Reducing the viscosity of aluminum sulfate suspensions using alkali metal compounds.

Abstract

The present invention relates to the use of at least one soluble alkali metal compound for adjusting, in particular reducing, the viscosity of an aluminium sulphate suspension, wherein this alkali metal is selected from sodium, potassium and / or lithium.

Description

[Technical field]

[0001] The present invention relates to a composition for adjusting, more particularly reducing, the viscosity of an aluminum sulfate suspension. The present invention further relates to an aluminum sulfate suspension. [Background technology]

[0002] Many materials are known that accelerate the setting and hardening of inorganic binder compositions. Known examples include strongly alkaline materials such as alkali metal hydroxides, alkali metal carbonates, alkali metal silicates, alkali metal aluminates, and alkaline earth metal chlorides.

[0003] However, non-alkali-containing accelerators are predominantly used, with aluminum sulfate suspension-based accelerators being one that have proven particularly effective and have a good price / performance relationship. A problem with such accelerators, however, is that their viscosity increases significantly with increasing active substance content. Among other things, the production, accurate metering and compatibility of the accelerator with the inorganic binder composition to be accelerated are complicated.

[0004] WO 2005 / 075381 A1, for example, describes a setting and hardening accelerator comprising aluminum hydroxide, aluminum sulfate and an organic acid, where the accelerator has a molar ratio of aluminum to organic acid of less than 0.65.

[0005] EP 0 812 812 B1 discloses non-alkali-containing accelerator dispersions based on aluminum sulfate and alkanolamines that are free of aluminum hydroxide.

[0006] However, the large amounts of acid and alkanolamine have the disadvantage that they may cause environmental pollution due to their leachability, and they are also disadvantageous in terms of cost.

[0007] EP 1 878 713 A1 (Construction Research and Technology GmbH) describes an accelerator for shotcrete or shotcrete mortar in the form of an aqueous dispersion containing 25% to 40% by weight of aluminum sulfate and aluminum hydroxide, the molar ratio of aluminum to sulfate in the dispersion being between 1.35 and 0.70. The aqueous dispersion also contains an inorganic stabilizer which comprises magnesium silicate in the form of sepiolite. When sepiolite is used in a proportion of 0.2 to 3% by weight, the results according to EP 1 878 713 A1 are not only that the dispersion is stabilized over a wide range of the intended amounts of aluminum and sulfate, but also that the viscosity of the shotcrete accelerator is advantageous.

[0008] However, the disadvantage of such accelerators is that in order to achieve a high active substance content, the addition of additional aluminum hydroxide is necessary, which leads to a high ratio of aluminum to sulfate, which is undesirable in some cases. The effect of this is the relatively high cost of the accelerator, due to the high cost of aluminum hydroxide. Moreover, although magnesium silicate, which is used as a stabilizer in the form of sepiolite, is a very good stabilizer for shotcrete accelerators, sepiolite has been found to be ineffective in reducing viscosity. On the contrary, the addition of sepiolite immediately after production always leads to an increase in the viscosity of the aluminum sulfate suspension.

[0009] This means that, although it is possible to stabilise aluminium sulphate suspensions with a relatively high active substance content, it is not possible to actively influence or control the viscosity of such aluminium sulphate suspensions, especially immediately after production.

[0010] In the applicant's unpublished European patent application No. 19207659.4 it has been shown that in some cases a reduction in the viscosity of aluminium sulphate suspensions can be achieved by the addition of magnesium compounds.

[0011] To reduce viscosity, however, there remains a need for solutions with improved efficacy and also less expensive solutions.

[0012] Thus, there remains a need for new and improved solutions which overcome, to the greatest extent possible, the aforementioned shortcomings. Summary of the Invention [Problem to be solved by the invention]

[0013] The present invention aims to provide a solution which allows the production of an aluminium sulphate suspension with the highest possible aluminium sulphate content at the lowest possible viscosity. More particularly, the low viscosity is achieved immediately after the addition of the soluble alkali metal compound to the aluminium sulphate suspension, and the low viscosity is preferably maintained at a later time point after the addition of the soluble alkali metal compound to the aluminium sulphate suspension. This is achieved in particular without affecting the aluminium to sulphate ratio and preferably without adversely affecting the efficacy of the other components of the aluminium sulphate suspension. The aluminium sulphate suspension should be particularly suitable as a very effective setting and / or hardening accelerator for compositions comprising inorganic binders, in particular for shotcrete or shotcrete mortar, the aluminium sulphate suspension being particularly suitable as a shotcrete accelerator. The solution should furthermore be capable of being carried out in a very cheap and simple manner. [Means for solving the problem]

[0014] Surprisingly, it was found that the object of the invention is achieved by the use as claimed in claim 1.

[0015] Thus, at least one soluble alkali metal compound is used to adjust, more particularly reduce, the viscosity of the aluminum sulphate suspension, where the alkali metal is selected from sodium, potassium and / or lithium.

[0016] As shown, the use of soluble alkali metal compounds makes it possible to significantly reduce the viscosity of the aluminium sulphate suspension at the same aluminium sulphate content and / or to significantly increase the aluminium sulphate content at the same viscosity. It is therefore possible in a simple manner to produce relatively cheap aluminium sulphate suspensions with a relatively low viscosity and a high aluminium sulphate content, which are particularly suitable as setting and hardening accelerators for shotcrete and mortar.

[0017] The use of at least one soluble alkali metal compound is particularly effective in reducing the viscosity of the aluminium sulphate suspension within a period of from 1 to 48 hours, preferably from 1 to 24 hours or from 1 to 12 hours, more particularly from 2 to 6 hours, after its addition to the aluminium sulphate suspension or after all of the components for producing the aluminium sulphate suspension have been mixed together. A particular advantage is that the viscosity spike which may occur within the first few hours after production of the aluminium sulphate suspension is dampened, which is an advantage for economical production.

[0018] Moreover, it has been shown that the soluble alkali metal compounds are effective as viscosity adjusting, more particularly reducing and / or maintaining agents even at later times, more particularly after 1 to 3 months, after their addition to the aluminum sulfate suspension, which is particularly the case when the aluminum sulfate suspension has a proportion of aluminum sulfate (Al2(SO4)3) of more than 34% by weight.

[0019] The use of a suitably selected soluble alkali metal compound makes it possible to avoid changes in the aluminum to sulfate ratio. The use of alkali metal aluminates, however, also makes it possible to increase the Al content in the suspension, which is usually, but not always, advantageous.

[0020] Alkali metal compounds of Na, K and Li can show better efficacy than magnesium compounds. Moreover, Na and K compounds are inexpensive compared to other chemicals, thus achieving a good price / performance relationship. Problems related to precipitation at high concentrations (precipitation of magnesium sulfate) that can occur when using magnesium compounds, for example, do not occur.

[0021] The soluble alkali metal compounds can also be directly combined with conventional magnesium silicate stabilizers, especially sepiolite, without adversely affecting the effectiveness of the soluble alkali metal compounds. For example, in aluminum sulfate suspensions, it is possible to use, if necessary, magnesium silicates, especially sepiolite, in combination with soluble alkali metal compounds, which allows the production of particularly stable aluminum sulfate suspensions with high active substance content and low viscosity.

[0022] In addition, potentially problematic and / or expensive materials such as alkanolamines, carboxylic acids and aluminium hydroxide can be omitted where necessary, without significant loss of promotion.

[0023] Further aspects of the invention are the subject matter of further independent claims. Particularly preferred embodiments of the invention are the subject matter of the dependent claims. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0024] In a first aspect, the present invention relates to the use of at least one soluble alkali metal compound for adjusting, more particularly reducing, the viscosity of an aluminum sulphate suspension, wherein the alkali metal is selected from sodium, potassium and / or lithium. Although a mixture of two or more soluble alkali metal compounds may be used, the use of only one alkali metal compound is generally preferred for practical reasons.

[0025] An "aluminum sulfate suspension" is a heterogeneous mixture of matter consisting of a liquid, more specifically water, and finely dispersed particles of aluminum sulfate therein. It is preferably an aqueous aluminum sulfate suspension. Not only the aluminum sulfate in particulate form, but also a part of the aluminum sulfate may be in dissolved and / or chemically modified form, more specifically an aqueous aluminum sulfate suspension. An example of a chemically modified form of aluminum sulfate is durbanite (AlOHSO4·5H2O). An aluminum sulfate suspension, in the present context, is not a pure solution, but rather finely dispersed particles of aluminum sulfate are always present in the liquid phase, more specifically water. In addition to the liquid and aluminum sulfate, the aluminum sulfate suspension may further contain components that may be in dissolved and / or solid form.

[0026] The aluminum sulfate suspension is particularly preferably a setting and / or hardening accelerator for inorganic binders (mineral binders), in particular a shotcrete accelerator. Correspondingly, the soluble alkali metal compound is preferably used to adjust the viscosity of the aluminum sulfate suspension-based setting and / or hardening accelerator, in particular for compositions containing inorganic binders such as cement, where the aluminum sulfate suspension is preferably a shotcrete accelerator, in particular for shotcrete or shotcrete mortar.

[0027] The term "set accelerator and / or hardening accelerator" refers more specifically to a substance to which an inorganic binder has been added, and which results in an increase in the compressive strength of the inorganic binder after a specified time after mixing, more specifically within a time period between 2 minutes and 24 hours after mixing, when compared to a blank sample containing no added substance / accelerator.

[0028] A "soluble alkali metal compound" in the present context is an alkali metal compound which is soluble to the extent of at least 5 g in 1 liter of distilled water adjusted to pH 2 with HCl at 25° C. and 1 bar pressure.

[0029] More specifically, in this context, "adjusting viscosity" means that the viscosity of the aluminum sulphate suspension is controlled and / or adjusted by the soluble alkali metal compound, more specifically, the presence of the soluble alkali metal compound modifies or reduces the viscosity of the aluminum sulphate suspension compared to the viscosity of an aluminum sulphate suspension of otherwise equivalent composition but not containing the soluble alkali metal compound.

[0030] The viscosity is more particularly measured according to the standard DIN EN ISO 2431:2011. This is preferably carried out in an ISO No. 6 or No. 4 cup and at a temperature of 23° C.

[0031] The weight percentages and molar ratios are in each case based on the ready-to-use aluminum sulfate suspension after viscosity adjustment, unless otherwise specified. The ready-to-use aluminum sulfate suspension is more particularly designed to be used directly as a setting accelerator and / or hardening accelerator. The ready-to-use aluminum sulfate suspension therefore comprises, besides aluminum sulfate and liquid, at least one soluble alkali metal compound and optionally further components present.

[0032] The aluminum sulphate suspension is preferably chloride free and is also preferably alkali free or low alkaline, despite the use of an alkali metal compound.

[0033] Typically, in construction chemistry, alkali-free means a composition having less than 1% by weight of alkali metal ions and / or alkaline earth metal ions, calculated as sodium oxide equivalent (Na2O), based on the total weight of the composition or the total weight of the aluminum sulfate suspension, whereas low alkali means a composition having 5% or less by weight of alkali metal ions and / or alkaline earth metal ions, calculated as sodium oxide equivalent (Na2O), based on the total weight of the composition or the total weight of the aluminum sulfate suspension.

[0034] Na2O equivalent refers to the amount by weight that would be obtained if all alkali metal ions (especially Na and K) were present as Na2O.

[0035] Typically, in construction chemistry, chloride-free means a composition having less than 0.1% by weight of chloride ions, based on the total weight of the composition or the total weight of the aluminum sulfate suspension.

[0036] The soluble alkali metal compounds are more particularly used to adjust the viscosity, more particularly to reduce the viscosity.

[0037] More specifically, the soluble alkali metal compound is used to adjust, more specifically reduce, the viscosity of the aluminum sulphate suspension, the adjustment, more specifically reduction, being preferably completed within a period of 1 to 168 hours, more preferably 1 to 48 hours, in particular 1 to 24 hours, after the aluminum sulphate suspension to which the soluble alkali metal compound has been added is obtained. In particular, the soluble alkali metal compound is capable of reducing the viscosity of the aluminum sulphate suspension within a period of 1 to 6 hours after the addition of the aluminum sulphate suspension or after mixing all of the components for producing the aluminum sulphate suspension, which is particularly advantageous in production.

[0038] In particular, once the viscosity has been adjusted, it remains stable over a long period, more particularly over a period of several months. The soluble alkali metal compounds are therefore particularly used to adjust, more particularly reduce, the viscosity of the aluminum sulfate suspension over a period of several months, very particularly preferably over a period of 1 to 3 months, after the aluminum sulfate suspension to which the soluble alkali metal compounds have been added has been obtained. This is in particular the case for aluminum sulfate suspensions having a proportion of more than 34% by weight of aluminum sulfate (Al2(SO4)3).

[0039] The soluble alkali metal compound can adjust, more specifically reduce, the viscosity within a period of 1 to 168 hours, preferably 1 to 48 hours, particularly 6 to 24 hours after the aluminum sulfate suspension to which the soluble alkali metal compound has been added is obtained, so that the viscosity of the aluminum sulfate suspension can be adjusted to the desired value even immediately after production. This allows shorter production times, since the aluminum sulfate suspension can be used as intended within a few hours after production, more specifically as a solidification accelerator and / or hardening accelerator.

[0040] The soluble alkali metal compound further allows for adjustment, more particularly reduction, of the viscosity over a long period of time, more particularly over a period of several months, after the aluminum sulfate suspension to which the soluble alkali metal compound has been added is obtained, so that a long-term reduction in viscosity can be achieved, and therefore the aluminum sulfate suspension having a substantially constant viscosity can be stored for a long period of time as required.

[0041] Soluble alkali metal compounds can therefore be used in a method for adjusting the viscosity of an aluminum sulphate suspension.

[0042] A further aspect of the invention is therefore a method for adjusting, more particularly reducing, the viscosity of an aluminium sulphate suspension, preferably within a period of 1 to 168 hours, preferably within a period of 1 to 48 hours, in particular within a period of 6 to 24 hours, after the aluminium sulphate suspension to which a soluble alkali metal compound has been added has been obtained, and / or a method for adjusting, more particularly reducing, the viscosity over an extended period, more particularly over a period of several months, which comprises: (a) initially charging an aqueous preparation of aluminum sulfate; and (b) mixing in at least one soluble alkali metal compound (c) optionally mixing in additional aluminum sulfate A method for obtaining an aluminum sulfate suspension comprising the steps of: or (a) initially charging an aqueous preparation of a soluble alkali metal compound; and (b) mixing in aluminum sulfate to obtain an aluminum sulfate suspension; The method includes:

[0043] All variations are possible. In some cases, alternating addition of the individual components is the preferred method. The preparation is in this context a solution or a suspension. An aqueous preparation is therefore a solution or suspension in water.

[0044] Aqueous preparations of aluminum sulfate are solutions or suspensions of aluminum sulfate in water. In the aqueous preparations it is also possible that some aluminum sulfate is present in dissolved form and some in suspended form.

[0045] The set accelerator and / or hardening accelerator according to the invention for compositions containing hydraulic binders, in particular for shotcrete or shotcrete mortar, is an aluminium sulphate suspension.

[0046] The soluble alkali metal compound can be added directly to the aluminum sulfate preparation during its formation. However, it is also possible to add the soluble alkali metal compound to the aluminum sulfate preparation immediately after its formation, for example within one hour after its formation. Finally, it is also possible to add the soluble alkali metal compound to the aluminum sulfate preparation only after a long period of time, for example after 5 days or more, since its formation.

[0047] The soluble alkali metal compound is preferably a basic alkali metal compound, which means that when added to acidified water, it is capable of increasing the pH of distilled water adjusted to pH 2 with HCl at 25° C. and 1 bar pressure.

[0048] The soluble alkali metal compound preferably comprises an alkali metal salt and / or an alkali metal complex.

[0049] The soluble alkali metal compounds used in accordance with the present invention allow the formulation of highly effective setting and / or hardening accelerators that are substantially free of calcium, which can be advantageous since calcium can sometimes retard the reaction or dissolution of cement clinker.

[0050] The alkali metal of the alkali metal compound is selected from sodium, potassium and / or lithium, with sodium and / or potassium being preferred.

[0051] In particular, the soluble alkali metal compound is an aluminate, oxide, hydroxide, carbonate, bicarbonate, nitrate, sulfate, phosphate, halide, formate, acetate, citrate, thiocyanate, silicate or mixtures thereof.

[0052] More preferably, the soluble alkali metal compound is an aluminate, oxide, hydroxide, carbonate, bicarbonate, nitrate, formate, acetate, citrate or mixtures thereof.

[0053] Preferably, the soluble alkali metal compound is sodium aluminate, sodium carbonate, sodium bicarbonate, sodium oxide, sodium hydroxide, potassium aluminate, potassium carbonate, potassium bicarbonate, potassium oxide, potassium hydroxide, lithium aluminate, lithium carbonate, lithium bicarbonate, lithium oxide, lithium hydroxide or mixtures thereof, preferably sodium or potassium compounds. Very particularly preferably, the alkali metal compound is selected from sodium aluminate, sodium carbonate, sodium bicarbonate, sodium oxide, sodium hydroxide, potassium aluminate or mixtures thereof.

[0054] These alkali metal compounds have been found to be particularly advantageous in the present context, since they make it possible to achieve a significant reduction in viscosity without adversely affecting the further components, and moreover, these substances are readily available.

[0055] In principle, however, it is also possible to use other soluble alkali metal compounds.

[0056] At least one soluble alkali metal compound, more particularly the abovementioned soluble alkali metal compounds, can be added, for example, in powder form or as an aqueous solution, to the aluminum sulfate suspension or during the production of the aluminum sulfate suspension. Sodium aluminate can be added, for example, as a powder or as an aqueous solution.

[0057] Preferably, the amount of soluble alkali metal compound is selected so that the proportion of alkali metal atoms is 0.02 to 5% by weight, more particularly 0.05 to 2% by weight, particularly preferably 0.1 to 1.4% by weight and in particular 0.2 to 0.7% by weight, based on the total weight of the aluminum sulphate suspension.

[0058] These amounts allow a particularly good viscosity reduction without having a significant adverse effect on the set-accelerating and / or hardening-accelerating properties of the aluminum sulphate suspension.

[0059] The aluminum sulfate suspension contains 19 to 40% by weight, more particularly 24 to 36% by weight, in particular 28 to 34% by weight, of sulfate (SO4 - ) ratio.

[0060] It is further preferred if the aluminum sulphate suspension has a proportion of aluminium (Al) of 3.5 to 10% by weight, more particularly 4.5 to 8.7% by weight, in particular 5.4 to 7% by weight, based on the total weight of the aluminum sulphate suspension.

[0061] With such proportions of aluminum and sulfate it is possible to produce aluminum sulfate suspensions with a high active substance content which show particularly good acceleration of setting and / or hardening.

[0062] The aluminium sulphate suspension advantageously comprises aluminium sulphate, aluminium hydroxide sulphate, sulphuric acid, aluminium hydroxide and / or aluminium hydroxide carbonate. Aluminium sulphate is particularly preferred.

[0063] The sulfate in the aluminum sulfate suspension comes in particular from aluminum sulfate, aluminum hydroxide sulfate and / or sulfuric acid. Aluminum sulfate is particularly preferred. In other words, the accelerator more specifically contains at least one of the substances described as sources of sulfate.

[0064] The aluminum in the promoter advantageously comes from aluminum sulfate, aluminum hydroxide sulfate, aluminum hydroxide and / or aluminum hydroxide carbonate. Aluminum sulfate is particularly preferred. In other words, the promoter more specifically contains at least one of the substances described as sources of aluminum.

[0065] In an advantageous embodiment, the aluminum sulphate suspension contains 22 to 46% by weight, more particularly 28 to 43% by weight, preferably 34 to 41% by weight, of aluminum sulphate (Al2(SO4)3), based on the total weight of the aluminum sulphate suspension.

[0066] The aluminum sulfate available for production may in particular contain various amounts of water of crystallization. The aluminum sulfate used is typically aluminum sulfate 14-hydrate (Al2(SO4)3 ≈14H2O), which is also called 17% aluminum sulfate, since it typically contains about 17% Al2O3.

[0067] The amounts of aluminum sulfate stated in this document are in each case based on Al2(SO4)3 without water of crystallization, unless otherwise specified. The amounts stated for the various reference compounds can be readily converted by reference to the following relationship: Al2(SO4)3·approximately 14H2O contains 57% by weight of Al2(SO4)3 or 17% by weight of Al2O3.

[0068] Aluminum sulfate can also be produced by the reaction of aluminum hydroxide and / or aluminum metal with sulfuric acid during the production of an aluminum sulfate suspension, with the formation of the corresponding sulfate ions in aqueous solution. Usually, aluminum sulfate can be produced by the reaction of basic aluminum compounds and / or aluminum metal with sulfuric acid.

[0069] In a further advantageous embodiment, the aluminum sulphate suspension contains 0.01 to 15% by weight, more particularly 0.05 to 5% by weight and particularly preferably 0.1 to 2% by weight of aluminum hydroxide, based on the total weight of the aluminum sulphate suspension.

[0070] It is therefore possible, for example, to effectively increase the aluminium content independently of the sulphate content of the aluminium sulphate suspension.

[0071] The aluminum hydroxide can be used in amorphous and / or crystalline form. It is advantageous to use amorphous aluminum hydroxide, especially since crystalline aluminum hydroxide typically only reacts sufficiently at temperatures above 130° C. and pressures above 1 bar. Aluminum hydroxide can also be used in the form of aluminum hydroxide carbonate, aluminum hydroxide sulfate, etc.

[0072] In an advantageous embodiment, the molar ratio of aluminum to sulfate in the aluminum sulfate suspension is 0.9 or less, preferably 0.85 or less, more preferably 0.8 or less, even more preferably 0.74 or less, very particularly preferably 0.7 or less, the molar ratio of aluminum:sulfate being in particular 2:3. In this case, the aluminum sulfate suspension can be produced particularly simply by suspending aluminum sulfate (Al2(SO4)3). In the inventive use of soluble alkali metal compounds, it is therefore possible to produce aluminum sulfate suspensions with a high active substance content and low viscosity.

[0073] In a further advantageous embodiment, the molar ratio of aluminum to sulfate in the aluminum sulfate suspension is in the range of 0.5 to 2, preferably 0.67 to 1.35, in particular 0.7 to 1.0. Such aluminum sulfate suspensions have improved efficacy for certain applications.

[0074] The aluminum sulfate suspension preferably has a water proportion of 30-80% by weight, more particularly 40-70% by weight, preferably 50-65% by weight, based on the total weight of the aluminum sulfate suspension. Water of crystallization in the components of the aluminum sulfate suspension, e.g. water of crystallization originating from aluminum sulfate, is included in the calculation here.

[0075] In a further advantageous embodiment, a soluble alkali metal compound is used to reduce the viscosity in combination with a magnesium compound, a calcium compound and / or an iron compound. In particular, both calcium and iron compounds are used. Without being bound to a particular theory, it is assumed that the calcium and iron compounds further enhance the effect of the soluble alkali metal compound. In a particularly preferred embodiment, a soluble alkali metal compound is used in combination with a magnesium compound to reduce the viscosity of the aluminum sulfate suspension.

[0076] The magnesium compounds, calcium compounds and / or iron compounds are in particular oxides, hydroxides, carbonates, nitrates, sulfates, phosphates, halides, formates, acetates and / or citrates.

[0077] The magnesium, calcium and / or iron compounds are preferably oxides, hydroxides, carbonates, nitrates, formates, acetates and / or citrates.

[0078] The calcium compound is particularly preferably calcium carbonate, calcium oxide and / or calcium hydroxide. Calcium oxide is particularly preferred. The magnesium compound is particularly preferably magnesium carbonate, magnesium oxide and / or magnesium hydroxide.

[0079] The calcium compounds are in particular Ca(OH)2, CaCO3 and / or CaO. CaO is particularly preferred. The magnesium compounds are in particular Mg(OH)2, MgCO3 and / or MgO. MgO is particularly preferred.

[0080] The amount of calcium or magnesium compound is in particular selected so that the calcium or magnesium atoms have a proportion of 0.001 to 4% by weight, preferably 0.01 to 2% by weight, more particularly 0.07 to 1.4% by weight and in particular 0.1 to 0.7% by weight, based on the total weight of the aluminum sulphate suspension.

[0081] When CaO is used as calcium compound, the proportion of CaO based on the total weight of the aluminum sulfate suspension is advantageously 0.001-5% by weight, preferably 0.01-3% by weight, more particularly 0.1-2% by weight and in particular 0.2-1% by weight.When MgO is used as magnesium compound, the proportion of MgO based on the total weight of the aluminum sulfate suspension is advantageously 0.001-5% by weight, preferably 0.01-3% by weight, more particularly 0.1-2% by weight and in particular 0.2-1% by weight.

[0082] The iron compound is particularly preferably an iron oxide, in particular Fe2O3.

[0083] The amount of iron compound is in particular selected so that the iron atoms have a proportion of 0.001 to 10% by weight, more particularly 0.1 to 5% by weight, in particular 0.2 to 2% by weight and very particularly preferably 0.1 to 0.6% by weight, based on the total weight of the aluminum sulfate suspension.

[0084] If Fe2O3 is used as the iron compound, the proportion of Fe2O3, based on the total weight of the aluminium sulphate suspension, is advantageously between 0.001 and 14.3% by weight, more particularly between 0.1 and 7.1% by weight and in particular between 0.2 and 2% by weight.

[0085] In a further advantageous embodiment, the aluminum sulphate suspension contains silica.

[0086] In this document, the term "silica" refers not only to orthosilicic acid, but also to all forms of silicon dioxide, i.e., orthosilicic anhydride, actual silicon dioxide, and also colloidal, precipitated or fumed silica or silica fume. Silica is preferably silicon dioxide or SiO2.

[0087] The silica is preferably present in an amount such that the silicon dioxide content, based on the total weight of the aluminum sulfate suspension, is between 0.001% and 5% by weight, preferably between 0.1% and 2% by weight, even more preferably between 0.2% and 1% by weight.

[0088] In addition, for the production of the aluminum sulfate suspension, it is possible to use at least one further divalent or more metal salt, more particularly a metal sulfate, preferably in an amount of 0.1 to 5% by weight, based on the total weight of the aluminum sulfate suspension. A particularly preferred further metal sulfate is manganese(II) sulfate. Iron sulfate is also suitable.

[0089] It may furthermore be advantageous if the aluminium sulphate suspension further comprises from 0.1 to 15% by weight, preferably from 0.1 to 5% by weight and in particular from 0.2 to 2% by weight of an alkanolamine, based on the total weight of the aluminium sulphate suspension. The alkanolamines used are advantageously monoethanolamine, diethanolamine, triethanolamine and / or methyldiisopropanolamine.

[0090] The aluminium sulphate suspension may furthermore contain stabilisers, such as bentonite, palygorskite (e.g. Actigel 208), kaolin and / or magnesium silicates, such as sepiolite.The aluminium sulphate suspension according to the invention is preferably free of organic plasticisers, in particular polycarboxylates, polycarboxylate esters and / or polycarboxylate ethers.

[0091] The aluminum sulfate suspension may in particular contain magnesium silicate, in particular sheet silicate and / or phyllosilicates, such as sepiolite and / or bentonite. If present, the proportion of magnesium silicate is advantageously 0.001-5% by weight, preferably 0.1-2% by weight, in particular 0.2-1% by weight, based on the total weight of the aluminum sulfate suspension. Magnesium silicate in this context is inert or insoluble under the above definition of solubility and contributes to phase stabilization.

[0092] In addition, soluble alkali metal compounds can be used in combination with magnesium silicates for adjusting, more particularly reducing, the viscosity of the aluminum sulfate suspension and for parallel stabilization. The magnesium silicates can in particular be sheet silicates and / or phyllosilicates, such as sepiolite and / or bentonite. Sepiolite is particularly preferred. It is preferred that magnesium silicates, in particular sepiolite, are used in a proportion of 0.001 to 5% by weight, preferably 0.1 to 2% by weight, in particular 0.2 to 1% by weight, based on the total weight of the aluminum sulfate suspension. The amount of soluble alkali metal compounds is preferably selected so that the alkali metal atoms have a proportion of 0.02 to 5% by weight, more particularly 0.05 to 2% by weight, particularly preferably 0.1 to 1.4% by weight, in particular 0.2 to 0.7% by weight, based on the total weight of the aluminum sulfate suspension.

[0093] The aluminum sulfate suspension may of course also contain further constituents. These may in particular be fluorine compounds, such as hydrofluoric acid, alkali metal fluorides and / or fluoro complexes, which, for example, allow a further increase in the promotion effect.

[0094] In particular, the aluminum sulfate suspension contains 0.01 to 10% by weight, more specifically 0.05 to 2% by weight, preferably 0.1 to 0.5% by weight, of fluoride based on the total weight of the aluminum sulfate suspension, which may enhance the accelerating effect of the aluminum sulfate suspension.

[0095] The aforementioned substances are more particularly present in solution at least partially as ions, but they may also occur in complexed or undissolved form, for example in an aluminum sulfate suspension.

[0096] Particularly advantageous aluminum sulfate suspensions comprise or consist, for example, of the following components (% by weight, in each case based on the total weight of the aluminum sulfate suspension): (a) 19% to 40% by weight, more particularly 24 to 36% by weight, especially 28 to 34% by weight, of sulfate; (b) 3.5 to 10% by weight, more specifically 4.5 to 8.7% by weight, and especially 5.4 to 7% by weight, of aluminum; (c) at least one soluble alkali metal compound in which the alkali metal is selected from sodium, potassium and / or lithium, in an amount such that the atoms of the alkali metal have a proportion of 0.02 to 5% by weight, more particularly 0.05 to 2% by weight, particularly preferably 0.1 to 1.4% by weight and in particular 0.2 to 0.7% by weight, based on the total weight of the aluminium sulphate suspension; (d) optionally 0.001 to 4% by weight, preferably 0.01 to 2% by weight, more particularly 0.07 to 1.4% by weight, and especially 0.1 to 0.7% by weight, of calcium or magnesium; (e) optionally 0.001 to 10% by weight, more particularly 0.1 to 5% by weight, in particular 0.2 to 2% by weight, very particularly preferably 0.1 to 0.6% by weight, of iron; (f) optionally, from 0.001% to 5% by weight, preferably from 0.1% to 2% by weight, and even more preferably from 0.2% to 1% by weight, of silicon dioxide or SiO2; and (g) Water, preferably with a remaining proportion of water up to 100% by weight, particularly preferably 30 to 77.48% by weight, more particularly 40 to 70% by weight, very particularly preferably 50 to 65% by weight.

[0097] Particularly preferred aluminum sulfate suspensions contain, for example, the following (% by weight, in each case based on the total weight of the aluminum sulfate suspension): (a) 22 to 46% by weight, more specifically 28 to 43% by weight, preferably 34 to 41% by weight, of aluminum sulfate (Al2(SO4)3); (b) optionally, 0.01 to 15% by weight, more particularly 0.05 to 5% by weight, particularly preferably 0.1 to 2% by weight, of aluminum hydroxide (Al(OH)3); (c) at least one soluble alkali metal compound in which the alkali metal is selected from sodium, potassium and / or lithium, in an amount such that the atoms of the alkali metal have a proportion of 0.02 to 5% by weight, more particularly 0.05 to 2% by weight, particularly preferably 0.1 to 1.4% by weight and in particular 0.2 to 0.7% by weight, based on the total weight of the aluminium sulphate suspension; (d) optionally 0.001 to 5% by weight, more particularly 0.1 to 2% by weight, in particular 0.2 to 1% by weight, of a calcium compound selected from calcium oxide and / or calcium hydroxide, or a magnesium compound selected from magnesium oxide and / or magnesium hydroxide; (e) optionally 0.001 to 10% by weight, more particularly 0.1 to 5% by weight, in particular 0.2 to 2% by weight, very particularly preferably 0.1 to 0.6% by weight, of iron; (f) optionally, 0.001% to 5% by weight, preferably 0.1% to 2% by weight, and even more preferably 0.2% to 1% by weight of silicon dioxide; (g) optionally 0.1 to 15% by weight, preferably 0.1 to 5% by weight, in particular 0.2 to 2% by weight, of an alkanolamine; (h) 0.01 to 10 wt. %, more specifically 0.05 to 2 wt. %, preferably 0.1 to 0.5 wt. % of fluoride; and (i) Water, preferably with a balance up to 100% by weight.

[0098] In preferred embodiments, the most preferred ranges and materials in each case are selected.

[0099] In a particularly preferred embodiment, the aluminum sulfate suspension comprises or consists, for example, of the following components (% by weight, in each case based on the total weight of the aluminum sulfate suspension): (a) 34-41% by weight aluminum sulfate (Al2(SO4)3); (b) at least one soluble alkali metal compound in which the alkali metal is selected from sodium, potassium and / or lithium, in an amount such that the atoms of the alkali metal have a proportion of 0.02 to 5% by weight, more particularly 0.05 to 2% by weight, particularly preferably 0.1 to 1.4% by weight and in particular 0.2 to 0.7% by weight, based on the total weight of the aluminium sulphate suspension; (c) 0.2 to 1% by weight of a calcium compound selected from calcium oxide and / or calcium hydroxide, or a magnesium compound selected from magnesium oxide and / or magnesium hydroxide; (d) optionally 0.001 to 14.3 wt. %, more particularly 0.1 to 7.1 wt. %, and especially 0.2 to 2 wt. % of iron oxide; (e) optionally, from 0.001% to 5% by weight, preferably from 0.1% to 2% by weight, and even more preferably from 0.2% to 1% by weight, of silicon dioxide; and (f) Water, preferably with a balance up to 100% by weight.

[0100] In further particularly preferred embodiments, the aluminum sulfate suspension comprises or consists, for example, of the following components (% by weight, in each case based on the total weight of the aluminum sulfate suspension): (a) 34-41% by weight aluminum sulfate (Al2(SO4)3); (b) at least one alkali metal aluminate, in particular sodium aluminate and / or potassium aluminate, as at least one soluble alkali metal compound in an amount such that the atoms of the alkali metal have a proportion of 0.02 to 5% by weight, more particularly 0.05 to 2% by weight, particularly preferably 0.1 to 1.4% by weight and in particular 0.2 to 0.7% by weight, based on the total weight of the aluminum sulfate suspension; (c) optionally 0.001 to 5% by weight, more particularly 0.1 to 2% by weight, in particular 0.2 to 1% by weight, of a calcium compound selected from calcium oxide and / or calcium hydroxide, or a magnesium compound selected from magnesium oxide and / or magnesium hydroxide; (d) optionally 0.001 to 5 wt. %, more particularly 0.1 to 2 wt. %, and especially 0.2 to 1 wt. % of iron oxide; (e) optionally, from 0.001% to 5% by weight, preferably from 0.1% to 2% by weight, and even more preferably from 0.2% to 1% by weight, of silicon dioxide; and (f) Water, preferably with a balance up to 100% by weight.

[0101] A further aspect of the invention relates to a process for producing the above-mentioned aluminum sulfate suspension, more particularly designed as a setting and / or hardening accelerator. The aforementioned components or substances are more particularly mixed to obtain an aqueous suspension. The individual substances can in principle be added in any order. An aluminum sulfate suspension can correspondingly be obtained by a process of this kind.

[0102] The aluminum sulfate suspension obtainable according to the invention may be used as a setting and / or hardening accelerator to accelerate the setting and / or hardening of inorganic binders (mineral binders) and / or inorganic binder compositions (mineral binder compositions), in particular mortar and / or concrete compositions, in particular shotcrete mortar and / or shotcrete.

[0103] The expression "inorganic binder" is more specifically understood to mean a binder that reacts with water to form a solid hydrate or hydrate phase. This can be, for example, a hydraulic binder (such as cement or hydraulic lime), a latent hydraulic binder (such as slag), a pozzolanic binder (such as fly ash) or a non-hydraulic binder (gypsum or white lime). An "inorganic binder composition" is correspondingly a composition that contains at least one inorganic binder.

[0104] Examples of inorganic binders, the hardening and / or setting of which can be accelerated by the aluminum sulphate suspension of the invention, are cements, such as Portland cements, blended cements, aluminous cements, calcium sulphoaluminate cements and lime, hydraulic lime and gypsum, or mixtures of two or more of the abovementioned inorganic binders.

[0105] More specifically, the inorganic binder or binder composition comprises a hydraulic binder, preferably cement. Particularly preferred is a cement with a cement clinker content of more than 35% by weight; more particularly, the cement is of CEM type I, II, III, IV or V (according to standard EN 197-1). The proportion of hydraulic binder in the total inorganic binder is advantageously at least 5% by weight, more particularly at least 20% by weight, preferably at least 35% by weight, in particular at least 65% by weight. In a further advantageous embodiment, the inorganic binder consists of hydraulic binder, in particular cement clinker, to the extent of at least 95% by weight.

[0106] However, it may also be advantageous if the binder composition contains other binders in addition to or instead of the hydraulic binder. These are in particular latent hydraulic and / or pozzolanic binders. Examples of suitable latent hydraulic and / or pozzolanic binders are slag, fly ash and / or silica dust. The binder composition may also contain inert substances, such as ground limestone, ground quartz and / or pigments.

[0107] In an advantageous embodiment, the inorganic binder contains 5 to 95% by weight, more particularly 5 to 65% by weight, in particular 15 to 35% by weight, of a latent hydraulic and / or pozzolanic binder.

[0108] The present invention further relates to a method for accelerating the setting and / or hardening of an inorganic binder or an inorganic binder composition, such as mortar or concrete, in which the above-mentioned aluminum sulfate suspension is added to the inorganic binder or inorganic binder composition as a setting and / or hardening accelerator in an amount of 0.1% to 15% by weight, more particularly 1% to 10% by weight, particularly preferably 4 to 8% by weight, based on the weight of the inorganic binder.

[0109] For example, the aluminum sulfate suspension can be added to a concrete or mortar composition, in particular a shotcrete or shotcrete mortar, which is used for coating a substrate, in particular the surfaces of tunnels, mines, excavations, harbors, wells and / or drains.

[0110] It is preferred to meter the aluminum sulfate suspension into the sprayed mortar or concrete by dry or wet spraying methods, which involve adding the aluminum sulfate suspension to the anhydrous or water-mixed binder in the conveying line, pre-wetting nozzle or spray nozzle, the sprayed mortar or concrete. Addition of the aluminum sulfate suspension at the concrete construction site is also possible.

[0111] It is also possible to add the aluminium sulphate suspension to concrete or mortar compositions, in particular shotcrete or shotcrete mortar, which are used for the production of freeform structures.

[0112] In addition, the aluminum sulfate suspension can be mixed into the concrete or mortar composition in the additive production process, preferably by a dynamic mixer.

[0113] The present invention also relates to a setting accelerator and / or hardening accelerator for a composition comprising an inorganic binder (mineral binder), wherein the setting accelerator and / or hardening accelerator is preferably a shotcrete accelerator and wherein the setting accelerator and / or hardening accelerator comprises: (a) 22 to 46% by weight, more specifically 28 to 43% by weight, preferably 34 to 41% by weight, of aluminum sulfate (Al2(SO4)3); (b) optionally, 0.01 to 15% by weight, more particularly 0.05 to 5% by weight, particularly preferably 0.1 to 2% by weight, of aluminum hydroxide (Al(OH)3); (c) optionally 0.001 to 5% by weight, more particularly 0.1 to 2% by weight, in particular 0.2 to 1% by weight, of a calcium compound selected from calcium oxide and / or calcium hydroxide, or a magnesium compound selected from magnesium oxide and / or magnesium hydroxide; (d) optionally 0.001 to 10% by weight, more particularly 0.1 to 5% by weight, in particular 0.2 to 2% by weight and very particularly preferably 0.1 to 0.6% by weight of iron; (e) optionally, 0.001% to 5% by weight, preferably 0.1% to 2% by weight, and even more preferably 0.2% to 1% by weight of silicon dioxide; (f) at least one soluble alkali metal compound in which the alkali metal is selected from sodium, potassium and / or lithium, in an amount such that the atoms of the alkali metal have a proportion of 0.02 to 5% by weight, more particularly 0.05 to 3% by weight, particularly preferably 0.1 to 1.4% by weight and in particular 0.2 to 0.7% by weight, based on the total weight of the aluminium sulphate suspension; (g) optionally 0.1 to 15% by weight, preferably 0.1 to 5% by weight, in particular 0.2 to 2% by weight, of an alkanolamine; (h) optionally, 0.01 to 10 wt. %, more specifically 0.05 to 2 wt. %, preferably 0.1 to 0.5 wt. % of fluoride; and (i) water, preferably in a proportion of the remainder up to 100% by weight; Includes.

[0114] Such a solidification accelerator and / or hardening accelerator preferably has a mass ratio of alkali metal atoms to aluminum sulfate (Al2(SO4)3) of 1 mg / g to 100 mg / g.

[0115] Advantageous set accelerators and / or hardening accelerators for compositions comprising inorganic binders, where the set accelerators and / or hardening accelerators are preferably shotcrete accelerators: (a) 22 to 46% by weight, more specifically 28 to 43% by weight, preferably 34 to 41% by weight, of aluminum sulfate (Al2(SO4)3); (b) optionally, 0.01 to 15% by weight, more particularly 0.05 to 5% by weight, particularly preferably 0.1 to 2% by weight, of aluminum hydroxide (Al(OH)3); (c) optionally 0.001 to 5% by weight, more particularly 0.1 to 2% by weight, in particular 0.2 to 1% by weight, of a calcium compound selected from calcium oxide and / or calcium hydroxide, or a magnesium compound selected from magnesium oxide and / or magnesium hydroxide; (d) optionally 0.001 to 10% by weight, more particularly 0.1 to 5% by weight, in particular 0.2 to 2% by weight and very particularly preferably 0.1 to 0.6% by weight of iron; (e) optionally, 0.001% to 5% by weight, preferably 0.1% to 2% by weight, and even more preferably 0.2% to 1% by weight of silicon dioxide; (f) at least one soluble alkali metal compound in which the alkali metal is selected from sodium, potassium and / or lithium, in an amount such that the atoms of the alkali metal have a proportion of 0.02 to 5% by weight, more particularly 0.05 to 3% by weight, particularly preferably 0.1 to 1.4% by weight and in particular 0.2 to 0.7% by weight, based on the total weight of the aluminium sulphate suspension; (g) optionally 0.1 to 15% by weight, preferably 0.1 to 5% by weight, in particular 0.2 to 2% by weight, of an alkanolamine; (h) optionally, 0.01 to 10 wt. %, more specifically 0.05 to 2 wt. %, preferably 0.1 to 0.5 wt. % of fluoride; and Water, preferably with a remaining proportion of water up to 100% by weight, and wherein the mass ratio of alkali metal atoms to aluminum sulfate (Al2(SO4)3) is 1 mg / g to 100 mg / g.

[0116] Further modifications and advantages of the present invention will be apparent to those skilled in the art from the following examples.

[0117] ILLUSTRATIVE EMBODIMENTS The following materials were used in the examples below.

[0118] [Table 1-1]

[0119] The values ​​listed below for the proportions of Al2(SO4)3·approximately 14H2O include water of crystallization. Al2(SO4)3·approximately 14H2O contains 57% by weight of Al2(SO4)3. Therefore, water of crystallization is also contained in Na2CO3·H2O.

[0120] In the NaOH and sodium aluminate solutions employed, the percentages of NaOH and NaAlO2 in the values ​​given below relate only to NaOH and sodium aluminate, excluding the water in the solution, the latter being included in the H2O.

[0121] The viscosity was measured according to the standard DIN EN ISO 2431:2011 using an ISO No. 6 cup at a temperature of 23° C. or an ISO No. 4 cup at a temperature of 23° C. In the tables below, "nd" means that the viscosity was not measurable. The times listed in the tables below relate to time t=0, which is the starting point when all of the components of the mixture are combined.

[0122] The components can generally be added to the mixture in powder form or as an aqueous solution. For example, powder-form materials and aqueous aluminum sulfate suspensions are both suitable as starting materials for the aluminum sulfate.

[0123] The aluminum sulfate suspension produced according to the invention has been found to be storage stable for several months and to have a viscosity suitable for practical use as a shotcrete accelerator in the region below 2000 mPa·s. EXAMPLES

[0124] Examples 1 to 4 Preparation of an aluminum sulfate suspension containing sodium aluminate A specified amount of water was first charged into a beaker. Then, while stirring (mechanical propeller stirrer at 650 rpm), Al2(SO4)3·14H2O and sodium aluminate (0% to 4% by weight) were added in several portions in the order and proportions shown in Table 1, and the suspension was stirred at room temperature for 6 hours.

[0125] [Table 1-2]

[0126] Viscosity was measured after the specified times and the results are summarized in Table 2.

[0127] [Table 2]

[0128] As can be seen from Table 2, the viscosity of the aluminum sulfate suspension can be significantly reduced in the first hours at high aluminum sulfate contents by the addition of sodium aluminate.

[0129] Examples 5 to 8 Preparation of an aluminum sulfate suspension containing sodium aluminate The experiments were carried out in the same manner as in Examples 1-4, but the order of addition was varied as shown in Table 3.

[0130] [Table 3]

[0131] Viscosity was measured after the specified times and the results are summarized in Table 4.

[0132] [Table 4]

[0133] As can be seen from Table 4, the viscosity of the aluminum sulfate suspension can be significantly reduced in the first hours by the addition of sodium aluminate at high aluminum sulfate contents.

[0134] Examples 9 to 14 Preparation of an aluminum sulfate suspension containing sodium aluminate The experiments were carried out in the same manner as in Examples 1-4, except that the amount of sodium aluminate and the order of addition were varied as shown in Table 5.

[0135] [Table 5]

[0136] Viscosity was measured after the specified times and the results are summarized in Table 6.

[0137] [Table 6]

[0138] Examples 15 to 19 Preparation of an aluminum sulfate suspension containing sodium aluminate The experiments were carried out in the same manner as in Examples 1-4, but a different sodium aluminate (Na aluminate B) was used and the order of addition was changed as shown in Table 7.

[0139] [Table 7]

[0140] Viscosity was measured after the specified times and the results are summarized in Table 8.

[0141] [Table 8]

[0142] As can be seen from Table 8, the viscosity of the aluminum sulfate suspension can be significantly reduced in the first hours by the addition of sodium aluminate at high aluminum sulfate contents.

[0143] Examples 20 to 25 Preparation of an aluminum sulfate suspension containing sodium aluminate The experiments were carried out in the same manner as in Examples 1-4, but with different sodium aluminates (Na aluminate B), as shown in Table 9.

[0144] [Table 9]

[0145] Viscosity was measured after the specified times and the results are summarized in Table 10.

[0146] [Table 10]

[0147] As can be seen from Table 10, the viscosity of the aluminum sulphate suspension can be significantly reduced in the first hours by the addition of sodium aluminate at high aluminum sulphate contents.

[0148] Examples 26 to 31 Preparation of an aluminum sulfate suspension containing sodium aluminate The experiments were carried out in the same manner as in Examples 1-4, but a different sodium aluminate (Na Aluminate B) was used and the order of addition was changed as shown in Table 11. In addition, a higher aluminum sulfate concentration was used and a dissolver disk was used for stirring instead of a propeller agitator. In all experiments, water loss was recorded but this was not compensated for.

[0149] [Table 11]

[0150] Viscosity was measured after the specified times and the results are summarized in Table 12.

[0151] [Table 12]

[0152] As can be seen from Table 12, the viscosity of the aluminium sulphate suspension can be significantly reduced within the first hours by the addition of sodium aluminate, even at very high aluminium sulphate contents.

[0153] Examples 32 to 37 Preparation of an aluminum sulfate suspension containing sodium hydroxide The experiments were carried out in the same manner as in Examples 1-4, but instead of sodium aluminate, sodium hydroxide solution (50%) was used as the alkali metal compound, as shown in Table 13.

[0154] [Table 13]

[0155] Viscosity was measured after the specified times and the results are summarized in Table 14.

[0156] [Table 14]

[0157] As can be seen from Table 14, the viscosity of the aluminum sulfate suspension can be significantly reduced in the first hours by the addition of NaOH at high aluminum sulfate contents.

[0158] Examples 38 to 43 Preparation of aluminum sulfate suspension containing sodium carbonate The experiments were carried out in the same manner as in Examples 1-4, except that sodium carbonate was used as the alkali metal compound instead of sodium aluminate, and the order of addition was changed as shown in Table 15.

[0159] [Table 15]

[0160] Viscosity was measured after the specified times and the results are summarized in Table 16.

[0161] [Table 16]

[0162] As can be seen from Table 16, the viscosity of the aluminum sulfate suspension can be significantly reduced in the first hours by the addition of Na2CO3 at high aluminum sulfate contents.

[0163] Examples 44 to 49 Preparation of an aluminum sulfate suspension containing potassium hydroxide The experiments were carried out in the same manner as in Examples 1-4, except that potassium hydroxide was used as the alkali metal compound instead of sodium aluminate, and the order of addition was changed as shown in Table 17.

[0164] [Table 17]

[0165] Viscosity was measured after the specified times and the results are summarized in Table 18.

[0166] [Table 18]

[0167] As can be seen from Table 18, the viscosity of the aluminum sulfate suspension can be significantly reduced in the first hours by the addition of KOH at high aluminum sulfate contents.

[0168] Examples 50 to 55 Preparation of an aluminum sulfate suspension containing lithium hydroxide The experiments were carried out in the same manner as in Examples 1-4, except that lithium hydroxide was used as the alkali metal compound instead of sodium aluminate, and the order of addition was changed as shown in Table 19.

[0169] [Table 19]

[0170] Viscosity was measured after the specified times and the results are summarized in Table 20.

[0171] [Table 20]

[0172] As can be seen from Table 20, the viscosity of the aluminum sulfate suspension can be significantly reduced in the first hours by the addition of LiOH at high aluminum sulfate contents.

[0173] Examples 56 to 61 Preparation of aluminum sulfate suspension containing potassium bicarbonate The experiments were carried out in the same manner as in Examples 1-4, except that potassium bicarbonate was used as the alkali metal compound instead of sodium aluminate, and the order of addition was changed as shown in Table 21.

[0174] [Table 21]

[0175] Viscosity was measured after the specified times and the results are summarized in Table 22.

[0176] [Table 22]

[0177] As can be seen from Table 22, the viscosity of the aluminum sulphate suspension can be significantly reduced in the first hours at high aluminum sulphate contents by the addition of potassium bicarbonate.

[0178] Summary of Results As can be seen from the examples, the viscosity of aluminum sulphate suspensions, even with high aluminum sulphate contents, can be significantly reduced in the first hours by the addition of soluble alkali metal compounds, in particular avoiding the spike in viscosity that usually occurs at the start.

[0179] Thus, the soluble alkali metal compounds can be used to control the viscosity of the aluminum sulfate suspension. The order and division of addition of the components is not critical.

[0180] All experiments were carried out at room temperature. As is known, viscosity reduction can generally be achieved by heating, but this is undesirable due to the time and energy required. The use of soluble alkali metal compounds according to the present invention means that heating to lower temperatures is sufficient or heating can be avoided altogether.

[0181] In addition, it has been found that the viscosity of the aluminum sulfate suspension thus produced can be maintained for more than three months without significant change.

[0182] The above described aluminum sulfate suspension has been found to be an excellent accelerator for shotcrete and shotcrete mortar.

[0183] While the above-described embodiments of the invention are preferred, it will be apparent that the invention is not limited to these embodiments and can be modified as desired within the scope of the present disclosure.

Claims

1. 1. Use of at least one soluble alkali metal compound for adjusting, more particularly reducing, the viscosity of an aluminum sulphate suspension, said alkali metal being selected from sodium, potassium and / or lithium.

2. 2. Use according to claim 1, wherein the aluminium sulphate suspension is a setting and / or hardening accelerator for compositions comprising mineral binders, the aluminium sulphate suspension being preferably a shotcrete accelerator.

3. 2. The use according to claim 1, wherein the alkali metal compound is an aluminate, oxide, hydroxide, carbonate, hydrogencarbonate, nitrate, sulfate, phosphate, halide, formate, citrate, thiocyanate, silicate and / or acetate.

4. 2. The use according to claim 1, wherein the alkali metal compound is selected from sodium aluminate, sodium carbonate, sodium bicarbonate, sodium oxide, sodium hydroxide, potassium aluminate, potassium carbonate, potassium bicarbonate, potassium oxide, potassium hydroxide, lithium aluminate, lithium carbonate, lithium bicarbonate, lithium oxide, lithium hydroxide or mixtures thereof.

5. 2. Use according to claim 1, in which the amount of the at least one alkali metal compound is selected so that the atoms of the alkali metal have a proportion of 0.02 to 5% by weight, more particularly 0.05 to 3% by weight, particularly preferably 0.1 to 1.4% by weight and in particular 0.2 to 0.7% by weight, based on the total weight of the aluminium sulphate suspension.

6. The aluminum sulfate suspension contains from 19 to 40% by weight, more particularly from 24 to 36% by weight, in particular from 28 to 34% by weight, of sulfate (SO 2 ), based on the total weight of the aluminum sulfate suspension. ４ － 2. Use according to claim 1, in which the aluminium sulphate suspension has a proportion of aluminium (Al) of 3.5 to 10% by weight, more particularly 4.5 to 8.7% by weight and in particular 5.4 to 7% by weight, based on the total weight of the aluminium sulphate suspension.

7. The aluminum sulfate suspension preferably contains 22 to 46 wt. %, more particularly 28 to 43 wt. %, preferably 34 to 41 wt. % aluminum sulfate (Al ２ (SO ４ ) ３ 2. The use according to claim 1, comprising

8. 2. Use according to claim 1, wherein the aluminium sulphate suspension contains 0.01 to 15% by weight, preferably 0.1 to 5% by weight, in particular 0.2 to 2% by weight, of aluminium hydroxide, based on the total weight of the aluminium sulphate suspension.

9. 2. Use according to claim 1, in which the molar ratio of aluminium to sulphate in the aluminium sulphate suspension is 0.9 or less, preferably 0.85 or less, more preferably 0.8 or less, even more preferably 0.74 or less, very particularly preferably 0.7 or less, in particular a molar ratio of aluminium:sulphate of 2:

3.

10. 2. Use according to claim 1, wherein the aluminium sulphate suspension further comprises from 0.1 to 15% by weight, preferably from 0.1 to 5% by weight and in particular from 0.2 to 2% by weight of an alkanolamine, based on the total weight of the aluminium sulphate suspension, the alkanolamine used being advantageously monoethanolamine, diethanolamine, triethanolamine and / or methyldiisopropanolamine.

11. 2. Use according to claim 1, wherein the alkali metal compound is added in powder form or as an aqueous solution to the aluminium sulphate suspension or during the production of the aluminium sulphate suspension.

12. The use according to any one of claims 1 to 11, wherein the alkali metal compound is used in combination with a calcium or magnesium compound to reduce the viscosity.

13. 13. The use according to claim 12, wherein the calcium or magnesium compound is an oxide, hydroxide, carbonate, nitrate, sulfate, phosphate, halide, formate, acetate and / or citrate.

14. 13. The use according to claim 12, wherein the calcium compound is calcium carbonate, calcium oxide and / or calcium hydroxide and the magnesium compound is magnesium carbonate, magnesium oxide and / or magnesium hydroxide.

15. 13. Use according to claim 12, in which the amount of calcium or magnesium compound is selected such that calcium or magnesium atoms have a proportion of 0.001 to 4% by weight, preferably 0.01 to 2% by weight, more particularly 0.07 to 1.4% by weight, in particular 0.1 to 0.7% by weight, based on the total weight of the aluminium sulphate suspension.

16. A setting accelerator and / or hardening accelerator for a composition comprising a mineral binder, said setting accelerator and / or hardening accelerator being preferably a shotcrete accelerator, Setting and / or hardening accelerators for compositions containing mineral binders: (a) 22 to 46 wt. %, more specifically 28 to 43 wt. %, preferably 34 to 41 wt. % aluminum sulfate (Al ２ (SO ４ ) ３ ; (b) optionally, 0.01 to 15 wt. %, more particularly 0.05 to 5 wt. %, and particularly preferably 0.1 to 2 wt. % aluminum hydroxide (Al(OH) ３ ). (c) optionally 0.001 to 5% by weight, more particularly 0.1 to 2% by weight, in particular 0.2 to 1% by weight, of a calcium compound selected from calcium oxide and / or calcium hydroxide, or a magnesium compound selected from magnesium oxide and / or magnesium hydroxide; (d) optionally 0.001 to 10% by weight, more particularly 0.1 to 5% by weight, in particular 0.2 to 2% by weight, very particularly preferably 0.1 to 0.6% by weight, of iron; (e) optionally, 0.001% to 5% by weight, preferably 0.1% to 2% by weight, and even more preferably 0.2% to 1% by weight of silicon dioxide; (f) at least one soluble alkali metal compound, in which the alkali metal is selected from sodium, potassium and / or lithium, in an amount in which the atoms of said alkali metal have a proportion of 0.02 to 5% by weight, more particularly 0.05 to 3% by weight, particularly preferably 0.1 to 1.4% by weight and in particular 0.2 to 0.7% by weight, based on the total weight of the aluminium sulphate suspension; (g) optionally 0.1 to 15% by weight, preferably 0.1 to 5% by weight, especially 0.2 to 2% by weight, of an alkanolamine; (h) optionally, 0.01 to 10 wt. %, more specifically 0.05 to 2 wt. %, preferably 0.1 to 0.5 wt. % fluoride; and (i) Water, preferably with the balance up to 100% by weight.

17. 17. The set accelerator and / or hardening accelerator according to claim 16, wherein the alkali metal compound is selected from sodium aluminate, sodium carbonate, sodium bicarbonate, sodium oxide, sodium hydroxide, potassium aluminate, potassium carbonate, potassium bicarbonate, potassium oxide, potassium hydroxide, lithium aluminate, lithium carbonate, lithium bicarbonate, lithium oxide, lithium hydroxide or mixtures thereof.