Construction materials based on inorganic binders containing a synergistically effective combination of hydrophobizing agents

Abstract

The present invention relates to a construction material based on inorganic binders comprising a synergistically effective hydrophobizing mixture. The present invention also relates to a method for processing such a construction material and to the use of the synergistically effective mixture for hydrophobizing a construction material based on inorganic binders.

Description

Technical Field

[0001] The present invention relates to construction materials based on inorganic binders containing synergistically effective hydrophobic mixtures. The present invention also relates to a method for processing such construction materials and to the use of synergistically effective mixtures for hydrophobizing construction materials based on inorganic binders.

Background Art

[0002] Construction materials based on inorganic binders, for example those made from clay, cement and plaster, are extremely common worldwide. Gypsum, in the form of hydraulic calcium sulfate such as α - and β - hemihydrate, or in the form of anhydrite I, II or III, is a very common building raw material and is used in a plurality of different formulations for different applications, for example, gypsum plasterboard in drywall installations, lime plastering for indoor use, tile adhesives, flooring areas, and in segments for handymen or Sunday DIYers.

[0003] Many construction materials based on inorganic binders are very sensitive to fluids in that they readily absorb water and other liquids. In particular, calcium sulfate (i.e., gypsum) building materials are very sensitive to water, which has hindered their frequent use in outdoor applications or in moisture-rich rooms with increased atmospheric moisture such as wet units or bathrooms. To overcome this problem, many efforts have been made to formulate construction materials based on inorganic binders such that the product becomes more hydrophobic or is provided with a hydrophobic coating, thereby obtaining a reduction in water absorption and / or an increase in water resistance.

[0004] To meet these unsolved requirements, various techniques for using liquid silicon-based compounds such as silanes, siloxanes, alkoxysilanes and / or organosilanes as hydrophobic components to obtain increased water resistance have been described, where a catalyst can be used and / or treatment can be carried out at an acidic or alkaline pH.

[0005] For example, European Patent Application Publication No. 1698602 (A1) describes a gypsum mixture having improved mechanical properties and hydrophobic properties, the gypsum mixture comprising at least one alkoxysilane and / or alkoxy-functionalized polysilane and a homogeneously dispersed additive consisting of a mineral acid and at least one salt of a metal of subgroups IIIB - VIII, IB or IIB, where the metal salt hardly catalyzes the silanol condensation. For the preparation of the gypsum mixture, the silane component and the metal salt are first mixed with water, and then a commercially available building gypsum is introduced into the aqueous mixture to prepare a gypsum paste.

[0006] Thus, silicone additives provide the desired hydrophobic effect, but one of the drawbacks of their use is that the silicone additive content required to provide the desired degree of hydrophobicity is relatively high. This is a significant cost factor because they are relatively expensive and relatively large amounts are required for building materials.

[0007] Another class of hydrophobizing agents frequently used with gypsum-containing building materials are the salts of fatty acids, whose water-repellent effect is based on their amphiphilic molecular properties. This compound consists of a hydrophobic non-polar hydrocarbon moiety and a hydrophilic polar end group (metal cation). When such a hydrophobizing agent is dispersed in water, the polar hydrophilic head of the molecule is attracted to the charged surface of the inorganic matter and adsorbs itself thereto, while the non-polar hydrophobic tail of the molecule protrudes outward and repels water. Thereby, a protective layer excellent in adhesion and water repellency is formed.

[0008] Fatty acids are more abundant and less expensive hydrophobic materials, but compared to silicon-based hydrophobizing agents, they do not provide the same hydrophobicity at equivalent contents in gypsum compositions, and there is concern that higher contents of fatty acid hydrophobizing agents may have an unfavorable impact on the processability and / or mechanical properties of the resulting gypsum compositions.

[0009] Other hydrophobizing agents proposed for gypsum compositions include peat products (see, for example, Misnikov O., "The hydrophobic modification of gypsum binder by peat products: physico-chemical and technological basis", Mires and Peat, Volume 21 (2018), pp. 1-14), and mixtures of redispersible powders and thixotropic agents as described in German Patent Application Publication No. 19506398 (A1).

[0010] Based on this state of the art, there is a need for a hydrophobizing agent that is particularly suitable for improving construction materials based on inorganic binders, can be used at relatively low additive concentrations to avoid changes in the mechanical properties of the product, while providing a high hydrophobic effect at low cost. This application addresses these needs.

DETAILED DESCRIPTION OF THE INVENTION

[0011] Surprisingly, in the research underlying the present invention, it has been found that the combination of a silicon-based hydrophobizing agent and a fatty acid salt-based hydrophobizing agent provides a synergistic interaction between the two hydrophobizing agents. Also, the combination of a silicon-based hydrophobizing agent and a salt or compound that provides a hydroxide provides a synergistic hydrophobizing interaction. Construction materials based on inorganic binders show a significant reduction in water uptake when part of the silicon-based hydrophobizing agent is replaced by a fatty acid salt-based hydrophobizing agent. Similarly, these construction materials show a significant reduction in water uptake when a salt or compound that provides a hydroxide is present in the construction material. In particular, the water uptake on the surface of these construction materials is reduced. Since the mixture of the hydrophobizing agent, the inorganic binder, and any additives can be formed mainly or completely from solid components, it is possible to provide, for example, a primer or plaster in solid form at the construction site, and the material can be processed by simply adding the required amount of water without the need for complex dosing of the hydrophobizing agent. Similarly, a mixture of the hydrophobizing agent, the inorganic binder, any additives, and water can be blended, for example, into a slurry and subsequently formed into building panels.

[0012] Accordingly, in a first aspect, the present invention provides a construction material based on an inorganic binder, comprising a synergistically effective mixture of an inorganic binder, a silicon-based hydrophobizing agent, and a fatty acid salt-based hydrophobizing agent or a corresponding precursor of the fatty acid salt-based hydrophobizing agent.

[0013] The inorganic binders according to the present invention include all particulate building materials in which the inorganic binder in dry / powder form can physically or preferably chemically harden when mixed with a fluid, for example water. Chemical hardening includes chemical reactions (e.g., hydration), and physical hardening can be, for example, drying. The inorganic binder can be a calcium sulfate-containing binder, such as gypsum, and its partially dehydrated forms, i.e., α- or β-hemihydrate (stucco) or anhydrite. The inorganic binder can also be lime, clay or cement binders (e.g., Portland cement, Portland cement blend, other kiln cements, calcium aluminate or calcium sulfoaluminate, magnesia cement, magnesium oxychloride cement, belite cement), and combinations thereof or can include them. The inorganic binder can be a hydraulic binder (e.g., cement, pozzolan, hydraulic lime, calcium sulfate hemihydrate or anhydrite, calcium silicate, clinker, fly ash), or a non-hydraulic binder (e.g., clay, non-hydraulic lime, water glass). Hydraulic binders harden by hydration, while non-hydraulic binders require, for example, exposure to carbon dioxide for hardening. Construction materials based on inorganic binders can further include various additives known to those skilled in the art, such as fillers, accelerators, retarders, rheology modifiers, hydrophobizing agents, refractory materials, etc. Apart from hardening, the manufacturing method of construction materials based on inorganic binders can further include a drying step.

[0014] In the case of calcium sulfate as an inorganic binder, the dehydrated forms (α- and β-hemihydrates and anhydrite) are rehydrated in the presence of water. In this hardening process, calcium sulfate dihydrate (i.e., gypsum) is formed. Calcium sulfate dihydrate crystals are linked and thus provide strength, but excess water needs to evaporate further for complete hardening of the material.

[0015] The term "construction material based on inorganic binder" in the present invention encompasses a processable / formable mixture containing an inorganic binder, as well as a cured / solidified mixture containing an inorganic binder. The cured / solidified mixture includes formed objects such as building boards (e.g., plasterboard or cement board), bricks, installed primers (e.g., installed plaster), installed mortars, installed fillers, installed joint compounds or installed screeds. The processable / formable mixture includes objects that have not yet been formed (i.e., powder mixtures), such as primers (e.g., plaster), mortars, fillers, joint compounds or screeds.

[0016] In this construction material, the term "synergistically effective mixture" is intended to indicate that the mixture provides better hydrophobic performance (e.g., a lower average total absorption rate with respect to water when measured according to EN 520:2004 5.9.2) than would be expected for the mixture based on the respective performance of any one of the components alone (the composition of the construction material being the same except for the components of the synergistically effective mixture). That is, for example, in the case of a synergistically effective mixture of hydrophobic agents, a silicon-based hydrophobic agent at a concentration of 0.5 wt% based on the weight of the construction material provides an average total absorption rate of 5% in the composition, a fatty acid salt-based hydrophobic agent at a concentration of 0.5 wt% provides an average total absorption rate of 15% in this composition, and a combination of the two (a total of 0.5 wt% of hydrophobic agent) in a 1:1 mixture would be expected to provide an average total absorption rate of 10%. The average total absorption rate of the synergistically effective mixture will be less than 10%.

[0017] Construction materials based on inorganic binders generally include mixtures of materials and can thus have chemically diverse surfaces and chemically diverse voids (e.g., capillary pores or larger non-capillary pores). Different types of functional groups, ions or defects may be present that can have different affinities for hydrophobizing agents. Without being bound by theory, synergistically effective mixtures are thought to utilize the heterogeneous chemical structure of the construction material, in particular the heterogeneous chemical structure of its voids, since they address the above-mentioned different affinities.

[0018] Typically, the hydrophobizing agents according to the invention are powder or particulate compositions. Precursors of fatty acid salt-based hydrophobizing agents, i.e., fatty acids or their esters, can be in the form of fats, free fatty acids or emulsions in one or both forms.

[0019] The term "fatty acid salt-based hydrophobizing agent or precursor of a fatty acid salt-based hydrophobizing agent" is intended to mean that this hydrophobizing agent is either a fatty acid salt or a fatty acid or its ester. Fatty acids or their esters can precipitate as fatty acid salts in the presence of monovalent, divalent or trivalent cations, and / or alkali salts or compounds providing each cation. The salts or compounds providing the cations may already be present in the construction material mixture or may be added only for this purpose. The cations necessary to form salts with fatty acids or their esters can be present in solution or on the surface of the inorganic phase. Suitable cations can preferably be selected from Na + , NH + , Ca 2+ , Mg 2+ , Zn 2+ , Fe 2+ , Fe 3+ and / or Al 3+ and suitable salts or compounds can preferably be Na + , NH + , Ca 2+ , Mg 2+ , Zn 2+ , Fe 2+ , Fe 3+ and / or Al 3+can contain a cation selected from

[0020] By monovalent, divalent or trivalent with respect to the cation of the salt is meant a cation having 1, 2 or 3 positive charges respectively, and a cation is considered "charged" when the atoms thereof have a lower electronegativity than the atoms to which they are bonded.

[0021] With respect to the silicon-based hydrophobizing agent, the present invention is not subject to any relevant restrictions, i.e., the silicon-based hydrophobizing agent can be in any form already described in the prior art with respect to silicon-based hydrophobizing agents in connection with structures containing non-organic inorganic binders. Particularly preferred silicon-based hydrophobizing agents include silanes, siloxanes including silsesquioxanes, and / or silicones.

[0022] Among silanes, alkoxysilanes are preferred. Particularly effective silanes for use as hydrophobizing agents have the general structure R 1 Si(OR 2 )3 and / or (R 1 )2Si(OR 2 )2, R 1 [wherein each R 1 and R 2 may be the same or different], and among them, R 1 Si(OR 2 )3 is preferred. Even more preferably, R 1 is C1-C6, most preferably C1-C4-alkyl, and R 2 are, independently of each other, C1-C3 alkyl optionally containing one or more hydroxyl groups, or a condensation product thereof. In this regard, it has been observed that shorter carbon chains as R 1 provide a better hydrophobizing effect compared to longer chains, and thus alkyls such as propyl (n- and iso), ethyl and methyl are particularly preferred as R 1 , and most preferably methyl.

[0023] In the process of providing a hydrophobic effect, OR 2 groups are hydrolyzed to SiOH, so R 2 groups are not very important for the performance of the silane as a hydrophobizing agent. However, in order to provide good stability of the hydrolyzed alcohol (HOR 2 ) in water, the alcohol should be sufficiently hydrophilic. Particularly preferred residues R 2 are methyl, ethyl, and moieties derived from glycols, such as hydroxyethyl, 2- or 3-hydroxypropyl, and 2,3-dihydroxypropyl.

[0024] A particularly preferred hydrophobizing agent based on silane is propyltrimethoxysilane. Another particularly preferred hydrophobizing agent based on silane is methylsilane where OR2 is ethylene glycol, and ethylene glycol may be present as OCH2CH2OH or may form a crosslink (as Si-OCH2CH2O-Si) between two Si atoms.

[0025] As will be apparent to those skilled in the art, the partial condensation products of the above silanes can be siloxanes (i.e., silicon-containing compounds having oxygen bridges, i.e., Si-O-Si bridges, preferably having 1, 2, 3, or 4 oxygen bridges). A particularly preferred group of silicon-based hydrophobizing agents is alkylsiloxanes, particularly methylsiloxanes or the corresponding silsesquioxanes.

[0026] Another type of preferred silicon-based hydrophobizing agent is silicone, which in the context of the present invention includes both silicones having alkyl groups and silicones having hydrogen bonded to the silicone. A particularly preferred silicone having bonded hydrogen is polymethylhydrogensiloxane, which preferably has terminal trimethylsiloxy groups.

[0027] The silicon-based hydrophobizing agent may contain only silicon compounds, but when used in dry form, it may also include silicon compounds that are coated on a carrier material and can be formulated together with a dispersion aid. It should be noted that when calculating the weight of the hydrophobizing agent for the purposes of the present invention, for example, the solvent of the dispersion of the hydrophobizing agent is not taken into account.

[0028] For the purposes of the present invention, commercially available silicon-based hydrophobizing agents, such as those of the Silres series by Wacker Chemie AG, in particular Silres Powder E, are particularly preferred. Other preferred commercially available silicon-based hydrophobizing agents are those of the DOWSIL™ series by Dow Chemical, in particular those containing DOWSIL™ GP SHP 50.

[0029] The content of the silicon-based hydrophobizing agent is usually in the range of 0.01 to 4.99% by weight, preferably in the range of 0.02 to 0.98% by weight, and most preferably in the range of 0.1 to 0.7% by weight, based on the dry weight of the construction material.

[0030] The fatty acid salt-based hydrophobizing agent is not subject to any significant restrictions. Each fatty acid forming the fatty acid salt-based hydrophobizing agent may be saturated or unsaturated. Preferably, the fatty acid in the fatty acid salt hydrophobizing agent is a C4-C 30 fatty acid, more preferably a C8-C 24 fatty acid, even more preferably a C 12 -C 22 fatty acid, or a mixture of such acids.

[0031] Exemplary suitable unsaturated fatty acids include, for example, palmitoleic acid, vaccenic acid, eicosenoic acid, cetoleic acid, linoleic acid, linolenic acid and oleic acid, with oleic acid being particularly preferred. Exemplary suitable saturated fatty acids include lauric acid, myristic acid, pentadecanoic acid, palmitic acid, margaric acid, nonadecanoic acid, arachidic acid, behenic acid, lignoceric acid, cerotic acid, montanic acid, melissic acid and stearic acid, with stearic acid being particularly preferred.

[0032] As described above, the fatty acid salt-based hydrophobing agent does not necessarily have to be used directly as a fatty acid, and may be used as a salt with a monovalent, divalent or trivalent cation. Particularly suitable monovalent, divalent or trivalent cations for the fatty acid salt-based hydrophobing agent are Na + 、NH + 、Ca 2+ 、Mg 2+ 、Zn 2+ 、Fe 2+ 、Fe 3+ and / or Al 3+ included. In a particularly preferred embodiment of the present invention, the monovalent or divalent cation of the fatty acid salt-based hydrophobing agent (i.e., soap) is Na + and / or Ca 2+ . The fatty acid salt-based hydrophobing agent may include salts of unsaturated fatty acids, such as linoleate, linolenate, oleate, ricinoleate, and / or salts of saturated fatty acids, such as laurate, myrestate, palmitate, stearate, and / or naphthenate, resinate or tallate. In a particularly preferred embodiment of the present invention, the fatty acid salt-based hydrophobing agent includes sodium oleate and / or calcium stearate.

[0033] In one preferred embodiment, the construction material of the present invention includes an unsaturated fatty acid salt-based hydrophobing agent, a saturated fatty acid salt-based hydrophobing agent, and a silicon-based hydrophobing agent. Preferably, in such a construction material, the ratio of unsaturated fatty acid to saturated fatty acid is about 3:1 to 1:3, more preferably about 2:1 to 1:2, and even more preferably about 1:1.

[0034] As described above, the construction material of the present invention can include a precursor of a fatty acid salt-based hydrophobizing agent as a partial or complete substitute for a fatty acid salt. In a preferred embodiment, this precursor of the hydrophobizing agent includes a fatty acid or its ester. These precursors can combine with a salt or compound that provides a cation to form a fatty acid-based hydrophobizing agent in situ. Also, the fatty acid salt-based hydrophobizing agent can exchange its cation. Thus, it can also combine with a salt or compound that provides a cation. The salt or compound that provides a cation can include a monovalent, divalent, or trivalent cation. Particularly suitable monovalent, divalent, or trivalent cations are Na + , NH + , Ca 2+ , Mg 2+ , Zn 2+ , Fe 2+ , Fe 3+ and / or Al 3+ . Alternatively, or in addition thereto, the salt or compound that may be suitable for supplying a cation for the fatty acid or its ester can be an alkaline earth metal salt or compound, aluminum hydroxide, zinc hydroxide, iron hydroxide, or Portland cement. As described above, these salts or compounds that provide a cation can also exchange with the existing cation and combine with the fatty acid salt-based hydrophobizing agent. Preferred alkaline earth metal salts or compounds are alkaline earth metal oxides (e.g., calcium oxide) and / or alkaline earth metal hydroxides (e.g., calcium hydroxide, magnesium hydroxide). A particularly preferred alkaline earth metal hydroxide for supplying a cation to the precursor of the fatty acid salt hydrophobizing agent is calcium hydroxide. Fatty acids generally have a higher affinity for polyvalent cations. When present, calcium cations are particularly preferred. This also means that a fatty acid salt-based hydrophobizing agent having a monovalent cation can easily exchange its monovalent cation, for example, with a calcium cation, in situ.

[0035] The content of the fatty acid salt-based hydrophobing agent is usually in the range of 0.01 to 4.99% by weight, preferably in the range of 0.02 to 0.98% by weight, and most preferably in the range of 0.1 to 0.7% by weight, based on the dry weight of the construction material. Alternatively, or in addition thereto, the silicon-based hydrophobing agent and the fatty acid salt-based hydrophobing agent can be incorporated at a weight ratio of 0.5 to 5:1, preferably 0.5 to 2:1.

[0036] In addition, the total content of all the hydrophobing agents in the construction material of the present invention can be 0.02 to 5% by weight, preferably 0.04 to 1% by weight, more preferably 0.2 to 0.8% by weight, based on the dry weight of the construction material. The total content of all the hydrophobing agents can refer to the total content of the silicon-based hydrophobing agent and the fatty acid salt-based hydrophobing agent, or only the silicon-based hydrophobing agent when the fatty acid salt-based hydrophobing agent is absent.

[0037] In the research underlying the present invention, it has been found that when a salt or compound providing a hydroxide containing preferably a monovalent, divalent or trivalent cation is incorporated in an amount such that it is present in a weight ratio of 2:1 to 20:1, preferably 5:1 to 16:1, based on the total weight of the silicon-based and fatty acid salt-based hydrophobing agents, the hydrophobing effect can be enhanced. More preferably, this salt or compound is an alkaline earth metal oxide or hydroxide, aluminum hydroxide, hydrated borate, hydrated phosphate, hydrated silicate, hydrated aluminosilicate, Portland cement or precipitated silica. When the salt or compound providing the hydroxide is an alkaline earth metal oxide or hydroxide, it is generally preferred that it is present in excess over the amount necessary to completely convert the (reactive) fatty acid salt or its precursor into the respective alkaline earth metal fatty acid salt. Most preferably, the alkaline earth metal oxide or hydroxide is selected from calcium oxide, calcium hydroxide or magnesium hydroxide. Since the oxide can react to form a hydroxide in an aqueous solution, it can provide hydroxide anions. In a particularly preferred embodiment, the salt providing the hydroxide is calcium hydroxide (Ca(OH)2).

[0038] Alternatively, the construction material based on an inorganic binder comprises an inorganic binder and a synergistically effective mixture of a salt or compound providing a hydroxide and a silicon-based hydrophobizing agent in a weight ratio of 2:1 to 20:1, preferably 5:1 to 16:1. Surprisingly, the combination of the salt or compound providing a hydroxide and the silicon-based hydrophobizing agent provides a hydrophobizing performance (e.g., a lower average total absorption rate with respect to water when measured according to EN 520:2004 5.9.2) better than the hydrophobizing performance expected for the silicon-based hydrophobizing agent alone. Preferably, this construction material can further comprise a fatty acid salt-based hydrophobizing agent or a precursor of a fatty acid salt-based hydrophobizing agent. Alternatively, or in addition thereto, the salt or compound providing a hydroxide in the above embodiments may be an alkaline earth metal oxide or hydroxide, aluminum hydroxide, hydrated borate, hydrated phosphate, hydrated silicate, hydrated aluminosilicate, Portland cement or precipitated silica. Preferably, the alkaline earth metal oxide or hydroxide may be calcium hydroxide, reactive calcium oxide or magnesium hydroxide. More preferably, the salt providing a hydroxide is calcium hydroxide (Ca(OH)2). Any applicable combination, as well as the foregoing preferred embodiments, is considered to be described for this alternative form.

[0039] Regarding the inorganic binder forming the basis of the construction material of the present invention, the present invention is not significantly limited and any conventional binder known to those skilled in the art can be used. A preferred inorganic binder for use in the present invention is a hydraulic binder. Preferably, the hydraulic binder comprises a calcium sulfate-based binder and / or a cement binder, and most preferably, the calcium sulfate-based binder comprises more than 60% by weight, preferably more than 80% by weight, more preferably more than 95% by weight of calcium sulfate based on the total weight of the inorganic binder. When the inorganic binder is based on calcium sulfate, the processable / formable mixture comprises α- and / or β-hemihydrate and / or anhydrite, while the cured / solidified mixture comprises >90% calcium sulfate dihydrate (i.e., gypsum) based on the total amount of calcium sulfate.

[0040] Depending on the composition, the construction material may contain an inorganic binder in a relatively wide range of contents, such as 10 to 98% by weight of the total weight of the construction material. In one embodiment, the content of the inorganic binder in the construction material is in the range of 10 to 50% by weight, particularly 15 to 40% by weight. In another embodiment, the content of the inorganic binder in the construction material is in the range of 60 to 98% by weight, particularly 70 to 95% by weight.

[0041] In addition to the above essential components, the construction material of the present invention may contain further additives to adjust or optimize one or more of its mechanical or processing properties. Such additives include, but are not limited to, retention modifiers, rheology modifiers, fillers, curing modifiers, pigments, dyes, fluxing agents, fibers (e.g., made from cellulose or synthetic materials or inorganic fibers), dispersible powders, adhesion promoting additives, thixotropic agents, antioxidants, resins, processing agents or elasticity imparting additives.

[0042] Possible fillers include, for example, rock powder or mineral powder, such as limestone filler, sand, such as silica sand, particularly those having a size of <2 mm, split, calcium sulfate dihydrate powder, perlite, vermiculite and zeolite. Depending on the content of the other components and the intended use, the filler can be used in a content of up to about 90% by weight (i.e., up to 88.98% by weight) of the composition.

[0043] Possible water retention modifiers or rheology modifiers include etherified polysaccharides, such as methylcellulose or methyl 2-hydroxyethylcellulose, polyglycol, polyacrylamide, natural clay and chemically modified clay. Such agents are usually used in an amount of up to 1% by weight, preferably up to 0.5% by weight, of the total construction material.

[0044] Possible hardening time adjusters include, for example, inorganic acids or their salts, phosphates, amino acids, degraded polyamides, such as those chlorinated with calcium, sugars, such as sugar salts, such as sodium gluconate, sulfates of Na, K, ammonium and Al, or finely divided calcium sulfate dihydrate. The hardening time adjuster is usually used in a total amount of up to 1% by weight, preferably up to 0.5% by weight, based on the dry weight of the construction material.

[0045] A typical composition for the construction material of the present invention containing calcium sulfate as an inorganic binder (all compounding ingredient contents are given on a dry basis based on the total dry weight of the construction material) can be as follows: - 10 to 98% by weight, preferably 20 to 80% by weight, of calcium sulfate binder, i.e., calcium sulfate anhydrite and / or alpha / beta calcium sulfate hemihydrate; - 1 to 15% by weight, preferably 2 to 10% by weight, of calcium hydroxide (or, for example, reactive calcium oxide, magnesium hydroxide, aluminum hydroxide, hydrated borate, hydrated phosphate, hydrated silicate, hydrated aluminosilicate, Portland cement or precipitated silica); - 0.01 to 4.99% by weight, preferably 0.02 to 0.98% by weight, of fatty acid salt-based hydrophobing agent, and 0.01 to 4.99% by weight, more preferably 0.02 to 0.98% by weight, of silicon-based hydrophobing agent (the total amount of hydrophobing agents is in the range of 0.02 to 5% by weight); - Up to 1% by weight of water retention adjuster or rheology modifier (for example, etherified polysaccharides, polyglycols, polyacrylamide, natural clay, chemically modified clay); - Up to 88.98% by weight of inorganic filler (for example, quartz or limestone sand, quartz or limestone powder, gypsum powder, perlite, vermiculite, zeolite); - Up to 1% by weight of hardening adjuster (i.e., retarder and accelerator, for example, organic acids or their salts, phosphates, amino acids, sugars, Na + / K + / NH4 + / Al 3+ sulfate, finely divided calcium sulfate dihydrate).

[0046] The construction materials of the present invention can be manufactured, (i) mixing water with an inorganic binder, a synergistically effective mixture of a silicon-based hydrophobizing agent and a fatty acid salt-based hydrophobizing agent or its corresponding precursor, and optional additional additives; (ii) shaping the construction materials; (iii) curing the construction materials; and including.

[0047] Alternatively, the construction materials of the present invention can be manufactured, (i) mixing water with an inorganic binder, a synergistically effective mixture of a salt or compound providing a hydroxide and a silicon-based hydrophobizing agent in a ratio of 2:1 to 20:1, and optional additional additives; (ii) shaping the construction materials; (iii) curing the construction materials; and including.

[0048] In the above method, the synergistically effective mixture in step (i) may further include a fatty acid salt-based hydrophobizing agent or a precursor of the fatty acid salt-based hydrophobizing agent.

[0049] The construction materials manufactured according to the described method can be boards or primers or screeds.

[0050] In a further aspect, the construction materials of the present invention can have an average total absorption rate of 10% or less, preferably 4% or less, more preferably 3.5% or less when measured according to EN520:2004, 5.9.2.

[0051] In a further aspect, the present invention relates to the use of a synergistically effective mixture of a silicon-based hydrophobizing agent and a fatty acid salt-based hydrophobizing agent precursor of a fatty acid salt-based hydrophobizing agent to achieve an average total absorption rate of 10% or less, preferably 4% or less when measured according to EN520:2004, 5.9.2 in the hydrophobization of construction materials based on inorganic binders.

[0052] Alternatively, the present invention relates to the use of a synergistically effective mixture of a silicon-based hydrophobizing agent and a salt or compound providing a hydroxide for achieving an average total absorption rate of 10% or less, preferably 4% or less when measured according to EN520:2004, 5.9.2 in the hydrophobization of construction materials based on inorganic binders.

[0053] Any of the above embodiments and alternatives are considered to be described in combination thereof, even if the combination is not explicitly mentioned, provided that the alternatives or embodiments do not clearly contradict each other.

[0054] The present invention will be further illustrated by the following examples, which should not be construed as having any limiting meaning for the present invention.

Examples

[0055] The plaster composition was formulated from calcium sulfate hemihydrate as an inorganic binder, a rheology modifier, a setting modifier and a filler by adding an appropriate amount of water to provide the required fluidity. An exemplary composition for Sample 6 is shown in Table 1.

[0056]

Table 1

[0057] Except for the hydrophobing agent and calcium hydroxide, all other samples have the same composition as Sample 6 shown in Table 1. This same composition is summarized as "plaster composition" in the first column of Table 2. The only other exceptions are Samples 1 and 8 where the total amount of the plaster composition is different. In both samples, the difference in the amount of the plaster composition is due only to the difference in the amount of calcium sulfate hemihydrate. Table 2 focuses on the components that were varied, namely calcium hydroxide (Ca(OH)₂), the silicon-based hydrophobing agent, and the fatty acid salt-based hydrophobing agent. More specifically, Baerophob ECO (a 1:1 mixture of sodium oleate and calcium stearate by Baerlocher GmbH) and Silres Powder E (a silane-based hydrophobing agent by Wacker Chemie AG) were used. All amounts are shown in parts by weight per 1000. The amount of the plaster composition containing the inorganic binder is shown on a dry basis.

[0058]

Table 2

[0059] The samples thus prepared were shaped (i.e., cast or molded), cured, and dried until they reached a constant weight. Subsequently, the average total absorption rate and, in the case of Sample 8, the capillary absorption rate of the sample were also measured.

[0060] To measure the average total absorption rate, a 4×4×16 cm prism of the cured composition was analyzed as described in EN 520:2004, 5.9.2.

[0061] For the measurement of the capillary absorption rate, the samples were evaluated according to EN 1015-18:2002.

[0062] The results of these tests are shown in Table 3 below.

[0063]

Table 3

[0064] As is clear from Table 3, samples containing only one of the hydrophobic agents (excluding Sample 2) provide only moderate hydrophobicization with a respective chemical content of about 0.5 wt% based on the dry weight of the construction material. Interestingly, the sample containing both calcium hydroxide and a silicon-based hydrophobic agent (Sample 2) provided a much lower absorption rate than Sample 3 having only the silicon-based hydrophobic agent.

[0065] The performance of Samples 5 - 7 is almost comparable to or slightly better than that of Sample 2, and significantly better than that of Samples 3 and 4 containing only one of the hydrophobic agents. In Sample 8 where the total hydrophobic agent content was slightly increased from 0.5 to 0.6 wt%, the average absorption rate further decreased.

Claims

1. A construction material based on an inorganic binder, comprising: an inorganic binder and a synergistically effective mixture of a salt or compound providing a hydroxide and a silicon-based hydrophobizing agent in a ratio of 2:1 to 20:1, further comprising a fatty acid salt-based hydrophobizing agent or a precursor of a fatty acid salt-based hydrophobizing agent, wherein the weight ratio of the silicon-based hydrophobizing agent to the fatty acid salt-based hydrophobizing agent or the precursor of the fatty acid salt-based hydrophobizing agent is 0.5:1 to 5:

1.

2. The construction material according to claim 1, wherein the salt or compound providing the hydroxide is calcium hydroxide, reactive calcium oxide or magnesium hydroxide.

3. The construction material according to claim 1 or 2, wherein the silicon-based hydrophobizing agent is selected from silanes, siloxanes and / or silicones.

4. The fatty acid in the fatty acid salt-based hydrophobing agent is C ４ -C ３０ fatty acid, or a mixture of such acids, the construction material according to any one of claims 1 to 3.

5. The construction material according to any one of claims 1 to 4, wherein the fatty acid salt-based hydrophobizing agent contains a monovalent, divalent or trivalent cation.

6. The construction material according to any one of claims 1 to 5, wherein the precursor of the fatty acid salt-based hydrophobizing agent binds to the cation of the salt or compound providing the cation.

7. The construction material according to any one of claims 1 to 6, further comprising a salt or compound providing a hydroxide in a ratio of 2:1 to 20:1 based on the total weight of the silicon-based and the fatty acid salt-based hydrophobizing agents.

8. The construction material according to any one of claims 1 to 7, wherein all the hydrophobizing agents are contained in a total content of 0.02 to 5% by weight based on the dry weight of the construction material.

9. The construction material according to any one of claims 1 to 8, wherein the inorganic binder is a hydraulic binder.

10. A method for manufacturing a construction material based on an inorganic binder, comprising: (i) mixing water with an inorganic binder and a synergistically effective mixture of a salt or compound providing a hydroxide and a silicon-based hydrophobizing agent in a ratio of 2:1 to 20:1, and an optional additional additive; (ii) shaping the construction material; (iii) curing the construction material, wherein the synergistically effective mixture in step (i) further comprises a fatty acid salt-based hydrophobizing agent or a precursor of a fatty acid salt-based hydrophobizing agent, and the weight ratio of the silicon-based hydrophobizing agent to the fatty acid salt-based hydrophobizing agent or the precursor of the fatty acid salt-based hydrophobizing agent is 0.5:1 to 5:

1.

11. ​ Use of a synergistically effective mixture of a silicon-based hydrophobizing agent and a salt or compound providing a hydroxide to achieve an average total absorption rate of 10% or less when measured in accordance with EN 520:2004, 5.9.2 in the hydrophobization of construction materials based on inorganic binders, wherein the synergistically effective mixture further comprises a fatty acid salt-based hydrophobizing agent or a precursor of a fatty acid salt-based hydrophobizing agent, and the weight ratio of the silicon-based hydrophobizing agent to the fatty acid salt-based hydrophobizing agent or the precursor of the fatty acid salt-based hydrophobizing agent is from 0.5:1 to 5:1.

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