METHOD FOR PRODUCING AN ARTICLE FOR USE IN THE FOUNDRY INDUSTRY, CORRESPONDING MOLD, CORE, FEED ELEMENT, OR MOLDING MATERIAL MIXTURE, AND DEVICES AND USES

Abstract

What is described is a process for producing an article for use in the foundry industry, selected from the group consisting of molds, cores, feeder elements and molding material mixtures, comprising the following steps: (S1) producing or providing a binder system comprising the following components in three spatially separate vessels: a component (A) comprising particulate amorphous silicon dioxide, a first liquid component (B) comprising waterglass, and a second liquid component (C) comprising aluminate ions dissolved in an aqueous phase, (S2) contacting a mold base material (D) and constituents of all the said components (A), (B) and (C) of the binder system in predetermined ratios in one or more steps, so as to result in a molding material mixture in which the aluminate ions and the particulate amorphous silicon dioxide are mixed wholly or partly into the waterglass, wherein steps (S1) and (S2) are conducted in a facility for producing molding material mixtures. Also described are a corresponding molding material mixture and apparatuses and uses

Claims

1. A process for producing an article for use in the foundry industry, selected from the group consisting of molds, cores, feeder elements and molding material mixtures, comprising the following steps: (S1) producing or providing a binder system comprising the following components in three spatially separate vessels: a component (A) comprising particulate amorphous silicon dioxide, a first liquid component (B) comprising waterglass,  and a second liquid component (C) comprising aluminate ions dissolved in an aqueous phase, (S2) contacting a mold base material (D) and constituents of all the said components (A), (B) and (C) of the binder system in predetermined ratios in one or more steps, so as to result in a molding material mixture in which the aluminate ions and the particulate amorphous silicon dioxide are mixed wholly or partly into the waterglass, wherein steps (S1) and (S2) are conducted in a facility for producing molding material mixtures.

2. The process as claimed in claim 1, wherein the contacting of mold base material (D) and constituents of all the said components (A), (B) and (C) of the binder system in predetermined ratios in one or more steps in step (S2) is conducted by using an amount of the first liquid component (B) present as a constituent of the binder system in step (S1) and/or an amount of the second liquid component (C) present as a constituent of the binder system in step (S1) and/or selected constituents of the first liquid component (B) after separation, preferably filtration, of the first liquid component (B) present in step (S1) as a constituent of the binder system and/or selected constituents of the first liquid component (C) after separation, preferably filtration, of the second liquid component (C) present in step (S1) as a constituent of the binder system in the contacting in step (S2), and/or wherein constituents and/or amounts of the first liquid component (B) and second liquid component (C) each present as a constituent of the binder system in step (S1), in step (S2), are first mixed in a predetermined ratio, so as to result in a mixture comprising waterglass and aluminate ions in predetermined proportions, and then the mold base material (D) is contacted with this mixture, preferably by (a) allowing a period of not more than 24 hours, preferably a period of not more than 12 hours, more preferably 4 hours, most preferably not more than 1 hour, between the mixing of the amounts or constituents of the said liquid components and the contacting of the mold base material with the resulting mixture and/or (b) contacting, preferably mixing, the mold base material with the resulting mixture of the amounts or constituents of the first liquid component (B) and the second liquid component (C) before solids are formed in the resulting mixture, or not mixing before the mold base material (D) is contacted (i) fully simultaneously, (ii) partly simultaneously or (iii) in any sequence successively with constituents or amounts of the first liquid component (B) and the second liquid component (C).

3. The process as claimed in claim 1, wherein, in step (S2), constituents or amounts of the first liquid component (B) are added at an individually predetermined dosing rate and/or constituents or amounts of the second liquid component (C) at an individually predetermined dosing rate (i) to the mold base material (D) and/or (ii) to constituents or amounts of another component of the binder system, preferably in an automated manner and/or by means of one or more dosing devices, wherein the facility for production of molding material mixtures preferably comprises: one or more dosing devices for metered addition of constituents or amounts of the first liquid component (B) and/or of constituents or amounts of the second liquid component (C) and/or of constituents or amounts of component (A) comprising particulate amorphous silicon dioxide and/or the mold base material (D) and an open-loop or closed-loop control device for the one dosing device or the multiple dosing devices, preferably a microprocessor-assisted open-loop or closed-loop control device.

4. The process as claimed in claim 1, wherein the total mass of the constituents or amounts of the first liquid component (B) and of the constituents or amounts of the second liquid component (C) used in the contacting in step (S2) comprises: 15% to 35% by weight, preferably 18% to 30% by weight, more preferably 20% to 30% by weight, most preferably 22-27% by weight, of silicon dioxide, 8% to 17% by weight of alkali metal oxide, preferably 10% to 17% by weight, more preferably 10% to 16% by weight, aluminate ions, calculated as Al.sub.2O.sub.3, in an amount up to 4.0% by weight, preferably 0.4% to 4.0% by weight, more preferably 0.45% to 3.5% by weight, even more preferably 0.75% to 3.0% by weight, preferably 1% to 2.5% by weight, particularly preferably 1.25% to 2% by weight, where the percentages by weight are based on the total mass of the constituents or amounts of the first liquid component (B) and of the constituents or amounts of the second liquid component (C) used in the contacting in step (S2) and/or where, in the total mass of the constituents or amounts of the first liquid component (B) and constituents or amounts of the second liquid component (C) used in step (S2), the mass ratio of alkali metal oxide to Al.sub.2O.sub.3 is in the range from 35:1 to 3:1, preferably in the range from 20:1 to 5:1, more preferably in the range from 15:1 to 7:1.

5. The process as claimed in claim 1, wherein, in step (S2), the temperature of the constituents or amounts of the first liquid component (B) used and of the constituents or amounts of the second liquid component (C) used at the start of the contacting or mixing are each within a range from 5 to 35° C. and/or wherein, in the total mass of the constituents or amounts of the first liquid component (B) and constituents or amounts of the second liquid component (C) used in step (S2), the mass ratio of Al.sub.2O.sub.3 to SiO.sub.2 is greater than 1:70, preferably greater than 1:69, more preferably greater than 1:64.

6. The process as claimed in claim 1, wherein constituents or amounts of component (A) comprising particulate amorphous silicon dioxide are contacted in step (S2) with the mold base material and with constituents or amounts of the first liquid component (B) and constituents or amounts of the second liquid component (C), wherein component (A) used as a constituent of the binder system in step (S1) (i) is particulate, preferably a powder or granular material, or (ii) is a suspension of particulate amorphous silicon dioxide and/or the constituents or amounts of component (A) used in step (S2), comprising particulate amorphous silicon dioxide, are used (i) in the form of a powder or granular material, preferably in the form of a powder, or (ii) as a suspension and/or the particulate amorphous silicon dioxide of component (A) is used as a constituent in step (S2) and is preferably selected from the group consisting of: particulate synthetic amorphous silicon dioxide containing silicon dioxide in a proportion of at least 80% by weight, based on the total mass of the particulate synthetic amorphous silicon dioxide, and at least carbon as secondary constituent, preferably producible by reducing quartz in an arc furnace; particulate synthetic amorphous silicon dioxide comprising oxidic zirconium as secondary constituent and preferably producible by thermal breakdown of ZrSiO.sub.4; particulate synthetic amorphous silicon dioxide producible by oxidizing metallic silicon by means of an oxygenous gas; particulate synthetic amorphous silicon dioxide producible by quenching a silicon dioxide melt; fumed silica, preferably producible by pyrolysis of silicon tetrachloride; and mixtures thereof and/or component (A) comprising particulate amorphous silicon dioxide additionally comprises one, two, three or more further constituents that are used as well in step (S2) and are independently selected from the group consisting of: particulate materials, preferably particulate inorganic materials, preferably selected from the group consisting of oxides of aluminum, preferably aluminum oxide in the alpha phase, bauxite, oxides of zirconium, preferably zirconium(IV) oxide, mixed aluminum/silicon oxides, zinc oxide, barium sulfate, phosphorus compounds, preferably tricalcium phosphate, sheet silicates, graphite, carbon black, glass beads, oxides of magnesium, borosilicates, ceramic hollow beads, oxidic boron compounds, preferably powdery oxidic boron compounds, and mixtures thereof, water-soluble materials, alkali metal hydroxides, surfactants, film formers, hydrophobizing agents, preferably organosilicon compounds, silanes, silicones and siloxanes, waxes, paraffins, metal soaps, and carbohydrates.

7. The process as claimed in claim 1, wherein the proportion of silicon dioxide in component (A) comprising particulate amorphous silicon dioxide, preferably the proportion of particulate amorphous silicon dioxide in component (A) comprising particulate amorphous silicon dioxide, is at least 25% by weight, preferably at least 30% by weight, more preferably at least 40% by weight, most preferably at least 50% by weight, based in each case on the total mass of component (A) comprising particulate amorphous silicon dioxide.

8. The process as claimed in claim 1, wherein the first liquid component (B) and/or second liquid component (C) present as a constituent of the binder system in step (S1) is/are used in step (S2) out of the respective vessel without further processing and/or wherein the first liquid component (B), preferably in the aqueous phase, comprises one or more alkali metals M from the group consisting of lithium, sodium and potassium, where the proportion of potassium ions, calculated as K.sub.2O, is preferably greater than 0.1% by weight, more preferably greater than 0.2% by weight, especially preferably greater than 0.5% by weight, most preferably greater than 1% by weight, and/or wherein the second liquid component (C) comprises one or more alkali metals M from the group consisting of lithium, sodium and potassium, where the proportion of potassium ions, calculated as K.sub.2O, is preferably greater than 0.1% by weight, more preferably greater than 0.2% by weight, especially preferably greater than 0.5% by weight, most preferably greater than 1% by weight, and/or wherein the total mass of the first liquid component (B) and of the second liquid component (C) comprises one or more alkali metals M from the group consisting of lithium, sodium and potassium, where the proportion of potassium ions, calculated as K.sub.2O, is preferably greater than 0.1% by weight, more preferably greater than 0.2% by weight, especially preferably greater than 0.5% by weight, most preferably greater than 1% by weight, and/or wherein the first liquid component (B), preferably in the aqueous phase, comprises a content of alkali metal silicate in the range from 20% by weight to 60% by weight, preferably in the range from 25% by weight to 50% by weight, based on the total mass of the first liquid component (B); and/or wherein the first liquid component (B), preferably in the aqueous phase, comprises waterglass with a molar SiO.sub.2/alkali metal oxide modulus in the range from 1.6 to 4.0.

9. The process as claimed in claim 1, wherein the first liquid component (B) and/or the second liquid component (C) additionally comprise(s) one, two or more further constituents that are used as well in step (S2) and are independently selected from the group consisting of: surface-active substances, especially surfactants, defoamers and wetting agents, alkali metal phosphates, oxidic boron compounds, preferably selected from the group consisting of borates, boric acids and boric anhydrides, and/or wherein the second liquid component (C) comprises dissolved alkali metal aluminates that are used in step (S2), and/or wherein the first liquid component (B) comprises a content of aluminate ions, calculated as Al.sub.2O.sub.3, of not greater than 0.4% by weight, preferably 0.1% by weight, and/or a content of lithium ions, calculated as LiO.sub.2, of not greater than 0.1% by weight, preferably not greater than 0.01% by weight, and/or a content of boron ions, calculated as B.sub.2O.sub.3, of not greater than 0.1% by weight, preferably not greater than 0.01% by weight, based in each case on the total mass of the first liquid component (B), and/or wherein the second liquid component (C) comprises in the aqueous phase, a content of aluminate ions, calculated as Al.sub.2O.sub.3, in the range from 0.4% by weight to 35% by weight, preferably in the range from 1% by weight to 30% by weight, more preferably in the range from 2.5% by weight to 25% by weight, most preferably 5% by weight to 23% by weight, and/or a content of lithium ions, calculated as LiO.sub.2, of not greater than 0.1% by weight, preferably not greater than 0.01% by weight, and/or a content of boron ions, calculated as B.sub.2O.sub.3, of not greater than 0.1% by weight, preferably not greater than 0.01% by weight, based in each case on the total mass of the second liquid component (C), and/or wherein the total mass of the constituents or amounts of the first liquid component (B) and constituents or amounts of the second liquid component (C) used in the contacting in step (S2) comprises a content of aluminate ions, calculated as Al.sub.2O.sub.3, in the range from 0.4% to 4.0% by weight, preferably 0.45% to 3.5% by weight, more preferably 0.75% to 3.0% by weight, even more preferably 1% to 2.5% by weight, preferably 1.25% to 2% by weight, and/or a content of lithium ions, calculated as LiO.sub.2, of not greater than 0.1% by weight, preferably not greater than 0.01% by weight, and/or a content of boron ions, calculated as B.sub.2O.sub.3, of not greater than 0.1% by weight, preferably not greater than 0.01% by weight, where the percentages by weight are based on the total mass of the constituents or amounts of the first liquid component (B) and of the constituents or amounts of the second liquid component (C) used in the contacting in step (S2).

10. The process as claimed in claim 1, wherein the article is produced in step (S2) using respective total masses of the mold base material (D) and of the respective constituents or amounts of component (A) comprising particulate amorphous silicon dioxide, of the first liquid component (B) and of the second liquid component (C), where: 0.1 to 3.0 parts by weight of component (A) comprising particulate amorphous silicon dioxide is used, preferably 0.3 to 2.0 parts by weight, based on 100 parts by weight of the total mass of the refractory mold base material (D) used, and/or constituents or amounts of the first liquid component (B) and constituents or amounts of the second liquid component (C) are used in the range from 0.5 to 20 parts by weight in total, preferably in the range from 0.5 to 7 parts by weight in total, more preferably in the range from 0.5 to 4 parts by weight in total, most preferably in the range from 0.7 to 3 parts by weight in total, based on 100 parts by weight of the amount of the refractory mold base material (D) used, and/or the ratio of the total mass of the constituents or amounts of the first liquid component (B) used to the total mass of the constituents or components of the second liquid component (C) used is in the range from 86:1 to 1:1, preferably in the range from 20:1 to 2:1, more preferably in the range from 10:1 to 3:1.

11. The process as claimed in claim 1, comprising the steps of (S3) three-dimensionally shaping the molding material mixture, preferably by means of a shaping mold, or by stepwise buildup by means of a 3D printer, (S4) curing the binder, so as to result in a mold, a core or a feeder element, wherein, preferably, in step (S4), the curing, at least in portions, is effected at a temperature in the range from 100° C. to 300° C., more preferably in the range from 140° C. to 250° C., even more preferably at a temperature in the range from 160° C. to 200° C., preferably at a temperature of 170° C. to 190° C., and/or the shaped molding material mixture is heated in a heatable shaping mold and/or the shaped molding material mixture is heated by contact with hot air and/or the shaped molding material mixture is heated by the action of microwaves and/or the shaped molding material mixture is heated by passage of current and/or the shaped molding material mixture is cured using carbon dioxide and/or the shaped molding material mixture is cured using esters.

12. A mold, core, feeder element or molding material mixture for use in a foundry, produced by a process as claimed in claim 1.

13. An apparatus in a foundry for production of an article selected from the group consisting of molds, cores, feeder elements and molding material mixtures, at least comprising: (i) separate reservoir vessels for or comprising: a first liquid component (B) comprising waterglass,  and a second liquid component (C) comprising aluminate ions dissolved in an aqueous phase, (ii) a dosing device for metered addition of defined amounts of the first liquid component (B) and the second liquid component (C) to a vessel for the purpose of contacting with at least one mold base material (D) and particulate amorphous silicon dioxide, preferably additionally at least comprising: (iii) separate reservoir vessels for or comprising: a component (A) comprising particulate amorphous silicon dioxide,  and a mold base material (D) (iv) a dosing device for metered addition of defined amounts of constituents or amounts of component (A) comprising particulate amorphous silicon dioxide  and the mold base material (D) for the purpose of contacting with at least waterglass and aluminate ions.

14. A process for producing an article for use in the foundry industry, selected from the group consisting of molds, cores, feeder elements and molding material mixtures, comprising using of an apparatus as claimed in claim 13 to perform the following steps: (S1) providing a binder system comprising the following components in three spatially separate vessels: a component (A) comprising particulate amorphous silicon dioxide, a first liquid component (B) comprising waterglass,  and a second liquid component (C) comprising aluminate ions dissolved in an aqueous phase, (S2) contacting a mold base material (D) and constituents of all the said components (A), (B) and (C) of the binder system in predetermined ratios in one or more steps, so as to result in a molding material mixture in which the aluminate ions and the particulate amorphous silicon dioxide are mixed wholly or partly into the waterglass, wherein is use for steps (S1) and (S2).

15. A method of increasing the moisture resistance of a mold base material (D) bound by a cured binder system, comprising: forming the cured binder system by combining a liquid component comprising aluminate ions dissolved in an aqueous phase, preferably dissolved alkali metal aluminates, as a second liquid component (C) of a curable binder system comprising: a component (A) comprising particulate amorphous silicon dioxide and a first liquid component (B) comprising waterglass.

16. A method of producing an article using the process as claimed in claim 1, comprising: utilizing liquid component (C) comprises aluminate ions dissolved in an aqueous phase, preferably dissolved alkali metal aluminates.

17. A method of producing a binder comprising: combining a component (A) comprising particulate amorphous silicon dioxide, a first liquid component (B) comprising waterglass, and a second liquid component (C) comprising aluminate ions dissolved in an aqueous phase, wherein the first liquid component (B) and the second liquid component (C) are mixed in a mass ratio in the range from 86:1 to 1:1.

18. The method of claim 17, wherein the first liquid component (B) and the second liquid component (C) are mixed in a mass ratio in the range from 20:1 to 2:1.

19. The method of claim 17, wherein the first liquid component (B) and the second liquid component (C) are mixed in a mass ratio in the range from 10:1 to 3:1

Description

EXAMPLE 1—DETERMINATION OF PARTICLE SIZE DISTRIBUTION BY MEANS OF LASER SCATTERING

[0427] The selection of the substances in this example is merely illustrative, and it is also possible to determine particle size distributions or medians of other particulate silicon dioxide species to be used in accordance with the invention by means of laser scattering according to the procedure in this example.

[0428] 1.1 Sample Preparation:

[0429] By way of example, particle size distributions of silica fume particles (CAS number: 69012-64-2) that are commercially available (from RW Silicium GmbH) and in particulate powder form from Si production, RW filler sieved [“RW-Fuller gesiebt”], and from ZrO.sub.2 production, RW filler Q1 Plus [“RW-Fuller Q1 plus”], were determined experimentally by means of laser scattering.

[0430] In each case, about 1 teaspoon of the particulate silicon dioxide was admixed with about 100 mL of demineralized water, and the resultant mixture was stirred with a magnetic stirrer (IKAMAG RET) at a stirrer speed of 500 revolutions per minute for 30 seconds. Subsequently, an ultrasound probe (from Hielscher; model: UP200HT) preadjusted to 100% amplitude, equipped with the S26d7 sonotrode (from Hielscher), was immersed into the sample, and the sample was sonicated therewith. The sonication was continuous (not pulsed). For the silica fume particles examined from Si production, RW filler sieved, and from ZrO.sub.2 production, RW filler Q1 plus, optimal sonication times of 300 seconds (for RW filler sieved) or 240 seconds (for RW filler Q1 Plus) were chosen, which had been ascertained beforehand as described in example 2.

[0431] 1.2 Laser Scattering Measurements:

[0432] The measurements were conducted with a Horiba LA-960 instrument (LA-960 hereinafter). For the measurements, circulation speed was set to 6, stirrer speed to 8, data recording for the sample to 30 000, con-vergence factor to 15, the mode of distribution to volume, and refractive index (R) to 1.50-0.01i (1.33 for demineralized water dispersion medium) and refractive index (B) to 1.50-0.01i (1.33 for demineralized water dispersion medium). Laser scattering measurements were conducted at room temperature (20° C. to 25° C.).

[0433] The measurement chamber of the LA-960 was filled to an extent of three quarters with demineralized water (maximum fill level). Then the stirrer was started at the set speed, the circulation was switched on and the water was degassed. Subsequently, a zero measurement was conducted with the parameters specified.

[0434] A disposable pipette was then used to take a 0.5-3.0 mL sample centrally from the sample prepared according to point 1.1 of the present example 1 immediately after the ultrasound treatment. Subsequently, the complete contents of the pipette were introduced into the measurement chamber, such that the transmittance of the red laser was between 80% and 90% and the transmittance of the blue laser was between 70% and 90%. Then the measurement was started. The measurements were evaluated in an automated manner on the basis of the parameters specified. For the silica fume particles examined from Si production (RW filler sieved), a particle size distribution was ascertained with a median of 0.23 micrometer, rounded to the second post-decimal place.

[0435] For the silica fume particles examined from ZrO.sub.2 production (RW filler Q1 Plus), a particle size distribution was ascertained with a median of 0.84 micrometer, rounded to the second post-decimal place.

EXAMPLE 2—DETERMINATION OF OPTIMAL SONICATION TIME

[0436] The optimal duration of ultrasound sonication, which is dependent on the type of sample, was ascertained by conducting a measurement series with different sonication times for each species of particulate silicon dioxide. This was done by extending the sonication time, starting from 10 seconds, by 10 seconds each time for every further sample, and determining the respective particle size distribution by means of laser scattering (LA-960) immediately after the end of sonication as described in point 1.2 of the present example 1. With increasing duration of sonication, the median ascertained in the particle size distribution fell at first, until it ultimately rose again at longer sonication times. For the ultrasound sonications described in point 1.1 of the present example 1, the sonication time chosen was that at which, in these measurements series, the lowest median of the particle size distribution was determined for the respective particle species; this sonication time is the “optimal” sonication time.

EXAMPLE 3—PRODUCTION OF ALKALI METAL ALUMINATE SOLUTIONS

[0437] This example describes, by way of example, the production of an alkali metal aluminate solution. The concentrations used here are merely by way of example, and it is also possible to use other concentrations; with regard to the corresponding properties see the above description.

[0438] 3.1 Production of a Potassium Aluminate Solution

[0439] For production of a potassium aluminate solution having a molar ratio of potassium oxide to aluminum oxide of 2.5:1 1 (also referred to hereinafter as “potassium aluminate soln. 1:2.5” or “potassium aluminate solution 1:2.5”), according to formulation 2019311 specified in table 1a (respectively identical formulation numbers in the present text each denote identical compositions), an initial charge of 45 percent potassium hydroxide was equilibrated to a temperature of 93±2° C. while stirring.

TABLE-US-00001 TABLE 1a Formulation 2019311 2019315 % by wt. % by wt. Water — 2.37 NaOH 33%.sup.1 — 77.63 KOH 45%.sup.2 80.00 — Apyral NH20.sup.3 20.00 20.00 Total 100.00 100.00 .sup.133% Spezial sodium hydroxide solution (CG Chemikalien, w = 32-34%, CAS No.: 1310-73-2) .sup.245% potassium hydroxide solution (CG Chemikalien, w = 44.7-45.3%, CAS No.: 1310-58-3) .sup.3Apyral NH20 (Nabaltec AG, aluminum hydroxide, w > 99.7%, CAS No.: 21645-51-2)

[0440] Then aluminum hydroxide powder (Apyral NH20, according to formulation 2019311, table 1a) was added with continuous stirring. The resultant mixture was heated to a temperature of 95° C.±2° C. and kept at that temperature until the solution was clear to the eye. Subsequently, the solution was cooled down to room temperature.

[0441] The molar composition of the resulting potassium aluminate solution according to formulation 2019311 is apparent from table 1 b.

TABLE-US-00002 TABLE 1b 2019311 2019315 H.sub.2O [mol %] 87.50 89.23 Na.sub.2O [mol %] 0.00 7.69 K.sub.2O [mol %] 8.93 0.00 Al.sub.2O.sub.3 [mol %] 3.57 3.08 MR.sup.4 2.5 2.5 .sup.4MR means molar ratio (MR) between M.sub.2O (with M = Na or K) and Al.sub.2O.sub.3 in the aluminate solution.

[0442] 3.2 Production of a Sodium Aluminate Solution

[0443] For production of a sodium aluminate solution having a molar ratio of sodium oxide to aluminum oxide of 2.5:1 (also referred to hereinafter as “sodium aluminate soln. 1:2.5” or “sodium aluminate solution 1:2.5”), according to formulation 2019315 specified in table 1a, a 33 percent sodium hydroxide solution was added to an initial charge of water and equilibrated to a temperature of 93±2° C. while stirring.

[0444] Then aluminum hydroxide powder (Apyral NH20, according to formulation 2019315, table 1a) was added with continuous stirring. The resultant mixture was heated to a temperature of 95° C.±2° C. and kept at that temperature until the solution was clear to the eye. Subsequently, the solution was cooled down to room temperature.

[0445] The molar composition of the resulting sodium aluminate solution according to formulation 2019315 is apparent from table 1 b.

EXAMPLE 4—EXAMPLE CALCULATIONS FOR DETERMINATION OF THE PERCENTAGES BY WEIGHT OF WATER AND METAL OXIDES

[0446] 4.1 Percentage by Weight of Na.sub.2O

[0447] The calculation below shows by way of example that the 33 percent NaOH solution used in formulation 2019315 formally comprises 25.6% by weight of Na.sub.2O in water. It is also possible to conduct corresponding calculations analogously for other concentrations.

[0448] The basis used here is the following equation:

Na.sub.2O+H.sub.2O.fwdarw.2NaOH

[0449] It follows that:

[00001]$\%\mathrm{by}\mathrm{wt}.\left({\mathrm{Na}}_{2}O\right)=\frac{M\left({\mathrm{Na}}_{2}O\right)}{2.Math.M\left(\mathrm{NaOH}\right)}.Math.100\%\mathrm{by}\mathrm{wt}.=\frac{61.98\frac{g}{\mathrm{mol}}}{79.99\frac{g}{\mathrm{mol}}}.Math.100\%\mathrm{by}\mathrm{wt}.=77,5\%\mathrm{by}\mathrm{wt}.$

[0450] In other words, NaOH contains 77.5% by weight of Na.sub.2O.

[0451] It follows that, for a 33 percent NaOH solution: [0452] % by wt. (Na.sub.2O in 33% NaOH)=33-77.5% by wt./100=25.6% by wt. [0453] % by wt. (H.sub.2O in 33% NaOH)=(100-25.6)% by wt.=74.4% by wt.

[0454] 4.2 Percentage by Weight of K.sub.2O

[0455] Analogously, a proportion of 37.8% by weight of K.sub.2O is found for the 45 percent KOH solution in water used in formulation 2019311.

[0456] 4.3 Percentage by Weight of Li.sub.2O

[0457] Analogously, a proportion of 35.6% by weight of Li.sub.2O is found for the LiOH monohydrate used in example 14.

[0458] The basis used here is the following equation:

Li.sub.2O+3H.sub.2O.fwdarw.2LiOH.Math.H.sub.2O

[0459] 4.4 Percentage by Weight of Sodium Aluminate Solution

[0460] The calculation below shows how the composition of a sodium aluminate solution is calculated analogously.

[0461] The basis used here (beyond the basis according to 4.1) is the following equation:

Al.sub.2O.sub.3+3H.sub.2O.fwdarw.2Al(OH).sub.3

[0462] It follows that:

[00002]$\%\mathrm{by}\mathrm{wt}.\left({\mathrm{Al}}_2{O}_3\right)=\frac{M\left({\mathrm{Al}}_2{O}_3\right)}{2.Math.M\left({\mathrm{Al}\left(\mathrm{OH}\right)}_3\right)}.Math.100\%\mathrm{by}\mathrm{wt}.=\frac{101.95\frac{g}{\mathrm{mol}}}{156.01\frac{g}{\mathrm{mol}}}.Math.100\%\mathrm{by}\mathrm{wt}.=65.4\%\mathrm{by}\mathrm{wt}.$

[0463] It follows that, for the solution according to formulation 2019315: [0464] % by wt. (Al.sub.2O.sub.3 in 2019315)=(20.Math.65.4% by wt.)/100=13.08% by wt. [0465] % by wt. (Na.sub.2O in 2019315)=(77.63.Math.25.6% by wt.)/100=19.87% by wt. [0466] % by wt. (H.sub.2O in 2019315)=(100−(13.08+19.87))% by wt.=67.05% by wt.

[0467] 4.5 Percentage by Weight of Potassium Aluminate Solution

[0468] Analogously, for the composition of a potassium aluminate solution according to formulation 2019311, a proportion of 30.24% by weight of K.sub.2O and 56.68% by weight of H.sub.2O is found.

[0469] 4.6 Percentage by Weight of B.sub.2O.sub.3

[0470] Analogously, a proportion of 36.5% by weight of B.sub.2O.sub.3 and 16.3% by weight of Na.sub.2O is found for the sodium tetraborate 10-hydrate used in example 14.

[0471] The basis used here is the following equation:

Na.sub.2[B.sub.4O.sub.5(OH).sub.4].Math.8H.sub.2O.fwdarw.Na.sub.2O+2B.sub.2O.sub.3+10H.sub.2O

EXAMPLE 5—PRODUCTION OF MOLDING MATERIAL MIXTURES

[0472] The production of molding material mixtures is described by way of an example formulation. The composition of the molding material mixtures is merely illustrative; the selection of substances used is also merely illustrative.

[0473] Unless stated otherwise, for the formulations specified in the present text of the examples (here, solely by way of example, the formulation according to table 2a), the liquid components (B) produced or provided (first liquid component, comprising waterglass) and (C) (second liquid component, comprising aluminate ions dissolved in an aqueous phase) are contacted with the component (A) produced or provided (component comprising amorphous silicon dioxide) and the mold base material (component D)) in such a way that the predetermined ratios according to table 2b exist (at least) in the contacting. The exact relative ratios of the liquid components (B) and (C) to one another are each apparent from the formulations detailed.

TABLE-US-00003 TABLE 2a Example formulation for liquid components of the molding material mixture Formulation 2019321 Liquid component % by wt. Water (B) 12.70 NaOH 33% (B) 12.90 48/50 HV waterglass.sup.5 (B) 67.40 EHS surfactant.sup.6 (B) 0.50 Sodium aluminate soln. 1:2.5 (C) 6.50 Total (B) + (C) 100.00 .sup.548/50 sodium waterglass (from BTC Europe GmbH) .sup.6Here and hereinafter: 2-ethylhexyl sulfate in water (from Hoesch)

TABLE-US-00004 TABLE 2b Predetermined ratios on contacting Component Liquid component PW.sup.7 (A) 0.6 (B) + (C) 2.1 (D) 100 .sup.7PW (here and hereinafter) means part(s) by weight

[0474] 5.1 Procedure: [0475] (a) For the purposes of this example, an amount of the particulate amorphous silicon dioxide species “RW-Fuller gesiebt” (with a median of the particle size distribution, rounded to the second post-decimal place, determined by means of laser scattering, of 0.23 micrometer) and an amount of the particulate amorphous silicon dioxide species “RW-Fuller Q1 Plus” (with a median of the particle size distribution, rounded to the second post-decimal place, determined by means of laser scattering, of 0.84 micrometer) were first dry-mixed with one another in a weight ratio of 1:1 (as an example of a component (A) comprising particulate amorphous silicon dioxide). Unless stated otherwise in the context of the text of the examples, the 1:1 mixture described here was always used as component (A) comprising particulate amorphous silicon dioxide. [0476] (b) In a separate vessel (as an example of a first liquid component (B), comprising waterglass), a waterglass binder was provided with a composition according to liquid component (B) from table 2a. Note: In further examples, this procedure is applied to other compositions that are then specified in each case. [0477] (c) In a separate vessel, a sodium aluminate solution was provided (prepared according to the above example 3.2; as an example of a second liquid component (C), comprising aluminate ions dissolved in an aqueous phase) having a molar ratio of sodium oxide and aluminum oxide of 2.5:1. Note: In further examples, this procedure is applied to other compositions that are then specified in each case. [0478] (d) In a contacting vessel, 100 PW of H32 quartz sand (from Quarzwerke GmbH, AFS grain fineness number 45) were provided and 0.6 PW of the 1:1 mixture of “RW-Füller gesiebt” and “RW-Füller Q1 Plus” described above in this example under (a) was mixed manually with the sand so as to result in a preliminary mixture. [0479] (e) Then liquid components (B) and (C), according to the relative ratios specified in table 2a, were each added individually to this preliminary mixture of solids in a total proportion of 2.1 PW (for the relative ratios specified in table 2a, added amounts of 0.1365 PW of the liquid component (C) defined therein and 1.9635 PW of the liquid component (B) defined therein are found here by way of example; the added amounts overall are thus: 0.1365 PW+1.9635 PW=2.1 PW). This was followed by mixing in a bull mixer (RN10/20 type, from Morek Multiserw) at 220 rpm for 120 seconds. This resulted in a molding material mixture as an example of an article for use in the foundry industry. The molding material mixture was suitable for production of molds, cores and feeder elements and was used accordingly in further in-house studies.

EXAMPLE 6—PRODUCTION OF TEST BARS

[0480] This example describes, by way of example, the production of test bars as an example of molds (moldings) or cores for the foundry industry; the dimensions of the test bars and the selection of substances used is merely by way of example.

[0481] 6.1 Procedure

[0482] Molding material mixtures produced according to example 5 were formed to test bars having the dimensions of 22.4 mm×22.4 mm×185 mm. (Note: Molding material mixtures produced from other compositions according to the procedure from example 5.1 were also processed in the manner described here to give test bars).

[0483] For this purpose, the molding material mixtures were introduced with compressed air (4 bar) and a shooting time of 3 seconds into a mold for test bars having a temperature of 180° C. Subsequently, the test bars were hot-cured at 180° C. for 30 seconds, while additionally being aerated with heated compressed air at an aeration pressure of 2 bar and an aeration and aeration hose temperature of 180° C. for the duration of the curing. Thereafter, the mold was opened and the cured test bars were removed. After removal from the mold, the test bars produced, for cooling under ambient air, were placed horizontally on a frame such that they rested on the frame only in the region of the two ends of their longest extent, and the test bars spanned a range of about 16 cm without contact between the contact surfaces.

EXAMPLE 7—DETERMINATION OF CORE WEIGHT

[0484] The test bars produced according to example 6, after a cooling time of about 1 hour under ambient air, were weighed on a laboratory balance (Entris 3202-1S type, from Sartorius). The core weight figures included in examples that follow correspond to an average from nine individual measurements (note: core weight was also determined in the manner described here for test bars produced from other molding material mixtures according to the procedure from example 6.1).

EXAMPLE 8—DETERMINATION OF HOT STRENGTH

[0485] Immediately after removal from the mold (i.e. before storage on a frame as described in example 6), test bars produced according to example 6 were introduced into a Georg Fischer strength tester, equipped with a 3-point bending device (from Morek Multiserw). 15 seconds after the mold had been opened, the force that led to fracture of the test bars was measured. The respective hot strength figure (in N/cm.sup.2) corresponds in each case to an average from three individual measurements and is rounded to 10 N/cm.sup.2 (note: hot strength was also determined in the manner described here for test bars produced from other molding material mixtures according to the procedure from example 6.1).

EXAMPLE 9—DETERMINATION OF ONE-HOUR STRENGTH

[0486] Test bars were produced according to example 6. After a cooling time of 1 hour (under ambient air and on the frame described in the above example 6) after removal from the mold, the respective test bars were introduced into a Georg Fischer strength tester, equipped with a 3-point bending device (from Morek Multiserw), and the force that led to fracture of the test bars was measured. The respective one-hour strength figure (in N/cm.sup.2) corresponds in each case to an average from three individual measurements and is rounded to 10 N/cm.sup.2 (note: one-hour strength was also determined in the manner described here for test bars produced from other molding material mixtures according to the procedure from example 6.1).

EXAMPLE 10—DETERMINATION OF MOISTURE STABILITY

[0487] Test bars, after a cooling time of 1 hour (under ambient air and on the frame described in the above example 6) on their respective frame, were stored under controlled conditions in a climate-controlled cabinet (VC 0034, from \kitsch) at 35° C. and 75% rel. humidity. For evaluation, the test bars were monitored by a camera (HomeVista type, from SECACAM). A photo of the test bars was taken every 10 minutes until they fractured; the time of the last photo on which the test bar has not completely broken is considered to be the measured time for moisture stability. The moisture stabilities reported each correspond to an average from three individual measurements (note: moisture stability was also determined in the manner described here for test bars produced from other molding material mixtures according to the procedure from example 6.1).

EXAMPLE 11—DETERMINATION OF CASTING QUALITY WITH REGARD TO SAND ADHESION

[0488] Test bars produced according to example 6 were placed into an outer sand mold in such a way that three of the four longitudinal sides of the core in each case came into contact with the molten metal in the casting process. The casting molds thus prepared were used to cast an aluminum alloy (EN AC-42100) at a casting temperature of about 750° C. After the melt had cooled, the castings were unpacked from the sand mold, the test bars were removed by high-frequency hammer impacts on the feeding region of the casting with a compressed air chipping hammer (P 2535 Pro type, from Atlas Copco), and the casting surface that was in contact with the test bar was blown with a compressed air gun. For each test bar composition, two corresponding castings were conducted in separate casting molds.

[0489] For relative comparison of casting quality, the casting surfaces that were in contact with the cores were assessed from the best casting quality to the worst casting quality for each mold. The assessment was conducted independently by two testers having several years of experience in the field of foundry technology. Casting quality was also determined for test bars produced from other molding material mixtures according to the procedure from example 6.1 in the manner described here.

EXAMPLE 12—DETERMINATION OF HIGH-TEMPERATURE PROPERTIES

[0490] Deformation under thermal stress was conducted analogously to the method specified in EP 2 097 192 B1 (cf. in particular paragraphs [0096]-[0099] in EP 2 097 192 B1), using a Hot Distortion Tester from Simpson Technologies Corporation. The results obtained with this instrument, from the point of view of the person skilled in the art, are equivalent to the results that were determined by means of hot distortion measurements by the BCIRA hot distortion test.

[0491] The test bars used here were produced according to example 6, with the sole difference that the test bars produced and used for the hot distortion tests had the dimensions of 25 mm×6 mm×120 mm and were placed on two supports such that the air can circulate freely around the test bars.

[0492] The effect of heating from one side during the hot distortion test is that the test specimen bends upward toward the cold side as a result of the thermal expansion of the hot side. This movement of the test specimen is labeled as “maximum expansion” in the curve. To the same extent as that to which the test specimen heats up overall, the binder begins to be converted to the thermoplastic state. On account of the thermoplastic properties of the various binder systems, the load applied by the load arm pushes the test specimen back downward. This downward movement along the ordinate at the zero line until fracture is referred to as “hot deformation”. The time elapsed between the commencement of the maximum expansion on the curve and fracture is referred to as “time until fracture” and is an important parameter.

[0493] By virtue of the apparatus, maximum thermoplastic deformation in the tests conducted is limited to 6 mm (deformation −6 mm). This point is therefore equated to the occurrence of a fracture.

[0494] High-temperature properties were also determined for test bars produced from other formulations according to the procedure from example 6.1 in the manner described here.

EXAMPLE 13—INCREASE IN THE ALUMINATE ION CONTENT IN THE BINDER

[0495] In order to represent the influence of the amount of aluminate ions used in the binder system, according to the procedure of example 5, molding material mixtures having a composition of liquid components (B) and (C) according to tables 3a and 3b were produced; the (calculated) molar compositions present in a mixture of liquid components (B) and (C) (according to the formulations from tables 3a and 3b) are reported in table 3c. Formulations 2019327, 2019321, 2019328 and 2019329 are inventive examples; formulation 2019326 is a noninventive comparative example (unlike in the process of the invention, no liquid component (C) comprising aluminate ions dissolved in an aqueous phase is used).

TABLE-US-00005 TABLE 3a Liquid Formulation component 2019326 2019327 2019321 Water (B) 13.55 13.10 12.70 NaOH 33% (B) 18.10 15.50 12.90 48/50 HV waterglass (B) 67.85 67.65 67.40 EHS surfactant (B) 0.50 0.50 0.50 Sodium aluminate (C) 3.25 6.50 soln. 1:2.5 Total (B) + (C) 100.00 100.00 100.00

TABLE-US-00006 TABLE 3b Formulation Liquid component 2019328 2019329 Water (B) 12.20 11.80 NaOH 33% (B) 10.40 7.90 48/50 HV waterglass (B) 67.15 66.90 EHS surfactant (B) 0.50 0.50 Sodium aluminate soln. 1:2.5 (C) 9.75 12.90 Total (B) + (C) 100.00 100.00

TABLE-US-00007 TABLE 3c Formulation 2019326 2019327 2019321 2019328 2019329 H.sub.2O 85.92 85.81 85.71 85.60 85.50 [mol %] SiO.sub.2 9.06 9.06 9.06 9.06 9.06 [mol %] Na.sub.2O 5.03 5.03 5.03 5.03 5.03 [mol %] Al.sub.2O.sub.3 0.00 0.10 0.20 0.30 0.40 [mol %] MR.sup.8 1.80 1.80 1.80 1.80 1.80 .sup.8MR (here and hereinafter) means molar ratio of SiO.sub.2 to Na.sub.2O in the solution.

[0496] According to the procedure from example 6, these molding material mixtures were used to produce test bars.

[0497] The formulations for the molding material mixtures were chosen here such that, even with a rising aluminum content, there was a uniform molar modulus (MR), a uniform SiO.sub.2 content and a uniform Na.sub.2O content in the respectively used amounts of liquid components (B) and (C).

[0498] For each of the formulations specified in tables 3a and 3b, a sufficient number of test bars were produced in order to determine core weight (according to example 7), hot strength (according to example 8), one-hour strength (according to example 9) and moisture stability (according to example 10); the results of these determinations are reported in table 4.

TABLE-US-00008 TABLE 4 Formulation 2019326 2019327 2019321 2019328 2019329 Core weight 148.52 148.60 148.57 147.97 147.99 Hot strength 180 180 190 180 190 [N/cm.sup.2] One-hour 550 510 540 480 490 strength [N/cm.sup.2] Moisture 453 840 1207 2067 1550 stability [min]

[0499] Even in the case of a composition with 0.10 mol % of Al.sub.2O.sub.3 (based on the combined total mass of liquid components (B) and (C) used; cf. table 3c), a significant increase in moisture stability was observed. For compositions with 0.2 mol %, 0.3 mol % and 0.4 mol % of Al.sub.2O.sub.3, compared to the (noninventive) comparative molding material mixture 2019326 devoid of aluminate ions, increases in moisture stability by more than a factor of 2 were even measured.

[0500] Hot strengths and one-hour strengths of all test bars were above the demands for industrial purposes.

[0501] For formulations 2019326, 2019321 and 2019329, additional test bars (according to example 6) were produced and the casting surface (according to example 11) was determined. For both cast parts each containing a test bar of formulations 2019326, 2019321 and 2019329, irrespective of the tester conducting the assessment, the sequence of casting quality was determined as follows: 2019329>2019321>2019326. For compositions with 0.2 mol % and 0.4 mol % of Al.sub.2O.sub.3, accordingly, compared to the (noninventive) comparative molding material mixture 2019326 devoid of aluminate ions, an improvement in casting quality was found.

[0502] For formulations 2019326, 2019321 and 2019329, additional test bars were produced and examined according to example 12. The more aluminate ions are present in the binder, the lower the slope (deformation per unit time) before attainment of the thermoplastic region. Thus, the region of the thermoplastic state for the comparative molding material mixture 2019326 devoid of aluminate ions sets in after 9 s, for a composition with 0.2 mol % after 10 s, and for a composition with 0.4 mol % actually not until 22 s. The total measurement time until fracture also increases with increasing amount of aluminate ions in the binder. In the case of the comparative molding material mixture, fracture occurs after a total time of 31 s, whereas fracture occurs after a total time of 35 s for a composition with 0.2 mol %, and fracture occurs only after a total time of 40 s for a composition with 0.4 mol %.

EXAMPLE 14—INFLUENCE OF ALUMINUM, LITHIUM AND BORON IONS ON MOISTURE STABILITY

[0503] According to the procedure of example 5, molding material mixtures having a composition of liquid components (B) and (C) according to tables 5a and 5b were produced; the (calculated) molar compositions present in a mixture of liquid components (B) and (C) (according to the formulations from tables 5a and 5b) are reported in table 5c. Formulations 2019321, 2019441 and 2019446 are inventive examples; formulations 2019326, 2019442 and 2019445 are noninventive comparative examples (unlike in the process of the invention, no liquid component (C) comprising aluminate ions dissolved in an aqueous phase is used).

TABLE-US-00009 TABLE 5a Liquid Formulation component 2019326 2019321 2019442 Water (B) 13.55 12.70 13.30 NaOH 33% (B) 18.10 12.90 17.10 48/50 HV waterglass (B) 67.85 67.40 67.55 LiOH monohydrate (B) Sodium tetraborate (B) 1.55 10-hydrate EHS surfactant (B) 0.50 0.50 0.50 Sodium aluminate (C) 6.50 soln. 1:2.5 Total (B) + (C) 100.00 100.00 100.00

TABLE-US-00010 TABLE 5b Liquid Formulation component 2019445 2019441 2019446 Water (B) 14.625 12.50 13.675 NaOH 33% (B) 16.15 11.85 11.10 48/50 HV waterglass (B) 67.10 67.55 LiOH monohydrate (B) 0.675 0.675 Sodium tetraborate (B) 1.55 10-hydrate EHS surfactant (B) 0.50 0.50 0.50 Sodium aluminate (C) 6.50 6.50 soln. 1:2.5 Total (B) + (C) 100.00

TABLE-US-00011 TABLE 5c Formulation 2019326 2019321 2019442 2019445 2019441 2019446 H.sub.2O [mol %] 85.92 85.71 85.71 85.92 85.51 85.70 SiO.sub.2 [mol %] 9.06 9.06 9.06 9.06 9.06 9.06 Na.sub.2O [mol %] 5.03 5.03 5.03 4.83 5.03 4.84 Li.sub.2O [mol %] 0.19 0.19 B.sub.2O.sub.3 [mol %] 0.20 0.20 Al.sub.2O.sub.3 [mol %] 0.00 0.20 0.20 0.20 MR 1.80 1.80 1.80 1.80 1.80 1.80

[0504] According to the procedure from example 6, these molding material mixtures were used to produce test bars.

[0505] For each of the formulations specified in tables 5a and 5b, a sufficient number of test bars were produced in order to determine core weight (according to example 7), hot strength (according to example 8), one-hour strength (according to example 9) and moisture stability (according to example 10); the results of these determinations are reported in table 6.

TABLE-US-00012 TABLE 6 Formulation 2019326 2019321 2019442 2019445 2019441 2019446 Core weight 148.50 148.32 148.44 148.40 148.35 148.21 Hot strength [N/cm.sup.2] 180 180 160 170 180 190 One-hour strength, cold [N/cm.sup.2] 560 520 510 530 480 500 Moisture stability [min] 563 1263 783 1087 2000 2340

[0506] The results show the influence of aluminate ions in the binder on moisture stability (and on further properties) of the moldings produced with this binder compared to the lithium compounds and boron compounds used to date in binders for increasing moisture stability. As a (noninventive) reference, a binder having an otherwise identical molar composition, but without one of the three moisture stability promoters, was tested (formulation 2019326).

[0507] The results show that the positive influence of the aluminate ions on moisture stability is greater than in the comparative examples with lithium compounds and boron compounds. Moreover, the results show that the use of aluminate ions in addition to boron compounds or lithium compounds brings about an additional increase in moisture stability compared to the sole use of boron compounds or lithium compounds.

[0508] Hot strengths and one-hour strengths of all test bars were above the demands for industrial purposes.

EXAMPLE 15—COMPARISON OF POTASSIUM ALUMINATE SOLUTION WITH SODIUM ALUMINATE SOLUTION IN THE BINDER

[0509] According to the procedure of example 5, molding material mixtures having a composition of liquid components (B) and (C) according to table 7a were produced; the (calculated) molar compositions present in a mixture of liquid components (B) and (C) (according to the formulations from table 7a) are reported in table 7b. Formulations 2019387 and 2019551 are inventive examples. With an otherwise identical composition of the liquid components of the binder system, the aluminate ions were introduced once in the form of a potassium aluminate solution (formulation 2019551) and once in the form of a sodium aluminate solution (formulation 2019387).

TABLE-US-00013 TABLE 7a Liquid Formulation component 2019387 2019551 Water (B) 11.80 13.15 NaOH 33% (B) 7.90 5.50 48/50 HV waterglass (B) 66.90 65.850 EHS surfactant (B) 0.50 0.50 Potassium aluminate solution 1:2.5 (C) 12.50 Sodium aluminate soln. 1:2.5 (C) 12.90 Total (B) + (C) 100.00 100.00

TABLE-US-00014 TABLE 7b Formulation 2019387 2019551 H.sub.2O [mol %] 85.50 85.50 SiO.sub.2 [mol %] 9.06 9.06 Na.sub.2O [mol %] 5.03 3.79 K.sub.2O [mol %] 1.25 Al.sub.2O.sub.3 [mol %] 0.40 0.40 MR 1.80 1.80

[0510] According to the procedure from example 6, these molding material mixtures were used to produce test bars.

[0511] For each of the formulations specified in table 7a, a sufficient number of test bars were produced in order to determine core weight (according to example 7), hot strength (according to example 8), one-hour strength (according to example 9) and moisture stability (according to example 10); the results of these determinations are reported in table 8.

TABLE-US-00015 TABLE 8 2019387 2019551 Core weight 147.85 148.82 Hot strength [N/cm.sup.2] 183 189 One-hour strength [N/cm.sup.2] 483 505 Moisture stability [min] 2140 3220

[0512] Surprisingly, the results show that the use of potassium aluminate distinctly increases moisture stability once again compared to the use of sodium aluminate. Additional in-house studies have additionally shown that it also makes no difference whether the potassium comes from the liquid component (B) or (C) (results not shown here).

EXAMPLE 16—COMBINED USE OF ALUMINATE IONS AND VARIOUS MICROSILICA SPECIES

[0513] According to the procedure of example 5, molding material mixtures having a composition of liquid components (B) and (C) according to table 9a were produced; the (calculated) molar compositions present in a mixture of liquid components (B) and (C) (according to the formulation from table 9a) are reported in table 9b. Formulation 2019650 is an inventive example.

[0514] In a first series of experiments (2019650-1), the 1:1 mixture of “RW-Fuller gesiebt” and “RW-Fuller Q1 Plus” used in example 5 was used as the 0.6 PW of component (A) comprising particulate amorphous silicon dioxide.

[0515] In a second series of experiments (2019650-2), with an otherwise unchanged procedure from that in ex-periment series 2019650-1, rather than 0.6 PW of the 1:1 mixture, 0.6 PW of “RW-Fuller Q1 Plus” was used (i.e. without “RW-Fuller gesiebt”).

[0516] In a third series of experiments (2019650-3), with an otherwise unchanged procedure from that in experi-ment series 2019650-1, rather than 0.6 PW of the 1:1 mixture, 0.6 PW of “RW-Fuller gesiebt” was used (i.e. without “RW-Fuller Q1 Plus”).

[0517] Formulations 2019650-1, 2019650-2 and 2019650-3 relate to inventive examples.

TABLE-US-00016 TABLE 9a Formulation Liquid component 2019650 Water (B) 13.275 NaOH 33% (B) 5.575 KOH 45% (B) 2.600 48/50 HV waterglass (B) 65.900 EHS surfactant (B) 0.150 Potassium aluminate solution 1:2.5 (C) 12.500 Total (B) + (C) 100.00

TABLE-US-00017 TABLE 9b Formulation 2019650 H.sub.2O [mol %] 85.50 SiO.sub.2 [mol %] 9.06 Na.sub.2O [mol %] 3.79 K.sub.2O [mol %] 1.25 Li.sub.2O [mol %] B.sub.2O.sub.3 [mol %] Al.sub.2O.sub.3 [mol %] 0.40 MR 1.80

[0518] According to the procedure from example 6, these molding material mixtures were used in each case to produce test bars.

[0519] For each of the series of experiments specified, a sufficient number of test bars were produced in order to determine core weight (according to example 7), hot strength (according to example 8), one-hour strength (according to example 9) and moisture stability (according to example 10); the results of these determinations are reported in table 10.

TABLE-US-00018 TABLE 10 2019650-1 2019650-2 2019650-3 Core weight   148.22 151.30   143.45 Hot strength [N/cm.sup.2] 190 180 200 One-hour strength [N/cm.sup.2] 500 520 460 Moisture stability [min] >15840.sup.7   1363 >15840.sup.7   .sup.7The tests were stopped after 15 840 minutes.

[0520] Surprisingly, the results show that the use of at least one part of a particulate amorphous SiO.sub.2 in component A that was produced in Si production by the reduction of quartz in an arc furnace (“RW-Fuller gesiebt”), compared to the use of component A comprising, as particulate amorphous silicon dioxide, only such particulate amorphous SiO.sub.2 that has been produced in the production of ZrO.sub.2 by thermal decomposition of ZrSiO.sub.4 (“RW-Fuller Q1 Plus”), once again distinctly increases moisture stability above expectations.

EXAMPLE 17—STABILITY TESTS

[0521] 17.1 A total of 4 combinations of a first liquid component (B) with a second liquid component (C) comprising sodium aluminate were produced. The compositions are apparent from tables 11a and 11 b.

[0522] The respective (calculated) molar compositions are given in table 11c.

TABLE-US-00019 TABLE 11a Liquid Formulation component 2019327 2019321 Water (B) 13.10 12.70 NaOH 33% (B) 15.50 12.90 48/50 HV waterglass (B) 67.65 67.40 EHS surfactant (B) 0.50 0.50 Sodium aluminate solution 1:2.5 (C) 3.25 6.50 Total (B) + (C) 100.00 100.00

TABLE-US-00020 TABLE 11b Liquid Formulation component 2019328 2019329 Water (B) 12.20 11.80 NaOH 33% (B) 10.40 7.90 48/50 HV waterglass (B) 67.15 66.90 EHS surfactant (B) 0.50 0.50 Sodium aluminate solution 1:2.5 (C) 9.75 12.90 Total (B) + (C) 100.00 100.00

TABLE-US-00021 TABLE 11c Formulation 2019327 2019321 2019328 2019329 H.sub.2O [mol %] 85.81 85.71 85.60 85.50 SiO.sub.2 [mol %] 9.06 9.06 9.06 9.06 Na.sub.2O [mol %] 5.03 5.03 5.03 5.03 Al.sub.2O.sub.3 [mol %] 0.10 0.20 0.30 0.40 MR 1.80 1.80 1.80 1.80

[0523] 17.2 A total of 4 combinations of a first liquid component (B) with a second liquid component (C) comprising potassium aluminate were produced. The compositions are apparent from tables 11d and 11e.

[0524] The respective (calculated) molar compositions are given in table 11f.

TABLE-US-00022 TABLE 11d Liquid Formulation component 2019684 2019644 Water (B) 14.36 13.95 NaOH 33% (B) 5.56 5.56 KOH 45% (B) 10.21 7.70 48/50 HV waterglass (B) 66.62 66.35 EHS surfactant (B) 0.15 0.15 Potassium aluminate solution 1:2.5 (C) 3.10 6.20 Total (B) + (C) 100.00 100.00

TABLE-US-00023 TABLE 11e Liquid Formulation component 2019647 2019650 Water (B) 13.65 13.275 NaOH 33% (B) 5.55 5.575 KOH 45% (B) 5.10 2.600 48/50 HV waterglass (B) 66.15 65.900 EHS surfactant (B) 0.15 0.150 Potassium aluminate solution 1:2.5 (C) 9.40 12.500 Total (B) + (C) 100.00 100.00

TABLE-US-00024 TABLE 11f 2019684 2019644 2019647 2019650 H.sub.2O [mol %] 85.80 85.70 85.60 85.50 SiO.sub.2 [mol %] 9.06 9.06 9.06 9.06 Na.sub.2O [mol %] 3.79 3.79 3.79 3.79 K.sub.2O [mol %] 1.25 1.25 1.25 1.25 Al.sub.2O.sub.3 [mol %] 0.10 0.20 0.30 0.40 MR 1.80 1.80 1.80 1.80

[0525] The combination according to formulations 2019327, 2019321, 2019328, 2019329, 2019684, 2019644, 2019647 and 201950 (as defined in tables 11a, 11 b, 11 d and 11e) was in each case introduced into a vessel, which was stored closed at room temperature (20° C.).

[0526] During the storage, the stability of the stored solutions was checked by inspection. As soon as precipitates and/or gel formation were observable by the naked eye, the solution was considered to be no longer stable from that juncture.

[0527] It was found that none of the samples tested was stable for longer than 6 months, and at least samples 2019329, 2019644, 2019467 and 2019550 were stable for less than 2 months.

EXAMPLE 18—COMPARISON WITH THE USE OF A PARTICULATE ALUMINATE SOURCE

[0528] In this example, the particulate amorphous silicon dioxide species “RW-Fuller gesiebt” (with a median of the particle size distribution, rounded to the second post-decimal place, determined by means of laser scattering, of 0.23 micrometer) was first dry-mixed with an amount of the particulate amorphous silicon dioxide species “RW-Fuller Q1 Plus” (with a median of the particle size distribution, rounded to the second post-decimal place, determined by means of laser scattering, of 0.84 micrometer) in a weight ratio of 1:1 to give a preliminary mixture (as an example of a component (A)). In a contacting vessel, 100 PW of H32 quartz sand (from Quarzwerke GmbH, AFS grain fineness number 45) and 0.6 PW of this preliminary mixture were mixed manually, so as to result in 100.6 parts by weight of a mixture of quartz sand (as an example of a mold base material (D)) and particulate amorphous silicon dioxide (component (A)).

[0529] In respective subsequent experiments, 100.6 parts by weight of that mixture together with 2.1 parts by weight in each case of [0530] (i) an aluminate ion-free waterglass binder (2019683) (cf. CE 18.1 in table 13; this is a component (B)), [0531] (ii) a mixture of powdery AlOH.sub.3 (Apyral NH20) and a waterglass binder (20200138) in a mixing ratio of 0.05:2.05 (cf. CE 18.2 in table 13; mixing of these constituents results in a first liquid component (B) comprising waterglass, into which AlOH.sub.3 has been mixed) and [0532] (iii) a mixture of binder constituents 2019666 (this is a component (B)) and 2019665 (this is a component (C)) in a mixing ratio of 1.78:0.32 (cf. E 18.3 in table 13; inventive example)

[0533] were added to the mixture of quartz sand and particulate amorphous silicon dioxide; this was then followed straight away by mixing in each case at 220 rpm in a bull mixer (RN10/20 type, from Morek Multiserw) for 120 seconds.

[0534] The resultant molding material mixtures were each processed according to the procedure from the above example 6 to give test bars. For each of the mixtures described, a sufficient number of test bars were produced in order to determine core weight (according to example 7), hot strength (according to example 8), one-hour strength (according to example 9) and moisture stability (according to example 10); the results of these determinations are reported in table 14.

TABLE-US-00025 TABLE 13 CE 18.2 Used E 18.3 2.05 PW Used 2020138 + 1.78 PW CE 18.1 0.5 PW 2019666 + Used Part 1 Part 2 Apyral Part 1 Part 2 0.32 PW 2019683 Apyral NH 20 20200138 NH 20 2019666 2019665 2019665 Component (B) Apyral NH 20 20200138 (B) (B) (C) (B) + (C) Water 14.676 13.650 13.325 15.684 — NaOH 33% 5.590 5.713 5.577 6.263 — KOH 45% 12.780 12.900 12.593 — 2.00 48/50 waterglass 66.820 67.600 65.990 77.895 16.00 EHS 0.134 0.137 0.134 0.158 — Al(OH).sub.3 100 2.381 — 82.00 Total 100 100 100 100 100 100 H.sub.2O [mol %] 85.90 74.99 85.67 85.51 85.49 SiO.sub.2 [mol %] 9.06 0.00 9.20 9.06 9.07 Na.sub.2O [mol %] 3.79 0.00 3.85 3.79 3.80 K.sub.2O [mol %] 1.25 0.00 1.27 1.25 1.24 Al.sub.2O.sub.3 [mol %] 0.00 25.01 0.00 0.38 0.40 Total 100 100 100 100.000 100.000

[0535] CE in this table means “comparative example”; E denotes an inventive example.

TABLE-US-00026 TABLE 14 Core Hot One-hour Moisture weight strength strength stability Binder [g] [N/cm.sup.2] [N/cm.sup.2] [min] CE 18.1 146.90 150 480 300 CE 18.2 146.86 150 480 340 B18.3 146.58 160 470 >1440.sup.9   .sup.9Experiments stopped after 1440 min.

[0536] It is apparent from the results that the mixture comprising powdery Al(OH).sub.3 (CE 18.2), by comparison with a mixture entirely devoid of Al(OH).sub.3 (CE 18.1), does not bring about any significant improvement in moisture stability (cf. example 10), whereas the mixture comprising dissolved Al(OH).sub.3 (E 18.3) considerably increases moisture stability.

EXAMPLE 19—VARIATION OF ALUMINATE ADDITION

[0537] Molding material mixtures from formulations 19.1-19.3, as apparent from table 15 below with reference to table 16, were used to create molding material mixtures analogously to example 5. The liquid components were added in such a way that they came into direct contact with one another only when the bull mixer was switched on.

TABLE-US-00027 TABLE 15 Addition Addition Addition Addition Mixture (D) [PW] (B) [PW] (C) [PW] (A) [PW] 19.1 H32 100.00 20200253 1.58 20200252 0.52 2019409 0.60 19.2 H32 100.00 20200255 1.68 20200254 0.42 2019409 0.60 19.3 H32 100.00 20200257 1.68 20200256 0.42 2019409 0.60

TABLE-US-00028 TABLE 16 20200253 + 20200255 + 20200257 + 20200252 20200254 20200256 Name 20200252 20200253 as per 19.1 20200254 20200255 as per 19.2 2020056 20200257 as per 19.3 H.sub.2O [% by wt.] 67.09 59.17 61.13 63.41 60.18 60.82 59.69 60.27 60.15 SiO.sub.2 [% by wt.] 0.00 29.57 22.25 0.00 27.62 22.10 0.00 27.41 21.92 Na.sub.2O [% by wt.] 19.05 11.07 13.05 16.64 12.13 13.03 15.55 12.25 12.91 K.sub.2O [% by wt.] 7.26 0.11 1.88 9.45 0.00 1.89 9.26 0.00 1.85 Al.sub.2O.sub.3 [% by wt.] 6.60 0.00 1.63 10.50 0.00 2.10 15.50 0.00 3.10 Remainder [% by wt.] 0.00 0.07 0.05 0.00 0.07 0.06 0.00 0.07 0.06 Total 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 100.00 MV 1.61 1.60 1.60

[0538] For each of the formulations specified in table 15, a sufficient number of test bars were produced in order to determine core weight (according to example 7), hot strength (according to example 8), one-hour strength (according to example 9) and moisture stability (according to example 10); the results of this determination are reported in table 17.

TABLE-US-00029 TABLE 17 Core Hot One-hour Moisture weight strength strength stability Mixture [g] [N/cm.sup.2] [N/cm.sup.2] [min] 19.1 147.6 140 430 1230 19.2 147.5 130 410 1670 19.3 147.1 130 350 5760

[0539] For mixtures 19.1 and 19.2 with an aluminate ion content (calculated as Al.sub.2O.sub.3) of 1.63% by weight and 2.1% by weight respectively (percentages by weight here are always based on the sum total of components (B) and (C) used), comparatively similar values are attained in each case for hot strength, one-hour strength, core weight and moisture stability. In the case of an Al.sub.2O.sub.3 content of 3.1% by weight (mixture 19.3), a significant rise in moisture stability/storage stability can be observed.