EP2451596A1

EP2451596A1 - Release agent for producing mould coatings

Info

Publication number: EP2451596A1
Application number: EP10717104A
Authority: EP
Inventors: Andreas Jattke; Thomas Linke; Klaus Seeger
Original assignee: Huettenes Albertus Chemische Werke GmbH
Current assignee: Huettenes Albertus Chemische Werke GmbH
Priority date: 2009-07-09
Filing date: 2010-04-21
Publication date: 2012-05-16
Anticipated expiration: 2030-04-21
Also published as: JP2012532027A; JP6147295B2; WO2011003637A1; DE202009010423U1; EP2451596B1; US20120126092A1; CN102481622A; PL2451596T3; US20140102657A1; US8771412B2; US8845802B2; CN102481622B; DE102009032668A1; JP2015166112A

Abstract

The present invention relates to a release agent for producing mould coatings by applying to inorganically or organically bound moulding materials in lost moulds or to cores for iron and steel casting. The ready-made release agent has a proportion by weight of 0.001% or more and less than 1% of inorganic hollow bodies that are made partially or entirely of crystalline material and have a softening point of 1000°C or higher.

Description

Sizing for the production of mold coatings

The present invention relates to a size for the production of mold coatings by application to inorganic or organic bonded moldings in lost molds or on cores for iron and steel casting.

Casting in a lost form is a common process for making end-to-end components. 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 are formed by cores. During production of the mold, the cavity is shaped into the molding material by means of a model of the casting to be produced. Inner contours are represented by cores formed in a separate core box. For lost molds and cores predominantly refractory granular materials such as washed, classified quartz sand are used as molding materials. Other materials include zirconium, chromite sands, chamottes, olivine sands, feldspathic sands and andalusite sands. To produce the casting molds, the molding materials are bound with inorganic or organic binders. In many cases, bentonites or other clays are used as inorganic binders. The molded materials are compacted to increase the strength. Frequently, in particular for the production of cores, are hardening, with used inorganic or organic resin binders bonded molding materials. Curing is due to a chemical reaction in a hot or cold process. Frequently, corresponding molding materials are also gassed for curing. Also, the curing of the binder can be done by heating the molding material and expelling a solvent, which then causes hardening.

Usually, the surfaces of the molds and cores are coated with a size. Ready-to-use sizes for coating molds and cores are suspensions of fine-grained, refractory to highly refractory inorganic materials in a carrier liquid, e.g. Water or a solvent. The sizing 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 sizing coat (sizing film) is formed. The drying of the size coat may be accomplished by the application of heat or radiant energy, e.g. by microwave radiation, or by drying in the room air done. In the case of solvent-containing sizing, the drying can also be carried out by burning off the solvent.

The size coatings should u.a. fulfill the following functions:

1. Improvement of the casting surface with regard to its smoothness

2. Clean separation between liquid metal and mold

3. Prevention of chemical reactions between molding material and melt, thereby facilitating the separation between molding material and casting

4. Prevention of surface defects on the casting, such as e.g. Gas bubbles, penetrations, leaf ribs and scabs.

The aforementioned functions 1 to 3 are usually fulfilled by combinations of various suitable refractory materials. As fireproof materials are here and

Minerals, the short term of the temperature load during casting by a

Resistant to molten iron, materials and minerals that can withstand the pouring heat of molten steel in the short term are regarded as highly refractory. As refractory material, for example, mineral oxides such as corundum, magnesite, quartz, chromite and olivine, furthermore silicates such as zirconium silicate, chamotte, andalusites, pyrophyllite, kaolinite, mica and other clay minerals are used individually or in combination. Graphite and coke are also used. The refractories are in a carrier liquid suspended. Solvents such as ethanol or isopropanol can serve as the carrier liquid, but today water is usually preferred as the carrier liquid.

Further bases for sizes are suspending agents, e.g. water swellable clays such as smectites, attapulgites or sepiolites or swellable organic thickeners such as e.g. CeIIu losederivate or polysaccharide. Further, a size includes a binder to fix the refractories on the molding material. As a rule, synthetic resins or synthetic resin dispersions are used here, e.g. Polyvinyl alcohol, polyacrylates, polyvinyl acetates and corresponding copolymers. Natural resins, dextrins, starches and peptides can also be used as binders. The aforementioned swellable clays can also take over the functions of the binder.

Finishes may contain further additives, in the case of aqueous sizes in particular preservatives and rheologically active additives and adjusters. Rheologically active additives and / or adjusting agents are used to adjust the flowability of the size desired for processing. In the case of aqueous sizes, wetting agents can also 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. Due to the complexity of today's castings, in particular the function of sizing coatings for the prevention of surface defects on the casting is gaining in importance. Because the core geometries are becoming ever more filigree and the shapes more and more complex, the demands on the molded materials and especially the sizes are increasing. Due to the thermal expansion of the sand contained in the molding material through the casting heat can break inorganic and in particular resin-bonded molds and cores, so that the liquid metal penetrates into the mold or the core. The resulting surface defects, e.g. Leaf ribs are difficult to remove.

The pyrolysis of resin-bonded molded materials by the casting heat produces gases. These can lead to casting defects. In this connection, various causes leading to the formation of these casting defects called gas defects can be distinguished. - A -

On the one hand, gas faults as described by H.G. Levelink, F.P.M.A. Julien and H. C. J. de Man in Foundry 67 (1980) 109. These "exogenous gases" are mainly produced by the pyrolysis of organic binders on contact with molten metal in the mold or core. These gases generate a gas pressure in the molding material, which, if it exceeds the metallostatic back pressure, can lead to gas defects in the casting, usually in its upper region. These gas bubbles usually have a smooth inner surface.

Another type of gas error is e.g. from Gy. Nandori and J. PaI. Miskoloc and K. Peukert in Foundry 83 (1996) 16 describe. These are gas bubbles that occur associated with slag jobs. The cause of such gas slag faults are "exogenous," i.e., from the molding material and mold cavity, and "endogenous," i. to look at the gases coming from the melt. These gases partially react with the melt, resulting in oxide-rich slags. These slags together with the remaining gases form gas faults. An influencing factor for the formation of these gas defects is the gas permeability of the molding material coated with the size coat.

In places where the surface of a core or mold is not sufficiently protected against melt penetration, penetration often occurs. These errors must be removed from the casting consuming. During the casting process, the sizing coating may peel off the core or the mold if a high gas pressure due to pyrolysis of the molding material binder builds up in the core and the sizing presents a high resistance to this pressure due to a low gas permeability. If the gas pressure exceeds the adhesive forces of the sizing coating on the core or the mold, the sizing will be abated. Casting errors caused by melting in the melt size particles are the result.

It has already been tried to develop sizing that counteract these casting defects. For example, by addition of platelet-shaped phyllosilicates such as calcined kaolins, pyrophyllites, talc and mica or other clay minerals to the size arise on the molds or cores sizing coatings that can be well deformed under the action of tensile forces. The individual platelets overlap one another and can cover so well elevations, which arise due to the thermal expansion of the sand in the molding material. Because of their dense Texture are sizing coatings containing platy phyllosilicates, but only slightly permeable to gas. Gases which form during the thermal decomposition of the binder of the molding material are thus difficult to pass through these layers, high gas pressures are formed which can lead to the abovementioned gas defects and purging defects.

The patent application WO 2007/025769 describes sizing agents (where they are also referred to as molding compositions together with molding material mixtures) which contain borosilicate glass in an amount of at least 0.001%, preferably at least 0.005% by weight, in particular at least 0.01% by weight contained on the solids content of the size. The proportion of borosilicate glass is preferably less than 5% by weight, more preferably less than 2% by weight and most preferably within a range of 0.01 to 1% by weight, in each case based on the solids content of the size. According to a particularly preferred embodiment, borosilicate glass in the form of hollow microspheres, ie hollow beads having a diameter in the order of preferably 5 to 500 .mu.m, more preferably 10 to 250 .mu.m, whose shell is constructed of borosilicate glass, is used. It is believed that the borosilicate glass melts under the influence of the temperature of the liquid metal, thereby releasing voids which can compensate for the volume expansion of the molding material caused by the casting heat. Preferably, the softening point of the borosilicate glass in the range of less than 1500 ⁰ C, more preferably in the range of 500 to 1000 ⁰ C is set. When using these sizes, flaking off the size coat under the influence of the liquid metal is expected to occur only extremely rarely. In addition, it was found that no leaf ribs form and a smooth casting surface is obtained.

Since, according to WO2007 / 025769, it is intended to melt the hollow spheres of borosilicate glass, the size coating has holes after the hollow spheres have melted, through which the liquid metal can penetrate to the surface of the core or the mold. So there is a risk of penetration errors. This problem can not be solved by the use of Borosilikatglaskugeln higher melting point, because glasses contain in addition to the network former boron oxide and so-called network converter such as sodium oxide and potassium oxide, all three compounds with virtually all of the above ingredients of sizing (except carbon or graphite) , especially all platelet-shaped clay minerals and silicates low form melting compounds. In addition, hollow spheres made of borosilicate glass are not very stable mechanically. Therefore, they are very easily broken under the pressure load inevitably involved in the preparation of sizing. Another disadvantage of using hollow spheres made of borosilicate glass is their strong alkalinity. This leads to an unfavorable change in the pH of the sizings. Therefore, according to a variant of the molding compound from WO2007 / 025769, the addition of an acid or an acid source is provided.

From WO 94/26440 sizing are known, based on the weight of the ready-to-use sizing a content of inorganic hollow spheres of 1 to 40%, preferably of at least 4%, or even at least 10%. The hollow spheres consist, for example, of silicates, in particular of aluminum, calcium, magnesium and / or zirconium, of oxides such as aluminum oxide, quartz, magnesite, mullite, chromite, zirconium oxide and / or titanium oxide, of borides, carbides and nitrides such as silicon carbide, titanium carbide, titanium boride, Boron nitride and / or boron carbide, or carbon. However, hollow spheres made of metal or glass can also be used. These hollow spheres are effective in several ways. Thus, the dense packing of the base particles in the sizing, which may be considered to be the main cause of the low gas permeability, is lightened by the beads and made more gas permeable. It is also assumed that at the beginning of the casting process the insulating properties of the hollow spheres and the gas-permeable size coatings cause a delayed heat transfer through the size into the molding material. Later, the hollow spheres melt in the casting heat and / or break under the casting pressure, causing numerous micro-defects in the size coat, thus increasing the gas permeability of the size coat.

Again, due to the large amount of melting hollow spheres, the possibility that can form holes in unfavorable overlap of individual hollow spheres in the size coat, so that the casting may have penetration errors. Due to the problems outlined above, it appears advantageous, instead of hollow spheres made of glass inorganic hollow body of materials, ie he a similar or similar composition as the above. also contained in the sizing refractory materials, in particular the platelet-shaped refractory materials and / or which react very slowly with the refractories contained in the sizing. For this purpose, the inorganic hollow body should have a high softening temperature, so that they do not melt during the casting process, and a higher mechanical stability than hollow spheres made of glass. Furthermore, it is desirable to reduce the need for hollow spheres without having to accept an increased incidence of casting defects.

These objects are achieved by a ready-to-use size for the production of mold coatings by application to inorganic or organic bonded moldings in lost molds or cores for iron and cast steel, which has a weight-based content of (i) 0.001% or more and (ii) contains less than 1% of inorganic hollow bodies, wherein the inorganic hollow body consist partially or completely of crystalline material.

Surprisingly, it has been found that, based on the total weight of the ready-to-use sizing, an addition of less than 1% of inorganic hollow bodies, which consist partially or completely of crystalline material, is sufficient to reduce the formation of gas defects, penetrations and leaf ribs. In particular, those gas defects that occur in connection with oxide-rich slags are reduced. This was not to be expected due to the disclosure in WO 94/26440. In the exemplary embodiments specified there, only sizes having a content by weight of hollow spheres of aluminum silicate of at least 4% of the ready-to-use size, ie four times the lower limit value of 1% specified there, were tested. From the comparison of the embodiments of WO 94/26440 with proportions of 0 and 4, 5 and 1 0% hollow spheres of aluminum silicate in the ready-made size is also clear that the gas permeability increases with the proportion of the hollow spheres, i. the advantageous effect of the hollow spheres seems to be the higher the larger the proportion of hollow spheres in the ready-to-use size.

Preferably, in the size of the invention, the proportion of inorganic hollow bodies which consist partly or completely of crystalline material is in the range of 0.001 to 0.99% of the weight of the ready-to-use size. Ready-to-use sizing is understood to mean that the base mass of the sizing has been diluted with a carrier liquid, for example water, such that one for coating molds or cores by means of one of the abovementioned techniques in the desired suspension is present in the desired layer thickness. For this purpose, the sizes are diluted with a carrier liquid, for example water to a suitable viscosity. In the case of the dipping application, the sizes to achieve the desired layer thickness of the size coat of, for example, 0.1 to 0.6 mm are typically at viscosities of 11, 5 sec. to 16 sec. measured in a 4 mm immersion discharge cup based on DIN 2321 1 diluted. For other application methods, other viscosities must be chosen accordingly. The determination of suitable viscosities and layer thicknesses is one of the skills of the skilled person.

The inorganic materials of which the inorganic hollow bodies are formed are distinguished by the presence of X-ray diffraction analysis of detectable crystalline structures. That In the materials of the hollow bodies there are regions with three-dimensionally-periodic order, whose extents are larger than the coherence length of the X-rays (about 10 nm), so that sharp reflections are observed in the X-ray diffraction analysis. The crystalline fraction is preferably 5% by weight or more, more preferably 20% by weight or more. In contrast, the material of the hollow spheres of borosilicate glass known from WO 2007/025769 is non-crystalline, because glass is a supercooled melt, i. it is in the amorphous state.

Preferably, the inorganic hollow body have a softening point of 1000 ⁰ C or higher, preferably 1 100 ⁰ C or higher, determined by a heating microscope. Particularly preferred inorganic hollow body with a softening point between 1200 ⁰ C nd 1450 ⁰ C, determined ngsmikroskop with a Erhitzu are. The determination of the softening point and the melting point of ceramics in a heating microscope is based on the measurement of the projection area of a cylindrical sample and its change with temperature. The softening point is the temperature at which the first detectable melt phenomena occur, which are manifested by smoothing of rough surfaces and the beginning of edge rounding. The hemisphere or melting point is the temperature at which the sample is deformed to a hemisphere by the formation of melt phases. The inorganic hollow bodies of the size according to the invention, which consist partially or completely of crystalline material, contain no boron oxides, which act as a network image ner for glasses, and thus no borosilicate glass. As a network converter acting compounds such as sodium and potassium oxide, which also as Flux act and reduce the melting temperature, are at best contained as impurities. Therefore, in the sizings of the present invention, the formation of low melting point compounds is suppressed by the reaction of the network walling agents and fluxes of sodium oxide and potassium oxide and the network former boron oxide with platy clay minerals and silicates commonly contained in the sizing. Preferably, in the inorganic hollow bodies to be used according to the invention, the content of the compounds which act as flux medium and network converter is preferably less than 4% by weight of sodium oxide and / or potassium oxide.

The inorganic hollow bodies consist for example of silicates, preferably of aluminum, calcium, magnesium or zirconium, or of oxides, preferably aluminum oxide, quartz, mullite, chromite, zirconium oxide and titanium oxide, or of carbides, preferably silicon carbide or boron carbide or of nitrides, preferably boron nitride or mixtures of these materials, or mixtures of inorganic hollow bodies of these materials are used. By hollow bodies are meant, without limitation to the spherical shape arbitrarily shaped three-dimensional structures having a cavity inside which occupies 15% or more, preferably 40% or more, more preferably 70% or more of the volume of the three-dimensional structure. This cavity can be completely enclosed by a shell of inorganic material, as in the case of hollow spheres, or incompletely enclosed, as in the case of a tube open at the ends, for example.

These inorganic hollow bodies are preferably hollow spheres having a diameter of less than 400 μm, preferably 10 to 300 μm, particularly preferably 10 to 150 μm.

The inorganic hollow bodies are characterized by a high mechanical stability, so that they can withstand the pressure load that inevitably occurs in the production of sizings. For this purpose, the inorganic hollow bodies to be used according to the invention preferably have compressive strengths of 10

MPa or higher, preferably 25 MPa or higher. The compressive strength of

Hollow bodies of glass are generally lower than 10 MPa. Thus, the hollow microspheres used in the embodiments of WO2007 / 025769 have a

Compressive strength of only 4 MPa. The compressive strengths can be in an isostatic

Pressure test based on the ASTM D3102-72 be determined. Preference is furthermore given to inorganic hollow bodies, in particular hollow spheres, having an outer diameter of from 10 to 150 μm.

Also preferred are inorganic hollow body, in particular hollow balls, having a Mohs hardness of 5 to 6. Also preferred are hollow body, in particular hollow balls with a compressive strength of 25 MPa or more.

Also preferred are inorganic hollow body, in particular hollow balls, with a cavity which occupies 70% or more of the total volume of the hollow body or the hollow sphere. Individual or all of the preferred properties of the inorganic hollow bodies are preferably realized in combination with each other.

Particular preference is given in the sizes according to the invention to individual, the majority or all of the inorganic hollow bodies used which are inorganic hollow spheres which form during the combustion of coal in power plants as part of the fly ash. These hollow spheres are deposited from the flue gas stream and are described under the name cenospheres (Cenospheres CAS No .: 93924-19-7). These inorganic hollow spheres preferably have the following properties:

an outer diameter in the range of 10 to 150 μm,

a cavity occupying 70% or more of the total volume of the hollow sphere;

a softening point of 1200 ⁰ C to 1450 ⁰ C a Mohs hardness of 5 to 6 and

a compressive strength of 25 MPa or higher.

However, since such hollow spheres are available only to a limited extent, the low content of the sizes according to the invention of such inorganic hollow bodies represents an advantage over the prior art according to WO 94/26440.

In a further preferred variant of the size of the invention, inorganic hollow bodies of carbon are used, preferably nano-hollow bodies

Carbon, for example carbon nanotubes or / and fullerenes. It is also possible to use mixtures of inorganic hollow bodies of carbon and inorganic hollow bodies of one or more of the other materials mentioned above.

Contains a ready-to-use size according to the invention

(a) inorganic hollow bodies which consist partly or completely of crystalline material,

and preferably

(b) one or more refractory or high refractory materials which are not hollow bodies as defined under (a),

(c) one or more carrier liquids, e.g. Water,

(d) one or more suspending agents, e.g. water-swellable clay minerals,

(e) one or more biocides,

(f) optionally one or more wetting agents,

(g) optionally one or more adjusting agents and / or rheological additives, (h) optionally one or more binders.

For the purpose of calculating the composition of the size, those substances which can be assigned to more than one of components (a) to (h) are to be assigned to the former of these components.

The present invention also relates to the use of a sizing agent of the invention for the production of a coating on a mold or core for use in the foundry.

The present invention also relates to a mold or a core for iron and steel casting, wherein the mold or the core on the surface facing the casting metal has a sizing coating u Mfassend the Trocknu ngsprod ukt a sizing invention, wherein the thickness of the sizing coat 0.05 mm or more, preferably 0.15 mm or more and more preferably 0.25 to 0.6 mm, and the use of such a mold or such a core for producing an iron or cast steel piece.

The present invention also encompasses a concentrate for the production of a ready-to-use size according to the invention, the concentrate having the following composition, based on its total weight:

(a) from 0.0011 to 3.5% of inorganic hollow bodies consisting partly or wholly of crystalline material, (b) 20 to 75% of one or more refractory or refractory materials other than hollow bodies as defined in (a),

(c) 15 to 80% of one or more carrier liquids, e.g. Water,

(d) 0.1 to 10% of one or more suspending agents, e.g. water-swellable clay minerals,

(e) 0.01 to 0.6% of one or more biocides,

(f) 0 to 4% of one or more wetting agents,

(g) 0 to 2% of one or more adjusters and / or rheological additives, (h) 0 to 2% of one or more binders.

For the purpose of calculating the composition of the concentrate, those substances which can be assigned to more than one of the components (a) to (h) are to be assigned to the former of these components.

The present invention also provides a process for the preparation of a size from a concentrate according to the invention described above, the process comprising the following steps:

Preparing or providing a concentrate as described above

Mixing of the concentrate with water or another carrier liquid in a mixture is such that mixing is obtained in a simple manner according to the invention. The present invention furthermore relates to a process for producing a size coat on a shaped body or core, comprising the steps:

Providing or providing a molded body or core to be coated, providing a ready-to-use sizing agent according to the invention, or curing such saccharides according to the above-mentioned inventive processes,

Applying the ready-to-use size to the core or the molding so that a size coat is formed having a thickness of 0.05 mm or more, preferably 0.15 mm or more, and more preferably 0.25 mm to 0.6 mm. The sizings according to the invention are applied to the lost molds or cores, for example by dipping, flooding, spraying or brushing, and then dried, preferably by the application of heat or microwave radiation, so that sizing coatings are formed on the molds or cores. EXEMPLARY EMBODIMENTS

A size having the composition shown in Table 1 is prepared by mixing the components with a stirrer and then breaking up by shearing for 10 minutes with a high speed rotating dissolver. Corresponding production methods are known to the person skilled in the art and e.g. described in patent application WO 94/26440.

Table 1

From this masterbatch, sizes A, B, C, D and E, the compositions of which are given in Table 2 below, were prepared by mixing with a dissolver disk and diluted with water as indicated to give ready-to-use sizes.

The sizings were applied by dipping on cored boxes prepared by the CoId Box method. The achieved coating thicknesses of the size coatings were 0.5 mm in the wet, matted state. Subsequently, the cores were dried in a drying oven at 150 ° C. for 30 minutes. All further investigations were carried out with the sized cores thus prepared (see Table 2). It turns out that when using the sizes according to the invention on the castings fewer leaf ribs and distortions are formed than when using a size according to the prior art with a higher proportion of inorganic hollow bodies.

Table 2

* Core produced by the CoId Box polyurethane process: 70 parts by weight quartz sand, 30 parts by weight chromite sand, 1.8 parts by weight resin components, tertiary amine catalyst.

FIG. 1 shows the results of measurements of the gas pressure as a function of time in a core coated with the abovementioned size A, B, C, D or E. The measuring method for determining the gas pressure in cores has been described by HG Levelink, FPMA Julien and HCJ de Man in Foundry 67 (1980) 109. The test temperature is 1445 ^° C. The composition of the cores is as follows:

50 parts by weight feldspathic sand

50 parts by weight of quartz sand

1.8 parts by weight of resin components

Surprisingly, it has been found that with the sizes B, C and D according to the invention sizing coatings on cores and molds are obtained after drying, which reduce the formation of gas defects despite a higher gas pressure in the molding material than in the comparative experiment with size E.

As can be seen from FIG. 1, in the absence of the inorganic hollow bodies in the size (comparative experiment with size A), the gas pressure in the molding material is markedly higher. It follows that even in comparison to the prior art (Comparative Example E) small proportion of inorganic hollow bodies in the sizes according to the invention sufficient to reduce the gas pressure so far that hardly any gas defects are observed on the castings. In particular, it is found in practice that such gas defects that occur associated with oxide-rich slags greatly reduced occurrence. However, sizing with higher levels of hollow spheres, due to their high gas permeability, act primarily against exogenous gas bubbles.

The tests with the sizes of Examples B-D show that at least comparable advantages are achieved with the sizes according to the invention as with the sizes according to WO 2007/025769, i. the formation of leaf ribs was reduced and spalling of the size coat prevented. In addition, the formation of penetrations was reduced or prevented.

With a size according to Example C cores were coated for the manufacture of engine parts, which were manufactured by the CoId box process. For a batch of 500 pieces, no exogenous gas faults and, in particular, gas faults associated with slag were observed.

Claims

claims

1. ready-to-use sizing for the production of moldings on lost molds or on cores for iron and steel casting,

wherein the size contains a weight fraction of 0.001% or more and less than 1% of inorganic hollow bodies,

characterized in that

the inorganic hollow body partially or completely made of crystalline material.

2. lurking according to claim 1

characterized in that

the size contains from 0.001% to 0.99% by weight of said inorganic hollow bodies.

3. sizing according to one of claims 1 or 2,

characterized in that

said inorganic hollow body have a softening point of 1000 ⁰ C or higher, preferably 1100 ⁰ C or higher, more preferably have a softening point between 1200 ⁰ C and 1450 ⁰ C.

4. sizing according to claim 1 to 3,

characterized in that

the said inorganic hollow body

Silicates, preferably of aluminum, calcium, magnesium or

Zircons, or out

Oxides, preferably alumina, quartz, MuMt, chromite, zirconium oxide or titanium oxide, or from

- Carbides, preferably silicon carbide or boron carbide, or from

Nitrides, preferably boron nitride, or from

Mixtures of these materials

consist

or

Mixtures of inorganic hollow bodies of these materials are.

5. sizing according to one of the preceding claims,

characterized in that the said inorganic hollow bodies are hollow spheres with a diameter of less than 400 μm, preferably 10 to 300 μm, particularly preferably 10 to 150 μm.

6. sizing according to one of the preceding claims,

characterized in that the said inorganic hollow body, preferably hollow spheres, have a cavity occupying 15% or more, preferably 40% or more, more preferably 70% or more, of the volume of the three-dimensional structure.

7. A sizing according to one of the preceding claims,

characterized in that said inorganic hollow bodies have compressive strengths of 10 MPa or higher, preferably 25 MPa or higher.

8. sizing according to one of the preceding claims,

characterized in that said inorganic hollow bodies

Hollow spheres with an outer diameter of 10 to 150 microns.

9. sizing according to one of the preceding claims,

characterized in that said inorganic hollow bodies have a Mohs hardness of 5 to 6.

10. sizing according to one of the preceding claims,

characterized in that the said inorganic hollow bodies have a compressive strength of more than 25 MPa.

11. sizing according to one of the preceding claims,

characterized in that said inorganic hollow bodies are hollow spheres with a cavity occupying 70% or more of the total volume of the hollow sphere.

12. sizing according to one of the preceding claims,

characterized in that individual, the majority or all of said inorganic hollow body are hollow spheres with

an outer diameter in the range of 10 to 150 μm,

a cavity occupying 70% or more of the total volume of the hollow sphere,

- A softening point of 1200 ⁰ C to 1450 ° C.

- a Mohs hardness of 5 to 6 and

- a compressive strength of 25 MPa or higher.

13. sizing according to one of the preceding claims,

characterized in that

the said inorganic hollow body hollow balls according to the CAS no. 93924-19-7 (Cenosheres), which form as part of the fly ash and are separated from the flue gas stream during the combustion of coal in power plants.

14. sizing according to one of claims 1 and 2,

characterized in that

said inorganic hollow body made of carbon or mixtures of inorganic hollow bodies of carbon and inorganic hollow bodies of one or more of the materials according to claim 3.

15. sizing according to claim 14, characterized in that said inorganic hollow body made of carbon nano-hollow body made of carbon, for example carbon nanotubes (carbon nanotubes) and / or fullerenes include.

16. Use of a sizing according to one of claims 1 to 15 for the production of a coating on a mold or a core for use in the foundry.

17. mold or core for iron and steel casting,

characterized in that

the mold or the core on the surface facing the casting metal has a size coat comprising the drying product of a size as defined in claims 1 to 15,

wherein the thickness of the size coat is 0.05 mm or more, preferably 0.15 mm or more and particularly preferably 0.25 to 0.6 mm.

18. Use of a mold or a core according to claim 17 for the production of an iron or cast steel piece. 19. A concentrate for the preparation of a ready-to-use sizing according to claims 1 to 15, wherein the concentrate has the following composition based on its total weight:

(A) 0.0011 to 3.5% of inorganic hollow bodies which consist partially or completely of crystalline material

(b) 20 to 75% of one or more refractory or high refractory

Materials which are not hollow bodies as defined under (a)

(c) 15 to 80% of one or more carrier liquids, e.g. Water.

(d) 0.1 to 10% of one or more suspending agents, e.g. water swellable clay minerals

(e) 0.01 to 0.6% of one or more biocides

(f) 0 to 4% of one or more wetting agents

(g) 0 to 2% of one or more actuators and / or rheological additives

(h) 0 to 2% of one or more binders 20. A process for the preparation of a size from the concentrate according to claim 19 comprising the steps

Preparing or providing a concentrate as defined in claim 16, mixing the concentrate with water or other carrier liquid in such a mixing ratio that a ready-to-use size as claimed in any one of claims 1 to 12 is obtained;

21. A method for producing a size coat on a molded article or core, comprising the steps of: Producing or providing a shaped body or core to be coated, providing a ready-to-use size as defined in claims 1 to 15 or producing such a size by the method according to claim 20,

- Apply and ready to use sizing on the core or the

Shaped body, so that a size coat is formed with a thickness of 0.05 mm or higher, preferably from 0.15 mm or higher, and more preferably from 0.25 mm to 0.6 mm.

22. The method according to claim 21,

characterized in that the application of the size is carried out by a method from the group consisting of dipping, flooding, spraying and brushing on the mold or the core.

23. The method according to claim 21 or 22,

characterized in that the drying of the sizing is effected by supplying heat or microwave radiation.