified here as the cumulative frequency distribution of the volume-average size distribution function indicates that 90 vol % of the primary particles have a particle size equal to or less than a specified value (eg 10 μm). A suitable instrument for measuring the particle size distribution is a laser diffraction instrument known per se, for example of the type "Mastersizer 3000" from Malvern, England, preferably of the type "Coulter LS 230" from Beckman Coulter, USA, and the measurement is preferably It is performed by the "PIDS" ("Polarization Intensity Differential Scattering") technique. Using the laser diffraction technique described above, the scattered light signal is evaluated according to the Mie theory, which in each case preferably also takes into account the refraction and absorption behavior of the primary particles.

Particle size distribution of the primary particles when the primary particles of particulate amorphous silicon dioxide are present as an aggregate and/or as an aggregate and/or otherwise as an association of a plurality of primary particles Before they are measured, they are preferably gently separated by mechanical means or similarly known per se, in order to exclude as far as possible distortions of the results.

As used herein, the term "secondary component" means that the particulate amorphous silicon dioxide of component (a) may be derived as impurities or deposits, for example, from upstream manufacturing and/or processing of particulate amorphous silicon dioxide. It indicates that it contains only a small amount of these secondary components. Said secondary component is in each case based on the total mass of the particulate amorphous silicon dioxide of component (a), preferably in an amount of 18 wt % (or mass proportion) or less, more preferably 12 wt % or less in an amount, most preferably in an amount of up to 8 wt %.

One of the secondary components described above in component (a) may be a Lewis acid. However, it is also possible for two or more Lewis acids and/or mixtures thereof to be included. "Lewis acid" in the context of the present invention is an acid according to the approach proposed by G. N. Lewis, according to which the acid is an electron pair acceptor, i.e. a molecule or ion with an incomplete inert gas configuration, and an electron pair provided by a Lewis base to form a so-called Lewis adduct with the base. Lewis acids are electrophilic, whereas Lewis bases are nucleophilic. Consequently, molecules and ions that are not acids may be interpreted as acids according to conventional concepts.

In addition to the above-mentioned components, the coating composition used according to the invention may contain further components, examples of which are esters, lactones and/or acid anhydrides, examples of which are methyl formate, ethyl formate, Propylene carbonate, γ-butyrolactone, diacetin, triacetin, the “dibasic esters” known per se (two of the dimethyl esters of dicarboxylic acids, in particular of glutaric acid, succinic acid and adipic acid) mixtures of the above), acetic anhydride, methyl carbonate and ε-caprolactone.

In one configuration, the use of the coating composition of the invention or the preferred use of the coating composition of the invention, wherein the coating composition comprises one or more or all of the following components:

- one or more biocides;

- one or more wetting agents;

- at least one rheological additive, and

- at least one binder, preferably polyvinyl alcohol.

Suitable biocides include microbicides, in particular conventional biocides such as bactericides, algicides and/or fungicides. The above-mentioned biocide can be preferably used. Suitable wetting agents are preferably those mentioned above. Suitable rheological additives are preferably those described above. Suitable binders are preferably those described above. Polyvinyl alcohol is a particularly preferred binder.

In another embodiment, the inventive use of the coating composition is preferred, wherein the coating composition has in each case less than 80 wt % solids, preferably less than 45 wt %, based on the total mass of the coating composition.

The coating composition used according to the invention is preferably used immediately, meaning that it is intended to be applied immediately to the casting mold or core. Alternatively, the coating composition used according to the invention may take the form of a concentrate, in which case it is intended to be diluted before application to the casting mold or core, in particular by addition of water or an aqueous mixture. This applies to all embodiments of the present invention unless otherwise stated or specified. In each individual case, the skilled person decides whether the coating composition should be used immediately or additionally diluted.

According to another embodiment, the coating composition is preferably polyvinyl, preferably in a total amount of up to 2 wt %, preferably in the range from 0.05 to 0.80 wt %, based in each case on the total mass of the coating composition. Particular preference is given to the invention or its preferred use, comprising at least one binder comprising an alcohol.

The solids content of the coating composition used according to the invention is determined in the present invention according to data sheet P79 of Verein Deutscher GieBereifachleute, section 6 version, March 1976.

According to another embodiment, the coating composition is used for the casting of metal melts having a temperature of > 900° C., preferably > 1250° C., preferably water glass used for casting metal melts comprising iron and/or steel- Particular preference is given to the invention or its preferred use of the coating composition, applied to a bonding mold or a waterglass-bonding core.

Also particularly preferred is the invention or a preferred use of the coating composition, wherein the coating composition is applied to a waterglass-bonded mold or a waterglass-bonded core used for casting iron or steel.

According to another embodiment, the coating composition comprises a waterglass-bonding mold or waterglass- at a temperature of >50°C, preferably >70°C of the waterglass-bonding core or waterglass-bonding mold, more preferably at a temperature of <100°C. Particular preference is given to the invention or the preferred use of the invention of the coating composition, applied to the bonding core. Surprisingly, the resulting mold or the resulting core formed or remaining under these conditions can be used for subsequent working and/or processing steps.

Another subject of the present invention is the use of an acid to set a pH of at most 5, preferably a pH of at most 4, in the aqueous phase of a coating composition applied to a waterglass-bonding mold or a waterglass-bonding core. The above-mentioned acids are preferably selected from the group consisting of inorganic and organic acids. The organic acids here are preferably from the group consisting of mono-, di- and tricarboxylic acids, preferably mono-, di- and tricarboxylic acids which are solid at 25°C and 1013 mbar, more preferably citric acid and oxalic acid is chosen The inorganic acid here is preferably selected from the group consisting of hydrochloric acid, nitric acid, phosphoric acid, and acidic phosphates such as aluminum phosphate, more preferably from the group consisting of hydrochloric acid, nitric acid and phosphoric acid. In one preferred variant of the above-mentioned inventive use of the acid, the waterglass-bonding mold or waterglass-bonding core comprises particulate amorphous silicon dioxide, and the acid is preferably used to set a pH of at most 4.

Another subject of the present invention is a method for producing a coated waterglass-bonding mold, preferably with high storage stability, or a coated waterglass-bonding core, which is used in the field of casting, preferably with high storage stability, comprising:

(1) providing or preparing a coating composition previously specified in the use of the coating composition according to the present invention;

(2) providing or manufacturing an uncoated waterglass-bonding mold or an uncoated waterglass-bonding core, and

(3) applying the coating composition provided or prepared in step (1) to the mold provided or prepared in step (2) or the core provided or prepared in step (2).

The coating composition prepared or provided in step (1) of the method of the present invention can be prepared by methods known per se. For example, a high-shear stirrer, such as a cog-wheel, may be introduced initially, with an appropriate amount of water, and the other ingredients for preparing the coating composition are subsequently added to the initial charge in each desired amount in each desired amount. Agitation may be accomplished using a suitable stirrer, such as a toothed-wheel stirrer or a dissolver stirrer. If necessary, the ingredients may be introduced in the conventional manner before or during the addition. Thus, for example, optionally, one or more rheological additives may be introduced using a high-shear agitator before or after being added to the initial water input and individually or with one or more refractories. If one or more refractories are not introduced together with the rheological additives added, they may be introduced and added separately to the initial water input. Thereafter, for example, the other components of the coating composition - optionally comprising rheological additives and/or refractories - are stirred in the initial water charge in any order and preferably using a high-shear stirrer. ingredients can be added, for example, one or more acids, optionally one or more refractory coating binders, optionally one or more biocides, optionally one or more wetting agents, optionally one or more antifoaming agents, optionally one or more pigments and/or or optionally one or more dyes.

The coating composition prepared or provided in step (1) of the method of the invention can be used immediately for application to a casting molding element, and thus in a concentration suitable for use, for example, as a dipping bath for a mold or a core. exist. The above-mentioned coating compositions are also prepared in a conventional manner first as a concentrate and thereafter, for example immediately before use of the coating composition, ready-to-use concentrations (or consistency) suitable for application to molds and/or cores. It is also possible, for example, to be diluted by further addition of water. Where amounts or conditions are described in the present specification for a coating composition to be used according to the invention, the coating composition referred to in each case is used immediately (in a casting mold or core immediately, unless explicitly stated otherwise). intended to be applied). It is not necessary to mix the individual components of the coating composition used according to the invention with each other only immediately prior to the intended coating operation onto the mold or core; Instead, because of the high storage stability of the coating composition used according to the invention, the mixing can be carried out at a much earlier stage.

The uncoated waterglass-bonding mold provided or produced in step (2) of the process of the invention or the uncoated waterglass-bonded core provided or produced is prepared in a customary manner, for example in WO 2006/024540 or WO 2009/056320 may be prepared as described in literature.

The application in step (3) of the coating composition provided or prepared in step (1) to a mold provided or prepared according to step (2) of the process of the invention or to a core provided or prepared is known per se. manner, preferably by the application method described above as suitable, more preferably by dipping of the mold or core in the coating composition used according to the invention, provided as a dipping bath.

In a preferred embodiment of the aforementioned method of the invention, the provided or fabricated mold or provided or fabricated core comprises particulate amorphous silicon dioxide.

In another preferred embodiment of the above-described method of the invention or of the preferred method according to the invention, the application to the mold is at a mold or core temperature of >50°C, preferably >70°C, more preferably at a temperature of <100°C. is performed in

Furthermore, other subject matter of the invention in each case

(X) a waterglass-bonding mold or waterglass-bonding core, and

(Y) A coated mold or coated core used in the casting field, comprising a coating comprising the above-described coating composition in the present use of the coating composition.

In one preferred embodiment of this subject matter of the invention, the coated mold or the coated core is preferably producible by the above-described method of the invention or a preferred method according to the invention.

Preference is given to the above-mentioned coated mold of the present invention or the above-mentioned coated core of the present invention, wherein the waterglass-bonding mold and/or the waterglass-bonding core comprises in each case particulate amorphous silicon dioxide.

The above-mentioned mold of the present invention and/or the above-mentioned core of the present invention is preferably used for the casting of a metal melt having a temperature of >900° C., preferably for the casting of a metal melt comprising iron and/or steel, further It is preferably used for casting of metal melts comprising iron and/or steel having a temperature of > 1250°C.

Also, the subject of the present invention is

(U) a coating composition comprising:

(a) at least one refractory material, and

(b) an aqueous phase having a pH of at most 5;

a coating composition for forming a coating on a waterglass-bonded mold or waterglass-bonded core used in the casting field;

(V) a binder comprising water glass, and

(W) A kit comprising particulate amorphous silicon dioxide as a separate component.

In a preferred alternative, the kit of the invention comprises a coating composition as component (U), wherein the coating composition is as described above in the invention use of the coating composition.

It has been found that the inventive use of the above-mentioned coating compositions has in particular the following advantages over similar or similarly used coating compositions known from the prior art, and/or demonstrates these advantages according to the aspects under consideration:

- improved strength of coated waterglass-bonded molds and/or cores producible therethrough, preferably waterglass-bonded molds and/or cores comprising particulate amorphous silicon dioxide;

- improved storage stability of coated waterglass-bonded molds and/or cores producible therethrough, preferably waterglass-bonded molds and/or cores comprising particulate amorphous silicon dioxide;

- improved atmospheric humidity resistance of coated waterglass-bonded molds and/or cores producible therethrough, preferably waterglass-bonded molds and/or cores comprising particulate amorphous silicon dioxide;

- hot molds and/or cores (i.e. cores and/or molds preferably having a temperature above 50°C, preferably in the range from 50 to 100°C), preferably waterglass-bonded molds and/or cores, more specifically improved applicability to waterglass-bonded molds and/or cores comprising particulate amorphous silicon dioxide; and/or

- molding elements for water glass-bonded casting, more particularly molds and/or cores, preferably particulate amorphous silicon dioxide, for casting of iron and/or steel, according to the invention use of the described coating composition improved availability of water glass-bonded molds and/or cores.

These advantages are valid with respect to other subjects and aspects of the present invention, with only necessary modifications.

Example

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

Example 1: Preparation of coating composition

Inventive coating compositions described in Table 1 ("SZ1") and also non-inventive comparative coating compositions ("SZ2" and "SZ3") were prepared in a conventional manner by mixing the respective described components with each other.

For this purpose, in each case the required amount of water was initially introduced into a glass beaker (in each case batch size, ca. 2 kg of coating composition as "concentrate", see Table 1), rheological additives and refractories (phyllosilicates) , zircon powder, graphite) were added, and these components were introduced in the usual manner using a high-shear dissolver stirrer for 3 minutes. The other components of the coating composition (see Table 1) were added in the proportions described, followed by stirring for an additional 2 minutes using a high-shear dissolver stirrer. This provided in each case the dilutable fire resistant coating composition concentrates listed in Table 1.

Reference to "DIN grind" in Table 1 indicates that each of the described components of the coating composition is present in a ground state, and the numerical value described (e.g., "80" represents "analyte with a mesh size of 80 μm") ) (according to DIN ISO 3310-1:2001-09) (according to DIN ISO 3310-1:2001-09), after sieving a sample of this component using an analyte sieve having a nominal mesh size of μm, each Residue remaining in the case is shown to be in the range of 1 to 10 wt %, based on the amount of sample used.

Table 1 shows the inventive and non-inventive coating compositions obtained as dilutable "concentrates", respectively.

coating composition
("Concentrate"): SZ1 SZ2 SZ3 ingredient: [wt%] [wt%] [wt%] water 44.1 46.0 47.1 Rheological Additives 1.5 5.0 1.5 Phyllosilicate (pyrophyllite, DIN　140 grind) ./. 26.0 11.0 phyllosilicate (mica, DIN 160 grind) 25.0 ./. 18.0 Zircon Powder (Zirconium Silicate, DIN 60 Grind) 14.0 9.0 10.0 Graphite (DIN 80 Grind) 11.0 8.0 11.0 polyvinyl acetate ./. 0.9 ./. Biocide (benzisothiazolinone, 10% wt/wt aqueous solution) 0.3 0.3 0.3 modified starch ./. 0.3 ./. polyvinyl alcohol 0.4 ./. 0.4 iron oxide (yellow) ./. 1.2 ./. wetting agent 0.6 0.3 0.6 antifoam 0.1 ./. 0.1 propylene carbonate ./. 3.0 ./. citric acid 3.0 ./. ./. Sum: 100.0 100.0 100.0

Immediately for the purpose intended here (preferably in the form of a dipping bath, for application to the mold and/or core by a dipping operation) the dilutable refractory coating composition concentrates described in Table 1 above are subsequently diluted with water). The coating composition used was prepared. The different properties of the ready-to-use coating compositions obtained in each case from the respective dilutions employed and also from the dilutions employed are shown in Table 2 below.

Table 2 shows the preparation and properties of ready-to-use (for dipping baths or dipping tanks) coating compositions.

coating composition
( dipping tank or dipping Immediate use as a bath): 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 Characteristics of the ready-to-use coating composition obtained from the above dilution: Density [g/ml] 1.32 1.36 1.35 flow time [sec] 13.5 13.7 13.3 pH 2.1 7.2 6.7

As is evident from Table 2, for the purposes intended herein, the coating composition applied to the test core by means of a dipping application or dipping bath has (i) the respective properties when applied to the test core, and also (ii) the coated test core. were prepared to ensure easy comparability of the respective obtained properties (density and flow time were set as similar as possible; however, the pH of the inventive coating composition SZ1 compared to the non-inventive coating compositions SZ2 and SZ3 was different).

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

The flow times of the ready-to-use coating compositions shown in Table 2 were determined according to standard test method DIN 53211 (1974) by measurement using a DIN 4 cup.

The pH values of the ready-to-use coating compositions shown in Table 2 were determined in each case according to the standard test method DIN 19260:2012-10 from suspension.

Coating compositions SZ1 and SZ3 each contained attapulgite as a rheological additive. The coating composition SZ2 was of the type described in the document WO00/05010.

Example 2: Investigation of softening of the casting core

To determine the softening (i.e., maximum reduction in flexural strength) of the casting core, test cores (test specimens) (according to "Core System 1" shown in Table 5) were tested on Multiserw's core shooting machine (model LUT, gas treatment pressure: 2 bar, shot time: 3.0 s; shooting pressure 4.0 bar). One hour after core preparation, the test cores were dipping at room temperature (25° C.) (condition: 1 sec immersion; 3 sec hold time in coating composition, 1 sec removed) of the ready-to-use coating compositions “SZ1”, “SZ2” as described above. and "SZ3" (see Table 2). The wet film thickness of the fire resistant coating was controlled in each case to about 250 μm. Thereafter, the coated test cores were dried in a forced-air oven under the conditions described below (1 hour at 120° C.), and the change in flexural strength under the drying conditions in each case was investigated.

The coated test cores were each dried over a time period of 1 hour, during which time their flexural strength (N/cm2, corresponding to the definition given in data sheet R 202 of Verein Deutscher GieBereifachleute, October 1978 edition) was in each case standard With the measuring program "Rg1v_B 870.0 N/cm2" (3-point bending strength), using standard test equipment of type "Multiserw-Morek LRu-2e", at different times during drying and at least once 1 hour after the end of the drying operation measured.

Table 3 shows, for the irradiated coated test cores, in each case the flexural strength in dry conditions, based on the flexural strength of each freshly coated (still wet) test core before the start of drying (initial value) in each case. The maximum reduction value of is expressed in %.

Table 3 shows the reduction in strength of the coated test cores in dry conditions.

Types of fire resistant coatings coated on test cores Maximum reduction in flexural strength when dry, of the initial value %as indicate Observation of core failure during drying SZ 1 80 No SZ 2 25 No SZ 3 0 Yes

The term "core failure" here and hereinafter in each case denotes the invalidation of the coated core during the drying process, the coated core being used in each case for the measurement of the flexural strength and also for the subsequent scheduled casting process. means it couldn't

As can be seen from the values shown in Table 3, in particular, the maximum reduction in flexural strength of the test cores coated with the inventive coating composition (SZ1) was significantly higher than that of the non-inventive comparative example coating compositions (SZ2 and SZ3). It was small. As is also evident from the values in Table 3, for the non-inventive comparative example coating composition SZ3, it was not possible to prepare a coated core usable in the selected conditions.

Example 3: Investigation of storage stability of coated and uncoated casting cores

To measure storage stability, water glass-bonded test cores (test specimens) were prepared in a conventional manner (in the same manner as described in Example 2), and their flexural strengths were measured immediately after preparation as described above. The coatings were measured in each case (1 hour storage time, relative humidity range 30-60%, storage temperature range 20-25°C); See Table 4 (item "Uncoated after 1 hour").

Corresponding test cores were also coated with coating compositions SZ1 and SZ3 at room temperature (25° C.) at room temperature (25° C.) one hour after core preparation (i.e., after each equal time interval from preparation), as indicated in Table 4 below, and in each case dipping ( Conditions: 1 second soak; 3 second hold time in coating composition, 1 second remove) (coating composition is specified as in Example 1) and in each case dried in a forced-air oven at 120° C. for 1 hour did. On the coated and dried test cores, a storage test was performed for a period of 4 days (as long as it was possible to manufacture coated cores, or unless core failure was previously observed). The temperature during storage was 35° C. in each case; The relative humidity was 75% in each case. After the end of the storage test, the flexural strength of the test cores was measured as described above. The results of the storage test are shown in Table 4 below. The test cores each used for all tests in Example 3 (“Core System 1”) were cores having the manufacturing conditions specified in Table 5 below.

Table 4 shows the measurements of the storage stability of the coated and uncoated casting cores.

core system 1 hour later uncoated Coated with type SZ1 after storage (4 days) Coated with type SZ3 after storage (4 days) at/during storage uncoated Flexural strength [N/cm2] One 300 149 not measurable Core failed after 131 minutes

As can be seen from the values shown in Table 4, in particular, the water glass-bonded test core coated with the inventive coating composition (SZ1) still had >40% of the initial strength after 4 days of storage, whereas the non-inventive comparative example coating Test cores coated with the composition (SZ3) were not available under similar conditions: their flexural strength was no longer measurable under the conditions described above, as they collapsed during storage. In the test conditions, the uncoated comparative core failed after 131 minutes, ie application of the coating composition of the present invention to the test core allowed the test core to stabilize in dry conditions.

Table 5 shows the manufacturing conditions of Core System 1.

parameter core system 1 Molding material (100 parts by weight) silica sand Binder (2.2 parts by weight) Alkali metal water glass solution, 25-35 wt % water glass content in water (wt/wt) Additives (1.0 parts by weight) Particulate amorphous silicon dioxide core box temperature 120℃ gas treatment temperature 150℃ curing time 30 seconds

Core System 1 consisted only of the molding material, binder and additive components as shown in Table 5.

The binder listed in Table 5 of Core System 1 was in this case the commercial alkali metal waterglass binder "Cordis® 8511" (Huttenes-Albertus Chemische Werke GmbH).

The additive listed in Table 5 of Core System 1 was in this case the commercial binder additive "Anorgit® 8396" (Huttenes-Albertus Chemische Werke GmbH) whose main component (≥ 95 wt %) is particulate amorphous silicon dioxide.

Example 4: Investigation of flexural strength of the coated core for casting

Waterglass-bonded test cores (test specimens) with and without a certain content of particulate amorphous silicon dioxide in each case were tested in a conventional manner (similar to that described in Example 2, but with intermediate maintenance of the core shooting machine used) after), and their flexural strengths were measured for comparative example purposes in each case uncoated immediately after preparation as described above (1 hour storage time at a temperature in the range of 20 to 25° C., 30 to 60% relative humidity). ) (see Table 7 for the manufacturing conditions of the test cores).

In addition, the test cores shown in Table 6 below were coated by dipping (condition: 1 sec immersion; 3 sec holding time in coating composition, 1 sec removal) (specified with the coating composition as in Example 1), in each case It was dried in a forced-air oven at 120° C. for 1 hour. After cooling to room temperature and storage time of 24 hours (relative humidity range 30-60%, temperature range 20-25° C.), the flexural strength was measured as described above for the coated and dried test cores.

Flexural strength measurement results are shown in Table 6 below. In this case, three different test cores (Core Systems A, B and C) were used, and their respective manufacturing conditions are shown in Table 7 below.

Table 6 shows the measurements of the flexural strength of the coated and uncoated casting cores.

1 hour later uncoated Coated with type SZ1 Coated with type SZ3 core system Flexural strength [N/cm2] A 401 335 Unable to manufacture coated cores B 413* 317 Unable to manufacture coated cores C (no particulate amorphous SiO ₂ ) 347 269 Unable to manufacture coated cores

* The deviation of the measured values and the corresponding values in Table 4 for the core system 1 is interpreted inevitably as a result of the maintenance of the core shooting machine.

As can be seen from the values shown in Table 6, the casting core coated with the coating composition of the present invention obtained high flexural strength. In addition, as the values in Table 6 show, using the coating composition (SZ1) of the present invention, the casting cores manufactured under different conditions can be successfully coated with good results (high flexural strength). On the other hand, in the case of the non-inventive comparative coating composition (SZ3), it was not possible to prepare a usable coated core under similar conditions.

Table 7 shows the manufacturing conditions of core systems A, B and C.

parameter core system A core system B core system C molding material Silica sand (100.0 parts by weight) Silica sand (100.0 parts by weight) Silica sand (100.0 parts by weight) bookbinder Alkali metal water glass solution, 25-35 wt % water glass content in water (wt/wt)
(2.2 parts by weight) Alkali metal water glass solution, 25-35 wt % water glass content in water (wt/wt)
(2.2 parts by weight) Alkali metal water glass solution, 25-35 wt % water glass content in water (wt/wt)
(3.2 parts by weight) additive Particulate amorphous silicon dioxide
(1.0 parts by weight) Particulate amorphous silicon dioxide
(1.0 parts by weight) doesn't exist core box temperature 120℃ 120℃ 120℃ gas treatment temperature 150℃ 150℃ 150℃ curing time 50 seconds 30 seconds 50 seconds

The binders and additives indicated for core systems A, B and C in Table 7 corresponded in each case to the binders ("Cordis® 8511") and additives ("Anorgit® 8396") indicated in relation to Table 5.

The aforementioned core systems A, B and C consisted in each case solely of the molding material shown in Table 7, the binder and optionally the additive components.

Claims (19)

(a) at least one refractory material, and
(b) an aqueous phase having a pH of at most 5;
A coating composition for forming a coating on a waterglass-bonded mold or waterglass-bonded core used in the casting field, wherein the waterglass-bonded mold or waterglass-bonded core comprises particulate amorphous silicon dioxide. According to claim 1,
Award (b) is
(b1) water, and
(b2) at least one acid having a pKa <5;
the ratio of the mass of component (b1) to the mass of component (b2) is in the range of 10:1 to 200:1,
and/or
the ratio of the mass of component (b1) to the total mass of the aqueous phase (b) is greater than 50%,
and/or
The aqueous phase is a coating composition having a pH of up to 4. 3. The method of claim 2,
component (b2) comprises at least one acid selected from the group consisting of inorganic and organic acids,
- the organic acid is selected from the group consisting of mono-, di- and tricarboxylic acids,
and/or
- the inorganic acid is selected from the group consisting of hydrochloric acid, nitric acid, phosphoric acid and acidic phosphate,
and/or
- a coating composition wherein the ratio of the total mass of inorganic and organic acids of component (b2) to the total mass of the coating composition is in the range of 0.1 to 10%. According to claim 1,
Component (a) is
- as particulate amorphous silicon dioxide,
the primary particles of particulate amorphous silicon dioxide are (i) spherical and have a sphericity of 0.9 or greater as determined by evaluation of two-dimensional microscopy images, and/or (ii) a D90 <10 μm determined by laser diffraction Have,
Particulate amorphous silicon dioxide comprising as secondary components (i) zirconium dioxide and/or (ii) Lewis acid in an amount of up to 18 wt %, based on the total mass of particulate amorphous silicon dioxide dioxide,
and/or
- selected from the group consisting of quartz, aluminum oxide, zirconium dioxide, aluminum silicate, phyllosilicate, zirconium silicate, olivine, talc, mica, graphite, coke, feldspar, diatomaceous earth, kaolin, calcined kaolin, metakaolinite, iron oxide and bauxite A coating composition comprising one or more substances that are According to claim 1,
the coating composition
containing one or more or all of the following ingredients:
- one or more biocides;
- one or more wetting agents;
- at least one rheological additive, and
- one or more binders;
and/or
has less than 80 wt % solids, based on the total mass of the coating composition,
and/or
A coating composition comprising one or more binders comprising polyvinyl alcohol in a total amount of 2 wt % or less, based on the total mass of the coating composition. According to claim 1,
The coating composition is applied to a waterglass-bonded mold or waterglass-bonded core used for casting metal melts having a temperature of >900°C,
and/or
The coating composition is applied to a waterglass-bonded mold or waterglass-bonded core used for casting iron or steel,
and/or
The coating composition is applied to the waterglass-bonding mold or waterglass-bonding core at a temperature of >50° C. of the waterglass-bonding core or waterglass-bonding mold. A method for producing a coated waterglass-bonded mold with high storage stability or a coated waterglass-bonded core with high storage stability, used in the casting field, comprising:
(1) providing or preparing a coating composition according to claim 1;
(2) providing or making an uncoated waterglass-bonded mold or uncoated waterglass-bonded core, wherein the provided or made mold or provided or made core comprises particulate amorphous silicon dioxide, and
(3) applying the coating composition provided or prepared in step (1) to the provided or manufactured mold or to the provided or manufactured core. 8. The method of claim 7,
A manufacturing method wherein the application to the mold is carried out at a temperature of the core or mold of >50°C. (X) a waterglass-bonded mold or waterglass-bonded core, wherein the waterglass-bonded mold and/or waterglass-bonded core comprises a waterglass-bonded mold or waterglass-bonded core comprising particulate amorphous silicon dioxide, and
(Y) a coating comprising the coating composition according to claim 1;
Coated molds or coated cores used in foundry applications. 10. The method of claim 9,
A coated mold or a coated core, producible by the method according to claim 7 . 10. The method of claim 9,
Coated molds or coated cores used for the casting of metal melts at temperatures > 900°C. (U) a coating composition comprising:
(a) at least one refractory material, and
(b) an aqueous phase having a pH of at most 5;
a coating composition for forming a coating on a waterglass-bonded mold or waterglass-bonded core used in the casting field;
(V) a binder comprising water glass, and
(W) comprising particulate amorphous silicon dioxide as a separate component,
A kit comprising the coating composition according to claim 1 as component (U). delete delete delete delete delete delete delete