METHOD FOR PRODUCING A MOULDING MATERIAL MIXTURE AND A MOULDED BODY THEREOF IN THE CASTING INDUSTRY AND KIT FOR USE IN THIS METHOD

Abstract

A description is given of a method for producing a molding material mixture or for producing a molding material mixture and a molding therefrom, preferably casting molds or cores, for use in the foundry industry, where the molding material mixture comprises a mold base material and a solution or dispersion comprising lithium-containing waterglass, comprising the following steps: (1) producing or providing a kit at least comprising as separate components: (K1) an aqueous solution or dispersion comprising waterglass and (K2a) a first waterglass-free solution or dispersion comprising lithium ions in solution in water, and also preferably (K2b) a second waterglass-free solution or dispersion, preferably o comprising lithium ions in solution in water with a lower concentration than in component (K2a), and thereafter (2) producing a mixture of the mold base material with a fraction of component (K1) and with a fraction of component (K2a), and also optionally with a fraction of component (K2b). Further described is an aforementioned kit, more particularly for application in the method of the invention. An installation is specified as well for producing an intermediate solution or dispersion, comprising lithium-containing waterglass, for use in producing a molding material mixture or for producing a molding material mixture and a molding therefrom.

Claims

1. A method for producing a molding material mixture or for producing a molding material mixture and a molding therefrom, where the molding material mixture comprises: (M1) a mold base material, and (M2) a solution or dispersion comprising lithium-containing waterglass, which possesses a molar Si02/M20 modulus in the range from 1.6 to 3.5, and in which the molar fraction of the Li20 within M20 is in the range from 0.05 to 0,60, comprising the following steps: (1) producing or providing a kit at least comprising the following separate components: (K1) an aqueous solution or dispersion comprising waterglass, where the SiO.sub.2 content is in the range from 20 to 34 wt %, based on the total mass of the solution or dispersion, and/or where the molar SiO.sub.2/M.sub.2O modulus is greater than the molar modulus of the lithium-containing waterglass in the molding material mixture being produced, and (K2a) a first waterglass-free solution or dispersion comprising lithium ions in solution in water, where the concentration of the lithium ions is in the range from 0.3 to 5.3 mol/Lcand the total concentration of the lithium, sodium and potassium ions is in the range from 0.3 to 28.0 mol/L, and thereafter (2) producing a mixture of the mold base material (M1) with a fraction of component (K1) and also with a fraction of component (K2a), where the solution or dispersion (M2) is formed by mixing together the components of the kit that are used, where M20 denotes in each case the total amount of lithium oxide, sodium oxide and potassium oxide.

2. The method as claimed in claim 1 for producing a molding material mixture and a molding therefrom, wherein the kit produced or provided in step (1) additionally comprises the following separate component: (K2b) a second waterglass-free solution or dispersion comprising alkali metal ions in solution in water, where the concentration of the lithium ions is lower than in component (K2a), and the total concentration of the lithium, sodium and potassium ions is in the range from 0.3 to 28.0 mol/L, and preferably the total concentration of the lithium, sodium and potassium ions of component (K2b) differs by not more than 20%, preferably by not more than 10%, from the total concentration of the lithium, sodium and potassium ions in component (K2a), and wherein step (2) comprises the following: (2) producing a mixture of the mold base material (M1) with a fraction of component (K1) and also with a fraction of component (K2a) and optionally a fraction of component (K2b), where the solution or dispersion (M2) is formed by mixing together the components of the kit that are used.

3. The method as claimed in claim 1, where the molding material mixture comprises: (M1) a mold base material, and (M2) a solution or dispersion comprising lithium-containing waterglass, which possesses a molar SiO.sub.2/M.sub.2O modulus in the range from 1.6 to 3.5, and in which the molar fraction of the Li.sub.2O within M.sub.2O is in the range from 0.05 to 0.60, comprising the following steps: (1) producing or providing a kit at least comprising the following separate components: (K1) an aqueous solution or dispersion comprising waterglass, where the SiO.sub.2 content is in the range from 20 to 34 wt %, based on the total mass of the solution or dispersion, and/or where the molar SiO.sub.2/M.sub.2O modulus is greater than the molar modulus of the lithium-containing waterglass in the molding material mixture being produced, (K2a) a first waterglass-free solution or dispersion comprising lithium ions in solution in water, where the concentration of the lithium ions is in the range from 0.3 to 5.3 mol/L, and the total concentration of the lithium, sodium and potassium ions is in the range from 0.3 to 28.0 mol/L, and (K2b) a second waterglass-free solution or dispersion comprising lithium ions in solution in water, where the concentration of the lithium ions is lower than in component (K2a) and is in the range from 0.1 to 5.0 mol/L, and the total concentration of the lithium, sodium and potassium ions is in the range from 0.3 to 28.0 mol/L, and the total concentration of the lithium, sodium and potassium ions differs by not more than 20%, from the total concentration of the lithium, sodium and potassium ions in component (K2a),and thereafter (2) producing a mixture of the mold base material (M1) with a fraction of component (K1) and also with a fraction of component (K2a) and with a fraction of component (K2b), where the solution or dispersion (M2) is formed by mixing together the components of the kit that are used, where M.sub.2O denotes in each case the total amount of lithium oxide, sodium oxide and potassium oxide.

4. The method as claimed in claim 1 for producing a molding material mixture and a molding therefrom, comprising the additional steps of establishing, determining or estimating one or more parameters selected from the group consisting of ambient temperature during the production of the molding, relative humidity during the production of the molding, temperature during the storage of the molding, relative humidity during the storage of the molding, absolute humidity during the production of the molding, absolute humidity during the storage of the molding, and storage duration of the molding, and controlling the fractions to be used of components (K2a) and (K2b) as a function of the established, determined or estimated parameter or parameters selected from the group consisting of ambient temperature during the production of the molding, relative humidity during the production of the molding, temperature during the storage of the molding, relative humidity during the storage of the molding, absolute humidity during the production of the molding, absolute humidity during the storage of the molding, and storage duration of the molding, and/or where the method is embodied as at least partial serial fabrication of a number of moldings, where, in the case of increase or expected increase in one or more parameters selected from the group consisting of ambient temperature during the production of the molding, relative humidity during the production of the molding, temperature during the storage of the molding, relative humidity during the storage of the molding, absolute humidity during the production of the molding, absolute humidity during the storage of the molding, and storage duration of the molding, the fractions that are used of component (K2a) are increased for the fabrication of the moldings and/or the molar fraction of the Li.sub.2O within M.sub.2O in the solution or dispersion (M2) is increased for the fabrication of the moldings.

5. The method as claimed in claim 3, where, for establishing, determining or estimating the one or more parameters selected from the group consisting of ambient temperature during the production of the molding, relative humidity during the production of the molding, temperature during the storage of the molding, relative humidity during the storage of the molding, absolute humidity during the production of the molding, absolute humidity during the storage of the molding, and storage duration of the molding, a data capture facility or data processing facility is provided, and to control the fractions that are to be used of components (K2a) and (K2b) as a function of the established, determined or estimated parameter or parameters, a control facility is provided, where, between the data capture facility or the data processing facility and the control facility, a data connection is set up to transfer parameter data.

6. The method as claimed in claim 1, where, during production of the molding material mixture, one or more constituents are additionally added which are selected from the group consisting of: (M3) particulate, amorphous silicon dioxide; barium sulfate; carbohydrates; phosphorus compounds; surface-active compounds; oxidic boron compounds; metal oxides; lubricants, esters and release agents.

7. The method as claimed in claim 1, where the first waterglass-free solution or dispersion (K2a) and optionally the second waterglass-free solution or dispersion (K2b) in each case comprise lithium hydroxide in solution in water.

8. The method as claimed in claim 2, where the aqueous solution or dispersion comprising waterglass (K1) has a pH in the range from 10.0 to 13.0, and/or the first waterglass-free solution or dispersion comprising lithium ions in solution in water (K2a) has a pH in the range from 8.0 to 14.0, and/or the second waterglass-free solution or dispersion comprising lithium ions in solution in water (K2b) has a pH in the range from 8.0 to 14.0.

9. The method as claimed in claim 1, where in step (2) first, in the absence of the mold base material, a solution or dispersion (M2) is formed by mixing together the components of the kit that is used, and thereafter a mixture of the or a fraction of the mold base material (M1) with a fraction or the total amount of the resulting solution or dispersion (M2) is formed and/or where the solution or dispersion (M2) produced, before the forming of the mixture with the mold base material (M1), contains no visible precipitates or gel fractions.

10. The method as claimed in claim 9, where the components of the kit that are used are mixed together to form the solution or dispersion (M2) in a mixing facility, where the mixing facility is a metering vessel or a mixing pipe.

11. The method as claimed in claim 9, where the fraction or the total amount of the solution or dispersion (M2) formed, before the forming of a mixture with the or a fraction of the mold base material (M1), is stored for a period of not more than 7 days in the mixing facility.

12. A kit for producing a solution or dispersion comprising lithium-containing waterglass, at least comprising the following separate components: (K1) an aqueous solution or dispersion comprising waterglass, where the SiO.sub.2 content is in the range from 20 to 34 wt %, based on the total mass of the solution or dispersion, and/or where the molar SiO.sub.2/M.sub.2O modulus is greater than the molar modulus of the lithium-containing waterglass being produced, and (K2a) a first waterglass-free solution or dispersion comprising lithium ions in solution in water, where the concentration of the lithium ions is in the range from 0.3 to 5.3 mol/L, and the total concentration of the lithium, sodium and potassium ions is in the range from 0.3 to 28.0 mol/L.

13. The kit as claimed in claim 12, additionally comprising as a further separate component (K2b) a second waterglass-free solution or dispersion comprising alkali metal ions in solution in water, where the concentration of the lithium ions is lower than in component (K2a) and is in the range from 0 to 5.0 mol/L, and the total concentration of the lithium, sodium and potassium ions is in the range from 0.3 to 28.0 mol L, and the total concentration of the lithium, sodium and potassium ions differs by not more than 20% from the total concentration of the lithium, sodium and potassium ions in component (K2a).

14. The kit as claimed in claim 12 for producing a solution or dispersion comprising lithium-containing waterglass, at least comprising the following separate components: (K1) an aqueous solution or dispersion comprising waterglass, where the SiO.sub.2 content is in the range from 20 to 34 wt %, based on the total mass of the solution or dispersion, and/or where the molar SiO.sub.2/M.sub.2O modulus is greater than the molar modulus of the lithium-containing waterglass under production, (K2a) a first waterglass-free solution or dispersion comprising lithium ions in solution in water, where the concentration of the lithium ions is in the range from 0.3 to 5.3 mol/L, and the total concentration of the lithium, sodium and potassium ions is in the range from 0.3 to 28.0 mol/L, and (K2b) a second waterglass-free solution or dispersion comprising lithium ions in solution in water, where, the concentration of the lithium ions is lower than in component (K2a) and is preferably in the range from 0.1 to 5.0 mol/L, more preferably in the range from 0.1 to 2.0 mol/L, and the total concentration of the lithium, sodium and potassium ions is in the range from 0.3 to 28.0 mol/L, and the total concentration of the lithium, sodium and potassium ions differs by not more than 20% from the total concentration of the lithium, sodium and potassium ions in component (K2a).

15. A method of producing a molding material mixture or for producing a molding material mixture and a molding therefrom, comprising providing a kit as claimed in claim 12. where the molding material mixture comprises: (M1) a mold base material, and (M2) a solution or dispersion comprising lithium-containing waterglass, which possesses a molar SiO.sub.2/M.sub.2O modulus in the range from 1.6 to 3.5, and in which the molar fraction of the Li.sub.2O within M.sub.2O is in the range from 0.05 to 0.60.

16. An installation for use in producing a molding material mixture or for producing a molding material mixture and a molding therefrom, where the installation at least comprises: a first storage tank (Z1), containing as first component an aqueous solution or dispersion (K1) comprising waterglass, where the SiO.sub.2 content is in the range from 20 to 34 wt %, based on the total mass of the solution or dispersion, and/or where the molar SiO.sub.2/M.sub.2O modulus is greater than the molar modulus of the lithium-containing waterglass in the molding material mixture under production, a second storage tank (Z2), containing as second component a first waterglass-free solution or dispersion (K2a), comprising lithium ions in solution in water, where the concentration of the lithium ions is in the range from 0.3 to 5.3 mol/L, and the total concentration of the lithium, sodium and potassium ions is in the range from 0.3 to 28.0 mol/L, a mixing facility (Z3), for mixing at least the first and the second components to produce an intermediate solution or dispersion, and where at least the first and the second storage tanks (Z1, Z2) are connected to the mixing facility (Z3) in each case by one or more lines (Z4), where M.sub.2O denotes in each case the total amount of lithium oxide, sodium oxide and potassium oxide, and/or where the lithium-containing waterglass in the intermediate solution or dispersion possesses a molar SiO2/M20 modulus in the range from 1.6 to 3.5 and/or in which the molar fraction of the Li.sub.2O within M.sub.2O is in the range from 0.05 to 0.60, where M.sub.2O denotes in each case the total amount of lithium oxide, sodium oxide and potassium oxide, and/or where the use takes place in a method as claimed in claim 1.

17. The installation as claimed in claim 16, further comprising a third storage tank (Z5), containing a second waterglass-free solution or dispersion (K2b) comprising alkali metal ions in solution in water, where the concentration of the lithium ions is lower than in component (K2a) and is in the range from 0 to 5.0 mol/L, and the total concentration of the lithium, sodium and potassium ions is in the range from 0.3 to 28.0 mol/L, and the total concentration of the lithium, sodium and potassium ions differs by not more than 20%, from the total concentration of the lithium, sodium and potassium ions in component (K2a), where the mixing facility (Z3) is embodied for mixing at least the first, second and third components, to produce the intermediate solution or dispersion, and where at least the first, the second and the third storage tank are connected to the mixing facility (Z3) in each case by one or more lines (Z4).

Description

FIGURES

[0203] FIG. 1 shows a schematic construction of a detail of an installation of the invention with the following installation components: a first storage tank (Z1), a second storage tank (Z2), a mixing facility (Z3), and one or more (here: a plurality of) lines (Z4) which connect the first and second storage tanks to the mixing facility.

[0204] FIG. 2 shows a schematic construction of a detail of an installation of the invention with the following installation components: a first storage tank (Z1), a second storage tank (Z2), a mixing facility (Z3) (here identical with the first storage tank (Z1)), and one or more (here: one) lines (Z4) which connect the first and second storage tanks to the mixing facility (the first storage tank and the mixing facility being identical).

[0205] FIG. 3 shows a schematic construction of a detail of an installation of the invention with the following installation components: a first storage tank (Z1), a second storage tank (Z2), a third storage tank (Z5), a mixing facility (Z3) and one or more (here: a plurality of) lines (Z4) which connect the first, second and third storage tanks to the mixing facility.

EXAMPLES

[0206] The examples are intended to describe in more detail and explain the invention without limiting its scope of protection.

[0207] Unless otherwise specified, work was carried out under customary laboratory conditions (25 C., standard pressure).

Example 1a

Exemplary Components (K1), (K2a) and (K2b)

[0208] Exemplary components (K1), (K2a) and (K2b) were produced in a conventional way, having the properties shown in table 1a.

TABLE-US-00001 TABLE 1a Exemplary components (K1), (K2a) and (K2b) Component Component Component Constituent (K1) (K2a) (K2b) Molar 2.7 n.s. n.s. SiO.sub.2/M.sub.2O modulus Solids 41 14 22 content [wt %] SiO.sub.2 content 29 0 0 [wt %] c (Li.sup.+) [mol/L] 0 2.4 0.3 c (Li.sup.+/Na.sup.+/K.sup.+) n.s. 3.0 3.0 [mol/L]

[0209] In table 1a, c (Li.sup.+) denotes the concentration of the lithium ions, and c (Li.sup.+/Na.sup.+/K.sup.+) denotes the total concentration of lithium, sodium and potassium ions. n.s. means that no value is stated in the cell in question. The figures for wt % are based in each case on the total mass of the corresponding component (K1), (K2a) or (K2b).

Example 1b

Determination of the pH in Components (K1), (K2a) and (K2b)

[0210] Preferred components (K1), (K2a) and (K2b) were produced in a conventional way. The pH values of the preferred components were subsequently determined in a conventional way. The results are reported below in table 1b:

TABLE-US-00002 TABLE 1b pH values of preferred components (K1), (K2a) and (K2b) Component Component Component Constituent (K1) (K2a) (K2b) pH 11.6 12.0 13.5

[0211] The other properties of the preferred components (K1), (K2a) and (K2b) are very similar to those from table 1a; there are no significant deviations.

Example 2

Production of Inventive Solutions or Dispersions Comprising Lithium-Containing Waterglass

[0212] Exemplary solutions or dispersions (M2) comprising lithium-containing waterglass are produced in accordance with the method of the invention, by conventional mixing of components (K1), (K2a) and optionally (K2b) with one another. The components used are in each case those specified in example 1. For this purpose, the respective fraction of component (K1) is introduced initially and the respective fraction of components (K2a) and optionally (K2b) is added. By shaking or stirring, the resulting solutions or dispersions (M2) are homogenized. The results are reported in table 2.

TABLE-US-00003 TABLE 2 Composition of inventively produced solutions or dispersions (M2) comprising lithium-containing waterglass Molar Solids Molar fraction SiO.sub.2/M.sub.2O content SiO.sub.2 content of Li.sub.2O within Composition (M2) modulus [wt %] [wt %] M.sub.2O Experiment 1: 2.3 38 26 0.11 (K1): 90 wt % (K2a): 10 wt % Experiment 2: 2.3 39 26 0.07 (K1): 90 wt % (K2a): 6 wt % (K2b): 4 wt % Experiment 3: 2.2 37 25 0.11 (K1): 85 wt % (K2a): 10 wt % (K2b): 5 wt % Experiment 4: 2.2 37 25 0.14 (K1): 85 wt % (K2a): 13 wt % (K2b): 2 wt %

Example 3

Production of Molding Material Mixtures

[0213] From the constituents indicated in table 4, molding material mixtures were produced by the method of the invention (molding material mixtures EF1 to EF3) and also by a conventional, noninventive method a comparative molding material mixture (VF1) was produced, in accordance with the protocol indicated below. All quantities in table 4 are reported in parts by weight.

[0214] The Binders used (cf. table 4) comprise the inventive solutions or dispersions comprising lithium-containing waterglass (M2), produced according to table 3, and, respectively, the noninventive solution or dispersion (M2v) (cf. binders ELI to EL3 and VL1). The Mold base material (M1) used in each case was silica sand (H31 from Quarzwerke GmbH, Frechen). The Additive used in each case was the commercial additive in powder form for foundry moldings, Anorgit 8610 (from Httenes-Albertus Chemische Werke Gesellschaft mit beschrnkter Haftung) whose constituents include particulate amorphous silicon dioxide.

TABLE-US-00004 TABLE 3 Composition of inventive solutions or dispersions (M2) and also comparative solution (M2v) produced Molar Solids Molar fraction Composition (M2) SiO.sub.2/M.sub.2O content SiO.sub.2 content of Li.sub.2O within or (M2v) modulus [wt %] [wt %] M.sub.2O EL1 (M2) 2.3 38 26 0.06 EL2 (M2) 2.2 38 26 0.08 EL3 (M2) 2.3 38 26 0.12 VL1 (M2v) 2.4 37 26 0

TABLE-US-00005 TABLE 4 Composition of the molding material mixtures Mold base material Binder/ Additive Experiment [parts by weight] [parts by weight] [parts by weight] EF1 100 EL1/(2.2) 1.3 EF2 100 EL2/(2.2) 1.3 EF3 100 EL3/(2.2) 1.3 VF1 100 VL1/(2.2) 1.3

[0215] The constituents of the molding material mixture were mixed in a laboratory paddle mixer (from Multiserw). For this purpose, the silica sand was introduced initially, and the additive in powder form was mixed in. Thereafter the premixed binder (cf. table 3) was added. The mixture was subsequently stirred for a total of two minutes. The resulting molding material mixtures were then each used for the investigations below.

Example 4

Production of Moldings

[0216] The molding material mixtures (cf. table 4) produced in example 3 were used to produce, with the aid of a heatable mold for production of flexural specimens (as indicated in the March 1974 M11 Merkblatt of the Verein deutscher Gieereifachleute), moldings (test specimens, i.e., standard flexural bars with dimensions of 22.4 mm22.4 mm165 mm), which were used for the following experiments:

[0217] The molding material mixtures were each introduced by means of compressed air (4 bar) into the mold (core box temperature 180 C.). The injection time was 3 s, followed by a hardening time of 30 s (delay time 3 s). To accelerate the hardening of the mixtures, hot air (2 bar gassing pressure, 180 C. gassing and gassing-hose temperature) was passed through the mold during the 30 s hardening time.

[0218] The test specimens produced represent moldings and stand as modelsas is usual in the field of art in questionof moldings which can be used in the foundry industry, such as io molds or cores.

Example 5

Investigating the Storage Stability of Moldings

[0219] The storage stability of waterglass-bound moldings is dependent on the ambient conditions, particularly on the air humidity. The higher the humidity, the greater the risk of damage to the molding (e.g., core damage). Damage to the molding is manifested, for example, in component failure (e.g., core fracture) or in a sharp decrease in the strength (low residual strength, relative to the cold strength). In the case of high humidity, moreover, there is uptake of water, which on casting may lead to gas defects (e.g., gas bubbles in the casting).

[0220] The investigations took place under defined conditions (temperature and relative humidity), monitored in each case by means of a data logger. The moldings (test specimens) are each characterized in table 5 (see Experiment column) by the molding material mixtures used to produce them (see example 3 and table 3).

[0221] 5.1. Determination of the Time to Component Failure

[0222] For determining the time to component failure (fracture of the test specimen), the test specimens were stored in a conditioned cabinet and the time to fracture was observed. The respective times in hours are reported in table 5, in each case as the average of three measurements.

[0223] 5.2. Determination of the Residual Strength of Test Specimens

[0224] The residual strength was determined by storing the test specimens for defined durations (see table 5) in the conditioned cabinet. The flexural strengths were measured subsequently, directly after removal from the conditioned cabinet.

[0225] The flexural strengths were determined by placing the test specimens produced in example 4 into a Georg-Fischer strength tester, equipped with a 3-point bending apparatus (from

[0226] Multiserw), and the force leading to the fracture of the test specimens was measured. The flexural strengths were measured after the durations indicated in table 5. The moldings (test specimens) are each characterized in table 5 (see Experiment column) by the molding material mixtures used to produce them (see example 3 and table 4).

[0227] The measurement values obtained (residual strengths expressed in % of the original value) are reported in table 5 as the average of three measurements in each case.

[0228] 5.3. Determination of the Water Absorption of Test Specimens

[0229] To determine the water absorption, the test specimens were weighed one hour after removal from the mold, and then stored in the conditioned cabinet for a defined time (see table 5). The test specimens were weighed again directly after removal from the conditioned cabinet. The resulting differences in weight (or differences in mass) in % are reported in table 5 as the average of three measurements.

TABLE-US-00006 TABLE 5 Storage stability of moldings Time to Water component absorption failure [h] Residual strength at after 24 h [%] 35 C., 35 C., 35 C., 79% rh, 25 C., 35 C., Experiment 79% rh, 90% rh, (31.3 g/m.sup.3)/[%] 64% rh, 63% rh, (Test (31.3 (35.7 After After (14.7 (25.0 specimen) g/m.sup.3) g/m.sup.3) 4 h 7 h g/m.sup.3) g/m.sup.3) EF1 12.9 5.8 66 39 n.d. n.d. EF2 18.5 7.4 72 49 0.12 0.14 EF3 25.8 9.4 78 68 0.08 0.12 VF1 6.4 2.9 30 0 0.21 0.22

[0230] In table 5, the rh means the relative humidity and the n.d. means not determined (i.e., no measurement value was determined). The figures 31.3 g/m.sup.3, 35.3 g/m.sup.3, 14.7 g/m.sup.3 and 25.0 g/m.sup.3 indicate the absolute humidity in each case.

[0231] From the measurement values reported in table 5 it is apparent that the moldings produced by a method of the invention with lithium-containing waterglass (test specimens EF1, EF2 and EF3) exhibit better storage stabilities than a comparative test specimen (VF1) produced by a noninventive method (without addition of lithium). Moldings produced in accordance with the invention showed better storage capability (see table 5, column Time io to component failure), greater residual strength after storage (see table 5, column

[0232] Residual strength at 35 C.) and lower water absorption (see table 5, column Water absorption) than a comparative molding not produced in accordance with the invention.

[0233] It is further apparent from table 5 that as the lithium ion content of the solutions or dispersions (M2) used for producing the moldings increases within the stated range, there was an improvement in the observed properties of storage stability (higher), residual strength (higher) and water absorption (lower) of the moldings. A higher water absorption on the part of the molding has the general effect of increasing the risk of evolution of gas during the casting operation and hence of a reduced quality to the casting as a result of the inclusion of gas bubbles.

[0234] The conclusion that can be made from these observations is that, depending on the respectively prevailing climatic conditions (especially ambient temperature and relative and/or absolute humidity), at the location of use of the method of the invention and/or of the kit of the invention and/or of the installation of the invention, a correspondingly flexibly adjustable lithium ion concentration in a solution or dispersion (M2) to be prepared (as possible with the method of the invention and/or with the kit of the invention) is advantageous, since it allows the desired properties of moldings, especially the desired storage properties of moldings bound with binders, to be established and/or controlled in a targeted way:

[0235] Where, for example, the relevant climatic conditions do not require this, i.e., in so far as less demanding relevant climatic conditions prevail, especially a relatively low humidity, it is possible to lower the lithium ion content in the solution or dispersion (M2), with a consequent saving in costs. This saving in costs has become even more significant in recent times because lithium compounds have become much more expensive, owing io primarily to increased demand in the battery industry.

[0236] 5.4. Effect of Duration of Storage of a Solution or Dispersion (M2) on the Storage Stability of Moldings

[0237] Components (K1), (K2a) and (K2b) of a solution or dispersion (M2) were used and were mixed with one another, or with one another and with the mold base material (M1), in the ways indicated here below, and under otherwise constant conditions: [0238] a) components (K1), (K2a) and (K2b) were mixed directly with the mold base material, without preliminary mixing. [0239] b) components (K1), (K2a) and (K2b) were premixed and the premix was subsequently mixed directly with the mold base material. [0240] c) components (K1), (K2a) and (K2b) were premixed and the premix was mixed one day after its production with the mold base material. [0241] d) components (K1), (K2a) and (K2b) were premixed and the premix was mixed two days after its production with the mold base material. [0242] e) components (K1), (K2a) and (K2b) were premixed and the premix was mixed three days after its production with the mold base material.

[0243] The molding material mixtures a) to e) obtained above were subsequently used to produce moldings (test specimens; see example 4) as indicated above, which were investigated for their storage stabilities (time to component failure; see example 5.1).

[0244] No significant differences were ascertained when measuring the storage stabilities of moldings (test specimens) produced by the method of the invention with the above-specified molding material mixtures a) to e).

[0245] From this result it is possible to conclude that the solutions or dispersions (M2) produced by the method of the invention can be stored for at least three days under the test conditions without any resultant quality impairments relevant to practice.

Example 6

Investigation of the storage stability of solutions or dispersions (M2)

[0246] Samples of the solution or dispersion (M2) produced in example 3, with the designation EL3, were stored in closed containers under the conditions specified in table 6, and their quality and consistency at the times indicated in table 6 were determined in each case by inspection, with the results reported likewise in table 6:

TABLE-US-00007 TABLE 6 Storage stability of a solution or dispersion (M2) Temperature [ C.] 1 day 1.5 days 3 days 6 days 8 days 20 ++ ++ ++ + 25 ++ ++ ++ + 30 ++ ++ + 50 ++ +

[0247] In table 6, the symbols have the following meanings++: no ascertainable change in the solution or dispersion (M2); +: slight change ascertainable in the solution or dispersion (M2), no adverse effect on quality; o: slight gelling detectable, solution or dispersion (M2) still suitable for use without adverse effect; : severe precipitation apparent, solution or dispersion (M2) no longer suitable for use without adverse effect (e.g., in pumps, filters, metering units).

[0248] From the results above it is evident that a solution or dispersion (M2) produced by the method of the invention, even under adverse storage conditions, could be used for up to 8 days (preferably up to 7 days) without deterioration in quality to an extent relevant for practice, for producing moldings for the foundry industry.

[0249] As is likewise evident from table 6, solutions or dispersions (M2) produced with an advantageous (high) lithium content can therefore be stored and used in industrial practice in premixed form in the short term or at best medium term. For long-term storage (over io several weeks, for instance), homogeneous (e.g., premixed) solutions or dispersions (M2) with an advantageous (high) lithium content are not suitable, however, for the reasons given before.

[0250] In accordance with the subject matter of the present invention, therefore, solutions or dispersions (M2) of this kind with an advantageous (high) lithium content ought not to be mixed until a short time or medium-term time before their actual industrial deployment, by mixing of separately stored components (K1), (K2a) and optionally (K2b) with one another, or with a mold base material, to give a molding material mixture.