INSULATING PRODUCT FOR THE REFRACTORY INDUSTRY, CORRESPONDING INSULATING MATERIALS AND PRODUCTS, AND USES

Abstract

An insulating product for the refractory industry or an insulating material as intermediate for production of such a product, and a corresponding insulating material/insulating product are provided. Likewise the use of a matrix encapsulation process in the production of an insulating product for the refractory industry and a corresponding insulating product and/or an insulating material as intermediate for production of such a product are provided.

Claims

1. An insulating product for the refractory industry or insulating material as intermediate for production of such a product, comprising a number of refractory composite particles, wherein these composite particles comprise particles of one or more refractory substances and nanoparticulate silicon dioxide that functions as binder or binder component for said particles of the refractory substances and wherein the composite particles present in the product or intermediate are characterized by (A) thermal stability at a temperature of 1600° C. or higher, determined by the sintering test, and/or (B) a thermal conductivity value at room temperature (20° C.) γR of ≤0.26 W/m*K.

2. The insulating product for the refractory industry or insulating material as intermediate for production of such a product as claimed in claim 1, wherein the product or intermediate is producible by a process, having the following steps: (a) producing composite particles having a grain size of less than 5 mm, determined by sieving, in a matrix encapsulation process having the following steps: (a1) producing droplets of a suspension composed of at least the following starting materials: as dispersed phases (i) one or more refractory substances selected from the group consisting of refractory solids and precursors of refractory solids, (ii) additionally one or more density-reducing substances selected from the group consisting of lightweight fillers having a respective bulk density in the range from 10 to 350 g/L and pyrolyzable fillers, and as continuous phase (iv) a solidifiable liquid, (a2) solidifying the solidifiable liquid, such that the droplets harden to give hardened droplets and the refractory substance(s) and the density-reducing substance(s) are encapsulated in the solidifying continuous phase, (a3) treating the hardened droplets so as to result in said composite particles, the treating comprising a thermal treatment, wherein step (a1), producing droplets of a suspension, further comprises as starting material as dispersed phase: (iii) colloidal silicon dioxide in addition to constituents (i) and (ii); and/or wherein the process comprises as an additional step: (b) mixing the composite particles produced in step (a3) with a binder comprising a binder component selected from the group consisting of alumina cements, calcium aluminate cements, monoaluminum phosphate or solution of monoaluminum phosphate, monomagnesium phosphate or solution of monomagnesium phosphate, phosphoric acid, inorganic phosphate, boron compounds, preferably boron oxide, magnesium sulfate or solution of magnesium sulfate, silica sol, sols of aluminum oxide, plastic clays, hydratable aluminum oxide binder, ethyl silicate and aluminum sulfate.

3. The insulating product for the refractory industry or insulating material as intermediate for production of such a product as claimed in claim 1, wherein the composite particles present in the product or intermediate are characterized by (B) a thermal conductivity value at room temperature (20° C.) γR of ≤0.07 W/m*K.

4. The insulating product for the refractory industry or insulating material as intermediate for production of such a product as claimed in claim 1, wherein the composite particles present in the product or intermediate are characterized by (C) a grain strength ≥1.5 N/mm.sup.2, determined to EN 13055-1, Annex A, Method 1, at a grain size in the range of 0.25-0.5 mm, and/or (D) a bulk density ≤750 g/L, and/or (E) a grain size of not more than 5 mm, determined by sieving, and/or (F) a water absorption capacity, determined via water absorption according to Enslin, of ≤4.5 mL/g.

5. The insulating product for the refractory industry or insulating material as intermediate for production of such a product as claimed in claim 4, wherein the composite particles present in the product or intermediate are characterized by (C) a grain strength ≥3.0 N/mm.sup.2, determined to EN 13055-1, Annex A, Method 1, at a grain size in the range of 0.25-0.5 mm, and/or (D) a bulk density ≤350 g/L, and/or (E) a grain size of not more than 1 mm, determined by sieving, and/or (F) a water absorption capacity, determined via water absorption according to Enslin, of ≤2.0 mL/g.

6. The insulating product for the refractory industry or insulating material as intermediate for production of such a product as claimed in claim 1, comprising the curing product of a binder component selected from the group consisting of: alumina cements, calcium aluminate cements, monoaluminum phosphate or solution of monoaluminum phosphate, monomagnesium phosphate or solution of monomagnesium phosphate, phosphoric acid, inorganic phosphate, boron compounds, magnesium sulfate or solution of magnesium sulfate, silica sol, sols of aluminum oxide, plastic clays, hydratable aluminum oxide binder, ethyl silicate and aluminum sulfate and/or additionally comprising one or more substances selected from the group consisting of: fireclay, lightweight fireclay, corundum, hollow spherical corundum, sintered corundum, fused corundum, sintered mullite, fused mullite, aluminum oxide (alumina), andalusite, kyanite, sillimanite, cordierite, clays, wollastonite, zirconium mullite, zirconium corundum, spheres of fly ash and vermiculite.

7. The insulating product for the refractory industry or the insulating material as intermediate for production of such a product as claimed in claim 1, wherein the insulating product or insulating material as intermediate is selected from the group consisting of shaped and unshaped refractory and highly refractory products.

8. The insulating product for the refractory industry or the insulating material as intermediate for production of such a product as claimed in claim 1, wherein the insulating product or insulating material as intermediate is selected from the group consisting of high-alumina bricks, fireclay bricks, refractory concretes, repair compounds, leveling compounds, mortars and adhesives, crucibles, ladle linings, casting launders, stopper compounds, immersion nozzles, slide gates, feed nozzles for metallurgy, pouring compounds, and furnace linings.

9. An insulating product for the refractory industry or insulating material as intermediate for production of such a product, comprising a number of refractory composite particles, where said refractory composite particles comprise particles of one or more refractory substances; and the curing product of a binder component selected from the group consisting of: alumina cements, calcium aluminate cements, monoaluminum phosphate or solution of monoaluminum phosphate, monomagnesium phosphate or solution of monomagnesium phosphate, phosphoric acid, inorganic phosphate, boron compounds, magnesium sulfate or solution of magnesium sulfate, silica sol, sols of aluminum oxide, plastic clays, hydratable aluminum oxide binder, ethyl silicate and aluminum sulfate, wherein the refractory composite particles present in the product or intermediate are characterized by (A) thermal stability at a temperature of 1600° C. or higher, determined by the sintering test, and/or (B) a thermal conductivity value at room temperature (20° C.) γR of ≤0.26 W/m*K.

10. The insulating product for the refractory industry or insulating material as intermediate for production of a product as claimed in claim 9, wherein the refractory composite particles present in the product or intermediate additionally comprise nanoparticulate silicon dioxide that functions as binder or binder component for said particles of the refractory substances.

11. The insulating product for the refractory industry or insulating material as intermediate for production of such a product as claimed in claim 9, wherein the composite particles present in the product or intermediate are characterized by (B) a thermal conductivity value at room temperature (20° C.) γR of ≤0.07 W/m*K.

12. The insulating product for the refractory industry or insulating material as intermediate for production of a product as claimed in claim 9, wherein the refractory composite particles present in the product or intermediate comprise: (C) a grain strength ≥1.5 N/mm.sup.2, determined to EN 13055-1, Annex A, Method 1, at a grain size in the range of 0.25-0.5 mm, and/or (D) a bulk density ≤750 g/L, and/or (E) a grain size of not more than 5.0 mm, determined by sieving, and/or (F) a water absorption capacity, determined via water absorption according to Enslin, of ≤4.5 mL/g.

13. The insulating product for the refractory industry or insulating material as intermediate for production of such a product as claimed in claim 12, wherein the composite particles present in the product or intermediate are characterized by (C) a grain strength ≥2.0 N/mm.sup.2, determined to EN 13055-1, Annex A, Method 1, at a grain size in the range of 0.25-0.5 mm, and/or (D) a bulk density ≤500 g/L, and/or (E) a grain size of not more than 2.0 mm, determined by sieving, and/or (F) a water absorption capacity, determined via water absorption according to Enslin, of ≤3.5 mL/g.

14. The insulating product for the refractory industry or insulating material as intermediate for production of such a product as claimed in claim 13, wherein the composite particles present in the product or intermediate are characterized by (C) a grain strength ≥3.0 N/mm.sup.2, determined to EN 13055-1, Annex A, Method 1, at a grain size in the range of 0.25-0.5 mm, and/or (D) a bulk density ≤350 g/L, and/or (E) a grain size of not more than 1.0 mm, determined by sieving, and/or (F) a water absorption capacity, determined via water absorption according to Enslin, of ≤2.0 mL/g.

15. The insulating product for the refractory industry or insulating material as intermediate for production of such a product as claimed in claim 9, additionally comprising one or more substances selected from the group consisting of fireclay, lightweight fireclay, corundum, hollow spherical corundum, sintered corundum, fused corundum, sintered mullite, fused mullite, aluminum oxide (alumina), andalusite, kyanite, sillimanite, cordierite, clays, wollastonite, zirconium mullite, zirconium corundum, spheres of fly ash and vermiculite.

16. The insulating product for the refractory industry or insulating material as intermediate for production of a product as claimed in claim 9, wherein the refractory composite particles present in the product or intermediate comprise one or more density-reducing substances selected from the group consisting of lightweight fillers having a respective bulk density in the range from 10 to 350 g/L and pyrolyzable fillers.

17. The insulating product for the refractory industry or insulating material as intermediate for production of a product as claimed in claim 16, wherein the pyrolyzable fillers include at least one filler selected from the group consisting of polymer beads and styrofoam beads.

18. The insulating product for the refractory industry or insulating material as intermediate for production of a product as claimed in claim 9, wherein the refractory substances include at least one substance selected from the group consisting of: oxides, nitrides and carbides, each comprising one or more elements from the group consisting of Si, Al, Zr, Ti, Mg and Ca, and mixed oxides, mixed carbides and mixed nitrides, each comprising one or more elements from the group consisting of Si, Al, Zr, Ti, Mg and Ca.

19. The insulating product for the refractory industry or insulating material as intermediate for production of a product as claimed in claim 9, wherein the refractory substances include at least one substance selected from the group consisting of: aluminum oxide, zirconium oxide, titanium dioxide, silicon dioxide, magnesium oxide, calcium oxide, calcium silicate, sheet silicates, aluminum silicates, magnesium aluminum silicate, silicon carbide, and boron nitride.

20. The insulating product for the refractory industry or insulating material as intermediate for production of a product as claimed in claim 9, wherein the product or intermediate is produced by a process comprising: (a) producing composite particles having a grain size of less than 5 mm, determined by sieving, in a matrix encapsulation process having the following steps: (a1) producing droplets of a suspension composed of at least the following starting materials: as dispersed phases (i) one or more refractory substances selected from the group consisting of refractory solids and precursors of refractory solids, (ii) additionally one or more density-reducing substances selected from the group consisting of lightweight fillers having a respective bulk density in the range from 10 to 350 g/L and pyrolyzable fillers, and as continuous phase (iv) a solidifiable liquid, (a2) solidifying the solidifiable liquid, such that the droplets harden to give hardened droplets and the refractory substance(s) and the density-reducing substance(s) are encapsulated in the solidifying continuous phase, (a3) treating the hardened droplets so as to result in said composite particles, the treating comprising a thermal treatment, (b) mixing the composite particles produced in step (a3) with a binder comprising a binder component selected from the group consisting of alumina cements, calcium aluminate cements, monoaluminum phosphate or solution of monoaluminum phosphate, monomagnesium phosphate or solution of monomagnesium phosphate, phosphoric acid, inorganic phosphate, boron compounds, magnesium sulfate or solution of magnesium sulfate, silica sol, sols of aluminum oxide, plastic clays, hydratable aluminum oxide binder, ethyl silicate and aluminum sulfate, and optionally, in step (b) or in a further step after step (a), mixing with one or more further substances to produce a curable refractory composition, and optionally curing the curable refractory composition.

Description

FIGURES

[0464] FIG. 1: FIG. 1 shows the residue in the crucible after the sintering test at 1600° C. on the B36 composite particles.

[0465] As can be seen in FIG. 1, a small proportion of the composite particles has sintered together, but at the same time there is still a considerable proportion in a pourable form.

[0466] FIG. 2:FIG. 2 shows the crucible residue after the sintering test at 1600° C. on the noninventive W250-6 composite particles.

[0467] As can be seen in FIG. 2, the crucible residue has sintered together, forming a coherent “crucible cake”.

[0468] FIG. 3: FIG. 3 shows an image of the crucible contents after the sintering test at 1600° C. on the noninventive KHP 108 composite particles.

[0469] As is clearly apparent, the contents of the crucible have fused to give a coherent mass.

[0470] FIG. 4: FIG. 4 shows a microscope image of the B36 composite particles after the sintering test at 1600° C.

[0471] As is very well apparent, the composite particles after the sintering test have still not formed any sinter necks.

[0472] FIG. 5: FIG. 5 shows a microscope image of the noninventive W250-6 composite particles after the sintering test at 1600° C.

[0473] It can be seen clearly that sinter necks have formed between the noninventive composite particles and the entirety of the noninventive composite particles has therefore combined to form a coherent “crucible cake”.

[0474] FIG. 6: FIG. 6 shows the residue in the crucible after the sintering test at 1700° C. on the B36 composite particles.

[0475] A small proportion of the composite particles has sintered together. However, a considerable proportion is still present in a pourable form.

[0476] FIG. 7: FIG. 7 shows the crucible residue after the sintering test at 1700° C. on the noninventive “Hargreaves” hollow spherical corundum composite particles.

[0477] It can be seen that the entirety of the noninventive composite particles has combined to form a coherent “crucible cake”.

[0478] FIG. 8: FIG. 8 shows the crucible residue after the sintering test at 1700° C. on the noninventive “KKW” hollow spherical corundum composite particles.

[0479] As is clearly apparent, the entirety of the noninventive composite particles has combined to form a coherent “crucible cake”.

[0480] FIG. 9: FIG. 9 shows a microscope image of the B36 composite particles after the sintering test at 1700° C.

[0481] As is very well apparent, the composite particles after the sintering test have still not formed any sinter necks.

[0482] FIG. 10: FIG. 10 shows a microscope image of the noninventive “Hargreaves” hollow spherical corundum composite particles after the sintering test at 1700° C.

[0483] The particles have melted superficially during the sintering test, as a result of which all noninventive composite particles have combined on solidification to form a coherent “crucible cake”.

[0484] FIG. 11: FIG. 11 shows an enlarged microscope image of FIG. 10 of the noninventive “KKW” hollow spherical corundum composite particles after the sintering test at 1700° C.

[0485] The particles have melted superficially during the sintering test, as a result of which all noninventive composite particles have combined on solidification to form a coherent “crucible cake”.

[0486] FIG. 12: In FIG. 12 is a scanning electron micrograph of the composite particles designated “B36” (see examples further down in the text).

[0487] FIG. 13: FIG. 13 shows an enlarged scanning electron micrograph of the composite particles designated “B36” (see examples further down in the text).

[0488] It can be seen very readily that the different refractory solids are individually surrounded by the continuous phase and hence are held together more securely, as a result of which the composite particles produced in accordance with the invention attain the desired dimensional stability and desired thermal stability.

[0489] FIG. 14: FIG. 14 shows a highly enlarged scanning electron micrograph of the “B36” composite particles.

[0490] FIG. 15: FIG. 15 shows the temperature in each case within the insulation materials of examples 4a (second intermediates of the invention, produced by the second process of the invention, lower temperature/time curve (gray)) and 4b (comparative example, upper temperature/time curve (black)), and of the crucibles produced from the respective second insulation materials, as a function of time after the casting operation.

[0491] It is readily apparent that a distinctly smaller (by about 30%) temperature rise is recorded in the insulation material 4a (see below for details), which indicates a distinctly lower thermal conductivity or better insulating effect compared to the noninventive comparative insulation material 4b (see below for details).

[0492] FIG. 16: FIG. 16 shows the residue in the crucible after the sintering test at 1600° C. on the C6 composite particles produced in accordance with the invention.

[0493] As can be seen in FIG. 16, only a small proportion of the composite particles has sintered together, but at the same time there is still a considerable proportion in a pourable form.

[0494] FIG. 17: FIG. 17 shows a microscope image of the C6 composite particles produced in accordance with the invention after the sintering test at 1600° C.

[0495] As is very well apparent, the composite particles produced in accordance with the invention after the sintering test have formed only a few sinter necks.

[0496] FIG. 18: FIG. 18 shows the crucible residue after the sintering test at 1700° C. on the “C6” composite particles produced in accordance with the invention.

[0497] As is readily apparent in FIG. 18, only a small proportion of the composite particles produced in accordance with the invention has sintered together. However, a considerable proportion is still present in a pourable form.

[0498] FIG. 19: FIG. 19 shows a microscope image of the C6 composite particles produced in accordance with the invention after the sintering test at 1700° C.

[0499] As is readily apparent in FIG. 19, the composite particles produced in accordance with the invention after the sintering test have formed only a few sinter necks.

[0500] The present invention is elucidated in detail hereinafter by examples:

EXAMPLES

[0501] Test Methods:

[0502] 1. Particle Size Determination:

[0503] The determination of the grain sizes of composite particles by sieving was effected in accordance with DIN 66165-2 (4.1987) using Method F specified therein (machine sieving with moving individual sieve or sieve set in gaseous static fluid). A vibratory sieving machine of the RETSCH AS 200 control type was used; the amplitude was set here to level 2; there was no interval sieving; the sieving time was 1 minute.

[0504] The determination of the grain sizes of lightweight fillers used in step (a) as density-reducing substance of component (ii) was likewise effected in accordance with DIN 66165-2 (4.1987) using Method F specified therein (machine sieving with moving individual sieve or sieve set in gaseous static fluid). A vibratory sieving machine of the RETSCH AS 200 control type was likewise used; the amplitude was set here to level 2; there was no interval sieving; the sieving time was 1 minute.

[0505] The determination of the grain sizes of refractory solids having a grain size of less than 0.1 mm was effected by sieving to DIN 66165-2 (4.1987) using Method D specified therein (machine sieving with a static individual sieve in gaseous moving fluid, with air jet sieve).

[0506] 2. Determination of Bulk Density:

[0507] Bulk density was determined to DIN EN ISO 60 2000-1.

[0508] 3. Determination of Water Absorption Capacity:

[0509] The determination of water absorption was conducted with the aid of an Enslin instrument. The evaluation is to DIN 18132:2012-04.

[0510] 4. Determination of Chemical Composition and Morphology:

[0511] The morphology of the samples was conducted with the aid of a JSM 6510 SEM from Jeol.

[0512] The chemical composition was conducted with the aid of an EDX analysis using an Oxford INCA EDX.

[0513] In addition, the morphology was determined using a VisiScope ZTL 350 light microscope with a Visicam 3.0 camera.

[0514] 5. Method of Determining Thermal Stability (Sintering Test):

[0515] The sintering test in the present invention for determining the thermal stability of various raw materials was conducted in accordance with the VDG [Society of German Foundry Experts] guideline sheet P26 “Prüfung von Formgrundstoffen” [Testing of mold raw materials]. An amount of particles of identical composition that was to be tested was subjected to a defined thermal treatment (for example 1600° C. or 1700° C. for a half hour in each case) in a Carbolite HTF 1800 furnace with an E 3216 type temperature regulator and then assessed by sieving by means of a defined mechanical stress.

[0516] Firstly, sieving of the amount of particles to be examined with a sieve of mesh size 0.5 mm (see table 2 below) or of 0.71 mm (see table 3 below) was conducted in order to ensure reproducibility and comparability of the different experiments.

[0517] Subsequently, the sieved particles were subjected to a defined thermal treatment with the following steps in an aluminum oxide crucible:

[0518] “pre-sintering” of the samples, at 900° C. in a preheated furnace for 30 min, in order to assure identical thermal stress on the comparative samples to the composite particles of the invention, heat treatment of the samples with a defined furnace cycle (Carbolite HTF 1800 furnace with E3216 type temperature regulator): from 25° C. to 200° C. at 1 K/min, then up to the final temperature (1600° C. over a half hour (see table 2 below) or 1700° C. over a half-hour (see table 3 below)) at 3 K/min and subsequent cooling to room temperature at 3 K/min.

[0519] Thereafter, the cooled particles were photographed with the aluminum oxide crucible (see FIG. 3 (particles melted), FIG. 6 and FIG. 7) or without the aluminum oxide crucible (see FIG. 1, FIG. 2 and FIG. 8) and, if the particles examined had not melted during the defined thermal treatment, the aluminum oxide crucible in which the particles examined were subjected to heat treatment was clamped in a sieving tower and was put under mechanical stress at an amplitude of 2 without interval sieving, i.e. sustained sieving, by defined sieving with a control sieve on a Retsch AS 200 for 1 minute in each case. The mesh size of the control sieve was adjusted to the maximum grain size to be expected in the particles examined (either 0.5 mm (see table 2 below) or 0.71 mm (see table 3 below)). The criterion employed is the ratio of sieve residue to sieve passage (cf. VDG guideline sheet P26 “Prüfung von Formgrundstoffen”, October 1999). In the case of a factor of sieve residue/sieve passage of greater than 1, the sample is considered to be sintered and therefore to be thermally unstable.

[0520] Sample-specific parameters, for example the grain size of the respective sample, were taken into account in the evaluation.

[0521] 6. Method of Determining Grain Strength

[0522] The grain strength of the samples was determined to DIN EN 13055-1:2008-08, Annex A (Method 1, agitating for 2*30 s with amplitude 0.5), at a grain size in the range of 0.25-0.5 mm.

Example 1

[0523] By step (a) of the first process of the invention, composite particles (C6) were produced with a grain size of less than 5 mm (also referred to hereinafter as “composite particles produced in accordance with the invention”), as described hereinbelow. The composition of the suspension used for the purpose is reported below in table 1.

[0524] Likewise produced by step (a) of the second process of the invention were composite particles (B36, B361) with a grain size of less than 5 mm, as described hereinbelow. Unless stated otherwise, the composite particles B36 and B361 were produced analogously to the composite particles C6.

[0525] (a1) Producing Droplets of a Suspension of Starting Materials:

[0526] A 1% aqueous sodium alginate solution was produced (1% by weight of sodium alginate from Alpichem with CAS No. 9005-38-3, based on the total mass of the aqueous solution).

[0527] The Sokalan® FTCP 5 dispersant from BASF was diluted with water to prepare a corresponding dispersion solution; the mass ratio of Sokalan® FTCP 5 to water was 1:2.

[0528] The 1% aqueous sodium alginate solution prepared and the dispersion solution prepared were subsequently mixed in a mixing ratio according to table 1, so as to give a solidifiable liquid (solidifiable liquid for use as continuous phase in the sense of constituent (iv) in step (a1) of the first process of the invention or in the sense of constituent (iv) in step (a1) of the second process of the invention.

[0529] While stirring, precursors of refractory solids and refractory solids selected in accordance with table 1 below (constituent (i) in step (a1)) were added to the solidifiable liquid, as was any colloidal silicon dioxide as a further constituent (constituent (iii) in step (a1), only for composite particles C6), until a creamy suspension was formed.

[0530] While stirring, thereafter, borosilicate beads were added to the creamy suspension in an amount corresponding to table 1 below as an example of a lightweight filler (constituent (ii) in step (a1)), followed by an amount of water according to table 1. The result is a diluted suspension.

TABLE-US-00001 TABLE 1 Ingredients for inventive production of composite particles (C6) and composite particles by the second process of the invention (B36, B361) Composition of the Starting Ingredients suspension material Constituent Manufacturer (parts by weight) Precursor of (i) Kaolin TEC Amberger Kaolin- 11.00 11.00 — refractory werke substances (i) Kärlicher Kärlicher Ton 5.00 5.00 — [% by wt.] Blauton -und Schamotte- werke Mannheim & Co.KG (i) Kaolin BASF — — 20.00 (Satintone  ®W (Whitetex)) Refractory (i) Nabalox ® Nabaltec AG 10.85 10.85 19.85 material NO315 [% by wt.] Lightweight (ii) Borosilicate 3M Deutschland 3.15 3.15 3.15 fillers glass beads GmbH [% by wt.] (product name: 3M Glass Bubbles K1) Bulk density of 60 g/L Colloidal (iii) Ludox ® TMA W. R. — — 12.00 SiO.sub.2 34% by wt. Grace & Co. in water CAS RN 55965-84-9 1% sodium (iv) Sodium Applichem 65.0 68.0 55.0 alginate alginate; solution CAS: [% by wt.] 9005-38-3 Dispersion (iv) Sokalan ® BASF 5.00 2.00 2.00 solution FT CP5 in [% by wt.] water (1.2) Water 20.00 30.00 10.00 [% by wt.] Resulting composite particles B36 B361 C6 Bulk density immediately before treatment in muffle 350 350 410 furnace [g/L] Bulk density after treatment in muffle furnace [g/L] 340 340 390 Water absorption after treatment in muffle furnace — 2.5 1.7 [mL/g] Grain strength after treatment in muffle furnace — 2.1 3.2 (grain size in the range from 0.25 to 0.5 mm) [N/mm.sup.2]

[0531] (a2) Solidifying the Solidifiable Liquid

[0532] The diluted suspension was introduced into plastic syringes and clamped into an LA-30 syringe pump. The feed rate was 12 to 15 mL/min. The diluted suspension in the syringes was then forced through a vibration nozzle, such that the diluted suspension dripped out of the vibration nozzle in uniform droplets. The droplets that dripped out of the vibration nozzle fell into an about 2% aqueous calcium chloride solution (CaCl.sub.2, product name “Calcium Chloride 2-hydrate powder for analysis ACS” from Applichem, CAS No. 10035-04-8, 2% by weight based on the total mass of the calcium chloride solution) and solidified, such that they hardened to give hardened droplets and the refractory substances and the borosilicate glass beads were encapsulated in the solidifying mixture (consisting of the 1% sodium alginate solution and the dispersion solution).

[0533] Note: The size of the hardened droplets was dependent on the composition of the diluted suspension, the delivery rate of the pump and the vibration frequency of the nozzle.

[0534] (a3) Treating the Hardened Droplets

[0535] Subsequently, the hardened droplets were skimmed off and washed in water.

[0536] Thereafter, the washed and hardened droplets were dried in a drying cabinet at 180° C. for 40 min. After the drying, the hardened droplets were free-flowing, and the bulk density thereof “immediately prior to treatment in muffle furnace” is reported in table 1.

[0537] Thereafter, the free-flowing hardened droplets were heated in a preheated muffle furnace at 950° C. for 30 minutes. After cooling, the result was composite particles produced in accordance with the invention that constitute excellent insulation materials for the refractory industry, preferably insulation materials as intermediates for production of insulating products for the refractory industry.

[0538] As can be inferred from the third-from-last line of table 1, the measured bulk densities of the composite particles of the invention produced are below 400 g/L. By a suitable choice of the refractory materials or precursors for refractory materials and the lightweight fillers, it is possible if necessary to further reduce the bulk density of the resulting composite particles produced in accordance with the invention.

[0539] As can be inferred from the last line of table 1, the “C6” composite particles produced by the process of the invention have a surprisingly high grain strength. It is assumed that this advantageous high strength is a result of the interaction of the factors of (j-1) thermal treatment at a temperature in the range from 900 to 980° C. in step (a3), (j-2) hardening of the solidifiable liquid, preferably of the alginate, in step (a2), and (j-3) the effect of the colloidal silicon dioxide in step (a1) as a binder. The energy expenditure for achieving a desired high grain strength can therefore be reduced in the thermal treatment in step (a3) of the process of the invention compared to other similar (known) processes.

Example 2: Sintering Tests

[0540] Sintering test at 1600° C. to compare the thermal stability of composite particles produced in accordance with the invention and not produced in accordance with the invention

[0541] In the sintering test described further up, “C6” composite particles produced by the first production process of the invention and “B36” composite particles produced by the second production process of the invention (step (a)) were tested by comparison with “KHP 108” composite particles not produced in accordance with the invention (core-shell particles from Chemex) and “W 205-6” particles not produced in accordance with the invention (“Weisse Spheres W250-6” product from Omega Minerals). The particles produced in accordance with the invention and the particles not produced in accordance with the invention had a grain size in the range from 0.25 to 0.5 mm. The sintering temperature was 1600° C. The control sieve for ascertaining the sieve residue and the sieve passage had a mesh size of 0.5 mm.

[0542] The results of the sintering test at 1600° C. are shown in table 2.

TABLE-US-00002 TABLE 2 Results of the sintering test at 1600° C. (pre-sintering of the samples, 30 min at 900° C. in the preheated furnace, then sintering temperature of 1600° C. for 30) “C6” composite particles Non- Non- produced inventive inventive “B36” in accordance “W250-6” “KHP 108” composite with the composite composite particles invention particles particles Grain size 0.25-0.5 0.25-0.5 0.25-0.5 0.25-0.5 [mm] Bulk density 340 390 390 540 [g/L] Result of Sieve residue/ Sieve residue/ Sieve residue/ completely sieving with sieve sieve sieve melted, no 0.5 mm passage = 0.4 passage = 0.7 passage = 28.4 sieving control sieve possible Macroscopic see FIG. 1 see FIG. 16 see FIG. 2 see FIG. 3 absorption after sintering Microscopic see FIG. 4 see FIG. 17 see FIG. 5 — absorption after sintering Result not sintered not sintered sintered melted

[0543] As can be inferred from table 2, the ratio of sieve residue to sieve passage for the “B36” and “C6” composite particles after the sintering is below 1, whereas this ratio for the composite particles not produced in accordance with the invention after the sintering is above 1. Thus, the thermal stability of the “B36” and “C6” composite particles at 1600° C. is better than that of the noninventive composite particles.

[0544] Sintering test at 1700° C. on composite particles produced in accordance with the invention and composite particles not produced in accordance with the invention

[0545] By the sintering test described further up, “C6” composite particles produced by the first production process of the invention and “B36” composite particles produced by the second process of the invention (step (a)) were tested by comparison with “Hargreaves” composite particles not produced in accordance with the invention (hollow spherical corundum with >98.8% Al.sub.2O.sub.3 from “Hargreaves raw material services GmbH”) and “KKW” composite particles not produced in accordance with the invention (hollow spherical corundum with >98.8% Al.sub.2O.sub.3 from “Imerys Fused Minerals Zschornewitz GmbH”). The grain sizes of the composite particles were always within the defined range from 0.18 to 0.71 mm. The sintering temperature was 1700° C. The control sieve for determining the sieve residue and the sieve passage had a mesh size of 0.71 mm.

[0546] The results of the sintering test at 1700° C. are shown in table 3:

TABLE-US-00003 TABLE 3 Results of the sintering test at 1700° C. (pre-sintering of the samples, 30 min at 900° C. in the preheated furnace, then sintering temperature of 1700° C. for 30 min) Composite Composite Composite particles particles not particles not produced in produced in produced in accordance accordance accordance with the Composite with the with the invention particles invention invention Designation “C6” “B36” “Hargreaves” “KKW” of the particles tested Grain size [mm] 0.18-0.71 0.18-0.71 0.18-0.71 0.18-0.71 Bulk density [g/L] 340 340 980 770 Result of sieving Sieve Sieve Sieve Sieve with 0.71 mm residue/ residue/ residue/ residue/ control sieve sieve sieve sieve sieve passage = passage = passage > passage > 0.9 0.7 1* 1* Macroscopic see FIG. 18 see FIG. 6 see FIG. 7 see FIG. 8 absorption after sintering Microscopic see FIG. 19 see FIG. 9 see FIG. 10 see FIG. 11 absorption after sintering Result not sintered not sintered sintered sintered * no breakup of the sinter cake by sieving possible

[0547] As can be inferred from table 3, the ratio of sieve residue to sieve passage for the “C6” and “B36” composite particles produced in accordance with the invention after the sintering is less than 1, whereas this ratio for the composite particles not produced in accordance with the invention after the sintering is greater than 1. Thus, the thermal stability of the “C6” composite particles produced in accordance with the invention and of the “B36” composite particles at 1700° C. is better than that of the composite particles not produced in accordance with the invention.

Example 3: “Surface Sealing”

[0548] The B36 composite particles (cf. table 1), after they had been heated at 900° C. for 30 minutes in a preheated oven, were surface sealed as follows.

[0549] The surface sealing was effected with an aqueous egg white solution that contained 6% by weight of high-gel egg white powder (product number 150063) from NOVENTUM Foods, based on the total weight of the resultant aqueous solution.

[0550] Subsequently, the B36 composite particles were mixed with the egg white solution produced in a weight ratio of composite particles to egg white solution of 2:1 and stirred in the resultant mixture until the egg white solution was completely absorbed. Subsequently, the composite particles treated with the egg white solution were dried in a drying cabinet at 110° C. for 40 minutes. The resultant composite particles are referred to as B36-egg white.

[0551] The finding of the water absorption capacity of B36 (without egg white coating) and B36-egg white (with egg white coating) composite particles with an Enslin instrument showed that the water absorption of the composite particles is reduced by an egg white coating from 1.6 mL/g (B36) to 0.1 mL/g (B36-egg white).

Example 4: Comparison of the Insulating Effect of Insulating Materials

[0552] For production of an insulating material as intermediate for production of an insulating product for the refractory industry, “B36” composite particles (production by the second process of the invention, steps (a1) to (a3), see example 1 and tables 1 and 2) were mixed with the further constituents specified below in table 4 (production by the second process of the invention, step (b), see below for details). The result was a second insulating material of the invention for the refractory industry (example 4a).

[0553] For comparison, a noninventive refractory insulation material was produced analogously to the above-detailed example 4a, except that there were no “B36” composite particles present and, instead, the proportion of lightweight fireclay (“fine grains”) was increased by the corresponding proportion by mass (see table 4, for details see below). The result was a noninventive conventional insulating material for the refractory industry (example 4b).

TABLE-US-00004 TABLE 4 Production of refractory insulation materials with and without composite particles B36 Example Example 4b 4a (comparison) Starting Starting Component Constituent weight [g] weight [g] Refractory material ISOSAT ®150 1000 1000 Refractory component B36 composite 174 — particles Refractory component Lightweight fire-clay 217 391 of grain size of 0.1-4 mm Refractory component Aluminum oxide, 261 261 calcined Refractory component Kyanite 87 87 Binder component Calcium aluminate 130 130 Water 130 130 ISOSAT ® 150 is a commercial refractory material having a content of about 57% by weight of Al.sub.2O.sub.3 and TiO.sub.2 and a content of about 2% by weight of Fe.sub.2O.sub.3.

[0554] The constituents for production of the insulation materials according to examples 4a (second process of the invention) and 4b (comparative example) were mixed with a Hobart mixer, by premixing all the dry constituents and then adding the water.

[0555] The two resultant insulation materials were each cast in the form of a crucible (the crucible with the insulation material 4a is a second insulating product of the invention) and dried at room temperature for 24 h. This was followed in each case by thermal treatment at 900° C. for 10 h (temperature regime: 80 K/h). After drying and thermal treatment, thermocouples (type K) for temperature measurement were each inserted into the two crucibles at identical positions within the insulation materials. Then the two crucibles were cast with iron (gray iron) at a temperature of 1500° C., with measurement and recording of the resultant temperature rise in the insulation material. The data were recorded with a PCE-T 390 digital thermometer (from PCE Deutschland GmbH).

[0556] The result of the temperature measurement is shown in the form of a graph in FIG. 15:

[0557] FIG. 15 shows the temperature in each case within the insulation materials of examples 4a (relating to a second insulation material of the invention, lower temperature/time curve (gray)) and 4b (comparative example, upper temperature/time curve (black)), and of the crucibles produced from the respective insulation materials, as a function of time after the casting operation (“heat transfer curves” of the insulation materials).

[0558] In the second insulation material 4a of the invention, a distinctly smaller (by about 30%) temperature rise than in the insulation material of comparative example 4b was recorded, which indicates a distinctly lower thermal conductivity or a higher insulating effect of the insulation material 4a compared to the noninventive comparative insulation material.

[0559] Such a distinctly improved insulation effect in a product for the refractory industry means a distinct saving of energy and costs on the industrial scale.

[0560] The (first) invention (first processes and products of the invention) is summarized in aspects 1 to 18 specified below.

[0561] 1. A process for producing an insulating product for the refractory industry or an insulating material as intermediate for producing such a product, having the following steps:

[0562] (a) producing composite particles having a grain size of less than 5 mm, determined by sieving, in a matrix encapsulation process having the following steps:

[0563] (a1) producing droplets of a suspension composed of at least the following starting materials: [0564] as dispersed phases [0565] (i) one or more refractory substances selected from the group consisting of refractory solids and precursors of refractory solids, [0566] (ii) additionally one or more density-reducing substances selected from the group consisting of lightweight fillers having a respective bulk density in the range from 10 to 350 g/L and pyrolyzable fillers, [0567] (iii) colloidal silicon dioxide in addition to constituents (i) and (ii); [0568] and as continuous phase [0569] (iv) a solidifiable liquid, [0570] (a2) solidifying the solidifiable liquid, such that the droplets harden to give hardened droplets and the refractory substance(s) and the density-reducing substance(s) are encapsulated in the solidifying continuous phase, [0571] (a3) treating the hardened droplets so as to result in said composite particles, the treating comprising a thermal treatment.

[0572] 2. The process according to aspect 1, wherein [0573] in step (a1) droplets are provided by means of one or more nozzles, preferably vibration nozzles, and/or [0574] in step (a2) the solidifying of the solidifiable liquid is induced by cooling, drying or chemical reaction.

[0575] 3. The process according to either of the preceding aspects, wherein the solidifiable liquid used in step (a1) is a liquid solidifiable by chemical reaction and the solidifying of the solidifiable liquid in step (a2) is induced by chemical reaction.

[0576] 4. The process according to any of the preceding aspects, wherein the solidifiable liquid is a liquid solidifiable by cation exchange reaction, preferably a liquid solidifiable by reaction with calcium ions and/or barium ions and/or manganese ions, preferably by reaction with calcium ions.

[0577] 5. The process according to any of the preceding aspects, wherein the solidifiable liquid is a liquid solidifiable by reaction with calcium ions, comprising one or more binders selected from the group consisting of alginate, PVA, chitosan and sulfoxyethyl cellulose, and/or an aqueous solution, wherein the solidifiable liquid is preferably an aqueous alginate solution.

[0578] 6. The process according to any of the preceding aspects, wherein the or at least one of the lightweight fillers used in step (a) as density-reducing substance of component (ii), preferably having a grain size of less than 0.8 mm, more preferably less than 0.5 mm, most preferably less than 0.3 mm, determined by sieving, is selected from the group consisting of: [0579] inorganic hollow beads, organic hollow beads, particles of porous and/or foamed material, [0580] rice husk ash, core-shell particles and calcined kieselguhr and/or [0581] wherein the or at least one of the pyrolyzable fillers used in step (a) as component (ii) is selected from the group consisting of: [0582] polymer beads and [0583] styrofoam beads.

[0584] 7. The process according to any of the preceding aspects, wherein the or at least one of the refractory solids used in step (a1) as refractory substance of component (i) is selected from the group consisting of: [0585] oxides, nitrides and carbides, each comprising one or more elements from the group consisting of Si, Al, Zr, Ti, Mg and Ca, and [0586] mixed oxides, mixed carbides and mixed nitrides, each comprising one or more elements from the group consisting of Si, Al, Zr, Ti, Mg and Ca,

[0587] wherein the or at least one of the refractory solids used in step (a1) as refractory substance of component (i) is preferably selected from the group consisting of: [0588] aluminum oxide, [0589] zirconium oxide, [0590] titanium dioxide, [0591] silicon dioxide, [0592] magnesium oxide, [0593] calcium oxide, [0594] calcium silicate, [0595] sheet silicates, preferably mica, [0596] aluminum silicates, [0597] magnesium aluminum silicate, preferably cordierite, [0598] silicon carbide, and [0599] boron nitride and/or

[0600] the precursor or at least one of the precursors of refractory solids used in step (a1) as refractory substance of component (i) is selected from the group consisting of [0601] aluminum hydroxide, [0602] magnesium hydroxide, [0603] sheet silicates, preferably kaolinite, montmorillonite and illite, [0604] clays, preferably kaolin and bentonite, [0605] phosphates and [0606] carbonates.

[0607] 8. The process according to any of the preceding aspects, wherein

[0608] the treating in step (a3) is conducted in such a way that the bulk density of the resulting composite particles is lower than the bulk density of the hardened droplets in the dried state and/or

[0609] said composite particles have a bulk density <750 g/L, preferably <500 g/L, more preferably <350 g/L.

[0610] 9. The process according to any of the preceding aspects, wherein at least some of the resultant composite particles in step (a3) and/or the composite particles used in step (b) have a grain size of less than 5.0 mm, preferably of less than 2.0 mm, determined by sieving.

[0611] 10. The process according to any of the preceding aspects, wherein component (i) comprises, as refractory substances, one or more precursors of refractory solids and the treating in step (a3) comprises a thermal treatment in which the precursors are converted to a refractory solid,

[0612] preferably wherein the precursor or at least one of the precursors of refractory solids is a clay and the treating in step (a3) comprises a thermal treatment at a temperature in the range from 900 to 980° C., such that the clay is converted to a refractory solid, wherein the clay preferably contains kaolinite and/or illite.

[0613] 11. The process according to any of the preceding aspects, preferably according to aspect 10, wherein the hardened droplets are treated in step (a3), so as to result in solid particles as intermediate, and wherein the surface of these solid particles is subsequently sealed, preferably by means of an organic coating composition or a silicon-containing binder, so as to result in said composite particles.

[0614] 12. The process according to any of the preceding aspects, comprising, as an additional step,

[0615] (b) mixing the composite particles produced in step (a) with a binder comprising a binder component selected from the group consisting of [0616] alumina cements, [0617] calcium aluminate cements, [0618] monoaluminum phosphate or solution of monoaluminum phosphate, [0619] monomagnesium phosphate or solution of monomagnesium phosphate, [0620] phosphoric acid, [0621] inorganic phosphate, [0622] boron compounds, preferably boron oxide, [0623] magnesium sulfate or solution of magnesium sulfate, [0624] silica sol, [0625] sols of aluminum oxide, [0626] plastic clays, [0627] hydratable aluminum oxide binder, [0628] ethyl silicate, [0629] aluminum sulfate, preferably

[0630] (b) mixing the composite particles produced in step (a) with a binder comprising a binder component selected from the group consisting of [0631] alumina cements, [0632] calcium aluminate cements, [0633] monoaluminum phosphate or solution of monoaluminum phosphate, [0634] monomagnesium phosphate or solution of monomagnesium phosphate, [0635] phosphoric acid, [0636] inorganic phosphate, [0637] boron compounds, preferably boron oxide, [0638] magnesium sulfate or solution of magnesium sulfate, [0639] silica sol, [0640] sols of aluminum oxide,

[0641] and optionally, in step (b) or in a further step after step (a), mixing with one or more further substances to produce a curable refractory composition,

[0642] and optionally curing the curable refractory composition.

[0643] 13. The process according to any of the preceding aspects, wherein the resultant composite particles in step (a3) are characterized by

[0644] (A) thermal stability at a temperature of 1600° C. or higher, determined by the sintering test, and/or

[0645] (B) a thermal conductivity value at room temperature (20° C.) γR of ≤0.26 W/m*K, preferably ≤0.10 W/m*K, more preferably ≤0.07 W/m*K, and/or

[0646] (C) a grain strength ≥1.5 N/mm.sup.2, preferably ≥2.0 N/mm.sup.2, more preferably ≥3.0 N/mm.sup.2, determined to EN 13055-1, Annex A, Method 1, at a grain size in the range of 0.25-0.5 mm, and/or

[0647] (D) a bulk density ≤750 g/L, preferably ≤500 g/L, more preferably ≤350 g/L, and/or

[0648] (E) a grain size of not more than 5 mm, preferably not more than 2 mm, more preferably not more than 1 mm, determined by sieving,

[0649] (F) a water absorption capacity, determined via water absorption according to Enslin, of ≤4.5, preferably ≤3.5 and more preferably ≤2.0 mL/g.

[0650] 14. The use of a matrix encapsulation methods, preferably using a nozzle, more preferably using a vibrating nozzle, for production of composite particles having a bulk density of <750 g/L, preferably <500 g/L, more preferably <350 g/L, in the production of an insulating product for the refractory industry that comprises a multitude of composite particles bonded to one another by a phase that acts as a binder.

[0651] 15. An insulating product for the refractory industry or insulating material as intermediate for production of such a product, comprising a number of refractory composite particles, wherein these composite particles comprise [0652] particles of one or more refractory substances and [0653] nanoparticulate silicon dioxide that functions as binder or binder component for said particles of the refractory substances and

[0654] wherein the product or intermediate is producible by a process according to any of aspects 1 to 13 and/or

[0655] wherein the composite particles present in the product or intermediate are characterized by [0656] (A) thermal stability at a temperature of 1600° C. or higher, determined by the sintering test, and/or [0657] (B) a thermal conductivity value at room temperature (20° C.) γR of ≤0.26 W/m*K, preferably ≤0.10 W/m*K, more preferably ≤0.07 W/m*K.

[0658] 16. The insulating product for the refractory industry or insulating material as intermediate for production of such a product according to aspect 15, wherein the composite particles present in the product or intermediate are characterized by

[0659] (C) a grain strength ≥1.5 N/mm.sup.2, preferably ≥2.0 N/mm.sup.2, more preferably ≥3.0 N/mm.sup.2, determined to EN 13055-1, Annex A, Method 1, at a grain size in the range of 0.25-0.5 mm, and/or

[0660] (D) a bulk density <750 g/L, preferably <500 g/L, more preferably <350 g/L, and/or

[0661] (E) a grain size of not more than 5.0 mm, preferably not more than 2.0 mm, more preferably not more than 1.0 mm, determined by sieving, and/or

[0662] (F) a water absorption capacity, determined via water absorption according to Enslin, of ≤4.5, preferably ≤3.5 and more preferably ≤2.0 mL/g.

[0663] 17. The insulating product for the refractory industry or insulating material as intermediate for production of such a product according to aspect 15 or 16, comprising the curing product of a binder component selected from the group consisting of: [0664] alumina cements, [0665] calcium aluminate cements, [0666] monoaluminum phosphate or solution of monoaluminum phosphate, [0667] monomagnesium phosphate or solution of monomagnesium phosphate, [0668] phosphoric acid, [0669] inorganic phosphate, [0670] boron compounds, preferably boron oxide, [0671] magnesium sulfate or solution of magnesium sulfate, [0672] silica sol, [0673] sols of aluminum oxide, [0674] plastic clays, [0675] hydratable aluminum oxide binder, [0676] ethyl silicate and [0677] aluminum sulfate.

[0678] 18. The insulating product for the refractory industry or insulating material as intermediate for production of such a product according to any of aspects 15 to 17, additionally comprising one or more substances selected from the group consisting of:

[0679] fireclay, lightweight fireclay, corundum, hollow spherical corundum, sintered corundum, fused corundum, sintered mullite, fused mullite, aluminum oxide (alumina), andalusite, kyanite, sillimanite, cordierite, clays, wollastonite, zirconium mullite, zirconium corundum, spheres of fly ash and vermiculite.

[0680] Second process and products of the invention (insulating product for the refractory industry or insulating material as intermediate for production of such a product) are summarized in aspects A1 to A17 specified below:

[0681] A1. A process for producing an insulating product for the refractory industry or an insulating material as intermediate for producing such a product, having the following steps:

[0682] (a) producing composite particles having a grain size of less than 5 mm, determined by sieving, in a matrix encapsulation process having the following steps: [0683] (a1) producing droplets of a suspension composed of at least the following starting materials: [0684] as dispersed phases [0685] (i) one or more refractory substances selected from the group consisting of refractory solids and precursors of refractory solids, [0686] (ii) additionally one or more density-reducing substances selected from the group consisting of lightweight fillers having a respective bulk density in the range from 10 to 350 g/L and pyrolyzable fillers, and as continuous phase [0687] (iv) a solidifiable liquid, [0688] (a2) solidifying the solidifiable liquid, such that the droplets harden to give hardened droplets and the refractory substance(s) and the density-reducing substance(s) are encapsulated in the solidifying continuous phase, [0689] (a3) treating the hardened droplets so as to result in said composite particles, the treating comprising a thermal treatment,

[0690] (b) mixing the composite particles produced in step (a3) with a binder comprising a binder component selected from the group consisting of [0691] alumina cements, [0692] calcium aluminate cements, [0693] monoaluminum phosphate or solution of monoaluminum phosphate, [0694] monomagnesium phosphate or solution of monomagnesium phosphate, [0695] phosphoric acid, [0696] inorganic phosphate, [0697] boron compounds, preferably boron oxide, [0698] magnesium sulfate or solution of magnesium sulfate, [0699] silica sol, [0700] sols of aluminum oxide, [0701] plastic clays, [0702] hydratable aluminum oxide binder, [0703] ethyl silicate and [0704] aluminum sulfate,

[0705] and optionally, in step (b) or in a further step after step (a), mixing with one or more further substances to produce a curable refractory composition,

[0706] and optionally curing the curable refractory composition.

[0707] A2. The process according to aspect A1, wherein [0708] in step (a1) droplets are provided by means of one or more nozzles, preferably vibration nozzles, and/or [0709] in step (a2) the solidifying of the solidifiable liquid is induced by cooling, drying or chemical reaction.

[0710] A3. The process according to either of the preceding aspects, wherein the solidifiable liquid used in step (a1) is a liquid solidifiable by chemical reaction and the solidifying of the solidifiable liquid in step (a2) is induced by chemical reaction.

[0711] A4. The process according to any of the preceding aspects, wherein the solidifiable liquid is a liquid solidifiable by cation exchange reaction, preferably a liquid solidifiable by reaction with calcium ions and/or barium ions and/or manganese ions, preferably by reaction with calcium ions.

[0712] A5. The process according to any of the preceding aspects, wherein the solidifiable liquid is a liquid solidifiable by reaction with calcium ions,

[0713] comprising one or more binders selected from the group consisting of alginate, PVA, chitosan and sulfoxyethyl cellulose, and/or

[0714] an aqueous solution,

[0715] wherein the solidifiable liquid is preferably an aqueous alginate solution.

[0716] A6. The process according to any of the preceding aspects, wherein the or at least one of the lightweight fillers used in step (a) as density-reducing substance of component (ii), preferably having a grain size of less than 0.8 mm, more preferably less than 0.5 mm, most preferably less than 0.3 mm, determined by sieving, is selected from the group consisting of: [0717] inorganic hollow beads, organic hollow beads, particles of porous and/or foamed material, rice husk ash, core-shell particles and calcined kieselguhr and/or

[0718] wherein the or at least one of the pyrolyzable fillers used in step (a) as component (ii) is selected from the group consisting of: [0719] polymer beads and [0720] styrofoam beads.

[0721] A7. The process according to any of the preceding aspects, wherein the or at least one of the refractory solids used in step (a1) as refractory substance of component (i) is selected from the group consisting of: [0722] oxides, nitrides and carbides, each comprising one or more elements from the group consisting of Si, Al, Zr, Ti, Mg and Ca, [0723] mixed oxides, mixed carbides and mixed nitrides, each comprising one or more elements from the group consisting of Si, Al, Zr, Ti, Mg and Ca,

[0724] wherein the or at least one of the refractory solids used in step (a1) as refractory substance of component (i) is preferably selected from the group consisting of: [0725] aluminum oxide, [0726] zirconium oxide, [0727] titanium dioxide, [0728] graphite, [0729] silicon dioxide, [0730] magnesium oxide, [0731] calcium oxide, [0732] calcium silicate, [0733] sheet silicates, preferably mica, [0734] aluminum silicates, [0735] magnesium aluminum silicate, preferably cordierite, [0736] silicon carbide, and [0737] boron nitride and/or

[0738] the precursor or at least one of the precursors of refractory solids used in step (a1) as refractory substance of component (i) is selected from the group consisting of [0739] aluminum hydroxide, [0740] magnesium hydroxide, [0741] sheet silicates, preferably kaolinite, montmorillonite and illite, [0742] clays, preferably kaolin and bentonite, [0743] phosphates and [0744] carbonates.

[0745] A8. The process according to any of the preceding aspects, wherein

[0746] the treating in step (a3) is conducted in such a way that the bulk density of the resulting composite particles is lower than the bulk density of the hardened droplets in the dried state and/or

[0747] said composite particles have a bulk density <750 g/L, preferably <500 g/L, more preferably <350 g/L.

[0748] A9. The process according to any of the preceding aspects, wherein at least some of the resultant composite particles in step (a3) and/or the composite particles used in step (b) have a grain size of less than 5.0 mm, preferably of less than 2.0 mm, determined by sieving.

[0749] A10. The process according to any of the preceding aspects, wherein component (i) comprises, as refractory substances, one or more precursors of refractory solids and the treating in step (a3) comprises a thermal treatment in which the precursors are converted to a refractory solid,

[0750] preferably wherein the precursor or at least one of the precursors of refractory solids is a clay and the treating in step (a3) comprises a thermal treatment at a temperature in the range from 900 to 980° C., such that the clay is converted to a refractory solid, wherein the clay preferably contains kaolinite and/or illite.

[0751] A11. The process according to any of the preceding aspects, preferably according to aspect 10, wherein the hardened droplets are treated in step (a3), so as to result in solid particles as intermediate, and wherein the surface of these solid particles is subsequently sealed, preferably by means of an organic coating composition or a silicon-containing binder, so as to result in said composite particles.

[0752] A12. The process according to any of the preceding aspects, comprising, as step (b), mixing the composite particles produced in step (a) with a binder comprising a binder component selected from the group consisting of [0753] alumina cements, [0754] calcium aluminate cements, [0755] monoaluminum phosphate or solution of monoaluminum phosphate, [0756] monomagnesium phosphate or solution of monomagnesium phosphate, [0757] phosphoric acid, [0758] inorganic phosphate, [0759] boron compounds, preferably boron oxide, [0760] magnesium sulfate or solution of magnesium sulfate, [0761] silica sol and [0762] sols of aluminum oxide.

[0763] A13. The process according to any of aspects 1 to 12, wherein step (a1) uses, as a further starting material for production of droplets of a suspension and as a dispersed phase,

[0764] (iii) colloidal silicon dioxide, preferably anionic colloidal silicon dioxide, in addition to constituents (i) and (ii).

[0765] A14. The process according to any of the preceding aspects, wherein the resultant composite particles in step (a3) are characterized by

[0766] (A) thermal stability at a temperature of 1600° C. or higher, determined by the sintering test, and/or

[0767] (B) a thermal conductivity value at room temperature (20° C.) γR of ≤0.26 W/m*K, preferably ≤0.10 W/m*K, more preferably ≤0.07 W/m*K, and/or

[0768] (C) a grain strength ≥1.5 N/mm.sup.2, preferably ≥2.0 N/mm.sup.2, more preferably ≥3.0 N/mm.sup.2, determined to EN 13055-1, Annex A, Method 1, at a grain size in the range of 0.25-0.5 mm, and/or

[0769] (D) a bulk density <750 g/L, preferably <500 g/L, more preferably <350 g/L, and/or

[0770] (E) a grain size of not more than 5 mm, preferably not more than 2 mm, more preferably not more than 1 mm, determined by sieving,

[0771] (F) a water absorption capacity, determined via water absorption according to Enslin, of ≤4.5, preferably ≤3.5 and more preferably ≤2.0 mL/g.

[0772] A15. An insulating product for the refractory industry or insulating material as intermediate for production of such a product, comprising [0773] a number of refractory composite particles, where said composite particles [0774] particles of one or more refractory substances and [0775] preferably nanoparticulate silicon dioxide that functions as binder or binder component for said particles of the refractory substances and [0776] the curing product of a binder component selected from the group consisting of: [0777] alumina cements, [0778] calcium aluminate cements, [0779] monoaluminum phosphate or solution of monoaluminum phosphate, [0780] monomagnesium phosphate or solution of monomagnesium phosphate, [0781] phosphoric acid, [0782] inorganic phosphate, [0783] boron compounds, preferably boron oxide, [0784] magnesium sulfate or solution of magnesium sulfate, [0785] silica sol, [0786] sols of aluminum oxide, [0787] plastic clays, [0788] hydratable aluminum oxide binder, [0789] ethyl silicate, [0790] aluminum sulfate,

[0791] wherein the product or intermediate is producible by a process according to any of aspects A1 to A11 and/or

[0792] wherein the composite particles present in the product or intermediate are characterized by [0793] (A) thermal stability at a temperature of 1600° C. or higher, determined by the sintering test, and/or [0794] (B) a thermal conductivity value at room temperature (20° C.) γR of ≤0.26 W/m*K, preferably ≤0.10 W/m*K, more preferably ≤0.07 W/m*K.

[0795] A16. The insulating product for the refractory industry or insulating material as intermediate for production of such a product according to aspect 15, wherein the composite particles present in the product or intermediate are characterized by

[0796] (C) a grain strength ≥1.5 N/mm.sup.2, preferably ≥2.0 N/mm.sup.2, more preferably ≥3.0 N/mm.sup.2, determined to EN 13055-1, Annex A, Method 1, at a grain size in the range of 0.25-0.5 mm, and/or

[0797] (D) a bulk density ≤750 g/L, preferably ≤500 g/L, more preferably ≤350 g/L, and/or

[0798] (E) a grain size of not more than 5 mm, preferably not more than 2 mm, more preferably not more than 1 mm, determined by sieving, and/or

[0799] (F) a water absorption capacity, determined via water absorption according to Enslin, of ≤4.5, preferably ≤3.5 and more preferably ≤2.0 mL/g.

[0800] A17. The insulating product for the refractory industry or insulating material as intermediate for production of such a product according to either of aspects A15 and A16, additionally comprising one or more substances selected from the group consisting of:

[0801] fireclay, lightweight fireclay, corundum, hollow spherical corundum, sintered corundum, fused corundum, sintered mullite, fused mullite, aluminum oxide (alumina), andalusite, kyanite, sillimanite, cordierite, clays, wollastonite, zirconium mullite, zirconium corundum, spheres of fly ash and vermiculite.